The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jul. 09, 1996
Filed:
Jun. 23, 1995
Shoichiro Kajiwara, Ashigarakami-gun, JP;
Hirokazu Serizawa, Ashigarakami-gun, JP;
Mitsubishi Gas Chemical Company, Inc., Tokyo, JP;
Abstract
An efficient method is proposed for the preparation of a highly purified aqueous hydrogen peroxide solution, which can be used even in a semiconductor process, from a crude aqueous solution containing metallic and inorganic impurities. The method comprises the steps of: (a) acidifying the crude solution by the addition of a specific amount of an acid such as sulfuric and nitric acids; and (b) passing the acidified crude solution through a column filled with a strongly acidic cation-exchange resin in the hydrogen-form or a mixture of the same with a strongly basic anion-exchange resin in the hydroxy-, carbonate- or hydrogencarbonate-form in a specified volume proportion so that the impurities are removed by ion-exchange. The efficiency of this purification treatment can be further enhanced by keeping the acidified crude solution for a certain length of time of, for example, at least 6 hours prior to the ion-exchange treatment in step (b).