DE2032175A1 - Process for the production of polyvinyl alcohol by hydrolysis of a polyvinyl ester - Google Patents

Description

HAN3 H. PONTANI Patent attorney 8752 Klelnosfheim be! Asdraffenburg Hirschpfad 3 - Tel. 06027/325

June 29, 1970

bu / HE - ■■■■■ '■■
BORDEN, INC., 350 Madison Avenue, New York, NY 10017 / USA

Process for the production of polyvinyl alcohol by hydrolysis of a polyvinyl ester

The invention relates to a process for the production of polyvinyl alcohol by hydrolysis of a polyvinyl ester · It consists in the fact that one at least about 25 #ige polyvinyl ester solution with a catalyst which is able to hydrolyze the ester, intimately mixed that one with the catalyst provided solution in elmHydrolysierzone passes that one the solution evenly on the surface of the solution provided with the catalyst, which was previously in the hydrolysis zone had been passed, applies, without mixing the two solutions, and that one to be hydrolyzed Solution through the hydrolyser zone in an evenly closed Flow (plug flow) passes without stirring.

Polyvinyl esters, such as polyvinyl acetate, are generally used as intermediates in the manufacture of polyvinyl alcohol . The polyvinyl ester is taken in a solvent

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Dissolved to form a varnish and then hydrolyzed with a suitable catalyst. For economic reasons, the concentration of the polyvinyl ester in the varnish should be as high as possible in order to optimize the throughput rate in the hydrolysis step and to reduce the costs for solvent recovery. The level of the varnish concentration to be used is limited in the case of the polyvinyl esters generally used in practice in that the varnish is characterized by a high solution viscosity which increases with the concentration and which must not exceed a certain critical tolerance limit because of the stirrer used. An upper limit on the solids concentration in the range up to about 25 wt .- ^ in commonly used varnish is typical of the production of usual grädigem polyvinyl alcohol having viscosities in the range of about 50 - ^r 100 cps at 20 ⁰ G 4 #iger aqueous solution * Attempts to increase the varnish concentration further in order to increase the throughput rate have not been successful, and even if one wishes to obtain a 25% by weight polyvinyl ester concentration it is common to polymerize vinyl ester at a conversion of 50 - 75 $> to terminate prematurely because the products with higher sales have too high a viscosity. Working with only partially converted polyvinyl ester, however, is costly because the unconverted monomer has to be recovered.

In the German patent application P 19 629 86.8 is. a procedure for the polymerization of vinyl esters for the production of

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Polyvinyl ester solutions have been suggested heretofore. The sera processes are used to produce polyvinyl ester solutions with their polyvinyl ester concentration twice as high as the "concentrations previously available in the industry. These esters can hydrolyzed to polyvinyl alcohols with a viscosity of 60-100 cps * Such polyvinyl esters and those that are usually produced at low solids concentrations Polyvinyl alcohols used are hydrolyzed either in batches or continuously been. However, these procedures were not entirely satisfactory In particular, the hydrolysis does not proceed uniformly and leads to non-uniform polyvinyl alcohols and difficulties in manufacturing such as cutting, grinding and drying the hydrolyzed ester. Furthermore requires the process for hydrolyzing polyvinyl ester, expensive equipment and numerous stages, reducing manufacturing costs can be increased considerably by polyvinyl alcohol. In particular, most of the known hydrolysis processes require learning heavy kneaders and / or masticators. Most importantly, the previous methods are handling require large volumes of polyvinyl ester solutions in order to obtain relatively small amounts of polyvinyl alcohol. In other words, it means that from 100 parts by weight Polyvinyl ester solution only about 10 parts by weight of polyvinyl alcohol.

can be obtained. Hit the after the procedure of the German Palest. tentapplication P 19 629 86.8V obtained polyvinyl alcohol

with a viscosity of 60 - 100 cpo to about 25 parts by weight

So far it has not been possible to obtain the yield in polyvinyl alcohol for all polyvinyl alcohol viscosity grades.

Surprisingly, there is now a process for the hydrolysis of Polyvinyl esters have been found, which can be carried out continuously and in which highly viscous polyvinyl ester solutions with a high solids content as well as with a low one Solids content can be used, and that to one substantially uniformly hydrolyze polyvinyl alcohol leads. The manufacturing cost of polyvinyl alcohol is high less than before.

In short, the present invention "consists of a polyvinyl ester in a method of hydrolyzing It involves the preparation of a polyvinyl ester having a solids concentration of at least about 25 * >> example, 25 -.? 60 ^c ß> and preferably about 35 - 50 ^L ß> ₉ and intimate mixing with a catalyst capable of hydrolyzing the ester, introduction of the solution provided with the catalyst into the hydrolyser, uniform application of the solution to the surface of the solution provided with the catalyst which had already been introduced into the hydrolysis zone beforehand. without mixing the two solutions, and moving the hydrolyzing solution through the hydrolyzing zone in an evenly blocked plus (plug flow) without stirring. In its preferred embodiment, the process is continuous.

Polyvinyl alcohol is .ir * allgoneinen by the tficltoeiiSt aeinor

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characterized aqueous solution "swar country through the 4 solution at 2O ⁰ C polyvinyl alcohols having a viscosity in the range of 50-125 cps are generally as." designates high vislcositätsgrädige polyvinyl alcohols "Those having a viscosity below 50 - 25 cps as" means viscosity Low viscosity levels and those with a viscosity of less than 25 cps are referred to as low ^{viscosity levels}

is
Erf present indungWur suitable preparation of polyvinyl alcohols of all three viscosity grade areas, whether the polyvinyl alcohols are completely or partially hydrolyzed.

Regarding the material to be used, it should be said that the polyvinyl ester used can be any ester which hydrolyzes to polyvinyl alcohol. Because of economical reasons polyvinyl acetate is preferably used; however, it is, for example, polyvinyl formate, polyvinyl propionate and polyvinyl butyrate or their mixtures are also suitable,

Bas when making the polyvinyl ester solution (or varnish) Solvents used can be any of the common alkanols be used for the production of polyvinyl ester solutions for hydrolysis can be used. Methanol is preferred; however, methanol, propanol and mixtures of methanol can also be used 20 "- 80 # methyl acetate can be used

There is an important aspect of the present invention in that ea is possible, the vinyl ester in solution up to

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polymerize complete or partial conversion, ma polymer solutions of a high viscosity with a high or Produce low solids content and use such solutions directly for the production of polyvinyl alcohol. So can the present process from the polymerization of the vinyl ester until hydrolysis is carried out continuously, * Complete conversion is preferred, since then the removal step of unreacted monomer (by stripping off the Solution) before adding ^ the catalyst and subsequent hydrolysis is not required.

The process is explained in the following drawing: The polyvinyl acetate solution used contained 35 parts by weight of acetate. The varnish 8 is continuously pumped into and through the mixer 10, where a catalyst solution is passed through a separate line 11 to and mixed with the varnish. The mixture obtained is continuously removed from the mixer 10 through a pipe 12 and passed into the hydrolysis vessel 13. Preferably, the Hydrolysiergefäß 13 is about 35 to 55 ° inclined from the horizontal and preferably about 40 to 50 ° .In the embodiment shown provides that hydrolyzes tube 13 is a tube having a uniform circular cross-section. The varnish is applied to the point A of the vessel 13 deposited. The point A is the point located at the substantially! Rate of fall in the trail of the varnish in the direction of the hydrolyzing varnish, which ensures _f that the varnish is distributed substantially uniformly over the surface of previously deposited varnish without NEN any -

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significant mixing of the two takes place. The varnish moves through the vessel 13 - and as it moves through it, the hydrolysis proceeds and the varnish gels to form a solid block 14. The inner or side walls of the vessel 13 are lined with a material 15 _9, the substantially any adhesion between AEEU surfaces of the vessel 13 eliminates "of the varnish and the block 14, coated or lined. This results in the block 14 advancing to the bottom end 16 of the vessel 13 where synchronized pullers 17 act to grip the moderately hard block and thereby help remove it from the vessel 13. The removal of the block 14 from the vessel 13 is coordinated with the rate of deposition of the varnish through the pipe 12 in such a way that the deposition point always remains at point A. It is understood that the varnish is filled into the vessel 13 at the beginning of the process is held while the bottom end 16, 16 is kept closed. As the hydrolysis proceeds and a solid block is formed, the bottom end 16 of the hydrolysing vessel is opened and the block removed, as noted above, to allow the varnish to be added at point A.

When the block 14 is removed, it is preferably separated into small units 17 by a cutting device 18 and the disc-shaped pieces 20 are roasted by a grinding device 19 grind to the desired size.

The gate parts, the kit .csc-r 7ϋ ± _: τ:? Πη dec IJ ^ ArolviL-rirvÄ-r / cOre- ,? '. "" jr.-r <"* ·] ρ

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vertical position also verimniegen simi? consist generally of more uniform hydrolysis, in obtaining a firm, uniform gel that is easier to handle. in purer polyvinyl · »alcohol solution properties in the ria for commonly used solvents and in a higher. bulk density»

The coating or liner 15 is a material that has a low affinity for polyvinyl alcohol such as polytetrafluoroethylene or polyethylene; but it is preferably a fluorinated ethylene-propylene polymer. Both "namely polytetrafluoroethylene and fluorinated ethylene-propylene resin are manufactured by du Pont de Nemours &Go" and referred to as Teflon TFE and Teflon PEP. The PEP contains tetrafluoroethylene polymerized with hexafluoropropylene. The coating 15 can be applied to the hydrolysis vessel 13 in a conventional manner. The entire vessel 13 can also be composed of such a viewing material. A standard casing can be used and, for example, use of about 70 mm thickness swar Iz & xm the coating or Piim to the interior of the Hydrolysiergefäßes 13 to line "with or without the use of adhesive agents and so as the coating or liner 15 »

Hydrolyzing means, as used here, that acyl groups of the polyvinyl esters are replaced by hydroxyl groups. The hydrolyzing can be carried out to the desired degree, cl.ji. for example '60' - 99%, by the usual known Ve.i'-i'ahren using v.'riase.i- _r βα & an acidif.oW3 Ιΰνϊ; ü ^ j

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BATH ORIGINAL

or suitable alcoholic © solvents, ie one-alkaline?.?.

carried out '

Catalyst contains Ywurdan »Suitable solvents for alkaline hydrolysing is · ': any common alcohol, but it is advantageous to use either methanol or mixtures of methanol with 20 - 80 # ethyl acetate, known under the trade name" Hethac " Use »Methanol mixtures with up to 40 μl of hexane can also be used. The alkaline catalyst is generally used in amounts between 0.5 and 5% by weight, based on the polyvinyl ester. A suitable alkaline catalyst is an alkali alkoxide. Others catalysts are alkali metal hydroxides. the preferred temperature for the hydrolysis varies swischen 20 and 55 ⁰ C. the catalyst in line 11, the drawing is preferably in a Natriumhydroryd

watery

50 ^ igenVXösiHig made with methyl alcohol to form a solution is mixed. The concentration of sodium hydroxide or other alkalis in the solution flowing through line 11, can be in a wide range, for example from 5 to 20 wt .- $ vary·

The invention is illustrated in more detail by the following examples.

With parts are meant parts by weight, if nothing to the contrary is specified.

example 1

A varnish was produced by dissolving fully reacted poly (vinyl acetate) granules in methanol, and a varnish with a solid acetate ingredient of 29%, a viscosity of

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1450OOcps and a water content of 4.5 #.

The varnish was in the apparatus, which is in the picture ^ z ic / t, liydrolyaiert. The vessel 13 was a tube with a diameter of 30.48 cm and a length of 365 * 76 cm with a surface coated on the inside with fluorinated ethylene-propylene polyamide ("ii · -?}. The vessel 13 was inclined at an angle of 45 °.

The varnish was placed in a blender with an aqueous sodium hydroxide solution (5 $> HaOH) in it at a rate of 0.0149 kg (0.033 pounds) of IaOH per 0.453 kg (pound) of polyvinyl. acetate was introduced and quickly incorporated into the varnish * The viscous mass was removed from the mixer and placed in the hy-

deposited drolysis pipe at a speed of 24.95 kg / min! the

The rate of bulk feed to the hydrolyzer tube has been set at the rate of removal of the hydrolyzed mass coordinated from the bottom of the pipe to secure the deposition of the mass * at point A of the attached figure.

Polyvinyl alcohol was pulled out of the pipe with the help of gravity and removed by pullers or rollers at a rate of 219.99 kg (485 pounds) per hour, cut and ground. The polyvinyl alcohol thus obtained had a viscosity of 64 cps and was uniform and complete hydrolyzed.

Example 2

The ancestors and eggs apparatus of Example 1 7 / uräen- / old uer except that the used% PoIyvinyXacetatjiörueir completely Tizagesetstes polyvinyl acetate used was "the nacli dam method eggs German patent application? IS 629 86.8 (Example 1} produced \ mräc .paa Bydrolyoiergefäß.war a _45:.? Tilted 37 0 cm to 43.18 cm rectangular tube deaasn Innorss bit ■ einem.-3 ilm of fluorinated Äthjrlen-Propylen.-Polymeriaat? au-.yg-a was dressed.

The varnish obtained had a solid acetate content of, a viscosity of 66,000 cps, and a water content of 6 ^c ß>. A composition was prepared by mixing a 5% sodium hydroxide solution with the varnish at a rate of 0.0181 kg (0.04 pounds) of sodium hydroxide solution per 0.4536 kg (pounds) of polyvinyl acetate.

The mass deposited in the hydrolyzing tube at one rate from 3β, 28 kg (80 pounds) per minute and that

became
Product Y is removed from the pipe at a rate of approximately 317.52 kg (700 pounds) per hour. The polyvinyl alcohol obtained was uniformly and completely hydrolyzed and had a viscosity of 65 cps.

A second sample was made using the same acetate hydrolyzer tube. The angle of the pipe and the pipe lining corresponded to the pipe used in Example 1. The varnish prepared had only one hard stof fgehs.lt of 34 ¹ / ".,

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The viscosity of this varnish was 33000 "cps and containing 5% of Lasser 'The mass Wirde under Yerv / sndung H & tr- ^ züeu ^ s" oei a speed τοπ O ₅ 0156 kg (0.03 pounds) ^^ i; hydroxide solution per 0.4536 kg (pound) acetate "manufactured Those deposition rate of the mass was 33.566 kg (74 pounds) per minute, and the rate of removal AEEA product from the tube was about 317.52 kg (700 pounds) per hour. The polyvinyl alcohol produced was uniformly and completely hydrolyzed and had a viscosity of 50 cps *

Example 3

Xn is a polymerisation fiber that is associated with

With a stirrer, thermometer and reflux condenser, softened water was added in an amount of 46.5 parts by weight and 0.330 parts of a 10% aqueous solution of 88% hydrolyzed vinyl alcohol. Stirring was started and the air was let through Nitrogen replaced by bubbling nitrogen under the liquid surface. 52.8 parts of vinyl acetate containing 5 parts per million hydroquinone were then added. The nitrogen addition was continued for 15 minutes. The nitrogen supply to the "reaction vessel was then straight over the surface the liquid relocated "Anschlies- send were" wet Benaoylperoxyd ", which contained 70 parts of benzoyl peroxide in 30 parts of water was added 0.212 parts perchlorethylene, 0.158 parts of hexadecene-1 and 0.066 parts; The reaction mixture was heated to reflux and maintained at a moderate reflux rate by either heating or cooling for 3% of the original requirement. After the temperature

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95 ° -0 had reached, the reaction temperature was maintained for 15 minutes and then reduced to 35 ^{0 C by cooling.} The polyvinyl acetate grains were separated from the water phase by centrifugation, washed and dried. Analysis indicated that vinyl acetate had converted to polymer of $ 98.5. Using the process of this example, low grain viscosities were obtained which, moreover, are essentially constant over a broad conversion range, but are slightly reduced from 35 to 30 cps in the range between 20 and 98.5% conversion.

The polyvinyl acetate of the present example was dissolved to 40 ^c ß> ■ ,, before 20,000 cps were obtained. The polyvinyl acetate was then hydrolyzed according to the procedure of Example 1 at a temperature of 35 ⁰ C (95 ° F) and there was obtained a polyvinyl alcohol containing the 1 # and the ash was hydrolyzed to $ 99>. The viscosities of the 4 # aqueous polyvinyl alcohol solutions were 93 ops.

The process of German patent application P 19 629 86.8 consists of polymerizing the vinyl ester to practically complete conversion in the presence of about O ₇ 05-1% by weight, based on vinyl ester, of a coast transfer agent and in the presence of 0.05-2 % By weight, based on vinyl ester, of a conditioning agent selected from the group of normal straight-chain oC-oils with about 10-20 carbon atoms. Chain transfer agents include tetrachlorethylene, carbon tetrachloride, otoff, acid aldshyd, tolaol and the like.

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Ala KonditioniertuagsiaittGl Isomman Dodecsn-l, Octadecon-l- "Hcixadecen ~ l and outer mixtures in embossing.

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- i

Claims (7)

-fs- Kly process for the production of polyvinyl alcohol by hydrolysis a polyvinyl ester, üadureil characterized that one produces at least about 25% polyvinyl ester solution, that one with this solution a catalyst that the ester au capable of hydrolyzing, intimately mixed that one with the Catalyst-provided solution in a hydrolysis zone passes that the solution evenly on a surface with the Solution containing a catalyst, which has already been that --.- lysing zone had been passed, and Vman applies the solution to be hydrolyzed in an evenly blocked flow (plug flow) moved through the hydrolysis zone without stirring. 2. The method according to claim 1, characterized in that the The hydrolysis zone is a tube at an angle of about Is inclined 35-55 °. 3. The method according to claim 1 or 2, characterized in that the walls of the hydrolysis zone with a fluorinated ethylene-propylene copolyniaren are coated or lined. 4. The method according to claim 1, characterized in that a polyvinyl ester _s. its ester is present in the solution at a concentration of at least about 25 #. Hit an oro catalyst that can hydrolyze the ester, Jioritinvir.rlich 009887/2038 and intimately mixed we & ₉ that the with the catalyst. see solution in a tubular hydrolysis zone _? c. which is inclined at an angle of 35 - 55 °, is directed that the solution is applied evenly to the surface of the solution ₉ provided with a catalyst, which had already been passed into the hydrolysis zone »and that the to be hydrolyzed © Solution is moved in evenly blocked flow (plug flow) through the hydrolysis zone without stirring, the surface of the hydrolysis zone © being lined with polymeric material so that the solution and the resultant hydrolysis product are not retained during passage through the hydrolysis zone. 5. The method according to claim 4 »characterized in that the polymeric surface lining made of fluorinated ethylene-propylene polymer consists. 6. The method according to any one of the preceding claims, according to the by hydrolysis of a practically completely polymerized Vinyl ester is a polyvinyl alcohol with a viscosity of 60-100 cps is produced,. marked by a) Polymerizing a vinyl ester monomer practically to complete conversion in the presence of about 0.05 to 1 wt .- ^, based on the vinyl ester, of a chain transfer agent and in the presence of about ¹ 0.05 to 2 # of a conditioning agent selected from the group normal straight-chain ci ~ 01efin® with about 10 - 20 carbon atoms? b) hydrolyzing the polyvinyl ester obtained in the form of a 009887/2038 BATH at least about 25 weight percent solution by intimate mixing this solution with a catalyst mixture in one Hy droly egg zone, evenly applying one with one Catalyst-provided mixture, which was previously in the Hydrolyser had been directed to the surface and agitating the au hydrolyzing mixture in uniform blocked flow (plug flow) through the hydrolysis zone without stirring. 7. The method according to claim 6, characterized in that the hydrolysis zone is a drill and that the pipe is at an angle is inclined from about 35 - 55 ° and that the walls of the hydrolyz « sierzone with a fluorinated ethylene-propylene-eopolymerisat are coated or lined 009887/2038 At. Blank page