JP4793158B2 - Method for producing acrylic acid polymer - Google Patents

Description

  The present invention relates to a method for producing an acrylic acid polymer. More specifically, the present invention relates to a method for producing an acrylic acid polymer that reuses a reaction solvent.

Various polymers are produced using a reaction solvent containing a water-soluble alcohol such as isopropanol.
For example, Patent Document 1 discloses a composition containing a polymer using acrylic acid or the like as a ceramic dispersant made of silicon carbide or the like, and a method for producing the same.
Patent Document 2 discloses a cleaning agent containing a polymer made of acrylic acid or the like obtained using a reaction solvent containing a water-soluble alcohol such as isopropanol, and an anionic surfactant.
Patent Document 3 discloses a maleate copolymer produced in an aqueous medium as an aqueous dispersant such as a pigment, clay, salt, metal ore, and oxide.
Patent Document 4 discloses a method of polymerizing in a solvent containing isopropanol using a specific chain transfer agent.
Patent Document 5 discloses a method of polymerizing a vinyl monomer in a solvent containing isopropanol in the presence of a vinyl copolymer having a specific average particle size.

JP 7-171370 A JP 7-216388 A JP-A-9-52040 JP-A-9-95501 Japanese Patent Laid-Open No. 10-265636

In the production of a resin or polymer using a water-soluble alcohol as described above, various methods for improving production cost, production efficiency, and the like have been studied.
For example, when a water-soluble alcohol such as isopropanol is used as a reaction solvent and a monomer containing acrylic acid is polymerized, the recovered isopropanol contains isopropyl acrylate after the obtained polymer is removed. If the polymer is reused as it is, the resulting polymer becomes turbid, resulting in poor appearance, and all of the recovered material has been regarded as industrial waste.
An object of the present invention is a case where water-soluble alcohol is reused when an acrylic acid polymer is repeatedly produced by polymerization of a monomer containing acrylic acid in an aqueous medium containing water-soluble alcohol as a reaction solvent. However, it is providing the manufacturing method of an acrylic acid type polymer which can obtain the polymer by which mixing of an impurity and the coloring or turbidity by it were suppressed.

The present invention relates to a water-soluble alcohol obtained by heating a polymerization solution after polymerization when repeatedly producing an acrylic acid-based polymer by polymerization of a monomer containing acrylic acid in an aqueous medium containing a water-soluble alcohol. Is a method for producing an acrylic acid polymer that is reused for the production of the next acrylic acid polymer, and the reaction solvent used for the next production is the above distillation. Acrylic acid heavy polymer, characterized in that the content of the esterified product composed of the acrylic acid and the water-soluble alcohol in the reaction solvent is 500 ppm by mass or less. It is a manufacturing method of coalescence.
The reaction solvent preferably contains a distillate containing the water-soluble alcohol obtained by heating the mixture of the distillate and the polymerization initiator to a temperature at which the water-soluble alcohol evaporates.
The reaction solvent is preferably obtained by diluting the distillate with water and / or water-soluble alcohol.
The water-soluble alcohol is preferably at least one selected from methanol, ethanol, n-propanol and isopropanol.

  According to the production method of the present invention, the use of a reaction solvent having an esterification product composed of the acrylic acid and the water-soluble alcohol of 500 mass ppm or less suppresses mixing of impurities and coloring or turbidity caused thereby. The obtained acrylic acid polymer can be obtained. As a result, the amount of industrial waste is reduced, and the amount of new water-soluble alcohol used can be reduced. This is particularly advantageous in terms of manufacturing costs.

  The method for producing an acrylic acid polymer of the present invention (hereinafter referred to as “the production method of the present invention”) is an acrylic acid polymer obtained by polymerizing a monomer containing acrylic acid in an aqueous medium containing a water-soluble alcohol. In the repeated production of the acrylic acid heavy polymer, the distillate mainly composed of water-soluble alcohol obtained by heating the polymerization solution after polymerization is reused for the production of the next acrylic acid polymer. A method for producing a coalescence, wherein a reaction solvent used for the next production is prepared using the distillate, and an ester comprising the acrylic acid and the water-soluble alcohol in the reaction solvent The content of the compound is 500 mass ppm or less.

The monomer may be only acrylic acid, or may be composed of acrylic acid and a compound copolymerizable with the acrylic acid. In addition, the usage-amount of acrylic acid becomes like this. Preferably it is 30 mass% or more with respect to the whole quantity of the said monomer, More preferably, it is 40-100 mass%, More preferably, it is 50-100 mass%.
Compounds that can be copolymerized with acrylic acid include unsaturated carboxylic acids and salts thereof (sodium salts, etc.), unsaturated acid anhydrides, unsaturated sulfonic acids and salts thereof (sodium salts, etc.), alkyl acrylates, acrylic acid Examples thereof include hydroxyalkyl esters, methacrylic acid alkyl esters, methacrylic acid hydroxyalkyl esters, unsaturated amides, esters of acrylic acid or methacrylic acid containing a polyalkylene oxide skeleton, and the like. These can be used alone or in combination of two or more.

Examples of the unsaturated carboxylic acid include methacrylic acid, maleic acid, itaconic acid and the like.
Examples of the unsaturated acid anhydride include maleic anhydride and itaconic anhydride.
As unsaturated sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, vinyl sulfonic acid, p-styrene sulfonic acid, acryloxybenzene sulfonic acid, methacryloxybenzene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, And sulfoethyl acrylate.

Examples of the alkyl acrylate include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, and the like.
Examples of the hydroxyalkyl acrylate include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, 3-hydroxybutyl acrylate, 4-hydroxybutyl acrylate, etc. Is mentioned.
Examples of the alkyl methacrylate include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, hexyl methacrylate, octyl methacrylate and the like.
Examples of the hydroxyalkyl methacrylate include 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 3-hydroxybutyl methacrylate, 4-hydroxybutyl methacrylate, and the like. Is mentioned.

Unsaturated amides include acrylamide, methacrylamide, N-hydroxymethylacrylamide, N-hydroxymethylmethacrylamide, N- (2-hydroxyethyl) acrylamide, N- (2-hydroxyethyl) methacrylamide, N, N-bis. (2-hydroxyethyl) acrylamide, N, N-bis (2-hydroxyethyl) methacrylamide and the like can be mentioned.
As esters of acrylic acid or methacrylic acid containing a polyalkylene oxide skeleton, polyethylene glycol monoacrylate, polypropylene glycol monoacrylate, polybutylene glycol monoacrylate, polyethylene glycol polypropylene glycol monoacrylate, polyethylene glycol polybutylene glycol monoacrylate, polypropylene glycol polyacrylate Butylene glycol monoacrylate, polyethylene glycol polypropylene glycol polybutylene glycol monoacrylate, polyethylene glycol monomethacrylate, polypropylene glycol monomethacrylate, polybutylene glycol monomethacrylate, polyethylene glycol polypropylene glycol monomethacrylate , Polyethylene glycol polybutylene glycol monomethacrylate, polypropylene glycol polybutylene glycol monomethacrylate, polyethylene glycol polypropylene glycol polybutylene glycol monomethacrylate, etc., polyalkylene glycol (the number of alkylene glycol units is 2 or more) monoacrylate or mono Methacrylic acid ester; methoxypolyethylene glycol monoacrylate, methoxypolypropylene glycol monoacrylate, methoxypolybutylene glycol monoacrylate, ethoxypolyethylene glycol monoacrylate, ethoxypolypropylene glycol monoacrylate, ethoxypolybutylene glycol monoacrylate, methoxypolyethyleneglycol Monoacrylic acid ester or monomethacrylic acid of alkoxy polyalkylene glycol, such as alkyl monomethacrylate, methoxypolypropylene glycol monomethacrylate, methoxypolybutylene glycol monomethacrylate, ethoxypolyethyleneglycol monomethacrylate, ethoxypolypropyleneglycolmonomethacrylate, ethoxypolybutyleneglycolmonomethacrylate, etc. Examples include esters.

In the production method of the present invention, the monomer is polymerized using an aqueous medium containing a water-soluble alcohol as a reaction solvent.
Examples of the water-soluble alcohol include methanol, ethanol, n-propanol, and isopropanol. These can be used alone or in combination of two or more. Moreover, it is preferable that isopropanol is included among these.

  Although the content rate of the water-soluble alcohol in an aqueous medium is not specifically limited, When the sum total of water and water-soluble alcohol is 100 mass parts, the mass ratio is normally (20-80 mass parts): (80- 20 parts by mass), preferably (30 to 70 parts by mass): (70 to 30 parts by mass). If the amount of water-soluble alcohol used is too large, the raw materials used may be limited in solubility in water.

  In the production method of the present invention, the monomer is polymerized using a reactor equipped with a thermometer, a stirrer, a reactor, and a reflux condenser.

As the polymerization method of the monomer, radical polymerization using a polymerization initiator is usually applied. The polymerization initiator may be any substance that decomposes under polymerization conditions to generate a free radical, and is selected according to the polymerization conditions. For example, a peroxide or an azo compound is used.
Peroxides include hydrogen peroxide; inorganic peroxides such as sodium persulfate, ammonium persulfate, and potassium persulfate; hydroperoxides, dialkyl peroxides, diacyl peroxides, peroxyesters, benzoyl peroxide, lauroyl peroxide And organic peroxides such as peracetic acid and persuccinic acid. Examples of the azo compound include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (2-methylbutyronitrile), and the like. Is mentioned.
Although the usage-amount of the said polymerization initiator changes with the kinds, polymerization conditions, etc., it is 0.1-5 mass parts normally with respect to 100 mass parts of said monomers.

Specific methods for polymerizing the monomer include (i) a method of adding a monomer and a polymerization initiator under stirring of an aqueous medium heated to a predetermined temperature, and (ii) a predetermined temperature. A method of adding a polymerization initiator under stirring of a monomer and an aqueous medium heated to (iii) while stirring an aqueous medium containing a part of the monomer heated to a predetermined temperature, Examples thereof include a method of adding a monomer and a polymerization initiator.
The polymerization temperature of the monomer is usually in the range of 50 to 100 ° C. in consideration of reactivity, load on the reactor, etc., and the polymerization proceeds while refluxing.

The polymerization solution after the polymerization comprises an aqueous medium containing a water-soluble alcohol, a polymer composed of the monomer dissolved in the aqueous medium, and an esterified product composed of the acrylic acid and the water-soluble alcohol. Contains.
Thereafter, in order to remove the aqueous medium to be reused, particularly the water-soluble alcohol, the polymerization solution is preferably heated to a temperature in the range of 40 to 100 ° C. and concentrated (the aqueous medium is distilled). At this time, until the content of the aqueous medium in the reaction solution after concentration (after distillation) becomes 30 to 70% by mass, and until the water-soluble alcohol in the remaining aqueous medium becomes 5% by mass or less. It is preferable to distill off. This concentration (distillation) may be performed under normal pressure or reduced pressure.

In order to obtain a final product from the reaction solution, a neutralizing agent may be used to partially neutralize (25% or more and less than 100%) or completely neutralize (100%). Examples of the neutralizing agent include sodium hydroxide (aqueous solution), ammonia (aqueous solution), potassium hydroxide (aqueous solution) and the like.
The weight average molecular weight (hereinafter referred to as “Mw”) of the acrylic acid polymer obtained as described above is usually 1,000 to 100,000, preferably 3,000 to 30,000. The HAZE measured according to JIS K7136 is preferably 50% or less, more preferably 40% or less.

  On the other hand, the distillate obtained by heating (distillation) mainly contains a water-soluble alcohol, that is, contains 20% by mass or more of this alcohol, and additionally contains at least water and the esterified product.

In the production method of the present invention, in order to reuse the distillate, the concentration of the esterified product in the reaction solvent prepared using the distillate is 500 ppm by mass or less, preferably 400 ppm by mass or less, More preferably, it is 300 mass ppm or less.
Examples of the method of using the distillate as a reaction solvent in which the concentration of the esterified product is further reduced are exemplified below.
(I) A distillate obtained by mixing the distillate and a polymerization initiator and then heating the resulting mixture to a temperature at which water-soluble alcohol evaporates is used as a reaction solvent.
(Ii) A liquid obtained by diluting the distillate with water and / or water-soluble alcohol is used as a reaction solvent.

In the method (i), in order to prevent the esterified product from volatilizing (distilling) by subsequent heating, first, the polymerization of the esterified product is advanced by a polymerization initiator. And the distillate containing water-soluble alcohol is obtained by heating to the temperature which water-soluble alcohol evaporates. This distillate is usually mainly a mixture of water-soluble alcohol and water.
As the polymerization initiator used in the method (i), those exemplified as the polymerization initiator used at the time of polymerization of the monomer can be used, but persulfates such as sodium persulfate are preferable. The amount of the polymerization initiator used is preferably 0.01 to 1 part by mass, more preferably 0.05 to 0.5 part by mass, when the distillate is 100 parts by mass. If it is the usage-amount of the said range, the said esterified substance will be easy to superpose | polymerize and the amount of esterified substances in the distillate obtained after that can be reduced.

The mixture is heated to a temperature at which at least the water-soluble alcohol evaporates. This temperature is selected according to the type of water-soluble alcohol, and more specifically, is an azeotropic temperature of water and water-soluble alcohol or higher. As described above, it is preferable to proceed the polymerization of the esterified product before the temperature at which the water-soluble alcohol evaporates. Therefore, after preparing the mixture, the mixture is heated to a temperature lower than the temperature at which the water-soluble alcohol evaporates. It is preferable to hold for a certain time (for example, 0.5 to 2 hours), and then raise the temperature under normal pressure or reduced pressure to recover a distillate containing a water-soluble alcohol. Prior to the distillation, the polymer of the esterified product may be filtered off.
The concentration of the esterified product in the distillate is preferably 500 ppm by mass or less, more preferably 400 ppm by mass or less, and still more preferably 300 ppm by mass or less.

The method (ii) is a method of diluting the distillate with water and / or water-soluble alcohol. What is necessary is just to select each usage-amount of the water used for dilution, and water-soluble alcohol so that it may become a composition of the reaction solvent used for the next manufacture.
The concentration of the esterified product in the preparation obtained by this method is preferably 500 ppm by mass or less, more preferably 400 ppm by mass or less, and still more preferably 300 ppm by mass or less.

Using the reaction solvent prepared as described above, an acrylic acid polymer can be repeatedly produced in the same manner as described above. That is, the distillate obtained by the above method (i) or the preparation obtained by (ii) may be used as it is, or may be used in combination with new water-soluble alcohol and / or water as necessary. When reusing, the polymerization is usually performed after measuring the content of the water-soluble alcohol in the recovery medium.
The weight average molecular weight (hereinafter referred to as “Mw”) of the acrylic acid polymer obtained by repeated production is usually 1,000 to 100,000, preferably 3,000 to 30,000.
The HAZE measured according to JIS K7136 is preferably 50% or less, more preferably 40% or less.

  In the present invention, even if the reaction solvent prepared as described above is used, the physical properties of the resulting acrylic acid polymer are within a predetermined range, and HAZE is suppressed to a low value. Moreover, the amount of industrial waste can be reduced by repeatedly using the distillate.

  Hereinafter, the present invention will be specifically described with reference to examples. In addition, this invention is not restrict | limited at all by these Examples.

Example 1
A tank reactor was charged with 750 kg of isopropanol (hereinafter referred to as “IPA”) and 750 kg of deionized water, and the temperature was raised to 80 ° C. Thereafter, while maintaining the temperature of the reaction system at 82 ° C. (boiling point of the reaction solution), an aqueous monomer solution obtained by diluting 700 kg of acrylic acid and 300 kg of 2-acrylamido-2-methylpropanesulfonic acid with 500 kg of deionized water while stirring Then, 80 kg of a 30% by mass aqueous sodium persulfate solution was added dropwise over 4 hours for polymerization. After dropwise addition of the whole amount, polymerization was further performed at 80 ° C. for 2 hours to complete the reaction.
Next, the pressure inside the reactor was reduced to 20 kPa, and 1,400 kg of distillate was recovered by heating (temperature 60 ° C.). The concentration of isopropyl acrylate contained in the distillate was 1,100 ppm by mass by gas chromatography.
Thereafter, the reaction solution remaining in the reactor was neutralized by supplying 1,100 kg of a 32% by mass aqueous sodium hydroxide solution to pH 7. Then, 250 kg of deionized water was supplied to obtain an acrylic acid polymer (1-a) having a solid content concentration of 40% by mass. The Mw by GPC of this acrylic acid polymer (1-a) is 10,000, and HAZE (“NDH2000” manufactured by Nippon Denshoku Industries Co., Ltd., using a 50 mm square cell) measured according to JIS K7136 is 15%.

Next, 1,400 kg of the recovered distillate was charged into another tank reactor, and 1.5 kg of sodium persulfate was further added and maintained at 75 ° C. for 1 hour. This mixture was heated (temperature 82 ° C.) to recover 1,200 kg of distillate (a mixture of IPA and water, IPA / water = 50/50). The concentration of isopropyl acrylate contained in the distillate was 50 mass ppm.
Thereafter, except that 1,200 kg of this distillate, 150 kg of new IPA, and 150 kg of deionized water were used as a reaction solvent (concentration of isopropyl acrylate of 40 mass ppm) and charged into the tank reactor of the reactor. In the same manner as above, an acrylic acid polymer (1-b) having a solid concentration of 40% by mass was produced. Mw by GPC of this acrylic acid polymer (1-b) was 10,000, and HAZE was 18% (see Table 1).

Example 2
In the same manner as in Example 1, an acrylic acid polymer (1-a) was obtained.
In the subsequent treatment, an acrylic acid polymer (2-b) was produced in the same manner as in Example 1 except that ammonium persulfate was used instead of sodium persulfate. Mw by GPC of this acrylic acid polymer (2-b) was 10,000, and HAZE was 20% (see Table 1).

Example 3
An acrylic acid polymer (3-a) was obtained in the same manner as in Example 1 except that a monomer aqueous solution obtained by diluting 1000 kg of acrylic acid with 500 kg of deionized water was used. Mw by GPC of this acrylic acid polymer (3-a) was 8,000, and HAZE was 10%.
In the subsequent treatment, an acrylic acid polymer (3-b) was produced in the same manner as above except that an aqueous monomer solution obtained by diluting 1,000 kg of acrylic acid with 500 kg of deionized water was used. Mw by GPC of this acrylic acid polymer (3-b) was 8,000, and HAZE was 11% (see Table 1).

Example 4
In the same manner as in Example 3, an acrylic acid polymer (3-a) was obtained.
After the polymerization, the pressure in the reactor was reduced to 10 kPa, and 1,400 kg of distillate was recovered. To this distillate, 700 kg of IPA for dilution and 500 kg of deionized water were supplied and stirred and mixed. The concentration of isopropyl acrylate at this time was 350 mass ppm.
Thereafter, an acrylic acid polymer (4-b) was produced in the same manner as in Example 3 except that 1,500 kg of the dilution was used as a reaction solvent. Mw by GPC of this acrylic acid polymer (4-b) was 8,000, and HAZE was 31% (see Table 1).

Comparative Example 1
In the same manner as in Example 1, an acrylic acid polymer (1-a) was obtained.
Thereafter, the pressure inside the reactor was reduced to 20 kPa, and 1,400 kg of distillate (isopropyl acetate concentration 1,100 mass ppm) recovered by heating (temperature 60 ° C.) was used. Similarly, an acrylic acid polymer (5-b) was produced. Mw by GPC of this acrylic acid polymer (5-b) was 10,000, and HAZE was 65% (see Table 1).

  The acrylic acid polymer produced by the method of the present invention is useful as a dispersant, a detergent builder, a dyeing assistant, a scale control agent, and the like, and in particular, a heavy polymer having an Mw in the range of 5,000 to 10,000. The coalescence is suitable as a dispersant for inorganic and organic materials.

Claims (4)

Mainly water-soluble alcohol obtained by heating the polymerization solution after polymerization when repeatedly producing acrylic acid-based polymer by polymerization of monomers containing acrylic acid in aqueous medium containing water-soluble alcohol A method for producing an acrylic acid polymer, wherein a distillate is reused for the production of the next acrylic acid polymer,
The reaction solvent used for the next production is prepared using the distillate, and the content of the esterified product composed of the acrylic acid and the water-soluble alcohol in the reaction solvent is 500 masses. A method for producing an acrylic acid polymer, characterized in that the content is not more than ppm.   The said reaction solvent contains the distillate containing this water-soluble alcohol obtained by heating the mixture of the said distillate and a polymerization initiator to the temperature at which water-soluble alcohol evaporates at least. A method for producing an acrylic acid polymer.   The method for producing an acrylic acid polymer according to claim 1, wherein the reaction solvent is obtained by diluting the distillate with water and / or a water-soluble alcohol.   The method for producing an acrylic acid polymer according to any one of claims 1 to 3, wherein the water-soluble alcohol is at least one selected from methanol, ethanol, n-propanol and isopropanol.