PROCESS FOR THE PREPARATION OF RADIATION CURABLE COMPOSITIONS
The present invention relates to a process for the preparation of a radiation curable composition comprising at least (meth)acrylic copolymer A and at least one radiation curable epoxy based compound B, said process comprising a first copolymerization step, and a subsequent esterification step.
1 . Process for the preparation of a radiation curable composition comprising at least one (meth)acrylic copolymer A and at least one radiation curable epoxy based compound B, said process comprising:
(a) in a first copolymerization step, the preparation of a (meth)acrylic copolymer A by copolymerization of monomers comprising:
(i) from 39 to 98.9 weight % of at least one (meth)acrylic monomer (a1),
(ii) from 0.1 to 60 weight % of at least one other copolymerizable monomer (a2) different from (meth)acrylic monomer (a1),
(iii) from 1 to 15 weight % of at least one copolymerizable monomer (a3) having at least one carboxylic acid group or group capable of forming a carboxylic acid group,
in the presence of at least one non-copolymerizable epoxy compound (b1) and
(b) in a subsequent esterification step, the preparation of a radiation curable epoxy based compound B by esterification of the non-copolymerizable epoxy compound (b1) with at least one radiation curable monomer having at least one carboxylic acid group (a4).
2 . Process according to claim 1 wherein the (meth)acrylic monomer (a1) is selected from alkyl (meth)acrylates having a Tg, when homopolymerized, of less than −30° C. and wherein the copolymerizable monomer (a2) is selected from monomers having a Tg, when homopolymerized, of more than −30° C.
3 . Process according to claim 1 wherein the (meth)acrylic monomer (a1) is selected from 2-ethylhexyl acrylate, butylacrylate and mixtures thereof.
4 . Process according to claim 1 wherein the copolymerizable monomer (a2) is selected from methyl (meth)acrylate, ethylacrylate, tert-butyl (meth)acrylate, vinyl acetate, styrene and mixtures thereof.
5 . Process according to claim 1 wherein the copolymerizable monomer (a3) is selected from (meth)acrylic acid.
6 . Process according to claim 1 wherein the radiation curable monomer (a4) is selected from (meth)acrylic acid.
7 . Process according to claim 1 wherein the non-copolymerizable epoxy compound (b1) is selected from glycidyl esters of saturated or unsaturated carboxylic acids, glycidyl ethers of aliphatic or aromatic polyols, and mixtures thereof.
8 . Process according to claim 1 wherein the non-copolymerizable epoxy compound (b1) is selected from the monoglycidyl esters of long chain alkyl carboxylic acids wherein the alkyl chain comprises from 6 to 24 carbon atoms.
9 . Process according to claim 1 wherein:
(i) from 5 to 60% by weight of non-copolymerizable epoxy compound (b1), and
(ii) from 40 to 95% by weight of monomers comprising the monomers (a1), (a2) and (a3) based on the total weight of non-copolymerizable epoxy compound (b1) and monomers comprising the monomers (a1), (a2) and (a3) are used in the copolymerization step.
10 . Process according to claim 1 wherein the amount of monomer (a4) used in the esterification step is such that the equivalent ratio of carboxylic acid groups of copolymerizable monomer (a4) to epoxy groups provided by the non-copolymerizable epoxy compound (b1) is from 0.9 to 1.1.
11 . Process according to claim 1 comprising a step wherein at least one compound C is added.
12 . A radiation curable composition obtainable by the process according to claim 1 .
13 . A radiation curable composition according to claim 12 comprising:
(i) from 20 to 93% by weight of (meth)acrylic copolymer A, and
(ii) from 7 to 80% by weight of radiation curable epoxy based compound B, based on the total weight of (meth)acrylic copolymer A and of radiation curable epoxy based compound B.
14 . A radiation curable composition according to claim 12 comprising:
(i) from 40 to 99% by weight of the radiation curable composition comprising the (meth)acrylic copolymer A and the radiation curable epoxy based compound B, and
(ii) from 1 to 60% by weight of at least one compound C, based on the total weight of (meth)acrylic copolymer A, radiation curable epoxy based compound B and compound C.
15 . Method of preparing an adhesive and/or pressure sensitive adhesive comprising the steps of:
(a) providing a radiation curable composition according to claim 12 ,
(b) applying said composition to a substrate,
(c) exposing said composition to an actinic radiation source to cure the said composition.
16 . Adhesives and/or pressure sensitive adhesives obtained from curing a composition according to claim 12 .