JP2002129495A - Method for improving strength of paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a paper strengthening agent for spray addition having physical properties favorable for the spray addition, i.e., sufficient adhesive effects even when the solution viscosity is relatively low. SOLUTION: A primary amino group-containing copolymer produced by polymerizing a monomer mixture consisting essentially of a primary amino group-containing acrylic monomer is sprayed on a wet web prior to drying or a paper after the drying.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for improving the strength of paper, and more particularly, to spraying a primary amino group-containing acrylic copolymer onto wet paper before drying or paper after drying. The present invention relates to a method for improving the strength of paper.

[0002]

2. Description of the Related Art Conventionally, in order to synthesize a polymer having a primary amino group, after polymerizing N-vinylcarboxylic acid amide,
The N-acyl group in the side chain was hydrolyzed with an acid or alkali to generate a primary amino group. However, this method cannot perform the hydrolysis reaction after polymerization,
Inevitably, the reaction conditions become severe. On the other hand, monomers having a primary amino group in the molecule are disclosed in US Pat. No. 3,037,96.
No. 9 and US Pat. No. 3,336,358. Since it is an acrylic monomer, copolymerization with other acrylic monomers is good, a polymer having a molecular weight of a certain level or more is produced, and there is no need for hydrolysis after polymerization. A polymer having a primary amino group has various unique properties as compared with other polymers because many primary amino groups are present in the molecule. In particular, since it has a high adsorptivity to hydrophilic fine particles, for example, when it is used as a flocculant for dewatering sludge, it has properties such as a decrease in the water content of the dewatered cake. In addition, it also has properties such as high adsorptivity to metal surfaces, relatively high compatibility with other water-soluble polymers, and polymer modification by reacting with other organic compounds having a functional group. Have.

On the other hand, there are two main purposes for applying, impregnating or spraying the wet paper before drying or the paper surface after drying. One is to improve printability,
The other is to increase the burst strength and the tensile strength. Starch, polyvinyl alcohol-
Or anionic polyacrylamide has been used. However, with the increase in printing speed, these surface treatment chemicals cannot always be said to be sufficient. There is a need for a surface treatment agent with higher functionality. Newspaper is the most demanded surface treatment agent. Newsprint paper has a very low degree of sizing, so that when applied or contained on the surface, a large part of the processing agent permeates into the paper. The ratio of staying on the surface is low. As a method for improving this, studies have been made to increase the concentration at the time of applying the treating agent, or to increase the ratio of the treating agent being cationic or amphoteric to be adsorbed on the paper surface, but the most suitable one has not been completed yet.

A paper-strengthening agent to be added to a papermaking raw material before papermaking has both anionic and amphoteric properties. Among these, the amphoteric paper strength enhancer is conventionally a copolymer of acrylamide and N, N-dialkylamino (meth) acrylate or N, N-dialkylamino (meth) acrylamide and (meth) acrylic acid. It has been used regularly. Also,
N, N-methylenebisacrylamide (JP-A-63-50597) is copolymerized as a cross-linking agent, and more recently, N, N-dimethylacrylamide is copolymerized to form a polymer having specific solution properties. Have been developed (JP-A-5-140893, JP-A-5-287693, JP-A-5-272092).
Or JP-A-7-97790). However, these N, N-dialkylamino (meth) acrylic
Or N, N-dialkylamino (meth) acrylamide is a cationic monomer comprising a tertiary amino group, and therefore has a weak hydrogen bonding ability. In other words, 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. On the other hand, a primary amino group has two active hydrogens, and therefore has a strong hydrogen bonding force. Conventionally, paper strength enhancers made of monomers having a primary amino group as raw materials have not been studied except for vinylamine-based polymers due to the problem of monomers as raw materials.

In view of the molecular weight of the polymer used as a paper strength enhancer, the effect as a paper strength enhancer is remarkable unless the molecular weight is a certain molecular weight or more, ie, hundreds of thousands or more. is not. Although the molecular weight is required to be a certain level or more, as the molecular weight increases, the viscosity of the solution will inevitably increase, and the handling of products and dispersion in papermaking raw materials will worsen,
Undesirable points occur. Crosslinking can reduce the apparent solution viscosity to a certain extent, but it is not always easy to control the apparent viscosity of the product. for that reason,
The current situation is that there is a demand for paper strength enhancement that has a sufficient molecular weight, has an excellent paper strength enhancement effect, and exhibits physical properties of low apparent viscosity that is easy to handle. In particular, when spraying wet paper before drying or paper after drying, spraying operation cannot be performed if the apparent viscosity is high, and a solution having a viscosity similar to that of water is ideally preferable. It is necessary to keep it as low as possible.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to develop a spray-added paper-strengthening agent which has favorable properties for spray-adding, that is, has a sufficient adhesive effect even if the solution viscosity is relatively low. .

[0007]

As a result of intensive studies to solve the above-mentioned problems, it has been found that a primary amino group-containing copolymer as described below can achieve the object. That is, the invention of claim 1 of the present invention relates to a primary amino group-containing copolymer produced by polymerizing a monomer mixture containing a cationic monomer represented by the following general formula (1) as an essential component. This is a method for improving paper strength, which comprises spraying wet paper before drying or paper after drying.

Embedded image R is hydrogen or methyl, A is oxygen or NH, B
Is a C2-C3 alkylene group or an alkoxylene group,
X is an anion

The invention of claim 2 is that the monomer mixture comprises 2 to 50% by mole of the monomer represented by the general formula (1) and 0% by weight of the anionic monomer represented by the following general formula (2). 2. The method for improving paper strength according to claim 1, wherein the method comprises from 20 to 20 mol% and from 30 to 98 mol% of acrylamide.

Embedded image R2 is hydrogen, methyl group or carboxymethyl group, A is SO3, C6H4SO3, CONHC (CH3) 2CH
2SO3 or COO, Y is hydrogen or cation R3
Is hydrogen or cation, or COOZ, Z is hydrogen or cation

According to a third aspect of the present invention, the monomer mixture comprises 1 to 35 mol% of the monomer represented by the general formula (1), and an anionic monomer represented by the general formula (2). To 20 mol%, a cationic monomer 1 represented by the following general formula (3)
The paper strength enhancing method according to claim 1, wherein the paper strength is from 15 to 15 mol% and acrylamide is from 30 to 98 mol%.

Embedded image R2 is hydrogen or methyl, R3 methyl or ethyl, R4 is methyl, ethyl or benzyl, R
5 is a hydrogen atom, a methyl group or an ethyl group, A is an oxygen atom or NH, B is a C2-C3 alkylene group or an alkoxylene group, X is an anion

The invention according to claim 4 is characterized in that the monomer represented by the general formula (1) is a salt of an organic acid or an inorganic acid of 2-aminoethyl methacrylate. It is a paper strength enhancing method according to any one of 1 to 3.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In order to produce a primary amino group-containing polymer used in the present invention, first, acrylamide or anionic monomer copolymerized with a cationic monomer represented by the general formula (1) is used. After adjusting the pH of the aqueous solution in which is mixed to 2 to 6, the polymerization is started by removing oxygen in the reaction system by replacing with nitrogen and adding a radical polymerizable initiator to form various polymers suitable for the purpose. Generate. As the polymerization method, aqueous solution polymerization, dispersion polymerization in salt water or an organic solvent, and the like are possible. However, in consideration of addition to papermaking raw materials, it is most practical to produce an aqueous polymer solution by aqueous solution polymerization. The concentration of the aqueous solution during the reaction is generally 5 to 30.
%, But preferably 15 to 25% by weight for easy control. The reaction temperature is usually 10 to 1
The reaction is carried out at a temperature of 00 ° C, preferably 20 to 80 ° C. Examples of the cationic monomer represented by the general formula (1) include 2
Salts of organic acids and inorganic acids such as -aminoethyl acrylate, 2-aminoethyl methacrylate, 3-aminopropyl acrylate and 3-aminopropyl methacrylate; Since these monomers are usually stored in the form of a salt, it is common to mix and dissolve the monomers with other copolymerizable monomers, and then adjust the pH.

Since the cationic monomer represented by the general formula (1) is an acrylic monomer, a good copolymerization reaction with various acrylic monomers is possible. For example, non-ionic monomers (meth) acrylamide, N, N-dimethylacrylamide, vinyl acetate, acrylonitrile, methyl acrylate, 2-hydroxyethyl (meth) acrylate, diacetone acrylamide, N-vinylpyrrolidone, -Vinylformamide, N-vinylacetamide and the like, and copolymerization with one or more nonionic monomers is also possible. An example of the most preferred nonionic monomer as a paper strength agent is acrylamide.

Further, it can be copolymerized with a monomer containing a tertiary amino group or a quaternary ammonium group. Examples of the tertiary amino group-containing monomer include dimethylaminoethyl (meth) acrylate and dimethylaminopropyl (meth) acrylamide. Examples of the acrylic-type quaternary ammonium group-containing monomer include (meth) acryloyloxyethyltrimethylammonium chloride, which is a quaternary compound of the tertiary amino group-containing monomer with methyl chloride or benzyl chloride, (Meth) acryloyloxy 2-hydroxypropyltrimethylammonium chloride, (meth) acryloylaminopropyltrimethylammonium chloride,
(Meth) acryloyloxyethyldimethylbenzylammonium chloride, (meth) acryloyloxy 2-hydroxypropyldimethylbenzylammonium chloride, (meth) acryloylaminopropyldimethylbenzylammonium chloride and the like can be mentioned. Also, dimethyldiallylammonium chloride and the like can be copolymerized.

The molar percentage of the primary amino group-containing monomer represented by the general formula (1) in the primary amino group-containing copolymer is 2 to 50 mol%, preferably 5 to 20 mol%. . When a tertiary amino group or a quaternary ammonium base is used in combination for copolymerization, the copolymerization molar percentage of the primary amino group-containing monomer represented by the general formula (1) is from 1 to 35 mol%. The tertiary amino group or quaternary ammonium group-containing monomer is present in an amount of 1 to 15 mol%. The copolymer mol% of the primary amino group-containing monomer represented by the general formula (1) with respect to all cationic monomers is as follows:
50 to 100 mol%. Since tertiary amino groups or quaternary ammonium bases generally do not have hydrogen bonds, they do not contribute much to the paper strength enhancing effect. Therefore, if the amount of the primary amino group-containing monomer is less than 50 mol%, the paper strength enhancing effect is undesirably reduced.

The primary amino group-containing polymer may be an amphoteric polymer containing an anionic group, and may be an anionic monomer such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, 2-acrylamide 2-methylpropane. It can be produced by copolymerizing sulfonic acid, styrenesulfonic acid and the like. The mol% of these anionic monomers in the polymer is 1 to 20 mol%, preferably 2 to 15 mol%. The molar percentage of the cationic monomer containing a primary amino group-containing acrylic monomer in the polymer used in the present invention is 2 to 50 mol%, preferably 2 to 20 mol%. . When a tertiary amino group or a quaternary ammonium base is used in combination for copolymerization, the copolymer mol% of the primary amino group-containing monomer represented by the general formula (1) is 1 to 35 mol%, The monomer containing a tertiary amino group or a quaternary ammonium base is 1
１５15 mol%. The copolymer mol% of the primary amino group-containing monomer represented by the general formula (1) with respect to all cationic monomers is 50 to 100 mol%.

The primary amino group-containing polymer of the present invention comprises N,
Cross-linked by polyfunctional monomers such as N-methylenebisacrylamide and ethylene glycol di (meth) acrylate, or by heat-reactive monomers such as N, N-dimethylacrylamide and N, N-diethylacrylamide Alternatively, a branched polymer can be produced.

The radical polymerization initiator for initiating the polymerization can be azo, peroxide or redox. Examples of oil-soluble azo initiators include:
2,2'-azobisisobutyronitrile, 1,1'-azobis (cyclohexanecarbonitrile), 2,2'-
Azobis (2-methylbutyronitrile), 2,2′-azobis (2-methylpropionate), 4,4-azobis (4-methoxyl, 2,4dimethyl) valeronitrile and the like, and a water-miscible solvent Dissolve and add. Examples of the water-soluble azo initiator include 2,2′-azobis (amidinopropane) dihydrochloride and 2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] Hydrogen chloride, 4,4′-azobis (4-cyanovaleric acid) and the like. Examples of the redox system include a combination of ammonium or potassium peroxodisulfate with sodium sulfite, sodium hydrogen sulfite, trimethylamine, tetramethylethylenediamine, or the like. Further, examples of peroxides include ammonium peroxodisulfate, hydrogen peroxide, benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, succinic peroxide, t-butylperoxy 2-ethylhexanoate and the like. Can be. Among these, particularly preferred initiators are 2,2′-azobis (amidinopropane) dihydrochloride, 2,2 ′, which is a water-soluble azo initiator.
-Azobis [2- (5-methyl-2-imidazoline-2
-Yl) propane].

The degree of polymerization of the primary amino group-containing polymer is about several hundred thousand to several million, preferably 500,000 to 500,000.
2 million. When expressed in terms of the viscosity of a 20% by weight aqueous solution, it is 1,000 to 20,000 mPa · s, and preferably 3,000 to 10,000 mPa · s.

When the primary amino group-containing polymer of the present invention is spray-added, the polymer concentration is about 0.1 to 5% by weight, although it varies depending on the amount added to paper. The spray addition to the paper after drying yields almost 100%, which is much more efficient than the so-called internal addition method which is added to the papermaking raw material before papermaking. Also, if wet paper before drying passes through the dehydration press and is added before the final press,
Since the moisture content of the wet paper is reduced, the ratio of the paper strength enhancer to be eliminated is reduced, and the addition efficiency is improved. As the addition amount,
0.02 to 2.0 g / m 2, preferably 0.05
0.5 g / m2. Applicable paper products include:
There is no particular limitation on the type of printing paper, such as high-quality and medium-quality printing paper, packaging paper, liner, and newsprint. In addition, conventionally used materials such as a surface sizing agent and an antifoaming agent for papermaking chemicals used in combination are not a problem if attention is paid to ionicity.

[0020]

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.

[0021]

SYNTHESIS EXAMPLES 1 to 6 Primary amino group-containing polymers were synthesized by an aqueous solution polymerization method according to the monomer composition shown in Table 1. Table 1 shows the results.

[0022]

Comparative Synthesis Examples 1 to 3 Polymers containing a tertiary amino group or a quaternary ammonium base were synthesized by an aqueous solution polymerization method according to the monomer composition shown in Table 1. Table 1 shows the results.

[0023]

Examples 1 to 6 Raw paper raw materials (LBKP / DIP / TM
P = 10/60/30, pH 6.88, total ss 2.40
%, Ash content 0.30%), pulp concentration 0.7% by weight
Was diluted with tap water. Using this papermaking raw material, 100
g / m 2 of paper was prepared. Paper making, band 1.0% (vs. dry pulp, the same applies hereinafter) and polyacrylamide polymer flocculant DR-1500 (manufactured by Hymo) as a retention aid,
0.015% was added, and the mixture was stirred for 20 seconds while stirring at 300 rpm with a stirrer, and then papermaking was performed by a tappi standard paper machine. The obtained wet paper was put on a direct reading balance together with the wire, and a solution prepared by diluting the prototypes -1 to -6 of Synthesis Examples 1 to 6 to a predetermined dilution concentration shown in Table 2 was applied at a pressure of 2.5. Spray coating was performed from a 10.0 g nozzle at atmospheric pressure.
This was returned to the sheet machine together with the wire, and the sheet machine was filled with water and drained of water filled under the wire to dehydrate under reduced pressure. A filter paper was placed on the sheet machine, and cuticle was applied three times to the filter paper. Transcribed. The transferred wet paper is sandwiched between two filter papers and pressed at a pressure of 3 kg / m2 for 5 minutes.
It was dried in a dryer. Thereafter, the humidity was adjusted at 20 ° C. and 65 RH for 20 hours, and the breaking length was calculated from the tensile strength (JIS-P8113), and the Steckigt sizing degree (JIS)
-P8122) and printability by an RI printability tester were measured. Table 2 shows the results.

[0024]

Comparative Examples 1 to 3 Comparative Example 1 in Table 1 as in Examples 1 to 6
Paper making and measurement were performed using Comparative Example 3 to Comparative Example 3. Table 2 shows the results
Shown in

[0025]

Examples 7 to 12 Papermaking raw materials (LBKP
, PH 6.23, total ss content 2.37
%, Ash content 0.41%) to produce 70 g / m2 paper. As additive chemicals, cationic starch, 0.2% by weight of papermaking raw material, neutral rosin size, 0.4%, sulfuric acid band 1.0%, and polyacrylamide polymer flocculant DR-1500 as retention aid (Manufactured by Haimo), 0.
015% in this order by a stirrer at 300 rpm
After adding at intervals of 15 seconds while stirring at m, the paper was made with a Tappi Standard paper machine. P after pre-chemical addition
H was around 6.2 in each case. The following addition method by spraying is the same as in Examples 1 to 6. Each measurement was performed in the same manner. Table 3 shows the results.

[0026]

Comparative Examples 4-6 Comparison of Table 1 as in Examples 7-12
Paper making, spray addition and measurement were performed using 1 to Comparative-3. Table 3 shows the results.

[0027]

Embodiments 13-18 CSF = 400
ml of papermaking raw material (pH 6.2, total ss2.0
%, Ash content 0.25%) and paper of 80 g / m 2 was made. Rosin size for acid, 0.15 as additive chemical
%, A sulfuric acid band of 1.5%, and 0.01% of a polyacrylamide-based polymer flocculant DR-1500 (manufactured by Hymo) as a retention aid were added in this order. The following addition method by spraying is the same as in Examples 1 to 6. Each measurement was performed in the same manner. Table 4 shows the results.

[0028]

Comparative Examples 7 to 9 In the same manner as in Examples 13 to 18, paper making, spray addition and measurement were carried out using Comparative-1 to Comparative-3 in Table 1. Table 4 shows the results.

[0029]

[Table 1] 2EMA (mol%): 2-aminoethyl methacrylate
AAM (mol%): acrylamide, DMM: dimethylaminoethyl methacrylate, anionic monomer (mol%): (1), (2), (3), (5), (7),
(8), (9) are acrylic acid, cationic monomer (mol%): (6) is dimethylaminoethyl methacrylate,
(10) is acroyloxyethylbenzyldimethylammonium chloride solution viscosity: 20% by weight aqueous solution, unit mPa · s, molecular weight: unit is 10,000,

[0030]

[Table 2] Degree of stiffness: second Specific rupture degree: unit, none RI printing suitability: Good in the order of △>△> ×.

[0031]

[Table 3] Degree of stiffness: second Specific rupture degree: unit, none RI printing suitability: Good in the order of △>△> ×.

[0032]

[Table 4] Stekihito size: second Specific burst: unit, none

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) D21H 19/20 D21H 19/20 A 23/50 23/50 F term (Reference) 4J100 AB07R AJ02R AJ08R AJ09R AL08Q AL08S AM15P AM21Q AM21S AP01R BA04Q BA04S BA32Q BA32S BA35R BA56R BC43S CA04 CA05 CA06 DA01 DA09 DA38 JA13 4L055 AA03 AA11 AC03 AC06 AC09 AG71 AG72 AG89 AH16 BD05 BD07 BE20 FA13 GA05 GA06 GA16 GA17 GA18

Claims (4)

[Claims] A wet paper before drying a primary amino group-containing copolymer produced by polymerizing a monomer mixture containing a cationic monomer represented by the following general formula (1) as an essential component: Alternatively, a method for improving the strength of paper characterized by spraying on paper after drying. Embedded image R1 is hydrogen or methyl, A is oxygen or NH,
B is a C2 to C3 alkylene or alkoxylene group; X is an anion 2. A monomer mixture comprising 2 to 50 mol% of a monomer represented by the general formula (1) and 0 to 20 mol% of an anionic monomer represented by the following general formula (2) 2. The composition according to claim 1, comprising 30 to 98 mol% of acrylamide.
The method for improving the strength of paper described in 1. Embedded image R2 is hydrogen, methyl or carboxymethyl, R3
Is hydrogen or carboxyl group, A is SO3, C6H4S
O3, CONHC (CH3) 2CH2SO3 or C
OO and Y are hydrogen or cation, or COOOZ or Z
Is hydrogen or cation 3. A monomer mixture comprising 1 to 35 mol% of a monomer represented by the general formula (1), 0 to 20 mol% of an anionic monomer represented by the general formula (2), The paper strength enhancing method according to claim 1, comprising 1 to 15 mol% of a cationic monomer represented by the following general formula (3) and 30 to 98 mol% of acrylamide. Embedded image R4 is hydrogen or methyl, R5 methyl or ethyl, R6 is methyl, ethyl or benzyl, R
7 is a hydrogen atom, a methyl group or an ethyl group, A is an oxygen atom or NH, B is a C2-C3 alkylene group or an alkoxylene group, X is an anion 4. A monomer represented by the general formula (1):
4. The paper-strengthening method according to claim 1, which is a salt of an organic acid or an inorganic acid of 2-aminoethyl methacrylate. [0001]