DE3545061C2 - - Google Patents

Description

The invention relates to highly reactive powdery one-component Coating agents based on polyepoxides and polymers containing carboxyl groups, primarily polyesters.

Powdery coating agents that are produced by sintering, by flame spraying or using the electrostatic powder spray method applied to a substrate - usually metal are known. They are said to be moderate to crosslink high temperatures within the shortest possible time Coatings can be baked. Here it should be noted that on the one hand when extruding the mixture from binders, pigments, fillers and optionally other aids at temperatures of 80 up to 160 ° C, preferably 90 to 120 ° C, no reaction between resin and hardener, on the other hand but a need for ever shorter burn-in times low temperatures, that is after increased reactivity.  

Although it is possible to use the resin component with such a to provide a high number of carboxyl groups for stoving conditions from 150-160 ° C / 30 minutes a complete Reaction is achieved; however occurs due to high acid number during the extrusion process unwanted pre-reaction, which can only be achieved by vigorous Cooling of the extrudate within tolerable limits can hold. The shelf life is also affected, that even at room temperature an undesirable Reaction takes place, which then the course of the powder coating and / or the mechanical properties of the stove enamel negatively influenced.

As is known, the hardening of carboxyl groups can be done Polymers with polyepoxides by catalysts such as e.g. B. Imidazole, dicyandiamide (JA 5 10 42 726), tris- (tetraethylammonium) - trimellitate (DE-OS 29 22 377), imidazolines (DE-OS 22 48 776), tetrahydropyrimidines (DE-OS 27 51 805, 32 11 301), benzotriazoles (EP-A 1 25 906), tertiary amines (JA 51 42 726, Polymer Bulletin 13, 237-244 (1985)).

In addition to sufficient reactivity and storage stability Epoxy resin coatings also have good adhesion, in particular on metallic surfaces. Especially Diglycidyl ether of bisphenol A with a melting point from 50 to 120 ° C and an epoxy equivalent weight of 400 up to 2000 pose difficulties in this regard. In In practice, however, coating agents only become competitive then when they are not only reactive and storage stable and lead to adhesive coatings, but if the result  manufactured coatings also high-gloss, are elastic and resistant to solvents.

Powder coating compositions with such properties are from DE-OS 30 41 834 (= US-PS 44 24 353, 44 55 475, 44 55 426) and 32 11 301 (= US-PS 45 10 288) known; but there was a need for further increased Reactivity with as little impairment as possible storage stability and paint properties.

Surprisingly, it has been found that a synergistic Effect occurs when you have a catalyst combination from amidine and tertiary amine. This Synergism is expressed in the fact that this catalyst combination is more effective than that same amount of the individual components or that for the same effect a smaller amount of catalyst combination than is required for the quantities of the individual components.

DE-OS 27 51 805, 30 41 834 and 32 11 301 describe for example amidine catalysts. None of these writings however, suggests that certain amounts of tertiary Amines the catalytic activity of amidines still significantly can increase.

The invention relates to powdered coating agents out

• A) Carboxyl group-containing polymer with an acid number from 10 to 150, preferably 20 to 120, in particular 30 to 50,  
• B) polyepoxide in a ratio that to a free Carboxyl group of polymer A 0.6 to 1.5, preferably 0.8 to 1.25, epoxy groups of polyepoxide B come,
• C) 0.1 to 5, preferably 0.5 to 2.5 wt .-%, based on the sum of A + B, catalyst and optionally
• D) auxiliaries and additives,

characterized in that the catalyst component C in turn

• 1) 10 to 90, preferably 20 to 80,% by weight of amidine and
• 2) 90 to 10, preferably 80 to 20,% by weight of tertiary amine,
  each based on the weight of component C.

The powdery coating compositions of the invention Coatings produced have an excellent Gloss, high hardness and elasticity, in particular Impact elasticity, as well as excellent whiteness, gloss retention and resistance to chalking in outdoor weathering.

Component A

The carboxyl group-containing to be used according to the invention Polymers A preferably melt in a temperature range from 20 to 150, in particular from 50 to 100 ° C.  (determined by differential thermal analysis). Your OH numbers are preferably below 20, in particular below 10.

Preferred carboxyl group-containing polymers A are carboxyl group containing copolymers and especially polyester carboxylic acids.

The esterification reaction to build up polyester polycarboxylic acids A can by known methods by esterification corresponding polycarboxylic acids and polyols, in particular Dicarboxylic acids and dialcohols, or by ester formation suitable derivatives of these alcohols and carboxylic acids, such as B. the anhydrides, acid chlorides, and also be produced with hydroxycarboxylic acids.

Preferred carboxyl group-containing copolymers A contain copolymerized units of 2-25% by weight of at least one copolymerizable α, β-ethylenically unsaturated carboxylic acid with 3-5 C atoms and 75-98% by weight of at least one further copolymerizable monomer. The α, β-ethylenically unsaturated carboxylic acids can be monocarboxylic acids or dicarboxylic acids or half esters of dicarboxylic acids with 1-12 C atoms in the alcohol component. Instead of the copolymerizable α, β-ethylenically unsaturated C ₃ -C ₅ carboxylic acids, it is also possible to use olefinically unsaturated copolymerizable monomers containing hydroxyl groups, such as hydroxy C ₂ -C ₄ alkyl esters of acrylic, methacrylic, fumaric, maleic or itaconic acid be built into the copolymer. The hydroxyl groups can then be reacted with carboxylic acid anhydrides such as. B. succinic anhydride, are converted into carboxyl-containing copolymers.

Examples of preferred polyester carboxylic acids A and carboxyl groups containing copolymers A are in DE-OS 30 41 834, the disclosure of which is hereby part of our description is explained.

Component B

The polyepoxides B to be used according to the invention are preferably solid, mostly resinous substances in the area from 30 to 140 ° C, preferably between 40 and 80 ° C (determined by differential thermal analysis) melt and which averaged more than one 1,2-epoxy group per Contain molecule.

On the one hand, these are polyepoxide compounds based on polyhydric phenols, for example Pyrocatechol, resorcinol, hydroquinone, from 4,4′-dihydroxy diphenylmethane, from 4,4'-dihydroxy-3,3'-dimethyl-diphenylmethane, from bisphenol A, from 4,4′-dihydroxydiphenylethane, from 4,4'-dihydroxydiphenylcyclohexane, from 4,4'-dihydroxy- 3,3'-dimethyldiphenylpropane, from 4,4'-dihydroxydiphenyl, from 4,4′-dihydroxydiphenyl sulfone, from tris- (4-hydroxyphenyl) - methane, from the chlorination and bromination products the diphenols mentioned above, in particular from bisphenol A; Novolaks (i.e., reaction products of mono- or polyhydric phenols with Aldehydes, especially formaldehyde, more acidic in the presence  Catalysts), from diphenols, which are esterified by 2 moles of the sodium salt of an aromatic oxycarboxylic acid with one mole of a dihaloalkane or dihalodialkyl ether were obtained (see GB-PS 10 17 612), from polyphenols, by condensation of phenols and long-chain, halogen paraffins containing at least 2 halogen atoms were obtained (see GB-PS 10 24 288).

Commercial, solid epoxy resins are preferred Type bisphenol A diglycidyl ether (i.e., reaction products of bisphenol A with epichlorohydrin), their epoxy equivalent weight between 400 and 2500 is used.

There are also compounds such as (poly) glycidyl esters formula

into question, in which R ^{1 is} a straight-chain or branched-chain, saturated or unsaturated aliphatic or aromatic hydrocarbon radical having 4-20 carbon atoms and n is a number from 1 to 4.

Compounds such as triglycidyl isocyanurate can also be used as the epoxy resin and / or its oligomers and triglycidylurazole as well as its oligomers and mixtures of the above Substance classes are used.  

Compounds such as triglycidyl isocyanurate are included considered the invention as an imide - not a tertiary amine; Compounds such as triglycidylurazole are in the Framework of the invention as urea - not as a tertiary Amine or amidine - considered.

Component C 1. Amidines

For the purposes of the invention, amidines are compounds which at least the structure once per molecule

included, provided that the C = N bond is not part of an aromatic system. The amidines include open chain, monocyclic (preferably 5- and 6-membered), bi- and polycyclic compounds, preferably up to 30, especially up to 18 carbon atoms included per molecule. The amidines are preferred free of epoxy groups. Amidines that are outside the amidine group  contain one or more tertiary amino groups, are in the context of the invention as amidine - not as tertiary amine - considered.

Examples of preferably used amidines C.1 are in DE-OS 30 18 023 (= US-PS 43 28 330), 32 11 301 (= US-PS 45 10 288) and 34 03 497 described, which are hereby declared part of this description will. Other amidines C.1 are e.g. B. in the DE-OS 15 45 855, 24 39 550, 27 22 514, 27 51 805, 3 04 93 131 disclosed.

Preferred amidines C.1 correspond to the formula

wherein
n 1 or 2,
R ² , R ^{3 is} a hydrogen atom, a C ₁ -C ₁₈ , preferably C ₁ -C ₄ alkyl radical, a C ₅ -C ₇ cycloalkyl radical, an aromatic radical with 6-10 C atoms, an ar-aliphatic radical with 7-13 C atoms,
where the residues are optionally halogen, hydroxy, amino, C ₁ -C ₄ alkylamino, di (C ₁ -C ₄ alkyl) amino, C ₁ -C ₄ alkoxy, phenoxy, C ₁ -C ₄ alkyl mercapto , C ₁ -C ₄ alkoxycarbonyl or nitro (preferably not more than three times in total) or optionally substituted by structural units -O-, -S-, C ₁ -C ₆ alkylamino or C ₅ -C ₇ cycloalkylamino (preferably not more often than twice) are interrupted,
R ⁴ , R ^{5 are} the substituents R ² - with the exception of hydrogen -,
Di (C ₁ -C ₆ alkyl) amino C ₂ -C ₁₂ alkyl,
Di- (C ₅ -C ₇ -cycloalkyl) -amino-C ₂ -C ₁₂ -alkyl,
or either
R ² and R ⁵ together and / or
R ³ and R ⁴ together or
R ² and R ³ together and / or
R ⁴ and R ⁵ together
a C₂-C₅-, preferably C ₂ -C ₃ -alkylene radical which is optionally interrupted by -O-, -S- or C ₁ -C ₆ -alkylamino (1 to 2 times),
Furthermore
R ³ at n = 1
a C ₁ -C ₃₆ alkyl radical, a C ₆ -C ₁₅ cycloalkyl radical, an araliphatic or aromatic radical with 6-36 C atoms, these radicals optionally being substituted by hydroxyl, carboxyl, C ₁ -C ₁₅ alkoxy, C ₆ -C ₁₈ -Aroxy, NR ⁶ R ⁷ (preferably not more than three times in total) substituted or
optionally interrupted by a keto group, 1 to 10 amide or ester group,
or a polyether residue of the structure

wherein R represents a hydrogen atom, C ₁ -C ₄ alkyl or phenyl,
R ⁶ , R ^{7 are} C ₁ -C ₆ alkyl, C ₅ -C ₇ cycloalkyl,
at n = 2
a C ₂ -C ₁₈ , preferably C ₂ -C ₆ alkylene radical, which may be replaced by -O-, -S-, NH-CO-, -NH-CO-O- or NR ⁶ (preferably not more than three times in total ) is interrupted,
mean.

Examples of preferred open-chain amidines C.1 are N, N-dimethylformamidine, N, N-dimethylacetamidine, N, N-diethylformamidine, N, N, N'-trimethylacetamidine, N, N-dimethyl N'-benzylacetamidine, N, N-dicyclohexyl-N'-methylacetamidine, N, N-dimethyl-N'-cyclohexylformamidine, N, N- Dimethyl-N'-tert-butylformamidine.

Examples of preferred monocyclic amidines C.1 are 1,2-dimethyl-Δ2-imidazoline, 1-methyl-2-phenyl-Δ2-imidazoline, 1 (N) -methyl-Δ2-imidazoline, 2-benzylimino-N-methylcaprolactam, 2-butylimino-N-methyl-butyrolactam,
1- (N) -methyl-Δ-2-tetrahydropyrimidine,
1-cyclohexyl-2-methyl-Δ2-tetrahydropyrimidine,
1-cyclohexyl-Δ2-tetrahydropyrimidine,
1-benzyl-2-butyl-Δ-tetrahydropyrimidine,
1-methyl-2-methyl-Δ-tetrahydropyrimidine,
1-butyl-2-methyl-Δ-tetrahydropyrimidine,
1- (2-ethylhexyl) -2-methyl-Δ-tetrahydropyrimidine,
1-dodecyl-2-methyl-Δ-tetrahydropyrimidine,
1- (1-methylcyclohexyl) -2-methyl-Δ2-tetrahydropyrimidine,
1- (2-methylhexyl) -2-methyl-Δ2-tetrahydropyrimidine,
1- (3,3,5-trimethylcyclohexyl) -2-methyl-Δ2-tetrahydropyrimidine,
1- (3-N, N-dimethylamino-propyl) -2-methyl-Δ2-tetrahydropyrimidine,
1- (2-N, N-dimethylaminoethyl) -2-methyl-Δ2-tetrahydropyrimidine,
1-methyl-4- (2-tetrahydroazepinyl) piperazine of the formula

Phenyl-methyl- (2-tetrahydroazepinyl) amine of the formula

Benzyl-methyl- (2-tetrahydroazepinyl) amine of the formula

and
4- (2-tetrahydroazepinyl) morpholine of the formula

Preferred bicyclic amidines C.1 are, for example
1,8-diaza-bicyclo [5,3,0] dec-7-ene,
1,8-diaza-bicyclo [5,4,0] -undec-7-ene,
1,7-diaza-bicyclo [4,4,0] dec-6-ene,
1,6-diaza-bicyclo [3,4,0] non-5-ene,
1,5-diaza-bicyclo [4,3,0] non-5-ene,
1,14-diaza-bicyclo [11,4,0] -heptadec-13-ene and
the connections of the formulas

Preferred amidines C.1, which have the guanidine structure (III) have the formula

wherein
p 1 or 2,
m is an integer from 1 to 3, but in the case of p = 2 only 1,
R ⁸ -R ^{11 is} a hydrogen atom,
C ₁ -C ₁₈ , preferably C ₁ -C ₄ alkyl, C ₅ -C ₁₀ , preferably C ₅ -C ₆ cycloalkyl, an araliphatic radical having 7 to 15, preferably 7 to 8, C atoms, one aromatic radical having 6 to 14 carbon atoms, preferably phenyl, these radicals optionally being replaced by -O-, -S-, -NH-CO-, -NH-CH-O- or NR ⁶ (preferably not more than three times in total) interrupted or by halogen, hydroxyl, carboxyl, amino, C ₁ -C ₄ alkylamino, di (C ₁ -C ₄ alkyl) amino, C ₁ -C ₄ alkyl mercapto, C ₁ -C ₄ alkoxy, C ₆ -C ₁₂ -roxy, nitrile, nitro, C ₁ -C ₄ -alkoxycarbonyl (preferably not more than three times in total) are substituted,
R ^{12 is} either R ⁸ -R ¹¹ or C ₂ -C ₄ -alkylene,
where for p = 1 either
R ⁸ and R ⁹ together and / or
R ¹¹ and R ¹² together or
R ⁹ and R ¹⁰ together and / or
R ⁹ and R ¹¹ together or
R ⁹ and R ¹⁰ together and / or
R ¹¹ and R ¹² together
a C ₁ -C ₆ alkylene radical, a C ₅ -C ₇ cycloalkylene radical, a C ₇ -C ₁₃ aralkylene radical or a C ₆ -C ₁₂ arylene radical, these radicals optionally being replaced by -O-, -S-, - NH-CO-, -NH-CO-O- or NR ⁶ (preferably not interrupted more than three times in total or by halogen, hydroxyl, carboxyl, amino, C ₁ -C ₄ alkylamino, di- (C ₁ -C ₄ - alkyl) amino, C ₁ -C ₄ alkyl mercapto, C ₁ -C ₄ alkoxy, C ₆ -C ₁₂ hydroxy, nitrile, nitro, C ₁ -C ₄ alkoxycarbonyl (preferably not more than three times in total) ,
mean.

Preferred amidines C.1 of the formula (XXV) are, for example, guanidine, bi- and triguanide,
N-methyl-guanidine,
N-ethyl guanidine,
N-butyl guanidine,
N-methyl-N'-ethyl-guanidine,
N, N′-dimethyl-guanidine,
N, N′-diethyl guanidine,
N-methyl-N'-isopropyl-guanidine,
N, N′-dibutyl guanidine,
N, N, N'-trimethyl-guanidine,
N, N, N ′, N′-tetramethyl-guanidine,
N, N, N ′, N′-tetraethyl-guanidine,
N-phenyl guanidine,
N, N′-diphenyl-guanidine,
N, N′-ditolyl guanidine,
N-formyl guanidine,
N-butyryl guanidine,
optionally mixed N, N, N ′, N ′, N ″ -mono- to penta- methyl-, ethyl-, (iso) propyl-, (iso) buytl-, (iso) -pentyl, hexyl-, 2-ethylhexyl -, heptyl, octyl, dodecyl, stearyl, hydroxymethyl, hydroxyethyl, hydroxypentyl, hydroxyethoxyethyl, hydroxyethylmercaptoethyl, ethoxypropyl, butoxyhexyl, cyanoethyl, cyanopentyl, butoxycarbonylmethyl, methoxycarbonylhexyl, dimethylamine Cyclopentyl, cyclohexyl, benzyl, chlorobenzyl, phenethyl, phenpropyl, dimethylaminophenethyl, phenyl, chlorophenyl, tolyl, (tert.) Butylphenyl, methoxyphenyl, ethoxycarbonylphenyl guanidines and also -bi- guanides or triguanides, -2-amino-imidazolines, -2-aminotetrahydropyrimidines, -2-amino-tetrahydro-1,3-diazepines, methylimino, ethylimino, cyanoethylimino, dibutylaminobutylimino, benzylimino, phenethylimino, phenylimino , Chlorphenylimino-, Tolylimino-carbonic acid-bismorpholide, -bispiperidid, -bishexamethylenimid, -bis-N'-methylpiperazid, N-methyl-, N-ethyl-, N- (iso) -propyl-, N - (Isobutyl) -, N- (iso) penthyl, N-hexyl, N-heptyl, N-decyl, N-dodecyl, N-stearyl, N-allyl, N-hexenyl -, N-Hydroxyethyl-, N-Hydroxyoctyl-, N - [(Poly) - (hydroxyethoxy) - ethyl] -, N- [Poly) - (hydroxypropoxy) -propyl] -, N-Methoxypropyl-, N- Cyanomethyl, N-cyanoethyl, N-cyanopentyl, N-methoxycarbonylmethyl, N-ethoxycarbonylethyl, N-aminoethyl, N-ethylaminopropyl, N-diethylamino-butyl, N-cyclopentyl, N-cyclohexyl, N-benzyl, N-phenethyl, N-phenyl, N-tolyl, N-chlorophenyl, N-dimethylaminophenyl, N-methoxyphenyl-tetrahydro-1H-imidazo [1,2-a] imidazole, methyl -tetrahydro-1H-imidazo- [1,2-a] imidazole, -dimethyl-tetrahydro-1H-imidazo- [1,2-a] imidazole, -hexahydro- 2H-pyrimido- [1,2- a] -pyrimidine, -hexahydro-imidazo- [1,2, - a] -pyrimidine, -tetrahydro-imidazo- [1,2, -] -pyrimidine, -dihydro-imidazo- [1,2-a] -benzopyrimidine , dihydro-benzimide-azo- [1,2-a] -pyrimidine, -hexahydro-imidazo- [1,2-a] -diazepine, -octahydro-pyrimido- [1,2-a] -diazepine, -octahydro- diazepino- [1,2-a] diazepine, and compound formulas

2. Tertiary amines

Preferred tertiary amines C.2 are compounds of the formula

NR ¹³ R ¹⁴ R ¹⁵ (XLII)

wherein
R ¹³ -R ¹⁵ C ₁ -C ₂₀ alkyl,
C ₅ -C ₇ cycloalkyl,
C ₇ -C ₁₃ aralkyl or
an aromatic residue with 6-12 C atoms,
or
R ¹³ , R ¹⁴ together
C ₄ -C ₆ alkylene, in which a methylene group can be replaced by -O-, -S-, -NH- or NR ¹⁶ , and
R ^{16 has} the meaning of R ¹³ -R ¹⁵ .

Preferred tertiary amines C.2 of the formula XLII are e.g. B. tri-i-propylamine, di-sec-butyl-methylamine, trinonylamine, dimethyltetradecylamine, dimethylstearylamine;
Dimethylcyclohexylamine, diethylcyclohexylamine, diethylcyclopentylamine, dimethylaniline, diethylaniline, di-i-propylaniline, dimethylbenzylamine, diethylbenzylamine;
N-methylpyrrolidine, N-methylpiperidine, N-phenylpyrrolidine, N-phenylpiperidine, N-benzylpyrrolidine, Nn-butylpiperidine, N-ethylazepine;
N-methylmorpholine, N-benzylmorpholine.

Other preferred tertiary amines C.2 correspond to the formula

R ¹³ R ¹⁴ NZ-NR ¹⁵ R ¹⁷ (XLIII)

wherein
R ¹⁵ , R ^{17 have} the meaning of R ¹³ , R ¹⁴ and
ZC ₂ -C ₂₀ alkylene,
-CH ₂ -X-CH ₂ -,
- (CH ₂ ) _r [OCH ₂ ] _s ] _t ,
XC ₅ -C ₇ cycloalkylene or a divalent aromatic radical with 6 to 12 C atoms,
r, s is an integer from 2 to 20,
t zero or a number from 1 to 10,
or
R ¹³ and R ¹⁵ together
-CH ₂ -CH ₂ -, -CH = CH- or -CHR ¹⁸ -CHR ¹⁸ - with
R ¹⁸ C ₁ -C ₄ alkyl
or
R ¹³ and R ¹⁴ together and / or
R ¹⁵ and R ¹⁷ together
C ₄ -C ₆ alkylene, in which a methylene group can be replaced by -O-, -S- or NR ¹⁶ ,
mean.

Preferred tertiary amines C.2 of the formula XLIII are e.g. B. tetramethylethylenediamine, bis [2- (N-dimethylamino) ethyl] ether, N, N, N ', N'-tetramethyl-p-xylylenediamine, N, N, N', N'- tetrabenzyl-xylylenediamine, 1 , 4-tetramethyl-p-phenylenediamine, 1,8-bis-dimethylaminonaphthalene, N, N, N ′, N′-tetramethyldiaminohexane;
N, N′-dimethyl-N, N′-diethylethylenediamine, N, N′-dimethyl-N, N′-dibenzylethylenediamine, N, N′-dimethyl-N, N′-di-n-butylethylenediamine, N, N ′ -Dimethyl-N, N'-diphenylethylenediamine;
Dimethylpiperazine, diethylpiperazine;
N- (2-dimethylaminoethyl) -N'-methyl-piperazine, N- (2-dimethylaminopropyl) piperidine, N- (2-dimethylaminopropyl) morpholine;
Bis (N-morpholine) ethane, bis (N-piperidino) ethane, bis (2-pyrrolidinoethyl) ether;
Diazabicyclooctane.

Other preferred tertiary amines C.2 are compounds of the formula

wherein
R ¹⁸ C ₁ -C ₄ alkyl,
R ^{19 represents} a hydrogen atom or a methyl group,
t 1 or 2 and
n is an integer from 1 to 10.

Preferred tertiary amines C.2 of the formula XLIV are, for example permethylated diethylene triamine, triethylene tetramine, -Tetraethylene pentamine, -Pentaethylene hexamine and the corresponding propylene polyamines.

Preferred tertiary amines C.2 are free of C = N double bonds; Amidines are not used in the context of this invention considered as tertiary amines C.2.

The preferred tertiary amines C.2 are dimethylbenzylamine, Tri-n-octylamine, diethylaniline, dimethylcyclohexylamine, Diazabicyclooctane, tetramethylguanidine.

Because of the volatility of the tertiary amines under curing conditions it is advisable to use tertiary amines, which have a boiling point of at least at normal pressure 60 ° C, preferably at least 80 ° C.

Instead of free tertiary amines C.2 can of course also compounds are used that are under curing conditions only release the free tertiary amines; Examples are the salts of volatile protons or Lewis acids such as B. the acetates.

Component D

If necessary, auxiliary substances and additives are to be used for example inert fillers and heat-stable dyes and pigments such as B. phthalocyanine pigments, azo dyes, Titanium dioxide, iron oxides and chromium oxide.  

They are usually used in effective amounts of up to 150 wt .-%, based on the sum of components A and B.

Other auxiliaries and additives are e.g. B. leveling agent, such as commercially available butyl acrylate oligomers or silicone oils, Deaerators such as benzoin, matting and smoothing agents.

Powder coatings are usually produced as follows:

The carboxyl group-containing polymer is chosen with the Polyepoxide of the catalyst combination and optionally other additives first mixed and in the melt homogenized. This can be done in suitable aggregates, such as e.g. B. heatable kneaders, but preferably by extrusion, take place, the extrusion temperature so too choose is that maximum shear force on the mixture acts. An upper temperature limit of 140 ° C should be used not be exceeded.

The extruded mass is after cooling to room temperature and after a suitable pre-crushing to a Powder coating ground, depending on the purpose average particle sizes of about 40-90 microns, but preferably below approx. 70 µm. A possibly existing coarse grain fraction of particle sizes of more than 90 µm is removed by sieving.  

Applying the powder coatings produced in this way to suitable ones Substrates can be made by the known methods, such as. B. by electrostatic powder spraying, vortex sintering, electrostatic fluidized bed sintering and flame spraying or by applying aqueous suspension according to conventional or electrical processes respectively.

After applying the powder coating according to one of the above The coated workpieces are used for curing heated to temperatures of 140 ° C or higher, the duration of the heating essentially according to the heat capacity of the coated workpiece or whose temperature is adjusted before coating.

The powders are used to coat household appliances, especially of metal parts, of metal parts in Automotive engineering, metal parts, the strong weather influences exposed, such as facade sheets, pipes, Wire mesh, of devices for forestry and agriculture, Bicycle and motorcycle frames, construction and installation elements, Housings for fluorescent tubes and Lighting systems.

The coatings primarily serve as corrosion protection or as protection against mechanical wear for objects from metals such as B. made of steel, cast steel, copper, Brass, bronze, gunmetal, aluminum and its alloys, galvanized substrates, but also made of porcelain, ceramics, Plastic and also some types of wood. You can also as electrically insulating coatings in electrical engineering,  e.g. B. for lights, switches, engine parts u. Ä. used will. The binders are preferred because of their excellent quality History of automotive accessories top coating used.

Obtain the parts and percentages given in the examples on the weight, unless otherwise noted.  

Examples General manufacture of a powder coating

A carboxyl polyester made from neopentyl glycol, terephthalic acid, Isophthalic acid, trimellitic anhydride, with a Softening point of 75 ° C (DTA) and an acid number of 35 was with amidine and with triglycidyl isocyanurate as well with titanium dioxide rutile and with leveling agent based of a commercially available acrylate oligmer first dry mixed. This mixture was placed on a laboratory extruder Temperatures of 80-120 ° C dispersed in the melt. The Extrudate was opened after cooling and pre-crushing a blower mill to an average grain size of 50 microns ground to a powder coating. After screening the existing coarse grain fraction of particle sizes above The ready-to-use powder coating was doubled to 90 µm Pickled, degreased test sheets (length 16.5 cm, width 65 mm, thickness 0.8 mm) with an electrostatic spray device at a negative voltage of approx. 60 kV sprayed on. The sheets were then at different Branded temperatures.

The coatings were after in a thickness of 50 microns the following practical methods for their properties checked:

• 1) Gel time of the powder coating (at 180 ° C) according to DIN draft 55 990, part 8;
  The gel or gel time gives information about the speed of the hardening reaction. The effectiveness of catalysis is clear here.
• 2) cupping values according to DIN 53 156 (according to Erichsen); slow deformation due to ball pressure from the back in mm.
• 3) impact deformation, backward = impact reverse based on ASTM G-14 with a weight of 1 kg and a ball diameter of 1/2 inch; Specification in inchpound (height of fall · weight);
  is measured with a ball drop device, model 304, from Erichsen, from the back of the film, ie from the uncoated sheet side. The impact test indicates whether the curing reaction has proceeded properly under the conditions mentioned (20 min / 170 ° C, 15 min / 180 ° C, 10 min / 200 ° C, 5 min / 220 ° C).
• 4) Degree of gloss according to Gardner, DIN 67 530, 60 ° C angle.
• 5) whiteness according to A. Berger;
  Yellowish-white coatings after repeated baking, ie again 15 min / 200 ° C and again 20 min / 220 ° C. The higher the number, the better the result.
• 6) Acetone strength
  Test for correct curing. For this, 1-50 double strokes are carried out with a cotton ball soaked in acetone:
  2 m after 50 strokes of matt, soft film
  2 lm after 50 strokes of slightly matt, soft film
  2 soft film after 50 strokes
  1 slightly surface-sensitive paint film after 50 strokes
  0 no change
• 7) Kink test
  To do this, the 0.8 mm thick, coated steel sheets are bent. There must be no film tear and no spalling.
  0 = passed;
  1 = individual cracks, conditionally passed;
  2 = many cracks, failed.
• 8) Course: Visual assessment of the paint surface.
• 9) The cross cut test according to DIN 53 151 resulted in the good in all examples and comparative experiments Assessment GT 0/0.

The test results are summarized in tables.

Recipes [in parts by weight]

Comparison 1a
55.1 polyester
0.1 dimethylbenzylamine
4.2 triglycidyl isocyanurate
0.6 leveling agent
40 TiO ₂ pigment

Comparison 1b
55.0 polyester
0.2 dimethylbenzylamine
4.2 triglycidyl isocyanurate
0.6 leveling agent
40 TiO ₂ pigment

Comparison 2a
55.0 polyester
0.2 amidine A
4.2 triglycidyl isocyanurate
0.6 leveling agent
40 TiO ₂ pigment

Comparison 2b
55.2 of a 2% solution of amidine A in polyester
4.2 parts of triglycidyl isocyanurate
0.6 leveling agent
40 TiO ₂ pigment

example 1
55.0 polyester
0.2 of a mixture of dimethylbenzylamine and amidine A in a weight ratio of 3: 7
4.2 triglycidyl isocyanurate
0.6 leveling agent
40 TiO ₂ pigment

Example 2
as example 1, however
0.2 of a mixture of dimethylbenzylamine
and amidine A in a weight ratio of 1: 1

Example 3
as example 1, however
0.2 of a mixture of dimethylbenzylamine
and amidine A in a weight ratio of 9: 1

Example 4
as example 1, however
0.2 of a mixture of amidine B and dimethylcyclohexylamine
in a weight ratio of 3: 7

Example 5
as example 1, however
0.2 of a mixture of amidine C and diazabicyclooctane
in a weight ratio of 3: 7

Example 6
as example 1, however
0.2 of a mixture of amidine D and tri-n-octylamine
in a weight ratio of 3: 7

Example 7
as example 1, however
0.2 of a mixture of tetramethylguanidine
and N, N-diethylphenylamine in a weight ratio of 3: 7

Amidines used

B: 1.8-diazabicyclo [5.4.0] -undecene
C: 1,6-diazabicyclo [4.3.0] non-5-ene

Leveling agent: polybutyl acrylate (®Acronal 4 F from BASF AG)  

Comparison 1 demonstrates the properties of a dimethylbenzylamine Catalysis:

With acceptable properties with the exception of the gloss level is it that the powder coating hardens too quickly leads to a bad course with a strong structure: in combination with the practically impossible exact dosage and even mixing when necessary lower amounts of catalyst result in the poor Suitability of this amine catalyst.  

The quantities used (0.1 or 0.2 parts by weight) are in both cases of such a magnitude that with Examples 1-3 according to the invention are compared can.

Comparison 2

The amidine catalyst is now tested here. In comparison 2a) 0.2 parts by weight of amidine are used, an order of magnitude corresponding to the amounts from Examples 1-3 corresponds approximately according to the invention. It can be seen that  at 0.2 parts by weight of amidine, the lacquer does not react completely; this results from the lack of acetone strength, the completely inadequate impact resistance and long gelling time.

In comparison 2b) 0.5 parts by weight of catalyst are Amidine type used. This usually gives sufficient Properties (of course depending on the related amidine Catalyst), but requires a relatively high consumption the (expensive) component.

Examples 1-3 (according to the invention)

These examples demonstrate the synergistic effect. They all contain less amidine and less tertiary Amine as the corresponding comparison tests.

Despite the lower amount of catalyst, better properties than obtained with the individual catalyst components. The properties go far beyond what could have been obtained with the individual components. Gel times and course are also excellent.

Examples 4-7 (According to the Invention)

These examples serve to further illustrate the invention.

Claims (6)

1. Powder coating agents

• A) carboxyl-containing polymer with an acid number of 10 to 150,
• B) polyepoxide in a ratio such that there are 0.6 to 1.5 epoxy groups of polyepoxide B per free carboxyl group of polymer A,
• C) 0.1 to 5 wt .-%, based on the sum of A + B, catalyst and optionally
• D) auxiliaries and additives,

characterized in that the catalyst component C in turn

• 1) 10 to 90 wt .-% amidine and
• 2) 90 to 10% by weight of tertiary amine, based in each case on the weight of component C,

2. coating agent according to claim 1, characterized in that the polymer A has an acid number of 20 to 120 owns.   3. coating agent according to claims 1 to 3, characterized in that the polymer A from the group consisting of polyester and acrylic polymer selected is. 4. coating agent according to claims 1 to 4, characterized in that polymer A and polyepoxide B in one Stand ratio that to a free carboxyl group of polymer A 0.8 to 1.25 epoxy groups of the polyepoxide B come. 5. coating agent according to claims 1 to 5, characterized in that the amount of catalyst C 0.5 up to 2.5% by weight, based on the sum of A + B.