KR20090034158A - Preparation of hydroxy acrylates - Google Patents

Abstract

A method for preparing hydroxy acrylates is provided to secure high yield and high purity without the generation of by-products by injecting one kind of a compound instead of an inhibitor and diester inhibitor. A method for preparing hydroxy(alkyl)acrylate obtained by reacting an acrylic acid compound with alkylene oxides in the presence of catalysts is characterized by injecting a compound represented by the chemical formula 1. In the chemical formula 1, R1 is C6~C12 aromatic ring which contains or does not contain N, an aromatic ring having a heterocycle which contains or does not contain N, or CnH2n-1 aliphatic hydrocarbon (wherein, n is an integer of 1~20); R2 is hydrogen or C1~C6 alkyl group; and x and y are an integer of 0-3 and 1-3 respectively, in case R1 is an aromatic ring.

Description

Preparation method of hydroxy acrylate {Preparation of Hydroxy Acrylates}

The present invention relates to a method for preparing hydroxy acrylate. More specifically, the present invention relates to a method of improving the selectivity of a reaction product in a method of synthesizing hydroxy (alkyl) acrylate by reacting acrylic acid or methacrylic acid with alkylene oxide such as ethylene oxide.

The hydroxy (alkyl) acrylates aimed at in the present invention are typically represented by the following structural formulas;

Here, usually, the value is n = 1 or more, and R4 represents a hydrogen atom, a straight or branched alkyl group having 1 to 6 carbon atoms, an allyl group having 1 to 6 carbon atoms, a phenyl having 6 to 16 carbon atoms, an alkylphenyl and a benzyl group. .

Generally, 2-hydroxyethyl (meth) acrylate is prepared from ethylene oxide and acrylic acid or methacrylic acid in the presence of a catalyst. Commonly used catalysts include iron-based, chromium-based, and amine-based catalysts, which are separated from the product after the reaction and recycled or disposed of with distillation residues.

In preparing hydroxyethyl (meth) acrylate using a catalyst, the reaction is generally prepared by injecting the raw materials into the reactor at one time and then converting them batchwise, or injecting each raw material in small amounts continuously or simultaneously. And the like have been disclosed.

All of the above injection methods lower the risk of accidents caused by dangerous ethylene oxide during the reaction and at the same time more efficiently remove the heat of reaction generated in the reaction, prevent polymerization of products and suppress the formation of by-products to the product after the reaction. It is evaluated as an effort to further improve selectivity.

The molar ratio of alkylene oxides such as ethylene oxide and the like injected to the reaction raw material acrylic acid or methacrylic acid is usually 0.5 to 10.0 molar ratio from the beginning or during the reaction, and more specifically 1.0 to 5.0 molar ratio is more preferred. do. After the reaction is completed, the conditions in the reactor are usually maintained in an excessive amount of ethylene oxide for the purpose of improving the yield by at least containing unreacted acrylic acid or methacrylic acid at the same time to facilitate the purification.

However, whether the conditions in which excessive amounts of acrylic acid or methacrylic acid are advantageous or the conditions in which excess alkylene oxides such as ethylene oxide is advantageous is favorable, depending on whether the skilled person possesses the purification technology and utility to use the following by-products. The excess may not affect the yield of the desired hydroxyalkyl (meth) acrylate as it may be.

However, in any of the above-described methods, there is a problem that alkylene glycol di (meth) acrylate, which is a diester body, and dialkylene glycol mono (meth) acrylate, which is a polymer of alkylene oxide, are easily produced by-products as impurities.

Among these by-products, the polymer can be removed as distillation, but the diester body is difficult to remove even by a purification method such as distillation, and controlling the content at the end of the reaction has become an important problem.

In other words, in the reaction between methacrylic acid and alkylene oxide, the catalyst forms a salt with methacrylic acid to activate the reaction with the alkylene oxide. In this case, as the reaction proceeds, the concentration of methacrylic acid in the reaction system is lowered, and as a result, the catalyst is known to combine with the produced hydroxyalkyl methacrylate to produce a diester body. Therefore, in order to suppress formation of a diester as described above, a method of terminating the reaction in a state in which unreacted methacrylic acid remains in excess is used.

However, even in this case, the remaining acid component is difficult to be removed by a purification method such as distillation, similarly to the diester body, so that even if the content of the diester body can be reduced, a problem of acid component increase occurs.

In order to solve this problem, Korean Laid-Open Patent Publication No. 2003-0036787 discloses a preparation method of adding a polymerization inhibitor during the reaction and adding a diester inhibitor after completion of the reaction or at the start of distillation.

However, in the case of the above method, there is a problem in that process inconvenience and process cost increase by adding two kinds of substances before and after the reaction, respectively.

Therefore, in the present invention, in order to solve the above problems, by-products are minimized in the manufacturing method of synthesizing hydroxy-based (alkyl) acrylate by reacting an acrylic acid compound with an alkylene oxide such as ethylene oxide. It is intended to improve the selectivity of reaction products.

In order to achieve the above object, the present invention in the synthesis of a hydroxy (alkyl) acrylate by reacting an acrylic acid compound with an alkylene oxide in the presence of a catalyst, when the reaction may be a polymerization inhibitor and a diester inhibitor in the formula Provided is a method for preparing a hydroxy-based (alkyl) acrylate with improved selectivity to the reaction product by adding one compound represented by 1.

Here, R1 is a C ₆ ~ C ₁₂ aromatic ring with or without N, an aromatic ring containing a hetero ring with or without N, or an aliphatic hydrocarbon of C _n H _{2n -1} (n is 1-20 And R2 is hydrogen or an alkyl group of C ₁ to C ₆ (x is an integer of 0 to 3, y is an integer of 1 to 3).

According to the present invention, the alkylene oxide may be sufficiently removed to prevent side reactions between the alkylene oxide and the reaction product in the purification process after the reaction. In addition, it is possible to prevent the overall yield decrease and the difficulty of the process operation due to the formation of unwanted polymer during the purification process. Therefore, instead of adding the polymerization inhibitor and the diester inhibitor, respectively, one compound may be added to provide a method capable of securing a high purity product in high yield without generation of byproducts.

Hereinafter, the present invention will be described in more detail with reference to specific chemical formulas, but the chemical formulas exemplified below are merely illustrative to help the present invention, and the scope of the present invention is not limited thereto.

R1 of Formula 1 may be, for example, an aromatic compound as described below.

For example, the compound of Formula 1 may be a quinoline compound represented by Formula 2 when R 1 is an aromatic ring including N.

Here, the positions of OH, -COOH, and -OR 2 which bind to the ring are arbitrary, and R 2 is as defined in Formula 1 above.

In addition, when R1 of the general formula (1) is a benzene ring of C _{6 It} may be a compound represented by the formula (3 to 5).

The compound represented by Chemical Formula 1 is preferably added in an amount of 0.1 to 5 mol% with respect to the acrylic acid compound as a raw material, and more preferably 0.1 to 3 mol%. In addition, the addition time of the said compound is not specifically limited, It is preferable to add together with the acrylic acid compound which is a raw material.

Although it does not specifically limit as said alkylene oxide in this invention, It is preferable that it is C2-C6, and it is more preferable that it is C2-C4. Specific examples of the alkylene oxide include ethylene oxide, propylene oxide, butylene oxide, and the like, and preferably ethylene oxide and propylene oxide.

In the present invention, the acrylic acid compound is preferably an acrylic acid compound represented by the following Chemical Formula 6, but other acrylic acid derivatives such as alkyl methacrylic acid may also be used.

Here, R <3> represents a hydrogen atom, a C1-C6 linear or branched alkyl group, a C2-C6 alkenyl group, a C6-C16 phenyl, alkylphenyl, and benzyl group.

Whether the conditions in which the acrylic acid compound is excessive in the mixing of the reactants or the conditions in which the alkylene oxide is excessive is advantageous may depend on the purification technique possessed by those skilled in the art and the utility of the following by-products. In other words, which compound is excessive is not particularly limited in obtaining the desired hydroxy-based (alkyl) acrylate. However, in order to simplify additional facilities and processes, it is preferable to use an alkylene oxide in an amount of about 0.5 to 10 moles per mole of the acrylic acid compound from the beginning of the reaction or while the reaction is in progress. More preferably, it may be 0.7 to 5 molar ratio, and most preferably 0.7 to 1.5 molar ratio.

In the prior art, phenolic compounds such as hydroquinone and methylhydroquinone, and amine compounds such as phenothiazines as polymerization inhibitors in order to prevent polymerization of (meth) acrylic acid or hydroxy-based (alkyl) acrylates as reaction products during the reaction. And phenylene diamines.

In addition, carboxylic acids such as maleic acid, salicylic acid, octanoic acid, adipic acid and phthalic acid or polyhydric alcohols such as glycerin, diethylene glycol and trimethylolpropane are added as a diester inhibitor after completion of the reaction or at the start of distillation for purification. .

However, the present invention can improve the selectivity of the reaction product by adding a compound represented by the formula (1) during the reaction as a compound acting as a polymerization inhibitor and diester inhibitor.

The acrylic acid compound and the alkylene oxide may be added at the same time in a batch, or may be sequentially or intermittently added. Here, continuous input means continuous supply in small quantities, and intermittent input means the type of input divided into any number of pulses.

After the reactants are injected into the reactor, an inert gas such as nitrogen or helium is flowed into the water system to minimize the amount of oxygen present in the system to minimize the risk of an accident that may occur during the reaction. If necessary, the system can be pressurized with an inert gas such as nitrogen, helium or argon to completely block the inflow of oxygen.

After purging the reactor sufficiently with an inert gas, the internal temperature of the reactor is raised to the reaction temperature in order to proceed with the reaction. The reaction temperature is within 40 ~ 120 ℃, preferably within 50 ~ 80 ℃. If the temperature is too high, the content of the diester material is high, and if the temperature is too low, the reaction rate is slow. Additional equipment or methods may be employed to circulate or cool some or all of the reactants out of the reactor to prevent excessive temperature rise of the reactor as the reaction proceeds, or to install cooling coils in the reactor to facilitate cooling.

After injecting a part of the reactant, the temperature of the reactor is gradually increased, and the alkylene oxide is injected by using a pressure pump. If necessary, all of the alkylene oxide may be added and then aged in a manner similar to a batch injection.

Preferably, alkylene oxide is introduced at an initial temperature of 60 ° C., and the temperature rise according to the exothermic reaction is controlled to 70 to 75 ° C. After the addition of the alkylene oxide was completed, the aging step was maintained by maintaining 70 ~ 75 ℃.

In addition, for the efficient control of the heat of reaction generated during the reaction, although not particularly limited, it is more preferable to inject the reactants in small portions, but such a process operation may be selected by a person skilled in the art by reviewing economics, process stability, workability, and the like. Can be.

As the reaction proceeds, the conversion rate of the acrylic acid compound increases proportionally up to a certain point with time, and after the reaction progresses to a certain degree, the contact probability between the reactants is lowered, and the reaction rate is gradually slowed.

As the reaction time increases, the selectivity of the hydroxy-based (alkyl) acrylates produced during the reaction decreases slightly but remains approximately constant. When the reaction reaches the end point, for example, when the conversion rate of the acrylic acid compound reaches 98% or more, the reaction rate becomes very slow and from this step, the production of ethylene glycol di (meth) acrylate as a by-product when ethylene oxide is used It starts to increase

The by-products occur rapidly when the reaction is almost finished, and may also show a slightly different pattern depending on the type of catalyst. For example, in the form of highly basic amines or compounds thereof and ion exchange resins in which they are fixed to a polymer support, at least 30% of hydroxyalkyl (meth) acrylates are converted to ethylene glycol di (meth) acrylates. Was observed. Therefore, in order to minimize the generation of such side reactions, it is desirable to minimize the time for which the conversion rate is 99% or more and to remove unreacted ethylene oxide from the reactor as soon as possible.

The by-product has a disadvantage in that physical separation is difficult because the difference between the boiling point and the hydroxy-based (alkyl) acrylate, which is a desired product in the present invention, is not large. In addition, even if only a small amount of the product is included in the purification to form a polymer to form a very poor condition to obtain the desired product yield is not fundamentally suitable for continuing the reaction.

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited to the examples.

Example 1

430 g of methacrylic acid and 1.7 g of 2,5-dihydroxy benzoic acid (0.22 mol% of methacrylic acid) were mixed in a 1 liter stainless steel reactor with an outer jacket attached.

1.98 g of chromic acetate was added to the reactor as a catalyst.

The reactor was purged with nitrogen three times to minimize the amount of oxygen contained in the reactor, and after raising the temperature to 60 ° C., 231 g of ethylene oxide was uniformly charged over one hour.

During constant velocity addition, the temperature inside the reactor was gradually increased by an exothermic reaction, and the internal temperature was maintained at 75 ° C. After the addition of ethylene oxide was completed, the reaction was continued at the same temperature for about 2 hours, and the conversion was over 99% using GC.

When the reaction was completed, the temperature of the reactor was lowered and the super charged ethylene oxide was removed under vacuum to prevent further reaction.

The selectivity of hydroxyethyl (meth) acrylate produced after the reaction was 96.2%. Diethylene glycol mono (meth) acrylate content was 3.05%, ethylene glycol di (meth) acrylate content was 0.16% as a by-product confirmed using G.C / Mass.

The reaction product was added to a 1L 3neck round bottom flask, and the purification was carried out while stirring. This purification gave 611 g of 2-hydroxyethyl (meth) acrylate as a product.

Example 2

The reaction was carried out in the same manner as in Example 1, except that 432.4 g of acrylic acid and 290.7 g of ethylene oxide and 2.03 g of 2,5-dihydroxy benzoic acid (0.22 mol% of acrylic acid) were mixed instead of methacrylic acid.

The selectivity of hydroxyethyl acrylate produced after the reaction was 90.2%. As a by-product confirmed using G.C / Mass, the content of diethylene glycol monoacrylate was 7.53%, and the content of ethylene glycol diacrylate was 1.82%.

The reaction product was purified in the same manner as in Example 1 to obtain 612 g of 2-hydroxyethyl acrylate.

Example 3

The reaction was carried out in the same manner as in Example 1, except that 5-methoxysalicylic acid was added at 0.22 mol% of methacrylic acid instead of 2,5-dihydroxy benzoic acid.

The selectivity of hydroxyethyl (meth) acrylate produced after the reaction was 95.3%. Diethylene glycol mono (meth) acrylate content was 2.81%, and ethylene glycol di (meth) acrylate content was 0.17% as a by-product confirmed using G.C / Mass.

The reaction product was purified in the same manner as in Example 1 to obtain 604 g of 2-hydroxyethyl (meth) acrylate.

Example 4

The reaction was carried out in the same manner as in Example 2, except that 5-methoxysalicylic acid was added at 0.22 mol% of acrylic acid instead of 2,5-dihydroxy benzoic acid.

The selectivity of hydroxyethyl acrylate produced after the reaction was 90.3%. Diethylene glycol monoacrylate content was 8.47%, and ethylene glycol di (meth) acrylate content was 1.81% as a by-product identified using G.C / Mass.

The reaction product was purified in the same manner as in Example 1 to obtain 613 g of 2-hydroxyethyl acrylate.

Example 5

The reaction was carried out in the same manner as in Example 1, except that 4-hydroxy-2-quinolinecarboxylic acid was added at 0.22 mol% of methacrylic acid instead of 2,5-dihydroxy benzoic acid.

The selectivity of hydroxyethyl (meth) acrylate produced after the reaction was 95.9%. As a by-product confirmed using G.C / Mass, the content of diethylene glycol mono (meth) acrylate was 2.97%, and the content of ethylene glycol di (meth) acrylate was 0.15%.

The reaction product was purified in the same manner as in Example 1 to obtain 605 g of 2-hydroxyethyl (meth) acrylate.

Example 6

The reaction was carried out in the same manner as in Example 2, except that 4-hydroxy-2-quinolinecarboxylic acid was added at 0.22 mol% of acrylic acid instead of 2,5-dihydroxy benzoic acid.

The selectivity of hydroxyethyl acrylate produced after the reaction was 89.7%. As a by-product confirmed using G.C / Mass, the content of diethylene glycol monoacrylate was 8.24%, and the content of ethylene glycol diacrylate was 1.78%.

The reaction product was purified in the same manner as in Example 1 to obtain 592 g of 2-hydroxyethyl acrylate.

Example 7

The reaction was carried out in the same manner as in Example 1, except that 5-hydroxy isophthalic acid was added at 0.22 mol% of methacrylic acid instead of 2,5-dihydroxy benzoic acid.

The selectivity of hydroxyethyl (meth) acrylate produced after the reaction was 96.7%. As a by-product confirmed using G.C / Mass, the content of diethylene glycol mono (meth) acrylate was 2.80%, and the content of ethylene glycol di (meth) acrylate was 0.08%.

The reaction product was purified in the same manner as in Example 1 to obtain 612 g of 2-hydroxyethyl (meth) acrylate.

Example 8

The reaction was carried out in the same manner as in Example 2, except that 5-hydroxy isophthalic acid was added at 0.22 mol% of acrylic acid instead of 2,5-dihydroxy benzoic acid.

The selectivity of hydroxyethyl acrylate produced after the reaction was 88.1%. As a by-product confirmed using G.C / Mass, the content of diethylene glycol monoacrylate was 7.98%, and the content of ethylene glycol diacrylate was 1.82%.

The reaction product was purified in the same manner as in Example 1 to obtain 587 g of 2-hydroxyethyl acrylate.

Comparative Example 1

The reaction was carried out in the same manner as in Example 1, except that 1.21 g of hydroquinone (0.22 mol% of methacrylic acid) was added as a polymerization inhibitor instead of 2,5-dihydroxy benzoic acid, and after the reaction, as a diester inhibitor. Purification was carried out by adding 1.82 g of salicylic acid.

The selectivity of hydroxyethyl (meth) acrylate produced after the reaction was 93.7%. As a by-product, the content of diethylene glycol mono (meth) acrylate was 3.23%, and the content of ethylene glycol di (meth) acrylate was 0.22%.

The reaction product was purified in the same manner as in Example 1 to obtain 590 g of 2-hydroxyethyl (meth) acrylate.

Comparative Example 2

The reaction was carried out in the same manner as in Example 2, except that 1.45 g of hydroquinone (0.22 mol% of acrylic acid) was added as an polymerization inhibitor instead of 2,5-dihydroxy benzoic acid, and after the reaction, salicylic acid was used as a diester inhibitor. It was purified by adding 1.82 g.

The selectivity of hydroxyethyl acrylate produced after the reaction was 88.1%. As a by-product, the content of diethylene glycol monoacrylate was 9.84%, and the content of ethylene glycol diacrylate was 1.98%.

The reaction product was purified in the same manner as in Example 1 to obtain 602 g of 2-hydroxyethyl acrylate.

Claims (11)

In a method for producing a hydroxy (alkyl) acrylate by reacting an acrylic acid compound with an alkylene oxide in the presence of a catalyst, a compound represented by the following formula (1) is added to the hydroxy (alkyl) acrylate Manufacturing method. [Formula 1]

Here, R1 is a C ₆ ~ C ₁₂ aromatic ring with or without N, an aromatic ring including a hetero ring with or without N or aliphatic hydrocarbon of C _n H _{2n -1} (n is 1-20 And R2 is hydrogen or an alkyl group of C ₁ to C ₆ (x and y are integers of 0 to 3 and 1 to 3, respectively, when R 1 is an aromatic ring). The method according to claim 1, wherein R 1 of Formula 1 is an aromatic compound as described below.

The method of claim 1, wherein the compound represented by Chemical Formula 1 is represented by the following Chemical Formulas 2 to 5. [Formula 2]

Here, the positions of OH, -COOH, and -OR 2 which bind to the ring are arbitrary, and R 2 is as defined in Formula 1 above. [Formula 3]

[Formula 4]

[Formula 5]

The method of claim 1, wherein the acrylic acid compound is an acrylic acid compound represented by the following formula (6) or a derivative thereof. [Formula 6]

Here, R <3> represents a hydrogen atom, a C1-C6 linear or branched alkyl group, a C1-C6 allyl group, a C6-C16 phenyl, alkylphenyl, and benzyl group. The method of claim 4, wherein the acrylic acid compound is acrylic acid or methacrylic acid. The method of claim 1, wherein the alkylene oxide is selected from the group consisting of ethylene oxide, propylene oxide and butylene oxide. The method of claim 1, wherein the compound of Formula 1 is added in the range of 0.1 to 5 mol% of the acrylic acid compound. The method of claim 7, wherein the compound of Formula 1 is added in an amount of 0.1 to 3 mol% of the acrylic acid compound. The method of claim 1, wherein the compound of Formula 1 is added with an acrylic acid compound. The method according to claim 1, wherein the molar ratio of alkylene oxide to the acrylic acid compound is 0.7 to 1.5. The method according to claim 1, wherein the reaction of the acrylic acid compound and the alkylene oxide is carried out at a temperature of 40 ~ 120 ℃ hydroxy- (alkyl) acrylate production method.