Binder resin for a toner for developing electrostatic images, and process for production thereof

A process for producing a binder resin for a toner, comprising:

• forming a first polymer providing a molecular weight distribution thereof according to GPC such that there is a main peak in the molecular weight range of 2,000 to 10,000 and having a ratio (Mw/Mn) of weight-average molecular weight (Mw)/number-average molecular weight (Mn).ltoreq.3.5 by solution polymerization of at least one monomer selected from styrene monomers, acrylic acid monomers, methacrylic acid monomers and derivatives thereof;
• dissolving the first polymer in a polymerizable monomer comprising at least one monomer selected from styrene monomers, acrylic acid monomers, methacrylic acid monomers and derivatives thereof to formulate a monomer composition;
• and
• subjecting the monomer composition to suspension polymerization in the presence of a crosslinking agent, thereby forming a resin composition comprising 10 to 70 wt. % of a THF(tetrahydrofuran)-insoluble component and a THF-soluble component;
• the THF-soluble component having a molecular weight distribution in GPC chromatogram thereof which provides a least one peak in the molecular weight range of 2,000 to 10,000 and at least one peak or shoulder in the molecular weight range of 15,000 to 100,000;
• where the ratio Mw/Mn for the THF-soluble component is .gtoreq.5;
• and wherein components having molecular weights of 10,000 or less are contained in a proportion of 10-50 wt. % of the total composition.