Patent GB-990078-A (GB)
Title: Self-supporting waterleaves from cellulose ester particles
Inventor: MAREK BRUNO STEFAN WLADIMIR
IPC: C08B3/00
Filed: 1962-09-26
Abstract: Self-supporting waterleaves free from natural fibres and comprising cellulose ester particles are formed by adding a solution of cellulose ester in acetic acid to an aqueous solution of acetic acid under conditions of agitation vigorous enough to produce cellulose ester particles capable of forming self-supporting waterleaves. Specified esters are cellulose triacetate, secondary acetate, butyrate and acetate-butyrate.  The necessary agitation may be achieved by stirrers operating at more than 1000 r.p.m., or by use of ultrasonic vibration.  The concentration of the cellulose ester in the acetic acid is desirably 6-10% by weight, and the concentration of the aqueous acetic acid used for precipitation may be 18-40% depending upon the concentration of ester and degree of esterification.  A plasticizer, e.g. dioctyl phthalate, may be added to the ester solution before precipitation or to an aqueous suspension of precipitated particles. The particles may also be coated with a natural or synthetic latex.  A water-soluble cationic polymer and a latex emulsion is added to an aqueous suspension of ester particles, and precipitation of the latex thereon is completed by adding a coagulant, e.g. an alum solution. In an example, a solution of cellulose triacetate in acetic acid is added to rapidly stirred (1,500 r.p.m.) aqueous acetic acid.  The precipitated ester particles are washed with water.  A polyamide, a polyacryl latex and alum are added to an aqueous solution of the particles to form cellulose acetate particles (1 part) coated with globuli of latex (2 parts).  Waterleaves are made consisting of 20% of these particles and 80% rayon fibres.ALSO:Self-supporting waterleaves free from natural fibres and comprising cellulose ester particles are formed by adding a solution of cellulose ester in acetic acid to an aqueous solution of acetic acid under conditions of agitation vigorous enough to produce cellulose ester particles capable of forming self-supporting waterleaves.  Specified esters are cellulose triacetate, secondary acetate, butyrate and acetate-butyrate. The necessary agitation may be achieved by stirrers operating at more than 1000 rpm, or by use of ultrasonic vibration.  The concentration of the cellulose ester in the acetic acid is desirably 6-10% by weight, and the concentration of the aqueous acetic acid used for precipitation may be 18-40% depending upon the concentration of ester and degree of esterification.  A plasticizer e.g. dioctyl phthalate may be added to the ester solution before precipitation or to an aqueous suspension of precipitation particles.  The particles may also be coated with a natural or synthetic latex.  A water-soluble cationic polymer and a latex emulsion is added to an aqueous suspension of ester particles, and precipitation of the latex thereon is completed by adding a coagulant e.g. an alum solution. Waterleaves may be made from plasticized or unplasticized, latex-coated or uncoated cellulose ester particles, mixed or unmixed with man-made fibres. The wet waterleaves can be removed from the wire screen in the usual way, and may then be heated, with or without use of binders or pressure, to effect bonding of the web by added binders, if any, or by fusion of the celluslose ester particles to any thermoplastic fibres present.  In an example, a solution of cellulose triacetate in acetic acid is added to rapidly stirred (1,500 rpm) aqueous acetic acid.  The precipitated ester particles are washed with water.  A polyamide, a polyacryl latex and alum are added to an aqueous solution of the particles to form cellulose acetate particles (1 part) coated with globuli of latex (2 parts). Waterleaves are made consisting of 20% of these particles and 80% rayon fibres.