JP3313652B2 - Production method of water-soluble polymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a water-soluble polymer. More specifically, the present invention relates to a method for producing a water-soluble polymer that can efficiently remove a water-soluble solvent used as a solvent.

[0002]

2. Description of the Related Art When a water-soluble polymer is produced, a mixed solvent composed of water and a water-soluble solvent is sometimes used as a solvent. In such a production method, after the polymerization is completed, the water-soluble solvent is distilled off, and then, if the polymer contains an acidic group, neutralization with an alkali agent is carried out. A polymer has been obtained. In the desolvation step of distilling off the water-soluble solvent, water is also distilled off together with the water-soluble solvent, but as the content of the water-soluble solvent in the system decreases, the composition ratio of water on the distillate side further increases. Will be expensive. Thus, the removal efficiency of the water-soluble solvent in the desolvation step cannot be said to be good, and a great deal of time and energy is required for the desolvation step.

For example, in Japanese Patent No. 2727398, a polymerization reaction is carried out in a solution of water and a water-soluble solvent, and after neutralization, the solvent is distilled off to obtain an aqueous solution of a copolymer salt. I have. However, in this method, the solvent is removed in a uniform state, and therefore, the efficiency of removing the water-soluble solvent cannot be improved.

[0004]

Accordingly, the present invention provides
In a method for producing a water-soluble polymer using a mixed solvent of water and a water-soluble solvent as a solvent in a polymerization reaction, it is intended to provide a method for producing a water-soluble polymer that can efficiently remove a water-soluble solvent after a polymerization reaction. With the goal.

[0005]

Means for Solving the Problems] That is, the gist of the present invention, in a mixed solvent consisting of (A) water and a water-soluble solvent, by polymerizing a hydrophilic monomer having an acidic group, the water-soluble polymer obtaining a polymer solution containing the step, and (B) the addition of alkali agent in the polymer solution obtained in step (a), the phase rich phase and a water-soluble solvent rich polymer
After phase separation into a liquid-liquid two-phase separation state, 20 to 1
By distillation at a distillation temperature of 20 ° C., manufacturing steps of removing the water-soluble solvent from the polymer solution including the water-soluble polymer
About the law.

[0006]

DETAILED DESCRIPTION OF THE INVENTION Step (A) The hydrophilic monomer having an acidic group used in the present invention comprises:
The alkali-neutralized product of the obtained polymer is not particularly limited as long as it forms a phase separation state with water. Further, a monomer having an acidic group refers to a 1% by weight aqueous solution of the monomer having a pH of 25.
It is 6 or less at ° C, and examples of the acidic group include a carboxyl group, a sulfo group, and a phospho group. The hydrophilic monomer refers to a substance having a solubility in water at 25 ° C. of 2% by weight or more, and the hydrophobic monomer refers to a property having a solubility in water at 25 ° C. of less than 2% by weight. Means

Specific examples of the hydrophilic monomer having an acidic group are as follows. (Meth) acrylic acid and their alkali metal salts and ammonium salts (note that (meth) acrylic acid means acrylic acid and methacrylic acid; the same applies to the compounds described below with (meth)); Acid, fumaric acid, itaconic acid and their alkali metal salts and ammonium salts; water-soluble aromatic vinyl monomers such as styrene sulfonic acid and its alkali metal salts; vinyl sulfonic acid, (meth) allyl sulfonic acid and their alkalis Metal salts and ammonium salts. These may be used alone or in combination of two or more.
However, the salt can be mixed with an unneutralized monomer within a range that does not cause phase separation in the polymerization process.

[0008]

[0009]

[0010]

[0011]

The water-soluble solvent that can be used in the production method of the present invention is not particularly limited as long as it is a solvent that can be uniformly mixed with water. Specific examples include methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol, acetone, methyl ethyl ketone, acetonitrile, and the like. These may be used alone or in combination of two or more.

The amount of the water-soluble solvent used in the mixed solvent of water and the water-soluble solvent is not particularly limited as long as it can be uniformly mixed with water at the time of polymerization and does not precipitate the produced polymer. For example, the weight ratio in the mixed solvent is water:
The water-soluble solvent is preferably in the range of 95: 5 to 5:95, and 8
The range of 0:20 to 20:80 is more preferable.

The content of all the monomers including the hydrophilic monomer having an acidic group in this step is determined from the total monomer and the mixed solvent from the viewpoint of industrially increasing the productivity. The raw material is preferably at least 20% by weight, more preferably at least 30% by weight. In addition, from the viewpoint of uniform mixing during polymerization, the content is preferably 60% by weight or less, more preferably 50% by weight or less. Therefore, as a specific example of the range of the content, 20 to
It is preferably 60% by weight, more preferably 30 to 50% by weight.

The polymerization of the monomer is usually carried out in the presence of a polymerization initiator. As the polymerization initiator, commonly used known ones can be used. For example, azobis (2-methylpropionamidine) hydrochloride, azobis (2-imidazolin-2-yl) propane hydrochloride, azobis (2-methylpropionamide) dihydrate, azobis (4-cyanovaleric acid), etc. Water-soluble azo-based initiators; oil-soluble azo-based initiators such as azobisisobutyronitrile, azobisisovaleronitrile, azobiscyanopentanoic acid; ammonium persulfate, sodium persulfate, potassium persulfate, hydrogen peroxide, etc. Water-soluble peroxides; oil-soluble peroxides such as benzoyl peroxide and lauroyl peroxide; and redox initiators such as a mixed system of hydrogen peroxide and a ferric compound, and a mixed system of sodium bisulfite and oxygen. The initiator may be used alone or in combination, and is not particularly limited as long as it is soluble in a mixed solvent system.

The amount of the polymerization initiator used is, for example, 10
0.05 to 10 parts by weight per 0 parts by weight is preferable,
0.1 to 3 parts by weight is more preferable. The amount is preferably 0.05 part by weight or more from the viewpoint of reducing unreacted monomer, and is preferably 10 parts by weight or less from the viewpoint of industrially improving economic efficiency.

The polymerization temperature is appropriately selected depending on the type of the monomer, water-soluble solvent, initiator and the like used. For example, 30 to 150 ° C is preferable, and 50 to 120 ° C is more preferable. The temperature is preferably 30 ° C. or higher from the viewpoint of performing rapid polymerization, and is preferably 150 ° C. or lower from the viewpoint of suppressing thermal decomposition at a high temperature. Further, the polymerization may be carried out while performing the stepwise or continuous partial neutralization with an alkali agent as long as the phase is not separated during the polymerization. According to this aspect, it is possible to control the pH in the polymerization reaction system, and thereby, there is an advantage that it is possible to control the single reactivity and the copolymerization reactivity depending on the type of the monomer used. The time required for the polymerization reaction is not particularly limited, but is preferably 1 to 10 hours.

Step (B) In this step, the polymer solution is subjected to phase separation to remove the water-soluble solvent. The phase state of the polymer solution changes depending on the content of the three components of the polymer salt, water, and the water-soluble solvent, and when the content of these three components satisfies a specific range ratio, the liquid-liquid two-phase separation is performed. Since the state, that is, the phase separation state referred to in the present invention is formed, in order to form the phase separation state of the polymer solution, in the present invention, an alkali agent is added to the polymer solution and the acidity of the polymer is increased. Neutralize some or all of the groups.

FIG. 1 shows a triangular phase diagram of sodium polyacrylate (weight average molecular weight: about 6,800), water and isopropyl alcohol at 25 ° C. as an example showing the phase state of the polymer solution. Depending on the content of the three components, the phase state of the polymer solution is largely homogeneous (area A), liquid-liquid two-phase separation (area B), and solid-liquid state where the polymer is precipitated (area C). It becomes a three-phase state. These regions vary depending on the structure and molecular weight of the polymer and the type of alkali agent and water-soluble solvent. Therefore, a phase separation state can be formed by appropriately setting these conditions.

The phase-separated state in the present invention refers to a state in which a polymer-rich phase and a water-soluble solvent-rich phase are separated by adding an alkali agent to a polymer solution, and the following effects are achieved. I can do it. Looking at the ratio of water to the water-soluble solvent in each phase in this phase separation state, the ratio of water in the former phase (polymer rich phase) is higher than that of the mixed solvent, and the latter phase (water-soluble solvent concentrated phase) The proportion of the water-soluble solvent in phase) is higher than that of the mixed solvent. That is, a phase in which the concentration of the water-soluble solvent is high can be formed by phase separation of the polymer solution. Therefore, removing the water-soluble solvent from the polymer solution in such a state is more efficient than removing the water-soluble solvent from a homogeneous polymer solution in which the water-soluble solvent is uniformly present in the polymer solution. It becomes possible to remove the water-soluble solvent. As a result, the time required for removal can be reduced, and the energy can be reduced. Furthermore, since the continuous phase is a water-soluble solvent concentrated phase, foaming of the polymer solution is reduced in removing the water-soluble solvent compared to a homogeneous system, and the operability of the removal operation is improved. When the removing operation is performed under reduced pressure, the effect is particularly remarkable. Also from this point, the production method of the present invention is an advantageous production method for improving productivity and economy.

Specific examples of the alkaline agent used in this step include hydroxides of alkali metals and alkaline earth metals such as sodium hydroxide, potassium hydroxide, calcium hydroxide and magnesium hydroxide; monoethanolamine, diethanolamine And hydroxyl-containing organic amines such as triethanolamine, monoisopropanolamine, N-methylethanolamine and dimethylaminopropanol; morpholine, ammonia and the like. These may be used alone or in combination of two or more. Of these, sodium hydroxide and potassium hydroxide are preferred.

As a mode of adding the alkali agent, there is a mode in which the alkali agent is added as it is or continuously or stepwise as an aqueous solution. The amount of the alkali agent to be added is appropriately selected depending on the composition and molecular weight of the polymer, the type of the water-soluble solvent, and the ratio of the polymer, the water-soluble solvent and water.

As a method for removing the water-soluble solvent from the polymer solution in a phase-separated state, for example, a method of distilling the polymer solution under normal pressure or reduced pressure may be mentioned. Vacuum distillation is preferred over distillation at normal pressure. The distillation temperature is preferably from 20 to 120 ° C, more preferably from 40 to 100 ° C. The temperature is preferably 120 ° C. or lower from the viewpoint of suppressing coloring of the polymer solution, and 20 from the viewpoint of lowering the viscosity of the mixed solution and increasing the efficiency of removing the water-soluble solvent.
C. or higher is preferred.

In this step, the content of the polymer in the polymer solution is preferably maintained at 70% by weight or less, more preferably 60 to 20% by weight, and particularly preferably 50 to 30% by weight. From the viewpoint of suppressing a rise in viscosity of the polymer solution when removing the water-soluble solvent, the content is 70%.
% By weight or less, and 20% by weight from the viewpoint of production efficiency.
The above is preferred.

From the viewpoint of simplification of operation and economy, the removal operation may be performed while adding an alkali agent to the polymer solution. Apart from this, it is also possible to appropriately add water at the end of the polymerization, at the time of addition of the alkali agent or during this step, in order to maintain the phase separation state of the polymer solution.

A water-soluble polymer can be obtained through the steps (A) and (B) as described above. The weight-average molecular weight of the obtained water-soluble polymer is 1,000 to 5
It is preferably 0000, and more preferably 3,000 to 30,000. The weight average molecular weight is preferably 1,000 or more from the viewpoint of widening the phase separation region and effectively utilizing the phase separation effect. The weight average molecular weight is preferably 50,000 or less from the industrial viewpoint such as suppressing the viscosity increase during phase separation and the viewpoint of securing an appropriate viscosity. The weight average molecular weight was determined by gel permeation chromatography (GP
Measure according to C).

[0027]

EXAMPLES The weight average molecular weight of polymers and copolymers was GPC.
Was measured under the following conditions. The column is Tosoh Corporation G
4000PWXL + G2500PWXL was used. The eluent used was 0.2 M phosphate buffer (pH 7) / acetonitrile = 90/10 (volume ratio). Flow rate 1 mL /
And detection was performed at 210 nm (UV). The molecular weight standard is polyacrylic acid (American Pol)
ymer Standards Corp. Was used.

Example 1 314 g of ion-exchanged water and 623 g of isopropyl alcohol were placed in a reactor, and the temperature was raised to 80 ° C. while introducing nitrogen. Next, 775 of an 80% by weight aqueous solution of acrylic acid was stirred.
g, and 83 g of a 15% by weight aqueous sodium persulfate solution as a polymerization initiator were added dropwise from different dropping funnels over 4 hours to carry out a polymerization reaction. After completion of the dropwise addition, the mixture was aged at 80 ° C. for 2 hours, and then diluted by adding 404 g of ion-exchanged water.

The solvent removal operation was carried out by heating at 80 ° C. under reduced pressure while dropping 682 g of a 49% by weight aqueous sodium hydroxide solution over 4 hours, and distilling 871 g over 8 hours to give a polymer content of 40% by weight. A polymer solution was obtained. The average distillate distillation rate was 109 g / hour. From the first hour to the seventh hour of the solvent removing step, the polymer solution was in a liquid-liquid two-phase separation state, and almost no foaming was observed. The content of isopropyl alcohol in the fraction was 71% by weight, and the recovery of isopropyl alcohol was 98%, which was a high recovery. The molecular weight of the obtained polymer was about 6800 in weight average molecular weight. When the content of isopropyl alcohol contained in the polymer solution was measured while maintaining the liquid-liquid two-phase separation state, the content in the entire polymer solution was 24 to 2.3% by weight, The content in the concentrated phase of the water-soluble solvent was 50 to 70% by weight.

[0030]

[0031]

Comparative Example 1 314 g of ion-exchanged water and 623 g of isopropyl alcohol were placed in a reactor, and the temperature was raised to 80 ° C. while introducing nitrogen. Next, 775 of an 80% by weight aqueous solution of acrylic acid was stirred.
g, and 83 g of a 15% by weight aqueous sodium persulfate solution as a polymerization initiator were added dropwise from different dropping funnels over 4 hours to carry out a polymerization reaction. After completion of the dropwise addition, the mixture was aged at 80 ° C. for 2 hours, and then diluted by adding 404 g of ion-exchanged water.

The solvent removal operation was performed by heating the polymer solution obtained at 80 ° C. under reduced pressure without adding an alkali agent. As a result, when the average fraction distillation speed was 50 g / hour or more, the foaming was so severe that the solvent removal operation could not be performed. Further, the content of isopropyl alcohol in the fraction at the point of time when the distillate amount was 871 g was 61% by weight, and the recovery rate was as low as 85%. At this point, since the viscosity in the system had increased, 300 g of ion-exchanged water was added and the solvent was removed in the same manner to obtain a further 300 g of fraction. as a result,
The content of isopropyl alcohol in the total distilled amount of 1171 g was 52% by weight, and the recovery was 98%. This desolvation step required 24 hours. Also, the phase state at that time is
It was always in a uniform state. Thereafter, 682 g of a 49% by weight aqueous solution of caustic soda was added to the polymer solution to give a polymer content of 40%.
A weight percent polymer solution was obtained. The molecular weight of the obtained polymer was about 6800 in weight average molecular weight.

Comparative Example 2 84 g of ion-exchanged water and 700 g of isopropyl alcohol were charged into a reactor, and the temperature was raised to 85 ° C. while introducing nitrogen. Next, with stirring, a monomer mixture composed of 200 g of acrylic acid, 400 g of methyl acrylate and 400 g of butyl acrylate, and azobis-2-amidinepropane (Wako Pure Chemical V-50) 1.6 as a polymerization initiator. A 220% by weight aqueous solution was dropped from each dropping funnel over 4 hours to carry out a polymerization reaction. After completion of the dropwise addition, the mixture was aged at 85 ° C. for 2 hours, and then diluted with 1370 g of ion-exchanged water.

The solvent removal operation was performed by heating at 80 ° C. under reduced pressure while dropping 473 g of a 30% by weight aqueous ammonia solution over 4 hours. As a result, the average distillate distillation speed was 50
At more than g / hr, foaming was severe and operation was not possible.
The content of isopropyl alcohol in the distillate at the time of the distilling amount of 992 g was 60% by weight, and the recovery rate was 85%.
% Was low. At this point, since the viscosity in the system had increased, 327 g of ion-exchanged water was added and the solvent was removed in the same manner.
A 0% by weight polymer solution was obtained. At this time, total distillate volume 131
The content of isopropyl alcohol in 9 g is 52% by weight.
As a result, the recovery rate was 98%. This desolvation step required 26 hours. The phase state at that time was always a uniform state. The molecular weight of the obtained copolymer was about 8,000 in weight average molecular weight.

[0036]

According to the present invention, foaming during the removal of the water-soluble solvent is suppressed by adding an alkali agent to the polymer solution and phase-separating the polymer solution to remove the water-soluble solvent. Provided is a method for producing a water-soluble polymer with high productivity, which can efficiently remove a water-soluble solvent.

[Brief description of the drawings]

FIG. 1 is a triangular phase diagram of sodium polyacrylate, water, and isopropyl alcohol.

[Explanation of symbols]

 A homogeneous region B liquid-liquid two-phase separation region C solid-liquid region

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C08F 2/04-2/10

Claims (3)

(57) [Claims] In 1. A (A) water and a water-soluble solvent comprising a mixed solvent, by polymerizing a hydrophilic monomer having an acidic group, the polymer solution obtaining a containing a water-soluble polymer and, ( B) An alkali agent is added to the polymer solution obtained in the above step (A), and a polymer- rich phase and a water-soluble solvent-rich phase are added .
After phase separation into a liquid-liquid two-phase separation state, 20 to 1
By distillation at a distillation temperature of 20 ° C., preparation of the polymer solution from the aqueous solvent process of including water-soluble polymer to remove. (2) In step (B), claim 1 Symbol mounting of the process to remove the water-soluble solvent while maintaining the polymer content below 70% by weight of the polymer solution. Wherein the weight average molecular weight of the resulting water-soluble polymer is 1,000 to 50,000 according to claim 1 or 2 A process according.