JP2544764B2 - Method for producing polyvinyl alcohol-based polymer with high degree of polymerization - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a method for producing a highly polymerized polyvinyl alcohol (hereinafter abbreviated as PVA) polymer. For more information,
Intrinsic viscosity obtained by emulsion polymerization is 1.5 dl / g or more, preferably greater than 3.2 dl / g High polymerization degree polyvinyl ester polymer has an intrinsic viscosity of 1.5 dl / g or more, preferably greater than 3.2 dl / g In obtaining a polyvinyl alcohol polymer having a high degree of polymerization, a polyvinyl ester polymer emulsion was mixed with methanol to obtain a substantially uniform solution, and the solution was continuously fed into a methanol bath together with a basic catalyst to obtain a final solution. The present invention relates to a method for producing a high-polymerization polyvinyl alcohol-based polymer having excellent solubility, which is characterized by saponifying so that the slurry concentration is 0.2% by weight or more and 10% by weight or less.

[Here, the intrinsic viscosity of the polyvinyl ester-based polymer is
The polyvinyl acetate polymer saponified and then reaceticated is defined as the value measured at 30 ° C. in acetone, and the intrinsic viscosity of the polyvinyl alcohol polymer is the polyvinyl alcohol polymer. Is defined as the value measured at 30 ° C. in acetone for polyvinyl acetate that has been re-acetylated.

B. Conventional technology PVA-based polymers have excellent interfacial properties and strength properties as a few crystalline water-soluble polymers, so
It is well known that it is used as a raw material for vinylon film and vinylon fiber, as well as being used as a stabilizer for fiber processing and emulsion.

However, the polymerization degree of the conventional PVA-based polymer is 2,000 as the upper limit, from the viewpoint of processing characteristics and ease of handling, and the fact that it is difficult to obtain a raw material polyvinyl acetate-based polymer having a high degree of polymerization. Only about 3000 special items are found.

On the other hand, rapid advances in processing technology in recent years have made it possible to process polymers having an ultra-high degree of polymerization, thereby succeeding in bringing out previously unknown physical properties. Even in the case of PVA-based polymers, by increasing the degree of polymerization, not only the physical properties in conventional applications are improved, but also new possibilities are expected in new fields such as high-strength fibers.

On the other hand, such a PVA polymer can be obtained by saponifying a polyvinyl ester polymer, especially a polyvinyl acetate polymer. The outline of the production process is [Production of polyvinyl acetate-based polymer → Preparation of polyvinyl acetate-based polymer in methanol solution → Saponification reaction → PVA]. As the saponification reaction, saponification rate, saponification degree control, A methanol decomposition reaction with a basic catalyst is usually adopted in consideration of the by-produced salt and the physical properties of the obtained PVA.

At the time of saponification, the most attention is paid to the problem of residual monomer and water. The former causes coloring of PVA,
The latter causes difficulties such as a decrease in saponification rate and an increase in the amount of required catalyst, resulting in an increase in the amount of salt produced as a by-product.

By the way, the saponification reaction of a polyvinyl acetate polymer is started by adding a basic catalyst to a methanol solution of a polyvinyl acetate polymer except in a very special case. This is because the saponification rate and the saponification degree can be controlled only when the catalyst is uniformly distributed over the whole, and the target PVA can be obtained without saponification unevenness. Therefore, when a polymerization method in a system in which a polymer is precipitated, for example, suspension polymerization or emulsion polymerization method is adopted, when the polyvinyl acetate polymer is taken out, it may be washed or dried for the above-mentioned reason. After sufficiently removing water and unreacted monomers, they are dissolved in methanol and flow to the process after saponification. Dissolving a squid polyvinyl acetate polymer in methanol becomes extremely difficult as the molecular weight increases, and it takes a lot of time to dissolve, which is a big problem.

The inventors of the present invention, as a method of overcoming the drawbacks of the process after the polymerization of the emulsion polymerization method, from the polyvinyl ester polymer emulsion, without separating and taking out the polymer, the emulsion of a specific particle size directly in a specific amount. We have already proposed a method to obtain PVA by pouring and dissolving it in methanol. (Japanese Patent Application No. 62-37155) By the way, the general process after the usual saponification reaction is [methanol solution preparation of polyvinyl acetate polymer → saponification reaction → pulverization → PVA]. In the case of a high degree of polymerization PVA polymer, it becomes difficult to dissolve it in water and an organic solvent as the degree of polymerization increases, so in order to obtain a high degree of polymerization PVA with excellent solubility, it is necessary to rely on pulverization by pulverization. Become.

A slurry saponification method is known as a method for obtaining a fine powder PVA-based polymer without requiring pulverization. However, when obtaining a methanol solution of a polyvinyl ester-based polymer from the emulsion polymerization method, water is mixed in the case of a polyvinyl ester-based polymer which is not a conventional high molecular weight, so that fine powder PVA-based polymer is obtained by the slurry saponification method. It is not possible.

C. Problem to be Solved by the Invention The present invention has an intrinsic viscosity obtained by an emulsion polymerization method of 1.5 dl / g or more, and preferably has a solubility from a high polymerization degree polyvinyl ester polymer of greater than 3.2 dl / g. , The intrinsic viscosity is 1.5d
An object of the present invention is to provide a novel production method that can be easily carried out on an industrial scale by overcoming the above-mentioned difficulties existing in producing a high-polymerization degree polyvinyl alcohol-based polymer having a l / g or more. .

D. Means for Solving the Problems The present inventors have found that the intrinsic viscosity obtained by the emulsion polymerization method is 1.5d.
l / g or more, preferably a highly polymerized polyvinyl ester polymer having an intrinsic viscosity of 1.5 dl / g or more, preferably more than 3.2 dl / g. As to the method for producing the above, as a result of diligent study, immediately after polymerization, the intrinsic viscosity was mixed with methanol without coagulating the polymer of the high-polymerization degree polyvinyl ester polymer emulsion having a polymerization degree of 1.5 dl / g or more. To obtain a substantially uniform solution, and the solution is continuously supplied into a methanol bath together with a basic catalyst, and saponification is performed so that the final slurry concentration is 0.2% by weight or more and 10% by weight or less. , The desired high degree of polymerization PVA with excellent solubility even without using the above-mentioned complicated technical means.
The inventors have completed the present invention by finding that a system polymer can be obtained very easily.

[Here, the intrinsic viscosity of the polyvinyl ester-based polymer is
The polyvinyl acetate polymer saponified and then reaceticated is defined as the value measured at 30 ° C. in acetone, and the intrinsic viscosity of the polyvinyl alcohol polymer is the polyvinyl alcohol polymer. Is defined as the value measured at 30 ° C. in acetone for polyvinyl acetate that has been re-acetylated. ] The production method of the present invention will be described in detail below.

The most important feature of the production method of the present invention is that the intrinsic viscosity obtained by emulsion polymerization has the intrinsic viscosity of 1.5 dl / g or more, preferably
From a high degree of polymerization polyvinyl ester-based polymer greater than 3.2 dl / g, especially polyvinyl acetate-based polymer emulsion, the intrinsic viscosity according to the above definition is 1.5 dl / g or more, preferably greater than 3.2 dl / g of solubility. In order to obtain an excellent high degree of polymerization PVA, the most problematic process in terms of time and energy, that is, the process of grinding in the case of normal saponification, and the process of removing water in the case of slurry saponification, To obtain a high degree of polymerization PVA with excellent solubility.

The emulsion obtained by the emulsion polymerization method is composed of water, a polymer, a monomer, a stabilizer, etc., and after removing unreacted monomers by distillation from a substantially homogeneous methanol solution obtained by mixing with methanol, polyvinyl Water is present in the methanol solution of the ester polymer.

Ordinary slurry saponification is difficult in a water-containing system, but in the present invention, surprisingly, a methanol solution containing 2 times as much water as the high-polymerization degree polyvinyl ester polymer is present together with a basic catalyst in methanol. It is continuously fed into the bath, and the final slurry concentration is 0.2 wt% or more, 10 wt%
Below, more preferably 0.5% by weight or more and 8% by weight or less, the resulting PVA-based polymer does not agglomerate into "Mamako", and becomes a slurry state very easily, and a high degree of polymerization PVA is obtained. I was able to do it.

If the intrinsic viscosity of the polyvinyl ester-based polymer is less than 1.5 dl / g, the PVA-based polymer produced will be aggregated to become "Mamako", and it will not be in a clean slurry state. It is necessary and not preferable.

If the final slurry concentration is less than 0.2% by weight,
Although there is no problem in the solubility of the high-polymerization degree polyvinyl alcohol-based polymer, it is not preferable because the slurry concentration becomes low and thus the subsequent processability becomes poor.

When the final slurry concentration is higher than 10% by weight, the PVA-based polymer produced is aggregated into "Mamako", and the desired slurry state is not seen.

As described above, in the present invention, the high-polymerization degree polyvinyl ester polymer emulsion is directly added to and dissolved in methanol to continuously dissolve it in a methanol bath together with a basic catalyst without removing water in the system more than necessary. It is characterized by obtaining a high degree of polymerization polyvinyl alcohol-based polymer having excellent solubility, the properties of the emulsion used are not particularly limited, but from the viewpoint of high quality and high degree of polymerization PVA production,
As a stabilizer, a low-molecular-weight surfactant, that is, a nonionic surfactant, a nonionic-anionic surfactant, or an anionic surfactant is preferably used, and the polymerization rate of the vinyl ester is 95% or less, preferably 90% or less,
It is more preferably 80% or less.

Examples of polyvinyl ester polymers include polymers such as vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, and the like, with vinyl acetate polymers being particularly preferred.

Further, it may be a copolymer obtained by copolymerizing the above vinyl ester monomers with a copolymerizable monomer, and examples of these monomers include (meth) acrylic acid, (meth) acrylic acid ester, itaconic acid or Examples thereof include esters thereof, maleic acid esters or maleic anhydride, (meth) acrylamide or derivatives thereof, vinyl chloride, vinyl fluoride, vinylidene chloride, vinylidene fluoride, acrylonitrile, vinylalkoxysilane and the like.

The production method of the present invention can be applied to the production of a highly polymerized PVA polymer having an intrinsic viscosity of 1.5 dl / g or more, but especially from a highly polymerized polyvinyl ester polymer emulsion to a highly polymerized PV.
It is effective for obtaining A-based polymer and has an intrinsic viscosity of 3.2 dl
Particularly effective in the case of high polymerization degree PVA of more than / g.

Further, in order to obtain a high degree of polymerization PVA, it is desirable that the polyvinyl ester polymer emulsion is obtained by emulsion polymerization in a mixed medium of water and methanol. The mixing ratio of water and methanol is by weight. It is desirable that

Examples of the basic catalyst used in the present invention include sodium hydroxide, potassium hydroxide or sodium methylate, potassium methylate, sodium ethylate and the like.

Further, in the present invention, the particle size of the high degree of polymerization PVA powder is 16 mesh or less, more preferably 60 mesh or less. If it is larger than 16 mesh, it takes time to dissolve, which is not preferable.

E. Action and effects of the invention The present invention is a polyvinyl ester polymer emulsion having a high degree of polymerization of 1.5 dl / g or more obtained by emulsion polymerization, and has an intrinsic viscosity of 1.5 dl / g or more with excellent solubility. In order to obtain a high degree of polymerization PVA, the process that has the most problems in terms of time and energy, that is, the process of grinding in the case of normal saponification and the process of removing water in the case of slurry saponification To provide a process for obtaining a highly polymerized PVA having a high degree of polymerization, which is a highly polymerized polyvinyl ester polymer emulsion directly mixed with methanol to obtain a substantially homogeneous solution, which is then added to a methanol bath. It was achieved by continuously feeding with basic melting and saponification so that the final slurry concentration was 0.2% by weight or less than 10% by weight.

The production method of the present invention has an intrinsic viscosity of 1.5 dl / g or more and is applicable to the production of an excellent highly polymerized PVA-based polymer having a high solubility, but the intrinsic viscosity is particularly 3.2 dl / g or more of the solubility. It is more effective for obtaining an excellent super high degree of polymerization PVA polymer.

Further, PVA-based polymer having a high degree of saponification is usually difficult to dissolve, but the PVA-based polymer having a high degree of saponification and a high degree of polymerization obtained by the production method of the present invention is a porous powder, and thus is dissolved. Is easy. In particular, the effect is remarkable when the saponification degree is 99.9 mol% or more.

Further, in the present invention, since water from emulsion is present in the methanol solution, stabilizers, by-produced salts, etc.
Impurities brought into the system polymer are effectively washed by the presence of water.

The PVA thus obtained can be used in conventional fields of application, and the high degree of polymerization PVA effectively obtained in the present invention is suitable as a PVA high strength sheet or PVA high strength fiber. Is used.

Hereinafter, the present invention will be described in more detail with reference to Examples.
The present invention is not limited thereby. In addition, "%" and "parts" in the examples are both "% by weight"
And "parts by weight".

Example 1 300 parts of ion-converted water, 300 parts of vinyl acetate, 100 parts of methanol, polyoxyethylene [POE (50)] nonylphenyl ether (in a reactor equipped with a stirrer, a thermometer, a nitrogen introducing tube and a cooling tube) Nonipol 500, manufactured by Sanyo Kasei Co., Ltd. 1
2 parts, 0.01 parts of FeSO ₄ 7H ₂ O, and 0.23 parts of Rongalit were weighed and boiled for 30 minutes, then cooled to −20 ° C. while introducing nitrogen, and separately adjusted with degassed ion-exchanged water 0.014% Polymerization was started while continuously adding hydrogen peroxide solution of 7 parts / hr uniformly. During the polymerization, the system was sealed with nitrogen gas to prevent oxygen from entering. After 2.5 hours, when the polymerization rate reached 50%, the addition of hydrogen peroxide was stopped, and then 0.5% was added.
Stirring was continued for a while to terminate the polymerization.

The emulsion obtained here was treated with methanol 1300 at room temperature.
0.5 parts of hydroquinone monomethyl ether was dissolved in 1 part (methanol / polymer = 20) and gradually added with stirring to dissolve, to obtain a substantially uniform solution.

Then, unreacted vinyl acetate monomer was removed under reduced pressure while adding methanol to obtain a water-containing methanol solution of polyvinyl acetate. (Polymer concentration 7.3%, water concentration 8.8%) Take a part of this solution and concentrate it at 5%, [NaOH] / [VA
c] (molar ratio) = 0.1, saponification at a temperature of 40 ° C, and 0.1 part of the obtained polyvinyl alcohol (PVA) is re-mixed in a mixed solution of 8 parts of acetic anhydride and 2 parts of pyridine at 105 ° C for 20 hours with occasional stirring. The intrinsic viscosity of polyvinyl acetate, which was acetylated and repeatedly purified by reprecipitation with an acetone-ether or acetone-water system, was measured at 30 ° C. in acetone. As a result, [η] = 4.20
(Dl / g). (Measurement by the dilution method using an Ubbelohde type viscosity tube) Next, 200 parts of methanol was charged in advance in a glass reaction vessel equipped with a stirrer and a cooling tube, and then the reaction vessel was cooled to 67%.
It was immersed in a constant temperature bath at ℃. Then, a water-containing methanol solution of the above-mentioned polyvinyl acetate (polymer concentration 5%, water concentration 6
%) 500 parts of a 7% methanol solution of sodium methylate and 100 parts of 7% methanol solution were continuously charged for 2 hours to carry out a saponification reaction. The obtained PVA slurry (final slurry concentration: 1.6%) was filtered through a glass filter, neutralized with acetic acid, and washed twice with 300 parts of methanol.

Then, it was dried in a drier at 40 ° C for 5 hours to obtain white fine powder.
I got PVA. The saponification degree was measured and found to be 99.7 mol%. Also. When the particle size was measured, all were 32 mesh or less, and 60% were fine powder PVA having 100 mesh or less.

This fine powder PVA was reacetated under the same conditions as above, and polyvinyl acetate which had been repeatedly reprecipitated and purified in the same manner as above, in acetone, when the intrinsic viscosity was measured at 30 ° C.,
[Η] = 4.20 (dl / g).

Furthermore, this fine powder has a high degree of polymerization PVA of 60 mesh or less, 1
When 1 part of 00 mesh or more and 100 parts of water were heated and stirred at 93 ° C., PVA disappeared after 5 minutes and a uniform solution was obtained.
Similarly, when 2 parts of the PVA and 100 parts of water were heated and stirred at 93 ° C., a uniform solution was obtained after 8 minutes.

Comparative Example 1 Polyvinyl acetate water-containing methanol solution of Example 1 (polymer concentration 7.3%, water concentration 8.8%, intrinsic viscosity [η] = 4.20
dl / g) at 40 ° C under [NaOH] / [VAc] (molar ratio) = 0.1
The saponification reaction was carried out under the condition of 5. The obtained gel-like PVA having an intrinsic viscosity [η] = 4.20 dl / g (measured for re-acetylated polyvinyl acetate) was pulverized and filtered, then similarly neutralized with acetic acid and washed twice with methanol. Then, it was dried in a drier at 40 ° C. for 5 hours to obtain PVA as a white powder. The saponification degree was measured and found to be 99.5 mol%.

Further, when a dissolution test was carried out in the same manner as in Example 1 for the fine powder high polymerization degree PVA of 60 mesh or less and 100 mesh or less, it took 10 minutes to dissolve when 1 part of PVA and 100 parts of water were used. And 2 parts of PVA and 100 parts of water dissolve 1
It took 5 minutes.

Comparative Example 2 A saponification reaction was carried out in the same manner as in Example 1 using a water-containing methanol solution of polyvinyl acetate having an intrinsic viscosity [η] = 0.84 dl / g (polymer concentration 30%, water concentration 10%). However, it was impossible to obtain a slurry of PVA because PVA aggregated.

Comparative Example 3 Intrinsic viscosity [η] = 1.70 obtained by conventional anhydrous saponification method
dl / g, saponification degree 99.9 mol% PVA, 60 mesh or less, 10
A dissolution test was conducted in the same manner as in Example 1 using a fine powder PVA having a particle size of 0 mesh or less. When 1 part of PVA and 100 parts of water were used, the dissolution test was conducted even after 30 minutes. No solution could be obtained.

As described above, the production method of the present invention is extremely effective for producing a highly polymerized PVA which is porous and has excellent solubility.

Claims (2)

(57) [Claims] 1. The intrinsic viscosity obtained by the emulsion polymerization method is 1.5 dl / g.
In obtaining a high degree of polymerization polyvinyl alcohol polymer having an intrinsic viscosity of 1.5 dl / g or more from the high degree of polymerization polyvinyl ester polymer, the polyvinyl ester polymer emulsion is mixed with methanol to be substantially uniform. A solution was obtained, and the solution was continuously fed into a methanol bath together with a basic catalyst, and the final slurry concentration was 0.2% by weight or more, 1
A method for producing a polyvinyl alcohol-based polymer having a high degree of polymerization, which is excellent in solubility, characterized by saponification so that the content is 0% by weight or less. [Here, the intrinsic viscosity of the polyvinyl ester-based polymer is defined by a value measured at 30 ° C. in acetone for polyvinyl acetate resaponified after saponifying the polyvinyl ester-based polymer. The intrinsic viscosity of a polymer is defined as a value measured at 30 ° C. in acetone for polyvinyl acetate obtained by reacetylating the polyvinyl alcohol polymer. ] 2. The production method according to claim 1, wherein the high degree of polymerization polyvinyl alcohol-based polymer obtained has an average particle size of 16 mesh or less.