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CN-120059024-B - Ethylene-vinyl alcohol copolymer, preparation method, application and film thereof

CN120059024BCN 120059024 BCN120059024 BCN 120059024BCN-120059024-B

Abstract

The invention relates to the field of resins, and discloses an ethylene-vinyl alcohol copolymer, a preparation method, application and a film thereof. The melt index of the copolymer at 190 ℃ and 21.6kg load is MFR 21.6 , the melt index of the copolymer at 190 ℃ and 5kg load is MFR 5 , the melt index of the copolymer at 190 ℃ and 2.16kg load is MFR 2.16 , and the MFR 21.6 、MFR 5 and the MFR 2.16 satisfy the following relationship that 10≤MFR 21.6 /MFR 2.16 -MFR 5 /MFR 2.16 ≤25. The ethylene-vinyl alcohol copolymer provided by the invention has better processing stability, so that the processing operation period is long, and the ethylene-vinyl alcohol copolymer also has fewer surface defect numbers and smaller crystal point defects.

Inventors

  • DOU YUQIN
  • LI YUAN
  • LEI DESONG
  • ZHU CHANGHAI
  • FAN JINHUA

Assignees

  • 中国石油化工股份有限公司
  • 中国石化集团重庆川维化工有限公司

Dates

Publication Date
20260508
Application Date
20231129

Claims (14)

  1. 1. An ethylene-vinyl alcohol copolymer characterized in that the melt index of the copolymer at 190℃and 21.6kg load is MFR 21.6 , the melt index of the copolymer at 190℃and 5kg load is MFR 5 , the melt index of the copolymer at 190℃and 2.16kg load is MFR 2.16 , The MFR 21.6 、MFR 5 and MFR 2.16 satisfy the following relationship: 14≤MFR 21.6 / MFR 2.16 - MFR 5 / MFR 2.16 ≤22。
  2. 2. The copolymer of claim 1, wherein the copolymer has a change in screw current of 1A or less when the film blowing machine is used; And/or the content of structural units derived from ethylene in the copolymer is 20 to 50mol%; And/or the copolymer has a melt index of 1-10g/10min at 190 ℃ under a load of 2.16 kg; And/or the weight average molecular weight of the copolymer is 20000-200000g/mol, the molecular weight distribution of the copolymer is 1-3; and/or, the copolymer has an intrinsic viscosity of 0.1 to 1dL/g at 25 ℃; and/or the alcoholysis degree of the copolymer is 99-99.9%.
  3. 3. The copolymer according to claim 2, wherein the content of structural units derived from ethylene in the copolymer is 22 to 48mol%.
  4. 4. A process for preparing the ethylene vinyl alcohol copolymer of any of claims 1-3, comprising: (1) Polymerizing vinyl acetate with ethylene in the presence of a first solvent and an initiator; (2) Sequentially mixing a second solvent and a terminator in the product of the step (1) to obtain an ethylene-vinyl acetate copolymer solution; (3) Contacting the ethylene-vinyl acetate copolymer solution with a base to obtain an ethylene-vinyl alcohol copolymer; The conditions for mixing the product of step (1) with the second solvent include a temperature of 40-70 ℃ and a time of 1-5 hours.
  5. 5. The process of claim 4, wherein the molar ratio of hydroxyl ions in the base to vinyl acetate building blocks in the ethylene vinyl acetate copolymer is from 0.005 to 0.045:1.
  6. 6. The process of claim 5, wherein the molar ratio of hydroxyl ions in the base to vinyl acetate building blocks in the ethylene-vinyl acetate copolymer is from 0.01 to 0.03:1.
  7. 7. The method according to claim 4 or 5, wherein the ethylene-vinyl acetate copolymer solution has an ethylene-vinyl acetate copolymer content of 40 to 60 wt%; and/or the contacting conditions include a temperature of 50-65 ℃ for 4-6 hours; And/or the pressure of the contact is normal pressure; And/or, the alkali is sodium hydroxide and/or potassium hydroxide.
  8. 8. The method of claim 4 or 5, wherein the second solvent is used in an amount of 1 to 30% by weight based on the weight of the vinyl acetate; and/or the dosage of the terminator is 100-5000ppm of the dosage of the vinyl acetate in the step (1); And/or the terminator is at least one selected from 2, 4-diphenyl-4-methyl-1-pentene, 1-diphenyl-2-trinitrophenylhydrazine, copper acetate, cuprous chloride and ferric trichloride; and/or the method further comprises removing ethylene in the product of step (1) in step (2).
  9. 9. The method of claim 8, wherein the amount of the terminating agent is 300-3000ppm based on the amount of the vinyl acetate of step (1).
  10. 10. The process of claim 8, wherein the means for removing ethylene is reduced pressure flash; And/or, the removing ethylene is after mixing the second solvent.
  11. 11. The process according to claim 4 or 5, wherein the conditions under which the product of step (1) is mixed with the terminator comprise a temperature of 10-40 ℃ for a time of 0.1-2h; and/or, the pressure at which the product of step (1) is mixed with the second solvent is 2-6MPaG; and/or the pressure at which the product of step (1) is mixed with the terminator is normal pressure.
  12. 12. Use of the ethylene-vinyl alcohol copolymer of any one of claims 1-3 in at least one of packaging materials, automotive fuel tanks, oxygen barrier floor heating pipes, textile materials and medical materials.
  13. 13. An ethylene vinyl alcohol film prepared from the copolymer of any one of claims 1-3.
  14. 14. The ethylene vinyl alcohol film of claim 13, wherein the film has a number of surface defects of 300/m 2 or less; And/or the number of crystal points of the film larger than 300 μm is not higher than 5%.

Description

Ethylene-vinyl alcohol copolymer, preparation method, application and film thereof Technical Field The invention relates to the field of resins, in particular to an ethylene-vinyl alcohol copolymer, a preparation method, application and a film thereof. Background Ethylene-vinyl alcohol copolymer (EVOH), especially ethylene-vinyl alcohol copolymer with ethylene content of 20-50mol%, has excellent gas barrier property, 10000 times of common polyethylene, and has transparency, processability, solvent resistance and antistatic property, so that it is widely used in the fields of packaging materials, automobile fuel tanks, oxygen-blocking floor heating pipes, textile materials, medical materials and the like. In the use process of ethylene-vinyl alcohol copolymer, usually, a melt processing mode is adopted, EVOH is used as a polymer with a polyhydroxy structure in a molecular structure, intermolecular dehydration and intramolecular dehydration under high temperature conditions are easy to generate, and therefore, the processing stability is reduced, and in particular, defects such as crystal points are generated in the film forming process. Disclosure of Invention The invention aims to solve the problems of unstable processing of ethylene-vinyl alcohol copolymer and defects generated in the film making process in the prior art, and provides an ethylene-vinyl alcohol copolymer, a preparation method, application and a film thereof. In order to achieve the above object, the first aspect of the present invention provides an ethylene-vinyl alcohol copolymer having a melt index of MFR 21.6 at 190℃and 21.6kg load, a melt index of MFR 5 at 190℃and 5kg load, a melt index of MFR 2.16 at 190℃and 2.16kg load, The MFR 21.6、MFR5 and MFR 2.16 satisfy the following relationship: 10≤MFR216/MFR216-MFR5/MFR216≤25。 In a second aspect, the present invention provides a process for preparing an ethylene vinyl alcohol copolymer, the process comprising: (1) Polymerizing vinyl acetate with ethylene in the presence of a first solvent and an initiator; (2) Sequentially mixing a second solvent and a terminator in the product of the step (1) to obtain an ethylene-vinyl acetate copolymer solution; (3) The ethylene-vinyl acetate copolymer solution is contacted with alkali to obtain the ethylene-vinyl alcohol copolymer. In a third aspect the invention provides an ethylene vinyl alcohol copolymer prepared by the process described above. In a fourth aspect, the present invention provides the use of the ethylene vinyl alcohol copolymer described above in at least one of packaging materials, automotive fuel tanks, oxygen barrier floor heating pipes, textile materials and medical materials. In a fifth aspect, the present invention provides an ethylene vinyl alcohol copolymer film made from the copolymer described above. By the technical scheme, the ethylene-vinyl alcohol copolymer provided by the invention has good processing stability, so that the processing operation period is long. More preferably, when the film is used for preparing the ethylene-vinyl alcohol film, the prepared film has fewer surface defects and smaller crystal point defects. Detailed Description The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein. In a first aspect the present invention provides an ethylene vinyl alcohol copolymer having a melt index at 190℃and 21.6kg load of MFR 21.6, a melt index at 190℃and 5kg load of MFR 5, a melt index at 190℃and 2.16kg load of MFR 2.16, The MFR 21.6、MFR5 and MFR 2.16 satisfy the following relationship: MFR 21.6/MFR2.16-MFR5/MFR2.16 is 10 or less and 25 or less, and may be 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25 or any two or more of these values. In the invention, the ethylene-vinyl alcohol copolymer has better processing stability in the above relation, so that the processing operation period is long, and when the ethylene-vinyl alcohol copolymer is used for preparing the ethylene-vinyl alcohol film, the prepared film has fewer surface defects and fewer crystal point defects. More preferably, the MFR 21.6/MFR2.16-MFR5/MFR2.16 is 12 or less and 22 or less. According to the present invention, the copolymer has a change in screw current of 1A or less when a film blowing machine is used in order to obtain better processing stability and a smaller number of surface defects and smaller crystal point defects. In the invention, the change of the screw current of the copolymer is less than or equal to 1A when a film blowing machine is used, and the copolymer has better processing stability. According