JP2010031390A - Printing paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printing paper not only having sizing performance effectively imparted by the use of a comparatively small amount of an internally added sizing agent, but also hardly causing delamination and generation of paper dust in printing and providing excellent printing surface property. <P>SOLUTION: The printing paper contains the internally added sizing agent for papermaking and a filler in a base paper, and is made by a paper machine. The internally added sizing agent for the papermaking contains an ampholytic copolymer having a hydrophobic group and obtained by quaternarizing at least a part of cationic groups as an active ingredient. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a printing paper that can be used in various printing methods such as offset printing and gravure printing.

  Printing paper used in large quantities by high-speed printers such as offset printers and gravure printers is important in that it can withstand the use of the printer, and it can be used for surface strength and delamination related to paper dust problems. The requirements for the interlaminar strength involved are very severe. Also, the printing paper is required to have a high printing surface feeling such as a clear image. In order to improve the marking surface, it is effective to raise the ash content in the paper. The increase in ash content in paper has the effect of improving smoothness in addition to that, but high ash differentiation increases the amount of paper dust generated in the printing press and increases the problem of delamination due to a decrease in interlayer strength. There is a problem that adversely affects printing workability.

  Furthermore, one of the qualities required of printing paper is the prevention of so-called “back-through”, a phenomenon in which printing can be seen through from the opposite side. It is known that increasing the opacity of paper is the most effective way to reduce strikethrough. As a method for increasing the opacity of paper, it is effective to increase the ash content in the paper by blending a filler having a high specific scattering coefficient and a large effect of increasing opacity. In particular, calcium carbonate is advantageous in that it has a high specific scattering coefficient and is cheaper than paper stock, and therefore, the blending amount of calcium carbonate in paper tends to increase gradually. However, printing operability is likely to deteriorate due to high ash differentiation as described above.

  Further, since the amount of fibers that can form interfiber bonds decreases due to an increase in the filler in the paper, the strength of the paper is significantly reduced when the filler is blended in a high amount. In recent years, with the intention of improving productivity, the speed and width of paper machines have been increased. However, as the speed of paper machines increases, the raw material does not stay on the wire and flows into the white water system. Yield tends to decrease. Further, when the filler is blended in a high amount, the amount of fibers forming the network is reduced, so that the yield on the wire is further lowered.

  As described above, there is a demand for the development of a technique for improving the printing workability while keeping a large amount of the filler in the paper, and the pre-aggregation obtained by processing the filler using the composite polyacrylamide copolymer. It is described that a surface paper strength agent is applied to a base paper to which a filler is added (see Patent Document 5).

  On the other hand, in the recent papermaking method using a large amount of filler, especially calcium carbonate, when neutral rosin known as an internal sizing agent is used, the effect of neutral rosin is significantly reduced and the required size characteristics (water absorption resistance) ), It is necessary to add a large amount of neutral rosin, so that papermaking stains and chemical costs increase. Neutral rosin also requires the addition of aluminum sulfate for the development of sizing properties.However, if aluminum sulfate is increased in order to improve sizing properties, the pH of the papermaking system decreases and calcium carbonate dissolves. Gypsum precipitates, causing defects and paper breaks.

  When AKD (alkyl ketene dimer) is used as an internally added sizing agent, if the amount added is large, not only will the paper machine become dirty, but the rise in size will be slow, so the amount of liquid absorbed by the size press will be low. There is a problem that the paper making speed decreases due to an increase in the drying load of the after dryer, and there is a problem that the paper quality is adversely affected because the friction coefficient is significantly decreased. Further, when ASA (alkenyl succinic anhydride) is used, there is a problem that if the addition amount is large, the paper machine is more easily stained than neutral rosin and AKD, and defects and paper breaks occur frequently.

  So far, as a sizing agent that can be used in neutral papermaking, it contains a hydrophobic group obtained by quaternizing a copolymer of a styrene homolog and an aminoalkyl ester of (meth) acrylic acid with an alkyl halide. A sizing agent comprising a quaternized product of a cationic polymer (see Patent Document 1) has been proposed. Furthermore, sizing agents that improve not only the size effect but also the strength and coefficient of friction of the paper are also known by optimizing the quaternizing agent species and cationic monomer species used in the sizing agent. . Specifically, the copolymer is replaced with an alkyl halide and quaternized with a hydrophobic group-containing cationic polymer obtained by quaternization with epihalohydrin (see Patent Document 2), styrenes ( There has been proposed a sizing agent (see Patent Document 3) composed of a copolymer containing, as constituent monomers, an aminoalkyl ester of (meth) acrylic acid, an aminoacrylamide of (meth) acrylic acid, or a quaternary salt thereof. Since these sizing agents are all cationic, they are self-fixed to an anionically charged pulp fiber without using a fixing agent such as a sulfuric acid band and impart sizing properties to paper. Neutral papermaking or alkaline papermaking is possible.

  Further, with the aim of further improving the size effect, a sizing agent comprising a rosin-bonded cationic polymer obtained by coexisting a predetermined amount of a rosin derivative when copolymerizing a hydrophobic monomer and a cationic monomer (Patent Document 4) See also). In this sizing agent, the bulky structure of rosin introduced into the polymer can impart high hydrophobicity after fixing to the pulp fiber, and in addition, the carboxyl group of the rosin ring interacts with calcium carbonate. It becomes insolubilized itself and the fixing by the cation group is further promoted. Therefore, the size effect can be greatly improved.

  However, the cationic sizing agents disclosed in Patent Documents 1 to 3 have a large room for improvement in the fixability to pulp fibers and the hydrophobicity after fixing in neutral paper or alkaline paper using a large amount of calcium carbonate as a filler. However, the present situation is that a satisfactory size effect cannot be obtained. Further, in the sizing agent of Patent Document 4, since the molecular weight of the rosin-bonded cationic polymer is easily influenced by the amount of rosin added, the self-fixing ability of the polymer to the pulp, that is, the size effect depends on the amount of rosin added. There was a drawback of being easily influenced. Furthermore, the sizing agent of Patent Document 4 has few polymer components that interact with calcium carbonate and contribute to hydrophobicity when the amount of rosin introduced into the polymer of the main chain is small or when unreacted rosin remains. Thus, the size effect may be insufficiently developed.

  In addition, the conventional cationic sizing agents including the sizing agents of Patent Documents 1 to 4 may interact with a wide variety of anionic substances existing in the actual papermaking system, so-called anionic trash, In such a case, the self-fixation to the pulp fiber is hindered, and there is a problem that it is difficult to effectively exhibit the size property. In particular, in neutral papermaking with a small amount of sulfuric acid band added, the amount of anionic trash tends to increase, so this problem appears more prominently. In addition, the technique of Patent Document 5 cannot provide sufficient size characteristics.

US Pat. No. 2,964,445 Japanese Patent Laid-Open No. 48-011407 Japanese Patent Laid-Open No. 03-167397 JP 2001-073292 A JP 2007-231426 A

  Therefore, the object of the present invention is to use calcium carbonate as a filler and effectively use a relatively small amount of an internally added sizing agent to effectively produce sizing even in neutral papermaking that does not use a sulfate band or uses a small amount of sulfate band. Is provided, and there is little generation of delamination or paper dust at the time of printing, and a printing paper excellent in printing surface feeling is provided.

In order to solve the above problems, the printing paper of the present invention is characterized by the following configuration.
(1) The printing paper of the invention according to claim 1 is a printing paper containing a papermaking internal sizing agent and a filler on a base paper and made by a paper machine, wherein the papermaking internal sizing agent is a hydrophobic group And an amphoteric copolymer obtained by quaternizing at least a part of a cationic group.
(2) In the printing paper of the invention according to claim 2, the amphoteric copolymer essentially comprises a hydrophobic monomer (A), a cationic monomer (B), and an anionic monomer (C), and the monomer (C) is obtained by polymerizing a monomer component having an anion equivalent of 0.1 to 90% of the cation equivalent of the monomer (B), and the quaternization rate of the cationic group is 40 mol. % Or more.
(3) The printing paper of the invention according to claim 3 is characterized in that a surface coating agent is applied and dried on the base paper.
(4) The printing paper of the invention according to claim 4 is characterized in that the filler is calcium carbonate.

According to the present invention, the following effects are exhibited.
(1) Even in neutral papermaking using calcium carbonate as a filler and not using a sulfuric acid band or using a small amount of sulfuric acid band, the printing paper of the present invention contains the internal sizing agent for papermaking of the present invention on the base paper. Therefore, excellent sizing properties can be imparted.
(2) In addition to the above-mentioned internal sizing agent for papermaking, by applying a surface coating agent on the base paper, the sizing property is further improved and there is no decrease in static and dynamic friction coefficient. There is little generation of paper dust and excellent printing surface feeling.

  The internally added sizing agent for papermaking used in the present invention comprises a zwitterionic copolymer having a hydrophobic group and at least a part of the cationic group being quaternized as an active ingredient. Among these, the ionic copolymer is a zwitterionic copolymer having a quaternization rate of not less than a specific value and a ratio of anion equivalent to cation equivalent within a predetermined range. An additive sizing agent is added to the pulp slurry and wet-made.

1. Zwitterionic copolymer The internal sizing agent for papermaking used in the present invention comprises a zwitterionic copolymer having a hydrophobic group and at least a part of the cationic group being quaternized as an active ingredient. To do. Thereby, calcium carbonate is used as a filler, and a size property can be efficiently imparted even in neutral papermaking without using a sulfate band or using a small amount of sulfate band. In addition, it is expected to be well self-fixed to the pulp fiber and effectively exhibit size properties in that the interaction with the anionic trash present in the actual papermaking system is small. As described above, the internal sizing agent for papermaking used in the present invention can impart excellent sizing properties very efficiently even under neutral papermaking conditions with a large amount of calcium carbonate and anion trash.

  The internal sizing agent for papermaking used in the present invention exhibits such an effect because the zwitterionic copolymer self-fixes to pulp and interacts with calcium carbonate within one polymer molecule. And ionic complexes can be formed within and between the polymers. In other words, by having the above-mentioned site in one molecule, it becomes possible to efficiently hydrophobize pulp and calcium carbonate, and by forming an ionic complex, the structure of a huge molecular aggregate can be formed. As a result, it is possible to improve the physical yield to the pulp fiber and to improve the self-fixing ability by relaxing the interaction with anion trash, etc., and effective size It is thought that expression is possible.

  Specifically, in neutral papermaking conditions where calcium carbonate is present and no sulfate band is present or the amount used is small, the calcium carbonate aqueous dispersion has different particle surface charges depending on the dilution state and pH. Since an anionic polymer may be added to improve the dispersibility of the particles, an anionic group such as a carboxyl group is effective as a functional group that interacts with calcium carbonate when the calcium carbonate has a positive charge. When a negative charge is present, a cationic group such as an amino group or an ammonium group is considered effective. Then, a monomer having a hydrophobic part such as styrene or (meth) acrylate having an alkyl group is copolymerized with a cationic monomer and an anionic monomer that are easily copolymerized with the monomer, so that carbon dioxide of any surface charge state is obtained. It is considered that an amphoteric site that interacts with calcium is introduced, and an excellent size can be efficiently imparted.

(Monomer component)
The amphoteric copolymer is preferably obtained by polymerizing monomer components essentially comprising a hydrophobic monomer (A), a cationic monomer (B), and an anionic monomer (C). . This amphoteric copolymer comprises a hydrophobic group derived from the hydrophobic monomer (A), a cationic group derived from the cationic monomer (B), and an anionic group derived from the anionic monomer (C). It is what has.
The hydrophobic monomers (A), styrenes, at least one is preferably used selected from the group consisting of (meth) C ₁ -C ₁₄ alkyl esters of acrylic acid (ester of alkyl having 1 to 14 carbon atoms) However, it is not limited to these, For example, (meth) acrylonitrile etc. can also be used. Only one type of hydrophobic monomer (A) may be used, or two or more types may be used. In the present specification, “(meth) acrylic acid” is a generic term for acrylic acid or methacrylic acid. Similarly, “(meth) acryl” means “acryl” or “methacryl”, “(meth) acrylo” means “acrylo” or “methacrylo”, “(meth) acrylate” means “acrylate” or “methacrylate”. , “(Meth) allyl” means “allyl” or “methallyl”, respectively.

Examples of the styrenes include styrene, α-methylstyrene, vinyl toluene, ethyl vinyl toluene, chloromethyl styrene, vinyl pyridine, and the like. Among these, styrene is preferable.
Examples of the C ₁ -C ₁₄ alkyl ester of (meth) acrylic acid include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, and iso-butyl (meth) ) Acrylate, t-butyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, and other aliphatic hydrocarbon esters, Examples include (meth) acrylic acid esters containing aromatic hydrocarbon groups. Among these, methyl (meth) acrylate, n-butyl (meth) acrylate, iso-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and lauryl (meth) acrylate are preferable.

As the cationic monomer (B), at least one selected from the group consisting of tertiary amino group-containing (meth) acrylamide and tertiary amino group-containing (meth) acrylate is preferably used, but is not limited thereto. Rather than, for example, primary or secondary amino group-containing (meth) acrylamide, primary or secondary amino group-containing (meth) acrylate, quaternary ammonium base-containing (meth) acrylamide, quaternary ammonium base-containing (meth) acrylate, diallyl Cationic monomers such as dialkylammonium halides can also be used. Only one type of cationic monomer (B) may be used, or two or more types may be used.
Examples of the tertiary amino group-containing (meth) acrylamide include dimethylaminoethyl (meth) acrylamide, dimethylaminopropyl (meth) acrylamide, diethylaminoethyl (meth) acrylamide, diethylaminopropyl (meth) acrylamide, dialkylaminoalkyl (meta ) Acrylamide and the like.
Examples of the tertiary amino group-containing (meth) acrylate include dimethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, diethylaminoethyl (meth) acrylate, diethylaminopropyl (meth) acrylate, dialkylaminoalkyl (meta ) Acrylate and the like.

Examples of the primary or secondary amino group-containing (meth) acrylamide include primary amino group-containing (meth) acrylamides such as aminoethyl (meth) acrylamide; methylaminoethyl (meth) acrylamide, ethylaminoethyl (meta) ) Secondary amino group-containing (meth) acrylamides such as acrylamide and t-butylaminoethyl (meth) acrylamide;
Examples of the primary or secondary amino group-containing (meth) acrylate include primary amino group-containing (meth) acrylates such as aminoethyl (meth) acrylate; methylaminoethyl (meth) acrylate, ethylaminoethyl (meth) acrylate And secondary amino group-containing (meth) acrylates such as t-butylaminoethyl (meth) acrylate.

  As the quaternary ammonium base-containing (meth) acrylamide and the quaternary ammonium base-containing (meth) acrylate, for example, the above-described tertiary amino group-containing (meth) acrylamide or tertiary amino group-containing (meth) acrylate will be described later. And mono-quaternary base-containing monomers quaternized with a quaternizing agent (for example, methyl chloride, benzyl chloride, methyl sulfate, epichlorohydrin, etc.). Specifically, acrylamidopropyltrimethylammonium chloride, acrylamidopropylbenzyldimethylammonium chloride, methacryloyloxyethyldimethylbenzylammonium chloride, acryloyloxyethyldimethylbenzylammonium chloride, (meth) acryloylaminoethyltrimethylammonium chloride, (meth) acryloyl Aminoethyltriethylammonium chloride, (meth) acryloyloxyethyltrimethylammonium chloride, (meth) acryloyloxyethyltriethylammonium chloride, etc. are mentioned.

The anionic monomer (C) is preferably at least one selected from the group consisting of α, β-unsaturated carboxylic acids and α, β-unsaturated sulfonic acids, but is not limited thereto. . One type of anionic monomer (C) may be sufficient, and 2 or more types may be sufficient as it.
Examples of the α, β-unsaturated carboxylic acids include (meth) acrylic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, citraconic acid, citraconic anhydride, and salts thereof (sodium salt, potassium salt). And ammonium salts).
Examples of the α, β-unsaturated sulfonic acids include vinyl sulfonic acid, (meth) allyl sulfonic acid, styrene sulfonic acid, sulfopropyl (meth) acrylate, 2- (meth) acrylamide-2-methylpropane sulfonic acid, And salts thereof (sodium salt, potassium salt, ammonium salt, etc.) and the like.

  In the monomer component, the anionic equivalent of the anionic monomer (C) is preferably 0.1 to 90% of the cation equivalent of the cationic monomer (B), more preferably 5 to 50%, More preferably, it is 5 to 20%. That is, the zwitterionic copolymer obtained by polymerizing the monomer component has a larger cation equivalent and a smaller anion equivalent tends to exhibit a size effect. When the cation equivalent is a value approximated or the same as the anion equivalent, or when the cation equivalent is smaller than the anion equivalent (specifically, when the ratio (percentage) of the anion equivalent to the cation equivalent exceeds 90%), Active anionic groups are reduced by excessively ionic interaction between the anion portion and the cation portion of the polymer. As a result, it tends to be difficult to express size efficiently due to factors such as lowering the fixing effect of cations on pulp fibers and worsening the orientation balance between hydrophobic and hydrophilic sites. Anionic equivalents of the anionic monomer (C) in the range are required.

Accordingly, the ratio of the anion equivalent to the cation equivalent in the zwitterionic copolymer obtained by polymerizing the monomer component is in the same range as above as well as the ratio of the anion equivalent to the cation equivalent in the monomer component. Is preferred. For example, when the monomer component is selected so that the monomer component is polymerized by a vinyl bond, when the cationic group and the anionic group are not involved in the polymerization, the cation equivalent in the zwitterionic copolymer The ratio of the anion equivalent to the cation is equal to the ratio of the anion equivalent to the cation equivalent in the monomer component.
The content ratio of each essential monomer in the monomer component is desirably set so that the ratio of the anion equivalent of the anionic monomer (C) to the cation equivalent of the cationic monomer (B) is in the range described above. There are no particular restrictions on the points other than. For example, the hydrophobic monomer (A) is about 60 to 90% by weight, the cationic monomer (B) is about 9 to 40% by weight, and the anionic monomer (C) is 1 to 10% by weight with respect to the total amount of the monomer components. % Is preferable.

  In addition to the above-described hydrophobic monomer (A), cationic monomer (B), and anionic monomer (C), the monomer component may further include other components as long as the effects of the present invention are not impaired. These monomers can also be included. Examples of other monomers include hydroxyl-containing (meth) acrylates that do not contain amino groups, such as hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate, (meth) acrylamide, dimethyl (meth) acrylamide, and diethyl (meth) ) Amide group-containing monomers not containing amino groups such as acrylamide and iso-propyl (meth) acrylamide, vinyl acetate, vinyl propionate, methyl vinyl ether and the like. Only one type of other monomer may be used, or two or more types may be used.

(polymerization)
The polymerization of the monomer component is not particularly limited, and for example, a known polymerization method such as bulk polymerization, solution polymerization, or emulsion polymerization can be employed. In addition, a known method such as batch, division, partial dripping, or total amount dripping may be appropriately adopted as a charging method for each monomer, initiator, and the like. The medium (solvent) for the polymerization may be appropriately selected from known ones according to the polymerization method.
There is no restriction | limiting in particular as a polymerization initiator which can be used for the said superposition | polymerization, For example, what is necessary is just to select an azo polymerization initiator, a peroxide polymerization initiator, and another initiator suitably. Moreover, the redox initiator which used the peroxide and the reducing agent together can also be used. Only 1 type may be used for a polymerization initiator and it may use 2 or more types together. The usage-amount of a polymerization initiator is not specifically limited, What is necessary is just to set suitably.

Examples of the azo polymerization initiator include azobismethylbutyronitrile, dimethylazobisisobutyrate, azobisdimethylvaleronitrile, azobisisobutyronitrile, azobis-2-amidinopropane hydrochloride, and the like. .
Examples of the peroxide polymerization initiator include benzoyl persulfate, t-butyl peroxybenzoate, t-butyl peroxyisopropyl monocarbonate, t-butyl peroxy-2-ethylhexanoate, cumene hydroperoxide, and the like. Organic peroxides, inorganic peroxides such as hydrogen peroxide, ammonium persulfate, and potassium persulfate.
As the redox initiator, for example, the above-described peroxide and a reducing agent such as sodium sulfite, iron (II) sulfate, iron (II) chloride, and tertiary amines may be used in combination.

In addition, the polymerization can be carried out in the presence of a chain transfer agent as necessary in order to prevent the increase in viscosity and carry out the reaction smoothly. As the chain transfer agent, an oil-soluble and water-soluble chain transfer agent can be appropriately selected. However, in general, when polymerizing in a lipophilic organic solvent, A water-soluble chain transfer agent is preferred when polymerizing in a hydrophilic organic solvent. Further, an oil-soluble chain transfer agent and a water-soluble chain transfer agent may be used in combination. Only 1 type may be used for a chain transfer agent and it may use 2 or more types together. Although the usage-amount of a chain transfer agent is not specifically limited, For example, about 1 to 5 weight% is preferable with respect to the monomer component whole quantity.
Examples of the oil-soluble chain transfer agent include mercaptans such as t-dodecyl mercaptan, n-dodecyl mercaptan, n-octyl mercaptan, dodecyl mercaptopropionate; hydrophobic allyl compounds such as (meth) allyl methacrylate; cumene, Examples thereof include carbon tetrachloride, α-methylstyrene dimer, terpinolene and the like.
Examples of the water-soluble chain transfer agent include mercaptans such as mercaptoethanol, thioglycerol, thiomalic acid, thioglycolic acid, and salts thereof; (meth) allyl alcohol, (meth) allylamine, (meth) allylsulfonic acid And hydrophilic allyl compounds such as salts thereof; ethanolamine, isopropyl alcohol and the like.

(Quaternization)
The amphoteric copolymer is obtained by quaternizing at least a part of the cationic group, and the quaternization rate of the cationic group of the amphoteric copolymer is 40 mol% or more. It is preferable that the content be 50 to 100 mol%. When the quaternization rate is less than 40 mol%, there is a possibility that an effective hydrophobicity imparting effect to pulp fibers and filler (calcium carbonate) may not be obtained when the papermaking pH is high.
In quaternizing the cationic group of the zwitterionic copolymer, the copolymer obtained after polymerizing the monomer component may be quaternized with a quaternizing agent, You may make it superpose | polymerize using a quaternary ammonium group containing monomer as a cationic monomer (B) of a monomer component.

  Examples of the quaternizing agent that can be used for quaternization include dimethyl sulfate, dimethyl carbonate, methyl chloride, allyl chloride, benzyl chloride, propylene oxide, butylene oxide, styrene oxide, epichlorohydrin, epibromohydrin, and ethylene chloro. Examples thereof include one or more of hydrin, 3-chloro-1,2-propanediol, 3-chloro-2-hydroxypropyltrimethylammonium chloride, glycidol, butyl glycidyl ether, allyl glycidyl ether, glycidyl methacrylate, and the like. Among these, epichlorohydrin and benzyl chloride are preferable.

(Average molecular weight)
The weight-average molecular weight of the zwitterionic copolymer is preferably 10,000 to 1,000,000, and more preferably 30,000 to 600,000. When the weight average molecular weight is less than 10,000, the yield of the sizing agent tends to be remarkably lowered and it becomes difficult to obtain the size effect. On the other hand, when it exceeds 1,000,000, the sizing agent is used in the papermaking drying process. Is not efficiently diffused in the paper, so that the sizing component may be non-uniformly present in the paper and the size effect may be reduced.

(Other)
The internal sizing agent for papermaking used in the present invention only needs to contain the zwitterionic copolymer as an active ingredient. For example, the zwitterionic copolymer itself may be used. It may be a solution or dispersion containing a polymer (for example, a reaction solution obtained by the polymerization and quaternization).

2. Base Paper The printing paper of the present invention is produced by adding the amphoteric copolymer to a pulp slurry and wet-making it with a paper machine.
(Addition amount)
In the present invention, the addition amount of the amphoteric copolymer per the dry weight of the pulp is usually 0.05 to 0.5 parts by weight, more preferably 0.05 to 0.3 parts by weight. .

(pulp)
The pulp fiber constituting the pulp slurry is not particularly limited, and wood pulp such as NBKP and LBKP; mechanical pulp such as TMP and GP; and those usually used for paper making such as deinked pulp (DIP), linter Non-wood pulp such as pulp, hemp, bagasse, kenaf, esparto grass, and straw; semi-synthetic fibers such as rayon and acetate; synthetic fibers such as polyolefin, polyamide, and polyester can be used.

(Filler)
A filler can be blended in the pulp slurry. The filler is not particularly limited as long as it is a filler generally used in acidic papermaking or neutral papermaking. For example, for neutral papermaking, clay, silica, kaolin, calcined kaolin, deramikaolin, heavy calcium carbonate, light calcium carbonate, magnesium carbonate, barium carbonate, titanium dioxide, zinc oxide, silicon oxide, amorphous silica, hydroxylated Inorganic fillers such as aluminum, calcium hydroxide, magnesium hydroxide, and zinc hydroxide, and organic fillers such as urea-formalin resin, polystyrene resin, phenol resin, and fine hollow particles are used alone or in appropriate combination of two or more. . In addition, recycled fillers made from papermaking sludge, deinking floss, etc. can also be used. In the present invention, it is preferable to use calcium carbonate because the amphoteric copolymer in the present invention is excellent in action on calcium carbonate, and calcium carbonate is inexpensive and excellent in optical properties. As the calcium carbonate, spindle-shaped or rosetta-type plasma calcium carbonate, in which the strikethrough is remarkably improved by the interaction with the internally added sizing agent, is preferable. Further, a calcium carbonate-silica composite (light calcium carbonate-silica composite described in JP2003-212539A or JP2005-219945A) can also be used. In acidic papermaking, a filler obtained by removing acid-soluble ones from the filler used in the neutral papermaking is used, and these are used alone or in appropriate combination of two or more. As a compounding quantity of a filler, 2-30 weight% is preferable with respect to pulp weight from points, such as opacity.

  In the present invention, the ash content in the paper is desirably 10% or more. If the ash content in the paper is 10% or less, the existing sizing agent having a relatively low molecular weight is adsorbed by the filler having a large specific surface area, and it becomes difficult to ensure the size property. This is because harmful effects are increased.

(Other additives)
In the pulp slurry, an internal paper strength enhancer such as polyacrylamide polymer, polyvinyl alcohol polymer, cationic starch, urea / formalin resin, melamine / formalin resin, etc., as long as the effect of the present invention is not impaired; Freeness and / or yield improver such as acrylamide and aminomethylacrylamide copolymer salt, cationic starch, polyethyleneimine, polyethylene oxide, acrylamide and sodium acrylate copolymer; rosin sizing agent, AKD sizing agent Internal sizing agents such as ASA-based sizing agents, petroleum-based sizing agents, and neutral rosin sizing agents; auxiliary agents such as ultraviolet ray preventing agents and anti-fading agents may be added.

(Paper making method)
The printing paper base paper of the present invention is particularly preferably a neutral paper obtained by neutral papermaking because the effects of the present invention can be exhibited significantly.
The type of the paper machine is not particularly limited, and it can be appropriately made with a long net paper machine, a twin wire paper machine, a gap former paper machine, a Yankee paper machine, or the like. The paper making speed is not particularly limited and may be made at a speed according to the setting of the paper machine, but is usually about 500 to 2000 m / min, and there are paper machines exceeding 2000 m / min. The press line pressure is used within the normal operating range.

3. Surface coating agent In this invention, it is preferable to apply | coat and dry a surface coating agent on a base paper.
(Coating equipment)
The apparatus for coating the surface coating agent of the present invention on the surface of the base paper is not particularly limited. Two roll size press, gate roll coater, rod metering size press, blade coater, bar coater, roll coater, air knife coater. A known apparatus such as a knife coater or a curtain coater can be appropriately selected and used. In the case of a clear coating liquid, it is a liquid film transfer system, and it is preferable to use a gate roll size press or a rod metering size press that can be applied at a high concentration and has a good size effect.

(Surface paper strength agent)
As the surface coating agent, it is desirable to apply and dry a clear coating liquid mainly containing a surface paper strength agent. As the surface paper strength agent, raw starch, oxidized starch, esterified starch, cationized starch, heat-modified starch, enzyme-modified starch, aldehyde-modified starch, hydroxyethylated starch and other modified starch, carboxymethylcellulose, hydroxyethylcellulose, methylcellulose Cellulose derivatives such as, polyvinyl alcohol, modified alcohols such as carboxyl-modified polyvinyl alcohol, styrene butadiene copolymer, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, polyvinyl chloride, polyvinylidene chloride, polyacrylic ester, poly Use acrylamide alone or in combination. Among them, a modified starch that is excellent in the effect of improving the surface strength is preferable.

(Coating amount)
The coating amount of the surface coating agent is preferably 0.05 g / m ^{2 to 3} g / m ² or less per side of the base paper. More preferably from ^{0.1g / m 2 ~2g / m 2} . If the amount of coating is small, the surface strength becomes weak, and among the offset printing methods, the heat drying type heat offset printing method uses ink with high viscosity (tack), so the paper is attached to the ink and taken off. The problem of so-called paper blur is likely to occur. If the amount of coating is large, the offset printing method uses fountain solution, which causes the Nepari problem (adhesive trouble caused by the transfer and accumulation of coating material on the blanket when a large amount of paper is printed). It becomes easy.

(Other ingredients)
If necessary, the surface coating agent may include various auxiliaries such as a surface sizing agent such as styrene acrylic acid, styrene maleic acid, an olefinic compound, and a cationic sizing agent, a dispersing agent, a water retention agent, and an antifoaming agent. Can be added.

(calendar)
After the surface coating agent is applied and dried, it is glossed by a finishing process such as a super calendar or a soft calendar. There are no particular limitations on the type and processing conditions of the calender device, and a public calender such as a normal calender made of metal roll, soft nip calender, or high temperature soft nip calender is selected as appropriate, and these are selected according to the quality target value of printing paper. The conditions may be set within the controllable range of the apparatus. In particular, in the case of a clear coating solution, a low linear pressure is preferable as long as bulky paper can be obtained and the smoothness of the paper can be maintained, and a soft nip calender is preferable.

4). Pigment Coating In the present invention, a pigment coating solution containing a pigment and an adhesive can be applied and dried on a base paper or after a surface coating agent is applied and dried.
・ Pigment Heavy calcium carbonate is mainly used as a pigment. Light calcium carbonate, kaolin, clay, talc, satin white, plastic pigment, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide are used according to the required quality. Silicic acid, silicate, colloidal silica and the like can be used. These pigments can be used alone or in combination of two or more as required.

・ Adhesives As adhesives, various copolymer emulsions such as styrene / butadiene, styrene / acrylic, ethylene / vinyl acetate, and synthetic adhesives such as polyvinyl alcohol and maleic anhydride copolymer, starch starch, Esterified starch, enzyme-modified starch, etherified starch or cold water soluble starch obtained by flash drying them is used. These adhesives are preferably used in the range of 5 to 35 parts by weight with respect to 100 parts by weight of the pigment. When the amount is too large, the viscosity of the coating liquid becomes high, and disadvantages such as operability problems such as difficulty in passing through piping and a screen occur, which is not preferable. If the amount is too small, sufficient surface strength cannot be obtained, which is not preferable.

- amount of coating coverage of the pigment coating layer is preferably per side ^{3g / m 2 ~25g / m 2} , more preferably ^{5g / m 2 ~15g / m 2} . When the coating amount is too small, sufficient base paper coverage cannot be obtained, and the ink deposition property tends to deteriorate. As with the surface coating agent, the coating apparatus can be appropriately selected from various coating apparatuses.

5). Action The reason why an excellent effect is obtained in the present invention is presumed as follows. The base paper has a hydrophobic group and an internal additive sizing agent containing a zwitterionic copolymer in which at least a part of the cationic group is quaternized as an active ingredient, thereby reducing the friction coefficient. Therefore, the size characteristic that cannot be achieved by the existing internal sizing agent can be effectively expressed. In addition, since the internal sizing agent contains a zwitterionic copolymer as an active ingredient, it has a site in one polymer molecule that self-fixes to pulp fibers and interacts with a filler such as calcium carbonate. Since it tends to stay together with the filler in the layer, it is considered that the interlayer strength of the paper is improved and it contributes to the suppression of the occurrence of delamination phenomenon during printing. Furthermore, it is considered that the surface properties such as surface strength and smoothness are improved by the application of the surface coating agent, and the interlayer strength is improved by penetrating into the base paper. Then, by applying a surface coating agent in addition to the internal sizing agent, the size property can be effectively expressed, so in the case of offset printing using fountain solution, the effect of the fountain solution on the paper It is possible to suppress the phenomenon that the surface strength is reduced and paper dust is generated or the printing surface is rough.

6). Types and Applications The printing paper of the present invention can be used in an offset printing method, a gravure printing method, a flexographic printing method, and other various printing methods, and there is no particular limitation. The basis weight and other physical properties are not limited as long as they are set within a desired range depending on the application, but for example, the basis weight is about 30 to 250 g / m ² , and preferably 30 to 150 g / m ² .

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated, naturally this invention is not limited to these. In the examples, “parts” and “%” respectively represent “parts by weight” and “% by weight” unless otherwise specified. In addition, the chemical addition rate indicates the solid content addition rate unless otherwise specified. When it is designated as solid, it indicates the addition rate of the chemical itself, not the solid content. For example, when 0.2% of a 1% chemical is added as a solid content, 20% is added in solid form.
In the following examples and comparative examples, the weight average molecular weight of the copolymer was measured by gel permeation chromatography under the following conditions.
Column: “Asahipak GF-7M HQ” manufactured by Showa Denko Co., Ltd., “Asahipak GF-310 HQ”
Equipment: “GPC SYSTEM-21H” manufactured by Showa Denko KK

<Manufacture of internal sizing agent>
(1) Synthesis example 1
30 parts by weight of styrene as a hydrophobic monomer, 50 parts by weight of butyl acrylate, 15 parts by weight of dimethylaminoethyl methacrylate, 3 parts by weight of dimethylaminopropylacrylamide, 1 part by weight of methacrylic acid as an anionic monomer, 1 part by weight of itaconic acid Into a four-necked flask, 2 parts by weight of t-dodecyl mercaptan as a chain transfer agent and 50 parts by weight of methyl isobutyl ketone as a solvent were heated to 85 ° C., and then benzoylpar as an initiator. 2.5 parts by weight of oxide was added, followed by polymerization at 90 ° C. for 3 hours. Next, 300 parts by weight of water and 7.7 parts by weight of 90% aqueous acetic acid were added to make it water-soluble, and then heated to distill off methyl isobutyl ketone. Thereafter, 8.5 parts by weight of epichlorohydrin was added as a quaternizing agent at 85 ° C. and reacted at the same temperature for 3 hours. At this time, the reaction solution after the reaction was completely water-soluble. Next, the mixture was cooled and diluted with water to obtain an aqueous solution having a solid content of 20% by weight containing a zwitterionic copolymer having a hydrophobic group, and this was used as an internal sizing agent for papermaking (1).
In addition, when the anion equivalent of the anionic monomer in the monomer component is expressed as a ratio (percentage) with respect to the cation equivalent of the cationic monomer, the cationic content of the copolymer in the obtained internal sizing agent is 24%. The quaternization ratio of the group was 80 mol%, and the weight average molecular weight was 26 × 10 ⁴ .

(2) Synthesis example 2
50 parts by weight of styrene as a hydrophobic monomer, 26 parts by weight of butyl methacrylate, 15 parts by weight of dimethylaminoethyl methacrylate, 6 parts by weight of dimethylaminopropyl acrylamide, 1 part by weight of methacrylic acid as an anionic monomer, 1 part by weight of acrylic acid A monomer component consisting of 1 part by weight of maleic anhydride, 1.5 parts by weight of thioglycolic acid as a chain transfer agent, and 50 parts by weight of isopropanol as a solvent are placed in a four-necked flask and heated to 85 ° C. Then, 2.5 parts by weight of 2,2-azobisisobutyronitrile was added as an initiator, followed by polymerization at 90 ° C. for 3 hours. Next, 300 parts by weight of water and 9 parts by weight of 90% aqueous acetic acid were added to make the solution water-soluble, and then distilled by heating to distill off isopropanol. Thereafter, 13.5 parts by weight of dimethylsulfuric acid as a quaternizing agent was added at 85 ° C. and reacted at the same temperature for 3 hours. At this time, the reaction solution after the reaction was completely water-soluble. Next, the mixture was cooled and diluted with water to obtain an aqueous solution having a solid content of 20% by weight containing a zwitterionic copolymer having a hydrophobic group, and this was used as an internal sizing agent (2) for papermaking.
In addition, when the anion equivalent of the anionic monomer in the monomer component is expressed as a ratio (percentage) to the cation equivalent of the cationic monomer, it is 34%, and the copolymer in the obtained internally added sizing agent has its cationic property. The quaternization ratio of the group was 80 mol%, and the weight average molecular weight was 35 × 10 ⁴ .

<Evaluation method>
The obtained printing paper was evaluated by the following method. The evaluation results are shown in Table 1.
(Ash content in paper): Measured according to JIS P 8251 and ISO 1762.
(Stick human sizing degree): Measured according to JIS P 8122.
(Friction coefficient): Measured according to JIS P 8147.
(Delamination, amount of paper dust, printing surface feeling): The obtained printing paper was printed on both sides with a sheet offset printer (KOMORI PERFECTOR44) at a speed of 8500 sheets per hour using a 46th-sheet sideways paper. Printing was performed, and the number of delaminations when 1000 sheets were printed was counted. As for the paper dust, the paper dust deposited on the blanket after 1000 sheets of printing was scraped off, the weight was measured, and the weight was expressed per 1000 cm ² . Furthermore, the printing surface feeling was evaluated visually (excellent = ◎, good = ○, slightly inferior = Δ, inferior = ×).

<Examples of printing paper production>
[Example 1]
For raw pulp (LBKP 100%) with freeness adjusted to 420 mL, 0.5% liquid sulfuric acid band with respect to pulp solids, cation-modified starch with 0.5% pulp solids, 0% pulp solids 0.05% internal sizing agent obtained in Synthesis Example 1 (1), light calcium carbonate with a solid content of pulp 20% ("TP-121" manufactured by Okutama Kogyo Co., Ltd.), yield improver with a solid content of pulp of 100 ppm The slurry was diluted to 1% after sequential addition. This sample was made at a paper making speed of 1200 m / min using a twin wire type paper machine to obtain a base paper. This base paper is coated with 1.3 g / m ² of oxidized starch (solid content concentration 5%) as a surface coating agent on a gate roll coater on both sides, with a basis weight of 64 g / m ² and a clear coating with an ash content of 13%. I got the printing paper for the factory.

[Example 2]
A printing paper was obtained in the same manner as in Example 1 except that the paper-adding sizing agent (1) was added to the pulp solid content in an amount of 0.08%.

[Example 3]
A printing paper was obtained in the same manner as in Example 1 except that the paper-adding sizing agent (1) was added in an amount of 0.1% to pulp solids in the papermaking process.

[Example 4]
In the production of the base paper, the examples except that 0.05% by weight of pulp solid content was added to the paper additive sizing agent (2) obtained in Synthesis Example 2 instead of the paper additive sizing agent (1). Printing paper was obtained as in 1.

[Example 5]
In the production of the base paper, the Example in Example 1 was carried out except that the internal additive size for papermaking (2) obtained in Synthesis Example 2 was added instead of the internal additive size for papermaking (1) and 0.08% solid content to pulp was added. Printing paper was obtained as in 1.

[Example 6]
In the production of the base paper, the examples except that 0.1% of the solid content of pulp was added to the internal additive sizing agent (2) obtained in Synthesis Example 2 instead of the internal additive sizing agent (1) for papermaking. Printing paper was obtained as in 1.

[Example 7]
A printing paper was obtained in the same manner as in Example 1 except that the surface coating agent was not applied.

[Example 8]
A printing paper was obtained in the same manner as in Example 1 except that in the papermaking, an internal sizing agent for papermaking (1) was added to the pulp solid content of 0.08% and the surface coating agent was not applied.

[Example 9]
Printing paper was obtained in the same manner as in Example 1 except that the paper-adding sizing agent (1) was added to the pulp solid content of 0.1% and the surface coating agent was not applied.

[Comparative Example 1]
A printing paper was obtained in the same manner as in Example 1 except that a neutral rosin sizing agent was added in an amount of 0.3% to pulp solid content instead of the internal additive sizing agent for papermaking (1).

[Comparative Example 2]
A printing paper was obtained in the same manner as in Example 1 except that the AKD sizing agent was added in an amount of 0.1% to pulp solid content instead of the internal additive sizing agent (1).

[Comparative Example 3]
A printing paper was obtained in the same manner as in Example 1 except that the ASA sizing agent was added in an amount of 0.1% to pulp solids instead of the paper making internal sizing agent (1).

[Comparative Example 4]
A printing paper is obtained in the same manner as in Example 1 except that a neutral rosin sizing agent is added to the pulp solid content 0.3% in place of the paper additive sizing agent (1) and no surface coating agent is applied. It was.

[Comparative Example 5]
A printing paper was obtained in the same manner as in Example 1 except that an AKD sizing agent was added in an amount of 0.1% to pulp solid content instead of the paper-made internal sizing agent (1) and the surface coating agent was not applied.

[Comparative Example 6]
A printing paper was obtained in the same manner as in Example 1 except that an ASA sizing agent was added in an amount of 0.1% to pulp solid content in place of the paper making internal sizing agent (1) and no surface coating agent was applied.

In Table 1, an addition rate shows the addition rate with respect to the pulp solid content of a copolymer. Table 1 shows the following.
(A) Examples 1 to 9 show that all evaluation results of size, friction coefficient, delamination, paper dust amount, and printing surface feeling are excellent. Examples 1 to 3 and Examples 4 to 6 differ in the synthesis example of the zwitterionic copolymer. Examples 7 to 9 are cases where there was no coating and drying of the surface coating agent. From this, it is shown that all evaluation results are excellent when the base paper contains an amphoteric copolymer in which at least a part of the cationic group is quaternized.

(I) Examples 1 to 6 and Comparative Examples 1 to 3 were compared with the results of measurement of the sizing degree, static and dynamic friction coefficients, and the results of delamination, amount of paper dust, and printing surface feeling. Nos. 1 to 6 show that the sizing property is good, the static and dynamic friction coefficients are not reduced, and the results of delamination, paper dust amount, and printing surface feeling are excellent. Similarly, comparing Examples 7 to 9 and Comparative Examples 4 to 6, Examples 7 to 9 have good sizing properties, no reduction in static and dynamic friction coefficients, delamination, paper dust amount, Each result of the printing surface feeling is excellent.

(C) With respect to the sizing degree, the sizing degree of Comparative Examples 1 to 3 is 23 seconds or less, whereas that of Examples 1 to 6 is 35 seconds or more. Indicates that the size is excellent. Moreover, since the steecht degree of Comparative Examples 4-6 is 15 seconds or less, that of Examples 7-9 is 24 seconds or more, Examples 7-9 are excellent in sizing. Is shown.

(D) Regarding the static and dynamic friction coefficients, the static friction coefficient of Comparative Example 2 shows 0.69, whereas that of Examples 1-6 shows a range of 0.90 to 0.92. Since the dynamic friction coefficient of Example 2 shows 0.41, while that of Examples 1 to 6 shows a range of 0.54 to 0.56, Examples 1 to 6 show friction coefficients. It is shown that there is no decrease in. The static friction coefficient of Comparative Example 5 is 0.71, while that of Examples 7 to 9 is 0.89 to 0.91, and the dynamic friction coefficient of Comparative Example 5 is 0.41. However, since the values of Examples 7 to 9 indicate 0.52 to 0.53, Example 7 indicates that there is no decrease in the friction coefficient.

(E) Regarding delamination, Comparative Examples 1 to 3 and Comparative Examples 4 to 6 have a delamination problem, while Examples 1 to 6 and Examples 7 to 9 have no or almost no problem. It is shown that. And since Examples 1-6 have 0 delamination, Example 7 has 5 sheets and Example 8 has 1 sheet, and therefore, the surface coating agent is applied onto the base paper and dried. It shows that no peeling problem occurs.
(F) Regarding the amount of paper dust, Comparative Examples 1 to 3 and Comparative Examples 4 to 6 have a problem with the amount of paper dust, while Examples 1 to 6 and Examples 7 to 9 have no problem. Show. And since Examples 1-6 have the amount of paper dust in the range of 7-15, since Example 7 is 19 and Example 8 is 15, apply | coat and dry a surface coating agent on a base paper. This indicates that the problem of the amount of paper dust can be further reduced.
(G) Regarding the printing surface feeling, Comparative Examples 1 to 3 and Comparative Examples 4 to 6 have a printing surface feeling problem, whereas Examples 7 to 9 are good. Since the printing surface feeling is improved without coating and drying, and Examples 1 to 6 are excellent, it is shown that the surface coating agent is further improved by coating and drying.
From the results of the above (e) to (ki), it can be seen that the evaluation results of delamination, paper dust amount and printing surface feeling are further improved by applying and drying the surface coating agent on the base paper.

  From the results of the above Examples 1-9 and Comparative Examples 1-6, the printing paper of the present invention contains a zwitterionic copolymer in which at least a part of the cationic group is quaternized on the base paper, Since the surface coating agent is coated and dried on the base paper, it is excellent in sizing and friction coefficient, produces less delamination and paper dust during printing, and provides a printing paper with excellent printing surface. It is clear that the object of the present invention has been achieved.

Claims (4)

A printing paper containing an internal sizing agent for papermaking and a filler on a base paper and made by a paper machine,
A printing paper characterized in that the internal sizing agent for papermaking contains a zwitterionic copolymer having a hydrophobic group and at least a part of a cationic group being quaternized as an active ingredient.   The zwitterionic copolymer essentially comprises a hydrophobic monomer (A), a cationic monomer (B), and an anionic monomer (C), and the anion equivalent of the monomer (C) is a cation of the monomer (B) The quaternization ratio of the cationic group is 40 mol% or more, which is obtained by polymerizing a monomer component having an equivalent amount of 0.1 to 90%. Printing paper.   The printing paper according to claim 1 or 2, wherein a surface coating agent is applied and dried on the base paper.   The printing paper according to claim 1, wherein the filler is calcium carbonate.