KR100789246B1 - Method for preventing rapid viscosity increase of polyvinyl alcohol - Google Patents

Abstract

The present invention comprises the steps of: a) dissolving a polyvinyl ester polymer in a mixed solvent consisting of 60 to 90% by weight of lower alcohol and 10 to 40% by weight of water; And b) advancing a saponification reaction by adding an alkali catalyst to the solution, thereby providing a method of preventing a sudden increase in viscosity of the polyvinyl alcohol. The production of polyvinyl alcohol using the method according to the present invention can prevent a sudden increase in viscosity and gelation of the polyvinyl alcohol prepared above, thereby limiting the selection of process conditions such as the shape of the agitator and the stirring speed. It can improve the workability in the subsequent molding step without causing.

Polyvinyl alcohol, saponification, polyvinyl ester, viscosity, gelling, mixed solvent

Description

Method for preventing rapid viscosity increase of polyvinyl alcohol

The present invention relates to a method for preventing a sudden increase in viscosity of the polyvinyl alcohol in the process of producing a polyvinyl alcohol by saponifying a polyvinyl ester polymer.

Polyvinyl alcohol is a unique polymer that is soluble in water. It was discovered by Herrman and Haehnel of Germany in 1924 and industrialized in Japan in 1948 after World War II and commercialized as a resin for textiles.

Polyvinyl alcohol (PVA) is a linear polymer containing a hydroxyl group (-OH) and has excellent solvent resistance and oil resistance. From these characteristics, it is easy to be formed into a film or fiber, has excellent surface properties, good mechanical and adhesive properties, has the properties of water-soluble polymers, and is biodegradable. It is widely used in adhesives, pharmaceuticals, and pharmaceutical polymers, and its use is expected to be more diverse in the future.

Polyvinyl alcohol cannot be manufactured by direct polymerization using monomers because of the tautomeric properties of vinyl alcohol monomers. It is dissolved in a solvent and saponified by adding a catalyst.

However, when the saponification reaction proceeds using the conventional method, there is a problem in that a gelation phenomenon occurs with a sudden increase in viscosity. The rapid viscosity rise and gelation phenomenon not only cause the selection of process conditions such as the shape and stirring speed of the stirrer in the process, but also lower the processability in the subsequent molding step.

The present inventors conducted a study to solve the problems of the prior art, effectively preventing the gelation phenomenon that occurs with the rapid increase in viscosity when using a solvent having a specific composition and composition ratio in the saponification of the polyvinyl ester-based polymer The present invention was completed by confirming that it can be done.

Accordingly, an object of the present invention is to provide a method of preventing a sudden increase in viscosity and gelation of the polyvinyl alcohol in the process of preparing a polyvinyl alcohol by saponifying a polyvinyl ester polymer.

In order to achieve the object of the present invention, the present invention comprises the steps of: a) dissolving a polyvinyl ester polymer in a mixed solvent consisting of 60 to 90% by weight of lower alcohol and 10 to 40% by weight of water; And b) adding an alkali catalyst to the solution to perform a saponification reaction to produce a polyvinyl alcohol, thereby providing a method of preventing a sudden increase in viscosity of the polyvinyl alcohol.

In the present invention, the polyvinyl ester polymer may be selected from the group consisting of polyvinylacetate, polyvinyl pivalate, polyvinyl formate and polyvinyl propionate.

In the present invention, the lower alcohol may be selected from the group consisting of methanol, ethanol, propanol and butanol.

In the present invention, the alkali catalyst may be sodium hydroxide or potassium hydroxide.

In the present invention, the polyvinyl ester polymer may be dissolved in 1 to 50 parts by weight based on 100 parts by weight of the mixed solvent.

In the present invention, the alkali catalyst may be added in an amount of 2 to 20 parts by weight based on 100 parts by weight of the polyvinyl ester polymer.

In the present invention, the temperature of the saponification reaction may be 30 ~ 60 ℃.

Hereinafter, the present invention will be described in more detail step by step.

The method of the present invention includes a) dissolving a polyvinyl ester-based polymer in a mixed solvent consisting of 60 to 90% by weight of lower alcohol and 10 to 40% by weight of water.

The polyvinyl ester-based polymer is not limited by its production method, molecular weight or stereoregularity, and includes all polyvinyl ester-based polymers. For example, the polyvinyl ester polymer may be prepared by conventional conventional methods such as bulk polymerization, solution polymerization, emulsion polymerization and suspension polymerization.

In the polymerization of the polyvinyl ester polymer, a known polymerization initiator such as 2,2-azobis isobutyronitrile, 2,2-azobis (4-methoxy-2,4-dimethylbareronitrile) benzoyl per Oxides, diisopropyl peroxy dicarbonate and the like can be used. The polymerization initiator may be generally used in an amount of 0.01 to 1.0% by weight based on the polyvinyl ester polymer.

The polyvinyl ester-based polymer may be selected from the group consisting of polyvinylacetate, polyvinyl pivalate, polyvinyl formate and polyvinyl propionate.

The lower alcohol may be selected from the group consisting of methanol, ethanol, propanol and butanol, for example. In terms of cost and solubility, methanol is preferred.

The mixed solvent according to the present invention used to dissolve the polyvinyl ester-based polymer consists of 60 to 90% by weight of lower alcohol and 10 to 40% by weight of water. In the case of using a mixed solvent of 90 to 100% by weight of lower alcohol and 0 to 10% by weight of water, there is a problem that a sudden increase in viscosity and gelation of polyvinyl alcohol prepared by saponifying a polyvinyl ester polymer occur. When using a mixed solvent of ~ 60% by weight of lower alcohol and 40-100% by weight of water, not only the solubility of the polyvinyl ester polymer is greatly lowered, but also the solubility of the produced polyvinyl alcohol is increased, resulting in precipitation of polyvinyl alcohol. There is a problem that cannot be recovered because it does not occur.

In the present invention, the amount of the polyvinyl ester-based polymer dissolved in the mixed solvent may vary depending on the molecular weight of the polyvinyl ester-based polymer, but the polyvinyl ester-based polymer is 1-50 to 100 parts by weight of the mixed solvent. It can be dissolved in parts by weight.

In addition, the method of the present invention includes the step of preparing a polyvinyl alcohol by b) adding a alkali catalyst to the solution to proceed with the saponification reaction.

The alkali catalyst may be sodium hydroxide or potassium hydroxide.

The alkali catalyst may be added in an amount of 2 to 20 parts by weight based on 100 parts by weight of the polyvinyl ester polymer. When the addition amount of the alkali catalyst is 2 parts by weight or less, the saponification reaction is too slow to produce a polyvinyl alcohol precipitate within 24 hours, if more than 20 parts by weight to increase the process cost by using an excessive amount of catalyst There is a problem. The addition of the alkali catalyst can be carried out with stirring.

The temperature of the saponification reaction may be 30 ~ 60 ℃. In addition, the saponification reaction may be carried out for 30 minutes or more, for example 40 to 120 minutes.

The production of polyvinyl alcohol using the method according to the present invention can prevent a sudden increase in viscosity and gelation of the polyvinyl alcohol prepared above, thereby limiting the selection of process conditions such as the shape of the agitator and the stirring speed. It is possible to improve the workability in subsequent molding steps without incurring this (see Table 5).

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are only intended to illustrate the invention, so the scope of the invention is not to be construed as limited by these examples.

<Example 1>

5 g of polyvinyl acetate, a polyvinyl ester polymer, was dissolved in a mixed solvent of 90 g of methanol and 10 g of water until completely dissolved at 60 ° C., and then lowered to 35 ° C., which is a saponification temperature, so that 0.15 g of sodium hydroxide, a saponification catalyst, was methanol. Dissolved in 20 g to proceed to the saponification reaction to prepare a polyvinyl alcohol.

<Examples 2 to 7>

A polyvinyl alcohol was prepared in the same manner as in Example 1, except for dissolving 5 g of polyvinyl acetate. The solvents used in Examples 2 to 7 were 85 g methanol and 15 g water mixed solvent, 80 g methanol and 20 g water mixed solvent, 75 g methanol and 25 g water mixed solvent, 70 g methanol and water 30, respectively. g mixed solvent, 65 g methanol and 35 g water, and 60 g methanol and 40 g water were used.

<Comparative Examples 1 to 14>

A polyvinyl alcohol was prepared in the same manner as in Example 1, except for dissolving 5 g of polyvinyl acetate. As a solvent used in Comparative Examples 1 to 14, a mixed solvent of 95 to 100 g of methanol and 0 to 5 g of water, and a mixed solvent of 0 to 55 g of methanol and 45 to 100 g of water were used.

The composition of the solvents used in Examples 1 to 7 and Comparative Examples 1 to 14 and the dissolution of polyvinylacetate are summarized in Table 1 below.

TABLE 1

Solvent composition Melting Methanol (g) Water (g) Comparative Example 1 100 0 O Comparative Example 2 95 5 O Example 1 90 10 O Example 2 85 15 O Example 3 80 20 O Example 4 75 25 O Example 5 70 30 O Example 6 65 35 O Example 7 60 40 O Comparative Example 3 55 45 O Comparative Example 4 50 50 O Comparative Example 5 45 55 X Comparative Example 6 40 60 X Comparative Example 7 35 65 X Comparative Example 8 30 70 X Comparative Example 9 25 75 X Comparative Example 10 20 80 X Comparative Example 11 15 85 X Comparative Example 12 10 90 X Comparative Example 13 5 95 X Comparative Example 14 0 100 X

<Example 8>

50 g of polyvinylacetate was dissolved in a mixed solvent of 90 g of methanol and 10 g of water until completely dissolved at 60 ° C., and then lowered to 35 ° C. of saponification temperature, and 1.5 g of sodium hydroxide, a saponification catalyst, was dissolved in 40 g of methanol. To proceed with the saponification reaction to prepare a polyvinyl alcohol.

<Examples 9 to 14>

Polyvinyl alcohol was prepared in the same manner as in Example 8, except that 50 g of polyvinyl acetate was dissolved. The solvents used in Examples 9 to 14 were 85 g methanol and 15 g water mixed solvent, 80 g methanol and 20 g water mixed solvent, 75 g methanol and 25 g water mixed solvent, 70 g methanol and water 30, respectively. g mixed solvent, 65 g methanol and 35 g water, and 60 g methanol and 40 g water were used.

<Comparative Examples 15 to 18>

Polyvinyl alcohol was prepared in the same manner as in Example 8, except that 50 g of polyvinyl acetate was dissolved. The solvents used in Comparative Examples 15 to 18 were mixed solvents of 100 g of methanol and 0 g of water, mixed solvents of 95 g of methanol and 5 g of water, mixed solvents of 55 g of methanol and 45 g of water, 50 g of methanol and 50 of water, respectively. g of mixed solvent was used. As in the results of Comparative Examples 5 to 14, when a mixed solvent having a water content of 55 g or more was used, polyvinylacetate could not be dissolved to produce polyvinyl alcohol.

The composition of the solvent used in Examples 8 to 14 and Comparative Examples 15 to 18 and the dissolution of polyvinylacetate are summarized in Table 2 below.

TABLE 2

Solvent composition Melting Methanol (g) Water (g) Comparative Example 15 100 0 O Comparative Example 16 95 5 O Example 8 90 10 O Example 9 85 15 O Example 10 80 20 O Example 11 75 25 O Example 12 70 30 O Example 13 65 35 O Example 14 60 40 O Comparative Example 17 55 45 O Comparative Example 18 50 50 O

<Example 15>

5 g of polyvinyl acetate, a polyvinyl ester polymer, was dissolved in a mixed solvent of 90 g of methanol and 10 g of water until it was completely dissolved, and then lowered to 35 ° C., a saponification temperature, and 1.0 g of sodium hydroxide, a saponification catalyst, was added to 20 g of methanol. Melt was added to proceed the saponification reaction to prepare a polyvinyl alcohol.

<Examples 16 to 21>

A polyvinyl alcohol was prepared in the same manner as in Example 15, except for dissolving 5 g of polyvinyl acetate. The solvents used in Examples 16-21 were 85 g methanol and 15 g water mixed solvent, 80 g methanol and 20 g water mixed solvent, 75 g methanol and 25 g water mixed solvent, 70 g methanol and water 30, respectively. g mixed solvent, 65 g methanol and 35 g water, and 60 g methanol and 40 g water were used.

<Comparative Examples 19 to 22>

A polyvinyl alcohol was prepared in the same manner as in Example 15, except for dissolving 5 g of polyvinyl acetate. The solvents used in Comparative Examples 19 to 22 were 100 g methanol and 0 g water mixed solvent, 95 g methanol and 5 g water mixed solvent, 55 g methanol and 45 g water mixed solvent, 50 g methanol and 50 water, respectively. g of mixed solvent was used. As in the results of Comparative Examples 5 to 14, when a mixed solvent having a water content of 55 g or more was used, polyvinylacetate could not be dissolved to produce polyvinyl alcohol.

The composition of the solvents used in Examples 15 to 21 and Comparative Examples 19 to 22 and the dissolution of polyvinylacetate are summarized in Table 3 below.

TABLE 3

Solvent composition Melting Methanol (g) Water (g) Comparative Example 19 100 0 O Comparative Example 20 95 5 O Example 15 90 10 O Example 16 85 15 O Example 17 80 20 O Example 18 75 25 O Example 19 70 30 O Example 20 65 35 O Example 21 60 40 O Comparative Example 21 55 45 O Comparative Example 22 50 50 O

<Example 22>

5 g of polyvinyl acetate, a polyvinyl ester polymer, was dissolved in a mixed solvent of 90 g of methanol and 10 g of water until it was completely dissolved, and then lowered to 55 ° C., a saponification temperature, and 0.15 g of sodium hydroxide, a saponification catalyst, was added to 20 g of methanol. Melt was added to proceed with the saponification reaction to prepare a polyvinyl alcohol.

<Examples 23 to 28>

Polyvinyl alcohol was prepared in the same manner as in Example 22, except for dissolving 5 g of polyvinylacetate. The solvents used in Examples 23 to 28 were 85 g methanol and 15 g water mixed solvent, 80 g methanol and 20 g water mixed solvent, 75 g methanol and 25 g water mixed solvent, 70 g methanol and water 30, respectively. g mixed solvent, 65 g methanol and 35 g water, and 60 g methanol and 40 g water were used.

<Comparative Examples 23 to 26>

Polyvinyl alcohol was prepared in the same manner as in Example 22, except for dissolving 5 g of polyvinylacetate. The solvents used in Comparative Examples 23 to 26 were 100 g methanol and 0 g water mixed solvent, 95 g methanol and 5 g water mixed solvent, 55 g methanol and 45 g water mixed solvent, 50 g methanol and 50 water, respectively. g of mixed solvent was used. As in the results of Comparative Examples 5 to 14, when a mixed solvent having a water content of 55 g or more was used, polyvinylacetate could not be dissolved to produce polyvinyl alcohol.

The composition of the solvents used in Examples 22 to 28 and Comparative Examples 23 to 26 and the dissolution of polyvinylacetate are summarized in Table 4 below.

TABLE 4

Solvent composition Melting Methanol (g) Water (g) Comparative Example 23 100 0 O Comparative Example 24 95 5 O Example 22 90 10 O Example 23 85 15 O Example 24 80 20 O Example 25 75 25 O Example 26 70 30 O Example 27 65 35 O Example 28 60 40 O Comparative Example 25 55 45 O Comparative Example 26 50 50 O

Comparative Example 27

5 g of polyvinyl acetate, a polyvinyl ester polymer, was dissolved in 100 g of methanol until completely dissolved at 60 ° C., and then lowered to 35 ° C., a saponification temperature, and dissolved in 0.05 g of sodium hydroxide, a saponification catalyst, in 20 g of methanol.

Experimental Example 1

The production or gelation of the polyvinyl alcohols prepared in Examples 1 to 28 and Comparative Examples 1 to 27 were observed. Whether or not polyvinyl alcohol was produced was confirmed by the occurrence of precipitates as the saponification proceeded, and the gelation was judged by the increase in the viscosity of the reactants and the occurrence of a phenomenon in which the reactants became a mass, and the results are shown in Table 5. It was.

TABLE 5

 Whether PVA is generated Gelation Comparative Example 1 O O Comparative Example 2 O O Example 1 O X Example 2 O X Example 3 O X Example 4 O X Example 5 O X Example 6 O X Example 7 O X Comparative Example 3 X X Comparative Example 4 X X

Table 5 (continued)

Whether PVA is generated Gelation Comparative Example 15 O O Comparative Example 16 O O Example 8 O X Example 9 O X Example 10 O X Example 11 O X Example 12 O X Example 13 O X Example 14 O X Comparative Example 17 X X Comparative Example 18 X X

Table 5 (continued)

 Whether PVA is generated Gelation Comparative Example 19 O O Comparative Example 20 O O Example 15 O X Example 16 O X Example 17 O X Example 18 O X Example 19 O X Example 20 O X Example 21 O X Comparative Example 21 X X Comparative Example 22 X X

Table 5 (continued)

 Whether PVA is generated Gelation Comparative Example 23 O O Comparative Example 24 O O Example 22 O X Example 23 O X Example 24 O X Example 25 O X Example 26 O X Example 27 O X Example 28 O X Comparative Example 25 X X Comparative Example 26 X X Comparative Example 27 X X

As shown in Table 5, when the amount of added catalyst was too small, no polyvinyl alcohol was produced even when the saponification reaction proceeded (see Comparative Example 27). In addition, in the mixed solvent of methanol and water, the gelation phenomenon occurs when the water content is too small, and the gelation phenomenon of the polyvinyl alcohol does not occur when the water content is too high, but precipitation does not occur to the extent that can be recovered.

According to the method according to the present invention from the results it can be confirmed that in the production of polyvinyl alcohol it is possible to prevent the sudden rise in viscosity and gelation of polyvinyl alcohol.

While the invention has been described in detail above with reference to the described embodiments, it will be apparent to those skilled in the art that various modifications and variations are possible within the scope and spirit of the invention, and such modifications and variations fall within the scope of the appended claims. It is also natural.

As described above, when the polyvinyl alcohol is prepared using the method according to the present invention, a sudden increase in viscosity and gelation of the prepared polyvinyl alcohol can be prevented, and accordingly, the form and stirring speed of the stirrer are processed. It is possible to improve the workability in the subsequent molding step without causing limitations in the selection of process conditions.

Claims (7)

a) dissolving the polyvinyl ester polymer in a mixed solvent consisting of 60 to 90% by weight of lower alcohol and 10 to 40% by weight of water; And b) preparing a polyvinyl alcohol by carrying out a saponification reaction by adding an alkali catalyst to the solution. Method of preventing a sudden increase in viscosity of the polyvinyl alcohol comprising a. The method of claim 1, The polyvinyl ester polymer is selected from the group consisting of polyvinylacetate, polyvinyl pivalate, polyvinyl formate and polyvinyl propionate. The method of claim 1, The lower alcohol is selected from the group consisting of methanol, ethanol, propanol and butanol. The method of claim 1, The alkali catalyst is sodium hydroxide or potassium hydroxide. The method of claim 1, The polyvinyl ester-based polymer is dissolved in 1 to 50 parts by weight based on 100 parts by weight of the mixed solvent. The method of claim 1, The alkali catalyst is added in an amount of 2 to 20 parts by weight based on 100 parts by weight of the polyvinyl ester polymer. The method of claim 1, The temperature of the saponification reaction is characterized in that 30 ~ 60 ℃.