HK1066837A - Method of producing cellulosic sheaths around fibers of textiles and textiles produced thereby - Google Patents

Description

Method for producing a cellulosic sheath surrounding textile fibres and textile products produced thereby

Background

In recent years, particularly in apparel, consumers have reduced the use of synthetic fabrics and blends, and employed 100% cotton fabrics that provide the best appearance and comfort. However, the use of 100% cotton yarn and fabrics also has disadvantages including the tendency to shrink and wrinkle. The most common method of controlling shrinkage and wrinkling of cotton yarns in garment garments is to crosslink the cotton fibers with formaldehyde-based resins. Formaldehyde is considered a hazardous chemical and handling hazard during processing. Since formaldehyde is a known carcinogen, fabrics that come into contact with the body are also considered dangerous. In addition, formaldehyde-based resins, when used to control shrinkage and wrinkling of cotton or cotton blend fabrics, reduce the abrasion resistance and strength properties of the fabrics and make them more susceptible to abrasion, wear, formation of holes and crease distortion. Although non-formaldehyde resins (such as polycarboxylic acids) have been invented, they are less effective, more expensive and also tend to lose fabric strength.

Pre-washing fabrics in a textile mill to control shrinkage is also not satisfactory because it wastes energy and gives the appearance of new clothes passing through. Mechanical compression has been used to control shrinkage of cotton fabrics. But this method is expensive because of the high operating losses and is not a permanent solution because the compressed garment tends to return to its pre-compressed dimensions. Furthermore, none of these methods addresses the tendency of cotton yarns to wrinkle. For these reasons, treating cotton yarns with resins is currently the preferred method of controlling shrinkage and wrinkling of cotton fabrics.

With the advent of hydrophobic synthetic textile fibers (e.g., polyester, polyacrylamide, polyolefin, polyacrylate, nylon, and the like), continuous filaments were available that had greater strength and more durability than staple fibers, and had fewer wrinkling and shrinkage problems. Shrinkage of fabrics made from these fibers can be controlled by using yarns beyond the heat treatment point of the synthetic fiber polymer. Products made from the synthetic yarns have excellent strength properties, dimensional stability and good color fastness to washing, dry washing and exposure. In the late sixties and the entire seventies of the twentieth century, knitted and woven fabrics using 100% polyester are very popular. More recently, continuous filament polyester fibers have also been cut into staple fibers and then spun into 100% staple yarns or blended with cotton or other natural fibers. Synthetic yarns and fabrics made from these yarns have many undesirable properties including a brilliant synthetic appearance, a slippery hand feel, limited moisture transfer capability, and a tendency to accumulate static charge. In addition, polyester fibers in the form of short fibers are prone to pilling and polyester fibers in the form of continuous filaments are prone to blocking (packing).

Some attempts have been made to produce fabrics that only combine the positive properties of both cotton and synthetic fibers. Such attempts include blending, sheath/core yarn spinning, and sheath/core fiber composites (grafting). These methods require modification of the fibers and cannot be satisfactorily performed on the fabric.

Conventional methods of blending cotton yarn with synthetic fibers have been less than completely successful because the mechanical and direct blends of polyester and cotton yarn tend to pill, cake and shrink, and may suffer from electrostatic aggregation, and may be uncomfortable to wear. In recent years, consumers have rejected the use of polyester and polyester blended fabrics and have relied on 100% cotton fabrics to provide the best appearance and comfort.

Yarns having a unique natural fiber sheath/synthetic fiber core configuration have been produced for many years (U.S. patents 4711079, 5497608, 5568719 and 5618479). A well-known method of spinning both homogeneous and composite yarns is ring spinning, which produces high quality strong yarns with low capital investment per spindle. However, ring spinning is a relatively slow process that produces only about 10-25 meters of yarn per minute, which greatly increases the cost of the final product. Moreover, the bonding of natural fibers is not well controlled; the resulting yarn has a non-uniform sheath fiber distribution on the core, including portions that do not have any sheath content. In addition, since no other previously known method can produce the strength or feel of ring spun yarn, the method is used when the requirement for yarn strength and feel justifies its high cost.

The concept of producing sheath/core fibre composites by grafting or coextrusion is a relatively new attempt to solve this problem (us patents 3824146, 5009954, 5272005, 5387383). In this process, the synthetic core fiber passes through a fiber coating die where it contacts the viscous rayon. Rayon coating was performed by passing the treated fibers through a sulfuric acid bath. The resulting composite fiber has the mechanical properties of the core fiber and the surface properties of rayon. Typically, the surface of the rayon is poorly adhered to the core, particularly if the latter has a smooth surface. Many adhesion promoters have been proposed with varying degrees of success, but the long reaction times required for acid curing make the process expensive and slow.

Accordingly, there is a need in the art to produce fabrics that have the positive properties of both cotton yarn and synthetic fibers, while eliminating their respective negative properties. It is further desirable that the process is also fast, economical and obvious to current textile manufacturing practices such as sanding, weaving, and dyeing.

Summary of The Invention

The present invention relates to a method of treating fabrics, garments, woven or nonwoven fabrics (herein included within the terms "matrix" or "fibrous matrix") or individual synthetic fibers or yarns made from synthetic fibers to create a permanently attached carbohydrate sheath around each synthetic fiber of the matrix. Carbohydrates have the properties required for cotton yarn, which is a type of carbohydrate. This treatment results in a matrix that exhibits the most desirable characteristics of a synthetic core while at the same time having the most desirable characteristics of a natural carbohydrate sheath. For example, it will exhibit the mechanical properties of synthetic core fibers and cotton-like surface properties. This technique may also be applied to individual synthetic fibers or yarns, as desired, prior to weaving, knitting, stitch-bonding, or other methods of woven or non-woven matrix formation.

More particularly, in the process of the invention, a synthetic fiber-containing article or substrate is contacted with an aqueous solution containing a water-soluble carbohydrate polymer or monomer. The carbohydrate monomers/polymers are then cross-linked to each other using a suitable cross-linking agent to form a durable carbohydrate sheath or encapsulating layer surrounding the synthetic fibers. The resulting treated substrate possessed tactile properties similar to cotton and exhibited hydrophilicity even after repeated water washing. In contrast, a matrix composed of untreated synthetic fibers is generally hydrophobic. One advantage of this process over those of the prior art is its ability to be applied directly to dyed and finished synthetic fibers by performing a pad/dry/cure process. Furthermore, the method is economical and can be easily implemented with textile finishing equipment currently in use.

The invention further relates to a method for treating fabrics, garments, woven or nonwoven fabrics made from natural fibers ("substrate" or "fibrous substrate") or individual natural fibers or yarns to create a permanently adhered carbohydrate skin or envelope layer around the fibers of the substrate. This gives the desirable properties of a cotton-like surface while retaining some of the functional properties of the natural fiber core.

Other components may be incorporated into the encapsulating layer in accordance with the present invention to impart durability to the synthetic or natural fibers or fabrics. In this way, the carbohydrate layer acts as a binder, encapsulating not only the matrix fibers, but also the compound incorporated into the outer layer.

Detailed Description

As used herein and in the appended claims, "a" means "one or more".

Application of a skin layer

In a preferred embodiment of the invention, synthetic, artificial or natural core materials in the form of fabrics are passed through a dyebath containing an aqueous solution of a water-soluble carbohydrate and a crosslinking agent and, if desired, a suitable crosslinking agent catalyst. This dye bath is referred to herein as a "carbohydrate polymer crust formulation" or "crust formulation". The fabric is padded, excess bath removed, heated to dryness, and then cured at a temperature sufficient to cause reaction between the crosslinking agent and the carbohydrate. Cross-links are formed between these compounds, forming a thin film of carbohydrate on the surface of the core. This layer is referred to herein as a "carbohydrate encapsulating layer", "carbohydrate sheath", "outer skin layer" or "skin". This same general method can also be applied to individual fibers, ribbons and shaped materials. This application is accomplished by contacting the substrate with the treatment solution by spraying, foaming, or any other means known in the art.

Non-limiting examples of water-soluble carbohydrate polymers include chemically modified cotton, dextran, diethylaminoethyl dextran, dextran sulfate, starch, chitin, chitosan, carboxymethyl cellulose (free acid or salt), diethylaminoethyl cellulose, hydroxyethyl cellulose, hydroxymethyl cellulose, chondroitin-4-sulfate, guar gum, hydroxypropyl guar gum, konjac, locust bean gum, xanthan gum, alginic acid (free acid or salt), carrageenan, and acrylonitrile grafted starch.

Any compound capable of binding to two or more nucleophilic components (e.g., hydroxyl, amine, thiol, etc.) can be used as a crosslinking agent to attach the hydroxyl groups on the carbohydrate sheath around and/or onto the core fiber. Those skilled in the art are familiar with the many possible crosslinking chemistries that may be used, including polycarboxylic acids, aminoplasts (N-methylol), isocyanates, epichlorohydrin, and crosslinkable silicone polymers. Presently preferred crosslinking agents are polycarboxylic acids and N-methylol compounds. Polycarboxylic acid crosslinking agents include butane tetracarboxylic acid, polymaleic acid, polyacrylic acid, citric acid, and the like. Catalysts for use with polycarboxylic acids are well known in the art, and include sodium hypophosphite. If the polycarboxylic acid has a large molecular weight (for example a MW > 10K polycarboxylic acid), no catalyst is required. N-methylol crosslinking agents include those used in permanent ironing applications such as dimethylol dihydroxyethylene urea (DMDHEU), triazinone, oolong, dimethylol carbamate, trimethylol triazine, dimethylol ethylene urea and dimethylol urea and polymers incorporating aminoplast monomers such as N-methylolacrylamide and N-methylolmethacrylamide. These aminoplast materials react with nucleophilic groups in the presence of a Lewis acid catalyst such as magnesium chloride or aluminum salts.

The present invention further relates to synthetic yarns, fibers, fabrics, finished goods or other textiles (encompassed herein under the terms "textile", "fibrous substrate" and "substrate") treated with the hydrophilic fabric finishing agents of the present invention. These textiles or fibrous substrates exhibit improved moisture absorption and permeability as compared to conventional synthetic and some man-made textiles. In addition, other properties of the fibers, such as fiber gloss, fabric feel or "hand", static dissipation capability, and fiber-to-fiber frictional noise characteristics, can be improved by the treatment.

The invention further relates to a method for treating natural or artificial substrates, such as wool and other keratin fibers, flax, rayon and the like. The carbohydrate sheath is coated to impart desirable properties to the cotton-like surface while retaining some of the functional properties of the natural core fiber. For example, wool fabrics have advantageous properties such as heat retention when wet, good drying properties, elasticity, extensibility, drapability and wrinkle resistance. However, wool is foreign (allogenic) to some people, shrinks and felts when washed, and gives a feeling of itching when worn against the skin. With the cellulosic outer layer of the invention, the wool is shrink-proof, non-foreign, aesthetically pleasing and comfortable, while retaining its advantageous properties.

In one embodiment, the method comprises contacting the keratin fibers with a finish, wherein the finish comprises a combination of polyelectrolyte carbohydrate polymers. Thus, a wool fiber, textile or fiber substrate is coated with a positively charged polysaccharide, such as an amine-containing chitosan, and then coated with a negatively charged polysaccharide, such as a carboxyl-containing alginic acid. The oppositely charged polymers form a complex skin on the wool fibers, making them less allergenic. The resulting composite is insoluble in organic solvents commonly used in commercial dry cleaning, such as tetrachloroethylene, making the coating permanent.

The properties imparted by the carbohydrate sheath or encapsulating layer do not interfere with the macroscopic properties of the fabric; that is, the sheath does not significantly increase the diameter of the fibers, and it does not fill the spaces between the fibers with large pieces of sheath material or clog the fabric. In addition, the treated fabric felt like cotton rather than polyester and showed improved moisture absorption.

Synthetic and natural textiles made by the present invention may be used in a number of ways, including but not limited to clothing, upholstery and other furniture, hospital and other medical applications, automotive fields, and the like; and Industrial applications, such as Adanue S., listed in Wellington Sears handbook of Industrial Textiles, pages 8-11 (technical publishing Co., Lancaster, PA, 1995).

Garments made from 100% cotton yarn in the form of garments are finished by post-treatment to improve "life" or aesthetic appeal to the consumer. Some properties may be imparted to textile articles in the form of garments by processing, including soft hand, shrinkage control, durable ironing, and unusual and unique appearance, depending on the process used. For example, denim is often wet-finished prior to sale to improve softness and shrinkage control, and softeners are often used in the final rinse. Lava rock, pumice stone, bleach and/or cellulase can be used to promote abrasion and to give the garment an abrasion-resistant look. These and similar post-treatment processes may be applied to the present invention to improve the aesthetic appeal of the finished garment. The carbohydrate sheath encapsulating the synthetic, man-made or natural fibers makes it possible to apply many of the same post-treatment processing techniques used on cotton to the treated synthetic, man-made or natural fabrics of the present invention.

Incorporation of auxiliary components into the cortex

According to the present invention, the application of a carbohydrate encapsulating layer to a fabric provides the opportunity to simultaneously finish the fabric with an adjunct component that does not inherently have the ability to durably bond to the fabric. In this manner, the carbohydrate sheath acts as a binder, imparting durability to the non-essential secondary components that are co-coated with the sheath finish. Alternatively, the adjunct component may have an affinity for the carbohydrate finish, and may be applied during processing after the carbohydrate encapsulating layer is applied. In another approach, the base fabric is imparted with many properties that are not possible without the use of an encapsulating layer.

Some examples of such adjunct ingredients include infrared absorbing compounds that can be permanently incorporated into the fabric to minimize detection from night vision equipment. Examples of infrared absorbing materials are carbon black, chitin resins, or compounds that generally absorb electromagnetic radiation having a wavelength of 1000 to 1200 nm. Fabrics treated with an encapsulating layer comprising an infrared absorbing material exhibit infrared absorbing capabilities as well as other beneficial properties attributed to the encapsulating layer, and such fabrics may be particularly beneficial in military applications.

Similarly, ultraviolet light screening compounds may be incorporated to protect the wearer of the garment or the fabric material itself from ultraviolet light. The fabric may be dyed by incorporating a colored pigment or dye into the outer layer. Magnetic colloid can be embedded in the outer skin to provide the fabric data storage capacity. Bioactive agents such as insect repellents, antibacterial agents and drugs, as well as fire retardant chemicals and antistatic agents may also be incorporated. In accordance with the present invention, odor-absorbing compounds and neutralizing agents (e.g., activated carbon or cyclodextrin) or materials that are desired to be released in a long-term manner, such as by using a hydrolyzable linker, may also be used.

In one embodiment, colloids (generally described as particles having an average diameter of 10 to 500 nanometers) are incorporated into the encapsulated skin formulation and bonded to the treated fabric. The colloidal particles are too small to be observed with a conventional microscope and as a result the individual particles will not be noticeable on the fabric. Some metal colloids, such as gold and silver, are of particular interest because of their light absorption (and hence coloration). The metal colloid absorbs light at the maximum absorption wavelength, which is related to the type and particle size of the metal. They have a wide range of uses in inventions involving biological and toxicological assays.

U.S. patent 5851777 to Hunter et al discloses the use of colloidal particles that bind to ligands and specifically bind some biological or toxicological moiety. Colored metal colloids are particularly claimed as one aspect of the invention. When a specific biological or toxicological moiety is added to a solution containing ligand-bound metal colloid particles, coordination with the moiety results in particle aggregation and a shift in the wavelength of maximum absorption (i.e., solution color). Hunter et al also disclose a number of related patents in which ligand-bound colloidal particles are used. An important aspect of these inventions is the ability to bind ligands to the surface of the particle through intermediate polymers. The intermediate polymer is either physically entrapped (partially) within the particle or durably absorbed onto the surface of the particle. The necessary intermediate polymer contains reactive groups that enable it to bind to the ligand. The disclosure of USP5851777 and those cited therein are incorporated herein by reference.

U.S. patent 6136044 to Todd discloses the use of metal colloids to color substrates such as fibers, yarns, and textiles. The substrate to be coloured is first placed in a dye bath containing a reducing agent, preferably an agent having a certain affinity for the substrate. After allowing sufficient time for the reducing agent to adsorb, the substrate is removed from the dye bath, optionally dried, and then placed in a second dye bath containing a dissolved metal salt corresponding to the metal colloid of interest. The adsorbed reducing agent reduces the salt to a colloid and serves as a nucleation site for particle growth. The resulting particles are adsorbed onto a matrix or optionally entangled with a matrix. The substrate is thus coloured with a colour adapted to the parameters of type of metal, particle size and amount of metal on the substrate. Since each of these parameters can be controlled, various shades can be obtained. The resulting color of the substrate is both wash and light fast. The method does not require the use of polymeric binders or other agents to provide colorfastness.

Some metal colloid suspensions, particularly silver and copper, and more particularly silver, have been demonstrated to have antibacterial activity against a broad spectrum of bacterial species. The Merck Index (10 th edition) considers silver "used to purify drinking water because of its toxicity to bacteria and lower life forms".

In one embodiment of this aspect of the invention, a metal colloid is incorporated into the skin formulation to color the fibrous substrate treated with the formulation. In another embodiment of this aspect of the invention, metal colloids having antimicrobial activity, preferably silver and copper, most preferably silver, are incorporated into the skin formulation. The fibrous substrates treated with the formulation have antimicrobial activity. In yet another embodiment of this aspect of the invention, the metal colloid is incorporated into the skin formulation in an amount sufficient to promote conductivity at the surface of the treated substrate, while the untreated substrate has little or no conductivity. The treated substrate thus has antistatic properties.

The metal colloid can be incorporated into the skin formulation by various methods. In one method, a metal colloid is prepared and then added to the skin formulation. The metal colloid may be prepared by reducing the metal salt by chemical, electrochemical or radiative methods known in the art. For example, sodium borohydride (chemical), electrical potential (electrochemical), or visible light (radiation) can be used to reduce silver salts to metallic silver. So-called "passivating agents" may be used in the metal colloid formulation; these agents may act as nucleating agents for particle growth and may also coat the particle surface to minimize aggregation of the particles. Common passivation agents include bovine serum albumin, casein and milk proteins (e.g. milk powder). The passivating agent preferably contains functional groups that react with the components of the skin formulation. More preferably, the passivating agent is physically entrapped within the colloidal particles to promote entrapment of the colloidal particles within the cortex.

The metal colloid may also be prepared directly within the skin formulation solution or with one or more components. The soluble metal salt of the colloid of interest is mixed with between one and all of the skin formulation components and then exposed to reducing conditions to initiate colloid formation. This approach offers potential advantages in that: a viscous solution of between one and all of the skin formulation components prevents the aggregation of adjacent colloidal particles. In addition, one or more components of the skin formulation may act as a passivating agent for the colloidal particles.

Incorporation of colorants

In another embodiment, the present invention may be used as a binder to fix colorants to fibers. The term "colorant" as used herein and in the appended claims refers to either a pigment (water insoluble) or a dye (water soluble).

While one of the primary objectives of carbohydrate-encapsulated finishes is to impart the "natural fiber" (e.g., cotton yarn) feel to synthetic fibers, the treated fibers have chemical and physical properties that are quite different from those of cotton fibers. There are at least three important differences:

first, the material making up the finish may be only chemically similar to, but different from, cotton fibers. Chemical differences have a significant impact on the efficiency of the various dyes.

Second, the sheath is highly cross-linked and thus tightly wraps the parent fiber. The skin layer cannot have a significant ability to swell in water, if it does, it will not resist washing with water. Conventional dyeing relies to a large extent on swelling of the fibers, allowing the dye to absorb into the fibers; this maximizes both fastness and depth of shade. Dyeing a skin-wrapped fabric may be ineffective using conventional techniques that rely on fiber swelling.

Third, the skin is very thin relative to the thickness of the fiber. In the case of core fibers without concomitant dyeing, the best uniform dyeing throughout the sheath produces only a ring-dyeing effect on the entire fiber; many core fibers have affinity for only a limited class of dyes, so ring dyeing is generally observed when the sheath is dyed with dyes that do not have affinity for the core fiber.

The colorant may be selected to match the color of the core fiber to give a darker shade, or the colorant may be selected as a different shade to give a "two-tone" effect. Most likely, although not necessarily, a colorant may be selected as a dark shade on top of the lighter colored core fiber. The result will be a "ring" dyed fabric. For denim, for example, this ring dyeing is common for 100% cotton fibers with vat dyes and indigo. Such dyeing is not readily performed on synthetic fibers, but is facilitated by the invention described herein. In one embodiment of the invention, the pigment is dispersed within or co-coated with the encapsulated skin. Another embodiment of the "two-tone" invention would have a separate dyeing step during the processing of the textile. The core fiber (dyed or undyed) is treated with a carbohydrate outer layer, followed by dyeing the fabric with a "cotton" dye. The dye will be selected to react or adhere to the outer surface rather than the inner core, or vice versa. For example, polyester fibers treated with a carbohydrate sheath may be selectively dyed with a dye specific to polyester, for coloring of the inner core (or not for white) and for dyeing of the outer layer with a dye specific to carbohydrate. Some common dyes for the outer layer include: a) physically absorbed dyes (direct dyes); b) dyes that will be mechanically retained (vat dyes and sulphur dyes); or c) a dye that will chemically react onto the carbohydrate surface (reactive dye). This technique provides a way to create a variety of effects and colors. By means of the invention, frosting (lighter color in the upper darker part), two-tone (two different colors) and "worn" (optionally wearing or hydrolysing the outer layer, giving a worn-out appearance) effects are all possible.

Coloring method

The terms "one-step" and "multi-step" as used herein refer to the number of steps required to process a fabric or fibrous substrate to have a pigmented skin layer. The "one-step" process may require several steps before the substrate is involved, but the colorant and skin will be applied to the fabric simultaneously. In the multi-step process, the colorant and skin are applied in separate steps.

A one-step method: the easiest approach is to incorporate the colorant into the base carbohydrate sheath formulation before the finish is applied to the fabric. The pigmented formulation is then applied according to conventional methods such as dipping, spraying or padding, with the latter method being preferred. The colorant is retained within the skin by means such as physical entanglement or encapsulation, electrostatic coordination, or chemical bonding to the skin material. In addition to the simplicity of processing, this approach may provide another advantage in that depth of tint can be achieved. The skin layer is up to 10 times less than the thickness of the fabric fiber it encapsulates, and possibly even less. Distributing the colorant evenly throughout the skin layer maximizes the amount of colorant applied. Uniform distribution also helps to ensure the "color fastness" of the colorant or is not easily removed by washing or other abrasive conditions. Potential disadvantages may include lack of equipment during the finishing process and/or difficulty in applying the colorant within the textile mill, difficulty in achieving uniform application and depth of shade in the padding process, and problems with cleaning and disposal of the pigmented skin finish.

The multi-step method comprises the following steps: in this process, a colorant is applied to a fabric that has been previously finished with a base carbohydrate sheath formulation. The applied formulation may optionally include a component having a particular affinity for the colorant. Alternatively, the finished fabric may be treated with a component having an affinity for both the skin layer and the colorant prior to exposure to the colorant. A potential advantage of this approach is the use of colorants that cannot be incorporated into the skin formulation without altering the stability or durability of the skin. Another advantage is that a significant aesthetic effect can be obtained compared to a one-step process. Disadvantages include color problems limited to the type of colorant that is effective and possible surface aggregation of the colorant, with concomitant poor depth of shade, crockfastness, and colorfastness. The skin layers are tightly cross-linked, preventing the colorant from penetrating the skin layers to any significant depth.

The following are some specific descriptions of methods of coloring with known dyes. One or both of the above-described methods may be applied to these methods.

Fixing a mordant: some metal species, known as mordants, form strong bonds with chemically reactive groups such as carboxylate and phenol functionalities; the resulting mordant complex does not dissociate in water and is often water insoluble. Since mordant-reactive chemical groups are found on many classes of dyes, mordant complexation provides a means of immobilizing insoluble dyes on or within a substance, particularly when the substance is also complexed with a mordant metal. Mordant metals include chromium, cobalt, nickel, aluminum, and zirconium.

In one step embodiment, the mordant and mordant-reactive dye are mixed into the base carbohydrate skin formulation. The mordant and mordant-reactive dye are mixed into the resulting colored formulation in an amount, order, and manner that contributes to the desired properties of the formulation. Preferably, the resulting formulation is stable, e.g., the mordant complex does not plate out. Stability is promoted by the coordination of mordants to reactive groups on the water-soluble polymer of the base skin formulation. However, if the base skin formulation is sufficiently viscous, the mordant complex can be sufficiently suspended within the formulation and water solubility may not be required. Mordants are added in any desired amount up to an amount that causes instability of aggregation within the base skin formulation. Dyes are optionally added in amounts up to which the binding capacity of the mordant in the added amount is fully utilized. The pigmented skin formulation is then applied to the fibrous substrate and the treated substrate is cured to fix the skin in place. The dye is durably incorporated within the skin layer by mordant complexation and by physical encapsulation.

In a multi-step embodiment, the mordant is mixed into the base carbohydrate skin formulation in an amount and manner that contributes to the desired properties of the resulting mordant-modified formulation. The mordant preferably forms a bond with the skin material, but in any case the resulting formulation is stable, e.g., the mordant complex does not precipitate out. Stability is promoted by the coordination of mordants to reactive groups on the water-soluble polymer of the base skin formulation. However, if the base skin formulation is sufficiently viscous, the mordant complex can be sufficiently suspended within the formulation and water solubility may not be required. Mordants are added in any desired amount up to an amount that causes instability of aggregation within the base skin formulation. The mordant-modified formulation is then applied to the substrate and the treated substrate is cured, thereby fixing the skin layer in place. The skin-wrapped fibrous substrate is then exposed to a mordant-reactive dye by techniques known to those skilled in the art. In one preferred method, the fibrous substrate is exposed to a solution containing the dye at a temperature and for a period of time that facilitates the complexation of the reactive groups on the dye with the mordant metal incorporated into the sheath. The dyed fibrous substrate is then dried. The dye is durably adhered to the skin layer by mordant complexation, but it is believed that the dye adheres only to the outer layer of the skin layer due to tight crosslinking within the outer layer.

In another multi-step embodiment, the skin-wrapped substrate is exposed to a mordant-metal solution. Mordant metals are exhausted onto the substrate by complexing with exposed reactive groups in the skin material. The mordant-treated fibrous substrate is then removed from the solution, optionally dried, and then exposed to a solution containing mordant-reactive dyes. The dye is exhausted to the skin layer by complexing with the mordant on the surface of the skin.

Other embodiments of such dyeing methods are readily understood, and although not mentioned, all such methods are considered to be within the scope of the present invention.

Pigments, vat dyes and sulfur dyes: vat and sulfur dyes are hybrids between dyes and pigments that are typically used to dye cotton yarns and other cellulose-based fibers. In their chemically reduced ("leuco") form, they are water-soluble dyes; but when oxidized they become insoluble pigments. In conventional fiber dyeing, the fiber is exposed to a reduced form of the dye, which facilitates penetration of the dye into the fiber. The fibers are then exposed to oxidizing conditions that induce the formation of insoluble particles that are adsorbed within the fibers. This hybridization behavior provides a number of approaches in which these dyes can be used as colorants within the skin formulation.

In the one-step process, a pigment or an oxidized reducing or sulfur dye is dispersed within a carbohydrate sheath formulation. Optionally including a surfactant to aid in dispersion. The viscous base skin formulation also helps to aid the lifetime of the dispersion by slowing the rate of sedimentation. The colorant may be added in the form of a solid powder or in the form of an aqueous dispersion. In both cases, particularly for the latter, it is desirable to add a colorant that does not dilute the skin formulation to such an extent that the skin loses durability or does not effectively provide its properties when applied to a substrate. Aqueous dispersions of pigments can be used under the trade mark "HiFast^TM"obtained from BASF. The pigmented skin formulation is then applied to a substrate and cured in place. The colorant is dispersed throughout the skin layer and remains in place by physical encapsulation.

In another one-step process, a leuco vat or sulfur dye solution is added to the skin formulation and the combined formulation is then oxidized to form a dispersion of colorant within the skin formulation. Optionally, it may be desirable to adjust the pH of the pigmented skin formulation to within the prescribed values required for the base skin formulation. The method provides partial encapsulation of the outer shell polymer material within the oxide particles. As noted above, the viscous base skin formulation helps aid the life of the dispersion by slowing the rate of settling of the particles. The resulting dispersion is then applied to a fibrous substrate, followed by curing of the fibrous substrate to secure the skin layer. The encapsulated colorant is securely retained by physical entanglement.

In another one-step process, one or more skin material components are added to a leuco, reduced or sulfur dye solution. The components are preferably added in amounts equivalent to their weight percentages in the base skin formulation. The amount of the component added more preferably significantly increases the viscosity of the solution. The leuco dye is then oxidized to form a dispersion of particles, preferably partially encapsulating the sheath material component. If desired, the remaining components of the base skin formulation are added, and the pH is adjusted to the specified values required for crosslinking. The pigmented formulation is then applied to the substrate and the substrate is cured to set the skin layer. The encapsulated colorant is securely retained by physical entanglement.

Other embodiments of such dyeing methods are readily understood, and although not mentioned, all such methods are considered to be within the scope of the present invention.

Modified reactive dyeing: commercially available reactive dyes are typically used to dye cotton and cellulose derived fibers. They contain functional groups that can react with nucleophilic sites at highly basic pH and elevated temperatures. They have very good colorfastness, since the dyes are covalently bound to the fibers. In the present invention, the skin material may not include suitable reactive sites, or may not be applied at a highly basic pH, either of which would prevent reaction with commercially active dyes. Another challenge with the use of reactive dyes is hydrolysis of the reactive sites; hydrolysis competes with the cellulose hydroxyl groups for the reactivity of the dye and results in ineffective dye application.

Various methods can be used to overcome the above difficulties. In one method, the dye is first modified by reaction with a bifunctional reagent; one functional group of the reagent reacts with the dye and the other functional group binds to the skin material. In the one-shot process, the modified dye is then added to the base carbohydrate sheath formulation, which may then be applied to the fibrous substrate. In another approach, a difunctional agent is added to the base skin formulation. The difunctional agent has one functional group that preferentially reacts with the reactive dye and the other functional group is bound to the skin material. The modified skin formulation is applied to a substrate and cured to fix the skin layer and bind the agent. In a multi-step process, the treated substrate is then dyed with a reactive dye that preferentially reacts with the remaining functional groups of the reagent. In yet another method, the sheath formulation incorporates a difunctional agent and the reactive dye is modified with a second difunctional agent. Each of these two reagents contains at least one functional group that preferentially reacts with functional groups on the other reagent. In this case one or more coating steps are conceivable. Similar ideas were proposed by Lewis and Vigo (Lewis, D.M., Lei, X; AATCC International Conference and inhibition Book of Papers, Oct4-7, 1992, 259-page 265; Vigo, T.L., Blanchard, E.J.; AATCC International Conference and inhibition Book of Papers, 1996, page 203-208; Vigo, T.L., Blanchard, E.J.; Textile Chemist and Colorist, vol 19, No.6 (1987); USP4678473), but in these cases, the cellulose fibers were modified rather than the skin layer.

Examples of functional groups that preferentially react with reactive dyes include amines and thiols, which are much more nucleophilic than water, and which eliminate unwanted hydrolysis. More preferably an amine. Examples of functional groups that can react with components in the carbohydrate skin layer include, but are not limited to, hydroxyl, amine, thiol, amido-formaldehyde condensates, cyclic anhydrides of 5-and 6-membered rings, dicarboxylic acid esters of cyclic anhydrides capable of forming 5-and 6-membered rings, and blocked isocyanates. Non-limiting examples of difunctional agents include ethylenediamine, ethanolamine, and aspartic acid.

It has also been found that incorporating dyes with carboxylic acid functionality or 1, 2-dihydroxyquinone structures into the sheath formulation provides a colorant formulation that imparts wash and rub resistant color to fibrous substrates treated with the formulation. Dyes that do not contain these functional groups are not wash and rub resistant. Examples of dyes having carboxylic acid groups include methyl red, mordant yellow 12, and mordant orange 1. Examples of the dye having a 1, 2-dihydroxyquinone structure include alizarin and purpurin. Without being bound by theory, it is believed that the carboxylic acid groups react with the electrophilic moieties of the skin material, and the hydroxyl groups in the 1, 2-dihydroxyquinone react with the electrophilic moieties of the skin material. The preferred nucleophilic moiety is a hydroxyl group and the preferred electrophilic moiety is a carboxylic acid group. The dye is retained within the skin by covalent bonds, so the dye functions according to the classification of "reactive" dyes.

Other embodiments of such dyeing methods are readily understood, and although not mentioned, all such methods are considered to be within the scope of the present invention.

Examples

And (3) experimental measurement:

wetting time: all wetting times are the average of six measurements. All the time given is the time required for a drop of distilled water placed on the sample to be completely absorbed. All times greater than 120 seconds were recorded and averaged to 120 seconds. During the measurement, all samples were raised so that neither the upper surface nor the lower surface of the sample contacted the solid surface.

Weight added (add-on) percent: the percent weight of the fabric after washing was measured by the difference in weight before and after acid cooking. A 4 inch x 4 inch sample was used in the following procedure:

1. the samples were dried on an aluminum pan of known weight. For drying, the samples were kept at 100 ℃ and 110 ℃ for 1 hour. The sample was cooled in a desiccator for 10 minutes. The pans containing the samples were then weighed.

2. The sample was placed in 200g of 70 wt% sulfuric acid solution for 45 minutes. The samples were stored at 70 ℃ in a shaking incubator.

3. The samples were rinsed 2 times with 250-.

4. The sample was dried and weighed as in step 1.

The "weight percent" is the difference between the weights measured in steps 1 and 4 divided by the weight of the dried cloth from step 1 multiplied by 100. The percentage of untreated control cellulose was subtracted from all samples and the untreated controls were normalized. For each treatment, 2 samples were measured and the measurements averaged to give the final percent cellulose.

Example 1

A. The formula is as follows:

the following aqueous solutions were prepared; 7% by weight of ultra-low viscosity carboxymethylcellulose sodium salt (degree of substitution 0.7, Aldrich Chemical Co., Milwaukee, Wis.), 25% by weight of Freerez NFR (BFGoodrich, Charlotte, NC), 5% by weight of Freecat 9(BFGoodrich) and 0.5% by weight of Ethox DA-9(Ethox Chemicals, Greenville, SC). The final pH was 3.47.

B, coating:

sanded tan Burlington Industries (Greensboro, NC) model 2606 polyester was dipped in the above solution and padded to 93% pick-up, dried at 250 ℃ F. for 5 minutes and cured at 390 ℃ F. for 30 seconds. The treated samples were then tested as described above.

C, result:

wetting time: 1 HL: 2.8 seconds

10 HL: 12.0 second

20 HL: 20.7 seconds

Weight percent of the weight: 1 HL: 5.5 percent

20HL：4.7％

Example 2

A. The formula is as follows:

aqueous solutions were prepared using 7 wt% ultra low viscosity sodium carboxymethyl cellulose (degree of substitution 0.7, Aldrich Chemical Co.), 6 wt% BTCA (1, 2, 3, 4-butanetetracarboxylic acid, Aldrich Chemical Co.), 4 wt% sodium hypophosphite monohydrate (Atlas Chemical, inc., San Diego, CA), and 0.5 wt% Ethox DA-9(Ethox Chemicals). The final pH was 3.30.

B, coating:

sanded tan Burlington Industries, model 2606 polyester, was dipped in the above solution and padding to 85% pick-up, dried at 250F for 5 minutes, and cured at 390F for 30 seconds. The treated samples were then tested as described above.

C, result:

wetting time: 1 HL: 3.7 seconds

10 HL: 6.0 seconds

20 HL: 5.3 seconds

Weight percent of the weight: 1 HL: 7.6 percent

20HL：4.8％

Example 3

A. The formula is as follows:

aqueous solutions were prepared using 7 wt% ultra low viscosity sodium carboxymethyl cellulose (degree of substitution 0.7, Aldrich chemical Co.), 4 wt% 75,000MW poly (acrylic acid) (Aldrich chemical Co.), and 0.5 wt% Ethox DA-9(Ethox Chemicals). The final pH was 3.31.

B, coating:

sanded, navy Burlington Industries, model 2606 polyester was dipped in the above solution and padded to 85% pick-up, dried at 250 ℃ F. for 5 minutes and cured at 390 ℃ F. for 30 seconds. The treated samples were then tested as described above.

C, result:

wetting time: 1 HL: 0.5 second

5 HL: 0 second

10 HL: 0 second

15 HL: 0.8 second

20 HL: 1.5 seconds

Example 4

A. The formula is as follows:

aqueous solutions were prepared using 7 wt% ultra low viscosity sodium carboxymethyl cellulose (degree of substitution 0.7, Aldrich chemical Co.), 4 wt% 75,000MW poly (acrylic acid) (Aldrich chemical Co.), and 0.5 wt% Ethox DA-9(Ethox Chemicals). The final pH was 4.51 and the viscosity was 556 cP.

B, coating:

sanded navy Burlington Industries 2606 polyester, model 2606, was dipped in the above solution and padding to 69% pick-up, dried at 250F for 5 minutes and cured at 390F for 30 seconds. The treated samples were then tested as described above.

C, result:

wetting time: 1 HL: 4.0 second

5 HL: 5.3 seconds

10 HL: 6.0 seconds

15 HL: 6.0 seconds

20 HL: 6.3 seconds

Example 5

Aqueous solutions were prepared using 4 wt% ultra low viscosity sodium carboxymethylcellulose (degree of substitution 0.7, aldrich chemical Co.), 5 wt% poly (acrylic acid) (MW 100,000-. The final pH was 3.8.

Example 6

Aqueous solutions were prepared using 4 wt% carboxymethylcellulose (Aqualon7L 2; Aqualon, a subsidiary of hercules chemical co.), 5 wt% poly (acrylic acid) (MW 100,000 ═ 125,000; Polacryl), 0.1 wt% wetacid NRW wetting agent (BFGoodrich, Chalotte, NC) and 0.05 wt% Kathon CG-preservative (Rohmand Haas, La port, TX). The final pH was 3.8.

The formulation was separately mixed with four different pigments in a ratio of 99% solution and 1% pigment on a wt/wt basis. The formulation is thoroughly mixed by homogenization while the pigment is added to the solution. The four pigments used were HiFast Golden Yellow, HiFast Red and SBlack (BASF, Charlotte, NC) and indigo paste 42% liquid (Buffalo ColorCorp., Parsippany, NJ). The colored formulation was then padded onto a 12 "x 15" sanded, woven, undyed microfiber polyester swatch (available from Burlington Industries, model 2606). For comparison, a solution without colorant was also padded onto the swatch. The swatches were dried at 190 ° F for 5 minutes and then cured at fabric temperatures of 322 to 335 ° F for 30 seconds. The sample cloths are respectively yellow, red, charcoal grey, blue and white with medium color. The various cloths were cut into 6 test pieces, which were washed 0, 1, 5, 10, 20 or 30 times with water according to AATCC method 143 (normal/cotton firmness). Visual evaluation of the color on each sample showed a slight color change or lightening after the first water wash, and very slight color changes were possible between one to five water washes. After five home washes, the color of each water wash appeared to remain unchanged. The hand of the colored sample was the same as the hand of the sample without the colorant. This indicates that the skin layer is an effective binder for pigments.

Example 7

The woven, sanded microfiber polyester was treated with the aqueous solution of example 6, then dried and cured at a fabric temperature of 350 ° F for 30 seconds. The treated polyester was then placed in a 100 ° F dye bath adjusted to pH 5.5 with acetic acid in a jet dyeing machine. After 10 minutes, 3% owf of Sandene8425 (polyethylene amine dye fixing agent, Clariant Corp.) was added to the bath, which was then heated to 160 ° F over 15 minutes. Sufficient sodium carbonate was added to raise the pH to 9.5 over 50 minutes, and then the dye bath was held at this temperature for an additional 15 minutes. The bath was then cooled to 100 ° F and the substrate rinsed with cold water for 10 minutes.

The dye bath was then heated to 100 ° F and the following components were added: sodium sulfate and SedgebufN (1g/L, Omnova Chemical), Sedgekil 832(1ml/L, antifoam from Omnova Chemical) and Solophenyl Navy BLE 250% (CibasC). Measuring the concentration and pH of the salt; the pH should be 5.5-6.0. The dye bath was heated to 180 ° F at a rate of 6 °/min and then ramped up to 250 ° F at a rate of 2 °/min. The dye bath was held at this temperature for 30 minutes and then cooled to 140 ° F. Drip dye bath and refill with water at 100 ° F; after 5 minutes, the dye bath was again dropped and refilled at 100 ° F. Sodium sulfate (7.5% owf), acetic acid (0.3% owf) and Burcofix 195(4 wt% owf, Burlington Chemical Company) were added to the dyebath. The dye bath was then heated to 140 ° F at a rate of 2 °/minute followed by a 15 minute hold at this temperature, after which the fabric was removed and dried. The resulting fabric had a deep navy color. Without the Sandene8425 application process, the substrate dyeing treatment of the comparative substrate resulted in a fabric that was only bluish, that is, the dyed fabric was not washable.

The following direct dyes can also be applied to the polyester using the procedure described above, but replacing SolophenylNavy BLE with BurcoRubine BL 200% (Burlington Chemical), Optisol Green BL, Indolylyellow SF-2RL, Pyrazol Orange LUF, Lumicase Grey 3LBN 200, Optisol Royal Blue 3RL, Pyrazol Turq FBL 400% (all obtained from Clariant Corp.) and Intrasil Black XTR (Yorkshire). All these dyes dye the fabric to a dark shade of the corresponding color. The substrate dyeing process of the control substrate without first applying Sandene8425 produced a dyed fabric that did not have wash fastness.

Example 8

The woven, sanded microfiber polyester was treated with the aqueous solution of example 6, then dried and cured at a fabric temperature of 350 ° F for 30 seconds. The treated polyester was then placed in a dye bath adjusted to a pH of 5.5 with acetic acid. To this bath was added 3% owf of Sandene8425 (polyethylene amine dye fixing agent, Clariant Corp.) which was then heated to 70 ℃ over 15 minutes. Sufficient sodium carbonate was added to raise the pH to 9.5 and then the dye bath was held at 70 ℃ for 15 minutes. The dye bath was cooled to room temperature and the substrate rinsed with cold water. The substrate is then dyed with reactive dyes at low salt concentration and neutral pH. The fibrous substrate is dyed to a dark color which is wash-fast without further treatment. The substrate dyeing process of the comparative substrate without first applying Sandene8425 produced a fabric that did not have wash fastness.

Example 9

Five solutions were prepared by mixing 100.0g of the aqueous solution of example 6 with 0.5g of one of the following dyes: alizarin, purpurin, methyl red, mordant orange 12, and mordant yellow 1. Sanded microfiber polyester swatches (available from burlington industries, model 2606, 12 "x 12") were padded in each formulation as described in example 6, then dried and cured. The colored samples were each cut into 4 swatches of 6 "and washed 0, 1, 20 or 30 times with water according to AATCC method 124-. The color fastness of each dye was qualitatively evaluated by visual inspection. The rub fastness of the swatches was evaluated by AATCC method 8-1996. The wetting time was observed as described above. The results are reported in the table below. Generally, a small decrease in color occurs between 0 and 1 water wash, and little color change occurs thereafter. The crockfastness at 0 to 1HL is typically 4.0 or better.

Alizarin methyl red mordant-dyed orange 1 mordant-dyed yellow 12 as dye

Color @0HL orange yellow peach orange powder red orange light brown yellow light yellow

Color @1HL orange-brown peach, orange, light yellow and light yellow

Color @20HL orange yellow peach orange, light yellow and light yellow

Color @30HL orange yellow peach orange, light yellow and light yellow

Dry crocking 5.04.04.04.04.5

@0HL

Dry crocking 5.04.05.05.04.5

@1HL

Dry crocking 5.05.05.05.05.0

@20HL

Wetting time 25.831.331.827.727.5

@0HL

Wetting time 3.52.34.85.74.5

@1HL

Wetting time 3.04.74.02.83.8

@20HL

Wetting time 5.314.24.210.08.3

@30HL

Example 10

The individual fibers of the polyester fabric treated with carboxymethylcellulose according to the invention (example 6, formulation before addition of the colorant) were observed by scanning electron microscopy (5000X). The cellulose sheath formed around the hydrophobic fibers was too thin to be detected in a scanning electron microscope. Thus, the properties imparted by the sheath do not interfere with the macroscopic properties of the fabric; that is, the sheath does not significantly increase the diameter of the fiber; it does not fill the spaces between the fibers or plug the fabric with large pieces of cellulose or the like. In addition, the treated fabric felt like cotton, not polyester, and showed improved wettability.

Example 11; the addition of an auxiliary agent into the skin layer: UV protection

The formula is as follows: an aqueous solution was prepared using 4 wt% carboxymethylcellulose (Aqualon7L 2; Aqualon, a subsidiary of hercules chemical co., inc.), 5 wt% poly (acrylic acid) (MW 100,000 ═ 125,000; polyacyl), 0.1 wt% wetacid NRW wetting agent (BFGoodrich, Chalotte, NC), 0.05 wt% Kathon CG-ICP preservative (Rohmand Haas, La port, TX), and 6 wt% titanium dioxide particles. Four titanium dioxide particles of different particle sizes are used in the present invention. Tronox CR-826 (mean particle size 200nm), Tronox CR-800 (mean particle size 190nm) from Kerr-McGeeChemicals, LLC, Oklahoma City, Oaklahoma, and UV-Titan L530 and L181 from Kemira Chemicals Canada Inc., Maitland, Ontario, respectively, having particle sizes of 30nm and 17 nm.

The woven black 100% polyester fabric was dipped in each solution, padded and dried at 195 ° F for 5 minutes, and cured at 335 ° F for 30 seconds. The durability of the Tronox samples when subjected to at least 25 home wash cycles (limit of testing) was measured by visual observation of white colored particles. The wash fastness of the UV-Titan samples was measured by the wetting time as previously described. The UV-Titan particles were coated with a polyol, and the fabric treated with it had increased hydrophilicity compared to the particles not treated identically with UV-Titan particles (see wetting time in table below):

table of example 11; wetting time

Sample (I)	10HL	25HL
			UV-TitanL181	0.3 second	1.0 second
UV-TitanL530	1.8 seconds	5.5 seconds
			Free of UV-Titan	7.7 seconds	12.0 second

Example 12; the addition of an auxiliary agent into the skin layer: activated carbon

A formulation similar to example 10 was prepared but with activated carbon powder (8 wt%) instead of titanium dioxide. This carbon is commercially available from Fluka Chemical (Milwaukee, Wis.) and has a particle size of about 40 microns. A woven, white 100% polyester fabric was treated with this solution, dried and cured as in example 10. Visual observation at 25 home washes showed that the charcoal (black) adhered to the fabric.

Example 13: the addition of an auxiliary agent into the skin layer: antistatic component

Aqueous solutions were prepared using 4 wt% carboxymethylcellulose (Aqualon7L 2; Aqualon, a subsidiary of hercules chemical co.), 5 wt% poly (acrylic acid) (MW 100,000 ═ 125,000; polyacyl), 0.1 wt% wetacid NRW wetting agent (BFGoodrich, Chalotte, NC), 0.05 wt% Kathon CG-ICP preservative (Rohmand Haas, La port, TX) and antistatic agent. The antistatic component used is; di (polyoxyethylene) hydroxymethylphosphonate commercially available from Akzo Nobel Chemicals Inc (Dobbs Ferry, NY) and sold as victstab HMP; and (3-chloro-2-hydroxypropyl) trimethylammonium chloride commercially available from Aldrich chemical (St. Louis, Mo.). Each additive was included at 5 wt% respectively. An undyed 100% polyester woven fabric was dipped in the above solution, padded to about 70 wt% pick-up, dried and cured at 335 ° F for 30 seconds. After repeated home washes, test method 115 using AATCC (American Association textile chemicals and colorists) 2000 "Electrical clinging of Fabrics: fabric to Metal Test ", the ability to prevent the formation of static electricity was measured. These samples were compared to untreated polyester fabric sheets and untreated woven 100% cotton fabric sheets (see table below). In this test method, the time required for the charge on the fabric sample to decrease to such an extent that the electrostatic attraction between the sample and the metal plate is reduced to the point that the fabric falls from the plate by gravity is measured.

Table of example 13; time (minutes) for the fabric to leave the metal sheet

Sample/additive	1HL	5HL	10HL	25HL
					Polyester/polyester	9.5	＞10	＞10	＞10
Cotton yarn/nonwoven	3.0	1.7	1.7	1.7
					polyester/Victstab HMP	1.2	0.9	3.2	＞10
Polyester/(3-chloro-2-hydroxypropyl) trimethyl ammonium chloride	0.0	0.0	2.6	＞10

Claims (17)

1. A composite fibrous substrate comprising core fibers and a carbohydrate sheath adhered around each of said core fibers, and wherein the carbohydrate sheath is adhered to itself by covalent bonds.

2. The composite fibrous substrate of claim 1 wherein the carbohydrate sheath further comprises at least one auxiliary component.

3. A composite fibrous substrate comprising core fibers and a carbohydrate sheath adhered around each of said core fibers, and wherein the fibrous substrate is prepared by:

contacting the fibrous substrate comprising core fibers with an aqueous solution of a water soluble carbohydrate and a crosslinking agent and optionally a suitable crosslinking agent catalyst;

heating the fibrous substrate to dryness; and

curing at a temperature sufficient to cause a reaction between the crosslinking agent and the carbohydrate.

4. The composite fibrous matrix of claim 3 wherein the aqueous solution further comprises at least one auxiliary component.

5. The composite fibrous substrate of claim 3 wherein the process further comprises the step of reacting the carbohydrate sheath with at least one auxiliary component to incorporate the auxiliary component onto or into the carbohydrate sheath.

6. The composite fibrous substrate of claim 2, 4 or 5 wherein the adjunct component is selected from the group consisting of colorants, metal colloids, magnetic colloids, infrared absorbing compounds, ultraviolet light screening compounds, biologically active agents, flame retardant chemicals, antistatic agents, odor absorbing compounds, neutralizing agents, and hydrolyzable linkers.

7. The composite fibrous matrix of any of claims 1-6 wherein the core fiber is a synthetic fiber.

8. The composite fibrous matrix of any of claims 1-6 wherein the core fiber is a rayon fiber.

9. The composite fibrous matrix of any of claims 1-6 wherein the core fiber is a natural fiber.

10. A method of making a composite fibrous substrate, the method comprising the steps of:

contacting the fibrous substrate comprising core fibers with an aqueous solution of a water soluble carbohydrate and a crosslinking agent and optionally a suitable crosslinking agent catalyst;

heating the fibrous substrate to dryness; and

curing at a temperature sufficient to cause a reaction between the crosslinking agent and the carbohydrate;

a composite fibrous substrate is obtained comprising a carbohydrate sheath adhered around each fiber of the substrate, and wherein the carbohydrate sheath is adhered to itself by covalent bonds.

11. The method of claim 10, wherein the aqueous solution further comprises at least one adjunct component.

12. The method of claim 10 further comprising the step of reacting the carbohydrate crust with at least one auxiliary component to incorporate the auxiliary component onto or into the carbohydrate crust.

13. The method of claim 11 or 12, wherein the auxiliary component is selected from the group consisting of colorants, metal colloids, magnetic colloids, infrared absorbing compounds, ultraviolet light screening compounds, biologically active agents, flame retardant chemicals, antistatic agents, odor absorbing compounds, neutralizing agents, and hydrolyzable linkers.

14. The method of any of claims 10-13, further comprising the step of treating the composite fibrous substrate with a post-processing treatment commonly used for cotton yarns.

15. The method of any of claims 10-14, wherein the core fiber is a synthetic fiber.

16. The method of any of claims 10-14, wherein the core fiber is a rayon fiber.

17. The method of any of claims 10-14, wherein the core fiber is a natural fiber.