Shin-etsu Chemical Co., Ltd.

Kazuhiro Kumakura

Toshihiko Kawakubo

Hiroshi Fukudome

Tadashi Amano

Hisatoshi Otsuka

Kazuo Shirota

Makoto Ooura

A method for producing a vinyl chloride type polymer is to produce the vinyl chloride type polymer by polymerizing a vinyl chloride monomer, or a mixture of a vinyl chloride monomer with a monomer copolymerizable with the vinyl chloride monomer in an aqueous medium by using a polymerization reactor. An aqueous solution of a copolymerized polyether having a weight-average molecular weight of 1,000 to 3,500 with a mole ratio of ethylene oxide to propylene oxide in the range of 10/90 to 60/40 and having an alkyl group or an aryl group at both the terminals thereof is charged into the polymerization reactor with an amount of 0.005 to 0.050 parts by weight as the copolymerized polyether relative to 100 parts by weight of the vinyl chloride monomer.

Method for producing vinyl chloride type polymer

A method for producing a vinyl chloride type polymer is to produce the vinyl chloride type polymer by polymerizing a vinyl chloride monomer, or a mixture of a vinyl chloride monomer with a monomer copolymerizable with the vinyl chloride monomer in an aqueous medium by using a polymerization reactor. An aqueous solution of a copolymerized polyether having a weight-average molecular weight of 1,000 to 3,500 with a mole ratio of ethylene oxide to propylene oxide in the range of 10/90 to 60/40 is charged into the polymerization reactor with an amount of 0.005 to 0.050 part by weight as the copolymerized polyether relative to 100 parts by weight of the vinyl chloride monomer.

There is disclosed a synthetic fused silica member used at a wavelength of 200 nm or less which has a hydroxyl group-content of 1 to 50 ppm and a fluorine-content of 100 to 1000 ppm, and contains no chlorine, and has a birefringence of the synthetic fused silica member of 2 nm/cm or less. The synthetic fused silica member can be used as a synthetic fused silica substrate for photomask, or in an optical system wherein a fluorine excimer laser is used as a light source. There can be provided a synthetic fused silica member which can efficiently transmit a light having a wavelength as 200 nm or less, especially fluorine excimer laser (157 nm), and does not suffer from lowering of transmittance due to damage.

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Kashima-gun, Japan

Kazuhiro Kumakura