Hollow resin particles and application thereof

1. Hollow resin particles comprising a thermoplastic resin shell and a hollow part surrounded by the shell;

wherein the thermoplastic resin is a polymer produced from a polymerizable component containing 0.6 to 3.0 wt % of a crosslinkable monomer having at least two polymerizable carbon-carbon double bonds per molecule and 97 to 99.4 wt % of an uncrosslinkable monomer having one polymerizable carbon-carbon double bond per molecule;

wherein a blowing agent is encapsulated in the hollow resin particles and the blowing agent contains 50 to 100 wt % of an organic compound having a vapor pressure higher than 100 kPa at 25° C.; and

wherein the encapsulation ratio of the blowing agent ranges from 3 to 13 wt % of the hollow resin particles.

2. The hollow resin particles as claimed in claim 1 , wherein the uncrosslinkable monomer contains a nitrile monomer in an amount ranging from 70 to 99.8 wt % of the uncrosslinkable monomer.

3. The hollow resin particles as claimed in claim 2 , wherein the amount of acrylonitrile in the uncrosslinkable monomer ranges from 60 to 93 wt %.

4. The hollow resin particles as claimed in claim 2 , wherein the nitrile monomer contains acrylonitrile and methacrylonitrile in a weight ratio of acrylonitrile to methacrylonitrile ranging from 65:35 to 99:1.

5. The hollow resin particles as claimed in claim 2 , wherein the uncrosslinkable monomer contains acrylonitrile and methyl methacrylate, and the total amount of the acrylonitrile and methyl methacrylate ranges from 90 to 100 wt % of the uncrosslinkable monomer.

6. The hollow resin particles as claimed in claim 1 , wherein the escape-initiation temperature of the blowing agent is not lower than 110° C.

7. Fine-particle-coated hollow resin particles comprising the hollow resin particles as claimed in claim 1 and a fine particle coating the outer surface of the shell of the hollow resin particles.

8. Wet-powdery hollow resin particles comprising the hollow resin particles as claimed in claim 1 and a liquid organic compound or water.

9. A process for producing hollow resin particles comprising;

a step 1 which comprises dispersing an oily mixture containing a polymerizable component and a blowing agent in an aqueous dispersion medium and polymerizing the polymerizable component into heat-expandable microspheres; and

a step 2 which comprises thermally expanding the heat-expandable microspheres produced in the step 1;

wherein, in the step 1, the polymerizable component contains 0.6 to 3.0 wt % of a crosslinkable monomer having at least two polymerizable carbon-carbon double bonds per molecule and 97 to 99.4 wt % of an uncrosslinkable monomer having one polymerizable carbon-carbon double bond per molecule, the amount of the blowing agent ranges from 4 to 15 parts by weight to 100 parts by weight of the polymerizable component, and the blowing agent contains 50 to 100 wt % of an organic compound having a vapor pressure higher than 100 kPa at 25° C.

10. The process for producing hollow resin particles as claimed in claim 9 , wherein the true specific gravity of the heat-expandable microspheres produced in the step 1 ranges from 1.02 to 1.3.

11. A composition comprising a base component and the hollow resin particles as claimed in claim 1 .

12. A formed product manufactured by forming or molding the composition as claimed in claim 11 .

13. A composition comprising a base component and the fine-particle-coated hollow resin particles as claimed in claim 7 .

14. A composition comprising a base component and the wet-powdery hollow resin particles as claimed in claim 8 .

15. A formed product manufactured by forming or molding the composition as claimed in claim 13 .

16. A formed product manufactured by forming or molding the composition as claimed in claim 14 .