JPH0234964B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a polyurethane-based two-component potting agent for electrical insulation, and more specifically, a two-component potting agent for electrical insulation that has excellent electrical insulation properties, cold and heat cycle resistance, flame retardance, castability, heat resistance, etc. Regarding. Traditionally, epoxy resins, silicone resins, etc. have been used as potting agents for electrical insulation such as in high-voltage coil parts, but recently polyurethane resins have been attracting attention as an alternative to these materials. Materials containing castor oil or its derivatives as a polyol component (for example, U.S. Pat. No. 3,362,921) are known. In particular, materials containing castor oil as a polyol component have superior electrical insulation properties compared to those using polybutadiene polyols, making them extremely suitable as potting agents for electrical insulation.However, on the other hand, they have poor mechanical strength. This could not necessarily be said to be sufficient due to the lack of. In general, to increase the mechanical strength of cured polyurethane products using castor oil-based polyols, it is known to use short chain diols, triols, etc., specifically, 2ethyl-1,3-hexanediol, N, Examples include N-bis(2-hydroxypropyl)aniline, 1.2.6-hexanetriol, and glycerin. However, when using these short-chain diols and triols, there are certain issues in terms of adhesion to electronic components and cases, storage stability when mixed, foamability in cured products, material strength at high temperatures, etc. I couldn't say it was enough. Therefore, the present inventors conducted intensive studies to overcome these drawbacks found in castor oil-based materials, and found that when a specific aromatic polyol is used in combination with castor oil in a specific ratio, material strength, heat resistance, etc. The present inventors have discovered that the material has improved heat and cold cycle resistance and electrical insulation properties, and have completed the present invention. The main object of the present invention is to provide a two-component potting agent for electrical insulation that has low viscosity, excellent workability, and excellent cold/heat cycle resistance, mechanical strength, and insulation properties. The purpose of the present invention is to provide a two-component potting agent for electrical insulation with excellent stability and safety. The object of the present invention is to combine 20 to 80% by weight of an aromatic polyol represented by the general formula below and 80 to 80% by weight of castor oil.
Polyol component (a) and flame retardant (b) consisting of 20% by weight
A two-component product for electrical insulation is produced by combining a solution A containing as an essential component and a solution B containing a low-volatile isocyanate component (c) selected from polyisocyanate compounds and their dimers and a plasticizer (d) as essential components. This is achieved by using a mold potting agent. Polyol component (a) used as liquid A of the present invention
is an aromatic polyol having hydroxyl groups at both ends, which is obtained by adding alkylene oxide to bisphenol A, 20 to 80% by weight, preferably 40 to 60% by weight, and 80 to 20% by weight, preferably 60 to 40% by weight of castor oil. % mixture. At this time, if the aromatic polyol component is too large, the viscosity will increase, impeding castability, and although the mechanical performance of the material will improve, elongation will decrease and it will not be able to withstand cold and hot cycles. On the other hand, too much castor oil
Although the viscosity decreases, the mechanical strength of the material decreases, and the elongation also decreases, making it impossible to withstand cold and hot cycles. The aromatic polyol used is a dihydric alcohol represented by the following general formula []. (In the formula, R is an alkyl group having 2 to 3 carbon atoms,
X is _-CH2- ,

[Formula] or -O-, Y is a halogen or a lower alkyl group, a and b are integers of 0 to 2, and m and n are each 1 to
Represents an integer of 3. ) Such polyols can be obtained by adding ethylene oxide or propylene oxide to phenols such as bisphenol F, bisphenol A, 4,4'-dihydroxyphenyl ether, chlorine-substituted products and bromine-substituted products thereof. Specific examples include BPX-11, BPX-
33 (all manufactured by Asahi Denka Kogyo Co., Ltd.), BA−P ₂ , BA−
Examples include P ₃ (manufactured by Nippon Nyukazai Co., Ltd.). At this time, if the amount of alkylene oxide added is too large, the hygroscopicity of the polyol component will increase, impairing storage stability, and will also cause foaming during curing and reduce mechanical properties, so the values of m and n should be 3 or less. need to be kept. Castor oil, which is another ingredient, is not particularly limited as long as it has been conventionally used for polyurethane, and specific examples include URIC H-30, URIC
Examples include LAV and URIC Special A (both manufactured by Ito Oil Co., Ltd.). It is necessary to add flame retardant (b) to liquid A as another essential component. Any flame retardant may be used as long as it can impart the desired flame retardancy to the cured product, and specific examples thereof include modified red phosphorus, antimony oxide, molybdenum compounds, boron compounds,
Examples include organic halogen compounds, phosphoric esters, and metal hydroxides. The blending amount of such flame retardant is not necessarily constant depending on the type of flame retardant and the required performance, and therefore it is selected as appropriate within a range that does not impair the casting workability of liquid A. When aluminum hydroxide is used in combination, 1 to 20 parts by weight of red phosphorus powder, preferably 3 to 15 parts by weight, and 5 to 100 parts by weight of aluminum hydroxide, preferably 20 to 70 parts by weight, per 100 parts by weight of polyol component (a). By adopting such a formulation, a high degree of flame retardancy can be imparted economically and without impairing casting workability. On the other hand, the B liquid used in the present invention contains a low-volatile isocyanate component (c) and a plasticizer (d) as essential components. Here, the term "low-volatile isocyanate component" refers to a non-prepolymerized polyisocyanate compound with a vapor pressure of 0.01 mmHg or less at 50°C, its dimer, or a mixture thereof, such as diphenylmethane. Examples include -4,4'-diisocyanate, its cycloadduct, polyphenylmethane polyisocyanate, and cycloadduct of tolylene diisocyanate. However, highly volatile compounds such as tolylene diisocyanate, which is commonly used, cannot be used from the standpoint of safety and hygiene. In the present invention, liquid B is prepared by mixing these polyisocyanate components (c) with a plasticizer (d). When the cured product is required to have a high degree of flame retardancy, it is preferable to use a flame-retardant plasticizer, such as a phosphate ester plasticizer. Tricresyl phosphate is also prized for its compatibility. The amount of such plasticizer is usually (c)
10 parts by weight or more, preferably 20 parts by weight per 100 parts by weight of ingredients
The amount is 80 parts by weight, and by adding a plasticizer, it is possible to improve the casting workability and improve the storage stability of Solution B, especially at low temperatures. The A and B solutions thus prepared are both low viscosity liquids, and can be easily mixed according to conventional methods and used for casting electrical parts such as earth leakage circuit breakers, automobile electrical components, condensers, igniters, etc. can do. At this time, the blending ratio of both liquids may be selected as appropriate, but usually the isocyanate group of liquid B is 1
It is preferable that the amount of active hydrogen in liquid A is in the range of 0.7 to 1.2 equivalents relative to the equivalent amount, and that the mixture is blended so that the viscosity of the mixture at 25° C. is 3000 centipoise or less. According to the present invention, a potting material having excellent stability of liquids A and B and excellent castability can be obtained.
The cured product of this material has appropriate mechanical strength, and also has excellent performance in terms of electrical insulation properties, cold/heat cycle resistance, flame retardance, etc. The present invention will be explained in more detail with reference to Examples below. Example 1 Propylene adduct of bisphenol A (trade name
BPX-11 or BPX-55 manufactured by Asahi Denka), castor oil (trade name URIC H-30, hydroxyl value 160mg)
KOH/g, manufactured by Ito Oil Co., Ltd.), aluminum hydroxide (trade name: Hygilite H-32I, manufactured by Showa Metal Industry Co., Ltd.), and modified red phosphorus (trade name: Noretsudo #120,
Solution A was prepared by stirring well (manufactured by Rin Kagaku Kogyo Co., Ltd.) for 30 minutes in a closed container under a nitrogen atmosphere according to the formulation method shown in Table 1. The solution viscosity of the thus prepared sample at 25°C was measured using a BM type viscometer. Since sample (A-1) had a high solution viscosity at 25°C, the viscosity was measured while keeping the temperature of the solution at 60°C.
Next, put this liquid A into a test tube with a diameter of 18 mmφ,
After being left for one week at -5°C, storage stability was observed. The results are shown in Table 1.

【table】

[Table] Example 2 The above tricresyl phosphate was added to 100 parts of diphenylmethane-4,4'-diisocyanate (trade name, Isonato-143L) or polymeric isocyanate (trade name: PAPI-135, both manufactured by Kasei Appdition Co., Ltd.). Mix a predetermined amount to make liquid B,
This B solution was allowed to stand at -5°C for one month, and the presence or absence of crystal precipitation was observed. For comparison, 1,4-polybutadiene diol (manufactured by ARCO, trade name R-45HT) 4
and 1 part of tolylene diisocyanate at 60°C for 8 hours (viscosity 25,000 cps/
A test was conducted in the same manner at 25° C. with an isocyanate group content of 9%, and the presence or absence of crystal precipitation was observed. The results are shown in Table 2.

[Table] From these results, the storage stability is extremely poor when no plasticizer is used (experiment numbers 2-1 and 2-2), and when prepolymerization is used (experiment number 2-2), the storage stability is extremely poor.
It can be seen that 3) also has poor storage stability. Example 3 Various A liquids prepared in Example 1 and B liquids (B-4, B-5) prepared in Example 2 were mixed so that hydroxide/isocyanate group = 1.05 (equivalent ratio),
After degassing, it was heated at 60°C for 5 hours to prepare a test piece. The castability of the mixture and the physical properties of the cured product were evaluated using predetermined methods, and the results are shown in Table 3.

【table】

Claims (1)

[Claims] 1. General formula (In the formula, R is an alkylene group having 2 to 3 carbon atoms, X is -CH ₂ -, [Formula] or -O-, Y is a halogen or a lower alkyl group,
a and b are integers of 0 to 2; A solution containing a) and a flame retardant (b) as essential components, and B containing a low-volatile isocyanate component (c) selected from polyisocyanate compounds and dimers thereof and a plasticizer (d) as essential components. A two-component potting agent for electrical insulation consisting of a liquid and a liquid.