Additive comprising porous calcium phosphate for synthetic resins, and synthetic resin composition

An additive for synthetic resins which comprises composite particles (MR) which are obtained by depositing a calcium phosphate compound (R) on support particles (M) having a petaloid porous structure, the composite particles satisfying the following formulas (a)-(h);

• (a) 0.1≦Dmr≦20 (μm)
• (b) 1≦Dmr/Dm≦5
• (c) 0.5≦Tmr1≦5 (% by weight)
• (d) 0.01≦Tmr1/Tm1<1
• (e) 0.3≦Tmr2≦3 (% by weight)
• (f) 0.01≦Tmr2/Tm2<1
• (g) 1≦αmr≦5, where α+dmr50/Dmr
• (h) 0≦βmr≦2, where β=(dmr90−dmr10)/dmr50
• wherein,
• Dmr:
• Average particle diameter (μm) of the composite particles (MR) measured by a photograph of a scanning electron microscope (SEM);
• Dm:
• Average particle diameter (μm) of the support particles (M) measured by a photograph of a scanning electron microscope (SEM);
• Tmr1:
• Heating loss (% by weight) at 500° C. of the composite particles (MR);
• Tm1:
• Heating loss (% by weight) at 500° C. of the support particles (M);
• Tmr2:
• Heating loss (% by weight) at 200° C. of the composite particles (MR);
• Tm2:
• Heating loss (% by weight) at 200° C. of the support particles (M);
• αmr:
• Dispersion coefficient of the composite particles (MR);
• dm50:
• 50% average particle diameter (μm) of the support-particles (M) measured by a particle size distribution tester using a microtrack FRA laser;
• dmr50:
• 50% average particle diameter (μm) of the composite particles (MR) measured by a particle size distribution tester using a microtrack FRA laser;
• βmr:
• Sharpness of the composite particles;
• dm90:
• 90% particle diameter of the total support particles (M) passed through a sieve measured by a particle size distribution tester using a microtrack FRA laser;
• dmr90:
• 90% particle diameter of the total composite particles (MR) passed through a sieve measured by a particle size distribution tester using a microtrack FRA laser;
• dm10:
• 10% particle diameter of the total support particles (M) passed through a sieve measured by a particle size distribution tester using a microtrack FRA laser;
• dmr10:
• 10% particle diameter of the total composite particles (MR) passed through a sieve measured by a particle size distribution tester using a microtrack FRA laser.