JPS6110932B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrically insulating prepreg as a spacer insulating prepreg used for insulating a superconducting conductor, and particularly to the above-mentioned prepreg having excellent strength and excellent temporary adhesion to a conductor. A superconducting conductor is one that has zero electrical resistance and a persistent current flows in liquid helium (-270°C), and spacer insulation prepregs used for this type of use usually have a continuous conductor between two running conductors. The drum is inserted into the drum and is temporarily bonded between the conductors through a heat-pressing process (in a state where it is firmly adhered to the surface to be adhered and can be temporarily fluidized and then hardened by heating). It is rolled up and stored. When it is used, it is shaped into a flat shape, diamond coil shape, etc. and heated to completely harden it. The prepreg subjected to the manufacturing process as described above is particularly required to have high tensile strength under normal conditions, high temporary bonding strength to the conductor, and no resin extrusion during crimping. This type of prepreg is made by impregnating a nonwoven fabric with a thermosetting resin composition to give it a semi-cured state and imparting temporary adhesion, or by attaching a nonwoven fabric to both sides of a polyester film, which is coated with an epoxy resin and fast-curing. There are prepregs, etc., in which a thermosetting resin composition containing an agent is arranged in a semi-cured form to improve strength and provide temporary adhesion, but nonwoven fabrics have poor tensile strength.
Temporary adhesion to the conductor is still insufficient, and since ordinary thermosetting resins semi-cure or harden through a flow process when heated, the resin protrudes during the above-mentioned crimping step, which causes uneven thickness. This has the disadvantage of causing poor appearance. As a result of extensive research to solve these technical problems, the inventors impregnated or coated a nonwoven fabric with substantially no heat shrinkability with a phenoxy resin, and further provided an epoxy resin composition layer on both sides of the nonwoven fabric. By adding a hot melt adhesive to the product, the above-mentioned problems were successfully solved all at once. Here, the average molecular weight of phenoxy resin is
It refers to a high molecular weight epoxy resin with a molecular weight of 10,000 to 100,000, which has a large reinforcing effect on nonwoven fabrics, and has a high melting point and does not flow when heated, so it does not extrude during pressure bonding. If the average molecular weight is too low, the reinforcing effect will be poor and there will be extrusion during pressure bonding, while if it is too high, it will be difficult to dissolve in ordinary solvents and the resulting impregnated sheet will tend to be hard. is used, and those with a molecular weight of 40,000 to 800,000 are particularly preferably used. A phenoxy resin or a phenoxy resin-based composition (hereinafter referred to as
The undercoating treatment agent) does not need to contain a curing agent, but if necessary, a curing agent such as butylated melamine resin or isocyanate resin that reacts with hydroxyl groups or epoxy groups, or a boron trifluoride-monoethylamine complex compound may be used. A curing accelerator such as may be added. The nonwoven fabric used in this invention is required to have substantially no heat shrinkage, that is, to have excellent thermal dimensional stability and high tensile strength, and is also required to have good impregnability and compatibility with phenoxy resin. selected with consideration. Examples of such products include “H-
8213” (Nippon Vilene Co., Ltd. product), “Spunbond” (Unitika Co., Ltd. product), “Axter” (Toray Industries, Ltd.)
polyester non-woven fabric such as ``JH-
There are heat-resistant nylon nonwoven fabrics such as ``1030CT'' (product of Nippon Vilene Co., Ltd.), ``Konex'' (product of Teijin Ltd.), and ``Nomex'' (product of DuPont). This nonwoven fabric usually has a thickness of 0.04 to 0.8 mm and a basis weight of ^about 15 to 300 g/m2.
~0.4mm is suitable. The undercoating treatment agent can be applied to the nonwoven fabric by a conventional method such as impregnating it with a solution, applying it by spraying or coating, and then drying it. In this case, the resin adhesion rate is usually 5 to 60% by weight, preferably 15 to 40% by weight, based on the undercoated sheet, in order to obtain the desired reinforcing effect. If the resin adhesion rate is too low, it is difficult to obtain a sufficient reinforcing effect on the nonwoven fabric, which is not preferable. On the other hand, if the amount increases too much, as will be explained later, there is a limit to the total amount of resin including the amount of resin provided on both sides of the undercoating sheet, so the amount of resin in the temporary adhesive layer on the surface must be reduced. There is a risk that the temporary adhesion to the conductor will deteriorate. The epoxy resin composition (hereinafter referred to as the top coating agent) placed on both sides of the undercoat treated sheet obtained in this way improves temporary adhesion to the conductor in the manufacturing process mentioned above, and also improves the temporary adhesion to the nonwoven fabric and the undercoat treatment sheet. In order to improve adhesion to processing agents, it is composed of a hot melt adhesive component as essential components in addition to a normal epoxy resin and a hardening agent, especially a fast-curing hardening agent. The molecular weight of the epoxy resin used for the top coating agent is
300 to 4000, and a bisphenol type epoxy resin with an epoxy equivalent of 140 to 5500 is suitable, and if necessary, a novolak type epoxy resin, alicyclic epoxy resin, brominated epoxy resin, polyglycol type epoxy resin, etc. can be used alone. Or they may be used together. As a curing agent, at 170℃ for less than 5 minutes, preferably
Preferably, imidazole-based curing agents, which gelatinize in about 2.5 minutes and have good storage stability, are used; in addition, polyamide resins, amine-based curing agents,
A curing agent such as an endogenous amine adduct-separated amine adduct precondensate, an amine salt, or an amine complex compound can be used alone or in combination. In addition to the above-mentioned epoxy resin and curing agent, hot melt adhesive components used in the top coating treatment agent include copolymerized nylon resin, methoxymethylated nylon resin, powdered polyethylene resin, butyral resin, polyvinyl formal resin, and hot melt polyamide resin. , these may be used alone or in combination. By blending these hot melt adhesive components into the top coating agent, excellent temporary adhesion to the conductor is provided, and adhesion to the bottom coating sheet is significantly improved.The preferred range of use is as follows: The amount is usually 550 to 200 parts by weight per 100 parts by weight of the epoxy resin in the top coating agent. If the hot melt adhesive component is too small relative to the epoxy resin in the top coating agent, there is a risk that the temporary adhesion to the conductor will be poor, and if it is too large, the adhesive strength with the conductor will be reduced in the cured product. This is undesirable because it tends to cause disadvantages and electrical properties such as dielectric breakdown voltage and volume resistivity deteriorate. In addition, if 5 to 30% by weight of the hot melt adhesive component is added to the above-mentioned undercoat treatment agent, the adhesiveness between the topcoat and undercoat treatment agents can be further improved and the electrical characteristics of the product after curing can be stabilized. show. To apply the top coating agent on both sides of the bottom coating sheet, if it is used as a solution, it can be done by impregnation, spraying, coating, etc., or if it is used as a powder, it can be done by spraying, static coating, etc. Conventional powder coating methods such as electrocoating, powder spraying, coating, etc. can be used. After the top coating agent is impregnated or applied in this manner, it may be dried or melted and applied in a semi-cured state to both surfaces of the bottom coating sheet. Powdered top coating agents are usually epoxy resin,
Resin components such as a curing agent and a hot melt adhesive component are selected to be solid at room temperature and have a melting point in the range of 50 to 150°C, and for practical purposes, those having a melting point of 60 to 120°C are preferred. This type of prepreg is usually stored as a tape or sheet wrapped around a drum, so if the melting point is less than 50℃, the resin will melt and flow in the summer and the curing reaction will gradually proceed, resulting in extremely poor shelf life. This is not preferable because it reduces the On the other hand, if the melting point of the resin exceeds 150°C, it is not preferable because it is difficult to melt during molding and cannot be cured. In addition to the above-mentioned advantages of using a powder with a melting point within the above-mentioned range, which improves temporary adhesion to the conductor and improves adhesion to the subbing sheet, It has the additional feature that it does not harden even if stored for a long time, and therefore, a faster curing agent can be used without any problems than when it is used in solution form, making it possible to perform the curing process in molding more efficiently. It should be noted that there is a recommended suitable range for the amount of the resin component in the top coating treatment agent in relation to the amount of resin attachment on the bottom coating sheet and the above-mentioned characteristics of the resulting product. That is, it is desirable that the resin content in the top coating agent be in the range of 10 to 40 parts by weight per 100 parts by weight of the resin content of the bottom coating sheet. However, the total amount of resin in the top coating agent and the bottom coating agent has its own limit due to the workability during pressure bonding, so the amount of resin deposited in the top coating agent must be selected in consideration of this point. A suitable adhesion range of this total resin amount to the weight of the prepreg is 30 to 80% by weight, and a range of 40 to 60% by weight is particularly desirable. If the total amount of resin is too small relative to the weight of the prepreg, there will be insufficient reinforcement of the nonwoven fabric or insufficient temporary adhesion to the conductor, while if it is too large, the resin will protrude during the above-mentioned pressing step, resulting in poor product quality. The thickness varies,
Further, since the flow of the resin increases, it is not possible to temporarily attach the resin to a fixed position, which is not preferable. The prepreg of the present invention is subjected to an undercoat treatment mainly using a high-molecular-weight phenoxy resin, so it has a large reinforcing effect on the nonwoven fabric, and has the characteristics that the resin does not protrude when it is crimped with a conductor. Furthermore, since both sides of the prepreg are coated with a hot melt adhesive component, it has excellent temporary adhesion to conductors. Furthermore, by using a powdered top coating agent, the product has the added feature of being able to withstand long-term storage. The present invention will be specifically explained below with reference to Examples. In the following, parts and % refer to parts by weight and % by weight, respectively. Example 1 Using a polyester nonwoven fabric "H-8213" (product of Nippon Vilene Co., Ltd.: thickness 0.35 mm, basis weight 150 g/ ^m2 ), bisphenol A-epichlorohydrin type phenoxy resin "Epicoat OL-53-B-40" was used. ” (Ciel Chemical Co., Ltd. product: average molecular weight 80,000) in a 30% methyl ethyl ketone solution, add the above phenoxy resin.
100 parts of polyamide resin "Tomide #1360" (Fuji Kasei Kogyo Co., Ltd. product: hot melt adhesive component) and curing agent (butylated melamine resin)
Add 10 parts and 50 parts of a 50% solution of "Super Betsucomin J-820" (product of Dainippon Ink & Chemicals Co., Ltd.), respectively, and immerse the whole in the solution adjusted to a 25% concentration to achieve a resin impregnation rate of 25%. A subbed-treated sheet was obtained. Next, this undercoating sheet was coated with bisphenol A-epichlorohydrin type epoxy resin "Epon #1007" (product of Ciel Chemical Co., Ltd., average molecular weight approx.
2900) 100 parts, 4,4'-diaminodiphenyl sulfone "4,4'DDS" (Ofrac product) 3.9
Part, diaminodiphenylmethane "Sumikyure"
0.8 parts of ``M'' (product of Sumitomo Chemical Co., Ltd.), 5 parts of 2-phenyl-4,5-dihydroxylimidazole ``Kyuazol 2PHZ'' (product of Shikoku Kasei Kogyo Co., Ltd.), and polyamide resin ``Tomide #1360'' (former). After immersing a blended resin consisting of 10 parts of methyl ethyl ketone and toluene in a solution adjusted to a 30% concentration with a mixed solvent of equal amounts of methyl ethyl ketone and toluene, it was dried at 100°C for 15 minutes, and the top coat resin was semi-cured on both sides of the bottom coat treated sheet. A prepreg of the present invention was obtained. The total resin impregnation rate of the obtained prepreg was 55%. Example 2 Polyamide nonwoven fabric "JH-1030CT" (product of Nippon Vilene Co., Ltd.: thickness 0.33 mm, basis weight 300 g/m <sup>2</sup> ) was used, and phenoxy resin "KXR-24" (product of Sumitomo Chemical Co., Ltd.) was used. To 100 parts of phenoxy resin, 20 parts of copolymerized nylon hot melt adhesive component "Platamide H-105P" (manufactured by Nippon Rilsan Co., Ltd.) was added to a 35% methyl ethyl ketone solution with an average molecular weight of approximately 50,000, making the total concentration 25%. The sheet was immersed in a solution adjusted to 30% and then dried at 100°C for 15 minutes to obtain a subbed sheet with a resin impregnation rate of 30%. Next, this undercoating sheet was coated with bisphenol A-epichlorohydrin epoxy resin "Epon #1001" (product of Ciel Chemical Co., Ltd.: average molecular weight approximately 900).
100 parts, copolymerized nylon hot melt adhesive component "Platamide H-105P" (mentioned above) 100 parts, powdered polyethylene hot melt adhesive component "Frozen"
20 parts of ``UF'' (manufactured by Seitetsu Kagaku Co., Ltd.) and 20 parts of 1-cyanoethyl-2-phenyl-4,5-di(cyanoethoxymethyl)imidazole ``Kyuazole 2PHZ-
After impregnating a compounded resin consisting of 5 parts of "CN" (product of Shikoku Kasei Kogyo Co., Ltd.) in a solution adjusted to a concentration of 30% with a mixed solvent of equal amounts of methyl ethyl ketone and toluol, the mixture was heated at 80°C.
The prepreg sheet of the present invention was dried for 15 minutes to obtain a prepreg sheet of the present invention in which the top coat resin was semi-cured on both sides of the bottom coat treated sheet. The total resin impregnation rate at this time is 60%
It was hot. Comparative Example 1 The polyester nonwoven fabric used in Example 1 was impregnated with a solution prepared by adjusting the top coating resin of Example 1 to a concentration of 30% under the same conditions as in Example 1, and the process of drying was repeated twice. As a result, a conventional prepreg sheet that does not use phenoxy resin for undercoating was obtained. The resin impregnation rate of the obtained sheet was 55%. Comparative Example 2 The polyamide nonwoven fabric used in Example 2 was impregnated with a solution of the blended resin for top coating of Example 2 adjusted to a concentration of 30%, and dried at 80° C. for 15 minutes. Impregnation and drying was carried out again under the same conditions to obtain a conventional prepreg sheet in which no phenoxy resin was used in the undercoat treatment. The total resin impregnation rate of the obtained sheet was 60%. Test example 1 <. Evaluation of physical properties of prepreg tape> Using a sample with a thickness of 0.45 mm and a width of 8 mm, JIS C2120
The results of measuring tensile strength and dielectric breakdown voltage according to Table 1 are as shown in Table 1, and the tape of the present invention was superior to the conventional tape in both cases.

[Table] <. Temporary adhesion evaluation of prepreg tape> Using a sample with a thickness of 0.45 mm and a width of 4 mm, it was placed on a rectangular copper wire preheated to 175°C, and the temperature was maintained at 175°C by pressing lightly from above to temporarily adhere for 2 minutes. As shown in Table 2, the 180° peel strength of the tape of this invention was superior to that of the conventional tape. In addition, using a sample with a thickness of 0.45 mm and a width of 8 mm, the temperature
Table 2 shows the results of observing the protrusion of the resin when the wire was pressed against a rectangular copper wire for 5 hours at 120° C. and a pressing rate of 20%.

[Table] Example 3 Using polyester nonwoven fabric "H-8213" (mentioned above), phenoxy To 100 parts of the resin, 10 parts of the polyamide resin "Tomide #1360" (mentioned above) was added, and the whole was immersed in a solution adjusted to a concentration of 20% to obtain a subbing-treated sheet with a resin impregnation rate of 25%. Next, as the top coating resin, we used bisphenol A-epichlorohydrin type epoxy resin “Epon #1002”.
(Ciel Chemical Co., Ltd. product: average molecular weight 900) 70 parts, copolymerized nylon hot melt adhesive component "Platamide H-105P" (mentioned above) 100 parts, powdered polyethylene hot melt adhesive component "Frocene UF" (stated above) )
20 parts, 2-methylimidazole "Kyuazole"
7 parts of ``2MZ'' (product of Shikoku Kasei Kogyo Co., Ltd.) and silica-based filler ``Aerosil'' (product of Nippon Aerosil Co., Ltd.)
A blended resin consisting of 5 parts was ground to obtain 60 mesh powder. This powder was applied to both sides of the undercoating sheet using an electrostatic coating method at 70°C.
A prepreg sheet of the present invention was obtained by heating and fusing for 1 minute. The total resin impregnation rate at this time is 55
It was %. Test Example 2 <Temporary adhesion property evaluation of prepreg tape> Using a sample with a width of 4 mm, when temporarily adhering it to a rectangular copper wire for 2 minutes at 175°C using the same method as in Test Example 1,
The 180° beer peel strength was as shown in Table 3.
Table 3 also shows the results of a temporary adhesion test similar to the above after storage at 40°C for one month. As is clear from Table 3, the peel strength in Example 3 was also good, and in particular in this case, it was found that the preservability was extremely excellent due to the powdery top coating treatment.

【table】

Claims (1)

[Scope of Claims] 1. An electrical insulation prepreg as a spacer insulation prepreg used for insulating superconducting conductors, which comprises on both sides of a nonwoven fabric impregnated or coated with phenoxy resin and having substantially no heat shrinkability,
A prepreg for electrical insulation comprising an epoxy resin composition containing a hot melt adhesive component. 2. The prepreg for electrical insulation according to claim 1, wherein a powdered epoxy resin composition is fused to both sides of the prepreg.