JP2010031386A - Printing paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printing paper exhibiting excellent sizing performance imparted even by neutral papermaking using calcium carbonate as a filler and using no or a slight amount of aluminium sulfate, and having a friction coefficient excellently prevented from being reduced without increasing a liquid absorption amount by a size press. <P>SOLUTION: The printing paper contains an internally filled sizing agent containing an ampholytic copolymer having a hydrophobic group and obtained by quaternarizing at least a part of cationic groups as an active ingredient, and an alkyl ketene dimer (AKD)-based sizing agent. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a printing paper that is excellent in suppressing the decrease in size and friction coefficient.

  The demand for the quality of printing paper is becoming higher year by year, but the requirement level for preventing the phenomenon that printing can be seen through from the opposite side, so-called “back-through”, is increasing. 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 has an advantage in that it has a high specific scattering coefficient and is inexpensive compared to paper stock. Therefore, the transition to neutral papermaking is progressing, and the amount of calcium carbonate in paper is gradually increasing. It tends to increase.

  However, an increase in paper filler such as calcium carbonate reduces the amount of fibers that can form fiber-to-fiber bonds, thus significantly reducing the strength of the paper. Also, in recent years, with the intention of improving productivity, the speed and width of paper machines are increasing, but as the speed of paper machines increases, the raw material does not stay on the wire and flows into the white water system. So-called yield reduction occurs. In addition, the yield on the wire is further reduced because the amount of fiber making up the network is reduced. In addition, it is known that the neutral rosin sizing agent, which is an internally added sizing agent, significantly reduces the effect of neutral sizing agent, which is a recent neutral paper making method using a large amount of filler, especially calcium carbonate, and ensures the required size. Therefore, it is necessary to add a large amount of neutral rosin, which causes problems such as paper-making stains and chemical costs. In addition, neutral rosin sizing agent requires the addition of aluminum sulfate for the expression of size, but when aluminum sulfate is increased, the pH of the papermaking system decreases and calcium carbonate dissolves. Or calcium sulfate (gypsum) precipitates, causing defects and paper breaks.

  Further, since the effect of the neutral rosin sizing agent is reduced when the ash content in the paper is increased, an alkyl ketene dimer sizing agent (hereinafter referred to as “AKD sizing agent”) is used as an internal sizing agent excellent in high ash content conditions. Sometimes. However, since the AKD sizing agent has a slow rise in size, the amount of liquid absorbed by the size press increases, and the drying load of the after dryer increases. To do. When the friction coefficient is lowered, the paper is slippery when the paper is cut, the paper is not aligned, and the number of defective cutting is increased, or the PPC paper has a transportability trouble (double feed or paper jam) in the copying machine. Further, when the amount of the AKD sizing agent added is large, the paper machine becomes dirty. In addition, when an ASA (alkenyl succinic anhydride) sizing agent is used, if it is added in a large amount, the paper machine tends to get dirty more than neutral rosin and AKD sizing agents, resulting in frequent defects and paper breaks.

  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. The polymer itself is insolubilized and the fixing by the cation group is further promoted. Therefore, the size effect can be greatly improved.

  In addition, by adding AKD and a cationized modified fatty acid size system as an internally added sizing agent, a technique has been proposed in which sizing can be obtained even on printing paper having an ash content of 15% or more without causing stains in the papermaking system. (Patent Document 5). Furthermore, a technique for improving the sizing degree by adding a synthetic sizing agent such as an anionic or cationic emulsion containing AKD and a metal salt such as aluminum sulfate has been proposed (Patent Document 6).

US Pat. No. 2,964,445 Japanese Patent Laid-Open No. 48-11407 Japanese Patent Application Laid-Open No. 3-16797 JP 2001-73292 A JP 2004-277728 A Japanese Patent Publication No. 64-6320

  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, in the case of cationic sizing agents, all of them have a strong cationic property, so that there is a drawback that the effect of the fluorescent dye is hindered, and there is a problem that it cannot be used for printing paper that requires high whiteness. It was.

  Patent Document 5 describes the use of cationized modified fatty acid-based sizing agent as a fixing agent, with an emphasis on using AKD as the main component of size development and increasing the fixability of AKD to pulp. It was difficult to obtain a friction coefficient in an appropriate range because AKD is mainly used. Patent Document 6 describes that the size effect is improved by using a metal salt such as aluminum sulfate after fixing a synthetic sizing agent such as AKD. The problem with the drug could not be improved.

  Therefore, the main problem of the present invention is that calcium carbonate is used as a filler, and even in neutral papermaking where no sulfate band is used or the amount of sulfate band used is small, excellent sizing can be imparted, and liquid absorption in a size press An object of the present invention is to provide a printing paper that is excellent in suppressing the decrease in the friction coefficient without increasing the amount.

In order to solve the above problems, the present invention has the following configuration.
(1) The printing paper of the invention according to claim 1 is a printing paper containing a sizing agent and a filler in a base paper, wherein the sizing agent has a hydrophobic group and at least a part of a cationic group is quaternized. It is characterized by being an internal sizing agent for papermaking and an alkyl ketene dimer-based sizing agent comprising the zwitterionic copolymer formed as an active ingredient.
(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 by containing 0.1 to 3 parts by weight of an alkyl ketene dimer sizing agent with respect to 1 part by weight of the zwitterionic copolymer.
(4) The printing paper of the invention according to claim 4 is characterized in that the filler is calcium carbonate.

The present invention contains an internal sizing agent for papermaking and an AKD sizing agent containing a zwitterionic copolymer having a hydrophobic group on the base paper and at least a part of the cationic group being quaternized as an active ingredient By doing so, the following effects are produced.
(1) Calcium carbonate is used as a filler, and even in neutral papermaking where no sulfate band is used or the amount of sulfate band used is small, strong size can be efficiently imparted. Precipitation of aluminum hydroxide and calcium sulfate (gypsum) can be avoided.
(2) Since the addition amount of the AKD sizing agent can be reduced, it is possible to obtain a printing paper excellent in suppressing the decrease in the friction coefficient without increasing the size press liquid absorption. Moreover, since the drying load of the after dryer is reduced and the reduction in the papermaking speed can be prevented, the operability is also improved.

  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 and an AKD sizing agent are added to a pulp slurry and subjected to wet papermaking.

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 size properties 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 is a polymer molecule that is self-fixed to pulp and interacts with calcium carbonate. It is presumed that the ionic complex 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 monomer (A) is preferably at least one selected from the group consisting of styrenes and C1-C14 alkyl esters of (meth) acrylic acid (alkyl esters having 1 to 14 carbon atoms). 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.
As the (meth) C ₁ -C ₁₄ alkyl esters of acrylic acid such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n- butyl (meth) acrylate, 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, 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 dialkylaminoalkyl (eg, dimethylaminoethyl (meth) acrylamide, dimethylaminopropyl (meth) acrylamide, diethylaminoethyl (meth) acrylamide, diethylaminopropyl (meth) acrylamide) ( And (meth) acrylamide.
Examples of the tertiary amino group-containing (meth) acrylate include dialkylaminoalkyl (eg, dimethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, diethylaminoethyl (meth) acrylate, diethylaminopropyl (meth) acrylate) ( And (meth) acrylate.

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) acrylamide 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. Alkyl ketene dimer (AKD) -based sizing agent The AKD sizing agent used in the present invention has the following general formula (1) (wherein R ₁ and R ₂ may be the same or different, and have about 8 to 36 carbon atoms ( Preferably, it is represented by an alkyl group having about 12-30, particularly preferably 12-20, or an alkenyl group having about 8-36 carbon atoms (preferably about 12-30, particularly preferably 12-20). Those are preferred. When the number of carbon atoms of R ₁ and / or R ₂ of the compound is less than 8, the hydrophobicity is small, and the size effect that is the intended purpose of the present invention tends to be difficult to obtain. In addition, when the number of carbon atoms of R ₁ and / or R ₂ of the compound exceeds 36, it is not particularly difficult to obtain a size effect, but it is difficult to obtain commercially.

(1)

As the alkyl group having about 8 to 36 carbon atoms, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, icosyl group , Henicosyl group, docosyl group, tricosyl group, tetracosyl group, pentacosyl group, hexacosyl group, heptacosyl group, octacosyl group, nonacosyl group, triacontyl group, dotriacontyl group, tritriacontyl group, 1-octyl-2-decyl group, 1-octyl And a hexyl-2-octyl group. Examples of the alkenyl group having about 8 to 36 carbon atoms include alkenyl groups having an unsaturated double bond inside such various alkyl groups. Specifically, octenyl group, nonenyl group, decenyl group, undecenyl group are exemplified. Group, dodecenyl group, tetradecenyl group, pentadecenyl group, hexadecenyl group, heptadecenyl group, octadecenyl group, nonadecenyl group, icocenyl group, henicocenyl group, dococenyl group, tricocenyl group, tetracocenyl group, pentacocenyl group, hexacocenyl group, heptacocenyl group, heptacocenyl group Nonacosenyl group, triacontenyl group, dotriacontenyl group, tritriacontenyl group, 1-octyl-2-decenyl group, 1-hexyl-2-octenyl group and the like can be exemplified.

  Specific examples of the AKD sizing agent include, for example, octylic acid, caprylic acid, nonanoic acid, decanoic acid, undecanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, eicosanoic acid, behenic acid, serotic acid, hentriacontanic acid Alkyl ketene dimers derived from saturated monobasic acids such as alkenyl ketene dimers derived from unsaturated monobasic acids such as oleic acid, linoleic acid, linolenic acid, eleostearic acid, arachidonic acid; coconut oil, palm oil Natural oil-derived ketene dimers prepared from natural oils such as olive oil, peanut oil, rapeseed oil, hydrogenated beef oil, lard, and the like. Among these, from the viewpoint of the size effect, alkyl ketene dimers derived from stearic acid and / or natural fat-derived ketene dimers prepared from hydrogenated beef tallow oil are preferred. These can be used in combination of two or more.

3. Printing paper The printing paper of the present invention is produced by adding the amphoteric copolymer and the AKD sizing agent to a pulp slurry and wet-making it.
(Addition amount)
As the addition amount of the amphoteric copolymer per pulp dry weight in the present invention, it is usually preferably 0.05 to 0.4 parts by weight, more preferably 0.1 to 0.3 parts by weight. It is. The amount of the AKD sizing agent added is preferably 0.05 to 0.15 parts by weight, more preferably 0.05 to 0.12 parts by weight, based on the absolute dry weight of the pulp. The use ratio of the copolymer and the AKD sizing agent is preferably 0.1 to 3 parts by weight, more preferably 0.1 to 2 parts by weight with respect to 1 part by weight of the copolymer. . If the proportion of the AKD sizing agent is too small, the size effect does not appear, and if the proportion of the AKD sizing agent is too large, the liquid absorption amount of the size press increases and the drying load of the after dryer increases. In addition, the friction coefficient is remarkably lowered, and the paper machine becomes dirty, which is disadvantageous economically. The amphoteric copolymer and AKD may be added separately or may be mixed in advance. Further, the order of addition of the zwitterionic copolymer and AKD may be any first.

  The reason why an excellent effect is obtained in the present invention is presumed as follows. The AKD sizing agent is a sizing agent that is suitable under conditions with high ash content in paper. However, the AKD sizing agent lowers the coefficient of friction, and the rise in sizing degree is slow, so the size press liquid absorption is likely to increase. On the other hand, the paper additive sizing agent used in the present invention is not as good as the AKD sizing agent in terms of sizing properties, but improves the sizing property without reducing the friction coefficient and increasing the size press liquid absorption. Can be made. Therefore, it is considered that by adding the AKD sizing agent and the paper additive sizing agent together in an appropriate ratio, a printing paper having a high sizing property, a fast sizing property, and an excellent friction coefficient can be obtained. It is done. The AKD sizing agent has a linear alkyl group having about 18 carbon atoms, which is very hydrophobic, as a hydrophobic group. The AKD sizing agent is used as an emulsion by dispersing a water-soluble polymer having a positive charge such as cationic starch in water as a protective colloid. Therefore, it is easy to adsorb to pulp fibers having an anionic group. On the other hand, the internal sizing agent for papermaking uses a zwitterionic copolymer as an active ingredient, so that a part that self-fixes to pulp fibers and interacts with a filler such as calcium carbonate in one polymer molecule. Therefore, the combined use of such an internal sizing agent for papermaking and an AKD sizing agent allows the fiber surface to be more uniformly coated with a sizing agent, so that high sizing properties can be obtained. It is done.

(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, or a mixture thereof 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 is excellent in action on calcium carbonate, and calcium carbonate is inexpensive and excellent in optical properties. As calcium carbonate, 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.

  Moreover, in this invention, it is desirable for the ash content in paper measured based on JISP8251 and ISO 1762 to be 10% or more. When the ash content in the paper is 10% or more, 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, sizing agents such as cationized starch, acrylamide copolymer (PAM polymer), paper strength agent such as PVA polymer, aluminum sulfate, and rosin resin, as long as the effects of the present invention are not impaired. Needless to say, various chemicals such as a filtering agent, a yield improver, a water-proofing agent, a fluorescent dye, or an ultraviolet ray preventing agent can be added. In particular, fluorescent dyes are preferably used to increase whiteness.

(Paper making method)
In particular, the printing paper of the present invention is 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 press line pressure is used within the normal operating range. The surface treatment agent may or may not be applied. When the surface treatment agent is applied, there are no particular limitations on the components of the surface treatment agent, and the size press type is also not limited, and a liquid film transfer type size press such as a two-roll size press, a gate roll size press, or a shim sizer. Etc. can be used as appropriate. The calendar is used at a linear pressure within the normal operating range. A soft calendar is also preferred.

  Examples of the surface treatment agent include raw starch, oxidized starch, esterified starch, cationized starch, enzyme-modified starch, aldehyde-modified starch, hydroxyethylated starch and other modified starches, and cellulose derivatives such as carboxymethylcellulose, hydroxyethylcellulose, and methylcellulose. , Polyvinyl alcohol, modified alcohol such as carboxyl-modified polyvinyl alcohol, styrene-butadiene copolymer, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, polyvinyl chloride, polyvinylidene chloride, polyacrylate ester, polyacrylamide, etc. Or can be used together. Of these, hydroxyethylated starch is preferred because of its excellent effect of improving surface strength. In addition to the above-mentioned agents, surface sizing agents such as styrene acrylic acid, styrene maleic acid, olefinic compounds, and cationic sizing agents can be applied to the surface treatment agent.

(Type, application)
The type of the printing paper of the present invention is arbitrary and is not particularly limited. For example, high-quality or medium-quality printing paper, newsprint paper, art paper, base paper such as cast coated paper, PPC paper, ink jet recording paper, laser printer Examples thereof include recording paper such as paper, thermal recording paper, and pressure-sensitive recording paper.

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

<Evaluation method>
The obtained printing paper was evaluated by the following method, and the results are shown in Table 1.
-Steffith sizing degree: Measured according to JIS P 8122.
-Friction coefficient: The static friction coefficient and the dynamic friction coefficient of the paper cut into A4 size after processing with a decurler (an apparatus for correcting the curl of paper) were measured according to ISO 15359.
-Size press liquid absorption: The liquid absorption in a 2-roll size press was measured.

<Synthesis example of amphoteric copolymer>
(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 .

<Printing paper production example 1>
[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 .05% internal sizing agent for papermaking (1) obtained in Synthesis Example 1, calcium carbonate with a solid content of 20% to pulp ("TP-121" manufactured by Okutama Kogyo Co., Ltd.), 0.15% with respect to a solid content of pulp AKD sizing agent (“AK-720H” manufactured by Harima Kasei Co., Ltd.) and a yield improver having a solid content of 100 ppm to pulp were sequentially added to prepare a paper stock. This stock was made using an on-top type twin wire paper machine at a paper making speed of 1200 m / min to obtain a printing paper (basis weight 64 g / m ² , ash content in paper 15%).

[Example 2]
Printing paper was obtained in the same manner as in Example 1 except that 0.2% of the solid additive for papermaking (1) was added to the solid content of 0.2% and 0.1% of the AKD sizing agent was added to the pulp.

[Example 3]
A printing paper was obtained in the same manner as in Example 1 except that the internal sizing agent for papermaking (1) was added in an amount of 0.35% to pulp solids and 0.05% of the AKD sizing agent was added to pulp.

[Example 4]
Instead of the internal sizing agent for papermaking (1), the internal sizing agent for papermaking (2) obtained in Synthesis Example 2 was added at 0.05% solid content to pulp, and the AKD sizing agent was added to 0.15 pulp. Printing paper was obtained in the same manner as in Example 1 except that% was added.

[Example 5]
Instead of the paper additive sizing agent (1), the paper additive sizing agent (2) obtained in Synthesis Example 2 was added at 0.2% solids to pulp, and the AKD sizing agent was added to pulp 0.1. Printing paper was obtained in the same manner as in Example 1 except that% was added.

[Example 6]
Instead of the internal sizing agent for papermaking (1), the internal sizing agent for papermaking (2) obtained in Synthesis Example 2 was added to a solid content of 0.35% to pulp, and the AKD sizing agent was added to 0.05 to pulp. Printing paper was obtained in the same manner as in Example 1 except that% was added.

[Comparative Example 1]
A printing paper was obtained in the same manner as in Example 1 except that the internal additive sizing agent (1) for papermaking was added with 0.3% solid content of pulp and no AKD sizing agent was added.

[Comparative Example 2]
A printing paper was obtained in the same manner as in Example 1 except that the internal sizing agent for papermaking was not added and the AKD sizing agent was added to the pulp solid content of 0.1%.

[Comparative Example 3]
A printing paper was obtained in the same manner as in Example 1 except that the internal sizing agent for papermaking was not added and the AKD sizing agent was added to the solid content of 0.2% to pulp.

[Comparative Example 4]
Example 1 except that the internal sizing agent for papermaking was not added, instead a neutral rosin sizing agent was added to the pulp solid content of 0.2%, and an AKD sizing agent was added to the pulp solid content of 0.1%. A printed paper was obtained in the same manner.

Table 1 shows the following.
In the present invention, the size of the size press liquid absorption amount from 55 ml / ^{m 2} good below poor in 56~59ml / ^{m 2,} very determined bad in 60 ml / ^{m 2} or more, the size of nice The human sizing degree was determined to be very good at 30 to 50 seconds, good at 20 to 29 seconds, bad at 9 to 19 seconds, and very bad at 0 to 9 seconds, and the coefficient of static friction was 0.55 to 0. .75, the coefficient of dynamic friction is preferably 0.40 to 0.55, and it was judged that there was a problem with the coefficient of friction being more or less than that, but specifically, the paper was slippery due to the lower coefficient of friction. Therefore, the paper is not aligned when the paper is cut, which causes a problem in the transportability in the copying machine.

(1) Examples 1 to 6 have a good size press water absorption, a very good Steecht sizing degree, and desirable static and dynamic friction coefficients. Has been shown to be excellent.
(2) For example, regarding the size press liquid absorption amount, the size press liquid absorption amount of Comparative Examples 2 to 4 is 56 ml / m ² or more, while that of Examples 1 to 6 is 55 ml / m ² or less. Therefore, Examples 1 to 6 indicate that the size press liquid absorption is good.
(3) With respect to the degree of sizing, the sizing degree of Comparative Examples 1, 2, and 4 is in the range of 17-24 seconds, whereas that of Examples 1-6 is in the range of 31-35 seconds. Therefore, Examples 1 to 6 are excellent in size. And when Example 1 (0.2% in total of an amphoteric copolymer and an AKD sizing agent) is compared with Comparative Example 3 (AKD sizing agent is 0.2%), the sizing agent addition ratio of both is Although equivalent, the static and dynamic friction coefficients of Comparative Example 3 are 0.51 and 0.31, while those of Example 1 are 0.55 and 0.41, so the base paper is zwitterionic. It has shown that the fall of a friction coefficient can be suppressed by mix | blending a copolymer and an AKD sizing agent.
(4) The static friction coefficients of Examples 1 to 6 are in the range of 0.55 to 0.58, and the dynamic friction coefficients of Examples 1 to 6 are in the range of 0.41 to 0.46. No. 6 shows that the static and dynamic friction coefficient values are desirable values, so that the reduction of the friction coefficient is suppressed.

  From the results of Examples 1 to 6 and Comparative Examples 1 to 4 described above, the printing paper of the present invention uses calcium carbonate as a filler, and in neutral papermaking that does not use a sulfate band or uses a small amount of sulfate band, By containing an internal sizing agent for papermaking having an active ingredient a zwitterionic copolymer having a hydrophobic group on the base paper and at least a part of the cationic group being quaternized, and an AKD sizing agent, A printing paper that can give excellent sizing properties and is excellent in suppressing the decrease in the friction coefficient without increasing the liquid absorption amount in the size press has been achieved, so the above-described problems of the present invention have been achieved. It is clear.

Claims (4)

Printing paper containing sizing agent and filler on the base paper,
An internal sizing agent for papermaking and an alkyl ketene dimer-based sizing agent comprising a zwitterionic copolymer in which the sizing agent has a hydrophobic group and at least a part of the cationic group is quaternized. Printing paper characterized by being.   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, comprising 0.1 to 3 parts by weight of an alkyl ketene dimer sizing agent with respect to 1 part by weight of the zwitterionic copolymer. The printing paper according to claim 1, wherein the filler is calcium carbonate.