Patent GB-1076177-A (GB)
Title: Improvement in production of micro porous films and coatings
IPC: D06N3/06
Filed: 1964-10-20
Abstract: A microporous film is formed by directing on to a smooth non-porous casting surface a spray of a solution of a polymer in a solvent and a spray of a non-solvent for the polymer, the non-solvent being miscible in all proportions with the solvent, the sprays coinciding at or before striking the casting surface. The solvent and non-solvent are then removed.  The polymer is coagulated to form a microporous coating on the casting surface and most of the polymer solvent is flushed away in the form of a solvent-non-solvent mixture. The remaining polymer solvent is dissolved out from the coating by means of a liquid miscible with the polymer solvent, but not a solvent for the polymer.  The coating is then dried and stripped from the casting surface as a microporous film.  The polymers used are preferably linear polyurethane condensation polymers such as polyesterurethanes and polyalkyleneetherurethanes. Polyvinyl chloride, polyalkyl acrylates, polyacrylonitrile and copolymers thereof and mixtures of vinyl polymers with linear polyurethanes may be used.  The polymer solvent may be N,N1-dimethyl formamide, dimethyl sulphoxide, tetrahydrofuran or tetramethylurea. The non-solvent is preferably water, but may be ethylene glycol or glycerol.  The microporous coating may be deposited in a porous substrate to form a microporous laminate layer which may be passed over smooth or embossing rolls, compacted, passed through a water bath to remove residual polymer solvent and finally passed through a drying chamber or over drying rolls.  The laminates may be used as leather substitutes. A continuous reciprocating traverse motion may be imparted to the coincident spray until a layer of polymer of the desired thickness is formed on the substrate. In two examples a non-woven fabric of 3-denier polypropylene fibre is coated with polyesterurethane by directing on to the fabric a spray of the polymer solution and a spray of water and in another example a non-woven polyterephthalate ester is coated in the same manner.ALSO:A microporous film is formed by directing on to a smooth non-porous casting surface a spray of a solution of a polymer in a solvent and a spray of a non-solvent being miscible in all proportions with the solvent, the sprays coinciding at or before striking the casting surface.  The polymer is coagulated to form a microporous coating on the casting surface and most of the polymer solvent is flushed away in the form of a solvent-non-solvent mixture.  The remaining polymer solvent is dissolved out from the coating by means of a liquid miscible with the polymer solvent, but not a solvent for the polymer. The coating is then dried and stripped from the casting surface as a microporous film.  The polymers used are preferably linear polyurethane condensation polymers such as polyesterurethanes and polyalkyleneetherurethanes.  Polyvinyl chloride, polyalkyl acrylates, polyacrylonitrile and copolymers thereof and mixtures of vinyl polymers with linear polyurethanes may be used.  The polymer solvent may be N,N-dimethyl formamide, dimethyl sulphoxide, tetrahydrofuran or tetramethylurea.  The non-solvent is preferably water, but may be ethylene glycol or glycerol.  The microporous coating may be deposited on a porous substrate to form a microporous laminate layer which may be passed over smooth or embossing rolls, compacted, passed through a water bath to remove residual polymer solvent and finally passed through a drying chamber or over drying rolls.  The laminates may be used as leather substitutes.