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
  • D21H21/14—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
  • D21H21/28—Colorants ; Pigments or opacifying agents
  • D21H21/285—Colorants ; Pigments or opacifying agents insoluble
• • 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
• • 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
  • D21H21/50—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 form
  • D21H21/52—Additives of definite length or shape

Definitions

• Paper pigment process for producing a paper product and paper product
• This invention relates to new organic paper pigments, a process for manufacturing a paper product, the use of the paper pigments according to the invention in the manufacture of a paper product, and to new paper products.
• Paper pigments can be divided into filler pigments or fillers and precoating and surface coating pigments. Except for some special surface coating pigments, paper pigments are inorganic mineral particles in structure. The pigments used for surface finishing are generally more finely divided than filler pigments, but the particle size of both is such that they contribute notably to the increase of the reflection surface. Paper pigments are light-scattering materials.
• paper pigments of course has also its limits. When certain limits are exceeded, the tensile properties of paper decrease dramatically and the need for using expensive additional chemicals, for example, increases.
• mineral pigments are hard materials in structure, causing easily wear in paper machines, finishing machines and printing machines. An excessive amount of mineral particles also generates linting during printing.
• Paper pigments are typically used in relatively great amounts in fine papers and magazine printing papers, but their use is increasing also in normal newsprint as well as in packing papers. Special products, such as laminated papers, bible paper, tobacco paper, etc. easily contain 40% of paper pigments. In newsprint the amount of paper pigments is today between 0-10% (kaolin, talc, special pigments), 20-30% (kaolin, talc) in uncoated magazines (SC), 0-25% in fine papers (kaolin, talc, chalk, T ⁇ O 2 ), and 0-10% in packing papers (kaolin, talc, chalk, TiO 2 ).
• An optimum particle size for a paper pigment would be 0.2-0.3 ⁇ m, i.e. approximately half of the average light wavelength, which thus produces maximum opacity.
• a typical particle size of a paper pigment in the filler use for example, is approximately 0.4-5 ⁇ m.
• the present mineral-based paper pigments can be classified as natural and synthetic materials. The former are of course less expensive, the latter often possess some of the above mentioned desired properties.
• Typical mineral-based paper pigments include titanium dioxide, kaolin, calcined kaolin, talc, gypsum, chalk, ground calcium carbonate (GCC), precipitated calcium carbonate (PCC), barium sulphate, Na Al silicate (Zeolex), Ca Al silicate, aluminium oxide, kieselguhr, zinc oxide, etc.
• GCC ground calcium carbonate
• PCC precipitated calcium carbonate
• Ca Al silicate Ca Al silicate
• aluminium oxide aluminium oxide
• kieselguhr zinc oxide
• zinc oxide etc.
• a more advanced calcium oxalate based paper pigment has been introduced to the market, which reduces somewhat the ash content of the final product and has lower density.
• Calcium carbonate is an alkaline paper pigment and hence it dissolves completely in water even at pH 6.5. Therefore its use is restricted to neutral and alkaline conditions only. For this reason the use of carbonates is strongly emphasized in the manufacture of wood-free papers.
• inorganic paper pigments such as the crystal structure
• properties of inorganic paper pigments have been developed to allow decreasing the density, for example, they are still relatively heavy as "stone materials".
• inorganic paper pigments notably reduce the calorific value of paper products and prevent or significantly reduce their utilization possibilities after use for example as a source of energy by burning.
• Disaccharides can be defined as any sugars that are composed of two monosaccharide units. They are crystalline carbohydrates, dissolving extremely well in water due to their hydroxyl functions, of which a part is natural and a part is synthetic.
• the most common disaccharides are natural saccharose (cane sugar and beet root sugar) and lactose (milk sugar) as well as maltose (a hydrolysis product of starch) and cellobiose (a hydrolysis product of cellulose).
• saccharose cane sugar and beet root sugar
• lactose milk sugar
• maltose a hydrolysis product of starch
• cellobiose a hydrolysis product of cellulose
• Disaccharides are optically active compounds, i.e. they contain chiral carbon atoms.
• saccharose consists of two optically active monosaccharides, namely D-glucose and D-fructose. Lactose, in turn, is composed of D-galactose and D-glucose. These two monosaccharides are joined together via a glucose link. This link may have further an ⁇ - or ⁇ -configuration and the disaccharide may be a mixture of a disaccharide comprising these two different link configurations.
• Maltose and cellobiose differ from each other in structure only with respect to this glucose link; both have two glucose units, which are combined with an ⁇ -glucoside link in maltose and with a ⁇ -glucoside link in cellobiose.
• saccharose is used as such as a food product and as an ingredient of food products. It is also used, like lactose, for example as additive components for pharmaceutical products due to its good preservability and harmlessness.
• the melting points of saccharose, lactose, maltose and cellobiose octaacetates change owing to minor structural differences in the following way: ⁇ - saccharose octaacetate: about 82-83°C, ⁇ -lactose octaacetate: about 136-137 0 C, ⁇ -maltose octaacetate: about 159-16O 0 C, and ⁇ -cellobiose octaacetate about 225°C. Since the acetate esters of disaccharides, for example, are inert molecules as such, no other noteworthy use has been found for them. Therefore, the production of disaccharide derivatives comprising longer alkyl or alkyl aryl ester chains has been insignificant.
• An objective of this invention is an organic paper pigment, poorly soluble in water, consisting of ester derivatives of disaccharide, the particle size of which is 0.15-50 ⁇ m.
• an objective of this invention is a process for producing a paper product, in which process an ester derivative of disaccharide, essentially insoluble in water, is used as a paper pigment.
• Another objective of the invention is the use of an essentially insoluble disaccharide as a paper pigment in the manufacture of a paper product.
• an objective of this invention is a paper product, for which paper product an ester derivative of disaccharide, poorly soluble in water, with a particle size of 0.15-50 ⁇ m, has been used as a paper pigment.
• the invention now discovered is based on the surprising observation that particles composed of ester derivatives of disaccharides can be used as paper pigments.
• This type of paper pigment is poorly soluble in water and has a high calorific value being an organic material.
• it is very lightweight and has good brightness and a sufficiently high melting point to be used as a paper pigment.
• Its properties can be adjusted by the selection of the disaccharide and the esterification substrate, for example, as well as by the selection of the esterification degree.
• the stereochemical structure of the paper pigment and thus the properties can be adjusted by the selection of the esterification catalyst.
• the paper pigments according to the invention can surprisingly be used as fillers, precoating pigments and coating pigments.
• the paper pigment can be refined to a suitable size for each purpose.
• the paper product in which the paper pigments according to the invention have been used, surprisingly showed excellent optical properties.
• Using the paper pigment according to the invention better opacity and light-scattering coefficient were achieved than for example with a high-opacity mineral pigment developed for a corresponding purpose.
• the tensile properties of the paper product were surprisingly at the same level.
• the calorific value of the paper products to be manufactured is notably higher than in corresponding paper products containing mineral-based paper pigments. This opens a possibility for a later use of the paper product or the slurry separated from it through deinking as bioenergy in combustion plants, for example.
• the paper products manufactured according to the invention are also lightweight. Grammages can be reduced without impairing the working characteristics of the final product. This reduces notably the transport costs, for example.
• paper pigments according to the invention are also soft, they do not cause wear in the paper, board, finishing and printing machines in the same way as the currently used hard mineral pigments.
• Figure 1 is a SEM image of refined lactose octaacetate (LOA), used in sheet tests, having an average particle size of less than 2 ⁇ m
• Figure 2 is a SEM image of a high-opacity PCC filler (Albacar HO) used as the reference filler, having an average particle size of less than 2 ⁇ m
• LOA lactose octaacetate
• Figure 3 shows the tensile index (Nm/g) as a function of the filler content (%) for test sheets, in which lactose octaacetate (LOA) or PCC has been used as filler,
• Figure 4 shows opacity (%) as a function of the filler content (%) for test sheets, in which lactose octaacetate (LOA) or PCC has been used as filler,
• Figure 5 shows gloss (%) as a function of the filler content (%) for test sheets, in which lactose octaacetate (LOA) or PCC has been used as filler,
• Figure 6 shows the light-scattering coefficient (m 2 /kg) as a function of the filler content (%) for test sheets, in which lactose octaacetate (LOA) or PCC has been used as filler.
• LOA lactose octaacetate
• the invention relates to a paper pigment, which is an ester derivative of a disaccharide, essentially insoluble in water, having a particle size of 0.15- 50 ⁇ m.
• a paper pigment which is an ester derivative of a disaccharide, essentially insoluble in water, having a particle size of 0.15- 50 ⁇ m.
• the particle size of the paper pigment according to the invention is 0.15-8 ⁇ m, and more preferably between 0.5-2 ⁇ m.
• the ester derivative of the disaccharide can be regarded here as essentially insoluble in water, of which a maximum of 2.5% by weight dissolves in water at the room temperature, preferably less than 1.5% by weight; and more preferably less than 1 % by weight.
• carboxylate chain of the ester derivative of the disaccharide according to the invention is short (C 2 i.e. acetate), a high, preferably a quantitative degree of convertion to esters of hydroxyl functions of the disaccharides is required to achieve poor solubility in water for the paper pigment according to the invention.
• Preferred C 2 carboxylate derivatives of disaccharides include lactose, saccharose, maltose and cellobiose octaacetates, for example.
• the paper pigment according to the invention may be C 2 -Ci 8 carboxylate of disaccharide, preferably it is C 2 -Cs carboxylate and more preferably C 2 -C6 carboxylate, with either a quantitative or a partial esterification degree of the hydroxyl functions of the disaccharides.
• the carbon atoms of C 2 -Ci 8 carboxylate can form straight or branched alkyl chains and saturated or unsaturated ring structures.
• the ester functions of the disaccharide can be C 2 -Ci 8 carboxylates that are either similar with each other or alternatively different from each other.
• the melting point of the paper pigment according to the invention should be over 75°C. Preferably it is over 85 0 C and more preferably the melting point of this ester derivative of the disaccharide is over 100 0 C.
• the disaccharide of the ester derivative of the disaccharide according to the invention can be for example any stereoform of lactose, saccharose, maltose or cellobiose, or a mixture of these stereoforms.
• the ester derivative of the disaccharide according to the invention can also be a mixture of the above mentioned disaccharides and further of their various stereoforms. Neither does the invention exclude the use of other disaccharides and their various stereoforms as the disaccharide of the ester derivative.
• the esterification of disaccharides can be performed, for example, by using natural carboxyl acids or their derivatives, such as anhydrides or acid chlorides.
• Especially preferred substrates are anhydrides, such as acetic anhydride.
• the stereochemistry of the product created can be adjusted by the selection of the catalyst, for example. It is also possible to use synthetic esterification substrates.
• a specially preferred paper pigment according to the invention is lactose octaacetate.
• Another preferred paper pigment according to the invention is saccharose octaacetate.
• the objective of the invention is also a process for producing a paper product, in which process an ester derivative of a disaccharide, essentially insoluble in water, is used as a paper pigment.
• the paper pigment according to the invention is defined as above.
• the paper pigment particle formed by the ester derivative of the disaccharide essentially insoluble in water can be a filler, the particle size of which is 0.15 ⁇ m - 50 ⁇ m, preferably 0.5 ⁇ m - 8 ⁇ m; and most preferably 1 ⁇ m - 2 ⁇ m.
• the paper pigment particle formed by the ester derivative of the disaccharide essentially insoluble in water can be a precoating pigment, the particle size of which is 0.15 ⁇ m - 2 ⁇ m, preferably 0.5 ⁇ m - 1.5 ⁇ m.
• the paper pigment particle formed by the ester derivative of disaccharide essentially insoluble in water can be a surface coating pigment, the particle size of which is 0.15 ⁇ m - 2 ⁇ m, preferably 0.5 ⁇ m -1.0 ⁇ m.
• the invention also relates to the use of an ester derivative of a disaccharide essentially insoluble in water in the manufacture of a paper product, in which this ester derivative of the disaccharide is used as a paper pigment, the particle size of which is 0.15 ⁇ m - 50 ⁇ m.
• the paper pigment according to the invention is defined as above.
• the 'paper product' is used here to refer to paper or board of any type or of any weight, white or colored.
• the paper pigment according to the invention can be used as a filler in the manufacture of the paper product.
• the particle size of ester derivatives of the disaccharide essentially insoluble in water is 0.15 ⁇ m - 50 ⁇ m, preferably 0.5 ⁇ m - 8 ⁇ m; and most preferably 1 ⁇ m - 2 ⁇ m.
• the paper pigment according to the invention can be used as a precoating pigment in the manufacture of a paper product.
• the particle size of ester derivatives of the disaccharide essentially insoluble in water is 0.15 ⁇ m - 2 ⁇ m, preferably 0.5 ⁇ m - 1.5 ⁇ m.
• the paper pigment according to the invention can be used as a surface coating pigment in the manufacture of the paper product.
• the particle size of ester derivatives of the disaccharide essentially insoluble in water is 0.15 ⁇ m - 2 ⁇ m, preferably 0.5 ⁇ m - 1.0 ⁇ m.
• the paper pigment according to the invention has good brightness; however, pigments with lower brightness can also be used to provide opacity in paper products for which brightness is not an important criterium.
• the invention also relates to a paper product, in which an ester derivative of a disaccharide, poorly soluble in water, the particle size of which is 0.15 ⁇ m - 50 ⁇ m, has been used as a paper pigment.
• the paper pigment according to the invention and the particle sizes providing various preferred properties to the paper product are defined as above.
• the portion of the ester derivative of the disaccharide, poorly soluble in water, from the total mass of the final product can vary between 1-55 % by weight, preferably 3-40 % by weight and most preferably 5-35 % by weight.
• organic paper pigments which have o very low density o excellent optical properties o very poor water solubility o high brightness o high calorific value o soft structure and easy workability to a suitable particle size o resistance in even acid paper production processes • production of paper pigments using disaccharides o disaccharides are a feedstock available worldwide and all year round o especially saccharose and lactose commodities o esterification reagents are typically natural carboxyl acids or their derivatives o inexpensive feedstock and production processes o the properties of the paper pigment are adjustable by changing the feedstock saccharide and esterification function
• ⁇ are user-friendly o have good strength properties.
• Lactose octaacetate ( ⁇ -lactose octaacetate) to be used as a paper pigment was produced in several batches with a standard procedure by esterif ⁇ cation of ⁇ -D- lactose (A.C.S reagent, Sigma-Aldrich) with an equimolar amount (8 equivalents) of acetic anhydride using sodium acetate as catalyst, diagram 1 (stereochemical structures not considered). The progress of the reaction was monitored with HPLC and the conversions of the reaction were practically quantitative. After carrying out the reaction, the product was separated from the reaction mixture by precipitating with water. After this the product was flushed with water and dried in a heating chamber (105-115 0 C). The extremely high purity degree of the products was still verified with HPLC before using them in sheet tests.
• the melting point of the prepared ⁇ -lactose octaacetate was measured and the result was 135.5-137°C.
• the product was refined using a Dyno laboratory mill.
• the particle size distribution was verified with SEM and with a measuring device for the particle size distribution (Malvern).
• the previously prepared lactose octaacetate was used as filler in consistencies of about 5 and 9 percent.
• the reference filler used was a commercially available high-opacity PCC filler (Albacar HO) in corresponding consistencies.
• the technical characteristics of the fillers are described in Table 1. LOA and PCC used in the sheet tests were scanned with SEM (Scanning Electron Microscopy), Figures 1 and 2. The average particle size of the fillers used is below 2 ⁇ m. It should be noted in the table that the density of lactose octaacetate is only 47% of the density of PCC used as the reference pigment.
• R457 refers to ISO brightness.
• the ISO brightness or the diffuse blue reflectance factor is a reflectance factor, which is determined with a device whose maximum receptor sensitivity coincides with a wavelength of 457 nm.
• opacity is a measure of untransparency of a paper product.
• the opacity of a completely untransparent material is 100% and that of a completely transparent material is 0%.
• ** the light-scattering coefficient is a measure indicating how well an indefinitely thin material layer scatters light.
• lactose octaacetate (LOA) used as paper pigment surprisingly provides the currently prepared paper sheets both a higher light-scattering coefficient and opacity than a corresponding amount of PCC used as reference. These excellent optical properties were achieved without notable impairing of the tensile index or tensile strength.
• LOA is an organic pigment
• PCC used as the reference pigment is specifically of the high opacity quality. In this way it was possible to increase the amount of a low-density organic material in the paper product not only by maintaining but also by simultaneously improving the optical properties of the final product without impairing notably the strengths of the final products.
• the optical properties achieved in the sheet tests 4 and 5 are comparable to the results obtained when using an inorganic filler.

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• 2005
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• 2006
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  • 2006-06-14 WO PCT/FI2006/000200 patent/WO2006134211A1/en active Application Filing
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