JP2010070872A - Coated paper - Google Patents

Abstract

The present invention provides a coated paper excellent in printing quality such as water-absorbing fleshing property, opacity after printing, and printing workability such as blanket piling and blanket dirt.
In a coated paper obtained by applying and drying a coating liquid composition containing a pigment, an adhesive, and a ketene dimer surface sizing agent on at least one surface of a base paper, the coating liquid composition Further contains a crosslinking agent, the adhesive contains at least a water-soluble polymer, and the blending ratio of each component of the coating liquid composition is 10 to 10 parts by mass in terms of solid content with respect to 100 parts by mass of the pigment. 300 parts by mass, 0.05 to 10 parts by mass of a ketene dimer surface sizing agent, and 0.0005 to 90 parts by mass of a crosslinking agent.
[Selection figure] None

Description

  The present invention relates to a coated paper whose surface is coated on various types of paper and paperboard. In particular, the present invention relates to a coated paper excellent in printing quality such as water-absorbing fleshing property, opacity after printing, and printing workability such as blanket piling and blanket dirt.

  Offset printing is the mainstream of recent commercial printing, including newsprint printing. Offset printing is a method in which a printing plate, usually called a PS plate, is prepared and dampening water and ink are supplied to the printing plate for printing. The printing plate is a lithographic plate, and the image area on the printing plate is treated to have an oleophilic surface, and the non-image area is treated to have a hydrophilic surface. When dampening water and ink are supplied to the printing plate, ink is attached to the image area and water is attached to the non-image area, and the ink is transferred from the printing plate to the paper through the blanket for printing. can do.

In this offset printing, an ink having a relatively strong tack is used, so that a strong surface strength is required. In particular, since dampening water adheres to the paper surface, it is required to have water resistance and to maintain a strong surface strength even when wet.
When paper having a surface with a weak surface strength is used, a pigment component coated on the paper surface may be eluted, and a phenomenon in which pigment or the like (pyringed material) accumulates on the blanket (blankette piling) may occur. Further, when the amount of the piled material increases, the ink may not be transferred well on the blanket, and there may be a trouble that causes a phenomenon that the printing portion is distorted (print surface blemishes).
With the introduction of color printing, where wetting with fountain solution is required multiple times, the demand for surface strength has become increasingly severe. In offset printing, a water film is formed on the surface of the blanket and the printing paper, and there is a case where a phenomenon that hydrophobic ink is difficult to be deposited (deterioration of water absorption property) may be observed. This phenomenon is particularly likely to occur in the case of color printing that requires multiple dampening with dampening water.

  In recent years, there has been a demand for weight reduction (low basis weight) for newsprint. In the case of low basis weight paper, there may be a phenomenon in which the printing on the front side can be seen through from the back side (back through). This phenomenon is particularly likely to occur in color printing in which a large amount of ink is applied to the same surface of the paper. Therefore, the development progress of paper that can maintain opacity, especially high opacity after printing, even at low basis weights. The demand is getting stronger.

  Thus, a technology for increasing the water resistance and surface strength of a newspaper by using calcium carbonate as a filler and applying a clear coating of a ketene dimer sizing agent has been disclosed (Patent Document 1). However, when a filler that provides sufficient opacity is used, the bond between pulps is hindered, resulting in a decrease in rigidity, resulting in deterioration in printing workability and inability to obtain an appropriate size. Have

  In addition, in order to improve troubles related to printing quality and printing workability such as water absorbability, post-printing opacity, blanket piling, etc., surface treatment agents consisting of surface sizing agents such as pigments, adhesives, alkyl ketene dimers, etc. Although the technique to apply | coat is disclosed (patent document 2), the size effect is inadequate and the effect of reducing the trouble which produces a stain | pollution | contamination on a blanket or a plate is low.

  Furthermore, a technique for providing a pigment coating layer made of a surface sizing agent such as a pigment, an adhesive, or an alkyl ketene dimer in a specific amount in order to achieve both water resistance and printability in a coated paper is disclosed. (Patent Document 3) is insufficient in the effect of improving water resistance and adversely affects the stickiness during printing.

Under the circumstances as described above, there has been a strong demand for the development of a coated paper excellent in printing quality such as water-absorbing property, opacity after printing, and printing workability such as blanket piling and blanket dirt.
Japanese Patent No. 2980833 JP 2006-169706 A JP 2005-105428 A

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a coated paper excellent in print quality and print workability.

The present invention includes the following inventions.
(1) In a coated paper obtained by applying and drying a coating liquid composition containing a pigment, an adhesive, and a ketene dimer surface sizing agent on at least one surface of a base paper, the coating liquid composition is: Furthermore, it contains a crosslinking agent, the adhesive contains at least a water-soluble polymer, and the blending ratio of each component of the coating liquid composition is 10 to 300 in terms of solid content with respect to 100 parts by mass of the pigment. Coated paper containing 0.05 to 10 parts by mass of a ketene dimer surface sizing agent and 0.0005 to 90 parts by mass of a crosslinking agent.

(2) The coated paper according to (1), wherein the water-soluble polymer is at least one selected from starch, casein, and polyvinyl alcohol.

(3) The coated paper according to (1) or (2), wherein the reactive group of the crosslinking agent is at least one selected from a methylol group or a lower alkyl compound thereof, an aldehyde group, an epoxy group, or an epihalohydrin group.

  In the coated paper of the present invention, the coating liquid composition applied to the base paper contains a specific amount of pigment, an adhesive containing at least a water-soluble polymer, a ketene dimer surface sizing agent, and a crosslinking agent. Thus, a coated paper having both high size, printing quality, and printing workability can be obtained.

  The present inventors diligently investigated the influence of various chemical substances on the phenomenon of sizing, printing quality, and printing workability in the presence of pigments on pigment-coated paper using a ketene dimer surface sizing agent. As a result, it was found that the size, printing quality, and printing workability were not deteriorated in the presence of a crosslinking agent and an adhesive containing at least a water-soluble polymer, and the present invention was completed.

  In the coating liquid composition using a ketene dimer sizing agent as a surface sizing agent with a pigment and an adhesive as main components, the present invention contains at least a water-soluble polymer as an adhesive, and further contains a crosslinking agent. A coating liquid composition capable of exhibiting high sizing properties on the coated paper is obtained. In addition, by applying the coating liquid composition to paper or paperboard, a coated paper having both high size and printing quality and good printing workability can be obtained while ensuring workability in the papermaking process. be able to. Since the present invention suppresses the phenomenon that the effect of the ketene dimer surface sizing agent is reduced in the presence of a pigment that is indispensable for improving the printing quality, by crosslinking a water-soluble polymer, When the coated paper contains no pigment or ketene dimer sizing agent, the reduction phenomenon does not occur. The same applies to polymer-based sizing agents in which size reduction does not occur even in the presence of pigments.

  That is, with respect to 100 parts by mass of pigment, 10 to 300 parts by mass of an adhesive containing at least a water-soluble polymer in terms of solid content, 0.05 to 10 parts by mass of a ketene dimer sizing agent, and 0.0005 of a crosslinking agent. By applying and drying a coating liquid composition containing ˜90 parts by mass on a base paper, a coated paper satisfying simultaneously high sizing properties, printing quality, and good printing workability can be obtained. If the pigment is not contained in the coating liquid, sufficient print quality cannot be obtained. When the blending ratio of the adhesive is less than 10 parts by mass with respect to 100 parts by mass of the pigment, the surface strength is weak and the printing workability is poor. Become scarce. The preferable range of the blending ratio of the adhesive is 10 to 200 parts by mass, and more preferably 13 to 150 parts by mass. If the sizing agent is not contained in the coating solution, sufficient sizing and surface strength cannot be obtained, and a sizing and surface strength equivalent to that of the ketene dimer sizing agent can be obtained with a surface sizing agent other than the ketene dimer sizing agent. In this case, a large amount of sizing agent is required, which may cause oil sensitization and the printing plate may become dirty. Further, if the blending ratio of the ketene dimer surface sizing agent is less than 0.05 parts by mass with respect to 100 parts by mass of the pigment, sufficient sizing properties cannot be obtained, and if it exceeds 10 parts by mass, the friction coefficient of the coated paper is increased. As it becomes too low, the cost becomes too high and the practicality becomes poor. Furthermore, if the blending ratio of the cross-linking agent is less than 0.0005 parts by mass, the effect of improving the size property is insufficient, and if it exceeds 90 parts by mass, the coating is agglomerated, resulting in coating unevenness and a decrease in printing quality. Therefore, it is not preferable. Therefore, it is only possible to apply a coating liquid composition having an appropriate blending ratio of an adhesive, a ketene dimer surface sizing agent, and a crosslinking agent to the pigment specified in the present invention on paper or paperboard, and then drying it. Coated paper satisfying both printing performance, printing workability, and good printing quality can be obtained.

  In the present invention, the pigment used in the coating liquid composition is not particularly limited. For example, heavy calcium carbonate, light calcium carbonate, kaolin, calcined kaolin, deramikaolin, talc, barium sulfate, zinc oxide , Magnesium carbonate, magnesium oxide, alumina, silica, magnesium aluminosilicate, particulate calcium silicate, particulate magnesium carbonate, particulate light calcium carbonate, white carbon, bentonite, zeolite, sericite, smectite, satin white, aluminum hydroxide, Known and publicly used pigments such as titanium oxide and plastic pigments are appropriately used.

The water-soluble polymer contained in the coating liquid composition used in the present invention needs to contain at least one of starch, casein, and polyvinyl alcohol. One or more kinds of adhesives other than the adhesive may be used in combination. Starch contained in the coating liquid composition used in the present invention is not particularly limited, starch purified from natural plants, hydroxyethylated starch, oxidized starch, etherified starch, esterified starch, cationized Examples include starch, hydrophobized starch, phosphate esterified starch, enzyme-modified starch, and cold water soluble starch obtained by flash drying them. Further, casein is not particularly limited when contained in the coating liquid composition used in the present invention, but milk casein is a representative example. Furthermore, the polyvinyl alcohol contained in the coating liquid composition used in the present invention is not particularly limited, but those having a degree of polymerization of about 200 to 5,000 and those having a partially saponified adhesive strength and operation. It is often used because of its good balance of properties, and the modified types include acetoacetyl-modified polyvinyl alcohol, cationized modified polyvinyl alcohol, sulfonated modified polyvinyl alcohol, carboxy modified polyvinyl alcohol, mercaptan modified polyvinyl alcohol, amino group modified polyvinyl alcohol, Examples include epoxy-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, long-chain alkyl ether-modified polyvinyl alcohol, and silicon-modified polyvinyl alcohol. Examples of adhesives other than starch, casein, and polyvinyl alcohol include soy protein, carboxymethyl cellulose, dextrin, mannan, chitosan, arabinogalactan, glycogen, inulin, pectin, hyaluronic acid, hydroxyethyl cellulose, and other natural polysaccharides and oligomers thereof. And derivatives thereof, natural proteins such as gelatin collagen and derivatives thereof, synthetic polymers and oligomers such as polylactic acid and peptides, sodium polyacrylate, polyethylene oxide, and polyacrylamide.
The proportion of the water-soluble polymer adhesive in the adhesive used in the present invention is preferably 5 to 100% by mass, and more preferably 10 to 100% by mass.

  Examples of the adhesive used in combination with the water-soluble polymer adhesive include a styrene-butadiene copolymer, an acrylonitrile-butadiene copolymer, a methyl methacrylate-butadiene copolymer, an alkyl acrylate copolymer system, Examples include various (co) polymer latexes such as polyvinyl acetate and ethylene-vinyl acetate. Among them, styrene-butadiene copolymers, acrylonitrile-butadiene copolymers, methyl methacrylate-butadiene copolymers Synthetic latexes such as are preferably used. The latex preferably has a glass transition temperature (hereinafter referred to as Tg) of −50 to 20 ° C. Latex in this Tg range develops tackiness at room temperature and has good adhesion to pigments and / or fillers, but has very low molecular polarity and adhesion to strongly hydrophilic cellulose fibers. Since it is difficult to produce, it is used in combination with water-soluble polymers such as starch having high adhesive strength with cellulose fibers, and only water-soluble polymers have the function of covering the adhesive strength to weak pigments and / or fillers. In the case of the coating liquid composition as in the present invention, the effect of mutual action of the latex and the water-soluble polymer is greatly affected. Here, the latex is preferably a core-shell type. In the case of a low Tg latex, the film-forming property is high, and since it is rubbery even at room temperature, it is easy to develop tackiness and has a high ability to adhere a pigment. However, it is easy to stick to the blanket and printing troubles are likely to occur. On the other hand, the high Tg latex has a low adhesion strength to the pigment, but it is difficult to cause nepari. The core-shell type latex has a high Tg shell and a low Tg core. In this structure, the adhesive strength of the pigment can be improved by good film-forming properties and tackiness derived from the Tg of the core, while suppressing Nepari, which greatly affects the physical properties of the surface layer of latex particles. The Tg of the shell is preferably 0 to 20 ° C, and the Tg of the core is preferably -50 to 0 ° C. If the Tg of the shell is less than 0 ° C., the tackiness is too strong, so that there is a possibility that nepari is likely to occur, and if it exceeds 20 ° C., the adhesion strength to the pigment may be reduced. If the core Tg is less than −50 ° C., the amount of styrene, which is a strong water-repellent component, decreases, so there is a possibility that the water absorbability during printing will be deteriorated. , There is a risk that strength developability deteriorates. In addition, the same effect can be obtained with a latex called a concentration gradient type in which the composition from the inside to the outside of the particle continuously changes, but the core-shell type is more preferable because the influence of Tg control appears more clearly. .

The ketene dimer surface sizing agent used in the present invention is classified into a waxy state and a liquid state. When the hydrocarbon group of the ketene dimer surface sizing agent is linear, it generally becomes a wax. When the chain length is shortened, even a straight chain becomes liquid, but a sufficient size effect cannot be obtained. The waxy ketene dimer surface sizing agent has a melting point of room temperature or higher, and is generally used in a state where the temperature of the coating liquid composition is 50 to 60 ° C. Wax-like ketene dimer surface sizing agents have a very high sizing effect and a lower friction coefficient than liquids. However, if the temperature of the coating liquid composition decreases due to a paper machine or coater being stopped due to paper breakage, etc. Is likely to occur and is difficult to handle. Therefore, the wax-like ketene dimer surface sizing agent is preferably used in combination with a surfactant such as a polymer sizing agent or a dispersing agent as a dispersing agent or wetting agent. When the hydrocarbon group of the ketene dimer surface sizing agent is branched, the ketene dimer surface sizing agent generally becomes liquid. When the chain length is long, it becomes branched or waxy, but when the chain length is kept liquid, a sufficient size effect can be obtained. The liquid ketene dimer surface sizing agent has a melting point of less than 10 ° C. and does not easily wrinkle even when the temperature of the coating liquid composition is lowered, and can be easily used alone as a sizing agent. When doing so, the decrease in size is significant. Therefore, the ketene dimer surface sizing agent is preferably in the form of wax rather than liquid.
Ketene dimer surface sizing agents include alkyl ketene dimer surface sizing agents in which the hydrocarbon group is a saturated hydrocarbon and alkenyl ketene dimer surface sizing agents in which the hydrocarbon group is an unsaturated hydrocarbon. Since the agent is inferior in size effect to the alkyl ketene dimer surface sizing agent by about 10%, the alkyl ketene dimer surface sizing agent is more desirable than the alkenyl ketene dimer surface sizing agent. Needless to say, two or more of these ketene dimer surface sizing agents can be used in combination.

  Furthermore, it is possible to use a surface sizing agent other than the ketene dimer surface sizing agent as the surface sizing agent. In the case of a waxy ketene dimer surface sizing agent, it is preferable to use it together with a polymer surface sizing agent. Examples of the surface sizing agent other than the ketene dimer surface sizing agent include reinforced rosin, rosin emulsion, alkenyl succinic anhydride type, and polymer type sizing agent. One of the constituent elements of the copolymer has a low degree of hindering the intermolecular bonding of water-soluble polymers used as adhesives, and does not reduce the water resistance of water-soluble polymers, and the Nepari phenomenon Is also preferable. On the other hand, the styrene-based surface sizing agent improves the surface contact angle and improves the water absorbability, but printing troubles such as sensitization of the printing plate are likely to occur.

The sizing agent having the olefinically unsaturated monomer as one of the constituent elements of the copolymer includes a hydrophobic unsaturated monomer and a carboxyl group-containing unsaturated monomer or a salt thereof as main constituent elements. A polymer, which contains an olefin monomer as a hydrophobic unsaturated monomer. The proportion of the olefinically unsaturated monomer in the hydrophobic monomer is preferably 60 to 100 mol%, more preferably 90 to 100 mol%.
Examples of the carboxyl group-containing unsaturated monomer include (meth) acrylic acid, maleic acid, maleic acid half ester, itaconic acid, itaconic acid half ester, citraconic acid, and fumaric acid.

The molar ratio of the hydrophobic unsaturated monomer to the carboxyl group-containing unsaturated monomer is not particularly limited, but the hydrophobic unsaturated monomer is 99.5 mol% or more, the carboxyl group-containing unsaturated monomer is If it is less than 0.5 mol%, printing troubles may occur, and if the carboxyl group-containing unsaturated monomer exceeds 3 mol%, the size effect is lowered, which is not preferable.
A mass average molecular weight as a polymer-based sizing agent is preferably in the range of 10,000 to 50,000 in view of the balance between size and operability. A material having a mass average molecular weight exceeding 50,000 is not preferable because it easily forms a complex with starch among the adhesives and easily causes printing trouble. In addition, those having a mass average molecular weight of less than 10,000 are not preferable because the size effect is hardly exhibited.

  The crosslinking agent used in the present invention is not particularly limited. For example, the reactive group is a methylol group or a lower alkylated product thereof, a monoaldehyde group, an epoxy group, an epihalohydrin group, an oxazoline group, an aziridinyl group, an isocyanate group, Examples thereof include a carbodiimide group, a vinyl ether group, a cyclocarbonate group, an alkoxysilane group, an alkylenediamine group, a dialdehyde group, a divalent metal salt or a trivalent metal salt, and oxides thereof.

  Among these, the reactive group is preferably a methylol group or a lower alkylated product thereof, an aldehyde group, an epoxy group, and / or a halohydrin group. A single crosslinking agent may contain a plurality of reactive groups.

  Examples of cross-linking agents having a methylol group or a lower alkylated product thereof as a reactive group include urea-formaldehyde resin, melamine-formaldehyde resin, polyamide polyurea-formaldehyde resin, alkylated methylol urea, alkylated methylol melamine, acetoguanamine, Examples thereof include condensates of benzoguanamine and formaldehyde.

  Examples of the crosslinking agent having a monoaldehyde group as a reactive group include formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde and the like, and examples of the crosslinking agent having a dialdehyde group include glyoxal, dialdehyde starch, and cyclic urea. -Glyoxal reactant, acrylamide-glyoxal reactant copolymer, malondialdehyde, succindialdehyde, glutardialdehyde, maleindialdehyde, phthaldialdehyde and the like.

  Examples of crosslinking agents having an epoxy group or an epihalohydrin group as a reactive group include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol diglycidyl ether, Diglycidylaniline, diglycidylamine, bisphenol A type diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, trimethylolpropane polyglycidyl ether, sorbitol polyglycidyl ether, sorbitan polyglycidyl ether, polyglycerol polyglycidyl ether , Polyamide-epoxy resin, epichlorohydrin, epibromohydrin, epiyo Hydrin, beta-methyl epichlorohydrin, beta-methyl epibromohydrin, beta-methyl-epi-iodo epichlorohydrin, polyamide epichlorohydrin.

  Examples of the crosslinking agent having an oxazoline group as a reactive group include 2,2′-bis- (2-oxazoline), 2,2′-methylene-bis- (2-oxazoline), 2,2′-ethylene- Bis- (2-oxazoline), 2,2′-trimethylene-bis- (2-oxazoline), 2,2′-tetramethylene-bis- (2-oxazoline), 2,2′-hexamethylene-bis- ( 2-oxazoline), 2,2'-octamethylene-bis- (2-oxazoline), 2,2'-ethylene-bis- (4,4'-dimethyl-2-oxazoline), 2,2'-p- Phenylene-bis- (2-oxazoline), 2,2'-m-phenylene-bis- (2-oxazoline), 2,2'-m-phenylene-bis- (4,4'-dimethyl-2-oxazoline) Bis- (2-oxa Sulfonyl cyclohexane) sulfide, bis - (2-oxa Zoni Runoru norbornane) sulfide, and the like.

  Examples of the crosslinking agent having an aziridinyl group as a reactive group include 1- (methylene-di-p-phenylene) bis-3,3-aziridinylurea, 1,1 ′-(hexamethylene) bis-3,3- Examples thereof include aziridinyl urea, ethylene bis- (2-aziridinyl propionate), 2,4,6-triaziridinyl-1,3,5-triazine and the like.

  Examples of cross-linking agents having an isocyanate group as a reactive group include tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, xylylene diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate and the like, and block these isocyanates Examples thereof include blocked products blocked with an agent. Examples of the blocking agent include phenol, ε-caprolactam, methyl ethyl ketoxime, active methylene compound, and the like.

  Specific examples of the divalent metal salt or trivalent metal salt and oxides thereof include magnesium, calcium, aluminum, iron, nickel and oxides thereof.

  It goes without saying that a crosslinking agent having a reactive group other than the above, such as an ethyleneimine group or a peroxide, can be used and can be used in combination.

  In addition, the coating liquid composition of the present invention further includes auxiliary agents for general coating liquid compositions such as antifoaming agents, slime control agents, water retention agents, lubricants, preservatives, thickeners, and dyes. It can be blended.

  As a method for producing the coating liquid composition of the present invention, a publicly known production method is appropriately used. For example, a pigment slurry is prepared by adding a dispersant to the pigment and dispersing it with a Coreless disperser. Subsequently, an adhesive and a ketene dimer surface sizing agent are added to the pigment slurry, followed by stirring and mixing. Finally, a cross-linking agent is added and sufficiently stirred and mixed to obtain a coating liquid composition used in the present invention. The order of adding these materials may be changed as appropriate.

In the coated paper according to the present invention, the base paper to which the coating liquid composition is applied is such as electrophotographic paper, printing / writing / graphic paper such as inkjet paper, newsprint paper, packaging paper, thin paper, hybrid paper, etc. It is a broad concept including ordinary thin paper, paperboard, cardboard and the like.
As pulp constituting such base paper, chemical pulp such as kraft pulp, sulfite pulp and soda pulp made from wood chips, semi-chemical pulp such as semi-chemical pulp, chemimechanical pulp, mechanical pulp such as thermomechanical pulp, Or, non-wood fiber pulp made from cocoon, sanjo, hemp, kenaf, etc., deinked pulp made from waste paper, etc. can be exemplified, and at least one of these, or two or more of these can be used as appropriate can do. In addition, although it does not specifically limit about the bleaching method at the time of manufacturing said chemical pulp, ECF pulp bleached without using molecular chlorine like chlorine gas at a bleaching process, Furthermore, like chlorine dioxide TCF pulp bleached without using a chlorine-based compound is preferably used from the viewpoint of environmental conservation.

It is preferable to mix | blend the compounding quantity of the filler mix | blended in the base paper used in this invention so that the filler amount which a base paper contains may be about 1-20 mass% of a base paper.
In addition, when amorphous silica or amorphous silicate is used alone or in combination with other fillers, it is preferable to blend so that amorphous silica or amorphous silicate is 1 to 10% by mass of the base paper mass. . When amorphous silica or amorphous silicate is used in combination with other fillers, it is preferably used in combination so that the total amount of filler is 15% by mass or less of the atomic mass.

  The base paper used in the present invention includes, in addition to these fillers, papermaking chemicals used in ordinary acidic papermaking and neutral papermaking, such as rosin sizing agent, reinforced rosin sizing agent, emulsion sizing agent, alkyl ketene dimer, etc. A sizing agent, a sizing agent fixing agent, a dry paper strength enhancer, a yield improver, a drainage improver, a water resistant agent, an antifoaming agent, a slime control agent, a dye and the like are added as necessary.

In the present invention, the pulp, filler, and paper material obtained by appropriately blending various papermaking chemicals are used as a long net machine, a round net machine, a long net and round net combination machine, a twin wire machine, an on-top twin. A base paper having a basis weight of about 30 to 150 g / m ² obtained by making paper with various paper machines such as a wire machine and a gap former machine is used.

  The pH of the base paper can be acidic or neutral, but neutral is preferable because the size effect is good. Also, using a size press, bill blade, gate roll coater, pre-metering size press, etc., one layer of base paper pre-coated with starch, polyvinyl alcohol, etc., or a coating liquid containing pigment and adhesive Precoated base paper can also be used.

In the coated paper of the present invention, the coating amount of the coating liquid composition is not particularly limited, but the single-side coating amount is preferably 0.5 to 20 g / m ^2, more preferably 0.8. 6-10 g / m ² . When the coating amount on one side is less than 0.5 g / m ² , the effect of improving the sizing property, printing workability, and printing quality obtained by applying the coating liquid composition is small, and when it exceeds 20 g / m ² Printing workability may be reduced.

  In the present invention, the apparatus for applying the coating liquid composition to the base paper is not particularly limited. For example, an ink line or a part-to-roll size press, a blade metalling size press, a rod metalling size press. Roll coaters such as gate roll coaters, trailing, flexible, roll applications, fountain applications, bevel type and vent type blade coaters such as short dwells, rod blade coaters, bar coaters, air knife coaters, curtain coaters, spray coaters, A publicly known apparatus such as a gravure coater is appropriately used. Moreover, you may apply by any of on-machine coating and off-machine coating. In addition, as a method of drying the wet coating layer after coating with a coating liquid composition, various systems, such as vapor drying, gas heater drying, electric heater drying, infrared heater drying, etc., are employable, for example.

  The coated paper of the present invention is coated with a coating liquid composition, dried and then smoothed by various calendar devices. Examples of the calendar device include a super calender and a soft calender. Generally used calendar devices such as a gloss calendar, a compact calendar, a mat super calendar, and a mat calendar are used as appropriate. As the calender finishing conditions, the temperature of the rigid roll, the calender pressure, the number of nips, the roll speed, the moisture before the calender, etc. are appropriately selected according to the required quality. Furthermore, the calendar device has an off type that is different from the coater and an on type that is integrated with the coater, but can be used in either case. The material of the calendar apparatus to be used is a roll that is mirror-finished with a metal or hard chrome plating on the surface of the rigid roll. As the elastic roll, a roll obtained by molding a resin roll such as urethane resin, epoxy resin, polyamide resin, phenol resin, polyacrylate resin, cotton, nylon, aramid resin or the like is used as appropriate. In addition, it is also possible to use a suitable combination of a water coating device, an electrostatic humidifier, a steam humidifier, and the like for humidity control and humidification of the coated paper after finishing with a calendar.

  As described above, the coated paper obtained by coating the coating liquid composition of the present invention has high sizing properties and printing quality, and it is possible to obtain good printing workability.

The present invention will be specifically described below with reference to examples. Of course, the present invention is not limited to these examples. Moreover, unless otherwise indicated, the part and% in an example show a mass part and mass%, respectively.
The following physical properties of the coated paper obtained in the following examples were measured, and the results are shown in Tables 1 to 4.

(Grease-sensitized)
The coated paper obtained in each example and comparative example is attached to a printing plate wet with tap water, and air-dried until it peels off naturally. After the coated paper is peeled off, the offset printing ink diluted 4 times with kerosene (Leo Echo Y manufactured by Toyo Ink Mfg. Co., Ltd.) is applied and lightly rinsed with tap water. The darkness of the ink remaining in the place where the coated paper was pasted was visually evaluated. Evaluation was performed by the following three-step evaluation.
<Evaluation criteria>
○: Almost no ink is observed on the printing plate, or even if it is recognized, there is no practical problem.
(Triangle | delta): Ink is recognized by a printing plate and there exists a problem practically.
X: The ink remains dark on the printing plate, and there is a problem in practical use.

(Coating unevenness)
About the coated paper obtained by each Example and the comparative example, the presence or absence of the coating nonuniformity of the coated paper surface was evaluated visually.
<Evaluation criteria>
○: Coating unevenness is hardly observed on the coated paper surface, or even if recognized, there is no practical problem.
(Triangle | delta): The coating nonuniformity is recognized by the coated paper surface, and there exists a problem practically.
X: Many coating unevenness is recognized on the coated paper surface, and there is a problem in practical use.

(Blanket dirt)
The coated paper obtained in each of the examples and comparative examples was printed in black using an offset rotary press (manufactured by Toshiba Machine Co., Ltd.) on which an aluminum plate made with a drawing rate of 10% (area ratio) was set. After printing 5000 copies, the stain on the blanket non-image area was visually evaluated. Evaluation was performed by the following five-step evaluation.
<Evaluation criteria>
5: Almost no dirt is observed.
4: Slight dirt is recognized.
3: Slight adhesion is observed, but there is no practical problem.
2: Dirt has adhered.
1: Dirt is significantly attached.
Those with an evaluation of less than 3 have practical problems.

(Initial contact angle)
About 1.0 second after 4.0 microliters of ion-exchange water was dripped about the coated paper obtained by each Example and the comparative example in 23 degreeC50% RH atmosphere with Dynamic Absorption Tester1100 (made by Fibro). The dynamic contact angle of was measured.

(Inking)
The coated paper obtained in each example and comparative example was printed at a speed of 600 rpm using an offset printing ink (manufactured by Toshiba Machine Co., Ltd.) and offset printing ink (Reo Echo Y manufactured by Toyo Ink Co., Ltd.). The ink printability of the obtained printed matter was visually evaluated in four stages.
<Evaluation criteria>
：: Very good ○: Excellent △: Somewhat problematic ×: There is a problem Note that evaluations of △ and × have practical problems.

(WET strength)
The coated paper obtained in each of Examples and Comparative Examples is cut into strips, and a sheet is prepared that is attached side by side on a sample mount (OK special art post 256 g / m ² ). In the RI printing tester (Ishikawajima Industrial Machinery Co., Ltd.), water was applied to the coated paper with a rubber roll dampened with wet gauze, and then immediately printed ink (SMX tack grade 15: manufactured by Toyo Ink Co., Ltd.) Was printed using 0.5 cc, and the degree of picking on the printed surface was visually evaluated. Evaluation was performed by the following five-step evaluation.
<Evaluation criteria>
5: No fiber is removed and no white spots occur.
4: The fibers are taken out very slightly, and the white spots are slightly seen (about 1 to 5 places).
3: A level where there is no problem in practical use although fibers are partially removed.
2: Fibers are observed on the entire surface, and the area ratio of white spots is less than 5%.
1: Fibers are observed on the entire surface, and the area ratio of white areas is 5% or more.
Those with an evaluation of less than 3 have practical problems.

(WET strength)
About the coated paper obtained by each Example and the comparative example, using the offset printing machine (Mitsubishi lithopia L-BT3-1100) which set the aluminum plate and blanket (DAY blanket 8891 by DAY international) only of a non-image part. Then, water printing was performed on all of the cylinders 1 to 4 without applying ink, and after 200 copies were printed, the water supply was stopped, and the degree of sticking of the coated paper to the blanket was visually evaluated. Evaluation was performed by the following five-step evaluation.
<Evaluation criteria>
5: No fiber removal occurs.
4: A very small amount of fiber was removed.
3: A level where there is no problem in practical use although fibers are partially removed.
2: Paper layer breakage occurred in part.
1: Paper layer breakage occurred on the entire surface.
Those with an evaluation of less than 3 have practical problems.

<Example 1>
Base paper: 10 parts by weight of softwood bleached kraft pulp, 20 parts by weight of thermomechanical pulp, and 70 parts by weight of deinked waste paper pulp are mixed and disaggregated. To the prepared pulp slurry, 0.5% of cationized starch (trade name: P3Y, manufactured by PIRAAB STARCH Co., Ltd.) per dry dry pulp and 2% of amorphous silica as a filler are added, and paper is made with a sulfuric acid band. The pH was adjusted to 6.5. The obtained paper stock was paper-made (basis weight: 40 g / m ² ) with a gap former type (MH former) paper machine. In addition, the said amorphous silica is an amorphous silica with an average particle diameter of 25 micrometers manufactured by the two-step neutralization reaction of a sodium silicate and a sulfuric acid, and it used it as a filler, without drying after manufacture.
Coating: As a coating solution composition, 100 parts by weight of light calcium carbonate (a) (trade name: TP-123, manufactured by Okutama Kogyo Co., Ltd.), oxidized modified corn starch (i) (trade name: Ace A, 133 parts by mass of Oji Cornstarch Co., Ltd., 5 parts by mass of a ketene dimer surface sizing agent (α) (trade name: SKS-2501, manufactured by Arakawa Chemical Co., Ltd.), a crosslinking agent having a methylol group as a reactive group ( A) (trade name: Sumirez Resin 633, manufactured by Taoka Chemical Co., Ltd.) 0.15 parts by mass in this order was stirred and mixed to prepare a pigment dispersion with a solid content concentration of 10%, and this coating solution composition objects in the base paper in an on-machine gate roll coater (manufactured by Mitsubishi Heavy Industries Co., Ltd.), the coating weight after drying was dried sided coating so that the per side 0.6 g / m ^2, a soft calender Go to a calender treatment at manufactured by Mitsubishi Heavy Industries, Ltd.), to obtain a coated paper.

<Example 2>
In the coating process, as a coating liquid composition, instead of the crosslinking agent (A) having a methylol group as a reactive group, a crosslinking agent having a lower alkylated product of a methylol group as a reactive group (trade name: Sumirez Resin 8% A coated paper was obtained in the same manner as in Example 1 except that AC was manufactured by Taoka Chemical Co., Ltd.

<Example 3>
In the coating process, as a coating liquid composition, a crosslinking agent having an aldehyde group as a reactive group instead of the crosslinking agent (A) having a methylol group as a reactive group (trade name: Sumirez Resin 5004, Taoka Chemical Co., Ltd.) A coated paper was obtained in the same manner as in Example 1 except that the product was manufactured by the company.

<Example 4>
In the coating process, instead of the crosslinking agent (A) having a methylol group as a reactive group, a crosslinking agent having an epoxy group as a reactive group (trade name: Sumirez Resin SPI-203 (50) H, Taoka Chemical Co., Ltd. A coated paper was obtained in the same manner as in Example 1 except that it was made.

<Example 5>
In the coating process, except that a crosslinking agent having an epihalohydrin group as a reactive group (trade name: WC-535, manufactured by Seiko PMC Co., Ltd.) instead of the crosslinking agent having a methylol group as a reactive group (A), A coated paper was obtained in the same manner as in Example 1.

<Example 6>
In the coating process, Examples were used except that 60 mass parts of casein (trade name: acid casein, manufactured by Nissei Kyoyoku Co., Ltd.) was used instead of 133 mass parts of the oxidized modified corn starch (i) as the coating liquid composition. In the same manner as in No. 1, coated paper was obtained.

<Example 7>
In the coating process, as a coating liquid composition, instead of the oxidized modified corn starch (i) 133 parts by mass, polyvinyl alcohol (trade name: Kuraray Poval PVA-103, manufactured by Kuraray Co., Ltd.) 45 parts by mass, A coated paper was obtained in the same manner as in Example 1.

<Example 8>
In the coating process, 5 parts by mass of oxidatively modified corn starch (i) instead of 133 parts by mass of oxidatively modified corn starch (i) as a coating liquid composition, a styrene-butadiene copolymer (core-shell type) (Product name: OJ1000H, manufactured by JSR Corporation) 8 parts by mass, 0.07 parts by mass of a ketene dimer surface sizing agent (α), and 0.001 part by mass of a crosslinking agent (A) having a methylol group as a reactive group Coated paper was obtained in the same manner as in Example 1 except that the parts were used.

<Example 9>
In the coating process, the coating liquid composition is coated on the base paper with an off-machine blade coater (Mitsubishi Heavy Industries, Ltd.) so that the coating amount after drying is 7 g / m ² per side and dried. A coated paper was obtained in the same manner as in Example 1 except that the calendar process was performed with a soft calendar (Mitsubishi Heavy Industries, Ltd.).

<Example 10>
In the papermaking process, the papermaking pH was adjusted to 5.8 with a sulfuric acid band, and in the coating process, the oxidized modified corn starch (i) was used instead of 133 parts by mass of the oxidized modified corn starch (i) as the coating solution composition. 50 parts by mass, polyvinyl alcohol (trade name: Kuraray Poval PVA-103, manufactured by Kuraray Co., Ltd.) is 40 parts by mass, and the crosslinking agent (A) having a methylol group as a reactive group is 65 parts by mass. In the same manner as in Example 1, a coated paper was obtained.

<Example 11>
A coated paper was obtained in the same manner as in Example 1 except that the papermaking pH was adjusted to 8.6 with a sulfuric acid band in the papermaking process.

<Example 12>
A coated paper was obtained in the same manner as in Example 1 except that in the paper making process, the pulp composition was bleached softwood and 5 parts by weight of kraft pulp and hardwood bleached and 95 parts by weight of kraft pulp.

<Example 13>
A coated paper was obtained in the same manner as in Example 1 except that, in the papermaking process, the coating solution composition was changed to 200 parts by mass of the oxidized modified corn starch (i).

<Example 14>
In the coating process, a coated paper was prepared in the same manner as in Example 1 except that kaolin (trade name: Milagros J, manufactured by Seal Co., Ltd.) was used instead of light calcium carbonate (a) as the coating liquid composition. Obtained.

<Comparative Example 1>
In the coating step, as a coating liquid composition, 133 parts by mass of oxidatively modified corn starch (i) and 5 parts by mass of a ketene dimer surface sizing agent (α) are added to 100 parts by mass of light calcium carbonate (a). To prepare a pigment dispersion with a solid content concentration of 10%, and this coating liquid composition is coated on a base paper with an on-machine gate roll coater (Mitsubishi Heavy Industries, Ltd.) and the coating amount after drying is one side. A coated paper was obtained in the same manner as in Example 1 except that both sides were coated and dried so as to be 0.6 g / m ² per unit.

<Comparative example 2>
In the coating step, a coated paper was obtained in the same manner as in Example 1 except that 0.0002 parts by mass of the crosslinking agent (A) having a methylol group as a reactive group was used as the coating liquid composition.

<Comparative Example 3>
In the coating step, a coated paper was obtained in the same manner as in Example 1 except that the coating solution composition was 200 parts by mass of the crosslinking agent (A) having a methylol group as a reactive group.

<Comparative example 4>
In the coating process, 40 parts by mass of a polymer surface sizing agent (trade name: PM-OT-25T, manufactured by Arakawa Chemical Industries, Ltd.) instead of the ketene dimer surface sizing agent (α) as the coating liquid composition. A coated paper was obtained in the same manner as in Example 1 except that.

<Comparative Example 5>
In the coating process, 100 parts by mass of oxidatively modified corn starch (i), 1 part by mass of a ketene dimer surface sizing agent (α) and 0.15 parts by mass of a crosslinking agent (A) having a methylol group as a reactive group are added in this order. The coating liquid composition was prepared by mixing and stirring at a coating paper composition, and the coating liquid composition was dried on an on-machine gate roll coater (manufactured by Mitsubishi Heavy Industries, Ltd.) on a base paper so that the coating amount after drying was 0.00. A coated paper was obtained in the same manner as in Example 1 except that both sides were coated and dried to 3 g / m ² .

<Comparative Example 6>
In the coating process, 15 parts of styrene-butadiene copolymer (core-shell type) (trade name: OJ1000H, manufactured by JSR Corporation) is used instead of 133 parts by mass of oxidized modified corn starch (i) as a coating liquid composition. Coated paper was obtained in the same manner as in Comparative Example 1 except that 0.07 parts by mass of the ketene dimer surface sizing agent (α) was used.

<Comparative Example 7>
In the coating step, a coated paper was obtained in the same manner as in Example 1 except that 5 parts by mass of the oxidized modified corn starch (i) was used as the coating liquid composition.

<Comparative Example 8>
In the coating step, coated paper was obtained in the same manner as in Example 1 except that the ketene dimer surface sizing agent (α) was changed to 0.03 parts by mass.

<Comparative Example 9>
In the coating step, a coated paper was obtained in the same manner as in Example 1 except that the coating liquid composition was changed to 500 parts by mass of the oxidized modified corn starch (i).

<Comparative Example 10> (corresponding to Example 1 of Japanese Patent No. 2980833)
Base paper: 5 parts by weight of stone grind pulp, 10 parts by weight of bleached softwood kraft pulp, 10 parts by weight of chemi-thermomechanical pulp, 15 parts by weight of thermomechanical pulp, 60 parts by weight of deinked waste paper pulp are mixed and disaggregated to prepare 0.7% of aluminum sulfate per dry pulp and 10% of calcium carbonate (trade name: Optical HP, manufactured by Imeris Co., Ltd., average particle size: 1.5 μm) were added to the pulp slurry. The obtained paper stock was made with a gap former type (MH former) paper machine.
Coating: Oxidized modified corn starch (trade name: SK-20, manufactured by Nippon Corn Starch Co., Ltd.) at a concentration of 9% as a surface treatment agent, and waxy alkylketene dimer (trade name: A-7, Arakawa Chemical Industries, Ltd.) The product is adjusted to a concentration of 0.9%, and the surface treatment agent is dried by a gate roll coater (Mitsubishi Heavy Industries, Ltd.) so that the coating amount of the surface treatment agent after drying is 0.14 g / m ² per side. The paper was coated on both sides and dried, and subjected to soft calendering under conditions of a nip pressure of 90 kg / cm ² , a temperature of 53 ° C., and a paper passing speed of 800 m / min to obtain a cold offset newsprint paper.

<Comparative example 11> (equivalent to Example 4 of JP-A-2005-105428)
In the coating process, as a surface treating agent, 20 parts by weight of primary kaolin (trade name: UW90, manufactured by Engelhard), 30 parts by weight of secondary kaolin (trade name: Kaoblite, manufactured by Seal), heavy calcium carbonate (Product name: FMT90, manufactured by Pfematic Co., Ltd.) 50 parts by mass, styrene-butadiene copolymer (core-shell type) (trade name: T-2500F, manufactured by JSR Corporation), 20 parts by mass, waxy ketene dimer surface This surface was adjusted to 3 parts by mass of a sizing agent (trade name: Size Pine K-910, manufactured by Arakawa Chemical Co., Ltd.) and 0.2 parts by mass of a dispersant (trade name: Aron T40, manufactured by Toa Gosei Chemical Co., Ltd.). Except that the treatment agent was coated on a gate roll coater (Mitsubishi Heavy Industries, Ltd.) and double-sided coated and dried so that the coating amount of the surface treatment agent after drying was 10 g / m ² per side. In the same manner as in No. 1, a newspaper printing paper for cold offset was obtained.

<Comparative example 12> (equivalent to Example 1 of JP-A-2006-169706)
In the coating process, cubic light calcium carbonate (trade name: Brilliant S15, manufactured by Shiroishi Kogyo Co., Ltd.) 100 parts by mass, oxidized modified corn starch (i) 80 parts by mass, polymer surface sizing agent Coated paper was obtained in the same manner as in Example 1 except that 3 parts by mass (trade name: PM-OT-25T, manufactured by Arakawa Chemical Industries, Ltd.) was used.

Examples 1 to 14 use starch, casein or polyvinyl alcohol, which is a water-soluble polymer, as an adhesive, mainly composed of a pigment and the adhesive, a ketene dimer surface sizing agent and a crosslinking agent (methylol group, methylol group). Lower alkylated product, aldehyde group, epoxy group or epihalohydrin group as a reactive group), so that the reduction in size and the sensitization of the printing plate are suppressed, and no cross-linking agent is contained. Compared with Example 1, the blanket stain suppression effect, size and surface strength were high, and at the same time, the print quality was good.
Since Comparative Examples 1 and 11 do not contain a crosslinking agent in the coating liquid composition, the comparative examples 1 and 11 contain a crosslinking agent in the coating liquid composition. The surface strength was low. In Comparative Example 2, since the amount of the crosslinking agent was too small, the blanket stain and Nepari suppression effect, the size, the print quality and the surface strength were low. In Comparative Example 3, since there were too many cross-linking agents, coating unevenness occurred, and print quality deteriorated. In Comparative Example 4, since the sizing agent is not a ketene dimer sizing agent, the addition of a sizing agent in an amount that exhibits the same sizing properties as the ketene dimer sizing agent makes the printing plate sensitized. In Comparative Examples 5 and 10, since the pigment was not contained in the coating liquid composition, the printing quality was low. Since Comparative Example 6 does not contain a water-soluble polymer-based adhesive, the water-soluble polymer-based adhesive is contained in the coating liquid composition. Compared to the examples, the blanket stain and the Nepari suppression effect, size characteristics and printing The quality and surface strength were low. Since Comparative Example 7 has too little adhesive and has a large amount of ketene dimer sizing agent and cross-linking agent compared to the adhesive, the blanket stain and Nepari suppression effect, surface strength is low, the printing plate is sensitized, and coating unevenness is caused. Occurred. In Comparative Example 8, since there was too little ketene dimer sizing agent, blanket stains and Nepari suppression effects, size properties, print quality and surface strength were low. In Comparative Example 9, the print quality was low because of too much adhesive. In Comparative Example 12, since the sizing agent was not a ketene dimer-based sizing agent, blanket stains and the effect of preventing Nepari, sizing properties, printing quality and surface strength were low, and printing quality was also low.

  As is apparent from Tables 1 to 4, the examples of the present invention showed higher printing workability, sizing properties, and printing quality at the same time than the comparative examples.

Claims (3)

  In a coated paper obtained by applying a coating liquid composition containing a pigment, an adhesive, and a ketene dimer surface sizing agent to at least one surface of a base paper, and drying the coating liquid composition, the coating liquid composition is further a crosslinking agent The adhesive contains at least a water-soluble polymer, and the blending ratio of each component of the coating liquid composition is 10 to 300 parts by mass of the adhesive in terms of solid content with respect to 100 parts by mass of the pigment, A coated paper comprising 0.05 to 10 parts by mass of a ketene dimer-based surface sizing agent and 0.0005 to 90 parts by mass of a crosslinking agent.   The coated paper according to claim 1, wherein the water-soluble polymer is at least one selected from starch, casein, and polyvinyl alcohol.   The reactive group of the said crosslinking agent is at least 1 sort (s) selected from a methylol group or its lower alkylated product, an aldehyde group, an epoxy group, or an epihalohydrin group, The coating of Claim 1 or Claim 2 characterized by the above-mentioned. paper.