JPS6284162A - Production of modified silicon nitride powder - Google Patents

Abstract

PURPOSE:To obtain modified silicon nitride powder having improved affinity to resins and suitably usable as a filler for various resins, by oxidizing silicon nitride powder in an aqueous solution of nitric acid and treating the product with a silane coupling agent. CONSTITUTION:Silicon nitride powder is added to preferably 1-7N aqueous solution of nitric acid to obtain a slurry solution, which is heat-treated (preferably at >=50 deg.C for 10min-10hr) and then treated with a silane coupling agent to obtain the objective modified silicon nitride powder. The necessary amount of the silane coupling agent (A g) preferably satisfies the formula A=[weight of powder (g)]X[specific surface area of powder (m<2>/g)]/[minimum covering area of silane coupling agent (m<2>/g)].

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing modified silicon nitride powder, particularly silicon nitride powder that can be suitably used as a filler for various resins.

(Prior Art and Problems) Demand for silicon nitride powder has recently increased rapidly as a raw material for heat-resistant and high-temperature structural materials and ceramic molded bodies.

Furthermore, since this powder is hard, has high chemical resistance and heat resistance, and is composed of fine primary particles, new uses are being discovered in addition to the above. One of these uses is as a filler that is uniformly dispersed into resins, and resins in which silicon nitride powder is dispersed generally have improved hardness, chemical resistance, and heat resistance.

In order to be uniformly dispersed in the resin and fully fulfill its role as a filler, the resin and particles must have good affinity, or so-called wetting, and if this is not sufficient, the expected effect may not be achieved. Moreover, when this dispersion is applied to various substrates, the adhesion is poor and it cannot be put to practical use.

Generally, silicon compounds containing oxygen have silanol groups on their surface interfaces, and are said to be chemically active to that extent. Although ordinary silicon nitride powder has an oxygen content of 3% or less, it is thought that silanol groups are unevenly distributed on the surface layer of each particle, and a certain level of activity was expected. However, silicon nitride powder, as it is, has the disadvantage that it is poorly compatible with resins and is difficult to disperse.

(Summary of the Invention) The present invention was obtained as a result of studies aimed at solving the above-mentioned problems and expanding the uses of silicon nitride powder. The particles are oxidized to increase the number of silanol groups on the surface layer, and then treated with a silane coupling agent to improve their affinity with resins.

(Explanation of constituent elements) The silicon nitride powder used in the present invention may be of any kind as long as it is used as a raw material for silicon nitride sintered bodies, but when considering its use as a filler for resin, It is preferable that the particles have a uniform shape and size.

In particular, it is obtained from amorphous silicon nitride, and the proportion of primary particles with a diameter of 1Qμ or more is 10% or less, the average particle size is 5μ or less, and the proportion of α crystal phase is 90% or less.
% or more is optimally used.

To oxidize silicon nitride powder with nitric acid, any nitric acid aqueous solution can be used, but a 0.5 to 8N aqueous solution,
In particular, a 1-7N aqueous solution is preferred. Silicon nitride powder is added to this nitric acid aqueous solution to form a slurry. The concentration of silicon nitride may be in any range as long as the mixture is in a slurry state, but it is 10 to 10 parts by weight per 100 parts by weight of the nitric acid aqueous solution.
100 parts is practical. This slurry solution is heat-treated to oxidize the silicon nitride powder, but any conditions may be used as long as oxidation occurs. The preferred temperature is 50°C or higher, and preferably lower than the boiling point of the nitric acid aqueous solution.
A practical treatment time is 10 minutes to 10 hours.

Thoroughly wash the nitrate IFi in this way with water,
It is necessary to repeat the washing operation until the pH of the washing water becomes 5 or higher.

The oxygen content of silicon nitride subjected to the above-described resistance treatment increases to a maximum of 10%.

Next, the oxidized silicon nitride powder is treated with a silane coupling agent. Treatment methods using silane coupling agents include:
The dry method involves spraying an aqueous solution of a silane coupling agent at the optimal concentration onto the powder in a stirred state, stirring and mixing it thoroughly, and then drying it. Preferably, there is a wet method in which the material is dispersed and slurried in water, a silane coupling agent is added thereto, and the solvent is removed and dried, but any method can be applied. In addition, a sufficiently effective method is to mix 1 to 3% of a silane coupling agent into the resin beforehand and then disperse the oxidizing agent silicon nitride powder.

There is a relationship between the amount of the silane coupling agent and the weight of the powder as shown in the following formula, and it is desirable that the amount of the silane coupling agent added satisfies this required amount.

Required amount of silane coupling agent (g) - Minimum coverage area of silane coupling agent (Td/q) For example, vinyltrichlorosilane and nyltris(β-methoxyethoxy)silane are used for unsaturated polyesters, vinyltriethoxysilane and vinyltrimethoxysilane are used for cross-linked polyethylene, and γ- is used for unsaturated polyesters. methacryloxypropyltrimethoxysilane,
β for epoxy resin, phenol resin, and melamine resin
-(3,4epoxycyclohexyl>ethyltrimethoxysilane, T-glycidoxypropyltrimethoxysilane, T-glycidoxygolopylmethyldiethoxysilane, N-β(ami,·°-thyl)γ-aminopropyltri Methoxysila〉 Epoxy resin, phenol resin, melamine resin, furan resin has N-β (aminoethyl)γ-
γ for anilpropylmethyldimethoxysilane, nylon resin, phenol resin, epoxy resin, and melamine resin.
- N for aminopropyltriethoxysilane, polyimide resin, epoxy resin, phenol resin, and melamine resin.
-phenyl-γ-aminopropyltrimethoxysilane,
γ-mercaptopropyltrimethoxysilane for rubber,
γ-chloropropyltrimethoxysilane is preferably used as the epoxy resin.

(Effect of the invention) When the modified silicon nitride powder, which has been converted into nitrate 111I by the method described above and treated with a silane coupling agent, is dispersed in a resin as a filler, the affinity between the resin and silicon nitride increases, and the As a result, the expected properties such as heat resistance, chemical resistance, and hardness were improved, and the hiding power of silicon nitride was also improved.
It does not cause the deterioration in adhesion that occurs due to the addition of silicon nitride.

(Example) Example 1 1 part by weight of vecrystalline silicon nitride powder (specific surface area 12 m/g, oxygen content 1.2%) was suspended in 10 parts by weight of 6N nitric acid aqueous solution and stirred at 80°C for 1 hour. After oxidizing the sample with distilled water, the sample was washed with distilled water until the pH of the washing solution became 6 or higher. When a small amount of silicon nitride was removed and dried, the oxygen content was measured and found to have increased to 5.3%.

To this silicon nitride, an aqueous solution in which 0.05 parts by weight of a silane coupling agent KBM-403 (manufactured by Shin-Etsu Chemical Co., Ltd.) was dissolved was added, stirred at room temperature for 2 hours while applying ultrasound, and then filtered. , and dried to obtain a modified silicon nitride powder.

A solution was prepared by dissolving ortho-cresol novolac type epoxy resin (epoxy equivalent: 210-220>52 parts by weight in 48 parts by weight of ethyl cellosolve acetate. 2.5 parts by weight of this solution, 1 part by weight of modified silicon nitride powder, silicon nitride) ball (diameter 10 m > 12 parts by weight, mixed at a ratio of 8
A dispersion was obtained by mixing for 3 hours at a rotation speed of 5-90 rpm.

Ebicure 3 manufactured by Yuka Shell Co., Ltd. was added to this dispersion as a curing agent.
010 was added and mixed in an amount of 1% based on the epoxy resin, and then coated on a copper plate to a film thickness of 13 microns. This was heated at 80° C. for 1 hour and then at 150° C. for 1 hour, and an adhesion test using an adhesive tape was conducted in accordance with JIS K5400.

When the copper plate was used after being puff-polished, the peeled area was 0%, and even when the copper plate was not puff-polished, it was 5% or less.

Comparative Example 11 The same procedure as in Example 1 was carried out except that the silicon nitride powder was not oxidized with nitric acid and treated with a silane coupling agent. As a result, the peeled area was 49% in the adhesion test to a puff-polished copper plate, and the peeled area was 49%. If not, it was 100%.

Comparative Example 2 Silicon nitride powder was carried out in the same manner as in Example 1 except that it was not oxidized with nitric acid. As a result, the peeling area was 5% in the adhesion test to the puff-polished copper plate, and the peeling area was 5% when the powder was not puff-polished. was 98%.

Claims (1)

[Claims] A method for producing modified silicon nitride powder, which comprises oxidizing silicon nitride powder in an aqueous nitric acid solution and then treating it with a silane coupling agent.