Two-step copolymerization process by controlling the temperature to prepare copolymer latex containing hard and soft monomer components
AssigneeCanadian Industries Limited
InventorsIan H. McEwan, Manubhai B. Patel
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Abstract
Improved process for the preparation of aqueous emulsions of addition copolymers having functional groups to provide thermosetting capability via condensation. The process improvement resides in reducing the amount of unwanted premature condensation of the functional group. The process has two steps, one consisting of polymerizing a portion of the monomer reactants at a temperature not above 60.degree. C. if the functional group is present and the other of continuing the polymerization with the addition of the remaining monomer reactants at a temperature not above 60.degree. C. and at a pH in the range of from 1 to 7. The process is of use in producing improved thermosetting enamels.
Claims8
An improved process for the preparation of an aqueous emulsion of a copolymer which copolymer comprises from 99 to 30 parts by weight of at least one main monomer selected from the group consisting of styrene, .alpha.-methyl styrene, acrylonitrile, alkyl acrylates, alkyl methacrylates, alkyl fumarates, alkyl maleates, wherein the alkyl radical includes radicals of 1 to 12 carbon atoms, vinyl esters and ethers of organic and inorganic acids, vinyl pyridine, chloro allyl carbamate, butadiene and ethylene, from 1 to 30 parts by weight of at least one functional monomer selected from N-methylol derivatives of the formula
- Y--NR.sub.1 --R.sub.2
- wherein
- R.sub.1 is R.sub.2 or H;
- R.sub.2 is CH.sub.2 OR.sub.3 ;
- R.sub.3 is H or C.sub.1 -C.sub.4 alkyl;
- and Y a 4-benzyl-6-amino triazinyl radical or a R.sub.4 CO-- radical wherein R.sub.4 is CH.sub.2 .dbd.CH--, CH.sub.2 .dbd.C (CH.sub.3)--, or CH.sub.2 .dbd.CH--CH.sub.2 --;
- from 0 to 25 parts by weight of an hydroxyl group-containing monomer;
- and from 0 to 15 parts by weight of an unsaturated aliphatic carboxylic acid wherein the aliphatic group includes radicals of C.sub.2 to C.sub.6, with the total parts by weight of monomers being 100, which process comprises carrying out the polymerization in aqueous medium, in two stages;
- the first stage consisting of polymerizing a portion of the above monomers, which does not include the functional monomer when a polymerization temperature above 60.degree. C. is used in the presence of a sufficient amount of an initiator selected from salts of persulphates and peroxyacids;
- the second stage consisting of continuing the polymerization at a temperature not exceeding 60.degree. C. and at a pH in the range of from 1 to 7, with the addition of the remaining portion of the monomers being made in the presence of an initiator redox system comprising a reducing agent and a peroxide component selected from hydrogen peroxide, ammonium persulphate, organic peroxides and hydro-peroxides, and alkyl percarbonates.
Dependencies are inferred from the claim text.