Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
  • D21H21/06—Paper forming aids
  • D21H21/10—Retention agents or drainage improvers
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/01—Waste products, e.g. sludge
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H23/00—Processes or apparatus for adding material to the pulp or to the paper
  • D21H23/02—Processes or apparatus for adding material to the pulp or to the paper characterised by the manner in which substances are added
  • D21H23/04—Addition to the pulp; After-treatment of added substances in the pulp

Definitions

• European Patent Specification publication number 0 041 056 teaches a method of paper manufacture in which inorganic filler, colloidal silica and cationic starch are added to an aqueous suspension of cellulose fibers upstream of the inlet to the papermaking machine for the purpose of enhancing paper strength and improving filler retention on the wire.
• Swedish Patent Application 850016206 teaches a method of paper manufacture in which an aqueous suspension of an inorganic filler is first mixed with pulp fines, whereafter a retention agent is added (coflocculation) and the flocs thus formed are introduced into the pulp suspension at a location upstream of the paper machine thereby improving filler retention and enhancing paper properties.
• U.S. Patent No. 4,889,594, issued to Gavelin teaches the use of an apparatus attached to a paper machine for use in co-flocculating filler and fine pulp.
• the manufacture of paper board does not incorporate the use of any fillers since it is unbleached fiber and does not require the brightness conveyed by the addition of fillers.
• the use of fillers would, in fact, hurt the overall strength of the paper board, which is its most important sheet property. Since paper board is primarily designed for strength, the use of a filler would not be appropriate. Accordingly, it is an object of this invention to provide an improved method of flocculating fines in the manufacture of paper board.
• the present invention relates to a method for manufacturing paper board, which contains no inorganic filler. Pulp fines from the white water system of the paper machine are mixed with one or more retention agents and then fed to the stock upstream of the paper machine. This introduces the fine/retention aid mixture prior to blending with the long fiber stock. Once flocculation takes place, the stock is drained to form a sheet and the sheet is dried.
• fine pulp is flocculated with the aid of one or more retention agents, prior to the pulp being introduced into the long fiber stock fed to the paper machine. This results in flocculation of the fine particles without flocculation of the long fiber with resulting loss of formation.
• Suitable retention agents for use in accordance with the present invention are any of the typical retention agents used in papermaking, including high molecular weight polymers which provide an irreversible bridge formation between particles.
• Anionic, cationic and nonionic polymers can be used herein.
• flocculation is effected in the presence of a small proportion of the total headbox furnish and when the flocs come into contact with the long fiber stock, at a later stage, the retention agent has already reacted and is, to a great extent, bound to active groups on the fine pulp.
• Retention of the flocs in the paper board is caused by two mutually contributory reaction processes.
• the flocs are filtered out and fasten in the meshes of the fiber network on those sites at which they are located when the fiber network is consolidated during the process of dewatering the stock on the wire of the paper machine.
• the cationic flocs are attracted to anionic fiber surfaces in the fiber network, which amplifies the filtering process and contributes towards uniform distribution of the flocs in the direction of the Z-axis of the paper.
• the method according to the invention is not dependent on the use of any particular kind of retention agent.
• the choice of retention agent depends on those demands placed on the process and on paper quality. A few retention agents which can be used in accordance with the invention are given below.
• Flocculants such as copolymers of acrylamide with cationic or anionic monomers, which can be obtained at various molecular weights and degrees of substitution.
• Coagulants including DADMACs, epi-DMAs, condensation products of ethylene dichloride and amines, polyethylene imine, modified polyethylene amines and polyamido amines. These coagulants may be used alone or in conjunction with flocculants in dual polymer programs.
• Nonionic flocculants such as polyacrylamide and polyethylene oxide. Both may be used with an enhancer such as phenol formaldehyde resins.
• Cationic starch can be added to the stock in order to increase the dry strength of the paper or to reduce the Z-potential of the system and cause coagulation of fine fraction.
• polymers of the type polyamide, polyamideamine condensate, cationic polystyrene latex, and inorganic compounds of the type alum, polyaluminum chloride and sodium aluminate can also be used as retention agents in accordance with the present invention.
• a cationic retention agent can be combined with an anionic agent, in which case the cationic agent is preferably prior to the addition of the anionic agent.
• a microparticle may also be added to any of the single or dual polymer programs described above.
• Particles currently in use include colloidal silica, bentonite, other smectite clays and anionic latex polymers.
• Suitable three-component systems for use in accordance with the invention are the combination cationic starch/anionic polyacrylamide/cationic polyacrylamide and the combination bentonite or colloidal silica/anionic polymer/cationic polymer.
• Suitable addition points for adding the retention aid according to the invention are any paper machine locations containing only fines, e.g., the tray, white water silo and suction side of the fan pump.
• the addition occurs at a point where at least a low level of turbulence occurs, e.g., the suction side of the fan pump.
• the foremost advantage is the increase in retention that occurs without a loss of dewatering, while increasing runnability and tensile/crush strength of the end product
• a second advantage is the reduced amount of retention aid that is required for use throughout the paper machine system. This reduction is realized because long fiber is not heated, as is done to paper fibers used in the production of finer paper grades.
• the lost time resulting from all wet-end breaks was reduced by ⁇ 58% when comparing the periods that the polymer was fed at the wire pit vs. those times when it was fed pre-screen.
• the average total lost minutes, when combining all wire pit vs. Pre-screen feed evaluation periods, was 70.3 minutes/day with normal polymer feed and 29.9 minutes/day with wire pit polymer feed. This represents a net gain in production time of 40.4 minutes/day or 0.675 hours/day. Using a production rate of 15.66 TPH, there is an increase in daily production of 10.54 Tons per Day @ 100% operating efficiency).
• Maintaining good formation means that forming area vacuums will remain at higher effective levels (less light and heavy areas where vacuum integrity can be lost), sending a more uniform sheet of higher consistency and wet web strength into the press section.- This can mean less opportunity for press picking, fewer wet-end breaks, and better opportunity for the wet presses to remove water and build internal sheet strength.
• Nalco® 7523 The drainage and drying effects of Nalco® 7523 on paper board manufacturing machipery were measured. Effects of the polymer on reel moisture, steam pressure, flatbox vacuums, and reel speed were calculated. Differences before, during, and after this evaluation on 33# heavyweights regarding average CFCO tests, average machine speeds, and average tons/hour were then measured. Nalco 7523 was added to the drive side of the wire pit at a target addition rate of 21b/ton. Three days later, Nalco 7523 flocculant was removed from the paper machine system at least at the same, if not slower, rate than it was taken out during previous evaluations. Some of the observations made during this time period where the feed rate was reduced from 2 lb/ton down to 0 lb/ton are as follows.
• the steam pressure Prior to decreasing the polymer dosage (i.e., 2 lb/ton), the steam pressure was at ⁇ 43 psi. Upon making the final reduction in dosage from 0.5 lb/ton) down to 0 lb/ton, the steam pressure reached a maximum level of ⁇ 94 psi. The 3rd section steam increased slightly from ⁇ 112 psi up to ⁇ 116 psi, throughout the removal of the polymer from the paper machine.
• the retention/drainage program of the invention was incorporated into a dual headbox Fourdrinier machine producing virgin unbleached kraft linerboard. It was found that by feeding the dual polymer retention program that had been in use at the machine to the wire pit (fines only) production was increased from 850 to over 900 tons per day. Significantly, a 2% reduction in white top liner furnish was realized as a result of improved retention of the brown unbleached kraft fines gained by the change in feed points.

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Applications Claiming Priority (2)

Publications (2)

Family

ID=24968080

Family Applications (1)

Country Status (6)

Cited By (3)

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• 1997
  • 1997-10-16 AU AU41885/97A patent/AU4188597A/en not_active Abandoned
  • 1997-10-22 NO NO974871A patent/NO974871L/no not_active Application Discontinuation
  • 1997-10-23 EP EP97308439A patent/EP0838550A3/de not_active Withdrawn
  • 1997-10-24 BR BR9705140A patent/BR9705140A/pt not_active Application Discontinuation
  • 1997-10-24 CA CA 2219332 patent/CA2219332A1/en not_active Abandoned
  • 1997-10-24 ID IDP973521A patent/ID18699A/id unknown

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