JP2004339170A - (meth)acrylic acid alkali metal salt and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a (meth)acrylic acid metal salt reduced in the polymer content and useful in various kinds of applications and to provide a method for producing the (meth)acrylic acid alkali metal salt by which polymerization can sufficiently be suppressed and to provide a production method scarcely producing gel-like material in piping and tanks and capable of stably producing the (meth)acrylic acid alkali metal salt over a long period. <P>SOLUTION: The (meth)acrylic acid alkali metal salt comprises an N-oxyl compound as a polymerization inhibitor and has ≤2,000 ppm water content. The method for producing the (meth)acrylic acid alkali metal salt comprises a step for obtaining a solution of (meth)acrylic acid alkali metal salt by neutralization of (meth)acrylic acid with a compound containing an alkali metal in the presence of the N-oxyl compound. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an alkali metal (meth) acrylate and a method for producing the same. More specifically, the present invention relates to an alkali metal (meth) acrylate used in the fields of a water-repellent surface treatment agent, a fiber treatment agent, a ship bottom antifouling paint, a silane coupling agent, and the like, and a method for producing the same.
[0002]
[Prior art]
The alkali metal (meth) acrylate is polymerizable and is used as a polymerizable monomer or as a raw material for introducing a polymerizable functional group into a compound, and is useful as an industrial raw material. Compound. Usually, it is supplied in the form of a powder, and for example, it is produced by a process of preparing an alkali metal (meth) acrylate solution and then pulverizing the solution. In the case of obtaining high-quality powder with a small content of the polymer as an impurity, a high durability of the alkali metal (meth) acrylate requires a short dwell time such as a spray drier. The (meth) acrylic acid alkali metal salt solution is transferred and dried, collected in a storage tank (product hopper) and filled into a container as a product. In such a manufacturing process, (meth) acrylic acid is used. Polymerization of the acid alkali metal salt easily generates a polymer or gel, which may cause a problem in the production process. For example, the stability of the solution is impaired, or gels that cannot be easily removed accumulate in the corners of pipes or tanks for transferring the aqueous solution of the alkali metal (meth) acrylate, or in the wire mesh in the strainer. Will be. When the accumulation of the gel-like substance increases, stable production for a long period of time becomes difficult.
[0003]
As a conventional production method relating to an alkali metal (meth) acrylate, a production method of sodium acrylate or sodium methacrylate powder crystals in which an aqueous solution of sodium acrylate or sodium methacrylate is spray-dried at a drying temperature of 80 to 200 ° C is disclosed. It was described in Examples that hydroquinone monomethyl ether was used, and when esterifying the obtained acrylic acid or sodium methacrylate powder crystals, phenyl-α-naphthylamine, N, N′- was used as a polymerization inhibitor. It is described that diphenyl-p-phenylenediamine, hydroquinone, phenothiazine, sulfur and the like are used (for example, see Patent Document 1). Further, when producing a potassium salt of acrylic acid or methacrylic acid by a neutralization reaction of acrylic acid or methacrylic acid with a potassium salt selected from potassium hydroxide or potassium carbonate, water or a lower alcohol is used as a solvent, and the reaction is terminated. A method for producing a potassium salt of acrylic acid or methacrylic acid, in which the pH is adjusted to 10 to 13 and the solvent is removed and the solvent is dried after completion of the reaction, is disclosed in which hydroquinone and hydroquinone monomethyl ether are used as polymerization inhibitors. In the examples, it is described that neutralization was carried out at 50 ° C. or lower (for example, see Patent Document 2). Furthermore, a method for producing an alkali metal salt of an unsaturated carboxylic acid by drying an aqueous liquid containing an alkali metal salt of an unsaturated carboxylic acid by contacting the aqueous liquid with a hot air fluid in a spray form to remove an aqueous component is disclosed. It is described that hydroquinone may be added as a polymerization inhibitor to an unsaturated carboxylic acid, and in Examples, it is described that neutralization is performed at 10 ° C. or lower (for example, see Patent Document 3).
[0004]
However, in these techniques, since the alkali metal (meth) acrylate is produced through a spray drying process at a high temperature, the aqueous solution of the alkali metal (meth) acrylate contains hydroquinone and hydroquinone monomethyl ether. However, in order to prevent inadvertent polymerization of alkali metal (meth) acrylate due to high temperature, a large amount of polymerization inhibitor must be used. When the polymerization inhibitor is used in such a large amount, it causes coloring. In addition, when a large amount of a polymerization inhibitor such as hydroquinone is contained in the alkali metal (meth) acrylate, for example, when polymerizing as a polymerizable monomer, a polymer having a sufficiently increased molecular weight is produced. It is disadvantageous to do. In addition, when the stability of the aqueous solution to heat as described above is insufficient, the operating temperature conditions of the optimal spray dryer used during spray drying can be restricted, and the temperature is increased to increase the spray drying efficiency. There was naturally a limit. In addition, in order to perform the drying process of the powder stably for a long period of time, it is necessary to maintain and adjust the temperature condition of the spray dryer in a narrow range even in a normal operation. In addition to improving these points, there is room for contrivance as a production method that can sufficiently suppress polymerization and coloring of the alkali metal (meth) acrylate in the drying step.
More specifically, since the alkali metal (meth) acrylate has high polymerizability, the residence time is short in order to suppress the side reaction that may occur in the drying step as low as possible and obtain a powder having a low polymer content. Spray dryers (spray dryers) are used, but in this case heat energy loss is relatively high. Therefore, since there is room for improvement in the thermal efficiency of the drying device, the polymerization in the production process of the alkali metal (meth) acrylate is performed not only by the spray drying method but also by other drying methods. There is room for constraining it sufficiently so that high quality products can be manufactured.
[0005]
As a method for obtaining powdered potassium acrylate, a method for producing powdered potassium acrylate in which a powder obtained by separating and drying from an aqueous solution is further contacted with a dry gas is disclosed, and the separation and drying is performed by a spray dryer. (See, for example, Patent Document 4). However, this technique does not discuss suppressing the polymerization of potassium acrylate in the production process. In addition, since the separation and drying of the aqueous solution has only been studied from the viewpoint of preventing agglomeration of the obtained powdered potassium acrylate, the polymerization of the alkali metal (meth) acrylate in the production process has been considered. There has been room for contrivance to achieve a production method that can be sufficiently suppressed.
[0006]
[Patent Document 1]
JP-A-47-31924 (page 1-2)
[Patent Document 2]
JP-B-48-20532 (page 1-2)
[Patent Document 3]
JP-A-49-11820 (pages 1-3)
[Patent Document 4]
JP-A-2003-12599 (page 2)
[0007]
[Problems to be solved by the invention]
The present invention has been made in view of the above situation, and has a reduced content of a polymer, and is useful in various applications, and it is possible to sufficiently suppress polymerization. It is an object of the present invention to provide a method for producing an alkali metal (meth) acrylate. It is another object of the present invention to provide a production method capable of producing an alkali metal (meth) acrylate salt in a stable manner for a long period of time without generating a gel-like substance in a pipe or a tank.
[0008]
[Means for Solving the Problems]
The present inventors have conducted various studies on a method for preventing the polymerization of the alkali metal (meth) acrylate in the above-mentioned production process. As a result, even if a general-purpose polymerization inhibitor such as hydroquinone was used, the production of the polymer was not sufficiently achieved. Although it cannot be suppressed, high-quality (meth) acrylic acid having a reduced polymer content by containing an N-oxyl compound in the alkali metal (meth) acrylate and specifying the water content is specified. It has been found that acid alkali metal salts can be used. When producing such an alkali metal (meth) acrylate, a 2,2,6,6-tetramethylpiperidino compound or the like is added to the alkali metal (meth) acrylate solution or slurry to be dried. By containing an N-oxyl compound, a remarkable polymerization inhibiting effect can be imparted. As a result, it has been found that the stability of a solution or the like can be improved, and the generation of a gel that cannot be easily removed in a pipe or a tank can be suppressed, and the inventors have conceived that the above problem can be solved brilliantly.
[0009]
Further, in the case of the N-oxyl compound, the polymerization inhibiting effect can be sufficiently exhibited even in a very small amount as compared with hydroquinone, so that a high-quality alkali metal (meth) acrylate without coloring can be obtained. In addition, since high-temperature treatment can be performed as compared with hydroquinone, it is possible to dry the alkali metal (meth) acrylate solution at a higher temperature, and to improve efficiency in the production of the alkali metal (meth) acrylate. I found that I could do that.
Further, in the drying apparatus used for producing the alkali metal (meth) acrylate of the present invention, there are various types, and there are many types having higher thermal efficiency than the spray drying apparatus. By using an N-oxyl compound to make the (meth) acrylic acid alkali metal salt solution have high stability, not only the spray drying apparatus but also the thermal efficiency other than the spray drying apparatus which could not be used conventionally can be obtained. Good drying equipment can be used. As a result, it has been found that thermal efficiency can be improved and polymerization can be suppressed to produce a high-quality alkali metal (meth) acrylate more efficiently. On the other hand, even in the case of using a spray drying apparatus, since the solution is more stable against heat, the range in which the alkali metal (meth) acrylate solution can be safely handled is expanded, and the productivity is increased. A stable alkali metal (meth) acrylate can be obtained even if the temperature setting conditions are wide. Therefore, even when a spray drying apparatus is used, it has been found that the method is a very useful production method, and the present invention has been achieved.
[0010]
That is, the present invention is an alkali metal (meth) acrylate containing a N-oxyl compound as a polymerization inhibitor and having a water content of 2000 ppm or less.
The present invention also provides a step of obtaining an alkali metal (meth) acrylate solution by a neutralization reaction between (meth) acrylic acid as an acid and a compound containing an alkali metal as a base in the presence of an N-oxyl compound. And a method for producing an alkali metal (meth) acrylate.
Hereinafter, the present invention will be described in detail.
[0011]
The alkali metal (meth) acrylate of the present invention contains an N-oxyl compound as a polymerization inhibitor and has a water content of 2000 ppm or less. ) When it is used as a raw material for a nucleophilic substitution reaction for introducing an acrylic group, it is not preferable because the yield cannot be sufficiently improved and the consolidation of the product is promoted. In the present invention, there is a tendency that the powder is liable to be clogged in proportion to the water content, and there is a possibility that a pipe for transferring the obtained alkali metal (meth) acrylate powder may be easily clogged. It is preferable that the water content is small, preferably 1500 ppm or less, more preferably 1000 ppm or less, still more preferably 800 ppm or less, still more preferably 600 ppm or less, even more preferably 550 ppm or less, It is more preferably at most 500 ppm, more preferably at most 350 ppm, particularly preferably at most 300 ppm, most preferably at most 250 ppm.
In a preferred embodiment, the alkali metal (meth) acrylate of the present invention is produced by the production method of the present invention disclosed below.
[0012]
The water content can be measured by the following method.
Method: Karl Fischer method
Measuring equipment: Automatic moisture meter KF-07 (Mitsubishi Chemical Corporation)
Titration solvent: methanol (special grade reagent)
Sample introduction method: Put the sample into the titration flask and dissolve it uniformly
Sampling and weighing atmosphere: air conditioned to 25% relative humidity
Sampling amount: 2.0 ± 0.2g
Waiting time for moisture measurement end point: 30 seconds
[0013]
Examples of the N-oxyl compound include 2,2,6,6-tetramethylpiperidine-1-oxyl, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl, 4,4 ′, 4 "-tris (2,2,6,6-tetramethylpiperidine-1-oxyl) phosphite, 2,2,4,4-tetramethylazetidine-1-oxyl, 2,2-dimethyl-4, 4-dipropylazetidine-1-oxyl, 2,2,5,5-tetramethylpyrrolidine-1-oxyl, 2,2,5,5-tetramethyl-3-oxopyrrolidine-1-oxyl, 6-aza -7,7-dimethyl-spiro (4,5) decane-6-oxyl, 2,2,6,6-tetramethyl-4-acetoxypiperidine-1-oxyl, 2,2,6,6-tetramethyl- 4-b Zoyloxypiperidine-1-oxyl and the like are preferred, and among these, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl, 4,4 ′, 4 ″ -tris (2, 2,6,6-Tetramethylpiperidine-1-oxyl) phosphite is preferred. One or more of these can be used.
[0014]
The content of the N-oxyl compound is preferably 0.000001% by mass or more, and more preferably 1% by mass or less based on the alkali metal (meth) acrylate. When the content is less than 0.000001% by mass, the content of the polymer may not be sufficiently reduced. Even when the content exceeds 1% by mass, the content of the polymer can be reduced. The effect corresponding to the content may not be obtained. More preferably, the content is 0.000005% by mass or more and 0.5% by mass or less. More preferably, it is 0.00001% by mass or more, and 0.1% by mass or less. Particularly preferably, it is 0.0005% by mass or more and 0.05% by mass or less. More preferably, it is 0.0008% by mass or more and 0.01% by mass or less. Most preferably, it is 0.001% by mass or more and 0.005% by mass or less.
[0015]
The N-oxyl compound in the present invention can be detected by ESR (Electron Spin Resonance) or EPR (Electron Paramagnetic Resonance) spectroscopy, high performance liquid gas chromatography, or the like. Among these, it is preferable to detect by high performance liquid gas chromatography.
[0016]
In the ESR (Electron Spin Resonance) or EPR (Electron Paramagnetic Resonance) spectroscopy, the N-oxyl compound has an N-oxyl radical, and the N-oxyl radical has at least one unpaired electron. , It can be detected by such a spectroscopic method. These spectroscopy is based on the magnetic properties of atoms, ions, molecules or molecular fragments with an odd number of electrons. This property is derived from the orbital motion of the unpaired electron around the nucleus and its rotation or both. A strong static magnetic field has a constant magnitude H₀Acting on the unpaired spin (rotational angular momentum) of the electron at, creates a couple that directs the magnetic moment of the electron in a direction that is parallel or antiparallel to the direction of the magnetic field. And precesses about the direction of the magnetic field at a frequency proportional to both the magnitude and the magnetic moment of the electron. This is usually called Larmor precession. Still a second high-frequency magnetic field H₁Is the steady magnetic field H₀When applied perpendicular to₁The field frequency ν is the Larmor precession frequency ν_LWhen it becomes the same as above, resonance occurs. When an electromagnetic wave having an appropriate frequency ν is incident, magnetic resonance absorption occurs, and the magnitude thereof can be measured.
[0017]
Usually a steady magnetic field H₀Has a constant size in the range of about 0.34 Tesla. High frequency magnetic field H₁Is continuously varied until resonance occurs. At an electric field strength of 0.34 Tesla, the absorption of N-oxyl radicals is in the wavelength region of ν = 1010 Hz.
The lower limit of detection of the ESR spectrum is 2 × 10¹¹Free radicals of ΔH can be detected. Here, ΔH is a half width or a maximum slope width in the case of a differential curve. If ΔH = 2.7 Gauss, this is 10^{− 8}mol / L. Speaking of typical N-oxyl compounds, for example, in the case of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl, the detection lower limit is about 0.001 ppm.
[0018]
In the high performance liquid chromatography, the quantification of the N-oxyl compound can be performed, for example, under the following conditions. The detection limit of high performance liquid chromatography is about 0.1 ppm.
<Analysis conditions for 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl>
Column: Inertsil PH 5 μm 4.6 mm id × 250 mm
Mobile phase; acetonitrile: water = 5: 95
Column temperature; 50 ° C
Flow rate: 1 ml / min
Detector: UV 240nm
Retention time: 15.62min
Injection volume: 10 μl
Detection limit; 0.1 ppm
[0019]
<Analysis conditions for 4,4 ′, 4 ″ -tris (2,2,6,6-tetramethylpiperidine-1-oxyl) phosphite>
Column: Inertsil PH 5 μm 4.6 mm id × 250 mm
Mobile phase; methanol: water = 7: 3
Column temperature; 50 ° C
Flow rate: 1 ml / min
Detector: UV 240nm
Retention time: 15.46min
Injection volume: 10 μl
Detection limit; 0.1 ppm
[0020]
The alkali metal (meth) acrylate of the present invention is preferably a powder having an average particle diameter in the range of 0.1 to 500 µm. If the powder has an average particle diameter of less than 0.1 μm, the powder has a strong cohesive force, so that an agglomerate is likely to be formed, and it is difficult for the powder to flow even when a dry gas is supplied. Even if the moisture around the powder is replaced after the removal, it may cause sticking. On the other hand, when the average particle diameter of the powder exceeds 500 μm, the powder may not easily flow, and a larger amount of dry gas is required. More preferably, it is 0.5 μm or more and 400 μm or less. More preferably, it is 1 μm or more and 300 μm or less.
The measurement of the average particle diameter can be performed according to the dry sieving test method of JIS K0069 “Sieving test method for chemical products”.
[0021]
The form of the alkali metal (meth) acrylate of the present invention may be any of flakes, tablets, granules, granules, and powders (powder), and among these, the powders described above are preferable. Further, alkali metal (meth) acrylates, particularly potassium acrylate, have a high hygroscopicity and are less susceptible to humidity as the specific surface area is smaller. Therefore, granules to flakes having a relatively small specific surface area are also preferable. is there.
[0022]
The alkali metal (meth) acrylate of the present invention preferably has a bulk specific gravity of 0.30 g / ml or more. More preferably, it is 0.35 g / ml or more. Further, it is preferably at most 1.20 g / ml. More preferably, it is 1.00 g / ml or less, further preferably, 0.60 g / ml or less, particularly preferably, 0.55 g / ml or less. It is a preferred embodiment that the alkali metal (meth) acrylate powder of the present invention has the above bulk specific gravity.
As a method for measuring the bulk specific gravity, the following method is suitable. First, an alkali metal (meth) acrylate is gently poured into a 100-ml cylindrical metal container for measuring bulk specific gravity, and is heaped into the cylindrical container. Next, a mountain is scraped off with a spatula having a straight side, the mass is measured, and the mass per 1 ml is calculated. Such a measurement is performed for ten samples, and the average value is obtained. The measurement is performed at 25 ° C. and 60% humidity.
[0023]
The content of the polymer in the alkali metal (meth) acrylate is preferably 0.2% by mass or less, assuming that the alkali metal (meth) acrylate is 100% by mass. The content is more preferably 0.1% by mass or less, and further preferably 0.07% by mass or less.
The content of the polymer can be measured under the following conditions.
<Polymer content measurement method>
Polymer amount: Calculated as area percentage by high performance liquid chromatography.
Column: Shimpack SCR-101H 7.8 mm id × 250 mm
(Made by Shimadzu Corporation)
Mobile phase; 15% of 85% phosphoric acid + 3 L of ultrapure water
Flow rate: 1 ml / min
Detector: HITACHI L-4000H UV detector (200 nm)
Pump; HITACHI L-6000
Retention time; polymer 4.3 minutes
Monomer 12.5 minutes
[0024]
When the concentration of the slurry obtained by dispersing in toluene is 40% by mass, the viscosity of the slurry of the alkali metal (meth) acrylate is preferably 600 mPa · s or less. It is more preferably 500 mPa · s or less, further preferably 200 mPa · s or less, and particularly preferably 100 mPa · s or less.
As a method for measuring the slurry viscosity, an alkali metal (meth) acrylate is charged into toluene (500 g) in an atmosphere at a temperature of 25 ° C. and a humidity of 25% such that the solid content concentration becomes 40% by mass. It is preferable that a slurry is stirred by a three-one motor at a rotation speed of 200 times / minute using a four-spring stirring blade to form a slurry, and the viscosity of the obtained slurry is measured by a BL-type viscometer.
Also, a dispersion can be prepared using alcohols instead of toluene. The alkyl group constituting the alcohol may have a branched chain. Examples of alcohols include methanol, ethanol, propanol, butanol, pentanol, octanol and the like. In addition, polyhydric alcohols can be used, and examples thereof include ethylene glycol, propylene glycol, glycerin, and 1,4-butanediol.
[0025]
The method for producing the alkali metal (meth) acrylate of the present invention is not particularly limited as long as it contains an N-oxyl compound and the amount of water falls within the above range. A production method comprising a step of obtaining a solution of an alkali metal (meth) acrylate by a neutralization reaction between (meth) acrylic acid and a compound containing an alkali metal in the presence of an N-oxyl compound is preferable. A method for producing an alkali metal (meth) acrylate is also one aspect of the present invention.
[0026]
In the method for producing an alkali metal (meth) acrylate according to the present invention, a solution of the alkali metal (meth) acrylate is obtained by the neutralization reaction between an acid and a base in the presence of an N-oxyl compound as described above. In a preferred embodiment, the (meth) acrylic acid is subjected to a neutralization reaction between the compound containing an alkali metal as the base and the (meth) acrylic acid as the acid in the presence of an N-oxyl compound. This is a form in which an acid alkali metal salt solution is prepared.
In the step of obtaining an alkali metal (meth) acrylate solution by a neutralization reaction between an acid and a base in the presence of the N-oxyl compound in the present invention, the alkali metal (meth) acrylate may be added at any stage of the production process. The N-oxyl compound may be present together with the salt. For example, the method of adding the N-oxyl compound includes (1) the preparation of the raw material used in the neutralization reaction and the N-oxyl compound in the neutralization reaction. An oxyl compound may be added, or an N-oxyl compound may be added to the (2) alkali metal (meth) acrylate solution after completion of the neutralization reaction. In the mode (1), the obtained solution can be stabilized, and in the modes (1) and (2), the polymerization in the step after obtaining the solution can be suppressed. Become. Preferably, it is in the form of (1) so that the N-oxyl compound is present during the neutralization reaction.
[0027]
The above-mentioned preparation methods include (1) a method in which (meth) acrylic acid is gradually added to a solution of a compound containing an alkali metal in the presence of an N-oxyl compound, and (2) (meth) acrylic acid. A method in which an alkali metal-containing compound is gradually added to an acid to prepare the same; (3) A method in which a solution of the alkali metal-containing compound in a solvent and (meth) acrylic acid are gradually added together to prepare the acid Etc. are preferred. For example, by gradually adding (meth) acrylic acid to an aqueous solution of an alkali metal hydroxide or an alkali metal carbonate, or by gradually adding an alkali metal alkoxide to (meth) acrylic acid, It can be prepared by preparing an alcohol solution of a metal salt or by gradually adding an aqueous solution of an alkali metal hydroxide and (meth) acrylic acid to water at the same time.
These neutralization reactions are preferably performed in an air atmosphere to prevent polymerization during the reaction.
[0028]
As the usage form of the N-oxyl compound in the above-mentioned preparation method, the N-oxyl compound may be mixed in advance with a solution of a compound containing an alkali metal, or may be mixed with (meth) acrylic acid in advance. Or may be mixed in advance with a solvent. Further, it may be gradually added together with a solution of a compound containing an alkali metal and / or (meth) acrylic acid. It is also possible to use (meth) acrylic acid containing a predetermined amount of an N-oxyl compound as (meth) acrylic acid as a raw material of the alkali metal (meth) acrylate.
[0029]
The amount of the N-oxyl compound used in the method for producing an alkali metal (meth) acrylate is appropriately set so that the content of the N-oxyl compound in the alkali metal (meth) acrylate falls within the above range. Is preferred. In a preferred embodiment of the method for producing an alkali metal (meth) acrylate of the present invention, the N-oxyl compound is contained in an amount of 0.000001 to 1% by mass based on the alkali metal (meth) acrylate. .
[0030]
As the solvent in the alkali metal (meth) acrylate solution, water, a mixed solution of water and an organic solvent soluble in water, and the like are suitable, and water is preferred. That is, a preferred form of the present invention is a form in which an aqueous solution of an alkali metal (meth) acrylate is prepared by a neutralization reaction between a compound containing an alkali metal and (meth) acrylic acid in the presence of an N-oxyl compound. It is.
Examples of the organic solvent include lower alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol and t-butyl alcohol; acetone, methyl ethyl ketone, diethyl ketone and the like. And the like lower ketones.
[0031]
In the present invention, an N-oxyl compound is used as a polymerization inhibitor, but if necessary, another polymerization inhibitor may be used in combination.
The other polymerization inhibitors are not particularly limited, and generally known polymerization inhibitors can be used. Examples thereof include hydroquinone, methylhydroquinone, hydroquinone monomethyl ether, tert-butylhydroquinone, and 2,6. Phenol compounds such as -di-tert-butylhydroquinone, 2,5-di-tert-butylhydroquinone, 2,4-dimethyl-6-tert-butylphenol, cresol and tert-butylcatechol; N-isopropyl-N'-phenyl -P-phenylenediamine, N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine, N- (1-methylheptyl) -N'-phenyl-p-phenylenediamine, N, N ' -Diphenyl-p-phenylenediamine, N, P-phenylenediamines such as' -di-2-naphthyl-p-phenylenediamine; amine compounds such as thiodiphenylamine and phenothiazine; Alkyl thiuram disulfides; methylene blue and the like are preferred.
One or more of these can be used. Further, if molecular oxygen is used in combination as needed, the polymerization inhibiting effect is further improved.
[0032]
The amount of the other polymerization inhibitor to be used may be appropriately adjusted depending on the operating conditions or the properties of the finally obtained alkali metal (meth) acrylate, and is not particularly limited. The amount of (N-oxyl compound and other polymerization inhibitor) is preferably 0.00001% by mass or more based on the alkali metal (meth) acrylate, and is 1% by mass or less. It is preferred that the amount be such. More preferably, it is 0.00005% by mass or more and 0.5% by mass or less. More preferably, it is 0.0001% by mass or more, and 0.1% by mass or less. In particular, when the content is 0.5% by mass or less, it is difficult to discolor even by heat during the manufacturing process, and the heat stability is sufficiently imparted. Further, if necessary, a derivative compound is produced using the alkali metal (meth) acrylate of the present invention, and then the compound is distilled or the like to reduce or remove the N-oxyl compound used in the present invention. And may be used in subsequent steps.
[0033]
In the above-mentioned preparation method, publicly known and well-known operations and conditions can be used in a wide range without any particular limitation, and it is preferable to perform the preparation in a neutralization pot. In this case, it is preferable that the neutralization pot is sufficiently cooled and stirred. The neutralization reaction temperature is preferably 0 ° C. or higher, and more preferably 70 ° C. or lower. When the temperature is lower than 0 ° C., the compound containing an alkali metal or (meth) acrylic acid may be coagulated. When the temperature is higher than 70 ° C., the (meth) acrylic acid may cause polymerization. More preferably, it is 10 ° C. or higher and 60 ° C. or lower. More preferably, it is 20 ° C. or higher and 50 ° C. or lower. The stirring speed may be appropriately set to such an extent that the compound containing an alkali metal and the (meth) acrylic acid can be sufficiently contacted.
[0034]
In the neutralization reaction, the pH at the end point of the reaction is preferably 7 or more, and more preferably 13 or less. If the pH is less than 7, the remaining (meth) acrylic acid increases, and there is a risk of polymerization during drying. If the pH exceeds 13, the amount of the remaining alkali metal-containing compound increases, and the final form The reaction using the alkali metal (meth) acrylate obtained as above may cause problems such as hydrolysis. More preferably, the pH is 8 or more, and the pH is 11 or less.
[0035]
As the above-mentioned compound containing an alkali metal, an alkali metal hydroxide, an alkali metal carbonate, an alkali metal alkoxide and the like are preferable, and as the alkali metal, lithium, sodium, potassium, rubidium, cesium and the like are preferable. Each of these can be used alone or in combination.
A preferred form of the alkali metal (meth) acrylate in the present invention is a form of a salt of (meth) acrylic acid with an alkali metal such as lithium, sodium, potassium, rubidium, and cesium. Among these, a salt with sodium or potassium is preferable from the viewpoint of reactivity and / or economy, and the alkali metal (meth) acrylate is a potassium (meth) acrylate. The manufacturing method is one of preferred embodiments of the present invention.
In the above (meth) acrylic acid, the above-mentioned other polymerization inhibitors such as hydroquinone and hydroquinone monomethyl ether may be added.
[0036]
The concentration of the alkali metal (meth) acrylate in the alkali metal (meth) acrylate solution is preferably 10% by mass or more at 25 ° C, and 70% by mass or less. preferable. When the content is less than 10% by mass, a large amount of heat may be required for drying the solution, and the drying apparatus may be large. If it exceeds 70% by mass, the reaction may be too violent, and problems such as crystallization and polymerization may occur. More preferably, it is 30% by mass or more and 65% by mass or less.
When the (meth) acrylic acid alkali metal salt solution is used while being heated to 50 ° C., the content is preferably 10% by mass or more, and more preferably 80% by mass or less. More preferably, it is 30% by mass or more and 75% by mass or less.
The alkali metal (meth) acrylate solution is preferably in a form in which the alkali metal (meth) acrylate is dissolved, but the method for producing an alkali metal (meth) acrylate of the present invention does not hinder the method. In this case, the alkali metal (meth) acrylate may be in a dispersed state or not in a dissolved state.
[0037]
In the present invention, it is preferable that the method further comprises a step of removing a solvent from the alkali metal (meth) acrylate solution in the presence of the N-oxyl compound. Such a production method is a preferred embodiment of the present invention. one of.
The method for removing the solvent is not particularly limited, but it is preferable to remove the solvent using a drying device.
As the drying device, any drying device can be used. For example, a flash drying device with a crusher, a spray drying device (spray dryer), a co-current rotary drying device, a groove type stirring drying device, a multi-stage fluidized bed Drying equipment, horizontal multi-chamber fluidized bed dryer, one-stage one-chamber fluidized bed dryer, batch type fluidized bed dryer, multi-stage band ventilation dryer, end face suction type ventilation rotary dryer, louver suction type vertical ventilation Various types of drying devices such as a drying device, a ventilation box type batch drying device, a conduction electrothermal cylindrical drying device (drum dryer), and a conduction heating type drying device can be used.
[0038]
As the conduction heating type drying apparatus, a compact disk dryer (CD dryer, manufactured by Nishimura Iron Works) or the like is suitable, and such a CD dryer indirectly heats a material by heat conduction from a heat source to perform drying. Dryer to do. The CD dryer uses not only the outer peripheral surface of the conventional cylindrical drum but also both side surfaces of the hollow disk as heat transfer surfaces. The conduction heating type drying apparatus generally has high thermal efficiency, and can be operated at a high rate of 80 to 85% in a CD dryer. Further, by using a CD dryer, it is possible to dry the alkali metal (meth) acrylate solution from the alkali metal (meth) acrylate solution powder to the powder of the alkali metal (meth) acrylate at once, and the drying step can be simplified. In addition, since the heating time is as short as 3 to 30 seconds, it is suitable for drying a compound such as an alkali metal (meth) acrylate which needs to be kept from being denatured by heat during drying as low as possible. It can be suitably used.
The conventional technique has a problem that if a powder having a polymerizable double bond such as an alkali metal (meth) acrylate stays at a high temperature for a long time during drying, the product quality is deteriorated due to polymerization. Yes, only a spray drier (spray drier) having a short residence time could necessarily be used for drying. However, in the present invention, the stability of the alkali metal (meth) acrylate solution to be dried to heat ( (Coloring stability and polymerization stability) are remarkably improved, so that not only a spray drying device (spray dryer) but also any drying device can be suitably used for solvent removal. . In addition, due to the effect of improving the stability, the spray dryer can be operated under a condition with higher thermal efficiency or under a higher temperature.
[0039]
Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 and 2 which are schematic views showing an example of an apparatus for producing an alkali metal (meth) acrylate powder. As the drying device, the spray drying device shown in FIG. 1 and the like is replaced with the above-described conduction heating type drying device (CD dryer), and a pipe for introducing a predetermined dry gas is provided. An experiment on the production of powder was conducted.
In the manufacturing apparatus shown in FIG. 1, a neutralization pot 101, an intermediate tank 102, a stock solution supply pump 103, an air filter 104, a blower 105, a hot air generator 106, a spray dryer 107, a cyclone 108, a bag filter 109, an exhaust gas blower 110 , A storage tank 111, a dry gas inlet line 112, a dry gas inlet 113, a dry gas outlet 114, a powder outlet 115, a damper 117, a rotary valve 119, and the like. I have.
[0040]
The neutralization pot 101 is provided with a stirring blade 116, and a solution is prepared by a neutralization reaction between an acid and a base in the presence of an N-oxyl compound. The neutralization pot 101 is connected to an intermediate tank 102 via a pipe 201, and the intermediate tank 102 is connected to a stock solution supply pump 103 via a pipe 202.
The spray drying apparatus 107 is a centrifugal stock solution atomizing apparatus that includes a spray board 118 that rotates at high speed and that can atomize a solution by centrifugal force and contact it with hot air to dry it. A stock solution supply pump 103 is connected to the spray drying device 107 via a pipe 203, and a hot air generator 106, a blower 105, a damper 117, and an air filter 104 are connected in this order from the spray drying device 107 side. . Further, the spray-drying device 107 is connected to the cyclone 108 via a pipe 204, and also connected to the storage tank 111 via a rotary valve 119 and a pipe 205.
[0041]
The cyclone 108 is a device that collects the dried (meth) acrylic acid alkali metal salt powder downward by centrifugal force, and the bottom thereof is stored in the storage tank 111 via the rotary valve 120 and the pipe 206. The top of the tower is connected to the bag filter 109 by a pipe 207.
The bag filter 109 is a device that collects fine powder, and the bottom is connected to the storage tank 111 via the rotary valve 121 and the pipe 208. An exhaust gas blower 110 is connected to the top of the bag filter 109 via a damper 122, and exhaust is performed from the exhaust gas blower 110.
The storage tank 111 has a dry gas inlet 113 connected to a dry gas inlet line 112 at a bottom thereof, a dry gas outlet 114 at an upper portion thereof, and a powder outlet 115 via a rotary valve 123. ing.
[0042]
Powders having a large particle diameter are collected from the lower part of the spray drying apparatus main body, and those having a smaller average particle diameter than not falling are collected by a cyclone. Similarly, powder from the lower part of the cyclone has a smaller average particle diameter than that of the main part of the spray dryer. The powder that does not fall and has the smallest average particle diameter is sent to the bag filter. In terms of parts by weight, based on 100 parts by weight of the finally obtained alkali metal (meth) acrylate powder, under the main body of the spray-drying apparatus: under the cyclone: under the bag filter, each in the range of 80 to 90 parts by weight: A range of 5 to 15 parts by weight: A preferred form is a fractionation so as to be in a range of 5 to 15 parts by weight.
In addition, in the storage tank, the pipe of the alkali metal (meth) acrylate powder from below the spray drying device main body, the pipe from below the cyclone, and the pipe from below the bag filter are respectively joined to the upper part of the storage tank. Thus, a preferred embodiment is one in which alkali metal (meth) acrylate powders having different average particle diameters can be collected. By adopting this form, it is possible to efficiently collect alkali metal (meth) acrylate powders having various average particle diameters and to produce alkali metal (meth) acrylate powder with good yield. If desired, there may be a step of appropriately cutting the fine powder.
[0043]
In the manufacturing apparatus shown in FIG. 2, double dampers 301 and 302 are used instead of the rotary valves 120 and 121 in the apparatus shown in FIG. Further, the storage tank 111 is provided with a cooler 303 connected to the powder discharge port 115, and the spray-drying device 107 is not connected to the storage tank 111, and the bottom thereof is connected to the cyclone 108 by a pipe 304. Are linked.
The cooler 303 is provided with a jacket 305 through which cooling water passes, and the jacket 305 has a cooling water inlet 306 and a cooling water outlet 307. The cooler 303 includes a rotary valve 308 for discharging the cooled powder.
[0044]
Next, the production process of the alkali metal (meth) acrylate powder to which the present invention is applied will be described with reference to FIGS.
In FIG. 1, an alkali metal (meth) acrylate solution is prepared in the neutralization pot 101 in the presence of an N-oxyl compound, and the solution prepared in the neutralization pot 101 is used as a step of removing the solvent. The gas is supplied to the spray drying device 107 through the pipe 203 by the supply pump 103, and the gas passed through the air filter 104 by the blower 105 is sent to the hot air generating device 106, and is supplied to the spray drying device 107 as hot air.
In the solvent removal step, a spray drying device (spray drying device) is used, but it is also possible to dry using the various drying devices described above in addition to the spray drying device.
Since the alkali metal (meth) acrylate containing an N-oxyl compound in the present invention has sufficiently improved thermal stability, sufficient heat can be given in the step of drying the solution containing the salt. . Further, the temperature range can be made higher in the spray drying apparatus, and the production efficiency can be improved.
[0045]
In the spray drying device 107, the solution is sent to the spraying plate 118, and the solution is atomized by the high speed rotation of the spraying plate 118, and is dried by contact with hot air to form an alkali metal (meth) acrylate powder. .
The spray-drying apparatus may be of any type such as a type in which a spray solution and hot air are in cocurrent contact, a type in which countercurrent contact is made, and a type in which the solution is once in countercurrent contact and then cocurrent. Further, the spray drying device 107 includes a spray plate 118 for spraying the solution, but a nozzle such as a pressurized nozzle, a two-fluid nozzle, or a pressurized two-fluid nozzle can also be used.
[0046]
The amount of the solution to be supplied to the spray dryer is preferably 0.7 kg / min or more, and more preferably 5.3 kg / min or less. More preferably, it is 1.0 kg / min or more and 3.3 kg / min or less.
[0047]
As the hot air, an inert gas such as air, carbon dioxide, nitrogen, and argon is suitable, and among them, air is preferably used.
The temperature, the water content and the supply amount of the hot air may be appropriately set depending on the concentration of the solution, the supply amount, and the like, but the temperature is preferably 150 ° C. or higher, and 250 ° C. or lower. preferable. If the temperature is lower than 150 ° C., the water content of the obtained powder may not be able to be sufficiently reduced, and if it is higher than 250 ° C., solid-state polymerization may be easily caused. More preferably, it is 160 ° C. or higher and 230 ° C. or lower.
It is not necessary to particularly define the water content. When air is used as the gas, the humidity is arbitrary because the air is used as it is. Since the hot air used here contains a large amount of water evaporated in the solvent removing step, the amount of water in the initial hot air is not particularly limited.
[0048]
The residence time of the powder in the spray dryer is preferably 10 seconds or more, and more preferably 120 seconds or less. More preferably, it is at least 15 seconds and at most 90 seconds. More preferably, it is at least 20 seconds and at most 60 seconds. The residence time (seconds) of the powder can be calculated by the following equation.
Retention time of powder (second) = Capacity of spray-drying device (m³) ÷ Hot air volume (m³/ Sec)
It is preferable that the conditions of such hot air are appropriately set so that the water content of the alkali metal (meth) acrylate powder after drying by the spray drying apparatus is within the above-mentioned range.
[0049]
The alkali metal (meth) acrylate powder obtained by drying with the spray dryer 107 passes through the pipe 204 and is collected in the cyclone 108. In the powder collected in the cyclone 108, relatively large particles accumulate below the cyclone 108, and small particles (fine powder) are sent to the bag filter 109 through the pipe 207 together with the gas. Large particles enter the storage tank 111 from the bottom of the cyclone 108 through the rotary valve 120 and the pipe 206. Further, the powder not collected by the cyclone 108 enters the storage tank 111 from the spray drying device 107 through the rotary valve 119 and the pipe 205.
In FIG. 2, the alkali metal (meth) acrylate powder obtained by drying with the spray drying device 107 passes through the pipe 304 and is collected in the cyclone 108. The powder collected by the cyclone 108 enters the storage tank 111 through the double dampers 301 and 302 instead of the rotary valves 120 and 121 in FIG.
[0050]
In the bag filter 109, the collected fine powder is dropped and collected by an air pulse. The lower part of the bag filter 109 may be heated from the viewpoint of preventing moisture absorption of the powder. The collected particles are sent to the storage tank 111 through the rotary valve 121 and the pipe 208, and small particles that cannot be collected by the bag filter 109 are discarded from the exhaust gas blower 110 through the damper 122. become.
[0051]
In the storage tank 111, alkali metal (meth) acrylate powder sent from the spray drying device 107, the cyclone 108 and the bag filter 109 is fed from a powder inlet (not shown). In this case, it is preferable that the dry gas supplied from the dry gas supply line 112 is supplied from the dry gas supply port 113 so that the alkali metal (meth) acrylate powder is suspended and suspended. By such a suspension, the moist gas around the powder particles is replaced by a dry gas. The wet gas is exhausted from the dry gas outlet 114.
[0052]
The term “suspension-suspension (bubbling) of the (meth) acrylic acid alkali metal salt powder” means that the dry gas enters between the particles, thereby causing the dampness around each particle of the (meth) acrylic acid alkali metal salt powder. Injecting a dry gas to flow a part or all of the powder so that the powder can be replaced with a body. In a preferred embodiment, the dry gas is introduced into the inside of the powder layer so that the powder is foamed by the dry gas.
The powder is an aggregate of a large number of solid particles, in a state in which an appropriate interaction force is acting between the particles, and when a gas is blown from a lower portion of the powder layer, the gas rises. With a property that can be easily flowed. The powder layer is powder accumulated in the storage tank.
[0053]
As the above-mentioned storage tank, an opening (powder inlet) for charging the alkali metal (meth) acrylate powder obtained in the solvent removing step into the storage tank and an alkali metal (meth) acrylate powder from the storage tank It is preferable to provide a port (powder discharge port) for filling the container with a dry gas, and a dry gas inlet and a dry gas outlet at the bottom of the storage tank. Is preferably charged. By suspending and suspending the alkali metal (meth) acrylate powder in this manner, the wet gas around the particles of the powder is replaced with a dry gas, and the wet gas that has come out of the powder layer is removed. Then, the air is exhausted from the dry gas outlet. In addition, another process may be included from the solvent removal process to the charging of the alkali metal (meth) acrylate powder into the storage tank. When the powder is charged into the container, the powder may be directly charged into the container from the powder discharge port, or may be charged into the container via, for example, a cooler.
[0054]
The alkali metal (meth) acrylate powder in the storage tank 111 passes through the rotary valve 123 and fills the container from the powder outlet 115. In addition, it is preferable that the temperature of the powder is reduced to a temperature suitable for filling by using a cooler 303 as shown in FIG. In this case, the temperature of the cooled powder is preferably 70 ° C. or lower, more preferably 60 ° C. or lower.
In the production method of the present invention, it is also a preferred embodiment that the (meth) acrylic acid alkali metal salt powder is suspended and suspended in a storage tank and then charged into a container via a cooler. By passing through a cooler, the temperature of the alkali metal (meth) acrylate powder can be reliably lowered, the heat storage when the powder is filled and stored in the container is suppressed, and the polymerization of the powder by the heat storage is suppressed. This is because storage stability can be imparted as a result.
[0055]
Examples of the container include a paper bag and a flexible container bag. More preferably, there is an inner layer or inner bag formed of a sealing material inside the container. As the sealing material, any material that does not allow water to permeate may be used, and a plastic film or the like is suitable, and polyvinylidene chloride is particularly preferable. It is also preferable that the film is a film in which an aluminum layer is laminated. As such a film, a film in which a thin film of aluminum is contained in a container is preferable, and a film obtained by performing a composite such as coating or laminating an aluminum foil is preferable. Such an aluminum thin film may be obtained by vapor deposition. In addition, as long as the container can be sealed, a metal container such as aluminum, SUS, or tin, or a plastic container may be used.
[0056]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to only these Examples. Unless otherwise specified, “parts” means “parts by weight” and “%” means “% by mass”.
[0057]
<Example 1>
Inner volume 6m³552 kg of pure water and 0.0097 kg of N-oxyl compound 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl while flowing cooling water through the jacket into a reactor equipped with a stirrer and jacket. While charging and stirring, 2056.6 kg of a 48% by mass aqueous solution of potassium hydroxide was charged. Next, 1268.2 kg of acrylic acid containing 200 ppm of methoxyhydroquinone was added dropwise over 4 hours. During the dropping, the dropping speed was appropriately adjusted so that the liquid temperature did not become 25 ° C. or higher. After the completion of the dropping, the pH of the aqueous solution was measured, and an aqueous solution of acrylic acid or potassium hydroxide was added so as to fall within the range of 8.1 to 9.5. Thus, 3786.8 kg of a 50% by mass aqueous solution of potassium acrylate was obtained. The concentration of the N-oxyl compound is 5 ppm with respect to potassium acrylate, and the concentration of methoxyhydroquinone is 131 ppm with respect to potassium acrylate. A drying experiment was performed using this aqueous solution.
[0058]
Drying was performed using a compact disk dryer (CD dryer) under the following conditions.
Type: CD-500 (manufactured by Nishimura Iron Works)
Disc diameter: 540mm
Heat transfer area: 0.4m²
Heat source: Saturated steam (pressure 343kPa)
Disk rotation speed: 2 rpm
Stock solution processing volume: 60 kg / h
[0059]
In the CD dryer, the aqueous solution of potassium acrylate is dried as follows. FIG. 3 shows a schematic diagram of a CD dryer.
The aqueous solution of potassium acrylate (concentration: 50% by mass) is placed in the raw material liquid tank 401, the raw material liquid tank 401 is placed below the chute 402, and the circulating pump suction side hose 403 is put in the raw material liquid tank 401. The dry powder tank 404 is placed under the chute 405 and the saturated steam is supplied to the disk 406 to rotate the disk 406. By rotating the circulation pump 407, the aqueous solution is supplied onto the disk 406 through the feed pipe 408. As the drying of the aqueous solution proceeds on the disk 406 by the saturated steam, a powder (powder) is obtained on the disk 406. If the drying is insufficient, the disk 406 can be sufficiently dried by reducing the rotation speed. Further, a ventilation fan 409 is installed in the CD dryer, and the evaporated water is quickly removed from the system. The powder on the disk 406 is scraped off by a scraper 410 and enters a dry powder tank 404. The aqueous solution that has not adhered to the surface of the disk 406 is collected in the chute 402 and returns to the raw material liquid tank 401. Such an operation is repeated to dry the aqueous solution of potassium acrylate.
In the example, a pressure of 343 kPa (3.5 kg / cm) was used as a heat source.²Since the saturated vapor of G) was supplied to the disk 406, the surface temperature of the disk 406 was in the range of 140 to 150 ° C.
[0060]
The dry powder tank 404 was handled in the following manners A and B, and both were in a good dry state.
Form A: Dry air with a dew point of 0 ° C. and a temperature of 25 ° C. was supplied from the bottom of the dry powder tank 404 at a rate of 10 L / min to prevent moisture absorption of the powder.
Form B: The periphery of the dry powder tank 404 was heated to 70 ° C. to lower the relative humidity, thereby preventing the powder from absorbing moisture.
[0061]
Therefore, as the CD dryer used in the step of drying the alkali metal (meth) acrylate, a dry gas is provided in a dry powder tank for collecting the alkali metal (meth) acrylate powder dried on the surface of the disk. It is a preferable embodiment that a device or a pipe capable of introducing the gas is provided. The dry gas introduced at this time is a dry gas having a relative humidity lower than the critical relative humidity of the powder, and the dry gas is charged into a dry powder tank of the CD dryer, and the (meth) acrylic acid in the tank is charged. By suspending and suspending the acid alkali metal salt, the moisture in the vicinity of the powder is replaced with dry air, and the dry gas supplied into the dry powder tank of the CD dryer is represented by the following formula (1):
X ≧ 3V / T (1)
(Where T is the residence time (s) of the powder in the dry powder tank, V is the volume (L) of the storage tank, and X is the charging rate (L / s) of the dry gas. )) Is a preferred form. More preferably, even after the drying step with a CD dryer is completed, a form in which a dry gas is introduced according to the above formula is preferable. Also, preferably, the following formula (2);
X ≧ 5V / T (2)
It is to be thrown in according to.
[0062]
The dry gas is supplied to the dry powder tank in the above-described embodiment A, but the dry gas is introduced into a position where the powder and the dry gas are suspended and suspended to sufficiently replace the dry gas and the wet gas. Is preferred. As long as the suspension is sufficiently performed, the introduction position of the dry gas may be on the side surface or the bottom surface of the dry powder tank. In addition, in order to perform the above-mentioned suspension and suspension efficiently, it is preferable that dry gas is introduced from the bottom of the tank.
[0063]
The residence time T of the powder in the dry powder tank is preferably 300 seconds or more, more preferably 600 seconds or more, further preferably 1800 seconds or more, and 10 hours or less. . Particularly preferably, it is 1800 seconds or more and 3 hours or less.
[0064]
As the CD dryer used in the step of drying the alkali metal (meth) acrylate, a dry powder tank for collecting the powder of the alkali metal (meth) acrylate dried on the surface of the disk is heated at a predetermined temperature. It is preferable that the apparatus is provided with a device capable of heating the substrate. Further, a form in which a device or a pipe capable of introducing a dry gas into the dry powder tank may be provided, and a form in which a device capable of heating the dry powder tank to a predetermined temperature may be provided. Absent. The temperature is preferably in the range of 80 ° C to 60 ° C.
[0065]
The obtained potassium acrylate powder had a water content of 0.08% by mass, and the mixed alcohol solution test (polymer test) was colorless and transparent. The amount of polymer measured by high performance liquid chromatography was 0.01% by mass or less.
[0066]
<Example 2>
The amount of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl was 0.0009 kg, the concentration of the N-oxyl compound was 0.5 ppm with respect to potassium acrylate, and the concentration of methoxyhydroquinone was with respect to potassium acrylate. On the other hand, the drying experiment was performed in the same manner as in Example 1 except that the concentration was 131 ppm. The obtained potassium acrylate powder had a water content of 0.09% by mass, and the mixed alcohol solution test (polymer test) was colorless and transparent. The amount of polymer measured by high performance liquid chromatography was 0.01% by mass or less.
[0067]
<Example 3>
The amount of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl was 0.000097 kg, the concentration of N-oxyl compound was 0.05 ppm based on potassium acrylate, and the concentration of methoxyhydroquinone was potassium acrylate. On the other hand, the drying experiment was performed in the same manner as in Example 1 except that the concentration was 131 ppm. The obtained potassium acrylate powder had a water content of 0.09% by mass, and the mixed alcohol solution test (polymer test) was colorless and transparent. The amount of the polymer measured by high performance liquid chromatography was 0.01% by mass or less.
[0068]
<Example 4>
4,4 ', 4 "-tris (2,2,6,6-tetramethylpiperidine-1-oxyl) phospho-, instead of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl Fight was used. The N-oxyl compound concentration was 5 ppm with respect to potassium acrylate, and the concentration of methoxyhydroquinone was 131 ppm with respect to potassium acrylate. A drying experiment was performed in the same manner as in Example 1 under other conditions. The obtained potassium acrylate powder had a water content of 0.075% by mass, and the mixed alcohol solution test (polymer test) was colorless and transparent. The amount of the polymer measured by high performance liquid chromatography was 0.01% by mass or less.
[0069]
<Example 5>
The amount of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl was 0.000097 kg, the concentration of N-oxyl compound was 0.005 ppm based on potassium acrylate, and the concentration of methoxyhydroquinone was potassium acrylate. On the other hand, the drying experiment was performed in the same manner as in Example 1 except that the concentration was 131 ppm. The obtained potassium acrylate powder had a water content of 0.09% by mass, and the mixed alcohol solution test (polymer test) was slightly suspended in white to precipitate a polymer component. The amount of polymer measured by high performance liquid chromatography was 0.17% by mass.
[0070]
<Example 6>
Under the same polymerization inhibitor conditions as in Example 5, a drying experiment was performed using a centrifugal spray dryer (Okawara Kakoki Co., Ltd., type OD-50, three-point collection). A 50% by mass aqueous solution of potassium acrylate was continuously sprayed from the top of the centrifugal spray dryer. The disk used was M type, diameter 125 mm, number of revolutions was 18000 rpm, raw material supply amount was 150 kg / h, inlet hot air temperature was 260 ° C., outlet temperature was 140 ° C., and as a result of continuous spray drying for 1 hour, the bulk specific gravity was 0. 69 kg of a potassium acrylate powder having 20 g / ml, a water content of 0.0095% by mass, a polymer amount of 0.12% by mass, and a ratio of particles having a particle diameter of less than 74 μm of 95% by mass were obtained. The yield was 92%.
[0071]
Note that the spray drying conditions in Example 6 are higher temperature conditions than the ordinary spray drying conditions. When spray drying an aqueous solution of an alkali metal (meth) acrylate using a normal inhibitor other than the N-oxyl compound, as shown in Comparative Example 4, when the inlet temperature exceeds 240 ° C., the stability rapidly increases. It becomes worse and the amount of polymer in the obtained powder increases. According to this, even in a spray drying apparatus in which the residence time of the powder is short, when the inlet temperature is as high as over 240 ° C., the amount of polymer contained in the dried powder rapidly increases. You can see that. In Example 6 above, such an inlet temperature is higher than 240 ° C., and even in a drying step employing strict spray drying conditions, the N-oxyl compound is used, and the solution has high heat stability. This indicates that the polymer amount of the powder is hardly increased.
[0072]
<Comparative Example 1>
Without adding the N-oxyl compound, the polymerization inhibitor was methoxyhydroquinone alone contained in acrylic acid, the concentration of methoxyhydroquinone was 131 ppm with respect to potassium acrylate, and the other conditions were the same as in Example 1. A drying experiment was performed using a CD dryer. The obtained potassium acrylate powder had a water content of 0.09% by mass. The mixed alcohol solution test (polymer test) was remarkably suspended in white, and a polymer component was precipitated. The polymer amount was 1.5% by mass.
[0073]
<Comparative Example 2>
In addition to methoxyhydroquinone contained in acrylic acid, phenothiazine was added at 200 ppm to potassium acrylate. As a polymerization inhibitor, the concentration of methoxyhydroquinone was 131 ppm with respect to potassium acrylate, the concentration of phenothiazine was 200 ppm with respect to potassium acrylate, and drying experiments were performed using a CD dryer under the other conditions as in Example 1. Was. The obtained potassium acrylate powder had a water content of 0.09% by mass. The mixed alcohol solution test (polymer test) was remarkably suspended in white, and a polymer component was precipitated. The polymer content was 1.3% by mass.
[0074]
<Comparative Example 3>
In addition to methoxyhydroquinone contained in acrylic acid, 300 ppm of hydroquinone was further added to potassium acrylate. As a polymerization inhibitor, the concentration of methoxyhydroquinone was set to 131 ppm with respect to potassium acrylate, the concentration of hydroquinone was set to 300 ppm with respect to potassium acrylate, and drying experiments were performed using a CD dryer under the other conditions as in Example 1. Was. The obtained potassium acrylate powder had a water content of 0.09% by mass. The mixed alcohol solution test (polymer test) was remarkably suspended in white, and a polymer component was precipitated. The polymer content was 1.2% by mass.
From the above comparative examples, it is understood that when the aqueous solution containing a polymerization inhibitor other than the N-oxyl compound is dried using an efficient dryer such as a CD dryer, a polymer is easily generated.
[0075]
<Comparative Example 4>
Under the same polymerization inhibitor conditions as in Comparative Example 3, a drying experiment was performed using a centrifugal spray dryer (Okawara Kakoki Co., Ltd., type OD-50, three-point collection). The drying conditions were the same as those in Example 6, which was more severe than the usual conditions for spray drying. A 50% by mass aqueous solution of potassium acrylate was continuously sprayed from the top of the centrifugal spray dryer. The disk used was M type, diameter 125 mm, number of revolutions was 18000 rpm, raw material supply amount was 150 kg / h, inlet hot air temperature was 260 ° C., outlet temperature was 140 ° C., and as a result of continuous spray drying for 1 hour, the bulk specific gravity was 0. 69 kg of potassium acrylate powder having 20 g / ml, a water content of 0.0095% by mass, a polymer amount of 0.78% by mass, and a ratio of particles having a particle diameter of less than 74 μm of 95% by mass were obtained. The yield was 92%. In Comparative Example 4, the drying conditions in Example 6 were spray drying conditions under somewhat severe conditions. When the aqueous solution using a polymerization inhibitor such as hydroquinone as shown in Comparative Example 3 was dried, the amount of polymer It can be seen that is increased. Therefore, it is considered that problems such as the continuous operation under the drying conditions, that is, the problem such as the above are likely to occur. Also, under these drying conditions, when the aqueous solution containing only a normal polymerization inhibitor is dried, it is expected that the polymer will be mixed and the product quality will be reduced.
[0076]
In this example, the concentration of the N-oxyl compound, the mixed alcohol dissolution test and the measurement of the polymer content were carried out by the following methods.
<Analysis conditions for 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl>
Column: Inertsil PH 5 μm 4.6 mm id × 250 mm
Mobile phase; acetonitrile: water = 5: 95
Column temperature; 50 ° C
Flow rate: 1 ml / min
Detector: UV 240nm
Retention time: 15.62min
Injection volume: 10 μl
Detection limit; 0.1 ppm
[0077]
<Analysis conditions for 4,4 ′, 4 ″ -tris (2,2,6,6-tetramethylpiperidine-1-oxyl) phosphite>
Column: Inertsil PH 5 μm 4.6 mm id × 250 mm
Mobile phase; methanol: water = 7: 3
Column temperature; 50 ° C
Flow rate: 1 ml / min
Detector: UV 240nm
Retention time: 15.46min
Injection volume: 10 μl
Detection limit; 0.1 ppm
[0078]
<Mixed alcohol dissolution test (simple polymer test)>
Potassium acrylate powder 3g
20 g of methanol
20 g of isopropanol
Was mixed. Since the polymer does not dissolve, it becomes cloudy and precipitates. If dissolved homogeneously in a colorless and transparent manner, almost no polymer is contained.
[0079]
<Polymer content measurement method>
Polymer amount: Calculated as area percentage by high performance liquid chromatography.
Column: Shimpack SCR-101H 7.8 mm id × 250 mm
(Made by Shimadzu Corporation)
Mobile phase; 15% of 85% phosphoric acid + 3 L of ultrapure water
Flow rate: 1 ml / min
Detector: HITACHI L-4000H UV detector (200 nm)
Pump; HITACHI L-6000
Retention time; polymer 4.3 minutes
Monomer 12.5 minutes
[0080]
【The invention's effect】
The alkali metal (meth) acrylate and the method for producing the same according to the present invention are metal (meth) acrylates having the above-mentioned constitution and having a reduced polymer content, and sufficiently suppress polymerization. This is a method for producing alkali metal (meth) acrylate, which is used in the fields of water repellent surface treatment agents, fiber treatment agents, antifouling paints for ship bottoms, silane coupling agents, etc. It is useful as a compound and its production method.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an example of an apparatus for producing an alkali metal (meth) acrylate to which the present invention is applied.
FIG. 2 is a schematic view showing an example of an apparatus for producing an alkali metal (meth) acrylate to which the present invention is applied.
FIG. 3 is a schematic diagram of a CD dryer used in the examples.
[Explanation of symbols]
101 Neutralizing pot
102 Intermediate tank
103 Stock solution supply pump
104 air filter
105 blower
106 Hot air generator
107 Spray dryer
108 cyclone
109 Bag Filter
110 Exhaust gas blower
111 storage tank
112 Dry gas input line
113 Dry gas inlet
114 Dry gas outlet
115 Powder outlet
116 stirring blade
117, 122 Damper
118 Sprayer
119-121, 123, 308 Rotary valve
201-208, 304 Piping
301, 302 Double damper
303 cooler
305 jacket
306 Cooling water inlet
307 Cooling water outlet
401 Raw material liquid tank
402, 405 Shoot
403 Circulation pump suction side hose
404 Dry powder tank
406 disk
407 Circulation pump
408 Feed pipe
409 Ventilation fan
410 scraper

Claims (6)

An alkali metal (meth) acrylate containing an N-oxyl compound as a polymerization inhibitor and having a water content of 2000 ppm or less. The alkali metal (meth) acrylate according to claim 1, wherein the average particle diameter of the alkali metal (meth) acrylate is in the range of 0.1 to 500 µm. 3. The alkali metal (meth) acrylate according to claim 1, wherein the content of the N-oxyl compound is 0.000001 to 1% by mass based on the alkali metal (meth) acrylate. 4. . A step of obtaining a solution of an alkali metal (meth) acrylate by a neutralization reaction between (meth) acrylic acid and a compound containing an alkali metal in the presence of an N-oxyl compound. ) A method for producing an alkali metal acrylate. The method for producing an alkali metal (meth) acrylate according to claim 4, further comprising a step of removing a solvent from the solution of the alkali metal (meth) acrylate in the presence of the N-oxyl compound. The method for producing an alkali metal (meth) acrylate according to claim 4 or 5, wherein the N-oxyl compound is contained in an amount of 0.000001 to 1% by mass.

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