JP3339048B2 - Manufacturing method of 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 the production of a coated paper in which a coating liquid having a pigment and an adhesive, which is excellent in high-speed operability and printability, is applied to base paper by a film transfer method.

[0002]

2. Description of the Related Art In recent years, demand for printing paper has tended to gradually increase. In particular, commercial printing fields such as advertising, mail order flyers, catalogs, brochures and multimedia,
It is characterized by a steady increase in demand for PC magazines and manuals. These printed materials have low commercial value, unlike high-end printing and publishing, but since it is important that the purpose is achieved as a medium for advertising and information transmission, low-cost, high-quality printed products are required. Accordingly, the cost reduction of paper users has been further strengthened, and the paper used is also becoming lower grade, thinner 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. It is important to increase productivity. Therefore, in recent years, many on-machine coating methods for efficiently performing paper making and coating simultaneously with one machine have been widely used as production equipment. However, using an on-machine coating system such as a gate roll coater or a film transfer coating system such as a blade or rod metering size press coater, a coating liquid containing a usual pigment and adhesive is applied to the base paper. At the present time, the maximum operating speed is about 1100 m / min, which is the limit of speeding up. One of the reasons that hinders the speed-up is a phenomenon called mist, in which the coating liquid is mist-like and scatters at the exit of the application roll nip. The mist starts to be generated even at a speed lower than 1100 m / min depending on the operating conditions. However, as the speed increases, the degree of the mist increases, causing a deterioration in the working environment. To fall into the product defect.

In the case of a gate roll coater, in particular, a similar problem of mist generation occurs, and at the same time, when the mechanical and thermal stability of the coating liquid is poor, the gap between the inner roll and the outer roll or between the inner roll and the application roll is reduced. As a result, a phenomenon called gum-up in which the coating liquid solidifies and adheres to the roll surface occurs due to the shearing force applied between the rolls having different roll diameters and peripheral speeds, thereby reducing operability. Further, peeling at the exit of the application roll nip becomes unstable, and a large number of peeling patterns occur. 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 coating properties of the base paper are reduced, resulting in uneven gloss after coating. And there is a problem that the surface state and printability deteriorate.

[0005]

SUMMARY OF THE INVENTION In view of the above situation, an object of the present invention is a problem in a manufacturing process of applying a film transfer method as described above at a high speed condition, particularly at a high speed of 1100 m / min or more. It is an object of the present invention to provide a coated paper having excellent operability and excellent surface condition and printing quality after coating.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies on the above-mentioned problems, and as a result, have found that a coating liquid containing a pigment and an adhesive is coated on base paper by a film transfer method. In the production method, a styrene / butadiene copolymer latex (A) having an average particle diameter of 40 to 70 nm as an adhesive and an average particle diameter of 110 to 140 are used.
A coating liquid containing a latex obtained by mixing a styrene-butadiene-based copolymer latex (B) with a mixing ratio of 30/70 ≦ A / B ≦ 70/30 (solid content weight ratio, the same applies hereinafter) in the range of 30/70. The present invention has been accomplished by coating at a coating speed of 1100 m / min or more .

The details of the present invention will be described below.

The present inventors have found that the problem of mist, peeling pattern and gum-up, which are more remarkably observed particularly when coating a coating liquid containing a pigment and an adhesive under a high speed condition of 1100 m / min or more, is high. It was correlated with the viscosity of the coating liquid under the shear rate, and it was confirmed that decreasing the viscosity of the coating liquid under the high shear rate was effective in solving these problems.

On the other hand, as one of solutions for lowering the viscosity of a coating solution under a high shear rate, several methods of mixing and using a latex having a small particle diameter and a latex having a large particle diameter have been proposed. For example, JP-A-61-1528
No. 97 proposes a method in which a latex (a) having an average particle diameter of 50 to 100 nm and a latex (b) having an average particle diameter of 150 to 1000 nm are mixed and used at a mixing ratio of 2/98 ≦ a / b ≦ 50/50. . However, the content is intended for coating by a blade system, and is not intended to improve the operability inherent to the film transfer system. JP-A-3-227496 discloses that the average particle size is 30 to 80 nm and the gel content is 75 to 100%.
Latex (a) having an average particle diameter of 100 to 200 n
A method in which a latex (b) having a gel content of 75 to 100% and a mixing ratio of 1/99 ≦ a / b ≦ 30/70 is proposed. However, its content is to improve the glossiness, surface strength, and water resistance of coated paper after printing,
It is not intended to improve the operability peculiar to the film transfer method, and the amount of the latex having a small particle diameter is small, so that the viscosity of the coating liquid under a high shear rate does not decrease much.

In order to solve the problems of high-speed operability such as mist and peeling pattern peculiar to the film transfer method, the present inventors have proposed a method of mixing and using latex having a small particle size and a latex having a large particle size, and optimal latex particles thereof. As a result of intensive studies on the diameter and the mixing ratio, the mixing ratio of the styrene-butadiene-based copolymer latex (A) having an average particle diameter of 40 to 70 nm and the styrene-butadiene-based copolymer latex (B) having an average particle diameter of 110 to 140 nm was determined. By applying a coating liquid containing a latex mixed within the range of 30/70 ≦ A / B ≦ 70/30, excellent high-speed operability is achieved, and the surface condition after printing and the printing surface strength (dry, (Wet strength). In the present invention, a coating liquid having a pigment and an adhesive is coated under a high-speed condition by a film transfer type coating apparatus. can not see. The reason for this is that by using a mixture of latex having a small particle diameter and latex having a large particle diameter, the filling property of the particles is increased, and the amount of free water (the amount of water related to flow) in the coating liquid is increased. This is considered to be because the viscosity at the shearing rate was lowered, and the coating film was split uniformly and transferred to paper.

When the compounding ratio of the latex (A) having a small particle diameter is 3
When it is less than 0%, the problem of operability such as mist and peeling pattern becomes remarkable because the decrease in the viscosity of the coating liquid at a high shear rate is small, and the surface condition after coating is inferior. Further, the dry strength is reduced due to a decrease in the area of adhesion to the pigment in the coating layer, and the trouble of picking of the printed portion near the interface between the coating layer and the base paper layer due to the tackiness of the ink during solid printing increases.

On the other hand, when the compounding ratio of the small particle size latex (A) is more than 70%, the viscosity of the coating liquid at a high shear rate is greatly reduced, and the operability is excellent, but the latex is difficult to produce. Due to the adverse effect of the hydrophilic emulsifier incorporated, the wet strength (the surface strength of the printed surface printed immediately after the dampening solution is applied during overprinting) is reduced. In addition, since the area of adhesion to the pigment is too large, the amount of voids in the coating layer is reduced, and the wet inking property (ink concentration on the printed surface printed immediately after the dampening solution is applied) is reduced.

The small particle size latex (A) has a particle size of 40
When a material smaller than nm is used, the adverse effect of the emulsifier becomes remarkable, the wet strength is reduced, and the wet inking property is also reduced as described above. When the particle size of latex (B) is 14
When a material having a size larger than 0 nm is used, the area of adhesion to the pigment decreases, and the dry strength decreases. When the particle size of the latex A is larger than 70 nm or when the particle size of the latex B is smaller than 110 nm, the decrease in the viscosity of the coating liquid at a high shear rate is small, and the mist and the peel pattern are small. Equal operability problems occur, and the surface condition is reduced.

As a pigment to be used, calcium carbonate having an average particle diameter of 0.5 to 1.2 μm is used in all pigments.
It is preferable to apply a coating liquid containing 0% by weight or more of a pigment. This is because by using a large amount of amorphous calcium carbonate having a small aspect ratio as a pigment, the filling properties of the pigment and each latex particle constituting the coating liquid are further improved, and the viscosity at a high shear rate is lower. It is thought that operability is improved. When the compounding amount is less than 40% by weight or when the particle size is smaller than 0.5 μm, the decrease in the viscosity of the coating liquid at a high shear rate is small, and the operability is likely to be reduced. When the particle diameter is larger than 1.2 μm, the viscosity of the coating liquid under a high shear rate is too low, and the coating liquid penetrates into the base paper, and the surface condition of the product and the glossiness of the white paper decrease. Tend to.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION As the pigment used in the present invention, it is preferable to use calcium carbonate having an average particle size of 0.5 to 1.2 μm, but it is generally used for papermaking. Inorganic pigments such as heavy calcium carbonate, light calcium carbonate, potassium olin, clay, delaminated clay, talc, satin white, silica, barium sulfate, calcium sulfate, zinc oxide and titanium dioxide, or organic pigments such as plastic pigment For example, those commonly used for coated paper can be used, and if necessary, used alone or in combination of two or more.

The composition of the styrene / butadiene copolymer latex (A) or (B) which is the adhesive of the present invention is a styrene / butadiene copolymer, a styrene / butadiene / acrylic copolymer or a modified product thereof. As the monomer, in addition to styrene and butadiene, methyl methacrylate and other vinyl-based unsaturated carboxylic acid ester compounds, acrylonitrile and other vinyl compounds, and acrylic acid and fumaric acid and other vinyl-based unsaturated carboxylic acids are copolymerized. Or modified with a small amount of a monomer having another functional group. These latexes may be used alone or in combination with other water-based adhesives depending on the quality of the coated paper required. The amount of latex used is 2 to 30 parts per 100 parts of pigment.
Parts, more preferably 3 to 18 parts. The gel content of the latex used in the present invention is preferably from 75 to 90% by weight from the viewpoint of improving gum-up.

Examples of the aqueous adhesive other than latex include proteins such as casein, soybean protein, and synthetic protein; synthetic resin adhesives such as polyvinyl alcohol, polyvinylpyrrolidone, olefin / maleic anhydride resin, and melamine resin; Oxidized starch, positive starch, esterified starch such as urea-phosphate esterified starch, etherified starch such as hydroxyethyl etherified starch, enzyme-modified starch, or cold water-soluble starch obtained by flash-drying them; carboxymethyl cellulose, hydroxy starch It is a usual coating adhesive such as a cellulose derivative such as ethyl cellulose or hydroxymethyl cellulose.

In the coating liquid of the present invention, various auxiliaries such as a dispersant, a thickener, a water retention agent, an antifoaming agent, and a waterproofing agent may be used in combination. Further, the concentration of the coating liquid is more preferably 35 to 60% by weight in solid content. If the amount is less than 35% by weight, the viscosity at a high shear rate becomes too low, and the surface properties and printability of the product decrease. On the other hand, if it is more than 60% by weight, the viscosity at a high shear rate becomes high. Mist is easily generated.

As the base paper, base paper having a basis weight of 30 to 100 g / m ² used for general coated paper for printing is preferable, and high quality paper and medium quality paper are selected and used according to the purpose.

As a film transfer type coating apparatus for coating the prepared coating liquid on the base paper, a gate roll coater, a blade or a rod metaling size press coater can be used. It may be used for any of the undercoats. The coating amount of the coating liquid is preferably in the range of ² to 10 g / m ^{2 in} 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. On the other hand, when the coating amount is more than 10 g / m ² , it is necessary to increase the coating liquid concentration. In this case, it becomes difficult to control the coating amount on the apparatus, and at the same time, a peeling pattern or a matte surface roughness is generated. It easily occurs on the paper surface.

The coated paper obtained by coating the base paper with the coating liquid and dried is manufactured as it is or by surface finishing such as a steel calender, a super calender, and a soft calender.

[0022]

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.

<Quality Evaluation Method> (1) Latex average particle diameter: A sample diluted to a concentration of 0.05 to 0.2% was prepared, the absorbance at a wavelength of 525 nm was measured, and determined by a calibration curve prepared in advance. (2) Pigment average particle diameter: Using a light transmission type particle size distribution analyzer SHC5000 manufactured by Seishin Enterprise, the 50% point of the weight cumulative distribution was measured as the average particle diameter.

(3) Dry strength: Using a RI-II type printing machine (manufactured by Meisho Seisakusho), using Toyo Ink TV-24, printing with a constant ink amount of 0.35 ml, and checking the degree of picking on the printing surface. The relative evaluation was made visually.

◎ = not generated at all, ＝= not generated at all, Δ = produced, × = produced significantly (4) Wet strength: RI-I type printing machine (manufactured by Meiji Seisakusho)
5 seconds after applying dampening water to the sample, using TK High Plus Red Ink (manufactured by Toyo Ink), printing at a constant ink volume of 0.3 ml, and manually printing the print marks on the rubber roll on the transfer paper. And the degree of picking was visually evaluated relative to each other.

＝= not generated at all, ＝= never generated, Δ = generated, X = remarkable (5) Wet inking property: Using a RI-I type printing machine (manufactured by Mei Seisakusho), wet the sample 5 seconds after adding water, TK
Printing was performed using High Plus Red Ink (manufactured by Toyo Ink) at a constant ink volume of 0.3 ml, and the ink density of the printed matter was measured. The higher the value, the better.

(6) Evaluation of mist generation: The state of mist generation was visually determined at the time of coating.

＝= no occurrence, ＝= no occurrence, Δ = occurring, × = significant occurrence (7) Peeling pattern occurrence evaluation: The occurrence of a peeling pattern during coating was visually judged.

＝= Not generated at all, ほ と ん ど = Not generated at all, Δ = Produced, X = Remarkably generated (8) Blank surface: Uneven gloss of blank paper was evaluated by visual observation.

＝= Not generated at all, ＝= Not generated at all, Δ = Produced, X = Remarkable generation [Example 1] 80 parts of light calcium carbonate having an average particle diameter of 0.70 μm in all pigments, kaolin To 20 parts, 0.3 part of sodium polyacrylate dispersant was added,
Dispersed in water using a Cowles disperser, 23 parts of phosphorylated ester starch as an adhesive, styrene / butadiene copolymer latex A having an average particle diameter of 60 nm, and 120
5 parts of a latex obtained by mixing styrene / butadiene copolymer latex B at a mixing ratio of 40/60 nm was blended to prepare an undercoat coating liquid having a solid concentration of 40%.

Further, sodium polyacrylate-based dispersant 0.1 part with respect to 65 parts of heavy calcium carbonate and 35 parts of kaolin.
3 parts were added and dispersed in water using a Cowles dispersing machine. As an adhesive, 4 parts of a phosphorylated starch and styrene.
10 parts of butadiene copolymer latex was blended to prepare a topcoat coating solution having a solid content of 65%.

Using a gate roll coater as a coating device for undercoating base paper containing bleached hardwood bleached kraft pulp having a basis weight of 54 g / m ² , the undercoat coating solution was applied at a coating speed of 1300 m / min. 4 g / m ² on both sides, and then soft-calendered (50 ° C., 80
kg / cm).

Further, as a coating apparatus for top coating, a blade coater was used, and a top coating liquid was applied on both sides at a solid content of 8 g / m ² on one side and dried. Further, using a two-roll, two-stack soft calender, gloss finishing was performed at a temperature of 160 ° C. and a linear pressure of 300 kg / cm.

Example 2 In preparing an undercoating coating solution,
Light calcium carbonate having an average particle diameter of 1.0 μm is used as a pigment, and a styrene / butadiene copolymer latex A having an average particle diameter of 50 nm and a styrene / butadiene copolymer latex B having an average particle diameter of 130 nm are mixed at a mixing ratio of 60/4.
A coated paper was produced in the same manner as in Example 1 except that latex mixed at a ratio of 0 was used.

Comparative Example 1 A coated paper was produced in the same manner as in Example 1 except that styrene / butadiene copolymer latex A having an average particle diameter of 35 nm was used.

Comparative Example 2 A coated paper was produced in the same manner as in Example 1 except that styrene / butadiene copolymer latex A having an average particle diameter of 100 nm was used.

Comparative Example 3 Heavy calcium carbonate having an average particle size of 0.40 μm was used, and the average particle size was 100
Styrene-butadiene copolymer latex B with nm
A coated paper was produced in the same manner as in Example 1 except that was used.

Comparative Example 4 A coated paper was produced in the same manner as in Example 1 except that styrene / butadiene copolymer latex B having an average particle size of 190 nm was used.

[Comparative Example 5] A styrene / butadiene copolymer latex A having an average particle diameter of 60 nm and 120 nm
A coated paper was produced in the same manner as in Example 1, except that a latex in which the mixing ratio of styrene / butadiene copolymer latex B was 10/90 was used.

Comparative Example 6 A styrene / butadiene copolymer latex A having an average particle diameter of 50 nm and 130 nm
A coated paper was manufactured in the same manner as in Example 2 except that a latex in which the mixing ratio of styrene / butadiene copolymer latex B was 85/15 was used.

Comparative Example 7 Heavy calcium carbonate having an average particle diameter of 1.4 μm was used, and the average particle diameter was 50 nm.
Styrene-butadiene copolymer latex A of 13
A coated paper was produced in the same manner as in Example 2 except that a latex obtained by mixing a 0 nm styrene / butadiene copolymer latex B at a blending ratio of 95/5 was used.

Comparative Example 8 Heavy calcium carbonate having an average particle diameter of 0.40 μm was used, and the average particle diameter was 50 n.
A coated paper was produced in the same manner as in Example 2, except that a latex in which a latex A of m and a latex B of 130 nm were mixed at a mixing ratio of 5/95 was used. Comparative Example 9 A coated paper was produced in the same manner as in Example 1, except that 5 parts of a styrene / butadiene copolymer latex having an average particle diameter of 96 nm was independently blended.

Example 3 50 parts of heavy calcium carbonate having an average particle diameter of 0.70 μm in all pigments and 5 parts of kaolin 5
To 0 part, 0.3 part of sodium polyacrylate-based dispersant was added, and dispersed in water using a Cowles disperser. As an adhesive, 6 parts of phosphorylated ester starch and an average particle diameter of 6 parts were used.
0 nm styrene / butadiene copolymer latex A
And 15 parts of a latex obtained by mixing styrene-butadiene copolymer latex B having a mixing ratio of 50/50 with 120 nm to prepare a coating liquid having a solid content concentration of 58%.

A base roll containing bleached kraft pulp having a basis weight of 54 g / m ^{2 and} a kraft pulp alone was coated with a gate roll coater at a coating speed of 1300 m / min and a solid content of 9 g / m ² per side.
After drying on both sides, soft calendering (70
° C, 200 kg / cm). [Comparative Example 10] The compounding ratio of styrene / butadiene copolymer latex A having an average particle diameter of 60 nm and styrene / butadiene copolymer latex B having an average particle diameter of 120 nm was 90/1.
A coated paper was produced in the same manner as in Example 3 except that latex mixed at a ratio of 0 was used.

Comparative Example 11 The average particle size was 0.45 μm
Using heavy calcium carbonate having an average particle diameter of 60
nm styrene-butadiene copolymer latex A,
A coated paper was produced in the same manner as in Example 3 except that a latex in which a 120-nm styrene / butadiene copolymer latex B was mixed at a mixing ratio of 10/90 was used.

The above results are shown in Tables 1 to 3.

[0047]

[Table 1]

[Table 2]

[Table 3] As is clear from Tables 1 to 3, Examples 1 and 2, which are multilayer coated papers, are extremely excellent in printing surface strength, wet inking property and operability. On the other hand, in Comparative Example 1, the wet strength and wet inking property were compared. In Comparative Example 2, the dry strength, operability and surface condition were compared. In Comparative Example 3, the operability and surface condition were compared. In Comparative Example 4, the dry strength was compared. In Example 5, the dry strength, operability, and surface state were compared. In Comparative Example 6, the wet strength and wet inking property were compared. In Comparative Example 7, the wet strength, wet inclination, and surface state were compared. The operability was inferior in Comparative Example 9 in terms of properties and surface properties.

Example 3, which is a single-layer coated paper, is excellent in printing surface strength, wet inking property and operability. Comparative Example 10 is inferior in wet strength and wet inking property. On the other hand, Comparative Example 11 is inferior in dry strength, operability and surface condition.

[0049]

According to the present invention, the operability, which is a problem in the manufacturing process of coating at a high speed condition, particularly at a high speed of 1100 m / min or more, using a film transfer system is improved, and the surface condition after coating is improved. Coated paper having excellent printing surface strength can be efficiently produced.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-8-325994 (JP, A) JP-A-61-97497 (JP, A) JP-A-63-99395 (JP, A) (58) Field (Int. Cl. ⁷ , DB name) D21H 19/00-19/84

Claims (2)

(57) [Claims] 1. A method for producing a coated paper in which a coating liquid containing a pigment and an adhesive is applied to base paper by a film transfer method, wherein the adhesive has an average particle diameter of 40 to 70 nm.
Is a styrene-butadiene-based copolymer latex (A) and a styrene-butadiene-based copolymer latex (B) having an average particle diameter of 110 to 140 nm in the range of 30/70 ≦ A / B ≦ 70/30. The coating liquid containing the latex mixed within is coated at a coating speed of 1100 m / min or more.
A method for producing coated paper, wherein the method is applied to base paper. 2. A pigment having an average particle size of 0.5 to 1.
2. The method for producing coated paper according to claim 1, wherein a coating liquid containing 2% by weight or more of calcium carbonate in the total pigment is 40% by weight or more.