| 摘要 |
PURPOSE:To produce a dispersant having superior dispersibility for a hydraulic material by irradiating a condensation product of naphthalene sulphonic acid or alkylnaphthalene sulphonic acid with formaldehyde or a salt thereof with gamma-rays. CONSTITUTION:A condensation product of formaldehyde with naphthalene sulphonic acid or alkylnaphthalene sulphonic acid as a single body or a mixture thereof or a salt of the condensation product is irradiated with gamma-rays. The irradiation of gamma-rays is performed preferably until the dose of the absorbed rays reaches 0.1X10<5>-1.0X10<7>Gy. The dispersant to be irradiated may be the aq. soln. of the condensation product as it is or of the salt of the condensation product, or powdered product thereof, but it is preferred to add 0.1-2,000ppm formaldehyde in the acidic or alkaline condition. Namely, change of the molecular weight of the condensation product is caused as the dose of the absorbed rays increases; the viscosity of the aq. soln. becomes higher, and the dispersibility also becomes higher.
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