KR20090120539A - Polyvinylalcohol microfibrillar fiber and preparation method thereof - Google Patents

Abstract

PURPOSE: Polyvinylalcohol microfibrillar fiber and a preparation method thereof are provided to reduce manufacturing processes through simple mechanical shearing manipulation using methanol as a saponification solvent. CONSTITUTION: A preparation method of polyvinylalcohol microfibrillar fiber includes a step for producing a solution by dissolving poly(vinyl pivalate/acetic acid vinyl) copolymers as a saponification solvent, and a step for shearing a mixed compound after agitating the solution and an alkali saponification solvent after injecting the alkali saponification solvent in the solution. The saponification solvent one organic solvent selected from methanol, tetrahydrofuran, acetone, methyl ethyl ketone or dioxane. The saponification solvent is comprised of hydroxide of 0.5 - 0.07 mole selected from a group consisting of potassium hydroxide, calcium hydroxide, sodium hydroxide, and their mixture and water of 0.1 - 0.8 mole.

Description

Polyvinyl alcohol microfibrillar fiber and preparation method thereof

The present invention is a polyvinyl alcohol (PVA) microfibrill fiber prepared by using a methanol and a specific saponifying agent during the process of saponifying a poly (vinyl pivalate / vinyl acetate) copolymer and mechanical shearing operation and a method of manufacturing the same It is about.

PVA fiber, first manufactured by Hermann, Germany in 1931 (German Patent No. 685,048 (1931)), has been in the spotlight as a textile and garment for 70 years since then. In particular, recently, it has been used as a high functional material such as a polarizing film, a medical polymer and a contact lens.

PVA used as a raw material of the PVA fiber is of two types, an atactic PVA as shown in the following formula (1) and a syndiotactic PVA as shown in the following formula (2).

[Formula 1]

[Formula 2]

However, the preparation of a full-arranged PVA, such as Formula 2, has not yet been made and is prepared by polymerizing a monomer having a side chain group causing steric hindrance as described in Japanese Patent Application Laid-Open No. 4-108,109 and saponifying it again. Even the alternating arrangement PVA content does not exceed 65% of the alternating diad group.

In order to prepare a high molecular weight PVA containing abundant alternating groups, it is necessary to use a monomer having an ester group causing steric hindrance or to improve the polymerization method so that a high molecular weight alternating precursor is obtained.

The reason is that PVA prepared from polyvinyl acetate obtained by polymerizing vinyl acetate by a general method such as bulk polymerization or solution polymerization is a hybrid array PVA and it is impossible to obtain a high molecular weight due to the frequent chain transfer reactions involved in radical polymerization. .

Many monomers are known for synthesizing precursors for the production of co-array, hybrid and alternating PVA. Vinyl trifluoride is widely used as a monomer for synthesizing precursors for alternating PVA. [K. Yamaura, K. Hirata, S. Tamura, and S. Matsmura, J. Polym. Sci .: Polym. Phys. Ed. , 23, 1703 (1985).

However, these monomers have the disadvantage that they are very expensive and do not express sufficient alternating order. Vinyl pivalate is known to express the best alternating arrangement due to the steric hindrance effect of the tertiary butyl group, but the saponification method is not easy and only recently, Yamamoto et al. Yamamoto, S. Yoda, H. Takase, T. Saso, O. Sangen, R. Fukae, M. Kamachi, and T. Sato, Polym. J. , 23, 185 (1991) or by Ha and Lyoo (Japanese and European Patent No. PCT / KR 95 / 00,065) to establish a saponification process.

However, this monomer is also relatively expensive compared to vinyl acetate, which is generally a monomer used for the synthesis of precursors for the preparation of PVA.

In order to prepare hybrid-array high molecular weight PVA and alternating-array PVA which cannot be obtained by the general method of producing PVA, the polymerization method needs to be improved, and the research directions are largely divided into four types of bulk polymerization, solution polymerization, emulsion polymerization and suspension polymerization. .

Bulk polymerization has a merit that relatively high molecular weight polyvinyl alcohol can be obtained because the probability of chain transfer is low since only monomer is present in the polymerization system.

Many researchers have described benzoylperoxide [M. Matsumoto and M. Maeda, Kobunshi Kagaku , 12, 428 (1955)], benzoyl steroyl peroxide [A. Voss and W. Heuer, German Patent, 666,866 (1934)], disteroyl peroxide and dilauroyl peroxide [S. Molnar, J. Polym. Sci .: Part AI , 10, 2245 (1972)] and difuroyl peroxide (JWL Fordham, GH McCain, and LE Alexander, J. Polym. Sci. , 39, 335 (1959)] and the like have been reported to bulk polymerization of vinyl acetate, but the heat of polymerization of vinyl acetate is very high compared to other vinyl monomers [SR Sandler and W. Karo, "Polymer Synthesis ", vol. 3, pp. 197-199, Academic Press, New York, 1980], because of this increase in the reaction rate, it is difficult to obtain a high molecular weight PVA effectively, and it is difficult to obtain a high level of conversion because the viscosity is not easy to control. .

According to US Patent No. 4,963,138, ultra-high molecular weight PVA having an intrinsic viscosity of more than 5 (dl / g) was synthesized by completely saponifying ultra high molecular weight polyvinyl acetate obtained by initiating vinyl acetate with ultraviolet rays and bulk polymerization at various low temperatures. , Imai, et al. [K. Imai, T. Shiomi, N. Oda, and H. Otsuka, J. Polym. Sci .: Polym. Chem. Ed. , 24, 3225 (1986)] prepared a high molecular weight PVA from polyvinyl acetate obtained by bulk polymerization of vinyl acetate at 60 ° C. with a small amount of azobisisobutyronitrile.

Go et al. [Y. Go, S. Matsuzawa, Y. Kondo, K. Nakamura, and T. Sakamoto, Kobunshi Kagaku , 25, 55 (1968)] are obtained by bulk polymerization of vinyl trifluoride acetate with benzoyl peroxide as an initiator at 60 ° C. The vinyl trifluoride acetate was subjected to amine decomposition to synthesize PVA having a high molecular weight of alternating arrangement having a number average degree of polymerization of 7,700 and an alternating diad group content of 55%.

Emulsion polymerization is a polymerization system that can increase the polymerization rate and polymerization rate, but vinyl acetate has a much higher growth reaction rate than other vinyl monomers. J. Flory, "Principles of Polymer Chemistry", pp. 106-161, Cornell University Press, Ithaca, 1953] and it is difficult to obtain high molecular weight polyvinyl alcohol due to the branching reaction due to the high reaction rate in this polymerization system.

Therefore, many special emulsion polymerizations have been attempted to obtain polyvinyl alcohol having excellent physical properties. Nikolaev et al. F. Nikolaev, KV Belogorodskaya, NP Kukushkina, and OA Pigulevskaya, USSR Patent, 1,016,305 (1978)] accept a manganese triacetylacetonate and use it as an initiator for low temperature emulsion polymerization. Polyvinyl acetate was synthesized, and Lanthier [R. Lanthier, U. S. Patent, 3,303, 174 (1967), prepared a polyarray having a polyarray having a number average degree of polymerization of 12,000 from polyvinyl acetate obtained by gamma irradiation emulsion polymerization of vinyl acetate at -15 ° C.

Recently, Yamamoto et al. [T. Yamamoto, S. Yoda, O. Sangen, and M. Kamachi, Polym. J. , 21, 1053 (1989)], in order to increase the alternator, vinyl pivalate was irradiated with UV at 0 ° C for emulsion polymerization, followed by saponification to obtain a number average degree of polymerization of 18,000 and an alternating diad group content of 62.8%. Ultra high molecular weight polyvinyl alcohol was prepared.

Solution polymerization is relatively easy to control viscosity and exotherm by solvents present in the reaction system, so ethyl acetate [A. Conix and J. Smets, J. Polym. Sci. , 10, 525 (1953)], dimethyl carbitol [K. Ito, J. Polym. Sci .: Part A-1 , 10, 1481 (1972)], acetic acid [LM Minsk and EW Taylor, US Patent, 2,582,055 (1952)], acetic acid / water [S. Okamura and T. Motoyama, J. Polym. Sci. , 17, 428 (1955)], dimethylformamide [CH Bamford, AD Jenkins, and R. Johnston, J. Polym. Sci. , 29, 355 (1958)], benzene [WR Sorenson and TW Campbell, "Preparative Methods of Polymer Chemistry", 2nd Ed., P. 238, Wiley Interscience, New York, 1968, alcohol system [M. Ueda and K. Kajitani, Macromol. Chem. , 108, 138 (1967) and ethylene chloride [WR Conn and HT Neher, J. Polym. Sci. , 5, 355 (1950)] have been studied for the solution polymerization of vinyl acetate using various solvents. However, this method has a high molecular weight PVA due to frequent branching and terminating reactions due to frequent chain transfer reactions to solvents. It is disadvantageous to obtain.

In order to synthesize polyvinyl acetate having excellent linearity and obtain high molecular weight PVA therefrom, redox solution polymerization has been attempted at low temperature [J. Furukawa and T. Tsuruta, J. Polym. Sci. , 28, 227 (1958)], this method has a disadvantage that the conversion rate is very low due to the coloring phenomenon caused by the metal catalyst.

Sorokin et al. [AY Sorokin, VA Kuzentsova, and TD Korneva, USSR Patent, 507,590 (1976)] synthesized vinyl acetate with a diacryl peroxide oligomer as an initiator to obtain a high molecular weight PVA having a number average molecular weight of 110,000 from Nakamae et al. [K. Nakamae et al, Polymer , 33, 2581 (1992)], a high school with 63% alternating diad group content by saponifying a precursor obtained by polymerizing ADMVN with an ultraviolet irradiation solution of vinyl trifluoride acetate at -78 ° C. Large array PVA was prepared and Kamiake and Ueda [K. Kamiake and F. ueda, Japan Patent, 62-064,807 (1987)] prepared a high molecular weight PVA from high molecular weight polyvinyl acetate obtained by polymerizing vinyl acetate with ultraviolet irradiation solution using acylphosphonate as a photoinitiator.

A general method for preparing PVA fibers is to prepare a parent polymer from monomers and saponify the parent polymer to obtain a PVA polymer, which is then solution-spinning or gel-spinning, followed by stretching and heat treatment. PVA fibers are prepared by orienting polymer molecular chains in parallel. And the continuous filament fibers are cut to a suitable length for the purpose to produce a short PVA fiber.

High-strength vinylon on the market ^?? Fiber (Japan, Kuraray Co., Ltd.) is also produced by the above general method.

Further, according to Japanese Patent Application Laid-Open No. 4-108109, saponification of a mother polymer prepared by polymerizing a monomer having a side chain group causing steric hindrance to prepare a high molecular weight PVA rich in alternating array groups, and then separating, washing and After drying, the solution is dissolved in a solvent to spin the solution, which is then stretched and dried to obtain PVA fibers. The spun fiber is cut by a special cutting device to obtain PVA short fibers.

In addition, a polypivalate vinyl polymer, which is a parent polymer of alternating PVA, which is known to have better mechanical properties, heat resistance, solvent resistance, chemical resistance, and weather resistance than hybrid arrangement PVA, is polymerized from vinyl pivalate monomer and saponified. In the case of manufacturing the alternating PVA [US Pat. No. 5,238,995], since the PVA short fibers are manufactured by a method similar to the above, there is a disadvantage in that the manufacturing process is cumbersome and expensive.

Accordingly, the present inventors in the conventional PVA short fiber manufacturing process, polyvinyl alcohol micro to omit the various processes of dissolving the synthesized PVA after the saponification process to form a solution or gel, spinning, stretching, heat treatment, washing and drying As a result of research efforts to produce fibrillated fibers in a more inexpensive manner, poly (pi) produced by any one polymerization method selected from the group consisting of bulk copolymerization, solution copolymerization, emulsion copolymerization and suspension copolymerization of vinyl pivalate and vinyl acetate High strength microfibrillated PVA short fibers can be produced by adding a specific alkali saponifier to a vinyl volatile / vinyl acetate) copolymer and simultaneously carrying out various kinds of stirrers and stirring speeds to perform mechanical shearing. The present invention was completed by finding out.

Accordingly, an object of the present invention is to prepare a copolymer of PVA by copolymerizing a relatively inexpensive vinyl acetate and vinyl pivalate in a variety of methods, and relatively low toxicity and inexpensive methanol instead of tetrahydrofuran which is currently known as the most ideal saponification solvent It is to provide a polyvinyl alcohol microfibrils obtained by shortening the manufacturing process by a simple mechanical shearing operation using a saponification solvent and a method for producing the same.

In order to achieve the above object, the present invention

Dissolving a poly (vinyl pivalate / vinyl acetate) copolymer with a saponification solvent to prepare a solution, and adding an alkaline saponifier to the solution and stirring, followed by mechanical shearing Provided is a method for producing vinyl alcohol microfibrils.

The poly (vinyl pivalate / vinyl acetate) copolymer is prepared by any one polymerization method selected from the group consisting of bulk copolymerization, solution copolymerization, emulsion copolymerization and suspension copolymerization.

The saponification solvent is any one of an organic solvent selected from methanol, tetrahydrofuran, acetone, methyl ethyl ketone or dioxane, more preferably methanol.

The alkali saponifying agent is composed of 0.005-0.07 mol of hydroxide and 0.01-0.8 mol of water selected from the group consisting of sodium hydroxide, potassium hydroxide, calcium hydroxide, lithium hydroxide and mixtures thereof.

If the content of the water increases beyond the above range, a large number of blocked hydroxyl groups are generated during the saponification reaction, and the reaction rate is slowed, which may cause a problem in that high strength PVA fibrils cannot be effectively produced.

The shear is preferably carried out a mechanical shearing operation at a shear rate of 100 to 5,000 rpm. The higher the shear rate within the range, the longer the fiber length and the smaller the thickness of the fiber appear, but if it is out of the range may cause a problem that the fiber is broken or the fiber itself is not produced.

In addition, the present invention is a polyvinyl alcohol microfibrils obtained by mechanically shearing after adding and stirring an alkali saponifier to a solution prepared by dissolving a poly (vinyl pivalate / vinyl acetate) copolymer with methanol. Provide fiber.

The fibers preferably have a microfibril structure with an average length of 0.1-1,000 mm and an average diameter of 0.5-100 μm.

In addition, the fibers preferably have an alternating arrangement group content of 51 to 62%, a saponification degree of 75.0 to 99.9 mol%, and a number average degree of polymerization of 100 to 10,000.

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

The manufacturing process of the conventionally known polyvinyl alcohol microfibrils fiber is first, the conventional methods of manufacturing a high-molecular high molecular weight polyvinyl alcohol microfibril fiber prepared using tetrahydrofuran as a saponification solvent is relatively expensive tetra Hydrofuran is used as a saponification solvent. Second, the complete oxygen removal is required by dissolving potassium hydroxide and a small amount of water effectively and using a high mechanical shearing operation. These methods suffered from high price of tetrahydrofuran and post-saponification wastewater treatment, as well as high mechanical shearing and perfect oxygen removal.

Accordingly, the present invention is a method for producing a polyvinyl alcohol microfibrillated fiber exhibiting a high degree of saponification similar to the case of using tetrahydrofuran while using an industrially low cost by supplementing the disadvantages of the conventional saponification method described above. It is to prepare polyvinyl alcohol microfibrill fibers by performing saponification with methanol, which is less toxic than tetrahydrofuran, at 40 ° C., at a relatively low temperature without shearing, and without complete oxygen removal.

By using this saponification method, poly (vinyl pivalate / vinyl acetate) copolymer prepared by any one polymerization method selected from the group consisting of bulk copolymerization, solution copolymerization, emulsion copolymerization and suspension copolymerization can be saponified easily and inexpensively. .

In more detail, first, the poly (vinyl pivalate / vinyl acetate) copolymer is dissolved in an organic solvent, and then the temperature of the solution is raised to 25-65 ° C. while stirring. When stirring at the stirring speed, the viscosity of the solution rapidly increases after the titration reaction time, and gel is formed in the solution.

This is due to the action of alkali in the saponification agent, acetyl and pivaloyl groups, which are the side chains of the molecular chain of the poly (vinyl pivalate / vinyl acetate) copolymer, are released to form hydrogen intermolecular hydrogen bonds. This is due to solidification without orientation.

If the solution is continuously stirred for a suitable time, the water in the saponification agent is regularly arranged between the molecular chains of PVA to crosslink the PVA molecules, thereby blocking the hydrogen bonds between molecules while maintaining intramolecular hydrogen bonds, thereby blocking the PVA main chain. The molecular chains are arranged so that they maintain a constant distance so that the entire reaction system is gelled and the arranged molecular chains are kept intact to obtain a solid fiber mass having a high orientation in the fiber axis direction.

Fibrillated fibers are obtained by separating and washing the saponified reactants thus obtained in methanol and subjecting them to mechanical shock or crushing using an ultrasonic crusher.

The saponification agent used in the present invention is a mixed solution of hydroxide and water, and any one selected from the group consisting of sodium hydroxide, potassium hydroxide, calcium hydroxide, lithium hydroxide and mixtures thereof with respect to 1 g of poly (vinyl pivalate / vinyl acetate). Consisting of 0.005-0.07 mol of hydroxide and 0.01-0.8 mol of water.

In addition, as the organic solvent used in the manufacturing process, an organic solvent such as methanol, tetrahydrofuran, acetone, methyl ethyl ketone or dioxane may be used, and it is possible to form fibers having excellent physical properties more cheaply, and to perform simple shearing operation. Methanol required is most preferred.

The polyvinyl alcohol microfibrillated fiber according to the present invention has properties similar to those of natural cotton or hemp fiber, and can be used for various purposes, and the conventional polyvinyl alcohol microfiber prepared by saponification process of polypivalate polymer The advantage is that it is produced in a more inexpensive way than the brill fiber.

It is also very useful as an alternative to asbestos, a carcinogen, because it has excellent thermal insulation due to a very fine microfibrillated structure having an average diameter of 0.5 to 100 μm and an average length of 0.1 to 1,000 mm.

In addition, since it has excellent affinity and alkali resistance with inorganic materials for building materials, it can be widely used in various fields including composite materials such as cement or concrete reinforcing fiber.

Tensile strength and tensile modulus of the polyvinyl alcohol microfibrillated fibers prepared according to an embodiment of the present invention were measured by a fiber tensile tester, and the polyvinyls produced by spinning and stretching were 15 g / d and 1,000 or less, respectively. Tensile properties similar to alcohol fibers could be obtained directly at the saponification stage.

The polyvinyl alcohol microfibrillated fiber according to the present invention has properties similar to those of natural cotton or hemp fiber, and can be used for various purposes, and the conventional polyvinyl alcohol microfiber prepared by saponification process of polypivalate polymer The advantage is that it is produced in a more inexpensive way than the brill fiber.

It is also very useful as an alternative to asbestos, a carcinogen, because of its excellent thermal insulation due to its microfibrillated structure.It also has excellent affinity and alkali resistance to inorganic materials for building materials. It can be widely used in various fields including.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the following examples are only for the purpose of clarifying the contents of the present invention, and the present invention is not limited by the examples.

Example 1

A 500 ml four-necked round flask equipped with a thermometer, a nitrogen inlet, an alkali saponifier dripping pipe, and an H-shaped anchor stirrer was used to obtain poly (pivalic acid) having a 3.82 intrinsic viscosity and a 60.2% content of alternating diad groups under a nitrogen stream. 1 g of vinyl / vinyl acetate copolymer was dissolved in 2.47 mol of methanol, and the solution was heated to 40 ° C., and 2.5 ml of a solution containing 0.03 mol of sodium hydroxide and 0.2 mol of water was slowly added thereto for 4 minutes while stirring at 100 rpm. Then, the stirring speed was raised to 1,000 rpm and the stirring was continued for 30 minutes, and the stirring speed was lowered to 700 rpm and stirred for 10 hours.

When the reaction solidified, it was separated into another container, 300 ml of methanol was added, and the fibrillated fiber was obtained by separating into fine fibers using a high speed mixer. This fiber was filtered and washed several times and dried in a vacuum oven to yield quantitative light yellow fibrous PVA.

Example 2

In the same apparatus as in Example 1, 1 g of a poly (vinyl pivalate / vinyl acetate) copolymer having an intrinsic viscosity of 4.03 and an alternating diad group content of 59.1% was dissolved in 2.47 mol of methanol, and then the temperature of the solution was 50. The solution was slowly added to 2.5 ml of a solution containing 0.03 mol of sodium hydroxide and 0.3 mol of water while stirring at 100 rpm and stirring at 100 rpm for 3 minutes, and then the stirring speed was increased to 1,000 rpm for 30 minutes, and the stirring speed was lowered to 500 rpm. Stir for 8 hours.

When the reaction solidified, it was separated into another container, 300 ml of methanol was added, and the fibrillated fiber was obtained by separating into fine fibers using a high speed mixer. This fiber was filtered and washed several times and dried in a vacuum oven to yield quantitative light yellow fibrous PVA.

Example 3

In the same apparatus as Example 1, 1 g of a poly (vinyl pivalate / vinyl acetate) copolymer having an intrinsic viscosity of 3.62 and an alternating diad group content of 58.0% was dissolved in 2.47 mol of methanol, and then the temperature of the solution was 40 2 ml of a solution mixed with 0.03 mol of sodium hydroxide and 0.3 mol of water was slowly added for 3 minutes while stirring at 200 rpm, and the stirring speed was increased to 1,000 rpm for 30 minutes, and the stirring speed was lowered to 700 rpm. Stir for 7 hours.

When the reaction solidified, it was separated into another container, 300 ml of methanol was added, and the fibrillated fiber was obtained by separating into fine fibers using a high speed mixer. This fiber was filtered and washed several times and dried in a vacuum oven to yield quantitative light yellow fibrous PVA.

Example 4

In the same apparatus as Example 1, 1 g of a poly (vinyl pivalate / vinyl acetate) copolymer having an intrinsic viscosity of 3.13 and an alternating diad group content of 56.2% was dissolved in 2.47 mol of methanol, and then the temperature of the solution was 50. 2 ml of a solution containing 0.02 mol of sodium hydroxide and 0.4 mol of water was slowly added thereto for 2 minutes while stirring at 200 rpm, and the stirring speed was increased to 1,000 rpm for 30 minutes, and the stirring speed was lowered to 700 rpm. Stir for 7 hours.

When the reaction solidified, it was separated into another container, 300 ml of methanol was added, and the fibrillated fiber was obtained by separating into fine fibers using a high speed mixer. The fibers were filtered and washed several times and dried in a vacuum oven to yield quantitative pale yellow fibrous PVA.

Example 5

In the same apparatus as in Example 1, 1 g of a poly (vinyl pivalate / vinyl acetate) copolymer having an intrinsic viscosity of 3.11 and an alternating diad group content of 52.4% was dissolved in 2.47 mol of methanol, and then the temperature of the solution was 50. 2 ml of a solution containing 0.02 mol of sodium hydroxide and 0.4 mol of water was slowly added thereto for 2 minutes while stirring at 200 rpm, and the stirring speed was increased to 800 rpm for 30 minutes, and the stirring speed was lowered to 500 rpm. Stir for 8 hours.

When the reaction solidified, it was separated into another container, 300 ml of methanol was added, and the fibrillated fiber was obtained by separating into fine fibers using a high speed mixer. This fiber was filtered and washed several times and dried in a vacuum oven to yield quantitative light yellow fibrous PVA.

Example 6

In the same device as Example 1, 1 g of a poly (vinyl pivalate / vinyl acetate) copolymer having an intrinsic viscosity of 3.72 and an alternating diad group content of 58.5% was dissolved in 2.47 mol of methanol, and then the temperature of the solution was 40 2 ml of a solution containing 0.03 mol of sodium hydroxide and 0.3 mol of water was slowly added to the mixture for 3 minutes while stirring at 200 rpm, and the stirring speed was increased to 800 rpm for 30 minutes, and the stirring speed was lowered to 400 rpm. Stir for 5 hours.

When the reaction solidified, it was separated into another vessel, 300 ml of methanol was added and separated into fine fibers using a high speed mixer to obtain fibrillated fibers. This fiber was filtered and washed several times and dried in a vacuum oven to yield quantitative light yellow fibrous PVA.

Example 7

In the same apparatus as Example 1, 1 g of a poly (vinyl pivalate / vinyl acetate) copolymer having an intrinsic viscosity of 3.26 and an alternating diad group content of 57.5% was dissolved in 2.47 mol of methanol, and then the temperature of the solution was 40 2 ml of a solution containing 0.02 mol of sodium hydroxide and 0.4 mol of water was slowly added to the mixture for 2 minutes while stirring at 200 rpm, and the stirring speed was increased to 900 rpm for 30 minutes, and the stirring speed was lowered to 500 rpm. Stir for 6 hours.

When the reaction solidified, it was separated into another container, 300 ml of methanol was added, and the fibrillated fiber was obtained by separating into fine fibers using a high speed mixer. This fiber was filtered and washed several times and dried in a vacuum oven to yield quantitative light yellow fibrous PVA.

Example 8

In the same apparatus as in Example 1, 1 g of a poly (vinyl pivalate / vinyl acetate) copolymer having an intrinsic viscosity of 3.22 and an alternating diad group content of 57.0% was dissolved in 2.47 mol of methanol, and then the temperature of the solution was 50. 2 ml of a solution containing 0.02 mol of sodium hydroxide and 0.3 mol of water was slowly added to the mixture for 2 minutes while stirring at 200 rpm, and the stirring speed was increased to 1,000 rpm for 30 minutes, and the stirring speed was lowered to 500 rpm. Stir for 8 hours.

When the reaction solidified, it was separated into another container, 300 ml of methanol was added, and the fibrillated fiber was obtained by separating into fine fibers using a high speed mixer. This fiber was filtered and washed several times and dried in a vacuum oven to yield quantitative light yellow fibrous PVA.

Example 9

In the same device as Example 1, 1 g of a poly (vinyl pivalate / vinyl acetate) copolymer having an intrinsic viscosity of 3.31 and an alternating diad group content of 55.8% was dissolved in 2.47 mol of methanol, and then the temperature of the solution was 50. 2 ml of a solution mixed with 0.03 mol of sodium hydroxide and 0.2 mol of water was slowly added to the mixture for 2 minutes while stirring at 200 rpm, and the stirring speed was increased to 1,100 rpm for 30 minutes, and the stirring speed was lowered to 500 rpm. Stir for 10 hours.

When the reaction solidified, it was separated into another container, 300 ml of methanol was added, and the fibrillated fiber was obtained by separating into fine fibers using a high speed mixer. This fiber was filtered and washed several times and dried in a vacuum oven to yield quantitative light yellow fibrous PVA.

Example 10

In the same apparatus as Example 1, 1 g of a poly (vinyl pivalate / vinyl acetate) copolymer having an intrinsic viscosity of 3.12 and an alternating diad group content of 53.1% was dissolved in 2.47 mol of methanol, and then the temperature of the solution was 50. 2 ml of a solution containing 0.02 mol of sodium hydroxide and 0.4 mol of water was slowly added to the mixture for 3 minutes while stirring at 200 rpm. Then, the stirring speed was increased to 1,000 rpm for 30 minutes and the stirring was continued at 500 rpm. Lowered and stirred for 9 hours.

When the reaction solidified, it was separated into another container, 300 ml of methanol was added, and the fibrillated fiber was obtained by separating into fine fibers using a high speed mixer. This fiber was filtered and washed several times and dried in a vacuum oven to yield quantitative light yellow fibrous PVA.

Comparative Example 1

In the same apparatus as in Example 1, 1 g of polypivalate having a number average degree of polymerization of 27,100 was dissolved in 1.23 mol of tetrahydrofuran, and then the temperature of the solution was raised to 60 ° C and stirred at 500 rpm, 0.209 mol of methanol and 0.0446 potassium hydroxide. 10 ml of a mixture of mol and 0.0831 mol of water was slowly added for 4 minutes, and then the stirring speed was increased to 10,000 rpm, and the stirring was continued for 5 minutes, and the stirring speed was lowered to 2,000 rpm and stirred for 10 minutes.

When the reaction solidified, it was separated into another container, 300 ml of methanol was added, and the fibrillated fiber was obtained by separating into fine fibers using a high speed mixer. This fiber was filtered and washed several times and dried in a vacuum oven to yield quantitative light yellow fibrous PVA.

Experimental Example 1

Table 1 shows the results of examining the properties of the PVA short fibers prepared in Examples 1 to 5 and Comparative Example 1 by the following methods.

At this time, the alternator content and the degree of saponification were obtained by NMR analysis (Nuclear Magnetic Resonance Spectroscopy), and the number average polymerization degree was extrapolated to 0% of the reduced viscosity measured using a Ubbelohde viscometer to obtain the intrinsic viscosity [η].

The intrinsic viscosity calculated as described above was converted to the number average degree of polymerization by the Mark-Houwink equation, and tensile strength and tensile modulus were calculated using Instron 4201. The prepared samples were carried out 20 times per sample under a holding distance of 20 mm and a cross head speed of 10 mm / min. The upper and lower limit values were subtracted from each other, and each was calculated using the load values obtained.

Alternator content (mol%) Saponification degree Number average degree of polymerization Tensile strength (g / d) Tensile Modulus (g / d) Example 1 60.2 99.9 8,600 15 800 Example 2 59.1 99.2 8,100 13 740 Example 3 58.0 97.4 7,700 12 700 Example 4 56.2 91.4 5,900 9 560 Example 5 52.4 86.4 5,100 7 420 Example 6 58.5 95.3 7,500 12 710 Example 7 57.5 90.5 6,100 10 580 Example 8 57.0 94.5 6,000 10 570 Example 9 55.8 99.8 5,900 9 570 Example 10 53.1 88.4 5,200 7 430 Comparative Example 1 64.0 99.6 16,700 21 1,060

Claims (7)

Dissolving a poly (vinyl pivalate / vinyl acetate) copolymer with a saponification solvent to prepare a solution, and adding an alkaline saponifier to the solution and stirring, followed by mechanical shearing Method for producing vinyl alcohol microfibrillated fiber. The method of claim 1, wherein the saponification solvent is any one of an organic solvent selected from methanol, tetrahydrofuran, acetone, methyl ethyl ketone or dioxane. The method of claim 1, wherein the alkali saponification agent is characterized in that consisting of 0.005-0.07 mol of any one hydroxide selected from the group consisting of sodium hydroxide, potassium hydroxide, calcium hydroxide, lithium hydroxide and mixtures thereof and 0.01-0.8 mol of water. Method for producing polyvinyl alcohol microfibrillated fiber. The method of claim 1, wherein the shear is a method of producing polyvinyl alcohol microfibrils, characterized in that the mechanical shearing at a shear rate of 100 to 5,000 rpm. A polyvinyl alcohol microfibrils fiber obtained by mechanically shearing after adding and stirring an alkali saponifier to a solution prepared by dissolving a poly (vinyl pivalate / vinyl acetate) copolymer with methanol. 6. The polyvinyl alcohol microfibrils fiber according to claim 5, wherein the fibers have a microfibrillated structure having an average length of 0.1-1,000 mm and an average diameter of 0.5-100 m. 6. The polyvinyl alcohol microfibrils fiber according to claim 5, wherein the fibers have an alternating diad group content of 51 to 62%, a saponification degree of 75.0 to 99.9 mol%, and a number average degree of polymerization of 100 to 10,000.