DE1025624B - Process for the production of polyvinyl alcohol - Google Patents

Description

The invention is concerned with the production of polyvinyl alcohol from polyvinyl esters of carboxylic acids especially by alcoholysis.

This saponification of polyvinyl esters is usually carried out in the presence of an acidic or alkaline catalyst carried out. Such catalysts can be hydrochloric acid or sulfuric acid or an alkali hydroxide or alkylate. However, it is difficult to carry out on an industrial scale.

If the saponification is carried out in the presence of water as hydrolysis of the ester, it is necessary to precipitate the polyvinyl alcohol formed from its aqueous solution, for example by adding larger Amount of ethyl alcohol, which reduces the solubility of polyvinyl alcohol in water. However, these are considerable Quantities of such a substance are required, and the success of the procedure also depends on the exact Check the temperature, the cooling speed and the agitation. The necessary separation of the Precipitant, which cannot be lost, causes additional costs.

If, on the other hand, the reaction is carried out as alcoholysis in a non-aqueous solution containing the alcohol required for this, the polyvinyl alcohol only separates out in powder form at the end of the reaction if a very dilute solution of the carboxylic acid polyvinyl ester is used as the starting point. In this case, large amounts of solvents are required, which for economic reasons must be recovered during manufacturing processes
of polyvinyl alcohol

Applicant:
Revertex Limited, London

Representative: Dipl.-Ing. H. Fecht, patent attorney,
Wiesbaden, Hohenlohestr. 21

Claimed priority:
Great Britain June 15, 1953

Clemens Bondy and Kurt Heiser, Harlow, Essex

(Great Britain),
have been named as inventors

The actual chemical conversion takes place in the solid phase (polyvinyl ester), in which the other two reactants Alcohol and catalyst have to diffuse in from the outside. Even if this is the case with this type of production because the solid phase is enveloped in a liquid phase, the disadvantage of difficult mechanical processing has been remedied, all the disadvantages of the

in relation to this, only small amounts of polyvinyl alcohol 30 solid phase are accepted, in particular be generated. poor mass transfer through diffusion, adsorption and

It is of course possible to use significantly less solvent, but then the polyvinyl alcohol will separate out not off. In this case it freezes

Withholding reaction products that affect the end product are alien. Since the reaction runs from the outside to the inside with each grain, the result is an incomplete reaction mixture to a gel which, as saponification progresses, becomes an inhomogeneous product. the Reaction hardened. Such a method requires invention is based on this known method Heavy machine equipment for mixing and through- for the production of polyvinyl alcohol from polyvinyl esters knead the reaction mass and also makes the exact of carboxylic acids by putting the ester in the presence of a Control of the degree of saponification difficult. Catalyst and an inert saturated aliphatic

It has already been proposed that the conversion of 40 hydrocarbons should be subjected to alcoholysis, of the polyvinyl ester of a lower aliphatic carbon- The method according to the invention, however, avoids one

acid in polyvinyl alcohol by means of alcoholysis and with the assistance of a catalyst in such a way that the polyvinyl alcohol in solid form, such as a powder

or semolina enters a liquid that is used for both the polyvinyl ester in methyl or ethyl alcohol alcohol required for alcoholysis - e.g. B. methyl dissolved, and the resulting solution is as a liquid phase alcohol - as well as an indifferent medium, which in a second liquid phase, namely in the saturated chemical does not interfere with the reaction process, polythene aliphatic hydrocarbon, emulsified or divinyl alcohol does not dissolve and polyvinyl ester practically does not dissolve and, at the same time, is subjected to alcoholysis; the and is at least partially miscible with methyl alcohol, 50 saturated aliphatic hydrocarbons being so ge

solid phase, without excessive amounts of alcohol that many times exceed the quantity required for alcoholysis to need. In the method according to the invention

z. B. light hydrocarbons in the form of certain petroleum fractions. In this case there is no homogeneous one System, but the reaction mixture consists of two phases, namely a solid and a liquid. Of the selects that it does not mix with the solvent substantially and has a different specific gravity than the solution; it is thereby possible in the context of the invention to pass the hydrocarbon through after the alcoholysis

709 908/446

3 4

Gravitational separation from the reaction mixture to esters of fatty acids that have more than 8 carbon atoms separate. and contain one or two free hydroxyl groups, poly-

The term polyvinyl alcohol should be used here and in ethylene glycols, condensation products of ethylene oxide The following refer to any product in which more than and organic acids, acid amides, amines, alcohols about 50% of the ester groups are saponified. These depending on 5 or phenols, abietic acid and its derivatives, poly type the implementation may only be incomplete methacrylic acid, partially acetalized polyvinyl alcohol constant saponification is often desirable, as for some and cellulose ethers. Of course, there are still number purposes an incompletely saponified or alcoholized rich other surface-active substances are available. Product versus the fully converted from tech- The process according to the present invention can be used in

is preferred for niche reasons. The termination of the presence of an acidic or an alkaline catalysis reaction can be done when working with two liquid tor.

Phases take place faster and more thoroughly than when working in the presence of an alkaline catalyst, such as

th with a solid and a liquid phase. Especially sodium or ivalium hydroxide or sodium or but you get a homogeneous product. Potassium methylate is the rate of reaction, however

In detail, the process according to the invention is significantly greater than in the case of an acidic catalyst. at as follows: After dissolving the polyvinyl ester using an alkaline catalyst, it is advisable to in a solvent that excludes moisture from the alcoholysis, as water is the catalyst The necessary methyl or ethyl alcohol exists and tends to inactivate it.

if necessary a diluent, e.g. B. methyl acetate, the catalyst can either be added to the reaction system

are containing the solution of the polyvinyl ester, which was also 20 i _n one portion or in more of the catalyst required successive added added in proportions such that the Katalysatorindifferenten liquid such. B. one of the mentioned concentration within suitable limits upright hydrocarbons, emulsified. The emulsion state is obtained before the catalyst is neutralized and is maintained during the alcoholysis. While this ends the reaction.

course of the reaction, any droplets of the poly 25 The catalyst concentration is advantageously zwivinylesterlösung see solidify separately for to a gel 0.05 ₀ and 5 ° and in the case of Natriumhydroxyds and eventually particles or granules of polyvinyl preferably between 0.2 and 1 ° ',,, based on the alcohol. The particles produced in this way can weight the polyvinyl ester solution.

quem are separated from the suspension medium. In the case of using other alkaline catalysts

The polyvinyl ester preferably used for the 3 ° gates, the preferred limits are the corresponding The practice of the invention is polyvinyl acetate and the stoichiometric equivalents of the above values. preferably used alcohol / ethyl alcohol. With the method described here, many things can be done

In the case, methyl acetate is a suitable diluent. Types of polyvinyl alcohol are made that are The liquid in which the solution of the polyvinyl ester differs by its molecular weight and content Is emulsified, must differ from the other constituents of the remaining polyvinyl acetate. The Mole Reaction Mixture, As already mentioned above, the chemical weight of polyvinyl alcohol depends on the molecular indifferent. It must be sufficiently viscous to withstand the weight of the polyvinyl acetate from which it is made Emulsify solution of the polyvinyl ester and was in the state. The level of residual polyvinyl acetate depends sufficient emulsification to be able to keep up each of the concentration of catalyst during the Droplets of the polyvinyl ester solution by itself solidified 40 reaction and depend on the length of time during which they and finally a particle or grain of polyvinyl is maintained.

alcohol forms. For this reason, the indifferent After the end of the alcoholysis, the polyvinyl

Liquid retain an appropriate viscosity, and alcohol from the reaction mixture through appropriate both in the presence of the reaction products as measures such as settling or filtering or also in the presence of the gravitational or centrifugal forces in the solution of the polyvinyl ester 45, any diluents used. The for this it is mostly to be established that the thus separated poly purpose Sufficient viscosity is greater than 15 centipoise of vinyl alcohol nor small amounts of the as suspension (cP) at reaction temperature. medium used indifferent liquid contains. In

If these conditions are met, the indifferent cases can be caused by treatment with the material Rent liquid, which serves as a suspending agent, is simply a solvent for the indifferent liquid in question can be recovered as they are cleaned separately. A preferred solvent for Phase forms which, at the end of the reaction mixture, is the treatment of polyvinyl alcohol. mixture is removed and after the separation without further of methyl alcohol and methyl acetate, as they are during Treatment can be reused as it forms before the reaction when this mixture is at or near mix remains unchanged. 55 their boiling point is used.

The indifferent for the purposes of the invention, this treatment is, however, more for a polyvinyl

Liquid liquids are effective in the chemical industry as alcohol, the polyvinyl acetate content of which is known as "white oils" (heavy liquid paraffins). Other than 15 ° '"is. If purified polyvinyl alcohol is to be produced from non-oxidable, chemically inert, viscous carbon less than 15 ° ^r ₀ polyvinyl acetate content, hydrogen oils are certain lubricating oils with a specific 60, it is usually preferable to fish in two or more stages, weighing from 0.85 to 0.92, preferably 0.87 to work.

0.89, at 20 ° C and a viscosity of 25 to 5000 cP, The in the first stage according to the above

preferably 120 to 500 cP, at 20 ° C. drive produced polyvinyl alcohol is then in a

To improve the state of the emulsion you can use the dilute solution of ivalium hydroxide or sodium reaction mixture Surfactants added- 65 hydroxyd suspended in methyl alcohol and the mixture which are either left in the indifferent liquid or at room temperature or elevated temperature, are soluble in the polyvinyl ester solution or in both. until further alcoholysis has taken place to the desired extent. Examples of surface-active substances that are suitable for the polyvinyl alcohols with less residual acetate

Purposes of the invention have proven to be useful, contents are produced more quickly if one works in two or more fatty acids with more than 8 carbon atoms, glycerol 70 even more stages. _s :

The invention is to be explained using the following examples:

example 1

41 kg of polyvinyl acetate (moisture content 1.5%, viscosity of the 8.6 percent by volume solution in dry benzene 7 cP at 25 ³ C) were dissolved in a mixture of 41 kg of methyl alcohol and 3.2 kg of methyl acetate. The solution was in a jacketed reaction vessel with a capacity of 120 1 with a multi-blade stirrer, which was operated at 400 rpm. ran.

While cooling water was running through the outer jacket of the reaction vessel, 6.8 kg of a solution containing 10 percent by weight sodium hydroxide in methyl alcohol were quickly added to the polyvinyl acetate solution and after ¹ 1/2

Mixing time of 1 minute 46 kg of Risella Oil 33 (a white oil from Shell Mex & BP Co. Ltd), which contained 110 g of stearic acid, was added to the reaction vessel over a period of 2 minutes. The reaction was left to itself for 1 hour, calculated from the time of the addition of sodium hydroxide, after which it was brought to a standstill by adding 195 ecm of glacial acetic acid.

The batch was then transferred to another vessel. There the risella oil rose and formed a cohesive layer that could be peeled off. After removing the oil including the portion included by the polyvinyl alcohol formed during the reaction and deposited on the bottom the solid residue was freed from the solvent. This solvent was redistilled. Of the The solid residue was then mixed with four portions of this redistilled solvent for half an hour each cooked.

After this treatment, the polyvinyl alcohol was completely drained of residual solvent in a dryer freed.

Example 2

41.5 kg of polyvinyl acetate (moisture content 1.75%, viscosity of the 8.6 percent by volume solution in benzene 12 cP at 25 ^:: C) were dissolved in a mixture of 27.5 kg of methyl alcohol and 19 kg of methyl acetate. 4.1 kg of a solution of 10 percent by weight sodium hydroxide in methyl alcohol were then mixed with the polyvinyl acetate solution in a steel vessel and with a 400 rpm. with constant stirring, 48 kg of Risella Oil 33 (a white oil from Shell Mex & BP Co. Ltd.) containing 170 g of dehydrated castor oil were added within

Added 2 minutes. The paraffin oil came from a similar previous batch and was saturated with the methyl alcohol-methyl acetate mixture that results from the reaction. The temperature of the reaction mixture was kept between 22 and 25 " C. After constant stirring for 32 minutes, the reaction was brought to a standstill by adding 350 ecm of glacial acetic acid, which was more than sufficient to neutralize the remaining sodium hydroxide catalyst made alkaline again by adding 100 ecm of a 15% strength methanolic ammonia solution. The crude polyvinyl alcohol obtained was purified in the manner described in Example 1 and contained 35% residual polyvinyl acetate. A 4.4% strength aqueous solution of the polyvinyl alcohol had a viscosity of 11 , 4 cP at 20 ^c C.

Example 3

In the same operation as in the previous example, 32 kg of polyvinyl acetate (moisture content 1.6%, viscosity of an 8.6 percent by volume solution in benzene 31.2 cP at 25 ^D C) together with 170 g of ethyl cellulose in a mixture of 35.5 kg of methanol and 20 kg of methyl acetate dissolved. 4.1 kg of a solution of 10 weight percent sodium hydroxide in methyl alcohol was stirred into the polyvinyl acetate and then 48 kg Risella oil 33. The temperature of the reaction mixture, which was initially 19 ° C, rose during the reaction at 24 ⁰ C. After 26 The reaction was interrupted for minutes by adding 250 ecm of glacial acetic acid. The resulting polyvinyl alcohol had a residual polyvinyl acetate content of 24.5% after cleaning. A 4.4% strength aqueous solution had a viscosity of 15.9 cP at 20 ° C.

Example 4

In the same operation as in the previous example, 41 kg of polyvinyl acetate (moisture content 2.4%, viscosity of an 8.6 percent by volume solution in benzene at 25 ° C. 11.2 cP) were dissolved in a mixture of 36 kg of methyl alcohol and 10 kg of methyl acetate. 4.1 kg of a solution of 10 percent by weight sodium hydroxide in methyl alcohol were mixed with the polyvinyl acetate solution and then 48 kg of Risella oil 33 (originating from a similar previous batch and saturated with the methyl alcohol-methyl acetate mixture present at the end of the reaction) were stirred in. The temperature at the start of the reaction was 20 ^; C. After 1 hour and 10 minutes, the reaction was terminated by adding 250 ecm of glacial acetic acid. The polyvinyl alcohol obtained was purified and had a residual polyvinyl acetate content of 23 ⁰ Z ₀ . A 4.4 ^0. ' ₀ ige aqueous solution had a viscosity of 9 cP at 20 "C.

Example 5

In the same operation as in the previous examples, 32 kg of polyvinyl acetate (moisture content 1.7%, viscosity of an 8.6 percent by volume solution in benzene 35 cP at 25 ° C.) were added to a mixture of 33.5 kg of methyl alcohol and 15.5 kg of methyl acetate solved. 3.6 kg of a solution of 10 percent by weight sodium hydroxide in methyl alcohol were stirred into the solution of the polyvinyl acetate and then 50 kg of Risella oil 33, which had been recovered from a previous, similar batch and with the methyl alcohol-methyl acetate mixture formed in the reaction were saturated. 110 grams of anhydrous castor oil was added to the Risella oil prior to mixing with the reaction batch. It took about 2 minutes to add the oil. After 30 minutes, another 1.8 kg of a solution of 10 percent by weight sodium hydroxide in methyl alcohol was added to the reaction mixture. After 68 minutes of uninterrupted stirring, the reaction was terminated by adding 130 ecm of glacial acetic acid. The resulting polyvinyl alcohol had after cleaning a residual polyvinyl acetate content of 20 ° Q ^1, and a 4.4% aqueous solution had a viscosity of 17.2 cP at ^20: C.

16 kg of the material prepared in this way were suspended in 35 kg of methyl alcohol containing 160 g of sodium hydroxide and placed in a reaction vessel with a slowly rotating lattice stirrer. The suspension was held at 52 ^: C for three hours. After cooling, the solution was neutralized by adding 30 ecm of glacial acetic acid and the polyvinyl alcohol was separated off from the solution by filtration. After drying, the material had a residual polyvinyl acetate content of 2.9%, and a 4.4% strength aqueous solution of the polyvinyl alcohol had a viscosity of 15 cP at 20 ^; C.

Example 6

250 g of polyvinyl acetate (moisture content 1.6%, viscosity of an 8.6% by volume solution in benzene 7.3 cP) were dissolved in 190 g of methyl alcohol and 20 g of methyl acetate. The solution was in a reaction vessel with a capacity of 11, which was equipped with a multi-blade stirrer, the with 600 rev / min. ran, was equipped. 40 g of a solution with 10 percent by weight sodium hydroxide in Methyl alcohol was stirred into the polyvinyl acetate solution and then 275 g of Caltex Regal Oil (from the Regent Oil Co. Ltd.) derived from a previous batch. The addition took about 1 minute. the The reaction was left to its own devices for 44 minutes and then terminated by adding 2 ecm of glacial acetic acid.

Example 7

225 g polyvinyl acetate (moisture content 0.3%, viscosity an 8.6 percent by volume solution in benzene (11.25 cP at 20 ° C.) was dissolved in 275 g of methyl alcohol. The solution was in a 1-1 reaction vessel that with multi-blade stirrer of 600 rev / min. was equipped. 25 g of a solution of 10 percent by weight sodium hydroxide in methyl alcohol was added to the polyvinyl acetate solution and then 275 g of Risella oil 33, the 1 g Contained anhydrous castor oil. The reaction was started after a duration of 52 minutes at 15 ° C. by adding 2 ecm of glacial acetic acid completed. The polyvinyl alcohol was made from the mixture of methyl alcohol-methyl acetate and Risella oil 33 separated and treated with six consecutive portions of a redistilled mixture from methyl alcohol-methyl acetate as obtained in the reaction, purified and finally dried. The remaining polyvinyl acetate content was 23.2%, and a 4.4% aqueous solution had one Viscosity of 8.2 cP at 20 ° C.

Claims (4)

Patent claims: 1. Process for the production of polyvinyl alcohol from polyvinyl esters of carboxylic acids by means of alcoholysis these esters in the presence of a catalyst and an inert saturated aliphatic hydrocarbon, characterized in that the polyvinyl ester is initially dissolved in a methyl or ethyl alcohol and emulsifying the obtained solution of the polyvinyl ester in the saturated aliphatic hydrocarbon or dispersed and subjected to alcoholysis, the saturated aliphatic hydrocarbon is chosen so that it does not substantially mix with the solvent and another specific one Has weight than the solution, and that the saturated aliphatic hydrocarbon after alcoholysis is separated from the reaction mixture by gravitational separation. 2. The method according to claim 1, characterized in that the basic liquid consists of a paraffin hydrocarbon with a specific gravity of 0.85 to 0.92, preferably between 0.87 and 0.89, at 20 ° C, and a viscosity of 25 to 5000 cP, preferably between 120 and 500 cP, at 20 ° C. 3. The method according to claim 1 or 2, characterized in that the reaction mixture has a surface-active Means is added. 4. The method according to any one of claims 1 to 3, characterized in that the reaction in a plurality of stages with intermediate separation of polyvinyl alcohol from the reaction mixture is carried out. Considered publications:
German patent specification No. 842 408. © 7OS9O8 / 446 2.58