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:
Feb. 21, 1984
Filed:
Mar. 28, 1983
Naoyuki Ifuku, Yokohama, JP;
Akio Kurokawa, Yokohama, JP;
Kenzo Seita, Yokohama, JP;
Kaoru Usami, Kamakura, JP;
Naoyuki Aikawa, Yokohama, JP;
Mitsui Toatsu Chemicals, Inc., Tokyo, JP;
Abstract
Disclosed is a process for producing fine particles of crosslinked urea-formaldehyde polymer which comprises the steps of synthesizing a precondensate of urea and formaldehyde, allowing the precondensate to react by the addition of an aqueous solution of an acid catalyst, and then neutralizing the reaction mixture, characterized in that the filtrate obtained in the filtration step for separating the polymer particles is recycled to the reaction system at the step of synthesizing a precondensate of urea and formaldehyde and/or the step of allowing the precondensate to react by the addition of an aqueous solution of an acid catalyst and in that the precondensate is obtained by reaction 1 mole of urea with 1.4 to 1.9 moles of formaldehyde at a pH of 6 to 10 and a temperature of 10 to 95.degree. C. While such fine particles of crosslinked urea-formaldehyde polymer are useful as a filler for improving certain properties (such as opacity and the like) of paper, disposal of the filtrate resulting from the filtration step for separating the polymer particles has been a serious problem. The disclosed process is carried out in a closed system by recycling of the filtrate and, moreover, the resulting polymer is in the form of fine particles having a diameter of 0.1 to 1.0.mu.and hence meets the requirements for a filler of paper (i.e., the capability of improving the opacity and other properties of paper).