KR20070071156A - Process for preparing high-tenacity polyvinyl alcohol fiber - Google Patents

Abstract

A method for manufacturing a PVA(Poly Vinyl Alcohol) fiber is provided to produce a PVA fiber having a high crystallization and high tenacity, thereby using the PVA fiber as a concrete reinforcing material and a rubber reinforcing material. A PVA is polymerized, wherein the PVA has a polymerization degree of 1500-7000, and a soponification degree of 99.0-100 mol%. A PVA spinning dope is formed by dissolving the obtained PVA in a mixing solvent consisting of dimethylsufoxide and methanol. An undrawing yarn is formed by wetting or wet-spinning the PVA spinning dope at a low temperature using an alkali precipitation bath. The undrawing yarn is cleansed, dried, and oil-processed, thereby manufacturing a PVA fiber.

Description

Process for preparing high-tenacity polyvinyl alcohol fiber

The present invention relates to a method for preparing high crystalline and high strength polyvinyl alcohol (hereinafter referred to as 'PVA') fibers and to PVA fibers obtained therefrom, and more particularly to dimethyl sulfoxide (hereinafter referred to as 'DMSO') and methanol. PVA spinning dope prepared by dissolving PVA of high polymerization degree and saponification degree in a mixed solvent mixed with the same, was spun into an alkali coagulation bath to remove acetyl groups remaining in the PVA polymer during coagulation to make the saponification degree of the fiber 99.9% or more. The present invention relates to a method for producing high crystalline and high strength PVA fibers, and to polyvinyl alcohol fibers suitable for industrial production therefrom.

PVA gel spinning has been actively researched and developed among various methods for producing industrial high strength PVA fibers. In general, PVA gel spinning is a method of producing a high strength fiber by mixing PVA and an organic solvent to prepare a uniform solution, and then by controlling the phase separation and the gelation rate in the spinning process to enable high magnification stretching. Such gel spinning has a disadvantage in that it has a high strength characteristic only when solidified at a low temperature.

In Japanese Patent Laid-Open No. H1-130799, a high-strength PVA fiber having a tensile strength of 10 g / d or more was produced by allowing spinning at low temperatures using a mixed solvent of an organic solvent and water. As such, when the organic solvent / water mixed solvent is used, the solidification temperature of the PVA spinning dope is lowered to enable gel spinning even at low temperatures, but it is difficult to separate and use methanol as the coagulation solvent, which makes industrial use difficult. . Recently, a method for gel spinning with DMSO alone has been developed for the industrialization of PVA gel spinning. However, in order to obtain high strength PVA fibers in such solvent wet and dry spinning, a high saponification PVA polymer of 99.9% or more should be used. Thus, it is not easy to prepare a high saponification polymer, and it is large to improve the fiber strength by high magnification thermal stretching. It is an obstacle.

An object of the present invention is to spin the PVA spinning dope prepared by dissolving PVA of high polymerization degree in a mixed solvent mixed with DMSO and methanol in an alkali coagulation bath to remove the acetyl group remaining in the PVA polymer during coagulation to improve the degree of saponification of the fiber. By at least%, to provide a method for producing high crystalline, high strength PVA fibers and PVA fibers obtained therefrom.

The present invention (1) a polymerization step of producing a polymerization degree of 1,500 to 7,000, saponification degree 99.0 to 100 mol% PVA; (2) a dissolution step of dissolving the PVA obtained in the polymerization step in a mixed solvent formed by mixing DMSO and methanol to prepare a PVA spinning dope; (3) preparing the unstretched yarn according to conventional wet-wet or wet spinning using the PVA spinning dope at low temperature using an alkali coagulation bath; And (4) provides a method for producing a high crystallinity and high strength polyvinyl alcohol fiber suitable for industrial use, including the step of washing, drying and emulsion treatment of the unstretched yarn.

In addition, the mixing ratio of the mixed solvent in the step (2) is preferably mixed 60 to 95% by weight of DMSO and 5 to 40% by weight of methanol.

In addition, the alkali additives added in the step (3) is preferably sodium hydroxide or sodium sulfate.

In addition, the concentration of the alkali additives added in the step (3) is preferably 0.5 to 20 wt%.

In addition, the present invention provides a polyvinyl alcohol fiber produced by the above method, the tensile strength of 16.5d / g or more, the elastic modulus of 400g / d or more.

Hereinafter, the present invention will be described in detail with reference to specific examples.

In the present invention, the degree of PVA polymerization is about 1,500 to 7,000, and preferably a high degree of polymerization PVA of 1,700 to 3,000 is effective. When the degree of polymerization is less than 1,500, it is difficult to form fibers, and when the degree of polymerization is greater than 7,000, the viscosity may be too high, thereby causing a problem that the spinning processability is lowered.

High-strength PVA fibers, which are mostly used in the field of industrial materials, need hot water resistance, so PVA having a saponification degree of 99.0 to 100 mol% is preferable.

Ethylene glycol, glycerin, and DMSO can be used as the organic solvent, but DMSO having the best solubility in PVA is suitable. Such DMSO is preferably used to be purified to a moisture content of several tens ppm or less.

Methanol mixed in DMSO is used in an amount of about 5 to 40% by volume, preferably 10 to 20% by volume. If the content of methanol in the solvent is less than 5% by volume, the gel spinning is impossible due to coagulation of the PVA spinning dope below 0 ° C. If it exceeds 40% by volume, the spinning dope is condensed, but the entire gel forms a turbidity. There may be a problem of not forming a gel.

PVA dope is preferably adjusted in concentration so that the viscosity is in the range of 50 to 4,000 poise (Poise), but 500 to 3,000 poise is effective to obtain excellent physical properties. When the viscosity is less than 50 poise, it is difficult to form fibers, and when the viscosity is more than 4,000 poise, there may be a problem that the fiber radioactivity is lowered.

The coagulation bath can spin at a temperature of -30 to 30 ° C, but -10 to 10 ° C is effective for uniform gel formation. If the coagulation bath temperature is less than -30 ° C, since 40% by volume of methanol in the solvent should be mixed, the PVA dissolving power is lowered, making it impossible to prepare a uniform PVA spinning dope. There may be a problem in that the radioactivity is lowered due to the impossibility of gel formation.

PVA fiber manufacturing methods include a dry method, a wet method, and a dry and wet method in which the two methods are mixed. However, the wet and dry method is effective in the high strength PVA fiber manufacturing method requiring a high magnification stretching process.

The air-gap may be 10 to 300 mm in the wet and dry method for preparing the PVA filament, but 20 to 100 mm is preferable for high magnification of thermal stretching. If the air-gap is less than 10 mm, workability deteriorates, whereas if it exceeds 300 mm, high magnification thermal stretching is impossible due to the higher degree of crystallinity than gelation degree, and productivity is improved because fusion between fibers occurs immediately after the nozzle. There may be a problem that is degraded.

The biggest feature of the present invention is to prepare PVA fibers of high strength and high modulus by adding alkali additives to the coagulation bath to remove acetyl groups remaining in the PVA polymer during coagulation to make the saponification degree of the fibers 99.9% or more.

As the alkali additive to be added to the coagulation bath, sodium hydroxide, sodium sulfate and the like are preferable. At this time, the total weight of the additive is preferably 0.5 to 20% by weight relative to the methanol coagulation bath. If the total weight of the additive is less than 0.5% by weight, it does not contribute to the improvement of physical properties such as PVA strength, elastic modulus, etc., and if the total weight exceeds 20% by weight, it causes a non-solvent velocity unevenness, leading to a decrease in fiber properties.

The heating method of the stretching process includes hot air heating and roller heating, but hot air heating 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. Heating at a temperature of 180 to 250 ° C. is possible but preferably 210 to 230 ° C. is suitable. If the heating temperature is less than 180 ° C, high magnification thermal stretching is not possible because the molecular chain is not sufficiently behaved, and if it exceeds 250 ° C, there may be a problem that the physical properties are degraded because PVA is easily decomposed.

In order to increase the crystallinity of the fiber thus produced, it is effective to heat-treat at a temperature of 5 to 10 ℃ higher than the stretching process. In this stretching process, it is characterized in that the heat stretching so that the total draw ratio is 18 times or more.

The high crystalline and high strength PVA fibers obtained by the method according to the present invention as described above can be stretched 18 times or more to provide a high strength PVA fiber having a tensile strength of at least 16.5g / d, elastic modulus of 400g / d or more.

Hereinafter, preferred embodiments and comparative examples of the present invention will be described.

The following examples are intended to illustrate the invention and should not be understood as limiting the scope of the invention.

Tensile strength, elastic modulus and elongation were measured according to KS K 0412 at a sample length of 10 cm and a tensile speed of 300 mm / min. In addition, the hot drawing process was carried out at a hot air temperature of 230 ° C. in the first step 200 ° C., 220 ° C. in the second step.

Example 1

PVA used 99.5 mol% and 3,300 respectively in the form of saponification and polymerization degree, and methanol and DMSO used a purified solvent having a water content of 100 ppm or less. A mixed solvent was prepared by mixing DMSO and methanol so that the methanol content of the solvent was 15% by volume, and PVA was dissolved to 18 wt% with respect to the PVA spinning dope. Thereafter, PVA fibers were prepared by wet and dry spinning using gel spinning. At this time, the number of nozzle odds and hole diameters were 1000 and 0.3 mm, respectively, and a circular nozzle having 5 L / D was used. The air gap was 30 mm, and the solvent in the coagulation bath was methanol, and sodium chloride was added to 5 wt% based on the total weight of the coagulation bath, and the temperature was maintained at 0 ° C. The hot drawing was carried out using a three-step hot air heating method, and the hot air heating temperature was performed at 230 ° C. as a first step of 200 ° C., two steps of 220 ° C., and three steps as heat treatment steps. The draw ratios for each stage were 4.5 and 1.64 times, and the total draw ratios were 18.5 times. As such, the PVA fiber prepared in the state of almost removing the spinning solvent was confirmed to be a high-strength PVA fiber having a strength of 19.5 g / d, an elastic modulus of 400 g / d, and an elongation of 5.0%.

Examples 2 and 3

To compare the strength, elastic modulus, elongation, and the like of the filament obtained by hot stretching at a high temperature by adjusting the sodium hydroxide addition ratio in the coagulation bath at the ratio as shown in Table 1.

Comparative Examples 1 and 2

Comparative Examples 1 and 2 compared the fiber properties in the case of hot stretching by adding ammonium sulfate and sodium sulfate in the coagulation bath and the results are shown in Table 1.

Comparative Example 3

Comparative Example 3 is the case of spinning and hot stretching without adding an alkali salt to the coagulation bath, the results are shown in Table 1.

division Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 PVA degree of polymerization 3300 3300 2000 3300 3300 3300 PVA saponification degree (mol%) 99.5 99.0 99.9 99.5 99.5 99.0 Type of coagulation salt / concentration (% by weight) NaOH / 5 NaOH / 20 NaOH / 5 _{(NH 4) 2 SO 4/} 10 Na ₂ SO _4/40 0 Total draw ratio 19 18 16 15 14 12 Tensile strength (g / d) 20 19.5 18 14 13 10 Modulus of elasticity (g / d) 460 400 350 250 240 200 Elongation (%) 5 5.5 6 6 8 5

As a result of the synthesis of the above embodiments, it was confirmed that when the PVA fiber according to the present invention can be obtained high strength PVA fiber of 20g / d. In addition, by adding NaOH to the coagulation bath to remove the acetyl group remaining in the polymer, high crystallinity and high strength PVA fibers could be produced. The high-strength PVA fibers produced as described above have excellent properties as rubber and rubber reinforcement materials, especially automobile brake hoses and tires, as well as cement and concrete reinforcement materials.

The high crystallinity and high strength PVA fibers produced by the present invention can provide high strength PVA fibers having excellent properties as rubber and rubber reinforcements such as automobile brake hoses and tires, as well as cement and concrete reinforcements.

Claims (6)

(1) a polymerization step of preparing a polymerization degree of 1,500 to 7,000 and a saponification degree of 99.0 to 100 mol% polyvinyl alcohol; (2) a dissolution step of dissolving the polyvinyl alcohol obtained in the polymerization step in a mixed solvent consisting of dimethyl sulfoxide and methanol to prepare a polyvinyl alcohol spinning dope; (3) preparing the unstretched yarn by wet or wet spinning the polyvinyl alcohol spinning dope using an alkali coagulation bath at low temperature; (4) A method for producing polyvinyl alcohol fibers, characterized in that it is produced by a method comprising the step of stretching by washing, drying and emulsion treatment of the unstretched yarn. The method of claim 1, The mixing ratio of the mixed solvent in the step (2) is a method for producing polyvinyl alcohol fibers, characterized in that 60 to 95% by weight of dimethyl sulfoxide and 5 to 40% by weight of methanol is mixed. The method of claim 1, The alkali additives added in the step (3) is a method of producing polyvinyl alcohol fibers, characterized in that sodium hydroxide or sodium sulfate. The method of claim 1, The concentration of the alkali additives added in step (3) is a method for producing polyvinyl alcohol fibers, characterized in that 0.5 to 20 wt%. The method of claim 1, Stretching in the step (4) is a method of producing a polyvinyl alcohol fiber comprising at least two temperature rising step. A high strength polyvinyl alcohol fiber, according to any one of claims 1 to 5, characterized in that the tensile strength is at least 16.5d / g, the elastic modulus is at least 400g / d.