Process for producing crystal nucleator composition and crystalline polymer composition

A process for producing a crystal nucleator composition comprising:

• a first step pulverizing 95% by mass or more of a crystal nucleator ingredient containing one or two or more kinds of compounds represented by the following general formula (I) to a primary particle diameter of 0.8 μm or smaller with a dry medium-stirring type pulverizer;
• and
• a second step mixing and pulverizing the pulverized crystal nucleator ingredient obtained in the previous step and a metal aliphatic carboxylate ingredient containing one or two or more kinds of metal aliphatic carboxylates represented by the following general formula (II):
• wherein R1 and R2 represent alkyl groups having 1 to 4 carbon atoms;
• R3 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms;
• R4 represents an aliphatic group having 1 to 30 carbon atoms, optionally having a branch, a hydroxyl group, or a cycloalkyl group;
• M represents an alkali metal atom or a magnesium atom;
• m represents 1 when M is an alkali metal atom, and m represents 2 when M is a magnesium atom.