GB499790A - Improvements in or relating to pigmented cellulose derivative coating compositions - Google Patents

Abstract

A water-wet pigment and a water-wet uncolloided cellulose derivative are mixed, in the absence of a solvent or solvent plasticizer, with a water-immiscible organic liquid which has preferential wetting properties for the pigment and is also a non-solvent softener for the cellulose derivative, and subsequently a non-volatile water-repellent material which is a colloiding or gelatinizing agent is added. The water which separates is then removed. In a modification, the water-wet pigment, the water-immiscible organic liquid and the colloiding or gelatinizing are mixed, the water which separates is removed, and the product is mixed with the uncolloided cellulose derivative until the latter is colloided and water separates. In an example (1), wet cellulose nitrate, Chinese blue pigment pulp and zinc oxide are kneaded with blown castor oil, after which dibutyl phthalate is added and kneading continued until there is a separation of water. After the water has been removed, additional pigment pulp and zinc oxide are incorporated and water again removed. The final stages of the removal of water may take place under reduced pressure. In another example, (3) wet cellulose nitrate, leaded zinc oxide and water are kneaded first with blown castor oil and then with dibutyl phthalate until water separates. In other examples, (4) wet cellulose nitrate, maroon pigment pulp and blown castor oil are mixed and kneaded with dibutyl phthalate, (5) and (6) wet cellulose nitrate, yellow (or orange) lead chromate pigment pulp and blown castor oil are mixed and kneaded with dibutyl phthalate, and (7) wet cellulose nitrate, carbon black, oil soluble nigrosine (in solvent naphtha) and water are mixed with blown castor oil and then kneaded with dibutyl phthalate. During the removal of water by the vacuum treatment, it is desirable to add a water-carrier such as petrol, toluene, butyl alcohol or butyl acetate. Instead of the blown oil used in the examples, also raw or blown cottonseed or coconut oils blown linseed oil, or water-immiscible alcohols such as cyclohexanol may be used. In place of the dibutyl phthalate there may be used cyclohexyl butyl phthalate, dimethyl and diethyl phthalates, tricresyl phosphate, the phthalate esters of ethers of ethylene glycol, or synthetic resin compositions, e.g. coconut oil modified alkyd resin.