GB960101A - Moulding composition - Google Patents

Abstract

Heat and/or pressure mouldable moulding compositions contain a binder and a filler comprising cellulose crystallite aggregates having an average level-off degree of polymerisation of 15 to 375 anhydroglucose units. The cellulose crystallite aggregates are the insoluble fraction obtained by the acid hydrolysis of cellulose, which fraction is free from amorphous cellulose. The crystallite aggregates may have been further reduced in size by mechanical disintegration or mixtures of disintegrated and undisintegrated aggregates may be used. The binder is defined as any plastic, resin or the like capable of being mixed with a filler material to form any type of suitable article. The binder may be a urea-formaldehyde, thiourea-formaldehyde, melamine-formaldehyde, phenol-formaldehyde or alkyd resin; an unsaturated polyester; a protein, e.g. zein or casein, plastic; vulcanised or unvulcanised polyisobutylene; cellulose acetate or acetate butyrate; polyvinyl chloride; a vinyl chloride-vinyl acetate copolymer; an acrylic resin; polyethylene or polypropylene; polyterpenes; fluorethylene and styrene polymers; petroleum resins; furans; silicones; polyamides, e.g. nylon; and polyurethanes. The compositions may also contain moulding catalysts, mould lubricants, plasticizers, pigments and auxiliary fillers such as cotton flock or fabric, wood pulp, asbestos, mica, glass fibre, regenerated cellulosefibre, linen, nylon, wood flour, and diatomaceous earth. In examples compositions of cellulose crystallite aggregates and the following materials are disclosed:- (1) aqueous urea-formaldehyde resin syrup, zinc stearate, a pigment and a catalyst; (2) aqueous melamine-formaldehyde precondensate, zinc stearate, a pigment and a latent curing catalyst; (3) cellulose acetate; (4) a 2-stage moulding resin formed by mixing an acid-catalyzed phenol-formaldehyde precondensate, hexamethylene tetramine, calcium hydroxide, and calcium stearate; (5) urea-formaldehyde precondensate and alum; (6) melamine-formaldehyde precondensate, hydrochloric acid (in Examples 5 and 6 the cellulose crystallite aggregates are mixed with a dilute aqueous solution of the resin etc. and stirred, the mixture is filtered and the residue used as a moulding composition); (7) vinyl chloridevinyl acetate copolymer (the composition being prepared by adding water to a suspension of the aggregates in an acetone solution of the copolymer); (8) phenol-formaldehyde condensate and hexamethylene-tetramine; (9) phenol-formaldehyde condensate or an aniline-formaldehyde resin or polyformaldehyde resin. Urea-formaldehyde resin syrup is prepared in Example 1 by condensing a mixture of urea and formalin in the presence of formic acid, hexamethylenetetramine and ammonium benzoate. Melamine-formaldehyde resin precondensate is prepared by heating a mixture of melamine and formalin neutralised by triethanolamine. Cellulose crystallite aggregates are prepared in examples 5 and 8 by hydrolysing wood pulp or sulphite wood pulp with 0.5% by weight aqueous solution of HCl for one hour at 121 DEG C. Specification 231,431 is referred to.