ENZYMATIC PRE-TREATMENT OF MARKET PULP TO IMPROVE FIBER DRAINAGE AND PHYSICAL PROPERTIES

Abstract

Methods for reducing the effects of wetlapping, drying, and hornification of pulp fibers and consequently increasing the pulp drainage and strength properties in the final product (i.e., paper) are provided. The method which has been developed creates a “value-added” product by the wastepaper supplier or at the pulp and/or deinking (recycled paper) mill—a wastepaper load/bale, wet pulp stock or wet lap, or dried pulp treated with or impregnated with enzymes that enhance the quality of the pulp or paper product when it is repulped and processed at the paper mill.

Claims

1. Enzyme treated pulp selected from the group consisting of dried pulp, wetlap pulp, or pulp in the form of market pulp sheets, bales of market pulp sheets, and dried crumbled pulp, wherein the treated pulp, when compared to pulp not treated with enzyme, (1) has increased pulp drainage characteristics when repulped, (2) produces sheets having improved strength when sheets are made from the repulped treated pulp, or (3) both, wherein the treated pulp was enzyme treated by administering an effective amount of enzyme formulation to pulp (1) after dewatering and drying of the pulp into dried pulp, wetlap pulp, or pulp in the form of market pulp sheets, bales of market pulp sheets, or dried crumbled pulp and (2) prior to subsequent repulping for the manufacturing of paper products, wherein the administered enzyme formulation is effective (1) to increase pulp drainage characteristics of the treated pulp when repulped, (2) to improve strength when sheets are made from the treated pulp, or (3) both, and wherein the enzyme formulation has at least one enzyme activity selected from the group consisting of cellulase activity, pectinase activity, endo-glucanase activity, cellbiohydrolase activity, hemicellulase activity, mannanase activity, xylanase activity, gamanase activity, pectin lyase activity, pectate lyase activity, lipase activity, and laccase activity.

2. The treated pulp of claim 1, wherein the pulp is recycled paper pulp.

3. The treated pulp of claim 1, wherein the pulp is virgin pulp.

4. The treated pulp of claim 1, wherein the enzyme formulation is administered at a virgin pulp mill or a wastepaper recycling plant.

5. The treated pulp of claim 4, wherein the enzyme formulation is administered at the virgin or recycling pulp plant to wet lap pulp.

6. The treated pulp of claim 4, wherein the enzyme formulation is administered at the virgin or recycling pulp plant to dry lapped pulp.

7. (canceled)

8. The treated pulp of claim 1, wherein the enzyme formulation is administered before the repulping of wetlap pulp as part of the paper manufacturing process.

9. (canceled)

10. The treated pulp of claim 1, wherein the enzyme formulation comprises one or more enzymes selected from the group consisting of cellulases, endo-glucanases, cellobiohydrolases, hemicellulases, mannanases, xylanases, pectinases, gamanases, pectin lyases, pectate lyases, lipases and laccases.

11. The treated pulp of claim 10, wherein the enzyme formulation is administered as a liquid or solid.

12. The treated pulp of claim 11, wherein the enzyme formulation is administered as a powder, dried, granulated, encapsulated, or pelletized form.

13. The treated pulp of claim 1, wherein the enzyme formulation is dosed with enzyme activity ranging from 5 to 600 units of enzymatic activity per 100 gram oven dried fiber.

14-17. (canceled)

18. The treated pulp of claim 1, wherein the properties of the paper products made from the pulp are altered as compared to paper products made from the pulp not treated with the enzyme formulation.

19-21. (canceled)

22. The treated pulp of claim 1, wherein the pulp is dried pulp.

23. The treated pulp of claim 1, wherein the pulp is wetlap pulp.

24. The treated pulp of claim 1, wherein the pulp is in the form of market pulp sheets, bales of market pulp sheets, or dried crumbled pulp.

25. The treated pulp of claim 1, wherein the enzyme is impregnated into market pulp sheets, bales of market pulp sheets, or dried crumbled pulp.

26-27. (canceled)

28. The treated pulp of claim 1, wherein the treated pulp is not processed at a paper making plant for a week or longer after administration of the enzyme formulation.

29. The treated pulp of claim 1, wherein the enzyme formulation has cellulase activity, pectinase activity, and at least one enzyme activity selected from the group consisting of endo-glucanase activity, cellbiohydrolase activity, hemicellulase activity, mannanase activity, xylanase activity, gamanase activity, pectin lyase activity, pectate lyase activity, lipase activity, and laccase activity.

30. The treated pulp of claim 29, wherein the enzyme formulation comprises one or more enzymes, wherein the one or more enzymes comprise at least one cellulase, at least one pectinase, and at least one enzyme selected from the group consisting of endo-glucanases, cellobiohydrolases, hemicellulases, mannanases, xylanases, gamanases, pectin lyases, pectate lyases, lipases and laccases.

31. The treated pulp of claim 1, wherein the enzyme composition is administered at a virgin pulp mill.

32. The treated pulp of claim 1, wherein the administration of the enzyme formulation impregnates the dried pulp, wetlap pulp, or pulp in the form of market pulp sheets, bales of market pulp sheets, or dried crumbled pulp with the enzyme formulation.

33. Enzyme treated dried pulp, wetlap pulp, or pulp in the form of market pulp sheets, bales of market pulp sheets, or dried crumbled pulp, wherein the treated pulp, when compared to pulp not treated with enzyme, (1) has increased pulp drainage characteristics when repulped, (2) produces sheets having improved strength when sheets are made from the repulped treated pulp, or (3) both, wherein the pulp was enzyme treated by administering, in a virgin pulp mill, an effective amount of enzyme formulation to virgin pulp after bleaching of the pulp and prior to dewatering and drying of the pulp into the dried pulp, wetlap pulp, or pulp in the form of market pulp sheets, bales of market pulp sheets, or dried crumbled pulp, wherein the administered enzyme formulation is effective (1) to increase pulp drainage characteristics of the treated pulp when repulped, (2) to improve strength when sheets are made from the treated pulp, or (3) both, and wherein the enzyme formulation has cellulase activity, pectinase activity, and at least one enzyme activity selected from the group consisting of endo-glucanase activity, cellbiohydrolase activity, hemicellulase activity, mannanase activity, xylanase activity, gamanase activity, pectin lyase activity, pectate lyase activity, lipase activity, and laccase activity.

34. The treated pulp of claim 33, wherein the enzyme formulation is administered prior to the pulp dryer.

35. The treated pulp of claim 33, wherein the enzyme formulation is administered prior to the wet lap machine.

36. The treated pulp of claim 33, wherein the enzyme formulation comprises one or more enzymes, wherein the one or more enzymes comprise at least one cellulase, at least one pectinase, and at least one enzyme selected from the group consisting of endo-glucanases, cellobiohydrolases, hemicellulases, mannanases, xylanases, gamanases, pectin lyases, pectate lyases, lipases and laccases.

37. The treated pulp of claim 36, wherein the enzyme formulation is administered as a liquid or solid.

38. The treated pulp of claim 37, wherein the enzyme formulation is administered as a powder, dried, granulated, encapsulated, or pelletized form.

39. The treated pulp of claim 33, wherein the enzyme formulation is dosed with enzyme activity ranging from 5 to 600 units of enzymatic activity per 100 gram oven dried fiber.

40. The treated pulp of claim 33, wherein the enzyme is administered at a temperature in the range of 10° C. to 90° C.

41. The treated pulp of claim 33, wherein the enzyme is administered at a pH range of 3.5 to 9.5.

42. The treated pulp of claim 33, wherein the enzyme is administered for at least 1 minute.

43. The treated pulp of claim 33, wherein the enzyme is administered with a consistency of 0.1% to 35%.

44. The treated pulp of claim 33, wherein the properties of the paper products made from the pulp are altered as compared to paper products made from pulp not treated with the enzyme formulation.

45. The treated pulp of claim 33, wherein the pulp is dried pulp.

46. The treated pulp of claim 33, wherein the pulp is wetlap pulp.

47. The treated pulp of claim 33, wherein the pulp is in the form of market pulp sheets, bales of market pulp sheets, or dried crumbled pulp.

48. The treated pulp of claim 33, wherein the treated pulp is not processed at a paper making plant for a week or longer after administration of the enzyme formulation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG. 1 is a flow chart of the processing of pulp preparation in a virgin pulp mill or wastepaper recycling mill and a paper mill using the pulp stocks, showing points of enzyme treatment to collected wastepaper furnish or in the deink plant or pulp mill prior to the eventual repulping of wet lap or dried pulp at a paper mill.

DETAILED DESCRIPTION OF THE INVENTION

I. Definitions

[0020] Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of skill in the art to which the disclosed invention belongs. Publications cited herein and the materials for which they are cited are specifically incorporated by reference.

[0021] The term “deinking plant” refers to a plant or mill which processes wastepaper into a recycled pulp which can be used to manufacture paper either onsite or offsite. Deinking plants remove various contaminants such as inks, fillers, coatings, and stickies/adhesives from wastepaper and produce clean recycled pulp to be used either onsite or offsite at paper machines.

[0022] The term “effective amount” refers to any amount which results in a predetermined or desired outcome. For example, an effective amount of an enzyme formulation intended to enhance strength means the amount of enzyme formulation which is effective to increase fiber strength properties in the final sheet compared to pulps not treated with the same enzyme formulation under the same conditions.

[0023] The term “enzymatic fiber modification” refers to any alteration or modification of the pulp fibers as a result of interaction with an enzyme. The modification can either be a direct or indirect result of the enzyme treatment.

[0024] “Recycled pulp” or “recycled fibers” refers to the pulp or fiber stock components of a paper or paperboard furnish that is derived from recovered paper and paperboard or wastepaper.

[0025] “Drying” of the pulp does not include processing of the pulp on the paper machine. As used herein, drying of the pulp refers to drying pulp that is eventually re-pulped before being processed on a paper machine. “Once dried” and “fully dried” are used interchangeably.

[0026] “Wet lap” pulp refers to virgin or deinked recycled pulp which is not made directly into paper, but rather is dewatered and pressed down to a roughly 45-50% solid content product which is then stored or shipped in bale or crumb cube form for later use.

II. Enzyme Formulations

[0027] Enzyme formulations for treatment of pulp in the pulp mill or deink plant include one or more enzymes effective to increase fiber strength and/or modify drainage of the pulp. Examples of enzymes that can be used to treat pulp as described herein include, but are not limited to, cellulases, endo glucanases, cellobiohydrolases, hemicellulases, mannanases, xylanases, pectinases, gamanases, pectin and pectate lyases, lipases and laccases.

[0028] The enzymes are typically used in combination, although this is not essential and pulp may only be treated with one type of enzyme or one class of enzyme such as cellulases. In one embodiment, the enzymes are added in a concentration ranging from between 5 to 600 enzyme activity units per 100 g OD fiber. Preferably, the concentration of the enzymes is between 20 to 200 enzyme units/100 g OD of fiber. The enzyme units can be determined as described below.

[0029] Measurement of Cellulase (Endo-β-1,4-Glucanase) Activity (CMCU)

[0030] Endo-β-1,4-glucanases (EC 3.2.1.4) attack β-(1,4) linkages in amorphous cellulose, carboxymethylcellulose (CMC), and phosphoric acid-swollen cellulose, to produce shorter-chain cellooligosaccharides that in turn may be hydrolyzed to cellobiose and glucose by exo-glucanase and beta glucosidase. This method relies on degradation of CMC chains, which causes a measurable reduction in the viscosity of the CMC gum solution. The chemicals used to determine cellulase activity include 0.30% of sodium carboxymethyl cellulose (CMC) gum, AQUALON® CMC 7 (Hercules Incorporated, Wilmington, Del.) in pH 5.2 500 mM acetate buffer as the substrate and using CELLULAST® 1.5L cellulase (Novozymes A/B, Denmark) as a standard cellulase with an activity of 20000 CMC Units/ml. A diluted enzyme sample or filtrate sample is mixed with 10.0 ml of gum solution for 10 minutes at 40° C. water bath and the viscosity is measured using Fisher Brand Glass Ubbelohde Viscometer Tubes. The reduction in viscosity is converted to CMC units based on the standard cellulase CELLULAST® 1.5L.

[0031] Measurement of Amylase Activity (AU)

[0032] Amylase (EC 3.2.1.1) catalyzes the degradation of starch (amylose). An iodine-iodide indicator solution can be used to indicate starch concentration which is detected spectrophotometrically at 500 nm. The amylase activity is determined using potato starch as a substrate. This method is based on the break-down of starch and the reaction is followed by an iodine titration. The initial blackish-blue color is formed when starch solution is mixed with an iodine solution, and the blue color is reduced gradually into reddish-brown which is measured using a spectrophotometer at 500 nm. One amylase unit (AU) is defined as the amount of amylase which, under the standard testing conditions, (37° C., 10 minutes and pH 5.6 of 100 ppm starch solution), generates 1 micromole of glucose per minute.

[0033] Measurement of Lipase Activity (PCU)

[0034] The APC™ assay is based on an enzyme-coupled reaction. Triglycerides are first hydrolyzed by the lipases to glycerols and free fatty acids. The glycerols produced from the reactions react with adenosine triphosphate, glycerol kinase, and glycerol-peroxidase. A dye is formed which can be measured spectrophotometrically at 540 nm. The increase in absorbance at 540 nm is directly proportional to free glycerol concentration in the sample. A quantitative determination of enzyme activity is made by testing a known standard of lipase at multiple dilution rates to obtain a standard curve. The lipase activity is calculated by comparing the absorbance attained to a standard lipase of known activity. The lipase activity is determined using APC™ Method according to U.S. Pat. No. 7,067,244.

[0035] Measurement of Pectinase Activity (PU)

[0036] Pectinases break down 1.0% pectin solution (Sigma P-9135) with pH 5.0 acetate buffer at 50 mM and results in galacturonic acid (BioChemika 48280). The concentration of pectin in the solution is determined by measuring the content of galacturonic acid. The treatment of pectin solution with sulfuric acid will develop a color in the presence of carbazole (Sigma C-5132), which measured at 520 nm, is proportional to the total pectin concentration. One unit of pectinase activity is the amount of pectinase needed to produce one mole of galacturonic acid at pH 5.0, temperature of 40° C. in 50 mM acetate buffer per minute.

[0037] Measurement of Xylanase Activity (XU)

[0038] The substrate employed is azurine-crosslinked wheat arabinoxylan. endo-1,4-β-D-xylanases hydrolyze the xylan backbone, releasing water soluble dyed fragments. The amount of released dyed fragments can be directly related to enzyme activity. The Xylazyme AX tablets are ordered from Megazyme International Ireland Ltd., Bray Business Park, Bray, Co. Wicklow, Ireland. The absorbance of these dyed fragments can be detected spectrophotometrically at 590 nm. A quantitative determination of enzyme activity is made by testing a known standard of xylanase at multiple dilution rates to obtain a standard curve. The standard curve correlates the enzyme activity of a known standard xylanase with absorbance. Novozymes Pulpzyme® HC has a standard activity unit of 40,000 XU/ml.

[0039] Measurement of Gamanase Activity (GU)

[0040] Gamanase breaks down galactomannans, such as bean gum, to reducing sugars which are measured with the DNS method. Locust bean gum at 0.1% (w/w) is used as the gamanase substrate. Enzyme is diluted with pH 6.8 50 mM phosphate buffer, added to the bean gum solution and incubated at 40° C. water bath for 20 minutes. Shake the samples well every 5-10 minutes and stop the reaction using 0.10 mL of 1M Na.sub.2CO.sub.3 solution, and then transfer 0.5 mL from each of the sample test tubes to glass test tubes to react with DNS solution and measure the absorbance at 575 nm. One unit of gamanase activity (GU/ml) is defined as the amount of enzyme generating 1 mole of reducing sugar released from 0.1% locust bean gum at pH 6.8 and 40° C. per minute.

[0041] Measurement of Laccase Activity (LAMU)

[0042] Laccase units (LAMU) are based on the rate of oxidation of syringdazine. 1 LAMU is defined as the amount of enzyme which, under standard conditions, such as pH 7.5 and 30° C., oxidizes 1 mole syringaldazine per minute. The laccase activity in LCU may also be determine using 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) as the substrate at 25° C. and pH 4.5. One unit of enzyme activity is defined as the amount of enzyme oxidizing 1 mole of ABTS per minute at temperature of 25° C. and pH 4.5.

[0043] The formulations can be provided in the form of a solution or granulated or powder enzymes that include compositions that adjust for pH and salt concentrations. In general, enzyme formulations can also include the appropriate buffer for optimal enzyme activity. One of skill in the art can optimize the conditions to maximize enzymatic activity using conventional techniques known in the art.

[0044] Commercially available enzyme formulations can also be applied in the method described herein. For example, Enzymatic Deinking Technologies (EDT), markets a line of products for fiber modification under the trade name of REFINASE®. REFINASE® products contain enzyme mixtures with at least one of the enzymes being a cellulase, endo-glucanase, cellobiohydrolase, hemicellulase, mannanase, xylanase, pectinase, pectin esterase, pectin and pectate lyase, gamanase, esterase, laccase or lipase. The dosage of the REFINASE® based on oven dried fiber or pulp ranges from 0.001% to 0.4%, with 0.025% to 0.15% based on OD fiber being more preferred.

[0045] In some embodiments the enzymes may be introduced in a dried, granulated, encapsulated, or pelletized form. Stabilizers such as metal ions and cationic polymers may optionally be added to the formulations. The enzyme formulations may be treated to improve storage stability. A method for producing solid granulates with improved storage stability is described for example U.S. Publication No. 2007/0111920 by Bauer, et al.

[0046] The formulations may additionally include one or more dispersants, which can be surfactants and/or polymers which may be used, for example, to enhance stability or activity of the enzymes.

III. Methods and Materials for Enzymatically Treating Pulp

[0047] Methods for reducing the effects of hornification and deterioration of pulp are described. The methods include treating virgin or recycled pulp at a pulp making plant, prior to transport to a paper making plant, with an enzyme formulation containing enzyme in an amount effective to increase pulp drainage characteristics of virgin pulp or recycled pulp and improve the strength of sheets made from the pulp. The various steps in the process of furnish collection and pulp stock preparation prior to making paper for both recycled and virgin paper are shown in FIG. 1.

[0048] In one embodiment, the pulp is treated with the enzyme formulation prior to drying into dry pulp (approximately 90-95% dry) or processing into wet lap pulp (approximately 45-50% dry). Prior to the drying or processing into wet lap pulp step refers to any time before the wetlap dewatering step used for wetlap pulps or the dewatering and drying steps involved in the production of dry pulps.

[0049] In a second embodiment, the enzyme formulation is applied to dry or wet pulp or impregnated into a bale of dried pulp or sheets of dried pulp. The dried pulp may be allowed to cool to a temperature at which the enzyme is not inactivated before administration or impregnation of the pulp. Enzyme is impregnated into the bales of pulp in a liquid or solid form at the pulp mill, prior to transport to the paper processing mill, either immediately after baling or after transport to a temporary storage facility. In this embodiment, there may be a period of a day, a few days, a week, a month, a few months, or longer prior to processing of the pulp at a paper product plant.

[0050] In a third embodiment, the enzyme formulation is applied to collected wastepaper furnish at the furnish processing or baling center prior to shipment to the paper recycling plant.

[0051] The pulp may optionally be treated with additives such as stabilizers and dispersants. These additives may be added alone or together with the enzymes at the same addition locations or separately at different locations.

[0052] The enzyme formulation is typically applied as a solution to the pulp stock but could also be added in dried or granulated enzyme form. Timing, concentration, temperature, pH and pulp consistency all play a role in pulp stock preparation. The stage of the process in which the enzyme treatment is applied can vary.

[0053] Treatment of Pulp with Enzyme Formulations

[0054] Several operating parameters in the pulp mill such as temperature or pH can be varied to alter the enzyme activity in order to modify pulp fiber characteristics such as drainage and physical properties.

[0055] Timing/Location of Enzyme Application

[0056] The point of the process in the pulp mill or deink plant at which the enzyme is applied is dependent on a variety of factors such as (1) the incubation time of the enzyme with the pulp; (2) the amount of time between the enzyme treatment and the drying or wet lapping step; (3) the amount of time between the drying or wet lapping of enzyme treated pulp and the time the pulp is used on a paper machine; and (4) the water loops in the pulp mill or deink plant. The incubation time of the enzyme with the pulp stock can vary. The pulp stock is treated with enzyme formulation for at least 1 minute, preferably more than five minutes, but the actual time can be for many months, while the pulp is in storage or transport, and the level of enzyme activity varies under the conditions of storage. Those skilled in addition of enzymes to warm, wet pulp stock will understand that the amount of enzyme activity will be substantially higher than when enzymes are provided in dry powder form to cooled, baled dry pulp in storage. The pulp is enzymatically treated for a period of time and in an amount and under conditions resulting in fiber modification and then the pulp is partially (i.e., formed into “wet-lap” pulp) or fully dried, then usually formed into bales. Alternatively, the wetlapped or dried pulp can be treated with enzyme after the wetlapping or drying process but while still in the pulp mill or deink plant. The dried pulp can be stored for at least up to three years before repulped and made into paper.

[0057] The enzyme treatment can be performed in tanks in the pulp mill before the final dewatering or drying step. Other equipment stages in which the methods can be performed include, but are not limited to, dump chests, bleach towers, feed tanks, high density towers, silo water, white water tanks and other parts of the mill where a minimum of 1 minute of contact time occurs or where process waters from the pre-drying or pre-wet lapping dewatering step return to a suitable part of the process for enzyme effect. Alternatively, the enzyme treatment in the deink plant or pulp mill can be applied after the wetlapping or drying step.

[0058] In preferred embodiments, the enzyme is administered to the wet pulp stock for at least 1 minute, preferably 5 minutes to 6 hours, and more preferably 10 minutes to 2 hours.

[0059] Temperature

[0060] It is well known in the art that enzyme activity is temperature and pH dependent. The enzyme treatments described herein are typically effective at temperatures of from 10° C. to 90° C. The more preferred temperature range is from about 15° C. to 60° C.

[0061] However, the temperature range can vary depending on the nature of the enzyme used and the optimal activity range for each enzyme.

[0062] pH

[0063] The pH of the pulp stock can generally be from about 3.5 to about 9.5 for most enzymes, more preferably from about 4.5 to 8.0. The pH of the stock can be adjusted using pH modifiers such as alum or aluminates, certain acids, carbon dioxide, and various alkalis such as sodium hydroxide.

[0064] Enzyme Concentration

[0065] The enzyme dosage depends on the specific enzyme and the other treatment conditions, in particular pulp consistency and temperature.

[0066] The enzymes may be used alone or in combination. The enzymes concentration preferably ranges between 5 to 600 enzyme units/100 g oven dried (“OD”) fiber. Preferably, the concentration of the enzymes is between 20 to 200 enzyme units/100 g OD of fiber. The enzyme units can be determined as described herein. The effective amount of enzyme is that which results in increased fiber drainage of the pulp relative to non-enzyme treated pulp and/or which enhances paper sheet strength of the paper made using the enzyme treated pulp. The method can result in increases in both fiber drainage and paper sheet strength (for paper made from the pulp).

[0067] In preferred embodiments, the enzyme is administrated to the wet pulp stock with a consistency of 0.1% to 35%, preferably 0.5% to 15%, and more preferably 1.0% to 10%.

[0068] Determination of Pulp Strength

[0069] The enzymatically modified fibers can result in increased strength in the final paper product. Fiber strength can be determined using many different measures which conform to the strength needs of the paper grade. Certain grades such as tissue focus on machine direction and cross direction tensile strength targets. Fine printing and writing grades also require tensile strength standards but additionally focus on surface printing ability. Packaging grades require a broad assortment of strength parameters including tensile, tear, Mullen burst, ring crush, STFI/SCT test, Concora, plybond, sizing test or box crush tests. Each of these tests is conducted according to industry standard testing equipment and methods. Increased paper strength is any increase in paper strength over the standard or usual paper strengths achieved relative to untreated paper or paper treated with a method such as starch, chemical processing or refining. Paper strength can be measured using TAPPI test methods T494 (tensile strength), T403 (burst strength), T414 (tear strength), and other standardized industry procedures.

[0070] Determination of Pulp Drainage

[0071] Pulp drainage is determined by the rate and degree to which water drains from a pulp stock. Two of the most widely used tests are the Canadian Standard Freeness test and the European Schopper-Riegler test. One liter of 0.3% or 0.2% consistency pulp stock, respectively, is drained over a conical object and the quantity of water which passes through an overflow tube is monitored. A quick draining stock creates a large overflow and results in a high number of ml of filtrate passing over the cone as calculated by a Canadian Standard Freeness test. Alternate methods of tracking drainage use vacuum systems whereby the time rate and maximum degree of water removal from a pulp suspension are tracked. Improved drainage on a paper machine is noted by changes in flat box vacuums or couch roll vacuums or the position of dry lines on a Fourdrinier forming table. Additionally, improvements in drainage may be noted in reductions in final sheet moisture with all other factors (e.g., machine speed, vacuums, sheet grammage, drying section pressure) remaining constant.

[0072] Increased pulp drainage is any increase in pulp drainage over the standard pulp drainage achieved without enzyme treatment as described herein and with other drainage affecting measures being accounted for.

[0073] The enzymatically treated dried or wet lapped pulp is re-pulped at a paper mill before manufacturing paper. The re-pulping can be performed using any re-pulping methods known in the art.

IV. Pulp and Pulp Fibers

[0074] Wet lapped and dried pulp with improved drainage characteristics and improved fiber strength is obtained by treatment with an effective amount of an enzyme(s) to increase the strength and/or drainage of the pulp and improve the strength of sheets made from enzyme-treated pulp compared to untreated pulps and sheets made from untreated pulp.

[0075] The pulp and pulp fibers can be derived from any of a number of sources. Pulp can be made from wood, fiber crops or other non-wood sources such as wheat straw or rice straw or grass. Wood pulp comes from softwood and hardwood trees. Softwood trees include spruce, pine, fir, larch and hemlock. Hardwoods include eucalyptus, aspen and birch. One source of fiber that is widely used due to its lower cost and ready availability is the market eucalyptus pulp (e.g., South American, Australian, or Iberian varieties). Application of enzymatic treatments to eucalyptus pulps is especially beneficial due to the lower strength aspects of this short fiber, this fiber's lower cost, and the relative significant improvement from enzymatic treatment in terms of drainage and strength.

[0076] The pulp can be virgin pulp or recycled pulp. Virgin pulp is pulp that has never been made into a final paper product. Recycled pulp refers to pulp that was recycled from waste paper such as through a deinking process.

[0077] The consistency of the pulp stock to be enzymatically treated can be between about 0.1% and 35%, more preferably between 0.5% and 10%. Alternatively, enzyme treatment can be applied to wetlap or fully dried pulps in the pulp mill. Consistency is defined as the oven dry weight of the fiber divided by the total weight of the fiber and water in the stock suspension.

[0078] Currently, pulp is made and dried (partially or completely) in a pulp mill or deinking plant. The dried pulp is then used in a paper mill for processing into paper. In most instances, the pulp mill does not adjoin the paper mill where the paper machine is located, thus the pulp from the pulp mill must be transported to the paper mill for further processing. However, as a result of the distance between the pulp mill and the paper mill it is not feasible to transport a wet pulp stock supply of pulp (“never-dried pulp”) for example, through a pipeline or in a large wet stock tank truck or rail car. Transport requires a more stable pulp product which can be stored economically for a long period of time as well as one which is not prohibitively expensive to transport. Wet pulp stock is significantly heavier than wet lap or fully dried pulp, and therefore significantly more expensive to transport. Therefore the pulp is fully or partially dried prior to transportation to the paper mill. In a preferred embodiment, the pulp is pulp that ultimately is dried and then re-pulped before the paper making process. In one embodiment, the pulp is mixed with the enzymes, as a powder or encapsulated in some sort of carrier, which then solubilizes and activates when the pulp is re-wetted prior to processing in the paper processing plant. Enzyme-treated virgin or recycled pulp can be dried to either wetlap (approximately 45-50% consistency or dry) or fully dried (approximately 90-95% dry) form.

[0079] Enzymatic fiber modification can result from increasing fibrillation of fibers resulting in more hydrogen bonds on the fiber and physical entanglement. Enzymatic fiber modification can also swell the outer layer of the fiber, reducing its density, and therefore making the fibers more “refining-able” resulting in more fibrils and delamination of outside fiber walls when processed through a mechanical refiner. Increases in drainage can occur due to the way in which the smaller micro fibrils from the enzyme treatment are produced or by certain changes to the colloidal phase of the pulp stock which enhances the water flow through the fibers.

[0080] In one embodiment, the enzyme fiber modification resulting in increased fiber drainage does not affect the paper sheet strength. In another embodiment the enzymatically treated pulp has both increased pulp drainage and paper sheet strength (for paper made from the pulp). It is possible that the enzyme modification does not affect fiber drainage but does improve paper sheet strength. Thus, the treatment affects drainage and strength individually and in combination.

[0081] The enzymatically treated dried or wet lapped pulp is re-pulped at a paper mill before manufacturing paper. The re-pulping can be performed using any re-pulping methods known in the art.

V. Wastepaper Loads or Bales Treated or Impregnated with Enzyme Formulation

[0082] Wastepaper loads or bales treated or impregnated with enzyme formulation effective to enhance drainage, strength and other pulp and paper properties in the paper making process can also be made by administering an effective amount of enzyme formulation to wastepaper loads or bales during the wastepaper collection that are later used to produce recycled papers. An enzyme formulation can be applied as solid or liquid to the surface, or more preferably, impregnated using high pressure nozzles to introduce the enzymes into the loads or bales.

[0083] The present invention will be further understood by reference to the following non-limiting examples.

EXAMPLES

Example 1: Impact of Enzymatic Treatment and Wet Lapping and Drying on Fully Bleached Kraft Hardwood Pulp

[0084] Materials and Methods

[0085] Experiments were conducted to determine the effect of enzyme, the effect of starch, and the wetlapping, drying and repulping on the treated pulp. The sheets were produced from the treated and control pulps with the similar conditions as follows: treatment temperature at 45° C., stock at about pH 6.4 with continuing mixing at 3.5% consistency for 45 minutes. The wet stock from the pulp mill was treated with enzyme alone and starch alone and the individually treated stocks are compared to non-treated stock. The non-treated stock, enzyme treated stock and starch treated stock were then split into two portions. The first portion was used for analysis as non-dewatered and dried stock. In this case the treated stock was measured for drainage and then sheets were made to measure sheet physical properties. The second portion was used for analysis of the post dewatering and drying impact of the treatment. The stock was dewatered with filter paper to about 25%, pressed at 50 psi for 2 minutes, and then dried on a speed dryer with surface temperature of 90-95° C. for 45 minutes. The dried pulp was then repulped with a disintegrator for 20k revolutions with tap water for drainage and then made into a sheet to determine the effect of wetlapping, drying and repulping following either enzyme or starch treatment or a no-treatment control. Hand sheets were made, conditioned and measured according to TAPPI T402, T205, T220, T403, T220 and T411.

[0086] Results

[0087] Table 1 shows the effect on drainage and sheet strength of an enzyme blend, Refinase® A alone, starch alone, and no treatment, followed by wet lapping and drying process.

TABLE-US-00001 TABLE 1 Effect of enzymes and starch on drainage and strength properties of fully bleached Kraft hardwood pulp. Physical Refinase ®, Starch, properties Treatment conditions Control 0.05% 2.0% Freeness, ml Never-dried 635 673 598 Wet-lapped, 607 647 610 dried and repulped Burst, kPa .Math. m.sup.2/g Never-dried 2.0 2.8 2.4 Wet-lapped, 1.2 1.6 1.0 dried and repulped Tensile, N .Math. m/g Never-dried 37.8 46.8 39.8 Wet-lapped, 24.2 28.5 19.7 dried and repulped

[0088] The term “Never-dried” above refers to no interim dewatering or wetlapping/drying step of the wet virgin Kraft eucalyptus pulp stock directly from the pulp mill prior to sheet manufacturing. The “Dewatered, dried and re-pulped” above refers to the processing of the pulp which was wet-lapped using filtration, dried and repulped following enzyme or starch treatment of the “Never-dried” wet pulp stock.

[0089] Treatment of never-dried pulp with starch improved the strength properties of pulp when compared to untreated pulp. The positive effect of the starch on strength did not carry through the wet-lapping and drying process. By contrast, enzyme treatment improved strength properties of treated pulp, even for pulp after the wet-lapping and drying process. As shown in Table 1, the enzymatic treatment is beneficial for improved drainage and fiber properties for many types of paper production.

Example 2: Impact of Enzymatic and Starch Treatment on Deinked Pulp Stock

[0090] Materials and Methods

[0091] A similar set of experiments as described in Example 1 was conducted on deinked pulp stock taken from the end of the deink plant where mixed office waste paper was a major furnish component. The deinked pulp was very clean with very low residual dirt. Its brightness was about 75% ISO. The deinked pulp was treated similarly as the virgin hardwood pulp used in Example 1.

[0092] Results

[0093] The results are shown in Table 2.

TABLE-US-00002 TABLE 2 Effect of enzymes and starch on drainage and strength of deinked pulp stock Physical Refinase ®, Starch, properties Treatment conditions Control 0.05% 1.0% Freeness, ml Never-dried 466 531 415 Dewatered, 438 524 485 dried and repulped Burst, kPa .Math. m.sup.2/g Never-dried 2.8 3.2 3.1 Dewatered, 2.3 2.7 2.2 dried and repulped Tensile, N .Math. m/g Never-dried 43.7 51.6 47.6 Dewatered, 33.3 38.3 32.9 dried and repulped

[0094] The dewatering, drying and repulping once again showed significant deterioration in pulp properties in terms of drainage and physical strength. The enzymatic treatment showed improvements in stock drainage and sheet strength compared to control results for both the never-dried and post-dewatering/drying treatments. By contrast, starch treatment alone was not effective in improving pulp drainage or strength properties of the resulting sheets produced after dewatering and drying.

Example 3: Impact of Enzymatic Treatment of Fully Bleached Kraft Loblolly Pulp

[0095] Materials and Methods

[0096] A wet pulp stock at about 3.6% consistency was collected from a southern Kraft pulp mill which makes bleached dry lap commercial products. The wet pulp stock was treated in a similar manner as described in Example 1 for hardwood pulp using Refinase® B at 0.05% based on OD fiber.

[0097] Results

[0098] The results are shown in Table 3.

TABLE-US-00003 TABLE 3 Effect of enzyme on bleached Loblolly Kraft pulp Physical Refinase ®, Starch, properties Treatment conditions Control 0.05% 1.0% Freeness, ml Never-dried 682 729 589 Dewatered, 665 728 683 dried and repulped Burst, kPa .Math. m.sup.2/g Never-dried 2.7 3.1 3.0 Dewatered, 1.9 2.4 2.1 dried and repulped Tensile, N .Math. m/g Never-dried 32.2 37.7 36.1 Dewatered, 24.2 28.4 22.1 dried and repulped

[0099] As in examples 1 and 2, the enzymatic treatment of never-dried pulps provided material gains to drainage and strength which carried through the dewatering and drying process as compared to the non-treated control. As in the other examples, the starch treatment prior to dewatering and drying failed to provide improvements in drainage of the post dewatered and dried pulp and the strength tests were inferior to those from the enzymatic treatment.

[0100] The methods described herein can be employed at a pulp mill to produce wet lapped or dried pulp for later use. This would be beneficial in view of the geographically dispersed users of the virgin and market deinked pulps.

[0101] Those skilled in the art will recognize, or be able to ascertain impact using no more than routine experimentation and equivalents to the specific embodiments of the invention described herein. Such equivalents are intended to be encompassed by the following claims.