Poly-.alpha.-amino acid particles, emulsions containing the same and process for preparing the same

A process for preparing hollow poly-.alpha.-amino acid particles which comprises:

• (a) preparing an oil-in-water emulsion from water, an organic solvent having a water solubility of 10 g/100 ml or less at 1 atm at 25.degree. C., and an emulsifier;
• (b) polymerizing an .alpha.-amino acid N-carboxy anhydride by emulsion polymerization in said oil-in-water emulsion to produce poly-.alpha.-amino acid polymer particles;
• (c) adding a solvent in which the poly-.alpha.-amino acid is only slightly soluble to the poly-.alpha.-amino acid polymer particles;
• and
• (d) removing said solvents;
• wherein said organic solvent is selected from the group consisting of halogenated aliphatic hydrocarbons, halogenated aromatic hydrocarbons, esters, ethers and hydrocarbons;
• and
• said solvent in which the poly-.alpha.-amino acid is only slightly soluble is selected from the group consisting of methyl alcohol, ethyl alcohol, isopropyl alcohol, acetone and methyl ethyl ketone.

Poly-.alpha.-amino acid particles, having:

• (a) an average particle size of 0.01 to 100 .mu.m;
• (b) a coefficient of variation for the average particle size of 1 to 30%;
• and
• (c) a molecular weight of the poly-.alpha.-amino acid of 5,000 to 500,000 daltons,
• wherein each of said particles comprises a hollow space.