Propylene glycol monomethyl ether acetate composition

Abstract

A propylene glycol monomethyl ether acetate composition containing propylene glycol 1-monomethyl ether 2-acetate and acetic acid, said propylene glycol monomethyl ether acetate composition optionally containing formic acid and / or propionic acid, wherein the total content of the acetic acid, the propionic acid, and the formic acid is 5-60 ppm with respect to 100 mass% of the propylene glycol monomethyl ether acetate composition, and the amount of dissolved oxygen (%) in the propylene glycol monomethyl ether acetate composition is 30.0% or less with respect to the saturated dissolved oxygen content of water at atmospheric pressure and 25° C.

Description

Propylene glycol monomethyl ether acetate composition

[0001] The present invention relates to propylene glycol monomethyl ether acetate compositions.

[0002] Propylene glycol monomethyl ether acetate (hereinafter also referred to as "PMA") is known as an organic solvent used in various applications. PMA is produced, for example, by a direct esterification reaction of propylene glycol monomethyl ether (hereinafter also referred to as "PM") with acetic acid under specific conditions (see, for example, Patent Document 1).

[0003] Chinese Patent Application Publication No. 1515537

[0004] When PMA obtained by the method described in Patent Document 1 was stored for a long period of time and its composition was confirmed, it was found that the purity of the PMA tended to decrease.

[0005] The present invention has been made in view of the above points, and an object of the present invention is to provide a propylene glycol monomethyl ether acetate composition having excellent storage stability.

[0006] The present inventors have found that a propylene glycol monomethyl ether acetate composition containing specific components can solve the above problems, and have completed the present invention.

[0007] That is, the present invention encompasses the following aspects: [1] A propylene glycol monomethyl ether acetate composition comprising propylene glycol 1-monomethyl ether 2-acetate and acetic acid, wherein the propylene glycol monomethyl ether acetate composition optionally contains formic acid and / or propionic acid, the sum of the contents of the acetic acid, the propionic acid, and the formic acid is 5 ppm or more and 60 ppm or less, based on 100% by mass of the propylene glycol monomethyl ether acetate composition, and the dissolved oxygen (%) of the propylene glycol monomethyl ether acetate composition is 30.0% or less, relative to the saturated dissolved oxygen amount in water at atmospheric pressure and 25°C. [2] The propylene glycol monomethyl ether acetate composition according to [1], wherein the difference in purity after subjecting the propylene glycol monomethyl ether acetate composition to the following test is 0.080% or less, as determined by the difference (R1-R2) between the area fraction R1 of the peak of propylene glycol 1-monomethyl ether 2-acetate measured by gas chromatography analysis under the following conditions before the test and the area fraction R2 of the peak of propylene glycol 1-monomethyl ether 2-acetate measured by gas chromatography analysis after the test. (Test) The propylene glycol monomethyl ether acetate composition is heated to 80°C in a nitrogen atmosphere in a borosilicate glass container and maintained at that temperature for 5 days. (Gas Chromatography Analysis Conditions) Analytical column: a column with a stationary phase of polyethylene glycol, length 30 m x inner diameter 0.25 mm x film thickness 0.25 μm Heating conditions: held at 50°C for 10 minutes, then heated to 250°C at 5°C / min Sample introduction temperature: 250°C Carrier gas: nitrogen Column gas flow rate: 1.0 mL / min Detector and detection temperature: hydrogen flame ionization detector, 250°C Control mode: column flow rate Split ratio: 50:1 Injection volume: 2.0 μL

[0008] According to the present invention, a propylene glycol monomethyl ether acetate composition having excellent storage stability can be provided.

[0009] Hereinafter, a mode for carrying out the present invention (hereinafter referred to as "the present embodiment") will be described in detail. The present embodiment is an example for explaining the present invention, and is not intended to limit the present invention to the following content. The present invention can be carried out by appropriately modifying it within the scope of its gist.

[0010] <Propylene glycol monomethyl ether acetate composition> The propylene glycol monomethyl ether acetate composition (hereinafter also referred to as "PMA composition") of this embodiment is a propylene glycol monomethyl ether acetate composition containing propylene glycol 1-monomethyl ether 2-acetate (hereinafter also referred to as "PGMEA") and acetic acid, wherein the propylene glycol monomethyl ether acetate composition optionally contains formic acid and / or propionic acid, the sum of the contents of the acetic acid, the propionic acid, and the formic acid is 5 ppm or more and 60 ppm or less, relative to 100% by mass of the propylene glycol monomethyl ether acetate composition, and the dissolved oxygen (%) of the propylene glycol monomethyl ether acetate composition is 30.0% or less, relative to the saturated dissolved oxygen amount in water at atmospheric pressure and 25°C. Due to this configuration, the PMA composition of this embodiment has excellent storage stability.

[0011] The reason why the PMA composition of this embodiment has excellent storage stability is not entirely clear, and while it is not intended to limit the reason, it is speculated as follows. During long-term storage of a propylene glycol monomethyl ether acetate composition, decomposition of PGMEA and the generation of impurities are thought to be one of the factors affecting storage stability. Examples of causes of decomposition of carboxylic acid esters such as PGMEA include hydrolysis. Generally, in the presence of acid, carboxylic acid esters hydrolyze to form carboxylic acids and alcohols. It is also believed that carboxylic acid esters tend to hydrolyze more when the acid content is high. Meanwhile, PGMEA has ester and ether bonds and is relatively stable against oxidation reactions. However, in the presence of a certain amount of oxygen and organic acid, oxidation reactions can be promoted, such as by the generation of peroxyacids, which can result in PGMEA decomposition. Thus, it is believed that simply adjusting the acid content in the PMA composition and also adjusting the amount of dissolved oxygen in the PMA composition inhibits PGMEA decomposition, thereby improving storage stability. However, the above is merely one possible reason why the PMA composition of this embodiment has excellent storage stability, and the mechanism of action of this embodiment is not limited to this.

[0012] The PMA composition of this embodiment can be used for industrial purposes, including, but not limited to, inks, thinners, pharmaceuticals and agricultural chemicals, plasticizers, surfactants, polymeric materials, lubricants, adhesives, detergents, electronic materials, and paints. Electronic materials include, but are not limited to, liquid crystal displays (LCDs) and semiconductor devices. Because of its excellent storage stability, the PMA composition of this embodiment is preferably used in the manufacture of semiconductor devices. Specific examples of applications related to the manufacture of semiconductor devices include, but are not limited to, cleaning solutions (e.g., treatment solutions for cleaning substrate surfaces after resist stripping), prewet solutions (e.g., treatment solutions used before resist coating to reduce resist solvent consumption), resist solvents (e.g., treatment solutions for dissolving photosensitizers and resins), developers (e.g., treatment solutions for removing soluble resins after exposure of negative resists), and strippers (e.g., treatment solutions used to remove hardened resists after etching). From the viewpoint of preventing product defects in the manufacture of semiconductor devices, the PMA composition of the present embodiment is preferably used as a resist solvent, a pre-wet liquid, a solvent for an edge rinse (rinse for removing resist from the outer periphery of a wafer) and a back rinse (rinse for removing resist from the back surface of a wafer) used during resist coating, a developer used during negative resist development, a rinse liquid used during rinsing of a negative resist after development, a cleaning liquid or rinse liquid used for removing resist after etching, and the like.

[0013] (Propylene glycol 1-monomethyl ether 2-acetate) PGMEA in the PMA composition of this embodiment can be identified and quantified, for example, by the following gas chromatography (hereinafter also referred to as "GC") analysis. (Gas Chromatography Analysis) Analytical column: a column having a polyethylene glycol stationary phase and a length of 30 m, an inner diameter of 0.25 mm, and a film thickness of 0.25 μm Heating conditions: maintained at 50° C. for 10 minutes, and then heated to 250° C. at 5° C. / min Sample introduction temperature: 250° C. Carrier gas: nitrogen Column gas flow rate: 1.0 mL / min Detector and detection temperature: flame ionization detector, 250° C. Control mode: column flow rate Split ratio: 50:1 Injection amount: 2.0 μL The content of PGMEA in the PMA composition of this embodiment can be appropriately determined depending on the application of the PMA composition of this embodiment, and is not particularly limited. However, from the viewpoint of use in applications requiring high purity, the peak area ratio to the total peak area in the chart obtained as a result of GC analysis is preferably 99.89% or more, more preferably 99.90% or more, and even more preferably 99.91% or more. In this embodiment, the "total peak area" refers to the sum of the areas of all peaks appearing in the chart obtained as a result of GC analysis. In this embodiment, "all peaks" can be specified as meaning all peaks that appear when the analysis is continued and stopped from a relative retention time of 0.14 to 2.95, assuming that the relative retention time of the PGMEA peak is 1.00.

[0014] (Dissolved Oxygen) From the viewpoint of storage stability, the dissolved oxygen (%) in the PMA composition of this embodiment is 30.0% or less, preferably 27.0% or less, and more preferably 24.0% or less, relative to the saturated dissolved oxygen amount in water at atmospheric pressure and 25°C. The dissolved oxygen (%) in the PMA composition of this embodiment can be determined as follows. That is, the saturated dissolved oxygen amount (mg / L) in water is measured in advance using a diaphragm-type galvanic cell oxygen sensor under conditions of atmospheric pressure of 101.3 kPa, room temperature of 25°C, and stirring, and this is taken as 100% saturation. Separately, the dissolved oxygen in the PMA composition is measured using a diaphragm-type galvanic cell oxygen sensor under conditions of atmospheric pressure of 101.3 kPa, room temperature of 25°C, and stirring, and the dissolved oxygen (%) in the PMA composition can be calculated as a ratio (%) to the 100% saturation. More specifically, the dissolved oxygen (%) can be measured using an organic solvent-compatible DO meter (model: B-506S) and an organic solvent DO measuring device (model: MA-300G-SL) manufactured by Iijima Electronics Co., Ltd., with the PMA composition filled in a measurement tank, using a stirrer (a PTFE (polytetrafluoroethylene) stirrer, cross-shaped, manufactured by Flon Industries, model: FK-10) and a stirrer (an ultra-thin digital stirrer manufactured by Kenis, model: KK) while stirring at a rotation speed of 1100 to 1400 rpm. The organic solvent-compatible DO meter can be span calibrated (calibration method: air calibration) at atmospheric pressure and 25 ° C. before starting measurement. The dissolved oxygen (%) can be adjusted to the above-mentioned range, for example, by adjusting the air / nitrogen ratio in step (f) described below.

[0015] (Formic Acid) The PMA composition of this embodiment may or may not contain formic acid. From the viewpoint of storage stability, the content of formic acid in the PMA composition of this embodiment is preferably 10 ppm or less, more preferably 5 ppm or less, and even more preferably below the detection limit (2 ppm or less), relative to 100% by mass of the PMA composition of this embodiment. The content can be measured based on the method described in the Examples below. The content can be adjusted to the above-mentioned range, for example, by performing the base treatment described below and then appropriately adding formic acid. The content can also be adjusted to the above-mentioned range, for example, by appropriately changing the conditions of the base treatment (e.g., treatment time, etc.) or by adjusting the amount of distillate in step (e) described below.

[0016] (Acetic Acid) The PMA composition of this embodiment contains acetic acid. The acetic acid content in the PMA composition of this embodiment is preferably 3 ppm or more, based on 100% by mass of the PMA composition of this embodiment, from the viewpoint of productivity, and preferably 58 ppm or less, based on 100% by mass of the PMA composition of this embodiment, from the viewpoint of storage stability. That is, the acetic acid content is preferably 3 ppm or more and 58 ppm or less, more preferably 5 ppm or more and 50 ppm or less, and even more preferably 7 ppm or more and 40 ppm or less, based on 100% by mass of the PMA composition of this embodiment. The content can be measured based on the method described in the Examples below. The content can be adjusted to the above-mentioned range, for example, by performing the base treatment described below and then appropriately adding acetic acid. The content can also be adjusted to the above-mentioned range, for example, by appropriately changing the base treatment conditions (e.g., treatment time, etc.) or by adjusting the amount of distillate in step (e) described below.

[0017] (Propionic Acid) The PMA composition of this embodiment may or may not contain propionic acid. From the viewpoint of storage stability, the propionic acid content in the PMA composition of this embodiment is preferably 30 ppm or less, more preferably 25 ppm or less, and even more preferably 20 ppm or less, based on 100% by mass of the PMA composition of this embodiment. The content can be measured based on the method described in the Examples below. The content can be adjusted to the above-mentioned range, for example, by performing the base treatment described below and then appropriately adding propionic acid. The content can also be adjusted to the above-mentioned range, for example, by appropriately changing the base treatment conditions (e.g., treatment time, etc.) or by adjusting the amount of distillate in step (e) described below.

[0018] (Sum of Contents of Acetic Acid, Propionic Acid, and Formic Acid) In this embodiment, from the viewpoint of storage stability, the sum of the contents of acetic acid, propionic acid, and formic acid in the PMA composition of this embodiment is 5 ppm to 60 ppm, preferably 8 ppm to 55 ppm, and more preferably 11 ppm to 50 ppm, based on 100% by mass of the PMA composition of this embodiment. The above contents can be measured based on the method described in the Examples below. The above contents can be adjusted to the above range, for example, by performing the base treatment described below and then appropriately adding formic acid, acetic acid, and / or propionic acid. The above contents can also be adjusted to the above range, for example, by appropriately changing the conditions of the base treatment (e.g., treatment time, etc.) or by adjusting the amount of distillate in step (e) described below.

[0019] (PM) The PMA composition of this embodiment may contain propylene glycol monomethyl ether (PM). From the viewpoint of storage stability, the PM content in the PMA composition of this embodiment is preferably 4.0 ppm or less, relative to 100% by mass of the PMA composition of this embodiment, and more preferably below the detection limit (2 ppm or less) in the GC analysis. The PM content can be measured based on the method described in the Examples below. The PM content can be adjusted to the above-mentioned range, for example, by azeotropic dehydration after esterification, followed by distillative purification, or the like.

[0020] From the viewpoint of storage stability, the difference in purity of the PMA composition of this embodiment after subjecting it to the following test is preferably 0.080% or less, more preferably 0.075% or less, and even more preferably 0.070% or less, as determined by the difference (R1-R2) between the area fraction R1 of the peak of propylene glycol 1-monomethyl ether 2-acetate measured by gas chromatography analysis under the conditions below before the test and the area fraction R2 of the peak of propylene glycol 1-monomethyl ether 2-acetate measured by gas chromatography analysis after the test. (Test) The propylene glycol monomethyl ether acetate composition is heated to 80°C in a nitrogen atmosphere in a borosilicate glass container and maintained for 5 days. The difference in purity can be measured based on the method described in the Examples below. The difference in purity can be adjusted to the above-mentioned range, for example, by adjusting the sum of the contents of formic acid, acetic acid, and propionic acid to the above-mentioned range and / or adjusting the dissolved oxygen content of the PMA composition to the above-mentioned range.

[0021] <Method for Producing PMA Composition> The method for producing the PMA composition of this embodiment is not particularly limited, but the following method (hereinafter also referred to as "Production Method A") is preferred. Production Method A preferably includes the steps of: (a) obtaining a first product containing PGMEA; (b) distilling the first product to obtain a second product; (c) treating the second product with a base to obtain a third product; (d) desalting the third product to obtain a fourth product; (e) distilling the fourth product under reduced pressure to remove high-boiling components and obtain a fifth product from the top of the column; and (f) distilling the fifth product under reduced pressure to remove low-boiling components, and then supplying a gas having a predetermined air / nitrogen ratio to the bottom of the distillation column to obtain a sixth product, the PMA composition, from the bottom of the column. The amounts of formic acid, acetic acid, propionic acid, and dissolved oxygen in the PMA composition can be adjusted by steps (c), (e), and (f). The above production method may further include a step (g) of adding formic acid, acetic acid, and / or propionic acid to the product obtained through the step (f) to obtain a PMA composition, in order to adjust the amounts of formic acid, acetic acid, and propionic acid in the PMA composition.

[0022] (Step (a)) In step (a), a first product containing PGMEA is obtained. Step (a) may include an operation for producing PGMEA based on a conventionally known method. The method for producing PGMEA is not particularly limited, but examples thereof include the method described in Chinese Patent Application Publication No. 1515537. Specifically, PGMEA can be produced by carrying out a direct esterification reaction between PM and acetic acid. The first product may contain raw materials, catalysts, by-products, etc. that can be used in the reaction for producing PGMEA.

[0023] (Step (b)) In step (b), the first product is distilled to obtain a second product. The specific distillation procedure is not particularly limited, and examples thereof include atmospheric distillation and reduced pressure distillation, and such distillation may be performed repeatedly. In this step, raw materials, catalysts, by-products, etc. that may be contained in the first product and that can be used in the reaction to produce PGMEA can be removed. The distillation conditions are not particularly limited, and the distillation can be performed with reference to the conditions described in Chinese Patent Application Publication No. 1515537, for example. The amounts of PM, formic acid, acetic acid, and propionic acid that may be contained in the second product may be greater than 4 ppm, greater than 10 ppm, greater than 58 ppm, and greater than 30 ppm, respectively, based on the second product being 100% by mass.

[0024] In step (c), the second product is subjected to a base treatment to obtain a third product. The conditions for the base treatment are preferably conditions that can reduce the amounts of formic acid, acetic acid, and propionic acid contained in the second product, and are not particularly limited. For example, the base treatment may be performed using Kyoward 500 (registered trademark) manufactured by Kyowa Chemical Industry Co., Ltd. In this case, the amounts of PM, formic acid, acetic acid, and propionic acid that may be contained in the third product can be adjusted by, for example, adjusting the amount of Kyoward 500 used and the treatment time. Kyoward 500, etc., used in the base treatment can be removed by filtration using a PTFE membrane filter or the like.

[0025] (Step (d)) In step (d), the third product is subjected to a desalting treatment to obtain a fourth product. The specific operation of the desalting treatment is not particularly limited, and examples thereof include flash distillation or water washing, and such treatments may be repeated. In this step, various salts that may be contained in the third product can be removed. The distillation conditions are not particularly limited, and the distillation can be carried out, for example, by supplying the third product at a linear velocity (LV) of 55 to 65 m / Hr to a flash drum heated to about 65 to 75°C under a reduced pressure (absolute pressure in the system during distillation; the same applies hereinafter) of 2.5 to 3.5 kPa.

[0026] (Step (e)) In step (e), the fourth product is distilled under reduced pressure to remove high-boiling components, thereby obtaining a fifth product from the top of the column. The specific operation of the vacuum distillation is not particularly limited, and vacuum distillation may be performed repeatedly. In this step, impurities having relatively high boiling points that may be contained in the fourth product can be removed. The distillation conditions are not particularly limited, but for example, the distillation can be performed by using a distillation column with approximately 20 theoretical plates, performing total reflux at a reduced pressure of 1.5 to 2.5 kPa and a column bottom temperature of 35 to 45°C, feeding the fourth product from the bottom of the column at a linear velocity of 25 to 35 m / Hr, and distilling 90 to 96% of the fifth product from the top of the column at a reflux ratio of 1 / 1.

[0027] (Step (f)) In step (f), the fifth product is distilled under reduced pressure to remove low-boiling components, and a gas having a predetermined air / nitrogen ratio is supplied to the bottom of the distillation column to obtain a PMA composition as a sixth product from the bottom. The gas supply conditions are not particularly limited as long as they can reduce the amount of dissolved oxygen in the PMA composition to a desired value. For example, the amount of dissolved oxygen tends to decrease by reducing the air / nitrogen ratio (i.e., the oxygen / nitrogen ratio) of the gas supplied. The air / nitrogen ratio can also be controlled as the oxygen partial pressure at the bottom of the distillation column, and the oxygen partial pressure is preferably 4.0 kPa or less, more preferably 3.5 kPa or less, and even more preferably 3.0 kPa or less. The distillation conditions are not particularly limited, and can be carried out, for example, using a distillation column having about 20 theoretical plates, at a reduced pressure of 1.5 to 2.5 kPa and a column bottom temperature of 45 to 55°C, by supplying a gas prepared to a predetermined air / nitrogen ratio from the column bottom at a linear velocity of 0.017 to 0.019 m / Hr, and removing a predetermined amount of low-boiling point components from the column top at a reflux ratio of 1 / 1. In step (f), the amount of water contained can also be adjusted by adjusting the reflux ratio and the amount of effluent from the column top.

[0028] (Step (g)) In step (g), formic acid, acetic acid, and / or propionic acid can be added to the product obtained through step (f) to adjust the amount of formic acid, acetic acid, and / or propionic acid in the PMA composition. The amount of formic acid, acetic acid, and / or propionic acid added is not particularly limited, but can be determined, for example, based on the difference between the formic acid content C1, acetic acid content C2, and propionic acid content C3 in the desired PMA composition and the formic acid content C1', acetic acid content C2', and propionic acid content C3' in the product obtained through step (f). Each content can be measured based on the method described in the Examples below.

[0029] The present embodiment will be described in more detail below based on examples, but the present embodiment is not limited to these examples.

[0030] [Example 1] (Step (a)) A first product containing PGMEA was synthesized by referring to the method described in Chinese Patent Application Publication No. 1515537. That is, PGMEA was synthesized by carrying out a direct esterification reaction between PM and acetic acid.

[0031] (Step (b)) Next, the first product containing PGMEA was introduced into a distillation column and subjected to atmospheric distillation. That is, at a reflux ratio of 1 / 4, a fraction containing unreacted raw materials was first distilled off, and then a fraction containing PGMEA was recovered.

[0032] Next, the fraction containing PGMEA obtained by atmospheric distillation was introduced into a distillation column and subjected to reduced pressure distillation. That is, the degree of vacuum in the distillation column was set to 21.3 kPa, the temperature in the distillation column was controlled to 110 ° C or less, the reflux ratio was set to 1 / 4, and the fraction at the top of the column (temperature 98-100 ° C) was recovered as the second product. The content of PGMEA in the obtained second product was 99.83% as the peak area ratio to the total peak area of ​​the chart obtained as a result of GC analysis. Furthermore, the amount of formic acid contained in the second product was below the detection limit (below the detection limit in HPLC analysis), taking the second product as 100% mass. The amounts of PM, acetic acid, and propionic acid contained in the second component were below the detection limit (below the detection limit in GC analysis), 60 ppm, and 150 ppm, respectively, taking the second product as 100% mass.

[0033] The content of formic acid in the second product was measured and confirmed by liquid chromatography analysis (HPLC analysis) under the following conditions. (Liquid Chromatography Analysis) Analytical apparatus: LC1260 Infinity II manufactured by Agilent Technologies Analytical column: TSKgel ODS-100V (5 μm, 250 × 4.6 mm I.D.) manufactured by Tosoh Corporation Detector and detection temperature: Differential refractive index detector, 35°C Column oven: 40°C Eluent: 0.1 wt% aqueous phosphoric acid solution Flow rate: 1.0 mL / min Injection amount: 20 μL In the above HPLC analysis, the content of formic acid was calculated by the absolute calibration curve method. In the following examples and comparative examples, the amount of formic acid was confirmed in the same manner as above.

[0034] The contents of PGMEA, PM, acetic acid and propionic acid in the second product were measured and confirmed by GC analysis under the following conditions. (Gas Chromatography Analysis) Analytical apparatus: Nexis GC-2030 manufactured by Shimadzu Corporation Analytical column: DB-WAX manufactured by Agilent Technologies (a column having a stationary phase of polyethylene glycol, a length of 30 m, an inner diameter of 0.25 mm, and a film thickness of 0.25 μm) Heating conditions: After holding at 50° C. for 10 minutes, the temperature was increased to 250° C. at 5° C. / min Sample introduction temperature: 250° C. Carrier gas: nitrogen Column gas flow rate: 1.0 mL / min Detector and detection temperature: hydrogen flame ionization detector, 250° C. Control mode: column flow rate Split ratio: 50:1 Injection amount: 2.0 μL In the above GC analysis, the content of PGMEA was calculated as the area percentage of the PGMEA peak relative to the total peak area of ​​the chart obtained as a result of GC analysis. The PM content was calculated as the percentage of the PM peak area relative to the total peak area in the chart obtained as a result of GC analysis. The contents of acetic acid and propionic acid were calculated by the absolute calibration curve method using GC analysis. In the following examples and comparative examples, the amounts of PGMEA, PM, acetic acid, and propionic acid were confirmed in the same manner as above.

[0035] (Step (c)) To the second product (100% by mass) obtained above, 0.7% by mass of Kyoward 500 (registered trademark) manufactured by Kyowa Chemical Industry Co., Ltd. was added, and the mixture was stirred for 60 minutes to remove formic acid, acetic acid, and propionic acid. The mixture was filtered through a PTFE membrane filter (model: T020A047A, pore size: 0.20 μm) manufactured by ADVANTEC to obtain a third product.

[0036] (Step (d)) Next, the third product was introduced into a distillation column and subjected to flash distillation. That is, the third product was supplied to a flash drum heated to about 70°C under a reduced pressure of 3 kPa at a linear velocity (LV) of 59 m / Hr, and 90 mass% (based on 100 mass% of the third product) was distilled from the top of the flash drum to obtain a fourth product.

[0037] (Step (e)) Next, the fourth product was introduced into a distillation column and subjected to reduced pressure distillation. That is, using a distillation column having about 20 theoretical plates, the degree of vacuum in the distillation column was set to 2.0 kPa, the temperature of the bottom of the distillation column was controlled to 40° C., the reflux ratio was set to 1 / 1, the fourth product was fed from the bottom of the column at a linear velocity of 30 m / Hr, and a 95% by mass fraction was recovered from the top of the column as the fifth product.

[0038] (Step (f)) Next, the fifth product was introduced into a distillation column and subjected to reduced pressure distillation. That is, using a distillation column with approximately 20 theoretical plates, the degree of vacuum in the distillation column was set to 2.0 kPa, and the temperature at the bottom of the distillation column was controlled to 50 ° C. An air / nitrogen mixed gas with an oxygen partial pressure of 0.05 kPa was supplied from the bottom of the column at a linear velocity of 0.018 m / Hr, and the reflux ratio was set to 1 / 1. 10% by mass of low-boiling components were distilled off from the top of the column, and the sixth product (PMA composition of Example 1) was recovered from the bottom of the column. The content of formic acid contained in the obtained PMA composition was below the detection limit as a peak area ratio relative to the total peak area in the chart obtained as a result of HPLC analysis. The contents of PM, acetic acid, and propionic acid contained in the obtained PMA composition were below the detection limit, 30.0 ppm, and 20.0 ppm, respectively, as peak area ratios relative to the total peak area in the chart obtained as a result of GC analysis. Furthermore, the amount of PGMEA contained in the PMA composition was measured, and the area ratio R1 of the peak of propylene glycol 1-monomethyl ether 2-acetate was 99.91% by area. In the following examples and comparative examples, the contents of formic acid, acetic acid, and propionic acid were also confirmed in the same manner as above.

[0039] (Dissolved oxygen measurement) The saturated dissolved oxygen amount (mg / L) of water was measured in advance using a diaphragm-type galvanic cell oxygen sensor under conditions of atmospheric pressure 101.3 kPa, room temperature 25 ° C, and stirring (rotation speed 1300 rpm), and this was taken as 100% saturation. Separately, using a diaphragm-type galvanic cell oxygen sensor, the dissolved oxygen in the PMA composition was measured under conditions of atmospheric pressure 101.3 kPa, room temperature 25 ° C, and stirring (rotation speed 1300 rpm), and calculated as a ratio (%) to the 100% saturation. That is, the dissolved oxygen (%) was measured using an organic solvent compatible DO meter (model: B-506S) and an organic solvent DO measuring device (model: MA-300G-SL) manufactured by Iijima Electronics Co., Ltd. The dissolved oxygen (%) contained in the PMA composition was measured and found to be 2.0% of the saturated dissolved oxygen content (mg / L) of water measured under conditions of atmospheric pressure of 101.3 kPa, room temperature of 25° C., and stirring. In the following examples and comparative examples, the dissolved oxygen (%) was also confirmed in the same manner as above.

[0040] The PMA composition was then subjected to the following test. Specifically, the PMA composition was placed in a 110 mL borosilicate glass container, which was then filled with nitrogen and sealed. The container was then heated using an incubator (product name "ST-110B1", manufactured by ESPEC) and maintained at 80°C for 5 days. The PMA composition after the test was subjected to GC analysis under the conditions described above, and the PGMEA content in the PMA composition after the test was measured as described above. The peak area ratio R2 of propylene glycol 1-monomethyl ether 2-acetate was 99.85 area%. That is, the difference in purity of PGMEA, R1-R2, was 0.06%. Details of the analysis results are shown in Table 1.

[0041] (Example 2) The PMA composition of Example 2 was obtained in the same manner as in Example 1, except that the amount of distillate from the top of the column in step (e) in Example 1 was changed to 93 mass%, and the oxygen partial pressure of the air / nitrogen mixed gas supplied from the bottom of the column in step (f) was changed to 0.85 kPa. This PMA composition was subjected to the same tests as in Example 1 and then subjected to the same gas chromatography analysis as in Example 1. Details of the analysis results are shown in Table 1.

[0042] (Example 3) The PMA composition of Example 3 was obtained in the same manner as in Example 1, except that the amount of distillate from the top of the column in step (e) in Example 1 was changed to 90 mass%, and the oxygen partial pressure of the air / nitrogen mixed gas supplied from the bottom of the column in step (f) was changed to 1.92 kPa. This PMA composition was subjected to the same tests as in Example 1 and then subjected to the same gas chromatography analysis as in Example 1. Details of the analysis results are shown in Table 1.

[0043] (Example 4) The PMA composition of Example 4 was obtained in the same manner as in Example 1, except that the amount of distillate from the top of the column in step (e) in Example 1 was changed to 94 mass%, and the oxygen partial pressure of the air / nitrogen mixed gas supplied from the bottom of the column in step (f) was changed to 1.92 kPa. This PMA composition was subjected to the same tests as in Example 1 and then subjected to the same gas chromatography analysis as in Example 1. Details of the analysis results are shown in Table 1.

[0044] Comparative Example 1 A PMA composition of Comparative Example 1 was obtained in the same manner as in Example 1, except that the amount of distillate from the top of the column in step (e) in Example 1 was changed to 96 mass% and the oxygen partial pressure of the air / nitrogen mixed gas supplied from the bottom of the column in step (f) was changed to 4.05 kPa. This PMA composition was subjected to the same tests as in Example 1 and then subjected to the same gas chromatography analysis as in Example 1. Details of the analysis results are shown in Table 1.

[0045]

Claims

1. A propylene glycol monomethyl ether acetate composition comprising propylene glycol 1 - monomethyl ether 2 - acetate and acetic acid, wherein the propylene glycol monomethyl ether acetate composition optionally contains formic acid and / or propionic acid, and the sum of the contents of the acetic acid, the propionic acid, and the formic acid is 5 ppm or more and 60 ppm or less based on 100% by mass of the propylene glycol monomethyl ether acetate composition, and the dissolved oxygen (%) of the propylene glycol monomethyl ether acetate composition is 30.0% or less with respect to the saturated dissolved oxygen amount of water at atmospheric pressure and 25°C.

2. For the propylene glycol monomethyl ether acetate composition according to claim 1, the difference in purity after subjecting the propylene glycol monomethyl ether acetate composition to the following test is 0.080% or less as the difference (R1 - R2) between the peak area ratio R1 of propylene glycol 1 - monomethyl ether 2 - acetate measured by subjecting to gas chromatography analysis under the following conditions before the test and the peak area ratio R2 of propylene glycol 1 - monomethyl ether 2 - acetate measured by subjecting to the gas chromatography analysis after the test. (Test) The propylene glycol monomethyl ether acetate composition is heated in a borosilicate glass container at 80°C under a nitrogen atmosphere and held for 5 days. (Conditions for gas chromatography analysis) Analytical column: A column with a stationary phase of polyethylene glycol, length 30 m × inner diameter 0.25 mm × film thickness 0.25 μm Temperature rising condition: Held at 50°C for 10 minutes and then heated to 250°C at 5°C / min Sample introduction temperature: 250°C Carrier gas: Nitrogen Gas flow rate of the column: 1.0 mL / min Detector and detection temperature: Hydrogen flame ionization detector, 250°C Control mode: Column flow Split ratio: 50:1 Injection volume: 2.0 μL

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