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Method for hydrolyzing polyvinyl acetate to prepare polyvinyl alcohol in high-temperature liquid water under catalysis of organic acid

A technology of polyvinyl acetate and high-temperature liquid water, which is applied in the field of preparing polyvinyl alcohol by hydrolyzing polyvinyl acetate under the catalysis of organic acids in high-temperature liquid water, can solve the problems of long reaction time, weak catalytic effect, and product molecular weight drop, and achieve Effects of increasing reaction speed, reducing depolymerization, and improving quality

Inactive Publication Date: 2011-05-18
ZHEJIANG UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Although high-temperature liquid water has a certain acid-base catalytic ability, its catalytic effect is weak. If the reaction is carried out under medium and non-catalytic conditions, it will inevitably lead to a long reaction time, which will cause the depolymerization of the polymer, and the molecular weight of the obtained product will be greatly reduced.

Method used

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  • Method for hydrolyzing polyvinyl acetate to prepare polyvinyl alcohol in high-temperature liquid water under catalysis of organic acid
  • Method for hydrolyzing polyvinyl acetate to prepare polyvinyl alcohol in high-temperature liquid water under catalysis of organic acid

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Effect test

Embodiment 1

[0033] 300g of acetic acid aqueous solution and 7.5g of polyvinyl acetate were added to the 500mL batch autoclave, the mass concentration of acetic acid in the acetic acid aqueous solution was 50g / L, the weight-average molecular weight of the raw material polyvinyl acetate was 38,000, and the acetic acid aqueous solution and polyvinyl acetate The mass ratio of esters was 40:1. Start stirring, heat up to boiling under normal pressure, open the exhaust valve for 2 minutes, and use water vapor to remove the air in the kettle; heat up to 200 ° C for hydrolysis for 600 min; the hydrolyzate is cooled and depressurized, and the water and acetic acid are evaporated under reduced pressure , and then vacuum-dried to obtain 3.7 g of a polyvinyl alcohol solid product. The product was analyzed, the degree of hydrolysis was 97.9%, the weight-average molecular weight was 37,500, and the distribution width was 2.7.

Embodiment 2

[0035]Add 300g of acetic acid aqueous solution and 15g of polyvinyl acetate in a 500mL intermittent autoclave, the mass concentration of acetic acid in the acetic acid aqueous solution is 35g / L, the weight average molecular weight of raw material polyvinyl acetate is 38,000, the acetic acid aqueous solution and polyvinyl acetate The mass ratio is 20:1. Start stirring, heat up to boiling under normal pressure, open the exhaust valve for 3 minutes, and use water vapor to remove the air in the kettle; heat up to 210°C for 480 minutes; cool the hydrolyzate, release the pressure, and evaporate water and acetic acid under reduced pressure , and then vacuum-dried to obtain 7.5 g of polyvinyl alcohol solid product. After analysis of the product, the degree of hydrolysis is 98.8%, the weight average molecular weight is 36,900, and the distribution width is 2.7.

Embodiment 3

[0037] Add 300g acetic acid aqueous solution and 10g polyvinyl acetate in a 500mL intermittent high-pressure reactor, the mass concentration of acetic acid in the acetic acid aqueous solution is 45g / L, the raw material polyvinyl acetate weight average molecular weight is 38,000, acetic acid aqueous solution and polyvinyl acetate The mass ratio is 30:1. Start stirring, heat up to boiling under normal pressure, open the exhaust valve for 4 minutes, and use water vapor to remove the air in the kettle; heat up to 220°C for 340 minutes; , and then vacuum-dried to obtain 5 g of polyvinyl alcohol solid product. After analysis of the product, the degree of hydrolysis is 99%, the weight average molecular weight is 34,800, and the distribution width is 2.7.

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Abstract

The invention discloses a method for hydrolyzing polyvinyl acetate to prepare polyvinyl alcohol in high-temperature liquid water under the catalysis of organic acid. The method comprises the following steps of: (1) adding an organic acid aqueous solution and polyvinyl acetate into a high-pressure reaction kettle, stirring, raising temperature to boiling under normal pressure and keeping a vent valve open for 2-4 minutes; (2) raising the temperature to 200-300 DEG C and hydrolyzing for 0.2-10 hours; and (3) cooling hydrolysis liquid and decompressing, steaming off water and organic acid under decompression, and then vacuum drying to obtain a solid polyvinyl alcohol product. The organic acid in the method is a green catalyst, and the addition of the organic acid can greatly improve the reaction velocity and reduce the polymer depolymerization so as to improve the quality of the product. Hydrolysis products can be used as fiber products such as civil clothing materials, industrial cord threads, filter screens, and the like, textile size, coatings, adhesive, paper making processing aids, packaging films, emulsifying agents, dispersing agents, oil drilling coagulant, soil improvement agents, medicine, cosmetics, and the like.

Description

technical field [0001] The invention relates to a method for preparing polyvinyl alcohol by hydrolysis of polyvinyl acetate under the catalysis of organic acid in high temperature liquid water. Background technique [0002] Polyvinyl acetate (PVAC) is also known as polyvinyl acetate. The molecular structure is (CH 2 -CH(OOCCH 3 )) n , An amorphous polymer obtained by polymerization of vinyl acetate, which is a thermoplastic resin. Depending on the polymerization method, colorless latex or colorless transparent bead solid can be obtained. Soluble in aromatic hydrocarbons, ketones, alcohols, esters and chloroform. Initiated by free radical initiators from vinyl acetate, it can be produced by emulsion, suspension, bulk and solution polymerization. Mainly used as coating, adhesive, paper, chewing gum base and fabric finishing agent. It can also be used as a raw material for polyvinyl alcohol and polyvinyl acetal. [0003] Polyvinyl alcohol (PVA) is a colorless and odorle...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C08F116/06C08F118/08C08F8/12
Inventor 吕秀阳张建飞刘体锋
Owner ZHEJIANG UNIV
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