Thermally foamable microsphere and production process thereof
AssigneeKureha Corporation
InventorsYoshikatsu Satake, Genzo Asai
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Abstract
The invention provides a thermally foamable microsphere whose shell is formed of a polymer that is obtained by the polymerization of a polymerizable monomer and a crosslinkable monomer at a proportion of greater than 1% by weight up to 5% by weight based on the polymerizable monomer and which has a maximum expansion ratio of at least 5. The invention also provides a process for the production of a thermally foamable microsphere having a maximum expansion ratio of at least 5 by the suspension polymerization of a polymerizable mixture containing a crosslinkable monomer at a proportion of greater than 1% by weight up to 5% by weight based on the polymerizable monomer.
Claims29
A thermally foamed microsphere having structure in which a foaming agent is encapsulated in a shell formed of a polymer, wherein:
- (1) the shell formed of a polymer is formed of;
- (a) a vinylidene chloride (co)polymer obtained by polymerization of vinylidene chloride alone or a mixture of vinylidene chloride with a vinyl monomer copolymerizable therewith as a polymerizable monomer, and a bifunctional crosslinkable monomer having two polymerizable carbon-carbon double bonds, or
- (b) a (meth)acrylonitrile co(polymer) obtained by polymerization of (meth)acrylonitrile alone or a mixture of (meth)acrylonitrile with a vinyl monomer copolymerizable therewith as a polymerizable monomer, and a bifunctional crosslinkable monomer having two polymerizable carbon-carbon double bonds,
- wherein the bifunctional crosslinkable monomer is a compound having a structure in which two polymerizable carbon-carbon double bonds are linked together via a flexible chain derived from a diol compound selected from the group consisting of polyethylene glycol, polypropylene glycol, an alkyidiol, an alkyl ether diol and an alkyl ester diol, and the bifunctional crosslinkable monomer is used at a proportion of 1.1 to 5% by weight based on the polymerizable monomer, and
- (2) a maximum expansion ratio of the thermally foamable microsphere is at least 5.
A process for producing a thennally foamable microsphere having a structure in which a foaming agent is encapsulated in a shell formed of a polymer that is obtained by subjecting a polymerizable mixture containing at least a foaming agent, a polymerizable monomer and a crosslinkable monomer to suspension polymerization in an aqueous dispersion medium, the process comprising subjecting the polymerizable mixture to suspension polymerization, wherein the polymerizable mixture contains a bifunctional crosslinkable monomer having two polymerizable carbon-carbon double bonds at a proportion of 1.1 to 5% by weight based on the polymerizable monomer, to obtain a thermally foamable microsphere having a maximum expansion ratio of at least 5,
- wherein the polymerizable monomer is monomer or a monomer mixture selected from the group consisting of;
- (a) vinylidene chloride alone or a mixture of vinylidene chloride with a vinyl monomer copolymerizable therewith, and
- (b) (meth)acrylonitrile alone or a mixture of (meth) acrylonitrile with a vinyl monomer copolymerizable therewith,
- and further wherein the bifunctional crosslinkable monomer is a comuound having a structure in which two polymerizable carbon-carbon double bonds are linked together via a flexible chain derived from a diol compound selected from the group consisting of polyethylene glycol, polypropylene gycol, an alkyldiol, an alkyl ether diol and an alkyl ester diol.
Dependencies are inferred from the claim text.