DE2312409A1 - HEAT-RESISTABLE EPOXY RESIN COMPOSITES AND THEIR USE FOR COATING SUBSTRATES - Google Patents

Description

Patent attorneys Dipl.-Ing. F. Wsick

Dipl.-Ing. H.W: iicKMANf, Pipl.-Phys. Dr. K. Fincke Dipl.-Ing. F. A. Weickmann, Dipl.-Chem. B. Huber

8'MUNICH 86, DEN

POST BOX S60 S20

MÖHLSTRASSE 22, NUMBER 48 39 21/22

<98392I / 22>

Case 15,937-P
H / BA / bgr

The Dow Chemical Company,

2030 Abbott Road, Midland, Michigan, USA

Thermosetting epoxy resins and their use for coating of substrates

The invention relates to thermosetting epoxy resin compositions and their use for coating substrates, in particular metal surfaces.

Coating compositions are based on epoxy resins currently produced in suitable reactors, optionally pigmented thereupon, up to the desired viscosity diluted and then applied to the respective substrates.

It has now been found that high molecular weight epoxy resin coatings with a molecular weight of more than 15,000 can be applied in situ to suitable substrates if a mixture of starting materials, usually a compound having more than one 1,2-epoxy group, a compound having more than one phenolic hydroxyl group and a suitable catalyst and optionally dyes, pigments,

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additives, solvents and regulating the peeling properties other common additives, applied to a suitable substrate and then heated, so that there is a reaction between the epoxy compound and the phenolic compound.

The coating compositions of the invention have under aViderem the advantage that they require less solvent than known coating compositions with the same application viscosity about the same molecular weight. ”Plus, it straps around novel coatings that were previously not available because they could only be obtained by the method of the invention can be produced.

So far it has not been possible to make coatings from the reaction products an epoxy compound having more than two 1,2-epoxy groups and a phenolic compound having two or more phenolic groups Hydroxyl groups or a compound with more than two phenolic hydroxyl groups and a compound with two or more 1,2-epoxy groups or a compound with more than two 1,2-epoxy groups and a compound with more than two phenolic hydroxyl groups, as these during usually gel during manufacture in the reactor. .

The invention therefore relates to coating compositions

a) an epoxy resin with several 1,2-epoxy groups,

b) a polyol with several phenolic hydroxyl groups and

c) a compound which catalyzes the reaction between a) and b), where a) and / or b) have an average functionality of more than 2.

For coating substrates to wear the epoxy resin compositions of the invention to the substrate and heated to this tens of seconds to 60 minutes to temperatures of 120 to 300 ⁰ C, preferably from 10 seconds to 30 minutes at 140 to 300 ° C.

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The invention also relates to epoxy resin dispersion paints, the

one

1) a liquid epoxy resin with more than / l »2-epoxy group or

a mixture of such resins and

2) a mixture of a) one solid phenol compound with more as a phenolic hydroxyl group and b) a catalyst, the mixture of the ph-enol compound and the catalyst is dispersed in the liquid epoxy resin and the ratio of epoxy resin to phenol compound is chosen j is that a product with a molecular weight of at least 15-000 can be created.

The term "liquid epoxy resins" also includes solid epoxy resins which are dissolved in a solvent for the epoxy resin which, however, is a nonsolvent for the phenolic compound. Specific examples of such solvents are xylene, toluene, 2-nitropropane, and commercially available, high-boiling aromatic solvent, for example having a boiling point 155-173 ° C, a flash point of 4l ₃ 7 C, an aromatic content of 98.9 $ and a Kauri butanol value of 92.

The dispersions are usually prepared by the fact that the melt of the solid phenolic compound with the catalyst mixed, then the mixture is cooled and the solid mass obtained is crushed to the desired particle size. The resulting Product then becomes liquid in a suitable manner such as in a ball mill, sand mill or dissolving kettle Epoxy resin dispersed.

The dispersion can also contain pigments, fillers, dyes and / or contain additives regulating the flow properties, these usually together with the catalyst be mixed with the molten phenolic compound.

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The dispersions have better storage stability than a mixture from solutions of the epoxy resin, the phenolic compound and the catalyst.

The cured epoxy resin compositions of the invention have molecular weights over 15,000, preferably over 19,000. These values relate refers to the weight average determined with the aid of gel permeation chromatography.

Specific examples of the epoxy resins used in the present invention are aromatic epoxy resins of the general formula I. and II, or their mixtures:

where A is a divalent hydrocarbon radical having 1 to 6 carbon atoms or the radicals

(I)

0 0

11 Il

-C-, -0-, -S-, -S-S-, -S- or

0 U

-S-Il

means X represents a hydrogen, chlorine or bromine atom and η has an average value of 0 to 15 , preferably 0.1 to 5j.

Q-CH ₂ -CH-CH ₂

, Λ

P-CH -CH-CH ₀ 2 2

(II)

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in which R is a hydrogen atom or an alkyl radical with I to carbon atoms, X is a hydrogen, chlorine or bromine atom or an alkyl radical with 1 to k carbon atoms and η has an average value of 0.1 to 5.

The epoxy resins used in the present invention are prepared in a conventional manner, for example by reacting a bisphenol compound with an epihalohydrin in the presence of a suitable catalyst or by reacting a liquid polyepoxide with a bisphenol in the presence of quaternary ammonium compounds, tertiary amines or phosphonium compounds .

Any aromatic epoxy resin with more than one 1,2-epoxy compound is suitable for the purposes of the invention.

Aliphatic epoxy resins can also be used within the scope of the invention can be used, e.g. the glycidyl ethers of aliphatic hydroxyl compounds with more than one aliphatic hydroxyl group. Specific examples of such compounds are glycols, e.g. ethylene glycol, propylene glycol, 1,4-butanediol, Neopentyl glycol, dibromoneopentyl glycol, dxchiorneopentyl glycol and glycerine, or their oxyalkylated derivatives, e.g. oxypropylated, oxyethylated and oxybutylated derivatives, or mixtures thereof. Butadiene diepoxide is also considered to be aliphatic Suitable for epoxy resin.

In addition, oxazolidinone-modified, aromatic or aliphatic epoxy resins can be used, which in addition to

pn via

Oxazolidinone groups contain more than / 1,2-epoxy groups.

Esterified epoxy resins, which are obtained by reacting an epoxy resin with more than one 1,2-epoxy group, are also suitable

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can be produced with a dicarboxylic acid, where. relationship is chosen so that there are at least two epoxy groups on each Carboxylic acid function come.

Specific examples of polyols used in the present invention with several phenolic hydroxyl groups are the polyphenols of the following general formulas or their mixtures:

(III)

(IV)

Η »Ο

0-CH ₀ -CH-CH ₀ -O

in which X and A have the meaning given for formula (I) and η has an average value of 2 to 5 _}, preferably 2 to 3 ₃ ;

OH

• c k

oIh o- | ch ₂ -ch-ch ₂ -o

OH

in which R and X have the meaning given for formula (II) and η has an average value of 2 to 9, preferably 3 to 5j

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has, y assumes the value O or 1 μηα A as defined in formula (I) is. '.

Resins of the general formula (VI) ₃ in which y has the value 1 are usually produced by reacting a bisphenol with an epoxy novolac resin. The compounds of the general formula (V) can be prepared by reacting excess bisphenol with a bisphenol diglycidyl ether in the presence of a suitable catalyst.

The reaction between the epoxy compound and the phenolic compound is e.g. by phosphonium salts of organic or inorganic acids, imidazoles, imidazolines and quaternaries Ammonium compounds catalyzed. However, any other catalysts are also suitable, which the implementation of a 1,2-epoxy group having a phenolic hydroxyl group is effective accelerate.

The catalysts are usually used in an amount of 0.001 to 10 percent by weight, preferably 0.05 to 5 percent by weight, based on the total weight of epoxy compound and Phenolic compound, used.

The inorganic and organic phosphonium compounds used as catalysts are phosphonium salts of an acid, of a half ester or an ester, which is composed of carbon, nitrogen, phosphorus, sulfur, silicon, chlorine, bromine, Derive iodine or boron. The phosphonium compounds have the general formula

R ₄ - PR ₂

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in the FL, R _? , R, and Rj, independently of one another, represent hydrogen atoms, ₃ aliphatic hydrocarbon radicals having 1 to 20 carbon atoms, optionally alkyl-substituted aromatic hydrocarbon radicals or radicals of the formula -R ^ -Y, where Rj- is an aliphatic hydrocarbon radical having 1 to 20 carbon atoms and Y is chlorine -, bromine, iodine or hydrogen atom or a nitro or hydroxyl group, X is the anion of an acid, an ester or a half ester, which is composed of carbon, nitrogen, phosphorus, sulfur, silicon, chlorine, bromine, iodine or boron, and m is the valence of the anion X.

Particularly suitable catalysts are ethyltriphenylphosphonium iodide, Ethyltriphenylphosphonium chloride, ethyltriphenylphosphonium thiocyanate, Ethyltriphenylphosphonium acetate as acetic acid complex, tetrabutylphosphonium iodide, tetrabutylphosphonium bromide and tetrabutylphosphonium acetate as an acetic acid complex.

Imidazoles suitable as catalysts are e.g. 2-styrylimidazole, 1-benzyl-2-methylimidazole, 2-methylimidazole, 2-butylimidazole or their mixtures ..

Suitable solvents are, for example, those containing bound oxygen Solvents such as acetone, methyl ethyl ketone, cyclohexanone, diacetone alcohol and mixtures thereof, glycol ethers, such as Ethylene glycol ethyl ether acetate, ethylene glycol methyl ether, ethylene glycol n-butyl ether, diethylene glycol ethyl ether, diethylene glycol n-butyl ether, Propylene glycol methyl ether, dipropylene glycol methyl ether and their mixtures or their mixture with aromatic solvents such as xylene, toluene and ethylbenzene. Halogenated solvents are also used as solvents, e.g. trichlorethylene and methylene chloride are suitable.

The thermosetting epoxy resin compositions of the invention are used for

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Coating metallic substrates, for example steel or aluminum, but are suitable, other substrates capable of withstanding temperatures of at least ⁰ C 13Q.

In the epoxy resin compositions of the invention, the ratio of epoxy resin to polyol depends on the desired molecular weight of the coating as well as the functionality of the output connections. The molecular weight of the epoxy resin is any Fall far lower than the molecular weight of the final coating. In general, however, one poses the ratio of epoxy resin to polyol such that the cured epoxy resin coatings have a molecular weight of at least 15,000. The proportions required for this in each case can be determined by simple experiments.

In order to initiate the reaction between the epoxy resin and the phenolic compound, the coated substrates are heated. The required heating time depends of course on the temperature used and the mass of the coated Substrate. With thin metal substrates, for example, heating to 300 C for a few seconds is sufficient to achieve a complete Effect curing; on the other hand, automobile bodies must be heated to 120 ° C. for up to 60 minutes in order to achieve a achieve full response.

The epoxy resin compositions of the invention are suitable for coating of automobile bodies, machines, systems and containers.

The examples illustrate the invention.

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Examples 1-3

Banded steel plates are made with different coating compounds coated, which contains a bisphenol A diglycidyl ether (DGEBA) with an epoxy equivalent weight of 187, bisphenol A, · Ethyl triphenylphosphonium acetate-acetic acid complex as a catalyst (ETPA * HAc) and ethylene glycol monomethyl ether (EGME) contained as a solvent. After the coating compounds have been applied, the steel plates are heated to 2O4 ° C for 30 minutes, coating films with a thickness of 0.03 mm in the dry state are formed. The individual coating compounds and the properties found are summarized in Table I.

TABLE I. 65 is ρ ie
2 excellent
net out
draws 3 1
3 Comparison
attempt B Components Comparative B e
attempt A 1 35 63 negative
71.4
positive
35.7 positive
285.7 60 63 DGEBA, weight
Parts 7o 0.33 37 16,979 29,931 40 37 Bisphenol-A,
Parts by weight 30th 33 0.32 0.30 - ETPA-HAc,
Parts by weight 0.35 75 33 33 33 EGME,
Parts by weight 33 2 75 75 75 Non-escapees
Components, % ¹⁵ 2 2 CM Gardner Visco
sity, poise * ) 2 Properties after 30 minutes Heat to 204 ⁰ C Physical brittle excellent
; draws very
brittle Spatula-tough
ability 2) negative
positive
17.8 negative
positive
35.7 negative
8.9 Backside
Impact resistant
speed (kg-cm) 7 752 21,893 1,300 Middle Mon

3)

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Be-i s ρ ί e lel | - 8th

By mixing an epoxy novolac resin with a functionality of 3.6 and an epoxy equivalent weight of 176, bisphenol-A, ethyltriphenylphosphonium acetate-acetic acid complex as a catalyst (ETPA'HAc) and ethylene glycol monomethyl ether (EGME) as a solvent, an epoxy solution is created high solids content. The solutions prepared with various ratios are then applied mm on bonderized steel panels to a dry film thickness of 0.03 and then cured 30 minutes at 20 ^ ⁰ C in an oven. Table II lists the ingredient levels used and the physical properties of the coatings obtained.

TABLE II Components
H B e
5 is ρ i
6th out
draws out
draws e 1
7th 2O4 ° C 8th Epoxy novolac,
Parts by weight 70 65 63 positive
285.7 positive
285.7 62 out
draws' 60 Bisphenol af
Parts by weight 30 35 37 out
draws out
draws 38 positive
285.7 40 ETPA-HAc 0.35 0.33 0.32 > 27.OOO > 27.0O0 0.31 out
draws 0.30 EGME. 33 33 33 33 > 27.OOO 33 Non-volatile
Components, % 75 75 75 75 75 Gardner Visco
sity, Poise I) 3.1 3.1 3.1 3.2 3.2 Properties after 30 minutes of heating Spatula-excellent
ability 2) out
draws Positive on the back
Impact Resistant 178.5
speed (kg-cm) positive
285.7 after 5 minutes of handling
treatment with methyl soft
ethyl ketone A) out
draws Middle Molecular > 27.OOO

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. - 12 -

Footnotes to Tables I and II

1) The Gardner viscosity is measured at 25 C;

2) To determine the spatula toughness, use the edge of a Steel spatula on the coated surface. If strong pressure is required to remove the coating, the toughness is rated as excellent. Is against only little pressure is required, the toughness is rated as poor;

3) weight average determined by gel permeation chromatography;

4) The properties after 5 minutes of treatment with methyl ethyl ketone are determined by soaking a cloth with the solvent and placing it on the coating and covered with a watch glass. After 5 minutes, the tested area is scratched with a steel spatula and rated Properties as excellent or soft, depending on the pressure required to remove the coating.

Example 9

A pigmented powder primer is made in the following ways:

Epoxy resin

Commercially available solid epoxy resin made from bisphenol A diglycidyl ether with an epoxy equivalent weight of 887 and a Durran softening point of 99 ° C.

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Phenolic compound

Solid phenolic compound kg by reacting a mixture of bisphenol A 63j5 diglyeidyläther mi.t an epoxy equivalent weight of I87, 77 _S 55 has been kg of bisphenol A and 40 g of a solution of 80prozentigen Ä'thyltriphenylphosphoniumacetat in methanol.

Procedural rule

A mixture of 68.6 g of the above solid epoxy resin, yiyH g of the above solid phenolic compound, 1.0 g of a conventional flux, and 0.45 g Äthyltriphenylphosphoniuma.eetat 10 minutes at 120 ⁰ C in a dissolution vessel of a melt blended, cooled, then and flaked. The product obtained is then mixed in a mixer in the dry state with 100 g of barium sulfate and then extruded at 100 ° C. in an extruder. The resulting mixture is cooled, flaked, pulverized and sieved. Part of the product with a particle size of at most 0.044 mm is electrostatically sprayed onto a bonded steel plate to a dry film thickness of 0.025 mm. Is obtained by heating in an oven for 30 minutes at 176.7 ⁰ C a coating film having an average molecular weight of 28,455 (weight average determined by gel permeation chromatography), has excellent adhesive strength for automotive topcoats of thermoplastic acrylic resins. The coating film withstands a rear-side impact test at 285.7 kg-cm at a dry layer thickness of 0.025 mm.

Example 10 Approach according to the invention A

A mixture of 37 g bisphenol A, 63 g bisphenol A diclycidyl ether with an epoxy equivalent weight of 190 and 0.5 g

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Ethyltriphenylphosphonium acetate-acetic acid complex as a catalyst is diluted with 100 g of methyl ethyl ketone to a non-volatile content of 50%. The viscosity of the mixture is determined with the Zahn cup No. 2 at 25 ° C to 18 seconds. The coating releases 100 g of solvent into the atmosphere per 100 g of the solid resin used.

Comparative approach B

100 g of a commercially available epoxy resin, which has been prepared from bisphenol A diglycidyl ether and bisphenol A, and 40 percent by weight of the reaction product with an average molecular weight of 25 OQO (weight average, determined by gel permeation chromatography), and 60 percent by weight methyl ethyl ketone as a solvent , is diluted with 128 g of methyl ethyl ketone to a content of non-volatile components of 17.8 %. The viscosity of the mixture is determined with the Zahn cup No. 2 at 25 ° C to 18 seconds. The coating gives per 100 g. of the solid resin used, 470 g of solvent were released into the atmosphere.

Approach A is applied to a steel plate and 30 minutes heated in an oven to 155 ° C. Approach B is also applied to a steel plate and the solvent is driven off by heating to 48.9 C for 110 minutes. The physical properties of the coatings obtained in each case and their molecular weights are shown in Table UT compiled.

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TABLE III Example IQ-A comparative batch B

amount of solvent released into the atmosphere per 100 g of the solid resin used, g 100 i | 70

Rear impact resistance

(kg-cm) positive positive

285.7 285.7

l80 conical bend over

Thorn positive positive

middle molecule ar ge v / i ent,

determined by gel permeation

chromatography 29-931 27,500

Comparative example

To demonstrate that a compound with two phenolic hydroxyl groups and an epoxy resin with more than two epoxy groups If no coating compositions can be produced by conventional methods, the following reaction is carried out

A reactor equipped with a stirrer and temperature control is charged with 35 _{parts by weight of bisphenol A 3} 65 parts by weight of an epoxy novolaek resin with a functionality of 3.6 and an epoxy equivalent weight of about 176.33 parts by weight of ethylene glycol monoethyl ether as solvent and 0.33 parts by weight of ethyl triphenylphosphonium acetate Acetic acid complex charged as a catalyst. The temperature is increased ^{to 120 ° C. with stirring.} After 15 minutes the contents of the reaction vessel have gelled.

3 0 9 8 3 8/11 S /

Example 11 A dispersion coating composition is prepared.

Production of an esterified epoxy resin (component I)

A reactor equipped with a stirrer and temperature control

1) wird.mit 86.1 parts by weight of a dicarboxylic acid, 213 ₅ 6

2)

Part by weight of an epoxy novolak resin, 0.3 part by weight of Ä'thyltriphenylphosphoniumacetat-acetic acid complex and 0.07 part by weight of sodium carbonate charged. After stirring the mixture at 150 ^° C. for one hour, the product is cooled and diluted with an aromatic solvent up to a content of non-volatile constituents of 80%. This product, designated as component I, has the following properties:

Acid number 2

Epoxy content l ~ b \ 2%

Gardner viscosity Z, - Z ^

Production of component II

99 »5 parts by weight of bisphenol-A are used as a melt with 0.5 Parts by weight of EthyItriphenylphosphoniumacetat-acetic acid complex mixed as a catalyst.

A dispersion coating compound is made through thorough Mixing the following ingredients made in a high speed mixer:

100 parts by weight of component I, 82.6 parts by weight of xylene, 27.6 parts by weight of component II and 3 drops of a die Fluid regulating agent. The dispersion obtained contains 50% non-volatile components and has a Gardner viscosity of 15-20 seconds.

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The dispersion will have a Gardner viscosity of 5 seconds diluted with xylene and then with the help of a wire-wound rod No. 12 on a washed with lye Aluminum sheet applied. The coated sheet is heated in an oven at 176.7 ° C. for 5 minutes, with a coating is obtained with a dry layer thickness of 0.0076 to 0.0152 mm. The coating withstands a ■ front impact strength test at 53> 56 kg-cm stood without break, as is evident from a copper sulfate staining test. The dispersion coating compound is extremely stable for more than 6 weeks.

Remarks:

'The dicarboxylic acid to 9755 g of a C-dicarboxylic acid having a molecular weight of about 845 and 3 weight percent Cu-tricarboxylic acids having a molecular weight of about 845, wherein the mixture has an acid number 191-197 besitzti

' The epoxy novolac resin has an epoxy equivalent weight of 180 and a functionality of 3 * 6;

The aromatic solvent consists of $ 98.9 of aromatics and at $ 1.1 from paraffins with a boiling range of 155 to 173 ° C;

The flux is * compatible with paints

Silicone resin with a specific gravity of 0.94 and one Refractive index of 1.465.

Example 12

From 186 g of the epoxy novolac resin from Example 11, 114 g Bisphenol-A, 100 g of ethylene glycol monoethyl ether, 98 g of ethylene glycol monobutyl ether acetate, 1.5 g of cellulose acetate butyrate resin as a flux and various amounts of the substances shown in Table IV

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The catalysts mentioned are used to produce coating compounds. For this purpose mischt.man the epoxy resin, bisphenol-Ä and the cellulose acetate butyratharz at 110 to 120 ⁰ C in molten. State. The mixture is then cooled and the solvents and the catalyst are added. The coating compositions are applied to test panels. The catalysts used and the results obtained are shown in Table IV.

catalyst
^ L / Λ \
ft ' - * * / TABEL IV layer
thickness (mm) Backside
Impact resistant
speed (kg-cm) Attempt-
No. MI ²⁾ / 0.2 test
plate Hardening
min / ° C 0.023-0.027 > 285.7. A. ΜΓ / 0.2 A ³⁾ 10 / 176.7 0.025 178.5 B. MI / 0.2 A. 5 / 176.7 0.01 > 285.7 C. MI / 0.2 A. 10 / 176.7 0.01 89.3-
178.5 D. MI / 0.2 A. 5 * / 176.7 0.027 > 285 ₅ 7 E. MI / 0.2 B ^ 5 / 176.7 0.027 <71.4 P. MI / 0.2 B. 4 / 176.7 0.027 not ge
hardens G MI / 0.2 B. - 3 / 176.7 0.025-0.027 <35.7 H MI / 0.2 B. 10 / 148.9 0.025-0.027 not
hardened I. MI / 0.2 B.
t- \ 8 / 148.9 0.027 > 107.1 J MI / 0.2 C ⁵ ' 4 / 176.7 0.027 <35.7 K ΜΓ / 0.2 C. 3 / 176.7 0.027 not
hardened L. MI / 0.5 C. 2 / 176.7 0.025-0.027 214.3 M. MI / 0.5 B. 10 / 176.7 0.025-0.027 214.3 N ETPPSCN / 0.6 B. 5 / 176.7 0.023-0.027 285.7 O ETPFSCN / 0.6 A. 10 / 176.7 0.025 '<285.7 P. A. 5 / 176.7

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£ -Catalyst, based on the non-volatile components the coating compounds;

² ^ 2-methylimidazole; Test plate A consists of 20-gauge bonderite;

Test plate B is made of cold rolled steel; Test plate C is made of aluminum; Ethyl triphenylphosphonium thioeyanate.

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Claims (8)

P a tent a η s ρ r ti c h e: 1. Heat-curable epoxy resin compositions, characterized in that that they a) an epoxy resin with more than one 1,2-epoxy group per • molecule, b) a polyol with more than one phenolic hydroxyl group per molecule and c) contain a catalyst the ratio of epoxy resin to polyol being adjusted so that the cured epoxy resin compositions have a molecular weight of at least 15,000. 2. Compounds according to claim 1, characterized in that they contain a solid epoxy resin, a solid polyol and a solid Contains catalyst in powder form. 3. masses according to claim 1, characterized in that the Polyol and the catalyst are dispersed in a liquid epoxy resin. 4. masses according to claims 1 or 2, characterized in that that the polyol and the catalyst are in a solution of the epoxy resin in a nonsolvent for the polyol and the catalyst are dispersed. 5. masses according to claims 1 to 3j, characterized in that that the epoxy resin, the polyol and the catalyst are present as an intimate mixture in a volatile solvent. 6. Compounds according to claims 1 to 5, characterized in that the epoxy resin and / or the polyol has a functionality of more than 2. 3098 38/1182 7. Use of the thermosetting epoxy resin compositions according to the Claims 1 to 6 for coating substrates, in particular made of metals. 8. Embodiment according to claim 7, characterized in that the coated substrates at temperatures of at least 120 C, preferably from 10 seconds to 30 minutes at! HO be up to 300 ⁰ C, cured. 309838/1182