JP2013108193A - Printing paper and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing printing paper with less colored streaks by a blade coater, a rod coater and a rod-metering film transfer method and to provide printing paper produced by the method.SOLUTION: There is provided a method for producing printing paper in which at least one coating layer is provided by applying a coating liquid containing a white pigment and a binder as main constituents and further containing a pigment for coloring on at least on one surface of base paper by any of a blade coater method, a rod coater method, and a rod-metering film transfer method. At least the pigment for coloring is obtained by dispersing pigment by an anionic high polymer. The anionic high polymer has a weight average molecular weight of 8,000-30,000 and the pigment for coloring has a volume average diameter of 0.1-0.5 μm by a precipitation method of measuring particle size of pigment.

Description

  The present invention relates to a printing paper manufacturing method. More specifically, the present invention relates to a method for producing a printing paper with less generation of colored stripes in a blade coater, a rod coater, and a rod metering film transfer.

  In general, a printing paper is provided with a coating layer mainly composed of a white pigment and a binder in order to impart aesthetics and printability. The coating layer enhances the quality of printed matter by imparting high whiteness, opacity and smoothness to the printing paper. In addition, printability is improved by improving ink acceptability. As printing methods, offset, gravure, electrophotography, and inkjet are generally used.

  For raw paper and white pigments, materials that are processed in white are often selected, but since these materials originally have a slight yellow or green color, the whiteness of the appearance is determined by blending blue or purple coloring pigments as auxiliary agents. There are many ways to increase A blade coater, rod coater, or rod metering film transfer suitable for mass production is usually used as a method of providing a coating layer, but there is a problem that colored streaks occur when the coating liquid is scraped off with a blade or rod. Therefore, improvement has been demanded in order to reduce the product yield of printing paper.

  As a method of reducing the occurrence of colored stripes, a method of adding a coloring pigment to water by adding a dispersing agent or a protective colloid agent and then adding it to a dispersion of a white pigment adjusted to an alkaline pH region and a binder (for example, Patent Document 1) and a method of adding an organic coloring pigment after adjusting a white pigment containing light calcium carbonate to an alkaline pH region (for example, see Patent Document 2) have been proposed, but sufficient improvement is obtained. Not.

JP 58-31194 A JP 2010-236115 A

  An object of the present invention is to provide a method for producing a printing paper with less generation of colored stripes in a blade coater, a rod coater, and a rod metering film transfer.

  As a result of intensive studies to solve the above problems, the present inventors have invented the following printing paper manufacturing method.

  That is, at least one surface of the base paper is mainly composed of a white pigment and a binder, and further contains a coloring pigment, and is applied by any one of a blade coater, a rod coater, and a rod metering film transfer. In the method for producing a printing paper provided with a coating layer, at least the coloring pigment is dispersed by an anionic polymer, and the weight average molecular weight of the anionic polymer is 8,000 to 30,000, A volume average diameter of the coloring pigment measured by a sedimentation type particle size measuring method is 0.1 to 0.5 μm.

  Moreover, in the preparation of the coating liquid for forming the coating layer, after mixing the white pigment and the coloring pigment, the binder is added after adjusting the pH of the coating liquid to 9.0 to 12.0. It is desirable.

  The printing paper manufacturing method of the present invention enables efficient production with a high yield with less generation of colored stripes in a blade coater, rod coater, and rod metering film transfer.

  Hereinafter, the printing paper manufacturing method of the present invention will be described in detail.

<Base paper>
As the base paper of the printing paper used in the present invention, it is possible to use a sheet of plant fibers such as wood pulp, cotton, hemp, bamboo, sugarcane, corn and kenaf.

  These fibers include heavy calcium carbonate, light calcium carbonate, kaolin, talc, clay, titanium dioxide, aluminum hydroxide, silica, alumina, various fillers such as organic pigments, binders, sizing agents, fixing agents, and yields. Various compounding agents such as an agent and a paper strength enhancer can be suitably contained.

As a method for obtaining a base paper by forming fibers into a sheet, a general wet papermaking method is used. The basis weight is not particularly limited, but 30 to 450 g / m ² is desirable.

  The base paper can be subjected to a surface size press in order to obtain the required size, surface strength, and air permeability. As the components of the surface size press solution, starch purified from natural plants, hydroxyethylated starch, oxidized starch, etherified starch, phosphate esterified starch, enzyme-modified starch and cold water soluble starch obtained by flash drying them, Examples thereof include acrylic surface sizing agents such as acrylic, styrene / acrylic, acrylic / vinyl acetate, and olefinic surface sizing agents such as styrene / maleic acid, styrene / olefin, olefin / maleic acid, diisobutylene / maleic acid, and the like.

<Coating layer>
In the present invention, the coating layer provided on at least one side of the base paper is mainly composed of a white pigment and a binder, and a coloring pigment is blended. The coating amount is not particularly limited, but is preferably ² to 40 g / m ^{2 in} total per one side.

  In the present invention, white pigments include kaolin, heavy calcium carbonate, light calcium carbonate, synthetic silica, talc, satin white, lithopone, titanium dioxide, alumina, aluminum hydroxide, zinc oxide, magnesium carbonate, organic pigments, or these Two or more types of complexes may be mentioned. These can be used alone or in combination.

  Examples of binders include latexes of various copolymers such as styrene / butadiene latex, acrylic, polyvinyl acetate, ethylene / vinyl acetate, polyvinyl alcohol, modified polyvinyl alcohol, sodium polyacrylate, polyethylene oxide, polyacrylamide, urea, or melamine. And water-soluble synthetic compounds such as polyethyleneimine, polyamide polyamine, and epichlorohydrin. Furthermore, starch purified from natural plants, hydroxyethylated starch, oxidized starch, etherified starch, phosphate esterified starch, enzyme-modified starch, cold water soluble starch obtained by flash drying them, dextrin, mannan, chitosan, Examples thereof include natural polysaccharides such as arabinogalactan, glycogen, inulin, pectin, hyaluronic acid, carboxymethylcellulose and hydroxyethylcellulose, oligomers thereof, and modified products thereof. Examples thereof include natural proteins such as casein, gelatin, soybean protein, collagen, and modified products thereof, and synthetic polymers and oligomers such as polylactic acid and peptides. These can be used alone or in combination. It is preferable that a binder is 5-30 mass parts with respect to 100 mass parts of white pigments.

  In the present invention, as the coloring pigment, a blue or purple-colored inorganic substance, organic substance, or a composite fine particle thereof is used. Typical materials include ultramarine, ultramarine, phthalocyanine, dioxazine, indigoid, anthraquinone, quinacridone, and xanthene.

  The weight average molecular weight of the anionic polymer used for stably dispersing the coloring pigment according to the present invention is preferably 8,000 to 30,000. The weight average molecular weight here is a value determined by the GPC method. When the weight average molecular weight of the anionic polymer is less than 8,000, the adsorption ability of the anionic polymer to the coloring pigment having a volume average diameter of 0.1 to 0.5 μm is decreased, and the dispersibility of the coloring pigment is reduced. This is not preferable because it is damaged and easily re-aggregates over time. Further, if the weight average molecular weight exceeds 30,000, the viscosity of the coloring pigment dispersion dispersed with the anionic polymer is increased, which is not preferable.

  Further, the volume average diameter of the coloring pigment according to the present invention by the sedimentation type particle size measuring method is preferably 0.1 to 0.5 μm. When the volume average diameter exceeds 0.5 μm, the dispersion stability of the color pigment is impaired, and in this case, re-aggregation easily occurs with time. The re-aggregation of the coloring pigment causes coloring stripes in the blade coater, rod coater, and rod metering film transfer. When the volume average diameter is less than 0.1 μm, the viscosity of the coloring pigment dispersion increases, which is not preferable. In the present invention, the volume average diameter of the coloring pigment is determined by a centrifugal sedimentation type particle size distribution measuring device, and representative examples include Nikkiso, Horiba, and Beckman Coulter products.

  What is necessary is just to adjust the quantity and pigment kind of the pigment for coloring mix | blended with the coating layer which concerns on this invention so that it may become desired whiteness as a printing paper. Although the compounding quantity of the coloring pigment with respect to a white pigment is not specifically limited, It is preferable that a coloring pigment is 0.00001-0.5 mass part with respect to 100 mass parts of white pigments.

  In the present invention, the anionic polymer used to stably disperse the coloring pigment has a structure having an anionic group such as carboxylic acid, sulfonic acid, sulfuric acid, phosphoric acid, phosphonic acid or the like that acts as a negative ion in water. It is a polymer having two or more and is provided as a salt such as sodium. Specific examples of the anionic polymer according to the present invention include sodium polyoxyethylenecarboxylate, carboxy-modified polyvinyl alcohol, sodium poly (meth) acrylate, sulfonated styrene (copolymerization) resin, naphthalene sulfonate formalin condensate, Examples include sodium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl ether phosphate, sodium polyoxyethylene alkyl phenyl ether phosphate, phosphate esterified starch, sodium alginate, sodium carboxymethyl cellulose, and sodium is potassium or ammonium. There may be. Moreover, the oxyethylene part may be partially or entirely oxypropylene. Of these, sodium polyacrylate is preferred, and other anionic groups and nonionic groups may be partially introduced as necessary. These may be used alone or in combination of two or more.

  In the present invention, the anionic polymer in which the coloring pigment is dispersed is preferably dispersed by using 10.0 to 0.01 parts by weight with respect to 100 parts by weight of the coloring pigment. Further preferred. The coloring pigment is preferably dispersed alone in water and then added to an aqueous dispersion mainly composed of a white pigment and a binder. Further, the coloring pigment is added while the aqueous dispersion of the white pigment is being stirred. It is preferable to add a binder and various auxiliaries after sufficiently mixing the mixture.

  In addition, the final pH of the coating liquid according to the present invention is preferably 9.0 to 12.0. By setting the pH within this pH range, the electrical repulsive force between the anionic polymers increases, thereby increasing the color pigment. Reaggregation is less likely to occur. The final pH of the more desirable coating solution is 9.5 to 11.0. Furthermore, it is more preferable that after mixing the white pigment and the coloring pigment, the pH is once adjusted to 9.0 to 12.0 and then mixed with the binder, and the re-aggregation of the coloring pigment is very unlikely to occur.

  For the coating layer according to the present invention, various auxiliary agents such as a thickener, an antifoaming agent, a surfactant, a pH adjuster, a dye, a water-proofing agent, and a lubricant are used as necessary. Can be contained.

  In the present invention, in addition to the coating layer by blade coater, rod coater, rod metering film transfer, it is possible to overlap the coating layer, and each method such as curtain (direct fountain), air knife, spray coater, casting, etc. Can be used as appropriate.

<Finish>
The offset printing paper for laminator processing in the present invention is calendered to obtain the required smoothness, density, air permeability, ink acceptability and glossiness. The apparatus is a combination of an elastic roll and a hard roll, and is called a machine calendar, a soft nip calendar, a super calendar, a multistage calendar, a multinip calendar, or the like. Also, a device composed of a combination of a belt and a roll can be used, which is called a shoe calender, a metal belt calender, or the like. As the microscopic shape of the roll surface, a mirror surface is preferably used in order to improve smoothness, but a matte surface or a surface processed for embossing may be used. In addition, the roll may be heated in order to enhance the calendar processing effect.

  The finally obtained printing paper is processed into a large or small sheet shape or roll shape according to the application, and becomes a product. During storage, it is preferable to apply moisture-proof packaging to avoid moisture absorption. The basis weight of the product is not particularly limited.

  Examples of the present invention will be described below, but the present invention is not limited to these examples. Further, “parts” and “%” shown in the examples indicate parts by mass and mass% of solid content unless otherwise specified.

(Example 1) to (Example 9) and (Comparative Example 1) to (Comparative Example 3)
Printing paper was prepared according to the following contents.

<Preparation of pulp slurry>
LBKP (Drainage 420 mlcsf) 80 parts NBKP (Drainage 450 mlcsf) 20 parts Light calcium carbonate filler (indicated by ash content in base paper) 9 parts Commercial cationized starch 1.0 part Commercial cationic polyacrylamide yield improver 0.03 Part Commercially available alkyl ketene dimer internal sizing agent 0.05 part Commercial sulfuric acid band 1.0 part <Preparation of base paper>
A pulp slurry was prepared using the above-mentioned pulp and internal chemicals in the above-described composition, and a base paper was made with a long net paper machine at a basis weight of 100.0 g / m ² . A total of 2.0 g / m ^{2 of} a surface-size press solution containing oxidized starch was applied to the base paper on both sides in terms of solid content.

<Preparation of coating solution>
(1) Commercial heavy calcium carbonate (volume average diameter 1.2 μm) 50 parts (2) Commercial primary kaolin (volume average diameter 2.3 μm) 50 parts (3) Coloring pigments (A to I) 0.1 part (4) Commercial styrene / butadiene latex binder 10 parts (5) Commercial phosphorylated starch 2 parts (6) Commercial printability improver 0.3 part (7) Commercial synthetic water retention agent (alkali thickening type) 0.1 Part

  (1) and (2) are pre-dispersed in water with a commercially available sodium polyacrylate dispersant (weight average molecular weight 5,000), and (3) is each method shown in the following <coloring pigment>. (4), (6), and (7) were already dispersed in water when they were obtained, and (5) was gelatinized by heating in a separate cooking tank. I used something.

<Coloring pigment>
In the coloring pigment A, phthalocyanine fine particles having a volume average diameter of 0.2 μm were dispersed with sodium polyacrylate having a weight average molecular weight of 8,000.
As the coloring pigment B, phthalocyanine fine particles having a volume average diameter of 0.2 μm were dispersed with sodium polyacrylate having a weight average molecular weight of 10,000.
As the coloring pigment C, phthalocyanine fine particles having a volume average diameter of 0.2 μm were dispersed with sodium polyacrylate having a weight average molecular weight of 30,000.
In the coloring pigment D, phthalocyanine fine particles having a volume average diameter of 0.1 μm were dispersed with sodium polyacrylate having a weight average molecular weight of 10,000.
As the coloring pigment E, dioxazine-based fine particles having a volume average diameter of 0.1 μm were dispersed with sodium polyacrylate having a weight average molecular weight of 10,000.
In the coloring pigment F, phthalocyanine fine particles having a volume average diameter of 0.5 μm were dispersed with sodium polyacrylate having a weight average molecular weight of 10,000.
As the coloring pigment G, phthalocyanine fine particles having a volume average diameter of 0.8 μm were dispersed with sodium polyacrylate having a weight average molecular weight of 10,000.
As the coloring pigment H, ultramarine fine particles having a volume average diameter of 0.8 μm were dispersed with sodium polyacrylate having a weight average molecular weight of 10,000.
As the coloring pigment I, phthalocyanine fine particles having a volume average diameter of 0.8 μm were dispersed with sodium polyacrylate having a weight average molecular weight of 5,000.

  (1) was put into a mixing tank and stirred with a stirring device with blades, and (2) to (7) were added in order thereto to prepare a coating solution. The coating solution was appropriately adjusted with water to a solid content concentration suitable for blade coating. In Examples 1 to 6 and Comparative Examples 1 to 3, after adding (7), the pH was adjusted to 10.0 with sodium hydroxide. In Examples 7 to 9, after blending (3), the pH shown in Table 1 was adjusted with sodium hydroxide, and (4) to (7) were further added. For Examples 7 and 9, the pH was finally adjusted to 10.0 again with sodium hydroxide.

These coating liquids were coated on both sides by a blade coating method, dried, and then subjected to a calendar process for smoothing. The coating amount was 15 g / m ² per side as a solid content.

<Colored streaks>
About the printing paper obtained from the manufacturing method of the said Example and the comparative example, the generation | occurrence | production number of the coloring streak was measured with the automatic fault detector using a high-speed camera. The quality criteria are as follows. However, intermediate evaluation, for example, 4.5 between 5 and 4.
5: There is no coloring stripe.
4: There are almost no colored stripes.
3: A level at which coloring streaks are generated but there is no practical problem.
2: There are many colored stripes.
1: There are very many colored stripes.

<Evaluation results>
In Examples 1 to 6, there was almost no generation of colored stripes in the blade coater, and good results were obtained. In Examples 7 to 9, after the white pigment and the coloring pigment were added, the pH was once adjusted appropriately, and further excellent results were shown. In Comparative Examples 1 to 3, there are many colored streaks, and it is necessary to remove these colored streaks in practical use.

  The printing paper manufacturing method of the present invention can be used for a printing paper manufacturing method for printing methods such as offset, gravure, ink jet, and electrophotography.

Claims (3)

  Apply at least one side of the base paper with a white pigment and a binder as a main component, and a coating liquid containing a coloring pigment by one of blade coater, rod coater, and rod metering film transfer. In the method for producing a printing paper provided with a layer, at least the coloring pigment is dispersed by an anionic polymer, the weight average molecular weight of the anionic polymer is 8,000 to 30,000, and the coloring A method for producing a printing paper, characterized in that a volume average diameter by a sedimentation-type particle size measuring method for a pigment is 0.1 to 0.5 μm.   In the preparation of the coating liquid for forming the coating layer, after mixing the white pigment and the coloring pigment, the binder is added after adjusting the pH of the coating liquid to 9.0 to 12.0. The printing paper manufacturing method according to claim 1.   A printing paper produced by the production method according to claim 1.