NL1000919C2 - Powder paint composition. - Google Patents

Description

- 1 -

POWDER PAINT COMPOSITION

The invention relates to a thermosetting powder paint composition comprising (i) a polymer with reactive groups for the crosslinker (ii) a crosslinker containing epoxy groups, the crosslinker having at least one Cs-C26 linear or branched aliphatic chain and an epoxy functionality greater than 1, the epoxy group being present on the aliphatic chain (iii) at least one catalyst for the reaction of polymer (i) with crosslinker (ii) (iv) at least one stabilizer (v) if desired other additives (vi) if desired pigment or dyes.

Such a composition is known from EP-A-20 600546. Although good coating properties can be obtained with the compositions as described, a further optimization is desired in resistance to discoloration during (long-term) exposure to high temperatures in electric or gas ovens.

This object is achieved in that the stabilizer (iv) uses a phosphite comprising at least one group of formula (1)

R1 - O

30 \ P-O-R3 (1). /

R2 - O

Wherein R1 is an aliphatic group, R2 is an aliphatic or aromatic group and R3 is an aromatic group, any aliphatic and aromatic group may be substituted.

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- 2 - PN 8336

The powder paint composition of the invention comprises a polymer and crosslinker (together the binder) as described in EP-A-600546. (The contents of EP-A-600546 are incorporated by reference in this description 5.) The polymer preferably has a Tg (glass transition temperature) greater than 40 ° C, especially greater than 60 ° C. The polymer viscosity is preferably less than 8000 dPas at 158 ° C, and will often be higher than 100 dPas (measured by Emila).

The molecular weight of the polymer is preferably greater than 1500, and preferably less than 7000.

The polymer is preferably a polyester, polyacrylate or polyether, with the reactive groups being carboxy, hydroxy, anhydride or epoxy. The polymer preferably has a functionality less than 1.25 meg / gram polymer, more particularly less than 0.9 meq / gram. The functionality is preferably higher than 0.18 meq / gram. Suitable polymers are described in EP-A-600546.

The crosslinker comprises linear or branched aliphatic chains with 5-26 carbon atoms on which epoxy groups are present. The amount of oxirane oxygen present as an epoxy group on the aliphatic chains is more than 0.1 meq / gram relative to the binder composition. Preferably this is more than 0.15 meq / gram, more particularly more than 0.25 meq / gram. The amount of oxirane oxygen on the aliphatic chains will usually be less than 1.3 meq / gram, and preferably less than 1.0 meq / gram.

The crosslinker preferably comprises linear or branched chains with more than 12 carbon atoms. Preferably, the aliphatic chains on which the epoxy groups are present are linear.

The amount of oxirane oxygen in the crosslinker is preferably more than 2% by weight, in particular more than 3% by weight. The amount is usually less than 20% by weight and in practice is often less than 15% by weight.

Preferably the epoxy group is not terminal.

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- 3 - PN 8336

Preferably, the epoxy group is not present at the α, β position relative to a heteroatom, and not present at the β, γ position relative to a carbon, if a double bond hetereoatom is bonded to that 5 carbon atom. In particular, the crosslinker mainly contains epoxy groups with a structure according to formula (2) 0 / \ 10 -CH2-CH-CH-CH2- (2)

Preferably the crosslinker comprises a plurality of aliphatic chains with one or more epoxy groups. The functionality of the crosslinker is preferably greater than 1.2, and in particular greater than 2.1. If the aliphatic chains are part of a polymeric crosslinker, the functionality is usually less than 50.

Examples of suitable crosslinkers are described in EP-A-600546. As crosslinker, for example, epoxidized fatty acid esters, epoxidized etherified fatty alcohols or epoxidized amidated fatty amines can be used. Epoxidized fatty acid ester is preferably used, such as, for example, epoxidized oils. Particularly suitable are, for example, epoxidized linseed or soybean oil.

The binder composition contains more than 50 wt% polymer and less than 50 wt% crosslinker. Preferably, the binder composition contains 98-70 wt% polymer, and 2-30 wt% crosslinker. Preferably, the binder is manufactured as described in WO-A-94/26808.

As a catalyst, a compound is used which catalyzes the reaction between the polymer (i) and the crosslinker (ii). Suitable catalysts are described, for example, in EP-A-600546. For acid-epoxy reactions, a nitrogen or metal-containing compound is preferably used as a catalyst. For epoxy anhydride reactions, one of the nitrogen or metal-containing compounds as described herein is preferably also used. For epoxy-hydroxy and epoxy-epoxy reactions, an additional cross-linking agent is preferably used in addition to a catalyst, such as, for example, a polyanhydride, dicyandiamide, polycarboxylic acid or a polyphenol. A nitrogen or metal-containing compound is preferably used as the catalyst. Dicyandiamides can also function as a catalyst.

Suitable nitrogen-containing compounds are, for example, compounds derived from imidazole, guanidine, tertiary amine and pyridine. In particular, guanidines and imidazoles such as, for example, tetramethylguanidine (TMG), acetyl-TMG, isocyanate-TMG adducts, 1-benzimidazole, 2-methylimidazole, 5,6-15 dimethyl-benzimidazole and 1-ethylimidazole, are very suitable good color stability.

As metal-containing compound, which is particularly suitable for acid-epoxy, hydroxy-epoxy-anhydride, epoxy-anhydride and epoxy-epoxy-anhydride reactions, for example, a metal hydroxide, metal alkoxide or metal carboxylate is used, wherein the metal can be selected from lithium, sodium, potassium, cesium, magnesium, calcium, tin, copper or zinc.

Lithium or sodium are preferably used as metal because they have a very good catalytic effect. Lithium is particularly preferred.

The metal compound preferably used is a metal alkoxide or metal carboxylate, the alkyl group having 1-30 carbon atoms. Preferably, a compound with more than 3, and in particular more than 6, carbon atoms is used.

A metal carboxylate is particularly preferred, because it proves to be particularly effective and easy to process.

Generally, the carboxylic acid (of the metal carboxylate) has a pKa between 3-8.

Suitable carboxylic acids are, for example, 1 0 0 0 91 9.

- PN 8336 saturated aliphatic mono- and dicarboxylic acids, unsaturated aliphatic acids, carbocyclic carboxylic acids, heterocyclic carboxylic acids, hydroxycarboxylic acids, alkoxycarboxylic acids, oxocarboxylic acids, aminocarboxylic acids and amide carboxylic acids.

Examples of saturated aliphatic monocarboxylic acids are formic, acetic, propionic, butyric, isobutyric, valeric, isovaleric, pivalic, lauric, myristic, palmitic, 10-octanoic, 2-ethylhexanoic, stearic, hydroxypivalic, and isononic acids. Other suitable aliphatic monocarboxylic acids are acids available with the Koch reaction such as, for example, 2,2-dimethylpropanoic acid, (pivalic acid, for example Versatic 5®, Versatic is a brand name of Shell), 2,2-dimethylbutanoic acid (for example, Versatic 6®), 2, 2-dimethylpentanoic acid (Versatic 7d®), 2-ethyl-2-methylbutanoic acid (Versatic 7e®), neononic acid (Versatic 7e®) and neodecanoic acid (Versatic 10®).

Examples of saturated aliphatic dicarboxylic acids are oxalic, malonic, succinic, glutaric, adipic, pimelic, turmeric, decanedicarboxylic, azelaic, and sebacic acids.

Examples of unsaturated aliphatic acids are acrylic acid, propiolic acid, methacrylic acid, crotonic acid (trans isomer), isocrotonic acid (cis isomer), oleic acid (cis isomer), linoleic acid, linolenic acid, elaidic acid (trans isomer), maleic acid, fumaric acid, citraconic acid and mesaconic acid.

Examples of carbocyclic carboxylic acids are camphoric acid, benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, naphthoic acid, toluic acid, hydratropic acid, atropic acid and cinnamic acid.

Examples of heterocyclic carboxylic acids are furoic acid (furan carboxylic acid), nicotinic acid, isonicotinic acid.

Examples of hydroxy, alkoxy and oxocarboxylic acids are glycolic acid, lactic acid, glycerol acid, 1 0 0 0; - 6 - PN 8336 malic, tartaric, tropic, benzil, salicylic, anisic, vanillic, veratrum, piperonic, callus, 6-oxohexanoic, 5-oxo-valeric, 3-oxovaleric, 3,5-dioxovaleric, 5 2-oxo 1-cyclohexane carboxylic acid, β-oxocyclohexane-proprionic acid, γ-οχο-6-chrysene butyric acid and β-οχο-3-pyridine propionic acid.

Preferably, decanoic acid, octanoic acid, 2-ethylhexanoic acid, stearic acid, lauric acid, neodecanoic acid, an acid obtained with the Koch reaction, decane dicarboxylic acid or benzoic acid are used. If desired, use can also be made of a mixture of 2 or more of the said compounds.

Suitable alcohols are, for example, mono-alcohols, diols and triols such as, for example, methanol, ethanol, propanol, isopropanol, butanol and isomers, glycol, neopentyl glycol, butanediol, hexanediol, cyclohexanedimethylol, glycerol, trimethylolpropane and tr is (hydroxyethyl) isocyanurate.

The amount of catalyst suitable for the reaction is preferably selected to provide the desired cure and flow. For example, with a suitable catalyst, curing takes place in 20 to 30 minutes at 150 ° C, or in 10 to 15 minutes at 180 ° C, up to 5 to 10 minutes at 200 ° C. The amount of catalyst is usually selected between 0.1 and 5% by weight and is preferably between 0.4 and 3% by weight relative to the binder.

In order to obtain good resistance to discoloration when exposed to high temperatures, it is necessary to use one or more stabilizers in the powder paint composition. According to the invention, at least one of the stabilizers is a phosphite with one or more groups of formula (1) 10 00 91 $.

35 - 7 - PN 8336

R1 - O

P-O-R3 (1) 5 R2 - 0 wherein R 1 is an aliphatic group, R 2 is an aliphatic or aromatic group and R 3 is an aromatic group, wherein the aliphatic and aromatic group may be substituted.

If the phosphite is a mono-, di- or triphosphite, the molecular weight is generally less than 1500, preferably less than 1000. If the phosphite is an oligo or polyphosphite, the molecular weight is generally less than 20,000.

The melting point of the phosphite is generally below 250 ° C and is preferably below 180 ° C because it provides good workability.

Preferably, the phosphite is a di- or triphosphite, because those compounds prove to be very effective.

The phosphite always has three groups attached to a phosphorus atom, which are bonded via an oxygen atom. The three groups are either aliphatic or aromatic, with at least one aliphatic and at least one aromatic.

The aliphatic and the aromatic groups can be substituted with aromatic and aliphatic groups. Heteroatoms such as, for example, oxygen, nitrogen, sulfur, phosphorus or halogens can also be present.

The different groups can also form bridging groups together, such as, for example, 1,3-propanediol based groups or 2,2'-bis-phenol based groups.

The aliphatic and aromatic groups can also form bridging groups for multiple phosphites, such as, for example, pentaeritrytol and bisphenol-A based 10 00 91 9. - 8 - PN 8336 groups.

The aliphatic and the aromatic groups each generally have a molecular weight of less than 600 and generally contain less than 5 carbon atoms.

The aromatic groups are preferably phenyl groups. The phenyl groups can be substituted with one or more alkyl, aryl, halogen, alkoxy or alkylamide groups.

Preferably, the phenyl groups are substituted with at least one or more linear or branched alkyl groups with 3-24 carbon atoms and / or with unsubstituted or substituted aryl groups with 6-36 carbon atoms. Preferably at least one of the substituents 15 is at the ortho site.

Examples of very suitable substituents are t-butyl, isopropyl, n-nonyl, isononyl, stearyl, phenyl, benzyl and isopropylphenyl.

The aliphatic groups are preferably linear or branched chain hydrocarbons, optionally with ether or amine groups. The aliphatic groups can contain aromatic or heterocyclic groups. Examples of suitable aliphatic groups are tris-hydroxyethyl isocyanurate, tris-hydroxyethylamine, pentaeritrytol, 2,2-cyclohexyl-1,3-propanediol, ethanol, dodecanol and 2-ethylhexanol.

A very suitable class of compounds is formed by phosphites, each phosphorus atom in the polyphosphite being surrounded by a 2,2-spiro-substituted 1,3-propanediol compound and a substituted phenol compound. The 2,2-spiro-substituted-1,3-propanediol compound may be 2,2-dialkyl-1,3-propanediol, but may also be part of a group comprising multiple 2,2-spiro-substituted-1,3- propanediol groups 35. The substituted phenolic compound can be a mono- or polyhydroxy compound, and can include, for example, 1-5 aryl groups.

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- 9 - PN 8336

Examples of suitable stabilizers are compounds of formulas 3, 4, 5 and 6 R4-0-OP .PO-0-R4 (3) '0- * No' where R4, H or one or more substituents on the aromatic ring ( 0) represents; 10 / ° - \ / —0— \ y— ° v.

r4_0_O-p yf ^^ PO-0-R4 (4) N0- / ^ R5 R5> -O4 ^ 15 where R4 has the aforementioned meaning, and where R5 together form an ether, (alkyl) amine or hydrocarbon bridge, or independently of each other hydrogen, hydroxy, alkoxy or alkyl of 1-6 carbon atoms; "<Ê> -OC> -: '· R4 —Jn 25 where R4 has the meaning defined above, and n is a number between 2-40; r6v v ~ 0 yR4 Ri 0 —v R6” <ï> o- <oX > ·> Where R4 has the above defined meaning, R6 each individually or in pairs represents a (cyclo) alkyl or aryl group 35 with 1-30 carbon atoms, and Y represents a bridge between the two phenyl groups or a sulfur, amine, i-propylamine, methyl, 2,2'-propyl or sulfoxide.

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- 10 - PN 8336

Preferably, the stabilizer is a bisphenyl pentaerythritol diphosphite as represented by formula (3).

Very suitable compounds with 2 alkyl groups and one atyl group per phosphite are, for example, bis- [2,4-di-tertiarybutyl-phenyl] -pentaerythritol-di-phosphite (Ultranox 626®), bis- [2,6-di-tertiarybutyl -4-methyl-phenyl] -pentaerythritol-di-phosphite (MARK PEP 36®), bis (2,4-dicumylphenyl) pentaerythritol diphosphite (Doverphos® S-9228), 10 and bis [nonylphenyl] pentaerythritol diphosphite (MARK PEP 4C®) .

Very suitable compounds with 2 aryl groups and an aliphatic group per phosphite are tris [2,2'-bis (6-tert-butyl (phenyl) ethylphosphite] amine (Irgafos® 12 from Ciba Geigy), 2,2-methylene bis- (4,6-di-t-butylphenyl) -15 octyl phosphite (MARK HP 10®) and bis (2,4-ditert-butyl-6-methylphenyl) ethyl phosphite.

Unexpectedly, it appears that the stabilizers according to the invention are effective for suppressing discoloration, while other stabilizers with somewhat similar structure give much less or hardly any improvement in discoloration resistance when exposed to high temperatures. Examples of ineffective compounds are compounds with three aliphatic groups on the phosphite (such as, for example, di-stearyl-pentaerithrytol diphosphite); or a compound having only aromatic groups such as, for example, tris- [2,4-ditertiarybutylphenyl] phosphite, tris-nonylphenylphosphite or tetrakis- [2,4-ditertiarybutylphenyl] -4,4'-biphenylene-diphosphonite.

The stabilizer according to the invention falls into the class of compounds which are also referred to as secondary antioxidants.

Preferably, a primary antioxidant is also used in the composition according to the invention.

Sterically hindered phenols are preferably used as primary antioxidants, such as, for example, Santowhite Powder®, Irganox 1010®, Irganox 245®, Irganox 1 0 0 0 91 9.

- 11 - PN 8336 1098 *, Sumiliser GA80 or Sumiliser GS. Substituted phenols such as Irganox 565 * are also very suitable. This class of compounds generally has a molecular weight of less than 2000, and the compounds contain one or more phenol groups - substituted in at least one ortho position (relative to the phenolic hydroxy). As the substituent, t-butyl, i-propyl, phenyl, methylphenyl, phenol, methylcyclohexyl, methyl and ethyl are very suitable. Preferably, the primary antioxidant contains 2 or more sterically hindered phenol groups.

Another very suitable type of primary antioxidant is an aromatic amine. Aromatic amines are less suitable for preventing discoloration in gas ovens (NOx). Aromatic amines can be used alone or in combination with another primary antioxidant. As the aromatic amine, 4,4'-di-cumyl-diphenylamine, 2,2,4-trimethyl-1,2-dihydroquinoline, 4,4-di-octyl-di-phenylamine or N, N'-di sec-butyl-para-phenylenediamine very suitable.

The effectiveness of the various primary and secondary antioxidants can be determined by simple tests, as will also be apparent from the examples. Although the aim is to choose the 25 stabilizers so that the powder paint gives good results in all discolouration tests, it can be advantageous to optimize a powder paint composition for ordinary ovens or gas ovens, because only in the second case discoloration under the influence of NO, role.

The powder paint composition preferably contains an effective amount of one or more stabilizers. The stabilizers are preferably used individually in an amount of between 0.05 and 2% by weight (on the total binder). In particular, between 0.25-35 1% by weight is used. When an aromatic amine is used in combination with a sterically hindered phenol, the amount of aromatic amine is generally 10 00 91 9.

PN 8336 is small, and an effective amount is, for example, an amount between 0.05-1.0% by weight on the total binder. Preferably an amount is chosen between 0.1 and 0.5% by weight.

Particularly preferred, at least one or more primary antioxidants are used in a total amount of 0.25-1 wt% (relative to the binder), and one or more secondary antioxidants in an amount of 0.5-1 wt% .%.

The discolouration resistance is preferably determined in various experiments.

First, there should be (virtually) no discoloration when curing. The powder paint is cured, for example, by heating the paint at 200 ° C for 10 min. The b * value (measured with a Dr. Lange Micro Color type Lmg 051; DIN 6174, CIE LAB 1976) is then preferably less than 0.5 (absolute).

The discolouration during prolonged heating in air circulation ovens is measured (usually relative to the normal cured coating) by exposing a test plate to the desired test conditions. Common tests are: 1 hr at 200 ° C, 30 min at 220 ° C and 10 min at 240 ° C. In the experiments with this application, the absolute b * value is given. Preferably, the (amounts of the) stabilizers are chosen such that the b * value (absolute) at 1 hr, 200 ° C heating is less than 3, particularly preferably less than 2, and that the b * value at 10 min, 240 ° C is less than 5, preferably less than 2.

Prolonged heating discoloration in gas ovens is measured in an "accelerated" test. Since NOx is present in gas furnaces, a representative discoloration effect is found by allowing the coating to cure in the presence of NOx at 215 ° C (10 35 min). The discoloration of the coating (b * value, absolute) at 10 °, NOx, 215 ° C is preferably smaller than 7, 10 00 91 9 by a suitable choice of the (quantity of) stabilizers.

- 13 - PN 8336 in particular less than 5.

These b * values can be measured in standard formulations, with respect to the binder 50 wt.% TiO2 (Kronos 2160 ·), 1.5 wt.% Resiflow PV5 ·, 0.5 wt.% Benzoin, a catalyst and stabilizers are used. Furthermore, a reference is measured, consisting of Uralac P5012 / TGIC in a standard formulation without addition of an additional catalyst or stabilizer.

In addition to the above-mentioned primary and secondary antioxidants, other additives can also be used that affect the color (stability) of the coating.

Such additives are usually not necessary to prevent discoloration in "overbake". Examples of such additives are thioethers, UV absorbing additives such as, for example, benzotriazoles and hydroxybenzophenones, HALS compounds and optical brighteners. Use of HALS compounds and UV absorbing additives can be useful in obtaining improved UV stability. Optical brighteners can be useful to make the color relatively white after curing. Examples of such additives are uvitex OB®, UV-sorb 108® metal iodides, nickel chelates, Tinuvin 292® and Tinuvin 900®.

In addition to the additives that influence the color (stability), other additives are often used, such as, for example, degassing agents (benzoin), liquid-promoting agents (polyalkyl acrylates) and, if desired, tribo-charge-promoting agents (sterically hindered amines).

The powder paint composition optionally contains pigments and / or fillers. As inorganic pigments, for example, titanium dioxide, zinc sulfide, iron oxide and chromium oxide, and azo compounds are very suitable as organic pigments. Fillers include, for example, metal oxides, silicates, melamine, carbonates and sulfates. (These pigments and fillers do not belong to 10 00 91 9.

- 14 - PN 8336 to "the binder".)

A powder film composition can be prepared by mixing the binder composition at a temperature above the melting point of the binder composition with the catalyst, the stabilizer and optionally pigments, other additives, and optionally additional curing agents.

The invention also relates to a binder composition suitable for use according to the invention, which binder composition comprises the polymer, the crosslinker and the stabilizer according to the invention.

Particularly preferred, the invention is carried out in a two-component system in which a first component comprises the polymer, the crosslinker and the stabilizer, and a second component a small part of the polymer (or another polymer) and the catalyst. For the preparation of the powder paint, the first component (most of the binder), the second component (often referred to as masterbatch), pigments and, if desired, other cross-linking agents or additives are first mixed in powder form, and then in an extruder above the melting point of the composition is mixed in such a short time (less than a few minutes) that virtually no reaction has taken place between the polymer and the crosslinker. The homogeneous mixture is cooled, crushed and ground to a powder with a particle size of less than 90 mm.

A very suitable way of preparing the first component is by the method as described in WO-A-94/26808. According to this method, the polymer is mixed with a crosslinker in, for example, a static mixer or a rotor / stator at a temperature at which the viscosity is less than 5000 dPas, in such a short time that virtually no reaction occurs between the polymer and the crosslinker. Generally, this mixing step is at a temperature between 140 ° C and 220 ° C

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- 15 - PN 8336 performed with the residence time of the mixed components being less than 60 sec. This method is particularly suitable if the crosslinker is a liquid or viscous substance at room temperature. The phosphite is preferably premixed with the crosslinker.

Instead of using the binder system as a single component, the various ingredients of the binder composition can also be mixed with the other ingredients of the powder paint during paint preparation.

Powder paints according to the invention can be applied in the usual manner, for example by electrostatic spraying of the powder on a grounded substrate and curing of the coating by exposure to heat at a suitable temperature for a sufficiently long period of time. The applied powder can for instance be heated in a gas oven, an electric oven or with the aid of infrared radiation.

Coatings of thermosetting powder paint compositions intended for industrial applications are further generally described in Misev, Powder Coatings, Chemistry and Technology, p. 141-173 (1991).

Compositions of the present invention can be used in powder coatings for application to metal, wood and plastic substrates. Examples are general purpose industrial coatings such as, for example, aluminum window frames, coatings for machinery and for example for cans, household and other small equipment such as, for example, air conditioning. The coatings are also very suitable in the automotive industry for coating external and / or internal parts of vehicles such as cars.

The invention is illustrated by the following non-limiting examples.

Example I

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- 16 - PN 8336

A powder paint was prepared by mixing a two-component system with 300 g of TiO2 (Kronos 2160®), 9 g of flux (Resiflow PV5®) and 3 g of degassing agent (benzoin), in a mixer. The two-component system consisted of a first component comprising 516 g of polyester with an acid number of 29, a viscosity of 820 dPas (measured according to Emila, 158 ° C) and a functionality of 2.1, 54 g of epoxidized linseed oil, 4.5 g of MARK PEP 36® (0.75 wt% on the binder) and 3 g Santhowhite Powder® (0.5 wt% on the binder). The first component was made by the method described in WO-A-94/26808. The second component consisted of 20 wt% lithium versatate (10) in a polyester resin as described above; 30 g of this was used. The mixture was melted and homogenized in an extruder (Prism, 16 mm) at 130 ° C, after which the homogeneous mixture was cooled, crushed and ground. A powder with particles smaller than 90 μτα. was sieved and electrostatically sprayed on an aluminum Q panel AL46 20 plate of 0.6 mm thickness. The curing time was 10 min at 200 ° C, and the resulting cured coating had a layer thickness of 50 μτη. The obtained coating had a good appearance and a good impact (60 inch / pound after a day, without cracks). The results of the discoloration tests are shown in Table 1.

Examples II-IV

Analogous to Example I, a powder paint and coating were prepared. However, instead of component (1) 30, 517 g of the polyester resin used therein was used. 54 g of epoxidized linseed oil was also added to the mixer, containing 3 g of Santowhite Powder® and, respectively, for example II: 4.5 g of MARK PEP 4C® 35, example III: 4.5 g of bis (2,4-ditert.butyl-6 methylphenyl) ethylphosphite Example IV: 4.5 g Irgafos 12® 10 00 91 9.

- 17 - PN 8336

The results of the discoloration tests are shown in Table 1. TABLE 1 Example "I | -Γ-

parameter1 * I II III IV

5 L * after 10 '200 ° C 96.2 96.3 96.6 97.1 a * after 10' 200 ° C 0.2 0.2 0.1 0.3 b * after 10 '200 ° C - 0.8 -0.6 -0.2 0.0 b * value after 1 hr 200 ° C 1.8 1.0 3.1 2.7 10 10 240 ° C 4.5 4.3 5.7 6.2 10 '215 ° C / NOx 6.2 5.1 5.7 5.7 After the last example a description is given of the tests used; the values given are the absolute 15 values as measured after calibration of the colorimeter.

Examples I-IV show that different secondary antioxidants according to the invention give good discoloration resistance in different tests.

20

Examples V-VII

Analogous to Example I, powder paints and coatings were prepared. However, instead of the master batch with catalyst, 600 g of the component (1) were used, and further respectively for: example V: 3 g lithium versatate example VI: 3 g tetramethylguanidine example VII: 3 g 1-benzylimidazole As extruder a Buss PLK 46 applied.

30 The results are shown in Table 2.

10 00 91 9.

- 18 - PN 8336 TABLE 2 Example

parameter V VI VII

L * 97.4 97.0 97.5 a * 0.4 0.3 0.3 5 b * 0.0 0.4 0.3 b * value after 1 hr 200 ° C 1.0 1.2 2 .6 10 '240 ° C 3.5 1.5 3.3 10' 215 ° C / NOx 6.2 7.0 8.8 10

Examples V-VII show that good discoloration resistance can be achieved with different types of catalysts.

Examples VIII-XI

Analogous to Example I, powder paints and coatings were prepared. However, use was now made of 172.2 g resin, 10 g masterbatch, 20.3 g epoxidized linseed oil with the secondary and primary antioxidant dispersed or dissolved therein. 8.6 g of secondary antioxidant and 5.7 g of Santowhite Powder® were added to 100 g of oil. In addition, 100 g of Kronos 2160® (TiO2), 3 g of Resiflow PV5® and 1 g of benzoin were mixed in each powder paint. Respectively, as a secondary antioxidant (0.75 wt% on binder) were used in Example XIII: MARK PEP 36® Example IX: Ultranox 626® Example X: MARK PEP 4C® Example XI: Doverphos S-9228® 30 The results of the tests are shown in table 3.

10 00 91 9.

- 19 - PN 8336 --------- TABLE 3 Example

parameter VIII ix X XI

L * 96.6 96.8 96.9 96.6 a * 0.1 0.3 0.4 0.2 5 b * 0.2 0.2 0.3 0.0 b * value after 1 hr 200 ° C 2.4 2.6 1.9 1.9 10 '240 ° C 2.9 3.9 3.4 2.4 10' 215 ° C / NOx 4.1 4.9 4.9 4, 0 10

Examples VIII-XI show that various secondary antioxidants of the invention give good discolouration resistance in "overbake", even if the powder paint is prepared in a slightly different way than the powder paints according to Examples I-IV.

Examples XII, XIII and Comparative Experiments AD Analogous to Example I, powder paints and 20 coatings were prepared with 90 g of component 1, 10 g of component 2 (using lithium stearate instead of lithium versatate (10)), 50 g TiO 2, 1.5 g Resiflow PV5®, 0.5 g benzoin, 0.5 g Santowhite Powder® and 1 g secondary antioxidant, using the following materials: for example XII: MARK PEP 36® for example XIII: ULTRANOX 626® for experiment A : trisnonylphenylphosphite (TNPP) for experiment B: Lankromark LE 109® (also a TNPP) 30 for experiment C: Irgafos P-EPQ® (is tetrakis- [2,4-ditertiarybutylpheny1] -4,4'-biphenylene diphosphonite for experiment D: Irganox B215® (mixture of 10 00 91 Si.

- 20 - PN 8336

Irganox 1010 * and Irgafos 168 * [1: 2]; Irganox 1010 is a primary antioxidant; Irgafos 168 is tris- (2,4-di-tert-butyl-5-phenyl) phosphite.

The results of stability tests are shown in Table 4.

TABLE 4 Example Experiment

parameter XII xm ABC D

10 L * 96.7 96.5 96.9 96.7 96.7 96.4 a * 0.4 0.3 0.4 0.3 0.4 0.4 b * 0.1 0.0 0 .6 0.3 0.5 0.6 b * value after 1 hr 200 ° C 1.6 1.3 2.6 1.7 2.5 2.9 15 10 ', 215 ° C NO * 6.7 6.1 8.1 10.2 7.0 10.1

These tests show that secondary antioxidants with only aromatic groups (Exp. AD) do not give good discolouration resistance: The b * after normal curing is already quite poor (> 0.5), and especially the discoloration in the NOx test is very strong.

Examples XIV-XVI and Comparative Experiments E and F

Analogous to Example XII, powder paints and coatings were prepared, varying the amounts of primary and secondary antioxidant as shown in Table 5.

10 00 91 9.

- 21 - PN 8336 AB TABLE 5 Experiment Example |

E F XIV XV XVI

Santowhite - 0.5 0.5 0.5 1.0

Powder® 5 MARK PEP 36® - - 0.5: -0 1.0

The results of the stability tests are shown in Table 6.

TABLE 6 Experiment Example

10 parameter E F XIV XV XVI

L * 96.4 96.4 96.7 96.7 96.8 a * 0.2 0.3 0.3 0.4 0.2 b * 0.6 0.6 0.2 0.0 0, 2 b * value after 15 60 '200 ° C 3.0 3.6 2.7 1.4 1.5 30' 220 ° C 5.0 5.0 4.2 2.4 1.8 10 ', 215 ° C NOx 4.8 5.3 3.5 3.1 3.2

These tests show that a secondary antioxidant according to the invention is necessary to obtain good discolouration resistance, while it also appears that different amounts can be used.

Examples XVII, XVIII and Comparative Experiment G 25 Powder paints and coatings were prepared analogously to Example I, with 138 g of acidic polyester resin, 8 g of masterbatch with 20 wt% lithium versatate (10), 13 g of epoxidized linseed oil (ELO, epoxy equivalent weight: 185 ), 80 g of titanium dioxide (Kronos 2160®), 2.4 g of flux, 0.8 g of Santowhite Powder® and respectively for Example XVII: 1.6 g of MARK PEP 36®, added 10 00 91 9.

- 22 - PN 8336 on the extruder,

for example XVIII: 0.8 g MARK PEP 36 · dispersed in the ELO

for experiment G: 1.6 g of Weston 618 added to the extruder (Weston 618 is distearyl pentaerithrytol diphosphite).

The results of the discoloration tests are shown in Table 7.

TABLE 7 Example Experiment

10 parameter XVII XVIII G

L * 95.7 96.6 96.8 a * -0.1 0.0 0.2 b * 0.0 -0.3 0.2 b * value after 15 60 2 00 ° C 1.6 0 .2 3.0 10 '240 ° C 2.2 0.3 6.1 10', 215 ° C, NOx 3.5 2.8 4.4

These tests show that a secondary antioxidant with aliphatic groups alone does not give good discoloration resistance (Test G). Furthermore, it appears to be advantageous to disperse or dissolve the secondary antioxidant in the crosslinker.

Examples XIX-XXIII

Powder paints and coatings were prepared analogous to Example I, each using 90 g of component 1 and 10 g of component 2 (with lithium stearate), 50 g of TiO 2, 1.5 g of Resiflow®, 0.5 g of benzoin and 1 g of MARK PEP 30 36. In addition, other stabilizers were used, as shown in Table 8. The results of the discoloration tests are also given there.

10 00 91 9.

- 23 - PN 8336 TABLE 8 Example

XIX XX XXI XXII XXIII

stabilizing Irgastab Chimators BZ561® sorb®

(0.25 g) 119 FL

(0.25 g)

Santo- 2,4 Irganox Irganox Santo-white di-3052® 565® white

Powder tert- (0.5 g) (0.5 g) Powder (0.5 g) butyl- (0.5 g)

phenol B

(0.5g) 1 5 parameter 1 L * 96.3 96.8 96.8 96.7 96.7 | a * 0.4 0.3 0.3 0.3 0.4 |

b * -0.1 0.2 0.1 0.4 -0.1 I

10 b * I

value B

after fl 60 '1.2 1.4 1.4 2.2 1.2

200 ° C

15 10 '6.7 6.2 7.1 6.3 7.1 215 ° C NOx

1 1 i l I

The above tests show that different primary antioxidants can be used in combination with the secondary antioxidants according to the invention, and that good discoloration resistance is obtained. Stabilizers other than primary and secondary antioxidants can also be used.

10 0 0 6: S- - 24 - PN 8336

Examples XXIV-XXV

Example I was repeated (for example XXIV). Also (Example XXV) 0.16 wt.% (Relative to the total composition) Naugard 445 · 5 was added before extrusion (Naugard 445® is 4,4'-dimethyl-di-phenylamine). The discoloration test results are shown in Table 9.

TABLE 9 Example

parameter XXIV XXV

10 L * 96.9 96.9 a * 0.2 0.4 b * -0.2 -0.2 b * value after 60 '200 ° C 1.0 0.6 15 10' 240 ° C 6, 2 2.3

This shows that Naugard 445® prevents discoloration at high temperature in combination with other stabilizers.

20

Test method

The degree of coloration was measured with a Dr.

Long Micro color (type LMG 051, method DIN 6174, Cie Lab 1976), in which the color of a coating of 50 / m thickness on an aluminum substrate is always measured after calibration of the device. To determine the color characteristic, the L *, a * and b * were measured on the cured paint (10 min cure at 200 ° C) j L * gives the degree of whiteness (white = 100, black = 0), a * the color between red and green, and b * the color between yellow and blue.

The 200 ° C, 1 hr overbake test (the b * value of which is given after the test in the examples described above) was performed by part of the test plate 10 00 91 9.

- 25 - PN 8336, and heat that part in an electrically heated oven with air circulation for 1 hour at 200 ° C. An absolute color measurement was performed unless otherwise indicated. Analogously, the test is performed at 5 240 ° C overbake for 10 min, or 220 ° C for 30 min.

The NOx test is a simulation of the discoloration that can occur in a gas oven. The test plate was placed in an air circulation oven (content “75 1) (215 ° C), in which a dish containing 1 g NaNO 2 had previously been placed, to which 1.5 g 30% acetic acid had been added. The air supply to the oven was always shut off for 9 minutes. Fresh air was supplied in the last minute so that the NOx gases are removed. Color 15 was measured as described above.

The test method is generally performed by simultaneously testing and comparing a series of coatings. The color measurement is in fact sensitive to, for example, small temperature deviations. A system that is known as good color stable is the Uralac® P5012 (DSM Resins) in combination with TGIC. A standard formulation of this results after curing (10 ', 200 ° C) in the following values: L * = 96.8, a * = 0.2, b * = 0.1; after 1 hr 200 ° C the 25 b * 0.4; after 10 '240 ° C the b * is 0.6 + 0.2; the 10 'NOx 215 ° C results in a b * of 3-4. If these values are found, the test has been performed correctly; under these conditions the values as defined in the claims can be measured reliably.

10 00 91 fe,

Claims (20)

26. PN 8336 A thermosetting powder paint composition comprising 5 (i) a polymer with reactive groups - for the crosslinker (ii) a crosslinker containing epoxy groups, the crosslinker having at least a C5-C2i linear or branched aliphatic chain and an epoxy functionality greater than 1, wherein the epoxy group is present on the aliphatic chain (iii) at least one catalyst for the reaction of polymer (i) with crosslinker (ii) (iv) at least one stabilizer 15 (v) if desired other additives (vi) if desired pigment or dyes, characterized in that as stabilizer (iv) a phosphite is used, which comprises at least one group of formula (1) R 1 - O \ PO-R 3 (1) / R2 - O wherein R1 is an aliphatic group, R2 is an aliphatic or aromatic group and wherein R3 is an aromatic group, any aliphatic and aromatic group may be substituted. Composition according to claim 1, characterized in that the stabilizer (iv) is a polyphosphite which is a substituted bisphenylpentaerythritol diphosphite. Composition according to any one of claims 1-2, characterized in that the aromatic groups are substituted with one or more alkyl, aryl, halogen, alkoxy or alkylamine groups. 10 0 0 91. 27. PN 8336 Composition according to any one of claims 1 to 3, characterized in that the aromatic groups are substituted with at least one or more linear or branched alkyl groups with 3-24 carbon atoms and / or with unsubstituted or 5 aryl groups with 6-36 carbon atoms . R2 - 0 / wherein R1 is an aliphatic group, R2 is an aliphatic or aromatic group and wherein R3 is an aromatic group, any aliphatic and aromatic group may be substituted. Composition according to any one of claims 1 to 4, characterized in that the aromatic groups are substituted at least at the ortho position. Composition according to any one of claims 1 to 5, characterized in that a nitrogen or metal-containing compound is used as the catalyst. 7. A composition according to any one of claims 1-6, characterized in that a lithium or sodium alkoxide or carboxylate is used, wherein the alkyl group has 1 to 30 carbon atoms. A composition according to any one of claims 1-7, characterized in that the composition also contains a primary antioxidant. Composition according to claim 8, characterized in that the composition contains a sterically hindered phenol compound as the primary antioxidant. 10. A composition according to claim 8, characterized in that the composition contains an aromatic amine as the primary antioxidant. Composition according to any one of claims 1-10, characterized in that the composition comprises an effective amount of stabilizers so that good discoloration resistance is obtained. A composition according to any one of claims 1-11, characterized in that the composition contains 0.05-2% by weight relative to the binder of any stabilizer used. 13. Coating consisting of a cured composition 35 according to any one of claims 1-12 on a substrate, wherein an effective amount of stabilizers is applied, such that the coating has a good quality. 28. PN 8336 has long-term heating resistance. Coating according to claim 13, characterized in that the discolouration resistance (b * measured according to DIN 6174, CIE LAB 1976) in a standard formulation after curing for 10 min at 200 ° C and at 60 min. 200 ° C overbake <3, and at 10 min.240 ° C overbake <5. Coating according to claim 14, characterized in that the discoloration resistance (b *) is 10 at 60 min 200 ° C overbake <2, and at 10 min 240 ° C overbake <2. Coating according to claim 13, characterized in that the discoloration resistance (b * measured according to DIN 6174 CIE LAB 1976) in a standard formulation after curing at 200 ° C for <15 min and curing at 10 min at 215 ° C, with NOx <7. Coating according to claim 16, characterized in that the discolouration resistance (b *) is cured with NOx <5 at 10 min. 215 ° C. 18. A binder composition for a thermosetting powder paint composition comprising (i) a polymer with crosslinker-reactive groups (ii) a crosslinker containing epoxy groups, the crosslinker having at least a C5-C26 linear or branched aliphatic chain and an epoxy functionality greater than 1, the epoxy group being present on the aliphatic chain (iii) at least one catalyst for the reaction of polymer (i) with crosslinker (ii) (iv) at least one stabilizer (v) if desired other additives, characterized which, as stabilizer (iv), is a phosphite comprising at least one group of formula (1) 10 0 0 δ »i 29. PN 8336 R1 - O P-O-R3 (1) 19. Two component system for a thermosetting powder paint composition with a first component comprising (i) a polymer with reactive groups - for the crosslinker (ii) a crosslinker containing epoxy groups, the crosslinker having at least a C5-C26 linear or branched aliphatic chain and an epoxy functionality greater than 1, wherein the epoxy group is present on the aliphatic chain (iv) at least one stabilizer and a second component comprising a polymer, and (iii) at least one catalyst for the reaction of polymer (i) with crosslinker (ii) characterized in that the stabilizer (iv) is a phosphite comprising at least one group of formula (1) R1 - O 30 \ PO-R3 (1) 2 / R2 - O 35, wherein R1 is an aliphatic group, R2 is an aliphatic or aromatic group and wherein R3 is an aromatic group, any aliphatic aromatic group may be substituted. 20. Composition and coating as substantially described in the description and the examples. 10 0 0 9U COOPERATION TREATY (PCT) REPORT ON NEWNESS RESEARCH OF INTERNATIONAL TYPE ION IDENTIFICATION OF THE NATIONAL APPLICATION Characteristic of the applicant or of the applicant 8336NL Dutch application no. net request for an examination of mtemaionaai type By the Institute for International Research (ISA) to the request for an examination of «ma tonal type logeekend nr. 4 August 1995 SN 26020 EN I. CLASSIFICATION OF THE SUBJECT (using different classifications (specify all rating symbols) According to the «ma tonal classification (IPC) Int.Cl.6: C 09 D 163/00, C 09 D 5/03, C 08 K 5/524, C 08 K 5/526, C 08 K 5/527 II. FIELDS OF TECHNIQUE EXAMINED __Researched minimum documentation_ Classification system__Classification symbols_ Int.Cl.6; C 09 D, C 08 K Examined documentation other than minimum documentation enter to the extent that such documents are included in the prayers examined Μ. 1 1 NO INQUIRY FOR CERTAIN CONCLUSIONS (comments on supplementary sheet) IV. | 1 LACK OF UNIT OF INVENTION (comments on supplement sheet) λ I-_J 1 Form PCT / 1SA / 201 (a) 08 1994