JP4666139B2 - Purification method of glycidyl methacrylate - Google Patents

Description

  In the present invention, when producing glycidyl methacrylate (hereinafter referred to as GMA) using epichlorohydrin (hereinafter referred to as EpCH) and methacrylic acid (hereinafter referred to as MAA) as raw materials, The present invention relates to a GMA purification method for efficiently reducing 1,3-dichloro-2-propanol (hereinafter referred to as 1,3-DCP) contained therein. GMA is used in various fields as a raw material for weather-resistant paints, powder paints, adhesives and the like.

The following method is known as an industrial method for producing GMA using EpCH and MAA as raw materials.
1) 3-Chloro-2-hydroxypropyl methacrylate (hereinafter referred to as MACE) is obtained from MAA and EpCH, and this is dehydrochlorinated with an alkali (for example, see Patent Document 1).
2) An alkali metal salt of MAA is obtained from MAA and alkali, and dechlorinated alkali from this and EpCH (see, for example, Patent Documents 1 and 2).

  In any of the above methods, since EpCH is used as a raw material, 1,3-DCP is contained in the reaction solution as a side reaction product. Since 1,3-DCP contains two chlorine atoms in one molecule, it not only causes a decrease in the purity of GMA, but can also be a causative substance that degrades performance when used in applications such as resins and paints. It is preferable to remove as much as possible. However, since the boiling point of 1,3-DCP is very close to that of GMA, separation by distillation requires considerable labor. Thus, several methods for reducing or removing 1,3-DCP have been proposed.

  A method of stripping crude GMA containing 1,3-DCP or the like in the presence of a quaternary ammonium salt while blowing a mixed gas of oxygen gas and inert gas is disclosed (for example, see Patent Document 3). . However, this method is very inefficient, such as heating a low-purity product for a long time and obtaining a purified product with a yield of 70%, and is not suitable for industrialization.

  Also disclosed is a method of heat-treating crude GMA containing a chlorine compound such as 1,3-DCP in the presence of a quaternary ammonium salt and an alkali metal substance (see, for example, Patent Document 4). It has been described that 1,3-DCP is decomposed into EpCH and hydrogen chloride by the quaternary ammonium salt, and the produced hydrogen chloride is neutralized with an alkali metal substance. Generation | occurrence | production was not confirmed, but when alkali metal substances, such as sodium hydroxide, were added to crude GMA conversely, it turned out that the remarkable fall of the GMA yield by the hydrolysis reaction of GMA occurs.

  As another method, a method of contacting crude GMA with a basic anion exchange resin (Cl type) is also known (see, for example, Patent Document 5 and Non-Patent Document 1). This is a method of generating EpCH and MACE from 1,3-DCP and GMA as shown in Formula 1 by the catalytic action of a basic anion exchange resin (Cl type). However, since the ion exchange resin is very expensive, it is economically disadvantageous, and since this reaction is an equilibrium reaction as will be described later, EpCH and MACE are required to sufficiently reduce 1,3-DCP. There is a problem that it can be applied only to coarse GMA with a sufficiently small amount.

(Formula 1) 1,3-DCP + GMA-> EpCH + MACE
Japanese Patent Laid-Open No. 7-118251 Japanese Patent Publication No. 1-20152 Patent No. 3018483 JP 7-309854 A JP 2000-212177 A GB Industrial Opportunities Ltd. , Havant, NO. 385, pages 283-284, May 1, 1996

  The present invention solves the above-mentioned problems in the prior art, and provides a purification method for efficiently reducing 1,3-DCP from crude GMA and obtaining GMA substantially free of 1,3-DCP. The purpose is to provide.

As a result of intensive studies to solve the above problems, the present inventors have found that when a quaternary ammonium salt is added to crude GMA containing 1,3-DCP, the same catalyst as a strongly basic anion exchange resin (Cl type) It has been found that EpCH and MACE are generated from 1,3-DCP and GMA (see Formula 1). Further, when this reaction was examined in detail, it was found to be an equilibrium reaction (equilibrium constant K = 2.6 at 70 ° C.). Therefore, if this reaction is carried out by distilling EpCH out of the system by reactive distillation, the reaction between 1,3-DCP and GMA proceeds advantageously, and further, if fractional operation is performed, EpCH can be efficiently retained. As a result, 1,3-DCP can be efficiently and sufficiently reduced. Further, after the reactive distillation, the alkylbenzene sulfonate is added, and then glycidyl methacrylate is recovered by distillation. It was found that side reactions were suppressed and glycidyl methacrylate purified with a high yield could be recovered, and the present invention was completed. That is, the present invention is as follows.
(1) A method for purifying glycidyl methacrylate obtained from epichlorohydrin and methacrylic acid as raw materials, wherein crude glycidyl methacrylate containing 1,3-dichloro-2-propanol as an impurity is separated from a partial condenser and In the presence of a quaternary ammonium salt in a reactor equipped with a vessel, while performing reactive distillation under reduced pressure, epichlorohydrin and glycidyl methacrylate generated in the reactive distillation are separated with a partial condenser. The outlet gas temperature of the partial condenser is adjusted to be equal to or higher than the boiling point of epichlorohydrin at the reduced pressure and lower than the boiling point of glycidyl methacrylate, and a liquid mainly composed of glycidyl methacrylate condensed in the partial condenser is recycled to the reactor. , said non by condensed gas containing epichlorohydrin which has not been condensed in the partial condenser at Zenchijimiki discharged out of the system After reducing the object method for purifying a crude glycidyl methacrylate, which comprises recovering glycidyl methacrylate by distillation.
(2) The method for purifying crude glycidyl methacrylate according to (1) above, wherein alkylbenzene sulfonate is further added after the reactive distillation.
(3) The method for purifying crude glycidyl methacrylate according to (2) above, wherein the alkylbenzenesulfonate is sodium p-toluenesulfonate.

  According to the present invention, GMA in which 1,3-DCP by-produced in the reaction is efficiently and sufficiently reduced can be produced in a high yield.

  Hereinafter, the present invention will be described in detail. GMA is generally synthesized using EpCH and MAA as raw materials, and the following two are known as industrial production methods. One is a method for producing GMA by synthesizing MACE by addition reaction of EpCH and MAA in the presence of a quaternary ammonium salt, and then cyclizing MACE by dehydrochlorination using a basic compound. . The other is a method in which an alkali metal salt of MAA is obtained from MAA and an alkali metal substance, and this is reacted with EpCH in the presence of a quaternary ammonium salt to produce GMA by dechlorinated alkali.

  As the quaternary ammonium salt used in these production methods, known substances can be used. For example, tetramethylammonium chloride, trimethylethylammonium chloride, dimethyldiethylammonium chloride, methyltriethylammonium chloride, tetraethylammonium chloride, trimethyl Examples thereof include benzylammonium chloride and triethylbenzylammonium chloride.

  In any of the production methods, in addition to the quaternary ammonium salt which is a catalyst, the synthesis solution contains a large amount of solids such as almost the same molar amount of alkali chloride as the produced GMA, and the purpose is to improve the yield. The synthesis reaction is carried out with an excess of EpCH. Therefore, usually, after the synthesis is completed, solids are removed from the synthesis solution by a method such as filtration or washing, and then unreacted excess EpCH is recovered by distillation, and then GMA is recovered by distillation. EpCH recovered by distillation is recycled as a synthetic raw material. Hereinafter, the process until the solid is removed from the synthesis liquid is referred to as a synthesis process, the liquid from which the solid is removed from the synthesis liquid is referred to as a mother liquor, and the process after the solid is removed is referred to as a distillation process.

  The distillation step may be a batch type or a continuous type, and simple distillation, rectification, thin film distillation and the like can be appropriately combined. The synthesis step is preferably carried out in the presence of a suitable polymerization inhibitor, and known compounds such as phenols, phenothiazines and N-oxyl compounds can be used, and these are also preferably used in the distillation step. Further, the polymerization can be further prevented by supplying molecular oxygen as required.

  In any of the above methods, since EpCH is used as a raw material, 1,3-DCP is contained as an impurity in the obtained GMA. Since 1,3-DCP has a boiling point very close to that of GMA, separation by distillation is impractical. That is, when EpMA is recovered in the distillation step as described above, and GMA is recovered, almost all of 1,3-DCP generated in the synthesis step is recovered together with GMA. Next, a purification method for reducing this will be described in detail.

  When a quaternary ammonium salt is added to crude GMA containing 1,3-DCP, the equilibrium reaction shown in the above formula 1 proceeds, and EpCH and MACE are generated. The produced EpCH is a low boiling point component with respect to GMA, and MACE has a sufficiently high boiling point with respect to GMA.

  Examples of the quaternary ammonium salt added in the purification step include tetramethylammonium chloride, trimethylethylammonium chloride, dimethyldiethylammonium chloride, methyltriethylammonium chloride, tetraethylammonium chloride, trimethylbenzylammonium chloride, and triethylbenzylammonium chloride. The The quaternary ammonium salt to be added may be used alone or in combination of two or more. Further, the quaternary ammonium salt to be added may be the same as or different from that used in the synthesis. The amount of quaternary ammonium salt used is 0.001 to 1%, preferably 0.01 to 0.5%, more preferably 0.02 to 0.4% based on the crude GMA. If it is less than this, the reaction will be slow, and if it is more, it is economically disadvantageous.

  The shape of the quaternary ammonium salt used in the purification process is not particularly limited. It may be in a powdered or granular solid state, or may be dispersed as a slurry in an aqueous solution or GMA. Usually, granular or powdery materials are used.

  The method for adding the quaternary ammonium salt is not particularly limited. In the case of a solid, it may be charged into the reactor by a hopper or the like, or may be added by being pushed away with a crude GMA or the like. Although it may be divided into several times, it is usually added all at once.

  The quaternary ammonium salt is preferably added to the crude GMA during the distillation process. Before the distillation step, the concentration of EpCH in the mother liquor is high, so not only the equilibrium reaction of the above formula 1 does not proceed, but also an undesirable side reaction due to the quaternary ammonium salt proceeds, and GMA is consumed and glycerol dimethacrylate is consumed. (Hereinafter referred to as GDMA), glycerol trimethacrylate (hereinafter referred to as GTMA) and the like are produced. Regarding the timing of addition, in order to favorably promote the above-described equilibrium reaction, when EpCH is distilled off from the mother liquor until the EpCH concentration in the crude GMA is 10% or less, preferably 3% or less, more preferably 1% or less, It is good to do. As described above, the method for distilling EpCH may be batch or continuous, simple distillation or rectification.

  In the present invention, a quaternary ammonium salt is added to crude GMA, and reactive distillation is performed under reduced pressure. At this time, the reaction is carried out while distilling EpCH out of the reaction system. This EpCH includes EpCH remaining in the crude GMA that could not be recovered from the mother liquor in addition to EpCH produced by the reaction. The reason why reactive distillation is carried out while distilling off EpCH is that the intended reaction (see Formula 1) is an equilibrium reaction, and thus the positive reaction is advantageously advanced.

  The reactor used for the reactive distillation in the present invention must be equipped with a partial condenser and a total condenser, but the shape of the reaction kettle itself is not particularly limited. For example, a jacket heating reactor equipped with a stirrer, a reactor having an external heat exchanger, and the like are exemplified. Further, it may also serve as a synthesis kettle, a distillation kettle when EpCH is recovered by batch distillation in the previous step of the reactive distillation, or a GMA is recovered by batch distillation in the subsequent step of the reactive distillation. It may also serve as a distillation kettle. Of course, a reaction kettle dedicated to the reactive distillation may be used. There is no particular limitation on the type and shape of the partial and full pressure reducers, and commonly used heat exchangers such as a multi-tube cylindrical type, a double-pipe type, a spiral type, a plate type, and an air-cooled type are used. The However, as will be described later, in the present invention, in order to control the temperature at the outlet of the condenser, it is necessary to use a heat exchanger such as a multi-tube cylindrical type that can easily control the temperature.

  About reaction distillation conditions, the pressure in a reaction kettle is set so that reaction temperature may be 50-150 degreeC, Preferably it is 60-120 degreeC, More preferably, it is 70-100 degreeC. Although there are some fluctuations depending on the composition of the pot liquid, it is usually 0.3 to 3 kPa, preferably 0.5 to 2 kPa, more preferably 0.7 to 1.5 kPa. If the pressure is too low, the reaction temperature will be low and the reaction will be slow. If the pressure is too high, the reaction temperature will be high and the risk of polymerization will increase. The treatment time depends on the reaction temperature, the amount of quaternary ammonium salt added, the composition of the crude GMA, etc., but is usually 0.5-3 hours, preferably 0.8-2 hours, more preferably 1-1. 5 hours.

  Since the vapor generated by the reactive distillation contains GMA together with EpCH, it is necessary to separate them with a partial condenser. Therefore, the outlet gas temperature of the partial condenser must be adjusted to be not less than the boiling point of EpCH and less than the boiling point of GMA at the pressure at which the reactive distillation is performed. The adjustment method is not particularly limited. For example, when a shell-and-tube heat exchanger is used for the condenser, water, hot water, reduced pressure steam, or other refrigerant is flowed to the shell side, and the heat exchanger outlet gas temperature is measured. Thus, the temperature and / or amount of the refrigerant may be controlled. In this way, when the temperature at the outlet of the condenser is adjusted, the main component of the liquid condensed in the partial condenser (hereinafter referred to as the fractionated liquid) is GMA, and since it hardly contains EpCH, it is recycled to the reactor. To do. On the other hand, since the gas that has not been condensed by the partial condenser contains a large amount of EpCH, it is condensed by the full condenser (hereinafter referred to as total condensed liquid) and then discharged out of the system. Although all the condensed liquid discharged out of the system may be discarded, it contains EpCH, which is a synthetic raw material, so it can be used as a synthetic raw material or recycled as EpCH by recycling it to the synthesis process or distillation process. However, it is preferable from the viewpoint of economical and environmental load reduction.

  From the reactor to the partial condenser, and from the partial condenser to the full condenser, fillers, shelves and the like may be installed to give a rectifying effect, but an empty tower may be used. It is the empty column that has little risk of polymerization, and the empty column is preferable because the boiling point difference between EpCH and GMA is large and separation is easy even at a reduced pressure of 0.3 to 3 kPa during reactive distillation.

  After 1,3-DCP in the crude GMA is reduced to 200 ppm or less, preferably 100 ppm or less, more preferably 50 ppm or less, alkylbenzene sulfonate is added as a quaternary ammonium salt deactivator. When GMA is recovered by distillation without reactive deactivator after reactive distillation, an undesirable side reaction due to the quaternary ammonium salt occurs in the liquor, and GMA is reduced to produce GDMA, GTMA and the like. It is. The alkylbenzene sulfonate used in the present invention is not particularly limited, and examples thereof include sodium o-toluenesulfonate, sodium p-toluenesulfonate, and potassium p-toluenesulfonate. The addition amount of the alkylbenzene sulfonate is 1 to 3 equivalents, preferably 1.1 to 2 equivalents, more preferably 1.2 to 1.5 equivalents of the quaternary ammonium salt.

  Inactivation of quaternary ammonium salts by alkylbenzene sulfonate proceeds very rapidly. Therefore, after addition of the alkyl benzene sulfonate, it may be held for 5 to 120 minutes, preferably 10 to 60 minutes, more preferably 15 to 30 minutes at the temperature at the end of the reactive distillation while stirring the kettle. For stirring, a stirrer may be used, or the pot liquid may be circulated with a pump or the like. In general, quaternary ammonium salts hardly dissolve in GMA, and even when alkylbenzenesulfonate is added to inactivate it, it hardly dissolves in GMA.

  After inactivating the quaternary ammonium salt with an alkylbenzene sulfonate, GMA is recovered by distillation to obtain a product. The distillation method is not particularly limited in the present invention. For example, the pot solution containing the slurry is distilled as it is after the inactivation, or the slurry is separated by a method such as filtration and then distilled in a rectifying column. It is possible. In the former method, GMA can be distilled in the reactive distiller. If the gas temperature at the outlet of the partial condenser is controlled to be lower than the boiling point of GMA as in the case of reactive distillation, can get.

  The purified GMA obtained by the method of the present invention is useful as a raw material for weather-resistant paints, powder paints, adhesives and the like.

  Hereinafter, although the present invention is explained based on an example and a comparative example, the present invention is not limited to these examples. That is, the manufacturing conditions and manufacturing methods of GMA described in the examples are examples, and can be changed as appropriate within the scope of the present invention. Various devices used are also examples and can be changed as appropriate. . For the analysis, a gas chromatograph (GC-1700, flame ionization detector (FID), manufactured by Shimadzu Corporation) was used. The detection limit for EpCH and 1,3-DCP was 10 ppm.

Reference Example 1 (Preparation of GMA synthesis solution)
In a glass flask equipped with a stirrer and a cooler having a decanter for oil-water separation, 1470 g of EpCH (purity> 99.9%), 116 g of sodium carbonate, polymerization inhibitor 2,2′-methylenebis (6-t-butyl- 4-methylphenol) 2 g was added, the pressure was reduced to 30 kPa, and the temperature was raised to 82 ° C. at which EpCH was boiled. The distillate was separated into an aqueous phase and an EpCH phase with a decanter, and 172 g of MAA was added dropwise over about 1 hour while refluxing the lower EpCH phase to the flask. After completion of the dropwise addition, the mixture was further refluxed for 30 minutes, then returned to normal pressure and heated to 120 ° C. at which EpCH was boiled.
Next, 0.6 g of tetramethylammonium chloride as a catalyst was added and reacted for 1 hour, and then cooled to room temperature, and a slurry of sodium chloride was removed using 480 g of water. The amount of the GMA synthesis solution thus obtained was 1400 g, and the composition was shown in Table 1.

Reference Example 2 (EpCH recovery)
1400 g of the GMA synthesis solution obtained in Reference Example 1 and 1.4 g of phenothiazine were charged in a glass flask equipped with a glass single distillation column (inner diameter 20 mm), and EpCH was recovered by gradually reducing the pressure while heating. At the end of EpCH recovery, the amount of the pot liquid was 180 g, the pot pressure was 1.5 kPa, the pot liquid temperature was 83 ° C., and the composition was shown in Table 1. The kettle liquid at the end of EpCH recovery was crude GMA.

Example 1
180 g of the crude GMA obtained in Reference Example 2 and 0.2 g of tetramethylammonium chloride were charged into a glass flask equipped with a jacketed condenser and a full condenser, and subjected to reactive distillation at 1.5 kPa for 1 hour. A single glass tube (inner diameter 20 mm) is used between the flask and the partial condenser, and between the partial condenser and the full condenser. Hot water of 68 ° C. is used for the jacket of the partial condenser, and −10 ° C. is used for the jacket of the full condenser. Of brine. All the condensed liquid was recycled to the kettle, and all the condensed liquid was received in the eggplant flask so as not to return to the kettle. The kettle liquid temperature after the reaction distillation was 85 ° C., and the kettle liquid composition was shown in Table 1. The gas outlet gas temperature was 61 to 64 ° C., and the total amount of the condensed liquid was 15 g.
After the reaction distillation was completed, 0.4 g of sodium p-toluenesulfonate was added, and as a result of collecting the product as a condensed solution while maintaining the same conditions as in the reactive distillation, the partial condenser, the total condenser, and the degree of vacuum were reduced. 1 g, 120 g of a condensed solution, and 45 g of the residue were obtained. The pot temperature at the end of product recovery was 94 ° C. The composition of the fractionated solution and the residue in the kettle is shown in Table 1. 1,3-DCP was not detected in the product. The GMA balance before and after product recovery was over 99.5%.

Example 2
Except for not adding sodium p-toluenesulfonate, reactive distillation and product recovery were performed in the same manner as in Example 1. As a result, 15 g of total condensed solution during reactive distillation, 1 g of total condensed solution during product recovery, partial condensation 120 g of liquid and 45 g of residue were obtained. The composition is shown in Table 1. 1,3-DCP was not detected in the product. The GMA balance before and after product recovery was 97%.

Comparative Example 1
180 g of crude GMA obtained in Reference Example 2 and 0.2 g of tetramethylammonium chloride were charged into a glass flask equipped with only a jacketed full condenser, and reactive distillation was performed at 1.5 kPa for 1 hour. A single glass tube (inner diameter: 20 mm) was used between the flask and the entire condenser, and -10 ° C brine was allowed to flow through the jacket of the entire condenser. All the condensed liquid was recycled to the kettle. The temperature of the pot liquid after the heat treatment was 85 ° C., and the pot liquid composition was shown in Table 1. The reaction was slower than in the Examples, and 0.05% of 1,3-DCP remained in the kettle after the reactive distillation.
After the reaction distillation, a jacketed condenser was installed between the flask and the total condenser, and 0.4 g of sodium p-toluenesulfonate was added and the product was recovered under the same conditions as in Example 1. 15 g of a liquid, 120 g of a condensed liquid, and 45 g of the residue were obtained. The composition of the fractionated solution and the residue in the kettle is shown in Table 1. Since the reduction of 1,3-DCP by reactive distillation was insufficient, 0.05% of 1,3-DCP was also mixed in the product. The GMA balance before and after product recovery was over 99.5%.

Comparative Example 2
Except that tetramethylammonium chloride and sodium p-toluenesulfonate were not added, distillation and product recovery were carried out in the same manner as in Example 1. As a result, 15 g of the total condensed solution during distillation and 1 g of the total condensed solution during product recovery were obtained. , 120 g of the condensed solution and 45 g of the residue were obtained. The composition is shown in Table 1. Since the catalyst tetramethylammonium chloride was not added, 1,3-DCP was hardly reduced, and 0.5% of 1,3-DCP was mixed in the product. The GMA balance before and after product recovery was over 99.5%.

ｎｄは検出限界以下

nd is below detection limit

Claims (3)

A method for purifying glycidyl methacrylate obtained from epichlorohydrin and methacrylic acid as raw materials, comprising crude glycidyl methacrylate containing 1,3-dichloro-2-propanol as an impurity, equipped with a partial condenser and a full condenser In separating the epichlorohydrin and glycidyl methacrylate generated by the reactive distillation in the presence of a quaternary ammonium salt in a reactor under reduced pressure, is adjusted to less than the outlet gas temperature of epichlorohydrin above the boiling point and glycidyl methacrylate in the vacuum boiling, the liquid mainly composed of glycidyl methacrylate condensed in the partial condenser is recycled to the reactor, partial condensation low the impurity by discharging a gas containing epichlorohydrin which has not been condensed out of the system condense Zenchijimiki in vessel A method for purifying crude glycidyl methacrylate, comprising reducing glycidyl methacrylate by distillation after reduction.   The method for purifying crude glycidyl methacrylate according to claim 1, further comprising adding an alkylbenzene sulfonate after the reactive distillation.   The method for purifying crude glycidyl methacrylate according to claim 2, wherein the alkylbenzene sulfonate is sodium p-toluenesulfonate.