JP2009242961A - Printing paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide printing paper which can impart an excellent sizing property, even when acid-free paper using calcium carbonate as a filler and not using aluminum sulfate or using a small amount of the aluminum sulfate is made, has a reduced reduction in fluorescence intensity, and is excellent in whiteness. <P>SOLUTION: Provided is the printing paper containing a paper-making internal sizing agent containing, as an active ingredient, a doubly ionic copolymer having hydrophobic groups and cationic groups which are at least partially quaternized, and a neutral rosin sizing agent. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a printing paper effectively sized by using a relatively small amount of an internal sizing agent.

  The demand for the quality of printing paper is becoming higher year by year, but the requirement level is high for preventing the phenomenon in which printing can be seen through from the opposite side, so-called “back-through”. 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 high optical properties and is inexpensive compared to paper stock. Tend to increase gradually.

  However, since the amount of fibers that can form fiber-to-fiber bonds decreases due to an increase in the filler in the paper, the strength of the paper is significantly reduced when the filler is highly blended. In recent years, the speed and width of paper machines have been increasing with the aim of improving productivity, but the higher the speed of the paper machine, the more the raw material does not stay on the wire and flows into the white water system. A so-called yield reduction tends to occur. 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. In addition, in the recent neutral papermaking method using a large amount of filler, especially calcium carbonate, the effect of the neutral rosin sizing agent, which is an internally added sizing agent, is significantly reduced, and a large amount of Since it is necessary to add a functional rosin, papermaking stains and an increase in chemical costs are problematic. Neutral rosin sizing agents require 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 will drop and calcium carbonate will dissolve, making papermaking. Gypsum deposits on the machine, causing defects and paper breaks.

  In addition, 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 soiled, but the rise in size will be slow, so the amount of liquid absorbed by the size press Increases the drying load of the after dryer, and there is a problem that the paper making speed is lowered, and the friction coefficient is remarkably lowered, which adversely affects the paper quality. 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, a sizing agent comprising a quaternized product of a hydrophobic group-containing cationic polymer obtained by quaternizing with an epihalohydrin instead of the alkyl halide (see Patent Document 2), and 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.

U.S. Pat. No. 2,964,445 Japanese Patent Laid-Open No. 48-11407 Japanese Patent Application Laid-Open No. 3-16797 JP 2001-73292 A

  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.

  Therefore, the main problem of the present invention is that calcium carbonate is used as a filler, and even in neutral papermaking that does not use a sulfate band or uses a small amount of sulfate band, excellent size can be imparted and the decrease in fluorescence intensity is small. It is to provide printing paper with excellent whiteness.

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 an internally added size for papermaking comprising a zwitterionic copolymer having a hydrophobic group and at least a part of a cationic group being quaternized as an active ingredient. And a neutral rosin sizing agent.
(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. It is characterized by being at least mol%.
(3) The printing paper of the invention according to claim 3 is characterized in that it contains 0.5 to 50 parts by weight of a neutral rosin sizing agent with respect to 1 part by weight of the zwitterionic copolymer.

According to the present invention, the following effects are exhibited.
(1) Calcium carbonate is used as a filler, and excellent neutrality can be imparted by including an internal sizing agent for papermaking even in neutral papermaking without using a sulfate band or using a small amount of sulfate band. .
(2) By using an internal sizing agent for papermaking and a neutral rosin sizing agent containing a hydrophobic group-containing zwitterionic copolymer as an active ingredient, a hydrophobic group-containing zwitterionic copolymer Since the addition amount can be reduced, the inhibitory effect on the fluorescent dye is small, and as a result, a printing paper having excellent whiteness can be obtained.
(3) Since the zwitterionic copolymer has a strong cationic property, the function of the neutral rosin sizing agent, which has traditionally been played by aluminum sulfate, can be replaced by a zwitterionic copolymer containing a hydrophobic group. can do. For this reason, even if it reduces the addition rate of aluminum sulfate, the effect of a neutral rosin sizing agent is exhibited. By reducing aluminum sulfate, the risk of defects due to gypsum precipitation and paper breaks can be reduced.

  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 a neutral rosin 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 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, 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) 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 , Secondary amino group-containing (meth) acrylates such as t-butylaminoethyl (meth) acrylate, and the like.
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.

As the anionic monomer (C), at least one selected from the group consisting of α, β-unsaturated carboxylic acids and α, β-unsaturated sulfonic acids is preferably used, 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 components 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, there is a tendency that it is difficult to efficiently exhibit the size property due to factors such as reducing the fixing action of the cation to the pulp fiber and worsening the orientation balance between the hydrophobic part and the hydrophilic part.
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 10 to 40% by weight, and the anionic monomer (C) is 1 to 10% by weight based on 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, if 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, the oil-soluble chain transfer agent is reversed. 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. Neutral rosin sizing agent The neutral rosin sizing agent used in the present invention refers to an emulsion-type rosin sizing agent that can be used in the neutral to alkaline region.
The neutral rosin sizing agent is produced by dispersing various rosin resins in water by a known emulsification method such as a solvent-type emulsification method, a solventless emulsification method, or a phase inversion emulsification method.
The rosin-based resin refers to at least one of rosins and rosin derivatives, or a combination of at least one rosin and at least one rosin derivative.
The rosin is a concept including an unmodified rosin such as a tall rosin, a gum rosin, and a wood rosin, a disproportionated rosin, a polymerized rosin, a hydrogenated rosin, an acid-modified rosin, or other chemically modified rosins.
Examples of the rosin derivative include rosin esters and acid-modified rosin esters, rosin-modified phenol resins, and epoxy-modified rosins.
The acid-modified rosins are those obtained by reacting the rosins with α, β-unsaturated carboxylic acids by a known method. Examples of the α, β-unsaturated carboxylic acids include fumaric acid, (anhydrous) maleic acid, itaconic acid, (anhydrous) citraconic acid, acrylic acid, and methacrylic acid.
The said rosin ester means what manufactured the said rosin and polyhydric alcohol by the well-known esterification method.
Examples of the polyhydric alcohol include ethylene glycol, propylene glycol, neopentyl glycol, trimethylene glycol, tetramethylene glycol, dihydric alcohols such as 1,3-butanediol and 1,6-hexanediol, glycerin, trimethylolpropane, Trivalent alcohols such as trimethylolethane and triethylolethane, tetravalent alcohols such as pentaerythritol and dipentaerythritol, or triethanolamine, tripropanolamine, triisopropanolamine, N-isobutyldiethanolamine, N-normalbutyldiethanolamine, etc. Amino alcohol and the like.
The acid-modified rosin esters can be obtained by reacting polyhydric alcohols and α, β-unsaturated carboxylic acids sequentially or simultaneously with the rosins. The esterification reaction with a polyhydric alcohol and Diels-Alder addition reaction with an α, β-unsaturated carboxylic acid are as described above.

3. Printing paper The printing paper of the present invention is produced by adding the amphoteric copolymer and neutral rosin sizing agent to a pulp slurry and wet-making it.
(Addition amount)
In the present invention, the addition amount of the zwitterionic copolymer per the dry weight of the pulp is preferably 0.05 to 0.5 parts by weight. Moreover, it is preferable that the addition amount of a neutral rosin size agent contains 0.05-2.0 weight part per dry weight with respect to a pulp. The use ratio of the copolymer and the neutral rosin sizing agent is preferably 0.5 to 50 parts by weight of the neutral rosin sizing agent with respect to 1 part by weight of the copolymer. More preferably, it is 1-20 weight part, More preferably, it is 1-10 weight part. When the proportion of the neutral rosin sizing agent is too small, the size effect is not exhibited, and when the amount of the copolymer is too large, the whitening effect of the fluorescent dye is greatly inhibited. If the proportion of the neutral rosin sizing agent is too large, the degree of sizing can be secured, but there is a high possibility that the paper machine will become dirty, which is economically disadvantageous.
The copolymer has a problem of reducing the whiteness by inhibiting the effect of the fluorescent dye because of its strong cationicity. In contrast, in the present invention, it is possible to reduce the amount of copolymer added to obtain the required size by using in combination with a neutral rosin sizing agent, and the copolymer is a fixing agent for a neutral rosin sizing agent. It is considered that high whiteness can be obtained while effectively imparting size to paper by increasing the effect of the neutral rosin sizing agent.

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

(Filler)
You may mix | blend a filler with the said 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, in 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 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.
In the present invention, the ash content in the paper is desirably 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 is no particular limitation on the components of the surface treatment agent, and the type of size press is also not limited, and a liquid film such as a two roll size press, a gate roll size press, or a rod metalling size press. A transfer size press or the like 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, polyacrylic acid ester, polyacrylamide, etc. Or they 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.
-Ash content in paper: measured in accordance with JIS P 8251 and ISO 1762.
-Steffith sizing degree: Measured according to JIS P 8122.
Fluorescent whitening intensity: Measured with a spectrophotometer CMS-35SPX manufactured by Murakami Color Research Laboratory Co., Ltd. The fluorescent whitening intensity referred to in the present invention is the difference between the whiteness measured with light including ultraviolet light and the whiteness measured with light not including ultraviolet light (the unit is the same as whiteness). The larger the value, the higher the fluorescent whitening intensity.

<Synthesis example of amphoteric copolymer>
(1) Synthesis example 1
As a chain transfer agent, a monomer component comprising 30 parts by weight of styrene, 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, and 1 part by weight of itaconic acid 2 parts by weight of t-dodecyl mercaptan and 50 parts by weight of methyl isobutyl ketone as a solvent were placed in a four-necked flask and heated to 85 ° C., then 2.5 parts by weight of benzoyl peroxide was added as an initiator, and then 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 is 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 (weight average molecular weight 260,000), which is used as an internal sizing agent for papermaking. (1).

(2) Synthesis example 2
A monomer comprising 50 parts by weight of styrene, 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, 1 part by weight of acrylic acid, and 1 part by weight of maleic anhydride. The components, 1.5 parts by weight of thioglycolic acid as a chain transfer agent, and 50 parts by weight of isopropanol as a solvent were placed in a four-necked flask and heated to 85 ° C., and then 2,2-azobisisobutyrate as an initiator. 2.5 parts by weight of nitrile was added, 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 is 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 (weight average molecular weight 350,000), and this is used as an internal sizing agent for papermaking. (2).

<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 .05% internal sizing agent for papermaking obtained in Synthesis Example 1 (1), calcium carbonate with a solid content of 20% to pulp ("TP-121" manufactured by Okutama Kogyo Co., Ltd.), 0.5% with respect to a solid content of pulp Neutral rosin sizing agent ("New Size 738" manufactured by Harima Kasei Co., Ltd.) Fluorescent dye with solid content of 0.2% for pulp solids, Yield improver for 100ppm of pulp solids were sequentially added, Prepared. 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]
A printing paper was prepared in the same manner as in Example 1 except that 0.1% of pulp solid content was added to paper-made internal sizing agent (1) and neutral rosin sizing agent was added to pulp solid content of 0.4%. Obtained.

[Example 3]
A printing paper was prepared in the same manner as in Example 1 except that the internal sizing agent for papermaking (1) was added with 0.2% solids content of pulp and 0.2% of the neutral rosin sizing agent was added. Obtained.

[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 to the pulp solid content of 0.05%, and the neutral rosin sizing agent was added to the pulp solid. A printing paper was obtained in the same manner as in Example 1 except that 0.5% was added.

[Example 5]
In place of the internal sizing agent for papermaking (1), the internal sizing agent for papermaking (2) obtained in Synthesis Example 2 was added at 0.1% to pulp solids, and the neutral rosin sizing agent was added to the solids to pulp. A printing paper was obtained in the same manner as in Example 1 except that 0.4% was added.

[Example 6]
Instead of the internal sizing agent for papermaking (1), 0.2% of the internal sizing agent for papermaking (2) obtained in Synthesis Example 2 was added to the pulp solids, and the neutral rosin sizing agent was added to the solids of the pulp. A printing paper was obtained in the same manner as in Example 1 except that 0.2% was added.

[Example 7]
Instead of the internal sizing agent for papermaking (1), 0.2% of the internal sizing agent for papermaking (2) obtained in Synthesis Example 2 was added to the pulp solids, and the neutral rosin sizing agent was added to the solids of the pulp. Printing paper was obtained in the same manner as in Example 1 except that 0.08% was added.

[Example 8]
Instead of the internal sizing agent for papermaking (1), the internal sizing agent for papermaking (2) obtained in Synthesis Example 2 was added to the pulp solid content of 0.05%, and the neutral rosin sizing agent was added to the pulp solid. A printing paper was obtained in the same manner as in Example 1 except that 2.7% was added.

[Comparative Example 1]
A printing paper was obtained in the same manner as in Example 1 except that 0.6% of the solid sizing agent aqueous solution (1) for papermaking was added and the neutral rosin sizing agent was not added.

[Comparative Example 2]
Instead of the internal sizing agent for papermaking (1), the internal sizing agent for papermaking (2) obtained in Synthesis Example 2 was added with 0.6% solid content to pulp, and no neutral rosin sizing agent was added. A printing paper was obtained in the same manner as in Example 1 except that.

[Comparative Example 3]
A printing paper was obtained in the same manner as in Example 1 except that the internal additive size for papermaking (1) was not used and a neutral rosin sizing agent was added to the solid content of pulp at 0.6%.

Table 1 shows the following.
1) From the comparison with Examples 1 to 8 and Comparative Example 3 in which a neutral rosin sizing agent was used alone without containing an internal sizing agent for papermaking, an attempt was made to ensure the sizing degree with the neutral rosin sizing agent alone. In the case of Comparative Example 3, where the sulfuric acid band addition rate is low, the sizing degree does not appear, but it can be seen that excellent sizing can be imparted by including the internal additive size additive for papermaking.
2) From the comparison between Examples 1 to 8 and Comparative Examples 1 and 2, a papermaking internal sizing agent containing a hydrophobic group-containing zwitterionic copolymer as an active ingredient and a neutral rosin sizing agent are used in combination. Thus, it is possible to obtain a printing paper having an excellent whiteness while maintaining an excellent sizing property at least by adding the hydrophobic group-containing zwitterionic copolymer.
3) Examples 1 to 8 containing an internal sizing agent for papermaking containing a zwitterionic copolymer as an active ingredient and a neutral rosin sizing agent, and an internal addition size for papermaking containing no neutral rosin sizing agent From comparison with Comparative Examples 1 and 2 using the agent alone, it can be seen that the fluorescent whitening intensity is greatly reduced when the paper-added sizing agent alone is intended to secure the same degree of sizing. On the contrary, it can be seen that the decrease in the fluorescent whitening intensity is suppressed by using in combination with the neutral rosin sizing agent.
4) Example 7 is a case where the addition rate of the neutral rosin sizing agent is smaller than that of Example 6, and the ratio of the neutral rosin sizing agent to the internal additive sizing agent for papermaking is less than 0.5 part. Although the decrease in the intensity of fluorescent whitening can be suppressed, the size effect of the neutral rosin sizing agent is hardly exhibited, and high sizing properties are difficult to obtain.

Claims (3)

  It contains an internal sizing agent for papermaking containing a hydrophobic group and an amphoteric copolymer in which at least a part of the cationic group is quaternized as an active ingredient, and a neutral rosin sizing agent And printing paper.   The zwitterionic copolymer essentially comprises a hydrophobic monomer (A), a cationic monomer (B), and an anionic monomer (C), and the anionic equivalent of the monomer (C) is that 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 a cation equivalent of 0.1 to 90%. Printing paper.   The printing paper according to claim 1 or 2, wherein 0.5 to 50 parts by weight of a neutral rosin sizing agent is contained with respect to 1 part by weight of the zwitterionic copolymer.