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
• • 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
  • D21H17/20—Macromolecular organic compounds
  • D21H17/33—Synthetic macromolecular compounds
• • 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
  • D21H17/20—Macromolecular organic compounds
  • D21H17/33—Synthetic macromolecular compounds
  • D21H17/34—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H17/36—Polyalkenyalcohols; Polyalkenylethers; Polyalkenylesters
• • 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
  • D21H17/20—Macromolecular organic compounds
  • D21H17/33—Synthetic macromolecular compounds
  • D21H17/34—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H17/37—Polymers of unsaturated acids or derivatives thereof, e.g. polyacrylates
• • 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
  • D21H17/20—Macromolecular organic compounds
  • D21H17/33—Synthetic macromolecular compounds
  • D21H17/34—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H17/41—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds containing ionic groups
  • D21H17/42—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds containing ionic groups anionic
• • 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
  • D21H17/20—Macromolecular organic compounds
  • D21H17/33—Synthetic macromolecular compounds
  • D21H17/46—Synthetic macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H17/47—Condensation polymers of aldehydes or ketones
• • 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
  • D21H23/22—Addition to the formed paper
  • D21H23/50—Spraying or projecting

Definitions

• the invention relates to a method for controlling deposit formation on calender rolls of a paper machine.
• a papermaking process starts with stock preparation where cellulosic fibers are mixed with water and mineral filler (usually clay or calcium carbonate).
• the obtained slurry is delivered by means of a head box on a forming fabric or press fabric or wire to form a fibrous web of cellulosic fibers at the forming section of the paper machine.
• water is drained in the draining section and the formed web is conducted to the press section including a series of roll presses where additional water is removed.
• the web is then conducted to the drying section of the paper machine where most of the remaining water is evaporated typically by means of steam-heated dryer drums.
• Post drying operations include calendering where the dry paper product passes between rolls under pressure, thereby improving the surface smoothness and gloss and making the caliper/thickness profile more uniform.
• calenders such as machine calanders where the rolls usually are steel rolls and include a heated roll (thermo roll), and supercalenders that use alternate hard and soft, heated rolls.
• pitch can accumulate in papermaking causing problems.
• "Pitch” is a term originally used to describe sticky materials which appear in paper making and originate from the wood raw material. However, nowadays the term “pitch” also includes for example ink and adhesive present in recycled paper. The term “stickies” is also used for such subtances.
• the pitch can deposit at various points in the paper making system. It can block fabrics and thus prevent drainage of the web. It can also adhere to the wires and/or dryer drums causing holes in the paper. Additionally it can deposit on press rolls or other rolls which come into direct or indirect contact with the paper material.
• EP 0 493 066 A discloses a method for the control of pitch in pulp or paper making which method comprises applying to the pulp or paper making equipment which is not in continuous contact with water a water soluble cationic polymer and a water soluble anionic polymer. These two polymers are applied separately. It is claimed that by using this combination of cationic and anionic polymers it is possible to obtain a coating on the pick up felt, paper forming wire, press roll and dandy roll which prevents pitch from adhering to them.
• the cationic polymer can be polyethylene imine or a protonated or quaternary ammonium polymer.
• the cationic polymer is derived from an amine and an epihalohydrin or a dicyandiamide formaldehyde condensate.
• the anionic polymer can be a sulphonate or carboxylate.
• a preferred anionic polymer is lignin sulphonate or polynaphtalene sulphonate.
• WO 2005/094403 A discloses a paper machine belt conditioning apparatus and method.
• a continuously rotating belt on which a fibrous web travels is sprayed with a conditioning chemical.
• conditioning chemicals including various surfactants, solvents, acid-based cleaners and alkaline cleaners.
• the apparatus may also include a doctor blade.
• WO 97/15646 A discloses a release agent for rolls, such as press rolls in papermaking.
• the release agent prevents the formation of deposits on the surface of the rolls.
• the release agent is in the form of a microemulsion which preferably comprises a deposit preventing component. This component is preferably a dicyandiamide formaldehyde condensate.
• US 5 256 254 discloses decreasing deposition of undesirable materials in the dryer section of a paper machine through application of a phosphate ester or a taurine.
• the phosphate ester or taurine may be added to the surface of the paper web via an aqueous spray.
• the invention relates generally to controlling deposit formation on paper machine rolls by spraying a chemical onto the surface of the paper.
• the chemical moves with the paper to the rolls protecting the same from collecting sticky material from the paper.
• anionic polymers when sprayed in a small amount in the form of a diluted aqueous solution on the surface of the paper, worked perfectly well preventing deposit formation on the rolls. At the same time paper dusting and linting were significantly reduced.
• a method for controlling deposit formation on calender rolls of a paper machine comprising applying at the dry end of a paper machine where the dry paper product passes between calender rolls under pressure an aqueous solution of an anionic polymer which comprises lignosulphonates, condensed naphthalene sulphonates or polymers comprising repeating units of sulphonic acids or salts of sulphonic acids and/or mixtures thereof on the surface of the paper for preventing the rolls from being contaminated by stickies and/or other depositable material from the paper.
• an anionic polymer which comprises lignosulphonates, condensed naphthalene sulphonates or polymers comprising repeating units of sulphonic acids or salts of sulphonic acids and/or mixtures thereof
• Paper machine is in this specification meant of include paper machines having an on-line calender or an off-line calender. In the latter case the calender is separate from the actual paper machine.
• the paper machines also include board machines.
• Said paper machine rolls include calender rolls and dryer rolls.
• the paper machine rolls are calender rolls, and more preferable thermo rolls of calenders, especially of supercalenders.
• the surface temperature of thermo rolls is typically at least 100°C.
• the anionic polymer used in the present invention is preferably not derived from natural products such as starch, cellulose or saccharides.
• the anionic polymers should be soluble in water.
• Suitable anionic polymers useful in the present invention include:
• Condensation products of aromatic sulphonic acids with formalin such as condensed naphtalene sulphonates.
• Dispersing anionic polymers and copolymers polymerized from anionic monomers, or charged to give an anionic form after polymerization.
• Said polymers comprise repeating units with anionic charges such as carboxylic acids, salts of carboxylic acids, sulphonic acids, salts of sulphonic acids, and/or mixtures thereof.
• Anionic copolymers may be produced by copolymerizing an anionic monomer with another anionic comonomer, an uncharged comonomer and/or a cationic comonomer.
• Anionic monomers may typically include acrylic acid, methacrylic acid, vinyl sulphonate, 2-acrylamide-2-methylpropanesulphonic acid, styrenesulphonic acid, or salts thereof and other corresponding monomers.
• Polymers charged to give an anionic form only after polymerization include hydrolyzed polyacrylamides and polymers produced from maleic anhydride.
• Anionic polymers may also contain different types of charged repeating units such as phosphates, like ethyleneglycol methacrylatephosphate, or phosphonic acids or salts thereof, like vinylphosphonic acid.
• phosphates like ethyleneglycol methacrylatephosphate
• phosphonic acids or salts thereof like vinylphosphonic acid.
• anionic polymers As examples of the anionic polymers described above following may be mentioned:
• the above mentioned salts of the polymers or monomers are preferably alkali metal salts, such as sodium or potassium, or alkaline earth metal salts, such as calcium or magnesium.
• a preferred anionic polymer comprises a condensation product of an aromatic sulphonic acid with formaldehyde such as naphtalenesulphonate formaldehyde condensate.
• the aqueous solution of the anionic polymer is applied in an amount preferably ranging from 0.001 to 0.5 gram per m 2 of the surface of the paper per side of the paper calculated as active substance. A more preferred amount ranges from 0.001 to 0.3 gram per m 2 , and a still more preferred amount ranges from 0.01 to 0.03 gram per m 2 of the surface of the paper calculated as active substance.
• the concentration of the aqueous solution of the anionic polymer is preferably from 0.01 to 20 % by weight, more preferably from 0.1 to 5 % by weight.
• the aqueous solution of the anionic polymer can be applied on one or both sides of the paper.
• the applying is preferably made by spraying.
• the paper to be calendered is normally moistured and some paper machines are equipped with a moistering shower or showers downstreams of the calender rolls. As disclosed here the aqueous solution of the anionic polymer is sprayed by means of said moisturing shower or showers.
• the aqueous solution of the anionic polymer can be applied on the web to be dried by per se known means, such as by spraying.
• the base paper was of mixture of peroxide-bleached thermo-mechanical pulp and bleached chemical pulp, the pase paper having 51 g/m 2 .
• the filler was kaolin and ground calcium carbonate and the content thereof was 33-34 %.
• the deposit formation on the first thermo roll was inspected.
• Example 3 A dicarboxylic ester in the form of an emulsion (reference)
• This product was diluted to a 2 % solution of the commercial product and on the surface of the paper.
• this product resulted in a clearly thinner yellowish, mat layer which was just detectable.
• the deposit was not formed as bands on the roll but was smooth in the cross direction. This product did not have any effect on dusting.
• This anionic polymer (CAS 36290-04-7) is a chemical which is typically used at the wet end of paper machines for pitch control.
• aqueous 30 % solution of this anionic polymer was diluted to give a 0.3 % aqueous solution (as active substance).
• This solution was sprayed on the surface of the paper as described above in the amount of 6.5 g/m 2 .
• the amount of the anionic polymer on the paper surface was about 0.02 g/m 2 calculated as active substance.
• This anionic polymer resulted in that no deposition at all was formed on the roll.
• the surface of the roll remained clear and glossy. Also the dusting was clearly reduced.
• An aqueous 30 % solution of this cationic polymer was diluted to give a 0.6 % aqueous solution (as active substance), and sprayed on the surface of the paper.
• This cationic polymer resulted in a thin smooth, mat layer over the whole thermo roll. Additionally, the precipitation was accumulated as one narrow ( ⁇ 1.0 cm) yellowish white band. The band was thin and could be removed by the doctor blade. As compared to Examples 2, 3 and 4, the dusting was clearly stronger.
• Example 4 representing the present invention worked perfectly well, whereas Examples 2, 3 and 5 were not satisfactory.

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• 2007
  • 2007-10-01 FI FI20070746A patent/FI121938B3/fi active IP Right Grant
• 2008
  • 2008-09-30 EP EP08805466.3A patent/EP2195487B1/en not_active Not-in-force
  • 2008-09-30 CN CN200880110009A patent/CN101815822A/zh active Pending
  • 2008-09-30 WO PCT/FI2008/050544 patent/WO2009043971A1/en active Application Filing
  • 2008-09-30 US US12/680,788 patent/US20110011546A1/en not_active Abandoned
  • 2008-09-30 CA CA2700412A patent/CA2700412A1/en not_active Abandoned

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