JPH0931406A - Dipping coating material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a dipping coating material improved in both mechanical strength and curability while retaining its resin content, thus extremely suitable for electrical and electronic parts, essentialy containing an aniline-modified phenolic resin and an epoxy resin. SOLUTION: This coating material essentially contains (A) an anilinemodified phenolic resin and (B) an epoxy resin (pref. cresol novolak-type epoxy resin <=500 in epoxy equivalent). The component A is obtained, in general, by reaction between a phenolic compound and an aldehyde in the presence of aniline and a divalent metal oxide or hydroxide. It is preferable that the aniline modification rate is 0.1-0.4mol per mol of the phenolic compound. Normally, the resin, the component A and the component B account for 5-50wt.%, 3-25wt.%, and 2-25wt.% of the whole coating composition, respectively. The weight ratio A/B is normally 100:(40-140). Besides, it is preferable that this coating material also contain silica as filter and a coupling agent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dipping paint which is extremely suitable for painting electric / electronic parts.

[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. Of these, the solvent-based dip coating method is a coating obtained by dissolving and dispersing a thermosetting resin such as a phenol resin or an epoxy resin in a solvent, a filler such as silica or calcium carbonate, and other additives. Is dipped, the solvent is evaporated at room temperature, and then heat curing treatment is performed to coat the part.

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.

[0004]

The dipping paint is
Since the filler content was high and the resin content was low, the coating film was weak and could easily be scratched or cracked. The resin content may be increased to improve the strength of the coating film. However, if the resin content is more than 30% by weight, the coefficient of thermal expansion increases, the thermal shock resistance performance extremely decreases, and a sufficient effect is obtained. The reality was that I couldn't get it.

Further, with the miniaturization and diversification of electronic / electrical parts, the use of heat-sensitive elements and materials is also increasing. In order to coat these materials with low heat resistance, the amount of the curing accelerator in the paint may be increased to give curability at low temperature, or a two-pack type paint may be used, but the price is expensive. However, the pot life (pot life) and storability are shortened, workability is deteriorated, and the appearance of the coating film is deteriorated.

There has been a long-felt need for a dipping coating composition having sufficient strength while maintaining a small coefficient of thermal expansion at a resin content of 30% by weight or less and curable at a low temperature. The present invention improves the strength and curability of a phenol resin-based dipping paint, which is generally inferior in strength, while maintaining the conventional resin content.

[0007]

The present invention is a dipping paint containing an aniline-modified phenol resin and an epoxy resin as essential components, preferably silica as a filler, and a coupling agent as an additive. It is a dipping paint. With such a composition, a dipping paint having excellent curability and good coating strength can be obtained.

The aniline-modified resole in the present invention is a phenol resin disclosed in JP-A-58-109525, that is, phenols and aldehydes are converted to aniline and oxides or hydroxides of divalent metals. It is an aniline-modified resole obtained by reacting in the presence. In the aniline-modified resole, the modification rate of aniline is in the range of 0.05 to 0.5 mol with respect to 1 mol of phenols, but 0.1 to 0.4 mol is the ease of resin production and dipping coating composition. It is preferable in terms of fast curing property. The amount of the aniline-modified resole compounded is usually 3 to 25% by weight of the total coating composition.

The epoxy resin used in the present invention is
It is not particularly limited as long as it is a solid epoxy resin having at least two epoxy groups in one molecule, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, aliphatic glycidyl ether type epoxy resin,
Examples include phenol novolac type epoxy resin, cresol novolac type epoxy resin, alicyclic epoxy resin, brominated epoxy resin, and various modified epoxy resins. Among these, those having an epoxy equivalent of 500 or less are preferable. One or more of these epoxy resins are blended in the coating composition. Among the epoxy resins, a preferable type is a novolac type epoxy resin, particularly a cresol novolac type epoxy resin, which has a well-balanced improvement in strength and curability.

The ratio of epoxy resin to the total composition is usually 2 to 25% by weight. The ratio of epoxy resin to 100 parts by weight of aniline-modified phenol resin is 40 to 1
40 parts by weight. If it is less than 40 parts by weight, the strength of the coating material is not sufficiently improved, and if it is more than 140 parts by weight, the adhesion to the base material is lowered. The ratio of the resin component to the whole composition is usually 5 to 50% by weight. If it is less than 5% by weight, the strength will be low, and if it exceeds 50% by weight, the coefficient of thermal expansion will be large and the thermal shock resistance will be deteriorated.

The reason why the dipping coating material of the present invention has a fast curing property, that is, the coating material can be cured at a low temperature in a short time is as follows.
It is considered that this is because the aniline molecule portion in the aniline-modified resole has a basic property, which accelerates the reaction between the aniline-modified resole and the epoxy resin. Furthermore, the cured resin obtained by reacting them has a large binding force and is excellent in strength.

In the present invention, silica is preferably added as a filler to further improve the strength. Silica includes crystalline silica, fused silica, and the like, and the shapes thereof are crushed, spherical, granular, hollow, and the like. Silica treated with a coupling agent is also suitably used, and two or more kinds of these silicas are mixed and used. You may. The ratio of silica to the whole composition is usually 50 to 95% by weight, and it can be used in combination with other fillers typified by calcium carbonate, aluminum hydroxide and the like.

In the present invention, more preferably, a coupling agent is used in order to enhance the affinity such as binding force, wettability and adhesion between the resin and the filler. As the coupling agent, a silane coupling agent, a titanate coupling agent,
Alternatively, there is an aluminum-based coupling agent and the like, and for the above-mentioned purpose, it is usually blended in an amount of 0.01 to 5.0 parts by weight with respect to the entire coating composition.

The dipping paint of the present invention is dissolved and dispersed in a solvent at the time of use. The solvent is a hydrocarbon solvent such as toluene and xylene, an alcohol solvent such as methanol and ethanol, a ketone solvent such as acetone and methyl ethyl ketone. In addition, one or more solvents such as ester-based, ether-based, ether alcohol-based, and ether ester-based solvents are added in appropriate amounts (depending on use conditions), preferably 5 to 40 parts by weight per 100 parts by weight of the composition. use.

In the present invention, a nitrogen compound typified by an imidazole derivative or a phosphorus compound-based curing accelerator typified by triphenylphosphine, a flame retardant aid typified by antimony trioxide, other leveling agents or defoaming agents. , Pigments and dyes can be blended in appropriate amounts as needed.

[0016]

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 "%" listed below are "parts by weight"
And "% by weight".

(1) Blending of coating material Example 1 100 parts of phenol, 150 parts of 37% formalin, 30 parts of aniline, and 3 parts of magnesium hydroxide as a catalyst were placed in a reaction kettle equipped with a stirrer and a reflux condenser, and the mixture was heated to 70 ° C. The temperature was raised to and kept at this temperature for 90 minutes. Then heat under vacuum,
Dehydration and release of free phenol were performed. Resin melting point is 8
When it reached 5 ° C., it was discharged from the reaction kettle and rapidly cooled to obtain a solid resol-type aniline-modified phenol resin (hereinafter referred to as aniline-modified resol [1]). 10 parts of aniline-modified resol [1], 10 parts of epoxy orthocresol novolak, 80 parts of crystalline silica, 20 parts of mixed solvent of acetone: methanol = 3: 1, 2 parts of silane coupling agent as an additive, and mixed with a stirrer. The mixture was mixed for 2 hours to prepare a paint. Further, the viscosity at 25 ° C. was adjusted to 1.5 Pa · s by diluting with the above mixed solvent.

Example 2 100 parts of phenol, 140 parts of 37% formalin, and 4 parts of zinc hydroxide as a catalyst were placed in a reaction kettle equipped with a stirrer and a reflux condenser, heated to 90 ° C., and 20 parts of aniline was added to 2 parts.
It was added dropwise in small portions over 0 minutes. While maintaining the temperature at 90 ° C., the reaction was further performed for 30 minutes. It was then heated under vacuum to dehydrate and release phenol. When the melting point of the resin reached 80 ° C., it was discharged from the reaction kettle and rapidly cooled to obtain a solid resol type aniline modified phenol resin (hereinafter referred to as aniline modified resol [2]). 10 parts of aniline modified resol [2], 10 parts of epoxy orthocresol novolak, 80 parts of crystalline silica, 20 parts of mixed solvent of acetone: methanol = 3: 1, 2 parts of silane coupling agent as an additive, and mixed with a stirrer. The mixture was mixed for 2 hours to prepare a paint. Further, the viscosity at 25 ° C. was adjusted to 1.5 Pa · s by diluting with the above mixed solvent.

Comparative Example 1 20 parts of aniline modified resol [1], calcium carbonate 8
25 parts of a mixed solvent of 0 part and acetone: methanol = 3: 1 was mixed and mixed with a stirrer for 2 hours to prepare a paint. Furthermore, the viscosity at 25 ° C is 1.
It was adjusted to 5 Pa · s.

Comparative Example 2 20 parts of aniline-modified resole [2], calcium carbonate 8
25 parts of a mixed solvent of 0 part and acetone: methanol = 3: 1 was mixed and mixed with a stirrer for 2 hours to prepare a paint. Furthermore, the viscosity at 25 ° C is 1.
It was adjusted to 5 Pa · s.

(2) Evaluation method A test piece (about 100 × 20 × 2 mm) was prepared from the obtained coating material and cured under predetermined conditions. The cured test piece was subjected to bending strength measurement (JIS K 7203), immersed in acetone, and the surface hardness after 1, 2 and 3 hours was measured with a Barcol hardness meter, which was used as an index of curability.

(3) Results As shown in Table 1, the dipping paints obtained in Examples 1 and 2 were sufficiently cured at 90 ° C. for 2 hours, and compared with the paints in Comparative Examples 1 and 2. The bending strength was three times or more.

[0023]

[Table 1]

[0024]

INDUSTRIAL APPLICABILITY The dipping coating composition of the present invention has excellent curability by incorporating aniline-modified resole and epoxy resin as resin components, preferably silica as a filler, and further a coupling agent. Since it exhibits strength, it is extremely suitable for electrical and electronic parts.

Claims (3)

[Claims] 1. A dipping paint comprising the following components (A) to (B) as essential components. (A) Aniline-modified phenol resin (B) Epoxy resin 2. A dipping paint comprising the following components (A) to (C) as essential components. (A) Aniline-modified phenol resin (B) Epoxy resin (C) Silica 3. The dipping paint according to claim 1, which further comprises a coupling agent.