DE2460768A1 - Process for the production of hardenable, heat-resistant unsaturated polyester resins, in particular for use in the electrical industry - Google Patents

Description

T-arnDurg, dea 20 Dec. 197 & 46Q768

Applicant: Company Dr. Beck & Co. AG, 2 Hamburg 28,

Grossmannstrasse 105

A method for producing curable heat-resistant unsaturated polyester resin, particularly for use in the electrical industry

The requirements of the electrical industry for heat resistance of the synthetic resins used as insulating materials have, as is well known, increased steadily over the past few decades. The reason lies in the increasing tendency towards miniaturization of electrical devices, in the increase in the power weight in electrical machines and the associated increase in temperature in the windings.

It should also be remembered that electrical machines in certain Manufacturing plants often have to be operated under high ambient temperatures.

The trend described is likely to continue in the future.

Low viscosity solutions of unsaturated polyesters in copolymerizable vinyl or allyl monomers, preferably in styrene, are used, among other things, as impregnating, trickling and casting resins in electrical insulation technology, especially for impregnation found for electrical windings and for potting electronic components.

In particular because of their economy, these Resins used extensively, their inadequate long-term heat resistance (limit temperature according to VDE O53O) however, prohibits use in the insulation classes F and above.

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It is known the heat resistance of curable Synthetic resins by increasing the crosslinking density, i.e. in the case of unsaturated polyester resins by increasing it the proportion of copolymerizable polyester double bonds, to increase.

Apart from the fact that even with the highest possible crosslinking density of unmodified resins, those related to insulation class F (limit temperature > 155 ° C) property requirements are not met, Because of their very compact molecular structure, resins of this type provide moldings with an undesirably high degree of brittleness.

From an earlier application by the applicant, DOS 15 70 273> is already known, the heat resistance of unsaturated polyester resins during polyester condensation by using monovalent carboxylic acids and / or hydroxyl compounds, the at least one 5- or 6-membered imide ring contain to increase.

The preferred use of trihydric alcohols also gives these unsaturated polyester resins a branched molecular structure.

While such, especially in saturated polyester resins for the wire coating sector in a similar form practiced principle of branching leads to an improved heat resistance, but decreases in the case of under discussion known unsaturated polyester resins, the mechanical strength at temperatures above 13O ⁰ C heavily on , for example, the caking number defined in accordance with DIN 46448 falls, an important figure for assessing the suitability of spool impregnating and trickling resins.

In the case of resins on this known basis, those in continuous impregnation systems, which are constantly increasing in importance are processed, there is also the relatively short processing time, i.e. the so-called pot life of the

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catalyzed resin mixture, a wider spread obstructive in the ¥ ege,

It is furthermore already known for the production to use saturated polyester alcohols that contain isocyanurate rings.

Thus, according to DOS 19 59935, the trihydric alcohol tris (2-hydroxyethyl) isocyanurate is used, whereby it is partially blocked in a first stage with a monocarboxylic acid in a molar ratio of 1: 1 and the resulting substance is cn ¹ dihydric alcohol with the other components are converted to polyester.

The heat resistance, especially the weight loss, of those made with these unsaturated polyesters Shaped body is not sufficient for use as insulation material of insulation class F.

Surprisingly, it is only the unsaturated polyester resins according to the invention that meet the requirements insulation class F.

The invention relates to a method of manufacture curable heat-resistant unsaturated polyester resins from mixtures of radically copolymerizable unsaturated monomers and unsaturated polyesters, the

a) residues of monovalent to polyvalent as essential components Contain carboxylic acids and mono- to polyhydric alcohols, some of which are residues of ethylene. cc-β-dicarboxylic acids and a further part of residues of monovalent five-membered imide rings containing carboxylic acids and / or alcohols and the

b) are soluble in unsaturated monomers and copolymerizable with them ",

which is characterized in that as five-membered Carboxylic acids and / or alcohols containing imide rings, those with a tetrahydrophthalimide ring or endo— methylene or alkyl tetrahydrophthalimide ring and as

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trivalent carboxylic acids and / or alcohols those with an isocyanurate ring can be used.

The invention further relates to a method which is characterized in that the moaiofunktionellen components and the trifunctional component in the molar Verhäl ± 3iis of 1: 1 to 3S3 I ₅ preferably from 3.0: 1 be used ": 1 to 3» 3 .

The invention also relates to a method that is characterized in that the content of the monovalent component containing the tetrahydrophthalimide at least 10 mol $ of the total components forming the unsaturated polyester.

According to a preferred embodiment of the invention, tris (2-hydroxyethyl) isocyanurate is used as a trivalent an alcohol containing isocyanurate is used.

According to a further preferred embodiment of the invention, tris (2-carboxyethyl) isocyanurate is used as trivalent carboxylic acid containing an isocyanurate ring used.

The invention also relates to unsaturated polyester resins made from mixtures of radicals copolymerizable monomers and unsaturated polyesters from mono- to polybasic carboxylic acids and monocarboxylic acids polyhydric alcohols, characterized in that they contain at least one in the polyester component monovalent radical with a tetrahydrophthalimide ring or endomethylene or alkyl tetrahydrophthalimide ring and contain at least one trivalent ester with an isocyanurate ring.

By using the aforementioned, an isocyanurate ring The aforementioned disadvantage of the known imide-containing starting materials containing trifunctional starting materials unsaturated polyester resins, the too short pot life of the catalyzed resin mixture surprisingly

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significantly improved. The pot life of the resins produced by the process according to the invention is about twice as long with the same kialysis than those of the already known unsaturated polyester resins containing imide groups.

Those produced by the process of the invention Resins are also very important when used as spool impregnating or dripping resins Improvement in the caking strength with normal and especially at elevated temperatures.

Compared with the conventional unsaturated polyester resins containing imide groups, the caking strength is higher at temperatures of 155 ° C three to four times higher.

Surprisingly, the weight losses are from the unsaturated polyester resins according to the invention produced moldings significantly lower than that of moldings according to DOS 19 59 935 can be obtained.

According to the invention, the characteristic constituents for the production of the unsaturated polyesters are used monofunctional, a tetrahydrophthalimide ring containing carboxylic acids or corresponding monofunctional alcohols are used.

Such substances are made from tetrahydrophthalic anhydride and aminocarboxylic acids or amino alcohols accessible, for example the preferred 2-Hydroxyäthyltetrahydrophthalimid from tetrahydrophthalic anhydride and aminoethanol.

Ο + H ₂ N - (CH ₂ ) ,, - OH

N - (CH ₂ ) - OH

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For the production of the resins described come apart from those according to the invention, an isocyanurate ring containing trifunctional alcohols and / or carboxylic acids and the aforementioned imide group-containing monofunctional starting materials and a number of others, from the chemistry of the unsaturated Polyester resins of well-known polybasic carboxylic acids and polyhydric alcohols are used.

In the first place here are the ethylene-α-ß-dicarboxylic acids or their anhydrides - preferably maleic anhydride or fumaric acid - to be mentioned. By their share in the total mixture is the crosslinking density and thus the property level of the cured unsaturated polyester resin significantly influenced. To modify the properties is part of the ethylene-α-ß-dicarboxylic acid replaced by saturated dicarboxylic acids. Easily accessible on a large scale Products such as adipic acid, isophthalic acid or ortho-phthalic acid (in the form of phthalic anhydride used) as well as dimerized fatty acids are preferred. The use of monocarboxylic acids, such as e.g. benzoic acid is possible. For the purposes of the invention, however, monocarboxylic acids containing imide groups, such as Carboxyalkyltetrahydrophthalimidebzw. the corresponding endomethylene or alkyl compounds preferred. Instead of a part, e.g. of the preferred tris (2-carboxyethyl) isocyanurate, others can also be used Tricarboxylic acids such as trimellitic acid (in the form of its anhydride) can be used.

The diols are also readily available on an industrial scale Products such as ethylene glycol, propylene glycol-1,2, Butylene glycol-1,3, 1,4-cyclohexanedimethanol and neopentyl glycol Possible monohydric alcohols for the purposes of the invention are the imide group-containing alcohols mentioned Alcohols, especially hydroxyalkyl tetrahydrophthalimides, are used, some of which are e.g. the preferred tris (2-hydroxyethyl) isocyanurate can be replaced by other trihydric alcohols such as trimethylolethane, trimethylolpropane or glycerine.

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The monohydric alcohols containing imide groups and / or carboxylic acids can be produced separately and then that used for polyester production Reaction mixture are added or else directly in the reaction mixture from their starting materials in the presence of other components of the unsaturated Polyesters are formed. In this last case, however, care must be taken that the Ethylene-α-β-dicarboxylic acids only after sufficient, -preferably complete formation of imide rings are added to the reaction mixture, to avoid unwanted side reactions.

The unsaturated polyesters are preferably produced by melt condensation at temperatures of up to 200 ^° C. with elimination of water. After the desired viscosity has been reached, the resins are dissolved in the monomer at acid numbers of approx. 10-20. Basically vinyl, allyl or acrylic monomers are suitable, the preferred monomer is styrene. However, it has been shown that some resins made using tris (2-hydroxyethyl) isocyanurate in a mixture of styrene and diallyl phthalate do better are soluble.

The resin solutions produced in this way, i.e. the unsaturated polyester resins, can, because of their excellent -Thermal and electrical properties are preferably used as electrical insulating resins. To Addition of commercially available organic peroxides such as tert-butyl perbenzoate, tert-butyl perisononate or tert-butyl perisooctoate, soluble organic Cobalt compounds such as e.g. Cobalt octpatate or cobalt naphthenate, Polymerization inhibitors such as, B »hydroquinone, 2,6-pimethylhydroquinone, tert, * -butylhydroquinone, p-Ghinon and optionally soluble organic dyes can be used, for example, as thermosetting resins Impregnating resins or trickling resins which can be processed particularly efficiently for the impregnation and consolidation of electrical coils, preferably in

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Electrical machine and transformer construction, for Use.

When using suitable peroxides such as benzoyl peroxide in combination with accelerators such as tertiary Amines or cobalt salts of organic acids can also be used as cold-curing casting resin for embedding of electronic devices and the like.

The invention is explained in more detail by means of the following examples.

Example 1;

556 g of tetrahydrophthalic anhydride and 221.6 g of monoethanolamine are mixed and slowly heated. The reaction temperature is maintained by cooling at 13O ⁰ C.

The water of reaction is then distilled off, finally under vacuum.

476 g of maleic anhydride, 38O g of neopentyl glycol, 1092 g of Empol 1022 (dimeric fatty acid), 316.8 g of trishydroxyethyl isocyanurate and 0.4 g of hydroquinone are added to this precursor. The mixture is heated and the water of reaction is distilled off. As the formation of water subsides, the temperature is slowly increased to a maximum of 210 ° C. Finally, condensation takes place in vacuo until the acid number is less than 25. The resin is ^{cooled to 85 °} C. and 862 g of styrene are added with rapid stirring. The viscosity according to DIN 53015 is adjusted to a value of 300 mPa.s by adding more styrene. The gel time according to DIN I6945 at 25 ⁰ C with 2 $ Methyläthylketonperoxxd (40% in DMP) is adjusted by the addition of benzoquinone to a value of 15 min..

The weight loss of a molded article produced therefrom after 7 days of storage at 250 ° C in air is 6.9 ^.

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Example 2:

146O g of the precursor produced according to Example 1 from tetrahydrophthalic anhydride and monoethanolamine are condensed in the melt with 1470 g of maleic anhydride, 78O g of neopentyl glycol, 655 g of trishydroxyethyl isocyanurate and 0.5 g of hydroquinone. The water of reaction is distilled off, and the temperature is increased to a maximum of 210 ° C. as the formation of water subsides. Finally, condensation takes place in vacuo until the acid number has fallen below 25. The resin is ^{cooled to 85 °} C. and 1000 g of styrene are added with rapid stirring. The viscosity according to DIN 53013 is adjusted to a value of 100 mPas by adding more styrene. The gel time at 100 ⁰ C with 0.1% of a solution of cobalt octoate in styrene 1Oxigen and 1% tert, butyl perbenzoate (95%) is adjusted by the addition of benzoquinone to a value of 15 min..

The weight loss of a molded article produced therefrom after 7 days of storage at 250 ° C. in air is $ 3.9.

example 3 '

h5 & g tetrahydrophthalic anhydride and 183 g monoethanolamine are mixed and slowly heated. The reaction temperature is kept ^{below 130 ° C. by cooling.} The water of reaction is then distilled off, finally under vacuum.

3 ^ 5 g of tris (2-carboxy-ethyl) isocyanurate, 294 g of maleic anhydride, 312 g of neopentyl glycol and 0.4 g of hydroquinone are added to this precursor. The mixture is heated and the water of reaction is distilled off. As the formation of water subsides, the temperature is increased to a maximum of 220 ° C. Finally, condensation is carried out in vacuo until the acid number has fallen below 30. The resin is ^{cooled to 85 °} C. and 1000 g of styrene and 0.3 g of benzoquinone are added with rapid stirring. The viscosity according to DIN 53015 is adjusted to a value of 100 mPas by adding more styrene. The gelation time at 100 ° C. with 0.1% of a 10% solution of cobalt octoate in styrene and Vfo tert -butyl perbenzoate (95%) is adjusted to a value of 15 minutes by adding benzoquinone.

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Claims (8)

Claims 1) Method of making curable heat resistant unsaturated polyester resins from mixtures of radically copolymerizable unsaturated monomers and unsaturated polyesters, the a) as essential constituents, residues of mono- to polyvalent carboxylic acids and mono- to polyhydric alcohols contain, some residues of ethylene-oc-ßdicarboxylic acids and a further portion of carboxylic acids containing residues of monovalent five-membered imide rings and / or alcohols and the b) are soluble in unsaturated monomers and copolymerizable with them, characterized in that as five-membered imide rings containing carboxylic acids and / or alcohols those with a tetrahydrophthalimide ring or endomethylene or alkyl tetrahydrophthalimide ring and as trivalent carboxylic acids and / or alcohols those with an isocyanurate ring are used. 2) Method according to claim 1, characterized in that the monofunctional components and the trifunctional Components in a molar ratio of 1: 1 to 3j3j1> preferably used from 3> Οί1 to 3 »3sl will. 3) Method according to one of claims 1 or 2, characterized in that the content of the monovalent the Tetrahydrophthalimide-containing component at least 10 mol% of the total unsaturated polyester forming components «, 4) Method according to one of claims 1 to 3 »characterized in that an isocyanurate as a trivalent 8 0 9827/0801 -W- A4 ring-containing alcohol tris (2-hydroxyethyl) isocyanurate is used. 5) Process according to one of claims 1 to k, characterized in that tris (2-carboxyethyl) isocyanurate is used as the trivalent carboxylic acid containing an isocyanurate ring. 6) "Unsaturated polyester resins made from mixtures of free radicals copolymerizable monomers and unsaturated polyesters from mono- to polybasic carboxylic acids and monohydric to polyhydric alcohols, characterized in that they are in the polyester component at least one monovalent radical with a tetrahydrophthalimide ring respectively. Endomethylene or alkyl tetrahydrophthalimide ring and contain at least one trivalent radical having an isocyanurate ring. 6 0 9827/0801