JP3256957B2 - Manufacturing method of coated paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a production method of coating a base paper with a coating liquid having a pigment and an adhesive and then performing soft calender treatment at a high temperature to finish the surface. The present invention relates to a method for producing a coated paper excellent in appearance, free from poor appearance and wrinkles.

[0002]

2. Description of the Related Art In recent years, demand for printing paper in the field of commercial printing for advertising and promotion such as flyers, catalogs, brochures, and direct mail has been growing. Although these commercial prints have low commercial value themselves, it is important that the purpose be achieved as an advertising medium, and therefore, low-cost, high-quality prints have been demanded.

[0003] In order to respond to such a vigorous demand for coated paper, it is an important technical problem for paper manufacturers to increase productivity and reduce costs while maintaining high quality.

[0004] Coated paper productivity is greatly affected by the surface finishing process. As a means for improving the productivity of the surface finishing step, a soft calender treatment under a high temperature condition is known (Japanese Patent Application Laid-Open No. 54-125712). This is because the coated paper, once coated with a conventional coating device (hereinafter referred to as a coater), is once wound and then processed using a super calender at low temperature and usually in a multi-stage nip condition of 10 to 14 stages. In contrast to the application of a coating liquid with a coater, a soft calender treatment is performed on-line at a high temperature after coating with a coating liquid to improve productivity. The conventional cotton roll used for the super calender has poor heat resistance due to the problem of internal heat generation, and is inferior in pressure resistance and durability, so there is a limit to speeding up. At present, the maximum speed that can be operated is about 800 m / min. . Therefore, two super calendars are required in order to be used in combination with a coater exceeding 1000 m / min in recent years, and it has to be taken off-line and once again wound up and applied to the super calendar, which means further space saving. But that's a problem. On the other hand, in the case of a soft calender having a plastic elastic roll with excellent heat resistance and pressure resistance,
Operation at a speed exceeding 1000 m / min is also possible, and productivity can be improved because the system can be installed in the coater online.

[0005] In addition, by treating at a high temperature with a smaller number of nips, space can be saved, and in terms of quality, the surface of the metal roll is transferred to the paper surface in a state where only the surface layer of the paper is plasticized by the high temperature. As compared with the super calender, when the paper is crushed to the same thickness, excellent surface properties and printability are obtained.

However, as the processing temperature of the soft calender is increased in order to improve the productivity, the surface properties such as glossiness and smoothness between the felt side and the wire side of the coated paper are greatly different from each other. Admitted the problem. In addition, the shrinkage of the paper increases due to heating, and in the case of rolled products, in the process of rolling printing after winding with a soft calendar,
It was recognized that poor winding and wrinkles occurred. In addition, for flat sheet products for sheet-fed printing, after soft calendering,
In the process of cutting with a cutter, packaging, and shipping, it was also recognized that problems such as poor packing appearance and wrinkles, such as poor appearance, occurred.

[0007]

SUMMARY OF THE INVENTION In view of the above situation, an object of the present invention is to reduce the front-back difference, which is a problem in quality control at the time of high-temperature soft calendering, to improve elongation and dimensional stability, An object of the present invention is to provide a coated paper which is excellent in appearance with less defective packing and less wrinkles.

[0008]

SUMMARY OF THE INVENTION The present inventors have found that, when soft calendering is performed at a high temperature, the felt side (hereinafter referred to as F side) of the coated paper is glossier than the wire side (hereinafter referred to as W side). The degree of smoothness, the degree of smoothness, etc., increased, and the difference in front and back surfaces was observed. In order to solve this problem, the paper passing conditions of the soft calender were examined repeatedly. As a result, at least 4 nips are required to eliminate the difference between the front and back, and the first nip is applied to the metal roll surface on the W side of the coated paper, and the second and third nips are applied to the metal roll surface. It was recognized that the difference between the front and back sides would be eliminated only by passing the paper so that the W side would hit the metal roll again so that the F side of the paper would hit the F side.

That is, at the time of high-temperature soft calendering, the surface of the coated paper that hit the metal roll side at the first nip in the region where the moisture of the coated paper is high is easily plasticized,
Since the smooth metal roll surface can be easily copied, the expression of the glossiness of the white paper and the smoothness are the highest. Therefore, first of all, it is necessary to pass the first nip so that the W surface having poor surface properties is brought into contact with the metal roll surface. Next, the second nip is F
It is necessary that the surface side hits the metal roll, and that the F side also touches the metal roll surface at the third nip. When the W side is applied to the third nip, the F side is necessarily in contact with the metal roll surface in the fourth nip. In this case, the W side of the third nip hits the metal roll surface in a region where the moisture of the coated paper is higher than that of the fourth nip.
Conversely, the surface property on the W surface side becomes too good as compared with the F surface side, and a front-back difference occurs. Further, when only one side of the coating surface is continuously applied to the metal roll surface, a difference in elongation occurs in the thickness direction of the paper, resulting in poor packing appearance and appearance. Also, even if the number of nips is larger than 4 nips, after 5 nips, calender processing will be performed in the area where the moisture of the coated paper is low, and the order of the coated surface corresponding to the metal roll surface will be different between the front and back. The effect is reduced, and there is no problem with any kind of paper passing.

In the case of high-temperature soft calendering, elongation and dimensional change due to shrinkage of the paper become large, and the appearance tends to deteriorate. However, in order to prevent these, the surface temperature of the fourth nip metal roll is set to 70 ° C. or less. Is preferable. This has the effect of lowering the surface temperature of the paper and reducing the temperature or moisture change width of the paper, thereby suppressing non-uniform dimensional changes due to heating or moisture absorption of the paper. As a result, poor winding appearance, poor packing appearance, and surface wrinkles are suppressed, and deterioration in appearance is unlikely to occur. The surface temperature of the metal roll at the fourth nip is more preferably 30 to 65 ° C.
The metal roll surface temperature from the first to the third nip is 90 to
200 ° C. is preferred. When the temperature is lower than 90 ° C., there is little difference between front and back, and there is little elongation or dimensional change, so that there is no problem that the appearance is deteriorated. However, the absolute values of the glossiness of the white paper and the smoothness itself tend to decrease. . On the other hand, when the temperature is higher than 200 ° C., the surface property of the coated surface corresponding to the metal roll surface at the first nip is excessively improved. 7
Even if the temperature is 0 ° C. or lower, the surface temperature of the paper becomes too high, and it becomes impossible to minimize elongation and dimensional change, so that the appearance tends to deteriorate.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, pigments used in coating liquids are mainly heavy calcium carbonate, light calcium carbonate, kaolin, clay, delaminated clay, talc, satin white, silica, barium sulfate. And inorganic pigments such as calcium sulfate, zinc oxide and titanium dioxide, and organic pigments such as plastic pigments. These pigments can be used alone or in combination of two or more as necessary. In the present invention, the adhesive used for the coating liquid is selected from latex or other water-based adhesives, if necessary, and one or more types are used. Examples of the latex include conjugated diene-based copolymer latex such as styrene-butadiene copolymer and methacrylate-butadiene copolymer, and vinyl-based polymer latex such as acrylate and / or methacrylate ester polymer or copolymer. Or those further modified with a monomer containing a functional group such as a carboxyl group. Also, as an aqueous adhesive other than latex,
For example, proteins such as casein, soy protein, and synthetic protein, polyvinyl alcohol, polyvinyl pyrrolidone, synthetic resin adhesives such as olefin / maleic anhydride resin, melamine resin, etc., esters such as oxidized starch, positive starch, and urea-phosphorylated starch. It is a general adhesive for coating such as etherified starch such as acetylated starch and hydroxyethyl etherified starch, starches such as dextrin and cellulose derivatives such as carboxymethylcellulose, hydroxyethylcellulose and hydroxymethylcellulose.

In the coating liquid of the present invention, various auxiliaries such as a dispersant, a thickener, a water retention agent, an antifoaming agent, and a waterproofing agent may be used in combination.

As the base paper, a paper base or paperboard base base paper having a basis weight of about 30 to 400 g / m ² used for general coated paper is appropriately used, but the paper making method is not particularly limited. . Any of base paper made by acidic papermaking, neutral papermaking, or alkaline papermaking using a fourdrinier machine including a top wire, a round netting machine, a paperboard machine combining two members, a Yankee dryer machine, etc. Of course, it is also possible to use a medium base paper containing mechanical pulp and a base paper containing recycled pulp and high quality base paper.

[0014] The coating liquid prepared is a blade coater, a bar coater, a roll coater, an air knife coater, a reverse roll coater, a curtain coater, a size press coater,
One or two or more layers are coated on one side or both sides using a gate roll coater or the like. Particularly when two or more layers are coated, a film transfer method such as a gate roll coater, a blade or a rod metaling size press coater is used for the undercoating of the coating liquid, and a fountain or a roll is used for the subsequent overcoating. It is preferable to adopt a blade system according to an application or the like. The coating amount is preferably 12 to 36 g / m ^{2 on} both sides.

The type of the soft calender used in the present invention is preferably a tandem type two rolls and four stacks in consideration of ease of paper passing and space saving. The tandem type is a type of soft calender in which two rolls of a pair of metal rolls and elastic rolls are arranged in parallel. The material of the elastic roll is preferably made of a modified urethane-based, epoxy-based, or polyether-based plastic having excellent heat resistance.

[0016]

The present invention will be specifically described below with reference to examples. In the examples, parts and% are parts by weight and% by weight, respectively.
Is shown. The quality evaluation method is as follows.

<Quality evaluation method> (1) Pigment average particle diameter: The average particle diameter was measured as the average particle diameter at the 50% point of the weight cumulative distribution using a light transmission type particle size distribution analyzer SHC5000 of Seishin Enterprise.

(2) Glossiness of blank paper: Angle 7 according to JIS P-8142
Measured at 5 degrees.

(3) Evaluation of appearance (surface wrinkle): The product wound up by a winder was left at room temperature for 24 hours as it was, and then visually evaluated for the degree of wrinkles generated partially in the machine direction on the winding surface layer. did.

○: No wrinkles were generated, Δ: Some wrinkles were generated, X: Many wrinkles were generated. (4) Packing evaluation: After cutting the product with a cutter, it was piled up on a wooden pallet stand and left overnight.
The degree of occurrence of skew (tilt, waving, etc.) due to paper elongation was visually evaluated.

◎: no inclination, ○: almost no inclination, Δ: occurrence of inclination, ×: noticeable occurrence of inclination. Example 1 A pigment having an average particle diameter of 0.70 μm as a pigment. 95 parts calcium carbonate and 0.50 μm kaolin 5
To 100 parts of a pigment containing 0.3 parts of a sodium polyacrylate dispersant, 0.3 part of a sodium polyacrylate dispersant was added, and dispersed in water using a Cowles disperser. A high-speed gate roll coater is used as an apparatus for undercoating a base paper coated with solely kraft pulp containing bleached hardwood having a basis weight of 59 g / m ² by blending 4 parts of styrene-butadiene copolymer latex to prepare an undercoat coating solution having a concentration of 38%. Was applied at a coating speed of 1000 m / min, and an undercoat coating liquid was applied on both sides at 7 g / m ² and dried.

Next, to 100 parts of the pigment containing 60 parts of the heavy calcium carbonate and 40 parts of kaolin, 0.3 part of a sodium polyacrylate-based dispersant was added and dispersed in water using a Cowles disperser. A coating solution having a concentration of 65% was prepared by blending 4 parts of a phosphorylated esterified starch and 10 parts of a carboxy-modified styrene / butadiene copolymer latex as an adhesive, and using a high speed fountain blade coater. At a speed of 1200 m / min, 16 g / m ² on both sides was overcoated and dried.

Further, a 2-roll / 4-stack soft calender (manufactured by Valmet) having an elastic roll having a Shore D hardness of 91 ° was used, and each of the first to third nips had a metal roll temperature of 160 ° C. and a linear pressure of 250 kg / cm. It was calendered at a constant temperature of 40 ° C. and 100 kg / cm at the fourth nip. At this time, the coated surface is W, F, F, W
The paper was passed so as to hit the metal roll surface of each nip in the order of the surface side.

Example 2 The above procedure was repeated except that the first to third nips each had a metal roll temperature of 130 ° C. and a constant linear pressure of 280 kg / cm, and the fourth nip had a calendering condition of 55 ° C. and 150 kg / cm. A coated paper was produced exactly as in Example 1.

Example 3 A coated paper was manufactured in exactly the same manner as in Example 1 except that the surface temperature of the metal roll of 1 to 3 nips was soft calendered at 90 ° C.

[Comparative Example 1] The coated surface was F at 1 to 4 nips,
A coated paper was manufactured in exactly the same manner as in Example 1 except that the paper was passed so as to hit the metal roll surface of each nip in the order of W, F and W surfaces.

[Comparative Example 2] The coated surface was F at 1 to 4 nips,
Coated paper was manufactured in exactly the same manner as in Example 1 except that the paper was passed so as to hit the metal roll surface of each nip in the order of F, W, and W surfaces.

[Comparative Example 3] The coated surface was W at 1-4 nips,
A coated paper was manufactured in exactly the same manner as in Example 1 except that the paper was passed so as to hit the metal roll surface of each nip in the order of F, W, and F sides.

[Comparative Example 4] The coated surface was W at 1-4 nips,
A coated paper was manufactured in exactly the same manner as in Example 1 except that the paper was passed so as to hit the metal roll surface of each nip in the order of W, F and F sides.

Comparative Example 5 A two-roll, five-stack soft calender was used.
A coated paper was manufactured in exactly the same manner as in Example 1 except that the fifth nip was at a temperature of 40 ° C. and the paper was passed so as to hit the metal roll surface in the order of W, W, W, W, and F sides.

The above results are shown in Tables 1 and 2.

[0032]

[Table 1]

[Table 2] As is clear from Tables 1 and 2, Examples 1 to 3 have no difference between the front and back sides of the glossiness of white paper, and are excellent in surface wrinkles and appearance of packing. On the other hand, Comparative Examples 1-4 have a large difference between the front and back sides. Comparative Example 5 has a large difference between the front and back sides, and is inferior in surface wrinkles and appearance of packing.

Accordingly, the coated paper produced according to the present invention provides an unprecedented stable quality, and its effect is extremely large.

[0034]

According to the present invention, there is obtained a coated paper which has no difference between front and back sides which is a problem in the method for producing coated paper by high-temperature soft calendering, has excellent appearance such as surface wrinkles and poor packing, and has improved productivity. it can.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yukio Fukudome 2-1-1, Iida-cho, Iwakuni-shi, Yamaguchi Prefecture Inside the Iwakuni Mill of Nihon Paper Industries Co., Ltd. (56) References JP-A-1-250493 (JP, A) JP-A-9-132893 (JP, A) JP-A-5-44192 (JP, A) JP-A-2-145895 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) D21H 11/00-27/42 D21G 1/00

Claims (2)

(57) [Claims] In a finishing step of coating a base paper with a coating liquid having a pigment and an adhesive, and then performing a surface treatment with a soft calender comprising a metal roll and an elastic roll, a metal roll surface of the first 4 nips is provided. Wherein the paper is passed so that the surface of the coated paper hits the order of the wire side, the felt side, the felt side, and the wire side. 2. The metal roll has a surface temperature of 90 to 200 ° C. up to the first to third nips of the soft calender,
2. The method for producing coated paper according to claim 1, wherein the paper is passed at a nip metal roll surface temperature of 70 [deg.] C. or less.