阅读说明：本技术 用于rma可交联涂料组合物的涂料体系 (Coating systems for RMA crosslinkable coating compositions ) 是由 F·万韦克 M·梅维森 A·蒂斯代尔 B·诺尔德维 于 2020-02-25 设计创作，主要内容包括：本发明涉及一种涂料体系,其包含粘结剂组合物和RMA可交联的组合物,该粘结剂组合物包含Mn为6,000-60,000g/mol、Mw为20,000-300,000g/mol、Tg为30-180℃和酸值为至多3.0mg KOH/g的聚合物,该RMA可交联的组合物包含在活化亚甲基或次甲基基团中具有至少2个酸性质子C-H的组分A,具有至少两个活化不饱和C＝C基团的组分B和碱交联催化剂C；及其用于提高RMA可交联涂料组合物的粘附力,特别是对木质基材的粘附力的用途。(The invention relates to a coating system comprising a binder composition comprising a polymer having an Mn of 6,000-; and their use for improving the adhesion of RMA crosslinkable coating compositions, in particular to wood substrates.)

1. A coating system for coating a substrate comprising a composition crosslinkable by a binder component P and RMA,

wherein the binder component P comprises at least one polymer PR having a number average molecular weight (Mn) of 6,000-60,000g/mol, a weight average molecular weight (Mw) of 20,000-300,000g/mol, a glass transition temperature (Tg) of 30 to 180 ℃ and an acid number of at most 3.0mg KOH/g,

the RMA crosslinkable composition comprises a component a having at least 2 acidic protons C-H in an activated methylene or methine group, a component B having at least two activated unsaturated C ═ C groups, a catalyst C for catalyzing the RMA crosslinking reaction between components a and B, and optionally a reactivity moderator D, with the proviso that a and B may be part of the same molecule.

2. The coating system according to claim 1, wherein the polymer PR in the binder component P is a (meth) acrylic copolymer.

3. The coating system according to claim 1 or 2, wherein component P further comprises at least one polymer PA different from polymer PR.

4. The coating system of any one of claims 1-3, wherein the binder component P is applied as a primer layer on the substrate, and wherein the RMA crosslinkable composition is applied on the primer layer.

5. A coating system according to any one of claims 1 to 3, wherein the binder component P and the RMA crosslinkable composition are mixed and applied as one layer on a substrate.

6. The coating system as claimed in any of claims 1 to 5, wherein the polymer PR has a number-average molecular weight (Mn) of 10,000-50,000g/mol, a weight-average molecular weight (Mw) of 50,000-250,000g/mol, a glass transition temperature (Tg) of 50 to 100 ℃ and an acid number of 0 to 3.0mg KOH/g.

7. The coating system according to any one of claims 1 to 6, wherein the binder component P comprises 5 to 50 wt% of a polymer PR, 50 to 85 wt% of one or more solvents and optionally 0 to 45 wt% of a polymer PA different from polymer PR.

8. The coating system according to any one of claims 1-7, wherein the RMA crosslinkable composition comprises a total of 30-70 wt% of the component A, component B, catalyst C, and optional reactivity moderator D, and 30-70 wt% of at least one organic solvent.

9. The coating system according to any one of claims 1-8, wherein the RMA crosslinkable coating composition comprises RMA crosslinkable components, wherein component A is predominantly malonate or acetoacetate ester, preferably malonate ester, and component B is acryloyl.

10. The coating system of any one of claims 1-9, wherein the relative amounts of RMA crosslinkable components in the RMA crosslinkable composition are selected such that the molar ratio of activated unsaturated reactive groups C ═ C in component B to activated acidic reactive groups C — H in component a is from 0.5 to 2.

11. The coating system according to any one of claims 1-10, wherein the reactive moderator D comprises X-H groups having a pKa that is at least one unit less than the pKa of the C-H groups in the main component a.

12. The coating system of any one of claims 1-11, wherein the catalyst C is a carbon dioxide-blocked strong base or a urethane-blocked catalyst.

13. The coating composition according to any one of claims 1 to 12, comprising 5 to 95 wt% of polymer PR, 5 to 95 wt% of RMA crosslinkable composition (total solids of component a, component B, catalyst C and optionally of reactivity moderator D) and optionally 0 to 90 wt% of polymer PA different from polymer PR, based on the total weight (solids) of RMA crosslinkable composition, polymer PR and polymer PA.

14. A method of applying the coating system of any one of claims 1 to 13 to a substrate, wherein the substrate is preferably a wood substrate.

15. The method of claim 14, comprising the steps of:

a) a layer comprising the binder component P is applied to the substrate surface, preferably with a dry film thickness of at least 10 μm, more preferably from 20 to 50 μm,

b) at least partially drying the layer, preferably at ambient conditions,

c) optionally repeating steps a) and b),

d) optionally grinding the layer obtained in step b) and/or c),

e) applying at least one layer (preferably a top coat) of a RMA crosslinkable coating composition on the layer obtained after step b), c) or d),

f) curing the RMA crosslinkable coating, preferably at ambient conditions.

16. The method of claim 14, comprising the steps of:

a) component P is mixed with the RMA crosslinkable composition,

b) applying a layer comprising a mixture of the component P and a composition crosslinkable by RMA, preferably having a dry film thickness of at least 10 μm, more preferably from 20 to 50 μm,

c) at least partially curing the layer, preferably at ambient conditions,

d) optionally repeating steps b) and c),

e) optionally grinding the layer obtained in step c) and/or d),

f) Optionally applying a top coat, optionally an RMA crosslinkable composition and curing said top coat on the layer obtained in step c), d) or e).

17. A coated substrate comprising at least one layer formed from a coating system according to any one of claims 1 to 13 or obtainable by a process according to any one of claims 14 to 16.

Technical Field

The present invention relates to a coating system for improving the adhesion of RMA crosslinked coatings to a substrate, a process for coating a substrate and the improved coated substrate obtainable by the present invention.

Background

RMA crosslinkable compositions are compositions comprising at least one RMA crosslinkable component comprising components a and B, each of components a and B comprising at least 2 reactive groups, wherein at least 2 reactive groups of component a are acidic protons (C-H) in activated methylene or methine groups (RMA donor groups) and at least 2 reactive groups of component B are activated unsaturated groups (ca ═ C) (RMA acceptor groups). These reactive groups effect crosslinking by Real Michael Addition (RMA) reaction between the at least one RMA crosslinkable component in the presence of a basic catalyst (C). Such RMA crosslinkable compositions are described in EP 2556108. Described herein is a specific catalyst C, which is a substituted carbonate catalyst that decomposes in the coating to produce carbon dioxide, which evaporates from the applied cured coating, and a strong base that initiates the RMA crosslinking reaction. The catalyst provides a longer pot life while at the same time acting as a readily escapeable CO ₂The coating of (2) is highly reactive.

The problem underlying this invention is that RMA crosslinkable compositions may sometimes exhibit undesirably low adhesion properties, especially when applied to wood surfaces.

WO2016/166371 describes a method for improving the adhesion of RMA crosslinked coatings on metal substrates by means of a coating system comprising an epoxy primer coating composition and an RMA crosslinkable coating composition. WO2018/210846 describes another method of improving the adhesion of RMA crosslinked coatings on metal substrates. However, applicants have found that while such coating systems may improve adhesion of RMA crosslinkable compositions on certain substrates, they are less suitable for applications requiring colorless and/or clear coats. Thus, there is still a need for coating systems for such applications, in particular on wood substrates, and for systems which allow to obtain coatings with good adhesion, sufficient hardness and mechanical properties and which allow curing within a few hours at relatively low or even room temperature. Furthermore, there is still a need for coating systems for so-called acidic substrates, in particular some wood substrates and/or putties.

The applicant has found a new coating system which overcomes the above problems. In particular, the applicant has found that the use of a binder component P comprising a specific polymer as primer or in combination with a RMA composition allows to obtain good curing speed and adhesion as well as mechanical and chemical properties, in particular on more acidic substrates, such as wood substrates.

The present invention therefore relates to a coating system for coating a substrate comprising a binder component P comprising at least one polymer PR having a number average molecular weight (Mn) of 6,000-60,000g/mol, a weight average molecular weight (Mw) of 20,000-300,000g/mol, a glass transition temperature (Tg) of 30-180 ℃ and an acid number of at most 3.0mg KOH/g, and a RMA crosslinkable composition comprising a component a having at least 2 acidic protons C-H in activated methylene or methine groups, a component B having at least two activated unsaturated C ═ C groups (provided that component a and component B may be part of the same molecule), a catalyst C for catalysing the RMA crosslinking reaction between components a and B, and optionally a reactive moderator D.

The invention also relates to a method for coating a substrate, in particular a wood substrate, with the coating system according to the invention, and to the coated substrate.

The binder component P used in the coating system of the present invention may be a water-based composition, but is preferably a so-called non-aqueous composition, typically a component comprising less than 10% water, preferably less than 5% water, more preferably less than 1% water or even substantially free of water.

The binder component P generally comprises at least one polymer PR and at least one solvent.

The number-average molecular weight (Mn) of the polymer PR used in the binder component P is preferably at least 10,000 g/mol. The Mn of the polymer PR is preferably not more than 50,000 g/mol. The weight-average molecular weight (Mw) of the polymer PR used in the binder component P is preferably at least 50,000 g/mol. The Mw of the polymer PR is preferably not more than 250,000 g/mol. The weight average molecular weight Mw and number average molecular weight Mn of the polymer are determined by gel permeation chromatography using polystyrene standards, more specifically using size exclusion chromatography, according to ASTM D3593.

The glass transition temperature (Tg) of the polymer PR used in the binder component P is preferably at least 40 c, most preferably at least 50 c. The glass transition temperature (Tg) of the polymer PR used in the binder component P is generally at most 180 ℃, preferably at most 110 ℃ and most preferably at most 100 ℃. The Tg of the polymers was measured according to DEN EN ISO 16805 and ISO 11357 using a Mettler DSC 822E calorimeter.

The acid number of the polymer PR used in the binder component P is generally from 0 to 3.0mg KOH/g. The acid number is preferably at most 2.0, most preferably at most 1.0. The acid number of the polymer was measured according to ASTM D1639-70.

The hydroxyl number of the polymer used in the binder component P, measured according to ASTM E222, is preferably from 10 to 120mg KOH/g.

The polymer PR may be selected from a variety of polymers, such as polyesters, (meth) acrylic polymers and copolymers, polycarbonates, poly (ester amides), polyurethanes, poly (urethane ureas), polyethers, and mixtures and hybrids thereof. Such polymers are generally known to the skilled person and are commercially available.

The polymer PR is preferably chosen from (meth) acrylic copolymers. Suitable (meth) acrylic copolymers can be obtained, for example, by (co) polymerizing (meth) acrylic monomers, optionally with other (meaning non- (meth) acrylic) ethylenically unsaturated comonomers, in the presence of a free radical initiator.

"ethylenically unsaturated monomer" means in the present invention a monomer having at least one carbon-carbon double bond which can undergo free radical polymerization.

When used to name the compounds of the present invention, the prefix "(meth) acryloyl" includes "acryloyl" and "methacryloyl", and refers to a compound comprising at least one CH₂A ═ CHCOO-group or CH₂＝CCH₃Compounds of COO-groups and mixtures thereof, and mixtures of such compounds.

The (meth) acrylic copolymer is preferably obtained from the polymerization of one or more hydroxyalkyl esters of (meth) acrylic acid (a1) and one or more non-functional (meth) acrylates (a2) and optionally one or more other functional (meth) acrylates (a3) and/or other (non (meth) acrylic) ethylenically unsaturated monomers (a 4).

The hydroxyalkyl esters of (meth) acrylic acid (a1) are preferably selected from those containing from 1 to 20, more preferably from 1 to 14, carbons in the alkyl group. Some non-limiting examples are hydroxymethyl (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, hydroxypentyl (meth) acrylate, hydroxyhexyl (meth) acrylate, hydroxyheptyl (meth) acrylate, hydroxyoctyl (meth) acrylate, hydroxynonyl (meth) acrylate, hydroxydecyl (meth) acrylate, hydroxyundecyl (meth) acrylate, hydroxydodecyl (meth) acrylate, hydroxytridecyl (meth) acrylate, hydroxytetradecyl (meth) acrylate. Polyethylene glycol esters of (meth) acrylic acid, polypropylene glycol esters of (meth) acrylic acid, and mixed polyethylene and polypropylene glycol esters of (meth) acrylic acid may also be used. Preferred hydroxyalkyl esters (a1) are hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate.

Preferred examples of the non-functional (meth) acrylic acid ester (a2) include esters of (meth) acrylic acid and crotonic acid with saturated alcohols containing 1 to 20, more preferably 1 to 14 carbon atoms. Preferred (meth) acrylates (a2) are linear, branched or cyclic alkyl (meth) acrylates having 1 to 20, more preferably 1 to 14 carbon atoms in the alkyl group, such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate and isobornyl (meth) acrylate and all isomers thereof. Heterocyclic (meth) acrylates, such as tetrahydrofurfuryl (meth) acrylate, may also be used. Preference is given to methacrylates, especially methyl methacrylate and lauryl methacrylate.

The monomer (a3) may be selected from functionalized (meth) acrylates, for example epoxy-functional (meth) acrylates, especially glycidyl (meth) acrylate, (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N-methylol (meth) acrylamide and monomers which contain a keto group in addition to a polymerizable group such as a (meth) acryloyl group or a (meth) acrylamide group, such as diacetone (meth) acrylamide, acetoacetoxy groups, such as acetoacetoxyethyl (meth) acrylate, or ureido (also known as 2-oxo-1-imidazolinyl), for example N- (2- (meth) acryloyloxyethyl) -ethyleneurea (also known as 2- (2-oxo-1-imidazolinyl) ethyl (meth) acrylate) or ureido (meth) acrylate).

Examples of other ethylenically unsaturated monomers (a4) include styrene derivatives, such as styrene and vinyltoluene, vinyl esters of (branched) monocarboxylic acids, monoalkyl esters of maleic acid, fumaric acid, itaconic acid, crotonic acid and maleic acid, and also vinyl acetate, N-vinylformamide, N-vinylpyrrolidone. N-vinylpyrrolidone is particularly preferred.

Preferred monomers (a4) are styrene derivatives, such as styrene, vinyltoluene, alpha-methylstyrene, ethylstyrene, isopropylstyrene, tert-butylstyrene, 2, 4-dimethylstyrene, diethylstyrene, o-methyl-isopropylstyrene, chlorostyrene, fluorostyrene, iodostyrene, bromostyrene, 2, 4-cyanostyrene, hydroxystyrene, nitrostyrene, phenylstyrene. Styrene is particularly preferred.

Mixtures of any of the listed monomers may also be used.

More preferably, monomers (a2) and (a4) are those whose homopolymers have a glass transition temperature (Tg) of at least, more preferably higher than 50 ℃, such as styrene, n-vinylpyrrolidone, dodecyl (meth) acrylate, methyl methacrylate and mixtures thereof.

Preferred (meth) acrylic copolymers for component P are copolymers of one or more hydroxyalkyl (meth) acrylates, in particular hydroxyethyl methacrylate, with one or more alkyl (meth) acrylates, wherein the alkyl is a linear, branched or cyclic alkyl group containing from 1 to 12 carbon atoms, in particular methacrylates, such as methyl methacrylate and lauryl methacrylate, and optionally styrene.

The (meth) acrylic copolymer preferably contains less than 5 wt% of acid functional monomers; and more preferably substantially free of acid functional monomers.

The (meth) acrylic copolymer is preferably obtained from:

5 to 50 wt.% of a hydroxy-functional (meth) acrylate (a1),

5-90 wt% of a non-functional (meth) acrylate (a2), and optionally

From 0 to 80% by weight of ethylenically unsaturated monomers (a4), especially styrene,

Based on the sum of (a1), (a2), and (a 4).

In one embodiment of the present invention, (a1), (a2), and (a4) add up to 100 wt%.

The polymer PR contained in the binder component P preferably comprises one or more (meth) acrylic copolymers, in particular as described above, and has a number average molecular weight (Mn) of 10,000-50,000g/mol, a weight average molecular weight (Mw) of 50,000-250,000g/mol, a glass transition temperature (Tg) of from 50 to 100 ℃ and an acid number of from 0 to 3.0 mgKOH/g. The polymer PR contained in the binder component P preferably consists essentially of one or more (meth) acrylic copolymers as described above.

In another preferred embodiment of the invention, the adhesive composition P comprises, in addition to one or more polymers PR as described above, one or more further polymers different from the polymer PR (hereinafter referred to as polymer PA). The glass transition temperature of the polymer PA may be below 30 ℃ and/or the Mn below 6,000 and/or the Mw below 20,000. The polymer PA is preferably obtained by polymerization of n-vinylpyrrolidone, more preferably together with one or more of the other monomers mentioned above. More preferably, the polymer PA is a copolymer comprising n-vinylpyrrolidone having an Mn of less than 6,000. The use of the polymer PA in combination with the polymer PR is very suitable for adsorbing tannins originating from wood species and/or acidic species contained in the substrate and thus improves the drying of the RMA crosslinkable composition of the invention.

In this embodiment of the invention, the binder composition P preferably comprises a polymer PR having a glass transition temperature (Tg) above 50 ℃ and another polymer PA having an Mn below 6,000. Applicants have found that such binder compositions allow for further improvement of the drying performance of the RMA compositions. In this embodiment of the invention, the binder composition P preferably comprises from 10 to 85% by weight, more preferably from 15 to 65% by weight, of the polymer PA and from 15 to 90% by weight, more preferably from 35 to 85% by weight, of the polymer PR, relative to the total weight of the polymers PR and PA.

Component P further preferably further comprises at least one organic solvent, more preferably one or more volatile organic compounds having a boiling point of 200 ℃ or less at atmospheric pressure. These solvents are generally used to dilute the composition to a viscosity suitable for application of component P to a substrate. Examples of suitable volatile organic compounds are hydrocarbons, such as toluene, xylene, toluene, xylene,100, ketones, terpenes such as dipentene or pine oil, halogenated hydrocarbons such as dichloromethane, ethers such as ethylene glycol dimethyl ether, esters such as ethyl acetate, ethyl propionate, butyl acetate, or ether esters such as methoxypropyl acetate or ethoxyethyl propionate. Mixtures of these compounds may also be used.

Component P may also optionally comprise one or more pigments (especially anti-corrosion pigments), fillers and other additives commonly known to those skilled in the art for coating applications, such as dispersants, anti-settling agents, sag control agents, light or uv stabilizers, flow modifiers, leveling agents, thickeners, defoamers, wetting agents, surfactants, adhesion promoters, coalescents, corrosion inhibitors, matting agents, flame retardants, slip additives, anti-fouling additives and anti-graffiti additives.

In one embodiment of the invention, component P may also comprise a curing agent, in particular an isocyanate-functional curing agent, and optionally a catalyst for catalyzing the reaction of the polymer PR with the curing agent.

In the coating system of the present invention, the binder component P preferably comprises 5 to 50 wt% of the polymer PR, more particularly the (meth) acrylic copolymer, optionally 0 to 45 wt% of the polymer PA, and 50 to 85 wt% of one or more solvents as described above.

The total amount of polymer PR (more specifically a (meth) acrylic polymer) in the binder component P is generally at least 5 wt%, preferably at least 15 wt%, more preferably at least 25 wt%, relative to the total weight of the binder component P. When used, the total amount of polymer PA (more specifically n-vinyl pyrrolidone-based polymer) in the binder component P is generally at least 5 wt%, preferably at least 15 wt%, more preferably at least 25 wt%, relative to the total weight of the binder component P. The total amount of solvent (more specifically butyl acetate or xylene) in the binder component P is preferably at least 45 wt%, more preferably at least 50 wt%, relative to the total weight of the binder component P. The total amount of solvent in the binder component P is generally not more than 95 wt%, preferably not more than 85 wt%, more preferably not more than 75 wt%, relative to the total weight of the binder component P.

The RMA crosslinkable composition used in the coating system of the present invention is typically a composition comprising at least one RMA crosslinkable component a comprising at least 2 reactive groups which are acidic protons (C-H) in an activated methylene or methine group (RMA donor group), at least one RMA crosslinkable component B comprising at least 2 activated unsaturated groups (C ═ C) (RMA acceptor groups), and at least one base catalyst (C). These reactive groups effect crosslinking by Real Michael Addition (RMA) reactions between the RMA crosslinkable components in the presence of the catalyst. Component a and component B may be part of different molecules or may be present on the same molecule. Such RMA crosslinkable compositions are described for example in EP 2556108; described herein is a specific catalyst C, which is a substituted carbonate catalyst that decomposes in the coating to produce carbon dioxide and a strong base, wherein the carbon dioxide evaporates from the applied cured coating and the strong base initiates the RMA crosslinking reaction. The catalyst provides a longer pot life while acting as a fugitive CO₂The coating of (2) is highly reactive. Suitable RMA crosslinkable compositions are known in the art; WO11/124663, WO11/124664 and WO11/124665 describe RMA crosslinkable compositions with a latent base catalyst comprising a carbon dioxide capped base catalyst which generates a strong base in the coating by carbon dioxide deblocking. WO14/166880 describes RMA crosslinkable compositions with catalysts that do not rely on carbon dioxide deblocking, which are particularly suitable for layers in which evaporation is hindered, for example thicker layers. WO13/050622, WO13/050623, WO13/050624 and WO13/050574 describe RMA crosslinkable compositions having specific pot life and open time moderators. WO16/166361, WO16/166381, WO16/166382 and WO2018/005077 further describe RMA crosslinkable compositions. The descriptions of various embodiments of RMA crosslinkable compositions in these prior art documents are incorporated herein by reference. With particular reference to the above prior art, all of the components of RMA crosslinkable composition A, B, C or D, their preparation, amounts used in RMA crosslinkable compositions, and methods of measurement and definitions are described in detail, and unless otherwise indicated, the descriptions thereof are incorporated herein by reference and apply. The most important features are summarized below.

Generally, it is preferred that component a of the RMA crosslinkable composition used in the present invention is a malonate or acetoacetate ester, preferably predominantly a malonate, and component B is a (meth) acryloyl compound, preferably an acryloyl compound. Preferably, one or more of components a in the RMA crosslinkable component predominantly comprises one type of component, predominantly meaning that preferably more than 50, 75, 90 and most preferably 100% of the C-H reactive groups in RMA crosslinkable component a are from one type of component a, preferably from malonate or acetoacetate, most preferably consisting essentially of malonate, and optionally acetoacetate as the remaining component a. The most preferred component B is acryloyl.

The one or more RMA crosslinkable components A and B may be monomers, but preferably at least one RMA crosslinkable component A or B is a polymer component having a weight average molecular weight Mw of at least 250g/mol, preferably a polymer having a Mw of 300-5000g/mol, more preferably 400-4000g/mol or 500-3000g/mol (determined by GPC).

According to one embodiment of the present invention, the one or more RMA crosslinkable components A and B are part of the same molecule, preferably a polymer component having a weight average molecular weight Mw of at least 250g/mol, more preferably a polymer having a Mw of 300-.

Preferably, the one or more RMA crosslinkable components a are one or more polymers selected from the group consisting of polyesters, alkyds, polyurethanes, polyacrylates, epoxies, polyamides and polyethylene resins, containing malonate and/or acetoacetate moieties in the backbone, side chains, termini or combinations thereof.

The relative amounts of RMA crosslinkable components in the RMA crosslinkable compositions are selected such that the molar ratio of activated unsaturated reactive groups C ═ C in component B to activated acidic reactive groups C — H in component a is from 0.5 to 2, preferably from 0.75 to 1.5 or from 0.8 to 1.2. If reactive diluents having 2C-H reactive groups (e.g.malonates) are present, these are also included in the total amount of C-H in the above-mentioned proportions, since they are RMA crosslinkable components.

The RMA crosslinkable composition preferably further comprises a reactive moderator D having X-H groups which are also michael addition donors reactive with component B under the action of catalyst C, wherein X is C, N, P, O or S, to improve the open time and thus the working time for applying the coating composition. The pKa (defined in an aqueous environment) of the X-H groups in component D (preferably the N-H group containing component) is preferably at least one unit, more preferably two units, less than the pKa of the C-H groups in the main component a; preferably, the pKa of the X-H groups in component D is below 13, preferably below 12, more preferably below 11, most preferably below 10; it is preferably higher than 7, more preferably higher than 8, more preferably higher than 8.5. Component D preferably comprises a molecule containing N-H as part of a group- (C ═ O) -NH- (C ═ O) -or a group-NH- (O ═ S ═ O) -, or a heterocycle in which the nitrogen of the N-H group is contained in a heterocycle, which is preferably selected from substituted or unsubstituted succinimides, glutarimides, hydantoins, triazoles, pyrazoles, imidazoles or uracils, preferably from succinimides, benzotriazoles and triazoles. The amount of component D is preferably from 0.1 to 10% by weight, preferably from 0.2 to 7% by weight, from 0.2 to 5% by weight, from 0.2 to 3% by weight, more preferably from 0.5 to 2% by weight, based on the total amount of the crosslinkable components A or B of RMA and of component D. The amount of component D is such that the amount of X-H groups in component D is not more than 30 mol%, preferably not more than 20 mol%, more preferably not more than 10 mol%, most preferably not more than 5 mol%, relative to the C-H donor groups in component A contained in the crosslinkable polymer.

In principle, the RMA crosslinking reaction can be catalyzed by any base known in the art. Some commonly used michael catalysts are alkali metal hydroxides, alkali metal alkoxides, quaternary ammonium hydroxides (e.g., tetraalkylammonium hydroxides), and amine compounds (e.g., diazepine compounds, guanidine compounds, amidines including cyclic amidines, pyridines, imidazolines). Suitable catalysts are described, for example, in EP1462501, which is hereby incorporated by reference.

Catalyst C is preferably a carbon dioxide-terminated strong base catalyst, more preferably a quaternary alkyl ammonium di-or alkyl carbonate (as described for example in EP 2556108). CO production due to this catalyst₂And are therefore particularly preferred for coatings having a thickness of up to 500, 400, 300, 200 or 150 microns.

Homogeneous base catalysts C, which are also more suitable for thicker coatings, are described in EP0326723, consisting of a combination of a tertiary amine and an epoxy compound, or in PCT/EP2014/056953, homogeneous catalysts C are described which are salts of basic anionic X-from an acidic X-H group-containing compound, wherein X is N, P, O, S or C, and wherein the anionic X-is a michael addition donor which is reactive with component B, and the anionic X-is characterized in that the pka (C) of the corresponding acid X-H is two or more units lower and lower than 10.5 than the pka (a) of the main component a. Suitable catalysts described in the prior art are incorporated herein by reference.

Another catalyst suitable for use in the present invention is a urethane-terminated catalyst such as described in WO 2018/005077.

Preferably, the RMA crosslinkable compositions for use in the present invention are substantially free of acidic components.

The RMA composition may comprise one or more organic solvents, preferably volatile organic solvents, necessary for dissolving certain components or for adjusting the RMA composition to a suitable processing viscosity. Organic solvents used in RMA crosslinkable compositions are common coating solvents, preferably those free of acid impurities, such as alkyl acetates (preferably butyl acetate or hexyl acetate), alcohols (preferably C2-C6 alcohols), N-alkyl pyrrolidines, glycol ethers, dipropylene glycol methyl ether, propylene glycol methyl ether acetates, ketones, and the like. The organic solvent is more preferably an alkyl acetate, especially butyl acetate. In one embodiment of the invention, an alcohol is also used as a solvent comprising 2 to 12 carbon atoms, as this may improve the pot life and/or open time of the RMA composition.

The amount of solvent may be between 0 and 90 wt%. According to a preferred embodiment of the present invention, the amount of volatile organic solvent in the RMA crosslinkable composition is at least 30 wt%. According to a preferred embodiment of the present invention the RMA crosslinkable composition comprises in total 15-70 wt. -%, more preferably 30-60 wt. -%, most preferably 40-60 wt. -% of said component a, component B, catalyst C and optionally a reactivity moderator D, preferably 30-85 wt. -%, more preferably 30-70 wt. -% of at least one organic solvent as described above.

Especially where low viscosity and low VOC are desired, the RMA crosslinkable composition preferably comprises one or more reactive diluents which react with RMA crosslinkable components a or B. The reactive diluent or diluents are preferably selected from monomeric or dimeric component a, monomeric or dimeric component B, compound a 'having only 1 reactive acidic proton (C-H) in the activated methylene or methine group, compound B' having only 1 reactive unsaturated group (C ═ C), most preferably alkyl acetoacetate, dialkyl malonate, limited molecular weight mono or diacrylate. The total amount of volatile organic solvent plus reactive solvent is between 0 and 70 wt% and the volatile organic solvent is less than 65 wt% relative to the total weight of the RMA composition.

The RMA composition can additionally comprise one or more additives such as pigments, fillers, dispersants, anti-settling agents, sag control agents, light or UV stabilizers, flow modifiers, leveling agents, thickeners, defoamers, wetting agents, surfactants, adhesion promoters, coalescents, corrosion inhibitors, matting agents, flame retardants, slip additives, anti-soil additives, anti-graffiti additives, and mixtures thereof.

In the coating system of the present invention, the relative weights of the RMA crosslinkable composition (total solids of component a, component B, catalyst C and optional reactive moderator D) and the polymer PR (solids) may vary from 5:95 to 95: 5.

According to a preferred embodiment of the invention, the binder component P is applied as a separate layer on the substrate and the RMA crosslinkable composition is applied on this layer. One or more layers of the binder component P may be applied prior to the application of one or more layers of the RMA crosslinkable composition.

The coating system may be in the form of a kit comprising a portion of the binder component P and one or more separate portions comprising components A, B and C and optionally D of the RMA crosslinkable composition. Alternatively, one or more of components A, B and C and optionally D can be part of a kit comprising binder component P.

According to another preferred embodiment of the invention, the binder component P and the RMA crosslinkable composition are mixed and applied as a layer on a substrate. According to this embodiment, the coating system comprises one or more components P comprising one or more polymers PR (in particular (meth) acrylic copolymers) and optionally one or more polymers PA, as described above, and one or more further RMA crosslinkable coating compositions. The present invention therefore also relates to a coating composition comprising 5 to 95 wt% of polymer PR and 5 to 95 wt% of RMA crosslinkable composition (total solids of component a, component B, catalyst C and optionally reactivity moderator D) and optionally 0 to 90 wt% of polymer PA, as described above. The amount of RMA crosslinkable composition in said composition further comprising polymer PR (solids) is preferably at least 20 wt. -%, more preferably at least 30 wt. -%, most preferably at least 50 wt. -%, based on the total weight (solids) of RMA crosslinkable composition and polymer PR, and optionally polymer PA. The amount of RMA crosslinkable composition in the composition further comprising polymer PR (solids) and optionally polymer PA is preferably not more than 90 wt. -%, more preferably not more than 75 wt. -%, most preferably not more than 70 wt. -%, based on the total weight (solids) of the RMA crosslinkable composition and polymer PR and optionally polymer PA. The present invention therefore also relates to coating compositions comprising from 65 to 99% by weight, preferably from 65 to 70% by weight, of component P and from 1 to 35% by weight of a RMA crosslinkable composition as described above.

In this embodiment, the total amount of RMA crosslinkable composition (total solids of component a, component B, catalyst C and optional reactive moderator D) and polymer PR (solids) and optional polymer PA in said composition is generally at least 10 wt.%, preferably at least 15 wt.%, and this amount preferably does not exceed 70 wt.%, more preferably does not exceed 50 wt.%, most preferably does not exceed 40 wt.%, and the composition further preferably comprises 20 to 90 wt.%, more preferably 50 to 85 wt.% of one or more solvents, and optionally one or more additives as described above for the binder component P and/or RMA crosslinkable composition. Combinations of different embodiments, in particular combinations of the preferred embodiments described above, are part of the present invention.

The coating systems of the present invention are typically used to prepare coatings on substrates. The present invention therefore also relates to a process for coating a substrate, in which a coating system as described above is applied to the substrate. The invention more particularly relates to a method of coating a substrate, wherein the binder component P is applied in one or more layers on the substrate, and then a layer of the RMA crosslinkable composition is applied on said one or more layers.

The invention also relates to the use of the binder component P as a primer on a substrate for improving the adhesion of RMA crosslinkable coatings, and to a method for coating a substrate with the coating system according to the invention.

The invention also relates in particular to a process for applying a RMA crosslinked coating on a substrate, comprising the steps of:

a) a layer comprising the binder component P as described above is applied to the substrate surface, preferably with a dry film thickness of at least 10 μm, more preferably from 20 to 50 μm,

b) at least partially drying the layer, preferably at a temperature of 10-50 ℃, more preferably at ambient conditions,

c) optionally repeating steps a) and b),

d) optionally grinding the layer obtained in step b) and/or c),

e) applying at least one layer (preferably a top coat) of a RMA crosslinkable coating composition on the layer obtained after step b), c) or d),

f) curing the RMA crosslinkable coating, preferably at a temperature of 10-50 ℃, more preferably at ambient conditions.

The invention further relates to a method for coating a substrate, preferably a wood substrate, comprising the steps of:

a) component P is mixed with the RMA crosslinkable composition as described above,

b) applying a layer comprising a mixture of the component P and a composition crosslinkable by RMA, preferably having a dry film thickness of at least 10 μm, more preferably from 20 to 50 μm,

c) at least partially curing the layer, preferably at ambient conditions,

d) optionally repeating steps b) and c),

e) optionally grinding the layer obtained in step c) and/or d),

f) Optionally applying a top coat, optionally an RMA crosslinkable composition and curing said top coat on the layer obtained in step c), d) or e).

The coating system of the present invention can be applied to a variety of substrates, and in particular the substrates can be pre-coated with one or more additional coating layers. Suitable substrates are metal, especially steel substrates, including all types of pretreated steel, such as galvanized, zinc (galvanized) and phosphated steel, aluminum substrates, including chromium-treated and non-chromium-treated aluminum; more heat-sensitive substrates, such as plastic substrates, in particular ABS substrates, polycarbonate substrates, ABS/polycarbonate substrates, glass fibres and carbon fibre reinforced plastics or composites, SMC (sheet moulding compounds), for example combinations of polyesters and glass fibres, in particular those for automotive applications, poly (ethylene terephthalate), poly (butylene terephthalate), polyamide 6, polyamide-6.6, (thermoplastic) polyolefins, poly (vinyl chloride), poly (methyl methacrylate) and polystyrene. The coating system may also be applied to multi-substrate assemblies consisting of metal and/or plastic parts with various pre-treatments and/or coatings, including those described above. According to a variant of the invention, the substrate may be coated with one or more polymeric PAs as described above, before coating with one or more layers of component P comprising polymer PR and optionally polymeric PA and then with one or more layers of RMA composition. Alternatively, the substrate may be coated with one or more polymers PA as described above before being coated with one or more coating compositions comprising 5-95 wt% of polymer PR and 5-95 wt% of RMA crosslinkable composition (total solids of component a, component B, catalyst C and optional reactive moderator D) and optionally 0-90 wt% of polymer PA.

Particularly suitable substrates are the so-called acidic substrates, such as unsaturated polyester putties and wood. The substrate is preferably wood or a wood composite, such as oak, mahogany and nut wood.

According to a particular embodiment of the invention, the substrate is sanded prior to application of the layer of binder component P and/or after at least partial drying of the layer of binder component P prior to application of the RMA coating composition.

In one embodiment of the present invention, the primer layer obtained from the binder component P is only partially cured when a layer of RMA crosslinkable coating composition is applied. This not only saves time, but also improves adhesion with subsequently applied RMA crosslinkable coatings. It may be advantageous to have at least some degree of cure in view of the coating appearance. The degree of cure of the partial cure can be determined by the skilled person, for example by taking less time than normal for full cure, and the conversion of the functional groups can be measured, for example, by spectroscopic techniques.

The curing temperature for both the binder component P and the RMA crosslinkable coating and the mixture of both can be much higher than ambient conditions, but a particular advantage of this coating system is that it can be cured at ambient conditions. The curing temperature may thus be between 0 and 100 ℃ but is preferably between 10 and 70 ℃ and more preferably between 10 and 50 ℃. Primer curing is typically carried out at ambient conditions, drying/curing overnight, i.e., 10 minutes to 20 hours. However, rapid curing can be achieved by forced drying at high temperatures.

The invention further relates more particularly to a process for coating a substrate, wherein a coating composition comprising a crosslinkable composition of a binder component P and RMA as described above is applied to the substrate and then cured. The curing temperature may be between 0 and 100 ℃ but is preferably between 10 and 70 ℃ and more preferably between 10 and 50 ℃.

The layer comprising the RMA crosslinkable composition may not be a top coat (top coat) and may also be coated with a further coating layer. Preferably, the RMA coating is a top coat, especially when a blocked catalyst such as a carbon dioxide blocked latent base catalyst is used.

In the different coating methods of the invention it is clear that more than one layer of the binder component P and/or RMA crosslinkable composition and/or mixtures thereof can be applied.

The coating system of the invention allows coated substrates to be obtained having particularly good adhesion, mechanical and chemical properties such as hardness and chemical resistance. Furthermore, the binder component P in the coating system of the present invention facilitates improved drying of the RMA crosslinkable composition of the present invention. In addition, the coated substrates have good appearance and durability and weatherability. The present invention also relates to a coated substrate comprising at least one layer formed from the coating system of any of the above embodiments.

Examples

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

Preparation of acrylic primer resin APR1

APR1 was prepared as follows: 1165.39g of butyl acetate, 19.31g of cumene hydroperoxide (90% in an aromatic solvent mixture), 6.08g of 2-hydroxyethyl methacrylate, 18.51g of lauryl methacrylate, 106.43g of methyl methacrylate and 3.07g of butyl acetate are charged into a pressure reactor and heated to 135 ℃ to a pressure of 1.5bar (absolute). Subsequently, 54.69g of 2-hydroxyethyl methacrylate, 166.63g of lauryl methacrylate, 957.87g of methyl methacrylate and 27.6g of butyl acetate were added over 60 minutes. After flushing with 56.79g of butyl acetate, the reaction temperature was kept at 135 ℃ for 3 hours. Then the6.82g of tert-butylperoxy-3, 5, 5-trimethylhexanoate in 6.82g of butyl acetate were added to the mixture above, followed by rinsing with 56.79g of butyl acetate. After 1 hour of reaction at 135 ℃, the reaction mixture was cooled to 90 ℃ and the resin was diluted with 1147.21g of butyl acetate, and the product was then filtered through a 10 μm filter bag. APR1 has the following characteristics: GPC M_n＝12,000g/mol，M_w60,000g/mol, acid value 0.3mgKOH/g, non-volatile content 35.6 wt%, viscosity 2.9Pa.s at 23 ℃, T _g＝62℃。

Acrylic resin APR2 was prepared in a similar manner to resin APR1, but using xylene as the solvent instead of butyl acetate. The properties of the resin are shown in Table 3.

Preparation of acrylic primer resin APR3

APR3 was prepared as follows: in the emulsion polymerization reactor, 362.1g of Methyl Ethyl Ketone (MEK) was charged and heated under reflux (86 ℃ C.). A monomer pre-emulsion was prepared by adding the following raw materials to a feed tank: 774.8g of n-vinyl-2-pyrrolidone (VP), 258.3g of Ethyl Acrylate (EA) and 13.0g of MEK. The feed was emulsified until a stable solution was obtained. A separate solution of 2.03g of initiator azo-bis-methylbutyronitrile (AMBN) and 103.2g of MEK was prepared in a separate metering vessel. The monomer and initiator solutions were added simultaneously to the reactor over 3 hours. During the polymerization, the reflux temperature rose to 88 ℃. The metering vessel of monomer was rinsed with 51.7g of MEK and the initiator vessel was rinsed with 9.7g of MEK. After rinsing, three subsequent doses of 2.4g of AMBN dissolved in 4.8g of MEK were added at 30 minute intervals. The metering vessel was then rinsed with 3.3g of MEK, the reaction mixture was cooled to room temperature, and the product was further diluted with MEK to obtain a final solid content of 50 wt%. APR3 has the following characteristics: GPC Mn is 1,800g/mol, Mw is 6,100g/mol, acid number is 0.3mgKOH/g, nonvolatile content is 50.0 wt%, Tg is 95 ℃.

Preparation of acrylic primer resin WAPR1

The waterborne acrylic primer resin WAPR1 was prepared as follows: in the emulsion polymerization reactor, 146.1g of Methyl Ethyl Ketone (MEK) was charged and heated under reflux (86 ℃ C.). A monomer pre-emulsion was prepared by adding the following raw materials to a feed tank: 312.6g of n-vinyl-2-pyrrolidone (VP), 104.2g of Ethyl Acrylate (EA) and 5.2g of MEK. The feed was emulsified until a stable solution was obtained. A separate solution of 0.82g of initiator azo-bis-methylbutyronitrile (AMBN) and 41.7g of MEK was prepared in a separate feed vessel. The monomer and initiator solutions were added simultaneously to the reactor over 3 hours. During the polymerization, the reflux temperature rose to 88 ℃. The metering vessel of monomer was rinsed with 20.9g of MEK and the initiator vessel was rinsed with 3.9g of MEK. After rinsing, three subsequent doses of 0.98g of AMBN dissolved in 2.0g of MEK were added at 30 minute intervals. The metering vessel was then rinsed with 31.3g of MEK, the reaction mixture was cooled to 75 ℃ and 269.6g of demineralized water were added to the mixture. Subsequently, the mixture of water and MEK was distilled off until the temperature reached 95 ℃. A solution of 1.55g of AMBN in 2.0g of MEK was added and the reaction mixture was held at 95 ℃ for 3 hours. Then 204.7g of demineralized water were added and vacuum distillation was carried out until the MEK content was < 0.1%. Additional water was added to obtain a final solids content of 50% and the product was cooled to room temperature. The WAPR31 has the following characteristics: GPC Mn was 12,600g/mol, Mw was 51,300g/mol, acid number was 0.2mg KOH/g, water content (Karl-Fisher) was 49.7%, Tg was 100 ℃.

Preparation of malonate polyester MPE1

MPE1 was prepared as follows: 629.6g of neopentyl glycol, 433.3g of hexahydrophthalic anhydride and 0.43g of butylstannoic acid were fed into a reactor equipped with a distillation column filled with Raschig rings. The mixture was polymerized to an acid value under nitrogen at 240 ℃<1mg KOH/g. The mixture was cooled to 130 ℃ and 585.2g of diethyl malonate was added. The reaction mixture was heated to 170 ℃ and ethanol was removed under reduced pressure. The resin was then cooled and diluted with butyl acetate to 85% solids to give an OH number of 16mg KOH/g, GPC M_n1750g/mol and a malonic acid equivalent of 350g/Eq (active C-heqw 175 g/Eq). All mentioned AV, OHV and EQW values were determined on the basis of solid resins.

Preparation of malonate polyester MPE2

MPE2 was prepared as follows: 382g of neopentyl glycol, 262.8g of hexahydrophthalic anhydride and 0.2g of butyl stannoic acid were fed to a reactor equipped with a distillation column filled with Raschig rings. The mixture was polymerized under nitrogen at 240 ℃ to an acid number <1mg KOH/g. The mixture was cooled to 130 ℃ and 355g of diethyl malonate were added. The reaction mixture was heated to 170 ℃ and ethanol was removed under reduced pressure. When the viscosity at 100 ℃ reached 0.5Pa.s, the material was cooled to 140 ℃ and 11.2g of solid succinimide was added. The mixture was stirred until all the succinimide was dissolved. The resin was further cooled and diluted to 85% solids with butyl acetate.

Preparation of malonate polyester MPE3

MPE3 was prepared as follows: 434.3g of neopentyl glycol, 183.2g of hexahydrophthalic anhydride, 82.7g of trimethylolpropane, 72.3g of coconut oil and 0.33g of butylstannoic acid are introduced into a reactor equipped with a distillation column filled with Raschig rings. The mixture was polymerized under nitrogen at 240 ℃ to an acid value <1 mgKOH/g. The mixture was cooled to 130 ℃ and 486g of diethyl malonate and 51.7g of ethyl acetoacetate were added. The reaction mixture was heated to 170 ℃ and ethanol was removed under reduced pressure. The resin was then cooled and diluted to 83.5% solids with butyl acetate to give a material with an OH number of 75mg KOH/g, GPC Mn of 1630g/mol, malonic acid equivalent of 395g/Eq (active C-H EQW 198g/Eq) and acetoacetate equivalent of 3014g/Eq (active C-H EQW 1507 g/Eq).

Preparation of malonate polyester MPE4

MPE4 was prepared as follows: 1519g of neopentyl glycol, 640.5g of hexahydrophthalic anhydride, 289.1g of trimethylolpropane, 253.1g of coconut oil and 1.10g of butylstannoic acid are introduced into a reactor equipped with a distillation column filled with Raschig rings. The mixture was polymerized under nitrogen at 240 ℃ to an acid number <1mg KOH/g. The mixture was cooled to 130 ℃ and 1700g of diethyl malonate and 180.6g of ethyl acetoacetate were added. The reaction mixture was heated to 170 ℃ and ethanol was removed under reduced pressure. The resin was then cooled to 120 ℃ and 53.2g of succinimide was added. The mixture was stirred until all the succinimide was dissolved. The resin was further cooled and diluted with butyl acetate to 82.6% solids to give a material with an OH number of 69mg KOH/g, GPC Mn of 1570g/mol, malonic acid equivalent weight of 397g/Eq (active C-heqw 199g/Eq) and acetoacetate equivalent weight of 3048g/Eq (active C-heqw 1524 g/Eq).

Preparation of malonate polyester MPE5

MPE5 was prepared as follows: 365.9g of neopentyl glycol (NOP), 391.9g of hexahydrophthalic anhydride (HHPA), 38.1g of Trimethylolpropane (TMP), 276.9g of isosorbide (IsoS) and 0.4g of butylstannoic acid (BSA) were introduced into a glass round-bottom reactor equipped with a distillation column filled with Raschig rings. The mixture was brought to a negative pressure of 100mbar while purging with a stream of nitrogen for 5 minutes, and subsequently brought to atmospheric pressure with nitrogen. This vacuum-nitrogen cycle was repeated 3 times. Thereafter, the mixture was heated to obtain a stirrable slurry, and then subjected to three additional vacuum-nitrogen cycles. Then, the temperature was raised to a maximum of 240 ℃ and the monomer mixture was polymerized while distilling off the condensed water under a nitrogen stream to an Acid Value (AV) <1mg KOH/g. The mixture was then cooled to 120 ℃ and 346.0g of diethyl malonate (DEM) and 122.9g of ethyl acetoacetate (EtAcac) were added. The reaction mixture was heated to 170 ℃ and ethanol was removed under a nitrogen flow first at atmospheric pressure and then under reduced pressure. The resin was then cooled and diluted with butyl acetate to 82.2% solids to give a material with an OH number (OHV) of 79mg KOH/g, GPC Mn of 1400g/mol, malonate active CH equivalent weight (EQW) of 301g/Eq, and acetoacetate CH EQW of 688 g/Eq. The total active CH EQW was 209 g/Eq.

Composition of catalyst C

Catalyst C consisted of 43.7g of aqueous tetrabutylammonium hydroxide solution (55%), 19.7g of diethyl carbonate, 31.8g of n-propanol and 4.8g of water.

Determination of the molecular weight and molecular weight distribution by GPC

Molecular weight and molecular weight distribution are determined by gel permeation chromatography using polystyrene standards, more specifically using size exclusion chromatography, according to ASTM D3593. The size exclusion apparatus used was an Alliance system (Degasys DG-1210 from Uniflows) consisting of a pump, autosampler and He degasser equipped with a PLgel 5 μm MIXED-C600 X7.5mm column and a PLlgel 5 μm guard column (50X 7.5mm-Polymer Laboratories). The column oven (Separations Analytical Instruments) was set at 30 ℃. Tetrahydrofuran (THF-Extra Dry, Biosolve 206347) + 2% acetic acid (Baker 6052) was used as eluent at a flow rate of 0.8 ml/min. Carbon disulfide (baker) was used as the marker. A Waters 410 refractometer was used as the detector. The injection volume was 100. mu.l, the concentration was 1.5 mg/ml. Polystyrene standards (Polymer Laboratories, Easical PS-1,2010-0501(M range 580g/mol-8,500,000g/mol) and Easical PS-2,2010-0601(M range 580g/mol-400,000g/mol)) were used for calibration using a third order polynomial. The software used for data analysis was empower (waters). In the graph of eluted weight fraction versus molecular weight thus obtained, Mn is the molecular weight at which 50% of the molecules have eluted and Mw is the molecular weight at which 50% of the total mass has eluted.

Measurement of glass transition temperature (Tg) by DSC method

The glass transition temperature Tg was determined according to DEN EN ISO 16805 and ISO 11357 using a Mettler DSC 822E calorimeter. First 7-12mg of the sample was heated to a temperature well above Tg at 120 ℃. This temperature was held for 5 minutes and then the temperature was reduced to at least 60 ℃ below the expected Tg in 10 minutes. Subsequently, the sample was heated to 120 ℃ at a ramp rate of 10 ℃/min. Tg is the temperature at the intersection of the baseline tangent and the maximum negative slope tangent in the heat flow versus temperature graph.

Acid number is measured according to method ASTM D1639-70.

Hydroxyl number is measured according to method ASTM E222-17.

General procedure for preparing RMA crosslinkable compositions

Malonate containing polymers or polymer mixtures (e.g. MPE1-MPE5 RMA crosslinkable component a as described above) are mixed with ditrimethylolpropane tetraacrylate (ditmtpta, RMA crosslinkable component B) and optionally with reactive moderator D (e.g. succinimide, 1,2, 4-triazole, ethyl acetoacetate), solvent (e.g. n-propanol, butyl acetate) and optionally pigments or other coating additives (e.g. flow and leveling additives, dispersants, uv stabilizers, defoamers etc.) and stirred until a homogeneous coating composition is obtained. All the mentioned formulations are activated by addition of catalyst C before application as a coating.

TABLE 1 RMA compositions

Examples 1 to 4

The acrylic resin APR1 was diluted to obtain a 20 wt% butyl acetate solution (examples 1 and 2) or a 30 wt% butyl acetate solution (examples 3 and 4). The solution was bar coated onto an oak veneer substrate board with a wet layer thickness of 125 μm and then dried under ambient conditions. The APR1 primer was sanded after 25 minutes and the RMA compositions (varnishes) D and E shown in Table 1 were bar-coated thereon to a wet layer thickness of 125 μm. The RMA varnish was dried under ambient conditions.

The adhesion of the coating system is measured according to the cross-hatch adhesion test of the protocol ISO/DIN 2409, ASTM D3359. The ratings are briefly as follows:

0: the cut edges were completely smooth, and none of the tetragonal lattices appeared to peel.

1: there was little coating flaking at the notch intersections, but the affected cross-hatched area was less than 5%.

2: the coating was peeled off at the intersection of the edge of the cut and the cut, and the area of the affected scribe was 5-15%.

3: the coating is partially or completely stripped in long strips along the edges of the cut, and/or partially or completely stripped in the square grids, and the affected grid area is 15-35%.

4: the coating is stripped along the edges of the cut in strip shape, and the same tetragonal lattice is partially or completely stripped. The area of the affected cross section is 35-65%.

5: the flaking condition is worse than 4.

Exfoliation or separation refers to delamination due to poor adhesion.

The drying of the RMA coating was evaluated with cotton balls according to the so-called TNO method. The degree of dryness was evaluated by dropping the cotton ball on the coated surface and leaving the cotton ball 10 seconds after applying a weight load of 1kg on the cotton ball. Drying is considered complete if no cotton balls remain stuck to the surface after blowing off the cotton balls, and incomplete if the cotton remains stuck to the surface.

The results are shown in Table 2.

TABLE 2 adhesion of coating systems consisting of RMA varnish compositions D and E to the primer APR1

Examples 5 and 6 and comparative examples 7R-13R

RMA crosslinkable composition E was applied as described in example 2 to a series of commercially available solvent-borne acrylic resins having the properties listed in table 3, applied to a veneer substrate at a wet layer thickness of 80 μm. The acrylic resin was applied at the non-volatile (NV) level listed in Table 3.

TABLE 3 Properties of solvent-borne acrylic resins

Drying and adhesion evaluation of RMA coatings were as described above and shown in table 4.

In addition, the RMA composition was applied directly to an oak veneer substrate without an acrylic primer layer (comparative example 13R).

TABLE 4

n/a is not suitable because of incomplete drying

It can be seen that acrylic resins having properties not in accordance with the claimed invention do not achieve satisfactory drying and adhesion simultaneously.

Examples 14-19 and comparative examples 20R-22R

In analogy to example 1, RMA compositions E, F and G were applied as a 50 μm wet top coat over the as-received substrates (comparative examples 20R, 21R and 21R) or over the substrates primed with acrylic APR 1.

The adhesion results obtained are listed in table 5.

TABLE 5

Examples	Primer APR 1-Wet layer thickness	RMA compositions	Adhesion force
				20R	Is free of	E	5
21R	Is free of	F	5
				22R	Is free of	G	5
14	50μm	E	0
				15	50μm	F	0
16	50μm	G	0
				17	80μm	E	0
18	80μm	F	0
				19	80μm	G	0

Examples 23 to 34 and 35 to 46

A blend of RMA crosslinkable composition comprising acrylic resin APR2 and 57/43 (by weight) mixture comprising MPE1 and MPE2 resulted in a 0.8 equivalent succinimide content per equivalent catalyst. Furthermore, the RMA crosslinkable composition comprises 2 catalyst equivalents of 1,2, 4-triazole as an additional reactivity moderator. DiTMPTA was used as the RMA acceptor with a donor/acceptor ratio of 1/1. In tables 7 and 8, the ratio between APR2 and RMA crosslinkable composition is expressed on a solid resin basis. The resin mixture was diluted to the solid content of the hybrid primer described in the table.

Table 7. composition crosslinkable by hybrid primer APR2 with RMA: data for 1 layer of the hybrid primer on oak

Excellent, + is good, +/-is good, unqualified, -is poor

In examples 35-46 shown in Table 8, a second layer of a blend of primer APR2 and an RMA composition was applied over the first layer.

Table 8: hybrid primer APR2 and RMA crosslinkable composition: data for 2 layers of the hybrid primer on oak

Excellent, + is good, +/-is good, unqualified, -is poor

The above results show that the blend of 45/55APR2/RMA composition provides the best performance compromise.

In another set of experiments, a first layer of a hybrid primer as described in examples 23 to 34 was topcoated with RMA varnish E (as described in table 1) and applied on different wood materials: oak, mahogany, and nut.

The topcoat has excellent adhesion as well as good hardness and chemical resistance.

Examples 48 to 52 and comparative examples 47R and 53R

In these examples, APR2 was mixed with vinylpyrrolidone-containing polymer APR3 in the proportions shown in table 9.

The sealant mixture thus obtained was bar-coated in one or two layers (wet thickness 100 μm; dry thickness 18 μm each) on the highly acidic substrates pterocarpus and Unsaturated Polyester (UP) putty, dried under ambient conditions, and then the RMA composition according to composition F (table 1) was spray-coated thereon in one layer and dried under ambient conditions.

For comparison, the results obtained by applying the RMA composition directly onto a substrate are also reported (comparative example 47R-no sealant).

TABLE 9

Excellent, + is good, +/-is good, unqualified, -is poor

As can be seen from the results in table 9, APR2 (example 48) greatly improved the drying of RMA crosslinkable varnish applied on the sealant layer.

Blending APR2 with APR3 (examples 49-52) further improves the drying properties of RMA crosslinkable varnishes, especially at APR3/APR2 ratios below 85/15 (example 52).

Example 55 and comparative example 54R

The aqueous sealant WAPR1 was applied to an acidic substrate: oak and water-based primers.

On oak wood, 1 layer (wet film thickness 125 μm, dry film thickness 31 μm) of WAPR1 was applied, diluted with water to a solids content of 25%. On this layer of WAPR1, RMA crosslinkable composition D was applied and evaluated for drying.

As can be seen from table 10, the WAPR1 greatly improved the drying of RMA crosslinkable compositions applied on the sealant compared to systems without sealant applied on oak (comparative example 54R).

On the aqueous primer, one or two layers of WAPR1 (wet film thickness 30 μm each, dry film thickness 15 μm) were applied. On top of this WAPR1 layer, RMA crosslinkable composition F was applied and evaluated for drying.

As can be seen from table 10, the WAPR1 greatly improved the drying of the RMA crosslinkable composition applied on the sealant compared to the system without the sealant applied on the WB primer.

Watch 10

Excellent, + is good, +/-good, -off-good, -bad.