JPS61296054A - Epoxy resin composition for producing transparent cured product - Google Patents

Abstract

PURPOSE:To obtain the titled composition having excellent mechanical properties, electrical properties, chemical resistance, etc., high heat-dissipation property and excellent transparency, by compounding an epoxy resin with a specific inorganic filler. CONSTITUTION:100pts.wt. of an epoxy resin in compounded with 20-200pts.wt. of an inorganic filler having a refractive index of 1.45-1.65 (25 deg.C), an oil- absorption of 15-75ml/100g and an average particle diameter of 0.2-30mum. The inorganic filler is aluminum hydroxide or sericite and the epoxy resin is preferably a diglycidyl ether-type epoxy resin having an epoxy equivalent of 180-2,000.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to an epoxy resin composition for producing a transparent cured product.

(Prior Art) Conventionally, epoxy resin compositions having various compositions are known. Furthermore, most of the conventional compositions contain fillers because it is necessary to impart physical properties such as mechanical strength to the resulting cured product.

However, the cured product obtained from a composition containing such a filler is opaque and has the disadvantage that its internal state cannot be confirmed.

Therefore, it was necessary to completely abandon the use of fillers when trying to obtain transparent cured products, but cured products obtained from compositions that do not contain fillers have poor mechanical strength, etc. There was a problem in that the physical properties of the material deteriorated and the applications were limited. (Problems to be Solved by the Invention) Although the product of the present invention contains an inorganic filler, the cured epoxy resin obtained therefrom has good transparency, and furthermore, this cured product has the following properties: It has excellent mechanical properties, electrical properties, chemical resistance, etc., as well as good heat dissipation properties.

Furthermore, the composition of the present invention is used for coating motors, etc., and exhibits excellent adhesion.

Transparent as used in the present invention does not necessarily mean completely transparent, but also includes semi-transparent. Normally, the light transmittance is 10% in haze value.
Hereinafter, if the parallel light transmittance is 85% or more, it is considered transparent.

(Means for Solving the Problems) The epoxy resin used as the main component in the present invention is not limited in structure, epoxy equivalent, molecular weight, etc., and any known resin can be used.

Specifically, bisphenol A-based, bisphenol F-based, and bisphenol S-based diglycidyl ether type epoxy resins and novolac type epoxy resins are preferred. In particular, diglycidyl ether type epoxy resins having an epoxy equivalent of 180 to 2,000 are preferred.

In addition, the inorganic filler used in the present invention has a refractive index (25°C > 1.45 to 1.65, an oil absorption amount of 15 to 75
It has physical properties of m1/average particle size of 0.2 to 30 pm00t.

If any one of these is not satisfied, the objective cannot be achieved. If the refractive index (25 DEG C.) of the inorganic filler used is outside the range of 1.45 to 1.65, the desired transparency cannot be obtained even if the other physical properties of the cured product are good. Oil absorption is also an indicator for determining the optimal amount of filler added to the main component epoxy resin. If the oil absorption is large, the viscosity will be high or thixotropy will occur at a certain resin-filler blending ratio. If the melting properties are large, the flowability during melting is small and the impregnating properties are poor. Conversely, if the oil absorption is small, the viscosity is low, and under certain conditions it will flow out and cause drips.

Particle size is also related to oil absorption; if the particle size is small, depending on the shape of the particles, the viscosity will generally be high and thixotropy will be high, and there is a risk that the specified amount of filler will not be added.

If the particle size is too large, the resin will not be able to fully enclose the filler particles, resulting in poor wettability, and the uniformity of the resin and filler will be lost during the crushing and classification processes.
Poor adhesion.

Examples of fillers that satisfy the above conditions include aluminum hydroxide, calcium silicate, sericite,
Kaolin (clay), silica, talc, and zeolite can be produced.

The amount of this filler used is usually 20 to 200 parts by weight, preferably 50 to 15 parts by weight, per 100 parts by weight of the epoxy resin.
The range is 0 parts by weight.

If the amount of filler is less than 20 parts by weight, the shrinkage will be large, causing cracks, cracks, etc., and the heat dissipation properties will be poor and the machinability will be insufficient. If the amount exceeds 200 parts by weight of the crushed filler, the melt viscosity will be high, the thixotropy will be high, and the impregnating property will be poor.

The composition of the present invention contains a curing agent, and examples of the curing agent include dicyandiamide, imidazole, modified products thereof, acid anhydrides, amines, and noblack phenol resin.

Among these, imidazole and its modified products are particularly preferable because they can be added in a small amount and the difference in refractive index does not change significantly in order to achieve all the objects of the present invention.

This curing agent is used in an amount necessary to cure the epoxy resin, and specifically in the case of imidazole, it is 0.2 to 4.0 parts by weight, preferably 0.5 parts by weight, based on 100 parts by weight of the epoxy resin. ~3.0 parts by weight.

In the case of imidazole, if the amount used is less than 0.2 parts by weight, curing is insufficient, and if it exceeds 4.0 parts by weight, the difference in refractive index becomes too large and the resulting cured product has poor transparency. As a result, the storage stability of the composition deteriorates.

In the present invention, there is no problem in using two or more types of curing agents in combination as long as the addition of the curing agent does not significantly change the difference in refractive index between the resin and the filler.

In the case of curing agents such as acid anhydrides, amines, or black phenol resins, it is sufficient that the amount used is about the chemical equivalent to the amount of epoxy.

The composition of the present invention is prepared by uniformly mixing the above components (epoxy resin, filler, curing agent).

The composition of the present invention may contain any additives, such as dyes, pigments, and leveling agents such as acrylic oligomers that do not impede transparency, as long as they do not impede the object of the present invention.

As described above, the composition of the present invention has excellent transparency and is therefore suitable for use in applications such as impregnating various coils and fixing coil ends. The excellent transparency means that, for example, when coating a coil of a motor or the like, the cured state can be confirmed with the naked eye, and the heating temperature and time during curing can be adjusted as appropriate.

In addition, the good heat dissipation property means that when applied to motor coil coating, there is no heat escape, which prevents the coil from burning.

(Examples and Comparative Examples) The present invention will be explained in more detail by Examples, and a Comparative Example will be shown. The present invention is not limited to the embodiments unless it exceeds the gist thereof. In the example, "center part" refers to the weight part.

Examples 1 to 5, Comparative Examples 1 to 3 A bisphenol A epoxy resin with an epoxy equivalent of 800 to 900, a filler, a curing agent, and an acrylic oligomer as a leveling agent were uniformly used in the composition and proportions (parts by weight) shown in the table below. were mixed to prepare an epoxy resin composition.

Each of the above compositions was pulverized in a conventional manner to obtain an appropriate particle size distribution suitable for powder coating, thereby preparing a powder coating.

The various physical properties of each prepared powder coating were investigated and were as shown in the table.

The methods for measuring and evaluating the physical properties in the table are as follows.

(1) Transparency: (a) Powder coating was applied to a mild steel plate (20 mm x 15 (1 m x 3.2 mm) preheated to 150 to 160°C,
When the coating was applied so that the coating thickness after curing was 0.3 to 0.5 degrees and the mild steel plate was maintained at 150 to 160°C, a cured coating was obtained. This cured coating film was peeled off from the mild steel plate, visually observed under visible light, and evaluated according to the following.

◎... Good transparency ○... Slightly cloudy, translucent ×... Opaque Manufactured by Iro Kogyo Co., Ltd., model ND
H-20D) was measured according to JISK 6714 and expressed as total transmittance.

(2) Gel time: Powder coating approximately 0.1 to 0.2 according to JIS C2104
ff, the paint was placed in a circular concave part of a hot plate maintained at 150°C, and the total time (seconds) until the paint gelled was measured, and this was taken as the gelation time.

(3) Impact strength square iron plate (60+ax 601aRx 3Jmm)
After applying the cured coating to one side of the film to a thickness of 0.3 to 0.41 tlll, heating it at 150°C for 30 minutes,
When these were then allowed to stand at room temperature, cured coating films were obtained.

Next, using a DuPont impact strength tester, a load of 1k was applied.
Various tests were conducted under the conditions of 1/8 inch percussion head, and the height at which no cracking occurred in the cured coating was measured.

(4) Prepare two rectangular iron plates with adhesive strength of 20mm x 100mm x 3.2cm, heat them to 150 to 160°C, and apply powder to a position approximately 15cm from the end of one longitudinal side of each iron plate. After applying the body paint, the two iron plates were placed one on top of the other so that the unpainted parts were on opposite sides and the painted parts faced each other.

Then, the overlapped part is sandwiched with a cock for 150~
After being left at 160° C. for 30 minutes and then left at room temperature, the two iron plates were attached and integrated by the paint on the overlapped portion.

This was used as a test piece, and its both ends were pulled using a universal tensile test drill to measure the total shear adhesive strength.

(5) Thermal conductivity mold (4Q trrm x 40 mm x 4
rrrm) Fill the container with powder paint, and heat it at 150℃ for 30 minutes, being careful not to create bubbles.
After heating for a minute, a cured product was obtained by cooling.

The thermal conductivity of this cured product was calculated using the following formula using a thermal conductivity measuring device (Shibayama Kagaku Kikai Seisakusho, model 5STC-18).

λ=(Q/l (TA-'rB)] t4λ: Thermal conductivity (C817 seconds・Boron・℃) Q Near Seven Doors Heat of evaporation of 1 ml (Cat) t: Time to obtain 1 ml of acetone (seconds) TA Boiling point of near 7 tons (℃) TB: Boiling point of benzene (℃) t: Thickness of sample (ryn) C: Cross-sectional area of sample (ffl) 2-1 Fine aluminum hydroxide powder 1.570 2
0~30 3.52-2 Silicon oxide fine powder
1.54.4-1. ．． 553 15~204゜IH
042-3 Calcium silicate fine powder], 620
2 To 30 8゜52-4 Heavy calcium carbonate fine powder 1.660 35-38 1.8 Measurement of oil absorption: Adopt the rubber calcium carbonate test method specified in JIS K 6223 (6.5>) and calculate from the following formula. Calculated.

A-v/×100 A: Oil absorption amount (ml/　　　) V: Amount of oil used until solidification (goods) S: Weight of sample 2) (Note 2) Hardening agent 4-12-methylimidazole

Claims (1)

[Claims] 1. Epoxy resin and a refractive index (25° C.) of 1.45 to 1.
65 and an inorganic filler having an oil absorption amount of 15 to 75 ml/100 g average particle size of 0.2 to 30 μm. 2. The epoxy resin composition according to claim 1, wherein the inorganic filler is aluminum hydroxide or sericite. 3. The epoxy resin composition according to claim 1 or 2, wherein the content of the inorganic filler is 20 to 200 parts by weight based on 100 parts by weight of the resin.