JPS6094692A - Production of cast coat paper - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing cast coated paper, and in particular, to efficiently produce high-gloss cast coated paper with improved curls and paper curls that are characteristic of cast coated paper. This is related to the method by which this can be done.

The manufacturing method for highly glossy coated paper called cast coated paper is to apply a wet coating layer containing mineral (1) material pigment and adhesive as main components to a mirror-finished heated surface to achieve a glossy finish. Sotocasting method (e.g., Japanese Patent Publication No. 2B-3407, Japanese Patent Publication No. 38-25160), a rewetting method in which the wet coating layer is once dried and then plasticized by re-wetting to form a heated finish with a mirror surface. Casting method (for example, U.S. Patent No. 2,759,847, Japanese Patent Publication No. 4B-3)
11005, JP-A-51-102111), heating the wet coating layer to a gel state to give it a mirror surface? , 1 knee 1:
Gelling casting method (for example, Japanese Patent Publication No. 311
-15751, Japanese Patent Publication No. 40-7207, U.S. Patent No. 3
377192, JP-A No. 51-4041 i1, JP-A No. 57-51896) and the like are known.

In both of these methods, a coating liquid mainly composed of mineral σn and adhesive is applied to base paper, and the coating layer, which has been made plastic with water, is applied to the surface of a heated finishing drum with a mirror surface using a press roll. They have a common feature in that they are pressed together, dried, and released to give a high-gloss finish. However, the cast coated paper obtained by these casting methods (2) has a strong gloss after being released from the specular drum;
Commonly, curls occur with the high-gloss cast finish side facing out and the back side (uncoated side or coated paper finish side) facing in, with the center direction of the paper as the axis, so-called reverse vertical curl.

This reverse vertical curl often causes paper feeding troubles on multi-color printing machines, which have recently become faster, and causes printing workability to become thicker (disturbed).

In order to improve this reverse vertical curl, curl breaker
However, since it is necessary to apply ironing with a roll to the highly glossy side, the gloss and smoothness, which are the characteristics of cast coated paper, are significantly impaired due to flattening. turn into. Moreover, this reverse vertical curl is more likely to occur as the drum temperature increases, especially at 100℃.
The tendency of occurrence increases rapidly when casting at higher temperatures. In addition, even if the press pressure is increased, the tendency to occur increases.
This may be a fatal defect in gel casting and rewetting casting methods that use high temperature and high pressure casting methods.

(3) In view of the current situation, the present inventors have conducted extensive research into improving this reverse tatelo curl phenomenon based on their many years of experience in producing cast coated paper. In particular, this phenomenon rarely occurs with art paper and coated paper, which are ordinary coated papers for printing, and is unique to cast manufacturing methods such as wet casting, rewetting casting, and gelling casting. Focusing on this phenomenon, we conducted extensive research into analyzing the phenomenon and improving it. As a result, in the cast manufacturing method, when the wet coated paper is pressed against the specular drum, the water content of the base paper is higher on the wet coated layer side, which is the cast surface.
Because there is less on the back side (non-cast side), the fibers of the base paper for the cast coating layer are stretched with a pressure roll in a more hydrated state than on the back side, and are then tightly fixed on the drum and dried. It was concluded that the reverse tatelo curl peculiar to cast paper occurs.

Based on this knowledge, and as a result of further intensive research, the inventors of the present invention have found that the reverse vertical curl (4) phenomenon, which has long been desired to be improved as a serious defect in the casting method, can be prevented by the cast after it has been peeled off from the cast drum. The present inventors have discovered that the coating layer can be effectively improved by applying steam to the surface of the coating layer, and have achieved the present invention.

It is not clear why the reverse vertical curl phenomenon is improved by the method of the present invention, but as mentioned above, the base paper fibers on the cast coated layer side, which are fixed with only one side being forcibly stretched, are It is presumed that the paper fibers return to the same original fiber length as the back side due to the influence of moisture, and as a result, the distortion is eliminated and the reverse vertical curl is improved.

In addition, as a method to improve the reverse vertical curl of cast coated paper, the non-cast side is treated with water before or after pressurization by the cast drum to make the moisture content on both sides the same level, and the fibers on the back side are stretched. A method of finishing the cast in the state has also been proposed. However, this method significantly increases the drying load on the cast drum, reducing the finishing speed by about half, and also has the disadvantage of reducing the smoothness of the back surface, so it is not necessarily a preferable improvement method in practice. (5) No. According to the method of the present invention, it is possible to improve the desired reverse vertical curl without having such disadvantages such as a decrease in operability or a decrease in back surface quality.

In the method of the present invention, the device for treating the cast surface with steam is not particularly limited, and any device may be used as long as it can apply steam to the surface to be coated. Generally, a device equipped with steam blowing grooves that is slightly longer than the inside of the paper is installed immediately after the first ram of the cast, and steam and air are fed into this device to continuously steam-treat the surface to be coated with the cast. good.

Note that it is also possible to use a device such as a humidity control device that applies steam to both the coated surface and the back surface of the cast at the same time, but even if the horizontal curl is improved in normal usage, it does not meet the purpose of the present invention. The reverse vertical curls that occur will not be improved. Therefore, when using such a humidity controller, either the steam should be applied only to the surface to be coated with the cast, or the amount of steam applied to the back side should be reduced to 1/2 of the amount of steam applied to the surface to be coated. 2
Hereinafter, it is necessary to process (6) by reducing glIl1 to more preferably 1/3 or less.

Further, regarding the treatment location, the treatment may be performed continuously using a cast coater, or may be performed using a separate device. Of course,
If necessary, a back side steam treatment device may be used in combination with a cast coated surface steam treatment device for improving reverse vertical curl.

In the method of the present invention, the optimum amount of steam to be applied to the cast surface is determined by the casting method, cast drum temperature, cast finishing speed, pulp properties of the base paper, paper basis weight, paint formulation, cast side coating amount, presence or absence of back coating, and its It is adjusted according to the coating amount, the structure of the steam spraying equipment, etc., and can be determined by testing as necessary.
Generally, it is desirable that the amount of water be in the range of 0.2 to 30 g per paper IM. The amount of steam processed is determined by measuring the amount of moist air blown, the humidity, the inside of the paper, the paper speed, etc.
It is expressed in terms of the amount of moisture in the moist air blown per 1M of paper.

If the amount of steam treatment is less than the optimum amount, the improvement effect of the inverted vertical curl of the present invention will be small; Later cast coated paper is RIT 80%
Under such high humidity conditions, loft 1 positive curl occurs. Therefore, the amount of steam processed is
The amount per M is preferably in the range of 0.2 to 30 g, more preferably 0.7 to 15 g, and most preferably 1 to 5 g.
It is adjusted within the range of.

In the method of the present invention, the coating composition used to form the coating layer is a composition containing pigments and adhesives as main components, similar to the conventional composition for Cath I coated paper.

Examples of pigments include clay, kaolin, aluminum hydroxide, calcium carbonate, titanium oxide, barium sulfate,
Zinc oxide, Sachin white, plastic pigment 1-
One or more types of general coated paper face paints such as I are used. In addition, adhesives include casein, soybean protein, methanol,
Proteins such as proteins extracted from unicellular bacterial cells such as Nishi 1 acid, conjugated diene polymers such as styrene-butadiene copolymer, methyl methacrylate-I-butadiene copolymer, etc. , acrylic polymer latex such as a polymer or copolymer of acrylic acid ester and/or methacrylic acid ester, vinyl polymer latex such as ethylene/vinyl acetate copolymer, or various polymers of these with carboxyl groups, etc. Alkali-soluble or alkali-insoluble polymer latex modified with functional group-containing monomers, synthetic resin adhesives such as polyvinyl alcohol, olefin/maleic anhydride resin, and melamine resin, positive starch,
General adhesives for coated paper such as starches such as oxidized starch, cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose can be used alone or in combination. These adhesives contain 5 to 50 parts by weight per 100 parts by weight of pigment,
Generally, it is used in a range of 10 to 30 parts by weight.

Various auxiliary agents such as antifoaming agents, coloring agents, mold release agents, and flow modifiers may also be used as appropriate.

The method of the present invention can be applied to various conventionally known cast coating methods as described above, and the types of cast coating papers include single-sided, double-sided, (9) thin paper, board, boss, etc. Effective for cast coated paper.

The present invention will be explained in more detail with reference to Examples below, but it is of course not limited thereto. Further, unless otherwise specified, parts and % in the examples indicate parts by weight and % by weight, respectively.

Example 12.3 A 42% concentration paint consisting of 30 parts of kaolin, 70 parts of calcium carbonate with an average particle size of about 0.2 microns, 10 parts of casein, and 16 parts (solid content) of carboxylated styrene-butadiene copolymer latex was prepared. Prepared. Apply this paint to 5 yen
It was coated on the back side of a base paper of 0 g/n (with an air knife coater) and dried with hot air at 140"C. The coating amount in this case was Log/n? on a dry basis. This coated paper was 1
l11 Applicable to regular super calender, back side coating 1
A base paper with lint was obtained.

Separately, a paint for Giast (10) with a concentration of 53% was prepared, consisting of 80 parts of kaolin, 1,120 parts of calsilyl carbonate, 10 parts of casein, and 1 part of styrene-butadiene (8 parts of combined latex).

This paint is cast using a wet-on-wet casting device as shown in Figure 1 (see Japanese Patent Publication No. 38-25160).
With this method, the surface of the back-coated base paper was coated to give a cast finish. That is, the first coating device (
1), apply the casting paint to a dry weight of fig/n, and then, while this coating layer is still wet, immediately apply the same casting paint to the second coating device (2). was coated at a dry weight of 9 g/rrr and immediately pressed against a chrome-plated cast drum (3) having a surface temperature of 90°C.After drying, the cast coated paper was released from the mold. The first steam treatment device (4)
Cast coated paper treated with steam in the proportions shown in the table (5)
I got it. The casting operation speed at this time was 55 m/min.

Comparative Example 1.2.3 Cast coated paper (5) was obtained in the same manner as in Example except that no steam treatment was performed after casting and the steam treatment amount was 0.05 g/rrr or 40 g/m. (11) Ta.

The appearance of reverse vertical curl on the cast-coated paper and the gloss of the cast-coated surface were evaluated as follows, and the results are shown in Table 1. As is clear from the results in Table 1, in each of the Examples of the present invention, the occurrence of reverse vertical curl was extremely efficiently improved compared to the Comparative Example without reducing the gloss of the cast coated paper.

[Evaluation of reverse vertical curl]

Cut the cast coated paper into 10cm x 10cm pieces at 20℃.
, hung in a constant temperature and humidity room with RH 50% for 24 hours, and the degree of curling was determined by measuring the curvature of the curled surface by half 1y1. (cm). The higher the number, the better.

[Evaluation of cast coated surface gloss]

Measured based on JIS-P8142 method. The higher the number, the better the gloss.

Example 4, Comparative Example 4 90 parts of coating clay, 1 part of Zajinpoite dispersion
0 part (solid content) was dispersed using Coles' part + 1 & Jm to make an ann soot slurry with a concentration of 62%.

(12) To this, add 0.5 parts of octyl alcohol as an antifoaming agent, 20 parts of a 15% aqueous solution of casein as an adhesive, and 20 parts of butadiene/methyl methacrylate copolymer latex (solid content), so that the solid content concentration is 45%. % coating liquid was obtained. This coating liquid has a pH of 9.5 and a viscosity of 360 cps (
Brookfield type viscosity needle, 60 rpm, 20°C). Using this coating liquid, rewet casting was carried out using an apparatus as shown in FIG. That is, 100g/r
The above coating liquid was coated on the base paper (6) of rr with an air knife coater (7) so that the dry coating amount was 22 g/rrr, and the paper moisture was reduced to 6% with an air foil dryer (8). Dry until dry.

The paper is then passed through a press nip (11) formed by a rubber-coated press roll (9) with a diameter of 750 mm and a chrome-plated cast drum (10) with a diameter of 1220 mm, and the polyethylene is fed through a nozzle (12). The coated layer was re-wetted with a re-wetting liquid consisting of a 0.5% aqueous solution of emulsion and pressed onto a cast drum (10) at a press nip pressure of 150 kg/ω (13). After drying, the cast coated paper was peeled off from the drum by a take-off roll (13) and wound up as a winder (14).

In addition, steam was applied using a steam box (15) under the conditions shown in Table 1 so that the steam acted on the surface of the cast coating layer. Moreover, in Comparative Example 4, such vapor application was not performed at all.

The appearance of reverse vertical curl and the glossiness of the cast coated paper are listed in Table 1 in four copies. As is clear from the results in Table 1, in the examples of the present invention, the occurrence of reverse vertical curls was extremely efficiently improved compared to the comparative examples.

Example 5, Comparative Example 5 75 parts of kaolin, 20 parts (solid content) of a heavy calcium carbonate dispersion containing 95% of particles with a particle size of 2 μ or less, and 0.5 parts of sodium polyacrylate using 5 parts of aluminum hydroxide as a dispersant. 0.5 part (solid content) of sodium pyrophosphate was used to prepare a pigment slurry with a concentration of 70%. To this, 13 parts of a 15% concentration casein aqueous solution, 17 parts (solid content) of styrene-butadiene co-(14) polymer latex were added and mixed, and further 0.25 part of ammonium oleate was added to give a concentration of 55%.
A concentrated coating liquid was obtained. The viscosity of the coating liquid was 1500 cps (Brookfield type viscosity needle, 60 rpm, 20°C).
H was 9.0. Using this coating liquid, gel casting was performed using the apparatus shown in FIG. That is, 90g/r
The above coating liquid was applied to the base paper (16) of d at a dry weight of 25 g/
The coated layer was coated with a roll coater (17) so that the coating layer was rrr, and then brought into contact with a 0.5% formic acid aqueous solution (18) to gel the coated layer.

A press roll (technique 9) with a diameter of 800 mm and a cast drum (2) with a diameter of 3000 mm with a surface temperature of 98 °C were used.
The gelled coating layer was pressed with the press nip (21) formed in step 0) at a press roll pressure of 100 kg/cm, and after drying, the cast speed was 30 m using a take-off roll (22).
/min, and apply 5g/rd of steam to the cast-coated paper surface in the steam box (23) to remove the cast-coated paper (
24). The cast-coated paper obtained had no reverse vertical curl at all and had strong gloss. As Comparative Example 5 (15), when the steam treatment on the cast paper surface in Example 5 was discontinued, reverse vertical curls with a radius of curvature of 10 cm or less occurred.

Table 1 ※・・・Horizontal positive curl

[Brief explanation of drawings]

Figures 1 to 3 are examples and comparisons (16) of the present invention. FIG. 2 is a schematic cross-sectional view of the cast finishing device used in the example. (17)

Claims (2)

[Claims] (1) A method for manufacturing cast coated paper in which a wet coating layer mainly composed of pigments and adhesives is pressed against the surface of a drum having a heated mirror surface, and then dried to give a high gloss finish, and is released from the drum. A method for producing cast-coated paper, which comprises: then applying steam to the surface of the cast-coated layer. (2) The manufacturing method according to claim 11, wherein the amount of steam acting on the cast coating layer is in the range of 0.2 to 30 g per 1 d of paper in terms of water amount.