Production of porous materials

Claim 3

A method as in claim 1 in which the proportion of said salt in said mixture is at least sufficient to improve the uniformity of the pore structure of the resulting product.

Claim 4

A method as in claim 1 in which the ratio of said polyurethane to said solvent is in the range iof 1:9 to 7:3.

Claim 5

Process as in claim 1 in which said solution has evenly distributed therethrough microscopic particles of sodium chloride and said solidifying is effected by the action of liquid water on a layer of said mixture on a support.

Claim 6

Process as in claim 4 in which said mixture of said solution and said microscopic particles is a smooth cream of spreadable consistency, said shaping of said mixture comprises spreading said mixture on to a temporary support and said solidifying comprises immersing said mixture on said support into water, and in which the solidified layer is stripped from said temporary support.

Claim 7

Process as in claim 5 in which said solvent comprises dimethylformamide.

Claim 8

Process as in claim 1 in which said solution has evenly distributed therethrough microscopic particles of sodium chloride of 7-25 micron particle size and in which a layer of said mixture is immersed in a bath of water to solidify said layer.

Claim 9

Process as in claim 7 in which said solution contains polyurethane and solvent in a ratio in the range of 1:2 to 1:4.

Claim 10

Product of the process of claim 1.

Claim 11

Product of the process of claim 8.

Claim 12

A process for producing a porous sheet material which comprises (a) uniformly dispersing from about 10 to about 50 parts by weight of an inorganic salt in 100 parts by weight of a film-forming polyester type polyurethane, (b) applying the coating solution on a fibrous substrate or a film-making plate, (c) coagulating the coating layer with an aqueous coagulation medium, the concentration of said inorganic salt in said coagulating medium being below about two-thirds its concentration at saturation, and at least sufficient to yield a porous sheet upon coagulation of said polyurethane, said inorganic salt being selected from the group consisting of sodium sulfate and sodium chloride.

Claim 13

A process for producing a porous sheet material which comprises (a) uniformly dispersing from about 10 to about 50 parts by weight of an inorganic salt in 100 parts by weight of a film-forming polyester type polyurethane, (b) applying the coating solution on a fibrous substrate or a film-making plate, (c) coagulating the coating layer with an aqueous coagulation medium, the concentration of said inorganic salt in said coagulating medium being below about two-thirds its concentration at saturation, and at least sufficient to yield a porous sheet upon coagulation of said polyurethane, said inorganic salt being selected from the group consisting of sodium sulfate and sodium chloride.

Claim 14

The process as in claim 11 wherein the concentration of the inorganic salt in the coagulating medium is less than one-third of its concentration at saturation.

Claim 15

The process as in claim 11, wherein the temperature of the coagulating medium is 20° C.

Claim 16

A process for producing a porous sheet material which comprises (a) uniformly dispersing from about 10 to about 50 parts by weight of an inorganic salt in 100 parts by weight of a film-forming polyester type polyurethane, (b) applying the coating solution on a fibrous substrate or a film-making plate, (c) coagulating the coating layer with water to yield a porous sheet upon coagulation of said polyurethane, said inorganic salt being selected from the group consisting of sodium sulfate and sodium chloride.

Claim 17

A process for producing a porous sheet material which comprises (a) uniformly dispersing from about 10 to about 50 parts by weight of an inorganic salt in 100 parts by weight of a film-forming polyester type polyurethane, (b) applying the coating solution on a fibrous substrate or a film-making plate, (c) coagulating the coating layer with water to yield a porous sheet upon coagulation of said polyurethane, said inorganic salt being selected from the group consisting of sodium sulfate and sodium chloride.

Claim 18

The process as in claim 14, wherein the temperature of the water is 20° C.

Claim 19

In a process for producing an artificial leather by applying a polyurethane polymer solution in an organic solvent as a coating layer onto a textile substrate, bathing the coated layer with a nonsolvent for the polymer until the layer has coagulated and then washing and drying to obtain a porous elastomeric layer, the improvement which comprises: carrying out said coating application with a solution of said polyurethane containing 21 to 33 parts by weight of polyurethane and 300 to 600% by weight, with reference to the polyurethane, of sodium sulfate in 79 to 67 parts by weight of an organic solvent which is miscible with water and which is a nonsolvent for sodium sulfate, the viscosity of said solution being at least 20 poises, measured at 20° C.; and subsequently washing out said solvent and said sodium sulfate from the coagulated layer and drying to form an elastomeric coating permeated with micropores.

Claim 20

In a process for producing an artificial leather by applying a polyurethane polymer solution in an organic solvent as a coating layer onto a textile substrate, bathing the coated layer with a nonsolvent for the polymer until the layer has coagulated and then washing and drying to obtain a porous elastomeric layer, the improvement which comprises: carrying out said coating application with a solution of said polyurethane containing 21 to 33 parts by weight of polyurethane and 300 to 600% by weight, with reference to the polyurethane, of sodium sulfate in 79 to 67 parts by weight of an organic solvent which is miscible with water and which is a nonsolvent for sodium sulfate, the viscosity of said solution being at least 20 poises, measured at 20° C.; and subsequently washing out said solvent and said sodium sulfate from the coagulated layer and drying to form an elastomeric coating permeated with micropores.

Claim 21

A process as claimed in claim 16 wherein said coating solution containing sodium sulfate is of dough-like consistency.

Claim 22

A process as claimed in claim 17 wherein said sodium sulfate has a particle size in the range 7-25 microns.

Claim 23

A process as claimed in claim 17 wherein said textile substrate is a woven or knitted fabric.

Claim 24

A process as claimed in claim 17 wherein said textile substrate is a bonded fibrous fleece.

Claim 25

A procss as claimed in claim 20 wherein said bonded fleece is a product prepared by impregnating a fibrous felt with a solution of elastomeric polyurethane in dimethyl formamide and then immersing said impregnated felt in water and drying.

Claim 26

A process as claimed in claim 17 wherein two of said polyurethane solutions containing said sodium sulfate are applied to the substrate in successive layers.

Claim 27

A process as claimed in claim 22 wherein both solutions are applied before coagulation with water.

Claim 28

A process as claimed in claim 17 wherein a second polyurethane solution free of salt is applied as a successive layer after the application of said polyurethane solution containing said sodium sulfate.

Claim 29

A process as claimed in claim 24 wherein both solutions are applied before coagulation with water.

Claim 30

A process as claimed in claim 17 wherein the polymer layer is embossed in a partly coagulated state.

Claim 31

A process as claimed in claim 17 wherein said solution of polyurethane consists essentially of 25 to 33 parts by weight of polyurethane and 300 to 600% by weight, with reference to the polyurethane, of sodium sulfate in 75 to 67 parts by weight of said organic solvent, such that the viscosity of said solution is at least 100 poises, measured at 20° C.