Chemistry of inorganic compounds – Silicon or compound thereof – Oxygen containing
Patent
1989-07-25
1990-12-18
Doll, John
Chemistry of inorganic compounds
Silicon or compound thereof
Oxygen containing
423161, 423167, 423169, 423173, C01B 3324, C01F 100
Patent
active
049785168
ABSTRACT:
A process for improving a purity and/or whiteness degree of a talc powder is disclosed. A talc powder with a particle size of about 0.8 mm or less containing impurities such as asbestos, etc. is treated with a phosphoric acid agent under heating at from 70.degree. to 250.degree. C. to remove impurities such as asbestos, etc. by utilizing the difference in the rate of dissolution as between the talc and the impurities. The phosphoric acid agent is one selected from the group consisting of phosphoric acid, pyrophosphoric acid, sodium phosphate, ammonium phosphate, calcium phosphate, sodium tripolyphosphate, sodium pyrophosphate, sodium hexametaphosphate and mixtures thereof. Thus, asbestos, which is considered to be carcinogenic, can be effectively removed from talc.
REFERENCES:
patent: 3533821 (1970-10-01), Lundquist
patent: 3965241 (1976-06-01), Baak et al.
patent: 4430249 (1984-02-01), Gate
Takeda et al., "Introduction of the Measurement of Working Environments," Jun. 5, 1981, pp. 362-365 (Revised 2nd Ed.) partial translation.
Shinohara Kozo
Yamada Osamu
Asada Mill Co., Ltd.
Cuomo Lori F.
Doll John
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