KR20200059855A - Method for producing glycol ethers with reduced discoloration - Google Patents

Abstract

The present invention relates to the prevention of discoloration of glycol ethers by the addition of a discoloration inhibitor. According to the present invention, it is possible to effectively solve a problem of product discoloration that can occur when an alkoxylation process of alkyl glycol ethers is added to increase the production amount of alkyl diglycol ethers in the preparation process of glycol ethers.

Description

Manufacturing method of glycol ethers with reduced discoloration {METHOD FOR PRODUCING GLYCOL ETHERS WITH REDUCED DISCOLORATION}

The present invention relates to a method for producing glycol ethers with reduced discoloration, and more particularly, to control discoloration of glycol ethers by adding a discoloration inhibitor when alkylene oxide is added for an alkoxylation reaction.

Glycol ether is a product produced through the alkoxylation reaction of alcohol and alkylene oxide, for example, butyl glycol ether (BG), butyl diglycol ether (BDG), butyl triglycol ether during ethoxylation reaction of butanol and ethylene oxide (BTG), butyl polyglycol ether (BPG) products. Ethylene oxide has an explosive range of 3% to 100%, so even if a small amount of ethylene oxide is exposed to air, there is a risk of explosion, so it is designed to convert 100% of the injected ethylene oxide in the glycol ether manufacturing process. In addition, the ethoxylation reaction is characterized by injecting excess alcohol for the purpose of heat removal of the reactor as an exothermic reaction.

In the case of butyl glycol ether (BG), it is frequently used as a solvent for water-based paints and nitrocellulose, and is used in printing inks, dyes, and detergents (liquid detergents, industrial detergents, dry cleaning, etc.). Butyl diglycol ether (BDG) is mainly used as an intermediate agent for products such as paints, dyes, and PVC, and is also used as a thinner for oil breaks. Recently, the demand for electronic detergent market has been increasing greatly.

In US Patent No. 3935279, the butyl glycol ether produced after the reaction of butanol and ethylene oxide for the purpose of selectively producing butyl diglycol ether (BDG), which is in great demand, is separated and put into a separate reactor. The process for preparing butyl diglycol ether (BDG) by reaction with ethylene oxide has been described. The addition of a process to convert butyl glycol ether (BG) to butyl diglycol ether (BDG) has the advantage of significantly increasing the production of butyl diglycol ether (BDG), while the residence time is more than doubled compared to conventional processes. Due to the problem that the products are exposed to heat for a long time, there is a problem of causing discoloration in the product.

Ethylene oxide used as an ethoxy reaction raw material is characterized by containing 50 ppm or less of aldehyde. In addition, butyl diglycol ether (BDG), butyl triglycol ether (BTG), and butyl polyglycol ether (BPG) are thermally decomposed to form additional aldehydes. The aldehyde thus produced forms a conjugated bond with butyl glycol ether (BG). The conjugated bond acts as a chromophore, so that an electron transfer phenomenon of a high energy level is easily generated through absorption of ultraviolet rays or visible light, and a complementary color of the absorbed wavelength is observed. Therefore, inhibiting the formation of conjugated bonds that form chromophores is an effective way to control the discoloration of glycol ethers.

U.S. Patent No. 3935279

In order to solve the discoloration problem of glycol ether, a method of introducing yellowing stability and ultraviolet stabilizer in the process may be used, but there is a problem that the effect is not large. In the present invention, to provide the most effective method for solving the problem of discoloration of the product that occurs when the ethoxylation process of butyl glycol ether (BG) is added to increase the production of butyl diglycol ether (BDG) during the production of glycol ether do.

In order to solve the above problems, the present invention, C _1-6 alkyl glycol ether, C _1-6 alkyl diglycol ether by primary alkoxylation by contacting C _1-6 alkanol with C _1-4 alkylene oxide, the first step to obtain a C _1-6 alkyl tree primary product comprising a glycol ether, and C _1-6 alkyl polyglycol ethers, and

A second product obtained by separating C _1-6 alkyl glycol ether from the primary product and then alkoxylating it secondarily by contacting with C _1-4 alkylene oxide to obtain a secondary product comprising C _1-6 alkyl diglycol ether. Including steps,

Provided is a method for preparing glycol ethers with reduced discoloration, wherein a discoloration inhibitor is added to control discoloration of the final product.

According to one embodiment, the discoloration inhibitor may be added together with C _1-4 alkylene oxide in the first step, the second step, or the first and second steps.

According to one embodiment, the discoloration inhibitor may be hydrazine (N ₂ H ₂ ).

According to one embodiment, the content of the discoloration inhibitor may be 50 to 500 ppm with respect to the total weight of C _1-6 alkanol and C _1-4 alkylene oxide.

According to the present invention, it is possible to effectively solve the problem of discoloration of the product that occurs when an ethoxylation process of butyl glycol ether (BG) is added to increase the production of butyl diglycol ether (BDG) during the production of glycol ether.

The present invention is a primary alkoxylation by contacting C _1-6 alkanol with C _1-4 alkylene oxide to C _1-6 alkyl glycol ether, C _1-6 alkyl diglycol ether, C _1-6 alkyl triglycol ether at, and C _1-6 comprising: a first step of obtaining a first product comprising an alkyl polyglycol ether, and the primary product by removing a C _1-6 alkyl glycol ether is contacted with C _1-4 alkylene oxides A second step of alkoxylation to obtain a secondary product comprising a C _1-6 alkyl diglycol ether, wherein a discoloration-preventing glycol is added to control the discoloration of the final product. It relates to a method for producing ethers.

In the present invention, the step of separating the alkyl glycol ether from the product from the primary alkoxylation process to further increase the production of alkyl diglycol ether in the production of glycol ether, and further secondary alkoxylation.

On the other hand, when an alkoxylation process of an alkyl glycol ether is added to increase the production amount of the alkyl diglycol ether, there is a problem that the products are exposed to heat for a long time due to an increase in residence time, causing discoloration.

Therefore, in the present invention, the occurrence of such discoloration can be controlled by adding a discoloration inhibitor during the reaction of the alkanol and alkylene oxide.

According to one embodiment, the discoloration inhibitor may be hydrazine (N ₂ H ₄ ).

The discoloration-preventing agent may be added together with the alkylene oxide, in the first step, alternatively in the second step, or alternatively, the discoloration-preventing agent may be added in both the first and second steps. .

The discoloration preventing agent may be added in an amount of 50 to 500 ppm, or in an amount of 100 to 500 ppm, or in an amount of 200 to 500 ppm, based on the total weight of the alkanol and alkylene oxide. When the content of the discoloration inhibitor is less than 50 ppm, the effect of preventing discoloration may not be large, and when the content of the discoloration inhibitor is more than 500 ppm, product purity may be deteriorated.

The alkanol may be selected from alkyl alcohols having 1 to 6 carbon atoms. According to one embodiment, the alkanol is butanol.

The alkylene oxide may be selected from alkylene oxides having 1 to 4 carbon atoms, and according to one embodiment, the alkylene oxide is ethylene oxide.

The alkanol to alkylene oxide may be used in a molar ratio of 3: 1 to 8: 1. According to one embodiment, the reaction molar ratio of the alkanol to alkylene oxide is 6: 1. If it is outside the range of the reaction molar ratio, problems such as explosion may occur due to a problem of heat removal during operation.

According to the present invention, a catalyst may be added during the alkoxylation reaction.

The catalyst may be a homogeneous base catalyst, for example, potassium hydroxide. The catalyst may be used in an amount of 20 to 100 ppm based on the total weight of the alkanol and alkylene oxide.

The alkoxylation reaction of the alkanol and alkylene oxide can be carried out for 3 to 10 hours at a temperature of 160 to 220 ° C and a pressure of 10 to 20 bar.

Thereafter, the product obtained from the alkoxylation reaction is sent to an alkanol recovery column to separate the alkanol from the product. Subsequently, the product obtained by separating the alkanol may be sequentially separated by an alkyl glycol ether, an alkyl diglycol ether, an alkyl triglycol ether, and an alkyl polyglycol ether through distillation in a distillation column.

A second alkoxylation reaction may be performed on the alkyl glycol ether separated from the distillation column using alkylene oxide.

The amount of the alkyl glycol ether and alkylene oxide to be injected is a molar ratio of 3: 1 to 8: 1, and a second alkoxylation reaction can be performed at a temperature of 160 to 220 ° C. and a pressure of 10 to 20 bar for 3 to 10 hours. have.

The product obtained from the second alkoxylation reaction may be injected again into the distillation column to separate an alkyl glycol ether, an alkyl diglycol ether, an alkyl triglycol ether, and an alkyl polyglycol ether.

Hereinafter, the operation and effect of the invention will be described in more detail through specific examples of the invention. However, this is provided as an example of the invention, and the scope of the invention is not limited in any way.

Example

Comparative Example 1

Butanol and ethylene oxide were injected into the PFR reactor at a molar ratio of 6: 1. Potassium hydroxide as a catalyst was injected in an amount of 40 ppm, and an ethoxylation reaction was performed at a reaction temperature of 190 ° C and a reaction pressure of 15 bar. The total reaction time was maintained for 5 hours to obtain crude glycol ether. The crude glycol ether was first sent to a butanol recovery column to separate butanol. Subsequently, butyl glycol ether (BG), butyl diglycol ether (BDG), butyl triglycol ether (BTG), and butyl polyglycol ether (BPG) were sequentially separated through distillation of three distillation columns arranged in series.

Table 1 shows the production yield of glycol ether through Comparative Example 1. Butyl glycol ether (BG) production was found to be the largest with 75% by weight.

BG BDG BTG BPG Manufacturing yield (% by weight) 75 20 4 One

Comparative Example 2

Butanol and ethylene oxide were injected into the PFR reactor at a molar ratio of 6: 1. As a catalyst, 40 ppm of potassium hydroxide was used, and the primary ethoxylation reaction was performed for 5 hours at a reaction temperature of 190 ° C and a reaction pressure of 15 bar to obtain crude glycol ether. The crude glycol ether was sent to a butanol recovery column to recover butanol. Subsequently, butyl glycol ether (BG), butyl diglycol ether (BDG), butyl triglycol ether (BTG), and butyl polyglycol ether (BPG) were sequentially separated through three distillation columns arranged in series.

At this time, unlike Comparative Example 1, the butyl glycol ether (BG) separated in the first column was injected into a separate PFR reactor to conduct a second ethoxylation reaction with ethylene oxide. At this time, the molar ratio of the injected butyl glycol ether and ethylene oxide was 6: 1, and the reaction was performed at a reaction temperature of 190 ° C and a reaction pressure of 15 bar for 5 hours. The produced product was again injected into a butyl glycol ether (BG) column to separate butyl glycol ether (BG), butyl diglycol ether (BDG), butyl triglycol ether (BTG), and butyl polyglycol ether (BPG).

Table 2 shows the production yield of the glycol ether prepared through Comparative Example 2. Since the ethoxylation reaction of butyl glycol ether (BG) was further performed, the production of butyl diglycol ether (BDG), butyl triglycol ether (BTG), and butyl polyglycol ether (BPG) was increased compared to Comparative Example 1. Able to know.

BG BDG BTG BPG Manufacturing yield (% by weight) 64 27 6 3

Example 1

In the first ethoxylation reaction of butanol and ethylene oxide, glycol ether was prepared in the same manner as in Comparative Example 2, except that 50 ppm of hydrazine (N ₂ H ₄ ), which is a discoloration inhibitor, was added to ethylene oxide. At this time, the production yield of the prepared glycol ether was the same as in Comparative Example 2.

Example 2

In the first ethoxylation reaction of butanol and ethylene oxide, a glycol ether was prepared in the same manner as in Comparative Example 2, except that 100 ppm of hydrazine (N ₂ H ₄ ), a discoloration inhibitor, was added to ethylene oxide. At this time, the production yield of the prepared glycol ether was the same as in Comparative Example 2.

Example 3

In the first ethoxylation reaction of butanol and ethylene oxide, glycol ether was prepared in the same manner as in Comparative Example 2, except that 200 ppm of hydrazine (N ₂ H ₄ ), which is a discoloration inhibitor, was added to ethylene oxide. At this time, the production yield of the prepared glycol ether was the same as in Comparative Example 2.

Example 4

In the first ethoxylation reaction of butanol and ethylene oxide, glycol ether was prepared in the same manner as in Comparative Example 2, except that 500 ppm of hydrazine (N ₂ H ₄ ), which is a discoloration inhibitor, was added to ethylene oxide. At this time, the production yield of the prepared glycol ether was the same as in Comparative Example 2.

Example 5

After the primary ethoxylation reaction of butanol and ethylene oxide, the produced and purified butyl glycol ether (BG) is injected into a separate reactor, followed by a second ethoxylation reaction of ethylene oxide with ethylene oxide, and hydrazine (N Glycol ether was prepared in the same manner as in Comparative Example 2, except that ₂ H ₄ ) was added at 200 ppm. At this time, the production yield of the prepared glycol ether was the same as in Comparative Example 2.

Experimental Example 1

Color analysis of the glycol ether products prepared in Comparative Examples 1 and 2 and Examples 1 to 5 (APHA color value, DIN-ISO-6271) was performed, and the results are shown in Table 3.

Hydrazine addition amount (ppm) APHA color Comparative Example 1 - 7 Comparative Example 2 - 122 Example 1 50 45 Example 2 100 22 Example 3 200 9 Example 4 500 6 Example 5 200 4

From the results of Table 3, when adding the butyl glycol ether (BG) ethoxylation process as in Comparative Example 2, it can be seen that APHA increased significantly. On the other hand, in Examples 1 to 5 using hydrazine as a discoloration inhibitor, it was confirmed that APHA can be effectively lowered. Particularly, when the addition amount of hydrazine was added at 200ppm or more, it was found that the butyl glycol ether (BG) ethoxylation process showed the same level of APHA as Comparative Example 1 without addition. In addition, through experiments investigating the effect of APHA on the location of the addition of hydrazine of Examples 3 and 5, it was found that it is effective to add hydrazine to the butyl glycol ether (BG) ethoxylation process rather than the butanol ethoxylation process.

Claims (7)

Primary alkoxylation by contacting C _1-6 alkanol with C _1-4 alkylene oxides to C _1-6 alkyl glycol ethers, C _1-6 alkyl diglycol ethers, C _1-6 alkyl triglycol ethers, and C A first step of obtaining a primary product comprising _1-6 alkyl polyglycol ether, and
A second product obtained by separating C _1-6 alkyl glycol ether from the primary product and then contacting with C _1-4 alkylene oxide to undergo secondary alkoxylation to obtain a secondary product comprising C _1-6 alkyl diglycol ether. Including steps,
A method for producing glycol ethers with reduced discoloration, wherein a discoloration inhibitor is added to control discoloration of the final product. The method according to claim 1, wherein the discoloration inhibitor is added together with C _1-4 alkylene oxide in the first step, the second step, or the first step and the second step. The method according to claim 1 or 2, wherein the discoloration inhibitor is hydrazine (N ₂ H ₄ ). The method according to claim 1 or 2, wherein the content of the discoloration inhibitor is 50 to 500 ppm based on the total weight of C _1-6 alkanol and C _1-4 alkylene oxide. The method according to claim 1 or 2, wherein the C _1-6 alkanol is butanol. The method according to claim 1 or 2, wherein the C _1-6 alkanol to C _1-4 alkylene oxide is used in a molar ratio of 3: 1 to 8: 1. The method according to claim 1 or 2, wherein the C _1-6 alkyl glycol ether to C _1-4 alkylene oxide is used in a molar ratio of 3: 1 to 8: 1.