JPH08269896A - Production of coated paper for printing - Google Patents

Abstract

PURPOSE: To provide a method for producing coated paper for printing which can solve the trouble of ink-picking up unevenness on offset printing to give high quality of printed products. CONSTITUTION: A base paper is coated with a water-based coating containing pigment and at least one selected from among starch or starch derivatives as a water-soluble adhesive and dried to form a dry coated layer, then finished to give coated paper for printing. The dry coated layer is coated with an aqueous solution of a penetration agent having a penetration power of <=50 seconds measured according to the canvas disk method to effect redistribution of the water-soluble adhesive in the coated layer and calendered.

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 for printing, and more particularly to a method for producing a coated paper for printing which is capable of eliminating unevenness of ink buildup of printing ink in offset printing and has a good printing finish.

[0002]

2. Description of the Related Art Among the drawbacks of printed matter in general offset printing, one of the problems caused by coated paper for printing is unevenness of ink deposition due to printing ink. This ink inking unevenness is called printing mottling or simply mottling, and further called eye unevenness. (Hereinafter, referred to as ink inking unevenness). The main cause of this unevenness of ink buildup is uneven trapping of the rear cylinder printing ink or uneven absorption of dampening water in offset printing for multicolor overprinting. Such ink unevenness is caused by uneven distribution of each component constituting the coating layer on the surface of the coating layer, and for coated paper or art paper with a relatively large coating amount, In particular, the uneven distribution of the adhesive on the surface of the coating layer has a great influence.

As an adhesive which is one of the main constituents of the coating layer, a water-soluble adhesive such as starch or starch derivative,
Alternatively, a copolymer emulsion such as a styrene-butadiene copolymer latex is used. While such an aqueous coating composition is applied to a base paper and dried to form a coating layer, the adhesive is unevenly moved to the base paper side or the surface side of the coating layer, whereby the inside of the coating layer or It is said that an uneven distribution of the adhesive occurs on the surface of the coating layer. In particular, water-soluble starch or the like is likely to cause non-uniform distribution, which easily causes unevenness of ink inking. In order to prevent such uneven transfer of the adhesive, it is necessary that the base paper has a uniform absorptivity, and that the drying condition avoids abrupt or excessive drying, resulting in a non-uniform distribution state. Consideration to avoid is required.

However, on the other hand, the speed of the coating machine is increasing in order to increase the productivity. Therefore, for example, as the drying conditions of the coating machine, a higher drying temperature,
A coating machine design that increases the drying capacity by increasing the air volume and speed is adopted, and further, coating machine operation such as humidity control of hot air circulation is made low. Has become. Therefore, by taking such operating conditions, there are many negative points for the quality of the coated paper. In particular, the water-soluble adhesive on the surface of the coating layer has a strong tendency to have a non-uniform distribution, and there is a problem that remarkable unevenness of ink inking occurs when offset printing or the like is performed on the resulting coated paper. Get up.

Therefore, as a method of enhancing the drying ability without deteriorating the unevenness of ink inking, there is known an example of performing infrared ray, particularly near infrared ray drying. However, since these methods are used exclusively in the early stages of drying,
Non-uniform transfer of the adhesive to the surface also occurs due to the subsequent hot air drying of the conventional type, and it is not satisfactory to eliminate the unevenness of ink deposition. In addition, performing all the drying steps by infrared rays is not a practically effective method from the viewpoint of drying capacity and energy consumption required for drying.

It is important for the base paper to have uniform absorbency, but due to the characteristics of the base paper production, non-uniformity cannot be avoided. For example, if an undercoat coating layer is provided to improve the uniformity. However, when it is subjected to sudden excessive drying, it is still not possible to satisfactorily suppress the uneven migration of the water-soluble adhesive.

A coating composition containing a pigment and an adhesive, particularly a water-soluble adhesive such as starch or starch derivative, is applied,
As an approach to prevent uneven migration of the adhesive that occurs in the drying process, examples of reducing the compounding amount of water-soluble starch that is particularly easy to migrate in the adhesive and immobilization of the coating composition There is known an example in which an auxiliary agent or the like for accelerating is added.
The former method is an effective method for eliminating unevenness of ink inking if there is no problem in terms of required quality and cost for the final product. On the other hand, when a coating composition having a reduced amount of starch is used, problems such as coating suitability (reduction in water retention) and product stiffness are likely to accompany. Therefore, this method is limited to a specific product, and cannot be applied to general coated paper for printing in general. Further, the latter method has drawbacks in that the viscosity of the coating material increases and the stability of the coating material (aging) is increased.

[0008]

The object of the present invention is to coat a base paper with a water-based adhesive, especially an aqueous coating composition (paint) containing a water-soluble starch or starch derivative, followed by a drying step. After the coating layer is provided through the process, it is a method for producing a coated paper for printing, which is subjected to a calender finish. Provided is a method for obtaining a coated paper for printing, which does not cause unevenness of ink inking and has a good printing finish.

[0009]

Means for Solving the Problems The present inventors have completed the present invention as a result of intensive studies on the relationship between the cause of ink unevenness and the distribution of the adhesive on the surface of the coating layer.
The present invention provides a method for producing a coated paper for printing, which comprises: providing a dry coating layer containing a water-soluble adhesive composed of at least one of starch or a starch derivative as a pigment and an adhesive on a base paper, and then finishing. The surface of the dried coating layer is coated with an aqueous penetrant liquid having a penetration force value of 50 seconds or less as measured by the canvas disk method to redistribute the water-soluble adhesive in the coating layer, A method for producing a coated paper for printing, which is characterized in that a render finish is performed.

[0010]

It has been empirically known that when a coating material containing a large amount of a water-soluble adhesive, particularly starch or a starch derivative, is used in a method for producing a coated paper for printing, unevenness of ink inking tends to occur. . This is because the water-soluble adhesive easily penetrates into the base paper at the time of coating, or the water-soluble adhesive easily moves as the water vapors and escapes from the surface of the coating layer during the drying process. is there. On the other hand, an aqueous emulsion (copolymer) latex has a relatively small proportion of migration with water, like a water-soluble adhesive, once it is formed into a film due to its compositional characteristics.

The method of the present invention is mainly applied to starch and starch on the base paper.
Water-based paint containing water-soluble adhesive such as starch derivative
After applying, 0.5-10% as paper moisture, more preferred
After drying once to 3-8%,
Penetration measured on the surface of the coating layer by the canvas disc method
The force value is 50 seconds or less, more preferably 30 seconds or less
1-10 g / m of permeating agent aqueous liquid per coated layer surface², Good
More preferably 2-6 g / m ²To be coated, then paper
If necessary, heat dry so that the water content is about 3-8%.
Etc. and do the calendar finish as it is, or again
Is for rolling up and then calendering.
It Therefore, in the present invention, a penetrant is added to the dry coating layer.
The coating of aqueous liquid plays an extremely important role.
is there.

That is, the action of the aqueous penetrant liquid is to coat a water-soluble adhesive such as starch or starch derivative which is non-uniformly distributed in the coating layer or on the surface layer, particularly on the surface layer of the coating layer in a very short time. It is to redistribute inside the layer. As a result, after the coated paper obtained is calendered to finish it as a coated paper for printing and then subjected to offset printing, a product in which the ink inking unevenness desired by the present invention is significantly reduced or eliminated is obtained. To be

As a matter of course, such an effect can be obtained even if the coating layer is simply water-coated and then directly dried without being forcibly dried and then calendered to obtain the same effect. It is not practical under the present conditions where it takes too much time and high-speed production is forced. Further, if forced thermal drying is performed in the case of water treatment, redistribution of the water-soluble adhesive in the coating layer can hardly be expected as a result.
This is because the water-soluble adhesive is once dispersed in water or heated and dried while it is in the swelling process, so that it is not redistributed but rather uneven distribution is promoted. It is estimated to be one.

On the other hand, in the case of the penetrant used in the present invention, the penetrating power into the coating layer is considerably stronger than that of ordinary water, and the water-soluble adhesive is swollen or redissolved in a short time to be redistributed. ,
Moreover, the strength of the penetrating force attracts the water-soluble adhesive to the inside of the coating layer. As a result, even if the coated paper coated with the penetrating agent aqueous solution is heat-dried, it does not become like water. Instead of simply returning to the original, the redistribution of the water-soluble adhesive is maintained as it is, and a more uniform distribution state is obtained.

This is because the coated paper obtained in an experiment conducted by the present inventors using a water-based paint containing a starch-based adhesive was confirmed by an iodine dyeing test method, and it was confirmed that the penetrant was treated. It was possible to clearly confirm the distinction between the applied and the unapplied. The iodine dyeing test is a starch distribution by heating iodine and adding iodine gas to the surface of the coating layer for a certain period of time, and then adding steam to dye the starch on the surface of the coating layer with iodine. You see the condition.

The canvas disk method used here is a measuring method generally used for measuring the osmotic force of an active agent, and a canvas punched out to a diameter of 1 inch is placed in an active agent solution and filtered. Hold the plateless goochi upside down and hold it in the liquid. When the canvas gets wet, it leaves the funnel, so measure the time until that time (Handbook of Surfactants / Ichiro Nishi et al .: Sangyo Tosho Co., Ltd., P86)
0). The shorter the time (seconds), the better the penetrating power.

In the canvas disk method, the value changes depending on the material and type of canvas, the liquid temperature at the time of measurement, and the like. Accordingly, in the present invention, the value of the penetrant (activator) aqueous liquid when the # 6 canvas made by Tosco Corp. is used as the canvas and the liquid temperature of the liquid to be measured is 25 ° C. and is measured by the canvas disc method ( Second) was defined as the penetrating power.

As described above, in the present invention, the penetrating power of the applied penetrant liquid is extremely important. By the way,
When the value of the penetrating force of the penetrating agent liquid measured by the canvas disk method exceeds 50 seconds, the penetrating agent liquid coated with the penetrating force is weak, and the water-soluble adhesive in the coating layer is After swelling or elution, it easily remains on the surface of the coating layer. as a result,
When heat drying is performed in this state, the dissolved water-soluble adhesive again forms a non-uniform distribution on the surface of the coating layer, and ink unevenness is not improved.

The coating amount of the penetrant liquid to be coated on the coating layer is not particularly limited, but from the viewpoint of obtaining the desired effects of the present invention, it is 1 to 10 g / m ² , preferably 2
It is desirable to adjust it at about 6 g / m ² . By the way, 1
If it is less than g / m ² , the effect of dissolution and redistribution of the water-soluble adhesive tends to be insufficient, while if it exceeds 10 g / m ² ,
Even when the penetrating power of the penetrant liquid is sufficiently high, the penetrant liquid remains on the surface of the coating layer, and when re-dried, the swollen and eluted water-soluble adhesive again forms an uneven distribution on the surface of the coating layer. There are concerns
There is a possibility that it cannot be expected to sufficiently eliminate the unevenness of ink buildup.

As the penetrant, any of anionic surfactants, cationic surfactants, nonionic surfactants and the like can be used and is not particularly limited, but according to the study of the present inventors, Nonionic surfactants having HLB values of 9 to 14, such as polyoxyethylene-polyoxypropylene condensates, primary alcohol ethoxylates, primary alcohol ethoxylates, nonylphenol ethoxylates, octylphenol ethoxylates, oleyl alcohol. Ethoxylate, lauryl alcohol ethoxylate, phenol ethoxylate, polyoxyethylene glycol oleate, polyoxyalkylene tallowate, sorbitan stearyl ester, sorbitan oleyl ester, polyoxyethylene sorbitan oleyl s Le, ethylene glycol distearate, fatty acid diethanolamide, fatty acid monoethanolamide amide, polyoxyethylene - fatty acid monoethanolamide amide or the like was effective in terms of relief-effect of eliminating inking uneven.

As a coating device for coating the coating layer with the penetrant aqueous liquid, for example, production of general coated paper for printing such as blade coater, air knife coater, roll coater, bar coater, gravure coater and spray coater. Various coating machines used in the field can be appropriately used. .

In the present invention, the water-soluble adhesive which is an essential component of the coating layer includes, for example, positive starch, oxidized starch,
Examples of the starch include starches such as enzyme-modified starch, thermochemically modified starch, etherified starch, esterified starch, and cold water-soluble starch, or starch derivatives. In addition to the above starch or starch derivative, for example, celluloses such as carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, olefin-maleic anhydride resin, and the following emulsion type adhesives which are alkali-soluble The same applies to a water-soluble synthetic resin adhesive.

A particularly excellent effect can be obtained when the content of these water-soluble adhesives (particularly starch and starch derivative) is 1 to 20% by weight, preferably 3 to 15% by weight based on the solid content of the coating layer. To be By the way, if it is less than 1% by weight, it is difficult to be targeted because ink unevenness is not originally generated, and such a coating has low water retention and poor coating suitability. On the other hand, when it exceeds 20% by weight, a considerable effect can be expected for the effect of reducing to eliminating ink inking unevenness, but it is difficult to increase the viscosity of the coating and make the coating layer water resistant, Coating suitability and other quality problems are likely to occur and may be impractical.

Further, the adhesive is not limited to the above water-soluble adhesive, and for example, a copolymer emulsion adhesive conventionally used in the field of coated paper manufacturing,
Specifically, a conjugated diene-based copolymer latex such as a styrene-butadiene copolymer or a methylmethacrylate-butadiene copolymer, an acrylic polymer such as a polymer or copolymer of acrylic acid ester and / or methacrylic acid ester. Latex, vinyl-based polymer latex such as ethylene-vinyl acetate copolymer, and various copolymers obtained by modifying these latexes with monomers containing functional groups such as carboxyl groups, and partially soluble alkali or insoluble alkali Alternatively, a copolymer latex can be appropriately used in combination.

Examples of the pigment which is the main component of the coating layer include clay, kaolin, aluminum hydroxide, calcium carbonate, titanium dioxide, barium sulfate, zinc oxide, satin white, calcium sulfate, talc and plastic pigments. One or more ordinary pigments for coated paper are appropriately selected and used.

The adhesive compounded in the paint forming the coating layer is adjusted in the range of 3 to 50% by weight, preferably 5 to 30% by weight, based on the solid content of the pigment. Furthermore, various auxiliary agents such as a water resistant agent, a defoaming agent, a colorant, a lubricant, and a flow modifier are appropriately blended in the paint.

When the base paper is coated with a coating material, a coating apparatus generally used in the field of producing coated paper, for example, a blade coater, an air knife coater, a roll coater, a reverse roll coater, a bar coater, a curtain coater. An on-machine or off-machine coater provided with a coating device such as a die slot coater, a gravure coater chanplex coater, or a size press coater is used to coat one side or both sides of the base paper in one or multiple layers. The solid content concentration of the paint at that time is generally about 40 to 75% by weight, but in consideration of operability, the range of 45 to 70% by weight is preferable.

As the base paper, a paper base or a board base base paper having a basis weight of about 30 to 400 g / m ² used for general printing coated paper is used, but the papermaking method is not particularly limited, and the acidic papermaking is used. , Alkaline paper may be used. Of course, a medium quality base paper containing high-yield pulp can also be used. Further, a base paper precoated with a size press, a roll coater, a blade coater or the like can also be used. The coating amount of the coating material applied to the base paper is generally about 3 to 50 g / m ^{2 in} terms of dry weight, but in consideration of the white paper quality of the obtained coated paper, coating suitability and printability, etc. It is desirable to adjust in the range of about 25 g / m ² .

As a calendar finishing method,
For example, various calenders composed of metal rolls or drums and elastic rolls such as a super calender, a gross calender, and a soft compact calender are used for on-machine or off-machine specifications.

As the method for drying the wet coating layer, various methods such as steam heating, hot air drying, gas heater heating, electric heater heating, infrared heater heating, high frequency heating, laser heating and electron beam heating can be used. it can.
Also, regarding the drying conditions, in the conventional drying, in order not to cause uneven transfer to the coating layer surface of the adhesive,
Although it was necessary to avoid rapid and excessive drying as much as possible, the method of the present invention does not require any special restrictions on the drying method, conditions and the like.

[0031]

The present invention will be specifically described below with reference to examples, but the present invention is not limited to these ranges. Unless otherwise specified, "parts" and "%" in the examples mean "parts by weight" and "% by weight", respectively. The evaluation method is as follows.

[Evaluation of printed matter] (Ink unevenness) Using a RI printing machine (manufactured by Akira Seisakusho Co., Ltd.), TOYOKING Mark Five New T for the first color
KU CC Indigo ink (manufactured by Toyo Ink Co., Ltd.) 0.5 ml was developed and the second color was the TOYOKING Mark Five T
= 13 0.3 ml of red ink (manufactured by Toyo Ink Co., Ltd.) was developed, and unevenness of the second color red ink was visually determined when overprinting while changing the time after the first color printing. ◎: Very good ○: Good △: Slightly poor ×:
Inferior

Example 1 [Preparation of paint] Heavy calcium carbonate (trade name: FMT-
90 / made by Phimatic Co., Ltd.) and 30 parts of kaolin (trade name: Amazon 88 / made by CADAM) 70 parts were dispersed in water using a Choles disperser to obtain a pigment slurry. Styrene-butadiene copolymer latex (product name: SN307, manufactured by Sumitomo Dow) 10 parts (solid content), oxidized starch paste solution (product name: Ace A / manufactured by Oji Corn Starch) 5 parts (solid content) in this slurry. , Waterproofing agent (trade name: Denacol PC1000 / Nagase Kasei Co., Ltd.) 0.2
Parts, a lubricant (trade name: Nopcoat C-104 / manufactured by San Nopco), and 0.2 parts of other auxiliaries were added and dispersed to prepare an aqueous paint having a solid content concentration of 55%.

[Production of Coated Paper] Using the above coating composition, a blade coater was used so that the dry weight per side was 15 g / m ² on a base paper having a surface area of 87.9 g / m ² .
Both sides were coated and dried with hot air to obtain a coated paper having a water content after drying of 6.0%. Then H as penetrant
A nonylphenol ethoxylate having an LB of 12 was used to prepare a 0.3% aqueous solution thereof, which was then supplied to a roll applicator, and an air-knife coater was used to adjust the coated paper to 4 g / m ² per side. After applying the penetrant aqueous solution on both sides thereof, hot air was blown to dry the paper so that the water content of the paper after drying was 6.0%. Then, the surface was finished by glossing with a super calender to obtain a coated paper for printing having a basis weight of 117.9 g / m ² . The 0.3% penetrant aqueous solution had a penetrating power of 12 seconds by the canvas disk method.

Example 2 A coated paper for printing was obtained in the same manner as in Example 1 except that the amount of the penetrant aqueous solution applied to the coated paper was 7 g / m ² per side.

Example 3 A coated paper for printing was obtained in the same manner as in Example 1 except that the concentration of the penetrant aqueous solution was changed to 0.5%. At this time, the measurement value of the penetrant aqueous solution by the canvas disk method was 3 seconds.

Example 4 A coated paper for printing was obtained in the same manner as in Example 1 except that the aqueous penetrant solution was a 0.2% aqueous solution of a dialkylsulfosuccinate ester salt. At this time, the value measured by the canvas disk method of the penetrant aqueous solution was 38 seconds.

Example 5 In Example 1, 50 parts of heavy calcium carbonate (trade name: FMT-90 / Pharmatic Co., Ltd.) as a pigment,
Kaolin (trade name: UW-90 / Engelhard Co., Ltd.) 47 parts and Satin White (trade name: Sachin White BL / Shiraishi Kogyo Co., Ltd.) 3 parts were used, and cold water soluble starch (trade name: high Coaster PC-11 /
A coated paper for printing was obtained in the same manner as in Example 1 except that 7 parts of Sanwa Starch Industry Co., Ltd.) was not added and the waterproofing agent was not added.

Example 6 A coated paper for printing was obtained in the same manner as in Example 5 except that the penetrant aqueous solution was changed to a 0.2% aqueous solution of dialkylsulfosuccinic acid ester salt. At this time, the value measured by the canvas disk method of the penetrant liquid was 38 seconds.

Example 7 A coated paper for printing was obtained in the same manner as in Example 1 except that the aqueous penetrant solution was applied to the coated paper with a gravure coater.

Comparative Example 1 A coated paper for printing was obtained in the same manner as in Example 1 except that the penetrant aqueous solution was replaced with ordinary tap water.
The value measured by the canvas disk method of water at this time is 100.
It was 0 seconds or more (measurement impossible).

Comparative Example 2 Example 1 was repeated except that the penetrant aqueous solution was changed to a 0.1% aqueous solution of nonylphenol ethoxylate having HLB of 14 and the coating amount per one side was 4 g / m ^2. A coated paper for printing was obtained in the same manner as in. 0.1 at this time
% Penetrant aqueous solution measured by the canvas disk method is 1
It was 00 seconds.

Comparative Example 3 The same as Example 1 except that the penetrant aqueous solution was changed to a 0.1% aqueous solution of an aromatic phosphoric acid ester salt and the coating amount per side was 4 g / m ^2. A coated paper for printing was obtained in the same manner. At this time, the value measured by the canvas disk method of the penetrant aqueous solution was 300 seconds.

Example 8 A coated paper for printing was obtained in the same manner as in Example 1 except that the amount of the penetrant aqueous solution applied per side was 1.0 g / m ² .

Example 9 A coated paper for printing was obtained in the same manner as in Example 1 except that the coating amount of the penetrant aqueous solution on one side was 12 g / m ² .

Regarding the coated paper thus obtained,
The above-described ink inking unevenness was evaluated. Table 1 summarizes the treatment conditions of the penetrant aqueous solution and the evaluation results of ink inking unevenness.
It was shown to.

[0047]

[Table 1]

[0048]

As is clear from the results shown in Table 1, the printing coated paper obtained by the manufacturing method of the present invention is a printing coating which is less likely to cause unevenness of inking of the printing ink and has a good printing finish. It was paper.

Claims (3)

[Claims] 1. A method for producing a coated paper for printing, which comprises: providing a dry coating layer containing a pigment and a water-soluble adhesive comprising at least one of starch or a starch derivative as an adhesive on the base paper, and then finishing. After redistributing the water-soluble adhesive in the coating layer by coating the dry coating layer surface with a penetrating agent aqueous solution having a penetration force value of 50 seconds or less measured by the canvas disk method, A method for producing a coated paper for printing, which comprises calendering. 2. The method for producing coated paper for printing according to claim 1, wherein the penetrant aqueous liquid having an osmotic force value of 30 seconds or less is used as the penetrant aqueous liquid. 3. The coating amount of the penetrant aqueous liquid is 1 per coated layer surface.
It is 10 g / m < ² >, The manufacturing method of the coated paper for printing of Claim 1 or Claim 2.