Abstract The present invention relates to the manufacture of titanium dioxide wherein titanium sulphate liquor is produced containing colloidal and suspended impurities which are flocculated and removed from the liquor before the titanium dioxide is obtained by hydrolysis. More particularly it relates to the improvement of such manufacture comprising mixing the liquor, prior to hydrolysis, with a solution of (a) a polymer of an acrylic acid ester of the general formula: CH2=CR3COO(CH2)xNR1R2 wherein x is 2, 3 or 4, R1 and R2 are each selected from the group consisting of hydrogen and alkyl groups containing up to eight carbon atoms and R3 is a member selected from the group consisting of hydrogen and methyl, or (b) a water-soluble salt of said ester or (c) a copolymer of said ester with an ethylenically unsaturated comonomer, or (d) a copolymer of a water-soluble salt of said ester with an ethylenically unsaturated comonomer; the polymer or copolymer having a molecular weight such that the viscosity of a 1 percent by weight aqueous solution thereof as measured in a No. 3 Suspended Level Viscometer at 25* C. is at least 40 centistokes, the comonomer being either water-soluble and present to the extent of not more than 40 percent by weight of the copolymer or water-insoluble and present to the extent of not more than 15 percent by weight of the copolymer.
Process according to claim 1 in which the copolymer is one whose 1 percent by weight aqueous solution viscosity measured in a No. 3 suspended level viscometer at 25* C. lies within the range 80 to 200 centistokes.
Claim 2
Dependent Claim
20 words
Process according to claim 1 in which the copolymer is derived from N,N-diethylamine ethyl acrylate or a water-soluble salt thereof.
Claim 3
Dependent Claim
26 words
Process according to claim 1 in which the comonomer is water-soluble and present to the extent of 3 to 30 percent by weight of the copolymer.
Claim 4
Dependent Claim
52 words
Process according to claim 1 in which the comonomer is acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, a water-soluble mono-alkyl ester of maleic or fumaric acid, an amide or hydroxyethyl ester or hydroxypropyl ester of any of these acids, vinyl pyrolidone or a water-soluble alkyl vinyl ether.
Claim 5
Dependent Claim
13 words
Process according to claim 5 in which the amide is acrylamide or methacrylamide.
Claim 6
Dependent Claim
27 words
Process according to claim 1 in which the comonomer is water-insoluble and present to the extent of from 3 to 10 percent by weight of the copolymer.
Claim 7
Dependent Claim
47 words
Process according to claim 1 in which the comonomer is water-insoluble and is an alkyl ester derived from acrylic or methacrylic acid and an alcohol of the formula CnH2n 1OH where n is 1 to 8, styrene, methyl styrene, vinyl acetate, vinyl propionate, vinyl butyrate or acrylonitrile.