Stabilizer for thiol-ene compositions
The present invention relates to stabilizers for thiol-ene compositions and to radiation curable thiol-ene compositions based thereon. Such radiation curable compositions can advantageously be used in inks, overprint varnishes, coatings, adhesives, for the making of 3D objects and for the making of solder resist and gel nails. Provided in particular is an inhibitor system (I) for thiol-ene compositions based on —at least one inhibitor compound (i) having a % DPPH radical scavenging activity of at least 90%, the inhibitor compound (i) being selected from substituted benzene compounds or substituted naphthalene compounds containing at least two substituents selected from the group consisting of hydroxyl groups and C1-C3 alkoxy groups bonded directly to the benzene or the naphthalene ring, —at least one acidic compound (ii) having a pKa between 1 and 3, and —at least one compound (iii) selected from the group consisting of phosphites and phosphonites, with the proviso that if the inhibitor compound (i) is a substituted benzene that it contains at least two hydroxyl groups bonded directly to the benzene ring. Also provided is an inhibitor system (II) for thiol-ene compositions based on that is based on —at least one inhibitor compound (i) having a % DPPH radical scavenging activity of at least 90%, the inhibitor compound (i) being selected from substituted benzene compounds or substituted naphthalene compounds containing at least two substituents selected from the group consisting of hydroxyl groups and C1-C3 alkoxy groups bonded directly to the benzene or the naphthalene ring, —at least one compound (iv) selected from the group consisting of spirophosphites, and —optionally, at least one acidic compound (ii) having a pKa between 1 and 3, and with the proviso that if the inhibitor compound (i) is a substituted benzene that it contains at least two hydroxyl groups bonded directly to the benzene ring.
1. An inhibitor system (I) for thiol-ene compositions based on
at least one inhibitor compound (i) having a % 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity of at least 90%, the inhibitor compound (i) being selected from substituted benzene compounds or substituted naphthalene compounds containing at least two substituents selected from the group consisting of hydroxyl groups and C1-C3 alkoxy groups bonded directly to the benzene or the naphthalene ring,
at least one acidic compound (ii) selected from the group consisting of oxalic acid, phosphoric acid, esters of phosphoric acid, and phenylphosphonic acid, and
at least one compound (iii) selected from the group consisting of phosphites and phosphonites,
with the proviso that if the inhibitor compound (i) is a substituted benzene that it contains at least two hydroxyl groups bonded directly to the benzene ring.
2. The inhibitor system according to claim 1 , wherein the at least one inhibitor compound (i) is selected from the group consisting of (ia) substituted benzenes containing at least two hydroxyl groups bonded directly to the benzene ring and (iib) substituted naphthalenes containing at least one hydroxyl and at least one methoxy group bonded directly to the naphthalene ring.
3. The inhibitor system according to claim 1 , wherein the at least one inhibitor compound (i) is selected from the group consisting of 4-methoxy-1-naphthol, catechol, tert-butyl catechol, hydroquinone, gallic acid, the esters of gallic acid, pyrogallol and 2,4,5-trihydroxybutyrophenone.
4. The inhibitor system according to claim 1 , wherein the at least one inhibitor compound (i) is selected from 4-methoxy-1-naphthol and/or from the esters of gallic acid.
5. The inhibitor system according to claim 1 , wherein the acidic compound (ii) is selected from oxalic acid and/or from the esters of phosphoric acid.
6. The inhibitor system according to claim 1 , wherein the phosphite (iii) is selected from triphenylphosphite and/or from substituted triphenylphosphites such as tris(2,4-di-tert-butylphenyl)phosphite.
7. The inhibitor system according to claim 1 , wherein the phosphite (iii) is selected from spirophosphites.
8. A process for the stabilization of thiol (meth)acrylate compositions, said process comprising incorporating the inhibitor system of claim 1 into thiol (meth)acrylate compositions.