JPH01139895A - Production of cast coat paper - Google Patents

Abstract

PURPOSE: To produce cast-coated paper having high surface strength at high speed by conducting the drying, rewetting and cast finishing of a coated layer under specific conditions respectively. CONSTITUTION: This cast-coated paper is produced as follows: (1) coating base paper 1 with a coating liquid [including pigment, adhesive (a latex including a latex having >=20 deg.C glass transition temperature in a content of >=30 wt.% based on the whole latex) and an auxiliary as main ingredients] using a roller coating unit 2 so as for the dry weight of the paper 1 to become ca. 25 g/m<2> ; (2) drying the paper in a drier 3 so as for the moisture content to become ca. 6 wt.% under a condition that the temperature of coat film doesn't exceed the glass transition temperature of the latex +30 deg.C; (3) making the paper pass through a press nip 6 and rewetting the surface of a coated layer with a rewetting liquid from a nozzle 7; (4) finishing the paper by pressing the paper onto a cast drum 5 at a temperature exceeding the glass transition temperature of the latex +30 deg.C, preferably at a temperature equal to or higher than the glass transition temperature of the latex +50 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing cast coated paper, particularly to improvements in the rewetting method.

[Conventional technology and its problems]

There are two methods of manufacturing highly glossy coated paper for printing called cast coated paper: the direct method, in which a wet coating layer is pressed against the surface of a heated drum for a glossy finish, and the wet coating layer is brought into contact with a coagulant solution. A coagulation method in which the wet coating layer is dried or semi-dried and then plasticized by rewetting and then pressed against the heated drum surface.・Cast method etc. are known.

All of these cast finishing methods have in common that the coating layer in a plastic state is pressed against the surface of a heated drum and then released from the mold, but the differences in the plasticity of the coating layer affect operability and yield. There is a difference in the quality of cast coated paper.

In other words, in the direct method, if the surface temperature of the heating drum is increased to over 100°C, the coating liquid will boil and the coating layer will be destroyed, so the drum temperature must be kept below 1100°C and the casting speed must be slow. becomes.

In the coagulation method, since the coating layer is gelatinized, it is possible to raise the temperature of the heating drum surface to over 100℃, but the coating layer contains a lot of water and has poor peelability from the drum. In addition, it is difficult to control the degree of coagulation of the coated layer, so finishing at high speed is not possible.

In the rewetting method, it is possible to dry the coating layer once and then raise the temperature of the heating drum surface to t-90 to 180℃, but it is necessary to rewet the coating layer once it has been dried. Therefore, the degree of plasticization is significantly lower than that of other methods.

In order to facilitate plasticization by rewetting, the rewetting liquid contains an amide compound (q# Kaisho 59-f 92797
However, the degree of plasticization is still low, and as a result, the coating layer does not adhere uniformly to the surface of the heating drum, resulting in a relatively homogeneous coating during operation at low speeds. Although coated paper with a strong gloss can be obtained, as the speed of operation increases, uneven gloss, pinhole-like spots, etc. occur, and the uniformity of the coated surface is rapidly lost.

In addition, in order to improve the adhesion of the coating layer to the heated drum, there is a method of smoothing the coating layer by applying a super calender before rewetting it, and a method of smoothing the coating layer before it is re-wetted, and a method of using a press roll when pressing the coating layer to the finished surface. Methods of increasing the pressure have also been proposed, but on the other hand, these methods significantly impair the advantages of cast coated paper, which are low tension and high bulk.

Additionally, a method has been proposed in which salts of zinc, aluminum, and magnesium are added to the coating liquid to make the coating layer porous and improve adhesion to the heating drum (Japanese Patent Laid-Open No. 146097/1983). However, this method reduces the surface strength of the finished cast coated paper and requires an increase in adhesive, so that the plasticization of the coated layer is not as good.

[Purpose of the invention]

In the Hariwet casting method of the present invention, the re-wetting solution makes it easy to plasticize the coating layer, thus eliminating pinhole-like spots.
The purpose of this paper is to produce cast paper that can be operated at high speed without causing uneven gloss, and has a strong surface strength.

[Structure of the invention]

The present inventors have conducted extensive research on a method for producing high-quality medium cast coated paper at high speed, and have determined that the coating layer temperature is the glass transition temperature of the latex added to the cast coating liquid.
T, G, )-) The coated layer is dried under a temperature condition not exceeding -50°C, re-wetted with a re-wetting solution, and the post-mortem latex τ, G,
The present inventors have discovered that high-quality cast paper with high surface strength can be produced at high speed by press-contacting the paper to a cast drum heated to a temperature exceeding +30° C., thereby achieving the present invention.

The present invention provides a method for producing cast coated paper, in which a coating layer mainly composed of pigments, adhesives, and auxiliary agents is re-wetted after drying, and is pressed against a heated mirror drum to give a high gloss finish.
A coating layer is coated on the base paper with a coating liquid containing 30 or more latexes with a glass transition temperature of 20° C. or more as an adhesive out of all the latexes, and the temperature of the coating film is T of the latex.
After drying and rewetting at temperatures not exceeding G+30°C, T
, G + 50° C. or higher, preferably T, G + 50° C. or higher, and press-contacts the paper to a cast drum for finishing.

The present invention will be explained in detail below.

In the present invention, the latex may be a conjugated diene polymer latex such as a styrene-butadiene polymer or a methyl methacrylate-butadiene copolymer, or an acrylic latex such as a polymer or copolymer of an acrylic acid ester and/or a methacrylic acid ester. Polymer latex, vinyl polymer latex such as ethylene-vinyl acetate copolymer, or various polymers thereof are functionally modified with a monomer containing a carboxyl Me functional group, and then alkali-soluble or alkali-insoluble polymers are prepared. Among the combined latexes, latexes with T and G of 20°C or higher, or latexes with two or more of d, T, and Gi, use one or more latexes with T and G of 20°C or higher alone or in combination. It can be added to a cast coating solution, or in combination with the following adhesives.

Adhesives used in combination with the above latex include casein,
Synthesis of proteins such as soybean protein and synthetic proteins, starches such as positive starch and oxidized starch, cellulose derivatives such as dimethyl cellulose and hydroxyethyl cellulose, hollyvinyl alcohol, olefin-maleic anhydride copolymer resin, and melamine resin, etc. Resin adhesives, conjugated diene polymer latex such as styrene-butadiene polymer, methyl methacrylate-butadiene copolymer, acrylic polymer such as acrylic ester and/or methacrylic ester polymer or copolymer Polymer latex, vinyl polymer latex such as ethylene-vinyl acetate copolymer, or alkali-soluble or alkali-insoluble polymers obtained by functionally modifying various polymers thereof with functional group-containing monomers such as carphocyclyl groups. Among latexes, latexes in which T and G are 20° C. or less may be used.

Latex with T and G of 20°C or higher or two or more of T and G, including latex with two or more T and Q of 20°C or higher 1j: Latex and/or casein with T and G of 20°C or lower , latex with ij, T, G of 20℃ or higher when used in combination with protein such as soybean protein, starch, etc., or d, T.
, one or more latex with two or more Gft? ,G
It is desirable that the ratio of latex having a temperature of 20°C or higher to the total latex is 30% or higher.

The adhesive is used in an amount of 5 to 50 parts by weight, generally 10 to 30 parts by weight, per 100 parts by weight of the pigment. Further, the structure of the latex may be a homogeneous structure, an intermittent structure, a continuous two-layer structure, or any other structure.

Further, the present invention includes at least one kind of sulfate, nitrate, acetate, or formate of aluminum, magnesium, or zinc as an auxiliary agent in the coating liquid containing the latex,
It also includes a method of rewetting the dry layer at a temperature of latex T, G + 30°C or lower, heating the latex to a temperature of T, G + 30°C or higher, preferably T, G + 50°C or higher, and pressing it against a cast drum for finishing. It is something that Furthermore, the present invention exhibits its effects regardless of the composition of the rewetting liquid.

In the rewet casting method, the coated-dry layer is rewetted with a rewetting solution and finished by being pressed against a heated drum. Also, the problem is how to make the adhesion to the drum easier.As mentioned above, it is necessary to change the type of rewetting liquid, smoothen the coating layer of the dry layer, or change the coating liquid. Although it has been considered to solve the problem by adding a coagulant to the latex, the present inventors investigated the film-forming properties of latex in order to fundamentally solve this problem. I found a method that works.

That is, latex has its own film-forming temperature, and we focused on the property that it does not form a film below the film-forming temperature.

The glass transition temperature (T, G) of latex is the point at which the segments of the polymer transition from a glassy state to a rubbery state;
When latex is dried at a temperature exceeding G9, dry strength and water resistance begin to develop, and a film is partially formed. τ,
As the temperature is further increased beyond Gft, the dry strength and water resistance increase, and the film formation μ increases, but it is thought that time, temperature, and pressure influence the formation of a complete film. Therefore, if the coating layer is dried under drying conditions such that the temperature of the coating layer is below T and G of the latex + 30°C, the latex in the coating layer will be completely removed if the drying time is normal for coated paper manufacturing. It does not form a film, has low dry strength, and does not exhibit water resistance, so it is presumed that the coated layer can be easily plasticized when rewetting with a rewetting solution.

When the latex is pressed against a cast drum heated to a temperature of TO + 30°C or higher after rewetting, the latex receives heat and forms a film, resulting in cast coated paper with good surface quality. The surface strength of the coating layer is also fully demonstrated.

As the pigment, common pigments for coated paper such as clay, kaolin, aluminum hydroxide, calshu carbonate A1 titanium oxide, barium sulfate, zinc oxide, satin white, and plastic pigments are used.

Further, as an auxiliary agent, salts such as sulfates, nitrates, acetates, or formates of zinc, aluminum, and magnesium may be used.

However, various auxiliary agents such as antifoaming agents, coloring agents, flow modifiers, and mold release agents can be used as appropriate.

In the present invention, the coating liquid is a blade coater, air knife coater, roll coater +, Fura V*-1-, curtain coater, champlex coater, bar coater, gravure coater, etc., which are generally used in the production of coated paper.
The base paper is coated in one layer or in multiple layers using an on-machine or off-machine coater equipped with a coating device such as a size breather footer.

At that time, the solid content concentration of the coating composition is generally 35 to 70.
Although it is based on weight, an amount in the range of 45 to 65 weight is preferable in consideration of operability.

The base paper used is paper pace or pod-based base paper with a weight of 30 to 40,017 m, which is used for general printing coated paper and cast coated paper.These base papers are made using acidic or alkaline papermaking methods. Of course, medium-quality base paper containing high-yield pulp of about 10% or more by weight can also be used.Also, pre-coated or coated paper with a general pigment coating on the back side of the cast coating layer can be used. Can also be used as base paper.

The coating amount of the coating composition on such base paper is 10% by dry weight.
〜5017 m'', but in terms of improving the quality of the resulting cast coated paper and the cast coating speed, it is 15~
Most preferably, it is adjusted within a range of 3517 m''.

In the rewet casting method, the final coating composition is coated onto the base paper and dried once, and the drying process is usually carried out using a hot air dryer, air foil dryer, air gap dryer, cylinder dryer, infrared dryer, electron beam dryer, etc. Drying equipment for coated paper is used.

The degree of drying of coated paper varies depending on the type of base paper, the type of coating composition, etc., but generally the paper moisture content is about 1 to 15%.
It is preferably dried to a dryness of about 5 to 10 degrees. The temperature of the coating layer during drying is as described above) Latex T, G
Dry carefully not to exceed +10°C.

After drying, apply a machine canonder to the coated paper as needed.
Although "F flt" processing such as super calender is carried out, it is necessary to avoid excessive processing that significantly impairs the bulk and hardness characteristic of cast coated paper.

The coating layer is then re-wetted according to the normal glue wet casting method and pressed against a heated mirror drum to achieve a strong gloss finish. In the method of the present invention, the mirror drum is particularly used as the coating liquid. Casting is finished at a temperature of dT, G + 50°C or higher, preferably dT, G + 50°C or higher, which is the highest of T and GO of the latex.

Note that the rewetting liquid is not particularly limited, and includes, for example, fresh water, hot water, hot water, a dead water solution containing a mold release agent,
Conventional rewetting fluids such as aqueous solutions containing amines such as dicyandiamide urea are used.

〔Example〕

The present invention will be specifically explained below with reference to Examples, but it is of course not limited to these. Note that parts and percentages in the columns indicate parts by weight and weight sl, respectively, unless otherwise specified.

Examples 1 to 4, Comparative Examples 1 to 3 80 parts of kaolin, 20 parts of light carbon, and 14 parts of sodium polyacrylate were dispersed in water using a splitter manufactured by Serini, and a pigment with a solid content concentration of 55. Prepare slurry 9.

In addition to this, 14 parts of tributyl 7 phosphate as an antifoaming agent,
10 parts (solid content) of a 15% casein aqueous solution dissolved using ammonia as an adhesive and the latex shown in Table 1 were added, and a release agent was added to form a polyethylene wax emulsion of 1.5 parts (solid content) t-0. Finally, ammonia and water were added to bring the solid content to 45 and the pH to 9.5.
Six types of coating liquids were obtained.

Using this coating liquid, rewet casting was performed using the apparatus shown in FIG. That is, the above coating liquid was applied to base paper 1 with a dry weight of 60 f/yH'' using a cool coater 2 so that the dry weight was 25 f/wr'', and the coating was applied in a dryer 3 under the conditions shown in Table 1. It was dried at the bottom to a moisture content of 6 cs. Next, the paper is passed through a press nip 6 formed by a rubber roll 4 and a chrome-plated cast drum 5, where the surface of the coated layer is re-wetted with a re-wetting liquid supplied from a nozzle 7, and then the drum shown in Table 1 Rotation speed 100 under temperature conditions
Pressing pressure 150 kg/min on cast drum 5
The paper was pressed with cns, and after drying, it was peeled off from the cast drum with a take-off roll 8 to produce 9 tons of cast coated paper. Table 1 shows the quality of the cast coated paper obtained.

Follow the instructions below to measure surface properties and white paper gloss.

[Surface properties] O...Good (surface defects) Δ... Slightly good ×...Poor [White paper gloss] Measured with a gloss meter (75°). (Nippon Denshoku Kogyo LLoVG-10 type gloss meter) Examples 5 to 6. Comparative Examples 4 to 5 80 parts of kaolin, 20 parts of light coal, and 14 parts of sodium polyacrylate were dispersed in water using a splitter manufactured by Serini Co., Ltd. to prepare a pigment slurry with a solid content concentration of 55.

In addition, 4 parts of tributyl 7-osphate α as an antifoaming agent,
As an adhesive, 10 parts (solid content) of a 15es casein aqueous solution dissolved using ammonia and the latex shown in Table 2 were added, and then 1.5 parts of Bolier and Chin Vine wax emulsion (solid content) were added as a release agent. ), and further added 10% aqueous solution of zinc sulfate (solid content) as an auxiliary agent, and then added ammonia and water to the forge to a solid content concentration of t-45 and pH ft of 9.5. Adjustments were made to obtain four types of coating liquids.

Using this coating liquid, rewet casting was performed using the apparatus shown in FIG. In other words, 6017m” (D
K paper I K drying f [jl125t/, * Coat the above coating liquid with roll coater 2 so that the moisture content becomes 6% in dryer 3 under the better conditions shown in Table 2. So dry. The paper is then passed through a press nip 6 formed by a chrome-plated cast drum 5 with a press roll 4, where the surface of the coating layer is rewetted with a rewetting liquid supplied from a nozzle 7, and then a second Under the drum temperature conditions shown in the table, it was pressed against a cast drum 5 at a rotation speed of 100 m/min at a press pressure of 15'Oky/cps, and after drying, it was peeled off from the cast drum using a take-off four-wheel 8 to form a cast coated paper 9. was manufactured.

The quality of the obtained cast coated paper is shown in Table 2.

[Effects of the Invention] As is clear from the results of each series of implementations, the method of the present invention can easily plasticize the coating layer when rewetting with the rewetting solution as described above, making it easier to cast. A cast surface with good adhesion to the drum and fewer defects can be obtained. Also, auxiliary agents (aluminum, magnesium, calcium,
It has the advantage that it does not require the use of zinc sulfates, nitrates, acetates or formates, or only requires the addition of a small amount, so the surface strength of the coating layer is not weakened.

Therefore, the rewetting method of casting can be easily carried out according to the present invention, and the casting speed can be greatly increased.

[Brief explanation of the drawing]

FIG. 1 shows a flow diagram of an apparatus for carrying out the invention. 1... Raw Wc, 2-... Roll roll jl-15... Drying WA, 4-... Press roll, 5-... Cast drum, 6-... Press nip, 8... Take-off 0-roll, 9.-Cast Coated Paper Procedures Amendment Written on March 25, 1986 Kunio Ogawa, Commissioner of the Patent Office 1. Indication of the case Patent Request No. 291727 of 1988 λ Name of the invention Method for manufacturing cast coated paper 5 Relationship with the case of the person making the amendment Patent applicant Address 4-7-5 Ginza, Chuo-ku, Tokyo Name Oji Paper Co., Ltd. Representative Kawage 2 Date of Part 1 amendment order Voluntary amendment & Subject of amendment 2 Amendment Contents (1) Delete "or 111 latex" on page 6, lines 18 and 19 of the specification. (2) On page 6, line 20, change “alone or in combination, or in addition” to “alone, or Itt4” 1゜(3)
From the last line of page 7 to line 2 of page 8, “or one---T, G is 20
℃ or more” is deleted. (4) On page 8, lines 5 to 7, “Or, T, G---T
, Latex with G of 20°C or higher" is deleted. (5) Delete "Also, -111 may be used as the structure of latex" in lines 11 to 13 of page 8. (6) Change “Examples 1 to 4” on page 14, line 8 to “Examples 1 to 4”
3”. (7) Column “3” in Table 1 on page 16 (Example 30tm
> and correct "14" to "13". (8) Change “Examples 5 to 6” on page 17, line 9 to “Examples 4 to 6”
5”. (9) In Table 2 on page 19, "Example 5" is corrected to "Example 4" and "〃6" is corrected to "〃5".

Claims (1)

[Scope of Claims] 1. A method for manufacturing cast coated paper, in which a coated layer mainly composed of pigments, adhesives, and auxiliary agents is dried, re-wetted, and then pressed against a heated mirror drum to give a strong gloss finish. After coating a base paper with a coating liquid containing latex as an adhesive containing 30% by weight or more of the total latex with a glass transition temperature of 20°C or higher, the temperature of the coating film is the glass transition temperature of the latex + 30°C. Dry under conditions not exceeding
A method for producing cast-coated paper, which comprises press-contacting the paper to a cast drum heated to a glass transition temperature +30° C. or higher after being re-wetted.