Patent GB-1056228-A (GB)
Title: A method of making a porous plastic sheet entrapping a plasticizer
IPC: B41M5/10
Filed: 1964-12-02
Abstract: Porous sheets having a plasticizer trapped in the pores thereof are made by mixing a latex of a thermoplastic polymer with the plasticizer, depositing the composition as a coating on to a substrate, and removing the water from the coating.  The substrate may be a permanent backing or else removed after formation of the film.  The removal of the water may be by evaporation or by absorption into the substrate and followed by treatment to coalesce the polymer into a porous sheet, e.g. by curing at room temperature or by heating the sheet to fusion.  A colouring agent may be included in the composition.  Materials disclosed include polymers of ethylene, vinyl acetate, acrylic compounds, vinyl chloride, styrene, vinylidene chloride and fluoride, together with butyl rubber and copolymers of vinyl chloride and vinyl acetate; styrene and acrylates, butadiene with one of styrene, vinyl toluene and acrylonitrile; vinyl pyrrolidone with one of vinyl acetate, ethyl acrylate, and styrene; as well as polyamides. Plasticizers used may be of the primary type which solvate the polymer such as phthalates, adipates, sebacates and phosphates of mono- and poly-hydric alcohols and phenols, dicarbitol phthalate, tris(butoxyethyl)-phosphate, 2-pyrrilidone, acetyltributylcitrate, and polypropylene glycol; as well as non-solvating secondary plasticizers such as mineral oil, castor oil and oleic acid.  The former are essential when the polymer will not otherwise form coherent films, and may be used in excess to form the products of the invention, but secondary plasticizers are preferred, in combination with primary plasticizers when necessary.ALSO:Waxless carbon papers are made by mixing a latex of a thermoplastic polymer with a plasticizer, depositing the composition as a coating on to a substrate, and removing the water from the coating to leave a coating having plasticizer entrapped in its pores. The water may be removed by evaporation or absorption into the substrate.  After removal of the water, the coating is treated to coalesce the polymer into a porous sheet e.g. by curing at room temperature or by heating to fusion. Materials disclosed include polymers of ethylene, vinyl chloride, vinyl acetate, styrene, acrylates, vinylidene chloride and fluoride together with butyl rubber and copolymers of butadiene with one of styrene, vinyl toluene, and acrylonitrile, vinyl chloride with vinyl acetate, styrene with acrylates, vinyl pyrrolidone with one of vinyl acetate, styrene and ethyl acrylate, as well as polyamides.  Plasticizers may be of the primary type which solvate the polymer e.g. phthalates, adipates, sebacates, and phosphates of mono- and polyhydric alcohols and phenols, dicarbitol phthalate, tris(butoxyethyl)phosphate, 2-pyrrolidone, acetyltributyl citrate, and polypropylene glycol; and of the non-solvating secondary type such as mineral oil, castor oil and oleic acid.  The former are essential when the polymer will not otherwise form a coherent film, and may be used in excess to form the products of the invention, but secondary plasticizers are preferred, in combination with primary plasticizers when needed.  Dyes, toners, and pigments may be used to colour the plasticizer where the products are used as transfer media in typewriter ribbons or carbon papers. Such colouring matter should be sufficiently compatible with the plasticizer to form an ink or marking material therewith.  Specified dyes include Flushed Alkali Blue, Oil Blue Black, ZBC, and Nubian Resin Black. In examples the substrates used are "Mylar" (Registered Trade Mark) and Weblon non-woven fabric.ALSO:Porous sheets having a plasticizer trapped in the pores thereof are made by mixing a latex of a thermoplastic polymer with the plasticizer, depositing the composition as a coating on to a substrate, and removing the water from the coating.  The removal of the water may be by evaporation or by absorption into the substrate and is followed by treatment to coalesce the polymer into a porous sheet, e.g. by curing at room temperature, or by heating the sheet to fusion.  A colouring agent may be included in the composition.  Materials disclosed include polymers of ethylene, vinyl chloride, vinyl acetate, styrene, acrylates., vinylidene chloride and fluoride, together with butyl rubber and copolymers of butadiene with one of styrene, vinyl toluene and acrylonitrile, vinyl chloride with vinyl acetate, styrene with acrylates, vinyl pyrrolidone with one of vinyl acetate, styrene and ethyl acrylate, as well as polyamides.  The plasticizers may be of the primary type which solvate the polymer, for example phthalates, adipates, sebacates, and phosphates of mono-and poly-hydric alcohols and phenols, dicarbitol phthalate, tris (butoxyethyl) phosphate, 2-pyrrolidone, acetyl tri-butyl citrate, and poly-propylene glycol; and of the non-solvating secondary type such as mineral oil, caster oil and oleic acid.  The former are essential when the polymer will not otherwise form a coherent film, and may be used in excess to form the products of the invention, but secondary plasticizers are preferred, in combination with primary plasticizers when necessary. In examples, the substrates used are 'MYLAR' (Registered Trade Mark) film, and 'WEBLON' non-woven fabric.