DUAL-CURING COATING COMPOSITIONS

Abstract

The present invention relates to polymerizable compositions which contain components that can be crosslinked both via isocyanurate bonds and by a radical reaction mechanism. The invention further relates to methods by way of which polymers can be produced from said compositions.

Claims

1.-15. (canceled)

16. A coating composition having a ratio of isocyanate groups to isocyanate-reactive groups of at least 2.0:1.0, comprising the following components: a) an isocyanate component A; b) at least one trimerization catalyst C; and c) at least one component selected from the group consisting of components B, D and E, where component B has at least one ethylenic double bond but no isocyanate-reactive group; component D has at least one isocyanate-reactive group and at least one ethylenic double bond in one molecule; and component E has both at least one isocyanate group and at least one ethylenic double bond in one molecule.

17. The composition as claimed in claim 16, containing at least one component D or E.

18. The composition as claimed in claim 16, containing at least one component B.

19. The composition as claimed in claim 16, wherein the molar ratio of isocyanate groups to isocyanate-reactive groups in the polymerizable composition is at least 4.0:1.0.

20. The composition as claimed in claim 16, additionally containing a component F suitable as a radiation-activated initiator for a free-radical polymerization of the ethylenic double bonds present in the polymerizable composition of the invention.

21. The composition as claimed in claim 16, wherein the proportion of components B, D and E is chosen such that the coating, after free-radical polymerization of the ethylenic double bonds present therein, does not run on a vertical surface.

22. The use of at least one component selected from the group consisting of components B, D and E for production of a coating composition having a ratio of isocyanate groups to isocyanate-reactive groups of at least 2.0:1.0, which contains an isocyanate component A and is polymerizable either by free-radical polymerization or by crosslinking of isocyanate groups with one another.

23. A process for producing a coating, comprising the steps of a) providing a coating composition as defined in claim 16; b) applying the coating composition to a surface; c) crosslinking at least some of the ethylenic double bonds present in said polymerizable composition; and d) crosslinking the isocyanate groups present in said polymerizable composition; wherein process step b) is conducted first, then process step c) and finally process step d).

24. The process as claimed in claim 23, wherein the polymerizable composition comprises at least one component D and the process comprises a further process step d) in which the isocyanate-reactive group of component D is crosslinked with an isocyanate group of the isocyanate component A or of a reaction product of the isocyanate component A.

25. The process as claimed in claim 23, wherein, in process step d), at least 50% of the free isocyanate groups present in isocyanate component A are converted to isocyanurate structural units.

26. The process as claimed in claim 23, wherein process steps b) and c) are conducted within an interval of not more than 120 seconds.

27. A coating obtainable by the process as claimed in claim 23.

28. A process for producing an adhesive bond, comprising the steps of a) providing a coating composition as defined in claim 16; b) applying the coating composition to a surface; c) polymerizing at least some of the ethylenic double bonds present in said polymerizable composition; d) compressing the at least one coated surface together with a further surface; and e) crosslinking the reactive isocyanate groups present in said polymerizable composition and the ethylenic double bonds as yet unconverted in process step c); wherein process steps c), d) and e) are conducted in any sequence after process step b).

29. A coated product obtainable by the process as claimed in claim 23.

30. A bonded product obtainable by the process as claimed in claim 28.

Description

EXAMPLES

[0164] General Details:

[0165] All percentages, unless stated otherwise, are based on percent by weight (% by weight).

[0166] The ambient temperature of 23 C. at the time of conduct of the experiments is referred to as RT (room temperature).

[0167] The methods detailed hereinafter for determination of the appropriate parameters were employed for conduction and evaluation of the examples and are also the methods for determination of the parameters of relevance in accordance with the invention in general.

[0168] Starting Compounds

[0169] Polyisocyanate A: HDI trimer (NCO functionality >3) with an NCO content of 23.0% by weight from Covestro AG. The viscosity is about 1200 mPa.Math.s at 23 C. (DIN EN ISO 3219/A.3).

[0170] Acrylate 1: hexanediol diacrylate (HDDA) was sourced with a purity of 99% by weight from abcr GmbH or with a purity of <=100% by weight from Sigma-Aldrich.

[0171] Acrylate 2: hydroxypropyl methacrylate (HPMA) was sourced with a purity of 98% by weight from abcr GmbH.

[0172] Potassium acetate was sourced with a purity of >99% by weight from ACROS.

[0173] Lucirin TPO-L is an ethyl (2,4,6-trimethylbenzoyl)phenylphosphinate from BASF.

[0174] Polyethylene glycol (PEG) 400 was sourced with a purity of >99% by weight from ACROS.

[0175] All raw materials except for the catalyst and HPMA were degassed under reduced pressure prior to use.

[0176] Preparation of the Catalysts:

[0177] Potassium acetate (5.0 g) was stirred in the PEG 400 (95.0 g) at RT until all of it had dissolved. In this way, a 5% by weight solution of potassium acetate in PEG 400 was obtained and was used as catalyst without further treatment.

[0178] Preparation of the Reaction Mixture

[0179] Unless stated otherwise, the reaction mixture was prepared by mixing polyisocyanate (A1-A2) and the acrylate(s) with an appropriate amount of catalyst, initiator and optionally additive at 23 C. in a Speedmixer DAC 150.1 FVZ from Hauschild at 2750 min.sup.1.

[0180] This was then knife-coated onto a glass plate (tin-free side, 250 m).

[0181] In a first crosslinking step, the layer applied was treated by means of UV curing with a gallium-doped mercury vapor lamp and an undoped mercury vapor lamp, both operated at 80 W/cm and with a belt speed of 5 m/min. The dose obtained under these conditions is 1400 mJ/cm.sup.2.

[0182] After the first crosslinking step, the plate was placed on its edge and it was observed whether the UV light-treated coating runs or not.

[0183] Subsequently, the coating was cured completely. For this purpose, it was introduced into an air circulation oven at 180 C. for 15 min.

[0184] Test Methods

[0185] Run-Off

[0186] The coated plate was placed onto a paper towel on its edge for 10 min, and a visual assessment was made as to whether the coating runs. If there is a perceptible change in the coating as a result of the upright position (for example formation of a bulge at the lower edge), the coating is classified as runs off.

[0187] Acetone Resistance

[0188] A small piece of cotton wool is soaked with acetone and placed onto the coating surface. Every minute, the piece of cotton wool was soaked again with acetone in order to compensate for the evaporation. For this purpose, the acetone was added by means of a wash bottle in order that the piece of cotton wool is not moved during the contact operation. After 1 min and 5 min, the acetone-soaked piece of cotton wool is removed, the affected site is dried off and an inspection is made immediately in order to anticipate any regeneration. The test area is inspected for changes visually and by touching by hand. Subsequently, an assessment is made as to whether and what changes have occurred in the test area.

[0189] An assessment is made of softening or discoloration of the coating surface. [0190] 0 no changes detectable [0191] 1 swelling ring, hard surface, merely visible alteration/trace of a change in hue [0192] 2 swelling ring, slight softening/slight change in hue [0193] 3 distinct softening (possible slight blistering)/moderate change in hue [0194] 4 significant softening (possibly significant blistering), can be scratched through down to the substrate/significant change in hue [0195] 5 coating completely destroyed without outside action/very significant change in hue

[0196] Hardness

[0197] Hardness is the mechanical resistance of a body to the penetration of another body. It is the quotient of measured indentation force and the contact area of the indentation body on penetration into the surface. The contact area is calculated with the known geometry of the penetration body and the measured indentation depth.

[0198] In the case of the instrumented indentation test (Martens hardness), indentation force and indentation depth are measured during the deformation, taking account of the elastic and plastic deformation. A pyramidal indentation body (Vickers tip) presses into the coating with rising test force.

[0199] Indentation force, indentation depth and indentation body geometry are used to calculate a Martens hardness value (HM).

[0200] Hardness was determined by means of a Fischerscope H100C in accordance with DIN EN ISO 14577-1.

[0201] The samples are conditioned under standard climatic conditions at 23 C. and 50% rel. humidity for at least 16 h and then analyzed. Choice of maximum indentation force either the same for all samples within the test series or individual assessment and adjustment for each sample. The adjustment criterion here is the Buckle rule, according to which the maximum indentation force is adjusted such that the penetration depth attained is not more than 10% of the coating thickness.

[0202] The measurement result reported in table 1 is the Martens hardness HM (F) in N/mm.sup.2 as an average from 5 measurements.

[0203] Visual Assessment

[0204] After complete curing, the film was visually assessed and briefly described.

[0205] Working Examples:

[0206] The amounts of polyisocyanate, acrylate, catalyst solution specified in table 1 were treated according to the abovementioned production method for reaction mixtures.

[0207] The reaction mixture was coated with a coating bar in a thickness of 250 m onto the tin-free side of a glass plate and then UV-treated with a gallium-doped mercury vapor lamp and an undoped mercury vapor lamp. Subsequently, the samples were cured in an air circulation oven at 180 C. for 15 min.

TABLE-US-00001 TABLE 1 Compositions and material properties of working examples 1-10 Results Catalyst + initiator Martens Resin composition Amount of hardness HM (F) Acetone resistance Amount of Amount of Amount of Amount of Lucirin [N/mm.sup.2] 1 min/5 min Visual observation Isocyanate A Acrylate 1 Acrylate 2 Cat. K1 TPOL-L After After After Runoff Appearance Ex. [g] [g] [g] [g] [g] curing exposure curing after exposure after curing B1 50.0 0.5 9.5 2.0 0.3 133 3/3 0/0 no homogeneous layer B2 50.0 0.375 7.125 2.0 0.3 126 4/4 0/0 no homogeneous layer B3 50.0 0.25 4.75 2.0 0.3 133 5/5 0/0 no homogeneous layer B4 50.0 0.375 9.5 2.0 0.3 130 3-4/4.sup. 0/0 no homogeneous layer B5 50.0 0.25 9.5 2.0 0.3 134 3-4/4.sup. .sup.0/0-1 no homogeneous layer B6 50.0 0.0 0 2.0 0.3 135 5/5 0/0 obvious homogeneous layer

[0208] All examples where the number is preceded by a B are inventive. All examples where the number is preceded by a V are comparative examples and noninventive. Comparative example 1 is prophetic.

[0209] All examples show a high Martens hardness HM (F) after complete curing.

[0210] Examples B1 to B5 show that runoff-free films are obtained after radiative curing and homogeneous clear hard films after complete curing.

[0211] Comparative example V1 shows that the straight isocyanate after radiative curing does not form a runoff-free layer.