US3514307A - Artificial suede from sanded polymer containing textile flock and method for producing the same - Google Patents

Description

United States Patent 3,514,307 ARTIFICIAL SUEDE FROM SANDED POLYMER CONTAINING TEXTILE FLOCK AND METHOD FOR PRODUCING THE SAME Victor L. Hallenbeck, Brecksville, Ohio, assignor to The B. F. Goodrich Company, New York, N.Y., a corporation of New York No Drawing. Filed Oct. 3, 1966, Ser. No. 583,990 Int. Cl. D06m 3/14; B44c 1/44 US. Cl. 117-8 5 Claims ABSTRACT OF THE DISCLOSURE A permeable artificial suede leather is made by dispersing textile fibers into an essentially linear polyurethane in solution, spreading the dispersion on a substrate, drying and sanding the polymer surface.

This invention relates to artificial suede-like materials and to a method of making the same.

In recent years much effort has been directed toward producing materials that will duplicate or surpass the properties, appearance and usefulness of natural leather.

Animal hides, particularly calf and cattle hides, are the major source of the natural product. The hides are tanned to convert them into marketable leathers useful for shoe uppers, luggage, upholstery, clothing and similar items. A wide varietyof finishes can be applied to leather; it can be dyed to virtually all colors, and given virtually any degree of stiffness and flexibility.

Suede leather is a specially processed material with a napped finish. It is widely used in items of Wearing apparel gloves, jackets, shoe uppers and similar items. A napped finish or surface is one of soft, fuzzy fibers. It is sometimes described as hairy or downy. Such a surface is usually produced on leather by buffing the hide, generally on the flesh side, against a rough surface such as a wire Wheel or grit abrasive material such as emery cloth or paper. Man-made leathers are generally laminate structures. The most promising such materials made to date consist of a textile backer layer, a textile reinforcing layer and a top film of synthetic polymer. The backer layer, generally a nonwoven fabric, is impregnated with filler and binder material. On top of this backer layer it is optional to place a reinforcing layer of woven fabric, and as the top layer a film of plastic such as polyvinyl or polyurethane is laid down. These operations must be performed in such a manner that the total construction has porosity or breatheability, so that when fashioned into a clothing item, the article will be comfortable to the wearer. Hides, from which leather is made, are naturally porous. As stated above, one can make suede leather from a tanned hide by bufiing it against an abrasive surface to create the napped finish of suede. When this technique is attempted with the man-made laminates mentioned above, all one does is tear away the top plastic film, exposing the reinforcing woven layer, if one is present, or the fibrous nonwoven backer layer. In effect one destroys the material that has taken many years of effort to develop. If the surface layer is initially laid down thickly enough that a roughened surface might be created by abrasion without reaching the second layer, the material will be economically prohibitive to produce or will have failed to duplicate the hand and flexibility of natural suede. Mere sanding of synthetic polymer film has not been known to produce a suede-like finish or napped surface.

There is thus a potential demand for a man-made suede leather, a microporous, permeable, flexible material with a fine nappecl finish or surface and properties of strength,

3,514,307 Patented May 26, 1970 drapability and hand equal to or better than natural suede leather. This invention provides such a material and a process for making it.

In the practice of this invention a solution of a mixture of 70-99 parts of polyurethane and 1-30 parts of polyvinyl chloride resin in an organic solvent therefore and containing 35-45 parts of fibers per 100 parts of polymer dispersed therein is spread on a backer surface, a woven or nonwoven fabric, and treated by known techniques in a bath of a liquid that is a nonsolvent for the polyurethane-polyvinyl polymer blend, but is miscible with the solvent therefore. The liquid nonsolvent removes the polymer solvent and precipitates the polyurethanepolyvinyl polymer blend in a cellular, microporous configuration containing the randomly dispersed fibers. When this laminate is subjected to a light buffing against an abrasive surface, a remarkable duplicate of the napped surface of natural suede is obtained. The randomly dispersed fibers, many of which are at the surface of the laminate to begin with, are exposed by the abrasive and as polymer is torn away from them, they remarkably and unexpectedly present a fine napped finish, feel and appearance. The laminate is air and water vapor permeable as made and has strength and other properties corresponding to those of leather, so that when the mapped surface is created, true man-made suede leather has been produced.

US. Pat. Nos. 3,169,885 and 3,222,208 show the preparation of leather-like materials from essentially linear polyurethane elastomers described in US. Pat. No. 2,871,218. These polyurethanes are combined in solution with 10% to 30% by weight of a fiber flock plus water containing either a colloidal magnesium aluminum silicate or carboxyrnethyl cellulose or a natural gum. This dispersion is coated on a textile substrate, leached in cold water, and air dried to produce a water vapor permeable structure with many leather-like properties. Despite the fact that they contain fibers as do the materials of the instant invention, the compositions of US. Pat. Nos. 3,169,885 and 3,222,208, when subjected to bufiing or sanding, do not produce the desirable napped surface characteristic of suede leather. The sanded materials have a soft waxy feel. While they have adequate permeability, these materials have low flex strength, running only 45,000 flexes on the Bally flexometer at 35 F. The difference in these results and those obtained by practice of the instant invention are attributed to the use, in the invention, of no added water and of a critical amount of fiber in the range of 35% to 45% by weight of the polyurethane polymer employed.

The polyesterurethane polymers employed in this invention are preferably blended with a homopolymer or copolymer of vinyl addition polymer in the ratio 70-99 parts polyesterurethane and 3*0l parts vinyl addition polymer with the sum of the polymers being equal to 100 parts. Polyvinyl butyral, polystyrene, poly (alphamethyl styrene), polyvinylidene chloride, polymers of methyl methacrylate including homopolymers thereof and copolymers thereof with minor amounts 25% by weight) of acrylic acid, methacrylic acid, methyl, acry late, ethyl acrylate, ethyl methacrylate, vinyl acetate, acrylonitrile and styrene may be used. Other useful vinyl polymers include copolymers of acrylonitrile, preferably with less than 50% by weight of esters of alphaolefinic monocarboxylic acids with saturated aliphatic monohydric alcohols of 1 to 8 carbon atoms, such as methyl, butyl, cyclohexyl and octyl acrylate. The most preferred vinyl addition polymers are homopolymers of vinyl chloride or copolymers of vinyl chloride containing at least by weight vinyl chloride, of vinyl acetate, acrylonitrile, vinylidene chloride, maleic, fumaric or acrylic acid esters. These vinyl chloride polymers are relatively inexpensive and are obtainable on the market. They are abrasion resistant and compatible with the polyesterurethanes employed in this invention. The vinyl addition polymers are generally plasticized with convention plasticizers such as di(2-ethyl hexyl) phthalate, dioctyl sebacate, dioctyl phosphate, dioctyl azetale, and tricresyl phosphate. Plasticizer is preferably added in the amount of 50-100 parts by Weight of plasticizer to 100 parts by weight of vinyl addition polymer employed.

Another optional ingredient, which in some cases is found to improve the spreadability of the polymer-fiber mixture, is polyethylene oxide, molecular weight range about 200-800, or polyethylene glycol monoalkyl ethers, molecular weight range 300-6000. These materials are preferably added in the range of 1 to 40 parts per 100 parts of total polymer.

The polymers used in the microporous coating on the textile backer to form leatherlike structures are preferably polyurethane condensation polymers. The preferred polymers are essentially linear and not heavily cross linked. Polyesterurethanes and polyalkyleneetherurethanes may be employed. The particular polymers employed are not a part of this invention. Typical polyesterurethanes which are useful include those described in U.S. Pat. No. 2,871,218. These polyesterurethanes are reaction products of one mol of essentially linear hydroxyl terminated polyester of a saturated, aliphatic glycol having from 2 to carbon atoms and having hydroxyl groups on its terminal carbon atoms and a carboxylic acid of the formula HOOC-RCOOH where R is an alkylene radical containing from 2 to 8 carbon atoms or the anhydride of such an acid, said polyester having an average molecular weight between 600 and 2000 and having an acid number less than 10, with from 1.1 to 3.1 mols of a diphenyl diisocyanate having an isocyanate group on each phenyl nucleus in the presence of 0.1 to 2.1 mols of a saturated, aliphatic free glycol containing from 2 to 10 carbon atoms and having hydroxyl groups on its terminal carbon atoms, the molar amount of said polyester and said free glycol combined being essentially equivalent to the molar amount of said diphenyl diisocyanate whereby there are essentially no unreacted isocyanate or hydroxyl groups in the reaction product.

The preferred basic polyesters which are utilized are those prepared by esterification of such dicarboxylic acids prepared by chain extending a prepolymer having a molecular weight from 750 to 10,000 with a compound having two active hydrogen atoms. One or more polyalkylene ether glycols are mixed with a molar excess of diisocyanate and the mixture is heated from 50 C. to 120 C. to form a polymer having terminal-NCO groups. Alternatively, one can react the diicocyanate with a molar excess of polyalkylene ether glycol and cap the resulting hydroxyl-terminated product by reacting it with more diisocyanate to form a prepolymer having terminal- NCO groups.

Useful'polyalkylene ether glycols include polyethylene ether glycol, polypropylene ether glycol, polydecamethylene ether glycol and mixtures thereof.

The diisocyanates useful for preparing the prepolymers include aromatic, aliphatic and cycloaliphatic diisocyanates such as m-phenylene diisocyanate, 1,6-hexamethylene diisocyanate, and 1,S-tetrahydronaphthalene diisocyanate.

The prepolymer of polyalkylene ether glycol and diisocyanate is chain-extended with a compound having two active hydrogen atoms to form a substantially linear polymer with molecular weights from 25,000 to 300,000. Favored chain-extenders include hydrazine, water, ethylene glycol and dimethyl piperazine. Polymers of this type are described in U.S. Pat. 2,692,873.

The textile backing layer employed as the base material in preparation of the artificial suede leather of this invention is preferably a nonwoven fabric. Nonwoven fabrics are porous, permeable, and, depending upon their fiber as adipic, succinic, pimelic and sebacic, particularly adipic acid.

Glycols used to prepare the polyester are preferably the straight chain glycols containing 2 to 10 carbon atoms such as butanediol-1,4 and decamethylenediol-l, 10. Any of these glycols, preferably butanediol-1,4, may be employed as the free glycol present when the polyester is reacted with the diisocyante. Diphenyl diisocyanates such as diphenyl methane diisocyanate, diphenyl methane-p,p-diioscyanate, and diphenyl ether diisocyanate are used to react with the mixture of polyester and free glycol.

For a preferred polyesterurethane of this type, a mixture of 1447 grams (1.074 mols) of hydroxyl poly(tetramethylene adipate), molecular Weight 849, hydroxyl number 130.4, acid number 0.89, and 109.6 grams (1.218

Polyalkylene ether glycolzdiisocyanate polymers prepared by the technique of chain extending prepolymers are also useful in my invention. These prepolymers are content, have varying degrees of suppleness, moisture absorption capacity and strength. Nonwoven fabrics are well known in the forms of mats, batts, felts and the like. They embody natural or artificial fibers formed into a web or batt by carding, garnetting, air-laying, water-laying, or other known methods. The nonwoven fabrics contain randomly distributed short staple fibers. They usually contain a small amount of binder adhesive, and for use as backer layers for leatherlike structures, they are impregnated with polymeric latices to the extent of 50% to 200% pickup by weight of latex on the fabric. Natural and synthetic fibers can be used to form the nonwoven fabrics. Cotton, ramie, nylon, polyester, polyacrylonitrile, polypropylene, rayon and the like can be used. Preferred fiber denier is about 0.5 to about 20 and preferred fiber lengths are 0.5 inch to about 3 inches. The density of the nonwoven fabrics may vary, in ounces per linear yard, from about 0.05 ounce to 9 or 10 ounces. In the case of the extremely light materials, a number of layers of fabrics are plied together to get any desired thickness and weight per yard. Non woven fabrics can be oriented, strengthened and densified by needle punching them on a loom that will pierce the mat up to 20,000 times per square inch with needles from 1 to 10 mils in diameter. The nonwoven fabrics are preferably dipped into a saturant material to add strength, integrity and dimensional stability. The fabric generally picks up 50% to 200% of its weight of saturant. Nonwoven fabrics are available in roll form on the market. They are dipped for saturation and impregnation into aqueous dispersions of carboxylic modified acrylic or meth acrylic latex, a carboxyl-modified butadiene-styrene latex, a carboxylic-modified butadiene acrylonitrile latex or a 10% to 25% by weight solution of one of the polyurethane polymers mentioned above in a solvent such as dimethylformamide.

Both natural and synthetic fibers are successfully employed as additives to the synthetic polymer films in the practice of this invention. The only restriction is that they be of a type of fiber generally found useful as a textile. Cotton, wool, ramie, cellulose, silk, rayon, nylon, polyacrylonitrile, polypropylene and polyurethane fibers have all been found to be useful in this invention. The fibers are preferably 0.5 to 1.5 mm. long. Shorter fibers, or dusts with particle sizes from 0.005 mm. to 0.150 mm. may also be used, either alone or blended with 0.5 mm. to 1.5 mm. fibers in amounts from 5% to preferably 10% to 25%, by weight, to provide desired variations in the napped surface. Fibers longer than 1.5 mm. tend to leave hanging threads after the sanding and bufling step. The weight ratio of fiber to polymer is critical and ranges from 35-45 parts fiber to 100 parts polymer. Fewer than 35 parts fiber gives surfaces that fail to give a napped surface after sanding and above 45 parts fiber gives mixtures that are too thick and viscous to process.

The solvent used in the practice of this invention should be miscible with the nonsolvent liquid that is used to precipitate the polyurethane polymer in a microporous configuration. N,N-dimethylformamide is a particularly useful solvent. Other acceptable solvents include dimethylsulfoxide, tetrahydrofuran, N,N'-dimethylacetamide, gamma butyrolactone and dioxane.

In brief, the process of the invention is to prepare a solution-suspension of polyurethane polymer and short fibers that is homogeneous in texture. This is spread by any acceptable means, such as doctor-knife, brush, dip, or calendar, on a woven or nonwoven backer material at 25 C. to 70 C. The thickness of the wet coating laid down preferably varies from about 25 mils to about 40 mils. If all the fiber employed is in the 0.5 mm. to 1.5 mm. length range, a wet thickness of about 40 mils will result in a dry, sanded thickness of about 20- mils. If the fiber content is composed of 50% by weight 0.5 to 1.5 mm. fibers and 50% dust or shorter fibers, a wet thickness of about 25 mils will yield a dry thickness of about 20 :mils in the surface layer. There is no advantage to spreading a wet layer of thickness greater than that which will result in a dry layer of the desired find thickness, for the excess material will just be ground off in the sanding step. In the compositions of this invention the fiber containing polymer layer deposited on the substrate and dried will be about 40 mils, preferably -40 mils thick before sanding. The sanding operation tends to level off any irregularities in the surface. It is interesting to note that once the sanding medium has abraded the entire surface area being treated, the feel or hand of that surface does not appear to vary no matter how much more of the overall surface thickness is sanded away, until the substrate level is reached by the sanding medium. To illustrate, a 25-mil dry film on a textile substrate may be sanded to a film thickness of 23 mils, 20 mils, mils, 5 mils or even about 2 mils, and in all cases it will present the same feel to a hand stroking the surface, with or against the grain of the fibers.

For economy and ease of production the coating layer should be no thicker than is found necessary to provide the desired degree of napped surface with a minimum of sanding and buffing. A water bath is employed to coagulate the coating containing the fibers and remove the solvent. Next the structure is dried, as in a forced air oven at 70 C. or over hot drier rolls. The top polymer surface, originally quite smooth, is now sanded as against 120-grit commercial sandpaper. Emory paper, Carborundum paper and other like abrasive sheets can be used. Since the surface layer of polymer and fiber is homogeneous, a suede like napped surface is produced by even a light degree of sanding, but the abrasive step can be continued to remove whatever amount of surface material is desired to reach the thickness of the piece that is intended.

The following examples will serve to illustrate this invention.

EXAMPLE I A rayon nonwoven web, formed by a carding and cross laying technique from 1.5 denier, 1.5" long fibers, weighing 9.5 oz. per sq. yd., thickness 0.047", needled to a level of 2000 punches per sq. in., is saturated in a 13 to 1 water to sodium bicarbonate solution and dried at 100 C. The Web picks up 22.4% carbonate by weight. It is next immersed in a 37.5% total solids, carboxyl modified, heat curable, polybutadiene latex containing 3.9% sodium bicarbonate (based on the rubber total solids), then immersed in 5% calcium chloride, followed by immersion in 5% acetic acid, then water washed and dried.

The soft, supple material produced is an excellent backer for artificial leather constructions. It weighs 20 oz. per sq. yd., shows a polymer pick up of 120% on weight of fiber, is 0.060 inch thick, has a density of 0.41 g./cc., moisture vapor permeability of 1156 g./ sq. m./ 24 hr. and a suppleness of 31.2 psi. (ASTM Dl388-55T).

A linear polyesterurethane polymer is prepared by following the teaching of U.S. Pat. No. 2,871,218. First 1000 g. (1.0 mol) of hydroxyl poly(tetramethylene adipate), molecular meight 1000, hydroxyl number 112, acid number 2.5, and 180 g. (2.0 mols) of butanediol-1,4 are mixed in a heated autoclave with stirring for 15 minutes at 10 mm. pressure at -105 C. Next 750 g. (3.0 mols) of diphenylmethane-p,p'-diisocyanate are added and stirred for 2 minutes. The melt is poured into lubricated metal trays and held in an oven at 140 C. for 3 hours.

One hundred parts of the polyesterurethane are dissolved in 400 parts dimethylformamide.

A 40-mil wet trickness coating of this solution is spread on the nonwoven rayon substrate described above at 65 C. and immersed in a water bath at 30 C. until the dimethylformamide is removed. The film is dried for 30 minutes at 100 C. After drying, the coating is a white, opaque, smooth, glossy film. The coating thickness is 20 mils and the moisture vapor transmission (MVT) is 138% that of a control sample of 4 oz. calfskin. This level of MVT indicates that a microporous film has been formed.

The laminate structure is buffed on a Curtin-Herbert oscillating drum sander using No. grit paper. The sanding merely roughens the laminate polymer surface and before any nap effect can be created, the entire thickness of the polymer film is in spots removed from the nonwoven textile backing layer.

EXAMPLE II The procedure of Example I is repeated except that before spreading the polyesterurethane solution on the nonwoven substrate, 40 parts of cotton fiber 0.5 mm. to 1.5 mm. long are dispersed therein by thorough stirring in an Eppenbach mixer.

The dried laminate structure has a dull, somewhat uneven surface appearance with no similarity to tanned leather. When the laminate is sanded in the Curtin-Herbert sander, this surface is converted to a napped, fibrous surface with the feel and appearance of natural suede leather. The moisture vapor transmission is 600 g./ sq. m./ 24 hrs. and the Bally flex at 35 F. is 145,000.

EXAMPLE III The procedure of Example II is repeated except that 30' parts of commercial polyvinyl chloride resin are added in place of 30 parts of the polyesterurethane. In addition, 30 parts of dioctyl azelate plasticizer for the polyvinyl chloride are added. Again an excellent feeling imitation suede leather is produced. The product is improved in flex strength over the product of Example II.

EXAMPLE IV The polyesterurethane of Example I is employed in the following recipe:

Material Parts Polyurethane 100 Polyethylene oxide (mol. wt. 400) 40 Cotton fibers (0.5 to 1.5 mm. long) 40 Dimethylformamide 360 Fibers are suspended in the solvent first. Next the polyethylene oxide and polymer are worked into solution. The temperature is carefully raised to 100 C. and held until solution is complete. The batch is cooled to 65 C. and knife coated onto the textile backer prepared as shown in Example 1. The dried laminate is sanded with 120 grit paper.

A sample of the suede like material produced passes 328,000 flexes at 35 F. in a Bally fiexometer. The moisture vapor transmission is 600 g./ sq. m./ 24 hrs.

EXAMPLE v v Material Parts r Polyesterurethane 70 9 Polyvinyl chloride 30 Dioctyl azelate 30 Polyethylene oxide (mol. wt. 400) 40 Cotton fibers 40 10 Dimethylformamide a- 360 I claim: r v 1. A suede leather-like material in the form of a fiexible' sheetwith a napped surface comprising a textile backer layer and a buffed and sanded surface layer on said backer layer, said surface layer comprising 70-99 parts of a polyurethane polymer, 1 parts of'a vinyl addition polymer, the total of said polymersbeing 100 parts, and from -45 parts of fibers per 100 parts of said polyurethane polymer plus said vinyl addition polymer, said fibers being selected from the group consisting of fibers 0.5 to 1.5 mm. long and fiber dusts with particle sizes from 0.005 to 0.150 mm. I

2. The process of making a synthetic suede leatherlike material comprising (1) making a homogeneous dispersion in a solvent for a polyurethane of -99 parts of said polyurethane, 30-1 parts of a vinyl addition polymer, the total of said polymers being equal to 100 parts, and 35-45 parts of textile fibers, said fibers being selected from the group consisting of fibers 0.5 to 1.5 mm. long and fiber dusts with particle sizes from 0.005 to 0.150 mm., coating said dispersion on a textile backer, removing said solvent by immersion of the structure in a bath of inert liquid that is miscible with said solvent, but is not a solvent for said polyurethane, drying to remove said inert solvent, and sanding the surface so produced to create a napped surface. I

3. The process of claim 2 wherein the polyurethane is .a linear polyesterurethane and the vinyl addition polymer is selected from the group consisting of polyvinyl chloride and copolymers of vinyl chloride containing at least vinyl chloride by weight.

4. The process of claim 2 wherein for each parts of said polyurethane plus said vinyl addition polymer 1 to 40 parts of a material selected from the group consisting of polyethylene oxide and polyethylene glycol monoalkyl ethers'are added. I H

5; The process of making a'synthetic suede leatherlike material comprising (1) making a homogeneousdispersion in a solvent for a polyesterurethane of. 70-99 parts I of said polyesterurethane from 30-1 parts of a polyvinylchloride polymer, the total of said polymer being 100'par'ts, from 3545 parts of textile fibers, said fibers being selected from the group consisting of fibers 0.5 mm. to 1.5 mm. long and fiber dusts with particle sizes from 0.005 to 0.150 mm. from 0.5 to 60 parts of a plasticizer for. said polyvinyl chloride resin, from 1 to 40 parts per 100 parts of total polymer of a material selected from the group consisting of polyethylene oxide and polyethylene glycol monoalkyl ethers, coating said dispersion on a textile backer, removing said solvent by immersion of the structure in a bath of inert liquid that is miscible with said solvent but'is not a solvent for said polyesterurethane, drying to remove said inert solvent, and sanding the surfaces so-produced to createa napped surface.

References Cited UNITED STATES PATENTS 3,169,885 2/1965 Golodner et a1 117-63 X 3,208,875 9/1965 Holden 117-l35.5 3,222,208 12/1965 Bertollo 117-63 3,284,274 11/ 1966 Hulslander et al. 117135.5 X 3,322,568 5/1967 Golodner 117-63 X 3,348,963 10/1967 Fukushima et a1. 117-161 X 3,384,502 5/1968 Japs 117-135.5 X

WILLIAM D. MARTIN, Primary Examiner T. G. DAVIS, Assistant Examiner U.S. Cl. X.R.