A RADIATION-CURABLE COATING COMPOSITION FOR IMPROVING THE SURFACE PROPERTIES OF PLASTICS

Abstract

The present invention relates to a specific radiation-curable coating composition for improving the surface adhesion of plastic parts and its uses as a primer coat, as a base coat or as a clear coat. The composition may be pigmented or unpigmented and may be cured by UV and/or EB. The invention also relates to cured coating resulting from this cure and to the coated plastic substrate with improved surface adhesion.

Claims

1. Radiation-curable coating composition comprising: A) from 20 to 60 wt.-% of at least one oligomer bearing at least one ethylenic unsaturation, B) from 0.1 to 35 wt.-% of at least one ethylenically unsaturated monomer having a surface tension measured according to contact angle method NF EN14370 which is lower than 35 mN/m, C) from 0.1 to 20 wt.-% of at least one ethylenically unsaturated monomer with high hydrophilicity having a Hansen solubility parameter δp, calculated according to the method described in “Hansen Solubility Parameters: a user's handbook” by Charles M. Hansen ISBN 068494-1525-5 (chapter I, table 1.1), higher than 4 MPa.sup.1/2, preferably higher than 5 MPa.sup.1/2, D) 0 to 10 wt.-% of at least one photoinitiator, E) 0 to 75 wt.-% of a reactive diluent selected from at least one ethylenically unsaturated monomer other than B) and C) and bearing at least one ethylenically unsaturated group, F) 0 to 20 wt.-% of a phosphoric ester comprising a (meth)acrylate group used as an adhesion promoter and wherein the sum of wt % of components A+B+C+D+E+F is 100%.

2. Radiation-curable coating composition according to claim 1, wherein the composition comprises: A) 20 to 50 wt.-% of said at least one oligomer A), with said oligomer comprising at least one oligomeric segment selected from polyurethane and/or poly(meth)acrylate and/or polyester segments and B) 0.1 to 30 wt.-% of said at least one ethylenically unsaturated monomer B), with said monomer B) being selected from the group consisting of tert-butyl cyclohexyl acrylate, isobornyl acrylate isodecyl acrylate, 3,5,5 trimethyl cyclohexyl acrylate and methacrylate, isooctyl acrylate, octyl decyl acrylate, tridecyl acrylate, lauryl 4EO acrylate (with lauryl bearing 4 ethoxy units) and C.sub.12-C.sub.15 alkyl methacrylate, C) 0.5 to 20 wt.-% of said at least one ethylenically unsaturated monomer C), wherein said monomer C) is selected from the group consisting of 2-ethoxyethyl acrylate, 2 (2-ethoxyethoxy)-ethyl acrylate and tetrahydrofufuryl acrylate, D) 0 to 5 wt.-% of said least one photoinitiator, E) 5 to 60 wt.-% of said reactive diluent F) 0 to 15 wt.-% of said phosphoric ester, wherein said phosphoric ester F) comprises monoesters of hydroxyalkyl (meth)acrylates with phosphoric acid.

3. Radiation curable coating composition according to claim 1, wherein said oligomer A), has a number average molecular weight Mn of from 1000 to 12000 as measured by GPC in THF with polystyrene standard calibration.

4. Radiation-curable coating composition according to claim 1, wherein the composition comprises components A), B), C) and E).

5. Radiation-curable coating composition according to claim 1, wherein the composition comprises components A), B), C) and D).

6. Radiation-curable coating composition according to claim 5, wherein component E) is present.

7. Radiation-curable coating composition according to claim 1, wherein the composition is a UV and/or an EB-curable composition.

8. (canceled)

9. (canceled)

10. (canceled)

11. Radiation-curable coating composition according to claim 1, wherein said oligomer A) is a urethane (meth)acrylate, polyester acrylate or an acrylic (meth)acrylate oligomer bearing at least two (meth)acrylic groups or a mixture of at least two of them.

12. Radiation-curable coating composition according to claim 1, wherein said oligomer A) is a urethane (meth)acrylate bearing free isocyanate groups.

13. Radiation-curable coating composition according to claim 12, wherein said oligomer A) has a content of free isocyanate groups from 0.5 to 20% by weight of —NCO groups.

14. Radiation-curable coating composition according to claim 1, wherein said oligomer A) is a urethane (meth)acrylate bearing from 2 to 6 (meth)acrylic groups.

15. Radiation curable coating composition according to claim 14, wherein said urethane (meth)acrylate oligomer comprises polyester segments based on polycaprolactone segments.

16. Radiation curable coating composition according to claim 1, wherein said oligomer A) is an acrylic (meth)acrylated oligomer.

17. Radiation-curable coating composition according to claim 1, wherein the composition is a pigmented or unpigmented coating composition.

18. (canceled)

19. Cured coating resulting from curing by radiation at least one layer of at least one curable coating composition as defined according to claim 1.

20. Cured coating according to claim 19, wherein the cured coating is a primer, a base coat or a clear coat.

21. A method of using a coating composition as defined according to claim 1, comprising applying the coating composition to a substrate and curing the coating composition.

22. The method according to claim 21, wherein the substrate comprises shaped parts containing plastics.

23. The method according to claim 21, wherein the composition is used in at least one layer or in one or in multiple layers on said substrate and is cured by UV and/or EB radiation for each of said layers.

24. The method according to claim 21, wherein said coating composition is used as a primer and/or as a base coat and/or as a clear coat or as a binary or as a ternary combination of these uses on said substrate.

25. The method according to claim 21, wherein said substrate is a plastic i-s selected from: thermoplastics, or mixtures thereof, fiber-reinforced polymers or composites derived from the thermoplastics or the thermosets or the mixtures thereof.

26. Shaped part comprising a plastic surface coated with at least one layer of a coating resulting from curing by radiation at least one coating composition as defined according to claim 1.

27. Shaped part according to claim 26, wherein said coating is a primer and/or a base coat and/or a clear coat.

28. (canceled)

29. Radiation-curable coating composition according to claim 1, wherein the composition comprises: A) from 20 to 50 wt.-% of said at least one oligomer A), wherein said at least one oligomer A) comprises at least two ethylenic unsaturations, B) from 0.1 to 30 wt.-% of said at least one ethylenically unsaturated monomer B), wherein said monomer B) is a (meth)acrylate monomer and the surface tension is lower than 32 mN/m, C) from 0.5 to 20 wt.-% of said at least one ethylenically unsaturated monomer C), wherein said monomer C) is a (meth)acrylate monomer, D) from 0 to 5 wt.-% of said least one photoinitiator, E) 5 to 60 wt.-% of said reactive diluent, wherein the least one ethylenically unsaturated group is a (meth)acrylic group, and F) 0 to 15 wt.-% of said phosphoric ester.

30. Radiation-curable coating composition according to claim 1, wherein the at least two ethylenic unsaturations of said at least one oligomer A) comprise (meth)acrylic groups.

31. Radiation-curable coating composition according to claim 14, wherein said (meth)acrylic groups of said oligomer A) comprise acrylate groups.

Description

EXPERIMENTAL

[0128] To illustrate the practice of the present invention, the following examples will be described, wherein parts are to be understood as parts by weight. The invention relates to the following examples. The examples are for identification purposes only and in no way limit the invention.

Examples

I. Polymers Used as Plastic Parts

[0129] A1) PP/EPDM, mineral filled, Finalloy® 720/1, received by Total Fina.
A2) PC/PET, mineral filled, Makroblend® UT235M, received by Covestro.

[0130] The commercially available polymers were transformed in the form of plaques by injection molding with known technique.

II. Paint Testing

II.A) Raw Materials for Coatings

[0131] II.A1) Wörwag primer slate gray conductive, received by KARL WÖRWAG Lack-und Farbenfabrik GmbH & Co KG.
II.A2) Base coat black uni MB 9040, received by BASF Coatings.
II.A3) Wörwag clear coat 11141, received by KARL WÖRWAG Lack-und Farbenfabrik GmbH & Co KG.

II.B) Additives

[0132] II.B1) WW hardener, received by KARL WÖRWAG Lack-und Farbenfabrik GmbH & Co KG.

II.C) UV-Und EB-Curable Raw Materials According to the Invention

[0133] II.C1) Primer-Formel, from Sartomer (see tables 1 and 2).
II.C2) BC (Base coat)-Formel, from Sartomer (see table 3).
II.C3) CC (Clear coat)-Formel, from Sartomer (see table 4).

Activation of the Plaques

[0134] Gas flame: Flaming of the plaques was realized by using city gas in the mix with air in the relation 1 to 8 and a distance of the burner head of 100 mm from the substrate surface.

Preparation

Primer and Isocyanate

[0135] 100 parts Wörwag primer slate gray conductive and 10 parts depending of the examples II. B1 were mixed shortly prior to use at 600 r.p.m. and with a disc known to a technician, for 3 min.

Base Coat and Isocyanate

[0136] 100 parts base coats black uni MB 9040 and 5 parts depending of the examples II.B1 were mixed shortly prior to use at 600 r.p.m. and with a disc known to a technician for 3 min.

Clear Coat and Isocyanate

[0137] 100 parts clear coat 11141 and 35 parts depending of the examples II.B1 were mixed shortly prior to use at 600 r.p.m. and with a disc known to a technician for 3 min. After activation and depending of the example, the plaques were coated with primer, base coat and clear coat under the following conditions:

[0138] Primer: Wörwag primer slate gray conductive, applied with a pistol in two hands to achieve a dry layer thickness of 12 μm. The primer was dried for 25 min at 85° C. and then, depending on the example, the base coat was applied.

[0139] Primer according to the present invention P1 or P2, applied with a pistol in two hands to achieve a dry layer thickness of 12 μm. Using lamp of company Heraus with power of 120 W at a conveyor speed of 10 m/min the curing was realized and depending on the example, the base coat was applied.

TABLE-US-00001 TABLE 1 Primer P1 formula according to the invention Component type vs Formula invention Supplier CN704 (35%) A) Polyester diacrylate Sartomer (Mw~5000 g:mol) SR9003 (16.5%) E) Reactive difunctional ″ diluent SR256 (13.2%) C) Hydrophilic monomer ″ SR217 (24.3%) B) Low surface tension ″ monomer SR454 (5%) E) Reactive thinner (diluent) ″ Benzo (2%) (Benzophenone) Darocure ® 1173 (4%) D) Photoinitiator

TABLE-US-00002 TABLE 2 Primer P2 formula according to the invention Formula Component type vs invention Supplier PRO21407 (35%) A) Urethane diacrylate Sartomer oligomer, with 4.9% free NCO (based on polyester) SR9003 (15%) E) Reactive difunctional diluent ″ SR256 (12%) C) Hydrophilic monomer ″ SR217(22%) B) Low surface tension ″ monomer SR9051 (10%) F) Acid based adhesion promoter ″ Benzo (2%) Darocure ® 1173 (4%) D) Photoinitiator Ciba

[0140] Base coat: black uni MB 9040, applied with a pistol in two hands to achieve a dry layer thickness of 15 μm. The base coat was dried for 25 min at 85° C. and then, depending on the example the clear coat was applied.

[0141] Base coat according to the present invention BC, applied with a pistol in two hands to achieve a dry layer thickness of 12 μm. Using lamp of company Heraus with power of 120 W at a conveyor speed of 10 m/min the curing was realized and then, depending on the example, the clear coat was applied.

TABLE-US-00003 TABLE 3 Base coat (BC) formula according to the invention Component type vs Formula invention Supplier CN820 (35%) A) Oligomer, diacrylate Sartomer Mw~11000 PRO21407(10%) A) Oligomer urethane ″ diacrylate with 4.9% free NCO SR9003 (15%) C) Reactive difunctional ″ diluent SR256 (12%) C) Hydrophilic monomer SR217(22%) B) Low surface tension ″ monomer Benzo (2%) Darocure ® 1173 (4%) D) Photoinitiator Ciba

[0142] Clear coat: Wörwag High gloss clear coat 11141, applied with a pistol in two hands to achieve a dry layer thickness of 35 μm. The clear coat was dried for 30 min at 85° C.

[0143] Clear coat according to the present invention: CC-Formel of Sartomer, applied with a pistol in two hands to achieve a dry layer thickness of 35 μm. Using lamp of company Heraus with power of 120 W at a conveyor speed of 10 m/min the curing was realized.

TABLE-US-00004 TABLE 4 Clear Coat formula according to the invention Component type vs Formula invention Supplier CN9210 (25%) A) Urethane hexaacrylate Sartomer oligomer, Mw~1500 CN9001 (10%) A) Urethane diacrylate ″ oligomer, Mw 3250 (based on polyester) SR238 (35%) E) Reactive difunctional ″ diluent SR833S (20%) E) Reactive difunctional ″ diluent SR285 (4%) C) Hydrophilic monomer ″ SR506 (3%) B) Low surface tension ″ monomer Irgacure ® 184 (3%) D) Photoinitiator BASF

[0144] Depending on the example also, the activation step was not realized. The nonactivated plaques were coated with primer, base coat and clear coat under the following conditions:

[0145] Primer: Wörwag Haftprimer slate gray conductive, applied with a pistol in two hands to achieve a dry layer thickness of 12 μm. The primer was dried for 25 min at 85° C. and then, depending of the example, the base coat was applied.

[0146] Primer according to the present invention: Primerformel of Sartomer, applied with a pistol in two hands to achieve a dry layer thickness of 12 μm. Using lamp of company Heraus with power of 120 W at a conveyor speed of 10 m/min the curing was realized and then, depending of the example, the base coat was applied.

[0147] Base coat: black uni MB 9040, applied with a pistol in two hands to achieve a dry layer thickness of 15 μm. The base coat was dried for 25 min at 85° C. and then, depending of the example the clear coat was applied.

[0148] Base coat according to the present invention: BC-Formel of Sartomer, applied with a pistol in two hands to achieve a dry layer thickness of 12 μm. Using lamp of company Heraus with power of 120 W at a conveyor speed of 10 m/min the curing was realized and then, depending of the example, the clear coat was applied.

[0149] Clear coat: Wörwag High gloss clear coat 11141, applied with a pistol in two hands to achieve a dry layer thickness of 35 μm. The clear coat was dried for 30 min at 85° C.

[0150] Clear coat according to the present invention: CC-Formel of Sartomer, applied with a pistol in two hands to achieve a dry layer thickness of 35 μm. Using lamp of company Heraus with power of 120 W at a conveyor speed of 10 m/min the curing was realized. After conditioning, the paint tests were realized.

[0151] The painted plaques were submitted to the following tests:

Steam Jet Test (SJ)

[0152] This test is used for examination of paint adhesion on painted plastic parts for exterior use as well as for test of delamination.

Procedure:

[0153] A sample preparation: even, size>5×13 cm.

[0154] B Impact: St. Andrews cross (according to DIN 55662 1. scratch>12 cm, 2. Scratch>5 cm).

[0155] C Positioning: fixed, jet centre in the middle of the St. Andrews cross, jet covers the long scratch.

[0156] D Testing: Sample is submitted the defined test parameters according to DIN55 662.

[0157] E Evaluation: visual evaluation using comparison photographs of DIN 55 662.

[0158] F Results: Evaluation in comparison with photographs of DIN 55 662, whereby cw 0 and 1=green, cw 2=yellow, cw 3 to 5=red.

[0159] Test parameter: according to DIN 55662 Verfahren B.

Steam Jet Test after Temperature Shock (SJ after TS)

[0160] The time for TS is 3 cycles. Each cycles was 15 h at 105° C., 30 min. At 23±2° C., 8 h at −40° C. and 30 min. at 23±2° C., than the above described steam jet, test was realized.

[0161] The results of SJ and SJ after TS tests are summarized in Table 5. 20 specimens were used for each test.

TABLE-US-00005 TABLE 5 Results for paint adhesion Exp. 1 comp 2 comp 3 4 5 comp 6 comp 7 8 9 10 11 12 Substrate Fin. 720 Makro. Fin. 720 Makro. Fin. 720 Makro. Fin. 720 Makro. Fin. 720 Makro. Fin. 720 Makro. UT235M UT235M UT235M UT235M UT235M UT235M Activation Y N Y N Y N Y N Y N Y N Y/N Primer R1471 R1471 P2 P1 R1471 R1471 R1471 R1471 R1471 R1471 P2 P1 Base Coat nothing nothing nothing nothing black uni black uni black uni black uni BC BC BC BC (BC) Clear Coat nothing nothing nothing nothing R3209E R3209E CC CC R3209E R3209E CC CC (CC) Steam 10 10 10  8  9  9  9  9  9  9 10 10 Jet(SJ)cw 0, 1 SJ > cw1  0  0  0  2  1  1  1  1  1  1  0  0 TS 15 16 18 19 17 19 18 20 18 20 20 20 cw 0, 1 TS > cw1  5  4  2  1  3  1  2  0  2  0  0  0

[0162] It is shown from these results that:

[0163] The use of the primer based on the invention improves the substrate adhesion compared to conventional compositions.

[0164] The use of the primer based on the invention improves the interlayer adhesion compared to conventional compositions.

[0165] The use of the primer based on the invention improves the substrate adhesion and the interlayer adhesion compared to conventional compositions.

[0166] The use of the base coat based on the invention improves the substrate adhesion compared to conventional compositions.

[0167] The use of the base coat based on the invention improves the interlayer adhesion compared to conventional compositions.

[0168] The use of the base coat based on the invention improves the substrate adhesion and the interlayer adhesion compared to conventional compositions.

[0169] The use of the clear coat based on the invention improves the substrate adhesion compared to conventional compositions.

[0170] The use of the clear coat based on the invention improves the interlayer adhesion compared to conventional compositions.

[0171] The use of the clear coat based on the invention improves the substrate adhesion and the interlayer adhesion compared to conventional compositions.