RU2789029C2 - Covering composition of powder material - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: group of inventions relates to a covering composition of powder material, which can be cured at low temperatures, to a method for the manufacture of such compositions, to a method for coating of products, using mentioned compositions, and to the resulting coated products. The covering composition of powder material contains one or more cross-linked components and a catalyst, where one or more cross-linked components are cross-linked using a real Michael addition (hereinafter – RMA) reaction. In this case, the powder covering composition contains: a) cross-linked component A having at least 2 acid donor groups C-H in activated methylene or methine, b) cross-linked component B having at least 2 activated unsaturated acceptor groups C=C, which react with component A of RMA reaction, forming a cross-linked mesh, c) latent catalyst system C containing a precursor of a strong base for catalysis of RMA crosslinking reaction with a delay at a curing temperature below 200°C. The catalyst system C is a latent catalyst system LCC having chemical latency, containing components, which react at the curing temperature to initiate a delayed reaction between cross-linked components A and B. Moreover, the mentioned latent catalytic system LCC contains, in LCC1 implementation option: a) weak base C2, b) activator C1 reacting with C2 or protonated C2 at the curing temperature, where the activator C1 is selected from a group containing epoxy, carbodiimide, oxetane, oxazoline, or aziridine functional components, preferably epoxy or carbodiimide. The system contains, in LCC2 implementation option: a) weak base C2, which is a donor S2 in the Michael reaction, and b) activator C1, which is an acceptor S1 in the Michael reaction, containing an activated unsaturated group C=C, reacting with S2 at the curing temperature, wherein, in case if S1 is acrylate, S2 has pKa of conjugate acid below 8, wherein pKa is defined as a value in an aqueous medium, and, in case if S1 is methacrylate, fumarate, itaconate, or maleate, S2 has pKa of conjugate acid below 10.5. A method for preparation of a covering composition of powder material, a method for coating of substrate of powder material, products coated with a powder composition, the use of a catalyst system C for catalysis of a crosslinking reaction in RMA crosslinking coating compositions of powder material at curing temperatures below 200°C, RMA crosslinking polymer, and its use in RMA crosslinking coatings of powder material, polymer containing groups of weak base C2, and its use as a latent main component of a catalyst of a covering composition of powder material are also described.

EFFECT: provision of a powder coating composition, which is cured at low temperatures with a high curing rate to obtain acceptable short curing times, but nevertheless with a sufficiently long film setting time at edges to ensure fluidity and coalescence, as well as to achieve good film formation with a good coating appearance.

24 cl, 15 tbl, 37 ex

Description

BACKGROUND OF THE INVENTION

[0001] The present invention relates to powder material coating compositions that can be cured at low temperatures, to methods for making such compositions, to methods for coating articles using said compositions, and to resulting coated articles. The present invention also relates to specific polymers and catalyst systems for use in powder coating compositions.

DESCRIPTION OF THE PRIOR ART

[0002] Powder material coatings are dry, finely divided, free-flowing solid materials at room temperature that have gained higher popularity than liquid coatings in recent years. Powder coatings are typically cured at elevated temperatures between 120°C and 200°C, most commonly between 140°C and 180°C. High temperatures are required to ensure sufficient binder flow to allow film formation and good surface appearance of the coating, as well as to achieve high reactivity for the crosslinking reaction. At low curing temperatures, reaction kinetics can be encountered that do not allow short curing times to be achieved when full development of mechanical and resistance properties is required; on the other hand, for those systems in which high reactivity of the components can be created, the coatings may have a poor appearance due to the relatively high viscosity of such systems at these lower temperatures, which increases rapidly as the curing reaction progresses: integrated over time the fluidity of such systems is too low to achieve sufficient alignment (see, for example, Progress in Organic Coatings, 72 page 26-33 (2011)). Especially when making thin films, the appearance can be limiting. In addition, very high reactivity can lead to problems due to premature reaction during the formation of powder paints in the extruder.

[0003] Because of this temperature limitation, powder coatings are not easily used when coating heat sensitive substrates such as medium density fibreboard (MDF), wood, plastics, and some metal alloys. Development continues to lower cure temperatures with a focus on green technologies and the associated reduction in energy costs and the ability to coat temperature sensitive substrates. Low temperature curing powder coatings also have an advantage when applied to heavy metal components because such components heat up slowly.

[0004] Recently, many efforts have been made to find powder coatings that cure at a lower temperature. Accordingly, the term "lower" temperatures in the field of powder coatings usually means a temperature well above room temperature, but less than 160°C, preferably less than 150°C, more preferably less than 140°C, and even more preferably less than 130 °C or even below 120°C. In general, it has been found difficult to achieve high enough reactivity to obtain the film crosslink density required for its effectiveness within an acceptable cure time window when using low cure temperatures, typically below 150°C, and especially at or below 140°C. so as to achieve suitable chemical resistance, mechanical properties such as impact resistance, flexibility, surface hardness and weather resistance, and at the same time also achieve good fluidity and coating appearance.

[0005] There are systems that cure at very low temperatures in the range of 120-130°C. These are typically epoxy cured polyester systems (eg triglycidyl isocyanurate (TGIC)). Typically, such systems suffer from unsatisfactory appearance and are used only to create textured coatings. Appearance can be improved by using lower Tg powders (requiring refrigeration) or developing powder coatings with crystalline components that melt between Tg and cure temperature, but both approaches present challenges.

[0006] Another approach to achieve low temperature curing of powder coatings is to use ultraviolet initiated radical curing for crosslinking. This makes it possible to combine low temperature curing and good appearance with limited curing time; however, this approach suffers from disadvantages such as the need for a radiation curing facility, non-uniform irradiation of complexly shaped substrates, potential problems with limited penetration depth into pigmented systems, and relatively high costs associated with binders and photoinitiators.

[0007] A common problem with the prior art crosslinkable low temperature curable compositions described is that the cure rate is slow, or that if the cure rate is higher, the resulting coating appearance is unsatisfactory and can create complications during extrusion molding. , or that components are used that are expensive or less environmentally desirable. Combining all requirements requires a system that inherently has the required level of reactivity and whose curing kinetics can be controlled to a high degree of detail to provide good appearance combined with a full improvement in chemical and mechanical resistance at complex combinations of cure time, cure temperature. and film thickness.

[0008] Therefore, there is still a need for a powder coating composition that can be cured at low temperatures at a high cure rate to give acceptable short cure times, but still with a sufficiently long set time at the edges to allow flow and coalescence, as well as to achieve good film formation with a good coating appearance. The film setting time at the edges refers herein to the time at the curing temperature before the course of the reaction increases the viscosity to such an extent that further ink flow becomes negligible.

SUMMARY OF THE INVENTION

[0009] The present invention solves one or more of these problems by providing a coating composition of powder material containing one or more crosslinkable components and a catalyst, characterized in that one or more crosslinkable components are crosslinked using a Michael reaction (Michael addition reaction) ( RMA), and this composition contains

a. a crosslinkable component A having at least 2 C-H acid donor groups in activated methylene or methine,

b. a crosslinkable component B having at least 2 activated unsaturated C=C acceptor groups that react with component A of the Michael reaction (RMA) to form a crosslinked network,

With. a latent catalyst system C containing a strong base or a strong base precursor to catalyze the RMA crosslinking reaction with some delay at a curing temperature below 200°C, preferably below 175°C, more preferably below 150°C, 140, 130 or even 120°C, and preferably at least 70°C, more preferably at least 80, 90 or 100°C,

wherein catalyst system C is a latent catalyst system LC selected from the group consisting of

a. a latent LCC catalyst system having a chemical latency containing components that react at a curing temperature to initiate a delayed reaction between crosslinkable components A and B, said latent LCC catalyst system comprising

in the LCC1 embodiment:

a) weak base C2,

b) C1 activator reacting with C2 or protonated C2 at curing temperature,

c) optionally a C3 acid, preferably a protonated C2;

in the LCC2 embodiment:

a) a weak base C2, which is an S2 donor in the Michael reaction, and

b) C1 activator, which is an S1 Michael acceptor and contains an activated unsaturated group C=C, reacting with S2 at the curing temperature,

c) optionally a C3 acid which is an S3 acid in which the corresponding base is also a Michael reaction donor, preferably a protonated S2,

and

when S1 is an acrylate, S2 has a conjugate acid pKa below 8, preferably below 7, and more preferably below 6, pKa being defined as a value in an aqueous medium, and

when S1 is methacrylate, fumarate, itaconate or maleate, S2 has a pKa of the conjugate acid below 10.5, preferably below 9, and more preferably below 8;

or combinations of embodiments LCC1 and LCC2,

b. a latent LCE catalyst system having an evaporative latency, comprising a base blocked by a volatile acid or a weak base which, when protonated, produces a volatile acid that evaporates at the curing temperature, and preferably additional free volatile acid.

c. a latent LCP catalyst system having a physical latency in which a catalyst system, preferably a strong base or a latent catalyst system, is present that is physically separated and not available for chemical reaction in the powder at or below the compounding temperature, and that is available for chemical reaction at the curing temperature, and this system is preferably selected from

a) a latent catalyst system LCP1 comprising a strong base catalyst having a melting point below the curing temperature and above the compounding temperature, preferably above 70, 80, 90 or 100°C, or

b) a latent LCP2 catalyst system containing an active strong base catalyst that is encapsulated or mixed with a material that releases the catalyst at a temperature below the curing temperature and above the compounding temperature, which material preferably has a melting temperature or, in the case of an amorphous material, a glass transition temperature below curing temperature and above the compounding temperature,

c) a latent LCP3 catalyst system containing a photogenerating base component that releases base when irradiated with a suitable wavelength,

or combinations of LCC, LCE and LCP catalyst systems.

[0010] The present inventors have found that the RMA powder coating composition is highly suitable for powder coatings that can be cured at low temperatures with a relatively high cure rate, acceptable short cure times, but still with a sufficiently long setting time. films around the edges to ensure film formation and achieve good crosslinking with good coating appearance using any of the latent base catalyst systems described in more detail below.

[0011] In another aspect, the present invention relates to a process for preparing a coating composition from a powder material in accordance with the present invention and to a method for coating a substrate with a powder material. In this method, the curing temperature Tcur is selected between 75 and 200°C, preferably between 80 and 180°C, and more preferably between 80 and 160, 150, 140, 130 or even 120°C, and preferably also uses infrared heating. Cure is preferably characterized by a cure profile determined by measuring the C=C unsaturated bond conversion of component B versus FTIR time, in which the ratio of time to change the degree of C=C conversion from 20% to 60% to the time to achieve 20% conversion is less than 1, preferably less than 0.8, 0.6, 0.4 or 0.3, with preferably the time to reach 60% conversion is less than 30, 20, 10 or 5 minutes, and preferably the time to reach 20% conversion is at least 1, preferably at least 2, 3, 5, 8 or 12 minutes when cured at 100°C. Preferably the melt viscosity at the curing temperature is less than 60 Pa·s, more preferably less than 40, 30, 20, 10 or even 5 Pa·s. Melt viscosity can be measured, for example, with a Brookfield CAP 2000 cone rheometer according to ASTM D4287 using a #5 spindle, and should be measured at the very beginning of the reaction or on a coating composition of powder material without catalyst activity.

[0012] The coating composition of the powder material has the particular advantage that it can be used at low curing temperatures, and therefore, in the method of powder coating a substrate, preferably a temperature sensitive substrate, a curing temperature of 75 to 140°C is preferably used, preferably from 80 to 130 or 120°C, and most preferably 100 to 120°C. This allows the powder coating process to be used for temperature sensitive substrates, preferably MDF, wood, plastic, or for temperature sensitive metal substrates such as alloys. The present invention therefore also relates in particular to such articles coated with the powder composition according to the present invention. It has been found that good coating properties can be obtained with good XLD crosslink density.

[0013] In another aspect, the present invention relates to the use of the latent catalyst systems described herein for preparing crosslinkable RMA powder coating compositions to catalyze the crosslinking reaction in crosslinkable RMA powder coating compositions at cure temperatures below 200°C, preferably below 180 °C, more preferably below 160, 140, or even 120°C, and above 75, 80, 90 or 100°C.

[0014] In yet another aspect, the present invention relates to a crosslinkable RMA polymer and to the use of said crosslinkable RMA polymer in crosslinkable RMA powder coatings. This crosslinkable RMA polymer is a crosslinkable RMA donor polymer. This crosslinkable RMA polymer is preferably selected from the group consisting of acrylic, polyester, polyamide ether and polyether urethane polymers containing

a. one or more components A containing at least 2 acid donor groups C-H in activated methylene or methine in the structure Z1(-C(-H)(-R)-)Z2, where R is hydrogen, hydrocarbon, oligomer or polymer, and Z1 and Z2 are the same or different electron withdrawing groups, preferably selected from keto, ester, cyano or aryl groups, preferably activated C-H derivatives having the structure according to formula 1:

Формула 1

Formula 1

where R is hydrogen or optionally substituted alkyl or aryl, and Y and Y' are identical or different groups of substituents, preferably alkyl, aralkyl, aryl or alkoxy, or where in formula 1 the group -C(=O)-Y and/or - C(=O)-Y' are substituted by CN or aryl, not more than one aryl, or where Y or Y' may be -NRR' (R and R' are hydrogen or optionally substituted alkyl), but preferably not both, said component A is preferably a malonate, acetoacetate, malonamide, acetoacetamide or cyanoacetate group, and most preferably a malonate group providing at least 50%, preferably 60%, 70% or even 80% of the total C-H acid groups in the crosslinkable component A in which R , Y or Y' provide bonding to the polymer,

b. optionally one or more components B containing at least 2 activated unsaturated RMA acceptor groups, preferably acryloyl, methacryloyl, itaconate, citraconate, crotonate, cinnamate, maleate or fumarate functional groups forming an A/B hybrid polymer, and

With. optionally one or more components of catalyst system C,

in which the polymer

a. has a GPC number average molecular weight Mn of at least 450 g/mol, preferably at least 1000, more preferably at least 1500, and most preferably at least 2000 g/mol,

b. has a weight average molecular weight Mw determined by GPC of at most 20,000 g/mol, preferably at most 15,000, more preferably at most 10,000, and most preferably at most 7500 g/mol,

c. preferably has a molecular weight distribution Mw/Mn less than 4, and more preferably less than 3,

d. has an equivalent weight EQW in C-H of at least 150, 250, 350, 450 or 550 g/mol, and preferably at most 2500, 2000, 1500, 1250 or 1000 g/mol, and a number average functionality of C-H reactive groups of 1-25, more preferably 1.5-15, even more preferably 2-15, and most preferably 2.5-10 C-H groups per molecule,

e. preferably has a melt viscosity at a temperature in the range of 100-140°C less than 60 Pa·s, and more preferably less than 40, 30, 20, 10 or even 5 Pa·s,

f. preferably contains amide, urea or urethane linkages and/or contains monomers with a high Tg value, preferably cycloaliphatic or aromatic monomers, in particular polyester monomers selected from the group consisting of 1,4-dimethylolcyclohexane (CHDM), tricyclodecane dimethanol (TCD-diol) , isosorbide, penta-spiroglycol or hydrogenated bisphenol A and tetramethylcyclobutanediol,

g. has a Tg above 25°C, preferably above 35°C, more preferably above 40, 50 or even 60°C, which is determined by DSC at a heating rate of 10°C/min, or is a crystalline polymer with a melting point of 40-150° C, preferably 130°C, preferably at least 50 or even 70°C, and preferably lower than 150, 130 or even lower than 120°C (which is determined by DSC at a heating rate of 10°C/min).

DETAILED DESCRIPTION OF THE INVENTION

[0015] The present inventors have found that the RMA powder material coating composition of the present invention, compared to conventional powder material coating compositions, can be cured at relatively low temperatures with a high cure rate. The latent system of the main catalyst ensures the film setting time at the edges and good leveling at low temperatures. A latent catalyst system is a catalyst system that delays the initial stages of curing at the curing temperature. This delay is controlled by the choice of catalyst system components and selected for the specific combination of crosslinkable RMA A and B components chosen to provide the preferred cure profile as will be described below. The RMA crosslinking reaction between components A and B requires the presence of a base, commonly referred to herein as a "strong base". This strong base is a base capable of catalyzing RMA at Tcur. In the present invention, as will be explained in more detail below, such a strong base is created by means of a latent catalyst system C. This latent catalyst system C may be an LCC chemical latent system (LCC1 and/or LCC2), an LCE evaporative latent system, or an LCP physical latent system, or a combination of at least two of these systems.

[0016] In one preferred embodiment, the powder material coating composition has an LCC catalyst system with chemical latency. A suitable LCC1 catalyst system contains

in the LCC1 embodiment:

a) weak base C2,

b) C1 activator reacting with C2 or protonated C2 at curing temperature,

c) optionally a C3 acid, preferably a protonated C2;

[0017] Chemical latency is determined by the time required for the chemical reaction of the weak base C2 with the activator C1 or S1 and preferably with the inclusion of acid C3 to further increase the latency.

[0018] In one preferred embodiment, the powder material coating composition comprises a chemically latent LCC1 catalyst system in which

- the C1 activator is selected from the group containing epoxy, carbodiimide, oxitane, oxazoline or aziridine functional components, preferably epoxy or carbodiimide, and in which

- the weak base C2 preferably has a pKa of the conjugate acid greater than 1, preferably 1.5, more preferably 2, and even more preferably at least 3 units lower than the pKa of the C-H acid groups of the main component A, and in which C2 is preferred is a weak base nucleophilic anion selected from the group consisting of carboxylate, phosphonate, sulfonate, halide or phenolate anions, or salts thereof, or a nonionic nucleophile, preferably a tertiary amine, and more preferably a weak base C2 is a weak base nucleophilic anion selected from the group consisting of carboxylate, halide or phenolate salts or 1,4-diazabicyclo[2.2.2]octane (DABCO), and

- the latent catalyst system preferably also contains a C3 acid having a pKa greater than 1, preferably 1.5, more preferably 2 and even more preferably at least 3 units lower than the pKa of the C-H acid groups of the main component A, wherein the acid C3 is preferably protonated C2.

[0019] In one alternative embodiment, the powder material coating composition comprises a chemically latent LCC2 catalyst system comprising:

a) a weak base C2, which is an S2 donor in the Michael reaction, and

b) C1 activator, which is an S1 Michael acceptor and contains an activated unsaturated group C=C, reacting with S2 at the curing temperature,

c) optionally a C3 acid which is an S3 acid in which the corresponding base is also a Michael reaction donor, preferably a protonated S2,

and

when S1 is an acrylate, S2 has a conjugate acid pKa below 8, preferably below 7, and more preferably below 6, pKa being defined as a value in an aqueous medium, and

when S1 is methacrylate, fumarate, itaconate or maleate, S2 has a pKa of the conjugate acid below 10.5, preferably below 9, and more preferably below 8.

[0020] Combinations of LCC1 and LCC2 embodiments are also possible. Preferably, the powder material coating composition comprises an LCC2 latent catalyst system embodiment wherein

- the weak base S2 is preferably selected from the group of phosphines, N-alkylimidazoles and fluorides, or is the nucleophilic anion of the weak base X ^- from a compound containing an acidic XH group, in which X is N, P, O, S or C, in which the anion X ^- is a Michael reaction donor reactive with the S1 activator and characterized by a pKa value of the corresponding conjugated acid XH of less than 8, which is further greater than 1, preferably 1.5, more preferably 2, and even more preferably at least 3 units lower than the pKa values of the acid groups CH of the main component A, and

- the latent catalyst system preferably also contains an acid S3 having a pKa value that is greater than 1, preferably 1.5, more preferably 2 and even more preferably at least 3 units lower than the pKa values of the C-H acid groups of the main component A, wherein the acid S3 is preferably the protonated S2.

[0021] For the S3 components or their deprotonated S2 versions in the LCC2 embodiment, in order to be able to provide a suitable kinetic profile, it is important that the reaction of these components with the Michael acceptor groups can proceed at a suitable rate to avoid too rapid a reaction and to provide a significant curing delay under thermal conditions relevant for powder coatings. Finding an appropriate reactivity window requires selecting the appropriate combination of S3 XH (or S2 X ^- ) components and acceptor functional groups used in powder paint formulations.

[0022] Patent document WO2014/16680 describes compositions that are RMA crosslinkable using a combination of XH acid and ^an X ^- acid anion as catalyst C, the X- anion also being a Michael reaction donor reactive with component B. This document mentions the use in powders, however, it focuses on compositions solvent-cured at room temperature (22° C. according to the examples) and does not describe powder material coating compositions cured at high temperature (i.e. above room temperature or ambient temperature). For such solvent-cured room temperature solvent-cured compositions, combinations of acrylate acceptor groups with XH components have been reported using XH/X- components such ^as succinimide, 1,2,4-triazole and benzotriazole as a catalyst. However, it has been found that such combinations do not work for high temperature curing powder paint compositions because they do not provide the desired amount of delay because the ability of X ^- anions to react with acrylates is too high.

[0023] It has been found that for powder paint compositions containing acrylate acceptor groups, an LCC2 catalyst system can be used in which the S1 components are acrylate acceptor groups and the S2 and S3 components are X ^- /XH components having a pKa lower than 8, more preferably below 7, 6, or even 5.5. Examples of useful XH components for powder paint compositions containing an acrylate scavenger include cyclic 1,3-diones as 1,3-cyclohexanedione (pKa 5.26) and dimedone (5,5-dimethyl-1,3-cyclohexanedione, pKa 5.15), ethyltrifluoroacetoacetate (7.6) and Meldrum's acid (4.97). Preferably, XH components are used which have a boiling point of at least 175°C, more preferably at least 200°C.

[0024] Additionally, it has been found that for powder paint compositions containing methacrylate, fumarate, maleate, or itaconate acceptor groups, an LCC2 catalyst system can be used in which the S1 components are the acceptor groups listed above, preferably methacrylate, taconate, or fumarate groups, and components S2 and S3 are X ^- /XH components having an acid pKa below 10.5, more preferably below 9.5, 8, or even below 7.

[0025] Mentioned pKa values are water pKa values at ambient conditions (21°C). They can be easily found in the literature, and if necessary, determined in aqueous solution using procedures known to the person skilled in the art. The pKa values of the respective components are listed below.

Succinimide 9.5 Isatin 10.3 Ethosuximide 9.3 Uracil 9.9 Phthalimide 8.3 4-nitro-2-methylimidazole 9.6 5,5-dimethylhydantoin 10.2 Phenol 10.0 1,2,4-triazole 10.2 Ethyl acetoacetate 10.7 1,2,3-triazole 9.4 Ethyl cyanoacetate 9.0 Benzotriazole 8.2 Acetylacetone 9.0 Benzenesulfamide 10.1 1,3-cyclohexanedione 5.3 Nitromethane 10.2 Saccharin 2.0 Nitroethane 8.6 barbituric acid 4.0 2-nitropropane 7.7 Diethylmalonate 13.0

[0026] The most preferred C1 activator in the LCC1 embodiment is an epoxy group. Suitable choices for epoxide as the preferred C1 activator are cycloaliphatic epoxides, epoxidized oils and glycidyl type epoxides. Suitable C1 components are described in US4749728 column 3 lines 21-56 and include C2-18 alkylene oxides and oligomers and/or polymers having epoxy functionality, including multiple epoxy functionality. Particularly suitable alkylene oxides include 1,2-hexylene oxide, t-butyl glycidyl ether, phenyl glycidyl ether, glycidyl acetate, versatic esters of glycidyl esters, glycidyl methacrylate, and glycidyl benzoate. Useful multifunctional epoxides include bisphenol A diglycidyl ether, as well as higher homologues of BPA epoxy resins, diglycidyl adipate, 1,4-diglycidyl butyl ether, novolac glycidyl esters, dibasic acid glycidyl esters such as Araldite PT910 and PT912 (Huntsman), TGIC and other commercial epoxy resins. Bisphenol A diglycidyl ether, as well as its higher molecular weight solid homologues, are the preferred epoxides. Also useful are acrylic (co)polymers having epoxy functionality derived from glycidyl methacrylate. In one preferred embodiment, the epoxy components are oligomeric or polymeric components with a Mn of at least 400 (750, 1000, 1500). Other epoxy compounds include 2-methyl-1,2-hexene oxide, 2-phenyl-1,2-propene oxide (alpha-methylstyrene oxide), 2-phenoxymethyl-1,2-propene oxide, epoxidized unsaturated oils or fatty esters, and also 1-phenylpropene oxide. Useful and preferred epoxides are carboxylic acid glycidyl esters, which can be on a carboxylic acid functional polymer or preferably on a highly branched hydrophobic carboxylic acid such as Cardura E10P (Versatic™ Acid 10 glycidyl ester). Most preferred are typical powdered epoxy crosslinkers: triglycidyl isocyanurate (TGIC), Araldite PT910 and PT912, as well as phenolic glycidyl ethers, which are solid in nature at ambient temperature.

[0027] Suitable examples of the weak base C2 in embodiment LCC1 are weak base nucleophilic anions selected from the group consisting of carboxylate, phosphonate, sulfonate, halide or phenolate anions, or salts thereof, or a non-ionic nucleophile, preferably a tertiary amine, and for the catalyst system The LCC according to Embodiment IC2 is preferably a weak base nucleophilic anion selected from the group consisting of carboxylate, halide or phenolate salts, and most preferably carboxylate salts, or 1,4-diazabicyclo[2.2.2]octane (DABCO). The C2 component can react with the C1 group, preferably the epoxy group, to form a strongly basic anionic adduct which can in principle start the reaction of the crosslinkable components. Alternatively, it can react through its conjugated acid form to form a non-acid adduct. Preferably, the C2 group of the weak base has no significant basicity relative to the acidic C-H groups of the crosslinkable component A, but can react with the epoxide under low temperature crosslinking conditions (e.g. typically less than 30, preferably 15 minutes at half at the intended cure temperature).

[0028] Another suitable example of a weak base C2 is a weak base nucleophilic anion selected from the group of a weak base anion X ^- containing an acid group XH of the compound, in which X is N, P, O, S or C, in which the anion X ^- is a Michael reaction donor reactive with a C1 activator and characterized by a pKa value of the corresponding conjugate acid XH that is greater than 1, preferably 1.5, more preferably 2, and even more preferably at least 3 units lower than the pKa values of the acidic CH groups of the main component A. These C2 components are defined as S2 for reaction with C=C acceptor groups S1 in the LCC2 embodiment, but can also act as a C2 nucleophile in the reaction with the C1 activator components in the LCC1 embodiment, for example, with an epoxy group, which can provide 2 pathways for the reaction according to the embodiment of LCC1 and LCC2.

[0029] The C2 group preferably reacts with the C1 groups at temperatures below 150°C, preferably 140, 130, 120, and preferably at least 70, 80, or 90°C on the curing window timescale. The rate of reaction of the C2 group with the C1 group at the cure temperature is slow enough to provide a useful edge film setting time and fast enough to provide sufficient cure within the intended time window.

[0030] The weak base C2, if an anion, is preferably added as a salt containing a cation that is not acidic. Non-acidic means having no hydrogen which competes for base with component A and thus does not inhibit the crosslinking reaction at the intended curing temperature. This cation is preferably substantially non-reactive with any components in the crosslinkable composition. These cations may be, for example, alkali metals, quaternary ammonium or phosphonium, as well as protonated "superbases" which are non-reactive with any of the components A, B or C in the crosslinkable composition. Suitable superbases are known in the art.

[0031] Preferably, the salt contains an alkali or alkaline earth metal cation, in particular lithium, sodium or potassium, or preferably a quaternary ammonium or phosphonium cation in accordance with the formula Y(R') ₄ in which Y represents N or P, and in which each from R' may be the same or different alkyl, aryl or aralkyl group, optionally linked to the polymer, or the cation is the amine of a protonated very strong base which is preferably selected from the group of amidines; preferably 1,8-diazabicyclo(5.4.0)undec-7-ene (DBU), or guanidines; preferably 1,1,3,3-tetramethylguanidine (TMG). R' may be substituted with substituents that do not or substantially do not interfere with the chemistry of the RMA crosslink, as is known to those skilled in the art. Most preferably R' is alkyl having 1-12, most preferably 1-4 carbon atoms.

[0032] Patent document EP0651023 describes a catalyst system for solvent-based crosslinkable RMA compositions containing Catalyst C containing a quaternary ammonium or phosphonium salt of chlorine, bromine, iodine, salicylate, polybasic carboxylate, nitrate, sulfonate, sulfate, sulfite, phosphate, or acid ester anion phosphate in combination with an epoxy compound.

[0033] Most preferably, the powder material coating composition comprises an LCC catalyst system further comprising a C3 acid having a pKa greater than 1, preferably 1.5, more preferably 2, and even more preferably at least 3 units lower than pKa of the C-H acid groups of the main component A, the C3 acid being preferably the protonated C2. Preferably the C3 acid and the C2 conjugate acid have a boiling point of at least 120°C, preferably 130°C, 150, 175, 200 or even 250°C. Preferably C3 is a carboxylic acid.

[0034] A preferred catalyst system is an LCC1 catalyst system that contains C1 epoxy groups, C2 weak base nucleophilic anion groups that react with a C1 epoxy group to form a C1/2 strongly basic anionic adduct, and most preferably also C3 acid groups. In a suitable LCC1 catalyst system, C2 is a carboxylate salt and C1 is an epoxide, carbodiimide, oxytane or oxazoline, more preferably an epoxide or carbodiimide, or alternatively C2 is DABCO and C1 is an epoxy group.

[0035] Without wishing to be bound by any particular theory, it is believed that the C2 nucleophilic anion reacts with the activator C1 epoxide to form a strong base, but this strong base is protonated by the C3 acid to form a salt (similar in function to C2) that will not directly strongly catalyze crosslinking reaction. This reaction scheme proceeds to substantially complete depletion of the C3 acid, which provides the edge setting time of the film because no significant amount of strong base is present during this time to significantly catalyze the reaction of the crosslinkable components. When the C3 acid is depleted, a strong base will form and remain in order to effectively catalyze the fast RMA crosslinking reaction. Alternatively, this cycle can also work similarly when an activation reaction with C1 takes place with protonated C2 species (protonated as a result of acid-base balance with the A component); also this pattern will result in the consumption of excess C3 acid, and the appearance of deprotonated A species as this cycle progresses further.

[0036] the Features and advantages of the present invention will become clear when considering the following exemplary reaction scheme.

In particular, for the case of carboxylates, epoxides and carboxylic acids as species C2, C1 and C3, this might look like this:

The reaction scheme, if the activator were to react via the protonated C2 form, would be illustrated by the following scheme:

[0037] The setting time of the film at the edges can be controlled by the amount of acid (C3), as well as the choice of amounts and reactivity of reagents C1 and C2. The C1 epoxide must be available to start the reaction, and preferably the molar amount of the epoxide is greater than the molar amount of the C3 acid.

[0038] In one embodiment, the C3 acid group is a protonated C2 anion group, preferably a C3 carboxylic acid and a C2 carboxylate, which, for example, can be formed by partial neutralization of an acid functional component, preferably a polymer containing acidic C3 groups for partial conversion to C2 anionic groups, this partial neutralization being preferably carried out with a hydroxide cation, preferably tetraalkylammonium hydroxide or tetraalkylphosphonium hydroxide. In another embodiment, the polymer-binding component C2 can be obtained by hydrolysis of the ester group in the polyester with the aforementioned hydroxides.

[0039] Ethyltriphenylphosphonic acid acetate is known as a catalyst for crosslinking epoxy functional polymers, as described in "ETPPAAc Solutions Ethyl triphenyl-phosphonium Acid Acetate", 20 April 2007 (2007-04-20), pages 1-2, XP055319211. However, nothing is known about the use of this compound as the C2 and C3 component in crosslinkable RMA powder coating compositions. It is further preferred that the boiling point of the C3 component and the acid conjugated with the C2 base be above the intended curing temperature of the powder material coating composition to prevent poorly controlled evaporation of these catalyst system components under curing conditions. Formic acid and acetic acid are less preferred C3 acids because they can evaporate during curing. Preferably, for an LCC type system, the C3 component and the C2 base conjugate acid have a boiling point higher than 120°C.

[0040] The LCC1 catalyst system is preferably a catalyst composition containing individual components C1, C2 and optionally C3. This is most convenient for blending with a particular combination of preferred donor and acceptor polymers. Alternatively, at least one of the components C1, C2, or C3 of the LCC1 catalyst system is a group on the crosslinkable components A or B, or on A and B. In this case, if one or more, but not all, groups C1, C2, and C3 are on stitched components A or B, or on A and B, the remaining component is added separately. In this case, usually and preferably both C2 and C3 are on the polymer and C1 is added separately, or C1 and C3 are on the polymer and C2 is added separately. This has the advantage of being flexible in optimizing reactivity parameters by simply adjusting the catalyst composition. In one convenient embodiment, both C2 and C3 are on the crosslinkable polymer component A and/or B, and C2 is preferably formed by partial neutralization of an acid-functional polymer containing an acidic C3 group with a backbone containing the cation described above to partially convert the acidic C3 groups into anionic groups C2. Another embodiment has a C2 component formed by hydrolysis of a polyester, such as component A polyester, and present as a polymer.

[0041] In one alternative embodiment, the coating composition of powder material contains a latent LCC2 catalyst system, in which the weak base C2 is selected from the group of phosphines, N-alkylimidazoles, fluorides and an anion X ^{- a} weak base from a compound containing an acidic XH group, in which X represents N, P, O, S or C, and the anion X ^- is a donor of the Michael reaction, capable of reacting with the activator S1, and is characterized by a pKa value of the corresponding conjugate acid XH, which is greater than 1, preferably 1.5, more preferably 2 and more preferably at least 3 units lower than the pKa value of the acid CH groups of the main component A. In this embodiment, the reaction of the weak base C2 with an unsaturated group with Michael acceptor characteristics (S1, which can be equal to B, but also may be another type of Michael reaction acceptor) causes the formation of a more catalytically active species with strong base, speeding up the reaction between components A and B.

[0042] In yet another embodiment, the powder material coating comprises a latent LCE catalyst system having an evaporative latency in which the reaction is delayed by a slow evaporation step of the acid species. In this embodiment, containing 1) a base, preferably a strong base blocked with a volatile acid, or alternatively 2) a weak base C2 which, when protonated with an excess of the weakly acid species A, forms a volatile acid, and in which the latent catalyst system optionally additionally contains additional volatile acid C3, wherein these volatile acids evaporate at the curing temperature Tcur and the boiling point of the acid is less than 300°C, preferably less than 250°C, 225, 200 or 150°C, and preferably above 100°C or 120°C. Quaternary ammonium or phosphonium salts of carboxylic acids having the above boiling point are preferred.

[0043] The powder material coating composition preferably contains

a. In the case of an LCC1 catalyst system, activator C1 in an amount of 1-600 µeq/g, preferably 10-400, more preferably 20-200 µeq/g, where µeq/g is the number of µeq relative to the total mass of binders A and B and the LCC catalyst system , or, in the case of an LCC2 catalyst system, S1 activator in an amount of at least 1 µeq/g, preferably at least 10, more preferably at least 20, and most preferably at least 40 µeq/g,

b. weak base C2 in an amount of 1-300 µeq/g, preferably 10-200, more preferably 20-100 µeq/g, relative to the total weight of binder components A and B and the LC catalyst system,

With. optional C3 acid in an amount of 1-500, preferably 10-400, more preferably 20-300 µeq/g, and most preferably 30-200 µeq/g,

d. moreover, preferably the amount of C1 or respectively S1

i. is higher than the amount of C3, preferably by 1-300 µeq/g, preferably 10-200, and more preferably 20-100 µeq/g, and

ii. preferably is higher than the amount of C2, and

iii. preferably higher than the sum of the amounts of C2 and C3.

[0044] In the case of an LCC2 catalyst system, there is no upper concentration limit for S1, since S1 can also be a B component. The catalyst also operates with less C1 than C2. However, this is less preferred as it may mean loss of C2. When the amount of C1, in particular epoxide, is higher than the amount of C2, these disadvantages are limited, since it can react with C2 and C3 or other nucleophilic residues, but still remain basic after the reaction, or it can be left online without any problems. However, an excess of C1 may be disadvantageous in terms of cost of C1 other than the epoxy group. It should be noted that a combination of LCC1 and LCE embodiments is possible, in which case C2 may be higher than C1 if C2 also forms a volatilizing acid and therefore also catalyzes as an LCE type catalyst. In addition, when the C3 acid is a volatile acid, it provides additional initial delay by evaporating the C3 retarding acid. This is a combination of LCC and LCE latent catalyst systems. In this case, requirement d.i above does not apply.

[0045] In addition, it is preferable that in the coating composition of the powder material

a. the weak base C2 was 10-100 mol.% of the sum of C2 and C3,

b. the amount of acid C3 was 20-400 mol.%, preferably 30-300 mol.% of the amount of C2,

With. and preferably the ratio of the molar amount of C1 to the sum of the amounts of C2 and C3 is at least 0.5, preferably at least 0.8, more preferably at least 1, and preferably at most 3, and more preferably at most 2,

d. the ratio of C1 to C3 is preferably at least 1, more preferably at least 1.5, and most preferably at least 2.

[0046] In one alternative embodiment, the powder material coating composition comprises an LCP latent catalyst system having a physical latency in which a catalyst system, preferably a strong base or a latent catalyst system, is present that is physically separated and inaccessible to chemical reaction in the powder at the compounding temperature Tcomp or lower, and which is available for chemical reaction at a curing temperature, preferably selected from

a) a latent catalyst system LCP1 comprising a catalyst having a melting point below the curing temperature and above the compounding temperature, preferably above 70, 80, 90 or 100°C, or

b) a latent LCP2 catalyst system containing an active catalyst that is encapsulated or mixed with a material that releases the catalyst at a temperature below the curing temperature and above the compounding temperature, which material preferably has a melting temperature or, in the case of an amorphous material, a glass transition temperature below the curing temperature and above the compounding temperature, or

c) a latent LCP3 catalyst system containing a photogenerating base component that releases base when irradiated with a suitable wavelength.

[0047] It should be noted that combinations of LCC, LCE and LCP catalyst systems are possible.

[0048] Patent document EP1813630 describes encapsulated base catalysts and processes for their preparation for crosslinkable RMA adhesives, which are incorporated herein by reference. These capsules can be made from base catalysts using paraffin and microcrystalline waxes to provide a shell or matrix. Patent document EP6224793 discloses an active ingredient encapsulated in a crystallizable or thermoplastic polymer. The melting or glass transition temperature for encapsulation is here selected between Tcomp and Tcur.

[0049] In an alternative embodiment of the LCP3, the latency of the catalyst system for high temperature curing of RMA curing powder coatings can be provided by photo generator (PBG) components that release base when irradiated with a suitable wavelength. The base generated is preferably a strong base, i.e. strong enough to catalyze the RMA reaction between A and B, or may be a weak base which is used as the C2 component in combination with the chemically latent LCC catalyst system.

PBGs for Michael reaction systems are described, for example, in patent document EP3395800 and in Progr. Org. Coat. (2019) 127, 222-230, Polymer (2017) 113 193-199, and React. Funct. Polym. (2018) 122 60-67. Base photogenerators offer high levels of reactivity control similar to radical photoinitiators; they also face similar complications, such as potential problems with uniform irradiation of complex shaped substrates, radiation penetration problems for pigmented coatings, and the need for special, expensive setups. The PBGs described herein may be used if the generated base has the required pKa and nucleophilicity values for the envisioned latent catalyst system. Preferably, highly basic species such as amidine, guanidine or carbanion are generated.

[0050] A powder coating composition with RMA-crosslinkable A and B components and a latent LC catalyst system, preferably an LCC catalyst system, and most preferably an LCC1 catalyst system, as described above, achieve target cure temperatures that are low compared to competing powder coatings. systems. Low curing temperatures are typically 75-150°C, preferably 80-130°C, more preferably 80-120°C or 80-110°C, and the curing temperature is chosen within this range, for example taking into account the temperature sensitivity of the substrates. Curing time depends on the selected curing temperature. Curing time is the time during which heat is applied at a curing temperature, such as in an oven, to achieve sufficient curing before cooling to room temperature. Within the above curing temperature ranges, this curing time is typically 1 or 2 to 50 minutes, preferably 2 or 5 to 40 minutes, and usually and most preferably 5 or 10 to 30 minutes. Curing may take place in an oven and preferably may also be accompanied by infrared heating.

[0051] The coating composition of the powder material according to the present invention preferably has a curing kinetic profile that can be determined by FTIR measurement of the conversion of the C=C unsaturated bonds of component B as a function of time at a curing temperature selected between 80, 90, 100°C and 200, 150, 135 or 120°C, where the ratio of time for C=C conversion from 20% to 60% to time to reach 20% conversion (determined by FTIR) is less than 1, preferably less than 0.8, 0.6, 0.4 or 0.3, and preferably the time to reach 60% conversion is less than 30 or 20 or 10 minutes. Preferably the powder paint has a curing kinetic profile such that the time to reach 20% conversion at 100°C is at least 1 minute, preferably at least 2, 3, 5, 8 or 12 minutes. The cure profile is set by the choice of catalyst system components for the selected combination of reagents A and B and cure temperature.

[0052] The powder coating process involves heating the substrates to a curing temperature, which means a significant expenditure of energy. The coating process using the powder coating composition of the present invention is more energy efficient because it operates at low temperatures while still providing sufficient curing, preferably within 50, 30, 20 or even 15 minutes of curing time, and with such a long time setting at the edges (before the formation of the structure) of the applied film of the coating, as far as possible. This composition preferably has a sigmoid cure profile with an initial period of maximum flow and low reaction conversion (edge film setting time), followed by a steep increase so that sufficient final conversion occurs within a limited cure time. The long film setting time at the edges maximizes the flow to structure formation, which allows for a good appearance of the coating. In addition to coating properties, the powder coating composition can be particularly advantageous for use in low temperature curing powder where, due to the kinetic profile of the catalyst system, premature crosslinking reaction or increase in molecular weight and viscosity during compounding and mixing of the components in the extruder is limited.

[0053] In addition, the powder material coating composition according to the present invention is preferably characterized in that

a. the crosslinkable component A contains at least 2 acid donor groups C-H in activated methylene or methine in the structure Z1(-C(-H)(-R)-)Z2, where R is hydrogen, hydrocarbon, oligomer or polymer, and Z1 and Z2 - the same or different electron-withdrawing groups, preferably selected from keto, ester, cyano or aryl groups, and preferably contains activated C-H derivatives having a structure according to formula 1:

Формула 1

Formula 1

where R is hydrogen or optionally substituted alkyl or aryl, and Y and Y' are identical or different groups of substituents, preferably alkyl, aralkyl, aryl or alkoxy, or where in formula 1 the group -C(=O)-Y and/or - C(=O)-Y' are substituted by CN or aryl, not more than one aryl, or where Y or Y' may be -NRR' (R and R' are hydrogen or optionally substituted alkyl), but preferably not both, moreover, R, Y or Y' optionally provide connection with an oligomer or polymer, and said component A is preferably a malonate, acetoacetate, malonamide, acetoacetamide or cyanoacetate group, preferably providing at least 50, preferably 60, 70 or even 80% of the total acid groups C-H in the cross-linked component A,

b. Component B containing at least 2 activated unsaturated RMA acceptor groups preferably comes from acryloyl, methacryloyl, itaconate, maleate or fumarate functional groups,

and preferably at least one, and more preferably both components A or B is a polymer, and

moreover, preferably the composition contains a total amount of C-H donor groups and C=C acceptor groups per gram of solid binders from 0.05 to 6 meq/g, and preferably the ratio of C=C acceptor groups to C-H donor groups is greater than 0.1 and less than 10.

[0054] Crosslinkable by Michael reaction (RMA) coating compositions containing crosslinkable components A and B are generally described for use in solvent-based systems in patent documents EP2556108, EP0808860 or EP1593727, the specific description of which for crosslinkable components A and B is considered as included in this document.

[0055] Components A and B, respectively, contain reactive donor and acceptor and acceptor functional groups RMA, which, upon curing, react to form a cross-linked network in the coating. The A and B components may be present on different molecules, but may also be present on the same molecule, referred to as an A/B hybrid component, or combinations thereof may be used. Preferably, components A and B are different molecules and are each independently in the form of polymers, oligomers, dimers or monomers. For coating applications, it is preferred that at least one of components A and B are oligomers or polymers. It should be noted that the activated methylene group CH2 contains 2 acid groups C-H. Even if, after the reaction of the first acid group C-H, the reaction of the second acid group C-H is more difficult, for example for the reaction with methacrylates compared to acrylates, the functionality of such an activated methylene group is considered to be 2. Reactive components A and B can also be combined in one hybrid molecule A /B. In this embodiment of the powder coating composition, both C-H and C=C reactive groups are present in one A-B molecule.

[0056] It is envisaged that one or more components of catalyst system C may also be combined in one molecule, optionally in combination with component A and/or B, although this component does not need to be an active catalyst component or a combination of two components that can catalytically form an active ingredient to prevent premature reaction at the stages of synthesis, formulation and powder formation. For example, this polymer may contain groups C1, C2 and/or C3, but not a combination of C1 and C2. From a formulation flexibility point of view, the components of Catalyst System C are most preferably added as separate components.

[0057] Preferably component A is a polymer, preferably polyester, polyurethane, acrylic, epoxy, or polycarbonate, having component A as a functional group and optionally one or more components B, or components from catalyst system C. Mixtures or hybrids of these types of polymers are also possible. . Suitable component A is a polymer selected from the group consisting of acrylic, polyester, polyesteramide and polyesterurethane.

[0058] Malonates or acetoacetates are the preferred types of donors in component A. Considering the high reactivity and durability in the most preferred embodiment of the crosslinkable composition, component A is a C-H malonate group-containing compound. Preferably, in the coating composition of the powder material, the majority of activated C-H groups are from malonate, i.e. greater than 50%, preferably greater than 60%, more preferably greater than 70%, and most preferably greater than 80% of all activated C-H groups in the coating compositions of the powder material were of malonate.

[0059] The advantages of the present invention are especially evident in critically complex compositions with relatively high concentrations and functionality of functional groups, for example, when component A is a compound, in particular an oligomer or polymer containing an average of 2-30, preferably 3-20 and more preferably 4-10 activated C-H groups per polymer chain. Preferred are components containing oligomeric and/or polymeric malonate groups, such as, for example, polyesters, polyurethanes, polyacrylates, epoxy resins, polyamides and polyvinyl resins or hybrids thereof, containing groups of the malonate type in the main chain, in the side chain, or in both of them.

[0060] The total amount of C-H donor groups and C=C acceptor groups per gram of solid binders, regardless of how they are distributed among the various crosslinkable components, is preferably 0.05-6 meq/g, more typically 0.10-4 meq/g, even more preferably 0.25-3 meq/g, and most preferably 0.5-2 meq/g. Preferably, the stoichiometry between components A and B is chosen such that the ratio of C=C reactive groups to C-H reactive groups is greater than 0.1, preferably greater than 0.2, more preferably greater than 0.3, and most preferably greater than 0 ,4, and in the case of acrylate functionality, B is preferably greater than 0.5 and most preferably greater than 0.75, and preferably less than 10, preferably 5, and more preferably less than 3, 2 or 1.5.

[0061] Malonate-containing polyesters can be obtained preferably by transesterification of methyl or ethyl diester of malonic acid with polyfunctional alcohols, which may be polymeric or oligomeric in nature, but may also be incorporated by Michael reaction with other components. Particularly preferred malonate-containing components for use with the present invention are malonate-containing oligomeric or polymeric esters, esters, urethanes and epoxy esters, as well as hybrids thereof, for example polyesterurethanes, containing 1-50, more preferably 2-10 malonate groups per molecule. The polymer components A can also be prepared in a known manner, for example by radical polymerization of ethylenically unsaturated monomers, for example (meth)acrylate functionalized with a functional group containing activated acidic C-H (donor) groups, preferably an acetoacetate or malonate group, in particular 2-(methacryloyloxy)ethylacetoacetate or -malonate. In practice, polyesters, polyamides and polyurethanes (as well as their hybrids) are preferred. It is also preferred that such malonate-containing components have a number average molecular weight (Mn) in the range of from about 100 to about 10000, preferably 500-5000, most preferably 1000-4000; and Mw less than 20000, preferably less than 10000, most preferably less than 6000 (expressed in polystyrene equivalents using GPC).

[0062] Suitable crosslinkable B components can generally be ethylenically unsaturated components in which the carbon-carbon double bond is activated by an electron withdrawing group, such as a carbonyl group at the alpha position. Representative examples of such components are disclosed in patent documents US2759913 (column 6, line 35 to column 7, line 45), DE-PS-835809 (column 3, line 16-41), US4871822 (column 2, line 14 to column 4 , line 14), US4602061 (col 3, line 14 to col 4, line 14), US4408018 (col 2, lines 19-68), and US4217396 (col 1, line 60 to col 2, line 64).

[0063] Acrylates, methacrylates, itaconates, fumarates and maleates are preferred. Itaconates, fumarates and maleates can be incorporated into the polyester or polyester urethane backbone. Preferred exemplary resins such as polyesters, polycarbonates, polyurethanes, polyamides, acrylic and epoxy resins (or hybrids thereof), polyethers and/or alkyd resins containing activated unsaturated groups may be mentioned. These include, for example, urethane (meth)acrylates obtained by reacting a polyisocyanate with a (meth)acrylic acid ester containing a hydroxyl group, for example a (meth)acrylic acid hydroxyalkyl ester or a component prepared by esterification of a polyhydroxyl component with a substoichiometric amount of (meth)acrylic acid ; polyester(meth)acrylates obtained by esterification of a hydroxyl-containing polyether with (meth)acrylic acid; multifunctional (meth)acrylates obtained by the reaction of hydroxyalkyl (meth)acrylate with a polybasic carboxylic acid and/or polyamine resin; poly(meth)acrylates obtained by the reaction of (meth)acrylic acid with an epoxy resin; and polyalkyl maleates obtained by the reaction of a monoalkyl maleate ester with an epoxy resin and/or a hydroxy-functional oligomer or polymer. In addition, polyesters terminated with glycidyl methacrylate are a preferred example. It is possible that the acceptor component contains several types of acceptor functional groups.

[0064] The most preferred activated unsaturated components B are unsaturated acryloyl, methacryloyl and fumarate functional components. Preferably, the number average functionality of activated C=C groups per molecule is 2-20, more preferably 2-10, and most preferably 3-6. The equivalent weight (EQW: average molecular weight per reactive functional group) is 100-5000, more preferably 200-2000, and the number average molecular weight of Mn is preferably 200-10000, more preferably 300-5000, even more preferably 400-3500 g/mol , and most preferably 1000-3000 g/mol.

[0065] For use in powder systems, the Tg value of component B is preferably greater than 25, 30, 35°C, more preferably at least 40, 45°C, most preferably at least 50°C, or even at least 60 °C, due to the need to ensure the stability of the powder. The Tg value is determined by DSC measurement as the midpoint at a heating rate of 10°C/min. If one of the components has a Tg significantly higher than 50° C., the Tg of the other components may be lower, which should be clear to a person skilled in the art.

[0066] A suitable component B is a urethane (meth)acrylate obtained by reacting a hydroxy- and (meth)acrylate-functional compound with an isocyanate to form urethane bonds, where the isocyanates are preferably at least partially di- or triisocyanates, preferably isophorone diisocyanate (IPDI). The urethane linkages themselves impart stiffness, but high Tg isocyanates are preferably used, such as cycloaliphatic or aromatic isocyanates, preferably cycloaliphatic. The amount of such isocyanates used is preferably chosen such that the Tg of said (meth)acrylate functional polymer is above 40, preferably above 45 or 50°C.

[0067] The coating composition of the powder material is preferably designed such that, after curing, the crosslink density (determined using DMTA, as will be described below) is at least 0.025 mmol/cm ³ , more preferably at least 0.05 mmol/cm ³ , and most preferably at least 0.08 mmol/cm ³ .

[0068] The coating composition of the powder material must keep the powder flowable under ambient conditions, and therefore preferably has a Tg value above 25°C, preferably above 30°C, more preferably above 35, 40, 50°C, defined as the average value of c using DSC at a heating rate of 10°C/min.

[0069] As described above, the preferred component A is a malonate-functional component. However, the incorporation of malonate functional groups tends to decrease the Tg, and it has been a challenge to create powder coating compositions based on malonate as the dominant component A with a sufficiently high Tg.

[0070] In view of achieving high Tg, the powder material coating composition preferably contains a crosslinkable A component, a B component, or an A/B hybrid component, amide, urea, or urethane linkages, and/or contains high Tg monomers, preferably cycloaliphatic or aromatic monomers, or, in the case of polyester, one or more monomers selected from the group consisting of 1,4-dimethylolcyclohexane (CHDM), tricyclodecane dimethanol (TCD-diol), isosorbide, penta-spiroglycol, hydrogenated bisphenol A, and tetramethylcyclobutanediol.

[0071] In addition, in view of achieving high Tg, the coating composition of the powder material contains a component B or hybrid component A/B, which is polyester (meth) acrylate, polyester urethane (meth) acrylate, epoxy (meth) acrylate or urethane (meth )acrylate, or is a polyester containing blocks of fumarate, maleate or itaconate, preferably fumarate, or is polyester terminated with an isocyanate or epoxy-functional activated unsaturated group.

[0072] The above measures to achieve high Tg in crosslinkable A or B components or A/B hybrid can be advantageously combined with the presence of crystalline components. The components in the powder coating composition may be amorphous or crystalline. When the components in the composition are completely amorphous, the Tg of these components should be sufficiently high, but this can be difficult to achieve in combination with low melt viscosity at low temperatures. Therefore, it may be preferred that the powder coating composition contains one or more components, preferably crosslinkable components A or B, or an A/B hybrid, or catalyst system C components, or separate different plasticizers, which are in a (semi-)crystalline state in coating composition of powder material and have a melting point of 40-150°C, preferably 50-130°C, more preferably from 60 or 70 to 120°C, and most preferably 60-110°C. Preferably one or more components A or B or components of the catalyst system C are (semi-)crystalline or a mixture of amorphous and (semi-)crystalline components, but the crystalline components can also be additives with no additional role in the crosslinking reaction. The crystalline components preferably have a Tg in the molten state below 50°C, or more preferably below 30, 20 or even 10°C, and a crystallized Tm value in the paint composition in the specified range. Crystalline components have a lower melt viscosity in the molten state, but do not decrease Tg when in the crystalline state. The advantage of a (semi-)crystalline polymer is that a higher Tg of the composition can be achieved in combination with a lower melt viscosity at the cure temperature due to the plasticizing effect of the melt. The amount of crystalline components is chosen, together with other Tg-influencing parameters, to obtain the correct balance of melt viscosity at an envisaged curing temperature of less than 60 Pa s, more preferably less than 50, 40, 30, 20, 10 or even 5 Pa s, and the Tg values of the powder paint are preferably above 35°C. During the preparation process, care must be taken to ensure that the crystallizable components are in a crystalline state in the powder coating when used.

[0073] Most preferably, the powder coating composition comprises a crosslinkable RMA polymer according to another aspect of the present invention, which has features adapted for use in a crosslinkable RMA powder coating composition. In particular, from the point of view of achieving good flow and leveling properties as well as good chemical and mechanical resistance, it has been found to be preferable in the coating composition of the powder material that at least one of the crosslinkable components A or B, or an A/B hybrid, is a polymer. , preferably selected from the group of acrylic, polyester, polyesteramide, polyesterurethane polymers, which

a) has a GPC number average molecular weight Mn of at least 450 g/mol, preferably at least 1000, more preferably at least 1500, and most preferably at least 2000 g/mol,

b) has a GPC weight average molecular weight Mw of at most 20000 g/mol, preferably at most 15000, more preferably at most 10000, and most preferably at most 7500 g/mol,

c) preferably has a molecular weight distribution Mw/Mn less than 4, and more preferably less than 3, and obviously greater than 1,

d) has an equivalent weight EQW in C-H or C=C of at least 150, 250, 350, 450 or 550 g/mol, and preferably at most 2500, 2000, 1500, 1250 or 1000 g/mol, and a number average functionality of the reactive groups C-H or C=C 1-25, more preferably 1.5-15, even more preferably 2-15, and most preferably 2.5-10 C-H groups per molecule,

e) preferably has a melt viscosity at a temperature in the range of 100-140°C of less than 60 Pa·s, and more preferably less than 40, 30, 20, 10 or even 5 Pa·s,

f) preferably contains amide, urea or urethane linkages and/or contains high Tg monomers, preferably cycloaliphatic or aromatic monomers, in particular polyester monomers selected from the group consisting of 1,4-dimethylolcyclohexane (CHDM), tricyclodencandimethanol (TCD- diol), isosorbide, penta-spiroglycol or hydrogenated bisphenol A and tetramethylcyclobutanediol,

g) has a Tg greater than 25°C, preferably greater than 35°C, more preferably greater than 40, 50 or even 60°C, which is determined as the midpoint by DSC at a heating rate of 10°C/min, or is a crystalline polymer with a temperature melting point 40-150°C, preferably 130°C, preferably at least 50 or even 70°C, and preferably lower than 150, 130 or even 120°C (which is determined by DSC at a heating rate of 10°C/min) .

[0074] It can be seen that RMA is also used to prepare the coating, starting with liquid (not powder) compositions. For example, patent document WO2016166371 describes crosslinkable RMA coating compositions using a catalyst system based on a carbon dioxide blocked catalyst of a strong base, a reactive component A such as malonated polyester, and a reactive component B.

[0075] The polymer properties Mn, Mw and Mw/Mn are selected taking into account, on the one hand, the desired stability of the powder, and on the other hand, the desired low melt viscosity, as well as the intended properties of the coating. A high Mn value is preferred to minimize the end group Tg lowering effects, on the other hand, a low Mw value is preferable because the melt viscosity is very strongly related to Mw, and a low viscosity is desirable; therefore, a low Mw/Mn is preferred.

[0076] In view of achieving a high Tg, the crosslinkable RMA polymer preferably contains amide, urea or urethane linkages and/or contains high Tg monomers, preferably cycloaliphatic or aromatic monomers, or in the case of polyester contains monomers selected from the group consisting of 1, 4-dimethylolcyclohexane (CHDM), TCD-diol, isosorbide, penta-spiroglycol or hydrogenated bisphenol A and tetramethylcyclobutanediol.

[0077] In the case where the RMA crosslinkable polymer is an A/B hybrid polymer, it is further preferred that the polymer also contains one or more component groups B selected from the group consisting of acrylate or methacrylate, fumarate, maleate and itaconate, preferably (meth)acrylate or fumarate. In addition, if used as a crystalline material, it is preferable that the crosslinkable RMA polymer has a crystallinity at a melting point of 40°C - 130°C, preferably at least 50 or even 70°C, and preferably lower than 150, 130 or even 120°C (determined by DSC at a heating rate of 10°C/min). Note that this is the melting point of the (pure) polymer, not the polymer in the blend.

[0078] In one preferred embodiment, a crosslinkable RMA polymer containing polyester, polyesteramide, polyesterurethane or urethane acrylate, which contains urea, urethane or amide bonds derived from cycloaliphatic or aromatic isocyanates, preferably cycloaliphatic isocyanates, has a Tg of at least 40°C, preferably at least 45 or 50°C and at most 120°C, and a number average molecular weight Mn of 450-10000, preferably 1000-3500 g/mol, and preferably a maximum Mw value of 20000, 10000 or 6000 g/mol, and also equipped with crosslinkable RMA components A or B, or both. The polymer can be prepared, for example, by reacting a polymer precursor containing said crosslinkable RMA groups with some cycloaliphatic or aromatic isocyanates to increase the Tg. The amount of such isocyanates added or urea/urethane bonds formed is chosen such that the Tg rises to at least 40°C, preferably to at least 45 or 50°C.

[0079] Preferably, the crosslinkable RMA polymer is a polyester or polyester urethane containing malonate as the dominant component A, and having a number average malonate functionality of 1-25, more preferably 1.5-15, even more preferably 2-15, and most preferably 2, 5-10 malonate groups per molecule, weight average molecular weight determined by GPC from 500 to 20000, preferably 1000-10000, and most preferably 2000-6000 g/mol, which is obtained by the reaction of a hydroxy- and malonate-functional polymer with an isocyanate to create urethane bonds.

[0080] In addition, this polymer may be an amorphous or (semi-)crystalline polymer, or a mixture thereof. Semi-crystalline means partially crystalline and partially amorphous. (Semi)-crystallinity should be determined using a DSC melting endotherm, target crystallinity is defined as having a DSC Tm peak melting point of at least 40°C, preferably at least 50°C, more preferably at least 60°C and preferably at most 130, 120, 110 or 100°C. The DSC determined Tg of such a component in a fully amorphous state is preferably less than 40°C, more preferably less than 30, 20 or even 10°C.

[0081] In view of improving the shelf life of the powder material coating composition, it has been found advantageous to use polymer-bound C2 and C3 functionalities, in particular a polymer containing a carboxylate and optionally also C2 and C3 carboxylic acid components. It is believed that the duration of storage is improved by reducing mobility and exposure to Tg. An additional advantage is that polymeric components with high EQWs compared to those with low EQWs are more easily blended into powder coating compositions, for example when formulations are made in an extruder, and the risk of inhomogeneity is reduced.

[0082] The present invention thus also relates to a polymer (C3/2 polymer) and its use as a latent base catalyst component in crosslinkable RMA coating compositions, said polymer having weak base C2 groups and optionally acidic C3 groups, with weak C2 groups bases are preferably formed by partial or complete neutralization of C3 acid groups on the polymer, C2 and C3 being preferably carboxylate and carboxylic acid groups, this polymer being preferably selected from the group consisting of acrylic, polyester, polyesteramide and polyesterurethane polymers, this polymer being optional contains C-H donor groups, C=C acceptor groups, or both, and this polymer preferably has

a) an acid value in unneutralized form of at least 3, more preferably 5, 7, 10, 15 or even 20 mg KOH/g, and preferably less than 100, 80, 70, 60 mg KOH/g,

b) a quaternary ammonium or phosphonium cation, preferably a tetrabutyl or ethyl ammonium cation,

c) a Mn value of at least 500, preferably at least 1000, or even 2000, and an Mw value of not more than 20000, preferably not more than 10000 or 6000,

d) if C-H donor groups and/or C=C acceptor groups are present; equivalent weight of the reactive C-H donor or C=C acceptor of at least 150, preferably at least 250, 350 or even 450 g/mol, and not more than 2000, preferably not more than 1500, 1200 or 1000 g/mol,

e) if there are no C-H donor groups and C=C acceptor groups, the acid number in unneutralized form is at least 10, more preferably 15, 20 mg KOH/g, and preferably less than 100, 80, 70, 60 mg KOH/g

[0083] Preferably, the CH-donor groups are of the malonate type functionality. The acceptor unsaturated groups are preferably acrylate, methacrylate, fumarate, maleate or itaconate groups. It is further preferred that the above-described C3/2 polymer has a high Tg or crystallinity, as defined above for the crosslinkable RMA polymer, by containing high Tg monomeric components and/or hard bonds.

[0084] The present invention also relates to the use of a crosslinkable RMA polymer in crosslinkable RMA powder coatings. The present invention further relates to a method for preparing a coating composition from a powder material, comprising the steps

a. Providing component A, component B, catalyst system C and optional additives,

b. Extrusion of the components, preferably at a temperature Tcomp below 140°C, more preferably below 120, 100, 90, or even below 80°C,

c. cooling,

d. molding an extruded mixture to obtain a granulate before, during or after cooling,

e. Optional addition of additional additives,

f. Grinding the granulate into powder.

[0085] Optionally added additives are usually one or more selected from the group consisting of pigments, dyes, dispersants, degassing aids, leveling additives, frosting additives, flame retardants, additives to improve film formation properties, for optical external type of coating, to improve mechanical properties, adhesion or stability properties such as color and UV stability.

[0086] Powder paints can also be designed to produce matte finishes using the same methods as traditional powder coating systems, either using additives or by intentional non-uniform crosslinking using either powder blend systems or polymer blend systems. with different reactivity.

[0087] Standard powder coating processing can be used, typically involving curing the extrudate immediately after it leaves the extruder by forcing the extrudate onto a cooling belt. The extruded ink may take the form of a solidified sheet as it travels along the cooling belt. At the end of the belt, the sheet is then broken into small pieces, preferably by means of a pin crusher, to obtain a granulate. There is no significant control over the shape of the granules, although a statistical maximum size is preferred. The ink granulate is then transferred to a micronizer classifier where the ink is ground to a very fine particle size distribution. This product is the ultimate powder coating. Where crystalline components are used, care must be taken to ensure that the crystallizable components are present in the powder paint in a crystalline state. This may, for example, involve choosing Tcomp below the melting points Tm of the crystallizable components, or, in the case where Tcomp is above Tm, crystallizing these components on cooling.

[0088] The present invention also relates to a method for coating a substrate with a powder material containing

a. Providing a powder having a coating composition of powder material in accordance with the present invention, or obtained using the process described above,

b. Applying a layer of powder to the surface of the substrate, and

c. Heating to a curing temperature Tcur of 75 to 200°C, preferably 80-180°C, and more preferably 80-160, 150, 140, 130 or even 120°C, optionally and preferably using infrared heating,

d. and curing at Tcur for a curing time preferably less than 40, 30, 20, 15, 10 or even 5 minutes.

[0089] In this method, curing at Tcur is preferably characterized by a cure profile, which is determined by measuring the C=C unsaturated bond conversion of the B component with FTIR as a function of time, in which the ratio of time to change the degree of C=C conversion is from 20% to 60% by time to reach 20% conversion is less than 1, preferably less than 0.8, 0.6, 0.4 or 0.3, and preferably the time to reach 60% conversion is less than 30 or 20 or 10 minutes , and the powder material coating composition at Tcur preferably has a melt viscosity at a cure temperature of less than 60 Pa·s, more preferably less than 40, 30, 20, 10, or even 5 Pa·s. Melt viscosity should be measured at the very beginning of the reaction or without the C2 component of the catalysis system.

[0090] In one preferred embodiment of this method, the curing temperature is 75-140°C, preferably 80-120°C, and the catalyst system C is the latent catalyst system described above, which allows powder coating on a temperature sensitive substrate, preferably MDF, wood, plastic, or temperature sensitive metal substrates such as alloys.

[0091] Therefore, the present invention also relates to articles coated with the coating composition of the powder material of the present invention, preferably having a temperature sensitive substrate such as MDF, wood, plastic or metal alloys, and in which the XLD crosslink density of the coating (determined by using DMTA) is at least 0.01, preferably at least 0.02, 0.04, 0.07 or even 0.1 mmol/cm ³ , and preferably less than 3, 2, 1.5, 1 , or even 0.7 mmol/cm ³ .

[0092] The present invention also relates to the use of catalyst system C described above to catalyze the crosslinking reaction in crosslinkable RMA powder coating compositions at cure temperatures below 200°C, preferably below 180°C, and more preferably below 160, 140, or even 120°C.

[0093] The present invention relates to powder coating compositions suitable for low temperature crosslinking of powder coating, typically at a curing temperature of 75-140°C, which can be used to powder coat heat sensitive substrates such as MDF, wood, plastic or temperature sensitive metal alloys. Coating compositions made of powder material contain a crosslinkable component A having at least 2 acid donor groups C-H in activated methylene or methine, a crosslinkable component B having at least 2 activated unsaturated C=C acceptor groups that react with component A via a Michael reaction under the action of catalyst system C, which is preferably a latent catalyst system. The present invention also relates to a process for producing such powder material coating compositions, to processes for coating articles using said powder material coating composition, and to the resulting coated articles. The present invention also relates to specific polymers for use in powder coatings and to the use of specific catalyst systems in such powder coating compositions.

[0094] Hereinafter, the present invention will be illustrated by the following examples.

Test Methods

[0095] Molar mass distribution of polymers was determined by gel permeation chromatography (GPC) on a PerkinElmer HPLC series 200 instrument using a refractive index (RI) detector and a PLgel column, THF as eluent, and calibrated with polystyrene standards. Experimental molecular weights are expressed as polystyrene equivalents.

[0096] Resin and ink glass transition temperatures reported herein are average Tg values determined by differential scanning calorimetry (DSC) using a heating rate of 10°C/min. The melting point is also determined by DSC using the same scan speed. To determine the heat of reaction as a function of time, DSC is used in isothermal mode after rapid heating (60°C/min) to the curing temperature to be studied.

[0097] XLD was measured by DTMA on a separate coating film prepared by applying the powder coating composition to PTFE coated panels and cured according to the selected cure profile. The cured coating can be easily removed from the panel in order to obtain a separate coating film. From this separate film, a sample for DMTA measurements 3 mm wide and 30 mm long was cut. The length between the DMTA tensile clamps was 30 mm. The DMTA measurement was performed at a frequency of 11 Hz and a heating rate of 5°C/min, and from its results the XLD crosslink density parameter (in mmol/cm ³ ) was estimated, as is known in the art. The XLD crosslink density parameter was determined according to the general procedure detailed in the ASTM manual MNL17-2ND (Dynamic Mechanical and Tensile Properties, 2012) using individual coating films measured under tension on a modified DMTA Rheovibron device (Toyo Baldwin, type DDV-II-C) at 11 Hz with a dynamic tensile strength of 0.03%. All measurements were performed in tension mode and at each temperature the tensile storage modulus E', tensile loss modulus E'' and tanδ (tanδ=E''/E') were determined. DMTA was performed on a separate cured coating with a layer thickness of approximately 30-50 microns, prepared on a non-adherent substrate. For unfilled coatings, the crosslink density can be directly calculated from the minimum tensile storage modulus E'min and the temperature Tmin (in Kelvin) at which this minimum E'min is found:

where R is the gas constant (8.314 J/mol/K) and νe is the crosslink density (= moles of elastically effective network chains per volume). The Tg value of the film can be determined from the DMTA curve either as related to the tanδ maximum or as related to the E'' maximum.

[0098] Gel time: A Coesfeld Material gel tester is used to determine gel time. Before testing, the gel tester is set to the required temperature and left to stabilize. A controlled amount of ground powder is placed on the heating plate of the gel tester and a timer is started. When the sample begins to melt, the material is mixed with a wooden cocktail stick in a circular motion. As the sample reacts, the viscosity increases until a point is reached where the material is no longer free-flowing and begins to form a sticky, cohesive bead. The end point is reached when the sample is in this state and can detach from the tip of the stick or from the surface of the hotplate. The test is repeated until at least two result sets are in agreement.

[0099] Solvent resistance for film coatings was evaluated by placing a cotton pad on the ball head of a 1 pound (0.454 kg) ball hammer. Then it was covered with a square with a side of 5 cm from a suitable fabric. The pad of cotton and fabric were attached to the hammer with a cable tie to ensure that the fabric was pulled tight without wrinkling, wrinkling or bagging. Sufficient methyl ethyl ketone (MEK) was applied to the fabric to completely wet the cotton without leaving excess solvent. The ball head of the hammer was placed on the surface of the prepared panel painted with the test paint. The hammer was pushed through the entire width of the panel and then returned to its original position. During this action, no pressure was exerted on the hammer from above or below. This amounted to one double friction and took approximately 1 s. This was repeated 300 times or until the coating was broken (rubbed down to the metal surface), whichever happened first. The result was the number of double rubs before the coating was rubbed, or 300 if no rub was observed.

[00100] The solvent resistance of the coating film was also evaluated using an acetone drop test. A 50 µl drop of acetone was placed on the panel for 30 s, and then the panel was visually inspected for signs of corrosion. The test panels were scored visually on a scale of 0 to 5. The scores were as follows: 0: no damage; 1: excellent, 2: good, 3: satisfactory, 4: poor, 5: complete failure of the coating layer.

[00101] To evaluate flow and appearance, the powder coated test panels were compared to a set of standard panels from the Powder Coating Institute (PCI). These panels represent the degrees of smoothness achievable with powder coatings and have graduated degrees of orange peel (flow) and powder smoothness from coarse to smooth. These standard panels consist of ten 4" x 6" panels that are painted black and labeled with their respective orange peel (flow) rating from 1 (poor) to 10 (excellent). The test panels were compared to standard panels in order to visually evaluate the appearance of the colored test panels. The test panels were assigned a flow value that most closely matched one of the standard panels.

[00102] For the subsequent conversion of acryloyl, FTIR Nicolet iC10 instruments equipped with a Specac Golden Gate ATR setup with an ATR diamond crystal included in the hot table were used. The formulated paint, dissolved in a solvent or as a powder paint, was applied directly to a hot bed at a given curing temperature. The conversion was monitored as a function of time using the integration of the 810 cm ^-1 acryloyl peak, using the 1760 C=O absorption band as a reference.

Abbreviations

Table 1: Description of abbreviations used in the examples.

NPG neopentyl glycol 1.6-HD 1,6-hexanediol CHDM 1,4-dimethylolcyclohexane IPA Isophthalic acid TPA terephthalic acid tBAA tert-butylacetoacetate IPDI isophorone diisocyanate HDI hexamethylene diisocyanate TBAOH tetrabutylammonium hydroxide TEAOH tetraethylammonium hydroxide TEA acetate tetraethylammonium acetate DCC dicyclohexylcarbodiimide DABCO 1,4-diazabicyclo[2.2.2]octane DTMPTA ditrimethylpropanetetraacrylate AV acid number Pure OHV net hydroxyl number OHV hydroxyl number wt% mass percent Mn number average molecular weight mw weight average molecular weight Tg glass transition temperature EQW equivalent weight

Araldite® ^PT912 glycidyl ether resin (Huntsman) Epoxy EQW is 154 Araldite® ^GT7004 bisphenol A epoxy resin (Huntsman) Epoxy EQW is 752 Cardura™ E10P glycidyl ether Versatic™ Acid 10 (Hexion) Epoxy EQW is 240 ^UVECOAT® 3005 unsaturated resin containing fumarate and methacrylate (Allnex) total EQW C=C is 723 (0.4 eq methacrylate and 1 eq fumarate per 1000 g); AV=6 mg KOH/g; Tg=48°C UVECOAT® ⁹¹⁴⁶ unsaturated methacrylate resin (Allnex) EQW C=C is 447; Tg=55°C;
GPC Mn=1481; Mw=5829 CRYLCOAT® ^1622-0 carboxyl polyester resin powder for coating (Allnex) AV=60 mg KOH/g; Tg=54°C; ^Fascat® 4100 chlorobutyltin dihydroxide (PMC) catalyst Acure 500 CO ₂ -blocked main catalyst (Allnex) Acure 510-100 malonate-functional polyester (Allnex) Resionflow PV 88 acrylic flow control agent (Worlee) ^MODAFLOW®
P6000 Silica-supported powder coating flow modifiers (Allnex)

Preparation of materials

Preparation of malonate resin M-1

[00103] A 2 liter round bottom reactor equipped with a 4-mouth lid, Pt-100 metal anchor, Dean-Stark trap with condenser and N ₂ inlet was charged with 510 g of CHDM and 153.7 g of IPA. The temperature of the reactor was smoothly raised to approximately 100°C and 0.26 g of Fascat 4101 was added. The temperature was further increased to 200°C and the reaction continued until the acid number was below 0.50 mg KOH/g . During the last part of the reaction, a stream of nitrogen was used to bring the reaction to completion. The temperature was lowered to 50° C. and 134.2 g of diethyl malonate was added. The reactor temperature was increased to 170° C. and maintained until no more ethanol was formed. After the transesterification was completed, the hydroxyl value of the polyester was measured. Then the reactor temperature was set to 60°C, and 284.40 g of IPDI was added over 3-4 hours, whereby the temperature increased to 155°C due to the exothermic reaction. After all of the IPDI had been added, the reactor was maintained for 30 min at 155°C in order to complete the reaction. The final OHV value was 46 mg KOH/g, determined by GPC Mn and Mw were 3343 and 7372 respectively, and the Tg value (DSC) was 64°C. The acid number was less than 1 mg KOH/g.

Preparation of malonate resin M-2

[00104] A 5 liter round bottom reactor equipped with a 4-mouth lid, a Pt-100 metal anchor, a packed column with a top thermometer, a condenser, a distillate collection vessel, a thermocouple, and an N ₂ inlet was charged with 2900 g of CHDM and 2300 g IPA. The reactor temperature was smoothly raised to approximately 100°C and 3 g of Fascat 4101 catalyst was added. The reaction temperature was then gradually increased to 230°C and the polymerization proceeded under nitrogen with continuous stirring until the reaction mixture became clear and the acid number did not fall below 2 mg KOH/g. Depending on the measured OHV and the theoretical target OHV (88 mg KOH/g), a calculated amount of CHDM was added to the reactor in order to compensate for glycol losses during polymerization. During the last part of the reaction, vacuum was used to bring the reaction to completion. The temperature was lowered to 120° C. and 406 g of diethyl malonate were added. The reactor temperature was then increased to 190° C. and maintained until no more ethanol was produced. The vacuum was then applied again to bring the reaction to completion. After the transesterification was completed, the hydroxyl value of the polyester was measured. The final OHV value was 35 mg KOH/g, determined by GPC Mn and Mw were 2150 and 5750 respectively, and the Tg value (DSC) was 42°C. The AV value was less than 1 mg KOH/g.

Preparation of malonate resin M-3

[00105] M-3 was prepared similarly to M-2. 1970 NPG, 1800 g TPA and 600 g IPA were loaded into a reactor and condensed to a very low acid number. 674 g of diethyl malonate was added to this oligomeric resin and further condensed by removing ethanol from the mixture. After transesterification was stopped, the resulting M-3 malonate resin had a final OHV of 16 mg KOH/g, determined by GPC, Mn and Mw were 3776 and 9774, respectively, and the Tg value (DSC) was 37°C. The EQW of malonate was 1000 and the acid number was less than 1 mg KOH/g.

Preparation of malonate resin M-4

[00106] M-4 was prepared similarly to M-2. 1840 g NPG, 2455 g isosorbide (80 wt%), 2746 g TPA and 1000 g IPA were loaded into the reactor and condensed with 7.50 g titanate catalyst to a very low acid number. 1247 g of diethyl malonate was added to this oligomeric resin and further condensed by removing ethanol from the mixture. After transesterification was stopped, the resulting M-4 malonate resin had a final OHV of 21 mg KOH/g, determined by GPC, Mn and Mw were 2183 and 5448, respectively, and the Tg value (DSC) was 61°C. The EQW of malonate was 1000 and the acid number was less than 1 mg KOH/g.

Preparation of Anhydride Modified Acid Functional Malonate Resin AHM-4

[00107] 700 g of M-4 malonate and 20.74 g of phthalic anhydride were added to a reactor equipped with a mechanical stirrer. The reaction was continued at 170°C with continuous stirring for 2.5 hours. The final product had an AV value of 16 mg KOH/g. The Mn and Mw determined by GPC were 1591 and 4084, respectively, and the Tg value (DSC) was 49°C.

Preparation of malonate carboxylate polymer MC

[00108] A malonate carboxylate polymer was prepared by hydrolysing a malonate polyester resin M-2 (Mn=2150) using a solution of TBAOH (55 wt% in water) at elevated temperature. Briefly, 45.3 g of M-2 malonate resin was first melted in a three-necked round flask fitted with a condenser. Once the resin had completely melted, 4.71 g of the TBAOH solution was added dropwise to the flask at 140°C. Then the water was completely driven out of the vessel. The final product had a GPC-determined Mn and Mw of 797 and 2772, respectively, and a base (carboxylate) concentration of 0.374 mol/kg.

Preparation of MB-1 Resin Masterbatch

[00109] For resin masterbatch synthesis, 1000 g of M-4 malonate polyester resin and 750 g of ^CRYLCOAT® 1622-0 were loaded into a 3 L reactor. This polymer mixture was then melted at 170° C. and homogenized by stirring. After that, the obtained homogenized polymer mixture was cooled to 150°C, followed by the addition of 343 g of a solution of TBAOH (55 wt.% in H ₂ O). Then the water was completely driven out of the vessel. Finally, vacuum was applied for 15 minutes to remove residual water from the polymer blend. The final product had an AV value of 28 and a Tg (DSC) of 36°C. The theoretical concentration of carboxylate was 0.217 mmol/g.

Preparation of acetoacetate resin AA-1

[00110] AA-1 was prepared by starting with the condensation of 484.1 parts of NPG (90 wt.% in water), 21.40 parts of trimethylolpropane, 681.5 parts of IPA and 0.55 parts of Fascat 4100 as a catalyst at 235°C , and in the last stages with vacuum, to an acid number below 1 mg KOH/g. To 2500 g of this material was added dropwise 327.80 g of tBAA at 170°C. The tert-butanol was distilled off while the reaction proceeded at 170°C until the evolution of volatile substances ceased. Finally, excess tBAA was removed in vacuo. The final OHV value was 3 mg KOH/g, determined by GPC Mn and Mw were 2150 and 15800 respectively, and the Tg value (DSC) was 44°C. The acid number was negligible; The EQW of acetoacetate was 2000 g/mol.

Preparation of urethane acrylate UA-1

[00111] For synthesis, a 0.5 L 4-neck round bottom reactor was charged with 116.10 g of 2-hydroxyethyl acrylate (purified over basic Al ₂ O ₃ ), 0.30 g of 2,6-di-tert-butyl -4-methylphenol and 0.30 g of dibutyltin dilaurate. The reactor temperature was raised to 55° C. and 111.2 g IPDI was added over 2.5 hours. After all the isocyanate was added, the reaction temperature was maintained at 55°C for 1 hour to complete the reaction. The resulting urethane acrylate had an acryloyl functionality of two.

Preparation of urethane acrylate UA-2

[00112] Urethane acrylate based on IPDI, hydroxypropylacrylate and glycerol was prepared with the addition of suitable polymerization inhibitors, as described, for example, in patent documents EP0410241A2 and EP0585742. A 5 L reactor equipped with a thermometer, stirrer, metering funnel and gas bubbling inlet was charged with 1020 parts of IPDI, 1.30 parts of dibutyltin dilaurate and 4.00 parts of hydroquinone. Then, 585 parts of hydroxypropylacrylate was gradually added so as to avoid the temperature rise above 50°C. After this addition was completed, 154 parts of glycerol were added. 15 min after completion of the exothermic reaction, the reaction product was poured onto a metal tray. The resulting urethane acrylate had GPC-determined Mn and Mw values of 744 and 1467, respectively, a Tg value (DSC) of 51° C., a residual isocyanate content of <0.1%, and a theoretical unsaturation EQW of 392.

Preparation of semi-crystalline urethane acrylate UA-3

A 5 L reactor equipped with a thermometer, stirrer, dosing funnel and gas sparging inlet was charged with 833 parts of IPDI, 913 parts of HDI, 4.20 parts of dibutyltin dilaurate and 5.00 parts of butylated hydroxytoluene (BHT). Then, 395 parts of hydroxypropylacrylate was added over 60 minutes so as to avoid the temperature rise above 35°C. After this addition was completed, 896 parts of 1,6-HD and 5 parts of BHT were added. 15 min after completion of the exothermic reaction, the reaction product was poured onto a metal tray. The resulting semi-crystalline urethane acrylate had a melting point of 125°C, a Tg (DSC) of 17.7°C, and a theoretical unsaturation EQW of 1004.

Preparation of Epoxy Acrylate Resin EA-1

[00113] 640 g of epoxy resin of bisphenol A (Mn ≈ 1075), 3.20 g of 4-methoxyphenol (MEHQ), 3.20 g of β-ionol and 4.73 g of ethyltriphenylphosphonium bromide were loaded into a 3 L reactor and heated to 135 °C with stirring. In a separate flask, 81.50 g of acrylic acid was mixed with 0.08 g of MEHQ and 0.03 g of phenothiazine and then added to the reactor over 30 minutes. The reaction was continued for another 5 hours at 130°C until completion (AV=0). The final product had a GPC determined Mn and Mw of 1399 and 4956 respectively, a Tg value (DSC) of 39°C and a theoretical unsaturation EQW of 637.

Preparation of Anhydride Modified Acid Functional Epoxy Acrylate Resin AHEA-1

[00114] 137.10 g of EA-1 epoxyacrylate and 16.20 g of phthalic anhydride were added to a reactor equipped with a mechanical stirrer. The reaction was continued at 140°C with continuous stirring for 3 hours. The final product had an AV value of 30, a Tg (DSC) of 36°C, and a GPC-defined Mn and Mw of 2509 and 11770, respectively.

Preparation of Fumarate Polyester Resin FP-1

[00115] A 5 liter round bottom reactor equipped with a 4-mouth lid, Pt-100 metal anchor, packed column with top thermometer, condenser, distillate collection vessel, thermocouple, and N ₂ inlet was charged with 1563 g NPG and 2150 g IPA. The reactor temperature was smoothly raised to approximately 100° C. and 3.5 g of monobutyl tin oxide (MBTO) catalyst was added. The reaction temperature was then gradually raised to 210° C. and the polymerization proceeded under nitrogen with continuous stirring until the reaction mixture became clear and the acid number dropped below 8 mg KOH/g. In the second stage, 1060 g of fumaric acid, 1.5 g of MEHQ and 1.05 g of phosphoric acid were added to the reactor. The polymerization was carried out under vacuum until the AV value was below 5 mg KOH/g. The final product obtained had an AV value of 4.4 mg KOH/g, an OHV of 46.3 mg KOH/g, a Tg (DSC) of 37°C, and a theoretical unsaturation EQW of 500.

Preparation of tetrabutylammonium benzoate

[00116] 104.79 g of a solution of TBAOH (55 wt.% in H ₂ O) and 48.85 g of benzoic acid were charged into a 250 ml round flask and mixed until all solids were dissolved. Depending on the pH of the solution, additional TBAOH or benzoic acid was added to bring the pH to 7. This solution was then concentrated by partial evaporation of the water and cooled to start crystallization. After the completion of crystallization, the resulting TBA benzoate was dried in a vacuum oven.

Curing profile of the catalyst system

[00117] Examples 1-9 used: M-1 malonate resin (12.0 g; 21.8 meq C-H reactive) and UA-1 urethane acrylate (4.46 g; 19.6 meq acryloyl) and butyl acetate solvent (11.1 g). The other components as well as the reaction time are shown in Table 2. Catalyst component C1 was Cardura™ E10P (CE-10), catalyst component C2 was tetrabutylammonium benzoate, and catalyst component C3 was benzoic or lauric acid. These compositions were cured at temperatures of 95 and 102°C.

[00118] The conversion was measured as a function of time in order to determine the kinetic form factor of the reaction 60-20/20 (SF60) and the form factor 80-20/20 (SF80). The conversion is measured after applying the composition to the heated ATR-FTIR table and measuring the conversion of the acryloyl groups, focusing on the 809 cm ^-1 band characteristic of the acryloyl functional group. The results are shown in Table 2 below.

[00119] Shape factors are a characteristic of the reaction kinetics of a crosslinkable composition. The 60-20/20 shape factor is the ratio of the time it takes from 20% to 60% acryloyl conversion to the time it takes to reach 20% conversion. Similarly, the shape factor 80-20/20 is the ratio of the time elapsed from 20% to 80% conversion of acryloyl to the time required to reach 20% conversion. Preferably, this form factor is low, indicating that there is a substantially long film setting time at the edges, allowing fluidity for film formation and a good coating appearance, as well as a small amount of time to achieve 20 to 60 or 80% of full cure. transformations.

[00120] An alternative method for determining the shape factor of the kinetic profile SF(DSC) is to use DSC (differential scanning calorimetry). In this method, we measure the reaction exotherm of a powder paint composition at an appropriate temperature as a function of time in an isothermal scan. The sample is heated to the curing temperature of interest at a rate of 60°C/min and the heat release is measured as a function of time from that point (t0). The exothermic peak is usually observed after a certain induction time and can be integrated to give the ΔHtotal value. This exotherm can be re-plotted after integration as the cumulative heat released after t0 and we can determine the time required to reach 20% or 60% of ∆Htotal in this isothermal run (t20 and t60). The shape factor SF(DSC) can be determined from the ratio of the time to reach 20 to 60 exothermic heat released (t60 - t20) to the time to reach 20% exothermic heat released (t20 - t0).

SF(DSC)=(t60 - t20)/ (t20 - t0)

[00121] This aspect ratio is preferably less than 1, more preferably less than 0.8, even more preferably less than 0.6, 0.4, and most preferably less than 0.3. In addition, the kinetics are preferably chosen such that (t20 - t0) under testing conditions at 100°C is preferably greater than 1 minute, more preferably greater than 2, 3, 5, 8, 12 minutes.

Table 2: Curing characteristics of examples 1-9

Amount of solids in µeq/g time up to 20% (min) time up to 60% time up to 80% FTIR
form factor FTIR
form factor Example Benzoate TBA benzoic acid lauric acid CE-10 (60-20)/20 (80-20)/20 Curing T (ºC) 1 15 15 4.84 10.35 14.55 1.14 2.01 102 2 15 7.5 22.5 27.38 36.28 41.42 0.33 0.51 102 3 15 3.8 nineteen 13.25 25.72 38.67 0.94 1.92 102 four 15 7.5 25 15.68 20.99 24.15 0.34 0.54 102 five thirty 15 50 17.83 20.28 22.01 0.14 0.23 95 6 thirty 15 50 22.29 25.71 27.82 0.15 0.25 95 7 thirty 15 50 17.97 21.84 23.93 0.22 0.33 95 8 60 thirty one hundred 15.32 17.45 18.69 0.14 0.22 95 nine 60 thirty one hundred 15.75 18.44 19.56 0.17 0.24 95

[00122] These examples show the advantage of catalyst latency due to the presence of C3. Preferably the shape factor 60-20/20 (SF60) is less than 1, more preferably less than 0.8, 0.6, 0.4 or 0.3, and preferably also SF80 is less than 1.5, and more preferably less 1, 0.5 or even 0.35.

[00123] In Example 10-11, M-4 malonate resin (5 g), UA-2 urethane acrylate (3.92 g), and ^Araldite® GT 7004 catalyst C1 component (1.14 g) were dissolved in acetone. To prepare the catalyst component C2, either TBAOH (0.24 g, 55 wt% in water) or TEAOH (0.33 g, 40 wt% in water) was neutralized with excess benzoic acid, respectively, in a separate flask. The amount of each catalyst component in the composition after neutralization is shown in Table 3. These two solutions were then combined and a thin film was cast onto a polypropylene panel. Thereafter, the acetone was removed in vacuo at 50°C and the collected solid was measured by isothermal DSC analysis at 120°C. The results of the isothermal DSC scans for Examples 10 and 11 show that approximately the same time is required to complete cure at 120°C for both Examples 10 and 11.

[00124] In Example 12, the anhydride-modified acid-functional malonate resin AHM-4 (5.0 g) was first dissolved in acetone and then partially neutralized with TBA hydroxide (0.21 g, 55 wt% in water). In a separate flask, UA-2 urethane acrylate (3.92 g) and C1 component of CE-10 catalyst (0.31 g) were also dissolved in acetone. The amount of each catalyst component in the composition after neutralization is shown in Table 3. These two solutions were then combined and a thin film was cast onto a polypropylene panel. Thereafter, the acetone was removed in vacuo at 50°C and the collected solid was measured by isothermal DSC analysis at 120°C.

[ ⁰⁰¹²⁵ ] In Example 13, M-4 malonate resin (5 g) and C1 component of Araldite® GT 7004 catalyst (1.76 g) were dissolved in acetone. In a separate flask, anhydride-modified AHEA-1 acid-functional epoxy acrylate resin (2.38 g) and EA-1 epoxy acrylate (1.28 g) were also dissolved in acetone and then partially neutralized with TBA hydroxide (0.37 g, 55 wt.% in water). The amount of each catalyst component in the formulation after neutralization is shown in Table 3. These two resulting solutions were then combined and a thin film was cast onto a polypropylene panel. Thereafter, the acetone was removed in vacuo at 50°C and the collected solid was measured by isothermal DSC analysis at 120°C.

Table 3. Curing characteristics of examples 10-13

Amount of solids in µeq/g time up to 20% (min) time up to 60% (min) DSC
form factor Example C2 C3 C1 (60-20)/20 Curing T (ºC) 10 50 50 150 6.8 8.45 0.24 120 eleven 50 50 150 8.32 9.37 0.13 120 12 65 65 178 8.82 11.03 0.25 120 13 74 45 220 3.9 6.32 0.62 120

[00126] Examples 10 and 11 showed that TBA benzoate has a similar reactivity to TEA benzoate at 120°C. This is also illustrated by the similar times required to reach 20% to 60% exothermic heat in isothermal runs.

[00127] In addition, the C3 component of the catalyst can be included in the backbone of component A as shown in Example 12 or component B as shown in Example 13. The corresponding C2 anions were then formed by partial neutralization of C3 with a hydroxide cation. The cure profile is illustrated by the shape factor DSC.

Powder paint compositions

[00128] Powder paint formulations P1-P11 were prepared and applied as powder paints. These coatings were formulated without pigments with stoichiometry such as to have a reactive acryloyl/C-H2 ratio of 2:1. Other components, including additives, are shown in Table 4. Catalyst component C1 is ^Araldite® PT 912 or ^Araldite® GT 7004; the catalyst component C2 is tetrabutylammonium benzoate (TBA benzoate), and the catalyst component C3 is benzoic acid. For the preparation of RMA powder coatings, a double extrusion process was used to ensure good mixing. First, the two resin components were pre-extruded at a relatively low extruder speed (100 rpm). The resulting pre-extruded materials were then milled and mixed with the catalyst components as well as the flow aid in a high speed Thermoprism Pilot Mixer 3 at 1500 rpm for 20 seconds and then re-extruded at a relatively high extruder speed (250 rpm). min). For both extrusion stages, the four barrel temperature zones were set to 15, 25, 80 and 100°C. After extrusion, the coatings were milled using a Kemutec laboratory grading micronizer. The classifier was set to 5.5 rpm, the rotor was set to 7 rpm, and the feed was set to 5.2 rpm. Coatings were sieved to 100 µm using Demi Finex laboratory vibrating sieves with a Russel Finex mesh with a mesh size of 100 µm. The formulation compositions (in m.h.) for P1 - P11 are shown in Table 4.

Table 4: Powder composition compositions P1 - P11

RMA Powder Coating Example P1 P2 P3 P4 P5 P6 P7 P8 P9 P10 P11 Component A M-2 229.00 229.00 229.00 409.52 333.72 M-3 167.80 154.00 200.00 224.00 AA-1 700.00 M-4 537.80 Component B UA-2 100.00 100.00 100.00 178.83 275.59 145.73 423.0 ^UVECOAT® 3005 121.60 UVECOAT® ⁹¹⁴⁶ 100.00 EA-1 200.00 FM-1 100.00 C components ^Araldite® PT 912 3.53 3.53 3.53 5.68 10.78 4.50 4.62 14.40 ^Araldite® GT
7004 59.90 22.56 25.27 Benzoate TBA 4.16 4.16 4.16 4.47 12.73 3.10 9.80 9.65 3.64 4.07 MC 26.77 Benzoic acid 0.00 0.70 1.40 1.50 2.14 1.84 5.00 3.24 1.37 Additives Resiflow PV88 2.60 2.60 2.60 4.58 10.00 3.91 2.50 2.50 2.50 ^MODAFLOW®
P6000 3.00 10.00

[00129] Powder paint formulations P12-P15 were prepared using MB-1 resin masterbatch and UA-2 urethane acrylate acceptor resin. Coatings P12-P14 were formulated without pigments and with stoichiometry such as to have a reactive acryloyl/C-H2 ratio of 2:1, 1:1 and 0.75:1, respectively. The P12 coating was formulated with 20% ^Kronos® 2160 pigment, and with a stoichiometry such as to have a reactive acryloyl/C-H2 ratio of 1:1. Catalyst component C1 was ^Araldite® GT 7004. To prepare RMA powder coatings, the resins and catalyst components were first ground and mixed using a GRINDOMIX knife mill (5000 rpm) for 5 seconds. This mixture was then fed through a TSA twin screw extruder running at 300 rpm. The five temperature zones of the extruder barrel were set to 60, 100, 120, 120 and 120°C. After extrusion, the coatings were ground twice using a GRINDOMIX knife mill (10,000 rpm) for 20 seconds. The coatings were then sieved using a 90 µm mechanical sieve.

[00130] Powder paint formulations P16-P19 were prepared using M-4 malonate resin and UA-2 urethane acrylate acceptor resin. Coatings P16-P19 were formulated without pigments with stoichiometry such as to have a reactive acryloyl/C-H2 ratio of 2:1. Other components, including additives, are shown in Table 5. For the P16 and P17 paints, the catalyst system contained a base blocked with a weak acid. For paint 16, the catalyst component C1 was ^Araldite® GT 700; and the C2 component was 1,4-diazabicyclo[2.2.2]octane (DABCO). For ink 17, the catalyst component C1 was dicyclohexylcarbodiimide (DCC); and component C2 was TBA benzoate. In all of the above cases, the C3 component of the catalyst was benzoic acid. RMA powder coatings were prepared using a process similar to P1-P11 powder coatings.

Table 5: Composition of powder coating compositions P16 - P19

RMA Powder Coating Example P16 P17 P18 P19 Component A M-4 300.00 300.00 254.00 254.00 Component B UA-2 236.00 236.00 200.00 200.00 C components ^Araldite® GT 7004 81.52 DCC 14.59 Benzoate TBA 9.75 8.57 TEA acetate 7.01 DABCO 3.04 Benzoic acid 0.33 1.31 6.62 2.88 Additives Resiflow PV88 2.50 2.50 2.50 2.50

[00131] Powder paint formulations P20-P21 were prepared using M-4 malonate resin and UA-2 urethane acrylate acceptor resin. The P20 coating was formulated without pigments, while the P21 coating was formulated with 20% ^Kronos® 2160 pigment. In both cases the stoichiometry was used to have a 2:1 reactive acryloyl/C-H2 ratio and approximately 10% ^MODAFLOW® P 6000 was added as a flow additive. Catalyst component C1 was ^Araldite® PT 912; the catalyst component C2 was TBA benzoate, and the catalyst component C3 was benzoic acid. RMA P18 and P19 Powder Coats were prepared using a process similar to P12-P15 Powder Coats.

[00132] Powder paint formulations P22-P24 were prepared using M-4 malonate resin, UA-2 urethane acrylate, and UA-3 semi-crystalline acceptor resins. Coatings P21-P23 were formulated without pigments with stoichiometry such that they have a reactive acryloyl/C-H2 ratio of 1.65:1. Other components, including additives, are shown in Table 6. Catalyst component C1 was ^Araldite® GT 7004; the catalyst component C2 was TBA benzoate, and the catalyst component C3 was benzoic acid. RMA powder coatings were prepared using a process similar to P1-P11 powder coatings.

Table 6: Composition of powder coating compositions P22 - P24

RMA Powder Coating Example P22 P23 P24 Component A M-4 172.00 172.00 172.00 Component B UA-2 100.00 100.00 100.00 UA-3 30.00 30.00 30.00 C components ^Araldite® GT 7004 30.04 35.16 41.55 Benzoate TBA 6.18 6.18 6.18 Benzoic acid 0.73 1.56 2.60

Powder Coating Evaluation

[00133] To evaluate the quality of the coating of the powder material, the resulting powders were applied to the panels using a Nordson Surecoat corona sprayer. Coatings were applied to 100mm x 300mm aluminum panels to evaluate appearance. Examples P1-P19 were cured at the indicated temperatures for 20 minutes. Paint P4 was cured for a shorter time, 10 min at 120°C. Paints 20 and 21 were applied to MDF and cured using infrared heat at 130°C. In all cases, the thickness of the cured film was 60-80 µm. Samples were cooled at ambient conditions and appearance and solvent resistance were measured between 24 and 36 hours after curing. The results of the evaluation of coatings are shown in Tables 7, 9, 10, 11 and 12. The code numbers of the examples correspond to the composition numbers given above.

Table 7. Summary of P1-P4 Powder Coating Evaluation Results.

Coating example DSC Tg
(°C) Curing temperature
(°C) Time (min) Gel time
(With) Film Tg (max E'')
(°C) Film thickness
(µm) XLD
(mmol / cm ³ ) Resistance to
solvent (friction with MEK) PCI PC1A 43 120 20 90 87 61 0.15 300 2 PC1B 140 20 39 89 61 0.17 300 2 PC2A 41 120 20 160 87 75 0.16 300 3 PC2B 140 20 70 90 71 0.17 300 five PC3A 40 120 20 324 87 68 0.16 300 6 PC3B 140 20 121 89 73 0.17 300 7 PC4A 40 120 20 232 89 62 0.22 300 five PC4B 140 20 99 92 79 0.27 300 8 PC4C 120 10 232 88 70 0.18 300 6

[00134] The cure of the P1-P4 coatings was also measured by FTIR after curing at 120°C as a function of time in order to determine the 60-20/20 kinetic shape factor (SF60) and the 80-20/20 shape factor (SF80) . The conversion was measured by measuring the conversion of acryloyl groups in the composition using FTIR, focusing on the 809 cm ^-1 band, which is characteristic of acryloyl. The results are shown in Table 4 below. It can be seen that in all cases, most of the conversion took place in the first 10 minutes when the samples containing benzoic acid create an induction time before the development of the maximum curing rate. The results of this induction time are seen as an improved appearance as illustrated by the PCI scores in the table above. The shape factors of the transformation curves presented earlier are defined and listed below in Table 8.

Table 8: Curing kinetics of paint formulations P1 - P4

Quantity in mEq/g of donor resin time up to 20% (min) time up to 60%
(min) time up to 80% (min) FTIR
form factor FTIR
form factor Example benzoate TBA benzoic
acid PT912 (60-20)/20 (80-20)/20 P1 50 0 one hundred 0.52 1.42 4.79 2.2 6.6 P2 50 25 one hundred 1.68 2.50 6.09 0.76 1.77 P3 50 50 one hundred 3.95 3.93 6.81 0.27 0.42 P4 thirty 50 60 5.6 nine 13 0.6 1.3

[00135] This data illustrates that the addition of the C3 component of benzoic acid provides latency to powder paint curing as illustrated by the shape factor.

Table 9. Summary of P5-P11 Powder Coating Evaluation Results.

Cover example DSC Tg
(°C) Curing temperature (°C) Time (min) Gel time
(With) Film Tg (max E'')
(°C) Film thickness
(µm) XLD
(mmol / cm ³ ) Solvent resistance (friction with MEK) PCI PC5A 43 140 20 137 82 78 0.15 290 3 PC5B 160 20 61 82 64 0.14 300 3 PC6A 38 120 20 360 73 70 0.35 226 five PC6B 140 20 192 76 80 0.35 230 6 PC7A n.d. 120 20 535 82 70 0.29 250 6 PC7B 140 20 231 82 72 0.20 230 6 PC8A 54 120 20 230 112 67 0.58 300 five PC9A 39 120 20 289 94 73 0.38 300 five PC9B 140 20 131 95 70 0.44 300 five PC10 36 140 20 95 91 79 0.24 300 five PC11 40 140 20 125 93 73 0.28 290 four

[00136] Examples P5-P11 show that variations can be made in the RMA coating composition for both component A and component B while still achieving good cure at relatively low temperature. This is illustrated by obtaining good results in XLD crosslink density and solvent resistance as shown in Table 9. Example PC8 was prepared with materials containing isosorbide and therefore has a much higher Tg than the rest of the examples.

Table 10. Summary of P12-P15 Powder Coating Evaluation Results.

Cover example DSC Tg
(°C) Curing temperature (°C) Gel Time
(s), 140°C Film thickness
(µm) Solvent resistance (stain test, acetone), PCI PC12 51 120 230 70-78 1-2 5-6 PC13 53 120 245 70-77 1-2 3-4 PC14 53 120 270 78-88 2-3 five PC15 52 120 260 78-87 2-3 3-4

[00137] Examples P12-P15 demonstrate that RMA coatings can be prepared with materials containing acid/carboxylate functional polyester to provide C2 and C3. The acryloyl/C-H2 ratio varied for different formulations (PC12-PC14) and an RMA pigment coat (PC15) was also prepared. Relatively good curing was achieved at 120°C in all of the above cases as illustrated by the results of the acetone drop test shown in Table 10.

Table 11. Summary of P16-P19 Powder Coating Evaluation Results.

Coating example DSC Tg
(°C) Curing temperature (°C) Film thickness
(µm) Solvent resistance (friction with MEK) PCI PC16A 46 120 73 10 four PC16B 140 70 110 four PC16C 150 73 150 texture PC17A 57 120 66 thirty 3 PC17B 130 65 70 3 PC17C 140 60 210 texture PC18A 54 120 80 70 four PC18B 140 88 300 four PC19A 53 120 60 300 3 PC19B 140 70 300 3

[00138] Examples PC16 and 17 were RMA powder coatings with an LCE catalyst system. Such a catalyst system is less preferred than LCC because it is difficult to control the evaporation of the volatile acid during the curing process. At a higher cure temperature, faster evaporation of the acid on the film surface can result in a cure rate gradient. As a result, textured surfaces were observed under such conditions due to faster curing at the film surface.

[00139] Good curing can be achieved for the LCC system using DABCO as the C2 component. This is illustrated by the good solvent resistance obtained for PC18.

[00140] Example PC19 demonstrates that carbodiimide can be used as an alternative to epoxide as a C1 catalyst component in an LCC system to achieve good curing at 120 and 140°C.

Table 12. Summary of P20 and P21 Powder Coating Evaluation Results.

Coating example DSC Tg
(°C) Curing temperature (°C) Time
(min) Gel time
(s), 140°C Pencil hardness Solvent resistance (drop test, acetone) Gloss, 20°/60° PC20 54 130 five 230 2H 1 44.5/89.8 PC21 54 130 2.5 255 2H 1 34.0/79.8

[00141] The results shown in Table 12 were obtained from application tests on MDF panels. As can be seen from these results, good curing and solvent resistance were achieved in a short time using infrared heating.

Table 13: Curing Kinetics of P22-P24 Paint Formulations

Quantity in mEq/g of donor resin time up to 20% (min) time up to 60%
(min) DSC
form factor Example benzoate TBA benzoic
acid GT 7004 (60-20)/20 Curing T (°C) P22 50 35 135 0.94 1.54 0.63 120 P23 50 75 175 1.93 2.54 0.32 120 P24 50 125 225 3.34 4.05 0.21 120

[00142] The curing of the P22-P24 coatings was measured using isothermal DSC scans at 120°C in order to determine the kinetic form factor SF(DSC) 60-20/20. The results are shown in Table 13 above. These data show that the addition of the C3 component of benzoic acid provides latency to the curing of the powder paint, as illustrated by a decrease in the shape factor of the DSC.

Curing Characteristics of LCC2 Latent Catalyst System for Acrylate Component B

[00143] Model formulations were prepared in butyl acetate solvent using a CO ₂ blocked base ( ^Acure® 500) as the LCC2 catalyst system, which deblocks very quickly at 100°C and which forms in combination with the S3 component to form an S2/S3 acid mixture XH and the conjugate base of the X-latent catalytic system LCC2.

[00144] The crosslinkable components used were 10 grams of ^Acure® 510-100 malonate-functional polyester and 4.95 grams of DTMPTA (with acrylate functionality). 0.72 g of ^Acure® 500 catalyst with or without S3 component was then added. When used XH components S3, they were added in the amount of 2 mmol. These solutions were deposited as thin films (with a target dry thickness of 60 µm) on an ATR crystal heated to 100° C. and the acrylate concentration as a function of time was monitored using FTIR.

[00145] Without the S3 additive, the film was immediately crosslinked and detached from the ATR crystal before the first FTIR measurement was taken. Similar observations were obtained with the addition of S3 in the form of succinimide (pKa=9.5) and 1,2,4-triazole (pKa=10.4). Thus, compounds X-H, which are known to be effective retarders for room temperature curing of acrylate-based compositions, have been found to be unsuitable for use at powder curing temperatures. In addition, insufficient retention was still observed with p-toluenesulfonamide (pKa=10.17) and 5,5-dimethylhydantoin (pKa=9.19).

[00146] Useful delayed cure under these curing conditions at 100°C can be observed for acrylate-based S1 compositions containing S3 components having lower pKa values. The table below shows the time taken to reach 20%, 50% and 60% C=C conversion.

Table 14: Curing characteristics of LCC2 S2 components for acrylate

S3 component pKa t(20%) min t(50%) min t(60%) min 1,3-cyclohexanedione 5.3 five 9.5 8 Meldrum's acid five 8 21 17 ethyltrifluoroacetoacetate 7.6 21 63 n.d. diethyl oxal propionate 23 51 n.d.

n.d.: not defined

[00147] It has been found that for Michael acceptor S1 other than acrylates such as methacrylates, fumarates and maleates, other requirements apply to the S3/S2 components to ensure sufficient retardation of the catalyst system.

Cure Characteristics of LCC2 Latent Catalyst System for Methacrylate Component B

[00148] For methacrylate functional components B, FTIR experiments were again performed on an ATR crystal heated to 100°C as described above. In this case, the same ^Acure® 510-100 donor (10 g) mixed with the (acrylate-functional) TMPTMA acceptor (2.4 g) was used. ^Acure® 500 Blocked Base Initiator was used in the formulation at a concentration of 50 µeq/g of solid binders; when XH species (forming S2 after neutralization) were used as S3, the amount relative to base is shown in the table below. The experiments were carried out as described above.

[00149] For such a composition based on S1/B methacrylate components, not containing any S3 component, we found that curing for this composition with high concentrations of acceptor and donor groups is quite fast at 100°C, and is essentially completed within minutes. When using succinimide, 1,2,4-triazole or benzotriazole, a useful curing delay can be obtained at these practical levels.

Table 15: Curing characteristics of LCC2 S2 components for methacrylate

pKa t(20%) min t(50%) min t(60%) min No 0.5 1.2 1.3 succinimide (2.3 eq/base) 9.5 5.3 12 15 1,2,4-triazole (6 eq/base) 10.4 2 2.8 3.2 benzotriazole (3 eq/base) 8.2 8 10.5 12

[00150] These examples show that X-H compounds having a pKa above 8 do not slow down effectively when S1 (=B) is an acrylate. Therefore, when S1 is an acrylate in the LCC2 catalyst system, it is preferable to use an X-H component with a pKa<8 as the S2 component. When component S1 (=B) is methacrylate in the LCC2 catalyst system, it is preferable to use component X-H with pKa below 10.5 as component S2.

Claims (96)

1. A powder coating composition containing one or more crosslinkable components and a catalyst, characterized in that one or more crosslinkable components are crosslinked using the Michael reaction (RMA), and this powder coating composition contains a) a crosslinkable component A having at least 2 acid donor groups C-H in activated methylene or methine, b) a crosslinkable B component having at least 2 activated unsaturated C=C acceptor groups which react with the A component via a Michael reaction (RMA) to form a crosslinked network, c) a latent catalyst system C containing a strong base precursor to catalyze the RMA crosslinking reaction with a delay at a curing temperature below 200°C, wherein catalyst system C is a latent LCC catalyst system having a chemical latency containing components that react at a curing temperature to initiate a reaction between crosslinkable components A and B with a delay, said latent LCC catalyst system comprising in the LCC1 embodiment: a) weak base C2, b) C1 activator reacting with C2 or protonated C2 at curing temperature, where the C1 activator is selected from the group containing epoxy, carbodiimide, oxetane, oxazoline or aziridine functional components, preferably epoxy or carbodiimide; in the LCC2 embodiment: a) a weak base C2, which is an S2 donor in the Michael reaction, and b) activator C1, which is an acceptor of S1 in the Michael reaction and contains an activated unsaturated group C=C, reacting with S2 at the curing temperature, and when S1 is an acrylate, S2 has a pKa of the conjugate acid below 8, the pKa being defined as the value in an aqueous medium, and when S1 is methacrylate, fumarate, itaconate or maleate, S2 has a pKa of the conjugate acid below 10.5. 2. The powder material coating composition of claim 1, wherein the latent catalyst system in the LCC1 embodiment further comprises a C3 acid, preferably a protonated C2. 3. A powder coating composition according to claim 1, wherein in an embodiment of the LCC1 latent catalyst system the weak base C2 has a pKa of the conjugate acid greater than 1, preferably 1.5, more preferably 2, and even more preferably at least 3 units lower than the pKa of the C-H acid groups of the main component A, and in which C2 is preferably a weak base nucleophilic anion selected from the group consisting of carboxylate, phosphonate, sulfonate, halide or phenolate anions, or salts thereof, or a non-ionic nucleophile, preferably a tertiary amine and more preferably a weak base C2 is a weak base nucleophilic anion selected from the group, consisting of carboxylate, halide or phenolate salts or 1,4-diazabicyclo[2.2.2]octane (DABCO), and the latent catalyst system preferably also contains a C3 acid having a pKa greater than 1, preferably 1.5, more preferably 2, and even more preferably at least 3 units lower than the pKa of the C-H acid groups of the main component A, wherein the C3 acid preferably is a protonated C2. 4. The powder material coating composition of claim 1, wherein the latent catalyst system in the LCC2 embodiment further comprises a C3 acid, which is an S3 acid, in which the corresponding base is also a Michael donor, preferably a protonated S2. 5. A powder coating composition according to claim 1 or 4, wherein in an embodiment of the LCC2 latent catalyst system the weak base S2 is preferably selected from the group of phosphines, N-alkylimidazoles and fluorides or is the nucleophilic anion of the weak base X ^- from a compound containing an acidic XH group, in which X is N, P, O, S or C, in which the anion X ^- is a Michael reaction donor reactive with the S1 activator and having a pKa value of the corresponding conjugate acid XH of less than 8, which is further greater than 1, preferably 1.5, more preferably 2, and still more preferably at least 3 units lower, than the pKa values of the acid groups CH of the main component A, and the latent catalyst system preferably also contains an acid S3 having a pKa value greater than 1, preferably 1.5, more preferably 2, and even more preferably at least 3 units lower than the pKa values of the C-H acid groups of the main component A , wherein the acid S3 is preferably the protonated S2. 6. Coating composition of powder material according to any one of paragraphs. 1-3, in which the weak base C2 is added as a salt containing a cation which is not acidic, preferably a cation according to the formula Y(R') ₄ , in which Y is N or P and in which each R' may be the same or different alkyl, aryl or aralkyl group, possibly linked to the polymer, or the cation is a protonated very strong basic amine which is preferably selected from the group of amidines, preferably 1,8-diazabicyclo(5.4.0)undec-7-ene ( DBU); or guanidines, preferably 1,1,3,3-tetramethylguanidine (TMG). 7. Coating composition of powder material according to any one of paragraphs. 1-6 containing a) in the case of an LCC1 catalyst system, activator C1 in an amount of 1-600 µeq/g, preferably 10-400, more preferably 20-200 µeq/g, where µeq/g is the amount of µeq relative to the total mass of binders A and B and the system LCC catalyst, or in the case of an LCC2 catalyst system, S1 activator in an amount of at least 1 µeq/g, preferably at least 10, more preferably at least 20 and most preferably at least 40 µeq/g, b) a weak base C2 in an amount of 1-300 µeq/g, preferably 10-200, more preferably 20-100 µeq/g, relative to the total weight of binders A and B and the LC catalyst system, c) optional C3 acid in an amount of 1-500, preferably 10-400, more preferably 20-300 µeq/g and most preferably 30-200 µeq/g, d) moreover, the number of C1 or respectively S1 i) is higher than the amount of C3, preferably by 1-300 µeq/g, preferably 10-200 and more preferably 20-100 µeq/g, and ii) is preferably higher than the amount of C2, and iii) more preferably is higher than the sum of the amounts of C2 and C3. 8. Coating composition of powder material according to any one of paragraphs. 1-7, in which a) weak base C2 is 10-100 mol.% of the sum of C2 and C3, b) the amount of acid C3 is 20-400 mol%, preferably 30-300 mol% of the amount of C2, c) preferably the ratio of the molar amount of C1 to the sum of the amounts of C2 and C3 is at least 0.5, preferably at least 0.8, more preferably at least 1, and preferably at most 3, and more preferably at most 2, d) the ratio of C1 to C3 is preferably at least 1, more preferably at least 1.5 and most preferably at least 2. 9. Coating composition of powder material according to any one of paragraphs. 1-8 having a cure profile determined by measuring the conversion of C=C unsaturated bonds of component B as a function of time using FTIR, at a cure temperature selectable between 80, 90, 100 and up to 200, 150, 135, or 120°C , in which the ratio of time to change the conversion C=C from 20 to 60% to the time to achieve 20% conversion is less than 1, preferably less than 0.8, 0.6, 0.4 or 0.3, and preferably the time to reach 60% conversion is less than 30, 20, 10 or 5 minutes, and preferably the time to reach 20% conversion at 100°C is at least 1, preferably at least 2, 3, 5, 8 or 12 minutes. 10. Coating composition of powder material according to any one of paragraphs. 1-9, in which a) the crosslinkable component A contains at least 2 acid donor groups C-H in activated methylene or methine in the structure Z1(-C(-H)(-R)-)Z2, where R is hydrogen, hydrocarbon, oligomer or polymer, and Z1 and Z2 are the same or different electron withdrawing groups, preferably selected from keto groups, ester groups, cyano groups or aryl groups, and preferably contains activated C-H derivatives having a structure according to formula 1

Formula 1, where R is hydrogen or optionally substituted alkyl or aryl and Y and Y' are identical or different substituent groups, preferably alkyl, aralkyl, aryl or alkoxy, or where in formula 1 the groups -C(=O)-Y and/or -C(=O)-Y' are substituted by a CN group or aryl, but not more than one aryl, or where Y or Y' may be a -NRR' group (R and R' are hydrogen or optionally substituted alkyl), but preferably not both, with R, Y or Y' optionally providing connection to an oligomer or polymer, and said component A is preferably a malonate, acetoacetate, malonamide, acetoacetamide or cyanoacetate group, preferably providing at least 50, preferably 60, 70 or even 80% of the total number of acid groups C-H in the crosslinked component A, b) Component B containing at least 2 activated unsaturated RMA acceptor groups, preferably derived from acryloyl, methacryloyl, itaconate, maleate or fumarate functional groups, and preferably at least one and more preferably both components A or B is a polymer, and where preferably the composition contains a total number of C-H donor groups and C=C acceptor groups per gram of solid binders from 0.05 to 6 meq/g and preferably the ratio of C=C acceptor groups to C-H donor groups is greater than 0.1 and less than 10. 11. Coating composition of powder material according to any one of paragraphs. 1-10, in which at least one of the crosslinkable components A or B or hybrid A/B is a polymer, preferably selected from the group of acrylic, polyester, polyesteramide, polyesterurethane polymers, which a) has a GPC number average molecular weight Mn of at least 450 g/mol, preferably at least 1000, more preferably at least 1500 and most preferably at least 2000 g/mol, b) has a GPC weight average molecular weight Mw of at most 20000 g/mol, preferably at most 15000, more preferably at most 10000 and most preferably at most 7500 g/mol, c) preferably has a molecular weight distribution Mw/Mn less than 4 and more preferably less than 3, d) has an equivalent weight EQW in C-H or C=C of at least 150, 250, 350, 450 or 550 g/mol and preferably at most 2500, 2000, 1500, 1250 or 1000 g/mol and a number average functionality of C-H reactive groups, or C=C 1-25, more preferably 1.5-15, even more preferably 2-15 and most preferably 2.5-10 C-H groups per molecule, e) preferably has a melt viscosity at a temperature in the range of 100-140° C. less than 60 Pa.s and more preferably less than 40, 30, 20, 10 or even 5 Pa.s, f) preferably contains amide, urea or urethane linkages and/or contains high Tg monomers, preferably cycloaliphatic or aromatic monomers, in particular polyester monomers selected from the group consisting of 1,4-dimethylolcyclohexane (CHDM), tricyclodencandimethanol (TCD- diol), isosorbide, penta-spiroglycol or hydrogenated bisphenol A and tetramethylcyclobutanediol, g) has a Tg greater than 25°C, preferably greater than 35°C, more preferably greater than 40, 50 or even 60°C, which is determined as the midpoint by DSC at a heating rate of 10°C/min, or is a crystalline polymer with a temperature melting point 40-150°C, preferably 130°C, preferably at least 50 or even 70°C and preferably lower than 120°C (which is determined by DSC at a heating rate of 10°C/min). 12. Coating composition of powder material according to any one of paragraphs. 1-11, containing one or more components A or B or components of the catalyst system C or separate different plasticizers, which are in a (semi-)crystalline state in powder and have a melting point of 40-130°C, preferably 50-120°C, more preferably 60-110°C and most preferably 60-100°C. 13. Coating composition of powder material according to any one of paragraphs. 1-12, in which component B is polyester (meth)acrylate, polyesterurethane (meth)acrylate, epoxy (meth)acrylate or urethane (meth)acrylate, or is a polyester containing blocks of fumarate, maleate or itaconate, preferably fumarate , or is a polyester, with an isocyanate end group or an epoxy-functional activated unsaturated group. 14. A method of preparing a coating composition from a powder material according to any one of paragraphs. 1-13, including stages: a) providing component A, component B and catalyst system C, b) extruding the components at a temperature Tcomp below 140°C, c) cooling, d) shaping the extruded mixture to obtain a granulate before, during or after cooling, e) grinding the granulate into powder. 15. The method according to claim 14, in which in step a), in addition to component A, component B and catalyst system C, additional additives are also added, and / or in which step c) includes an annealing step to ensure crystallization of the crystallizing components, and/or wherein further additives are also added to the powder prior to the step of grinding the granulate. 16. A method for coating a substrate with a powder material, including a) providing a powder having a coating composition of powder material according to any one of paragraphs. 1-13 or obtained using the method according to any one of paragraphs. 14-15, b) depositing a layer of powder on the surface of the substrate, which is a temperature sensitive substrate, and c) heating to curing temperature Tcur from 75 to 200°C, d) wherein the melt viscosity at the curing temperature Tcur is less than 60 Pa⋅s, e) and curing at Tcur for a curing time of less than 40 minutes. 17. Products coated with a powder having a coating composition according to any one of paragraphs. 1-13 or obtained using the method according to any one of paragraphs. 14-15 having a temperature sensitive substrate and in which the crosslink density of the XLD coating (determined by DMTA) is at least 0.01 mmol/mL and less than 3 mmol/mL. 18. The use of system C catalyst according to any one of paragraphs. 1-13 in preparing crosslinkable RMA powder coating compositions to catalyze the crosslinking reaction in crosslinkable RMA powder coating compositions at curing temperatures below 200°C. 19. A crosslinkable RMA polymer suitable as a component of the coating composition of powder material according to claim 1, selected from the group consisting of acrylic, polyester and polyester urethane polymers containing as a functional group one or more components A containing at least 2 acid donor groups C-H in activated methylene or methine in the structure Z1(-C(-H)(-R)-)Z2, where R is hydrogen, hydrocarbon, oligomer or polymer, and Z1 and Z2 are the same or different electron withdrawing groups selected from keto groups, ester groups, cyano groups or aryl groups, while this polymer a) has a GPC number average molecular weight Mn of at least 450 g/mol, b) has a weight average molecular weight Mw determined by GPC of at most 20,000 g/mol, c) has an EQW equivalent weight in C-H of at least 150 g/mol and a number average functionality of C-H reactive groups of 1-25 C-H groups per molecule, d) has a Tg above 25°C as determined by DSC at a heating rate of 10°C/min, or is a crystalline polymer with a melting point of 40-150°C (as determined by DSC at a heating rate of 10°C/min) . 20. The crosslinkable RMA polymer according to claim 19, wherein one or more components A contain an activated C-H derivative having a structure in accordance with formula 1

Formula 1, where R is hydrogen or optionally substituted alkyl or aryl and Y and Y' are identical or different substituent groups, preferably alkyl, aralkyl, aryl or alkoxy, or where in formula 1 the groups -C(=O)-Y and/or -C(=O)-Y' are substituted by CN or aryl, but not more than one aryl, or where Y or Y' may be NRR' (R and R' are hydrogen or optionally substituted alkyl), but preferably not both , wherein said component A is preferably a malonate or acetoacetate group and most preferably a malonate group providing at least 50%, preferably 60%, 70% or even 80% of the total C-H acid groups in the crosslinkable component A, with R, Y or Y' provide a bond with the polymer, and where the polymer contains: a) optionally one or more B components containing at least 2 activated unsaturated RMA acceptor groups, preferably acryloyl, methacryloyl, maleate or fumarate functional groups forming an A/B hybrid polymer, and b) optionally one or more components of catalyst system C, while this polymer a) preferably has a molecular weight distribution Mw/Mn less than 4 and more preferably less than 3, b) preferably has a melt viscosity at a temperature in the range of 100-140° C. less than 60 Pa.s and more preferably less than 40, 30, 20, 10 or even 5 Pa.s, c) preferably contains amide, urea or urethane linkages and/or contains high Tg monomers, preferably cycloaliphatic or aromatic monomers, in particular polyester monomers selected from the group consisting of 1,4-dimethylolcyclohexane (CHDM), tricyclodencandimethanol (TCD- diol), isosorbide, penta-spiroglycol or hydrogenated bisphenol A and tetramethylcyclobutanediol. 21. A polymer suitable as a component of a powder coating composition according to claim 1, containing C2 weak base groups and where this polymer is selected from the group consisting of acrylic, polyester and polyester urethane polymers, and this polymer has a) acid value in non-neutralized form of at least 3 mg KOH/g, b) a quaternary ammonium or phosphonium cation, c) Mn value is at least 500 and Mw value is not greater than 20000. 22. The polymer according to claim 21, where this polymer additionally contains acidic C3 groups, and the C2 groups of a weak base are formed by partial or complete neutralization of acidic C3 groups on the polymer, and C2 and C3 are preferably carboxylate and carboxylic acid groups, and / or this polymer additionally contains C-H donor groups, C=C acceptor groups, or both; and this polymer d) if C-H donor groups and/or C=C acceptor groups are present, has an EQW of a reactive C-H donor or C=C acceptor of at least 150 g/mol and not more than 2000 g/mol, e) if C-H donor groups and C=C acceptor groups are absent, has an acid value in unneutralized form of at least 10 mg KOH/g. 23. Use of the crosslinkable RMA resin according to claim 19 or 20 in crosslinkable RMA powder coatings based on the powder coating composition according to claim 1. 24. The use of a polymer according to any one of paragraphs. 21, 22 as a latent main component of the powder coating composition catalyst according to claim 1.