JP3306859B2 - Method for producing coated paper for offset printing and coated paper - Google Patents

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 good quality when a coating liquid containing a pigment and an adhesive is coated on a base paper 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 respond to such a vigorous demand, paper manufacturers have been increasing the width and speed of coating apparatuses in order to produce products more efficiently and reduce costs, while maintaining high quality. Improving productivity is an important technical issue.

[0004] As a method of producing coated paper, an off-machine coating method that is usually used in which papermaking and coating are performed in separate steps, and an on-machine coating method in which papermaking and coating are performed simultaneously by one machine. The on-machine coating method is characterized in that the production cost of the product can be reduced as compared with the off-machine coating method, and a product with a price competitiveness can be manufactured. In the case of multi-layer coated paper in particular, the base paper is coated with an undercoat coating liquid containing an inexpensive pigment on-machine and then coated with a top coating liquid to produce a product that is cheaper than single-layer coated paper. Can,
In addition, in terms of quality, the coating of base paper is improved by the undercoating, and the surface condition and printing quality are also improved. Also in the production of paper, products with 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 coated on a base paper using a gate roll coater, a blade or a rod metaling size press coater used in an on-machine coating method, the maximum operating speed up to the present has been reached. About 1
100 m / min is the limit of speeding up. One of the reasons that hinders the speed-up is a phenomenon called mist, in which a coating liquid becomes mist and scatters at the exit of an application roll nip in the case of a blade or rod metering size press coater. Mist is 1 depending on operating conditions.
It starts to occur even at a speed lower than 100 m / min, but the degree increases as the speed becomes higher, causing the working environment to deteriorate. At the same time, when the peripheral rolls are soiled and further dried and solidified, they fall onto the paper surface, causing product defects. Become. Also, in the case of a gate roll coater, a similar problem of mist generation occurs, and when the mechanical stability of the coating liquid is inferior, as between the inner roll and the outer roll or between the inner roll and the applicator roll. Due to the shearing force applied between the rolls having different roll diameters and peripheral speeds, a phenomenon called gum-up in which the coating liquid solidifies and adheres to the roll surface occurs, thereby reducing operability. These problems can be reduced by lowering the concentration of the coating liquid.However, the drying load is increased, and the coating liquid penetrates more into the base paper, and the base paper coatability is poor. However, there is a problem that the surface properties and printability deteriorate.

Japanese Patent Application Laid-Open No. 63-99395 discloses that the amount of styrene / butadiene, the glass transition point, the particle size, and the amount of the latex are regulated to improve the gum up in the gate roll coating and the contamination of the 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. Also, in JP-A-7-189188,
When the transfer roll coating solution is used at a concentration of 58% or more,
By adjusting the mold viscosity to 1500 cps or less,
It says that good coating is possible. However, when these coating liquids are coated at a low speed, there is no problem. However, when the coating liquid is coated at a high speed, there is a problem that mist generation and gum-up become more conspicuous under high-speed operation conditions of 1100 m / min or more. Was.

In the production of double coated paper, the undercoat pigment coating composition in the production of coated paper for rotary offset printing is disclosed in JP-A-64-33297. %, A composition containing 4 to 13 parts of a starch derivative as an adhesive and 0 to 5 parts by weight of a synthetic polymer (latex) is disclosed. It is said that the undercoat pigment coating of this composition improves blister resistance and surface strength at the time of rotary offset printing, glossiness of blank paper, etc.However, nothing is described about the operability specific to a film transfer type coating apparatus. Not.

[0008]

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

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on the above problems, and as a result, have found that a base paper is coated with a coating liquid containing a pigment and an adhesive. In the manufacturing method, 70 to 100% by weight of heavy calcium carbonate and 100 to 90% by weight of a copolymer latex having a gel content of 70 to 90% by weight as an adhesive were used based on 100 parts of the pigment.
By coating a base paper with a coating liquid containing a weight part and having a viscosity of 35 to 60 cps at a high shear rate (10 ⁶ sec ^-1 ) by a film transfer type coating apparatus, high-speed conditions, particularly At 1100 m / min or more, mist and gum up, which are problems, could be improved. Further, by using this coated paper as an undercoated paper and further applying an overcoating liquid for adjusting to a desired surface quality, a coated paper for offset printing having good quality can be obtained. did it.

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

The copolymer latex used in the present invention comprises:
The gel content is 70-90% by weight, and the compounding amount is 1-10.
Use parts by weight. When a base paper is coated with a coating liquid containing a latex having a gel content of less than 70%, the mechanical stability of the latex is inferior, so that the roll force and the peripheral speed differ from each other due to the shearing force applied between the rolls, resulting in gum up on the roll surface. Occurred, which reduced the operability, and appeared more remarkably especially at a high speed of 1100 m / min or more. Latexes having a gel content higher than 90% generally do not function as adhesives. When the amount is less than 1 part by weight, the wet strength and the dry strength are low. On the other hand, when the amount is more than 10 parts by weight, the surface properties are inferior due to the influence of latex shrinkage during drying, the mechanical stability of the coating liquid is further inferior, and gum up occurs.

Further, the inventors of the present invention have conducted intensive studies to solve the problem of mist generation, which appears more remarkably under a high-speed operation condition of 1100 m / min or more. Although no specific relationship could be found with the measured viscosity, the high shear rate (10 ⁶ seconds
^-1 ) A correlation was found with the viscosity below. The viscosity of the coating liquid at a high shear rate (10 ⁶ sec ^-1 ) is 60 cp.
It was recognized that the generation of mist can be significantly reduced by setting it to s or less. On the other hand, if the viscosity is lower than 35 cps, the coating liquid excessively soaks into the base paper, so that the coatability after coating is poor and the surface state and coating unevenness occur. In the present invention, the viscosity under a high shear rate (10 ⁶ sec ^-1 ) means
It means a value measured by a high-pressure capillary viscometer (manufactured by Anton Pearl).

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 30 to 30 parts by weight, more preferably 15 to 23 parts by weight. This makes it possible to impart rigidity to the paper and maintain appropriate viscosity and water retention of the coating liquid. 5
When the amount is less than part by weight, the viscosity of the coating liquid is too low, and the coating amount is reduced in the film transfer roll system, so that the target coating amount is hardly obtained, and the surface strength tends to be inferior. 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 easily generated. At a low concentration, coating can be performed without mist, but the coating property tends to be reduced. In particular, when this coating liquid is applied undercoating, and further overcoated with an overcoating liquid, it is preferably 15 to 23 parts by weight in terms of surface strength, surface condition and the like.

In the present invention, the film transfer type coating apparatus can use a gate roll coater, a blade or a rod metering size press coater. When a rod metering size press is used, it is desirable to use a rod with a smooth surface in order to avoid streak generation during operation. Further, by setting the diameter of the rod to 30 to 50 mm, more preferable operability and quality can be obtained. With a rod having a diameter of less than 30 mm, the ability to form a film tends to be reduced and the surface condition tends to be inferior.

Further, in the present invention, in a method for producing a coated paper for offset printing wherein a base paper is coated with a coating liquid at least twice, 70 to 100% by weight of heavy calcium carbonate is added to 100 parts of a pigment. Gel content 70-9 as agent
It contains 1 to 10 parts by weight of a copolymer latex of 0% by weight and has a viscosity of 3 at a high shear rate (10 ⁶ sec ^-1 ).
A conventional multi-layer coating is performed by applying a coating liquid prepared at 5 to 60 cps on a base paper surface with a film transfer type coating apparatus, and further applying a separately prepared top coating liquid thereon. It is possible to obtain coated paper for offset printing which is higher in productivity, lower in cost, and more excellent in surface properties such as smoothness or glossiness of white paper than coated in a single layer, compared with a single layer.

[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, styrene / acryl, vinyl acetate / acryl, butadiene / methyl methacryl, etc. Latex or a modified product of a chemical reaction of these various copolymer latexes can be easily used.

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

In the coating liquid of the present invention, various auxiliaries, such as a dispersant, a thickener, a water retention agent, a defoaming agent, and a water-proofing agent, which are blended in a general pigment for coated paper may be used. Further, the solid content concentration of the coating liquid may be in a range where the viscosity under a high shear rate is 35 to 60 cps, and preferably 40 to 55% by weight. If it is lower than 40% by weight, the viscosity under a high shear rate tends to be low, and if it is higher than 55% by weight,
Since the viscosity under a high shear rate increases, it is difficult to maintain an appropriate viscosity. As the base paper, base paper having a basis weight of 30 to 200 g / m ² used for general printing coated paper is preferable, and high quality paper and medium quality paper are selected and used according to the purpose.

The amount of coating on the base paper surface is preferably in the range of ² to 10 g / m ² in terms of solid content per 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
/ M ² , it is necessary to increase the concentration of the coating liquid. In this case, it is difficult to control the coating amount on the apparatus, and at the same time, it becomes difficult to control the surface roughness or roll of orange peel or the like. Patterns tend to occur on the paper surface.

The base paper may be coated with a coating liquid, dried and then subjected to a gloss finish such as a steel calender, a super calender, or a soft calender treatment.

Next, in the present invention, when the coating is performed at least twice, the above-mentioned ones contained in the undercoating coating liquid on the base paper surface are used.

The pigment, adhesive composition, blending amount, coating amount and the like are not particularly limited with respect to the overcoating coating solution, and generally used pigments and adhesives may be used. The coating liquid concentration is preferably from 60 to 68%, and the coating amount of the top coating liquid is usually preferably from 6 to 14 g / m ^{2 in} solid content per one surface. The number of times of undercoating and overcoating may be one or more.

It is preferable that the coated paper which has been dried after being coated with the top coating liquid is subjected to glossing such as 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 heavy calcium carbonate having an average particle diameter of 0.7 μm and 20 parts of kaolin of 1.5 μm, 0.3 part of a sodium polyacrylate dispersant was added. The mixture was dispersed in water using a dispersing machine, and 5 parts of a styrene / butadiene copolymer latex having a gel content of 80% as an adhesive and 25 parts of oxidized starch were blended to prepare a coating solution having a solid content of 50%. High shear rate (10 ⁶
The viscosity under sec- ¹ ) was 54 cps.

Using a high-speed gate roll coater as a coating device, a coating liquid is applied to a base paper containing bleached hardwood bleached kraft pulp having a basis weight of 54 g / m ² at a coating speed of 1200 m / min.
After applying ² g / m ² of solid content per 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 when preparing a coating liquid.

Example 3 A coating liquid was prepared in the same manner as described above except that 7 parts of a styrene / butadiene copolymer latex having a gel content of 80% was used and the solid content of the coating liquid was changed to 46%. A coated paper was produced as in Example 1.

Example 4 35 mm in diameter as a coating device
A coated paper was manufactured in the same manner as in Example 1 except that a coating liquid was applied at a coating speed of 1400 m / min using a rod metering size press coater having a rod having a smooth surface.

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 when preparing a 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 when preparing a coating liquid.

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

Comparative Example 4 A coated paper was produced in the same manner as in Example 1 except that 11 parts of a styrene / butadiene copolymer latex were used when preparing the coating liquid.

The above results are shown in Table 1.

[0036]

[Table 1] As is clear from Table 1, in Examples 1 to 4, coated paper which is free of gum up and mist, has good high-speed operability, and can be used as a flyer, lower-grade printing paper and under-coated paper in terms of quality. Could be obtained. In Comparative Examples 1 to 4, high-speed operability was inferior.

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

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

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

Further, 8 g / m ² of solid content per side was coated on both sides at a coating speed of 1200 m / min using a high-speed blade coater. Further, gloss finishing was performed using a 12-stage super calendar. Example 6 When preparing an undercoat 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 undercoat coating solution,
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 content of the coating liquid was changed to 46%.

[Embodiment 8] 35 mm in diameter as a coating device
A coated paper was manufactured in the same manner as in Example 5, except that a primer coating liquid was applied at a coating speed of 1400 m / min using a rod metering size press coater having a rod having a smooth surface.

Example 9 In preparing an undercoat coating solution,
Heavy calcium carbonate having an average particle size of 0.7 μm
A coated paper was produced in the same manner as in Example 5, except that some parts were used.

Comparative Example 5 When 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 size of 1.0 μm,
10 parts of 0.55 μm kaolin, 8.5 parts of phosphorylated esterified starch and 2.5 parts of a styrene-butadiene copolymer latex having a gel content of 28% were blended to give a coating solution solids concentration of 64%. Except for the above, a coated paper was manufactured in the same manner as in Example 5.

Comparative Example 7 When preparing an undercoating 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 When 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 a styrene / butadiene copolymer latex having a gel content of 80% were used.

[Comparative Example 9] When preparing an undercoat coating liquid,
Heavy calcium carbonate having 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 results are shown in Table 2.

[0050]

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

Quality Evaluation Method> (1) Average Particle Diameter of Heavy Calcium Carbonate SHIN5000
Was used to measure the 50% point of the weight cumulative distribution as the average particle diameter.

(2) Latex gel content About 0.3 g of latex was spread thinly on a slide glass.
Dry in a dryer at 50 ° C. until a film is formed. The latex film is immersed in about 50 ml of toluene for 24 hours, filtered with a glass filter, and the filtrate is dried with a dryer at 105 ° C., and the weight of the toluene-soluble component is measured. The gel content was calculated from the weight of the toluene-soluble component obtained by the following equation.

Gel content (%) = (weight of dry film−weight of soluble matter in toluene) × 100 / (weight of dry film) (3) Evaluation of high-speed fluidity High-speed fluidity was evaluated by the following capillary viscosity value. The undercoating coating solution was kept at 45 ° C., and the diameter was 0.4 mm and the tube length was 1 using a high-pressure capillary viscometer HVA6 manufactured by Anton Paar.
Viscosity value measured using a 0 mm capillary at a shear rate of 1 × 10 ⁶ sec ^-1 .

(4) Blank glossiness Measured at an angle of 75 degrees according to JIS P-8142.

(5) Glossiness after printing Using an RI-II type printing tester, printing was performed using 0.35 cc of Sakata Inks offset printing ink (trade name: Diatone GSL Red), and after standing overnight, 75-degree gloss The degree was measured.

(6) Smoothness JAPAN Tappi No. 5 Measured by Oken type smoothness tester.

(7) Printing Surface Strength Using a RI-II type printing machine (manufactured by Meisho Seisakusho), using Toyo Ink's TV-24, printing at a rotation speed of 40 rpm and an ink amount of 0.35 cc, the printing surface was printed. The relative degree of picking was visually evaluated.

＝= No occurrence, ＝= Nearly occurrence Δ = Yes, X = Severe occurrence (8) Blank paper surface The unevenness of the glossiness of the blank paper was visually evaluated relative to each other.

◎ = No unevenness, ＝= Almost no unevenness △ = Some unevenness, X = Severe unevenness (9) Evaluation of mist generation The mist generation state when coated by the film transfer method is visually judged. did.

◎ = Not generated at all, ○ = Almost not generated △ = Generated, × = Remarkable generation (10) Evaluation of gum-up occurrence Gum-up occurrence status when coated continuously for a long time by the film transfer method Was visually determined.

＝= Gum-up does not occur even in continuous operation for 24 hours or more. ＝= Gum-up occurs in continuous operation for 24 hours. Δ = Gum-up occurs in continuous operation for 8 hours. Gum-up is observed in continuous operation for 4 hours

[0062]

According to the present invention, a film transfer method is used,
Under high-speed conditions, especially at a high speed of 1100 m / min or more, operability, which is a problem in the manufacturing process of coating the coating liquid, is improved, and the surface condition (surface coverage, gloss unevenness) of the product and the printing surface strength are excellent. Thus, a coated paper for offset printing can be obtained.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hideki Fujiwara 5-21-1, Oji, Kita-ku, Tokyo Nippon Paper Industries Central Research Laboratory (56) References JP-A-63-99395 (JP, A) Kaihei 7-189188 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) D21H 19/36-19/84

Claims (5)

(57) [Claims] 1. A method for producing a coated paper for offset printing wherein a base paper is coated with a coating liquid containing a pigment and an adhesive, wherein 70 parts of heavy calcium carbonate is added to 100 parts of the pigment.
100% by weight, gel content 70-90% by weight as adhesive
1 to 10 parts by weight of a copolymer latex having a viscosity of 35 to 60 under a high shear rate (10 6 sec -1).
A method for producing coated paper for offset printing, which comprises applying a coating liquid adjusted to cps to base paper with a film transfer type coating apparatus. 2. The method for producing coated paper for offset printing according to claim 1, wherein the coating liquid 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 used as an adhesive.
The method for producing a coated paper for offset printing according to claim 1, wherein the coating liquid is contained in a coating liquid of 30 to 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 method according to claim 1, wherein the coating speed is 1100 m / min or more.
Further on the coated paper manufactured by the manufacturing method according to 1,
Offset manufactured by applying the adjusted topcoat coating liquid
Coated paper for printing.