Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – Waste paper or textile waste
Patent
1994-07-22
1998-11-24
Chin, Peter
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
Waste paper or textile waste
162 72, 162DIG3, D21C 502
Patent
active
058401571
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a deinking agent for reclaiming waste paper used in preparing reclaimed pulp from printed waste paper such as newspaper, magazine, wood free paper, computer printout paper and copying paper, as well as a method for using the deinking agent.
More specifically, the present invention pertains to a deinking agent which is suitable for use in a process for deinking printed waste paper through flotation and which not only permits the preparation of high quality reclaimed pulp having high brightness and a low content of residual ink, but also ensures stable workability of the deinking method, as well as a method of using the deinking agent.
BACKGROUND ART
Printed waste paper has long been reclaimed to give a feedstock for papermaking. In particular, recently, the reclamation of printed waste paper has been increasingly important from the viewpoint of saving natural resources, energy saving and environmental protection and, along therewith, the reclaimed pulp have been required to have such high quality as high brightness and a low content of residual ink.
In general, the deinking methods are roughly divided into two groups, i.e., washing methods and flotation methods. There have been known and/or reported various articles and knowledges concerning these processing methods, deinking mechanisms and differences in quality between deinking agents used in these processing methods. These articles and knowledges are disclosed in, for instance, Pulp & Paper, 1986, November, p. 59; Japanese Journal of Paper Technology, 1980, August, p. 37; and U.S. Pat. No. 4,483,741.
Having summarized the foregoing articles and knowledges and experiences obtained through previous practical operations, the washing method generally comprises the step of repeatedly diluting and/or dehydrating a pulp slurry defibered by a pulper, or separating the ink removed from starting waste paper and dispersed in the pulp slurry using a washing equipment such as a screen or a centrifugal cleaner. In this respect, the degree of ink-removal is greatly affected by, mainly, mechanical effects of washing equipments such as screw presses, screens, cleaners and filters. The washing method requires a large amount of water and, therefore, suffers from various problems from the viewpoint of saving natural resources and energy saving. Moreover, the washing method is greatly dependent upon mechanical effects of equipments used and accordingly, the workability in each step is regarded as of major importance. In particular, if a deinking agent having a strong foaming ability is used, various troubles in each equipment or step arise due to the foaming and this results in the reduction of workability and an increase of the electric power consumption and therefore, the deinking agent used in the washing method must have a low foaming ability or a foaming-inhibitory ability. Moreover, the removed ink particles must be finely dispersed in the pulp slurry for the improvement of the washing method in the deinking efficiency.
On the other hand, the flotation method comprises making to adhere removed ink particles to foams mainly generated in a flotator to thus separate the ink particles from the pulp and, in contrast with the washing method, the ink is removed mainly through chemical processes, i.e., the deinking mechanism of the flotation method is quite different from that of the washing method. In general, the deinking process which makes use of the flotation method comprises an optional step called as washing or dehydration step, but the ink is mainly removed in the flotation process. Moreover, the flotation method requires the use of water in an amount smaller than that required for the washing method and is thus also advantageous from the viewpoint of saving natural resources. In addition, ink particles removed during the flotation process in the flotation method must agglomerate into large particles having a large size as compared with the washing method for the improvement of the flotation method in the deinking ef
REFERENCES:
patent: 4483741 (1984-11-01), Maloney et al.
patent: 4964949 (1990-10-01), Hamaguchi et al.
patent: 5223089 (1993-06-01), Kato
Japanese Journal of Paper Technology, Aug. 1980, pp. 37-43.
T. W. Woodward, "Appropriate Chemical Additives are Key to Improved Deinking Operations," pp. 59-63, 1986 Pulp & Paper.
English language abstract of Japanese Patent No. 5-71086.
English language abstract of Japanese Patent No. 62-250291.
English lanugage abstract of Japanese Patent No. 55-51892.
English language abstract of Japanese Patent No. 53-31804.
English language abstract of Japanese Patent No. 62-177291.
English language abstract of Japanese Patent No. 63-165591.
English language abstract of Japanese Patent No. 63-85195.
English language abstract of Japanese Patent No. 51-13762.
Hagiwara Masaaki
Hirakouchi Yoshie
Chin Peter
Lion Corporation
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