JP2905545B2 - High strength and high modulus polyvinyl alcohol fiber with excellent hot water resistance - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a polyvinyl alcohol (hereinafter abbreviated as PVA) fiber having a high strength and a high elastic modulus and excellent in hot water resistance. PVA suitable for applications that require hot water resistance for materials and composite reinforcement
It relates to a system fiber.

(Prior art) Conventional PVA fiber has higher strength and elastic modulus than polyamide, polyester and polyacrylonitrile fiber, and is used as a substitute for asbestos fiber in addition to being used as the main application fiber for industrial materials. It is also used for fibers for cement reinforcement.

In recent technology, PVA with higher strength and higher elastic modulus
Japanese Patent Application Laid-Open No. 59-100710, which applies the concept of gel spinning and ultra-drawing of high molecular weight polyethylene as a method for obtaining a system fiber.
And JP-A-59-130314 and JP-A-61-108711 have been proposed. However, even with these methods, even though PVA-based fibers having high strength and high elastic modulus can be obtained, they cannot be provided with high hot water resistance required in some application fields.

Attempts to increase the hot water resistance of PVA-based fibers have long begun with water-insolubilization treatment by acetalization.However, in recent high-polymerization and high-strength PVA-based fibers, the molecular orientation of the amorphous part has progressed and the dimensional stability to water has increased. Can be achieved without performing the above-described water insolubilization treatment. But for example 120 ° C
It quickly melted in hot water, and was still unsatisfactory for applications such as reinforcement for autoclaved cement moldings and ropes that are susceptible to frictional heat.

Also, as disclosed in JP-A-1-156517 and JP-A-1-207435, or as disclosed in JP-A-1-104815, a method of improving hot water resistance by crosslinking treatment with a peroxide compound, an isocyanate compound, boric acid, or the like is described. It is known. However, these methods crosslink prior to stretching, impairing stretchability, and lowering the strength and elastic modulus due to insufficient molecular orientation. On the other hand, when trying to crosslink after stretching, to swell the fiber to strengthen the penetration of the crosslinking agent inside the fiber,
It is necessary to perform high temperature heat treatment.
There was a problem that PVA was decomposed and damaged, and the elastic modulus of strength was easily reduced.

(Problems to be Solved by the Invention) In view of the above background, the present inventors intend to provide a PVA-based fiber excellent in hot water resistance while maintaining high strength and high elastic modulus.

(Means for Solving the Problems) As a result of intensive studies for solving the above problems, the present inventors have found fibers that maintain a strength elastic modulus corresponding to the degree of polymerization of a PVA-based polymer and have extremely high hot water resistance. This has led to the present invention.

By the way, when the degree of polymerization of PVA increases, the strength elastic modulus and the hot water resistance generally improve, but the fiber of the present invention is far more compared with the fiber obtained by the conventional method when compared with the same degree of polymerization. High strength and high modulus PVA with extremely high hot water resistance
It is intended to provide a system fiber. That is, the present invention relates to a fiber comprising a polyvinyl alcohol-based polymer having a viscosity average degree of polymerization of 3,000 or more, which is obtained by adding a surfactant to a spinning dope, spinning and drawing, and having a hot water dissolution temperature of the following formula: A high-strength high-modulus PVA fiber excellent in hot water resistance, which satisfies the above, and has a tensile strength of 16 g / d or more and an elastic modulus of 350 g / d or more.

WTb ≧ 1.2 _A ^0.35 +115 ( _A ≧ 3,000) where WTb is the hot water dissolution temperature _A under a load of 200 mg / d _A is the viscosity average degree of polymerization of the PVA polymer.

Such a PVA-based fiber having high strength and high elasticity excellent in hot water resistance of the present invention can be obtained, for example, by adopting a method of adding a surfactant to a stock solution of PVA and removing it in a spinning step. can get. Hereinafter, the fiber of the present invention and the production method thereof will be described in detail, but the fiber of the present invention is not limited to the following production method.

The PVA-based polymer used in the present invention has a viscosity average degree of polymerization of 3,000 or more, preferably 6,000 or more, more preferably 10,000 or more, determined from the intrinsic viscosity of an aqueous solution at 30 ° C., and has a saponification degree of 98 mol. % Or more and a linear PVA with a low degree of branching is preferred. It is also possible to add an additive such as a copolymer of 2 mol% or less of another vinyl compound or 3 wt% or less of boric acid, an antioxidant and an ultraviolet absorber. When the degree of polymerization is less than 3,000, the effect of improving the hot water resistance is almost nil.

In the present invention, as a solvent for the PVA polymer used, ethylene glycol, trimethylene glycol, diethylene glycol, polyhydric alcohols such as glycerin, dimethyl sulfoxide, dimethylformamide, diethylene triamine, water and a mixed system of two or more of these, Alternatively, a rodan salt aqueous solution, a propanol aqueous solution and the like can be mentioned. Among these, polyhydric alcohol, dimethyl sulfoxide, and a mixed solvent thereof with water are preferable for obtaining transparent and uniform gel fibers.

Preferably, the surfactant is dispersed or dissolved in the PVA solution in a size of 100 μm or less. If there is a large agglomerate exceeding 500μ, the fiber may be broken at the time of spinning, the molecular orientation may be disturbed, or a defect may be easily formed in a void at the time of removal, and the fiber performance may be reduced. Surfactants can be either nonionic, anionic, cationic, or amphoteric surfactants that are dispersed or dissolved in the PVA solvent in fine particles and have little decomposition or coloring. There is no problem at all.

The addition method to the PVA solution is a method in which the surfactant is uniformly dispersed or dissolved, such as adding and mixing before the PVA is dissolved in the solvent, or dispersing or dissolving the surfactant in the solvent in advance, and adding the PVA solution on the way. If so, either is good.

The amount of addition is 1% by weight or more, preferably 3% by weight or more based on PVA, but if it is 20% by weight or more, the effect of hot water resistance does not change, and on the contrary, it takes time and effort to remove it.

In this production method, a PVA-based polymer solution (stock solution) to which the surfactant is added is extruded from a nozzle into a fibrous form by a dry method, a wet method, and a dry-wet method (gel spinning method). Any method can be employed, but in order to obtain a high-strength high-modulus fiber excellent in heat-resistant water as the object of the present invention, a wet method or a dry-wet method in which the PVA concentration is reduced is used. preferable.

Examples of the coagulation bath include alcohols such as methanol and ethanol, acetone and a mixture thereof with a solvent or water, or an aqueous solution of an inorganic salt such as an alkali or sodium sulfate, and those obtained by adding a surfactant to the coagulation bath. Either is acceptable.

In this production method, it is necessary to remove the surfactant added until the solvent is extracted and dried, and the remaining amount is 2% by weight or less, preferably 1% by weight or less based on the PVA fiber.

If a large amount of the surfactant remains in the fiber, the affinity for water increases, or the penetration of water into the fiber is promoted, and the hot water resistance is lowered, which is not preferable.

The reason why the hot water is improved by adding and removing the surfactant is not clear, but when the PVA is dissolved, the spread and entanglement of the PVA molecular chains in the solution are changed by the addition of the surfactant, and It is considered that the removal of the surfactant together with the gel formation causes an increase in the number of tie molecules between the PVA microcrystals and a change in the microstructure, which is said to be likely to be oriented by subsequent stretching.

The thus obtained dried spun yarn is hot-drawn by a conventional method to enhance the orientation and crystallization of PVA molecular chains. In the spinning step, it is preferable to perform wet stretching in a state of containing a solvent in a 2 to 6 times state in terms of promoting orientation, but the total stretching ratio including the wet stretching ratio is 16 times or more, preferably 18 times or more, and more preferably. Is more than 20 times.

The temperature of hot stretching is 200 ° C. or higher, preferably 230 ° C. or higher, and high-temperature high-magnification stretching involves high orientation and high crystallization, and is desirable because it also improves the strength, the elastic modulus and the hot water resistance. Care must be taken to ensure that PVA does not decompose.

The hot water dissolution temperature of the PVA-based fiber in the present invention satisfies the following equation based on experimental data, and belongs to the upper portion of the hatched portion in FIG.

WTb ≧ 1.2 _A ^0.35 +115 ( _A ≧ 3,000) However, WTb indicates the hot water dissolution temperature, and after hanging a single fiber with a load of 200 mg per denier on 25 single fibers,
It means the temperature at which the fiber is melted by heating at a heating rate of 2 ° C./min. Under a load of 200 mg / d, the fibers do not shrink and fuse, but under a low load, the fibers tend to shrink, and the data vary widely.

_A is the viscosity-average degree of polymerization of the PVA-based polymer.
It is a value obtained from the measured value of the limiting viscosity [η] of the aqueous solution at 30 ° C. according to the formula of log _A = 1.63 log ([η] × 10 ⁴ /8.29) according to −6726.

Generally, the hot water dissolution temperature increases as the degree of polymerization increases,
The drawn fiber of the prior art without surfactant added has a lower temperature than the present invention (below the shaded area in FIG. 1), and the fiber of the present invention maintains a hot water dissolution temperature higher by 5 to 50 ° C. at any polymerization degree. I do.

The fiber in the present invention has a tensile strength of 16 g / d or more and an elastic modulus of 3
It has a value of 50 g / d or more, but these values also increase as the degree of polymerization increases, for example, at a degree of polymerization of 4,000, the strength is about 18 g / d, the elastic modulus is about 400 g / d, and at the degree of polymerization of 17,000, the strength is about 22 g / d, the elasticity. The rate becomes about 500 g / d.

On the other hand, when a known crosslinking treatment or the like is performed without the addition of a surfactant, the hot water resistance for each degree of polymerization is the same as that of the present invention, but the strength and elastic modulus are low, and the strength as in the present invention is low. Fiber having high elastic modulus and high hot water resistance was not obtained.

(Effect of the Invention) The fiber of the present invention is a PVA-based fiber having high hot water resistance, high strength and high elasticity, which has not been seen in the past, and is used for industrial materials such as ropes and canvases, asbestos substitute cement reinforcing material, and tire reinforcing material. It can be expected to be widely used for hose reinforcement for high temperature and high pressure, reinforcement for FRP, cement reinforcement for autoclave curing, etc.

(Examples) Hereinafter, the present invention will be described more specifically with reference to examples.

The tensile strength and elongation and the elastic modulus are based on JISL-1013, and the yarn conditioned beforehand is tested at a test length of 20 cm with an initial load of 0.25 g / d and 100%.
The breaking elongation at break and the initial elastic modulus were determined at a tensile rate of% / min, and an average value of 10 or more points was adopted. Denier was measured by a gravimetric method.

Examples 1 and 2 and Comparative Examples 1 and 2 The viscosity average degree of polymerization was 7,000 (Example 1) and 18,000
The fully saponified PVA of (Example 2) was mixed with glycerin so as to be 9% by weight and 5% by weight, respectively, and at the same time, the surfactant of sucrose fatty acid ester was 5% by weight based on PVA.
And dissolved at 180 ° C.

In each of Examples 1 and 2, a clear solution was obtained.
Next, the solution was discharged into the air from a nozzle having 150 holes and a hole diameter of 0.17 mm, and dropped into a coagulation bath 25 mm below. The composition of the coagulation liquid is methanol / glycerin = 7/3 (weight ratio)
And the temperature was kept at 0 ° C. At this stage, in each case, a transparent gel-like fiber having a shape close to a perfect circle was obtained.
About 90% to 90% of the solvent and surfactant were extracted. continue
After stretching 4 times wet in methanol at 40 ° C, and almost completely extracting the solvent and surfactant in the subsequent methanol bath
It was dried with hot air at 80 ° C. to obtain a spun yarn.

The residual amount of the surfactant was determined by NMR.
5% by weight, Example 2 could not be detected.

Next, when the degree of polymerization was 7,000, the total stretching ratio was 19.6 times in a hot-air oven at 250 ° C., and when the degree of polymerization was 18,000, the total stretching ratio was 18.5 times in a hot-air oven at 256 ° C. .

As Comparative Examples 1 and 2, the cases where no surfactant was added in Examples 1 and 2 were carried out, and the results of fiber performance are also shown in Table 1.

In Example 1 having a degree of polymerization of 7,000, the yarn strength was 19.6 g / d, the elastic modulus was 492 g / d, the hot water dissolution temperature was 159 g / d, and the hot water resistance was particularly improved as compared with Comparative Example 1 in which no surfactant was added. Was seen.

In Example 2 having a degree of polymerization of 18,000, the strength was 22.4 g / d, and the elastic modulus was 537.
g / d, higher strength and higher elasticity, and the hot water dissolution temperature is 178 ° C, which is about 3 times that of Comparative Example 2 in which no surfactant is added.
0 ° C higher. In particular, the fiber obtained in Example 2
It gives a different image from VA fiber and can be used for a wide range of applications as described above.

In addition, the dynamic elastic modulus E 'obtained from the viscoelasticity measurement was 25 ° C and 10 ° C.
In the ratio E ' ₁₀₀ / E' ₂₅ at 0 ° C., Examples 1 and 2 with the addition of the activator both gave higher values than Comparative Examples 1 and 2 without the addition. This means that the molecular motion at high temperature is constrained, and it is thought that the amorphous part connects the crystals in a stronger state, which is supposed to be a factor in increasing the hot water resistance. Is done.

Example 3 PV having a viscosity average degree of polymerization of 17,000 and a saponification degree of 99.9 mol%
A was dissolved in dimethyl sulfoxide to a concentration of 5% by weight. Nonipol-500 (trade name, manufactured by Sanyo Chemical Co., Ltd., Was added to PVA in an amount of 5% by weight. Dissolution was performed at 98 ° C. with stirring for 3-5 hours. The obtained solution was spin-dry-spun in a methanol bath at room temperature, stretched by 5.0 times in wet heat, and then dried with hot air to remove methanol as a solvent. Further, it was drawn by a two-stage radiant heater at 170 ° C. and 235 ° C. to obtain a drawn yarn having a total draw ratio of 23.0 times.

The residual amount of the surfactant in the dried spinning yarn was 0.08% by weight, and there was no breakage of the single yarn after 8 hours of drawing, which confirmed that the fiber had few defects and morphological irregularities. No whitening phenomenon was observed in the drawn yarn. The obtained drawn yarn had a yarn strength of 20.6 g / d and an elastic modulus of 498 g / d. Single yarn has a denier of 3.8, a strength of 22.2 g / d, an elongation of 3.2%, and an elasticity of 520 g / d.
d. In addition, the hot water dissolution temperature was 152 ° C, and it became a high-strength, high-elastic fiber with excellent hot water resistance.

Example 4 PVA having a viscosity average degree of polymerization of 4,100 and a saponification degree of 99.5 mol%
Was mixed with dimethyl sulfoxide so as to be 8% by weight, and at the same time, 3% by weight of POE (40) nonylphenol ether was added and dissolved at 90 ° C. The obtained solution was slightly cloudy, and the fine particles of the surfactant were dispersed.
Next, the solution was discharged into a coagulation bath from a nozzle having 300 holes and a hole diameter of 0.12 mm, and wet-spun. The coagulation bath was ethanol / dimethyl sulfoxide = 8/2 (weight ratio), and the temperature was kept at 10 ° C. Subsequently, it is stretched 5 times in ethanol,
Further, the solvent and surfactant were almost completely extracted in an ethanol bath, and dried to obtain a spun yarn.

 The residual amount of the surfactant was 0.22% by weight.

Next, the raw yarn was drawn in a hot air oven at 236 ° C. so that the total draw ratio became 19.2 times. The yarn strength of the obtained drawn yarn is
18.5 g / d, the elastic modulus was 435 g / d, and the hot water dissolution temperature was 148 ° C., indicating that the PVA fiber had high strength and high elastic modulus with excellent hot water resistance.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the hot water dissolution temperature (WTb) and the degree of polymerization ( _A ) of the PVA-based polymer. Indicates that it belongs to the range below the oblique line.

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Kenji Nagamatsu 1621 Sazu, Kurashiki-shi, Okayama Pref. Kuraray Co., Ltd. Examiner Ruka Fuchino (56) References JP-A-1-104815 (JP, A) JP-A Sho 47-16724 (JP, A) JP-A-3-167310 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) D01F 6/14

Claims (1)

(57) [Claims] 1. A fiber comprising a polyvinyl alcohol-based polymer having a viscosity average degree of polymerization of 3,000 or more, which is obtained by adding a surfactant to a spinning solution, spinning and drawing, and having a hot water dissolution temperature represented by the following formula: Satisfaction and tensile strength is 16g / d or more,
A high-strength, high-modulus polyvinyl alcohol fiber excellent in hot water resistance, having an elastic modulus of 350 g / d or more. WTb ≧ 1.2P _A ^0.35 +115 (P _A ≧ 3,000) where WTb is the hot water dissolution temperature under a load of 200mg / d, PA is the viscosity average degree of polymerization of polyvinyl alcohol polymer