DE2312409C2 - Thermosetting epoxy resin compositions and their use for coating substrates - Google Patents

Description

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

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

It has now been found that high molecular weight Molecular weight lipoxy resin coatings of more than 15,000 iri situ on suitable substrates let apply, if nian a mixture of Starting materials, namely a compound with more than one 1,2'epoxy group, a compound with more than one phenolic hydroxyl group and a suitable catalyst and optionally dyes, Pigments, additives regulating the flow properties, solvents and other common additives Applies suitable substrate and this is then heated so that there is a reaction between the epoxy compound and the phenolic compound is therefore the subject of the invention are epoxy resin compositions Claim 1. The coating compositions of the invention have, inter alia, the advantage that they are in the same Application viscosity require fewer solvents than known coating compositions of about the same Molecular weight. It also involves novel coatings that were previously not available stood because they can only be produced from the epoxy resin compositions according to the invention.

It was previously not possible to produce coatings from the reaction products of an epoxy compound with more than two 1,2-epoxy groups and a phenolic compound having two or more phenolic hydroxyl groups or a compound having more than two phenolic hydroxyl groups and a compound having two or more 1,2-epoxy groups or a compound with more than two 1,2-epoxy groups and one compound to produce with more than two phenolischeri hydroxyl groups, since these during the production in the Reactors usually gel.

A particular embodiment of 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) one catalyzing the reaction between a) and b) Compound, 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.

One embodiment of the invention are epoxy resin dispersion paints, the

1) a liquid epoxy resin with more than one 1,2-epoxy group or a mixture of such resins and

2) a mixture of a) a solid phenolic compound having more than one phenolic hydroxyl group and b) contain a catalyst, wherein the mixture of the phenolic compound and the Catalyst is dispersed in the liquid epoxy resin and the ratio of epoxy resin to phenolic compound is so chosen. that a product with a molecular weight of at least 15,000 is formed can.

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 commercial, high-boiling, aromatic solvents, 7. B. with a boiling point of 155 to 173 ° Ο, a flash point of 41.7 ° C, an aromatic content of 98, 9% and a Kauri'Butanoi value of 92.

The dispersions are usually thereby produced by the melt of the solid phenolic compound mixed with the catalyst, then the mixture cools the solid mass obtained on the

desired particle size crushed, resulting Pas The product is then suitably processed, e.g. in a ball mill, a sand mill or a dissolving kettle], dispersed in the liquid epoxy resin.

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

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

The cured epoxy resin compositions of the invention have molecular weights in excess of 15,000, preferably over 19,000. These values relate 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 general formulas I and It or their mixtures:

CH ₂ -CH-CH ₂ -O
OH X

Ο -) - CH ₂ -CH CH ₂ (I)

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

O OO

- C— —O— —S— —S — S— —S— or —S -

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

0-CH ₂ -CH CH ₂

Ο -CH ₂ -CH CH ₂

O -CH ₂ -CH CH ₂

(II)

in which R is a hydrogen atom or an alkyl radical having 1 to 4 carbon atoms, X is a hydrogen, chlorine or bromine atom or an alkyl radical having 1 to 4 carbon atoms and η has an average value of 0.1 to 5

The epoxy resins used in the invention are prepared in a conventional manner, e.g. B. through implementation a bisphenol compound with an epihalohydrin in the presence of a suitable catalyst or by reacting a liquid polyepoxide with an eo 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 for purposes of the invention suitable.

Aliphatic epoxy resins can also be used in the context of the invention, e.g. B «the glycidyl ethers aliphatic hydroxyl compounds with more than one aliphatic hydroxyl group. Specific examples for such compounds are glycols, e.g. B. ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, Dibromoneopentyl glycol, dichloro neopentyl glycol and glycerol, or their oxyalkylated derivatives, e.g. B. oxypropylated, oxyäthyüerte and oxybutylated derivatives, or their mixtures. Butadiene diepoxide is also available as aliphatic epoxy resin suitable.

In addition, oxazolidinone-modified, aromatic or aliphatic epoxy resins can be used which contain more than one 1,2-epoxy group in addition to oxazolidinone groups.

Furthermore, esterified epoxy resins are suitable, which are formed by reacting an epoxy resin with more than a 1,2'EpoxygrUppe with a dicarboxylic acid leave, the ratio being chosen so that at least two epoxy groups per carboxylic acid

5 6

function are the polyphenols of the following general

Specific examples of formulas used according to the invention or their mixtures: Polyols with multiple phenolic hydroxyl groups

OH

OH (IV)

0-CH ₂ -CH-CH ₂ O

OH

in which X and A have the meaning given for formula (I) and /; a mean value of 2 to 5, preferably 1 to 3;

O-

-CH ₂ -CH-CH ₂ -OIG

OH
R "

- H

CH ₂ -CH-CH ₂ -OIG
OH

H (VI)

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 5, / assumes the value O or 1 and A is as defined in formula (I).

Resins of the general formula (VI) in which y is 1 are usually prepared by reacting a bisphenol with an epoxy novolak 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. B. by Phosphoniumsaize organic or inorganic acids, imidazoles, imidazolines and quaternary ammonium compounds catalyzed. However, any other catalysts are also suitable, which the implementation of a 1,2-Epoxygn. "Ipe with a phenolic hydroxyl group accelerate effectively.

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

The inorganic used as quay i'ysätof en and organic phosphonium compounds are phosphonium salts of an acid, a half ester or a

Esters derived from carbon, nitrogen, phosphorus, sulfur, silicon, chlorine, bromine, iodine or boron. The phosphonium compounds have the general formula

R ₁

R ₄ -PR ₂

R,

in the direction R2. Rj and R4, independently of one another, represent hydrogen atoms, aliphatic hydrocarbon radicals with 1 to 20 carbon atoms, optionally alkyl-substituted aromatic hydrocarbon radicals or radicals of the formula - R ₅ - Y, where R5 is an aliphatic hydrocarbon radical with I to 20 carbon atoms and Y is chlorine or bromine -, iodine or hydrogen atom or a nitro or hydroxyl group. X represents the anion of an acid, an ester or a half-ester, which is different from carbon, nitrogen. Phosphorus. Sulfur, silicon, chlorine, bromine. Derived from iodine or boron, and m is the valence of the anion X.
Especially suitable catalysts are

Ethyhriphenylphosphonium iodide,

Ethyl triphenylphosphonium chloride,

Ethyhriphenylphosphonium thiocyanate,

Ethyl triphenylphosphonium acetate
as an acetic acid complex.

Tetrabutylphosphonium iodide.

Tetrabutylphosphonium bromide and

Tetrabutyl phosphonium acetate

as an acetic acid complex.

Examples of imidazoles suitable as catalysts are 2-styrylimidazole. i-Benzyl-2-methylimidazole, 3-methyliniidazole. 2-butylimidazole or mixtures thereof.

Suitable solvents are, for example, solvents containing bound oxygen, 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. As solvents are also halogenated solvents, for. B. trichlorethylene and methylene chloride are suitable.

The thermosetting epoxy resin compositions of the invention are used to coat metallic substrates, e.g. B. made of steel or aluminum ₍ however, other substrates which »withstand ^{temperatures of at least 130 ° C. are also suitable.}

In the epoxy resin compositions of the invention it depends Ratio of epoxy resin to polyol of the desired molecular weight of the coating as well as of the Functionality of the output connections. The molecular weight of the epoxy resin is in any case far lower than the molecular weight of the final coating. One sets the ratio of Epoxy resin to polyol such that the cured epoxy resin coatings have a molecular weight of at least 15,000. The respective necessary rviengcnvernäiinisic iäää by simple Determine attempts.

In order to set the reaction between the epoxy resin and the phenolic compound in motion, the coated substrates are heated. The required heating time depends of course on the temperature used and the mass of the coated substrate. In the case of thin metal substrates, z. B. heating to 300 ° C for a few seconds. to bring about complete curing; on the other hand, automobile bodies have to be ^{heated to 120 °} C. for up to 60 minutes in order to achieve a complete reaction.

The epoxy resin compositions of the invention are suitable for coating automobile bodies. Machinery.

Systems and containers.

Examples t-3

Bonded steel plates are coated with various coating compounds that contain a bisphenol A diglycidyl ether (DGEBA) with an epoxy equivalent weight of 187, bisphenol A, ethyltriphenylphosphonium acetate-acetic acid complex as a catalyst (ET-

PA ■ HAc) and ethylene glycol monomethyl ether (EGME) as solvents. After the coating compounds have been applied, the steel plates are ^{heated to 204 °} C. for 30 minutes, coating films with a thickness of 0.03 mm being formed in the dry state. The individual coating compositions and the properties found are listed in Table I.

Table I.

Components 'Comparative example 2 63 3 Vendeichs attempt A 1 37 60 attempt B DGEBA, part by weight 70 65 032 40 63 Bisphenol A parts by weight 30th 35 33 030 37 EPTA - HAc, parts by weight 035 033 75 33 - EGME, part by weight 33 33 2 75 33 Volatile components,% 75 75 2 75 Gardner viscosity. Poise ¹ ) 2 2 2

ίο

Continue Tune

Constituent parts

Comparison attempt Λ

example
I.

Comparison
attempt B

Physical Properties

■ Laughing for 30 minutes, heating to 204 ° G

Spatula toughness ² ) brittle out out » draws draws Back impact strength (kg / cm) negative negative positive 35.7 71.4 285.7 positive positive 17.8 35.7 Average molecular weight ³ ) 7752 16979 29931 Examples 4 - 8 high solids content
nen m? "<* en relation

excellent
negative
71.4
positive
35.7
21893

very brittle

negative
8.9

1300

By blending an epoxy novolak resin having a functionality of 3.6 and an epoxy equivalent weight von t76, bisphenol-A, ethyltriphenylphosphonium acetate-acetic acid complex as a catalyst (ET-PA ■ HAc) and ethylene glycol monomethyl ether (EGME) is using an epoxy solution as the solvent

Table H.

the then applied to Bonderized steel panels to a dry film thickness of 0.03 mm and subsequently cured for 30 minutes at 204 ⁰ C in an oven. Table II shows the amounts of ingredients used and the physical properties of the

coatings obtained.

Components example 70 5 65 6th 63 7th 62 8th 60 4th 30th 35 37 38 40 Epoxy novolak, parts by weight 0.35 0.33 0.32 0.31 0.30 Bisphenol-A, parts by weight 33 33 33 33 33 EPTA · HAc 75 75 75 75 75 EGME 3.1 3.1 3.1 3.2 3.2 Non-volatile components,% Gardner viscosity, poise ¹ ) properties out out out out out After 30 minutes of heating at 204 ⁰ C draws draws draws draws draws Spatula toughness ² ) positive positive positive positive positive 1784 285.7 285.7 285.7 285.7 Back impact strength (kg / cm) very soft out out out out After 5 minutes of treatment draws draws draws draws with methyl ethyl ketone ⁴ ) > 27,000 > 27,000 > 27,000 > 27,000 > 27,000 Average molecular weights

') The Gardner viscosity is measured at 25 ° C;

² ) To determine the toughness of the spatula, strong pressure is required with the edge of a steel spatula on the coated surface in order to remove the top coat. The toughness is rated as excellent. the toughness is rated as poor; -G

^J ) weight average determined by gel permeation chromatography; |

· *) The properties after 5 minutes of treatment with methyl ethyl ketone are determined by wiping a cloth with the Soak the solvent, place it on the coating and cover it with a watch glass. After 5 minutes, the tested S parts are scratched with a steel spatula and rates the properties as ausjj depending on the pressure required to remove the coating drawn or soft. !

Example 9

A pigmented powder primer is applied manufactured in the following way:

Epoxy resin

Commercially available solid epoxy resin made from bisphenol A diglycidyl ether with an epoxy equivalent weight

out of 887
99 ° C

and a Durran softening point of

Phenolic compound §

Solid phenolic compound vdt by reacting a mixture of ö3ß kg of bisphenol-A-dig ^ cidyiäther nsi an epoxy equivalent weight of 187, 77.55 kjg bisphenol A and 40 g of a solution 80prozenu'gen

Ethyltriphenylphosphonium acetate has been prepared in methanol.

use
Procedural rule

A mixture of 68.6 g of the above solid epoxy resin, 3M g of the above solid phenol compound, 1.0 g of a conventional flux and 0.45 g Äthyltriphenylphdsphoniumaceläl is 10 minutes at 120 ° C mixed as melt in a dissolving tank, then cooled and flaked. The product obtained is then in a mixer irti dry state with 100 g of barium sulfate are mixed and then extruded at 100 ° C. in an extruder. The received Mixture is cooled, flaked, pulverized and sieved. Part of the product with a particle size from a maximum of 0.044 mm to a dry film thickness of 0.025 mm is electrostatically bonded to a Sprayed steel plate. A coating film is obtained by heating in an oven at! 76.7T for 30 minutes with an average molecular weight of 28 455 (weight average determined by gel permeation chromatography), the excellent adhesive strength for automotive top coverings made from thermoplastic acrylic resins owns. The coating film withstands a reverse side impact test at a dry layer thickness of 0.025 mm stood at 285.7 kg-cm.

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

Table III

30 of 190 and 0.5 g of Ethyltriphenylphosphoniumacetat-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 for 18 seconds. The coating releases 100 g of solvent into the atmosphere per 100 g of the solid resin used.

Comparative clause B

100 g of a commercially available epoxy resin made from bisphenol-A diglycidyl ether and bisphenol-A and 40 weight percent of the average molecular weight reaction product of 25,000 (weight average, determined by gel permeation chromatography) and 60 percent by weight Methyl ethyl ketone as a solvent is used with 128 g of methyl ethyl ketone to a content of non-volatile components diluted by 17.8%. the The viscosity of the mixture is determined with the Zahn cup No. 2 at 25 "C for 18 seconds. The Coating releases 470 g of solvent into the atmosphere per 100 g of the solid resin used.

Batch A is applied to a steel plate and heated to 155 ° C. in an oven for 30 minutes. The mixture B is also applied to a steel panel and the solvent is expelled by HO minutes lasting heating at 48.9 ⁰ C. The physical properties of the coatings obtained in each case and their molecular weights are shown in Table III.

Example I0-A

Comparative salt B

Released into the atmosphere per 100g of the solid resin used Amount of solvent, g

Back impact strength (kg / cm)

180 ° conical bend over mandrel

Average molecular weight as determined by gel permeation chromatography

100 470 positive 285.7 positive 285.7 positive positive

29931

27 500

Comparative example

To prove that from a compound with two phenolic hydroxyl groups and an epoxy resin With more than two epoxy groups, no coating compounds 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, 65 parts by weight of an epoxy novolak 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 033 parts by weight of ethyltriphenylphosphonium acetate Acetic acid complex charged as catalyst. The temperature is ^{increased to 120 °} C. with stirring. After 15 minutes, the contents of the reaction vessel have gelled

Example 11

A dispensing coating composition is produced

Production of an esterified epoxy resin
(Component I)

A reactor equipped with a stirrer and temperature control is charged with 86.1 parts by weight of a dicarboxylic acid, 213.6 parts by weight of an epoxy novolak resin ² ), 03 parts by weight of ethyl triphenylphosphonium acetate-acetic acid complex and 0.07 parts by weight

share sodium carbonate charged After stirring the mixture at 150 ^° C. for one hour, the product is cooled and ^{diluted with an aromatic solvent 3} ) to a non-volatile content of 80%. This product, designated as component I, has the following properties:

Acid number 2

Epoxy content 132%

Gardner viscosity Z3-Z ₃

65 Manufacture of component II

39.5 parts by weight of Sisphesct-A are used as a melt with 0.5 parts by weight of Ethyltriphenylphosphoniumäce-

ity acetic acid complex mixed as a catalyst.

A dispersion coating composition is made by thoroughly mixing the following ingredients in produced by a high-speed mixer:

100 parts by weight of component I ₁ 82.6 parts by weight of xylene, 27.6 parts by weight of component II and 3 drops of an agent regulating the flow properties ⁴ ). The dispersion obtained contains 50% non-volatile constituents and has a Gardner viscosity of 15-20 seconds.

The dispersion is diluted with xylene to a Gardner viscosity of 5 seconds and then applied to an aluminum sheet washed with lye using a wire-wound rod No. 12. The coated sheet is heated for 5 minutes in an oven to 176.7 ⁰ C to obtain a coating having a Trockenjchichldicke of 0.0076 to 0.0152 mm is obtained. The coating withstands a front impact strength test at 53.56 kg-cm without breaking, as is the case

IO

15 results from a copper sulfate staining test. The dispersion coating is extremely stable for more than 6 weeks.

Example 12

From 186 g of the epoxy novolak resin from Example 11, g bisphenol-A, 100 g EthyleHglykoimcnoäth ^ läther, g Äihylenglykolmonobutylätheracetat, 1.5 g cellulose acetate-butyrate resin as a flux and various amounts of the catalysts mentioned in Table IV coating compounds are prepared. For this purpose, mixing the epoxy resin, bisphenols and the cellulose acetate butyratharz at 110 to 12O ⁰ G in a 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.

Table IV

Experiment no. Catalyst% ')

Test plate hardening min / ° C layer thickness (mm)

Back impact strength (kg / cm)

A.
B.
C.
D.

M.
M.
O
P.

MP) /0.2
MI /0.2
MI /0.2
MI /0.2

MI / 0.2
MI /0.2
Ml / 0.2

Ml /0.2
MI / 0.2

MI /0.2
MI / 0.2
MI / 0.2

MI / 0.5
MI / 0.5
ETPPSCN «) / 0.6
ETPPSCN / 0.6

A- ')
A.
A.
A. 10 / 176.7
5 / 176.7
10 / 176.7
5 / 176.7 B.
B. 5 / 176.7
4 / 176.7
3 / 176.7 CQ CQ 10 / 148.9
8 / 148.9 C)
C.
C. 4 / 176.7
3 / 176.7
2 / 176.7 >> coca 10 / 176.7
5 / 176.7
5 / 176.7
5 / 176.7

0.023-0.027
0.025
0.001
0.001

0.027
0.027
0.027

0.025-0.027
0.025-0.027

0.027
0.027
0.027

0.025-0.027
0.025-0.027
0.023
0.025

"/ • -Catalyst, based on the non-volatile components of the coating wet;

2-methylimidazole;

Test plate A consists of 20gauge bonderite; Test plate B is made of cold rolled steel; Test plate C is made of aluminum; Ethyl triphenylphosphonium thiocyanate.

> 285.7 178.5

> 285.7

89.3-178.5

> 285.7

<71.4

not hardened

<35.7

not hardened

> 107.1

<35.7

not hardened

214.3 214.3 285.7

<285.7

Remarks:

·) The dicarboxylic acid consists of 97% of a C36 dicarboxylic acid with a molecular weight of about 845 and 3 weight percent Cst-tricarboxylic acids with a Molecular weight of about 845, the mixture having an acid number of 19t to 157;

*) the epoxy novolak resin has an epoxy equivalent weight of 180 and a functionality of 3.6; the aromatic solvent consists of 983% Aromatics and 1.1% from paraffins with a boiling range of 155 to 173 ° C;

the flux is a paint compatible silicone resin with a specific gravity of 034 and a refractive index of 1.465.

Claims (9)

Patent claims: 1. Thermosetting epoxy resin compositions, thereby characterized in that they consist of a) an epoxy resin with more than one 1,2-epoxy group per molecule, b) a polyol with more than one phenolic OH group per molecule, c) 0.001 to 10 wt .-%, based on the total weight of epoxy compound and Phenolic compound, one of the reaction between a) and b) catalyzing compound, the ratio of epoxy resin to polyol as is set so that the cured epoxy resin is masses a molecular weight of at least 15,000 have, d) optionally pigments, fillers, dyes, solvents and / or the flow properties regulating additives. 2. Compounds according to claim 1, characterized in that they are a solid Epoxyhar ?, a solid Polyo! and a solid catalyst in powder form. 3. Compounds according to claim 1, characterized in that the polyol and the catalyst in one liquid epoxy resin are present in dispersed form. 4. Compositions according to claims 1 or 2, characterized in that the polyol and the catalyst in a solution of the epoxy resin in a nonsolvent for the polyol and the catalyst present dispersed. 5. masses according to claims 1 to 3, characterized in that the epoxy resin, the polyol and the catalyst is 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 have a functionality greater than 2. 7. Compounds according to claims 1 to 6, characterized in that a polyol is used which from an epoxy resin used together with this polyol by replacing the glycidyloxy groups derived by hydroxyl groups 8. Use of the thermosetting epoxy resin compositions according to claims 1 to 7 for Coating of substrates. 9. Use of the thermosetting epoxy resin compositions according to claims 1 to 7 for Coating of metals.