US20040159413A1

US20040159413A1 - Cellulosic fiber web treatment systems and associated processes

Info

Publication number: US20040159413A1
Application number: US10/356,844
Authority: US
Inventors: Jay Taylor; Brian Herrin
Original assignee: Rayonier Products and Financial Services Co
Current assignee: Rayonier Products and Financial Services Co
Priority date: 2003-02-03
Filing date: 2003-02-03
Publication date: 2004-08-19

Abstract

Systems and processes are provided for the treatment of cellulosic pulp rolls. Generally, the systems and processes apply a series of compositions, such as debonding compositions, binder compositions and lubricant compositions, to cellulosic fiber webs provided on pulp rolls. The systems and processes provide a cost effective means by which to form cellulosic fiber pellets which may then be incorporated into a variety of end uses.

Description

FIELD OF THE INVENTION

This invention relates to systems and processes for treating cellulosic fiber webs. The invention more specifically relates to systems and processes by which to produce treated cellulosic fiber webs that may subsequently be formed into cellulosic fiber pellets suitable for use in a variety of applications.

BACKGROUND OF THE INVENTION

Cellulosic fibers are used in a wide variety of applications. For example, cellulosic fibers have historically been used to produce paper and absorbent products. Cellulosic fibers are currently being introduced into a much wider range of end uses, however. One of the factors promoting the market expansion for cellulosic fibers has been the development of higher performance cellulosic fibers. For example, cellulosic fibers are now available which provide improved reinforcing properties, i.e. exhibit superior tensile properties. Higher tensile strength cellulosic fibers are particularly attractive for use in composites, e.g. reinforced resins. Cellulose fiber reinforced resins may be used to form any type of extruded article, including injection molded parts and the like. Injection molded parts incorporating cellulosic fibers include automotive parts, sporting goods, computer chips, and the like.

Cellulosic materials are especially attractive for use as reinforcing fiber because they have relatively low densities in comparison to the more commonly employed glass fiber reinforcements. Such weight savings can be highly advantageous, particularly in automotive applications. In addition to the reduction in weight, cellulosic fibers are not abrasive to processing equipment in comparison to glass fibers or high density mineral fibers. Thermoplastic resins incorporating cellulosic fibers are described in U.S. Pat. No. 6,270,883, and U.S. patent application Ser. No. 10/165,502 (filed Jun. 7, 2002) both of which are hereby incorporated by reference in their entirety.

Due to their high value added, emerging markets such as reinforced resin applications are extremely attractive to pulp manufacturers. However, pulp mills have not historically been configured to provide cellulosic fibers in a readily extrudable form. More specifically, pulp mills generally supply their customers with either cut sheets or wide web goods referred to as “pulp rolls.” Traditional pulp mill customers subsequently process the pulp rolls through an attrition mill or other defiberizer prior to forming paper, fibers, nonwovens and the like. In contrast, reinforced resin manufacturers typically receive raw materials in the form of chips or pellets. For example, fiber reinforced resins are typically produced by introducing pellets or chips containing the reinforcing fiber into an extruder, along with pellets or chips of the given resin.

For the past several years, pulp manufacturers have begun to reconfigure their processes to produce cellulosic fiber in a form suitable for use in extrusion processes and the like. Pelletization and granulation are methods to produce forms of cellulose pulp fibers suitable for extrusion. Granulation is generally performed using a rotary knife cutter to break up the cellulosic pulp fibers within the incoming pulp sheets or rolls. Unfortunately, the granulation process typically reduces the average fiber length. This decreased cellulose fiber length typically translates into decreased physical properties in the resulting composite. Pelletizing processes preserve the fiber length, and hence mechanical properties, to a much greater extent than granulation processes. For example, pelletized cellulosic fibers typically have an average fiber length ranging between about 0.8 to 2.5 mm.

Heretofore, pelletization processes have involved the use of “never-dried” cellulosic streams, i.e. cellulosic slurries, taken from one or more side streams diverted from a particular pulping process. The cellulosic slurries were subsequently combined with various additives, e.g. binders and the like, in one or more mixing tanks and then dried to form fiber pellets. Fiber pellets are generally comprised of cellulosic pulp fibers that are cohesively bound by a suitable amount of at least one water soluble binder. The resulting fiber pellets may then be readily fed into extrusion equipment and blended with various resins.

However, the formation of fiber pellets using side streams requires a significant amount of planning. More specifically, the production schedule must provide for the formation of a sufficient amount of cellulosic pulp to satisfy both the fiber pellet production needs and the conventional pulp roll orders. This can be problematic, as pulp mills produce cellulosic fiber on a massive scale and production schedules must therefore be set well in advance. It would thus be beneficial to produce fiber pellets from material kept in inventory. It would further be advantageous to produce fiber pellets from cellulosic fiber in a form that is readily available from a number of pulp manufacturers and/or pulping locations.

Consequently, a need exists in the art for systems and processes by which to form cellulosic fiber pellets without interrupting pulp mill production schedules. There further remains a need in the art for systems and processes by which to form cellulosic fiber pellets from raw material that is readily available from a number of manufacturers and/or pulping locations.

BRIEF SUMMARY OF THE INVENTION

The present invention provides cellulosic fiber web treatment systems that generally include a cellulosic fiber web source, at least one spray applicator; at least one powder applicator; at least one atomizer, and a repulper. The spray applicator directs debonding composition onto a first surface of the cellulosic fiber web. The rolling nip press extracts excess water from the saturated web exiting the spray applicator. The powder applicator directs a binder composition onto a first surface of the pressed web. The atomizer directs a lubricant composition onto a first surface of the surface of the powder coated web. The repulper then defibrilizes the lubricated web.

The present invention further provides treated cellulosic fiber webs and processes associated with the advantageous cellulosic fiber web treatment system.

The pulp roll treatment system of the invention provides a means by which to produce treated cellulose fibers from pulp rolls without interruption to the pulp mill production schedule. The treated cellulose fibers may then be processed into fiber pellets suitable for a wide variety of uses, including reinforced resins. The pulp roll treatment system of the invention further allows the formation of treated cellulose fibers from any manufacturer of pulp rolls.

Further understanding of the processes and systems of the invention will be understood with reference to the drawings and detailed description which follows herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein: [0013]
FIG. 1 represents a schematic drawing of a pulp roll treatment system in accordance with one embodiment of the present invention. [0014]
FIG. 2 represents a schematic drawing of a spray applicator in accordance with one embodiment of the present invention. [0015]
FIG. 3 represents a schematic drawing of a powder applicator in accordance with one embodiment of the present invention.[0016]

DETAILED DESCRIPTION OF THE INVENTION

The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout [0017]
The pulp roll treatment systems of the invention are generally formed from a series of applicators that each applies one or more chemical agents to one or both surfaces of a cellulosic fiber web provided as a pulp roll. The treated cellulosic fiber web is subsequently repulped and the repulped cellulosic fiber may be supplied to any pelletizer known in the art. Surprisingly, the various chemical agents dispensed onto the surface of the cellulosic fiber web are distributed fairly homogeneously throughout the thickness of the cellulosic sheet and thus produce fiber pellets exhibiting fairly uniform properties. [0018]
Referring now to FIG. 1, an exemplary pulp [0019] roll treatment system 10 in accordance with one embodiment of the invention is provided. The pulp roll treatment system 10 generally includes a source of cellulosic fiber web, such as a pulp roll supply frame 12, at least one spray applicator, at least one nip press 16, at least one powder applicator 18, at least one atomizer 20 and a repulper 18.
The pulp [0020] roll supply frame 12 is used to provide supply the treatment system 10 with a cellulosic fiber web 22 put up on a cylindrical package known in the art as a cellulosic pulp roll 24. Any roll goods frame or wide web winding apparatus known in the art of wide web goods may be employed as the pulp roll supply frame 12. In one beneficial embodiment, the pulp roll supply frame is an “A-frame.”
As used herein the term “pulp roll” is used in a generic sense to refer to any roll goods and/or wide web goods formed from a continuous but finite length of cellulosic fiber web. The cellulosic fiber web is generally formed from a composition that includes cellulosic fibers, any optional pulping binders and/or additives and residual water. The cellulosic fiber web supplied on pulp rolls typically contains fairly small amounts of residual water. For example, the [0021] cellulosic fiber 22 web generally contains from about 90 to 100 weight percent solids, such as from about 93 to 99 weight percent solids as it is unwound from the pulp roll 24.
By treating cellulosic fiber webs rather than cellulosic slurries, cellulosic fiber pellets and the like may be produced without interrupting pulp mill production schedules. The treatment of cellulosic fiber webs rather than cellulosic slurries further allows for the formation of cellulosic fiber pellets or the like from raw material that is readily available from many different manufacturers and/or pulping locations. [0022]
The [0023] cellulosic fiber web 22 may be formed from any type of cellulosic pulp fiber known in the art of pulp production. In beneficial embodiments the cellulosic pulp fibers within the cellulosic fiber web 22 generally exhibit an alpha-cellulose purity of greater than about 80% by weight. In advantageous embodiments, the cellulosic pulp fibers may have an alpha-cellulose purity greater than about 90% by weight. In further beneficial aspects of these embodiments, the cellulosic pulp fibers may have an alpha-cellulose content of greater than about 95% by weight, such as an alpha-cellulose content of greater than about 96% by weight, and advantageously greater than 98%.
The cellulosic pulp fibers forming the [0024] cellulosic fiber web 22 may further beneficially possess low amounts of residual lignin. For example, the cellulosic pulp fibers can have a lignin content less than about 2% by weight, such as lignin contents of less than about 1% by weight or less than about 0.5% by weight.
Exemplary cellulosic pulp fibers include those formed from either ULTRANIER™-J, RAYFLOC™-J-LD, POROSANIER™-J-HP, ETHENIER™-F-UHV, SULFATATE™-H-J-HD and PLACETATE™-F pulps, each of which are commercially available from Rayonier, Performance Fibers (Jesup, Ga.). All of these pulps have an alpha-cellulose purity of about 95% or greater with the exception of RALFLOC™-J, which has alpha-cellulose content of about 86%. All are softwood pulps with the exception of SULFATATE™-H-J, which is manufactured from hardwood fibers. The PLACETATE™ and ETHENIER™ grades are sulfite pulps whereas the others are kraft pulps. In advantageous embodiments, the cellulosic pulp fibers are TerraCel™ 10J fibers. [0025]
Further exemplary cellulosic pulps from which the pulp roll may be formed include ESTERCELL™ and VISCOCELL™ (International Paper—Natchez, Miss.), SUPERSOFT™ (International Paper—Texarkana, Tex.), BORREGAARD UHV-S™ (Borregaard, Sarpsborg, Norway), SAICCOR ACETATE™ and SAICCOR VISCOSE™ (Saiccor-Umkomass, South Africa), Weyerhaeuser MAC II™ (Weyerhaeuser, Cosmopolis, Wash.), Buckeye A-5™ and Buckeye COTTON LINTERS™ (Buckeye Technologies—Perry, Fla. and Memphis, Tenn., respectively). [0026]
The cellulosic pulp fibers may be derived from either a softwood pulp source or hardwood pulp source or mixtures thereof. Exemplary softwood pulp sources include trees such as various pines (Slash pine, Loblolly pine, White pine, Caribbean pine), Western hemlock, various spruces, (e.g., Sitka Spruce), Douglas fir and/or mixtures of same. Exemplary hardwood pulp sources include trees such as sweet gum, black gum, maple, oak, eucalyptus, poplar, beech, and aspen or mixtures thereof. [0027]
The cellulosic pulp fibers within the [0028] cellulosic fiber web 22 may be of any length that is sufficient to impart suitable reinforcing properties to the resulting composite. In advantageous embodiments, the cellulosic fibers are characterized by an average length, e.g., a weighted average fiber length (“WAFL”) length, between about 0.1 to 6 mm. In advantageous aspects of the invention the average fiber length is around 0.8 mm. In alternative beneficial aspects, the cellulose fibers are characterized by an average length of about 1.8 mm.
[0029] Cellulosic fiber webs 22 having any basis weight known in the art of pulp formation may be used in conjunction with the pulp roll treatment system 10. For example, cellulosic fiber webs having a basis weight ranging from about 300 to 1000 grams per square meter (“gsm”), such as a basis weight ranging from about 600 to 900 gsm, may be processed using the pulp roll treatment system 10.
The pulp [0030] roll treatment system 10 may be used to process any width of pulp roll 24 known in the art. For example, the pulp roll treatment system 24 may be used to process pulp rolls 24 ranging in width from about 12 to 160 inches.
As shown in FIG. 1, the [0031] cellulosic fiber web 22 is transported from the pulp roll supply frame 12 over a first transport roll 26 and under and/or over at least one spray applicator 14. As shown in FIG. 1, spray applicators may be present on both sides of the cellulosic fiber web 14 and 14 a, respectively, to treat both the upper 28 lower 30 surfaces of the cellulosic fiber web. In alternative embodiments, the pulp roll treatment system includes one or more spray applicators positioned either above or below the cellulosic fiber web. For ease of reference, the upper surface of the cellulosic fiber web 28 traveling through the pulp roll treatment system 10 may be referred to as a “first surface,” while the lower surface of the cellulosic web 30 traveling through the pulp roll treatment system 10 may be referred to as a “second surface.”
As shown in FIG. 2, the [0032] spray applicator 14 generally includes a linear array of spray nozzles 32 arranged across the width of the cellulosic fiber web 22. In the beneficial embodiment illustrated in FIG. 2, a single row of spray nozzles 32 spans the width of the cellulosic fiber web 22 in the transverse direction, i.e. a single row of spray nozzles 32 is positioned substantially perpendicular to the direction of travel for the cellulosic fiber web 22. The spray nozzles 32 are typically arranged so that they apply either slightly overlapping or otherwise contiguous spray patterns 34, thereby ensuring consistent application across the cellulosic fiber web. In beneficial embodiments, the spray nozzles 32 are positioned at a center to center distance ranging from about 1 to 36 inches, such as a distance of about 6 to 24 inches. In advantageous embodiments the spray applicator 14 includes from 1 to 14 spray nozzles 32.
The spray nozzles [0033] 32 may have any configuration known in the art to provide uniform coverage across a finite area, including elliptical and circular configurations. In one advantageous embodiment, the spray nozzles 32 have an elliptical configuration that produces a substantially elongated fan spray pattern 34 approximately 12 inches in diameter. The spray nozzles 32 operate at pressures known in the art, such as pressures generally ranging from about 50 to 100 psi.
The [0034] spray applicator 14 is used to apply an effective amount of a debonding composition to the cellulosic fiber web 22. The term “composition” is used herein in a generic sense to mean a chemical formulation that may include one or more chemical components. The debonding composition typically includes one or more debonding agents, water and optional hydrophobic agents and/or lubricants.
The debonding composition facilitates the dispersion of the pulp fiber mass into individual cellulosic fibers. Consequently, the debonding composition usually contains a debonding agent. Typical debonding agents include surfactants, such as non-ionic surfactants. One exemplary debonding agent is BEROCELL™ 509, commercially available from Eka Chemicals, Paper Chemicals Division. The debonding agent may be included in the debonding composition in any effective amount, such as an amount ranging from about 0.0 to 5.0 weight percent, and more particularly from about 0.5 to 1.5 weight percent, based on the weight of the debonding composition (“bodc”). [0035]
The water within the debonding composition acts as a debonding aid and a penetration aid in transporting the debonding composition throughout the thickness of the fiber web. Water may be included in the debonding composition in any effective amount, such as an amount ranging from about 0 to 100 weight percent bodc, and more particularly from about 98 to 100 weight percent bodc. [0036]
The debonding composition may further contain one or more hydrophobic agents to decrease the moisture intake of the dry pellets and to improve the mechanical properties of the final product. Exemplary hydrophobic agents include rosin, AKD or ASA hydrophobic sizing agents, and styrene, acrylate, or methacrylate ester monomers. In advantageous embodiments, HERCON® 79 (an alkyl ketene dimer/AKD) sizing agent from Hercules Inc. is included within the debonding composition as a hydrophobic agent. The optional hydrophobic agent may be included in the debonding composition in any effective amount, such as an amount ranging from about 1 to 10 lb/ton, and more particularly from about 2 to 6 lb/ton, based on the weight of the cellulosic fiber (“bocf”). [0037]
A sufficient amount of the debonding composition is applied to the fiber web to saturate it. As used herein, the term “saturate” means that the web contains water in excess of that present within the [0038] raw pulp roll 24. The debonding composition is typically applied to the cellulosic fiber web 22 in amounts ranging from about 0 to 3000 pounds per hour, such as amounts ranging from about 175 to 2200 pounds per hour. Consequently, the debonding agent is generally present within the saturated web 36 in amounts ranging from about 0 to 5 weight percent, bocf. In one beneficial embodiment, the debonding agent is present in the saturated web 36 in an amount of about 1.0 weight percent, bocf. The saturated web 36 further typically contains about 0 to 50.0 weight percent water, such as about 45.0 weight percent water, bocf. The optional low viscosity lubricants are generally present within the saturated web 36 in amounts ranging from about 0 to 5 weight percent, bocf, such as an amount of about 2.0 weight percent, bocf. The optional hydrophobic agent is generally present within the saturated web 36 in amounts ranging from about 0 to 6.0 weight percent, bocf. In one beneficial embodiment, the optional hydrophobic agent is present in the saturated web 36 in an amount of about 2.0 weight percent, bocf.
The debonding composition may have any viscosity suitable for use in conjunction with spray coating. The debonding composition is typically characterized by a viscosity ranging from about 0.5 to 5.0 cps, such as a viscosity of about 0.8 to 2.0 cps. [0039]
Returning now to FIG. 1, the saturated [0040] web 36 exiting the spray applicator 14,14 a is transported through a nip press 16, such as a rolling nip press, to remove excess water from the saturated web 36. Rolling nip presses are well known in the art and are typically formed by applying pressure between two contiguous, co-rotating rolls 37, generally referred to as nip rolls. In beneficial embodiments, the co-rotating rolls 37 are stainless steel rolls. In alternative advantageous embodiments, the nip rolls 37 may be conditioned rolls. Exemplary conditioned rolls include rolls that have been coated with ceramic, rubber or polytetrafluoroethylene, as known in the art. The nip pressure between the rolls 37 generally ranges from about 50 to 150 psi, such as about 100 psi. The nip roll 37 rotation speed generally matches the line speed of the pulp roll treatment system 10. Alternatively, the nip roll 37 rotation speed may exceed the line speed of the pulp roll treatment system 10 by a factor ranging from about 1.01 to 1.50.
Although excess water is removed from the saturated [0041] web 36, at least a substantial portion of the remainder of the debonding composition, i.e. the debonding agent, hydrophobic agent and/or lubricant, is not removed by the nip and thus remains in the pressed web. The pressed web 16 exiting the rolling nip press generally contains from about 40 to 50% water. The excess water removed from the saturated web 36 may be collected in a catch pan 38 or the like positioned beneath the nip press 16 and either disposed of or recycled.
Upon exiting the [0042] nip press 16, the pressed web 40 is subsequently directed under one or more powder applicators 18 which apply a binder composition to the surface of the pressed web 40. The powder applicator 18 may have any configuration known in the art to apply powder to the surface of a wide web substrate. As shown in FIG. 3, in advantageous embodiments the powder applicator 18 may be in the form of an elongated funnel-shaped body 42 (i.e. an elongated frusticonical shape) terminating in a mesh screen 44. Powder 46 is introduced into the top of the powder applicator 18 and deposited onto the pressed web 40 by vibrating or shaking the body 42 of the powder applicator 18 so as to transport loose powder 46 through the mesh screen 44. The mesh screen 44 may be of any mesh size typically associated with powder coating. For example, the mesh screen 44 may have a mesh size ranging from about 1 to 5 mm, such as a mesh size of about 3 mm. The binder composition is typically characterized by a powder size ranging from about 50 to 500 microns, such as powder size ranging from about 100 to 200 microns.
As shown in FIG. 3, the [0043] powder applicator 18 spans the width of the pressed web 40 in the transverse direction. In advantageous embodiments, a single powder applicator 18 spans the full width of the pressed web 40, as shown in FIG. 3. In alternative embodiments, two or more powder applicators, each spanning the full width of the pressed web, are included in the pulp roll treatment system. In the advantageous embodiment illustrated in FIG. 3, a single powder applicator 18 applies binder composition to a first surface of the pressed web 40. In alternative embodiments, a series of transport rolls may be used to position the pressed web so that both sides of the pressed web may be directed under powder applicators and binder composition thus applied to first and second surfaces of the pressed web.
The binder composition applied by the [0044] powder applicator 18 generally includes at least one water soluble binder, along with optional coupling agents. One of the primary purposes of the water soluble binder is to provide integrity to the cellulose pulp fibers so that they may be subjected to downstream processes, such as melt blending, extrusion and the like. The water soluble binder is further believed to aid in dispersing the cellulosic fibers within the matrix polymer used to form the final product, e.g. reinforced resin and the like. Any polymer having sufficient hydrophilicty to impart water solubility and exhibiting a molecular weight ranging from about 50×10³to 25×10⁶Daltons may be employed as the water soluble binder.
Exemplary water soluble binders include a variety of polymers, such as polyacrylamide, polyacrylic acid, polyvinyl alcohol, polyethylene glycol, and poly(n-vinylpyrroliddinone) and mixtures thereof. Further suitable water soluble binders include salt substituted celluloses, such as sodium carboxymethyl cellulose, sodium hydroxyethylcellulose, sodium carboxymethylhydroxyethylcellulose, sodium hydroxypropylcellulose and the like, as well as mixtures thereof. In advantageous embodiments of the invention, polyacrylamide (“PAM”) is employed as the water soluble binder. PAM is commercially available from a number of suppliers, including Aldrich Chemicals. [0045]
The water soluble binder may be present within the binder composition in any amount effective to provide adequate integrity to the cellulosic fibers during downstream processing and/or to impart adequate dispersion properties. For example, the water soluble binder may beneficially be present within the binder composition in amounts ranging from about 0.0 to 100.0 weight percent, such as in amounts ranging from about 25.0 to 75.0 weight percent based on the weight of the binder composition (“bobc”). In advantageous embodiments, the water soluble binder is present in the binder composition in an amount of about 50.0 weight percent, bobc. [0046]
Advantageously, the water soluble binder is capable of producing high viscosity solutions. The water soluble binder is typically characterized by a molecular weight in excess of 50,000. In one advantageous aspect of the invention, the water soluble binder exhibits a molecular weight of about 15×10[0047] ⁶daltons.
One or more coupling agents may also be included within the binder composition. Exemplary coupling agents include titanates, zirconates, silanes, and mixtures thereof. In one advantageous embodiment, the coupling agent is derived from silane. The coupling agent may typically be included in the binder composition in amounts ranging from about 0 to 1.0 weight percent, bobc. In advantageous embodiments, the coupling agent may be incorporated into the binder composition in an amount of about 0.10 weight percent, bobc. [0048]
The binder composition is generally applied to the pressed [0049] web 40 in amounts ranging from about 0 to 30 pounds per hour, such as an amount ranging from about 10 to 20 pounds per hour. Consequently, the water soluble binder may be present within the pressed web 40 in amounts ranging from about 0.1 to 5.0 weight percent, bocf.
The binder composition may have any particle size suitable for use in conjunction with powder coating. The binder composition is typically characterized by a particle size ranging from about 50 to 500 microns, such as a particle size of about 100 to 200 microns. [0050]
Returning now to FIG. 1, the powder coated [0051] web 48 exiting the powder applicator 18 passes over one or more carrier rolls 50. The carrier roll 50 provides support to the powder coated web 48 as it travels through the pulp treatment system 10, thus eliminating any sagging that might otherwise occur. The carrier roll 50 is advantageously a stainless steel roll. In alternative embodiments, the carrier roll 50 may be a conditioned roll. Exemplary conditioned rolls include rolls that have been coated with ceramic, rubber or polytetrafluoro ethylene, as known in the art. The carrier roll 50 rotates in the direction of web travel at approximately the same speed as the pulp treatment system 10 line speed.
In alternative aspects of the invention, one or more of the carrier rolls [0052] 50 may be substituted with any wide web coater known in the art. For example, in advantageous embodiments, the carrier roll 50 may be replaced by a roll coater, such as a gravure coater, knife coater, kiss roll coater and the like, which may then be used to apply a liquid composition to the surface of the powder coated web.
After passing over the [0053] carrier roll 50, the powder coated web 48 passes under and/or over one or more atomizers 20 that deposits a lubricant composition onto the surface of the powder coated web 48. Comparable to the spray nozzle configuration illustrated in FIG. 2, the atomizer 20 generally includes a linear array of atomizer heads arranged across the width of the powder coated web 48. In one beneficial embodiment, a single row of atomizer heads is spatially arranged to span the powder coated web 48 in the transverse direction, i.e. a single row of atomizer heads is positioned substantially perpendicular to the direction of travel for the powder coated web 48. The atomizer heads are typically arranged so that they apply either slightly overlapping or otherwise contiguous coating patterns, thereby ensuring consistent application across the powder coated web 48. In beneficial embodiments, the atomizer heads are positioned at a center to center distance ranging from about 1 to 24 inches within the atomizer, such as a distance of about 6 to 12 inches.
The atomizer heads may have any configuration known in the art to provide uniform coverage across a finite area, including elliptical and circular configurations. In one advantageous embodiment, the atomizer heads have an elliptical configuration that produces a substantially elongated fan pattern approximately 12 inches in diameter. The atomizer heads operate at pressures known in the art, such as pressures generally ranging from about 0 to 150 psi, and more particularly ranging from about 50 to 100 psi. In advantageous embodiments, the atomizer includes from about 1 to 14 atomizer heads. [0054]
Comparable to the spray applicator configuration shown in FIG. 2, a [0055] single atomizer 20 may span the full width of the powder coated web 48. In alternative embodiments, two or more atomizers, each spanning the full width of the powder coated web, are included in the pulp roll treatment system. In the advantageous embodiment illustrated in FIG. 1, a single atomizer 20 applies lubricant composition to a first surface of the powder coated web 48. In alternative embodiments, a series of transport rolls may be used to position the powder coated web so that both sides of the web may be directed under atomizers and lubricant composition thus applied to both the first and second surfaces of the powder coated web.
The lubricant composition generally includes at least one lubricant. Although not wishing to be bound by theory, the lubricant composition is believed to provide improved fiber dispersion and reduce discoloration within the reinforced resin or composite which will be ultimately formed from the fiber pellets. Although again not wishing to be bound by theory, Applicants hypothesize that the lubricant composition may decrease the number of fiber clumps within the reinforced resin or composite. A decrease in the number of fiber clumps would be expected to provide more uniform properties, such as mechanical properties and the like, across the cross section of the reinforced resin or composite ultimately produced. However, although believed to impart a host of beneficial properties to the present invention, lubricant compositions are generally considered to be detrimental to adhesion. More specifically, lubricant compositions are known for use as release agents to eliminate the adhesion between surfaces. Consequently, it is altogether unexpected that the inclusion of a suitable lubricant composition enhances the optical and fiber dispersion characteristics of the present invention without substantial detriment to the remaining physical properties. [0056]
Any compound which is (a) compatible with both cellulosic fibers and the matrix polymer used to form the ultimate reinforced resin or composite, (b) is thermally stable during composite processing and (c) provides lubricating properties to the cellulosic fibers may be included in the lubricant composition. The lubricant composition advantageously exhibits minimal weight loss, e.g. less than 5%, at temperatures of up to about 260° C. Exemplary lubricants include silicone oil, waxes such as fatty amides, metal sterates and mixtures thereof. In one advantageous embodiment, silicone oil is included in the lubricant composition. One suitable commercially available silicone oil is SF96-350 silicone oil from GE Silicones. [0057]
In advantageous embodiments, the lubricant composition includes a mixture of silicone oil and one or more fatty amides. Suitable fatty amides include ethylene bisstearamid (“EBS”) and oleyl palmitamide. In beneficial aspects of such embodiments, the fatty amide is EBS. EBS is commercially available from a number of suppliers, including Aldrich Chemicals. The lubricant composition may advantageously include silicone oil and fatty amide in any effective weight ratio, such as about a 2:1 weight ratio. For example, the lubricant composition may include silicone oil in an amount of about 67 weight percent, based on the weight of the lubricant composition (“bowl”) and EBS in an amount of about 33 weight percent, bowl. [0058]
The lubricants may also beneficially have a molecular weight ranging from about 10,000 to 80,000 daltons. In advantageous embodiments of these aspects, lubricants characterized by a molecular weight ranging from about 15,000 to 60,0000 daltons, such as lubricants exhibiting a molecular weight of about 30,000 to 50,000 daltons, may be employed. [0059]
The lubricant composition may be applied to the powder coated [0060] web 48 in any amount sufficient to impart adequate dispersion and/or release properties to the reinforced resin or composite ultimately formed. The lubricant composition is generally applied to the powder coated web in amounts ranging from about 0 to 50 pounds per hour, such as an amount ranging from about 10 to 25 pounds per hour. Consequently, the lubricant is typically present within the lubricated web 52 in amounts ranging from about 1.0 to 10 weight percent, bocf.
The lubricant composition may have any viscosity suitable for atomization. The lubricant composition is typically characterized by a viscosity ranging from about 10 to 100 cps, such as a viscosity of about 30 to 60 cps. [0061]
The lubricated [0062] web 52 exiting the atomizer 20 is directed by a second transport roll 54 into a repulper 18. The repulper 18 generally defiberizes the lubricated web 52 exiting the atomizer 20, i.e. separates the cellulose within the lubricated web 52 into individual filaments. Any repulper 18 known in the art for use with cellulosic fiber webs may be employed. In advantageous embodiments, a repulper that defibrillates or breaks apart the fiber web using rotating breaker bars is used, such as a pulp shredder/repulper from Franklin-Miller Inc. The repulped treated cellulosic fiber may then be bagged or otherwise stored until needed or sold. The repulped treated cellulosic fiber may be either sold as is or formed into fiber pellets prior to sale.
The instant pulp [0063] roll treatment systems 10 are capable of treating significant throughputs of material at high rates of speed. For example, the pulp roll treatments systems 10 can treat up to about 3000 pounds per hour of cellulosic fiber web 22 at speeds of up to about 30 feet per minute.
As noted above, the repulped cellulosic fiber may be subjected to a fiber pelletization process (not shown). Pelletization may be accomplished by any means known in the art. Specifically, a pelletizer, such as a Kahl pelletizing mill, may then be used to form cylindrical fiber pellets from the repulped cellulosic fiber. The pellet mill may be operated at conditions known in the art, such as at discharge rates ranging between 0.1 to 0.3 kg/min. Pellet mills typically produce fiber pellets exhibiting a moisture content of about 50 to 60%. Consequently, the fiber pellets are usually dried overnight at 190° F. Typical fiber pellets range from about 3 to 8 mm in diameter with a length of about 3.0 to 9.0 mm. The fiber pellets generally have a density of around 0.6 g/cm[0064] ³. The cellulosic fiber length within the fiber pellets generally ranges from about 0.5 to 4.0 mm, such as a length of about 1.8 mm. The fiber pellets provide improved material handling properties and easier feeding characteristics for melt blending operations, such as those employed in the production of reinforced resins and composites.
The primary purpose of the fiber pellet preparation process is to produce cellulosic pulp fibers in a form suitable for incorporation into reinforced resins and composites. Consequently, the fiber pellets prepared above may be used to form complex three dimensional articles by molding and the like. Molding compositions may include the fiber pellets alone or in combination with additional amounts of the same or different matrix polymers. Further, additional additives known in the molding arts may be included within the molding composition, as well. As used herein, the term “molding” is meant to encompass any process in which heat and pressure is applied to the fiber pellets to transform them into more complex three dimensional articles. Exemplary molding operations thus include injection molding, compression molding, blow molding and rotational molding, as well as various extrusion and pultrusion processes. Molded articles formed in accordance may define fairly complex three-dimensional objects, such as objects defining multiple sharp corner radii and the like. One advantageous embodiment of the present invention comprises injection molding the fiber pellets into complex finished articles, such as molded products employed within the automotive industry and the like. [0065]
Many modifications and other embodiments of the invention will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. [0066]

Claims

That which is claimed:

1. A cellulosic fiber treatment system comprising:

(a) a source of cellulosic fiber web, said cellulosic fiber web defining first and second surfaces;

(b) at least one spray applicator to direct a debonding composition onto the first surface of the cellulosic fiber web;

(c) at least one rolling nip press to extract excess water from the saturated web;

(d) at least one powder applicator to direct a binder composition onto the first surface of the pressed web;

(e) at least one atomizer to direct a lubricant composition onto the first surface of the surface of the powder coated web; and

(f) a repulper to defibrilize the lubricated web.

2. A cellulosic fiber web treatment system according to claim 1, wherein said spray applicator comprises at least one linear array of spray nozzles arranged across the width of the cellulosic fiber web.

3. A cellulosic fiber web treatment system according to claim 2, wherein said spray nozzles span the cellulosic fiber web in the transverse direction.

4. A cellulosic fiber web treatment system according to claim 2, wherein said spray nozzles are positioned at a center to center distance ranging from about 1 to 36 inches.

5. A cellulosic fiber web treatment system according to claim 1 including more than one spray applicators, said more than one spray applicators directing debonding composition onto both the first and second surfaces of the cellulosic fiber web.

6. A cellulosic fiber web treatment system according to claim 1, wherein said rolling nip press comprises two co-rotating rolls.

7. A cellulosic fiber web treatment system according to claim 6, wherein said co-rotating rolls define an outer surface formed from a material selected from stainless steel, ceramic, rubber or polytetrafluoroethylene.

8. A cellulosic fiber web treatment system according to claim 1, wherein said powder applicator comprises an elongated funnel-shaped body terminating in a mesh screen.

9. A cellulosic fiber web treatment system according to claim 8, wherein the mesh screen has a mesh size ranging from about 1 to 5 mm.

10. A cellulosic fiber web treatment system according to claim 1, wherein said powder applicator spans the width of the cellulosic fiber web in the transverse direction.

11. A cellulosic fiber web treatment system according to claim 1 including more than one powder applicators, said more than one powder applicators directing binder composition onto both the first and second surfaces of the cellulosic fiber web.

12. A cellulosic fiber web treatment system according to claim 1, wherein said atomizer comprises a linear array of atomizer heads arranged across the width of the cellulosic fiber web.

13. A cellulosic fiber web treatment system according to claim 1, wherein said atomizer comprises a single row of atomizer heads spatially arranged to span the cellulosic fiber web in the transverse direction.

14. A cellulosic fiber web treatment system according to claim 1, wherein said atomizer heads are positioned at a center to center distance ranging from about 1 to 24 inches.

15. A cellulosic fiber web treatment system according to claim 1 including more than one atomizers, said more than one atomizers directing lubricant composition onto both the first and second surfaces of the cellulosic fiber web.

16. A cellulosic fiber web treatment system according to claim 1, wherein said repulper comprises rotating breaker bars.

17. A cellulosic fiber web treatment system according to claim 1, further comprising a fiber pelletizer.

18. A cellulosic fiber web treatment method comprising:

(a) supplying a cellulosic fiber web to a treatment system;

(b) applying an effective amount of a debonding composition onto at least a first surface of the cellulosic fiber web;

(c) extracting excess water from the cellulosic fiber web;

(d) applying an effective amount of a binder composition onto at least the first surface of the cellulosic fiber web;

(e) applying an effective amount of a lubricant composition onto at least the first surface of the cellulosic fiber web; and

(f) defibrilizing the lubricated web.

19. A cellulosic fiber web treatment method according to claim 18, wherein the debonding composition is applied to at least the first surface of the cellulosic fiber web in an amount ranging from about 0 to 3000 pounds per hour.

20. A cellulosic fiber web treatment method according to claim 18, wherein the extracting step is operated at a nip pressure ranging from about 50 to 150 psi.

21. A cellulosic fiber web treatment method according to claim 18, wherein the binder composition is applied to the surface of the pressed web in an amount ranging from about 0 to 30 pounds per hour.

22. A cellulosic fiber web treatment method according to claim 18, wherein the lubricant composition is applied to the surface of the powder coated web in an amount ranging from about 0 to 50 pounds per hour.

23. A treated cellulosic fiber web comprising:

(a) a cellulosic fiber web;

(b) an effective amount of a debonding composition;

(d) an effective amount of a binder composition; and

(e) an effective amount of a lubricant composition.

24. A treated cellulosic fiber web according to claim 23, wherein said cellulosic fiber web is formed from cellulosic pulp fibers having an alpha-cellulose purity of greater than about 80% by weight.

25. A treated cellulosic fiber web according to claim 24, wherein said cellulosic pulp fibers have an alpha-cellulose purity greater than about 98% by weight.

26. A treated cellulosic fiber web according to claim 23, wherein said debonding composition includes at least one surfactant as a debonding agent.

27. A treated cellulosic fiber web according to claim 26, wherein said debonding agent is present within the treated cellulosic fiber web in amounts ranging from about 0 to 5 weight percent, based on the weight of the cellulosic pulp fibers.

28. A treated cellulosic fiber web according to claim 23, wherein said binder composition includes at least one water soluble binder selected from polyacrylamide, polyacrylic acid, poly(n-vinyl pyrroliddinone), sodium carboxymethyl cellulose, polyvinyl alcohol, polyethylene glycol, sodium hydroxy ethyl cellulose, sodium carboxy methyl hydroxy ethyl cellulose, sodium hydroxy propyl cellulose and mixtures thereof.

29. A treated cellulosic fiber web according to claim 28, wherein said water soluble binder is polyacrylamide.

30. A treated cellulosic fiber web according to claim 28, wherein said at least one water soluble binder is present in an amount of about 0.1 to 1.0 weight percent, based on the weight of the cellulosic pulp fibers.

31. A treated cellulosic fiber web according to claim 23, wherein said lubricant composition includes at least one lubricant selected from silicone oil, fatty amides, metal stearates, and mixtures thereof.

32. A treated cellulosic fiber web according to claim 31, wherein said lubricant is a mixture comprising silicone oil and ethylene bisstearamid.

33. A treated cellulosic fiber web according to claim 32, wherein said silicone oil is present at about a 2:1 weight ratio in comparison to said ethylene bisstearamid.

34. A treated cellulosic fiber web according to claim 31, wherein said at least one lubricant is present in an amount ranging from about 1.0 to 10.0 weight percent, based on the weight of the cellulosic pulp fibers.

35. A treated cellulosic fiber web according to claim 23, wherein said binder composition further comprises at least one coupling agent selected from titanates, zirconates, silanes and mixtures thereof.

36. A treated cellulosic fiber web according to claim 35, wherein said coupling agent is present in said binder composition in an amount of up to about 1.0 weight percent, based on the weight of the binder composition.

37. A treated cellulosic fiber web according to claim 23 comprising:

cellulosic pulp fibers having an alpha-cellulose purity of greater than 80% by weight;

a debonding agent comprising surfactant;

a water soluble binder comprising polyacrylamide; and

a lubricant mixture comprising silicone oil and ethylene bisstearamid.

38. A treated cellulosic fiber web according to claim 37, wherein said debonding agent is present in an amount of up to about 5.0 weight percent, based on the weight of the cellulosic pulp fiber;

said water soluble binder is present in an amount ranging from about 0.1 to 1.0 weight percent, based on the weight of the cellulosic pulp fiber; and

said lubricant mixture is present in an amount ranging from about 1.0 to 10.0 weight percent, based on the weight of the cellulosic pulp fiber.