JP2005194660A - Method for producing coated paper for printing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable a long-term stable operation in the production of a coated paper for printing even by a high-speed coating of ≥1,500 m/min by reducing abrasion of a blade and eliminating coating defects such as scratch, streak and bleeding. <P>SOLUTION: The method for producing the coated paper comprises coating a coating liquid containing ≥20 pts.wt. ground calcium carbonate based on 100 pts.wt. whole pigment, and a binder on a paper base so that the attached amount of the coated liquid expressed in terms of solid may be 5-20 g/m<SP>2</SP>per one surface at a coating speed of ≥1,500 m/min by a blade coater. The tip of the blade of the blade coater is subjected to a surface-processing treatment by a material consisting essentially of a metal oxide or a metal carbonate. The Vickers hardness of a part subjected to the surface-processing treatment is HV 600-1,300, and the point angle thereof is 30-50°. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a coated paper for printing which reduces blade wear and enables high-speed stable operation with a blade coater.

  In recent years, with the increasing demand for coated paper production, it has become necessary to increase its production speed. For this reason, for coating machines, the coating speed is increased, the paper width is increased and the coating agent solids are increased. Therefore, it is necessary to cope with high concentration of water.

  For this reason, blade coaters that have high-speed coating suitability and high paper quality are frequently used. That is, the blade coater is excellent in high-speed coating suitability, adjustment performance in a wide range of coating amount, coating suitability of high viscosity / high concentration paint, smoothness of the coated surface, etc. Compared with the features such as simple equipment, easy profile, low noise and easy operation, there are several types represented by tip (bevel) type and vent type. Blade coaters are generally known.

  In this coating method using a blade coater, a coating agent is supplied from a coating liquid supply means to the surface of a wide base paper that travels by the rotation of a backing roll, and the amount of the coating agent is supplied to a blade provided in the blade coater. Coating is performed by bringing a blade edge portion (tip bevel surface) into contact with a paper surface to generate a blade linear pressure in this portion, and adjusting and controlling the blade linear pressure. Thus, since the control of the coating agent amount by the blade coater is mainly performed by a reaction force obtained by mechanically deforming the blade, a high-carbon steel plate is usually suitable, cost, It was used from the viewpoint of the spring force of the material itself.

However, with a blade made of such a high carbon steel plate, a good coating result can be obtained within a certain time from the start of coating. There was a drawback that the conditions changed intermittently. Such a change in the wear of the doctor blade appears as a decrease in the coating amount, and in order to control this, it is necessary to reduce the linear pressure of the doctor blade, but as a result, the deformation amount of the doctor blade decreases, Due to this, various coating irregularities appear in the width direction of the coated base paper, and the coating surface feeling, that is, the judgment of whether or not the coating layer is uniformly coated becomes worse, and further the coating The paper width direction profile becomes worse. Thus, when the profile deteriorates, the doctor blade must be frequently replaced with a new one after several hours of use, which causes operational problems. Further, the degree of blade wear varies depending on the coating liquid. In particular, in the case of a lightweight coating having a coating amount of 12 g / m ² or less with a coating liquid containing calcium carbonate, the blade wear is very likely to proceed. There was a problem.

  On the other hand, in blade coating, various methods have been conventionally proposed for the purpose of suppressing and avoiding the occurrence of coating defects such as streak, scratch and bleeding. For example, in Patent Document 1 below, the bevel surface of the blade is coated with hard chrome plating, coated with a metal oxide or metal carbide such as alumina, or further coated with ceramic or the like, and is in contact with the base paper. Discloses a coating method in which the roughness Ra of the bevel surface of the blade is specified to be 0.2 μm or less. In the following Patent Document 2, the base material of the coating blade contains chromium or is a base material whose surface is processed with chromium, and the base material of the base material is provided with a nitriding treatment layer nitrided from the surface or surface of the base material. Blades have been proposed. In the following Patent Document 3, in a method for producing a coated paper in which a coating liquid containing a pigment and an adhesive is coated on a base paper on-machine, an undercoat coating liquid is coated using a film transfer type coating apparatus. Then, using a fountain-applied blade coater, apply the top coat solution in the range of fountain angle of 40-60 °, blade tip angle of 45-50 °, and blade thickness of 0.45-0.60 mm. A method of manufacturing a multilayer coated paper to be covered is disclosed. Further, in Patent Document 4 below, for gravure printing, the surface of the blade is coated with chrome plating, and the coating liquid is applied by a blade coater provided with a blade having a surface roughness of 0.2 μm or less. A method for producing coated paper is disclosed.

However, according to Patent Documents 1 to 4, although the wear of the blade can be suppressed to some extent, it is possible to extend the time that can be stably operated as compared with a blade made of a high-carbon steel plate that exists conventionally, In particular, when the coating speed exceeds 1500 m / min, there is a problem that coating defects such as streaks, scratches and bleeding due to the fluidity and water retention of the coating liquid tend to occur remarkably.
JP-A-8-260388 Japanese Patent Laid-Open No. 2002-254014 JP-A-11-131387 JP 2001-303487 A

  The present invention has been made in view of the above-described circumstances, and its object is to reduce blade wear and reduce scratches in the production of coated paper for printing by high-speed coating of 1500 m / min or more. Another object of the present invention is to provide a method for producing a coated paper for printing that eliminates coating defects such as streak and bleeding and enables stable operation for a long time.

  The inventors of the present invention have conducted extensive research on how to suppress blade wear even when high-speed coating with a blade coater is performed and enable stable operation for a long time. While the liquid is a coating liquid containing heavy calcium carbonate at a certain concentration or more (20 parts by weight or more) in the pigment, while preventing fluidity deterioration of the coating liquid under a high shear rate, It has been found that this can be achieved by subjecting the tip of the blade to surface processing with a metal oxide or metal carbide and defining the Vickers hardness and tip angle of the surface processing portion within a predetermined range.

The present invention has been made based on such a viewpoint, and the above-mentioned problems can be achieved by the following (1), (2) and (3).
(1) On a paper substrate, a coating liquid containing 20 parts by weight or more of heavy calcium carbonate with respect to 100 parts by weight of the total pigment and containing an adhesive is coated on one side with a solid content of the coating liquid. The coating is performed at a coating speed of 1500 m / min or more with a blade coater so as to be 5 to ²⁰ g / m ^2, and the blade tip of the blade coater is made of a material mainly composed of metal oxide or metal carbide. A method for producing a coated paper for printing, wherein a processing treatment is performed and the surface processing portion has a Vickers hardness of Hv 600 to 1300 and a tip angle of 30 to 50 degrees.
(2) The printing coating according to the above (1), wherein the solid content concentration of the coating liquid is 50 to 72% and the capillary viscosity at a shear rate of 10 ⁵ sec ⁻¹ is 70 mPa · s or less. A method of manufacturing paper.
(3) The heavy calcium carbonate is a wet heavy calcium carbonate having an average particle size in the range of 0.3 to 2.0 μm and a weight ratio of the particle size exceeding 2.0 μm of 10% or less. The manufacturing method of the coated paper for printing as described in said (1) or (2) which is.

  According to the method for producing a coated paper for printing according to the present invention, in the production of the coated paper for printing by high-speed coating of 1500 m / min or more, the wear of the blade is reduced and coating such as scratch, streak, bleeding, etc. Defects can be eliminated and stable operation for a long time can be achieved.

Hereinafter, the present invention will be described in more detail.
The raw material pulp of the base material of the coated paper for printing used in the present invention is not particularly limited. For example, chemical pulp such as softwood kraft pulp (NBKP), hardwood kraft pulp (LBKP), GP, RGP, PGW, Mechanical pulp such as SGP, BCTMP, and CTMP, waste paper pulp, or non-wood pulp such as kenaf, bamboo, hemp, and straw can be used alone or in admixture of two or more. As fillers, inorganic fillers such as talc, calcium carbonate, titanium dioxide, clay, calcined clay, synthetic zeolite and silica, and organic fillers such as polystyrene latex and urea formalin resin can be used. Moreover, you may apply | coat the paper strength enhancer well-known in manufacture of printing papers, such as starch, polyvinyl alcohol, polyacrylamide, in a size press process. An undercoat layer mainly composed of a pigment and an adhesive can also be provided.

On the other hand, the basis weight of the substrate is not particularly limited, and may be a basis weight of a general printing coated paper, specifically, a basis weight of 25 to 300 g / m ² . Further, the paper making method of the base material is not particularly limited, and any of acid paper making and alkaline paper making may be used.

  The component of the coating liquid used in the present invention is mainly composed of a pigment and an adhesive, and contains 20 parts by weight or more of heavy calcium carbonate as a pigment with respect to 100 parts by weight of the total pigment. If it is less than 20 parts by weight, the rheology modification effect of heavy calcium carbonate, that is, the decrease in viscosity due to the increase in shear rate cannot be expected in high-speed blade coaters, specifically, high-speed coating of 1500 m / min or more. There is a risk that coating defects such as streak and bleeding may occur. Heavy calcium carbonate may be produced by either dry pulverization or wet pulverization, but it is desirable to use a wet type that is easy to control the particle size and particle size distribution and has good fluidity. In addition, wet heavy calcium carbonate having an average particle diameter in the range of 0.3 to 2.0 μm and a weight ratio of the particle diameter exceeding 2.0 μm being 10% or less is more preferably used.

  As pigments other than heavy calcium carbonate, depending on applications and needs, clay, delaminated clay, calcined clay, light calcium carbonate, titanium dioxide, calcium sulfate, barium sulfate, aluminum hydroxide, satin white, zinc oxide, Various known pigments such as inorganic pigments such as magnesium carbonate and talc, and organic pigments such as polystyrene particles, urea formalin particles, styrene / acrylic copolymer particles, and polyethylene particles may be contained. Two or more of these pigments may be mixed.

  Examples of the adhesive used for the coated paper for printing include conjugated diene copolymers such as styrene / butadiene copolymer latex, methyl methacrylate / butadiene copolymer latex, and styrene / methyl methacrylate / butadiene copolymer latex. Polymer latex, acrylic latex and / or methacrylic ester polymer or copolymer latex, etc. acrylic latex, ethylene / vinyl acetate polymer latex and other vinyl latex, and these various polymer latexes as carboxyl groups, etc. Alkali partially soluble or insoluble latex modified with any functional group-containing monomer, oxidized starch, urea phosphated starch, hydroxyethyl etherified starch, starch such as dextrin, casein, synthetic protein, soy protein Known proteins, etc. Various adhesives can be used. These adhesives may be used alone or in combination of two or more.

  Furthermore, in addition to the pigments and adhesives described above, various auxiliary agents such as dispersants, lubricants, thickeners, antifoaming agents, water-proofing agents, colorants and the like can be appropriately blended according to the purpose of use and needs. it can.

More preferably, the coating liquid used in the present invention has physical properties such that the solid content concentration is 50 to 72% and the capillary viscosity at a shear rate of 10 ⁵ sec ⁻¹ is 70 mPa · s or less. It is. If the solid concentration is less than 50%, the drying load after coating increases, and the coating layer strength decreases and the amount of adhesive in the coating solution must be increased to compensate for this. If pulled, there is a risk that problems such as a decrease in ink acceptability associated with a decrease in the void amount of the coating layer may occur. On the other hand, if it exceeds 72%, the viscosity of the coating solution greatly changes due to a slight change in the solid content concentration, and stable coating becomes difficult. On the other hand, when the capillary viscosity exceeds 70 mPa · s, coating defects such as scratches, streaks, and bleeding tend to occur in high-speed coating at 1500 m / min or more. More preferably, the solid content concentration is 55 to 68%, and the capillary viscosity is 60 mPa · s or less.

The coating agent described above is applied by a blade coater. As the coating apparatus, either an on-machine in which the paper machine and the coater are integrated, or an off-coater in which the paper machine and the coater are separated may be used. With a blade coater, a coating layer surface with higher smoothness can be obtained, so that a coated paper for printing with excellent printability can be obtained, and high-speed coating (for example, 1500 m / min or more) is possible. Used for reasons such as high productivity. On the other hand, in the high speed coating of the blade coater, the coating liquid is placed under a high shear rate (10 ⁵ sec ⁻¹ or more) when passing through the blade, and as a result, coating defects due to deterioration of the fluidity of the coating liquid. There is a drawback that it is easy to occur.

  In order to prevent the deterioration of the fluidity, 20 parts by weight or more of heavy calcium carbonate is added to all pigments as described above. However, although the fluidity is improved by adding heavy calcium carbonate, the hardness of heavy calcium carbonate is 1.5 times higher than kaolin and 3 times higher than talc. As the coating speed increases, however, it progresses at an accelerated rate, causing a problem that hinders continuous operation (usually 8 hours or more).

Therefore, in the present invention, in order to reduce the wear of the blade, enable continuous operation at a coating speed of 1500 m / min or more, and obtain a coated paper with excellent surface properties, the tip of the blade is subjected to metal oxidation. Surface processing is performed with a material mainly composed of a metal or a metal carbide, and a blade having a Vickers hardness of Hv 600 to 1300 and a tip angle of 30 to 50 degrees is used. Examples of the metal oxide include alumina (Al ₂ O ₃ ), chromium oxide (Cr ₂ O ₃ ), zirconia (ZrO ₂ ), zircon (ZrSiO ₄ ), titania (TiO ₂ ), and the like. Examples include tungsten carbide (WC) and chromium carbide (Cr ₃ C ₂ ). As the surface processing method, methods such as gas flame spraying and plasma spraying are employed. Among these, the use of a blade obtained by surface-treating a metal oxide mainly composed of alumina by plasma spraying is particularly preferable from the viewpoint of the surface smoothness of the coated paper to be obtained. The thickness of the surface processed material layer is not particularly limited as long as it is within the above-mentioned hardness range, but 0.05 to 0.4 mm is particularly desirable.

  If the Vickers hardness (Hv) of the tip processed portion is less than 600, there will be no effect of preventing wear, and if the Vickers hardness (Hv) exceeds 1300, wear will be extremely slow, and profile control of the coating amount will be difficult. Therefore, it is not preferable. Vickers hardness Hv750-1150 is a more suitable range.

  If the tip angle of the blade is less than 30 degrees, the coating liquid tends to be excessively applied, and the coating amount control becomes difficult, and coating defects such as bleeding and scratches are likely to occur. On the other hand, when the angle exceeds 50 degrees, it is difficult to apply the coating liquid. In this case, it is difficult to control the coating amount, and it is difficult to control the profile of the coating amount. A more preferable range of the blade tip angle is 32 to 48 degrees.

  The thickness and width of the base material of the blade are not particularly limited, but considering the profile control of the coating amount, the surface quality of the obtained coating layer surface, the thickness is 0.3 to 0.7 mm, the width is The thickness is preferably 65 to 110 mm, and more preferably 0.45 to 0.65 mm in thickness and 70 to 100 mm in width. The material is preferably high carbon steel, but for example, materials such as stainless steel, cast steel, ceramic, heat resistant plastic, aluminum, and copper can also be used.

On the other hand, the coating amount of the coating agent is 5 to 20 g / m ² per side in terms of solid content. If it is less than 5 g / m ² , the covering property of the base paper is insufficient and satisfactory smoothness cannot be obtained. If it exceeds 20 g / m ² , it becomes difficult to control the profile of the coating amount and the coating is increased due to an increase in the drying load. There is a problem that the work speed is limited. More preferably 7~15g / ^{m 2.}

  After coating the coating agent with a blade coater, for example, the coating for main printing is performed by various known heating methods such as hot air heating, infrared heater heating, gas heater heating, steam heating, electric heater heating, and high-frequency heating. The paper can be dried. In addition, about drying conditions, it is necessary to adjust suitably according to the chemical | medical agent etc. to be used. In addition, a known smoothing apparatus such as a super calender, soft calender, gloss calender, or rough surface mat roll calender is appropriately used on-machine or off-machine after coating and drying in order to further improve the smoothness. However, the pressurization mode, the number of pressurization nips, heating, and other conditions are appropriately adjusted according to a normal smoothing apparatus.

[Example 1]
Papermaking pulp slurry consisting of 80% by weight of LBKP and 20% by weight of NBKP, 0.3% by weight of neutral sizing agent (alkyl ketene dimer), and calcium carbonate added as a filler so that the ash content is 10%. Paper was made by a machine, and a coated base paper having a basis weight of 50 g / m ² was prepared by applying oxidized starch in a size press process so that the solid content was 2 g / m ^{2 on} both sides.

  As a pigment for the coating liquid, 50 parts by weight of wet-pulverized heavy calcium carbonate having an average particle diameter of 0.7 μm and a weight ratio of the particle diameter exceeding 2 μ of 8%, and 50 weight of clay having an average particle diameter of 0.7 μm Part, using 10 parts by weight of styrene-butadiene copolymer latex and 3 parts by weight of phosphate esterified starch as an adhesive, and 0.5 parts by weight of calcium stearate as an auxiliary, Water was added to this coating solution to adjust the solid content concentration to 65%.

This coating solution is continuously applied to the base paper for 24 hours at a coating speed of 1900 m / min using a blade with the following specifications so that the coating amount per side is 10 g / m ^{2 on a} solid basis. It was.

Blade specification;
<Surface treatment> Alumina spraying (main component Al ₂ O ₃ ), thickness 200 μm, Vickers hardness; Hv900
<Tip angle> 40 degrees <Base material> Material: High carbon steel, thickness: 0.5 mm, width: 80 mm
After the above coating and drying, a 12-stage super calendar process was applied to obtain a coated paper for printing.

[Example 2]
A coated paper for printing was obtained in the same manner as in Example 1 except that the tip angle of the blade was changed to 30 degrees.

Example 3
A coated paper for printing was obtained in the same manner as in Example 1 except that the tip angle of the blade was changed to 50 degrees.

Example 4
A coated paper for printing was obtained in the same manner as in Example 1 except that the surface treatment of the blade was changed to a material mainly composed of alumina and zirconia, and the Vickers hardness was changed to Hv600.

Example 5
A coated paper for printing was obtained in the same manner as in Example 1 except that the surface treatment of the blade was replaced with a material mainly composed of chromium oxide and the Vickers hardness was replaced with Hv1300.

Example 6
As a pigment of the coating liquid, 20 parts by weight of wet-pulverized heavy calcium carbonate having an average particle diameter of 0.7 μm and a weight ratio of the particle diameter exceeding 2 μ is 8%, and 80 weight of clay having an average particle diameter of 0.7 μm. The coated paper for printing was obtained in the same manner as in Example 1 except that the part and solid content concentrations were changed to 50%.

Example 7
As the pigment of the coating liquid, except that the weight ratio of the weight average particle diameter of 0.7 μm and the particle diameter exceeding 2 μ is 8%, wet heavy calcium carbonate is 100 parts by weight, and the solid content concentration is changed to 72%. In the same manner as in Example 1, a coated paper for printing was obtained.

[Comparative Example 1]
A coated paper for printing was obtained in the same manner as in Example 1 except that the tip angle of the blade was changed to 25 degrees.

[Comparative Example 2]
A coated paper for printing was obtained in the same manner as in Example 1 except that the tip angle of the blade was changed to 55 degrees.

[Comparative Example 3]
A coated paper for printing was obtained in the same manner as in Example 1, except that the surface treatment of the blade was changed to a material mainly composed of alumina and zirconia and the Vickers hardness was changed to Hv580.

[Comparative Example 4]
A coated paper for printing was obtained in the same manner as in Example 1 except that the surface treatment of the blade was replaced with a material mainly composed of chromium oxide and the Vickers hardness was replaced with Hv1350.

[Comparative Example 5]
As a pigment for the coating solution, 15 parts by weight of wet-pulverized heavy calcium carbonate having an average particle diameter of 0.7 μm and a weight ratio of the particle diameter exceeding 2 μ is 8%, and 85 weight of clay having an average particle diameter of 0.7 μm. The coated paper for printing was obtained in the same manner as in Example 1 except that the part and solid content concentrations were changed to 50%.

[Comparative Example 6]
A coated paper for printing was obtained in the same manner as in Example 1 except that the solid content concentration of the coating liquid was changed to 48%.

[Comparative Example 7]
As the pigment of the coating liquid, except that the weight ratio of the weight average particle diameter of 0.7 μm and the particle diameter exceeding 2 μ is 8% wet heavy calcium carbonate is 100 parts by weight, and the solid content concentration is changed to 73%. In the same manner as in Example 1, a coated paper for printing was obtained.

[Comparative Example 8]
A coated paper for printing was obtained in the same manner as in Example 1 except that the blade was replaced with a blade plated with chrome (Hv 950, tip angle 40 degrees).

(Capillary viscosity measurement method)
Using “High Flow Simulator HF2002C” manufactured by Yonekura Seisakusho Co., Ltd., the measurement conditions were a load of 2 kN and a nozzle diameter of 0.25 mm.

(Evaluation methods)
<Coating operability>
A continuous operation is performed for 24 hours at a coating speed of 1900 m / min. During this period, the occurrence of coating defects such as streak, scratch and bleeding is observed. The evaluation was made in three stages: “a few defects are generated but there is no problem in practical use”, and “a coating defect is remarkably generated and is a problem”.
<Abrasion of blade>
The blade after continuous operation for 24 hours at a coating speed of 1900 m / min was visually evaluated, and “Abrasion progress is scarce”, “Abrasion progress is observed but no problem”, and “Abrasion” The progress of "is a serious problem".
<Coating surface>
Visually evaluate the coating surface properties (smoothness, gloss unevenness, etc.) of the coated paper for printing obtained by supercalendering the coated paper after continuous operation for 24 hours at a coating speed of 1900 m / min. “No gloss unevenness and smooth surface”, ○ “Slight gloss unevenness but no problem in practical use” and × “Gloss unevenness is a serious problem”. The results are shown in Table 1. In addition, this invention is not limited to the range of this Example.

  As described above, in the case of the coated paper according to the present example, it is understood that all of the coating operability, the blade wearability, and the coating surface feeling are satisfied with a good balance.

Claims (3)

On a paper base material, a coating liquid containing 20 parts by weight or more of heavy calcium carbonate with respect to 100 parts by weight of all pigments and containing an adhesive, the solid content adhesion amount of the coating liquid is 5 to 5 per side. A blade coater is applied at a coating speed of 1500 m / min or more so that the surface becomes 20 g / m ^2, and the blade tip of the blade coater is surface-treated with a material mainly composed of metal oxide or metal carbide. A method for producing a coated paper for printing, wherein the surface-treated portion has a Vickers hardness of Hv 600 to 1300 and a tip angle of 30 to 50 degrees. 2. The production of coated paper for printing according to claim 1, wherein the coating liquid has a solid content concentration of 50 to 72% and a capillary viscosity at a shear rate of 10 ⁵ sec ⁻¹ of 70 mPa · s or less. Method. The heavy calcium carbonate is wet heavy calcium carbonate having an average particle diameter in the range of 0.3 to 2.0 μm and a weight ratio of the particle diameter exceeding 2.0 μm of 10% or less. Item 3. A method for producing a coated paper for printing according to Item 1 or 2.