JP3401780B2 - Method for producing glossy coated paper for gravure printing - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to the production of a gloss coated paper for gravure printing, in which a base paper is coated with a coating liquid containing a pigment and an adhesive, at a low cost to produce a product excellent in quality and operability. The present invention relates to a method for producing a glossy coated paper for gravure printing.

[0002]

2. Description of the Related Art In recent years, demand for printing paper has increased in the commercial printing field for the purpose of advertising and publicity such as leaflets, catalogs, pamphlets, direct mails. In addition, gravure printing paper can also reproduce vivid colors and deep images, so demand for female publication magazines and fashion catalogs is growing, and in recent years, gravure printing paper has gradually become a part of this fashion mail order catalog field. It tends to be used more often. On the other hand, manufacturers that provide these catalogs to consumers tend to use lighter weight papers to reduce costs due to revisions in postage. However, as the weight becomes lighter, opacity and print strikethrough become more problematic. Therefore, a paper having high opacity and low print strikethrough even with a low basis weight is required. Further, in the case of catalog use, if the color of the printed matter and the color of the actual article are different, there is a problem (complaint, returned goods, etc.).

Generally, as a means for improving opacity and print strike-through, use of a filler having a large specific surface area (white carbon, finely divided silica, etc.), a filler having a high refractive index, a pigment (titanium dioxide, etc.), and a bulky coating. There are methods such as the use of pigments (plastic pigments, etc.) that form a work layer, lowering the density by high-temperature calendering, and increasing the use of mechanical pulp. However, these fillers and pigments are generally expensive,
When it is used as a coating liquid, the viscosity tends to be high and there is a problem of poor operability. In addition, the whiteness decreases as the mechanical pulp is added. Therefore, especially for lightweight coated papers, light calcium carbonate with a specific shape (spindle shape, columnar shape, needle shape, etc.) is used as the base paper internal filler or coating liquid in consideration of the overall quality balance and operability. In recent years, the method used for pigments tends to be adopted frequently.

Gravure printing is a method in which ink is applied to the entire plate first, then ink other than the image area is scraped off with a doctor, and the ink accumulated in the recesses is transferred to the paper under pressure. The miss dot rate becomes a big problem. Therefore, in order to smoothly and uniformly transfer the ink from the hard metal roll, smoothness (in particular, smoothness under printing pressure), cushioning property and oil absorption property are required.

Therefore, even with gravure printing paper, particularly gloss,
When producing gloss-coated paper having excellent smoothness, machine calenders, super calenders and the like are generally treated with high linear pressure in order to obtain high smoothness. However, when the calendering treatment is performed at a high linear pressure, the density of the paper is largely increased, and as a result, the rigidity and the feeling of hand are reduced, and the high-grade feeling of the coated paper is impaired. Therefore, if a large amount of starch is used to increase the rigidity, the paper becomes hard and loses its cushioning property, resulting in a high miss dot rate. Therefore, efforts have been made to minimize the amount of starch used in surface sizing or coating liquids. However, if the amount of starch in the coating liquid is too small, the coating liquid may be dried. When post-calendering is performed, piling trouble (roll stain due to the pigment being picked up on the roll side) is aggravated, and there is a problem of significantly impairing operability.

In JP-A-6-73698, columnar light calcium carbonate is used as a coating pigment under specific conditions, and a very mild calender treatment is carried out to make the matte coated paper for gravure printing uncoated. Although it is described that the transparency, print strikethrough, and whiteness are improved, when the glossy coated paper is subjected to the usual strong canender treatment, it does not appear bulky.
Poor opacity and print strike-through.

Further, in Japanese Patent Laid-Open No. 3-40895,
It has been shown that by blending kaolin having a bulk density of 0.5 g / cm ³ or less and columnar light calcium carbonate in an amount of 10% by weight or more, high smoothness and low misdot rate can be obtained. The opacity, print strike-through, and operability were not practically sufficient.

[0008]

In view of the above situation, an object of the present invention is to provide a gloss coated paper for gravure printing, which is excellent in bulk, smoothness, opacity and print strikethrough, and has a low misdot rate. It is to provide a glossy coated paper for gravure printing, which is excellent in finish, has no piling trouble and is excellent in operability, at low cost.

[0009]

Means for Solving the Problems As a result of intensive studies on the above problems, the present inventors have found that as a pigment component, quicklime is added to water or weakly in the causticizing step of the pulp manufacturing process by the sulfate method or the soda method. after slaked in a liquid, a green liquor
A needle-like or columnar light calcium carbonate produced by a causticizing reaction is used in the pigment in an amount of 30 to 70% by weight and an amount of reducing terminal groups as an adhesive is in the range of 0.3 to 0.7 mmol / g, or The present invention has been accomplished by applying a coating liquid containing the derivative onto a base paper.

The details of the present invention will be described below.

The blending amount of the needle-like or columnar light calcium carbonate of the present invention must be 30 to 70% by weight.
If the amount is less than 30% by weight, the opacity, print strikethrough, and misdot rate are poor, and if the amount is more than 70% by weight, the viscosity of the coating liquid becomes too high. In that case, stactite and bleeding (a phenomenon in which agglomerates of the coating liquid adhere to the blade edge of the blade) occur frequently, and the operability is significantly impaired.

The starch of the present invention has a reducing terminal group content of 0.3 to 0.7 mmol. When starch having a reducing terminal group amount of less than 0.3 mmol is used, the shrinkage of the coating liquid during drying becomes large and the orientation of the pigment is disturbed, so that the glossiness of the white paper is reduced. Therefore, when the calendering linear pressure is increased to increase the white paper glossiness, the bulk and opacity decrease. If a reducing terminal group content of more than 0.7 mmol is used, the coating strength of the starch itself becomes too low, and as a result, the cohesive strength of the coating layer decreases, resulting in frequent piling. still,
The amount of reducing end groups of the present invention is a value measured by the Wilstedder-Schudel method.

Further, in the present invention, in the causticizing step of the pulp manufacturing step by the sulfate method or the soda method,
After slaked quicklime with water or a weak liquor, it is highly print finish miss dot rate and excellent low obtained by using a needle-like or columnar precipitated calcium carbonate produced by causticizing reaction using green liquor Admitted. Conventionally used acicular or columnar calcium carbonates are all produced by a synthetic reaction in which carbon dioxide gas is blown into lime milk (hereinafter referred to as the carbon dioxide gas method), and are compared with those produced by the present invention. High miss dot rate and poor print finish,
Streaks are also likely to occur. It is not clear why the light calcium carbonate produced by the causticizing reaction of the present invention has a low misdot rate and is excellent in printing finish as compared with that produced by the conventional carbon dioxide method, but it is not the case by the carbon dioxide method. On the contrary, since the immersion heat in water is small (hydrophilicity or water wettability is small), the lipophilicity to the ink is conversely high, and as a result, the oil absorption is excellent and the misdot rate is low. Further, since the one produced by the causticizing method has weaker cohesiveness than the one produced by the carbon dioxide method, it is considered that the viscosity of the coating liquid is low and streaks are less likely to occur. The light calcium carbonate used in the present invention is a by-product in the production of white liquor, which is the main product of the causticizing process, so compared with the light calcium carbonate obtained by the conventional method of reacting lime milk with carbon dioxide gas. And can be manufactured at a very low cost.

The acicular or columnar light calcium carbonate of the present invention has a major axis of 3.0 to 5.0 μm and a minor axis of 0.2.
It is preferable to use those having a thickness of 0.5 μm. If the minor axis is less than 0.2 μm or if the major axis is less than 3.0 μm, the specific surface area becomes too large and the cohesive strength of the coating layer is significantly reduced, resulting in piling during calendaring ( The pigment or the like on the surface of the coating layer is peeled off and adheres to the surface of the roll), and the operability is likely to be significantly impaired. Further, when the minor axis is larger than 0.5 μm, the specific scattering coefficient is lowered, so that the opacity and print strikethrough are apt to be lowered. When the major axis is larger than 5.0 μm, when the coating liquid is applied with a blade coater, the streak tends to occur frequently because the blade edge of the blade is easily caught.

As described above, by using the light calcium carbonate having a specific shape and the specific starch produced by the causticizing reaction, the bulk, smoothness, opacity,
It is possible to produce a glossy coated paper for gravure printing, which is excellent in print strike-through, has a low misdot rate, an excellent print finish, and has excellent operability without piling trouble at low cost.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Light calcium carbonate having a specific shape defined in the present invention is a green calcium after slaked quicklime with water or a weak liquid in a causticizing step of a pulp manufacturing process by a sulfate method or a soda method. using those produced by causticizing reaction by using a liquid.

In the pulp production process by the sulfate method or the soda method, in order to isolate the fibrin in the wood, it is cooked at a high temperature and a high pressure using a chemical solution in which sodium hydroxide and sodium sulfide are mixed. Then, the fibrin is separated and refined into a pulp as a solid phase, and the chemical liquid and the eluted components other than the fibrin from the wood are collected as pulp waste liquid (black liquor) and concentrated and burned. At that time, the organic substances in the black liquor are recovered as a heat source, and the inorganic substances are mainly recovered as sodium carbonate and sodium sulfide. These inorganic substances are called smelt and are taken out from the recovery boiler in a molten state.
The smelt extracted from the recovery boiler is dissolved by water or a weak liquid (a dilute solution in which the white liquor components generated when the calcium carbonate sludge formed by the reaction shown below is washed are partially dissolved) and dissolved in green liquor. Becomes

The causticizing step is a step for converting sodium carbonate in green liquor into sodium hydroxide, which is a cooking chemical, and is a slaked reaction (1) for converting quicklime into slaked lime and mixing slaked lime and green liquor. It consists of a causticizing reaction (2) that produces sodium hydroxide and calcium carbonate. The liquid containing sodium hydroxide obtained by the causticizing reaction is called white liquor, which is separated from calcium carbonate, clarified, and sent to the cooking process. In the present invention, calcium carbonate which has been separated and recovered and washed thoroughly with water is used.

CaO + H ₂ O → Ca (OH) ₂ (1): Solubilization reaction Ca (OH) ₂ + Na ₂ CO ₃ → CaCO ₃ + 2NaOH (2): Causticization reaction Further, needle-like or columnar lightness specified in the present invention Calcium carbonate can be manufactured according to the following method.
That is, a liquid (water or weak liquid) having a pH of 5.5 to 13.5 so that the quicklime concentration is 20 to 60% by weight is added to the quicklime containing 0.1 to 10% by weight of calcium carbonate. A first stage step of adding liquor to produce lime milk and / or lime mud by stirring and mixing while mixing, and then producing lime milk and / or lime mud in the causticizing step to produce white liquor It is produced by sequentially adding a predetermined amount of green liquor required for the lime milk and / or lime mud at a constant addition rate and performing a causticizing reaction at a reaction temperature of 20 to 105 ° C. It is a thing.

Regarding the pigments used in addition to the above,
Although not particularly specified, generally used light calcium carbonate, heavy calcium carbonate, kaolin, clay, talc, satin white, silica, titanium dioxide and other inorganic pigments, and organic pigments such as plastic pigments. Etc. can be used in combination of one or more.

The starch used as the adhesive for the coating liquid of the present invention has an amount of reducing terminal groups of 0.3 to 0.7 mmol / g.
If the starch or its derivative within the range of
Regardless of its type, enzyme-modified starch, cold water-soluble starch, phosphate esterified starch, etherified starch, or oxidized starch is used. The blending amount is preferably 1 to 8 parts by weight with respect to 100 parts by weight of the pigment. If the amount is more than 8 parts by weight, the paper becomes too hard and the cushioning property is lowered, and the miss dot rate tends to be high. When the amount is less than 1 part by weight, the cohesive strength of the coating layer is lowered, so that piling occurs frequently, streaks due to vessels present on the paper surface occur frequently, and blade operability also tends to deteriorate. In addition to the above-mentioned starch, the adhesive used in the coating liquid may be a latex or other water-based adhesive, if necessary, one or two.
Select and use at least one species. As the latex, a conjugated diene-based copolymer latex such as a styrene / butadiene copolymer or a methacrylate / butadiene copolymer, a vinyl-based polymer latex such as a polymer or copolymer of acrylic acid ester and / or methacrylic acid ester. ,
Alternatively, these are further modified with a functional group-containing monomer such as a carboxyl group. In addition, as an aqueous adhesive other than latex, for example, proteins such as casein, soybean protein, synthetic protein, polyvinyl alcohol, polyvinylpyrrolidone, olefin / maleic anhydride resin, synthetic resin adhesives such as melamine resin, carboxymethyl cellulose, It is an ordinary coating adhesive such as cellulose derivatives such as hydroxyethyl cellulose and hydroxymethyl cellulose.

The coating liquid of the present invention may contain various auxiliaries such as a dispersant, a thickener, a water retention agent, a defoaming agent, and a water resistant agent, which are mixed with a usual pigment for coated paper.

The base paper is preferably a base paper having a basis weight of 30 to 100 g / m ² which is used for a general coated paper for printing, and high-quality paper or medium-quality paper is selected and used according to the purpose.

The concentration of the coating liquid of the present invention is preferably 50 to 65% by weight, and the coating amount is usually 6 to 14 in terms of solid content on one side.
g / m ² is preferred.

The coating apparatus is not particularly limited, but a roll application type or fountain nozzle type blade coater is mainly used, but other film transfer type coating apparatuses such as a gate roll coater, a blade or a rod are also used. A metalling size press coater, an air knife coater, or the like can be used, and the base paper is coated with the above-mentioned pigment coating liquid in a single layer or multiple layers.

The coated paper coated with the coating liquid and dried is gloss-finished by a finishing process such as a super calender or a soft calender as usual. The gloss coated paper of the present invention has a white paper gloss of 50% or more.

[0027]

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited thereto. In addition, part and% in an example show a weight part and weight%, respectively.

<Quality evaluation method> (1) Amount of reducing end groups (Wilstetter-Schudel method) Utilizing a reaction in which reducing end groups are selected by alkaline iodine solution (NaIO) and quantitatively oxidized to form carboxyl groups Then, the amount of I2 consumed for the oxidation as shown in the following reaction was calculated from the amount of reducing end groups (mmol) per 1 g of the dried starch.
Ask for.

CH ₂ OH (CHOH) nCHO + I ₂ +
3NaOH → CH ₂ OH (CHOH) nCOONa +
2NaI + 2H ₂ O Residual I ₂ + 2Na ₂ S ₂ O ₃ → Na ₂ S ₄ O ₆ +2
Observation of NaI (2) light calcium carbonate morphology: The product was washed with water, filtered, dried, and the shape, the minor axis, and the average value of the major axis were measured with a scanning electron microscope (JEOL JSM-5300).

(3) White paper glossiness: Measured at an angle of 75 degrees in accordance with JIS P-8142.

(4) Oken type smoothness: J. It was measured according to TAPPI Paper Pulp Test Method No. 5m-74.

(5) Opacity: Measured according to JIS P-81388.

(6) Print strike-through: Using a RI-I type printer (manufactured by Akira Seisakusho Co., Ltd.), the sheet printed on one side with a constant ink density (1.5) was left for 24 hours, and then the print-through was printed on the back side. The degree was visually evaluated.

○ = very little strike-through, △ = somewhat strike-through, × = significant strike-through (7) Miss dot ratio: using Ministry of Finance Printing Bureau type gravure printing tester (Kumagaya Riki Kogyo) A test piece was printed using halftone dot gravure as a pattern. The ratio of the number of miss dots generated to the total number of halftone dots is shown as a miss dot rate in%.
The smaller the number, the better.

(8) Pilling evaluation: During supercalendering, the degree to which the pigment adhered to the metal roll or elastic roll and the roll became white was visually evaluated.

◎ = No piling, ○ = Slight piling, △ = A lot of piling, × = Remarkable piling (9) Evaluation of blade operability: Occurrence of staractite or streak during blade coating Was visually evaluated.

⊚ = staractite, no streak generated, ◯ = staractite, streak slightly generated, Δ = staractite, streak generated a lot, × = staractite, streak significantly generated [Example 1] Kraft pulp Produced in the causticizing step of the manufacturing process, the major axis is 4.5 μm and the minor axis is 0.4 μm.
m to 40 parts of acicular light calcium carbonate, 10 parts of heavy calcium carbonate and 50 parts of kaolin, 1 part of sodium polyacrylate-based dispersant was added, and dispersed in water using a Cowles disperser. Then, 2.5 parts of cold water-soluble starch having an amount of reducing terminal groups of 0.65 mmol / g as an adhesive, 7 parts of alkali-sensitive styrene-butadiene-based copolymer latex, and 0.5 part of carboxymethyl cellulose as a water retention agent, Further, an auxiliary agent such as a water-proofing agent and a release agent is added to prepare a coating liquid having a solid content concentration of 61%, and a fountain blade coater is used.
/ Min, and a 13.5 g / m ² in terms of solid per side content sided coated, dried base paper having a basis weight of 42 g / m ^2, the basis weight 69g
A coated paper of / m ² was obtained. Furthermore, it was finished with a 12-stage super calendar so that the glossiness of the white paper would be 68%.

Example 2 50 parts of columnar light calcium carbonate having a major axis of 3.5 μm and a minor axis of 0.3 μm, 30 parts of heavy calcium carbonate and 20 parts of kaolin were blended,
A coated paper was produced in the same manner as in Example 1 except that a phosphorylated esterified starch having a reducing end group amount of 0.40 mmol / g was used.

Example 3 A pigment containing 60 parts of acicular light calcium carbonate having a major axis of 4.0 μm and a minor axis of 0.4 μm, 30 parts of heavy calcium carbonate and 10 parts of kaolin was used. A coated paper was produced in the same manner as in Example 1 except that enzyme-modified cold water-soluble starch having a reducing end group amount of 0.60 mmol / g was used.

[Comparative Example 1] A coated paper was produced in the same manner as in Example 1 except that amorphous calcium carbonate was used.

[Comparative Example 2] 8 needle-like light calcium carbonate
A coated paper was produced in the same manner as in Example 1 except that a pigment containing 0 part and 20 parts of kaolin was used.

[Comparative Example 3] 1 columnar light calcium carbonate was used.
A coated paper was produced in the same manner as in Example 2 except that 5 parts, 40 parts of ground calcium carbonate and 45 parts of kaolin were used.

[Comparative Example 4] The amount of reducing end groups was 0.21 mm.
A coated paper was produced in the same manner as in Example 1 except that a phosphate esterified starch having an ol / g was used.

[Comparative Example 5] The amount of reducing end groups was 0.75 mm.
A coated paper was produced in the same manner as in Example 1 except that enzyme-modified cold water-soluble starch (ol / g) was used.

Comparative Example 6 A coated paper was produced in the same manner as in Example 2 except that columnar light calcium carbonate having a major axis of 3.5 μm and a minor axis of 0.3 μm produced by the carbon dioxide method was used. .

The above results are shown in Table 1.

[0047]

[Table 1] As is clear from Table 1, Examples 1 to 3 have bulk, smoothness,
High opacity, printing strikethrough, miss dot rate, and excellent operability (piling, blade operability).

On the other hand, Comparative Example 1 is inferior in bulk, opacity, print strikethrough, and miss dot rate. Comparative Example 2 is inferior in blade operability and piling. Comparative Example 3 is inferior in bulk, opacity, print strike-through, and miss dot rate. Comparative Example 4
Are inferior in bulk, opacity, and print strike-through. Comparative Example 5 is inferior to piling. Comparative Example 6 is inferior in misdot rate and blade operability.

Therefore, the glossy coated paper for gravure printing produced by the present invention gives an unprecedentedly excellent coated paper quality, and its effect is extremely great.

[0050]

EFFECTS OF THE INVENTION A glossy coated paper for gravure printing, which is excellent in bulk, smoothness, opacity, print strike-through, has a low misdot rate, is excellent in printing finish, and has excellent operability without piling trouble at low cost. Obtainable.

Continuation of front page (56) Reference JP-A-3-40895 (JP, A) JP-A-61-53112 (JP, A) JP-A-1-226719 (JP, A) JP-A-2-210096 (JP , A) JP-A-6-306794 (JP, A) JP-A-7-102499 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) D21H 11/00-27/42

Claims (2)

(57) [Claims] 1. A method for producing a glossy coated paper for gravure printing, wherein a base paper is coated with a coating liquid containing a pigment and an adhesive, and a causticizing step of a pulp manufacturing step by a sulfate method or a soda method as a pigment component. After slaked quicklime with water or weak liquid, needle-like or columnar light calcium carbonate produced by causticizing reaction with green liquor is added in an amount of 30 to 70% by weight in the pigment and a reducing end group amount as an adhesive. Is 0.3-0.7 mm
A method for producing a glossy coated paper for gravure printing, which comprises applying a coating liquid containing starch or a derivative thereof within the range of ol / g. 2. The acicular or columnar light calcium carbonate has a major axis of 3.0 to 5.0 μm and a minor axis of 0.2 to 0.5 μm.
It exists in the range of m, The manufacturing method of the gloss coated paper for gravure printing of Claim 1 characterized by the above-mentioned.