FI104377B - Heat-curable coating system - Google Patents

Abstract

The invention relates to a heat-curable coating system which contains no epoxide groups and is based on carboxyl-functional polyester resins and ss-hydroxyalkylamides and, if desired, further conventional additives, the coating system containing as binder resin (a) at least one saturated polyester having an acid number of 15 to 75 mg of KOH/g, an OH number of not more than 10 mg of KOH/g and a glass transition temperature of greater than 45 DEG C, which is composed of aliphatic diols and more than 80 mol% of isophthalic acid, and as crosslinking agent (b) at least one hydroxyalkylamide having at least two hydroxyalkyl groups. The invention also relates to a process for the preparation of heat-curable coating systems which contain no epoxide groups and are based on carboxyl-functional polyester resins, in which components a), b) and, if desired, further conventional additives of the coating system according to claims 1 to 11 are mixed in the melt at from 80 to 130 DEG C, discharged, granulated, ground and then screened to a particle size of less than 90 mu m. The invention relates finally to the use of the coating system.

Description

, 104377 Heat-curing coating system. - Värmehärdbart belägg-ningssystem.

The invention relates to epoxy-free thermosetting, particularly weatherproof coating systems based on carboxy-functional polyester resins and β-hydroxyalkylamides, to their preparation and use, as well as to protective layers of these coating systems.

Thermosetting powder lacquers do not provide any organic solvents when added and therefore have clear environmental advantages over liquid lacquers. The crosslinking in heat occurs by polyaddition or polycondensation reactions between the functional groups contained in the binder systems. Typical binder systems include epoxide resin / hardener, polyester / epoxide, polyester / isocyanate, acrylate / epoxide, acrylate / isocyanate, acrylate / dicarboxylic acid and the like. These binder systems differ not only in their lacquer technical properties but also in their outdoor weather resistance, so much has been done. *: ·. Efforts have been made to develop binder systems for powder lacquers with a particularly good ·· outdoor weather resistance. .sex. Powder lacquers based on acrylate systems give the most advantageous results here, but they have only •••• inadequate lacquer technical properties or cause unacceptable contamination of other powder coating systems, which is why they are used only very limited.

Polyester / Epoxy .I.Side powder lacquers containing only 4-25% by weight of polyepoxy- ••• resin, which are expected to have a low improved weather resistance due to polyepoxide content. For the purposes of this patent: The described solid polyester resins, having an acid number of 30 to about ** 00, consist of at least 50% of the reaction product of an organic hydrocarboxylic acid anhydride or mixture of these anhydrides with up to 50% of dibasic, unsaturated or unsaturated , an aromatic or cycloaliphatic carboxylic acid and a hydroxy number 15 to 50 polyester resin. The aromatic carboxylic acids used in the preparation of this polyester resin comprise o-phthalic acid, terephthalic acid, isophthalic acid or their esters with lower aliphatic alcohols, as well as up to 10 mol% polybasic, aliphatic carboxylic acids such as adipic acids, for example, tri-mellitic acid (Trimellithsäure) or pyromellitic acid (Py-romellithsäure). A preferred divalent aromatic carboxylic acid is terephthalic acid.

The diols used include alkoxylated 4,4-isopropylidene diphenol with an average number of 2-6 oxyethylene or oxypropylene groups, glycidyl esters and / or divalent alcohols such as 2,2-dimethylpropanediol-1,3, propylene glycol- 1,2, 1,4-cyclohexanedimethanol, ethylene glycol or diethylene glycol. Further, up to 10 mol% aliphatic alcohols, trivalent or polyhydric alcohols such as trimethylol propane or pentaerythritol may be used.

The hydroxyl-functional polyester resin is prepared by known methods by heating all the reactants with stirring to a temperature of about 240 ° C and removing the water formed during the crosslinking reaction in vacuo. The reaction of the thus obtained hydroxyl group-containing polyester resin with the polybasic carboxylic acid anhydride to form a carboxyl-functional polyester resin is then carried out over a period of 1-3 hours at 180-250 ° C under an inert gas atmosphere.

Trisglycidyl isocyanurate (TGIC) is preferably used as the polyepoxide compound.

DE-A-104377 DE-A-26 18 729 discloses thermosetting powder lacquers of carboxylated polyester resins and epoxy compounds, wherein the carboxylated polyester resins used contain the same monomer components but differ in their manufacturing process. According to DE-A-26 18 729, at least a trivalent aromatic carboxylic acid is formed already in the first step, i.e. during the preparation of the polyester resin containing hydroxyl groups, and the reaction to the carboxyl-functional polyester resin is subsequently carried out by reaction with isophthalic acid. The advantage of this process is justified by the improved wear resistance and lacquer technical properties of powder lacquers made from carboxyl-functional polyester resin.

Another patent, U.S. Pat. No. 4,379,895, also describes the preparation of so-called acid-masked polyester resins for polyester / epoxide powder lacquers using the same monomer components as suggested in the aforementioned patent. Here again, the difference is essentially only in the manufacturing process.

«4 f • I t

Although all the patents disclosed so far also describe the use with isophthalic acid as a monomeric component, the aromatic carboxylic acid is preferably terephthalic acid and in no way advises; that the advantageous use of isophthalic acid can provide polyester ester / epoxy powder lacquers with improved weather resistance. One disadvantage of using isophthalic acid was much lower varnish properties compared to terephthalic acid, in particular insufficient impact strength.

»» T t * m DE application 40 32 855 now requires powder coatings, • ♦. having good UV resistance in combination with good mechanical properties after relatively short curing times, comprising powder coatings comprising a polyester resin having an acid number of 15 to 70 and a hydroxy number of less than 10, polyepoxide compound 104377 4 and common additives. The polyester resin consists essentially of dicarboxylic acids, glycolene and monomers having a functionality of 3 or more, wherein at least 15 mol% isophthalic acid and at least 5 mol% 1,4-cyclohexanedicarboxylic acid are used as dicarboxylic acids, and at least 50 mol% aliphatic glycols having from 5 to 11 carbon atoms and up to 50 mol% aliphatic glycols having from 2 to 6 carbon atoms and containing monomers having 3 or more functionalities in an amount of up to 8 mol% of dicarboxylic acid plus glycols. Particularly good results are obtained with 75-90% IPS and 10-25 mol% 1,4-dicyclohexanedicarboxylic acid.

The epoxide resin proposed as the crosslinking agent has a functionality of 2 or more, and epoxide compounds are preferably used without a phenolic carbon-oxygen bond, since this bond is particularly photosensitive. Preferred polyepoxide compounds are therefore trisglycidyl isocyanurate (TGIC), diglycidyl terephthalate or diglycidylhexahydrophthalate.

Another patent, EP 0 522 648 A1, proposes weather-resistant powder lacquers of glycide-functional acrylates and carboxyl-functional polyester resins having a composition similar to that of DE

I I

. sa 40 32 855. Insufficient mechanical properties and

• I I

"** However, due to the risk of contamination, such powder coatings do not yet meet commercial requirements.

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Likewise, weatherproof powder coatings on the basis of carboxyl-functional polyester resins and polyepoxide compounds such as, for example, trisglycidyl isocyanurate (TGIC) are described / in *, in US-P 5,097,006 and EP 0 561 102. These I 9

I ', the polyester resins are mainly composed of cyclohexanedicarboxylic acid, 10-100 mol% of cycloaliphatic diols, * *, fV / specially hydrogenated bisphenol A or mixtures thereof, ·: ··: 90-0 mol% branched glycols or polyols having from 2 to 12 carbon atoms, for example 2,2-dimethyl-1,3-10,437,777 of propanediol.

However, the use of poly-epoxide compounds, in particular trisglycidyl isocyanurate (TGIC) as a crosslinker, has the major disadvantage of all patents used in the manufacture of weatherproof powder lacquers. But polyepoxide compounds, and in particular TGIC, have great toxic potential and are therefore undesirable in powder lacquers, which otherwise are remarkable for their excellent ecological and toxicological properties.

U.S. Patent 4,076,917 describes epoxy-free binder systems of carboxy-functional polymers which do not contain ester linkages and β-hydroxyalkylamides, and also refers to the possibility of using such binder systems as a powder coat. The crosslinking is effected by reaction of the β-hydroxyl groups of the alkanolamide with the carboxyl groups. Compared to polyepoxide compounds, β-hydroxyamides are absolutely toxicologically acceptable. However, as with TGIC, carboxy-functional polyesters containing in particular dicarboxylic acid, in particular isophthalic acid, and therefore having .1 inadequate mechanical properties are required to achieve very good weather resistance.

International Patent PCT Publication No. WO 91/14745 discloses a modification of weatherproof powder coating containing carboxyl functional polyester resins having a high content of isophthalic acid and β-hydroxyalkyl amides as crosslinking agents. , with semi - crystalline polyester resins,. with an acid number between 10 and 70 [mg KOH / g] for insufficient granules • ♦ · ·. ·: ·. to improve its chanical properties.

The special disadvantage of semi-crystalline polyester resins is the low * 1 * glass transition point, which results in insufficient storage stability of powder coatings.

• · ·. t 6 104377

On the other hand, semicrystalline polyester resins containing difunctional carboxylic acids, for example, terephthalic acid, exhibit reduced UV resistance even in small amounts of modified powder coatings.

Thus, a binder system which satisfies the requirements for toxicity, improved weather resistance, sufficient storage stability and good lacquer technical properties has not yet been proposed in the prior art.

The object of the present invention is to provide a toxicologically acceptable coating system which, to the greatest extent possible, meets all the requirements for weather resistance, good storage stability and wear and mechanical properties.

This problem is solved by the development of a thermosetting, epoxy-free, weatherproof coating system based on carboxyl-functional polyester resins and β-hydroxyalkylamides, which has very good lacquer technical properties, excellent wear resistance and good shelf life according to claim 1 or -

III

Or the process of claims 12 and 13, or the patent. . 14 through the protective layer.

The present invention relates in particular to a coating system of at least one special saturated polyester binder as a resin a), in particular, being composed of aliphatic diols. and predominantly isophthalic acid - #> · | ·, which may be replaced by up to 20 molar parts, total acid -: * · *: on the basis of the amount of other aliphatic or cycloaliphatic dicarboxylic or polycarboxylic acids or ** ·] anhydrides, and hydroxylamide as a crosslinking agent b).

* * • · · • * * 7 104377

The polyester resin a) has an acid number between 15 and 75, an OH number of not more than 10 and a glass point above 45 eC. The crosslinking agent b) is at least one β-hydroxyalkylamide having at least two β-hydroxyamide groups. In addition, the coating system may include the usual additives c) for the manufacture and use of powder lacquers.

The polyols of the polyester resin are composed of 0 to 10 parts by weight of at least one straight-chain diol having at least 4 C atoms and at least 50 parts by weight of at least one branched aliphatic diol having at least 4 C atoms and up to 50 an aliphatic diol having less than 4 C atoms and / or at least one cyclic aliphatic diol, wherein the saturated polyester contains at least one monomer having a functionality of at least 3, based on the total acid and diol content, based on the total acid and diol content.

These monomers are preferably polycarboxylic acids, their anhydrides and polyols, preferably in a proportion of 3 to 6 molar parts.

.! Preferred monomers having a functionality of at least 1 · 3 are, for example, 3-basic aliphatic, cycloaliphatic or aromatic carboxylic acids or their anhydrides.

In this case, trimellitic anhydride is particularly preferred.

• · ·

Polyols include, for example, trimethylolpropane, trimethylol (V) ethane, glycerol and tris (2-hydroxyethyl) isocyanurate, of which trimethylolpropane is preferred.

. 1 1 1 · «·

The carboxy-functional polyester resin is composed of at least 80 parts by weight of isophthalic acid and up to 20 parts by weight of one or more aliphatic or cycloaliphatic dicarboxylic acids.

I I I f I

acid, with aliphatic dicarboxylic acids having from 6 to 22 carbon atoms, such as adipic acid, azelaic acid, sebacic acid and dodecanedioic acid being preferred. Preferred cyclic 104377 8 aliphatic acids are cyclohexanedicarboxylic acids. In a preferred embodiment, the polyester resins are formed from 3 to 7 moles of straight-chain aliphatic diols having at least 4 C atoms, with hexanediol-1.6 and diols having 12 to 20 C atoms being particularly preferred, and especially preferred having 13-15 C atoms. A preferred branched diol having more than 4 C atoms is 2,2-dimethyl-1,3-propanediol.

One particularly preferred diol composition is comprised of 3 to 7 parts by weight of straight chain diols having at least 4 C atoms, at least 75 parts by weight of branched diols having at least 4 C atoms, and up to 22 moles of straight chain diols having less than 4 C atoms .

The cross-linking component (b) of the β-hydroxylalkylamides must contain at least 2 β-hydroxylalkylamide groups per molecule and be substantially characterized by the general formula I:

HO-CH-CH2-N-CO-R2-CO-N-CH2-CH-OH I

II

R1 R3 R <R1 <where R1 is the same or different alkyl groups having 1 to 4 carbon atoms or hydrogen, R2 is an aliphatic, cycloaliphatic, araliphatic or aromatic group, "" R1 and R4 are (HO-CH-CH2) -,

A: I

R 1 or the same or different alkyl groups having 1 to 4 carbon atoms or hydrogen.

• · · • · · 1

· I

Preferred β-hydroxyalkylamides for use in powder varnishes are: ## STR4 ## - tis-bis [N, N'-di (β-hydroxyethyl)] -adipamide or bis [N, N'-di (β-hydroxypropyl)] - adipamide «1» · · 9 104377

Particularly preferred is bis [N, N'-di (δ-hydroxyethyl)] adipamide. As a technical product, it may still contain a small proportion of di- and trimers. Above 140 ° C, it crosslinks rapidly with the crosslinking resin, carboxyl-functional polyester resins, resulting in very good lacquer technical properties.

In order to achieve good lacquer technical properties, 0.5 to 1.5, in particular 0.8 to 1.2, hydroxylalkylamide groups per carboxyl functional polyester resin are required.

Common additives c) for the manufacture and use of powder lacquers include pigments, fillers, abrasion and degassing additives, heat, UV and / or HALS stabilizers or abrasive additives, such as wax.

The carboxyl-functional polyester resins of the invention are prepared in a known manner by heating all the monomer components together in the presence of standard esterification catalysts to a temperature of about 250 ° C and separating the reaction water formed, or. a two-step process, wherein in the first step *; is formed in the presence of an excess of polyol, a hydroxyl functional * ♦ ·· thionic polyester, and this is subjected to a second step

I I I

···: react with one or more polybasic carboxylic acids or their anhydrides to form a carboxyl functional polyester resin.

• · »• · · ·

The coating systems according to the invention are manufactured in particular by extrusion of all components of the coating system at temperatures between 80 ° C and 130 ° C. Subsequently, the extrudate is cooled, milled and: screened to a particle size of less than 90 μτα. In principle, other methods of preparation are also suitable for preparing coating systems, such as mixing components in solution and subsequently mixing or removing solvent by distillation.

The application of the coating systems of the invention is accomplished by methods common to powder coaters, for example by means of electrostatic powder jet devices, by abrasive or corona method or by vortex bed method or the like.

The thermosetting, epoxy-free coating systems of the invention have good storage stability and, after crosslinking at 150 to 200 ° C, have very good wear resistance and mechanical properties. They exhibit remarkably good weather and UVB resistance and are additionally absolutely toxicologically acceptable. They also meet the requirements of the state of the art for ecologically sound coating materials.

Contrary to prior art coatings, the coating systems of the invention have very good mechanical properties in combination with good wear resistance despite the high proportion of isophthalic acid which is nevertheless essential for good weather resistance.

The preparation and properties of carboxyl-functional, specific polyester resins *. * *, As well as the coating systems, are illustrated by the following examples: - Example 1 (2-step process) 2-1 all the diols are added to the esterification reactor equipped with a temperature sensor, a stirrer, a reflux column and a distillation bridge, and melted at 140 ° C under an inert nitrogen atmosphere maintained throughout the reaction. ·: ··; With less stirring, the less reactive diacids (diacid / 11-104377 diol to molar ratio of about 1: 1.12) are added, as well as a crude, optionally esterification catalyst, and the internal temperature is gradually raised to 235 ° C. The reaction is continued until no more distillate is formed and the acid number is less than 10 mg KOH / g. More reactive diacids are then added and the esterification is continued until the desired acid number is reached. Part of this second step is performed under possibly reduced pressure (<10 kPa).

Example II (1-step process) All diols are added to a 2-1 esterification reactor equipped with a temperature sensor, a stirrer, a reflux column and a distillation bridge, and melted at 140 ° C under an inert nitrogen atmosphere maintained throughout the reaction. If all diacids are equally active, all diacids are added as well as any esterification catalyst under stirring, and the internal temperature is gradually raised to 235 ° C. The reaction is continued until no more distillate is formed and the desired acid number is reached. The last part of this process is performed under possibly reduced pressure.

Manufacture of Coating Systems I *

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, For all polyester resins described in Table 1,

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The following formulation was prepared.

542.8 parts by weight of polyester resin 47.2 parts by weight Primid XL-552 400.0 parts by weight Kronos 2160 titanium dioxide 8.0 parts by weight Resiflow PV 88 0 · · · 2.0 parts by weight benzoine 100.0 parts by weight f 1) Bis [N, N'-di (8-hydroxyethyl)] -adipamide commercial product from Rohm & Haas 104377 12 2) Polyacrylate based flux

you from Worle-Chemie GmbH

The ingredients of the formulation are blended dry in a Henschel mixer at 700 rpm for 30 s, and then extruded with a "Buss-Co-Kneter" extruder (PLK 46) at a jacket temperature of 100 ° C, a cooled screw and a screw rotation speed of 150 rpm. The extrudate is cooled, ground and sieved to less than 90 μια.

The lacquer tests are carried out with trichloroethane degreased steel sheets (thickness 0.8 mm) at a cure temperature of 180 eC and a lacquer film thickness of 60-80 μια.

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Table la:

Example 12 3 4567 8 9 (Vert) (Vert) TPS 10.0 10.0 IPS 88.0 78.0 88.0 98.0 88.0 90.0 86.0 98.0 87.0

ADI

CHDS 10.0 10.0 10.0 10.0 10.0 10.0 THA 2.0 2.0 2.0 2.0 2.0 4.0 2.0 3.0 KPG 82.8 82, 9 83.0 82.8 87.8 78.9 86.9 88.0 84.9

EG

HD 5.0 5.0 5.0 5.0 5.0 5.0 5.0 c12-14-diol TKP 2.0 2.0 2.0 2.0 2.0 4.0 2.0 1 , 0 SZ 48 51 52 51 51 50 51 51 50 SV 11 21 29 14 12 14 11 19 18 TGj, es 58 59 62 61 62 58 57 66 58 TGpL 55 56 59 58 59 55 54 62 54! '· I 10' 160 160 160 160 160 160 160 160 160. I 20 '160 160 160 160 160 160 160 160 160 E 10' 10 10 10 9.9 3.4 10 10 2.8 10 • f 4 I - E 20 '10 10 10 9.9 4.1 10 10 3 , 5 10 ·; ·. VERL1 1-2 2-3 3-4 3-4 2 4-5 1 3-4 1-2 CUV2 740 580 560 730 755 770 540 760 590 • · «• · * · • · · * · · · 84 14 104377

Table lb:

Pre 10 11 12 13 14 15 16 17 18 9 character __________ (vert) (vert) (vert) TPS __________ 94.0__ IPS 89.0 87.0 89.0 98.0 93.0 83.0 100 14, 0__n, 90 ADI 5.0 2.0 n 10 __________ John-CHDS 10.0 10.0 10.0 15.0 Acrylic --- scx-817 TMA 1.0 3.0 1.0 2.0 2 , 0 2.0

____________DE

NPG 81.0 81.9 84.0 80.6 84.9 87.8 79.2 87.8 40 32 - —----------- 855 1) es 7.0 - ---------—-- HD 5.0 5.0 5.0 3.0 5.0 Poly «- ester 7.0 resin diol_______________ IMP__3.0 3.0 1.0 2 , 0 2,0 2,0 4,0 ___ η ^ _6__ SZ__51__52__50__51 48 49__52__33__50__55 SV 29 34 12__9 18__6__38__35__42__ TO> M__58__59__58__54__54 60__63__64__64__68 TO, L__55__56__56__60__ 160__160-160-160 ___61__61 65 110 '160 160__160 __ <10 __ <10 E10 '__ 10 10 4.3 10 7.2 4.9 10__10 __ <1 __ <1 E20' __ 10__10__5.6 10 8.8 5.9 10 10 <1 <1 VEKL1__3-4__4 2__1-2 2-. 3 1-2__5 ___ 2__3__3 QUV * __ 710 595 700 790 750 760 870__330__790__1800

Carboxy-functional acrylic resin from SC Johnson Polymer, USA

Ads in mol% 15 104377

Ingredients and Test Characteristics TPS * = Terephthalic Acid IPS = Isophthalic Acid ADI * »Adipic Acid CHDS Cyclohexanedicarboxylic Acid TMA Trimellitic Acid Anhydride NPG ** Neopentyl Glycol EG = Ethylene Glycol T12 C12 Hexane Methanol melt viscosity up to 160 ° C (JCJ plate / cone)

in Pa.s TCPES glass point PES

TCPL = powder lacquer glass point I 10 '= Impact, reverse; inch pound (ASTM D 2794) I 20 '= - "- E 10' Erichsen recess, mm (DIN 53 156) E 20 '= -" - VERL1 »Visual wear resistance rating: 1-5 (1 best wear resistance) •« * QUV2 = Quick Weather Test (Atlas QUV) UVB Light. sun hours to 50% residual gloss »Comparison of Examples 1-19 is very recognizable that the purpose of the invention, i.e., epoxide-free In particular, Examples 1, 13 and 14 combine to provide a toxicologically acceptable coating system having a very good weather resistance, sufficient storage stability, and very good abrasion and mechanical properties. «··· in the product. Further, from Examples 2 and 3, it can be seen that already a proportion of only 10 mol% aromatic dicarboxylic acid, for example: Y: terephthalic acid, causes a marked decrease in UVB light resistance. Comparative Example 18 contains a prior art carboxy-functional polyester resin from DE 40 32 855 which, in addition to a very high proportion of iso-phthalic acid, contains about 10 mol% of cyclohexane dicarboxylic acid. Trisglycidyl isocyanurate is proposed as the crosslinking agent. Although this polyester resin has very good conditions for good weather resistance, the lacquer technical properties are completely inadequate when used with the toxic crosslinker component Primid XL-552. Therefore, it was surprising and unpredictable that the special carboxyl-functional polyester resins of the invention, in combination with a high isophthalic acid anhydride mouthpiece in combination with Primid XL-552, have excellent lacquer properties.

Comparative Example 19 depicts a carboxyl-functional acrylic resin from SC Johnson Polymer, USA, with Primid XL-552 as a crosslinker. This system has a very good weather resistance, known for acrylic resins, but it is completely inadequate in terms of lacquer technology.

Neither of Comparative Examples 18 and 19 thus combines the object of the invention, i.e., toxicological acceptability with very good weather resistance, good lacquer technical properties and good storage stability.

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Claims (15)

17 104377 A thermosetting epoxide-free coating system based on carboxyl-functional polyester resins and β-hydroxylalkylamides and optionally other common additives, wherein the coating system comprises as binder resin (a) at least one saturated polyester having an acid number of 10 and 45 ° C consisting of 80 to 100 parts by weight of isophthalic acid and 0 to 20 parts by weight of one or more aliphatic or cycloaliphatic dicarboxylic acids, the total amount of dicarboxylic acid, and aliphatic diols consisting of, based on the total number of diols, at least 4 C atoms, at least 50 mole of branched aliphatic diol containing at least 4 C atoms, at most 50 mole parts of at least one branched chain aliphatic diol having less than 4 C atoms and / or cycloaliphatic diol a, as well as, based on the total amount of dicarboxylic acids and diols, from 2 to 8 parts by weight of at least one monomer having a functionality of at least 3 and as the crosslinking agent (b) at least one hydroxyalkylamide having at least two hydroxylalkylamide groups. Coating system according to claim 1, characterized in that between 0.5 and 1.5 β-hydroxylamide groups of the cross-linking agent (b) are available per carboxyl group in the binder resin (a). 104377 18 Coating system according to Claim 1 or 2, characterized in that the crosslinking agent b) is a poly-functional β-hydroxyalkylamide having the following general formula HO-CH-CH, -N-CO-R2-CO-N-CH2-CH- OH (I) III II Rj R3 R4 Rj wherein R1 is the same or different alkyl groups having 1 to 4 carbon atoms or hydrogen, R2 is an aliphatic, cycloaliphatic, araliphatic or aromatic group, R1 and R4 are (HO-CH- CH 2) -, hydrogen, or the same or different alkyl groups of 1 to 1 having 1 to 4 carbon atoms. Coating system according to claim 1 or 2, characterized in that the other dicarboxylic acid is an aliphatic dicarboxylic acid having from 6 to 12 carbon atoms, preferably adipic acid, azelaic acid, sebacic acid t '' · "'or dodecanedioic acid, or cycloaliphatic dicarboxylic acid. ° / having from 8 to 22 carbon atoms, preferably cyclohexane dicarboxylic acid. A coating system according to claim 1 or 2; characterized in that the straight-chain diol having at least 4 C atoms is a diol having 4 to 22 C atoms, with hexanediol-1,6 and / or diols having from 12 to 4 being preferred. 20 C atoms, most particularly those having 13 to 15 C atoms. «· I • 1 Ψ« Coating system according to claim 1 or 2, characterized in that the branched aliphatic diol is dimethyl-1,3-propanediol. * I 104377 19 Coating system according to claim 1, characterized in that the monomer having at least 3 functional groups is polycarboxyls, their anhydrides or polyols. Coating system according to claim 7, characterized in that the proportion of monomers containing at least 3 functional groups is between 3 and 6 molar parts. Coating system according to one of the preceding claims, characterized in that the proportion of straight-chain aliphatic diols containing at least 4 carbon atoms is at least 2 molar parts, preferably 3 to 7 molar parts. Coating system according to Claim 1 or 2, characterized in that the crosslinking agent (b) is bis [N, N '-di (β-hydroxyethyl)] adipamide or bis [N, N' -di (β-hydroxypropyl)] - adipamide. A process for the preparation of thermosetting, epoxy-based coating systems based on carboxyl-functional polyester resins, characterized in that the coating systems according to claims 1 to 10 comprise components a), b) and optionally other conventional additives. mixing in a melt at 80-130 ° C, emptying, granulating, grinding and sieving to a particle size of less than 90 µ · · · ...; pm. • t / »i; i Use of a coating system according to claims 1-10 for the manufacture of powder lacquers having a lacquer: erityisen particularly good weather resistance and very good lacquer technical properties; ; women, as well as excellent durability 4 '·' and good shelf life. «· L f Ί3. Use according to claim 12, characterized in that the lacquers have a QUV value of> 550 and a 110/120 value of> 150. 104377 20 Use of a coating system according to claims 1-10 for the manufacture of protective layers from powder lacquers by the electric or corona powder spraying method or by the vortex bed method. 15. A protective layer, characterized in that it can be manufactured from a coating system according to claims 1-10. «Ii 1 {1« <* I «<· • t · I« * «« I »I Ψ *« • * «« «» · t ·· «» ··· I · i «· •« Ift »« «· · ♦ · f ·« «· I it 'I rfi» l' · r 1 i «t 1 * <I« · «f« m 21 104377