CN114207214A - Coated paper and method for producing same - Google Patents
Coated paper and method for producing same Download PDFInfo
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- CN114207214A CN114207214A CN202080055168.6A CN202080055168A CN114207214A CN 114207214 A CN114207214 A CN 114207214A CN 202080055168 A CN202080055168 A CN 202080055168A CN 114207214 A CN114207214 A CN 114207214A
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- dextrin
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- 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
- D21H19/44—Coatings with pigments characterised by the other ingredients, e.g. the binder or dispersing agent
- D21H19/54—Starch
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- 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
- D21H19/44—Coatings with pigments characterised by the other ingredients, e.g. the binder or dispersing agent
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Abstract
The invention aims to efficiently produce coated paper with excellent surface gloss. According to the present invention, there is provided coated paper having a pigment-coated layer comprising a pigment and an adhesive on a base paper, wherein the adhesive in the present invention comprises a first dextrin and a second dextrin, the weight-average molecular weight (M1) of the first dextrin and the weight-average molecular weight (M2) of the second dextrin are both less than 500kDa, and M1-M2 are 60kDa or less.
Description
Technical Field
The present invention relates to coated paper and a method for producing coated paper. In particular, the present invention relates to a coated paper containing dextrin as a binder (adhesive) for a pigment coating layer.
Background
In general, when producing coated paper, a coating layer mainly composed of a pigment and an adhesive for binding the pigment is formed in order to improve printing suitability. As the adhesive, an adhesive derived from a petroleum-based synthetic material is mainly used from the viewpoints of good coating fluidity, good coating adaptability in a coating apparatus, easy application of print surface strength as coated paper quality, and the like.
However, in recent years, attention has been paid not to a synthetic material of petroleum type but to a material which is inexpensive and has excellent biodegradability due to cost reduction, enhancement of environmental consciousness, and the like. Among them, an adhesive using a starch-based material as a raw material has been attracting attention (patent document 1). However, if a large amount of starch-based material is added to the coating material (pigment coating liquid), the viscosity of the coating material increases significantly, and the workability and coating suitability deteriorate. Even if the viscosity is adjusted by diluting the coating material, the load of the drying step after coating becomes large due to the increase of the water content, and the productivity is adversely affected by, for example, the reduction of the coating speed. Further, even if the coating speed is reduced for production, the coating concentration is low and the water retentivity of the coating material is lowered, so that the penetration of the coating material into the base paper is large, and the quality deterioration such as the reduction of the white paper gloss and the reduction of the surface strength cannot be avoided.
Therefore, patent document 2 proposes a technique of using a starch-based polymer having a low viscosity after a certain period of time has elapsed from the start of cooking as an adhesive when an aqueous slurry containing the starch-based polymer is cooked. In addition, patent document 3 proposes to improve the water retention characteristics of the coating liquid by using a plurality of dextrins having an average molecular weight of 50kDa or more and different molecular weights in combination.
Documents of the prior art
Patent document
Patent document 1: japanese patent application laid-open No. 2010-84311
Patent document 2: international publication WO2012/133487
Patent document 3: japanese patent laid-open publication No. 2016-526111
Disclosure of Invention
However, in the technique described in patent document 2, the felt deposition tends to occur easily in offset printing, and particularly, the felt deposition is significantly deteriorated when the coating liquid concentration is low. The felt pile means that paper dust and ink are piled up and raised on the periphery of the painting line part on the felt. In addition, the technique described in patent document 3 tends to reduce the gloss expression of the coated paper.
The high concentration of the coating liquid contributes to improvement in productivity due to reduction in drying load by reduction in moisture, and contributes to improvement in surface strength by reduction in penetration of the coating liquid into the base paper. However, if the concentration of the coating liquid is high, the viscosity increases, and the workability and coating suitability deteriorate, so that the coating liquid is actually diluted and used to such an extent that the drying load and the surface strength are not adversely affected.
In view of the above circumstances, an object of the present invention is to search for a starch-based adhesive which does not increase the viscosity of a coating material too much even when a large amount of the coating material is blended in the coating material, can improve the white paper gloss and the printing gloss of a coated paper, and can suppress the deposition on a felt at the time of offset printing, and to develop a technique for producing a coated paper of high quality with high workability.
As a result of intensive studies to solve the above problems, it has been found that coated paper having excellent surface gloss can be produced by using specific dextrins having different molecular weights in combination, and the present invention has been completed.
The present invention includes the following inventions, but is not limited thereto.
(1) A coated paper having a pigment coating layer comprising a pigment and a binder on a base paper, wherein the binder comprises a first dextrin and a second dextrin, the weight average molecular weight of the first dextrin (M1) and the weight average molecular weight of the second dextrin (M2) are both less than 500kDa, and M1-M2 are 60kDa or less.
(2) The coated paper according to (1), wherein the combined ratio (weight ratio) of the first dextrin and the second dextrin is 2: 8-8: 2.
(3) the coated paper according to (1) or (2), wherein the first dextrin and the second dextrin are both white dextrins.
(4) The coated paper according to any one of (1) to (3), wherein M1 and M2 are both 150 to 400 kDa.
(5) A method of making coated paper comprising: a step of preparing a coating liquid containing a pigment and an adhesive, and a step of applying the coating liquid to base paper; the adhesive comprises a first dextrin and a second dextrin, wherein the weight-average molecular weight (M1) of the first dextrin and the weight-average molecular weight (M2) of the second dextrin are both less than 500kDa, and M1-M2 are less than 60 kDa.
According to the present invention, the fluidity of the coating liquid is good, and the workability of the coating liquid is easy, so that the coating adaptability is excellent, and the operation efficiency in the production of the coated paper is improved. Further, since the water retentivity of the coating liquid is improved, the penetration of the coating liquid into the base paper is suppressed, and therefore, the gloss expression of the obtained coated paper is improved, and various coated paper qualities such as the suppression of the accumulation are improved.
Detailed Description
The coated paper of the present invention is not particularly limited as long as it is a coated paper having a pigment coating layer containing a white pigment and an adhesive provided on a base paper, and it may be a coated paper for printing used in offset printing, gravure printing, relief printing, or the like, or a white paperboard having a pigment coating layer on a paperboard base paper.
The coated paper of the present invention has 1 or more pigment coating layers containing a pigment on a base paper. The base paper may be coated with a coating liquid (size press liquid) containing no pigment or may not be coated with the coating liquid.
The coated paper of the present invention preferably has 10 wt% or more of ash in the paper, and more preferably 30 wt% or more of ash in the paper. In the case of coated printing paper, it is preferable to increase the ash content to increase the opacity.
Dextrin
In the present invention, a pigment coating liquid mainly containing a pigment, a binder (binder) and water is used for providing the pigment coating layer, and a starch-based polymer having a specific molecular weight (weight average molecular weight) is added as the binder (binder). In the present invention, dextrin is used as the starch-based polymer, but since the viscosity after a certain period of time has elapsed after cooking is particularly low, the viscosity of the pigment coating liquid is not greatly increased even when the starch-based polymer is blended into the pigment coating liquid, and the concentration of the pigment coating liquid can be increased, thereby improving the printing quality of the coated paper. That is, the penetration of the coating material into the base paper is suppressed, and the effective coating layer is increased, so that various coated papers are improved in quality such as an improvement in gloss expression and an improvement in surface strength.
In the present invention, a plurality of dextrins having different molecular weights are used as the binder. Dextrin can be obtained by hydrolyzing starch, and dextrin having different molecular weights can be produced by adjusting the degree of hydrolysis. As described above, in the present invention, the binder for the pigment coating layer is composed of the first dextrin and the second dextrin, the weight average molecular weight (M1) of the first dextrin and the weight average molecular weight (M2) of the second dextrin are both less than 500kDa, and M1-M2 are 60kDa or less.
The molecular weight of the mixture of two dextrins for use in the invention is less than 500kDa in weight average molecular weight. Preferably 450kDa or less, more preferably 400kDa or less, still more preferably 350kDa or less, and may be 300kDa or less. When the molecular weight is too large, the viscosity of the paste becomes high, and the viscosity at the time of blending the coating material increases, which may result in poor workability. The molecular weight of the mixture of two types of dextrins used in the present invention is preferably 100kDa or more, more preferably 150kDa or more, and still more preferably 200kDa or more.
The weight average molecular weight of the dextrin used in the present invention is preferably 100kDa or more, more preferably 150kDa or more, and still more preferably 200kDa or more. When the molecular weight is too small, felt deposition during printing with an offset rotary press is likely to occur. This is considered to be because the coating layer is insufficient in strength because the coating layer is lowered in water retentivity to cause sedimentation of the binder and the binder does not stay on the surface of the coating layer, and the coating layer is peeled off and deposited on the felt at the time of printing. In order to prevent such accumulation, the concentration of the coating liquid may be increased, but if the concentration of the coating liquid is increased, the workability is deteriorated.
Further, in the present invention, the two dextrins used in combination preferably have a weight average molecular weight of 100kDa or more and less than 500kDa, respectively. When the low molecular weight dextrin is less than 100kDa, the viscosity of the coating liquid becomes low, and therefore the surface strength may become low. In addition, when the molecular weight of the high molecular weight dextrin is 500kDa or more, the paste viscosity of dextrin may be excessively increased to deteriorate the workability, and the viscosity may be excessively increased at the time of blending the coating material. In the present invention, since two types of dextrins having the above molecular weight ranges are used, the advantages of using a dextrin having a high molecular weight and a dextrin having a low molecular weight can be enjoyed. That is, the surface strength of the paper can be improved without impairing the workability.
In addition, the difference in molecular weight between the two dextrins is preferably less than 60 kDa. When the difference between the molecular weights of the two dextrins exceeds 60kDa, the high molecular weight dextrin causes shrinkage of the paper surface, and thus the gloss may be reduced. The difference between the molecular weights of the two dextrins may be small, for example, 10kDa or more.
In the present invention, the weight average molecular weight can be measured by, for example, a size exclusion chromatography multi-angle light scattering method (SEC-MALS method).
In a preferred embodiment, the dextrin of the present invention has a slurry viscosity of 1000mPa · s or less after cooking under certain conditions. When dextrin is contained in the coating liquid, heating for dissolving dextrin is required. Therefore, the viscosity of the slurry after cooking under a certain condition is important, and the dextrin of the present invention can make the slurry highly concentrated because the viscosity of the slurry after cooking is low. Starch compounds are typically suspended in water and heated, and the starch granules absorb water and gradually swell. If the heating is continued, the starch grains are finally disintegrated to become a gel. This phenomenon is called gelatinization (gelation). At this time, the starch suspension gradually became transparent from a cloudy state, and the viscosity rapidly increased. The particles absorb water to the maximum extent and the viscosity is maximized, and the viscosity is reduced by disintegration of the particles. In the present invention, dextrin is used which has a viscosity in a certain range when the temperature is lowered and left to stand after the viscosity reaches the maximum by cooking.
For example, cold water-soluble starches such as pregelatinized starch have low slurry viscosity, but these cold water-soluble starches are processed so as to be soluble in cold water, and dextrin and the like have high expressivity in surface strength, and are advantageous. Therefore, the starch-based polymer compound of the present invention preferably has a solubility in water at 20 ℃ of less than 20%.
The behavior of such a starch-based polymer can be measured using a measuring apparatus such as a Rapid Visco Analyzer (RVA, model RVA-4, manufactured by New Port Scientific Co.). In a preferred embodiment of the present invention, dextrin is used which has a viscosity of 1000 mPas or less at 50 ℃ 16 minutes after the start of cooking when starch-based polymer slurry having a concentration of 35% by weight is cooked under the following cooking conditions. In one embodiment of the present invention, dextrin is used as the binder for the pigment coating layer, and the slurry is cooked (cooking) to exhibit the adhesive strength as the binder.
< RVA viscosity measuring Condition >
The paddle was rotated under the following conditions, and the torque applied to the paddle was measured to calculate the viscosity.
(conditions of agitation)
10 seconds after the start of measurement: 960rpm
Thereafter: 160rpm
(cooking conditions)
0-5 min: heating to 98 deg.C in 5 min
5-9 min: keeping the temperature at 98 DEG C
9-12 min: cooling to 50 deg.C in 3 min
12-16 min: keeping at 50 deg.C
The viscosity of dextrin measured as described above at the stage of being held at 50 ℃ after cooking for 16 minutes is preferably 1000mPa · s or less, more preferably 850mPa · s or less.
The dextrin of the present invention preferably has a maximum viscosity of 2000mPa · s or less, more preferably 1600mPa · s or less, due to gelatinization of starch when the viscosity is measured under the above-described conditions using RVA. If the maximum viscosity at the time of gelatinization is within such a range, handling is easy, and excessive viscosity increase does not occur when blending in a coating liquid.
The dextrin of the present invention preferably has the above viscosity, and the modification method and the like are not particularly limited, and the kind of the raw material and the like are also free. Preferred raw materials for dextrin used in the present invention include corn, potato, tapioca starch, and the like, and waxy corn (waxy corn) and tapioca starch are particularly preferred.
In the present invention, the binder is preferably a calcined dextrin such as white dextrin because of its low viscosity and high viscosity stability. Dextrin is a generic name of a starch-based polymer obtained by hydrolyzing starch, and α -glucose is polymerized by a glycosidic bond and is also called Dextrin (Dextrin). The molecular weight of starch is generally high, but dextrin is an intermediate product generated in the hydrolysis step of starch, and conventionally has a molecular weight of about an oligomer (a substance to which several to several tens of glucose are bonded). The roasted dextrin is one produced by adding an acid and roasting the mixture in dry heat, and includes white dextrin, yellow dextrin, British gum and the like. In the present invention, white dextrin is particularly preferably used. If the white dextrin is further hydrolyzed, it becomes so-called yellow dextrin, but if it is yellow dextrin, the stability is low and there is a possibility that the pigment coating layer is colored, so it is preferable to use white dextrin in the present invention.
The white dextrin of the present invention is preferably a dextrin having many branched chains. If the number of branches is large, the strength is easily exhibited. The degree of branching is considered to be related to the inertia radius, and if the molecular weight is the same, the branched chain is more when the inertia radius is small, and the branched chain is linear when the inertia radius is large. Therefore, the white dextrin of the present invention is preferably small in radius of inertia.
The dextrin of the present invention has good fluidity when blended in a coating liquid. If the fluidity is improved, the coating liquid concentration can be increased, the penetration of the coating liquid can be suppressed, and the effective coating layer can be increased, so that the gloss appearance can be improved, the whiteness can be improved, the surface strength can be improved, and other various coated paper qualities can be improved.
In a preferred embodiment, the amount of dextrin used in the present invention is about 0.1 to 30 parts by weight, more preferably about 0.5 to 15 parts by weight, based on 100 parts by weight of the pigment.
In the present invention, the dextrin alone may be used as the adhesive, but the dextrin may be used in combination with an adhesive conventionally used for coating paper. Examples of the adhesives other than the dextrin include synthetic adhesives such as various copolymers (latex) of styrene-butadiene, styrene-acrylic, ethylene-vinyl acetate, butadiene-methyl methacrylate, vinyl acetate-butyl acrylate, etc., polyvinyl alcohol, maleic anhydride copolymers, acrylic acid-methyl methacrylate copolymers, etc.; proteins such as casein, soybean protein, and synthetic protein; starches such as oxidized starch, positive starch, urea-phosphorylated starch, and etherified starch such as hydroxyethyl etherified starch other than the high molecular weight compounds derived from the above-mentioned starches; and common adhesives for coated paper such as cellulose derivatives including carboxymethyl cellulose, hydroxyethyl cellulose, and hydroxymethyl cellulose. The adhesive may be used in an amount of 1 or more. In the present invention, it is preferable to use a latex having different characteristics from the starch-based polymer compound as the binder, and in this case, it is preferable to use dextrin in an amount larger than the amount of the latex used. The use of both dextrin and latex can provide advantages, but in order to more exert the effects of the present invention, it is preferable to increase the amount of dextrin used.
In a preferred embodiment of the present invention, the latex is not used as a binder, or is used in an amount of 4 parts by weight or less based on 100 parts by weight of the pigment. The amount of the latex used is preferably 2.5 parts by weight or less. By not using latex or reducing the amount of latex used, there can be obtained advantages of preventing fouling of the backup roll, improving the anti-bubbling property, and reducing the cost by reducing the use of expensive latex.
In the present invention, the total amount of the binder in the coating liquid is not particularly limited, but is preferably 5 to 50 parts by weight, more preferably about 5 to 30 parts by weight, and still more preferably 5 to 12 parts by weight, based on 100 parts by weight of the pigment. When dextrin and other adhesives are used in combination as the adhesive, the total amount thereof is preferably within the above range.
In the present invention, the method for preparing the coating liquid is not particularly limited, and may be appropriately adjusted according to the type of the coater. When a blade coater is used, the solid content concentration of the coating liquid is preferably 40 to 70 wt%, more preferably 50 to 65 wt%. The viscosity of the coating liquid is preferably 50 to 3500 mPas, more preferably 100 to 2500 mPas, and may be 150 to 1500 mPas or 200 to 500 mPas by using a B-type viscometer according to JIS K7117-1.
In the present invention, various additives blended with a conventional pigment for coated paper, such as a dispersant, a thickener, a water retention agent, a defoaming agent, a water resistance agent, and a colorant, can be appropriately used as needed.
Coating colour
The pigment (white pigment) used in the coating layer of the present invention is not particularly limited, and pigments conventionally used for coating paper may be used, and for example, inorganic pigments such as kaolin, clay, engineered kaolin, coating clay, ground calcium carbonate, light calcium carbonate, talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicate, colloidal silica, satin white, and the like, and organic pigments such as compact, hollow, or core-shell type pigments may be used singly or in combination of 2 or more kinds as necessary. In addition, as the type of pigment, heavy calcium carbonate and light calcium carbonate are preferable from the viewpoint of a small amount of binder required and the ability to increase the surface strength and the high whiteness with a small amount of binder, and light calcium carbonate having uniform particle size and shape is particularly preferable from the viewpoint of also increasing opacity. The lofty coating structure is intended to scatter light efficiently.
When calcium carbonate is added to the coating liquid, the content of light calcium carbonate, heavy calcium carbonate, or the total of both is preferably 50 parts by weight or more, more preferably 70 parts by weight or more, and still more preferably 80 parts by weight or more, based on 100 parts by weight of the pigment. From the viewpoint of forming a uniform coating layer on the base paper, the average particle diameter is preferably 0.2 to 5 μm, and more preferably 0.3 to 3 μm, as measured by a laser diffraction particle size distribution measuring instrument such as Mastersizer S manufactured by Malvern.
Coating of
In the present invention, any coating machine can be used as long as it is a commonly used coating machine. The coating machine may be an on-machine coater or an off-machine coater, and if the coating machine is an on-machine coater, roll coaters such as a size press coater, a gate roll coater, a bar metering size press coater, a billblade coater, a blade metering size press coater, a short dwell blade coater, a spray melt blade coater, and the like may be used. The coating speed is not particularly limited, but in the prior art, the blade coater is preferably 500 to 1800 m/min, and the size press coater is preferably 500 to 2000 m/min.
In the present invention, the method for drying the wet coating layer is not limited, and various methods such as a steam-superheating cylinder, a heated hot air dryer, a gas heater dryer, an electric heater dryer, and an infrared heater dryer may be used alone or in combination.
The amount of the coating liquid to be applied in the present invention may be suitably selected depending on the application, but is generally 2 to 13g/m in terms of solid content per one surface2And may be 4 to 11g/m2、6～9g/m2。
The concentration of the coating liquid of the present invention is not particularly limited, but may be 40% by weight or more, preferably about 55% by weight to 75% by weight, in consideration of the printing quality. In the present invention, since the specific dextrin is used as the binder, the coating liquid can be made to have a high concentration. However, if the concentration of the coating liquid is too high, the coating liquid thickens and the workability is deteriorated. In the present invention, it is more preferably 65% by weight or less, whereby the workability can be kept good. From the viewpoint of handling properties, the coating liquid of the present invention may have a brookfield viscosity (B-type viscosity, 60rpm) of 50 to 3500mPa · s, preferably about 100 to 3000mPa · s, more preferably about 150 to 2000mPa · s, and may have a brookfield viscosity (B-type viscosity), or may have a brookfield viscosity of 200 to 1000mPa · s.
Base paper
The coated paper of the present invention has at least a raw paper layer. The base paper can be produced by a known method, for example, by making paper from a paper stock (stock) in a wire section, and then feeding the paper to a press section and a pre-dryer section. The base paper used in the present invention may be a single-layer paper or a multi-layer paper, but when white board paper is produced, a multi-layer paper is preferably used. The method for producing the base paper of the present invention is not particularly limited, and the base paper can be produced by a known method using a known raw material. The base paper used in the present invention is not particularly limited, and generally used fine paper, medium paper, ground paper, on-machine coated paper, cast coated paper, synthetic paper, resin printed paper, plastic film and the like can be used without exception.
The basis weight of the base paper of the present invention is not particularly limited, and may be suitably selected depending on the application, and may be, for example, 30 to 150g/m2And may be 33 to 100g/m2、35～75g/m2。
As a pulp raw material used for the base paper of the present invention, chemical pulp can be used. In addition to chemical pulp, various pulps may be used depending on the application, and examples thereof include deinked pulp (DIP), ground wood pulp (GP), refiner ground wood pulp (RGP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), chemi-ground pulp (CGP), semichemical pulp (SCP), and the like. Deinked pulp used may be classified waste paper such as high-grade paper, medium-grade paper, low-grade paper, newspaper, leaflet, magazine, or the like, or mixed non-classified waste paper thereof.
In the present invention, a known filler can be used as a filler for the base paper, and examples thereof include an inorganic filler such as ground calcium carbonate, light calcium carbonate, clay, silica, a light calcium carbonate-silica composite, kaolin, calcined kaolin, coated kaolin, white carbon, talc, magnesium carbonate, barium sulfate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc oxide, titanium oxide, amorphous silica produced by neutralization of mineral products based on sodium silicate, and an organic filler such as urea resin, melamine resin, polystyrene resin, phenol resin, and the like, which can be used alone or in combination. Among them, heavy calcium carbonate and light calcium carbonate, which are typical fillers in neutral paper and alkali paper, are preferably used to increase opacity. The filler content in the paper is not particularly limited, but is preferably 1 to 40% by weight of solid content, and more preferably 10 to 35% by weight of solid content.
In the present invention, a known additive for papermaking can be used. For example, internal additives for papermaking such as aluminum sulfate, various anionic, cationic, nonionic or amphoteric retention improving agents, drainability improving agents, various paper strength enhancers, and internal sizing agents can be used as necessary. The dry paper strength improver may be polyacrylamide or cationized starch, and the wet paper strength improver may be polyamidoamine epichlorohydrin. These chemical agents may be added within a range in which the texture, handling properties, and the like are not affected. Examples of the neutral sizing agent include alkyl ketene dimer, alkenyl succinic anhydride, and neutral rosin sizing agent. Further, dyes, fluorescent brighteners, pH adjusting agents, antifoaming agents, pitch control agents, slime control agents, and the like may be added as necessary.
The method for making the base paper in the present invention is not particularly limited, and can be carried out using a fourdrinier machine including a top wire or the like, a top wire former (on top former), a gap former, a cylinder machine, a board machine including both a fourdrinier machine and a cylinder machine, a yankee dryer machine, and the like. The pH during papermaking may be any of acidic, neutral, and alkaline, and is preferably neutral or alkaline. The papermaking speed is not particularly limited.
The coated paper of the present invention may have a transparent (Clear) coating layer on one or both sides of the base paper. By applying transparent coating to the base paper, the surface strength and smoothness of the base paper can be improved, and the coatability when applying pigment can be improved. In the present invention, the transparent coating layer may contain the starch-derived polymer compound of the present invention as a binder. The amount of the transparent coating is preferably 0.1 to 4.0g/m in terms of solid content per one side2More preferably 0.5 to 2.5g/m2。
In the present invention, the transparent coating means that a coating liquid (surface treatment liquid) containing various starches such as starch and oxidized starch, and water-soluble polymers such as polyacrylamide and polyvinyl alcohol as main components is applied (size press) to a base paper using a coating machine (coater) such as a size press, a gate roll coater, a sizing press for pre-metering, a curtain coater or a spray coater.
In the present invention, it is preferable to smooth the base paper in advance by subjecting the base paper before coating to a precalendering treatment by an on-line soft calender, an on-line cold calender or the like, in order to uniformize the coating layer after coating. In this case, the treatment line pressure is preferably 30 to 100kN/m, more preferably 50 to 100 kN/m. The moisture content of the base paper in the pre-calender treatment is also important, and the moisture content is preferably 3 to 5%.
Surface treatment
In the present invention, the paper produced as described above is subjected to surface treatment as necessary. The smoothing treatment may be performed by a smoothing treatment device such as a general supercalender, a gloss calender (gross calender), a soft calender, a thermo-compression calender, or a shoe calender. The smoothing apparatus is suitably used on or off the machine, and the form of the pressing apparatus, the number of pressing clips, the heating, and the like may be suitably adjusted. In a preferred embodiment, the coated paper of the present invention may be surface treated with a calender such as a supercalender, a high temperature soft nip calender, or the like. The surface treatment can improve the smoothness and gloss of the coated paper. In the present invention, a soft nip calender treatment is preferable. By performing soft nip calender treatment, whiteness and opacity are improved. In the soft nip calender treatment, the linear pressure of the metal roller with the surface temperature of 20-60 ℃ is 30-60 kN/m, and more preferably 40-60 kN/m. In addition, if the surface temperature of the metal roller is treated by a high-temperature soft nip calender at 40-250 ℃, the linear pressure is 60-400 kN/m, preferably 150-300 kN/m, and more preferably 100-350 kN/m. When the temperature is increased, the gloss and smoothness of the surface of the coated paper are improved.
Examples
The present invention will be described in detail below with reference to specific examples, but the present invention is not limited to the following examples. In the present specification,%, parts, etc. are based on weight, and numerical ranges are described as including the endpoints thereof.
Method for preparing roasted dextrin
Calcined dextrin was produced by adding hydrochloric acid to raw corn starch and heating at 130 ℃ for 90 minutes using a professional shear mixer (Atlantic machine). Specifically, white calcined dextrins having different molecular weights were obtained by changing the amount of hydrochloric acid added as follows.
[ Table 1]
The weight average molecular weight of the calcined dextrin can be measured by using GPC under the following measurement conditions.
Separation column: shodex GPC KB-806M 2 root, Shodex GPC KB-8021 root
Column temperature: 40 deg.C
Mobile phase solvent: aqueous sodium nitrate solution (0.1mol/L)
Flow rate of mobile phase: 0.5mL/min
Injection amount: 300 μ L
Detector 1: multi-angle light scattering detector (manufactured by Wyatt Corp. "DAWN HELEOSII")
Detector 2: refractive Index (RI) detector (model 2414 manufactured by Waters Co.)
Sample: [ cooking ] stirring at 100 ℃ for 20 minutes, [ concentration ]0.4 w/v%, [ filtration ] pore size of the chromatography plate 0.45 μm (manufactured by Kurabo)
Data processing: ASTRA (manufactured by Wyatt Corp.)
Evaluation method
(1) Weight per unit area: measured according to JIS P8124.
(2) And (3) thickness of paper: measured according to JIS P8118.
(3) Density: the weight per unit area and the thickness of the paper were determined in accordance with JIS P8118.
(4) Gloss of white paper
Measured at an angle of 75 degrees in accordance with JIS P-8142.
(5) Gloss of printing
After 4-color (ink, blue, red, yellow) printing was performed using an offset plate transfer machine (Toshiba offset BT600) and an offset printing ink (LEO-X M, Toyo ink Co., Ltd.), the surface of the blue solid portion of the printed matter was measured in accordance with JIS P8142.
(6) Ash content: measured according to JIS P8251.
(7) Type B viscosity of the coating
The prepared coating solution was measured at a liquid temperature of 30 ℃ and a rotational speed of 60rpm using a type B viscometer (model: LVDV-I, manufactured by Yinzhong Kogyo Co., Ltd.).
(8) High shear viscosity of the coating
The prepared dope was measured with a pendulum bob at a liquid temperature of 30 ℃ and a rotational speed of 8800rpm and F2.5 using a Hencury high shear viscometer (model: DV-10, manufactured by Kaltec Scientific Co., Ltd.).
Production and evaluation of pigment-coated paper
A pulp slurry composed of 65 parts of waste paper pulp, 20 parts of NBKP and 15 parts of LBKP was added with precipitated calcium carbonate as a filler so that the ash content in the paper became 16%, and 0.7 part of cationized starch and 0.3 part of Polyacrylamide (PAM) as an internal paper strength agent to prepare a paper stock.
Using the paper stock, paper was made by a paper machine of a gap former type in the form of a roll and a doctor blade former at a paper making speed of 1500 m/min, and wet paper was dewatered and dried in a press section by two shoe presses connected in series (press line pressure 1000kN/m, transfer belt in contact with the wire side of the second paper) to obtain 35.7g/m2The medium-grade coating base paper of (1).
Next, 1.5 parts of a carboxyl-modified styrene-butadiene copolymer latex (NP100C) as a binder and 10.0 parts of calcined dextrin were added to 100 parts of ground calcium carbonate (FMT 97: average particle size: 0.90 μm) as a pigment to prepare a coating solution. Dextrin having a deviation of average molecular weight of 300kDa or more was used in combination in production example 1 (comparative example), and dextrin having a difference of average molecular weight of about 50kDa was used in combination in production example 2 (example).
The coating liquid was used in an amount of 7.0g/m per one side of base paper2The coating liquid was continuously applied to both surfaces of the substrate by a blade coater of a spray-melt system and dried.
Next, in the finishing step, a 2-roll 6-set soft calender having an elastic roll with a shore D94 ° hardness was used, and the surface temperature of each metal roll was set to 130 ℃, and the nip pressure was set to 250kN/m, to perform surface treatment of the coated paper.
Since the paper making, coating and calender treatment were continuously carried out, the coating speed and calender speed were also 1500 m/min.
[ Table 2]
As is clear from the table, when dextrins having different molecular weights were used in combination, coated paper having excellent white paper gloss and print gloss was obtained in production example 2 in which the difference between the weight average molecular weights of the dextrins was 50 kDa.
Claims (5)
1. A coated paper having a pigment coating layer containing a pigment and a binder on a base paper,
the adhesive comprises a first dextrin and a second dextrin, wherein the weight-average molecular weight M1 of the first dextrin and the weight-average molecular weight M2 of the second dextrin are both less than 500kDa, and M1-M2 are less than 60 kDa.
2. The coated paper of claim 1, wherein the combined ratio of the first dextrin to the second dextrin is 2: 8-8: 2.
3. coated paper according to claim 1 or 2, wherein the first and second dextrins are both white dextrins.
4. The coated paper according to any one of claims 1 to 3, wherein M1 and M2 are each 150 to 400 kDa.
5. A method of making coated paper comprising:
a process for preparing a coating liquid containing a pigment and a binder, and
coating the coating liquid on base paper;
the adhesive comprises a first dextrin and a second dextrin, wherein the weight-average molecular weight M1 of the first dextrin and the weight-average molecular weight M2 of the second dextrin are both less than 500kDa, and M1-M2 are less than 60 kDa.
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| JP2019-143831 | 2019-08-05 | ||
| JP2019143831 | 2019-08-05 | ||
| PCT/JP2020/029304 WO2021024917A1 (en) | 2019-08-05 | 2020-07-30 | Coated paper and method for producing same |
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| CN114207214A true CN114207214A (en) | 2022-03-18 |
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| JP (1) | JP7000632B2 (en) |
| KR (1) | KR20220037517A (en) |
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| JP2015183301A (en) * | 2014-03-20 | 2015-10-22 | 日本製紙株式会社 | Coated paper and method of producing the same |
| CN105143552A (en) * | 2013-04-24 | 2015-12-09 | 罗盖特公司 | Dextrin-based coating slips |
| JP2017179680A (en) * | 2016-03-31 | 2017-10-05 | 日本製紙株式会社 | Coated paper |
| JP2017179275A (en) * | 2016-03-31 | 2017-10-05 | 日本製紙株式会社 | Starch for coated paper |
| JP2018162551A (en) * | 2018-06-25 | 2018-10-18 | 日本製紙株式会社 | Coated paper and production method thereof |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5241446B2 (en) | 2008-09-03 | 2013-07-17 | 花王株式会社 | Manufacturing method of coated paper |
| JP5798182B2 (en) | 2011-03-31 | 2015-10-21 | 日本製紙株式会社 | Coated paper and method for producing the same |
-
2020
- 2020-07-30 WO PCT/JP2020/029304 patent/WO2021024917A1/en active Application Filing
- 2020-07-30 JP JP2021537275A patent/JP7000632B2/en active Active
- 2020-07-30 KR KR1020227007263A patent/KR20220037517A/en unknown
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|---|---|---|---|---|
| JPH05195489A (en) * | 1992-01-22 | 1993-08-03 | Honen Corp | Starch composition for coating paper |
| CN102864675A (en) * | 2011-06-07 | 2013-01-09 | 王子制纸株式会社 | Manufacturing method of coated paper for printing |
| US20140329104A1 (en) * | 2011-11-18 | 2014-11-06 | Roquette Freres | Coating slips based on partially soluble dextrins of high molecular weight |
| CN104411884A (en) * | 2012-07-06 | 2015-03-11 | 罗盖特公司 | Coating slips for paper and cardboard containing a dextrin with a high amylopectin content |
| JP2014208936A (en) * | 2013-03-29 | 2014-11-06 | 日本製紙株式会社 | Coated paper |
| CN105143552A (en) * | 2013-04-24 | 2015-12-09 | 罗盖特公司 | Dextrin-based coating slips |
| JP2015183301A (en) * | 2014-03-20 | 2015-10-22 | 日本製紙株式会社 | Coated paper and method of producing the same |
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| JP2017179680A (en) * | 2016-03-31 | 2017-10-05 | 日本製紙株式会社 | Coated paper |
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| JP2018162551A (en) * | 2018-06-25 | 2018-10-18 | 日本製紙株式会社 | Coated paper and production method thereof |
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| JP7000632B2 (en) | 2022-02-10 |
| KR20220037517A (en) | 2022-03-24 |
| WO2021024917A1 (en) | 2021-02-11 |
| JPWO2021024917A1 (en) | 2021-10-21 |
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