JP2013023520A - Method for producing cationic or amphoteric polymer, dehydrating agent for sludge, and retention aid agent for papermaking - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently producing a polymer which has a high molecular weight and which is excellent in water solubility, in a method for producing a cationic or amphoteric water-soluble polymer.SOLUTION: A gel polymer obtained by aqueous solution polymerization of a monomer mixture including a cationic monomer and a nonionic monomer, or a monomer mixture including a cationic monomer, a nonionic monomer, and an anionic monomer is dried in the presence of a hydroxy carboxylic acid and/or a salt thereof.

Description

  The present invention relates to a method for producing a cationic or amphoteric polymer. In detail, it is related with the manufacturing method of a powdery high molecular polymer with few insoluble matters. This polymer is useful as an agent for paper making processes such as a flocculant such as a sludge dehydrating agent, a papermaking viscosity agent, and a yield improver.

  Acrylamide or methacrylamide (hereinafter collectively referred to as “(meth) acrylamide”; hereinafter, other compounds are also indicated in the same manner) and methyl chloride quaternary salt of dimethylaminoethyl (meth) acrylate, ( Cationic or amphoteric water-soluble polymers typified by copolymers with (meth) acrylic acid or the like are widely used in various industries as polymer flocculants, papermaking process chemicals and the like. In these applications, in general, the higher the molecular weight, the better the performance, and a polymer having a very high molecular weight exceeding several million is required. In some cases, polymerization is performed by adding a crosslinking agent to improve the performance.

  Such a high molecular weight polymer is used after being dissolved in a concentration of about 0.05 to 0.5% at the time of use. However, as the molecular weight increases, gel or sol insoluble matter that does not completely dissolve is easily produced as a by-product in the resulting polymer. In particular, when a large amount of (meth) acrylamide is contained as a monomer, crosslinking by imidization reaction is likely to occur during polymerization. Furthermore, amphoteric high molecular weight polymers tend to be insolubilized when (meth) acrylamide and anionic groups are imide-bonded or cationic groups and anionic groups are ionically bonded at multiple points. is there. If a large amount of insoluble matter is generated in the polymer, it may cause troubles such as a pump or a strainer that handles the aqueous solution of the polymer for various purposes. For example, when this high molecular weight polymer is used as a papermaking chemical, insoluble substances may be squeezed into the paper during the papermaking process, causing defects.

  Many attempts have been made to remove insoluble matter using a strainer or the like. However, when there are many insoluble matters, the strainer is likely to be clogged, increasing the maintenance burden. Further, insoluble matter that has passed through the strainer or the like may be mixed into the paper stock. Therefore, in the use of papermaking chemicals, it is necessary that substantially no insoluble substances are present in the polymer. In general, in order to prevent the insoluble matter from forming in the polymer, it is necessary to lower the molecular weight of the polymer. Moreover, when making a high molecular polymer into a particle, it is necessary to dry at a low temperature and to grind | pulverize under the relaxed conditions. Therefore, production efficiency is poor.

  Further, in order to obtain a high molecular weight polymer having a small amount of insoluble matter, a method of polymerizing at a lower monomer concentration and drying the resulting high molecular polymer at a low temperature is employed. Yes. This method has a low production efficiency because of a long drying time.

  Patent Document 1 discloses a method for producing an acrylamide polymer in which a polymerization initiator and an ascorbic acid derivative are allowed to coexist when a monomer mainly composed of acrylamide is polymerized in an aqueous solvent.

  Patent Document 2 discloses a method for producing a high-molecular-weight acrylamide polymer that generates a small amount of water-insoluble matter in the drying step. When drying a hydrous acrylamide polymer, 2-mercapto is used before the drying step. The coexistence of pendabenzimidazole is disclosed.

  However, the polymer produced by any method is not fully satisfactory with respect to water solubility.

  As described above, there is currently no satisfactory method for efficiently producing a cationic or amphoteric polymer having excellent water solubility.

JP 05-247136 A JP-A-55-165906

  An object of the present invention is to provide a method for efficiently producing a polymer having a high molecular weight and excellent water solubility in a method for producing a cationic or amphoteric polymer.

  As a result of intensive studies to solve the above problems, the present inventors have included a cationic monomer and a nonionic monomer, or have a cationic monomer, a nonionic monomer, and an anionic property. A gel-like polymer obtained by subjecting a monomer mixture containing a monomer to aqueous solution polymerization is dried in the presence of hydroxycarboxylic acid and / or a salt thereof to obtain a high molecular weight and insoluble matter. The present inventors have found that a high-molecular polymer in which the production of is highly suppressed can be produced, and have completed the present invention.

  The present invention for solving the above problems is described below.

[1] A monomer mixture containing a cationic monomer and a nonionic monomer,
Alternatively, a cationic or amphoteric polymer is obtained by polymerizing an aqueous solution of a monomer mixture containing a cationic monomer, a nonionic monomer, and an anionic monomer to obtain a gel polymer, and drying the gel polymer. A method for producing a polymer of
A method for producing a cationic or amphoteric polymer, characterized in that a hydroxycarboxylic acid and a salt thereof, or a hydroxycarboxylic acid or a salt thereof is present in the gel polymer at the time of drying.

[2]
The method for producing a cationic or amphoteric polymer according to [1], wherein the drying temperature of the gel polymer is 70 ° C or higher.

  [3] The method for producing a cationic or amphoteric polymer according to [1], wherein the hydroxycarboxylic acid and a salt thereof, or the hydroxycarboxylic acid or a salt thereof is present in an aqueous solution of the monomer mixture.

  [4] The total amount of the hydroxycarboxylic acid and the salt thereof, or the hydroxycarboxylic acid or the salt thereof is 0.05 to 5.0 parts by mass with respect to 100 parts by mass of the monomer mixture [1]. A method for producing the cationic or amphoteric polymer as described in 1.

  [5] The method for producing a cationic or amphoteric polymer according to [1], wherein the hydroxycarboxylic acid is an aliphatic hydroxycarboxylic acid.

  [6] The method for producing a cationic or amphoteric polymer according to [1], wherein the hydroxycarboxylic acid is any one of citric acid, malic acid, and tartaric acid.

[7] The cation according to [1], wherein the cationic monomer is at least one selected from a tertiary salt or a quaternary salt of dialkylaminoalkyl (meth) acrylate or dialkylaminoalkyl (meth) acrylamide. Method for producing hydrophilic or amphoteric polymer.

  [8] The method for producing a cationic or amphoteric polymer according to [1], wherein the polymerization is initiated by thermal initiation, redox initiation, or photoinitiation.

  [9] The method for producing a cationic or amphoteric polymer according to [2], wherein the aqueous solution of the monomer mixture has a pH of 2.0 to 4.5.

  [10] A sludge dewatering agent comprising a polymer obtained by the production method according to [1].

  [11] A yield improving agent for papermaking, comprising a polymer obtained by the production method according to [1].

  According to this production method, a polymer having a high molecular weight and very little insoluble matter can be produced. In addition, according to the present production method, even when the drying temperature and pulverization rate of the polymer are increased, the generation of insoluble matter is very small.

  Hereinafter, a method for producing the polymer of the present invention (hereinafter also referred to as “the present production method”) will be described in detail.

  First, a monomer mixture containing a cationic monomer and a nonionic monomer, or a monomer mixture containing a cationic monomer, a nonionic monomer, and an anionic monomer is used as an aqueous solution weight. Polymerization is performed by a legal method to produce a gel polymer. Thereafter, the gel polymer is dried and pulverized to produce a powdery polymer. In this production method, the gel polymer is dried in the presence of hydroxycarboxylic acid and / or a salt thereof.

(1) Cationic monomer The cationic monomer used in the present invention is a dialkylaminoalkyl (meth) acrylate represented by the following formula (1) and a dialkylaminoalkyl represented by the following formula (2). (Meth) acrylamide and their tertiary and quaternary salts are preferred.

In Formula 1, R ₁ represents a hydrogen atom or a methyl group. R ₂ represents an alkylene group having 2 to 8 carbon atoms. R ₃ and R ₄ represent an alkyl group having 1 to 8 carbon atoms or a hydroxyalkyl group, and each may be the same or different.

In Formula 2, R ₅ represents a hydrogen atom or a methyl group. R ₆ represents an alkylene group having 2 to 8 carbon atoms. R ₇ and R ₈ represent an alkyl group having 1 to 8 carbon atoms or a hydroxyalkyl group, and each may be the same or different.

  Specific examples include dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, dimethylaminopropyl acrylamide, dimethylaminopropyl methacrylamide and tertiary and quaternary salts thereof. Examples of the tertiary salt and quaternary salt include hydrochloride, sulfate, methyl chloride quaternary salt, dimethyl sulfate quaternary salt, and benzyl chloride quaternary salt. These may be used alone or in combination of two or more.

(2) Nonionic monomer Examples of the nonionic monomer used in the present invention include acrylamide, methacrylamide, N, N-dimethylacrylamide, N-vinylpyrrolidone, N-vinylformamide, and N-vinylacetamide. Is done. In particular, acrylamide and / or methacrylamide (hereinafter referred to as “(meth) acrylamide”) is preferably used.

(3) Anionic monomer The anionic monomer used in the present invention is a monobasic acid having one vinyl group such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, and citraconic acid. And dibasic acid. In particular, acrylic acid and / or methacrylic acid (hereinafter referred to as “(meth) acrylic acid”) is preferably used. These may be used alone or in combination of two or more.

(4) Monomer mixture The monomer mixture contains the aforementioned cationic monomer and nonionic monomer as essential components, and an anionic monomer as a desired component. This monomer mixture is copolymerized to form a gel polymer (described later).

  The molar ratio of the cationic monomer, nonionic monomer, and anionic monomer in the monomer mixture is as follows: cationic monomer: nonionic monomer: anionic monomer = 2 to 70: 20-98: 0-45 are preferable and 2-60: 28-98: 0-40 are especially preferable.

  The monomer mixture is an aqueous solution (hereinafter, also simply referred to as “monomer aqueous solution”). The method for adjusting the monomer aqueous solution is not particularly limited. An aqueous solution of each monomer may be mixed, or an aqueous solution may be prepared after mixing each monomer in advance.

  In addition, other monomers such as styrene, acrylonitrile, (meth) acrylic acid ester and the like are appropriately blended so long as the water solubility of the monomer mixture and the resulting polymer is not impaired. Also good.

(5) Hydroxycarboxylic acids In the present invention, in the drying step of a gel polymer obtained by polymerizing the monomer mixture (described later), the gel polymer and hydroxycarboxylic acids coexist. To do.

  As hydroxycarboxylic acids, hydroxycarboxylic acids and salts thereof can be used. Hydroxycarboxylic acids are preferably water-soluble and are difficult to volatilize and decompose when the gel polymer is dried.

  Examples of hydroxycarboxylic acids include citric acid, malic acid, tartaric acid, glycolic acid, gluconic acid, lactic acid, mandelic acid, α-oxyisobutyric acid, dimethylolpropionic acid, tartronic acid, glyceric acid, 2-hydroxybutyric acid, and 3-hydroxybutyric acid. , Γ-hydroxybutyric acid, 2-hydroxyisobutyric acid, citramalic acid, isocitric acid, leucine acid, mevalonic acid, pantoic acid, ricinoleic acid, ricinaleic acid, cerebuloic acid, quinic acid, shikimic acid.

  Of these, aliphatic α-hydroxycarboxylic acids are preferred. The hydroxycarboxylic acid preferably has 10 or less carbon atoms, particularly preferably 3 to 6 carbon atoms.

  The number of hydroxyl groups in the hydroxycarboxylic acid is preferably 4 or less, particularly preferably 1 to 2. The number of carboxyl groups in the hydroxycarboxylic acid is preferably 4 or less, particularly preferably 1 to 2.

  Particularly preferred hydroxycarboxylic acids are citric acid, malic acid and tartaric acid.

  Examples of the hydroxycarboxylate include alkali metal salts such as sodium salt and potassium salt of the above hydroxycarboxylic acid, and alkaline earth metal salts such as calcium salt and magnesium salt.

  Hydroxycarboxylic acids are used alone or in combination of two or more.

  The amount of the hydroxycarboxylic acids to coexist in the gel polymer is 0.05 to 5.0 parts by mass, preferably 0.10 to 4.0 parts by mass with respect to 100 parts by mass of the gel polymer. If it is less than 0.05 mass part, the effect which suppresses the production | generation of an insoluble matter is not seen. In the case where the hydroxycarboxylic acid is added to the monomer aqueous solution from the beginning for polymerization, when the amount of the hydroxycarboxylic acid exceeds 5.0 parts by mass, the molecular weight of the resulting high molecular polymer is lowered.

  The method for allowing the hydroxycarboxylic acids to coexist at the time of drying the gel polymer is not particularly limited. The hydroxycarboxylic acids can be added at any time before drying is started. It is preferable to add hydroxycarboxylic acids in advance to the monomer aqueous solution that is the raw material for the gel polymer.

  When the hydroxycarboxylic acids are added to the aqueous monomer solution, the hydroxycarboxylic acids may be added in a solid state or may be added in the form of an aqueous solution in advance. Hydroxycarboxylic acids also have a function as a pH buffer for the monomer aqueous solution described later.

(6) Polymerization of monomer mixture The monomer mixture is polymerized by a solution polymerization method. The solution polymerization method is a method in which the monomer mixture is polymerized in a solvent in which both the monomer mixture and a polymer obtained by polymerizing the monomer mixture are dissolved. In the present invention, water is used as the solvent. The existence of a small amount of an organic solvent inevitably added in the polymerization process is not denied.

  The solution polymerization method in the present invention does not include a so-called emulsion polymerization method. In the polymer obtained by the solution polymerization method, only a polymer, a small amount of unreacted monomer, a solvent (water), and a small amount of a polymerization initiator are present. On the other hand, in addition to the above, fats and oils, surfactants and the like remain in the polymer obtained by the emulsion polymerization method. Since the polymer produced by the solution polymerization method does not contain fats and oils, surfactants and the like, it can be suitably used as a sludge dewatering agent or a papermaking yield improver.

  The solution polymerization method in the present invention is preferably an adiabatic polymerization method. The adiabatic polymerization method is a solution polymerization method in which the polymerization reaction is allowed to proceed without performing artificial heating or heat removal from the outside during the polymerization reaction. It does not indicate whether the polymerization vessel is adiabatic or whether the polymerization vessel is temperature-controlled. In the adiabatic polymerization method, as the polymerization reaction proceeds, the reaction temperature (temperature of the reaction solution) rises due to reaction heat. When the polymerization reaction is almost complete, the temperature rise stops and reaches the maximum temperature. In the adiabatic polymerization method, the temperature is not controlled during the polymerization reaction. Therefore, the polymerization temperature varies in a wide range.

  The production method will be described more specifically below.

  First, a cationic monomer, a nonionic monomer, and, if necessary, an anionic monomer are dissolved in water to prepare an aqueous monomer solution.

  The density | concentration of all the monomers in a monomer aqueous solution is 20-70 mass%, and 30-60 mass% is preferable. When the concentration of the monomer is less than 20% by mass, the progress of the polymerization reaction is delayed, and the amount of unreacted monomer remaining after the completion of the polymerization reaction is increased. When the concentration of the monomer exceeds 70% by mass, the polymerization reaction proceeds rapidly and the aqueous monomer solution foams due to water evaporation. As a result, equipment troubles may be caused.

  The monomer aqueous solution may be prepared by any method. For example, the monomer aqueous solution can be prepared by simply dissolving the monomer in water.

  Also, an aqueous solution is prepared by mixing a cationic monomer and a nonionic monomer with an anionic monomer before the acid group is neutralized, and a predetermined amount of an alkaline substance is added thereto. Thus, an aqueous monomer solution can also be prepared. When an alkaline substance is added to the aqueous solution, the acid group of the anionic monomer is neutralized. When acrylic acid is used as the anionic monomer, the pH of the aqueous solution is adjusted to 4.0 to 4.9 using an alkaline substance, so that 35 to 80 mol% of the acid group of acrylic acid is reduced. Neutralized by the alkaline substance.

  Cationic monomers such as dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, and their hydrochlorides and sulfates, methyl chloride quaternary salts, dimethyl sulfate quaternary salts and benzyl chloride quaternary salts are ester groups. It has a structure. These cationic monomers having an ester group structure may be hydrolyzed by an alkaline substance. In order to avoid hydrolysis, when adding an alkaline substance to an aqueous solution containing these cationic monomers, it is preferable to keep the aqueous solution as low as possible. Moreover, when adding an alkaline substance to aqueous solution, it is preferable to diffuse the alkaline substance to add rapidly in aqueous solution by adding it slowly, stirring strongly.

  Next, hydroxycarboxylic acid and / or a salt thereof is added to the aqueous monomer solution.

  The pH of the aqueous monomer solution before polymerization is preferably in the range of 2.0 to 4.5. If the pH is outside this range, it is adjusted with a pH adjuster. Examples of the pH adjuster include inorganic acids such as hydrochloric acid and sulfuric acid, organic acids such as formic acid, acetic acid and propionic acid, and bases such as sodium hydroxide, potassium hydroxide and ammonia.

  Next, after removing dissolved oxygen in the monomer aqueous solution using nitrogen gas or the like, the polymerization reaction is started. The polymerization reaction is started by adding a polymerization initiator to the aqueous monomer solution prepared by the above method. The polymerization start temperature, that is, the temperature of the monomer aqueous solution at the start of the polymerization is preferably -5 to 30 ° C. When the monomer concentration is high, the polymerization start temperature is set low, and when the monomer concentration is low, the polymerization start temperature is set high. As the polymerization initiator, a redox polymerization initiator or a photopolymerization initiator is preferable.

  The redox initiator can be prepared by combining a known oxidizing agent and a reducing agent. Examples of the oxidizing agent include ammonium persulfate, potassium persulfate, hydrogen peroxide, and tertiary butyl hydroperoxide. Examples of the reducing agent include ferrous sulfate, ferrous ammonium sulfate, sodium hydrogen sulfite, and trimethylamine. The addition amount of the redox initiator is preferably 1 to 200 ppm with respect to the mass of the monomer aqueous solution for both the oxidizing agent and the reducing agent. Polymerization can be started by adding each aqueous solution of an oxidizing agent and a reducing agent to the aqueous monomer solution immediately before the start of polymerization.

  Examples of the photopolymerization initiator include benzophenone, anthraquinone, acylphosphine oxide compounds, and azo compounds. The addition amount of the photopolymerization initiator is preferably 200 to 5000 ppm with respect to the mass of the monomer aqueous solution. Polymerization can be initiated by adding a photopolymerization initiator to the monomer aqueous solution and irradiating light containing light having the maximum absorption wavelength of the photopolymerization initiator. Examples of the light source include a high pressure mercury lamp and a low pressure mercury lamp.

  In the case of redox polymerization, an azo polymerization initiator may be added in advance to the aqueous monomer solution for the purpose of promoting polymerization at a high temperature in the latter half of the polymerization reaction.

  As the azo polymerization initiator, 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 4,4′-azobis (4-cyanovaleric acid), 2,2′-azobis (2 , 4-dimethylvaleronitrile), 2,2′-azobis (2-methylpropionitrile), 2,2′-azobis (2-methylbutyronitrile), 2,2′-azobis (2-amidinopropane) Dihydrochloride, 2,2'-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride, 2,2'-azobis [2- (3,4,5,6-tetrahydropyrimidine-2 -Yl) propane] dihydrochloride, dimethyl 2,2'-azobis (2-methylpropionate), 4,4'-azobis (4-cyanopentanoic acid), 1,1'-azobis (cyclohexane-1- Carbonitrile), , 2′-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) -2-hydroxylethyl] -propionamide, 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) ) -Propionamide], 2,2′-azobis [N- (2-propenyl) -2-methylpropionamide]. These may be used alone or in combination of two or more.

  The total amount of the azo polymerization initiator added is preferably 100 ppm or more, particularly preferably 200 to 10,000 ppm, based on the mass of the monomer aqueous solution. When the azo polymerization initiator is water-soluble, the azo polymerization initiator may be added directly to the monomer aqueous solution, or the azo polymerization initiator may be added in advance to the monomer aqueous solution. Also good. When the azo polymerization initiator is water-insoluble, the polymerization may be difficult to start even if the azo polymerization initiator is directly added to the monomer aqueous solution. In this case, the azo polymerization initiator may be dissolved in a polar organic solvent such as methanol having a relatively low chain mobility and easily mixed with water, and then added to the aqueous solution of the monomer mixture.

  A chain transfer agent, a pH adjuster, etc. may be added to the aqueous solution of the monomer mixture, if necessary, in addition to the aforementioned monomers and polymerization initiators. The hydroxycarboxylic acids described above also act as a pH buffer for the aqueous monomer solution.

  The polymerization reaction is conducted adiabatically. In this case, the polymerization reaction usually reaches a maximum temperature of 50 to 100 ° C. within 30 minutes to 5 hours after the start of polymerization, and is almost completed. The aqueous solution containing the high molecular polymer obtained by the polymerization reaction is in the form of a gel at normal temperature (hereinafter also referred to as “gel polymer”).

  The polymerization reaction can be carried out batchwise in a suitable reaction vessel, or the monomer aqueous solution can be continuously poured onto a belt such as a belt conveyor to carry out the polymerization reaction continuously.

  The gel polymer obtained by the above polymerization reaction may be subjected to a heat treatment for the purpose of reducing the content of residual monomers such as acrylamide. The heat treatment is performed by heating the gel polymer in a reaction vessel or on a belt conveyor. Alternatively, the gel polymer is cut into a suitable size, sealed with a vinyl bag, and then heated in a heating bath such as a hot water bath. The heat treatment conditions are 70 to 100 ° C., and preferably 1 to 5 hours.

(7) Drying of gel polymer A powder polymer can be obtained by drying and pulverizing a gel polymer by a known method. The drying temperature is preferably 70 ° C. or higher, and particularly preferably 80 ° C. or higher. When the drying temperature is 70 ° C. or higher, the drying time can be shortened, so that the production efficiency is good.

  If the particle size of the polymer polymer powder is too large, it takes time to dissolve the polymer in water. On the other hand, when the particle size of the powder is too fine, when the polymer is added to water, it is difficult to dissolve by forming a so-called powdered particle having a gelled surface. The particle size of the high-molecular polymer is preferably 50% by mass or more, particularly preferably 80% by mass or more, based on 20 to 80 mesh.

(8) Polymer Polymer The polymer polymer obtained as described above has a viscosity at 25 ° C. (hereinafter referred to as “0”) of a 4% sodium chloride aqueous solution containing 0.5% by mass of the polymer. .5% salt viscosity ”is 10 to 100 mPa · s, preferably 15 to 90 mPa · s. When the viscosity is less than 10 mPa · s, the amount of the high-molecular polymer added to sufficiently dewater the sludge increases, which is not economical. When the viscosity exceeds 100 mPa · s, viscosity is generated in the sludge floc formed, and the dewatering performance of the sludge is lowered.

(9) Others The production examples of the polymer described in (6) to (8) have been described with respect to the case where hydroxycarboxylic acids are added to the monomer aqueous solution. The hydroxycarboxylic acids are gel polymers. It may be added before drying. That is, it may be added during the polymerization reaction or may be added to the gel polymer after the completion of the polymerization reaction. As a method of allowing the hydroxycarboxylic acid to be present in the gel polymer, there is a method of adding the hydroxycarboxylic acid after finely cutting the gel polymer into particles. However, this method is somewhat difficult. Therefore, it is preferable to add hydroxycarboxylic acids to the monomer aqueous solution in advance.

(10) Sludge dewatering agent The cationic or amphoteric polymer produced by the production method of the present invention can be used as a sludge dewatering agent. The sludge dewatering agent may contain a cationic or amphoteric polymer and other components such as a sulfuric acid band and a polyiron sulfate within the range where the effects of the present invention are exerted. good. In addition, additives such as sodium hydrogen sulfate, sodium sulfate, and sulfamic acid may be blended in order to stably maintain the polymer solution.

  When the cationic or amphoteric polymer produced by the production method of the present invention is used as a sludge dehydrating agent, the sludge is treated as follows.

  First, a 0.2 to 1.0 mass% aqueous solution of a polymer is prepared (hereinafter, this aqueous solution is also referred to as “sludge dehydrating agent aqueous solution”). Next, this sludge dewatering agent aqueous solution is added to the sludge to be treated to promote sludge floc formation. 0.1-5 mass% is preferable as a high molecular polymer with respect to the solid content mass of sludge, and, as for the addition amount of the dehydrating agent for sludge, 0.3-2 mass% is especially preferable.

  The sludge flocs formed as described above are dehydrated using a pressure dehydrator such as a belt press, a screw press or a filter press, or a pressure dehydrator such as a centrifugal separator or a vacuum filter. The sludge to which the dewatering agent for sludge is added has a coarse floc formed. Therefore, sludge is easily dehydrated, and the moisture content of the dewatered cake is reduced. In addition, the dewatering efficiency of the dehydrator increases, and the amount of sludge treatment per unit time increases.

  The sludge dewatering agent of the present invention is suitable for the treatment of sludge discharged from general industrial wastewater treatment plants, sewage treatment plants and human waste treatment plants, and sludge discharged from organic industrial wastewater treatment processes. Organic industrial wastewater is wastewater that contains a large amount of organic matter, has a high BOD value, and is purified by microorganisms. Examples include waste water discharged from food factories such as bread manufacturing plants, soft drink manufacturing plants, and ham manufacturing plants, waste water discharged from slaughterhouses, and waste water discharged from petrochemical plants. Examples of the sludge include raw sludge, surplus activated sludge, mixed sludge of surplus activated sludge and primary settled sludge, and digested sludge obtained by digesting them. In addition, it is particularly effective for biological sludge produced by general industrial wastewater treatment, mixed sludge containing agglomerated sludge, and the like.

  The above dewatering agent for sludge includes inorganic coagulants such as polyaluminum chloride, sulfate band, ferric chloride, ferrous sulfate, ferric sulfate, polyiron (polysulfate, polyiron chloride), and sodium aluminate. It can also be used together. When the sludge dehydrating agent and the inorganic coagulant are used in combination, the order of addition to the sludge does not matter.

(11) Process chemical for papermaking The cationic or amphoteric polymer produced by the production method of the present invention can be suitably used as a chemical for papermaking process, particularly as a yield improver.

  When the cationic or amphoteric polymer produced by the production method of the present invention is used as a yield improver, papermaking is performed as follows.

  First, a 0.02-0.3 mass% aqueous solution of a polymer is prepared (hereinafter, this aqueous solution is also referred to as “yield improving agent aqueous solution”). This yield improver aqueous solution is added to the pulp suspension in a paper machine. Thereafter, the pulp suspension to which the yield improver has been added is made using a paper machine.

  The addition amount of the yield improver is preferably 10 to 2000 ppm, particularly preferably 50 to 1000 ppm, per dry solid content of the pulp. The pulp concentration in the pulp suspension is preferably 0.01 to 2.0% by mass, particularly preferably 0.05 to 1.0% by mass.

  The yield improvement effect is affected by where the aqueous solution of the yield improver is added to the pulp suspension in the paper machine. In general, the yield increases as the place where the aqueous solution for improving yield is added to the pulp suspension is closer to the place where the pulp suspension is ejected onto the papermaking wire. However, if it is too close, the texture of the paper to be made may deteriorate. Therefore, the place of addition is appropriately determined in consideration of the texture of the paper to be made. For example, the outlet of the white water pump and the inlet or outlet of the screen disposed thereafter are preferable.

  Hereinafter, the present invention will be described specifically by way of examples. The present invention is not limited to these examples.

[Measurement method of 0.5% salt viscosity]
To 500 mL of pure water, 20.8 g of sodium chloride and an evaluation sample (polymer) were added in an amount of 0.50% by mass and sufficiently dissolved to prepare a sample solution. Using a B-type rotational viscometer, the viscosity of this sample solution at 25 ° C. was measured.

[Measurement method of insoluble matter]
Simulated industrial water was prepared according to the composition shown in Table 1. 5 kg of simulated industrial water is placed in a 5 L container, the temperature is adjusted to 20-25 ° C., and a sample for evaluation (polymer) is stirred while stirring an inclined four-blade stirring blade having a diameter of about 7 cm at 500 rpm. 9.0 g of citric acid anhydride 1.0 g was gradually added as a pH adjuster. After completion of the addition, they were stirred for 60 minutes to dissolve them. The solution was passed through a 60 mesh standard sieve having a diameter of 20 cm under natural gravity. After the droplets were broken, the number of residues on the sieve was counted as undissolved and evaluated according to the following evaluation criteria.

Evaluation criteria A: The number of undissolved substances on the sieve is 10 or less. B: The number of undissolved substances on the sieve is 11-20. 101 or more

Example 1
A mixture of 259 g of 50 mass% acrylamide (AM) aqueous solution, 310 g of 79 mass% dimethylaminoethyl acrylate methyl chloride quaternary salt (DAC), 31 g of 80 mass% acrylic acid (AA) aqueous solution, and 400 g of distilled water A monomer aqueous solution was prepared. The total monomer concentration of this aqueous monomer solution is 40% by mass. The composition (molar ratio) of the monomer dissolved in the monomer aqueous solution is DAC / AM / AA = 38/52/10.

While adjusting the temperature of the aqueous monomer solution to 5 ° C., nitrogen was introduced into the aqueous monomer solution and deoxygenated for about 30 minutes. Thereafter, 8.0 g of citric acid anhydrous salt (2.0% by mass with respect to all monomers) was added to the aqueous monomer solution, and the pH (5 ° C.) was adjusted to 2.4 using aqueous ammonia. Next, a 10% by mass aqueous solution of 2,2′-azobis (2-amidinopropane) dihydrochloride (hereinafter abbreviated as “V-50”) is used as a photopolymerization initiator in this monomer aqueous solution. 0 mL was added and polymerization was started under a 0.40 mW / cm ² ultraviolet lamp.

  The temperature of the polymerization solution reached a maximum value of 82.3 ° C. after 13 minutes and 30 seconds. Thereafter, the ultraviolet irradiation was continued for another hour. As a result, a gel polymer was obtained. The gel polymer was taken out from the reaction vessel, and the center of the gel polymer was cut using a meat chopper having a hole diameter of 6 mm. Then, this cut gel polymer was dried for 10 hours in an air dryer at 80 ° C. and pulverized using a rotary mill type pulverizer to obtain a polymer polymer powder. The high molecular weight polymer powder was classified using a standard sieve, and an 18-83 mesh fraction was collected and used as an evaluation sample. Table 2 shows the measurement results of 0.5% salt viscosity and insoluble matter measured using this sample for evaluation.

(Examples 2 to 11)
Polymerization and drying operations were performed under the same conditions as in Example 1 except that the composition ratio of each monomer, the type and addition amount of hydroxycarboxylic acid, the reaction start temperature, and the pH were set to the values shown in Table 2. Coalescence was obtained. Note that dilute hydrochloric acid or aqueous ammonia was used to adjust the pH. The measurement results of 0.5% salt viscosity and insoluble content are shown in Table 2.

(Comparative Examples 1-6)
Polymerization and drying operations were carried out under the same conditions as in Example 1 except that the substances listed in Table 2 were added instead of the hydroxycarboxylic acid to obtain a polymer. Note that dilute hydrochloric acid or aqueous ammonia was used to adjust the pH. The measurement results of 0.5% salt viscosity and insoluble content are shown in Table 2.

(Example 12)
A monomer aqueous solution was prepared by mixing 524 g of a 50% by mass acrylamide (AM) aqueous solution, 48 g of a 79% by mass methyl chloride quaternary salt (DAC) aqueous solution of dimethylaminoethyl acrylate, and 428 g of distilled water. The total monomer concentration of this aqueous monomer solution is 30% by mass. The composition (molar ratio) of the monomer dissolved in the monomer aqueous solution is DAC / AM = 5/95.

While adjusting the temperature of the aqueous monomer solution to 5 ° C., nitrogen was introduced into the aqueous monomer solution and deoxygenated for about 30 minutes. Thereafter, 6.0 g of citric acid anhydrous salt (2.0% by mass with respect to the total monomers) was added to the aqueous monomer solution, and the pH (5 ° C.) was adjusted to 4.0 using aqueous ammonia. Next, 4.5 mL of a 10% by mass aqueous solution of V-50 was added as a photopolymerization initiator to the aqueous monomer solution, and polymerization was initiated under a 0.40 mW / cm ² ultraviolet lamp.

  The temperature of the polymerization solution reached a maximum value of 83.1 ° C. after 12:00. Thereafter, the ultraviolet irradiation was continued for another hour. As a result, a gel polymer was obtained. The gel polymer was taken out from the reaction vessel, and the center of the gel polymer was cut using a meat chopper having a hole diameter of 6 mm. Then, this cut gel polymer was dried for 10 hours in an air dryer at 80 ° C. and pulverized using a rotary mill type pulverizer to obtain a polymer polymer powder. The high molecular weight polymer powder was classified using a standard sieve, and an 18-83 mesh fraction was collected and used as an evaluation sample. Table 3 shows the measurement results of 0.5% salt viscosity and insoluble content measured using this sample for evaluation.

(Examples 13 to 15)
Polymerization and drying operations were carried out under the same conditions as in Example 12 except that the composition ratio of each monomer, the type and addition amount of hydroxycarboxylic acid, the reaction start temperature, and the pH were set to the values shown in Table 3. Coalescence was obtained. Note that dilute hydrochloric acid or aqueous ammonia was used to adjust the pH. The measurement results of 0.5% salt viscosity and insoluble content are shown in Table 3.

(Comparative Examples 7 to 10)
Polymerization and drying operations were carried out under the same conditions as in Example 12 except that citric acid (anhydrous salt) was not added, to obtain a polymer. Note that dilute hydrochloric acid or aqueous ammonia was used to adjust the pH. The measurement results of 0.5% salt viscosity and insoluble content are shown in Table 3.

(Example 16)
79% by mass dimethylaminoethyl acrylate methyl chloride quaternized (DAC) aqueous solution, 79% by mass dimethylaminoethyl methacrylate methyl chloride quaternized (DMC) aqueous solution, 80% by mass acrylic acid (AA) aqueous solution, 50% by mass acrylamide (AM) Aqueous solution was mixed at a ratio shown in Table 4, and water was added so that the total monomer concentration was 38% by mass to prepare a monomer aqueous solution. The pH (25 ° C.) of this aqueous monomer solution was 2.4. A 20 mass% sodium hydroxide aqueous solution was added to 1400 g of this monomer aqueous solution with stirring until the neutralization rate of acrylic acid reached 35 mol%. The pH (25 ° C.) of the aqueous monomer solution after the addition was 4.0. Moreover, the addition amount of 20 mass% sodium hydroxide aqueous solution was 55.8g.

  Subsequently, 10.6 g of citric acid (2.0% by mass with respect to the total monomers) and 50 g of an aqueous solution containing 2.3 g of V-50 were added to the aqueous monomer solution, and cooled to 0 ° C. This monomer aqueous solution was put into a stainless steel dewar. Thereafter, nitrogen was introduced into the aqueous monomer solution in the dewar at a rate of 5 L / min to sufficiently deoxygenate.

  Ammonium persulfate (used as a 1% by weight aqueous solution) in an amount of 25 ppm relative to the total monomer weight, and sodium bisulfite (used as a 1% by weight aqueous solution) in an amount of 25 ppm relative to the total monomer weight, Each was taken in a syringe, and these were simultaneously put into a dewar, and stirred rapidly to initiate the polymerization reaction.

  After the start of the polymerization reaction, the polymerization reaction was continued for 3 hours by leaving it alone. As a result, a gel polymer was obtained. Thereafter, this gel polymer was taken out from the dewar, and the center of the gel polymer was cut using a meat chopper having a hole diameter of 6 mm. Thereafter, 50 g of the cut gel polymer is dried in a 70 ° C. hot air circulating dryer for 2 hours and pulverized for 1 minute using a high-speed rotary blade pulverizer to obtain a polymer polymer powder. Obtained. The high molecular weight polymer powder was classified using a standard sieve, and a 20-60 mesh fraction was collected and used as an evaluation sample. Table 4 shows the measurement results of 0.5% salt viscosity and insoluble content measured using this sample for evaluation.

(Examples 17 to 18)
Polymerization and drying operations were performed under the same conditions as in Example 16 except that the types and addition amounts of hydroxycarboxylic acid, reaction initiation temperature, and pH were changed to the values shown in Table 4 to obtain a polymer. Dilute hydrochloric acid or ammonia water was used for pH adjustment. In Example 18, the amounts of ammonium persulfate and sodium bisulfite added were each 21 ppm based on the total monomer mass. The measurement results of 0.5% salt viscosity and insoluble content are shown in Table 4.

(Comparative Example 11)
Polymerization and drying operations were performed under the same conditions as in Example 16 except that the hydroxycarboxylic acid was not added to obtain a high molecular polymer. Note that dilute hydrochloric acid or aqueous ammonia was used to adjust the pH. The measurement results of 0.5% salt viscosity and insoluble content are shown in Table 4.

  The relationship between the drying temperature of the gel polymer and the amount of insoluble matter generated was investigated. The gel polymers obtained in Example 1 and Comparative Example 1 were each chopped and dried using an air dryer. The drying temperature and drying time are as shown in Table 5. Thereafter, the dried polymer was pulverized using a rotary mill type pulverizer to obtain a powdery polymer. The high molecular weight polymer powder was classified using a standard sieve, and an 18-83 mesh fraction was collected and used as an evaluation sample. The insoluble content was measured using this sample for evaluation, and the results are shown in Table 5. In addition, the drying time shown in Table 5 is the time when the solid content of the gel polymer reaches 93%.

  The gel polymer obtained in Example 1 generates less insoluble matter even when the drying temperature is higher than that of the gel polymer obtained in Comparative Example 1. Therefore, the drying time can be greatly shortened.

(Sludge dewatering agent test example)
The sludge dehydrating agent was obtained by mixing 95 parts by mass of each of the polymer polymer powders obtained in Example 1, Example 15, Comparative Example 1 and Comparative Example 6 and 5 parts by mass of sulfamic acid. This sludge dewatering agent 0.20% by mass was dissolved in ion-exchanged water to obtain a sludge dewatering agent aqueous solution. This sludge dewatering agent aqueous solution was added to 500 mL of sewage sludge having the following properties and stirred. The amount of sludge dehydrating agent added was 1.2% by mass in terms of solid content with respect to the dry solid content of sewage sludge.

[Properties of sewage sludge]
pH: 6.2
TS: 23,400 mg / L
VTS: 83.6% TS
SS: 19,500mg / L
VSS: 83.0% SS
Crude suspended matter: 35.2% SS (60 mesh method)
m-Alkalinity: 140 (CaCO ₃ mg / L)

  By adding the sludge dewatering agent, flocs were formed in the sewage sludge. The flocs formed in the sewage sludge were observed to evaluate the cohesiveness. Then, the time for this sewage sludge to pass through an 80-mesh wire mesh was measured, and the filtration rate was measured. Further, the cake remaining on the wire mesh was dehydrated using a small belt press machine (0.2 Mpa, using Seiya weave filter cloth manufactured by Shikishima canvas), and the moisture content of the obtained dehydrated cake was measured. These results are shown in Table 6.

  The high molecular polymers obtained in Example 1 and Example 15 have equivalent or higher agglomeration performance, filterability and dehydrating property than Comparative Examples 1 and 6 in which hydroxycarboxylic acid is not used. There was no degradation in performance.

(Test example of yield improver for papermaking)
90 parts by mass of the respective polymer polymer powders obtained in Example 1 and Comparative Example 1 and 10 parts by mass of anhydrous citric acid were mixed to obtain a yield improver for papermaking. A yield improver aqueous solution was obtained by dissolving 0.10% by mass of this paper improver in ion exchange water. This yield improver aqueous solution was added to a test pulp slurry having the following properties, and the yield rate and formation index were measured under the following test conditions. The results are shown in Table 7. The formation index was evaluated by obtaining a pulp slurry under the same conditions as the yield performance test conditions, gently dispersing in a dilution water using a square sheet machine, and making paper. The addition amount of the paper making yield improver was 0.025% by mass in terms of solid content with respect to the dry pulp solid content.

  In the test example, in contrast to the comparative example in which no hydroxycarboxylic acid is used, in the example in which the hydroxycarboxylic acid is added, the total yield rate and the fine yield rate are equal to or higher, and the performance is reduced. There wasn't.

[Yield performance test conditions for papermaking raw materials]
Papermaking type Fine paper-neutral papermaking model Paper: Hardwood bleached kraft pulp / 1.0% by mass
Filling ratio in paper: sedimentation (light) calcium carbonate / 20% by weight vs. pulp Test water: Simulated industrial water (Table 1)
Test apparatus: Laboratory test machine BTG-Mutec DFR-04
Test conditions
Stirring speed: 800rpm
Filtration surface: 60 mesh
[Condition Index Measurement Conditions]
Target basis weight: 70 g / m ³
Measuring device: 3D sheet analyzer manufactured by M / K Systems

Claims (11)

A monomer mixture comprising a cationic monomer and a nonionic monomer,
Alternatively, a cationic or amphoteric polymer is obtained by polymerizing an aqueous solution of a monomer mixture containing a cationic monomer, a nonionic monomer, and an anionic monomer to obtain a gel polymer, and drying the gel polymer. A method for producing a polymer of
A method for producing a cationic or amphoteric polymer, characterized in that a hydroxycarboxylic acid and a salt thereof, or a hydroxycarboxylic acid or a salt thereof is present in the gel polymer at the time of drying.   The method for producing a cationic or amphoteric polymer according to claim 1, wherein a drying temperature of the gel polymer is 70 ° C or higher.   The method for producing a cationic or amphoteric polymer according to claim 1, wherein the hydroxycarboxylic acid and a salt thereof, or the hydroxycarboxylic acid or a salt thereof is present in an aqueous solution of the monomer mixture.   The total addition amount of the said hydroxycarboxylic acid and its salt, or the said hydroxycarboxylic acid or its salt is 0.05-5.0 mass parts with respect to 100 mass parts of said monomer mixtures. A method for producing a cationic or amphoteric polymer.   The method for producing a cationic or amphoteric polymer according to claim 1, wherein the hydroxycarboxylic acid has 3 to 6 carbon atoms.   The method for producing a cationic or amphoteric polymer according to claim 1, wherein the hydroxycarboxylic acid is any one of citric acid, malic acid, and tartaric acid. The cationic or amphoteric of claim 1, wherein the cationic monomer is at least one selected from a tertiary salt or quaternary salt of dialkylaminoalkyl (meth) acrylate or dialkylaminoalkyl (meth) acrylamide. A method for producing a high molecular weight polymer.   The method for producing a cationic or amphoteric polymer according to claim 1, wherein the polymerization is initiated by thermal initiation, redox initiation or photoinitiation.   The method for producing a cationic or amphoteric polymer according to claim 2, wherein the pH of the aqueous solution of the monomer mixture is 2.0 to 4.5.   The sludge dehydrating agent containing the high molecular polymer obtained by the manufacturing method of Claim 1.   A paper production yield improver comprising a polymer obtained by the production method according to claim 1.