Thermally expandable microcapsule and foam-molded article

Abstract

The present invention has its object to provide a thermally expandable microcapsule, which shows excellent heat resistance and a high expansion ratio and thereby can be suitably used for molding processes involving high shearing force, such as kneading molding, calender molding, extrusion molding, and injection molding. The present invention also has its object to provide a foamed product using the thermally expandable microcapsule. The present invention relates to a thermally expandable microcapsule, which comprises: a shell made of a polymer; and a volatile expansion agent as a core agent encapsulated in the shell, the storage elastic modulus (E′) of the shell at a temperature of 200° C. and a frequency of 10 Hz being 1×10 5 N/m 2 or more, the storage elastic modulus (E′) of the shell at a temperature of 250° C. and a frequency of 10 Hz being 1×10 5 N/m 2 or more, and a maximum displacement amount measured by thermomechanical analysis being 300 μm or more.

1 . A thermally expandable microcapsule, which comprises:
 a shell made of a polymer; and   a volatile expansion agent as a core agent encapsulated in the shell,   a storage elastic modulus (E′) of the shell at a temperature of 200° C. and a frequency of 10 Hz being 1×10 5  N/m 2  or more,   the storage elastic modulus (E′) of the shell at a temperature of 250° C. and a frequency of 10 Hz being 1×10 5  N/m 2  or more, and   a maximum displacement amount measured by thermomechanical analysis being 300 μm or more.   
     
     
         2 . A thermally expandable microcapsule, which comprises
 a shell made of a polymer; and   a volatile expansion agent as a core agent encapsulated in the shell,   a storage elastic modulus (E′) of the shell at a temperature of 200° C. and a frequency of 10 Hz being 1×10 5  N/m 2  or more,   the storage elastic modulus (E′) of the shell at a temperature of 250° C. and a frequency of 10 Hz being 1×10 5  N/m 2  or more, and   an expansion ratio upon heating at a temperature of 200° C. for 1 minute being 20 times or more in volume.   
     
     
         3 . The thermally expandable microcapsule according to  claim 1 ,
 wherein the ratio tanδ of a storage elastic modulus (G′) to a loss elastic modulus (G″) of the shell at a temperature of 200° C. and a frequency of 10 Hz is 0.4 or less, and   the ratio tanδ of the storage elastic modulus (G′) to the loss elastic modulus (G″) of the shell at a temperature of 200° C. and a frequency of 0.01 Hz is 0.4 or less.   
     
     
         4 . The thermally expandable microcapsule according to  claim 1 ,
 wherein the storage elastic modulus (G′) of the shell at a temperature of 200° C. and a frequency of 10 Hz is 1×10 5  N/m 2  or more, and   the storage elastic modulus (G′) of the shell at a temperature of 200° C. and a frequency of 0.01 Hz is 1×10 4  N/m 2  or more.   
     
     
         5 . The thermally expandable microcapsule according to  claim 1 ,
 wherein the shell comprises a polymer obtainable by polymerizing a monomer mixture that contains 95% by weight or more of (meth)acrylonitrile, the (meth)acrylonitrile containing 70% by weight or more of acrylonitrile, and   a degree of crosslinkage is 60% by weight or more.   
     
     
         6 . The thermally expandable microcapsule according to  claim 1 ,
 wherein the shell comprises a polymer obtainable by polymerizing a monomer mixture which contains:   30 to 70% by weight of at least one polymerizable monomer (I) selected from the group consisting of acrylonitrile, methacrylonitrile, and vinylidene chloride; and   5 to 40% by weight of a radically-polymerizable unsaturated C 3-8  carboxylic acid monomer (II) having a carboxyl group; and   a polymerizable monomer (III) having two or more double bonds in a molecule.   
     
     
         7 . The thermally expandable microcapsule according to  claim 6 ,
 wherein the polymerizable monomer (III) is one of triethylene glycol diacrylate, and polyethylene glycol diacrylate that has a weight-average molecular weight of 200 to 600.   
     
     
         8 . The thermally expandable microcapsule according to  claim 6 ,
 wherein the monomer mixture comprises 0.05 to 3% by weight of a polymerizable monomer (III).   
     
     
         9 . The thermally expandable microcapsule according to  claim 6 ,
 wherein the monomer mixture further comprises 0.1 to 10% by weight of metal cation hydroxide (IV).   
     
     
         10 . The thermally expandable microcapsule according to  claim 1 ,
 wherein the maximum foaming temperature of the thermally expandable microcapsule is 200° C. or higher.   
     
     
         11 . A foamed product,
 which comprises the thermally expandable microcapsule according to  claim 1 .   
     
     
         12 . The thermally expandable microcapsule according to  claim 2 ,
 wherein the ratio tans of a storage elastic modulus (G′) to a loss elastic modulus (G″) of the shell at a temperature of 200° C. and a frequency of 10 Hz is 0.4 or less, and   the ratio tanδ of the storage elastic modulus (G′) to the loss elastic modulus (G″) of the shell at a temperature of 200° C. and a frequency of 0.01 Hz is 0.4 or less.   
     
     
         13 . The thermally expandable microcapsule according to  claim 2 ,
 wherein the storage elastic modulus (G′) of the shell at a temperature of 200° C. and a frequency of 10 Hz is 1×10 5  N/m 2  or more, and   the storage elastic modulus (G′) of the shell at a temperature of 200° C. and a frequency of 0.01 Hz is 1×10 4  N/m 2  or more.   
     
     
         14 . The thermally expandable microcapsule according to  claim 2 ,
 wherein the shell comprises a polymer obtainable by polymerizing a monomer mixture that contains 95% by weight or more of (meth)acrylonitrile, the (meth)acrylonitrile containing 70% by weight or more of acrylonitrile, and   a degree of crosslinkage is 60% by weight or more.   
     
     
         15 . The thermally expandable microcapsule according to  claim 2 ,
 wherein the shell comprises a polymer obtainable by polymerizing a monomer mixture which contains:   30 to 70% by weight of at least one polymerizable monomer (I) selected from the group consisting of acrylonitrile, methacrylonitrile, and vinylidene chloride; and   5 to 40% by weight of a radically-polymerizable unsaturated C 3-8  carboxylic acid monomer (II) having a carboxyl group; and   a polymerizable monomer (III) having two or more double bonds in a molecule.   
     
     
         16 . The thermally expandable microcapsule according to  claim 15 ,
 wherein the polymerizable monomer (III) is one of triethylene glycol diacrylate, and polyethylene glycol diacrylate that has a weight-average molecular weight of 200 to 600.   
     
     
         17 . The thermally expandable microcapsule according to  claim 15 ,
 wherein the monomer mixture comprises 0.05 to 3% by weight of a polymerizable monomer (III).   
     
     
         18 . The thermally expandable microcapsule according to  claim 15 ,
 wherein the monomer mixture further comprises 0.1 to 10% by weight of metal cation hydroxide (IV).   
     
     
         19 . The thermally expandable microcapsule according to  claim 2 ,
 wherein the maximum foaming temperature of the thermally expandable microcapsule is 200° C. or higher.   
     
     
         20 . A foamed product,
 which comprises the thermally expandable microcapsule according to  claim 2 .