JP3044706B2 - Coated paper for gravure printing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing coated paper for gravure printing by high-temperature calendering. The present invention relates to a method for efficiently producing a coated paper for gravure printing provided with the method.

[0002]

2. Description of the Related Art Gravure printing is intaglio printing in which the ink in the concave portions of the plate is transferred under pressure and has excellent gradation reproducibility, and is therefore used in commercial printing fields such as magazines, catalogs and pamphlets. ing.

[0003] In gravure printing, misprints occur because the printing plate is a hard metal roll compared to offset printing, and the printing plate surface is difficult to completely adhere to the paper during printing. Therefore, smoothness and cushioning property are important for the base paper and the coating layer of the coated paper for gravure printing.

[0004] In order to improve the smoothness of the surface of the coating layer of the coated paper for gravure printing, pigments having a high aspect ratio (clay, delaminated clay,
Talc). As a technique for imparting smoothness to the coating layer, a low glass transition temperature (about -4
(About 0 ° C.) Synthetic copolymer polymer latex is blended. In addition, as a method of mechanically smoothing the surface of the coating layer of the coated paper for gravure printing, a surface treatment is generally performed using a super calender. Further, in order to improve the glossiness of the stamp surface, a pigment having a high aspect ratio is blended in the coating layer composition to smooth the coating layer.

However, the incorporation of a large amount of a pigment having a high aspect ratio into the coating layer composition increases the viscosity of the coating solution, making it difficult to handle the solution, resulting in streaks,
It causes coating defects such as scratching and bleeding. Therefore, at present, the solid content concentration of the paint cannot be increased so much. As a result, it is necessary to increase the drying conditions, which leads to an increase in cost.

A copolymer latex is a polymer compound obtained by copolymerizing monomers such as styrene, butadiene and methyl methacrylate, and mainly uses butadiene and styrene in many cases. Polybutadiene has a glass transition temperature of -82 ° C., and polystyrene has a temperature of 100 ° C. The glass transition temperature of the copolymer latex can be adjusted by changing the compounding ratio of the monomers. The copolymer latex used for gravure printing coated paper (hereinafter gravure latex) and the copolymer latex used for offset printing coated paper (hereinafter referred to as offset latex) usually have different monomer compositions due to the difference in their printing methods. Different ones are used. What is known as a gravure latex is softened by adding a large amount of butadiene having a low glass transition temperature in order to enhance the cushioning property of the coating layer, and the glass transition temperature is usually about -40 ° C. . For example, JP-A-60-22489
No. 5 describes that "in a low region having a glass transition temperature of -25 ° C. or lower, the polymer is imparted with flexibility, the cushioning property of the coated paper is improved, and excellent gravure printing suitability is exhibited." This is because if the glass transition temperature increases, the coating layer becomes hard and the number of misdots increases. However, latex having a low glass transition temperature has good suitability for gravure printing, but has the following problems.

[0007] The coated paper for gravure printing is usually 6 gm after coating.
Supercalendering is performed under pressure using a roll heated to 0 to 80 ° C. However, a gravure latex having a low glass transition temperature is easily melted, and an operational trouble such as calendar contamination adhering to the heated roll is likely to occur. In addition, when coated paper is used as a rolled product, the problem of blocking, in which the paper surface adheres to the front and back surfaces, tends to occur.

The particle size of the gravure latex is 1
In many cases, the latex has a particle size of 20 Å or more.
It is specified that the thickness is in the range of 00 to 4000 angstroms, and it is described that the effect of reducing halftone dot dropout is not sufficiently exerted when it is less than 2000 angstroms. However, as the particle size of the latex increases, the viscosity of the coating liquid, particularly in the high shear rate region, increases. Conventionally, starch, casein, carboxymethylcellulose and the like have been used as a water retention agent in order to enhance the water retention ability of the coating liquid.
These are intended to improve the water retention of the coating liquid by increasing the viscosity of the coating liquid in a low shear rate region. However, at the same time, the viscosity in the high shear rate region also increases. As described above, the conventional gravure printing coating liquid has a high viscosity in a high shear rate region due to the properties of a pigment, an adhesive or a water retention agent that is blended to improve the printability and operability of the coated paper. Become. The increase in the viscosity of the coating liquid in the high shear region increases the shear stress of the coating liquid, and requires a coating amount control corresponding to the stress. As a result, it is necessary to increase the blade pressure in a commonly used blade coater. In other coating methods, it is necessary to increase the pressure of a bar, a roll, air, etc., as in the case of the blade pressure. Since the surface coated with high pressure is easily roughened, the smoothness is deteriorated and the gloss is reduced. In addition, the pressurization of the blade tends to cause streak-like coating defects such as paper breakage, streak, and scratching, resulting in severe blade wear and reduced operability of the coater.

This tendency becomes more conspicuous as the coating speed increases and the paint concentration increases.
With the increase in the speed of m / min or more or the increase in the coating solution concentration of 60% or more, there is a demand for a coating material having an appropriate viscosity in an even higher shear rate region. On the other hand, with the diversification of printing methods, the demand for printing paper has also increased, and various technologies have been developed accordingly. As for the calendar finishing method, many methods using a high-temperature calendar have been proposed instead of the conventional super calendar, and it is reported that the glossiness of blank paper, the glossiness of the stamp surface, the opacity, the rigidity, etc. are improved with the increase in finishing speed. Have been.

[0010] In a method for producing a general coated paper which is subjected to a high-temperature calendering treatment, for example, Japanese Patent Application Laid-Open No. 7-300799 proposes to use a latex having a glass transition temperature of 25 ° C or more. However, when a coated paper for gravure printing is manufactured using this latex, the coated layer becomes hard because the latex is hard, and as a result, smoothness does not easily appear due to calendering, and the cushioning property of the coated layer is also reduced. Due to the inferiority, misdots at the time of gravure printing increase, which is not suitable as a latex for gravure printing.

[0011]

SUMMARY OF THE INVENTION In view of the above situation, an object of the present invention is to use a high-temperature calendar of 100 ° C. or more, and particularly to prevent the calendar from being stained during operation, to have excellent gloss and high rigidity, An object of the present invention is to efficiently provide a coated paper for gravure printing which has no blocking at the time of winding, has a low dot loss rate at the time of gravure printing, and has excellent printability.

[0012]

SUMMARY OF THE INVENTION The present invention relates to a coated paper for gravure printing obtained by coating a base paper with a coating liquid containing a pigment and an adhesive as main components, drying and calendering. As a solid, a copolymer latex having a glass transition temperature of -20 to 20 ° C. was used as a solid, and 3 parts based on 100 parts of the pigment.
In addition to containing 10 to 10 parts by weight, calendering is performed with a high-temperature calender consisting of an elastic roll and a metal roll heated to 100 ° C. or higher, so that there is no calendar dirt during operation, excellent gloss, high opacity, and rigidity. The present inventors have found that a coated paper for gravure printing having a high white balance, a low dot loss rate during gravure printing, and excellent white paper quality and printability can be efficiently produced, and the present invention has been completed.

The glass transition temperature of a copolymer latex used as an adhesive compounded in a printing coating liquid is -20.
It is important that it is ２０20 ° C. By using a material in this range, a coated paper having hardness suitable for high-temperature calendering and cushioning property suitable for gravure printing can be obtained. That is, since a coating layer formed using a copolymer latex having a glass transition temperature exceeding 20 ° C. becomes hard, the dot missing rate during gravure printing becomes high, which is not suitable for gravure printing. When a copolymer latex having a glass transition temperature of less than −20 ° C. is used, the stickiness of the latex is high. The so-called blocking in which the papers adhere to each other during picking tends to occur, which is inappropriate for operation.

It is important that the copolymer latex be used in an amount of 3 to 10 parts by weight based on 100 parts by weight of the pigment as a solid content of the latex. Coated paper manufactured with less than 3 parts by weight of the copolymer latex is not suitable for gravure printing because the surface strength of the coated layer is weakened. Coated paper produced in an amount of more than 10 parts by weight of the copolymer latex also has a hard coating layer, insufficient cushioning properties, and is not suitable for gravure printing.

It is important that calendering is performed using a high-temperature calender comprising an elastic roll and a metal roll heated to 100 ° C. or higher. If the water content of the coated paper is appropriate, the higher the metal roll temperature, the lower the nip pressure or the shorter the residence time, the smoother the base paper or the coated layer can be. I can't get it. Preferably, the treatment is performed at 150 ° C to 250 ° C. When high-temperature calendering is performed under the conditions for obtaining blank gloss and stamped gloss obtained using a conventional super calender, that is, lowering the calender pressure or shortening the nip residence time by performing high-speed calendering In addition, the density of the coating layer and the base paper are reduced, the opacity is increased, the stiffness is increased, and the same or better halftone dot loss rate in gravure printing is exhibited. In addition, when high-temperature calendering is performed under the conditions for obtaining opacity and rigidity obtained by using a conventional super calender, high values of white paper glossiness and stamp surface glossiness are obtained. Further, the processing speed is higher than that of the conventional super calender processing, and the change of the winding frame can be omitted.

As the auxiliary agent used in the present invention, it is preferable to use an acrylic synthetic water retention agent and / or hydroxyethyl cellulose. Specific examples of the acrylic synthetic water retention agent include Alco Gum L-37 manufactured by Alco Chemical Co., Ltd.
Acrylic synthetic water retention agents such as ASE-95 and Rohm & Haas Co., Ltd., especially Alcogum L-83 and L-89 from Alco Chemical Co., Ltd.
It is particularly preferable to use an association type acrylic synthetic water retention agent represented by TT-935 manufactured by Haas Corporation.

The associative acrylic synthetic water retention agent functions to improve the water retention of the paint and to lower the high shear viscosity of the paint. Therefore, while being suitable for high-speed coating, the coating is not pushed into the coating base paper during coating, making the coating layer on the base paper bulky and improving the cushioning property of the coating layer. The rate tends to be low. Hydroxyethylcellulose has the same effect, and is remarkable when clay or the like is used as a pigment.

[0018]

DETAILED DESCRIPTION OF THE INVENTION The pigment used in the present invention is not particularly limited, and kaolin, clay, delaminated clay, heavy calcium carbonate, light calcium carbonate, talc, which are conventionally used for coated paper, are used. , Titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicate, colloidal silica, inorganic pigments such as satin white, and organic pigments such as plastic pigments. These pigments may be used alone or in combination of two or more as required. Can be used in a mixture.

As the adhesive used in the present invention, a copolymer latex having a glass transition temperature of -20 ° C. to 20 ° C. may be used alone or in a mixture of several kinds, as long as the object of the present invention is not impaired. And other adhesives such as starch and the like. The copolymer latex includes not only rubber-based latex but also synthetic resin emulsion, and conjugated diene-based copolymer latex such as styrene / butadiene copolymer, methacrylate / butadiene copolymer, acrylic ester and / or Or a vinyl polymer latex such as a methacrylate polymer or copolymer, or an alkali-soluble, alkali-swellable or alkali-insoluble polymer latex obtained by modifying these various polymer latexes with a carboxyl group or the like; One or more kinds of various synthetic resin polymers called binder pigments are appropriately selected and used.

Further, as an adhesive other than latex,
For example, proteins such as casein, soy protein, and synthetic protein; synthetic resin adhesives such as polyvinyl alcohol, olefin / maleic anhydride resin, and melamine resin; oxidized starch, positive starch, urea phosphate esterified starch, and hydroxyethyl etherified starch One or more kinds of ordinary coating adhesives such as etherified starch and starch such as dextrin; cellulose derivatives such as carboxymethyl cellulose, hydroxyethyl cellulose and hydroxymethyl cellulose may be appropriately selected and used. Among them, starch-based adhesives and cellulose-based adhesives having high water retention can be used as water retention agents.

The adjusted coating liquid is supplied to a blade coater,
Bar coater, roll coater, air knife coater,
Using a reverse roll coater, a curtain coater, a size press coater, a gate roll coater, or the like, one or two or more layers are coated on both sides of the base paper one by one.

As the base paper for coating, a paper base or paperboard base paper having a basis weight of about 30 to 400 g / m 2 used for general coated paper is appropriately used. The papermaking method of the base paper is not particularly limited, and a long net machine including a top wire or the like, a round netting machine, a paperboard machine combining the two, a Yankee dryer machine, etc.
Either neutral paper or base paper made by alkaline papermaking may be used. Needless to say, a medium base paper containing mechanical pulp and a base paper containing recovered waste paper pulp can also be used. Also, using a size press, a bill blade, a gate roll coater, or a pre-metalling size press, pre-coat one or more layers of base paper pre-coated with starch, polyvinyl alcohol, etc., or a coating liquid containing pigment and adhesive. Coated base paper that has been processed can also be used.

As a method for drying the wet coating layer, various methods such as a steam heating cylinder, a heated hot air dryer, a gas heater dryer, an electric heater dryer, an infrared heater dryer and a high frequency heater dryer are used alone or in combination. .

In the present invention, as described above, a coating solution containing a copolymer latex having a glass transition temperature of -20 to 20 ° C. is applied and dried, and then subjected to pressure finishing with a high-temperature calender at 100 ° C. or higher. However, such a calender includes a high-temperature soft nip calender having a smaller number of nips than a super calender and capable of finishing at a high speed using an elastic roll and a metal roll having high hardness.

In a high temperature soft nip calender, not only temperature but also nip residence time are important. From this point, the actual operation is such that the equivalent roll diameter is 300 mm or more, and the Shore D hardness of the elastic roll is 80 to 100 (preferably 85 to 95). Min, linear pressure 100-400kg
/ Cm, the calendering nip number 2 nip or more at a calender pre-coated paper moisture of 5 to 8%. still,
The roll equivalent diameter refers to the equivalent diameter of a roll (AV lons et al., 1990) expressed by AV Lyons et al. (1990 TAPPI Finishing and Converting, P5).

(Roll equivalent diameter) = (soft roll diameter) ×
(Chill roll diameter) / {(Soft roll diameter) + (Chill roll diameter)}

[0027]

The present invention will be described in more detail with reference to the following examples, but it is needless to say that the present invention is not limited to these examples. Unless otherwise specified, parts and% in the examples indicate% by weight, respectively. The obtained coated paper for gravure printing was tested based on the following evaluation method.

[White Paper Gloss] Measured according to JIS P8142.

[Printed surface glossiness] Using a Ministry of Finance type gravure printing machine, printing speed 40 m / min, printing pressure 10 kgf / c
m, and the surface of the obtained printed matter is JIS P81
42.

[Dot Reproducibility] The dot missing rate of the coated paper printed by the gravure printing method described above was visually evaluated.

：: extremely good, ：: good, Δ: slightly poor, ×: poor [Stiffness] The stiffness was measured based on JIS P 8143, and the evaluation was carried out according to the following criteria.

：: extremely good, ：: good, Δ: slightly poor, ×: poor [Coating layer surface strength] 0.4 cc of SMX tack grade 15 (manufactured by Toyo Ink Mfg. Co., Ltd.) was evenly spread on a rubber roll, and RI After printing using a printing machine, backing was performed, and the peeled state was visually evaluated according to the following criteria.

◎: extremely good, ：: good, Δ: slightly inferior, ×: inferior [Opacity] Opacity was measured based on JIS P 8138. [Calendar stain and blocking] Calender metal roll surface and after calendering The degree of blocking of the winding was visually evaluated based on the following criteria.

◎: extremely good, ：: good, Δ: slightly poor, ×: poor [Example 1] [Preparation of coating liquid] First-class kaolin (U manufactured by Engelhard Co., Ltd.)
W-90), 10 parts of secondary kaolin (Hydrapers, manufactured by Huber) and 20 parts of fine heavy calcium carbonate (FMT-90, manufactured by Fimatec), and 20 parts of polyacrylic acid as a dispersant. Add 0.2 parts of soda and disperse with a Serie mixer.
Was prepared. 0.2 parts of a non-associative acrylic synthetic water retention agent (Alco Gum L-37 manufactured by Alco Chemical Co., Ltd.) and a non-thickening styrene-butadiene copolymer latex A (glass transition) were added to the pigment slurry thus obtained. (Temperature -10 ° C), and 4 parts of water were further added to obtain a coating liquid having a concentration of 63%. [Base Paper] A medium paper having a basis weight of 42 g / m ² was used as a coating base paper.

[Manufacture of Coated Paper] The above-mentioned base paper was coated with the above-mentioned coating liquid by a blade coater at a coating speed of 800 m / min such that the coated amount per side was 12 g / m ^{2 in} dry weight. Both sides were coated and dried so that the paper moisture became 5.5%.

[Calendar] Then, the roll equivalent diameter is 30.
0 mm, metal roll surface temperature 150 ° C., elastic roller Shore D hardness 85, paper passing speed 500 m / min, linear pressure 90 kg
The coated paper was obtained by performing a calendering treatment with a soft nip calender under the condition of 2 nips / calender nip.

Example 2 In the preparation of the coating solution of Example 1, non-thickening styrene / butadiene copolymer latex A (glass transition temperature -10 ° C.) was replaced with 4 parts of non-thickening Type styrene-butadiene copolymer latex B
(Glass transition temperature: 15 ° C.) Coated paper was obtained in the same manner as in Example 1 except that the amount was changed to 7 parts.

[Example 3] In the preparation of the coating liquid of Example 1, a method similar to that of Example 1 was used except that hydroxyethyl cellulose was used as a water retention agent instead of the non-associative acrylic synthetic water retention agent. A coated paper was obtained.

Example 4 The preparation of the coating liquid of Example 1 was repeated except that the amount of half of the non-associative acrylic synthetic water retention agent was changed to hydroxyethyl cellulose as the water retention agent. Coated paper was obtained in the same manner as in Example 1.

[Example 5] A pigment composed of 60 parts of fine heavy calcium carbonate (FMT-90, manufactured by Fimatec) and 40 parts of secondary kaolin (Hydrapers, manufactured by Huber) was used as a dispersing agent. Acid soda 0.2
Was added and dispersed with a Serie mixer to prepare a pigment slurry having a solid content of 70%. 10 parts of styrene-butadiene copolymer latex C (glass transition temperature: 20 ° C.) and 5 parts of oxidized starch (M-210, manufactured by Shikishima Starch Co., Ltd.) were added to the pigment slurry thus obtained, and water was further added. A coating solution having a concentration of 63% was obtained. This coating solution is applied to a medium-quality base paper having a basis weight of about 42 g / m ² ,
An undercoating base paper was obtained by performing double-side coating with a blade coater so that the dry weight was 4 g / m ² , and this was used as a coating base paper, and the coating liquid of Example 1 was applied to the upper layer at 8 g / m ² . Except for the above, a coated paper was obtained in the same manner as in Example 1.

Comparative Example 1 The preparation of the coating liquid of Example 1 was repeated except that the number of non-thickening styrene / butadiene copolymer latex A was changed to 2.5 parts.
A coated paper was obtained in the same manner as described above.

Comparative Example 2 The same procedure as in Example 1 was carried out except that the number of non-thickening styrene / butadiene copolymer latex A was changed to 12 parts in the preparation of the coating liquid of Example 1. A coated paper was obtained by the method.

Comparative Example 3 In the preparation of the coating solution of Example 1, the glass transition point was changed to a non-thickening type styrene / butadiene copolymer latex A having a glass transition point of -10 ° C. Example 1 except that the styrene / butadiene copolymer latex D for gravure at -40 ° C was changed.
A coated paper was obtained in the same manner as described above.

[Comparative Example 4] In preparing the coating solution of Example 1, the glass transition point was changed to 25 instead of the non-thickening type styrene-butadiene copolymer latex having a glass transition point of -10 ° C. A coated paper was obtained in the same manner as in Example 1 except that the temperature was changed to styrene / butadiene copolymer latex E at ℃.

Comparative Example 5 A coated paper was obtained in the same manner as in Example 1 except that the roll temperature of the soft calender of Example 1 was changed to 80 ° C.

Comparative Example 6 The procedure of Example 1 was repeated, except that the calendering was performed with a super calendar at a roll temperature of 70 ° C., 4 nips, a calender linear pressure of 200 kg / cm, and a paper passing speed of 10 m / min. A coated paper was obtained in the same manner as in Example 1.

Table 1 shows the above results.

[0048]

[Table 1]

[0049]

According to the constitution of the present invention, excellent white paper which is free from calendar stains during operation, excellent in gloss, high in rigidity, free from blocking during winding, has a low dot loss rate in gravure printing, and is particularly excellent. Coated paper for gravure printing having quality and printability can be efficiently obtained.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-53994 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) D21H 19/00-27/42

Claims (2)

(57) [Claims] 1. A coated paper for gravure printing obtained by applying and drying a coating liquid containing a pigment and an adhesive on a base paper, wherein the adhesive has a glass transition temperature of -20 to 20 ° C. The combined latex is used as a solid, and
A coated paper for gravure printing, containing 10 to 10 parts by weight, and finishing the obtained coated paper by passing it through a high-temperature calender comprising an elastic roll and a metal roll heated to 100 ° C. or higher. 2. The coated paper for gravure printing according to claim 1, wherein the coating liquid contains an acrylic synthetic water retention agent and / or hydroxyethyl cellulose.