阅读说明：本技术 纤维素纤维加工 (Cellulosic fiber processing ) 是由 埃里卡·N·福德 瑞安·德维尔 汉娜·德蒙 于 2019-10-04 设计创作，主要内容包括：本发明公开了强化再生纤维素纤维的干和湿韧度可以通过添加糖二酸例如(但不限于)葡萄糖二酸来进行。在某些实施方式中,还描述了通过本公开的方法生产的包含糖二酸或其盐的再生纤维素纤维。所述生产的纤维至少部分由于包含所述糖二酸而具有有利性质。(The present invention discloses that strengthening the dry and wet tenacity of regenerated cellulose fibers can be performed by adding a saccharic acid such as, but not limited to, glucaric acid. In certain embodiments, regenerated cellulose fibers comprising saccharic acid or salt thereof produced by the methods of the present disclosure are also described. The produced fiber has advantageous properties at least in part due to the inclusion of the saccharic acid.)

1. A method of processing cellulosic fibers, the method comprising:

combining cellulosic material and saccharic acid in a first solvent to produce a first mixture comprising 0.1-10 wt.% saccharic acid;

agitating the first mixture, thereby dissolving the cellulosic material and producing a first solution;

spinning the first solution to produce a cellulose fiber solution;

extruding the cellulose fiber solution into a first bath comprising a second solvent to provide as-spun fibers; and

the nascent fiber is thermally drawn through a second bath comprising oil to produce regenerated fiber.

2. The method of claim 1, wherein the saccharic acid is glucaric acid.

3. The method of claim 1 or 2, wherein the cellulosic material is present in the first mixture at a concentration of about 60% to about 99.9% weight/volume.

4. The method of any one of claims 1-3, wherein the first solvent comprises sodium hydroxide, urea, N-methylmorpholine-N-oxide (NMMO) hydrate, dimethylacetamide (DMAc), N-methylformamide (NMF), lithium chloride(LiCl), lithium bromide (LiBr), lithium fluoride (LiF), dimethyl sulfoxide (DMSO), Dimethylformamide (DMF), 1-methyl-2-pyrrolidone (NMP), methyl-pyrrolidones, N-methylmorpholine-N-oxide (NMO), diallylimidazolium methoxyacetate ([ A2 im)][CH₃OCH₂COO]) Pyridinium and imidazolium, or combinations thereof.

5. The method of any one of claims 1-4, wherein the first solvent comprises dimethylacetamide (DMAc) and lithium chloride, the lithium chloride being present in the solvent at 3% to 9% weight/volume.

6. The method of any one of claims 1-5, wherein the second solvent comprises methanol, acetone, isopropanol, water, or a combination thereof.

7. The method of any one of claims 1-6, wherein the cellulosic material is an activated cellulose powder.

8. The method of claim 7, wherein the activated cellulose powder is derived from cotton waste or agricultural waste.

9. The method of any one of claims 1-8, further comprising adding one or more additives to the neutralized cellulose solution prior to extruding the neutralized cellulose solution.

10. The method of claim 9, wherein the one or more additives comprise water repellents, colorants, UV stabilizers, UV absorbers, UV blockers, antioxidants, stabilizers, flame retardants, and combinations thereof.

11. The method of any of claims 1-10, further comprising aging the nascent fiber to provide an aged nascent fiber, thereby stretching the aged nascent fiber.

12. The method of any one of claims 1-11, further comprising producing the cellulosic material by a method comprising:

milling a cellulosic starting material to produce a cellulosic fines;

mercerizing the cellulose fine powder in a sodium hydroxide aqueous solution;

neutralizing the mercerized solution with an acid;

rinsing and collecting fibers in the mercerized solution; and

drying the fibers.

13. Regenerated cellulose fibers produced by the method of any one of claims 1-12.

14. The regenerated cellulose fibers according to claim 13 having an average fiber diameter of about 10-50 μ ι η.

15. The regenerated cellulose fibers of claim 13 or 14 having a tenacity greater than about 5 grams per denier.

16. The regenerated cellulose fibers of any one of claims 13-15 having a specific modulus greater than about 250 grams per denier.

17. The regenerated cellulose fibers according to any one of claims 13-16 having a tensile strength greater than about 500 MPa.

18. The regenerated cellulose fibers according to any one of claims 13-17 having a linear density of less than about 15 denier.

19. The regenerated cellulose fibers according to any of claims 13-18, wherein the fibers are meltblown, spunbond or as-spun.

20. A fibrous product comprising the regenerated cellulose fibers according to any one of claims 1-19.

21. The fibrous article of claim 20 wherein the article is selected from the group consisting of a yarn, a fabric, a meltblown web, a spunbond web, an as-spun web, a thermally bonded web, a hydroentangled web, a nonwoven fabric, or combinations thereof.

Technical Field

The subject matter of the present disclosure relates to the production of cellulose fibers. More specifically, the present disclosure relates to systems and methods for cellulose fiber reinforcement using saccharic acid.

Background

Materials composed of cellulose fibers are widely used in the packaging and clothing industry, particularly where strength is required. Substrates composed of cellulosic materials are typically reinforced by the addition of polymeric materials. However, such polymeric materials often impart undesirable characteristics to the cellulosic material, such as reduced sensitivity to water vapor, water, and/or solvents. Furthermore, materials treated with polymeric materials often result in products that are too hard and/or brittle. In addition, the cost of producing polymer-based fibers (e.g., high performance fibers) with increased strength can be prohibitive, making such fibers costly.

Disclosure of Invention

The present disclosure relates to cellulosic fiber reinforcement. In one aspect, a method of processing cellulose fibers comprises: combining cellulosic material and saccharic acid in a first solvent to produce a first mixture comprising 0.1-10 wt.% saccharic acid; agitating the first mixture, thereby dissolving the cellulosic material and producing a first solution; spinning the first solution to produce a cellulose fiber solution; extruding the cellulose fiber solution into a first bath comprising a second solvent to provide as-spun fibers; and thermally drawing the nascent fiber through a second bath comprising oil to produce regenerated fiber.

In certain embodiments, the saccharic acid is glucaric acid.

In certain embodiments, the cellulosic fibers are present in the first mixture at a concentration of about 60% to about 99.9% weight/volume.

In certain embodiments, the first solvent is an aprotic solvent, an ionic organic hydrate, or an aqueous solvent. In some cases, the first solvent comprises a lithium halide. In some cases, the first solvent comprises an antioxidant such as a gallic acid ester.

In certain embodiments, the second solvent comprises methanol, acetone, isopropanol, water, or a combination thereof.

In certain embodiments, the cellulosic material is activated cellulose powder. In some cases, the activated cellulose powder is derived from cotton waste or agricultural waste.

In certain embodiments, the method further comprises adding one or more additives to the neutralized cellulose solution prior to extruding the neutralized cellulose solution. In various embodiments, the one or more additives may include water repellents, colorants, UV stabilizers, UV absorbers, UV blockers, antioxidants, stabilizers, flame retardants, and combinations thereof.

In certain embodiments, the method further comprises aging the nascent fiber to provide an aged nascent fiber, wherein the aged nascent fiber is drawn.

In certain embodiments, the method further comprises producing the cellulosic material by a process comprising: milling a cellulosic starting material to produce a cellulosic fines; mercerizing the cellulose fine powder in a sodium hydroxide aqueous solution; neutralizing the mercerized solution with an acid; sodium hydroxide was added, then the temperature of the resulting solution was raised, followed by cooling to room temperature and centrifuging the cooled solution.

In certain embodiments, the presently disclosed subject matter relates to regenerated cellulose fibers produced by the presently disclosed methods.

In certain embodiments, the regenerated cellulose fibers have an average diameter of about 10 to 50 μm.

In certain embodiments, the regenerated cellulose fibers have a tenacity greater than about 5 grams per denier.

In certain embodiments, the regenerated cellulose fibers have a specific modulus greater than about 250 grams per denier.

In certain embodiments, the regenerated cellulose fibers have a tensile strength greater than about 500 MPa.

In certain embodiments, the regenerated cellulose fibers have a linear density of less than about 15 denier.

In certain embodiments, the regenerated cellulose fibers are meltblown, spunbond, or as-spun.

In certain embodiments, the presently disclosed subject matter relates to fibrous articles comprising the presently disclosed fibers.

In certain embodiments, the fibrous article is selected from the group consisting of a yarn, a fabric, a meltblown web, a spunbond web, an as-spun web, a thermally bonded web, a hydroentangled web, a nonwoven fabric, or a combination thereof.

The materials, techniques, or methods involved in the processing of cellulosic fibers are not particularly required to include all of the details described herein in order to obtain certain benefits described in accordance with the present disclosure. Accordingly, the specific examples described herein are intended as exemplary applications of the described technology, and alternatives are possible.

Drawings

This patent or application document contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the office upon request and payment of the necessary fee.

Fig. 1 illustrates an exemplary process for processing cellulose fibers.

Fig. 2 shows a schematic diagram of an exemplary system for extruding, aging, and stretching cellulosic fibers.

Fig. 3A and 3B are images of fibers prepared in the presence and absence of glucaric acid obtained by confocal microscopy.

Fig. 4A and 4B are images illustrating the dissolution of a milled cotton sample in the absence and presence of glucaric acid.

FIG. 5 is a photograph showing the dissolution of a sample of ground cotton with and without acid treatment and dried after mercerization.

FIG. 6 is a graph depicting a sample of ground cotton before and after mercerization pretreatment.

Fig. 7A is a photograph of a 4-filament yarn produced according to certain embodiments of the presently disclosed subject matter.

Fig. 7B is a confocal micrograph of a fiber cross section from the 4-filament yarn of fig. 7A.

Fig. 8A shows tensile test data for the dry condition sample, and fig. 8B shows tensile test data for the wet condition sample.

FIG. 9 is a photograph of an exemplary fiber used for the loop test.

Detailed Description

The present disclosure relates to enhancing the dry and wet tenacity of regenerated cellulose fibers. More specifically, the methods disclosed herein strengthen cellulosic fibers by adding a saccharic acid such as (but not limited to) glucaric acid or galactaric acid. In certain instances, the regenerated cellulosic material can be processed and used as a starting material, such as pre-or post-consumer cotton waste, agricultural waste (e.g., bagasse), and used paper products. That is, the methods and techniques disclosed herein may also be applied to natural (i.e., non-regenerated) cellulose fibers.

Regenerated cellulose fibers are generally weaker than natural cellulose fibers. In particular, thermo-chemical processing is required to improve mechanical properties due to the reduced molecular weight of regenerated cellulose fibers. Using the process of the present disclosure, the wet and dry tenacity of regenerated cellulose fibers can be improved by adding saccharic acid to the spinning solution (spinning solution).

The term "tenacity" refers to the unit tensile strength of a monofilament fiber, calculated by dividing the breaking tension by its linear density. Wet tenacity and dry tenacity refer to the tensile test of the fiber in the dry and wet states, respectively. The wet and dry tenacity of the fibers can be determined according to ASTM D3822-07, the entire contents of which are incorporated herein by reference. In certain embodiments, the presently disclosed subject matter further comprises regenerated cellulose fibers comprising saccharic acid or salt thereof produced by the presently disclosed methods. Without being bound by a particular theory, it appears that the resulting fiber has advantageous properties due, at least in part, to the inclusion of the saccharic acid.

I. Definition of

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In case of conflict, the present document, including definitions, will control. Preferred methods and materials are described below, although methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. The materials, methods, and examples disclosed herein are illustrative only and not intended to be limiting.

The terms "comprising," "including," "having," "may," and variations thereof, are intended to be open-ended transition phrases, terms, or words, that do not exclude the possibility of additional acts or structures. No specific number of an indication includes a plural indication unless the context clearly dictates otherwise. The present disclosure also contemplates other embodiments that "comprise" or "consist essentially of the embodiments or elements presented herein, whether or not explicitly stated.

For recitation of numerical ranges herein, each intervening number between them with equal precision is explicitly contemplated. For example, for the range of 6-9, the numbers 7 and 8 are contemplated in addition to 6 and 9, and for the range of 6.0-7.0, the numbers 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, and 7.0 are specifically contemplated.

The term "about" when used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes at least the degree of error associated with measurement of the particular quantity). The modifier "about" should also be considered as disclosing the range defined by the absolute values of the two endpoints. For example, the expression "about 2 to about 4" also discloses the range "2 to 4". The term "about" may refer to plus or minus 10% of the number indicated. For example, "about 10%" may indicate a range of 9% to 11%, and "about 1" may mean 0.9-1.1. Other meanings of "about" may be apparent from the context, for example, rounding off, so that "about 1" may also mean 0.5 to 1.4.

The definitions of particular functional groups and chemical terms are described in more detail below. For the purposes of this disclosure, chemical Elements are identified according to the Periodic Table of Elements (CAS version, Handbook of Chemistry and Physics, 75 th edition, inner cover), and specific functional groups are generally defined as described therein. In addition, the general principles of Organic Chemistry, as well as specific functional components and reactivities are described in Organic Chemistry (Organic Chemistry, Thomas Sorrell, University Science Books, Sausaltio, 1999), Smith and March's March Advanced Organic Chemistry (March's Advanced Organic Chemistry, 5 th edition, John Wiley & Sons, Inc., New York,2001), Larock's Integrated Organic Transformations (Comprehensive Organic Transformations, VCH Publishers, Inc., New York,1989), Some of the Modern Methods of Organic Synthesis of Carrus (Sound models of Organic Synthesis, 3 rd edition, catalytic University Press, bridge,1987), each of which is incorporated herein by reference.

Exemplary materials that can be used in the exemplary methods and systems

A variety of different types of cellulosic fibers may be used in the exemplary methods and systems disclosed herein. These and other materials that may be used in the exemplary methods and systems are discussed below.

A. Cellulose fiber

Cellulosic fibers are a type of fiber made from pulp (e.g., wood pulp) using a solvent fiber spinning process. Any desired pulp may be used, such as, but not limited to, hardwood pulp, softwood pulp, cotton linters, bagasse, hemp, flax, bamboo, kenaf, grass, straw, linseed, jute, ramie, bast, sisal, and/or any other plant having a fibrous bast. Suitable hardwood pulps may be selected from one or more of acacia, alder, birch, catalpa, gum, maple, oak, eucalyptus, poplar, beech, poplar, and the like. Suitable softwood pulp may be selected from one or more of southern pine, white pine, caribbean pine, western hemlock, spruce, douglas fir, and the like.

Regenerated cellulose fibers are fibers prepared by regenerating (e.g., returning to solid form) from a solution containing dissolved cellulose fibers. As set forth in more detail below, the process of the present disclosure includes dissolving the cellulosic material in a solvent (spinning dope) and spinning the resulting solution into fibers. It has been found that the addition of a saccharic acid (e.g., glucaric acid) to the spinning dope strengthens the resulting regenerated fiber.

B. Exemplary solvents containing saccharic acid

Certain solvents used during operation of the exemplary methods disclosed herein comprise saccharic acid. The solvents discussed in this section are used during the dissolution operation of the cellulose fibers.

1. Exemplary sugar diacids

Saccharic acids are a class of sugar acids in which the terminal hydroxyl and carbonyl groups of the sugar have been replaced by terminal carboxylic acids. The saccharic acid can be characterized by the formula HOOC- (CHOH) n-COOH. Examples of saccharic acids suitable for use in the methods of the present disclosure include glucaric acid, tartaric acid, galactaric acid (also known as mucic acid), xylaric acid, ribosylic acid, arabinosylic acid, ribosylic acid, lyxosylic acid, mannosylic acid, and/or idosylic acid.

In certain embodiments, the selected saccharic acid is glucaric acid or a salt thereof. In particular, the glucaric acid can include a diacid form, a lactone form (e.g., 1, 4-lactone and 3, 6-lactone), or a combination thereof, of glucaric acid.

The glucaric acid can be a salt and can be fully or partially neutralized. The counterion of the glucarate salt may include, but is not limited to, sodium, potassium, ammonium, zinc, lithium, or combinations thereof. For example, the glucaric acid can be a mono-ammonium salt, a di-ammonium salt, a sodium salt, a potassium salt, or a combination thereof. Without being bound by a particular theory, it is believed that the free hydroxyl and carboxylic acid groups of the glucaric acid undergo strong intermolecular secondary bonding with hydroxyl groups of the matrix polymer, particularly the dissolved cellulose polymer.

In certain embodiments, the glucaric acid can have a structural formula set forth in formula (I).

However, in certain embodiments, the glucaric acid can have a structural formula as set forth in formula (II) below.

In formula (II), Z + may be selected from hydrogen, sodium, potassium, N (R1)₄Zinc, lithium and combinations thereof.

In certain embodiments, the glucaric acid can be selected from one or more of formulas (III), (IV), or (V).

In certain embodiments, the glucaric acid can be provided by one or more biosynthetic methods. For example, the glucaric acid can be provided by microbial fermentation. Thus, the glucaric acid can be provided in a cost-effective manner. In other embodiments, the glucaric acid can be provided by oxidizing a sugar (e.g., glucose) with an oxidizing agent (e.g., nitric acid).

2. Additional exemplary solvent Components

Generally, exemplary solvents for dissolving the cellulosic material are aprotic, ionic organic hydrates, or aqueous solvents. In various embodiments, an exemplary solvent can comprise a lithium halide. In various embodiments, an exemplary solvent can comprise an antioxidant. Certain exemplary solvents may comprise both a lithium halide and an antioxidant. As noted above, saccharic acid is added to these solvent systems.

The solvent medium may be an aprotic solvent. Exemplary aprotic solvents that can be used in the methods and systems disclosed herein include dimethylacetamide (DMAc), Dimethylformamide (DMF), n-methylformamide (NMF), Dimethylsulfoxide (DMSO), 1-methyl-2-pyrrolidone (NMP), and methyl-pyrrolidinones, sometimes in combination with salts.

The solvent medium may be an ionic organic hydrate. Exemplary ionic organic hydrates include N-methylmorpholine-N-oxide (NMO), diallylimidazolium methoxyacetate ([ A2 im)][CH₃OCH₂COO]) Pyridinium and imidazolium with acetic acid, formic acid, dimethyl phosphate and chloride anions.

The solvent medium may be water-based. For example, an exemplary solvent may be an aqueous sodium hydroxide (NaOH) solution or an aqueous urea solution.

In some cases, the aprotic solvent, ionic organic hydrate solvent, or aqueous solvent may further comprise a lithium halide. Exemplary lithium halides include lithium chloride (LiCl), lithium fluoride (LiF), and lithium bromide (LiBr). In some cases, the solvent, such as NMO, can effectively dissolve the cellulosic material in the absence of lithium halide.

In various embodiments, the lithium halide may be present in the solvent at 3-20 w/v%, 5 w/v% to 15 w/v%, 4 w/v% to 10 w/v%, 7 w/v% to 12 w/v%, 12 w/v% to 18 w/v%, 3 w/v% to 9 w/v%, or 8 w/v% to 14 w/v% of the solution.

The solvent may also comprise one or more antioxidants. Exemplary antioxidants include gallic acid esters, for example dodecyl gallate, propyl gallate and lauryl gallate may be added. The one or more gallic acid esters can be added to the solvent at about 0.1 wt/vol% to 0.3 wt/vol% or about 0.2 wt/vol%.

Exemplary methods

A. Exemplary cellulose activation

Typically, the raw materials used in the exemplary cellulose fiber processing disclosed below are pre-treated to produce an "activated cellulose powder". The activated cellulose powder may be obtained in various ways, for example by milling or grinding a cellulose starting material, which may be a cellulose cake, into a fine powder. In some cases, the powder has a No. 20 metal mesh size (about 840 μm). After milling, the resulting flour may be dried. For example, the powder may be dried at 85 ℃ for at least 4 hours. In certain embodiments, the meal may be stored in a dryer prior to further processing.

The fines are then mercerized in an aqueous solvent such as sodium hydroxide (NaOH). Mercerization may be carried out at room temperature. Mercerization is the caustic treatment of cellulose, which swells the fibers by breaking the hydrogen bonding between cellulose chains. The treatment comprises an aqueous solution of up to 25% sodium hydroxide at room temperature or lower. For example, mercerization may involve treating the dry powder with a 20 wt/vol% aqueous solution of sodium hydroxide (NaOH) at 23 ℃ for 5 hours.

In certain embodiments, the fibers may be rinsed and collected after mercerization and dried (e.g., at 80 ℃). Experimental tests have shown that drying the fibers after mercerization and before neutralization can improve the dissolution of cellulose in downstream processes, such as after spinning operation 110 discussed below.

The NaOH/milled cellulose mixture is then neutralized with a strong or weak acid. As an example, the pH may be neutralized with 4N sulfuric acid. Next, the fibers may be rinsed and collected, and then dried. For example, drying may be carried out at 80 ℃.

Next, the dry powder can be added to a dissolution solvent, which can be NaOH or DMAc/LiCl containing urea. In some cases, the dissolution solvent may comprise lauryl gallate. In some cases, the temperature of the solution may be increased to 120 ℃ to 130 ℃ and then decreased to room temperature. The resulting dope can then be centrifuged to completely dissolve the fine fibers and degas the dope.

B. Exemplary cellulose fiber processing

Fig. 1 illustrates an exemplary method 100 for processing cellulose fibers. In general, the method 100 produces cellulosic fibers having improved strength properties compared to the starting raw cellulosic fibers. The starting materials for the process 100 may include recycled fibers and/or natural fibers. Other embodiments may include more or fewer operations.

The method 100 includes combining cellulosic material and saccharic acid in a first solvent to produce a first mixture, which is described below as operations 102, 104, and 106. The method 100 may begin by adding cellulosic material to a first solvent (operation 102). Typically, the cellulosic material is activated cellulose powder. Typically, the cellulosic material has been previously dried. In various embodiments, the cellulosic material is added such that the cellulosic material is present in the solution at a concentration of about 60% to about 99.9% weight/volume.

Various desired solvents may be used as the first solvent in operation 102. Exemplary solvents are aprotic solvents, ionic organic hydrates or aqueous solvents. In some cases, the first solvent comprises a lithium halide. In some cases, the first solvent comprises an antioxidant such as a gallic acid ester. Exemplary solvents, potential components, and possible relative amounts are described in more detail above and are not repeated here for the sake of brevity.

Alternatively, an indirect dissolution process, such as the viscose rayon process, may be used. In the viscose rayon process, cellulose is mixed with CS₂Combining to form cellulose xanthate, which is in aqueous NaOHIs soluble, resulting in a viscose solution for fiber spinning. The spun fiber is treated with an acid solution to convert the derivative back to cellulose.

Saccharic acid is also added to the first solvent (operation 104). In some cases, the saccharic acid is added before the cellulosic material is added or dissolved in the solvent (operation 104). Exemplary saccharic acids include, but are not limited to, glucaric acid and galactaric acid. The saccharic acid is added to the solution (operation 104) such that the saccharic acid is present in the solution at a concentration of about 0.01% to about 10% weight/volume.

Optionally, one or more additives may be added (operation 106) to the first solvent, which may be a mixture of solvent, cellulosic material, and saccharic acid. The one or more additives may include water repellents, colorants, UV stabilizers, UV absorbers, UV blockers, antioxidants, stabilizers, flame retardants, and combinations thereof.

Next, the solution is stirred (operation 108). Stirring (operation 108) may include agitating the solution at a desired temperature for a desired time. In certain embodiments (e.g., depending on the solvent used), the desired temperature may be room temperature. However, in certain embodiments, the desired temperature may be above (e.g., about 60 ℃ to 100 ℃) or below (e.g., about 10 ℃ or less) room temperature. The desired time may range from about 15 minutes to several hours.

The solution may then be spun (operation 110) using any known method to dissolve the cellulosic material in the solution. As one example, the solution may be centrifuged during operation 108. In other embodiments, sonication, high shear homogenization, and kneading reactions may be used to dissolve the cellulosic material in the solution.

Next, the solution may be extruded (operation 112) into a second solvent to provide as-spun fibers. The second solvent may comprise methanol, acetone, isopropanol, water, or a combination thereof. In some cases, an air gap is provided between the extrusion device and the bath. Dry spraying of the dope in the air gap can elongate the entangled polymer chains before coagulation in the second solvent.

In certain embodiments, the method 100 may include thermally drawing the nascent fiber through a bath comprising an oil (e.g., silicone oil) (operation 114) to produce the regenerated fiber. In some cases, the as-spun fibers may be aged in the second solvent and then the aged or as-spun fibers are drawn through the bath comprising oil. It should be recognized, however, that in certain embodiments, melt blown, spunbond and/or as-spun processes may be used. Thus, the fibers may be meltblown fibers, spunbond fibers, and/or as-spun fibers.

Exemplary System

Fig. 2 shows a schematic diagram of an exemplary system 200 for extruding and drawing cellulosic fibers. One or more components shown in system 200 may be used to perform operations 112 and 114 of method 100 discussed above. Other embodiments may include more or fewer components.

The system 200 includes an extrusion apparatus 202 that can produce extruded cellulosic fibers, such as nascent fibers. Typically, a solution containing dissolved cellulose fibers at a neutral pH is provided to the extrusion apparatus 202. When pressure is applied to the extrusion apparatus 202, the cellulose fibers enter the bath 204 through an orifice. The diameter of the orifice and the applied pressure may vary with the type of fiber desired. For example, the orifice may be provided by a 19 gauge needle having an inner diameter of about 0.69 mm.

Between the extrusion apparatus 202 and the bath 204 is an air gap 203. The air gap between the aperture and the first bath may be about 1mm to about 10mm, for example about 2mm to about 8mm, 3mm to 5mm or about 2mm to about 7 mm.

Bath 204 contains one or more solvents, which may be at a higher or lower temperature than the solution in extrusion apparatus 202. The solvent in bath 204 may include methanol, acetone, isopropanol, water, or combinations thereof. In certain embodiments, the solvent in the bath 204 is at 0 ℃, -10 ℃, -20 ℃, -25 ℃, or-35 ℃ and comprises a mixture of methanol and acetone. After the nascent fibers are coagulated in the first bath, they may be collected on a rotary winder 206.

After the nascent fiber is produced, it may be aged in bath 208, which contains the same or similar solvent as bath 204, but is typically at a higher temperature (e.g., above 0 ℃) than bath 204, to provide an aged nascent fiber. The as-spun fibers may be aged for about 1 hour to about 48 hours. In certain embodiments, the nascent fiber is aged in bath 208 at 5 ℃ for 24 hours. By this step, the nascent fiber (and aged nascent fiber) may also be referred to as a polymer gel.

The fibers may then be drawn through 1 to 4 stages of oil in bath 210. An exemplary oil is silicone oil. Typically, the oil in bath 210 is at a high temperature compared to bath 204 and bath 208, for example the oil in bath 210 may be at 90 ℃ to 240 ℃. The Draw Ratio (DR) of each stage of fiber drawing may be calculated as DR ═ V₂/V₁In which V is₁Is the speed of the fiber feed winder 212 and V₂Is the speed of the take up winder 214.

Different feed rates and draw ratios may be used in the process of the present disclosure. For example, the process can include a feed rate of about 0.1 meters per minute (m/min) to about 20 m/min. Additionally, the method can include a draw ratio of about 1 to about 20. In certain embodiments, the process may have a total draw ratio of from about 25 to about 160, for example from about 30 to about 150 or from about 35 to about 85. As used herein, "total draw ratio" refers to the cumulative draw ratio of each drawing stage conducted in bath 210 containing silicone oil.

Aspects of exemplary regenerated fibers

Exemplary regenerated fibers can be described in terms of various different components and chemical characteristics and physical properties of the fibers. Various aspects are discussed below.

A. Components of exemplary recycled fibers

In certain embodiments, the regenerated fibers may include one or more additives that provide one or more beneficial properties to the fibers. The term "additive" refers to a water repellent, colorant, UV stabilizer, UV absorber, UV blocker, antioxidant, stabilizer, flame retardant, or any other compound that enhances the appearance or performance characteristics of the resulting fiber. Suitable additives may include, but are not limited to, lignin, carbon nanotubes, nanofillers, or combinations thereof. The additives may be present in the fibers at a concentration of about 0.1 to 50 weight percent based on the total weight of the fibers. Thus, the additive may be present in an amount of about 1 to 45, 5 to 30, or 10 to 20 weight percent.

In certain embodiments, the regenerated fibers of the present disclosure may comprise lignin. Lignin is a complex polymer that is part of the secondary cell wall in plants and certain algae, filling the spaces between cellulose, hemicellulose and pectin that form the cell wall. Lignin covalently binds to hemicellulose, cross-linking different polysaccharides and thus increasing the mechanical strength of the cell wall. In certain embodiments, the regenerated fiber may comprise about 0.1 to 50 weight percent lignin, based on the total weight of the fiber. For example, the lignin content of the regenerated fiber may be about 1-25, 1-30, 5-30, or 8-20 weight percent lignin.

Lignin can be used in a variety of different forms. For example, lignin may be provided as an aqueous paste of pine wood chips. Additionally, the lignin provided as a solution may have an acidic pH, e.g. pH 2-4. In certain embodiments, purification may be performed by dissolving the lignin in a solvent (e.g., acetone) followed by filtration to remove the insoluble lignin fraction. Purifying the lignin can improve the tensile properties of the resulting fiber (e.g., higher fiber elongation and/or less tensile failure).

The regenerated fibers may have any desired diameter depending on the production method used. For example, the fibers may have a diameter of about 10-50 μm, such as about 15-45, 20-40, or 25-35 μm.

Due at least in part to the saccharic acid, the regenerated cellulose fibers of the present disclosure may have increased tenacity as compared to regenerated fibers produced in the absence of the saccharic acid. In particular, the regenerated fibers of the present disclosure may have a tenacity of at least 1.5 times, 2 times, 2.5 times, 3 times, 4 times, 5 times, or 10 times that of regenerated cellulose fibers produced in the absence of saccharic acid. For example, the recycled fibers of the present disclosure may have a tenacity of about 3 to 15 grams per denier. Thus, the regenerated fibers may have a tenacity greater than about 5, 6, 7, 8, or 9 grams per denier, greater than 6 grams per denier, greater than 7 grams per denier, greater than 8 grams per denier, or greater than 9 grams per denier.

In certain embodiments, the regenerated cellulose fibers may have a saccharic acid concentration of about 0.01% to about 10% by total weight of the fibers. Thus, the fiber may comprise about 0.01% to 8%, 0.8% to 5%, or 1% to 4% of the saccharic acid.

B. Exemplary physical Properties of exemplary fibers produced

In certain embodiments, the resulting fibers may have a specific modulus of about 200 grams/denier to about 1200 grams/denier. Thus, the fibers may have a specific modulus of greater than about 230, 250, 300, 350, 400, or 450 grams per denier. The term "specific modulus" refers to the modulus of elasticity (young's modulus) divided by the bulk mass density of the material (e.g., weight per unit volume). Young's modulus is a mechanical property that measures the stiffness of a material (e.g., uniaxial stress or force per unit surface divided by strain). Specific modulus and young's modulus may be determined according to ASTM D3039 and ASTM D790, which are incorporated herein by reference.

The fibers can have a tensile strength of about 150MPa to about 2000 MPa. The fibers may have a tensile strength above 500MPa, above 550MPa, above 600MPa, above 650MPa, above 700MPa, above 750MPa, above 800MPa, above 900MPa or above 1000 MPa. The tensile strength of a material refers to the amount of maximum stress that can be applied to the material before breaking or failing (e.g., the rate and/or ease at which a fiber tears or splits).

In certain embodiments, the resulting fibers may have a linear density of about 3 to 30 denier, such as about 3 to 25, 3 to 20, or 3 to 15 denier. In certain embodiments, the regenerated cellulose fibers may have a linear density of less than about 17 denier, such as less than about 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, or 5 denier.

As mentioned above, the regenerated fibers can be used for a large number of different applications due to their advantageous properties. One such application is the use of the fibers as part of a fibrous article such as, but not limited to, yarns, fabrics, meltblown webs, spunbond webs, gel spun webs, needle punched webs, thermally bonded webs, hydroentangled webs, nonwoven fabrics, and combinations thereof.

In addition, the fibers may be used in applications requiring high performance fibers. Examples of these types of applications include carbon fibers, tire cord, radiation shielding, and precursors to fiber reinforced plastics.

Detailed Description

Experimental examples vi

The compositions and methods of this invention will be better understood by reference to the following examples, which are intended as an illustration of the scope of the invention and not as a limitation.

Example 1: mercerizing pretreatment of cellulose

3.0+/-0.05 grams of ground cellulose powder was added to 500mL of cold (23 ℃ C.) 20% NaOH solution. The suspension was mechanically stirred for 1 hour. The solid was then filtered off and washed until the filtrate became neutral (pH 6-7). The treated cellulose is then air dried. The cellulose was observed to dissolve into an almost transparent solution.

Example 2: mercerizing pretreatment of cotton pulp

A 20% aqueous NaOH solution was prepared. 3.0+/-0.05 grams of cotton pulp was added to the 20% NaOH solution and stirred at 250rpm for 1 hour at room temperature (20-23 ℃). The solution was filtered under vacuum using a steel fine mesh and a buchner funnel. The filtered dry pulp was added to 30mL of white vinegar (5% acetic acid) and stirred for 5-10 minutes to neutralize the pH of the solution to 6-7. The solution was filtered through a steel fine mesh under vacuum using a buchner funnel. The filtered pulp was added to 60mL of distilled water and stirred at room temperature for 5-10 minutes. The water rinse and filtration steps were repeated until the pulp was completely washed (pH became neutral, sodium was removed). The pulp was then dried in an oven at 85 ℃ for at least 4 hours. The dried pulp was stored at room temperature in a vacuum-sealed dryer until used for dissolution or property studies.

Example 3: effect of NaOH Pre-treatment on dissolution

A 3 wt% sample of ground regenerated cotton cellulose that has not been mercerized is added to a solution of 8% LiCl/DMAc +0.2 wt% dodecyl gallate +10 wt% glucaric acid. The solution was stirred at 120 ℃ (oil bath) for 1 hour. The solution was stirred at room temperature for an additional 1 hour. A sample of the dope was centrifuged (2500rpm, 20 minutes) and the supernatant was used for the drop test.

Incomplete dissolution of the sample was observed. The sample also did not appear to have a high viscosity. Deposits were observed after centrifugation, indicating very poor dissolution conditions.

The coagulation test (in water) produces a weak droplet that is easily broken. It was therefore concluded that mercerization pre-treatment is an important step in the LiCl/DMAc dissolution process, having an effect on the dissolution efficiency of the milled cellulose samples.

Example 4: effect of anti-plasticizer

Antiplasticizers are known to enhance the tensile properties and/or mechanical strength of fibers. Sample 1 was prepared by adding cellulose fibers (degree of polymerization 600-800) to a 3 wt% DMAc/LiCl solution. Sample 2 was prepared by adding cellulose fibers (degree of polymerization 600-800) to a 10% glucaric acid solution. SEM images of the resulting fibers of samples 1 and 2 are shown in fig. 3A and 3B, respectively.

The fibers of sample 1 of fig. 3A are shown at 1x zoom to have an image size of 1280x1280 μm. The fibers have a thickness of 1.8x 10-9m²Area of (d), diameter of 48 μm, 1580000g/m³A cellulose density of 26 denier and 29 dtex.

The fibers of sample 2 of fig. 3B were shown to have an image size of 1280x1280 μm at 1x zoom. The fibers have a thickness of 1.74x 10-9m²Area of (d), diameter of 47 μm, 11500000g/m³A cellulose density of 23 denier and 26 dtex.

Example 5: dissolution test

To prepare sample 6, the oil bath was heated to 130 ℃.4 grams LiCl and 0.1 gram lauryl gallate were added to 50mL DMAc. The solution was heated in an oil bath for preheating. A 1.5 gram sample of treated cotton was added to the heated solution and stirred for 1 hour. The suspension was then cooled to room temperature and stirring was continued for 1 hour as shown in the photograph of fig. 4A.

To prepare sample 7, the oil bath was heated to 130 ℃.4 grams LiCl, 0.1 grams lauryl gallate and 0.15 grams glucaric acid were added to 50mL DMAc. The solution was heated in an oil bath for preheating. A 1.5 gram sample of treated cotton was added to the heated solution and stirred for 1 hour. The suspension was then cooled to 70-80 ℃ and then subjected to rapid temperature quenching by manual shaking of tap water/flask. A sudden appearance of complete dissolution was observed by quenching the reaction, as shown in fig. 4B.

Example 6: effect of pretreatment on cellulose dissolution

Experiments were performed to assess the possible effect of the pretreatment operation on cellulose dissolution.

Sample 3 was prepared by mercerizing a sample of ground cotton (degree of polymerization 600-800). A suspension of 5% (w/w) ground cotton in 20% NaOH was prepared. The suspension was stirred at room temperature for 5 hours. 400mL of 4N sulfuric acid was then added to neutralize the suspension to pH 7.0. The sample was collected by filtration and then dried at 80 ℃. Complete dissolution of the sample was observed during the dissolution test.

Sample 4 was prepared by omitting the mercerization pretreatment of the ground cotton sample (degree of polymerization 600-800). A suspension of 5% (w/w) ground cotton in 20% NaOH was prepared. The suspension was stirred at room temperature for 5 hours. The sample was then washed with water to neutralize to a pH of 7.0. The sample was collected by filtration and then dried at 80 ℃.

Sample 5 was prepared by adding 20 grams of mercerized cotton cellulose from sample 4 and treating with 400mL of 4N sulfuric acid at room temperature for 30-40 minutes. The sample was collected by filtration and then washed with tap water to pH 7.0. The sample was then dried at 80 ℃ for 4 hours.

Fig. 5 is a photograph of sample 3, sample 4 and sample 5 from left to right. It was observed that sample 5 exhibited very poor cellulose dissolution performance without acid treatment as shown in fig. 5. It was further observed that with an additional acid treatment step (sample 4), the cellulose dissolution improved (although not yet completely dissolved).

Example 7: crystallinity testing of milled cotton samples

A comparison was made between the ground cotton sample before mercerization (sample 8) and the ground cotton sample after mercerization (sample 9), as shown in fig. 6 below. 1429cm^-1Reduction of Peak sum 895cm^-1An increase in peaks indicates a decrease in crystallinity after mercerization. The red ovals indicate that the intermolecular and intramolecular hydrogen bonding of cellulose has changed, pointing to the transition of the crystal structure from cellulose I to II.

Example 8: production of samples of woven cellulose fibers

Cellulose fibers (degree of polymerization 600-800) (3 wt.% cellulose) were obtained from the shirts. A solution of 10% glucaric acid, 7% DMAc/LiCl and 0.2% dodecyl gallate was prepared. Subjecting the solution to a water coagulation bath. A 4-filament yarn was produced using a feed rate of 10mL/min and a take-up speed of 6-7m/min as shown in fig. 7A and 7B.

Example 9: physical Property testing

The fibers of the regenerated cotton are ground into short fiber powder. The average degree of polymerization of these fibers was 600-800DP (i.e., medium DP). The weight to volume ratio (weight/volume) of fibers from regenerated cotton to solvent is 5-8%. The solvent contained 8 w/v% lithium chloride/dimethylacetamide (LiCl/DMAc) and 0.2 wt% lauryl gallate. The solution was dissolved at 120 ℃ for 3 hours and stirring was continued at room temperature for 1 hour. The spinning dope solution was centrifuged at 2500rpm for 20 min. The spinning dope was centrifuged to separate any undissolved powder to obtain an even more homogeneous dope.

5 samples S1-S5 were tested and are briefly described in Table 1 below. For samples S1, S4, and S5, cotton was ground, mercerized, neutralized with 4N sulfuric acid, and dried at 80 ℃. For samples S2 and S3, cotton was ground, mercerized, neutralized with 4N sulfuric acid, and dried at 80 ℃.

TABLE 1 samples tested during example 9

Sample (I)	The following steps are described: weight/weight percent of additive to cellulose
		S1	Pure cellulose
S2	10% Glucaric Acid (GA) -cellulose
		S3	10% GA-cellulose
S4	10% GA-cellulose
		S5	10% galactaric acid (MA) -cellulose

For each of samples S1-S5, various mechanical properties were obtained experimentally, with the results detailed in table 2 below. When used in table 2, "gf" is grams force, and denier is g/9000 m. The Linear Density measurements were obtained in accordance with ASTM D1577 "Standard Test Methods for Linear Density of Textile Fibers" (Standard Test Methods of Textile Fibers). Specific Modulus values were obtained in accordance with ASTM D3379-75(1989) e1 "Standard Test Method for Tensile Strength and Young's Modulus of High Modulus monofilament Materials" (Standard Test Method for Tensile Strength and Young's modules for High-Module Single-fiber Materials) (withdrawn in 1998). Tenacity values, including those shown in FIGS. 9A and 9B, were obtained according to ASTM D3822, "Standard Test Methods for Tensile Properties of Standard Textile Fibers".

Tensile test parameters: the test was carried out at a nominal length of 25mm using a crosshead speed of 15mm/min and a 5lb load cell. At least 15 representative samples were tested and the most reproducible mechanical properties were reported. Fig. 8A shows tensile test data for the dry condition sample, and fig. 8B shows tensile test data for the wet condition sample. As shown in fig. 8A and 8B, the addition of saccharic acid improved the strength and tensile properties of the resulting fiber.

TABLE 2 Experimental results of tests performed on the samples shown in TABLE 1

Loop tests were also performed on samples S1-S5. Specifically, the data shown in Table 3 below were obtained following ASTM D3217 "Standard Test method for Breaking Tenacity of Textile Fibers in Loop or structural form" (Standard Test Methods for Breaking Tenacity of Manufactured Textile Fibers in Loop or finish Configurations). Tensile test parameters: the test was carried out at a nominal length of 25mm using a crosshead speed of 15mm/min and a 5lb load cell. At least 15 representative samples were tested and the most reproducible mechanical properties were reported. Fig. 9 is a photograph of exemplary fibers used for the loop test, specifically S2-10% glucaric acid-cellulose fibers.

TABLE 3 results of the Ring test

The foregoing detailed description and examples are merely illustrative and are not to be construed as limiting the scope of the disclosure. Various changes and modifications to the embodiments of the present disclosure will be apparent to those skilled in the art. Such changes and modifications, including but not limited to those related to chemical structures, substituents, derivatives, intermediates, syntheses, compositions, formulations, or methods of use, may be made without departing from the spirit and scope of the disclosure.