US2055635A - Artificial leather manufacture - Google Patents

Description

30 and, when folded, to assume Patented Sept. 29, 1936 2,055,635 ARTIFICIAL LEATHER MANUFACTURE Milton 0. Schur, Berlin, N. 11., assignor to Brown Company, Berlin, N. H., a. corporation of Maine No Drawing. Application February 18, 1931,

Serial No.

9 Claims.

The subject of this invention is the manufacture of artificial leather, and more, particularly one which is intended to receive a dressing or finishing material, and, if desired, to undergo an embossing operation which imparts thereto the grain effect of natural leathers. Such dressed or finished leathers simulating vici kid, calfskin, snakeskin, sealskin, alligator, or the like, are applicable in many connections, for instance as shoe 10 uppers, upholstering material, pocketbooks, book covers, etc., especially when they are possessed of many of the important characteristics of natural leather, such as toughness, flexibility, stretchability, and feel.

In making a high grade finished artificial leather, it is sometimes the practice to start with a bibulous web, mat, fabric, or other base of cellulose fiber and to impregnate the base with a suitable binder, such as rubber in liquid form, e. g.,

with a rubber solution or with an aqueous rubber dispersion. Upon drying the impregnated base, especially an impregnated web of interfelted cellulose fiber, it is found that it has leather-like qualities to a marked degree. When such an artificial leather is dressed or finished with socalled water-finishes or lacquer-finishes, as are natural leathers, such as calfskin, I have observed that, unlike natural leathers, it tends to give a somewhat spotty or blotohy appearance,

one or more comparatively coarse, permanent, and unsightly wrinkles at the region of fiexure. It occurred to me that in order to improve such an artificial leather from the standpoint of finish, one must follow more closely in the path that the natural product lea When natural leather, such as calfskin, is examined under the microscope, it is found "to consist of a more or less tangled mass of comao paratively coarse fibers surfaced on its grain or skin side with a tenaciously adherent, elastic skin or sheet which is fine-textured and relatively thin. After reflecting upon the natural product and comparing it with thought dawned on me that, whereas nature had provided a skin on natural leather enabling it to take a finish and to be flexed or stretched without injury, such a skin and the service rendered thereby were absent in an artificial leather. In

other words even when the artificial leather contained a foundation of interfelted short fibers, such as wood pulp, the body of nated fibers had a texture or structure too coarse to receive directly thereon a finish without suffering defacement of the finish when subjected to fiexure, stretch and other stresses of use.

In accordance with the present invention, therefore, I surface a sheet of artificial leather in the form of a rubber-impregnated base, preferthe artificial product; the

rubber-impregably of unwoven cellulose fiber, grained, flexible skin simulating in its physical characteristics and in its ability to take water and lacquer finishes, the skin on a natural leather. The artificial leather on which the skin is imposed may be one which has been made by impregnating a bibulous web of interfelted cellulose fiber, e. g., a loosely-formed web of a wood pulp of high alpha. cellulose content, with rubber latex and then drying. When the as a shoe upper material or for analogous purposes, the rubber-impregnated web preferably has sufficient residual porosity to permit breathing of the foot. So, too, the skin imposed thereon is preferably pervious to water vapor and ably possesses a feel similar to that of natural leather.

There are various and modes of procedure falling skin-forming compositions within the ambit gone through the steps of dipping bibulous sheets of interfelted cellulose fiber in latex, squeezing the sheets free of excess latex, and drying, he will have a leather-like product possessing a resldual degree of porosity. The surface of the artificial leather thus produced is then preferably scoured, as by wire brushes or sand, to remove surface inequalities and to promote bonding of its fibers with the skin or skin-forming composition to be applied. When a skin-forming composition is employed, it may be sprayed onto the surface of the artificial leather to form anniform skin of the desired caliper. A composition found eminently satisfactory may be made by diluting about 100 parts of the usual latex of commerce (about 33% solids content) with about 50 parts of water and mixing about 25 parts of powdered cellulose therewith. The powdered cellulose may advantageously be a wood pulp which has been mechanically reduced to fine particle size, as in a ball mill, for instance to particles passing through a ZOO-mesh screen. If desired, 5 parts, more or less, of the powdered cellulose in the foregoing skin-forming composition may be replaced by a corresponding proportion of waterglass solution of a specific gravity of, say, 1.2. The surfaced sheet of artificial leather may be dried either at room temperature or under heat, whereupon it may be mechanically worked or boarded. contains added sulphur, zinc oxide-and an accelerator of vulcanization and the sheet surfaced therewith is dried under heat, the skin will become vulcanized. Otherwise, the skin may be vulcanized as by dipping the surfaced sheet into a dilute solution of sulphur-chloride or by passing it through an atmosphere of sulphur chloride vapor. The dried, and, if desired, vulcanized skin affords a surface for finishing remarkably superior to the surface of the artificial leather before If the skin-forming composition with a closeultimate product is to be used 10 prefer- 15 Assuming that one has already 20 surfaced artificial leather. The skin easily takes either a water or a lacquer finish, responding in this respect like natural leather. The finished product resists defacement by scufiing to a much greater degree than a similar product which has been finished without a skin, and it is capable of being fiexed or folded Without leaving permanently unsightly wrinkles.

If desired, the sheet of artificial leather may be plated or embossed either before or after the application of the usual leather dressing or finish, which may be a water finish, such as a film of blood albumin, or a lacguer finish, such as a film having a nitrocellulose ase.

The function of the latex in the skin-forming composition is to impart toughness, elasticity, and flexibility thereto. It may be replaced by rubber artificially dispersed in water or by rubber cement, all of which forms of rubber may be termed generically liquid rubber. The function of the pulverulent cellulose is to impart pores to the skin as well as to furnish particles to whicheither a water or a lacquer finish will adhere firmly and to avoid a rubbery feel in the skin. The presence of waterglass in the compo sition tends to make it smooth and uniform and further to add hardness to the skin. It is interesting to note that the mechanical working of the dried, surfaced sheet reduces the tackiness of the rubber surface or skin and increases the limpness and toughness of the foundation and skin, especially when latex has been used to furnish the rubber in the foundation and in the skin. While it is known that the mechanical working of freshly coagulated rubber toughens the rubber, nevertheless so far as I know, I am the first to apply the principle of mechanical working to a dry, rubber-impregnated cellulose fiber base having an adherent dry rubber skin to toughen the skin and simultaneously to render the foundation and the skin limp.

Other skin-forming media, such as a mixture of glue and formaldehyde preferably containing glycerine, of viscose and glycerine, or of latex and viscose and/or waterglass may be used, as these have been found to yield results answering to a greater or less degree the requirements of my invention. Any of these skin-forming compositions, however, preferably contain powdered cellulose, for the reason already given. Other pore-imparting fillers, such as talc, may conceivably be used together with, or in place of the powdered cellulose fiber, but, to date, the smooth feel coupled with the porosity afforded by the powdered cellulose fiber has not been surpassed. The powdered cellulose fiber also possesses the advantage over, say, a palpably fibrous material in that the composition in which it is used lends itself better to spraying or spreading as an even or smooth skin and in that the skin does not develop a feathery appearance especially after use. Rather than being formed directly on the artificial leather base, the skin may be preformed, in which case it may be combined with, or carried by, a thin tissue of interfelted fibers or a thin woven'fabric. The preformed skin may be fixed onto the artificial leather base by a suitable binder.

I claim: 1. An artificial leather comprising a rubberimpregnated base of unwoven fibers having a smooth surface and carrying an elastic, wean resistant skin on such surface, such skin comprising a dried-out mixture of rubber latex and viscose.

2. An artificial leather comprising a rubberimpregnated base of unwoven fibers having a smooth surface and carrying an elastic, wearresistant skin on such surface, such skin comprising a dried-out mixture of rubber latex and waterglass.

3. An artificial leather comprising a rubberimpregnated base of unwoven fibers having a smooth surface and carrying an elastic, wearresistant skin on such surface, such skin comprising a dried-out mixture of rubber latex, viscose, and waterglass.

4. An artificial leather comprising a rubberimpregnated base of unwoven fibers having a smooth surface and carrying an elastic, wearresistant skin on such surface, such skin comprising a dried-out mixture of rubber latex and viscose throughout which powdered cellulose is distributed to lend enhanced perviousness to water vapor thereto.

5. An artificial leather comprising a rubberimpregnated base of unwoven fibers having a smooth surface and carrying an elastic, wearresistant skin on such surface, such skin comprising a dried-out mixture of rubber latex and waterglass throughout which powdered cellulose is distributed to lend enhanced perviousness to water vapor thereto.

6. An artificial leather comprising a rubberimpregnated base of unwoven fibers having a smooth surface and carrying an elastic, wearresistant skin on such surface, such skin comprising a dried-out mixture of rubber latex, viscose, and waterglass throughout which powdered cellulose is distributed to lend enhanced perviousness to water vapor thereto.

7. An artificial leather comprising a rubberimpregnated base of unwoven fibres having a smooth surface and carrying an elastic, wearresistant skin on such surface. such skin including a dried-out mixture of rubber latex and an additional skin-forming medium comprising a binding means in suficient quantity to add hardness to the skin and make it smooth and uniform.

8. An artificial leather comprising a rubberimpregnated base of unwoven fibres having a smooth surface and carrying an elastic, wearresistant skin on such surface, such skin including a dried-out mixture of rubber latex, an additional skin-forming medium comprising a binding means in sufficient quantity to add hardness to the skin and make it smooth and uniform, and powdered cellulose that lends to the skin enhanced perviousness to water vapor.

9. The process which comprises impregnating a sheet of unwoven fibres with a rubber-carrying liquid vehicle, drying the impregnated sheet to remove the liquid vehicle and to form a leatherlike material, applying as a skin coat to the rubber-impregnated sheet a mixture including rubber latex and an additional skin-forming me- MILTON o. SCHUR.