GB989683A - Detergent tablets and processes for manufacturing them - Google Patents

Abstract

Detergent briquettes which disintegrate readily in water are produced by mixing together a non-ionic detergent and a normally solid water-soluble inorganic salt, producing therefrom, e.g. by spray-drying, a particulate composition containing up to 21%, most preferably 7-14%, moisture, coating the particles with 3-20% of a soluble silicate and raising the moisture content thereof to 16-25%, most preferably 17.5-20.5%, by application of (e.g. by spraying) an aqueous silicate solution, pressing the coated particles into a briquette (e.g. at a pressure of 10-100 p.s.i.), and then applying thereto 0.25-5% of a readily water-soluble organic film-forming polymer. The non-ionic detergent which most preferably comprises 7-12% of the aqueous slurry to be dried, is suitably a block copolymer of ethylene and propylene oxides, alkylene oxide condensates with alkylphenols, fatty alcohols, fatty acids and with esters and ethers of sugar alcohols but is most commonly a nonylphenoxypolyethenoxyethanol having 9-10 ethoxy groups in the molecule. The inorganic salt generally comprises 30-75%, of which 30-50% consists of sodium tripolyphosphate and the remainder, if any, comprises sodium silicate (Na2O : SiO2 of 1 : 2.35), sodium sulphate, and sodium and potassium carbonates. In addition, such anionic detergents as sodium alkylbenzene sulphonate, alkyl sulphate, fatty acid monoglyceride sulphate, and N-acyl-N-methyl tauride in which the alkyl or acyl groups contain 12-15 carbon atoms in amounts of 1-5%, and C12- 18-alkanols in amounts of 0.5-5% may also be included. The silicate solution with which the particles are sprayed preferably consists of a 25-46%, preferably a 35-37%, solution of a sodium silicate (Na2O : SiO2 of 1 : 2-1 : 3, preferably 1 : 2.35) and the coated particles preferably have diameters in the range 0.25-4 mm. After this coating, the particles are preferably treated with a talc which passes a 200 mesh (U.S.S.) sieve in a amount of 0.5-5%, and are then screened to pass a 6-60 mesh before being compacted into a briquette. The water-soluble polymer coating applied to the briquette may comprise polyvinylpyrrolidone, sodium carboxymethyl cellulose, or hydroxypropylmethylcellulose, but preferably consists of a polyvinyl alcohol having a weight average degree of polymerization of 30-300 and which contains 10-30% polyvinyl acetate; the polymer is suitably applied by spraying as a 10-25% solution to yield 0.25-1% polymer on the final tablet (average coating thickness of 0.01-0.8 mm.). The polymer solution to be sprayed may contain sodium bicarbonate, ethylene glycol or sorbitol. The final briquettes may be packed in moisture-proof bags or sleeves, e.g. of polyethylene.