JPS637205B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a liquid rubber flame-retardant composition that can be easily cast, impregnated, or coated, and has excellent rubber elasticity, high electrical insulation properties, and flame retardancy after curing. Conventionally, when electrical discharge occurs in electrical equipment such as molded transformers and transformers, organic materials used as insulators decompose and form carbonaceous precipitates, which in turn form low-resistance conductive paths. This causes premature destruction of electrical equipment. Furthermore, since these electrical devices are normally used for long periods of time in various environments such as high temperature, high humidity, and dusty atmospheres, tracking failure may occur. Furthermore, a combustion accident may occur from an arc caused by a sudden short circuit accident. Therefore, molding materials used as insulating materials are required to have a high degree of electrical insulation, as well as arc resistance, tracking resistance, and flame retardancy in order to prevent accidents such as those mentioned above. ing. As a method to satisfy these required characteristics, commonly used molding materials such as ethylene propylene terpolymer, elastic materials such as butyl rubber,
A method is known that uses a composition in which hydrated alumina (Al ₂ O ₃ , BH ₂ O) is mixed as a flame-retardant filler into a thermosetting resin such as an epoxy resin or an unsaturated polyester resin. Furthermore, compositions that use halogen-based additive flame retardants are also known. However, these methods not only cannot be expected to be effective unless a large amount of hydrated alumina or flame retardant is blended, but also may cause a significant deterioration of electrical properties. In addition, the above-mentioned epoxy resins and unsaturated polyester resins are liquid molding materials that can be molded and have excellent workability, but the cured products have low arc resistance and tracking resistance, as well as poor hydrolysis resistance. Currently, there are restrictions on use outdoors and in environments with high temperatures and humidity. On the other hand, EPT rubber and butyl rubber, which are elastic materials, are suitable molding materials because they have a high degree of insulation and are stable in various environments. However, EPT rubber and butyl rubber have very large molecular weights and poor fluidity, so they cannot be used at high temperatures or
Electrical equipment requires high pressure and must be manufactured by compression molding, extrusion molding, transfer molding, etc. When manufacturing electrical equipment using the above-mentioned molding method, the embedded material may be deformed or misaligned due to high temperatures and pressures, and the fluidity of the rubber may be poor, causing gaps between the coil layers and the primary coil. In many cases, rubber is not completely injected into the insulation space of the secondary coil, etc., resulting in insulation failure. In order to prevent these insulation defects, conventional moldings have had the disadvantage of requiring reinforcement against the pressure of the embedded material and sufficient insulation treatment before molding. Furthermore, since molding is performed at high temperature and high pressure, expensive equipment and molds are required, and energy consumption is also large, so this method cannot be said to be preferable in terms of the manufacturing process. The liquid rubber used in the present invention, which will be described later, uses a compound represented by the general formula (2) as a curing agent for hydrogenated polyhydroxybutadiene polymer as a main ingredient, so the bond that extends the molecular chain (curing reaction) is a urethane bond.

In [Formula], the main chain skeleton is a polyolefin structure connected by methylene chains. (However, R ₁ , R ₂ , and R ₃ represent lower alkyl groups, and n represents an integer of 1 to 4.) Flame retardation of such polyolefins is usually done using antimony oxide, organic halogen compounds, or phosphate esters. Methods of adding compounds and methods of blending or copolymerizing vinyl chloride with resin have been used. However, these methods have problems such as the fact that the antimony oxide and phosphate ester compounds themselves are toxic, that they generate halogen gases when burned, and that the type and amount of flame retardant used can degrade electrical and mechanical properties. contains the problem of Another flame retardant method is to fill the product with an inorganic compound containing water of crystallization, but in this case a considerable amount of the inorganic compound must be mixed in to obtain sufficient flame retardancy. The mechanical properties of the resin are significantly reduced. Therefore, although the former and latter flame retardant methods are considered appropriate for making polyolefin resins flame retardant depending on the application, many problems still remain. As described above, conventional liquid rubbers are required to have low viscosity and long pot life, but the toxicity of flame retardants and deterioration of the physical properties of resins have become problems, and an appropriate flame retardant method has not been established. That is the reality. The present invention was developed in view of the above-mentioned drawbacks, and allows manufacturing of all kinds of electrical equipment by vacuum casting and impregnation processes that do not require high temperatures or high pressures, and has extremely excellent elasticity after curing. As a result of intensive research to obtain a liquid rubber flame retardant composition with excellent flame retardancy, arc resistance, and tracking resistance, the present invention was completed. That is, the gist of the present invention is to apply water to a liquid rubber composed of an isocyanate compound represented by the above general formula (2) as a curing agent for a mixture of a hydrogenated polyhydroxybutadiene polymer and a bishydroxy compound. By blending Japanese alumina and magnesium hydroxide within a specific range, the greatest advantages of liquid rubber, such as casting workability and impregnation workability, are not reduced, and the cured product has excellent flame retardancy, electrical insulation, A liquid rubber flame retardant composition with excellent arc resistance, tracking resistance, water resistance, and heat resistance was obtained. The hydrogenated polyhydroxybutadiene polymer used in the present invention has an average number of hydroxyl groups of 1.5 or more per molecule, preferably 1.7 to 5.0. In particular, it is preferable that the polymer chain contains 60% by weight or more of butadiene residues consisting of 1,4 bonds, and more preferably that the above-mentioned butadiene residues are present in the polymer chain.
Contains 60% by weight or more and 40% by weight of styrene residue.
The following are used: The above butadiene residue is
If it is less than 60% by weight, the heat resistance will not be sufficient and the rubber elasticity will be poor. On the other hand, if the styrene residue is 40% by weight or more, the elasticity will be insufficient. A specific example of a hydrogenated product of this polyhydroxybutadiene polymer is a 1,3-butadiene homopolymer or a vinyl monomer such as styrene, acrylonitrile, methacrylic acid, vinyltoluene or vinyl acetate in an amount of 50% by weight based on butadiene.
The following copolymers are hydrogenated using a conventional method. In addition, as a bishydroxy compound to be mixed with the hydrogenated product of polyhydroxybutadiene polymer, a dihydric alcohol represented by the following structural formula (1) is used. (However, in the formula, R represents a lower alkyl group having 2 to 4 carbon atoms.) For example, 1,1-isopropylidene-bis(P-phenylene-oxy)-diethanol or 1,1-isopropylidene-bis(P-phenylene-oxy)-diethanol can be used. Redenbis (P
-phenylene-oxy)di-2-propanol,
1,1-isopropylidene-bis(P-phenylene-oxy)-dibutanol and the like are commercially available. These can be used alone or in combination of two or more. The blending ratio of the bishydroxy compound is the hydrogenated product of the polyhydroxybutadiene polymer.
The object of the present invention can be achieved by adding 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. Further, in carrying out the present invention, the isocyanate compound which is an essential curing agent is an isocyanate compound represented by the following structural formula (1). (However, in the formula, R ₁ , R ₂ , and R ₃ represent lower alkyl groups, and n represents an integer of 1 to 4.) Alternatively, an isocyanate prepolymer that is an adduct of the isocyanate and glycol may be used as appropriate. can. The isocyanate represented by the above formula (1) has lower reactivity with active hydrogen than general isocyanate compounds such as 2,4-toluene diisocyanate and 4,4'-diphenylmethane diisocyanate, so the polyhydroxybutadiene polymer When the hydrogenated compound and the bishydroxy compound are used as a curing agent, the pot life is extended and the 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. The use of aromatic isocyanate as a curing agent can improve the above-mentioned drawbacks, but the pot life becomes extremely short, resulting in a decrease in workability. However, for the mixture of the hydrogenated polyhydroxybutadiene polymer and the pishydroxy compound in the above specific ratio according to the present invention,
The isocyanate represented by (2) is used as a curing agent in an amount corresponding to 0.9 to 1.3 equivalents of isocyanate groups, that is, 10 to 51 parts by weight, per equivalent of hydroxyl groups in the mixture consisting of the hydrogenated compound and the pishydroxy compound. This eliminates the above drawbacks. If the isocyanate used as a 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. Furthermore, the hydrated alumina used in the present invention is an inorganic compound represented by the general formula Al ₂ O ₃ .3H ₂ O, and commercially available products can be used as appropriate. Hydrated alumina gradually releases water of crystallization (starts at about 200°C) before the thermal decomposition temperature of the cured liquid rubber (starts around 250°C and decomposes rapidly at about 400°C). Suitable as a flame retardant for rubber. Furthermore, the magnesium hydroxide used in the present invention has the general formula
It is represented by Mg(OH) ₂ , and commercially available products can also be used as appropriate. Magnesium hydroxide is about 300
The release of water of crystallization begins at 350°C and is completely released at around 350°C, so it exhibits the most effective flame retardant effect as a flame retardant for liquid rubber. The flame retardant used in the present invention is free from toxicity as described above, is inexpensive, and is suitable as a flame retardant for liquid rubber, but neither of the two flame retardants can be used alone. For example, in the case of hydrated alumina alone, if it is added to the liquid rubber in an amount that provides sufficient flame retardancy, the cured product will have significantly lower elasticity and very little elongation. Furthermore, when magnesium hydroxide is used alone, the viscosity of the base agent increases significantly, resulting in a compound with poor casting and impregnation workability, and the strength of the cured product is also reduced. Although it is not possible to use hydrated alumina and magnesium hydroxide alone as flame retardants for such liquid rubber, the present inventors have determined that hydrated alumina and magnesium hydroxide cannot be used alone as flame retardants for such liquid rubber, but they can be used in specific proportions that fully consider the thermal decomposition characteristics of liquid rubber and the reinforcing properties of cured products. By combining both flame retardants,
A new fact has been discovered that shows that the object of the present invention can be fully achieved. A suitable ratio of hydrated alumina and magnesium hydroxide for carrying out the present invention is 60 to 150 parts by weight of hydrated alumina to 100 parts by weight of the hydrogenated material of the liquid rubber main ingredient, that is, polyhydroxybutadiene polymer. Both are blended with magnesium hydroxide in a range of 5 to 50 parts by weight. Outside this range, the cured product of the liquid rubber may not have sufficient flame retardancy, or the casting and impregnating workability and properties of the cured product may be significantly reduced, which is not preferable. Next, in order to specifically explain the present invention, reference examples and examples will be described, but the present invention is not limited only to these reference examples and 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 dioxane 100 g were placed in autoclave 1, hydrogen pressure 10 Kg/cm ² , reaction temperature 80 ℃
Hydrogenation was carried out to obtain a hydrogenated polyhydroxybutadiene polymer (hydrogenation rate: 95%). Reference example 2 Poly, which is a polyhydroxybutadiene polymer
BDCS-15 (Arco 1,4-trans 60 mol%, 1,4-cis 20 mol%, 1,2-vinyl 20
Mol%, hydroxyl value 42, butadiene to styrene 75 pairs
25 (weight ratio)) was hydrogenated in the same manner as in Reference Example 1 to obtain a hydrogenated polyhydroxybutadiene polymer (hydrogenation rate 98%). Reference example 3 Polyhydroxybutadiene polymer
NISSOPBG-2000 (manufactured by Nippon Soda Co., Ltd., 1,2-
100 g of vinyl (90 mol%, 1,4-bond 10 mol%, hydroxyl value 58) was hydrogenated in the same manner as in Reference Example 1 to obtain a hydrogenated polyhydroxybutadiene polymer (hydrogenation rate 98%). . Example 1 100 g of the hydrogenated polyhydroxybutadiene polymer obtained in Reference Example 1, 10 g of 1,1-isopropylidene-bis(P-phenylene-oxy)di-2-propanol, and hydrated alumina (manufactured by Showa Denko) Place 125 g of Hygilite H-31), 25 g of magnesium hydroxide (Kisuma 4AF, manufactured by Kyowa Kagaku Co., Ltd.), and 3 g of carbon black in a container, heat and stir at 80°C, and then uniformly disperse the filler and carbon black. Therefore, kneading was performed using three rolls to obtain a sheet-like kneaded product. The kneaded material was placed in a beaker at 300°C and heated in an oil bath at 90°C. Next, 15.2 g of 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate was added and mixed, and the time from the time the temperature reached 90°C (initial viscosity 51 lbs.) to the time the viscosity reached 1000 poises was measured. The time was 27 minutes. In addition, the mixture prepared in the same manner as above was heated to 90°C.
After stirring and defoaming, the mixture was poured into a polypropylene mold. After pouring, heat the mold at 150℃ for 1 hour and make a 20cm x 20
A cured sheet measuring cm x 0.2 cm was obtained. Mechanical properties (tensile strength, elongation) and electrical properties (volume resistivity, arc resistance, tracking resistance) of this cured sheet
The flammability, water resistance, and heat resistance were investigated. The results of these measurements are shown in Table 1.

【table】

[Table] Examples 2 to 9 Hydrogenated products of the polyhydroxybutadiene polymers obtained in Examples 1 to 3, bishydroxy compounds, hydrated alumina, magnesium hydroxide, and carbon black were mixed in the amounts shown in Table 2. The mixture was kneaded in the same manner as in Example 1 to obtain a sheet-like kneaded product. 3-Isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate was added to the kneaded product in the amount shown in Table 2 in the same manner as in Example 1, and the change in viscosity was measured. Cured sheets were also prepared in the same manner and the properties of the cured materials were measured. The results of these measurements are shown in Table 2.

[Table] As shown in Table 2, the liquid rubber flame retardant composition according to the present invention contains 100 parts by weight of a hydrogenated polyhydroxybutadiene polymer and 5 to 40 parts by weight of a bishydroxy compound represented by the general formula (1). The main ingredient is a mixture of 60 to 150 parts by weight of hydrated alumina as a flame retardant filler and 5 to 50 parts by weight of magnesium hydroxide, and a curing agent of the general formula By using the specific isocyanate compound shown in (2), a liquid rubber composition having a viscosity and pot life sufficient for casting or impregnation operations can be obtained. Examples of the cured product of this composition are shown in Tables 1 and 2, which show electrical insulation, arc resistance, tracking resistance, water resistance, heat resistance,
It is a rubber elastic body with excellent flame retardancy, and its industrial value is extremely large.

Claims (1)

[Claims] 1. 5 to 40 parts by weight of a bishydroxy compound represented by general formula (1), 60 to 60 parts by weight of hydrated alumina, based on 100% by weight of hydrogenated polyhydroxybutadiene polymer.
150 parts by weight, 5 to 50 parts by weight of magnesium hydroxide,
and a liquid rubber flame retardant composition comprising an isocyanate compound represented by formula (2) as a curing agent. (However, in the formula, R represents an alkyl group having 2 to 4 carbon atoms.) (However, in the formula, R ₁ , R ₂ , and R ₃ represent a lower alkyl group, and n represents an integer of 1 to 4.) 2 As a hydrogenated product of a polyhydroxybutadiene polymer, 1, The liquid rubber flame-retardant composition according to claim 1, characterized in that a hydrogenated product of a polyhydroxybutadiene polymer containing 60% by weight or more of butadiene residues consisting of 4 bonds is used. 3 As a hydrogenated product of polyhydroxybutadiene polymer, 60% by weight of butadiene residues are added to the polymer chain.
2. The liquid rubber flame retardant composition according to claim 1, which uses a hydrogenated polyhydroxybutadiene polymer containing styrene residues of 40% by weight or less. 4 0.9 to 0.9 to 0.9 to 0.9 to 0.9 to 0.9 to 0.9 to 0.9 to 0.9 as isocyanate groups to the hydroxyl equivalent of a mixture consisting of a hydrogenated product of a polyhydroxybutadiene polymer and a bishydroxy compound.
The liquid rubber flame retardant composition according to any one of claims 1 to 3, which contains a curing agent in an amount equivalent to 1.3 equivalents.