Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C5/00—Other processes for obtaining cellulose, e.g. cooking cotton linters ; Processes characterised by the choice of cellulose-containing starting materials
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H11/00—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only
  • D21H11/12—Pulp from non-woody plants or crops, e.g. cotton, flax, straw, bagasse

Definitions

• This invention relates to a process for making raw cotton linters into sheet form and more particularly to a process for making raw cotton linters into sheet form that is substantially free of any extraneous chemicals. This invention also relates to the sheeted raw cotton linters composition prepared from the above process.
• cellulose derivatives Prior to the present invention, manufacturers of cellulose derivatives have traditionally used highly purified cellulose furnishes derived from cotton linters or wood to make cellulose ethers. These materials are fabricated into rolls of paper sheets for ease of handling. The extensive purification of raw cotton linters to make purified cotton linters added cost and, in certain instances, created environmental problems.
• the “steep press” cellulose ether production process involves initially subjecting purified cellulose to a highly concentrated aqueous caustic solution. After an appropriate period of time, the swollen mass is compressed in a manner that removes excess caustic solution where upon it is shredded. The resulting alkali cellulose is then mixed and reacted with appropriate reagents to form the desired cellulose derivative of interest. Use of stacked sheets of cellulose facilitates distribution of the caustic solution.
• a common practice involves shredding the sheet prior to adding derivatizing reagents. Due to the inherent difficulty in attaining uniform alkalization as well as uniformly mixing the derivatizing reagents within the shredded alkali cellulose, the production of high quality derivatives is difficult by this process. Nevertheless this processing method provides a simple, relatively inexpensive means for producing cellulose ether derivatives.
• the present invention is directed to a process for making a raw cotton linters matted sheet comprising a) dispersing a loose mass of raw cotton linters in water, b) removing a portion of the water from the dispersed loose mass, and c) pressing the wet loose mass of raw cotton linters into a resulting matted sheet.
• the present invention is also related to the raw cotton linters composition that is prepared by the above-mentioned process.
• raw cotton linters fabricated into a sheet serves as a raw material suitable for the production of high performance cellulose derivatives.
• the resulting derivatives are especially well suited for demanding nonregulated applications such as paint, construction, and oil field.
• Raw linters can be processed using conventional papermaking processes.
• raw cotton linters are converted to sheet form using a conventional paper machine to provide a raw material especially well suited for the production of high performance cellulose derivatives.
• sheet refers to matted, non woven web that is held together by pressure (that is commonly referred to a paper) that has been cut into rectangular pieces as well as that which has been wound into rolls.
• the use of raw cotton linters in this physical form permits cellulose derivative manufacturers to utilize existing manufacturing assets to produce high performance products at substantially reduced cost. The cost reduction stems both from the elimination of many purification steps heretofore practiced, as well as other unexpected benefits found for a raw linters-based sheet. It has been found that the resulting derivatives are especially well suited for demanding applications in nonregulated industries such as paint, construction, and oil field.
• an example of a process for producing the matted sheets of raw cotton linters includes a step wherein bales of raw linters are broken apart and dispersed in a low solids water slurry to form a pulp.
• the resulting pulp can be formed into a sheet using a variety of papermaking processes. It is preferred that the sheet be made without any chemicals, fillers, or other additives traditionally employed by the papermaking industry.
• the raw cotton linters fibers not or minimally be subjected to processes such as disk refiners that are designed to fibrillate the fiber's surface. Fibrillated materials occupy a greater volume which decreases the amount of material that can be loaded into a cellulose reactor. Both dry and wet cleaning processes may be employed to remove impurities prior to the formation of the paper sheet. Examples of such impurities include, but are not limited to, inorganic materials as well as cottonseed hull fragments.
• Basis weight refers to the weight per unit area of a representative sample of the raw cotton linters matted sheet. It is preferred that the sheet be dried to a moisture content of 2 to 20% water. It is most preferred that sheet be dried to a moisture content in the range of 4-12%. The drying should not be done in a manner that causes hornification of the cellulose. Hornification refers to excessive drying of cellulose which renders the material less reactive in subsequent derivatization reactions. It is generally attributed to the formation of strong hydrogen bonds between cellulose anhydroglucose units that are difficult to disrupt.
• the raw cotton linters sheet undergo shredding and/or cutting prior to chemical derivitization.
• the raw cotton linters sheet is fed to at least one cutter whereupon it is cut in a manner that the fibers become individually separated from each other prior to being used to make cellulose ethers.
• the sheet undergo shredding and/or cutting prior to chemical derivatization.
• the sheet is feed to at least one cutter whereupon it is cut in a manner that the fibers become individually separated from each other and reduced in length.
• Both dry and wet cleaning processes may be employed to remove impurities prior to the formation of the paper sheet.
• impurities include, but are not limited to, inorganic materials as well as cottonseed hull fragments.
• Mechanical dry cleaning methods may be employed prior to the formation of the pulp slurry.
• An example of appropriate dry cleaning equipment is a Continental Eagle IMPCO LC-410D Linters Cleaner.
• Wet cleaning methods include screen-based processes, both pressurized and nonpressurized, which are particularly useful for removing larger contaminants. Examples of such a process are the Voith Minisorter screen and vibrating flat screens.
• centrifugal cleaners G. A.
• the concentration of other chemical species present on or in the cotton linters fibers may be significantly reduced by appropriate processing.
• wax and oil residues are typically found on the surface of raw cotton linters fibers.
• Washing or extraction with appropriate organic solvents e.g., alcohols, ether
• organic solvents e.g., alcohols, ether
• elevated temperatures preferably 70 C to 95° C., and more preferably above 85 C can be employed. This operation may be conveniently performed during the pulping of the cotton linters.
• Other synergistic additives such as soaps may also be employed to promote the extraction and removal impurities.
• the use of organic solvents can present additional difficulties in their complete removal, disposal, and/or purification for re-use. For such processes pulping followed by de-watering may be desirable to remove excess waxes and oils.
• a variety of processes may be used to form the sheet including, but not limited to, Fourdrinier, cylinder, wet (J. B. Calkin (ed), Modern Pulp and Paper Making , (Reinhold Publishers, New York: 1957), p. 16) machines, belt washers, and disk savealls.
• Examples of inclined wire Fourdrinier machines include Tampella Sandy Hill Deltaformer®, Dörries Hydraformer®, and the Neue Bruderhas No-Wo Former®.
• a variety of pressing methods may be employed. Examples of appropriate processes include two roll presses, shoe (extended-nip) presses, and platen presses. A series of nips, typically three, in which the pressure progressively increases at each successive nip represents a most preferred embodiment.
• the sheet be dried to a moisture content of 2 to 20% and most preferably in the range of 4-12%.
• the drying should be done in a manner that does not cause hornification of the cellulose since this can result in a cellulose that will not be uniformly swollen by alkali.
• a variety of processes may be used to dry to sheet including heated cylinder “dryer cans”, through-air dryer processes, and pulp dryers (e.g., Flakt pulp dryer).
• Calendering of the dry or partially-dry sheet may be used to improve sheet density, thickness uniformity, and mechanical properties.
• the optimum dimensional, base weight, density, and mechanical property characteristics of the sheet are determined by the specific cellulose derivative process characteristics.
• typical cellulose cutters used for industrial manufacturing processes range in width from 0.25 to 2.5 m, most preferably in the range of 0.50 to 1.25 m wide.
• the sheet fed to such cutters should be approximately the same width, but no wider than, the width of the knives of the rotary cutter.
• the basis weight of the sheet is preferably in the range of 250 to 900 g/m 2 and most preferably in the range of 400 to 700 g/m 2 .
• Sheet thickness is preferably in the range of 0.04 to 0.30 cm, most preferably in the range of 0.08 to 0.20 cm, and should vary by less than most preferably ⁇ 5% within the sheet.
• This combination of base weight and thickness implies a range of bulk density of the matted sheet.
• High bulk density is generally desirable, since it results in lower shipping costs and less frequent roll changes.
• mechanical properties of the sheet the primary concern for materials in roll form is that they be able to be unwound without breaking or tearing. Since materials are unwound at relatively slow, uniform rates into cutters, this does not generally present a problem since the material must have a minimum tensile strength to be consistently wound during paper manufacturing.
• Second cut raw linters were initially pulped in a Tornado pulper for 30 minutes. The pulp was subsequently transferred to a blend chest whereupon it was diluted to 1.0% consistency after which it was transferred to a machine chest. Paper was then produced using a 1.1 m Deltaformer paper machine at a headbox consistency of 0.08% without the use of any additional papermaking chemicals or fillers. The sheet was dried on the machine to a final moisture content of 3.5%. The resulting raw linters sheet had a basis weight of 700 g/m 2 with a caliper of 2.0 mm.

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• Paper (AREA)
• Polysaccharides And Polysaccharide Derivatives (AREA)
• Manufacture Of Macromolecular Shaped Articles (AREA)

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Citations (5)

• 2005
  • 2005-07-19 US US11/184,935 patent/US20060016568A1/en not_active Abandoned
  • 2005-07-19 EP EP05774719A patent/EP1769120A2/fr not_active Withdrawn
  • 2005-07-19 BR BRPI0513531-1A patent/BRPI0513531A/pt not_active Application Discontinuation
  • 2005-07-19 WO PCT/US2005/025714 patent/WO2006014716A2/fr active Application Filing
  • 2005-07-19 CN CNA2005800237139A patent/CN1985048A/zh active Pending
  • 2005-07-20 AR ARP050103002A patent/AR053753A1/es unknown

Patent Citations (5)

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