Japan Synthetic Rubber Co., Ltd.

Nobuo Kawashima

Hiroshi Tadenuma

Fujio Sakurai

Hollow polymer particles having at least two polymer layers, wherein (1) the particles have an average particle diameter in the range of 0.15 to 20 micrometers, (2) each of the particles has an average equivalent hollow diameter/equivalent particle diameter in the range of 0.2 to 0.8, (3) the proportion of a toluene-insoluble portion of the particles is 20 to 90% by weight, (4) the polymer particles have a melt flow rate at 180.degree. C. under 10 kgf/cm.sup.2 of 0.1 to 1 g/10 min., (5) the inside layer of the two polymer layers is composed of a crosslinked polymer and (6) the outside layer of the two polymer layers is composd of a non-crosslinked polymer. This invention also provides hollow crosslinked polymer particles wherein the proportion of a toluene-insoluble portion of the particles exceeds 85% by weight, the melt flow rate of the polymer particles at 180.degree. C. under 10 kgf/cm.sup.2 is less than 0.2 g/10 min., and the outside layer is composed of a crosslinked polymer. The hollow polymer particles are useful, for example, as a pigment, and for a paper coating composition and a general-purpose coating composition.

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Yokkaichi, Japan

Nobuo Kawashima