JPH08198809A - Propylene glycol monoalkyl ether ester compound and its preparation - Google Patents

Abstract

PURPOSE: To obtain a propylene glycol monoalkyl ether ester compound useful, for example, as a paint having excellent solubility and low toxicity, by the reaction at a high temperature in the presence of any acid catalyst and an azeotropic agent.

CONSTITUTION: This compound shown by the formula (R¹ is ethyl or propyl; R² is methyl or ethyl) is obtained by the reaction of (C) propylene glycol monoalkyl ether with (D) an organic acid (e.g. acetic or propionic acid) at 80°C or higher in the presence of (A) an acid catalyst (a strong acid selected from sulfuric, p-toluenesulfonic, and methanesulfonic acids) and (B) an azeotropic agent (one selected from benzene, toluene, xylene, and cyclohexane). Removal of unreacted acid and water from the obtained crude product by distillation gives the objective compound having high purity. It is preferable that a C/D molar ratio is 0.6-3.0 and a volume ratio of component B is 6-30% per the total volume of the starting material.

COPYRIGHT: (C)1996,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a propylene glycol monoalkyl ether ester compound and a method for producing the same.

[0002]

2. Description of the Related Art Organic ester compounds are excellent solvents widely used in the synthetic resin industry as solvents for paints, inks, adhesives, detergents, etc. At present, ether compounds are mainly classified into two types, namely E series and P series. E-series ether compounds are synthesized from alcohol and ethylene oxide, while P-series ether compounds are synthesized from alcohol and propylene oxide. Recently, E-series ethers and their acetate compounds have been found to, when absorbed by the human body, decompose into alkoxyacetate ethers, which in turn make red blood cells abnormal and toxic to the reproductive organs. On the other hand, the P series does not cause these damages. Currently, some P-series propylene glycol monomethyl ether acetates have low solubility in unsaturated polyester or polyurethane resins, and their coatings have poor drying properties. Therefore, there is an urgent need to develop a solvent that has excellent solubility and dryness as well as low toxicity.

In order to meet the demands of this market, the applicant provides a novel propylene glycol monomethyl ether propionate compound and a method for producing the same in Japanese Patent Application No. 5-152223, and then in Japanese Patent Application No. 6-110879. Provided are propylene glycol monomethyl ether butyrate, its isomers, and a method for producing the same. These earlier applications are incorporated herein by reference. Subsequent research in this area has led to the successful development of new compounds.

[0004]

The first problem to be solved by the invention is to provide a novel propylene monoalkyl ether ester compound. The second object is to provide a method for producing the propylene monoalkyl ether ester compound. A third object is to provide utilization of the novel propylene glycol monoalkyl ether ester compound.

[0005]

[Means for Solving the Problems] The first problem is the following general formula:

Embedded image A propylene glycol monoalkyl ether ester compound having (in the above formula, R ₁ represents an ethyl group or a propyl group, and R ₂ represents a methyl group or an ethyl group) is solved. Here, the compound is obtained by reacting propylene glycol monoalkyl ether as a starting material with an organic acid selected from the group consisting of acetic acid and propionic acid. The novel compound represented by the above general formula is propylene glycol monoethyl ether acetate (PGEA), propylene glycol monoethyl ether propionate (P
GEP), propylene glycol monopropyl ether acetate (PGPA) and propylene glycol monopropyl ether propionate (PGPP).

The second problem is to react with propylene glycol monoalkyl ether and acetic acid or propionic acid at a high temperature of 80 ° C. or higher in the presence of an acidic catalyst and an azeotropic agent to esterify the crude propylene glycol monoalkyl ether ester. A method for producing a propylene glycol monoalkyl ether ester compound, which comprises a step of producing a compound and a step of removing unreacted acid and water by distillation to obtain a high-purity propylene glycol monoalkyl ether ester compound Will be resolved. In this production method, propylene glycol monoethyl ether (PGE) synthesized from ethanol and propylene oxide is reacted with acetic acid or propionic acid in the presence of an acidic catalyst and an azeotropic agent to produce propylene glycol monoethyl ether acetate (PGEA). ) Or propylene glycol monoethyl ether propionate (PGEP) is formed. Alternatively, propylene glycol monopropyl ether acetate (PGPA) produced by reacting propylene glycol monopropyl ether (PGP) synthesized from propanol and propylene oxide with acetic acid or propionic acid in the presence of an acidic catalyst and an azeotropic agent, or propylene Glycol monopropyl ether propionate (PGPP) is formed.

A third problem is the solvent of novel propylene glycol monoalkyl ether ester compounds, especially in the field of paints, inks and adhesives, and above all as the solvent of detergents used in the electronics industry and cleaning. Solved by providing utilization.

The method for producing a propylene glycol monoalkyl ether ester compound of the present invention includes a batch process and a continuous process. Generally, when the water generated during the reaction is not removed, the reaction system quickly reaches an equilibrium state, which hinders the improvement in productivity and is therefore inconvenient for industrial production. Therefore, in the production method of the present invention, an aromatic compound such as benzene, toluene, xylene and cyclohexane is azeotropically distilled in the reaction system regardless of whether a batch process or a continuous process is adopted. It is added as an agent. The azeotropic agent must be incompatible with water and exhibit an azeotropic effect with water.
Aromatic compounds are perfect in meeting this need.

In the batch process, the reactants and the azeotropic agent are placed in a reactor and allowed to react at the azeotropic point while removing water and circulating the azeotropic agent. After completion of the reaction, the product and the azeotropic agent are separated by fractional distillation to obtain a highly pure product.

In the continuous process, the starting materials are fed at a predetermined flow rate, while water is continuously recovered from the top of the fractionation tower during the reaction process. The azeotrope is circulated, while the product (PGEA or PGEP or P
The reaction system containing GPA or PGPP) is transferred to a rectification column for fractional distillation to remove a small amount of unreacted ether and acid. This gives a product of high purity.

According to the method for producing a propylene glycol monoalkyl ether ester compound of the present invention, the starting material PGE or PGP and acetic acid or propionic acid are at 80 ° C.
Esterification is carried out by reacting in the presence of an acidic catalyst and an azeotropic agent at the above high temperature to produce crude PGEA or PGEP or PGPA or PGPP. The product is then separated by rectification to remove unreacted acid and water formed, yielding highly pure PGEA or PGEP or PGPA or PGPP.

For the starting materials, the molar ratio of PGE or PGP to acetic acid or propionic acid (molar ratio of PGE or PGP to acetic acid or propionic acid) is generally 0.6.
The preferred molar ratio is 1.1 to 1.5 in which PGE or PGP is present in excess with respect to acetic acid or propionic acid. When the molar ratio is smaller than 0.6 or larger than 3.0, both components of the reaction system leave an unreacted residue in excess after the reaction is completed, and a large amount of energy is consumed during the rectification process. Not only that, the rectification time required becomes longer and the production amount is reduced. When the acetic acid or propionic acid is in excessive excess, that is, when the molar ratio is less than 0.6, the reaction rate is significantly reduced. The reason for this is not clear, but it seems that the acidic catalyst is buffered.

The catalyst used in the present invention includes inorganic acids such as sulfuric acid, hydrochloric acid and phosphoric acid, and oxalic acid,
There are organic acids such as citric acid, p-toluenesulfonic acid and methanesulfonic acid, and particularly strong acids such as sulfuric acid, p-toluenesulfonic acid and methanesulfonic acid are preferable. The propylene glycol monoalkyl ether ester compound obtained according to the present invention has a boiling point of PGEA of 155 ° C.
The boiling point of PGEP is 170 ° C., the boiling point of PGPA is 175 ° C., and the boiling point of PGPP is 190 ° C.

The substances resulting from the metabolism of the products obtained according to the invention have a low toxicity to the reproductive organs.
The NOEL (NO Observed Effect Level) published by the US Environmental Protection Agency for E-series and P-series rabbits was 30 pp each.
m and 3000 ppm. The ester compound of the present invention belongs to the P series and has almost no effect on the reproductive organs.

Furthermore, the products of the invention have a high solubility in various resins. For example, the final solvent percentage of conventional propylene glycol monomethyl ether acetate to alkyd resin is 70%, while that of the novel product of the present invention is above 90%, proving to be a good solvent. .

In the production method of the present invention, when the reaction is completed, the reaction system must be treated by double rectification. Primary rectification is a dehydration and deacidification process. In order to increase efficiency and save energy, azeotropic agent selected from aromatic organic solvent of benzene, toluene, xylene and cyclohexane is 6 to 30% based on the whole starting material.
To reduce the azeotropic temperature during rectification. During secondary rectification, the only remaining two components, ether and ester, are completely fractionally distilled based on the difference in the boiling points of the two components.
This gives a product of high purity.

[0017]

The present invention will now be described by way of the following examples, which are intended to be illustrative only, without limiting the invention thereto.

Example 1 Propylene glycol monoethyl ether (PGE) 1392 was placed in a reactor having a volume of 3 liters.
ml and 572 ml acetic acid were added. Xylene 200 after mixing
ml and 10 g of p-toluenesulfonic acid were added. Then, the temperature was brought to a reflux temperature of 140 ° C. and the reaction was carried out for 5 hours.
During this time, dehydration was performed simultaneously to effectively promote the reaction. As a result of analyzing the reaction liquid by gas chromatography,
The composition was found to be as follows: Composition of reaction solution: Propylene glycol monoethyl ether acetate (PGEA) 65.49% Propylene glycol monoethyl ether (PGE) 20.46% Acetic acid 5.35% Xylene 8.21% Water 0.49% Treated by double rectification, 99.9%
A propylene glycol monoethyl ether acetate compound having the above purity was obtained.

The propylene glycol monoethyl ether acetate compound is characterized by the NMR ¹ H spectrum shown in FIG. 1 and by the mass spectrogram shown in FIG. 2, whereby its chemical structure is of the formula:

Embedded image It was decided to be.

EXAMPLE 2 1392 ml of propylene glycol monoethyl ether and 572 ml of acetic acid were placed in a reactor having a volume of 3 liters. After mixing, p-toluenesulfonic acid 1
0 g was added. Then, the temperature was brought to a reflux temperature of 98.5 ° C. and the reaction was carried out for 5 hours. Since no azeotropic agent was added, the aqueous layer did not separate and reached equilibrium immediately. This reaction solution was analyzed by gas chromatography and found to have the following composition. Composition of reaction solution: Propylene glycol monoethyl ether acetate (PGEA) 41.27% Propylene glycol monoethyl ether (PGE) 37.74% Acetic acid 15.32% Water 5.67%

Example 3 1392 ml of propylene glycol monoethyl ether and 746 ml of propionic acid were placed in a reactor having a volume of 3 liters. After mixing, 200 ml of xylene
And 10 g of p-toluenesulfonic acid were added. Then, the temperature was brought to a reflux temperature of 145 ° C. and the reaction was carried out for 5 hours. During this time, dehydration was performed simultaneously to effectively promote the reaction. As a result of analyzing the reaction solution by gas chromatography, it was found that the composition was as follows. Composition of reaction solution: Propylene glycol monoethyl ether propionate (PGEP) 64.78% Propylene glycol monoethyl ether (PGE) 19.53% Propionic acid 6.58% Xylene 8.57% Water 0.54% This solution Is further processed by double rectification, 99.9%
A propylene glycol monoethyl ether propionate compound having the above purity was obtained.

The propylene glycol monoethyl ether propionate compound was characterized by the NMR ¹ H spectrum shown in FIG. 3 and by the mass spectrogram shown in FIG. 4, whereby its chemical structure was of the formula:

[Chemical 4] It was decided to be.

Example 4 1392 ml of propylene glycol monoethyl ether and 746 ml of propionic acid were placed in a reactor having a volume of 3 liters. After mixing, 10 g of p-toluenesulfonic acid was added. Then, the temperature was brought to an azeotropic temperature of water and propionic acid of 103.5 ° C., and the mixture was refluxed and reacted for 5 hours. Since no azeotropic agent is added, the aqueous layer does not separate,
Equilibrium was reached soon. This reaction solution was analyzed by gas chromatography and found to have the following composition. Composition of reaction solution: Propylene glycol monopropyl ether acetate (PGPA) 40.58% Propylene glycol monoethyl ether (PGE) 36.39% Propionic acid 18.45% Water 4.58%

Example 5 1600 ml of propylene glycol monopropyl ether and 572 ml of acetic acid were placed in a reactor having a volume of 3 liters. After mixing, 200 ml of xylene and p
10 g of toluenesulfonic acid were added. Then, the temperature was brought to a reflux temperature of 147 ° C. and the reaction was carried out for 5 hours. During this time, dehydration was performed simultaneously to effectively promote the reaction. As a result of analyzing the reaction solution by gas chromatography, it was found that the composition was as follows. Composition of reaction solution: Propylene glycol monopropyl ether acetate (PGPA) 64.45% Propylene glycol monopropyl ether (PGP) 21.35% Acetic acid 5.03% Xylene 8.60% Water 0.57% Treated by double rectification, 99.9%
A propylene glycol monopropyl ether acetate compound having the above purity was obtained.

The propylene glycol monopropyl ether acetate compound was characterized by the NMR ¹ H spectrum shown in FIG. 5 and by the mass spectrogram shown in FIG. 6, whereby its chemical structure was of the formula:

Embedded image It was decided to be.

Example 6 1600 ml of propylene glycol monopropyl ether and 572 ml of acetic acid were placed in a reactor having a volume of 3 liters. After mixing, 10 g of p-toluenesulfonic acid was added. Then, the temperature was brought to the reflux temperature of 107.5 ° C. and the reaction was carried out for 5 hours. Since no azeotropic agent was added, the aqueous layer did not separate and reached equilibrium immediately. This reaction solution was analyzed by gas chromatography and found to have the following composition. Composition of reaction solution: Propylene glycol monopropyl ether acetate (PGPA) 40.60% Propylene glycol monopropyl ether (PGP) 40.29% Acetic acid 14.54% Water 4.57%

Example 7 In a reactor having a volume of 3 liters, 1600 ml of propylene glycol monopropyl ether and 746 ml of propionic acid were placed. Xylene 200 after mixing
ml and 10 g of p-toluenesulfonic acid were added. Then, the temperature was brought to a reflux temperature of 150 ° C. and the reaction was carried out for 5 hours.
During this time, dehydration was performed simultaneously to effectively promote the reaction. As a result of analyzing the reaction liquid by gas chromatography,
The composition was found to be as follows: Composition of reaction solution: Propylene glycol monopropyl ether propionate (PGPP) 63.80% Propylene glycol monopropyl ether 20.67% Propionic acid 6.28% Xylene 8.65% Water 0.60% Treated by heavy rectification, 99.9%
A propylene glycol monopropyl ether propionate compound having the above purity was obtained.

The propylene glycol monopropyl ether propionate compound is characterized by the NMR ¹ H spectrum shown in FIG. 7 and by the mass spectrogram shown in FIG. 8, whereby its chemical structure is of the formula:

[Chemical 6] It was decided to be.

(Example 8) 1600 ml of propylene glycol monopropyl ether and 746 ml of propionic acid were placed in a reactor having a volume of 3 liters. After mixing, 10 g of p-toluenesulfonic acid was added. Then the temperature is 103.5 ℃
The mixture was refluxed for 5 hours at the azeotropic temperature of water and propionic acid. Since no azeotrope was added, the aqueous phase did not separate and quickly reached equilibrium. This reaction solution was analyzed by gas chromatography and found to have the following composition. Composition of reaction solution: Propylene glycol monopropyl ether propionate (PGPP) 40.47% Propylene glycol monopropyl ether (PGP) 37.96% Propionic acid 16.97% Water 4.60%

[0030]

INDUSTRIAL APPLICABILITY As described in detail above, the present invention can provide a propylene glycol monoalkyl ether ester compound having excellent solubility and low toxicity. This propylene glycol monoalkyl ether ester compound is suitable as a solvent in the paint, ink, adhesive and detergent industries.

[Brief description of drawings]

FIG. 1 Propylene glycol monoethyl ether acetate (PGEA) obtained in Example 1 of the present invention
It is a diagram showing the NMR ¹ H spectrum.

FIG. 2 Propylene glycol monoethyl ether acetate (PGEA) obtained in Example 1 of the present invention
It is a figure which shows the mass spectrum of.

FIG. 3 shows propylene glycol monoethyl ether propionate (PGE) obtained in Example 3 of the present invention.
It is a diagram showing the NMR ¹ H spectrum P).

FIG. 4 shows propylene glycol monoethyl ether propionate (PGE) obtained in Example 3 of the present invention.
It is a figure which shows the mass spectrum of P).

FIG. 5: Propylene glycol monopropyl ether acetate (PGP) obtained in Example 5 of the present invention.
It is a diagram showing the NMR ¹ H spectrum A).

FIG. 6: Propylene glycol monopropyl ether acetate (PGP) obtained in Example 5 of the present invention.
It is a figure which shows the mass spectrum of A).

FIG. 7: Propylene glycol monopropyl ether propionate (PG obtained in Example 7 of the present invention)
It is a diagram showing the NMR ¹ H spectrum of PP).

FIG. 8: Propylene glycol monopropyl ether propionate (PG obtained in Example 1 of the present invention)
It is a figure which shows the mass spectrum of (PP).

Claims (9)

[Claims] 1. The following general formula: In the above formula, R ₁ represents an ethyl group or a propyl group, and R ₂ represents a methyl group or an ethyl group. 2. The propylene glycol monoalkyl ether ester compound according to claim 1, which is produced by reacting a propylene glycol monoalkyl ether with an organic acid selected from the group consisting of acetic acid and propionic acid. 3. The method for producing a propylene glycol monoalkyl ether ester compound according to claim 1, wherein the propylene glycol monoalkyl ether, acetic acid and acetic acid at a high temperature of 80 ° C. or higher in the presence of an acidic catalyst and an azeotropic agent. A step of producing a crude propylene glycol monoalkyl ether ester compound by reacting with an organic acid selected from the group consisting of propionic acid to produce a crude propylene glycol monoalkyl ether ester compound, and removing unreacted acid and water by distillation to obtain high-purity propylene glycol monoalkyl ether compound. A method for producing a propylene glycol monoalkyl ether ester compound, which comprises the step of obtaining an alkyl ether ester compound. 4. The method according to claim 3, wherein the molar ratio of propylene glycol monoalkyl ether and the organic acid is in the range of 0.6 to 3.0. 5. The method according to claim 3, wherein the acidic catalyst is a strong acid selected from the group consisting of sulfuric acid, p-toluenesulfonic acid and methanesulfonic acid. 6. The production method according to claim 3, wherein the azeotropic agent is selected from the group consisting of benzene, toluene, xylene, and cyclohexane. 7. The method according to claim 6, wherein the azeotropic agent is used in an amount of 6 to 30% by volume based on the total volume of the propylene glycol monoalkyl ether ester compound and the organic acid. 8. Use of the propylene monoalkyl ether ester compound according to claim 1 as a solvent. 9. Use according to claim 8 as a solvent for paints, inks, adhesives or cleaning agents.