DE2003411A1 - Stoving enamels - Google Patents

Description

FARBENFABRIKEN BAYER AG

LEVERKUSBN-Biyeivrerk 26, Jan. \ 970 Patent Department University Fr / HG

Stoving enamels

The invention relates to stoving enamels containing epoxy and graft copolymers containing hydroxyl groups and with the epoxy and / or hydroxyl groups in the heat-reacting hardeners.

It is known to use graft polymers based on bisphenol A, To use 2-hydroxymethyl-5-norbornene and other olefinically unsaturated monomers for the production of coatings. These However, graft polymers are practically free of epoxide groups or have only a very low content of epoxy groups and can only be achieved by baking with triazinaldehyde resins or Urea aldehyde resins converted into crosslinked films and coatings will. Such graft polymers have a high proportion of homopolymers or copolymers of the graft polymers as admixture. They therefore separate easily and result in films that do not are very resistant to solvents (see USA patent, 3,028,359).

The object of the present invention was to produce both solvent-containing and solvent-free stoving enamels based on polyepoxides of polyhydric phenols, in particular based on diepoxides of 2,2-bis- (4-hydroxyphenyl-) propane (bisphenol A) and polyfunctional carboxylic acids, acid anhydrides, Polyamides of polycarboxylic acids, methylolated polyamides of polycarboxylic acids, lactams and derivatives, dicyandiamide and / or depeen derivatives, polyphenols, polyureas, methylo-

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lated polyureas, compounds containing alkoxymethyl groups, which not only have good resistance to chalking, high Light resistance, high gloss, but at the same time improved adhesion to copper, aluminum, zinc, iron, etc. and have improved compatibility with organic solvents, which is advantageous for solvent-based paints.

The object was achieved in that, if necessary, modified, Graft polymers containing acid and / or acid anhydride groups with more than one epoxy group in the molecule in combination with for baking enamels based on epoxy resins containing hydroxyl groups customary hardeners such as polycarboxylic anhydrides, polycarboxylic acids, polyamides of polycarboxylic acids, methylolated polyamides of polycarboxylic acids, lactams and derivatives, dicyandiamide and derivatives, polyphenols, polyureas, methylolated polyureas, Alkoxymethyl groups, preferably alkoxymethyl isocyanates and compounds containing more than 1 molecule of bound alkoxymethyl isocyanate per molecule.

The invention thus relates to solvent-based or solvent-free stoving varnishes, e.g. in powder form, to be applied to the surface to be painted, with a content of

A) optionally modified graft polymers from 1 to 7 $> hydroxyl-containing epoxy compounds of polyhydric phenols with more than one epoxy group in the molecule, the epoxides used as the graft base with a mixture of

a) 99.5-60 wt .- # methyl acrylate and

b) 0.5-40% by weight of ethylenically unsaturated carboxylic acid and / or ethylenically unsaturated carboxylic acid anhydride as well

c) 0-20 wt .- # (always based on total monomers, their Sum 100 wt .- ^) of others for copolymerization suitable, acid group-free, ethylenically unsaturated compounds

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have been grafted and the proportion of the graft base in the Graft copolymer is 30-98 wt .- # and.

B) one or more hardeners from the group Polycarbonsaurean- " hydrides, polycarboxylic acids, polyamides of polycarboxylic acids, methylolated Polyamides of polycarboxylic acids, lactams and derivatives, dicyandiamide and derivatives, polyphenols, polyureas, methylolated polyureas containing alkoxymethyl groups Compounds, especially alkoxymethylisοcyanate and more Alkoxymethylis bound as 1 molecule ο cya.nat per "molecule containing compounds,

As a graft base, the graft polymers contain epoxy compounds which are derived from polyhydric phenols and which contain 1 to 7% hydroxyl groups. ™

The following are mentioned as polyhydric phenols:

Bisphenol A | ~ 2,2-bis- (p-hydroxyphenyl) -propane3, 2,2-bis- (p-hydroxyphenyl) -methane, 4 »4'-dihydroxydiphenyl sulfone, novolak from Phenol, cresol or tert. Butylphenol with formaldehyde, resorcinol or hydroquinone.

However, polyepoxides can also be used as the graft base which meet the above conditions and which are derived from polyalcohols such as 1,3-butanediol, 1,4-butanediol, 2,2-dimethylpropanediol-1,3, trimethylolpropane, pentaerythritol, from aniline, from 4.4 ^l -bis (W-methylamino) -diphenylmethane, from isocyanuric acid or from olefinically unsaturated compounds which are converted into polyepoxides by peroxidation.

However, the corresponding polyepoxides are preferably multivalent Phenols, especially bisphenol A, with an epoxide equivalent from 180 to 4000 in the graft polymers as the graft base contain. (The epoxy equivalent of a compound is the amount of grams that contains 1 gram equivalent of epoxy groups.)

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The abovementioned polyepoxides of the polyhydric phenols can furthermore be modified, only fulfilling the conditions must be that the end product has more than one epoxy group per molecule and alcoholic groups. Among the modified Epoxides of the polyhydric phenols are soluble reaction products of the polyepoxides of the polyhydric phenols with polyamines such as hexamethylene diamine, diethylene triamine, triethylene tetramine, tetraethylene pentamine, dipropylene triamine, hydrogenated 4i4 '~ Diaminodiphei! Iylmethane or with monoamines such as butylamine, Oleylamine, cyclohexylamine, etc.

with cyclic carboxylic acid anhydrides such as phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, Methylhexahydrophthalic anhydride, endomethylenetetrahydrophthalic acid anhydride, diglycolic anhydride, etc. with carboxylic acids such as phthalic acid, tetrahydrophthalic acid, Hexahydrophthalic acid, methylhexahydrophthalic acid, adipic acid, Diglycolic acid, abietic acid, stearic acid, etc. with polyalcohols such as 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, Dodecanediol-1,12, etc.

with phenol, urea or melamine formaldehyde resins, with diisocyanate, tolylene diisocyanate, 4,4'-diisocyanatodiphenylmethane, hexamethylene diisocyanate, xylylene diisocyanate, isophorone diisocyanate, <k , E -diisocyanatocaproic acid esters with 1 to 8 carbon atoms in the alcohol residue and

with for the urethanization of up to 5 ^ of the hydroxyl groups Understood sufficient amounts of monoisocyanate such as methoxymethyl isocyanate.

The use of the modified polyepoxides described above of polyhydric phenols leads to the "modified graft polymers" after the graft copolymerization.

As monomers, which are contained in the graft polymers in grafted form, mixtures come into question, which from

a) 99.5-60% by weight, preferably 99-75% by weight, methyl methacrylate and

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. -ft b) 0.5-40 wt, preferably 1-25 wt. -ft of ethylenically. unsaturated carboxylic acid with 3-5 C atoms and / or ethylenically unsaturated carboxylic acid anhydride with 3-5 C atoms, such as * acrylic acid, methacrylic acid, maleic acid, itaconic acid, half esters of maleic acid and itaconic acid with 1 to 18 »preferably 1 to 8 C- Atoms in the alcohol radical, which can be prepared in a known manner from the corresponding anhydrides and monoalcohols or glycols, maleic anhydride, itaconic anhydride. Acrylic acid occupies a preferred position, ^{1 which} gives the graft copolymers particularly good lacquer properties.

c) 0 - 2Q wt .- # (based on the sum of the monomers) of other ethylenically unsaturated compounds such as ä monoolefins of 2 to 6 carbon atoms such as ethylene, propylene, butylene; conjugated diolefins with 4 to 6 carbon atoms such as butadiene, isoprene, dimethyl butadiene, 2-chlorobutadiene, 2,3-dichlorobutadiene; Esters of acrylic acid with 1 to 18 carbon atoms, preferably 1 to 8 carbon atoms and methacrylic acid with 2 to 18, preferably 2 to 8 carbon atoms in the alcohol radical, such as methyl acrylate, ethyl acrylate, butyl acrylate, ethyl methacrylate, butyl methacrylate, vinyl ester with 2 to 7 carbon atoms in the carbonic acid residue such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl benzoate; Vinyl compounds such as vinyl chloride, vinylidene chloride, styrene, methyl vinyl sulfone, N-vinylpyrrolldone, methyl styrene, oi. -Methylstyrene, ^^ oc-methyl-pisopropylstyrene, methyl vinyl ketone, acrylonitrile ,. Methacrylonitrile, allyl alcohol, hydroxyalkyl esters of methacrylic and acrylic acid, especially β- hydroxyethyl and / 3 -hydroxypropyl esters of methacrylic and acrylic acid, diesters of maleic and itaconic acid, which are obtained in a known manner from 1 mol of the corresponding anhydride and 2 mol of a monoalcohol or glycols with 2 to 8 carbon atoms can be produced, acrylic acid amide, methacrylic acid amide, N-methylol alkyl ethers of acrylic or methacrylic acid amide.8, in particular the N-Metiiy Io lme thy lathers, the um-SBtzungsprodukte of methoxymethyl isocyanate with β-hydroxy

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ethyl acrylate, with ft> -hydroxypropyl acrylate, with fh -hydroxyethyl methacrylate and with / ^ - hydroxypropyl methacrylate; AlIyI glycidyl ether, butadiene monoxide, glycidyl acrylate, glycidyl methacrylate.

When using both epoxy and acid groups with respect to indifferent monomers, the storage-stable resins are obtained.

Preferred monomers of group c) are acrylic acid esters with 1 to 18, preferably 1 to θ carbon atoms in the alcohol radical such as methyl, ethyl, propyl, butyl acrylate, methacrylic acid ester with 2 to 18, preferably 2 to θ carbon atoms in the alcohol radical, such as ethyl, propyl, butyl methacrylate, and also vinyl acetate, Acrylonitrile, styrene.

The preparation of the graft copolymers can be carried out either in the presence or in the absence of solvents. Suitable solvents are, for example, benzene, toluene, xylene, chlorobenzene, o-dichlorobenzene, butyl acetate, glycol monomethyl ether, ethyl glycol acetate, methyl isobutyl ketone, mixtures of the aforementioned solvents or, in the absence of esterification catalysts and isocyanate groups, mixtures of xylene and ethyl glycol, butanol. The grafting itself can be carried out such that the polyepoxide is added dropwise to the monomer or the monomer mixture at temperatures of 15 to 15O ⁰ C, preferably at 40 to 140 ⁰ C and at the same polymerized in the presence of free radicals.

The work is generally carried out at an elevated temperature, although in special cases and if, for example, a maximum yield can be dispensed with, temperatures above room temperature can also be used sufficient.

To carry out the grafting reaction, radical formers and / or Heat and / or high-energy radiation, possibly in combination

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tion used with photosensitizers.

The graft polymers to be used according to the invention can be incorporated with aliphatic polymers during or after the graft copolymerization Epoxides such as ethylene oxide and propylene oxide, optionally to be uncrosslinked under pressure, for the production of stoving enamels implement suitable polyepoxides.

The graft polymers obtained are uncrosslinked, easily soluble products with molecular weights of about 600 to 12,000, preferably from 800 to 10,000. A numerous conversion reactions, for example with amines, acid anhydrides, carboxylic acids via the epoxy group are accessible.

In addition to the epoxide groups, the graft copolymers used according to the invention also have a relatively high content of Acid or acid anhydride groups. It is surprising that she despite the high content of groups that react with one another, they do not cross-link to form gel-like products within a short period of time, but rather are present as low-viscosity solutions or result in low-viscosity solutions even after long storage in various systems.

If the coatings are to be applied to the surface to be painted in the form of powders or as a melt % , the solutions of the graft copolymers in suitable solvents can be used without difficulty at temperatures up to 140 ^° C. - with rapid operation such as, for example, when the product is in an evaporation screw or is freed in a film evaporator the solvent, temperatures of more than 200 ⁰ C are apringharten possible, clearly-soluble resins are evaporated. The grafted polyepoxides described are only slightly changed by prolonged thermal stress.

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The graft copolymers described are according to the invention with polyfunctional hardeners that work with the epoxy and / or the Hydroxyl groups at higher temperatures, addition and / or condensation reactions result, hardened.

Such hardeners are for example: Aliphatic and aromatic polycarboxylic anhydrides such as phthalic anhydride, tetrahydrophthalic anhydride, Terephthalic anhydride, hexahydrophthalic anhydride, Methylhexahydrophthalic anhydride, endomethylenetetrahydrophthalic anhydride, Mellitic anhydride, pyromellitic anhydride, Diglycolic anhydride, adipic anhydride, trimellitic anhydride etc., preferably phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, Trimellitic anhydride, pyromellitic anhydride, adipic anhydride. To achieve a sufficient Degree of crosslinking grafted epoxy resin and anhydride are used in such a ratio that on one Epoxy group 0.3 to 1.5 »preferably 0.5 to 1.3 carboxylic acid anhydride groups omitted.

Aliphatic and aromatic polycarboxylic acids such as phthalic acid, terephthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, methylhexahydrophthalic acid, Adipic acid, diglycolic acid, pyromellitic acid, Trimellite acid, etc., preferably phthalic acid, tetrahydrophthalic acid , Hexahydrophthalic acid, methylhexahydrophthalic acid, Adipic acid. According to the invention, there are 0.5 to 3, preferably 1 to 2.5, carboxyl groups for each epoxy group in the resin-hardener mixture.

Polyamides of polycarboxylic acids such as adipic acid diamide, hexahydrophthalic acid diamide, 4-chloroisophthalic acid diajnide, etc., preferably Adipic acid diamide and so much polycarboxylic acid polyamide is used that 0.3 to 1.5 »is preferably used for an epoxy group 0.7 to 1.3 carboxamide groups are omitted.

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Methylolated polyamides of polycarboxylic acids, preferably bis-N-methyloladipic acid diamide, Bis-N-methylolphthalic acid diamide, bis-N-methylolhexahydrophthalic acid diamide, Bis-N-methylol-4-niethylhexahydrophthalic acid diamide, Bis-N-methylol tetrahydrophthalic acid diamide. According to the invention, so much methylolated polyamide is used that 0.3 to 2.5 per hydroxyl group of the epoxy resin preferably 0.6 to 1.5 methylol groups are omitted.

Lactams and derivatives such as pyrrolidone, caprolactam, undecalactam, Dodecalactam and N-methylolated lactams, preferably caprolactam and N-methylol caprolactam. To achieve a sufficient Crosslinking is 0.2 to 1, preferably 0.3 to 0.7 lactam molecules and 0.2 to 1.5, preferably 0.3 to 1.2, per epoxide group Molecules of N-methylolactam used. ^ j

Dicyandiamide and its derivatives such as N-methyloldicyandiamide, di- and trimethyloldicyandiamide. According to the invention, there are 0.08 to 0.6, preferably 0.12 to 0.5, dicyandiamide molecules per epoxide group. Dicyandiamide partially substituted on the nitrogen can of course be used in a correspondingly larger amount in the degree of substitution can be used. Methylolated dicyandiamide, which contains more than 2 methylol groups in the molecule, is advantageous in such Amounts used that account for 0.3 to 2.5, preferably 0.5 to 1.5, methylol groups per hydroxyl group of the epoxy resin.

Polyphenols such as hydroquinone, resorcinol, catechol, 4,4'-Bis- ™ hydroxydiphenyl, 2,2-bis- (4-hydroxyphenyl) -propane, phloroglucinol, etc., resins such as novolaks and resols, which by acidic or alkaline Condensation from phenols such as phenol, KreBol, 2,2-bis (4-hydroxyphenyl) propane and formaldehyde, especially 2,2-bis (4-hydroxyphenyl) propane and phenol-formaldehyde resins from phenol and / or cresol and formaldehyde. According to the invention resin and hardener are mixed in such a ratio that 0.3 to 2, preferably 0.5 to 1.5, for an epoxy group there are no phenolic OH groups.

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Polyureas such as those obtained by reacting ammonia with polyisocyanates (for the formation of such Polyisocyanates suitable for ureas are e.g. tolylene diisocyanate, 4,4'-diisocyanatodiphenylmethane, 4,4'-diisocyanatodicyclohexylmethane, Tetramethylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, Isophorone diisocyanate, &, f -diisocyanatocaproic acid ester with 1 to 8 carbon atoms in the alcohol residue, triisocyanatohexylbiuret and deesen higher homologues), in particular Polyureas from hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, Isophorone diisocyanate, tolylene diisocyanate, triisocyanatohexylbiuret and its higher homologues and ammonia. at If there is sufficient crosslinking, 0.3 to 1.5, preferably 0.7 to 1.3 urea groups are accounted for by one epoxy group.

Methylolated polyureas, preferably the methylolated polyureas from hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, Isophorone diisocyanate, tolylene diisocyanate, triisocyanatohexylbiuret and its higher homologues and ammonia. According to the invention, as much methylolated polyurea is used as that 0.3 to 2.5 », preferably 0.6 to 1.5 methylol groups are allotted to an OH group of the epoxy resin.

Compounds containing alkoxymethyl groups such as are known, for example, from the methylolated compounds described above Process can also produce alkoxymethyl isocyanates such as methoxymethyl isocyanate and their reaction products with water, at least one NH and more than one 0-H, COOH, S-H group-containing compounds without the use of a catalyst manufactured in accordance with German Auslegeschrift 1 244 410 can be. Compounds containing OH groups are also understood as meaning polyphenols such as 2,2-bis- (4-hydroxyphenyl) propane. Since all other methylol ethers have to be produced in a different way by etherification of methylol compounds, They always contain catalysts that increase the resistance of the mixture of epoxy resin and hardener in the liquid phase, especially in the melt (in the extruder). Preferably be

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used: methoxymethyl isocyanate and its reaction products with ethanediol, propanediol (1,2), butanediol (1,3), butanediol (1,4), 2,2-bis (4-hydroxyphenyl) propane, linear or branched OH-containing polyethers and polyesters, ethylenediamine, diethylenetriamine. Grafted epoxy resin and alkoxymethyl groups are used to achieve a sufficient degree of crosslinking containing hardener mixed in such amounts that the ratio of the hydroxyl groups of the epoxy resin to the sum of free Isocyanate and alkoxymethyl groups of the hardener 1: 0.3 to 1: 2.5> is preferably 1: 0.6 to 1: 1.5.

Mixtures of the hardeners mentioned can also be used according to the invention. It is sometimes advantageous to combine di- and higher-functional crosslinkers in order to achieve * a sufficient degree of crosslinking.

It is often also beneficial to use the hardeners mentioned together with those which react with the grafted epoxy resins even at room temperature, such as using polyamines.

To accelerate the curing, the catalysts used in epoxy chemistry, such as tert. Amines, especially those that carry two methyl groups on the nitrogen (benzyldimethylamine), also N-methylpiperidine, pentamethyldiethylenetriamine, 1,3-bis-dimethylaminobutane, 2,4,6-tris (dimethylaminomethyl) phenol, phosphonium salts, such as methyl ^ j triphenylphosphonium iodide or ethyltriphenylphosphonium chloride, metal salts of organic acids such as zinc-2-ethylcaproate and dibutyltin dilaurate in amounts of up to 2 #, preferably up to $ 0.5, calculated on the sum of the reactants.

When using alkoxymethyl groups, the crosslinking can be Hardener by inorganic and organic acids, as described in German Auslegeschrift 1 244 410, be be accelerated.

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The stoving enamels according to the invention can optionally be made from grafted epoxy resin and hardener, especially if special effects are to be achieved, additives are added. Such Additives are, for example, plasticizers or compounds containing epoxy groups. Exemplary for those containing epoxy groups Connections are mentioned:

Monoglycidäther from tert. Butylphenol, epoxy resins made from bisphenol A and epichlorohydrin with more than one terminal epoxy group and an epoxy equivalent of approx. 200 to 5,000, linear or branched adducts made from organic compounds containing more than one hydroxyl group, polyisocyanates and epoxy alcohols such as those obtained from a linear polyester from adipic acid and ethylene glycol with a molecular weight of about 2,000 and an OH content of 1.7 #, hexamethylene diisocyanate and 1-glycidyloxybutanol- (3) can be prepared. These additives can be up to 150 percent according to the invention in quantities of -. $> (Calculated on grafted epoxy resin), are preferably added up to 100%.

Grafted epoxy resin, hardener and optionally catalyst and additive are applied to the surface to be painted either in solution or in substance well mixed. In substance, it is advantageous to mix in the melt, to get a homogeneous mass.

The paints according to the invention can be used with those customary in the paint industry Pigments and dyes are mixed.

It is surprising that the grafted used according to the invention Polyepoxides less when extruded with pigment and / or dye, hardener and possibly catalyst in the melt crosslink more easily than the corresponding non-grafted epoxy resins, provided that the molecular weight is the same Curing at higher temperatures has practically the same reactivity as the corresponding non-grafted epoxy resins demonstrate.

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The paints and coating compositions according to the invention are customary Varnish solvents such as aromatic hydrocarbons such as toluene, xylene, esters such as ethyl glycol acetate, alcohols such as Easily soluble butanol, glycol, ethyl glycol, ketones such as methyl isobutyl ketone. The paint solutions show a good flow.

The paints and coating compositions according to the invention can be in liquid, for example in solution or from the melt, or in solid Form by the usual methods such as brushing, rolling, spraying, pouring, the fluidized bed process or the electrostatic Powder spray methods are applied to the object to be coated.

When epoxy resin and hardener no condensation reactions with each other enter, practically any layer thickness can be achieved in one operation.

Paints applied in powder form sinter together to form a closed film when heated.

The cross-linking of the paint films is carried out at temperatures between 60 and 300 ⁰ C, preferably between 100 and 26O ⁰ C.

The cured paint films are characterized by particularly good resistance to chalking, gloss and light. Other advantages the films obtained from the paints and coatings according to the invention are good elasticity and chemical resistance, the great hardness and excellent adhesion on old paintwork and metals, e.g. copper, brass, aluminum, zinc, Iron etc.

The method of the invention is illustrated by the following examples explained in more detail. The parts mentioned in the examples are parts by weight, unless otherwise noted.

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Examples

A Production of a by graft polymerization of methacrylic acid methyl ester and acrylic acid-modified epoxy resin (resin A) as the starting product for Examples 1 to 4.

450 parts of a higher molecular weight epoxy resin made from 2,2-bis- (4-hydroxyphenyl) -propane and epichlorohydrin with an epoxy equivalent of approx. 395 with secondary hydroxyl and terminal epoxy groups, which contains 3.1 $> OH, are in 150 vol. -Parts of xylene dissolved. The solution is mixed with 363 parts of xylene in a three-necked flask equipped with a thermometer, stirrer, reflux condenser and coolable dropping funnel, and traces of oxygen are removed by introducing an oxygen-free stream of nitrogen. In the course of 3 hours, the mixture of 300 parts of methacrylic is added to the epoxy resin solution ^{at 120 ° C.}

acid methyl ester, 16.5 parts of acrylic acid and 4.5 parts of OL , CC azobisisobutyronitrile were added dropwise. After a further 30 minutes at 120 ^° C., the graft copolymerization has ended. Monomer conversion approx. $ 79>, epoxy equivalent of the clear, low-viscosity solution 1130, acid number of the solution 9.7. The graft copolymer contains polymerized units of 1.8 % acrylic acid and 34 % methyl methacrylate.

The solution is evaporated at temperatures between 80 and HO ⁰ C in vacuo to a spring hard, readily soluble resin having an epoxy equivalent of 705, an acid number of 9.0 and a softening point of 80-83 ⁰ C.

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example 1

100 wt. Tie. of the epoxy resin A, which has an epoxy equivalent of 705, were with 50 parts by weight. Titanium dioxide (rutile quality) and 18.2 parts by weight. Trimellitic anhydride mixed and then extruded. The jacket temperature of 80 ⁰ C was extrudes, the residence time of 20 seconds and the temperature of the exiting melt 115 ° C.

After solidification, the melt was granulated in a cutting mill and then finely ground on a fan mill. Afterward the powder was freed from particles with a grain size of over 80 ρ 0 by sieving.

The powder obtained in this way could be sprayed electrostatically at a voltage of 50 kV. Degreased metal sheets served as a base. It was ^{baked at 160 °} C. for 30 minutes. The film thickness was between 80 and 120 μm, depending on the amount applied; the films were hard and had good adhesion. (Powder coating I)

A powder coating prepared like I was used for comparison became; it consisted of 100 parts by weight of a commercially available epoxy resin based on bisphenol A and epichlorohydrin with an epoxy equivalent of 975.50 parts by weight of titanium dioxide, rutile and 13.15 parts by weight of trimellitic anhydride. (Powder coating II) The metal sheets coated with this powder coating had hard films with good adhesion.

Sheets painted with powder coating I and II were made in the Atlas Weathero meter exposed. The films of powder coating I were clearly superior to those produced with II: after 300 hours they showed Powder coating II-films medium-thick chalking (level 2 of a Kreldungsscala), while the powder coating I films only after 520 hours reached the same degree of erection (level 2). I is therefore 3 1 in terms of resistance to chalking

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\ ^l UH Ά> / W, LH

Chalking scale: Level O = no chalking

Level 1 = weak chalking

Level 2 = medium chalking

Level 3 = heavy chalking

Level 4 = very strong chalking

It was also found that the powder coating I films the II films were clearly superior in color fastness or yellowing fastness: The II film changed the color tone from level 1.0 after 300 hours in the Weatherometer according to level 2.0, while I only reached about the same level 2.2 after 520 hours; the The initial value was 1.3.

Color or level 0 = not yellowed

Yellowing scale: Level 1 = slightly yellowed

Level 2 = yellowed Level 3 = heavily yellowed Level 4 = very heavily yellowed.

At 160 ⁰ C for 30 minutes branded films of the powder coatings I and II were exposed for 6 days in the xenon test device. While the II-film had changed after this time from the initial hue of 1.0 to 2.9, that is, it had yellowed strongly, the I-film did not change.

This showed the significantly better light stability or yellowing resistance of the powder coating I with the grafted one Epoxy resin A as a binder.

In powder coating I and II, two carboxyl groups were created for each epoxy group brought to reaction.

Even with incomplete crosslinking or curing of the epoxy resin, i.e. when the ratio of epoxy group: carboxyl group was reduced to 1: 1, the superiority of this was shown Resin compared to the commercially available powder coating II:

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7+

Example 2 ;

100 parts by weight of the above-described grafted epoxy resin under A were processed with 50 parts by weight of titanium dioxide, rutile type, and 8.25 parts by weight of trimellitic anhydride analogous to I and II to give a powder coating that was easily sprayable electrostatically (= powder coating III). It was baked for 30 minutes at 160 ^° C.

In the Weatherometer, Powder Coating III films only showed a chalking grade of 3.0 after 608 hours, while the color tone changed from Level 0.9 had changed to 1.8.

After 6 days of exposure to xenon, the III films were changed from level 0.9 to 1.7.

Example 3 :

A lacquer was produced from a solution of 100 parts of the grafted epoxy resin A in 100 parts. Methyl isobutyl ketone xylene ethyl glycol (1: 1: 1), the solution of 14 tsp. 2,2-bis (4-hydroxyphenyl) propane in 60 tlen. of the same mixed solution and 1 part of dibutyltin dilaurate.

Baking for 30 minutes at 210 ^° C. gave a clear, colorless, elastic, solvent-resistant film with good weather and light resistance.

Example 4 :

Paints were produced from a solution of 100 parts. resin A in 100 tsp. a mixture of equal parts methyl isobutyl ketone, xylene and ethyl glycol and

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a.) 16 Tien. Caprolactam, dissolved in 60 tienes, of the same solvent mixture a and 1 part of dibutyl tin dilaurate.

b) 20 tsp. N-methylolcaprolactam in 60 parts. dea same Solvent mixture and 1 part dibutyltin dilaurate.

c) 20.8 parts. Adipic acid in 60 parts. Ethanol.

d) 17 tsp. 4-chloroisophthalic acid diamide, dissolved in 100 parts. hot ethanol.

e) 17 tsp. Hexamethylene bismethoxymethyl urea dissolved in 60 tsp. hot cyclohexanone.

f) 23.6 parts. of a bisurethane from 2 molecules of methoxymethyl isocyanate and 1 molecule of 2,2-bis (4-hydroxyphenyl) propane, dissolved in 200 parts. of the same solvent mixture and 1 part of dibutyltin (IV) dilaurate.

Through 30 (d, f 60) minutes of baking at 210 ⁰ C (e at 170 ⁰ C, f at 195 ⁰ C) to degreased metal sheets was movies obtained to those of non-grafted epoxy resin based on bisphenol A and epichlorohydrin and the same Hardeners were superior in terms of weather and light resistance, gloss retention and adhesion to steel.

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B Production of a by graft copolymerization of methacrylic acid methyl ester, Acrylic acid butyl ester and acrylic acid-modified epoxy resin (resin B) as a starting product for examples 5 and 6.

6750 TIe. the higher molecular weight described in A as the graft base Epoxy resin from 2,2-bis- (4-hydroxyphenyl-) propane and epichlorohydrin are sold in 2250 Tlen. Xylene dissolved. the The solution is in a heated VA stirred tank equipped with a thermometer, Reflux condenser, stirrer and coolable dropping funnel is equipped with 5500 Tlen. Xylene mixed and with the introduction of an oxygen-free nitrogen stream of traces Frees oxygen. In the course of 3 1/2 hours, the mixture of 4050 parts is added to the epoxy resin solution at 120. Methacrylic acid methyl ester, 450 tsp. Acrylic acid butyl ester, 247.5 parts. Acrylic acid and 67 *, 5 parts. oc, cL'-azobisisobutyronitrile added dropwise. After a further 21/2 hours at 120 ° C., the graft copolymerization is complete completed.

A clear solution with a viscosity of 1250 cP (t = 22 C), an epoxy equivalent of 1400 and an acid number of 9.3 is obtained. The Pfropfcopolymerisnt polymerized units of 2% acrylic acid, butyl acrylate and 3% $ 32> methacrylate, based on graft.

To produce a tack-free powder, the epoxy resin is freed from the solvent at 155 ° C./15 mm Hg in an evaporation screw with a residence time of approx. 4 minutes. The result is a slightly-soluble resin having an epoxy equivalent of 745, an acid number of 8.2 and a softening point 78-80 ⁰ C.

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Example 5 :

100 wt. Tie. of the epoxy resin B with an epoxy equivalent of 745 were with 50 wt. TIn. Titanium dioxide, rutile type, and 17.2 wt. Tin. Trimellitic anhydride as indicated in Example 1 mixed, extruded, granulated, ground and sieved. The powder formed in this way could be sprayed electrostatically well. The applied voltage was between 40 and 60 KV, depending on the desired layer thickness (powder coating IV).

It was baked for 15 minutes at 200 ^° C., for comparison powder coating II from Example 1 was used and it was also baked for ^{15 minutes at 200 ° C.} Sheets exposed in the Atlas Weatherometer showed a chalking grade of 2.0 after 300 hours for powder coating II pilmen, but only after 400 hours for IV films. IV films are therefore significantly more resistant to chalking.

The same films showed after 6 days of exposure in the xenon test device for II-films a yellowing of level 1.0 after level 2.9, for IV films on the other hand from 1.0 to 1.7. The powder coating IV films are therefore more light-resistant.

In the case of powder coatings II and IV, two carboxyl groups were used for each epoxy group.

Example 6 :

100 tIe. Resin B were 53.5 Tlen. Titanium dioxide, rutile quality and 7 parts. a diurea from toluene diisocyanate (65 fi 2,4- and 35 # 2,6-diisocyanate) and ammonia (molar ratio 1: 2) premixed and then extruded. The Mnnteltemperatur of the extruder was 80 ⁰ C, the residence time see 20th and the temperature of the exiting melt 110 °.

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10983? / IULH

The powder obtained as described in Example 1 was electrostatically sprayed onto degreased metal sheets at a voltage of 50 KV and stoved at 200 ^° C. for 30 minutes. An elastic, glossy, weather-resistant film was obtained.

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C The starting product for Example 7 is a mixture of Tlen. of the grafted epoxy resin described under A and 18 Tlen. a diepoxide of the following idealized constitution

CHP-CH-CH ₂ -O-CH ₂ -CH ₂ -CH-O-CO-NH- (CH ₂ J ₆ -HH-CO-ORO-CO-NH

^CH 3 (CH ₀ J ₁

CH ₂ -CH-CH ₂ -O-Ch ₂ -CH ₂ -CH-O-CO-NH- (CH ₂ ) ₆ -NH-C0-0-R-0-C0-NH

o 'ch.

- HO-R-OH = linear polyester made from adipic acid and ethylene glycol with a molecular weight of approx. 2000, OH content 1.7 %, the epoxide was formed by the addition of a monoisocyanate from 1-glycidyl oxybutanol (3) and hexamethylene diisocyanate the bisurethane of 2 moles of the polyester and the above-described 1 mole of hexamethylene diisocyanate obtained at temperatures of about 40 ⁰ C - is used.

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Example 7 ;

100 parts by weight. the epoxy resin mixture were with 18.2 parts by weight. Trimellitic anhydride and with 50 wt. Tin. Titanium dioxide, rutile type, mixed, extruded, granulated, ground and sieved as indicated in Example 1. The resulting powder settled spray well electrostatically; the voltage applied was between 40 and 60 KV (powder coating V).

By powder coatings V and II, for comparison, panels were sprayed and baked for 15 minutes at 200 G ^0. The films formed in this way were exposed in the weatherometer and in the xenon test device. The film thickness was 80 µ.

After 300 hours, the powder coating II films showed a chalking stage 2.0 corresponds to a medium-strength chalking, while the V-films were still without any chalking after 340 hours. After 6 Days of exposure to xenon, the II films showed a yellowing from the original level 1 to 2.9; changed at the same time the V-films changed from 1.0 to 1.2, thus remained practically without yellowing.

It is therefore the better light and chalk (weather) resistance of powder coating V with epoxy resin C. In the case of powder coatings II and V, each epoxy group was initially used two carboxyl groups calculated.

Example 8 :

100 parts by weight. of the grafted epoxy resin B were 8.9 wt. TIn. a commercial dicyandiamide derivative (Epicure 108; commercial product of SHELL), with an H-active equivalent weight of 66, as hardener and 50 wt. tin. Titanium dioxide, rutile type, mixed and then homogenized by melting in an extruder. The jacket temperature of the extruder was 80 ^° C., the dwell time 20 seconds and the outlet temperature of the melt HO ⁰ C.

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After solidification, the melt was granulated on a cutting mill, then ground on a fan mill and finally the particles with a grain size above 80 u were removed by sieving. The powder coating obtained in this way can be negative charge, very well under a voltage of 60 KV using a commercially available electrostatic spray gun Apply to well-degreased metal sheets.

After baking for 15 minutes at 160 ^° C., smooth, hard films were produced, with a thickness of about 70-80 μm. (Anetrichfilme VI)

In a completely analogous way, a comparative powder coating based on a commercially available epoxy resin made from bisphenol was produced A and epichlorohydrin, with an epoxide equivalent of 925 »also 100% with the crosslinker listed above and reacted pigmented in the same amount as well as paint films produced. (Paint films VII)

(In both powder coatings, one active hydrogen was used for each epoxy group of the crosslinker (hardener).)

The following chalking was exposed in the Atlas Weatherometer

after 400 600 hours no change
Trace chalking
medium chalk
strong chalking
floury topping Films VI
Films VII 0
2.0 2.0
canceled Chalk scale: 0
1
2
3
4th

Thus, it is proven that the epoxy resin is much better weather- and chalk-resistant paint films.

hey A 1? 7 ⁽ * 1 -Ρ / 1-

1 (J ίί Η Ά ? / 1 4

Claims (6)

Patent claims: 1) Stoving enamels with a content of A optionally modified graft polymers from 1 to 7% hydroxyl-containing epoxy compounds of polyhydric phenols with more than one epoxide group in the molecule, the epoxides used as the graft base with a mixture of a) 99.5-60 wt .- ^ methyl methacrylate and b) 0.5-40 wt .- # of ethylenically unsaturated carboxylic acid and / or ethylenically unsaturated carboxylic acid anhydride and " c) 0 - 20 wt .- ^, always based on total monomers, their Total is 100 wt .- ^, on others for copolymerization suitable, acid group-free, ethylenically unsaturated compounds are grafted and the proportion of the graft base in the graft copolymer is 30-98 wt .- # and B one or more hardeners from the group consisting of polycarboxylic acid anhydrides, polycarboxylic acids, polyamides of polycarboxylic acids, methylolated polyamides of polycarboxylic acids, lactams and derivatives, dicyandiamide and derivatives, polyphenols, polyureas, methylolated polyureas, alkoxy- J methyl groups containing compounds, in particular alkoxymethyl isocyanates and molecules more than 1koxymethyl isocyanates Bound alkoxymethyl isocyanate _{t the} molecule-containing compounds. 2) stoving enamels according to claim 1, characterized in that the graft base is an epoxy resin based on 2,2-bis- (4-hydroxyphenyl) propane, which has an epoxy equivalent of 180 to 4000 is used. Le A 12 791 - 25 - 3) Stoving enamels according to Claims 1 and 2, characterized in that the ethylenically unsaturated acids and / or acid anhydrides Acrylic acid, methacrylic acid, maleic acid, itaconic acid, half esters of maleic and itaconic acid with 1 to 18, preferably 1 to 8 carbon atoms in the alcohol radical, maleic anhydride, itaconic anhydride in the grafted polyepoxides are bound. 4) stoving enamels according to claims 1 to 3, characterized in that in addition to methacrylic acid methyl ester and ethylenically unsaturated Acid and / or ethylenically unsaturated acid anhydride as further monomer (s) ester of acrylic acid with 1 to 18, esters of methacrylic acid with 2 to "8, vinyl acetate, acrylonitrile, styrene bound in the grafted polyepoxides are. 5) Stoving enamels according to Claims 1 to 4, characterized in that the epoxy component is a mixture of grafted polyepoxide and optionally several other epoxy compounds, preferably a reactive diluent such as monoglycidic ether from tert-butylphenol, epoxy resins made from bisphenol A and epichlorohydrin with more than one terminal epoxy group and an epoxy equivalent of approx. 200 to 5000, linear or branched adducts of polyhydroxides, polyisocyanate and epoxy alcohols is used. 6) stoving enamels according to claim 5, characterized in that the epoxy component is a mixture of grafted polyepoxide and up to 150 #, preferably up to 100 # (calculated on grafted polyepoxide), another epoxy compound is used. Le A 12 791 - 26 - 109837/1448