UV absorber-containing urethane acrylate

Abstract

The present invention relates to a UV absorber-comprising urethane acrylate, to a process for its preparation, and to the use thereof. The UV absorber is chemically bonded into the system. The UV absorber-comprising urethane acrylate has the formula (I): ##STR00001##

Claims

1. A UV absorber-comprising urethane acrylate of formula (I): ##STR00015## wherein R.sub.1 is a hydrogen or a methyl radical, Q is a linker of hydroxyalkyl (meth)acrylate selected from the group consisting of 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 3-hydroxy-2,2-dimethylpropyl (meth)acrylate, T is a nucleus of an aliphatic or cycloaliphatic polyisocyanates T(NCO).sub.m which have cyclic isocyanurate, uretdione, iminooxadiazinedione or oxadiazinetrione structures, as well as branched biuret structures in the case of cycloaliphatic polyisocyanates, m corresponds to the original average NCO functionality of the polyisocyanate used and is equal to or greater than 2, A represents an optionally substituted linear or branched linker from carbon, oxygen, nitrogen, sulfur, phosphorus and/or silicon in the chain, and x represents an average molar content of the bonded UV absorber radical and is less than m.

2. The UV absorber-comprising urethane acrylate according to claim 1, wherein the urethane acrylate has the structure according to formula (I-1): ##STR00016## wherein Z represents an optionally substituted linear or branched C.sub.1-20-alkylene radical or C.sub.1-20-alkylene ether radical, and T, Q, m, x and R.sub.1 have the meanings given above for the compounds of formula (I).

3. A process for the preparation of a UV absorber-comprising urethane acrylate, comprising the steps: a) reacting a compound of the formula: ##STR00017## wherein X represents branched or unbranched C.sub.1-20-alkyl and R represents branched or unbranched C.sub.1-20-alkyl, C.sub.4-12-cycloalkyl, or C.sub.6-12-aryl optionally substituted by C.sub.1-12-alkyl, C.sub.1-12-alkoxy, CN and/or by halogen with an at least difunctional alcohol; b) reacting the product obtained in step a) with bi) an aliphatic or cycloaliphatic, isocyanate group-comprising urethane acrylate which has cyclic isocyanurate, uretdione, iminooxadiazinedione or oxadiazinetrione structures or, in the case of a cycloaliphatic urethane acrylate, can further have branched biuret structures, and/or with bii) an aliphatic or cycloaliphatic, isocyanate group-comprising polyisocyanate which has cyclic isocyanurate, uretdione, iminooxadiazinedione or oxadiazinetrione structures or, in the case of a cycloaliphatic polyisocyanate, can further have branched biuret structures, wherein the reaction in step b) further takes place in the presence of a hydroxyalkyl (meth)acrylate and/or after the reaction in step b) the resulting product is further reacted with a hydroxyalkyl (meth)acrylate.

4. The process according to claim 3, wherein in step a) in formula X represents CH(CH.sub.3).

5. The process according to claim 3, wherein in step a) in formula R represents n-octyl or isooctyl.

6. The process according to claim 3, wherein in step a) the at least difunctional alcohol is selected from the group 2-butyl-2-ethyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-methyl-1,3-propanediol and/or 2,2-dimethyl-1,3-propanediol.

7. The process according to claim 3, wherein the product obtained from step a) is selected from: ##STR00018## ##STR00019##

8. The process according to claim 3, wherein in step b) the isocyanate group-comprising urethane acrylate is obtainable by reacting a 1,6-hexamethylene diisocyanate isocyanurate with a hydroxyalkyl (meth)acrylate.

9. The process according to claim 3, wherein in and/or after step b) the hydroxyalkyl (meth)acrylate is selected from the group 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate and/or 3-hydroxy-2,2-dimethylpropyl (meth)acrylate.

10. A coating composition comprising the UV absorber-comprising urethane acrylate according to claim 1.

11. The coating composition according to claim 10, comprising: i) UV absorber-comprising urethane acrylate according to claim 1 in an amount of from 0.1 to 50 parts by weight, ii) from 12 to 70 parts by weight of at least one C.sub.2-C.sub.12-diol diacrylate or C.sub.2-C.sub.12-diol dimethacrylate, wherein C.sub.2-C.sub.12 represents a linear alkylene radical which can optionally be substituted by a methyl group or can be interrupted by one or more oxygen atom(s) and optionally substituted by one or more methyl group(s), iii) from 12 to 40 parts by weight of an alkoxylated, preferably ethoxylated, mono-, di-, tri-, tetra-, penta- or hexa-acrylate or alkoxylated, preferably ethoxylated, mono-, di-, tri-, tetra-, penta- or hexa-methacrylate, iv) from 0 to 40 parts by weight of at least one monomer selected from the group comprising pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, dipentaerythritol tetramethacrylate, dipentaerythritol pentamethacrylate, dipentaerythritol hexamethacrylate and possible reaction products thereof with aliphatic or aromatic diisocyanates, v) from 5 to 60 parts by weight of at least one further mono-, di- or tri-acrylate or mono-, di- or tri-methacrylate, wherein the sum of the parts by weight of components i) to v) is 100 parts by weight, and the coating composition additionally comprises at least vi) from 0.1 to 10 parts by weight of at least one photoinitiator.

12. A method for coating a substrate, comprising the steps: applying the coating composition according to claim 10 to a substrate, curing the applied coating composition by irradiation with UV light.

13. The method according to claim 12, wherein the substrate is a thermoplastic substrate.

14. The method according to claim 12, wherein the substrate is a polycarbonate substrate.

15. A coated substrate obtained by a method according to claim 12.

Description

EXAMPLES

(1) The invention will be described further by means of the following examples, but without being limited thereto.

Example 1

(2) ##STR00011##

(3) 400 g of Tinuvin 479 (BASF), 945 g of 2-butyl-2-ethyl-1,3-propanediol (Aldrich) and 29 g of dibutyltin oxide (Aldrich) were weighed, combined and stirred for 5 hours at 155 C. The octanol that formed was then distilled off under a vacuum of from 10 to 20 mbar. The mixture was cooled and stirred into 2500 ml of methanol. The precipitate was filtered off and dried in vacuo. The solid was dissolved in 700 ml of a mixture of toluene/ethyl acetate (8:1). The solution was filtered through a layer (10 cm thick) of silica gel. The filtrate was concentrated by evaporation. The solid was suspended in methanol, brought onto the filter and then dried at 40 C. in vacuo. This product is also referred to in the following examples as the intermediate of formula (IV-4).

(4) Yield 366 g (88% of theory)

(5) Melting point 80.2 C.

(6) Elemental analysis: C.sub.45H.sub.45N.sub.3O.sub.5 (707.88)

(7) Calc.: C76.36; 116.41; N5.94.

(8) Found: C76.00; H6.40; N5.90.

Example 2

(9) Analogously to Example 1 there were prepared from 153 g of Tinuvin 479 and 300 g of 2,2-diethyl-1,3-propanediol 125 g (80% of theory) of the intermediate of formula (IV-3).

(10) ##STR00012##

(11) Melting point 107 C.

(12) Elemental analysis: C.sub.43H.sub.41N.sub.3O.sub.5 (679.82)

(13) Calc.: C75.97; 1-16.08; N6.18.

(14) Found: C75.60; 1-16.20; N6.20.

Example 3

(15) Analogously to Example 1 there were prepared from 400 g of Tinuvin 479 and 532 g of 2-methyl-1,3-propanediol 294 g (78% of theory) of the intermediate of formula (IV-1).

(16) ##STR00013##

(17) Melting point 153 C.

(18) Elemental analysis: C.sub.40H.sub.35N.sub.3O.sub.5 (637.74)

(19) Calc.: C75.34; H5.53; N6.59.

(20) Found: C75.30; 1-15.70; N6.50.

Example 4

(21) Analogously to Example 1 there were prepared from 899.9 g of Tinuvin 479 and 1382.6 g of 2,2-dimethyl-1,3-propanediol 722.7 g (83.5% of theory) of the intermediate of formula (IV-2).

(22) ##STR00014##

(23) Melting point 173 C.

Example 5

(24) Desmolux D100 (Bayer MaterialScience) is an isocyanate group-comprising urethane acrylate, free of reactive diluent, with a viscosity (23 C.) of 10,0002500 mPas and an NCO content of 12.81%.

(25) 6.8 g of the intermediate obtained from Example 2 were dissolved in 11.61 g of 2-hydroxyethyl acrylate at 100 C. The solution was cooled to 65 C. and added, with stirring, to the Desmolux D1.00 (66 g) preheated to 65 C. The reaction mixture was stirred for a further 5 hours at 65 C. A further 10.5 g of 2-hydroxyethyl acrylate were added to the reaction mixture, and it was allowed to react for 2 hours. Heating was discontinued. 40.65 g of isopropanol were added and stirred in. A clear light-yellow liquid of medium viscosity formed. The residual NCO content was <0.1%, the solids content was 70 wt. %. The effective UV absorber content (remainder of the substance from Example 2) in the resin was 7.5 wt % (solid/solid).

Example 6

(26) 28.55 g of the intermediate obtained from Example 2 were dissolved in a mixture of 50 g of butyl acetate and 11.61 g of 2-hydroxyethyl acrylate at 100 C. The solution was cooled to 65 C. and added, with stirring, to the Desmolux D100 (66 g) preheated to 65 C. The reaction mixture was stirred for a further 6 hours at 65 C. A further 6.8 g of 2-hydroxyethyl acrylate were added to the reaction mixture, and it was allowed to react for 2 hours. Butyl acetate was distilled off completely in vacuo (1-2 mbar) and at a bath temperature of 40 C. 48.5 g of isopropanol were added and stirred in at 65 C. A clear yellow liquid of medium viscosity (product of Example 6) with a residual NCO content of <0.1%, a viscosity (23 C.) of 282 mPas and a solids content of 70 wt. % was obtained. The effective UV absorber content (remainder of the substance from Example 2) in the resin was 25 wt % (solid/solid).

Example 7

(27) 68 g of the intermediate obtained from Example 2 were dissolved in 150 g of butyl acetate at 100 C. The solution was cooled to 90 C. and added, with stirring, to the Desmolux D100 (66 g) preheated to 90 C. The reaction mixture was stirred for a further 8 hours at 90 C. and then cooled to 65 C. 11.7 g of 2-hydroxyethyl acrylate were added to the reaction mixture, and it was allowed to react for 2 hours. Butyl acetate was distilled off completely in vacuo (1-2 mbar) and at a bath temperature of from 60 to 80 C. A clear yellow-orange liquid of very high viscosity (solid at room temperature) (product of Example 7) with a residual NCO content of <0.1%, a viscosity (80 C.) of 60,000 mPas and a solids content of 100 wt. % was obtained. The effective UV absorber content (remainder of the substance from Example 2) in the resin was 46 wt. % (solid/solid).

(28) 30 g of 1-methoxy-2-propanol are added at 100 C. to 70 g of resin (product of Example 7). A clear yellow viscous liquid with a viscosity (23 C.) of 2110 mPas and a solids content of 70 wt. % is obtained.

Example 8

(29) 2101.3 g of the intermediate obtained from Example 4 were dissolved in 3877.6 g of diacetone alcohol at 130 C. The solution was cooled to 80 C., filtered through a T1000 filter (Seitz) and added, with stirring, to the Desmolux D100 (5280.0 g) preheated to 90 C. The reaction mixture was stirred for a further 4 hours at 90 C. and then cooled to 80 C. The NCO content was determined. The calculated amount of 862.0 g of 2-hydroxyethyl acrylate was then added to the reaction mixture, and it was allowed to react for 8 hours. The mixture was then discontinued, cooled and pressed into waiting vessels through a T5500 filter (Seitz).

(30) Yield: 11,568 g

(31) NCO content of the product: <0.1%; tin content: <1 mg/kg

(32) Analytical gel permeation chromatography: M.sub.w=2.06*10.sup.3; M.sub.n=1.02*10.sup.3. Amount by weight of molecules with molar mass between 500 and 800 g/mol: 2.4%. This shows that the intermediate obtained from Example 4 has for the most part reacted to completion and is bonded to urethane acrylate. Solids content of the product (after 2 hours at 140 C.): 70.4%; viscosity (23 C.): 8480 mPas.

Example 9

(33) 21.5 g of the intermediate obtained from Example 1 in powder form were added in portions, with stirring, to the Desmolux D100 (66 g) preheated to 95 C. The reaction mixture was stirred for a further 4 hours at 95 C. and then cooled to 80 C. 19.8 g of 2-hydroxyethyl acrylate were added to the reaction mixture, and it was allowed to react for 2 hours. Heating was discontinued. 45.9 g of isopropanol were added to the clear yellow liquid resin and stirred in. A clear light-yellow liquid of medium viscosity formed. Residual NCO content: <0.1%, viscosity (23 C.): 618 mPas, solids content: 70 wt. %. The effective UV absorber content (remainder of the substance from Example 4) in the resin was 20 wt. % (solid/solid).

Example 10

(34) 28.55 g of the intermediate obtained from Example 1 in powder form were added in portions, with stirring, to the Desmolux D100 (66 g) preheated to 95 C. The reaction mixture was stirred for a further 4 hours at 95 C. and then cooled to 80 C. 18.7 g of 2-hydroxyethyl acrylate were added to the reaction mixture, and it was allowed to react for 2 hours. Heating was discontinued. 48.5 g of 1-methoxy-2-propanol were added to the clear yellow liquid resin and stirred in. A clear light-yellow liquid of medium viscosity formed. Residual NCO content: <0.1%, viscosity (23 C.): 1360 mPas, solids content: 70 wt. %. The effective UV absorber content (remainder of the substance from Example 4) in the resin was 25 wt. % (solid on solid).

Example 11

(35) For the production of a scratch-resistant coating, the following coating composition (Base coat G) was used as the base coat. The amounts by weight of the components were:

(36) 1,6-Hexanediol diacrylate (HDDA) 48.8;

(37) Trimethylolpropane triacrylate (TMPTA) 20.7;

(38) Ethoxylated TMPTA 20.7;

(39) Pentaerythritol tetraacrylate (PTTA) 9.8

(40) Total: 100 parts by weight.

(41) For the production of a coating composition according to the invention, the following components were combined:

(42) TABLE-US-00001 UV absorber (product from Example 9; 6.00 70% solid in isopropanol) Base coat G 22.40 Isopropanol 26.20 Irgacure 184 (BASF) 1.20 Darocur 4265 (BASF) 0.06 Tinuvin 123 (BASF) 0.14

(43) Total: 56 parts by weight. The coating composition had a solids content of 50% and a viscosity (23 C.) of less than 10 mPas.

Example 12

(44) For the production of a coating composition according to the invention, the following components were combined:

(45) TABLE-US-00002 UV absorber (product from Example 10; 4.80 70% solid in 1-methoxy-2-propanol) Base coat G (Example 11) 23.24 1-Methoxy-2-propanol 26.56 Irgacure 184 (BASF) 1.20 Darocur 4265 (BASF) 0.06 Tinuvin 123 (BASF) 0.14

(46) Total: 56 parts by weight. The coating composition had a solids content of 50% and a viscosity (23 C.) of less than 10 mPas.

Example 13

Comparative Example

(47) For the production of a comparative coating composition, the following components were combined:

(48) TABLE-US-00003 Base coat G (Example 11) 26.60 1-Methoxy-2-propanol 28.00 Irgacure 184 (BASF) 1.20 Darocur 4265 (BASF) 0.06 Tinuvin 123 (BASF) 0.14

(49) Total: 56 parts by weight. The coating composition had a solids content of 50% and a viscosity (23 C.) of less than 10 mPas.

Example 14

(50) From a polycarbonate (PC) film (Makrofol DE 1-1 cc, thickness 500 m) provided with laminating films on both sides, the laminating films were removed from both sides. The films were coated without wet cleaning and without thermal pretreatment.

(51) The liquid coating formulations from Examples 11, 12 and 13 were applied to the films by means of the Zehntner ZAA 2300 film applicator coater (universal coating knife, drawing speed 30 mm/s). The coatings were dried at 60 C. for 10 minutes and cured with a mercury radiator (power 80 W/cm lamp length) with a dose of about 3000 mJ/cm.sup.2.

(52) The layer thickness of the coatings was measured by observing the cut edge under an optical microscope. Methodincident light, bright field, 500 magnification.

(53) The extinction of the coating according to the invention after application to a polycarbonate film and subsequent curing was determined at 350 nm by means of a Cary 50 UV-Vis spectrophotometer from Varian Inc., USA, an uncoated but otherwise identical polycarbonate film being used as the background spectrum.

(54) The pencil hardness according to ISO 15184, the adhesion according to the cross-cut test (ISO 2409) and the solvent resistance to butanol, methyl ethyl ketone, ethyl acetate and N-ethylpyrrolidone (1 hour; in accordance with EN ISO 2812-3:2007) were determined.

(55) TABLE-US-00004 Example 11 Example 12 Example 13 Layer thickness (m) 10 20 10 Optical density (350 nm) 2.61 3.19 0.02 Adhesion (cross-cut) 0 (OK) 0 (OK) 0 (OK) Adhesion (after 4 hours 0 (OK) 0 (OK) 0 (OK) in boiling water) Solvent resistance (in all 0 (OK) all 0 (OK) all 0 (OK) above-mentioned solvents, 1 hour) Pencil hardness HB HB HB

(56) The values show that, by the introduction according to the invention of the UV absorbers, high absorbing power in the UV range can be produced. Nevertheless, the UV absorbers according to the invention do not affect the adhesion, solvent resistance and hardness of the coating at all.

Example 15

(57) In order to test the UV-protecting action of the UV absorber-comprising coating on the substrate, the samples were subjected to an accelerated weathering test SAE J 2412. Exposure time: to a radiation dose of 64,000 kJ/m.sup.2. The colour change of the sample was measured in L*,a*,b* coordinates and shown as the total colour difference E.

(58) TABLE-US-00005 Example 11 Example 12 Example 13 Colour values L*, a*, 95.1; 0.7; 2.2 95.2; 0.7; 2.2 95.0; 0.7; 2.3 b* before irradiation Colour values L*, a*, 94.9; 0.8; 2.4 95.0; 0.8; 2.4 93.9; 2.5; 9.9 b* after 64,000 kJ/m.sup.2 Total colour difference 0.3 0.3 7.9 E* by weathering

(59) The values show that the UV absorbers according to the invention, when introduced into a scratch-resistant coating, permit only a minimal change in the colour of the substrate by weathering. Unprotected substrates yellow to a considerable degree.