Weyerhaeuser Company Limited

Weyerhaeuser

Frank R Hunter

David W Park

Peter A Graef

Colin Elston

Clifford R Bolstad

James F Lincoln

Mark W Bowns

Fred E Olmstead

Allan R Carney

Alkiviadis G Dimakis

James Fl Lincoln

An apparatus is disclosed for preparing a quantity of individual treated fibers from one or more fiber mats. The apparatus comprises a fiber treatment zone, and a conveyor for conveying each mat through the fiber treatment zone. In the treatment zone each mat is impregnated by an applicator with a treatment material, such as a crosslinking substance, and conveyed directly to an attrition device. The attrition device fiberizes the mats to form a fiber output having a low nit level, such as no more than about three, and a dryer both dries the fiber output and cures the crosslinking substance. The fiberizer is configured to minimize the accumulation of fiber at locations therein. Fiber is transported from the attrition device to the dryer at a high velocity under reduced pressure to promote drying. A heated retention bin is provided after drying to increase curing time in the system. A thermobonding agent may be added to the dried and cured fibers to enhance the wet strength of webs made from the fiber.

Method and apparatus for crosslinking individualized cellulose fibers

The invention is a method of enhancing the strength of paper products, particularly the dry strength, without adversely affecting repulpability. It is also directed to the resulting products. It is particularly applicable but not limited to products with significant amounts of secondary fiber in the furnish. Preferably, about 10-30% of the fiber is separated from the furnish at some point prior to sheeting. This is treated with a cationic wet strength resin which is allowed to bond to the fiber. Cationic polyamide-epichlorohydrin resins are particularly useful. The treated fiber is them mixed with the untreated balance of the fiber at some point before the paper machine. Screnning fines on repulping do not normally exceed 2-3%.

Method of enhancing strength of paper products and the resulting products

The invention is directed to a composition of matter useful as a paper impregnant, to the method of its use, and to the products produced by the method. Poly (diphenylmethane diisocyanate) or PMDI has been used in the past as a paper impregnant with or without propylene carbonate as a diluent. These products have generally required pressing under high pressures and at elevated temperatures. It has now been found that triacetin and/or triethyl citrate in usages up to about 20% of PMDI give superior performance in impregnated products. The modified PMDI will cure at essentially ambient conditions in times as short as 1-2 days to insoluble polyureas with low residual amounts of isocyanates and reaction byproducts such as 4,4'-diaminodiphenylmethane. The treated papers can be used in applications of which skins for sandwich panels and high strength corrugated board would be exemplary.

Isocyanate impregnating compositions

Wood veneers having enhanced strength and/or stiffness, wood products made therefrom, and methods for manufacturing such veneers and wood products are disclosed. A treated veneer having enhanced strength and stiffness has a population of compacted wood cells extending across at least a portion of the length and width dimensions and into the thickness dimension of the veneer to confer an increased density level, and thus increased strength and/or stiffness levels, to the veneer. Interspersed in the compacted wood cells is a non-saturating loading level of a cured rigid thermoset material which maintains compaction of the compacted cells even after prolonged soaking in water. The preferred loading level is just what is required to maintain compaction of the cells. The preferred thermoset material is polyurea which is formed from a polyisocyanate resin applied to at least one major surface of the veneer followed by hot-pressing the veneer. The strength and/or stiffness increase, compared to untreated veneer, is about 10 to 150 percent. Treated veneers can be made into various multiple-ply wood products such as laminated veneer lumber and plywood, thereby providing a way to convert relatively weak lumber from fast-grown trees into premium-grade construction material.

Wood veneers and products therefrom having enhanced strength and

Cellulose products treated with isocyanate compositions

Apparatus for crosslinking individualized cellulose fibers

The invention is a method of making a wet formed, sheeted, readily reslurriable sheeted crosslinked cellulose and the products made by the method. Crosslinked wood pulp fibers tend to be quite brittle. If crosslinked while in sheeted form, the sheets cannot be readily defibered, either in a wet or dry state, without serious fiber degradation. The sheet products of the present invention can be easily redispersed or repulped in water without significant fiber breakage. The present products are made by including within the sheet, while still in wet form, a debonding or softening agent which is preferably added before the latent crosslinking reactant. Most preferably the debonder is added prior to the headbox of a paper machine and the crosslinking reactant is applied near the end of the forming wire or at the press section. The treated sheet is dried conventionally. Crosslinking may occur entirely during drying or during a period of additional heating, usually at a temperature in excess of 100.degree. C. for a short period of time. Conventional debonding agents and crosslinking reactants are suitable. The softening agent apparently reduces or prevents adhesive bonding between adjacent fibers caused by polymer formation external to the fibers under reaction conditions.

Crosslinked cellulose products and method for their preparation

A laminated product has an organic polymer layer on at least one surface of a substrate of cellulosic material impregnated with polyisocyanate. The substrate is preferably made from substantially delignified cellulosic material and an isocyanate resin. The isocyanate resin comprises a polyisocyanate, preferably PMDI, and may include a miscible organic solvent, preferably one such as propylene carbonate having a high boiling point and low flammability and toxicity. The substrate may be cured with an uncured overlay sheet positioned on the cured substrate and then cured to bond the substrate and overlay. Alternatively, a cured overlay may be adhesively or otherwise secured to a previously cured substrate. As yet another alternative, an uncured overlay sheet and uncured substrate may be placed in position and simultaneously cured. An overlay may be positioned on one or both major surfaces of a substrate sheet.

Laminated composites of polyurea-cellulose and methods for their

The invention is a method of making a wet formed, sheeted, readily reslurriable sheeted crosslinked cellulose and the products made by the method. Crosslinked wood pulp fibers tend to be quite brittle. If crosslinked while in sheeted form, the sheets cannot be readily defibered, either in a wet or dry state, without serious fiber degradation. The sheet products of the present invention can be easily redispersed or repulped in water without significant fiber breakage. The present products are made by including within the sheet, while still in wet form, a debonding or softening agent which is preferably added before the latent crosslinking reactant. Most preferably the debonder is added prior to the headbox of a paper machine and the crosslinking reactant is applied near the end of the forming wire or at the press section. The treated sheet is dried conventionally. Crosslinking may occur entirely during drying or during a period of additional heating, usually at a temperature in excess of 100.degree. C. for a short period of time. Conventional debonding agents and crosslinking reactants are suitable. The softening agent apparently reduces or prevents adhesive bonding between adjacent fibers caused by polymer formation external to the fiber under reaction conditions.

A method is disclosed for producing a polyureacellulose composite material from substantially delignified cellulosic material and an isocyanate resin. The isocyanate resin comprises a polyisocyanate, preferably PMDI, and a miscible organic solvent, preferably one such as propylene carbonate having a high boiling point and low flammability and toxicity. The composite surprisingly exhibits values of physical parameters that are at least as good as, and sometimes far superior to, corresponding parameters of similar composites made using neat (undiluted) polyisocyanate. Single- and multiple-ply composites can be made, employing only a single curing step.

Isocyanate modified cellulose products and method for their manufacture

The invention is a method of making a cellulose based polymeric material and the products of the invention. A cellulosic substrate is impregnated with an essentially uncatalyzed polyfunctinal isocyanate and pressed at elevated temperature and pressure. The substrate may be a chemical or thermomechanical pulp or paper while the isocyanate is preferably diphenylmethane diisocyanate or its oligomers. Pressing conditions are preferably in the range of about 150.degree.-245.degree. C. at pressures in the range of about 2700-8300 kPa for times less than 2 minutes. Moisture content of the cellulosic substrate is not highly critical and may be as high as 7% without adverse effects. The product is especially useful as overlays and for forming strong, water resistant laminates which can be molded in either flat or three dimensional forms.

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Bellevue, WA, United States of America

Frank R Hunter