JP2005060305A - Method for preventing polymerization of alkali metal (meth)acrylate solution - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for preventing the polymerization of an alkali metal (meth)acrylate solution by which the oligomerization of a solution and the formation of a polymer in piping are prevented, and, as a result, the production process can be stabilized because the polymerizability of the solution is reduced, and the treatment can safely be carried out. <P>SOLUTION: The method for preventing the polymerization of the alkali metal (meth)acrylate solution is the method for preventing the polymerization of a remaining liquid attached to or staying in the metallic piping and/or a tank in a step for transporting the alkali metal (meth)acrylate solution by using the metallic piping and/or the tank, and involves a step for removing the remaining alkali metal (meth)acrylate solution attached to and/or staying in the metallic piping and/or the tank by cleaning the metallic piping and/or the tank with a liquid after the transportation thereof. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a method for preventing polymerization of an alkali metal (meth) acrylate solution. More specifically, in the step of producing a (meth) acrylic acid alkali metal salt powder that is useful as an industrial raw material from a (meth) acrylic acid alkali metal salt solution, the occurrence of problems due to polymerization of the solution is prevented. Regarding the method.

The (meth) acrylic acid alkali metal salt is used for synthesizing various (meth) acrylic acid esters and the like, and is a useful compound as an industrial raw material. Usually, it will be supplied in the form of a powder, and for example, it will be manufactured by a process of preparing a (meth) acrylic acid alkali metal salt solution and then pulverizing it. In such a process, the (meth) acrylic acid alkali metal salt solution is transferred to a drying device, dried, collected in a product hopper (storage tank), and filled into a product form. In doing so, metal pipes and / or tanks are used, and in these, polymerization occurs and gel is generated, resulting in problems in the manufacturing process. For example, the stability of the solution may be impaired, or a gel that cannot be easily removed may be generated in a pipe or a tank.

With respect to the conventional method for preventing polymerization of an alkali metal salt solution of (meth) acrylic acid, water or a lower alcohol is used as a solvent during neutralization, the pH at the end of the reaction is set to 10 to 13, and the solvent is removed after the end of the reaction In addition, it is disclosed that hydroquinone, hydroquinone monomethyl ether, or the like is used as a polymerization inhibitor in a method for producing a potassium salt of acrylic acid or methacrylic acid to be dried (see, for example, Patent Document 1). Further, in the method for producing sodium acrylate or sodium methacrylate powder crystals, in which a sodium acrylate or sodium methacrylate aqueous solution is spray-dried at a drying temperature of 80 to 200 ° C., when the powder crystals are used as esters, phenyl is used as a polymerization inhibitor. It is disclosed that -α-naphthylamine, N, N′-diphenyl-p-phenylenediamine, hydroquinone, phenothiazine, sulfur and the like are used (for example, see Patent Document 2).

Further, in the method of producing an unsaturated carboxylic acid alkali metal salt by drying an aqueous liquid containing an unsaturated carboxylic acid alkali metal salt in a spray form by contacting with a hot air fluid to remove the aqueous component, Discloses that hydroquinone may be added as a polymerization inhibitor (see, for example, Patent Document 3).
However, in these prior arts, the polymerization inhibitor is used to suppress the formation of the polymer and to prevent the polymer from being contained as an impurity. However, the solvent is removed and dried after the completion of the neutralization reaction. At this time, since the purpose is to suppress the formation of a polymer when the powder crystal is used as an ester or during the neutralization reaction of an unsaturated carboxylic acid, the production of (meth) acrylic acid alkali metal salt powder Prevention of the formation of a polymer during and after the transfer of the (meth) acrylic acid alkali metal salt solution in the process has not been studied. Therefore, in this respect, since it is not possible to sufficiently prevent the formation of the polymer, etc., in order to prevent problems such as the formation of the polymer in the transfer step of the (meth) acrylic acid alkali metal salt solution. There was room for ingenuity.
Japanese Examined Patent Publication No. 48-20532 (page 1-2) JP 47-31924 A (page 1-2) Japanese Patent Laid-Open No. 49-11820 (page 1-2)

The present invention has been made in view of the above-described situation, and there is no oligomerization of the solution and no formation of the polymer in the pipe, and as a result, the polymerizability of the solution is reduced, so that it is stable in the manufacturing process and handled safely. An object of the present invention is to provide a method for preventing polymerization of an alkali metal salt solution of (meth) acrylic acid that makes it possible.

The inventors of the present invention have studied various methods for preventing the polymerization of the (meth) acrylic acid alkali metal salt solution. As a result, the (meth) acrylic acid alkali metal salt solution is transferred using a metal pipe and / or tank. Focusing on the fact that prevention of polymerization during the process is effective in suppressing problems in the manufacturing process, and after the transfer of the (meth) acrylic acid alkali metal salt solution is completed, in the metal pipe and / or tank The liquid is washed to prevent polymerization of the residual liquid adhering or staying in the metal pipe and / or tank, so that there is no oligomerization of the solution and formation of polymer in the pipe, resulting in the solution of the solution. It has been found that the polymerization process becomes stable and the manufacturing process becomes stable and can be handled safely, and the above problems can be solved brilliantly. Arrival was. That is, when the solution remains in the pipe and / or tank, a part thereof is polymerized to become a polymer. This polymer is uniformly dissolved in the solution. Even if the polymerization amount is extremely small, the stability of the solution is impaired, and the polymerizability becomes high. In addition, a polymer that cannot be easily washed is formed on the inner wall of the metal pipe, and polymerization is induced from such a location. In addition, a metal component may be contained in a raw material such as NaOH used for neutralization, and this metal component may be activated to induce gelation. However, if washing is always performed with a liquid such as water after the piping and / or tank is used, there is no oligomerization of the solution and no polymer is formed in the piping, resulting in a decrease in the polymerizability of the solution, which is extremely stable. Thus, the present invention has been achieved by finding that it can be handled safely, is not polymerized in the pipe, and does not block the pipe.
Thus, after the transfer of the (meth) acrylic acid alkali metal salt solution is finished, the generated pipe or possible polymerization can be prevented by washing the inside of the metal pipe and / or tank with liquid. As a result, the solution can be handled stably and safely.
Moreover, in the polymerization prevention method of the (meth) acrylic acid alkali metal salt solution of the present invention, it is possible to sufficiently reduce the content of the polymer by applying it to the production of the (meth) acrylic acid alkali metal salt. Thus, an alkali metal (meth) acrylate having excellent stability can be obtained.

That is, the present invention is a method for preventing polymerization of the residual liquid adhering or staying in the metal pipe and / or tank in the step of transferring the (meth) acrylic acid alkali metal salt solution using the metal pipe and / or tank. In this case, after the transfer, the metal pipe and / or the tank is subjected to a liquid cleaning to remove the remaining (meth) acrylic acid alkali metal salt solution that has adhered and / or stayed (meth). This is a method for preventing polymerization of an alkali metal acrylate solution.
The present invention is described in detail below.

In the method of preventing polymerization of the alkali metal salt solution of (meth) acrylate of the present invention, polymerization is prevented when the solution is transferred and / or stored using at least one of a metal pipe and a metal tank. It is applied when the solution is transferred and / or stored multiple times. After the solution is transferred and / or stored, the metal pipes and / or tanks are washed with liquid and adhered to the inside. And / or removal of the remaining (meth) acrylic acid alkali metal salt solution will prevent polymerization in subsequent transport and / or storage of the solution. The (meth) acrylic acid alkali metal salt solution only needs to be one in which the (meth) acrylic acid alkali metal salt is dissolved in a solvent, and the neutralization reaction between the compound containing the alkali metal and (meth) acrylic acid. It is preferable that it is prepared by. As a transfer form of such a (meth) acrylic acid alkali metal salt solution, for example, the step of preparing a (meth) acrylic acid alkali metal salt solution is repeated, and the (meth) acrylic acid alkali metal prepared in a neutralization kettle is used. Examples include a form in which the salt solution is repeatedly transferred to the drying step, a form in which the salt solution is continuously transferred, and the like. Moreover, as a storage form of the (meth) acrylic acid alkali metal salt solution, for example, in the middle of transferring the (meth) acrylic acid alkali metal salt solution prepared in the neutralization kettle to the drying step through a metal pipe or the like, Examples include a form in which the solution is temporarily stored in a tank or the like, and a form in which a solution is repeatedly prepared in a neutralization pot and the solution is stored in an intermediate tank or the like.

In the liquid washing step, as a washing method, a method of washing by pouring a liquid into a metal pipe and / or tank is suitable, and (1) pouring the liquid into the metal pipe and / or tank. (2) A method in which the liquid poured into the metal pipe and / or tank is kept for a certain period of time, and then the liquid is poured out. These methods may be used in combination, and the inner wall of the metal pipe and / or tank may be washed with a brush or the like.

In the liquid washing step, washing is performed to such an extent that gels or solutions staying in metal pipes and / or tanks or attached to inner walls are removed, but by the method (1) above In the case of cleaning, the flow rate of the liquid is preferably 1 kg / min or more and 200 kg / min or less. More preferably, it is 20 kg / min or more and 100 kg / min or less. Moreover, as time to continue flowing a liquid, 10 minutes or more and 180 minutes or less are preferable. More preferably, it is 30 minutes or more and 120 minutes or less.
In the case of cleaning by the above method (2), it is sufficient to pour an amount of liquid that can sufficiently fill the metal pipe and / or tank to be cleaned. It is preferable to pour an amount of liquid that does not exceed the volume.

In the above liquid cleaning process, cleaning may be performed at the end of one transfer and / or storage, or may be cleaned at the end of a plurality of transfers and / or storage, but may be completed at one transfer and / or storage. It is preferable to wash every time. As a result, the effects of the present invention, such as preventing polymerization of the remaining (meth) acrylic acid alkali metal salt solution in the metal pipe and / or tank and preventing induction of gelation, are more fully demonstrated. Will be.
In addition, when preparing a (meth) acrylic acid alkali metal salt solution by a neutralization reaction between an alkali metal-containing compound and (meth) acrylic acid, the (meth) acrylic acid alkali metal prepared in a neutralization kettle It is preferable to wash the metal piping and / or tank between the neutralization kettle and the drying process after all or part of the salt solution has been transferred to the drying process.
In the cleaning of the metal pipe and / or tank, it is preferable to start cleaning within 60 minutes after transfer and / or storage, and it is more preferable to start cleaning within 30 minutes. In addition, the number of washings performed after the completion of the transfer and / or storage and before the start of the next transfer and / or storage may be one or more, and the temperature, (meth) acrylic What is necessary is just to set suitably by the density | concentration of an acid alkali metal salt solution, the frequency | count of a transfer, etc., but 1 time or more and 20 times or less are preferable. More preferably, it is 1 time or more and 10 times or less. In addition, the frequency | count of washing | cleaning is the frequency | count that the liquid was poured out of metal piping and / or a tank.

In the liquid washing step, the liquid used for washing may be a liquid that can remove a small amount of polymer produced in the metal pipe and / or tank from the metal pipe and / or tank, For example, water, a mixed solution of water and an organic solvent, or the like is preferable. Among these, it is preferable to use water. Thus, the form in which the washing in the liquid washing step is performed with water is one of the preferred embodiments of the present invention.
Examples of the organic solvent include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol, t-butyl alcohol and other lower alcohols; acetone, methyl ethyl ketone, diethyl ketone and the like Is preferred. These can use 1 type (s) or 2 or more types.
The temperature of the liquid may be set as appropriate depending on the temperature, the concentration of the alkali metal salt solution (meth) acrylate, the number of transfers, and the like, but is preferably 0 ° C. or higher and 40 ° C. or lower. More preferably, they are 5 degreeC or more and 30 degrees C or less.

The liquid used for the washing also preferably has a pH of 6 to 14, more preferably a pH of 6 to 8. The liquid used for washing | cleaning can be reused by performing a filtration process as needed.
Further, in the liquid washing step, washing is preferably performed until the difference between the pH of the outlet portion of the discharged washing liquid and the pH of the washing liquid before being used for washing becomes 1.0 or less, and 0.5 or less. It is more preferable to wash until it becomes, and it is still more preferable to wash until it becomes 0.3 or less. For example, when the (meth) acrylic acid alkali metal salt solution has a pH of 9.0 and water having a pH of 7.0 is used as the cleaning liquid, the pH of the water used for the cleaning is preferably 8.0 to 7.0. Until the pH is in the range of 7.5 to 7.0, more preferably the pH is in the range of 7.3 to 7.0, and most preferably the pH is 7. The cleaning is performed until zero. For example, when the (meth) acrylic acid alkali metal salt solution has a pH of 9.0, and the pH 9.0 liquid is used as the cleaning liquid, the end point of the cleaning is the specific gravity of the cleaning liquid at the outlet portion and the alkali (meth) acrylate. It can also be determined by comparing the specific gravity of the metal salt solution. More specifically, the outlet of the cleaning liquid is a valve 409 that is an outlet of the cleaning liquid arranged in the pipe shown in FIG. 3 in the process described later, and the cleaning liquid is a liquid discharged from the outlet. is there.

In the present invention, metal pipes and / or tanks are used for transferring and / or storing (meth) acrylic acid alkali metal salt solutions. When metal pipes and / or tanks are used, the polymerization of the (meth) acrylic acid alkali metal salt solution is promoted. In such a case, the effects of the present invention are exhibited.
As said metal piping, piping made from stainless steel etc. can be mentioned, In the polymerization prevention method of the (meth) acrylic-acid alkali metal salt solution of this invention, it can apply preferably to stainless steel piping. As the stainless steel, SUS304, SUS316, Hastelloy and the like are suitable.
The length of the metal pipe may be set as appropriate, but it is preferable to shorten it because it is easy to maintain a stable solution. For example, in the metal pipe connecting the neutralization kettle and the intermediate tank, 500 m or less. It is preferable that More preferably, it is 300 m or less. Moreover, 50 cm or more is preferable and 1 m or more is more preferable. The thickness may be set as appropriate, but the diameter is preferably 1 cm or more and 30 cm or less. More preferably, it is 1.5 cm or more and 10 cm or less.

Examples of the metal tank include SUS304, SUS316, Hastelloy neutralization kettle, intermediate tank, and the like. The capacity is preferably 1 L or more and 15000 L or less. More preferably, it is 50L or more and 10,000L or less. More preferably, it is 100L or more and 10000L or less. In addition, as long as the effect of this invention is exhibited, it is also possible to use resin piping, resin tanks, etc. made from vinyl chloride.

In the present invention, for example, a straight pipe portion or a bent portion in a metal pipe, a strainer installed between a neutralization kettle and a drying device, a portion where a solution such as a reservoir or a dead space is likely to adhere and / or remain. Polymerization of the (meth) acrylic acid alkali metal salt solution in can be sufficiently prevented. Thus, it is one of preferred embodiments that the present invention is configured to prevent polymerization of the residual liquid in at least one of the straight pipe portion, the bent portion, the dead space portion, and the strainer portion. .

The (meth) acrylic acid alkali metal salt solution in the present invention is preferably prepared by a neutralization reaction between a compound containing an alkali metal and (meth) acrylic acid, as described above. ) A method of gradually adding (meth) acrylic acid to a solution of a compound containing alkali metal, and (B) A method of gradually adding a compound containing alkali metal to (meth) acrylic acid. Preferred is a method, (C) a method in which a solution of a compound containing an alkali metal and (meth) acrylic acid are gradually added together in a solvent as described above. For example, (meth) acrylic acid is added by gradually adding (meth) acrylic acid to an aqueous solution of alkali metal hydroxide or alkali metal carbonate, or by gradually adding alkali metal alkoxide to (meth) acrylic acid. It can be prepared by preparing an alcohol solution of a metal salt or gradually adding an aqueous solution of an alkali metal hydroxide and (meth) acrylic acid gradually into water. These neutralization reactions are preferably carried out in an air atmosphere in order to prevent polymerization during the reaction.
As the solvent in the (meth) acrylic acid alkali metal salt solution, water, a mixed solution of water and an organic solvent soluble in water, and the like are suitable, and water is preferred. The organic solvent is the same as that described above.
The (meth) acrylic acid alkali metal salt solution in the present invention is preferably in the form of an aqueous solution. That is, it is a preferable form to use an aqueous solution of an alkali metal (meth) acrylate.

In the above preparation method, it is preferable to sufficiently cool and stir in the neutralization kettle as described above. The neutralization reaction temperature is preferably 0 ° C. or higher and 70 ° C. or lower. If it is lower than 0 ° C, the alkali metal-containing compound or (meth) acrylic acid may be solidified, and if it exceeds 70 ° C, (meth) acrylic acid may cause polymerization. More preferably, it is 10 degreeC or more and 60 degrees C or less. More preferably, it is 20 degreeC or more and 50 degrees C or less. What is necessary is just to set suitably as a stirring speed to such an extent that the compound containing an alkali metal and (meth) acrylic acid can fully contact.

In the neutralization reaction, the pH at the reaction end point is preferably 7 or more and 13 or less. If the pH is less than 7, the remaining (meth) acrylic acid increases and polymerization may occur during drying. If the pH exceeds 13, the remaining alkali metal-containing compound increases, and the final form There is a possibility of causing problems such as hydrolysis in the reaction using the alkali metal (meth) acrylate obtained as above. More preferably, the pH is 8 or more and 11 or less.

As the above-mentioned compound containing an alkali metal, an alkali metal hydroxide, an alkali metal carbonate, an alkali metal alkoxide, or the like is preferable. As an alkali metal, lithium, sodium, potassium, rubidium, cesium, or the like is preferable. Each of these can be used alone or in combination of two or more.
A preferable form of the (meth) acrylic acid alkali metal salt in the present invention is a form of a salt of (meth) acrylic acid and 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 a (meth) acrylic acid alkali metal salt solution in which the (meth) acrylic acid alkali metal salt is a (meth) acrylic acid potassium salt. This polymerization prevention method is one of the preferred embodiments of the present invention.
In the (meth) acrylic acid, a polymerization inhibitor such as hydroquinone or hydroquinone monomethyl ether may be added.
In addition, when the potassium (meth) acrylate is produced, if the alkali metal hydroxide used in the neutralization step is potassium hydroxide, (meth) acrylic acid remaining after the neutralization step or adhering to the pipe Since potassium solution is a compound that is particularly easily polymerized, gels are likely to accumulate. This reason is presumed to be due to the influence of components contained in KOH used for neutralization. Therefore, it becomes a very preferable embodiment for obtaining the effect of the present invention. In particular, in the case of potassium acrylate, the gel is easily accumulated.

In the above (meth) acrylic acid alkali metal salt solution, it is a preferable form to contain a polymerization inhibitor. Examples of the polymerization inhibitor include N-oxyl compounds; hydroquinone, methyl hydroquinone, hydroquinone monomethyl ether, tert-butyl hydroquinone, 2,6-di-tert-butyl hydroquinone, 2,5-di-tert-butyl hydroquinone, 2 , 4-dimethyl-6-tert-butylphenol, cresol, tert-butylcatechol, and other phenol compounds; 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, N'-di-2-naphthyl-p -P-Phenylenedia, such as phenylenediamine Down like; thiodiphenylamine, amine compounds such as phenothiazine; tetrabutyl thiuram disulfide, tetra-propyl disulfide, tetraethyl thiuram disulfide, tetra-alkyl thiuram disulfides such as tetramethylthiuram disulfide; methylene blue and the like. These can use 1 type (s) or 2 or more types. Moreover, if molecular oxygen is used together as necessary, the polymerization inhibition effect is further improved. By containing a polymerization inhibitor in the (meth) acrylic acid alkali metal salt solution, it is possible to suppress polymerization during the process, polymerization due to heat during spray drying, and other inadvertent polymerization during storage. . The content of the polymerization inhibitor is preferably 1 to 500 ppm. Even if the amount increases, it does not become so high in terms of the polymerization inhibition effect above a predetermined level, so it is not necessary to add a predetermined amount or more. Moreover, when using too much (meth) acrylic-acid alkali metal salt which is the form of this case when there is too much, it is because the polymerizability of an acryloyl group may be reduced. Moreover, when using an N-oxyl compound as said polymerization inhibitor, it is also possible to reduce the content.

As content of the said N-oxyl compound, it is preferable that it is 0.000001 mass% or more and 1 mass% or less with respect to (meth) acrylic-acid alkali metal salt. If it is less than 0.000001% by mass, the content of the polymer may not be sufficiently reduced, and even if it exceeds 1% by mass, the content of the polymer can be reduced. There is a possibility that the effect corresponding to the content cannot be obtained. More preferably, they are 0.000005 mass% or more and 0.5 mass% or less. More preferably, it is 0.00001 mass% or more and 0.1 mass% or less. Most preferably, it is 0.0005 mass% or more and 0.05 mass% or less. More preferably, it is 0.0008 mass% or more and 0.01 mass% or less. Most preferably, it is 0.001 mass% or more and 0.005 mass% or less.

The concentration of the (meth) acrylic acid alkali metal salt in the (meth) acrylic acid alkali metal salt solution is preferably 10% by mass or more and 70% by mass or less at 25 ° C. If the amount is less than 10% by mass, a large amount of heat may be required when the solution is dried, and the drying apparatus may be large. If it exceeds 70% by mass, problems such as crystallization and polymerization may occur. More preferably, it is 30 mass% or more and 65 mass% or less.
When the (meth) acrylic acid alkali metal salt solution is used in a state heated to 50 ° C., the content is preferably 10% by mass or more and 80% by mass or less. More preferably, it is 30 mass% or more and 75 mass% or less.
Further, the (meth) acrylic acid alkali metal salt solution is preferably in a form in which the (meth) acrylic acid alkali metal salt is dissolved. However, the method for preventing polymerization of the (meth) acrylic acid alkali metal salt solution of the present invention has a problem. If not, the alkali metal (meth) acrylate may be dispersed.

The present invention is a method preferably applied to the production of (meth) acrylic acid alkali metal salt powder, and the powder is preferably produced by removing the solvent from the solution. Therefore, the (meth) acrylic acid alkali metal salt powder comprising the step of performing the polymerization prevention method of the (meth) acrylic acid alkali metal salt solution and the drying step of removing the solvent from the (meth) acrylic acid alkali metal salt solution The body manufacturing method is a preferred embodiment of the present invention.
Further, a production plant of (meth) acrylic acid alkali metal salt powder to which such a production method is applied, that is, a step of performing a polymerization prevention method, and a drying step of removing the solvent from the (meth) acrylic acid alkali metal salt solution A production plant capable of performing the above is one of the preferred embodiments of the present invention.

As a method for removing the solvent, it is preferable to remove the solvent using a drying device in the drying step (separation drying step), and any drying device can be used as the drying device. For example, a crusher Attached air dryer, spray dryer (spray dryer), co-current rotary dryer, grooved stirring dryer, multi-stage fluidized bed dryer, horizontal multi-chamber fluidized bed dryer, one-stage one-chamber fluidized bed dryer, Batch type fluidized bed drying device, multi-stage band ventilation drying device, end face suction type ventilation rotary drying device, louver suction type vertical ventilation drying device, ventilation box type batch drying device, conduction electric heating type cylindrical drying device (drum dryer) Various drying apparatuses such as a conductive heating type drying apparatus can be used.

Hereinafter, an embodiment of the present invention will be described with reference to FIG. 1 and FIG. 2 which are schematic diagrams showing an example of an apparatus for producing (meth) acrylic acid alkali metal salt powder.
In the manufacturing apparatus shown in FIG. 1, the neutralization pot 101, the intermediate tank 102, the undiluted solution supply pump 103, the air filter 104, the blower 105, the hot air generator 106, the spray drying apparatus 107, the cyclone 108, the bag filter 109, and the exhaust gas blower 110. A storage tank 111, a dry gas input line 112, a dry gas input port 113, a dry gas discharge port 114, a powder discharge port 115, a damper 117, a rotary valve 119, and the like, which are connected by a pipe 201 or the like. Yes.

The neutralization pot 101 is provided with a stirring blade 116, and a (meth) acrylic acid alkali metal salt solution is prepared. The neutralization pot 101 is connected to an intermediate tank 102 by a pipe 201, and the intermediate tank 102 is connected to a stock solution supply pump 103 through a pipe 202.
The spray drying device 107 includes a spray disc 118 that rotates at high speed, and is a centrifugal undiluted solution atomizer that can dry a solution by atomizing the solution by centrifugal force and bringing it into contact with hot air. The stock solution supply pump 103 is connected to the spray drying device 107 via a pipe 203, and the hot air generator 106, the blower 105, the damper 117, and the air filter 104 are connected in this order from the spray drying device 107 side. . Further, the spray drying apparatus 107 is connected to the cyclone 108 via a pipe 204 and is also connected to the storage tank 111 via a rotary valve 119 and a pipe 205.

The cyclone 108 is a device that collects (meth) acrylic acid alkali metal salt powder obtained by drying downward by centrifugal force. The bottom of the cyclone 108 is placed in the storage tank 111 via the rotary valve 120 and the pipe 206. The tower tops are connected to the bag filter 109 by a pipe 207.
The bag filter 109 is a device that collects fine fine powder, and its bottom is connected to the storage tank 111 via a rotary valve 121 and a pipe 208. An exhaust gas blower 110 is connected to the top of the bag filter 109 via a damper 122, and exhaust gas is discharged from the exhaust gas blower 110.
The storage tank 111 is provided with a dry gas inlet 113 connected to the dry gas inlet line 112 at the bottom and a dry gas outlet 114 at the top, and a powder outlet 115 via a rotary valve 123. ing.

The powder from the bottom of the spray drying apparatus main body is a group of powders having a large particle diameter, and those having a smaller average particle diameter than that not collected here are collected by a cyclone. Similarly, the powder from under the cyclone is collected with an average particle size slightly smaller than that under the spray dryer main body. And the powder with the smallest average particle diameter which does not fall here is sent to a bag filter. In terms of parts by weight, based on 100 parts by weight of the finally obtained (meth) acrylic acid alkali metal salt powder, the range of 80 to 90 parts by weight under the spray dryer main unit: under the cyclone: under the bag filter, respectively: A range of 5 to 15 parts by weight: A form that is fractionated so as to be in a range of 5 to 15 parts by weight is preferable.
In addition, in the storage tank, the pipe of (meth) acrylic acid alkali metal salt powder from the bottom of the spray dryer unit, the pipe from the cyclone, and the pipe from the bottom of the bag filter are joined to the upper part of the storage tank. In addition, a form in which (meth) acrylic acid alkali metal salt powders having different average particle diameters can be collected is a preferable form. By adopting this form, it is possible to efficiently collect (meth) acrylic acid alkali metal salt powders having various average particle diameters and produce (meth) acrylic acid alkali metal salt powders with high yield. If desired, there may be a step of appropriately cutting the fine powder.

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 includes a cooler 303 connected to the powder discharge port 115, and the spray drying apparatus 107 is not connected to the storage tank 111, and the bottom thereof is connected to the cyclone 108 by the pipe 304. It is connected.
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.

Next, the manufacturing process of the (meth) acrylic-acid alkali metal salt powder to which this invention is applied is demonstrated using FIG.1 and FIG.2.
In FIG. 1, a (meth) acrylic acid alkali metal salt solution is prepared in a neutralization pot 101, and the solution is stored in an intermediate tank 102 through a pipe 201. The stored solution is supplied to the spray drying device 107 through the pipe 203 by the stock solution supply pump 103, and the gas passing through the air filter 104 is sent to the hot air generator 106 by the blower 105, and the spray drying device 107 is supplied. Is supplied as hot air to remove the solvent of the alkali metal (meth) acrylate solution.
In the present invention, the neutralization kettle 1, the pipe 101, the intermediate tank 2, and the pipe 102 are washed with a liquid such as water after the transfer of the (meth) acrylic acid alkali metal salt solution to the spray drying apparatus 107 is completed. become. By such washing, the generated gel or the possible polymerization can be prevented in advance, and the solution can be handled stably and safely.
In the solvent removal step, a spray drying device (spray drying device) is used. However, in addition to the spray drying device, it is possible to dry using various drying devices as described above.

In the spray drying device 107, the solution is sent to the spray platen 118, atomized by the high speed rotation of the spray platen 118, and dried by contacting with hot air to become (meth) acrylic acid alkali metal salt powder. .
The spray drying apparatus may be of any form such as a form in which a spray solution and hot air are in cocurrent contact, a form in which countercurrent contact is made, or a form in which cocurrent contact is made after a countercurrent contact. Further, the spray drying device 107 includes a spray board 118 for spraying the solution, but a nozzle such as a pressure nozzle, a two-fluid nozzle, a pressure two-fluid nozzle, or the like can also be used.

The amount of the solution supplied to the spray dryer is preferably 0.7 kg / min or more and 5.3 kg / min or less. More preferably, it is 1.0 kg / min or more and 3.3 kg / min or less.

As the hot air, air, inert gases such as carbon dioxide, nitrogen, and argon are suitable, and among these, air is preferably used.
The temperature, water content and supply amount of the hot air may be appropriately set depending on the concentration of the solution, the supply amount, etc., but the temperature is preferably 150 ° C. or higher and 250 ° C. or lower. If the temperature is lower than 150 ° C, the moisture content of the resulting powder may not be sufficiently reduced, and if it exceeds 250 ° C, solid phase polymerization may be liable to occur. More preferably, it is 160 degreeC or more and 230 degrees C or less.
Moreover, it is not necessary to prescribe | regulate especially as a moisture content. When air is used as the gas, the atmosphere is used as it is, so the humidity is arbitrary. Since the hot air used here contains a large amount of water evaporated in the solvent removal step, the amount of water in the initial hot air is not particularly limited.

The residence time of the powder in the spray dryer is preferably 10 seconds or more and 120 seconds or less. More preferably, it is 15 seconds or more and 90 seconds or less. More preferably, it is 20 seconds or more and 60 seconds or less. The residence time (seconds) of the powder can be calculated by the following formula.
Residence time of powder (seconds) = capacity of spray dryer (m ³ ) ÷ volume of hot air (m ³ / s)
Such hot air conditions are preferably set as appropriate so that the water content of the (meth) acrylic acid alkali metal salt powder after drying by the spray dryer is suitable.

The (meth) acrylic acid alkali metal salt powder obtained by drying with the spray drying apparatus 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 under 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. In addition, powder that is 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 (meth) acrylic acid alkali metal salt powder obtained by drying with the spray dryer 107 passes through the pipe 304 and is collected in the cyclone 108. Further, 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.

In the bag filter 109, the collected fine powder is dropped downward by an air pulse and collected. 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 the small particles that cannot be collected by the bag filter 109 are discarded from the exhaust gas blower 110 through the damper 122. become.

In addition to FIGS. 1 and 2, as shown in FIG. 4, the spray drying device 107 and the cyclone 108 which are the separation and drying devices are connected in parallel to the powder transfer pipe 501. A mode in which the space between the transfer pipe 501 is separated by double dampers 301 and 309 or a rotary valve is preferable. More preferably, the bag filter 109 is also connected in parallel with the powder transfer pipe 501. Similarly, the double damper 302 or the gap between the bag filter 109 and the gas transfer pipe 501 is provided. It is a form separated by a rotary valve. Further, the transfer pipe 501 is preferably in a form in which a transfer gas is introduced from another path (arrow 504 in FIG. 4) and the powder is transferred (arrow 505 in FIG. 4). The transferred powder may be collected in the small cyclone 502. In this case, the powder collected in the small cyclone 502 is put into the storage tank 111 via the double damper 310 or the like, and is stored in the storage tank. It is preferable that fine powder that is not put into 111 passes through the pipe 503 (arrow 506 in FIG. 4) and is collected by the bag filter 109.
At this time, although it is a carrier gas introduced into the transfer pipe, a gas having a dew point of 12 ° C. or less and a temperature of 35 to 95 ° C. is used, and the linear velocity in the gas transfer pipe is set to 5 m / s or more. Maintaining the supply amount (X) of the (meth) acrylic acid alkali metal salt powder from the step of separating and drying into the transfer pipe in a range of 5 to 150 kg / hr, the gas into the transfer pipe The supply amount (Y) is preferably in the range of 5 to 5000 m ³ / hr.
More preferably, the dew point of the carrier gas is 10 ° C. or lower. More preferably, it is 5 degrees C or less, More preferably, it is 0 degrees C or less, Most preferably, it is -5 degrees C or less.
The mode of introducing gas to perform the transfer as maximum powder transfer amount that can be transported in the gas 1 m ³ in the above transfer pipe is 30kg or less.
Specifically, the supply amount (X (kg / hr)) of the (meth) acrylic acid alkali metal salt powder and the supply amount of gas (Y (m ³ ) from the separation and drying step into the transfer pipe. / Hr)) and the following formula representing the ratio:
X / Y
Is more preferably 30 or less, further 10 or less, still more preferably 5 or less, still more preferably 3 or less, and most preferably 1 or less. In addition, although the lower limit, the value of the above formula is small, it corresponds to a case where a small amount of powder is transferred with a large amount of gas. This is very unfavorable because it is very disadvantageous in terms of process manufacturing costs. Therefore, in the present invention, in a more preferred embodiment, the lower limit of the above formula is 0.001 or more. More preferably, it is 0.005 or more. Incidentally, the value of this equation being 0.005 is a condition for supplying a transfer gas of 5000 m ³ per hour and supplying and transferring 25 kg of the powder. More preferably, it is 0.01 or more. For example, a value of 0.08 for this equation is a condition for supplying 1200 m ^{3 of} transfer gas per hour and supplying 100 kg of the powder for transfer. More preferably, it is 0.05 or more, More preferably, it is 0.1 or more.

By installing the transfer pipe 501 as described above, the moisture accompanying the powder obtained after the spray drying is replaced with a gas introduced from another path without being introduced into the transfer pipe. Or it can be diluted. Therefore, moisture can be effectively removed from the powder during the transfer, and the temperature of the powder can be lowered. Therefore, the method for producing the alkali metal salt powder of (meth) acrylic acid salt including the polymerization prevention method of the present invention as a pre-process of the process of installing the transfer pipe into which the carrier gas is introduced under the specific conditions as described above Is a preferred embodiment. The figure of this form is shown in FIG. 4, and the number is not shown, but in the process of installing the transfer pipe, the spray drying device 107 and the cyclone 108 are in the lower part of the spray drying device 107. In addition to the transfer pipe 501, a pipe for flowing a hot air stream accompanied by a large amount of moisture after spray drying to the cyclone is connected. The hot air flow accompanying the wet air is further separated from the powder by the cyclone 108 and discharged out of the manufacturing system through the bag filter 109 (arrow 507 in FIG. 4). Each device and the transfer pipe 501 are separated by a double damper 301 or the like, and the hot air flow accompanying the moisture is not directly introduced into the transfer pipe 501. Therefore, when transferring the powder, the transfer step is a preferred mode. Moreover, after the said transfer process, in the storage tank 111, a dry gas is introduce | transduced as needed. Further, the powder is discharged from the storage tank 111 through the powder discharge port 115 (arrow 508 in FIG. 4).

In the storage tank 111, (meth) acrylic acid alkali metal salt powder sent from the spray drying device 107, the cyclone 108 and the bag filter 109 is charged from a powder inlet (not shown). In this case, it is preferable that the (meth) acrylic acid alkali metal salt powder is suspended in suspension by supplying the dry gas supplied from the dry gas input line 112 through the dry gas input port 113. By such suspension in suspension, the wet gas around the powder particles is replaced with dry gas. The wet gas is exhausted from the dry gas discharge port 114.

The suspension suspension (bubble) of the (meth) acrylic acid alkali metal salt powder means that the dry gas enters between the particles, so that the moist air around each particle of the (meth) acrylic acid alkali metal salt powder. In order to be able to replace the body, a part of or all of the powder is flowed by introducing a dry gas. A preferred form is to put the dry gas into the powder layer so that the powder is foamed by the dry gas.
The dry gas to be introduced is in a form having a dew point of 0 ° C. or lower and a temperature of 20 to 80 ° C., more preferably 30 to 70 ° C. By using the dry gas under these conditions, the above suspension suspension can be performed more effectively, and the inadvertent polymerization of the target (meth) acrylic acid alkali metal salt is suppressed. You can also.
The powder is an aggregate of a large number of solid particles, in which a moderate interaction force is acting between the particles, and when the gas is blown from the lower part of the powder layer, the gas rises. Therefore, it can be easily fluidized. The powder layer is a powder accumulated in the storage tank.

In the present invention, the dry gas to be charged is represented by the following formula (1);
X ≧ 3V / T (1)
(In the formula, T is the residence time (s) of the powder in the storage tank, V is the volume (L) of the storage tank, and X is the input speed (L / s) of the dry gas. .) Is preferably introduced in accordance with. More preferably, the following formula (2);
X ≧ 5V / T (2)
Is to be put into compliance.
The residence time T of the powder in the storage tank is preferably 300 seconds or longer and 864000 seconds (10 days) or shorter. More preferably, it is 600 seconds or more and 86400 seconds (one day) or less. More preferably, it is 1800 seconds or more and 10 hours or less. More preferably, it is 1800 seconds or more and 5 hours or less. Particularly preferably, it is 3 hours or less.

As said storage tank, the (meth) acrylic-acid alkali metal salt powder from the opening (powder input port) which puts the (meth) acrylic-acid alkali metal salt powder obtained by the solvent removal process into a storage tank, and a storage tank It is preferable that the container is further provided with a dry gas inlet and a dry gas outlet at the bottom of the storage tank. Is preferably introduced. Thus, by suspending (meth) acrylic acid alkali metal salt powder in suspension, the wet gas around the powder particles is replaced with dry gas, and the wet gas that has flowed out of the powder layer is Then, the gas is exhausted from the dry gas discharge port. In addition, another process may be included from the solvent removal process to the charging of the (meth) acrylic acid alkali metal salt powder into the storage tank. When filling the container with powder, the container may be filled directly from the powder discharge port, or may be filled into the container via, for example, a cooler.

The (meth) acrylic acid alkali metal salt powder in the storage tank 111 passes through the rotary valve 123 and is filled into the container from the powder discharge port 115. Further, it is preferable that the container is filled after the temperature of the powder is lowered to a preferable temperature by using a cooler 303 as shown in FIG. In this case, the temperature of the cooled powder is preferably 70 ° C. or less, and more preferably 60 ° C. or less.
In the production method of the present invention, a form in which (meth) acrylic acid alkali metal salt powder is suspended and suspended in a storage tank and then filled into a container through a cooler is also a preferred form. The temperature of the (meth) acrylic acid alkali metal salt powder can be reliably lowered by passing through the cooler, suppresses heat storage when the powder is filled and stored in the container, and polymerizes the powder by heat storage. This is because it can be prevented, and as a result, storage stability can be imparted.

Examples of the container include a paper bag and a flexible container bag. More preferably, there is an inner layer or inner bag made of a sealing material inside the container. The sealing material is not particularly limited as long as it does not allow water to permeate, and a plastic film or the like is preferable. Among them, polyvinylidene chloride is preferable. A film in which an aluminum layer is laminated is also preferable. As such a film, a film in which an aluminum thin film is put in a container structure is preferable. For example, a film in which aluminum foil is coated or laminated is preferably used. Such an aluminum thin film may be obtained by vapor deposition. Further, as long as the container can be sealed, a metal container such as aluminum, SUS, or tin, or a plastic container may be used.

Hereinafter, an embodiment of the present invention will be further described with reference to FIG. 3 which is a schematic view showing an example of an aqueous solution of an alkali metal salt of (meth) acrylate.
The (meth) acrylic acid alkali metal salt aqueous solution transfer line shown in FIG. 3 includes a neutralization kettle 404, an intermediate tank 407, and a spray drying device 408. The neutralization kettle 404, the intermediate tank 407, and the intermediate tank 407 are spray dried. The apparatus 408 is connected to each other via a metal pipe, a valve 409, and a liquid feed pump 406. The neutralization kettle 404 is connected to a line 401 for introducing (meth) acrylic acid, a line 402 for introducing an alkali metal compound, and a line 403 for introducing pure water. A strainer 405 is provided in the middle of the metal pipe. is set up. Further, a pure water cleaning line 410 is connected in the middle of the transfer line.
In the (meth) acrylic acid alkali metal salt aqueous solution transfer line, the raw materials are charged into the neutralization kettle 404 from the (meth) acrylic acid charging line 401, the alkali metal compound charging line 402 and the pure water charging line 403, respectively. An aqueous (meth) acrylic acid alkali metal salt solution is prepared. The aqueous solution is transferred and / or stored in the intermediate tank 407 and the spray drying device 408 through a metal pipe. After the aqueous solution is transferred and / or stored, if the neutralization kettle 404 is used, the pure water is supplied from the pure water input line 403. And (meth) acrylic acid alkali metal salt adhering to and / or staying on the metal pipe, the neutralization kettle 404, the intermediate tank 407, the strainer 405, etc. by supplying water from the pure water washing line 410 and washing. The aqueous solution will be removed. Further, after cleaning, the cleaning liquid is discharged from a valve 409 connected to the pipe. In this way, the aqueous solution is washed after being transferred and / or stored, and after washing, the washing solution after washing is extracted from a valve installed in the pipe. That is, in the present invention, after washing with liquid, it is used for washing liquid. It is a preferred embodiment to drain the liquid through a valve installed in the piping.

As a preferred embodiment of the present invention, such a form shown in FIG. 3 is mentioned. In transferring and / or storing an aqueous solution of an alkali metal (meth) acrylate, a metal pipe, a strainer (a foreign matter removing wire mesh filtration device). ), A liquid feed line in which a liquid feed pump, an intermediate tank, a valve and the like are appropriately combined is preferably used. This liquid feed line includes a straight pipe part, a bent part, a dead space part, a strainer part, a liquid feed pump part, etc., but any part is a place where the solution tends to accumulate after the transfer process, and time has passed. As a result, undesirable polymerization can be induced from such points. When a polymer is generated, the gel no longer easily dissolves in water, and therefore, a great amount of labor and time are consumed for the removal work. In addition, it is difficult to completely remove the gel from the line once polymerized, and the gel stuck to the minute irregularities on the pipe surface or the gel stuck to the gap of the mesh part of the strainer is another polymerization. Therefore, even if the liquid feed line once polymerized is completely washed and reused, as long as the liquid feed line is used, there is a problem that polymerization troubles frequently occur. Therefore, before the above polymerization can occur, it is a preferred embodiment of the present invention to remove the solution in advance by washing the reservoir of the liquid that causes inadvertent polymerization. is there. In addition to the above-mentioned places where the liquid tends to stay, there may be places where the liquid tends to stay similarly depending on the installation conditions of piping and equipment. It is a preferred embodiment of the present invention to wash a portion where the liquid is liable to stay other than the portions described above.

In the (meth) acrylic acid alkali metal salt powder obtained in the present invention, the water content is preferably 600 ppm or less. If it exceeds 600 ppm, fouling due to powder tends to occur in the pneumatic transport line 5 and the piping, and clogging may occur easily. More preferably, it is 550 ppm or less, More preferably, it is 500 ppm or less, More preferably, it is 350 ppm or less, Especially preferably, it is 300 ppm or less, Most preferably, it is 250 ppm or less.

The water content can be measured by the following method.
Method: Karl Fischer method Measuring instrument: Automatic moisture analyzer KF-07 (Mitsubishi Chemical Corporation)
Titration solvent: Methanol (special grade reagent)
Sample introduction method: Sample collection into a titration flask and uniformly dissolved Sample weighing and weighing atmosphere: Air sampled to a relative humidity of 25% Sample collection amount: 2.0 ± 0.2 g
Moisture measurement end point waiting time: 30 paper

The alkali metal salt (meth) acrylate obtained in the present invention is preferably a powder having an average particle size in the range of 0.1 to 500 μm. When the average particle size is less than 0.1 μm, the agglomeration force between the powders is strong, so that aggregates are easily formed, and it is difficult to flow even when a dry gas is added. Subsequent replacement of moisture around the powder may cause sticking. On the other hand, when the average particle diameter of the powder exceeds 500 μm, there is a possibility that the powder cannot 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, they are 1 micrometer or more and 300 micrometers or less.
The average particle size can be measured according to the dry sieving test method of JIS K0069 “Chemical Product Sieving Test Method”.

In addition, the form of the alkali metal (meth) acrylate obtained in the present invention may be any form of flakes, tablets, granules, granules, and powders (powder). preferable. In addition, (meth) acrylic acid alkali metal salts, particularly potassium acrylate, are more hygroscopic and less susceptible to humidity as the specific surface area is smaller. Therefore, granules to flakes having a relatively small specific surface area are also preferred forms. is there.

The alkali metal (meth) acrylate obtained in 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. Moreover, it is preferable that it is 1.20 g / ml or less. More preferably, it is 1.00 g / ml or less, More preferably, it is 0.60 g / ml or less, Most preferably, it is 0.55 g / ml or less. It becomes a preferable form that the (meth) acrylic acid alkali metal salt in this invention has the said bulk specific gravity.
As the 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 piled up in the cylindrical container. Next, after scraping off the mountain with a spatula with a straight side, the mass is measured and the mass per ml is calculated. Such measurement is performed on 10 samples, and the average value is obtained. The measurement is performed at 25 ° C. and a humidity of 60%.

As said (meth) acrylic-acid alkali metal salt, when a polymer content makes 100 mass% of (meth) acrylic-acid alkali metal salts, it is preferable that it is 0.2 mass% or less. More preferably, it is 0.1 mass% or less, More preferably, it is 0.07 mass% or less.
The content of the polymer can be measured under the following conditions.
<Polymer content measurement method>
Polymer amount: Calculated by area percentage by high performance liquid chromatography.
Column; Shimpack SCR-101H 7.8 mm id × 250 mm (manufactured by Shimadzu Corporation)
Mobile phase: 85% phosphoric acid 15ml + ultrapure water 3L
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

The alkali metal (meth) acrylate may be in a form dispersed in an organic solvent such as toluene. At this time, when the density | concentration of the slurry obtained by disperse | distributing in toluene is 40 mass%, it is preferable that this slurry viscosity is 600 mPa * s or less. More preferably, it is 500 mPa * s or less, More preferably, it is 200 mPa * s or less, Most preferably, it is 100 mPa * s or less. At this time, a preferable solid content concentration is 5 to 50%, more preferably 10 to 40%. If the concentration is out of the above range, the viscosity becomes too high and the handling becomes difficult. By handling the powder as a slurry, solidification or agglomeration due to moisture absorption or the like of the powder can be prevented.
As a method for measuring the slurry viscosity, an alkali metal (meth) acrylate is charged into toluene (500 g) in an atmosphere of a temperature of 25 ° C. and a humidity of 25% so that the solid concentration is 40% by mass, It is preferable to use a four-blade stirring blade to stir at a rotation speed of 200 times / minute with a three-one motor to form a slurry, and measure the viscosity of the obtained slurry with a BL type viscometer.
Moreover, it can replace with toluene and can also be set as a dispersion using alcohol. The alkyl group constituting the alcohol may include a branched chain. Examples of alcohols include methanol, ethanol, propanol, butanol, pentanol, octanol and the like. Polyhydric alcohols can also be used, and examples thereof include ethylene glycol, propylene glycol, glycerin, 1,4-butanediol and the like.

The method for preventing polymerization of a (meth) acrylic acid alkali metal salt solution according to the present invention has the above-described configuration, and there is no oligomerization of the solution and no formation of a polymer in the pipe. As a result, the polymerizability of the solution is reduced. Alkali metal (meth) acrylate, which is stable in the manufacturing process and enables safe handling, and is a compound useful as an industrial raw material used to synthesize various (meth) acrylic acid esters. It is also useful in the salt production method.

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples. Unless otherwise specified, “part” means “part by weight” and “%” means “mass%”.

Example 1
<Neutralization reaction>
To a 6 m ³ stirrer and a reaction kettle with a jacket, 552 kg of pure water was charged while flowing cooling water through the jacket, and 2056.6 kg of 48 mass% potassium hydroxide aqueous solution was charged with stirring. 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 exceed 25 ° C. After completion of the dropping, the pH of the aqueous solution was measured, and acrylic acid or an aqueous potassium hydroxide solution was added so as to fall within the range of 8.1 to 9.5. In this way, 3876.8 kg of 50 mass% potassium acrylate aqueous solution was obtained. The concentration of methoxyhydroquinone was 65 ppm with respect to a 50 mass% potassium acrylate aqueous solution. A transfer test was performed using this aqueous solution.

<Transport test>
From the reaction vessel in which the neutralization reaction was performed, 3876.8 kg of a 50% by mass potassium acrylate aqueous solution was transferred to an intermediate tank having an internal volume of 15 m ³ via a 50 m pipe made of SUS304 having an inner diameter of 65 mm. After completion of the transfer, 50 L of the potassium acrylate aqueous solution remaining in the transfer pipe was extracted from the T-shaped pipe part 2 m before the intermediate tank. Next, 500 L of pure water was poured into the empty neutralization kettle over 20 minutes so that the inner wall and the top plate were washed away, and the inside of the neutralization kettle was washed. Next, this cleaning liquid 500L was poured into a pipe made of SUS304 having an inner diameter of 65 mm and a length of 50 m connected to the intermediate tank, and the pipe was washed while extracting the cleaning liquid from the T-shaped pipe portion 2 m before the intermediate tank. This series of washing operations was performed once immediately after the neutralization liquid was transferred and repeated for 30 days. After 30 days, the 50 m pipe was disassembled into 10 points from the flange joint, and the state inside the pipe was observed visually or using an endoscope for each of the decomposed pipes. As a result, there was no adhesion of gel in all 10 pipes. Moreover, even if it tried touching the inside of piping with a finger, there was no touch which was made into slimy.

Example 2
<Neutralization reaction>
Into a reactor equipped with a stirrer and jacket with an internal volume of 6 m ³ , 1554.8 kg of pure water was charged while flowing cooling water through the jacket, and 131.2 kg of 48 mass% sodium hydroxide aqueous solution was charged while stirring. Next, 1133.9 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 exceed 25 ° C. After completion of the dropwise addition, the pH of the aqueous solution was measured, and acrylic acid or 48% aqueous sodium hydroxide solution was added so as to fall within the range of 8.1 to 9.5. Thus, 4000 kg of a 37 mass% sodium acrylate aqueous solution was obtained. The concentration of methoxyhydroquinone is 57 ppm with respect to 37% by mass sodium acrylate. A transfer test was performed using this aqueous solution.

<Transport test>
From the reaction vessel in which the neutralization reaction was performed, 4000 kg of a 37% by mass sodium acrylate aqueous solution was transferred to an intermediate tank having an internal volume of 15 m ³ via a 50 m pipe made of SUS304 having an inner diameter of 65 mm. Moreover, the aqueous solution was transferred from the intermediate tank to the spray drying apparatus, and the following drying test was performed. After completion of the transfer, 50 L of the sodium acrylate aqueous solution remaining in the transfer pipe was extracted from the T-shaped pipe part 2 m before the intermediate tank. Next, 500 L of pure water was poured into the empty neutralization kettle over 20 minutes so that the inner wall and the top plate were washed away, and the inside of the neutralization kettle was washed. Next, this cleaning liquid 500L was poured into a pipe made of SUS304 having an inner diameter of 65 mm and a length of 50 m connected to the intermediate tank, and the pipe was washed while extracting the cleaning liquid from the T-shaped pipe portion 2 m before the intermediate tank. Moreover, the said solution was extracted from the piping to a spray-drying apparatus similarly to the above, and it wash | cleaned. The pH of the extracted washing liquid was 7.2. Further, the intermediate tank 407 was also cleaned by supplying pure water from the pure water input line 410.
This series of washing operations was performed once immediately after the neutralization liquid was transferred and repeated for 30 days. After 30 days, the 50 m pipe was disassembled from the flange joint portion, and the state inside the pipe was observed visually or using an endoscope for each pipe disassembled into 10 points. As a result, there was no adhesion of gel in all 10 pipes. Moreover, even if it tried touching the inside of piping with a finger, there was no touch which was made into slimy.

<Drying test>
A 50 mass% sodium acrylate aqueous solution was continuously sprayed from the top of a centrifugal spray drying apparatus (Okawara Kako Co., Ltd., model OD-50, cyclone single point collection). The disk used was M type, the diameter was 125 mm, the rotation speed was 18000 rpm, and the raw material supply rate was 80 kg / h. The temperature of the hot air flow used was 170 ° C., and the supply amount was adjusted to 3000 m ³ / h. The water content of the sodium acrylate powder obtained under the centrifugal spray dryer was 250 ppm. In addition, the inlet temperature of the hot airflow in the said spray dryer was adjusted to 170 degreeC, and the exit temperature was adjusted to 120 degreeC.
Thereafter, in the step shown in FIG. 2, the powder was supplied to the transfer pipe from below the spray dryer via a double damper. When supplied to the transfer pipe, the temperature of the powder was 120 ° C. At this time, dry air was supplied to the transfer pipe as a dry gas from another supply port. At this time, the temperature of the dry air was 70 ° C. and the dew point was 0 ° C.
As described above, the powder was manufactured according to FIG.

Comparative Example 1
<Neutralization reaction>
A neutralization reaction was carried out in the same manner as in Example 1.
<Transfer wipe>
From the reaction vessel in which the neutralization reaction was performed, 3876.8 kg of a 50% by mass potassium acrylate aqueous solution was transferred to an intermediate tank having an internal volume of 15 m ³ via a 50 m pipe made of SUS304 having an inner diameter of 65 mm. After the transfer, the potassium acrylate aqueous solution remaining in the piping portion was not extracted. Also, the reaction kettle and piping were not washed with pure water. When this operation was repeated, the piping was blocked on the 8th day, making it impossible to transfer. When the 50 m pipe was disassembled from the flange joint and the amount and position of the plug were confirmed, about 20 L of potassium acrylate polymer gel was clogged at a position 10 m to 15 m from the reaction kettle. This gel was difficult to dissolve in pure water.

Comparative Example 2
<Neutralization reaction>
A neutralization reaction was carried out in the same manner as in Example 2.
<Transport test>
From the reaction vessel in which the neutralization reaction was performed, 4000 kg of a 37% by mass sodium acrylate aqueous solution was transferred to an intermediate tank having an internal volume of 15 m ³ via a 50 m pipe made of SUS304 having an inner diameter of 65 mm. After the transfer, the sodium acrylate aqueous solution remaining in the piping portion was not extracted. Also, the reaction kettle and piping were not washed with pure water. When this operation was repeated, the piping was clogged on the 14th day and transfer was impossible. When the 50 m pipe was disassembled from the flange joint part and the amount and position of the plug were confirmed, about 10 L of sodium acrylate polymer gel was clogged at a position of 12 to 15 m from the reaction kettle. This gel was difficult to dissolve in pure water.

The method for preventing polymerization of the (meth) acrylic acid alkali metal salt solution according to the present invention includes the step of transferring the metal pipe and / or the metal tank to the metal pipe and / or the metal tank after the (meth) acrylic acid alkali metal salt solution is transferred. By washing with a liquid, the solution can be handled extremely stably and safely, and it is possible to suppress clogging of the pipes. It can be applied to a method for producing an alkali metal (meth) acrylate which is a compound useful as an industrial raw material, and can also be used for transferring a solution of a compound that is easily polymerized.

FIG. 1 is a schematic view showing an example of an apparatus for producing (meth) acrylic acid alkali metal salt powder to which the present invention is applied. FIG. 2 is a schematic view showing an example of an apparatus for producing (meth) acrylic acid alkali metal salt powder to which the present invention is applied. FIG. 3 is a schematic view showing an example of a transfer line of an aqueous solution of an alkali metal (meth) acrylate to which the present invention is applied. FIG. 4 is a schematic view showing an example of an apparatus for producing (meth) acrylic acid alkali metal salt powder to which the present invention is applied.

Explanation of symbols

101, 404 Neutral tank 102, 407 Intermediate tank 103 Stock solution supply pump 104 Air filter 105 Blower 106 Hot air generator 107, 408 Spray dryer 108 Cyclone 109 Bag filter 110 Exhaust gas blower 111 Storage tank 112 Dry gas input line 113 Dry gas input Mouth 114 Dry gas outlet 115 Powder outlet 116 Stirring blade 117, 122 Damper 118 Spray disc 119-121, 123, 308 Rotary valve 201-208, 304, 503 Piping 301, 302, 309, 310 Double damper 303 Cooler 305 Jacket 306 Cooling water inlet 307 Cooling water outlet 401 (meth) acrylic acid inlet line 402 Alkali metal mixture inlet line 403 Pure water inlet line 405 Strainer (For removing foreign matter wire mesh filter )
406 Liquid feed pump 409 Valve 410 Pure water cleaning line 501 Transfer pipe 502 Small cyclone 504 Transfer gas 505 Powder flow 506 Fine powder recovery 507 Hot air exhaust 508 Powder discharge (container filling, etc.)

Claims (6)

A method for preventing polymerization of the residual liquid adhering to or staying in the metal pipe and / or tank in the step of transferring the alkali metal salt of (meth) acrylate using the metal pipe and / or tank. Thereafter, the metal pipe and / or the tank is washed with a liquid to remove the remaining (meth) acrylic acid alkali metal salt solution that has adhered and / or stayed therein. A method for preventing polymerization of an alkali metal acrylate solution. The method for preventing polymerization of the alkali metal salt solution (meth) acrylate is characterized by preventing polymerization of the residual liquid in at least one of a straight pipe part, a bent part, a dead space part and a strainer part. The method for preventing polymerization of the (meth) acrylic acid alkali metal salt solution according to claim 1. The method for preventing polymerization of a (meth) acrylic acid alkali metal salt solution according to claim 1 or 2, wherein the washing in the liquid washing step is performed with water. 4. The (meth) acrylic acid alkali metal salt solution according to claim 1, wherein the polymerization preventing method comprises discharging the liquid used for the liquid cleaning through a valve installed in a pipe after the liquid cleaning. Polymerization prevention method. The liquid cleaning step is performed until the difference between the pH of the discharged cleaning liquid at the outlet portion and the pH of the cleaning liquid before being used for cleaning becomes 1.0 or less. 3. The method for preventing polymerization of an alkali metal salt solution of (meth) acrylic acid according to 3 or 4. A step of performing a method for preventing polymerization of an alkali metal salt solution of (meth) acrylic acid salt according to claim 1, 2, 3, 4 or 5, and a drying step of removing a solvent from the alkali metal salt solution of (meth) acrylic acid. A method for producing a (meth) acrylic acid alkali metal salt powder, comprising:

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