DE2434676A1 - Polyepoxide electrical insulation compsn - comprising pheol, bisphenol A formaldehyde condensation prod as crosslinking agent - Google Patents

Abstract

Heat hardenable polymeric mixts. for electrical insulation with lasting heat resistance and a process for their prepn. is claimed comprising epoxy cpds. and a phenolformaldehyde movable hardener, the novolak being the condensation prod. of phenol, at least one >1 nuclear phenol and formaldehyde. The compsns. have lasting heat as well as chemical resistance and may be used as a wire and metal electrical insulation coatings, casting or moulding bodies, and other conventional uses esp. as adhesives for printed circuits and in transformer and electromotors.

Description

Thermally curable plastic mixtures and processes for their production The invention relates to thermally curable plastic mixtures for generation electrically insulating substances made from epoxy compounds and a phenol-formaldehyde condensation product consist of the novolak type as a hardener.

Such plastic mixtures as they are from the Swiss patent No. 359 883 are known, e.g. B. used as a coating. The known Plastic mixtures of this type have excellent mechanical properties at room temperature and electrical properties and good solvent resistance, with increased However, their mechanical strength deteriorates rapidly at high temperatures. The relatively long novolak chains produced by the usual methods Novolaks are namely in spite of the complete hardening with the Epoxy-0 connections thermoplastic at temperatures above about 100 C, therefore the use of this The known plastic mixtures mentioned are hardly justifiable at temperatures above 0 100 C.

The invention is now based on the object of thermally curable plastic mixtures for the production of electrically insulating materials and processes for their production indicate that of epoxy compounds and a phenol-formaldehyde condensation product exist as hardeners and which also have a high permanent temperature resistance.

This object is achieved in the plastic mixtures according to the invention, which are characterized in that the phenol-formaldehyde condensation product one based on of phenol and at least one polynuclear phenol is.

The molar ratio of the phenols to the formaldehyde in the phenol-formaldehyde condensation product is 1: 0.2 to 1 = 1 According to an advantageous embodiment of the invention, in the Phenol-formaldehyde condensation product used as polynuclear phenol bisphenol A.

According to another advantageous embodiment of the invention exist the polynuclear phenols based on the phenol-formaldehyde condensation product essentially of dihydroxydiphenylmethane The invention on which the invention is based The task is also achieved by the method according to the invention, which is characterized is that you have a mixture of phenol and at least one polynuclear phenol added to an aqueous solution of formaldehyde, by means of a volatile acid sets an acidic environment, the mixed with the solution mixture to completion the polycondensation process at an elevated temperature, in particular at least at Ksndensat reflux temperature, separates the resin formed, it in one Dissolves organic solvent and finally mixes with a polyepoxy compound.

In an advantageous embodiment of the method according to the invention is essentially used to produce the mixture of phenol and polynuclear Dihydroxydiphenylmethane existing phenols, initially phenol and formaldehyde in added to an aqueous solution in a molar ratio of phenol to formaldehyde of about 1: 0.5, a volatile acid sets an acidic environment that mixed with the solution Phenol until the end of the condensation process at an elevated temperature, in particular kept at least at the condensate reflux temperature and the so formed, to a small proportion of free phenol and otherwise mainly of dihydroxydiphenylmethane existing Gedes mixed separated, whereby the formation / phenol-formaldehyde condensation product on the basis of this mixture at a molar ratio of the initial amount of phenol to formaldehyde approximately equal to 1: 0.3 takes place.

The curable plastic mixtures according to the invention find above all their use as a binder for electrical insulation materials, especially for manufacture of base materials for printed circuits and in general everywhere there, where to put the material at elevated permanent temperatures or fluctuating temperatures is used, i.e. where a high permanent temperature resistance is required. Furthermore they are suitable for the production of slot wedges for electric motors, components for generators and transformers and generally where the material of the thermal class F must conform to ASTM.

Except in the case of laminates, the plastic mixtures according to the invention can be used Also as a base resin for paints with good chemical resistance, especially with increased Use temperatures, e.g. B. for wire enamels, for the surface protection of metals, for bonds, castings and pressed bodies. The plastic mixtures according to the invention can therefore, in each case in a formulation adapted to the application, in filled or unfilled state, in the form of solutions, emulsions, lacquers, molding compounds, Sinter powders, dipping resins, casting resins, impregnating resins, laminating resins, adhesives, Fillers, etc.

be used.

The invention is explained in detail below with the aid of examples.

Example 1: A novolak resin is made by adding 10 moles (940 G) Phenol (monohydroxybenzene) 2 moles (456 g) bisphenol A, 8.4 moles (700 g) of a 37% aqueous solution of formaldehyde and 0.015 mol (1.5 g) of conc. Hydrochloric acid mixed together at 20-30 ° C. The mixture is then brought to reflux temperature (100 - 1020C), which should be held for 60 minutes. Which are clear at the beginning The mixture that has become becomes cloudy after about 15 minutes, the mixture turning into a Water layer and a resin layer separate. After the condensation, it is distilled the water at a temperature of less than 100 0C under vacuum so far, until the temperature of the product at a vacuum of about 100 Torr to 100-110 0C increases. The thus dehydrated product is cooled to 70 0C and with acetone on one Solids content of approx. 65% diluted.

The hydroxy equivalent of the product corresponds to 113 g of solid resin. That so produced novolak resin is mixed with an epoxy compound, namely im equimolar ratio.

One mixes z. B. 1900 g of a diepoxide of bisphenol A with a Epoxy equivalent of 190 g with 1735 g of a 65% solution of the above novolak resin and sets the mixture to accelerate the curing rate 0.1 - 1% Benzyldimethylamine based on the solids content of the solution. With this solution a glass fabric with a weight per unit area of 200 g / m2 is made using conventional methods soaked. Several layers of the prepreg obtained in this way are placed in a heated press at 20 kg / cm2 and 700C for one hour to the finished epoxy glass hard fabric pressed and hardened.

Example 2: A novolak resin is made by adding 10 moles (940 g) phenol (monohydroxybenzene), 5 moles (405 g) of a 37% aqueous solution of Formaldehyde and P, 015 mol (1.5 g) conc.

Hydrochloric acid mixed together at 20-30 ° C. The mix will afterward heated to reflux temperature (100-1020C), which is to be maintained for 60 minutes. The mixture, which became clear at the beginning, becomes cloudy after about 30 minutes, whereby it becomes separates the mixture into a water layer and a resin layer. After condensation the water is distilled at a temperature of less than 1000C under vacuum so far, until the temperature of the product at a vacuum of about 100 Torr 100 - 110 C rises.

The product dehydrated in this way is cooled to 700.degree.

The intermediate product thus prepared is mixed with a further 3 mol (243 g) a 37% aqueous formaldehyde solution and 0.010 mol (1.0 g) conc. hydrochloric acid mixed and refluxed for an additional hour. After condensation the water is distilled off without a vacuum until the product is anhydrous and the Resin melt has reached a temperature of 110 - 115 C. That so drained Resin is cooled to 75-80 ° C. and in the warm state with 300 g of isopropyl alcohol diluted. The product, cooled to 40 ° C., is diluted with an additional 300 g of acetone.

The hydroxy equivalent of the product corresponds to 112 g on the solid resin based. The novolak resin produced in this way, which is essentially a polynuclear phenol a dihydroxydiphenylmethane crosslinked via a methylene bridge in the ortho position is mixed with an epoxy compound in an equimolar ratio. One mixes z. B. 1900 g of a diepoxide of bisphenol A with one epoxy equivalent of 190 g with 1725 g of a 65% solution of the above novolak resin and sets the Mixture to accelerate the curing rate 0.1 - 1% benzyldimethylamine based on the solids content of the solution. This solution creates a glass fabric Impregnated with a surface weight of 200 g / m2 using the usual methods. Several Layers of the prepreg thus obtained are placed in a heated press at 20 kgXcm2 and 170 ° C = during one and hardened.

Example 3: The novolak according to Example 1 is made with a polyepoxy compound mixed in an equimolar ratio. To this end, 1170 g of a polyepoxy resin are mixed with epoxy equivalent of 180 g with 1040 g of a 65% solution of the above novolak resin and sets the mixture to accelerate the curing rate 0.1 - 1% Benzyldimethylamine based on the solids content of the solution. With this solution a glass fabric, as indicated in Example 1, is impregnated and pressed.

Example 4: The novolak according to Example 2 is made with a polyepoxy compound mixed in equimolar proportions. To this end, 1170 g of a polyepoxy resin are mixed with an epoxy equivalent of 180 g with 1120 g of a 65 ° »strength solution of the novolak resin according to Example 2 and continues the mixture to accelerate the curing rate 0.1 - 1% benzyldimethylamine based on the solids content of the solution. With A glass fabric, as indicated in Examples 1 and 2, is impregnated with this solution and pressed.

Claims (6)

Claims. 1. Thermally curable plastic mixtures for electrical generation insulating materials of high permanent temperature resistance, essentially consisting of from epoxy compounds and a phenol-formaldehyde condensation product of the Novalak type as a hardener for this, characterized in that the phenol-formaldehyde condensation product is one based on phenol and at least one polynuclear phenol. 2. Mixtures according to claim 1, characterized in that the molar ratio of phenols to formaldehyde in the phenol-formaldehyde condensation product 1: 0.2 to 1: 1. 3. Mixtures according to claim 1 or 2, characterized in that one uses bisphenol A as a polynuclear phenol. 4. Mixtures according to claim 1 or 2, characterized in that the polynuclear phenols based on the phenol-formaldehyde condensation product essentially consist of dihydroxydiphenylmethane. 5. Process for the production of thermally curable plastic mixtures according to one of claims 1 - 4, characterized in that a mixture of Phenol and at least one polynuclear phenol with an aqueous solution of formaldehyde added, sets an acidic environment by means of a volatile acid, which with the Solution mixed mixture up to the conclusion of the polycondensation process on increased Temperature, in particular at least at the condensate reflux temperature, keeps the formed Separate resin, dissolve it in an organic solvent and finally with a Polyepoxy compound mixes. 6. The method according to claim 5 for the production of thermally curable plastic mixtures according to claim 4, characterized in that to produce the mixture from Phenol and polynuclear, consisting essentially of dihydroxydiphenylmethane Phenols, initially phenol and formaldehyde in an aqueous solution in a molar ratio Phenol: formaldehyde added at about 1: 0.5, a volatile acid turns acidic Setting the environment, the phenol mixed with the solution until the condensation process is complete at an elevated temperature, in particular at least at the condensate reflux temperature holds and the so formed, to a small extent from free phenol and otherwise predominantly consisting of dihydroxydiphenylmethane separates mixture, and that further the formation of the phenol-formaldehyde condensation product based on this mixture with a molar ratio of the initial amount of phenol to formaldehyde approximately equal to 1: 0.3 takes place.