JPH111891A - Production of coated paper and coated paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing coated paper having no difference in surface properties between its obverse and its reverse to be problematic in quality control, little difference between the obverse and the reverse of printing surfaces and high smoothness by coating base paper, which is made by squeezing water and drying, with a coating solution containing pigments and adhesives. SOLUTION: This production process of coated paper comprises treating base paper prepared by squeezing water from wet paper using a shoe press in the press part of a paper making machine and drying the base paper and/or prime-coated paper made by coating a coating solution on the base paper with a soft calender constituted of a metal roll and an elastic roll at 40-90 deg.C surface temperature of the metal roll and 30-150 kg/cm linear pressure and coating the treated paper with a coating solution containing a pigment and an adhesive.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a coated paper in which a coating liquid containing a pigment and an adhesive is applied to a base paper produced by a shoe press in a press part of a paper machine. It is.

[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.
Accordingly, in recent years, the papermaking speed has been further increased, and accordingly, higher water squeezing and higher dryness (dryness) have been required. In order to achieve higher dryness at a lower cost, technology for efficiently water-pressing with a press nip is playing an increasingly important role.

Therefore, in recent years, the nip width has been reduced to 150 to 150 mm in comparison with a conventional roll press having a nip width of about 20 to 50 mm.
Shoe presses, which are as wide as 300 mm and have excellent water squeezing properties, have been used in paperboard machines until now.

[0005] The shoe press generally has a structure in which a shoe is placed in a sleeve or a cylinder made of abrasion-resistant plastic called a blanket, and comes into contact with a rotating sleeve through a lubricating oil film. Pressed against the opposing roll. The surface of the sleeve is provided with blind holes or grooves to improve water squeezing. It is said that the shoe press has an advantage that the dryness can be increased, so that the steam cost can be reduced, and that the wet paper strength is improved, so that the running property of the paper is improved and the breakage of the paper is reduced.

[0006] However, in the case of a single felt type shoe press, there is a problem that there is a difference between the front and back sides of the paper surface contacting the felt side and the paper surface contacting the roll side. That is, the surface of the paper contacting the felt side is roughened, and the surface properties are lower than the surface contacting the roll side. The main cause of this difference is the quality of the felt, which depends on whether uniform pressure distribution is possible, whether the water extraction pattern is kept constant, and the like. Efforts are being made by each felt manufacturer to optimize the felt design.However, the speed of printing presses has increased, and user demands for print finish have become even stronger. The difference has not yet reached a satisfactory level. As described above, the importance of the shoe press is expected to increase further with the speeding up of the paper machine in the future, and it is indispensable to solve the problem of front and back differences in paper quality.

[0007]

SUMMARY OF THE INVENTION In view of the above situation, an object of the present invention is to squeeze wet paper using a shoe press in a press part of a base paper machine and apply pigment and adhesive to dried base paper. Provided is a method for producing a coated paper in which a coating liquid containing the coating liquid is coated, wherein there is no difference in surface properties which is a problem in quality control, there is little difference between the printed surface and the printed surface, and a highly smooth coated paper is produced. Is to do.

[0008]

When the wet paper is squeezed with a single felt shoe press, the surface of the paper contacting the felt side is roughened, and the smoothness of the paper is smoother than the surface contacting the roll side. In order to solve the problem that the difference between front and back is reduced, the wet paper web is squeezed with a shoe press, and further, using a conventional roll press, the squeezed water is squeezed with one or more multi-stage nips. He acknowledged that the difference between front and back generated by the press could be corrected to some extent. However, depending on papermaking conditions (wet part specifications, dewatering conditions, etc.),
In addition, the problem that a front-back difference occurs was recognized.

Therefore, the present inventors have further studied and as a result, the base paper dried by squeezing water with a shoe press and / or the base paper coated with a coating liquid on the base paper is coated with a metal roll and an elastic coating. The surface temperature of the metal roll of the soft calender made of rolls is 40 to 90 ° C, and the linear pressure is 30 to 150 kg /
cm, after coating with a coating liquid having a pigment and an adhesive, it was possible to obtain a highly smooth coated paper with no difference in surface properties between front and back and a small difference in front and back of the printed surface. . When performing a calendering process using a soft calender composed of a metal roll and an elastic roll, when the surface temperature and the linear pressure of the metal roll exceeded certain conditions, occurrence of a front-back difference was recognized. When the metal roll is treated at a high temperature exceeding 90 ° C. or when the linear pressure is treated at a high linear pressure exceeding 150 kg / cm, the surface of the paper in contact with the metal roll surface is
The very smooth surface of the metal roll is copied to the paper, resulting in a surface that is too smooth compared to the surface of the paper in contact with the resilient roll surface to produce a front-back difference. Conversely, when the surface temperature is lower than 40 ° C. or when the linear pressure is lower than 30 kg / cm, the problem of promoting the difference between the front and back does not occur. The problem that the surface properties (smoothness, surface state, etc.) after the application of the liquid is reduced occurs.

In order to eliminate the difference between the front and back sides, the present inventors have proposed a method of passing a paper in a soft calendering process. It was found that it was desirable to pass the paper so as to contact the surface of the metal roll.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, base paper is made by a commonly used fourdrinier former, a gap-type twin-wire former, or a hybrid former having a latter half of a four-sided net formed by twin wires. Next, the press part normally has 2 to 5 sets of nips composed of 2 to 3 press rolls, and conventional roll presses except for the shoe press have a nip width of about 20 to 50 mm made of granite or A plain press made of artificial stone stone rolls, a cell made of gunmetal, high chrome steel, and stainless steel by centrifugal casting, and a suction press made of rolls coated with rubber, and a synthetic rubber coated or stainless steel surface in the circumferential direction. For example, a grooved press made of rolls grooved at a constant width, depth, and pitch is used. The shoe press has a nip width of approximately 150 to
It is in the range of 250 mm, and the paper is passed between the press roll that is driven to rotate and the pressure shoe that is pushed up by hydraulic pressure,
Sleeve (blanket) between felt and pressure shoe
It is a type to run. In addition, in the shoe press,
There are two types, a single felt that squeezes water by applying felt only to one side of the wet paper and a double felt that squeezes water by applying both sides of the wet paper to the felt. In the present invention, a shoe press of a single felt is used.

As for the arrangement of the press, it is preferable that at least the final nip is water-squeezed by a conventional roll press method, and that the shoe press be used in the preceding nip.

Next, the base paper dried by a dryer through a press part using a shoe press is coated with an undercoat by a film transfer system such as a gate roll coater, a blade or a rod metaling size press coater, or a two roll size press coater. Is done. in this case,
As a coating liquid for undercoating, a clear coating liquid containing a water-soluble binder such as starch or a derivative thereof and, if necessary, an auxiliary agent, or a pigment coating liquid containing various papermaking pigments is used. When using a pigment in the undercoat coating liquid, mainly heavy calcium carbonate, light calcium carbonate,
Kaolin, clay, delaminated clay, talc,
Satin white, silica, barium sulfate, calcium sulfate, zinc oxide, inorganic pigments such as titanium dioxide, organic pigments such as plastic pigments can be used,
These pigments can be used alone or in combination of two or more, if necessary.

The adhesive used for the undercoating coating liquid may be a latex or other water-based adhesive if necessary.
Select and use two or more species. 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.

Examples of the aqueous adhesive other than latex include proteins such as casein, soybean protein, and synthetic protein; synthetic resin-based adhesives such as polyvinyl alcohol, polyvinylpyrrolidone, olefin / maleic anhydride resin, and melamine resin; Oxidized starch, positive starch, esterified starch such as urea-phosphate esterified starch, etherified starch such as hydroxyethyl etherified starch, starches such as dextrin, cellulose derivatives such as carboxymethylcellulose, hydroxyethylcellulose and hydroxymethylcellulose. It is a coating adhesive.

In the undercoat 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 base paper, acid paper, neutral paper,
Basis weight 30-100g / m made by alkaline papermaking method
Any of about ^two types of base paper may be used. Of course, a medium-quality base paper including mechanical pulp, a base paper including recovered waste paper pulp, and a high-quality base paper can also be used.

The undercoated paper obtained by applying the undercoat to the base paper is dried and then subjected to a soft calender treatment by the method used in the present invention. That is, the undercoating paper of the present invention, before soft calendering, base paper coated with clear coating liquid,
It includes those coated with a pigment coating liquid containing a pigment and an adhesive. The base paper before the undercoating may be subjected to a soft calendering treatment. When both the undercoating and the overcoating liquid have a pigment and an adhesive, the base paper may be subjected to a soft calendering treatment before each.

The type of the soft calender used in the present invention is preferably two rolls of tandem type and one stack 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. The elastic roll has a hardness of Shore D85 to Shore D85.
It is desirable to use 93. By this soft calendering treatment, it is possible to improve the quality of the coated paper which is then overcoated with a coating liquid containing a pigment and an adhesive.

The top coat of the present invention may be an on-machine coat system or an off-machine coat system, and a fountain application type or roll application type blade coater is generally used as an application device.

The pigments, adhesives, auxiliaries and the like used in the overcoating liquid are not particularly limited, and may be appropriately selected and used similarly to the undercoating liquid. After the top coat is applied, the product is finished as it is, or is finished with a gloss finish using a super calender or soft calender of 10 to 14 steps.

Also, the present invention is particularly excellent in high-speed operability of 800 m / min or more by integrating papermaking, coating and calendering, and continuously producing a coated paper by passing the paper.
There is no difference between the front and back of the coated paper, and a highly smooth coated paper can be obtained.

[0023]

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

(2) Smoothness of final product: J
APAN Tappi No. 5 Measured with an Oken-type smoothness tester.

(3) Evaluation of difference in appearance front and back: The product wound up by a winder was sampled, and the fine surface condition of the surface was visually evaluated relative to each other.

○: no difference between front and back, △: slight difference between front and back, ×: large difference between front and back [Example 1] 75% of hardwood bleached kraft pulp and 25% of softwood bleached kraft pulp are blended with all pulp And
A pulp slurry was prepared. Next, 6% of light calcium carbonate, 0.03% of alkyl ketene dimer, cationized starch and colloidal silica as a retention aid were added to the pulp slurry, and an on-top type twin wire machine was used at 1000 m / min. After papermaking, the paper was pressed and pressed with a 4-nip press. At that time, a shoe press was placed at the third nip, and the paper was passed so that the felt surface (F surface) of the paper was in contact with the felt side of the shoe press. The other nips were squeezed using a conventional plain press. At this time, the basis weight of the base paper is 46
g / m ² .

After further drying with a pre-dryer, an undercoat was applied with a gate roll coater. The undercoat coating liquid used at that time was prepared by adding 0.3 parts of a sodium polyacrylate dispersant to 100 parts of a pigment containing 95 parts of heavy calcium carbonate and 5 parts of kaolin as a pigment, and dispersing Cowles. The mixture is dispersed in water using a mixer, and 29 parts of a phosphorylated esterified starch and 2 parts of a carboxy-modified styrene / butadiene copolymer latex are blended as an adhesive to adjust the concentration to 38%. 6 g / m ^{2 was} applied on both sides in an absolutely dry state, and dried with an after dryer.

Next, a pair of metal rolls and a Shore hardness D9
Using a one-stack soft calender consisting of elastic rolls wound with a resin cover of 0, temperature of 45 ° C and linear pressure of 50k
The paper was passed under the conditions of g / cm and the F (felt) surface of the paper was in contact with the metal roll surface. Further, an overcoat was applied with an on-machine blade coater.

The overcoating liquid used at that time contained 70 parts of the above-mentioned heavy calcium carbonate as a pigment and the above-mentioned kaolin 30
To 100 parts of a pigment containing 100 parts of a pigment, 0.3 part of a sodium polyacrylate-based dispersant was added, and dispersed in water using a Cowles disperser. As an adhesive, 4 parts of a phosphorylated starch and carboxy-modified were used. 11 parts of a styrene / butadiene copolymer latex was blended to adjust the concentration to 64%, and this coating solution was applied on both sides by drying at 16 g / m ² and dried.

Further, glossing was performed using a 2-roll / 4-stack soft calender having an elastic roll having a Shore D hardness of 90 ° and a metal roll.

[Example 2] The steps of papermaking → water squeezing → undercoating → soft calender → overcoating → soft calender were integrated, and the soft calender after the undercoating was subjected to a temperature of 60 ° C. and a linear pressure of 100 kg / cm. The coated paper was manufactured in exactly the same manner as in Example 1 except that the coated paper was manufactured by processing under the conditions described above and continuously passing the paper.

Example 3 An undercoating coating solution was applied and dried, and then softened at a temperature of 80 ° C. and a linear pressure of 125 kg / cm so that the W (wire) surface of the paper was in contact with the metal roll surface. A coated paper was produced in exactly the same manner as in Example 1 except that the paper was subjected to a calender treatment.

Comparative Example 1 A coated paper was manufactured in the same manner as in Example 1, except that the undercoating coating liquid was applied, dried, and then subjected to a soft calender treatment at a temperature of 55 ° C. and a linear pressure of 250 kg / cm. .

Comparative Example 2 A coated paper was manufactured in exactly the same manner as in Example 1 except that the undercoat coating liquid was applied, dried, and then subjected to a soft calender treatment at a temperature of 130 ° C. and a linear pressure of 40 kg / cm. .

Comparative Example 3 A coated paper was manufactured in the same manner as in Example 1 except that the undercoat coating liquid was applied, dried, and then subjected to a soft calender treatment at a temperature of 45 ° C. and a linear pressure of 25 kg / cm. .

Comparative Example 4 A coated paper was produced in exactly the same manner as in Example 1 except that the undercoat coating liquid was applied, dried, and then subjected to a soft calender treatment at a temperature of 35 ° C. and a linear pressure of 50 kg / cm. .

Comparative Example 5 A coated paper was manufactured in exactly the same manner as in Example 1 except that the undercoat coating liquid was applied, dried, and then subjected to a soft calender treatment at a temperature of 120 ° C. and a linear pressure of 180 kg / cm. .

Comparative Example 6 A coated paper was manufactured in exactly the same manner as in Example 1 except that the undercoat coating liquid was applied, dried, and then subjected to a soft calender treatment at a temperature of 35 ° C. and a linear pressure of 25 kg / cm. .

The above results are shown in Tables 1 and 2.

[0041]

[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 in terms of blank gloss, product smoothness, and appearance, and are excellent in smoothness.

On the other hand, both Comparative Examples 1 and 2 have a large difference between the front and back sides, and Comparative Examples 3 and 4 have a low white paper glossiness and low product smoothness, and a large difference between the front and back sides. Comparative Example 5 has a large front-back difference. Comparative Example 6 has low blank gloss and smoothness.

Accordingly, the coated paper manufactured according to the present invention provides a stable quality which has never been obtained before, and the effect is extremely large.

[0044]

According to the present invention, there is provided a method for producing a coated paper in which a coating liquid having a pigment and an adhesive is applied to a base paper produced by using a shoe press. A highly smooth coated paper with little difference between the front and back surfaces can be obtained.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Masahiro Hirakawa 2-81-1, Iida-cho, Iwakuni-shi, Yamaguchi Japan Inside the Iwakuni Mill of Paper Mills (72) Inventor Yukio Fukudome 2--8, Iida-cho, Iwakuni-shi, Yamaguchi No. 1 Inside of Iwakuni Mill of Japan Paper

Claims (4)

[Claims] 1. A method for producing a coated paper in which a base paper is coated with a coating liquid having a pigment and an adhesive, wherein the wet paper is squeezed and dried using a shoe press in a press part of a base paper machine. // The base paper coated with a coating liquid on the base paper is coated with a soft calender composed of a metal roll and an elastic roll.
A method for producing coated paper, which comprises applying a coating liquid having a pigment and an adhesive after treating under a condition of 150 kg / cm. 2. The method for producing a coated paper according to claim 1, wherein in the soft calendering process, the surface of the paper contacting the felt side with the shoe press contacts the metal roll surface of the soft calender. . 3. The coated paper manufacturing method according to claim 1, wherein a final nip of the press part is a roll press, and a preceding stage is a shoe press. 4. Coated paper manufactured by the manufacturing method according to claim 1.