JPH06102777B2 - Electrical insulating paint composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION << Industrial Applicability >> The present invention relates to an electrically insulating coating composition, particularly from 60 ° C. to 100 ° C.
The present invention relates to an electric insulating coating composition that is curable in a temperature range of ℃ and has excellent heat resistance, flame retardancy, solvent resistance, moisture resistance and the like.

《Prior art》 Electrical insulating paints, especially embedded compounds, have traditionally consisted of a compound consisting of a polycondensation-curing type organopolysiloxane and a polycondensation catalyst, an inorganic powder, and an organic solvent. Had been used. However, to cure these compounds, a high temperature of 150 ° C or higher is usually required, and even if a strong catalyst is used, the curing temperature can only be lowered to about 120 ° C. In reality, it takes time, productivity is not improved due to poor production efficiency, and satisfactory performance cannot always be obtained.

In such a situation, recently, in order to prevent the thermal fuse from being damaged, there are many kinds of electric parts to be embedded in one case, and especially as the thermal fuse is embedded, There is an increasing demand for a compound that is preferably cured at about 70 ° C.

From such a viewpoint, conventionally, an alkenyl group-containing organopolysiloxane and a hydrogen organopolysiloxane containing a hydrogen atom directly bonded to a silicon atom are subjected to an addition reaction in the presence of a platinum-based catalyst to be cured.

<< Problems to be Solved by the Invention >> In this case, it is necessary to eliminate the silanol group by a condensation reaction in the process of producing the alkenyl group-containing organopolysiloxane that is a reaction product. This is because when the silanol group remains, aside from the addition reaction, the hydrogen organopolysiloxane containing a hydrogen atom directly bonded to a silicon atom and the silanol group react with each other by the catalytic action of the platinum compound to dehydrate. This is to prevent the inconvenience that the pot life is shortened due to the occurrence of elementary and condensation reactions. However, in conventional compositions,
In eliminating the silanol group, a strong alkali or a strong acid must be used as a catalyst, which causes polymerization of the alkenyl group and makes it difficult to obtain the desired alkenyl group-containing organopolysiloxane.

As a result of intensive studies to solve the above-mentioned drawbacks, the present inventors have found that an alkenyl group-containing organopolysiloxane is
Used to eliminate the silanol group by a condensation reaction by forming a copolymer composed of a tetrafunctional siloxane unit (Q unit), a trifunctional siloxane unit (T unit) and a monofunctional siloxane unit (M unit) The catalyst to be used can be a weakly alkaline or weakly acidic substance, which makes it possible to easily obtain the desired alkenyl group-containing organopolysiloxane containing no silanol groups, while excluding the Q and M siloxane unit components, In the case of using an alkenyl group-containing organopolysiloxane composed of T and bifunctional D units, it was found that the silanol group cannot be eliminated by a catalyst of a weak alkali or a weakly acidic substance, and the present invention was reached.

Therefore, the first object of the present invention is to have a long pot life,
An object is to provide an electrically insulating coating composition that can be cured at a low temperature of 60 ° C to 100 ° C.

A second object of the present invention is to provide an alkenyl group-containing organopolysiloxane that does not contain silanol groups.

<< Means for Solving the Problems >> The above-mentioned various objects of the present invention include (A) general formula And a is a copolymer composed of three types of siloxane units represented by 0, 1 and 3, and the alkenyl group-containing organopoly having at least two alkenyl groups in one molecule of the copolymer. Siloxane, (B) general formula Is a polymer and / or copolymer of at least one or more siloxane units represented by, and at least two or more hydrogen atoms are directly bonded to silicon atoms in one molecule of the polymer and / or copolymer. Bound hydrogen organopolysiloxane, (C) catalytic amount of platinum compound, and (D) one or more metal oxides and / or at least one
It was achieved by an electrically insulating coating composition characterized by comprising an inorganic powder composed of a double oxide of one kind of metal.

General formula as component (A) In, R ¹ represents an unsubstituted or substituted monovalent hydrocarbon group, particularly an alkyl group having 1 to 6 carbon atoms, a phenyl group,
An alkenyl group and the like are preferable. a is 0, 1 and 3,
When a is 0, it is represented by the general formula SiO ₂ , when it is 1, it is represented by R ¹ SiO _3/2 , and when it is 3, it is represented by (R ¹ ) ₃ SiO _1/2 . As a specific example, when a is 0, Si (OCH ₃ ) ₄ , Si (OC ₂ H ₅ ) ₄ , S
alkyl silicates such as i (OC ₃ H ₇ ) ₄ , tetrahalogenated silicon halides represented by SiX ₄ and partial hydrolysates thereof,
It is a tetrafunctional siloxane unit or the like obtained by hydrolysis and condensation using water glass or the like as a raw material.

When a is 1, it represents a general formula R ¹ SiO _3/2 unit and represents trifunctional organotrichlorosilanes such as CH ₃ SiCl ₃ , C ₂ H ₅
SiCl ₃ , C ₃ H ₇ SiCl ₃ , C ₄ H ₉ SiCl ₃ , CH ₂ = CH.SiCl ₃ , C ₆ H ₅ SiCl ₃ and organotrialkoxysilane, such _{CH 3 Si (OCH 3) 3} , CH 3 Si (OC 2 H 5) 3, C 2 H 5 Si (OCH 3) 3, C 2 H 5 Si _{(OC 2 H 5) 3,} C 3 H 7 Si (OCH 3) 3, C 4 H 9 Si (OCH 3) 3, CH 2 = CHSi (OCH 3) 3, CH 2 = CHSi (OC 2 H 5) ₃ , _{C 6 H 5 Si (OCH 3} ) 3, C 6 H 5 Si (OC 2 H 5) is a siloxane unit obtained by hydrolysis condensation from ₃ like.

When a is 3, it represents a siloxane having (R ¹ ) ₃ SiO _1/2 units. Specific examples include (CH ₃ ) ₃ SiCl, (CH ₃ ) ₂ · CH ₂ = CH · SiCl, (C ₂ H ₅ ) ₃ SiCl, (CH ₃ ) ₂ C ₆ H ₅ SiCl, (C ₂ H ₅ ) ₂ CH ₂ = CHSiCl and other triorganochlorosilanes, and dimers [(CH ₃ ) ₃ Si] ₂ O and [(CH ₃ ) ₂ (CH ₂ = CH) obtained by hydrolysis and condensation reaction of these Si] ₂ O, [(C ₂ H _{5) 3} Si] ₂ O, _{[(CH 3) 2 (C 6} H 5) Si ] ₂ O, _{[(C 2 H 5) 2 (} CH 2 = CH) Si ] A monofunctional siloxane unit obtained by hydrolysis condensation using ₂ O or the like as a raw material.

When the number of R ¹ , that is, the value of a is 0, the monomer is tetrafunctional, when it is 1, it is trifunctional, and when it is 3, it is monofunctional.
Co-hydrolyzing and condensing a mixture of these monomers in which a is 0, 1, 3 or / and a partial hydrolysis-condensation product thereof,
An alkenyl group-containing organopolysiloxane can be obtained.

In this case, it is necessary to preliminarily mix one molecule of the copolymer with at least two alkenyl groups.

In addition, the compounding molar ratio of the siloxane units of each functionality generally shows that the more the tetrafunctional siloxane unit is, the harder and brittle the cured product is. When the proportion of trifunctional siloxane units is high and the content of tetrafunctional siloxane units is low, the hardness of the cured product decreases and the brittleness also decreases. When the amount of monofunctional siloxane units is large, the copolymer becomes a viscous liquid, and the cured product thereof is soft and may remain liquid without being cured. Therefore, the blending molar ratio of each functional siloxane unit is naturally limited.

The preferable blending molar ratio of each is 0.5 to 1.3 for the monofunctional siloxane unit, 0.6 to 1.4 for the tetrafunctional siloxane unit, and 0.1 to 0.8 for the trifunctional siloxane unit. By selecting such a blending ratio, the electrical insulating coating composition of the present invention can be cured at a low temperature, and the properties such as heat resistance after curing, flame retardancy, solvent resistance and moisture resistance are good. It can be anything.

Further, two or more alkenyl groups are contained in one molecule of the copolymer, and the preferable content of the alkenyl groups is 5 mol%.
˜30 mol%, optimally 10 mol% to 20 mol%.

Therefore, it is not necessary that all R ^1's are the same.

The most preferred alkenyl groups are CH ₂ ═CH— and Is. As the organic group R ¹ other than the alkenyl group, -CH ₃ is most preferable from the viewpoint of heat resistance, flame retardancy, solvent resistance, moisture resistance, curability and the like. There is no problem in partially introducing an alkyl group having a large number of carbon atoms or a phenyl group in order to impart special uses and characteristics.

General formula that is the component (B) R ² represents an alkyl group having 1 to 6 carbon atoms, a phenyl group or a hydrogen atom, and b represents 0, 1, 2 or 3.

The component (B) is a polymer composed of at least one or more kinds of siloxane units, and is a hydrogen organopolysiloxane containing at least two or more hydrogen atoms directly bonded to silicon atoms in one molecule. Specific examples thereof include the following.

H ・ (CH ₃ ) ₂・ SiOSi (CH ₃ ) ₂・ H, In the above formula, m is 2 or more, n is 0 or more, and p is a rational number of 1 or more, and each is a number equal to or less than the degree of polymerization of a molecule having compatibility with the aforementioned alkenyl group-containing organopolysiloxane. . Further, (C ₂ H ₅ O) ₄ Si and / or its partial hydrolyzate and CH ₃ · H · Si (OCH ₃ ) ₂ or (CH ₃ ) ₃ SiO
Co-hydrolysis condensate with Si (CH ₃ ) ₃ as well as CH ₃ Si (OC
H ₃ ) ₃ added co-hydrolyzed condensate or C ₆ H ₅ SiC ₃ , CH ₃ · H · SiCl ₂ , (CH ₃ ) ₂ SiCl ₂ co-hydrolyzed condensate, etc. Is exemplified.

The blending amount of these hydrogen organopolysiloxanes is not particularly limited, however, with respect to one alkenyl group of the alkenyl group-containing organopolysiloxane,
The number of hydrogen atoms directly bonded to silicon atoms is 0.7-10
The amount corresponding to the individual is a proper amount.

The catalytic amount of the platinum compound is one known as a catalyst for addition reaction of an alkenyl group and a hydrogen atom directly bonded to a silicon atom, for example, chloroplatinic acid, a complex of chloroplatinic acid and an olefin, or a vinylsiloxane, and a chloride. It can be appropriately selected and used from alcoholic solutions of platinic acid and the like.

The amount of the platinum compound is not particularly limited, but usually the total amount of the alkenyl group-containing organopolysiloxane and the hydrogen organopolysiloxane containing a hydrogen atom directly bonded to a silicon atom is 1,000,000 parts by weight. On the other hand, the amount of platinum metal may be in the range of 1 to 400 parts by weight.

In the present invention, in order to control the addition reaction rate by the addition of the platinum compound, an additive known as a retarder of the addition reaction, for example, an alkynyl alcohol compound,
Amines, mercaptans and the like can be appropriately added.

As the inorganic powder used in the present invention, at least one kind of metal oxide and / or at least one kind of metal double oxide is used. Specifically, as metal oxides, Al ₂ O ₃ , SiO ₂ , MgO, Fe ₂ O ₃ , ZnO, Sb
₂ O ₃ , TiO ₂ , Fe ₃ O ₄ , CuO, C ₀ O, etc., but especially Al ₂ O ₃ , S
iO ₂ , MgO, Fe ₂ O _{3 and the} like are preferable.

Examples of the metal complex oxide include Al ₂ O ₃ .2SiO ₂ (clay), 3MgO.4SiO ₂ (talc), Al ₂ O ₃ .5SiO ₂ (bentonite), and the like. The blending amount of these inorganic powders varies depending on the form and application of the coating material, but usually 100 parts by weight of these inorganic powders are the total amount of the alkenyl group-containing organopolysiloxane and the hydrogen atom-containing hydrogen organopolysiloxane. Is 5
It is preferably about 1,000 parts by weight.

This is because it is preferable to use a large amount of inorganic powder in applications such as the sealing of the end of embedded resistors and sheathed heaters. As a coating agent for the surface insulation protection of printed circuit boards, inorganic powder should be used. This is because a smaller amount of the body is preferable for its performance.

The particle size of the above-mentioned inorganic powder is not particularly limited, but is usually 200 μm or less, preferably 100 μm or less. Is preferably changed.

Since the electrical insulating coating composition of the present invention can be cured at a much lower temperature than conventional compositions, it is possible to mold or apply electrical and electronic parts which are easily damaged at a relatively low temperature all together. It is possible to improve work efficiency and productivity.

Moreover, since the crosslinking is more densely performed than the conventional curing method by polycondensation, the solvent resistance and the moisture resistance are improved despite the low temperature curing.

Further, since the hardness of the resin itself can be improved by using a siloxane unit composed of a tetrafunctional unit, a mixture of the alkenyl group-containing organopolysiloxane and the hydrogen atom-containing organopolysiloxane directly bonded to a silicon atom can be used. The compounding ratio with respect to the inorganic powder can be reduced as compared with the conventional one, whereby heat resistance and flame retardancy are improved.

<< Effects of the Invention >> As described in detail above, the electrical insulating coating composition of the present invention is
In addition to curing at temperatures as low as ~ 100 ° C, cured products with excellent electrical insulation properties, such as excellent heat resistance, flame retardancy, solvent resistance, and moisture resistance, can be obtained. , Paints for molding of capacitors, and I
It is suitable for applications such as molds for C, LSI, etc., sealants for terminal parts such as cassette heaters, sheathed heaters, adhesive sealants for bases of light bulbs, and insulating paints for heating parts such as heating appliances.

<< Examples >> The present invention will be described in more detail below with reference to Examples, but the present invention is not limited thereto. All "parts" in the examples represent parts by weight.

Example 1. 1,000 parts of ethyl polysilicate (SiO ₂ content 40% product), 324 parts of hexamethyldisiloxane, 176 parts of vinyltrimethoxysilane and 204 parts of toluene were refluxed with a condenser, a thermometer, and a four-necked stirrer. I put it in the flask. Next, a mixed solution of 18 parts of 35% hydrochloric acid and 18 parts of isopropanol was added to the above mixture while stirring, and then 360 parts of water was added dropwise over 1 hour. As a result, the temperature in the system rose to 45 ° C, but after further heating and hydrolysis at 76 ° C under reflux for 5 hours, 2,000 parts of water was added to wash and separate the water phase. I went repeatedly until I became sexual. Then, the organic phase was transferred to a four-necked flask, azeotropically dehydrated to adjust the nonvolatile content to 80%, 8 parts of sodium hydrogen carbonate was added, and the mixture was heated at 120 ° C. for 7 hours for polymerization.

Next, after adding toluene to adjust the nonvolatile content to 60%, 35
% 12% hydrochloric acid and 60 parts water were added and neutralized at 90 ° C. for 2 hours, and residual hydrochloric acid was removed by washing with water until the aqueous phase became neutral.
The organic phase was azeotropically dehydrated and cooled, 10 parts of anhydrous sodium sulfate was further added for dehydration, and then filtered. Platinum catalyst was added to the obtained varnish as platinum metal so as to be 24 ppm and mixed so as to be uniform. The properties of the varnish thus obtained were as follows.

Appearance: Light yellow transparent liquid, nonvolatile content: 60.3%, viscosity: 7.2cs, specific gravity: 1.031, solvent: toluene.

The compounding molar ratio of the monofunctional siloxane unit to the tetrafunctional siloxane unit and the trifunctional siloxane unit was 0.6: 1.0: 0.
18, vinyl group content is 10.0 mol%, 100 g of varnish
It contained 0.088 mol of vinyl groups.

Next, after mixing 20 parts of the obtained varnish with 70 parts of natural silica (Grand Colts) powder and 5 parts of bentonite, an average composition further containing hydrogen directly bonded to silicon atoms. 2 parts of hydrogenorganopolysiloxane are added, and then toluene is added until a paste is formed. Next, toluene was volatilized so that the thickness of the molded product was 1 mm, and then the mixture was heated and cured at 70 ° C. for 3 hours. With respect to the electrical properties of this molded product, the withstand voltage was 28 kv / mm, the volume resistivity was 5.6 × 10 ¹⁴ Ω-cm, and the solvent resistance to freon was good.

Example 2. Methyl polysilicate (SiO ₂ content 51% product) 700 parts, hexamethyldisiloxane 434 parts, vinyltrimethoxysilane 4
18 parts and xylene 254 parts were charged into a four-necked flask equipped with a reflux condenser, a thermometer and a stirrer. Next, while stirring the above mixture, a mixed solution of 15 parts of 35% hydrochloric acid and 15 parts of isopropanol was added, 420 parts of water was added dropwise over 1 hour and 20 minutes, and the hydrolysis reaction was performed for 5 hours while heating to 69 ° C. under reflux. I went. Next, 2,000 parts of water was added until the aqueous phase became neutral, and the operation of washing with water and liquid separation was repeated. Then, the organic phase was azeotropically distilled to remove water, and the nonvolatile content was adjusted to 80%. Next, add 7 parts of sodium hydrogen carbonate, heat at 120 ° C. for 7 hours for polymerization, and then add xylene to adjust the nonvolatile content to 60%, and further add 11 parts of 35% hydrochloric acid and 50 parts of water. 2 at 90 ℃
After neutralizing for a period of time, washing and water separation were repeated until neutrality was obtained, and then the organic phase was dehydrated. Next, a platinum catalyst was added as platinum metal to the resin content of the varnish obtained by filtration so as to be 50 ppm and mixed. The properties of the varnish thus obtained were as follows.

Appearance: Light yellow transparent liquid Nonvolatile matter: 59.5%, viscosity: 6.8cs, specific gravity: 1.027, solvent: xylene.

The compounding molar ratio of the monofunctional siloxane unit to the tetrafunctional siloxane unit and the trifunctional siloxane unit is 0.9: 0: 0.4.
7, vinyl group content is 20.0 mol%, 100 g of varnish
It contained 0.166 mol of vinyl groups.

Next, to 100 parts of the obtained varnish, 50 parts of Fe ₂ O ₃ (red iron oxide) and 70 parts of alumina powder were mixed, and then xylene was added to form a paste, which was further kneaded with a three-roll to form a red paste. It was made.

Average composition formula of the obtained paste The hydrogen organopolysiloxane represented by 80
Then, xylene was added until the viscosity became easy to apply. The obtained coating liquid was applied on an iron plate to a thickness of 0.1 mm, and heated and cured at 70 ° C. for 3 hours. The electrical characteristics of the coating film after curing have a withstand voltage of 6.0 kv / 0.1 mm and a volume resistivity of
It was 8.0 × 10 ¹⁵ Ω-cm, and the solvent resistance to 1,1,1 trichloroethane was good.

Example 3. 600 parts of methyl polysilicate (51% SiO ₂ product), 454.4 parts of hexamethyldisiloxane, 317 parts of vinyltrimethoxysilane, 194.5 parts of methyltrimethoxysilane and 256 parts of xylene are reflux condenser, thermometer and The mixture was placed in a four-necked flask equipped with a stirrer. While stirring the resulting mixture
A mixed solution of 15 parts of 35% hydrochloric acid and 15 parts of isopropanol was added, and then 880 parts of water was added dropwise over 2 hours, and then 69 ° C.
The hydrolysis reaction was carried out under reflux for 5 hours. Next, washing with water by adding 2,000 parts of water and separation were repeated until the aqueous phase became neutral. The organic phase was dehydrated azeotropically to adjust the nonvolatile content to 80%, 7 parts of sodium hydrogen carbonate was added, and the mixture was heated at 120 ° C. for 7 hours to carry out polymerization.
Next, xylene was added to adjust the non-volatile content to 60%, 11 parts of 35% hydrochloric acid and 50 parts of water were added, and the mixture was neutralized at 90 ° C for 2 hours, then washed with water until it became neutral, and repeatedly separated. It was A platinum catalyst was added to and mixed with the resin component of the obtained varnish obtained by dehydrating and filtering the organic phase so as to be 40 ppm as platinum metal.

The properties of the varnish thus obtained were as follows.

Appearance: Light yellow transparent liquid, nonvolatile content: 60.5%, viscosity: 7.6cs, specific gravity: 1.300, solvent: xylene.

The compounding molar ratio of the monofunctional siloxane unit to the tetrafunctional siloxane unit and the trifunctional siloxane unit was 1.1: 1.0: 0.
7. The vinyl group content was 15 mol%, and 0.126 mol of vinyl group was contained in 100 g of varnish.

Next, 100 parts of natural silica (Grand Colts) powder and 50 parts of magnesia powder were kneaded with 50 parts of the obtained varnish, and toluene was added to form a paste. 15 parts of the hydrogen polysiloxane used in Example 1 was mixed with the obtained paste, and the mixture was applied onto an iron plate provided with a frame having a thickness of 1 mm, and 70 ° C. under a pressure of ² kg / cm ² . It was heat-molded for 2 hours. The electric characteristics of the obtained molded product were a withstand voltage of 30 kv / mm, a volume resistivity of 3.5 × 10 ¹⁵ Ω-cm, and a good solvent resistance to tetrachloroethylene.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display area C08L 83/07 LRP

Claims (1)

[Claims] 1. A general formula (A) (R ¹ represents an unsubstituted or substituted monovalent hydrocarbon group,
a represents 0, 1 and 3, and is a copolymer composed of three kinds of siloxane units, and the alkenyl group-containing organopolysiloxane containing at least two alkenyl groups in one molecule of the copolymer. , (B) General formula (R ² represents a hydrogen atom or an unsubstituted or substituted monovalent hydrocarbon group, and b represents 0 or a positive integer of 1 to 3)
Hydrogen having at least one hydrogen atom directly bonded to a silicon atom in one molecule of the polymer or copolymer having at least one siloxane unit represented by An organopolysiloxane, (C) a catalytic amount of a platinum compound, and (D) an inorganic powder comprising one or more metal oxides and / or one or more metal double oxides. Electrical insulating coating composition.