JPH04327295A - Production of coated paper for printing - Google Patents

Abstract

PURPOSE:To produce high-quality coated paper for printing in excellent continuous workability by using base paper having specific wetting value in calendering treatment by spraying saturated steam. CONSTITUTION:Base paper having -0.30 to 0.20g dynamic wetting value is used, 0.05-5.0% based on total pigment of a crosslinking agent is added to a coating solution composition and a calendering roll is prevented from staining to produce the objective coated paper.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for producing coated paper for printing, and in particular, by studying calendering technology, base paper, and coating composition, it is possible to produce coated paper for printing with high bulk and high quality. It relates to a method of manufacturing with good performance.

0002

2. Description of the Related Art Coated paper for printing is increasing significantly as a printing paper that meets the needs of users in today's world where printed matter is becoming increasingly visual and sophisticated. And especially ink receptivity
There is a demand for coated paper for printing that has even better qualities such as printing smoothness and printing gloss. In order to obtain the excellent quality of these coated papers for printing, there are many technical factors, and calendering technology cannot be ignored as an important technology.

[0003] Calendering technology improves the paper appearance and printing effect by passing the paper through a pressure nip that combines rolls made of materials such as metal, fiber, and resin to smooth the paper surface. Depending on the properties of the roll surface, there are gloss calendars for high-gloss paper and matte calendars for matte paper.

[0004] In general, in order to obtain a highly smooth and glossy surface, it is necessary to increase the nip pressure, which results in a loss of paper thickness and paper stiffness. As methods for solving this problem, methods of calendering using heated high-temperature rolls and methods of calendering by spraying steam are known, but each method has advantages as well as drawbacks.

[0005] The former method using heated high-temperature rolls is effective when paper is passed at low speeds, but at high speeds, the time during the nip is shortened, so heat is transferred to the paper surface in a short time. It becomes difficult to plasticize. The latter method of atomizing steam has been studied in the past, and recently, a method using superheated steam instead of the saturated steam used in the present invention has been proposed in Japanese Patent Application Laid-Open No. 160993/1993.

[0006] However, when the coated paper is plasticized by spraying steam and then subjected to calender treatment, minute portions of the coated paper surface are picked up by the roll, resulting in the phenomenon that the roll surface turns white and cloudy.
So-called roll staining occurs. Even if this phenomenon is not found to be a problem in a small-scale laboratory test, it is a problem in actual continuous operation. In addition, when heated steam is used, roll fouling becomes more severe, which may further deteriorate operability. In addition, when the roll temperature is increased to improve quality, and when calendering is performed by spraying steam, roll stains tend to become particularly noticeable.

[0007] Normally, in the production of coated paper for printing, 1
Since continuous operation is carried out for approximately 0,000 m, actual operation would be impossible if the rolls had to be maintained every several thousand m.

[0008] As described above, the main point of the technology of calendering by spraying saturated steam is to fully demonstrate its effects and to stabilize the operability, but there are insufficient The current situation is that no research has been done on it, and it is not being utilized as an actual manufacturing technology.

[0009]

[Problems to be Solved by the Invention] The present invention provides a technology for performing calender treatment by spraying saturated steam by using a base paper with specific surface properties and a coating composition containing a specific crosslinking agent. An object of the present invention is to provide a method for producing coated printing paper that is bulky, has excellent smoothness, and has high gloss with good operability.

0010

[Means for Solving the Problems] The present invention provides a printing coating in which a coating composition containing a pigment and an adhesive as main components is coated on a base paper, dried, and then calendered by spraying saturated steam onto the paper. In the method for manufacturing a cover paper, the dynamic wettability value of the base paper is -0.30 to
+0.20g of base paper is used, and the coating composition contains 0.05 to 5.0% by weight of a crosslinking agent based on the total pigment. .

[0011]

[Function] The present inventors investigated the operability of a method of calendering by spraying saturated steam, and found that the coating layer sprayed with steam is plasticized by the heat and moisture.
The pressurized nip of the calendar makes it easier to smooth and promotes the orientation of pigments, but at the same time, the adhesive in the coating layer swells and melts, reducing the strength of the coating layer and causing damage to the coating layer. It was found that a small portion of the product continued to adhere to the surface of the calender roll, making continuous operation impossible.

[0012] Therefore, we conducted extensive research focusing on the strength of the coating layer adhesive in a plasticized state and the surface properties of the base paper, and added a crosslinking agent to the coating composition to create a network between the adhesive molecules. It has been found that the object of the present invention can be achieved because a decrease in the strength of the adhesive can be suppressed even in a state where it is plasticized by saturated steam. Then, they discovered that the effect is significant only when the dynamic wettability value of the base paper used is a specific value, and finally completed this invention.

[0013] In the present invention, the "dynamic wetting value" of base paper refers to a 2 cm x 5 cm paper test piece placed in water at a depth of 12 mm in the longitudinal direction.
The test piece is immersed in stationary pure water at a speed of 16 mm/sec, and the force applied to the test piece is measured 2 seconds after the start of immersion, and the buoyant force due to the immersion volume of the test piece is added to this measured value. .

Generally, at the moment when the test piece comes into contact with water, the contact angle θ is 0<θ<90°, so an upward force acts on the test piece and the wetting value shows a negative value. After that, as the wetting of the test piece progresses, the contact angle θ increases, and when θ = 90°, the upward force becomes zero, and as the wetting progresses further, θ > 90°.
°, and a downward force acts on the test piece, causing the wetting value to turn positive.

In the present invention, the dynamic wettability value is measured using "Dynamic Wettability" manufactured by Reska.
Tester WETT-3000" was used.

[0016] In the present invention, the dynamic wettability value 2 seconds after immersion in water is -0.30 to +0.20 g, more preferably -0.2.
A base paper in the range of 5 to +0.10 g is used. Incidentally, if the dynamic wetting value of the base paper is greater than +0.20g, even if the coating liquid specified in the present invention is used, the amount of water in the coating layer will be reduced by the time the coating layer is dried in the drying process. As moisture rapidly penetrates into the base paper, the adhesive and cross-linking agent in the coating layer also move toward the base paper, resulting in a decrease in the amount of adhesive and cross-linking agent on the surface of the coating layer, resulting in a sufficient network. is not formed, resulting in extremely bad roll stains.

On the other hand, if the dynamic wetting value of the base paper is less than -0.30 g, the adhesion between the base paper and the coating layer will be greatly reduced, and even if a sufficient network is formed within the coating layer, Since partial peeling occurs at the interface between the base paper and the coating layer, the desired effects of the present invention cannot be obtained.

The dynamic wetting value of the base paper can be adjusted by adjusting the pulp composition,
Individual papermaking conditions such as beating conditions, type and amount of filler added, paper strength agent, internal sizing agent, paper surface pH, surface sizing agent, surface treatment agent, drying conditions, etc. can be selected as appropriate. Further, the dynamic wetting value of the base paper as used in the present invention has no linear correlation with the values of Cobb water absorption and Steckcht sizing, which have been conventionally used as parameters to indicate the properties of the base paper.

The weight per unit area of the base paper is not particularly limited, and is generally selected from a range of about 30 to 400 g/m 2 as appropriate depending on the purpose.

Next, in the present invention, the amount of the crosslinking agent to be added to the coating composition is 0.05 to 5.0 with respect to the total pigment.
It needs to be in weight%. If the amount of crosslinking agent added is less than 0.05% by weight, the effect of creating a three-dimensional structure of the adhesive molecules will be low, and therefore the effect of preventing roll staining will be insufficient, and if continuous operation is continued, roll stains will occur, making it impossible to operate. It becomes. On the other hand, if the addition rate of the crosslinking agent exceeds 5.0% by weight and is used in large quantities, not only will the effect of increasing the crosslinking agent be extremely small, but the viscosity of the coating liquid will increase and the operability during coating will deteriorate. This is not desirable because it causes

Therefore, the amount of crosslinking agent added is 0.05 to 5.0% by weight, more preferably 0.1 to 3.0% by weight based on the total pigment.
It is desirable to adjust the amount as appropriate within the range of 0% by weight.

The crosslinking agent of the present invention may be the same as the crosslinking agent generally used in the paper manufacturing industry to impart water resistance for applications such as offset printing, labels, and outdoor posters, and is suitable for the latest paper processing. Handbook (edited by Tech Times) P. 46
9 provides an overview. The molecular weight and molecular structure of the crosslinking agent are not particularly limited, but those having two or more aldehyde groups as reactive groups, such as glyoxal, or those having two or more epoxy groups, such as glycols, etc. Diglycidyl ethers, polyglycidyl ethers of polyols, diglycidyl esters of dicarboxylic acids, etc., as well as zirconium compounds such as zirconium acetate, ammonium zirconium carbonate, zirconium sulfate, etc., have a remarkable effect, greatly increasing the roll fouling prevention effect. I was able to improve it.

In the method of the present invention, the calender smoothing effect is further enhanced by adjusting the surface temperature of the calender roll to a range of 50 to 250°C. Furthermore, in the case of an on-machine calender in which the calender is installed immediately after the coater drying device, the method of the present invention is particularly required because roll fouling will reduce overall operability. .

In the method of the present invention, the pulp composition of the base paper includes bleached, unbleached, semi-bleached NKP, LKP, etc. used for high-quality or medium-quality coated printing paper, and newspapers, magazines, information paper, etc. Recycled waste paper pulp obtained by processing printing paper or the like, or high-yield pulp such as SGP, TMP, RGP, CTMP, etc., is used, and the blending ratio is not particularly specified and may be adjusted as appropriate.

[0025] The method of making the base paper is not particularly limited; for example, acid paper making is performed using a fourdrinier machine including a top wire or twin wire, a single layer or multilayer round net machine, a machine using a combination of the two, a Yankee dryer machine, etc. , neutral paper, or alkaline paper may be used, and surface treatment or preliminary coating may be performed using various size presses, bill blade coaters, or the like.

Pigments in the coating composition used in the method of the present invention include, for example, clay, kaolin, calcined kaolin, delaminated kaolin, structured kaolin,
One or more of the usual coated paper pigments such as aluminum hydroxide, heavy calcium carbonate, light calcium carbonate, titanium dioxide, barium sulfate, zinc oxide, satin white, talc, plastic pigments, binder pigments, etc. It is selected and used as appropriate.

Furthermore, examples of adhesives include proteins such as casein, soybean protein, and synthetic proteins; conjugated diene copolymer latex such as styrene-butadiene copolymer;
Acrylic polymer latices such as polymers or copolymers of acrylic esters and/or methacrylic esters, vinyl polymer latexes such as ethylene/vinyl acetate polymers, or various polymer latexes such as those with carboxyl groups, etc. Alkali-soluble, alkali-swellable, or alkali-insoluble polymer latex modified with functional group-containing monomers, various synthetic resin polymers called binder pigments, polyvinyl alcohol, olefin-maleic anhydride resin, melamine resin, etc. One or more types of common adhesives for coated paper, such as synthetic resin adhesives, starches such as oxidized starch, positive starch, esterified starch, and dextrin, and cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose. are selected and used as appropriate.

The adhesive is blended in an amount of 4 to 50 parts by weight, more preferably 10 to 30 parts by weight, based on 100 parts by weight of the pigment. In addition, various auxiliary agents such as an antifoaming agent, a coloring agent, a mold release agent, and a flow modifier are suitably blended into the coating liquid as required. In the present invention, as described above, it is important to add the crosslinking agent in an amount of 0.05 to 5.0% by weight based on the total pigment depending on the situation.

Coating machines used in the method of the present invention include those used in general coated paper production, such as blade coaters, air knife coaters, roll coaters, reverse roll coaters, bar coaters, bill blade coaters, and curtain coaters. The coating liquid is coated on the base paper in one layer or in multiple layers by an on-machine or off-machine coater equipped with a double-sided or single-sided coating device such as a die slot coater, a gravure coater, a Champlex coater, or a size press coater.

[0030] The solid content concentration of the coating liquid at that time is generally 40
〜75% by weight, but considering operability, it is 45〜75% by weight.
A range of 70% by weight is preferred.

[0031] Methods for drying the wet coating layer include conventionally known steam heating, hot air heating, gas heater heating, high frequency heating, electric heater heating, infrared heater heating, laser heating, electron beam heating, etc. Various drying methods can be adopted as appropriate.

In the method of the present invention, the coated paper thus obtained is calendered by spraying saturated steam, but the amount of steam, calender pressure, and number of nips are not particularly limited. It is selected as appropriate depending on the required quality. As the calendar in the present invention, various types of calendars such as a super calendar, a gross calendar, and a soft compact calendar are used in on-machine or off-machine formats. The on-machine calendar referred to herein is not limited to a paper machine, but also includes an on-coater machine calendar built into a coating machine.

[0033]

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

Examples 1 to 3 Kaolin in all pigments (trade name: UW-90, manufactured by EMC)
70 parts, 25 parts of atomized heavy calcium carbonate, Sachin White dispersion (trade name: Sachin White, manufactured by Shiraishi Kogyo Co., Ltd.)
5 parts (solid content) and 0.2% (solid content) of sodium polyacrylate based on the total pigment were dispersed using a Coles disperser to prepare a slurry with a solid content concentration of 66%. In this slurry, 4 parts of oxidized starch (solid content) per 100 parts of total pigment,
12 parts (solid content) of styrene-butadiene copolymer latex and a crosslinking agent were added based on the type and addition rate (% of total pigment) shown in Table 1, and then water was added to form a coating with a solid content concentration of 56%. A liquid was prepared.

This coating liquid was applied to the base paper when the dynamic wetting value was -0.
20g (Example 1), -0.05g (Example 2), +0
．． 10g (Example 3)
g/m2 base paper, 15 g/m2 dry weight per side
Coat both sides with a blade coater so that
It was dried in a hot air dryer at 0°C to obtain a double-sided coated paper with a moisture content of 5.8%.

The thus obtained double-sided coated paper was passed through a calender consisting of a metal roll and an elastic roll, with the surface temperature of the metal roll set to 40°C, and saturated steam was sprayed to smooth the paper. did. The linear pressure at this time is 250Kg/c
m, and the speed was 400 m/min.

Table 1 shows the conditions of Examples 1 to 3, namely, the dynamic wetting value of the base paper, the type and addition rate of the crosslinking agent in the coating liquid, the continuous operability, and the quality evaluation results of the coated paper.

Example 4 The surface temperature of the metal roll of the calender was 110°C and the linear pressure was 1
50Kg/cm, except that the crosslinking agent shown in Table 1 was used.
The same method as in Example 1 was used. Table 1 shows the conditions and results at this time.

Example 5 A 1-nip calender was installed in the coater immediately after the dryer, and the surface temperature of the metal roll was kept at 90°C.
It was carried out in the same manner as in Example 1, except that the linear pressure was 200 kg/cm and the type and addition rate of the crosslinking agent were as shown in Table 1.
Table 1 shows each condition and result.

Comparative Example 1 A double-sided coated paper was obtained in the same manner as in Example 2, except that a base paper with a dynamic wetting value of +0.30 g was used. Table 1 shows the continuous operation performance and the quality evaluation results of the coated paper.

Comparative Example 2 A double-sided coated paper was obtained in the same manner as in Example 2, except that a base paper with a dynamic wetting value of -0.35 g was used. The results are shown in Table 1.

Comparative Examples 3 to 4 Example 1 except that the type and addition rate of the crosslinking agent were as shown in Table 1.
The results are shown in Table 1.

[Measurement method and evaluation method] Glossiness: Measured according to JIS-P8142. The higher the number, the better the gloss. Continuous operation: ○: Continuous operation for 10 hours or more is possible. ×: Latex, pigment adhesive, etc. peeled off from the coating layer and adhered to the calender roll surface, making continuous operation for 10 hours or more impossible.

[0044]

[Table 1]

[0045]

[Effects of the Invention] As is clear from the results of the examples shown in Table 1, the coated paper for printing obtained by the method of the present invention has excellent continuous operability and coated paper gloss. Met.

Claims (6)

[Claims] [Claim 1] A method for producing coated paper for printing, which comprises coating a base paper with a coating composition containing a pigment and an adhesive as main components, drying the base paper, and then calendering the paper by spraying the paper with saturated steam. A base paper with a dynamic wetting value of -0.30 to +0.20 g is used, and the coating composition contains a crosslinking agent of 0.05 g based on the total pigment.
A method for producing coated paper for printing, characterized in that the content is 5.0% by weight. [Claim 2] The surface temperature of the calender roll is 50 to 25.
The method for producing coated paper for printing according to claim 1, wherein the temperature is 0°C. 3. The method for producing coated paper for printing according to claim 1, wherein the reactive group of the crosslinking agent is an aldehyde group. 4. The method for producing coated paper for printing according to claim 1, wherein the reactive group of the crosslinking agent is an epoxy group. 5. The method for producing coated paper for printing according to claim 1, wherein the crosslinking agent is a zirconium compound. 6. The method for producing coated paper for printing according to claim 1, wherein the calendar is a calendar installed immediately after the coater drying device.