JPH01198658A - Flame-retardant epoxy resin composition - Google Patents

Abstract

PURPOSE:To obtain the above composition having excellent impregnation property into winding and effective in suppressing the lowering of the impregnation speed into winding caused by the long-term vacuum stirring especially in the case of using an automatic pouring machine, by compounding hydrated alumina having a specific particle size distribution as a filler. CONSTITUTION:(A) An epoxy resin is compounded with (B) 0.6-1.3 equivalent (based on 1 equivalent of epoxy group of the component A) of an acid anhydride hardener (e.g. methyltetrahydrophthalic anhydride), (C) 0.1-5pts.wt. (based on 100pts.wt. of the component B) of a cure accelerator (e.g. 2-ethyl-4- methylimidazole), (D) 5-20pts.wt. (based on 100pts.wt. of the component A) of red phosphorus and (E) 80-220pts.wt. (based on 100pts.wt. of the component A) of a filler consisting of hydrated alumina produced by precipitation wet classification process and having an average particle diameter of 6-10mum, cumulative wt.% of >=85wt.% corresponding to particle diameter of <=15mum, 15-35wt.% corresponding to the diameter of <=5mum and <=13wt.% corresponding to the diameter of <=3mum.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a flame-retardant epoxy resin composition, and more specifically, it has excellent impregnation properties between windings, and is particularly suitable for long-term use when using an automatic injection machine. The present invention relates to a flame-retardant epoxy resin composition that has significantly improved impregnability between windings during vacuum stirring.

[Conventional technology]

Conventionally, epoxy resin compositions have excellent electrical properties, mechanical properties, and crack resistance, as well as excellent adhesion to various materials, and have therefore been widely used for electrical insulation, particularly for casting. In particular, flame-retardant epoxy resin compositions are used for insulation treatment of high-voltage parts, that is, impregnation casting, for the purpose of improving insulation protection, high voltage characteristics (arc resistance, tracking properties), crack resistance, and flame retardance. For example, a composition in which an acid anhydride-curing epoxy resin contains a large amount of a filler and a flame retardant is used.

However, flame-retardant epoxy resin compositions conventionally used for impregnating and casting flyback transformers do not satisfactorily impregnate the inside of coils wound with ultra-fine wires, e.g. There was a drawback that corona sometimes occurred and caused a rare short circuit. Furthermore, when conventional resin compositions are cured for a short period of time, there is a problem in that the resin is cured before sufficient impregnation between the windings is achieved, resulting in poor impregnation. Furthermore, when producing flyback transformers using streamlined automatic injection equipment, injection is performed under high vacuum in order to sufficiently impregnate the resin between the ultra-fine wires, but at this time, the resin is stirred in advance. Vacuum defoaming is performed for a long time to sufficiently remove air bubbles contained in the resin, and the longer the vacuum defoaming time, the greater the effect. However, due to such long-term stirring, the blended filler is likely to be re-pulverized, producing fine particle components, and when the inside of the ultra-fine wire is impregnated with resin, this fine particle component will clog the upper part of the ultra-fine wire, causing impregnation. It causes a decline in sexual performance.

[Problem to be solved by the invention]

An object of the present invention is to eliminate the drawbacks of the prior art, to provide excellent impregnating properties between the windings, and to significantly reduce the drop in impregnating properties between the windings due to long-term vacuum stirring, especially when using an automatic injection machine. An object of the present invention is to provide an improved flame-retardant epoxy resin composition.

[Means for Solving the Problem] As a result of intensive research, the present inventors have achieved the above object by using hydrated alumina produced by a special method and having a specific particle size distribution as a filler. The present invention was achieved by discovering that

The present invention provides a flame-retardant epoxy resin composition containing an epoxy resin, an acid anhydride curing agent, a curing accelerator, red phosphorus, and a filler, which is produced by a precipitation wet classification method and has an average The particle size is 6 to 10 μm, and the cumulative weight percent of particles with a particle size of 15 μm or less is 85% or more, the cumulative weight percent of particles with a particle size of 5 μm or less is 15 to 35%, and the particle size is 3 μm.
The present invention relates to a flame retardant epoxy resin composition using hydrated alumina having a particle size distribution with a cumulative weight percent of m or less of 13% or less.

The epoxy resin used in the present invention has more than one epoxy group in the molecule, for example, bisphenol A epoxy resin obtained from bisphenol A and epichlorohydrin, bisphenol A type epoxy resin obtained from bisphenol F and epichlorohydrin, etc. Bisphenol F type epoxy resin obtained from phthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, glycidyl ester of polycarboxylic acids such as cepatic acid and dodecanoic acid, 1,4-butadiol, 1.
Glycidyl ethers of polyhydric alcohols such as 6-hexanediol, polyethylene glycol, polypropylene glycol, trimethylolpropane, alicyclic epoxy resins such as 3,4-epoxycyclohexylmethyl (3,4-epoxycyclohexane) carboxylate, liquid polybutadiene Examples include epoxidized products of.

Examples of the acid anhydride curing agent used in the present invention include methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, phthalic anhydride, hexahydrofihydrophthalic anhydride, endomethylenetetrahydrophthalic anhydride, dodecenylsuccinic anhydride, and octenyl Examples include succinic anhydride, polyazelaic acid polyanhydride, and the like. The blending amount of the acid anhydride curing agent is preferably 0.6 to 1.3 equivalents per equivalent of the epoxy group contained in the epoxy resin.

The curing accelerator used in the present invention is used to accelerate the curing reaction, and includes imidazoles such as 2-ethyl 4-methylimidazole, ■-cyanoethyl 4-methylimidazole, 1-benzyl 2-ethylimidazole, and derivatives thereof; Examples include tertiary amines. Although the amount of the curing accelerator is not particularly limited, it is preferably 0.1 to 5.0 parts by weight per 100 parts by weight of the acid anhydride curing agent.

In the present invention, red phosphorus is used as a flame retardant, for example, in addition to red phosphorus, which has a flame retardant effect, red phosphorus surface-coated with resins such as phenol resin, furan resin, fluororesin, and melamine resin, and aluminum compounds. Modified red phosphorus whose surface is coated with an inorganic compound such as , magnesium compound or zinc compound is used. The blending amount of red phosphorus is preferably 5 to 20 parts by weight, particularly preferably 10 to 15 parts by weight, per 100 parts by weight of the epoxy resin.

The hydrated alumina used as a filler in the present invention is produced by a precipitation wet classification method and has an average particle size of 6 to 10 am.
and has the particle size distribution described below.

Generally, hydrated alumina is produced by reacting the raw material bauxite with sodium hydroxide under pressure and heat in an autolape, and then the resulting sodium aluminate solution is heated and stirred in a precipitation tank to form hydrated alumina of a predetermined particle size. The crystals are precipitated and then classified by gravity in a thinner, resulting in a particle size of 601I.
The hydrated alumina crystals of m are pulverized by wet or dry pulverization, and hydrated alumina having a predetermined particle size distribution is obtained by wet classification or dry classification, which is then washed with water, filtered, and dehydrated.

On the other hand, when hydrated alumina used in the present invention is precipitated from a sodium aluminate solution in a precipitation tank, in order to obtain a predetermined particle size distribution, the amount of hydrated alumina seeds added to the precipitation tank, The precipitation temperature and stirring time are appropriately adjusted to obtain a predetermined average particle size and particle size distribution, and the resulting crystals are not crushed using a crusher, but are produced by wet classification followed by washing with water, filtration, and dehydration. The hydrated alumina used in the present invention produced by the precipitation wet classification method as described above has an average particle size of 6 to 10 μm, a cumulative weight percent of particles with a particle size of 15 μm or less is 85 or more, and a particle size of 5 μm or less. Cumulative weight% of
is 15 to 35%, and the cumulative weight% of particles with a particle size of 3 μm or less is 1
It has a particle size distribution of 3% or less.

When the average particle size exceeds 10 μm or when the particle size is 15
If the cumulative weight % of micrometers or less is less than 85, the hydrated alumina in the composition will have a high settling tendency. On the other hand, the particle size is 5
When the cumulative weight % of micrometers or less is less than 15%, the viscosity of the composition tends to increase as the amount of fine particles in the filler decreases. Average particle size is less than 6μm or particle size is 5μm
If the cumulative weight % of particles having a diameter of 3 μm or less exceeds 35%, or if the cumulative weight % of particles having a particle diameter of 3 μm or less exceeds 13%, impregnating properties into the coil when the composition is injected into the coil decrease.

The shape of conventionally used hydrated alumina, which is produced by pulverizing with a wet or dry pulverizer and then wet or dry classification, is amorphous, whereas hydrated alumina is produced by the precipitation wet classification method used in the present invention. Since the hydrated alumina is almost spherical, re-grinding does not occur even if it is forcibly stirred while being dispersed in the composition, and it is thought that the generation of fine particle components is extremely reduced.

In the present invention, hydrated alumina is effective in making the composition of the present invention flame retardant and further improving arc resistance and tracking resistance. , average particle size is 6-10
µm and having the specified particle size distribution, the resulting flame retardant epoxy composition was tested to UL94 with a thickness of 1/16 inch.
It has a high flame retardancy of v-0, has excellent arc resistance and tracking resistance, and is also extremely excellent in impregnating the resin between the windings of the coil.

When vacuum-injecting the flame-retardant epoxy resin composition of the present invention into a wound coil, the components in the flame-retardant epoxy resin composition are mixed in advance into a base resin (an epoxy resin, a reactive epoxy resin as a diluent), and a reactive epoxy resin as a diluent. , red phosphorus, hydrated alumina, etc.)
and curing agents (acid anhydride curing agents, curing accelerators, etc.).
Each has an independent capacity with a stirring blade of 150 to 200
Place it in two tanks of 1, and achieve an ultimate vacuum of 1 to 3 torr.
, vacuum stirring and defoaming are performed at a temperature of 30 to 60°C for 2 hours or more. Next, the base material and curing agent are metered and mixed in predetermined amounts through a sealed metering pump into a coil set in a vacuum of 2 to 10 torr, and injected from a nozzle, and the coil, which has been returned to normal pressure, is carried into a furnace. and harden. The epoxy resin composition is preferably cured at 65-80°C for 3-6 hours and then at 100-120°C for 3-6 hours.

During this injection, the viscosity of the base agent is approximately 600 to 120Qpo.
ISE (25°C), the viscosity is high, so in order to remove the bubbles contained, it was heated to 30-60°C and heated to 200°C.
Vacuum defoaming is performed at a stirring speed of ~300 rpm, and the larger the tank capacity, the longer the time for this stirring and defoaming.

When conventional hydrated alumina is used, if the stirring and defoaming time is prolonged, the hydrated alumina will be re-pulverized and fine particle components will be generated, and the impregnation of the resin between the windings of the injection hardened coil will be significantly reduced. It becomes what it is. When using this conventional hydrated alumina, the base material is sampled from inside the tank over time, dissolved in acetone, and the sedimentation rate of the hydrated alumina is measured in a test tube. The speed is slow, that is, the generation of fine particle components can be confirmed. On the other hand, in the case of the hydrated alumina used in the present invention, the sedimentation rate does not change even if the stirring and defoaming time increases, and the generation of fine particle components is extremely small, and the injection-hardened coil does not contain resin between the windings. The deterioration in impregnating properties is extremely small.

The amount of hydrated alumina in the resin composition of the present invention is preferably 80 to 220 parts by weight, particularly 120 to 180 parts by weight, per 100 parts by weight of the epoxy resin.

The flame-retardant epoxy resin composition of the present invention includes, for example, colorants such as titanium white, red iron oxide, ferric oxide, and carbon, silane coupling agents, titanium coupling agents,
A silicone antifoaming agent or the like may be added as necessary.

〔Effect of the invention〕

The flame-retardant epoxy resin composition of the present invention has excellent impregnating properties between the windings, and in particular, significantly improves the decline in impregnating properties between the windings due to long-term vacuum stirring when using an automatic injection machine. Moreover, it has excellent arc resistance and tracking resistance, and exhibits flame retardancy of 94V-0.

The flame-retardant epoxy resin composition of the present invention can be used for impregnating and casting high-voltage electrical parts such as flyback transformers, ignition coils, various power transformers, and solenoid coils.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to Examples. "1 part" in the following means parts by weight.

Each characteristic was measured by the method shown below.

(1) Particle size distribution of filler: using Sedaygraph 5000ET manufactured by Shimadzu Corporation, sample concentration approximately 8% by weight, starting particle size 50 μm, dispersion liquid hexane-sodium metaphosphate 0°1% by weight, ultrasonic cleaning 20 minutes as preliminary dispersion. The measurement was carried out for 1 minute.

(2) Clay: Measured at 25°C using a B-type rotational viscometer.
It was measured with

(3) Model sedimentation: A sample was poured into a polyethylene test tube with a diameter of 18 mm to a height of 130 mm, and the
After further curing at 110 °C for 3 hours, the burning residue was measured at 1 cm each of the upper and lower ends of the cured product.
The difference between the top and bottom was calculated. The larger the difference, the greater the settling of the filler during curing.

(4) Model impregnability: A polyethylene test tube with a diameter of 15+ma is filled with glass beads having an average particle diameter of 60 μm while being vibrated at a height of 40+nm.

Next, the sample was injected to a height of 80++n under a reduced pressure of 10 torr, and then (
It was cured under the same curing conditions as in 3), and the model impregnation rate was calculated using the following formula.

W.

Wo: Initial weight of glass beads (g) Wl: Weight of glass beads in unimpregnated area (g) Model impregnation rate is to calculate the amount of sample impregnated into glass beads during curing, and the weight of glass beads in unimpregnated area A small amount indicates excellent impregnating properties.

(5) Actual machine impregnability - A model coil was created by winding 250 strands of urelene wire with a diameter of 0.05 mm around a modified polyphenylene oxide bobbin (10 slits), and the bobbin was placed in a case made of the same material and heated at 100"C. After preheating for 1.5 hours, a sample at 35°C was injected for 30 seconds under a reduced pressure of 5 torr, and then returned to normal pressure.Then, after curing under the above curing conditions, the center part was cut, polished, and inserted between the windings. The impregnation rate of the sample was observed under a microscope.The impregnation rate was calculated for each slit using the following formula.

Impregnation rate (%") = (1--)

Actual machine impregnation was evaluated using the following criteria.

O: Impregnation rate 99% or more Δ: Less than 99 to 97%
, placed in a round can with a height of 100 mm, and stirred continuously for 4 hours at a rotation speed of 1000 to 1300 rpm using a lab stirrer (Model LS-50 manufactured by Yamato Kagaku Co., Ltd., stainless steel, 4 blades, 50 mm diameter). Then, 10g of the main ingredient was stirred.
was placed in a glass test tube with a diameter of 18 mm, thoroughly dissolved with acetone, the acetone was adjusted to a test tube height of 100 mm, and the mixture was left at 25°C for 1 hour to measure the sedimentation rate of the filler and stirred. The presence or absence of re-grinding of the filler was investigated in comparison with untreated products. That is, when hydrated alumina is re-pulverized by continuous stirring and fine particle components are generated, the sedimentation rate is slow and the height of the acetone supernatant layer becomes small.

Model crushability (sedimentability) rating is 1: The height of the supernatant after standing was evaluated using the following criteria.

○: Height of acetone supernatant 40 mm or more ×: Height of acetone supernatant less than 40 am On the other hand, a predetermined amount of a curing agent (mainly a mixture of an acid anhydride curing agent and a curing accelerator) was blended into the stirred main ingredient, and the above (4) ) model impregnation rate was measured.

(7) Arc resistance: Measured according to JIS K6911.

(8) Tracking resistance: IECpublication
112.

(9) Flame retardancy: According to UL94, test piece thickness 1.5/8
Evaluation was made using a torso sample.

Examples 1 to 4 Using the filler shown in Table 1, hydrated alumina A or B,
The resin composition of the present invention was obtained by blending the base resin and curing agent shown in Table 2 at the compounding ratio shown in Table 2, and its properties were evaluated.

All of the resin compositions of the present invention have a sedimentation property of 0.8 to 1.5.
%, and model impregnation is excellent at over 94%.
Actual machine impregnation also showed good results. Regarding the agitation and pulverization properties, the acetone sedimentation of the filler after forced stirring is large, and the generation of fine particles is small compared to the initial stage, and the model impregnation property is also 92.
%, and the flame retardancy was 94V-0.

Comparative Examples 1 to 5 Using fillers C, D, B, F, or C shown in Table 1, resin compositions were prepared by blending the main ingredients and curing agents shown in Table 2 at the compounding ratios shown in Table 2. obtained, and its properties were evaluated.

Filler C used in Comparative Example 1 is a filler with a high content of fine particles of 3 μm or less (5%), and the characteristics of the composition are that the model impregnation property is 66% and the actual machine impregnation property is △ (97 to 99%). The rate was poor.

The filler used in Comparative Example 2 was 6% less than 5 μm, and 3 μm.
A filler that contains almost no particulate matter, with 0% of m or less.
The properties of the composition are excellent in model impregnation rate and actual machine impregnation rate, but the viscosity is 2200 poise, which is about twice as high as that of the example (it has poor workability and also has a settling property of 4.7%).
, and the sedimentation during curing was large.

Filler E used in Comparative Example 3 was created by a dry pulverization method, and the composition has excellent sedimentation properties, but the model impregnability is 55% and the actual machine impregnation is × (97% or less). and worse (furthermore, the acetone supernatant height is X (40 m).
(less than m), fine particle components were generated, and the model impregnability was therefore significantly lower than the initial level.

Filler F used in Comparative Example 4 was prepared by a dry pulverization method, and the composition has excellent sedimentation properties, model impregnation properties, and actual machine impregnation properties, but the agitation and pulverization properties are poor due to the height of the acetone supernatant. At X (less than 40 mm), fine particle components are generated,
Therefore, the model impregnability was significantly lower than the initial level.

Filler G used in Comparative Example 5 was created by a dry pulverization method, and the filler has a large proportion of coarse particles, 80% of which are 15 μm or less (20% are larger than 15 μm), and the composition has a property of sedimentation. is as high as 10.5%, the filler significantly settles during hardening, and the acetone supernatant height of the agitated and crushed raw material is
(less than 0+nm), fine particle components are generated, and therefore model impregnability (Note) 1) Bisphenol type epoxy resin manufactured by Shell Chemical Co., Ltd. 2) Reactive diluent manufactured by Nagase Ciba Co., Ltd. Product name rDY-02243) Manufactured by Rin Kagaku Co., Ltd. Phenol-coated modified red phosphorus 4) Methyltetrahydrophthalic anhydride manufactured by Hitachi Chemical Co., Ltd. 5) Product name “Curezol 2E4MZJ” manufactured by Shikoku Chemical Co., Ltd. 6) Tris-dimethylaminomethylphenol manufactured by Hitachi Chemical Co., Ltd.

Claims (1)

[Claims] 1. In a flame-retardant epoxy resin composition containing an epoxy resin, an acid anhydride curing agent, a curing accelerator, red phosphorus, and a filler, the filler is produced by a precipitation wet classification method and has an average particle size of is 6 to 10 μm, and the particle size is 1
Cumulative weight % of 5 μm or less is 85% or more, particle size is 5 μm
A flame-retardant epoxy resin composition comprising hydrated alumina having a particle size distribution in which the following cumulative weight % is 15 to 35% and the cumulative weight % of particles having a particle size of 3 μm or less is 13% or less.