JPH0681208A - High modulus polyvinyl alcohol fiber and method for producing the same - Google Patents

Abstract

(57) [Summary] [Purpose] To obtain a polyvinyl alcohol fiber having a so-called high elastic modulus, which enters the shaded area in the right figure. [Structure] A solution of a polyvinyl alcohol-based polymer having a viscosity average degree of polymerization of 1500 or more and a syndiotacticity of 58% or more is spun and stretched at a total stretching ratio of 18 times or more. While applying a high tension of 2.5 g / d or more, 1% or more of stretching is performed under a temperature condition lower than the maximum temperature during the stretching.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a high syndiopolyvinyl alcohol having a high elastic modulus (hereinafter abbreviated as PVA).
The present invention relates to a system fiber and a manufacturing method thereof. The fiber of the present invention is a reinforcing material such as rubber or plastic or a rope,
It is a high syndio PVA fiber suitable for general industrial materials such as fishing nets, tents, and civil engineering sheets.

[0002]

2. Description of the Related Art Conventional PVA-based fibers are superior to polyamide, polyester, and polyacrylonitrile-based fibers in strength, elastic modulus, weather resistance, chemical resistance, adhesiveness, etc., and are unique to the industrial material field. Has pioneered the use of.
Recently, it has been attracting attention as a fiber for cement reinforcement (alternative to asbestos fiber) that makes use of the characteristics of alkali resistance.
Further, if PVA-based fibers with higher strength and higher elastic modulus are developed, a product excellent in safety, durability, and lightness as a reinforcing material for rubber or plastic can be expected.

According to the tacticity evaluation method of the present invention (details will be described later), the three-dimensional structure of the PVA-based polymer, which is a raw material for PVA-based fibers currently on the market, has a syndiotacticity of 53 to 53 according to the diad display. 54% atactic body. Moreover, the fibers obtained from the PVA-based polymer had insufficient oriented crystallization, low strength and elastic modulus, and were not satisfactory in wet heat resistance and heat resistance. As a method for obtaining a PVA-based fiber having high strength and high elastic modulus, a concept of gel spinning-super stretching of high molecular weight polyethylene, for example, the technique described in JP-A-60-194109 is applied, and JP-A-59- 100710, JP-A-59-130314, JP-A-61-10871.
The method described in Japanese Patent No. 1 or the like is known. These methods involve dissolving a high degree of polymerization PVA in a solvent, cooling and gelling or coagulating by a dry-wet method to form a yarn, extracting the solvent, and stretching at a high draw ratio by dry heat stretching, but it is still satisfactory. No elastic modulus was obtained. In addition, since the intermolecular water-based bond was weak due to atactic PVA, the wet heat resistance and heat resistance were low due to the low crystallinity.

Recently, a method of forming a PVA-based polymer rich in syndiotacticity into fibers for the purpose of improving these properties has been disclosed in JP-A-61-108713 and JP-A-4-1-1.
No. 08109 is disclosed. However, the elastic modulus of the fibers obtained by these methods varies depending on the polymerization degree of the PVA-based polymer, but it has not been sufficient yet. on the other hand,
In order to obtain a PVA-based fiber having a high elastic modulus, stretching at a high ratio,
It must have a highly oriented and highly crystallized structure,
For that purpose, it is necessary to draw near the melting point of PVA.
However, the melting point of PVA is close to the decomposition temperature, and when stretching is carried out at a high temperature for a long period of time, the PVA is decomposed and the fibers are colored, resulting in a decrease in strength and elastic modulus. In addition, the higher the temperature is near the melting point, the easier the orientation is relaxed during stretching and the PVA molecular chain is removed, so that the elastic modulus is likely to be lowered. In particular, the intermolecular water-based bond is strong,
High syndio-PVA-based fibers that are easily crystallized require molecular chains to move easily at high temperatures and must be stretched, in which case the above-mentioned defects tend to occur.

[0005]

SUMMARY OF THE INVENTION Therefore, the present invention is to suppress the decomposition and orientation relaxation while stretching the high syndio-PVA type fiber having high crystallinity and moist heat resistance and heat resistance, and to improve strength and elastic modulus. It is intended to provide a fiber in which tie molecules connecting the involved crystals are highly oriented.

[0006]

Means for Solving the Problems That is, the present invention is to draw a PVA fiber having a viscosity average degree of polymerization of 1500 or more and a syndiotacticity of 58% or more at a high temperature and a high draw ratio,
High-strength additional stretching is performed at a lower temperature to enhance crystalline and amorphous molecular orientation, and high syndio-PVA with high elastic modulus.
It is intended to provide a system fiber, that is, a viscosity average degree of polymerization of 1500 or more and a syndiotacticity of 58.
% Of polyvinyl alcohol-based polymer,
A high syndiopolyvinyl alcohol fiber characterized by having a single fiber elastic modulus (MY) satisfying the following formula, and YM ≧ 7.8 (P) ^0.36 +400 (P: viscosity average degree of polymerization) viscosity average polymerization The total draw ratio is at least 18 times at a temperature of 230 ° C. or higher by dissolving a polyvinyl alcohol-based polymer having a degree of 1500 or more and a syndiotacticity of 58% or more in a solvent and spinning it. And then further stretched at a temperature lower than the maximum temperature in the stretching, an elongation rate of 1% or more and a tension of 2.5 g / d or more, and a high syndiopolyvinyl alcohol fiber. Is a manufacturing method of.

The contents of the present invention will be described in more detail below. The degree of polymerization of the PVA-based polymer referred to in the present invention means a viscosity average degree of polymerization obtained by a viscosity method in an acetone solution at 30 ° C. described later. In the present invention, it is necessary to use one having a degree of polymerization of 1500 or more. The higher the average degree of polymerization of PVA, the greater the number of tie molecules penetrating between the crystals, and the more easily the fibers having high strength and high elastic modulus are obtained, and the higher the moist heat resistance and heat resistance are. The PVA polymerization degree is preferably 1500 or more, more preferably 10,000 or more.

In the present invention, the PVA-based polymer satisfying the above-mentioned degree of polymerization has a syndiotacticity of 58% or more by dyad display, and when it is lower than this, the crystal orientation is lowered and the performance is high. It's hard to get good fiber. The syndiotacticity is preferably 60% or more, but if it exceeds 70%, high crystallization tends to cause solubility in a solvent and a reduction in draw ratio.

In the present invention, the tacticity represented by the diad is the deuterated dimethyl sulfoxide (d).
↓ Syndiotacticity (T. Moritani eta by triad display obtained by proton NMR measurement of PVA polymer dissolved in 6-DMSO)
l. , Macromolecules, 5, 577 (1
972)), which is a value calculated from the syndiotacticity (S), the heterotacticity (H), and the isotacticity (I) by the following equation. s = S + H / 2 (Diad display syndiotacticity) i = I + H / 2 (Diad display isotacticity)

The PVA may be copolymerized with 5 mol% or less of a modifier and an unsaponifiable material (eg vinyl pivalate, vinyl trichloroacetate, etc.). 5 more
There is no problem even if an additive such as boric acid, an antioxidant, an ultraviolet absorber, a crystallization inhibitor, or a surfactant is added in an amount of not more than wt% for the purpose of suppressing decomposition and improving stretchability.

As the solvent for the PVA-based polymer, those used in a conventional method can be adopted, for example, ethylene glycol, trimethylene glycol, diethylene glycol,
There are polyhydric alcohols such as glycerin, mixed solvents of them with water, dimethylsulfoxide, dimethylformamide, diethylenetriamine, mixed solvents of them with water, and mixed solvents of propyl alcohol or rhodane salt with water. . Among these, the solvent which is gelled by quenching is convenient for producing a uniform gel by amorphizing, fixing by entanglement in the molecular chain, delaying solvent extraction, etc. to obtain a high elastic modulus fiber.

A conventional spinning method can be adopted as the spinning method, and it may be wet, dry or dry, but dry and wet gel spinning is preferred. The coagulation bath may also be a commonly used one, for example, alcohols such as methanol and ethanol, acetone, ether, an alkaline aqueous solution, a sodium sulfate aqueous solution, and a mixed solution thereof. Since high syndio-PVA polymer is easier to crystallize than atactic PVA, the solvent-containing fiber after spinning is kept at a low temperature of 20 ° C. or lower to suppress crystallization, and the solvent extraction is slowly performed to obtain a homogeneous gel fiber. Good to get

Although wet stretching may or may not be performed in a state of containing a solvent, it is preferable to perform stretching at a rate of 3 times or more at 70 ° C. or lower in the steps up to drying. 70 wet stretching
The reason why the temperature is 3 times or more below ℃ is to decrease the crystallinity,
The purpose is to weaken the intermolecular hydrogen bond to facilitate the movement of the molecular chain so that the dry heat drawing in the final step can be performed at a high ratio, and the sticking between the single yarns is reduced. P
The solvent for the VA polymer may be extracted with any of alcohol, acetone, water and the like, but lower alcohols such as methanol and ethanol are preferable.

After that, it must be dried to remove the extractant and the like, and the temperature is 130 ° C. or lower, preferably 70 to 100 ° C. If it exceeds 130 ° C., crystallization will increase, and it will be difficult to increase the magnification in subsequent stretching.

In the present invention, in order to enhance the orientation of the PVA molecular chain, it has to be stretched at a high ratio at a high temperature. The heating device may be a contact or non-contact heater, a hot air oven, a liquid bath such as silicon, and the heating atmosphere may be in air or in an inert gas such as N ↓ 2 or CO ↓ 2. In order to industrially enable high-stretching, it is preferable to use a heater or a hot air oven in the air to provide a temperature difference of two or more stages.

The stretching temperature should finally be 230 ° C. or higher. If the temperature is less than 230 ° C, the draw ratio decreases, and the orientation and crystallization do not proceed, so it is difficult to obtain a high elastic modulus fiber. Here, the stretching temperature means the maximum measured temperature of the heater or the hot-air stove. The optimum temperature varies depending on the degree of polymerization, solvent and spinning method, but initially 160 to prevent melting and high crystallization of the fiber.
210 ° C. is preferred, and the higher the degree of polymerization is, the higher the temperature becomes in the second and subsequent stages. For example, the degree of polymerization of 4000 is 235 to 255 ° C., the degree of polymerization of 10,000 is 240 to 260 ° C., the degree of polymerization is 17,000.
Then, it is desirable to set the temperature to 250 to 265 ° C. However, P
It is difficult to obtain a high-strength, high-modulus fiber when the drawing tension is lowered to a state where the drawing tension is lowered due to the coloring phenomenon due to the decomposition of VA and the flow phenomenon of the molecular chain due to partial melting.

In the present invention, the total draw ratio must be 18 times or more, preferably 20 times or more. Here, the total draw ratio means a value obtained by multiplying the wet draw ratio and the dry heat draw ratio.
Generally, the strength and elastic modulus increase in proportion to the total draw ratio, and the draw ratio increases in proportion to temperature, but at a high temperature such as a decrease in draw tension or decomposition due to the flow of molecular chains (melting, leaving). On the contrary, the strength and the elastic modulus decrease. Therefore, there is a limit in obtaining higher strength and elastic modulus only by high temperature drawing.

The inventors of the present invention have diligently studied how to increase the crystallographic and amorphous orientations, particularly regarding the high elastic modulus of the high syndio-PVA fiber, and as a result, use a temperature lower than the maximum drawing temperature, and The stretching tension is 2. at an elongation rate of 1% or more.
It was found that the film was additionally stretched so as to have a rate of 5 g / d or more. That is, it was possible to obtain a high elastic modulus fiber satisfying the following formula by orienting the molecular chains higher under high tension and increasing crystallization while suppressing decomposition and orientation relaxation. YM ≧ 7.8 (P) ^0.36 +400 (YM: Single fiber elastic modulus (g / d) P: High syndio P
(Viscosity average degree of polymerization of VA polymer)

In order to obtain the single fiber elastic modulus satisfying this expression, it is preferable to increase the draw ratio and the tension so that decomposition, fluff and yarn breakage do not occur in any drawing process. The molecular orientation coefficient α is 0.92 or more, preferably 0.95 or more. The temperature during the additional stretching correlates with the elongation rate and the tension during the additional stretching, and the tension during the additional stretching is 2.5 g / d or more when the elongation rate during the additional stretching is 1% or more. It is necessary to set below the temperature. Specifically, it depends on the degree of polymerization, for example, 4000
At 225 to 240 ° C. and a polymerization degree of 17,000 at 245 to
The temperature is 260 ° C., and if the temperature exceeds 260 ° C., additional stretching, lowering of tension or decomposition occurs, which is not preferable.

The elongation is 1% or more, preferably 2% or more, but if it is less than 1%, high tension makes it difficult to proceed with high orientation. Further, the higher the elongation is, the higher the orientation and the higher the elastic modulus are. However, it is not preferable that the higher the elongation becomes, the higher the fluff or yarn breakage occurs and the fiber defect caused by the molecular chain breakage occurs. The tension during additional stretching also depends on the degree of polymerization, but is 2.5 g / d or more,
It is preferably 3 g / d or more. If it is less than 2.5 g / d, sometimes the orientation of the amorphous (tie molecule) is not sufficient, and the strength and elastic modulus tend to decrease. Further, when the fiber after the additional drawing is colored from yellow to brown, decomposition is occurring, and in this case, it is necessary to increase the speed to shorten the residence time of the additional drawing. By the additional stretching, the crystallinity was increased together with the molecular orientation, the wet heat resistance and the heat resistance were improved, and it was a high syndio-PVA-based fiber with high performance not seen in the past.

In the present invention, stretching is performed at a total stretching ratio of 18 times or more and then additional stretching is performed. However, stretching at a total stretching ratio of 18 times or more and additional stretching are distinguished by the tension and temperature during stretching. To be done. That is, the stretched fiber has a tension higher than that at the time of stretching, a tension of 2.5 g / d or more, and a temperature lower than the maximum temperature at the time of stretching (often used in the final stage of the stretching process in general). Moreover, if the stretching is 1% or more, the stretching corresponds to the additional stretching referred to in the present invention. Therefore, since the additional drawing needs to have a higher tension than that of the previous drawing, the drawn yarn is wound around a roller once, for example, to cut off the tension during the previous drawing, and then a new larger tension is applied. And a method of additional stretching is used. From this, for example, in a stretching method in which two rollers are divided into multiple stages and stretching is performed while applying different amounts of heat in each stage, the final stage may be lower than the temperature of the stage immediately before that. However, in such a case, since the tension does not change between the rollers, the final stage does not correspond to the additional stretching referred to in the present invention.

[0022]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the examples. Various physical properties and parameters in the examples are measured by the following methods.

(1) Viscosity Average Degree of Polymerization of PVA Polymer (P) It was determined from the intrinsic viscosity (measured at 30 ° C.) of acetone of vinyl acetate obtained by acetylating a high syndio PVA polymer by the following formula. P = ([η] × 1000 / 7.94) ^{1 / 0.62}

(2) Degree of decrease in degree of polymerization After the drawn yarn or the additional drawn yarn is dissolved in hot water at 130 to 140 ° C in the absence of oxygen, the viscosity average degree of polymerization of the drawn yarn or the additional drawn yarn is the same as in (1). P'was determined and the rate of decrease of the polymer with respect to P was calculated by the following equation. Degree of decrease in degree of polymerization = (P-P ') / P x 100 (%)

(3) Tensile Strength / Elongation of Single Yarn, Initial Elastic Modulus According to JIS L-1013, pre-conditioned humidity monofilaments are attached to a mount so that the test length is 10 cm, and 25 ° C. × 60%.
Leave it for 12 hours or more. Then Instron 1122 2
Using a chuck for kg, an initial load of 1/20 g / d and a tensile speed of 50% / min were used to obtain the breaking elongation and the initial elastic modulus, and an average value of n ≧ 20 was adopted. Denier is 1/1
It was cut to 30 cm under a load of 0 g / d and determined by a gravimetric method. The single fiber after denier measurement was used to measure the strength and elongation, and the elastic modulus, and each fiber was made to correspond to denier.

(4) Orientation coefficient α Pulse direct reading viscoelasticity measuring instrument DD manufactured by Orientec Co., Ltd.
Using a V-5-B type, the velocity C of a sound wave of 10 KHz along the fiber axis was measured and compared with the sound velocity Cu (2.2 km / sec) of a non-oriented sample obtained from a cast film of PVA. The molecular orientation coefficient α was calculated from the following equation of Mosley. α = 1-Cu ² / C ²

(5) Hot water disconnection temperature WTb A load of 2 mg per denier was applied to 25 single fibers,
It was hung in the middle of a glass cylindrical sealed container filled with water, and water was heated from the surroundings at a rate of 1 to 2 ° C./min to raise the temperature, and the temperature at which the fiber was melted was measured.

(6) Melting point (MP) Differential calorimetric analyzer (Model DSC, manufactured by Perkin Elmer Co., Ltd.
-2C), 10 mg of a fiber having a cut length of about 1 mm was collected, and the melting point (endothermic peak temperature) at a temperature rise of 10 ° C./min in a nitrogen stream was measured.

(7) Crystallinity Xc A wide angle X-ray diffractometer RAD-rc type manufactured by Rigaku Denki Co., Ltd. was used, CuKα rays of 40 kv100 mA was used as a radiation source, and a graphite monochromator and a scintillation counter were used. The scanning speed was 1.0 ° / min for 2θ = 5 to 35 ° and was calculated from the crystal peak area ratio to the entire area.

Examples 1 to 3 and Comparative Examples 1 and 2 Obtained by saponifying vinyl polypivalate having a viscosity average degree of polymerization of 1850 (Example 1), 4000 (Example 2) and 10,000 (Example 3). Syndiotacticity is 61.5% and saponification degree is 99.8, 99.5 and 9 respectively.
High syndio-PVA of 9.7 mol% was added at a concentration of 16
It was dissolved in dimethyl sulfoxide at 120 ° C. so that the weight%, 11% by weight, and 5.5% by weight were obtained. The dissolver was a closed system, and the inside of the system was replaced with N ↓ 2 gas and then kept under reduced pressure to suppress color decomposition of PVA. Then, each solution is 150 ℃
Then, it was discharged from a nozzle having a hole diameter of 0.15 mm and the number of holes was 200 and solidified by a dry-wet method. The coagulation bath composition was methanol / dimethyl sulfoxide = 7/3 (weight ratio), and the temperature was 7 ° C. Then, the film was stretched by 4 times wet in methanol at 40 ° C., then dimethyl sulfoxide was almost completely extracted with methanol, dried with hot air at 100 ° C., and wound on a bobbin.

The obtained spun raw yarn was fed at a speed of 2 m / min in Example 1 in a hot air oven at 170-200-250 ° C. for a total draw ratio of 2
1.4 times, Example 2 was 2 at 170-210-255 ° C.
0.1 times, Example 3 is 1 at 190-220-260 ° C.
It was stretched to 9.7 times. The stretching tensions are 2.0 and 2.7, respectively.
3.5 g / d, single fiber denier is 3.2,
It was 2.9 and 2.6 dr. Then draw the drawn yarn at a speed of 8 m
The additional stretching was carried out by a hot-air stove at a speed of 1 / min.
C, residence time 15 seconds, elongation rate 3.2%. Tension 3.1g /
d, Example 2 is 248 ° C., residence time is 16 seconds, elongation rate is 2.
The tensile strength was 7%, the tension was 3.7 g / d, Example 3 was 252 ° C., the residence time was 17 seconds, the elongation rate was 1.9%, and the tension was 4.2 g / d. Table 1 shows the physical properties of each drawn yarn and additional drawn yarn obtained. In addition, as Comparative Example 1, the physical property values are also shown in Table 1 in the case where the additional stretching conditions in Example 3 were an elongation rate of 0.8% and a tension of 2.0 g / d.

Further, as Comparative Example 2, atactic PVA obtained from conventional polyvinyl acetate having a viscosity average degree of polymerization of 1100, a syndiotacticity of 53.4% and a saponification degree of 99.8 mol% was used. The same spinning as in Example 3 was performed. However, regarding the stretching, the melting point is low, so 170-20
The total stretching ratio is 19.5 times at 0 to 250 ° C, and the additional stretching is 2
Conducted at 45 ° C., elongation rate 2.1%, tension 3.0 g / d,
The evaluation results are also shown in Table 1.

[0033]

[Table 1]

The higher the degree of polymerization, the higher the monofilament strength and elastic modulus of the drawn yarn and the post-drawn yarn, but in each of Examples 1 to 3, the performance is improved by the additional drawing, and the elastic modulus YM is shown in FIG. It was within the shaded area. Further, the orientation coefficient α obtained from the sound velocity increases by additional stretching, and in Examples 1 to 3, 0.94 to 0.95.
Therefore, it is suggested that the strength and elastic modulus are improved. Furthermore, the features of high syndio PVA are brought out by additional stretching,
It had a high crystallinity, a high melting point and a high resistance to moist heat (high WTb), and had properties not found in the conventional atactic PVA shown in Comparative Example 2. In particular, the high degree of polymerization and high syndio PVA of Example 3 was a fiber having a high added value in a reinforcing material of rubber or plastic, a fishing net, a rope, a civil engineering sheet and the like. In Comparative Example 1, the extension ratio and the tension of the additional stretching were lowered in Example 3, but the requirements of the present invention were not satisfied, so YM was a value below the curve in FIG. Although atactic PVA was used in Comparative Example 2, the performance was one step lower than that of Syndio PVA having the same degree of polymerization, although an additional stretching effect was observed.

Example 4 and Comparative Example 3 Viscosity average degree of polymerization 23,00, syndiotacticity 6
High syndio PVA with 1.7% and saponification degree of 99.2 mol%
Was dissolved in glycerin at 200 ° C. to a concentration of 4.5% by weight. Then, the solution was heated to 230 ° C. and the pore size was adjusted to 0.
20m, discharged from a nozzle with 60 holes and 20m
It was made to fall in the coagulation bath under m. Coagulation composition is methanol /
Glycerin = 7/3 (weight ratio), and the temperature was 0 ° C. Wet stretching is performed 4 times in methanol at 40 ° C. After solvent extraction, it was dried with hot air at 100 ° C and wound on a bobbin. The obtained spun raw yarn was placed in a radiation furnace at 190 ° C to 263 ° C for 1.5 minutes.
It was supplied at a rate of m / min and stretched at a stretching tension of 4.3 g / d and a total stretching ratio of 18.8. The drawn yarn has a single fiber denier of 2.6, a strength of 26.4 g / d, and an elastic modulus of 650 g.
Was / d. Subsequently, additional drawing was carried out at a 258 ° C. radiant furnace at an input speed of 6.5 m / min with an elongation rate of 2.4% and a tension of 5.1 g / d. The strength of the additional stretched yarn was 28.3 g / d, and the elastic modulus was 708 g / d. It has become a fiber with a high elastic modulus like never before. As Comparative Example 3, the stretching temperature in Example 4 was 267 ° C.
Although the total draw ratio was increased to 19.7 times, the tension at the time of drawing decreased to 2.9 g / d, and the obtained drawn yarn was slightly yellowish. The degree of decrease in the degree of polymerization was 16.1 of Example 4.
% As high as 25.0%, and single fiber strength is 21.6 g
/ D and the elastic modulus were as low as 595 g / d, and the effect of additional stretching was confirmed. Note that α was 0.90, and it was found that orientation relaxation occurred due to the high temperature.

[Brief description of drawings]

FIG. 1 shows the relationship between the PVA polymerization degree P and the initial elastic modulus YM of a single fiber. The shaded area in the figure represents the scope of the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomoyuki Sano 1621 Sakata, Kurashiki City, Okayama Prefecture Kuraray Co., Ltd.

Claims (2)

[Claims] 1. A polyvinyl alcohol-based polymer having a viscosity average degree of polymerization of 1500 or more and a syndiotacticity of 58% or more, and a single fiber elastic modulus (YM) satisfying the following formula: Syndio polyvinyl alcohol fiber. YM ≧ 7.8 (P) ^0.36 +400 (P: viscosity average degree of polymerization) 2. A spinning raw yarn obtained by dissolving a polyvinyl alcohol polymer having a viscosity average degree of polymerization of 1500 or more and a syndiotacticity of 58% or more in a solvent and spinning the same at a temperature of 230 ° C. or more. After stretching so that the stretching ratio is at least 18 times, the stretching ratio is 1% or more and the tension is 2.5 g at a temperature lower than the maximum temperature in the stretching.
/ D or more and further stretched, a method for producing a high syndiopolyvinyl alcohol fiber.