US3837983A

US3837983A - Simulated leather fabric

Info

Publication number: US3837983A
Application number: US00135707A
Authority: US
Inventors: W Strahl; D Nichols
Original assignee: Koracorp Ind Inc
Current assignee: Koracorp Ind Inc
Priority date: 1969-02-20
Filing date: 1971-04-20
Publication date: 1974-09-24
Anticipated expiration: 1991-09-24

Abstract

A SIMULATED LATHER FABRIC WHICH IS CHARACTERIZED BY A RANDOM GRAIN APPEARANCE IN WHICH THE FABRIC COMPRISES A BASE STRUCTURE HAVING PROJECTIONS FROM AT LEAST ONE SURFACE, FOR EXAMPLE, A TRICOT KNIT HAVING AT LEAST TWO YARN SYSTEMS, AT LEAST ONE OF WHICH COMPRISES THERMOPLASTIC YARNS CAPABLE OF ASSUMING A "SET," AND IS KNIT WITH CONVENTIONAL YARN TENSION DURING THE KNITTING OPERATION. THE OTHER SYSTEM IS OVERFED DURING THE KNITTING OPERATION TO PROVIDE PROJECTIONS IN THE NATURE OF A LOOPED PILE ON ONE SURFACE OF THE FABRIC. THE BASE FABRIC IS TENSIONED AND GIVEN A PARTIAL OR TEMPORARY SET TO IMPART LATENT CONTRACTILE FORCES THERETO, AND THEN IS COATED WITH A THIN STABILIZED FILM OF FLEXIBLE MATERIAL OF UNIFORM THICKNESS ON THE SURFACE CONTANING THE PROJECTIONS. THE COATING IS BONDED TO THE FABRIC AND THE COATED FABRIC IS THEN FURTHER TREATED WHILE RELAXED TO ACTIVATE THE LATENT FORCES WHICH THEREUPON DEVELOP A RANDOM GRAIN APPEARANCE WHICH SIMULATES THE APPEARANCE OF NATURAL LEATHER.

Description

sq. 24, m14 W.A.S +RAHL am. Y 5313.983

SIMULATED LEATHER FABRIC original Filed Feb. 2o, 1969 2 sneetsfsnm 1 l WOLFGANG A. STRA-HL DONALD S NICHOLS 'I NVENTO RSZ l Sept. 24, 1974 w. A sTRAHL. ETAL vSIMULATED LEATHER FABRIC origina; Filedv Feb. 2o, 1959 2. Sheets-#Sheet 2 AT Tvs.4

United States Patent O 3,837,983 SIMULATED LEATHER FABRIC Wolfgang A. Strahl, Souderton, and Donald S. Nichols, Doylestown, Pa., assignors to Koracorp Industries, Inc.

Continuation of abandoned application Ser. No. 802,755,

Feb. 20, 1969. This application Apr. 20, 1971, Ser.

Int. Cl. B321) /02; D06r 3/04 U.S. 'CL 161-53 10 Claims ABSTRACT OF THE DISCLOSURE A simulated leather fabric which is characterized by a random grain appearance in which the fabric comprises a base structure having projections from at least one surface, for example, a tricot knit having at least two yarn systems, at least one of which comprises thern1oplastic yarns capable of assuming a set, and is knit with conventional yarn tension during the knitting operation. The other system is overfed during the knitting operation to provide projections in the nature of a looped pile on one surface of the fabric. The base fabric is tensioned and given a partial or temporary set to impart latent contractile forces thereto, and then is coated with a thin stabilized film of flexible material of uniform thickness on the surface containing the projections. The coating is bonded to the fabric and the coated fabric is then further treated while relaxed to activate the latent forces which thereupon develop a random grain appearance which simulates the appearance of natural leather.

This is a continuation in part of my copending application Ser. No. 802,755, filed Feb. 20, 1969, now abandoned, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION The present invention provides an improved method for producing a coated fabric in which a heavy-grained leather is simulated in a highly efiicient and effective manner, and which exhibits the hand, drape, stability and other functional properties of natural leather.

Another object of the invention is to provide a method wherein the characteristics of the product are controllable within wide limits to produce a fabric having the characteristics desired for a particular end use.

More specifically, the present invention provides a method of making a novel fabric which may be made by first knitting a base fabric using at least two yarn systems, at least one of which is knited under normal tensions and is comprised of hydrophobic or thermoplastic yarns capable of assuming a set, and the other of -which is knit so as to provide projections or a looped pile effect on one surface of the fabric.

The fabric is subjected to a first finishing operation which imparts latent contractile forces in thel fabric by a temporary set and stabilizes the fabric for the application of a film of uniform thickness thereto. The film applied to the fabric is preferably a synthetic plastic so that it may be cured to a thin flexible coating which is permanently bonded to the looped surface of the fabric. Following application and curing of the film, the coated fabric is subjected to a post treatment which overcomes the temporary set and activates the contractile forces to permit relaxation and contraction of the fabric and development of a grained effect in the coating. The post treating operates to impart to the fabric a permanent set which crystallized the hydrophobic yarn, providing dimensional stability to the nished fabric. When processed in accordance with the inventionthe fabric not only has the appearance of a heavy-grained leather, but also possesses other desirable characteristics of such leather.

All of the objects of the invention are more fully set forth hereinafter with references to the accompanying drawings wherein:

FIG. l is a photographic representation of a fabric made in accordance with the present invention and exhibiting the random-grained appearance desired;

FIG. 2 is a side view of the fabric shown in FIG. l;

FIGS. 3 and 4 are greatly enlarged sectional views taken on the lines 3-3 and 4-4 of FIG. l;

FIG. 5 is a stitch diagram illustrating the construction of the base fabric embodied in the product illustrated in FIGS. 1 4; and

FIG. 6 is a block diagram illustrating the processing steps employed in the manufacture of a product in accordance with the present invention.

Referring now to the drawings, FIG. 1 illustrates a coated fabric made in accordance with the present invention which consists of a knitted base structure 12 and a coating 13. lIn accordance with the invention, the fabric base structure 12 comprises a fabric which is knit with at least two yarn systems, one of which is knit under conventional knitting tensions so as to provide a relatively flat knitted structure. The other of the yarn systems is overfed or otherwise knit so that the yarns thereof project out of the plane of the flat structure of the first system on one surface so as to provide projections or a looped pile effect. As shown in FIGS. 3 and 4, the coating 13 comprises a self-sustaining film which is adhered to the projections of the second system of yarns. As shown in these figures, the film exhibits undulations or wrinkles which impart to the finished fabric a grained surface, the grain being of random frequency and orientation, as is characteristic of natura-l leathers.

Referring now to FIG. 5, the knitting structure embodied in the base fabric may be a tricot knit, as is formed in a conventional warp knitting machine. As shown in this figure, the fabric comprises a system of yarns 21 which is fully threaded so as to knit on all of the needles of the machine and which is :controlled to knit in a pattern 1-2/1-0. In the present instance, the second system of yarns 22 is likewise fully threaded so as to knit on every needle and is controlled to knit 0-1/4-3. Thus, as shown in FIG. 5, the yarns 21 are knit to provide knitted loops 23 alternately in adjacent wales. The yarns 22 are knit alternately to provide knitted loops 25 in laterally-spaced wales with underlaps 26 spanning between these Wales and across the intermediate wales. Because of the tension in the yarns 21 and the overfeeding of the yarns 22, the knitted

loops

23 and 25 are coated alternately left and right along each Wale. Furthermore, the overfeeding of the yarn 22 causes the loops 25 to project from the surface as shown, to prow'de a relatively loose looped pile effect. In the illustrated embodiment, the yarns 21 are of much smaller denier than the yarns 22, and the overfeed vof the yarns 22 is at least twice the feed of the yarns 21 so that overall coverage is provided on the looped side of the fabric by the projecting loops 25.

The knitted base fabric may take other forms, and other knitting mechanisms may be used for making the fabric. Of prime importance is the location of projecting yarn portions of one yarn system to substantially cover the interknitted structure of the other yarn system with the projections anchored in the interknitted structure with a degree of freedom to be displaced relative thereto in order to permit accommodation to contractile forces activated in the interknitted .structure in subsequent steps. For example, the base fabric structure may be knitted on a warp knitter having a terry attachment or other pileforming mechanism, or on a weft knitter with a fleece or other attachment.

In order to set up latent contractile forces in their interknitted structure, at least the yarns 21 are thermoplastic in character and are capable of assuming a set by reason of their thermoplastic qualities. These charactistics of the yarns enable the fabric, following the knitting operation, to be given a temporary set or stabilization. In accordance with the invention, the fabric is tensioned or distorted to a pre-.selected degree and is subjected to dry heat so as to effect incomplete crystallization or set of the thermoplastic yarns. For example, in the case where the yarns 21 are nylon, a heat treatment of 400 degrees F. is applied to the fabric for a 4 to 6 second interval while the fabric is stretched on a tenter frame, although other tensioning devices may be employed. The specific dimensions to which the fabric is stretched during the temporary stabilization determine the latent internal contractile forces which are imparted to the fabric in this procedure, and thus determine the amount of grain development in the finished product. Thus the tensioning operation is correlated with the subsequent steps and with the construction of the knitted fabric itself in order to produce the desired results.

It may be preferred to dye the fabric 12 prior to the setting operation, and to this end the fabric from the knitting machine is subjected to conventional dying procedures in which the dye temperatures and times are selected so as to avoid premature shrinking of the yarns 21. The fabric normally is relaxed during the dying operation so as to insure thorough penetration of the dyestuff into and throughout the fabric. When dyed prior to the first heat treatment, this heat treatment may serve to dry and .stabilize the dye at the same time the latent contractile forces are temporarily set into the fabric.

Following the heat treatment of the fabric 12, a coating is applied to the fabric to deposit thereon a thin film 13 of predetermined thickness. In order to prevent penetration of the coating material into the body of the heat set fabric and insure uniformity in thickness throughout the film, it is preferred to utilize a pre-formed film in the coating operation. Preferably, the film is formed on a release paper or similar carrier to a predetermined uniform film thickness, which imparts to the fabric the desired fiexibility, hand, drape, and other physical characteristics. A tie coat may be applied to the exposed surface of the film while on the carrier, and the lm is applied to the fabric on the looped side thereof while the fabric is substantially relaxed and free from active internal stress. Thereupon the film 13 is bonded to the projecting loops 25 of the yarns 22 over the entire surface of the heat-set fabric by a curing operation. The thickness of the tie coat is selected to insure against excessive penetration of the bond into the body of the fabric so that the bond is in the nature of a surface-to-surface bond which anchors the film to the outer extremities of the knitted loops 25 of the yarns `22 without bonding to the

underlaps

24 and 26 of the yarns or to the loops 23 of the yarns 21. A firm bond between the film and the yarn 22 may be assured by passing the fabric with the coating applied thereto between a pressure nip which effects a solid merger of the film with the yarn loops 25. The coated fabric is then passed through an oven or other curing or stabilizing apparatus to dry and cure or stabilize the tie coat so as to both band and stabilize the coated film on the base fabric 12.

The composition of the film may be varied within wide limits to provide the desired chemical and physical properties in the finished product. Preferably the film coating comprises a composition of a synthetic plastic which stabilizes to a soft fiexible film of uniform thickness. It has been found that a low molecular weight compound produces a finer grain in the finished product than a high molecular weight, and that the low molecular weight compound is slightly more flexible than a high molecular weight compound. Typical synthetic plastic suitable for the present invention includes polyethylene, polypropylene, polyurethane, acrylic polymers, etc. A particularly suitable film is that obtained using a polyurethane based on isocyanate-polyol reactions. If thermoplastic films are employed, best results are obtained if the softening point of the film is above the temperature of the various processing steps. If breathability of the product is desired, provided bythe use of a poromeric material or by the use of a non-poromeric material which is subsequently needlepunched. When using a thermal setting plastic, the film is cured to a stable condition by heat prior to activation of the latent contractile forces. When using a thermoplastic material, the film is stabilized prior to activation and the temperatures during activation land drying are maintained below the melting point of the thermoplastic material.

If it is desired to provide an antique finish to the product, the film may be prepared on release paper or another carrier having grooves or other indentations therein. The antique effect is obtained by applying a darktoned composition onto the paper and scraping it so as to lodge the dark-toned composition into the grooves or indentations of the paper prior to the formation of the film on the paper. The body of the film is preferably formed of a compatible composition, but with a lighter tone. The compositions may be pigmented as desired or may be dyed or otherwise treated to obtain the desired tonal effect. Again depending upon the characteristics desired in the final product, the release paper may be either smooth or grained, the graining effected by a grained release paper being of minute proportions relative to the heavy random-grained effect obtained by the subsequent treatment operations.

The intermediate product resulting from the coating operation comprises a base fabric which has latent contractile forces heat set and stabilized therein, along with a coating which has likewise been cured or stabilized to a stable condition. Following the coating operation, and in accordance with the invention, the intermediate product is then subjected to a further heat treatment while it is relaxed and preferably while it is agitated. This subsequent treatment overrides the temporary set imparted to the base fabric and activates the contractile forces to permit the yarns 21 in the base fabric to shrink or contract to their original condition while maintaining the stability of the film. Depending upon the conditions imparted during the first treatment, the contraction of the yarns 21 causes widthwise or lengthwise contraction of the base fabric, or preferably both. The contraction of the base fabric under the bonded and stabilized film, resulting from the activation of the latent contractile forces in this treatment step, causes the film coated on the fabric to pucker or wrinkle and develop undulations which provide a grained appearance (see the undulations 30 in FIGS. 3 and 4).

Analysis of the product indicates that the coating exhibits a grained effect which is truly random by reason of the minute wrinkling and creasing of the coating as it is subjected to contractile forces activated in the base fabric. These contractile forces are believed to be free to act `by reason of the slippage of the yarns 22 throughout the fabric structure imparted by the yarns 21. The character of the projecting loops 25, and their loose covering of the entire surface of the base fabric imparts a random frequency and orientation to the undulations 30, as shown in FIG. 1. As indicated above, the degree to which the graining of the product is effected is dependent not only upon the degree of stretching imparted to the base fabric during the initial temporary setting thereof, but is also dependent upon the character or the composition of the film, the amount of overfeeding or depth and density of the loopiness on the adherent surface of the base fabric, and the degree of agitation imparted to the product during the final heat setting operation.

.Finishing may be accomplished in open width or may be accomplished in rope form. It has been found that effective grain development is attained by agitating the coated product through a bath of boiling water for a time sufficient to obtain complete crystallization of the thermoplastic yarns. The completion of the finishing operation preferably includes the application of dry heat with mechanical relaxation, for example, by tumble drying the' product after its removal from the boiling water. This final treatment may also be accomplished by agitating the fabric in an autoclave while it is relaxed at a temperature and pressure sufficient to effect complete shrinkage or crystallization of the thermoplastic yarns. Following the treatment of the fabric while relaxed, it may be cooled and stored in open width so as to remove any wrinkles and creases from the base knit structure of the product. The thermoplastic nature of the yarns in the base fabric imparts a permanent stabilization to the final product which therefore provides a degree of wrinkle-resistance comparable to natural leathers.

Where it is desired to dye the entire product, the dying may be accomplished concurrently with the wet agitation of the coated intermediate product by the addition of dyestuff to the bath of boiling water.

In order `to facilitate full relaxation of the fabric and complete activation of the latent contractile forces, it has been found that the addition of a cationic or nonionic softener to the base fabric assists in the development of the grain. When the fabric is dyed prior to coating, the softener is preferably applied after the dying operation and before the coating step so that uniform penetration of the softener throughout the fabric structure is attained.

Thus, it is apparent that the present invention provides a= random-grain development in a product comprising a base fabric structure having on one surface thereof a thin film of soft flexible material. The base fabric structure is characterized by a loop-pile effect on the coated side and a smooth surface on the other side embodying thermoplastic yarns capable of receiving and molding a permanent set. The grain effect is obtained by random undulations in the film resulting from contraction of the base fabric after bonding of the film to the outer extremities of the projection on the looped surface. The undulations appear in randomly arranged lines extending both walewise and coursewise of the fabric structure in a manner similar to the graining of natural leathers.

As indicated, the film is bonded to the outer extremities of the projections on the fabric. This terminology is meant to indicate that there is substantially no bonding of the film to the base of the fabric. Thus, the structure wherein the film is bonded to the projections at a point near the base structure would still be suitable for the present invention. The closeness of the film to the base structure tends to determine the degree of grain development which is obtained. Thus, when the film is closer to `the base structure which may mean that it is bonded at a point farther down on the projection, the grain development is generally less pronounced.

Although fabrics having projections in the form of knitted fabrics having raised loops by virtue of the knitting process have been disclosed, any shrinkable fabric having the projections thereon to which the film may be bonded may be used in this invention. For example, fabrics which do not have loops by virtue of the process from which they are formed may have loops developed by pulling the threads on one or both sides to from the loops. Further, any other type of projection is suitable. For example, the loops may be broken so that yarns rather than loops project from the fabric. For example, a fabric having projecting loops may be treated with a sueding machine or other device to break the loops. Further, the loops may be sueded to the point where they have not yet become broken. In addition to knitted fabrics, woven fabrics, non-woven fabrics and pile fabrics may be used.

Among the knitted fabrics, a wide variety of fabrics may be used. The table below sets forth various three-bar and two-bar tricot fabrics which are acceptable.

3-bar Tiroot, Fabrics Quality Runners, inches inches Front bar... 40 den. nyln..- 1-0/1-2 53 2) Midfne bar o o-o/a-a 8% 23 Back ban... 50 den. viscose. 3-4/1-0 129 Front bar 40 den. nylon..- 1-0/1-2 51 (b) Middle bar do o o/44 8 48 Back ban-.. 60 den. viscose- 3-4/10 114% Front bar... 40 den. nylon." 1-0/1-2 49 (C) Middle bar do i-i/do 8% 10% Back ban... 50 den. viscose- 3-4/1-0 120% Front bar.-- 40 den. nylon 1-0/1-2 52% (d) Middle bar do do/a-a 8% 21 Back bar do 3-4/1-0 102 Front bar-" 40 den. nylon-- 1-0/0-1 38 (e) Midtne bar do oai/4 4 8% 58 Back bar do 3-4/1-0 120 2-bar Tricot Fabrics Front bar... 40 den. nylon-- 1-0/1-2 40 (D {Baek bar do 4-3/0-1 i 6% i 145 (g) {Front bar 40 den. nylon 1-0/1-2 8 i 42% "n' Back bar -do 4-3/0-1 148 Front bar... 40 den. nylon-- 1-0/1-2 45 (h)"'" {Back bar do 4-3/0-1 l 10 i 151 Front bar 40 den. nylon... 1-0/1-2 44 (D {Back bar do 4 3/0-1 i 9% i 148% Front bar 40 den. nylon.- 0-1/2-1 43 (l) {Baek bar do 3-4/1o i 6% i 322 The illustrated embodiment of the invention comprises a base fabric structure knitted on a 28 gauge tricot warp knitter, with two bars fully threaded. The front bar was operated to knit 1-2/1-0 and the back bar was operated to knit 1 0/3-4. The front bar of the machine was threaded with 20 denier` 7 filament semi-dull nylon and the back bar was threaded With 50 denier 20 filament bright rayon. The feed ratio between the front and back bars was set to 0.345:1, and the knitting density was courses on the machine with a quality of 6 inches. An analysis of the base fabric shows the fabric to consist of 88% rayon and 12% nylon. In the first finishing, the fabric was tensioned at 400 degrees F for 4 to 6 seconds with dry heat and then coated with a 2 mil film by the use of a tie coat of less than l mil dry. The coating was cured at 250 degrees F. in an oven and then was passed into a boiling water bath while relaxed to obtain the desired shrinkage of the base fabric structure and development of the grain effect. The product was then tumble dried with dry heat; and cooled in open width.

A similar product Was produced using l5 denier monofilament semi-dull nylon in the front bar and 40 denier 13 filament semi-dull nylon in the back bar.

It is preferred to use a relatively low twist multifilament yarn in the projecting portions of the base fabric so as to obtain a broad coverage of the coated surface of the base fabric which enables firm bonding of the film to the outer extremities of the projections without substantial penetration toward their bases which are interknit in the fabric structure. Although the foregoing examples embody rigid producer yarns, textured yarns may also be used with good effect.

While particular examples of the present invention have been illustrated and described herein, it is not intended to limit the invention to such disclosure, but changes and modifications may be made therein and thereto within the scope of the following claims.

We claim:

1. A simulated leather product comprising Va base fabric structure and a coating on one surface thereof, said base fabric structure comprising a knitted fabric having loop projections which have been knitted into the fabric covering at least one surface thereof, said loop projections being raised by virtue of the knitting operation, said projections being substantially uniform in height, said coating comprising a flexible thin fihn of uniform thickness having undulations of random frequency and orientation providing a grained surface texture, developed by the contraction of said fabric bonded to said lm, said film being securely bonded to the outer extremities of said projections only and said fabric and film having no permanent compression caused by grain formation.

2. A simulated leather product according to claim 1 wherein said base fabric structure comprises a knitted fabric having two yarn systems, the yarns of one system lforming said projections and comprising low-twistmultifilament yarns of substantial denier relative to the denier of the yarns of said other said system.

3. A simulated leather product according to claim 2 wherein the projections of said one yarn system comprise knitted loops providing an overall loose-pile coverage on one surface of the fabric said loops formed from yarn in the back warp.

4. A simulated leather product according to claim 3 wherein the yarns of said one system have underlaps spanning between laterally spaced wales in said fabric and traversing the intermediate wales.

5. A product according to claim 4 wherein the yarns of said other system are of a thermoplastic character so that the fabric is capable of receiving and holding a set, said yarns having knitted loops disposed alternately in adjacent Wales and underlaps extending in zig-zag runs between said adjacent wales, so that when said yarns are set, said fabric is stabilized.

6. A simulated leather product according to claim 1 wherein said tilm is a synthetic plastic.

7. The simulated leather product of claim 1 wherein said film is a synthetic plastic having a high molecular Weight.

8. The simulated leather product of claim- 1 wherein said film is a synthetic plastic having a low molecular weight.

9. The simulated leather product of claim 1 wherein said film is poromeric.

10. The simulated leather product of claim 9 wherein said film has been needle-punched.

References Cited UNITED STATES PATENTS 3,277,673 10/1966 Lesley 66-86 R 2,518,407 8/1950 Weinberg 161-76 3,336,183 8/1967 Larner, Jr., et al. 161-156 3,366,528 11/1968 Takekawa 161-89 3,383,263 5/1968 Storti 161-97 3,444,035 5/1969 lBushnell 161-156 3,574,106 4/1971 Bragg, Ir 161-53 3,576,703 4/1971 Baker et al. 161-77 3,655,474 4/1972 Constantine 156--183 3,539,436 1l/1970 Hamand 161-89' 3,481,821 12/1969 Brunner et al 161-89 3,532,529 10/1970 Endo et al. 161--89' GEORGE F. LESMES, Primary Examiner C. E. LIPSEY, Assistant Examiner U.S. Cl. X.R.

66-191; 156-148, 183; 161--49, 89, 116, 128, Dig. 2, 67