WO2007008228A1 - Natural cellulosic fiber bundles from cornhusk and a method for making the same - Google Patents

Abstract

The present invention is directed to natural cellulosic fiber bundles from cornhusks preferably having a length, width, strength, elongation, or other properties desirable for textile and other applications. For example, the fiber bundles may have a length that is greater than that of ultimate cornhusk fibers and a fineness of at least about 1 denier and no greater than about 300 denier. The present invention is also directed to textiles that comprise the fiber bundles. Additionally, the present invention is directed to a method for extracting such natural cellulosic fiber bundles from cornhusks, the method comprising performing an alkali treatment, an enzyme treatment, or both to separate the fiber bundles from connecting material in the cornhusks.

Description

Atty Docket No: 46589/56970

NATURAL CELLULOSIC FIBER BUNDLES FROM CORNHUSK AND A METHOD FOR MAKING THE SAME

BACKGROUND OF THE INVENTION

1. FIELD OF THE INVENTION

The present invention relates to the field of textiles, specifically to a novel method for the production of natural cellulosic fiber bundles from cornhusk that are suitable for, among other things, textile applications.

2. DESCRIPTION OF THE RELATED TECHNOLOGY

Cellulose is the most abundantly available organic matter on earth. Cellulose in its natural and regenerated form is a major source of fiber for textile applications. Globally, farming generates millions of tons of agricultural byproducts each year. Some of the byproducts are used as animal feed and for other small scale applications. Many of the agricultural byproducts contain substantial amounts of cellulose, especially in fibrous form. Using agricultural byproducts would benefit the grower economically. Additionally, utilizing these byproducts would provide environmental benefits because the amount of byproducts being disposed of would be reduced. Yet another environmental benefit is that products made using these agricultural byproducts may be made 100% bio-degradable (See, e.g., Chen et al., U.S. Pat. No. 6,083,582).

Natural cellulosic fibers are from various parts of the plants. The fibers are mainly classified as seed fibers (e.g., from cotton and kapok), stem or bast fibers (e.g., from flax, jute, hemp, kenaf, and sugarcane), and leaf fibers (e.g., from pineapple, banana). These fibers may be from plants grown primarily for the fibers (e.g., cotton, flax, hemp, kenaf, etc.) or from plants in which the fibers are primarily considered a byproduct coconut (the fibers are often referred to as "coir"), sugarcane, banana, and pineapple. The byproduct- type fibers have not been used extensively for several reasons including limited availability, difficulty in extraction, lesser performance-related properties, and limited growing regions. A general classification of natural textile fibers known to those of ordinary skill in the art is provided in Table A below. Conspicuously missing from the listed subgrupos of cellulose fiber classifications are "husk fibers" despite the fact that cornhusk is readily available throughout a wide range of geographic regions.

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TABLE A

CLASSIFICATION OF NATURAL TEXTILE FIBERS*

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Textile Fibers from the stalks or stems and leaves of plants are conventionally extracted by a process known as "retting." A traditional retting process is dew retting, which utilizes bacteria and fungi in the environment to delignify the fibers to a state suitable for processing using conventional textile machinery. Dew retting, however, tends to be inconsistent, tends to result in poor fiber quality, usually can only be performed in limited geographical regions, and occupies agricultural land during the retting process (see, e.g., Akin et al., Textiles Research Journal 69 (10), 747-753 (1999)). Chemical methods for retting have been used and these typically produce fibers that are more consistent and with improved physical properties compared to dew-retted fibers. Typical chemical-retting methods use alkalies in combination with other chemicals. Due to the environmental and waste disposal concerns, however, alternatives to chemical retting are being investigated (see, e.g., Wang et al., Textile Research Journal 73(4), 339-344 (2003)). For example, enzymatic retting is being researched as a more ecological-friendly process for fiber extraction. Cost, quality of fibers obtained, and difficulty in controlling the process have, thusfar, limited the use of enzyme retting in commercial scale applications. Cornhusk contains about 40% cellulose, about 45% hemicellulose, about 7% lignin, about 2% protein and about 3% ash (see, e.g., Branka et al., Journal of Agricultural Food

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Chemistry, 34, 1019-1024 (1986)). Cellulose fibers in comhusk are interconnected with each other to form large bundles that are hundreds of micrometers to millimeters wide. These large bundles are connected to each other by films. The cellulose fibers and fiber bundles are connected, primarily, by lignin and hemicellulose. The ultimate fibers in cornhusk are about 0.5 to about 1 mm in length. These ultimate fibers, which may also be referred to as single fibers or individual cells, are considered to be too short, too weak, or both for textile applications. In general, for a fiber to be considered suitable for textile use, among other things, it preferably has a length that is at least about 1 ,000 times its diameter. For practical purposes, it preferred that the fiber length is at least about 1.0 cm. Additionally, a fiber preferably has an adequate tensile strength such as at least about 1 gram per denier. Denier is the common term used to describe the fineness or linear density of a textile material that is quantified as the materials weight in grams per 9,000 meters of that material.

Although the above-described retting processes have been used to produce natural cellulosic fibers from stalks or stems and leaves of plants, to date there has been no process for treating comhusks to yield natural cellulosic fibers from husk that are suitable , for textile use. More specifically, using known methods for treating bast and leaf fibers to treat cornhusk results in fibers or fiber bundles that are too coarse, too small, too weak, or a combination of negative attributes that prevent their use in textile applications. Accordingly, there is a need for a method of processing cornhusk to yield natural cellulosic fiber bundles that are suitable for textile applications.

BRIEF SUMMARY OF THE INVENTION Briefly, therefore, the present invention is directed to a method for extracting natural cellulosic fiber bundles from cornhusks, the method comprising performing an alkali treatment on a cornhusk material to partially delignifiy the cornhusk material thereby yielding the extracted natural cellulosic fiber bundles having a length that is greater than that of ultimate cornhusk fibers and a fineness of at least about 1 denier and no greater than about 300 denier. The present invention is also directed to method for extracting natural cellulosic fiber bundles from cornhusks, the method comprising: performing a first portion of an enzyme treatment on a cornhusk material, the first portion of the enzyme treatment comprising contacting the cornhusk material with a first enzyme solution that comprises a

3186456 3 Atty Docket No: 46589/56970 xylanase at a concentration that is between about 0.05 and about 5 percent by weight of the cornhusk material for a duration of about 10 to about 60 minutes to form a first mixture having an first enzyme solution-to-husk ratio between about 1 :1 and about 100:1 and is at a temperature within a range of about 10 to about 65 ⁰C; separating the first mixture into a first solids portion comprising the cornhusk material and a first liquid portion comprising the first enzyme solution; performing an alkali treatment on the first solids portion, the alkali treatment comprising contacting the cornhusk material with an alkali solution for a duration of about 15 to about 90 minutes to form a second mixture having a alkali solution- to-husk ratio between about 1:1 and about 100:1 and is at a temperature within a range of about 60 to about 100 ⁰C, wherein the alkali solution comprises an alkali compound and has a normality that is between about 0.05 and about 2.5N; separating the second mixture into a second solids portion comprising the cornhusk material and a second liquid portion comprising the alkali solution; performing a second portion of the enzyme treatment on the second solids portion, the second portion of the enzyme treatment comprising contacting the cornhusk material with a second enzyme solution that comprises a cellulase at a concentration that is between about 0.05 and about 5 percent by weight of the cornhusk material for a duration of about 10 to about 60 minutes to form a third mixture having an second enzyme solution-to-husk ratio between about 1 :1 and about 100:1 and is at a temperature within a range of about 10 to about 65 ⁰C; and separating the third mixture into a second solids portion comprising the natural cellulosic fiber bundles and a third liquid portion comprising the second enzyme solution.

Additionally, the present invention is directed to natural cellulosic fiber bundles extracted from cornhusk, the natural cellulosic fiber bundles comprising a length greater than that of cornhusk ultimate fibers and a fineness that is between about 1 and about 300 denier.

Still further, the present invention is directed to a textile comprising natural cellulosic fiber bundles extracted from cornhusk, wherein the natural cellulosic fiber bundles have a length greater than that of cornhusk ultimate fibers and a fineness that is between about 1 and about 300 denier.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 are pictures from a scanning electron microscope or a light microscope of cornhusk fibers. Figure 1a is a longitudinal view of a single cornhusk fiber. Figure 1b is a longitudinal view of an untreated cornhusk strand. Figure 1c is a longitudinal view of a

3186456 4 Atty Docket No: 46589/56970 cornhusk fiber bundle of the present invention. Figure 1d is a cross-sectional view of untreated cornhusk strand. Figure 1e is a cross-sectional view of a cornhusk fiber bundle of the present invention.

Figure 2 is graph of stress versus strain comparing fibers of the present invention (i.e., cornhusk fiber bundles) to other types of natural cellulosic fibers.

DETAILED DESCRIPTION OF THE INVENTION

The present invention, among other things, is directed to a process for treating a cellulosic fiber source such as cornhusk to yield natural cellulosic fiber bundles therefrom that are preferably suitable for a variety of applications including textiles. Such fiber bundles themselves are another aspect of the present invention. In fact, it has been discovered that selecting or controlling one or more parameters of the method of the present invention allows for one or more physical properties (e.g., length, strength, elongation, and other properties) of the resulting cornhusk fiber bundles to be controlled, modified, customized, or tailored depending on their desired end use.

Yet another aspect of the present invention is directed to the end use application of such fiber bundles. For example, the present invention is also directed to textiles that comprise the natural cellulosic fiber bundles from husk. A specific textile example is that the fiber bundles of the present invention may be processed according to any conventional and appropriate method to produce yarns that comprise the cornhusk fiber bundles (e.g., between about 10% to about 100% by weight of the cornhusk fiber bundles). Such yarns may be used to make a variety of products. Alternatively, fibers of the present invention may be used to make textiles without being transformed into yarn (e.g., non-woven textiles). Advantageously, the fiber bundles of the present invention may be processed like any other natural cellulosic fiber. Thus, the fiber bundles or products comprising or made from them may be bleached, mercerized, dyed, or a combination thereof according to a variety of known methods. The fields in which such textile-related products may be used include apparel, industrial uses, and medical uses. Another application for the fiber bundles of the present invention is fiber reinforced composite structures. For example, the fiber bundles of the present invention may be used in fiber reinforced plastics and foams.

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1. Producing Natural Cellulosic Fibers

As set forth above, one aspect of the present invention is a novel method of extracting natural cellulosic fiber bundles from a cellulosic fiber source such as comhusk. Preferably, the method of the present invention is carried out such that the resulting fiber bundles are suitable for textile application. It is important to note that although the present description is focused on treating cornhusk, the method of the present invention is not limited to extracting fibers from cornhusk. In fact, it is expected that the method of the present invention may be suitable for extracting fibers from other cellulosic fiber sources such as stem, leaf, shell, and floss from sugarcane, kenaf, coir, sorghum, pineapple, banana, dogbane, and milkweed, as appropriate.

a. Cornhusk

Conventional natural cellulosic fiber materials (excepting cotton and kapok) are multicellular and to be useful they typically are in the form of groups of individual cells known as fiber bundles, rather than as individual cells. Likewise, cornhusk cellulose fibers are multicellular and their individual cells are generally considered to be too small to be useful for textile and other industrial applications. The ultimate fibers in cornhusk are about 0.5 mm to about 1 mm in length and about 100 μm in width. Lignin, hemicellulose, and other binding substances bind individual cells into a fiber bundle suitable for textile and other industrial applications. Typically, fiber bundles are obtained from larger vascular bundles in plants by partially removing lignin and other constituents such as hemicellulose, pectin, and wax by retting (see above).

Individual cells in cornhusk are ribbon-like and twisted along their length with periodic reversal in the direction of twists, and tapered ends, similar to a cotton fiber, but much smaller than a cotton fiber. These natural convolutions increase the fiber-to-fiber contact and increase the cohesiveness, which is a desirable property for spinning fibers. Figure 1a is a SEM picture of an individual or a single cell of cellulose in cornhusk obtained by maceration. As shown in Figure 1a, the individual cell has a smooth and clean surface because most of the binding materials have been removed. This single cell had a length of about 0.3-0.4 mm and a width of about 15-20 micrometers. Figure 1b is a SEM picture of the surface of an untreated cornhusk strand that was mechanically removed from the husk. Figure 1b shows that the strand is rough with a thick layer of protective material and cellular deposits. Individual cells are held together by lignin,

3186456 6 Atty Docket No: 46589/56970 hemicellulose, pectin, and other binding materials within this layer. Figure 1 (d) is a picture of a cross-section of a cornhusk showing a vascular bundle of fibers obtained using a light microscope. Figure 1(d) shows a vascular bundle of fibers within encrusting substances.

The method of the present invention breaks down at least a portion of this protective layer and the binding materials to obtain fiber bundles with desired properties. Figure 1c is a SEM picture of a cornhusk fiber bundle of the present invention obtained after performing the method of the present invention. Figure 1e is a picture of a cross- section of a cornhusk fiber bundle of the present invention obtained after performing the method of the present invention. Both pictures of the fiber bundles show single cells that are held together by lignin and other substances and a fiber bundle with an irregular surface. It is the extent of removal of the binding materials, which may be varied by controlling or selecting the extraction conditions, that is believed to determine the fineness or width of the fiber bundles, structure, and other properties of the cornhusk fiber bundles. An interesting feature of the fiber cells in cornhusks is the presence of a large lumen, larger than the width of the cell wall in most cells, reducing the bulk density and perhaps increasing the absorbency of the fibers. Additionally, the large lumen provides a hollow region that acts as a thermal and air insulator. This property may make corn fibers useful in fiber reinforced composites that are designed to act as thermal and air insulators in automobiles and other applications. In accordance with the present invention, cornhusks from any variety of corn plants, grown under any climatic conditions may be used as a source for natural cellulose fibers. Further, the method of the present invention may be performed on undried or green husk or dried husk. Preferably the cornhusk is dried before the treatment. If the cornhusks are unusually dirty, the method of the present invention may include washing the husks with an appropriate solvent (e.g., water) to remove impurities, foreign matter, and other materials soluble or partially soluble in the solvent before performing the remainder of the method of the present invention.

The cellulosic fibers in cornhusks (i.e., the vascular fiber bundles) typically have a length that is between about 2 and about 20 centimeters. Depending on the intended use for the extracted fiber bundles, they may be segregated based on their length and used as such. Alternatively, the length may be controlled or selected by, for example, cutting, shearing, tearing, sawing, or any other appropriate way of dividing or separating fibers into smaller lengths. Advantageously, this ability to select or determine the length of the fiber

3186456 7 Atty Docket No: 46589/56970 bundles allows for cornhusk to be a source of fiber suitable for both short and long staple spinning systems.

Conventionally, fibers with a length of at least about 12 cm are processed as long staple fibers, whereas fibers with a length of at least about 2 cm and less than about 12 cm are processed as short staple fibers. For example, if it is desired for the extracted fiber bundles to be processed using a cotton spinning system, it is desirable for the extracted fibers have a length that is similar to that of cotton fibers (between 1.5 and about 5.5 centimeters), and, as such, the extracted fiber bundles may be cut to have lengths between about 2 and about 3 cm. This dividing or separating may be performed at essentially any point in time. In one embodiment of the present invention, the fibers are cut before being extracted from the husk. In alternative embodiments, the fibers are cut at any point during the extraction process or after the extraction process is complete. In addition to mechanically dividing or separating fibers, the length of fibers may be controlled by the extraction process. Specifically, relatively stronger or harsher treatment conditions tend to produce a larger percentage of fiber bundles suitable for short staple processing.

b. Extraction of fiber bundles from comhusks

The method of extracting fiber bundles from cornhusk of the present invention comprises, in general, performing an alkali treatment of cornhusk material, an enzyme treatment of cornhusk material, or both treatments to break down, or decompose lignin and any other materials or films connecting the cellulose fibers in cornhusk, or cellulose itself. Preferably, the cornhusks are subjected to both treatments. In such an embodiment, the enzyme treatment may be performed before, during, or after the alkali treatment, or a combination thereof. Both types of treatments preferably comprise contacting the cornhusk with a solution comprising: an alkali compound that is at least partially soluble in the solute (preferably water), an enzyme compound that is at least partially soluble, or both. Although it is possible for the alkali and enzyme treatments to be performed concurrently (i.e., the alkali and enzyme compounds are in the same solution), this is generally not preferred. Preferably, the process comprises sequential treatments with one or more alkali-containing solutions and one or more enzyme-containing solutions. For example, in one embodiment the enzyme treatments comprises treating the cornhusks with two enzyme solutions wherein the enzymes in the solutions are different.

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The break down of lignin and other materials or films is controlled so that the cellulose fibers of the cornhusk (i.e., vascular fibers) are partially delignified to yield the cellulosic fiber bundles of the present invention that are finer than the vascular fibers, but longer than ultimate cells. Preferably, the cellulosic fiber bundles of the present invention are of a fineness and length suitable for textile applications. In other words, the break down is controlled so that a substantial portion of the vascular fiber bundles are separated from the husk without being reducing to non-bound ultimate fibers or individual cells. It is believed that the method of the present invention may yield up to about 30% by weight of the cornhusks in the form of extracted fiber bundles, which may be described as "long fibers," that comprise a multiplicity, a group, or a bundle of connected ultimate fibers or individual cells. For example, fiber bundles with lengths between about 1.5 and about 23 cm having linear densities between about 10 and about 140 denier have been obtained with the method of present invention. Typically, the method of the present invention is carried out so that the length of the fiber bundles or long fibers is between about 1.5 and about 20 cm. At a minimum, however, they are longer than an ultimate fiber, which is typically between about 0.5 and about 1.5 mm in length. In addition to producing the fiber bundles, the process of the present invention usually reduces a portion of the cornhusk fibers to ultimate fibers (up to about 20% by weight of the treated cornhusks).

i. Alkali treatment

The alkali treatment comprises contacting or mixing cornhusk material (e.g., precut cornhusks, uncut cornhusks, pre-treated cornhusks (i.e., cornhusks previously treated with an alkali treatment or an enzyme treatment) or untreated cornhusk, or a combination thereof) with an alkali compound. Although the alkali compound may be anhydrous, it is preferably dissolved in a solvent (i.e., a solution comprising an alkali compound (an "alkali solution")). The alkali solution may be aqueous or non-aqueous. The cornhusks are partially delignified as described above by controlling or selecting one or more parameters associated with the alkali treatment. A list of such exemplary parameters includes the concentration of alkali in the solution, the temperature of the mixture (e.g., preferably less than 100 ⁰C), the ratio of alkali solution to husk (also referred to as the liquor-to-husk ratio), the duration the alkali solution and husk are in contact, and the pressure at which the solution and husk are in contact. These parameters are generally interrelated, for example, the duration of treatment tends to depend on the concentration of alkali and the temperature at which the treatment is carried out. In general, it has been discovered that

3186456 9 Atty Docket No: 46589/56970 shorter treatment times at higher temperatures and concentrations are preferred for practical reasons and for commercial application.

In one embodiment, the alkali treatment comprises contacting or mixing the comhusks, precut or not, or pre-treated cornhusk material (alkali or enzyme) with an aqueous alkali solution having a normality that is between about 0.05 and about 2.5 N to form a mixture having a liquor-to-husk ratio that is between about 1:1 and about 100:1 that is maintained within the temperature range of about 60 to about 100 ⁰C. Preferably, the cornhusk and alkali solution are in contact for a duration of about 15 to about 90 minutes. It should be noted that the alkali solution may comprise "strong" alkalis such as alkaline metal or alkaline-earth metal hydroxides, "weak" alkalis such as alkaline metal or alkaline-earth metal carbonates, or a combination thereof may be used. Depending on the strength of the alkali solution, however, it is generally desirable to adjust the other alkali treatment parameters as appropriate to ultimately partially delignifiy the cornhusk and extract the desired corn husk fiber bundles. For example, if the alkali solution comprises, largely, strong alkali compounds such as sodium hydroxide, the treatment conditions are preferably such that the normality of the solution is between about 0.1 and about 1.0 N, the temperature is between about 60 and about 100 ⁰C, the duration is between about 15 and about 45 minutes, and the liquor-to-husk ratio is between about 5:1 and about 50:1. More preferably, the solution's normality is about 0.3 N, the temperature is about 95 ⁰C, the duration is about 30 minutes, and the liquor-to-husk ratio is about 15:1. If weak alkalis, such as sodium carbonate, are used, treatment conditions of about 1 to about 2 N at boil for about 40 to about 90 minutes are preferable. More preferably, the solution's normality is about 1.5 N, the solution is maintained at the boiling point, the duration is about 70 minutes, and the liquor-to-husk ratio is about 15:1. It should be noted that the extraction process, including the alkaline and enzyme treatments, is preferably performed at atmospheric pressure. The process of alkaline extraction may be carried out in any appropriate container. Preferably, the container is closed under atmospheric conditions, but an open container may be used. Further, the solutions and mixtures may be heated using any appropriate method. Preferably, the extraction process is carried out using equipment having precise temperature control.

After the treatment is complete, the solid portion and liquid portion of the mixture are preferably separated by any appropriate method such as straining or filtration. The liquid portion may be treated to remove compounds dissolved or removed from the cornhusk to yield a purified alkali solution that may be reused for further extraction. This

3186456 ^■ 10 Atty Docket No: 46589/56970 reduces the disposal problems and would also help reduce the cost of extraction. The solid portion, although not required, may be rinsed with water (preferably cold water). Washing is preferably continued until essentially all of the dissolved lignin and other materials are removed. No special washing apparatus is required. Washing can be done in any suitable way so as to easily remove the impurities and dissolved substances, while ensuring that the fibers are not washed away. After washing, the fibers are preferably subjected to an optional removal of excess water by any appropriate method (e.g., centrifuge or vacuum slot).

Additionally, the solid portion, preferably after being rinsed, may be treated with an acidic solution to neutralize any remaining alkali. Like rinsing, this neutralization step is optional. In general, any remaining alkali will be neutralized with a dilute acid solution, for example, an acetic acid solution. If acetic acid is used, the acid concentration may be between about 10 and about 30%, preferably about 10%, and the liquid-to-fiber ratio is preferably at least about 5:1 and more preferably about 10:1. The neutralized fibers are preferably rinsed in water and the excess water removed as described above.

The solid portion may be dried at any point or points during or after the extraction process. Preferably, the fiber bundles are at least dried after the extraction process is complete. The drying of fibers can be carried out at ambient temperature or at higher temperature using any appropriate device or method such as hot air ovens and infrared driers. The drying time depends on the extent of moisture desired in the fibers. It is preferred that after the extraction process is complete, the fibers are dried so that they are dry-to-the-touch to reduce or avoid bacterial and fungal decomposition due to the presence of moisture.

ii. Enzyme treatment

The enzyme treatment comprises contacting or mixing the comhusks, precut or not, or pre-treated cornhusk material (with alkali or enzyme) with one or more enzymes selected to degrade lignin, hemicellulose, cellulose, or a combination thereof. Examples of such enzymes include xylanase-type enzymes and cellulase-type enzymes. Such types of enzymes are commercially available from Novozymes of Franklin, North Carolina. For example, PULPZYME is a xylanase-type enzyme that, without being held to a particular theory, is believed to depolymerize hemicellulose and break the covalent link between lignin and carbohydrates in comhusks. The depolymerized hemicellulose and separated lignin may be removed by washing. Cellulases are enzyme complexes that

3186456 1 1 Atty Docket No: 46589/56970 generally comprise three main units: endoglucanases, cellobihydrolases, and β- glucosidases. It is believed that endoglucanases attack the cellulose chains at random, cellobiohydrolases hydrolyze the cellulose chains from the nonreducing end, and β- glucosidases hydrolyze the cellulobiose into glucose. Cellulases may be used to remove short fibers that are not suitable for textile applications. In general, the comhusks are treated with one or more enzymes (i.e., subjected to the enzyme treatment) to improve the fineness of the extracted fiber bundles, mechanical properties of the fibers bundles, or both.

As with the alkali treatment, enzyme treatment parameters (e.g., concentration, time, temperature) affect the degree of delignification, and, as a result, they are preferably selected or controlled so as not reduce the fibers from the comhusk to primarily ultimate fibers. This is especially important for cellulases because they are capable of damaging the cellulose in the cornhusk fibers resulting in decreased fiber strength.

In one embodiment, the enzyme treatment comprises contacting or mixing the cornhusks, precut or not, or pre-treated cornhusk material (alkali or enzyme) with one or more solutions comprising one or more enzymes (i.e., "enzyme solutions") having an enzyme concentration that is between about 0.01 and about 10% (w/v) of fibers for a duration that is between about 1 and about 120 minutes. Preferably, the enzyme solution- to-husk ratio (liquor-to-husk ratio) is between about 1:1 and about 100:1. Preferably, the mixture of corn material and enzyme solution is maintained between about 10 and about 75 ⁰C. More preferably, the concentration is between about 0.1 and about 1% (w/v) of fibers, the duration is between about 10 and about 60 minutes, the liquor-to-husk ratio is between about 5:1 and about 20:1 , and the temperature is between about 25 and about 65 ⁰C. These parameters are generally interrelated, for example, the duration of treatment tends to depend on the concentration of enzyme and the temperature at which the treatment is carried out. In one embodiment the cornhusk material is treated with an enzyme solution at a concentration of about 5%, the temperature is about 50 ⁰C, the duration is about 60 minutes, and the liquor-to-husk ratio is about 20:1. During the enzyme treatment, it is preferred for the mixture of enzyme solution and cornhusk to have a pH that is between about 4 and about 6.

In one embodiment the cornhusk material is subjected to an enzyme treatment that comprises a xylanase-type enzyme and a cellulase-type enzyme. In this embodiment enzyme treatment preferably comprises two separate, sub-treatments: a treatment with a solution comprising the xylanase-type enzyme and a treatment with a solution comprising

3186456 12 Atty Docket No: 46589/56970 the cellulase-type enzyme. Preferably, xylanase-type enzyme treatment is performed before the cellulase-type enzyme treatment. In one embodiment, the extraction process comprises treating the cornhusk material with a xylanase solution, followed by an alkali solution, followed by a cellulase solution. In another embodiment, the extraction process comprises treating the cornhusk material with an alkali solution, followed by a xylanase solution, followed by a cellulase solution.

It should be noted that the experimental results to date indicate that using an alkali treatment without an enzyme treatment to extract fibers from comhusks tends to yield fiber bundles that are relatively coarse and of lower-quality (e.g., decreased strength), or primarily small hydrolyzed ultimate fibers. Such coarse fiber bundles had deniers of about 180 and higher and were obtained using a relatively low concentration of alkali, shorter processing time, and lower temperature. The strength of these fibers is typically low at about 1 gram per denier. Some of the possible reasons for the lower strength of the coarser fibers are discussed below. In contrast, if higher alkali concentrations, and a longer treatment duration or higher temperature are used, most of the cellulose in the cornhusks tended to hydrolyzed into small ultimate fibers, and the fiber yield tended to be low.

Experimental results to date also indicate that using only an enzyme treatment typically provides less than optimum results. Specifically, using enzymes alone makes breaking down the outside layer of protective material on the cornhusks difficult. This difficulty tends to exist even over wide ranges of enzyme concentration, pH, treatment duration, and temperature. Because of this difficulty, using an enzyme treatment on cornhusks without using an alkali treatment tends to remove the weak fibrous parts that connect the long thick strands of cornhusk, but the long thick strands of cornhusk tend to retain a large portion, if not all, of their outer covering.

2. Natural Cellulosic Fiber Bundles from Cornhusks

In addition to length, the fiber bundles extracted from cornhusks using the method of the present invention may be characterized using common textile properties. For example, the fineness of the fibers may be characterized, for example, in denier by weighing a known length of fibers. Fibers of the present invention may have a fineness that is between about 1 and about 300 denier. In one embodiment the fiber bundles may be as fine as 12 denier. In another embodiment the fiber bundles have a fineness that is

3186456 13 Atty Docket No: 46589/56970 between about 12 and about 120 denier. In yet another embodiment the fineness is between about 80 and about 140 denier.

Additionally, fibers may be characterized based on their strength (tenacity). In one embodiment the natural cellulosic fiber bundles of the invention have a strength of at least about 1 gram per denier. In another embodiment the strength is at least about 2 grams per denier. In another it is about 2.5 grams per denier.

The natural cellulosic fiber bundles may be characterized based on their elongation percentage. In one embodiment the fiber bundles have an elongation of at least about 2%. In another the elongation is at least about 5%. In another the elongation is at least about 10%. fibers have a regain of about 9% at 65% relative humidity and 95 °F. In yet another embodiment the elongation is between about 9 and about 12 percent.

Still further, the natural cellulosic fiber bundles may be characterized based on their moisture regain. Moisture regain tends to be important for fiber processing and for comfort during wear. In one embodiment the fiber bundles have a moisture regain that is between about 8.5 and about 9.5 percent. In comparison, the moisture regains of cotton and wool are about 8 and 16%, respectively.

The mechanical properties of textile fibers - the responses to applied forces and deformations - are particularly important properties for selecting fibers because they affect the behavior of the fibers during processing and to the properties of the final product. A comparison of some extracted corn fiber bundles and conventional natural textile fibers is set forth in Table B.

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Table B

Comparison of Some Fiber Properties between Cornhusk and Other Common Fibers

* For a specific condition as disclosed in Example 8.

¹ Handbook of Fiber Chemistry (1998).

² Paper and Composites from Agro-Based Resources (1996).

³ Indira Doraiswamy (1993). ⁴ BiIHe J. Collier (1992).

The physical properties and the appearance of the cornhusk fibers tend to be in- between those of cotton and flax, two of the most widely used cellulose fibers in the world. For textile applications, strength of at least 1 gram per denier is preferred with an elongation of at least 2%. Cornhusk fibers tend to have higher breaking elongation than cotton and other natural cellulosic fibers. The higher elongation is believed to be useful for processing and increase comfort during wear. It is expected that these cornhusk fibers will provide unique and desirable properties to textiles when blended with other fibers, especially synthetics. From Table B, it is evident that fibers from cornhusk meet the basic requirements for textile fibers.

Advantageously, the cornhusk fiber bundles of the present invention may be processed according to conventional textile processing methods. For example, they may be subjected to conventional beaching and spinning operations just as any other natural cellulosic fiber. Further, the cornhusk fibers of the present invention may be processed to make textiles including yams that are made entirely of husk fibers or the husk fibers may be blended with any other desired fiber (e.g., wool, cotton, linen, polyester, etc.).

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3. Examples a. Comhusk Materials

Cornhusks were collected form fully mature plants in the greenhouses at the University of Nebraska, Lincoln and from cornfields in Nebraska. The collected cornhusks were cleaned by hand to remove the tassel, leaves, and other parts of the corn plant. Some cornhusks were treated un-cut other cornhusks were cut into pieces having lengths between about 2 and about 3 cm using an INGENTO model A6T paper cutter. The cornhusk were cut so that the fibers obtained therefrom would have lengths similar to that of cotton, which would make them suitable for processing using a cotton spinning system.

b. Testing Methods

The amount of pure cellulose in the corn fibers was determined using the Norman and Jenkins method. Fiber fineness (linear density) was calculated in terms of denier, defined as the weight in grams per 9000 m of the fiber, by weighing a known length of the fibers.

Tensile properties of the fibers were obtained using an lnstron fiber testing machine. A gauge length of 25 mm and crosshead speed of 18 mm min^"1 was used. Five sets of twenty fibers each were tested to determine the denier and tensile properties. The average strength, elongation, modulus and work or rupture are reported along with the standard deviation between the sets of fibers tested. All the fiber property tests were conducted under the standard testing conditions of 21 ⁰C and 65% relative humidity.

Moisture regain of the fibers was determined using ASTM method D 2654. The test includes oven drying the fibers at 105 ⁰C for 4 hours and then allowing the sample to absorb water under the standard testing conditions for 24 hours. The percent regain was calculated as the ratio of the amount of water absorbed to the dry weight of the sample.

A Hitachi model S2000N SEM was used to investigate the morphological characteristics of individual fibers and fiber bundles. For observation in the SEM, the fibers were laid down on an aluminum stub using a conductive adhesive tape and were sputter-coated with gold palladium prior to observations. Cross-sections of the samples were prepared according to standard methods. An Olympus AX70 fluorescence microscope with 40 x lens was used to observe the cross-sections of untreated cornhusks and the extracted fibers.

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X-Ray diffraction was used to study the physical structure of the fiber along with its constituents. X-ray diffraction patterns of corn fibers were recorded from 2θ=0° to 30° using a Philips PW 1050/81 diffractometer. Specimens to be observed were powered in a Wiley mill to pass a 2 mm mesh. The powder was mounted into a cavity holder to record the X-ray diffraction. The degree of crystallinity was calculated by integrating the area under the diffracted peaks after accounting for the amorphous and background scatter. Crystallite size was calculated using the Scherer's equation. X-ray diffraction pictures were obtained using a Bruker smart apex ccd camera. Averages of 8 readings were taken, each for 300 seconds at a sample to detector distance of 5.9 cm.

c. Experiment 1 - Alkali treatments at room temperature

Partial decomposition of the cornhusk into thick strands was observed when cornhusk was allowed to stay in an aqueous alkali (NaOH) solution for about 24 hours in concentrations that were between about 0.1 and about 1.0 N at room temperature for a week. Only water soluble materials were removed whereas the lignin and hemicellulose were not affected by these treatments.

d. Example 2 - Extraction with sodium hydroxide at elevated temperatures Cornhusk pieces were treated using sodium hydroxide solutions at different concentrations (between about 0.05 and about 1.0 N), for varying durations (between about 20 and about 90 minutes), and at varying temperatures (between about 60 °C and boiling) to obtain the fiber bundles. Extraction was carried out in atmospheric conditions using glass beakers. Temperature controllable hot plates were used to heat the solutions. Alkali at the required concentration was dissolved in water; the solution was heated to the required temperature before adding the cornhusk. After the treatment time, the treated husk was washed in tap water. A 20% acetic acid solution was used to neutralize any alkali remaining on the washed material. The fibers were again rinsed in water and air- dried at ambient temperature.

It was found that changing the concentration, time, and temperature affected the fiber quality (in terms of fineness of the fibers) and also the yield of the fibers. Generally, at lower concentrations and temperatures, and shorter durations, husk was partially disintegrated forming thick brownish yellow strands. While husk treated with boiling solutions tended to be completely dissolved after about 50 minutes, even at low alkali

3186456 17 Atty Docket No: 46589/56970 concentrations. It was determined that mixtures with solutions having a sodium hydroxide concentration that was between about 0.1 and 0.2 N maintained at the boiling point for about 45 minutes produced desirably fine fiber bundles at a yield that was between about 5 and about 8% based on the weight of cornhusk used. It should be noted that even at such solution concentrations cornhusk tended to completely hydrolyzed after 60 minutes at the boiling point. Without being bound to a particular theory, it was believed that this hydrolysis was due to the presence of oxygen.

e. Example 3 - Reducing Agent According to the conditions in example 2, a reducing agent (sodium hydrosulfite) was added in an attempt to prevent oxidation of the fibers. The addition of sodium hydrosulfite in the alkali solution at concentrations between about 1 and about 10% on weight of the cornhusks was tested. No effect was observed on improving the quality or yield of fibers.

f. Example 4 - Controlling the concentration of available oxygen

To minimize the amount of oxygen available during extraction, experiments were conducted in closed containers using hot-air ovens to control the temperature. Alkali concentrations from between about 0.2 N and about 0.7 N at temperatures between about 60⁰C and about 100°C were used. The treatment time was between 20 and about 90 minutes depending on the concentration and temperature. The experimental conditions used during the controlled oxygen trials are set forth in Table C. After the treatment, the fibers were cleaned in water, neutralized in acid and rinsed in water and allowed to air-dry at room temperature. The fiber qualities and fiber yield were similar to those obtained in Example 2 for each particular combination of concentration, time, and temperature.

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Table C

g. Example 5

For industrial application and mass production, it most likely would be desirable to use higher concentration of alkali and temperature and reducing the treatment time to the minimum. As such further tests similar to those set forth in Examples 1 and 2 were performed and it was found that fiber bundles of acceptable quality were produced at a yield of about 8% using an alkali concentration between about 0.3 and about 0.7 N at a temperature in the range of about 80⁰C to about 95°C for a duration between about 20 and about 70 minutes.

h. Example 6 - ratio of liquor to husk

To reduce the cost, consumption of chemicals, and waste, further testing was performed to in an attempt to determine an optimum range for the ratio of liquor (alkali solution) to husk. Trials were done varying the liquor to husk ratio (by weight) from about 30:1 to about 8:1 according to the conditions as in Examples 1 and 2. It was determined

3186456 19 Atty Docket No: 46589/56970 that acceptable fibers bundles were consistently extracted at a rate of about 8% at liquor- to-husk ratios no greater than about 15:1.

i. Example 7 - treatment with cellulase Fibers that had already been extracted by exposure to an alkali solution were treated with cellulase-containing solutions of varying concentration to study what effect, if any, such treatments would have on reducing the diameter, or increasing the fineness of the fiber bundles. Aqueous cellulase solutions having a cellulase concentration that was between about 2% and about 10% by weight of the fibers were tested at about 60 ⁰C for about 60 minutes. The tested fibers were dissolved within ten minutes of the treatment, even at the low concentration of about 2%. This indicated that cellulase is an effect agent for the improvement of fiber fineness and that the concentration of cellulase in an enzyme solution is preferably less than about 2%, and that a preferable treatment duration is, most likely, less than about 10 minutes. Further testing to date, however, determined that an enzyme treatment involving a cellulase-containing solution preferably comprises the following parameters: a cellulase concentration that is between about 0.5 and about 1.5%, a temperature that is between about 45 and about 60 ⁰C, a pH that is between about 4 and about 7, for a duration that is between about 5 and about 30 minutes. An enzyme treatment performed according to these parameters may be used to decrease fiber denier between about 10 and about 50%.

j. Example 8 - treatment with sodium carbonate

Sodium carbonate is a weaker alkali compared to sodium hydroxide. Solutions comprising sodium carbonate were tested in which the concentrations of sodium carbonate were between about 1 N and about 2 N. The solutions were maintained at the boiling point and the cornhusks were treated for durations that were between about 40 and about 90 minutes. After the alkali treatment the fibers were washed with water, then neutralized with a 10% acetic acid solution, rinsed with water again, and then air-dried at ambient temperature. The extracted fiber bundles were coarse, specifically larger than 70 denier, and brownish yellow in color. Compared to the tested sodium hydroxide solutions, the sodium carbonate solutions tended to have higher fiber yields. Specifically, the sodium carbonate solutions tested under these conditions had fiber yields between about 10 and about 12%.

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k. Example 9

Uncut cornhusks were treated with a solution of about 2 % sodium hydroxide for about 2 hours at about 80 ⁰C using a liquor-to-husk ratio of about 20:1. The treated fibers were thoroughly washed in warm tap water to remove the dissolved substances, and the fibers obtained were dried under ambient conditions. The alkali extracted fibers were treated with an about 5 % pulpzyme and cellulase solution at about 50° C for about 30 minutes using a material to liquor-to-husk ratio of about 20:1 and maintaining the pH of the enzyme solution between about 5 and about 5.5. The enzyme treated fibers were thoroughly rinsed in water and dried under ambient conditions.

The tested fibers had a crystallinity of about 50% as shown in Table D, which is a comparison of fiber structures, and as indicated by the X-ray diffraction peaks. Although the percent crystallinity of corn fibers is lower than that of the commonly used natural cellulose fibers, fibers obtained from agricultural byproducts such as pineapple and banana leaves have similar crystallinities of about 50%. The presence of higher amounts of noncellulosic substances is a major reason for the lower crystallinity of fibers obtained from lignocellulosic agricultural byproducts.

The lower crystallinity of corn fibers relative to the more common natural cellulose fibers such as cotton, linen, and jute provide unique characteristics to the corn fibers. For example, the lower crystallinity corresponds to a larger amount of amorphous regions, which tends to make corn fibers be more accessible to water and other chemicals (i.e., relatively higher moisture regain and chemical absorptions).

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Table D

Comparison of Fiber Structure

K)

Pineapple leaf fibers

Table E

Comparison of Fiber Properties

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As indicated in Table E, fibers with lengths suitable for processing on the long staple machinery and for blending with most long staple fibers including wool can be extracted from cornhusks. Depending on the treatment conditions, fiber bundles equivalent to the length of the comhusk (about 20 to about 25 cm) can be extracted. Cornhusks can also be cut into any required length to obtain fibers suitable for processing on the short staple machinery. The long staple corn fibers had finenesses between 80 and about 140 denier and tended to be relatively coarser than the short staple corn fibers. In long fibers, a relatively higher number of individual cells are held together by the binding substances such as lignin and hemicellulose. Without being bound to a particular theory, it is believed that the higher number of individual cells and higher amount of binding materials in the fiber bundle not only make it coarser, but also decrease the tensile strength of the fiber bundle. More specifically it is believed that the higher number of individual cells and presence of encrusting substances increase the number of weak spots in the fiber consequently decreasing the fiber strength. Regardless, the tensile strength of the long staple corn fibers test was similar to that of wool, but less than that of other natural cellulosic fibers (see Table E).

The tested corn fibers, however, tended to have a substantially higher percentage of elongation than other natural cellulosic fibers (see Table E). Without being bound to a particular theory, it is believed that the higher elongation of corn fibers is due primarily to their relatively poor orientation and lower degree of crystallinity. The spiral angle, which is the arrangement of the cellulose fibrils to the fiber axis, is also believed to play a significant role in determining the extensibility of multicellular fibers. Generally, the extensibility of fibers increases with increasing spiral angle. This is why coir, which has a spiral angle of about 45 degrees, has a very high extensibility of about 30%. The relatively high elongation percentage of the corn fibers gives them unique properties in terms of the modulus and work of rupture. Specifically, the modulus of the corn fibers was determined to be similar to that of wool, but lower than that of the other natural fibers listed in Table E. The lower modulus provides corn fibers a softer hand and, therefore, products made from them are expected to be comfortable to wear. Since corn fibers have the highest work of rupture among the natural cellulose fibers reported in Table E, corn fibers are also expected to be highly durable. The relatively high extensibility, low modulus, and high durability provides corn fibers unique properties that may be especially useful for blending with relatively inextensible fibers such as linen and jute. Also, the moisture absorption of corn fibers is similar to that of cotton and ramie.

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The combination of the foregoing properties, among other things, make corn fibers a unique fiber for producing textiles and easily processed on conventional textile machinery.

I. Example 10 Fibers were obtained from cornhusks by a combined chemical and enzymatic extraction. Cornhusks were treated with 0.5N sodium hydroxide solution for 60 minutes at 95 ⁰C with 5% of cornhusks by weight in the alkali solution. The treated slurry was washed in water to remove the dissolved substances and the coarse fibers obtained were neutralized using 10% (v/v) acetic acid solution. The neutralized fibers were dried under ambient conditions. The fibers were then subjected to an enzyme treatment with a solution comprising pulpzyme and cellulase. An enzyme concentration of 5% on the weight of the fibers with about 5% (w/v) of fibers in the enzyme solution, and a treatment time of 60 minutes at 50 ⁰C were used. Fibers obtained after the enzyme treatment were washed in water and dried under ambient conditions. The fiber yields ranged from 15- 20% with fiber fineness between 12-120 denier.

Natural cellulosic fibers contain anywhere between 60-95% cellulose. Hemicellulose, lignin, pectin, waxes and proteins are the remaining constituents, their proportion depending on the conditions of growth, fiber source, and method of fiber extraction. Table F shows that corn fibers contain about 80-87% cellulose, a relatively higher quantity when compared to linen and jute. Most of the hemicellulose is removed during fiber extraction and the remaining hemicellulose, lignin and pectin hold the individual cells in the form of a fiber bundle.

Table F

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The physical structure of a fiber describes the amount of crystalline (ordered) and amorphous (disordered) material, their orientation to the fiber axis and the size of the crystals present in a fiber. All celluloses, such as cotton, ramie and wood, have the same polymer and similar crystal structures, but the fibers have greatly different properties. The differences are due to the differences in the orientation of the crystalline and amorphous regions with respect to the fiber axis, in the size and perfection of the crystalline regions, in the relative amounts of crystalline and amorphous materials, and in amounts and type of non-cellulosic material. Corn fibers vary considerably in these parameters relative to the other most common natural fibers as seen from Table G. In comparison to commercially available cotton, linen, and jute fibers, corn fibers have a lower percentage of crystallinity, lower orientation with respect to the fiber's axis, and smaller crystal size than cotton.

Table G

Lower percent crystallinity means, of course, less strength, but also increased elongation, higher moisture regain and more available sites for chemical reactions. The amorphous regions are the regions responsible for the increased elongation, because when the fiber is stretched, molecules in these regions can align themselves to become more oriented to the fiber axes without rupture. Molecules in crystalline regions cannot move easily, and fibers with large percent crystallinity tend to be brittle. Amorphous regions with lots of void space between molecules are also easily accessible to water and chemicals. Therefore corn fibers have higher moisture regain than cotton and would have more easily accessible sites for reactions with dyes and other chemicals as well as greater pliability and elongation.

In addition to crystallinity, the size of crystals also influences the ability of a fiber to absorb water (moisture regain) or other chemicals. Smaller crystal size means more surface area of the fiber and therefore higher accessibility to water and other chemicals.

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Smaller crystals decrease the distance between layers of cellulose, increasing the capillary effect that brings higher moisture and other absorptions.

Fiber strength, however, is partly determined by the orientation of the crystalline regions to the fiber axis. The orientation of the crystals in the fiber is determined from their X-ray diffraction patterns, commonly called fiber diagrams. The fiber diagram of corn fiber shows diffraction arcs much longer and broader than those in cotton, indicating poor orientation of the crystals to the fiber axis. In addition, the broadening of the arcs in corn fibers along the radius of the pattern is characteristic of crystallites that are either very smaller very imperfect. The lower degree of the orientation means fibers that exhibit less strength, because the stress placed upon the fibers may not be in the direction of the strong crystalline regions.

The lower degree of crystallinity and crystal orientation (conversely the higher amount of amorphous regions) of cellulose in cornhusk is what gives corn fibers lower strength than the three most popular cellulosic fibers, but corn fibers have increased elongation, higher moisture regain, and more accessible sites for dyes and other chemicals.

The fiber properties, like strength, elongation, modulus, and moisture regain, are measurable properties that are used to help compare one fiber's performance with another. Fiber properties are determined by fiber structure, but fiber properties provide more meaningful physical comparisons between fibers than do fiber structure comparisons. Often, fiber properties are unique, and that uniqueness is used in combination with other fibers to create materials with the best properties for a particular application.

Tensile tests measure the behavior of fibers when a force of deformation is applied along the fiber axis in terms of tenacity, percent elongation, initial modulus and work of rupture. Tenacity is defined as the specific stress corresponding with the maximum force on a force-extension curve and indicates the load that a fiber can bear before it breaks. Generally, natural fibers have a characteristic higher tenacity and lower elongation or vice- versa. The tensile behavior of the fibers in terms of the modulus and work of rupture are obtained from the stress-strain curves shown in Figure 2, the curves for cotton, linen and jute are from the data in literature. Modulus of a fiber measures the slope of the force elongation curve and is a measure of the stiffness of the material, that is its resistance to extension. The higher modulus of a material, and less it extends for a given force. Cotton has a lower modulus than linen and jute and is therefore more flexible and soft. Work of

3186456 26 Atty Docket No: 46589/56970 rupture is a measure of the toughness of the material and is the total energy required to break the material and depends on both the tenacity and elongation of a fiber. Higher work of rupture means a more durable fabric even though the fiber has low strength. For example, although wool has lower tenacity than cotton, it is more durable due to its high elongation and therefore higher work of rupture. Jute has low work of rupture and hence is less durable than linen and cotton.

Corn fiber has the unique advantage of moderate strength but with higher toughness, low modulus and higher elongation as reported in Table H. These properties make it highly durable but pliable and soft, a property desired for apparel and similar applications. The work of rupture for corn fibers is higher than cotton, however, so that though weaker, corn fiber is tougher or more durable to wear. Therefore, with the unique and exceptional blend of moderate strength, high elongation, great pliability and toughness, corn fibers are ideal for all practical applications utilizing natural fibers.

Table H

The higher moisture regain of corn fibers in comparison to cotton is due to the lower crystallinity and crystal size of cellulose in corn fibers. As predicted by chemical and physical structure, the higher amount of accessible regions, surface area and capillary effect contribute to the higher regain of corn fibers. Although linen and jute fibers have higher crystallinity than corn fibers, their relatively higher moisture regain is due to the presence of non-cellulosic substances, especially hemicellulose and pectin, which are hydrophilic. The high moisture regain of corn fibers suggests that apparel made from corn fibers would be comfortable to wear. The unique corn fiber properties compare favorably with those of other common natural cellulosic fibers which make them suitable for use in all fibrous applications.

3186456 27 Atty Docket No: 46589/56970 m. Example 11 - Fiber processing

Fiber bundles from cornhusk were blended with cotton and polyester and processed on ring and rotor spinning machines. The 50 gram spinning test was used to evaluate the spinnability of the fibers (Landstreet et al., Textile Research Journal, August 1992, 665-669). Cornhusk fiber bundles were blended with cotton in the ration of 35:65 (corn:cotton) and processed on the open end spinning machine to product 30 and 84 tex yarns. Cornhusk fiber bundles were also blended with cotton in the ratio of 50:50, 30:70, and 20:80 and processed on a ring frame to make 30, 38, and 50 tex yarns for each blend. Additionally, cornhusk fiber bundles were blended with polyester fibers at a ratio of 35:65 (corn: polyester) and processed on the ring frame to produce a 23 tex yarn. Control yarns of the same sizes were made form 100% cotton and a 35:65 cotton:polyester blend. The strength and elongation of the corn blended yarns were comparable to the control yarns. The cornhusk fiber-containing yarns were suitable for apparel and other textile applications. Some specific results of the yarn processing trials are set forth in Tables I-K.

Table I

Table J

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Table K

The yarns made from the 35% corn and 65% cotton blend were knitted into a garment. The garment was dyed using direct red 80. Studies on the dyeing behavior of corn fibers using direct, reactive, vat, and sulfur dyes show that corn fibers have a dyeability similar to that of cotton.

n. Example 12 - Bleaching

Fiber bundles of the present invention were bleached using 3 grams per liter of 30% hydrogen peroxide at 90 ⁰C for 60 minutes with about 7% (w/v) of fibers in the bleaching solution. Included therein was 10 grams per liter of sodium silicate as a stabilizing agent along with 0.5 g/l of sodium hydroxide and 1.8 g/l of sodium carbonate to maintain the pH at about 10.5.

A Hunterlab UltrascanXE spectrophotometer was used to determine the color of the unbleached and bleached fibers. The color of the fibers was measured in terms of the Yellowness Index (Yl) and Whiteness Index (Wl) according to ASTM standard E313-98.

Bleaching of corn fibers resulted in removal of the natural yellow color of the fibers, reduction in denier, and an increase in the strength of the fibers. Raw unbleached corn fibers had a Yl of 43 whereas the bleached fibers had a Wl of 98. As described earlier, the single cells in corn fibers are very short, and the fibers are formed by binding these single cells together with lignin and other binding substances. Therefore, the strength of the corn fibers is depends, in part, on the perfection of the binding between the single cells. It is believed that stronger bindings between the single cells are much less vulnerable than the weaker bindings to the attack by the bleaching agents. Therefore, it is believed that weak bindings in the corn fiber were preferentially removed during bleaching, resulting in a decrease in denier by about 30% and an increase in strength by about 13%. Although bleaching eliminates some of the weak bindings in the fiber, it may also damage the cellulose polymers through oxidation. However, the net increase in fiber strength

3186456 29 Atty Docket No: 46589/56970 indicates that if the bleaching conditions are well controlled, the damage to the fiber may be minimized.

In conclusion, the natural comhusk fiber bundles of the present invention have unique properties such as good pliability, moderate strength, durability, high elongation, and high moisture regain. The potential availability of more than 9 million tons of corn fiber every year at a price competitive to the prevailing cotton price is believed to make them attractive to industries utilizing natural fibers and also to consumers. The several benefits possible to agriculture, industrial materials, energy and the environment by using corn fibers are expected to make these fibers preferable over the currently available natural and man-made fibers for certain applications.

U.S. Provisional Application No. 60/520,875, filed on November 18, 2003, is incorporated by reference herein in its entirety. Further, all other references cited in this specification, including without limitation all patents, journal articles, brochures, manuals, periodicals, texts, manuscripts, website publications, and any and all other publications, are hereby incorporated by reference. The discussion of the references herein is intended merely to summarize the assertions made by their authors and no admission is made that any reference constitutes prior art. Applicants reserve the right to challenge the accuracy and pertinence of the cited references.

It is to be understood that the above description is intended to be illustrative and not restrictive. Many embodiments will be apparent to those of skill in the art upon reading the above description. The scope of the invention should therefore be determined not with reference to the above description alone, but should be determined with reference to the claims and the full scope of equivalents to which such claims are entitled.

When introducing elements of the present invention or an embodiment thereof, the articles "a", "an", "the" and "said" are intended to mean that there are one or more of the elements. The terms "comprising", "including" and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements. Additionally, it is to be understood an embodiment that "consists essentially of" or "consists of specified constituents may also contain reaction products of said constituents.

The recitation of numerical ranges by endpoints includes all numbers subsumed within that range. For example, a range described as being between 1 and 5 includes 1 , 1.6, 2, 2.8, 3, 3.2, 4, 4.75, and 5.

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Claims

Atty Docket No: 46589/56970CLAIMSWhat is claimed is:

1. A method for extracting natural cellulosic fiber bundles from cornhusks, the method comprising performing an alkali treatment on a cornhusk material to partially delignifiy the cornhusk material thereby yielding the extracted natural cellulosic fiber bundles having a length that is greater than that of ultimate cornhusk fibers and a fineness of at least about 1 denier and no greater than about 300 denier.

2. The method of claim 1 wherein the natural cellulosic fiber bundles have a length that is between about 0.5 and about 20 centimeters and a fineness that is between about 12 and about 180 denier.

3. The method of claim 1 wherein the alkali treatment comprises contacting the cornhusk material with an alkali solution for a duration of about 15 to about 90 minutes to form a mixture having an alkali solution-to-husk ratio between about 1 :1 and about 100:1 and a temperature within a range of about 60 to about 100 ⁰C, wherein the alkali solution comprises an alkali compound and has a normality that is between about 0.05 and about 2.5N.

4. The method of claim 3 wherein the alkali compound is selected from the group consisting of alkali metal hydroxide, alkaline earth metal hydroxides, alkali metal carbonates, alkaline earth metal carbonates, and combinations thereof.

5. The method of claim 4 wherein the alkali compound is sodium hydroxide, the normality of the alkali solution is between about 0.05 and about 1.0 N, the temperature of the mixture is between about 60 and about 100 ⁰C, the duration is between about 15 and about 45 minutes, and the alkali solution-to-husk ratio is between about 5:1 and about 50:1.

6. The method of claim 4 wherein the alkali compound is sodium carbonate, the normality of the alkali solution is between about 1 and about 2 N, the temperature of the mixture is the boiling point, and the duration is between about 40 and about 90 minutes.

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7. The method of claim 1 further comprising performing an enzyme treatment on the cornhusk material to depolymerize hemicellulose, break covalent links between lignin and carbohydrates, and decompose cellulose chains in the cornhusk material, or a combination thereof.

8. The method of claim 7 wherein the enzyme treatment comprises contacting the cornhusk material with an enzyme solution that comprises an enzyme at a concentration that is between about 0.05 and about 5 percent by weight of the cornhusk material for a duration of about 10 to about 60 minutes to form a mixture having an enzyme solution-to- husk ratio between about 1 :1 and about 100:1 and is at a temperature within a range of about 10 to about 65 ⁰C.

9. The method of claim 8 wherein the enzyme is a pulpzyme-type enzyme, a cellulase-type enzyme, or a combination thereof.

10. The method of claim 9 wherein the pulpzyme-type enzyme is a xylanase, and the cellulose-type enzyme is selected from the group consisting of endoglucanases, cellobiohydrolases, β-glucosidases, and combinations thereof.

11. A method for extracting natural cellulosic fiber bundles from comhusks, the method comprising: performing a first portion of an enzyme treatment on a cornhusk material, the first portion of the enzyme treatment comprising contacting the cornhusk material with a first enzyme solution that comprises a xylanase at a concentration that is between about 0.05 and about 5 percent by weight of the cornhusk material for a duration of about 10 to about 60 minutes to form a first mixture having an first enzyme solution-to-husk ratio between about 1 : 1 and about 100: 1 and is at a temperature within a range of about 10 to about 65 ⁰C; separating the first mixture into a first solids portion comprising the cornhusk material and a first liquid portion comprising the first enzyme solution; performing an alkali treatment on the first solids portion, the alkali treatment comprising contacting the cornhusk materia! with an alkali solution for a duration of about 15 to about 90 minutes to form a second mixture having a alkali solution-to-husk ratio between about 1 : 1 and about 100: 1 and is at a temperature within a range of about 60 to

3186456 32 Atty Docket No: 46589/56970 about 100 ⁰C, wherein the alkali solution comprises an alkali compound and has a normality that is between about 0.05 and about 2.5N; separating the second mixture into a second solids portion comprising the cornhusk material and a second liquid portion comprising the alkali solution; performing a second portion of the enzyme treatment on the second solids portion, the second portion of the enzyme treatment comprising contacting the cornhusk material with a second enzyme solution that comprises a cellulase at a concentration that is between about 0.05 and about 5 percent by weight of the cornhusk material for a duration of about 10 to about 60 minutes to form a third mixture having an second enzyme solution-to-husk ratio between about 1 :1 and about 100:1 and is at a temperature within a range of about 10 to about 65 ⁰C; and separating the third mixture into a second solids portion comprising the natural cellulosic fiber bundles and a third liquid portion comprising the second enzyme solution.

12. The method of claim 11 further comprising: rinsing the first solids portion, the second solids portion, and third solids portion with water; contacting the rinsed second solids portion with an acid solution to neutralize any remaining alkali solution and then rinsing the second solids portion; and drying the rinsed natural cellulosic fiber bundles.

13. Natural cellulosic fiber bundles extracted from cornhusk, the natural cellulosic fiber bundles comprising a length greater than that of cornhusk ultimate fibers and a fineness that is between about 1 and about 300 denier.

14. The natural cellulosic fiber bundles of claim 11 wherein the length is greater than about 2 centimeters and the fineness is between about 12 and about 120 denier.

15. The natural cellolosic fiber bundles of claim 11 wherein the fineness is between about 80 and about 140 denier.

16. The natural cellulosic fiber bundles of claim 12 wherein the length is less than about 12 centimeters.

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17. The natural cellulosic fiber bundles of claim 12 wherein the length is at least about 12 centimeters.

18. The natural cellulosic fiber bundles of claim 11 further comprising a strength of at least about 1 gram per denier and an elongation of at least about 5%.

19. The natural cellulosic fiber bundles of claim 11 further comprising a strength of at least about 2 grams per denier and an elongation of at least about 10%.

20. The natural cellulosic fiber bundles of claim 11 further comprising a moisture regain that is between about 8.5 and about 9.5 percent.

21. A textile comprising natural cellulosic fiber bundles extracted from comhusk, wherein the natural cellulosic fiber bundles have a length greater than that of cornhusk ultimate fibers and a fineness that is between about 1 and about 300 denier.

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