JP7008555B2 - Epoxy resin composition for dip coating - Google Patents

Description

The present invention relates to epoxy resin compositions suitable for use in dip coatings.

There are a wide variety of electronic components such as filters, oscillators, discriminators, traps, and thermistor elements, and the appearance of these electronic components can be broadly composed of the electronic component body and terminals. Many of these electronic components are known to have an electronic component body and terminals coated with an insulating resin in order to maintain insulating properties (Patent Document 1).

Japanese Unexamined Patent Publication No. 6-244002

However, in recent years, such electronic components have become smaller and have higher output, and sudden temperature changes (high temperatures) from the electronic component body accelerate the deterioration of the electronic component body or cause a failure. Although heat resistance and flame retardancy performance have been required to be improved for insulating resin parts, they are still unsatisfactory, and due to environmental considerations, the use of flame retardants such as halogen and phosphorus should be avoided. Is desired.
Therefore, the present inventors selected a metal hydrate as a flame retardant and contained it in an epoxy resin until the desired flame retardant performance was obtained. As a result, the viscosity of the resin composition became too high, and electronic parts were used. It could not be inserted into the resin composition well, and it became unusable as a resin composition for dip coating.
Further, when the content of the metal hydrate was reduced to the extent that the electronic component could be successfully inserted into the resin composition, the desired flame retardant performance could not be obtained. Further, a rocking denaturing agent is usually added to the resin composition for dip coating in order to prevent liquid dripping, but when the content of the rocking denaturing agent is reduced, the electronic component is contained in the resin composition. When it was heat-cured after being inserted into and removed from the container, the liquid drips and becomes unusable as a resin composition for dip coating.

An object of the present invention is an epoxy capable of forming a flame-retardant cured product while maintaining excellent dip performance (both ease of inserting electronic components into a resin composition and prevention of liquid dripping). It is an object of the present invention to provide an electric / electronic element having a coating layer composed of a resin composition and a cured product of the epoxy resin composition.

The present inventors adjust the blending amount of the silica powder in at least one of the first liquid containing the epoxy resin liquid at room temperature and the second liquid containing the curing agent and the curing accelerator, and the mass average granules. We have found that the above problems can be solved by using a plurality of hydrated metal-based flame retardants having different diameters in combination and adjusting the blending amount (preferably, further ratio) thereof, and have completed the present invention. That is, according to the present invention, an epoxy resin composition having the following constitution is provided. Further, according to the present invention, there is provided an electric / electronic device in which a coat layer composed of a cured product obtained by curing an epoxy resin composition having the structure shown below is formed at least in a part thereof.

In the following, (A): epoxy resin liquid at room temperature, (B): silica powder, (C): curing agent, (D): curing accelerator, (E): hydrated metal flame retardant, (A) , (C), (D) and, if necessary, a reactive diluent: resin content.
At this time, the epoxy resin composition of the present invention is an epoxy resin composition for dip coating for forming a cured product conforming to the UL94V-0 standard.
It has a first liquid containing (A) and a second liquid containing (C) and (D).
At least one of the first liquid and the second liquid further contains (B) and a plurality of (E) having different mass average particle sizes.
It is characterized in that the blending amount of (B) with respect to 100 parts by mass of the resin content is 2 to 8 parts by mass, and the total blending amount of (E) with respect to 100 parts by mass of the resin content is 130 to 190 parts by mass. do.

In the following, among all the metal hydrated flame retardants to be combined, the one having the maximum mass average particle size among the (E) is the first metal hydrated metal flame retardant (E1), the mass average particle size. The second hydrated metal-based flame retardant (E2) has a minimum value of. At this time, in the epoxy resin composition of the present invention, (E1) has a mass ratio of (E1): 3 or more and 5 or less with respect to (E2): 1 in all (E) to be combined. And (E2) can be included.
In the epoxy resin composition of the present invention, both (E1) and (E2) can be composed of aluminum hydroxide.

In the following, among (A), (A1): bisphenol A type epoxy resin and (A2): glycidylamine type epoxy resin. At this time, in the epoxy resin composition of the present invention, (A) contains (A1) and (A2), and (A1): 1 in all (A), (A2) is 0.05. It can be contained in a mass ratio of 0.7 or more and 0.7 or less.

In the following, among (B), (B1): fumed silica treated with a silane coupling agent having an alkyl group, and (B2): fumed silica treated with a silicone oil. At this time, in the epoxy resin composition of the present invention, (B) contains (B1) and (B2), and (B1): 1 and (B2) are 0.5 in all (B). It can be contained in a mass ratio of 4.0 or more.

In the following, among (C), (C1): an acid anhydride-based curing agent, and among (D), (D1): an imidazole-based curing accelerator. At this time, in the epoxy resin composition of the present invention, (C) contains (C1) and (D) contains (D1), and the blending amount of (D) with respect to 100 parts by mass of (C) is 0. It can be 5 to 10 parts by mass.

In the epoxy resin composition of the present invention, the blending amount of the silica powder in at least one of the first liquid containing the epoxy resin liquid at room temperature and the second liquid containing the curing agent and the curing accelerator is adjusted, and the blending amount of the silica powder is adjusted. A plurality of metal hydrated flame retardants having different mass average particle sizes are used in combination, and the blending amount (preferably, further ratio) thereof is adjusted. Therefore, an epoxy resin composition capable of forming a cured product with flame retardancy while maintaining excellent dip performance (combining ease of insertion and prevention of liquid dripping) and curing of the epoxy resin composition. It is possible to provide an electric / electronic element having a coat layer made of an object.

The details of the present invention will be described below.
In the following description, when the term "resin content" is used, it includes (A): epoxy resin liquid at room temperature, (C): curing agent, (D): curing accelerator, and if necessary. It shall mean the total components of possible reactive diluents.
The epoxy resin composition for dip coating of the present invention is composed of a first liquid and a second liquid, the first liquid contains (A) at least a liquid epoxy resin at room temperature, and the second liquid is (C). Includes a curing agent and (D) curing accelerator. The silica powder (B) and the metal hydrated flame retardant (E) are contained in at least one of the first liquid and the second liquid.

First, the components used in the first liquid will be described.
<(A)>
The epoxy resin (A) used in the first liquid can be used without particular limitation as long as it is liquid at room temperature. Examples of such an epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, alicyclic epoxy resin, aliphatic epoxy resin, brominated bisphenol A type epoxy resin, phenol-novolak type or cresol-novolak type. Epoxy resin, brominated novolak type epoxy resin, hydrogenated bisphenol A type or AD type epoxy resin, propylene glycol diglycidyl ether, pentaeristol polyglycidyl ether and other aliphatic epoxy resins, aliphatic or aromatic amines A glycidylamine type epoxy resin obtained from epichlorohydrin, a glycidyl ester type epoxy resin obtained from an aliphatic or aromatic carboxylic acid and epichlorohydrin, a heterocyclic epoxy resin, a biphenol type epoxy resin and the like can be used. Among them, it is preferable to contain a bisphenol A type epoxy resin from the viewpoint of heat resistance and mechanical strength. The epoxy resin (A) may be used alone or in combination of two or more.

Further, in the field where heat resistance is required, it can be dealt with by containing a glycidylamine type epoxy resin together with the bisphenol A type epoxy resin. Specific examples of the glycidylamine type epoxy resin include tetraglycidyldiaminodiphenylmethanes, glycidyl compounds of aminophenol, glycidylanilines, and glycidyl compounds of xylene diamine.

Among them, tetraglycidyldiaminodiphenylmethanes (tetraglycidylamine type epoxy resin) are preferable from the viewpoint of the balance between performance and cost.
Commercially available products of tetraglycidyldiaminodiphenylmethane include Sumiepoxy ELM434, Sumiepoxy ELM434HV (manufactured by Sumitomo Chemical Corporation); Epototo YH434, Epototo YH434L (manufactured by Nippon Steel & Sumitomo Metal Corporation); Araldite MY9612, Araldite MY9634, Araldite MY9663 (above, Huntsman Advanced Materials); jER604 (Mitsubishi Chemical); Bake1ite EPR494, Bake1ite EPR495, Bake1ite EPR495, Bake1ite EPR496, Bake1ite EPR496, Bake1 Can be mentioned

When the glycidylamine type epoxy resin is contained together with the bisphenol A type epoxy resin, it is preferable to contain both in a mass ratio of the former: 1 to the latter: 0.05 to 0.7. By blending both in such a mass ratio, it is expected that the heat resistance will be improved while maintaining the dip coat property (easiness of insertion).

The epoxy equivalent of (A) is not particularly limited, but is preferably 400 or less, more preferably 300 or less. If the epoxy equivalent is too high, the viscosity of the flame-retardant epoxy resin composition increases, the workability of the dip coat is inferior, the glass transition point is further lowered, and the cured product tends to be inferior in heat resistance. Epoxy equivalents are measured by a method according to JIS K7236.

A reactive diluent may be added to the first liquid, if necessary, for the purpose of reducing the viscosity of the resin composition of the present invention. As the reactive diluent that can be used, for example, an epoxy compound having an epoxy group in the molecule and having a viscosity of 500 mPa · s or less at 25 ° C. is used.
Examples of such a reactive diluent include those conventionally used for reducing viscosity, for example, butyl glycidyl ether, phenyl glycidyl ether, alkylphenol glycidyl ether, allyl glycidyl ether, butanediol glycidyl ether, hexanediol di. Examples thereof include glycidyl ether and neopentyl glycol diglycidyl ether.

When the reactive diluent is added, the amount added is 50% by mass or less, preferably 1 to 40% by mass, more preferably 5 to 5 to the total of the mixture of the epoxy resin (A) and the reactive diluent. It is 35% by mass. If it exceeds 50% by mass, the properties of the cured product may deteriorate.
Further, (A) includes (A1) and (A2), and (A2) is 0.05 or more and 0.7 or less with respect to (A1): 1 in all (A). When contained, the amount of the reactive diluent added is 2 to 50% by mass, preferably 10 to 40% by mass, based on the total of the mixture of (A1) and (A2) and the reactive diluent. %, More preferably 15 to 35% by mass. Within such a range, the dip coat property (easiness of insertion) can be further improved while maintaining the heat resistance.

Next, each component used in the second liquid will be described.
<(C) and (D)>
In the present invention, it is preferable to use methyl anhydride as the (C) curing agent used in the second liquid and 1-benzyl-2-phenylimidazole as the (D) curing accelerator used in the second liquid. ..

If a combination of a curing agent other than the above and a curing accelerator is used, crystallization after long-term storage cannot be prevented. In addition, when the above combination is used, as compared with the case where another combination, for example, a combination of methylimidazole anhydride and 2-ethyl-4-methylimidazole or 1-benzyl-2-methylimidazole, is used, at the time of storage. For example, 3- or 4-methyl-1,2,3,6-tetrahydrophthalic acid or 3- or 4-methyl-hexahydrophthalic acid and 1-benzyl-2-phenylimidazole. The glass transition temperature is higher than when the combination is used.

The mixing ratio of (C) and (D) is preferably in the range of 100: 0.5 to 100:10 in terms of mass ratio, but it is appropriate depending on the characteristics of the cured product to be obtained, for example, the curing rate and the glass transition temperature. You can select it.

If the proportion of 1-benzyl-2-phenylimidazole as a preferable example of (D) is smaller than this range, the curing rate becomes slower, and 1-benzyl-2-phenylimidazole as a preferable example of (D) is used. The effect is not obtained, and even if it is blended beyond this range, the effect corresponding to the amount used cannot be obtained. The preferred blending ratio is in the range of 100: 1 to 100: 7, more preferably 100: 2 to 100: 5.

As a method for preparing a curing agent composition using (C) and (D), a method of mixing a curing agent and a curing accelerator can be appropriately selected from the conventional methods, but the curing agent composition is particularly weighed in advance (). C) and (D) are mixed and stirred and mixed for 30 to 60 minutes with a stirrer such as a dissolver while heating to 70 to 90 ° C. It is preferable to prepare the curing agent composition by returning to room temperature after stirring and mixing.

Next, the blending ratio of (C) is preferably in the range of 0.8 to 1.2 equivalents with respect to 1 equivalent of the epoxy group in the case of a functional group of the resin to be used in combination, for example, an epoxy resin. If the blending ratio of (C) is less than this range, the reactivity becomes low, the time required for curing becomes long, and the cured physical properties tend to decrease, which is the production efficiency and the product. It causes deterioration of quality.

On the other hand, if it exceeds this range, curing may become too fast depending on the blending ratio of other components. When this tendency becomes remarkable, uniform curing is less likely to occur, a cured product is locally generated, and the characteristics of the resin layer are deteriorated.
In order to obtain an appropriate reaction rate and a uniform cured product, the range of 0.85 to 1.15 equivalents is more preferable, and the range of 0.9 to 1.1 equivalents is particularly preferable.

Next, each component used in at least one of the first liquid and the second liquid will be described.
<(B)>
(B) used in the present invention is silica powder, which is a component added as a rocking denaturing agent. Examples of the silica powder used in the present invention include fumed silica. Examples of the fumed silica include hydrophilic silica and hydrophobic silica, and in the present invention, it is effective to use two kinds of hydrophobic silica in combination. Such silica powder can be expected to improve the liquid dripping prevention property and the shaking denaturation of the resin composition. In the present invention, sway denaturation refers to the property that the apparent viscosity temporarily decreases by subjecting it to shear deformation in an isothermal state, and the original apparent viscosity recovers over time after being left to stand. It means that the air bleeding property, which will be described later, is improved when the above is improved.

The average particle size of the silica powder is preferably 5 to 200 nm as the average primary particle size. This is because the larger the specific surface area, the greater the effect of imparting sway denaturation. More preferably, it is 5 to 40 nm.

The hydrophobic silica is, for example, fumed silica (B1) treated with a silane coupling agent having an alkyl group, having a primary particle size of 5 to 200 nm and a specific surface area (BET) of 125 to 175 m ² / g. Things can be mentioned. (B1) exhibits the ability to prevent liquid dripping in a liquid resin at room temperature. Further, it has a feature that it takes a long time to recover to the apparent viscosity, and it is possible to improve the shaking denaturation.

As the hydrophobic silica, in addition to (B1), for example, fumed silica (B2) treated with silicone oil has a primary particle size of 5 to 200 nm and a specific surface area (BET) of 80 to 120 m ² / g. Can be mentioned. (B2) exhibits the performance of preventing liquid dripping in a liquid resin at room temperature and high temperature (curing) and improving shape retention.

Examples of the hydrophilic silica include those having no treatment on the surface, a primary particle diameter of 5 to 200 nm, and a specific surface area (BET) of 270 to 330 m ² / g.

The primary particle diameters of the hydrophilic silica and the hydrophobic silica can be measured by, for example, a dynamic light scattering method.

Here, the blending amount of (B) needs to be 2 to 8 parts by mass with respect to 100 parts by mass of the resin content. This is because the blending amount is too small and the liquid dripping prevention property is deteriorated. On the contrary, if the blending amount is too large, the air bleeding property is deteriorated, which is not preferable. Considering the liquid dripping prevention property and the air bleeding property, the range is more preferably 4 to 6 parts by mass.

Further, in the silica powder blended in such an amount, when (B1) and (B2) are used in combination, the blending ratio of (B2) is 0.5 or more with respect to (B1): 1. It is preferably contained in a mass ratio of 4.0 or less, and more preferably 1.0 or more and 2.0 or less.
When the ratio of (B2) is contained in a mass ratio of less than 0.5 with respect to (B1): 1, liquid dripping is likely to occur. On the other hand, when it is contained in a mass ratio of more than 4.0, the air release property tends to deteriorate.

(B) may be blended in either one of the first liquid and the second liquid, or may be blended in both. From the viewpoint of ease of mixing the first liquid and the second liquid, it is preferable to adjust the viscosities of the first liquid and the second liquid to the same extent.
Considering the dip performance of the epoxy resin composition (easiness of inserting electronic components and prevention of liquid dripping), the viscosity of the first liquid and the second liquid after mixing is, for example, 150 to the viscosity at 25 ° C. 350 Pa · s is preferable, more preferably 200 to 300 Pa · s, and particularly preferably 220 to 280 Pa · s.

<(E)>
It is essential that (E) used in the present invention comprises a combination of a plurality of metal hydrated flame retardants (aluminum hydroxide, magnesium hydroxide). In particular, as the metal hydrated flame retardant, at least two or more kinds of metal hydrated flame retardants having different mass average particle sizes are used in combination. In addition to this, among all the metal hydrated flame retardants used, the one having the maximum mass average particle size is defined as the first hydrated metal flame retardant (E1), and the mass average particle size is the minimum value. When the second hydrated metal flame retardant (E2) is used as the second flame retardant, in all the hydrated metal flame retardants used, (E2): 1 and (E1): 3 or more and 5 or less. It is preferable to contain (E1) and (E2) so as to have a mass ratio of (preferably 3.5 to 4.5).
Two or more kinds of metal hydrated flame retardants containing the first metal hydrated flame retardant (E1) and the second metal hydrated flame retardant (E2) having such a specific relationship within a predetermined mass ratio range. It is expected that the ease of inserting electronic parts will be improved by using these in combination.

The sizes of (E1) and (E2) are, in terms of mass average particle size, (E1): 5 to 40 μm, preferably 15 to 30 μm, (E2): 0.1 to 3 μm, preferably 0.7 to 2.5 μm. Is preferable.

(E1) used in combination with (E2) can be used after adjusting its particle size distribution. The particle size distribution may be adjusted by classifying and removing the relatively large particle size contained in (E1) to be used by a centrifugal force type wind classifier, a dry classifier, a sieving machine or the like.
In this example, in particular, as (E1) indicating the maximum mass average particle diameter, one having a mass average particle diameter of 10 to 30 times the mass average particle diameter of (E2) indicating the minimum mass average particle diameter is used. Is preferable. By using (E1) and (E2) having such a relationship in combination, the workability at the time of dip coating, particularly the ease of inserting electronic components, is likely to be improved.

In this example, it is essential that the total blending ratio of all the metal hydrated flame retardants (E) is in the range of 130 to 190 parts by mass with respect to 100 parts by mass of the resin content. If the mixing ratio is less than 130 parts by mass, the flame retardancy is inconvenient, and if it exceeds 190 parts by mass, the workability at the time of dip coating and the mechanical strength after curing are inconvenient. Not preferred. From the viewpoint of imparting flame retardancy while maintaining workability and mechanical strength as a resin composition for dip coating, the blending ratio is preferably 140 parts by mass or more, particularly preferably 150 parts by mass or more, and 180 parts by mass or less. In particular, 170 parts by mass or less is preferable.

In addition, both (E1) and (E2) used in this invention may be a surface-untreated product or a surface-treated product with a silane coupling agent, either or both. Examples of the silane coupling agent include those having a vinyl group, a methacrylate group, a glycidyl group, and an amino group at the terminal, and for example, epoxysilane (epoxy group-containing silane coupling agent) is preferable.

Specific examples of the epoxysilane include glycidoxy group-containing trialkoxysilanes such as γ-glycidoxypropyltrimethoxysilane (γ-GPS) and γ-glycidoxypropylmethyldiethoxysilane, and β- (3,4-epoxy). Cyclohexyl) Ethyltrimethoxysilane, β- (3,4-epylcyclohexyl) ethyltriethoxysilane, β- (3,4-epylcyclohexyl) ethyltripropoxysilane, β- (3,4-epylcyclohexyl) ethyltributoxy Silane, γ- (3,4-epoxycyclohexyl) propyltrimethoxysilane, γ- (3,4-epoxycyclohexyl) propyltriethoxysilane, δ- (3,4-epoxycyclohexyl) butyltrimethoxysilane, δ- ( Examples thereof include epoxyalkylalkoxysilanes such as 3,4-epyloxycyclohexyl) butyltriethoxysilane.
When the hydrated metal flame retardant is treated with a silane coupling agent, only one of the silane coupling agents may be used, or two or more of them may be used in combination.

As a method of surface treatment with a silane coupling agent, it is possible to perform the treatment by a commonly used method. For example, it can be obtained by dry-blending a hydrated metal-based flame retardant that has not been surface-treated in advance, performing a wet treatment, or blending a silane coupling agent at the time of kneading. The content of the silane coupling agent to be used is appropriately added in an amount sufficient for surface treatment, and specifically, 0.1 to 2.5% by weight, preferably 0.1 to 2.5% by weight, based on the metal hydrated flame retardant. Is 0.2 to 1.8% by weight, more preferably 0.3 to 1.0% by weight.

It is also possible to obtain a commercially available product of a metal hydrated flame retardant that has already been treated with a silane coupling agent. Examples of the epoxysilane-treated aluminum hydroxide include B303STE (mass average particle diameter 17 μm: manufactured by Nippon Light Metal Co., Ltd.).

(E) may be blended in either one of the first liquid and the second liquid, or may be blended in both. In that case, it is preferable to weigh the blending ratio of the first liquid and the second liquid of (B) described above and the viscosity of each liquid at 25 ° C. and blend them as appropriate.

In addition to the components described above, the epoxy resin composition for dip coating of the present invention contains, if necessary, a powder filler other than the silica powder and the hydrated metal system, as long as the effects of the present invention are not impaired. Other flame retardants, colorants, and other additives can be blended. Examples of the powder filler include crystalline silica, molten silica, calcium carbonate, talc, mica, alumina, white carbon, zirconia, titanium white, red iron oxide, silicon carbide, boron nitride, aluminum nitride, silicon nitride, magnesia, magnesium silicate and the like. Can be mentioned. Examples of the flame retardant include powdered organic halogen compounds, red phosphorus, phosphoric acid esters, antimony trioxide and the like. Examples of the colorant include various pigments / dyes such as carbon black and cobalt blue. In addition, these components may be blended in either 1st liquid and 2nd liquid, or may be blended in both. From the viewpoint of preventing the filler from precipitating, it is preferable to add it to the first liquid.

As described above, the epoxy resin composition for dip coating of the present invention has a first liquid containing (A) an epoxy resin liquid at room temperature and a second liquid containing (C) a curing agent and (D) a curing accelerator. And a predetermined ratio of (B) silica powder and (E) hydrated metal-based flame retardant contained in at least one of the first liquid and the second liquid, and both liquids are contained in a predetermined ratio at the time of use. Used as a mixture.

As the stirring / mixing device for obtaining the first liquid, for example, a rotation / revolution mixer, a planetary mixer, or the like can be used. On the other hand, the second liquid is prepared by stirring and mixing while heating with a stirrer such as a dissolver.

The epoxy resin composition for dip coating of the present invention is contained in at least one of a first liquid containing an epoxy resin (A) liquid at room temperature and a second liquid containing a curing agent (C) and a curing accelerator (D). In addition to adjusting the blending amount of the silica powder (B, B1, B2) in the above, a plurality of hydrated metal-based flame retardants (E, E1, E2) having different mass average particle sizes are used in combination, and the blending amount thereof ( Preferably, the ratio) is further adjusted. Therefore, an epoxy resin composition capable of forming a cured product having flame retardancy and heat resistance while maintaining excellent dip performance (combining ease of insertion and prevention of liquid dripping) and the epoxy resin composition. It is possible to provide an electric / electronic element having a coat layer made of a cured product of an object.

The electric / electronic element is not particularly limited, and examples thereof include a thermistor element used as a temperature sensor. Examples of the coat layer in this case include an insulating coat layer that covers the vicinity of the other end of a lead wire (a wire having a small diameter copper wire insulated and coated with resin) having one end connected to an electrode of the thermistor element.

When the electric / electronic element is dip-coated, the thickness of the coating layer is usually 1 to 4 mm in many cases. However, when the coating is thinner than 1 mm, or when the viscosity of the raw material resin liquid is high and it is difficult to obtain a predetermined film thickness, etc., a reactive diluent (previously) for the purpose of reducing the viscosity of the resin composition of the present invention. It is better to add the above).

Hereinafter, the present invention will be specifically described based on experimental examples (including Examples and Comparative Examples), but the present invention is not limited to these Examples. In the following description, "parts" shall indicate "parts by mass". The total chlorine content and the saponified chlorine content of the epoxy resin are values measured in accordance with JIS K7243.

1. 1. Preparation of Epoxy Resin Composition [Experimental Example 1]
(A) Epoxy resin (1) as a liquid epoxy resin at room temperature: 80 parts, (B) First silica (B1) as silica powder (1): 4 parts, and (B2) Second silica (1): 7 parts, (E) first flame retardant (1) as a hydrated metal flame retardant (1): 240 parts, and (E2) second flame retardant (1): 60 parts. , Reactive retardant (1): 20 parts and carbon black (manufactured by Mitsubishi Chemical Corporation, Mitsubishi Carbon Black MA100): 2 parts were added, and then stirred and mixed for 2 hours to prepare the first liquid. The first liquid was prepared by using a rotation / revolution mixer and stirring at a rotation speed of 1500 rpm.

Further, (C) curing agent (1): 101 parts and (D) 1-benzyl-2-phenylimidazole as a curing accelerator (Curesol 1B2PZ manufactured by Shikoku Chemicals Corporation): 3.1 parts by a conventional method. The second solution was prepared by adding and then mixing.
Then, the obtained first liquid and the second liquid were mixed to obtain an epoxy resin composition.

The details of each of the above components are as follows.
Epoxy resin (1): Bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation, jER828; epoxy equivalent 189)
First silica (1): Hydrophobic silica (fumed silica treated with a silane coupling agent having an alkyl group, Aerosil R805, manufactured by Nippon Aerosil Co., Ltd.)
Second silica (1): Hydrophobic silica (fumed silica treated with silicone oil, manufactured by Nippon Aerosil Co., Ltd., Aerosil R202)
First flame retardant (1): Aluminum hydroxide (manufactured by Nippon Light Metal Co., Ltd., SB303; mass average particle size 26 μm)
-Second flame retardant (1): Aluminum hydroxide (manufactured by Nippon Light Metal Co., Ltd., SB143; mass average particle size 2 μm)
Reactive Diluent (1): Cyclohexanedimethanol diglycidyl ether (manufactured by CVC Specialty Chemicals, ERISYS GE-22)
-Curing agent (1): Methyl hymicic acid anhydride (MHAC-P, manufactured by Hitachi Kasei Co., Ltd.)

[Experimental Examples 2-26]
The first and second liquids were prepared in the same manner as in Experimental Example 1 except that the blending components and / or blending amounts of the first and second liquids were changed as shown in Tables 1 and 3, and further, these were prepared. The first liquid and the second liquid were mixed to obtain an epoxy resin composition.

The components other than the components used in Experimental Examples 2 and later shown in Tables 1 and 3 are as follows.
Epoxy resin (2): Tetraglycidyl diaminodiphenylmethane type epoxy resin (manufactured by Mitsubishi Chemical Corporation, jER604: epoxy equivalent 120)
First silica (2): Hydrophobic silica (fumed silica treated with a silane coupling agent having an alkyl group, manufactured by Aerosil Japan, Aerosil R-812)
Second silica (2): Hydrophobic silica (fumed silica treated with silicone oil, manufactured by Cabot, Cabosil TS720)
-First flame retardant (2): Magnesium hydroxide (manufactured by Konoshima Chemical Co., Ltd., # 300, mass average particle size 7 μm)
-Second flame retardant (2): Magnesium hydroxide (manufactured by Kyowa Chemical Industry Co., Ltd., 200-6H, mass average particle size 0.5 μm)
-Curing agent (2): Methylhexahydrophthalic anhydride (HN-5500, manufactured by Hitachi Kasei Co., Ltd.)

2. 2. Evaluation Various characteristics of the epoxy resin composition obtained in each experimental example were evaluated by the methods shown below. The results are shown in Tables 2 and 4.

(2-1) Viscosity Using a rotary viscometer (manufactured by Toki Sangyo Co., Ltd., trade name TVE-35 type viscometer), the viscosity (Pa · s) 1 minute after mixing the first liquid and the second liquid is measured. It was measured at 25 ° C.

(2-2) Curability (time until gelation)
Using a device compliant with JIS C2161, the time (seconds) until the epoxy resin composition 0.4 cc immediately after mixing was gelled on a hot plate at 150 ° C. was measured and evaluated according to the following criteria.
"○": Less than 600 seconds (good curability)
"X": 600 seconds or more (poor curability) * Due to insufficient reactivity

(2-3) Heat resistance (glass transition temperature)
Differential scanning calorimetry (DSC) was performed on the cured product obtained by heating and curing the epoxy resin composition at 150 ° C. for 1 hour and then at 180 ° C. for 3 hours, and the glass transition temperature was determined under the following conditions. Tg (° C.) was measured and evaluated according to the following criteria. Measuring device: DSC6220 manufactured by SII Nanotechnology, sample amount: 10 mg, measurement atmosphere: nitrogen atmosphere, temperature rise rate: 20 ° C / min, measurement temperature: 25 ° C to 200 ° C
"◎": Tg is 145 ° C or higher (heat resistance is extremely good)
"○": Tg is 120 ° C or higher and lower than 145 ° C (good heat resistance)
"X": Tg is less than 120 ° C (poor heat resistance)

(2-4) Strength (flexural strength)
For the cured product obtained by heating and curing the epoxy resin composition at 150 ° C. for 1 hour and then at 180 ° C. for 3 hours, the bending strength was measured in accordance with JIS K6911, and the bending strength was measured according to the following criteria. evaluated.
"○": 70 MPa or more (good cured product strength, reliability (heat impact resistance, etc.))
"X": Less than 70 MPa (poor cured product strength, no reliability (heat impact resistance, etc.))

(2-5) A cured product obtained by heating and curing a flame-retardant epoxy resin composition at 150 ° C. for 1 hour and then at 180 ° C. for 3 hours in accordance with the vertical combustion test method of UL94. , Evaluated according to the following criteria.
"○": Conforms to UL94V-0 standard (good flame retardancy)
"X": Does not conform to UL94V-0 standard (poor flame retardancy)

(2-6) Dip coat property (easy to insert)
The state of the electric wire when the φ1.3 mm × 2 parallel vinyl chloride resin insulated electric wires were inserted into the mixed liquid obtained by stirring and mixing the two liquids was evaluated according to the following criteria.
"◎": Inserted vertically into the liquid without feeling resistance to the wire (extremely easy to insert)
"○": I feel some resistance to the wire, but it is inserted vertically into the liquid (easy to insert).
"△": I feel resistance to the wire, but it is inserted vertically into the liquid (can be inserted).
"×": Feeling a large resistance to the wire, it bends and is inserted into the liquid (it is not easy to insert)

(2-7) Dip coat property (prevention of liquid dripping)
The thermistor sensor was dipped in a container containing the mixed solution obtained by stirring and mixing the two solutions, and the shape immediately after the dip coating and after heating at 150 ° C. for 1 hour was evaluated according to the following criteria. ..
"○": Liquid does not collect under the thermistor sensor and retains the shape of the sensor (excellent liquid dripping prevention)
"△": The sensor does not drip from the thermistor sensor, but the liquid collects underneath and the sensor shape cannot be maintained (good liquid dripping prevention).
"×": The one that hangs down from the thermistor sensor. (Poor liquid dripping prevention property)

(2-8) Air bleeding property A container containing about 10 g of the mixed solution obtained by stirring and mixing the two solutions is placed in a decompression device, and the pressure is reduced to 1 to 5 Torr. At that time, the time for maintaining the highest point of the expansion height of the liquid level was measured and evaluated according to the following criteria.
"○": Less than 5 seconds (very good air release)
"△": Less than 10 seconds (good air release)
"X": 10 seconds or more (poor air release)

3-1. Consideration 1
As shown in Tables 1 and 2, the epoxy resin compositions of Experimental Examples 1 to 14 use appropriate amounts of (B) and (E), and (B) uses two types of hydrophobic silica. Since (E) uses a combination of two or more metal hydrated flame retardants with different mass average particle sizes, it is flame retardant while achieving both ease of insertion and prevention of liquid dripping. The grant was planned.
Among them, in the epoxy resin compositions of Experimental Examples 1, 4, 5, and 6, the mass average particle diameters were all in the range of (E1): 5 to 40 μm and (E2): 0.1 to 3 μm. The ease of insertion was all good. In particular, since Experimental Example 1 had (E1): 15 to 30 μm and (E2): 0.7 to 2.5 μm, the ease of inserting the thermistor sensor was extremely good as compared with Experimental Examples 4, 5 and 6. It became.

Further, in Experimental Examples 1 to 8, (B1), (B2), (E1), and (E2) are all blended in the first liquid, and are not blended in the second liquid. Therefore, there was a difference in viscosity between the first liquid and the second liquid. On the other hand, in Experimental Examples 9 to 14, at least one of (B1), (B2), (E1), and (E2) was blended with the first liquid and the second liquid, so that the first liquid and the second liquid were mixed. The difference in the viscosity of the second liquid was small, and it was easier to mix and the workability was better than in Experimental Examples 1 to 8.

On the other hand, in the epoxy resin composition of Experimental Example 15, the blending amount of (E) with respect to 100 parts by mass of the resin content was an appropriate amount (165 parts by mass), but a plurality of (E) having different mass average particle diameters. The thermistor sensor was inferior in ease of insertion and air bleeding as compared with Experimental Examples 1 to 14.
The epoxy resin composition of Experimental Example 16 contained an appropriate amount (165 parts by mass) of (E) with respect to 100 parts by mass of the resin, but did not contain a plurality of (E) having different mass average particle sizes. In addition, the compounding amount of (B) was reduced to the extent that the thermistor sensor could be inserted, and further, (B) did not use two types of hydrophobic silica. The liquid dripping prevention property became inferior.

In the epoxy resin composition of Experimental Example 17, (B) used two types of hydrophobic silica, but the blending amount of (B) with respect to 100 parts by mass of the resin content exceeded the upper limit (9.3). (Mass part), the viscosity became too high, and the ease of inserting the thermistor sensor and the air bleeding property were inferior to those of Experimental Examples 1 to 14.
In the epoxy resin composition of Experimental Example 18, (E) used a combination of two or more kinds of metal hydrated flame retardants having different mass average particle diameters, but (E) was used with respect to 100 parts by mass of the resin. Since the total compounding amount exceeded the upper limit value (290 parts by mass), the ease of inserting the thermista sensor and the air bleeding property were inferior to those of Experimental Examples 1 to 14.

3-2. Consideration 2
As shown in Tables 3 and 4, Experimental Examples 19 to 26 used (A1): bisphenol A type epoxy resin and (A2): glycidylamine type epoxy resin as (A). In all the evaluation items, the evaluation was equal to or higher than that of Experimental Example 1.
In particular, Experimental Examples 20 to 25 contained (A1): 1 in a mass ratio of (A2): 0.05 or more and 0.7 or less, but were heat resistant or easy to insert. Either of the sexes was evaluated as more than Experimental Example 1.

Claims (7)

An epoxy resin composition for dip coating for forming a cured product conforming to the UL94V-0 standard.
It has a first liquid containing (A) shown below and a second liquid containing (C) and (D) shown below.
At least one of the first liquid and the second liquid further contains (B) shown below and a plurality of (E) shown below having different mass average particle sizes.
When the reactive diluent contained in (A), (C), (D) and, if necessary, is a resin content, the blending amount of (B) is 2 to 8 parts by mass with respect to 100 parts by mass of the resin content. Moreover, the epoxy resin composition in which the total blending amount of (E) with respect to 100 parts by mass of the resin content is 130 to 190 parts by mass.
(A): Epoxy resin (B) liquid at room temperature: Silica powder (C): Curing agent (D): Curing accelerator (E): Moisture metal-based flame retardant Of all the metal hydrate flame retardants to be combined (E), the one having the maximum mass average particle size is defined as the first hydrated metal flame retardant (E1), and the mass average particle size is the smallest. When the second hydrated metal-based flame retardant (E2) is used as the one showing the value, the mass of (E1): 3 or more and 5 or less with respect to (E2): 1 in all the (E) to be combined. The epoxy resin composition according to claim 1, which comprises (E1) and (E2) so as to be a ratio. The epoxy resin composition according to claim 1 or 2, wherein both (E1) and (E2) are made of aluminum hydroxide. (A) includes (A1) and (A2) shown below, and the mass ratio of (A2) to 0.05 or more and 0.7 or less with respect to (A1): 1 in all (A). The epoxy resin composition according to any one of claims 1 to 3 contained in.
(A1): Bisphenol A type epoxy resin (A2): Glycidylamine type epoxy resin (B) includes (B1) and (B2) shown below, and the mass ratio of (B2) to 0.5 or more and 4.0 or less with respect to (B1): 1 in all (B). The epoxy resin composition according to any one of claims 1 to 4, which is contained in 1.
(B1): Fumed silica treated with a silane coupling agent having an alkyl group (B2): Fumed silica treated with a silicone oil (C) contains (C1) shown below, and (D) contains (D1) shown below, and the blending amount of the component (D) with respect to 100 parts by mass (C) is 0.5 to 10 parts by mass. The epoxy resin composition according to any one of claims 1 to 5.
(C1): Acid anhydride-based curing agent (D1): Imidazole-based curing accelerator An electric / electronic device in which a coat layer made of a cured product of the epoxy resin composition according to any one of claims 1 to 6 is formed at least in a part thereof.