JPH08119901A - Production of (meth)acrylic acid ester - Google Patents

Abstract

PURPOSE: To provide an industrially advantageous process for the production of a high-purity (meth)acrylic acid ester having faint color and furthermore containing little by-products and polymers. CONSTITUTION: The esterification reaction of acrylic acid or methacrylic acid with an alcohol is carried out by heating the reaction liquid with an externally heated heat-exchanger while suppressing the temperature difference between the reaction liquid and the heat source to 30 deg.C or below.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an acrylic acid or methacrylic acid ester (hereinafter, acrylic and methacrylic are collectively referred to as (meth) acrylic), which not only causes less coloring but also produces by-products and The present invention provides an industrially advantageous method for producing a high-purity (meth) acrylic acid ester having a small amount of a polymer, and can be widely used in the chemical industry for producing a (meth) acrylic acid ester.

[0002]

2. Description of the Related Art (Meth) acrylic acid ester is a synthetic resin,
It is widely used as a raw material for paints, pressure-sensitive adhesives and other polymer products. Naturally, these raw materials are required to be colorless and transparent in order to prevent them from being inadvertently colored. However, in the esterification reaction of (meth) acrylic acid and alcohol,
It is believed that this is due to the reaction temperature, reaction time, type of catalyst used, amount used, etc., but the (meth) acrylic acid ester obtained is often colored, and countermeasures against it are strongly required. Coloring in the esterification reaction is the production of olefin by the intramolecular dehydration reaction based on the above reasons, (meth)
It is considered to be due to the formation of dimer acid by the dimerization of acrylic acid, the formation of oxides due to oxygen used as a polymerization inhibitor, etc. Some of these can be removed by distillation, but distillation at high boiling points Drastic measures are required for those that are difficult or must be distilled at high temperatures.

As a means for solving this problem, a large amount of polymerization inhibitor is used, or a polymerization inhibitor having a small coloring property is being developed, as in the method disclosed in JP-A-58-174346. Further, as in the method disclosed in Japanese Patent Laid-Open No. 61-165349, a special method has been proposed in which a coloring substance is adsorbed and removed by performing a reaction in the presence of activated carbon or activated clay. On the other hand, as in the method disclosed in Japanese Examined Patent Publication No. 6-37425, in order to shorten the heating time, a method of supplying a vaporized entrainer to the reactor has been proposed.

[0004]

However, the above-mentioned conventional methods have the following problems. That is, the method of adding a large amount of the polymerization inhibitor does not have an effect on the formation of the oxide and is easily colored at a high temperature, and the addition of a large amount of the polymerization inhibitor also has a problem that product quality is deteriorated. There is. In addition, JP-A-58-174346
In the case of using a special polymerization inhibitor with a low coloring property disclosed in No. 3, it is necessary to also carry out a technique for removing the polymerization inhibitor in order to obtain the final product. Similar to the method using a special solid adsorbent, it is complicated in terms of equipment and operation and is economically unsuitable. Furthermore, the method of blowing the entrainer vapor into the reaction liquid absorbs vibrations and shocks caused by the vapor, so that the location and the amount of the vapor to be blown are limited, and a special shock absorber is required. Are also more complex and economically disadvantageous. The present inventors have conducted various studies in search of a method for producing a (meth) acrylic acid ester that does not have the drawbacks of the conventional method.

[0005]

[Means for Solving the Problems] The present inventors obtain it by esterifying a (meth) acrylic acid with an alcohol.
As a result of examining the cause of coloring of the (meth) acrylic acid ester, the degree of coloring is greatly related to temperature and time, and in particular, the influence of temperature at a portion in contact with a heating source is remarkable, The higher the temperature in the part, the more not only coloring but also the formation of by-products and polymers is significant, and it is judged that they are the cause of coloring, and by suppressing their formation, coloring of (meth) acrylic acid ester As a result of repeated earnest studies, we thought that it could be prevented from occurring, and as a result, there was little coloring due to the esterification reaction of (meth) acrylic acid and alcohol.
The inventors have found a method for producing a (meth) acrylic acid ester and completed the present invention.

That is, the present invention relates to the esterification reaction of acrylic acid or methacrylic acid with an alcohol,
The present invention relates to a method for producing acrylic acid or methacrylic acid ester, characterized in that the reaction solution is heated by an external heating type heat exchanger and the difference between the reaction solution temperature and the heating source temperature is suppressed to 30 ° C. or less. Relates to a method for producing acrylic acid or methacrylic acid ester in the above-mentioned production method, wherein the external heating type heat exchanger is a forced circulation type heat exchanger.

The present invention will be described in more detail below. One feature of the present invention is that the reaction solution is heated by an external heating type heat exchanger, and as the external heating type heat exchanger used, a jacket type heat exchanger and a thermosiphon type heat exchanger may also be used. However, it is considered that the forced circulation type heat exchanger in which the liquid is less likely to stay on the heat transfer surface and the contact time of the reaction liquid with the high temperature part is short inhibits the production of the polymer. It is a heat exchanger which achieves the object efficiently and is preferable for the present invention. As a forced circulation type heat exchanger, it is common to forcibly circulate the reaction liquid through the heat exchanger by a pump or the like, while partially evaporating the circulating liquid. Also used in the present invention. As a heat exchanger type, a multi-tube heat exchanger,
Examples include a spiral heat exchanger and a plate heat exchanger. The ratio of the amount of evaporation to the total amount of circulation in the heat exchanger is about 1 to 20% which is generally known.

Further, the present invention is also characterized in that the difference between the temperature of the reaction liquid and the temperature of the heating source is suppressed to 30 ° C. or less. For that purpose, the external heating heat exchanger used in the present invention is used. Must have an overall heat transfer coefficient U [kj / m ² / Hr / ° C.] and a heat transfer area A [m ² ] that satisfy the equation (1). In equation (1), Q is the required heating amount [kj / Hr]
Is the difference [° C.] between the reaction solution temperature and the heating source temperature. In the present invention, the value of Δt is preferably as small as possible, but if it is too small, the heat transfer area A becomes large and the facility cost becomes high, which is economically disadvantageous. Is 3 to 20 ° C. Further, when the temperature of the heating medium is 200 ° C. or higher, coloring on the surface of the heater and formation of by-products and polymers become remarkable,
It is preferable to avoid using an external heating type heat exchanger whose heating source temperature is 200 ° C. or higher.

[0009]

[Formula 1] A = Q / (U × Δt) (1) Formula

The (meth) acrylic acid ester that can be produced by the production method of the present invention is diverse, and specific examples thereof include methyl (meth) acrylate, ethyl (meth) acrylate, and propyl (meth) acrylate. , Butyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, alkyl or cycloalkyl ester of acrylic acid such as nonyl (meth) acrylate, ethylene Examples thereof include polyfunctional (meth) acrylates such as glycol di (meth) acrylate and glycerin tri (meth) acrylate, but the (meth) acrylic acid ester applied to the present invention is not limited thereto. Since the esterification reaction of (meth) acrylic acid and alcohol is an equilibrium reaction, it is necessary to remove water or (meth) acrylic acid ester produced by the reaction to the outside of the system, the acrylic acid ester itself or an excess alcohol, Azeotropic distillation removal with an entrainer is employed. That is, the (meth) acrylic acid ester obtained by the esterification reaction with a monofunctional alcohol having 3 or less carbon atoms is
The (meth) acrylic acid ester is removed azeotropically to the outside of the system, and the reaction is accelerated. On the other hand, for the (meth) acrylic acid ester obtained by the esterification reaction with a monofunctional alcohol having 4 or more carbon atoms or a polyfunctional alcohol having 2 or more carbon atoms, the water produced by the reaction is used in excess of alcohol or Water is removed to the outside of the system by azeotropic distillation using an entrainer having a lower boiling point than the alcohol and (meth) acrylic acid ester used, and the reaction is accelerated.
It is economically preferable that the excess alcohol or entrainer used at this time be recovered by a separation operation such as distillation or static separation and reused. Examples of the entrainer include hydrocarbons such as hexane, heptane, octane, benzene, toluene, xylene and cyclohexane. The reaction temperature is 50 to 200 ° C., preferably 70 to 15
It is carried out at a temperature of 0 ° C., but if it is as low as possible, there will be less troubles such as coloring, by-products and polymerization. The operating pressure is generally atmospheric pressure, but depending on the raw material alcohol and entrainer used, the operating pressure may be reduced pressure in order to lower the reaction temperature. The esterification reaction of the present invention is generally carried out in the presence of an acid catalyst, and the reaction catalyst used is a Lewis acid such as sulfuric acid, paratoluenesulfonic acid or methanesulfonic acid which is generally used in the esterification reaction. Examples thereof include acid or cation type ion exchange resins. In the present invention, as a polymerization inhibitor for the polymerizable liquid used, polymerization of aromatic amines such as phenothiazine and phenol compounds such as hydroquinone and its derivatives which are generally used when handling the polymerizable liquid. Inhibitors are used as in the prior art. Further, oxygen is also used as a polymerization inhibitor, and oxygen dissolved in the polymerizable liquid has a great effect as a polymerization inhibitor, and the reaction is carried out in an atmosphere of a gas containing oxygen or contains oxygen. By introducing the gas to the reaction solution and bubbling (aeration), the dissolved oxygen effectively works as a polymerization inhibitor. The oxygen-containing gas used to dissolve oxygen is not particularly limited, but if the oxygen concentration is high, such as air, an explosive mixed gas (explosive gas) is formed, which is dangerous. Therefore, it is preferable that the oxygen concentration is suppressed to 21% by volume (air) or less. Further, when the oxygen concentration is lower than 3% by volume, the oxygen partial pressure decreases, and it is difficult to obtain a high dissolved oxygen concentration. Therefore, it is preferable that the oxygen concentration be 3% by volume or more. After completion of the reaction, the reaction solution is neutralized with an alkali such as caustic soda and the unreacted raw materials are removed.
By washing and removing salts and unreacted materials with water and distillative removal of unreacted raw materials and entrainers, it is possible to obtain a high-purity (meth) acrylic acid ester having not only little coloring but also few by-products and polymers.

[0011]

The details of the reason why the present invention is excellent for producing a high-purity (meth) acrylic acid ester not only with less coloring but also with less by-products and polymers is unknown, but the reaction solution heating It is thought that by reducing the temperature at the contact part of the reactor with the reactor as much as possible, by mitigating the overheated state at the boundary part, problems such as coloring, by-products and polymerization are suppressed. . Further, if a forced circulation type heat exchanger is adopted, the contact surface with the heater is constantly washed away with the circulating liquid, and the liquid does not stagnate on the contact surface, so troubles such as coloring, by-products and polymerization are especially It is considered that the decrease is remarkable. Furthermore, the polymerization of the liquid stagnating on the contact surface and the adhesion of scale are prevented, which enables stable operation without degrading the performance of the heat exchanger.

[0012]

EXAMPLES The present invention will be described in detail below with reference to examples and comparative examples. Example 1 Per hour, 1212 g of n-octanol, 656 g of acrylic acid, 5 g of water, 310 g of toluene as an entrainer,
Sulfuric acid 8g, hydroquinone monomethyl ether 3g 1
0L flask, overall heat transfer coefficient is 200kj / m ² / Hr / ℃
And a coil-type heat exchanger with a heat transfer area of 0.3 m ² (using silicon oil as a heating source), a rectification column, a vapor condenser at the top, and a condensate separator in a vitreous reactor continuously. It was supplied and reacted at 120 ° C. so that the reaction residence time was 4 hours. The water produced by the reaction is distilled off azeotropically with the entrainer, condensed in the overhead vapor condenser, and then separated into water and the entrainer in the condensate separator, and the water (about 150 g /
Hr) was removed to the outside of the system, and the entrainer was supplied as reflux to the rectification column. When the temperature of the silicone oil of the heating source was measured, it was about 132 ° C., and the temperature difference Δt between the reaction solution temperature and the heating source was 12 ° C. The unknown content including high boiling components in the liquid obtained by the reaction was about 3% by weight. When the liquid was neutralized with caustic soda and purified, the color tone (APH
A) is 5 or less, and n-octyl acrylate with no coloring is 1
387 g was obtained.

Example 2 829 g of butanol and 719 acrylic acid per hour
g, water 10 g, entrainer n-hexane 200 g, sulfuric acid 10 g, hydroquinone monomethyl ether 2 g
0L flask, overall heat transfer coefficient 210kj / m ² / Hr / ℃
And a coil-type heat exchanger with a heat transfer area of 0.5 m ² (using silicon oil as a heating source), a rectification column, a vapor condenser at the top of the column, and a vitreous reaction device consisting of a condensate separator continuously. It was supplied and reacted at 110 ° C. so that the reaction residence time was 3 hours. The water produced by the reaction is azeotropically distilled with an entrainer, condensed in the overhead vapor condenser, and then separated into water and an entrainer by a condensate separator to give water (about 170 g /
Hr) was removed to the outside of the system, and the entrainer was supplied as reflux to the rectification column. When the temperature of the silicone oil of the heating source was measured, it was about 125 ° C., and the temperature difference Δt between the reaction liquid temperature and the heating source was 15 ° C. The content of unclear components including high boiling components in the liquid obtained by the reaction was about 2% by weight. When the liquid was neutralized with caustic soda and purified, the color tone (APH
A) butyl acrylate with a coloring of 5 or less is 1125
g was obtained.

Comparative Example 1 120 ° C. under the same conditions, the same equipment and the same operation as in Example 1.
The reaction was carried out. However, the heater has an overall heat transfer coefficient of 20.
The coil heat exchanger was changed to 0 kj / m ² / Hr / ° C and the heat transfer area was 0.1 m ² (using silicon oil as a heating source). When the temperature of the silicone oil of the heating source was measured, it was about 156 ° C., and the temperature difference Δt between the reaction solution temperature and the heating source was 36 ° C. The unknown content including the high boiling point content in the liquid obtained by the reaction was about 13% by weight, and when the liquid was neutralized and purified with caustic soda under the same conditions as in Example 2, the color tone (APHA) was 15 Only 1040 g of slightly colored n-octyl acrylate was obtained.

Comparative Example 2 110 ° C. under the same conditions, the same equipment and the same operation as in Example 2.
The reaction was carried out. However, the heater has an overall heat transfer coefficient of 21.
It was changed to a coil type heat exchanger (using silicon oil as a heating source) having 0 kj / m ² / Hr / ° C and a heat transfer area of 0.2 m ² . When the temperature of the silicone oil of the heating source was measured, it was about 151 ° C., and the temperature difference Δt between the reaction solution temperature and the heating source was 41 ° C. The unknown content including the high-boiling component in the liquid obtained by the reaction was about 8% by weight, and the liquid was neutralized and purified with caustic soda under the same conditions as in Example 2 to give a color tone (A
PHA) 10 and slightly colored butyl acrylate 9
Only 56g was obtained.

[0016]

EFFECTS OF THE INVENTION According to the present invention, there is provided a method for producing a highly pure (meth) acrylic acid ester which is not only less colored but has less by-products and polymers in a stable operation. Has an extremely large effect on the chemical industry for producing (meth) acrylic acid ester.

Claims (2)

[Claims] 1. In the esterification reaction of acrylic acid or methacrylic acid with alcohol, the reaction solution is heated by an external heating type heat exchanger, and the difference between the reaction solution temperature and the heating source temperature is suppressed to 30 ° C. or less. A method for producing an acrylic acid or methacrylic acid ester, comprising: 2. The method for producing acrylic acid or methacrylic acid ester according to claim 1, wherein the external heating type heat exchanger is a forced circulation type heat exchanger.