Method for preparing polyvinyl alcohol with low polymerization degree

A low degree of polymerization, polyvinyl alcohol technology, applied in the field of polyvinyl alcohol preparation, can solve the problems of increasing separation and recovery processes, large dithioethanol, environmental impact, etc., and achieves easy separation and recovery, low market price, and environmental impact. small effect

Inactive Publication Date: 2011-06-29
HUNAN XIANGWEI
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

If dithioethanol is used as the chain transfer agent, because dithioethanol is not easy to separate, it is necessary to increase the separation and recovery process, thereby increasing production costs, and dithioethanol has a large
[0012] Toxicity, has a great impact on the environment, and its stench will affect the sensory quality of the product
Therefore the operability, economy and practicability of the above-mentioned chain transfer agent need to be improved

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0018] Take 100g of vinyl acetate with a purity of 99.9%, and add 54g of methanol into a 400ml three-neck flask, then add 0.12g of azobisisobutyronitrile, stir in a water bath and heat to 62°C, add chain transfer agent acetaldehyde dropwise for 180min, and maintain polymerization Reaction 5h, stop the reaction.

[0019] Distill the product with methanol at about 75°C to remove vinyl acetate monomer to obtain polyvinyl acetate and methanol solution, add NaOH at 40-55°C for alcoholysis, last for 90min, stop the reaction, wash and dry, and polymerize the obtained product The degree is 300, and the polymerization rate is 89%.

Embodiment 2

[0021] Take 100g of vinyl acetate with a purity of 99.9%, and add 54g of methanol into a 400ml three-necked flask, then add 0.12g of azobisisobutyronitrile, stir in a water bath and heat to 62°C, add the chain transfer agent acetaldehyde dropwise, dropwise for 240min, and keep Polymerization reaction 5h, stop the reaction.

[0022] Distill the product with methanol at about 75°C to remove vinyl acetate monomer to obtain polyvinyl acetate and methanol solution, add NaOH at 40-55°C for alcoholysis, last for 90min, stop the reaction, wash and dry, and polymerize the obtained product The degree is 200, and the polymerization rate is 85%.

[0023] According to the comparison of Example 1 and Example 2, with the same reagent, increase the amount of chain transfer agent acetaldehyde and prolong the dropping time, the degree of polymerization of the product obtained decreases, and the polymerization rate is not much different, which shows that the use of this type of chain transfer ag...

Embodiment 3

[0025] Take 100g of vinyl acetate with a purity of 99.9%, add 25g of methanol into a 400ml three-necked flask, then add 0.08g of azobisisobutyronitrile, stir in a water bath and heat to 62°C, add chain transfer agent acetaldehyde dropwise, and drop 2- 5 drops, added dropwise for 150 minutes, maintained the polymerization reaction for 3 hours, and stopped the reaction.

[0026] Distill the product with methanol at about 75°C to remove vinyl acetate monomer to obtain polyvinyl acetate and methanol solution, add NaOH at 40-55°C for alcoholysis, last for 90min, stop the reaction, wash and dry, and polymerize the obtained product The degree is 380, and the polymerization rate is 76.5%.

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Abstract

The invention provides a method for preparing polyvinyl alcohol with low polymerization degree, which comprises: mixing a vinylacetate monomer and a methanol solvent in a mass ratio of (50-80):20, adding azodiisobutyronitrile serving as an initiator in an amount which is 0.05 to 0.5 percent based on the mass of the monomer, uniformly dripping aldehyde serving as a chain transfer agent in an amount which is 0.2 to 5 percent based on the mass of the monomer, and reacting for 2 to 5 hours at 50 to 71 DEG C to obtain polyvinyl acetate with low polymerization degree; dissolving the polyvinyl acetate in methanol to obtain polyvinyl acetate methanol solution at a concentration of 15 to 40 percent; and adding NaOH at 40 to 55 DEG C according to a NaOH to polymer molar ratio of 0.003 to 0.02, and performing alcoholysis for 10 to 90 minutes to obtain polyvinyl alcohol with low polymerization degree.

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. Background technique [0002] Polyvinyl alcohol is an important water-soluble polymer compound developed in the early 1950s. It is widely used in the production of fibers, and can also be used as chemical fiber fabric slurry, coating, adhesive, emulsifier, papermaking processing aid, etc. With the continuous development of science and technology, the demand for polyvinyl alcohol with different degrees of polymerization and alcoholysis is becoming increasingly urgent. From many studies at home and abroad, it can be seen that PVA products are developing towards high and low poles, that is, the degree of polymerization and the degree of alcoholysis are developing in two directions: higher and lower. These PVA products with different degrees of polymerization and alcoholysis have the characteris...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C08F118/08C08F2/38C08F8/00
Inventor 曾卫国李自启易重庆李泽武唐松乔朱泽礼肖勤建刘振辉肖平龚堃侯英杰
Owner HUNAN XIANGWEI
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