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
  • 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
• • 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
  • D21H17/21—Macromolecular organic compounds of natural origin; Derivatives thereof
  • D21H17/24—Polysaccharides
  • D21H17/25—Cellulose
• • 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
  • D21H17/21—Macromolecular organic compounds of natural origin; Derivatives thereof
  • D21H17/24—Polysaccharides
  • D21H17/28—Starch
• • 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
  • D21H17/63—Inorganic compounds
  • D21H17/67—Water-insoluble compounds, e.g. fillers, pigments
  • D21H17/675—Oxides, hydroxides or carbonates
• • 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
  • D21H21/14—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 characterised by function or properties in or on the paper
  • D21H21/18—Reinforcing agents
  • D21H21/20—Wet strength agents
• • 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

• the present invention relates to a method according to the preamble of claim 1 for producing a fibrous web on a paper or board machine.
• the fibrous web is formed from an aqueous furnish containing lignocellulosic fibres, mainly derived from a deciduous tree species, along with fillers and conventional additives, if any.
• the present invention also concerns a method according to the preamble of claim 26 of producing a polyelectrolyte complex as well as novel paper and board products according to the preamble of claim 29.
• mineral fillers are incorporated into most printing papers and board products in order to improve opacity, to save fibres and improve printing results.
• the fibres Prior to papermaking the fibres are conventionally beaten to enhance bonding and strength properties. Fibre straightening, internal and external fibrillation and fines generation contribute to improved bonding between the fibres. However, the beating process is energy consuming, gives inefficient fibre treatment and is fibre length cutting.
• various polymeric materials can be added to the furnish for modifying the properties of the fibres, e.g. for fibre sizing. It is also known in the art to use both cationic and anionic polymers.
• JP Patent Application No. 2004250803 (Japan Maize Prod.), titled “Method for producing amphoteric starch polyion complex and method for producing paper", discloses a preproduced complex for improving drainage properties (measured as Schopper-Riegler or Standard Canadian Freeness) and filler retention.
• the conventional way of improving (internal) bonding of fine papers is to increase beating and refining as explained above.
• papers such as uncoated fine papers
• fibrous products of the above kind having good mechanical properties, such as a combination of improved bonding strength and bending stiffness, at a high bulk, said fibres being subjected to a minimum or no beating before papermaking.
• the present invention is based on the finding that by treating the fibres with a preformed polyelectrolyte complex before papermaking, the properties of the paper can be improved at higher filler contents and higher short fibre contents can be reached.
• a polyelectrolyte complex for example to unbeaten pulp it is possible to improve both bulk and strength properties (bending stiffness, Scott Bond and tensile strength).
• high light scattering is also maintained with the treatment of unbeaten pulp with a polyelectrolyte complex. As a result strong sheets can be obtained without loss of light scattering.
• the method of producing a polyelectrolyte complex formed by a cationic polymer and an anionic polymer comprises typically the step of mixing together, under turbulent mixing conditions, a first liquid flow (Q 1 ) containing the anionic polymer and a second liquid flow (Q 2 ) containing the anionic polymer, the turbulent mixing conditions being obtained by converging, at predetermined flow rates, the liquid flows to form integral or combined flow containing the mixed polymers at predetermined ratios.
• the present invention provides a fibrous product which comprises a fibrous matrix containing at least 50 % of fibres derived from deciduous tree, and further containing about 0.05 to 5.0 % of a polyelectrolyte complex, the amount being calculated on the dry weight of the paper (board).
• the method according to the present invention of producing fibrous webs is mainly characterized by what is stated in the characterizing part of claim 1.
• the method of producing the polyelectrolyte complex is characterized by what is stated in the characterizing part of claim 26, and the fibrous product according to the present invention is characterized by what is stated in the characterizing part of claim 29.
• the present invention can also be used to reduce the grammage of the paper without loosing strength and optical properties, which gives economical benefits. Stock sizing is also improved.
• a polyelectrolyte complex (PEC) treatment of fibres of the present kind can be utilised for improvement of fibre and paper properties combined with reduced energy consumption for refining.
• Increase of filler content, improvement of formation, improvement of printing properties and reduced grammage are additional benefits.
• PEC can be tailored to contain either a negative or a positive net charge. Good effects on retention have been observed with cationic PEC treatment, which of those being most interesting to implement is product/mill specific.
• the present invention provides a method of producing a fibrous web on a paper or cardboard machine from an aqueous furnish containing fibres mainly derived from a deciduous tree species. All normal hardwoods (and softwoods) are suitable for use in the present method and will give similar results. Most interesting wood qualities for the production of hardwood-based papers are birch, beech, aspen, poplar, oak and eucalyptus.
• the deciduous fibres material can comprise fibres from one single wood species or a mixture of several.
• softwood fibres can be incorporated into the furnish.
• the softwood fibres are normally used for improving strength properties.
• fibres of pine (trees of the Pinus family) or spruce (trees of the Picea family) are used.
• the fibre composition comprises 40 to 100 % hardwood fibres and 60 to 0 % of softwood fibres.
• At least 50 %, preferably at least 60 %, by weight of the fibres are formed by fibres of a deciduous wood species.
• 60 to 100 %, preferably 80 to 100 %, by weight of the fibres are comprised of deciduous wood fibres.
• the actual fibre composition will be selected depending on optical and mechanical properties of the paper product.
• the fibres can be produced by mechanical, chemimechanical or chemical pulping.
• Groundwood, pressure groundwood, thermomechanical and chemi thermomechanical pulping are examples of suitable mechanical pulping methods.
• the chemical pulp can be produced by kraft, soda, sulphite or organosolv pulping.
• the furnish typically contains particulate fillers.
• various clay and calcium carbonate grades including ground calcium carbonate and precipitated calcium carbonate.
• These fillers can be incorporated freely in amounts up to about 40 %, based on the total dry weight of the paper/board, although 5 to 35, and in particular about 8 to 30 % are conventional and about 20 % is typical.
• the present invention allows for an increase of the filler content from about 20 to about 30 without impairing strength properties of the web, which is a surprising and rather valuable result.
• the furnish may also contain other conventional additives, such as sizing agents and retention agents, including AKD or ASA resins, rosins and ionic and polymeric retention agents.
• additives such as sizing agents and retention agents, including AKD or ASA resins, rosins and ionic and polymeric retention agents.
• Many of the additives in the paper furnish serve to ensure that the fibers have the required properties to attract and bond.
• the amount of such additives does not exceed 5 % by the dry weight of the paper/board, typically the amount is in the range of about 0.1 to 4 % by weight.
• the components of the furnish are fed to the wet end of the paper machine at a consistency (of fibres) of about 0.2 to 2 % in the aqueous phase, in particular about 1 %.
• the fibres are modified by contacting them with a polyelectrolyte complex.
• the modification step comprises typically admixing, continuously or intermittently, the fibres of the furnish with a polyelectrolyte complex before adding fillers and any additives.
• the mixing and contacting time can amount to about 1 second to about 24 hours, typically some 10 seconds to 5 hours is sufficient and times in the range of about 1 minute to about 1 hour are preferred.
• the pH is in the range of 4 to 9, preferably 5 to 8, the temperature in the range of 10 to 65 °C and the pulp consistency from 0.1 to 5 %, preferably 2 to 4 %.
• the polyelectrolyte complex (in the following also abbreviated PEC) is preformed and added as such (cf. below).
• the fibres can be treated with a polymer having a net charge.
• a portion of one of the components of the complex is used for improving attachment.
• the pre-treatment step is preferably carried out separately from the admixing with the PEC.
• the treatment is carried out with a cationic polymer.
• a cationic polymer typically, the same polymer that is used as a cationic component of the complex is also employed for the pre-treatment, although it is possible to pre-treat the fibres with a first cationic component and to use a second for forming the complex.
• the total amount of cationic polymer employed during the treatment about 10 to 95 % by weight of the polymer, preferably 20 to 90 % by weight and in particular about 20 to 60 % by weight is separately attached to the fibrous material in a pre-treatment step.
• the affinity of the polyelectrolyte complexes for fibres is increased, in particular when the polyelectrolyte complex has a negative net charge.
• a cationic polymer By treating the fibres with a cationic polymer, attachment of negatively charged polyelectrolyte complexes to the fibre surface is facilitated.
• cationic polyelectrolyte complexes pre-treatment is generally not needed.
• the pre-treatment increases the effects of the PEC. It would appear that the cationic polymer, such as polyamideamine epichlorhydrine (PAE) or other polyamine-derived polymers, which have a tertiary or quaternary amine functionality, enable increased attachment of PEC to the fibres.
• PAE polyamideamine epichlorhydrine
• the modification step comprises two stages, whereby in the first step, the fibres are treated with a cationic polymer component and in the second the thus obtained fibres are contacted with the preformed complex, in particular with a complex which has a predominantly anionic net charge.
• the contacting times can be of equal length in both stages and as explained above.
• the invention comprises three interesting embodiments with regards to the degree of beating of the fibres which are to be treated.
• the fibrous web is produced from fibres which have not been subjected to beating before web formation. This embodiment will save considerable amounts of energy.
• the fibrous web is produced from fibres, which have been subjected only to a moderate degree of beating amounting to less than 50 kWh/ton of fibrous material. This embodiment will provide for a reduction in beating energy and improved bonding.
• the fibres which are used for producing the web are subjected to beating energy input in excess of 50 kWh/ton and up to 400 kWh/ton of fibrous material. Improved bonding will be achieved.
• the degree of refining for the fibres is low, preferable so low that only fibre bundles are clearly separated from each other.
• the energy consumption of beating or refining can be reduced to less than 50 kWh/ton of dry fibres, preferably to between 20-50 kWh.
• the refining degree is, as a Schopper-Riegler (SR) number, maximally about 20 to 21 SR or less, and as CSF (Canadian Standard Freeness) between 700 and 500 ml. It is possible to use completely unbeaten fibres as part of the furnish for papermaking. As a result of the preferred embodiments of using either unbeaten or only moderately beaten fibres, drainage of the fibrous web on the paper machine is improved, which facilitates production at higher machine speeds.
• SR Schopper-Riegler
• the polyelectrolyte complex used in the present invention is a complex formed by a cationic polymer and an anionic polymer.
• the polyelectrolyte complex typically is charged, and in particular it has a negative net charge, but it can also have a positive net charge.
• the cationic polymers can be selected, for example, from the group consisting of:
• cationic polymer is formed by polyamide derivatives with tertiary and quaternary amine functionality.
• Another type of cationic polymer is formed by carbohydrate polymers, such as cationized starch.
• the anionic polymer is, for example, derived from a carbohydrate polymer having a negative net charge. Examples of such polymers are anionic cellulose derivatives, hemicellulose derivatives, starches and mixtures thereof.
• Synthetic anionic polymers may include polyacrylic acid, polymethacrylic acid, polyvinylamine, and polymers containing carboxyl groups, primary and secondary amine functionalities as well as mixtures of two or more of the aforementioned polymers.
• the polyelectrolyte complex comprises polyamide amine epichlorhydrine (PAE) or cationized starch and carboxymethyl cellulose (CMC) or a similar cellulose derivative.
• PAE polyamide amine epichlorhydrine
• CMC carboxymethyl cellulose
• the PEC can be made by adding a polyamide amine epichlohydrine resin (PAE) to carboxymethyl cellulose (CMC) having a degree of substitution between 0.4 and 1.3 and preferably forming that PEC in water.
• PAE polyamide amine epichlohydrine resin
• CMC carboxymethyl cellulose
• molar ratios of PAE to CMC of about 1:1 to 1:5 can be used. But preferably, a proportion based on charge density is used.
• the charge ratio (meq/g of cationic polymer/meq/g of anionic polymer as absolute value) most often used is in the range of 0.3 to 1.5.
• the components of the PEC it is preferred to contact the components of the PEC at turbulent conditions, e.g., under intensive agitation by dynamic or static mixers.
• the turbulence can be generated by utilizing the velocity differences of two feeds flowing at different flow rates.
• the contacting can be carried out in a continuous operation or batch-wise or semibatch-wise, although continuous or semibatch operation is preferred.
• polymer complexes are prepared in a mixing chamber by combining two converging flows, one with the cationic component and one with the anionic component, at predetermined flow rates.
• the flow rate of one component, Q 1 is greater than that of the other component, Q 2 .
• the anionic or the cationic component should have a greater flow rate - if the complex should be anionic, then the anionic component should have a greater flow rate and vice versa.
• the ratio Q 1 to Q 2 can vary in the range of approximately 1 to 50, although a ratio of about 2 to 20 and in particular about 6 to 10 has been found satisfactory. Experiments have been carried out with a ratio of about 8.
• the converging flow streams can be accomplished by injecting the flow of one component into another.
• the cationic component flowing at a smaller flow rate, is injected into the flow of the anionic component, and vice versa for a cationic complex.
• the flows are concurrent or at least essentially concurrent.
• the two components are combined by arranging the feed conduits of the components inside each other.
• the feed conduit of a first component can be arranged inside the feed conduit of a second component with the feed nozzle of the first component opening into the feed conduit of the second component.
• the first component at a lower flow rate, is fed or injected into the flow of the second component. It is also possible to have several injection points for the first component arranged inside the feed conduit of the second component.
• the feeds can be recirculated by recovering the flow of the second component after the addition of the first component and then recycle that flow for injection of more of the first component until the desired ratio between the two components is reached.
• a continuous or semicontinuous (semibatch) operation is achieved.
• the above arrangement allows for cost efficient, on-site production of PEC.
• the described operation mode which is not the only way to produce the complex, the storage volumes can be reduced and there is no greater risk for PEC deterioration. But other configurations aside from the one described above, are possible in producing polylectrolyte complexes in a large scale.
• the PEC should have a net charge.
• the net anionic charge is preferably at least -0.1 meq/g, typically about -0.4 to -4.0 meq/g .
• the net cationic charge is preferably at least 0.1 meq/g, typically about 0.4 to 4.0 meq/g.
• Cryoscopic transmission electron microscopy images of PEC show a size range of 1-500 nm in diameter.
• the effect of the PEC is found already at 0.01 % of paper dry weight and amounts in excess of 10 wt-% do not significantly further improve any property. Normally the best addition amount is found to be 0.05 to 5 wt-% based on paper dry weight.
• a filler in an amount of 1 to 50 wt-% based on dry paper/board weight, preferably about 5 to 40 wt-%, in particular about 20 to 30 wt-%, and other paper chemicals are added to the pulp slurry, which is then fed to the paper machine.
• the present invention provides considerable advantages as was explained above. To reiterate briefly, it allows for - with maintained or even improved mechanical and optical properties - one or several of the following improvements:
• One particularly interesting aspect of the invention is that it, at a given light scattering, is possible to get a stronger and stiffer sheet compared to by beating.
• the invention is particularly well suited for the production of generally any kind of paper and board, e.g. printing and graphic papers and cartoon boards.
• suitable paper qualities include any kind of coated and uncoated wood free and wood containing papers.
• PAE was charged, in an amount of 2.0 wt-% based on total dry weight of paper, to a pulp slurry at 3 % pulp consistency.
• the pulp slurry consisting of 80 % bleached birch kraft pulp (refined to 20 SR) and 20 % bleached softwood kraft pulp (refined to 24 SR).
• 2.0 wt- % of the complex PAE+CMC (PEC) was added and the slurry was stirred vigorously.
• the filler (20 and 28 wt-% PCC), 0.2 % stock starch, 0.16 % ASA-size and retention aids (consisting of polyacrylamide and bentonite) were added and the slurry was fed to a small laboratory paper machine and an 80 g/m 2 paper was made. The strength properties were compared with a paper from a non-pretreated pulp furnish.
• Table 1 The results are shown in Table 1 below: Table 1: 80/20 Birch kraft pulp/Softwood kraft pulp. Birch pulp refined to 20 SR and the softwood pulp to 24 SR.
• the pretreatment procedure can also be used to significantly improve the strength properties at the lower filler level. This feature is evident from a comparison of Trials 1.1 and 1.2.
• PAE was charged, in an amount of 2.0 wt-% based on total dry weight of paper to a pulp slurry at 3 % pulp consistency.
• the pulp slurry consisting of 80 wt-% birch kraft pulp and to a second slurry consisting of 100 wt-% birch kraft pulp.
• the birch pulp was bleached kraft pulp refined to 20 SR.
• the first slurry contained 20 wt-% (and the second 0 %) bleached softwood kraft pulp refined to 24 SR.
• 2.0 wt-% of the complex PAE+CMC (PEC) was added and the slurry was stirred vigorously.
• the filler (20 % PCC) and conventional additives comprising 0.2 % stock starch, 0.16 % ASA-size and retention aids (consisting of polyacrylamide and bentonite) were added and the slurry was fed to a small laboratory paper machine and an 80 g/m 2 paper was made.
• Table 2 The strength properties of the papers made from PEC treated fibres were compared with a paper from an untreated furnish, and the results appear from Table 2: Table 2: 80 and 100 % birch kraft pulp/20 and 0 % softwood kraft pulp. The birch pulp refined to 20 SR and the softwood pulp to 24 SR. 20 % PCC.
• the filler (20 % PCC), 0.2 % stock starch, 0.16% ASA-size and retention aids (consisting of polyacrylamide and bentonite) were added and the slurry was fed to a small laboratory paper machine and a paper having the grammage 80 g/m 2 was made.
• PAE was charged, in an amount of 0.5-2.0 wt-% based on dry weight of paper, to a pulp slurry at 3 % pulp consistency.
• the pulp slurry consisting of 70 % bleached mixed hardwood pulp (refined to 22 SR) and 30 % bleached softwood kraft pulp (refined to 24 SR).
• 0.5-2.0 wt-% of the anionic complex PEC:A1-3 PAE+CMC was added and the slurry was stirred vigorously. After further 5-30 minutes 25 % PCC, AKD sizing and retention agents were added.
• the cationic complex PEC:C1-3 (cationic starch DS 0.17+CMC) was added, without pre-treatment, in an amount of 0.5-2.0 wt-% based on dry weight of paper. Filler, sizing and retention agents were added in the same way as with PEC:A1-3. Except for trial PEC:C2*, where no retention agents were added.
• the slurry was fed to a small laboratory paper machine and 80 g/m 2 paper was made. The strength properties were compared with a non-pretreated reference. The results are shown in Table 4 below: Table 4: Anionic PEC:A1-3 (PAE+CMC) and cationic PEC:C1-3 (cationic starch+CMC) complexes. 70/30 Mixed hardwood/softwood kraft pulp.
• the anionic complex PEC:A gave better strength properties than the cationic complex PEC:C.
• the cationic complex gave, however, higher tear index and Scott Bond than the untreated reference.

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Cited By (17)

Citations (10)

• 2006
  • 2006-10-31 EP EP06396017A patent/EP1918455A1/de not_active Withdrawn
• 2007
  • 2007-10-29 RU RU2007139692/12A patent/RU2007139692A/ru not_active Application Discontinuation

Patent Citations (10)

Non-Patent Citations (1)

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