KR20020049853A - Process for preparing high-tenacity polyvinyl alcohol fiber - Google Patents

Abstract

PURPOSE: A process of preparing polyvinylalcohol fiber having a tensile strength of 25 g/d or more and an elongation of 25 times by mixing polyvinyl alcohol and ethylene/vinyl alcohol copolymer in a suitable mixing rate is provided. Therefor, the fiber is used as a tire cord, in particular cement and concrete reinforcing material and rubber reinforcing material for hydraulic oil hose. CONSTITUTION: A mixture of ethylene/vinyl alcohol copolymer(EVOH) and polyvinyl alcohol(PVA) in a ratio of 0.5:99.5 to 15:85 is dissolved in dimehylsulfoxide(DMSO) to produce a PVA dope, which is spun to produce high strength polyvinyl alcohol having a polymerization degree of 1,500 to 7,000. The EVOH and PVA have a saponification degree of 99.0 mol% or more.

Description

Process for preparing high-tenacity polyvinyl alcohol fiber

The present invention relates to a method for producing high strength polyvinyl alcohol fibers, and more particularly, in the method for producing high strength polyvinyl alcohol fibers, poly (ethylene-co-vinyl alcohol) (EVOH) and polyvinyl alcohol (PVA) It relates to a method for producing a high strength polyvinyl alcohol fiber comprising the step of dissolving the EVOH / PVA mixture containing in dimethyl sulfoxide (DMSO) to produce a PVA dope, and spinning the PVA dope.

Polyvinyl alcohol (hereinafter referred to as "PVA") has a planar zig-zag molecular structure similar to that of polyethylene, and thus is a representative raw material capable of producing high strength fibers with high orientation and density. PVA fibers exhibit higher strength and modulus than polyamide, polyester and polyacrylonitrile fibers, which are general purpose fibers, and are particularly used as various industrial materials because of their excellent adhesion, water dispersibility, alkali resistance and chemical resistance. Recently, various reinforcing agents such as concrete and cement reinforcing agents and rubber and plastics have been used, and in addition, research and development are being actively conducted as materials having high application potential in new fields. In particular, in recent years, since the materials used in various industrial fields require even higher tensile strength, intensive research and development of high-strength PVA fibers is required.

To date, various methods have been developed for obtaining high strength PVA fibers. For example, U.S. Patent No. 4,440,711 uses a gel spinning method (see U.S. Patent No. 4,698,194) to obtain PVA fibers by obtaining a high-strength polyethylene fiber by a high magnification stretching process using high molecular weight polyethylene as a raw material. A method of obtaining PVA fibers is disclosed. Gel spinning method is a general method for producing high strength fibers by mixing a polymer and a solvent to prepare a uniform solution, and by controlling the phase separation and the gelation rate in the spinning process to achieve high magnification.

However, the method of US Pat. No. 4,440,711 has the following disadvantages. Since PVA has a very strong intermolecular hydrogen bond by hydroxyl groups present in a large amount in the molecule, it is not possible to draw higher magnification than polyethylene fiber using the conventional gel spinning method. That is, in order to manufacture high-strength PVA fibers, it is necessary to enable thermal stretching of 25 times or more, but hydrogen bonding between PVA molecules limits such high magnification and acts as a major cause of PVA fiber strength reduction. In addition, the high-polymerization PVA used in the U.S. Patent No. 4,440,711 has no productivity, and when the polyol is used as a solvent, the workability is poor, and thus, development of a new method for producing a high strength PVA fiber has been required.

In this regard, a new method of using inorganic compounds to suppress the intermolecular hydrogen bonding of PVA fibers has been published. Japanese Patent Laid-Open No. 62-149909 discloses a method for producing a high strength / high modulus PVA fiber having a total draw ratio of 20 or more using a boron-based compound so as to have a tensile strength of 18 g / d or more and an elastic modulus of 350 g / d or more. However, the addition of such an inorganic compound complicates the manufacturing process and causes the durability of the product when the added compound remains in the final product.

An object of the present invention is to solve the problems of the prior art as described above, using poly (ethylene-co-vinyl alcohol) as a hydrogen bonding inhibitor between polyvinyl alcohol molecules, high magnification stretching necessary for improving the strength of polyvinyl alcohol fibers. It is to provide a method for producing a high strength polyvinyl alcohol fiber that is realized.

That is, the present invention is a method for producing high strength polyvinyl alcohol fibers, wherein the EVOH / PVA mixture containing poly (ethylene-co-vinyl alcohol) (EVOH) and polyvinyl alcohol (PVA) to dimethyl sulfoxide (DMSO) It provides a method of producing a high-strength polyvinyl alcohol fiber comprising the step of dissolving to prepare a PVA dope, and spinning the PVA dope.

Hereinafter, the manufacturing method of the high strength polyvinyl alcohol fiber of this invention is demonstrated in detail.

Poly (ethylene-co-vinylalcohol) (hereinafter referred to as "EVOH") used as a hydrogen bonding inhibitor in the method for producing high strength polyvinyl alcohol (PVA) fibers of the present invention is ethylene and vinyl alcohol. It is a copolymer of, has various properties according to the ratio of two components, and has excellent gas barrier property, and is widely used in places where protection from oxygen is required. In addition, since the hydroxyl group present in the EVOH molecule has excellent properties such as hydrophilicity, chemical resistance, and electrostatic resistance, it is used to prepare fibers for various uses by mixing various plastic polymers in an appropriate ratio. In the present invention, it is preferable to use EVOH having a content of vinyl alcohol of 30 to 70 mol%, preferably 50 to 70 mol%.

The PVA used in the present invention is preferably used having a degree of polymerization of 1500 to 7000, preferably 1700 to 3000. If the degree of polymerization is less than 1500, it is difficult to form fibers, and if the degree of polymerization is greater than 7000, the viscosity is too high and the radioactivity is poor.

On the other hand, the high-strength PVA fibers used as industrial materials in most cases because hot water resistance is required, the degree of saponification of the EVOH and PVA should be at least 99.0 mol%. If the degree of saponification of EVOH and PVA is less than 99.0 mol%, the acetyl group remaining in the molecule interferes with the crystallization of the PVA fiber, thereby making the fiber easily swell / dissolve in hot water. In addition, these acetyl groups cause degradation reactions, thereby degrading the durability of the final product.

The weight ratio of poly (ethylene-co-vinyl alcohol) and polyvinyl alcohol in the EVOH / PVA mixture is 0.5 to 99.5 to 15 Vs. 85, preferably 5 to 95 to 15 to 85.

The viscosity of the PVA dope obtained by dissolving the EVOH / PVA mixture in DMSO is preferably in the range of 50 to 4000 Poise, more preferably 500 to 3000 Poise. If the viscosity of PVA dope is less than 50, fiber formation is difficult, and if it exceeds 4000, fiber spinning is inferior.

According to the method of the present invention, the spinning of the PVA dope is preferably done in a wet and dry manner. Many methods, such as a dry method, a wet method, and a wet method, are used for the high-strength PVA fiber spinning method, but recently, the wet and dry spinning method which can draw high magnification is mostly used. For example, Japanese Patent Publication No. 60-126312 discloses a PVA fiber having a tensile strength of 15 g / d or more and an elastic modulus of 300 g / d or more by using a wet and dry spinning method that controls an air gap within a range of 20 to 300 mm. Disclosed is a method of preparing the same.

The air gap may be 20 to 300 mm in the wet and dry spinning method for preparing a conventional PVA filament, but in the present invention, a narrow air gap of 30 to 100 mm is preferable for high magnification thermal stretching. If the air gap is less than 20, the workability is inferior. On the contrary, if the air gap is greater than 300, high magnification thermal stretching is impossible because the crystallinity is larger than the degree of gelation.

In general, the hot drawing process in the production of high strength PVA fibers is very important for improving the strength and hot water resistance of the PVA fibers. The heating method of the hot drawing process includes hot air heating and roller heating, which is more effective for producing high-strength PVA fibers because the filament is in contact with the roller surface and the fiber surface is easily damaged. According to the high-strength PVA fiber manufacturing method of the present invention, the hot air heating hot drawing process is carried out at a temperature of 140 to 230 ℃, preferably at a temperature of 160 to 200 ℃. At temperatures below 140 ° C., the PVA molecular chain does not behave sufficiently, so high magnification thermal stretching is not possible, and at temperatures above 230 ° C., EVOH is easily decomposed, resulting in deterioration of physical properties.

According to the high-strength polyvinyl alcohol fiber production method of the present invention, by using a mixture of PVA and a small amount of EVOH as a raw material, (i) the melting point of EVOH is 123 to 205 ℃ melting point of PVA depending on the content of vinyl alcohol Since it is lower than ℃, it is possible to achieve high magnification stretching at a relatively low temperature, that is, 200 ° C. or lower, compared with the case of using only PVA, and (ii) the stretching ratio of PVA fibers which is currently industrially available is about 17 times, It is possible to increase by more than 25 times.

PVA fibers prepared according to the method of the present invention described above have a high strength of 25g / d or more of tensile strength, and is also suitable for clothing because the skin contact improves in proportion to the EVOH content in the PVA dope.

Hereinafter, the present invention will be described in more detail with reference to examples, but these examples are for illustrative purposes only and should not be construed as limiting the present invention.

Example 1

18 weights of EVOH / PVA (5/95) mixture of EVOH (99.5 mol% saponification, 70 mol% vinyl alcohol content) and PVA (99.5 mol% saponification degree, polymerization degree 2500) in powder form in a weight ratio of 5 to 95 The part was mixed with 100 parts by weight of DMSO to swell at room temperature and then dissolved at 130 ° C. to prepare a uniform PVA dope. Subsequently, the PVA filament was spun by a dry wet gel spinning method. The nozzle used for spinning was a circular nozzle with an L / D of 5, with 200 holes in the nozzles and a hole diameter of 0.5 mm. When spinning, the air gap was 50 mm, and methanol was used as a solvent in the coagulation bath. The coagulation bath maintained the conditions of DMSO / methanol mixture ratio 20/80, the temperature of 20 ℃ or less. If the solvent remains in the filament, it is the main cause of the final filament properties deterioration by causing discoloration of the filament in the subsequent hot stretching process, so that after passing through the extraction tank was adjusted so that there is no solvent DMSO in the PVA filament.

Hot stretching was performed using a three stage hot air heating drawing machine. At this time, the hot air heating temperature was 190 ° C. in the first step, 195 ° C. in the second step, and 195 ° C. in the third step. The physical properties of the PVA fibers obtained therefrom were measured and shown in Table 1 below.

Example 2

PVA fibers were prepared in the same manner as in Example 1, except that the EVOH / PVA (10/90) mixture in which EVOH and PVA were mixed at a weight ratio of 10 to 90 was used. The physical properties of the PVA fibers obtained therefrom were measured and shown in Table 1 below.

Example 3

PVA fibers were prepared in the same manner as in Example 1, except that the EVOH / PVA (15/85) mixture in which EVOH and PVA were mixed at a weight ratio of 15 to 85 was used. The physical properties of the PVA fibers obtained therefrom were measured and shown in Table 1 below.

Comparative Example 1

PVA fibers were prepared in the same manner as in Example 1, except that the EVOH / PVA mixture was replaced with PVA. The physical properties of the PVA fibers obtained therefrom were measured and shown in Table 1 below.

Comparative Example 2

PVA fibers were prepared in the same manner as in Example 1, except that the EVOH / PVA (20/80) mixture in which EVOH and PVA were mixed at a weight ratio of 20 to 80 was used. The physical properties of the PVA fibers obtained therefrom were measured and shown in Table 1 below.

Comparative Example 3

PVA fibers were prepared in the same manner as in Example 1, except that EVOH having 5% vinyl alcohol content was used instead of EVOH having 70% mol of vinyl alcohol when preparing an EVOH / PVA (5/95) mixture. It was. The physical properties of the PVA fibers obtained therefrom were measured and shown in Table 1 below.

Comparative Example 4

PVA fibers were prepared in the same manner as in Example 1, except that PVA having a polymerization degree of 1000 was used instead of PVA having a polymerization degree of 2500 when preparing an EVOH / PVA (5/95) mixture. The physical properties of the PVA fibers obtained therefrom were measured and shown in Table 1 below.

division Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 PVA degree of polymerization 2500 2500 2500 2500 2500 2500 1000 Vinyl alcohol content in EVOH (mol%) 70 70 70 - 70 5 70 EVOH / PVA (% by weight) 5/95 10/90 15/85 0/100 20/80 5/95 5/95 Total draw ratio 26 27 28 17 30 20 10 Tensile strength (g / d) 30 28 26 20 15 20 12 Modulus of elasticity (g / d) 330 315 310 350 250 280 100 Elongation (%) 8 8 9 5 12 6 4

[Measurement Method]

Tensile strength, modulus and elongation: KSK O412 (sample length 10cm, tensile speed 30cm / min)

As described in detail above, according to the method for producing high-strength polyvinyl alcohol fibers of the present invention, by mixing a poly (ethylene-co-vinyl alcohol) in an appropriate ratio of polyvinyl alcohol, PVA intermolecular interfering with high magnification stretching of PVA fibers By inhibiting hydrogen bonding, it is possible to stretch in total 25 times or more to provide a high strength PVA fiber having a tensile strength of 25 g / d or more. The high strength PVA fibers of the present invention are not only usable as cement and concrete reinforcements, but also are particularly useful as rubber reinforcements such as automobile brake hoses and tires.

Claims (6)

In the method for producing high strength polyvinyl alcohol fibers, an EVOH / PVA mixture comprising poly (ethylene-co-vinyl alcohol) (EVOH) and polyvinyl alcohol (PVA) is dissolved in dimethyl sulfoxide (DMSO) to prepare PVA dope. A method of producing a high strength polyvinyl alcohol fiber comprising the step of manufacturing and spinning the PVA dope. The method of claim 1, The poly (ethylene-co-vinyl alcohol) (EVOH) and polyvinyl alcohol (PVA) is a method for producing high strength polyvinyl alcohol fibers, characterized in that the degree of saponification 99.0 mol% or more. The method of claim 1, Method of producing a high strength polyvinyl alcohol fiber, characterized in that the vinyl alcohol content of the poly (ethylene-co-vinyl alcohol) is 30 to 70 mol%. The method of claim 1, Method for producing a high strength polyvinyl alcohol fiber, characterized in that the polymerization degree of the polyvinyl alcohol is 1500 to 7000. The method of claim 1, Method for producing a high strength polyvinyl alcohol fiber, characterized in that the weight ratio of poly (ethylene-co-vinyl alcohol) and polyvinyl alcohol in the EVOH / PVA mixture is 0.5 to 99.5 to 15 to 85. The method of claim 1, The spinning is a method of producing a high strength polyvinyl alcohol fiber, characterized in that the wet and dry.