Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
  • B32B5/14—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by a layer differing constitutionally or physically in different parts, e.g. denser near its faces
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B29/00—Layered products comprising a layer of paper or cardboard
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B1/00—Layered products having a non-planar shape
  • B32B1/08—Tubular products
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B29/00—Layered products comprising a layer of paper or cardboard
  • B32B29/02—Layered products comprising a layer of paper or cardboard next to a fibrous or filamentary layer
• • 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
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/02—Material of vegetable origin
• • 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
  • D21H27/00—Special paper not otherwise provided for, e.g. made by multi-step processes
  • D21H27/30—Multi-ply
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2262/00—Composition or structural features of fibres which form a fibrous or filamentary layer or are present as additives
  • B32B2262/06—Vegetal fibres
  • B32B2262/062—Cellulose fibres, e.g. cotton
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2264/00—Composition or properties of particles which form a particulate layer or are present as additives
  • B32B2264/06—Vegetal particles
  • B32B2264/062—Cellulose particles, e.g. cotton
  • B32B2264/067—Wood particles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/70—Other properties
  • B32B2307/72—Density
  • B32B2307/722—Non-uniform density

Definitions

• the invention relates to paperboard sheets, a process for making them, and to paperboard tubes made from such sheets.
• Paperboard is used in a wide variety of applications throughout numerous industries. For example, paperboard sheets are used as slip sheets for separating products, as a backing for laminates and as floor mats. Paperboard is also used to make partitions and roofing felt as needed for the construction of residential and commercial buildings. Additionally, paperboard sheet material can be wound into tubes and used as winding cores for winding filamentary materials such as yarns and threads, or for winding continuous sheet materials such as paper, plastic film, and metal foils or sheets. Such tubes can also be used to make containers for food products such as frozen juices, bread dough and snack products. Paperboard tubes are used as forms in the construction industry, e.g., for molding concrete columns and the like.
• the physical characteristics of individual paperboard sheets are tailored to a particular end use. For example, heavy-duty applications may require tubes produced from sheets of greater tensile or compressive strength.
• strength, compressibility and absorption are physical properties commonly tailored to suit particular applications. Each of these properties is dependent to some extent on the density of the manufactured paperboard sheet. Relatively high-density paperboard tends to be stronger, less compressible and generally non-absorbent. Low-density sheets however, tend to be weaker, more compressible or sponge-like and thus capable of greater absorption.
• low-density paperboard is produced by preparing an aqueous slurry or "stock" that contains cellulose fibers, fillers and additives.
• the necessary cellulose fiber is generally drawn from waste paper such as recycled newsprint, magazines, scraps from old paperboard tubes and corrugated boxes.
• waste paper such as recycled newsprint, magazines, scraps from old paperboard tubes and corrugated boxes.
• one known low-density paperboard as disclosed by U.S. Patent No.
• the web is dewatered further in a press and then dried in a dryer.
• Secondary operations such as the micronization process described above, add additional and often prohibitive costs to papermaking. It is desirable then, to produce a low-cost, high-yield paperboard of relatively low-density and of moderate tensile strength that does not require filler micronization. Further, it is desirable that a low-density paperboard be produced from readily available materials so as to preserve any cost reductions while providing the broadest possible engineering flexibility and thereby potentially serving a range of applications.
• the present invention addresses the above needs and achieves other advantages by providing a low-density paperboard sheet of at least one paperboard layer made from a stock that includes a proportion of standard wood flour or fine sawdust in addition to traditional cellulose fibers.
• the proportion of sawdust can be up to 40% or more by weight.
• the sawdust of the present invention does not require a costly refining or micronization operation in order to produce low-density, high-yield paperboard sheets.
• the fine sawdust described for use according to the present invention is of a type readily produced by thin curf band saw blades. Commercial sawmills commonly use these blades and, in fact, sell the desired sawdust daily by the ton, for use as boiler fuel.
• the fine sawdust of the present invention does not require a costly micronization operation. Instead, only a simple sifting or screening step is needed to remove excessively large pieces of wood.
• the screened sawdust is then placed in the stock with the cellulose fibers.
• the stock is fed into a distribution chamber, also called a headbox, former, forming chamber, vat, or the like, depending on the paperboard making machine used.
• the distribution chamber injects the stock onto a forming wire, and provides the necessary turbulence to the stock to keep it well dispersed.
• the stock is dewatered through the forming wire, then pressed and dried as discussed above.
• the low- density paperboard of the present invention may be readily produced via standard papermaking machines that are commonly known in the art (e.g., fourdrinier, cylinder, etc.). Standard paperboard making machines may be provided with multiple distribution chambers to produce paperboard sheets of multiple layers.
• a paperboard layer consists of a single web of paperboard material that has been injected onto a forming wire from a given distribution chamber as discussed above. Often, these individual webs or layers are removed from their respective forming wires and placed one atop the other, dewatered in a press and then dried. The layering of paperboard in this way encourages bonding between fibers of adjacent layers, thereby joining the layers firmly together and ultimately resulting in a unitary paperboard sheet.
• a multi-layer sheet can be produced by injecting multiple stock flows through a multiple-slice distribution chamber onto a forming wire.
• low-density paperboard sheets may possess a single layer or multiple layers.
• the various layers may be produced from stocks of differing sawdust filler concentrations.
• sheets may be produced that have layers of various densities.
• Relatively low-density paperboard, as referenced in this application is that which has been produced from a stock having greater than 1 percent sawdust by weight.
• layering paperboard of various densities allows paperboard designers to minimize manufacturing costs while simultaneously tailoring the physical properties of their designs to meet the requirements of a given application.
• paperboard sheets as described in this application may be converted into partitions, support posts, slip sheets, floor mats or the like which serve to protect delicate objects from damage.
• the desired cushioning properties may be attained without need for additional and often costly lining or coating operations.
• the above- described paperboard sheets may be slit to a desired width to form low-density paperboard plies. Such plies may be convolutely or spirally wound about an axis to form a wound low-density paperboard tube.
• Such tubes may have an abundance of practical uses, among them may be as winding cores for plastic film or other similar elastic products that benefit from a moderately compressible winding core.
• the tubes of the present invention may have any cross-section shape that can be formed by wrapping the tube around an appropriately shaped mandrel.
• the tube can be formed in a rectangular shape with rounded corners.
• Layer - A paperboard layer comprises a single web of paperboard material formed from a given stock.
• Sheet - A paperboard sheet comprises either a single layer of paperboard (in which case "sheet” and “layer” are interchangeable), or multiple layers of paperboard stacked atop one another and joined together to form a multi-layer structure; the various layers can be formed from the same or different stocks.
• Ply - The term “ply” is essentially interchangeable with “sheet”, except that "ply” is used when referring to an individual discrete sheet that is incorporated into a paperboard product such as a paperboard tube, partition, floor mat, slip sheet or the like.
• a paperboard tube may comprise multiple plies wound one atop another to form a "multi-ply” tube.
• an aqueous slurry or "stock” is prepared containing cellulose fibers, fillers and additives.
• the primary “filler” used in accordance with the present invention is wood flour or fine sawdust.
• the sawdust is of a standard type, commonly sold by sawmills as boiler fuel.
• the sawdust is sifted with a .125 inch screen (3175 micron) to remove excessively large wood chips.
• the sifted sawdust is then placed in the stock with the cellulose fibers.
• the precise proportion of sawdust to fiber will change per application; however, most applications call for a sawdust content of an individual sheet ranging from 1% - 40% by weight.
• the sawdust content of a given sheet is between 1 and 6 % by weight.
• the sawdust content per sheet is between 10 and 20 % by weight
• the sawdust content per individual sheet is between 1 and 30 % by weight.
• the sawdust of the present invention advantageously does not require a micronization or pre-drying operation. Contrary to Gomez's finding that wood fillers must be pulverized to a mean particle size of less than 150 microns, it has been found that sawdust with a mean particle size ranging broadly from 350 microns to 3175 microns can be used effectively as a component in the paperboard of the present invention. In one preferred embodiment, 95 % of acceptable sawdust was too large to pass through a 354-micron screen. Additionally, with an acceptable residual moisture content as high as 30% - 50%, the sawdust of the present invention does not require extensive pre-drying operations.
• the stock is then injected from a distribution chamber onto a forming wire.
• Various types of papermaking processes can be used, including single-wire fourdrinier processes or multiple cylinder-type processes. Water is then drained from the stock through the forming wire so that a wet web of paper remains. The web or layer of paperboard is dewatered further in a press section and then dried in a dryer section. The low-density sheet produced by this process may then be fed into a number of conversion operations that transform the sheet into products such as partitions, corrugated boxes, paperboard tubes or the like. Typically, to produce a multi-layer sheet multiple vats of stock are prepared having potentially differing compositions.
• paperboard sheets include layers of differing sawdust filler concentrations so as to produce multilayer paperboard sheets. For example, layers of relatively lower (or zero) filler concentration may be included to reinforce what would otherwise be relatively weak low-density sheets while simultaneously yielding material cost reductions. As noted above, such multi-layer formation provides paperboard designers with the flexibility to streamline their designs to possess only those physical properties required for a given application.
• low-cost floor mats having ample padding (low-density layer) and a relatively non-absorbent upper surface (high- density layer) to prevent soiling, may readily be provided.
• one or more relatively low-density layers may be sandwiched between two relatively high-density "liner" layers forming a paperboard sheet useful for nearly all of the paperboard applications described above.
• lined sheets are often easier to manufacture than single layer low-density sheets as the high-density layers provide smooth surfaces that accommodate more intimate contact with paperboard machine dryer surfaces.
• a low-density sheet having at least one low-density layer may be used as a ply in a wound paperboard tube.
• Tubes according to the present invention may be produced from one or more plies via spiral winding, or alternatively, may be produced from a single ply via convolute winding.
• the sawdust composition directly impacts the density of the ply layers, which in turn directly impacts physical characteristics such as strength, compressibility and absorption.
• tubes of moderate strength for a given application e.g., snack containers
• denser plies may be used to reinforce weaker, low-density plies so as to limit manufacturing costs while simultaneously ensuring adequate performance of the resulting tube.
• tubes produced from relatively low-density plies may be selected for their relative elasticity.
• winding cores used to roll plastic film are optimally produced from compressible materials having at least a moderate elasticity. This allows the stretched film, which is itself elastic, and subject to temperature induced expansion and contraction, to exert considerable force on the winding cores over time without damaging the cores.
• the relatively low-density layers of Sheet 2 were comprised of 30% sawdust by weight, which equated to approximately 15%> sawdust by weight of the resulting four-layer sheet.
• the outer high-density layers of both Sheet 1 and Sheet 2 contained no wood sawdust.
• a relatively low-density, high-yield, paperboard sheet of afleast moderate tensile strength may be produced according to the present invention.
• the relatively high-density layers of Sheets 1 and 2 were produced from control stocks having significantly differing densities. Accordingly, it is most useful to compare each relatively low-density sheet against their respective control sheet, rather than attempting to compare one against the other.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Paper (AREA)
• Laminated Bodies (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

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Citations (8)

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• 2003
  • 2003-09-05 US US10/656,416 patent/US20050051290A1/en not_active Abandoned
• 2004
  • 2004-08-30 MX MXPA06002584A patent/MXPA06002584A/es unknown
  • 2004-08-30 CA CA002537863A patent/CA2537863A1/en not_active Abandoned
  • 2004-08-30 WO PCT/US2004/028242 patent/WO2005026438A1/en active Search and Examination
  • 2004-08-30 EP EP04782676A patent/EP1660722A1/en not_active Withdrawn

Patent Citations (8)

Non-Patent Citations (2)

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