JPH0873704A - Heat-resistant dripping-impregnating resin - Google Patents

Abstract

PURPOSE: To provide a heat-resistant dripping-impregnating resin capable of shortening the curing time of a dripping-impregnating resin for use as an insulat ing material for use in various electric apparatuses, excellent in general-purpose properties with an increase in the maximum permissible service temp. thereof, and satisfactory in mechanical strength and temp. characteristics of a cure product thereof. CONSTITUTION: A bisphenol epoxy resin is mixed with, and heated and stirred together with a cresol novolak epoxy resin for heightening the heat resistance thereof, an alicyclic epoxy resin for heightening the mechanical strength and temp. characteristics thereof, and pentaerythritol for imparting thereto a flexibility to obtain a heat-resistant dripping-impregnating resin. Tetrahydrophthalic anhydride is used as a curing agent, while 1,8-diaza-bicyclo(5,4,0)-undene-7 oleate is used as a curing accelerator.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-resistant dropping-impregnated resin which is curable for a short time and used as an insulating material for various electric devices.

[0002]

2. Description of the Related Art Generally, as a resin for drop impregnation, a resin having a maximum allowable temperature of 180 ° C. or higher, which is usually called a heat-resistant type C, is commercially available. However, it takes a long time of about 24 hours to completely cure them. Therefore, there is a difficulty in increasing the production efficiency of various electric devices, and in particular, from the viewpoint of improving the productivity, development of a heat-resistant dropping-impregnated resin with a shortened curing time has been desired.

On the other hand, there are epoxy resins that can be cured in a short time in about 2 to 3 hours as a drop impregnating resin.
Since it has a temperature of 55 ° C., it has low versatility, and there is a demand for a resin with high versatility by increasing the maximum allowable temperature as various electric devices are made compact and have high output.

[0004]

Epoxy resins, which have hitherto been known as materials having a short curing time, have not only excellent electrical characteristics and adhesiveness, but also the chemical structure of the resin itself and the curing agent. A cured product having various properties can be obtained by elucidating and selecting a material, and therefore, it is attracting attention as a heat-resistant dropping-impregnated resin that is curable for a short time.

However, the cured product of the dropping-impregnated resin using this epoxy resin as a raw material has a drawback in that it is fragile in terms of mechanical strength, and particularly in the case of high heat resistance, the cured product is cracked. There is a fear of occurrence of the above, which is a problem in maintaining high reliability of electric equipment.

The present invention has been made in view of the above-mentioned points, and the curing time can be shortened, the maximum allowable temperature can be increased, and the versatility can be improved. It is an object of the present invention to provide a heat-resistant drop-impregnated resin that satisfies the desired strength and temperature characteristics.

[0007]

In order to achieve the above object, the present invention provides a cresol novolac type epoxy resin for enhancing heat resistance of a bisphenol type epoxy resin as a main component, and a cresol novolak type epoxy resin for enhancing mechanical strength and temperature characteristics. Provided is a heat-resistant dropping impregnated resin obtained by mixing a cycloaliphatic epoxy resin and pentaerythritol for imparting flexibility and heating and stirring the mixture.

The compounding ratio is 40 to 75% by weight of bisphenol type epoxy resin, 10 to 40% by weight of cresol novolac type epoxy resin, 10 to 40% by weight of cycloaliphatic type epoxy resin, and 5 to pentaerythritol.
30% by weight.

Further, tetrahydrophthalic unhydride is used as a curing agent added to the drip impregnated resin, and 1,8-diaza-bicyclo (5,
4, 0) Unden-7 oleate is used, the curing agent is 0.8 to 1.2 mol based on the main agent, and the curing accelerator is 0.5 to 5% by weight based on the main agent. The ratio of

Further, a curing agent and a curing accelerator are mixed and added to the dropping impregnated resin in a weight ratio of 1: 1.

[0011]

According to the heat-resistant dropping impregnated resin, the heat resistance temperature index tends to decrease as the amount of the flexibility-imparting agent added increases, but the amount of the flexibility-imparting agent added is 30%. Even when the temperature reached the above, the heat resistance temperature index was 280 ° C. or higher, and it was possible to obtain a heat resistant temperature index that can be applied to a dropping impregnation resin called a general heat resistant C type.

Further, according to the crack resistance test of the obtained cured product, the exponential average of the cured product sample using only the conventional epoxy resin was 3.8, whereas this example was applied. The cured product thus obtained had an index average of 11, and it was confirmed that the cured product was significantly improved in terms of mechanical strength and temperature characteristics.

Further, in the cured product according to this example, the gel time, which is the time required for the drip impregnated resin to completely solidify from the semi-molten state, is much shorter than the gel time when only the conventional epoxy resin is used. As a result, the curing time can be shortened, the processing time when applied to the manufacturing process of various electric devices can be significantly shortened, and the productivity of these devices can be improved, which is a remarkable effect.

[0014]

EXAMPLES Specific examples of the heat-resistant drop-impregnated resin according to the present invention will be described below. In this example, a heat-resistant material obtained by heating and stirring a mixture of an epoxy resin, which has a short curing time, as a main component, with a material that enhances heat resistance, a material that enhances mechanical strength and temperature characteristics, and a material that imparts flexibility. The basic composition of the resin is the impregnating resin.

In order to check the characteristics of the obtained dropping impregnated resin, a curing agent and a curing accelerator are added to this dropping impregnated resin, and the mixture is stirred and heated while maintaining appropriate temperature conditions and predetermined time. Curing was performed, and the properties of the obtained cured product were checked and a crack resistance test was performed.

First, the method for producing the dropping impregnated resin will be described.
Bisphenol type epoxy resin (brand name Epicoat 828, epoxy equivalent = 195 as an example) as a main agent, and cresol novolac type epoxy resin (brand name YDCN701, epoxy equivalent = 210 as an example) as a material for enhancing heat resistance, and mechanical strength and temperature characteristics Cycloaliphatic epoxy resin as a material to enhance
R4221, epoxy equivalent = 140) and pentaerythritol (trade name PE as an example) were mixed as a material for imparting flexibility, and each predetermined amount was placed in a stainless beaker and stirred while heating at a temperature of 80 ° C. To obtain a drop-impregnated resin.

The mixing ratio of the above components is, for example, 40 to 75% by weight of bisphenol type epoxy resin, 10 to 40% by weight of cresol novolac type epoxy resin, 10 to 40% by weight of cycloaliphatic type epoxy resin, and pentaerythritol. Was 5 to 30% by weight.

Next, tetrahydrophthalic unhydride which is an acid anhydride as a curing agent (trade name H as an example)
N-2200, epoxy equivalent = 166) and 1,8-diaza-bicyclo (5,4,0) unden-7.oleate as a curing accelerator (trade name SA102 as an example).
Was added in an appropriate amount and stirred until uniform. The curing agent was used in a proportion of 0.8 to 1.2 mol with respect to the base material, and the curing accelerator was used in a proportion of 0.5 to 5% by weight with respect to the base material.

Then, a curing agent and a curing accelerator are mixed with the main component in a weight ratio of 1: 1 and sufficiently stirred and then heated in a temperature range of 130 ° C. to 200 ° C. for about 3 hours. A cured product according to this example was obtained.

Next, the properties of the obtained cured product were checked. FIG. 1 is a graph in which the abscissa represents the added amount (% by weight) of the flexibility-imparting agent (pentaerythritol) and the ordinate represents the heat resistance temperature index (TGI) according to the NEMA standard.

According to FIG. 1, the heat resistance temperature index tends to decrease as the amount of the flexibility-imparting agent added increases. However, even if the amount of the flexibility-imparting agent added reaches 30%, the heat resistance temperature index is 280 ° C. or higher, and it is understood that the resin can be applied to the dropping impregnating resin commonly referred to as heat resistance C type. It

Further, a crack resistance test of the obtained cured product was carried out. 1 to 12 of the crack resistance test according to Table 1
Change in temperature (° C) as a test condition in the cycle,
The test time and index are shown as a list.

[0023]

[Table 1]

Cycle 1 in Table 1 is an unloaded state, and Cycle 2 is the cured product of 25 (° C.) to 5 (° C.).
It is shown that the test conditions are such that the temperature drops to 10 minutes. If no crack is generated in the cured product in this cycle 2, the index is "1". Hereinafter, a crack resistance test is performed under the conditions shown in the table from cycle 3 to cycle 11 to obtain an index "2" to an index "10", and all the test conditions of cycle 11 and above are cycle 12, the index is It was set to "11".

For comparison, when the above-mentioned crack resistance test was carried out on a cured product sample using only a conventional epoxy resin, the index average of a plurality of samples was 3.8. It was confirmed that the index average of the cured product to which this example was applied was 11, that is, the test condition of cycle 11 or more was cleared.

Further, the cured product according to this embodiment has a temperature of 120.
Gel time at ℃ 15.0 minutes, temperature 135
The gel time at ℃ was 9.2 minutes, the gel time at a temperature of 150 ℃ was 4.8 minutes. It was confirmed that this gel time is the time from the semi-molten state of the dropping impregnated resin to the complete solidification, which was much shorter than the gel time when only the conventional epoxy resin was used.

[0027]

As described in detail above, by using the heat-resistant dropping impregnating resin according to the present invention, the brittleness of the conventional dropping impregnating resin using the epoxy resin as a material is eliminated. The mechanical strength and temperature characteristics of the obtained cured product can be significantly improved.

Further, in the cured product according to this example, the gel time, which is the time required for the drip impregnated resin to completely solidify from the semi-molten state, is much shorter than the gel time when only the conventional epoxy resin is used. Therefore, the curing time can be shortened, and the processing time when applied to the manufacturing process of various electric devices can be significantly shortened to improve the productivity.

Further, since the maximum allowable temperature is increased along with the shortening of the curing time, versatility satisfying the requirements accompanying downsizing and high output of various electric equipment is obtained,
It is possible to provide a heat-resistant dropping-impregnated resin that can highly maintain the reliability of an electric device in combination with the improvement of the mechanical strength.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the addition amount of a flexibility-imparting agent and the heat resistance temperature index (TGI) of the cured product obtained in this example.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H02K 15/12 C

Claims (4)

[Claims] 1. A cresol novolac type epoxy resin for increasing heat resistance, a cycloaliphatic type epoxy resin for increasing mechanical strength and temperature characteristics, and a penta for imparting flexibility to a bisphenol type epoxy resin. A heat-resistant drop-impregnated resin obtained by mixing erythritol, heating and stirring. 2. The bisphenol type epoxy resin
0 to 75% by weight, cresol novolac type epoxy resin 10 to 40% by weight, cycloaliphatic type epoxy resin 10
~ 40 wt%, pentaerythritol 5-30 wt%
The heat-resistant drop-impregnated resin according to claim 1, wherein the blending ratio is 1. 3. A tetrahydrophthalic anhydride is used as a curing agent added to the dropping impregnated resin and 1,8-diaza-bicyclo (5,
4,0) Unden-7.oleate, the curing agent is used in a proportion of 0.8 to 1.2 mol based on the main agent, and the curing accelerator is 0.5 to 5% by weight based on the main agent. The heat-resistant drop-impregnated resin according to claim 1, which is defined as a ratio. 4. The heat-resistant drop-impregnated resin according to claim 1, wherein a curing agent and a hardening accelerator are mixed and added to the drop-impregnated resin in a weight ratio of 1: 1.