Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – Waste paper or textile waste
Patent
1997-05-07
1999-10-19
Nguyen, Dean T.
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
Waste paper or textile waste
D21C 502
Patent
active
059683139
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to the recycling of fiber products, especially printed paper products. Particularly, although not exclusively, the invention relates to a collector chemical formulation for use in the recycling of fiber products and a process for recycling fiber products involving subjecting them to a mechanical treatment to separate fibers, removing print therefrom (commonly known as "deinking") and recovering the fibers.
The recycling of paper products is now an important industry. Initially, paper products, particularly for the box and board industry, were recycled without deinking. A later development was the use of waste paper as a source of fibers for the production of newsprint but now waste paper products can be deinked and used for higher quality papers, for example tissue, cartridge and writing papers.
A common method of paper recycling, called flotation deinking, is to subject waste paper to a mechanical pulping treatment to break the paper down into fibers in an aqueous medium, and then to use a flotation technique to remove ink, which may be followed by a washing step. To remove the ink, a chemical, commonly referred to as a collector chemical, is present, and air is introduced at the bottom of the flotation chamber. The air, in the presence of the collector chemical, transports ink to the surface of the aqueous medium. At the surface, the ink-rich foam is removed by mechanical means.
Within the deinking industry there is a well-established practice for the deinking of newspaper/magazine furnishes commonly used for newsprint production. This entails alkaline pulping at fairly high pH levels (10-11) for the detachment of ink from fibers followed by alkaline flotation with soaps, being alkali metal salts of selected non-alkoxylated fatty acids. These may be added (a) as fatty acids direct to the pulper whereby in-situ saponification occurs or (b) as fatty acids via an external intermediary saponification step with the resultant soap dosed to the pulper and/or to the deinking (typically flotation) cell or (c) as soaps or soap solutions per se to the pulper and/or to the deinking (typically flotation) cell.
Saponification requires a relatively high pH. However, a relatively high pH may lead to yellowing of the fiber pulp. To combat this, hydrogen peroxide is added during pulping. However, such conditions increase the chemical and/or biological oxygen demand of the effluent from the process. Furthermore, the subsequent process of paper making is either an acid or neutral process, so the more alkaline the aqueous medium in the deinking chamber is, the more acid is required for subsequent paper-making. Operating at a lower pH could therefore bring about substantial environmental benefits. It must also be borne in mind that there is a certain degree of hysteresis in the matter of pH of solutions containing paper pulp because of the absorption of alkaline or acid moieties within fibers.
Synthetic surface active agents, generally fatty acid alkoxylates and fatty alcohol alkoxylates, are sometimes used in deinking processes, instead of soaps, but are expensive, and may give rise to foaming which is difficult to control. Also, whilst they may give good results in laboratory tests, they are thought to work less well in commercial practice.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an advantageous process for recycling fiber products.
According to the invention, there is provided a process for recycling fiber products, the process employing an aqueous deinking medium containing an effective amount of a collector chemical which comprises a surface active agent which is or can be derived from lanolin.
Preferred are alkoxylated alcohols, alkoxylated polyols, alkoxylated acids, and esters of such alcohols, polyols and/or acids, when such alcohols, polyols, acids and esters are derived from lanolin or are of a type which can be derived from lanolin (whether or not they actually are derived from lanolin). They may be ethoxylated (EO), propoxy
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Morton International Inc.
Nguyen Dean T.
Rauchfuss, Jr. George W.
White Gerald K.
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