DE1207033B - Thixotropic, storage-stable coating agents that can be hardened by heat - Google Patents

Description

Thixotropic, storage-stable coating agents which can be hardened by heat The invention relates to oven-drying, thixotropic coating agents made from thixotropic Epoxy resins which contain practically no volatile components.

For winding industrial electrical machines, in particular electric motors, protection against accidental water splashes is required aqueous solutions, which reduce the performance of the insulation up to the point where the apparatus becomes ineffective. Such protection is often achieved by allowing the application of varnish and the hardening treatment to follow one another between dives. The application of numerous coatings of varnish, which for Moderate protection is necessary, and so is the appearance of what is so treated Item is bad due to immersion and uneven drying of the paint. There have also been molded protective caps made from high-temperature melting thermoplastic or thermosetting materials are used.

The large amount of material used in the pressed caps is reduced the heat transfer from the apparatus, resulting in a short at high temperatures Lifetime leads.

It has now been found that you can use a coating agent that is below contains, inter alia, a thixotropic epoxy resin, overcoming the disadvantages outlined above can and a single thin thermoset coating of 0.25 to about 2 mm can produce, which is therefore significantly thinner than the coatings previously used and the heat from the apparatus dissipates faster to the outside.

The thixotropic, storage-resistant coating agent to be cured by heat according to the invention is characterized in that it contains 100 parts by weight of a resin composition Contains the following components: A. approximately 25 to 600in of a low molecular weight Epoxy terminated with epoxy groups and an epoxy equivalent of approximately 120 to 220 and / or an epoxy novolak resin, e.g. about 5 to 350 in a polymerized Fatty acid, C. up to 20 ° lo of an organic reactive diluent, containing at least one epoxy group, such as. B. glycidyl ether of a monovalent Nuclear-substituted phenol, or other epoxy group-containing diluents, such as B. octylene, nonylene or decylene oxide, D. about 1 to 100 / o of a thixotropic By means of such. B. silica aerogels, bentonite clays or metal soaps, and E. approximately 1 to 4% of a curing catalyst and up to 100 parts by weight of finely divided inorganic fillers.

The compound has a particularly long pot life and hardens without it Run-off or drop formation.

Films of a certain thickness can be produced from this. Of the thermoset coating adheres well, and the apparatus coated with it face opposite the usual paints improved electrical and mechanical properties, if they are exposed to moisture, dust, high temperatures and heat shock.

It is already known mixtures of bentonite and aliphatic to use quaternary ammonium salts as a thixotropic aid and by addition of polyamides or alkyds modified with polyamides to increase the thixotropy.

It is also known that the thixotropy in paints by adding fillers, such as. B. talc or bentonite can be generated.

In the literature, there are already references to which concrete types are better suited for polar and non-polar liquids.

The low molecular weight epoxy resins (A) used for the preparation of the invention Coating agents are used, are obtained by methods already known through implementation at least a polyhydric phenol with at least an epihalohydrin in an alkaline medium.

Particularly suitable phenols for the preparation of such resinous ones polymeric epoxy compounds contain at least two phenolic hydroxyl groups per molecule. Polynuclear phenols are particularly suitable, with the benzene nuclei are connected by carbon bridges, such as. B. 4,4-Di- oxydimethylmethane, 4,4 ' - Dioxydiphenylmethylmethane and 4,4'-Dioxydiphenylmethane.

Mostly epichlorohydrin is used as epihalohydrin. One can but also z. B. use epibromohydrin.

The glycidyl polyethers used are a mixture of glycidyl polyethers of various molecular sizes and roughly correspond to the following formula: where n is an integer. such as B. 0, 1, 2. 3 ... and R represents a divalent hydrocarbon radical of the dihydric phenol.

The glycidyl polyethers have a 1,2-epoxy equivalency that is greater than 1.0. Below 1,2-epoxy equivalency is the mean number of 1,2-epoxy groups per molecule of glycidyl ether.

In addition to the epoxy resins obtained in a known manner, can also Use epoxy novolak resins according to the invention as starting material (A). Such epoxy novolak resins are known to be obtained by reacting an epihalohydrin with a novolak resin an aldehyde and a monovalent, mononuclear alkylphenol, its alkyl group contains at least 4 carbon atoms. The novolak resin then contains im Average about three to twelve phenolic hydroxyl groups per molecule. Under novolak resin a fusible phenol aldehyde resin is to be understood, which by reaction at least of a phenol with at least one aldehyde in the ratio of 1 mole of phenol to about 0.5 up to 0.85 moles of aldehyde is produced in the presence of an acid catalyst.

Although a novolak resin of formaldehyde is generally preferred is, novolak resins of other aldehydes, such as. B. of acetaldehyde, des Chloraldehyde, butyraldehyde or furfuraldehyde can be used. In order to the epoxy novolak resin sufficiently soluble in organic solvents such as. B. in saturated aliphatic hydrocarbons, it is essential that the novolak resin is obtained from an alkylphenol. its alkyl group 4 to 18 Contains carbon atoms.

The alkyl group can be a straight chain. Generally will however, preference is given to the novolak of a phenol that has a branched branched one Has alkyl chain. Suitable alkylphenols that are advantageous for the manufacture of the epoxy novolak resin can be used, are, for. B. butylphenol, tert-butylphenol, tert-amylphenol, hexylphenol, 2-ethylhexylphenol, diisobutylphenol, no- "xtlphenol, Isononylphenol, decylphenol, dodecylphenol, isododecylphenol and 3-pentadecylphenol.

It is recommended to use p-alkylphenols.

But also o-alkylphenol and mixtures of p- and o-alkylphenols, the alkyl groups of which contain at least 4 carbon atoms are suitable.

About 1 mole of alkali metal hydroxide. such as B.

Sodium hydroxide, or potassium hydroxide, has a phenolic hydroxyl equivalent of novolak resin is used. It does not have to be exactly 1 equivalent of the alkali hydroxide to 1 equivalent of the novolak resin. In general, an excess z. B. 1.02, 1.05 or 1.1 moles of hydroxide per equivalent of novolak resin is used.

It is advantageous to keep the reaction components at a low level at the beginning Add amount of water, preferably 0.1 to 2 percent by weight, based on the weight of epichlorohydrin and novolak resin.

The epoxy novolak resins obtained are at room temperature (20 "C) very viscous or solid. The normally solid resins are fusible. The resins have a complicated chemical structure.

According to the analytical test results, 60 to 900/0 are and more of the hydrogen atoms of the phenolic hydroxyl group of the original Novolak resin replaced by glycidyl residues. The epoxy novolak resins also contain an estimable amount of alcoholic hydroxyl groups, which are abundant in 2,3-dihydroxypropyl residues are present, which are the hydrogen atoms of phenolic hydroxyl groups in the original Have replaced novolak resin. The resin contains a small amount of chlorine, something is present in the 3-chloro-2-hydroxypropyl groups and somewhat in the complex groups des 3-chloro-2- (3-chloro-2-hydroxypropyloxy) propyl and 3-chloro-2- (2,3-epoxypropyloxy) propyl. which are bound to the phenolic ether oxygen atoms in the epoxy resin. That Product may contain a few phenolic hydroxyl groups, and most of them do less than 0.3 per molecule.

Other suitable resinous starting materials (A) contain epoxy derivatives of alkyl-substituted cyclohexanes, such as. B. 3,4-epoxy-6-methyl-cyclohexylmethyl -3,4-epoxy-6-methylcyclohexane. The homologues of this resin are also for that Use according to the invention suitable.

The polymerized fatty acids (B) in the coating agent according to the invention contain polymerized fatty acids made from unsaturated fatty acids by dimerization or trimerization. The acidic component consists essentially from a dimerization or trimerization product of a monobasic, dibasic and / or tribasic carboxylic acid, which has a carbon atom chain of approximately 10 to 20 carbon atoms per molecule, and mixtures thereof.

Such unsaturated fatty acids are e.g. B. myristoleic acid, linoleic acid, Linolenic acid, hypogic acid and erucic acid. The preparation of such acids is described z. See U.S. Patent 2,482,761. One suitable trimerized acid is trilinoleic acid of the general formula HOOC - C52HM - COOH which with low Quantities of monomeric and dimerized acids can be mixed. Trimerized Linoleic acid is found in cottonseed, corn, and flaxseed oils. They react Double bonds of the acids to connect the hydrocarbon residues and one to form trimerized acid which still has double bonds in a larger molecule contains and three carboxyl groups.

The commercially available trimerized linoleic acid has a molecular weight from about 800.

As stated above, according to the invention are polymerized by the Fatty acid (B) about 5 to 35 percent by weight based on the total weight of the resin (A) - used. A polymerized fatty acid is particularly advantageous used, which contains a larger amount of trimerized acid. The products, which contain a greater amount of the trimerized acid are harder and less flexible than those containing a larger amount of dimerized acid. But when If a higher degree of flexibility is desired, the coating composition should be larger Amount of dimerized acid included.

The coating agent according to the invention also contains an organic one reactive diluent (C) in an amount up to about 20 percent by weight, containing at least one epoxy group. Preferably a glycidyl ether becomes one monohydric phenol is used, the nucleus of which is substituted by an unsaturated one Hydrocarbon with 10 to 28 carbon atoms that has one or more ethylene bonds may contain. Suitable monohydric phenols are e.g. B. geranyl phenol, cardanol (A. M. P a q u i n, epoxy compounds and epoxy resins, 1958, p. 220, paragraph 2, and p. 279 above) and Ginkol (is an alcohol with the empirical formula Cs4H4sOH. Hackh's Chemical Dictionary 1944).

Other epoxy group-containing diluents are e.g. B. octylene oxide, Nonylene oxide, decylene oxide, limonene dioxide and vinylcyclohexene dioxide and the like.

Furthermore, the coating composition according to the invention contains 1 to 10% of one thixotropic agent (D).

This means (D) keeps the resin in such a state that the electrical device applied coating hardens without running or dripping. Suitable thixotropic materials are silica aerogels, bentonite clays, which one have a high percentage of montmorillonites, various metal soaps such as B. aluminum palmitate or stearate and calcium, zinc and magnesium soaps from palmitin and stearic acids and like commercially available thixotropes.

The coating agent according to the invention contains the curing catalyst (E) preferably a metal amine chelate, e.g. boron trifluoride-amine complexes such as monoethylamine or piperidine complex.

The metal amine chelates, which according to the invention are used as a curing catalyst Can be used can be made from 1 mole of a metal ester of general formula M (OR) 4 and 2 moles of triethanolamine, with 2 moles after the reaction of the low-boiling alcohol ROH are distilled off.

Suitable metal amine chelates are e.g. B. titanium amine chelate and silicon amine chelate. Particularly good results have been achieved with titanium amine chelate. This is known per se as a chelating agent and corresponds to the following formula where R and R 'can be aliphatic or aromatic radicals or mixtures thereof.

The following procedures a, fl, y and b do not describe them here claimed production of the starting materials.

Method a Preparation of Liquid Glycidyl Polyether 513 parts (2.25 mol) 4,4'-Dioxyddiphenyldimethylmethane (bisphenol "A") and 2081 parts (22.5 mol) Epichlorohydrin and 10.4 parts of water are placed in a reaction vessel provided with Stirrer, cooling and heating device, a cooler and a receiver are given. Inside 188 parts of 97.5% sodium hydroxide are added for a few hours. The temperature in the reaction vessel is not higher than 100 "C and is usually not higher than 95" C. After adding the sodium hydroxide, the excess water and epichlorohydrin become removed in vacuo at 50 mm Hg and 1500C. It is cooled to 90 ° C. and 36 parts of benzene are added added, cools further to 40 ° C. and separates by adding salt. After filtering off and washing the salt with an additional 36 parts of benzene, the washing benzene with the The filtrate was combined and returned to the reaction vessel. After distilling off the polyether resin is heated in vacuo to 125 ° C. by means of benzene. The distillation is continued until a temperature of 170 "C at 25 mm Hg is reached in the reaction vessel is.

The glycidyl polyether has a viscosity of Z-3 (Gardner-Holdt scale).

A solid glycidyl polyether can be prepared analogously from 1,4 Share epichlorohydrin and 1 mole of bisphenol "A".

Method fl. Production of an epoxy novolak resin, wherein the novolak a condensate of p-tert-butylphenol and formaldehyde is 328 parts of novolak resin dissolved in 920 parts of epichlorohydrin and 5 parts of water. 82 parts of sodium hydroxide cookies are distributed over approximately equal parts. The first part becomes the solution below Stir added and the mixture is quickly heated to about 80 "C.

The heating is then interrupted, and by the heat of reaction the temperature rises to about 100 "C. At intervals of 10 minutes, the remaining Parts of sodium hydroxide added, the temperature at 95 to 1000C held will. After all the sodium hydroxide has been added, the mixture is stirred and 1 Boiled under reflux for an hour. Epichlorohydrin and water are then at atmospheric pressure distilled off at an internal temperature of about 1300C.

About 450 parts of benzene are added to the still warm mixture, and the precipitated sodium chloride is removed by filtration. The benzene will distilled off in vacuo. At a temperature of about 140 "C and a pressure from 4 mm Hg 398 parts of epoxy novolak resin are obtained. Instead of epichlorohydrin epibromohydrin can also be used.

Method y A diluent (C) is prepared according to known methods made from the following components: 1500 parts Cardanol (vacuum distilled), 1425 parts of epichlorohydrin (97%), 450 parts of sodium hydroxide (500 / above aqueous Solution), 14 parts of hydrochloric acid (18% HCl), 750 parts of toluene.

A tared 5-liter three-necked flask, which is equipped with a stirrer, thermometer, Funnel and reflux condenser is provided, is filled with cardanol and epichlorohydrin. The temperature of the solution is raised to 60 "C, and sodium hydroxide is then added during 20 minutes added, the temperature between 60 and holds 65 "C.

The mixture is then refluxed at 104 "C. for 2 hours and neutralized with hydrochloric acid after cooling to room temperature. That neutralized The reaction mixture is freed from excess epichlorohydrin and water in vacuo. The last traces of water are at an internal temperature of 100 "C and a pressure of 2 mm Hg. Toluene is added to the reaction mixture and from at the sodium chloride formed by the reaction is filtered off.

The filtrate is freed from the solvent at 20 mm Hg. The last volatile traces are removed at 1009C and 2 mm Hg. 1803.5 parts are obtained Glycidyl polyether of cardanol with a viscosity of 62 cP at 25 "C. to B r o k fi e! d and an epoxy equivalent of 518.

Process b Production of suitable curing catalysts: a) 1 mole of triethanolamine titanate and 1 mole of trihexylene glycol biborate are in a suitable Given the reaction vessel and heated to 90 to 135C C for 3 to 4 hours. The reaction product is a clear yellow liquid. b) 2 moles of triethanolamine titanate and 1 mole of trihexylene glycol biborate are placed in a suitable reaction vessel and about 3 to 4 hours to 100 Heated to 135 "C. The reaction product is a clear yellow, slightly viscous liquid. c) 3 moles of triethanolamine titanate and 2 moles of trihexylene glycol biborate are poured into a suitable Given the reaction vessel and heated to 100 to 1350 C for 3 to 4 hours. The reaction product is a clear, slightly yellow liquid. The invention is illustrated by the following examples explained: Example 1 100 parts of a combination of the materials mentioned (A) and (B) with the percent ranges previously described are placed in a reaction vessel given. If materials (A) and (B) are completely compatible, the remaining Materials (C), (D) and (E) can be added directly with stirring. In some In some cases, however, it will be necessary to heat the mixture until it is polymeric Fatty acid has been dissolved. After that, the reactive diluent will be used (C), the thixotropic substance (D) and the hardener (E) are added to the mixture. so the desired amount of inorganic filler is also added and done Stir or grind spread.

The coating power is noticeably dependent both on nature and also on the degree of dispersion of the thixotropic agent (D). For reasons of economy will generally use part of the base resin and / or the thixotropic agent ground with the reactive diluent first. The grinding continues, until there is no further increase in consistency with repeated grinding. This pre-ground mixture of thixotropic material, resin and reactive Diluent can then be added to the residue of the compound mechanical mixing, stirring or preferably by grinding in a 3-roller mixing roller. This is intended to achieve such a dispersion of the thixotropic material, that it has the ability to apply a coating of controllable thickness on the long electrical device to be protected. If there is insufficient dispersion the degree of thixotropy will decrease rapidly. Such a connection will mostly run off during hardening, leaving a thin coating, which is not enough to have an electrical apparatus against water and aqueous solutions to protect.

The masses that have a pot life of 8 to 15 days at room temperature can be used as such, or it can be up to 100 percent by weight other agents are added, such as. B. a leveling agent, dyes, finely divided inorganic fillers and the like, as coatings for electrical equipment, e.g. B. electrical coils, motors, windings, etc. Plating is preferred executed under vacuum so that the coating agent penetrates and all parts of the electrical Facility covered. The coated article is then heat treated. He will be on Heated about 65 to 176 "C until the coating is completely hardened.

Example 2 33.4 parts of epoxy resin (A), 28.4 parts of trimerized acid (B) and 3 parts of diluent (C) are placed in a reaction vessel. After this the components are intimately mixed, 35.2 parts of clay containing bentonite are added, and the mixture is ground into a uniform dispersion of the filler material. The mass, which has a pot life of 1 to 2 weeks at room temperature, will Used to coat electrical coils and windings and burned in at 93 "C.

The device part coated in this way shows excellent insulation and heat distribution properties.

Example 3 55 parts of epoxy resin (A), 30 parts of dimerized acid (B) and 15 parts of the diluent (C) are mixed. Then 1 part of the according to (b) added hardener produced. The relatively thin syrup is used for impregnation used. The resin penetrates deep into the electrical equipment and secures it complete insulation during the subsequent heat curing.

According to the present invention, as from the above shows an improved thixotropic resin composition produced according to the invention is suitable for isolating electrical equipment. Characteristic for The hardened coating is its toughness, good flexibility and durability against moisture, which is of great advantage when covering electrical equipment is. The coatings are easy to manufacture, and the resin compositions used have a longer pot life and good thixotropic properties.

Claims (6)

Claims: 1. Thermosetting thixotropic storage-stable Coating agents, in particular for insulating electrical components and devices based on epoxy resins, d u r c h marked that it is 100 parts by weight a resin composition composed of the following components: A. approximately 25 to 60% a low molecular weight epoxy resin with terminal epoxy groups and one epoxy equivalent from about 120 to 220 and / or an epoxy novolak resin, B. about 5 to 35 ° lo of a polymerized fatty acid, C. up to 20oln of an organic reactive Diluent containing at least one epoxy group, e.g. B. glycidyl ether a monohydric ring-substituted phenol, or other epoxy-containing Diluents such as B. octylene, nonylene or decylene oxide, D. about 1 to 1001o of a thixotropic agent, such as. B. silica aerogels, bentonite clays or metal soaps, and E. about 1 to 40 parts by weight of a curing catalyst and up to 100 parts by weight finely divided inorganic fillers. 2. coating agent according to claim 1, characterized in that the Viscosity of the low molecular weight epoxy resin (A) is 600 to 900 cps. 3. coating agent according to claim 1 and 2, characterized in that that the polymerized fatty acid (B) has a molecular weight of about 400 to 800 Has. 4. coating agent according to claim 1 to 3, characterized in that that the diluent (C) is a long chain monoepoxy resin with one epoxy equivalent from 300 to 500. 5. coating agent according to claim 1 to 4, characterized in that that a metal amine chelate is used as hardener (E). 6. Process for the preparation of the coating agent according to claim 1 to 5, characterized in that the materials (A) and (B) are mixed with heating and then the substances (C). (D) and (E) are added, the filler being stirred in last or is ground. Publications considered: Farbe und Lack, 1956, p. 394 and 542; 1957, p. 77; 1958, p.329 and 201; K a r s t e n, lacquer raw material tables, 1959, p. 210; Manual, Bentone 18 C, German edition by Süd-Chemie A. G., Munich, P. 3, 4 and 29.