Abstract: An additive for synthetic resins is provided which comprises particles of a petaloid hydroxyapatite represented by a chemical formula Ca10(PO4)6(OH)2, having the specified particle diameter, degree of dispersion: and specific surface area, and a synthetic resin composition blended with the additive is also provided. By the use of the additive of the present invention, a film satisfying anti-blocking property, transparency and anti-scratch property can be obtained.

Abstract: The fine particles of peraloid porous hydroxyapatite are provided, which have an atomic ratio of Ca/P in a range of 1.62-1.72 and the chemical formula Ca.sub.5 (PO.sub.4).sub.3 (OH). The particles are comprised of micropores having a petaloid porous structure not only on the surface but also in the inside of the particles, and have the specific particle diameter of the specific particle size, micropore diameter of the specific particle size, the specific surface of the specific range, static and pressurized percentage of voids of the specific range. The particles have superior dispersibility and are useful in the fields such as carriers for pharmaceuticals and so on, adsorbents, absorbents, sustained-release materials, filtering agents, biological materials, fillers for plastics, and anti-blocking agents for films and so on.

Abstract: An additive for synthetic resins is provided. The additive comprises particles surface-coated with a petaloid porous hydroxyapatite having a chemical formula Ca.sub.5 (PO.sub.4).sub.3 (OH) and the petaloid porous hydroxyapatite is not less than 5% by weight of the particles. The additive can be added to any kinds of synthetic resins. If the additive is used in a polyethylene film, blocking of the film is not only prevented, but good transparency and good anti-scratch ability are imparted, and if the additive is used in a polyester, a film having good slipperiness, anti-abrasion and less coarse protrusions can be provided.

Abstract: An additive for synthetic resins is provided. The additive comprises particles surface-coated with a petaloid porous hydroxyapatite having a chemical formula Ca.sub.5 (PO.sub.4 ).sub.3 (OH) and the petaloid porous hydroxyapatite is not less than 5% by weight of the particles. The additive can be added to any kinds of synthetic resins. If the additive is used in a polyethylene film, blocking of the film is not only prevented, but good transparency and good anti-scratch ability are imparted, and if the additive is used in a polyester, a film having good slipperiness, anti-abrasion and less coarse protrusions can be provided.

Abstract: A monodisperse spherical, ellipsoidal or plate-like vaterite calcium carbonate almost free from secondary aggregation is disclosed. The vaterite type calcium carbonate is prepared by the steps of adding 5-20 times mol equivalent of water with respect to unslaked lime to a methanol suspension of 0.5-12 weight % of unslaked lime and/or slaked lime (in case of slaked, conversion is to be made into unslaked lime of the same mol) to prepare of a mixture of methanol, unslaked lime and/or slaked lime and water, letting carbon dioxide gas through said mixture, adjusting the temperature in the carbonation reaction system to not less than 30.degree. C. before arrival of conductivity within carbonation reaction system at the maximal point on conductivity variation curve in the carbonation reaction system and adjusting the time from start of carbonation reaction to the point where the conductivity is 100 .mu.S/cm to be less than 1,000 minutes.

Abstract: A monodisperse spherical, ellipsoidal or plate-like vaterite calcium carbonate almost free from secondary aggregation is disclosed. The vaterite type calcium carbonate is prepared by the steps of adding 5-20 times mol equivalent of water with respect to unslaked lime to a methanol suspension of 0.5-12 weight % of unslaked lime and/or slaked lime (in case of slaked, conversion is to be made into unslaked lime of the same mol) to prepare of a mixture of methanol, unslaked lime and/or slaked lime and water, letting carbon dioxide gas through said mixture, adjusting the temperature in the carbonation reaction systemto not less than 30.degree. C. before arrival of conductivity within carbonation reaction system at the maximal point on conductivity variation curve in the carbonation reaction system and adjusting the time from start of carbonation reaction to the point where the conductivity is 100.mu. S/cm to be less than 1,000 minutes.