JP2002124130A - Electric insulation material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electric insulation material made of polyurethane resin which is easy to decompose, and excellent in mechanical property of electric insulation, flexibility, or the like. SOLUTION: The electric insulation material is made of a polyurethane gel containing specific volume of specific constitutive unit whose hardness is 30 or less (in conformity to Asker C), and tear strength is 0.5 MPa or less (in conformity to JIS K 6251).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an electric insulating material using a polyurethane gel. More specifically, electrical insulation,
The present invention relates to an electrical insulating material using a polyurethane gel which has excellent flexibility and excellent dismantling performance.

[0002]

2. Description of the Related Art Conventionally, polyurethane gel has been widely used as a sealing material for electrical insulation for protecting electric components due to its excellent mechanical properties, excellent flexibility and low electrical conductivity. Had been. In other words, electrical insulating materials such as electric parts need to completely seal the electric parts at the time of normal use. It is necessary to insert such a sheet, flexibility is required for that purpose, and it is required that the deformed sheet is restored after the leakage is confirmed. In addition, a function that can be easily removed when replacing parts is also required.

On the other hand, in recent years, there has been an increasing demand for labor saving and recycling of parts such as electric products. For example, labor saving of parts used in products and disassembling and reusing of used parts etc. are easy. The development of new materials that can be used has been desired. In this case, as for the insulating sheet of the electric component material, a material which is easy to dismantle while maintaining various functions such as electric insulation and strength of the sheet has been desired.

Conventionally, in order to satisfy these requirements, attempts have been made to add a plasticizer using castor oil-based polyol as a polyol component of the polyurethane gel. However, while meeting requirements for various functions such as electrical insulation, there is a problem in terms of dismantling performance, such as not being easily broken when bent. Therefore, the inventors of the present application have conducted intensive studies to solve the above problems, and found that a polyurethane gel containing a specific component in a specific ratio has excellent electrical insulation and flexibility, and is easy to disassemble, The present invention has been completed.

[0005]

SUMMARY OF THE INVENTION The present invention aims to solve the problems associated with the prior art as described above,
An object of the present invention is to provide an electrically insulating material made of a polyurethane gel which is excellent in flexibility and is easily disassembled.

[0006]

The electrical insulating material according to the present invention has a hardness of 3
0 or less (according to AskerC), the tear strength is 0.5 MPa or less (according to JIS K6251), and the following general formula (I)

[0007]

Embedded image

[In the formula (I), m is an integer of 1 to 5, and n is 1
Represents an integer of from 5 to 5].
It is characterized by comprising a polyurethane gel containing 0% by mass. The polyurethane gel has the following general formula (II)

[0009]

Embedded image

[In the formula (II), m is an integer of 1 to 5, and n is 1
It is preferable to use a polyurethane gel obtained by reacting the polyol with an organic polyisocyanate represented by the following formula: The polyol is preferably at least one selected from aliphatic polyhydric alcohols, polyester polyols, polyether polyols, and castor oil-based polyols.

The NCO / OH group equivalent ratio between the organic polyisocyanate represented by the general formula (II) and the polyol is preferably in the range of 0.80 to 1.8.

[0012]

DETAILED DESCRIPTION OF THE INVENTION [Electrically Insulating Material] An electrically insulating material comprising a polyurethane gel according to the present invention is AskerC.
The hardness based on (standard of the Japan Rubber Association) is 30 or less, preferably 25 or less, more preferably 1 to 24.
Tear strength based on IS K6251 is 0.5 MPa
Or less, preferably 0.3 MPa or less, more preferably 0.01 to 0.25 MPa, and the following general formula (I)

[0013]

Embedded image

[In the formula (I), m is an integer of 1 to 5, and n is 1
Represents an integer of from 5 to 5].
The polyurethane gel contains 0% by mass, preferably 2.0 to 9% by mass, and more preferably 3 to 8.5% by mass. When the content of the constituent unit derived from the organic polyisocyanate in the polyurethane gel is 1.5% by mass or more, the curing is good, and when the content is 10% by mass or less, the hardness and the tear strength are in more preferable ranges, Also, it is easy to dismantle.

It should be noted that, in the present specification, a polyurethane gel is different from a hydrous gel and is a so-called liquid segment gel (Liquid segment gel) composed of a liquid segment which shows a gel state even without containing water. Segment Ge
l). For this reason, the electric insulating material made of the polyurethane gel according to the present invention maintains the gel state (soft gel-like elastic body) regardless of the water content, and has shape recovery properties, dismantling properties, and the like.

The content of the polyurethane gel in the electric insulating material according to the present invention is usually 60% by mass or more, preferably 90% by mass or more, and particularly preferably 98% by mass or more. Further, the electric insulating material may be substantially composed of only the polyurethane gel. Such a polyurethane gel can be produced from an organic polyisocyanate and a polyol, and if necessary, a plasticizer (a viscosity reducing agent), a stabilizer, a surfactant, a catalyst, a foam stabilizer, and other additives (difficulty in the art). Flame retardants, pigments, ultraviolet absorbers, antioxidants, etc.). Hereinafter, these components will be described.

[Organic polyisocyanate] As the organic polyisocyanate, the following general formula (II)

[0018]

Embedded image

[In the formula (II), m is an integer of 1 to 5, and n is 1
And an integer of from 5 to 5] can be used. Specific examples of such a polycyclic aliphatic diisocyanate include 2,5 (6)
-Diisocyanatomethylbicyclo [2,2,1] heptane, 2-isocyanatomethyl-5 (6) -isocyanatoethylbicyclo [2,2,1] heptane, 2,5
(6) -diisocyanatoethylbicyclo [2,2
1] Heptane, 2,5 (6) -diisocyanatopropylbicyclo [2,2,1] heptane, 2,5 (6) -diisocyanatebutylbicyclo [2,2,1] heptane, 2,5 (6) -diisocyanate Pentylbicyclo [2,2,1] heptane and the like. These may be used alone or in combination of two or more. In addition, other organic polyisocyanates other than these organic polyisocyanates that can be used for producing ordinary polyurethane resins can also be used in combination.

Examples of such other organic polyisocyanates include, for example, tolylene diisocyanate (TD
I), hydrogenated tolylene diisocyanate, 4,4 ′ diphenylmethane diisocyanate, diphenylmethane diisocyanate (MDI), polymeric MDI (PMDI), xylylene diisocyanate (XDI), aromatic isocyanates such as 1,5-naphthalenediisocyanate (NDI), Aliphatic isocyanates such as hexamethylene diisocyanate (HDI), 4,
4 'methylene bis (cyclohexyl isocyanate),
Isophorone diisocyanate (IPDI), hydrogenated XDI (H6XDI),
Examples include alicyclic polyisocyanates such as hydrogenated MDI (H12MDI) and norbornane diisocyanate methyl (NBDI). Further, modified products of the above-mentioned isocyanates, such as carbodiimide-modified isocyanates, isocyanurate-modified products, and prepolymers, can also be used. When these other organic polyisocyanates are used in combination, the above-mentioned general formula
It is desirable that the organic polyisocyanate represented by (II) is used in an amount of preferably at least 60% by mass, more preferably at least 80% by mass, particularly preferably at least 90% by mass in the total organic polyisocyanate.

[Polyol] As the polyol used for producing the polyurethane gel according to the electric insulating material of the present invention, any polyol may be used as long as it is used for a usual polyurethane composition. 1
Species may be used alone or in combination of two or more.

Specific examples of such polyols include relatively low molecular weight polyhydric alcohols, high molecular weight aliphatic hydrocarbon polyols, polyether polyols, polyester polyols, polycaprolactone polyols, polycarbonate polyols, and polyether polyols. Alternatively, a modified product of a polyester polyol, a castor oil-based polyol, or a polymer polyol may be used.

Among these, a high molecular weight aliphatic hydrocarbon polyol such as polybutadiene polyol, a castor oil-based polyol or a mixture thereof is preferably used. (Polyhydric alcohol) Examples of the relatively low molecular weight polyhydric alcohol include ethylene glycol (EG),
Diethylene glycol (DEG), propylene glycol (PG), dipropylene glycol (DPG), 1,3-butanediol (1,3-BD), 1,4-butanediol (1,4-
BD), dihydric alcohols such as 4,4'-dihydroxyphenylpropane and 4,4'-dihydroxyphenylmethane, glycerin, 1,1,1-trimethylolpropane (TMP), 1,2,5-
Examples include trihydric alcohols such as hexanetriol, and polyhydric alcohols having four or more valences such as pentaerythritol, glucose, sucrose, and sorbitol. (Polymer Aliphatic Hydrocarbon Polyol) Examples of the high molecular weight aliphatic hydrocarbon polyol include polymers of unsaturated hydrocarbons such as polyvinyl alcohol, polyisobutylene polyol, polybutadiene polyol, and polyisoprene polyol. Examples include a high molecular weight polyol having a hydroxyl group. These polyols are GPC
Number average molecular weight measured in the above is preferably 1000 to 50
And the hydroxyl value is preferably from 20 to 170.
It is desirably about mgKOH / g. Such a polyol can be prepared by a known method. For example, polyvinyl alcohol can be obtained by polymerizing vinyl acetate and saponifying the obtained polyvinyl acetic acid by a conventional method. The polybutadiene polyol or polyisoprene polyol can be obtained by hydrating an unsaturated bond of a polymer obtained by a conventional method with an acid catalyst such as sulfuric acid.

(Polyether polyol) As the polyether polyol, addition polymerization of one or more of polyhydric alcohols having relatively low molecular weight and one or more of ethylene oxide, propylene oxide, butylene oxide and the like is carried out. And polytetramethylene ether glycol (PTMEG) obtained by ring-opening polymerization of tetrahydrofuran.

Such a polyether polyol is represented by G
Number average molecular weight measured by PC is preferably 1000 to
5,000, and the hydroxyl value is preferably 20-1.
It is desirably about 70 mgKOH / g. (Polyester polyol) As the polyester polyol, one or more of ethylene glycol, propylene glycol, butanediol, butylene glycol, diethylene glycol, pentanediol, hexanediol, glycerin, trimethylolpropane, and other low molecular weight polyols are used. Glutaric acid,
Polyester polyols obtained by condensation polymerization with one or two or more of adipic acid, sebacic acid, terephthalic acid, isophthalic acid, dimer acid or other low-molecular dicarboxylic acids or oligomeric acids and ring-opening polymerization of caprolactone, etc. Is mentioned.

Such a polyester polyol is represented by G
The number average molecular weight measured by PC is preferably 500 to 5
000, and the hydroxyl value is preferably 20 to 35.
It is desirable that the amount is about 0 mgKOH / g. (Polycaprolactone polyol) The polycaprolactone polyol is a polyol obtained from ε-caprolactone and a polyhydric alcohol, and usually has a number average molecular weight of 500 to 4000 and a hydroxyl value of 30 to 240 mg KO.
It is preferably about H / g. As the polyhydric alcohol, the polyhydric alcohol used for the polyester polyol can be used. (Polycarbonate polyol) Examples of the polycarbonate polyol include 1,4-butanediol, 1,6
-Polyhydric alcohols such as hexanediol, and dimethyl carbonate, is a straight-chain aliphatic diol obtained by a condensation reaction such as diethyl carbonate, usually number average molecular weight measured by GPC, preferably in the range of 500 to 2000 And those having a hydroxyl value of about 60 to 200 mgKOH / g are preferred. (Modified product of polyether polyol or polyester polyol) Examples of the modified product of the polyether polyol or polyester polyol include, for example, graft polymerization of an ethylenically unsaturated compound such as acrylonitrile, styrene, or methyl methacrylate to the polyether polyol or polyester polyol. And the like. The amount to be used may be appropriately set in accordance with the intended physical properties of the product, and is usually 5 to 250 parts, preferably 10 to 250 parts by weight per 100 parts by weight of the main ingredient (A).
Desirably 150 parts.

Such a modified polyether polyol or polyester polyol has a number average molecular weight measured by GPC of preferably in the range of 500 to 5,000, and a hydroxyl value of preferably 20 to 350 mgKOH /.
It is desirably about g. (Castor oil-based polyol) Examples of the castor oil-based polyol include castor oil, dehydrated castor oil, and esterified polyols of ricinoleic acid, a castor oil fatty acid, with the low-molecular-weight polyol, polyether polyol, or polyester polyol. Among these, castor oil, dehydrated castor oil and the like are preferably used. Such a castor oil-based polyol has a functional group number of 2
Those having the above-mentioned are preferable, and those having 3 functional groups are more preferable. For example, it is preferable to use Euri H-30 (hydroxyl value 160 mg KOH / g, functional group number 3) manufactured by Ito Oil Co., Ltd., and Euri H-57 (hydroxyl value 100 mg KOH / g, functional group number 3) manufactured by Ito Oil Co., Ltd. it can. The molecular weight per hydroxyl group of the castor oil-based polyol is not particularly limited, but is preferably from 100 to 1,000, and more preferably from 200 to 500. (Polymer polyol) The polyether polyol may be used as a polymer polyol. This polymer polyol is a vinyl polymer particle-dispersed polyol obtained by dispersion-polymerizing an ethylenically unsaturated group-containing monomer such as acrylonitrile or styrene using a radical initiator such as azobisisobutyronitrile in a polyether polyol. The polymer concentration in such a polyether polyol is 2 to 50% by mass, preferably 1% by mass.
It is desirably about 0 to 40% by mass. As a vinyl polymer, at least 30% by mass of styrene,
Preferably, a polymer polyol containing 50% by mass or more is desirable. [Thickener] The polyurethane gel according to the present invention may optionally contain a plasticizer, a high-boiling solvent or the like as a thickener. <Plasticizer> Specific examples of the plasticizer include dioctyl phthalate, dibutyl phthalate, and dioctyl adipate. <High boiling point solvent> As the high boiling point solvent, specifically,
Chlorinated paraffins, petroleum hydrocarbon oils and the like can be mentioned. [Other additives] The polyurethane gel according to the electric insulating material of the present invention may contain other additives as necessary. Other additives include, for example, phosphate ester flame retardants, pigments, ultraviolet absorbers, curing accelerators, moisture absorbers, and the like. [Production method of polyurethane gel] The production method of the polyurethane gel according to the electric insulating material of the present invention is not particularly limited,
For example, it can be produced by reacting the polyol and the organic polyisocyanate by a known method. In the reaction, if necessary, the phosphate ester-based flame retardant, pigment, ultraviolet absorber, curing accelerator, moisture absorber, and the like can be used in combination. These additives may be used by being mixed in advance with either a polyol or an organic polyisocyanate, or may be added alone during the reaction.

The mixing temperature of the polyol and the organic polyisocyanate is not particularly limited, but it is preferable that the reaction is carried out usually at 0 to 150 ° C., preferably at 25 to 100 ° C. The resulting mixture cures and a polyurethane gel can be obtained. The ratio at the time of mixing the polyol and the organic polyisocyanate is an NCO / OH group equivalent ratio, preferably 0.80 to 1.8, and more preferably 0.80 to 1.8.
-1.3, particularly preferably 0.85-1.25. When the NCO / OH group equivalent ratio is 0.80 or more, curing becomes more complete, and when the equivalent ratio is 1.8 or less, it contributes to suppression of foaming, which is preferable.

The polyurethane gel thus obtained can be molded and processed into a desired electric insulating material by a known molding and processing method. Such molding and processing methods include injection molding, extrusion molding, calendar molding,
Known methods such as press molding, blow molding, and a casting method can be employed.

The electric insulating material thus obtained is
It can be used as various electric insulating materials such as automotive electrical equipment, sealing materials in the field of electronics and electrics, insulation of printed circuit boards, electric cables and electric cable joint insulating materials.

[0031]

According to the present invention, it is possible to obtain an electric insulating material made of a polyurethane gel which is excellent in mechanical properties such as electric insulation and flexibility and is easily disassembled.

[0032]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples. In the examples and comparative examples, “parts” represents “parts by mass” and “%” represents “% by mass”.

[0033]

Example 1 Polybutadiene polyol (trade name: R, manufactured by Idemitsu Petrochemical Co., Ltd.) was used as the polyol component (a).
-45HT, hydroxyl value: 46 mgKOH / g) 39.0
And dioctyl phthalate (DOP) as a thickener
59.0 parts and 3,5-t-butyl-4 as a stabilizer
-Hydroxyphenyl propionate (manufactured by Ciba Specialty Chemical Company, trade name: Irganox 107)
6) 1.0 part, and dibutyl laurate (manufactured by Sankyokisei Co., Ltd., trade name: StanBL) as a curing accelerator
1.0 part with stirring under a nitrogen stream to produce a curing agent.

3.3 parts of norbornane diisocyanate (NBDI, manufactured by Mitsui Chemicals, Inc.) as the polyisocyanate component (b) and 46.7 parts of DOP as a viscosity reducing agent were stirred and mixed under a nitrogen stream to form a main component. Was manufactured. 50.0 parts of the main agent produced in this manner and 100.
And 0 parts were uniformly mixed and stirred to obtain a polyurethane resin composition. In this composition, the content of the polyisocyanate component (b) was 2.2%, and the NCO / OH group equivalent ratio was 1.00.

[0035]

Example 2 Polybutadiene polyol (trade name: R, manufactured by Idemitsu Petrochemical Co., Ltd.) was used as the polyol component (a).
-15HT, hydroxyl value: 105 ngKOH / g) 6
5.0 parts, 33.5 parts DOP, and Irganox 1
076 and 1.0 part of StanBL were stirred and mixed under a nitrogen stream to produce a curing agent.

As the polyisocyanate component (b), N
12.6 parts of BDI and 37.4 parts of DOP were stirred and mixed under a nitrogen stream to produce a base material. 50.0 parts of the main agent and 100.0 parts of the curing agent thus produced were uniformly mixed and stirred to obtain a polyurethane resin composition. The content of the polyisocyanate component (b) in this composition was 8.4.
%, And the NCO / OH group equivalent ratio was 1.01.

[0037]

Example 3 As a polyol component (a), R-15H
60.0 parts of T, 38.5 parts of DOP, 1.0 part of Irganox 1076 and 0.5 part of StanBL were stirred and mixed under a nitrogen stream to produce a curing agent. 12.6 parts of NBD1 as a polyisocyanate component (b), DOP
Was stirred and mixed under a nitrogen stream to produce a main ingredient.

50.0 parts of the base material produced as described above,
100.0 parts of a curing agent were uniformly mixed and stirred to obtain a polyurethane resin composition. The content of the polyisocyanate component (b) in this composition was 8.4%, and the NCO / OH group equivalent ratio was 1.09.

[0039]

Example 4 20.0 parts of castor oil (hydroxyl value: 160 mgKOH / g) as a polyol component (a), DO
78.5 parts of P, 1.0 part of Irganox 1076,
0.5 parts of StanBL was stirred and mixed under a nitrogen stream to prepare a curing agent. As the polyisocyanate component (b),
6.0 parts of NBDI, a high boiling solvent containing distyrylxylene as a main component as a viscosity reducing agent (Nippon Petrochemical Co., Ltd., trade name: Nisseki Hisol SAS-LH) 44.0
The parts were stirred and mixed under a nitrogen stream to produce a main ingredient.

The polyurethane resin composition was obtained by uniformly stirring 50.0 parts of the thus prepared main agent and 100.0 parts of the curing agent. In this composition, the content of the polyisocyanate component (b) was 4.0%, and the NCO / OH group equivalent ratio was 1.02.

[0041]

Example 5 As the polyol component (a), R-45H was used.
58.0 parts of T, 40.5 parts of DOP, 1.0 part of Irganox 1076 and 0.5 part of StanBL were stirred and mixed in a nitrogen stream to produce a curing agent. As the polyisocyanate component (b), 6.0 parts of NBD1 and 4 parts of DOP
4.0 parts were stirred and mixed under a nitrogen stream to produce a main ingredient.

The thus-prepared 50.0 parts of the main ingredient and 100.0 parts of the curing agent were uniformly mixed and stirred to obtain a polyurethane resin composition. The content of the polyisocyanate component (b) in this composition was 4.0%, and the NCO / OH group equivalent ratio was 1.22.

[0043]

Comparative Example 1 As a polyol component (a), R-45H was used.
24.5 parts of T, 73.5 parts of DOP, 1.0 part of Irganox 1076 and 1.0 part of StanBL were stirred and mixed under a nitrogen stream to produce a curing agent. 2.1 parts of NBDI and 4 parts of DOP as the polyisocyanate component (b)
7.9 parts were stirred and mixed under a nitrogen stream to produce a main ingredient.

50.0 parts of the main agent thus produced and 100.0 parts of the curing agent were uniformly mixed and stirred to obtain a polyurethane resin composition. The content of the polyisocyanate component (b) in this composition was 1.4%, and the NCO / OH group equivalent ratio was 1.02.

[0045]

Comparative Example 2 As a polyol component (a), R-15H
85.5 parts of T, 13.0 parts of DOP, 1.0 part of Irganox 1076 and 0.5 part of StanBL were stirred and mixed in a nitrogen stream to produce a curing agent. As the polyisocyanate component (b), 16.5 parts of NBDI and 33.5 parts of DOP were stirred and mixed under a nitrogen stream to produce a main ingredient.

The thus-prepared 50.0 parts of the base material and 100.0 parts of the curing agent were uniformly mixed and stirred to obtain a polyurethane resin composition. In this composition, the content of the polyisocyanate component (b) was 11.0%, and the NCO / OH group equivalent ratio was 1.00. <Physical properties test> After mixing and stirring the main components and the curing agents of Examples 1 to 5 and Comparative Examples 1 and 2 uniformly at a predetermined ratio, the resulting polyurethane composition was used to measure AskerC hardness, foamability and disassembly. The block-shaped molded product piece (5
0 mm × 50 mm, thickness 10 mm) and a sheet (2 mm thick) used for a tensile test,
After curing at 7 ° C. for 7 days, physical properties were measured.

The composition of Comparative Example 1 was not cured even after curing at 23 ° C. for 7 days, and the test could not be carried out. The physical property test was performed on the following items under the following conditions. AskerC (hardness test): It was carried out according to the Japan Rubber Association Standard. Tear strength: Performed according to JIS K6251.

Test piece: Dumbbell-shaped No. 3 Tensile speed: 500 mm / min Foamability: The presence or absence of bubbles in the block-shaped molded product was visually determined. Disassembly: Judgment was made by bending the block-shaped molded product by hand. ◎: easily broken by bending by hand ×: not broken by bending by hand The above results are shown in Table 1.

The compositions obtained in Examples 1 to 5 had no foaming phenomenon and could be easily disassembled by hand. The composition obtained in Comparative Example 1 was uncured even after curing at 23 ° C. for 7 days, and the composition of Comparative Example 2 had high hardness and tensile strength and could not be easily dismantled by hand.

[0050]

[Table 1]

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Seiji Nagahisa 1077 Yasumasa, Isumi-machi, Isumi-gun, Chiba Prefecture Inside the Chiba Plant of Nippon Kasei Chemical Co., Ltd. (72) Inventor Tsune Kawanabe Kasama, Sakae-ku, Yokohama-shi, Kanagawa 1190-cho Mitsui Chemical Co., Ltd. (72) Inventor Takashi Abe 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture Inside Mitsui Chemical Co., Ltd. (72) Kaoru Ueno 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Chemicals In-house F-term (reference) 4J034 BA02 BA03 CA03 CA04 CA05 CB03 CB07 CC03 CD04 DF01 DF02 DF16 DF20 DF21 DF24 DG03 DG04 DG05 DG06 DG08 DP17 DP19 DQ02 EA12 HA01 HA07 HC03 HC12 HC17 HC22 HC45 HC46 HC67 HC61 HC64 HC06 HC64 QB15 RA14 5G305 AA07 AA14 AB01 AB17 AB35 BA12 CA18

Claims (4)

[Claims] 1. Hardness is 30 or less (based on Asker C)
And a tear strength of 0.5 MPa or less (JIS K
6251) according to the following general formula (I): [In the formula (I), m is an integer of 1 to 5 and n is an integer of 1 to 5] A polyurethane gel containing the structural unit represented by 1.5 to 10% by mass. An electrical insulating material characterized by the following. 2. The polyurethane gel according to the following general formula (I)
I) [In the formula (II), m represents an integer of 1 to 5, and n represents an integer of 1 to 5], and is a polyurethane gel obtained by reacting an organic polyisocyanate represented by the following formula with a polyol. The electrical insulating material according to claim 1. 3. The method according to claim 1, wherein the polyol is at least one selected from aliphatic polyhydric alcohols, polyester polyols, polyether polyols and castor oil-based polyols.
3. The electrically insulating material according to claim 2, which is a seed. 4. An NCO / OH group equivalent ratio between the organic polyisocyanate and the polyol is from 0.80 to 1.8.
The electrically insulating material according to claim 2, wherein