GB683544A - - Google Patents

Abstract

683,544. Enamels. DU PONT DE NEMOURS & CO., E. I. Feb. 7, 1950 [April 13, 1949], No. 3143/50. Class 56. A vitreous enamel composition suitable for application to light metals and having a reduced tendency to " tear " comprises a frit comprising, in mol percentages, PbO 10-18, SiO, 38-65, Li 2 O5-12, Na 2 O 0-22, K 2 O 0-20, TiO 2 0-11, with an addition of 0.2-10 per cent of sodium silicate and 0.2-5 per cent of a group consisting of sodium and potassium metaborate based on the weight of the frit. The total alkali metal oxide content is 25-36 mol per cent and the ratio Si 1 O 2 +(2ÎTiO 2 )/alkalioxide is 1.8-3.0. The sodium silicate and alkali metal metaborate are preferably added as mill additions to the frit prior to grinding. The metaborate may be formed in situ in the enamel by adding boric acid or borax and sufficient sodium or potassium hydroxide to form the metaborate. The sodium silicate may be added in the form of water glass. The silicate and metaborate may be mixed together and with other mill additions such as ceramic pigments, dispersing agents, bonding agents, &c., before being added to the frit. Three examples are given showing the weight and mol percentages of the frit, these examples with the weight percentages of the frits are as follows:- (i) 20 parts KOH, 23 parts H 3 BO 3 , 43 parts white lead (2PbCO 3 -Pb(OH) 2 as dispersing agent, and 15 parts of aqueous water glass solution containing 63 per cent water and 37 per cent Na 2 O.4SiO 2 are mixed, and one part of the mixture added to 19 parts of the following frit, PbO 44.6, SiO 2 29.6, Li 2 O 2.3, Na 2 O 13.3, TiO 2 10.2 with 0-1.9 parts of inorganic pigment or opacifier. (ii) 35.4 parts KOH, 3.9 parts H 3 BO 3 , 25.6 parts water glass solution containing 63 per cent water are mixed and one part of the mixture is added to 12.5 parts of the following frit, PbO 37.4, SiO, 30.0, Li 2 O 2.3, Na 2 O 13.8, K 2 O 2.2, TiO 2 12.7, Sb 2 O 3 1.6, with 0.75 part of coloured inorganic pigment such as lead antimonate. (iii) 4.7 parts NaOH, 22.2 parts borax, 47 parts water glass solution containing 63 per cent water and 26.1 per cent Na 2 O.4SiO 2 are mixed and one part of the mixture is added to 4 parts of the following frit, PbO 34.2, SiO, 27.8, Li 2 O 2.4, Na 2 O 13.9, K 2 O 2.8, TiO, 13.7, Sb 2 O 3 2.8, BaO 2.4 with 0.4 part of coloured inorganic pigment or opacifier, e.g., TiO 2 . The mixtures when milled, applied by spraying, dried, and fired at 920-980 degrees F. are free from "tearing," "crawling," and "microtearing." Specifications 564,597 and 580,688 are referred to.