JPS6314729B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a liquid rubber composition that can be easily cast, impregnated, or coated, and has excellent rubber elasticity and high electrical insulation properties after curing. Conventionally, polyurethanes obtained by a method of reacting polyglycol and polyisocyanate are well known as casting or impregnating compositions or coating agents having rubber elasticity. The properties of these polyurethanes are influenced by the type of polyglycol and are appropriately selected depending on the intended use. For example, many elastomers use polyesters and polyethers containing hydroxyl groups, which have excellent hydrolysis resistance, heat resistance,
Poor electrical insulation properties. On the other hand, polyisocyanate used as a curing agent easily reacts with a compound having active hydrogen to form a chemical bond. For this reason, when used as a polyurethane elastomer, coating agent, adhesive, etc., it becomes a so-called two-component mixture that is mixed immediately before use, and the storage stability of the mixed solution is extremely short. Therefore, it is suitable for applications where mixing and curing takes place in a short period of time, and applications where cured products containing a few voids do not cause problems in use, but are suitable for large cast objects or impregnated objects that require a high degree of electrical insulation. To do so, many problems must be solved. For example, if the curing speed is very fast, the curing reaction will proceed without completely eliminating voids that are introduced during casting or impregnation, which is a major factor in causing insulation failure in electrical equipment. Furthermore, as mentioned above, cured products using polyester or polyether as the glycol component have poor hydrolysis resistance, heat resistance, and electrical insulation properties, so it is preferable to use them as insulating materials for electrical equipment that will be used for a long time. do not have. Therefore, there are almost no examples of using rubber-like or urethane elastomers, which require a high degree of electrical insulation. Insulating materials that have rubber elasticity and require a high degree of electrical insulation include butyl rubber and ethylene rubber.
Propylene rubber is the most commonly used rubber and has very good properties. However, butyl rubber and ethylene/propylene rubber have large molecular weights and therefore have very poor fluidity, making it impossible to manufacture various products by casting or impregnating processes like the aforementioned urethane elastomers. Generally, press molding and transfer molding are performed under high temperature and high pressure, and the same is true when applying insulation treatment to electrical equipment. When electrical equipment is insulated using the above-described molding method, the embedded material may be deformed or displaced due to the high temperature and pressure. Furthermore, when insulating between the layers of a coil around which electric wire is wound, the fluidity of the rubber raw material is very poor, so the rubber is not completely injected between the layers of the coil, resulting in poor insulation. Therefore, when insulating a very narrow gap such as between coil layers, it is necessary to perform interlayer insulation before molding, which is not a preferable method in terms of the manufacturing process. Furthermore, since molding is carried out at high temperatures and pressures, expensive equipment and molds are required, and energy consumption increases. In view of the above drawbacks, the present inventors have developed a thermosetting elastic material that has significantly improved workability compared to conventional urethane elastomers and has excellent mechanical properties, electrical properties, hydrolysis resistance, and heat resistance of the cured product. As a result of extensive research in order to obtain the desired results, the present invention was completed. That is, the gist of the present invention is to use a mixture of a hydrogenated polyhydroxybutadiene polymer and a bishydroxy compound of formula (1) in a specific ratio as a curing agent.
The present invention is characterized by using a diisocyanate compound of the formula (2), and provides a liquid rubber composition which has excellent workability and has significantly improved hydrolysis resistance, electrical insulation properties, and heat resistance of the cured product. The hydrogenated polyhydroxybutadiene polymer has an average number of hydroxyl groups of 1.5 or more per molecule, preferably 1.7 to 5.0. The number of these hydroxyl groups should correspond to the number of isocyanate groups used as a curing agent.
For example, when the number of hydroxyl groups is 2 or less, an isocyanate compound capable of forming a crosslinked structure can be selected and used depending on the required properties. As the hydrogenated product of this polyhydroxybutadiene polymer, for example, a homopolymer of 1,3-butadiene or a copolymer in which the content of vinyl monomer is usually 50% by weight or less, preferably 40% by weight or less with respect to butadiene. Some are hydrogenated. If the content of the vinyl monomer is 50% by weight or more, it is not preferable because the cured product will have poor elasticity. Examples of the vinyl monomer include styrene, acrylonitrile, methacrylic acid, acrylic acid, vinyltoluene, and vinyl acetate. Note that the homopolymer has 1.4-
It contains a butadiene residue consisting of a bond and a butadiene residue consisting of a 1,2-bond, and it is known that the proportions of these butadiene residues are different. In the present invention, any homopolymer can be used, but in particular, one in which the polymer chain contains 60% by weight or more of butadiene residues consisting of 1,4-bonds, and furthermore, 40% by weight or less of styrene residues. Those that exist are preferably used. If the butadiene residue consisting of the 1.4-bond is less than 60% by weight, the cured product will have poor elasticity and heat resistance. A specific example of the hydrogenated polyhydroxybutadiene polymer is ARCO's
Poly BD, R-45M, R-45HT, CS-15, CN
-15, and NISSO PBG-1000 manufactured by Nippon Soda,
There are products obtained by hydrogenating polyhydroxybutadiene such as PBG-2000 and PBG-3000 using a Raney catalyst or a stabilized nickel catalyst, and the hydrogenation rate is preferably 50% or more. More than one species can be mixed and used by adjusting the number of hydroxyl groups. If the hydrogenation rate is less than 50%, oxidative deterioration of the cured product occurs and heat resistance decreases, which is not preferable. The bishydroxy compound used in the present invention has the following structural formula: (However, R is an alkylene group of 2 to 4) It is a dihydric alcohol represented by, for example, 1.1
-isopropylidene-bis(P-phenylene-oxy)-diethanol, 1.1-isopropylidene-bis(P-phenylene-oxy)di-2-propanol, 1.1-isopropylidene-bis(P-
Phenylene-oxy)-dibutanol and the like are commercially available, and these can be used alone or in combination. The mixing ratio of the bishydroxy compound is the hydrogenated product of the polyhydroxybutadiene polymer.
The object of the present invention can be achieved by mixing 5 to 40 parts by weight per 100 parts by weight. If the amount of the bishydroxy compound is less than 5 parts by weight, it is not preferable because the heat resistance and mechanical properties of the cured product will deteriorate. Further, if the amount is 40 parts by weight or more, the elasticity of the cured product will be significantly lowered and the permanent elongation will be increased, so it is preferable that the bishydroxy compound be in the above range. Furthermore, the isocyanate compound which is an essential curing agent in carrying out the present invention is an isocyanate compound represented by the following structural formula.

[Formula] (wherein R ₁ , R ₂ and R ₃ are lower alkyl groups, and n is an integer of 1 to 4.) Alternatively, an isocyanate prepolymer which is an adduct of the above-mentioned isocyanate and glycol can be used as appropriate. The isocyanate has lower reactivity to active hydrogen than general isocyanate compounds such as 2.4-toluene diisocyanate and 4.4'-diphenylmethane diisocyanate, so it is difficult to combine the hydrogenated product of the polyhydroxybutadiene polymer with the bishydroxy compound. When used as a hardening agent in mixtures, the pot life is extended and workability during casting and impregnation is greatly improved. However, when the above-mentioned isocyanate is used as a curing agent for the hydrogenated polyhydroxybutadiene polymer alone, the cured product does not have sufficient moist heat deterioration characteristics or heat resistance, which deviates from the purpose of the present invention. If aromatic isocyanate is used as a curing agent, the above-mentioned drawbacks can be improved, but the pot life becomes extremely short, resulting in a decrease in workability. However, when a hydrogenated polyhydroxybutadiene polymer and a bishydroxy compound are mixed within the above range, the above isocyanate is used as a curing agent.
The object of the present invention can only be achieved by incorporating 10 to 51 parts by weight. If the isocyanate content of the curing agent is outside the above range, it is not preferable because after heat curing, only a sticky cured product or a cured product with very poor elasticity will be obtained. The liquid rubber composition of the present invention is
Long pot life during casting and impregnation work, and 50~
It can be easily thermally cured by heating at 150°C, and the curing time can also be adjusted by selecting the curing temperature and reaction catalyst. The liquid rubber composition of the present invention may also contain commonly used reinforcing fillers such as carbon black, talc, calcined clay, silicate, calcium carbonate, and hydrated alumina, as well as anti-aging agents and other additives as necessary. It is also possible to use a mixture of antioxidants, ultraviolet absorbers, fungicides, coupling agents, etc. The cured product obtained from the composition of the present invention is a rubber-like elastic body with excellent mechanical properties, hydrolysis resistance, heat resistance, electrical insulation properties, etc. The liquid rubber composition of the present invention can be used as a casting or impregnating composition or a coating agent, and as an adhesive, a potting agent for electronic parts, a coating agent, and an industrial rubber material for belts, hoses, etc.
It is extremely useful industrially for use in anti-vibration rubber, packing, etc. Next, the liquid rubber composition of the present invention will be described in detail with reference to reference agents and examples, but the present invention is not limited to these examples. Reference example 1 Poly, which is a polyhydroxybutadiene polymer
BDR-45M (manufactured by Arco, 1.4-trans 60 mol%, 1.4-cis 20 mol%, 1.2-vinyl 20 mol%, hydroxyl value 44) 120 g, Raney nickel catalyst 10
g and 100 g of dioxane were placed in autoclave 1 and hydrogenated at a hydrogen pressure of 10 Kg/cm ² and a reaction temperature of 80° C. to obtain a hydrogenated polyhydroxybutadiene polymer (hydrogenation rate of 95%). Reference example 2 Poly, which is a polyhydroxybutadiene polymer
BDCS-15 (manufactured by Arco, 1.4-trans 60 mol%, 1.4-cis 20 mol%, 1.2-vinyl 20 mol%,
100 g of a copolymer with a hydroxyl value of 42 and a ratio of butadiene to styrene of 75 to 25 (weight ratio) was hydrogenated in the same manner as in Reference Example 1 to obtain a hydrogenated polyhydroxybutadiene polymer (hydrogenation rate of 98%). Obtained. Reference example 3 Polyhydroxybutadiene polymer
NISSO PBG-2000 (manufactured by Nippon Soda Co., Ltd., 1.2-vinyl 90 mol%, 1.4-bond 10 mol%, hydroxyl value 58)
100 g was hydrogenated in the same manner as in Reference Example 1 to obtain a hydrogenated polyhydroxybutadiene polymer (hydrogenation rate 98%). Example 1 100g of hydrogenated polyhydroxybutadiene polymer obtained in Reference Example 1 and 1.1-isopropylidene-
Place 10g of bis(P-phenylene-oxy)di-2-propanol in a 200c.c. tall beaker, stir thoroughly in an 80℃ oil bath, and add 15.2g of 3-isocyanatomethyl-3.5.5-trimethylcyclohexylsiisocyanate. and mixed. This liquid mixture was transferred to an oil bath at 100°C, and the time from when it reached 100°C (initial viscosity of 30 poise) until it reached 1000 poise was measured. The time was 38 minutes. Next, a mixed solution separately prepared in the same amount as above was defoamed at 80° C. and poured into a polypropylene mold. After pouring, heat the mold at 150°C for 1 hour and make a 40cm
A cured sheet of 40 cm x 0.2 cm was obtained. The mechanical properties (tensile strength, elongation), electrical properties (volume resistivity), and electrical and mechanical properties after moist heat deterioration and after thermal deterioration of this cured sheet were determined according to JISK6301.
Measured according to JISK6911. The results of these measurements are shown in Table 2. Examples 2 to 10 Bishydroxy compounds were mixed in various ratios in the same manner as in Example 1 to 100 g of the hydrogenated polyhydroxybutadiene polymer obtained in Reference Examples 1 to 3. Next, a predetermined amount of 3-isocyanatemethyl-3.5.5-trimethylcyclohexyl isocyanate was added to these mixtures, and the viscosity increase was measured in the same manner as in Example 1. The composition and viscosity measurement results are shown in Table 1. Also,
A cured sheet with a thickness of 2 mm was prepared in the same manner as in Example 1, and its mechanical properties, electrical properties, moist heat deterioration characteristics, and thermal deterioration characteristics were measured. The results of these measurements are shown in Table 2.

【table】

【table】

[Table] As is clear from Tables 1 and 2, in the liquid rubber composition of the present invention, since the viscosity of the mixed liquid increases gradually, it not only significantly improves workability during casting and impregnation, but also The present invention provides a cured product that has excellent mechanical and electrical properties, heat resistance, and hydrolysis resistance. As mentioned above, the liquid rubber composition of the present invention not only has significantly improved workability compared to conventional urethane elastomers, but also improves the mechanical properties, electrical properties, and hydrolysis resistance of the resulting cured product. It has excellent heat resistance and has extremely high industrial value.

Claims (1)

[Claims] 1. An isocyanate represented by formula (2) is used as a curing agent for a polyol containing a hydrogenated polyhydroxybutadiene polymer and a bishydroxy compound represented by formula (1). liquid rubber composition. (However, R is an alkylene group having 2 to 4 carbon atoms) However, R ₁ , R ₂ and R ₃ are lower alkyl groups,
n represents an integer of 1 to 4. ) 2 A patent claim characterized in that a hydrogenated product of a polyhydroxybutadiene polymer in which 60% by weight or more of butadiene residues consisting of 1,4-bonds is present in the polymer chain is used as the hydrogenated product of a polyhydroxybutadiene polymer. The liquid rubber composition according to item 1. 3. As a hydrogenated product of a polyhydroxybutadiene polymer, it is recommended to use a hydrogenated product of a polyhydroxybutadiene polymer in which 60% by weight or more of butadiene residues and 40% by weight or less of styrene residues are present in the polymer chain. Characteristic claim 1
The liquid rubber composition described in . 4. The method according to any one of claims 1 to 3, characterized in that 5 to 40 parts by weight of the bishydroxy compound is blended to 100 parts by weight of the hydrogenated polyhydroxybutadiene polymer. Liquid rubber composition.