A method and device for removing impurities from a propylene glycol monomethyl ether acetate recovery liquid

Abstract

This invention relates to a method and equipment for removing impurities from propylene glycol monomethyl ether acetate recovery solution that can remove acetic acid. The above technical solution employs a two-stage vacuum distillation process, and an alkaline ion exchange resin is installed in the distillation column. This effectively removes acetic acid from the propylene glycol monomethyl ether acetate recovery solution, preventing acetic acid from corroding equipment and generating metal ions. The purified propylene glycol monomethyl ether acetate solution has an acetic acid content ≤0.01% and a single metal ion content ≤1 ppb, meeting electronic-grade standards and allowing for recycling, thus saving raw material costs.

Description

Technical Field

[0001] This invention relates to the field of electronic manufacturing, and in particular to a method and equipment for removing impurities from propylene glycol monomethyl ether acetate recovery solution. Background Technology

[0002] In the electronics manufacturing and optoelectronic industries, acetic acid is used in the production process. Therefore, propylene glycol monomethyl ether acetate (PMA) often contains acetic acid after use, requiring removal before recycling. The traditional method for removing acetic acid involves adding an alkaline solution to the waste liquid, allowing the alkali to neutralize the acetic acid. However, in an alkaline environment, PMA decomposes into acetic acid and propylene glycol methyl ether, resulting in a persistent trace amount of acetic acid in the waste liquid. Current technologies either employ direct distillation or azeotropic distillation for purification. However, during distillation, acetic acid corrodes the stainless steel components of the distillation column, generating iron, chromium, and nickel ions, primarily iron. This results in an excessive amount of these metal ions remaining in the final purified PMA. Consequently, the PMA obtained using these methods is unsuitable for electronic-grade use. Summary of the Invention

[0003] In view of the above problems, this application provides a method and equipment for removing impurities from propylene glycol monomethyl ether acetate recovery liquid containing acetic acid. This technical solution can conveniently and quickly obtain electronic-grade propylene glycol monomethyl ether acetate from propylene glycol monomethyl ether acetate recovery liquid containing acetic acid using simple equipment. It can be recycled in production, saving process costs, avoiding waste of raw materials and environmental pollution, and is energy-saving and environmentally friendly, thus possessing economic and social value.

[0004] The first aspect of this application provides a method for removing impurities from propylene glycol monomethyl ether acetate recovery solution, comprising the following steps:

[0005] First distillation: The propylene glycol monomethyl ether acetate recovery liquid is passed into the first distillation column for vacuum distillation to obtain the first mixture and the first gaseous substance;

[0006] Secondary distillation: The first mixture is subjected to vacuum distillation in a second distillation column, the middle of which is equipped with an alkaline ion exchange resin to obtain a second mixture and a second gaseous substance;

[0007] Condensation: The second gaseous substance is condensed to obtain a purified propylene glycol monomethyl ether acetate solution.

[0008] Unlike existing technologies, the above technical solution adopts vacuum distillation and continuous vacuum distillation, and an alkaline ion exchange resin is installed in the vacuum distillation column to effectively remove acetic acid from the propylene glycol monomethyl ether acetate recovery solution. This avoids acetic acid corrosion of equipment and generation of metal ions, resulting in an acetic acid content of ≤0.01% and a single metal ion content of ≤1ppb in the purified propylene glycol monomethyl ether acetate solution, which meets electronic grade requirements and can be used for recycling, saving raw material costs.

[0009] In some embodiments, the basic ion exchange resin is 330 weakly basic epoxy anion exchange resin produced by Anhui Samsung Resin Technology Co., Ltd. The applicant discovered during research and development that using this resin in the distillation process reduces the acetic acid content and the metal ion content in the purified solution, achieving electronic-grade usage standards.

[0010] In some embodiments, the content of propylene glycol monomethyl ether acetate in the propylene glycol monomethyl ether acetate recovery solution is 95%-99.5%, and the content of acetic acid is ≤0.5%. In some embodiments, if the acetic acid content in the recovery solution is above 0.5%, it can be reduced to below 0.5% by first adding alkali for neutralization, and then the impurity removal method described in this application can be used.

[0011] In some embodiments, the first and second distillation columns are made of stainless steel. Since acetic acid corrodes stainless steel, the distillate also contains stainless steel metal ions corroded by acetic acid during the distillation process. These metal ions include iron, chromium, and nickel ions; iron ions are the most abundant. Therefore, when detecting metal ions in the purified solution, only the iron ion content needs to be measured. If the iron ion content is less than ≤1 ppb, it indicates that the content of other metal ions is also less than ≤1 ppb.

[0012] In some embodiments, the first distillation column operates at a pressure of 20 kPa and an operating temperature of 93-98°C.

[0013] The first distillation column uses vacuum distillation. Water has a boiling point of 100℃, acetic acid has a boiling point of 117.9℃, and PMA has a boiling point of 145℃-146℃. Acetic acid is soluble in both water and PMA. The first gaseous phase separated at the top of the column includes water, light organic impurities, and a small amount of acetic acid. Some of the acetic acid vaporizes in the middle section of the distillation column, while PMA and some acetic acid remain liquid at the bottom. The first distillation column removes organic matter, water, and some acetic acid.

[0014] In some embodiments, the operating pressure of the second distillation column is 10-15 kPa, and the operating temperature is 78-95°C, which meets the usage conditions of the alkaline resin. Vacuum distillation is used, with an operating pressure below one atmosphere, which lowers the boiling points of each phase, allowing vapor to be generated at low temperatures. Both PMA and acetic acid in the first mixture vaporize in the second distillation column and rise to the top. During this rise, acetic acid is absorbed by the alkaline resin, while PMA is discharged from the vapor phase. Because acetic acid is rapidly absorbed by the alkaline resin in the distillation column, its corrosive effect on the column is limited, thus reducing the metal ion content in the purified solution to meet electronic grade usage standards. Heavy component impurities remain at the bottom of the distillation column.

[0015] In some embodiments, the propylene glycol monomethyl ether acetate purified solution contains propylene glycol monomethyl ether acetate content ≥ 99.7%, acetic acid content ≤ 0.01%, and monometallic ion content ≤ 1 ppb.

[0016] Acetic acid content ≤ 0.01%, single metal ion content ≤ 1 ppb. Single metal ion content refers to the content of a single metal impurity in the purified solution; the purified solution may contain multiple metal ions.

[0017] The second aspect of this application provides a distillation apparatus for removing impurities from the propylene glycol monomethyl ether acetate recovery liquid described in the first aspect of this application, comprising a first distillation column and a second distillation column, wherein the bottom of the first distillation column and the middle of the second distillation column are connected by a first pipeline, and an exchange chamber is provided in the middle of the second distillation column, wherein an ion exchange resin is provided in the exchange chamber.

[0018] Unlike existing technologies, the above-mentioned technical solution employs a two-stage distillation process and incorporates alkaline ion exchange resin within the distillation column. This effectively removes acetic acid from the propylene glycol monomethyl ether acetate recovery solution, resulting in an acetic acid content of ≤0.01% and a single metal ion content of ≤1 ppb in the purified propylene glycol monomethyl ether acetate solution. This meets electronic-grade requirements and can be used in recycle production, saving on raw material costs.

[0019] The most abundant metal ion in the stainless steel of the distillation column corroded by acetic acid is iron. Therefore, when detecting metal ions in the purified solution, as long as the iron ion content is below 1 ppb, it indicates that the content of other metal ions is also below 1 ppb.

[0020] In some embodiments, the outlet of the first pipeline is below the exchange chamber. That is, the inlet of the first mixed liquid is at the bottom of the exchange chamber, which allows the resin in the exchange chamber to more quickly adsorb the acetic acid in the first mixed liquid, while the upper part of the distillation column (the upper part of the exchange chamber) is basically not corroded by acetic acid, and no metal ions will seep out and mix in the second gaseous substances, affecting the quality of the recovered liquid.

[0021] In some embodiments, a pressure pump is provided on the first pipeline.

[0022] In some embodiments, the upper part of the first distillation column is connected to a first condenser, and the lower part of the first distillation column is connected to a first reboiler.

[0023] In some embodiments, the upper part of the second distillation column is connected to a second condenser, and the lower part of the second distillation column is connected to a second reboiler.

[0024] In some embodiments, a portion of the gaseous substance is condensed by a condenser and then refluxed back into the distillation column; a portion of the mixture is boiled by a reboiler and then refluxed back into the distillation column to maintain the continuous operation of the distillation column.

[0025] The above description of the invention is merely an overview of the technical solution of this application. In order to enable those skilled in the art to better understand the technical solution of this application and to implement it based on the textual description, and to make the above-mentioned objectives and other objectives, features and advantages of this application easier to understand, the following description is provided in conjunction with the specific embodiments and accompanying drawings of this application. Attached Figure Description

[0026] The accompanying drawings are only used to illustrate the principles, implementation methods, applications, features, and effects of specific embodiments of this application and other related content, and should not be considered as limitations on this application.

[0027] In the accompanying drawings of the instruction manual:

[0028] Figure 1 This is a schematic diagram of the distillation equipment in Example 1.

[0029] The reference numerals used in the above figures are explained as follows:

[0030] T-101, First Distillation Column,

[0031] T-102, Second Distillation Column

[0032] T-103, ion exchange resin,

[0033] M-1, Exchange Container

[0034] P-101, pressure pump,

[0035] E-101, First Reboiler

[0036] E-102, First Condenser

[0037] E-103, Second Reboiler

[0038] E-104, Second Condenser. Detailed Implementation

[0039] To illustrate the possible application scenarios, technical principles, implementable specific solutions, and achievable objectives and effects of this application in detail, the following description, in conjunction with the listed specific embodiments and accompanying drawings, provides a detailed explanation. The embodiments described herein are merely illustrative of the technical solutions of this application and are therefore intended to limit the scope of protection of this application.

[0040] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.

[0041] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the use of related terms herein is merely for the purpose of describing particular embodiments and is not intended to limit this application.

[0042] In the description of this application, the term "and / or" is used to describe the logical relationship between objects, indicating that three relationships can exist. For example, A and / or B means: A exists, B exists, and A and B exist simultaneously. Additionally, the character " / " in this document generally indicates that the preceding and following objects have an "or" logical relationship.

[0043] In this application, terms such as “first” and “second” are used only to distinguish one entity or operation from another, and do not necessarily require or imply any actual quantity, hierarchy or order relationship between these entities or operations.

[0044] Unless otherwise specified, the use of terms such as “comprising,” “including,” “having,” or other similar expressions in this application is intended to cover non-exclusive inclusion, which does not exclude the presence of additional elements in a process, method, or product that includes the stated elements, such that a process, method, or product that includes a list of elements may include not only those defined elements but also other elements not expressly listed, or elements inherent to such a process, method, or product.

[0045] As understood in the Examination Guidelines, in this application, expressions such as "greater than," "less than," and "exceeding" are understood to exclude the stated number; expressions such as "above," "below," and "within" are understood to include the stated number. Furthermore, in the description of the embodiments in this application, "multiple" means two or more (including two), and similar expressions related to "multiple" are also understood in this way, such as "multiple groups" and "multiple times," unless otherwise explicitly specified.

[0046] In the description of the embodiments of this application, the space-related expressions used, such as "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "vertical," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," indicate the orientation or positional relationship based on the orientation or positional relationship shown in the specific embodiments or drawings. They are only for the purpose of describing the specific embodiments of this application or for the reader's understanding, and do not indicate or imply that the device or component referred to must have a specific position, a specific orientation, or be constructed or operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0047] Unless otherwise expressly specified or limited, the terms "installation," "connection," "linking," "fixing," and "setting," as used in the description of the embodiments of this application, should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral setting; it can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two components or the interaction between two components. For those skilled in the art to which this application pertains, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0048] Example 1: A distillation apparatus for removing impurities from propylene glycol monomethyl ether acetate recovery liquid.

[0049] like Figure 1The distillation apparatus for removing impurities from propylene glycol monomethyl ether acetate recovery liquid, as shown, includes a first distillation column T-101 and a second distillation column T-102. The bottom of the first distillation column T-101 and the middle of the second distillation column T-102 are connected by a first pipeline. An exchange chamber M-1 is provided in the middle of the second distillation column T-102, and an ion exchange resin T-103 is installed in the exchange chamber M-1. The outlet of the first pipeline is below the exchange chamber M-1. This allows for more rapid adsorption of acetic acid in the first mixture by the resin in the exchange chamber M-1, while the upper part of the distillation column (the upper part of the exchange chamber) is essentially not corroded by acetic acid, preventing the leakage of metal ions and the introduction of second gaseous substances that could affect the quality of the recovery liquid. A pressure pump P-101 is installed on the first pipeline. The upper part of the first distillation column T-101 is connected to a first condenser E-102, and the lower part of the first distillation column T-101 is connected to a first reboiler E-101. The upper part of the second distillation column T-102 is connected to the second condenser E-104, and the lower part of the second distillation column T-102 is connected to the second reboiler E-103. Part of the gaseous substance is condensed by the condenser and then refluxed back into the distillation column; part of the mixture is boiled by the reboiler and then refluxed back into the distillation column, maintaining the continuous operation of the distillation column. The ion exchange resin T-103 is a 330 weakly basic epoxy anion exchange resin produced by Anhui Samsung Resin Technology Co., Ltd.

[0050] The ion exchange resin is considered ineffective when the acetic acid content in the purified solution is >0.01% and the iron ion content is >1 ppb. After the ion exchange resin T-103 becomes ineffective, the exchange chamber M1 can be opened to replace the resin. The ineffective resin can be regenerated according to the instructions.

[0051] The first distillation column employs vacuum distillation at 20 kPa, with an operating temperature of 93-98℃. The first gaseous phase separated at the top of the column includes water, light organic impurities, and a small amount of acetic acid. Some of the acetic acid vaporizes in the middle section of the distillation column, while PMA and some acetic acid remain liquid at the bottom. The first distillation column removes organic matter, water, and some acetic acid.

[0052] The second distillation column operates at a pressure of 10-15 kPa and a temperature of 78-95°C, meeting the requirements for use with alkaline resin. Vacuum distillation is employed, with an operating pressure below one atmosphere, which lowers the boiling points of each phase, allowing vapor to be generated at low temperatures. Both PMA and acetic acid in the first mixture vaporize within the second distillation column, rising to the top. During this ascent, acetic acid is absorbed by the alkaline resin, while PMA is discharged from the vapor phase. Heavy impurities remain at the bottom of the column. Because acetic acid is rapidly absorbed by the alkaline resin in the distillation column, its corrosive effect on the column is limited, resulting in a corresponding reduction in the metal ion content of the purified solution, meeting electronic-grade usage standards.

[0053] Example 2

[0054] The composition of the propylene glycol monomethyl ether acetate recovery solution is: PMA 99.5%, acetic acid 0.02%, water 0.1%, organic impurities 0.038%, and iron ions 10000 ppb.

[0055] The distillation apparatus used for removing impurities from the propylene glycol monomethyl ether acetate recovery solution in Example 1 was employed to purify the recovery solution by distillation, including the following steps:

[0056] First distillation: The propylene glycol monomethyl ether acetate recovery liquid is fed into the first distillation column for vacuum distillation. The operating pressure of vacuum distillation is 20 kPa and the operating temperature is 93-98℃.

[0057] The first mixture and the first gaseous substance are obtained from the bottom of the distillation column; the composition of the first mixture is: PMA 99.6%, acetic acid 0.02%, and water 0.03%.

[0058] Secondary distillation: The first mixture is fed from the bottom of the first distillation column into the middle of the second distillation column using a pressure pump for vacuum distillation. The operating pressure of vacuum distillation is 10-15 kPa, and the operating temperature is 78-95℃. PMA and acetic acid in the first mixture vaporize, while the acetic acid adsorbed by the alkaline ion exchange resin in the middle of the second distillation column prevents it from entering the upper part of the column, causing corrosion and increasing the metal ion content. This yields the second mixture and the second gaseous phase.

[0059] Condensation: The second gaseous substance was condensed to obtain a purified propylene glycol monomethyl ether acetate solution. The components of the purified solution were: PMA 99.9%, acetic acid 0.005%, water 0.03%, and iron ions 1 ppb.

[0060] A portion of the gaseous substance is condensed by a condenser and then refluxed back into the distillation column; a portion of the mixture is boiled by a reboiler and then refluxed back into the distillation column to maintain the continuous operation of the distillation column.

[0061] Example 3

[0062] The composition of the propylene glycol monomethyl ether acetate recovery solution is: PMA 96.7%, acetic acid 0.3%, water 1%, organic impurities 2%, and iron ions 10000 ppb.

[0063] The distillation apparatus used for removing impurities from the propylene glycol monomethyl ether acetate recovery solution in Example 1 was employed to purify the recovery solution by distillation, including the following steps:

[0064] First distillation: The propylene glycol monomethyl ether acetate recovery liquid is fed into the first distillation column for vacuum distillation. The operating pressure of vacuum distillation is 20 kPa and the operating temperature is 93-98℃. The first mixture and the first gaseous substance are obtained from the bottom of the distillation column. The composition of the first mixture is: PMA 99%, acetic acid 0.02%, and water 0.03%.

[0065] Secondary distillation: The first mixture is fed from the bottom of the first distillation column into the middle of the second distillation column using a pressure pump for vacuum distillation. The operating pressure of vacuum distillation is 10-15 kPa, and the operating temperature is 78-95℃. In this process, PMA and acetic acid in the first mixture vaporize, while the acetic acid adsorbed by the alkaline ion exchange resin in the middle of the second distillation column prevents it from entering the upper part of the column, thus avoiding corrosion and increasing the metal ion content. This process yields the second mixture and the second gaseous phase.

[0066] Condensation: The second gaseous substance was condensed to obtain a purified propylene glycol monomethyl ether acetate solution. The components of the purified solution were: PMA 99.7%, acetic acid 0.005%, water 0.03%, and iron ions 1 ppb.

[0067] A portion of the gaseous substance is condensed by a condenser and then refluxed back into the distillation column; a portion of the mixture is boiled by a reboiler and then refluxed back into the distillation column to maintain the continuous operation of the distillation column.

[0068] Example 4

[0069] The composition of the propylene glycol monomethyl ether acetate recovery solution is: PMA 95%, acetic acid 0.5%, water 1%, and organic impurities 3.5%.

[0070] The distillation apparatus used for removing impurities from the propylene glycol monomethyl ether acetate recovery solution in Example 1 was employed to purify the recovery solution by distillation, including the following steps:

[0071] First distillation: The propylene glycol monomethyl ether acetate recovery liquid is fed into the first distillation column for vacuum distillation, and the first mixture and the first gaseous substance are obtained from the bottom of the distillation column; the operating pressure of vacuum distillation is 20 kPa and the operating temperature is 93-98℃;

[0072] Secondary distillation: The first mixture is fed from the bottom of the first distillation column into the middle of the second distillation column using a pressure pump for vacuum distillation. The operating pressure of vacuum distillation is 10-15 kPa, and the operating temperature is 78-95℃. In this process, PMA and acetic acid in the first mixture vaporize, while the acetic acid adsorbed by the alkaline ion exchange resin in the middle of the second distillation column prevents it from entering the upper part of the column, thus avoiding corrosion and increasing the metal ion content. This process yields the second mixture and the second gaseous phase.

[0073] Condensation: The second gaseous substance was condensed to obtain a purified propylene glycol monomethyl ether acetate solution. The components of the purified solution were: PMA 99.7%, acetic acid 0.006%, water 0.03%, and iron ions 1 ppb.

[0074] A portion of the gaseous substance is condensed by a condenser and then refluxed back into the distillation column; a portion of the mixture is boiled by a reboiler and then refluxed back into the distillation column to maintain the continuous operation of the distillation column.

[0075] Finally, it should be noted that although the above embodiments have been described in the text and drawings of this application, this should not limit the scope of patent protection of this application. Any technical solutions that are based on the essential concept of this application and utilize the content described in the text and drawings of this application, resulting in equivalent structural or procedural substitutions or modifications, as well as the direct or indirect application of the technical solutions of the above embodiments to other related technical fields, are all included within the scope of patent protection of this application.

Claims

1. A method for removing impurities from propylene glycol monomethyl ether acetate recovery solution, characterized in that, Includes the following steps: First distillation: The propylene glycol monomethyl ether acetate recovery liquid is passed into the first distillation column for vacuum distillation to obtain a first mixture and a first gaseous substance. The propylene glycol monomethyl ether acetate recovery liquid contains 95%-99.5% propylene glycol monomethyl ether acetate and ≤0.5% acetic acid. Secondary distillation: The first mixture is subjected to vacuum distillation in a second distillation column to obtain a second mixture and a second gaseous substance; the operating pressure of the second distillation column is 10-15 kPa and the operating temperature is 78-95℃; an exchange chamber is provided in the middle of the second distillation column, and an alkaline ion exchange resin is provided in the exchange chamber, wherein the alkaline ion exchange resin is 330 weakly basic epoxy anion exchange resin. Condensation: The second gaseous substance is condensed to obtain a purified propylene glycol monomethyl ether acetate solution.

2. The method according to claim 1, characterized in that, The first distillation column operates at a pressure of 20 kPa and a temperature of 93-98°C.

3. The method according to claim 1, characterized in that, The purified propylene glycol monomethyl ether acetate solution contains propylene glycol monomethyl ether acetate with a content of ≥99.7%, acetic acid with a content of ≤0.01%, and monometallic ion with a content of ≤1 ppb.

4. A distillation apparatus for removing impurities from the propylene glycol monomethyl ether acetate recovery liquid according to any one of claims 1-3, characterized in that, It includes a first distillation column and a second distillation column. The bottom of the first distillation column is connected to the middle of the second distillation column through a first pipeline. An exchange chamber is provided in the middle of the second distillation column. The exchange chamber is provided with an alkaline ion exchange resin, which is a 330 weakly basic epoxy anion exchange resin.

5. The distillation apparatus according to claim 4, characterized in that, The upper part of the first distillation column is connected to the first condenser, and the lower part of the first distillation column is connected to the first reboiler.

6. The distillation apparatus according to claim 4, wherein the upper part of the second distillation column is connected to a second condenser, and the lower part of the second distillation column is connected to a second reboiler.

7. The distillation apparatus according to claim 4, characterized in that, A portion of the gaseous substance is condensed by a condenser and then refluxed back into the distillation column; a portion of the mixture is boiled by a reboiler and then refluxed back into the distillation column.

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