Spherical organic polymer-silicon compound composite particles, hollow particles and their production methods

Abstract

The present invention is to provide hollow particles with a low degree of agglomeration and having a high roundness, and a process for producing them.

Hollow particles comprising a silicon compound, having an average particle size of from 5 to 65 nm and an average roundness of at least 0.90, and having a shell comprising the silicon compound and having a thickness of from 1 to 20 nm. Further, a method for producing hollow particles, which comprises adding sulfuric acid to a liquid containing spherical organic polymer-silicon compound composite particles having a core comprising an organic polymer and a shell comprising a silicon compound in a medium containing at least 95 mass % of water, followed by heating to carbonize the organic polymer thereby to convert it to a carbide, and subjecting the carbide to decomposition using a liquid oxidizing agent other than sulfuric acid.

Description

TECHNICAL FIELD[0001]The present invention relates to spherical organic polymer-silicon compound composite particles, hollow particles, and methods for producing such spherical organic polymer-silicon compound composite particles and hollow particles.BACKGROUND ART[0002]In recent years, along with progress of downsizing and layer thickness reduction of various industrial components, reduction in the size of starting materials used is in progress. With respect to a powder used as various starting materials, fine particles having a particle size of several to several tens nanometer are required as particles constituting the powder. Further, for application which requires high fluidity or high filling properties of particles, hollow spherical particles excellent in such performance are heavily used.[0003]Various hollow spherical particles have been studied as an antireflection material, a low dielectric material, a filler such as an insulating material, a carrier for drug delivery syst...

AI Technical Summary

Benefits of technology

[0030]By using the spherical organic polymer-silicon compound composite particles of the present invention, a powder comprising fine hollow particles with a low degree of agglomeration, having a high roundness, and a slurry obtained by dispersing the hollow particles, can be obtained.

Problems solved by technology

Further, the composite particles are bonded by subsequent heating for core removal, whereby they are formed into strong agglomerates, such being problematic.

However, it is unclear whether the organic polymer covered with an inorganic oxide can be decomposed by such a method.

As a method for producing spherical organic polymer-silicon compound composite particles, a method of preliminarily preparing a core of an organic polymer and covering it with a shell of a silicon compound is commonly employed, but conventional spherical organic polymer-silicon compound composite particles have the following problems.

However, by such a method, although spherical composite particles of from 0.07 μm (70 nm) to 50 μm are obtained, particles of from 5 to 65 nm which are smaller than the above particles are not obtained.

Further, the following other methods have been proposed, but they have such problems that a preparation procedure is complicated since covering with silica is carried out in a multilayer manner (Patent Document 4), or no fine particles less than 100 nm can be obtained (Non-Patent Document 1) in the same manner as disclosed in Patent Document 3.

However, such conventional template methods have the following problems.

However, calcium carbonate or zinc oxide to be used as the core is crystalline and has a crystal habit, and the crystal habit is reflected even on the core-shell composite particles covered with silica and the hollow particles from which the core is removed, whereby no spherical hollow particles can be obtained (Patent Documents 2, 5 and 6).

If the average roundness of the hollow particles is less than 0.90, when the particles are used as a filler, fluidity and filling properties tend to be insufficient, and properties intrinsic to the hollow particles, such as a low refractive index, a low dielectric constant and a high porosity may not sufficiently be obtained.

And, the particles are bonded by subsequent heating at high temperature for pyrolysis or burning of the core, whereby the particles are formed into strong agglomerates, such being problematic.

However, by this method, when the salt solution is prepared, a large amount of a salt is added to a slurry containing the core-shell composite particles, and accordingly the core-shell composite particles which are in a hydrophilic colloidal state, are agglomerated by salting out at that point, whereby no sufficient effect of preventing agglomeration can be obtained.

However, it is unclear whether the organic polymer covered with an inorganic oxide can be decomposed by such a method since there is no application example.