CN112707988A - Method for removing sodium acetate impurities in EVOH - Google Patents
Method for removing sodium acetate impurities in EVOH Download PDFInfo
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- CN112707988A CN112707988A CN201911019296.0A CN201911019296A CN112707988A CN 112707988 A CN112707988 A CN 112707988A CN 201911019296 A CN201911019296 A CN 201911019296A CN 112707988 A CN112707988 A CN 112707988A
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Abstract
The invention belongs to the technical field of copolymers containing monomers with 4 carbon atoms and only one carbon-carbon double bond, and particularly relates to a method for removing sodium acetate impurities in an ethylene-vinyl alcohol copolymer. The method comprises the following steps: the ethylene-vinyl alcohol copolymer resin obtained by alcoholysis was brought into a semi-molten state and washed in that state, and then the EVOH resin was extruded, pelletized, and then screw-extruded again and washed. The method can obviously reduce the content of sodium acetate impurities in the ethylene-vinyl alcohol copolymer.
Description
Technical Field
The invention belongs to the technical field of copolymers containing monomers with 4 carbon atoms and only one carbon-carbon double bond, and particularly relates to a method for removing sodium acetate impurities in EVOH.
Background
Ethylene vinyl silicate (EVAL), also known as EVOH resin, is a crystalline polymer with a chain-type molecular structure, and the ratio of ethylene to vinyl alcohol is usually 20% to 40% and 60% to 80%, and the industrial preparation is carried out in two steps, i.e. first, an ethylene-vinyl acetate copolymer is prepared by polymerization, and then, an alcoholysis (or saponification) reaction is carried out to obtain the ethylene-vinyl alcohol copolymer ("performance, application and market prospects of EVOH resin", dawn, acetaldehyde acetic acid chemical engineering, No. 1 in 2013, No. 1 to 7 in column 1 on page 18, No. 12/31 in 2013).
EVOH resin is the resin having the lowest air permeability among synthetic resins so far. Besides excellent gas barrier property, EVOH has high glossiness and low turbidity, and the optical performance of EVOH can be compared with OPP. In addition, EVOH has good antistatic property and oil resistance, and is easy to print (research on the improvement performance of EVOH resin, Pengzhouxian et al, plastics science and technology, No. 4 of 2000, No. 1, No. 6 of the left column of page 23, published as 2000, 08-31). EVOH is excellent in transparency, gloss, mechanical strength, stretchability, abrasion resistance, cold resistance and surface strength, and has the highest thermal stability in high-performance barrier resins, which enables waste materials produced during processing to be recycled. EVOH has excellent oil resistance and organic solvent resistance, so that EVOH can be used for packaging oil foods, agrochemicals, organic solvents and the like; the EVOH has the antistatic performance, can be used for packaging electronic products and the like, can be regenerated, does not contain nitrogen and dioxin, only contains carbon, oxygen and hydrogen as structural components, does not generate toxic gas after combustion, has half of combustion heat compared with ethylene, and is a green and environment-friendly product. Worldwide EVOH demand is growing at a rate of about 10% per year ("high barrier ethylene vinyl alcohol (EVOH) profile", rochon et al, chemical automation and instrumentation, 2011, volume 38, line 8, page 915, left column, paragraph 1, lines 11-22, published 2011, 12 months 12).
At present, a considerable part of impurities such as sodium acetate and the like in the ethylene-vinyl alcohol copolymer prepared by the prior art can not be effectively removed.
Disclosure of Invention
In view of the above, the present invention provides a method for removing sodium acetate impurities from an ethylene-vinyl alcohol copolymer, which can significantly reduce the content of sodium acetate impurities in the ethylene-vinyl alcohol copolymer.
The parts are parts by mass unless otherwise specified.
In order to achieve the purpose, the technical scheme of the invention is as follows:
the method for removing sodium acetate impurities in the ethylene-vinyl alcohol copolymer comprises the following steps: the ethylene-vinyl alcohol copolymer resin obtained by alcoholysis was brought into a semi-molten state and washed in that state, and then the EVOH resin was extruded, pelletized, and then screw-extruded again and washed.
The semi-molten state refers to a translucent state having fluidity.
The inventors have surprisingly found that the following steps are included: the ethylene-vinyl alcohol copolymer resin obtained by alcoholysis is in a semi-molten state, and is washed in the semi-molten state, and then the EVOH resin is extruded, granulated and then is subjected to screw extrusion and washing again, so that the content of impurities such as sodium acetate in the prepared ethylene-vinyl alcohol copolymer can be obviously reduced, and the material consumption and energy consumption are obviously reduced.
Further, the temperature and pressure were controlled so that the ethylene-vinyl alcohol copolymer resin became a semi-molten state.
Further, the temperature is 60-170 ℃ and the pressure is 0-0.3 MPa.
Further, the extrusion is a screw extrusion.
Further, the cleaning of the particles is specifically cleaning by contact with water in a countercurrent manner.
Further, the washing means that water with the mass of 6-10 times of that of the ethylene-vinyl alcohol copolymer resin is added into the ethylene-vinyl alcohol copolymer resin and continuously stirred, and the washing is continuously carried out for 1-3 hours.
Further, the method for removing impurities in the ethylene-vinyl alcohol copolymer comprises the following steps of controlling the temperature to be 60-170 ℃ and the pressure to be 0-0.3MPa to enable the ethylene-vinyl alcohol copolymer resin obtained by alcoholysis to be in a semi-molten state, adding water with the mass being 6-10 times of that of the ethylene-vinyl alcohol copolymer resin into the ethylene-vinyl alcohol copolymer resin, continuously stirring, continuously cleaning for 1-3 hours, then extruding the EVOH resin, carrying out spiral extrusion again after pelletizing, adding water with the mass being 6-10 times of that of the ethylene-vinyl alcohol copolymer resin into the ethylene-vinyl alcohol copolymer resin, continuously stirring, and continuously cleaning for 1-3 hours.
The invention has the beneficial effects that:
the method can obviously reduce the impurity content in the ethylene-vinyl alcohol copolymer, and the sodium acetate content in the processed ethylene-vinyl alcohol copolymer is less than or equal to 800 ppm.
The method of the invention can obviously improve the appearance of the ethylene-vinyl alcohol copolymer, and the treated ethylene-vinyl alcohol copolymer has smooth appearance and white color.
The method can obviously improve the heat resistance of the ethylene-vinyl alcohol copolymer, and the treated ethylene-vinyl alcohol copolymer is treated at the constant temperature of 230 ℃ for 5-20 minutes, and the yellowness index YI of the ethylene-vinyl alcohol copolymer is less than or equal to 11.
The method of the invention obviously reduces the energy consumption and material consumption, and the water consumption in the cleaning process is reduced by 46.7-53.3%.
Drawings
FIG. 1 is a schematic diagram of the process of examples 1 to 4.
Detailed Description
The examples are provided for better illustration of the present invention, but the present invention is not limited to the examples. Therefore, those skilled in the art should make insubstantial modifications and adaptations to the embodiments of the present invention in light of the above teachings and remain within the scope of the invention.
The following detection method for the content of sodium acetate is as follows: freezing and crushing the ethylene-vinyl alcohol copolymer, sieving the ethylene-vinyl alcohol copolymer by a 40-mesh sieve, taking 20-50 g of the ethylene-vinyl alcohol copolymer, extracting and washing the ethylene-vinyl alcohol copolymer by 100ml of deionized water at the temperature of 95-100 ℃, diluting the extract by 5 times of the deionized water, quantitatively analyzing the diluted extract by an ion chromatograph, and calculating the content of sodium acetate;
the following appearance detection methods were: the whiter the appearance, the better the heat resistance;
the detection method of the following yellowness index comprises the following steps: 30 g of ethylene-vinyl alcohol copolymer particles were spread on a white polytetrafluoroethylene tray having a size of 10cm × 10cm, the tray was moved into an oven, the temperature in the oven was set at 230 ℃, the temperature was maintained at this temperature for 5, 10, and 20 minutes, and then the tray was taken out, and the yellowness index YI of the sample was measured by a color difference meter, and a smaller YI value indicates a lower coloring degree.
Example 1
The method for removing sodium acetate impurities in the ethylene-vinyl alcohol copolymer comprises the following specific steps:
introducing the EVOH solution obtained by alcoholysis into a specific kettle-type container, wherein the kettle-type container is provided with an EVOH resin solution feeding port, a cleaning solution feeding port and a cleaning waste liquid discharging port, is also provided with a stirring device and a jacket heating device, the temperature is controlled to be 120 ℃, the pressure is 0.1MPa, so that the EVOH resin is in a semi-molten state, then adding water with the mass being 8 times that of the EVOH resin into the ethylene-vinyl alcohol copolymer resin in the semi-molten state, continuously stirring, continuously cleaning for 1 hour, and continuously discharging the cleaning waste liquid containing alcoholysis byproducts out of the system.
The EVOH particles discharged from the kettle type container are extruded and cut into particles by an EVOH extruder, then the particles enter an inclined upward groove type container, the container has spiral conveying and extruding functions, the EVOH particles are in countercurrent contact with water (the using amount of the water is 7 times of the mass of the resin) to be repeatedly extruded and cleaned in the process of conveying the EVOH particles to an outlet end after entering the container, the water temperature is controlled to be 45 ℃, and under the continuous extrusion action, the sodium acetate solution wrapped in the particles is extruded out and is discharged from a waste liquid outlet along with the cleaning water.
Example 2
The method for removing sodium acetate impurities in the ethylene-vinyl alcohol copolymer comprises the following specific steps:
introducing the EVOH solution obtained by alcoholysis into a specific kettle-type container, wherein the kettle-type container is provided with an EVOH resin solution feeding port, a cleaning solution feeding port and a cleaning waste liquid discharging port, is also provided with a stirring device and a jacket heating device, the temperature is controlled at 110 ℃, the pressure is 0.05MPa, so that the EVOH resin is in a semi-molten state, then adding water with the mass being 8 times that of the EVOH resin into the ethylene-vinyl alcohol copolymer resin in the semi-molten state, continuously stirring, continuously cleaning for 1 hour, and continuously discharging the cleaning waste liquid containing alcoholysis byproducts out of the system.
The EVOH particles discharged from the kettle type container are extruded and cut into particles by an EVOH extruder, then the particles enter an inclined upward groove type container, the container has spiral conveying and extruding functions, the EVOH particles are in countercurrent contact with water (the using amount of the water is 6 times of the mass of the resin) to be repeatedly extruded and cleaned for 1 hour after entering the container and in the process of conveying the EVOH particles to an outlet end, the water temperature is controlled to be 45 ℃, and under the continuous extrusion action, the sodium acetate solution wrapped in the particles is extruded out and is discharged from a waste liquid outlet along with the cleaning water.
Example 3
The method for removing sodium acetate impurities in the ethylene-vinyl alcohol copolymer comprises the following specific steps:
introducing the EVOH solution obtained by alcoholysis into a specific kettle-type container, wherein the kettle-type container is provided with an EVOH resin solution feeding port, a cleaning solution feeding port and a cleaning waste liquid discharging port, is also provided with a stirring device and a jacket heating device, the temperature is controlled at 128 ℃, the pressure is 0.15MPa, so that the EVOH resin is in a semi-molten state, then adding water with the mass being 8 times that of the EVOH resin into the ethylene-vinyl alcohol copolymer resin in the semi-molten state, continuously stirring, continuously cleaning for 1 hour, and continuously discharging the cleaning waste liquid containing alcoholysis byproducts out of the system.
The EVOH particles discharged from the kettle type container are extruded and cut into particles by an EVOH extruder, then the particles enter an inclined upward groove type container, the container has spiral conveying and extruding functions, the EVOH particles are in countercurrent contact with water (the using amount of the water is 8 times of the mass of resin) to be repeatedly extruded and cleaned for 1 hour after entering the container and in the process of conveying the EVOH particles to an outlet end, the water temperature is controlled to be 45 ℃, and under the continuous extrusion action, the sodium acetate solution wrapped in the particles is extruded out and is discharged from a waste liquid outlet along with the cleaning water.
Example 4
The method for removing sodium acetate impurities in the ethylene-vinyl alcohol copolymer comprises the following specific steps:
introducing the EVOH solution obtained by alcoholysis into a specific kettle-type container, wherein the kettle-type container is provided with an EVOH resin solution feeding port, a cleaning solution feeding port and a cleaning waste liquid discharging port, is also provided with a stirring device and a jacket heating device, the temperature is controlled to be 120 ℃, the pressure is 0.1MPa, so that the EVOH resin is in a semi-molten state, then adding water with the mass being 8 times that of the EVOH resin into the ethylene-vinyl alcohol copolymer resin in the semi-molten state, continuously stirring, continuously cleaning for 1 hour, and continuously discharging the cleaning waste liquid containing alcoholysis byproducts out of the system.
The EVOH particles discharged from the kettle type container are extruded and cut into particles by an EVOH extruder, then the particles enter an inclined upward groove type container, the container has spiral conveying and extruding functions, the EVOH particles are in countercurrent contact with water (the using amount of the water is 7 times of the mass of resin) to be repeatedly extruded and cleaned for 1 hour after entering the container and in the process of conveying the EVOH particles to an outlet end, the water temperature is controlled to be 50 ℃, and under the continuous extrusion action, the sodium acetate solution wrapped in the particles is extruded out and is discharged from a waste liquid outlet along with the cleaning water.
Comparative example 1
The method for removing sodium acetate impurities in the ethylene-vinyl alcohol copolymer specifically comprises the following steps:
extruding the ethylene-vinyl alcohol copolymer solution obtained by alcoholysis into an aqueous solution at 0-10 ℃ by an extrusion device with a pore plate, separating out the ethylene-vinyl alcohol copolymer solution into strips, and cutting the strips into particles by adopting a general cutting mode. And (3) adding water which is 5 times of the ethylene-vinyl alcohol copolymer particles into a kettle type container with a stirring device to clean the particle materials, washing for 2 hours each time, and repeatedly cleaning for 6 times.
Performance testing
The ethylene-vinyl alcohol copolymers prepared in examples 1 to 4 and comparative example 1 were examined for appearance, yellowness index and sodium acetate content; meanwhile, the water consumption during the washing of the ethylene-vinyl alcohol copolymers obtained in examples 1 to 4 and comparative example 1 was examined, and the results are shown in Table 1.
Table 1 results of performance testing
As can be seen from table 1, the ethylene-vinyl alcohol copolymers obtained by the treatments of examples 1 to 4 have significantly improved appearance, significantly reduced yellowness index YI, and significantly reduced sodium acetate content, as compared to comparative example 1. Therefore, the method provided by the invention can obviously reduce the content of impurities such as sodium acetate and the like in the ethylene-vinyl alcohol copolymer, obviously improve the heat resistance of the ethylene-vinyl alcohol copolymer and obviously improve the coloring degree of the ethylene-vinyl alcohol copolymer.
As can be seen from Table 1, the water consumption of examples 1 to 4 was reduced by 46.7% to 53.3% as compared with that of comparative example 1. Therefore, the invention proves that the energy consumption and the material consumption are obviously reduced.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.
Claims (7)
1. The method for removing sodium acetate impurities in the ethylene-vinyl alcohol copolymer is characterized by comprising the following steps: the ethylene-vinyl alcohol copolymer resin obtained by alcoholysis was brought into a semi-molten state and washed in that state, and then the EVOH resin was extruded, pelletized, and then screw-extruded again and washed.
2. The method according to claim 1, wherein the temperature and pressure are controlled so that the ethylene-vinyl alcohol copolymer resin becomes a semi-molten state.
3. The process according to claim 2, wherein the temperature is 60 to 170 ℃ and the pressure is 0 to 0.3 MPa.
4. A method according to any of claims 1-3, wherein the extrusion is a screw extrusion.
5. Method according to any of claims 1 to 4, wherein the washing of the particles is in particular a counter current contact washing with water.
6. The method according to any one of claims 1 to 5, wherein the washing is carried out by adding water in an amount of 6 to 10 times the mass of the ethylene-vinyl alcohol copolymer resin to the ethylene-vinyl alcohol copolymer resin and continuously stirring for 1 to 3 hours.
7. The method according to any one of claims 1 to 6, comprising the steps of controlling the temperature to 60 to 170 ℃ and the pressure to 0 to 0.3MPa to bring the alcoholysis-obtained ethylene-vinyl alcohol copolymer resin into a semi-molten state, adding 6 to 10 times the mass of water to the ethylene-vinyl alcohol copolymer resin while stirring, continuously washing for 1 to 3 hours, extruding the EVOH resin, pelletizing, carrying out screw extrusion again, adding 6 to 10 times the mass of water to the ethylene-vinyl alcohol copolymer resin while stirring, and continuously washing for 1 to 3 hours.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201911019296.0A CN112707988A (en) | 2019-10-24 | 2019-10-24 | Method for removing sodium acetate impurities in EVOH |
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8183337B1 (en) * | 2009-04-29 | 2012-05-22 | Abbott Cardiovascular Systems Inc. | Method of purifying ethylene vinyl alcohol copolymers for use with implantable medical devices |
| CN102549025A (en) * | 2009-10-07 | 2012-07-04 | 日本合成化学工业株式会社 | Process for producing ethylene/vinyl alcohol copolymer |
| CN103980400A (en) * | 2013-02-08 | 2014-08-13 | 北京化工大学 | Preparation method of particles of copolymer containing ethylene and vinyl alcohol structural units |
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- 2019-10-24 CN CN201911019296.0A patent/CN112707988A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8183337B1 (en) * | 2009-04-29 | 2012-05-22 | Abbott Cardiovascular Systems Inc. | Method of purifying ethylene vinyl alcohol copolymers for use with implantable medical devices |
| CN102549025A (en) * | 2009-10-07 | 2012-07-04 | 日本合成化学工业株式会社 | Process for producing ethylene/vinyl alcohol copolymer |
| CN103980400A (en) * | 2013-02-08 | 2014-08-13 | 北京化工大学 | Preparation method of particles of copolymer containing ethylene and vinyl alcohol structural units |
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