Liquid radiation-curable formulation, in particular for use in stereolithography

A process for the preparation of a cured product, which comprises treating a liquid radiation-curable formulation comprising at least one compound that contains free radically polymerisable groups, and at least one photoinitiator suitable for the polymerisation, which formulation additionally comprises a polyoxyalkylene-polysiloxane block copolymer which is selected from copolymers of the chemical formulae ##STR24## in which formulae the individual symbols have the following meanings:

• R.sup.1 is a member selected from hydrogen and C.sub.1 -C.sub.8 alkyl;
• c is a number from 1 to 8 corresponding to the average number of carbon atoms of an akylene unit in a polyoxyalkylene group (C.sub.c H.sub.2c O).sub.d ;
• d is an integer from 1 to 100;
• g is an integer from 1 to 4;
• [T] is a group selected from the groups of formulae T1 to T12:
• ##STR25## [PS] is a polysiloxane of formula ##STR26## R.sup.2 is a group selected from methyl and phenyl;
• b is an integer from 1 to 100;
• [Alk] is an alkylene group of 3 to 10 carbon atoms;
• [Alk.sup.1 ] is an alkylene group of 1 to 20 carbon atoms;
• m is a number from 1 to 8 corresponding to the average number of carbon atoms of an alkylene unit in a polyoxyalkylene group (C.sub.m H.sub.2m O).sub.n ;
• n is an integer from 1 to 50;
• [G] is a group of formula ##STR27## X is an atom selected from oxygen and sulfur;
• [D] is a divalent hydrocarbon radical containing at least 2 carbon atoms;
• e is an integer from 1 to 100, and
• f is an integer from 1 to 50
• with actinic radiation
• with the proviso that when the formulation comprises a polyoxyalkylene-polysiloxane block copolymer of formula (III) then the compounds that contain free radically polymerisable groups are a mixture comprising the following components:
• (i) a difunctional monomeric or polymeric acrylate or methacrylate;
• (ii) an acrylate or methacrylate having a (meth)acrylate functionality greater than 2;
• (iii) an unsaturated monomer of formula ##STR28## wherein R.sup.5 is a member selected from hydrogen and methyl, and
• R.sup.6 is a radical of formula ##STR29## wherein R.sup.7 is a radical from the group consisting of tetrahydrofurfuryl, cyclohexyl, 2-phenoxyethyl, benzyl, isobornyl, glycidyl, dicyclopentyl, morpholinoethyl, dimethylaminoethyl and straight-chain and branched C.sub.1 -C.sub.2 alkyl radicals, or if R.sup.5 is a hydrogen atom, R.sup.6, in addition to the radicals cited above, can also be a radical selected from the group consisting of pyrrolidon-2-yl, imidazonyl, carbazolyl, anthracenyl, phenyl, C.sub.5 -C.sub.8 cycloalkyl, naphthenyl, 2-norbornyl, pyridyl, N-caprolactamyl, formamidyl, acetamidyl and toluolyl.