CN114426592A - Process for producing ethylene-vinyl alcohol copolymer - Google Patents
Process for producing ethylene-vinyl alcohol copolymer Download PDFInfo
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- CN114426592A CN114426592A CN202011096489.9A CN202011096489A CN114426592A CN 114426592 A CN114426592 A CN 114426592A CN 202011096489 A CN202011096489 A CN 202011096489A CN 114426592 A CN114426592 A CN 114426592A
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Abstract
The invention belongs to the technical field of copolymers containing 4 carbon atom monomers and only one carbon-carbon double bond, and particularly relates to a production method of an ethylene-vinyl alcohol copolymer. The production method of the ethylene-vinyl alcohol copolymer takes ethylene and vinyl acetate as raw materials, and sequentially comprises the steps of rectification and concentration after the polymerization step and before the alcoholysis step. The method of the invention can obviously improve the operation stability in the production process of the ethylene-vinyl alcohol copolymer.
Description
Technical Field
The invention belongs to the technical field of copolymers containing 4 carbon atom monomers and only one carbon-carbon double bond, and particularly relates to a production method of an ethylene-vinyl alcohol copolymer.
Background
Ethylene-vinyl alcohol copolymer (EVOH) is a crystalline polymer having a chain structure and composed of a vinyl segment (E) and a vinyl alcohol-based segment (VA) and is prepared from ethylene-vinyl acetate copolymer (EVA) by saponification or partial saponification reaction ("the properties and preparation points of EVOH", Li Juan, printing technology, No. 2 of 2011, No. 1, lines 1 to 4 of the left column on page 46 and No. 4, lines 1 to 3 of the right column on page 46, published 2011 12/31).
The ethylene-vinyl alcohol copolymer has the characteristics of high barrier property, moisture absorption property, mechanical strength, elastic modulus and flexibility, gloss, transparency and weather resistance, environmental protection safety, aroma retention property, molding processability, antistatic property, good printing effect, dust adsorption resistance, aging resistance, heat resistance, oil resistance, organic solvent resistance and the like ("the performance, application and market prospect" of EVOH resin, dawn, acetaldehyde acetic acid chemical engineering, No. 1 in 2013, No. 2, No. 1 in the left column of page 18, No. 4, No. 8 in the right column of page 19, No. 2013, No. 12/31 in 2013, and "the performance of ethylene-vinyl alcohol copolymer and its application in the field of intervening embolism", zhang qing et al, biomedical engineering research, No. 30, No. 2 in the volume 30, No. 1-5 in the left column of page 109, No. 12/31 in 2011).
At present, ethylene-vinyl alcohol copolymer is widely applied to the fields of packaging, fiber, capillary catalyst carrier, composite construction of refractory materials, antibacterial materials, antioxidant materials, textile materials and the like with other materials (the research progress of ethylene-vinyl alcohol copolymer, paradox and the like, petrochemical industry, 42 th volume of 2013, 12 th period, 2 nd section, 4 th to 10 th line on left column of page 1405, 12 th month and 31 th day of 2013).
However, the ethylene-vinyl alcohol copolymer prepared by the existing process has poor operation stability.
Disclosure of Invention
In view of the above, the present invention is directed to a method for producing an ethylene-vinyl alcohol copolymer.
In order to achieve the purpose, the technical scheme of the invention is as follows:
the production method of ethylene-vinyl alcohol copolymer uses ethylene and vinyl acetate as raw material, and includes the polymerization and alcoholysis procedures in turn, and after the polymerization procedure and before the alcoholysis procedure, the rectification and concentration procedures are also included in turn.
The inventor unexpectedly discovers that ethylene and vinyl acetate are taken as raw materials and sequentially comprise a polymerization process and an alcoholysis process, and the rectification process and the concentration process are sequentially carried out after the polymerization process and before the alcoholysis process; the process for producing an ethylene-vinyl alcohol copolymer of (2) is excellent in running stability.
Further, the solvent used in the polymerization process includes methanol, ethanol, propanol or tert-butanol.
Further, the solvent used in the polymerization process includes methanol.
Further, the concentration of the ethylene-vinyl acetate polymer resin liquid is controlled to be 20 wt% -60 wt% in the polymerization process.
Further, the concentration of the ethylene-vinyl acetate polymer resin liquid is controlled to be 30 wt% -50 wt% in the polymerization process.
Further, the parameters of the rectification process are set as follows: introducing gas-phase methanol, ethanol, propanol or tert-butanol from the bottom of the rectifying tower, introducing ethylene-vinyl acetate polymerization resin liquid from the top, and rectifying under normal pressure.
Further, the mass ratio of the gas phase methanol, ethanol, propanol or tert-butanol to the resin liquid is 0.5: 1-5:1, wherein the mass ratio of the gas-phase methanol, ethanol, propanol or tert-butanol to the resin liquid is 0.5: 1-5:1.
Further, the method further comprises a flash evaporation step after the polymerization step and before the rectification step.
Further, the pressure of the flash evaporator is controlled to be 0.1-0.5MPa in the flash evaporation process.
The invention has the beneficial effects that:
the method of the invention can obviously improve the operation stability in the production process of the ethylene-vinyl alcohol copolymer.
The method is simple and is beneficial to realizing industrial production.
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.
Analysis of the feed liquid: analyzing vinyl acetate, methanol and the like in the mixed liquid by adopting a chromatographic analysis method, detecting by using a hydrogen flame ion detector, and quantifying by using an internal standard method to obtain the content of each component;
the method for detecting the concentration of the resin liquid comprises the following steps: analyzing by adopting a thermal weight loss method for obtaining solid residues through heating evaporation, weighing a certain amount of resin liquid, continuously heating to 120 ℃, heating to constant weight, and calculating the concentration of the resin liquid as solid quantity;
the conversion rate of vinyl acetate is according to the formula
Calculation was performed (where m1 is the mass of vinyl acetate added and m2 is the mass of vinyl acetate remaining in the solution after the reaction).
Example 1
The production method of the ethylene-vinyl alcohol copolymer comprises the following specific steps:
A. polymerization: continuously introducing 400kg/h of vinyl acetate into a polymerization kettle, continuously introducing 100kg/h of methanol solution containing 0.1% (wt) of azobisisobutyronitrile initiator, adjusting the polymerization pressure to be 4.0MPa (G) through ethylene pressure, continuously reacting for 6 hours, discharging, and detecting that the solid content of the polymer resin solution is 30 wt% and the vinyl acetate conversion rate is 35%;
B. flash evaporation: feeding the resin liquid discharged from the polymerization kettle into a flash evaporator for flash evaporation, controlling the pressure of the flash evaporator to be 0.2MPa (G), controlling the ethylene content of the resin liquid after flash evaporation to be 0.2 wt%, and feeding the resin liquid into a rectification process;
C. and (3) rectification: introducing gas-phase methanol with the mass 2.4 times that of the resin liquid through the bottom of the rectifying tower, controlling the reflux quantity of condensate (namely condensate obtained by condensing azeotrope discharged from the top of the rectifying tower) which flows back to the rectifying tower to be 135kg/h, and allowing the resin liquid at the bottom to enter a thickener;
D. concentrating: controlling the extraction flow to be 450kg/h in the concentrator through an extraction gear pump, controlling the liquid level in the concentrator to be stable, and detecting that the concentration of the resin liquid extracted by the concentrator is 42 wt%;
E. alcoholysis: and adding the concentrated resin liquid into an alcoholysis reactor for alcoholysis, wherein the concentration of the resin liquid after alcoholysis is 25 wt%, the alcoholysis process is stable during alcoholysis, the grain-sized particles are uniform, and the conditions of difficult molding, material breakage and the like do not occur after continuous and stable operation for more than 30 days.
Example 2
The production method of the ethylene-vinyl alcohol copolymer comprises the following specific steps:
A. the polymerization process was the same as that of example 1;
B. flash evaporation: controlling the flash pressure of the flash evaporator to be 0.3MPa (G), controlling the ethylene content of the resin liquid after flash evaporation to be 0.2 wt%, and feeding the resin liquid into a rectification process;
C. and (3) rectification: introducing gas-phase methanol with the mass of 3.2 times of that of the resin liquid into the bottom of the rectifying tower, controlling the reflux quantity of condensate (namely condensate obtained by condensing azeotrope discharged from the top of the rectifying tower) which flows back to the rectifying tower to be 135kg/h, and allowing the resin liquid at the bottom to enter a thickener;
D. concentrating: controlling the extraction flow to be 530kg/h in the concentrator through an extraction gear pump, controlling the liquid level in the concentrator to be stable, and controlling the concentration of the resin liquid extracted by the concentrator to be 36 wt%;
E. alcoholysis: and adding the concentrated resin liquid into an alcoholysis reactor for alcoholysis, wherein the concentration of the resin liquid after alcoholysis is 22 wt%, the alcoholysis process is stable during alcoholysis, the grain-sized particles are uniform, and the conditions of difficult molding, material breakage and the like do not occur after continuous stable operation for more than 30 days.
Example 3
The production method of the ethylene-vinyl alcohol copolymer comprises the following specific steps:
A. polymerization: continuously introducing 400kg/h of vinyl acetate into a polymerization kettle, continuously introducing 120kg/h of methanol solution containing 0.15 wt% of azodiisobutyronitrile initiator, adjusting the polymerization pressure to be 4.2MPa (G) through ethylene pressure, continuously reacting for 8 hours, discharging, and detecting that the solid content of the polymer resin solution is 42 wt% and the conversion rate of the vinyl acetate is 52%
B. Flash evaporation: controlling the flash pressure of the flash evaporator to be 0.3MPa (G), controlling the ethylene content of the resin liquid after flash evaporation to be 0.2%, and feeding the resin liquid into a rectification process.
C. And (3) rectification: introducing gas phase methanol with the weight 3.2 times that of the resin liquid through the bottom of the rectifying tower, controlling the reflux amount of condensate (namely condensate obtained by condensing azeotrope discharged from the top of the rectifying tower) refluxing to the rectifying tower to be 220kg/h, and allowing the resin liquid at the bottom to enter a thickener.
D. Concentrating: the extraction flow rate is controlled to be 650kg/h in the concentrator through an extraction gear pump, the liquid level in the concentrator is controlled to be stable, and the concentration of the resin liquid extracted by analysis is 48%.
E. Alcoholysis: and adding the concentrated resin liquid into an alcoholysis reactor for alcoholysis, wherein the concentration of the resin liquid after alcoholysis is 28%, the alcoholysis process is stable during alcoholysis, the grain-sized particles are uniform, and the conditions of difficult molding, material breakage and the like do not occur when the resin liquid continuously and stably runs for more than 30 days.
Example 4
The production method of the ethylene-vinyl alcohol copolymer comprises the following specific steps:
A. polymerization: 400kg/h of vinyl acetate is continuously fed into a polymerization kettle, 120kg/h of methanol solution containing 0.15 wt% of azodiisobutyronitrile initiator is continuously fed into the polymerization kettle, the polymerization pressure is adjusted to be 4.0MPa (G) through ethylene pressure, discharging is carried out after 4 hours of continuous reaction, and through detection, the solid content of the polymerization resin liquid is 36 wt%, and the conversion rate of the vinyl acetate is 42%.
B. Flash evaporation: the flash evaporation process was the same as that of example 3;
C. and (3) rectification: introducing gas phase methanol 2.6 times the weight of the resin liquid into the bottom of the rectifying tower, controlling the reflux amount of condensate (namely condensate obtained by condensing azeotrope discharged from the top of the rectifying tower) refluxing to the rectifying tower to be 220kg/h, and allowing the resin liquid at the bottom to enter a thickener.
D. Concentrating: the production flow rate is controlled to be 520kg/h in the concentrator through a production gear pump, the liquid level in the concentrator is controlled to be stable, and the concentration of the resin liquid produced by the concentrator is 42 wt% through detection.
E. Alcoholysis: and adding the concentrated resin liquid into an alcoholysis reactor for alcoholysis, wherein the concentration of the resin liquid after alcoholysis is 25 wt%, the alcoholysis process is stable during alcoholysis, the grain-sized particles are uniform, and the conditions of difficult molding, material breakage and the like do not occur after continuous and stable operation for more than 30 days.
Comparative example 1
The production method of the ethylene-vinyl alcohol copolymer comprises the following specific steps:
A. polymerization: the polymerization kettle is continuously filled with 400kg/h of vinyl acetate, 100kg/h of methanol solution containing 0.1 wt% of azodiisobutyronitrile initiator is continuously filled, the polymerization pressure is adjusted to be 4.0MPa (G) through ethylene pressure, discharging is carried out after continuous reaction for 6 hours, and through detection, the solid content of the polymer resin liquid is 30 wt% and the conversion rate of the vinyl acetate is 35%.
B. Flash evaporation: and (3) feeding the resin liquid discharged from the polymerization kettle into a flash evaporator for flash evaporation, controlling the pressure of the flash evaporator to be 0.2MPa (G), controlling the ethylene content of the resin liquid after flash evaporation to be 0.2 wt%, and feeding the resin liquid into a rectification process.
C. And (3) rectification: introducing gas phase methanol 2.4 times of the weight of the resin liquid into the bottom of the rectifier, controlling the reflux quantity of condensate (condensed condensate of azeotrope discharged from the top of the rectifier) refluxed to the rectifier to be 135kg/h, and directly introducing the resin liquid at the bottom into alcoholysis.
D. Alcoholysis: adding the rectified resin liquid into an alcoholysis reactor for alcoholysis, wherein the concentration of the resin liquid after alcoholysis is 17 wt%, and after operation for several hours, grain cutting and winding are often generated, so that a large amount of resin materials are discharged, and grain cutting stability is influenced.
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. The production method of ethylene-vinyl alcohol copolymer uses ethylene and vinyl acetate as raw material, and includes the polymerization and alcoholysis procedures in turn, and is characterized by that after the polymerization procedure and before the alcoholysis procedure, the rectification and concentration procedures are also included in turn.
2. The method of claim 1, wherein the solvent used in the polymerization process comprises methanol, ethanol, propanol or tert-butanol.
3. The method of claim 2, wherein the solvent used in the polymerization process comprises methanol.
4. The production method according to any one of claims 1 to 3, wherein the polymerization step controls the concentration of the ethylene-vinyl acetate polymer resin liquid to be 20 wt% to 60 wt%.
5. The production method according to claim 4, wherein the concentration of the ethylene-vinyl acetate polymer resin liquid in the polymerization step is controlled to be 30 to 50 wt%.
6. The production method according to any one of claims 2 to 5, wherein the parameters of the rectification process are set as follows: introducing gas-phase methanol, ethanol, propanol or tert-butanol from the bottom of the rectifying tower, introducing ethylene-vinyl acetate polymerization resin liquid from the top, and rectifying under normal pressure.
7. The production method according to claim 6, wherein the mass ratio of the gas-phase methanol, ethanol, propanol or tert-butanol to the resin liquid is 0.5: 1-5:1, wherein the mass ratio of the gas-phase methanol, ethanol, propanol or tert-butanol to the resin liquid is 0.5: 1-5:1.
8. The production method according to any one of claims 2 to 7, further comprising a flash evaporation step after the polymerization step and before the rectification step.
9. The production method according to claim 8, wherein the flash evaporation process controls the pressure of the flash evaporator to 0.1 to 0.5 MPa.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115894769B (en) * | 2022-11-29 | 2024-05-17 | 清华大学 | Process for preparing ethylene-vinyl alcohol copolymer |
Citations (5)
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|---|---|---|---|---|
| JPS4738634Y1 (en) * | 1970-05-23 | 1972-11-22 | ||
| JP2002060403A (en) * | 2000-06-06 | 2002-02-26 | Kuraray Co Ltd | Preparation process of ethylene/vinyl acetate copolymer and its saponified material |
| CN1285631C (en) * | 2003-07-01 | 2006-11-22 | 长春石油化学股份有限公司 | Process for continuously producing ethylene-vinyl-acetic ester copolymer and reaction system thereof |
| CN106146719A (en) * | 2015-04-17 | 2016-11-23 | 中国石油化工集团公司 | A kind of preparation method of ethylene-vinyl alcohol copolymer |
| CN106188365A (en) * | 2015-04-17 | 2016-12-07 | 中国石油化工集团公司 | A kind of ethylene-vinyl alcohol copolymer and preparation method thereof |
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- 2020-10-14 CN CN202011096489.9A patent/CN114426592A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS4738634Y1 (en) * | 1970-05-23 | 1972-11-22 | ||
| JP2002060403A (en) * | 2000-06-06 | 2002-02-26 | Kuraray Co Ltd | Preparation process of ethylene/vinyl acetate copolymer and its saponified material |
| CN1285631C (en) * | 2003-07-01 | 2006-11-22 | 长春石油化学股份有限公司 | Process for continuously producing ethylene-vinyl-acetic ester copolymer and reaction system thereof |
| CN106146719A (en) * | 2015-04-17 | 2016-11-23 | 中国石油化工集团公司 | A kind of preparation method of ethylene-vinyl alcohol copolymer |
| CN106188365A (en) * | 2015-04-17 | 2016-12-07 | 中国石油化工集团公司 | A kind of ethylene-vinyl alcohol copolymer and preparation method thereof |
Non-Patent Citations (1)
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115894769B (en) * | 2022-11-29 | 2024-05-17 | 清华大学 | Process for preparing ethylene-vinyl alcohol copolymer |
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