RADIATION-CURABLE COATING COMPOSITION, METHOD FOR PRODUCING SCRATCH-RESISTANT COATINGS, USE OF THE COATING COMPOSITION, AND SUBSTRATE COATED WITH A COATING COMPOSITION

Abstract

The present invention relates to a radiation-curable coating composition, especially for producing a scratch-resistant coating on polycarbonate surfaces, comprising at least one urethane acrylate of an isocyanurate trimer of 1,6-hexamethylene diisocyanate and butanediol monoacrylate. The invention also relates to a method for producing scratch-resistant coatings on polycarbonate surfaces, to the use of the coating composition, and to a substrate coated accordingly.

Claims

1. A radiation-curable coating composition, comprising: i) 45.0 to 59.0 wt % of a urethane acrylate prepared from an isocyanurate trimer of 1,6-hexamethylene diisocyanate and butanediol monoacrylate, wherein the isocyanurate trimer has an NCO content in a range of 19.6 to 24.0 wt % and an equivalent weight of 175 to 214, and the urethane acrylate has a weight ratio of the isocyanurate trimer to the butanediol monoacrylate in a range of 1.0:0.65 to 1.0:0.9; ii) 25.0 to 37.0 wt % of a tetrafunctional polyester acrylate monomer; iii) 8.0 to 12.0 wt % of a component A selected from the group consisting of a diol diacrylate ester, a one monoacrylate ester, and mixtures thereof; iv) 2.3 to 3.5 wt % of a photoinitiator; v) 2.1 to 3.1 wt % of at least one a reactive acryloyltriazole UV absorber; vi) 1.5 to 2.0 wt % of a nonreactive UV absorber; vii) 0.7 to 1.0 wt % of a sterically hindered amine; viii) 0.4 to 0.9 wt % of a flow control additive; where the weight percentage ranges are based on a sum of the solid content of components i) to viii), their sum making 100 wt %.

2. The coating composition of claim 1, which comprises 45.0 to 55.0 wt % of the urethane acrylate, based on a sum of the solids contents of components i) to viii).

3. The coating composition of claim 1, wherein the tetrafunctional polyester acrylate monomer has an ether bond.

4. The coating composition of claim 1, wherein component iii) is a diol diacrylate ester.

5. The coating composition of claim 1, wherein the component iii) is a diol diacrylate ester having 2 to 12 carbon atoms in the longest carbon chain.

6. The coating composition of claim 1, wherein the photoinitiator comprises a phosphorus-containing compound.

7. The coating composition of claim 1, wherein the photoinitiator comprises a mixture of a phosphorus-containing compound an aromatic ?-hydroxy ketone.

8. The coating composition of claim 1, wherein the reactive acryloyltriazole UV absorber is an acryloylphenolbenzotriazole.

9. The coating composition of claim 1, wherein the sterically hindered amine is a diester of sebacic acid.

10. The coating composition of claim 1, which is curable with UV radiation.

11. The coating composition of claim 1, which is a clearcoat material.

12. A method for producing a scratch-resistant coating on a polycarbonate surface, the method comprising: i) applying a coating composition of claim 1 to a polycarbonate surface, and ii) curing the coating composition with UV radiation.

13. The method of claim 12, wherein the scratch-resistant coating has a dry film thickness in a range of 8 to 25 ?m.

14. A method for protecting a vehicle headlamp from scratches, effects of weathering, or both scratches and effects of weathering, the method comprising: i) coating the vehicle headlamp with a coating composition of claim 1.

15. A substrate coated with a cured coating composition of claim 1.

Description

PREPARATION EXAMPLE 1: PREPARATION OF URETHANE ACRYLATE 1 BY DE 696 15 819 T2 (COMPARATIVE)

[0057] The base resin is prepared by mixing together the following components in the stated proportions (expressed in grams):

TABLE-US-00001 DESMODUR 2010 (BAYER) 44.7 Butanediol monoacrylate 15.3 TMP formal (LAROMER 8887) 38.4 Dibutyltin dilaurate 0.152 Ethyl acetate 1.368

PREPARATION EXAMPLE 2: PREPARATION OF URETHANE ACRYLATE 2 (INVENTIVE)

[0058] A 1000 ml three-neck flask is charged with 170.70 g of the isocyanate trimer (Desmodur N3300, from Bayer). The apparatus is fitted with a KPG blade stirrer, a dropping funnel, and a gas supply section for the introduction of lean air.

[0059] The isocyanate is diluted with 83.05 g of the reactive diluents di-TMP tetraacrylate (Ebecryl 140 from Allnex). Additionally, the initial charge is stabilized with 0.4 g of hydroquinone (from MitsuiChemicals) and then the solution is heated to 40? C.

[0060] As soon as the reaction temperature is reached, a mixture of 133.75 g of butanediol monoacrylate (from BASF SE), 0.05 g of Coscat 83 (from Erbsloh), 49.25 g of hexanediol diacrylate (Laromer HDDA from BASF SE), 61.05 g of di-TMP-tetraacrylate (Ebecryl 140 from Allnex), and 1.75 g of methoxypropanol (Solvenon PM from BASF SE) is added dropwise. During the addition time (approximately 4 hours), the reaction temperature of 60? C. must not be exceeded.

[0061] After the end of the addition, the reaction mixture is held at 60? C. and the NCO content is determined hourly. When the NCO content of 0% is reached, the product mixture is cooled to 50? C. and filtered.

[0062] Coscat 83 is an organobismuth compound, which is used as a catalyst for the formation of urethane.

[0063] Using the two urethane acrylates described above, radiation-curable coating compositions were produced. The raw materials used were as follows:

TABLE-US-00002 HOSTAVIN TB-02 Mixture of a triazine UV absorber with an acylated light stabilizer based on a sterically hindered amine Irgacure TPO-L Photoinitiator Ethylphenyl (2,4,6- trimethylbenzoyl)phosphinate Irgacure 184 Photoinitiator (1-hydroxy- cyclohexyl phenyl ketone) Irgacure 819 Photoinitiator (bis(2,4,6-tri- methylbenzoyl)phenylphosphine oxide) EFKA-3883 Flow control additive (polysiloxane-modified polymer) EFKA-3888 Flow control additive (polysiloxane-modified polyisocyanate) SARBOX SB400 Film-forming additive (methacrylate oligomer containing carboxylic acid and carboxylic anhydride) CHISORB 593 UV absorber (2-(2-hydroxy-5-methacrylo- yloxyethylphenyl)-2H-benzotriazole) TINUVIN 400 UV absorber (hydroxyphenyltriazine) TINUVIN 123 Sterically hindered amine (HALS) based (Bis(octyloxy- on an amino ether functionality (NOR-HALS) tetramethylpiperidyl) sebacate)

[0064] In accordance with table 1 below, inventive and noninventive coating compositions were produced. The numerical FIGURES in table 1 denote parts by weight.

TABLE-US-00003 TABLE 1 Coating material # 1 2 3 4 5 6 Urethane acrylate 1 65.789 64.641 65.789 Urethane acrylate 1 without Laromer 8887 Urethane acrylate 2 65.789 63.842 Urethane acrylate 2 without Ebecryl 140 39.474 and without hexanediol diacrylate; with Laromer 8887 TRIMETHYLOLPROPANE FORMAL ACRYLATE, 26.316 commercial product: Laromer 8887 DI-TMP TETRAACRYLATE HEXANEDIOL DIACRYLATE HOSTAVIN TB-02 LIQUID 1.754 1.754 1.754 1.754 ORTHO-METHYL BENZOYLFORMATE, commercial 1.140 1.140 1.140 1.120 1.140 product: Vicure 55 (photoinitiator) Irgacure TPO-L 0.614 0.614 0.614 0.603 0.614 IRGACURE 184 1.596 IRGACURE 819, 100% 0.511 EFKA-3883, 70% BA/IB 0.877 0.877 0.877 0.862 0.877 0.758 EFKA-3888, 44% BA 0.877 0.877 0.877 0.862 0.877 SARBOX SB 400, 70% PM 2.632 2.632 2.632 2.586 2.632 METHYLAL, TECHN. 26.316 26.316 26.316 25.856 29.846 CHISORB 593 1.724 1.724 TINUVIN 400 1.164 1.149 TINUVIN 123 0.582 0.575 BUTYL ACETATE 98-100% 26.316 100.00 100.00 100.00 100.00 100.00 100.00 Coating material # 7 8 9 10 11 12 Urethane acrylate 1 67.568 63.842 Urethane acrylate 1 without Laromer 8887 39.474 Urethane acrylate 2 63.842 64.975 62.252 Urethane acrylate 2 without Ebecryl 140 and without hexanediol diacrylate; with Laromer 8887 TRIMETHYLOLPROPANE FORMAL ACRYLATE, commercial product: Laromer 8887 DI-TMP TETRAACRYLATE 19.737 HEXANEDIOL DIACRYLATE 6.579 HOSTAVIN TB-02 LIQUID 1.802 1.733 1.754 ORTHO-METHYL BENZOYLFORMATE, commercial 1.171 1.140 product: Vicure 55 (photoinitiator) Irgacure TPO-L 0.631 0.614 IRGACURE 184 1.596 1.596 1.624 1.556 IRGACURE 819, 100% 0.511 0.511 0.520 0.498 EFKA-3883, 70% BA/IB 0.758 0.901 0.758 0.772 0.739 0.877 EFKA-3888, 44% BA 0.901 0.877 SARBOX SB 400, 70% PM 2.490 2.632 METHYLAL, TECHN. 27.027 26.316 CHISORB 593 1.724 1.724 1.681 TINUVIN 400 1.149 1.149 1.121 TINUVIN 123 0.575 0.575 0.560 BUTYL ACETATE 98-100% 29.846 29.846 30.376 29.109 100.00 100.00 100.00 100.00 100.00 100.00

[0065] Coating compositions 1 to 12 were applied and cured as follows:

[0066] Spray application took place using a gravity-fed cup gun (e.g., DeVilbiss GTI gravity spray gun) spraying with 3 bar compressed air through a 1.5 mm nozzle. The required film thickness was applied in 2 spray passes. Flash-off: 1 minute at 23? C., 5 minutes 80-90? C. in forced air oven, then 30 seconds cooling.

[0067] Curing with UV radiation: 2.5-3.5 J/cm.sup.2 (dose measured with IL390 from International Light).

[0068] The film thickness achieved for the coating produced from the coating composition (dry film thickness) was 11-18 ?m; the IPL (interpenetration layer) thickness was 3-5 ?m.

[0069] Measurements of film/layer thickness were made using a white light interferometer (e.g., from Fuchs, with the designation FTM-Lite UVNIR film thickness gauge). The haze determined following application of the samples is to be <1%.

[0070] The haze was measured using the BYK-Gardner Haze-Gard Plus instrument. This instrument is a standardized instrument for the measurement of transparency in accordance with ASTM standard D1003-13. The instrument is used to determine the optical quality of transparent coatings. Using this instrument, the initial haze and also the haze after implementation of scratching tests (the Taber Abraser test) are measured.

[0071] The scratch resistance of the cured coating films was tested as follows:

[0072] The scratch resistance test took place using the 5155 Abraser device from Taber Industries. The scratch tests were conducted, and testing carried out, in accordance with the ASTM standard ASTM D1044-13 (Standard Test Method for Resistance of Transparent Plastics to Surface Abrasion, Standard by ASTM International, Sep. 1, 2013). Evaluation took place in accordance with the ASTM standard ASTM D1003-13 (Standard Test Method for Haze and Luminous Transmittance of Transparent Plastics).

[0073] Scratch resistance values ascertained were as follows:

TABLE-US-00004 TABLE 2 Taber abraser (ASTM D 1044) 1 2 3 4 5 6 Film thickness in ?m 14-16 14-15 14-16 13-14 15-16 13-14 Haze before test (%) 0.53 ? 0.16 0.27 ? 0.00 0.29 ? 0.06 1.56 ? 0.16 0.49 ? 0.05 0.45 ? 0.06 Refacing stone ST-11, CS 10F, 300T 20.3 ? 0.46 8.91 ? 0.16 16.4 ? 0.82 24.1 ? 2.57 19.2 ? 1.32 12.2 ? 0.88 ? haze 19.8 8.64 16.1 22.5 18.7 11.7 Taber abraser (ASTM D 1044) 7 8 9 10 11 12 Film thickness in ?m 14-16 14-16 14-16 14-16 15-16 15-17 Haze before test (%) 0.31 ? 0.04 0.45 ? 0.08 2.94 ? 0.36 0.39 ? 0.04 0.31 ? 0.09 0.56 ? 0.03 Refacing stone ST-11, CS 10F, 300T 13.3 ? 0.39 18.1 ? 0.70 20.7 ? 1.21 12.6 ? 0.37 13.6 ? 0.71 35.3 ? 2.50 ? haze 13.0 17.7 17.8 12.2 13.3 34.7

Evaluation

[0074] Scratch resistance for the coatings on polycarbonate lamp housings is good when they exhibit a ? haze of ?15 (after 300 revolutions in the Taber Abraser test) when the Taber Abraser test is conducted.

[0075] Highly scratch-resistant systems are those exhibiting a ? haze of below 10 (after 300 revolutions in the Taber Abraser test).