SU475862A1 - The method of obtaining polyvinyl alcohol - Google Patents

Description

The invention relates to the production of polyvinyl alcohol with high color indices and can be used in the production of polyvinyl acetals, polyvinyl acetate dispersions, fibers, films that are subject to high optical requirements.

A method of producing polyvinyl alcohol by alkaline alcoholysis of a polyvinyl ester is known. However, the resulting product is highly colored, its aqueous solutions are rapidly exposed to microorganisms, which reduces its optical performance and narrows its scope.

The purpose of the invention is to prevent the coloring of the final product and the appearance of mold in its aqueous solutions and to simplify the regeneration of waste products.

This is achieved by treating the reaction mass after the end of alcoholysis with hydrogen peroxide.

Polyvinyl acetate, polyvinyl propionate, polyvinyl stearate, etc. are used as polyvinyl ester.

The most preferred content of hydrogen peroxide in the reaction mixture is 1–3% by weight of polyvinyl ether.

Example 1. (control). A 500 ml round-bottomed flask equipped with a stirrer, a reflux condenser, and a dispenser for polyvinyl ether are charged with 190 ml of methanol and 26.8 ml of a methanol solution of alkali with a concentration of 37.8%. After 10 minutes of stirring at 30-35 ° C, 351 g of a 28.2% metaiolic solution of polyvinyl acetate (PVA) is charged to the flask for 1.5 hours. Then (after holding for 30 minutes) a second portion of the alkali solution is loaded in a quantity of 13.4 ml.

The reaction is continued at 30-35 ° C for 30 minutes and at 56-58 ° C for 45 minutes.

The characteristics of the product obtained are as follows:

The content of residual ace0, 91 tatnyh groups,%

The viscosity of a 4% aqueous 5.3 solution;

Powder color

Cream

Chromaticity of 4% aqueous K ° 3 shkarastvora PVA ly nipp

Transparency,%

68 30

Whiteness

PR and ME 2. The process is carried out as in Example 1, but after completion of the alcoholysis reaction at 56-58 ° C, 7 ml of hydrogen peroxide (2% by weight of PVA) with a concentration of 28.5% are introduced. The reaction mixture is stirred for 30 minutes at 56-58 ° C. Product characteristics are as follows: Acetate content 1,2 groups,% Viscosity 4%, 5.6% solution, recourse Powder color white Chromaticity 4% -water No. % 72 Whiteness98 Example 3. (control). The process is carried out according to the conditions of Example 1, but ethanol is used for methanol. The characteristics of the product are given below: Content of acetate groups,% Viscosity of 4% solution, cps Color of powder Dark brown Chromaticity of 4% aqueous N °8 scale of solution solution Example 4. The process is carried out in the absence of hydrogen peroxide similar to measure 2, only instead methanol using ethanol. The characteristics of the product are as follows: Content: Acetate 3.5 groups,% Viscosity: 4%, 5% water; 5 ipacTBOpa; cmr Powder color; White Color of 4% water No. 1 solution scale; NIELP Example 5 (control). The process is carried out analogously to example 1, instead of PVA, nolivinylpropio is used. The characteristics of the product are given below: Acetate content of 1.5 groups,% Powder color Yellow The chromaticity of 4% aqueous AB 4 solution solution scale EXAMPLE 6 , but instead of PVA, polyvinyl propionate is used. The characteristics of the product are as follows: Acetate content of 1.8 groups,% Color of powder White Color of 4% water Afb About the scale of PPIIP solution Below are shown the properties of the obtained PVA rasters in terms of microresistance aldehyde content (examples 1-6). volume of 4% 7 90 5 120 8 45 aqueous solution of PVA to the effects of microorganisms, 24 hours a day of aldehyde 0.07 0.01 0.067 0.01 0.47 guides in PVA mother liquors,% Subject of the invention Method of obtaining polyvinyl alcohol by m alkaline alcoholysis of a complex of polyanil ether, characterized in that, in order to prevent the coloring of the end product of mold in its aqueous solutions and to simplify the regeneration of production outflows, the reaction mass after the end of the alcoholysis is treated by pereysyu hydrogen.