阅读说明：本技术 声学制品及其方法 (Acoustic article and method thereof ) 是由 米歇尔·M·莫克 迈克尔·R·贝里甘 尼克勒·D·佩特科维奇 乔纳森·H·亚历山大 迈克尔· 于 2020-04-13 设计创作，主要内容包括：本发明提供了声学制品和相关方法,该声学制品包括多孔层和容纳在该多孔层中的异质填料。该异质填料可包括粘土、硅藻土、石墨、玻璃泡、聚合物填料、非层状硅酸盐、植物基填料或它们的组合物,并且可具有1微米至1000微米的中值粒度和0.1m～(2)/g至800m～(2)/g的比表面积。该声学制品可具有100MKS Rayls至8000MKS Rayls的总体流动阻力。该声学制品可用作吸声体、减震器和/或隔声体和隔热体。(The present invention provides acoustic articles and related methods that include a porous layer and a heterogeneous filler contained in the porous layer. The heterogeneous filler may include clay, diatomaceous earth, graphite, glass bubbles, polymeric fillers, non-layered silicates, plant-based fillersOr a combination thereof, and may have a median particle size of from 1 micron to 1000 microns and 0.1m 2 G to 800m 2 Specific surface area in g. The acoustic article can have an overall flow resistance of 100MKS Rayls to 8000MKS Rayls. The acoustic article can be used as a sound absorber, shock absorber, and/or sound insulator and thermal insulator.)

1. An acoustic article, comprising:

a porous layer; and

a heterogeneous filler contained in the porous layer, wherein the heterogeneous filler has a median particle size of 1 to 100 microns and 0.1m²G to 100m²A specific surface area per gram of the polymer,

wherein the acoustic article has a flow resistance of 100MKS Rayls to 8000MKS Rayls.

2. An acoustic article, comprising:

a porous layer; and

a heterogeneous filler contained in the porous layer, wherein the heterogeneous filler has a median particle size of 100 to 800 microns and 100m²G to 800m²A specific surface area per gram of the polymer,

wherein the acoustic article has a flow resistance of 100MKS Rayls to 8000MKS Rayls.

3. An acoustic article, comprising:

a porous layer; and

a heterogeneous filler contained in the porous layer, wherein the heterogeneous filler has a median particle size of 100 to 1000 microns and 1m²G to 100m²A specific surface area per gram of the polymer,

wherein the acoustic article has a flow resistance of 100MKS Rayls to 8000MKS Rayls.

4. The acoustic article of any of claims 1-3, wherein the heterogeneous filler comprises clay, diatomaceous earth, graphite, glass bubbles, polymeric fillers, non-layered silicates, plant-based fillers, or combinations thereof.

5. The acoustic article of claim 4, wherein the heterogeneous filler comprises a non-layered silicate, and wherein the non-layered silicate is an alkali metal silicate, an alkaline earth metal silicate, a non-zeolitic aluminosilicate, or a geopolymer.

6. The acoustic article of claim 4, wherein the heterogeneous filler comprises graphite, and wherein the graphite is unexpanded graphite.

7. The acoustic article of claim 4, wherein the heterogeneous filler comprises a porous polymer filler, and wherein the porous polymer filler comprises a polyolefin foam, polyvinylpyrrolidone, divinylbenzene-maleic anhydride, styrene-divinylbenzene, or polyacrylate.

8. An acoustic article, comprising:

a porous layer; and

a heterogeneous filler contained in the porous layer, wherein the heterogeneous filler comprises diatomaceous earth, a plant-based filler, non-expanded graphite, polyolefin foam, or a combination thereof, the heterogeneous filler having from 1 micron to 1000 micronsMedian particle size of (2) and 0.1m²G to 800m²A specific surface area per gram of the polymer,

wherein the acoustic article has a flow resistance of 100MKS Rayls to 8000MKS Rayls.

9. The acoustic article of claim 8 wherein the heterogeneous filler comprises diatomaceous earth, and wherein the diatomaceous earth has a median particle size of 5 to 40 microns and 1m²G to 50m²Specific surface area in g.

10. The acoustic article of claim 8, wherein the heterogeneous filler comprises a plant-based filler, and wherein the plant-based filler is a polymer having a median particle size of 10 microns to 1000 microns and 0.1m²G to 200m²Specific surface area of wood flour/g.

11. The acoustic article of claim 8, wherein the heterogeneous filler comprises non-expanded graphite, and wherein the non-expanded graphite has a median particle size of 1 to 1000 microns and 0.1m²G to 500m²Specific surface area in g.

12. The acoustic article of claim 8, wherein the heterogeneous filler comprises a polyolefin foam, and wherein the polyolefin foam has a median particle size of 100 to 1000 microns and 1m²G to 100m²Specific surface area in g.

13. The acoustic article of any of claims 1-12, wherein the heterogeneous filler is agglomerated.

14. The acoustic article of any of claims 1-13, wherein the heterogeneous filler has a Dv50/Dv90 particle size ratio of 0.25 to 1.

15. The acoustic article of any of claims 1-14 wherein the porous layer comprises a nonwoven fibrous layer having a plurality of fibers.

16. A method of making an acoustic article, the method comprising:

directly forming a nonwoven fibrous web;

delivering a heterogeneous filler comprising diatomaceous earth, a plant-based filler, non-expanded graphite, a polyolefin foam, or a combination thereof into the nonwoven fibrous web while the nonwoven fibrous web is being directly formed, the heterogeneous filler having a median particle size of 1 to 1000 microns and 0.1m²G to 800m²A specific surface area per gram of the polymer,

wherein the acoustic article has a flow resistance of 100MKS Rayls to 8000MKS Rayls.

17. A method of using the acoustic article of any of claims 1-15, the method comprising: the acoustic article is disposed adjacent to a surface to dampen vibrations of the surface.

18. A method of using the acoustic article of any of claims 1-15, the method comprising: the acoustic article is disposed adjacent to an air chamber to absorb acoustic energy transmitted through the air chamber.

Technical Field

Described herein are acoustic articles suitable for use in thermal and acoustic insulation. The provided acoustic articles may be particularly useful for reducing noise in automotive and aerospace applications.

Background

The customer demand for faster, safer, quieter, and heavier vehicles continues to drive improvements in automotive and aerospace technologies. Using conventional techniques, implementing such improvements tends to increase vehicle weight, thereby reducing fuel economy. Lightweight solutions are available and these solutions come with counter-balancing factors such as cost, complexity and manufacturing challenges. Developing such solutions can be a technical challenge, as measures taken to reduce weight often reduce performance in other areas.

Sound absorbers for addressing noise, vibration, and harshness of sound vibrations in vehicles represent an obvious example of such trade-offs. To improve fuel efficiency, automotive and aerospace manufacturers have replaced many heavy-duty steel components with lighter-weight materials, such as aluminum and plastic. However, as vehicle structures become lighter, noise tends to become increasingly difficult to attenuate due to mass laws. According to the law of mass, the sound insulation of a solid cell generally increases by about 5dB for every doubling of mass. Thus, lighter materials are generally disadvantageous compared to heavier materials.

Conventional sound absorbing materials include felt, foam, fiberglass, and polyester materials. These materials are typically provided in relatively high thicknesses to effectively absorb air noise over a wide range of frequencies. This results in a bulky absorber, which reduces the cabin space available to the vehicle occupants.

Disclosure of Invention

In an effort to improve the acoustic solution, it was recognized that noise may come from different sources. Some of the noise is carried by structural vibrations, which generate acoustic energy that propagates and is transmitted to the air, thereby generating airborne noise. Damping materials made of heavy viscous materials are conventionally used to control structural vibrations. Other kinds of airborne noise may be generated directly, such as airborne noise from the wind or vehicle driveline. Conventionally, soft, flexible materials (such as fibrous batts or foams) are used to absorb acoustic energy to control airborne noise.

Dense viscous materials have desirable characteristics for sound absorbers, but can add significant weight to the vehicle. Furthermore, the dimensional requirements for such materials can be significant. The performance of conventional sound absorbers can be estimated by comparing the magnitude of the sound waves with the thickness of the absorber. In order to effectively absorb lower frequencies, these sound absorbers generally need to have a thickness of at least about 10% of the wavelength of the incoming sound waves.

For some applications, this is a problem because there may be geometric and/or volume constraints defined by the space in which the acoustic absorber is to be installed. These constraints may be encountered, for example, when insulating aerospace or motor vehicles. In order to maximize cabin space, it is generally desirable to absorb sound in as thin a configuration as possible. However, due to their long wavelength, low frequency noise tends to propagate easily through thin acoustic absorbers.

Here, it has been found that certain porous and/or fine organic and inorganic particles exhibit excellent absorption over a wide frequency range and may exhibit synergistic acoustic properties when incorporated into certain porous layers. This behavior has been observed in polymer compositions and inorganic compositions such as clay particles, diatomaceous earth, plant-based fillers, non-layered silicates, and non-expanded graphite. These porous and/or fine particles may be embedded in the cracks of the porous medium to create a characteristic acoustic absorption profile. Such acoustic distributions may be tuned by a combination of particle characteristics and the manner in which the particle characteristics are presented within the porous medium.

The distribution is the product of particle composition, particle surface area and particle size. Certain combinations of these materials can provide a high level of sound absorption in a thin layered construction, both at high and low frequencies.

In a first aspect, an acoustic article is provided. The acoustic article includes: a porous layer; and a heterogeneous filler contained in the porous layer, wherein the heterogeneous filler has a median particle size of 1 to 100 microns and 0.1m²G to 100m²A specific surface area per gram, wherein the acoustic article has a flow resistance of 100MKS Rayls to 8000MKS Rayls.

In a second aspect, there is provided an acoustic article comprising: a porous layer; and

a heterogeneous filler contained in the porous layer, wherein the heterogeneous filler has a median particle size of 100 to 800 microns and 100m²G to 800m²A specific surface area per gram, wherein the acoustic article has a flow resistance of 100MKS Rayls to 8000MKS Rayls.

In a third aspect, an acoustic article is provided, the acoustic article comprising: a porous layer; and

a heterogeneous filler contained in the porous layer, wherein the heterogeneous filler has a median particle size of 100 to 1000 microns and 1m²G to 100m²A specific surface area of/g, wherein the acoustic article hasThere is a flow resistance of 100MKS Rayls to 8000MKS Rayls.

In a fourth aspect, an acoustic article is provided, the acoustic article comprising: a porous layer; and

a heterogeneous filler contained in the porous layer, wherein the heterogeneous filler comprises diatomaceous earth, a plant-based filler, non-expanded graphite, a polyolefin foam, or a combination thereof, the heterogeneous filler having a median particle size of 1 to 1000 microns and 0.1m²G to 800m²A specific surface area per gram, wherein the acoustic article has a flow resistance of 100MKS Rayls to 8000MKS Rayls.

In a fifth aspect, there is provided a method of making an acoustic article, the method comprising:

directly forming a nonwoven fibrous web; delivering a heterogeneous filler directly into the nonwoven fibrous web as it is formed, the heterogeneous filler comprising diatomaceous earth, a plant-based filler, unexpanded graphite, polyolefin foam, or a combination thereof, the heterogeneous filler having a median particle size of 1 to 1000 microns and 0.1m²G to 800m²A specific surface area per gram, wherein the acoustic article has a flow resistance of 100MKS Rayls to 8000MKS Rayls.

In a sixth aspect, a method of using an acoustic article is provided, the method comprising: an acoustic article is disposed adjacent to the surface to dampen vibrations of the surface.

In a seventh aspect, a method of using an acoustic article is provided, the method comprising: an acoustic article is disposed adjacent the air chamber to absorb acoustic energy transmitted through the air chamber.

Drawings

Fig. 1-13 are side elevation views of single and multilayer acoustic articles according to various embodiments;

fig. 14 is a graph illustrating absorption coefficients as a function of frequency for various acoustic article embodiments.

Repeat use of reference characters in the present specification and drawings is intended to represent same or analogous features or elements of the disclosure. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the scope and spirit of the principles of this disclosure. The figures may not be drawn to scale.

Definition of

As used herein:

unless otherwise indicated, "average" means exponential average.

"copolymer" refers to a polymer made from repeat units of two or more different polymers, and includes random, block, and star (e.g., dendritic) copolymers.

By "dimensionally stable" is meant a structure that substantially retains its shape under gravity without assistance (i.e., does not soften).

By "die" is meant a processing assembly comprising at least one orifice used in polymer melt processing and fiber extrusion processes, including but not limited to melt blowing.

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

By "embedded" is meant that the particles are dispersed and physically and/or adhesively retained in the fibers of the web.

"glass transition temperature (or T) of a polymer_g) "refers to the temperature at which there is a reversible transition from a hard and relatively brittle" glass "state to a viscous or rubbery state in an amorphous polymer (or in amorphous regions within a semi-crystalline polymer) as the temperature increases.

The "median fiber diameter" of the fibers in the nonwoven fibrous layer is determined by: preparing one or more images of the fibrous structure, such as by using a scanning electron microscope; measuring the transverse dimension of the clearly visible fibers in one or more images, thereby obtaining the total number of fiber diameters; and calculating a median fiber diameter based on the total number of fiber diameters.

"nonwoven fibrous layer" means a plurality 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.

"oriented" when used with respect to a fiber means that at least a portion of the polymer molecules within the fiber are aligned with the longitudinal axis of the fiber, such as by using a drawing process or attenuation device as the fiber stream exits the die.

"particle" refers to different pieces or individual portions of a material in a finely divided form (i.e., primary particles) or aggregates thereof. The primary particles may include flakes, powders, and fibers, and may agglomerate, physically interfit, electrostatically associate, or otherwise associate to form aggregates. In some cases, particles in the form of aggregates of individual particles may be formed as described in U.S. Pat. No. 5,332,426(Tang et al).

"Polymer" means a relatively high molecular weight material having a molecular weight of at least 10,000 g/mol.

By "porous" is meant comprising pores or voids.

"shrinkage" means a reduction in the size of the fibrous nonwoven layer after being heated to 150 ℃ for 7 days, based on the test method described in U.S. patent publication 2016/0298266(Zillig et al);

"size" refers to the longest dimension of a given object or surface.

By "substantially" is meant an amount that is at least 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%, 99.99%, or 99.999%, or 100% in majority or majority.

Detailed Description

As used herein, the terms "preferred" and "preferably" refer to embodiments described herein that may provide certain benefits under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the invention.

As used herein and in the appended claims, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a" or "the" component may include one or more components or equivalents thereof known to those skilled in the art. Additionally, the term "and/or" means one or all of the listed elements or a combination of any two or more of the listed elements.

It is noted that the term "comprises" and its variants, when appearing in the appended description, have no limiting meaning. Furthermore, "a," "an," "the," "at least one," and "one or more" are used interchangeably herein. Relative terms such as left, right, forward, rearward, top, bottom, side, upper, lower, horizontal, vertical, and the like may be used herein and if so, they are from the perspective as viewed in the particular drawing. However, these terms are only used to simplify the description, and do not limit the scope of the present invention in any way.

Reference throughout this specification to "one embodiment," "certain embodiments," "one or more embodiments," or "an embodiment" means that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Thus, the appearances of the phrases such as "in one or more embodiments," "in certain embodiments," "in one embodiment," or "in an embodiment" in various places throughout this specification are not necessarily referring to the same embodiment of the invention.

The present disclosure relates to acoustic articles, assemblies, and methods thereof for use as sound absorbers, shock absorbers, and/or sound insulators, and thermal insulators. Acoustic articles and components generally include one or more porous layers and one or more heterogeneous fillers in contact with the one or more porous layers. Optionally, acoustic articles and assemblies are provided that include one or more non-porous barrier layers, resonators, and/or air gaps adjacent to one or more porous layers. The structural and functional characteristics of each of these components are described in subsequent subsections.

Acoustic article

Exemplary acoustic articles are shown in fig. 1-13 and described below. These acoustic articles can effectively address both structure-related noise and undesirable vibrations. In some embodiments, the acoustic article may be disposed on the substrate or placed adjacent to the air cavity to absorb acoustic energy transmitted through the substrate or the air cavity, respectively. In other embodiments, the acoustic article may be placed adjacent to a surface to dampen vibrations of the surface.

The damping application comprises a near field damping application. Near-field damping is a mechanism for dissipating the vibrational energy of a structure by controlling the non-propagating and propagating waves that are generated near the surface (near-field region) of the structure by the structure's vibrations. In the near field region, the oscillating fluid and the incompressible fluid flow parallel to the surface of the structure, where the intensity of these flows gradually decreases with increasing distance from the surface of the vibrating structure. The energy intensity of this region may be significant, and thus the energy dissipation of this region may help to damp the structural vibrations.

The near field region may be defined as 30 cm to 0cm, 15 cm to 0cm, 10cm to 0cm, 8 cm to 0cm, 5cm to 0cm relative to the surface of a given substrate (or structure). Here, "0 cm" is defined as being located at the surface of the substrate.

Further details regarding near-field damping are described in Nichols N.Kim, Seungkyu Lee, J.Stuart Bolton, Sean Holland and Taewook Yoo "Structural damping by using fibrous materials" (SAE technical paper 2015-01-2239, 2015).

As shown in these figures, useful acoustic articles include both single layer constructions and multilayer constructions. Unless otherwise specifically indicated, it should be understood that one or more additional layers or surface treatments may be present on either major surface of a given acoustic article, or between other adjacent layers of the acoustic article.

Fig. 1 shows a single layer acoustic article, referred to hereinafter by the numeral 100. Article 100 includes a porous layer 102 and a plurality of heterogeneous fillers 104 dispersed therein. In this embodiment, the heterogeneous filler 104 is uniformly dispersed in the porous layer throughout the thickness of the porous layer 102, as shown.

For exemplary purposes, the porous layer 102 is depicted herein as a fibrous nonwoven layer comprised of a plurality of fibers, although other types of porous layers (e.g., open cell foam, particulate bed) may also be used. Useful porous layers are described in detail in the separate section entitled "porous layer" below.

A heterogeneous filler 104 having desired acoustic properties is embedded in the plurality of fibers of the porous layer 102. Heterogeneous filler 104 may be present in an amount of 1 to 99, 10 to 90, 15 to 85, 20 to 80, or in some embodiments, less than, equal to, or greater than 1, 2, 3, 4, 5, 7,10, 12, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 97, 98, or 99 weight percent relative to the combined weight of porous layer 102 and heterogeneous filler 104.

Examples of heterogeneous fillers that impart acoustical benefits include porous and/or fine fillers such as clays, diatomaceous earth, graphite, glass bubbles, porous polymeric fillers, non-layered silicates, plant-based fillers, and combinations thereof. A detailed description of these heterogeneous fillers is provided in a later section entitled "heterogeneous fillers".

The heterogeneous filler 104 in the porous layer 102 may affect the average fiber-to-fiber spacing within the nonwoven fibrous structure of the porous layer 102. The extent to which this occurs depends on, for example, the particle size of the heterogeneous filler 104 and the loading of the heterogeneous filler 104 within the porous layer 102. The porous layer 102 may have an average fiber-to-fiber spacing of 0 microns to 1000 microns, 10 microns to 500 microns, 20 microns to 300 microns, or in some embodiments, less than, equal to, or greater than 0 microns, 1 micron, 2 microns, 3 microns, 4 microns, 5 microns, 7 microns, 10 microns, 11 microns, 12 microns, 15 microns, 17 microns, 20 microns, 25 microns, 30 microns, 35 microns, 40 microns, 45 microns, 50 microns, 60 microns, 70 microns, 80 microns, 90 microns, 100 microns, 110 microns, 120 microns, 150 microns, 170 microns, 200 microns, 250 microns, 300 microns, 350 microns, 400 microns, 450 microns, 500 microns, 600 microns, 700 microns, 800 microns, 900 microns, or 1000 microns.

In contrast, the heterogeneous filler 104 within the acoustic article 100 has an inter-particulate (i.e., particle-to-particle) spacing that is at least partially dependent on its loading and the structural properties of the porous layer 102. The heterogeneous filler 104 can have an average interparticle spacing of 20 microns to 4000 microns, 50 microns to 2000 microns, 100 microns to 1000 microns, or in some embodiments, less than, equal to, or greater than 20 microns, 25 microns, 30 microns, 35 microns, 40 microns, 45 microns, 50 microns, 60 microns, 70 microns, 80 microns, 90 microns, 100 microns, 110 microns, 120 microns, 150 microns, 170 microns, 200 microns, 250 microns, 300 microns, 350 microns, 400 microns, 450 microns, 500 microns, 600 microns, 700 microns, 800 microns, 900 microns, 1000 microns, 1100 microns, 1200 microns, 1500 microns, 1700 microns, 2000 microns, 2500 microns, 3000 microns, 3500 microns, or 4000 microns.

The average fiber-to-fiber spacing, particle-to-fiber spacing, and particle-to-particle spacing may be obtained using X-ray microtomography, which is a non-destructive 3D imaging technique in which the contrast mechanism is the absorption of X-rays by components within the sample being examined. The X-ray source illuminates the sample and the detection system collects 2D X radiographic images projected at discrete angular positions as the sample rotates.

The collection of the projected 2D images is performed by a process called reconstruction to produce a stack of 2D slice images along the sample rotation axis. The reconstructed 2D slice images may be examined individually as a series of images or may be used together to generate a 3D volume containing the examination sample. The measurements can be made, for example, using a Skyscan 1172 (Bruker micro ct, Kontich, Belgium, to corning Belgium) X-ray microtomography scanner at a suitable resolution (e.g., 1-3 microns) and X-ray source settings of 40kV and 250 μ Α.

The reconstructed image may then be processed to separate the positions of the particles or particles and fibers within the scanned specimen. The grey level threshold may allow the particles to be isolated from the lower density material in the porous layer and allow the particles and fibers to be isolated from the lower density noise in the data set. Processing may be performed using, for example, CTAnalyzer software (v 1.16.4 Bruker micct, inc. Belgium, v 1.16.4 Bruker micct, Kontich) to obtain average particle-to-particle, particle-to-fiber, and fiber-to-fiber spacings.

The desired thickness of the porous layer 102 is highly application dependent and therefore need not be particularly limited. The porous layer 102 may have an overall thickness of 1 micron to 10 centimeters, 30 microns to 1 centimeter, 50 microns to 5000 millimeters, or in some embodiments, less than, equal to, or greater than 1 micron, 2 microns, 5 microns, 10 microns, 20 microns, 30 microns, 40 microns, 50 microns, 100 microns, 200 microns, 500 microns, 1 millimeter, 2 millimeters, 3 millimeters, 4 millimeters, 5 millimeters, 7 millimeters, 10 millimeters, 20 millimeters, 50 millimeters, 70 millimeters, or 100 millimeters.

Advantageously, the combination of the porous layer 102 and the heterogeneous filler 104 can significantly enhance sound absorption at low sound frequencies (such as sound frequencies of 50Hz to 500 Hz) while maintaining sound absorption at higher sound frequencies in excess of 500 Hz.

In some embodiments, the addition of a heterogeneous filler within a sound frequency of less than, equal to, or greater than 50Hz, 55Hz, 60Hz, 65Hz, 70Hz, 75Hz, 80Hz, 85Hz, 90Hz, 95Hz, 100Hz, 105Hz, 110Hz, 115Hz, 120Hz, 125Hz, 130Hz, 135Hz, 140Hz, 145Hz, 150Hz, 155Hz, 160Hz, 165Hz, 170Hz, 175Hz, 180Hz, 185Hz, 190Hz, 195Hz, 200Hz, 210Hz, 220Hz, 230Hz, 240Hz, 250Hz, 260Hz, 270Hz, 280Hz, 290Hz, 300Hz, 400Hz, 500Hz, 700Hz, 1000Hz, 2000Hz, 3000Hz, 4000Hz, 5000Hz, 7000Hz, or 10,000Hz can significantly increase the sound absorption of an acoustic article.

Fig. 2 shows an article 200 according to a bi-layer embodiment, which is comprised of a first porous layer 202 containing heterogeneous filler 204 and a second porous layer 206 that does not contain heterogeneous filler 204. As shown, second porous layer 206 extends across and directly contacts first porous layer 202. First porous layer 202 may have similar characteristics to those of porous layer 102 already described with respect to fig. 1.

Other embodiments are also possible. For example, the heterogeneous filler may be only partially embedded in the first porous layer, with some of the heterogeneous filler residing outside of that layer. In another embodiment, substantially no heterogeneous filler is embedded in the first porous layer, while substantially all of the heterogeneous filler is present in the bed of particles of heterogeneous filler confined between the first porous layer and the second porous layer, neither of the first porous layer and the second porous layer being filled.

Referring again to fig. 2, the thickness of second porous layer 206 is substantially greater than the thickness of first porous layer 202. Depending on the nature of the noise to be attenuated, it may be advantageous for the thickness of first porous layer 202 to be significantly greater than the thickness of second porous layer 206. The thickness of one porous layer may be less than, equal to, or greater than 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 110%, 120%, 130%, 140%, 150%, 200%, 250%, 300%, 400%, 500%, 600%, 700%, 800%, 900%, or 1000% of the thickness of the other porous layer.

One or more additional layers may be disposed between these layers or extend along the outwardly facing major surfaces of first porous layer 202 and second porous layer 206. An example of such a configuration is shown in fig. 3. Fig. 3 depicts an article 300 having three porous layers, wherein first porous layer 302 and third porous layer 308 are unfilled and second porous layer 304 is filled and sandwiched between the first two layers.

In multilayer constructions (e.g., articles 200, 300 of fig. 2 and 3), an unfilled porous layer may improve the low frequency performance of the overall acoustic article. To achieve high sound absorption, the acoustic impedance of the article may approach the characteristic impedance of the surrounding fluid. If the surrounding fluid is air, the characteristic impedance is the product of the density and the speed of sound of the air medium. Thus, the porous layer may help match the acoustic impedance of the multilayer article to the characteristic impedance of the surrounding medium.

Specific acoustic impedance z at the surface of the material for the case of normal incident plane waves_surfCan be described as followsFormula (II):

z_surf＝p/v|_x＝L＝-jz_ccot(kx)|_x＝L

wherein p is sound pressure, v is particle velocity, k is sound wave number, x is distance from the substrate surface, and z is_cAre the characteristic impedance of air, and they can be obtained from the following relation:

k＝2πf/c

z_c＝(ρK)^1/2

where f denotes the frequency, c denotes the sound velocity of air, and ρ and K are the density and bulk modulus of air, respectively. The highest sound absorption occurs when the specific acoustic impedance at the surface becomes zero. Thus, sound absorbing materials generally follow a quarter wave rule, where a quarter wave corresponds to the thickness of the material. The quarter wavelength corresponds to the frequency at which the material exhibits its first peak absorption.

Reducing the speed of sound improves low frequency performance without increasing material thickness. At the surface where the material is placed against the rigid wall, the surface impedance becomes infinite, since the upper particle velocities v and x are both close to zero. Based on the above relationship, it is surmised that the heterogeneous filler within the porous layer can help lower the frequency that provides zero acoustic impedance at the surface of the material by changing the wavelength within the material and providing a pressure reducing effect. In some embodiments, the addition of the heterogeneous filler can also result in a reduction in reflection of sound waves within the acoustic article. Reducing the pressure also lowers the acoustic impedance so that some sound can penetrate the bulk acoustic article and help trap more acoustic energy within the bulk acoustic article, thereby improving noise dissipation and hence barrier performance.

In the above embodiments, the heterogeneous filler is substantially free from each other and any porous layer; that is, the particles of the heterogeneous filler are not physically attached to each other and are capable of at least limited movement or oscillation independent of the surrounding structure. In these cases, the embedded particles can move and vibrate within the fibers of the nonwoven material largely independently of the fibers themselves.

Alternatively, at least some of the heterogeneous fillers may be physically bonded to the porous layer in which they are disposed. In some embodiments, these physical bonds are created by incorporating a binder (e.g., binder fibers) within a porous layer that can become tacky and adhere to the filler particles upon application of heat. In order to preserve the acoustic properties of the heterogeneous filler, it is generally preferred that the binder does not significantly flow into the pores of the filler particles.

It should be understood that further embodiments are possible wherein the acoustic article is composed of four, five, six, seven or even more porous layers, wherein at least one porous layer contains or is otherwise in contact with a heterogeneous filler.

Fig. 4 shows a side view of another acoustic article 400 having first and second porous layers 402 and 404 and a heterogeneous filler layer 420 disposed between porous layers 402 and 404. The porous layers 402, 404 and heterogeneous filler 420 are similar to the porous layers described with respect to figure 1 and figure 3. In this embodiment, the porous layers 402, 404 may not only contribute to the acoustic performance of the article 400, but also serve to physically confine and secure the heterogeneous filler 420 to the space between the porous layers 402, 404.

In this embodiment, the heterogeneous packing 420 is not embedded in the porous layers 402, 404, but is formed as a bed of particles. The article 400 is also divided into a plurality of segmented chambers 430 by walls 432 to provide a quilted structure. The chambers 430 are located in a lateral direction relative to each other, with each chamber 430 containing a first porous layer 402, a heterogeneous filler layer 420, and a second porous layer 404 as shown. Optionally, the chamber 430 may have a two-dimensional grid configuration in plan view.

The walls 432 separating the chambers 430 from each other need not be limited in composition and may or may not be porous. In a preferred embodiment, wall 432 is made of a flexible polymeric film, scrim, or perforated film having low flow resistance. Advantageously, the wall 432 provides improved securement of the heterogeneous filler 420 in the acoustic article 400, and may also improve acoustic performance by providing grazing wave dissipation based on the presence of lateral boundaries within the article 400.

Other aspects of article 400 are described in co-pending international patent application PCT/US18/56671(Lee et al), filed on 2018, 10, 19.

Fig. 5 shows an acoustic article 500 that uses a perforated membrane as the porous layer. The acoustic article 500 includes a heterogeneous filler 520 confined between the first perforated film 502 and the second perforated film 504. The films 502, 504 have a plurality of apertures 503, 505 (or through-holes) extending through the respective perforated films 502, 504 in a direction perpendicular to the major surfaces of the article 500. Optionally and as shown, the plurality of apertures 503, 505 are arranged in a two-dimensional pattern having a regular center-to-center spacing between adjacent apertures.

In the embodiment shown, film 504 is significantly thicker than film 502. Additionally, the bore 503 is generally cylindrical, while the bore 505 has tapered sidewalls to create an opening having a generally conical shape. As shown in fig. 5, the heterogeneous filler 520 resides within the generally conical opening and is securely held between the membranes 502, 504 because the particles of the heterogeneous filler 520 are significantly larger than the narrowest width of the openings 503, 505. In an alternative embodiment, the heterogeneous filler may be trapped between a pair of symmetrically disposed perforated films.

The membranes 502, 504 may be coupled to each other by any known method. They may be attached using adhesives, thermal lamination, and/or mechanical coupling. Either of the films 502, 504 may also be coupled to the fibrous nonwoven layer as previously described using either of these methods. In some embodiments, the fibrous nonwoven layer comprises adhesive polymer fibers that facilitate its attachment to the heterogeneous filler, the perforated film, or another fibrous nonwoven layer. Suitable adhesive fibers include binder fibers made from, for example, styrene-isoprene-styrene or polyethylene/polypropylene copolymers.

In another embodiment, an acoustic article may be provided in which one of the membranes 502, 504 is eliminated.

In yet another embodiment, perforated film 502 may be replaced with another porous layer, such as a barrier scrim. The barrier scrim is a thin porous layer that exhibits high flow resistance (e.g., up to 2000MKS Rayls). In some embodiments, the barrier scrim is a nonwoven fibrous web having a thickness of less than 5000 microns and has negligible bending stiffness.

The inclusion of a barrier layer such as a barrier scrim may further enhance the acoustic performance, particularly at lower frequencies. The barrier layer can have a flow resistance of 10MKS Rayls to 8000MKS Rayls, 20MKS Rayls to 3000MKS Rayls, or 50MKS Rayls to 1000MKS Rayls. In some embodiments, the flow resistance through the barrier layer is less than, equal to, or greater than 10MKS Rayls, 20MKS Rayls, 30MKS Rayls, 40MKS Rayls, 50MKS Rayls, 70MKS Rayls, 100MKS Rayls, 200MKS Rayls, 300MKS Rayls, 400MKS Rayls, 500MKS Rayls, 600MKS, 700MKS Rayls, 1000MKS Rayls, 1100MKS Rayls, 1200MKS Rayls, 1500MKS Rayls, 1700MKS Rayls, 2000MKS Rayls, 2500MKS Rayls, 3000MKS, 3500MKS Rayls, 4000MKS Rayls, 4500MKS Rayls, 5500MKS Rayls, 6000MKS Rayls, 6500MKS, 5000MKS Rayls, 7500MKS, 8000MKS, or 8000MKS Rayls.

The barrier layer can have a thickness of 1 micron to 10 centimeters, 30 microns to 1 centimeter, 50 microns to 5000 microns, or in some embodiments, less than, equal to, or greater than 10 microns, 20 microns, 30 microns, 40 microns, 50 microns, 70 microns, 100 microns, 200 microns, 500 microns, 1 millimeter, 2 millimeters, 5 millimeters, 10 millimeters, 20 millimeters, 30 millimeters, 40 millimeters, 50 millimeters, 60 millimeters, 70 millimeters, 80 millimeters, 90 millimeters, or 100 millimeters (10 centimeters).

Fig. 6 shows an acoustic article 600 in which porous layers have different loadings of heterogeneous filler. In this configuration, the article 600 has a first porous layer 602 with a high relative loading of heterogeneous filler 604, a second porous layer 606 with a low relative loading of heterogeneous filler 604', and a third porous layer 608 that is free of any heterogeneous filler. The heterogeneous fillers 604, 604' may or may not have the same composition. The heterogeneous fillers 604, 604' may or may not have the same median particle size. Likewise, the porous layers 602, 606, 608 are intended to be generic herein and thus may or may not have the same composition and structure.

If the heterogeneous fillers 604, 604' have the same composition and particle size, the article 600 has discrete layers with a density that gradually decreases from the top of the article 600 to the bottom of the article 600, as shown in FIG. 6. Advantages of this configuration include design freedom and customization, reduced cost and adjustability, enabling enhanced sound absorption at certain frequencies as desired.

Fig. 7 shows an acoustic article 700 in which a bulk porous layer 702 contains heterogeneous fillers 704 of two different particle sizes. The heterogeneous filler 704 can have a bimodal distribution of particle sizes (as shown here) or some other multimodal distribution. Alternatively, the heterogeneous filler 704 can have a unimodal but broad distribution. By mixing heterogeneous fillers with different particle sizes together, the overall filler loading can be increased because smaller particles can occupy the cracks formed by the larger particles.

Fig. 8 shows an acoustic article 800 using a porous layer 802 containing a density gradient of heterogeneous filler 804. As shown, the density is greatest near its top major surface and least near its bottom major surface.

Fig. 9 shows an acoustic article 900 having a two-layer construction, which is comprised of a first porous layer 902 containing a plurality of first heterogeneous fillers 904 and a second porous layer 906 containing a plurality of second heterogeneous fillers 908. The porous layers 902, 906 are in flat contact with each other and may be made of the same or different materials. As shown, the median particle size of heterogeneous filler 908 is greater than the median particle size of heterogeneous filler 904.

Fig. 10-13 illustrate additional variations and combinations of the acoustic layers previously presented. For example, fig. 10 shows an acoustic article 1000 in which a first porous layer 1002 is a perforated film disposed on a second porous layer 1004 comprised of a nonwoven fibrous web containing a plurality of heterogeneous fillers 1006. The layers 1002, 1004 are backed by a third porous layer 1008 that is unfilled and also made from a nonwoven fibrous web. As noted above, these configurations allow the acoustic behavior of the overall acoustic article to be tuned to suit a particular application. Such acoustic behavior may include a combination of reflection, absorption, and noise cancellation.

Fig. 11 shows an acoustic article 1100 that has some similarities to article 1000, but includes a first porous layer 1102 that is a particle-filled perforated film. The perforated film includes a plurality of perforations 1106, which, as shown, include heterogeneous filler 1104. The second porous layer 1108 and the third porous layer 1110 underlying the first porous layer 1102 are generally similar to those described with respect to the article 1000 in fig. 10.

Fig. 12 shows an acoustic article 1200 that is also similar to the article 1000 in fig. 10, except that the acoustic article includes a fourth porous layer 1208 extending across the first, second, and third porous layers 1202, 1204, 1206, with a heterogeneous filler 1207 embedded in the second porous layer 1204. The fourth porous layer 1208 is a perforated film that does not contain or directly contacts the heterogeneous filler 1207.

Fig. 13 shows an acoustic article 1300 coupled to a substrate 1350. The acoustic article 1300 has first and second porous layers 1302, 1304 that are somewhat similar to the first and second porous layers of the acoustic article 500 in fig. 5. The heterogeneous fill 1306 resides within the second porous layer 1304 and is mechanically retained within the perforations of the second porous layer 1304 by the first porous layer 1302. A third porous layer 1305 (which is comprised of a nonwoven fibrous web) extends across and directly contacts the second porous layer 1304, which is in turn bonded to the substrate 1350.

Substrates include structural components such as parts of automobiles or airplanes and building substrates. Structural examples include molded panels (e.g., door panels), aircraft frames, wall insulation, and integrated piping. The substrate may also include components beside these structural examples, such as carpet, trunk pads, fender pads, front of instrument panels, flooring systems, wall panels, and duct insulation. In some cases, the substrate may be spaced apart from the acoustic article, as is the case with hood liners, canopies, aircraft panels, drapes, and ceiling tiles. Additional applications for these materials include filter media, surgical drapes and wipes, liquid and gas filters, clothing, blankets, furniture, vehicles (e.g., for airplanes, rotorcraft, trains, and motor vehicles), electronics (e.g., for televisions, computers, servers, data storage devices, and power supplies), air handling systems, furniture upholstery, and personal protective equipment.

In the aforementioned acoustic article, the degree of compactness of a given layer depends on the degree to which the heterogeneous filler is loaded into the layer. The solidity may be increased if the heterogeneous filler particles occupy the space that would otherwise remain as voids in the porous layer. However, if the addition of the heterogeneous filler opens the structure of the porous layer, thereby generating voids that do not exist originally, the degree of compactness may also be reduced.

As used herein, solidity is a property that is inversely proportional to density and represents web permeability and porosity (solidity formulas are provided in the examples). A low solidity corresponds to a high permeability and a high porosity. When filled with heterogeneous fillers, the provided porous layer may have a solidity of 5% to 40%, 8% to 35%, 10% to 30%, or in some embodiments, less than, equal to, or greater than 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 15%, 17%, 20%, 22%, 25%, 27%, 30%, 32%, 25%, 37%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%. The compactness of the porous layer in unfilled form provided may be less than, equal to, or greater than 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 15%, 17%, 20%, 22%, 25%, 27%, 30%, 32%, 25%, 37%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%.

Any of the foregoing acoustic articles may further comprise one or more closed air gaps between adjacent layers. The air gap may act as a resonant cavity to enhance transmission losses through the acoustic article at a particular frequency. The air gap may act as an acoustic resonator based on quarter-wave theory. According to this theory, peak sound absorption occurs at a frequency representing a quarter wavelength of the thickness of the acoustic layer. A larger air gap switches peak sound absorption to lower frequencies. For example, a 5cm thick air gap may have a peak absorption at 1600Hz, while a 10cm air gap may produce a peak absorption at 800 Hz.

The air gap may have any thickness that allows it to function as an acoustic resonator. Generally, depending on the acoustic frequency of interest, the thickness of the air gap may be 10 microns to 10 centimeters, 500 microns to 5 centimeters, 1 millimeter to 3 centimeters, or in some embodiments, less than, equal to, or greater than 10 microns, 20 microns, 30 microns, 40 microns, 50 microns, 70 microns, 100 microns, 200 microns, 500 microns, 1 millimeter, 2 millimeters, 5 millimeters, 10 millimeters, 20 millimeters, 30 millimeters, 40 millimeters, 50 millimeters, 60 millimeters, 70 millimeters, 80 millimeters, 90 millimeters, or 100 millimeters (10 centimeters).

The provided acoustic article may also include a layer comprising a plurality of helmholtz resonators in contact with the porous layer. This layer may be disposed on either major surface of the acoustic article or between other adjacent layers within the acoustic article.

A helmholtz resonator is essentially a tiny container filled with air, where the container has an open port. The volume of air within the container has some elasticity that allows it to vibrate and dissipate acoustic energy at a particular frequency or range of frequencies. The helmholtz resonators may be arranged in a two-dimensional array extending along a major surface of the acoustic article. Although not intended to be limiting, examples of suitable helmholtz resonators include, for example, those described in international publication WO2013169788(Castiglione et al).

A composite acoustic article including helmholtz resonators may have a relatively low density of heterogeneous filler. For example, less than 50% of the total void volume may be occupied by heterogeneous fillers. Heterogeneous filler particles can have non-uniform orientation and/or irregular shape. For example, the asymmetric elongated particle may reside within the hole with its small end facing downward, its large end facing downward, or in a transverse orientation. Each orientation produces its own characteristic absorption. Because the provided acoustic articles contain a variety of different particle orientations within the porous layer, these articles can be absorbed over a wider frequency range than Helmholtz resonators alone.

Fig. 14 illustrates the broad spectrum acoustic behavior that can be obtained by varying the particle size of the heterogeneous filler. Five different acoustic articles, referred to as types 1-5, are shown here in a granular bed configuration. It should be understood that similar acoustic behavior can be obtained by disposing the same or similar heterogeneous filler in other porous layers, including non-woven fibrous layers and foams.

In this figure, the absorption coefficient is plotted as a function of frequency, as measured for the heterogeneous filler provided below:

type 1: porous poly (divinylbenzene-maleic anhydride) diameter <250 microns

Type 2: silica gel, 150 ion diameter 250 micron

Type 3: porous poly (divinylbenzene-maleic anhydride) 250-420 microns in diameter

Type 4: porous poly (divinylbenzene-maleic anhydride) 420-595 micron diameter

Type 5: porous poly (divinylbenzene-maleic anhydride) with diameter >595 μm

Porous layer

The provided acoustic article includes one or more porous layers. Useful porous layers include, but are not limited to, nonwoven fibrous layers, perforated films, particulate beds, and open cell structures such as open cell foams, glass fibers, webs, woven fabrics, and combinations thereof. The porous layer is generally permeable so that air or some other fluid can freely communicate between the opposite sides of the layer. Such layers may also be semi-permeable (permeable along some but not all thickness dimensions) or impermeable.

Certain nonwoven fibrous layers may be effective sound absorbers even if they do not contain heterogeneous fillers. For example, a nonwoven material comprising a plurality of fine fibers can be very effective at attenuating high acoustic frequencies. In this frequency range, the surface area of the structure promotes viscous dissipation of noise, a process that converts acoustic energy into heat.

The nonwoven layer can be made from a wide variety of materials, including organic and inorganic materials. One type of inorganic fiber nonwoven material is glass fiber. Glass fibers are typically made by melting silica and other minerals in a furnace and then extruding them through a spinneret containing tiny orifices to produce a stream of molten glass. Under the direction of the hot air flow, these flows are cooled into fibers and deposited onto a conveyor belt, where the fibers are interlaced with each other to obtain a non-woven glass fiber layer.

The polymeric nonwoven layer may be made using a melt blown process. The meltblown nonwoven fibrous layer may comprise microfibers. In melt blowing, one or more thermoplastic polymer streams are extruded through a die containing densely arranged orifices. These polymer streams are attenuated by converging streams of high velocity hot air to form fine fibers, which are then collected on a surface to provide a layer of meltblown nonwoven fibers. Depending on the selected operating parameters, the collected fibers may be semi-continuous or substantially discontinuous.

The polymeric nonwoven layer may also be prepared by a process known as melt spinning. In melt spinning, nonwoven fibers are extruded as filaments out of a set of orifices and allowed to cool and solidify to form fibers. The filaments pass through an air space that can contain a stream of moving air to help cool the filaments and pass through an attenuation (i.e., drawing) unit to at least partially draw the filaments. Fibers prepared by a melt spinning process can be "spunbond," whereby a web comprising a set of melt spun fibers is collected as a fiber web and optionally subjected to one or more bonding operations to fuse the fibers to one another. Melt spun fibers generally have larger diameters than meltblown fibers.

Polymers suitable for use in melt blown or melt spun processes include polyolefins such as polypropylene and polyethylene, polyesters, polyethylene terephthalate, polybutylene terephthalate, polyamides, polyurethanes, polybutylene, polylactic acid, polyphenylene sulfide, polysulfone, liquid crystal polymers, ethylene-vinyl acetate copolymers, polyacrylonitrile, cyclic polyolefins, and copolymers and blends thereof.

The nonwoven fibers may be made from thermoplastic semicrystalline polymers such as semicrystalline polyesters. Useful polyesters include aliphatic polyesters. Nonwoven materials based on aliphatic polyester fibers may be particularly advantageous in high temperature applications to resist degradation or shrinkage. This property can be achieved by making the nonwoven fibrous layer using a melt blown process, wherein the melt blown fibers are immediately subjected to a controlled in-air heat treatment operation as they exit the melt blown fibers from the plurality of orifices. The controlled aerial heat treatment operation is conducted at a temperature below the melting temperature of a portion of the meltblown fibers and 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 aerial heat treatment operation. Details regarding in-flight heat treatment are described in U.S. patent publication 2016/0298266(Zillig et al).

The molecular weight of the aliphatic polyesters that may be used need not be particularly limited and may range from 15,000g/mol to 6,000,000g/mol, 20,000g/mol to 2,000,000g/mol, 40,000g/mol to 1,000,000g/mol, or in some embodiments less than, equal to, or greater than 15,000 g/mol; 20,000 g/mol; 25,000 g/mol; 30,000 g/mol; 35,000 g/mol; 40,000 g/mol; 45,000 g/mol; 50,000 g/mol; 60,000 g/mol; 70,000 g/mol; 80,000 g/mol; 90,000 g/mol; 100,000 g/mol; 200,000 g/mol; 500,000 g/mol; 700,000 g/mol; 1,000,000 g/mol; 2,000,000 g/mol; 3,000,000 g/mol; 4,000,000 g/mol; 5,000,000 g/mol; or 6,000,000 g/mol.

The fibers of the nonwoven fibrous layer can have any suitable diameter. The fibers can have a median fiber diameter of 0.1 to 10 microns, 0.3 to 6 microns, 0.3 to 3 microns, or in some embodiments, less than, equal to, or greater than 0.1 microns, 0.2 microns, 0.3 microns, 0.4 microns, 0.5 microns, 0.6 microns, 0.7 microns, 0.8 microns, 0.9 microns, 1 micron, 1.5 microns, 2 microns, 2.5 microns, 3 microns, 3.5 microns, 4 microns, 4.5 microns, 5 microns, 5.5 microns, 6 microns, 6.5 microns, 7 microns, 7.5 microns, 8 microns, 8.5 microns, 9 microns, 9.5 microns, 10 microns, 11 microns, 12 microns, 13 microns, 14 microns, 15 microns, 16 microns, 17 microns, 18 microns, 19 microns, 20 microns, 22 microns, 25 microns, 27 microns, 30 microns, 32 microns, 35 microns, 37 microns, 40 microns, 42 microns, 45 microns, 47 microns, 53 microns, 47 microns, 25 microns, 8 microns, 5 microns, 6 microns, 5 microns, 7 microns, 8 microns, 7 microns, 8 microns, 5 microns, 8 microns, 7 microns, 8 microns, and 7 microns, 55 microns, 57 microns or 60 microns.

Optionally, at least some of the plurality of fibers in the nonwoven fibrous layer are physically bonded to each other or to the heterogeneous filler. Generally, this has the effect of increasing the stiffness and/or strength of the acoustic article, which may be desirable in certain applications. Conventional bonding techniques include the use of heat and pressure applied in a point bonding process or by passing the nonwoven fibrous layer through smooth calender rolls. However, such processes may result in deformation of the fibers or compaction of the fiber web, which may or may not be desirable.

Alternatively, attachment between fibers or between fibers and heterogeneous filler may be achieved by incorporating a binder into the nonwoven fibrous layer. In some embodiments, the binder is provided by a liquid or solid powder. In some embodiments, the binder is provided by short binder fibers, which may be injected into the polymer stream during the meltblowing process. The binder fibers have a melting temperature that is significantly lower than the melting temperature of the remaining structural fibers and act to secure the fibers to one another.

Other methods for bonding fibers to one another are set forth in, for example, U.S. patent publication 2008/0038976(Berrigan et al) and U.S. patent 7,279,440(Berrigan et al). In one technique, the collected fiber web and fibers are subjected to a controlled heating and quenching operation that includes forcibly passing a stream of gas through the web, the gas stream being heated to a temperature sufficient to soften the fibers sufficiently to cause the fibers to bond together at fiber intersections, wherein the period of time during which the heated stream is applied is extremely short without completely melting the fibers; and immediately thereafter forcibly passing a stream of gas at a temperature at least 50 ℃ lower than the heated stream through the web to quench the fibers.

In some embodiments, the fibrous polymer has a high glass transition temperature, which may be preferred when the acoustic article is to be used in a high temperature environment. Certain nonwoven fibrous layers shrink significantly when heated to even moderate temperatures in subsequent processing or use, such as when used as insulation. When meltblown fibers comprise thermoplastic polyesters or their copolymers, and particularly those of semi-crystalline nature, such shrinkage can be problematic for some applications.

In some embodiments, a nonwoven fibrous layer is provided having at least one densified layer adjacent to a layer that is not densified. Either or both of the dense layer and the non-dense layer may be loaded with heterogeneous fillers. The dense layer may provide a variety of potential benefits. Such a layer, if sufficiently dense, may be disposed on the outermost surface of the acoustic article and act as a barrier to prevent the heterogeneous filler particles from escaping from the acoustic article. Densification of the nonwoven layer may also enhance structural integrity, provide dimensional stability, and enable the nonwoven layer to be molded into a three-dimensional shape. Advantageously, the molded acoustic article can assume a customized shape that fully utilizes its disposal space.

In some embodiments, the densified layer and adjacent non-densified layers are prepared from an integral nonwoven fibrous layer that initially has a uniform density, and then subjected to heat and/or pressure to produce a densified layer on its outermost surface. Methods of producing a densified layer on a nonwoven fibrous web, as well as additional options and advantages, are described in co-pending international patent application PCT/CN2017/101857(You et al).

In some embodiments, the dense layer has a uniform distribution of polymer fibers throughout the layer. Alternatively, the distribution of the polymeric fibers may vary across the major surface of the nonwoven fibrous layer. Such a configuration may be appropriate where, for example, the acoustic response is dependent on its position along the major surface.

The median fiber diameter of the dense and non-dense portions of the nonwoven fibrous layer may be substantially preserved. The above-described process generally enables the fibers to fuse to one another in the densified regions without significantly melting the fibers. In most cases, it is preferable to avoid melting the fibers to maintain the acoustic benefits derived from the surface area within the dense layer of the nonwoven fibrous layer.

Other nonwoven fibrous layers that may be used in the acoustic article include recycled textile fibers, sometimes referred to as low quality fibers. The recycled textile fibers can be formed into a nonwoven structure using an airlaid process in which air walls blow the fibers onto a perforated collection drum having a negative pressure within the drum. Air is pulled through the drum and the fibers are collected outside the drum where they are removed as a fibrous web. Due to the air turbulence, the fibers do not have any ordered orientation and therefore may exhibit relatively uniform strength characteristics in all directions.

One or more additional fiber populations may be incorporated into the nonwoven fibrous layer. The difference between fiber populations may be based on, for example, composition, median fiber diameter, and/or median fiber length.

For example, the nonwoven fibrous layer can include a plurality of first fibers having a median diameter of up to 10 microns and a plurality of second fibers having a median diameter of at least 10 microns. Fibers having different diameters may be advantageous for various reasons. Including thicker second fibers may improve the resiliency, crush resistance of the nonwoven fibrous layer and help maintain the overall loft of the web. The second fibers may be made from any of the polymeric materials previously described with respect to the first fibers and may be made from a melt blown or melt spun process.

In some embodiments, the second fibers are staple fibers alternating with the plurality of first fibers. These staple fibers may be provided as crimped fibers to improve the overall bulk of the fibrous web. The staple fibers may include binder fibers, which may be made from any of the above-described polymer fibers. Structural fibers may include, but are not limited to, any of the above-mentioned polymeric fibers as well as inorganic fibers, such as ceramic fibers, glass fibers, and metal fibers; and organic fibers (such as cellulose fibers).

The first fibers and the second fibers may independently have any of the compositions, structures, and characteristics previously described with respect to nonwoven fibrous layers comprising only a single fiber group. Additional features and benefits associated with the combination of the first and second fibers are described in U.S. patent 8,906,815(Moore et al).

The nonwoven fibrous layer can provide a number of technical advantages, at least some of which are unexpected. One advantage derives from the surface area of the nonwoven fibrous layer. The retention of the surface area provided by the fibers in combination with the heterogeneous filler having a high surface area enables even a relatively small weight (or thickness) of the acoustic material to provide a high level of performance as a sound absorber.

These nonwovens can also be made of fibrous materials that can withstand high temperatures, where conventional insulation materials can thermally degrade or fail. This applies to insulation in automotive and aerospace applications, which typically operate in environments that are not only noisy, but can reach extreme temperatures. These materials may be highly elastic such that they can be compressed and rebound to fill the available space within a given cavity. Finally, as noted above, these nonwoven fibrous layers may also be shaped to fit a substrate or cavity in a given application, if desired, to facilitate installation by an operator.

In some embodiments, the porous layer consists of a perforated film. The perforated membrane consists of a solid layer having a plurality of perforations or through-holes extending through the solid layer. The perforations allow fluid communication between the air spaces on opposite sides of the wall. Microporous membranes are perforated membranes having openings on the order of microns in diameter. These perforated membranes are typically made of polymeric materials, but may be made of other materials, including metals.

Like the nonwoven fibrous layer, the perforated film may have a configuration that makes it sound absorptive. Conceptually, a plug of air resides within the perforation and acts as a mass component within the resonant system. These mass components vibrate within the perforations and dissipate acoustic energy due to friction between the plug of air and the walls of the perforations. If the perforated membrane is placed close to the air cavity, dissipation of acoustic energy may also occur by destructive interference at the perforation entrance of sound waves reflected back into the perforation from the opposite direction. The absorption of acoustic energy occurs with substantially zero net flow of fluid through the acoustic article.

The perforations may have dimensions (e.g., perforation diameter, shape, and length) suitable to achieve the desired acoustic performance in a given frequency range. Acoustic performance can be measured, for example, by reflecting sound off of the perforated membrane and characterizing the reduction in acoustic intensity compared to results from a control sample.

In the drawings, the perforations are provided along the entire surface of the perforated film. Alternatively, the wall may be only partially perforated-i.e. perforated in some areas but non-perforated in other areas.

The perforated film can be made relatively thin compared to other porous layers, while maintaining its sound absorbing properties. The overall thickness of the perforated membrane can be 1 micron to 2 millimeters, 30 microns to 1.5 millimeters, 50 microns to 1 millimeter, or in some embodiments, less than, equal to, or greater than 1 micron, 2 microns, 5 microns, 10 microns, 20 microns, 30 microns, 40 microns, 50 microns, 100 microns, 200 microns, 500 microns, 700 microns, 1 millimeter, 1.1 millimeters, 1.2 millimeters, 1.5 millimeters, 1.7 millimeters, or 2 millimeters. In embodiments where thickness is not limiting, perforated sheets are used in place of the perforated film, wherein the perforated sheets have a thickness of at most 3 millimeters, 5 millimeters, 10 millimeters, 30 millimeters, 50 millimeters, 100 millimeters, or even 200 millimeters.

The perforations may have a variety of different shapes and sizes, and may be produced by any of a variety of molding, cutting, or stamping operations. The cross-section of the perforations may be, for example, circular, square or hexagonal. In some embodiments, the perforations consist of a series of elongated slits.

Although the perforations may have a consistent diameter along their length, it is possible to use perforations having a conical truncated shape, a truncated pyramidal shape, or otherwise having at least some tapered sidewalls along their length, as described in co-pending international patent application PCT/US18/56671(Lee et al; see, e.g., fig. 15 a-15 c and associated description). The taper in the sidewalls may be selected to accommodate heterogeneous packing within the through-holes. The tapering of the perforations also narrows one side of the apertures, a feature that may help prevent heterogeneous filler from escaping through the perforated film.

Optionally and as shown in the figures, the perforations have a generally consistent spacing relative to one another. If so, the perforations may be arranged in a two-dimensional grid pattern or a staggered pattern. The perforations may also be arranged in a random configuration on the wall, wherein the perforation positions are irregular, but nevertheless the perforations are evenly distributed on the wall on a macroscopic scale.

In some embodiments, the perforations are substantially uniform in diameter along the wall. Alternatively, the perforations may have some distribution of diameters. In any case, the perforations can have an average narrowest diameter that is less than, equal to, or greater than 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 120, 150, 170, 200, 250, 300, 350, 400, 450, 500, 600, 700, 800, 900, 1000, 1500, 2000, 2500, 3000, 4000, or 5000 microns. For clarity, the diameter of a non-circular hole is defined herein as the diameter of a circle having an area equivalent to the non-circular hole in plan view.

The porosity of a perforated film is a dimensionless quantity that represents the portion of a given volume that is not occupied by the film. In a simplified representation, the perforations may be assumed to be cylindrical, in which case the porosity is rather similar to the percentage of the surface area of the wall in plan view that is replaced by the perforations. In exemplary embodiments, the wall may have a porosity of 0.1% to 80%, 0.5% to 70%, or 0.5% to 60%. In some embodiments, the porosity of the wall is less than, equal to, or greater than 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.7%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, or 80%.

The membrane material may have a modulus (e.g., flexural modulus) that is suitably tuned to vibrate in response to incident sound waves having an associated frequency. Together with the vibration of the air plug within the perforation, the local vibration of the wall itself may dissipate acoustic energy and enhance transmission losses through the acoustic article. The flexural modulus of the wall, which reflects the stiffness, also directly affects its acoustic transfer impedance.

In some embodiments, the film comprises a material having a flexural modulus of 0.2GPa to 10GPa, 0.2GPa to 7GPa, 0.2GPa to 4GPa, or in some embodiments less than, equal to, or greater than 0.2GPa, 0.3GPa, 0.4GPa, 0.5GPa, 0.7GPa, 1GPa, 2GPa, 3GPa, 4GPa, 5GPa, 6GPa, 7GPa, 8GPa, 9GPa, 10GPa, 12GPa, 15GPa, 17GPa, 20GPa, 25GPa, 30GPa, 35GPa, 40GPa, 50GPa, 60GPa, 70GPa, 80GPa, 90GPa, 100GPa, 120GPa, 140GPa, 160GPa, 180GPa, 200GPa, or 210 GPa.

Suitable thermoplastic polymers typically have a flexural modulus in the range of 0.2GPa to 5 GPa. In some embodiments, the addition of fibers or other fillers can increase the flexural modulus of these materials to 20 GPa. Thermoset polymers generally have a flexural modulus in the range of 5GPa to 40 GPa. Useful polymers include polyolefins, polyesters, fluoropolymers, polylactic acid, polyphenylene sulfide, polyacrylates, polyvinyl chloride, polycarbonates, polyurethanes, and blends thereof.

Exemplary perforated film configurations, methods of making the same, and acoustical performance characteristics are described in U.S. Pat. Nos. 6,617,002(Wood), 6,977,109(Wood), and 7,731,878(Wood), 9,238,203(Scheibner et al), and U.S. Pat. publication No. 2005/0104245 (Wood).

In some embodiments, the porous layer consists of a bed of particles. The particle bed may be made entirely of heterogeneous packing. Alternatively, the particulate bed may comprise at least some particles that are not heterogeneous packing. The particulate bed may comprise any of the heterogeneous fillers, zeolites, Metal Organic Frameworks (MOFs), perlite, alumina, glass beads, and mixtures thereof described herein. No particles, some particles, or all particles in the particle bed may be acoustically active.

The porosity of the particulate bed may be adjusted based in part on the size distribution of the particles. The particles may be in the range of 0.1 microns to 2000 microns, 5 microns to 1000 microns, 10 microns to 500 microns, or in some embodiments, less than, equal to, or greater than 0.1 microns, 0.5 microns, 1 micron, 2 microns, 5 microns, 10 microns, 20 microns, 30 microns, 40 microns, 50 microns, 70 microns, 100 microns, 200 microns, 300 microns, 400 microns, 500 microns, 700 microns, 1000 microns, 1500 microns, or 2000 microns.

The aforementioned porous layers can generally be characterized by the ratio of the frequency space of their specific acoustic impedance or pressure differential across the layer to the effective velocity of the layer surface in proximity. For example, in a theoretical model based on a rigid membrane with perforations, the velocities are generated by air inflow and outflow holes. If the membrane is flexible, the movement of the wall may contribute to the acoustic impedance calculation. The specific acoustic impedance generally varies with frequency and is a complex number, reflecting the fact that pressure and velocity waves can be out of phase with each other.

As used herein, a particular acoustic impedance is measured in units of MKS Rayl, where 1MK SRayl equals 1 Pascal seconds per meter (Pa s m)^-1) Or, equivalently, 1 Newton-seconds per cubic meter (N.s.m)^-3) Or alternatively, 1kg · s^-1·m^-2。

The porous layer may also be characterized by its transfer resistance. For perforated films, the transfer impedance is the difference between the acoustic impedance of the incident side of the porous layer and the acoustic impedance that would be observed in the absence of the perforated film (i.e., the acoustic impedance of the air cavity alone).

Flow resistance is a low frequency limit of the transfer impedance. Experimentally, this can be estimated by blowing known low velocity air at the porous layer and measuring the pressure drop associated therewith. The flow resistance may be determined as the measured pressure drop divided by the velocity.

For embodiments including a perforated membrane, the flow resistance through the perforated membrane alone (without the heterogeneous filler) may be from 50MKS Rayl to 8000MKS Rayl, from 100MKS Rayl to 4000MKS Rayl, or from 400MKS Rayl to 3000MKS Rayl. In some embodiments, the flow resistance through the perforated membrane can be less than, equal to, or greater than 50MKS Rayl, 60MKS Rayl, 70MKS Rayl, 80MKS Rayl, 90MKS Rayl, 100MKS Rayl, 120MKS Rayl, 140MKS Rayl, 160MKS Rayl, 180MKS Rayl, 200MKS Rayl, 250MKS Rayl, 300MKS Rayl, 350MKS Rayl, 400MKS Rayl, 450MKS Rayl, 500MKS Rayl, 550MKS Rayl, 600MKS Rayl, 650MKS Rayl, 700MKS Rayl, 750MKS Rayl, 800MKS Rayl, 850MKS Rayl, 900MKS Rayl, 950MKS Rayl, 1000MKS Rayl, 1100MKS Rayl, 1200MKS Rayl, 1300MKS RaKS Rayl, 1400MKS RaKS Rayl, 1500MKS Rayl, 1600MKS Rayl, 1700MKS RaK Rayl, 4000MKS RaK, 3000MKS, MKS Rayl, 3000MKS Rayl, 150MKS Rayl, 3000MKS Rayl, 150MKS Rayl, 150MKS RaK Rayl, 150MKS Rayl, 3000MKS Rayl, 150MKS Rayl, M150 MKS Rayl, M150 MKS Rayl, M K, M150 MKS Rayl, M K, M150 MKS Rayl, K, M K, K, K, K, K, K, K, 7000MKS Rayl, 7500MKS Rayl or 8000MKS Rayl.

For embodiments including a nonwoven fibrous layer, the flow resistance through the nonwoven fibrous layer alone (without the alloplastic filler) can be from 50MKS Rayl to 8000MKS Rayl, from 100MKS Rayl to 4000MKS Rayl, or from 400MKS Rayl to 3000MKS Rayl. In some embodiments, the flow resistance through the nonwoven fibrous layer can be less than, equal to, or greater than 50MKS Rayl, 60MKS Rayl, 70MKS Rayl, 80MKS Rayl, 90MKS Rayl, 100MKS Rayl, 120MKS Rayl, 140MKS Rayl, 160MKS Rayl, 180MKS Rayl, 200MKS Rayl, 250MKS Rayl, 300MKS Rayl, 350MKS Rayl, 400MKS Rayl, 450MKS Rayl, 500MKS Rayl, 550MKS Rayl, 600MKS Rayl, 650MKS Rayl, 700MKS Rayl, 750MKS Rayl, 800MKS Rayl, 850MKS Rayl, 900MKS Rayl, 950MKS Rayl, 1000MKS Rayl, 1100MKS Rayl, 1200MKS Rayl, 1400MKS Rayl, 1500MKS Rayl, 1600MKS Rayl, 1700MKS Rayl, 4000MKS Rayl, 3000MKS, 7000MKS Rayl, 7500MKS Rayl or 8000MKS Rayl.

The flow resistance through the overall acoustic article may be from 100MKS Rayl to 8000MKS Rayl, 120MKS Rayl to 5000MKS Rayl, or 150MKS Rayl to 4000MKS Rayl. In some embodiments, the flow resistance through the overall acoustic article is less than, equal to, or greater than 10MKS Rayls, 20MKS Rayls, 30MKS Rayls, 40MKS Rayls, 50MKS Rayls, 70MKS Rayls, 100MKS Rayls, 120MKS Rayls, 150MKS Rayls, 180MKS Rayls, 200MKS Rayls, 250MKS Rayls, 300MKS, 400MKS Rayls, 500MKS Rayls, 600MKS Rayls, 700MKS Rayls, 1000MKS Rayls, 1100MKS, 1200MKS Rayls, 1500MKS, 1700MKS, 2000MKS, 2500MKS Rayls, 3000MKS Rayls, 3500MKS Rayls, 4000MKS, 4500, 5500, 7500, 8000MKS, 7000MKS Rayls, or 7000MKS Rayls.

Heterogeneous packing

The acoustic articles described herein may incorporate one or more heterogeneous fillers capable of providing enhanced acoustic properties. Each of the heterogeneous fillers mentioned in the above embodiments may independently have different properties, as described below.

Exemplary heterogeneous fillers include porous and/or fine heterogeneous fillers. Porous and/or fine fillers that may be incorporated into the provided acoustic articles include particles of clay, diatomaceous earth, graphite, glass bubbles, polymeric fillers, non-layered silicates, plant-based fillers, and mixtures thereof. The filler particles can have various shapes including flake, powder, and fiber shapes. In some cases, the particles may be primary particles that agglomerate (i.e., aggregate) into larger particles.

Clay fillers are widely available and commonly used in rubber compounding applications to provide reinforcement and improved physical or processing characteristics. As used herein, clay includes any of a variety of hydrated aluminosilicate minerals that occur in nature and generally exhibit a stacked platelet-like microstructure. The main component of clay is kaolin. Kaolin (sometimes referred to as kaolinite) is characterized by alternating layers of alumina and silica. Another useful clay is bentonite, an aluminosilicate clay consisting primarily of montmorillonite. Other clays may be purely synthetic and are not obtained from natural sources. One such synthetic clay is LAPONITE, which consists of layers of silica, octahedrally coordinated magnesium and alkali metal ions.

In some cases, the clay filler may be converted to other materials by a heating process known as calcination. The calcination temperature may be in the range of 800 ℃ to 1000 ℃. At these temperatures, the hydration water in the clay can be driven off. When fully calcined, the individual mineral platelets become fused together and the clay may become relatively inert.

The heterogeneous filler may also include non-layered silicate materials. Non-layered silicates include alkali metal silicates, alkaline earth metal silicates, non-zeolitic aluminosilicates, and geopolymers. Such materials may or may not be zeolites. An example of a non-zeolitic aluminosilicate material is nepheline, which is an aluminosilicate of sodium and potassium.

Diatomaceous earth is made from fossil remains of tiny aquatic organisms called diatoms. These fossil remains are composed primarily of silica, but also contain small amounts of alumina and iron oxide. In the filler form, the diatomaceous earth is a powder having a polydisperse particle size distribution generally in the range of 10 microns to 200 microns. Optionally, the diatomaceous earth may be mechanically treated by grinding or the like to reduce its median particle size. Similar to the clay materials described above, the diatomaceous earth may be calcined to remove impurities and undesirable volatile components. Chemical treatment may also be used to remove impurities.

The graphite filler may be made of expanded graphite, unexpanded graphite, or mixtures thereof. Graphite is a crystalline allotrope form of carbon, available from natural sources, and can also be synthetically produced by heating petroleum coke in a furnace to about 3000 ℃. Graphite is not expanded in its naturally occurring form. By in sp containing graphite²Intercalation compounds (such as sulphuric acid) between the hybrid carbon sheets, which can convert the graphite into expanded graphite. The graphite particles or flakes may then be heated to a temperature above the exfoliation temperature of graphite (typically between 150 ℃ and 300 ℃), which causes the graphite layers to separate from each other and expand to several times their original thickness.

Although not necessarily graphite, other forms of porous carbon may be used as the heterogeneous filler. Useful porous carbons include activated carbon and vermiculite carbon fillers, which have unique acoustic properties based on their different porosities. Details regarding these materials are described in co-pending international patent application PCT/US18/56671(Lee et al), and the disclosure of the porous carbon filler thereof is expressly incorporated herein by reference.

The porous polymeric fillers may have a wide range of porosities, making them suitable for sound absorption at frequencies below 1000 Hz. These absorption characteristics have been observed in many polymer compositions, including polypropylene, divinylbenzene-maleic anhydride, styrene-divinylbenzene, and acrylic polymers. Porous polymeric fillers include open cell foams, closed cell foams, and combinations thereof. Examples of fillers comprised of open cell polymeric foams include polyolefin foam fillers available under the trade name ACCUREL MP from the winning Industries of Essen, Germany (Evonik Industries AG in Essen, Germany).

In some cases, the filler may be agglomerated (i.e., coagulated). The primary filler particles may aggregate with each other through particle-to-particle interactions. Such interaction may result from secondary adhesive or electrostatic forces. In some embodiments, at least some of the polymer particles sinter together under slight pressure and heat to form agglomerates. The heat may be provided using any known method, including steam, high frequency radiation, infrared radiation, or hot air. Aggregation of the particles may also be achieved by the use of a binder or adhesive.

The particle aggregates may be regularly shaped or irregularly shaped. Preferably, the aggregates are held together in the intended use, with most of the particles retaining their specified size, but not necessarily being "crush resistant". In some embodiments, the pores within the acoustic article may be completely carried by the created fracture spaces between the primary filler particles.

The plant-based filler includes a cellulosic filler, such as wood flour. Wood flour consists of fine wood particles, typically obtained from wood-processing operations such as sawing, milling, planing, wiring, drilling, and sanding. Other plant-based fillers include flax, jute, sisal, hemp, wheat and rice straw, rice hulls, ash, starch and lignin. Some of these fillers are fibrous in nature and have beneficial effects as lightweight reinforcing fillers in composites. The cork and waste shells of nuts contain cellulose and lignin. The plant-based filler can be highly porous.

Other possible heterogeneous fillers may include bio-based fillers that are not plant-based. These fillers include filler particles derived from waste streams such as chicken feathers or shells. The filler may also originate from other biological products than fungi, sponges and plants.

The heterogeneous fillers described above can independently have any suitable median particle size. When incorporated into a given porous layer, the filler particles may be sized to produce fracture voids having a desired size distribution. Such voids may represent spaces between filler particles, nonwoven fibers (if present), polymeric or inorganic struts (if present), or a combination thereof. The median particle size of the filler particles is a parameter that can also be used to adjust the permeability (and overall flow resistance) of the acoustic article.

The heterogeneous filler can have a median particle size of from 1 micron to 1000 microns, from 1 micron to 100 microns, from 100 microns to 1000 microns, from 100 microns to 800 microns, or in some embodiments, less than, equal to, or greater than 1 micron, 2 microns, 3 microns, 4 microns, 5 microns, 7 microns, 10 microns, 15 microns, 20 microns, 25 microns, 30 microns, 35 microns, 40 microns, 45 microns, 50 microns, 60 microns, 70 microns, 80 microns, 90 microns, 100 microns, 150 microns, 200 microns, 250 microns, 300 microns, 350 microns, 400 microns, 450 microns, 500 microns, 600 microns, 700 microns, 800 microns, 900 microns, or 1000 microns.

The heterogeneous filler disposed within a given porous layer may have any suitable particle size distribution to provide a desired acoustic response. The particle size distribution may be monodisperse or polydisperse. The particle size distribution may be unimodal or multimodal, regardless of how much of the heterogeneous filler composition is present in the porous layer. The Dv50/Dv90 particle size ratio of the heterogeneous filler can be 0.25 to 1, 0.3 to 0.9, 0.4 to 0.8, or, in some embodiments, less than, equal to, or greater than 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, or 1.

Dv50 and Dv90 may be defined by volume weighted size distribution as determined using laser light scattering. Assuming a volume-weighted distribution, Dv50 refers to the median particle diameter, and Dv90 refers to the particle diameter at which 90% of the total volume of the filler particles have a smaller diameter. Such distributions can also be tuned by excluding particles of certain diameters using test sieving.

The heterogeneous fillers described above can independently have any suitable specific surface area. Heterogeneous fillers may exhibit high surface areas based on their porous nature. Having a high surface area may reflect the high complexity and tortuosity of the pore structure, resulting in greater internal reflection and energy transfer to the solid structure through frictional losses. Advantageously, this may be manifested as an absorption of airborne noise.

The heterogeneous filler may have a specific surface area of 0.1m²G to 100m²/g、1m²G to 100m²/g、100m²G to800m²/g、0.1m²G to 800m²A/g, or in some embodiments, less than, equal to, or greater than 0.1m²/g、0.2m²/g、0.5m²/g、0.7m²/g、1m²/g、2m²/g、5m²/g、10m²/g、20m²/g、50m²/g、100m²/g、120m²/g、150m²/g、200m²/g、250m²/g、300m²/g、350m²/g、400m²/g、450m²/g、500m²/g、6000m²/g、700m²/g、800m²/g、900m²/g、1000m²/g、1500m²/g、2000m²/g、2500m²/g、3000m²/g、3500m²/g、4000m²/g、4500m²/g、5000m²/g、6000m²/g、7000m²/g、8000m²/g、9000m²In g or 10,000m²/g。

Surface area can be measured based on the adsorption of nitrogen or krypton onto the surface of a given material at liquid nitrogen temperature. These measurements can be performed using an instrument known as a gas adsorption analyzer. In this measurement, an isotherm (volume of gas adsorbed per unit mass at standard temperature and pressure versus relative pressure) can be generated by dosing a gas to a sample. The specific surface area can then be calculated by applying a modified form of the Langmuir formula, known as the brunauer-emert-taylor (BET) formula, to the isotherm. This value is referred to as the BET specific surface area. In some embodiments, the specific surface area is BET specific surface area, as described herein.

In some embodiments, the heterogeneous filler is characterized by extremely fine pores. The heterogeneous filler can have an average pore size of 0.4 nm to 50 microns, 1nm to 40 microns, 2.5 nm to 30 microns, or in some embodiments, less than, equal to, or greater than 0.1 nm, 0.2 nm, 0.3 nm, 0.4 nm, 0.5 nm, 1nm, 1.2 nm, 1.5 nm, 1.7 nm, 2nm, 3 nm, 4 nm, 5nm, 7 nm, 10nm, 15 nm, 20nm, 25 nm, 30 nm, 40 nm, 50nm, 70 nm, 100nm, 150 nm, 200nm, 250 nm, 300nm, 350 nm, 400nm, 450 nm, 500nm, 600 nm, 700 nm, 800 nm, 900 nm, 1 micron, 2 microns, 3 microns, 4 microns, 5 microns, 7 microns, 10 microns, 15 microns, 20 microns, 25 microns, 30 microns, 35 microns, 40 microns, 45 microns, or 50 microns.

Heterogeneous filler particles can have pore sizes much smaller than conventional fillers used in acoustic applications. For example, the diameter of the smallest pores of certain polymers with intrinsic microporosity may be less than 2 nm. In contrast, calcined diatomaceous earth contains pores that are typically hundreds of nanometers to tens of micrometers. Generally, the heterogeneous filler may have a minimum pore diameter of at most 10000nm, at most 5000nm, at most 2000nm, at most 1000nm, at most 500nm, at most 400nm, at most 300nm, at most 200nm, at most 100nm, at most 50nm, at most 20nm, at most 10nm, at most 5nm, at most 2, and at most 1 nm.

The heterogeneous filler may have a thickness of 0.01cm³G to 5cm³Total pore volume in g. In some embodiments, the total pore internal volume can be less than, equal to, or greater than 0.01cm³/g、0.02cm³/g、0.05cm³/g、0.07cm³/g、0.1cm³/g、0.2cm³/g、0.3cm³/g、0.4cm³/g、0.5cm³/g、0.7cm³/g、1cm³/g、1.2cm³/g、1.4cm³/g、1.6cm³/g、1.8cm³/g、2cm³/g、2.5cm³/g、3cm³/g、3.5cm³/g、4cm³/g、4.5cm³G or 5cm³/g。

The bonding of the heterogeneous filler to the porous layer may be facilitated by modifying the particle surface via a silane or other metal or metalloid complex. Depending on the functional groups present, intermolecular or intramolecular bonding to the layer can be achieved. The polymer heterogeneous filler (or aggregate containing polymer binder) can be modified in a number of ways, including various forms of grafting, solvent treatment, and electron beam irradiation. These modifications may also promote the adhesion of the particles to the porous layer.

Manufacturing method

Any of a variety of suitable manufacturing methods may be used to assemble the provided acoustic articles.

For embodiments in which the porous layer is a nonwoven fibrous web, the heterogeneous filler may be incorporated into the constituent fibers during or after the direct formation of the fibers. In the case of nonwoven fibrous webs made using, for example, a meltblown process, the heterogeneous filler may be transported and co-mixed with the molten polymer stream as it is blown onto a rotating collection drum. The heterogeneous filler may be entrained within a stream of heated air that converges with the heated air used to attenuate the meltblown fibers. An exemplary process is described in U.S. Pat. No. 3,971,373 (Braun). In a similar manner, the particles of the heterogeneous filler may be conveyed to an airlaid process, such as a process for making a porous layer made of recycled textile fibers (i.e., low quality fibers).

The heterogeneous filler may also be added after the nonwoven fibrous layer is made. For example, the porosity of the nonwoven fibrous layer may enable the heterogeneous filler to penetrate into its crevice spaces by uniformly dispersing the heterogeneous filler into a liquid medium (such as water) and then roll or slurry coating the particle-filled medium onto the nonwoven porous layer. As an alternative to using a liquid medium, the heterogeneous filler may be entrained in a gas stream (such as an air stream) and then the stream directed toward the nonwoven layer to fill the nonwoven layer.

Alternatively, the heterogeneous filler may also be embedded in the porous layer by stirring. In one embodiment of the method, a layer of nonwoven fibers is placed on a flat surface and a cylindrical conduit is placed thereon to define a coating area. Particles of the heterogeneous filler can then be poured into the conduit and the assembly shaken until the particles completely migrate through their open pores into the nonwoven structure. A similar approach can be used for porous layers consisting of open-cell foams.

Construction of the multilayer acoustic article and attachment to the substrate may include one or more lamination steps. Lamination may be accomplished using adhesive bonding. Preferably, any adhesive layer used does not prevent sound penetration into the absorbent layer. Alternatively or in combination, physical entanglement of the fibers can be used to improve interlayer adhesion. Mechanical bonds (using, for example, fasteners) are also possible.

The acoustic article may also be edge sealed to prevent particles from escaping. Such constraints may be implemented by: densifying the edge, filling the edge with resin, quilting the acoustic article, or completely encapsulating the acoustic article in a sleeve to prevent migration or expulsion of particles. An edge seal may be desirable to improve product life, durability, and ease of handling and installation. The edge sealing may also be performed for aesthetic reasons.

In yet another embodiment, the nonwoven fibrous layers may be sequentially sprayed with binder and then with filler particles. In some cases, the adhesive may be provided in the form of hot melt fibers.

Although not intended to be limiting, various exemplary embodiments are listed below:

1. an acoustic article, comprising: a porous layer; and a heterogeneous filler contained in the porous layer, wherein the heterogeneous filler has a median particle size of 1 to 100 microns and 0.1m²G to 100m²A specific surface area per gram, wherein the acoustic article has a flow resistance of 100MKS Rayls to 8000MKS Rayls.

2. An acoustic article, comprising: a porous layer; and a heterogeneous filler contained in the porous layer, wherein the heterogeneous filler has a median particle size of 100 to 800 microns and 100m²G to 800m²A specific surface area per gram, wherein the acoustic article has a flow resistance of 100MKS Rayls to 8000MKS Rayls.

3. An acoustic article, comprising: a porous layer; and a heterogeneous filler contained in the porous layer, wherein the heterogeneous filler has a median particle size of 100 to 1000 microns and 1m²G to 100m²A specific surface area per gram, wherein the acoustic article has a flow resistance of 100MKS Rayls to 8000MKS Rayls.

4. The acoustic article of any of embodiments 1-3, wherein the heterogeneous filler comprises clay, diatomaceous earth, graphite, glass bubbles, polymeric fillers, non-layered silicates, plant-based fillers, or combinations thereof.

5. The acoustic article of embodiment 4, wherein the heterogeneous filler comprises a non-layered silicate, and wherein the non-layered silicate is an alkali metal silicate, an alkaline earth metal silicate, a non-zeolitic aluminosilicate, or a geopolymer.

6. The acoustic article of embodiment 4, wherein the heterogeneous filler comprises graphite, and wherein the graphite is unexpanded graphite.

7. The acoustic article of embodiment 4, wherein the heterogeneous filler comprises a porous polymeric filler, and wherein the porous polymeric filler comprises a polyolefin foam, polyvinylpyrrolidone, divinylbenzene-maleic anhydride, styrene-divinylbenzene, or polyacrylate.

8. The acoustic article of embodiment 4, wherein the heterogeneous filler comprises a plant-based filler, and wherein the plant-based filler comprises wood flour.

9. An acoustic article, comprising: a porous layer; and a heterogeneous filler contained in the porous layer, wherein the heterogeneous filler comprises diatomaceous earth, a plant-based filler, non-expanded graphite, a polyolefin foam, or a combination thereof, the heterogeneous filler having a median particle size of 1 to 1000 microns and 0.1m²G to 800m²A specific surface area per gram, wherein the acoustic article has a flow resistance of 100MKS Rayls to 8000MKS Rayls.

10. The acoustic article of embodiment 9, wherein the heterogeneous filler comprises diatomaceous earth, and wherein the diatomaceous earth has a median particle size of 5 to 40 microns and 1m²G to 50m²Specific surface area in g.

11. The acoustic article of embodiment 10, wherein the heterogeneous filler has 1m²G to 40m²Specific surface area in g.

12. The acoustic article of embodiment 11, wherein the heterogeneous filler has 20m²G to 40m²Specific surface area in g.

13. Sound according to embodiment 9An article of manufacture, wherein the heterogeneous filler comprises a plant-based filler, and wherein the plant-based filler is a filler having a median particle size of 10 microns to 1000 microns and 0.1m²G to 200m²Specific surface area of wood flour/g.

14. The acoustic article of embodiment 13, wherein the wood flour has a median particle size of 50 micrometers to 800 micrometers and 0.1m²G to 50m²Specific surface area in g.

15. The acoustic article of embodiment 14, wherein the wood flour has a median particle size of 50 micrometers to 400 micrometers and 0.1m²G to 10m²Specific surface area in g.

16. The acoustic article of embodiment 9, wherein the heterogeneous filler comprises non-expanded graphite, and wherein the non-expanded graphite has a median particle size of 1 to 1000 microns and 0.1m²G to 500m²Specific surface area in g.

17. The acoustic article of embodiment 16, wherein the unexpanded graphite has a median particle size of 5 to 800 micrometers and 1m²G to 300m²Specific surface area in g.

18. The acoustic article of embodiment 17, wherein the unexpanded graphite has a median particle size of 100 to 1000 microns and 1m²G to 100m²Specific surface area in g.

19. The acoustic article of embodiment 9, wherein the heterogeneous filler comprises a polyolefin foam, and wherein the polyolefin foam has a median particle size of 100 to 1000 microns and 1m²G to 100m²Specific surface area in g.

20. The acoustic article of embodiment 19, wherein the polyolefin foam has a median particle size of 100 to 500 microns and 1m²G to 50m²Specific surface area in g.

21. The acoustic article of embodiment 20, wherein the polyolefin foam has a median particle size of 100 to 200 microns and 5m²G to 35m²Specific surface area in g.

22. The acoustic article of any of embodiments 1-21, wherein the heterogeneous filler is dispersed throughout the thickness of the porous layer.

23. The acoustic article of any of embodiments 1-22, wherein the heterogeneous filler has an open cell structure.

24. The acoustic article of any of embodiments 1-23, wherein the heterogeneous filler is agglomerated.

25. The acoustic article of any of embodiments 1-24, wherein the heterogeneous filler has a Dv50/Dv90 particle size ratio of 0.25 to 1.

26. The acoustic article of embodiment 25, wherein the heterogeneous filler has a Dv50/Dv90 particle size ratio of 0.3 to 0.9.

27. The acoustic article of embodiment 26, wherein the heterogeneous filler has a Dv50/Dv90 particle size ratio of 0.4 to 0.8.

28. The acoustic article of any of embodiments 1-27 wherein porous layer comprises a nonwoven fibrous layer having a plurality of fibers.

29. The acoustic article of embodiment 28 wherein the plurality of fibers have a median fiber diameter of 0.1 to 2000 microns.

30. The acoustic article of embodiment 29, wherein the plurality of fibers have a median fiber diameter from 5 microns to 1000 microns.

31. The acoustic article of embodiment 30, wherein the plurality of fibers have a median fiber diameter from 10 microns to 500 microns.

32. The acoustic article of any of embodiments 28 through 31, wherein the plurality of fibers comprises a polymer selected from the group consisting of polyolefin, polypropylene, polyethylene, polyester, polyethylene terephthalate, polybutylene terephthalate, polyamide, nylon 6, polyurethane, polybutylene, polylactic acid, polyphenylene sulfide, polysulfone, liquid crystal polymer, ethylene-vinyl acetate copolymer, polyacrylonitrile, cyclic polyolefin, or copolymers or blends thereof.

33. The acoustic article of any of embodiments 28-32, wherein the plurality of fibers comprises a thermoplastic semi-crystalline polymer.

34. The acoustic article of any of embodiments 28-33, wherein the plurality of fibers comprises meltblown fibers.

35. The acoustic article of any of embodiments 28-34, wherein the plurality of fibers comprises recycled textile fibers.

36. The acoustic article of any of embodiments 28-35, wherein the plurality of fibers comprise glass fibers or ceramic fibers.

37. The acoustic article of any of embodiments 28-36, wherein the plurality of fibers has an average fiber-to-fiber spacing of 0 millimeters to 1000 millimeters.

38. The acoustic article of embodiment 37, wherein the plurality of fibers has an average fiber-to-fiber spacing of 10 to 500 micrometers.

39. The acoustic article of embodiment 38, wherein the plurality of fibers has an average fiber-to-fiber spacing of 20 to 300 microns.

40. The acoustic article of any of embodiments 1-27 wherein the porous layer comprises an open-cell polymeric foam.

41. The acoustic article of any of embodiments 1-27 wherein the porous layer comprises a perforated film.

42. The acoustic article of embodiment 41, wherein the perforated film has a thickness of 1 micron to 10 centimeters.

43. The acoustic article of embodiment 42, wherein the perforated film has a thickness of 30 micrometers to 1 centimeter.

44. The acoustic article of embodiment 43, wherein the perforated film has a thickness of 50 microns to 5000 microns.

45. The acoustic article of any of embodiments 41-44, wherein perforations have an average narrowest diameter of 10 to 5000 microns.

46. The acoustic article of embodiment 45, wherein the perforations have an average narrowest diameter of 10 to 3000 microns.

47. The acoustic article of embodiment 46, wherein the perforations have an average narrowest diameter of between 20 microns and 1500 microns.

48. The acoustic article of any of embodiments 41-47 wherein the perforated membrane comprises a material having a flexural modulus of 0.2GPa to 10 GPa.

49. The acoustic article of embodiment 48 wherein the perforated membrane comprises a material having a flexural modulus of 0.2GPa to 7 GPa.

50. The acoustic article of embodiment 49 wherein the perforated membrane comprises a material having a flexural modulus of 0.2GPa to 4 GPa.

51. The acoustic article of any of embodiments 1-50, wherein the heterogeneous filler has an average interparticle spacing of 20 microns to 4000 microns.

52. The acoustic article of embodiment 51, wherein the heterogeneous filler has an average interparticle spacing of 50 microns to 2000 microns.

53. The acoustic article of embodiment 52, wherein the heterogeneous filler has an average interparticle spacing of 100 microns to 1000 microns.

54. The acoustic article of any of embodiments 1-53 wherein the porous layer filled with the heterogeneous filler has a solidity of 5% to 40%.

55. The acoustic article of any of embodiments 54 wherein the porous layer filled with the heterogeneous filler has a solidity of 8% to 35%.

56. The acoustic article of any of embodiments 55 wherein the porous layer filled with the heterogeneous filler has a solidity of 10% to 30%.

57. The acoustic article of any of embodiments 1-56, further comprising a plurality of Helmholtz resonators in contact with the porous layer.

58. A method of making an acoustic article, the method comprising: directly forming a nonwoven fibrous web; delivering a heterogeneous filler comprising diatomaceous earth, a plant-based filler, non-expanded graphite, a polyolefin foam, or a combination thereof into a nonwoven fibrous web while the nonwoven fibrous web is being directly formed, the heterogeneous filler having a median particle size of 1 to 1000 microns and 0.1m²G to 800m²A specific surface area per gram, wherein the acoustic article has a flow resistance of 100MKS Rayls to 8000MKS RaylsForce.

59. The method of embodiment 58, wherein the nonwoven fibrous web is formed directly using a melt blown or air laid process.

60. The method of any of embodiments 58 or 59, wherein the nonwoven fibrous web comprises a nonwoven fibrous web comprising a plurality of fibers with the heterogeneous filler at least partially embedded in the plurality of fibers.

61. A method of using the acoustic article of any of embodiments 1-57, the method comprising: an acoustic article is disposed adjacent to the surface to dampen vibrations of the surface.

62. A method of using the acoustic article of any of embodiments 1-57, the method comprising: an acoustic article is disposed adjacent the air chamber to absorb acoustic energy transmitted through the air chamber.

63. The method of using an acoustic article according to embodiment 62, wherein the absorbing of the acoustic energy occurs with substantially zero net flow of the fluid through the acoustic article.

Examples

Objects and advantages of this disclosure are further illustrated by the following non-limiting examples, but the particular materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit this disclosure.

All parts, percentages, ratios, and the like in the examples and the remainder of the specification are by weight unless otherwise indicated.

Table 1: material

Test method

Laser scattering particle size analysis

The size distribution of unsorted materials was measured by laser light scattering using Horiba LA-950V2 (Horiba ltd., Kyoto, Japan), dispersions of the given materials were prepared in water or Methyl Ethyl Ketone (MEK) with solids content of the respective materials ranging from about 0.3 wt% to 0.5 wt%, these dispersions were added to a measuring cell containing the respective solvents for the dispersions, this addition was carried out until the transmittance was between the recommended levels for the instrument.

Gas adsorption

Materials were analyzed using a Micromeritics ASAP 2020 (Micromeritics Instrument corp., Norcross, GA) GAs adsorption analyzer. The specimens were loaded into 1.27cm (1/2 inch) diameter ball-shaped Michco sample tubes and evacuated at 0.4Pa to 0.9Pa (3 microns to 7 microns Hg). The temperature and time of the exhaust gas are given in table 2. After nitrogen adsorption analysis, free space measurements were performed using helium, both at ambient temperature and 77K. Isotherms were measured at 77K using nitrogen and multipoint Brunauer-Emmet-Teller (BET) specific surface area calculations were performed over a pressure range between 0.025P/Po and 0.3P/Po. The exact point used for this calculation varies from sample to obtain a positive C value.

Bulk density

Bulk density was measured according to ASTM D7481-18, method A (bulk Density).

Skeleton density-hydrometer method

The skeletal density of the material was obtained using a macucpyc II 1340 TEC pycnometer (macs instruments, nokros, georgia, usa). Helium gas is used. Prior to obtaining the measurements, the instrument is calibrated for the measured volume using a specified trackable volume of metal spheres. Measurements were made using a 3.5cc cup and were made at ambient temperature.

Normal incidence acoustic absorption

Normal incidence acoustic Absorption was tested according to ASTM E1050-12 "Standard Test Method for Impedance and Absorption of Acoustic Materials Using a Tube, Two Microphones and a Digital Frequency Analysis System" for Acoustic Material Absorption. Using Bruel from Denmark&Company (Bruel)&(Denmark)) of the TYPE 4206 impedance tube kit (50 HZ-6.4 KHZ) (IMPEDANCE TUBE KIT (50 HZ-6.4 KHZ) TYPE 4206). The impedance tube was 63 millimeters (mm) in diameter and oriented vertically with the microphone positioned above the sample chamber. The normal incidence absorption coefficient is reported relative to one-third octave band frequency, abbreviated "α". Two samples were tested for each material and the average normal incidence absorption coefficient was recorded.

Air Flow Resistance (AFR) test 1

The Airflow Resistance of the 13.5cm (5.25 inch) samples was measured according to ASTMC-522-03 (re-approved in 2009) "Standard Test Method for air flow Resistance of Acoustic Materials". The instrument used was a "SIGMA static airflow resistance meter" (available from Mecanum, Sherbrooke, Canada) running the "SIGMA-X" software

Air Flow Resistance (AFR) test 2

A TSI.TModel m.8130 high speed automatic filter tester (commercially available from TSI limited (TSI Inc.)) operates with particle generation and measurement off. The flow rate was adjusted to 11.1 Liters Per Minute (LPM) and the two annular panels masked the measurement area to a circle of 41.3mm (1.625 inches) in diameter, providing equivalent results for a sample of 114.3mm (4.5 inches) in diameter measured at 85 LPM. The sample was placed on the lower circular plenum opening and engaged with the AFT. MKS pressure transducers (commercially available from MKS Instruments) in the apparatus measure in mm H₂Pressure drop in O. Using AFR [ MKS Rayls]71.035 × pressure drop (in mm H)₂O in units, measured at 85 LPM) converts the measurement to MKS Rayls.

Particle preparation

Particle agglomeration

Particle agglomeration was performed using the following materials: CLOISITE Na +, Laponite RD, iM30K, CLARCEL 78, TC307, and A4958. RHOPLEX VSR-50 was used as a binder. The weight percentages of acoustically active particles, binder, and Deionized (DI) water used to produce the agglomerated particles are listed in table 2.

Table 2: batch of particle agglomerates

The materials were mixed in a kitchen aid KFC3511GA food processor (whidipol Corporation, Benton Charter Township, MI). During the addition of the binder and the aqueous suspension, the material is broken up periodically using a spatula to ensure uniform distribution of the binder. After mixing, the aggregate was heated at 50 ℃ overnight to dry. Once dried, the condensate was classified using two wire screens (Retsch GmbH, Haan, Germany) the first having 1 millimeter (mm) openings and the second having 106 micron openings. Further acoustic testing was performed using any agglomerated material that passed through a 1mm screen and was blocked by a 106 micron screen.

Calcination of

CLARCEL 78 was loaded into a porcelain crucible and heated in a Lindberg/Blue M heavy box furnace (thermo fisher Scientific, Waltham, MA) at 600 ℃ under static air for twelve hours.

Grinding

The DVB-MA cellular copolymer material was milled using a rotary mill with a 2.0mm screen produced by IKA (Wilmington, NC). The abrasive material was then screened to isolate all materials of size <30 mesh (DVB-MA-1), 30x40 mesh (DVB-MA-2), 40x60 mesh (DVB-MA-3) and >60 mesh (DVB-MA-4) using U.S. standard test nos. 30, 40 and 60 wire mesh screens (ASTM E-11 standard; hogenotogler and co., inc., Columbia, MD) and a Meinzer II screen shaker (CSC Scientific Company, inc., Fairfax, VA) of fel farland, maryland, operating fifteen minutes prior to collecting the isolated material.

Geopolymer assemblies

A parent sodium GEOPOLYMER sample (geopolmer) was prepared by dissolving potassium hydroxide (85% in water, Millipore Sigma company of Burlington, massachusetts (Millipore Sigma, Burlington, MA)) in deionized water, followed by the addition of a proportional amount of sodium silicate ("STAR," PQ Crop, Malvern, PA) and metakaolin powder (Metamax, BASF Ludwigshafen, Germany). The mixture was stirred vigorously for about 10 minutes and then poured into a plastic container. The parent geopolymer was formulated in the following molar ratios: Si/Al 2.8, Na/Al 3, H₂O/Al 10. Polycondensation was carried out in a closed vessel in a laboratory oven at 60 ℃ for 24 hours. After more than one week of aging, the zirconia milling media containing the abrasive particles are oxidized using a SPEX 8000 mixer mill (SPEXSamplePrep, Metuchen, N.J.)Grinding geopolymer samples in zirconium containers. Ground geopolymers were classified using two wire mesh screens (Retsch GmbH, Haan, Germany, leigh ltd., first wire mesh screen having 1 millimeter (mm) openings and a second wire mesh screen having 106 micron openings.

Particle/agglomeration characterization

Samples (agglomerated and non-agglomerated) were subjected to laser scattering particle size analysis, gas adsorption, surface area, bulk density and skeletal density testing and characterized as shown in table 3. Particles (agglomerated or non-agglomerated) were dispersed in MEK for laser scattering particle size analysis as shown in table 3. Data are obtained from the manufacturer and geometric calculations are measured by assuming the d10 sphere size of the particles.

Table 3: characteristics of the particles

Normal incidence acoustic absorption tests were performed on the particles (agglomerated and non-agglomerated) and the results are shown in table 4. The sample particles were poured into a vertically mounted tube, which formed a 20mm thick bed of particles, with the exception of CLARCEL 78-calcined agglomerates, CLOISITE Na + -agglomerates, and GEOPOLYMER particles. They produced particle bed thicknesses of 15mm, 15mm and 10 mm. The designation "n/a" indicates that no peak occurs at a prescribed frequency.

Table 4: acoustic properties of particles

Examples 1-19(EX 1-EX 19) and comparative example 1(CE1)

Nonwoven meltblown webs were prepared by a process similar to that described in Wente, Van a., "ultra-fine Thermoplastic Fibers" (Industrial and Engineering Chemistry, volume 48, page 1342 and below (1956) (Wente, Van a., "Superfine Thermoplastic Fibers" in Industrial Engineering Chemistry, vol.48, pages 1342et seq. (1956)) and in naval research laboratory's report 4364 (published 5/25 1954, Wente, Van a., Boone, c.d., and Fluharty, e.l. entitled "Manufacture of ultra-fine Organic Fibers" (man failure of ultra Organic Fibers) ", except that a drill die was used to produce the Fibers.

MF650Y polypropylene resin was extruded through a die into a high velocity stream of hot air that draws out and attenuates polypropylene blown microfibers prior to their solidification and collection. According to the method of U.S. Pat. No. 3,971,373(Braun), the pellets are fed into a stream of polypropylene blown microfibers. The blend of polypropylene blown microfibers and particles were collected in a random fashion on a nylon belt to give a particle loaded polypropylene BMF web layer. The fibrous web is then removed from the nylon tape to provide the final article. The prepared sample configurations are shown in table 5. The thickness of the sample was measured using a thickness tester having a test foot size of 5cm × 12.5cm under an applied pressure of 150 Pa. The samples were subjected to Air Flow Resistance (AFR) test 1. The solidity is calculated based on equation 1. The results are shown in Table 5.

Table 5: sample construction and test results

The samples were subjected to normal incidence acoustic absorption testing and the results are shown in table 6. For acoustic absorption, the sample pan was punched out with a 64mm diameter punch and mounted between two circular open mesh metal screens (63mm and 68mm) spaced 5mm above 20mm air space. The air space is defined by two 10mm spacer rings (internal diameter 61 mm); the 63mm metal screen rests on the top spacer ring 5mm below the lip of the sample chamber volume, while the 68mm metal screen rests on the lip of the impedance tube sample volume. The contribution of the spacers and screens to alpha is also provided in table 6.

Table 6: acoustic test results

Examples 20 to 21(EX20-EX21)

Two samples of greater thickness loaded with MP1004 were prepared according to the method described for examples 1-20. The results of the prepared sample texture, percent solidity, and Air Flow Resistance (AFR) test 2 are shown in table 7.

Table 7: sample construction and test results

The samples were subjected to normal incidence acoustic absorption testing and the results are shown in table 8. For acoustic absorption, the sample plate was punched out with a 64mm diameter punch and placed directly into a sample chamber with a gap height set to 15 mm.

Table 8: acoustic test results

Examples 22-28 (EX 22-EX 28) and comparative example 2(CE2)

Examples were prepared from a web made by melt blowing 3860X resin heated to 230 ℃ extruded at a rate of 0.30 grams/hole/min into sonic heated air at 320 ℃ with an air flow rate of 9.26 cubic meters/min. The collector consisted of a 76cm diameter drum and a 25cm diameter drum, with the drums spaced 1cm apart, and the surface speed of each drum was 254 cm/min. The drum was run with a running nip and covered 80% of the open area and 3mm staggered holes were punched.

The die exit of the gap between the barrels was 43cm and the fiber was centered over the gap. Preparation of 106 g/cm²The web of (2) had a web thickness of 18.1mm and an effective fiber diameter of 7.7 microns. One side of the web has holes with a diameter below 40 microns and the other side, corresponding to the smaller cylinders, has holes with a diameter above 300 microns.

The web was rolled onto a flat surface, a sample pan of BMF nonwoven was punched out with a 64mm diameter punch, and approximately 0.2-0.3 grams of particles were placed on the BMF surface. The sample was then loaded onto a vibrating table for 1 minute and the final mass was calculated to account for the particles being shaken out. The sample configurations are shown in table 9. Airflow resistance (AFR) test 2 was performed after the acoustic measurements were taken and the results are shown in table 9. During the pressure drop measurement, some particles are displaced, and therefore this measurement is assumed to be the lower limit of the potential pressure drop.

Table 9: sample construction and test results

The samples were subjected to normal incidence acoustic absorption testing and the results are shown in table 10, except that only one sample was tested.

Table 10: acoustic test results

Examples 29-34 (EX 29-EX 34) and comparative examples 3-12 (CE 3-CE 12)

Inferior material (Janesville Acoustics, Southfield, Mi, mn) was physically separated into discrete fibers using a lando recycling shredder model RRS 36 (available from Rando Machine Corporation, major, NY) with a feed roll set at 152.4 mm/min (0.5 ft/min) and a main drum set at 500 RPM. The opened fibers have any remaining unopened clumps that were manually removed. 400 grams of opened fibers were mixed with 100 grams of 2d melt PET/PET bicomponent (length: 38mm, 2.0 denier) produced by Huvis corporation (Seoul, Korea) and 100 grams of sample pellets. These mixtures were made into a web on top of a scrim (available as "10.5 # CARRIER TISSUE, GRADE 3533" from Little torrent Corporation of Milwaukee, Wis.) following the procedure outlined in example 1 of U.S. Pat. No. 9,580,848(Henderson et al). The results of the sample configuration and Air Flow Resistance (AFR) test 2 are shown in table 11.

Table 11: sample construction and test results

For CE3, CE4, CE7, and CE11, the scrim attachment to the sample was too strong to be removed (DNR-not removed) and thus airflow resistance (AFR) test 2 (DNT-not tested) could not be performed.

The sample was subjected to a normal incidence acoustic absorption test. For acoustic absorption, the sample plate was punched out with a 64mm diameter punch and placed directly into a sample chamber with a gap height set to 7 mm.

For one form of normal incidence acoustic absorption testing, a sample disc was punched out with a 64mm diameter punch and placed directly into a sample chamber with a gap height set to 7 mm. The measurements were performed in two cases: 1) the scrim side faces up; and 2) scrim removed (for AC 32x60 and XG-3) or scrim side down (for control, where scrim adhesion was good). The results are shown in Table 12.

Table 12: acoustic test results

In another configuration of the normal incidence acoustic absorption test, a disc sample was punched out with a 68mm punch and placed onto a 68mm wire mesh wafer over a 20mm gap. Prior to measurement, the scrim was removed from the AC 32x60 sample and the XG-3 sample while the control (particle ═ none) sample was tested scrim side down. The results are reported in table 13.

Table 13: acoustic test results

In yet another configuration of the normal incidence acoustic absorption test, a sample with particles is tested in a 2-layer and 3-layer stack directly in the sample chamber. The test gap height in CE9 was 18mm, 24mm in CE10, 15mm in EX32, and 20mm in EX 33. The test results are recorded in table 14.

Table 14: acoustic test results

The Sound Absorption test was also performed on the samples according to SAE J2883 "Laboratory Measurement of Random incident Sound Absorption test Using a Small Reverberation chamber" to test Sound Absorption. The instrument used was "ALPHA CABIN" available from Otto Inc. of Winterthur, Switzerland. In the test, 1.20m was used in a 10mm frame at 22 ℃ and 55% humidity²The material of (1). The results are shown in Table 15. In CE11, the sample tested was a scrim placed face up. For CE12 and EX34, the scrim was placed face up and then removed prior to testing.

Table 15: acoustic test results

Examples 35-56 (EX 35-EX 56) and comparative examples 13-17 (CE 13-CE 19)

Discs were cut from CE3 poor quality nonwoven fibrous webs using a 64mm punch. The discs were weighed and then loaded with particles by manually rubbing the particles into the non-scrim surface of the nonwoven disc. Once the surface was completely filled with particles, the pan was shaken to remove excess particles and reweighed. For normal incidence acoustic absorption, the sample is loaded into the test tube with the particle-loaded surface facing upward. The sample chamber has a depth of 7mm and is completely occupied by a given disc. The results are shown in Table 16. Airflow resistance (AFR) test 1 results were recorded after acoustic measurements and are shown in table 16.

Table 16: sample construction and test results

The samples were subjected to normal incidence acoustic absorption testing and the sample discs were placed directly in the sample chamber with a gap height set at 7 mm. The results are shown in Table 17.

Table 17: acoustic test results

Examples 57-58 (EX 57-EX 58) and comparative example 20(CE20)

A2.54 cm (1 inch) thick polyester acoustic absorbent foam (available under the trade designation "J81 Tufcote" from AEARO Technologies, Indianapolis, IN, Indiana) was used as the base substrate.A 64mm diameter punch was used to punch out the sample discs and remove the skin from both surfaces of the discs using a razor.0.3 g of particles were hand spread across the entire surface on each disc. the results of sample construction and Air Flow Resistance (AFR) test 2 are shown IN Table 18.

Table 18: sample construction and test results

The samples were subjected to normal incidence acoustic absorption testing and the sample discs were placed directly in the sample chamber with a gap height set at 20 mm. The results are shown in Table 19. Only one sample was tested per particle.

Table 19: acoustic test results

Example 59(EX59) and comparative examples 21 to 22(CE 21-22)

A fiberglass material (hood liner taken from 2018 honda odesai Elite) was used as the base substrate. The scrim was removed from either side and the sample disc was punched out with a 64mm diameter punch. On each tray, 0.3g of particles were spread by hand over the entire surface. The results of the sample configuration and Air Flow Resistance (AFR) test 2 are shown in table 20. Only one sample was tested per particle.

Table 20: sample construction and test results

The samples were subjected to normal incidence acoustic absorption testing and the sample discs were placed directly in the sample chamber with a gap height set at 20 mm. The results are shown in Table 21.

Table 21: acoustic test results

Examples 60-93(EX 60-EX 93) and comparative examples 23-26(CE 23-CE 26)

Microperforated films were prepared as described in U.S. patent 6,617,002 (Wood). For MF-1, a film grade polypropylene resin PP-1 extruded polypropylene film (1.5mm thick) was used, with 3 wt% black masterbatch added (PP3019, available from RTP Company of Winona, mn. united States, of vanna, mn.) for MF-2, a film grade polypropylene resin PP-1 extruded polypropylene film (0.52mm thick) was used, with red masterbatch added (199X141358SS-57495, available from RTP Company), the film was embossed and heat treated to create apertures, the embossing creates apertures, as described in co-pending international patent application PCT/US18/56671(Lee et al), filed on 19/10/2018.

Table 22: pore size of microperforated film

The sample discs were punched out with a 68mm diameter punch. For each disc, the particles were hand-spread into the larger opening side, attempting to fill the opening. The sample configurations and results of the Air Flow Resistance (AFR) test 1 for some of the samples are shown in table 23. (DNT ═ not tested).

Table 23: sample construction and test results

The sample was tested for normal incidence acoustic absorption and the sample pan was placed directly above a 68mm metal screen which rested on the lip of the sample chamber with a gap height set to 20 mm. Where a single composite construct is reported, the composite is measured once, the particles are shaken out, and then the same particles are introduced into the same microperforated film for a second acoustic measurement. In the case where two composite configurations were reported, two sets of particles and films were measured. The results were not averaged. The results of MF-1 are shown in Table 24, and the results of MF-2 are shown in Table 25.

Table 24: test results of MF-1

Table 25: test results of MF-2

All cited references, patents, and patent applications in the above application for letters patent are incorporated by reference herein in their entirety in a consistent manner. In the event of inconsistencies or contradictions between the incorporated reference parts and the present application, the information in the preceding description shall prevail. The preceding description, given to enable one of ordinary skill in the art to practice the claimed disclosure, is not to be construed as limiting the scope of the disclosure, which is defined by the claims and all equivalents thereto.