KR101043464B1 - Method and apparatus for production of polyvinyl alcohol with high degree of saponification - Google Patents

Abstract

The present invention relates to a method for producing polyvinyl alcohol and an apparatus for manufacturing the same, and more particularly, in the production of polyvinyl alcohol through a saponification reaction of a polyvinyl ester solution and a catalyst mixture, a purification column is installed on top of a saponification reactor. A method and apparatus for producing polyvinyl alcohol capable of simultaneously performing saponification and by-product removal in a reactor.

According to the present invention, when saponification of the polyvinyl ester solution occurs, by completely removing the by-product alkyl acetate, a single reaction can yield a polyvinyl alcohol product having a very high degree of saponification of 99.9% or more, thereby greatly reducing the amount of solvent used. This can lead to a dramatic reduction in solvent recovery costs. In addition, since the amount of catalyst used can be significantly reduced, it is possible to manufacture a polyvinyl alcohol product having excellent whiteness.

Polyvinyl alcohol, saponification, purification column, by-product removal

Description

TECHNICAL AND APPARATUS FOR PRODUCTION OF POLYVINYL ALCOHOL WITH HIGH DEGREE OF SAPONIFICATION

1 is a view showing a preferred embodiment of the polyvinyl alcohol production apparatus according to the present invention.

2 is a view showing another preferred embodiment of the polyvinyl alcohol production apparatus according to the present invention.

* Description of Major Symbols in Drawings *

1: catalyst solution input line 2: polyvinyl ester solution input line

3: stirrer 4: reactor

5: Alcohol solvent / alkyl acetate azeotrope purification column

6: By-product Discharge Line 7: Neutralizer Input Line

8: Product Slurry Recovery Line 9: Fruit Supply Line

10: fruit recovery line 11: vaporized mixed solvent supply line

12: Three Way Valve 13: Refrigerant Supply Line

14: condenser 15: solvent drain line

16: reboiler 17: vaporized solvent feed line

18: solvent supply line

The present invention relates to a method for producing polyvinyl alcohol and an apparatus for manufacturing the same, and more particularly, a purification column is installed on top of a saponification reactor during saponification of polyvinyl ester to effectively remove alkyl acetate produced during the reaction in a small amount of the reactor. The present invention relates to a method for producing polyvinyl alcohol having a saponification degree of 99.9% or more as a saponification catalyst, and an apparatus for producing the same.

Polyvinyl alcohol (hereinafter referred to as 'PVA') discovered in 1924 by Hermann and Haehnel during saponification of polyvinyl acetate is a hydroxy group-containing linear produced by saponifying a vinyl ester-based polymer such as polyvinyl acetate. As a crystalline polymer, it has excellent solvent resistance and oil resistance. PVA is known to have a wide range of applications depending on molecular weight, degree of saponification, and stereoregularity ranging from gels, clothing or industrial textiles, separation filters and medical polymers.

Recently, studies on the manufacture and application of high value-added high functional PVA have been actively conducted. Due to the excellent optical properties of PVA, when the film is produced, it has excellent transparency and high birefringence when stretched, has been spotlighted as various optical polymer films, it is also used as a polarizing film for LCD. In order to be used for polarizing film, manufactured PVA should have high degree of polymerization and high degree of soap and high level of technology is required to meet these conditions. Only a few companies manufacture polyvinyl alcohol that can be used for polarizing film. I'm doing it.

On the other hand, PVA is not directly polymerized due to tautomerization of vinyl alcohol monomers, and is a continuous series of polyvinyl esters prepared after preparing polyvinyl esters by emulsifying, suspending and bulk polymerization of vinyl ester monomers, preferably vinyl acetate. This can be achieved through a batch or batch saponification process.

The most typical method of saponification reaction using polyvinyl ester is to completely dissolve polyvinyl ester in solvents of alcohols and then proceed with the reaction using strong acid or base as catalyst. As a by-product, alkyl acetate is produced by the number of moles of ester of the polyvinyl ester. As the concentration of the alkyl acetate produced increases, the rate of saponification decreases and the degree of saponification no longer improves due to the reaction equilibrium constant.

To solve this problem, U.S. Patent No. 6,800,687 uses two tower reactors and adjusts the pressure of the two reactors so that the pressure of the first reactor is kept lower than the pressure of the second reactor and the methanol vapor is added during the reaction. The present invention provides a method of improving saponification while using a small amount of catalyst when saponifying an ethylene vinyl acetate copolymer by stripping methyl acetate as a secondary reactant. However, this method requires two reactors, and since a large amount of methanol is used to strip methyl acetate as a by-product, there is a problem that the energy cost for methanol recovery is increased as well as the manufacturing cost due to the amount of methanol used.

In addition, U.S. Patent No. 6,743,859 uses a reactor equipped with a stirrer and a reactor in a tower form to perform a saponification reaction first in a reactor equipped with a stirrer, and then transfer to a tower type reactor for further saponification reaction. In the case of supplying a heat source to the tower-type reactor to remove the methyl acetate to provide a method for improving the degree of saponification. This method has the advantage of reducing the methanol consumption compared to the US Patent No. 6,800,687, but still requires a tower-type reactor and the loss of methanol as a solvent when methyl acetate is removed using a heat source There is a problem.

On the other hand, Korean Patent Laid-Open Publication No. 2005-0136273 provides a method of improving saponification by using two reactors equipped with a stirrer and removing a solvent between a first reaction and a second reaction. However, this method also requires additional reactors, and there is a problem in that an additional device for effectively removing the solvent and an increase in solvent consumption due to the secondary saponification reaction.

In other words, combining the prior art claiming that a high degree of saponification can be obtained, there are still common problems such as the need for an additional device, an increase in the amount of solvent used, and thus an additional energy cost in recovering the solvent.

In order to solve the problems of the prior art as described above, the present invention provides a high degree of saponification of 99.9% or more without additional equipment by effectively removing alkyl acetate which is a reaction by-product generated when polyvinyl ester is converted to polyvinyl alcohol and at the same time hinders saponification. Providing a method for producing a polyvinyl alcohol having excellent whiteness can be prepared and can be produced, PVA having a high purity, and can reduce the energy cost and solvent loss when recovering the used solvent with high purity. For the purpose of

In order to achieve the above object, the present invention

(a) introducing a polyvinyl ester solution and a catalyst into the reactor;

(b) saponifying the mixture including the polyvinyl ester solution and the catalyst in a reactor, and removing the alkyl acetate which is a reaction byproduct from the purification column attached to the top of the reactor;

(c) adding a neutralizing agent after the saponification reaction;

It provides a method for producing polyvinyl alcohol, comprising a.

In addition, the present invention in the polyvinyl alcohol production apparatus prepared by the saponification reaction of the polyvinyl ester solution and the catalyst mixture, a purification column for removing alcohol solvents and alkyl acetate azeotrope on the reactor in which the saponification reaction proceeds It provides a device for producing polyvinyl alcohol, characterized in that the mounting.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

In the present invention, the byproduct alkyl acetate is generated as the saponification reaction proceeds, and the reaction is simply expressed as in Scheme 1 below.

(In the above formula, OAc means an ester group (acetate), and R means an alkyl group determined by alcohol type.)

In the saponification reaction, one molecule of an ester of polyvinyl ester reacts with an alcohol which is a solvent and a reactant on a catalyst to be converted into an alcohol group, and an ester of one molecule is produced as a by-product. The equilibrium constant K of the reaction is represented by Equation 1 below. Is expressed.

Equilibrium constant K = [-OH] [ROAc] / [-OAc] [ROH]

(In the formula, [-OH], [-OAc] means the molar concentration of the alcohol group and the molar concentration of the ester group in the polymer chain, respectively.)

 The equilibrium constant K is constant when the temperature is constant, and as the reaction proceeds, [ROAc] increases, so that it is difficult to continuously increase the concentration of [-OH]. Thus, by removing [ROAc], the reaction equilibrium can be shifted to the right to improve [-OH]. Therefore, in the present invention, by installing a purification column on the top of the saponification reactor, there is a technical feature to effectively remove [ROAc] that hinders the rise of [-OH].

Hereinafter, the present invention will be described in detail according to the steps of the production method.

(a) mixing a polyvinyl ester solution and a catalyst

Step (a) is a step of mixing the polyvinyl ester solution with a catalyst required for the reaction.

Polyvinyl alcohol cannot be prepared by direct polymerization through vinyl alcohol monomers due to tautomerization of vinyl alcohol, and in general, polyvinyl alcohol can be produced by polymerizing vinyl ester monomers to produce polyvinyl esters and then saponifying. Can be. The polyvinyl ester solution of the present invention can be prepared by dissolving polyvinyl ester particles using an alcohol solvent, preferably methanol, or by solution polymerization of polyvinyl ester.

The polyvinyl ester solution preferably has a polyvinyl ester concentration of 3 to 50% by weight in the solution. The concentration is 3 If the content is less than% by weight, the viscosity is low, so it is easy to prepare polyvinyl ester solution and saponification reaction, but the amount of solvent used is very high, so the production cost of polyvinyl alcohol is increased, If the content exceeds 50% by weight, the viscosity of the polyvinyl ester solution rises rapidly, so that it is not easy to transport, and when the polyvinyl ester solution is prepared, the solute polyvinyl ester is not easily dissolved in the solvent methanol. There is an enormous time consuming problem.

The polyvinyl ester solution may include hydrogen peroxide solution or may be treated with ozone to improve thermal stability and color of polyvinyl alcohol, which is a product prepared by a saponification reaction before being stirred with a catalyst. By doing so, it is possible to prevent the double bond at the terminal of the polyvinyl ester from being formed as an aldehyde group when the saponification reaction proceeds, thereby lowering the thermal stability.

The catalyst may be a strong inorganic acid such as hydrochloric acid, sulfuric acid, phosphoric acid, or a base such as sodium hydroxide, sodium phosphate, methoxides, or the like, and it is preferable to use a base, more preferably sodium hydroxide. This is because the saponification reaction rate is very slow when the acid is used as a catalyst and the thermal stability is lowered, so that the color may be slightly lower than the polyvinyl alcohol prepared using the base.

The catalyst can be used in the form of a solution by mixing with water or alcohol solvents. The catalyst is preferably used in 0.01 to 10% by weight based on the content of the polyvinyl ester. If the content is less than 0.01% by weight, there is a problem that the reaction rate is very slow, and when the content is over 10% by weight, a large amount of salt is generated after neutralization, and a large amount of solvent is required at the time of washing. There is a problem of lowering the thermal stability of polyvinyl alcohol.

(b) saponifying the mixture including the polyvinyl ester solution and the catalyst in a reactor, and removing the alkyl acetate which is a reaction byproduct from the purification column attached to the top of the reactor;

The step (b) is a saponification reaction of the polyvinyl ester solution in a reactor equipped with a purification column, which is a production apparatus of the present invention, to efficiently remove the alkyl acetate which is the reaction by-product from the stirred mixture in step (a). It is a step of removing the alkyl acetate.

In the polyvinyl alcohol production apparatus, a purification column is installed at the top of the reactor to continuously remove alkylacetate, a reaction byproduct generated as the saponification reaction proceeds, during the reaction.

The purification column is a device for separating the azeotrope composition of the reaction product by-product alkyl acetate and the solvent alcohol may be used in the form of a packed column, multi-stage column or a mixture of multi-column and packed column, in the case of a multi-stage column Preference is given to columns having 50 stages at. If it is less than three stages, the separation of azeotrope is difficult, and a considerable amount of solvent is lost when removing the alkyl acetate, which makes it difficult to efficiently remove the alkyl acetate from the reactant. The amount of hold-up may be too large to increase the slurry concentration of the reactant, thereby causing a problem in that the stirring of the reactant is not smooth.

The saponification reaction is preferably a reaction temperature of -10 to 100 ℃, more preferably 35 to 70 ℃. If the temperature is less than -10 ℃, there may be a problem that the reaction rate is significantly reduced, if the temperature exceeds 100 ℃, the loss of sodium hydroxide catalyst is generated by the alkyl acetate formed during the saponification reaction of the polyvinyl ester required catalyst amount There may be a problem with this increase.

Operation of the purification column may be performed at the conversion stage at the beginning of the reaction, and then, after the column is heated, the reflux ratio may be adjusted to remove the alkyl acetate, or the alkyl acetate may be removed from the beginning of the reaction. If the column is operated from the beginning of the reaction, the column may not be preheated sufficiently, so the column may not operate properly. Therefore, it is preferable to remove the alkyl acetate by controlling the reflux ratio after the column is heated at the initial stage.

As another method of operation, the additionally equipped reboiler device can be used to raise the column through the heated pure solvent in the reboiler device, and after the temperature is raised to a predetermined temperature, the operation of the pure solvent is converted into the reaction mixed solvent. In this case, by-product alkylacetate may be removed from the beginning of the reaction.

(c) introducing a neutralizing agent

The neutralization of the polyvinyl alcohol slurry by adding a neutralizing agent after the saponification and purification of step (b) is completed.

The neutralizing agent may be selected according to the catalyst used, and when the catalyst is a base type, an acid type may be used, and when the catalyst is an acid type, a base type may be used.

The neutralizing agent may be used in an amount of 0.5 to 2 moles based on the content of the catalyst.

The prepared polyvinyl alcohol slurry may be prepared as polyvinyl alcohol final particles through dehydration, washing with water, rehydration and drying.

Hereinafter, with reference to the accompanying drawings to be described in more detail with respect to the apparatus for producing a polyvinyl alcohol of the present invention.

Figure 1 shows one embodiment of the apparatus for producing polyvinyl alcohol according to the present invention.

First, the polyvinyl ester solution and the catalyst are introduced into the polyvinyl ester solution input line (2) and the catalyst solution input line (1), respectively, and mixed using a stirrer (3) of a general type.

The mixture is subjected to a saponification reaction in a general jacketed reactor (4). Alkyl acetate generated during the saponification reaction is vaporized and moved to the alcohol solvent / alkyl acetate azeotrope purification column 5 through the mixed solvent supply line 11, separated, and then discharged by the by-product discharge line 6. At this time, the reactor serves as a reboiler of the purification column and operates in a conversion flow before the purification column is preheated, but when the temperature of the purification column reaches a steady state, a method of removing alkyl acetate by a by-product discharge line (6) is preferred. It is also possible to remove by-products.

The reactor 4 and the purification column 5 may be supplied with heat through the fruit supply line 9, and the fruit is drawn out through the fruit recovery line 10. The condenser 14 condenses using the refrigerant supplied through the refrigerant supply line 13.

After completion of the saponification reaction and purification, a neutralizing agent is added to the neutralizing agent input line 7 to neutralize the polyvinyl alcohol slurry liquid, and the obtained slurry is recovered to the polyvinyl alcohol slurry recovery line 8.

The recovered polyvinyl alcohol slurry can be dehydrated, washed with water and then dehydrated and dried to obtain final particles. When dehydration, the solvent mixed with salt does not have alkyl acetate, so a high purity solvent can be obtained using an evaporator.

Figure 2 shows another embodiment of the apparatus for producing polyvinyl alcohol according to the present invention.

In the case of FIG. 2, unlike FIG. 1, by first heating up the column using a pure solvent contained in the reboiler 16 attached to the column, when the column reaches a steady state, the reaction product is converted into a reaction mixture solvent, which is a by-product. It is characterized by the ability to remove alkyl acetates.

After confirming that the reboiler 16 attached to the column has sufficient solvent, operate the three-way valve 12 toward the reboiler 16 and heat the reboiler 16 with pure solvent. The azeotropic composition tablet column 5 is preheated. At this time, it operates by conversion flow. After the temperature of the column reaches the reaction operation temperature, the three-way valve 12 is operated toward the saponification reactor 4, and the polyvinyl ester solution and the catalyst are respectively added to the polyvinyl ester solution inlet line 2 and the catalyst solution inlet line ( 1) and mix using a stirrer (3) of the general form. The mixture may be subjected to a saponification reaction in a general jacketed reactor (4). Alkyl acetate, a by-product generated during the saponification reaction, is separated by an alcohol solvent / alkyl acetate azeotrope composition purification column 5 and then discharged by a by-product discharge line 6. In this case, the reactor serves as a reboiler of the purification column. After completion of the saponification reaction and purification, a neutralizing agent is added to the neutralizing agent input line 7 to neutralize the polyvinyl alcohol slurry liquid, and the obtained slurry is recovered to the polyvinyl alcohol slurry recovery line 8. The recovered polyvinyl alcohol slurry is dehydrated, washed with water and then dehydrated and dried to obtain final particles. When dehydration, the solvent mixed with salt does not have alkyl acetate, so a high purity solvent can be obtained using an evaporator.

Hereinafter, one preferred embodiment of a method for preparing polyvinyl alcohol for the purpose of understanding the present invention, but the following examples are merely to illustrate the present invention is not limited to the scope of the following examples.

[ Example ]

Example 1

200 kg of polyvinylacetate methanol solution having a concentration of 10% was introduced into a reactor equipped with a 10-column tray column shown in FIG. 1 and then stirred with sodium hydroxide at a weight ratio of 1: 0.001 with respect to polyvinylacetate as a catalyst. The saponification reaction was carried out at 70 ° C. for 2 hours. During the initial 30 minutes after the start of the reaction, the column was operated in inverted flow and the alcohol solvent / alkyl acetate mixture per hour was fed into the by-product discharge line while supplying heat at 110,000 kcal / hr per hour to the reactor. The reflux ratio was adjusted to 40 to 20 so that 5 kg was generated. After one hour and 30 minutes, the saponification reaction and the column operation were terminated, acetic acid and the same number of moles of acetic acid were added thereto, and stirred for 10 minutes to obtain a polyvinyl alcohol slurry after neutralization.

The obtained polyvinyl alcohol slurry was dehydrated using a centrifuge and washed with 100 kg of methanol. The washed polyvinyl alcohol slurry was dehydrated again by centrifugation and dried at 70 ° C. for 4 hours in a nitrogen atmosphere to obtain a polyvinyl alcohol product. The solvent mixture obtained by two dehydration was recovered using a high-purity methanol solvent using an evaporator.

Example 2

The polyvinyl alcohol product was obtained after the experiment under the same conditions except that 55,000 kcal / hr of calories per hour was supplied to the reactor during the saponification reaction in Example 1.

Example 3

200 kg of polyvinylacetate methanol solution having a concentration of 10% was introduced into a reactor equipped with a 10-stage tray column and a reboiler separately shown in FIG. 2, and then stirred with sodium hydroxide as a catalyst to polyvinylacetate as a weight ratio. 1: 0.05 was added and the saponification reaction was performed at 70 ° C. for 1 hour 30 minutes. The column was run in inverted flow with pure solvent for the first 30 minutes prior to the start of the reaction. At this time, the amount of heat supplied per hour was 110,000 kcal / hr. After 30 minutes, the three-way valve was operated toward the reactor and operated while controlling the reflux ratio from 40 to 20 to generate 5 kg of alcohol solvent / alkyl acetate mixture per hour as a by-product discharge line while supplying heat at 110,000 kcal / hr. After one hour and 30 minutes, the saponification reaction and the column operation were terminated, acetic acid and the same number of moles of acetic acid were added thereto, and stirred for 10 minutes to obtain a polyvinyl alcohol slurry after neutralization.

The obtained polyvinyl alcohol slurry after dehydration using a centrifuge

Washed with 100 kg of methanol. The washed polyvinyl alcohol slurry was dehydrated again by centrifugation and dried at 70 ° C. for 4 hours in a nitrogen atmosphere to obtain a polyvinyl alcohol product. The solvent mixture obtained by two dehydration was recovered using a high-purity methanol solvent using an evaporator.

[ Comparative example ]

Comparative example  One

200 kg of polyvinylacetate methanol solution having a concentration of 10% was added to a reactor without a column in FIG. 1, and stirred with sodium hydroxide as a catalyst so that the weight ratio was 1: 0.001 with respect to polyvinylacetate. The saponification reaction proceeded for a time. After completion of the saponification reaction, acetic acid and the same number of moles of acetic acid were added thereto, followed by stirring for 10 minutes to obtain a polyvinyl alcohol slurry after neutralization.

The obtained polyvinyl alcohol slurry was dehydrated using a centrifuge and washed with 100 kg of methanol. The washed polyvinyl alcohol slurry was dehydrated again by centrifugation and dried at 70 ° C. for 4 hours in a nitrogen atmosphere to obtain a polyvinyl alcohol product. The solvent mixture obtained by two times of dehydration is transferred to the same column as the alcohol solvent / alkyl acetate azeotrope purification column of FIG. Vaporization recovered the methanol solution to the top. At this time, 300,000 kcal of heat was supplied to the alcohol solvent / alkyl acetate azeotrope purification column, and the reflux ratio was operated at 66 for 1 hour 30 minutes.

Comparative Example 2

Polyvinyl alcohol was prepared in the same manner as in Comparative Example 1 except that sodium hydroxide was added in a weight ratio of 1: 0.03 to polyvinylacetate as a catalyst during the saponification reaction. The solvent mixture obtained by two dehydration was transferred to the same column as the alcohol solvent / alkyl acetate azeotrope purification column of FIG. Vaporization to recover the methanol solution to the top. At this time, 110,000 kcal of heat was supplied to the alcohol solvent / alkyl acetate azeotrope purification column, and the reflux ratio was operated at 36 hours for 1 hour 30 minutes.

Comparative Example 3

The polyvinyl alcohol slurry prepared in the same manner as in Comparative Example 2 was dehydrated in a centrifugal separator, and then polyvinyl alcohol was prepared in the same manner as in Comparative Example 2, except that 300 kg of methanol was used for washing. The solvent mixture liquid obtained by two times of dehydration collect | recovered the solvent using the method similar to the comparative example 2.

Physical properties of the polyvinyl alcohol prepared in Examples and Comparative Examples were measured by the following method and the results are shown in Table 1 below.

-Saponification degree (mol%): It measured based on JIS-K-6726.

-Whiteness: 100g of polyvinyl alcohol prepared is put into a blender, made into a powder form, and after making the same polyvinyl alcohol particle size in all experiments, it is observed and then white (white) ) As 5 and yellow as 1.

The energy costs, purity and waste used in solvent recovery in the examples and comparative examples are shown in Table 2 below.

-Solvent purity: The purity of methanol obtained at the bottom of the reactor or purification column is defined as follows.

Solvent Purity = Alcohol Solvent Amount / (Alcohol Solvent Amount + Alkyl Acetate Amount + Water Amount) * 100

-Lost solvent amount: Total amount of alcohol solvent discharged by the by-product discharge line

When comparing the apparatus of the present invention and the existing apparatus through Table 1, PVA having a high degree of saponification of 99.9% or more is produced even when a small amount of catalyst is used when the apparatus and the manufacturing method of the present invention are used. Despite the high catalyst usage, the degree of saponification is low. In addition, when the amount of washing methanol is the same, it can be seen that the whiteness was excellent when using this apparatus.

Looking at the solvent recovery side through Table 2, it can be seen that the use of the device and the manufacturing method of the present invention at the time of solvent recovery having a purity of 99% is significantly lower energy consumption than using the conventional method. In addition, in the case of the existing method, the amount of catalyst used is increased, and the amount of methanol used for washing is increased for the whiteness of the final product, and thus the energy cost at the time of solvent recovery is very high compared with the case of using the apparatus and manufacturing method of the present invention.

As described above, the present invention is equipped with a column capable of removing alkyl acetate in the saponification reactor has the effect of producing a PVA having a high saponification degree of 99.9% or more even with a small amount of catalyst. In addition, since a small amount of catalyst is used, a product having a high whiteness can be obtained only by washing in mild conditions, and the amount of solvent used as a whole can be greatly reduced, thereby reducing the solvent recovery cost, and saponification once. Since it is possible to obtain a high degree of saponification alone, there is an effect that can reduce the cost of the reactor apparatus.

Although described in detail above with reference to the specific embodiments of the present invention, it will be apparent to those skilled in the art that various changes and modifications can be made within the scope and spirit of the present invention, and such modifications and modifications belong to the appended claims. It is also natural.

Claims (13)

(a) introducing a polyvinyl ester solution and a catalyst into the reactor; (b) saponifying the mixture including the polyvinyl ester solution and the catalyst in a reactor, and removing the alkyl acetate which is a reaction byproduct from the purification column attached to the top of the reactor; And (c) adding a neutralizing agent after the saponification reaction; Method for producing a polyvinyl alcohol, characterized in that comprises a. The method of claim 1, The polyvinyl ester solution is a method for producing polyvinyl alcohol, characterized in that the concentration of the polyvinyl ester is 3 to 50% by weight. The method of claim 1, The polyvinyl alcohol solution is a method of producing polyvinyl alcohol, characterized in that the pre-treatment with hydrogen peroxide or ozone. The method of claim 1, The catalyst is a method for producing polyvinyl alcohol, characterized in that the acidic or basic solution. The method of claim 1, The content of the catalyst is a method for producing polyvinyl alcohol, characterized in that 0.01 to 10% by weight relative to the total content of the polyvinyl ester. The method of claim 1, The temperature of the saponification reaction is a method of producing polyvinyl alcohol, characterized in that -10 to 100 ℃. The method of claim 1, Removing the alkyl acetate which is the reaction by-product of step (b) is performed simultaneously with the saponification reaction or after the saponification reaction is carried out after the temperature of the column reaches the reaction temperature. . The method of claim 1, Method for producing a polyvinyl alcohol, characterized in that further comprising the step of dehydration, water washing, re-dehydration and drying for the polyvinyl alcohol slurry passed through step (c). In the manufacturing apparatus of polyvinyl alcohol produced by saponification reaction of a polyvinyl ester solution and a catalyst mixture, Apparatus for producing a polyvinyl alcohol, characterized in that the purification column for removing the alcohol solvent and alkyl acetate azeotrope on the reactor top is the saponification reaction proceeds. 10. The method of claim 9, The reactor is connected to the catalyst solution input line and the polyvinyl ester solution input line and the apparatus for producing polyvinyl alcohol, characterized in that the stirrer is installed. 10. The method of claim 9, The purification column is a packing tower, multi-stage column or a device for producing polyvinyl alcohol, characterized in that the mixture of these forms. The method of claim 11, The multi-stage tower is an apparatus for producing polyvinyl alcohol, characterized in that consisting of 3 to 50 stages. 10. The method of claim 9, The purification column is connected to the reboiler, the apparatus for producing polyvinyl alcohol, characterized in that installed so that the heated solvent is added to the purification column.

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