JP5500965B2 - Manufacturing method of purified monomer products - Google Patents

Description

  The present invention relates to a purified monomer product and a method for producing the same.

  Conventionally, hydroxyalkyl (meth) acrylates have been synthesized by reacting (meth) acrylic acid with alkylene oxide. In this reaction, as a side reaction, high-boiling impurities such as diesters in which (meth) acrylic acid is reacted with hydroxyalkyl (meth) acrylate and dialkylene glycol monoesters in which alkylene oxide is reacted with hydroxyalkyl (meth) acrylate Produces.

  Since the target product, hydroxyalkyl (meth) acrylate, has a relatively high boiling point and is easily polymerized, purification thereof is often performed by flash distillation under high vacuum. However, the separation between the hydroxyalkyl (meth) acrylate and the by-product is not always sufficient, and it has been particularly difficult to reduce the amount of high-boiling impurities.

  Then, the refinement | purification method using a thin film evaporator is examined. In Patent Document 1, in producing 2-hydroxyethyl (meth) acrylate by reacting (meth) acrylic acid and ethylene oxide, after removing the unreacted ethylene oxide by introducing the reaction solution to a degassing tower, A method for removing high boiling impurities in a thin film evaporator is described. Patent Document 2 discloses that a feed liquid that is hydroxyalkyl (meth) acrylate containing high-boiling impurities is sent to a thin-film evaporator, and a distillate mainly containing hydroxyalkyl (meth) acrylate and high-boiling impurities are contained. A method is described in which the bottom liquid is separated, and the bottom liquid is mixed with the feed liquid and sent again to the thin film evaporator.

JP-A-11-240853 JP 2003-286228 A

  However, when purifying a polymerizable monomer such as hydroxyalkyl (meth) acrylate using a thin film evaporator, the temperature must be set low in order to suppress the polymerization. In order to increase the purity of the distillate, it is not possible to increase the distillate rate (the ratio of the distillate to the supply).

  Then, in the method described in Patent Document 1, the amount of 2-hydroxyethyl (meth) acrylate that is not separated and discharged into the bottoms together with the high-boiling impurities and discarded is large. In the method described in Patent Document 2, since the bottoms are mixed with the supply liquid, the amount of the hydroxyalkyl (meth) acrylate to be discarded can be suppressed to some extent, but as the distillation proceeds, the amount of the hydroxyalkyl (meth) acrylate increases. Since the concentration of boiling point impurities is increased, the purity of the resulting hydroxyalkyl (meth) acrylate is decreased. Therefore, the bottoms containing the hydroxyalkyl (meth) acrylate must be discarded at a certain stage. Therefore, in the methods described in Patent Documents 1 and 2, the yield of the target product has been reduced.

  An object of the present invention is to provide a method for producing a highly purified monomer product with high yield from a monomer such as hydroxyalkyl (meth) acrylate and a crude monomer product containing a high-boiling impurity having a higher boiling point. To do.

The present invention provides a first monomer crude product containing monomer and higher boiling impurities present in a supply tank to a thin film evaporator at a first feed rate, from a monomer refined product. The first distillate is separated from the first distillate containing the monomer and the high-boiling impurities, and then the first distillate is present in the supply tank. A purification step for mixing with the monomer crude product, and a second monomer crude product present in the supply tank at the end of the purification step is supplied to the thin film evaporator at a second supply rate, so that the monomer and the high boiling point are supplied. A recovery step for separating the second distillate containing impurities and the second bottoms containing the high-boiling impurities in this order, wherein the second supply rate is the first supply production method der slower than the speed monomers purified product Te, wherein the monomer is a method for producing a monomer purified product a hydroxyalkyl (meth) acrylate.

  According to the present invention, a purified monomer product having a high yield can be obtained from a crude monomer product containing a monomer such as hydroxyalkyl (meth) acrylate and a high boiling point impurity having a higher boiling point.

It is a schematic block diagram of the apparatus which can be used for the purification method of the monomer which concerns on this invention.

  FIG. 1 is a schematic configuration diagram of an apparatus that can be used in the method for purifying a monomer according to the present invention.

  First, a monomer crude product containing a monomer and a high-boiling impurity having a boiling point higher than that is charged into the supply tank 10 through the monomer crude product charging line 5.

  A monomer is a compound to be purified in a crude monomer product, and usually has thermal polymerizability. Specific examples thereof include (meth) acrylic acid; methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, and stearyl (meth). Alkyl (meth) acrylates such as acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate; cyclohexyl (meth) acrylate; phenyl (meth) acrylate; benzyl (meth) acrylate; isobornyl (meth) acrylate; glycidyl (meth) ) Acrylate; tetrahydrofurfuryl (meth) acrylate; allyl (meth) acrylate, trifluoroethyl (meth) acrylate; acrylic acid; methyl acrylate, ethyl acrylate, n-buty Alkyl acrylates such as acrylate, isobutyl acrylate, tert-butyl acrylate, stearyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, cyclohexyl acrylate; phenyl acrylate; benzyl acrylate; isobornyl acrylate; glycidyl acrylate; tetrahydrofurfuryl acrylate; Fluoroethyl acrylate; Dialkylaminoethyl (meth) acrylate such as dimethylaminoethyl (meth) acrylate, dimethylaminoethylmethyl chloride salt (meth) acrylate, dimethylaminoethylbenzyl chloride salt (meth) acrylate, diethylaminoethyl (meth) acrylate; Ethylene glycol di (meth) acryl , Triethylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, polybutylene glycol di (meth) acrylate, trimethylolpropane tri ( Di- and tri (meth) acrylates such as meth) acrylate; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, etc. Hydroxyalkyl (meth) acrylates; hydroxyalkyl acrylates such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate; The Among these, it is suitable for purification of hydroxyalkyl (meth) acrylate, which itself has a high boiling point and is difficult to separate from high boiling point impurities. The purity of the monomer crude product (the concentration of the monomer in the monomer crude product) is typically 90 to 96% by mass.

  The high boiling point impurities contained in the crude monomer product are compounds that should be removed by refining the crude monomer product, such as compounds that are by-produced during the synthesis of the monomer. For example, crude hydroxyalkyl (meth) acrylate obtained by reacting (meth) acrylic acid with alkylene oxide includes diesters obtained by reacting hydroxyalkyl (meth) acrylate with (meth) acrylic acid, and hydroxyalkyl (meth) Dialkylene glycol monoesters obtained by reacting an acrylate with an alkylene oxide are included. The concentration of high boiling impurities in the monomer crude product is typically 3-10% by weight.

  In addition, reaction of (meth) acrylic acid and alkylene oxide is 1.0-1.2 mol with respect to 1 mol of (meth) acrylic acid in presence of a catalyst and a polymerization inhibitor, Preferably it is 1.03-1. Reaction of 10 moles of alkylene oxide gives the crude hydroxyalkyl (meth) acrylate. Examples of the alkylene oxide include ethylene oxide, propylene oxide, 1,2-butylene oxide, and 2,3-propylene oxide, and ethylene oxide is preferable.

  As the catalyst used here, a known catalyst may be used. For example, various amines, quaternary ammonium salts, iron compounds, chromium compounds, or (meth) acrylic acid metal compounds may be used alone or in combination. Can be used. The addition amount of the catalyst is preferably 0.01 to 10 parts by mass and more preferably 0.03 to 3 parts by mass with respect to 100 parts by mass of (meth) acrylic acid.

  Examples of the polymerization inhibitor include hydroquinone, hydroquinone monomethyl ether, catechol, phenothiazine, N-oxyl compound, N, N-di-2-naphthyl-p-phenylenediamine, nitric acid, nitrate, and the like. As for the addition amount of a polymerization inhibitor, 0.01-1 mass part is preferable with respect to 100 mass parts of (meth) acrylic acid.

  The reaction may be either a batch type or a continuous type, and the reaction temperature is usually about 50 to 80 ° C.

  The crude monomer product may contain impurities having a boiling point lower than that of the monomer (hereinafter referred to as “low boiling point impurities”). However, it is preferable to perform a step of removing low boiling point impurities from the crude monomer product in advance.

  The method for purifying monomers according to the present invention is performed in a batch system, and the monomer crude product charged in the supply tank 10 is purified by the purification process and recovery process described below to obtain a purified monomer product.

[Purification process]
In the refining process, the crude monomer product (referred to as the first monomer crude product here) present in the supply tank 10 at the start of the refining process is passed through the monomer crude product supply line 15 using a pump (not shown) or the like. The thin film evaporator 20 is supplied. And the 1st monomer crude product is distilled with the thin film evaporator 20, and it isolate | separates into the 1st distillate which consists of a monomer refined product, and the 1st bottoms containing a monomer and a high boiling point impurity.

  The purified monomer product obtained as the first distillate contains the monomer with the desired purity, and may contain a small amount of high-boiling impurities and low-boiling impurities. The purity of the purified monomer product (the concentration of the monomer in the purified monomer product) is typically 97% by mass or more.

  As the thin film evaporator, a falling film thin film evaporator, a centrifugal thin film evaporator, or the like can be used. The conditions for distillation using a thin film evaporator are appropriately determined according to the type and physical properties of the first monomer crude product, the separation capability of the thin film evaporator, etc., so that a purified monomer product containing the monomer with the desired purity can be obtained. Can be set. For example, in the case of 2-hydroxyethyl (meth) acrylate, the reaction solution is heated to 60 to 140 ° C., preferably 80 to 125 ° C. under a reduced pressure of 0.05 to 0.5 kPa, preferably 0.07 to 0.2 kPa. Supply rate to the heated thin film evaporator 0.5-2.5 parts by mass, preferably 1.3-1.8 parts by mass, distillate rate 0.4-0.8, preferably 0.5-0. The purified 2-hydroxyethyl (meth) acrylate having a purity of 97% by mass or more can be obtained by evaporating at 7.

  The first distillate composed of the purified monomer product is discharged from the thin film evaporator 20 through the distillate discharge line 25. During this purification step, the monomer purified product is removed from the monomer purified product discharge line 35 by switching the distillate switch 30 so that the distillate discharge line 25 and the monomer purified product discharge line 35 communicate with each other. It can be taken out.

  On the other hand, a first bottom liquid containing monomer and high-boiling impurities is obtained as a residue, and is discharged from the thin film evaporator 20 through the bottom liquid discharge line 26. And during this refinement | purification process, the 1st bottom liquid is circulated by changing the bottom liquid switch 40 so that the bottom liquid discharge line 26 and the bottom liquid circulation line 45 may communicate. The supply tank 10 can be charged again through the line 45. The first bottom liquid put into the supply tank 10 is mixed with the first crude crude product present in the supply tank 10.

  In this way, by mixing the first bottom liquid with the first monomer crude product present in the supply tank 10, a mixture of the monomer and the first monomer crude product contained in the first bottom liquid. Is sent to the thin film evaporator 20 and distilled, so that the yield of the purified monomer product is improved.

[Recovery process]
In the recovery step that follows the purification step, the monomer crude product (herein referred to as the second monomer crude product) present in the supply tank 10 at the end of the purification step is replaced with a monomer using a pump (not shown) or the like. The thin film evaporator 20 is supplied through the crude product supply line 15. And it isolate | separates into the 2nd distillate containing a monomer and a high boiling point impurity, and the 2nd bottom liquid containing a high boiling point impurity.

  Here, the supply rate (second supply rate) of the second crude monomer product in the recovery step is slower than the supply rate (first supply rate) of the first crude crude product in the purification step. If the second feed rate is made slower than the first feed rate in this way, the distillation rate can be increased even if the distillation conditions by the thin film evaporator remain the same, and the large amount of monomer in the second monomer crude product can be increased. A portion is obtained as a second distillate. The second supply rate may be set so that the distillation rate in the recovery step is 1.2 to 1.7 times (preferably 1.3 to 1.5 times) the distillation rate in the purification step. The first supply rate is preferably 0.5 to 0.9 times, and more preferably 0.5 to 0.7 times. When the second supply rate is 0.5 times or more of the first supply rate, the time for the recovery process becomes longer and the productivity tends to be improved. On the other hand, when the second supply rate is 0.9 times or less of the first supply rate, the amount of heat applied to the thin film evaporator can be reduced, so that monomer polymerization or the like tends to be prevented.

  The second distillate is discharged from the thin film evaporator 20 through the distillate discharge line 25. During this recovery step, the second distillate is recovered by switching the distillate switch 30 so that the distillate discharge line 25 and the distillate recovery line 36 communicate with each other. It can be put into the buffer tank 50 through the line 36.

  For example, the second distillate charged into the buffer tank 50 can be mixed with another monomer crude product (herein referred to as a third monomer crude product) and distilled again. Specifically, the second distillate is supplied to the supply tank 10 into which another batch of the third monomer crude product is charged using a pump (not shown) or the like through the distillate reuse line 55. 10 can be charged. By doing so, the second distillate is also distilled again when another batch is distilled, and the yield of the purified monomer product can be further increased.

  On the other hand, a second bottomed liquid containing high-boiling impurities is obtained as a residue and discharged from the thin film evaporator 20 through the bottomed liquid discharge line 26. And during this refining process, by switching the bottom discharge switch 40 so that the bottom discharge discharge line 26 and the high boiling point impurity discharge line 46 communicate with each other, The discharged liquid can be taken out. Since the amount of monomer contained in the second bottoms is small, loss of monomer can be minimized even if the second bottoms are discarded.

  In addition, the timing which starts a collection | recovery process should just be before it becomes impossible to obtain the monomer purity product of the target purity in a refinement | purification process. For example, when the amount of the first distillate obtained in the purification step becomes 70 to 95% by mass, preferably 80 to 90% by mass, based on the amount of the first monomer crude product at the start of the purification step, The recovery process can be started. If the amount of the first distillate obtained in the purification step is less than 70% by mass of the amount of the first monomer crude product, the amount of monomer purified product obtained in the purification step will be small. On the other hand, if the amount of the first distillate obtained in the purification step is more than 95% by mass of the amount of the first monomer crude product, it may be impossible to obtain a purified monomer product having the desired purity in the purification step. There is sex.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail by an Example and a comparative example using 2-hydroxyethyl methacrylate crude product, this invention is not limited to these Examples. In addition, the purity of the 2-hydroxyethyl methacrylate crude product and the purified 2-hydroxyethyl methacrylate product and the concentration of high boiling impurities were analyzed by gas chromatography.

(Reaction of methacrylic acid with ethylene oxide)
A 2 L autoclave equipped with a stirrer was charged with 861 parts by mass of methacrylic acid as a raw material, 2.7 parts by mass of chromium acetate as a catalyst, and 2.2 parts by mass of hydroquinone as a polymerization inhibitor. 484 parts by mass of oxide was added. The inside of the system was pressurized to 300 kPa with nitrogen pressure with nitrogen, and then gradually heated in an oil bath with stirring so that the temperature reached 75 ° C. in about 1 hour. Thereafter, the reaction liquid was maintained at 75 ° C. by adjusting the heating, and when the amount of residual methacrylic acid reached 0.5% by mass (reaction time: 7.0 hours), the autoclave was cooled under a water bath under reduced pressure. To remove unreacted ethylene oxide. After the inside of the system reached 30 ° C. at 2 kPa, the system was held for 15 minutes, and then returned to normal pressure with nitrogen.

  By the above method, 1290 mass parts of 2-hydroxyethyl methacrylate crude products were obtained. The purity of the 2-hydroxyethyl methacrylate crude product was 95.5% by mass, and the concentration of high-boiling impurities (diesters and dialkylene glycol monoesters) was 4.1% by mass.

[Example 1]
The 2-hydroxyethyl methacrylate crude product was used as the first monomer crude product and purified using the apparatus shown in FIG.

(Purification process)
1290 parts by mass of crude 2-hydroxyethyl methacrylate was charged into the supply tank 10 via the monomer crude product charging line 5. Then, the 2-hydroxyethyl methacrylate crude product was supplied from the supply tank 10 to the thin film evaporator 20 via the monomer crude product supply line 15 using a metering pump at 155 parts by mass per hour. The evaporation surface of the thin film evaporator was heated by supplying silicon oil heated to around 100 ° C. to the outside, and the pressure in the thin film evaporator was set to 0.13 kPa. At this time, the distillation rate of the distillate was 81 to 92 parts by mass per hour. The 2-hydroxyethyl methacrylate purified product separated in the thin film evaporator 20 was taken out from the monomer purified product discharge line 35. On the other hand, the bottoms containing 2-hydroxyethyl methacrylate and high-boiling impurities obtained as a residue are cooled to 25-30 ° C. using a glass Liebig condenser tube in which water at 15 ° C. is flown as a refrigerant, All of the liquid was sent to the supply tank 10 via the liquid discharge line 26 and the bottom liquid circulation line 45. And in the supply tank 10, the bottoms and the liquid in a supply tank were mixed, and this liquid mixture was sent to the thin film evaporator 20. FIG.

  And the refinement | purification process was performed until the quantity of the obtained 2-hydroxyethyl methacrylate refined product became 85 mass% of the 2-hydroxyethyl methacrylate crude product at the time of a refinement | purification process start. The purity of the obtained 2-hydroxyethyl methacrylate purified product was 98% by mass.

(Recovery process)
At the end of the purification step, the 2-hydroxyethyl methacrylate crude product (second monomer crude product) remaining in the supply tank 10 was supplied to the thin film evaporator 20 at 88 parts by mass per hour in the same manner as in the purification step. This feed solution was evaporated under the same conditions as in the purification step. At this time, the distillation rate of the distillate was 64 to 74 parts by mass per hour. The distillate separated in the thin film evaporator 20 was sent to the buffer tank 50 via the distillate discharge line 25 and the distillate recovery line 36 and recovered. On the other hand, the bottom liquid obtained as a residue was discharged via the bottom liquid discharge line 26 and the high boiling point impurity discharge line 46. And the collection | recovery process was performed until the liquid of the supply tank 10 was exhausted.

  By this recovery process, most of 2-hydroxyethyl methacrylate remaining in the supply tank 10 at the start of the recovery process could be recovered as a distillate.

[Example 2]
(Purification process)
The distillate obtained in the recovery step of Example 1 was mixed with the second batch of 2-hydroxyethyl methacrylate crude product (third monomer crude product), and the mixture was used as the first monomer crude product. Was performed under the same conditions as in the purification step of Example 1. The amount of the obtained 2-hydroxyethyl methacrylate purified product was 1.14 times that of Example 1, and the purity was 97% by mass.

(Recovery process)
The same operation as in Example 1 was performed. By this recovery step, most of the 2-hydroxyethyl methacrylate remaining in the supply tank 10 at the start of the recovery step could be recovered as the second distillate.

[Comparative Example 1]
The purification process was performed until the liquid in the supply tank 10 was exhausted without performing the recovery process under the same conditions as the purification process in Example 1. The purity of the obtained 2-hydroxyethyl methacrylate purified product was 95% by mass.

[Comparative Example 2]
The recovery step was performed under the same conditions as in Example 1 except that the recovery step was performed under the same conditions as in the purification step. The purity of the obtained 2-hydroxyethyl methacrylate purified product was 98% by mass. However, the amount of distillate obtained in the recovery step was small, and the amount of 2-hydroxyethyl methacrylate recovered was small.

[Comparative Example 3]
In the recovery process, the evaporation surface of the thin film evaporator is heated to around 140 ° C., and at the end of the purification process, the 2-hydroxyethyl methacrylate crude product (second monomer crude product) remaining in the supply tank 10 is 160 parts by mass per hour. The test was performed under the same conditions as in Example 1 except that the thin film evaporator was supplied. At this time, the distillation rate of the distillate was 112 to 128 parts by mass per hour. However, polymer was seen in the thin film evaporator after 15 minutes.

5 Monomer crude product input line 10 Supply tank 15 Monomer crude product supply line 20 Thin film evaporator 25 Distillate discharge line 26 Canned liquid discharge line 30 Distillate switch 35 Monomer purified product discharge line 36 Distillate recovery line 40 Bottom discharge switch 45 Bottom discharge circulation line 46 High boiling point impurity discharge line 50 Buffer tank 55 Distillate reuse line

Claims (3)

A first monomer crude product containing monomers and higher boiling impurities present in the supply tank is fed to the thin film evaporator at a first feed rate to produce a first monomer product. After separating into a distillate and a first bottom liquid containing the monomer and the high-boiling impurities, the first bottom liquid is converted into a first monomer crude product present in the supply tank. A purification step of mixing;
A second distillate containing the monomer and the high-boiling impurities is supplied to the thin film evaporator at a second supply rate with the second monomer crude product present in the supply tank at the end of the purification step. And a recovery step of separating into a second bottomed liquid containing the high-boiling impurities in this order, wherein the second supply rate is a method for producing a purified monomer product that is slower than the first supply rate. There,
A method for producing a purified monomer product, wherein the monomer is hydroxyalkyl (meth) acrylate.   The said collection | recovery process is started when the quantity of said 1st distillate becomes 70-95 mass% of the quantity of said 1st monomer crude product at the time of the said refinement | purification process start. Monomer purified product manufacturing method.   The monomer concentrate according to claim 1 or 2, further comprising a step of mixing the second distillate with another batch of a third monomer crude product containing a monomer and a high-boiling impurity having a higher boiling point. Product manufacturing method.

Images