Free radical polymerization using acidified ethoxylated conjugated fatty ether surfactants
The free radical initiated addition polymerization of ethylenically unsaturated, particularly acrylic monomers in which the dispersed phase is stabilised by a surfactant including at least one anionic surfactant compound of the formula (I): R 1 —(OA) n —X where R 1 is C 16 to C 22 hydrocarbyl including at least two double bonds; OA is oxyalkylene group; n is from 2 to 60; and X includes at least one acidic H atom, and is particularly a phosphate ester group, or a salt thereof, is described. The use of the surfactants of the formula (I) enable efficient emulsification and thus polymerization at temperatures above those at which non-ionic unsaturated surfactants are effective. The polymer latex products give polymer films having good water resistance properties.
1. A method of free radical initiated addition polymerisation of at least one ethylenically unsaturated monomer which is or includes at least 50% by weight of at least one acrylic monomer, in which the dispersed phase is stabilised by a surfactant including at least one anionic surfactant compound of the formula (I):
R 1 —(OA) n —X (I)
where
R 1 is a C 16 to C 22 alkyl group including at least two double bonds;
OA is an oxyalkylene group;
n is from 2to 60; and
X is a phosphorus acid group including at least one acidic H atom, or a salt thereof.
2. A method as claimed in claim 1 wherein the group R 1 is a C 16 to C 22 alkyl group including two double bonds which are conjugated.
3. A method as claimed in claim 1 wherein for at least 50% of the compound(s) of the formula (I), X is a phosphate group: —O—P—(O)(OH) 2 or a salt thereof.
4. A method as claimed in claim 1 wherein for at least 65% of the compound(s) of the formula (I), X is a phosphate group: —O—P—(O)(OH) 2 or a salt thereof.
5. A method as claimed in claim 1 wherein the group OA is an oxyethylene group and n is from 5 to 30.
6. A method as claimed in claim 1 wherein the acrylic monomer(s) represent at least 75% by weight of the ethylenicaliy unsaturated monomer(s).
7. A method as claimed in claim 1 wherein the amount of anionic surfactant used is from 0.25 to 5 parts by weight surfactant per 100 parts by weight total monomer.
8. A method as claimed in claim 1 wherein the temperature of the polymerisation reaction is from 60 to 100° C.