Process for production of thermally expandable beads and application thereof

Abstract

The invention provides a process for the production of thermally expandable beads which exhibit a high expansion ratio and give hollow fine particles excellent in the resistance to repeated compression through thermal expansion and application thereof. A process for the production of thermally expandable beads which are each constituted of both a shell made of a thermoplastic resin and a blowing agent that is enveloped in the shell and has a boiling point not higher than the softening point of the thermoplastic resin, which comprises the step of polymerizing a polymerizable component in an aqueous medium where the polymerizable component and the blowing agent are dispersed in the presence of an oxygen-containing aluminum salt and / or a hydrate thereof and at least one water-soluble compoundselected from among polyalkylene imines which have molecular weights of 1000 or above and each bear at least one structure constituted of an alkyl group substituted with a hydrophilic functional group selected from between carboxylic acid (salt) group and phosphonic acid (salt) group and a nitrogen atom attached to the alkyl group.

Description

technical field [0001] The invention relates to a preparation method and application of heat-expandable microspheres. Background technique [0002] Heat-expandable microspheres have a structure including a shell of a thermoplastic resin and a blowing agent enclosed in the shell, and are generally called heat-expandable microcapsules. Thermoplastic resins generally include vinylidene chloride-based copolymers, acrylonitrile-based copolymers, and acrylic-based copolymers; and blowing agents mainly used include hydrocarbons such as isobutane and isopentane (see Patent Document 1). Patent Document 2 discloses thermally expandable microcapsules having high thermal durability, for example, comprising a thermoplastic resin prepared from a component containing 80% by weight or more of a nitrile monomer, 20% by weight or less of a non-nitrile monomer, and a crosslinking agent the shells of those. The method prepares heat-expandable microcapsules in an aqueous dispersion medium...

AI Technical Summary

Problems solved by technology

As described above, although the durability of hollow fine particles to repeated compression has been studied in various ways, hollow fine particles with sufficiently improved durability to repeated compression have not been prepared.

The hollow fine particles obtained by thermally expanding the heat-expandable microcapsules described in Patent Document 3 are also poor in durability against repeated compression

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