JPH0931407A - Electrical insulation coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electrical insulation coating composition improved in resistance to heat discoloration, essentially comprising a phenolic resin prepared from a specific substituted phenolic compound, an epoxy resin and a filler. SOLUTION: This coating composition essentially comprises (A) a novolak- type phenolic resin prepared by reaction between a phenolic compound of the formula (R<1> is H, 1-8C alkyl, OH, etc.; R<2> is a 1-8C alkyl, OH phenyl, etc.) and an aldehyde compound in the presence of an acid catalyst and/or organic acid metal salt catalyst, (B) an epoxy resin (pref. bisphenol-type or cresol novolak-type epoxy resin) and (C) a filler (e.g. alumina, talc). It is preferable that the unreacted phenolic compound content is <=2wt.% and weight-average molecular weight 300-1,300. Normally, the components A and B account for 5-50wt.% of the whole composition, the component A 30-70wt.% of the whole resin, and the weight ratio A/B is (30:70) to (70:30). The component C normally accounts for 50-95wt.% of the composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to electric / electronic parts, particularly various capacitors, varistor, or hybrid I.
The present invention relates to a coating composition for forming an electrically insulating protective coating on C and the like.

[0002]

2. Description of the Related Art Many electric and electronic parts are provided with an insulating coating for the purpose of protection from moisture and mechanical protection. The characteristics of this insulating paint are directly the moisture resistance of the parts,
It has a great influence on mechanical properties. Examples of methods for coating these parts include a solvent-based dip coating method, a casting method, a powder coating method, and a molding method. Among them, the solvent-based dip coating method is a thermosetting resin such as a phenol resin or an epoxy resin, a filler such as silica and calcium carbonate, and other additives are dissolved and dispersed in a solvent to obtain a component, It is a method of dipping and evaporating the solvent at room temperature, followed by heat curing to coat the parts.

Paint used in the solvent-based dip coating method,
That is, the dipping coating contains a large amount of filler, and the cured coating film is generally porous and has a small coefficient of thermal expansion and is excellent in thermal shock resistance. In particular, solvent-based dip coating materials have excellent thermal shock resistance as a resin encapsulating material in the field of hybrid ICs, that is, a chip coating material that partially covers semiconductor chips and the like, or an exterior material that covers a circuit board on which molded parts and the like are mounted. And the amount of use is increasing.

When a component which is insulation-coated with a paint is mounted on a substrate or the like, it is generally fixed by soldering. At this time, the coating film is exposed to heat of several hundreds of degrees, but if the heat resistance is weak, it discolors and the appearance is greatly impaired. It is considered that this is because the bond of the aromatic ring of the main component, phenol resin, is broken by heat.

[0005]

In order to solve the problem of heat discoloration of the paint, a method of covering the heat discoloration by coloring with carbon black or the like is partially adopted, but this is an essential improvement. However, the actual situation is that the insulation is lowered and the adhesion is impaired.

The present inventor has conducted research to improve the heat resistance level of a coating composition that generally does not have good heat discoloration resistance, and as a result, a phenol resin containing a specific substituted phenol compound has significantly improved heat discoloration resistance. As a result, they have completed the present invention.

[0007]

Means for Solving the Problems The present invention provides a composition for electrical insulation coating, wherein an essential component is a phenol resin, an epoxy resin, a filler, and other additives.

Embedded image (R ¹ = H, C _{1 to} C ₈ alkyl group, OH, OR, N
R ₂ , phenyl group; R ² = C ₁ -C ₈ alkyl group, O
H, OR, NR ₂ , phenyl group, C (CH ₃ ) ₂ C ₆ H ₄ O
H; R = H, C ₁ -C ₄ alkyl group) and a aldehyde compound are reacted with an acidic catalyst, an organic acid metal salt catalyst, or a combination of two or more thereof. A composition for electrical insulation coating, characterized by using a novolac type phenolic resin.

That is, the coating composition of the present invention prevents the bond in the aromatic ring from being broken at a high temperature by introducing a substituent into the aromatic ring of the phenol resin which is a component that easily changes color.
Furthermore, since the unreacted phenol compound contained in the component is also a cause of discoloration, preferably, the unreacted phenol compound in the coating composition is removed to greatly improve the heat discoloration resistance.

The composition for electrical insulation coating of the present invention comprises (I)
There are two types: one that is supplied in the form of powder and is made into a solution by adding a solvent at the time of use; When the former is supplied in powder form, the resin component has the characteristic that the resin has better storability than when it is made into a solution, and in the latter case, it is used immediately after receiving the supply. It has the advantage that it can be used, and each is used according to the needs.

The phenolic resin used in the present invention preferably contains 2% or less of unreacted phenolic compound,
It is a novolac type phenolic resin having a weight average molecular weight of 300 to 1300. The amount of unreacted phenolic compound is 2
If it exceeds 5% by weight, the heat discoloration resistance is insufficiently improved. Further, if the weight average molecular weight is less than 300, the storage stability in the powder state is poor (the powder is likely to be solidified), and if it is more than 1300, the reactivity with the epoxy resin is lowered. The compounding amount of the phenol resin is usually 30 to 70 of the total resin content.
%. When the ratio is higher or lower than this ratio, the ratio of the unreacted portion is increased during the reaction with the epoxy resin, and the strength is lowered, so that it should be avoided.

In the present invention, the phenol resin is addition-condensed with a phenol compound represented by the above chemical formula (1) and a formaldehyde compound under an acidic catalyst, an organic acid metal salt catalyst, or a combination of two or more thereof. It is a novolac type phenolic resin obtained by the reaction. Further, a modified resin obtained by modifying the novolac type phenolic resin with a silicon compound, an epoxy compound, rubber or the like can also be used.

Examples of the phenol compound include cresol, xylenol, resorcin, paratertiarybutylphenol, paraoctylphenol, paraphenylphenol, orthocresol, paracresol, paraethylphenol, parapropylphenol, paratertiarybutylphenol, paraoctylphenol,
It is a phenol compound such as paranonylphenol, metacresol, 3,5-xylenol, resorcinol, catechol, bisphenol A and bisphenol F, and is one or more selected from these. The formaldehyde compound is an aqueous formaldehyde solution (formalin), paraformaldehyde, trioxane, or the like, and these can be used in combination.

The epoxy resin used in the present invention is
Solid epoxy resin having at least two epoxy groups in one molecule, such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, aliphatic glycidyl ether type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin. , Alicyclic epoxy resins, brominated epoxy resins, various modified epoxy resins, and the like, and it is possible to use several kinds of them in combination. A bisphenol type or cresol novolac type epoxy resin is preferable in terms of heat discoloration resistance and coating film adhesion.

As described above, the resin compounded in the present invention is a phenol resin and an epoxy resin, which is usually 5 to 50% by weight of the total composition composition. Since the curing of the resin component depends on the reaction between the phenol resin and the epoxy resin, phenol resin / epoxy resin = 30/70 to 70/30
(Weight ratio) If the compounding ratio is out of this range, the resin cannot be sufficiently cured and the strength of the composition is reduced.

In the present invention, the moisture resistance of the composition is improved,
Silicone resin can be used for the purpose of lowering the elastic modulus. Here, the silicone resin is a general term for silicone resins including organopolysiloxane and the like, and it is more preferable that the silicone resin has a reactive substituent such as a hydroxyl group, an amine group or an epoxy group. When compounding more than 50% of the total resin content when blending silicone resin, mechanical properties such as strength and adhesion, and workability when coating parts are significantly reduced. To do.

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, which is in a crushed, spherical, granular or hollow shape, and is not limited. . Also, two or more of these fillers can be used in combination. A filler treated with a coupling agent is also preferably used. The compounding ratio of the filler is usually 50 to 95% by weight of the whole composition. When the blending amount is less than 50% by weight, the thermal shock resistance is lowered and the price becomes expensive. This is because if the amount is more than 95% by weight, the paintability of the coating material is deteriorated.

The solvent used in the present invention is a hydrocarbon solvent such as toluene or xylene, an alcohol solvent such as methanol or ethanol, a ketone solvent such as acetone or methyl ethyl ketone, and an ester solvent, an ether solvent, an ether alcohol solvent. , An ether ester solvent or the like is used in an appropriate amount of 1 type or 2 types or more (depending on use conditions), but preferably 5 to 30% of the total composition.
Used by blending by weight%.

In the present invention, it is preferable to use a coupling agent in order to enhance the affinity such as binding strength, wettability and adhesion between the resin and the filler and the coating composition and the parts. Examples of the coupling agent include a silane coupling agent, a titanate coupling agent, an aluminum coupling agent, etc.
Add 5.0 wt%.

Other additives include nitrogen compounds typified by imidazole derivatives, phosphorus compound-based curing accelerators typified by triphenylphosphine, flame retardant auxiliaries typified by antimony trioxide, other leveling agents, and quenching agents. A proper amount of a foaming agent, a pigment and a dye can be blended if necessary.

[0021]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited to the examples. All "parts" and "%" described in the examples and comparative examples refer to "parts by weight" and "% by weight".

Example 1 Paratertiary butylphenol (PTBP) 100
Parts and 90% 37% formalin, 10 oxalic acid as catalyst
Was charged, the reaction was carried out at a temperature of 100 ° C. until the unreacted PTBP was 1% or less, and then dehydration was performed under vacuum,
Solid novolac type phenolic resin with a melting point of 85 ° C (hereinafter,
Novolak A) was obtained.

Example 2 100 parts of orthocresol and 90 parts of 37% formalin,
10 parts of oxalic acid was charged as a catalyst, and 2 at a temperature of 100 degrees.
The reaction was carried out for a time, and then dehydration was performed under vacuum. Then, unreacted cresol was reacted at 200 ° C. until it became 0.5% or less to obtain a solid novolac type cresol resin (hereinafter referred to as novolac B) having a melting point of 90 ° C.

Comparative Example 1 100 parts of phenol and 150 parts of 37% formalin, 15 parts of 28% ammonia water as a catalyst and 0.5 part of calcium hydroxide were charged and reacted at a temperature of 100 ° C. for 40 minutes, followed by dehydration under vacuum. Was performed to obtain a solid resol-type phenol resin having a melting point of 67 ° C. (hereinafter, referred to as “resole”).

The powder resin composition was obtained by pulverizing and mixing in the mixing ratios shown in Table 1. 25 parts of a mixed solvent of acetone / methanol = 3/1 was added to 100 parts of the compositions of Examples 1 to 6 and Comparative Examples 1 and 2, and mixed for 2 hours to prepare a paste. And the viscosity at 25 ° C. was adjusted to 1.5 Pa · s. Coating was performed using the paste prepared as described above, and after heat treatment at 150 ° C. for 1 hour, heat discoloration resistance was observed. Table 1 shows the measurement results.

[0026]

[Table 1]

(Measurement method) 1. Heat-resistant discoloration test A cured coating film cured at 150 ° C for 1 hour is heated at 200 ° C to 2 ° C.
It was immersed in a solder bath at 50 ° C. and 300 ° C. to 350 ° C. for 5 seconds, and the color change was confirmed. 2. Bending Strength A test piece (about 100 × 20 × 2) was prepared from the obtained paste and cured at 150 ° C. for 1 hour. The bending strength (JIS K 7203) of this test piece was measured.

[0028]

The coating composition of the present invention can improve the heat discoloration resistance by introducing a substituent into the aromatic ring of the phenol resin. Furthermore, by removing the unreacted phenol compound in the resin component, more excellent heat discoloration resistance can be obtained.

Claims (2)

[Claims] 1. In a composition for electrical insulation coating containing a phenol resin, an epoxy resin, and a filler as an essential component, the phenol resin has a general formula: (R ¹ = H, C _{1 to} C ₈ alkyl group, OH, OR, N
R ₂ , phenyl group; R ² = C ₁ -C ₈ alkyl group, O
H, OR, NR ₂ , phenyl group, C (CH ₃ ) ₂ C ₆ H ₄ O
H; R = H, C ₁ -C ₄ alkyl group) and a aldehyde compound are reacted with an acidic catalyst, an organic acid metal salt catalyst, or a combination of two or more thereof. A novolac-type phenolic resin, which is a composition for electrical insulation coating. 2. The phenolic resin as defined in the preceding paragraph has an unreacted phenolic compound content of 2% by weight or less and a weight average molecular weight of 300 to 130.
The composition for electrical insulation coating according to claim 1, which is a novolac type phenol resin of No. 0.