Patent GB-487835-A (GB)
Title: Manufacture of improved pigments
IPC: C09B69/10
Filed: 1936-12-22
Abstract: Pigments such as lamp black, Prussian blue and titanium dioxide are combined with the condensation products of aldehydes and aminotriazines obtained, for example, as described in Specifications 455,008, 468,677, and 468,746, [all in Group IV]. Condensation products from aminotriazines and aldehydes with other substances capable of condensation, such as phenol, urea, aniline or alcohol may also be used or the aminotriazine-aldehyde condensation products may be used in admixture with condensation products for phenol, urea or amine resins, or with various artificial and natural resins.  The aminotriazine condensation products, which may be used at various stages of condensation, envelope the pigment and may be hardened at any stage.  The usual substances employed in pigment manufacture, such as aluminium hydroxide, green earth, tannic acid, colophony, tartar emetic, barium or calcium sulphate, zinc oxide or sulphide or titanium oxide may be incorporated.  The resulting pigments have high stability to hot water and soap solutions, a transparency when ground with oil, and a low specific gravity (1,4-1,6).  In example (7) melamine, dissolved in aqueous formaldehyde solution, is heated on a water-bath for 1/2 hour, evaporated in a vacuum to dryness, redissolved in hot water and added to a fine suspension of titanium dioxide in water, whereupon hydrochloric acid is added and the mixture is heated for 1 hour; on neutralization, a thick precipitate is formed, which is ground wet, filtered and dried to give a pure white pigment.  Lamp black may be similarly treated.ALSO:Soluble or insoluble dyestuffs or pigments are combined with the condensation products of aldehydes and aminotriazines to give pigments of a high stability to hot water and soap solutions; alternatively, dyestuff intermediates are combined with the condensation products and subsequently converted into the dyestuffs by coupling, condensation &c.  The condensation products described in Specifications 455,008, 468,677, and 468,746 may be used.  Condensation products from aminotriazines and aldehydes with other substances capable of condensation, such as phenol, urea, aniline or alcohol may also be used or the aminotriazine-aldehyde condensation products may be used in admixture with condensation products from phenol, urea or amine resins, or with various artificial or natural resins.  The aminotriazine condensation products may be used at various stages of condensation and at any stage of the manufacture of the pigment they may be hardened, usually by the application of heat.  The addition of a basic substance, for example triethanolamine or ethylene diamine, during the condensation increases the affinity for dyestuffs containing acid groups.  Similarly the addition of an acid substance, for example tartaric or citric acid, improves the affinity for basic dyestuffs.  The lakes may also be prepared in the presence of the usual substances employed in pigment manufacture, such as aluminium hydroxide, green earth, tannic acid, colophony, tartar emetic, barium or calcium sulphate, zinc oxide or sulphide or titanium oxide.  They have high stability to hot water and soap solutions, a transparency when ground with oil and a low specific gravity (1,4-1,6) and serve as colouring matters for oil and size paints, printing inks, artificial masses such as linoleum or plastic masses.  The following examples are specified: (1) (a) melamine is dissolved in aqueous formaldehyde solution and an aqueous solution of the dyestuff added at 80 DEG  C. whereupon sulphuric acid is added and a coloured resin is precipitated which after standing is ground wet, filtered, washed, dried and hardened for 4 hours at 140 DEG  C.; the finished product can be easily ground.  (1) (b) The formaldehyde aminotriazine solution of (a) is heated for 1/2 hour on the water bath to produce a product of limited solubility in water, whereupon the dyestuff is added and a pigment is prepared as in (1) (a).  A table is given showing the properties of lakes prepared by these two processes from numerous dyes including Kiton red, Orange II, Alizarine sapphire blue, Cotton yellow, Auramine G, and Benzyl green B.  (2) The solution of the condensation product described in (1) (b) is evaporated in a vacuum to dryness and the resulting powder mixed with a solution of the dyestuff, Alizarine sapphire blue B, Eosine J or Fast green JJO, in hot water and the mixture is hardened in thin layers for 5 hours at 140 DEG  C., the product is ground under water, filtered and dried. (3) The powder of (2) is hardened for 2 hours at 120 DEG  C., and added to a solution of the dyestuff, whereupon the lake is formed; it is filtered, dried and hardened for 2 hours at 120 DEG  C.; the dyestuffs specified are Alizarine green G, Kiton fast yellow 3G, Safranine GOOO, Violet B, the chromium compound of 1 : 2-aminonaphthol-4-sulphonic acid --> 1-naphthol-8-sulphamide and that of 4-chloro-2-aminophenol-6-sulphonic acid --> 2 : 4-dioxyquinoline. (4) (a) Rhodamine B is treated as in (2) except that tartaric acid is added to the dye and the pigment is filtered off before hardening. (4) (b) Orange II is treated as in (4) (a) the tartaric acid being replaced by a mixture of triethanolamine and formic acid.  (4) (c) Acid violet 6BN is treated similarly in conjunction with ethylene diamine hydrate.  (5) Condensation products of formaldehyde and melam, chloromelamine or monophenylmelamine in the presence of ethyl alcohol, sulphuric acid and formic acid, are similarly used.  (6) Indanthrene blue R is treated as in (1) (a).  (7) A suspension of titanium dioxide is treated with a solution of the powder of (2) and hydrochloric acid; on neutralization the thick precipitate is ground wet, filtered and dried yielding a pure white pigment; lamp black may be similarly treated.  (8) Melamine, urea and formaldehyde are condensed, Direct sky blue dissolved in water added and then sulphuric acid and the resulting lake is filtered and hardened. (9) Guanidine carbonate is employed similarly to the urea of (8). (10) Triethanolamine, melamine and formaldehyde are condensed, sulphuric acid is added and the solution similarly used to produce a lake from Orange II.  (11) Trimethylol-melamine, tartaric acid, Violet B and methyl alcohol are heated until a clear solution is obtained; this is evaporated to dryness and the product is hardened.  (12) An alcoholic hydrochloric acid solution of hexamethylol-melamine is used to form a lake of Fast green JJO. (13) and (14) Acetaldehyde and ethyl alcohol or benzaldehyde and benzyl alcohol are condensed respectively with melamine, the products are suspended in water and sulphuric acid is added followed by the dyestuff solution; the lakes are hardened at 110 DEG  C. for 4 and 16 hours respectively.  A sample has been furnished under Sect. 2 (5) of a pigment made by combining Indigosol O with the condensation product of (1) (b) rendered insoluble in cold water by heating with hydrochloric acid, and treating with nitrous acid.