Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – Waste paper or textile waste
Reexamination Certificate
2000-05-23
2001-09-04
Nguyen, Dean T. (Department: 1731)
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
Waste paper or textile waste
C162S100000, C162S196000, C428S357000, C206S083500, C100S001000
Reexamination Certificate
active
06284094
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the processing of recycled paper and more particularly the provision of paper bales using pulp compatible binding for the bales.
BACKGROUND OF THE INVENTION
Recycling paper has become a major industry. Paper of all types is collected at a collection site and compacted into bales that can be efficiently transported to a recycling pulp mill. The baling process typically involves the use of high strength steel wire. The paper is compressed in a compressor and then the wire is wrapped, e.g., in six strands around the bale to hold the bale in the compressed and handleable state. The bales approach, e.g., 100 cubic feet and weigh on the order of 1,200 pounds.
The bales are loaded, e.g., in trucks, using forklift trucks and hauled to the mill site. At the mill site, the wire strands are cut and the paper placed on conveyors to be conveyed to a pulping tank. The pulping tank is typically a continuous process and the paper is rapidly reduced to pulp and then through various follow-up processes, the pulp is cleaned and cycled into the paper making stage.
A major problem with the system described above is the handling of the wire binding. In the first instance, the bales are maintained in a compressed state by the wire strands. As the strands are cut, the wire will snap apart and the whipping wire produces a serious threat to the safety of the bale handlers.
The wire is typically loaded onto the conveyor along with the paper released from the bale. Often one of the strands is not cut so as to assist in handling and in any event, a substantial portion of the wire strands is placed on the conveyor and conveyed into the pulping tank (pulper). The wire strands can and do get wrapped around the pulleys and cogs of the conveyor. The strands that get dumped into the pulping tank get screened out of the pulp but remain in the tank and have to be periodically removed from the pulping tank. The process has to be stopped and the wires removed and collected to subsequently be loaded onto trucks for disposal. Further, the wire while contained in the pulper causes undue wear and tear of the pulper, all at a substantial cost to the recycling process.
BRIEF DESCRIPTION OF THE INVENTION
A solution to the problem as above described is the replacement of the wire with another form of binding. However, adequate replacement binding that was previously known utilized a plastic material that is incompatible with the pulping process and has to be removed before it reaches the pulping stage.
The basic concept of the present invention is the use of a paper binding, i.e., a continuous paper sheeting twisted into cord form. A significant benefit of a paper binding or cord is that the cord can then simply be recycled through the pulping process. Also, the cord can remain secured to the bale, i.e., it is not required to cut prior to pulping, to thereby avoid safety concerns and to avoid having the cord getting wrapped around the pulleys of the conveyor. Once the bales are introduced to the pulp, the high heat, moisture and agitation rapidly degrade the paper cord and releases the paper for pulping in the conventional manner. With the use of the paper cord, there is no need to stop the process for wire removal and the cost of removing, gathering, loading and disposal of the wire strands is eliminated.
The problem with the paper binding (cord) is that heretofore no such paper bindings having the required strength for securing a 1,000 to 2,000 pound compressed paper bale could be located and certainly not in the pulping industry. The binding desired needs to have a tensile strength on the order of 250-300 pounds. Also, paper binding that was available was found to rapidly lose the already inadequate strength it had when exposed to moisture. It is not practical to insure that paper bales will be free of moisture even though moisture content is minimized.
The breakthrough came from a chance observation of a cord binding that was being used for tying hops. It was observed that young boys could climb up and down the binding without breaking the binding. The boys were at least over 100 pounds and the binding was obviously exposed to moisture. Upon investigation, it was learned that the binding was made of twisted strips of U.S. grade wet lap paper. Wet lap paper is itself resistant to moisture and it is theorized that the twisting of the paper strips and the further twisting that results when applying a tensile force, seals the cord interior and prevents significant penetration of moisture. The wet lap paper binding has enhanced strength with up to 8% moisture and doesn't begin to lose that strength until the moisture content exceeds 12%. Baled recycling paper rarely exceeds 12% moisture content and the wet lap paper binding is very acceptable if it can be made strong enough.
Whereas a smooth consistent binding is considered desirable, e.g., to avoid weak points, it was not known how to make the desired binding having the strength required for the paper bales (250-300 pounds). After many attempts at increasing strength, what worked was the use of a wider strip of the wet lap paper (a 35 pound test paper that is 8-10 inches wide as compared to the prior strips having 3-3½ inch width). The machinery for twisting the paper was modified to accommodate the extra width and the twisting process as then applied produced a smooth quarter inch diameter paper binding that achieved the desired 250 pound plus tensile strength. Tests conducted on the paper binding as applied to recycling paper bales established that it indeed securely bound the bales, it retained its strength under moist conditions, e.g., 12%, and it could be placed into the pulping tank where the binding is rapidly dissolved into the pulp and then processed with the pulp with no detrimental affect to the pulp.
The invention will be more fully appreciated upon reference to the following detailed description and drawings referred to therein.
REFERENCES:
patent: 5066363 (1991-11-01), Lee et al.
patent: 6022618 (2000-02-01), Arai
Barth Colleen
Carpenter Kathleen
Carpenter Ronald
Russell Shannon
Harrington Robert L.
Nguyen Dean T.
Western Paper Wire, Inc.
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