Patent GB-1132594-A (GB)
Title: Improvements relating to artificial leather
Inventor: SHARP FRANK
IPC: D06N3/00
Filed: 1964-08-13
Abstract: 1,132,594. Artificial leather. POROUS PLASTICS Ltd. 12 Nov., 1965 [13 Aug., 1964; 21 Oct., 1964], Nos. 45688/65 and 43030/64. Heading B2E. A material suitable for use as a replacement for leather includes at least a surface zone of microporous polymeric plastics material including a polyurethane and a surface active agent comprising either a wetting agent comprising an alkali metal salt of a bis (alkyl) sulphosuccinate which renders the microporous surface zone hydrophilic or wettable, or a proofing agent comprising a long chain polymer of dialkyl or aryl alkyl siloxane units or silicone resin which renders the microporous surface zone hydrophobic or water repellant, and a base zone derived from a fibrous material and including a polymeric. plastics material including a polyurethane. The surface of the surface zone may be dried and then spray coated with a mixture of a material comprising a polyurethane (the lacquer working material) and a solvent therefor, and the coated surface zone exposed to conditions suitable to effect curing of the polyurethane. The lacquer working material may be diluted with cyclohexanone to give a solution containing approximately 2.5% by wt. of solids. The base zone may also contain either the wetting agent which renders the base zone hydrophilic or wettable, or the proofing agent which renders the base zone hydrophobic or water repellant. The material may be for use as a shoe upper material in which the surface zone includes the proofing agent and the base zone includes the wetting agent, or as a shoe lining material in which the surface zone and the base zone both include the wetting agent. The base zone is formed by impregnating a fibrous material with a mixture comprising a solution of a polymeric plastics base working material including a polyurethane, in a solvent which is not a solvent for the fibrous material, and removing the solvent by exposing the impregnated fibrous material to at least one leaching agent which is not a solvent for the base working material or the fibrous material, so as to make the base working material porous. The wetting or proofing agent, if present in the base zone, may be present in the mixture or in contact with the fibrous material before it is impregnated with the mixture. The agent may be mixed with the solvent for the base working material so as to be distributed throughout the mixture, and the solvent for the base working material may be a solvent for the agent. Prior to impregnation, the fibrous material may oe treated so as to reduce the wettability of the individual elements of the fibrous material; the fibrous material may be soaked under reduced pressure in a fibre proofing agent which comprises a long chain polymer of dialkyl or aryl alkyl siloxane units or a silicone resin, for a suitable length of time, and then the soaked fibrous material is subjected to a temperature and for a time sufficient to cause the proofing agent to adhere to the fibres. The fire proofing agent may be a solution of a silicone resin in methyl ethyl ketone containing approximately 2.5% by wt. solids. The fibrous material may be a mechanically entangled felt, made from Terylene (Tm) polypropylene, reconstituted collagen, or staple nylon fibre, the soaked nylon felt being dried at about 85‹C and then heated at about 140‹C for five minutes to cause the fire proofing agent to adhere to the fibres. The surface zone may be formed by coating a mixture comprising a polymeric plastics working material including a polyurethane, a solid removable filler e.g. sodium chloride, and a solvent for the working material which is not a solvent for the filler, and the wetting agent or the proofing agent, on a suitably prepared smooth surface of the base zone e.g. prepared by slitting the base zone parallel to its major plane, and coagulating the working material and removing the solvent and filler by exposing the coating to at least one leaching agent to leave the working material in a microporous solid form. The wetting or proofing agent may be mixed with the solvent for the working material, and may also be a solvent for the agent, so as to be distributed throughout the mixture. Prior to the removal of the solvent the surface of the coating may be exposed to the solvent leaching agent and to forces in addition to those of gravity so as to modify the configuration of the surface. The exposure of the surface to the solvent leaching agent may be for a time sufficient only to cause the material near the surface to gel and is not sufficient to remove all of the solvent. Exposure of the surface to the solvent leaching agent may be completed before the surface is exposed to the forces. The surface may be exposed initially to the leaching agent and then the forces are exerted on the surface by passing the coated base zone through a calender roll having the roll in contact with the surface shaped so as to form the desired surface configuration. The calendering may be carried out while the coating is substantially at room temperature e.g. 25‹C. The exposure of the surface to the solvent leaching agent may not be completed before the surface is exposed to the forces, for example, by spraying the surface with the solvent leaching agent, the droplet size of the spray being chosen for the particular finish it is desired to produce, or by placing the surface of the coating in contact with a surface, the gelling surface, formed to produce the desired surface configuration in the coating, the gelling surface being wetted with the solvent leaching agent. The gelling surface may consist of a woven material wetted with leaching agent, a solid calender roll provided with a feed of solvent leaching agent to its nip, or a hollow porous calender roll supplied with the solvent leaching agent from within the roll under a pressure sufficient to maintain the exterior of the roll in a wetted state. Examples of polyurethanes and solvents are given. The uncoated surface of the fibrous base may be treated by, for example, grinding, combing or carding, to raise the fibres.