JPH0742398B2 - Composition for electrical insulation coating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to an insulating coating for electronic parts, particularly an exterior coating for forming a protective coating for electrical insulation on various capacitors and hybrid ICs.

[Prior art]

Electronic parts are coated with an insulating coating for the purpose of protection from moisture and mechanical protection.

The characteristics of this insulating paint directly affect the moisture resistance and mechanical characteristics of electronic components.

On the other hand, as a coating method for electronic parts, there are a solvent-based dip coating method, a casting method, a powder coating method, a molding method and the like.

In this solvent-based dip coating method, electronic components are dip-coated with a paint prepared by compounding a solvent with a composition consisting of a thermosetting resin, a filler, a thixotropic agent, an additive, etc., and the solvent is partially evaporated by air drying. After that, it is a method of heating and curing to coat the electronic component.

When higher humidity resistance is required, a method of impregnating these electronic parts with wax or silicon is adopted.

The material used in the solvent-based dip coating method contains a large amount of filler, and the cured coating film has a coefficient of thermal expansion as low as that of ceramics and has low internal stress, so it has excellent thermal shock resistance.

It is especially suitable for hybrid ICs that use large capacitors, varistors, and large circuit boards.

Although this solvent-based dip coating material has the above-mentioned preferable characteristics, it is unavoidable that the coating composition tends to become non-uniform due to the sedimentation of the filler during the dipping operation because it contains a large amount of the filler. . For this reason, it is necessary to constantly apply a stirring operation to the coating liquid and to pay attention to uniformization of the coating liquid, and from this aspect, development of a material in which the sedimentation of the filler is slower is desired.

In addition, with the increase in the size of parts, it is desired to develop a material with less sagging during dipping work.

And, as a problem when supplying the material in the form of a solution, a large amount of the filler in the material settles with the lapse of time, becomes a hard sediment, and takes a lot of man-hours to make the sediment uniform during dip coating, A soft cake of sediment is desired.

Moreover, since the solvent-based dip coating material contains a large amount of the filler as described above, the cured coating film is generally porous.

In order to improve various properties as a protective paint, it is desired to develop a material that retains its original function and develops a more dense coating film.

[Object of the Invention]

The present inventors have conducted research to improve the above-mentioned problems, and as a result, a thermosetting resin component in a solvent-based dip coating material in which essential components are a thermosetting resin, a filler, a thixotropic agent, and an additive. Resol type phenolic resin using a nitrogen-containing compound catalyst as, by using organic bentonite as a thixotropic component, sedimentation of the filler of the material,
It was found that problems such as soft cake of sediment and sagging property can be solved, and the cured coating film can be densified.

An object of the present invention is to provide a coating material which has excellent coating film characteristics and dip coating workability and is easy to handle.

[Structure of Invention]

As the coating material used in the solvent-based dip coating method, there are those that are supplied in powder form and are added by adding a solvent at the time of use to form a solution, and those that are added by adding a solvent in advance to form a solution (basto form) There are two.

The former resin, which is supplied in the form of powder, is characterized in that it has a better resin storability than that of the latter, which is in the form of a solution, and is used properly.

The present invention relates to a composition for electrical insulation coating in which essential components are a thermosetting resin, a filler, a thixotropic agent, and an additive. The thermosetting resin component is a resol-type phenol whose main component is a nitrogen-containing compound catalyst. A resin (hereinafter referred to as a resol type phenol resin), specifically, (a) only a resol type phenol resin or (b) a resol type phenol resin and a novolac type phenol resin, (2) the thixotropic component is organic. A composition for electrical insulation coating, comprising bentonite.

The resol type phenol resin used in the present invention is usually 1 mol or more of formaldehyde, preferably 1.1 to 1.8 mol, per 1 mol of phenol, and a nitrogen-containing compound catalyst as a catalyst, or a nitrogen-containing compound and an alkaline earth metal catalyst. Is a resin that has been condensed and dehydrated by a conventional method by using together.

The phenols mentioned here are alkylphenols such as phenol, cresol, xylenol, resorcin, and paratertiarybutylphenol, paraoctylphenol, paranonylphenol, and paraphenylphenol.

The formaldehyde may be paraformaldehyde in addition to the formalin aqueous solution.

The nitrogen-containing compound is ammonia, triethylamine, triethanolamine, diethyleneamine, aniline, hexamethylenetetramine and the like. The alkaline earth metal is an oxide or hydroxide of an alkaline earth metal such as calcium, magnesium or barium.

The resol-type phenol resin obtained from the nitrogen-containing compound and the catalyst containing the nitrogen-containing compound and the alkaline earth metal in combination is an essential resin for improving various electric characteristics because the cured product has good moisture resistance.

On the other hand, in the case of a resol using an alkali metal catalyst such as sodium hydroxide, the electrical insulation is deteriorated.

The resol type phenolic resin used in the present invention is more preferably an ammonia resol using ammonia and hexamethylenetetramine as a reaction catalyst. A preferable catalyst amount is ₃ as NH _{3 with} respect to 100 parts of phenol.
~ 15 copies.

The novolak type phenolic resin used in the present invention uses the phenols and formaldehyde described in the resol type phenolic resin, and organic acids such as oxalic acid and inorganic acids such as hydrochloric acid and sulfuric acid as catalysts, and organic acids such as zinc acetate. It is a resin that is condensed and dehydrated by a conventional method using one or more salts.

When a novolac type phenol resin is blended as the thermosetting resin component of the present invention, the strength can be further improved. The effect of further improving the sagging property and the drying property can be expected.

When the thermosetting resin component is a resol type phenolic resin and a novolak type phenolic resin, if the proportion of the novolak type phenolic resin is high, the solvent resistance will deteriorate. The proportion is preferably 55 to 85% by weight of the resol type phenolic resin and 45 to 15% by weight of the novolac type phenolic resin.

Further, the addition amount of the thermosetting resin component is 5 to the filler.
It is preferably 20% by weight.

The filler used in the present invention is an inorganic filler such as calcium carbonate, alumina, talc, crystalline silica, fused silica, and sintered aluminum silicate, but is not limited thereto. Further, one or more of these fillers can be used in combination. From the viewpoint of solder heat resistance, strength, and prevention of sedimentation, it is preferable to use crystalline silica or fused silica.

The powdery thixotropic agent generally includes metal soaps such as aluminum stearate, fine powder silica, surface-treated calcium carbonate, bentonite, kaolin, clay, resin acid amide wax, and organic bentonite.

In the present invention, organic bentonite (amine-bonded bentonite complex) is used as a main component of the thixotropic agent, and the sedimentation property, soft cake formation of the sediment, and sagging property can be improved.

Further, in the present invention, the denseness of the cured coating film can be greatly improved. It is considered that the improvement of the compactness is due to the synergistic effect of the resol type phenol resin and the organic bentonite. The addition amount of the thixotropic agent is preferably 0.2 to 2.0% by weight based on the filler.

Solvents used in the present invention include hydrocarbon solvents such as toluene and xylene, alcohol solvents such as ethyl alcohol, ketone solvents such as acetone and methyl ethyl ketone, and others, ester-based, ether-based, ether alcohol-based, ether ester-based solvents. Use one or more solvents such as.

About additives, silane coupling agents and titanium coupling agents are used as fillers to improve adhesion.
It is preferable to contain 1 to 2.0% by weight.

As other additives, defoaming agents, pigments, dyes and the like can be added in appropriate amounts.

〔The invention's effect〕

As described above, the insulating coating composition of the present invention is excellent in thermal shock resistance as a solvent-based dip coating material containing a large amount of a filler when blended with a solvent, as well as sedimentation stability and sag. Excellent in handling dip workability paste.

Further, what is important is that the cured coating film becomes dense and various properties as an exterior coating material are greatly improved. It is considered that this is due to the synergistic effect of the resol type phenol resin and the organic bentonite.

〔Example〕

Hereinafter, examples and comparative examples of the present invention will be described. However, the present invention is not limited to the examples.
Moreover, all "parts" and "%" described herein mean "parts by weight" and "% by weight".

Production Example 1 94 parts phenol, 146 parts 37% formalin, 28 as catalyst
% 15% aqueous ammonia and 0.5 part calcium hydroxide are charged and reacted at a temperature of 100 ° C for 40 minutes, then dehydrated under vacuum to give a solid resol type phenolic resin (hereinafter referred to as solid resol A) having a melting point of 67 ° C. Obtained.

Production Example 2 A solid resol type phenol resin having a melting point of 70 ° C. (hereinafter referred to as solid resol B) was obtained in the same manner as in Production Example 1 except that 20 parts of 28% Ammonia water was used as a catalyst.

Production Example 3 94 parts of phenol, 60 parts of 37% formalin, and 1 part of oxalic acid as a catalyst were charged, the temperature was 100 ° C. for 3 hours, and then dehydration was performed under vacuum to obtain a novolac type phenol resin having a melting point of 70 ° C. It was

Examples 1 to 3 and Comparative Examples 1 to 3 were pulverized and mixed at the compounding ratios shown in Table 1 to obtain powder resin compositions.

To 100 parts of the powder compositions of Examples 1 to 3 and Comparative Examples 1 to 25, 25 parts of a mixed solvent of acetone: methanol = 3: 1 was blended and mixed for 2 hours to prepare a paste. The viscosity at 25 ° C was adjusted to 15 poise by diluting with.

The paste prepared as described above was used to measure the sedimentation property, the condition of the sediment, the sag property, the compactness, and the bending strength. The evaluation results are shown in Table-1.

The measurement (evaluation) method of each characteristic is as follows.

1. Sedimentation: 100 ml paste (1
5 poises) and let stand for 5 minutes to start separating the supernatant.
The sedimentation stability of the paste was evaluated from the separated amount (ml) after the elapse of time.

2. Hardness of sediment: After adjusting the paste, a glass rod was inserted into the paste that was left at room temperature for one month, and the hardness of the paste sediment was observed.

3. Sagging property: With respect to the paste which was stored at room temperature for one month after adjusting the paste, the slide glass was immersed in the longitudinal direction by about half, slowly pulled up and turned upside down, and the degree of sagging was visually observed.

Those without sagging were marked with ◯, and those with sagging were marked with x.

4. Denseness: After dropping the paste on a ceramic substrate to a diameter of about 10 mm, it was air-dried and cured at 150 ° C for 30 minutes.

After dipping this test piece in a red dye solution at 80 ° C for 30 minutes,
The test piece was cut, the degree of impregnation of the dye solution (impregnation rate%) was determined, and the denseness of the coating film was grasped.

5. Bending strength: Approximately 1 thickness of coating material on a mold with a width of 30 mm and a length of 100 mm
Pour the product to a temperature of 24 mm, air dry at room temperature for 24 hours, and
It was heated at 150 ° C. for 30 minutes to be cured.

Take it out of the mold and use a bending strength tester to measure this test piece for 2 m.
Bending strength was measured at a load rate of m / min.

Claims (2)

[Claims] 1. A composition for electrical insulation coating, which comprises a thermosetting resin, a filler, a thixotropic agent and an additive as essential components,
The thermosetting resin component is a resol-type phenol resin whose main component is a nitrogen-containing compound catalyst, and a thixotropic agent main component is organic bentonite. 2. The composition for electrical insulation coating according to claim 1, wherein the thermosetting resin component comprises a resol type phenol resin and a novolac type phenol resin using a nitrogen-containing compound catalyst.