Radiation-curable compounds

Abstract

The invention relates to low-viscosity formulations of radiation-curable compounds, to processes for preparing them, to their use, and to inks, printing-inks, and print varnishes that comprise them.

Claims

1. A polyurethane composition, comprising: a polyurethane A, 0.5% to 4% by weight of water, based on an amount of the polyurethane A, and optionally, a polyfunctional polymerization compound B, wherein the polyurethane A comprises, in reacted form: (a) an organic polyisocyanate comprising an allophanate group and having an NCO functionality of at least 2, synthesized from an aliphatic C.sub.4 to C.sub.20 alkylene diisocyanate, (b) a compound having at least one isocyanate-reactive group and at least one radically polymerizable unsaturated group, (c) a photoinitiator having at least one isocyanate-reactive group, (d) optionally, a further diisocyanate, polyisocyanate, or both, which is different from (a), (e) optionally, a compound having at least two isocyanate-reactive groups, and (f) optionally, a compound having precisely one isocyanate-reactive group, wherein the polyurethane composition has a viscosity of not more than 400 Pas, measured according to DIN EN ISO 3219 (shear rate D. 100 s.sup.−1) at 23° C.

2. The polyurethane composition of claim 1, wherein the photoinitiator having at least one isocyanate-reactive group (c) is a compound selected from the group consisting of ##STR00005## wherein R.sup.3, R.sup.4, and R.sup.5 each independently of one another are hydrogen, an alkyl group comprising 1 to 4 carbon atoms or an alkyloxy group comprising 1 to 4 carbon atoms, p is 0 or an integer from 1 to 10, Y.sub.i for i=1 to p independently of one another are selected from the group consisting of —CH.sub.2—CH.sub.2—O—, —CH.sub.2—CH(CH.sub.3)—O—, —CH(CH.sub.3)—CH.sub.2—O—, —CH.sub.2—C(CH.sub.3).sub.2—O—, —C(CH.sub.3).sub.2—CH.sub.2—O—, —CH.sub.2—CHVin-O—, —CHVin-CH.sub.2—O—, —CH.sub.2—CHPh-O—, and —CHPh-CH.sub.2—O, Ph is phenyl, and Vin is vinyl.

3. The polyurethane composition of claim 1, wherein the photoinitiator having at least one isocyanate-reactive group (c) is selected from the group consisting of 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-hydroxycyclohexyl phenyl ketone, 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)benzyl]phenyl}-2-methylpropan-1-one, 2-hydroxy-1-[4-[hydroxy[4-(2-hydroxy-2-methylpropanoyl)phenyl]methyl]phenyl]-2-methyl-propan-1-one, [4-[3-(4-benzoylphenoxy)-2-hydroxypropoxy]phenyl]phenylmethanone, benzoin, benzoin isobutyl ether, benzoin tetrahydropyranyl ether, benzoin methyl ether, benzoin ethyl ether, benzoin butyl ether, benzoin isopropyl ether, 7H-benzoin methyl ether, 2-hydroxy-2,2-dimethylacetophenone, and 1-hydroxyacetophenone.

4. An ink, printing-ink or print varnish, comprising: the polyurethane composition of claim 1, the polyfunctional polymerizable compound B, optionally, a pigment, optionally, a further photoinitiator, and optionally, an additive.

5. The ink, printing-ink or print varnish of claim 4, comprising the further photoinitiator, which is selected from the group consisting of 2,4,6-trimethylbenzoyldiphenylphosphine oxide, ethyl 2,4,6-trimethylbenzoylphenylphosphinate, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2-benzyl-2-dimethylamino-4′-morpholinobutyrophenone, 2-(dimethylamino)-1-(4-morpholinophenyl)-2-(p-tolylmethyl)butan-1-one, 2-hydroxy-1-[4-[[4-(2-hydroxy-2-methylpropanoyl)phenyl]methyl]phenyl]-2-methylpropan-1-one, a polymeric benzophenone derivative, a polymeric thioxanthone derivative, a polymeric α-amino ketone, and a silsesquioxane compound having at least one initiating group.

6. A method of printing on a material selected from the group consisting of polyamide, polyethylene, polypropylene, polyester, polyethylene terephthalate, polystyrene, paper, paperboard, cardboard, plastics-coated paper, plastics-coated paperboard, plastics-coated cardboard, aluminum, and an aluminum-coated polymeric films, comprising contacting the ink, printing-ink or varnish of claim 4 with the material.

7. The method of claim 6, wherein the material is a food packaging, a cosmetic packaging material, or a pharmaceutical packaging material.

8. The method of claim 6, further comprising treating the ink, printing-ink or print varnish with actinic radiation.

9. The polyurethane composition of claim 1, wherein the C.sub.4 to C.sub.20 alklene diisocyanate is hexamethylene diisocyanate.

10. The polyurethane composition of claim 1, wherein (b) is bonded via allophanate groups to (a).

11. The polyurethane composition of claim 1, which comprises (d).

12. The polyurethane composition of claim 1, which comprises (e).

13. The polyurethane composition of claim 1, which comprises (f).

14. The polyurethane composition of claim 1, which comprises 0.75% to 4% by weight of water, based on an amount of the polyurethane A.

15. The polyurethane composition of claim 1, which comprises 1% to 4% by weight of water, based on an amount of the polyurethane A.

16. The polyurethane composition of claim 1, which comprises 1.25% to 4% by weight of water, based on an amount of the polyurethane A.

17. The polyurethane composition of claim 1, which comprises 1.5% to 3% by weight of water, based on an amount of the polyurethane A.

18. The composition of claim 1, which has a viscosity of less than 300 Pas, measured according to DIN EN ISO 3219 (shear rate D, 100 s.sup.−1) at 23° C.

19. The composition of claim 1, which has a viscosity of less than 250 Pas, measured according to DIN EN ISO 3219 (shear rate D, 100 s.sup.−1) at 23° C.

20. The composition of claim 1, which has a viscosity of less than 200 Pas, measured according to DIN EN ISO 3219 (shear rate D, 100 s.sup.−1) at 23° C.

21. A method of preparing the polyurethane composition of claim 1, comprising adding 0.5% to 4% by weight of water to polyurethane A, based on an amount of the polyurethane A.

Description

EXAMPLES

(1) Laromer® LR 8863 of BASF SE, Ludwigshafen, is a commercial triacrylate of trimethylolpropane which has on average 3.5-fold ethoxylation.

(2) Laromer® 9000 from BASF SE, Ludwigshafen, is a commercial polyisocyanate containing allophanate groups, of formula (I) above, in which acrylate groups are bonded via allophanate groups. The NCO content is 14.5% to 15.5% by weight.

(3) Irgacure® 2959 from BASF SE, Ludwigshafen, is a commercial photoinitiator of the α-hydroxy ketone type (1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one).

(4) Irgastab® UV22 from BASF SE, Ludwigshafen, is a commercial stabilizer comprising quinone methide in solution in an acrylate of propoxylated glycerol.

Example 1

(5) 86 parts of a polyether acrylate (Laromer® LR 8863), 120 parts of an isocyanato acrylate (Laromer® LR9000), 79 parts of a photoinitiator (Irgacure® 2959), 0.1 part of Borchi® Kat 24 (bismuth carboxylate), and 0.9 part of a further stabilizer (Irgastab® UV22) were introduced into a reaction flask and heated to 80° C. They were then reacted at 80-85° C. until the NCO value had dropped to <0.8%, whereupon the equivalent amount of ethanol was added, calculated relative to NCO, and reaction was continued until the NCO value had dropped to 0. The batch was then cooled, admixed with 3% of water, and discharged.

Example 1a

(6) 86 parts of a polyether acrylate (Laromer® LR 8863), 100 parts of an isocyanato acrylate (Laromer® LR9000), 79 parts of a photoinitiator (Irgacure® 2959), 0.1 part of Borchi® Kat 24 (bismuth carboxylate), and 0.9 part of a further stabilizer (Irgastab®UV22) were introduced into a reaction flask and heated to 80° C. They were then reacted at 80-85° C. until the NCO value had dropped to <0.8%, whereupon the equivalent amount of ethanol was added, calculated relative to NCO, and reaction was continued until the NCO value had dropped to 0. The batch was then cooled, admixed with 3% of water, and discharged. The GPC spectrum shows that there is still about 6% of unreacted Irgacure® 2959 present.

Comparative Example 1

(7) 86 parts of a polyether acrylate (Laromer® LR 8863), 120 parts of an isocyanato acrylate (Laromer® LR9000), and 79 parts of a photoinitiator (Irgacure® 2959), were introduced into a reaction flask and heated to 80° C. Reaction was then continued at 80-85° C. to bring the NCO value to <0.8%. After about 20 hours, the photoinitiator had still not completely reacted. Before the value reached <0.8% (about 12 hours), however, crosslinking occurred.

(8) Comparative example 1 shows that it is necessary to react the free NCO groups with a component (f).

Comparative Example 2

(9) 86 parts of a polyether acrylate (Laromer® LR 8863), 120 parts of an isocyanato acrylate (Laromer® LR9000), 79 parts of a photoinitiator (Irgacure® 2959), and 0.9 part of a further stabilizer (Irgastab® UV22) were introduced into a reaction flask and heated to 80° C. They were then reacted at 80-85° C. until the NCO value had dropped to <0.8%, whereupon the equivalent amount of ethanol was added, calculated relative to NCO, and reaction was continued until the NCO value had dropped to 0. The batch was then cooled and admixed with 5% of water. The reaction mixture became cloudy.

(10) Comparative example 2 shows that the formulations of the invention turn cloudy if too much water is added.

Example 2

(11) 86 parts of a polyether acrylate (Laromer® LR 8863), 120 parts of an isocyanato acrylate (Laromer® LR9000), 79 parts of a photoinitiator (Irgacure® 2959), 50 ppm of Borchi® Kat 24 (bismuth carboxylate), and 0.015 part of a further stabilizer (Irgastab®UV22) were introduced into a reaction flask and heated to 80° C. They were then reacted at 80-85° C. until the NCO value had dropped to <0.8%, whereupon the equivalent amount of ethanol was added, calculated relative to NCO, and reaction was continued until the NCO value had dropped to 0. The GPC chromatogram showed complete reaction of the photoinitiator. Then a further part of the UV22 stabilizer was added and the batch was cooled, admixed with 2% of water, and discharged.

Example 3

(12) 86 parts of a polyether acrylate (Laromer® LR 8863), 120 parts of an isocyanato acrylate (Laromer® LR9000), 79 parts of a photoinitiator (Irgacure® 2959), 50 ppm of Borchi® Kat 22 (zinc carboxylate), and 0.015 part of a further stabilizer (Irgastab® UV22) were introduced into a reaction flask and heated to 80° C. They were then reacted at 80-85° C. until the NCO value had dropped to <0.8%, whereupon the equivalent amount of ethanol was added, calculated relative to NCO, and reaction was continued until the NCO value had dropped to 0. The GPC chromatogram showed complete reaction of the photoinitiator. Then 1.5 further parts of the UV22 stabilizer were added and the batch was cooled, admixed with 2% of water, and discharged.

Example 4

(13) 86 parts of a polyether acrylate (Laromer® LR 8863), 120 parts of an isocyanato acrylate (Laromer® LR9000), 79 parts of a photoinitiator (Irgacure® 2959), 50 ppm of tetrabutyl orthotitanate, and 0.015 part of a further stabilizer (Irgastab® UV22) were introduced into a reaction flask and heated to 80° C. They were then reacted at 80-85° C. until the NCO value had dropped to <0.8%, whereupon the equivalent amount of ethanol was added, calculated relative to NCO, and reaction was continued until the NCO value had dropped to 0. The GPC chromatogram showed complete reaction of the photoinitiator. Then 1.5 further parts of the UV22 stabilizer were added and the batch was cooled, admixed with 2% of water, and discharged.

Example 5

(14) 86 parts of a polyether acrylate (Laromer® LR 8863), 120 parts of an isocyanato acrylate (Laromer® LR9000), 79 parts of a photoinitiator (Irgacure® 2959), 50 ppm of Borchi® Kat 315 (bismuth carboxylate), and 0.015 part of a further stabilizer (Irgastabt UV22) were introduced into a reaction flask and heated to 80° C. They were then reacted at 80-85° C. until the NCO value had dropped to <0.8%, whereupon the equivalent amount of ethanol was added, calculated relative to NCO, and reaction was continued until the NCO value had dropped to 0. The GPC chromatogram showed complete reaction of the photoinitiator. Then 1.5 further parts of the UV22 stabilizer were added and the batch was cooled, admixed with 2% of water, and discharged.

Example 6

(15) 86 parts of a polyether acrylate (Laromer® LR 8863), 120 parts of an isocyanato acrylate (Laromer® LR9000), 79 parts of a photoinitiator (Irgacure® 2959), 50 ppm of Borchi® Kat 315 (bismuth carboxylate), and 0.015 part of a further stabilizer (Irgastabe UV22) were introduced into a reaction flask and heated to 80° C. They were then reacted at 80-85° C. until the NCO value had dropped to <0.8%, whereupon the equivalent amount of Lutensol TO3 (C13 alcohol ethoxylate, BASF SE) was added, calculated relative to NCO, and reaction was continued until the NCO value had dropped to 0. The GPC chromatogram showed complete reaction of the photoinitiator. Then 1.5 further parts of the UV22 stabilizer were added and the batch was cooled, admixed with 2% of water, and discharged.

(16) Use Examples

Example 7

(17) A product was prepared in analogy to example 1, as a 70% strength by weight solution in Laromer® LR 8863, without addition of water, and was mixed with different amounts of water, followed by examination of the appearance and the viscosity.

(18) TABLE-US-00001 Viscosity Fluidity at at 25° C. 25° C. Miscibility none 600 Pas no clear 1% water 322 Pas poor clear 2% water 170 Pas good clear 5% water  82 Pas very good cloudy

(19) It is seen that without the addition of water, the formulation is not fluid, and on addition of too much water, it turns cloudy. There is therefore a narrow window remaining, within which both the viscosity and the performance properties are favorable.

Example 8

(20) Various incorporable photoinitiators in accordance with the present invention and in accordance with DE 10 2006 047863 were prepared and were formulated with radiation-curable acrylates to give a print varnish.

(21) Example 5 from DE 10 2006 047863 was repeated and was considered as pure initiator, based on its photoinitiator content (comparative a), or as coating material, based on its reactive diluent content (comparative c).

(22) Using the formulations, determinations were made of the cure rate, viscosity, gloss, abrasion stability, and solvent resistance.

(23) For this purpose, the varnish was coated using a 6 μm wire doctor onto a Leneta card, and exposed using a M-30-2×1-BLKU UV unit from IST, which is equipped with a 200 W/cm Hg medium-pressure lamp with adjustable power. The cure rate was determined using the fingernail. When the surface showed no scratches, the varnish was considered to be cured.

(24) The gloss was determined at 60° on Leneta card using a Byk-Gardner micro-tri-gloss gloss meter. After 5 double rubs (back and forth) with a Scotch Brite® 07448 pad (from 3M), the abrasion resistance was determined by means of the drop in gloss.

(25) TABLE-US-00002 Com- parative Comparative Comparative a b Inventive c Example 5 from 15.0 DE 10 2006 047863 Example 2 from 15 DE 10 2006 047863 (i.e., no water) Example 5, i.e., 15.0 containing 2% by weight water Example 5 from 100 DE 10 2006 047863 Laromer ® LR 8986 27 27 27 Laromer ® PO77F 33 33 33 Tripropylene glycol 39.8 39.8 39.8 diacrylate EFKA 7305 0.2 0.2 0.2 Sum total 100 100 100 Cure rate 3 m/min 18 m/min 15 m/min 5 m/min Viscosity of reaction 0.2 Pas 600 Pas 170 Pas — mixture Viscosity of coating 0.3 Pas 0.6 Pas 0.4 Pas 0.2 Pas material Gloss 85 92 92 70 Abrasion resistance 49 77 77 61 (residual gloss after 5 double rubs with Scotch Brite 07448 (3M)) MEK resistance <10 30 30 30 double rubs Laromer ® LR 8986 is a commercial mixture of epoxy acrylate and triacrylate of ethoxylated trimethylolpropane, from BASF SE, Ludwigshafen. Laromer ® PO 77F is a commercial, amine-modified, approximately trifunctional polyether acrylate from BASF SE, Ludwigshafen. EFKA 7305 is a commercial additive for flow and surface smoothness, from BASF SE, Ludwigshafen.

(26) It is seen that in the inventive example it is possible to lower the viscosity even of the print varnish by addition of water. In comparative b, however, the reaction mixture according to example 2 from DE 10 2006 047863 (i.e., no water) is not fluid and is therefore difficult to formulate, and also the viscosity of the print varnish is too high for an optimum coating outcome.

(27) From comparatives a and c it is apparent that example 5 from DE 10 2006 047863, in direct comparison with the inventive example, exhibits poorer performance properties, such as a lower residual gloss and poorer abrasion resistance, and has inadequate reactivity.

Example 9

(28) The photoinitiators of the invention from example 5 (in example 9a), and example 6 (in example 9b) were used in an offset printing-ink, with Irgacure® 2959 selected as comparative. The concentration of Irgacure® 2959 in the comparative example corresponded to the concentration of the chromophore in the photoinitiator of the invention. All of the components were mixed and dispersed on a Bühler laboratory roll mill, until all of the photoinitiators had dissolved.

(29) The printing-ink was then printed with a coat weight of 1.7 g/m.sup.2 onto coated cardboard, using an offset sample printing instrument from Prüfbau, and exposed using a M-30-2×1-BLKU UV exposure unit from IST at 80 W/cm (aluminum reflectors). Through-cure was determined using the REL Tester (PTC instrument, from Prüfbau). The colored density was determined using an SPM55 densitometer from GretagMacbeth.

(30) TABLE-US-00003 Ex. 9a Ex. 9b Comparative Heliogen Blue D7088 16 16 16 Ebecryl 657 19 19 20 Ebecryl 3700 17 17 18 Laromer ® PE 9084 19 19 20 Laromer ® GPTA 16 16 19 Luwax ® AF30 1 1 1 Irgacure ® 369 4 4 4 Irgacure ® 2959 2 Initiator from example 5 8 Initiator from example 6 8 Sum total 100 100 100 Cure rate 180 180 130 m/min Color density of print 1.41 153 1.37

(31) Surprisingly it is found that the initiators of the invention, for the same chromophore concentration, in fact have a markedly higher cure rate than the comparative example. The color density, as a measure of the intensity of the colored print, is in fact higher for example 9b, where a fatty acid alcohol was used, than in the case of the other experiments, which points additionally to a dispersing of the photoinitiator of the invention.