Process for creating fabrics with branched fibrils

Abstract

The present process involves applying a plasticizer- or solvent-containing solution to a subject fabric, preferably under heated conditions, and then mechanically abrading the treated fabric. The process results in the rearrangement of the fabric structure, as a plurality of branched fibrils are created along the length of the yarn filaments. Thus, the molecular weight of the fabric's yarns and, therefore, the strength of the polymer chains are maintained. Fabrics made from this process, which exhibit a silk-like hand that results from the presence of multiple integral fibrils and branched fibrils, are also provided.

Description

TECHNICAL FIELD

The present disclosure relates to a process for creating fine-scale multiple fibrils and branched fibrils that are integrally connected to the filaments from which they protrude. The process involves mechanically abrading, preferably under heated conditions, a fabric to which a plasticizer- or solvent-containing solution has been applied. The fabric containing such a fibrillated structure is also disclosed.

BACKGROUND

All patents described herein are hereby incorporated by reference.

There have been numerous attempts to modify synthetic fabrics (particularly polyester) to improve their hand and/or appearance. Conventionally, sanding or napping of the fabric has been used to soften the hand and, in the case of continuous filament polyester fabric, to deluster the fabric. Sanding alone, however, typically results in large numbers of broken yarn ends, in which the broken ends have substantially the same diameter as the originating yarns, thereby yielding a fabric with a somewhat harsh hand and whitened and blurred surface.

Efforts to modify the surface of synthetic-containing fabric with specialized finishing equipment have also been used with some degree of success. Various abrading mechanisms have been employed, including abrasion with sandpaper, diamond grit, and the like, as described in U.S. Pat. No. 5,058,329 and U.S. Pat. No. 5,109,630, both to Love et al.; U.S. Pat. No. 5,815,896 to Dischler; and U.S. Pat. No. 5,819,816 to Dischler. Further, subject fabrics have also been modified by treatment with high-pressure streams of air or water, as described in U.S. Pat. No. 4,918,795 to Dischler; U.S. Pat. No. 5,033,143 to Love, III; and U.S. Pat. No. 6,546,605 to Emery et al. The success of these efforts has been largely dependent on the starting fabric and the desired results. However, these approaches failed to create the multiple and branched fibrillated structure that is characteristic of the present process and product.

Others have attempted to create fibrillated, scale-like textile structures through the use of chemical application combined with face-finishing techniques. U.S. Pat. Nos. 4,421,513 and 4,331,724 to Su describe a process for fibrillating polyester materials, which involves lowering the molecular weight of the polyester, treating it with a 100% concentrated swelling agent, and abrading the fabric. The result of this process is a fabric that has scale-like fibrils projecting away from the convex portion of the filament curvature (that is, the fibrils are produced only on one side of the fabric at places along the filament that are exposed to abrasion). The fabric is also weakened because of the process used to reduce the molecular weight of the polyester. These references do not contemplate a dual-sided treatment of the fabric or a method to enhance fibrillation to create multiple fibrils and fibrils with multiple splitting.

An apparatus and process are described in U.S. Pat. Nos. 5,058,329 and 5,109,630 to Love et al. to implement the art described in the Su patents. The process abrades fabric against a roll covered with rounded tungsten-carbide particles, after saturating the fabric with 100% methylene chloride at room temperature. The teachings of Love et al. fail to disclose a fabric having multiple fibrils and branched fibrils that are integrally connected to the filaments from which they protrude.

Yet another method of modifying fabrics is described in U.S. Pat. No. 4,259,393 to Marco. Marco teaches treating a fabric containing texturized polyester filaments with an alkaline solution in a jet-dyeing machine in order to chemically break a substantial number of the filaments. When the fibers break, the broken ends split into multiple filaments as a result of their exposure to the alkaline solution at preferred temperatures of between 45° C. and 55° C. Marco suggests that smaller filaments should project from each broken end. Like the Su and Love et al. references discussed above, Marco does not present a method for creating the multiple fibrils or branched fibrils that are characteristic of the present product.

SUMMARY

The present process involves applying a plasticizer- or solvent-containing solution to a subject fabric, preferably under heated conditions, and then mechanically abrading the treated fabric. The process results in the rearrangement of the fabric structure, as a plurality of branched fibrils are created along the length of the yarn filaments. Thus, the molecular weight of the fabric's yarns and, therefore, the strength of the polymer chains are maintained.

Benefits of the present process and product include, in one preferred embodiment, the use of relatively inexpensive yarns made entirely of single-component polymers (as opposed to the use of multi-component filaments that are commonly described as being easily splittable or “island-in-the-sea”-type filaments). Fabrics made from the present process retain their surface sharpness or clarify, making it possible to create fibrillated fabrics with fine-gauge stylized appearances. Further, fabrics made from this process exhibit a silk-like hand that results from the presence of multiple integral fibrils and branched fibrils. In fact, the process achieves a microdenier-like soft hand without the limitations of using microdenier fibers, which include poor abrasion resistance, difficulty in and a relatively higher expense of dyeing, and poor lightfastness.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow-chart of the process of making a fibrillated fabric; and

FIGS. 2 through 6 are photomicrographs of fibrillated fabrics of the present disclosure, taken with an AMRAY scanning electron microscope, Model 1845 FE (1991).

DETAILED DESCRIPTION

As used herein, “fiber” is defined as a unit of matter, either natural or manufactured, that forms the basic element of fabrics and other textile structures. A fiber is characterized by having a length at least 100 times its diameter or width.

“Fibrillation” is defined as the act or process of forming fibrils, such as by breaking up a fiber into the minute fibrous elements from which the main structure is formed.

“Fibril” is defined as a tiny, threadlike element of a natural or synthetic fiber that is still integrally attached to its parent filament at one or both ends. A “branched fibril” is a threadlike element of a natural or synthetic fiber that is split into multiple smaller elements, all of the smaller elements originating from and being integrally attached to the parent filament.

Fibrillation results in a fabric with finer filaments, as a plurality of fibrils is formed from a portion of the filaments that is moved away from the main body of the filaments. Thus, fibrillation is not an additive or subtractive process, but rather a fiber rearrangement process. The advantage of this approach is that the fabric's overall weight is essentially unchanged.

Turning now to the drawings, FIG. 1 provides a flowchart of the preferred present process for creating integral, branched fibrils on a subject fabric. Step 10 is to provide a fabric for modification. Fabrics contemplated for use with the present process include woven fabrics, knit fabrics, nonwoven fabrics, braided fabrics, pile fabrics, scrims, composites, spacer fabrics, and other fabric constructions as may be conventionally processed through a sander.

The fabrics may be made of yarns containing fiber types such as polyesters, polyamides, polypropylenes, olefins and polyolefins, polyurethanes, aramids (such as Kevlar), acrylics, modacrylics, blends of any of these fibers with one or more other fibers, and blends of any of these fiber types with natural fibers (such as cotton). The presence of natural fibers will not inhibit the effects of the present process on the synthetic components of the fabric and may enhance certain characteristics of the natural fibers (e.g., hand). Preferably, the yarns are continuous filament yarns, although the process may be applied to spun yarns as well. Most preferably, the yarns are polyester.

Before being subjected to the present process, the fabric may be dyed; calendered; embossed; coated; sheared; screen patterned; digitally patterned by hot air, water, lasers, or the like; combined into a composite; or printed. In one embodiment as will be discussed herein, the fabric is in its greige state when processed.

Step 20 involves the application of a chemical agent (specifically, a fiber-specific plasticizer- or solvent-containing solution) to the fabric. Suitable application techniques include dipping, spraying, foam coating, and other methods that may be known to those of skill in the art. Preferably, the plasticizer or solvent is part of an aqueous solution. Suitable amounts of plasticizing agent range from about 0.1% to about 100% of the weight of the solution and, preferably, are from about 0.1% to about 10% of the weight of the solution.

Alternatively, step 20 can be accomplished in a batch-dyeing process (including jet-dyeing, beck dyeing, and the like), in which the fabric is placed in a pressurized vessel and baths are exhausted onto the fabric. In this environment, the fabric is typically agitated in a rope form. Calculations of the amount of necessary fiber-specific plasticizer or solvent would be based on the weight of the fabric, rather than the weight of the solution. Preferably, when using a jet-dye machine, the plasticizing agent or solvent should be present in an amount of between about 0.1% to about 10% of the weight of the fabric.

Preferred plasticizers for polyester include phenolic compounds (such as o-phenylphenol, p-phenylphenol, and methyl cresotinate), chlorinated aromatic compounds (such as o-dichlorobenzene and 1,3,5-trichlorobenzene), aromatic hydrocarbons and ethers (such as biphenyl, methylbiphenyl, diphenyl oxide, 1-methylnapthalene, 2-methylnaphthalene), aromatic esters (such as methyl benzoate, butyl benzoate, benzyl benzoate, and ethyl hexyl benzoate), and phthalates (such as dimethyl phthalate, diethyl phthalate, diallyl phthalate, and dimethyl terephthalate). Of these plasticizers for use with polyester fibers, ethyl hexyl benzoate is preferred at amounts from about 0.1% to about 10% of the weight of the solution.

Alternatively, certain solvents in which the fiber type may be at least slightly soluble may be used in place of the plasticizer. Examples of such solvents for use with polyester include n-methyl-2-pyrrolidone, propylene glycol n-butyl ether, propylene glycol n-phenyl ether, dipropylene glycol methyl ether, di-basic esters, and imidazole-containing solvents.

Solvents useful for other fiber types are documented in Handbook of Polymer-Liquid Interaction Parameters and Solubility Parameters by Allan F. M. Barton (published 1990). By way of example only and not limitation, solvents suitable for use with polyamides include trifluoroethanol, trichloroethanol, phenol, cresols, halogenated acetic acids, and sulfuric acid. Examples of solvents suitable for use with polypropylenes include n-hexane, 1-propanol, 1-butanol, methylcyclohexane, and tetrachloromethane.

One advantage of the present approach, when using plasticizer-containing solutions, is a decrease in the amount of chemical agent that is used to modify the fabric (for example, as compared with solvent-based systems). A further benefit is that the plasticizer- and solvent-containing solutions contemplated for use herein are relatively easy and safe to use in large-scale manufacturing. Yet another benefit of using plasticizer-containing solutions is that it provides a vehicle for the fibrillation of the fabric's fibers without the destruction of the fibers (that is, the fabric's structure is rearranged without significant weight or strength loss).

Step 30 is the optional application of heat to the fabric to which the plasticizer-containing solution has been added. Step 30 can be accomplished either simultaneously with the application of the plasticizer-containing solution or subsequent to the application of the plasticizer-containing solution. It has been found that having the plasticizer-treated fabric hot can accelerate and enhance the fibrillation process, but it is not required. To achieve maximum productivity, temperatures at the site of abrasion in the range of 40° C. to 100° C. are preferred, depending on the fiber type and plasticizing agent being used.

Step 40 is the mechanical abrasion of the fabric. Preferably, the fabric is mechanically abraded on both sides, although one-sided abrasion is also possible. The fabric can be abraded using techniques such as needling; napping; napping with diamond-coated napping wire; gritless sanding; patterned sanding against an embossed surface; shot-peening; sand-blasting; particle bombardment; ice-blasting; tumbling; brushing; impregnated brush rolls; ultrasonic agitation; stone-washing; sueding; engraved or patterned roll abrasion; constricting through a jet orifice; impacting against or with another material, such as the same or a different fabric, abrasive substrates, steel wool, diamond grit rolls, tungsten carbide rolls, etched or scarred rolls, or sandpaper rolls; and the like. The preferred abrading technique is described in U.S. Pat. No. 5,819,816 to Dischler, in which the fabric is abraded against a plurality of diamond-grit rolls, allowing fabric-abrading speeds of up to 200 yards per minute. The mechanical abrasion of a fabric treated with a fiber-specific plasticizer results in a fabric whose filaments contain a plurality of integral, branched fibrils.

Steps 50 through 80 are optional steps. Step 50 involves washing the fabric to remove any remaining plasticizer. Step 60 involves dyeing the fabric to a desired shade. Step 60 may also occur before Step 20, for instance, in cases where the fabric is dyed before being treated or where the fabric is made from pre-dyed yarns. Step 70 involves drying the fabric. Step 80 involves printing the fabric, if so desired. Step 80 may also occur before Step 20, for instance, as with the dyeing step.

The following Examples are representative of the present process and product.

EXAMPLE 1

A sample of woven 100% polyester continuous filament fabric was placed in a tensioning device, which applied about 12 pounds of tension per linear inch in the warp direction of the fabric. The tensioning device held the fabric close to a surface heated to about 125° C. A chemical treatment of 100% 1-methyl-imidazole was applied to the fabric until saturated. Immediately thereafter, an orbital abrasion device (having a piece of the untreated fabric as an abrasive) was pressed against the saturated fabric at a pressure of about 2 pounds per square inch, abrading the saturated fabric for a period of about 3 minutes. The sample was then removed from the heated surface and rinsed. The fabric was examined using a scanning electron microscope, as shown in FIG. 2.

FIG. 2 is a photomicrograph at a 125× level of magnification of a plain-woven continuous filament polyester fabric, which illustrates the fibrillation that is characteristic of the present product. The photomicrograph shows a plurality of abraded fibrils that extend from and are integral to the originating filaments. The fibrils, which are randomly oriented with respect to the filaments from which they originated, are present in the warp and fill direction of the fabric. FIG. 2 also illustrates that the fibrils can possess a very high aspect ratio.

EXAMPLE 2

A sample of woven 100% polyester continuous filament fabric was placed in a tensioning device, which applied about 12 pounds of tension per linear inch in the warp direction of the fabric. The tensioning device held the fabric close to a surface heated to about 125° C. A chemical treatment of 100% polyethylene glycol methyl ether (molecular weight=750) was applied to the fabric until saturated. Immediately thereafter, an orbital abrasion device (having a piece of the untreated fabric as an abrasive) was pressed against the saturated fabric at a pressure of about 2 pounds per square inch, abrading the saturated fabric for a period of about 3 minutes. The sample was then removed from the heated surface and rinsed. The fabric was examined using a scanning electron microscope, as shown in FIG. 3.

FIG. 3 is a photomicrograph at a 500× level of magnification of a plain-woven continuous filament polyester fabric, which illustrates the fibrillation that is characteristic of the present product. The photomicrograph shows considerable branched fibrillation of a broken filament in the fabric and overall fibrillation of the unbroken filaments. The breaking of filaments is a potential side effect of the present process that is deleterious to the overall strength of the fabric, but which may further modify the fabric hand.

EXAMPLE 3

A sample of woven 100% polyester continuous filament fabric was immersed for thirty minutes in an aqueous chemical solution, brought to a rolling boil, including methyl benzoate at 9.5% of the weight of the solution and surfactants at 0.5% of the weight of the solution. The fabric was then placed in a tensioning device, which applied about 12 pounds of tension per linear inch in the warp direction of the fabric. The tensioning device was positioned over and held the fabric close to a porous steam vessel where steam was allowed to percolate through the fabric to reach a temperature approaching about 100° C. Immediately thereafter, an orbital abrasion device (having a piece of the untreated fabric as an abrasive) was pressed against the saturated fabric at a pressure of about 2 pounds per square inch, abrading the saturated fabric for a period of about 3 minutes. The sample was then removed from the heated surface and rinsed. The fabric was examined using a scanning electron microscope, as shown in FIG. 4.

FIG. 4 is a photomicrograph at a 500× level of magnification of a woven continuous filament polyester fabric, which illustrates the fibrillation that is characteristic of the present product and which further illustrates the intended effect of high aspect ratio fibrils that extend from parent filaments that are unbroken.

EXAMPLE 4

An aqueous bath was created containing 3% vinylimidazole and 3% butyl benzoate-based plasticizer, both based on the weight of the solution. A 2-inch wide sample of woven 100% solution dyed polyester fabric having texturized continuous filaments was subjected to a continuous dip through the aqueous bath and over a system of rolls. The fabric was abraded by threading the fabric through the rolls such that the fabric rubbed against itself under tension and in opposing directions over a two-inch long zone of abrasion. The aqueous bath was recirculated to maintain a temperature of between 60° C. and 80° C. The pressure used to tension the fabric was about 40 pounds per linear inch in the warp direction. The fabric was subjected to 120 cycles of abrasion. The fabric was examined using a scanning electron microscope, as shown in FIG. 5.

FIG. 5 is a photomicrograph at a 250× level of magnification of a woven continuous filament polyester fabric, which shows the presence of fibrillation on texturized polyester fibers that resulted from the process described above.

EXAMPLE 5

An aqueous bath was created containing 0.5% ethyl hexyl benzoate-based plasticizer, which was heated in a dip pan by a steam jacket to maintain a temperature of about 70° C. A sample of a jacquard woven 100% polyester continuous filament fabric having solution dyed yarns was passed through the aqueous bath and subsequently squeezed through nip rolls. The fabric was incidentally cooled before being subjected to abrasion by a plurality of diamond-grit rolls over which the fabric was threaded. The diamond-grit rolls were not heated, although the addition of heat to the abrasive rolls or the abrading environment may be preferred in some embodiments. The fabric was taken up and rinsed. The fabric was examined using a scanning electron microscope, as shown in FIG. 6.

FIG. 6 is a photomicrograph at a 150× level of magnification of a woven continuous filament polyester fabric, which provides further evidence of branched fibrillation.

Thus, from the Examples, it can be appreciated that fine-scale multiple and branched fibrillation structure results from the use of the present process. Fabrics fibrillated according to this approach may be useful as automotive fabrics, napery fabrics, apparel fabrics, substrate fabrics, and for other end-uses where a modified fabric surface is desired. By way of example only and not limitation, the fabric can be fibrillated in its greige state, dyed, and then combined with another material to make a composite that is useful as automotive seat cushions.

Claims

1. A process for creating a fibrillated fabric, said fabric comprising a plurality of continuous filament yarns, said process comprising the steps of:

(a) providing a fabric;

(b) applying a fiber-specific chemical agent to said fabric, said fiber-specific chemical agent comprising a plasticizer or solvent-containing solution; and

(c) abrading said fabric to which the fiber-specific chemical agent has been applied, such that at least some of said continuous filament yarns of said fabric have fibers from which multiple integral fibrils and multiple branched fibrils protrude, thereby imparting in said fabric a silk-like hand.

2. The process of claim 1 wherein said fabric is selected from the group consisting of woven fabrics, knit fabrics, nonwoven fabrics, braided fabrics, pile fabrics, scrims, and composites containing at least one of these fabrics.

3. The process of claim 2 wherein said fabric is a woven fabric.

4. The process of claim 2 wherein said fabric is a knit fabric.

5. The process of claim 1 wherein said continuous filament yarns are selected from the group consisting of polyesters, polyamides, polypropylenes, olefins, polyolefins, polyurethanes, aramids, acrylics, modacrylics, blends of any of these fibers with one or more other fibers, and blends of any of these fiber types with natural fibers.

6. The process of claim 5 wherein said yarns are polyester.

7. The process of claim 6 wherein said fiber-specific chemical agent is a plasticizer selected from the group consisting of phenolic compounds, chlorinated aromatic compounds, aromatic hydrocarbons and ethers, aromatic esters, and phthalates.

8. The process of claim 7 wherein said plasticizer is present in an amount of between about 0.1% to about 10% of the weight of an aqueous solution into which said fabric is immersed in step (b).

9. The process of claim 6 wherein said fiber-specific chemical agent is a solvent selected from the group consisting of n-methyl-2-pyrrolidone, propylene glycol n-butyl ether, propylene glycol n-phenyl ether, dipropylene glycol methyl ether, di-basic esters, and imidazole-containing solvents.

10. The process of claim 1 wherein said fabric to which the fiber-specific chemical agent has been applied is heated between step (b) and step (c).

11. The process of claim 1 wherein said fabric to which the fiber-specific chemical agent has been applied is heated simultaneous with step (c).

12. The process of claim 10 wherein said fabric is heated to temperatures of between 40° C. and 100° C.

13. The process of claim 1 wherein said abrading is accomplished by a technique selected from the group consisting of needling; napping; napping with diamond-coated napping wire; gritless sanding; patterned sanding against an embossed surface; shot-peening; sand-blasting; particle bombardment; ice-blasting; tumbling; brushing; impregnated brush rolls; ultrasonic agitation; stone-washing; sueding; engraved roll abrasion; patterned roll abrasion; constricting through a jet orifice; and impacting against or with another material, said other material being selected from the group consisting of the same fabric, a different fabric, abrasive substrates, steel wool, diamond grit rolls, tungsten carbide rolls, etched rolls, scarred rolls, and sandpaper rolls.

14. The process of claim 13 wherein said abrading is accomplished by impacting said fabric against or with another material.

15. The process of claim 1 wherein said fabric is dyed after step (c).

16. The process of claim 1 wherein said fabric is printed after step (c).

17-25. (canceled)