Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – With formation of web or article
Reexamination Certificate
1998-11-30
2002-06-11
Chin, Peter (Department: 1731)
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
With formation of web or article
C162S025000, C162S072000, C162S073000, C162S091000, C162S141000
Reexamination Certificate
active
06402887
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of paper manufacture, and in particular relates to paper production from industrial wood waste using a biomechanical or kraft pulping process.
BACKGROUND OF THE INVENTION
Preservation of forests and increasing environmental awareness have focused research on the development of alternative sources of wood fiber for paper making. Industrial wood waste is an unexploited source of material for paper making. Industrial wood waste includes kiln dried, air dried and green wood from industrial, residential, sawmill, construction and demolition sources. Millions of tons of industrial wood waste are produced in the United States each year. Currently, industrial wood waste is used for such applications as mulch cover, colored mulch, animal bedding, daily landfill and boiler fuel as described in Conrad, P.,
BioCycle
36:11, 70-72, 1995.
Many methods of making pulp from wood for producing paper are known. Wood is composed primarily of cellulose polymer fibers held together in fiber bundles by lignin. Cellulose is the most abundant polysaccharide in nature and is a linear polymer of repeating beta-D-glucopyranose units. Lignins are polymers of polyphenolic units. The lignin polymerization process results in the formation of randomly branched and cross-linked structures. Lignins can be broadly classified into two groups: Guaiacyl lignins which are largely present in conifers and guaiacyl-syringyl lignins which are found in all angiosperms.
The purpose of pulping is to separate the cellulose fibers from other wood components such as lignin. The degree of separation obtained is described as freeness. It is generally desirable to produce long, fibers with a high level of fibrillation. Increased fibrillation increases fiber strength due to increased fiber-fiber contact.
Pulping processes may be divided into three classes: mechanical, chemical, and hybrid systems. These different processes produce pulp with different fiber characteristics, which in turn results in paper having different characteristics. Because of the different characteristics of paper produced by mechanical and chemical processes, it is often advantageous to mix chemical and mechanical pulps to form a final product.
Mechanical pulping is an energy intensive process involving the use of mechanical force to separate wood fibers. Mechanical pulping processes generate heat from friction which acts to soften lignin and resins within the wood, resulting in the freeing of cellulose fibers. Mechanical pulping processes result in a high yield of usable fiber and paper with high bulk, good opacity, and excellent printability. However, the paper has relatively low strength and tendency to turn yellow over time. Examples of mechanical pulping include stone ground wood and refiner mechanical pulping where the wood is simply ground or abraded in water the during milling operation.
Chemical pulping processes result in hydrolysis of lignin polymer bonds, freeing the cellulose fibers. The paper produced by chemical pulping has high strength. However, chemical processes produce a low yield of fiber and require significant waste treatment. The main chemical processes used in the United States are kraft pulping and sulfite pulping. About 85% of the pulp in the United States is produced by kraft pulping. Kraft pulping is characterized by cooking wood chips in an alkaline cooking liquor containing NaOH and Na
2
S.
Several hybrid pulping techniques exist which combine pulping techniques. Combined pulping techniques include thermomechanical pulping, chemirefinermechanical pulping and chemithermormechanical pulping. These processes have gained popularity because they require a lower capital investment and produce higher yields of pulp than standard chemical methods and produce stronger paper than mechanical methods.
The paper industry has recently entered the age of biotechnology with the development of methods for the use of various enzyme systems in production of pulp. For a review of the enzymology of pulping, see Enzymes for Pulp and Paper Processing, Jefferies and Viikari eds., American Chemical Society, Washington, D.C., 1997. The most successful use of enzymes in paper manufacture has been the use of hemicellulases such as xylanase for enzymatic pre-bleaching of kraft pulp. The enzymatic pre-treatment reduces the amount of chemicals needed to attain desired brightness. However, the paper industry has been slow to utilize some of the new enzyme technologies. One problem is that wood and pulp degrade slowly. Secondly, enzymes often require very specific conditions for activity making the degradation difficult to control in a mill.
One solution to these problems is to utilize a fungus containing desirable enzyme systems to selectively degrade wood. White-rot fungi have been successfully utilized in the production of pulp. For a review of biopulping, see Akhtar et al., Fungal Delignification and Biomechanical Pulping of Wood, in
Advances in Biochemical Engineering/Biotechnology,
T. Scheper ed., Springer-Verlag, Berlin, 1997. White-rot fungal hyphae enter the cell lumina of virgin wood and rapidly colonize the ray parenchyma cells which contain free sugars and other nutrients. The radial arrangement of the ray parenchyma facilitates hyphae access into the wood and allows widespread distribution of fungal hyphae in the wood. Once the free sugars and other nutrients are depleted, degradation of the cell wall proceeds because the fungus utilizes cell wall materials such as lignin as an energy source. The degradation 1of lignin is extensive throughout the cell walls, and may originate from only one or two hyphal filaments. The degradation of lignin and the softening of the cell walls confer positive benefits in subsequent pulping procedures. Wood degradation by white-rot fungi is influenced by the amount and type of lignin present in the wood. Different species of trees have different types and concentrations of the two main lignin types. As a result, a particular white-rot fungi may degrade some species of woods better than other species of wood.
In the biopulping process, virgin wood is mechanically reduced to wood chips. These wood chips are inoculated with a nutrient medium and a white-rot fungus. The inoculated chips are ventilated at an appropriate temperature and humidity to allow fungal growth. After a period of about one to four weeks, the chips are harvested and used in pulping processes. The use of these fungal treated chips in refiner mechanical pulping has resulted in substantial energy savings and produced paper with increased burst and tear strength. U.S. Pat. 5,055,159 (Blanchett, et al.) discloses a method of biopulping using a white-rot fungus.
Ceriporiopsis subvermispora
was found to confer the greatest energy savings for mechanical pulping. U.S. Pat. 5,620,564 (Akhtar) discloses a method of treating wood chips with a nutrient adjuvant at the same time as inoculation with
C. subvermispora.
Treatment of the substrate wood chips with a nutrient greatly reduces the amount of fungus needed to inoculate the wood chips. U.S. Pat. 5,460,697 (Akhtar, et al.) discloses a method of sterilizing-wood chips with a sulfite salt which allows growth of white-rot fungi. These patents are incorporated by reference.
Industrial wood waste has found little use in paper production for several reasons. First, contaminating material may be damaging to paper mill machinery. As a result, industrial wood waste must be cleaned before it can be passed through a paper mill. Second, industrial wood waste is a non-uniform material, consisting of a mixture of species of wood. Third, pulping of wood waste generally results in pulp characterized by short fiber length, which results in paper with poor strength qualities. As a result, pulp resulting from wood waste must be mixed with pulp produced from virgin timber.
Industrial wood waste represents a vast untapped source of wood fiber for the production of paper. However, industrial wood waste has not been utilized as a major source of wood fiber.
S
Ahmed Aziz
Akhtar Masood
Horn Eric G.
Lentz Michael J.
Scott Gary M.
Biopulping International, Inc.
Chin Peter
Frenchick Grady J.
King Karen B.
Michael & Best & Friedrich LLP
LandOfFree
Biopulping industrial wood waste does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Biopulping industrial wood waste, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Biopulping industrial wood waste will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2959853