JP2002212898A - Method for freeness improvement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a paper making method for improving freeness, by solving the disadvantage of reduction in flocculating performances in a high pH range 7-9 of paper making pH among performances of a Hofmann reactant and using a Hofmann product reactant-based polymer exhibiting an excellent effect even at a neutral or alkali paper making pH. SOLUTION: This method for improving freeness comprises adding a cationic polymer containing a quaternary ammonium base to a molecule obtained by subjecting a polymer composed of 50-90 mol% of acrylamide, 10-50 mol% of a diallylamine-based monomer, and 0-20 mol% of a copolymerizable another monomer and a hypohalite to a Hofmann reaction in an alkali range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for improving drainage, and more particularly, to an acrylamide polymer having a specific monomer as a copolymer component, and a hypohalite, in an alkaline region. By adding a cationic polymer obtained by the Hoffman reaction to the papermaking raw material before papermaking, the water content on the wire and the wet paper after press dewatering are reduced, the papermaking speed is accelerated, and the productivity is increased. The present invention relates to a method for improving drainage for improving water filtration.

[0002]

2. Description of the Related Art In the production of paper, various approaches can be considered to improve productivity, but the drainage on the wire and the water content after dehydration pressing are reduced to increase the papermaking speed.
A drainage improver is added to the papermaking raw material before papermaking in order to reduce the amount of steam used in the dryer and improve productivity. Polyethyleneimine has been used for a long time, but has various drawbacks such as a large amount of addition, a high cost, and foaming of water for use, and various improved inventions have been made. For example, a method of adding a Hoffman reactant of polyacrylamide (JP-A-2-175706) and a method of adding a polyvinylamine-based polymer (JP-A-63-1)
No. 65412), or a method using a benzyl group-containing acrylic cationic copolymer and colloidal silica in combination (Japanese Patent Application Laid-Open No. 9-279498). However, each of these drugs has its own problems. That is, the production process of the polyvinyliamine-based polymer is complicated, and the method of using the benzyl group-containing acrylic cationic copolymer and colloidal silica in combination is very strict in quality control in order to use the optimal colloidal silica. Is necessary.

On the other hand, in order to synthesize a polyvinylamine-based polymer which is a typical example of a polymer having a primary amine, N-
After polymerization of vinyl carboxylic acid amide or polyvinyl amidine-based polymer, after copolymerization of N-vinyl carboxylic acid amide and acrylonitrile, N-
An acyl group is hydrolyzed with an acid or an alkali to form a primary amino group or an amidine group. 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, it has a high dye-fixing property, and when used as a flocculant for dewatering sludge, the water content of the dewatered cake is reduced. Having.

A Hoffman reaction product of a polyacrylamide-based polymer having a primary amine has an advantage that its production is easier than the production of a vinylamine-based polymer, and it has been widely used as a drainage improver. If the pH is relatively high, such as 7 to 9, due to the amino group, there is a problem that the coagulation performance is reduced. Further, among the methods for performing a Hoffman reaction of an acrylamide copolymer, a Hoffman reaction product of a copolymer of an acrylamide monomer having a sulfone group and acrylamide is disclosed in JP-A-2000-1.
No. 29591 discloses this. Acrylic ester and acrylamide monomers are described in the detailed description of the invention as examples of other copolymerizable monomers, but examples of diallylamine monomers are not described.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to improve the performance of a Hoffman reactant by adjusting the papermaking pH to a high pH such as 7 to 9.
In the area, to solve the drawback that the coagulation performance is reduced, and to provide a papermaking method that improves drainage by using a Hoffman reactant polymer that exhibits excellent effects even when the papermaking pH is neutral and alkaline. Yes.

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the following inventions have been reached. That is, the invention of claim 1 of the present invention relates to a papermaking raw material before papermaking in which 50 to 90 mol% of acrylamide, 10 to 50 mol% of diallylamine-based monomer and 0 to 20 mol% of another copolymerizable monomer. The present invention relates to a method for improving drainage, characterized by adding a cationic polymer obtained by performing a Hoffman reaction between a polymer comprising mol% and a hypohalite in an alkaline region.

According to a second aspect of the present invention, the content of the primary amino group in the cationic polymer obtained by the Huffman reaction is 15 mol% to 70 mol%. It is a method for improving drainage described.

The invention according to claim 3 is the method for improving drainage according to claim 1, wherein the diallylamine-based monomer is dimethyldiallylammonium chloride.

The invention according to claim 4 is characterized in that the acrylamide 5
The weight average molecular weight of the polymer comprising 0 to 90 mol%, 10 to 50 mol% of diallylamine monomer and 5 to 20 mol% of other copolymerizable monomer is 1,000,000 to 10,000,000. The method for improving drainage according to claim 1, characterized in that:

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The polyacrylamide polymer Hoffman reactant of the present invention first polymerizes an acrylamide polymer. Since the Hoffman reaction is carried out in a strongly alkaline region, the monomer to be copolymerized in order to introduce a quaternary ammonium base into the copolymer must have alkali-hydrolyzability. Therefore, the monomers that can be used are diallylammonium salt monomers, such as diallyldimethylammonium chloride, diallylmethylbenzylammonium chloride, diallyldiethylammonium chloride, and diallylethylbenzylammonium chloride.
Neutral to weakly alkaline, hydrolysis-resistant vinylpyrrolidone, dimethylaminopropyl (meth) acrylamide, and the like cannot exist in a strongly alkaline state and are excluded from the scope of the present invention.

In addition to the acrylamide and diallylammonium salt monomers, the monomers used for copolymerization must also have hydrolysis resistance. Examples of such monomers include ethylene, styrene, (meth) acrylic acid, itaconic acid or maleic acid.

The copolymerization ratio of acrylamide and diallylamine monomer is 50 to 90 mol% of acrylamide, 10 to 50 mol% of diallylamine monomer and 0 to 20 mol% of other copolymerizable monomer. is there. In the method for improving drainage of the present invention, the ratio of the acrylamide structural unit in the copolymer is important because the primary amine in the Hoffman reaction product is strongly related to the dewatering property of the papermaking raw material. That is, the copolymerization ratio of acrylamide in the copolymer is 50 to 9
0 mol%. If it is less than 50 mol%, the acrylamide structural unit is small, the content of the generated primary amino group is reduced, and the dewatering property of the papermaking raw material is undesirably reduced. Also,
The copolymerization ratio of the diallylamine-based monomer is 10 to 50 mol%. If it is less than 10 mol%, the content of the quaternary ammonium base is too small, and the papermaking pH is neutral to weakly alkaline,
Performance decreases. Further, when the copolymerization ratio of the diallylamine-based monomer is higher than 50 mol%, the degree of polymerization of the copolymer decreases, and the function as a drainage improver cannot be performed.
Therefore, the copolymerization ratio of acrylamide is 50 to 90 mol%, preferably 50 to 70 mol%.

The content of the primary amino group in the polymer after the Huffman reaction modification is from 15 mol% to 70 mol%,
Preferably it is 20 to 70 mol%. 15 mol%
When the content is less than 1, when the content of the primary amino group is reduced as described above, the dewatering property of the papermaking raw material is reduced, which is not preferable. Also, when an attempt is made to introduce a primary amino group higher than 70 mol%, the amount of added hypohalous acid increases,
The raw material polyacrylamide-based polymer is cut, and the effect is reduced due to a decrease in molecular weight, which is not preferable.

The polymerization method of the copolymer before the Huffman reaction modification may be a known polymerization method such as an aqueous solution polymerization method, a water-in-oil emulsion polymerization method, a water-in-oil dispersion polymerization method, or a dispersion polymerization method in a salt aqueous solution. Can be synthesized. Therefore, as the polymerization concentration, it can be carried out in the range of 5 to 60% by weight,
Preferably, it is carried out at 20 to 50% by weight. The reaction can be performed at a temperature of 10 to 100 ° C.

The polymerization rate of the diallylamine-based monomer is much lower than that of acrylamide. At the same time, if all the monomers are charged, the acrylamide completes the polymerization first, and the remaining diallylamine-based monomer is used alone thereafter. It is highly probable that a homopolymer is produced by polymerization and a mixture of a homopolymer of a diallylamine-based monomer and a copolymer composition greatly deviating from the charged monomer molar ratio is high. Therefore, the diallylamine-based monomer used in the polymerization is charged in whole or in part to the polymerization system first, and the acrylamide is supplied to the polymerization system by dividing the monomer used or continuously supplying the monomer. It is necessary to devise such as adopting Therefore, the number of divisions or the continuous supply speed is appropriately determined in consideration of the reaction time, workability, and the like. The polymerization initiator to be added is
At the start, the basic addition method is to add it to the monomer solution.However, after that, the addition at the same time as the additional acrylamide monomer, or the time difference between the addition of the additional acrylamide and the polymerization temperature, The concentration is determined in consideration of the consumption rate of both monomers, depending on the polymerization concentration, the copolymerization molar ratio of the diallylamine-based monomer and acrylamide, and the like. Also, in the case of continuous supply, it is necessary to add an additional initiator after supplying all the monomers. If the initiator is added at once, the degree of polymerization is decreased, and the reaction of acrylamide proceeds unfavorably with respect to the diallylamine-based monomer.

The basic prescription is that the diallylamine-based monomer is used in an amount of 2/3 or less of the total amount or in some cases.
When ／ is put in the reactor and acrylamide is divided and supplied, １ ／ to ６ of the used amount is put into the reactor, and the rest is divided into about ３ to ６. Supply. At this time, it is fundamental to add an appropriate weight at a constant interval over a period of several hours to about 10 hours in accordance with the progress of the polymerization.

By random copolymerizing the diallylamine-based monomer and acrylamide as far as possible, the effect of preventing the primary amino group from deteriorating is also effective. That is, the primary amino group forms a lactam ring with the acid amide group of the adjacent acrylamide, and loses cationicity. If the adjacent side chain is a secondary amine to quaternary ammonium base of a diallylamine-based monomer, lactam formation does not occur, loss of the primary amino group is suppressed, and deterioration of the Hoffman reactant does not occur.

Further, the cationic polymer obtained by the Huffman reaction of the present invention can prevent insolubilization of the polymer due to the reaction with a sulfate group because a quaternary ammonium base is present in the molecule. Polymers having a large number of primary amino groups in the molecule, such as polyvinylamine, have been insolubilized by a cross-linkable complex with a sulfate group, but their use has been limited. However, the cationic polymer of the present invention has widened its application range because its disadvantage has been eliminated.

The radical polymerization initiator for initiating the polymerization of the copolymer before the Huffman reaction modification can be polymerized by any of an azo type, a peroxide type and a redox type. Examples of the oil-soluble azo initiator include 2,2′-azobisisobutyronitrile, 1,1′-azobis (cyclohexanecarbonitrile), 2,2′-azobis (2-methylbutyronitrile), 2,2'-azobis (2-methylpropionate) and the like are dissolved in a water-miscible solvent and added. Examples of the water-soluble azo initiator include 2,2′-
Azobis (amidinopropane) dichloride, 2,
2'-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dichloride, 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. Most preferred of these initiators are water-soluble azo initiators2.
2′-azobis (amidinopropane) dichloride,
2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] hydride and the like.

The weight average molecular weight of the polyacrylamide copolymer before the Hoffman reaction is 1,000,000 to 10,000,000, preferably 1,000,000 to 5,000,000. If it is less than 1,000,000, the cohesive force is insufficient and the drainage on the wire is reduced,
Further, even when the amount exceeds 10 million, the cohesive force does not change much, the solution viscosity becomes too high, the dispersibility becomes poor, and the handling of the aqueous solution becomes poor, so there is no particular advantage.

Next, the conditions of the Hoffman reaction will be described. Examples of the hypohalous acid used include sodium hypochlorite, potassium hypochlorite, sodium hypobromite, potassium hypobromite, sodium hypoiodite, potassium hypoiodite and the like. Examples of the coexisting alkali include sodium hydroxide and potassium hydroxide. The amount of hypohalous acid added is 10 mol% based on amide groups.
To 150 mol%, preferably 20 to 120 mol%. In addition, as the amount of coexisting alkali,
It is 10 to 250 mol% based on the amide group. The reaction is 30
It is carried out at a temperature of 80 ° C., preferably at a temperature of 30-60 ° C.
After the reaction, the solution pH is neutralized to a range of 5 to 7.5. 7.
When it is higher than 5, hydrolysis of the remaining acid amide group occurs, and an anionic group increases, which is not preferable. Even at a pH lower than 5, the formation of a lactam ring and the like are not preferred.

The place where the cationic polymer generated by the Hoffman reaction of the present invention is added may be before the fan pump or at the entrance or exit of the screen.

The papermaking pH to which the method for improving drainage of the present invention can be applied exhibits an excellent effect in acidic papermaking to neutral papermaking as compared with other treatment methods. Therefore, there is an advantage in the papermaking pH in the range of 4.0 to 9.0. High quality or medium quality printing paper,
Alternatively, it is a core paperboard or a paperboard such as a liner.

[0024]

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.

(Synthesis Example 1) In a 500 mL four-necked flask equipped with a thermometer, a stirrer, a nitrogen inlet tube, a monomer supply tube connected to a peristaltic pump (SMP-21, manufactured by Tokyo Rika Kikai) and a condenser. 94.7 g of a 65% aqueous solution of dimethyldiallylammonium chloride, 42.1 g of a 50% aqueous solution of acrylamide and 2 parts of deionized water
After 50 g of the solution was injected, the internal temperature was maintained at 30 ± 2 ° C., and the atmosphere was replaced with nitrogen for 20 minutes while stirring, followed by 2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane. 0.82 g of a 10% aqueous solution of hydrogen dichloride was added (0.1% by weight of monomer). After reacting for 1 hour while keeping the internal temperature at 30 ± 2 ° C., 42.1 g of the 50% aqueous solution of acrylamide was added, and 1 hour later, 4
2.1 g was added, and the stirring was stopped because the viscosity of the reaction product increased after 3 hours. After further reacting for 5 hours, the polymerization was stopped. The mol% of dimethyldiallylammonium chloride and acrylamide after the completion of the monomer supply is 30:70. The gel reaction was swollen for one day and diluted to 18% by weight. Then, the weight average molecular weight was measured by a molecular weight measuring device (DLS-7000 manufactured by Otsuka Electronics Co., Ltd.) by a static light scattering method, and the reaction rate of dimethyldiallylammonium chloride was measured by a colloid titration method. Table 1 shows the results.

A solution prepared by diluting a solution obtained by mixing sodium hypochlorite with 50 mol% or 90 mol% of acrylamide with respect to 30 mol% or 70 mol of acrylamide in terms of available chlorine was diluted to 18 wt%. The mixture was added to the polymer, and the temperature was kept at 30 to 35 ° C. to carry out the Hoffman reaction. These two types of samples are referred to as prototype-1 and prototype-2. The primary amination rate after the completion of the reaction was calculated by measuring the total amount of cations in the polymer and subtracting the equivalent of the quaternary ammonium base before the reaction.

(Synthesis Example 2) A 10/90 and 50/50 copolymer of dimethyldiallylammonium chloride and acrylamide was polymerized in the same manner as in Synthesis Example 1, and then a cationic group having a primary amino group was formed by Hoffman reaction. Polymers were synthesized (prototypes 3 to 6). Table 1 shows the results.

(Comparative Synthesis Example) A copolymer composed of 5/95 of dimethyldiallylammonium chloride and acrylamide was polymerized, and then a cationic polymer having a primary amino group was synthesized by Hoffman reaction. In addition, a cationic polymer in which a primary amino group was introduced from an acrylamide homopolymer by a Hoffman reaction was also synthesized (Comparative Examples 1 to 4). Table 1 shows the results.

[0029]

Examples 1 to 12 After disintegrating used newspaper into a 2% dispersion, the Canadian Standard Freeness (CS) was used.
F) Refined to 180 mL by value display. This dispersion was added to 0.
It was diluted to 4% by weight and used for a drainage test. The pH of the pulp slurry after the stock was adjusted was 6.2. Prepared 0.
The 4% by weight dispersion is collected in a 1000 mL measuring cylinder, 400 ppm of the prototype 1 to 6 are added to the solution, and the graduated cylinder is turned upside down 5 times. It was measured. Thereafter, the pulp remaining on the mesh of the CSF tester is filled in a double-bottomed centrifuge tube on which a filter cloth with a lower portion of 100 mesh is laid,
The pulp was dewatered using a digital centrifuge under the conditions of 3000 rpm for 5 minutes (assuming dewatered cuticle on the machine). After measuring the weight of the dewatered pulp, 1
Dry at 05 ° C for 20 hours and measure its weight. afterwards,
The ash yield is measured by incineration at 900 ° C. for 2 hours and measuring the weight of the inorganic component. In addition, the same test was carried out in the case where a sulfate band was added at 2% with respect to pulp. Table 2 shows the results.

[0030]

Comparative Examples 1 to 8 Tests were conducted in the same manner as in Examples 1 to 6, except that Comparative-1 to Comparative-4 were used. Table 2 shows the results.

As is clear from Table 2, there is no significant difference between the prototype of the present invention and the comparative product when no sulfate band is added, but when the sulfate band is added, the prototype of the present invention does not. Examples 1 to 6 using -1 to prototype -6 show the amount of drainage,
It can be seen that the ash retention rate and the moisture content when centrifugal dehydration are performed are less reduced in the effect than in the samples without Comparative Examples -1 to -4. This is presumed to be due to the effect of the quaternary ammonium base derived from dimethyldiallylammonium chloride, the effect of the sulfate group being less reduced.

[0032]

Examples 13 to 18 By the same operation as in Examples 1 to 12, raw materials for core base paper (pH 7.72, total ss 2.36)
% And ash content of 0.11%) were tested for drainage and dehydration under neutral papermaking conditions. Prototype-1 in Table 1 as additive chemical
-Prototype-6 was added at 300 ppm, and the drainage, dehydration and ash content were measured. Table 3 shows the results.

[0033]

Comparative Examples 9 to 13 Tests were performed in the same manner as in Examples 13 to 18, except that Comparative Examples 1 to 4 were used. Table 3 shows the results.

As is apparent from Table 3, there is no significant difference between the prototype of the present invention and the comparative product when no sulfuric acid band is added, but when the sulfuric acid band is added, the prototype of the present invention does not. In Examples 13 to 18 using -1 to -6, the amount of drainage, the ash yield and the water content when centrifugal dehydration were performed,
It can be seen that the decrease in the effect is smaller than in the case of no addition as compared with the samples of Comparative-1 to Comparative-4. This is presumed to be due to the effect of the quaternary ammonium base derived from dimethyldiallylammonium chloride, the effect of the sulfate group being less reduced.

[0035]

[Table 1] AAM: acrylamide, DD: dimethyldiallylammonium chloride, primary amino group: mol%

[0036]

[Table 2] Drainage: ml, water content:%, ash retention:%

[0037]

[Table 3] Drainage: ml, water content:%, ash retention:%

Claims (4)

[Claims] 1. A papermaking raw material before papermaking, wherein acrylamide is 50 to 90 mol% and diallylamine monomer is 10 to 50 mol%.
The addition of a cationic polymer obtained by subjecting a polymer consisting of 0 to 20 mol% of another monomer and 0 to 20 mol% of a copolymerizable monomer and a hypohalite to a Hoffman reaction in an alkaline region. Characteristic method for improving drainage. 2. The cationic polymer obtained by the Hoffman reaction has a primary amino group content of 15%.
The method for improving drainage according to claim 1, wherein the amount is from mol% to 70 mol%. 3. The method according to claim 1, wherein the diallylamine-based monomer is dimethyldiallylammonium chloride. 4. The acrylamide 50 to 90 mol%,
2. The weight average molecular weight of a polymer comprising 10 to 50 mol% of a diallylamine monomer and 0 to 20 mol% of another copolymerizable monomer is 1,000,000 to 10,000,000. 3. The method for improving drainage described in 1. above.