DE1770580A1 - Process for the production of modified polyvinyl alcohols - Google Patents

Description

June 4, 1968 for patent application Fw Dp * Stk / schv

576O

Process for the preparation of modified polyvinyl alcohols

Ee is known. The use of polyvinyl alcohols for the production of polyvinyl alcohols in diapered form, and this use is increasingly being used. In addition to polyvinyl alcohols, modified polyvinyl alcohols are becoming increasingly important for the production of polymer dispersions. Modified polyvinyl alcohols suitable for dispersions are partially saponified polyvinyl alcohols with residual acyl contents of, for example, 10 or 25 % , which differ largely from the corresponding fully solidified polyvinyl alcohols in terms of their chemical and physical properties, such as solubility in water, viscosity of the aqueous solution Modified polyvinyl alcohols suitable for dispersions are also those products into which sulfo and / or aldehyde groups have been incorporated.

With these substances, which act as emulsifiers and protective colloids

and prevent sedimentation of the diapered nose

Obtain emulsions and dispersions with excellent stability and particularly valuable properties.

109845/1443

BATH ORIGINAL

17705 * 0

Modified polyvinyl alcohols containing aldehyde groups are generally prepared by acid-catalyzed transesterification of vinyl esters with the addition of small amounts of aliphatic aldehydes. During the transesterification reaction, an acetal mixture of the polyvinyl alcohol takes place at the same time. The acetal contents of the modified polyvinyl alcohols are generally between 1 and 10 %.

This process of producing the modified polyvinyl alcohols with acetal contents of up to 10 JL by means of catalyzed transesterification is, however, a technical one. senr au: 'wendijt and has some disadvantages: For example, only dilute alcoholic solutions of polyvinyl esters can be used. In addition, the acid-catalyzed transesterification requires very long reaction times of 13 to 25 hours. . ·

It has now been found that, surprisingly, the water-soluble modified polyvinyl alcohols with acetal contents Hs of 10 % can be produced in a particularly advantageous manner if concentrated suspensions of polyvinyl alcohols are used as starting materials and these polyvinyl alcohols are reacted in an acidic medium with aliphatic aldehydes in a heterogeneous reaction.

For this purpose, polyvinyl alcohols with? .B. K values (according to Fikentscher) of J50 to 90 are used, which were produced in a simple manner, for example by alkali-catalyzed transesterification, from polyvinyl esters, for example polyvinyl acetate, obtained by a suspension (pearl, block or solvent polymerization process) polyether are vinyl alcohols then by addition of suitable organic compounds in which polyvinyl alcohol is insoluble, manufactured concentrated suspensions, which up to 50% polyvinyl alcohol, preferably 15 to 25 't> t contain. as the organic compounds, for example alcohols or aliphatic and arjmatische hydrocarbons such as Methanol, ethanol, pentane, hexane, benzene, toluene, etc. The polyvinyl alcohols are reacted in a heterogeneous reaction • with aliphatic aldehydes with generally up to 6 carbon atoms, ¹ preferably with aldehydes with 2 or 4 carbon atoms The amounts of aldehyde used are generally between 1 and 10 pounds, but preferably between 3 and 7 pounds, based on the polyvinyl alcohol used

109845 / UA3 BAD original

hol crowd. Strong acids such as hydrochloric acid, sulfuric acid, oleum, perchloric acid, sulfonic acids are used for all catalysts, which are used in amounts of 3 to 8%, preferably 4 to 5%, based on the polyvinyl alcohol.

The process according to the invention can be carried out at temperatures between 0 and bO.degree. Reaction temperatures between 30 and VO ⁰ C are particularly favorable, since in this case the required reaction times are less than 3 hours. If the reaction temperature is below 50 ° C., the reaction rate is slower. At higher temperatures, e.g. above B ^ C, the reaction mixture begins to turn brown. ■

This process, the water-soluble modified polyvinyl alcohols with acetal contents of up to 10 ^ directly from polyvinyl alcohols To produce reaction with aldehydes in heterogeneous reaction has compared to the previously used acid-catalyzed process

FoIy

Transesterification of vinyl esters has considerable advantages:

The reaction takes place in concentrated suspensions, the required reaction times are short and are 2 to 3 hours. It can be used Any polyvinyl alcohol which has been prepared by one of known methods. The heterogeneous reaction takes place with a turnover of almost 100 pipers. As a result of the short reaction times, the reaction can be carried out continuously or discontinuously. This process is therefore technically very simple and particularly economical to carry out.

Example 1

The starting material used is a partially mixed polyvinyl alcohol with a residual acetyl content of 12% and a K value of 30, which was produced by alkali-catalyzed transesterification of polyvinyl acetate obtained by a block polymerisation process.

100.0 parts by weight of this polyvinyl alcohol are suspended in 300.0 parts by weight of benzene. This suspension is mixed with 20.0 parts by weight of 20 # aqueous perchloric acid and 6.5 parts by weight of acetaldehyde and heated 2.5 hours 65 ⁰ C. _v

After the reaction mixture has cooled down, the product is filtered off, washed with benzene and dried. "The modified polyvinyl alcohol obtained has an acetal content

from C, 3 to 6.5 %> 1Q4fiiC / iiii

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Game 2

A fully saponified polyvinyl alcohol is used with a K value of 60, the alkali-catalyzed transesterification of polyvinyl ester obtained by a solution polymerization process was produced.

Iige suspension produced Dieee suspension with ·;; from 100.0 parts by weight of this Polyvinylalcohols and 565 parts by weight of methanol, a 15 is ,, 'ό Gt w. parts 93 jL>' ir & T Schwof oleic acid? and mixed with 4.6 parts by weight of n-butyraldehyde and heated to 6C ⁰ C for 2 hours. After the reaction, the modified polyvinyl alcohol is filtered off, washed with methanol and dried.
The polyvinyl alcohol obtained has a content of 4.7 to

Example ^

a fully saponified polyvinyl alcohol rrii a ·. K value of YO used, the alkali-catalyzed transesterification from to polyvinyl acetate obtained from a bead polymerisation process was produced from bead polymer.

100.0 parts by weight of this polyvinyl alcohol are suspended in 5C5 parts by weight of ethanol. To this suspension, 5. Γ parts by weight of propionaldehyde and 4.5 parts by weight of Benzolsull'oneuure are added; then the batch is ^{heated to 70 °} C. for 2 hours. * After cooling down, the modified polyvinyl alcohol is filtered off,

washed with ethanol and dried.
• The product shown has an acetal content of 5.0 to 5.2 %. ·

BATH ORIGINAL

Claims (1)

- > -S-- 17705W Claim. '■ Process for the preparation of water-soluble modified polyvinyl alcohols with acetal contents of up to 10 % duroh conversion of polyvinyl alcohol with aldehydes in an acidic medium, characterized in that the reaction is carried out in a heterogeneous phase with polyvinyl alcohol in suspended form. BAD ORlGJNAt