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
  • D21H21/02—Agents for preventing deposition on the paper mill equipment, e.g. pitch or slime control

Definitions

• This invention concerns a method of controlling tch in pulps for use in making paper. f ⁇ More particularly, this invention concerns a method o controlling the buildup of pitch on equipment used for pulping and the improved dispersion of pitch in pulps.
• Pitch carried over from wood or bark pulped to make papermaking furnishes, is formed of a complex mixture of oleophilic, water insoluble, low molecular weight, essentially non-polar resins comprising fatty and resin acids with ionisable hydrophillic groups, fatty and resin acid esters, sterols, di and tri-glycerides, terpenes and waxes and various alcohols, hydrocarbons and neutral compounds associated with these resins.
• the resins tend to agglomerate to form sticky films or pitch balls, which in turn can give rise to spotting in the final paper product, wire spots, localised sticky spots on rolls, holes in the paper sheet, poor paper formation, felt plugging or sticking on dryer and calender rolls.
• SUBSTITUTE SHEET is necessary, however, is that the pitch be dispersed as tiny non-harmful aggregated or agglomerated particles and retained in this fine particulateform rather than as larger harmful globs in the paper sheet. Simply flocculating pitch will not give good pitch control; the pitch must be made to attach to either the cellulosic fibres or to any particulate matter used as filler in the paper sheet, or preferably to both. Pitch retained in large floes causes breaks and undesirable dark specks in the finished paper sheet, while pitch not retained but in small floes tends to accumulate in the papermaking facility's white water system".
• Efforts to control pitch deposit problems by dispersing or precipitating the pitch have traditionally involved the use of alum salts; ultrafine crystalline talc; anionic, cationic and non-ionic dispersants, polymeric retention aids and mixtures of these materials. More recently, water soluble zirconium salt complexes and organotitaniu chemicals have been suggested as pitch control agents.
• Papermakers alum (A12(SO4)3-14H20) , liquid sodium aluminate (20-25.5% A1203) and polyaluminium chloride are the primary alumina sources used for pitch control. Above pH 3 hydrolysis of the salts occur and a variety of hydroxy-aluminium complexes are formed depending upon the hydroxide ion concentration. Hydroxyl bridging occurs forming dimers and higher order polymer species (ligands) . The formation of these desirable short chain relatively low molecular weight polymer species is primarily influenced by the system pH, temperature (the higher the better) , the
• ⁇ * pH is preferably around 4.5 although in practice an operating range of 4.0-5.5 is fairly typiccal.
• pitch control with aluminium salts is a combination of a flocculation mechanism, where the pitch particles are entrapped by the polymeric aluminostructure, and the formation of a cationic complex with the resin and fatty acid components of the pitch, which in turn is then adsorbed onto the pulp fibres.
• a sodium aluminate/alum combination is generally preferred because there is no need for caustic soda to be used to control pH, it minimises sulphate ion build up in closed white water systems and it limits iron contamination thus making it easier to meet brightness specifications.
• Typical consumption figures are: alum 5-25 Kg/tonne and 45% sodium aluminate 5-10 Kg/tonne.
• Ultrafine talc with a surface area of from 10 to 15m 2/gm has been used for pitch control in pulp paper mills and in particular in those mills that are processing Kraft or sulphite pulps, i.e. where the pitch is present in a partially saponified state.
• the dispersed pitch particles are adsorbed on to the hydrophobic talc platelets and then retained in the paper.
• a use rate of 10-40 Kg/tonne is required.
• a wide range of surfactants and short chain polymeric dispersants have been used to maintain pitch in a dispersed state within the paper making circuit. These dispersants function by charge and/or steric hinderance mechanisms.
• Anionic dispersants such as lignin sulphonates,
• SHEET polynaphthalene sulphonates and polyacrylates increase the electronegative charge on the pitch particles, i.e. they peptize the pitch particles and inhibit agglomeration.
• Nonionic surfactants result in steric repulsion of the pitch and depending on the type and concentration can soften and emulsify pitch deposits already formed. Since dispersants do not attach the pitch to the pulp fibres, they have limited use in controlling severe pitch problems such as is generated in TMP mills. An excess of dispersant can result in a substantial build up in the concentration of pitch in closed white water systems. Usage rates for pitch dispersants are typically in the range of 5-100 ppm on the stock.
• polyquaternary ammonium polymers for pitch control has been promoted in recent years. The control mechanism is described by T Hassler, Tappi Journal, June 1988, p 195 onwards.
• the low molecular weight cationic polymers which are commercially available are believed to be linear and/or partially crosslinked polydiallyldimethyl ammonium chloride (polyDADMAC) and copolymers of epichlorohydrin and short chain aliphatic secondary amines. A typical use rate would be from 1.25- 2.3 Kg/tonne.
• JS-A- 4964955 which comprises (1) adding to a pitch-containing furnish a particulate composite substance at comprising (a) a water soluble cationic polymer adsorbed onto (b) an essentially water insoluble particulate substrate carrying an anionic charge, and (2) adsorbing pitch onto said composite to form discrete, finely dispersed pitch-containg aggregates in the furnish.
• any essentially water-insoluble particulate organic or inorganic substance may be employed as the substrate, including phyllosilicate minerals, kaolin, talc, mica, montmorillonite, chlorite and pseudolayer silicates, though Kaolin is particularly preferred.
• SUBSTITUTE SHEET Japanese patent application No 62-245908 discloses a method for reinforcing paper strength by adding bentonite to a pulp after a cationic paper strength reinforcing agent has been mixed in the pulp. It is noted in the patent application that the process, apart from improving the paper strength, also solves pitch troubles. It is disclosed in Example 1 and Example 2 that a minimum of 10 Kg/tonne (1% relative to pulp) of bentonite was added to a pulp which had been previously treated with reinforcing agent and alum. Whilst this method appears suitable for improving paper strength, retention and pitch problems, as a method for controlling pitch alone, this process would tend to be uneconomic.
• a method for the control of pitch in a pulp comprises sequentially adding to and mixing with the pulp (1) 1-10 Kg/tonne of pulp dry solids of a low molecular weight, high cationic charge, polymeric, water-soluble species and (2) 0.5- ⁇ 1 0 Kg/tonne of pulp dry solids of montmorillonite clay particles, which clay particles do not have a water-soluble cationic polymer adsorbed thereon.
• the low molecular weight, high cationic charge, polymeric, watersoluble species may be organic but is preferably inorganic and is
• SUBSTIT preferably present in an amount of 2 to 6 Kg/Tonne of pulp.
• the polymeric species has a low molecular » weight, preferably below lmillion and more preferably below 0.5 million. ft If an organic species is used, it is preferably a polymer of the type disclosed on column 9, line 50, to column 10, line 34, of US-A- 4964955.
• the polymer preferably has a cationic charge density of at least 5 m.eq/gm, preferably a charge density of from 6 to 7 m.eq./g or more.
• the polymer is not a Mannich polymer.
• an inorganic species is used, it is preferably papermakers alum, sodium aluminate, poly aluminium chloride, poly aluminium silicate or an other inorganic water soluble salt of aluminium.
• sodium aluminate is used in the present invention.
• Montmorillonite clays are distinguished by their ability to be water swellable. Synthetic water swellable clays, such as Laponite (Laporte Industries Limited) , are understood to have similar properties to montmorillonite clays and are therefore included within the scope of the present invention. Bentonite is the preferred montmorillonite. Preferably, the amount of montmorillonite added to the pulp is from about 1 Kg/Tonne to less than 10 Kg/Tonne, more preferably from about 2 Kg/Tonne to about 5 Kg/Tonne.
• SUBSTITUTE SHEET substantially to alkali (e.g. sodium, potassium or ammonium) bentonite, or a bentonite in intimate association with a water soluble, highly charged anionic polymer, e.g. Lapotain available from Laporte Industries Limited.
• alkali e.g. sodium, potassium or ammonium
• a bentonite in intimate association with a water soluble, highly charged anionic polymer, e.g. Lapotain available from Laporte Industries Limited.
• the thick stock samples taken from either the refiner or the latency stock chest, were diluted and aged at 180°F with tap water processed through a laboratory scale disintegrator and adjusted to 1 % consistency.
• Pulp stock samples (after treatment) are sieved through a 60 mesh screen, the resulting low solids solution is placed in 50 ml or 100 ml centrifuge tubes and spun for 30 mins at 40OOrpm.
• PROSET 2830 ⁇ 2Kg/t PROSET 2830 @ lKg/t
• PROSET 1820 is an epichlorohydrindimethylamine polymer available from Vinings Industries Inc.
• POLYMIN SK is a polyamidoamine available from BASF
• SCPX 572 is a high swelling bentonite clay available from Southern Clay Products
• Fulgel 300/2 is an anionically modified bentonite available from Laporte Industries Limited
• PAC polyaluminium chloride
• PROSET 2830 is an epichlorohydrindimethylamine crosslinked with a shori chain aliphatic amine available from Vinings Industries Inc
• GADORGEL is a high swelling bentonite clay available from Laporte Industries Ltd.
• FULGEL 300 id a high swelling bentonite clay available from Laporte Industries Ltd
• SCPX 590 is a high swelling bentonite clay available from Southern Clay Products
• SCPX 592 Is a high swelling bentonite clay modified with a low molecular weight anionic polymer available from Southern Clay Products
• SCPX 590/2 is a bentonite clay modified with anionic polymer available from Southern Clay Products
• SCPX 592/2 is a bentonite clay modified with an anionic polymer available from Southern Clay Products
• ACCOFLOC HCX is an hectorite clay available from American Colloids Inc.

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• Paper (AREA)
• Working-Up Tar And Pitch (AREA)

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Publications (2)

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• 1991
  • 1991-12-21 GB GB919127173A patent/GB9127173D0/en active Pending
• 1992
  • 1992-12-15 BR BR9206974A patent/BR9206974A/pt not_active IP Right Cessation
  • 1992-12-15 EP EP9393900173A patent/EP0617749A4/en not_active Withdrawn
  • 1992-12-15 FI FI942954A patent/FI942954A7/fi unknown
  • 1992-12-15 WO PCT/US1992/010835 patent/WO1993013265A1/en not_active Application Discontinuation
  • 1992-12-15 CA CA002126347A patent/CA2126347A1/en not_active Abandoned
  • 1992-12-15 JP JP5511729A patent/JPH07506150A/ja active Pending
  • 1992-12-15 AU AU32504/93A patent/AU657389B2/en not_active Ceased
  • 1992-12-21 ZA ZA929910A patent/ZA929910B/xx unknown
• 1994
  • 1994-06-20 NO NO942353A patent/NO942353L/no unknown

Patent Citations (1)

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