Epoxy resin compositions comprising epoxy and vinyl ester groups

Abstract

Epoxy resin composition comprising a) the reaction product formed from a1) one or more epoxy compounds having at least two epoxy groups, and a2) 0.2 to 0.9 mol of acrylic acid or methacrylic acid or mixtures thereof per mole of epoxy groups, as component A; b) a solvent comprising vinyl groups as component B.

Claims

1. A coating composition, consisting of: i) 100 parts by weight of an epoxy resin comprising a) the reaction product formed from a1) one or more epoxy compounds having at least two epoxy groups being selected from bisphenol A diglycidyl ether, a phenol novolac glycidyl ether, and a cresol novolac glycidyl ether, and a2) 0.3 to 0.7 mol of acrylic acid or methacrylic acid or mixtures thereof per mole of epoxy groups, as component A; b) a solvent comprising vinyl groups as component B selected from the group consisting of butanediol di(meth)acrylate, hexanediol di(meth)acrylate, dipropylene glycol di(meth)acrylate and tripropylene glycol di(meth)acrylate; the solvent comprising vinyl groups of component B consisting to an extent of at least 90% by weight of solvents comprising difunctional vinyl groups, based on the sum of all solvents comprising vinyl groups, ii) 0.1 to 10 parts by weight of a free radical-forming polymerization initiator, iii) 0.1 to 5 parts by weight of a hardener, which is a Lewis acid selected from complexes of BF.sub.3 and BCl.sub.3 with tertiary amines, and iv) optionally a polymerization inhibitor.

2. A method of insulating electric and/or electronic components and devices, comprising the step of impregnating the electric or electronic components and devices with the coating composition according to claim 1.

3. A method for insulating electric motors used in cooling units, comprising: impregnating the electric motors with the coating composition according to claim 1 to hermetically shield them from their environment.

4. The coating composition of claim 1, wherein the free radical-forming polymerization initiator is selected from the group consisting of 4,4-dimethylbenzyl ketal, 4,4-dimethoxybenzoin, benzoin methyl ether, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, dicumyl peroxide, di-tert-butyl peroxide, and tert-butyl perbenzoate.

Description

EXAMPLES

Example 1

(1) A three-neck flask with thermometer, stirrer and reflux condenser is charged with 633.6 g of bisphenol A epoxy resin (trade name E44, epoxide equivalent of 227.27 g/mol, corresponding to 2.788 epoxy groups), 100.45 g of acrylic acid (corresponding to 1.394 carboxyl groups), 0.528 g of hydroquinone and 0.6336 g of tetramethylammonium chloride. The mixture is heated to 105 C. After 3 hours, the mixture has an acid number of 1.0 mg KOH/g.

(2) The procedure is as in Example 1, except with the amounts of the individual components specified in Table 1.

(3) TABLE-US-00001 TABLE 1 Examples 2 3 Epoxy resin E-44 633.6 g 633.6 g Acrylic acid 85 g 115 g Tetramethylammonium 0.5 g 0.8 g chloride Hydroquinone 0.4 g 0.7 g Acid number 0.2 mg KOH/g 1.5 mg KOH/g Resin name A-2 A-3

Example 4

(4) 620.26 g of a cresol novolac of the F-51 type (epoxide equivalent of 196.08 g/mol, corresponding to an average of 3.162 epoxy groups per molecule) are heated to 65 C. 0.4 g of hydroquinone, 94.91 g of acrylic acid (corresponding to 1.317 carboxyl groups per molecule of the epoxy compound) and 0.738 g of tetramethylammonium chloride are added, and the mixture is left to react under air at 105 C. When the acid number declines below 1 mg KOH/g, the reaction is stopped by cooling. The resin obtained is named A-4.

Examples 5 and 6

(5) Resins A-5 and A-6 are, as described in Example 4, produced with the amounts of the individual components listed in Table 2.

(6) TABLE-US-00002 TABLE 2 Examples 5 6 Cresol novolac F-51 620.26 g 620.26 g Acrylic acid 80 g 115 g Tetramethylammonium 0.5 g 0.9 g chloride Hydroquinone 0.3 g 0.5 g Acid number 0.15 mg KOH/g 1.14 mg KOH/g Resin name A-5 A-6

Examples 7 to 11

(7) By mixing resins A-1 to A-6 with butanediol dimethacrylate, dicumyl peroxide and boron trichloride-dimethyloctylamine complex, fully formulated impregnating resin coating compositions for electrical insulation were produced. The compositions and properties thereof are reproduced in Table 3.

(8) TABLE-US-00003 TABLE 3 Examples 7 8 9 10 11 A-1 35 g A-2 65 g 40 g A-3 43 g A-4 25 g A-5 60 g 19 g A-6 16 g Butanediol 35 g 40 g 40 g 41 g 38 g dimethacrylate Dicumyl peroxide 1 g 1 g 1 g 1 g 1 g BCl.sub.3-dimethyloctylamine 2 g 2 g 2 g 2 g 2 g Properties Viscosity 320 525 500 427 395 (mPa .Math. s, 23 C.) Gel time in min, 5.51 4.82 4.96 5.10 5.28 8 g@120 C. Baking resistance, 243 334 296 283 262 at 23 C. in N Shore D hardness 68 102 95 84 75

(9) The gel time is determined to DIN 16945, and the baking resistance to IEC 61033.

(10) For the use of windings impregnated with impregnating resin in hermetic motors, for example in refrigerators, what is called an oil test must be passed. This is conducted as follows:

(11) Helical coils made from MW 35 enamelled wire are produced as described in ASTM D 2519. The helical coils are immersed into the impregnating bath and hardened at 150 C. for 3 hours. A Parr bomb is filled with 500 ml of mineral oil. Five helical coils are introduced into the oil. The bomb is closed. Thereafter, it is filled with approx. 0.5 kg of Frigen R 22 (or 410) via a valve. The bomb is stored at 120 C. for 168 hours. After cooling and decompression, the helical coils are removed and dried with paper. Baking resistance is tested and compared with that before the oil test. A 10% decline is still tolerable.

(12) The baking resistances to ASTM2519-2 in N are reproduced in Table 4.

(13) TABLE-US-00004 TABLE 4 Examples 7 8 9 10 11 Before the oil test 243.10 334.52 296.78 283.09 262.40 After the oil test 221.73 326.11 290.04 277.45 238.52

Comparative Example 1

(14) An impregnating resin which does not contain any free oxirane groups and is as described in Example 1 of U.S. Pat. No. 5,984,647 is produced and tested as described above.

(15) The results in comparison with the results of Example 11 are reproduced in Table 5.

(16) The breakdown resistance (breakdown voltage) was determined to IEC 60464 part 2, and the extraction values by weighing the helical coils before and after the oil test.

(17) TABLE-US-00005 TABLE 5 Impregnating resin Example 11 Comparative example 1 Breakdown voltage (V/my) 1.59 1.32 R22 extraction (%) 0.21 0.37 R 410 extraction (%) 0.18 0.21 Baking resistance (N) 262 117 before the oil test Baking resistance (N) 238 113 after the oil test

(18) The inventive impregnating resin according to Example 11 has lower extraction values than, and twice the baking resistance of, the impregnating resin according to Comparative example 1.