JP4099950B2 - Method for producing cyclohexyl (meth) acrylate - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing high-purity cyclohexyl acrylate or cyclohexyl methacrylate (hereinafter, acrylic acid or methacrylic acid is abbreviated as (meth) acrylic acid), and more specifically (meth) acrylic acid and cyclohexanol. A crude ester obtained by esterification in the presence of a catalyst, or a crude ester obtained by subjecting a (meth) acrylic acid ester and cyclohexanol to transesterification in the presence of a catalyst to a high purity (meta ) It relates to a method for producing cyclohexyl acrylate.
[0002]
[Prior art]
Cyclohexyl (meth) acrylate is an important monomer that is used in various applications such as optical materials such as lenses and prisms, molding materials, paint materials, and adhesive materials, either alone or copolymerized with other monomers. It is.
[0003]
Conventionally, cyclohexyl (meth) acrylate is an esterification method in which (meth) acrylic acid and cyclohexanol are esterified using a catalyst such as an inorganic acid, an organic sulfonic acid, or a strongly acidic ion exchange resin, or titanium or tin. It is industrially produced by a transesterification method using an organometallic compound containing, for example, a catalyst.
[0004]
In the production of cyclohexyl (meth) acrylate by the esterification method, (meth) acrylic acid and cyclohexanol are usually reacted using an acidic catalyst in the presence of a polymerization inhibitor. After completion of the reaction, the reaction product is washed with an alkaline aqueous solution such as an aqueous sodium hydroxide solution, whereby an acidic catalyst, (meth) acrylic acid and the like are separated, and crude (meth) acrylic acid cyclohexyl (hereinafter referred to as crude ester) is produced. can get.
[0005]
The crude ester obtained as described above is, for example, sent to the first stage distillation column and distilled, as employed in the invention according to JP-A-63-99037. First, the low boiling point in the crude ester is reduced. Ingredients are removed. That is, in the first distillation column, cyclohexanol or the like, which is a low boiling point component, is distilled from the top of the column, and cyclohexyl (meth) acrylate from which the low boiling point component has been removed is removed from the bottom of the column. Thereafter, the cyclohexyl (meth) acrylate from which the low-boiling components have been removed is sent to the second-stage distillation column, where it is distilled to take out the high-boiling components from the bottom of the column, and from the top of the (meth) Cyclohexyl acrylate is removed. The cyclohexyl (meth) acrylate is further purified by means such as distillation as necessary to obtain high-purity cyclohexyl (meth) acrylate.
[0006]
That is, in a normal industrial production method, the low-boiling components of the crude ester are separated in the first distillation column, then the high-boiling components are separated in the second distillation column, and the product (meth) acrylate cyclohexyl is obtained. It is manufactured. The reason for going through such a production order is that if distillation is performed in the reverse order, the low boiling point components are distilled twice, and extra thermal energy is required for the distillation.
[0007]
[Problems to be solved by the invention]
The inventors of the present invention have studied various distillation methods for crude esters for the purpose of producing high-purity cyclohexyl (meth) acrylate, and then separated low-boiling components in the first-stage distillation column, and then in the second-stage distillation column. In the case of using the conventional method for producing cyclohexyl (meth) acrylate that separates high-boiling components in the distillation column of (meth) acrylic acid, cyclohexanol, cyclohexene, etc. in the resulting cyclohexyl (meth) acrylate Has been found to be present in concentrations exceeding expectations, and their removal is associated with difficulties.
[0008]
As a result of intensive studies aimed at elucidating this cause, the present inventors have found that these impurities are mainly caused by the high boiling point causative substance produced during the esterification reaction and have some action, and the first and second stages. It came to be estimated that it was produced by decomposing cyclohexyl (meth) acrylate and other by-products during the purification process by distillation. That is, it was speculated that the impurities were substances generated during distillation from the heated can liquid component.
[0009]
As a result of the above examinations and considerations, the present inventors have found that in the purification step of the crude ester by distillation, by removing these causative substances in advance at the beginning of the purification step, a decomposition product of by-products in the subsequent purification step. The present invention has been completed by conceiving that cyclohexyl (meth) acrylate with higher purity can be easily produced without fail, and the object of the present invention is high purity ( The object is to provide a process for producing cyclohexyl methacrylate.
[0010]
[Means for solving the problems]
The present invention that solves the above problems is described below.
[0011]
[1] A crude ester obtained by esterifying (meth) acrylic acid and cyclohexanol in the presence of a catalyst, or a crude ester obtained by transesterifying (meth) acrylic acid ester and cyclohexanol in the presence of a catalyst. When producing cyclohexyl (meth) acrylate by purifying an ester, it is characterized by removing high boiling impurities in the crude ester by the first stage distillation and then removing low boiling impurities by the second stage distillation. A method for producing cyclohexyl (meth) acrylate.
[0012]
Hereinafter, the present invention will be described in detail.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
The crude ester which is a raw material for producing high-purity cyclohexyl (meth) acrylate in the present invention may be produced by an esterification method or may be produced by a transesterification method.
[0014]
In the esterification method, (meth) acrylic acid and cyclohexanol are reacted in the presence of a catalyst to produce a crude ester mainly composed of cyclohexyl (meth) acrylate.
[0015]
The mixing ratio of (meth) acrylic acid and cyclohexanol is preferably 1.0 to 1.5 mol of cyclohexanol with respect to 1 mol of (meth) acrylic acid.
[0016]
As the catalyst used for the esterification reaction, an acidic catalyst such as an inorganic acid such as sulfuric acid, an organic sulfonic acid, or a strongly acidic ion exchange resin is preferable. Examples of the organic sulfonic acid include p-toluenesulfonic acid, methanesulfonic acid, benzenesulfonic acid, xylenesulfonic acid and the like.
[0017]
The addition amount of the catalyst is 0.5 to 10 mol%, preferably 1 to 5 mol%, based on cyclohexanol.
[0018]
The esterification reaction is performed in the presence of a polymerization inhibitor. As the polymerization inhibitor, known ones can be used, and hydroquinone, hydroquinone monomethyl ether, phenothiazine, 2,4-dimethyl-6-tertiary butylphenol, etc. can be exemplified, and the amount used is 0. (meth) acrylic acid. It is 001-5 mass%, Preferably it is 0.01-2 mass%.
[0019]
In order to facilitate the distillation of water produced by the esterification reaction, it is preferable that a dehydrating agent (organic solvent) be present in the reaction system in addition to the above components. Examples of such dehydrating agents include aromatic hydrocarbons such as benzene, toluene and xylene, saturated hydrocarbons such as n-hexane, cyclohexane, heptane and octane, and ethers such as diisopropyl ether.
[0020]
As reaction conditions for advancing the esterification reaction, the temperature is usually from 70 to 150 ° C., preferably from 80 to 130 ° C. The pressure in the reaction system may be ordinary pressure, and may be reduced as necessary.
[0021]
The reaction time is usually preferably from 0.5 to 10 hours, more preferably from 3 to 8 hours. During the reaction, it is preferable to supply air to the reaction system as an auxiliary means for preventing polymerization.
[0022]
The reaction solution obtained by the esterification reaction is then washed with an aqueous alkali solution such as sodium hydroxide (neutralization step) to remove the catalyst and unreacted (meth) acrylic acid. As a result, a crude ester containing cyclohexyl (meth) acrylate, which is a starting material of the method of the present invention, as a main component is obtained. The method for producing the crude ester is known per se.
[0023]
The crude ester used in the present invention is not limited to the one produced by the esterification reaction, and may be one produced by a known transesterification method or any other method.
[0024]
In the transesterification method, (meth) acrylic acid ester and cyclohexanol are transesterified in the presence of a catalyst to produce cyclohexyl (meth) acrylic acid. Examples of the (meth) acrylic acid ester include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and butyl (meth) acrylate. The amount of (meth) acrylic acid ester used is 1 to 10 mol, preferably 1.2 to 5 mol, per 1 mol of cyclohexanol. The higher the amount of (meth) acrylic acid ester used, the higher the reaction rate. However, the lower the amount, the higher the productivity per volume.
[0025]
Examples of the catalyst used for the transesterification include tetramethoxy titanium, dibutyl tin oxide, dioctyl tin oxide, and the like. 0.01-2 mass% is preferable with respect to the total amount of (meth) acrylic acid ester and cyclohexanol, and, as for the usage-amount of a catalyst, 0.02-1 mass% is more preferable.
[0026]
The transesterification reaction is usually carried out using a batch reactor equipped with a distillation column. The reaction temperature is determined by the distillation temperature of the distilled alcohol. The reaction is preferably performed under reduced pressure. As in the esterification method, it is preferable to prevent polymerization by coexisting a polymerization inhibitor, air or oxygen. The manufacturing method of the crude ester by the said transesterification method is also well-known.
[0027]
In the present invention, starting from a crude ester mainly composed of hexyl (meth) acrylate produced by the various production methods as described above, (meth) acrylic acid in the crude ester is obtained by performing the first stage distillation. By removing high-boiling impurities from hexyl first, and then performing second-stage distillation to remove low-boiling impurities from cyclohexyl (meth) acrylate, and if necessary, further post-treatment such as rectification, High purity (meth) acrylic acid hexyl is produced.
[0028]
The content of cyclohexyl (meth) acrylate in the crude ester which is the starting material of the present invention is usually 70 to 90% by mass.
[0029]
As described above, the first-stage distillation removes higher boiling impurities than cyclohexyl (meth) acrylate, and examples of the high boiling impurities include Michael adducts such as (meth) acrylic acid, cyclohexanol sulfate, and the like. .
[0030]
As the first stage distillation column, a batch type distillation column or a continuous type distillation column can be used.
[0031]
The boiling point of cyclohexyl acrylate: 184 ° C., the boiling point of cyclohexyl methacrylate: 210 ° C., the boiling point of cyclohexanol: 161 ° C., the boiling point of cyclohexene: 82 ° C., and the boiling point of acrylic acid: 141 ° C.
[0032]
The number of theoretical columns of the distillation column used for the first distillation is 5 or more, preferably 5 to 10 is sufficient. As the distillation column, any of a packed column using a packing such as a cascade mini-ring and a plate column can be used. The reflux ratio is about 1, preferably 0.8-2. By distilling under these conditions, it is possible to sufficiently suppress the high boiling point impurities from distilling from the top of the column. Distillation is preferably performed under reduced pressure to prevent polymerization. Moreover, superposition | polymerization can be suppressed by supplying air to the can liquid in a distillation tower.
[0033]
When a batch distillation column is used, it is preferable to distill cyclohexyl (meth) acrylate while maintaining the top pressure at 15 kPa to 3 kPa. In this case, the tower bottom temperature is preferably 110 ± 10 ° C. Moreover, high boiling point impurities are separated from the bottom of the column as a can.
[0034]
In the case of continuous distillation, in order to stabilize the operation of the distillation column, a step of previously distilling off the dehydrating agent added during the esterification reaction or transesterification reaction may be provided before the first stage distillation. preferable. This step may be before or after the neutralization step of washing with the alkaline aqueous solution. When the crude ester from which the dehydrating agent has been distilled off is continuously distilled, the column top pressure is preferably 4 ± 1 kPa, the column top temperature is 80 ± 10 ° C., and the column bottom temperature is preferably 100 to 120 ° C. The distillation yield is about 95%, and the can liquid is generally discarded about 5%.
[0035]
As described above, the second-stage distillation is to distill off lower boiling impurities than cyclohexyl (meth) acrylate. As low boiling impurities, (meth) acrylic acid, cyclohexanol, cyclohexene, and dehydrating agent were used. There are hydrocarbons and ethers.
[0036]
As the second stage distillation column, a batch type distillation column or a continuous type distillation column can be used. As the distillation column, those having a theoretical plate number of 10 to 20 are preferable. As the distillation column, any of a packed column using a packing such as a cascade mini-ring and a plate column can be used. The reflux ratio is preferably about 3 to 5. In the case of batch distillation in which polymerization can be prevented by supplying air to the can in the distillation column, the operating conditions are substantially the same as the operating conditions of the first-stage batch distillation tower.
[0037]
In the case of continuous distillation, the column top pressure is preferably 4 ± 1 kPa, the column top temperature is 80 ± 10 ° C., and the column bottom temperature is preferably 100 to 110 ° C. The distillation yield is close to 100%.
[0038]
The product, high-purity cyclohexyl (meth) acrylate, is withdrawn from the bottom of the second distillation column. This may be further rectified if necessary. The theoretical plate number of the rectification column is determined by the required product purity, but usually 10 to 20 plates are preferable.
[0039]
The purified high-purity cyclohexyl (meth) acrylate has a purity of 99.8% or more, residual acrylic acid 0.01% or less, residual cyclohexanol 0.1% or less, cyclohexene 0.05% or less (mass basis). ) Of high purity.
[0040]
Hereinafter, the present invention will be described more specifically with reference to examples.
[0041]
【Example】
Example 1
(Production of crude ester)
In a 1 L four-necked flask equipped with a stirrer, 288 g of acrylic acid, 420 g of cyclohexanol, 80 g of n-hexane as a dehydrating agent, 3 g of sulfuric acid as a reaction catalyst, and 1 g of phenothiazine as a polymerization inhibitor are added azeotropically with water and n-hexane. Was allowed to react at a temperature of 90 to 120 ° C. for 6 hours. The reaction rate of acrylic acid was 95%.
[0042]
After completion of the reaction, 1N-sodium hydroxide aqueous solution was added to the obtained reaction solution with stirring, the pH of the lower aqueous layer was adjusted to 12, and then the aqueous layer and the organic layer were separated, whereby sulfuric acid and unreacted water were separated. The reaction acrylic acid was separated from the reaction solution to obtain a crude ester (cyclohexyl acrylate purity 80%).
[0043]
(Purification of crude ester)
710 g of the crude ester was placed in a flask equipped with a rectifying column, and distilled by simple distillation while gradually changing the top pressure from 15 kPa to 3 kPa, thereby separating high-boiling impurities.
[0044]
Next, 670 g of this distillate is put into a flask equipped with a rectifying column, 0.5 g of phenothiazine is added and heated, and 140 g of low-boiling impurities such as acrylic acid, cyclohexanol and cyclohexene are added at a column top pressure of 4 kPa. Distilled off. Thereafter, cyclohexyl acrylate was distilled at a tower top pressure of 3 kPa, thereby obtaining 500 g of high-purity cyclohexyl acrylate as a product (high boiling amount removed was 30 g).
[0045]
The purity of the high purity cyclohexyl acrylate was 99.9% and contained 0.001% acrylic acid, 0.010% cyclohexanol, and 0.005% (mass basis) cyclohexene as impurities.
[0046]
Comparative Example 1
710 g of the crude ester produced in Example 1 was placed in a flask equipped with the same rectification tower as in Example 1, 0.5 g of phenothiazine was added and heated, and 80 g of dehydrating agent n-hexane was distilled at a tower top pressure of 15 kPa. Left. Subsequently, 60 g of low boiling point impurities such as acrylic acid, cyclohexanol, cyclohexene and the like were distilled off at a tower top pressure of 4 kPa (the removed high boiling point was 60 g). Thereafter, 500 g of cyclohexyl acrylate was distilled at a tower top pressure of 3 kPa. The purity of cyclohexyl acrylate was 99.6% and contained 0.020% acrylic acid, 0.20% cyclohexanol and 0.040% cyclohexene (mass basis) as impurities.
[0047]
【The invention's effect】
In the present invention, since the high boiling impurities in the crude ester are removed by the first-stage distillation column, the decomposition product of the Michael adduct, (meth) acrylic, which is considered to be produced with the high boiling impurities as a causative substance. A decomposition product of acid cyclohexyl, a decomposition product of sulfate ester, and the like are not generated in the subsequent purification process. For this reason, in this manufacturing method, highly purified cyclohexyl (meth) acrylate can be manufactured easily.

Claims (3)

(Meth) reaction solution obtained by esterification of acrylic acid with cyclohexanol in the presence of a catalyst, or (meth) purifying the reaction solution obtained by the acrylic acid ester and cyclohexanol transesterified in the presence of a catalyst In producing cyclohexyl (meth) acrylate, the reaction solution was washed with an alkaline aqueous solution to obtain a crude ester. Then, in a batch distillation column, the column top pressure was 15 kPa to 3 kPa, and the column bottom temperature was 110 ± 10 ° C. In the continuous distillation column, the high-boiling impurities in the crude ester are removed by performing the first-stage distillation at a column top pressure of 4 ± 1 kPa and a column bottom temperature of 100 to 120 ° C. A method for producing cyclohexyl (meth) acrylate, wherein low boiling point impurities are removed by distillation. The method for producing cyclohexyl (meth) acrylate according to claim 1, wherein the first stage distillation is performed at a reflux ratio of 0.8 to 2 using a distillation column having 5 to 10 theoretical plates. The second-stage distillation is carried out under conditions of a tower top pressure of 15 kPa to 3 kPa and a tower bottom temperature of 110 ± 10 ° C. in a batch distillation tower, and a tower top pressure of 4 ± 1 kPa and a tower bottom temperature of 100 to 110 in a continuous distillation tower. The method for producing cyclohexyl (meth) acrylate according to claim 1, which is carried out at a temperature of ° C.