Mitsui Toatsu Chemicals, Incorporated

Tamami Fukui

Kenji Uchiyama

Nobuhiro Hirayama

Shoji Kawasaki

Katsuru Matsumoto

Katsuo Uramoto

A resin composition for an electrophotographic toner is here disclosed which comprises an ethylene series high polymer (Y) and an ethylene series polymer (X) prepared from 100 parts of a bifunctional ethylene series unsaturated monomer and 0.01-10 parts by weight of a substance having three or more peroxide groups in the molecule and/or a substance having one or more unsaturated functional groups and one or more peroxide groups in the molecule, Mw/Mb (Mw is weight-average molecular weight, and Mb is weight-average molecular weight between crosslinking points) of said polymer (X) being from 2 to 99, Mw of said polymer (X) being 50,000 or less. This resin composition is excellent in the balance of various physical properties required for the toner, and particularly, it is excellent in offset resistance and toner strength.

Resin composition for electrophotographic toner

A resin composition for use in an electrophotographic toner which comprises an ethylenic polymer (L) having a M.sub.w of not greater than 20,000 and an acid value of 2 to 100 mg KOH/g, and an ethylenic polymer (H) having a M.sub.w of not less than 150,000, a M.sub.w /M.sub.n ratio of not less than 5.0 and a time constant for triboelectric charging (.tau.) of 1.2 to 25, the ethylenic polymers (L) and (H) being present in a weight ratio ranging from 15:85 to 85:15. This resin composition can improve the triboelectric charging properties of the toner.

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Yokohama, Japan

Tamami Fukui