KR19980017972A - Polyvinyl alcohol microfibrillated fiber and preparation method thereof - Google Patents

Abstract

The present invention relates to a polyvinyl alcohol microfibrillated fiber by a saponification process of a high-shift high molecular weight poly (vinyl pivalate / vinyl acetate) copolymer, and more particularly, to processes such as spinning and stretching. Polyvinyl alcohol micros prepared by performing a special shearing agent and a high shearing operation to give orientation to alternating molecular chains during the saponification of poly (vinyl pivalate / vinyl acetate) copolymer with polyvinyl alcohol A fibrillated fiber and a method for producing the same.

Description

Polyvinyl alcohol microfibrillated fiber and preparation method thereof

1A to 1D are photomicrographs of 200 times the appearance of polyvinyl alcohol microfibrils made from the poly (vinyl pivalate / vinyl acetate) copolymer of the present invention.

Alternating diad group content: a, 56.8%; b, 58.4%, c, 59.6%; d, 61.5%.

The present invention relates to a polyvinyl alcohol microfibrillated fiber and a method of manufacturing the same, and more specifically, to a specific saponification agent during the process of saponifying a poly (vinyl pivalate / vinyl acetate) copolymer, The present invention relates to a polyvinyl alcohol microfibrillated fiber prepared by carrying out a shearing operation and a method of manufacturing the same.

First manufactured by German Hermann in 1931 (German Patent No. 685,048 (1931)), polyvinyl alcohol fibers have been in the spotlight as apparel and industrial fibers for about 60 years, and ongoing research is being conducted.

There are two types of polyvinyl alcohol used as a raw material of polyvinyl alcohol fibers: atactic polyvinyl alcohol as shown in the following structural formula (a) and syndiotactic polyvinyl alcohol as shown in the following structural formula (b).

However, the production of trans-altered polyvinyl alcohol as shown in Structural Formula (b) has not been made so far, and as disclosed in Japanese Patent Application Laid-open No. Hei 4-108,109, a monomer having a side chain group causing steric hindrance is polymerized and Even the alternating polyvinyl alcohol prepared by saponification again does not exceed 65% of the alternating diad group content.

A general method for preparing polyvinyl alcohol fibers is to prepare a parent polymer from monomers, saponify the parent polymer to obtain a polyvinyl alcohol polymer, which is then subjected to solution spinning (solutioin-spinning) or gel spinning (gel-spinning). Polyvinyl alcohol fibers are prepared by stretching and heat treating the polymer molecular chains in parallel. Then, the continuous filament fibers are cut to a suitable length for their use to produce polyvinyl alcohol short fibers. High strength vinylon on the market Fiber (Japan, Kuraray Co., Ltd.) is also produced by the above general method.

In addition, according to Japanese Patent Application Laid-open No. Hei 4-108,109, a high molecular weight polyvinyl alcohol rich in alternating array groups was prepared by saponifying a mother polymer prepared by polymerizing monomers having side chain groups causing steric hindrance. After separation, washing and drying, the solution is dissolved in a solvent to spin the solution, and then stretched and dried to obtain a polyvinyl alcohol fiber. Thereafter, the spun fiber is cut with a special cutting device to obtain polyvinyl alcohol short fibers.

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

Meanwhile, Ha and Ryu produced polyvinyl alcohol microfibrils short fibers by performing a mechanical shearing operation of a polypivalate polymer with a special saponifying agent. More specifically, Yamamoto et al. [T. Polyvinyl alcohol having a saponification degree of 99 mol% or more can be produced by the saponification method of the polypival acid polymer shown by Yamamoto, et al., Polymer Journal, 23, 185 (1991). Hydrogen groups are produced in a very short time by the vigorous and rapid reaction of vinyl fumes, forming strong intermolecular hydrogen bonds, and thus force is applied in various directions, thus preventing orientation in one direction. As a result, after saponification is completed, gels or precipitates are formed, so as to suppress intramolecular hydrogen bonds, Hawa flows use a small amount of water to promote molecular chain orientation and impart strong mechanical shearing force. Polyvinyl alcohol microfibrils short fibers were prepared directly in the process. The content of alternating diad groups of the polyvinyl alcohol short fibers produced in the invention of Rivera shows a value of 55 to 64%.

Accordingly, the inventors of the present invention omit the general processes of dissolving the polyvinyl alcohol synthesized after the saponification process to form a solution or a gel and spinning after stretching, heat treatment, washing and drying in the conventional polyvinyl alcohol short fiber manufacturing process. In order to prepare polyvinyl alcohol microfibrils short fibers in a more inexpensive way, a main alkaline soaping agent was added to a poly (vinyl pivalate / vinyl acetate) copolymer prepared by copolymerizing vinyl pivalate and vinyl acetate. At the same time, the present invention was completed by producing a high-strength polyvinyl alcohol microfibrils short fiber by performing a high mechanical shearing operation by various combinations of agitators and stirring speeds.

The present invention aims to produce polyvinyl alcohol micropolymer by copolymerizing relatively inexpensive vinyl acetate and vinyl pivalate, and shorten the manufacturing process by simple saponification operation to produce polyvinyl alcohol microfibrils short fibers. .

Hereinafter, the present invention will be described in detail.

The present invention is a polyvinyl alcohol short fibers produced by saponifying a poly (vinyl pivalate / vinyl acetate) copolymer, having an average length of 0.1 to 1,000 mm, and having a microfibrillated structure of an average diameter of 0.5 to 100 μm, The polyvinyl alcohol fibers having an alternating diad group content of 51 to 64%, a saponification degree of 85.0 to 99.9 mol%, and a number average degree of polymerization of 2,500 to 20,000 are featured.

In more detail, the process of preparing the microfibrillated polyvinyl alcohol fiber of the present invention is first dissolved in a poly (vinyl pivalate / vinyl acetate) copolymer in an organic solvent, followed by removing oxygen while stirring to increase the temperature of the solution. After increasing the temperature to ˜65 ° C., the alkaline saponification agent was slowly added and stirred at a stirring speed of 10,000 rpm. After the titration reaction time, the viscosity of the solution rapidly increased, and gel was formed in the solution. This is due to the action of alkali in the saponifying agent, and the acetyl group and pivaloyl group corresponding to the side chain are separated from the molecular chain of the poly (vinyl pivalate / vinyl acetate) copolymer to form hydrogen bonds between molecules in a specific direction. This is due to solidification without the orientation of.

If the solution is continuously stirred for a suitable time, water in the saponification agent is regularly arranged between the molecular chains of polyvinyl alcohol to crosslink the polyvinyl alcohol molecules, thereby maintaining hydrogen intermolecular hydrogen bonds while maintaining intramolecular hydrogen bonds. The blockade is arranged to arrange the molecular chains so that the polyvinyl alcohol main chains 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 side direction. The saponified reactants thus obtained are added to methanol to separate and wash, subjected to mechanical impact or crushed using an ultrasonic crusher to obtain microfibrillated fibers. The saponifying agent used in preparing the polyvinyl alcohol microfibrils short fibers of the present invention is a mixed solution of potassium hydroxide, methanol and water, and poly (vinyl pivalate / vinyl acetate) 1 × 10 ⁻⁷ to 2 × 10 ⁻⁶ mol in respect it consists of potassium ^{1 × 10 -2 ~ 3 × 10} -1 mol, methanol ^{1 × 10 -2 ~ 5 × 10} -1 mole water and 3 × 10 ^-3 ~ 2 mol. In addition, an organic polar solvent such as tetrahydrofuran, acetone, methyl ethyl ketone or dioxane may be used as the organic solvent used in the manufacturing process, and tetrahydrofuran is most effective in forming fibers having excellent physical properties.

The polyvinyl alcohol short fibers according to the present invention have properties similar to those of natural cotton or hemp fibers, and can be used for various purposes, and existing polyvinyl alcohol microfibrils prepared by the saponification process of polypival acid polymers. The advantage is that it is produced in a less expensive way than fiber. It is also very useful as an alternative to asbestos, a carcinogen, because of its excellent cohesion due to its very fine microfibrillated structure with 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 the embodiment of the present invention were measured by a fiber tensile tester, and the polyvinyls produced by spinning and drawing at 20 g / d and 1,000 or more, respectively. Tensile properties similar to alcohol fibers could be obtained directly in the saponification step.

Hereinafter, the present invention will be described in detail with reference to the following Examples, but the scope of the present invention is not limited by the following Examples.

Example 1

A 500 ml four-necked round flask equipped with a thermometer, a nitrogen inlet, an alkali saponifier redness tube, and an H-shaped anchor stirrer, had a intrinsic viscosity of 3.99 under nitrogen stream and 61.5% of an alternating diad group. (1 g) was dissolved in tetrahydrofuran (100 ml, 1.23 mol), then the temperature of the solution was raised to 60 ° C. and stirred at 500 rpm, methanol (7.5 ml, 1.84 × 10 ⁻¹ mol), hydroxide Slowly add 9 ml of a solution of potassium (2.3 g, 4.01 × 10 ^-2 mol) and water (1.5 ml, 8.31 × 10 ^-2 mol) for 4 minutes, then increase the stirring speed to 10,000 rpm and continue for 5 minutes. Stirring was again reduced 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 quantitatively pale yellow fibrous polyvinyl alcohol.

Example 2

In the same device as in Example 1, a poly (vinyl pivalate / vinyl acetate) copolymer (1 g) having an intrinsic viscosity of 4.38 and an alternating diad group content of 59.6% was added to tetrahydrofuran (100 ml, 1.23 mol). After dissolving, the temperature of the solution was raised to 60 ° C. and stirred at 500 rpm, methanol (7.0 ml, 1.72 × 10 ⁻¹ mol), potassium hydroxide (2.3 g, 4.01 × 10 ⁻² mol), and water (2.0 ml, 1.11 × 9 ml of the solution mixed with 10 ^-1 mol) was slowly added for 3 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 decreased to 2,000 rpm and the stirring was continued 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. The fibers were filtered and washed several times and dried in a vacuum oven to yield quantitatively pale yellow fibrous polyvinyl alcohol.

Example 3

In the same apparatus as Example 1, a poly (vinyl pivalate / vinyl acetate) copolymer (1 g) having an intrinsic viscosity of 4.16 and an alternating diad group content of 58.4% was added to tetrahydrofuran (100 ml, 1.23 mol). After dissolving, the temperature of the solution was raised to 60 ° C. and stirred at 500 rpm, methanol (6.5 ml, 1.60 × 1.0 ^-1 mol), potassium hydroxide (2.1 g, 3.65 × 10 ^-2 mol) and water (2.0 ml, 1.11 × 8.5 ml of the solution mixed with 10 ^-1 mol) was slowly added for 2 minutes, and then the stirring speed was increased to 10,000 rpm and the stirring was continued for 4 minutes, and the stirring speed was reduced to 2,000 rpm and the stirring was continued 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 quantitatively pale yellow fibrous polyvinyl alcohol.

Example 4

In the same apparatus as Example 1, a poly (vinyl pivalate / vinyl acetate) copolymer (1 g) having an intrinsic viscosity of 3.66 and an alternating diad group content of 56.8% was added to tetrahydrofuran (100 ml, 1.23 mol). After dissolving, the temperature of the solution was raised to 60 ° C. and stirred at 500 rpm, methanol (6 ml, 1.48 × 10 ⁻¹ mol), potassium hydroxide (2.1 g, 3.65 × 10 ⁻² mol) and water (2.5 ml, 1.39 × 10 ^-1 mol) mixed solution was slowly added for 2 minutes, and then the stirring speed was increased to 10,000 rpm and the stirring was continued for 3 minutes, and then the stirring speed was reduced to 2,000 rpm and the stirring was carried out for 7 minutes. When the reaction solidified, it was separated into another vessel, 300 ml of methanol was added, and the fibrillated fibers were 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 quantitatively pale yellow fibrous polyvinyl alcohol.

Example 5

In the same apparatus as Example 1, a poly (vinyl pivalate / vinyl acetate) copolymer (1 g) having an intrinsic viscosity of 3.16 and a content of alternating diad groups of 53.2% was added to tetrahydrofuran (100 ml, 1.23 mol). After dissolving, the temperature of the solution was raised to 60 ° C. and stirred at 500 rpm, methanol (5.5 ml, 1.35 × 10 ⁻¹ mol), potassium hydroxide (2.0 g, 3.49 × 10 ⁻² mol) and water (2.5 ml, 1.39 × 8 ml of the solution mixed with 10 ^-1 mol) was slowly added for 1.5 minutes, and then the stirring speed was increased to 10,000 rpm and the stirring was continued for 2 minutes, and the stirring speed was reduced to 2,000 rpm and the stirring was continued for 7 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 obtain a light yellow fibrous polyvinyl alcohol.

Comparative Example 1

In the same apparatus as in Example 1, polypivalate (1 g, 2.88 × 10 ^-7 mol) having a number average degree of polymerization of 27,100 was dissolved in tetrahydrofuran (100 ml, 1.23 mol), and then the temperature of the solution was increased to 60 ° C. 10 ml of a mixture of methanol (8.5 ml, 2.09 × 10 ^-1 mol), potassium hydroxide (2.5 g, 4.46 × 10 ^-2 mol) and water (1.5 ml, 8.31 × 10 ^-2 mol) with rising and stirring at 500 rpm The mixture 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 decreased to 2,000 rpm, and the stirring was continued 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 quantitatively pale yellow fibrous polyvinyl alcohol.

The properties of the polyvinyl alcohol short fibers prepared by Examples 1 to 5 and Comparative Example 1 are as shown in the following [Table].

[table]

Thus, polyvinyl alcohol microfibrils prepared from poly (vinyl pivalate / vinyl acetate) copolymers as seen in the micrographs magnified 200 times of FIGS. 1A-1D through the embodiments as described above. In each case, FIG. 1a shows an alternating diad group content of 56.8%, FIG. 1b shows an alternating diad group content of 58.4%, and FIG. 1c shows an alternating diad group content of 59.6%. 1d is a polyvinyl alcohol microfibrillated fiber having an alternating diad group content of 61.5%.

Although the present invention has been described in detail only with respect to the embodiments described, it will be apparent to those skilled in the art that various modifications and variations are possible within the technical spirit of the present invention, and such variations and modifications are within the scope of the appended claims. .

Claims (5)

A method for producing polyvinyl alcohol microfibrils, characterized in that the poly (vinyl pivalate / vinyl acetate) copolymer is dissolved in an organic solvent, followed by saponification with a saponification agent, and mechanically shearing at a shear rate of 100 rpm or more. The method of claim 1, And said organic solvent is selected from the group consisting of organic polar solvents such as tetrahydrofuran, acetone, methyl ethyl ketone or dioxane. The method of claim 2, The organic solvent is tetrahydrofuran, characterized in that the polyvinyl alcohol microfibrils fiber manufacturing method. The method according to claim 1, wherein the saponifying agent is potassium hydroxide 1 × 10 ^-2 to 3 × 10 ^-1 mol, methanol 1 to 1 × 10 ^-7 to 2 × 10 ^-6 mol of poly (vinyl pivalate / vinyl acetate) Method for producing polyvinyl alcohol short fibers, characterized in that consisting of × 10 ^-2 ~ 5 × 10 ^-1 mol and 3 × 10 ^-3 ~ 2 mol of water. Prepared by the method of claim 1, the average length is 0.1 ~ 1,000mm, has an average diameter of 0.5 ~ 100μm microfibrillated structure, the content of the alternating diad group 51 ~ 64%, the degree of saponification 85.0 ~ 99.9 Polyvinyl alcohol microfibrillated fiber having a mol% and a number average degree of polymerization of 2,500 to 20,000.