JP6812697B2 - Polymer aqueous solution - Google Patents

Description

The present invention relates to an aqueous polymer solution containing an amphoteric polymer containing an acrylamide monomer unit, a cationic monomer unit, and an acrylic acid monomer unit, and a polymer containing a vinylamine monomer unit. More specifically, the present invention relates to a method for providing a stable mixed aqueous solution of an amphoteric polymer and a vinylamine monomer unit-containing polymer useful as a water treatment field or a paper chemical.

The vinylamine monomer unit-containing polymer obtained by (partially) hydrolyzing the N-vinylcarboxylic acid amide monomer unit-containing polymer can be used as a flocculant, a papermaking agent, a fiber treatment agent, a paint additive, etc. It is widely used, and polymers having various molecular weights are used in a wide range from high molecular weight polymers having a molecular weight of 4 million or more to low molecular weight polymers having a molecular weight of 100,000 or less depending on the application.

On the other hand, the amphoteric polymer has a specific structure containing a cationic monomer unit and an anionic monomer unit in the molecule, and thus has high performance in a flocculant, a paper chemical, a fiber treatment agent, a paint additive, and the like. It is widely used as a drug.

These polymers may be used at the same time in order to further improve the performance. As an example, the following method is known.
(1) A method for producing paper, paperboard and cardboard having high drying strength using a trivalent cationic polymer, a water-soluble cationic polymer, and at least one water-soluble amphoteric polymer. (Patent Document 1)
(2) An additive for papermaking containing a cationic water-soluble polymer or an amphoteric water-soluble polymer and a water-soluble polymer having a vinylamine structural unit. (Patent Document 2)

Further, the range of the hydrogen ion concentration (pH) of the aqueous solution mixed with the polymer may be defined to improve the performance. As an example, the following method is known.
(3) A polymer flocculant having a pH of an aqueous solution having a concentration of 0.1% by weight of 4.0 or less (Patent Document 3).

When a plurality of polymers are used at the same time, it is efficient to prepare and use a mixture of the respective polymers in advance. Examples of the form of the mixed polymer include an aqueous solution, a powder (dissolve at the time of use), an emulsion and the like, but the aqueous solution is most preferable in consideration of ease of mixing operation, handleability at the time of use, and stability.

However, the vinylamine monomer unit-containing polymer has a primary amino group in the side chain, is very cationic, and easily forms an ionic bond when there is an anionic substance in the same solution. When a mixture of polymers is prepared with an aqueous solution, the ion-bonded polymer forms a crosslinked structure, resulting in an increase in the viscosity of the aqueous solution and lack of fluidity due to gelation, resulting in lack of stability. A method for improving stability when a cationic polymer and an anionic polymer are mixed is described in the following cited documents, but the effect is not sufficient. (Patent Document 4) Further improvement is required for any of the above methods.

Special Table 2012-530196A Japanese Unexamined Patent Publication No. 2014-1473 Japanese Unexamined Patent Publication No. 8-112504 Japanese Unexamined Patent Publication No. 4-298300

An object of the present invention is to provide a mixed polymer aqueous solution that can withstand long-term storage by preventing a decrease in stability due to an increase in aqueous solution viscosity and lack of fluidity due to gelation, which has been conventionally caused.

As a result of diligent studies in view of the above problems, the present inventor has a weight containing an amphoteric polymer containing an acrylamide monomer unit, a cationic monomer unit, and an acrylate monomer unit and a vinylamine monomer unit. We found that when the pH of the aqueous solution mixed with the coalescence was adjusted within a certain range, the stability was dramatically increased, and it was found that a mixture of an amphoteric polymer and a vinylamine monomer unit-containing polymer, which are highly useful in each field. We have reached the present invention, which can provide an aqueous solution.

That is, the present invention uses (a) a nonionic monomer unit, (b) a cationic monomer unit, and (c) an amphoteric polymer (A) having an acrylic acid monomer unit and a vinylamine monomer unit. A mixed aqueous solution containing the polymer (B) having the same, the pH of the mixed aqueous solution at 25 ° C. is 1.0 or more and 3.0 or less, and after the mixed aqueous solution is adjusted and stored for 7 days or more, after storage. The ratio of the viscosity of the aqueous solution before storage to 1.5 is 0.8 or more and 1.5 or less.

Further, in the present invention, the (b) cationic monomer unit contained in the polymer (A) is a dialkylaminoalkyl (meth) acrylate or a tertiary or quaternary salt of dialkylaminoalkyl (meth) acrylamide. It relates to the said mixed aqueous solution which is one or more monomer units selected from.

The present invention also relates to the above-mentioned mixed aqueous solution in which the ratio of the vinylamine monomer unit of the polymer (B) to the total monomer unit of the polymer (B) is 10 mol% or more and 80 mol% or less.

The present invention also relates to the above-mentioned mixed aqueous solution in which the ratio of (c) to the total of (a), (b) and (c) of the polymer (A) is 1 mol% or more and 50 mol% or less.

Further, in the present invention, the salt generated by the acid and the base added when adjusting the hydrogen ion concentration (pH) of the mixed aqueous solution is 0.1 by mass percentage with respect to the acid added in the mixed aqueous solution. With respect to the above-mentioned mixed aqueous solution to which% or more and 100% or less are added.

Furthermore, the present invention relates to a method for storing a mixed aqueous solution according to any one of the above items, wherein the storage period from immediately after preparation to immediately before use is 14 days or more.

The mixed aqueous solution of the amphoteric polymer and the vinylamine monomer unit-containing polymer of the present invention prevents the deterioration of stability due to the increase in the viscosity of the aqueous solution and the lack of fluidity due to gelation, which have been conventionally caused, and for a long period of time. It is possible to provide an aqueous mixed polymer solution that can withstand storage.

The definitions of the following terms apply throughout the specification and claims.
By "monomer" is meant a compound having an ethylenically unsaturated bond.
The "unit" in the polymer is a structural unit derived from the monomer formed by polymerizing the monomer, or a part of the structural unit is converted into another structure by treating the polymer. It means a structural unit.
The "N-vinylformamide monomer unit-containing polymer" has a homopolymer composed of N-vinylformamide monomer units, or an N-vinylformamide monomer unit and other constituent units. It means a copolymer (excluding a copolymer having an N-vinylformamide monomer unit and a vinylamine monomer unit).
The "vinylamine monomer unit-containing polymer" means a homopolymer composed of vinylamine monomer units or a copolymer having a vinylamine monomer unit and other constituent units. The vinylamine monomer unit may be in the salt state.
The "amphoteric polymer" is a copolymer composed of an acrylamide monomer unit, a cationic monomer unit, an acrylic acid monomer unit, or a copolymer having these constituent units and other constituent units. Means a polymer. The cationic monomer unit and the acrylic acid monomer unit may be in a salt state.
The “strong acid” means a compound having an acid dissociation constant pKa of 0 or less in an aqueous solution at 25 ° C.
The "strong base" means a compound having a basic acid dissociation constant pKb of 0 or less in an aqueous solution at 25 ° C.
By "(meth) acrylic acid ester" is meant at least one of an acrylic acid ester and a methacrylic acid ester.
By "(meth) acrylonitrile" is meant at least one of acrylonitrile and methacrylonitrile.
"(Meta) acrylate" means at least one of acrylate and methacrylate.
"(Meta) acrylamide" means at least one of acrylamide and methacrylamide.

In the present invention, the amphoteric polymer (A) is a copolymer of a nonionic monomer (a), a cationic monomer (b), and an acrylic acid monomer (c). Nonionic monomers include (meth) acrylamide, N, N-dimethylacrylamide, acrylonitrile, (meth) acrylate-2-hydroxyethyl, diacetoneacrylamide, N-vinylpyrrolidone, N-vinylformamide, and N-vinyl. Examples thereof include acetoamide and acryloylmorpholine. In particular, (meth) acrylamide, N-vinylformamide, and N-vinylacetamide are preferable. Examples of the cationic monomer include an amine salt of dialkylaminoalkyl (meth) acrylate or a cationic monomer derived from an alkyl chloride quaternized product, or an amine salt of dialkylaminoalkyl (meth) acryamide or an alkyl chloride quaternized product. Examples thereof include cationic monomers derived from. In particular, a dialkylaminoalkyl (meth) acrylatealkyl chloride quaternary product is preferable. As the monomer, one type of cationic monomer may be used alone, or two or more types may be used in combination. Further, examples of acrylic acid (salt) include acrylic acid, sodium acrylate, ammon acrylate, calcium acrylate, zinc acrylate and the like.

Among the copolymerization ratios of the polymer (A) (a), (b) and (c), the ratio of (c) is preferably 1 mol% or more. Further, it is preferably 55 mol% or less, more preferably 40 mol% or less, and further preferably 30 mol% or less. If the ratio of (c) is lower than 1 mol%, a sufficient coagulation effect will not be exhibited when used as a coagulant, a paper chemical, a fiber treatment agent, a paint additive, or the like. If the proportion of (c) is higher than 55 mol%, the possibility of causing an ionic bond with the polymer (B) increases, and the stability of the mixed aqueous solution decreases.

Various production methods are known for the vinylamine monomer unit-containing polymer (B). Among them, the N-vinylformamide monomer unit-containing polymer (C) is hydrolyzed in the presence of a strong acid or a strong base. A method of decomposing to produce a polymer containing a vinylamine monomer unit is generally performed.

In the present invention, the polymer (A) and the polymer (B) may contain a monomer other than the above-mentioned monomer as a monomer component.

Other monomers include (meth) acrylic acid, salts of (meth) acrylic acid, (meth) acrylic acid esters, (meth) acrylonitrile, (meth) acrylamide, N-alkyl (meth) acrylamide, N, N. -Dialkyl (meth) acrylamide, dialkylaminoethyl (meth) acrylamide, dialkylaminoethyl (meth) acrylamide salt or quaternary product, dialkylaminopropyl (meth) acrylamide, dialkylaminopropyl (meth) acrylamide salt or quaternary product , Diacetone acrylamide, N-vinylpyrrolidone, N-vinylcaprolactam, vinyl acetate and the like.

The N-vinylformamide monomer unit-containing polymer (C), which is a precursor of the polymer (A) and the polymer (B), is prepared by a known method, for example, an aqueous solution polymerization method, or emulsification using water and an organic solvent. It can be produced by a legal method or a suspension polymerization method.

Further, if necessary, an initiator, a solvent, other known additives and the like may be contained in addition to the monomer component.

The initiator may be appropriately selected from known initiators according to the polymerization method adopted. Examples of the initiator include an azo-based initiator, a redox-based initiator, a peroxide-based initiator, a photoinitiator, and the like.

The solvent may be appropriately selected from known solvents according to the polymerization method adopted. Examples of the solvent include water, hydrocarbon solvents and the like.

Examples of other additives include gel quality improvers (polyalkylene glycols and the like), pH adjusters (phosphoric acid and the like), inorganic salts, chain transfer agents, emulsifiers (dispersion stabilizers), sensitizers and the like.

The hydrolysis treatment of the N-vinylformamide monomer unit-containing polymer (C) is carried out in the presence of water. Specifically, the hydrolysis treatment involves the state of the aqueous gel of the massive polymer (C), the state of the non-aqueous solvent dispersion of the fine particle gel of the polymer (C), and the powdery polymer (C). , It is carried out in a state of being dissolved or dispersed in water.

The hydrolysis treatment of the polymer (C) is carried out in the presence of a strong acid or a strong base. As the strong acid, monovalent mineral acids such as hydrochloric acid and nitric acid are preferable. As the strong base, lithium hydroxide, sodium hydroxide, potassium hydroxide and the like are preferable.

The hydrolysis rate of the formamide group of the polymer (C), that is, the ratio of the vinylamine monomer unit is preferably 10 mol% or more out of 100 mol% of the formamide group before the hydrolysis treatment. If the target hydrolysis rate is too low, it may be difficult to accurately control the hydrolysis rate. The upper limit of the hydrolysis rate is preferably 95 mol% or less of 100 mol% of formamide groups before the hydrolysis treatment. If it is higher than 95 mol%, it is more likely to cause an ionic bond with the polymer (A), and the stability of the mixed aqueous solution is lowered.

The temperature at which the polymer (C) is hydrolyzed is preferably 50 ° C. or higher. Further, it is preferably 100 ° C. or lower. When the temperature at which the hydrolysis treatment is performed is 50 ° C. or higher, the hydrolysis reaction is promoted and a desired hydrolysis rate can be obtained in a relatively short time. When the temperature at the time of the hydrolysis treatment is 100 ° C. or lower, a high-quality vinylamine monomer unit-containing polymer can be obtained without causing a decrease in molecular weight or insolubilization due to heat.

The polymer (B) contains formic acid produced by hydrolysis of the formamide group of the N-vinylformamide monomer unit-containing polymer, and ammonia, formic acid, and acetaldehyde produced by hydrolysis of N-methoxyethylformamide.

Since acetaldehyde may cause insolubilization due to cross-linking of the vinylamine monomer unit-containing polymer during the hydrolysis treatment, it is preferable to remove acetaldehyde by a known method. Specific examples thereof include a method of reducing with a reducing agent and a method of oxime with hydroxylamine.

The polymer (A) and the polymer (B) of the present invention may be used at the same time for improving performance, and may be mixed with an aqueous solution in advance in consideration of ease of handling during use. The aqueous polymer solution can be produced by a known method, for example, a method of stirring and mixing a dried or powdered polymer in water, a method of performing aqueous solution polymerization from the time of polymer production, or the like. As a method for mixing the polymer aqueous solution, a known method, for example, a method of adding the other polymer aqueous solution to the dissolution tank of the polymer aqueous solution, a method of mixing each polymer aqueous solution with a line mixer, or the like is used. Can be done.

In the mixed aqueous solution of the present invention, the pH of the aqueous solution is 1.0 to 3.0. The polymer (A) having an anionic constituent unit and the polymer (B) having a very high cationic constituent unit are easily ionic bonded. The ionic-bonded polymer forms a crosslinked structure, which causes an increase in the viscosity of the aqueous solution and a lack of fluidity due to gelation, resulting in a decrease in stability. However, when the degree of dissociation of acrylic acid for each pH was calculated, the dissociation of acrylic acid was almost suppressed at pH 3.0 or lower, and the carboxyl group of acrylic acid did not act as an anion group, so that the ion with the polymer (B) was formed. No binding occurs and the stability of the aqueous solution is dramatically improved. On the other hand, even if the pH is lowered below 1.0, ionic bonding with the polymer (B) does not occur, but it is not realistic because a large amount of strong acid must be used to reduce the pH to 1.0 or less. ..

Known inorganic or organic acidic substances can be used to adjust the pH of the polymer mixed aqueous solution from 1.0 to 3.0. A monovalent acid is used in the present invention because the polyvalent acid produces a polyvalent anion and forms a crosslinked bond with the polymer (B). Specific examples thereof include hydrochloric acid, sulfamic acid, acetic acid, formic acid and the like.

In some cases, the polymer mixed aqueous solution of the present invention may have time to be used after production of the aqueous solution, such as storage and transportation to a customer. When the polymer mixed aqueous solution is prepared according to the conditions of the present invention, the longer the period from the time of adjusting the aqueous solution to immediately before use, the more effective the stability of the aqueous solution is. It is preferable to apply the polymer mixed aqueous solution of the present invention when the period from the time of adjusting the aqueous solution to immediately before use is 7 days or more, and more preferably to apply the polymer mixed aqueous solution of the present invention when it is 14 days or more. ..

Further, in order to prevent the pH of the polymer mixed aqueous solution of the present invention from rising with time, a buffer salt may be added. As the buffer salt, a salt formed of an acid and a base added when adjusting the pH is preferable. The base is not particularly limited, and may be appropriately selected from strong bases such as lithium hydroxide, sodium hydroxide, potassium hydroxide and calcium hydroxide, and weak bases such as ammonia, iron hydroxide and magnesium hydroxide. For example, when the pH is adjusted with formic acid, fluctuations in pH can be suppressed by appropriately adding sodium formate, ammonium formate, or the like. The amount of the buffer salt added is preferably 0.1% or more, more preferably 1% or more, based on the acid added when adjusting the pH. Further, it is preferably 100% or less, and more preferably 50% or less.

In the mixed aqueous solution of the amphoteric polymer (A) and the vinylamine monomer unit-containing polymer (B) of the present invention described above, the hydrogen ion concentration (pH) of the aqueous solution is adjusted to 1.0 or more and 3.0 or less. Therefore, the storage stability can be dramatically improved.

Conventionally, the carboxyl group of the acrylic acid monomer unit of the polymer (A) and the amino group of the polymer (B) are easily ionically bonded, and the aqueous solution is stabilized due to an increase in the viscosity of the aqueous solution and lack of fluidity due to gelation. The sex was reduced. In the present invention, it has been found that there is a close relationship between the degree of dissociation of the carboxyl group of the acrylic acid monomer unit calculated from the pH of the aqueous solution and the increase in viscosity due to the ionic bond between the polymer (A) and the polymer (B). It was.
In particular, the longer the period from the time of adjusting the aqueous solution to immediately before use, the greater the advantage of applying the polymer mixed aqueous solution of the present invention.

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples as long as the gist of the present invention is not exceeded.
The physical characteristics of the polymer in Examples and Comparative Examples were measured by the following methods.

(Measurement of hydrogen ion concentration (pH))
A pH meter calibrated at two points with a pH standard solution (pH 4.01, 6.86) was impregnated with a polymer aqueous solution whose temperature was controlled to 25 ° C., and the point at which the value was maintained for 1 minute was defined as the pH of the polymer aqueous solution. did.

(Measurement of viscosity of mixed polymer aqueous solution)
The temperature of the aqueous polymer solution was 25 ° C., Brookfield viscometer, 6 to 60 rpm, rotor No. It was measured under the condition of 3. The viscosity was expressed as mPa · s (25 ° C.).

(Measurement of the ratio of vinylamine monomer unit)
An aqueous solution of the vinylamine monomer unit-containing polymer is dissolved in deionized water so that the concentration of the vinylamine monomer unit-containing polymer is 0.025% by mass, and at pH 2.5, using toluidine blue as an indicator, 1 It was titrated with a / 400N aqueous solution of polyvinyl sulfate. The ratio of vinylamine monomer units is calculated by calculating the cation equivalent of the vinylamine monomer unit-containing polymer from the titration amount and determining the hydrolysis rate of the formamide group of the N-vinylformamide monomer unit-containing polymer by the following formula. (Mole%) was calculated.
Percentage of vinylamine monomer units (mol%) = cation equivalent x 100 / ((1000- (cation equivalent x 79.5)) / 71 + cation equivalent)

(Measurement of acrylic acid monomer unit ratio of amphoteric polymer)
Dissolve the amphoteric polymer in deionized water so that the concentration of the amphoteric polymer is 0.005% by mass, add 0.5 mL of a 0.1N sodium hydroxide aqueous solution to a 100 g solution, and further add 1/200 of the methyl glycol. 5 mL of chitosan solution was added and mixed. The mixed solution was titrated with a 1/400 specified aqueous solution of potassium polyvinyl sulfate using toluidine blue as an indicator. The anion equivalent of the polymer was calculated from the titration amount, and the acrylic acid monomer unit ratio (mol%) of the amphoteric polymer was determined by the following formula.
Acrylic acid monomer unit ratio (mol%) = 71 x anion equivalent / (1000- (anion equivalent x 23))

(Synthesis Example 1 (Method for Producing Amphoteric Polymer Aqueous Solution (D)))
248 g of 50 mass% acrylamide aqueous solution, 174 g of 79 mass% dialkylaminoalkyl acrylate alkyl chloride quaternary solution, 27.5 g of 50 mass% acrylic acid aqueous solution, 101 g of deionized water, diphenyl (2,4) as an initiator. A monomer solution was prepared by uniformly dissolving 0.0825 g of 6-trimethylbenzoyl) phosphine oxide, 0.055 g of "AF108" (a surfactant manufactured by Toho Chemical Co., Ltd.), and 0.099 g of hypophosphoric acid, and nitrogen gas was prepared. Was aerated to remove dissolved oxygen.

A polyethylene terephthalate film (base film 12 μm thick, PVDC coat 4 μm thick) is laid on the bottom surface of a tray-shaped container (bottom surface 235 mm × 235 mm) whose bottom surface is made of stainless steel, the monomer solution is put therein, and the upper part is covered with a polyethylene terephthalate film. did. From above, a fluorescent chemical lamp was irradiated on the irradiated surface so as to have an intensity of 8.5 W / m ² . During the irradiation period, cold water at 10 ° C. was sprayed on the stainless steel surface of the container from the lower part of the container to remove the heat of polymerization. The temperature, which was 15 ° C. before irradiation, reached a maximum temperature of 80 ° C. after 15 minutes. After 30 minutes from the start of irradiation, the irradiation intensity was increased to 53 W / m ² , and the polymerization was continued for 15 minutes to obtain an amphoteric polymer hydrogel.

The hydrogel was pulverized with a meat chopper to obtain particles having a size of about 4 to 5 mm, and then dried in a ventilation dryer at 60 ° C. for 16 hours. Then, it was pulverized again with a rotary pulverizer having a 1 mmφ screen to obtain an amphoteric polymer powder. Next, 480.75 g of deionized water weighed in a 500 mL beaker was stirred with a two-stage parallel stirring blade, and 17.5 g of polymer powder and 1.75 g of sodium sulfamate were gradually added thereto, and the mixture was stirred and mixed for 4 hours. An aqueous solution of an amphoteric polymer (D) was obtained. The anion ratio derived from the acrylic acid monomer unit of the amphoteric polymer aqueous solution (D) was measured and found to be 8.1 mol%.

(Synthesis Example 2 (Method for Producing Amphoteric Polymer Aqueous Solution (E)))
The same procedure as in Synthesis Example 1 was carried out except that 198 g of a 50 mass% acrylamide aqueous solution, 174 g of a 79 mass% dialkylaminoalkyl acrylate alkyl chloride quaternized aqueous solution, and 77 g of a 50 mass% acrylic acid aqueous solution were changed. A coalesced aqueous solution (E) was obtained. The anion ratio derived from the acrylic acid monomer unit of the amphoteric polymer aqueous solution (E) was measured and found to be 21 mol%.

(Synthesis Example 3 (Method for Producing Amphoteric Polymer Aqueous Solution (F)))
The same operation as in Synthesis Example 1 was carried out except that 86 g of the 50 mass% acrylamide aqueous solution, 174 g of the 79 mass% dialkylaminoalkyl acrylate alkyl chloride quaternized aqueous solution, and 189 g of the 50 mass% acrylic acid aqueous solution were changed. A coalesced aqueous solution (F) was obtained. The anion ratio derived from the acrylic acid monomer unit of the amphoteric polymer aqueous solution (F) was measured and found to be 53 mol%.

(Method for producing N-vinylformamide)
N-vinylformamide (purity 92%) was obtained by using formamide and acetaldehyde as raw materials and passing through the intermediate N-methoxyethylformamide by the method described in JP-A-61-97301.

(Method for producing N-vinylformamide monomer unit-containing polymer)
After mixing 15 g of deionized water and 80 g of N-vinylformamide, sodium hypophosphate (0.2 parts by mass with respect to N-vinylformamide (100 parts by mass)), 2,2'- Add azobis (2-amidinopropane) dihydrochloride (V-50, manufactured by Wako Pure Chemical Industries, Ltd.) (0.4 parts by mass with respect to N-vinylformamide (100 parts by mass)) to mix for polymerization. (D) was obtained.
In a reaction vessel equipped with a stirrer, dropping funnel and jacket, 480 mL of cyclohexane, 5.6 g of emulsifier (polyoxyethylene alkyl ether, HLB: 14), 20 g of 20 mass% ammonium chloride aqueous solution, 24 g of deionized water. I put in. The above-mentioned polymerization mixture (d) was added dropwise over 3 hours under a nitrogen gas atmosphere, heating at 55 ° C. and stirring, and further maintained at 56 ° C. for 2 hours to obtain a polymerization product (e).
Further, the temperature is raised to 70 to 77 ° C. to condense the evaporated water and cyclohexane, and the operation of refluxing only cyclohexane is performed for 30 minutes to dehydrate the mixture to obtain a powdery N-vinylformamide monomer unit-containing polymer. It was.

(Synthesis Example 4 (Method for Producing Aqueous Polymer Solution (f) Containing Vinyl Amine Monomer Unit))
115.1 g of water, 8.8 g of 48 mass% sodium hydroxide aqueous solution and 10.5 g of sodium dithionate are mixed in an aqueous solution, and the powdered N-vinylformamide monomer unit obtained by the above operation. 15 g of the contained polymer is added little by little, dissolved at 50 ° C. for 2 hours, hydrolyzed at 80 ° C. for 3 hours, and 35% by mass of hydrochloric acid is added little by little to add a single amount of vinylamine in an aqueous solution. A body unit-containing polymer was obtained. When the vinylamine monomer unit ratio of the vinylamine monomer unit-containing polymer (f) was measured, it was 50 mol%.

(Synthesis Example 5 (Method for producing aqueous solution (g) of polymer containing vinylamine monomer unit))
The same operation as in Synthesis Example 4 was carried out except that 130.4 g of water, 1.8 g of 48 mass% sodium hydroxide aqueous solution, and 2.1 g of 35 mass% hydrochloric acid were changed, and the vinyl amine unit was contained in the aqueous solution state. A polymer (g) was obtained. The vinylamine monomer unit ratio of the vinylamine unit-containing polymer was measured and found to be 12 mol%.

(Synthesis Example 6 (Method for Producing Aqueous Polymer Solution (h) Containing Vinyl Amine Monomer Unit))
The same operation as in Synthesis Example 4 was carried out except that 103.5 g of water, 14.1 g of 48 mass% sodium hydroxide aqueous solution, and 16.7 g of 35 mass% hydrochloric acid were changed, and the vinyl amine unit was contained in the aqueous solution state. The polymer (h) was obtained. The vinylamine monomer unit ratio of the vinylamine unit-containing polymer was measured and found to be 78 mol%.

(Synthesis Example 7 (Method for Producing Aqueous Polymer (i) Containing Vinyl Amine Monomer Unit))
The same operation as in Synthesis Example 4 was carried out except that 94.8 g of water, 17.6 g of 48% by mass sodium hydroxide aqueous solution, and 22.0 g of 35% by mass hydrochloric acid were changed, and the vinylamine unit was contained in the aqueous solution state. The polymer (h) was obtained. The vinylamine monomer unit ratio of the vinylamine unit-containing polymer was measured and found to be 92 mol%.

(Example 1)
42.9 g of the amphoteric polymer aqueous solution (D), 5 g of the vinylamine monomer unit-containing polymer aqueous solution (f), and 2.1 g of deionized water were mixed well, and the pH was adjusted to 3.0 with 35% by mass hydrochloric acid. Adjusted to be. The viscosity of this aqueous solution was measured and found to be 1,600 mPa · s.
Next, the mixed aqueous solution was stored in an incubator at 40 ° C. for 7 days, and the viscosity was remeasured. As a result, it was 1,580 mPa · s, and the ratio to the viscosity before storage was 0.99, and no significant change was observed. I couldn't.

(Example 2)
The same operation as in Example 1 was carried out except that the pH of the mixture was adjusted to 2.1. The viscosity before storage was 1,490 mPa · s, and the viscosity after storage was 1,450 mPa · s. The ratio to the viscosity before storage was 0.97, and no significant change was observed.

(Example 3)
The same operation as in Example 1 was carried out except that the pH of the mixture was adjusted to 1.1. The viscosity before storage was 1,110 mPa · s, and the viscosity after storage was 1050 mPa · s. The ratio to the viscosity before storage was 0.95, and no significant change was observed.

(Comparative Example 1)
The same operation as in Example 1 was performed except that the pH of the mixture was not adjusted. The pH of the mixture was 3.5. The viscosity before storage was 1,600 mPa · s, and the viscosity after storage was 3,470 mPa · s. The ratio to the viscosity before storage was 2.17, thickening was confirmed, and the fluidity was significantly reduced.

(Example 4)
The same operation as in Example 1 was performed except that the storage period of the mixed solution was 14 days. The viscosity before storage was 1,600 mPa · s, and the viscosity after storage was 1,550 mPa · s. The ratio to the viscosity before storage was 0.97, and no significant change was observed.

(Example 5)
The same operation as in Example 1 was performed except that the storage period of the mixed solution was set to 30 days. The viscosity before storage was 1,600 mPa · s, and the viscosity after storage was 1,730 mPa · s. The ratio to the viscosity before storage was 1.08, and no significant change was observed.

(Comparative Example 2)
The same operation as in Comparative Example 1 was performed except that the storage period of the mixed solution was 14 days. The viscosity before storage was 1,600 mPa · s, and the viscosity after storage was 5,270 mPa · s. The ratio to the viscosity before storage was 3.30, thickening was confirmed, and the fluidity was significantly reduced.

(Example 6)
The same operation as in Example 1 was carried out except that the amphoteric polymer (D) was changed to the amphoteric polymer (E). The viscosity before storage was 1,790 mPa · s, and the viscosity after storage was 1,840 mPa · s. The ratio to the viscosity before storage was 1.03, and no significant change was observed.

(Example 7)
The same operation as in Example 1 was carried out except that the vinylamine monomer unit-containing polymer aqueous solution (f) was changed to the vinylamine monomer unit-containing polymer aqueous solution (g). The viscosity before storage was 3,200 mPa · s, and the viscosity after storage was 2,960 mPa · s. The ratio to the viscosity before storage was 0.92, and no significant change was observed.

(Example 8)
The same operation as in Example 1 was carried out except that the vinylamine monomer unit-containing polymer aqueous solution (f) was changed to the vinylamine monomer unit-containing polymer aqueous solution (h). The viscosity before storage was 1,330 mPa · s, and the viscosity after storage was 1,440 mPa · s. The ratio to the viscosity before storage was 1.08, and no significant change was observed.

(Example 9)
The same operation as in Example 1 was carried out except that the amphoteric polymer (D) was changed to the amphoteric polymer (F). The viscosity before storage was 1,790 mPa · s, and the viscosity after storage was 2,150 mPa · s. The ratio to the viscosity before storage was 1.20, and although the viscosity was slightly increased, no significant change in fluidity was observed.

(Example 10)
The same operation as in Example 1 was carried out except that the vinylamine monomer unit-containing polymer aqueous solution (f) was changed to the vinylamine monomer unit-containing polymer aqueous solution (i). The viscosity before storage was 1,210 mPa · s, and the viscosity after storage was 1,480 mPa · s. The ratio to the viscosity before storage was 1.22, and although the viscosity was slightly increased, no significant change in fluidity was observed.

(Example 11)
42.9 g of the amphoteric polymer aqueous solution (D), 5 g of the vinylamine monomer unit-containing polymer aqueous solution (f), and 2.1 g of deionized water were mixed well, and the pH was adjusted to 3.0 with formic acid and ammonium formate. Adjusted to be. The viscosity of this aqueous solution was measured and found to be 1,600 mPa · s.
Next, the mixed aqueous solution was stored in an incubator at 40 ° C. for 30 days, and the viscosity was remeasured. As a result, it was 1,620 mPa · s, and the ratio to the viscosity before storage was 1.01, and no significant change was observed. I couldn't.

When the pH of the mixed aqueous solution of the amphoteric polymer and the vinylamine monomer unit-containing polymer was adjusted in the range of 1.0 to 3.0 and stored in Examples 1 to 3 and Examples 6 to 8, the aqueous solution was stored. There was almost no change in viscosity.

On the other hand, in Comparative Example 1, when the pH of the aqueous solution deviates from the above pH range, the acrylic acid monomer unit in the amphoteric polymer dissociates and an ionic bond is formed with the vinylamine monomer unit. Therefore, the aqueous solution is stored during storage. Caused thickening.

Further, in Examples 4, 5 and Comparative Example 2, when the storage period was extended, when the pH of the aqueous solution was within the above pH range, there was almost no change in the viscosity of the aqueous solution, but when it was out of the above pH range. As in Comparative Example 1, the viscosity increased significantly, and the longer the storage period, the greater the increase.

Further, in Examples 9 and 10, although the stability of the aqueous solution was increased by adjusting the pH of the aqueous solution within a predetermined range, the ratio of acrylic acid monomer units in the amphoteric polymer or vinylamine alone was used. Since the vinylamine monomer unit ratio of the polymer containing the body unit was large, the amount of change in the aqueous solution viscosity was large.

Further, in Example 11, when a buffer salt was added, the stability was further increased and the change in viscosity was suppressed.

From the above, by adjusting the pH of the mixed aqueous solution of the amphoteric polymer and the vinylamine monomer unit-containing polymer to the range of 1.0 or more and 3.0 or less, an aqueous solution having extremely high stability can be obtained. Was confirmed.

The mixed aqueous solution of the polymer of the present invention is useful in a wide range of fields such as coagulants, paper chemicals, fiber treatment agents, and paint additives.

Claims (6)

An amphoteric polymer (A) having a nonionic monomer unit, (b) a cationic monomer unit, and (c) an acrylic acid monomer unit, and a polymer (B) having a vinylamine monomer unit. The pH of the mixed aqueous solution at 25 ° C. is 1.0 or more and 3.0 or less, and the viscosity of the aqueous solution after storage when the mixed aqueous solution is stored at 40 ° C. for 7 days or more after adjustment. A mixed aqueous solution having a ratio of the viscosity of the aqueous solution before storage to 0.8 or more and 1.5 or less. One type in which the (b) cationic monomer unit contained in the polymer (A) is selected from a dialkylaminoalkyl (meth) acrylate or a tertiary or quaternary salt of dialkylaminoalkyl (meth) acrylamide. The mixed aqueous solution according to claim 1, which is the above-mentioned monomer unit. The mixed aqueous solution according to claim 1 or 2, wherein the ratio of the vinylamine monomer unit of the polymer (B) to the total monomer unit of the polymer (B) is 10 mol% or more and 80 mol% or less. The invention according to any one of claims 1 to 3, wherein the ratio of (c) to the total of (a), (b) and (c) of the polymer (A) is 1 mol% or more and 50 mol% or less. Mixed aqueous solution. A salt formed by the acid and base added when adjusting the hydrogen ion concentration (pH) of the mixed aqueous solution is added in a mass percentage of 0.1% or more and 100% or less with respect to the acid added in the mixed aqueous solution. The mixed aqueous solution according to any one of claims 1 to 4. A method for storing a mixed aqueous solution according to any one of claims 1 to 5, wherein the storage period from immediately after adjustment to immediately before use is 14 days or more.