JP2009161885A - Papermaking surface sizing agent - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water-soluble type papermaking surface sizing agent having excellent various sizing effects such as Steckigt sizing degree, pen writing sizing degree, inkjet suitability etc. <P>SOLUTION: The papermaking surface sizing agent contains a copolymer obtained by copolymerizing a monomer component comprising at least a styrene-based monomer component, an anionic vinyl monomer component and a crosslinkable monomer component, has a weight-average molecular weight of 20,000-100,000 and the ratio of weight-average molecular weight/number-average molecular weight of <2.5. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a surface sizing agent for papermaking.

The surface sizing agent for papermaking is a chemical that can give a sizing effect (controls the liquid absorbency of the paper and suppresses ink bleeding, etc.) by applying it to the paper. And size effects such as writing suitability and ink jet suitability can be improved. As such a surface sizing agent, for example, a surface sizing agent containing a copolymer mainly composed of a hydrophobic unsaturated monomer such as styrene and an anionic vinyl monomer such as (meth) acrylic acid (see Patent Document 1). )It has been known.

Such surface sizing agents for papermaking are generally classified roughly into an emulsion type and an aqueous solution type. The former is superior in size effect because the ratio of hydrophobic unsaturated monomer can be designed to be relatively high, but the surface sizing agent can be applied under strong shearing force, such as rod metalling size press and gate roll method. A large amount of soot may be generated in the method of performing. On the other hand, the latter is excellent in mechanical stability, but it is necessary to use a large amount of hydrophilic unsaturated monomer in order to impart uniform water solubility and stabilize the product, resulting in insufficient size effect.

JP-A-8-095282

An object of the present invention is to provide a water-soluble surface sizing agent for papermaking, which is excellent in various sizing effects such as sizing human sizing degree, pen writing ability and ink jetting ability.

As a result of studies to solve the above problems, the present inventor has a styrene-based monomer component as a main component, and is obtained by polymerizing a specific anionic vinyl monomer component and a crosslinkable monomer component, and has a weight average molecular weight. It was found that the above-mentioned problems can be solved by using a copolymer having a specific range and a molecular weight distribution narrowed to a certain level or less, thereby completing the present invention.

That is, the present invention provides a weight average molecular weight of 20,000 to 100,000, weight average obtained by copolymerizing at least a monomer component containing a styrene monomer component, an anionic vinyl monomer component, and a crosslinkable monomer component. A surface sizing agent for papermaking containing a copolymer having a molecular weight / number average molecular weight ratio of 1 or more and less than 2.5. A surface sizing agent for papermaking containing 59 to 84% by weight of a styrene monomer component, 15 to 40% by weight of an anionic vinyl monomer component, and 0.0001 to 3% by weight of a crosslinkable monomer component in all monomer components; The surface sizing agent for papermaking as described above, wherein the functional monomer is (meth) acrylamides and / or (meth) acrylic acid esters. A surface sizing agent for papermaking, wherein the copolymer is water-soluble. A surface sizing agent for papermaking having a solids concentration of 23 to 32% by weight and a Brookfield viscosity at 25 ° C. of 10 to 500 mPa · s.

The surface sizing agent for papermaking of the present invention is capable of stable operation because it does not generate wrinkles in a coating method such as a rod metering size press or a gate roll, and various size effects ( In particular, it has excellent steecht size, pen writing ability, and ink jetting ability.

The surface sizing agent for papermaking of the present invention has a weight average molecular weight of 20,000 to 100, obtained by copolymerizing at least a monomer component containing a styrene monomer component, an anionic vinyl monomer component, and a crosslinkable monomer component. And a copolymer having a weight average molecular weight (Mw) to number average molecular weight (Mn) ratio (hereinafter referred to as Mw / Mn ratio) of 1 or more and less than 2.5. In addition, a weight average molecular weight and a number average molecular weight are the polystyrene conversion values by a gel permeation chromatography method.

As a styrene-type monomer which comprises the copolymer of this invention, it does not specifically limit and a well-known thing can be used. Specific examples include styrene, α-methylstyrene, vinyl toluene, and the like.

The anionic vinyl monomer constituting the copolymer of the present invention can be used without particular limitation as long as it has one radical polymerizable functional group having an anionic functional group or a salt thereof in the molecule. . Specifically, for example, unsaturated monocarboxylic acids such as (meth) acrylic acid (meaning acrylic acid or methacrylic acid; hereinafter the same), maleic acid, itaconic acid, citraconic acid, fumaric acid, muconic acid, etc. Unsaturated dicarboxylic acid, anhydride of dicarboxylic acid, half ester obtained by reacting dicarboxylic acid with each monohydric alcohol; sulfonic acid group-containing unsaturated such as vinylsulfonic acid, 2-acrylamido-methyl-propanesulfonic acid, etc. Monomers; Phosphoric acid group-containing unsaturated monomers such as 2- (meth) acryloyloxyethyl acid phosphate; and alkali metal salts such as sodium salts and potassium salts, alkaline earth metal salts, ammonium salts, and organic bases Is mentioned. In addition, as a substituent of the said half ester, a C1-C18 linear or branched alkyl group can be illustrated, for example, a methyl group, an ethyl group, n-propyl group, n-butyl group, isobutyl Group, t-butyl group, neopentyl group, n-hexyl group, cyclohexyl group, 2 ethylhexyl group, decyl group, palmityl group, stearyl group and the like. Examples of other half-ester substituents include hydroxyalkyl groups such as 2-hydroxyethyl group and 2-hydroxypropyl group, and benzyl group. Of these half-ester substituents, alkyl groups having about 1 to 12 carbon atoms are preferred. When the viscosity of the surface sizing agent aqueous solution for papermaking according to the present invention is increased and the surface sizing agent is applied by a method in which the surface sizing agent is applied under a strong shearing force, a large amount of wrinkles are generated, so that the operation stability during coating is stable This is because the sex becomes worse. Among the anionic monomers exemplified above, (meth) acrylic acid or (meth) acrylic acid neutralized salt is preferable in that it is excellent in copolymerizability with a styrene monomer and has a good size effect.

Examples of the crosslinkable monomer constituting the copolymer of the present invention include those having a plurality of radically polymerizable functional groups in the molecule, and the fact that methyl group or methylene group hydrogen in the molecule is extracted. Any known polymer can be used as long as it can introduce many branched structures into the polymer.
As what has a some radical polymerizable functional group in a molecule | numerator, a 2-4 functional crosslinkable monomer is mentioned. Specifically, as the bifunctional crosslinkable monomer, di (meth) acrylates such as ethylene glycol di (meth) acrylate and diethylene glycol di (meth) acrylate, methylene bis (meth) acrylamide, and ethylene bis (meth) Examples thereof include bis (meth) acrylamides such as acrylamide and hexamethylenebis (meth) acrylamide, divinyl esters such as divinyl adipate and divinyl sebacate, diallyldimethylammonium, diallyl phthalate, diallyl chlorendate, and divinylbenzene.
Examples of the trifunctional monomer include 1,3,5 triacryloylhexahydro-S-triazine, triallyl isocyanurate, triallylamine, triallyl trimellitate, N, N-diallylacrylamide and the like.
Examples of the tetrafunctional monomer include tetramethylolmethane tetraacrylate, tetraallyl pyromellitate, N, N, N ′, N′-tetraallyl-1,4 diaminobutane, tetraallylamine salt, tetraallyloxyethane, and the like.
In addition, N, N-dimethyl (meth) acrylamide, diacetone (meth) acrylamide, and isopropyl (meth) acrylamide are also used as crosslinkable monomers to utilize the fact that methyl or methylene group hydrogen in the molecule is extracted. Can be used. These can be used individually by 1 type and in combination of 2 or more types. Among these, methylenebisacrylamide, N, N-dimethylacrylamide, or tetramethylolmethane tetraacrylate is preferable because the reaction control during production is easy.
By using such a crosslinkable monomer, the molecular weight of the copolymer is increased, and when applied to paper, the penetration of the sizing agent into the paper is suppressed, and it is presumed that the size effect is enhanced.

The proportion of the monomer component of the copolymer, which is the main component of the paper sizing agent of the present invention, is preferably 59 to 84% by weight of a styrene monomer component, from the viewpoint of securing a sufficient size effect, an anion About 15 to 40% by weight of the ionic vinyl monomer component, about 0.0001 to 3% by weight of the crosslinkable monomer component, more preferably about 64 to 79% by weight of the styrenic monomer component, and the anionic vinyl monomer component and The cationic monomer component is about 20 to 35% by weight and the crosslinkable monomer component is about 0.001 to 2% by weight.

By making the styrene monomer component 59% by weight or more, the hydrophobicity of the resulting copolymer is improved and the size effect is improved, and it is preferable to make the solid content concentration high by making it 84% by weight or less. In this case, it is preferable because an appropriate water-solubility can be imparted, gelation is difficult, and a uniform surface sizing agent for papermaking can be obtained. Furthermore, by setting the crosslinkable monomer component to 0.0001 mol% or more and 3 mol% or less, the polymer in the low molecular weight region decreases, the Mw / Mn ratio decreases, and the polymer in the high molecular weight region increases. This is preferable because the size effect is improved.

The copolymer of the present invention can be used in combination with other monomers that can be copolymerized with the monomer component constituting the copolymer, if necessary, as long as the object of the present invention is not impaired. Examples of other monomers include monofunctional (meth) acrylic esters such as methyl methacrylate, (meth) acrylonitrile, vinyl acetate, (meth) acrylamide, α-olefins having 6 to 22 carbon atoms, vinyl pyrrolidone, and the like. Is mentioned. Moreover, the usage-amount of this monomer is less than 20 weight% normally in a copolymer, Preferably it is less than 10 weight%. Moreover, you may use a well-known chain transfer agent together in the range which does not impair the objective of this invention.

Although the manufacturing method of the copolymer of this invention is not specifically limited, Various well-known polymerization methods, such as aqueous solution polymerization and suspension polymerization, are employable.

For example, when the solution polymerization method is adopted, a styrene monomer, an anionic vinyl monomer component, a crosslinkable monomer, and other optional monomers used as necessary in a reaction vessel equipped with an appropriate heating device and a stirrer. Then, water and an organic solvent are added to the container to dissolve these monomer components. Furthermore, a known polymerization initiator is added and mixed, the temperature in the reaction system is raised to about 80 to 130 ° C. in a nitrogen stream, neutralized after performing the polymerization reaction for about 4 hours under reflux, It can be produced by distilling off the organic solvent.

Preferably, before distilling off the organic solvent, a polymerization inhibitor such as hydroquinone is added, or during the polymerization, a reducing agent such as sodium bisulfite, or a persulfate such as ammonium persulfate or potassium persulfate By adding a redox initiator combined with a reducing agent such as sodium hydrogen sulfite, the progress of polymerization is prevented in the organic solvent distillation step, and the adjustment of the weight average molecular weight and Mw / Mn ratio described later is easy. Thus, a product having a high concentration and a low viscosity can be obtained. The types and amounts of the polymerization inhibitor, reducing agent and redox initiator are not particularly limited, and known ones can be used.

As the organic solvent used for solution polymerization, aromatic hydrocarbons such as benzene and toluene, lower ketones such as acetone and methyl ethyl ketone, alcohols such as n-propyl alcohol and iso-propyl alcohol, and the like can be used. . The polymerization initiator is not particularly limited, but for example, azo compounds such as 2,2′-azobisisobutyronitrile, 2,2′-azobis-2,4-methylvaleronitrile, benzoyl peroxide, cumene hydro Examples thereof include organic peroxides such as peroxide, t-butyl hydroperoxide, dicumyl peroxide, and lauryl peroxide. The amount of the polymerization initiator used may be appropriately determined in consideration of the polymerization rate, the molecular weight of the copolymer to be obtained, and the like. About 1 to 3% by weight is preferable.

The copolymer of the present invention needs to have a weight average molecular weight of 20,000 to 100,000 and an Mw / Mn ratio of 1 or more and less than 2.5. When the weight average molecular weight is less than 20,000, a sufficient size effect cannot be obtained. In addition, when the weight average molecular weight exceeds 100,000, it is impossible to impart an appropriate water solubility, and thus it is difficult to form a uniform surface sizing agent for papermaking that is difficult to gel, is stable, has good handleability and good operability. On the other hand, when the Mw / Mn ratio exceeds 2.5, a sufficient size effect cannot be obtained because many low molecular weight polymers are present in the obtained copolymer.
In addition, the weight average molecular weight in this invention and a number average molecular weight are the polystyrene conversion values by a gel permeation chromatography method.

The copolymer thus obtained has a solid content concentration of usually 23 to 32% by weight, a viscosity (B-type viscometer: 25 ° C.) in the range of the solid content concentration of usually 10 to 500 mPa · s, and a pH of usually 8. It is adjusted to be 0 to 10.0, and is used as a surface sizing agent for papermaking, which has a high concentration and a relatively low viscosity, and is excellent in size performance and handleability.

The paper-making surface sizing agent of the present invention can be used alone for coating, but water-soluble polymers such as starch, carboxymethyl cellulose, acrylamide polymers, polyvinyl alcohol, antifoaming agents, anti-slip agents, preservatives, It can also be used as a coating liquid by mixing with a rusting agent, a thickener, a pH adjuster, an antioxidant, a film increasing aid, a pigment, and a dye.

The surface sizing agent for papermaking of the present invention is applied to the above various base papers using a conventionally known coating method such as impregnation method, size press method, calendar method, spray method, gate roll coater, etc. . The coating amount is usually about 0.001 to 5 g / m ² (solid content), preferably 0.005 to 1 g / m ² .

Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto.
The molecular weight and viscosity of the obtained water-soluble paper surface sizing agent were measured by the following methods. The results are shown in Table 1. Hereinafter, “parts” and “%” are all based on weight.
(Molecular weight)
The weight average molecular weight and the number average molecular weight were measured as polystyrene conversion values by gel permeation chromatography (HLC8120GPC, used column TSKgel SuperH-RC, TSKgel SuperHM-L, developing solvent THF).
(viscosity)
The obtained paper sizing agent was put into a 225 ml mayonnaise bottle and measured at 25 ° C. using a B-type viscometer.

Example 1
In a flask equipped with a stirrer, a condenser, a nitrogen inlet tube and a thermometer, 85 parts of isopropyl alcohol, 43 parts of ion-exchanged water, 116.8 parts of styrene, 78.8 parts of 80% acrylic acid, 0.18 parts of methylenebisacrylamide While stirring the mixed monomer mixture under a nitrogen stream, the temperature was raised to 70 ° C., and t-butyl peroxy-2 ethylhexanoate (trade name “Perbutyl O” manufactured by Nippon Oil & Fats Co., Ltd.) was added. The part was prepared. Further, the temperature was raised to 80 to 90 ° C. and kept for 4 hours. Next, 200 parts of ion-exchanged water, 0.045 part of hydroquinone and 92 parts of a 48% aqueous potassium hydroxide solution (equivalent to neutralization of 90% acrylic acid) were neutralized and isopropyl alcohol was distilled off to obtain a copolymer. The solid content concentration was adjusted to 25%, and this was used as a water-soluble surface sizing agent for papermaking. Table 1 shows the characteristic values of the obtained water-soluble surface sizing agent for papermaking.

(Examples 2 to 5)
It was produced in the same manner as in Example 1 except that the amounts of styrene and anionic vinyl monomer components acrylic acid and methylenebisacrylamide used were changed to those shown in Table 1 (% by weight).

(Example 6)
It was produced in the same manner as in Example 1 except that methylenebisacrylamide, which is a crosslinkable monomer component, was changed to N, N dimethylacrylamide.

(Example 7)
It was produced in the same manner as in Example 1 except that methylenebisacrylamide, which is a crosslinkable monomer component, was changed to tetramethylolmethane tetraacrylate.

(Example 8)
It was produced in the same manner as in Example 1 except that acrylic acid as an anionic vinyl monomer was changed to methacrylic acid.

Example 9
It was produced in the same manner as in Example 1 except that butyl methacrylate was used in combination as another optional copolymerizable monomer and the amounts of each component used were those listed in Table 1.

(Example 10)
In a flask equipped with a stirrer, a condenser, a nitrogen inlet tube and a thermometer, 85 parts of isopropyl alcohol, 43 parts of ion-exchanged water, 116.8 parts of styrene, 78.8 parts of 80% acrylic acid, 0.18 parts of methylenebisacrylamide While stirring the mixed monomer mixture under a nitrogen stream, the temperature was raised to 70 ° C., and t-butyl peroxy-2 ethylhexanoate (trade name “Perbutyl O” manufactured by Nippon Oil & Fats Co., Ltd.) was added. The part was prepared. The temperature was further raised to 80 to 90 ° C. and kept for 3 hours. Next, 0.9 part of ammonium persulfate dissolved in 10 parts of ion-exchanged water and 0.38 part of sodium hydrogen sulfite dissolved in 10 parts of ion-exchanged water were charged and kept warm for 1 hour. Next, 200 parts of ion-exchanged water and 92 parts of 48% potassium hydroxide aqueous solution (equivalent to 90% neutralization with acrylic acid) were added to neutralize, and isopropyl alcohol was distilled off to make the solid content concentration of the copolymer 25%. This was used as a water-soluble surface sizing agent for papermaking. Table 1 shows the characteristic values of the obtained water-soluble surface sizing agent for papermaking.

(Example 11)
This was produced in the same manner as in Example 10 except that the amounts of styrene and anionic vinyl monomer components acrylic acid and methylenebisacrylamide used were changed to those shown in Table 1 (% by weight).

(Comparative Examples 1-3)
It was produced in the same manner as in Example 1 except that the amounts of styrene and anionic vinyl monomer components acrylic acid and methylenebisacrylamide used were changed to those shown in Table 2 (% by weight).

(Comparative Example 4)
It was produced in the same manner as in Example 1 except that the crosslinkable monomer component methylenebisacrylamide was not used.

(Comparative Example 5)
It was produced in the same manner as in Example 1 except that hydroquinone was not used.

(Performance test of surface sizing agent)
Using each water-soluble surface sizing agent obtained as described above, a coating solution is prepared, and this is applied to an uncoated paper, and its size effect (Stichht sizing degree, pen writing sizing degree), and The performance for inkjet suitability was tested.
Surface sizing agent, starch (trade name “Oji Ace A”, manufactured by Oji Cornstarch Co., Ltd.), and inorganic salts such as sodium chloride were mixed at a ratio of 0.4: 5.0: 1.0 (weight ratio). A coating solution was prepared. Next, uncoated neutral high-quality base paper (basis weight 65 g / m ² , steecht size degree 5 seconds) is prepared, and the coating liquid is applied to one side with a bar coater at a liquid absorption of 12 g / m ² . The coated paper was dried by passing through a rotary drum dryer at 105 ° C. for 1 minute and subjected to the following performance test.

(Stick human sizing degree)
The sized sizing degree (seconds) of the coated paper subjected to the size treatment was measured according to JIS P-8122. The larger the value, the better the sizing degree. The results are shown in Table 3.

(Pen writing size)
Regarding the coated paper subjected to the size treatment, J. Org. Tappi No. 12 was used to measure the pen writing size. The larger the value, the better the sizing degree. The results are shown in Table 3.

(Inkjet aptitude evaluation (print density test))
Ink jet suitability was evaluated by printing monochromatic (pigment) on each size-printed printing paper using a Canon Inkjet printer BJ-300J. Next, the density of the printed part obtained using a reflection densitometer (trade name “Gretag D186”, manufactured by Gretag Macbeth Co., Ltd.) was measured. The larger the value, the higher the print density. The results are shown in Table 3.

(Inkjet aptitude evaluation (feathering test))
For evaluation of feathering, straight lines and characters with a constant line width that are orthogonal in monochrome (pigment) are printed on the coated paper subjected to the above size processing using an inkjet printer BJ-300J manufactured by Canon Inc. This was done by visually evaluating the blurring of the straight lines and the outer edges of the letters. The case where there was no feathering was set as 6, and the case where ink was smeared and characters could not be identified was set as 1. The results are shown in Table 3.

（表中の各記号）
ＢＭＡ：メタクリル酸ブチル
ＭＢＡＡ：メチレンビスアクリルアミド
ＤＭＡＡ：Ｎ，Ｎジメチルアクリルアミド
ＴＭＭＴＡ：テトラメチロールメタンテトラアクリレート
Ｍｗ：重量平均分子量
Ｍｎ：数平均分子量

(Each symbol in the table)
BMA: butyl methacrylate MBAA: methylenebisacrylamide DMAA: N, N dimethylacrylamide TMMTA: tetramethylol methane tetraacrylate Mw: weight average molecular weight Mn: number average molecular weight

（表中の各記号）
ＢＭＡ：メタクリル酸ブチル
ＭＢＡＡ：メチレンビスアクリルアミド
ＤＭＡＡ：Ｎ，Ｎジメチルアクリルアミド
ＴＭＭＴＡ：テトラメチロールメタンテトラアクリレート
Ｍｗ：重量平均分子量
Ｍｎ：数平均分子量
＊：得られた共重合体がゲル化したため測定することができなかった。

(Each symbol in the table)
BMA: butyl methacrylate MBAA: methylene bisacrylamide DMAA: N, N dimethylacrylamide TMMTA: tetramethylol methane tetraacrylate Mw: weight average molecular weight Mn: number average molecular weight *: Since the obtained copolymer has gelled, it can be measured. could not.

＊：得られた共重合体がゲル化したため測定することができなかった。

*: Since the obtained copolymer was gelled, it could not be measured.

Claims (5)

A weight average molecular weight of 20,000 to 100,000 and a weight average molecular weight / number average molecular weight obtained by copolymerizing at least a monomer component containing a styrene monomer component, an anionic vinyl monomer component, and a crosslinkable monomer component. A paper-making surface sizing agent comprising a copolymer having a ratio of 1 or more and less than 2.5. The paper-made surface size according to claim 1, comprising 59 to 84% by weight of a styrene-based monomer component, 15 to 40% by weight of an anionic vinyl monomer component, and 0.0001 to 3% by weight of a crosslinkable monomer component in all monomer components. Agent. The surface sizing agent for papermaking according to any one of claims 1 to 2, wherein the crosslinkable monomer is (meth) acrylamides and / or (meth) acrylic acid esters. The surface sizing agent for papermaking according to any one of claims 1 to 3, wherein the copolymer is water-soluble. The surface sizing agent for papermaking according to any one of claims 1 to 4, wherein the surface sizing agent for papermaking has a solid content concentration of 23 to 32% by weight and a Brookfield viscosity at 25 ° C of 10 to 500 mPa · s.