JPH0660218B2 - Method for producing high degree of polymerization polyvinyl ester polymer - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel method for producing a high degree of polymerization polyvinyl ester polymer. Polyvinyl ester polymers, especially polyvinyl acetate polymers, are widely used as base polymers for adhesives and paints, and are extremely important as raw material resins for polyvinyl alcohol (hereinafter abbreviated as PVA) polymers. is there. This PVA-based polymer has excellent interfacial properties and strength properties as a few crystalline water-soluble polymers, and therefore it is used as a stabilizer for paper processing, fiber processing, emulsion, vinylon film, etc. As is well known, it also occupies an important position as a raw material for vinylon fiber and vinylon fiber. However, the degree of polymerization of the conventional PVA-based polymer is 2000 as the upper limit, from the viewpoints of processing characteristics and handleability, and it is difficult to obtain a polyvinyl acetate-based polymer as a raw material having a high degree of polymerization, Only about 3000 items are seen as special items. On the other hand, rapid progress in processing technology in recent years has enabled processing of a polymer in an ultra-high degree of polymerization region, 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 physical properties in conventional applications are improved, but also new possibilities are expected in new fields such as high-strength fibers.

[0002]

2. Description of the Related Art Generally, it is known that a polymer having a high degree of polymerization can be obtained by polymerizing at a low temperature at a low speed, and there are some examples of vinyl acetate. [For example,
A. R. Shultz; Am. Chem. So
c. 76, 3422 (1954), G.I. M. Burn
ett, M .; H. George, H .; W. Melvil
le; J. Polym. Sci. 16 volumes, 31 (1
955), M.A. Matsumoto, Y .; Ohyana
gi; Polym. Sci. Volume 46, 148
(1960), USP 4,463,138 (Alli
However, since all of these methods are bulk polymerization methods and the polymerization system has an extremely high viscosity, stirring is difficult, a homogeneous polymer cannot be obtained, and heat removal becomes difficult. I have a problem. Therefore, it is considered that production on an industrial scale using these bulk polymerization methods would be almost impossible.

[0003]

The present invention solves the above problems and provides a novel method for producing a polyvinyl ester polymer having a high degree of polymerization easily on an industrial scale. Is what you are trying to do.

[0004]

Means for Solving the Problems As a result of intensive studies on the production method by which the present inventors can easily obtain a polyvinyl ester-based polymer having a high degree of polymerization on an industrial scale,
By suspension-polymerizing a vinyl ester monomer at a polymerization temperature of 20 ° C. or less and a polymerization rate of 10% / hour or less, the intrinsic viscosity is 1.5 (deciliter / g) (hereinafter, deciliter / g is abbreviated as dl / g). The present invention has been completed by finding that a polyvinyl ester-based polymer having a high degree of polymerization as described above can be obtained. [Here, the intrinsic viscosity of the polyvinyl ester-based polymer is defined as a value measured at 30 ° C. in acetone with respect to polyvinyl acetate resaponified after saponification of the polyvinyl ester-based polymer. It is defined as the rate of conversion of vinyl ester monomer into polymer per hour. ]

The suspension polymerization of the present invention is carried out at a low polymerization temperature of 20 ° C. or lower and at a low polymerization rate of 10% / hour or less. Careful attention is required in this respect. That is, since the radical concentration of the polymerization system is low, it is easily affected by oxygen and impurities of the polymerization system. In particular, oxygen acts as a strong inhibitor, so special care must be taken regarding its removal from the polymerization system before polymerization and its entry into the polymerization system during polymerization. The vinyl ester monomers are preferably purified by a conventional method before use.

Examples of the vinyl ester monomer used in the present invention include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate and the like.
Vinyl acetate is particularly preferred for obtaining VA. It is also possible to copolymerize a monomer copolymerizable with the above vinyl ester monomers, and examples of these monomers include (meth) acrylic acid, (meth) acrylic acid ester, itaconic acid or its ester, and maleic acid. Examples thereof include esters or maleic anhydride, (meth) acrylamide or derivatives thereof, vinyl chloride, vinyl fluoride, vinylidene chloride, vinylidene fluoride, acrylonitrile, and vinylalkoxysilane. The stabilizer used for the polymerization may be a PVA-based polymer, a cellulose-based polymer, a surfactant, etc., but these stabilizers should be selected in consideration of the interfacial characteristics at the low temperature polymerization temperature. There is.

The polymerization can be initiated by (1) thermal decomposition of the peroxide or azo compound, or (2) irradiation of light, radiation, plasma or the like. In the method (1), benzoyl peroxide, 2,2′-azobisisobutyronitrile or the like used in ordinary polymerization cannot be used, and a low temperature decomposition type such as diisopropyl peroxydicarbonate or isobutyl peroxide is used. , 2,2'-azobis (4-methoxy-2,4
-Dimethylvaleronitrile) and the like are preferably used. In the case of (2), it is possible to irradiate with ultraviolet rays, γ rays, plasma or the like, and it is also possible to use a sensitizer such as 2,2′-azobisisobutyronitrile at the time of irradiation with ultraviolet rays.

The present invention provides a method for obtaining a polyvinyl ester polymer having a high degree of polymerization, and the intrinsic viscosity of the polyvinyl ester polymer is 1.5 (dl / g).
The above is indispensable, preferably 2.0 (dl / g) or more, more preferably 2.5 (dl / g) or more, and it is desirable to be as large as possible. Therefore, the polymerization temperature is 20 ° C. or lower, preferably 15 ° C. or lower, more preferably 1
The object of the present invention is achieved by carrying out suspension polymerization at 0 ° C. or less and at a polymerization rate of 10% / hour or less, preferably 7.5% / hour or less, more preferably 1% / hour or less. . The polymerization rate of the present invention is controlled by adjusting the amount of the initiator added to the polymerization system or adjusting the irradiation intensity of light, radiation or the like. When the polymerization temperature is 0 ° C. or lower, the polymerization can be performed by adding a water-soluble substance to lower the freezing point. As the water-soluble substance, alcohols, glycols, glycerin, etc. and so-called inorganic salts such as NaCl, KCl, etc. are used, but especially NaCl, K
Inorganic salts such as Cl are preferable because they have a large molar freezing point depression and have little influence on polymerization.

The polyvinyl ester polymer obtained by suspension polymerization is further saponified to give P
A VA polymer can be obtained. The saponification reaction in this case can be carried out according to a conventional method, but after dissolution in methanol or ethanol, NaOH, NaOCH ₃ , NaOC ₂ H
A method by alcoholysis using ₅ or the like as a catalyst is preferable.

[0010]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. In addition, "%" and "part" in Examples mean "% by weight" and "part by weight", respectively.

Example 1 PV was placed in a reactor equipped with a thermometer, a nitrogen introducing tube and a cooling tube.
A-217 (polymerization degree 1700, saponification degree 88 mol%,
0.3 part of distilled water (manufactured by Kuraray Co., Ltd.) and 3000 parts of distilled water were charged, PVA-217 was dissolved at 90 ° C., and then cooled in a thermostat while introducing nitrogen until the internal temperature reached 15 ° C. After replacing 1500 parts of vinyl acetate monomer purified by a conventional method with nitrogen at 60 ° C., while introducing nitrogen,
5.4 parts of 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile) was quickly dissolved in the mixture cooled to 0 ° C and charged into an aqueous PVA-217 solution with stirring to start polymerization. During the polymerization, the polymerization system was sealed with nitrogen gas to prevent oxygen from entering. Polymerization is at 15 ° C. and rate is 7.
Progressed at 5% / hour. 48 hours later, under reduced pressure at 15 ° C 5
The unreacted monomer was removed for a period of time, the pearl-like polymer produced was filtered and washed repeatedly with water, and then dried under reduced pressure at 30 ° C. The weight of the polymer obtained after drying was 1210 parts. A part of the obtained polyvinyl acetate was dissolved in methanol, the concentration was 6%, and [NaOH] / [VAc] = 0.
05, saponified at a temperature of 40 ℃ 0.1 of PVA obtained
Parts were reacetated in a mixed solution of 8 parts of acetic anhydride and 2 parts of pyridine at 105 ° C. for 20 hours with occasional stirring, and polyvinyl acetate obtained by repeating reprecipitation purification with an acetone-ether or acetone-water system was used. When the intrinsic viscosity was measured at ° C, it was [η] = 2.52 (dl / g).
(Measurement by the dilution method using an Ubbelohde type viscosity tube) Further, the above polyvinyl acetate was dissolved in methanol,
Saponification under the same conditions as above, saponification degree 98.9 mol%
Of PVA was obtained. This PVA was reacetated under the same conditions as above, and the intrinsic viscosity of polyvinyl acetate that had been repeatedly reprecipitated and refined in the same manner as above was measured in acetone at 30 ° C. to find that [η] = 2.52 (dl / G).

Comparative Example 1 2,2′-azobisisobutyronitrile (0.3 part) was used as a polymerization initiator, and the polymerization temperature was 60 ° C. and the polymerization rate was 12.5.
Polymerization was carried out in the same manner as in Example 1 except that the polymerization was carried out at a rate of% / hour to obtain 1360 parts of polyvinyl acetate. Further, a part thereof was saponified in the same manner as in Example 1 to obtain PVA. Immediately after polymerization, [η] of polyvinyl acetate and [η] of polyvinyl acetate obtained by reacetylating PVA are 2.25 (dl / g), respectively.
And 1.14 (dl / g).

Example 2 PV was placed in a reactor equipped with a thermometer, a nitrogen introducing tube and a cooling tube.
A-217 (polymerization degree 1700, saponification degree 88 mol%,
(Kuraray Co., Ltd.) 0.3 parts, sodium chloride 15 parts, and distilled water 3000 parts were charged and PVA-217 at 90 ° C.
After melting the mixture, while introducing nitrogen, the internal temperature in the constant temperature bath is -5.
Cooled to 0 ° C. 1,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile) was obtained by purifying 1500 parts of vinyl acetate monomer purified by a conventional method at 60 ° C and then cooling to -5 ° C while introducing nitrogen. 12.5 parts were quickly dissolved and charged into an aqueous PVA-217 solution with stirring to start polymerization. During the polymerization, the polymerization system was sealed with nitrogen gas to prevent oxygen from entering. The polymerization proceeded at -5 ° C at 1% / hour. After 120 hours of polymerization, unreacted monomers were removed at -5 ° C under reduced pressure for 24 hours, the pearl-like polymer produced was repeatedly filtered and washed with water, and then dried at 30 ° C under reduced pressure. The weight of the polymer after drying was 720. A part of this polyvinyl acetate was dissolved in methanol and the concentration was 6%, and [NaOH] / [V
Ac] = 0.05, saponified at 40 ° C. to obtain PV
When A was re-acetylated in the same manner as in Example 1 and the intrinsic viscosity was measured at 30 ° C. in acetone, [η] = 2.95 (dl /
g). Also, the above polyvinyl acetate was dissolved in methanol and saponified under the same conditions as above to obtain PVA. This PVA was reaceticated in the same manner as above, and the intrinsic viscosity was measured in acetone at 30 ° C., [η] = 2.
It was 95 (dl / g).

[0014]

The greatest feature of the present invention is that the polymerization temperature is 20 ° C.
It is characterized by suspension polymerization at the following low temperature and at a low polymerization rate of 10% / hour, whereby a polyvinyl ester polymer having a high degree of polymerization can be obtained, and engineering such as stirring and heat removal during polymerization is performed. Problems are solved. Further, it is easy to separate and purify the produced polyvinyl ester polymer, especially to remove unreacted monomers, which is advantageous for the saponification reaction to obtain the polyvinyl alcohol polymer. By saponifying the high degree of polymerization polyvinyl ester polymer of the present invention by a conventional method, a PVA type polymer having a high degree of polymerization can be easily obtained. This is a PVA type high strength sheet or a PVA type high strength sheet. It is preferably used as a fiber.

Claims (1)

[Claims] 1. A vinyl ester monomer having a polymerization temperature of 2
Intrinsic viscosity of 1.5 (deciliter /
g) A method for producing a high degree of polymerization polyvinyl ester polymer as described above. [Here, the intrinsic viscosity of the polyvinyl ester-based polymer is defined as a value measured at 30 ° C. in acetone with respect to polyvinyl acetate resaponified after saponification of the polyvinyl ester-based polymer. It is defined as the rate of conversion of vinyl ester monomer into polymer per hour. ]