JPH11100793A - Cationic polymer microparticle and papermaking using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a remarkable improvement in filler yield by adding a specific cationic polymer microparticle to a stock in the neutral papermaking. SOLUTION: The cationic polymer microparticle for addition to a stock is obtained by carrying out the emulsion copolymerization of 70-95 wt.% ethylenically unsaturated monomer represented by the formula (R1 is H or CH3 ; R2 is phenyl or acetoxyl), e.g. styrene with 0-30 wt.% cationic monomer such as methacrylamidopropyltrimethylammonium chloride and 1-2 wt.% cationic surfactant such as cetylmethyltrimethylammonium bromide using 0.5-5 wt.% cationic polymerization initiator such as 2,2-azobis(N,N'-dimethylene- isobutylamine)dihydrochloride. The resultant microparticle has cationic properties at pH <=11 and <=100 nm particle diameter. The microparticle in an amount of 0.04-2.0 wt.% based on the bone-dry solid content of the stock is added thereto and a water-soluble anionic acrylamide having >=1000,000 molecular weight is then added thereto.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a novel cationic polymer microparticle and a method for using the same to improve the yield of filler in neutral papermaking.

[0002]

2. Description of the Related Art As a conventional method for improving the yield of filler in acidic papermaking, a method of adding polyacrylamide having a relatively high molecular weight and a low cationic charge density, followed by addition of a sulfate band has been used. In recent years, the technology for producing inexpensive calcium carbonate fillers with excellent optical properties has advanced, and calcium carbonate has been replaced with paper fillers from acid papermaking, which used clay minerals such as kaolin and talc as the fillers. Neutral papermaking has become popular. When paper is made using calcium carbonate as a filler, the pH of the papermaking system becomes 7 to 9 due to the buffer effect of calcium carbonate. In this neutral to alkaline region, aluminum ion species use a conventional sulfate band and cationic polyacrylamide because the degree of cationicity is extremely reduced as compared with the case of acidic and the coagulation effect of the stock is reduced. The method of improving the yield could not obtain a sufficient filler yield. Therefore, instead of the sulfate band, a polymer having a relatively low molecular weight and a high cationic charge density having a quaternary amino group exhibiting a cationic property even in a neutral state, such as diallyldimethylammonium chloride, has been used.

[0003] However, when a polymer having a relatively low molecular weight and a high cationic charge density is adsorbed on an anionic fiber or filler, a flat adsorption conformation is obtained due to the high charge density of the polymer. After adding a polymer having a relatively low molecular weight and a high cationic charge density to the papermaking system to coat the anionic surface of the fiber or filler, a cationic polymer having a relatively high molecular weight and a low charge density is added. When added, the expected yield cannot be obtained because the adsorption sites for fibers and fillers are not sufficiently present on their surface. Furthermore, since the polymer having a low molecular weight and a high cationic charge density adsorbed on the fiber penetrates into the pores of the fiber, the charge of the fiber decreases with time, causing a change in the yield.

Therefore, USP 4,798,653 cationic colloidal silica and a relatively high molecular weight water-soluble polymer are used in combination with a yield system, and USP 5,340,865 reverse cationic microemulsion polymerization synthesized by a microemulsion polymerization method. It has been reported that polyacrylamide improves pulp retention, indicating that cationic microparticles are potentially effective as retention aids. However, the cationic colloidal silicas of USP 4,798,653 show cationicity in acidic condition, but decrease as pH increases. USP 5,34
In No. 0865, since a water-soluble polymer has a basic skeleton, when a synthetic polymer is dispersed in an aqueous phase, it swells, so that it was difficult to obtain polymer particles having a small particle size in an aqueous solution.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for improving the yield of filler in neutral papermaking, which meets the needs of the relevant technical field as described above and overcomes the drawbacks of the conventional methods. Is what you do.

[0006]

Means for Solving the Problems The present inventors have proposed a novel yield improver having a cationic property at a pH of 11 or less,
We have developed cationic polymer microparticles with a particle size of less than 100nm. By adding the cationic polymer microparticles alone or the cationic polymer microparticles, and then adding a water-soluble anionic polyacrylamide having a molecular weight of 1,000,000 or more to the paper stock,
The yield of filler in neutral papermaking can be improved.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

The cationic polymer microparticle of the present invention is polymerized from the following a) to d), has a cationic property at pH 11 or less, and has a particle size of 100 nm or less.

A) an ethylenically unsaturated monomer, b) a cationic monomer, c) a cationic surfactant, and d) a cationic polymerization initiator; ) Is 0-30% by weight, c) is 1-2
%, D) is preferably synthesized in a weight ratio of 0.5 to 5% by weight.

The cationic polymer microparticles of the present invention can be produced by emulsion polymerization using a surfactant and microemulsion polymerization using a relatively large amount of a surfactant. The cationic monomer is used to improve the charge density of the cationic polymer microparticle, but the cationic polymer microparticle can be produced without using it.

Examples of the ethylenically unsaturated monomer used in the present invention include styrene, (-methylstyrene, chlorostyrene, butadiene, methylmethacrylate and the like. Can be used.

[0012]

Embedded image (However, R ₁ represents H or CH ₃ , R ₂ represents a phenyl group or an acetoxyl group) The cationic monomer used in the present invention is methacrylaminopropyltrimethylammonium chloride, diallyldimethylammonium chloride, acryloxyethyltriethyl. It is at least one selected from radically polymerizable cationic monomers such as ammonium chloride.

The cationic surfactant used in the present invention is at least one selected from cationic surfactants such as cetyltrimethylammonium bromide, dodecyltrimethylammonium bromide, and mystriltrimethylammonium bromide. The cationic surfactant emulsifier may be used in combination with a cationic polymer such as cationic starch or cationic polyacrylamide.
As the cationic surfactant, it is also possible to use a polymerizable surfactant, and in this case, it plays a role of both the cationic surfactant and the cationic monomer.

The cationic polymerization initiator used in the present invention includes 2,2-azobis (N, N'-dimethylene-isobutylamidine) dihydrochloride and 2,2-azobis (2-methylpropionamidine) dihydrochloride. Chloride,
Any radical polymerization-capable cationic polymerization initiator such as 2-2-azobis (isobutylnitrile) dihydrochloride can be used.

The cationic polymer microparticles of the present invention can be used in combination with the above-mentioned cationic drug and nonionic drug. For example, it can be produced by a combination of a cationic polymerization initiator, a nonionic surfactant and a nonionic monomer. Cationic polymer microparticles can be produced without the presence of a cationic monomer or cationic surfactant. For example, cationic polymer microparticles can be synthesized only by using styrene and a cationic polymerization initiator. That is, it is possible to produce cationic polymer microparticles by combining at least one of a cationic surfactant, a cationic polymerization initiator, a cationic monomer and an ethylenically unsaturated monomer.

Since the cationic polymer microparticles of the present invention are insoluble in water, it is not necessary to use a crosslinking agent. A crosslinking agent may be used as long as it does not affect the particle size of the cationic polymer microparticles. When a cross-linking agent is used, a lipophilic cross-linking agent such as divinylbenzene is desirable, but a water-soluble cross-linking agent such as N, N'-methylenebisacrylamide can also be used.

When the cationic polymer microparticles of the present invention are added to the stock containing pulp and filler in the papermaking process, effective patch aggregation and cross-linking aggregation are simultaneously formed, thereby improving the yield of the filler. Becomes possible. The addition amount is preferably 0.04% by weight or more and 2.0% by weight or less based on the absolutely dry solid content of the stock including pulp and filler.
Also, the particle size must be 100 nm or less,
If the thickness exceeds 00 nm, effective patch aggregation and cross-linking aggregation will not be formed, so that the filler yield will not be significantly improved.

Further, by adding a relatively high molecular weight anionic polyacrylamide having a molecular weight of 1,000,000 or more after adding the cationic polymer microparticles of the present invention, the yield of filler can be more remarkably improved. This is because, when added to cationic polymer microparticles, an effective cationic patch is formed in the anionic pulp slurry, and when anionic polyacrylamide is added thereto, the anionic polyacrylamide is added between the cationic patches. Since acrylamide is crosslinked, it is considered that a remarkable improvement in yield can be obtained. The addition amount of the anionic polyacrylamide is preferably 0.005% by weight or more and 2.0% by weight or less based on the absolutely dry solid content of the stock containing pulp and filler.

[0019]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples.

Synthesis Example 1 A reactor equipped with a mechanical stirrer was charged with ion-exchanged water (150 g) and styrene (11.2 g).
g), methacrylamidopropyltrimethylammonium chloride (7.4 g), cetyltrimethylammonium bromide (3.25 g), and divinylbenzene (0.56 g)
And nitrogen gas was passed through the solution in the reactor for 30 minutes.
Until heated. After the reactor temperature stabilizes at 60 ° C., the cationic polymerization initiator 2,2-azobis (N, N′-dimethylene)
-Isobutylamidine) dihydrochloride 0.17 g in 5 ml
Dissolved in ion-exchanged water was added. Polymer synthesis was performed for 4 hours while stirring at 500 rpm while nitrogen was passed.
After completion of the synthesis, ultracentrifugation was performed twice at 60,000 rpm to remove the cationic surfactant and unreacted monomer. The particle size of this cationic polymer microparticle is 52.5n
m, and the charge density was 2.91 ueq / m ² .

[Comparative Synthesis Example 1] A reactor equipped with a mechanical stirrer was charged with ion-exchanged water (150 g) and styrene (11.2 g).
g) and divinylbenzene (0.56 g) were charged, and nitrogen gas was passed through the solution in the reactor for 30 minutes and heated to 60 ° C.
After the temperature of the reactor was stabilized at 60 ° C., a solution prepared by dissolving 0.17 g of 2,2-azobis (N, N-dimethylene-isobutylamidine) dihydrochloride in 5 ml of ion-exchanged water was added. . Polymer synthesis was performed for 4 hours while stirring at 500 rpm while nitrogen was passed. After synthesis,
Ultracentrifugation was performed twice at 60,000 rpm to remove the cationic surfactant and unreacted monomer. The particle size of this cationic polymer microparticle is 364 nm, and the charge density is
It was 2.50ueq / m ² .

Example 1 Retention of light calcium carbonate (PCC) was measured using a 200-mesh wire dynamic drainage jar (DDJ).
The stirring speed during the DDJ test was 800 rpm. 0.4%
Made of bleached hardwood kraft pulp and 0.1% PCC
ml of the stock was added to DDJ, and after stirring for 15 seconds, the cationic microparticles produced in Synthesis Example 1 were added. After stirring for another 15 seconds, 150 ml of the filtrate was collected. Hydrochloric acid was added to the filtrate to adjust the pH to 3.0 or less, and PCC was completely dissolved.
The yield of PCC was measured by chelate titration with TA, and the results are shown in Table 1. The yield of PCC improved as the amount of cationic microparticles added increased.

[0023]

[Table 1]

Example 2 A DDJ test was conducted using the same stock as in Example 1. After stirring at a stirring speed of 800 rpm for 15 seconds, the cationic microparticles used in Example 1 were added at 0.4% based on the solid content of the stock, and stirring was further continued for 15 seconds, followed by anionic polyacrylamide (molecular weight: 400 10,000, hereinafter abbreviated as anionic PAM)
, And stirring was continued for 15 seconds.
The CC yield was measured. When both cationic polymer microparticles and anionic PAM were used, the yield of PCC was further improved.

[0025]

[Table 2]

[Comparative Example 1] A DDJ test was performed in the same manner as in Example 1 using the cationic polymer microparticles having a particle size of 364 nm produced in Comparative Synthesis Example 1, and PC
The yield of C was measured, and the results are shown in Table 3. Particle size 10
When it exceeds 0 nm, the yield of PCC did not improve even if the amount of the cationic polymer microparticles was increased.

[0027]

[Table 3]

Comparative Example 2 The stock used in Example 1 was D
Used for DJ test, after stirring for 15 seconds, cationic polyacrylamide (molecular weight 4 million, below cationic PA
M) (abbreviated as M) in the amount shown in Table 4 with respect to the solid content of the stock. After stirring for 15 seconds, 150 ml of the filtrate was collected, and the yield of PCC was measured in the same manner as in Example 1. 4
It was shown to.

Comparative Example 3 The stock used in Example 1 was D
For the DJ test, after continuing stirring for 15 seconds, 0.04% of polydiallyldimethylammonium chloride was added to the solid content of the stock. Stirring was continued for 15 seconds, and cationic PAM was added to the solid content of the stock. After stirring for 15 seconds, 150 ml of the filtrate was collected, and the yield of PCC was measured in the same manner as in Example 1. The results are shown in Table 4. As shown in Table 4, even when the amount of the cationic PAM alone or the combination of the cationic PAM and polydiallyldimethylammonium chloride was increased, the improvement of the PCC yield leveled off.
The yield of CC is low.

[0030]

[Table 4]

[0031]

By using the cationic polymer microparticles of the present invention, the yield of calcium carbonate as a filler in neutral papermaking can be greatly improved. In addition, since the inlet concentration of the paper machine can be reduced, fluctuations in the basis weight of the paper can be suppressed, the texture can be improved, and the amount of runoff materials can be reduced.

Claims (5)

[Claims] 1. (a) styrene, (b) methacrylamidopropyltrimethylammonium chloride, (c) cetyltrimethylammonium bromide, and (d) 2,2-azobis (N, N'-dimethylene-isobutylamidine) dihydro. A cationic polymer microparticle which is polymerized from chloride and has a pH of 11 or less and has a cationic property and is added to a stock having a particle size of 100 nm or less. (A) Formula 1: embedded image (Where R ₁ represents H or CH ₃ , R ₂ represents a phenyl group C ₆ H ₅ or an acetoxyl group COOCH ₃ ), (b) methacrylamidopropyltrimethylammonium chloride , Diallyldimethylammonium chloride,
(C) at least one selected cationic surfactant of acryloxyethyltriethylammonium chloride, And (d) a cationic polymerization initiator, which is polymerized from (excluding the combination of the compound of claim 1), has a pH of 11 or less, and has a particle size of 100 nm.
Cationic polymer microparticles for addition to the following stocks: 3. The method according to claim 1, wherein the ethylenically unsaturated monomer (a) is 70%.
~ 95% by weight, 0-30% by weight of the cationic monomer (b),
The cationic surfactant (c) is polymerized in a weight ratio of 1 to 2% by weight, and the cationic polymerization initiator (d) is polymerized in a weight ratio of 0.5 to 5% by weight. Cationic polymer microparticles. 4. A papermaking method for neutral papermaking, wherein the cationic polymer microparticle according to claim 1 or 2 is added to a stock to improve the yield of filler. 5. In a neutral papermaking, a filler is obtained by adding a cationic polymer microparticle according to claim 1 or 2, and then adding a water-soluble anionic polyacrylamide having a molecular weight of 1,000,000 or more to the stock. Papermaking method characterized by improving the yield of papermaking.