JP2002227095A - Paper strengthening agent and paper strengthening method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a paper strengthening agent enabling itself to be made into a highly concentrated liquid product form even with increased molecular weight, having high paper strengthening effect and easy to handle as well and having quick solubility, and to provide a paper strengthening method using the above agent. SOLUTION: This paper strengthening agent consists of a polymer dispersion produced by subjecting a monomer mixture to dispersion polymerization process in an aqueous salt solution in the presence of a dispersant of ionic polymer soluble in the aqueous salt solution; wherein the monomer mixture comprises a tertiary amino group-containing cationic monomer, a quaternary amino group- containing cationic monomer, a specific anionic monomer and (meth)acrylamide in a specific molar ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper strength enhancer and a paper strength enhancing method, and more particularly, to a method for preparing a monomer (mixture) containing a specific monomer as an essential component in an aqueous salt solution. The present invention relates to a paper strength enhancer comprising a dispersion of a water-soluble cationic copolymer produced by a dispersion polymerization method in the presence of an ionic polymer dispersant soluble in the aqueous salt solution, and to a method of using the same.

[0002]

2. Description of the Related Art Paper strength enhancers are usually used in both anionic and amphoteric forms. Among them, the amphoteric paper strength enhancers are conventionally acrylamide and N, N-dialkylamino (meth) acrylate or N, N-dialkylamino (meth) acrylate.
Copolymers of acrylamide and the like and (meth) acrylic acid have been generally used. Further, as a crosslinking agent, N, N-methylenebisacrylamide or the like (Japanese Unexamined Patent Publication No.
No. 3,505,597), and more recently, N, N-dimethylacrylamide has been copolymerized to develop a paper strength agent comprising a polymer exhibiting specific solution physical properties (JP-A-5-140893). Publication, Japanese Patent Laid-Open No. 5-2
87693, JP-A-5-272092 or JP-A-7-97790).

[0003] The paper strength enhancing effect is caused by the hydrogen bonding strength between the hydroxyl group in the cellulose molecule and the side chain having hydrogen bonding strength in the paper strength enhancing agent. In addition, the molecular weight of the polymer used as the paper strength enhancer also affects the effect. That is, the effect as a paper strength enhancer is not remarkable unless the molecular weight is not less than a certain molecular weight, that is, several hundred thousand or more. The molecular weight of the paper-strength enhancer added to the wet end conventionally used is about several hundred thousand to one million, and the type in which the crosslinkable monomer is copolymerized with this is two million to five million.
A million. Since the crosslinkable polymer can reduce the apparent solution viscosity, its concentration is barely 15
-20% by weight product form can be maintained. However, if the molecular weight becomes so high, it is predicted that the limit of the product concentration is already 20% by weight. It is not possible to further increase the product concentration in the form of a mere aqueous solution. Therefore, a different form of paper strength agent from the current state is required.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a paper-strengthening agent which has a remarkable effect even if the molecular weight becomes several million.
An object of the present invention is to provide a paper strength enhancer which can be formed into a high-concentration product form, has a high paper strength enhancement effect, is easy to handle, and has a high solubility, and provides a paper strength enhancer method.

[0005]

Means for Solving the Problems The present inventor has made intensive studies to solve the above-mentioned problems, and as a result, has reached the following invention. That is, the invention of claim 1 of the present invention provides a tertiary amino group-containing cationic monomer represented by the following general formula (1), 2 to 25 mol%, and a quaternary amino group represented by the following general formula (2). Containing cationic monomer 0 to 10 mol%, anionic monomer 2 represented by the following general formula (3)
A monomer mixture consisting of -25 mol% and 40-96 mol% of (meth) acrylamide is produced by a dispersion polymerization method in a salt aqueous solution in the presence of a dispersant comprising an ionic polymer soluble in the salt aqueous solution. And a paper strength agent comprising a polymer dispersion.

Embedded image R1 is hydrogen or methyl; R2 and R3 are methyl, ethyl, 2-hydroxypropyl or benzyl, which may be the same or different; A is an oxygen atom or NH; B is a C2-C3 alkylene group; Or an alkoxylene group, X1 is an anion

Embedded image R4 is hydrogen or a methyl group; R5, R6, and R7 are a methyl group, an ethyl group, a 2-hydroxypropyl group, or a benzyl group, which may be the same or different; A is an oxygen atom or NH; B is C2 to C3; Alkylene group or alkoxylene group, X2 is an anion

Embedded image R8 is hydrogen, methyl or carboxymethyl, R9
Is hydrogen or carboxyl group, A is SO3, C6H4S
O3, CONHC (CH3) 2CH2SO3 or C
OO and Y are hydrogen or cation

According to a second aspect of the present invention, the dispersant comprising the ionic polymer has an ion equivalent of 1.50 meq / g or more;
The paper strength enhancer according to claim 1, wherein the strength is not more than 15.0 meq / g.

The invention of claim 3 is the paper-strengthening agent according to claim 1 or 2, wherein the dispersant comprising the ionic polymer is 1 to 10% by weight based on the monomer. It is.

A fourth aspect of the present invention is the paper strength enhancer according to the first or second aspect, wherein the salt constituting the salt aqueous solution contains at least one kind of polyanionic salt.

The invention of claim 5 is characterized in that the paper strength enhancer according to any one of claims 1 to 3 is diluted with water to form an aqueous solution, and then added to the papermaking raw material before papermaking. Is the way.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The paper strength enhancer of the present invention contains a tertiary amino group-containing cationic monomer or, if necessary, a quaternary amino group-containing cationic monomer, and further comprises an anionic monomer. Polymer prepared by a dispersion polymerization method in the presence of a dispersant consisting of an ionic polymer soluble in a salt aqueous solution in a salt aqueous solution in a salt solution and a monomer mixture comprising 40 to 96 mol% of (meth) acrylamide Consists of a dispersion. A water-soluble polymer comprising a polymer fine particle dispersion dispersed in a salt aqueous solution can be produced according to JP-A-62-15251. In this method, an ionic monomer or an ionic monomer and a nonionic monomer are stirred in a salt aqueous solution in the presence of a dispersant composed of an ionic polymer soluble in the salt aqueous solution. A dispersion of the produced polymer fine particles having a particle size of 100 mμ or less can be produced.

Next, a specific manufacturing method will be described. As the inorganic salts constituting the salt aqueous solution, polyvalent anion salts are more preferable, and sulfates or phosphates are suitable.Specifically,
Examples thereof include ammonium sulfate, sodium sulfate, magnesium sulfate, aluminum sulfate, ammonium hydrogen phosphate, sodium hydrogen phosphate, and potassium hydrogen phosphate. It is preferable to use these salts as an aqueous solution having a concentration of 15% or more. Dissolve the monomers in this,
In addition, coexist with a dispersant consisting of an ionic polymer,
Is adjusted to 2 to 5, and after substitution with nitrogen, polymerization is started with a polymerization initiator.

The polymerization concentration is 15% as the monomer concentration.
% To 35% by weight, preferably 20% to 35% by weight.
30% by weight. As a method of the embedding, the polymerization may be started at once, the embedding may be performed at once, or may be appropriately divided and performed. That is, the monomer concentration is a concentration after completion of the polymerization step.

Examples of the tertiary amino group-containing cationic monomer represented by the general formula (1) include dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, and dimethylaminopropyl (meth) acrylate. ) Acrylamide, diethylaminopropyl (meth) acrylamide and the like. If necessary, a quaternary ammonium salt group-containing cationic monomer represented by the general formula (2) is copolymerized, and examples thereof include (meth) acryloyloxyethyltrimethylammonium chloride,
(Meth) acryloyloxyethyldimethylbenzylammonium chloride, (meth) acryloylaminopropylacryloyloxyethyltrimethylammonium chloride, (meth) acryloylaminopropylacryloyloxyethyldimethylbenzylammonium chloride,
(Meth) acryloyloxy 2-hydroxypropyltrimethylammonium chloride and the like. Further, examples of the anionic monomer represented by the general formula (3) include (meth) acrylic acid, itaconic acid, maleic acid, styrenesulfonic acid, and acrylamide 2-methylpropanesulfonic acid.

The copolymer mol% of these monomers is as follows:
2 to 25 mol% of the tertiary amino group-containing cationic monomer represented by the general formula (1), 0 to 10 mol% of the quaternary ammonium base-containing cationic monomer represented by the general formula (2), When the anionic monomer represented by the general formula (3) is 2
-25 mol%, (meth) acrylamide is 40-96 mol%, preferably, the tertiary amino group-containing cationic monomer represented by the general formula (1) is 4-10 mol%, and the general formula (2) 0 to 5 mol% of the quaternary ammonium salt group-containing cationic monomer represented by the formula), 4 to 10 mol% of the anionic monomer represented by the general formula (3), and 75 to 92 mol of (meth) acrylamide. %.

It is also a useful method to modify the polymer by appropriately copolymerizing a copolymerizable nonionic monomer. Examples of such monomers include:
N, N-dimethylacrylamide, vinyl acetate, acrylonitrile, methyl acrylate, (meth) acrylic acid 2
-Hydroxyethyl, diacetone acrylamide, N-
Examples include vinylpyrrolidone, N-vinylformamide, N-vinylacetamide and the like.

The dispersant comprising an ionic polymer to be co-polymerized is an ionic monomer or a polymer or copolymer of an ionic monomer and a nonionic monomer. Examples of such ionic polymers include (meth) acryloyloxyethyltrimethylammonium chloride,
Polymers such as (meth) acryloylaminopropyltrimethylammonium chloride and dimethyldiallylammonium chloride. Also, a copolymer with a nonionic monomer can be used. Examples of non-ionic monomers include:
Acrylamide, N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone, N, N-dimethylacrylamide, acrylonitrile, diacetoneacrylamide, 2-hydroxyethyl (meth) acryle
And a copolymer with acrylamide is preferred. The amount of the polymer dispersant comprising the ionic polymer is 0.5 to 10% by weight, preferably 1 to 5% by weight, based on the monomer. If it is 0.5% or less, there is no effect as a dispersant, and if it is 10% or more, it is disadvantageous in terms of cost and the properties of the produced polymer dispersion are different, which is outside the object of the present invention.

The polymerization conditions are usually determined as appropriate depending on the monomers used and the molar percentage of the copolymer.
Perform at 0 ° C. For the initiation of polymerization, a radical polymerization initiator is used. These initiators may be either oil-soluble or water-soluble, and can be polymerized by any of azo, peroxide and redox systems. Examples of the oil-soluble azo initiator include 2,2′-azobisisobutyronitrile,
1,1′-azobis (cyclohexanecarbonitrile), 2,2′-azobis (2-methylbutyronitrile), 2,2′-azobis (2-methylpropione-
G) 4,4-azobis (4-methoxy-2,4dimethyl) valeronitrile and the like, which are dissolved in a water-miscible solvent and added.

Examples of water-soluble azo initiators include 2,
2′-azobis (amidinopropane) dichloride,
2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride, 4, 4 ′
-Azobis (4-cyanovaleric acid) and the like. Examples of the redox system include a combination of ammonium peroxodisulfate with sodium sulfite, sodium hydrogen sulfite, trimethylamine, tetramethylethylenediamine, and the like. Further examples of peroxides are ammonium or potassium peroxodisulfate,
Examples include hydrogen peroxide, benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, succinic peroxide, t-butylperoxy 2-ethylhexanoate and the like. Most preferred among these initiators are water-soluble azo initiators2,
2′-azobis (amidinopropane) dichloride,
2,2'-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride.

The present invention comprises two points: polymerization in an aqueous salt solution to precipitate the generated water-soluble cationic monomer, and control of the precipitation state of the polymer so as to be fine particles. Precipitation of the polymer by the aqueous solution of the polyvalent anion salt is a conventionally known phenomenon easily explained from the Hoffmeister series and the like. Cationic monomer units having a benzyl group are particularly prone to salting out, followed by amide groups. The effect manifestation mechanism of the two kinds of additive polymers is as follows.
Although it is unknown, it is presumed that the action of providing an appropriate polymerization field and preventing the association by the electric repulsion acts. In particular, a water-soluble cationic polymer insoluble in an aqueous salt solution shows complicated behavior such as dissolution in an aqueous salt solution when a monomer coexists, and has not reached a state where a reliable theoretical explanation can be given.

The molecular weight of the paper-strength enhancer comprising an amphoteric polymer constituting the dispersion liquid is 1,000,000 to 1,000,000 in weight average molecular weight.
8 million, preferably 2 million to 6 million. If it is less than 2,000,000, the paper strength enhancing effect is insufficient, and if it is more than 8,000,000, the papermaking raw materials are too agglomerated and the formation of paper is undesirably found.

Since the paper strength enhancer of the present invention is composed of a dispersion liquid of polymer fine particles, it is generally dissolved in water to form an aqueous solution, and then added to the papermaking raw material before papermaking. As the addition concentration, a dispersion is prepared as a polymer aqueous solution of about 0.2 to 2% by weight, and 0.05 to 2% by weight based on the dry solid content of the papermaking raw material.
It is a guideline to add a certain amount. The type of papermaking raw material is mainly paperboard such as liner and core base paper, but it can be applied to other printing paper. The papermaking pH can be controlled by adjusting the monomer composition even when the pH is 8 to 9 which is acidic to weakly alkaline.

[0022]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples. However, the present invention is not limited to the following Examples unless it exceeds the gist thereof.

[0023]

Example 1 A four-necked 500 ml separable flask equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen inlet tube was charged with 126.9 g of deionized water and 120.0 g of ammonium sulfate.
g, sodium sulfate 18.2 g, dimethylaminoethyl methacrylate 19.5 g, acryloyloxyethyl dimethylbenzyl ammonium chloride 80% 9.7 g, 6
0% acrylic acid: 11.1 g, 50% acrylamide 1
84.8 g was added to make a uniform mixed solution, and a 20% aqueous solution of acryloyloxyethyltrimethylammonium chloride homopolymer (solution viscosity: 17,320 mP) was used as a dispersant.
a.s) 21.9 g (3.5% by weight based on monomer) and 1.3 g of 10% isopropyl alcohol as a polymerization degree regulator
(0.1% by weight of monomer) was added and completely dissolved. Thereafter, nitrogen is introduced from a nitrogen introduction tube while stirring to remove dissolved oxygen. During this time, 30 to 3
Adjust internal temperature to 2 ° C. 30 minutes after nitrogen introduction, 2,
2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] ghydrochloride g (based on monomer,
100 ppm) to initiate polymerization. 8 after initiation of polymerization
After a certain time, 0.65 g of the initiator was added, and the polymerization was continued for another 15 hours to complete the reaction. This prototype is referred to as prototype-1. The composition of this prototype-1 is dimethylaminoethyl methacrylate / acryloyloxyethyldimethylbenzylammonium chloride / acrylic acid / acrylamide = 8/2/6/84 (mol%),
The dispersion viscosity was 1370 mPa · s. In addition, a molecular weight measuring device (DLS-70 manufactured by Otsuka Electronics Co., Ltd.)
00), the weight average molecular weight was measured. Table 1 shows the results
Shown in

[0024]

Example 2 A four-necked 500 ml separable flask equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen inlet tube was charged with 122.4 g of deionized water and 120.0 g of ammonium sulfate.
g, sodium sulfate 25.0 g, dimethylaminoethyl methacrylate 24.6 g, 60% acrylic acid: 15.2
g, 50% acrylamide (182.8 g) to give a uniform mixed solution, and as a dispersant, a 20% aqueous solution acryloyloxyethyltrimethylammonium chloride homopolymer (solution viscosity 17, 320 mPa · s) 31.3 g (based on monomer) 5.0% by weight) and 1.3 g of 10% isopropyl alcohol as a polymerization degree regulator (0.1% by weight of monomer)
Was added and completely dissolved. Thereafter, nitrogen is introduced from a nitrogen introduction tube while stirring to remove dissolved oxygen. During this time, the internal temperature is adjusted to 30 ± 2 ° C. using a thermostatic water bath. Thirty minutes after the introduction of nitrogen, 2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] g (about 100 ppm) of dihydrochloride was added to initiate polymerization. . Eight hours after the start of the polymerization, 0.65 g of the initiator was added, and the polymerization was continued for another 15 hours to complete the reaction. This prototype is referred to as prototype-2. This prototype-
The composition of No. 2 was dimethylaminoethyl methacrylate / acrylic acid / acrylamide = 10/8/82 (mol%), and the dispersion viscosity was 1810 mPa · s. In addition, a molecular weight measuring device using a static light scattering method (DL made by Otsuka Electronics Co., Ltd.)
S-7000). Table 1 shows the results.

[0025]

Example 3 In a four-necked 500 ml separable flask equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen inlet tube, 135.3 g of deionized water and 115.2 g of ammonium sulfate.
g, ammonium chloride 15.4 g, dimethylaminoethyl methacrylate 19.9 g, 60% acrylic acid: 7.7
g, itaconic acid 4.1 g, 50% acrylamide 19
3.0 g was added to make a uniform mixed solution, and 2
0% aqueous solution acryloyloxyethyltrimethylammonium chloride homopolymer (solution viscosity 17, 320 mPa
S) 21.9 g (3.5% by weight based on monomer) and 1.3 g of 10% isopropyl alcohol as a polymerization degree regulator
(Based on 0.07% by weight of the monomer) and completely dissolved. Thereafter, nitrogen is introduced from a nitrogen introduction tube while stirring to remove dissolved oxygen. During this time, 30 ± 2
Adjust internal temperature to ° C. 30 minutes after nitrogen introduction, 2, 2 '
-Azobis [2- (5-methyl-2-imidazoline-2
-Yl) propane] g of dihydrochloride (to monomer, 10
0 ppm) to initiate polymerization. Eight hours after the start of the polymerization, 0.65 g of the initiator was added, and the polymerization was continued for another 15 hours to complete the reaction. This prototype is referred to as prototype-3. The composition of this prototype 2 was dimethylaminoethyl methacrylate / acrylic acid / itaconic acid / acrylamide = 8/4/2/86 (mol%), and the dispersion viscosity was 940 mPa · s. Also, the weight average molecular weight was measured in the same manner. Table 1 shows the results.

[0026]

Examples 4 to 6 By the same operation as in Examples 1 to 3, dimethylaminoethyl methacrylate / acryloyloxyethyltrimethylammonium salt / acrylic acid / acrylamide = 10/3/6/81 (mol%) (prototype-
4), dimethylaminoethyl methacrylate / acryloyloxyethyldimethylbenzylammonium salt / acrylic acid / acrylamide = 5/2/11/82 (mol%) (prototype-5), dimethylaminoethyl methacrylate / acrylic acid / itacon Acid / acrylamide = 8/6 /
A paper strength agent composed of each polymer dispersion composed of 2/84 (mol%) (prototype-6) was synthesized. Table 1 shows the results.

[0027]

Comparative Examples 1-3 At a monomer concentration of 20% by weight, dimethylaminoethyl methacrylate / acryloyloxyethyldimethylbenzylammonium salt / acrylic acid / acrylamide = 8/2/6/84 by an aqueous solution polymerization method.
(Mol%) (Comparative-1), dimethylaminoethyl methacrylate / acrylic acid / acrylamide = 10/9/82
(Mol%) (Comparative-2), dimethylaminoethyl methacrylate / acrylic acid / itaconic acid / acrylamide = 8
/ 4/2/86 (mol%) (comparative-3) was adjusted to pH 3.0-3.5 with 80% sulfuric acid or sodium hydroxide, and then ammonium peroxydisulfate and sulfurous acid were added. Polymerization was performed at an initiation temperature of 35 ° C. using sodium hydrogen as an initiator to synthesize a paper strength enhancer.
Table 1 shows the results.

[0028]

Examples 7 to 12 Papermaking test of a paper-strengthening agent comprising the dispersion of the present invention using a raw material for a liner (SS content 2.54%, pH 5.52, ash content 0.20%) at a papermaking site. Was done. After making this papermaking raw material a concentration of 0.7%, a commercially available emulsion sizing agent was added to pulp at 0.10%, aluminum sulfate (8.0% as Al2 O3 content) to pulp at 2.5%.
Was added to adjust the pH to 5.31, and each of Prototypes 1 to 6 of Examples 1 to 6 was diluted with water to form a 0.5% aqueous solution, and then 0.3% was added, followed by stirring for 20 seconds. After that, the paper was made with a tappi standard sheet machine so as to have a basis weight of 100 g / m 2, the obtained wet paper was pressed at 5 kg / cm 2 for 2 minutes, and then dried with a 105 ° C. rotary dryer for 3 minutes to obtain a hand-made paper. Obtained. This handmade paper was conditioned at 20 ° C. and 65% HR for 24 hours, and then subjected to a specific burst strength according to JIS P8112. TAPPI paper pulp test method NO. The internal bond strength was measured according to 18-77.
Table 2 shows the results.

[0029]

Comparative Examples 4 to 6 By the same operation as in Examples 7 to 12,
Comparative Examples 1 to 3 of Comparative Examples 1 to 3 were tested.
Table 2 shows the results.

[0030]

[Table 1] DMM: dimethylaminoethyl methacrylate AMB: acryloyloxyethylbenzyldimethylammonium chloride DMQ: acryloyloxyethyltrimethylammonium chloride AAC: acrylic acid, IA: itaconic acid, AAM: acrylamide Dispersion viscosity: mPa · s Molecular weight: 10,000

[0031]

[Table 2] Internal bond strength: Kgf / in2

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J011 KA02 KA04 KA05 KA08 KA28 KA29 KB14 KB29 4J100 AB07S AJ02S AJ08S AJ09S AL08Q AL08R AL66R AM15P AM19Q AM21S BA03R BA31Q BA32R BA56Q BA56R BA56S CA05 AG06 EA29 EA32 FA13 FA30

Claims (5)

[Claims] 1. A tertiary amino group-containing cationic monomer represented by the following general formula (1): 2 to 25 mol%, and a quaternary amino group-containing cationic monomer represented by the following general formula (2): A monomer mixture consisting of 10 to 10 mol%, 2 to 25 mol% of an anionic monomer represented by the following general formula (3) and 40 to 96 mol% of (meth) acrylamide is added to the aqueous salt solution in the aqueous salt solution. A paper strength enhancer comprising a polymer dispersion prepared by a dispersion polymerization method in the presence of a dispersant comprising a soluble ionic polymer. Embedded image R1 is hydrogen or methyl; R2 and R3 are methyl, ethyl, 2-hydroxypropyl or benzyl, which may be the same or different; A is an oxygen atom or NH; B is a C2-C3 alkylene group; Or an alkoxylene group, X1 is an anion R4 is hydrogen or a methyl group; R5, R6, and R7 are a methyl group, an ethyl group, a 2-hydroxypropyl group, or a benzyl group, which may be the same or different; A is an oxygen atom or NH; B is C2 to C3; An alkylene group or an alkoxylene group, and X2 is an anion. R8 is hydrogen, methyl or carboxymethyl, R9
Is hydrogen or carboxyl group, A is SO3, C6H4S
O3, CONHC (CH3) 2CH2SO3 or C
OO and Y are hydrogen or cation 2. The dispersant comprising the ionic polymer has an ion equivalent of 1.50 meq / g or more and 15.0 meq / g or more.
The paper strength agent according to claim 1, which is not more than g. 3. The dispersant comprising the ionic polymer,
The paper strength enhancer according to claim 1 or 2, wherein the amount is 1 to 10% by weight based on the monomer. 4. The paper strength enhancer according to claim 1, wherein the salt constituting the aqueous salt solution contains at least one polyvalent anionic salt. 5. A paper-strengthening method comprising diluting the paper-strengthening agent according to claim 1 with water to form an aqueous solution, and then adding it to a papermaking raw material before papermaking.