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CN-121991276-A - Ultra-low viscosity modified polyvinyl alcohol and production method and application thereof

CN121991276ACN 121991276 ACN121991276 ACN 121991276ACN-121991276-A

Abstract

The invention provides a production method of ultra-low viscosity modified polyvinyl alcohol, which is prepared by taking vinyl acetate as a main monomer raw material to polymerize and then alcoholysis, methanol is taken as a solvent, and simultaneously, a polyene compound is added as a second monomer to copolymerize with the vinyl acetate monomer, wherein the proportion of the solvent is lower than 40% by mass of a polymerization reaction system. The elongation at break of the water-soluble film prepared from the ultra-low viscosity PVA is improved by 6-13% compared with that of the conventional PVA, the problem of unsatisfactory toughness of the low viscosity PVA film is solved, and the water-soluble film is beneficial to better application of the PVA water-soluble film.

Inventors

  • WU CHUNLIN
  • WU GANG
  • SHANG JINZHI
  • LI YUHONG
  • DAI MEIRONG

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
  • 重庆川维科技有限公司

Dates

Publication Date
20260508
Application Date
20241108

Claims (10)

  1. 1. The production method of the ultra-low viscosity modified polyvinyl alcohol is characterized in that the polyvinyl alcohol is prepared by taking vinyl acetate as a main monomer raw material to polymerize and then alcoholysis, and methanol is taken as a solvent.
  2. 2. The method of claim 1, wherein the second monomer is an olefin, alcohol, or ether having two or more unsaturated ethylenic bonds, or any combination thereof.
  3. 3. The method of claim 2, wherein the second monomer is selected from the group consisting of cycloheptatriene, triallylmethanol, karaenol 11, decyiprenol, perhexenol, pentaerythritol triallyl ether, a turpentine (terpene, terpenoid) myrcene fraction glycolate, or any combination thereof.
  4. 4. The production method according to claim 3, wherein the ratio of the amounts of the vinyl acetate monomer, the second monomer and the solvent in the polymerization reaction system is 60.0 to 70.0:0.01 to 0.1:30.0 to 40.0 by mass.
  5. 5. The process according to claim 4, wherein the polymerization reaction system uses azobisisobutyronitrile as an initiator in an amount of 0.01 to 0.5% relative to the mass of the vinyl acetate monomer, and the polymerization reaction is carried out at a temperature of 50 to 70℃for 4 to 6 hours.
  6. 6. The process according to claim 5, further comprising subjecting the polymer obtained by the polymerization reaction to the alcoholysis after the polymer has been purified to a purity of more than 99% by rectification at 70 to 80 ℃.
  7. 7. The process according to claim 6, wherein the alcoholysis is carried out by subjecting a methanol solution of the polymerization product to alcoholysis with a sodium hydroxide-methanol solution at 40-45 ℃ for 0.6-1h in a molar ratio of vinyl acetate monomer to sodium hydroxide of 1:0.005-0.01 in the polymer.
  8. 8. The production method according to claim 7, characterized in that it comprises the following steps: Adding vinyl acetate monomer, second monomer and solvent according to the mass ratio of 60.0-70.0:0.01-0.1:30.0-40.0, adding initiator accounting for 0.01-0.5% of the mass of the vinyl acetate, reacting for 4-6 hours at 50-70 ℃ to obtain vinyl acetate copolymer, rectifying and purifying the vinyl acetate copolymer polymerization solution at 70-80 ℃ to obtain the vinyl acetate copolymer with the purity of more than 99.0%; The alcoholysis reaction comprises preparing a methanol solution with the mass concentration of 20-45% from the purified vinyl acetate copolymer, mixing the methanol solution with a sodium hydroxide methanol solution with the mass concentration of 20-40% in a ratio of enabling the molar ratio of the vinyl acetate copolymer to the sodium hydroxide in the mixed solution to be 1:0.005-0.01, carrying out alcoholysis for 0.6-1h at the temperature of 40-45 ℃, completely separating solid from liquid after the alcoholysis reaction, separating solids, putting the formed block into a pulverizer for pulverizing, adding acetic acid to neutralize alkali which does not participate in the reaction, and then putting the obtained product into an oven for drying at the temperature of 75-85 ℃ for 3-4 hours to obtain the modified polyvinyl alcohol.
  9. 9. An ultra-low viscosity modified polyvinyl alcohol produced by the production method according to any one of claims 1 to 8.
  10. 10. Use of the ultra-low viscosity modified polyvinyl alcohol of claim 9 to improve the toughness of water-soluble films.

Description

Ultra-low viscosity modified polyvinyl alcohol and production method and application thereof Technical Field The invention belongs to the technical field of polyvinyl alcohol, and particularly relates to a production method of ultra-low viscosity polyvinyl alcohol and a film prepared by the production method. Background Polyvinyl alcohol (PVA) is a water-soluble high-molecular polymer, and is prepared by polymerizing vinyl acetate and then conducting alkali alcoholysis to obtain a polymer. PVA has better strong adhesion, film flexibility, smoothness, oil resistance, solvent resistance, colloid protection, gas barrier property, abrasion resistance and water resistance after special treatment. Therefore, PVA is widely used, and its downstream products include vinylon, paint, adhesive, fiber slurry, paper treating agent, emulsifier, dispersant, film, medical material and building automobile-modified material, and the application fields relate to textile, food, medicine, building, wood processing, paper making, printing, agriculture, metallurgy and other industries ("the production status and market prospect of polyvinyl alcohol", wei Shaodong et al, "chemical intermediate", 2006, 12 th, pages 4 to 6, 10). The properties of PVA are determined by the degree of polymerization, viscosity, and degree of alcoholysis. In general, the degree of polymerization varies in proportion to the viscosity index ("state of production and market prospect analysis of polyvinyl alcohol", gu Mingfen et al, yunnan chemical industry, 2012, volume 39, 5, pages 36 to 40). Currently, the development trend of the world PVA industry is to develop into a high-low grade, namely a high-definition product with high polymerization degree (high viscosity) and high alcoholysis degree and a special product with low polymerization degree (low viscosity) and low alcoholysis degree (the production status and market prospect of polyvinyl alcohol, wei Shaodong and the like, chemical industry intermediate, 12 th 2006, pages 4-6 and 10). The low-viscosity PVA means a PVA product having a viscosity of 6.0X10 -3 Pa.s or less (i.e., 6.0 Pa.s) measured at ordinary temperature at a mass fraction of 4% ("Water-soluble high molecular Compound polyvinyl alcohol type trademark and application", mo Hongan, paper-making chemical, vol.15, no. 3, pages 45 to 46 in 2003). The molecular weight of the low viscosity PVA is between several thousands and several tens of thousands, and its viscosity is generally in the range of 1.0 to 6.0 Pa.s. The low viscosity PVA products mainly comprise PVA05, PVA04, PVA03 and other products (the marks respectively represent viscosity indexes of 5 Pa.s, 4mPa.s and 3 mPa.s), and the main products comprise 098-05, 088-05, 098-04, 088-03 and other products (the first half part of the marks represents alcoholysis index, namely 98% or 88% alcoholysis index, and the second half part represents the viscosity index as described above). They have good water solubility, film forming property, biodegradability and other properties, and have unique application in specific application fields such as medicine, daily chemicals, electronics, adhesives, textile processing and other fields. The PVA production technology has been developed for many years, the production technology of low-viscosity PVA is mature, the production technology of low-viscosity PVA products with the viscosity of 4.0-6.0 Pa.s is mature, but the production technology of ultra-low-viscosity PVA with the viscosity of 2-4mPa.s has some problems. The Chinese patent document CN104558319A discloses a method for improving the molding of low-viscosity polyvinyl alcohol, which takes vinyl acetate as a raw material and methanol as a solvent, and comprises the steps of polymerization and alcoholysis, wherein the specific process is as follows: After passing 50-60% vinyl acetate methanol solution through a preheater, feeding the solution into a first polymerization kettle, and carrying out solution polymerization under the action of an initiator; after the polymerization rate reaches 25.0-28.0%, the polymerization solution is fed into a second polymerization kettle to continue polymerization, the polymerization rate of vinyl acetate is raised to about 90-99%, the polymerization reaction of vinyl acetate is carried out in methanol solution, a countercurrent condenser is arranged on the polymerization kettle, the evaporated vinyl acetate and methanol vapor are condensed and then returned to the polymerization kettle, the polymerization reaction temperature is stabilized at 60-70 ℃ by adopting jacket warm water for heat preservation, the total polymerization time is 2.5-6 hours, the VAC polymerization rate is 90-99%, the polyvinyl acetate-methanol solution from the second polymerization kettle is fed into a rectifying tower, methanol vapor is blown in from the bottom of the tower, the unreacted vinyl acetate forms methanol azeotropic solution, the methanol solution of polyvinyl acetate is taken