GB859729A - Pigmented amino plastic resinous materials - Google Patents

Abstract

A TiO2 pigment of the rutile type is coated (see Group III) with hydrous oxides of aluminium and silicon, the coating is calcined and the resulting pigment is either added to a urea- or melamine formaldehyde resin and used to impregnate fibrous sheets for making laminates, or is added to paper pulp and the paper formed therefrom is impregnated with a urea- or melamine-formaldehyde resin. The laminae may if desired be of glass fibres fabrics or wood products, and it is also stated that the pigments may be used in preparing pigmented resinous materials in the form of massive moulded products. The pigmented products of the invention are less liable to discolour. Pigmented paper laminates may be made according to the invention by impregnating paper with an aqueous alcoholic slurry of coated pigment in aminoplast resin, drying and hot-pressing a number of superposed laminae or by adding the pigment to paper stock, forming sheets and impregnating a number of them with an aqueous alcoholic solution of resin prior to laminating by hot pressure. In the example TiO2 coated with AI2O3 and Si O2 was added to aqueous alcoholic urea-or melamine formaldehyde resin. Sheets of filter paper were impregnated with the slurry, dried and hot-pressed together. The discolourations were measured and compared with the controls after exposure under sun lamps.ALSO:Titania of the rutile modification is coated with hydrous oxides of aluminium and silicon, and the coating is calcined preferably for 1 to 3 hours at 650 DEG -800 DEG C. The pigments are used with aminoplastic resinous material (see Group IV(a)). An aqueous slurry of TiO2 pigment is mixed successively or simultaneously with aqueous solutions of aluminium and silicon compounds and the hydrous oxides are precipitated on to the TiO2. The mol ratio of alumina to silica may vary from 1:1 to 2:1, but is preferably 1:1. The two together constitute 2-15% by weight of the TiO2. Suitable aluminium compounds are the sulphate, nitrate chloride or sodium or potassium aluminate. Suitable silicon compounds are sodium, potassium or ammonium silicate. Preferably the silicate solution is added before the aluminium compound. In Examples (1) pigment A is prepared by adding aqueous sodium silicate and aluminium sulphate successively to an aqueous slurry of calcined rutile TiO2. Caustic soda was added to a pH of 7.0, to produce with heating to 60 DEG C. a 1:1 molar coating of the two hydrous oxides. The coated pigment is filtered off, washed, dried, calcined at 725 DEG C., dry milled and pulverized. (2) In making pigment B, the sodium silicate solution was made alkaline before addition. (3) For pigment C, solutions of alkaline sodium silicate and aluminium sulphate were simultaneously added to the TiO2.