JPH06295620A - Polyurethane mixture for electric insulation - Google Patents

Abstract

PURPOSE:To improve characteristics to be poured in, electric insulation property and mechanical strength by generating a polyurethane mixture through a process to mix castor oil with specified liquid to enhance the poured characteristics. CONSTITUTION:5-25 pts. by wt. of polyhydric alcohol is mixed in 75-95 pts. by wt. of castor oil as polyole of recinoleic having fatty acid containg hydroxyl group 90%, thereby improving poured characteristic as well as enhancing electircal insulation characteristic and mechanical strength. Further, through a process of mixing liquefied MDI or polymeric MDI therein the poured characteristic is improved. At this time, the mixing ratio of liquid B comprising the liquefied MDI as well as polyhydric alcohol liquid A is set such that the ratio of NCO and OH included in the two is in a range of 0.8-1.2. It is thus possible to provide a polyurethane mixture excellent in electric insulation characteristic, mechanical strength and pored characteristic.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyurethane mixture for electrical insulation, which is excellent in electrical insulation and mechanical strength and has good injection properties.

[0002]

2. Description of the Related Art Polyurethane resins are characterized by having a urethane bond by the reaction of a polyol and a polyisocyanate, and resins having a wide range of properties from soft to hard have been obtained by combining various polyols and polyisocyanates. Examples of the polyol include polyether polyol, polytetramethylene ether glycol, tetrahydrofuran; alkylene oxide copolymerized polyol, polyester polyol, polybutadiene polyol, and other polyols. There are many types of polyisocyanates in addition to TDI and MDI, but both are most commonly used.

[0003]

Polyurethane resins obtained by combining these polyols and polyisocyanates generally have lower electrical insulating properties and mechanical strength than epoxy resins and unsaturated polyester resins, and therefore these types of properties are required. It is blocked from being used for alleged uses. For example, polyurethane obtained by combining polybutadiene polyol and polyisocyanate has excellent electrical insulation properties, but has the disadvantages of high viscosity, poor injection properties, softened cured products and low mechanical strength. Polyurethane obtained from castor oil and polyisocyanate, which are other natural polyols, is known to have relatively good electrical insulation properties. It has a low viscosity and good injection properties, but its mechanical strength is insufficient, and it has an electrical insulation property. It is hoped that the performance will be even higher.

It is an object of the present invention to provide a polyurethane blend for electrical insulation which has improved injectability, electrical insulation and mechanical strength.

[0005]

DISCLOSURE OF THE INVENTION According to the present invention, as a polyol, a liquid A comprising 75 to 95 parts by weight of castor oil and 5 to 25 parts by weight of a low molecular weight polyhydric alcohol having a molecular weight of 62 to 134 and a liquefied polyisocyanate are used. It is a mixture of liquid B consisting of MDI and / or polymeric MDI, and the mixing ratio of liquid A and liquid B is N
Mix so that the ratio of CO and OH is in the range of 0.8 to 1.2.

[0006]

According to the above constitution, castor oil as a polyol is ricinoleic acid having about 90% of the constituent fatty acids having a hydroxyl group, and when this is mixed with a polyhydric alcohol, the injection property becomes good and at the same time polyisocyanate is obtained. By using liquefied MDI (diphenylmethane diisocyanate) modified to be liquid at room temperature or polymeric MDI that is liquid at room temperature, the injection property becomes good, and the electrical insulation and mechanical strength can be improved.

The castor oil used in the present invention is obtained by refining a non-drying oil obtained from the seeds of castor beans by a pressing method. Since about 90% of the constituent fatty acids are ricinoleic acid having a hydroxyl group, When mixed with isocyanate, it reacts to form a polyurethane resin.

The polyhydric alcohol used in the present invention includes ethylene glycol (molecular weight 62), diethylene glycol (molecular weight 106), propylene glycol (molecular weight 7).
6), dipropylene glycol (molecular weight 134), 1,
There are 4-butanediol (molecular weight 90), 1,3-butanediol (molecular weight 90), glycerin (molecular weight 92) and the like.

Although many kinds of polyisocyanates have been put to practical use as raw materials for polyurethane, those suitable for the present invention include liquefied MDI (diphenylmethane diisocyanate) modified to a liquid at room temperature by a carbodiimidization reaction and a dimer. It is a polymeric MDI that is easy to handle because it contains multimers up to a quantity and is liquid at room temperature.

The ratio of castor oil and polyhydric alcohol in the liquid A in the present invention is appropriately in the range of 75 to 95 parts by weight of castor oil and 5 to 25 parts by weight of polyhydric alcohol, and the ratio of polyhydric alcohol. When the amount is less than 5 parts by weight, the effect of improving the electric insulation and mechanical strength is insufficient, and when the amount is more than 25 parts by weight, the exothermic temperature rise when mixing and reacting with the polyisocyanate of the liquid B is extremely high, which is desirable. Absent. The optimum ratio of castor oil to polyhydric alcohol is selected from the above range in consideration of the properties required depending on the type of polyhydric alcohol and the application of the polyurethane resin.

In the present invention, the mixing ratio of castor oil, polyhydric alcohol A liquid and liquid B consisting of liquid MDI is such that the ratio of NCO and OH contained in both is in the range of 0.8 to 1.2 depending on the required characteristics. It is selected appropriately.

Others The composition of the present invention may contain an inorganic powder filler, a colorant, a flame retardant, etc. depending on the intended use, and it does not prevent the incorporation of a small amount of a polyol other than castor oil. .

[0013]

EXAMPLES The present invention will be described below with reference to Examples and Comparative Examples.

Test samples of Examples 1 to 5 and Comparative Examples 1 to 5 having the compositions shown in Table 1 were prepared, and the evaluation items shown in the lower column of Table 1 were evaluated.

[0015]

[Table 1]

Example 1 Liquid A consisting of 95 parts by weight of castor oil and 5 parts by weight of ethylene glycol and liquid B consisting of liquefied MDI were separately degassed under vacuum, and liquids A and B were mixed at a ratio of 100: 65 (weight ratio). After mixing at a ratio and degassing in a vacuum again, the mixture is poured into a mold, left at room temperature for 16 hours, and then left at 80 ° C. for 4 hours for curing to be 100 × 100.
A 2 mm sheet was prepared. The volume resistivity of this sheet was measured in order to check the electrical insulation property.
It was 10 ¹⁴ Ω-cm. Moreover, the result of measuring the tensile speed as the mechanical strength was 1.9 kg / mm ² . In addition,
The initial viscosity after mixing the liquids A and B was 360 cp, and it was confirmed that the liquids flowed well and were excellent in injectability. A,
When the liquid B is mixed, it reacts and cures at room temperature, but at that time, the exothermic temperature rises. If the temperature rise of the heat generation is too large, problems such as melting and deformation of the insulation coating material of the electric wire occur in applications where the electric wire is embedded. A in a 100 ml beaker
When 100 g of the mixed solution B was weighed and the maximum exothermic temperature in the central portion was measured, it was 74 ° C.

Examples 2 to 5 Tests were conducted in the same manner as in Example 1 except that the composition of polyurethane was changed to that shown in Examples 2 to 5 in Table 1. The results are summarized in Table 1. From this result, Example 2
It was confirmed that the polyurethane mixture of No. 5 had good injectability, electrical insulation and mechanical strength.

Comparative Examples 1 to 5 Tests were carried out in the same manner as in Example 1 except that the compositions of the polyurethane admixtures were changed to those shown in Comparative Examples 1 to 5 of Table 1. The results are summarized in Table 1.

The compositions of Comparative Examples 1 and 2 have much lower tensile strength than the compositions of Examples 1 to 5 and have a volume resistivity of 10 ¹³
The order of Ω-cm is insufficient.

The composition of Comparative Example 3 showed a large increase in exothermic temperature during curing, and the composition of Comparative Example 4 had a high initial mixing viscosity, poor injectability, and low tensile strength. The composition of Comparative Example 5 is a polyether polyol to which ethylene glycol is added, but the mechanical strength and the electrical insulation are insufficient.

[0021]

INDUSTRIAL APPLICABILITY As described above, the admixture according to the present invention is excellent in injection properties, mechanical strength and electrical insulation properties, and is suitable for applications such as injection insulation of connection parts of electric cables and electric parts. .

Claims (2)

[Claims] 1. A liquid prepared by mixing castor oil with a low molecular weight polyhydric alcohol and a liquefied MDI and / or a polymeric M.
A polyurethane mixture for electrical insulation, characterized in that it is mixed with liquid B consisting of DI. 2. A low molecular weight polyhydric alcohol 5 in which the liquid A is in the range of 75 to 95 parts by weight of castor oil and a molecular weight of 62 to 134.
25 parts by weight, and the mixture of liquid A and liquid B is mixed so that the ratio of NCO and OH contained in both liquids is in the range of 0.8 to 1.2. Polyurethane blend.