JP2986855B2 - Cationic polyacrylamide - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a cationic polyacrylamide mainly used as a paper strength enhancer, a drainage improver, and a flocculant, and more specifically, to a polyacrylamide. The high temperature,
The present invention relates to a cationic polyacrylamide obtained by performing a Hoffman decomposition reaction in a short time.

[Conventional technology and its problems]

In recent years, the ratio of waste paper to pulp raw material has tended to increase due to the deterioration of raw material circumstances. Reflecting this situation,
There is a need for a paper strength enhancer that exhibits more paper strength.
On the other hand, it is indispensable to increase the dehydration rate of pulp in order to increase productivity also in operation, and there is a need for a chemical that further improves drainage. Further, there is a high demand for chemicals for improving the drying property due to a demand for reducing the unit of steam used in paper production costs.

The Hoffman degradation product of polyacrylamide (hereinafter referred to as Hoffman PAM) is a cationic resin having a primary amino group directly bonded to the polymer main chain, and has conventionally been used as a drainage improver or a paper strength enhancer in the paper manufacturing process. Has been used as The characteristic of Hoffman PAM lies in the strength of cohesive strength. However, not only the improvement of drainage but also the improvement of the strength between fibers due to the hydrogen bond of the primary amino group, which is a cationic group, is another type of cationic polymer. It can be said that this is an excellent feature not found in acrylamide.

Hoffman PAM excellent in such cohesive force has been conventionally used as a drainage improver or a retention improver in a papermaking process or a water treatment process. In order to further improve the performance such as drainage, it is easily achieved by increasing the molecular weight of the polymer. However, it is generally said that the Hoffman decomposition reaction performed in a low temperature range of 30 ° C. or lower has excellent performance.Under such temperature conditions, the viscosity of a high-molecular-weight PAM aqueous solution increases. Mixing with the liquid became difficult, and the reaction rate could not be increased. In addition, if the concentration during the reaction is reduced to avoid an increase in viscosity, there is a problem in that the reactivity is hindered, and it becomes difficult to obtain a Hoffman decomposition product having a desired modification rate. Furthermore, Hoffman degradation products of PAM always have the problem of deterioration over time.
If PAM is stored for a long time, there is a risk of gelation,
It has not been used in general.

[Means for solving the problem]

In view of the above points, the inventors of the present invention can perform a Hoffman decomposition reaction of polyacrylamide in a short time under high-temperature conditions, which have not been conventionally considered, so that a Hoffman decomposition product of high-molecular-weight polyacrylamide can be obtained favorably. And found the present invention. In addition, in the present invention, since the Hoffman decomposition reaction can be continuously performed at the papermaking site, problems such as deterioration with time and gelation during the storage process can be avoided, and drainage and yield can be improved. It has become possible to produce and utilize cationic polyacrylamide useful as a papermaking additive excellent in water resistance or a flocculant for water treatment.

 That is, the following invention is provided.

(1) An acrylamide-based polymer having a weight-average molecular weight in the range of 500,000 to 15,000,000 is converted into an acrylamide-based polymer and a hypohalite under an alkaline region of at least pH 11 or higher at a temperature of 65 to 100 ° C. (T) A cationic polyacrylamide obtained by performing the reaction within a short time (t) specified below in the range.

e ^{15,150 / (273 + T)} × 2.5 × 10 ⁻²⁰ ≦ t (sec) ≦ e ^{15,150 / (273 + T)} × 10 ⁻¹⁸ +30 (T is a reaction temperature.) (2) The cationic polyacrylamide according to claim 1. Is added to the pulp slurry immediately after the reaction.

(3) A method for enhancing paper strength, comprising adding the cationic polyacrylamide according to claim 1 to a pulp slurry immediately after the reaction.

(4) A water treatment method comprising adding the cationic polyacrylamide according to claim 1 to a suspension immediately after the reaction.

[Specific conditions for carrying out the invention]

 Hereinafter, the present invention will be described in detail.

Hoffman PAM used in the present invention is a homopolymer of acrylamide (or methacrylamide), a copolymer of acrylamide (or methacrylamide) with one or more unsaturated monomers, and further a starch. It refers to a product obtained by subjecting a graft copolymer to a water-soluble polymer such as polyvinyl alcohol or the like to a Hoffman decomposition reaction with a hypohalite under an acrylic region.

Examples of the copolymerizable monomer include a hydrophilic monomer, an ionic monomer, and a lipophilic monomer, and one or more of these monomers can be used. Specifically, as a hydrophilic monomer, for example, diacetone acrylamide, N, N-dimethylacrylamide, N, N-dimethylmethacrylamide,
N-ethylmethacrylamide, N-ethylacrylamide, N, N-dimethylacrylamide, N, N-diethylacrylamide, N-propylacrylamide, N-acryloylpyrrolidine, N-acryloylpiperidine, N-
Examples include acryloyl morpholine, hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate, various methoxypolyethylene glycol (meth) acrylates, N-vinyl-2-pyrrolidone, and the like.

Examples of the ionic monomer include acrylic acid, methacrylic acid, itaconic acid, vinyl sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, styrene sulfonic acid, and 2-
Acrylamide-2-phenylpropanesulfonic acid, 2
-Acids such as acrylamide-2-methylpropanesulfonic acid and salts thereof, N, N-dimethylaminoethyl methacrylate, N, N-diethylaminoethyl methacrylate, N, N-dimethylaminoethyl acrylate, N, N-dimethylaminopropyl Examples thereof include amines such as methacrylamide and N, N-dimethylaminopropylacrylamide, and salts thereof.

As the lipophilic monomer, for example, acrylonitrile, N,
N-di-n-propylacrylamide, Nn-butylacrylamide, Nn-hexylacrylamide, N
-N-hexyl methacrylamide, Nn-octylacrylamide, Nn-octyl methacrylamide, N
N- such as -tert-octylacrylamide, N-dodecylacrylamide, Nn-dodecylmethacrylamide, etc.
Alkyl (meth) acrylamide derivative, N, N-diglycidylacrylamide, N, N-diglycidylmethacrylamide, N- (4-glycidoxybutyl) acrylamide, N- (4-glycidoxybutyl) methacrylamide, N N- (ω-glycidoxyalkyl) (meth) acrylamide derivatives such as-(5-glycidoxypentyl) acrylamide, N- (6-glycidoxyhexyl) acrylamide, methyl (meth) acrylate, ethyl (meth) Acrylate, butyl (meth) acrylate,
(Meth) acrylate derivatives such as lauryl (meth) acrylate, 2-ethylhexyl (meth) acrylate and glycidyl (meth) acrylate; olefins such as acrylonitrile, methacrylonitrile, vinyl acetate, vinyl chloride, vinylidene chloride, ethylene, propylene, and butene Styrene, divinylbenzene, α-methylstyrene, butadiene, isoprene and the like.
The amount of the unsaturated monomer used for the copolymerization varies depending on the type of the unsaturated monomer and the combination thereof, and cannot be determined unconditionally, but is generally in the range of 0 to 50% by weight.

In the present invention, a crosslinkable monomer can also be used.
Examples of the crosslinkable monomer include a monomer having at least two or more double bonds in a molecule and an N-alkoxymethyl (meth) acrylamide derivative. Specific examples of the former include methylenebisacrylamide, diallylacrylamide, triacrylformal, diacryloylimide, ethylene glycol acrylate, ethylene glycol dimethacrylate, propylene glycol diacrylate, 1,3-butylene glycol dimethacrylate, 4-butylene glycol dimethacrylate, glycerol dimethacrylate neopentyl glycol dimethacrylate, trimethylolpropane triacrylate, divinylbenzene, diallyl phthalate and the like can be used.

The N-alkoxymethyl (meth) acrylamide derivatives include N-hydroxymethyl (meth) acrylamide, for example, N-methylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-
Ethoxymethyl (meth) acrylamide, Nn-butoxymethyl (meth) acrylamide, N-tert.-butoxymethyl (meth) acrylamide and the like can be used.

The amount of the crosslinking agent used varies depending on the type of the crosslinking monomer and cannot be unconditionally determined, but is usually 0.0001 to 20 mol%, preferably 0.001 to 10 mol%.

As the water-soluble polymer for graft-copolymerizing the above-mentioned monomers, any of a natural polymer and a synthetic polymer can be used. Starch and oxidized starch of various origins as a natural system, carboxyl starch, dialdehyde starch, modified products such as cationized starch, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, cellulose derivatives such as hydroxyethyl cellulose, alginic acid, agar, pectin, carrageenan, dextran, Pullulan, konjac, gum arabic, casein, gelatin and the like can be mentioned. Examples of the synthetic system include polyvinyl alcohol, polyvinyl ether, polyvinylpyrrolidone, polyethyleneimine, polyethyleneimine, polyethylene glycol, polypropylene glycol, polymaleic acid copolymer, polyacrylic acid, and polyacrylamide. The amount of the monomer added to the water-soluble polymer is in the range of 0.1 to 10.0 times based on the water-soluble polymer.

Next, the above monomers are polymerized to produce polyacrylamide.Radical polymerization is preferable as the polymerization method, and water, alcohol, and a polar solvent such as dimethylformamide can be used as the polymerization solvent. Since the Hoffman decomposition reaction is carried out in an aqueous solution, aqueous polymerization is preferred. At that time, the monomer concentration is 2 to 30% by weight, preferably 5 to
30% by weight. The polymerization initiator is not particularly limited as long as it is water-soluble, and is usually used after being dissolved in an aqueous monomer solution. Specifically, in the peroxide system, for example, ammonium persulfate, potassium persulfate, hydrogen peroxide, tert-butyl peroxide and the like can be mentioned. In this case, it can be used alone, but can also be used as a redox polymerizer in combination with a reducing agent. As the reducing agent, for example, sulfites, bisulfites, iron, copper, lower ionization salts such as cobalt, N,
Organic amines such as N, N ', N'-tetramethylethylenediamine, and reducing sugars such as aldose and ketose can be mentioned.

As the azo compound, 2,2'-azobis-2-
Amidinopropane hydrochloride, 2,2'-azobis-2,4-dimethylvaleronitrile, 4,4'-azobis-4-cyanovaleic acid and salts thereof can be used. Furthermore,
Two or more of the above-mentioned polymerization initiators can be used in combination. In addition, when graft-polymerizing a water-soluble polymer, in addition to the above-described polymerization initiator as a polymerization initiator, it is also possible to use a transition metal ion such as ceric ion, ferric ion, and the like. You may use together with a polymerization initiator.

The amount of the initiator to be added is not particularly limited depending on the type and combination of the initiator, the polymerization atmosphere, the polymerization initiation temperature, the polymerization concentration, etc., but is generally 0.001 to 1.0% by weight, preferably 0.002 to 0.8% by weight based on the monomer. % By weight. In the case of the redox system, the amount of the reducing agent added is 0.1 to 200%, preferably 0.2 to 150%, based on the mole of the initiator.

The polymerization temperature is lower in the case of a single polymerization initiator and generally lower.
The temperature is 30 to 90 ° C., which is lower in the case of the redox polymerization initiator, and is generally 5 to 50 ° C. Further, it is not necessary to keep the same temperature during the polymerization, and the temperature may be changed as appropriate with the progress of the polymerization. Generally, the temperature is raised by polymerization heat generated as the polymerization proceeds. The atmosphere in the polymerization vessel at that time is not particularly limited, but it is preferable to replace the atmosphere with an inert gas such as a nitrogen gas in order to promptly carry out the polymerization. Although the polymerization time is not particularly limited, it is generally 1 to
20 hours.

The molecular weight of polyacrylamide can be controlled by the amount of the polymerization initiator, the temperature of the polymerization initiator, and the polymerization concentration when performing the polymerization reaction. That is, although the specific numerical values differ depending on the type and combination of the monomers used, they cannot be described unconditionally, but the amount of the polymerization initiator is reduced.
By lowering the polymerization initiator temperature and increasing the polymerization concentration, polyacrylamide having a high molecular weight can be obtained.

The weight average molecular weight of the polyacrylamide produced by the above method was measured by GPC analysis (for example, Shodex OHpak B-800).
Series) and can range from 500,000 to 15 million. The present invention is limited to this molecular weight range, preferably in the range of 500,000 to 10,000,000, and more preferably in the range of 600,000 to 2,000,000.

Next, a Hoffman decomposition reaction of the polyacrylamide produced by the above method is performed. At that time, when the production of polyacrylamide as a raw material is carried out with an aqueous solution, the Hoffman decomposition reaction can be carried out as it is, but it can be diluted if necessary and provided for the reaction. In the case of a graft copolymer, ungrafted polyacrylamide is also by-produced, but it is usually subjected to the reaction without separation.

The Hoffman decomposition reaction is carried out by allowing a hypohalite to act on an amide group of polyacrylamide in the presence of an alkaline substance. Examples of hypohalous acid include hypochlorous acid, hypobromite, and hypoiodine. Acids. Examples of hypochlorite include metal hypochlorite or alkaline earth metal salts, and specifically, sodium hypochlorite, potassium hypochlorite, lithium hypochlorite, and hypochlorous acid. There are calcium, magnesium hypochlorite, barium hypochlorite and the like. Similarly, hypobromite and hypoiodite include alkali metal or alkaline earth metal salts of hypobromite and hypoiodite. It is also possible to generate a hypohalite by blowing a halogen gas into an alkaline solution. On the other hand, examples of the alkaline substance include an alkali metal hydroxide, an alkaline earth metal hydroxide, and an alkali metal carbonate. Among them, an alkali metal hydroxide is preferable, and sodium hydroxide,
Potassium hydroxide, lithium hydroxide and the like can be mentioned. The amount of the above-mentioned substance added to polyacrylamide is 0.05 to 2.0 mol, preferably 0.1 to 1.5 mol, based on the amide group in hypohalous acid, and 0.05 to 4.0 mol, preferably, 0.1 to 1.5 mol in the alkaline substance. 0.1 to 3.0 mol. The pH at that time is generally in the range of 11-14. The concentration of polyacrylamide at that time is generally 0.1 to 15% by weight, but it is usually in the range of 0.1 to 10% by weight because if the reaction concentration becomes high, stirring becomes difficult and gelation easily occurs. Is preferred. Further, when the reaction concentration is less than 1%, there is a problem that the reaction rate becomes slow. Therefore, the concentration is more preferably 1 to 10% by weight.

Compounds having an amino group or a hydroxyl group in the molecule such as dimethylaminoethanol, diethylaminoethanol, dimethylaminopropanol, choline chloride, benzyl chloride quaternary product of dimethylaminoethanol, polyethylene glycol, and polypropylene glycol when performing the Hoffman decomposition reaction. May be allowed to coexist to cause the reaction.

 On the other hand, the reaction temperature ranges from 65 to 100 ° C.

Next, the Hoffman decomposition reaction is performed in a short time within the above-mentioned temperature range.However, the reaction time depends on the reaction temperature and the polymer concentration in the reaction solution, but cannot be said unconditionally.
For example, when the polymer concentration is 1% by weight, it is enough within 65 minutes at 65 ° C. and within several tens seconds at 80 ° C. Further, the higher the polymer concentration, the shorter the reaction time. The relationship between the reaction time (t) and the reaction temperature (T) is roughly represented by the following two relational expressions, and the reaction time (t) may be within the range between the following two relational expressions. A suitable result can be obtained by performing the reaction.

The cationic polyacrylamide produced under the above conditions has a cation equivalent measured by colloid titration at pH 2 in the range of approximately 0 to 10.0 meq / g, and the cation equivalent is controlled by the amount of hypohalite added. can do. Further, since the reaction is carried out in an alkaline region, the amide group is hydrolyzed and a carboxyl group is by-produced. The amount of by-product is indicated by an anion equivalent measured by colloid titration at pH 10, and is generally in a range of 0 to 10.0 meq / g. The amount of the by-product can be controlled by the amount of the added alkaline substance.

Next, after carrying out the reaction under the above conditions, it is preferable to stop the reaction in order to suppress the progress of the side reaction. However, when used immediately after the reaction, it may not be necessary to stop the reaction.

The reaction can be stopped by (1) adding a reducing agent,
Methods such as (2) cooling and (3) lowering the pH of the solution by adding an acid can be used alone or in combination. (1) is a method of inactivating remaining hypohalite and the like by reaction with a reducing agent. Examples of the reducing agent used include sodium sulfite, sodium thiosulfate, ethyl malonate, thioglycerol, triethylamine and the like. The amount of the reducing agent used is usually 0.005 to 0.15 times the molar amount of hypohalous acid used in the reaction,
Preferably it is 0.01 to 0.10 moles. Generally, at the end of the Hoffman decomposition reaction, a compound having active chlorine such as unreacted hypohalite remains. If such a reaction solution is used as a paper strengthening agent, it may cause rust in a paper machine. Therefore, a reducing agent is usually used to inactivate active chlorine. However, the hypohalite reacts in an equimolar or less with respect to the acrylamide unit mole number of the polymer, and when the reaction is performed at a high temperature, almost no unreacted hypohalite remains at the end of the reaction. . Therefore,
It can also be used as a paper strength agent without deactivating active chlorine using a reducing agent. The method (2) is a method of suppressing the progress of the reaction by cooling. Examples of the method include a method of cooling using a heat exchanger and a method of diluting with cold water.
The temperature at that time is usually 50 ° C or lower, preferably 45 ° C or lower, more preferably 40 ° C or lower. In (3), the Huffman decomposition reaction is suppressed by lowering the pH of the solution at the end of the reaction, which usually shows an alkaline pH of 12 to 13, using an acid, and at the same time, the progress of the hydrolysis reaction is suppressed. The pH at that time may be neutral or lower, and is preferably in the range of pH 4 to 6. Examples of the acid used for pH adjustment include mineral acids such as hydrochloric acid, sulfuric acid, phosphoric acid, and nitric acid, and organic acids such as formic acid, acetic acid, and citric acid. The reaction termination method can be appropriately selected from (1) to (3) depending on the reaction conditions, and these methods may be combined.

Next, the reaction solution stopped by the above method can be used as it is as an aqueous solution of cationic polyacrylamide. In addition, the aqueous solution of the cationic polyacrylamide obtained by the above method can be stored in a tank and used as needed. The storage temperature at that time may be a low temperature that does not freeze the aqueous solution, preferably 10 to 15
° C. However, if it is used within a relatively short time, it can be stored at room temperature and can be stored for about one month.

Since the cationic polyacrylamide of the present invention can be produced in an extremely short time, on-site operation, such as installing a production apparatus near a place (plant) where it is used, becomes possible. This is a major feature of the present invention, and it is possible to optimize an effective papermaking method. At this time, if the reaction is carried out under the condition that the amount of hypohalite used is lower than the amide group of polyacrylamide, it is possible to prevent free hypohalous acid ions from remaining in the solution. I can do it. Therefore, in this case, it is possible to add the pulp slurry or the like without stopping the reaction.

The cationic polyacrylamide produced according to the present invention can be applied to the fields where ordinary water-soluble cationic polymers are used. Among them, the fields of medicine and polymer flocculants used for papermaking are mainly used. And so on. In the field of paper chemicals, cationic polymers are used in various fields of paper manufacturing processes, but the cationic polyacrylamide produced by the method of the present invention is used in the step of making pulp, The addition thereof has a great effect for improving drainage for improving drainage of water, and for enhancing paper strength for enhancing mechanical strength of paper. These may be more effective when combined with a water-soluble anionic resin. The water-soluble anionic resin used at this time is a carboxyl group, a sulfonic acid group,
A water-soluble resin containing an anionic substituent such as a phosphate group or a salt thereof, such as an anionic acrylamide resin, an anionic polyvinyl alcohol resin, carboxymethyl cellulose, carboxymethylated starch, sodium alginate, etc. Can be mentioned.

The method of using the cationic polyacrylamide of the present invention for the purpose of improving drainage may be performed according to a conventionally known method. However, a feature of the method of the present invention resides in that polyacrylamide and hypohalite are reacted at a high temperature for a short time and then immediately added to the pulp slurry. The term "immediately" as used herein means that the aqueous solution after the reaction is taken out of the pipe, transported in the same pipe without being transferred to the outside, and added to the pulp slurry. More specifically, the aqueous solution after the reaction may be directly added to the pulp slurry through a pipe, or a stock tank may be provided between them to temporarily stay there, and then the amount may be adjusted and added.
The residence time of the reaction solution in the pipe may be within a range where the aqueous solution after the reaction does not deteriorate. However, if the length is too long, the device for retaining the liquid becomes large, and the features of the present invention cannot be utilized. Therefore, in order to carry out the present invention suitably,
It is preferably added within 5 hours after the reaction, more preferably within 1 hour, and even more preferably within 10 minutes.

Further, at that time, it may be diluted with water and added depending on the concentration of the cationic polyacrylamide after the reaction. Although it varies depending on the type of pulp, the speed of papermaking, etc., and is not explicitly mentioned, the concentration of the cationic polyacrylamide when added is generally 0.1 to 10% by weight, preferably 0.5 to 10% by weight.
It is 5% by weight, more preferably 0.8 to 2% by weight. At this time, the cationic polyacrylamide of the present invention can be used alone, but if necessary, papermaking is performed in combination with a sulfate band, an anionic resin and the like. These agents can be added in any order or simultaneously. Alternatively, the cationic polyacrylamide and the water-soluble anionic resin can be added after mixing at pH 9 or more. The addition ratio of the cationic polyacrylamide and the water-soluble anionic resin can be arbitrarily selected, and is in the range of 100: 0 to 10:90 in terms of the solid content weight. The amount of addition is 0.00% based on the dry solid weight of the pulp.
It is in the range of 5 to 3% by weight, preferably 0.01 to 1% by weight. The adding place may be any place before the wet sheet is formed, and it is usually better to add the place near the papermaking wire part. In the present invention, the pulp slurry can be added to the solution immediately after the Hoffman decomposition reaction without stopping the reaction or without stopping the reaction. In either case, the solution can be added without diluting the solution, but it is preferable to add the solution after diluting it with water to a polymer solid content of 0.1 to 10% as necessary.

By producing paper by the above method, drainage is greatly increased, drainage of pulp is improved, and productivity is improved. Further, since the drying property of the pulp sheet is improved, the amount of steam used is reduced, leading to a reduction in production cost.

The method of using the cationic polyacrylamide of the present invention for the purpose of a paper strength agent may be performed according to a conventionally known method. At this time, the cationic polyacrylamide of the present invention can be used alone, but if necessary, papermaking is performed in combination with a sulfate band, an anionic resin and the like. These agents can be added in any order or simultaneously. Further, it can be added after mixing the cationic polyacrylamide and the anionic resin at pH 9 or more. The addition ratio of the cationic polyacrylamide and the anionic resin can be arbitrarily selected, and is in the range of 100: 0 to 10:90 in terms of the weight of the solid content. The amount of addition is 0.01 to 5% by weight, preferably 0.05 to 2% by weight, based on the dry solid content of the pulp. The addition site can be added before the wet sheet is formed, but even after the wet sheet is formed, especially when manufacturing a laminated paper, it can be added by spray coating or roll coater coating. It is possible.

Further, at that time, it may be diluted with water and added depending on the concentration of the cationic polyacrylamide after the reaction. Although it varies depending on the type of pulp, the speed of papermaking, etc., and is not explicitly mentioned, the concentration of the cationic polyacrylamide when added is generally 0.1 to 10% by weight, preferably 0.5 to 10% by weight.
It is 5% by weight, more preferably 0.8 to 2% by weight.

The paper manufactured by the above method is excellent in paper strength, specifically, burst strength, Z-axis strength, compressive strength, and the like. Therefore, when the method of the present invention is applied, when used for a material such as corrugated cardboard or newsprint in which waste paper occupies a high proportion, the effect is very large, and paper with high paper strength can be produced. Further, by applying the present invention not only to corrugated paper and newsprint but also to paper requiring strength, it becomes possible to produce paper having excellent paper strength.

On the other hand, in the field of polymer flocculants, the cationic polyacrylamide produced by the method of the present invention is discharged as domestic wastewater among various wastewaters, especially human waste / sewage, excess sludge discharged from biological treatment such as activated sludge, and the like. This is effective for coagulation and dehydration of organic suspensions. As a method of using the polymer coagulant of the present invention, when used for coagulation of wastewater or the like, the amount of addition is 0.01 to 1,000 ppm in solid content with respect to wastewater,
Preferably it is 0.1 to 100 ppm, and it can be applied to either the coagulation sedimentation method or the pressure flotation method. Also aggregate sediment,
When used as a dehydrating agent for sludge, the amount added is 0.01 to 50% by weight, preferably 0.2 to 10% by weight, based on the dry solids of sludge, etc. Then, an aqueous solution of a polymer flocculant is added to sludge or the like, and the mixture is stirred or mixed directly in a pipe to form flocculated floc, followed by filtration and dehydration. As a dehydration method, vacuum dehydration, centrifugal dehydration using a decanter or the like, capillary dehydration, pressure dehydration using a screw press dehydrator, a filter press dehydrator, a belt press dehydrator, or the like can be applied.

Further, in the present invention, a polyacrylamide is subjected to a Hoffman decomposition reaction at a high temperature for a short time to produce a cationic polyacrylamide, so that it has become possible in some respects that could not be achieved conventionally. First, in the case of high molecular weight polyacrylamide, mixing with hypochlorite becomes a problem because the viscosity becomes high when performing the Hoffman decomposition reaction.However, in the high temperature reaction according to the present invention, the viscosity decreases, so that the reaction is performed at a low temperature. Is improved as compared with the case of carrying out, and as a result, the Hoffman decomposition reaction rate is improved.

Then, surprisingly, it shows better paper strength than cationic polyacrylamide obtained by performing the same reaction at low temperature for a long time. Although the reason for this is not necessarily clear, the effect is remarkable when added to a pulp slurry or the like without performing a reaction stopping operation, and the reaction intermediate N-chloro group, Other,
It is considered that the functional group generated due to the high temperature directly or indirectly contributes to the development of paper strength. Therefore, it is more desirable to add without performing the reaction stop operation, but if the reaction is not stopped, deterioration occurs over time,
It must be added immediately after the reaction. The term "immediately" as used herein means that the aqueous solution after the reaction is taken out of the pipe, transported in the same pipe without being transferred to the outside, and added to the pulp slurry. More specifically, the aqueous solution after the reaction may be directly added to the pulp slurry through a pipe, or a stock tank may be provided between them to temporarily stay there, and then the amount may be adjusted and added. The residence time of the reaction solution in the pipe may be within a range where the aqueous solution after the reaction does not deteriorate. However, if the length is too long, the device for retaining the liquid becomes large, and the features of the present invention cannot be utilized. Therefore, in order to carry out the present invention suitably, it is preferable to add within 5 hours after the reaction, more preferably within 1 hour, even more preferably within 10 minutes.

Further, in addition to the above-mentioned uses, the present invention can be applied to various fields such as water-based paints, water-based films, microcapsules, petroleum mining and recovery agents, adhesives, fiber treatment agents, dyeing processing aids, and pigment dispersants.

[Examples] Next, the present invention will be described with reference to examples, but the present invention is not necessarily limited to the following examples. %
Certain items are by weight unless otherwise specified.

Production Example 1 In a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen gas inlet tube, 375 g of 40% acrylamide and 1,125 g of water were placed.
And then adjusted to pH 4.5 with a 10% aqueous sulfuric acid solution. Thereafter, the internal temperature was raised to 40 ° C. while blowing nitrogen gas. While stirring, a 10% aqueous solution of ammonium persulfate and a 10% aqueous solution of sodium bisulfite were added to initiate polymerization. Thereafter, the temperature was maintained at 85 ° C, and 3 hours after the start of the polymerization, 1,500 g of water was added to complete the polymerization reaction. As a result, a nonvolatile content of 5.2%, a Brookfield viscosity at 25 ° C of 457 cps and a stable acrylamide-based weight of pH 4.3 were obtained. A combined aqueous solution was obtained. The weight average molecular weight of this polymer was analyzed by liquid chromatography (Shodex OH-paK B-806 + B-805 column, eluent: 0.05M-KCl) and found to be 857,000.

Production Example 2 375 g of 40% acrylamide and 1,625 g of water were placed in a four-necked flask equipped with a stirrer, reflux cooling, a thermometer, and a nitrogen gas inlet tube.
And then adjusted to pH 4.5 with a 10% aqueous sulfuric acid solution. Thereafter, the internal temperature was raised to 45 ° C. while blowing nitrogen gas. While stirring, a 10% aqueous solution of ammonium persulfate and a 10% aqueous solution of sodium bisulfite were added to initiate polymerization. Thereafter, the temperature was maintained at 85 ° C., and 3 hours after the start of the polymerization, 1,000 g of water was added to complete the polymerization reaction. As a result, a nonvolatile content of 5.1%, a Brookfield viscosity at 25 ° C. of 375 cps and a stable acrylamide-based weight of pH 4.3 were obtained. A combined aqueous solution was obtained. The weight average molecular weight of this polymer was analyzed by liquid chromatography (Shodex OH-paK B-806 + B-805 column, eluent: 0.05M-KCl) and found to be 650,000.

Production Example 3 A four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen gas inlet tube was charged with 375 g of 40% acrylamide and 625 g of water, and then adjusted to pH 4.5 with a 10% aqueous sulfuric acid solution.
Thereafter, the internal temperature was raised to 30 ° C. while blowing nitrogen gas. While stirring, a 10% aqueous solution of ammonium persulfate and a 10% aqueous solution of sodium bisulfite were added to initiate polymerization. Thereafter, the temperature was maintained at 85 ° C., and 3 hours after the start of the polymerization, 2,000 g of water was added to complete the polymerization reaction. As a result, the nonvolatile content was 5.2%, and the Brookfield viscosity at 25 ° C. was 957.
A stable acrylamide polymer aqueous solution having a cps of pH 4.3 was obtained. The weight average molecular weight of this polymer was analyzed by liquid chromatography (Shodex OH-paK B-806 + B-805 column, solvent: 0.05M-KCl) to find that it was 1,057,000.
Met.

Example 1 5.2% aqueous solution of polyacrylamide 5 obtained in Production Example 1
Take 7.7 g in a 500 ml beaker, and add 16.9 g of a mixed solution of sodium hypochlorite and NaOH (sodium hypochlorite concentration: 1.0 mol / kg, NaOH concentration: 2.0 mol / kg) once while heating and stirring at 80 ° C. After 20 seconds, 225.4 g of 5 ° C. cold water was added to stop the reaction to obtain a 1% cationic polyacrylamide solution (hereinafter Hoffman PAM (a)). A part of the reaction product is taken in an aqueous solution having a pH of 2 and 1 / toluidine blue is used as an indicator.
Colloid titration with a 400N-potassium polyvinyl sulfonate aqueous solution gave a cation value of 4.4 meq./g. In the following tests, Hoffman PAM (a) was used immediately after production.

Example 2 5% aqueous solution of 5.1% polyacrylamide obtained in Production Example 2
8.5 g is placed in a 500 ml beaker, and 16.9 g of a mixed solution of sodium hypochlorite and NaOH (sodium hypochlorite concentration: 1.0 mol / kg, NaOH concentration: 2.0 mol / kg) is once heated and stirred at 80 ° C. After 20 seconds, 224.3 g of 5 ° C. cold water was added to stop the reaction to obtain a 1% cationic polyacrylamide solution (hereinafter Hoffman PAM (b)). A part of the reaction product is taken in an aqueous solution having a pH of 2 and 1 / toluidine blue is used as an indicator.
Colloid titration with a 400N-potassium polyvinyl sulfonate aqueous solution gave a cation value of 4.4 meq./g. In the following tests, Hoffman PAM (b) was used immediately after production.

Example 3 5.2% aqueous solution of polyacrylamide obtained in Production Example 3 5
Take 7.7 g in a 500 ml beaker, and add 16.9 g of a mixed solution of sodium hypochlorite and NaOH (sodium hypochlorite concentration: 1.0 mol / kg, NaOH concentration: 2.0 mol / kg) once while heating and stirring at 80 ° C. After 20 seconds, 225.4 g of 5 ° C. cold water was added to stop the reaction to obtain a 1% cationic polyacrylamide solution (hereinafter Hoffman PAM (c)). A part of the reaction product is taken in an aqueous solution having a pH of 2 and 1 / toluidine blue is used as an indicator.
Colloid titration with a 400 N aqueous solution of potassium polyvinylsulfonate gave a cation value of 4.3 meq./g. In the following tests, Hoffman PAM (c) was used immediately after production.

Comparative Example 1 5.0% aqueous solution of polyacrylamide (weight average molecular weight:
80,000) 30.0 g in a 500 ml beaker, 16.9 g of a mixed solution of sodium hypochlorite and NaOH (sodium hypochlorite concentration: 1.0 mol / kg, NaOH concentration: 2.0 mol / kg) with stirring at 80 ° C. Was added all at once, and after 20 seconds, 253.1 g of 5 ° C. cold water was added to stop the reaction to obtain a 1% cationic polyacrylamide solution (hereinafter referred to as Hoffman PAM (d). The colloid was the same as in Example 1. As a result of titration, the cation value was 4.4 meq./g.

Comparative Example 2 5.2% aqueous solution of polyacrylamide obtained in Production Example 1 5
7.7 g is placed in a 500 ml beaker, and a mixed solution of sodium hypochlorite and NaOH (sodium hypochlorite concentration:
1.0 mol / kg, NaOH concentration: 2.0 mol / kg) 16.9 g was added all at once, and 2 hours later, 225.4 g of cold water at 5 ° C. was added to stop the reaction, and a 1% cationic polyacrylamide solution (hereinafter Hoffman) was added. PAM (e) was obtained and colloid titration was performed in the same manner as in Example 1. As a result, the cation value was 3.7 meq./g.

Comparative Example 3 Weak anionic polyacrylamide having a weight average molecular weight of about 17 million (manufactured by Mitsui Cyanamid Co., Ltd., Acofloc A)
-100) 3.0 g was dissolved in 1% -KCl aqueous solution 117 g, and a mixed solution of sodium hypochlorite and NaOH (sodium hypochlorite concentration: 1.0 mol / kg, NaOH concentration: 2.0 mol / kg) 16.9
g at once, and after 20 seconds, 163.1 g of 5 ° C. cold water was added to stop the reaction to obtain a 1% cationic polyacrylamide solution (hereinafter referred to as Hoffman PAM (f). In the same manner as in Example 1, When colloid titration was performed, the cation value was 3.8 meq./
g.

Papermaking Example 1 A commercially available rosin emulsion sizing agent was added to a pulp slurry having a beating degree (Canadian Standard Freeness, hereinafter referred to as CSF) of 443 ml of 0.4% pulp slurry obtained from waste corrugated cardboard and 0.30% based on dry weight of pulp. And stirred for 2 minutes. Subsequently, 2.0% of aluminum sulfate was added on a dry weight basis, and the mixture was further stirred for 1 minute. At this time, the pH of the pulp slurry was 5.1. Example 1
0.40% by weight of Hoffman PAM (a) obtained in
Was added. After further stirring for 1 minute, a portion of the pulp slurry obtained was taken and the CSF was removed according to JIS P8121.
Was measured, and the rest was made with a TAPPI square sheet machine.
Then, it is dried for 2 hours in a blow dryer at 110 ° C.
± 3 g / m ² handmade paper was obtained. This handmade paper is JIS-P-81
"Specific compressive strength" according to No. 26, "Specific burst strength according to JIS-P-8112" and "Z-axis strength" were measured using an internal bond tester manufactured by Kumagaya Riki Kogyo. The results are shown in Table 1.

Papermaking Examples 2-3 The Hoffman PAM (b) produced in Example 2 and the Hoffman PAM (c) produced in Example 3 were mixed at 0.40% by dry weight.
A hand-making test was carried out in the same manner as in Papermaking Example 1 except for the addition of%. The results are shown in Table 1.

Papermaking Comparative Example 1 A papermaking test was conducted in the same manner as in Papermaking Example 1, except that the cationic polyacrylamide (Hoffman PAM (d)) obtained in Comparative Example 1 was added at 0.40% on a dry weight basis. Was. The results are shown in Table 1.

Papermaking Comparative Examples 2 and 3 Papermaking Examples 1 and 2 were repeated except that the cationic polyacrylamides (Hoffman PAM (e) and Hoffman PAM (f)) obtained in Comparative Examples 2 and 3 were added at 0.40% on a dry weight basis. A hand-making test was performed in the same manner. The results are shown in Table 1.

Coagulation experiment example 1 night soil mixed sludge (digested sludge / excess sludge = 1/3, solid content 1.4
5%) 150 ml was placed in a 300 ml beaker, and 20 ml of a 1% aqueous solution of the cationic polyacrylamide prepared in Example 1 was added.
Was added. After stirring for 1 minute, the flocculated floc was subjected to natural filtration using a Buchner funnel (filtration area 100 cm ² , filter cloth 60 mesh Tetron), and the amount of the gravity-dehydrated filtrate was measured.
109ml, 110ml after 20 seconds, 111ml after 30 seconds, 112ml after 60 seconds
Met. Furthermore, the flocculated floc after gravity dehydration is rotated
The water content of the dehydrated cake obtained by centrifugal dehydration at 3000 rpm for 5 minutes was measured and found to be 85%.

[Effect of the Invention] In the case of decomposing a high-molecular-weight polyacrylamide into Hoffman, if the reaction is carried out at a low temperature as in the past, the viscosity of the solution becomes high, and the mixing with the hypochlorite used for the reaction becomes difficult. It was extremely difficult. On the other hand, when the reaction is performed with a dilute aqueous solution for the purpose of lowering the viscosity of high molecular weight polyacrylamide,
There was a disadvantage that the reaction rate was significantly reduced. In the present invention, the miscibility is improved by performing the Hoffman decomposition reaction at a high temperature, and it is possible to produce a cationic polyacrylamide with a high reaction rate by completing the reaction in a short time. As a result, it has become possible to use cationic polyacrylamide exhibiting excellent performance in drainage and paper strength.

Furthermore, according to the present invention, by performing the Hoffman decomposition reaction in a short time, the production apparatus can be miniaturized, and the reaction apparatus can be installed at the site where cationic polyacrylamide is used. Sexual problems can now be avoided.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ identification code FI D21H 17/34 D21H 17/34 B (58) Field surveyed (Int.Cl. ⁶ , DB name) C08F 8 / 12,8 / 44,20 / 56 C02F 1/56 B01D 21/01 D21H 17/34

Claims (4)

(57) [Claims] An acrylamide polymer having a weight-average molecular weight in the range of 500,000 to 15,000,000 is reacted with a acrylamide polymer and a hypohalite at 65 to 100 ° C. under an alkaline region of at least pH 11 or more. A cationic polyacrylamide obtained by performing a reaction within a short time (t) specified below in the temperature (T) range. e ^{15,150 / (273 + T)} × 2.5 × 10 ⁻²⁰ ≦ t (sec) ≦ e ^{15,150 / (273 + T)} × 10 ⁻¹⁸ +30 (T is the reaction temperature.) 2. A method for enhancing paper strength, comprising adding the cationic polyacrylamide according to claim 1 to a pulp slurry immediately after the reaction. 3. A method for improving drainage, comprising adding the cationic polyacrylamide according to claim 1 to a pulp slurry immediately after the reaction. 4. A water treatment method comprising adding the cationic polyacrylamide according to claim 1 to a suspension immediately after the reaction.