JPS6328938B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a polyurethane insulated wire that has brazing properties and excellent heat resistance and crazing resistance. Polyurethane insulated wires have brazing properties that allow them to be soldered without peeling off the insulating film coated on the conductor, and are therefore widely used in coil windings for light electrical applications. In recent years, as equipment has become smaller and lighter, insulated wires have emerged that have heat resistance of Class B and F, which is even higher than the heat resistance class E of conventional polyurethane insulated wires, without impairing the soldering properties. desired. Furthermore, polyurethane insulated wires have drawbacks such as crazing and the formation of pinholes (underwater pinholes) when elongated by 3%, and preventing this has also been a technical issue. The brazing properties and heat resistance properties of polyurethane insulated wires are in a trade-off relationship; improving one will impair the other. Conventionally, using a general polyisocyanate block as a crosslinking component has not improved the properties. Due to the limitations, the present invention synthesizes a new polyisocyanate block body,
An insulating paint made by dissolving this and an oligomer or prepolymer containing activated hydrogen in an organic solvent was applied and baked onto a conductor, and a heat-resistant polyurethane insulated wire was successfully obtained. On the other hand, various polyurethane insulated wires with improved crazing have been developed, but these generally have low thermal properties and contain activated hydrogen as a polyol component blended into the polyisocyanate block body, which is a crosslinking component. However, instead of a general-purpose polyester prepolymer with a small molecular weight and a hydroxyl equivalent of about 70 to 150, we use an epoxy prepolymer with activated hydrogen and a molecular weight of 3000 and a hydroxyl equivalent of about 300, which is completely non-crazing. However, when a pinhole test is performed by applying 12 V DC while being stretched in 0.2% saline, crazing occurs. In addition, it is also possible to use a difunctional isocyanate block as the polyisocyanate component, such as a block obtained by stabilizing diphenylmethane diisocyanate with xylenoleic acid, but even this method cannot completely prevent craze. The present invention has also succeeded in solving this problem of crazing resistance. The novel isocyanate crosslinking agent developed by the present inventors is a diisocyanate block obtained by reacting a diol having a spiroacetal ring with a diisocyanate compound and blocking the remaining isocyanate groups with a phenol compound. Specifically,
constitutive formula (In the formula, R ₁ is

【formula】

【formula】

[Formula] R ₂ is

【formula】

【formula】

【formula】

【formula】

Each group of [Formula] is shown. ). Since a diol having a spiroacetal ring has a spiroacetal ring as its skeleton and alcoholic hydroxyl groups at both ends, it easily reacts with a diisocyanate compound to form a urethane bond. This reaction is carried out with an excess amount of diisocyanate,
A diisocyanate block obtained by blocking and stabilizing the remaining isocyanate groups with a phenol-based compound is difunctional and has an extremely long molecular chain compared to conventional diisocyanate blocks. Synthesis Example 1 Synthesis of spiroacetal-modified toluene diisocyanate block (SPG-TDI-cresol crosslinking agent) 91.2 g of spiroacetal glycol ( 0.3 mol), 261.2 g of xylene as a reaction diluent, and 0.8 g of triethylamine as a catalyst were weighed and added, and stirred thoroughly to uniformly disperse the mixture. Next, 104.4 g (0.6 mol) of weighed toluene diisocyanate was placed in a separating funnel.
This is gradually added dropwise to react with spiroacetal glycol. At this time, the temperature of the reaction system is approximately 70℃
rise to During this time, stir thoroughly. When the temperature of the reaction system returns to room temperature, m-cresol is further added to block the remaining isocyanate groups.
Add 64.8g, infrared absorption band of isocyanate 2240
Continue stirring until it is confirmed that cm ^-1 is gone. At the end of the reaction, the solid content of the reaction system is 30%.
Add 348g of m-cresol so that
-TDI-cresol block solution. Synthesis Example 2 Synthesis of spiroacetal-modified diphenylmethane diisocyanate block (SPG-MDI-cresol crosslinker) In a 4-neck separable flask equipped with a thermometer, stirrer, cooling tube, and separating funnel, add spiroacetal glycol 91.2 g (0.3 mol), 306 g of xylene as reaction diluent, triethylamine as catalyst
Weigh and add 0.8g and stir thoroughly to disperse uniformly. Next, in a separating funnel, 150 g (0.6 mol) of diphenylmethane diisocyanate was added to 45
It is heated as a liquid at ℃ and then gradually added dropwise to react with spiroacetal glycol. At this time, the temperature of the reaction system rises to 50-60°C. During this time, stir thoroughly. When the temperature of the reaction system returned to room temperature, 64.8 g of m-cresol was added to block the remaining isocyanate groups, and stirring was continued until it was confirmed that the infrared absorption band of isocyanate at 2240 cm ^-1 disappeared. do. When the reaction was completed, 408 g of m-cresol was added so that the solid content of the reaction system was 30% to prepare an SPG-MDI-cresol block solution. In addition to the above bifunctional blocked isocyanate having a spiroacetal ring, a trifunctional blocked isocyanate having an isocyanuric ring is used as a crosslinking component in the present invention. Isocyanur modified triisocyanate block is CT
It is commercially available as -stable (product name manufactured by Bayer, West Germany). The OH component for reacting with the above bifunctional and trifunctional blocked isocyanate crosslinking agent to form a urethane bond is a prepolymer having an alcoholic hydroxyl group, preferably a prepolymer having an activated hydrogen, a molecular weight of 3000 or more, and a hydroxyl equivalent of about 300. Epoxy prepolymers are used. Example Using the spiroacetal-modified diisocyanate blocks and isocyanur-modified triisocyanate blocks obtained in Synthesis Examples 1 and 2 as crosslinking agents, a prepolymer having an alcoholic hydroxyl group was blended with the composition shown in the table below, and cresol and A polyurethane insulation paint was prepared by dissolving the resin in a mixed solvent of xylol to a resin concentration of 30%.
This paint was applied to a copper wire having a conductor diameter of 0.35 mm in a uniform thickness and baked to produce a polyurethane insulated wire according to the present invention.

[Table] The properties of the obtained polyurethane insulated wire are shown in the table below. As a comparative example, the characteristics of a conventionally known general-purpose polyurethane insulated wire that does not contain spiroacetal rings in the coating composition are shown.

【table】

[Table] As mentioned above, the blocked isocyanate crosslinking agent having a spiroacetal ring used in the present invention has an extremely long molecular wire compared to conventional diisocyanate blocks, and this is reacted with a prepolymer having an alcoholic hydroxyl group. In this case, the distance between crosslinks can be increased, and the molecular structure of the insulating film becomes more similar to a linear molecule. Therefore, in the polyurethane insulated wire according to the present invention, flexibility is imparted to the coating, and heat resistance is significantly improved due to the oxidation-resistant effect of the spiro ring having four oxygen atoms in the ring. That is, as is clear from the characteristic table, the residual rate of dielectric breakdown voltage after heat aging, which indicates resistance to aging, is as high as 59 to 68%, and the TGI value calculated from the heating loss curve of the insulation film is also high.
It shows a high value of 142-152. At the same time, the problem of crazing, which had been a technical problem in the past, was completely resolved. Furthermore, in the present invention, as the isocyanate crosslinking component, 2 having a spiroacetal ring is used.
Since a functional blocked isocyanate and a trifunctional blocked isocyanate having an isocyanuric ring were used together, the reduction in the thermal softening temperature of the film that would occur due to the low crosslinking density when only a bifunctional blocked isocyanate with a long molecular chain was used could be avoided. It has the effect of preventing heat resistance without impairing it. In addition, the blocking isocyanate crosslinking agent is a prepolymer with NCO groups and alcoholic hydroxyl groups.
The reason why the reaction equivalent ratio with the OH group was limited to a ratio of 1:0.7 to 1.2 is because if it deviates from this range, the crosslinking reaction will be insufficient and the insulating film will become thermally and mechanically brittle. be.

Claims (1)

[Claims] 1 A blocked isocyanate obtained by the reaction of a diol having a spiroacetal ring and a diisocyanate compound and a blocked isocyanate having an isocyanuric ring are used as crosslinking components, and a prepolymer having an alcoholic hydroxyl group is added to this as a crosslinking component.
The NCO groups of the above-mentioned blocked isocyanate crosslinking agents and the OH groups of the above-mentioned prepolymer are added at a reaction equivalent ratio of 1:0.7 to 1.2, and an insulating coating obtained by dissolving in an organic solvent is applied directly onto the conductor or A polyurethane insulated wire characterized by being coated and baked through an insulating film.