Patent GB-1002225-A (GB)
Title: Cellular polymeric sheet material and method of making same
IPC: D06N3/00
Filed: 1963-07-29
Abstract: A coated sheet material comprises a layer of polymeric material in the form of a honeycomb-like cellular structure, at least 50% of the volume of the layer being composed of contiguous elongated cells having (a) an average diameter of from 20-200 microns, (b) a substantially perpendicular orientation of their longest dimension in relation to the plane of the surface of the sheet, and (c) thin microporous cell walls which, by virtue of their microporosity, render the cells intercommunicating in adherence with a surface or each of the two surfaces of a porous fibrous sheet material.  The sheet material may have a permeability value of at least 1,000.  The porous fibrous sheet material may be a non-woven fabric, a woven or knitted fabric, non-fibrous porous polymeric material such as microporous or perforated film, a paper-like material or leather, the fibres of which may be natural or synthetic, crimped or straight, organic or inorganic, continuous filament or staple, or of papermaking length or a composite sheet material comprising a woven fabric integrally united to a surface of a non-woven fabric by a porous mass of the same flexible polymeric material as the cellular layer, the woven fabric being adhered to and contiguous with the cellular layer, the porous mass extending from its integral relationship with the cellular layer through the woven fabric and through at least the adjacent surface of the non-woven fabric.  The surface of the or each of the cellular layers furthest from the fibrous sheet material may be in a cut-away condition whereby the majority of the cells in the surface of the layer or each of the layers have a diameter of at least 10 microns.  The free surface of the cellular layer or one of the cellular layers has in superposed adherence therewith a microporous vapour permeable layer of polymeric material in which the pores are intercommunicating and are predominantly less than 20 microns in diameter.  The elongated cells are tapered such that their diameters become progressively smaller from the surface of the cellular layer in contact with the substrate to the opposite surface of the layer.  The polymeric material of the cellular structure may be flexible, elastomeric, and may have an initial modulus below 1,0 gram per denier.  The polymeric materials specified are polyurethane, vinyl halide polymers (including copolymers with other ethylenically unsaturated monomers), polyamides, polyesteramides, polyesters, polyvinyl butyral polyalphamethyl styrene, polyvinylidene chloride, polymers of alkyl esters of acrylic and methacrylic acids, chlorosulphonated polyethylene, copolymers of butadiene and acrylonitrile, polystyrene, and cellulose esters and ethers.  At least 51% by weight of the polymeric material of the cellular structure may consist of a polyurethane elastomer which may be the product of first reacting an organic diisocyanate with a polyalkylene ether glycol or a hydroxyl-terminated polyester, examples of which are given, to produce an isocyanate-terminated polyurethane prepolymer, and then reacting the resulting prepolymer with a chain extender comprising a compound having two active hydrogen atoms bonded to amino-nitrogen atoms, examples of which are given; up to 49% by weight of the polymeric material consisting of a vinyl chloride polymer: or at least 51% by weight of the polymeric material may consist of a vinyl chloride polymer, which may contain a plasticizer therefor; up to 49% by weight of the polymeric material consisting of a polyurethane elastomer.  The polymeric material of the cellular structure may be flexible and the cellular layer may be coated with a wear resistant layer of flexible polymeric material.  The uncoated and coated supported sheet material may take the form of man-made suede and leather-like sheet material having good smoothness and grain-back characteristics respectively.  The sheet material may be produced by applying to a substrate a layer of a solution of polymeric material, coagulating the layer into a honeycomb-like cellular structure, as defined, by bathing it in a liquid which is a non-solvent for the polymeric material and is at least partially miscible with the solvent of the solution, removing substantially all of the solvent from the layer, e.g. by further bathing the layer with the non-solvent liquid, and removing substantially all of the non-solvent from the resulting substantially solvent-free honeycomb-like cellular layer, e.g. by drying it in a heat zone. The layer of solution applied to the substrate may have sufficient thickness to produce a honeycomb-like layer which is over 10 mils thick when fully dry.  The exposed surface of the honeycomb-like layer may be abraded sufficiently to leave the majority of the cells in the exposed surface with a diameter of at least 10 microns.  The layer of solution may be applied to both surfaces of the substrate and both layers are coagulated simultaneously, or only to one surface of the substrate and the layer coagulated at least initially with warm non-solvent, the resulting product having a permeability value of at least 1,000.  The dried honeycomb-like layer may be coated with a microporous vapour permeable layer of polymeric material in which the pores are intercommunicating and are predominantly less than 20 microns in diameter by applying to the exposed surface of the honeycomb layer a layer of flexible polymeric material dispersed in a liquid solvent for the polymer, which may be prepared by adding liquid non-solvent for the polymeric material to a solution of the polymeric material in sufficient amount to convert the solution to a substantially colloidal polymeric dispersion, coagulating the layer into a microporous structure by bathing it with a non-solvent for the polymer that is at least partially miscible with the solvent, removing substantially all of the solvent from the layer, and removing substantially all the non-solvent from the resulting solvent free layer.  The solvent of both coating compositions may be dimethyl formamide, many other examples being given, and the non-solvent used for bathing both layers may be water, again many other examples are given, the layer of solution having a polymer solids content of 10-30% by weight, a viscosity of 10-500 poises at 24  DEG C., and being of sufficient thickness so that the dried layer is over 10 mils thick.  The polymer solution may be applied by knife-coating, dipping, brushing, spraying, or extruding.  The solution layer can be interspersed between two or more substrates to form a honeycomb-like cellular bonding layer. Specifications 849,155, 919,500 and 946,069 are referred to.