JP7169139B2 - Epoxy resin composition for dip coating - Google Patents

Description

The present invention relates to an epoxy resin composition suitable for dip coating.

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

JP-A-6-244002

However, in recent years, such electronic components have become smaller and more powerful, so sudden temperature changes (high temperatures) from the electronic component body accelerate the deterioration of the electronic component body and cause failure. , There is a demand for improved heat resistance and flame retardancy of the insulating resin part, but nothing has been satisfactory yet. Also, in consideration of the environment, the use of flame retardants such as halogens and phosphorus should be avoided. is desired.
Therefore, the present inventors selected a metal hydrate as a flame retardant and added it to the epoxy resin until the desired flame retardancy was obtained. It could not be inserted well into the resin composition, and the resin composition became unusable for dip coating.
Moreover, when the content of the metal hydrate was reduced to such an extent that the electronic component could be successfully inserted into the resin composition, the desired flame retardancy could not be obtained. In addition, a thixotropic agent is usually added to the resin composition for dip coating in order to prevent liquid dripping. When the resin composition was heat-cured after being inserted into and removed from the mold, the resin composition dripped and became unusable as a resin composition for dip coating.

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

The present inventors adjusted the amount of silica powder in at least one of the first liquid containing an epoxy resin that is liquid at room temperature and the second liquid containing a curing agent and a curing accelerator, The inventors have found that the above-mentioned problems can be solved by using a sum metal flame retardant and adjusting the blending amount thereof, and have completed the present invention. That is, according to the present invention, an epoxy resin composition having the constitution shown below is provided. Further, according to the present invention, there is provided an electrical/electronic device at least partially formed with a coat layer composed of a cured product obtained by curing an epoxy resin composition having the constitution described below.

Below, (A): liquid epoxy resin at room temperature, (B): silica powder, (C): curing agent, (D): curing accelerator, (E): hydration treated with silane coupling agent Metallic flame retardants, (A), (C), (D), and reactive diluents included as necessary: 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,
having 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 comprising (B) and (E);
The amount of (B) is 2 to 8 parts by mass with respect to 100 parts by mass of resin, and the amount of (E) is 130 to 190 parts by mass with respect to 100 parts by mass of resin. .

In the following, of (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) includes (A1) and (A2), and in total (A), (A1): 1, (A2): 0.05 It can be contained at a mass ratio of 0.7 or less.

In the epoxy resin composition of the present invention, (E) can be composed of aluminum hydroxide.

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

In the following, (C1) is defined as an acid anhydride-based curing agent in (C), and (D1) is defined as an imidazole-based curing accelerator in (D). At this time, in the epoxy resin composition of the present invention, (C) contains (C1), (D) contains (D1), and the blending amount of (D) with respect to 100 parts by mass of (C) is 0.1. It can be 5 to 10 parts by mass.

In the epoxy resin composition of the present invention, the blending amount of silica powder in at least one of the first liquid containing the epoxy resin that is liquid at room temperature and the second liquid containing the curing agent and the curing accelerator is adjusted. A specific hydrated metal-based flame retardant is used and its blending amount is adjusted. For this reason, an epoxy resin composition capable of forming a cured product imparted with flame retardancy while maintaining excellent dipping performance (both ease of insertion and prevention of liquid dripping), and curing of the epoxy resin composition It is possible to provide an electrical/electronic device having a coating layer composed of a material.

The details of the present invention are described below.
In the following description, when the term "resin component" is used, it includes (A): an epoxy resin that is liquid at room temperature, (C): a curing agent, (D): a curing accelerator, and, if necessary, shall mean the total component of the reactive diluent that may be
The epoxy resin composition for dip coating of the present invention comprises a first liquid and a second liquid, the first liquid containing (A) at least an epoxy resin that is liquid at room temperature, and the second liquid containing (C) It contains a curing agent and (D) a curing accelerator. (B) silica powder and (E) a metal hydrate-based flame retardant 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 (A) epoxy resin used in the first liquid can be used without particular limitation as long as it is liquid at room temperature. Examples of such epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, alicyclic epoxy resins, aliphatic epoxy resins, brominated bisphenol A type epoxy resins, phenol-novolak type or cresol-novolak type epoxy resins. Epoxy resin, brominated novolak type epoxy resin, hydrogenated bisphenol A type or AD type epoxy resin, propylene glycol diglycidyl ether, pentaerythritol polyglycidyl ether, etc. 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 (A1) bisphenol A type epoxy resin from the viewpoint of heat resistance and mechanical strength. The epoxy resins (A) may be used singly or in combination of two or more.

Moreover, in the field where heat resistance is required, it can be dealt with by containing (A2) a glycidylamine type epoxy resin together with (A1). Specific examples of (A2) include tetraglycidyldiaminodiphenylmethanes, glycidyl compounds of aminophenol, glycidylanilines, and glycidyl compounds of xylenediamine.

Among them, tetraglycidyldiaminodiphenylmethanes (tetraglycidylamine type epoxy resins) are preferable from the viewpoint of the balance between performance and cost. Commercially available products of tetraglycidyldiaminodiphenylmethanes include Sumiepoxy ELM434 and Sumepoxy ELM434HV (manufactured by Sumitomo Chemical Co., Ltd.); Araldite MY9612, Araldite MY9634, Araldite MY9663 (manufactured by Huntsman Advanced Materials); jER604 (manufactured by Mitsubishi Chemical Corporation); mentioned

When (A) contains both (A1) and (A2) in (A), both should be contained at a mass ratio of (A1): 1: (A2): 0.05 to 0.7. is preferred. By blending the two at such a mass ratio, it is expected that the heat resistance will be improved while maintaining the dip coatability (easiness of insertion).

Although the epoxy equivalent of (A) is not particularly limited, it 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 dip coating is deteriorated, the glass transition point is lowered, and the cured product tends to be inferior in heat resistance. An epoxy equivalent is measured by the method based on JISK7236.

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

When a reactive diluent is added, the amount added is 40% by mass or less, preferably 1 to 35, based on the mixture of the epoxy resin (A) and the reactive diluent for viscosity reduction added here. % by mass, more preferably 5 to 30% by mass. If it exceeds 40% by mass, the properties of the cured product may deteriorate.

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

If a combination of a curing agent and a curing accelerator other than those described above is used, crystallization after long-term storage cannot be prevented. Also, when using the above combinations, compared to other combinations, such as the combination of methylhimic anhydride and 2-ethyl-4-methylimidazole or 1-benzyl-2-methylimidazole, during storage of 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. You can choose.

If the ratio of 1-benzyl-2-phenylimidazole as a preferred example of (D) is less than this range, the curing speed becomes slow, etc. 1-benzyl-2-phenylimidazole as a preferred example of (D) is used. Moreover, even if it exceeds this range, the effect corresponding to the amount used cannot be obtained. Therefore, the mixing ratio of (C) and (D) is more preferably 100:1 to 100:7, more preferably 100:2 to 100:5.

The method of preparing the curing agent composition using (C) and (D) can be appropriately selected from conventional methods of mixing a curing agent and a curing accelerator. C) and (D) are mixed, and while being heated to 70 to 90° C., they are stirred and mixed with a stirrer such as a dissolver for 30 to 60 minutes. After stirring and mixing, the curing agent composition is preferably prepared by returning to room temperature.

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

On the other hand, when this range is exceeded, curing may become too fast depending on the blending ratio of other components. When this tendency becomes conspicuous, uniform curing becomes difficult to occur, and cured products are generated locally, degrading the properties of the resin layer.
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 thixotropic agent. Silica powder used in the present invention includes fumed silica. Examples of the fumed silica include hydrophilic silica and hydrophobic silica. In the present invention, it is effective to use two types of hydrophobic silica in combination. Such silica powder can be expected to improve the anti-sagging property and thixotropy of the resin composition. In the present invention, thixotropy refers to a property in which the apparent viscosity temporarily decreases when shear deformation is applied in an isothermal state, and the original apparent viscosity recovers over time after standing still. This means that an improvement in the air release property, which will be described later, is improved.

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

Examples of hydrophobic silica include fumed silica (B1) treated with a silane coupling agent having an alkyl group, having a primary particle diameter of 5 to 200 nm and a specific surface area (BET) of 125 to 175 m ² /g. things are mentioned. (B1) exhibits the ability to prevent dripping in a liquid resin at room temperature. Furthermore, it has a feature that it takes a long time to recover to the apparent viscosity, and the thixotropy can be improved.

As the hydrophobic silica, in addition to (B1), for example, fumed silica (B2) treated with silicone oil has a primary particle diameter of 5 to 200 nm and a specific surface area (BET) of 80 to 120 m ² /g. are listed. (B2) prevents dripping in a liquid resin at room temperature and at high temperature (curing), and exhibits the ability to improve shape retention.

Examples of hydrophilic silica include those whose surface is not subjected to any treatment, which have a primary particle size of 5 to 200 nm and a specific surface area (BET) of 270 to 330 m ² /g.

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

Here, the blending amount of (B) should be 2 to 8 parts by mass with respect to 100 parts by mass of the resin. This is because if the blending amount is too small, the anti-sagging property is deteriorated, and conversely, if it is too large, the air-releasing property is deteriorated, which is not preferable. In consideration of anti-dripping property and air-releasing property, it is more preferably in the range of 4 to 6 parts by mass.

In addition, in the silica powder blended in such an amount, the blending ratio when (B1) and (B2) are used together is that the ratio of (B2) is 0.5 or more with respect to (B1): 1 It is preferably contained at a mass ratio of 4.0 or less, more preferably from 1.0 to 2.0.
When the proportion of (B2) is less than 0.5 with respect to (B1):1, liquid dripping is likely to occur. On the other hand, when it is contained at 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 dipping performance of the epoxy resin composition (easiness of inserting electronic components and anti-dripping property), the viscosity after mixing the first liquid and the second liquid is, for example, 150 to 150 at 25°C. It is preferably 350 Pa·s, more preferably 200 to 300 Pa·s, and particularly preferably 220 to 280 Pa·s.

<(E)>
(E) used in the present invention must consist of a silane-treated (treated with a silane coupling agent) hydrated metal-based flame retardant (aluminum hydroxide, magnesium hydroxide). By using the silane-treated one, it is expected to impart excellent water resistance to the cured product. In the present invention, as (E), both a non-surface-treated metal hydrate flame retardant and a silane-treated metal hydrate flame retardant may be used in combination.

When the hydrated metal flame retardant used as (E) is treated with a treating agent such as fatty acid, linseed oil, or a titanium coupling agent, the treating agent acts as a curing catalyst during the preparation of the epoxy resin composition, Moisture in the system may cause the above (A) to react and harden or thicken. Therefore, for example, (E) is dehydrated in advance in the absence of (A), and then (A) is added to this (when included in the first liquid), or It is necessary to add an additive or use a two-liquid type (that is, do not include (E) in the first liquid).

Silane coupling agents include those having a terminal vinyl group, methacryloxy group, glycidyl group, amino group, etc. For example, epoxysilane (epoxy group-containing silane coupling agent) is preferred. A silane coupling agent generally has a structure represented by R--Si(OR') ₃ (a plurality of R's may be the same or different). Epoxysilane (epoxy group-containing silane coupling agent) includes an epoxy group in the functional group represented by R′. Epoxy groups are usually bonded to Si via a divalent linking group. Examples of the divalent linking group include linking groups included in specific example compounds described later. On the other hand, the functional group represented by R' is usually an alkyl group and is hydrolyzed in an aqueous solvent to form silanol (Si--OH). The number of carbon atoms in the alkyl group represented by R' is, for example, 1-10, preferably 1-3.

Specific examples of epoxysilanes include γ-glycidoxypropyltrimethoxysilane (γ-GPS), glycidoxy group-containing trialkoxysilanes such as γ-glycidoxypropylmethyldiethoxysilane, β-(3,4-epoxy cyclohexyl)ethyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltriethoxysilane, β-(3,4-epoxycyclohexyl)ethyltripropoxysilane, β-(3,4-epoxycyclohexyl)ethyltributoxysilane Silane, γ-(3,4-epoxycyclohexyl)propyltrimethoxysilane, γ-(3,4-epoxycyclohexyl)propyltriethoxysilane, δ-(3,4-epoxycyclohexyl)butyltrimethoxysilane, δ-( and epoxyalkylalkoxysilanes such as 3,4-epoxycyclohexyl)butyltriethoxysilane.

When the hydrated metal flame retardant is treated with a silane coupling agent, either one kind of silane coupling agent may be used alone, or two or more kinds may be used in combination.

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

It is also possible to obtain commercially available hydrated metal flame retardants that have already been treated with a silane coupling agent.
Specific examples of magnesium hydroxide surface-treated with a silane coupling agent include Kisuma 5L (mass average particle size 0.8 μm), Kisuma 5N (mass average particle size 0.7 μm), and Kisuma 5P (mass average particle size diameter 0.8 μm) (manufactured by Kyowa Kagaku Co., Ltd.), Finemag MO-E (manufactured by TMG Co., Ltd.), and the like. Examples of surface-untreated magnesium hydroxide include Kisuma 5 (manufactured by Kyowa Kagaku Co., Ltd.) and Magniffin H5 (manufactured by Albemarle).
Examples of epoxysilane-treated aluminum hydroxide include B303STE (mass average particle size: 17 μm: manufactured by Nippon Light Metal Co., Ltd.), BF013ST (mass average particle size: 1 μm: manufactured by Nippon Light Metal Co., Ltd.), and methacryloxy-silane-treated aluminum hydroxide. B153STM (mass average particle diameter 12 μm: manufactured by Nippon Light Metal Co., Ltd.) and the like can be mentioned as examples.

The size of (E) is preferably 5 to 40 μm, preferably 15 to 30 μm, in mass average particle diameter. This is for facilitating the improvement of workability during dip coating, particularly the easiness of inserting electronic components.

(E) can be used after adjusting its particle size distribution. The particle size distribution can be adjusted by classifying and removing relatively large particle sizes contained in E to be used by means of a centrifugal air force classifier, a dry classifier, a sieving machine, or the like.

In this example, the mixing ratio of the metal hydrate flame retardant (E) treated with a silane coupling agent must be in the range of 130 to 190 parts by weight per 100 parts by weight of the resin. If the blending ratio is less than 130 parts by mass, flame retardancy will be adversely affected, and if it exceeds 190 parts by mass, workability during dip coating and mechanical strength after curing will be adversely affected. I don't like it. 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. , 170 parts by mass or less is particularly preferred.

(E) may be blended in either one of the first liquid and the second liquid, or may be blended in both. In this case, it is preferable to mix the first liquid and the second liquid (B) in consideration of the mixing ratio of the first and second liquids and the viscosity of each liquid at 25°C.

In addition to the components described above, the epoxy resin composition for dip coating of the present invention may optionally contain a powder filler other than the silica powder, the above-described metal hydrate, as long as the effects of the present invention are not impaired. Other flame retardants, colorants, and other additives can be blended. Examples of powder fillers include crystalline silica, fused 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. is mentioned. Examples of flame retardants include powdery organic halogen compounds, red phosphorus, phosphate esters, antimony trioxide, and the like. Examples of coloring agents include various pigments and dyes such as carbon black and cobalt blue. These components may be blended in either one of the first liquid and the second liquid, or may be blended in both. From the viewpoint of preventing sedimentation of the filler, it is preferably blended in the first liquid.

As described above, the epoxy resin composition for dip coating of the present invention comprises (A) a first liquid containing an epoxy resin that is 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 flame retardant contained in at least one of the first liquid and the second liquid, and when used, both liquids are mixed at a predetermined ratio used in combination.

As a stirring and 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 includes at least one of a first liquid containing an epoxy resin (A) that is liquid at room temperature and a second liquid containing a curing agent (C) and a curing accelerator (D). and the hydrated metal flame retardant (E) treated with a silane coupling agent are adjusted. For this reason, an epoxy resin composition capable of forming a cured product imparted with flame retardancy and heat resistance while maintaining excellent dipping performance (both ease of insertion and resistance to dripping), and the epoxy resin composition It is possible to provide an electric/electronic device having a coat layer composed of a cured product.

The electric/electronic element is not particularly limited, but includes, for example, a thermistor element used as a temperature sensor. In this case, the coat layer is, for example, an insulating coat layer covering the vicinity of the other end of a lead wire (an electric wire in which a thin copper wire is coated with an insulating resin with a resin) one end of which is connected to the electrode of the thermistor element.

The thickness of the coating layer in the case of dip-coating the electric/electronic element is usually 1 to 4 mm in many cases. However, when the coating thickness is less than 1 mm, or when it is difficult to obtain a predetermined film thickness due to the high viscosity of the raw material resin liquid, a reactive diluent (precursor) is used for the purpose of reducing the viscosity of the resin composition of the present invention. It is better to add

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 "mass parts". The total chlorine content and saponifiable chlorine content of the epoxy resin are values measured according to JIS K7243.

1. Preparation of epoxy resin composition [Experimental example 1]
(A) Epoxy resin (1): 80 parts as epoxy resin liquid at room temperature, (B1) first silica (1): 4 parts as silica powder, and (B2) second Silica (1): 7 parts, (E) flame retardant (1) as a metal hydrate flame retardant treated with a silane coupling agent: 300 parts, reactive diluent (1): 20 parts, Carbon black (Mitsubishi Carbon Black MA100, manufactured by Mitsubishi Chemical Co., Ltd.): 2 parts was added, followed by stirring and mixing for 2 hours to prepare a first liquid. A rotation-revolution mixer was used for the preparation of the first liquid, and the mixture was stirred at a rotation speed of 1500 rpm.

Further, (C) curing agent (1): 101 parts, (D) 1-benzyl-2-phenylimidazole (Curesol 1B2PZ, manufactured by Shikoku Kasei Co., Ltd.) as a curing accelerator: 3.1 parts by a conventional method. A second liquid was prepared by adding and then mixing.
After that, the obtained first liquid and 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, manufactured by Nippon Aerosil Co., Ltd., Aerosil R805)
- Second silica (1): Hydrophobic silica (fumed silica treated with silicone oil, manufactured by Nippon Aerosil Co., Ltd., Aerosil R202)
- Flame retardant (1): Epoxysilane-treated aluminum hydroxide (B303STE manufactured by Nippon Light Metal Co., Ltd.; mass average particle diameter 17 µm)
- Reactive diluent (1): cyclohexanedimethanol diglycidyl ether (manufactured by CVC Specialty Chemicals, ERISYS GE-22)
- Curing agent (1): Methylhimic anhydride (manufactured by Hitachi Chemical Co., Ltd., MHAC-P)

[Experimental Examples 2 to 26]
Liquids 1 and 2 were prepared in the same manner as in Experimental Example 1, except that the ingredients and/or amounts of the liquids 1 and 2 were changed as shown in Tables 1 and 2. An epoxy resin composition was obtained by mixing the first liquid and the second liquid.

The components used in Experimental Example 2 and later shown in Tables 1 and 3 are as follows.
- Epoxy resin (2): Tetraglycidyldiaminodiphenylmethane 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 Nippon Aerosil Co., Ltd., Aerosil R-812)
- Second silica (2): Hydrophobic silica (fumed silica treated with silicone oil, manufactured by Cabot Corporation, CABOSIL TS720)
- Flame retardant (2): methacryloxy silane-treated aluminum hydroxide (manufactured by Nippon Light Metal Co., Ltd., B153STM; mass average particle diameter 12 µm)
- Flame retardant (3): Epoxysilane-treated magnesium hydroxide (mass average particle size 12 µm)
- Flame retardant (4): surface-untreated aluminum hydroxide (manufactured by Nippon Light Metal Co., Ltd., SB303; mass average particle diameter 26 µm)
- Curing agent (2): methylhexahydrophthalic anhydride (manufactured by Hitachi Chemical Co., Ltd., HN-5500)

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

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

(2-2) Curability (time to gelation)
Using an apparatus conforming to JIS C2161, the time (seconds) required for 0.4 cc of the epoxy resin composition immediately after mixing to gel 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 measured under the following conditions. - Tg (°C) was measured and evaluated according to the following criteria. Measuring device: DSC6220 manufactured by SII Nanotechnology Co., Ltd. Sample amount: 10 mg Measurement atmosphere: Nitrogen atmosphere Heating rate: 20°C/min Measurement temperature: 25°C to 200°C
"◎": Tg is 145 ° C. or higher (extremely good heat resistance)
"○": Tg is 120 ° C. or more and less than 145 ° C. (good heat resistance)
"x": Tg is less than 120 ° C. (poor heat resistance)

(2-4) Strength (bending strength)
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 was measured for bending strength in accordance with JIS K6911. evaluated with
"○": 70 MPa or more (good cured product properties, reliable (thermal shock resistance, etc.))
“×”: less than 70 MPa (cured product properties are poor, no reliability (thermal shock resistance, etc.))

(2-5) Flame Retardancy 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 conforms to the UL94 vertical burning test method. and evaluated according to the following criteria.
"○": conforms to UL94V-0 standard (good flame retardancy)
"×": Does not conform to UL94V-0 standard (poor flame retardancy)

(2-6) Dip coatability (easiness of insertion)
Two parallel vinyl chloride resin insulated wires with a diameter of 1.3 mm were inserted into a mixed solution obtained by stirring and mixing the two solutions, and the state of the wires was evaluated according to the following criteria.
"◎": The wire can be inserted vertically into the liquid without feeling any resistance (extremely easy insertion)
"○": A little resistance is felt in the wire, but it is inserted vertically into the liquid (easy to insert)
"△": Resistance is felt in the wire, but it is inserted vertically into the liquid (insertion possible)
"X": The wire feels a large resistance and bends and is inserted into the liquid (insertion is not easy)

(2-7) Dip coat property (liquid drip prevention property)
A thermistor sensor was dipped in a container containing a mixed liquid obtained by stirring and mixing the two liquids, and the shape immediately after dip coating and after heating at 150°C for 1 hour was evaluated according to the following criteria. .
"○": The sensor does not accumulate below the thermistor sensor, and the shape of the sensor is maintained (Extremely good anti-drip property)
"△": Does not drip from the thermistor sensor, but the liquid accumulates below and the sensor shape cannot be maintained (good liquid drip prevention)
"X": A state of dripping from the thermistor sensor. (Poor anti-drip property)

(2-8) Air Release A container containing about 10 g of the mixed liquid obtained by stirring and mixing the two liquids 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 swelling height of the liquid surface was measured and evaluated according to the following criteria.
"○": Less than 5 seconds (extremely good air release)
"△": less than 10 seconds (good air release)
"x": 10 seconds or more (poor air release)

(2-9) Water resistance The epoxy resin composition was cured by heating at 150°C for 1 hour and then at 180°C for 3 hours. After 1 hour, it was taken out and cooled to room temperature. The volume resistivity of each cured product before and after immersion in hot water was measured by a method based on JIS K6911, and evaluated according to the following criteria. For each experimental example evaluated, the volume resistivity of the cured product before immersion was RM1, and the volume resistivity of the cured product after immersion was RM2.
"〇": The difference in the number of digits between RM1 and RM2 (RM1-RM2) is less than 5 digits "X": The difference in the number of digits between RM1 and RM2 (RM1-RM2) is 5 digits or more

3-1. Consideration 1
As shown in Tables 1 and 2, the epoxy resin compositions of Experimental Examples 1 to 5 and 7 to 14 have appropriate blending amounts of (B) and (E), and (B) is two types of hydrophobic (E) used a silane-treated hydrated metal flame retardant. As a result, the cured product was imparted with flame retardancy and excellent water resistance while achieving both ease of insertion and anti-dripping properties.
Among them, the epoxy resin compositions of Experimental Examples 2, 3 and 9 used tetraglycidyldiaminodiphenylmethane type epoxy resin. As a result, compared with the epoxy resin compositions of Experimental Examples 1, 4, 5, 7, 8 and 10-14, the heat resistance was extremely good.

Further, in Experimental Examples 1 to 5, 7, and 8, (B1), (B2), and (E) 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), and (E) was added to the first liquid and the second liquid. The difference in viscosity was small, and compared with Experimental Examples 1 to 5, 7, and 8, mixing was easy and workability was good.

On the other hand, in the epoxy resin composition of Experimental Example 6, the amount of (E) blended with respect to 100 parts by mass of the resin content was an appropriate amount (147 parts by mass), but as (E) the flame retardant (1) to ( 3) was used. As a result, compared with Experimental Examples 1 to 5, 7, and 8, the ease of inserting the thermistor sensor and the ability to release air were inferior. Furthermore, compared with Experimental Example 1, the water resistance was inferior.
The epoxy resin composition of Experimental Example 15 contained an appropriate amount (165 parts by mass) of (E) with respect to 100 parts by mass of the resin content. ~(3) was used. As a result, compared with Experimental Examples 1 to 5, 7, and 8, the ease of inserting the thermistor sensor and the ability to release air were inferior.
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 content. In addition to using, the amount of (B) was reduced to the extent that the thermistor sensor could be inserted, and (B) did not use two types of hydrophobic silica. As a result, compared with Experimental Examples 1 to 5, 7 and 8, the anti-drip property was inferior.

The epoxy resin composition of Experimental Example 17 used two types of hydrophobic silica as (B), and used a silane-treated hydrated metal flame retardant as (E). The blending amount of (B) with respect to 100 parts by mass of the resin content exceeded the upper limit (9.3 parts by mass). As a result, the viscosity became too high, and compared with Experimental Examples 1 to 5, 7, and 8, the easiness of inserting the thermistor sensor and the ability to release air were inferior.
The epoxy resin composition of Experimental Example 18 used two types of hydrophobic silica as (B), and used a silane-treated hydrated metal flame retardant as (E). The total compounding amount of (E) with respect to the resin content of 1 part was over the upper limit (294 parts by mass). As a result, compared with Experimental Examples 1 to 5, 7, and 8, the ease of inserting the thermistor sensor and the ability to release air were inferior.

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). The evaluation was equal to or higher than that of Experimental Example 1 in all evaluation items.
In particular, in Experimental Examples 20 to 25, (A2) was contained at a mass ratio of 0.05 or more and 0.7 or less with respect to (A1): 1, but heat resistance or easy insertion Either sex was evaluated as 10 or more in Experimental Example.

Claims (6)

An epoxy resin composition for dip coating for forming a cured product conforming to the UL94V-0 standard,
A first liquid containing (A) shown below, and a second liquid containing (C) and (D) shown below, where (C) contains (C1) shown below ,
At least one of the first liquid and the second liquid further includes (B) and (E) shown below,
When (A), (C), (D) and the reactive diluent included as necessary are the resin content, the amount of (B) is 2 to 8 parts by mass per 100 parts by mass of the resin content. and an epoxy resin composition in which the amount of (E) is 130 to 190 parts by mass with respect to 100 parts by mass of the resin.
(A): Liquid epoxy resin at room temperature (B): Silica powder (C): Curing agent
(C1): acid anhydride curing agent
(D): Curing accelerator (E): Hydrated metal-based flame retardant treated with a silane coupling agent (A) includes (A1) and (A2) shown below, and in all (A), (A1): 1, (A2): 0.05 or more and 0.7 or less mass ratio The epoxy resin composition according to claim 1, which is contained in.
(A1): bisphenol A type epoxy resin (A2): glycidylamine type epoxy resin 3. The epoxy resin composition according to claim 1, wherein (E) comprises aluminum hydroxide. (B) includes (B1) and (B2) shown below, and in all (B), (B1): 1, (B2): 0.5 or more and 4.0 or less mass ratio The epoxy resin composition according to any one of claims 1 to 3, which is contained in.
(B1): fumed silica treated with a silane coupling agent having an alkyl group (B2): fumed silica treated with silicone oil 5. The epoxy resin according to any one of claims 1 to 4, wherein ( D) contains (D1) shown below, and the amount of component (D) blended relative to 100 parts by mass of (C) is 0.5 to 10 parts by mass. Composition.
( D1): imidazole curing accelerator An electric/electronic device at least partially formed with a coating layer composed of a cured product of the epoxy resin composition according to any one of claims 1 to 5.