JPH0648723A - Flaky particle of alkali metal aluminosilicate and its production - Google Patents

Abstract

PURPOSE:To obtain flaky particles of an alkali metal aluminosilicate by mixing an alkali metal-based flux to an aluminum-containing raw material and a silicon- containing raw material or a raw material containing aluminum and silicon and heat-treating the obtained mixture. CONSTITUTION:The mixing ratio of an aluminum-containing raw material (e.g. aluminum sulfate having particle diameter of <=5mum) to a silicon-containing raw material (e.g. silica glass powder having particle diameter of <=5mum) depends upon the composition of the objective flaky particle, however, the growth of the flaky particle is promoted by increasing the ratio of the silicon component. The amount of the alkali metal-based flux (e.g. potassium sulfate) is 0.1-20 times weight based on the total weight of the aluminum and silicon in terms of oxide. The mixture is mixed by using a ball mill, etc., and heat- treated at 1000-1600 deg.C to obtain the objective flaky particle of an alkali metal aluminosilicate having a (maximum diameter)/thickness ratio of >=3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to novel alkali aluminosilicate thin plate particles and a method for producing the same. The thin plate particles of ceramics are used as a reinforcing material for composite materials such as plastics, metals and ceramics for the purpose of improving their mechanical properties. In addition, it has characteristics such as exhibiting better coverage and orientation than needle-shaped particles and spherical particles, and is widely used as a resin pigment, printing ink, paint, glass, enamel, dental material and cosmetic base material. Expected to be used.

[0002]

2. Description of the Related Art Conventionally, SiC, BN, graphite and the like have been known as thin plate particles, but alkali aluminosilicate thin plate particles have not been known.

[0003]

The conventionally known thin plate-like particles are expensive and their application range is limited, and a simple and efficient method for producing the thin plate-like particles is desired. The present invention has been made for the purpose of providing a novel alkali aluminosilicate thin plate particle and a method for producing the same.

[0004]

That is, the present invention is a thin plate-like particle containing aluminum, silicon and an alkali metal as main components, and the ratio of the maximum diameter to the thickness of the particle is 3 or more. Alkali aluminosilicate thin plate particles, which are characterized by a heat treatment of a mixture of a raw material containing aluminum, a raw material containing silicon and an alkali metal-based melting agent.

The present invention will be described in more detail below. The specific composition of the alkali aluminosilicate which aluminum present invention, silicon and alkali metals as a main component, the _{K 2 O-Al 2 O 3} -SiO 2 _{system, K 2 O · Al 2 O} 3 · 6Si
O ₂ , K ₂ O ・ Al ₂ O ₃・ 4SiO ₂ , K ₂ O ・ Al ₂ O ₃・ 2SiO ₂ , K ₂
There are compounds such as O ・ Al ₂ O ₃・ SiO _2, and in the Na ₂ O--Al ₂ O ₃ --SiO ₂ system, Na ₂ O ・ Al ₂ O ₃・ 6SiO ₂ , Na ₂ O ・ Al ₂ O ₃・Examples include compounds such as 2SiO ₂ . The alkali aluminosilicate thin plate-like particles of the present invention have a ratio of maximum diameter to particle thickness of 3
As described above, the number of particles is preferably 5 or more, and specifically, the maximum particle diameter is about 3 to 60 μm and the thickness is about 0.05 to 15 μm. The alkali aluminosilicate thin plate particles of the present invention contain aluminum, silicon and an alkali metal as main components, but those containing an additive component in addition to the main components are also included in the scope of the present invention.

Next, the manufacturing method of the present invention will be described. Specific examples of the raw material containing aluminum include oxides of aluminum, hydroxides, oxyoxides, chlorides, nitrates, sulfates, oxalates, formates, acetates, organic acid salts such as alkoxides, and Examples include metals.
Of these, a raw material that generates activated alumina by thermal decomposition of aluminum sulfate or the like is preferable. When the raw material is in the form of powder, the particle size is preferably small, specifically 5 μm or less.

Specific examples of the raw material containing silicon include oxides of silicon (including glass), hydroxides, oxyoxides, chlorides, nitrates, sulfuric acid, oxalates, formates and acetates. Examples thereof include organic acid salts such as alkoxides, metals, and the like, but those that become an oxide after heat treatment and do not leave impurities are preferable. When the raw material is in the form of powder, its particle size is preferably fine, specifically 5 μm or less. Alternatively, a compound of aluminum and silicon such as mullite or a solid solution may be used as a raw material.

The mixing ratio of the raw material containing aluminum and the raw material containing silicon varies depending on the composition of the target thin plate particles, but the growth of the thin plate particles tends to be promoted as the mixing ratio of the silicon component increases. There is. Further, when the mixing ratio of the raw material containing aluminum and the raw material containing silicon is different from the composition of the target thin plate particles, the excess aluminum component or silicon component is a compound containing each component as the second phase. , Remain in the reaction product as a solid solution or glass phase.

As the alkali metal type melting agent used in the present invention, alkali metal sulfates and chlorides are suitable. Specifically, it is lithium sulfate, sodium sulfate, potassium sulfate, lithium chloride, sodium chloride, potassium chloride and hydrates thereof. Also, it can be added in the form of a composite compound of an alkali metal-based melting agent and a compound containing aluminum and / or silicon.

The addition amount of the melting agent is related to the composition of the target thin plate-like particles, but if it is small, the growth of the thin plate-like particles is hindered and the thin plate-like particles tend to agglomerate with each other. Its effect is small. Therefore, the optimum addition amount varies depending on the intended thin plate particle composition and the type of the melting agent to be used, etc., but is not particularly limited, but is 0.1 to 0.1% of the total weight of aluminum and silicon-containing raw material converted to oxides of aluminum and silicon. It is preferable to add 20 times the weight, more preferably 1 to 10 times.

The raw material of the additive component used when adding the additive component is not particularly limited, but is a simple substance, an alloy, an oxide, a hydroxide, an oxyoxide, a chloride, a nitrate, a sulfate, an oxalate or a formate. , Acetates, organic acid salts such as alkoxides, and mixtures thereof, and complex compounds composed of two or more components. As a method of adding the additive component, there is a method of mixing with other raw materials in the form of powder or solution. When used in the powder form, the particle size is preferably small, and specifically 5 μm or less.

The method of mixing the raw material containing aluminum and silicon, the alkali metal-based melting agent, and the additive component added as necessary is not particularly limited as long as it can be uniformly mixed, and a known method is known. It can be performed by either a dry method or a wet method. The dry type means mixing by a usual mixing method such as a mortar, a mixer and a ball mill. The wet method is a method of mixing raw materials in a solution form. When the wet method is used, it is preferable to add a drying step before the heat treatment.

The optimum heat treatment temperature of the mixture varies depending on the composition, but is 1000 to 1600 ° C., preferably 1200 to 1500
℃. If the heat treatment temperature is lower than 1000 ° C, the reaction for producing thin plate particles is not promoted, and if it exceeds 1600 ° C, the heat treatment facility cost and energy consumption increase, which is not preferable. For the heat treatment, a metal container such as Pt that can be used at a high temperature, various ceramic containers, or the like can be used. It is preferable that these containers are hard to react with the raw material containing aluminum and silicon in the mixture, the alkali metal-based melting agent, and the like. It is also possible to suppress the reaction with the container by heat-treating the mixture formed by pressure molding or the like.

When it is necessary to isolate the thin plate-like particles from the reaction product containing the melting agent, the isolation method includes hot hydrochloric acid, hot sulfuric acid, hot nitric acid, hydrofluoric acid or a mixture thereof, and alkali such as hot caustic soda. Alternatively, hot water or the like may be used to remove the melting agent and other water-soluble substances, followed by sufficient washing with water. In addition, when there is a by-product of the glass phase and it is difficult to remove it by the above method, it can be dissolved and removed by hydrothermal treatment with the acid or alkali. When there is a water-insoluble by-product, thin plate-like particles may be separated from the residue by a treatment such as decantation and then sufficiently washed with water.

[0015]

EXAMPLES Examples of the present invention will be specifically described below, but the present invention is not limited to these examples. [Example 1-6] Table aluminum sulfate powder so as to have the composition shown in _{1 (Al 2 (SO 4)} 3, reagent) and silica glass powder (SiO _2, manufactured by Denki Kagaku Kogyo KK) was weighed, to this An alkali metal-based melting agent (potassium sulfate (K ₂ SO ₄ , reagent)) in a weight ratio shown in Table 1 was weighed with respect to the total weight of aluminum and silicon oxides in the raw material containing aluminum and silicon. And added by a ball mill for 20 hours. The obtained mixture was heat-treated at the temperature shown in Table 1 for 3 hours.
An acid was added to this reaction product for hydrothermal treatment to separate thin plate-like particles, which were then thoroughly washed with water and dried.

Table 1 shows the color, maximum diameter, thickness and ratio of maximum diameter to thickness of the obtained thin plate particles. As a result of investigating the crystal structure by X-ray diffraction, all the samples had KAlSi _{2
O 6 (K 2 O · Al} 2 O 3 · 4SiO 2) was found to be crystalline structure. KAlSi ₂ O ₆ is a crystalline phase with a melting point of 1686 ° C. In the morphological observation with an electron microscope, a hexagonal thin plate was also seen.

[0017]

[Table 1]

[0018]

INDUSTRIAL APPLICABILITY The present invention is an alkali aluminosilicate thin plate-like particle and a method for producing the same. The alkali aluminosilicate thin plate-like particle of the present invention is used as a reinforcing material for improving the mechanical properties of composite materials such as plastics, metals and ceramics. It exhibits excellent properties, and also has features such as exhibiting better coverage and orientation than needle-shaped particles and spherical particles,
It is expected to be widely used as pigments for resins, printing inks, paints, glass, enamel, dental materials and cosmetic base materials. Furthermore, according to the method of the present invention, it is possible to efficiently produce the alkali aluminosilicate thin plate-like particles of the present invention.

Claims (2)

[Claims] 1. Alkali aluminosilicate thin plate-like particles, which are thin plate-like particles containing aluminum, silicon and an alkali metal as main components, and the ratio of the maximum diameter to the thickness of the particles is 3 or more. 2. The alkali aluminosilicate according to claim 1, wherein a raw material containing aluminum and a raw material containing silicon, or a mixture of a raw material containing aluminum and silicon and an alkali metal-based melting agent is heat-treated. Method for producing thin plate-like particles.