Method of preparing vinyl alcohol with low degree of polymerization

A technology of low polymerization degree and polyvinyl alcohol, which is applied in the field of preparation of low polymerization degree polyvinyl alcohol and low polymerization degree polyvinyl alcohol, which can solve the problems of low production efficiency, increase and decrease of solvent methanol ratio, and achieve recovery The effect of small quantity and high production efficiency

Inactive Publication Date: 2007-10-17
ZHONGBEI UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0008] Although polyvinyl alcohol with a low degree of polymerization can be prepared by using a lower monomer-to-solvent ratio, or using chloroform as a molecular weight regulator, the degree of polymerization can generally only be reduced to about 500-600. If you want to further prepare polyvinyl alcohol with a lower degree of polymerization (50-300), it is impractical to simply reduce the proportion of monomers and increase the proportion of solvent methanol. Not only the recovery of solvent methanol The amount is too large, the production efficiency is too low, and the conversion rate of the monomer is too low, so it is not suitable for industrial production

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0022] Add 30g of vinyl acetate and 10g of methanol into a 250mL four-necked flask equipped with a stirrer, a thermometer and a reflux condenser, then add 0.06g of azobisisobutyronitrile, place the four-necked flask in a water bath, and heat it while stirring The temperature was raised to 70°C, 0.8 mL of dimercaptoethanol was added dropwise for 90 minutes, the polymerization was maintained for 3.5 hours, and the reaction was stopped. The polymer was slowly placed in water to form a film, and then vacuum-dried. The obtained polyvinyl acetate has a degree of polymerization of 66 and a yield of 73%.

[0023] Take 20g of polyvinyl acetate, break it into small pieces, put it into a 250mL four-neck flask, add 110mL of methanol, heat to dissolve the polyvinyl acetate, lower the temperature to 35°C, and add 2% methanol solution of sodium hydroxide dropwise over 30 minutes 12mL, maintain the alcoholysis time for 1.5h, stop the reaction, and dry the polyvinyl alcohol product after alcoh...

Embodiment 2

[0025] Add 20g of vinyl acetate and 8g of methanol into a 250mL four-necked flask equipped with a stirrer, a thermometer and a reflux condenser, then add 0.05g of azobisisobutyronitrile, place the four-necked flask in a water bath, and heat it while stirring The temperature was raised to 60°C, 0.3 mL of dimercaptoethanol was added dropwise for 60 minutes, the polymerization reaction was maintained for 3 hours, and the reaction was stopped. The polymer was slowly placed in water to form a film, and then vacuum-dried. The obtained polyvinyl acetate has a degree of polymerization of 264 and a yield of 76%.

[0026]Take 15g of polyvinyl acetate, break it into small pieces, put it into a 250mL four-neck flask, add 110mL of methanol, heat to dissolve the polyvinyl acetate, lower the temperature to 38°C, and add 1% methanol solution of sodium hydroxide dropwise over 30 minutes 20mL, maintain the alcoholysis time for 2h, stop the reaction, and dry the polyvinyl alcohol product after a...

Embodiment 3

[0028] Add 25g of vinyl acetate and 6g of methanol into a 250mL four-necked flask equipped with a stirrer, a thermometer and a reflux condenser, then add 0.05g of azobisisobutyronitrile, place the four-necked flask in a water bath, and heat it while stirring The temperature was raised to 65°C, 0.6 mL of dimercaptoethanol was added dropwise for 90 minutes, the polymerization reaction was maintained for 3 hours, and the reaction was stopped. The polymer was slowly placed in water to form a film, and then vacuum-dried. The obtained polyvinyl acetate has a degree of polymerization of 149 and a yield of 78%.

[0029] Take 15g of polyvinyl acetate, break it into small pieces, put it into a 250mL four-necked flask, add 110mL of methanol, heat to dissolve the polyvinyl acetate completely, cool down to 40°C, add 1.5% sodium hydroxide methanol solution 15mL dropwise over 30min , maintain the alcoholysis time of 2.5h, stop the reaction, and dry the polyvinyl alcohol product after the alc...

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Abstract

The invention relates to a method for producing low polymerization degree polyvinyl alcohol including: mixing the monomer vinyl acetate with solvent carbinol in a mass ratio of 60-80:20, adding ignition primer diisopropyl azodicarboxylate taking 0.1-0.5% of the monomer mass and chain transfer agent 2-mercaptoethanol taking 0.1-0.5% of the monomer mass, producing low polymerization degree polyvinyl acetate by solution polymerization method; dissolving the low polymerization degree polyvinyl acetate in the carbinol to get polyvinyl acetate carbinol solution, adding NaOH carbinol solution, alcoholysis to get low polymerization degree polyvinyl alcohol. The inventive method can produce low polymerization degree polyvinyl alcohol with a low polymerization degree of 50-500.

Description

technical field [0001] The invention relates to a method for preparing polyvinyl alcohol, in particular to a method for preparing polyvinyl alcohol with a low degree of polymerization. The preparation method of the invention can obtain polyvinyl alcohol with a degree of polymerization of 50-500. Background technique [0002] Polyvinyl alcohol (PVA) is an important water-soluble polymer, and its use is mainly divided into two aspects: fiber and non-fiber. The original use of polyvinyl alcohol was mainly for synthetic fibers, but in recent years, the role of polyvinyl alcohol has gradually developed in the direction of non-fiber, especially the high and low poles, that is, the degree of polymerization and the degree of alcoholysis have developed in two directions: higher and lower. . These polyvinyl alcohol products with different degrees of polymerization and alcoholysis have attracted people's attention because of their special properties, high added value and shortage. ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C08F116/06C08F118/08C08F8/00C08F2/38
Inventor 张巧玲程原谢龙
Owner ZHONGBEI UNIV
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