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
  • D21H17/21—Macromolecular organic compounds of natural origin; Derivatives thereof
  • D21H17/24—Polysaccharides
• • 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
  • D21H17/69—Water-insoluble compounds, e.g. fillers, pigments modified, e.g. by association with other compositions prior to incorporation in the pulp or paper
• • 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
  • D21H19/00—Coated paper; Coating material
  • D21H19/36—Coatings with pigments
  • D21H19/38—Coatings with pigments characterised by the pigments
  • D21H19/42—Coatings with pigments characterised by the pigments at least partly organic
• • 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
• • 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 the use of semi-organic sugar compounds as fillers and coating pigments of paper and board.
• the invention is also directed to a process for producing and coating paper and board.
• the purpose of coating is to endow paper and board with a surface of maximum smoothness and uniformity of quality for improving optical properties and printability.
• the coating consists of pigments e.g. kaolin, ground calcium carbonate (GCC), and talc, and further, a binder such as latex and starch, and may also contain additives such as dispersing agents, agents for pH adjustment, lubricants and microbicides.
• the pigment typically comprises from 80 to 95 %, by weight of the coating, and thus has a particularly great significance for the optical properties of the coating like opacity, brightness and gloss. Brightness is improved by low absorption of light and high light scattering coefficient of the pigment, the latter also improving the opacity. Gloss is influenced among other things by the particle size of the pigment and by a post-coating treatment such as calendering.
• fillers are added to the pulp.
• the amount of the filler depends on the product to be produced, said amount typically ranging between 4 and 10 % in LWC paper and between 15 and 30 % in chemical pulp paper, relative to the weight of the base paper.
• Fillers include e.g. kaolin, calcium carbonate, and titanium dioxide.
• Optical properties and printability of paper and board are also influenced by fillers. Optical properties of paper and board may be improved by increasing both the proportion of pigments in the coating and the amount of fillers in the base paper. This, however, significantly reduces the strength properties and runnability of paper and board.
• Strength properties of paper may also be improved by refining the pulp, and adding fines, which, however, often reduces the opacity.
• Optical properties and bonding strength are some of the most crucial properties of printing papers. Generally in boards and papers, especially in papers for graphical applications, there is a need to improve the strength properties without any adverse effects on the optical properties.
• waste material consisting of e.g. fillers are separated from the fibre material suitable for recycling.
• the waste material thus separated, or waste paper as such may be incinerated for instance for energy production.
• Burning of waste papers containing inorganic mineral pigments for energy production results in great amounts of ash, the disposal of which causes problems.
• Within the European Union aims concerning the proportion of bioenergy in the total energy production to be reached by 2010 are set. To reach these aims, it is also desirable to use as much renewable organic materials as possible in papers and boards.
• inorganic mineral pigments are abrasive, thus accelerating wear of apparatuses. They also increase the weight of paper and board. There is an ever growing need for increasingly lighter papers for magazines, catalogues and the like, furnished, however, with high quality printing properties.
• Organic fillers such as a urea-formaldehyde pigment have been developed, such pigments being, however, expensive and often having poorer optical properties in comparison to mineral pigments, and thus the use thereof is rare.
• Japanese document JP 2003073993 discloses a base paper containg fillers for a wall paper comprising an aqueous emulsion resin, a salt of an alkali or alkaline earth metal of an inorganic acid or carboxylic acid e.g. calcium lactate being used in the coating of said base paper.
• the purpose of the present invention is the elimination of the problems associated with the prior art, or at least the substantial reduction thereof by using in the production of paper and board a filler allowing for a substantial improvement of the strength properties of paper and board in comparison with mineral fillers, while obtaining comparable optical properties.
• the invention is based on the surprising finding that a semi-organic sugar compound may be used as a filler and a coating agent of paper and board.
• the use of said semi-organic sugar compounds has several advantages in comparison with that of fillers and coating pigments of the prior art.
• Critical properties of paper and board particularly strength properties such as bending stiffness, bonding strength and tensile strength may be favourably influenced by said semi-organic sugar compounds, thus also improving the runnability of paper and board, among other things.
• Also concerning optical properties nearly the same level as by using mineral fillers is reached. It is also possible to reduce surface weights of paper and board, and wear of machines by using semi-organic sugar compounds. It is also significant that the use of semi-organic sugar compounds in the production and coating of paper and board allows for the increase of the proportion of renewable organic materials in paper and board, and the improvement of the exploitation of papers and boards removed from recycling process by incineration.
• An object of the invention is the use of semi-organic sugar compounds as fillers and coating pigments of paper and board.
• Another object of the invention is to provide a process for producing paper and board.
• Still another object of the invention is to provide a process for coating paper and board.
• the invention relates to the use of semi-organic sugar compounds in the production of paper and board.
• semi-organic sugar compounds refer to sugar compounds having an inorganic moiety and an organic sugar moiety produced from a base and a sugar by methods known as such, said sugar compounds being poorly soluble or insoluble in water.
• the semi-organic sugar compounds to be used according to the present invention are obtained as reaction products of sugars and bases. Under suitable conditions, the reaction product of these starting materials is poorly soluble or insoluble in water.
• Sugar compounds to be used according to the invention may be produced by e.g. applying the Steffen process used in sugar industry, said process and the apparatus therefor being described e.g. in the document GB 228 741.
• saccharose liquor is treated with calcium oxide giving an insoluble precipitate called saccharate.
• the sugar used in the production of the semi-organic sugar compound to be used according to the invention may be any monosaccharide, disaccharide, oligosaccharide or a mixture thereof.
• the base may be any alkaline earth or alkali metal oxide, or a mixture thereof.
• the semi-organic sugar compound may be used as a filler of paper and board to improve the combination of the strength and optical properties of the product.
• the semi-organic sugar compound may be used as a coating pigment of paper and board.
• the semi- organic sugar compound is added to the pulp in the form of crystals of a sugar compound poorly soluble or insoluble in water, followed by the production of paper in a conventional manner.
• the semi- organic sugar compound in the form of sugar compound crystals poorly soluble or insoluble in water is applied as a slurry or as a mixture with coating aids on a paper or board web by any known method.
• the semi-organic sugar compounds are named after corresponding salts of sugar acids, an example being calcium saccharate.
• the structure of these compounds does not comply with this nomenclature as pointed out e.g. by J. Grabka in his article discussing the chemical structure of calcium saccharates, Etude de Ia structure chimique des saccharates et desar-carbonates de calcium, Industries Alimentaires et Agricoles, vol 110(10) (1993), pages 714 - 719.
• calcium lactate used in the coating of the wall paper base in Japanese patent publication JP 2003073993 refers to a salt of an alkaline earth metal of a carboxylic acid, and not to a semi-organic sugar compound suitable for the present invention.
• Figures Ia and Ib show electron micrographs, respectively as a 120Ox and a 5000x magnification of the wire side surface of the paper sheet prepared according to Example 1, containing tricalcium saccharate as the filler.
• Figures 2a and 2b show electron micrographs, respectively as 1200x magnification of the topside and as 5000x magnification of the wire side surfaces of the paper sheet prepared according to Example 2, containing tricalcium lactate as the filler.
• Figures 3 a and 3b are graphs showing the light scattering coefficients of sheets prepared according to the invention, containing respectively 6 % and 14 %, by weight, of tricalcium saccharate (Ca-SACC) and lactate (Ca-LACT), as a function of tensile strength index (figure 3a), or bonding strength (figure 3b). Sheets containing 6 and 14 %, by weight, of precipitated calcium carbonate (PCC) serve as controls.
• Ca-SACC tricalcium saccharate
• Ca-LACT lactate
• PCC precipitated calcium carbonate
• Figures 4a and 4b are graphs showing the tensile strength indices (figure 4a), or bending stiffness (figure 4b) of sheets prepared according to the invention, containing tricalcium saccharate (Ca-SACC) and lactate (Ca-LACT), as a function of filler content (% by weight). Sheets containing precipitated calcium carbonate (PCC) serve as controls.
• Ca-SACC tricalcium saccharate
• Ca-LACT lactate
• PCC precipitated calcium carbonate
• Figures 5a — 5c are graphs showing the light scattering coefficients (figure 5a), brightness (figure 5b), and opacity (figure 5c) of sheets prepared according to the invention, containing tricalcium saccharate (Ca-SACC) and lactate (Ca-LACT), as a function of filler content (% by weight). Sheets containing precipitated calcium carbonate (PCC) serve as controls.
• Ci-SACC tricalcium saccharate
• Ca-LACT lactate
• PCC precipitated calcium carbonate
• the semi-organic sugar compounds to be used according to the invention may be produced by reacting a sugar with a base in an aqueous solution, yielding a reaction product in the form of crystals of a sugar compound, said crystals being poorly soluble or insoluble in water.
• Said semi-organic sugar compounds to be used according to the invention may be produced using the Steffen process or by any other known manner.
• the sugar used for the production of the semi-organic sugar compounds may be any monosaccharide, disaccharide, oligosaccharide or a mixture thereof, for instance saccharose, lactose, maltose, or cellobiose.
• Sugars useful for the production of the semi-organic sugar compound may also be obtained for instance by the hydrolysis of the soluble carbohydrates formed in the production of mechanical pulp.
• sugars from other waste streams, particularly waste streams of food industry e.g. sugar production plants and dairies, as well as waste streams of forest industry are useful.
• Preferable sugars include saccharose and lactose.
• the base to be used in the production of the semi-organic sugar compound may be an oxide of an alkaline earth or alkali metal, or a mixture thereof.
• Exemplary bases include calcium, magnesium, strontium, and barium oxides.
• the base is preferably calcium oxide.
• the particle size of the semi-organic sugar compounds to be used according to the invention as fillers and coating pigments of paper and board preferably ranges from 0.05 to 10 ⁇ m.
• An aqueous saccharose solution with a concentration of 5 - 12 %, by weight, is prepared. While mixing vigorously, CaO is added to the solution, said CaO forming Ca(OH) 2 in water.
• CaO is added to the saccharose solution in a ratio of CaO to saccharose of 1:1, monocalcium saccharate readily soluble in water is obtained as the reaction product.
• an excess of CaO relative to saccharose is added to the saccharose solution, the equilibrium of the dissolution reaction is shifted in the direction of the dicalcium saccharate soluble in water. Heating of the dicalcium. saccharate solution to a temperature of at least 58 0 C results in the formation of crystals of tricalcium saccharate complex poorly soluble in water.
• Theoretical amount of CaO necessary to form tricalcium saccharate is 3 moles CaO for one mole of saccharose. A small excess of CaO relative to the theoretical CaO amount is necessary for the stability of the tricalcium saccharate. CaO is added in an amount of 3 to 6 moles, preferably 3 to 4 moles for one saccharose mole to produce tricalcium saccharate.
• the equilibrium of the reaction is shifted in the direction of the dicalcium saccharate which is soluble in water.
• the tricalcium saccharate complex may be recrystalli- zed by elevating the temperature again to a temperature of at least 58 0 C.
• the temperature of the slurry containing crystals of tricalcium saccharate is elevated above 90 °C, or an excess of solid Ca(OH) 2 is present, tricalcium saccharate decomposes to give monocalcium saccharate.
• the aqueous slurry of the semi-organic sugar compound obtained as described above having a temperature between 58 and 90 0 C to keep the compound in the form of a crystallized complex poorly soluble or insoluble in water, may be used as such as a filler and coating pigment of paper and board. Due to the excess of base, said aqueous slurry containing crystals of the semi-organic sugar compound also comprises unreacted free base elevating the pH of the slurry. To avoid a slurry too basic to be used as such as a filler of paper and board, the excess of the base to be added to the sugar solution should result in a slurry containing unreacted free base in an amount of not more than 30 % by weight of the sugar compound. The amount of the free base contributes to the properties of paper and board, lower amounts of the free base giving better strength properties, whereas higher amounts give improved optical properties.
• the sugar compound may be precipitated to yield crystals thereof, which are poorly soluble or insoluble in water, by elevating the temperature of the solution to a range between 58 and 90 0 C prior to the use thereof as a filler or coating pigment of paper and board.
• precipitating conditions such as mixing speed, heating profile, and final temperature in a suitable way, the semi- organic sugar compound is obtained in the form having an optimal particle size for the intended application.
• the crystals of the semi-organic sugar compound obtained as described above are separated from the slurry heated to a temperature between 58 and 90 0 C, for instance by filtering, or by evaporation of the water, so that only crystals of the semi-organic sugar compound and the base not reacted with the sugar remain.
• the semi-organic sugar compound retains its crystalline form also below 58 0 C.
• the semi-organic sugar compound useful as a filler and coating pigment of paper and board that the specific surface area, brightness, and purity of the base such as an oxide of alkaline earth or alkali metal used in the production of the compound are as high as possible, and no carbon dioxide is present in the base.
• the semi-organic sugar compound useful as a filler and coating pigment of paper and board that no impurities are present in the sugar used in the production of the compound.
• the particle size of the semi-organic sugar compound to be used as a filler of paper and board is preferably between 1 and 2 ⁇ m.
• Said semi-organic sugar compound is a suitable filler both for fine papers and papers containing mechanical pulp, for example LWC, ULWC, MWC, and SC.
• the semi-organic sugar compound may also be used as a coating pigment for papers containing mechanical pulp such as LWC printing papers, and for boards, such as FBB board.
• the particle size of the sugar compound to be used as a coating pigment is preferably from 0.2 to 1 ⁇ m.
• said semi-organic sugar compound is added to the pulp during the production of paper or board in the form of the slurry described above heated to a temperature of 58 to 90 0 C to keep the sugar compound in the form of a crystalline complex poorly soluble or insoluble in water.
• the filler is added at any suitable point of the system prior to the press, preferably in the short circuit, and particularly preferably next to the head box such as on the suction side of the mixing pump, or in the vicinity of the feed pump of the head box to give paper or board containing the filler comprising said semi-organic sugar compound in an amount ranging from 1 to 50 % by weight, followed by the production of the paper or board in a conventional manner.
• the temperature should be controlled to keep the semi-organic sugar compound in a crystalline form. Drying may be carried out in a conventional manner as a contact, or cylinder drying, the cylinder used typically having a surface temperature varying from 100 to 160 0 C, but it may also be performed with any other drying process.
• said semi-organic sugar compound is applied as the slurry described above, heated to a temperature between 58 and 90 0 C to keep the sugar compound in the form of a crystalline complex poorly soluble or insoluble in water, said slurry being used either as such or admixed with known binders used in coating pigments like starch, or latex, thickening agents such as carboxymethylcellulose, or with other additives to give a coating paste typically comprising the pigment containing said semi-organic sugar compound in proportions varying from 80 to 95 % by weight.
• Application to the paper or board web may be carried out using any known coating method. During the production of and coating with the coating paste, the temperature should be controlled to keep the semi-organic sugar compound in a crystalline form.
• the use of the semi-organic sugar compounds according to the invention allows for the increase of the proportion of renewable organic materials in papers and boards, and the improvement of the utilization of papers and boards removed from the recycling system by combustion.
• the disposal of compostable materials in landfills will be prohibited in the future, and thus combustion remains to be an important alternative for waste disposal.
• the production of the semi-organic sugar compounds to be used according to the invention is clearly environmentally friendlier than that of urea-formaldehyde resin, an organic pigment used in similar application, the production of said resin requiring the use of chemicals hazardous for both humans and the environment.
• the environmental acceptance of the use of the present invention may still be improved by using sugars from industrial waste streams in the production of the semi-organic sugar compounds.
• various carbohydrates are for instance found in sidestreams from food and forest industry. Of these, particularly sugars are readily soluble in water.
• whey mainly consisting of milk sugar, or lactose
• Various carbohydrates are also found for instance in the forest industry in connection of dissolved and colloidal substances separated in pulp production. Novel applications for such organic materials in the production of paper and board may be found following recovery and treatment thereof for instance by hydrolysis of longer carbohydrates to shorter ones, or conversion of water-soluble carbohydrate molecules into a form poorly soluble or insoluble in water.
• Example 1 Use of tricalcium saccharate as a filler in paper
• Saccharose (Suomen Sokeri Oy) was dissolved in water to give a 12 % saccharose solution, by weight, followed by cooling the solution to a temperature below 10 0 C.
• An excess of CaO (so-called PCC grade, Nordkalk Oyj) was added to the solution during three minutes while mixing vigorously, the ratio of CaO to the saccharate being 5:1.
• the reaction was exothermal, the final temperature of the reaction mixture being about 22 0 C.
• the temperature was elevated to 60 0 C to precipitate the dicalcium saccharate in the aqueous solution to yield crystals of tricalcium saccharate.
• Chemical pulp comprising 70 % of dry chemical birch pulp and 30 % of dry chemical softwood pulp was refined in a Valley hollander to give a tensile strength of about 50 Nm/g. Sheets having surface weights of 60 g/m 2 were produced according to the standard SCAN-C26:76. Controlling the temperature was important to keep calcium saccharate in the form of the poorly water-soluble tricalcium saccharate. Hot (53 0 C) tap water was added to the chemical pulp, followed by heating thereof to a temperature of 60 0 C using a heater immersed into the pulp tank. Hot water was added to the sheet mould prior to the addition of the filler to adjust the temperature of the sheet in the mould to a value between 58 and 60 0 C.
• the calcium saccharate solution prepared above was heated to 60 0 C to precipitate the crystals of tricalcium saccharate, followed by dispensing the slurry to the pulp to provide filler contents of 6 and 14 %, by weight.
• the sheets were pressed with a wet press using drying plates and compression in two steps at a pressure of 400 ⁇ 10 kPa. Drying was performed under standard conditions at 23 0 C, and at a relative humidity of 50 %.
• the optical and strength properties of the sheets were determined under standard conditions. Light scattering coefficients, brightness and opacity were assayed using the methods SCAN-P 8:93, SCAN-P 3:93, and SCAN-P 8:93. Tensile strength index, bonding strength as the Scott Bond value, and bending stiffness were assayed with the methods SCAN-P 67:93, TAPPI T 569 and TAPPI T 489. Moreover, SEM graphs were taken from both surfaces of the sheets.
• Example 2 Use of tricalcium lactate as a filler in paper
• Lactose (Valio Oy) was dissolved in water to give a 12 % lactose solution, by weight, followed by cooling the solution to a temperature below 7 0 C.
• An excess of CaO (so-called PCC grade, Nordkalk Oyj) was added to the solution during three minutes while mixing vigorously, the ratio of CaO to the lactate being 5:1.
• the reaction was exothermal, the final temperature of the reaction mixture being about 17 0 C.
• the temperature was elevated to 60 °C to precipitate crystals of tricalcium lactate.
• optical and strength properties of the sheets were determined proceeding as in example 1. Moreover, SEM graphs were taken from both surfaces of the sheets.
• Sugar compounds are in crystalline form in the sheets as revealed by figures Ib and 2b showing electron micrographs in 5000x magnification of the sheets produced above, containing tricalcium saccharate and tricalcium lactate as fillers.
• Figures 3 a and 3b are graphs showing the light scattering coefficients of the sheets as a function of the tensile strength index, and the bonding strength, respectively.
• improved strength properties are attained by using the semi-organic sugar compounds, particularly tricalcium lactate, in comparison to those obtained with the precipitated calcium carbonate (PCC), serving as the control, the optical properties being comparable with those obtained with PCC.
• PCC precipitated calcium carbonate
• the improved strength properties obtained by the inventive use of the semi-organic sugar compounds are also obvious from figures 4a and 4b showing, respectively, graphs of the tensile strength index, and bending stiffness as a function of the filler content.
• Figures 5a, 5b, and 5c are graphs showing the light scattering coefficients, the brightness, and the opacity of the sheets as a function of the filler content, respectively. As seen from the figures 5a - 5c, the optical properties are comparable to those obtained with PCC, and particularly concerning the opacity, the level reached with PCC is also attained using said sugar compounds.

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• 2005
  • 2005-12-23 FI FI20055697A patent/FI20055697L/fi not_active Application Discontinuation
• 2006
  • 2006-12-19 WO PCT/FI2006/050564 patent/WO2007082985A1/en active Application Filing
  • 2006-12-19 BR BRPI0620633-6A patent/BRPI0620633A2/pt not_active IP Right Cessation
  • 2006-12-19 EP EP06820140A patent/EP1963574A1/en not_active Withdrawn

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