JP4998727B2 - Method for producing unsaturated carboxylic acid polymer powder for thickening - Google Patents

Description

The present invention, less residual monomers in the polymer remain unreacted, a method of manufacturing a soluble increasing crosslinking type viscosity for carboxyl-containing polymer powder in water, an acrylic resin manufacturing technology Belongs to.

  Crosslinkable carboxylic acid group-containing polymer powders that are soluble in water are used in cosmetics such as creams, lotions, toothpastes, and shampoos, thickeners such as water-based paints, water-based adhesives, and sealants, and pharmaceutical patches and cooling It is used in various fields as an improvement in the formability of sheets, and further as an adhesion improver, an anti-settling agent for pigments and aggregates.

These water-soluble cross-linked carboxylic acid group-containing polymer powders, that is, water-soluble cross-linked polymer powders containing olefinic unsaturated carboxylic acids as main constituent monomers, must be prepared by precipitation polymerization. There are many.
For example, Japanese Patent Publication No. 35-8246, Japanese Patent Publication No. 52-6789, Japanese Patent Publication No. 59-80411, Japanese Patent Publication No. 59-232107, Japanese Patent Publication No. 63-295609. Detailed descriptions are well known in JP-A-1-217170, JP-A-2-22312, JP-A-2-258813, and German Publication 2927132.

In these precipitation polymerization processes, the polymer formed immediately after the start of polymerization becomes insoluble in the solvent used by the polymerization reaction, and the polymer is precipitated from the solvent and becomes a slurry.
By removing the solvent from the slurry-like reaction product, a powdery polymer powder can be obtained. The method for removing the solvent is generally performed in a vacuum dryer.

When the solvent is removed, the residual monomer is also considerably removed. For example, acrylic acid has a boiling point of 141 ° C. at normal pressure and is not easy to reduce by drying under reduced pressure. In the obtained polymer powder such as polyacrylic acid, a considerable amount of monomer is usually present.
However, since acrylic acid and the like are irritating to the skin, when using polyacrylic acid or the like in which acrylic acid or the like remains in pharmaceuticals, cosmetics or cooling sheets, including this polyacrylic acid, There is a strong demand for reduction of monomers remaining in the polymer powder.

As a method for reducing the residual monomer, for example, Japanese Patent Application Laid-Open No. 63-295609 (Patent Document 1) discloses a method for producing a polycarboxylic acid having a residual monomer of 0.2% by weight or less. Has been.
Specifically, the crosslinking type weight in which the residual monomer is reduced by neutralizing 1% by weight or more of carboxylic acid of an acid monomer such as acrylic acid and further using a mixed solvent with alkyl acetate as a polymerization solvent. Combined powder is obtained.

However, in this method for producing a polycarboxylic acid, it is essential to remove the water generated by neutralization. If the water is not sufficiently removed, various problems occur.
That is, the polymer precipitated in a state where a trace amount of water remains is easily aggregated, and the aggregate easily adheres to the wall of the reaction kettle and the stirring blade, and makes the slurry viscosity of the reaction mixture very high. Or
As a result, the particle size of the final product powder becomes large, or in some cases it cannot be pulverized and powdered, or due to deposits, unreacted monomers increase due to a decrease in heat conduction, It causes problems such as variations in quality due to overheating and a decrease in yield.
JP 63-295609 A (Claims)

  In view of the present situation, the inventors of the present invention can easily obtain a water-soluble crosslinking type thickening carboxylic acid group-containing polymer powder soluble in water and having reduced residual monomers. We examined to provide.

As a result, when the acrylic acid polymer powder for thickening is produced by precipitation polymerization, after removing the solvent by a conventional method, further thickening is obtained by heating at a specific temperature and heating time. It has been found that the monomer remaining in the acrylic acid polymer powder for use can be reduced, and the present invention has been completed.

但し、式中Ｙは加熱時間（時間）を、Ｔは加熱温度（℃）を表す。
Ａ，Ｂは定数で、Ａ＝４，２１８、Ｂ＝−１０．２２である。 That is, the invention according to claim 1 of the present invention is
A monomer mainly composed of an olefinic unsaturated carboxylic acid having 3 to 5 carbon atoms is polymerized using a radical initiator in a solvent in which the monomer is dissolved but the polymer is not dissolved,
By separating and heating the deposited slurry-like polymer, causes the distillate the solvent,
Even after solvent distillation is complete,
Continue heating while flowing an inert gas into and out of a dryer under a reduced pressure of 0.02 MPa or less under the conditions of heating temperature and time adjusted based on the following formulas 1 and 2. To obtain a polymer powder having a 0.2% by weight neutralized aqueous solution viscosity of 5,000 mPa · s or more and a residual monomer of 1,000 ppm or less. A method for producing a coalesced powder.

In the formula, Y represents the heating time (hour), and T represents the heating temperature (° C.).
A and B are constants, and A = 4, 218 and B = -10.22.

The invention according to claim 2 of the present invention is
In the manufacturing method of the unsaturated carboxylic acid-type polymer powder for thickening of Claim 1,
The monomer is
70-100 mass% of the structural component is occupied with the olefin type unsaturated carboxylic acid which has 3-5 carbon atoms.

The invention according to claim 3 of the present invention is
In the manufacturing method of the unsaturated carboxylic acid-type polymer powder for thickening of Claim 1 or 2,
The monomer is
It is characterized by containing a crosslinking agent as a constituent component.

The invention according to claim 4 of the present invention is
In the manufacturing method of the unsaturated carboxylic acid-type polymer powder for thickening of Claim 3,
The crosslinking agent is
It is characterized by being tetraallyloxyethane, pentaerythritol tetraallyl ether, pentaerythritol triallyl ether, pentaerythritol diallyl ether, diethylene glycol diallyl ether, trimethylolpropane triallyl ether, trimethylolpropane diallyl ether or triallyl isocyanurate Is.

The invention according to claim 5 of the present invention is
In the manufacturing method of the unsaturated carboxylic acid-type polymer powder for thickening in any one of Claims 1-4,
The solvent is
It consists of a single solvent selected from aliphatic hydrocarbons having 4 to 12 carbon atoms.

The invention according to claim 6 of the present invention is
In the method for producing an unsaturated carboxylic acid polymer powder for thickening according to claim 5,
The aliphatic hydrocarbon is
It is n-hexane or cyclohexane.

The invention according to claim 7 of the present invention is
In the manufacturing method of the unsaturated carboxylic acid-type polymer powder for thickening in any one of Claims 1-6 ,
The inflow of the inert gas is
This is characterized in that the inert gas flows in an amount of 0.1 to 20 times the capacity of the dryer per hour.

According to the method for producing the unsaturated carboxylic acid polymer powder for thickening of the present invention, even after the completion of the distillation of the solvent, under the condition of the heating temperature and time adjusted based on the specific conditions, 0.02 MPa By continuing heating while flowing an inert gas into and out of a dryer under the following reduced pressure, the amount of unreacted monomer remaining in the polymer is increased to 1000 ppm or less. Unsaturated carboxylic acid polymer powder can be easily obtained.
Furthermore, since the resulting polymer has a low residual monomer content of 1,000 ppm or less, it has been widely used as a polymer for thickening drugs, cosmetics, and cooling sheets that have been limited in use. An excellent effect that can be achieved.

The unsaturated carboxylic acid polymer for thickening in the present invention is obtained by polymerizing a monomer mainly composed of an olefinic unsaturated carboxylic acid having 3 to 5 carbon atoms.
Examples of the olefinic unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid, itaconic acid, crotonic acid, and salts thereof.
These monomers preferably account for 70 to 100% by mass of the total amount of monomers to be polymerized.

Among these, as the unsaturated carboxylic acid, acrylic acid and methacrylic acid are particularly preferable because they have good performance as a thickener for the resulting polymer.
Acrylic acid is easily available from the market and is more preferable.

In the unsaturated carboxylic acid polymer powder for thickening of the present invention, other vinyl monomers other than the olefinic unsaturated carboxylic acid having 3 to 5 carbon atoms are also in the range of less than 0 to 30% by mass. What constitutes a constituent monomer is also included.
Although it differs depending on the type and amount of composition, almost the same effect can be obtained.

  Specific examples of other vinyl monomers include styrene, alkyl vinyl ether, vinylidene chloride, acrylic acid esters, methacrylic acid esters, acrylamides, methacrylamides, N-vinylformamide, N-vinylacetamide, Examples thereof include unsaturated sulfonic acids such as vinyl acetate, vinyl pyrrolidone, acrylonitrile, methacrylonitrile, 2-acrylamido-2-methylpropane sulfonic acid, (meth) allyl sulfonic acid, styrene sulfonic acid, and derivatives thereof.

  Specific examples of acrylic esters and methacrylic esters include (meth) acrylic esters such as methyl, ethyl, butyl, isobutyl, octyl, lauryl, stearyl acrylate, 2-methoxyethyl acrylate, 2-ethoxy Examples include (meth) acrylic acid esters having an ether bond such as ethyl acrylate, hydroxy group-containing monomers such as 2-hydroxyethyl acrylate and 2-hydroxypropyl methacrylate, and glycidyl methacrylate.

  Specific examples of acrylamides and methacrylamides include acrylamide, methacrylamide, dimethylacrylamide, diethylacrylamide, dimethylaminopropylacrylamide, and isopropylacrylamide.

  Furthermore, macromonomers such as terminal methacrylate polymethyl methacrylate, terminal styryl polymethyl methacrylate, terminal methacrylate polystyrene, terminal methacrylate polyethylene glycol, and terminal methacrylate acrylonitrile styrene copolymer can also be used.

Similarly, maleic acid, fumaric acid, itaconic acid, and esters thereof can be used.
If necessary, trimethoxy vinyl silane, tri et butoxyethyl vinyl silanes, also including γ- methacryloxypropyl trimethoxysilane can be used.

In the present invention, a crosslinking agent is also used as a constituent monomer.
Examples of the cross-linking agent include cross-linkable monomers selected from polyalkenyl polyether monomers, polyvalent vinyl monomers, or mixtures thereof.

  Specific cross-linkable monomers include tetraallyloxyethane, pentaerythritol tetraallyl ether, pentaerythritol triallyl ether, pentaerythritol diallyl ether, diethylene glycol diallyl ether, trimethylolpropane triallyl ether, trimethylolpropane diallyl ether or And triallyl isocyanurate.

  The amount of the crosslinkable monomer used is determined in consideration of the water solubility of the unsaturated carboxylic acid polymer to be obtained and its solution properties, particularly the thickening properties, but with respect to 100 parts by mass of the total amount of monomers. 0.1 to 2.0 parts by mass is preferable.

Examples of the radical initiator used in the production method of the present invention include compounds selected from peroxides, azo initiators, and the like, or mixtures thereof.
The amount used is preferably 0.001 to 2.00 parts by mass, and more preferably 0.005 to 1.0 parts by mass with respect to 100 parts by mass of the total amount of monomers.

  Specific examples of the peroxide include benzoyl peroxide, lauroyl peroxide, t-butyl hydroperoxide, and di (2-ethylhexyl) peroxydicarbonate.

  Specific examples of the azo initiator include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile, 4,4′-azobis-4-cyanovaleric acid, 2,2′-azobis (2-amidinopropane) dihydrochloride and the like.

The solvent in the production method of the present invention is a solvent that dissolves the unsaturated carboxylic acid monomer but does not dissolve the polymer.
Specific solvents include those shown by the above prior art, but from ketones, esters, alcohols, aliphatic hydrocarbons having 4 to 12 carbon atoms, and aromatic hydrocarbons having 6 to 8 carbon atoms. Examples thereof include at least one selected solvent.

  As the solvent to be used, it is preferable to avoid mixing and using the recovered solvent from the viewpoint of reuse of the recovered solvent, and a single solvent selected from aliphatic hydrocarbons having 4 to 12 carbon atoms is used. Is preferred.

The use of polar solvents such as ketones, esters and alcohols alone is likely to cause a chain transfer reaction with a growing radical during polymerization of an unsaturated carboxylic acid, resulting in a low molecular weight polymer, resulting in poor viscosity increase. It is preferable to avoid it because it tends to be a polymer.

  Furthermore, in aromatic hydrocarbon solvents such as benzene, toluene, xylene, etc., since a trace amount of solvent remains in the obtained water-soluble crosslinked copolymer powder, the use of these solvents should be avoided. preferable.

  From the above, in the present invention, among the above aliphatic hydrocarbons, n-hexane or cyclohexane is useful because it can be obtained at a low price from the market.

  In the production method of the present invention, a surfactant may be used to reduce the viscosity of the polymerization slurry.

In the precipitation polymerization in the production method of the present invention, the constituent monomers may be divided into two or more, sequentially charged in a polymerization vessel, and sequentially or dividedly polymerized.
Alternatively, the cross-linking agent and the radical initiator may be polymerized by split charging each time two or more times.

The polymerization temperature in the production method of the present invention is preferably 50 ° C. or higher and the boiling point or lower of the solvent system used under atmospheric pressure.
When the polymerization temperature is less than 50 ° C., decomposition of the radical initiator does not proceed sufficiently, and it is preferable to avoid it because it takes too much time for the polymerization reaction.

The addition amount of the polymerization temperature and the radical initiator, powders of unsaturated carboxylic acid-based polymer obtained Oite to the present invention, in a thickening, its 0.2 mass% neutralized aqueous solution viscosity, 5 Therefore , it is necessary to set so as to obtain a polymer having such a viscosity.

When the pH of an aqueous solution in which 0.2% by mass of a water-soluble crosslinked copolymer powder is uniformly dissolved is in the range of 6 to 9, B-type viscometer).
In the case of carboxylic acid, neutralize with caustic soda, caustic potash, sodium carbonate, aqueous ammonia, triethylamine, monoethanolamine, diethanolamine, triethanolamine, 2-amino-2-methyl-1-propanol, and adjust the pH to 6-9. It measures in the range of.

The polymerization process, typically, have preferred to polymerize after removal of the water by refluxing the solvent and the like used.
In the polymerization, it is also preferable to perform polymerization while lowering the reflux temperature of the solvent by applying some pressure reduction under reflux conditions to suppress bumping of the solvent due to the generation of polymer aggregates.
Conversely, polymerization is possible even under self-pressurization in a closed container or under forced pressurization.

  Furthermore, in order to reduce the unreacted monomer and, in turn, to reduce the residual monomer in the resulting polymer, after the main polymerization reaction is completed and the slurry-like reaction product is obtained, radicals are obtained. It is preferable to take measures to polymerize and reduce unreacted monomers by adding (following) an initiator and heating.

In these precipitation polymerization processes, the polymer formed immediately after the start of the polymerization becomes insoluble in the solvent used as the medium, and the polymer is precipitated in the solvent to form a slurry.
By removing the solvent from the slurry-like polymerization reaction product, a powdery polymer can be obtained.

It is preferable that the conversion ratio of the monomer to the polymer is 92% by mass or more in the slurry state before the solvent removal because the monomer remaining in the polymer powder after the solvent removal is reduced. More preferably, it is 95 mass% or more.

The method for removing the solvent can be performed with a normal dryer such as a ventilator, but is generally performed with a vacuum dryer.
The vacuum dryer preferably has a stirring blade inside, and a horizontal type or a nauter type is used.
A pressure filtration type vacuum dryer can also be used. However, the filter medium is clogged, so that the replacement of the filter medium is complicated.
Furthermore, when replacing the filter medium, there is a risk of fire due to the remaining solvent, which is not a preferable method.

The removal of the solvent is performed by adjusting the external temperature and internal pressure according to the equipment used.
For example, acrylic acid has a boiling point of 141 ° C. at normal pressure and can be reduced by vacuum drying, which is easy to remove the solvent. In a heating condition for removing the solvent, for example, in a processing condition such as drying for several hours at 90 to 120 ° C. in a normal ventilation dryer, the polymer with a small amount of residual monomer is I can't get it.

Therefore, by solvent removal operation, even after the solvent is no longer distilled, to remove the residual monomer in the polymer powder, it is necessary to continue heating.
As heating conditions, a treatment for 3 to 50 hours is preferable in a state where the external temperature is 90 to 125 ° C. and the internal pressure is 0.02 MPa or less.

  Furthermore, in order to reliably lower the residual monomer in the polymer powder, it is more preferable to perform the treatment at an external temperature of 100 to 118 ° C. and an internal pressure of 0.015 MPa or less.

In particular, the heat treatment is performed on the basis of the heating temperature and time satisfying the formula 1 and formula 2, removing the residual monomers can be efficiently performed.

Furthermore, in order to reduce the residual monomer, heat treatment is performed in an air flow atmosphere, specifically, an inert gas having a capacity of 0.1 to 20 times the capacity of the dryer per hour is introduced into the dryer. It is preferable to heat-treat the dryer with an air flow atmosphere while maintaining the internal pressure .
In addition, as the air flow atmosphere, for example, the internal pressure of the dryer is reduced to 0.02 MPa or less, and then returned to the normal pressure of 0.1013 MPa due to the inflow of dry nitrogen in a short time, and then the pressure is increased again. A method of heating while repeating the treatment is also preferable.

In the heating for reduction removal and residual monomers of the solvent, the treatment at 125 ° C. or higher temperatures may exceed the glass transition temperature of the unsaturated carboxylic acid-based polymer, as a result, dryer It is preferable to avoid this because a lump can be formed and this can cause damage to the dryer as well as the quality of the polymer powder.

By such heat treatment, the residual monomer in the unsaturated carboxylic acid polymer prepared by precipitation polymerization can be surely reduced.
Accordingly, the residual monomer can be made 1,000 ppm or less .

The method for measuring the residual monomer in this invention is based on gas chromatography or liquid chromatography, not on titration analysis with potassium iodide-sodium thiosulfate.
In the titration analysis method using potassium iodide-sodium thiosulfate, since the unreacted vinyl group derived from the crosslinking agent is measured, the true residual monomer amount cannot be determined.

  In this invention, the measurement method of the residual monomer by gas chromatography or liquid chromatography and the measurement method of 2% neutralization viscosity were performed by the following methods.

<Residual monomer measurement by gas chromatography>
About 1.2 g of unsaturated carboxylic acid polymer powder is taken into a 50 ml volumetric flask and accurately weighed, and then about 30 ml of methyl isobutyl ketone is added.
Next, 2 ml of an internal standard solution (a solution in which methyl isobutyl ketone is added to 1.0 g of butyl acetate to make a total volume of 100 ml) is added accurately, and then 4 ml of methanol is added accurately.
Then, it is added with methyl isobutyl ketone so that the total amount is accurately 50 ml, shaken well, and then allowed to stand for 15 minutes or more.
After standing, the mixture is filtered through a membrane filter having a pore size of 0.50 μm, and 1 μl of the filtrate is collected and measured with a gas chromatograph.
<Gas chromatography measurement conditions>
Instrument: GC-2014 (gas chromatograph)
Gas phase: Pure nitrogen (purity 99.9995% or more)
Column: Shinwa Kagaku ULBON HR-20M (PEG-20M equivalent) 0.25 mmI. D. × 25m Film thickness 0.5μm
INJECTION: 160 ° C
FID: 250 ° C
Column initial temperature: 70 ° C. 5.5 min
Column heating rate: 20 ° C / min
Column final temperature: 180 ° C. 5.0 min
Column flow rate: 1.3 ml / min

<Measurement of residual monomer by liquid chromatography>
Take 0.03 g of unsaturated carboxylic acid polymer powder in a 50 ml Erlenmeyer flask, add 20 ml of mobile phase, and stir with a magnetic stirrer for 2 hours.
After stirring, the solution dissolved with ultrasonic waves for 1 hour was filtered through a membrane filter having a pore size of 0.50 μm, and 20 μl of the filtrate was collected and measured with a high performance liquid chromatograph.
<Liquid chromatography measurement conditions>
Instrument name: JASCO high performance liquid chromatography set Detector: UV / VIS detector UV-970
Column: inertsil ODS-3 4.6 mmφ × 150 mm (GL Science Co., Ltd.)
Pre-column: Cartridge guard column Column temperature: 40 ° C
Eluent: 20 mM H ₂ KPO ₄ · H ₂ O (90) / acetonitrile (10)
Flow rate: 1.0 ml / min
Injection volume: 20 μl
Detection wavelength: UV-210nm

<0.2% neutralized viscosity>
To a 1000 ml beaker, 200 g of ion-exchanged water is accurately weighed, and 0.4 g of accurately weighed polymer powder is gradually added while stirring with a magnetic stirrer.
Stirring is continued slowly after adding the whole amount, and when it is confirmed that the whole amount of the polymer powder is dissolved, 0.4 ml of 10N-NaOH aqueous solution is added accurately and stirred well.
When it was confirmed that the pH was in the range of 6.5 to 8.5, the viscosity at a temperature of 25 ± 1 ° C. was measured using a BH viscometer (rotor number: No. 6, rotation speed: 20 rpm, measurement time: 30 seconds later) ) To measure.

<Comparative Example 1>
Into a 250 L polymerization vessel made of SUS304 equipped with a dehydrator, 75 kg of n-hexane, 15 kg of acrylic acid and 105 g of pentaerythritol triallyl ether were added, and stirring was started at a rotational speed of 60 rpm.
The external temperature was set to 75 ° C. and the temperature was raised. After maintaining the reflux state for about 1 hour, the temperature was cooled to 40 ° C.
When the moisture of the mixed liquid before reflux was measured with a Karl Fischer moisture meter, 750 ppm of moisture was contained, but after 1 hour of reflux, the moisture was reduced to 150 ppm.
Nitrogen gas was blown into the liquid at a flow rate of 300 L / hr for about 1 hour, and then the temperature was raised. The external temperature was adjusted so that the internal temperature was 63 to 65 ° C., and 3 g of 2,2′-azobis (2,4-dimethylvaleronitrile) was added after the internal temperature was stabilized.
The cloudiness was confirmed after 10 minutes, and the internal temperature was controlled at 63 to 66 ° C. for 10 hours after the cloudiness was confirmed.
10 hours after cloudiness, 15 g of 2,2′-azobis (2,4-dimethylvaleronitrile) was added (tracked), the internal temperature was kept at 68 ° C. for 4 hours, and then cooled to obtain a slurry-like reaction product Got.
The number of rotations of stirring was appropriately increased depending on the viscosity of the slurry. The nitrogen input was reduced to 20 L / hr after confirming cloudiness.

The residual acrylic acid in the slurry-like reaction product was measured by gas chromatography, and the polymerization conversion rate of acrylic acid was calculated to be 96.7% by mass.
About 8 kg of this slurry was put into a horizontal dryer having a capacity of 20 L, and the solvent and residual monomer were removed at an external temperature of 80 ° C. and normal pressure.
When the solvent distillate decreased, the internal pressure was gradually reduced.
When the internal pressure is 0.02 MPa or less and solvent distillation is not observed, the external temperature is raised to 90 ° C. or more and 125 ° C. or less to confirm that the solvent distillation is completely stopped, and the necessary amount of reaction The product (polymer powder) was collected, the residual monomer amount and 0.2% neutralized viscosity (Brookfield) were measured, and the results are shown in Table 1.

< Reference Examples 1-3>
The reaction product (polymer powder) from which the solvent was not distilled in Comparative Example 1 was collected, and heating was continued under the conditions shown in Table 1.
The internal pressure at that time was maintained at 0.015 MPa or less.
The amount of residual monomer and 0.2% neutralized viscosity (Brookfield) of the sample obtained for a predetermined time were measured, and the results are shown in Table 1.

<Comparative example 2>
60 kg of cyclohexane, 15 kg of acrylic acid, 0.3 kg of vinyl acetate, 75 g of tetraallyloxyethane and 150 g of sorbitan monooleate were charged into a 250 L polymerization vessel made of SUS304 equipped with a dehydrator, and then rotated at 50 rpm. Stirring was started.
The external temperature was set to 85 ° C. and the temperature was raised. After maintaining the reflux state for about 1 hour, the temperature was cooled to 40 ° C.
When the moisture of the mixed liquid before reflux was measured with a Karl Fischer moisture meter, it contained 330 ppm of moisture, but after 1 hour of reflux, the moisture was reduced to 120 ppm.
Nitrogen gas was blown into the liquid at a flow rate of 300 L / hr for about 1 hour, and then the temperature was raised.
The outside temperature was adjusted so that the inside temperature was 68 to 70 ° C., and after the inside temperature was stabilized, 4.5 g of 2,2′-azobisbutyronitrile was added.
The cloudiness was confirmed after 8 minutes, and the internal temperature was controlled at 68 to 72 ° C. for 8 hours after the cloudiness was confirmed.
8 hours after cloudiness, 15 g of 2,2′-azobisbutyronitrile was added (follow-up), and the reflux temperature was maintained at 80 ° C. for 4 hours, followed by cooling to obtain a slurry-like reaction product. It was.
The number of rotations of stirring was appropriately increased depending on the viscosity of the slurry. The nitrogen input amount, after confirming the cloudy, dropped to 20L / hr.

The residual acrylic acid of the slurry-like reaction product was measured by gas chromatography, was calculated polymerization conversion rate of acrylic acid was 95.7 wt%.
About 8 kg of this slurry was put into a horizontal dryer having a capacity of 20 L, and the solvent and residual monomer were removed at an external temperature of 90 ° C. and normal pressure.
When the solvent distillate decreased, the internal pressure was gradually reduced.
When the internal pressure is 0.02 MPa or less and solvent distillation is not observed, the external temperature is raised to 95 ° C. or more and 125 ° C. or less to confirm that the solvent distillation is completely stopped, and the necessary amount of reaction The product (polymer powder) was collected, the residual monomer amount and 0.2% neutralized viscosity (Brookfield) were measured, and the results are shown in Table 2.

< Reference Examples 4 to 6>
The reaction product (polymer powder) from which the solvent was not distilled in Comparative Example 2 was collected, and heating was continued under the conditions shown in Table 2.
The internal pressure at that time was maintained at 0.015 MPa or less.
Samples obtained at a predetermined time were measured for residual monomer amount and 0.2% neutralized viscosity (Brookfield). The results are shown in Table 2.

<Example 1>
The reaction product (polymer powder) in which the solvent was no longer distilled in Comparative Example 2 was collected, and under the conditions shown in Table 2, the heating was continued, and immediately after the solvent was no longer distilled, Drying of 10 L / hr of dry nitrogen was introduced from the bottom of the dryer, and drying was continued under a nitrogen stream. The internal pressure was maintained at 0.025 MPa or less even during nitrogen inflow.
Samples obtained at a predetermined time were measured for residual monomer amount and 0.2% neutralized viscosity (Brookfield). The results are shown in Table 2.

<Comparative Example 3>
After charging 60 kg cyclohexane, 10 kg ethyl acetate, 15 kg acrylic acid, 75 g vinyl acetate, 105 g triallyl isocyanurate and 7.5 g sodium carbonate into a 250 L polymerization kettle made of SUS304 equipped with a dehydrator Stirring was started at a rotation speed of 50 rpm.
The external temperature was set to 85 ° C., the temperature was raised, and 10 kg of the solvent was cut accurately, and then the reflux state was maintained for about 1 hour, followed by cooling to 40 ° C.
When the moisture of the mixed liquid before the solvent cut was measured with a Karl Fischer moisture meter, it contained 1030 ppm of moisture, but after 1 hour of refluxing, the moisture was reduced to 270 ppm.
Nitrogen gas was blown into the liquid at a flow rate of 300 L / hr for about 1 hour, and then the temperature was raised.
The external temperature was adjusted so that the internal temperature was 68 to 70 ° C., and 7.5 g of 2,2′-azobisbutyronitrile was added after the internal temperature was stabilized.
The cloudiness was confirmed after 10 minutes, and the internal temperature was controlled at 68 to 72 ° C. for 10 hours after the cloudiness was confirmed.
10 hours after cloudiness, 60 g of 2,2′-azobis (2,4dimethylvaleronitrile) was added (follow-up), and the external temperature was maintained at 80 ° C. for 5 hours, then cooled and slurried. A reaction product was obtained.
The number of rotations of stirring was appropriately increased depending on the viscosity of the slurry. The nitrogen input amount, after confirming the cloudy, dropped to 20L / hr.

The residual acrylic acid in the slurry-like reaction product was measured by gas chromatography, and the polymerization conversion rate of acrylic acid was calculated to be 97.7% by mass.
About 8 kg of this slurry was put into a horizontal dryer having a capacity of 20 L, and the solvent and residual monomer were removed at an external temperature of 90 ° C. and normal pressure.
When the solvent distillate decreased, the internal pressure was gradually reduced.
When the internal pressure is 0.02 MPa or less and solvent distillation is not observed, the external temperature is raised to 95 ° C. or more and 125 ° C. or less to confirm that the solvent distillation is completely stopped, and the necessary amount of reaction The product (polymer powder) was collected and the residual monomer amount and 0.2% neutralized viscosity (Brookfield) were measured. The results are shown in Table 3.

<Reference Examples 7 to 9 >
The reaction product (polymer powder) in which the solvent was not distilled out in Comparative Example 3 was collected, and heating was continued under the conditions shown in Table 3.
The internal pressure at that time maintained 0.015 or less MPa.
Samples obtained at a predetermined time were measured for residual monomer amount and 0.2% neutralized viscosity (Brookfield). The results are shown in Table 3.

<Example 2 >
The reaction product (polymer powder) in which the solvent was no longer distilled in Comparative Example 3 was collected, and under the conditions shown in Table 3, the heating was continued, and immediately after the solvent was no longer distilled, 50 L / hr of dry nitrogen was introduced from the bottom of the dryer, and drying was continued under a nitrogen stream. The internal pressure was maintained at 0.03 MPa or less even during nitrogen inflow.
Samples obtained at a predetermined time were measured for residual monomer amount and 0.2% neutralized viscosity (Brookfield). The results are shown in Table 3.

<Comparative example 4>
After charging 67.5 kg of n-hexane, 15 kg of acrylic acid, and 90 g of pentaerythritol triallyl ether into a 250 L polymerization vessel made of SUS304 equipped with a dehydrator, stirring was started at a rotation speed of 50 rpm. .
The external temperature was set to 75 ° C. and the temperature was raised. After maintaining the reflux state for about 1 hour, the temperature was cooled to 40 ° C.
When the moisture of the mixed liquid before reflux was measured with a Karl Fischer moisture meter, it contained 1030 ppm of moisture, but after 1 hour of reflux, the moisture was reduced to 270 ppm.
Nitrogen gas was blown into the liquid at a flow rate of 300 L / hr for about 1 hour, and then the temperature was raised.
The external temperature was adjusted so that the internal temperature was 64 to 66 ° C., and 4.5 g of dilauryl peroxide was added after the internal temperature was stabilized.
The cloudiness was confirmed after 15 minutes, and the internal temperature was controlled at 68 to 72 ° C. for 15 hours after the cloudiness was confirmed.
15 hours after white turbidity, 15 g of 2,2′-azobisisobutyronitrile was added (tracked), the external temperature was kept at 75 ° C. for 4 hours and then cooled and cooled to obtain a slurry-like reaction product Got.
The number of rotations of stirring was appropriately increased depending on the viscosity of the slurry. The nitrogen input amount, after confirming the cloudy, dropped to 20L / hr.

The residual acrylic acid in the slurry-like reaction product was measured by gas chromatography, and the conversion rate of acrylic acid was calculated to be 98.3% by mass.
About 8 kg of this slurry was put into a horizontal dryer having a capacity of 20 L, and the solvent and residual monomer were removed at an external temperature of 90 ° C. and normal pressure. When the solvent distillate decreased, the internal pressure was gradually reduced.
When the internal pressure is 0.02 MPa or less and solvent distillation is not observed, the external temperature is raised to 95 ° C. or more and 125 ° C. or less to confirm that the solvent distillation is completely stopped, and the required amount of reaction The product (polymer powder) was collected and the amount of residual monomer and 0.2% neutralized viscosity (Brookfield) were measured. The results are shown in Table 4.

< Reference Examples 10 and 11 >
The reaction product (polymer powder) in which the solvent was not distilled in Comparative Example 4 was collected, and heating was continued under the conditions shown in Table 4.
The internal pressure at that time was maintained at 0.015 MPa or less.
Samples obtained at a predetermined time were measured for residual monomer amount and 0.2% neutralized viscosity (Brookfield). The results are shown in Table 4.

<Example 3 >
The reaction product (polymer powder) in which the solvent was no longer distilled in Comparative Example 4 was collected, and under the conditions shown in Table 4, the heating was continued, and immediately after the solvent was no longer distilled, Drying was continued by injecting 20 L / hr of dry nitrogen from the bottom of the dryer. The internal pressure at that time was maintained at 0.015 MPa or less.
Samples obtained at a predetermined time were measured for residual monomer amount and 0.2% neutralized viscosity (Brookfield). The results are shown in Table 4.

<Examples 4 and 5 >
In Comparative Example 4, the reaction product (polymer powder) from which distillation of the solvent ceased was collected, and 3 to ⁵ kg of powder per 1 m ² was spread on a sheet made of fluororesin as uniform as possible. Under the indicated conditions, the heating was continued, and immediately after the solvent was no longer distilled, drying was continued by flowing dry nitrogen from the bottom of the dryer under the conditions shown in Table 4.
Even during the inflow of nitrogen, the internal pressure was maintained at 0.03 MPa or less.
Samples obtained at a predetermined time were measured for residual monomer amount and 0.2% neutralized viscosity (Brookfield). The results are shown in Table 4.

The water-soluble cross-linked carboxylic acid group-containing polymer powder obtained in the present invention is composed of thickeners such as water-based paints, water-based adhesives, and sealing agents, and anti-settling agents for pigments and aggregates. Ru is used in various fields as such.
Furthermore, due to the low amount of residual monomers, thickening agents such as cosmetics such as creams, lotions, toothpastes, shampoos, etc. for human skin, improvement in the formability of pharmaceutical patches and cooling sheets, and It can be widely used as an adhesion improver and can be used in various fields.

Claims (7)

A monomer mainly composed of an olefinic unsaturated carboxylic acid having 3 to 5 carbon atoms is polymerized using a radical initiator in a solvent in which the monomer is dissolved but the polymer is not dissolved,
By separating and heating the deposited slurry-like polymer, causes the distillate the solvent,
Even after solvent distillation is complete,
Continue heating while flowing an inert gas into and out of a dryer under a reduced pressure of 0.02 MPa or less under the conditions of heating temperature and time adjusted based on the following formulas 1 and 2. To obtain a polymer powder having a 0.2% by weight neutralized aqueous solution viscosity of 5,000 mPa · s or more and a residual monomer of 1,000 ppm or less. A method for producing a coalesced powder.

In the formula, Y represents the heating time (hour), and T represents the heating temperature (° C.).
A and B are constants, and A = 4, 218 and B = -10.22. The monomer is
The unsaturated carboxylic acid heavy for thickening according to claim 1, wherein 70 to 100% by mass of the constituent component is occupied by an olefinic unsaturated carboxylic acid having 3 to 5 carbon atoms. A method for producing a coalesced powder. The monomer is
The method for producing an unsaturated carboxylic acid polymer powder for thickening according to claim 1 or 2, wherein the composition contains a crosslinking agent as a constituent component. The crosslinking agent is
It is characterized by being tetraallyloxyethane, pentaerythritol tetraallyl ether, pentaerythritol triallyl ether, pentaerythritol diallyl ether, diethylene glycol diallyl ether, trimethylolpropane triallyl ether, trimethylolpropane diallyl ether or triallyl isocyanurate The manufacturing method of the unsaturated carboxylic acid-type polymer powder for thickening of Claim 3. The solvent is
The unsaturated carboxylic acid polymer powder for thickening according to any one of claims 1 to 4, comprising a single solvent selected from aliphatic hydrocarbons having 4 to 12 carbon atoms. Manufacturing method. The aliphatic hydrocarbon is
It is n-hexane or cyclohexane, The manufacturing method of the unsaturated carboxylic acid-type polymer powder for thickening of Claim 5 characterized by the above-mentioned. The inflow of the inert gas is
The unsaturated carboxylic acid system for thickening according to any one of claims 1 to 6, wherein the inert gas flows in an amount of 0.1 to 20 times the capacity of the dryer per hour. Production method of polymer powder.