JPH09170195A - Production of coated paper for offset printing and coated paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for producing a coated paper for offset printing using a film-transfer process in high quality and improving the operational problem inherent to a process for the application of a coating liquid at a high speed and provide a coated paper produced by this process. SOLUTION: This process for producing a coated paper for offset printing comprises the application of a coating liquid containing a pigment and an adhesive to a base paper. Concretely, a coating liquid having a viscosity of 35-60 cps at high shearing rate (100<6> sec<-1> ) and containing 100 pts.wt. of a pigment, 70-100 pts.wt. of ground limestone and 1-10 pts.wt. of a copolymer latex having a gel content of 70-90wt.% is applied to a base paper by a film-transfer type coating machine.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated paper for offset printing, which is excellent in high-speed operability and has good quality when a base paper is coated with a coating liquid containing a pigment and an adhesive by a film transfer method. And a coated paper thereof.

[0002]

2. Description of the Related Art In recent years, demand for printing paper has tended to gradually increase. In particular, it is characterized by growing demand in the commercial printing field for advertisements and advertisements such as flyers, catalogs, pamphlets, and direct mail. Although these commercial prints have low commercial value themselves, it is important that the purpose be achieved as an advertising medium, so low-cost, good-quality prints are required, and paper users are becoming more cost-conscious. And the use of paper is also getting lower and lighter.

In order to meet such a strong demand, a paper manufacturer is promoting widening and speeding up of a coating apparatus in order to produce a product more efficiently and reduce costs, while maintaining high quality. Improving productivity is an important technical issue.

[0004] As a production method of coated paper, an off-machine coating method which is usually used in which paper making and coating are performed in separate steps, and an on-machine coating method in which paper making and coating are simultaneously performed by one machine In comparison with the off-machine coating method, the on-machine coating method has a feature that the manufacturing cost of the product can be suppressed and a product having a price competitiveness can be manufactured. In particular, in the case of multi-layer coated paper, an undercoat coating solution containing an inexpensive pigment is applied on-machine to the base paper, and then an overcoat coating solution is applied to produce a cheaper product than a single-layer coated paper. You can
In addition, in terms of quality, since the coverage of the base paper is improved by the undercoat coating, and the surface condition and print quality are also improved, not only conventional high-grade grades (art paper) but also coatings with a smaller coating amount have been used in recent years. In the manufacture of paper, products using multi-layer coating are increasing. For this reason, there is a demand for an even higher speed of a film transfer coating apparatus which is an on-machine coating method.

However, when a normal coating liquid is applied to the base paper by using a gate roll coater, a blade or a rod metalling size press coater used in the on-machine coating method, the maximum operating speed has so far been reached. About 1
100 m / min is the limit for speeding up. One of the causes of hindering this speed increase is a phenomenon called mist in the case of a blade or rod metering size press coater, in which the coating liquid is atomized and scattered at the exit of the application roll nip. Mist is 1 depending on operating conditions
Although it starts to occur even at a speed lower than 100 m / min, the higher the condition becomes, the more it worsens the working environment, and at the same time, the peripheral rolls are soiled and, if further dried and solidified, they fall onto the paper surface, resulting in product defects. Become. Also, in the case of a gate roll coater, a similar problem of mist generation occurs, and at the same time, if the mechanical stability of the coating liquid is poor, it may occur between the inner roll and the outer roll or between the inner roll and the applicator roll. A shearing force applied between rolls having different roll diameters and peripheral speeds causes a phenomenon called gum-up in which the coating liquid coagulates and adheres to the roll surface, which lowers operability. These problems can be reduced by decreasing the concentration of the coating liquid, but in addition to increasing the drying load, the amount of the coating liquid soaking into the base paper increases and the coverage of the base paper is poor, resulting in uneven gloss after coating. However, there is a problem in that the surface quality and printability deteriorate.

JP-A-63-99395 discloses that the amount of styrene / butadiene, the glass transition point, the particle size, and the amount of a latex are specified to improve gum up in gate roll coating and contamination of an applicator roll. It is carried out. However, it describes that the effect is at a coating speed of 600 m / min or more, but does not describe the actual high-speed condition. Further, in Japanese Patent Laid-Open No. 7-189188,
Transfer roll coating liquid with a concentration of 58% or more, B
By adjusting the mold viscosity below 1500 cps,
It says that good coating can be done. However, there is no problem when these coating liquids are applied at a low speed, but there is a problem that mist generation and gum up become more remarkable when applied at a high speed, especially under high-speed operating conditions of 1100 m / min or more. It was

Further, regarding the undercoat pigment coating composition in the production of rotary offset printing coated paper in the production of double coated paper, JP-A-64-33297 discloses a heavy calcium carbonate in an amount of 70 to 100% by weight. %, 4 to 13 parts of starch derivative as an adhesive and 0 to 5 parts by weight of synthetic polymer (latex) are disclosed. It is said that the undercoat pigment coating of this composition improves the blister resistance, surface strength, and glossiness of white paper during rotary offset printing, but nothing is said about the operability peculiar to the film transfer type coating device. Not not.

[0008]

In view of the above situation, an object of the present invention is to use a film transfer system and apply a coating liquid even under high speed conditions, particularly at a high speed of 1100 m / min or more. Another object of the present invention is to provide a method for producing coated paper for offset printing and a coated paper which are excellent in operability and which are excellent in quality in the production process.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies on the above-mentioned problems, and as a result, have found that a base paper is coated with a coating liquid containing a pigment and an adhesive to form an offset printing coated paper. In the production method, 70 to 100 wt% of heavy calcium carbonate and 1 to 10 of copolymer latex having a gel content of 70 to 90 wt% as an adhesive with respect to 100 parts of pigment.
By coating the base paper with a coating liquid containing a part by weight and having a viscosity at a high shear rate (10 ⁶ sec ^-1 ) adjusted to 35 to 60 cps, a high speed condition, especially At 1100 m / min or more, the problematic mist and gum up could be improved. Further, this coated paper is used as an undercoat coated paper, and by further applying an overcoat coating liquid for adjusting to a desired surface quality, an offset printing coated paper of good quality can be obtained. did it.

The heavy calcium carbonate used in the present invention is
70 to 100% by weight is required for 100 parts of the pigment, and when the heavy calcium carbonate is lower than 70% by weight, the viscosity of the coating liquid at a high shear rate becomes too high and a mist is generated. Admitted that.

The copolymer latex used in the present invention is
The gel content is 70 to 90% by weight, and the compounding amount is 1 to 10
Parts by weight are used. When a base paper is coated with a coating liquid containing a latex with a gel content of less than 70%, the mechanical stability of the latex is inferior and the roll diameter and peripheral speed differ from each other due to the shearing force applied between the rolls to gum up the roll surface. Occurred, which deteriorated the operability, and was more remarkable especially at a high speed of 1100 m / min or more. Also, a latex having a gel content of more than 90% generally does not function as an adhesive. When the amount is less than 1 part by weight, the wet strength and dry strength are low. On the other hand, when the amount is more than 10 parts by weight, the surface property is deteriorated due to the influence of the shrinkage of the latex during drying, and the mechanical stability of the coating liquid is further deteriorated to cause gum up.

Further, the inventors of the present invention have conducted extensive studies in order to solve the problem of mist generation, which appears more remarkably under high-speed operating conditions of 1100 m / min or more, and as a result, the B-type viscosity which is usually used in operating control is obtained. It was not able to find a particular relationship in viscosity by meter, high shear rate ⁽¹⁰⁶ sec
^-1 ) Correlation was found with the viscosity below. Viscosity of coating liquid under high shear rate (10 ⁶ sec ^-1 ) is 60 cp
It was confirmed that the occurrence of mist can be significantly reduced by setting the value to s or less. On the other hand, if the viscosity is lower than 35 cps, the coating liquid excessively penetrates into the base paper, resulting in poor coverage after coating, resulting in surface state and coating unevenness. In the present invention, the viscosity at a high shear rate (10 ⁶ sec ^-1 ) means
It means a value measured by a high pressure capillary viscometer (manufactured by Anton Paar).

As an adhesive other than the copolymer latex used in the present invention, a water-soluble adhesive, particularly a starch derivative, may be used.
It is desirable to add 15 to 23 parts by weight, preferably 30 to 30 parts by weight. As a result, it is possible to impart rigidity to the paper and maintain the appropriate viscosity and water retention of the coating liquid. 5
When the amount is less than the weight part, the viscosity of the coating liquid is too low, and the coating amount in the film transfer roll system is small, the target coating amount is difficult to be obtained, and the surface strength tends to be poor. When the amount is more than 30 parts by weight, the viscosity of the coating liquid at a high shear rate is too high and mist is likely to occur. At low concentration, coating can be performed without mist, but the coating property tends to deteriorate. In particular, when this coating liquid is applied as an undercoat and the top coating liquid is applied as an overcoat, the amount is preferably 15 to 23 parts by weight in terms of surface strength, surface state and the like.

In the present invention, the film transfer type coating device may be a gate roll coater, a blade or a rod metalling size press coater. When using a rod metering size press, it is desirable to use a rod with a smooth surface in order to avoid the occurrence of streaks during operation. Further, by setting the diameter of the rod to 30 to 50 mm, more preferable operability and quality can be obtained. A rod having a diameter of less than 30 mm tends to deteriorate the film forming ability and deteriorates the surface state, and a rod having a diameter of more than 50 mm does not change the effect, so that there is no need to particularly increase the diameter.

Further, in the present invention, in a method for producing a coated paper for offset printing in which a coating liquid is applied at least twice to a base paper, 70 to 100% by weight of heavy calcium carbonate is adhered to 100 parts of pigment. Gel content 70 to 9 as an agent
It contains 1 to 10 parts by weight of 0% by weight of copolymer latex and has a viscosity of 3 at a high shear rate (10 ⁶ sec ^-1 ).
The coating solution prepared at 5 to 60 cps is applied as an undercoat on the surface of the base paper by a film transfer type coating apparatus, and then a separately prepared topcoat coating solution is applied as an overcoat to form a conventional multilayer coating. It is possible to obtain a coated paper for offset printing, which has higher productivity, lower cost, and more excellent surface properties such as smoothness or white paper glossiness than those coated with a single layer, as compared with a work or the like.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Pigments other than heavy calcium carbonate used in the present invention include light calcium carbonate, kaolin, clay, satin white, aluminum hydroxide, talc, titanium oxide, silica, plastic pigment and the like.

The type of copolymer latex used in the present invention is not particularly limited, but various copolymers such as styrene / butadiene type, styrene / acrylic type, vinyl acetate / acrylic type and butadiene / methylmethacrylic type copolymers. A latex or a modified product of a chemical reaction of these various copolymer latexes is easy to use.

In addition to latex, in order to maintain the water retention of the coating layer and increase the internal bond strength of the base paper, oxidized starch, esterified starch, enzyme-modified starch, etherified starch, and those obtained by flash drying are used. It is preferable to use one or more kinds of water-soluble polymer adhesives such as casein and polyvinyl alcohol in addition to the starch derivative such as cold water-soluble starch.

The coating liquid of the present invention may contain various auxiliaries such as a dispersant, a thickener, a water retention agent, a defoaming agent, and a water resistant agent, which are mixed with a usual pigment for coated paper. Further, the solid content concentration of the coating liquid may be in a range such that the viscosity at a high shear rate becomes 35 to 60 cps, and preferably 40 to 55% by weight. When it is lower than 40% by weight, the viscosity under high shear rate tends to be low, and when it is higher than 55% by weight,
Since the viscosity at high shear rates becomes high, it is difficult to maintain an appropriate viscosity. The base paper is preferably a base paper having a basis weight of 30 to 200 g / m ² used for general coated paper for printing, and high-quality paper or medium-quality paper is selected and used according to the purpose.

The coating amount on the surface of the base paper is preferably in the range of ² to 10 g / m ² in terms of solid content on one side of the base paper. When the coating amount is less than 2 g / m ^{2, the} concentration of the coating liquid has to be greatly reduced due to limitations in the apparatus, and as a result, the coating properties of the base paper and the surface state are liable to be reduced. 10g
Conversely, if the amount of coating is larger than / m ² , it is necessary to increase the concentration of the coating liquid. In this case, it becomes difficult to control the coating amount on the equipment, and at the same time, the surface roughness of the surface such as orange peel and rolls Patterns tend to develop on the paper surface.

After the base paper is coated with the coating liquid and dried, gloss finishing such as steel calendering, super calendering and soft calendering may be performed.

In the present invention, when the coating is applied at least twice, the above-mentioned one is used as the material contained in the undercoat coating liquid on the surface of the base paper.

The pigment, adhesive composition, blending amount, coating amount and the like of the top coating liquid are not particularly limited, and commonly used pigments and adhesives may be used. The concentration of the coating liquid is preferably 60 to 68%, and the coating amount of the top coating liquid is usually preferably 6 to 14 g / m ² in terms of solid content per one surface. Further, the number of times of undercoating and topcoating may be one or more.

The coated paper that has been dried after the application of the overcoat coating liquid is preferably subjected to gloss finishing by a super calender or a soft calender as a final finishing step as usual.

[0025]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited by these examples. In the examples, parts and% indicate parts by weight and% by weight, respectively.

EXAMPLE 1 To 80 parts of calcium carbonate having an average particle diameter of 0.7 μm and 20 parts of kaolin having an average particle size of 1.5 μm, 0.3 part of a sodium polyacrylate-based dispersant was added, and Cowles was added. It was dispersed in water using a disperser, and 5 parts of a styrene / butadiene copolymer latex having a gel content of 80% and 25 parts of oxidized starch were mixed as an adhesive to prepare a coating liquid having a solid content of 50%. High shear rate (10 ⁶
The viscosity under second ^-1 ) was 54 cps.

A coating solution containing a bleached kraft pulp bleached from hardwood having a basis weight of 54 g / m ² was coated with a coating liquid at a coating speed of 1200 m / min using a high speed gate roll coater as a coating device.
After applying ² g / m ² of solid content on one side to both sides and drying, soft calender treatment (conditions: 50 ° C., 100 kg
/ Cm).

[Example 2] A coated paper was produced in the same manner as in Example 1 except that a styrene-butadiene copolymer latex having a gel content of 87% was used in preparing the coating liquid.

[Example 3] When a coating liquid was prepared, 7 parts of styrene-butadiene copolymer latex having a gel content of 80% was used, and the solid concentration of the coating liquid was 46%. A coated paper was produced as in Example 1.

[Embodiment 4] A coating apparatus having a diameter of 35 mm
A coated paper was produced in the same manner as in Example 1 except that a rod metalling size press coater having a rod with a smooth surface was used and the coating liquid was applied at a coating speed of 1400 m / min.

[Comparative Example 1] A coated paper was produced in the same manner as in Example 1 except that a styrene-butadiene copolymer latex having a gel content of 60% was used in preparing the coating liquid.

[Comparative Example 2] A coated paper was produced in the same manner as in Example 1 except that a styrene-butadiene copolymer latex having a gel content of 40% was used in preparing the coating liquid.

[Comparative Example 3] When preparing a coating liquid, 60 parts of heavy calcium carbonate having an average particle diameter of 0.7 μm and 1.5 parts of
A coated paper was produced in the same manner as in Example 1 except that 40 parts of μm kaolin was used.

[Comparative Example 4] A coated paper was produced in the same manner as in Example 1 except that 11 parts of styrene / butadiene copolymer latex was blended when the coating liquid was prepared.

The above results are shown in Table 1.

[0036]

[Table 1] As is clear from Table 1, in Examples 1 to 4, there is no gum-up and mist generation, high-speed operability is good, and in terms of quality, coated paper that can be used as leaflets, lower-grade printing paper, and under-coated paper. I was able to get In Comparative Examples 1 to 4, high-speed operability was poor.

Example 5 90 parts of ground calcium carbonate having an average particle size of 0.7 μm and kaolin 10 having an average particle size of 0.55 μm
0.3 parts of sodium polyacrylate-based dispersant was added to each part and dispersed in water using a Cowles disperser, and 17 parts of oxidized starch as an adhesive and a styrene-butadiene copolymer having a gel content of 80% were used. 5 parts of the polymerized latex was blended to prepare an undercoat coating liquid having a solid content concentration of 50%. The viscosity under high shear rate (10 ⁶ sec ^-1 ) was 51 cps.

Further, 0.3 parts of a sodium polyacrylate type dispersant was added to 60 parts of heavy calcium carbonate having an average particle diameter of 0.5 μm and 40 parts of kaolin, and the resulting mixture was added to water using a Cowles disperser. After dispersion, 5 parts of oxidized starch and 10 parts of styrene / butadiene copolymer latex were mixed as an adhesive to prepare a top coating liquid having a solid content of 65%.

Hardwood bleached kraft pulp alone with a basis weight of 54 g / m ² was coated with an undercoat coating liquid at a coating speed of 1200 m / min on both sides with a solid content of 5 g / m ² on both sides using a high speed gate roll coater. After coating and drying, a soft calendar treatment (conditions: 50 ° C., 100 kg / cm) was performed.

Further, the top coating liquid was applied to both surfaces at a coating speed of 1200 m / min and a solid content of 8 g / m ² per one surface using a high speed blade coater. Furthermore, gloss finishing was performed using a 12-step super calendar. [Example 6] When preparing a base coating liquid, the gel content was 8
A coated paper was produced in the same manner as in Example 5 except that 7% styrene / butadiene copolymer latex was used.

[Example 7] In preparing an undercoating liquid,
A coated paper was produced in the same manner as in Example 5 except that 7 parts of a styrene / butadiene copolymer latex having a gel content of 80% was used and the solid concentration of the coating liquid was 46%.

[Embodiment 8] A coating apparatus having a diameter of 35 mm
A coated paper was produced in the same manner as in Example 5, except that a rod metalling size press coater having a rod with a smooth surface was used and the undercoat coating liquid was applied at a coating speed of 1400 m / min.

[Example 9] In preparing an undercoating liquid,
100 grams of ground calcium carbonate with an average particle size of 0.7 μm
A coated paper was produced in the same manner as in Example 5 except that the parts were used.

[Comparative Example 5] In preparing an undercoat coating liquid,
A coated paper was produced in the same manner as in Example 5 except that a styrene / butadiene copolymer latex having a gel content of 50% was used.

[Comparative Example 6] In preparing an undercoat coating liquid,
90 parts of heavy calcium carbonate having an average particle diameter of 1.0 μm,
10 parts of 0.55 μm kaolin and 8.5 parts of phosphoric esterified starch and 2.5 parts of styrene-butadiene copolymer latex having a gel content of 28% were blended to make the solid concentration of the coating liquid 64%. A coated paper was produced in the same manner as in Example 5 except for the above.

[Comparative Example 7] In preparing an undercoat coating liquid,
A coated paper was produced in the same manner as in Example 5 except that 17 parts of oxidized starch and 0.5 part of a styrene-butadiene copolymer latex having a gel content of 80% were used.

[Comparative Example 8] In preparing an undercoat coating liquid,
A coated paper was produced in the same manner as in Example 5 except that 17 parts of oxidized starch and 11 parts of styrene / butadiene copolymer latex having a gel content of 80% were used.

[Comparative Example 9] In preparing an undercoat coating liquid,
60 g of ground calcium carbonate with an average particle size of 0.7 μm
Parts, except that 40 parts of 0.55 μm kaolin was used,
A coated paper was produced in the same manner as in Example 5.

The above results are shown in Table 2.

[0050]

[Table 2] As is clear from Table 2, in Examples 5 to 9, the coated papers were excellent in high-speed operability and could be used as general and advanced printing papers in terms of quality. On the other hand, in Comparative Examples 5 to 9, there were some inferior in high-speed operability and inferior in quality.

Quality evaluation method> (1) Average particle size of heavy calcium carbonate Seishin Enterprise Optical transmission type particle size distribution measuring device SHC5000
Was measured as the average particle size at the 50% point of the cumulative weight distribution.

(2) Latex gel content About 0.3 g of latex was spread thinly on a slide glass,
It is dried in a dryer at 50 ° C. until it becomes a film. The latex film is immersed in about 50 ml of toluene for a whole day and night, filtered through a glass filter, and then the filtrate is dried by a drier at 105 ° C. to measure the weight of toluene-soluble matter. The gel content was calculated from the weight of the toluene-soluble matter obtained here by the following formula.

Gel content (%) = (dry film weight−toluene soluble content weight) × 100 / (dry film weight) (3) High-speed fluidity evaluation High-speed fluidity was evaluated by the following capillary viscosity value. The undercoat coating liquid is kept warm at 45 ° C., using a high pressure capillary viscometer HVA6 type manufactured by Anton Paar Co., diameter 0.4 mm, pipe length 1
Viscosity value measured under conditions of a shear rate of 1 × 10 ⁶ sec ⁻¹ using a 0 mm capillary tube.

(4) Glossiness of blank paper: Measured at an angle of 75 degrees in accordance with JIS P-8142.

(5) Gloss after printing Using an RI-II type printing tester, 0.35 cc of ink for Sakata Inks offset printing (trade name: Diatone GSL Red) was printed, and after leaving it for one day and night, it was glossed at 75 degrees. The degree was measured.

(6) Smoothness Measured with a Japan Tappi No5 Oken type smoothness tester.

(7) Printing surface strength Using an RI-II type printing machine (manufactured by Akira Seisakusho) and a TV-24 manufactured by Toyo Ink, printing was performed at a rotation speed of 40 rpm and an ink amount of 0.35 cc-constant, and the printing surface was printed. The degree of picking was evaluated relative to each other visually.

⊚ = No occurrence, ◯ = Almost no occurrence, Δ = Occurrence, × = Significant occurrence (8) Blank paper surface unevenness of white paper glossiness was visually evaluated relative to each other.

⊚ = No unevenness, ○ = Almost unevenness △ = Unevenness, × = Significant unevenness (9) Mist generation evaluation Visually judge the mist generation state when coated by the film transfer method. did.

⊚ = No occurrence, ◯ = Almost no occurrence, Δ = Occurrence, × = Significant occurrence (10) Gum-up occurrence evaluation Gum-up occurrence status when continuously coated for a long time by the film transfer method. Was visually determined.

◎ = Gum-up does not occur even after continuous operation for 24 hours or more ○ = Gum-up occurs during continuous operation for 24 hours △ = Gum-up occurs during continuous operation for 8 hours × = Occurrence of gum up is observed in 4 hours of continuous operation.

[0062]

According to the present invention, a film transfer method is used,
Improves operability, which is a problem in the manufacturing process of applying the coating liquid under high-speed conditions, especially at a high speed of 1100 m / min or more, and is excellent in the surface condition (surface coverage, uneven gloss) and printing surface strength of the product. It is possible to obtain a coated paper for offset printing.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Hideki Fujiwara 5-21-1, Oji, Kita-ku, Tokyo Inside Central Research Institute, Nippon Paper Industries Co., Ltd.

Claims (7)

[Claims] 1. A method for producing a coated paper for offset printing, which comprises coating a base paper with a coating liquid containing a pigment and an adhesive, and adding 100 to 70 parts of pigment to 70 parts of heavy calcium carbonate.
100% by weight, gel content 70-90% by weight as an adhesive
1 to 10 parts by weight of the copolymer latex, which has a viscosity of 35 to 60 at a high shear rate (10 ⁶ sec ^-1 ).
A method for producing coated paper for offset printing, which comprises coating a base paper with a coating liquid prepared to have a cps by a film transfer type coating device. 2. The method for producing coated paper for offset printing according to claim 1, wherein the coating solution contains 4 to 8 parts by weight of a copolymer latex having a gel content of 70 to 90% by weight. 3. A starch derivative is further added as an adhesive.
The method for producing a coated paper for offset printing according to claim 1 or 2, wherein the coating liquid is contained in an amount of -30 parts by weight. 4. The method for producing coated paper for offset printing according to claim 1, wherein the coating speed is 1100 m / min or more. 5. The offset according to claim 1, wherein the film transfer type coating device is a gate roll coater or a rod metalling size press coater having a rod with a smooth surface. Method for producing coated paper for printing. 6. A coating for offset printing, which comprises applying a separately prepared topcoat coating liquid onto the coated paper produced by the production method according to any one of claims 1 to 5. Paper manufacturing method. 7. A coated paper for offset printing manufactured by the manufacturing method according to claim 1.