Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – Waste paper or textile waste
Reexamination Certificate
2001-01-04
2002-10-01
Nguyen, Dean T. (Department: 1731)
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
Waste paper or textile waste
C162S005000, C162S006000, C162S007000, C162S008000
Reexamination Certificate
active
06458240
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to treating waste paper, waste paperboard or the like for use in recycle paper products. More specifically, though not exclusively, this invention relates to a process for preparing recycle paper pulp from difficult to process waste materials, such as paper stock provided with latex or other polymeric coatings, ultraviolet (UV) cured ink coated stock, and adhesive-containing paper products.
2. Background
There is a growing tendency to recycle waste paper as a source of feedstock for the manufacture of paper products. However, it is very difficult to process certain paper products such as polymer or plastic coated paper products. Examples of such products include milk cartons, ice cream containers, glossy papers, coated boards and the like. Older conventional processes are not only expensive but also may be environmentally unfriendly as they can result in additional undesirable waste products that need to be disposed of.
Relatively new technologies have attempted to address some of these problems. For example, in an article by H. Mamers entitled “The Siropulper—a new concept in wastepaper recovery” (APPITA, vol. 32, No. 2, pp. 124-128, September, 1978), the use of an explosive release digester is described for defibering purposes which may be used in connection with de-inking. The article suggests that hydrodynamic forces of the explosive discharge combine with the chemical effects of a thermal treatment process to release the ink particles from the fibers, reducing the chemical demand of the process. The pressure increase to achieve the required hydrodynamic conditions is effected by injecting pressurized inert gas into a reactor or digester. Although this method appears to have addressed several of the disadvantages of earlier recycle methods, this method still does not produce the product of desired quality, especially as to its appearance, since it produces darker product. Similarly, various other processes have been developed specifically to address environmental and economic concerns in the processing of waste paper products. One such process is generally known as the drum pulping method, which, however, is not very effective as the moisture used in this process can not effectively defiber the waste paper. In addition, the particle sizes of residual contaminants in waste paper furnish produced by this method are generally not acceptable.
Still more recently, a joint development by Wisconsin Tissue Mills and Stake Technology Ltd. was described in a paper entitled “Steam Explosion Technology and Fiber Recycling” presented at a TAPPI conference in March of 1991. The system described in that paper and related literature includes a digesting chamber where high temperature and pressure are maintained throughout the dwell time, following which the treated waste paper materials are discharged into air at atmospheric pressure and room temperature. The paper lists three runs in which the temperature range was 190° C. to 203° C., the dwell time was four minutes, and the pressure was approximately 400 psi. The process is described as resulting in particle sizes of residual contaminants of from ½ to {fraction (1/10)} that of the contaminants in waste paper furnish produced by repulping without steam treatment. A major disadvantage of this method is that relatively high temperature and pressure conditions are needed. Explosive decompression of the drum chamber to discharge the furnish is not very desirable. Furthermore, downstream operations involve several steps to clean the pulp including removing the color bodies and other materials.
It is an object of this invention to further advance the art of recovery of wastepaper and like material and in particular to provide a process for de-inking the waste paper and to remove contaminants from the treated product.
A further object of this invention is to provide a process which not only addresses all of the above-mentioned problems but also provides a method which is economically attractive to use commercially.
A still further object of this invention is to provide a process for the recovery of difficult to process waste papers which are provided with polymeric coatings such as latex coatings or plastic coatings and UV cured ink paper products using moderate temperature and pressure conditions.
Yet still another object of this invention is to provide a process whereby difficult to process inked paper-containing and polymer-containing waste materials with polymeric coatings or components can be readily converted to recyclable pulp by separating the paper from the polymer components such that the ink and other color bodies are trapped in the polymeric waste as it separates and agglomerates from the pulped paper fraction.
The following references are of general interest: U.S. Pat. No. 4,343,679 discloses a process for reclaiming waste paper without deinking which involves pulping waste paper in the presence of soft water; U.S. Pat. No. 4,381,969 discloses a process for the generation of waste paper, which comprises pulping the waste paper with an aqueous alkaline solution; U.S. Pat. No. 5,122,228 discloses a method of treatment of wastepaper at high temperature in the range of 160° C. to about 230° C. wherein the furnish is treated in a digester with or without added chemicals but in the presence of saturated steam; U.S. Pat. No. 5,262,003 discloses a process of preparing a suspension of papermaking fibers in water for use in the making of paper, which includes the steps of treating a mass of fibrous materials with steam under pressure in two separate vessels; U.S. Pat. No. 5,302,245 discloses a process for the treatment of wastepaper, which provides for removal of both ink particles and non-ink contaminants; U.S. Pat. No. 5,714,040 discloses a method for recovering fiber from printed wastepaper by loading the wastepaper and water into a continuous batch fiber recovery apparatus; U.S. Pat. No. 5,772,847 discloses a method for processing recycling mill sludge into pulp; U.S. Pat. No. 5,795,479 discloses an apparatus and method for waste recycling and conversion in which municipal solid waste is classified as to density as well as size in a perforated inclined trommel; U.S. Pat. No. 5,895,556 discloses a wastepaper treatment process for the recycle and re-use of wastepaper, which involves treating wastepaper in a repulper with a surfactant in the absence of repulper chemicals, such as caustic, silicate, and peroxide; U.S. Pat. No. 5,900,111 discloses a process for sanitizing post-consumer wastepaper fibers for liquid packages and containers, a paper product for food packaging and a liquid food container, wherein the process involves treatment of a slurry of paper fibers from recycle with hydrogen peroxide; and U.S. Pat. No. 5,958,179 discloses a process for increasing pulp whiteness by bleaching printed wastepaper under intense dispersing mechanical treatment.
All of the references described above and hereafter are incorporated herein by reference in their entirety.
SUMMARY OF THE INVENTION
It has been found that paper pulp can be readily separated from difficult to process waste materials utilizing an improved waste treatment process. This process produces high quality paper pulp, which is substantially free of polymeric and color body contaminants. Significantly, the process of the present invention involves considerably fewer steps than conventional processes and advantageously generates less downstream waste.
Thus, in accordance with the practice of this invention there is provided a process for recycling waste materials including waste paper and polymeric waste material comprising the following steps: a) in a first step, the waste materials along with suitable amounts of water are introduced into a pressure vessel wherein the pressure vessel is equipped with agitating means providing shear to thoroughly mix the components of the solid wastes; b) a suitable chemical aid is also introduced into the pressure vessel either during, after or befo
Bouchette Michael P.
Thomas Hazen C.
Winkler Wayne F.
Ferrell Michael W.
Georgia-Pacific Corporation
Nguyen Dean T.
LandOfFree
Method for removing contaminants from fibers in recycle... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for removing contaminants from fibers in recycle..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for removing contaminants from fibers in recycle... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2989945