CN112707986A - Method for purifying ethylene-vinyl alcohol copolymer - Google Patents
Method for purifying ethylene-vinyl alcohol copolymer Download PDFInfo
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- CN112707986A CN112707986A CN201911018264.9A CN201911018264A CN112707986A CN 112707986 A CN112707986 A CN 112707986A CN 201911018264 A CN201911018264 A CN 201911018264A CN 112707986 A CN112707986 A CN 112707986A
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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 purification method of an ethylene-vinyl alcohol copolymer. The purification method comprises the following steps: the ethylene-vinyl alcohol copolymer resin obtained by alcoholysis was brought into a semi-molten state, and slurry washing was continued in this state. The method can remarkably improve the cleaning efficiency and reduce the water consumption.
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 purification method of an ethylene-vinyl alcohol copolymer.
Background
Ethylene-vinyl alcohol copolymers (EVOH) are alcoholysis products formed from saponification or partial saponification of ethylene-vinyl acetate copolymers (EVA). The industrial production of ethylene-vinyl alcohol copolymers can be divided into two steps of polymerization and alcoholysis: under the pressure of 4-5MPa, tert-butyl alcohol is used as a solvent, ethylene and vinyl acetate are subjected to radical copolymerization reaction to generate EVA, and then methanol is used as a solvent, and strong base is used as a catalyst to obtain EVOH (the performance and preparation points of the EVOH are Li Juan, printing technology, No. 2 of 2011, No. 1-8 of the penultimate 1 on the right column of page 46, published day 2011, No. 04 and No. 28).
The ethylene-vinyl alcohol copolymer is a crystalline polymer having a chain structure, and is composed of a vinyl segment (E) and a vinyl alcohol segment (VA), wherein the proportion of the E segment is usually 20% to 40%, and the proportion of the VA segment is usually 60% to 80%, and the copolymer can be regarded as a modified product of polyvinyl alcohol (PVA). The ethylene-vinyl alcohol copolymer, polyvinylidene chloride (PVDC) and Polyamide (PA) are called three-layer barrier material, and are a novel high-molecular synthetic material integrating the processability of ethylene polymer and the gas barrier property of vinyl alcohol polymer. EVOH has excellent processability and extraordinary barrier properties to smell, solvent and the like, and also has the characteristics of good transparency, glossiness, elasticity, wear resistance, weather resistance and high mechanical strength (the key points of the performance and preparation of EVOH, Li Juan, printing technology, No. 2 of 2011, No. 1 to No. 6 of the left column on page 46, No. 04 and No. 28 of 2011), application and research progress of ethylene-vinyl alcohol copolymer, Marek, plastics technology, No. 13 of 2005, No. 1 to No. 8 of the left column on page 54, No. 2, No. 5 to No. 8 of the left column on page 54, and No. 06 and No. 30 of 2005). Therefore, the ethylene-vinyl alcohol copolymer is widely used in the fields of packaging of oil-containing foods, edible oils, mineral oils, agricultural chemicals, organic solvents, and the like ("properties and applications of ethylene-vinyl alcohol copolymer", Liu Ming Jiang, et al, Proc. of Tianjin light industry academy, 1997, 2 nd, page 71, 3 rd, lines 1-2, published 1997, 10/31). In addition, the ethylene-vinyl alcohol copolymer is also used for clothing processing manufacturing, manufacturing of medical permselective membranes, manufacturing of automobile fuel tanks or liners, members of air-conditioning equipment, as a metal protective coating, heating piping materials, and the like ("performance, application, and market prospects of EVOH resin", dawn, acetaldehyde acetalization, No. 1, No. 3 lines of the last 1 st column on page 20, No. 2 lines of the right column on page 20, No. 3 lines of the right column on page 20, No. 1-2 lines of the right column on page 20, No. 4, No. 13 lines of the right column on page 20, No. 12/31 days of 2013).
At present, the method for removing impurities in the production process of EVOH is to repeatedly wash EVOH for many times after the EVOH is solidified into particles, and the method has high material consumption and energy consumption.
Disclosure of Invention
In view of the above, the present invention aims to provide a method for purifying an ethylene-vinyl alcohol copolymer, which can significantly reduce water consumption.
Furthermore, the inventors have found that impurities in EVOH are usually removed during the production process by repeatedly washing EVOH with water after solidifying EVOH into pellets, and that a considerable amount of impurities such as sodium acetate cannot be effectively washed out.
In order to achieve the purpose, the technical scheme of the invention is as follows:
a process for purifying an ethylene-vinyl alcohol copolymer comprising the steps of: the ethylene-vinyl alcohol copolymer resin obtained by alcoholysis was brought into a semi-molten state, and slurry washing was continued in this state.
The semi-molten state refers to a translucent state having fluidity.
The inventors have surprisingly found that, including the copolymerization, alcoholysis and washing steps, the washing is specifically: the ethylene-vinyl alcohol copolymer resin was brought into a semi-molten state, and slurry washing was continued in this state. Can obviously shorten the cleaning time and reduce the water consumption, and can greatly reduce the content of impurities such as sodium acetate and the like in the ethylene-vinyl alcohol copolymer.
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 slurry washing means washing for 5 to 7 hours according to the mass ratio of the ethylene-vinyl alcohol copolymer resin to the water of 1:8 to 1: 10.
Further, the purified ethylene-vinyl alcohol copolymer is treated at 230 ℃ for 5-20min, and the yellowness index YI is less than or equal to 11.
Further, the content of sodium acetate in the purified ethylene-vinyl alcohol copolymer is less than or equal to 900 ppm.
The sodium acetate content is referred to relative to the ethylene vinyl alcohol copolymer.
The invention has the beneficial effects that:
the method of the invention obviously reduces the energy consumption and material consumption, shortens the cleaning time by 41.7-58.3%, and reduces the water consumption in the cleaning process by 66.7-73.3%.
The method can obviously reduce the content of impurities such as sodium acetate in the ethylene-vinyl alcohol copolymer, and the content of the sodium acetate in the obtained ethylene-vinyl alcohol copolymer is less than or equal to 900 ppm.
The method can obviously improve the heat resistance of the ethylene-vinyl alcohol copolymer, and the obtained ethylene-vinyl alcohol copolymer is processed for 5-20 minutes at the constant temperature of 230 ℃, and the yellowness index YI of the ethylene-vinyl alcohol copolymer is less than or equal to 11.
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 20-50g 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: 30g 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 purifying the ethylene-vinyl alcohol copolymer specifically comprises the following 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, controls the pressure to be 0.1MPa and the temperature to be 120 ℃, enables the ethylene-vinyl alcohol copolymer resin to be in a semi-molten state, then adds water with the mass of 9 times of that of the ethylene-vinyl alcohol copolymer resin in the semi-molten state, continuously stirs the mixture, continuously cleans the mixture for 5 hours, and continuously discharges the cleaning waste liquid out of the system.
Example 2
The method for purifying the ethylene-vinyl alcohol copolymer specifically comprises the following 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, and is also provided with a stirring device and a jacket heating device, the pressure is controlled to be 0.05MPa, the temperature is controlled to be 110 ℃, the ethylene-vinyl alcohol copolymer resin obtained by alcoholysis is in a semi-molten state, then water with the mass being 8 times that of the ethylene-vinyl alcohol copolymer resin in the semi-molten state is added into the ethylene-vinyl alcohol copolymer resin and is continuously stirred, the ethylene-vinyl alcohol copolymer resin is continuously cleaned for 6 hours, and the cleaning waste liquid is continuously discharged out.
Example 3
The method for purifying the ethylene-vinyl alcohol copolymer specifically comprises the following 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, and is also provided with a stirring device and a jacket heating device, the pressure is controlled to be 0.15MPa, the temperature is controlled to be 128 ℃, the ethylene-vinyl alcohol copolymer resin obtained by alcoholysis is in a semi-molten state, then water with the mass being 8 times that of the ethylene-vinyl alcohol copolymer resin in the semi-molten state is added into the ethylene-vinyl alcohol copolymer resin, the mixture is continuously stirred, the mixture is continuously cleaned for 5 hours, and the cleaning waste liquid is continuously discharged out of the system.
Example 4
The method for purifying the ethylene-vinyl alcohol copolymer specifically comprises the following 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, and is also provided with a stirring device and a jacket heating device, the pressure is controlled to be 0.1MPa, the temperature is controlled to be 120 ℃, the ethylene-vinyl alcohol copolymer resin obtained by alcoholysis is in a semi-molten state, then water with the mass being 10 times that of the ethylene-vinyl alcohol copolymer resin in the semi-molten state is added into the ethylene-vinyl alcohol copolymer resin and is continuously stirred, continuous cleaning is carried out for 7 hours, and the cleaning waste liquid is continuously discharged out of the system.
Comparative example 1
The method for purifying 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 YI 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 in examples 1 to 4 had smooth appearances and relatively white hues; the yellowness index YI is less than or equal to 11, and the sodium acetate content is less than or equal to 900 ppm. The method provided by the invention has the advantages that the content of impurities such as sodium acetate in the ethylene-vinyl alcohol copolymer is obviously reduced, and the heat resistance of the ethylene-vinyl alcohol copolymer is obviously improved.
As can be seen from Table 1, the ethylene-vinyl alcohol copolymers obtained in examples 1 to 4 had a reduced water consumption in the washing process of 66.7% to 73.3% and a shortened time period of 41.7% to 58.3% as compared with 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 (9)
1. A method for purifying an ethylene-vinyl alcohol copolymer, comprising the steps of: the ethylene-vinyl alcohol copolymer resin obtained by alcoholysis was brought into a semi-molten state, and slurry washing was continued in this state.
2. The purification 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 purification process according to claim 2, characterized in that the temperature is 60-170 ℃ and the pressure is 0-0.3 MPa.
4. The purification method according to any one of claims 1 to 3, wherein the slurry washing is carried out for 5 to 7 hours at a mass ratio of the ethylene-vinyl alcohol copolymer resin to water of 1:8 to 1: 10.
5. The purification process according to any one of claims 1 to 3, wherein the purified ethylene-vinyl alcohol copolymer is treated at 230 ℃ for 5 to 20min and has a yellowness index YI of 11 or less.
6. The purification process according to claim 4, wherein the purified ethylene-vinyl alcohol copolymer is treated at 230 ℃ for 5 to 20min and has a yellowness index YI of 11 or less.
7. The purification method according to any one of claims 1 to 3, wherein the purified ethylene-vinyl alcohol copolymer has a sodium acetate content of 900ppm or less.
8. The purification method according to claim 4, wherein the purified ethylene-vinyl alcohol copolymer has a sodium acetate content of 900ppm or less.
9. The purification method according to claim 5, wherein the purified ethylene-vinyl alcohol copolymer has a sodium acetate content of 900ppm or less.
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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 CN201911018264.9A patent/CN112707986A/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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