Stabilizer for thiol-ene compositions

Abstract

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.

Claims

1. An inhibitor system (II) 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 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.

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. A method for stabilizing thiol (meth)acrylate compositions comprising adding the inhibitor system (II) of claim 1 to a thiol (meth)acrylate composition.

7. A radiation curable thiol (meth)acrylate composition (III) comprising at least one inhibitor system according to claim 1, at least one thiol compound (v), and further at least one (meth)acrylated compound (vi).

8. The radiation curable thiol (meth)acrylate composition of claim 7, wherein the at least one thiol compound (v) comprises at least three thiol groups.

9. The radiation curable thiol (meth)acrylate composition of claim 7, wherein the at least one thiol compound (v) is selected from the group consisting of pentaerythritol tetrakis (3-mercaptopropionate), pentaerythritol tetrakis (3-mercaptobutylate), trimethylolpropane tris (3-mercaptopropionate) and trimethylolpropane tris (3-mercaptobutylate).

10. The radiation curable thiol (meth)acrylate composition of claim 7, wherein the (meth)acrylated compound is selected from (poly)urethane (meth)acrylates, (poly)ester (meth)acrylates, (poly)ether (meth)acrylates, epoxy (meth)acrylates and/or (meth)acrylated (meth)acrylics.

11. The radiation curable thiol (meth)acrylate composition of claim 7 comprising from 10 ppm to 5% by weight of compounds (i), from 10 ppm to 30% by weight of compounds (ii), from 1 to 70% by weight of compounds (v) and from 30 to 99% by weight of compounds (vi).

12. The radiation curable composition of claim 7, wherein the ratio of compounds (vi) to compounds (v) is from 95:5 to 30:70.

13. A method of making inks, overprint varnishes, coating compositions, adhesives, 3D objects, solder resist, and gel nails comprising adding the radiation curable thiol (meth)acrylate composition (III) of claim 7 to at least one of inks, overprint varnishes, coating compositions, adhesives, 3D objects, solder resist, and gel nails.

Description

EXAMPLES

(1) Radiation curable thiol (meth)acrylate compositions are prepared by stirring all ingredients at room temperature in a suitable recipient (e.g. a brown vial, wrapped in aluminum foil). When mixtures are ready, the recipients containing the mixtures are put in an oven at 60° C. for 10 days. Mixtures are daily checked and when a gel (0-100% of bulk liquid) is observed it is reported as ‘gel after X days’. When a mixture is still liquid after 10 days (NO gel), the cone-plate viscosity is measured with constant shear rate 20 1/s at 25° C. and reported in mPa.Math.s.

(2) Amounts are in parts (g).

(3) TABLE-US-00001 TABLE 1 The use of phenolic anti-oxidants (i) only Composition EX1R EX2R EX3R EX4R EX5R EX6R EBECRYL LEO 10501, Tri functional 75 75 75 90 75 75 acrylate-diluting oligomer (vi) Pentaerythritol tetrakis (3- 25 25 25 10 25 mercaptopropionate) (v) Pentaerythritol tetrakis (3- 25 mecraptobutylate) (v) 4-methoxy-1-naphthol (i) 0 .025 0.05 0.1 0.025 0.1 Pyrogallol (i) 0.1 Viscosity (mPa .Math. s at 25° C.) at day 0 105 105 105 80 123 105 Gel (after X days) 1 3 4 NO 5 7 Viscosity (mPa .Math. s at 25° C.) at day X / / / 101 / /

(4) Comparative Examples 1R to 6R: an inhibitor system based on inhibitor compounds (i) solely proved inefficient, even for 4-methoxy-1-naphtol. In general gel formation was observed after a few days only. No true stable thiol (meth)acrylate mixtures were obtained at elevated amounts of thiol compounds (v).

(5) TABLE-US-00002 TABLE 2 The combination of an acid compound (ii) with phenolic anti-oxidants (i) Composition EX7R EX8R EX9R EBECRYL LEO 10501, Tri functional acrylate- 75 75 75 diluting oligomer (vi) Pentaerythritol tetrakis (3-mercaptopropionate) (v) 25 25 25 4-methoxy-1-naphthol (i) 0.025 0.05 0.1 EBECRYL 168 (ii) 0.1 0.1 0.1 Viscosity (mPa .Math. s at 25° C.) at day 0 105 105 105 Gel (after X days) 1 1 1 Viscosity (mPa .Math. s at 25° C.) at day X / / /

(6) The above shows that inhibitor systems based on an acid compound (ii) and phenolic antioxidants (i) only proved not sufficient either (Comparative Examples 7R to 9R). Again, a gel formed rapidly.

(7) In contrast therewith inhibitor systems (I) based on compounds (i), (ii) and (iii) according to the invention significantly improved the stability of thiol (meth)acrylate compositions as shown in Table 4.

(8) TABLE-US-00003 TABLE 3 The combination of phosphites (iii) with phenolic anti-oxidants (i) Composition EX10R EX11R EX12R EX13R EX14R EBECRYL LEO 10501, Tri functional acrylate- 75 75 75 80 80 diluting oligomer (vi) Pentaerythritol tetrakis (3-mercaptopropionate) (v) 25 25 25 20 20 4-methoxy-1-naphthol (i) 0 0.025 0.1 0.025 0.05 Triphenyl phosphite (iii) 0.1 0.1 0.1 0.1 0.1 Viscosity (mPa .Math. s at 25° C.) at day 0 105 105 105 105 105 Gel (after X days) 1 4 5 2 2 Viscosity (mPa .Math. s at 25° C.) at day X / / / / /

(9) The above shows that an inhibitor system based on phosphites (iii) and phenolic antioxidants (i) only provided no solution either (Comparative Examples 10R to 14R). Again, gel formation was observed after a couple of days.

(10) In contrast therewith inhibitor systems (I) based on compounds (i), (ii) and (iii) according to the invention significantly improved the stability of thiol (meth)acrylate compositions as shown in Table 4.

(11) TABLE-US-00004 TABLE 4 Compositions (III) of the invention are able to stabilize thiol (meth)acrylate mixtures Composition EX15 EX16 EX17 EX18 EX19 EX20R EX21R EX22R EX23R EX24R EX25R EBECRYL LEO 10501, Tri functional acrylate- 75 75 75 75 75 75 75 75 75 75 diluting oligomer (vi) EBECRYL 1291, Hexa functional aliphatic 80 urethane acrylate (vi) Pentaerythritol tetrakis (3- 25 25 25 25 20 25 25 25 25 25 25 mecraptopropionate) (v) EBECRYL ® 168 (ii) 0.05 0.05 0.05 0.1 0.05 0.1 0.05 0.05 0.05 0.1 0.1 Triphenyl phosphite (iii) 0.05 0.05 0.05 0.1 0.05 0.1 0.05 0.05 0.05 0.1 0.1 4-methoxy-1-naphthol (i) 0.025 0.05 0.05 Butylated Hydroxy Toluene 0.05 0.5 Butylated Hydroxy Anisole 0.05 0.5 4-methoxyphenol 0.05 0.5 Pyrogallol (i) 0.05 Propyl gallate (i) 0.5 Viscosity (mPa .Math. s at 25° C.) at day 0 105 105 105 105 20800 105 105 105 105 105 105 Gel (after X days) NO NO NO NO NO 1 1 1 1 1 1 Viscosity (mPa .Math. s at 25° C.) at day X 113 113 110 115 29000 / / / / / /

(12) Compositions 15 to 19 are compositions (III) according to the invention, comprising an inhibitor system (I) according to the invention. As follows clearly from the results shown in Table 4, the addition of acidic compounds (ii) to compounds (i) and (iii) according to the invention yielded unexpected results. The stability of the thiol (meth)acrylate mixture improved significantly. No gel is formed at elevated temperatures and the viscosity increase is negligible after 10 days at 60° C. 4-methoxy-1-naphthol (an inhibitor compound (i) according to the invention) proved most efficient. Already at levels as low as 250 ppm stable thiol (meth)acrylate compositions were obtained, even at elevated thiol concentrations (v).

(13) Comparative Examples 20R to 25R show the importance of phenolic oxidants (i) according to the invention: If other types of phenolic antioxidants were used, then even when used at elevated amounts, their incorporation could not prevent gel formation. More, a gel formed as early as of day 1.

(14) The results of Table 5 below show that similar results could be obtained with other acids (ii) according to the invention (Examples 26 to 27). These results further show that acids with a pKa outside the claimed range from 1 to 3 proved inefficient. Stronger acids like PTSA (p-toluene sulphonic acid, pKa=−2.8) or weaker acids like acrylic acid (pKa=4.25) proved not very efficient (Comparative Examples 28R to 29R).

(15) The results of Table 6 below show that inhibitor systems (II) according to the invention are very efficient as well. When spirophosphites (iv) are used then acidic compounds (ii) according to the invention are not really needed. When we compare the results obtained with Comparative Example 30R with results obtained with Example 31 according to the invention, then we see that gel formation is delayed by using an inhibitor system (II) according to the invention. When 4-methoxy-1-naphtol was used at higher amounts, even for compositions containing 25 wt % of thiols no gel formation was observed after 10 days (Example 32). For lower amounts of thiols (v) lower amounts of 4-methoxy-1-naphtol sufficed (Examples 33 and 34). The addition of acidic compounds (ii) to the thiol (meth)acrylate composition may further improve its stability.

(16) TABLE-US-00005 TABLE 5 Combination of phosphites (iii), acids (ii) and phenolic anti-oxidants (i) Composition Ex26 EX27 EX28R Ex29R EBECRYL LEO 10501, Tri functional acrylate- 75 75 75 75 diluting oligomer (vi) Pentaerythritol tetrakis (3-mercaptopropionate) (v) 25 25 25 25 Triphenyl phosphite (iii) 0.05 0.05 0.05 0.05 4-methoxy-1-naphthol (i) 0.05 0.05 0.05 0.05 EBECRYL ® 168 (ii) 0.05 Oxalic acid (ii) 0.05 Acrylic acid 0.05 PTSA 0.05 Viscosity (mPa .Math. s at 25° C.) at day 0 105 105 105 105 Gel (after X days) NO NO 9 1 Viscosity (mPa .Math. s at 25° C.) at day X 113 110 / /

(17) TABLE-US-00006 TABLE 6 The use of spiro-phosphites (iv) Composition Ex30R EX31 EX32 EX33 EX34 EBECRYL LEO 10501, Tri functional acrylate- 75 75 75 80 80 diluting oligomer (vi) Pentaerythritol tetrakis (3-mercaptopropionate) (v) 25 25 25 20 20 4-methoxy-1-naphthol (i) 0 0.025 0.1 0.025 0.05 Spiro phosphite (iv) 0.1 0.1 0.1 0.1 0.1 Viscosity (mPa .Math. s at 25° C.) at day 0 105 105 105 94 94 Gel (after X days) 1 3 NO NO NO Viscosity (mPa .Math. s at 25° C.) at day X / / 115 105 105