Coating system for RMA crosslinkable coating compositions

Abstract

The invention relates to a coating system comprising I) a primer coating composition comprising a binder component PA that contains primary amine functionality blocked with a ketone or aldehyde, a binder component PB that contains acetoacetate or acetoacetamide functional groups and II) a RMA crosslinkable coating composition a component A with at least two acidic protons C—H in activated methylene or methine groups, a component B with at least two activated unsaturated C═C groups and a base crosslinking catalyst C. The invention also relates to the use of the specified primer coating composition for improving adhesion of a RMA crosslinkable coating composition, in particular to metal substrates, to a method for coating a substrate and to coated substrates coated with the coating system of the invention.

Claims

1. A coating system comprising I. a primer coating composition comprising a. a binder component PA that contains primary amine functionality blocked with a ketone or aldehyde, b. a binder component PB that contains acetoacetate or acetoacetamide functional groups, which components PA and PB form an organic binder network in a cured primer coating, and c. optionally one or more other binder components PC that are co-reactive with the component PA or PB, in an amount less than 20 wt % relative to a total weight of binder solids in the primer coating composition, wherein a total amount of the binder component PA, binder component PB and optional other binder components PC in the primer composition is at least 80 wt % relative to a total dry solids weight of the primer composition not including pigments, and wherein a ratio of the acetoacetate or the acetoacetamide functional groups in the component PB to ketimine or aldimine functional groups in the component PA is between 1:3 and 3:1; and II. a Real Michael Addition (RMA) crosslinkable coating composition comprising, a) a component A with at least two acidic protons C-H in activated methylene or methine groups, b) a component B with at least two activated unsaturated C=C groups, c) a catalyst C for catalyzing the RMA crosslinking reaction between components A and B, and d) optionally a reactivity moderator D, which RMA components A and B form an organic binder network in a cured RMA crosslinked coating.

2. The coating system of claim 1, wherein the primer coating composition comprises the one or more other binder components PC that are co-reactive with component PA or PB, in an amount less than 10 wt % relative to the total weight of the binder solids in the primer coating composition.

3. The coating system of claim 1, wherein the ketone or aldehyde, is volatile, having a boiling point below 200° C.

4. The coating system of claim 1, wherein a number average functionality Fn of ketimine or aldimine groups in component PA is at least 2 and below 20, and wherein the ketimine or aldimine equivalent weight of component PA is at least 120 g/mole and below 2000 g/mole.

5. The coating system of claim 1, wherein component PA is the reaction product of a. an amine compound according to formula I: H.sub.2N {-(CH.sub.2)n-NH}.sub.m-(CH2)n-NH.sub.2 with n being 2 or 3, and m being 1 or 2, b. epoxides, isocyanates or electrodeficient unsaturated C=C double bonds, having a reactive functionality towards secondary amine group —NH in the amine compound, and c. a ketone or aldehyde for blocking the primary amine groups of the amine compound.

6. The coating system of claim 1, wherein the number average acetoacetate/acetoacetamide functionality Fn of component PB is at least 2 and less than 20 and the acetoacetate or acetoacetamide equivalent weight of component PB is at least 100 and at most 2500 g/mol.

7. The coating system of claim 1, wherein component PB comprises an acrylic (co-)polymer in which the acetoacetate or acetoacetamide functional groups are introduced a. through (co-)polymerization of an acetoacetate- or acetoacetamide functional (meth-)acrylic comonomer, or b. wherein the acetoacetate functional group is introduced by transesterification of an acetoacetate-ester of a low molecular weight alcohol, with a polyfunctional hydroxyl structure of a molecular weight below 1000 g/mole.

8. The coating system of claim 1, wherein in the primer composition component PB is an polyacrylic or polyester resin comprising acetoacetate functional groups and wherein the component PA is ketimine modified acrylic or epoxy.

9. The coating system of claim 1, wherein the total amount of the binder component PA, binder component PB and optional other binder components PC in the primer composition is at least 90 wt % relative to the total dry solids weight of the primer composition not including pigments.

10. The coating system of claim 1, wherein the ratio of acetoacetate or acetoacetamide functional groups in component PB to ketimine or aldimine functional groups in component PA, is between 1:2 and 2:1.

11. The coating system of claim 1, wherein the RMA crosslinkable coating composition comprises a RMA crosslinkable component with components A being predominantly malonate or an acetoacetate and component B being an acryloyl.

12. The coating system of claim 1, in the form of a kit of parts comprising one or more parts comprising the components PA and PB of the primer coating composition and one or more separate parts comprising the components A, B and C of the RMA crosslinkable composition.

13. A method for applying a RMA crosslinked coating on a substrate using the coating system according to claim 1, comprising the steps of a) applying on a surface of the substrate, a layer of the primer coating composition of the coating system, b) at least partially curing the layer of the primer coating composition to form a primer layer, c) applying over the primer layer, a layer of the RMA crosslinkable coating composition of the coating system, and d) curing the layer of the RMA crosslinkable coating composition.

14. A coated substrate comprising a primer and a coating layer formed from the coating system according to claim 1.

15. A coated substrate comprising a primer and a coating layer formed from the method according to claim 13.

Description

EXAMPLES

(1) The following is a description of certain embodiments of the invention, given by way of example only.

(2) Adhesion Test:

(3) The results of adhesion stated in the following examples are based on the cross cut adhesion test following the ISO/DIN 2409, ASTM D3359 protocol. The ranking is briefly summarized as follows:

(4) 0: The edges of the cuts are completely smooth; none of the squares of the lattice is detached.

(5) 1: Detachment of small flakes of the coating at the intersection of the cuts. A cross-cut area not significantly greater than 5% is affected.

(6) 2: The coating has flaked along the edges and/or at the intersection of the cuts. A cross-cut area significantly greater than 5%, but not significantly greater than 15% is affected.

(7) 3: The coating has flaked along the edges partly or wholly in large ribbons, and/or it has flaked partly or wholly on different parts of the squares. A cross-cut area significantly greater than 15%, but not significantly greater than 35%, is affected.

(8) 4: The coating has flaked along the edges of the cuts in large ribbons and/or same squares have detached partly or wholly. A cross-cut area significantly greater than 35%, but not significantly greater than 65% is affected.

(9) 5: Any degree of flaking that cannot even be classified by classification 4.

(10) Metal Substrate:

(11) To test the adhesion of given examples and comparative examples, films were applied onto a metal substrate Bonderite® 1000. Bonderite® is a trade name of the German producer “Henkel”.

(12) General Procedure for Preparation of RMA Crosslinkable Paint

(13) A malonate containing polymer (RMA crosslinkable component A) is mixed with TMPTA (Trimethylolpropane triacrylate) (RMA crosslinkable component B) and the thinner n-propanol and optionally with pigments or other coating additives and stirred till a homogenous coating composition was obtained. Prior to application as a coating, all mentioned formulations were activated by adding the stated amount of latent base catalyst which is a tetrabutyl ammoniumhydroxide TBAH solution reactively blocked with di-methylcarbonate or di-ethylcarbonate, with a base concentration of 0.7 to 0.928 meq/g solution (see procedure for preparation of catalyst solutions).

(14) Preparation of Malonated Polyester Resins MPE1

(15) This resin is prepared as follows: into a reactor provided with a distilling column filed with Raschig rings were brought 382 g of neopentyl glycol, 262.8 g of hexahydrophthalic anhydride and 0.2 g of butyl stannoic acid. The mixture was polymerised at 240° C. under nitrogen to an acid value of 0.2 mg KOH/g. The mixture was cooled down to 130° C. and 355 g of diethylmalonate was added. The reaction mixture was heated to 170° C. and ethanol was removed under reduced pressure. The resins was diluted with butyl acetate to 85% solids, to yield a material with OH value of 16 mg KOH/g, GPC Mn=1750 g/mole, and a malonate equivalent weight of 350 (active C—H EQW 175).

(16) Preparation of Malonated Alkyd MA1

(17) MA1 is a malonated alkyd (Acure 510-300, available from Allnex) using coconut oil as the oil component, an oil length of 30%, an OH value of 108 mg KOH/g, a GPC Mn of 1800 g/mole and a Mw of 4350 g/mole. The malonate equivalent weight of this material is 360 (active C—H equivalent weight 180).

(18) Paint Preparation: Paints a, B and C

(19) Paint A was prepared by mixing the components as described in Table 1 below. Paint A is based on malonated polyester resin MPE1 and TMPTA.

(20) TABLE-US-00001 TABLE 1 Real Michael Addition Clear Paint Component Paint A MPE1 10.00 TMPTA 3.47 Silmer ACR-D2** 0.03 Methyl propyl ketone 5.00 **Silmer ACR-D2 is reactive silicone comprising multi-functional or linear-difunctional silicone pre-polymers with reactive terminal end groups being acrylates.

(21) Paint B was prepared by making a mill base using TMPTA (550-100 in Table 2) and then letting it down to make a Real Michael Addition paint with malonated alkyd resin MA1 (510-300 in Table 2), TMP-tri acetoacetate, (510-400 in Table 2) and TMPTA (550-100 in Table 2).

(22) TABLE-US-00002 TABLE 2 Real Michael Addition White Paint B Mill base 550-100 1005 Disperbyk 163 63.6 Kronos 2310 2112 Letdown 510-300 1390 510-400 245 550-100 24 Isopropanol 227 80:20 MAK:IBIB 433 TOTAL Part A 5499.25 MAK:IBIB is methylamylketone:isobutylisobutyrate. Disperbyk 163 is: Wetting and dispersing additive from Byk Kronos2310 is: titanium dioxide pigment
Catalyst Preparation Examples:

(23) Catalyst compositions were prepared by mixing components specified in Table 3.

(24) TABLE-US-00003 TABLE 3 Catalyst compositions Component Catalyst 1 Catalyst 2 Aqueous TBAH 35.8 (40%) Aqueous TBAH 267.6 (55%) Diethylcarbonate 0 121.19 Dimethylcarbonate 21.7 0 n-propanol 0 182.4 2-propanol 1.5 0 DI Water 19.2 29.88
Preparation of Acrylic Ketac Primer Example 1.

(25) A clear primer paint was made by thoroughly mixing 224.75 g of an acetoacetate functional acrylic resin, Setalux 17-1450 with 45 g of methyl amyl ketone and mixing fifty grams thereof with 9.27 g of a ketimine functional compound A, and 5.43 g of methyl isobutyl ketone.

(26) Ketimine functional compound A is a tetrafunctional ketimine compound, which is the reaction product of 2 moles of DETA (diethylenetriamine) on 1 mole of DGEBPA (Bisphenol A diglycidyl ether) wherein the primary amine groups are blocked as ketimine by reacting with excess MIBK (Methyl isobutyl ketone).

(27) The clear primer paint of Example 1 was sprayed onto a Bonderite® 1000 treated steel panel and allowed to dry overnight (16 hours). The next day 58.49 g of Paint A was catalyzed with 1.97 g of Catalyst 1, thoroughly mixed and then sprayed onto the primed panel and allowed to air-dry overnight (16 hours). The next day adhesion was tested using the cross-cut adhesion test as described in ASTM D3359 and found to be very good, ASTM rating 0.

Comparative Example 1: Epoxy Primer

(28) An epoxy primer, Aquapon 97-137 was activated with hardener 97-1200 at the volume ratio suggested by the producer (PPG) and sprayed onto a Bonderite®1000 steel panel and allowed to air-dry overnight (16 hours). The next day 58.49 g of Paint A was catalyzed with 1.97 g of Catalyst 1, thoroughly mixed and then sprayed onto the epoxy primed panel and allowed to air-dry overnight (16 hours). The next day adhesion was tested using the cross-cut adhesion test as described in ASTM D3359 and found to be very bad, ASTM rating 5.

(29) Preparation of Polyester Ketac Primer Example 2.

(30) A pigmented polyester Ketac primer was made by first making a millbase as shown in Table 4 and then making the letdown also shown in Table 4 and adding and mixing to 84.15 g thereof (Part A in Table 4) an amount of 15.85 g of a ketimine functional compound A.

(31) A mixture of two different acetoacetate functional polyesters (primer binder component PB) were used: Setal 26-3705 is an acetoacetate functional polyester. Setal 26-3701 is tri-methyl propanol (TMP) functionalized with acetoacetate. The ketimine functional component PA used in the examples is always the above described ketimine functional compound A. The ratio of Ketimine to acetoacetate functional groups in all examples was 1.21 to 1.

(32) TABLE-US-00004 TABLE 4 Ketac Pigmented Primer Millbase Wt. Description Setal 26-3705 123.32 AcetoAcetate functional polyester Setal 26-3701 38.15 AcetoAcetate functional polyester Disperbyk 110 26.07 Pigment dispersant Vansil W40 60.78 extender pigment Vantalc 4000 60.78 extender pigment R900 283.63 TiO2 Gamma Sperse 80 243.17 Calcium carbonate Heucophos ZAPP 162.09 phosphate pigment Bentone SD1 2.01 anti-settling clay TOTAL 1000.0 Letdown - Part A Description Millbase 857.23 n-Butyl Acetate 70.96 solvent Methy Amyl Ketone 70.96 solvent Dow Paint Additive #3 0.85 surface active additive TOTAL 1000.0 Paint Weight Part A 84.15 Setalux 10-1440 15.85 Ketimine functional resin

(33) The primer was then sprayed onto a Bonderite®1000 steel panel and allowed to air-dry overnight (16 hours). The next day 50 g of Paint B was mixed with 1.34 g of Catalyst 2, thoroughly mixed and then sprayed onto the Ketac primed panel and allowed to air-dry overnight (16 hours). After 3 days, adhesion was tested using the cross-cut adhesion test as described in ASTM D3359 and found to be very good, ASTM rating 0. Next the panel was placed onto a QCT test cabinet set at 40° C. and exposed to condensing humidity for 135 hours. The adhesion was tested again using the cross-cut adhesion test as described in ASTM D3359 and found to be very good, ASTM rating 0.

Comparative Example 2: Epoxy Primer

(34) An epoxy paint, Devran 201H was activated with hardener at the volume ratio suggested by the producer (IP) and sprayed onto a Bonderite®1000 steel panel and allowed to air-dry for 48 hours. The epoxy primed panel was then painted with a Real Michael Addition paint by mixing 50 g of Paint B with 1.34 g of Catalyst 2, thoroughly and then sprayed onto the epoxy primed panel and allowed to air-dry overnight (16 hours). After 3 days, adhesion was tested using the cross-cut adhesion test as described in ASTM D3359 and found to be okay, ASTM rating 3. Next the panel was placed onto a QCT test cabinet set at 40° C. and exposed to condensing humidity for 135 hours. The adhesion was tested again using the cross-cut adhesion test as described in ASTM D3359 and found to be very bad, ASTM rating 5.

Example 3

(35) The primer described in Table 4 was spray-applied to plastic substrates listed in Table 5. The primer was then baked for 30 minutes at 65° C. The primed panels were then painted with a Real Michael Addition paint by mixing 50 g of Paint B with 1.34 g of Catalyst 2. The panel was then baked for 30 minutes at 65° C. Adhesion was tested using the cross-cut adhesion test as described in ASTM D3359 and found to be good, ASTM rating 0. Next the panels were placed onto a QCT test cabinet set at 40° C. and exposed to condensing humidity for 168 hours. The adhesion was tested again using the cross-cut adhesion test as described in ASTM D3359 and found to be good, ASTM rating

(36) TABLE-US-00005 TABLE 5 plastic substrates ABS Polycarbonate Polycarbonate/ABS blend

(37) Thus, the invention has been described by reference to certain embodiments discussed above. It will be recognized that these embodiments are susceptible to various modifications and alternative forms well known to those of skill in the art.