JP2012224680A - (meta)acrylic acid copolymer, method of producing the same, and application therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a (meta)acrylate copolymer having sufficient gel resistance.SOLUTION: The (meta)acrylic acid copolymer includes, based on 100 mol% of structure derived from total monomer, as essential structural units, a structural unit (a) derived from a monomer expressed by General Formula (1), of 5 mol% or more to 25 mol% or less, a structural unit (b) derived from (meta)acrylic acid (salt thereof) of 50 mol% or more to 88 mol% or less, and a structural unit (c) derived from maleic acid (salt thereof) of 7 mol% or more to 25 mol% or less, and has a weight-averaged molecular weight of 1,000-30,000. In the General Formula (1), Rrepresents hydrogen atom or methyl group, and X and Y each independently represent hydroxyl group or sulfonic acid (salt thereof) group, wherein at least one of X and Y represents sulfonic acid (salt thereof) group.

Description

The present invention relates to a (meth) acrylic acid copolymer suitably used for a scale inhibitor or the like and a method for producing the same.

Conventionally, among water-soluble polymers such as (meth) acrylic acid-based polymers, those having a low molecular weight are suitably used for scale inhibitors and the like by utilizing their excellent chelating ability and dispersibility. . However, scale inhibitors are used in highly concentrated cooling water systems to conserve resources and save water, are used in water systems with high hardness for reasons such as water quality degradation, or have high salt concentrations such as seawater. Although it may be used in an aqueous system, in such a case, there is a problem that the polymer gels and precipitates, and the scale preventing ability is remarkably lowered.

  In Patent Document 1, the structural unit (a) derived from the (meth) acrylic acid monomer (A) represented by the following general formula (1) and the (meth) acrylic acid monomer (A) are copolymerized. A copolymer having a structural unit (b) derived from a possible monoethylenically unsaturated monomer (B), and at least one of the ends of the main chain, a sulfonic acid group (provided that the sulfonic acid group is ammonium A (meth) acrylic acid copolymer having a salt, an alkali metal salt, or a salt of an organic amine group, wherein the structural unit (b) has the following general formula: It contains at least the structural unit (b1) derived from the (meth) allyl ether monomer (B1) represented by (2), and the mutual proportion of the structural unit (a) and the structural unit (b1) Unit (a) 70-95 mol%, said structural unit (b1) 5-30 A le%, gelation resistance degree of gelation resistance test in an aqueous system containing calcium ions is 100 to 1500 (meth) acrylic acid copolymer is disclosed.

(In the formula, R ¹ represents a hydrogen atom or a methyl group, and X represents a hydrogen atom, a metal atom, an ammonium group, or an organic amine group.)

(Wherein R ² represents a hydrogen atom or a methyl group, and Y and Z each independently represent a hydroxyl group or a sulfonic acid group (provided that the monovalent metal salt, divalent metal salt, ammonium salt, or organic amine group) It may be a salt.))
In Patent Document 1, the copolymer is a synergistic effect of a sulfonic acid group in a side chain, which is a structural unit derived from the (meth) allyl ether monomer, and a sulfonic acid group introduced at the end of the main chain. Thus, it is disclosed that the gel resistance performance is remarkably improved.

  However, the above-mentioned copolymer has room for improving the dispersibility of calcium carbonate in order to suppress the generation and growth of scale in order to meet the demands of more demanding customers as a water treatment agent, for example.

JP 2002-3536 A

Thus, although various polymers have been reported in the past, the present situation is that they are not sufficiently meeting the requirements for water-based applications such as water treatment. Specifically, in water treatment applications, at high hardness, in addition to the ability to suppress gelation and precipitation (gel resistance), the ability to disperse calcium carbonate to suppress the formation and growth of scale (carbonic acid) There is a strong demand for calcium dispersibility.
Accordingly, the present invention provides a copolymer having improved gel resistance and high dispersibility of calcium carbonate when used in the above-mentioned aqueous system, and a method for producing the same. Objective.

As a result of intensive studies on various polymers / copolymers to achieve the above object, the present inventors have found that a specific (meth) acrylic acid-based copolymer has excellent gel resistance and calcium carbonate. It was found that it has a dispersibility of Based on the above findings, the present invention has been completed.
That is, the copolymer of the present invention has a structure derived from a monomer represented by the following general formula (1) of 5 mol% to 25 mol% with respect to 100 mol% of the structure derived from all monomers. Unit (a), 50 to 88 mol% of (meth) acrylic acid (salt) derived structural unit (b), 7 to 25 mol% of maleic acid (salt) derived structural unit (c ) As an essential structural unit, and is a (meth) acrylic acid copolymer having a weight average molecular weight of 1000 to 30000.

In general formula (1), R ₂ represents a hydrogen atom or a methyl group, and X and Y each independently represent a hydroxyl group or a sulfonic acid (salt) group (provided that at least one of X and Y is sulfonic acid) (Salt) group).

Since the copolymer of the present invention exhibits excellent gel resistance and calcium carbonate dispersibility, it can be suitably used for water treatment agents (particularly scale inhibitors).

Hereinafter, the present invention will be described in detail.

[(Meth) acrylic acid copolymer (also referred to as a copolymer of the present invention)]
The copolymer of the present invention essentially has a specific proportion of the structural unit (a) derived from the monomer represented by the following general formula (1).

In general formula (1), R ₂ represents a hydrogen atom or a methyl group, and X and Y each independently represent a hydroxyl group or a sulfonic acid (salt) group (provided that at least one of X and Y is sulfonic acid) (Salt) group).
The sulfonic acid (salt) refers to sulfonic acid and sulfonate.
The salt in the sulfonate is a metal salt, an ammonium salt, or an organic amine salt. Specifically, alkali metal salts such as sodium salt, lithium salt and potassium salt; alkaline earth metal salts such as magnesium salt and calcium salt; transition metal salts such as iron salt; monoethanolamine salt, diethanolamine salt, Alkanolamine salts such as ethanolamine salts; alkylamine salts such as monoethylamine salts, diethylamine salts, and triethylamine salts; salts of organic amines such as polyamines such as ethylenediamine salts and triethylenediamine salts; Of these, sodium salts and potassium salts are particularly preferable.

  The structural unit (a) derived from the monomer represented by the general formula (1) is specifically represented by the following general formula (2).

In general formula (2), R ₂ represents a hydrogen atom or a methyl group, and X and Y each independently represent a hydroxyl group or a sulfonic acid (salt) group (provided that at least one of X and Y is sulfonic acid) (Salt) group).
When the copolymer of the present invention has “structural unit (a) derived from the monomer represented by the general formula (1)”, the finally obtained polymer has the general formula (2). Is included.
When the copolymer of the present invention has a predetermined amount of the structural unit (a) derived from the monomer represented by the general formula (1), the gel resistance is remarkably improved. Since the structural unit (a) does not contain an ester group or an amide group, it is highly stable even under conditions in the production process of the polymer and in the production process of various products containing the polymer. It is possible to improve.

  In the copolymer of the present invention, the structural unit (a) derived from the monomer represented by the general formula (1) is 5 mol% or more and 25 mol% with respect to 100 mol% of the structure derived from all monomers. It has the following ratio. In the present invention, the structure derived from all monomers is the structural unit (a) derived from the monomer represented by the general formula (1), or the structure derived from (meth) acrylic acid (salt) (b ), A structural unit (c) derived from maleic acid (salt), and a structural unit (e) derived from other monomers. When the structural unit (a) represented by the general formula (1) is within the above range, the gel resistance of the copolymer is excellent. When the structural unit (a) represented by the general formula (1) is less than the above range, the gel resistance tends to be lowered. When the structural unit (a) represented by the general formula (1) is larger than the above range, the ability to suppress the scale tends to decrease due to a decrease in the adsorption power to calcium carbonate. In addition, the copolymer of the present invention contains a structural unit (b) derived from (meth) acrylic acid (salt) and a structural unit (c) derived from maleic acid (salt) in the above range, whereby a carboxyl group Therefore, a good dispersibility of calcium carbonate is also exhibited. The proportion of the structural unit (a) with respect to 100 mol% of the structure derived from all monomers is preferably 5 mol% or more and 20 mol% or less, more preferably 5 mol% or more and 15 mol% or less, Preferably they are 6 mol% or more and 10 mol% or less.

  The copolymer of the present invention has a molar fraction Yb of the structural unit (b) and a molar fraction Yc of the structural unit (c) when the molar fraction Y of the structural units derived from all monomers is 1. Is preferably represented by the following general formula.

When Yb and Yc satisfy the above formula, the content of the carboxylic acid (salt) group of the copolymer becomes appropriate, and the ability to suppress the scale of the copolymer tends to be improved.

<Structural unit derived from (meth) acrylic acid (salt)>
The copolymer of the present invention essentially has a specific proportion of structural units (b) derived from (meth) acrylic acid (salt) (also referred to as monomer (B)).
(Meth) acrylic acid (salt) refers to acrylic acid, acrylate, methacrylic acid, and methacrylate. The salt in the (meth) acrylate is the same as the salt in the sulfonate. Similarly, the (meth) acrylic acid salt is particularly preferably a sodium salt or potassium salt of (meth) acrylic acid.

The structural unit (b) derived from (meth) acrylic acid (salt) is a structure in which the polymerizable unsaturated double bond of (meth) acrylic acid (salt) is a single bond, for example (meth) When the acrylic acid (salt) is sodium acrylate, the structural unit (b) can be represented by —CH ₂ —CH (COONa) —. When the copolymer of the present invention has “structural unit (b) derived from (meth) acrylic acid (salt)”, the finally obtained polymer is a polymer of (meth) acrylic acid (salt). It is meant to include structural units in which sex unsaturated double bonds are replaced with single bonds.

In the copolymer of the present invention, the structural unit (b) derived from (meth) acrylic acid (salt) is in a proportion of 50 mol% to 88 mol% with respect to 100 mol% of the structure derived from all monomers. Have. In the present invention, the structure derived from all monomers is derived from the structural unit (a) derived from the monomer represented by the general formula (1) and (meth) acrylic acid (salt) as described above. The structural unit (b) derived from maleic acid (salt), and the structural unit (e) derived from other monomers.
When the structural unit (b) derived from (meth) acrylic acid (salt) is within the above range, the gel resistance and chelating ability of the copolymer and the dispersibility of calcium carbonate tend to be excellent. . The ratio of the structural unit (b) to 100 mol% of the structure derived from all monomers is preferably 60 mol% or more and 88 mol% or less, more preferably 70 mol% or more and 88 mol% or less, and still more preferably. It is 78 mol% or more and 86 mol% or less.

<Structural unit derived from maleic acid (salt)>
The copolymer of the present invention essentially has a specific proportion of structural units (c) derived from maleic acid (salt) (also referred to as monomer (C)).
Maleic acid (salt) refers to maleic acid and maleic acid salt (monosalt of maleic acid, disalt of maleic acid). The salt in the maleate is the same as the salt in the sulfonate. Similarly, the maleate is particularly preferably a sodium salt or potassium salt of maleate.

  The structural unit (c) derived from maleic acid (salt) is a structure in which the polymerizable unsaturated double bond of maleic acid (salt) is a single bond. For example, maleic acid (salt) is maleic acid 1 In the case of sodium, the structural unit (c) can be represented by —CH (COOH) —CH (COONa) —. The copolymer of the present invention has “structural unit (c) derived from maleic acid (salt)” means that the finally obtained polymer is a polymerizable unsaturated double bond of maleic acid (salt). It is meant to include structural units in which the bond is replaced with a single bond.

The copolymer of the present invention has a structural unit (c) derived from maleic acid (salt) at a ratio of 7 mol% to 25 mol% with respect to 100 mol% of the structure derived from all monomers. In the present invention, the structure derived from all monomers is derived from the structural unit (a) derived from the monomer represented by the general formula (1) and (meth) acrylic acid (salt) as described above. The structural unit (b) derived from maleic acid (salt), and the structural unit (e) derived from other monomers.
If the structural unit (c) derived from maleic acid (salt) is within the above range, the gel resistance and chelating ability of the copolymer and the dispersibility of calcium carbonate are excellent. The ratio of the structural unit (c) to 100 mol% of the structure derived from all monomers is preferably 7 mol% or more and 20 mol% or less, more preferably 7 mol% or more and 15 mol% or less, and further preferably It is 8 mol% or more and 12 mol% or less. If the structural unit (c) derived from maleic acid (salt) is lower than the above range, the ability to suppress the scale tends to decrease due to a decrease in the adsorptive power of the copolymer to calcium carbonate or the like. When the structural unit (c) derived from maleic acid (salt) is higher than the above range, the scale-inhibiting ability tends to decrease due to a decrease in gel resistance of the copolymer.

<Structural units derived from other monomers>
The copolymer of the present invention comprises a structural unit (a) represented by the general formula (1), a structural unit (b) derived from (meth) acrylic acid (salt), and a structural unit derived from maleic acid (salt). In addition to (c), it may have a structural unit (e) derived from another monomer (also referred to as monomer (E)).
The other monomer is preferably a monomer copolymerizable with any of the monomers (A) to (C).
The other monomer may be a salt, and the salt in that case is the same as the salt in the sulfonate. Similarly, when it is a salt, sodium salt and potassium salt are particularly preferable.

The structural unit (e) derived from the other monomer is a structure in which the polymerizable unsaturated double bond of the other monomer is a single bond. For example, the monomer (E) is methyl acrylate. In this case, the structural unit (e) derived from another monomer can be represented by —CH ₂ —CH (COOCH ₃ ) —.
The copolymer of the present invention has “structural unit (e) derived from other monomer” means that the finally obtained polymer has an unsaturated double bond of another monomer as a single unit. Means including structural units replaced by bonds.

  The copolymer of the present invention has structural units (e) derived from other monomers at a ratio of 0 mol% to 8 mol% with respect to 100 mol% of the structure derived from all monomers. May be. In the present invention, the structure derived from all monomers is as described above. When the structural unit (e) derived from the other monomer exceeds the above range, it is not preferable because both gel resistance and chelating ability cannot be achieved or the scale prevention ability of calcium carbonate tends to decrease. . The proportion of the structural unit (e) with respect to 100 mol% of the structure derived from all monomers is preferably 0 mol% or more and 8 mol% or less, more preferably 0 mol% or more and 5 mol% or less, particularly preferably. It is 0 mol% or more and 3 mol% or less.

The other monomer (E) is not particularly limited and is appropriately selected depending on the desired effect. Specifically, unsaturated monocarboxylic acids other than the monomer (B) and salts thereof such as crotonic acid, α-hydroxyacrylic acid, α-hydroxymethylacrylic acid and derivatives thereof; itaconic acid, fumaric acid Unsaturated dicarboxylic acids other than the above monomer (C) such as acid, 2-methyleneglutaric acid and their salts; vinylsulfonic acid, 1-acrylamide-1-propanesulfonic acid, 2-acrylamido-2-propanesulfonic acid 2- (meth) acrylamide-2-methyl-1-propanesulfonic acid, (meth) allyloxybenzenesulfonic acid, styrenesulfonic acid, sulfoethyl (meth) acrylate, sulfopropyl (meth) acrylate, (meth) allylsulfonic acid Sulfonic acid group-containing monomers other than the monomer (A) such as isoprenesulfonic acid and salts thereof Monomer: (meth) allyl alcohol, monomer obtained by adding alkylene oxide to isoprenol, polyalkylene glycol chain-containing monomer such as (meth) acrylic acid ester of alkoxyalkylene glycol; N-vinylpyrrolidone, N-vinylformamide N-vinyl monomers such as N-vinylacetamide, N-vinyl-N-methylformamide, N-vinyl-N-methylacetamide, N-vinyloxazolidone; (meth) acrylamide, N, N-dimethylacrylamide, N Amide monomers such as isopropyl acrylamide; Allyl ether monomers such as (meth) allyl alcohol; Isoprene monomers such as isoprenol; Butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dodecyl (Meta) Acrelay (Meth) acrylic acid alkyl ester monomers such as hydroxyethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, 2-hydroxybutyl (meth) ) Acrylate, 4-hydroxybutyl (meth) acrylate, α-hydroxymethylethyl (meth) acrylate, hydroxypentyl (meth) acrylate, hydroxyneopentyl (meth) acrylate, hydroxyhexyl (meth) acrylate and other (meth) acrylic acid Hydroxyalkyl monomers; vinyl aryl monomers such as styrene, indene and vinylaniline, isobutylene and vinyl acetate; heterocyclic aromatic hydrocarbon groups such as vinylpyridine and vinylimidazole and amino Vinyl aromatic amino group-containing monomers having a group, and quaternized products and salts thereof; aminoalkyl (meth) acrylates such as dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, dimethylaminopropyl acrylate, and aminoethyl methacrylate; These quaternized compounds and salts; allylamines such as diallylamine and diallyldimethylamine and their quaternized compounds and salts; (i) epoxy ring of (meth) allyl glycidyl ether, isoprenyl glycidyl ether, vinyl glycidyl ether ( ii) Dialkylamines such as dimethylamine, diethylamine, diisopropylamine and di-n-butylamine, alkanolamines such as diethanolamine and diisopropanolamine, amino acids such as iminodiacetic acid and glycine Carboxylic acids, morpholine, quaternary compound or salt amine of monomers and obtained by reacting such cyclic amines pyrrole etc., etc., can be mentioned.
Moreover, the said other monomer (E) may be used individually by 1 type, or may be used with the form of a 2 or more types of mixture.

<Other structural units>
The copolymer of the present invention preferably has a sulfonic acid (salt) group at the end of at least one main chain of the polymer molecule. Having a sulfonic acid (salt) group at at least one main chain terminal means having one or two or more main chain terminals having a sulfonic acid (salt) group, for example, a linear polymer molecule. 2 may have a sulfonic acid (salt) group at the terminal end of the main chain, and may have a sulfonic acid (salt) group at three or more main chain terminals as long as it is a branched polymer molecule. . The gel resistance tends to be further improved by having a sulfonic acid (salt) group at at least one main chain terminal. The ratio (mass%) of the sulfonic acid group at the end of the main chain of the polymer molecule with respect to 100 mass% of the total mass of the copolymer is more preferably 0.01 mass% or more and 5 mass% or less. In addition, when calculating the mass% of the sulfonic acid group at the molecular terminal with respect to the total mass of the copolymer, it is calculated in terms of acid, and if applicable, it is calculated in terms of amine.

As a method for forming a structural unit containing a sulfonic acid group at the molecular end of the copolymer, a monomer containing monomers (A), (B), (C), etc., is added to bisulfite (salts) ( A method of polymerizing in the presence of sulfurous acid, bisulfite, dithionic acid, metabisulfite, and salts thereof is preferably used. In the above case, the bisulfite (salt) acts as a chain transfer agent or the like, whereby the sulfonic acid group is incorporated into the polymer molecule.
The sulfonic acid group at the molecular end of the copolymer can be measured, for example, by ¹ HNMR.

<Molecular weight of (meth) acrylic acid copolymer>
The weight average molecular weight Mw of the (meth) acrylic acid polymer according to the present invention is 1000 to 30000, preferably 5000 to 25000, and more preferably 10,000 to 20000. If the weight average molecular weight is within this range, the (meth) acrylic acid polymer tends to improve the chelating ability. Therefore, it can be used more suitably for applications such as scale inhibitors. When the weight average molecular weight of the (meth) acrylic acid polymer is less than 1000, the ability to suppress scale tends to decrease as the adsorptive power to calcium carbonate decreases. Moreover, when the weight average molecular weight of a (meth) acrylic acid type polymer exceeds 30000, the coagulation effect | action with respect to a calcium carbonate comes to work, and it exists in the tendency for a scale suppression ability to fall.

  The dispersity (Mw / Mn) of the (meth) acrylic acid polymer according to the present invention is 1.5 to 10.0, preferably 1.8 to 8.0, more preferably 2.0 to 6. .0. When the degree of dispersion is less than 1.5, the synthesis becomes complicated. On the other hand, when the dispersity exceeds 10.0, components effective in performance are reduced, and there is a risk of performance degradation.

  In addition, the said weight average molecular weight (Mw) and number average molecular weight (Mn) are measured by the method described in the below-mentioned Example.

<Gel resistance of copolymer>
In the gel resistance test of the present invention, pure water, boric acid-sodium borate pH buffer solution, aqueous copolymer solution, and calcium chloride solution are sequentially added to a 500 mL conical beaker, and the copolymer is added at a solid content concentration of 100 mg. / L, calcium test solution 200mgCaCO ₃ / L, pH 8.5 each prepared, sealed with polyvinylidene chloride film, left in a constant temperature bath at 90 ° C for 1 hour It is to evaluate sex. When precipitation occurs, it can be said that the gel resistance is extremely low. In the case where precipitation did not occur, the mixture was stirred and then placed in a quartz cell having an optical path length of 5 cm, and the absorbance (a) at a UV wavelength of 380 nm was measured. As a blank, a test solution obtained by removing the calcium chloride solution from the above test solution was prepared, the same operation was performed to measure the absorbance (b), and the degree of gelation was determined from the following formula.
Gelation degree = (a) − (b)
It can be said that the smaller the numerical value of the degree of gelation, the higher the gel resistance.
The copolymer of the present invention preferably has a gelation degree of less than 0.100. By being the said range, it can use preferably as additives, such as a water treatment agent. More preferably, it is less than 0.050.

<Calcium scavenging ability of copolymer>
The (meth) acrylic acid copolymer of the present invention preferably exhibits a good calcium capturing ability.
The calcium ion scavenging ability (mgCaCO ₃ / g) is defined as the number of mg obtained by converting the calcium ion captured by 1 g of the water-soluble polymer into the amount of calcium carbonate, and how much the water-soluble polymer has the calcium ion in the water. It is an index indicating whether to capture. When a water-soluble polymer with high calcium ion scavenging ability is used, when added to a water treatment agent, the calcium ions in the water are trapped or adsorbed to the crystal nuclei that form the scale, thereby generating or growing the scale. It becomes possible to suppress.
In the present invention, the calcium ion scavenging ability is a value measured by the method and conditions described in Examples described later.
The copolymer of the present invention preferably has a calcium ion scavenging ability of 200 mg CaCO ₃ / g or more. By being the said range, it can use preferably as additives, such as a water treatment agent. More preferably 220mgCaCO ₃ / g or more, further preferably 240mgCaCO ₃ / g or more. There is no particular limitation on the upper limit of the calcium ion trapping ability, is, for example 500mgCaCO ₃ / g or less.

<Dispersibility of copolymer calcium carbonate>
The (meth) acrylic acid copolymer of the present invention preferably exhibits good calcium carbonate dispersibility. By expressing good dispersibility of calcium carbonate, it becomes possible to suppress the formation and growth of calcium carbonate scale.
In the present invention, the dispersibility of calcium carbonate is a value measured by the method and conditions described in Examples described later.

[Method for producing (meth) acrylic acid copolymer]
<Monomer composition>
The production method of the copolymer of the present invention is such that all monomers (total of monomers (A), (B), (C), and (E)) are used in an amount of 5 mol% or more with respect to 100 mol%. 25 mol% or less of the monomer represented by the general formula (1) (monomer (A)) and the amount of all monomers used is 100 mol% to 50 mol% to 88 mol% ( It is preferable to copolymerize with (meth) acrylic acid (salt) (monomer (B)) and 7 to 25 mol% maleic acid (salt) (monomer (C)) as essential components.
In the method for producing a copolymer of the present invention, the monomer (A), monomer (B) and monomer (C) may be used alone or in combination of two or more. I do not care. In the method for producing a copolymer of the present invention, in addition to the monomer (A), the monomer (B), and the monomer (C), the other monomer (E) is added as necessary. Further, it may be copolymerized.
The proportion of the monomer (E) used in the method for producing a copolymer of the present invention is 100 mol% of all monomers (total of monomers (A), (B), (C), and (E)). On the other hand, it is preferable to set it to 0 mol% or more and 8 mol% or less. Also when using the monomer (E) which is the said arbitrary component, 1 type may be used or 2 types may be used.
The method for producing a copolymer of the present invention is such that each of the monomers used in producing the copolymer is from the viewpoint that the obtained copolymer exhibits more preferable gel resistance and calcium carbonate scale-preventing ability. The composition ratio of the monomer (A) is 5 mol% or more and 20 mol% or less, the monomer (B) is 60 mol% or more and 88 mol% or less, with respect to 100 mol% of all monomers. More preferably, the monomer (C) is 7 mol% or more and 20 mol% or less, and the monomer (E) is 0 to 8 mol%. More preferably, the monomer (A) is 5 mol% or more and 15 mol% or less, the monomer (B) is 70 mol% or more and 88 mol% or less, and the monomer (C) is 7 mol% or more. 15 mol% or less, the monomer (E) is 0 to 5 mol%, and particularly preferably, the monomer (A) is 6 mol% or more and 10 mol% or less, and the monomer (B) is 78 mol% or more and 86 mol% or less, the monomer (C) is 8 mol% or more and 12 mol% or less, and the monomer (E) is 0 to 3 mol%. The total amount of the monomers (A), (B), (C) and (E) is 100 mol%.

<Initiator>
In the method for producing a copolymer of the present invention, the monomers (A), (B), (C), and (E) (sometimes referred to as monomer composition) are present in the presence of a polymerization initiator. Polymerization is preferred.
As the initiator, known ones can be used, for example, hydrogen peroxide; persulfates such as sodium persulfate, potassium persulfate, ammonium persulfate; dimethyl 2,2′-azobis (2-methylpro Pionate), 2,2′-azobis (isobutyronitrile), 2,2′-azobis (2-methylbutyronitrile), 2,2′-azobis (2,4-dimethylvaleronitrile), 2, 2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2′-azobis (isobutyric acid) dimethyl, 4,4′-azobis (4-cyanovaleric acid), 2,2′-azobis (2-Methylpropionamidine) dihydrochloride, 2,2′-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] n hydrate, 2,2′-azobis [2- (2- Imidazoline- 2-yl) propane] dihydrochloride, 2,2′-azobis [2- (2-imidazolin-2-yl) propane] disulfate dihydrate, 1,1′-azobis (cyclohexane-1-carbohydrate) Suitable are azo compounds such as nitrile); organic peroxides such as benzoyl peroxide, lauroyl peroxide, peracetic acid, di-t-butyl peroxide, cumene hydroperoxide, and the like. Among these polymerization initiators, since the gel resistance of the resulting polymer tends to be improved, it is preferable to use a persulfate as described later.
The amount of the initiator used is not particularly limited as long as it is an amount capable of initiating the copolymerization of the monomer (A), (B), (C) and, if necessary, another monomer (E). 15 g or less with respect to 1 mol of all monomer components consisting of monomers (A), (B), (C) and, if necessary, other monomers (E), unless otherwise specified in More preferably, it is 1 to 12 g.

<Chain transfer agent>
In the method for producing a copolymer of the present invention, a chain transfer agent may be used as a molecular weight regulator of the polymer as long as it does not adversely affect polymerization. Specific examples of the chain transfer agent include mercaptoethanol, thioglycerol, thioglycolic acid, 2-mercaptopropion, 3-mercaptopropion, thiomalic acid, octyl thioglycolate, octyl 3-mercaptopropionate, 2- Thiol chain transfer agents such as mercaptoethanesulfonic acid, n-dodecyl mercaptan, octyl mercaptan, butylthioglycolate; halides such as carbon tetrachloride, methylene chloride, bromoform, bromotrichloroethane; Secondary alcohol; phosphorous acid, hypophosphorous acid, and salts thereof (sodium hypophosphite, potassium hypophosphite, etc.), sulfurous acid, bisulfite, dithionite, metabisulfite, and salts thereof ( Sodium bisulfite, potassium bisulfite, sub Sodium dithionite, potassium dithionite, sodium metabisulfite, metabisulfite potassium, etc.) and the like, and the like lower oxides and salts thereof. The chain transfer agent may be used alone or in the form of a mixture of two or more.
The use of a chain transfer agent has the advantage that the copolymer to be produced can be prevented from having a higher molecular weight than necessary, and a low molecular weight copolymer can be produced efficiently. Among these, in the copolymerization reaction according to the present invention, it is preferable to use bisulfites as described above. Thereby, it becomes possible to introduce a sulfonic acid group quantitatively to the end of the main chain of the copolymer to be obtained, and it is possible to improve the gel resistance. Further, it is preferable to use bisulfites as the chain transfer agent because the color tone of the copolymer (composition) can be improved.
In the production method of the present invention, the addition amount of the chain transfer agent should be such that the monomers (A), (B), (C) and, if necessary, other monomers (E) are polymerized well. Unless otherwise specified, all monomer components preferably consisting of monomers (A), (B), (C) and, if necessary, other monomers (E) It is 1-20g with respect to 1 mol, More preferably, it is 2-15g.

<Preferable combination of initiator and chain transfer agent (also referred to as initiator system)>
In the method for producing a copolymer of the present invention, it is preferable to use a combination of one or more persulfates and bisulfites as an initiator system. As a result, a sulfonic acid group is introduced into the terminal or side chain to obtain a low molecular weight water-soluble polymer that is excellent in gel resistance in addition to dispersibility and chelate ability, and effectively exhibits the effects of the present invention. be able to. By adding bisulfites to the initiator system in addition to the persulfate, it is possible to suppress the resulting polymer from having a higher molecular weight than necessary, and to efficiently produce a low molecular weight polymer.

Specific examples of the persulfate include sodium persulfate, potassium persulfate, and ammonium persulfate.
In the present invention, bisulfites are as described above, and specific examples include sodium bisulfite, potassium bisulfite, and ammonium bisulfite.
When the above-mentioned persulfate and bisulfite are used in combination, the addition ratio of 0.1 to 5 parts by weight, preferably 0.2 to 3 parts by weight of bisulfite is 1 part by weight of persulfate. Preferably it exists in the range of 0.2-2 mass parts. When the amount of bisulfite is less than 0.1 part by mass with respect to 1 part by mass of persulfate, the effect of bisulfite tends to decrease. Therefore, the introduction amount of the sulfonic acid group at the terminal of the polymer is decreased, and the effect of improving the gel resistance of the copolymer tends to be reduced. Further, the weight average molecular weight of the (meth) acrylic acid copolymer tends to be high. On the other hand, when the amount of bisulfite exceeds 5 parts by mass with respect to 1 part by mass of persulfate, the bisulfite is excessively supplied in the polymerization reaction system in such a state that the effect of bisulfite is not obtained as much as the addition ratio. Tend to be used (wasted). For this reason, excess bisulfites are decomposed in the polymerization reaction system, and a large amount of sulfurous acid gas is generated. In addition, many impurities in the (meth) acrylic acid copolymer are generated, and the performance of the resulting (meth) acrylic copolymer tends to be lowered. In addition, impurities tend to precipitate during holding at a low temperature.

  When using the above-mentioned persulfate and bisulfite, the total amount of persulfate and bisulfite is 2 to 20 g, preferably 2 to 15 g, more preferably, per mole of monomer. 3 to 10 g, more preferably 4 to 8 g. When the addition amount of the persulfate and bisulfite is less than 2 g, the molecular weight of the resulting polymer tends to increase. In addition, the sulfonic acid group introduced into the terminal of the resulting (meth) acrylic acid copolymer tends to decrease. On the other hand, when the addition amount exceeds 20 g, the effects of persulfate and bisulfite cannot be obtained as the addition amount increases, and conversely, the purity of the resulting (meth) acrylic acid copolymer decreases. There is a tendency.

  The persulfate may be added in the form of a persulfate solution (preferably an aqueous solution) dissolved in a solvent described later, preferably water. The concentration when used as the persulfate solution (preferably an aqueous solution) is 1 to 35% by mass, preferably 5 to 35% by mass, and more preferably 10 to 30% by mass. Here, when the concentration of the persulfate solution is less than 1% by mass, the concentration of the product decreases, and transportation and storage become complicated. On the other hand, when the concentration of the persulfate solution exceeds 35% by mass, handling becomes difficult.

  The bisulfites may be added in the form of a bisulfite solution (preferably an aqueous solution) after being dissolved in a solvent described later, preferably water. The concentration when used as the bisulfite solution (preferably an aqueous solution) is 10 to 42% by mass, preferably 20 to 42% by mass, and more preferably 32 to 42% by mass. Here, when the concentration of the bisulfite solution is less than 10% by mass, the concentration of the product is lowered, and transportation and storage become complicated. On the other hand, when the concentration of the bisulfite solution exceeds 42% by mass, handling becomes difficult.

<Other additives>
In the method for producing a copolymer of the present invention, as an additive other than an initiator and a chain transfer agent that can be used in a polymerization reaction system when the monomer is polymerized in an aqueous solution, the action of the present invention An appropriate amount of an appropriate additive can be added within a range that does not affect the effect. For example, heavy metal concentration adjusting agents, pH adjusting agents and the like are used.
The heavy metal concentration adjusting agent is not particularly limited, and a polyvalent metal compound or a simple substance can be used. Specifically, vanadium oxytrichloride, vanadium trichloride, vanadyl oxalate, vanadyl sulfate, vanadic anhydride, ammonium metavanadate, ammonium sulfate hypovanadas [(NH ₄ ) 2SO ₄ · VSO ₄ · 6H ₂ O], ammonium sulfate Vanadas [(NH ₄ ) V (SO ₄ ) ₂ · 12H ₂ O], copper (II) acetate, copper (II), copper bromide (II), copper (II) acetyl acetate, cupric ammonium chloride, Copper ammonium chloride, copper carbonate, copper (II) chloride, copper citrate (II), copper formate (II), copper hydroxide (II), copper nitrate, copper naphthenate, copper oleate (II), copper maleate , Copper phosphate, copper (II) sulfate, cuprous chloride, copper (I) cyanide, copper iodide, copper (I) oxide, copper thiocyanate, iron acetyl acetonate, iron citrate ammo Ni, Ferric ammonium oxalate, Ammonium iron sulfate, Ferric ammonium sulfate, Iron citrate, Iron fumarate, Iron maleate, Ferrous lactate, Ferric nitrate, Iron pentacarbonyl, Ferric phosphate Water-soluble polyvalent metal salts such as ferric pyrophosphate; polyvalent metal oxides such as vanadium pentoxide, copper (II) oxide, ferrous oxide, ferric oxide; iron (III) sulfide, iron sulfide (II), polyvalent metal sulfides such as copper sulfide; copper powder and iron powder.
In the method for producing a copolymer of the present invention, when the heavy metal concentration adjusting agent is used, for example, the resulting (meth) acrylic acid copolymer composition has a heavy metal ion concentration of 0.05 to 10 ppm. May be used for

<Polymerization solvent>
In the method for producing the copolymer of the present invention, the above monomers are usually polymerized in a solvent. In this case, the solvent used in the polymerization reaction system is water, alcohol, glycol, glycerin, polyethylene glycol. Aqueous solvents such as the like are preferred, and water is particularly preferred. These may be used alone or in combination of two or more. Moreover, in order to improve the solubility of the monomer in the solvent, an organic solvent may be appropriately added as long as it does not adversely affect the polymerization of each monomer.
Specifically, the organic solvent is selected from one or more types selected from lower alcohols such as methanol and ethanol; amides such as dimethylformaldehyde; ethers such as diethyl ether and dioxane; sell.
The amount of the solvent used is in the range of 40 to 200 mass%, preferably 45 to 180 mass%, more preferably 50 to 150 mass%, based on the total amount of monomers. When the amount of the solvent used is less than 10% by mass, the molecular weight becomes high. On the other hand, when the usage-amount of this solvent exceeds 200 mass%, the density | concentration of the manufactured (meth) acrylic-acid type copolymer will become low, and solvent removal will be needed depending on the case. It should be noted that most or all of the solvent may be charged into the reaction vessel at the initial stage of polymerization. For example, a part of the solvent may be added (dropped) appropriately into the reaction system alone during the polymerization. The monomer component, the initiator component, and other additives may be appropriately added (dropped) into the reaction system during the polymerization together with these components in the form of being previously dissolved in a solvent.

<Polymerization temperature>
The polymerization temperature in the polymerization of the monomer is not particularly limited. Since a polymer can be produced efficiently, the polymerization temperature is preferably 50 ° C. or higher, and more preferably 70 ° C. or higher. The polymerization temperature is preferably 99 ° C. or lower, and more preferably 95 ° C. or lower. When the polymerization temperature is lower than 25 ° C., the molecular weight increases and impurities increase. In addition, since the polymerization time takes too long, productivity is lowered. On the other hand, when the polymerization temperature is 99 ° C. or lower, it is preferable that bisulfite can be prevented from being decomposed and generating a large amount of sulfurous acid gas when bisulfite is used as an initiator system. The polymerization temperature here refers to the temperature of the reaction solution in the reaction system.

  In particular, in the case of the method of starting polymerization from room temperature (room temperature starting method), for example, when polymerization is performed in 180 minutes per batch (180 minute formulation), within 70 minutes, preferably 0 to 50 It is made to reach the set temperature (within the range of the polymerization temperature defined above, preferably 70 to 90 ° C., more preferably about 80 to 90 ° C.) in minutes, more preferably 0 to 30 minutes. Thereafter, it is desirable to maintain the set temperature until the polymerization is completed. When the temperature rise time is out of the above range, the resulting (meth) acrylic acid copolymer may have a high molecular weight. In addition, although the example of the polymerization time is shown as 180 minutes, if the prescription of the polymerization time is different, referring to the example, the temperature increase time is set so that the ratio of the temperature increase time to the polymerization time is the same. Is desirable.

<Reaction system pressure, reaction atmosphere>
When polymerizing the monomer, the pressure in the reaction system is not particularly limited. The pressure may be any of normal pressure (atmospheric pressure), reduced pressure, and increased pressure. Preferably, when bisulfite is used as the initiator system, the polymerization is carried out under normal pressure or under pressure in order to prevent the release of sulfurous acid gas during polymerization and to reduce the molecular weight. It is good. In addition, when polymerization is performed under normal pressure (atmospheric pressure), it is not necessary to provide a pressurizing device or a decompressing device, and it is not necessary to use a pressure-resistant reaction vessel or pipe. For this reason, normal pressure (atmospheric pressure) is preferable from the viewpoint of production cost. That is, optimal pressure conditions may be set as appropriate depending on the intended use of the resulting (meth) acrylic acid copolymer.
The atmosphere in the reaction system may be maintained in an air atmosphere, but an inert atmosphere is preferable. For example, it is desirable to replace the inside of the system with an inert gas such as nitrogen before the start of polymerization. Thereby, atmospheric gas (for example, oxygen gas etc.) in the reaction system dissolves in the liquid phase and acts as a polymerization inhibitor. As a result, the initiator (persulfate, etc.) is prevented from being deactivated and reduced, and the molecular weight can be further reduced.

<Neutralization degree during polymerization>
In the production method of the present invention, the polymerization reaction of the monomer is preferably performed under acidic conditions. By carrying out under acidic conditions, the increase in the viscosity of the aqueous solution of the polymerization reaction system can be suppressed, and a low molecular weight (meth) acrylic acid copolymer can be produced satisfactorily. In addition, since the polymerization reaction can proceed under a higher concentration condition than before, the production efficiency can be significantly increased. In particular, by reducing the degree of neutralization during polymerization to 0 to 25 mol%, the effect of reducing the initiator amount can be synergistically increased, and the effect of reducing impurities can be significantly improved. Furthermore, it is desirable to adjust the reaction solution during polymerization so that the pH at 25 ° C. is 1-6. By carrying out the polymerization reaction under such acidic conditions, the polymerization can be carried out at a high concentration and in one stage. Therefore, it is possible to omit the concentration step which was necessary in some cases in the conventional manufacturing method. Therefore, the productivity of the (meth) acrylic acid copolymer is greatly improved, and an increase in production cost can be suppressed.

  Among the above acidic conditions, the pH of the reaction solution during polymerization at 25 ° C. is 1 to 6, preferably 1 to 5, and more preferably 1 to 4. When the pH is less than 1, for example, when bisulfite is used as an initiator system, generation of sulfurous acid gas and corrosion of the apparatus may occur. On the other hand, when the pH exceeds 6, when bisulfites are used as the initiator system, the efficiency of bisulfites decreases and the molecular weight increases.

  Examples of the pH adjuster for adjusting the pH of the reaction solution during the polymerization include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and alkaline earth metal waters such as calcium hydroxide and magnesium hydroxide. Examples thereof include oxides, organic amine salts such as ammonia, monoethanolamine, and triethanolamine. These may be used alone or in combination of two or more. Among these, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide are preferable, and sodium hydroxide is particularly preferable. In the present invention, these may be simply referred to as “pH adjusting agent” or “neutralizing agent”.

  The degree of neutralization during the polymerization is preferably from 0 to 25 mol%, more preferably from 1 to 15 mol%, still more preferably from 2 to 10 mol%. If the degree of neutralization during the polymerization is within such a range, it is possible to perform the copolymerization best, to reduce impurities, and to produce a polymer having good gel resistance. Moreover, the viscosity of the aqueous solution of the polymerization reaction system does not increase, and a low molecular weight polymer can be produced satisfactorily. In addition, since the polymerization reaction can proceed under a higher concentration condition than before, the production efficiency can be significantly increased. On the other hand, when the degree of neutralization during polymerization exceeds 25 mol%, the chain transfer efficiency of bisulfites may decrease and the molecular weight may increase. In addition, as the polymerization proceeds, the viscosity of the aqueous solution in the polymerization reaction system increases significantly. As a result, the molecular weight of the resulting polymer increases more than necessary, and a low molecular weight polymer cannot be obtained. Furthermore, the effect of reducing the degree of neutralization cannot be fully exhibited, and it may be difficult to significantly reduce impurities.

  The neutralization method here is not particularly limited. For example, a salt of (meth) acrylic acid such as sodium (meth) acrylate may be used as a part of the raw material, and an alkali metal hydroxide such as sodium hydroxide is used as a neutralizing agent. You may neutralize during superposition | polymerization and you may use these together. Moreover, the addition form of the neutralizing agent at the time of neutralization may be solid, or may be an aqueous solution dissolved in an appropriate solvent, preferably water. The concentration of the aqueous solution when the aqueous solution is used is 10 to 60% by mass, preferably 20 to 55% by mass, and more preferably 30 to 50% by mass. When the concentration of the aqueous solution is less than 10% by mass, the concentration of the product decreases, and transportation and storage become complicated. On the other hand, when it exceeds 60 mass%, there exists a possibility of precipitation, and since a viscosity also becomes high, liquid feeding becomes complicated.

<Additional conditions of raw materials>
In the polymerization, the monomers (A), (B), (E), the initiator, the chain transfer agent and other additives are preliminarily used in an appropriate solvent (preferably the same kind as the solvent for the liquid to be dropped. Solvent (solvent), monomer solution, initiator solution, chain transfer agent solution and other additive solutions, each of which was charged into the reaction vessel (aqueous) solvent (adjusted to a predetermined temperature if necessary) It is preferable to perform polymerization while continuously dropping over a predetermined dropping time.
Regarding the monomer (C), the residual monomer is decreased and the chelating ability of the resulting polymer is improved. Therefore, a part or all of the monomer (C) is added to the reaction system before the polymerization is started (initial stage). Preparation) is preferred.
Further, a part of the aqueous solvent may be dropped later, separately from the initially charged solvent prepared in advance in a container in the reaction system. However, the production method of the present invention is not limited to these. For example, regarding the dropping method, it may be dropped continuously or may be dropped in several portions intermittently. One or two or more of the monomers may be initially charged in part or in whole (that is, it can be considered that all or part of the monomer is added dropwise at the start of polymerization). Also, the dropping rate (dropping amount) of one or more monomers may be dropped constantly (constant amount) from the start to the end of dropping, or may be dropped over time depending on the polymerization temperature or the like. The dropping speed (dropping amount) may be changed. Moreover, even if it does not dripping all the dripping components similarly, you may shift the start time and the end time for every dripping component, or you may shorten or extend dripping time. Thus, the manufacturing method of this invention can be changed suitably in the range which does not impair the effect of this invention. Moreover, when each component is dripped in the form of a solution, you may heat a dripped solution to the same extent as the polymerization temperature in a reaction system. In this way, when the polymerization temperature is kept constant, temperature variation is small and temperature adjustment is easy.

  When bisulfites are used as the initiator system, the molecular weight at the initial stage of polymerization of bisulfites greatly affects the final molecular weight. For this reason, in order to lower the initial molecular weight, 5 to 20% by mass of bisulfite or a solution thereof is added (dropped) within 60 minutes, preferably within 30 minutes, more preferably within 10 minutes from the start of polymerization. desirable. In particular, as described later, this is effective when the polymerization is started from room temperature.

  In addition, among the dropping components in the polymerization, when bisulfite is used as an initiator system, the bisulfite or the dropping time of the solution thereof is preferably 1 to 30 minutes from the end of dropping of the monomer, preferably Is preferably 1 to 20 minutes, more preferably 1 to 15 minutes. Thereby, the amount of bisulfites after completion | finish of superposition | polymerization can be reduced, and generation | occurrence | production of sulfurous acid gas by this bisulfites and formation of an impurity can be suppressed effectively. For this reason, after the polymerization is completed, impurities formed by dissolving the sulfurous acid gas in the gas phase in the liquid phase can be significantly reduced. When bisulfite remains after the completion of the polymerization, impurities are generated, leading to deterioration of the performance of the polymer and precipitation of impurities when kept at a low temperature. Therefore, it is desirable that the initiator containing the bisulfite is consumed and does not remain at the end of the polymerization.

  Here, when the dropping end time of the bisulfite (solution) can be made shorter than the dropping end time of the monomer by less than 1 minute, the bisulfite may remain after completion of the polymerization. In such a case, the end of dropping bisulfite or its solution and the end of dropping monomer are simultaneous, or the end of dropping bisulfite (solution) is more complete than the end of dropping monomer. Includes slow cases. In such a case, it tends to be difficult to effectively and effectively suppress the generation of sulfurous acid gas and the formation of impurities, which may adversely affect the thermal stability of the polymer from which the remaining initiator is obtained. On the other hand, when the completion time of the addition of the bisulfite or the solution thereof is more than 30 minutes earlier than the completion time of the addition of the monomer, the bisulfite has been consumed by the end of the polymerization. For this reason, the molecular weight tends to increase. In addition, the bisulfite dropping rate is higher than the monomer dropping rate during the polymerization, and a large amount of the bisulfite is added in a short time, so that a large amount of impurities and sulfite gas tend to be generated during this dropping period. .

  Moreover, in the case of using a bisulfite as an initiator system among the dropping components at the time of polymerization, the dropping end time of the persulfate (solution) is 1 to 30 minutes from the dropping end time of the monomer, Preferably it is delayed for 1 to 25 minutes, more preferably 1 to 20 minutes. Thereby, the amount of monomer components remaining after the completion of polymerization can be reduced, and impurities caused by the remaining monomers can be significantly reduced.

  Here, in the case where the dropping end time of the persulfate (solution) can be delayed by less than 1 minute from the dropping end time of the monomer, the monomer component may remain after completion of the polymerization. In such cases, the end of dropping of the persulfate (solution) and the end of dropping of the monomer are simultaneous, or the end of dropping of the persulfate (solution) is more complete than the end of dropping of the monomer. The early case is included. In such a case, it tends to be difficult to effectively and effectively suppress the formation of impurities. On the other hand, when the persulfate (solution) dropping end time is more than 30 minutes later than the monomer dropping end time, the persulfate or its decomposition product remains after the completion of polymerization to form impurities. There is a fear.

<Polymerization time>
In the polymerization, even when bisulfite is used as an initiator system at a low polymerization temperature, it is more important to suppress the generation of sulfurous acid gas and prevent the formation of impurities. For this reason, it is preferable to make the total dropping time during polymerization 120 to 600 minutes, preferably 150 to 450 minutes, more preferably 180 to 300 minutes. When the total dropping time is less than 120 minutes, the effects of the persulfate solution and the bisulfite solution added as the initiator system tend to be reduced. Therefore, the amount of sulfur-containing groups such as sulfonic acid groups introduced into the terminals and side chains tends to decrease with respect to the obtained (meth) acrylic acid copolymer. As a result, the weight average molecular weight of the polymer tends to increase. Moreover, it may occur that bisulfite exists excessively by being dripped in the reaction system in a short time. For this reason, such excessive bisulfite is decomposed to generate sulfurous acid gas, which may be released out of the system or may form impurities. However, it tends to be improved by carrying out the polymerization temperature and the initiator amount in a specific range that is low. On the other hand, when the total dropping time exceeds 600 minutes, the generation of sulfurous acid gas is suppressed, so that the resulting polymer has good performance. However, the productivity of the (meth) acrylic acid copolymer is lowered, and the use application may be limited. The total dropping time here means the time from the start of dropping the first dropping component (not necessarily one component) to the completion of dropping the last dropping component (not necessarily one component).

<Polymerization concentration>
The solid content concentration in the aqueous solution (that is, the polymerization solid content concentration of the monomer) at the time when the dropping of the above components is completed and the polymerization reaction in the polymerization reaction system is completed is preferably 35% by mass or more, more preferably It is 40-70 mass%, More preferably, it is 45-65 mass%. Thus, if the solid content concentration at the end of the polymerization reaction is 35% by mass or more, the polymerization can be carried out at a high concentration and in one stage. Therefore, a low molecular weight (meth) acrylic acid copolymer can be obtained efficiently. For example, the concentration step that was necessary in some cases in the conventional manufacturing method can be omitted. Therefore, the manufacturing efficiency can be greatly increased. As a result, the productivity of the (meth) acrylic acid copolymer is greatly improved, and an increase in production cost can be suppressed.

  Here, when the solid-formation concentration is less than 35% by mass, the productivity of the (meth) acrylic acid copolymer may not be significantly improved. For example, it becomes difficult to omit the concentration step.

  When the solid content concentration is increased in the polymerization reaction system, the viscosity of the reaction solution increases remarkably with the progress of the polymerization reaction, and the weight average molecular weight of the resulting polymer tends to increase significantly. However, by carrying out the polymerization reaction on the acidic side (pH at 25 ° C. is 1 to 6 and the neutralization degree of carboxylic acid is in the range of 0 to 25 mol%), the viscosity of the reaction solution accompanying the progress of the polymerization reaction can be reduced. The rise can be suppressed. Therefore, a polymer having a low molecular weight can be obtained even when the polymerization reaction is carried out under a high concentration condition, and the production efficiency of the polymer can be greatly increased.

  Here, the time point when the polymerization reaction is completed may be a time point when the dropping of all of the dropping components is completed, but preferably refers to a time point when a predetermined aging time has elapsed (polymerization is completed). .

<Aging process>
The aging time is usually 1 to 120 minutes, preferably 5 to 90 minutes, more preferably 10 to 60 minutes. When the aging time is less than 1 minute, the monomer component may remain due to insufficient aging, which may cause impurities due to the residual monomer, resulting in performance degradation. On the other hand, when the aging time exceeds 120 minutes, the polymer solution may be colored. In addition, since the polymerization has already been completed, it is uneconomical to apply a further polymerization temperature.

  Further, during the aging, the polymerization temperature is applied because it is within the polymerization reaction period and is included in the polymerization. Therefore, the temperature here may also be maintained at a constant temperature (preferably the temperature at the end of dropping), or the temperature may be changed over time during aging. Therefore, the polymerization time refers to the above total dropping time + ripening time, and refers to the time required from the first titration start point to the ripening end point.

<Process after polymerization>
In the method for producing a (meth) acrylic acid copolymer according to the present invention, the polymerization is preferably performed under acidic conditions as described above. Therefore, the neutralization degree (carboxylic acid final neutralization degree) of the carboxylic acid of the (meth) acrylic acid copolymer to be obtained is determined by appropriately adding an appropriate alkaline component as a post-treatment as needed after the polymerization is completed. You may set to a predetermined range by adding.

  The final neutralization degree is not particularly limited because it varies depending on the intended use. When used as an acidic polymer, the final neutralization degree of carboxylic acid is preferably 0 to 75 mol%, more preferably 0 to 70 mol%. When used as a neutral or alkaline polymer, the degree of final neutralization of carboxylic acid is preferably 75 to 100 mol%, more preferably 85 to 99 mol%. Further, when the final neutralization degree when used as a neutral or alkaline polymer exceeds 99 mol%, the aqueous polymer solution may be colored.

  Examples of the alkali component include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; alkaline earth metal hydroxides such as calcium hydroxide and magnesium hydroxide; ammonia, monoethanolamine, diethanolamine, Examples thereof include those represented by organic amines such as triethanolamine. Only one type of alkali component may be used, or a mixture of two or more types may be used.

In addition, when the reaction system is used without being neutralized as described above, since the inside of the reaction system is acidic, toxic sulfurous acid gas (SO ₂ gas) remains in the atmosphere in the reaction system. There may be. In such a case, it is desirable to decompose by adding a peroxide such as hydrogen peroxide or to expel it by introducing (blowing) air or nitrogen gas.

<Other manufacturing conditions>
The (meth) acrylic acid-based copolymer of the present invention may be produced in a batch manner or in a continuous manner.

[Copolymer composition of the present invention]
The copolymer composition of the present invention contains the (meth) acrylic acid copolymer of the present invention as an essential component, and may contain only the copolymer of the present invention. 1 or more chosen from an agent residue, a residual monomer, the by-product at the time of superposition | polymerization, and a water | moisture content. It is preferable that the copolymer composition of this invention contains 1-100 mass% of copolymers of this invention with respect to 100 mass% of copolymer compositions of this invention. One of the forms of a preferable copolymer composition is a form which contains 40-60 mass% of copolymers, and contains 40-60 mass% of water.
Since it affects physical properties such as the dispersibility of calcium carbonate of the copolymer composition, it is preferable that the residual monomer is as small as possible. Specifically, the residual maleic acid (salt) is preferably 3000 ppm or less with respect to the solid content of the copolymer composition. Here, the amount of maleic acid (salt) is calculated in terms of acid type (that is, in the case of maleate, the mass% is calculated as maleic acid which is the acid type), and the amount of residual maleic acid is calculated.

[Usage of copolymer and copolymer composition of the present invention]
The copolymer (or copolymer composition) of the present invention comprises a water treatment agent, a scale inhibitor (scale inhibitor), a fiber treatment agent, a dispersant, a metal ion sealant, a thickener, various binders, and an emulsifier. , Skin care agents, hair care agents and the like.

<Water treatment agent>
The copolymer (or copolymer composition) of the present invention can be used as a water treatment agent. If necessary, the water treatment agent may contain a polymerized phosphate, phosphonate, anticorrosive, slime control agent, and chelating agent as other compounding agents.

  The water treatment agent is useful for scale prevention in a cooling water circulation system, a boiler water circulation system, a seawater desalination apparatus, a reverse osmosis membrane treatment apparatus, a pulp digester, a black liquor concentration tank, and the like. Further, any appropriate water-soluble polymer may be included as long as it does not affect the performance and effects.

<Fiber treatment agent>
The copolymer (or copolymer composition) of the present invention can be used as a fiber treatment agent. The fiber treatment agent includes at least one selected from the group consisting of a dye, a peroxide, and a surfactant, and the copolymer (or copolymer composition) of the present invention.

  The content of the copolymer of the present invention in the fiber treatment agent is preferably 1 to 100% by weight, more preferably 5 to 100% by weight, based on the entire fiber treatment agent. Further, any appropriate water-soluble polymer may be included as long as the performance and effects are not affected.

  Below, the compounding example of the fiber processing agent which is closer to embodiment is shown. This fiber treatment agent can be used in the steps of refining, dyeing, bleaching and soaping in fiber treatment. Examples of dyeing agents, peroxides and surfactants include those usually used for fiber treatment agents.

  The blending ratio of the copolymer of the present invention and at least one selected from the group consisting of a dye, a peroxide and a surfactant is, for example, for improving the whiteness, color unevenness, and dyeing tempering of the fiber. Includes 0.1 to 100 weight percent of at least one selected from the group consisting of a staining agent, a peroxide and a surfactant with respect to 1 weight part of the copolymer of the present invention in terms of a pure amount of the fiber treatment agent. It is preferable to use a composition blended at a ratio of parts as a fiber treatment agent.

  Arbitrary appropriate fiber can be employ | adopted as a fiber which can use the said fiber processing agent. Examples thereof include cellulosic fibers such as cotton and hemp, chemical fibers such as nylon and polyester, animal fibers such as wool and silk, semi-synthetic fibers such as human silk, and woven fabrics and blended products thereof.

  When the fiber treatment agent is applied to the refining process, it is preferable to blend the copolymer of the present invention with an alkali agent and a surfactant. When applied to the bleaching step, it is preferable to blend the copolymer of the present invention, a peroxide, and a silicic acid-based agent such as sodium silicate as a decomposition inhibitor for the alkaline bleaching agent.

<Inorganic pigment dispersant>
The copolymer (or copolymer composition) of the present invention can be used as an inorganic pigment dispersant. In the inorganic pigment dispersant, condensed phosphoric acid and its salt, phosphonic acid and its salt, and polyvinyl alcohol may be used as other compounding agents as required.

  The content of the copolymer of the present invention in the inorganic pigment dispersant is preferably 5 to 100% by weight with respect to the whole inorganic pigment dispersant. Further, any appropriate water-soluble polymer may be included as long as it does not affect the performance and effect.

  The inorganic pigment dispersant can exhibit good performance as a dispersant for heavy or light calcium carbonate or clay inorganic pigment used in paper coating. For example, by adding a small amount of an inorganic pigment dispersant to an inorganic pigment and dispersing it in water, high concentration calcium carbonate having low viscosity and high fluidity and good aging stability of their performance. High concentration inorganic pigment slurries such as slurries can be produced.

  When the inorganic pigment dispersant is used as a dispersant for an inorganic pigment, the amount of the inorganic pigment dispersant used is preferably 0.05 to 2.0 parts by weight with respect to 100 parts by weight of the inorganic pigment. When the amount of the inorganic pigment dispersant used is within the above range, a sufficient dispersion effect can be obtained, and an effect commensurate with the addition amount can be obtained, which can be economically advantageous.

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples. Unless otherwise specified, “part” means “part by mass” and “%” means “% by mass”.
The determination of the monomer and the measurement and evaluation of the weight average molecular weight of the copolymer were carried out according to the following methods.

<Monomer determination method>
The measurement of the content of monomers and the like was performed using liquid chromatography under the following conditions.
Apparatus: L-7000 series detector manufactured by Hitachi, Ltd .: UV detector L-7400 manufactured by Hitachi, Ltd.
Column: Shodex RSpak DE-413L manufactured by Showa Denko KK
Flow rate: 1.0 ml / min
Column temperature: 40 ° C
Mobile phase: 0.1% aqueous phosphoric acid solution.

<Measurement conditions of weight average molecular weight>
Equipment: HLC-8320GPC manufactured by Tosoh Corporation
Detector: RI
Column: Shodex Asahipak GF-310-HQ, GF-710-HQ, GF-1G 7B manufactured by Showa Denko KK
Column temperature: 40 ° C
Flow rate: 0.5 ml / min
Calibration curve: POLYACRYLIC ACID STANDARD made by Soka Science Co., Ltd.
Eluent: 0.1N sodium acetate aqueous solution.

<Measurement of solid content>
In an oven heated to 120 ° C., the copolymer of the present invention (1.0 g of the copolymer composition of the present invention plus 1.0 g of water) was allowed to stand for 2 hours for drying treatment. From the weight change before and after drying, the solid content (%) and the volatile component (%) were calculated.

<Measurement of gel resistance>
It measured by the above-mentioned gel resistance test.

<Measurement of chelating ability (calcium ion capturing ability)>
In a beaker with a capacity of 100 cc, 50 g of a 0.001 mol / L calcium chloride aqueous solution was sampled, and 10 mg of the copolymer was added in terms of solid content. Next, the pH of this aqueous solution was adjusted to 9-11 with dilute sodium hydroxide. Then, 1 ml of 4 mol / L potassium chloride aqueous solution was added as a calcium ion electrode stabilizer under stirring.
Using an ion analyzer (EA920 type, manufactured by Orion) and a calcium ion electrode (93-20 type, manufactured by Orion), free calcium ions were measured, and how many milligrams of calcium in terms of calcium carbonate per 1 g of copolymer. Whether ions were chelated (calcium ion capturing ability, which is one type of chelating ability) was calculated. The unit of calcium ion scavenging ability is “mgCaCO ₃ / g”.

<Calcium carbonate dispersibility of copolymer>
After adding 0.3 g of calcium carbonate (manufactured by Wako Pure Chemicals, Wako Grade 1) to a test tube (made by IWAKI GLASS: diameter 18 mm, height 180 mm), boric acid-boric acid so that the total amount including calcium carbonate is 30 g. Sodium pH buffer solution, pure water, and aqueous copolymer solution were added in order to prepare a pH 8.5 dispersibility test solution containing the copolymer at a solid content concentration of 50 mg / L. After sealing with a lid, the test tube was shaken to disperse the calcium carbonate uniformly. Thereafter, the test tube was allowed to stand at room temperature (about 20 ° C.) for 3 hours. When the appearance after 3 hours is observed and the calcium carbonate is kept sufficiently dispersed and is clouded up to the top of the test solution, it can be said that the dispersibility of the calcium carbonate is high.
Judgment was made based on the following criteria.
○: Cloudy up to the top of the test solution.
X: Not cloudy up to the top of the test solution.

<Example 1>
In a 2.5 L SUS316 separable flask equipped with a thermometer, reflux condenser, and stirrer, 346.6 g of pure water and 58.8 g (0.6 mol) of maleic anhydride (hereinafter referred to as MA) Molle salt 0.0299 g (the mass of iron (II) with respect to the total charge (herein, the total charge is the weight of all inputs including the neutralization step after completion of the polymerization. The same shall apply hereinafter). ), The temperature was raised to 87 ° C. with stirring (initial charge).
Next, under stirring, in a polymerization reaction system at a constant temperature of 87 ° C., an aqueous 80% by mass acrylic acid solution (hereinafter referred to as 80% AA) 432.4 g (4.8 mol), 40% by mass 3-allyloxy-2-hydroxy-1 -Sodium propanesulfonate aqueous solution (hereinafter referred to as 40% HAPS) 327.0 g (0.6 mol), 15 mass% sodium persulfate aqueous solution (hereinafter referred to as 15% NaPS) 144.0 g, 35 mass% sodium bisulfite aqueous solution 92.6 g (hereinafter referred to as 35% SBS) was dropped from separate dropping nozzles. The dropping time was 80 minutes AA for 180 minutes, 40% HAPS for 120 minutes, 35% SBS for 170 minutes, and 15% NaPS for 200 minutes. Moreover, regarding the dripping start time, all dripping liquids started dripping simultaneously. As for 15% NaPS, 72.0 g was continuously dropped at a constant dropping rate from 0 to 130 minutes, and the remaining 72.0 g was continuously dropped at 130 to 200 minutes at a constant dropping rate. 80% AA, 40% HAPS, and 35% SBS were dripped continuously at a constant drip rate during each drip time.
After completion of the dropwise addition, the reaction solution was kept at 87 ° C. for 30 minutes to complete the polymerization. Thus, the copolymer composition (polymer composition (1)) of the present invention having a solid content concentration of 42% by mass was obtained (the copolymer of the present invention contained is referred to as polymer (1)). ).

<Examples 2 to 4>
In Example 1, except having changed the conditions described in Table 1, it carried out similarly to Example 1, and obtained polymer composition (2)-(4) (The copolymer contained is a polymer (2 ) To (4)).

<Comparative Example 1>
302.5 g of pure water was charged into a 2.5 L SUS316 separable flask equipped with a thermometer, a reflux condenser, and a stirrer, and the temperature was raised to the boiling point with stirring (initial charging).
Next, under stirring, 80% AA 720.0 g (8.0 mol), 15% NaPS 106.7 g, 35% SBS 182.9 g, and pure water 126.5 g were respectively added to the polymerization reaction system at the boiling point reflux state from separate dropping nozzles. For 120 minutes. Moreover, regarding the dripping start time, all dripping liquids started dripping simultaneously.
After completion of the dropwise addition, the reaction solution was maintained at the boiling point reflux state for an additional 30 minutes and aged to complete the polymerization. Thereafter, 600 g of 48% sodium hydroxide (hereinafter referred to as 48% NaOH) was neutralized by gradually dropping into the resulting reaction solution while stirring. In this way, a comparative polymer composition (comparative polymer composition (1)) having a solid content concentration of 46% by mass was obtained (referred to as the comparative polymer (1)).

<Comparative Examples 2-4>
As the comparative polymer (2), the structural unit (a): the structural unit (b): the structural unit (c) is 10:45:45 and the Mw is 11,000, and the comparative polymer (3) is the structural polymer. Unit (a): Structural unit (b): Structural unit (c) is 10:55:55, Mw is 27,000 polymer, Comparative polymer (4), Structural unit (b): Structural unit (c ) Was 90:10 and Mw was 11,000.

<Example 6>
Using the obtained polymers (1) to (4) and comparative polymers (1) to (4), the molecular weight measurement, the calcium carbonate dispersibility evaluation, and the gel resistance were determined by the methods described above. Test and measurement of residual maleic acid amount. The results are shown in Table 2 below.

From the above evaluation results, it was revealed that the copolymer of the present invention has better dispersibility of calcium carbonate and gel resistance as compared with conventional polymers.

  The copolymer of the present invention has high gel resistance, calcium carbonate dispersibility, and chelating ability. Therefore, when it uses for additives, such as a water treatment agent (especially scale inhibitor) and a dispersing agent, the outstanding performance can be exhibited.

Claims (4)

The structural unit (a) derived from the monomer represented by the following general formula (1) of 5 mol% to 25 mol% with respect to 100 mol% of the structure derived from all monomers, 50 mol% to 88 mol A copolymer having, as an essential structural unit, a structural unit (b) derived from (meth) acrylic acid (salt) of 7 mol% or less and a structural unit (c) derived from maleic acid (salt) of 7 mol% or more and 25 mol% or less. A (meth) acrylic acid copolymer having a weight average molecular weight of 1,000 to 30,000.

In general formula (1), R ₂ represents a hydrogen atom or a methyl group, and X and Y each independently represent a hydroxyl group or a sulfonic acid (salt) group (provided that at least one of X and Y is sulfonic acid) (Salt) group). A copolymer composition comprising the (meth) acrylic acid copolymer according to claim 1,
The maleic acid content is 0 to 3000 ppm based on the solid content of the copolymer composition.
Copolymer composition. 5 mol% or more and 25 mol% or less of the monomer represented by the following general formula (1), 50 mol% or more and 88 mol% or less (meth) acrylic acid (salt) with respect to 100 mol% of all monomers ), 7 mol% or more and 25 mol% or less of maleic acid (salt),
The method for producing a (meth) acrylic acid-based copolymer according to claim 1, wherein the copolymer is copolymerized as essential.

In general formula (1), R ₂ represents a hydrogen atom or a methyl group, and X and Y each independently represent a hydroxyl group or a sulfonic acid (salt) group (provided that at least one of X and Y is sulfonic acid) (Salt) group). A water treatment agent comprising the (meth) acrylic acid copolymer according to claim 1.