阅读说明：本技术 包含阻燃聚合物的陶瓷涂覆的纤维以及制备非织造结构的方法 (Ceramic coated fibers comprising flame retardant polymers and methods of making nonwoven structures ) 是由 任丽赟 吴平凡 丹尼尔·J·齐利格 萨钦·塔瓦尔 乔纳森·H·亚历山大 余大华 莫塞斯· 于 2018-12-14 设计创作，主要内容包括：本发明提供了包括由阻燃聚合物制成的陶瓷涂覆的熔喷非织造纤维的尺寸上稳定的纤维结构,以及用于生成此类阻燃非织造纤维结构的方法。所述熔喷纤维包含聚(苯硫醚)而无任何卤化阻燃添加剂,并且具有陶瓷涂层,所述聚(苯硫醚)的量足以使所述非织造纤维结构通过例如UL 94 V0、FAR 25.853(a)、FAR 25.856(a)和CA法规第19条的一个或多个耐火性测试。一离开熔喷模具的至少一个孔,立即使所述熔喷纤维在低于所述聚(苯硫醚)的熔融温度的温度下经历受控的飞行热处理,以便向所述纤维赋予尺寸上的稳定性。包括经飞行热处理的熔喷纤维的所述非织造纤维结构表现出的收缩小于在仅包括未经历受控的飞行热处理操作的纤维的非织造纤维结构上测量的收缩,通常表现出小于15％的收缩。(Dimensionally stable fibrous structures comprising ceramic coated meltblown nonwoven fibers made from flame retardant polymers are provided, as well as methods for forming such flame retardant nonwoven fibrous structures. The meltblown fibers comprise poly (phenylene sulfide) in an amount sufficient to allow the nonwoven fibrous structure to pass one or more fire resistance tests, such as UL 94V0, FAR25.853(a), FAR25.856(a), and CA regulation, article 19, without any halogenated flame retardant additives, and with a ceramic coating. Immediately upon exiting at least one orifice of a meltblowing die, said meltblown fibers are subjected to a controlled in-flight thermal treatment at a temperature below the melting temperature of said poly (phenylene sulfide) to impart dimensional stability to said fibers. The nonwoven fibrous structure comprising the in-flight heat treated meltblown fibers exhibits a shrinkage that is less than the shrinkage measured on a nonwoven fibrous structure comprising only fibers that have not been subjected to a controlled in-flight heat treatment operation, typically exhibiting a shrinkage of less than 15%.)

1. A refractory ceramic coated nonwoven fibrous structure, comprising:

a plurality of meltblown fibers comprising poly (phenylene sulfide) in an amount sufficient for the nonwoven fibrous structure to exhibit fire resistance via testing by one or more tests selected from UL 94V0, FAR25.853(a), FAR25.856(a), AITM20007A, and AITM3-0005, without any halogenated flame retardant additives; and

a ceramic coating on the surface of the plurality of melt blown fibers, wherein the nonwoven fibrous structure is dimensionally stable and exhibits less than 15% shrinkage, optionally wherein the plurality of melt blown fibers do not comprise a nucleating agent in an amount effective to effect nucleation, optionally wherein the ceramic coating comprises a ceramic selected from the group consisting of metal oxides, metal nitrides, metal carbides, metal oxynitrides, metal oxyborides, and combinations thereof.

2. The nonwoven fibrous structure of claim 1, wherein the ceramic coating comprises aluminum oxide, indium oxide, magnesium oxide, niobium oxide, silicon oxide, tantalum oxide, tin oxide, titanium oxide, zinc oxide, zirconium oxide, boron carbide, silicon carbide, tungsten carbide, aluminum nitride, boron nitride, silicon nitride, aluminum oxynitride, boron oxynitride, silicon oxynitride, zirconium oxyboride, titanium oxyboride, and a combination thereof.

3. The nonwoven fibrous structure according to claim 1, wherein the ceramic coating has a thickness of from 5nm to 10 microns.

4. The nonwoven fibrous structure of claim 1, further comprising a plurality of staple fibers.

5. The nonwoven fibrous structure of claim 4, wherein the plurality of staple fibers are non-meltblown fibers.

6. The nonwoven fibrous structure according to claim 4, wherein the plurality of staple fibers comprise (polyphenylene sulfide) staple fibers, non-heat stabilized poly (ethylene terephthalate) staple fibers, poly (ethylene naphthalate) staple fibers, oxidized poly (acrylonitrile) staple fibers, aromatic polyaramide staple fibers, glass staple fibers, ceramic staple fibers, metal staple fibers, carbon staple fibers, or combinations thereof.

7. The nonwoven fibrous structure according to claim 4 wherein the plurality of short fibers occupy no more than 90% by weight of the nonwoven fibrous structure.

8. The nonwoven fibrous structure of claim 1, wherein the plurality of meltblown fibers further comprises a thermoplastic semicrystalline (co) polymer selected from the group consisting of poly (ethylene terephthalate), poly (butylene terephthalate), poly (ethylene naphthalate), poly (lactic acid), poly (hydroxy) butyrate, poly (trimethylene terephthalate), polycarbonate, Polyetherimide (PEI), and combinations thereof.

9. The nonwoven fibrous structure of claim 8, wherein the amount of the thermoplastic semi-crystalline (co) polymer is no more than 50% by weight of the plurality of meltblown fibers.

10. The nonwoven fibrous structure of claim 1, wherein the plurality of meltblown fibers further comprises at least one thermoplastic amorphous (co) polymer in an amount of no more than 15 wt% of the weight of the nonwoven fibrous structure.

11. The nonwoven fibrous structure of claim 1 further comprising a plurality of particles, optionally wherein the plurality of particles comprises inorganic particles.

12. The nonwoven fibrous structure according to claim 11, wherein the plurality of particles comprises flame retardant particles, intumescent particles, or a combination thereof.

13. The nonwoven fibrous structure according to claim 11 wherein the plurality of particles are present in an amount of no greater than 40 percent by weight based on the weight of the nonwoven fibrous structure.

14. The nonwoven fibrous structure according to claim 1 wherein the nonwoven fibrous structure is selected from a mat, a web, a sheet, a scrim, a fabric, or combinations thereof.

15. An article comprising the nonwoven fibrous structure according to claim 1,

wherein the article is selected from the group consisting of thermal insulation articles, acoustic insulation articles, fluid filtration articles, wipes, surgical drapes, wound dressings, garments, respirators, or combinations thereof.

16. The article of claim 15, wherein the nonwoven fibrous structure has a thickness of from 0.5cm to 10.5 cm.

17. A method for making a refractory ceramic coated nonwoven fibrous structure, the method comprising:

forming a plurality of meltblown fibers by passing a molten stream comprising polyphenylene sulfide through a plurality of orifices of a meltblowing die;

immediately upon the meltblown fibers of step (a) exiting the plurality of holes, subjecting at least a portion of the meltblown fibers to a controlled in-flight thermal treatment operation, wherein the controlled in-flight thermal treatment operation is conducted at a temperature below the melting temperature of the portion of the meltblown fibers for a time sufficient to effect stress relaxation of at least a portion of the molecules within the portion of the fibers subjected to the controlled in-flight thermal treatment operation;

collecting at least some of the portion of the meltblown fibers that were subjected to the controlled in-flight thermal treatment operation on a collector to form a nonwoven fibrous structure; and

applying a ceramic coating on the surface of the plurality of melt blown fibers, wherein the nonwoven fibrous structure exhibits a shrinkage that is less than the shrinkage measured on an identically prepared structure that has not been subjected to the controlled in-flight heat treatment operation, and wherein the nonwoven fibrous structure further exhibits fire resistance via testing by one or more selected from the group consisting of UL 94V0, FAR25.853(a), FAR25.856(a), AITM20007A, and AITM3-0005, optionally wherein the plurality of melt blown fibers do not include a nucleating agent in an amount effective to achieve nucleation, without any added flame retardant additives.

18. The method of claim 17, wherein applying a ceramic coating on the surfaces of the plurality of melt blown fibers is performed using one or more Physical Vapor Deposition (PVD) methods selected from the group consisting of Atomic Layer Deposition (ALD), Chemical Vapor Deposition (CVD), Electron Beam Vapor Deposition (EBVD), Laser Ablation Vapor Deposition (LAVD), Low Pressure Chemical Vapor Deposition (LPCVD), Plasma Enhanced Chemical Vapor Deposition (PECVD), Plasma Assisted Chemical Vapor Deposition (PACVD), Thermal Vapor Deposition (TVD), reactive sputtering, and sputtering.

19. The method of claim 17, wherein the ceramic coating comprises aluminum oxide, indium oxide, magnesium oxide, niobium oxide, silicon oxide, tantalum oxide, tin oxide, titanium oxide, zinc oxide, zirconium oxide, boron carbide, silicon carbide, tungsten carbide, aluminum nitride, boron nitride, silicon nitride, aluminum oxynitride, boron oxynitride, silicon oxynitride, zirconium oxyboride, titanium oxyboride, and a combination thereof.

20. The method of claim 17, wherein the ceramic coating has a thickness of 5nm to 10 microns.

Technical Field

The present disclosure relates to dimensionally stable ceramic coated fibers comprising flame retardant polymers, and more particularly, to methods of making dimensionally stable, flame retardant nonwoven fibrous structures comprising such fibers.

Background

Melt blowing is a process for forming a nonwoven fibrous web of thermoplastic (co) polymer fibers. In a typical meltblown process, one or more thermoplastic (co) polymer streams are extruded through a die containing closely spaced orifices and attenuated by the convergence of high velocity hot air streams to form microfibers, which are collected to form a meltblown nonwoven fibrous web.

Thermoplastic (co) polymers commonly used to form conventional meltblown nonwoven fibrous webs include Polyethylene (PE) and polypropylene (PP). Meltblown nonwoven fibrous webs are suitable for use in a variety of applications including acoustic and thermal insulation, filtration media, surgical drapes and wipes, and the like.

Disclosure of Invention

One of the drawbacks of conventional meltblown nonwoven fibrous webs is that they tend to shrink even when heated to moderate temperatures during subsequent processing or use, for example, as insulation. Such shrinkage can be particularly problematic when the meltblown fibers comprise thermoplastic polyester (co) polymers; for example, poly (ethylene terephthalate), poly (lactic acid), poly (ethylene naphthalate), or combinations thereof; in some applications, this may be desirable in order to obtain higher temperature performance.

Another limitation of such conventional meltblown nonwoven fibrous webs is that the fibers typically comprise materials that are not fire resistant, often necessitating the addition of flame retardant agents (i.e., flame retardants) to the fibers if the nonwoven fibrous web is intended for use in applications limited by fire or flame propagation regulations, such as regulations limiting materials used in passenger car insulation articles. Certain halogenated flame retardants have recently become disfavored, in part, due to the persistence of their environment. Accordingly, it is desirable to develop a melt blown process for producing a flame resistant, dimensionally stable melt blown nonwoven fibrous structure that is free of halogenated flame retardants.

It is also desirable to produce flame retardant nonwoven structures for use in high temperature (e.g., temperatures of about 150 ℃ to about 400 ℃) environments, for example, as insulation articles that may be used in high temperature automotive, aerospace, construction, and electronic applications. Nonwoven fibrous structures known for use in high temperature applications typically employ inorganic fibers such as glass fibers, basalt fibers, or ceramic fibers that are incorporated into the nonwoven fibrous structure with an organic binder such as a phenolic resin. However, the organic binders used in these high temperature flame retardant nonwoven structures may degrade the flame resistance, flame propagation, and self-extinguishing characteristics of the resulting high temperature flame retardant structures.

Also, melamine foams, polyimide foams andfelts are known high temperature refractory materials. While some of these materials may self-extinguish upon removal of the flame, it is difficult for existing materials to provide a reliable flame barrier to prevent the flame from propagating to other structures or components in contact with the resulting high temperature flame-retardant structure. We have found that the formation of a fire resistant barrier (e.g. char layer) may be important to prevent flame propagation during a fire event and thus improve both the fire resistance and fire retardant characteristics of the resulting high temperature fire retardant structure.

Accordingly, in one aspect, the present disclosure describes a ceramic coated nonwoven fibrous structure comprising a plurality of meltblown fibers comprising a flame retardant polymer. The nonwoven fibrous structure exhibits fire resistance and/or flame retardancy without any added halogenated flame retardant, as evidenced by one or more tests selected from UL 94V0, FAR25.853, FAR25.856, AITM20007A, AITM3-0005 and california regulation, article 19. Preferably, the nonwoven fibrous structure is dimensionally stable and exhibits less than 15% shrinkage.

In certain exemplary embodiments, it may be desirable to include a non-halogenated flame retardant in the nonwoven fibrous structure. In other exemplary embodiments, the meltblown fibers do not contain flame retardant agents other than flame retardant polymers (i.e., flame retardants). In certain exemplary embodiments, the meltblown fibers do not contain a nucleating agent in an amount effective to achieve nucleation.

In another aspect, the present disclosure describes a method for producing a ceramic coated nonwoven fibrous structure comprising a plurality of meltblown fibers comprising a flame retardant polymer, and more particularly, a method for producing a dimensionally stable, ceramic coated meltblown nonwoven fibrous structure comprising a flame retardant polymer.

In some exemplary embodiments, the method includes forming a plurality of meltblown fibers by passing a molten polymer stream comprising poly (phenylene sulfide) through a plurality of orifices of a meltblowing die, immediately subjecting at least a portion of the meltblown fibers to a controlled in-flight heat treatment operation as soon as the meltblown fibers exit the plurality of orifices, wherein the controlled in-flight heat treatment operation is conducted at a temperature below the melting temperature of the portion of the meltblown fibers for a time sufficient to effect stress relaxation of at least a portion of the molecules within the portion of the fibers subjected to the controlled in-flight heat treatment operation; collecting at least some of the portion of the meltblown fibers that have undergone the controlled in-flight thermal treatment operation on a collector to form a nonwoven fibrous structure; and applying a ceramic coating on the surface of the plurality of meltblown fibers. The ceramic-coated nonwoven fibrous structures are dimensionally stable and exhibit shrinkage (as determined using the methods described herein) that is less than the shrinkage measured on an identically prepared structure that has not been subjected to a controlled in-flight heat treatment operation.

In other exemplary embodiments, the method includes providing a melt stream comprising a thermoplastic material including a high proportion (i.e., at least 50 weight percent based on the weight of the meltblown fibers) of poly (phenylene sulfide) to a meltblowing die; melt blowing a thermoplastic material into at least one fiber; immediately after exiting the meltblowing die, subjecting at least one fiber to a controlled in-flight heat treatment operation conducted at a temperature below the melting temperature of the poly (phenylene sulfide) for a time sufficient for the nonwoven fibrous structure to exhibit a shrinkage (when tested using the method described herein) that is less than the shrinkage measured on an identically prepared structure that has not been subjected to the controlled in-flight heat treatment operation, prior to collection as a nonwoven fibrous structure on a collector; and applying a ceramic coating on a surface of the at least one fiber. Preferably, the thermoplastic material does not contain a nucleating agent in an amount effective to achieve nucleation.

In certain presently preferred embodiments, the method includes collecting at least one fiber subjected to a controlled in-flight heat treatment operation on a collector to form a nonwoven fibrous structure. The application of the ceramic coating on the surface of the at least one fiber may occur before, during, or after collection on a collector to form the nonwoven fibrous structure.

Various exemplary embodiments of the present disclosure are further illustrated by the following list of exemplary embodiments, which should not be construed to unduly limit the present disclosure:

list of exemplary embodiments：

A. A nonwoven fibrous structure, comprising:

a plurality of meltblown fibers comprising poly (phenylene sulfide) in an amount sufficient for the nonwoven fibrous structure to exhibit fire resistance via testing by one or more tests selected from UL 94V0, FAR25.853(a), FAR25.856(a), AITM20007A, AITM3-0005 and California regulations article 19, without any halogenated flame retardant additives; and a ceramic coating on the surface of the plurality of meltblown fibers, wherein the nonwoven fibrous structure is dimensionally stable and exhibits less than 15% shrinkage, optionally wherein the plurality of meltblown fibers do not comprise a nucleating agent in an amount effective to effect nucleation, optionally wherein the ceramic coating comprises a ceramic selected from the group consisting of metal oxides, metal nitrides, metal carbides, metal oxynitrides, metal oxyborides, and a combination thereof.

B. The nonwoven fibrous structure according to embodiment a, wherein the ceramic coating comprises aluminum oxide, indium oxide, magnesium oxide, niobium oxide, silicon oxide, tantalum oxide, tin oxide, titanium oxide, zinc oxide, zirconium oxide, boron carbide, silicon carbide, tungsten carbide, aluminum nitride, boron nitride, silicon nitride, aluminum oxynitride, boron oxynitride, silicon oxynitride, zirconium oxyboride, titanium oxyboride, and a combination thereof.

C. The nonwoven fibrous structure according to embodiment a or B, wherein the ceramic coating has a thickness of from 5nm to 10 microns.

D. The nonwoven fibrous structure according to any one of the preceding embodiments, further comprising a plurality of short fibers.

E. The nonwoven fibrous structure according to embodiment D, wherein the plurality of staple fibers are non-meltblown fibers.

F. The nonwoven fibrous structure according to embodiment D or E, wherein the plurality of staple fibers comprises (polyphenylene sulfide) staple fibers, non-heat stabilized poly (ethylene terephthalate) staple fibers, poly (ethylene naphthalate) staple fibers, oxidized poly (acrylonitrile) staple fibers, aromatic polyaramide staple fibers, glass staple fibers, ceramic staple fibers, metal staple fibers, carbon staple fibers, or combinations thereof.

G. The nonwoven fibrous structure according to any of embodiments D-F, wherein the plurality of short fibers occupy no more than 90% by weight of the nonwoven fibrous structure.

H. The nonwoven fibrous structure according to any preceding embodiment, wherein the plurality of meltblown fibers further comprises a thermoplastic semicrystalline (co) polymer selected from the group consisting of poly (ethylene terephthalate), poly (butylene terephthalate), poly (ethylene naphthalate), poly (lactic acid), poly (hydroxy) butyrate, poly (trimethylene terephthalate), polycarbonate, Polyetherimide (PEI), or combinations thereof.

I. The nonwoven fibrous structure according to any preceding embodiment, wherein the plurality of meltblown fibers further comprises at least one thermoplastic amorphous (co) polymer in an amount of no more than 15 wt% of the weight of the plurality of meltblown fibers.

J. The nonwoven fibrous structure according to embodiment F or G, wherein the amount of the thermoplastic semi-crystalline (co) polymer is no more than 50% by weight of the plurality of meltblown fibers.

K. The nonwoven fibrous structure according to any preceding embodiment, wherein the plurality of meltblown fibers exhibit an average fiber diameter or a median fiber diameter of no more than about 10 microns.

L. the nonwoven fibrous structure according to any one of the preceding embodiments, exhibiting a solidity of from about 0.5% to about 12%.

M. the nonwoven fibrous structure according to any preceding embodiment, the nonwoven fibrous structure exhibiting a basis weight of from 40gsm to about 1,000 gsm.

N. the nonwoven fibrous structure according to any one of the preceding embodiments, wherein the compressive strength as measured using the test method disclosed herein is greater than 1 kPa.

O. the nonwoven fibrous structure according to any one of the preceding embodiments, wherein the maximum load tensile strength as measured using the test method disclosed herein is greater than 10 newtons.

P. the nonwoven fibrous structure according to any one of the preceding embodiments, further comprising a plurality of particles, optionally wherein the plurality of particles comprises inorganic particles.

Q. the nonwoven fibrous structure according to embodiment P, wherein the plurality of particles comprises flame retardant particles, intumescent particles, or a combination thereof.

R. the nonwoven fibrous structure according to embodiments P or Q, wherein the plurality of particles are present in an amount of no greater than 40% by weight, based on the weight of the nonwoven fibrous structure.

S. the nonwoven fibrous structure according to any one of the preceding embodiments, wherein the nonwoven fibrous structure is selected from a mat, a web, a sheet, a scrim, a fabric, or a combination thereof.

An article comprising the nonwoven fibrous structure according to any preceding embodiment, wherein the article is selected from the group consisting of a thermal insulation article, an acoustic insulation article, a fluid filtration article, a wipe, a surgical drape, a wound dressing, a garment, a respirator, or a combination thereof.

U. the article of embodiment T, wherein the nonwoven fibrous structure has a thickness of from 0.5cm to 10.5 cm.

V. a process for making a nonwoven fibrous structure, the process comprising:

forming a plurality of meltblown fibers by passing a molten stream comprising polyphenylene sulfide through a plurality of orifices of a meltblowing die; subjecting at least a portion of said meltblown fibers to a controlled in-flight heat treatment operation as soon as said meltblown fibers exit said plurality of orifices, wherein said controlled in-flight heat treatment operation is conducted at a temperature below the melting temperature of said portion of said meltblown fibers for a time sufficient to effect stress relaxation of at least a portion of the molecules within said portion of said fibers subjected to said controlled in-flight heat treatment operation; collecting at least some of the portion of the meltblown fibers that were subjected to the controlled in-flight thermal treatment operation on a collector to form a nonwoven fibrous structure; and applying a ceramic coating on the surface of the plurality of melt blown fibers, wherein the nonwoven fibrous structure exhibits a shrinkage that is less than the shrinkage measured on an identically prepared structure that has not been subjected to the controlled in-flight heat treatment operation of step (b), and wherein the nonwoven fibrous structure further exhibits fire resistance without any added flame retardant additives via testing by one or more selected from UL 94V0, FAR25.853(a), FAR25.856(a), AITM20007A, AITM3-0005, and california regulation article 19, optionally wherein the plurality of melt blown fibers do not include a nucleating agent in an amount effective to achieve nucleation.

W. the method of embodiment V, wherein applying a ceramic coating on the surfaces of the plurality of meltblown fibers is performed using one or more Physical Vapor Deposition (PVD) processes selected from Atomic Layer Deposition (ALD), Chemical Vapor Deposition (CVD), Electron Beam Vapor Deposition (EBVD), Laser Ablation Vapor Deposition (LAVD), Low Pressure Chemical Vapor Deposition (LPCVD), Plasma Enhanced Chemical Vapor Deposition (PECVD), Plasma Assisted Chemical Vapor Deposition (PACVD), Thermal Vapor Deposition (TVD), reactive sputtering, and sputtering.

X. the method of embodiments V or W, wherein the ceramic coating comprises aluminum oxide, indium oxide, magnesium oxide, niobium oxide, silicon oxide, tantalum oxide, tin oxide, titanium oxide, zinc oxide, zirconium oxide, boron carbide, silicon carbide, tungsten carbide, aluminum nitride, boron nitride, silicon nitride, aluminum oxynitride, boron oxynitride, silicon oxynitride, zirconium oxyboride, titanium oxyboride, and a combination thereof.

Y. the method of any one of embodiments V-X, wherein the ceramic coating has a thickness of 5nm to 10 microns.

Drawings

The present disclosure may be more completely understood in consideration of the following detailed description of various embodiments of the disclosure in connection with the accompanying drawings, in which it is to be understood by those of ordinary skill in the art that the drawings are merely illustrative of certain exemplary embodiments and are not intended to limit the broader aspects of the disclosure.

FIG. 1A is a general schematic diagram of an exemplary apparatus for forming meltblown fibers and in-flight heat treating the meltblown fibers in an exemplary embodiment of the disclosure.

FIG. 1B is a general schematic diagram of another exemplary apparatus for forming meltblown fibers and in-flight heat treating the meltblown fibers in an exemplary embodiment of the disclosure.

Repeat use of reference characters in the present specification and drawings is intended to represent same or analogous features or elements of the disclosure. While the above-identified drawing figures, which may not be drawn to scale, illustrate various embodiments of the disclosure, other embodiments are also contemplated, as noted in the detailed description.

Detailed Description

In the following detailed description, reference is made to the accompanying set of drawings that form a part hereof, and in which is shown by way of illustration specific embodiments. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit of the present disclosure. The following detailed description is, therefore, not to be taken in a limiting sense.

Unless otherwise indicated, all numbers expressing feature sizes, amounts, and physical characteristics used in the specification and claims are to be understood as being modified in all instances by the term "about". Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings disclosed herein. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claimed embodiments, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Moreover, the use of numerical ranges having endpoints includes all numbers within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5), as well as any narrower range or single value within that range.

Glossary：

Certain terms are used throughout the description and claims, and although mostly known, some explanation may be required. It should be understood that, as used herein:

the terms "about," "approximately," or "approximately" in reference to a numerical value or geometry means +/-five percent of the value of the internal angle between adjacent sides of the numerical value or geometry having a generally accepted number of sides, expressly including any narrower range within +/-five percent of the numerical value or angular value, as well as the exact numerical value or angular value. For example, a temperature of "about" 100 ℃ refers to a temperature from 95 ℃ to 105 ℃, but also expressly includes any narrower temperature range or even a single temperature within that range, including, for example, a temperature of exactly 100 ℃.

The term "substantially" with reference to a characteristic or feature means that the characteristic or feature appears to be within 2% of the characteristic or feature, but also expressly includes any narrower range within 2% of the characteristic or feature and the precise value of the characteristic or feature. For example, a "substantially" transparent substrate refers to a substrate that transmits 98% to 100% of incident light.

The terms "a", "an" and "the" include plural referents unless the content clearly dictates otherwise. Thus, for example, reference to a material comprising "a compound" includes mixtures of two or more compounds.

The term "or" is generally employed in its sense including "and/or" unless the content clearly dictates otherwise.

The term "(co) polymer" means a relatively high molecular weight material having a molecular weight of at least about 10,000 g/mole (in some embodiments, in the range of 10,000 g/mole to 5,000,000 g/mole). The term "(co) polymers" or "(co) polymers" includes homopolymers and copolymers, as well as homopolymers or copolymers that may be formed in a miscible blend, e.g., by coextrusion or by reaction, including, e.g., transesterification. The term "(co) polymer" includes random, block and star (e.g., dendritic) (co) polymers.

The terms "meltblown" and "meltblown process" refer to processes in which a nonwoven fibrous web is formed by: extruding molten fiber-forming material comprising one or more thermoplastic (co) polymers through at least one or more orifices to form filaments while contacting the filaments with air or other attenuating fluid to attenuate the filaments into dispersed fibers, followed by collecting the attenuated fibers. An exemplary melt blowing process is taught, for example, in U.S. patent 6,607,624 (Berrigan).

The term "meltblown fibers" means fibers prepared by meltblowing or meltblowing. The term is generally used to refer to staple fibers formed from one or more molten streams of one or more thermoplastic (co) polymers that are extruded from one or more orifices of a melt blowing die and then cooled to form vulcanized fibers and webs containing the vulcanized fibers therein. These designations are used only for convenience of description. In the methods described herein, there may be no clear line of demarcation between the locally stiffened fibers and the fibers that still contain a slightly tacky and/or semi-molten surface.

The term "die" means a processing assembly including at least one orifice used in polymer melt processing and fiber extrusion processes, including but not limited to melt blowing.

The term "discontinuous" when used with respect to a fiber or collection of fibers means that the fibers have a substantially limited aspect ratio (e.g., a ratio of length to diameter of, for example, less than about 10,000).

The term "oriented" when used with respect to a fiber means that at least a portion of the (co) polymer molecules within the fiber are aligned with the longitudinal axis of the fiber, for example, by using a drawing process or attenuator as the fiber stream exits the die.

The term "nonwoven fibrous web" or "nonwoven web" means a collection of fibers characterized by entanglement or point bonding of the fibers to form a sheet or mat exhibiting a structure of individual fibers or filaments which are interwoven, but in a manner different from a knitted fabric.

The term "monocomponent" when used with respect to a fiber or collection of fibers means fibers having substantially the same composition across their cross-section; monocomponent includes blends (i.e., (co) polymer mixtures) or additive-containing materials in which a continuous phase of substantially uniform composition extends across the cross-section of the fiber and over the length of the fiber.

The term "directly collected fibers" describes fibers that are formed and collected into a web in essentially one operation by extruding molten fibers from a set of orifices and collecting at least partially stiffened fibers as fibers on a collector surface without the filaments or fibers contacting a deflector or the like between the orifices and the collector surface.

The term "pleat" describes a nonwoven fibrous structure or web in which at least a portion of the web is folded to form a configuration comprising a plurality of generally parallel, oppositely oriented rows of folds. Likewise, pleating of nonwoven fibrous structures or webs as a whole is distinguished from crimping of individual fibers.

The term "self-supporting" as used with respect to nonwoven fibrous structures (e.g., nonwoven fibrous webs, etc.) describes that the structures do not include a contiguous reinforcement layer of wires, mesh, or other stiffening material, even though pleated filter elements comprising such matrices may include tip stabilization (e.g., planar wire facers) or perimeter reinforcement (e.g., edge adhesives or filter frames) to reinforce selected portions of the filter element. Alternatively or additionally, the term "self-supporting" describes a filter element that is resistant to deformation without the need for reinforcement layers, bicomponent fibers, adhesives, or other reinforcements in the filter media.

The term "web basis weight" is calculated from the weight of a 10cm by 10cm web sample and is typically expressed in grams per square meter (gsm).

The "web thickness" was measured on a 10cm x 10cm web sample using a thickness tester with a test foot size of 5cm x 12.5cm under an applied pressure of 150 Pa.

The term "bulk density" is the mass per unit volume of the bulk polymer or polymer blend making up the web, and is taken from the literature.

The term "solidity" is a nonwoven web property that is inversely related to density and web penetration characteristics and porosity (low solidity corresponds to high permeability and high porosity) and is defined by the following equation:

the terms "average fiber diameter" and "median fiber diameter" for fibers in a given nonwoven meltblown fiber structure (e.g., web) or component population are determined by: generating one or more images of the fibrous structure, such as by using a scanning electron microscope; measuring the fiber diameter of the clearly visible fibers in one or more images, thereby obtaining a total number x of fiber diameters; and calculating the average or median fiber diameter of the x fiber diameters. Typically, x is greater than or equal to about 50, and desirably in the range of about 50 to about 500. However, in some cases, x may be chosen as small as 300 or even 200. These smaller values of x may be particularly useful for large diameter fibers, or for highly entangled fibers.

For (co) polymers or (co) polymer fibers or fiber webs, the term "nominal melting point" corresponds to the temperature at which the maximum peak in the first heat total heat flow profile obtained using Modulated Differential Scanning Calorimetry (MDSC) as described herein occurs in the melted region of the (co) polymer or fiber (if there is only one maximum in the melted region); and if there is more than one maximum, the more than one maximum indicates more than one nominal melting point (e.g., due to the presence of two different crystalline phases) as the temperature at which the highest amplitude melting peak occurs.

The terms "particle" and "particle" are essentially used interchangeably. Generally, particles or granules mean different small pieces or individual portions of a material in a finely divided form. However, a particle may also comprise a collection of individual particles related or grouped together in a finely divided form. Thus, the individual particles used in certain exemplary embodiments of the present disclosure may be aggregated, physically associated with each other, electrostatically associated, or otherwise associated to form particles. In some cases, particles in the form of aggregates of individual particles may be intentionally formed, such as those described in U.S. Pat. No. 5,332,426(Tang et al).

The term "porous" with reference to a meltblown nonwoven fibrous structure or web means breathable. The term "porous" with reference to particles means permeable to gas or liquid.

The term "particle packing method" or "particle packing method" means a method of adding particles to a fiber stream or fiber web while it is being formed. Exemplary particle packing methods are set forth, for example, in U.S. Pat. Nos. 4,818,464(Lau) and 4,100,324(Anderson et al).

The term "particulate-loaded media" or "particulate-loaded nonwoven fibrous web" means a nonwoven fibrous web having an open structure of entangled discrete fiber masses containing particles entrapped within or bonded to the fibers, which particles are chemically active.

The term "entrapped" means that the particles are dispersed and physically fixed in the fibers of the web. Generally, there is point and line contact along the fibers and particles so that almost the entire surface area of the particles is available for interaction with the fluid.

Various exemplary embodiments of the present disclosure will now be described with particular reference to the accompanying drawings. Various modifications and alterations may be made to the exemplary embodiments of the present disclosure without departing from the spirit and scope thereof. Accordingly, it is to be understood that the embodiments of the present disclosure are not to be limited to the exemplary embodiments described below, but are to be controlled by the limitations set forth in the claims and any equivalents thereof.

The present disclosure describes methods and related apparatus for making fire-resistant, ceramic-coated, meltblown nonwoven fibrous structures (e.g., mats, webs, sheets, scrims, fabrics, etc.) from fibers comprising, consisting essentially of, or consisting of poly (phenylene sulfide) and optionally a semi-crystalline polyester (co) polymer or combination of semi-crystalline polyester (co) polymers. Preferably, the nonwoven fibrous structure is dimensionally stable.

Prior to the apparatus and methods of the present disclosure, it was difficult to melt-blow thermoplastic (co) polymer fibers comprising crystalline or semi-crystalline polyester (co) polymers, particularly such fibers having a diameter or thickness of less than about 10 microns. To melt-blow such fibers, the corresponding thermoplastic polyester (co) polymer must typically be heated to a temperature well above its nominal melting point.

Such high temperature heating of thermoplastic polyester (co) polymers can lead to one or any combination of problems that can include, for example, excessive degradation of the (co) polymer, brittle and fragile fibrous webs, and the formation of particulate (co) polymer (commonly referred to as "sand") during melt blowing. Even when melt blown polyester (co) polymer fibers are produced using conventional processes, fibrous webs and other fibrous structures made from such fibers often exhibit excessive shrinkage or other poor dimensional stability at temperatures at or above the glass transition temperature of the polyester (co) polymer used to make the fibers.

The present inventors have discovered a method of melt-blowing fibers and forming fire-resistant, dimensionally stable, ceramic-coated melt-blown nonwoven fibrous structures (e.g., mats, webs, sheets, scrims, fabrics, etc.) that uses a thermoplastic (co) polymer comprising poly (phenylene sulfide) and optionally at least one thermoplastic semi-crystalline polyester (co) polymer or thermoplastic semi-crystalline polyester (co) polymers.

Such fibers exhibit several desirable properties, including, for example, one or any combination of the following: relatively low cost (e.g., manufacturing and/or raw material cost), durability, reduced shrinkage upon thermal exposure, increased dimensional stability at elevated temperatures, fire resistance or fire retardancy, and reduced smoke generation and smoke toxicity in a fire. The present disclosure may also be used to provide environmentally friendly non-halogenated flame resistant polyester based nonwoven fibrous structures.

Because the meltblown fibers are made with (co) polymeric materials that are dimensionally stable at elevated temperatures, nonwoven fibrous structures (e.g., mats, webs, sheets, scrims, fabrics, and the like) made from such fibers and articles made from such fibrous structures (e.g., thermal insulation, acoustic and insulation articles, liquid and gas screens, garments, and personal protective equipment) can be used in higher temperature environments while exhibiting only slight, if any, shrinkage. The development of dimensionally stable fire resistant meltblown nonwoven fibrous structures (e.g., webs) that will not shrink significantly upon exposure to heat provided according to embodiments of the present disclosure would broaden the usefulness and industrial applications of such webs. Such meltblown microfiber webs may be particularly suitable for use as thermal and high temperature acoustical articles.

Nonwoven fibrous structures

In one aspect, the present disclosure provides a nonwoven fibrous structure comprising: a plurality of meltblown fibers comprising poly (phenylene sulfide) in an amount sufficient for the nonwoven fibrous structure to exhibit fire resistance via testing by one or more tests selected from the group consisting of UL 94V0, FAR25.853(a), FAR25.856(a), AITM20007A, and AITM3-0005, without any halogenated flame retardant additives; and a ceramic coating on a surface of the plurality of meltblown fibers. The nonwoven fibrous structure is preferably dimensionally stable and exhibits less than 15% shrinkage. In certain exemplary embodiments, the plurality of meltblown fibers do not comprise a nucleating agent in an amount effective to achieve nucleation.

In certain embodiments, the ceramic coating comprises a ceramic selected from a metal oxide, a metal nitride, a metal carbide, a metal oxynitride, a metal oxyboride, or a combination thereof. Preferably, the ceramic coating comprises aluminum oxide, indium oxide, magnesium oxide, niobium oxide, silicon oxide, tantalum oxide, tin oxide, titanium oxide, zinc oxide, zirconium oxide, boron carbide, silicon carbide, tungsten carbide, aluminum nitride, boron nitride, silicon nitride, aluminum oxynitride, boron oxynitride, silicon oxynitride, zirconium oxyboride, titanium oxyboride, and combinations thereof.

The ceramic coating may form a continuous layer on the surface of the plurality of meltblown fibers, or may form a semi-continuous or discontinuous layer on the surface of the plurality of meltblown fibers. The ceramic coating may form a continuous layer on the surface of the nonwoven fibrous structure, or may form a semi-continuous or discontinuous layer on the surface of the nonwoven fibrous structure. The ceramic coating may be applied to one or more surfaces of the nonwoven fibrous structure, including one or both of the opposing major surfaces of the nonwoven fibrous structure.

The thickness of the ceramic coating is typically 5nm to 10 micrometers (μm); 50nm to 5 μm, 100nm to 4 μm, 200nm to 3 μm, 300nm to 2 μm; or even 400nm to 1 μm. The thickness of the ceramic coating is preferably at least 1nm, 5nm, 50nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm or even 1 μm. The thickness of the ceramic coating is preferably not more than 50 μm, 40 μm, 30 μm, 20 μm, 10 μm, 5 μm, 4 μm, 3 μm, 2 μm or even 1 μm.

The nonwoven fibrous structure may take a variety of forms including a mat, a web, a sheet, a scrim, a fabric, and combinations thereof. After in-flight heat treatment and collection of the meltblown fibers as a nonwoven fibrous structure, the nonwoven fibrous structure exhibits a shrinkage (as determined using the shrinkage test method described below) of less than about 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, or even 1%, as further described below.

Meltblown fibers

Meltblown nonwoven fibrous structures or webs of the present disclosure generally comprise meltblown fibers which may be considered staple fibers. However, depending on the selected operating parameters, such as the degree of solidification of the molten state, the collected fibers may be semi-continuous or substantially discontinuous.

In certain exemplary embodiments, the meltblown fibers of the present disclosure may be oriented (i.e., have a molecular orientation).

In some exemplary embodiments, the meltblown fibers in the nonwoven fibrous structure or web may exhibit a median fiber diameter (determined using the test method described below) of no more than about 10 micrometers (μm), 9 μm, 8 μm, 7 μm, 5 μm, 4 μm, 3 μm, 2 μm, or even 1 μm.

In certain such exemplary embodiments, the nonwoven fibrous structure exhibits an average caliper of from about 0.5% to about 12%; about 1% to about 11%; about 1.5% to about 10%; about 2% to about 9%; a solidity of from about 2.5% to about 7.5, or even from about 3% to about 5%.

In other such exemplary embodiments, the nonwoven fibrous structure exhibits from 40 grams per square meter (gsm) to about 1,000 gsm; from about 100gsm to about 900 gsm; from about 150gsm to about 800 gsm; from about 175gsm to about 700 gsm; a basis weight of from about 200gsm to about 600gsm, or even from about 250gsm to about 500 gsm.

In further such exemplary embodiments, the nonwoven fibrous structure exhibits a tenacity greater than 1kPa, greater than 2kPa, greater than 3kPa, greater than 4kPa, greater than 5kPa, or even greater than 7.5kPa as measured using the test method disclosed below; and typically less than 15kPa, 14kPa, 13kPa, 12kPa, 11kPa or 10kPa compressive strength.

The mechanical strength of the nonwoven fibrous structure is preferably sufficient to prevent tearing during handling and installation. In some exemplary embodiments, the nonwoven fibrous structure exhibits greater than 10 newtons (N), greater than 15N, greater than 20N, greater than 25N, or even greater than 30N as measured using the test methods disclosed below; and generally less than a maximum load tensile strength of 100N, 90N, 80N, 70N, 60N, or even 50N.

In some exemplary embodiments, the nonwoven fibrous structure may exhibit an overall tensile strength (tensile strength averaged in the md and the cd) of from 10N to 100N, from 20N to 50N, from 30N to 40N, or in some embodiments, less than, equal to, or greater than 10N, 11N, 12N, 15N, 17N, 20N, 22N, 25N, 27N, 30N, 32N, 35N, 37N, 40N, 42N, 45N, 47N, or even 50N.

Meltblown fiber component

Meltblown fibers include poly (phenylene sulfide), and may optionally include additional materials, such as at least one thermoplastic semi-crystalline (co) polymer, or a blend of at least one thermoplastic semi-crystalline polyester (co) polymer and at least one other (co) polymer, to form a (co) polymer blend.

Poly (phenylene sulfide)

The melt blown nonwoven fibers of the present disclosure comprise poly (phenylene sulfide) (PPS) in an amount sufficient to cause the nonwoven fibrous structure to exhibit fire resistance via testing by one or more tests selected from UL 94V0, FAR25.853(a), FAR25.856(a), AITM20007A, and AITM3-0005, without any added flame retardant additives (other than PPS).

Generally, the greater the amount of PPS included in the meltblown fibers, the greater the fire resistance of the resulting nonwoven fibrous structure. The amount of PPS included in the melt blown fibers will depend to some extent on the other components included in the nonwoven fibrous structure, as well as the other components included in the melt blown nonwoven fibers.

If the nonwoven fibrous structure includes only meltblown fibers, the amount of PPS in the meltblown fibers may vary as low as 30, 40, 50, 60, 70, 80, or even 90 percent by weight, based on the weight of the meltblown fibers. The maximum amount of PPS in the meltblown fibers may be 100, 90, 80, 70, 60, or even 50 weight percent based on the weight of the meltblown fibers.

If the nonwoven fibrous structure includes non-PPS staple fibers in addition to the meltblown fibers, the PPS should generally constitute a significant amount of the meltblown fibers. In such cases, the amount of PPS in the meltblown fibers may vary as low as 50, 60, 70, 80, or even 90 weight percent based on the weight of the meltblown fibers. The maximum amount of PPS in the meltblown fibers may be 100, 90, 80, 70, or even 60 weight percent.

Without any added flame retardant additive (other than PPS), the nonwoven fibrous structure exhibits fire resistance via one or more tests selected from Underwriter's Laboratories UL 94V0, Federal Aviation Regulations (FAR) 25.853(a), FAR25.856(a), FAR 85.853, FAR85.856(a), Airbus industry Test Method (Airbus Industries Test (AITM))20007A, AITM3-0005, and california regulation No. 19.

UL 94V0 is a fire resistance standard for automotive materials and requires combustion to be stopped within ten seconds after removing the flame from a vertical test specimen of a nonwoven fibrous structure.

FAR25.853 is an aerospace standard for testing the fire resistance of materials by evaluating the self-extinguishing performance of the test material under fire exposure conditions. In performing the FAR25.853 test method, test specimens of defined dimensions are placed vertically and exposed to a standardized horizontal flame source (gas torch). For FAR25.853(a), the gas torch was applied for sixty seconds. For FAR25.853 (b), the gas torch was applied for twelve seconds.

FAR25.853(a) test suspension 3/4 "(about 1.9cm) fire spread in a vertical 2" x 12 "(about 5.1cm x 30.5cm) standard test specimen into a flame of 1/2" (about 3.8cm) from a standardized horizontal flame source (gas torch) for sixty seconds. Requirements by FAR25.853(a) include:

(1) the test sample self-extinguished in no more than 15 seconds;

(2) the charred length of the test sample was a maximum of 8 inches (20.32 cm); and

(3) the maximum burning time of any droplet from the test sample was 5 seconds.

FAR25.856 is an aerospace standard for testing the fire resistance of materials by evaluating the self-extinguishing performance of standard test specimens under conditions of high radiation temperature and fire exposure. The most stringent element of FAR25.856 is the Radiant Panel Test (RPT) under FAR25.856(a), which requires exposure of standard test specimens to extremely high radiant temperatures and standardized flame sources while remaining in an upright position.

To pass the radiant panel test at FAR25.856(a), the test specimen must exhibit a flame propagation of less than 2 inches (about 5.1cm) from the point of flame contact on the test specimen, and a flame hold time (i.e., the self-extinguishing time after removal of the flame source) of less than three seconds.

AITM20007A And AITM3-0005 are industry standard test methods for smoke generation And smoke toxicity of aircraft insulation when exposed to fire, as established by air passenger industry ABD 0031 (air passenger Industries, Ltd.) And available at https:// www.govmark.com/services/air space-Rail-And-Transportation/air-test-list.

Fire resistance, fire retardancy and flame propagation requirements of thermal and acoustical insulation materials were specified in Chapter 720 of California construction Code (CBC) 2013, California Code 19http:// osfm.fire.ca.gov/codedevelopment/pdf/wgfsbim/CaBldgCodeInsulFireTests201402 25.pdfAnd (4) obtaining.

PPS resins in the form of slabs or pellets are commercially produced by various manufacturers. PPS polymers are available in either linear or crosslinked (non-linear) form. The linear form of PPS polymer is generally preferred for melt blown fibers due to its lower melt viscosity and reduced viscoelasticity.

Suitable commercially available PPS resins include, for example, PPS under the trade name dic^TMThe resins obtained (PPS of the linear and crosslinked type, obtained from DIC International (USA) LLC, Parsipanib, N.J.) were,

(Linear type PPS, available from plastics Co., Ltd., Tokyo, Japan),

And

(available from Schulman, Co., Ohio) engineering plastics, Inc. (A. Schulman, Co., Ohio),(Linear type, available from Celanese corporation, Owen, Tex.) of,(available from Tosoh, Inc., Tosoh, Japan) from Tosoh corporation,

(Linear and crosslinked types of PPS available from Solvay specialty polymers, Inc., Solvay specialty polymers, Belgium, Brussels),(Linear type PPS, available from Albis Plastics Co., Texas.) and TORELINA^TM(Linear PPS, available from Toray Industries, Inc., Tokyo, Japan).

Optionally thermoplastic semicrystalline (co) polymers

In other exemplary embodiments, the nonwoven fibrous structure according to any of the above embodiments comprises fibers comprising poly (phenylene sulfide) and optionally at least one thermoplastic semi-crystalline (co) polymer, or a blend of at least one thermoplastic semi-crystalline polyester (co) polymer and at least one other (co) polymer to form a blend of (co) polymers.

In exemplary embodiments, the at least one thermoplastic semi-crystalline (co) polymer comprises an aliphatic polyester (co) polymer, an aromatic polyester (co) polymer, or a combination thereof. In certain exemplary embodiments, the thermoplastic semi-crystalline (co) polymer comprises polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, poly (lactic acid), polyhydroxybutyrate, polytrimethylene terephthalate, or combinations thereof.

Generally, any formable semicrystalline fibrous (co) polymer material can be used to make the fibers and webs of the present disclosure. The thermoplastic (co) polymeric material may comprise a blend of a polyester polymer and at least one other polymer to form a polymer blend of two or more polymer phases. The polyester polymer may desirably be an aliphatic polyester, an aromatic polyester, or a combination of an aliphatic polyester and an aromatic polyester.

Preferably, the thermoplastic semi-crystalline (co) polymer is selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, poly (lactic acid), polyhydroxybutyrate, polytrimethylene terephthalate, polycarbonate, Polyetherimide (PEI), or combinations thereof.

More preferably, the thermoplastic semi-crystalline (co) polymer is one or more thermoplastic, semi-crystalline polyester (co) polymers. Suitable thermoplastic semi-crystalline polyester (co) polymers include polyethylene terephthalate (PET), poly (lactic acid) (PLA), polyethylene naphthalate (PEN), and combinations thereof. The specific polymers listed here are merely examples, and a variety of other (co) polymeric or fiber-forming materials may be used.

The thermoplastic polyester (co) polymer may form a major portion or phase of the optional thermoplastic (co) polymer material. When the thermoplastic polyester (co) polymer forms a substantial part of the thermoplastic (co) polymer material, the thermoplastic (co) polymer material can be more easily melt blown and the resulting fibers exhibit advantageous mechanical and thermal properties. For example, a polyester (co) polymer content of at least about 50, 60, 70, 80, 90, or even 100 weight percent may form the major polymeric portion or phase of the thermoplastic (co) polymeric material.

Acceptable mechanical properties or characteristics may include, for example, tensile strength, initial modulus, thickness, and the like. The fibers can be considered to exhibit acceptable thermal properties, such as when a nonwoven web made from the fibers exhibits a linear shrinkage of less than about 30 percent, 25 percent, 20 percent, or 15 percent, and generally less than or equal to about 10 percent or 5 percent, after heating to a temperature of about 150 ℃ for about 4 hours.

In some such embodiments, the amount of the thermoplastic semi-crystalline (co) polymer is at least 1 wt%, 2.5 wt%, 5 wt%, 10 wt%, 15 wt%, or even 20 wt%; and up to 30, 25, 20, 15, 10, or even 5 weight percent based on the total weight of the plurality of meltblown fibers.

The fibers may also be formed from blends of materials, including materials to which certain additives have been added, such as pigments or dyes. Bicomponent fibers, such as sheath-core bicomponent fibers or side-by-side bicomponent fibers, may be used ("bicomponent" in the present invention includes fibers having two or more components, where each component occupies a separate portion of the fiber cross-section and extends the entire fiber length).

However, the present disclosure is most advantageous in that it uses monocomponent fibers, which have many benefits (e.g., less complexity in manufacture and composition; monocomponent fibers having substantially the same composition across their cross-section; monocomponent includes blends or additive-containing materials in which a continuous phase of uniform composition extends across the cross-section as well as the entire fiber length), and can be conveniently bonded and imparted with additional bonding and/or forming capabilities through the application of various embodiments of the present disclosure.

In some exemplary embodiments of the present disclosure, different fiber-forming materials may be extruded through different orifices of an extrusion head in order to prepare a web comprising a mixture of fibers. In further exemplary embodiments, other materials, such as staple fibers and/or particulate materials, are incorporated into the fiber stream prior to or during collection of the meltblown fibers prepared according to the methods of the present disclosure in order to prepare a blended web.

For example, other staple fibers may be blended in the manner set forth in U.S. Pat. No.4,118,531; or particulate material may be introduced and captured in the web in the manner taught in U.S. patent 3,971,373; or a micro web as proposed in us patent 4,813,948 may be blended into the web. Alternatively, the fibers made by the present disclosure may be introduced into other fiber streams to make blends of fibers.

Fibers having a substantially circular cross-section are most commonly prepared, but other cross-sectional shapes may also be employed. Generally, fibers having a substantially circular cross-section made using the methods of the present disclosure can vary widely in diameter. Microfiber sizes (about 10 microns or less in diameter) can be obtained and provide a number of benefits; but fibers with larger diameters can also be made and used for certain applications; typically the fibers have a diameter of 20 microns or less. Commercially desirable fibers have diameters of less than or equal to about 9 microns, 8 microns, 7 microns, 6 microns, or even 5 microns or less. Even commercially desirable fibers have a diameter of 4 microns, 3 microns, 2 microns, or 1 micron or less.

Thermoplastic amorphous (co) polymers

In certain exemplary embodiments, the plurality of meltblown fibers further comprises at least one thermoplastic amorphous (co) polymer. In some exemplary embodiments, the plurality of meltblown fibers comprises at least one thermoplastic amorphous (co) polymer in an amount greater than 1, 2, 3,4, or even 5 weight percent based on the total weight of the plurality of meltblown fibers. In certain such exemplary embodiments, the plurality of meltblown fibers are present at a level of at least 1 wt.%, 2 wt.%, 3 wt.%, 4 wt.%, 5 wt.%, 7.5 wt.%, or even 10 wt.%, based on the total weight of the plurality of meltblown fibers; and at most 15, 14, 13, 12, 11 or even 10 wt% of at least one thermoplastic amorphous (co) polymer.

Optional non-woven fibrous Structure (Web) component

In further exemplary embodiments, the nonwoven meltblown fiber structures of the present disclosure may further comprise one or more optional components. The optional components may be used alone or in any combination suitable for the end use application of the nonwoven meltblown fiber structure. These non-limiting, currently preferred optional components include an optional staple fiber component, an optional electret fiber component, and an optional particulate component, as further described below.

Optional short fiber component

In some exemplary embodiments, the nonwoven fibrous web may additionally comprise staple fibers. Generally, staple fibers are used as bulking fibers, for example, to reduce the cost or improve the properties of a meltblown nonwoven fibrous web.

Preferably, the plurality of staple fibers comprise poly (phenylene sulfide) staple fibers, non-heat stabilized poly (ethylene terephthalate) staple fibers, poly (ethylene naphthalate) staple fibers, oxidized poly (acrylonitrile) staple fibers, aromatic polyaramide staple fibers, glass staple fibers, ceramic staple fibers, metal staple fibers, carbon staple fibers, or combinations thereof.

The size and amount of discrete non-meltblown bulking fibers used to form the nonwoven fibrous web, if included, will depend on the desired characteristics of the nonwoven fibrous web 100 (i.e., bulk, openness, softness, drape) and the desired loading of chemically active particulates. Generally, the larger the fiber diameter, the greater the fiber length, and the presence of wrinkles in the fibers will result in a more open and lofty nonwoven article. Generally, small and shorter fibers will result in a more compact nonwoven article.

The staple fibers can have virtually any cross-sectional shape, but staple fibers having a substantially circular cross-sectional shape are typical. Generally, the staple fibers have a diameter of 20 microns or less. The staple fibers may comprise microfibers (about 10 microns or less in diameter) or sub-micrometer fibers (1 micron or less in diameter); however, staple fibers having larger diameters can also be prepared and used for certain applications.

In some exemplary embodiments, the plurality of staple fibers exhibits a median fiber median diameter of less than or equal to about 20 microns, 15 microns, 10 microns, 9 microns, 8 microns, 7 microns, 6 microns, 5 microns, 4 microns, 3 microns, 2 or even 1 micron or less. In some such exemplary embodiments, the plurality of staple fibers exhibit a median fiber diameter of at least 0.5 microns, 1.0 microns, 2.0 microns, 3.0 microns, 4.0 microns, 5.0 microns, 7.5 microns, or even 10 microns.

In further exemplary embodiments, the plurality of staple fibers constitutes at least 0%, 1%, 5%, 10%, 15%, 20%, or even 25% by weight of the nonwoven fibrous structure. In some such embodiments, the plurality of short fibers constitutes no more than 99%, 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, 10%, or even 5% by weight of the nonwoven fibrous structure.

Non-limiting examples of suitable aromatic polyaramid staple fibers include those known under the trade name

From Dupont^TMGroup (DuPont)^TMCorp) (Wilmington, Delaware) andfrom fibre threads^TMCompany (Fiber-Line)^TMCorp.) (hartfeld, pa) commercially available.

Non-limiting examples of suitable glass staple fibers include those available under the trade nameBy Vitex^TMShenggobain group (Vetrotex)^TMSaint-Gobain Corp.) (DE guo aachen) andthose marketed by john semawell (Johns Manville, Corp.) (walehem, germany).

Non-limiting examples of suitable ceramic fibers include any metal oxide, metal carbide, or metal nitride, including but not limited to silicon oxide, aluminum oxide, zirconium oxide, silicon carbide, tungsten carbide, silicon nitride, and the like.

Non-limiting examples of suitable metal fibers include those made of any metal or metal alloy (e.g., iron, titanium, tungsten, platinum, copper, nickel, cobalt, etc.).

Non-limiting examples of suitable carbon fibers include graphite fibers, activated carbon fibers, poly (acrylonitrile) -derived carbon fibers, and the like.

In some exemplary embodiments, natural staple fibers may also be used in the nonwoven fibrous structure. Non-limiting examples of suitable natural staple fibers include those of bamboo, cotton, wool, jute, agave, sisal, coconut, soybean, hemp, and the like. The natural fiber component used may be natural fibers or recycled waste fibers, e.g., recycled fibers regenerated from clothing cuts, carpet manufacturing, fiber manufacturing, textile processing, and the like. Preferably, the natural staple fibers are treated with a flame retardant to improve their flame resistance.

In certain exemplary embodiments, the staple fibers are non-meltblown staple fibers. Non-limiting examples of suitable non-meltblown staple fibers include monocomponent synthetic fibers, semi-synthetic fibers, polymeric fibers, metal fibers, carbon fibers, ceramic fibers, and natural fibers. Synthetic and/or semi-synthetic polymer fibers include those made from polyesters (e.g., polyethylene terephthalate), nylons (e.g., hexamethylene adipamide, polycaprolactam), polypropylene, acrylic (formed from polymers of acrylonitrile), rayon, cellulose acetate, polyvinylidene chloride-vinyl chloride copolymers, vinyl chloride-acrylonitrile copolymers, and the like.

Optional electret fibrous component

The nonwoven meltblown fibrous webs of the present disclosure may optionally include electret fibers. Suitable electret fibers are described in U.S. Pat. nos. 4,215,682; 5,641,555, respectively; 5,643,507, respectively; 5,658,640, respectively; 5,658,641, respectively; 6,420,024, respectively; 6,645,618, 6,849,329; and 7,691,168, the entire disclosures of which are incorporated herein by reference.

Suitable electret fibers can be produced by: melt blowing fibers in an electric field, for example by melting a suitable dielectric material such as a polymer containing polar molecules or wax, passing the molten material through a melt blowing die to form discrete fibers, and then allowing the molten polymer to resolidify while exposing the discrete fibers to a strong electrostatic field. Electret fibers can also be made by: such as using electron beams, corona discharge, electron injection, electrical breakdown across a gap or dielectric barrier, etc., to embed excess charge into a highly insulating dielectric material (e.g., polymer or wax). Particularly suitable electret fibers are hydrocharged fibers.

Optional particlesComponents

In further exemplary embodiments, the nonwoven fibrous structure further comprises a plurality of particulates. The plurality of particles may include organic particles and/or inorganic particles. In some exemplary embodiments, the plurality of particles consists essentially of inorganic particles. In certain such embodiments, the plurality of particles comprises flame retardant particles, expanded particles, or a combination thereof.

Generally, the plurality of particles can be at least 1, 2.5, 5, 10, 15, 20, or even 25 weight percent based on the weight of the nonwoven fibrous structure; and is present in an amount no greater than 50, 45, 40, 35, or even 30 weight percent.

Preferably, the nonwoven fibrous structure is free of halogenated flame retardant additives, including halogenated flame retardant particles. Included within the scope of halogenated flame retardant additives are halogen substituted benzenes exemplified by tetrabromobenzene, hexachlorobenzene, hexabromobenzene; biphenyls such as 2,2' -dichlorobiphenyl, 2,4' -dibromobiphenyl, 2,4' -dichlorobiphenyl, hexabromobiphenyl, octabromobiphenyl and decabromobiphenyl; halogenated diphenyl ethers containing 2 to 10 halogen atoms; chlorine-containing aromatic polycarbonates, and mixtures of any of the foregoing.

Optionally, the nonwoven fibrous structure may also contain one or more non-halogenated flame retardants, including non-halogenated flame retardant particles. Useful flame retardant particles include non-halogenated organic compounds, organic phosphorus-containing compounds (such as organic phosphates), inorganic compounds, and inherently flame retardant polymers, such as, for example, PPS.

These particulate additives may be added to or incorporated into the polymer matrix of the meltblown nonwoven fibrous structure in an amount sufficient to render the combustible polymer flame retardant as determined via the meltblown nonwoven fibrous structure by one or more tests selected from UL 94V0, FAR25.853(a), FAR25.856(a), AITM20007A, AITM3-0005 and california regulation article 19.

The nature of the non-halogenated flame retardant particles is not critical and a single type of particle may be used. Optionally, it may be found desirable to use a mixture of two or more individual non-halogenated flame retardant particles.

Among useful organophosphorus particles are those containing organophosphorus compounds, phosphorus-nitrogen compounds, and halogenated organophosphorus compounds. The organophosphorus compounds generally function as flame retardants by forming a protective liquid or charring barrier that allows minimal polymer degradation products to escape to the flame and/or act as an insulating barrier that minimizes heat transfer.

Generally, preferred phosphorus compounds are selected from organic phosphonic acids, phosphonates, phosphinates, phosphine oxides, phosphines, phosphites or phosphates. Exemplified is triphenylphosphine oxide. These may be used alone or in admixture with hexabromobenzene or chlorinated biphenyls and optionally antimony oxide. Phosphorus-containing flame retardant additives are described, for example, on pages 976-98 of Kirk-Othmer (supra).

Typical examples of suitable phosphates include phenyl didodecyl phosphate, phenyl bisneopentyl phosphate, styrene hydrogen phosphate, phenyl-bis-3, 5,5 '-trimethylhexyl phosphate, ethyl diphenyl phosphate, 2-ethylhexyl di (p-tolyl) phosphate, diphenyl hydrogen phosphate, bis (2-ethylhexyl) p-tolyl phosphate, tri (tolyl) phosphate, bis (2-ethylhexyl) -phenyl phosphate, tri (nonylphenyl) phosphate, phenyl methyl hydrogen phosphate, di (dodecyl) p-tolyl phosphate, tricresyl phosphate, triphenyl phosphate, halogenated triphenyl phosphate, dibutyl phenyl phosphate, 2-chloroethyl diphenyl phosphate, p-tolyl bis (2,5,5' -trimethylhexyl) phosphate, di (dodecyl) p-tolyl phosphate, tri (tolyl) phosphate, halogenated triphenyl phosphate, dibutyl phenyl phosphate, 2-ethylhexyl diphenyl phosphate, diphenyl hydrogen phosphate, and the like. Triphenyl phosphate is a particularly useful flame retardant additive, typically used in combination with hexabromobenzene and optionally antimony oxide.

Also suitable as flame-retardant particles are those of compounds containing phosphorus-nitrogen bonds, such as phosphorus ester amides, phosphoric acid amides, phosphonic acid amides or phosphinic acid amides.

Inorganic flame retardant particles useful therein include those comprising antimony such as antimony trioxide, antimony pentoxide, and sodium antimonate; boron such as barium metaborate, boric acid, sodium borate, and zinc borate; aluminum, such as aluminum trihydrate; magnesium, such as magnesium hydroxide; molybdenum, such as molybdenum oxide, ammonium molybdate, and zinc molybdate, phosphorus, such as phosphoric acid; and tin, such as zinc stannate. The mode of action is typically variable and may include inert gas dilution (by, for example, liberating water) and thermal quenching (by endothermic degradation of the additive). Useful inorganic additives are described, for example, on pages 936-54 of Kirk-Othmer (supra).

The flame retardant particles may also be comprised of one or more inherently flame retardant (co) polymers. Inherently flame retardant (co) polymers, due to their chemical structure, either fail to support combustion or self-extinguish. These polymers typically have increased stability at higher temperatures by incorporating stronger bonds (such as aromatic rings or inorganic bonds) or being highly halogenated in the backbone of the polymer.

Examples of inherently flame retardant polymers include, for example, poly (phenylene sulfide), poly (vinyl chloride), poly (vinylidene chloride), chlorinated polyethylene, polyimide, polybenzimidazole, polyetherketone, polyphosphazene, and polycarbonate.

Useful inherently flame retardant films typically have a Limiting Oxygen Index (LOI) of at least 28%, as determined by ASTM D-2863-91.

The particle size (median diameter) of the flame retardant particles should generally be less than the diameter of the meltblown fibers incorporated therein. Preferably, the particle size is less than one-half, more preferably less than one-third, even more preferably less than one-fourth, even more preferably less than one-fifth, and most preferably less than one-tenth the diameter of the meltblown fibers into which they are incorporated. Generally, the smaller the median diameter of the flame retardant particles, or the larger the surface area presented by the particles, the more effective the flame retardant properties.

Flame retardant particles are typically incorporated into meltblown fibers by adding the particles to the polymer melt prior to formation of the meltblown fibers. The particles may be added neat or incorporated into a diluent or additional (co) polymer.

When inherently flame retardant polymers are used as the flame retardant particles, they can be melt blended if compatible. Alternatively, the inherently flame retardant polymer may be added as fine particles dispersed in the polymer melt. Additives that are stable at the polymer melt temperature should be carefully selected.

Optionally, the nonwoven fibrous structure may additionally or alternatively include intumescent particles, which may be incorporated into the meltblown fibers. Expanded particles useful in preparing nonwoven fibrous structures according to the present disclosure include, but are not limited to, expandable vermiculite, treated expandable vermiculite, partially dehydrated expandable vermiculite, expandable perlite, expandable graphite, expandable hydrated alkali metal silicate (e.g., expandable granular sodium silicate, such as of the general type described in U.S. patent 4,273,879, and available, for example, under the trade designation "EXPANTROL" from 3M Company (st. paul, MN)) of st paul, minnesota, and mixtures thereof.

One particular example of commercially available expanded particles is the expandable graphite sheet commercially available from UCAR Carbon Co (UCAR Carbon Co., Ohio) under the trade designation GRAFGUARD Grade 160-50.

In various embodiments, the expanded particulates may be present at zero weight percent, at least about 1 weight percent, at least about 5 weight percent, at least about 10 weight percent, at least about 20 weight percent, or at least about 30 weight percent, based on the total weight of the nonwoven fibrous structure. In another embodiment, the expanded particulates may be present in an amount up to about 40 weight percent, up to about 30 weight percent, or up to about 25 weight percent, up to about 20 weight percent, based on the total weight of the nonwoven fibrous structure.

The expanded particles may be used in combination with any suitable inorganic fibers, including, for example, ceramic fibers, biosoluble fibers, glass fibers, mineral wool, basalt fibers, and the like.

Optionally, the nonwoven fibrous structure may also include heat sink particles. Suitable endothermic particles can include, for example, any inorganic particles that include a compound capable of releasing water (e.g., hydrated water) at temperatures, for example, between 200 ℃ and 400 ℃. Thus, suitable endothermic particles may comprise materials such as alumina trihydrate, magnesium hydroxide, and the like.

Specific types of heat absorbing particles may be used alone; or at least two or more different types of endothermic particles may be used in combination. In various embodiments, the heat sink particles may be present at zero weight percent, at least about 2 weight percent, at least about 5 weight percent, at least about 10 weight percent, at least about 20 weight percent, or at least about 30 weight percent, based on the total weight of the meltblown nonwoven fibrous structure. The heat sink particles can be used in combination with any suitable inorganic fibers, including, for example, ceramic fibers, biosoluble fibers, glass fibers, mineral wool, basalt fibers, and the like, and can also be used in combination with any suitable intumescent particles.

In further exemplary embodiments, the particles comprise one or more inorganic insulating particles. Suitable insulating particles can include, for example, any inorganic compound that, when present in the nonwoven fibrous structure, can enhance the thermal insulation properties of the web, for example, without increasing the weight or density of the nonwoven fibrous structure in an unacceptable manner. Inorganic particulate particles comprising relatively high porosity may be particularly suitable for these purposes.

Suitable insulating particles may comprise materials such as fumed silica, precipitated silica, diatomaceous earth, fuller's earth, expanded perlite, silicate clay and other clays, silica gel, glass bubbles, ceramic microspheres, talc, and the like.

One of ordinary skill in the art will recognize that there may not be a distinct line of demarcation between the insulating particles and, for example, certain endothermic or intumescent particles). Specific types of insulating particles may be used alone; or at least two or more different types of insulating particles may be used in combination.

In various embodiments, the insulating particles may be present at zero weight percent, at least about 5 weight percent, at least about 10 weight percent, at least about 20 weight percent, at least about 40 weight percent, or at least about 60 weight percent, based on the total weight of the meltblown nonwoven fibrous structure.

The insulating particles can be used in combination with any suitable inorganic fibers, including, for example, ceramic fibers, biosoluble fibers, glass fibers, mineral wool, basalt fibers, and the like, and can also be used in combination with any suitable intumescent and/or endothermic particles.

Exemplary nonwoven fibrous structures according to the present disclosure may also advantageously comprise a plurality of chemically active particulates. The chemically active particles may be any discrete particles that are solid at room temperature and that can undergo chemical interaction with an external liquid phase. Exemplary chemical interactions include adsorption, absorption, chemical reactions, catalysis of chemical reactions, dissolution, and the like.

Additionally, in any of the above exemplary embodiments, the chemically active particles may advantageously be selected from: sorbent particles (e.g., adsorbent particles, absorbent particles, etc.), desiccant particles (e.g., particles comprising hygroscopic substances such as, for example, calcium chloride, calcium sulfate, etc., which cause or maintain a dry state in the area proximate thereto), biocide particles, microcapsules, and combinations thereof. In any of the above embodiments, the chemically active particulates may be selected from: activated carbon particles, activated alumina particles, silica gel particles, anion exchange resin particles, cation exchange resin particles, molecular sieve particles, diatomaceous earth particles, antimicrobial compound particles, metal particles, and combinations thereof.

In one exemplary embodiment of a nonwoven fibrous web particularly suited for use as a fluid filtration article, the chemically active particles are sorbent particles. A variety of sorbent particles may be employed. Sorbent particles include mineral particles, synthetic particles, natural sorbent particles, or combinations thereof. Advantageously, the sorbent particles will be capable of absorbing or adsorbing the gas, aerosol or liquid expected to be present under the conditions of intended use.

The sorbent particles can be in any useful form, including beads, flakes, granules, or agglomerates. Preferred sorbent particles include activated carbon; silica gel; activated alumina and other metal oxides; metal particles (e.g., silver particles) that can remove a component from a fluid by adsorption or chemical reaction; particulate catalysts, for example, hopcalite (which can catalyze the oxidation of carbon monoxide); clays and other minerals treated with acidic solutions (such as acetic acid) or basic solutions (such as aqueous sodium hydroxide); an ion exchange resin; molecular sieves and other zeolites; a biocide; fungicides and virucidal agents. Activated carbon and activated alumina are particularly preferred sorbent particles at present. Mixtures of sorbent particles may also be employed (e.g., to absorb gas mixtures), but in practice it may be better to produce a multi-layer sheet article employing separate sorbent particles in each layer for processing the gas mixture.

In one exemplary embodiment of a nonwoven fibrous web particularly useful as a gas filtration article, the chemically active sorbent particles are selected to be gas sorbents or absorbent particles. For example, the gas adsorbent particles may include activated carbon, charcoal, zeolites, molecular sieves, acid gas adsorbents, arsenic reducing materials, iodinated resins, and the like. For example, the absorbent particles may also include natural porous particulate matter (such as diatomaceous earth, clay) or synthetic particulate foams (such as melamine, rubber, urethane, polyester, polyethylene, silicone, and cellulose.

In certain exemplary embodiments of nonwoven fibrous webs particularly useful as liquid filtration articles, the sorbent particles comprise activated carbon, diatomaceous earth, ion exchange resins (e.g., anion exchange resins, cation exchange resins, or combinations thereof), molecular sieves, metal ion exchange sorbents, activated alumina, antimicrobial compounds, or combinations thereof. Certain exemplary embodiments provide a fibrous web having a sorbent particle density in the range of from about 0.20 to about 0.5 g/cc.

Various sizes and amounts of sorbent chemically active particles can be used to form nonwoven fibrous webs. In an exemplary embodiment, the median size of the diameters of the sorbent particles is greater than 1 mm. In another exemplary embodiment, the median size of the diameters of the sorbent particles is less than 1 cm. In further embodiments, a combination of particle sizes may be used. In a further exemplary embodiment, the sorbent particles comprise a mixture of large particles and small particles.

The desired sorbent particle size can vary widely, and is typically selected based in part on the intended conditions of use. As a general guide, sorbent particles that are particularly useful in fluid filtration applications may vary in size, with a median diameter of from about 0.001 μm to about 3000 μm. Generally, the median diameter of the sorbent particles is from about 0.01 μm to about 1500 μm, more typically from about 0.02 μm to about 750 μm, and most typically from about 0.05 μm to about 300 μm.

In certain exemplary embodiments, the sorbent particles may comprise nanoparticles having a population median diameter of less than 1 μm. Porous nanoparticles may have the advantage of providing a large surface area for adsorbing (e.g., absorbing and/or adsorbing) contaminants from the fluid medium. In such exemplary embodiments using ultra-fine or nano-particles, it may be preferred that the particles be adhesively bonded to the fibers with an adhesive (e.g., a hot melt adhesive) and/or the application of heat to the meltblown nonwoven fibrous web (i.e., thermal bonding).

Mixtures of sorbent particles having different size ranges (e.g., bimodal mixtures) may also be used, but in practice it may be better to prepare a multi-layer sheet article that employs larger sorbent particles in the upstream layer and smaller sorbent particles in the downstream layer. At least 80 wt% of the sorbent particles, more typically at least 84 wt% and most typically at least 90 wt% of the sorbent particles are embedded in the web. Expressed in terms of web basis weight, the sorbent particle loading may be, for example: at least about 500gsm of relatively fine (e.g., submicron-sized) sorbent particles, and at least about 2000gsm of relatively coarse (e.g., micron-sized) sorbent particles.

In some exemplary embodiments, the chemically active particles are metal particles. Metal particles can be used to form a polished nonwoven fibrous web. The metal particles may be in the form of short fibers or ribbon-like segments or may be in the form of cereal-like particles. The metal particles may include any type of metal, such as, but not limited to, a blend of one or more of silver (which has antibacterial/antimicrobial properties), copper (which has algaecidal properties), or a chemically active metal.

In other exemplary embodiments, the chemically active particulate is a solid biocide or antimicrobial agent. Examples of solid biocides and biocides include halogen-containing compounds such as sodium dichloroisocyanurate dihydrate, benzalkonium chloride, dialkyl hydantoin halides, and triclosan.

In further exemplary embodiments, the chemically active particulates are microcapsules. Some suitable microcapsules are described in U.S. Pat. No. 3,516,941(Matson), and include examples of microcapsules that can be used as chemically active particles. The microcapsules may be loaded with solid or liquid biocides or antimicrobials. One of the main qualities of microcapsules is: using mechanical stress, the particles can be crushed in order to release the substance contained therein. Thus, during use of the nonwoven fibrous web, the microcapsules will be broken up due to the pressure exerted on the nonwoven fibrous web, which will release the substance contained in the microcapsules.

In certain such exemplary embodiments, it may be advantageous to use at least one particle having a surface that can be made tacky or "sticky" to bond the particles together to form a mesh or support nonwoven fibrous web for the fibrous component. In this regard, useful particles may include polymers, for example, thermoplastic polymers, which may be in the form of staple fibers. Suitable polymers include polyolefins, particularly thermoplastic elastomers (TPE) (e.g., VISTA MAXX commercially available from Exxon-Mobile Chemical Company, Houston, Tex.) VISTA MAX^TM). In further exemplary embodiments, it may be preferred to include granules of TPE, particularly as a skin or surface coating, as TPEs are generally somewhat tacky, which may help bond the granules together to form a three-dimensional network prior to addition of fibers to form a nonwoven fiber web. In certain exemplary embodiments, VISTAMAXX is included^TMThe granules of TPE can provide improved resistance to harsh chemical environments, particularly at low pH (e.g., pH of no more than about 3) and high pH (e.g., pH of at least about 9), as well as in organic solvents.

Particulate matter having any suitable size or shape may be selected. Suitable particles can have various physical forms (e.g., solid particles, porous particles, hollow bubbles, agglomerates, discontinuous fibers, short fibers, flakes, etc.); shapes (e.g., spherical, elliptical, polygonal, acicular, etc.); shape uniformity (e.g., monodisperse, substantially uniform, non-uniform or irregular, etc.); compositions (e.g., inorganic particles, organic particles, or combinations thereof); and dimensions (e.g., submicron dimensions, micro dimensions, etc.).

With particular reference to particle size, in some exemplary embodiments, it may be desirable to control the size of the population of particles. In certain exemplary embodiments, the particulates are generally physically entrained or entrapped in the nonwoven fibrous web. In such embodiments, the population of particles is generally selected to have a median diameter of at least 50 μm, more generally at least 75 μm, and still more generally at least 100 μm.

In other exemplary embodiments, it may be preferable to use finer particles that are adhesively bonded to the fibers with an adhesive, such as a hot melt adhesive, and/or the application of heat to one or both of the thermoplastic particles or thermoplastic fibers (i.e., thermal bonding). In such embodiments, it is generally preferred that the particles have a median particle size of at least 25 μm, more typically at least 30 μm, most typically at least 40 μm. In some exemplary embodiments, the chemically active particulates have a median size of 1cm in diameter. In other embodiments, the median size of the chemically active particulates is less than 1mm, more typically less than 25 microns, and even more typically less than 10 microns.

However, in other exemplary embodiments where both adhesive and thermal bonding are used to adhere the particles to the fibers, the particles may comprise a population of sub-micron sized particles having a population median diameter of less than 1 micron (μm), more typically less than about 0.9 μm, even more typically less than about 0.5 μm, and most typically less than about 0.25 μm. Such submicron-sized particles may be particularly useful in applications requiring high surface area and/or high absorbency and/or adsorptive capacity. In further exemplary embodiments, the population median diameter of the population of sub-micron sized particles is at least 0.001 μm, more typically at least about 0.01 μm, most typically at least about 0.1 μm, and most typically at least about 0.2 μm.

In further exemplary embodiments, the particles comprise a population of micro-sized particles having a population median diameter of at most about 2000 μm, more typically at most about 1000 μm, and most typically at most about 500 μm. In other exemplary embodiments, the particles comprise a population of micro-sized particles having a population median diameter of at most about 10 μm, more typically at most about 5 μm, and even more typically at most about 2 μm (e.g., ultrafine microfibers).

Multiple types of particles may also be used within a single finished web. By using multiple types of particles, a continuous particulate fiber web can be produced even if one of the particle types is not bonded to other particles of the same type. An example of this type of system would be one in which two types of particles are used, one type of particle binding the particles (e.g., discontinuous polymeric fiber particles) together and the other type of particle functioning as an active particle (e.g., sorbent particle (e.g., activated carbon)) for the desired use of the web. Such exemplary embodiments may be particularly useful in fluid filtration applications.

For example, a variety of different loadings of chemically active particulates relative to the total weight of the fibrous web may be used depending on the density of the chemically active particulates, the size of the chemically active particulates, and/or the desired properties of the final nonwoven fibrous web article. In one embodiment, the chemically active particulates comprise less than 90 weight percent of the total nonwoven article weight. In one embodiment, the chemically active particulates comprise at least 10 weight percent of the total nonwoven article weight.

In any of the above embodiments, the chemically active particulates may advantageously be distributed throughout the entire thickness of the nonwoven fibrous web. However, in some of the above embodiments, the chemically active particulates are preferentially distributed substantially on the major surface of the nonwoven fibrous web.

Further, it should be understood that any combination of one or more of the above chemically active particulates may be used to form a nonwoven fibrous web according to the present disclosure.

Nonwoven fibrous article

Nonwoven meltblown fiber structures may be prepared using the materials described above and the following meltblowing apparatus and process. In some exemplary embodiments, the nonwoven meltblown fibrous structures take the form of a mat, web, sheet, scrim, or combination thereof.

In some particular exemplary embodiments, the meltblown nonwoven fibrous structure or web may advantageously include electrically charged meltblown fibers, such as electret fibers. In certain exemplary embodiments, the meltblown nonwoven fibrous structure or web is porous. In some further exemplary embodiments, the meltblown nonwoven fibrous structure or web may advantageously be self-supporting. In further exemplary embodiments, the meltblown nonwoven fibrous structure or web may advantageously be folded to form, for example, a filtration medium, such as a liquid (e.g., water) or gas (e.g., air) filter, a heating ventilation or air conditioning (HVAC) filter, or a respirator for personal protection. For example, U.S. patent 6,740,137 discloses a nonwoven web for use in a collapsible pleated filter element.

The webs of the present disclosure may themselves be used in, for example, filter media, decorative fabrics or protective or covering devices. Or they may be used in conjunction with other webs or structures, for example as supports for other fibrous layers deposited or laminated on the web, or present in a multilayer filter media, or as a substrate onto which a membrane may be cast. They may be processed after preparation, such as by passing them through smooth calender rolls to form smooth surface webs or through forming equipment to form them into three-dimensional shapes.

The fibrous structures of the present disclosure may also comprise at least one or more other types of fibers (not shown), such as, for example, staple or other discontinuous fibers, melt-spun continuous fibers, or combinations thereof. Exemplary fibrous structures of the present invention may be formed, for example, as nonwoven webs that may be wound about a tube or other core to form a roll and may be stored for subsequent processing or passed directly to another processing step. The web may also be cut directly into individual sheets or mats after the web is manufactured or at some time thereafter.

The meltblown nonwoven fibrous structure or web may be used to make any suitable article, such as a thermal insulation article, an acoustic insulation article, a fluid filtration article, a wipe, a surgical drape, a wound dressing, a garment, a respirator, or a combination thereof. Thermal or acoustical insulation articles can be used as insulation components for vehicles such as trains, airplanes, automobiles, and ships. Other articles, such as, for example, bedding, drapes, tents, insulation articles, liquid and gas screens, wipes, garments, garment components, personal protective equipment, respirators, and the like, may also be prepared using the meltblown nonwoven fibrous structures described in this disclosure.

The thickness of the nonwoven fibrous structure may advantageously be selected to be at least 0.5cm, 1cm, 1.5cm, 2cm, 2.5cm or 3 cm; and up to 10.5cm, 10cm, 9.5 cm, 9cm, 8.5 cm, 8cm or even 7.5 cm.

Flexible, drapeable, and compact nonwoven fibrous webs may be preferred for certain applications, for example, as furnace filters or gas filtration respirators. The density of such nonwoven fibrous webs is typically greater than 75kg/m³And is usually greater than 100kg/m³Or even 120100 kg/m³. However, open, lofty nonwoven fibrous webs suitable for use in certain fluid filtration applications typically have 60kg/m³The maximum density of (c). Certain nonwoven fibrous webs according to the present disclosure may advantageously have a solidity of less than 20%, more typically less than 15%, even more preferably less than 10%.

Among other advantages, meltblown fibers and meltblown nonwoven fibrous structures (e.g., webs) are fire resistant and dimensionally stable even when heated to or used at elevated temperatures. Thus, in exemplary embodiments, the present disclosure provides a flame resistant and dimensionally stable nonwoven fibrous structure produced using any of the above-described apparatus and methods.

In some specific exemplary embodiments, the nonwoven fiber generation and in-flight thermal treatment process provides fibers and nonwoven fibrous webs comprising fibers that are not susceptible to shrinkage and degradation in higher temperature applications, such as providing acoustical insulation in automobiles, trains, airplanes, boats, or other vehicles.

Additionally, exemplary nonwoven fibrous webs of the present disclosure may exhibit a compressive strength of greater than 1 kilopascal (kPa), greater than 1.2kPa, greater than 1.3kPa, greater than 1.4kPa, or even greater than 1.5kPa, as measured using the test methods disclosed herein. Further, exemplary nonwoven fibrous webs of the present disclosure may exhibit a maximum load tensile strength of greater than 10 newtons (N), greater than 50N, greater than 100N, greater than 200N, or even greater than 300N, as measured using the test methods disclosed herein.

Melt blowing equipment

In a further exemplary embodiment, the present disclosure provides an apparatus comprising a meltblowing die, a device for controlled in-flight thermal treatment of meltblown fibers at a temperature below the melting temperature of the meltblown fibers ejected from the meltblowing die, and a collector for collecting the in-flight thermally treated meltblown fibers.

Referring now to fig. 1A, there is shown a general side view of an exemplary apparatus 15 for practicing embodiments of the present disclosure as a direct web production method and apparatus, wherein fiber-forming (co) polymeric material is converted to a web in one substantially direct operation. The apparatus 15 consists of a conventional Blown Microfiber (BMF) production configuration, as taught, for example, in van Wente, "ultra-fine thermoplastic Fibers", Industrial Engineering Chemistry, volume 48, p.1342, 1956 (van Wente, "Superfine thermoplastic Fibers", Industrial Engineering Chemistry, Vol.48, pages 1342etsec (1956)) or in van Wente, A., Boone, C, naval research laboratory report No.4364 (report No.4364of the Naval research laboratories, published May 25,1954 entered "manufacturing of ultra-fine organic Fibers" on 25.5.1954 (book, Boone, C.). This configuration consists of an extruder 10 having a hopper 11 for pelletized or powdered (co) polymer resin and a series of heating jackets 12 that heat the extruder barrel to melt the (co) polymer resin to form a molten (co) polymer. The molten (co) polymer leaving the extruder barrel enters pump 14, a process that allows for improved control of the flow of molten (co) polymer through downstream components of the apparatus.

Optionally, the molten (co) polymer, after leaving the pump 14, flows into an optional mixing device 15 comprising a delivery pipe 16 containing, for example, a mixing device such as a KENIX type static mixer 18. A series of heating jackets 20 control the temperature of the molten (co) polymer as it passes through the delivery tube 16. Mixing device 15 also optionally includes a feed inlet 22 near the inlet end of the delivery tube, which is connected to an optional high pressure metering pump 24 capable of injecting optional additives into the molten (co) polymer stream as it enters static mixer 18.

After the molten (co) polymer stream exits optional transfer tube 16, it is transferred through a melt Blowing (BMF) die 26 comprising at least one orifice through which the molten (co) polymer stream is conveyed while impinging the (co) polymer stream with a high velocity stream of hot air that serves to elongate and attenuate the molten (co) polymer stream to form microfibers.

Referring now to fig. 1B, there is shown a general side view of another exemplary apparatus 15' for practicing embodiments of the present disclosure as a direct web production method and apparatus, wherein fiber-forming molten (co) polymeric material is converted to a web in one substantially direct operation. Apparatus 15' includes a conventional melt Blown Microfiber (BMF) production configuration, as described above, for example as taught by van Wente. This configuration consists of an extruder 10 having a hopper 11 for granular or powder (co) polymer resin, which heats the (co) polymer resin to form a molten stream of the (co) polymer resin. The molten stream of (co) polymer resin enters a melt Blowing (BMF) die 26 comprising at least one orifice 11 through which a stream 33 of molten (co) polymer passes while impinging on the exiting stream 33 of (co) polymer, a high velocity hot air stream is formed by passing gas from a gas supply manifold 25 through a gas inlet 15, exiting the die 26 at gas jets 23 and 23', which function to draw out and attenuate the molten (co) polymer stream into microfibers. The velocity of the gas jet may be controlled by, for example, adjusting the pressure and/or flow rate of the gas flow and/or by controlling the gas inlet size 27 (i.e., gap).

In the apparatus or process shown in FIG. 1a or FIG. 1b, immediately after the molten (co) polymer fibers exit at least one orifice 11 of a meltblowing die 15 or meltblowing die 15 ', the stream of molten (co) polymer fibers is subjected to controlled in-flight thermal treatment using device 32 and/or device 32' at a temperature below the melting temperature of the poly (phenylene sulfide) that makes up the fibers. In some exemplary embodiments, the means 32 and/or the means 32' for controlled flight thermal treatment of meltblown fibers ejected from a meltblowing die are selected from the group consisting of radiant heaters, natural convection heaters, forced air convection heaters, and combinations thereof.

In some exemplary embodiments, the means for controlled flight thermal treatment of the meltblown fibers issuing from the meltblowing die is one or more forced air convection heaters 32 and/or 32' positioned to impinge the stream of meltblown fibers either directly or indirectly (e.g., using entrained ambient air) immediately after the stream of meltblown fibers exits the meltblowing die 26, as shown in FIG. 1 b. In certain exemplary embodiments, the means for controlled flight heat treatment of the meltblown fiber stream immediately after it exits the meltblowing die 26 is one or more heaters 32 and/or heaters 32' (e.g., at least one infrared heater, such as a quartz lamp infrared heater as described in the examples) as shown in FIG. 1 a.

By "immediately after exiting the meltblowing die" is meant that controlled in-flight heat treatment of the meltblown fibers occurs within a heat treatment distance 21 that extends from at least one orifice 11 through which a stream 33 of molten (co) polymer is conveyed. The heat treatment distance 21 may be as short as 0mm, 0.1mm, 0.2mm, 0.3mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, or even 1 mm. Preferably, the heat treatment distance does not exceed 50mm, 40mm, 30mm, 20mm, 10mm, or even 5 mm. Preferably, the total distance of heat treatment is from 0.1mm to 50mm, from 0.2mm to 49mm, from 0.3mm to 48mm, from 0.4mm to 47mm, from 0.4mm to 46mm, from 0.5mm to 45mm, from 0.6mm to 44mm, from 0.7mm to 43mm, from 0.8mm to 42mm, from 0.9mm to 41mm, or even from 1mm or more to 40mm or less.

During or after the in-flight heat treatment, the microfibers begin to harden, forming a cohesive web 30 upon reaching the collector 28. This process is particularly preferred because it enables the production of fine diameter fibers that can be directly formed into a meltblown nonwoven fibrous web without the use of subsequent bonding processes.

Melt blowing process

In a further exemplary embodiment, the present disclosure provides a method comprising:

a) forming a plurality of meltblown fibers by passing a molten stream comprising polyphenylene sulfide through a plurality of orifices of a meltblowing die;

b) immediately subjecting at least a portion of the meltblown fibers of step (a) to a controlled in-flight heat treatment operation as soon as the meltblown fibers exit the plurality of orifices, wherein the controlled in-flight heat treatment operation is conducted at a temperature below the melting temperature of the portion of the meltblown fibers for a time sufficient to effect stress relaxation of at least a portion of the molecules within the portion of the fibers subjected to the controlled in-flight heat treatment operation; and

c) collecting at least some of the portion of the meltblown fibers that were subjected to the controlled in-flight heat treatment operation of step (b) on a collector to form a nonwoven fibrous structure, wherein the nonwoven fibrous structure exhibits a shrinkage that is less than the shrinkage measured on an identically prepared structure that was not subjected to the controlled in-flight heat treatment operation of step (b), and wherein the nonwoven fibrous structure further exhibits a fire resistance without any added flame retardant additive via testing by one or more tests selected from UL 94V0, FAR25.853(a), FAR25.856(a), AITM20007A, AITM3-0005 and CA regulation article 19. In some exemplary embodiments, the plurality of meltblown fibers do not include a nucleating agent in an amount effective to achieve nucleation.

In the meltblown process, the poly (phenylene sulfide) and any optional thermoplastic (co) polymers are melted to form a molten (co) polymer material, which is then extruded through one or more orifices of a meltblown die. In some exemplary embodiments, a melt blowing process may include forming (e.g., extruding) molten (co) polymeric material into at least one or more fibrous preforms, which are then conveyed through at least one orifice of a melt blowing die, and hardening (e.g., by cooling) the at least one fiber into at least one fiber. The molten (co) polymer material is typically still in a molten state while the preform is being prepared and the preform is passed through the at least one orifice of the meltblowing die.

In any of the foregoing processes, it should be performed at a temperature range that is hot enough to enable the thermoplastic (co) polymeric material to be meltblown but not hot enough to cause unacceptable deterioration of the thermoplastic (co) polymeric material. For example, melt blowing may be performed at a temperature that causes the poly (phenylene sulfide) and any optional thermoplastic (co) polymer materials to reach a temperature within the following ranges: at least about 200 ℃, 225 ℃, 250 ℃, 260 ℃, 270 ℃, 280 ℃ or even at least 290 ℃; to less than or equal to about 360 ℃, 350 ℃, 340 ℃, 330 ℃, 320 ℃, 310 ℃, or even 300 ℃.

Controlled in-flight thermal processing method

The controlled flight thermal treatment operation may be performed using radiant heating, natural convection heating, forced air convection heating, or a combination thereof. Suitable radiant heating may be achieved using, for example, infrared or halogen lamp heating systems. Suitable infrared (e.g., quartz lamp) radiant heating systems are available from Research, Inc., idenpurl, minnesota; infrared Heating technology, LLC, oak ridge, tennessee; and Roberts Goden, Inc. (Roberts-Gordon, LLC), Buffalo, N.Y.. Suitable forced air convection heating systems are available from Roberts Gordon, LLC, bremsstra, new york; applied Thermal Systems, Inc., Chart Konjac, Tennessee; and from Chromalox Precision Heat and Control, Pittsburgh, Pa.

Generally, in-flight heat treatment is carried out at the following temperatures: at least about 50 ℃, 70 ℃, 80 ℃,90 ℃,100 ℃; to a maximum of about 340 ℃, 330 ℃, 320 ℃, 310 ℃, 300 ℃, 275 ℃, 250 ℃, 225 ℃, 200 ℃, 175 ℃, 150 ℃, 125 ℃ or even 110 ℃.

Generally, the controlled in-flight thermal treatment operation has at least about 0.001 seconds, 0.005 seconds, 0.01 seconds, 0.05 seconds, 0.1 seconds, 0.5 seconds, or even 0.75 seconds; to a duration of no more than about 1.5 seconds, 1.4 seconds, 1.3 seconds, 1.2 seconds, 1.1 seconds, 1.0 seconds, 0.9 seconds, or even 0.8 seconds.

As noted above, the preferred temperature at which the in-flight heat treatment is carried out will depend, at least in part, on the thermal properties of the poly (phenylene sulfide) and any optional thermoplastic (co) polymers comprising the fibers.

In some exemplary embodiments, the (co) polymer optionally includes at least one semi-crystalline (co) polymer selected from aliphatic polyester (co) polymers, aromatic polyester (co) polymers, or combinations thereof. In certain exemplary embodiments, the semi-crystalline (co) polymer comprises polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, poly (lactic acid), polyhydroxybutyrate, polytrimethylene terephthalate, or combinations thereof. In certain exemplary embodiments, the at least one thermoplastic semi-crystalline (co) polymer comprises a blend of a polyester (co) polymer with at least one other (co) polymer used to form the polymer blend.

In any of the foregoing embodiments, the controlled in-flight thermal treatment operation typically subjects the meltblown fibers to a temperature above the glass transition temperature of the poly (phenylene sulfide). In some exemplary embodiments, the controlled in-flight heat treatment operation prevents the (co) polymer comprising the fibers from cooling below their respective glass transition temperatures for a time sufficient for at least some degree of stress relaxation of the (co) polymer molecules to occur.

Without wishing to be bound by any particular theory, it is currently believed that when semi-crystalline (co) polymer fibers are treated using in-flight heat treatment immediately after they exit the die orifice and exit the meltblowing die, the (co) polymer molecules within the meltblown fibers will undergo stress relaxation immediately after exiting the die orifice, but remain in a molten or semi-molten state. Thus, the meltblown fibers are morphologically refined to produce new properties and utilities compared to the same meltblown fibers without in-flight heat treatment.

"stress relaxation" as used herein in its broadest term means simply changing the morphology of oriented semicrystalline (co) polymer fibers; we understand the molecular structure of one or more (co) polymers in the as-flown thermally treated fibers of the present disclosure (we do not wish to be bound by the "understanding" described herein, which generally involves some theoretical considerations).

The orientation of the (co) polymer chains in the fiber and the degree of stress relaxation of the semi-crystalline thermoplastic (co) polymer molecules within the fiber achieved by the in-flight heat treatment as described in this disclosure may be influenced by the selection of the following operating parameters: such as the nature of the (co) polymer material used, the temperature of the air stream introduced by the air knife to fibrillate the open-celled polymer stream, the temperature and duration of the flying heat treatment of the meltblown fibers, the velocity of the fiber stream, and/or the degree of densification of the fibers at the point of first contact with the collector surface,

currently, we believe that the stress relaxation achieved by the in-flight heat treatment according to the present disclosure can be used to reduce the number and/or increase the size of crystalline nuclei or "seeds" used to induce crystallization of the (co) polymer material making up the nonwoven fibers. Classical nucleation theories such as F.L. Binsbergen ("Natural and Artificial heterogeneous nucleation in Polymer Crystallization"; Journal of Polymer Science: Collection of monographs of polymers, Vol.59, No. 1, pp.11-29, 1977 ("Natural and Artificial hetereogenous nucleation in Polymer Crystallization, Journal of Polymer Science: Polymer Symposia, Volume 59, Issue 1, pages 11-29 (1977)), suggest that various fiber forming process parameters such as temperature change over time/heat treatment, quench cooling, mechanical action, or ultrasound, acoustic or ionizing radiation treatment generally lead to the formation of fibers from semi-crystalline materials such as PET, in which crystal nucleation is enhanced in the region between the glass transition and the onset of cold Crystallization. Such fiber materials prepared by conventional methods "exhibit substantial nucleation" when heated to temperatures even 10 ℃ above the glass transition temperature of the (co) polymer material from which the fiber is composed.

In contrast, web materials made using the in-flight heat treatment methods of the present disclosure typically exhibit a delay in cold crystallization onset or a decrease in the degree of crystallization when heated above the glass transition temperature. It is also often observed that the delay in the onset of cold crystallization or reduction in the degree of crystallization exhibited when the in-flight heat treated fibers are heated above their glass transition temperature helps to reduce the heat-induced shrinkage of a nonwoven fibrous web comprising such in-flight heat treated fibers.

Thus, in some exemplary embodiments of the in-flight heat treatment process, the fibers remain at a relatively high temperature for a short controlled time immediately after exiting the meltblown die orifice while still in-flight. Generally, the fibers undergo a flight treatment at a temperature above the glass transition temperature of the (co) polymer material comprising the fiber, and in some embodiments, as high as or higher than the nominal melting point of the (co) polymer material from which the fiber is made, and for a time sufficient to achieve at least some degree of stress relaxation of the (co) polymer molecules comprising the fiber.

Additionally, in certain exemplary embodiments, it is believed that the in-flight heat treatment process affects the crystallization behavior and average grain size of slower crystallizing materials, such as PET and PLA, thereby altering the shrinkage behavior of nonwoven fibrous webs comprising these materials when heated above the glass transition temperature of these materials. It is believed that such in situ fine tuning and reduction in the density of polymer nucleation sites within the (co) polymer material forming the fibers upon-flight heat treatment can reduce the total number of polymer nucleation by removing smaller sized "seeds" from the (co) polymer through physical (thermal) or chemical changes (e.g., crosslinking) in the (co) polymer chains, thereby resulting in a more thermally stable web exhibiting less heat shrinkage.

This improved low shrinkage behavior is believed to be due, at least in part, to a delay in the crystallization process during subsequent thermal exposure or processing, possibly due to a reduction in the content of crystalline nuclei or "seed" structures present in the (co) polymer to create a stronger chain-chain arrangement of the (co) polymer that disrupts the molecular order. According toIt is believed that the in situ reduction in the number of nuclei or "seeds" or the increase in size results in a nonwoven fibrous web having relatively low crystallinity and greater dimensional stability at higher temperatures, particularly when heated to the glass transition temperature (T) of the (co) polymer material comprising the fibers_g) And in particular heated to the cold crystallization temperature (T) of the (co) polymer material constituting the fibre_cc) Or higher.

Optional method steps

The random molten (co) polymer streams ejected from one or more orifices of the meltblowing die produced by the foregoing process can be readily combined into discrete non-meltblown fibers or particles that are fed into the fiber stream during or after in-flight thermal treatment of the meltblown fibers.

Thus, in some exemplary embodiments, the method further comprises adding a plurality of particles to the meltblown fibers before, during, or after the in-flight heat treatment operation. In further exemplary embodiments, the method additionally or alternatively includes adding a plurality of non-meltblown fibers to the meltblown fibers during or after the in-flight heat treatment operation.

In particular, the optional particulates and/or non-meltblown fibers may advantageously be added during in-flight heat treatment, or during collection as a meltblown nonwoven fibrous web, for example as disclosed in U.S. patent 4,100,324. These added non-meltblown fibers or particles can be entangled into a fibrous matrix without the need for additional binders or bonding processes. These added non-meltblown fibers or particles can be incorporated into the meltblown nonwoven fibrous web, adding additional features to the meltblown nonwoven fibrous web, such as bulk, abrasiveness, softness, antistatic properties, fluid-wicking properties, fluid-absorbing properties, and the like.

Various methods conventionally used in addition to fiber forming methods may be used in conjunction with the fibers as they exit one or more orifices of the meltblowing die. Such methods include spraying a polish, binder, or other material onto the fibers, applying an electrostatic charge to the fibers, applying a mist of water to the fibers, and the like. In addition, a variety of materials may be added to the collected web, including binders, adhesives, finishes, and other webs or films. For example, prior to collection, the extruded fibers or filaments may undergo a number of additional processing steps not shown in fig. 1, such as further drawing, spraying, and the like.

In some embodiments, it may be preferred to employ electrostatic charging for the meltblown fibers. Thus, in certain exemplary embodiments, the meltblown fibers may be subjected to an electret charging process. One exemplary electret charging method is hydrocharging. Hydrocharging of the fibers can be carried out using a variety of techniques including impinging, soaking or condensing a polar fluid onto the fibers followed by drying so that the fibers become charged. Representative patents describing hydrocharging include U.S. Pat. nos. 5,496,507; 5,908,598; 6,375,886B 1; 6,406,657B 1; 6,454,986 and 6,743,464B 1. Preferably, water is used as the polar hydrocharging liquid, and the medium is preferably exposed to the polar hydrocharging liquid using a liquid jet or stream of droplets provided by any suitable spraying device.

The equipment that can be used to hydroentangle the fibers can generally be used to conduct the hydrocharging, but the pressure at which the operation is conducted in the hydrocharging is lower than the pressure typically used in hydroentanglement. U.S. Pat. No. 5,496,507 describes an exemplary apparatus in which water jets or water droplet streams are impinged onto fibers in web form under pressure sufficient to provide a subsequently dried media with electret charge that enhances filtration.

The pressure necessary to obtain the best results may vary according to the following factors: the type of sprayer used, the type of polymer used to form the fibers, the thickness and density of the web, and whether a pretreatment such as corona discharge was performed prior to hydrocharging. Generally, pressures in the range of about 69kPa to about 3450kPa are suitable. Preferably, the water used to provide the water droplets is relatively pure. Distilled or deionized water is preferred over tap water.

In addition to or instead of hydrocharging, the electret fibers may be charged via other charging techniques, including electrostatic charging (e.g., as described in U.S. Pat. nos. 4,215,682, 5,401,446, and 6,119,691), tribocharging (e.g., as described in U.S. Pat. No.4,798,850), or plasma fluorination (e.g., as described in U.S. Pat. No. 6,397,458B 1). Corona charging followed by hydrocharging, and plasma fluorination followed by hydrocharging are particularly suitable charging techniques used in combination.

After collection, the accumulated material 30 may additionally or alternatively be threaded into a storage reel for subsequent processing as desired. Typically, once the collected meltblown nonwoven fibrous web 30 is collected, it may be conveyed to other equipment, such as calenders, embossing stations, laminators, cutters, and the like; or it may be passed through a drive roller and wound into a storage roll.

Other fluids that may be used include water sprayed onto the fibers, e.g., heated water or steam for heating the fibers, and relatively cooler water for quenching the fibers.

Apparatus and method for applying ceramic coatings

In another aspect, the present disclosure describes a method for making a nonwoven fibrous structure, the method comprising: forming a plurality of meltblown fibers by passing a molten stream comprising polyphenylene sulfide through a plurality of orifices of a meltblowing die; immediately subjecting at least a portion of the meltblown fibers to a controlled in-flight heat treatment operation as soon as the meltblown fibers exit the plurality of orifices, wherein the controlled in-flight heat treatment operation is conducted at a temperature below the melting temperature of the portion of the meltblown fibers for a time sufficient to effect stress relaxation of at least a portion of the molecules within the portion of the fibers subjected to the controlled in-flight heat treatment operation; collecting at least some of the portion of the meltblown fibers that have undergone the controlled in-flight thermal treatment operation on a collector to form a nonwoven fibrous structure; and applying a ceramic coating on the surface of the plurality of meltblown fibers.

The nonwoven fibrous structure is preferably dimensionally and exhibits a shrinkage that is less than that measured on an identically prepared structure that has not been subjected to a controlled in-flight heat treatment operation. The nonwoven fibrous structure preferably exhibits fire resistance without any added flame retardant additives via one or more tests selected from UL 94V0, FAR25.853(a), FAR25.856(a), AITM20007A, AITM3-0005 and CA regulation article 19. Preferably, the plurality of meltblown fibers do not contain a nucleating agent in an amount effective to achieve nucleation.

In other aspects, the method includes providing a melt stream comprising a thermoplastic material including a high proportion (i.e., at least 50 weight percent based on the weight of the meltblown fibers) of poly (phenylene sulfide) to a meltblowing die; melt blowing a thermoplastic material into at least one fiber; immediately after exiting the meltblowing die, subjecting at least one fiber to a controlled in-flight heat treatment operation conducted at a temperature below the melting temperature of the poly (phenylene sulfide) for a time sufficient for the nonwoven fibrous structure to exhibit a shrinkage (when tested using the method described herein) that is less than the shrinkage measured on an identically prepared structure that has not been subjected to the controlled in-flight heat treatment operation, prior to collection as a nonwoven fibrous structure on a collector; and applying a ceramic coating on a surface of the at least one fiber. Preferably, the thermoplastic material does not contain a nucleating agent in an amount effective to achieve nucleation.

In certain presently preferred embodiments, the method includes collecting at least one fiber subjected to a controlled in-flight heat treatment operation on a collector to form a nonwoven fibrous structure. The application of the ceramic coating on the surface of the at least one fiber may occur before, during, or after collection on a collector to form the nonwoven fibrous structure.

The ceramic coating on the surface of the plurality of meltblown fibers may be formed using techniques employed in the vacuum coating art. The ceramic coating may advantageously be applied using a Physical Vapor Deposition (PVD) process. PVD methods encompass a wide range of vapor coating techniques and are a general term used to describe a variety of methods for depositing solid films by condensing solid materials in vaporized form onto various surfaces.

PVD processes typically involve physically ejecting the material as atoms or molecules and allowing these atoms or molecules to condense and nucleate on the substrate. Gas phase materials may consist of ions or plasma and tend to undergo a chemical reaction with the gases introduced into the gas phase, known as reactive deposition, to form new compounds.

In some embodiments, applying the ceramic coating on the surface of the plurality of melt blown fibers is performed using one or more Physical Vapor Deposition (PVD) methods selected from the group consisting of Atomic Layer Deposition (ALD), filtered and unfiltered Cathodic Arc Deposition (CAD) using non-reactive or reactive components, Chemical Vapor Deposition (CVD), Electron Beam Vapor Deposition (EBVD), Laser Ablation Vapor Deposition (LAVD), Low Pressure Chemical Vapor Deposition (LPCVD), Plasma Enhanced Chemical Vapor Deposition (PECVD), Plasma Assisted Chemical Vapor Deposition (PACVD), Thermal Vapor Deposition (TVD), reactive sputtering, and combinations of these methods.

Sputtering is one presently preferred method. Suitable sputtering apparatus and methods are disclosed in the following documents: parsons, "Sputter deposition methods", Thin Film method II, Academic Press, Chapter II-4, 1991, pp.177-207 (Parsons, "Sputter deposition Processes", Thin Film Processes II, Academic Press, Inc., Chapter II-4, (1991), pp.177-207); thornton, Chapter V, "Coating Deposition by Sputtering", "development and application of film and Coating Deposition techniques", 1982, page 170-243, Noise Press, New Jersey (Thornton, Chapter 5, "Coating Deposition by spraying,", Deposition technologies for Films and Coatings, development and Applications, (1982), pp.170-243, non-yes Publications, New Jersey); and Vossen et al, "Glow discharge sputter Deposition", Thin Film methods, Academic Press, Chapter 11-1, 1978, pages 12-73 (Vossen et al, "Glow discharge sputter Deposition," Thin Film Processes, Academic Press, Inc., Chapter 11-1, (1978), pp.12-73), the entire disclosures of which are incorporated herein by reference in their entirety.

Enhanced barrier properties have been observed when the inorganic layer is formed by high energy deposition techniques such as sputtering compared to lower energy techniques such as conventional chemical vapor deposition methods. Without being bound by theory, it is believed that the enhanced properties are due to the condensed matter reaching the substrate having greater kinetic energy, thereby forming a lower void fraction due to compaction.

A variety of ceramic materials may be used. Preferred ceramic materials include metal oxides, metal nitrides, metal carbides, metal oxyborides, metal oxynitrides, and combinations thereof. In certain embodiments, the ceramic coating comprises aluminum oxide, indium oxide, magnesium oxide, niobium oxide, silicon oxide, tantalum oxide, tin oxide, titanium oxide, zinc oxide, zirconium oxide, boron carbide, silicon carbide, tungsten carbide, aluminum nitride, boron nitride, silicon nitride, aluminum oxynitride, boron oxynitride, silicon oxynitride, zirconium oxyboride, titanium oxyboride, and combinations thereof. Alumina, magnesia, silica and combinations thereof are presently preferred ceramic materials, with magnesia being particularly presently preferred.

The smoothness and continuity of the ceramic coating and the adhesion of the ceramic coating to the underlying nonwoven fibrous structure may be enhanced by a pretreatment (e.g., a plasma pretreatment or corona pretreatment).

Certain of the various embodiments of the present disclosure are further illustrated in the following illustrative examples. Some examples are identified as comparative examples because they do not exhibit certain characteristics (such as dimensional stability, e.g., low shrinkage, increased compressive strength, increased tensile strength, fire resistance, etc.); however, the comparative examples may be used for other purposes and establish novel and unobvious features of the examples.