JPH01156517A - High-strength and high-modulus polyvinyl alcohol fiber having excellent hot-water resistance and production of said fiber - Google Patents

Abstract

PURPOSE:To obtain the title fiber useful for the reinforcement of rubber such as tire cord, V-belt or hose or as a rope, conveyor belt, fishing net, etc., by spinning a dope of a PVA polymer having high polymerization degree and drawing the obtained fiber under specific condition. CONSTITUTION:The objective fiber having a tensile strength of >=15g/d, preferably >=20g/d, an elastic modulus of >=250g/d, preferably >=300g/d, a hot-water resistance of >=120 deg.C, preferably >=130 deg.C and a steam resistance index of >=50, preferably >=60 can be produced by spinning a dope of a PVA polymer having a polymerization degree of >=1,500, preferably >=3,500, drawing the obtained fiber at a draw ratio of >=3, preferably 3.5-7, treating the drawn fiber with a crosslinking agent (e.g., hydroperoxide) and subjecting to a dry-heat treatment at a draw ratio of >=3.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is applied to organic high-strength I&'' navy blue with excellent hot water resistance, especially industrial materials such as rubber reinforcing materials, robes, seat bells, fishing nets, and marine materials. The present invention relates to a high-strength, high-modulus fiber with excellent hot water resistance that is useful in applications, and a method for producing the same.

[Prior Art] Conventionally, polyvinyl alcohol (hereinafter abbreviated as PVA) fibers have been used as rubber reinforcing materials, due to their excellent mechanical properties.
Widely used in industrial fields such as cement reinforcement, robes, seat belts, and fishing nets.

However, since the polymer itself of PVA-based fibers is essentially soluble in water, the application of PVA-based fibers to fields that require water-resistant properties such as hot water resistance and steam resistance has been greatly restricted.

As a means for improving the water resistance properties, which are an essential drawback of PVA fibers, a method has been generally known in which PVA fibers are reacted with an aldehyde such as formalin to insolubilize (acetalize) the fibers. There is. In this method, in order to insolubilize PVA fibers, it is necessary to perform acetalization treatment with a degree of acetalization of 20 to 30 mol% or more, which improves water resistance properties, but
On the other hand, this results in disturbing the fiber structure of the PVA fiber itself, resulting in a decrease in crystallinity, degree of orientation, etc., and the mechanical properties of the fiber are significantly impaired. Therefore, improvement measures that do not involve this type of mechanical property cannot be applied to industrial fibers that require a high level of mechanical performance, and have been limited to textile fibers for clothing.

JP-A-60-126312 discloses that the degree of polymerization is 150
An improved means for improving hot water resistance without impairing mechanical properties is disclosed by dry/wet spinning PVA with a high polymerization degree of 0 or more and stretching the resulting yarn by 20 times or more. This method aims to improve hot water resistance without impairing mechanical properties by utilizing the effect of using a high polymerization degree PVA polymer and the effect of reducing amorphous parts due to a highly oriented structure during fiberization. It is. However, no matter how highly oriented it is, it cannot be said to have sufficient hot water resistance because it cannot form a perfect crystal and the amorphous portion remains.

[Problems to be Solved by the Invention] In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to provide a PVA fiber having excellent mechanical properties and hot water resistance, and a method for producing the same.

[Means for Solving the Problems] The above objects of the present invention are as follows: (1) A polyvinyl alcohol polymer having a degree of polymerization of at least 1500, a tensile strength of 15 g/d or more, and an elastic modulus of 250 g/d or more; and a high-strength, high-modulus polyvinyl alcohol fiber with excellent hot water resistance, which has a hot water resistance of 120° C. or higher and a steam resistance index of 50 or higher.

(2) A polyvinyl alcohol polymer solution having a degree of polymerization of at least 1500 is spun, and the resulting yarn is drawn at least three times. Thereafter, the drawn yarn is treated with a cross-linking agent, and then subjected to dry heat stretching at a stretching ratio of 3x or more to obtain a high-strength, high-modulus polyvinyl alcohol fiber with excellent hot water resistance. manufacturing method.

This can be achieved by

That is, the PVA fiber according to the present invention has at least 15
00, preferably 2500 or more, preferably 35
It is composed of a polymer with a high polymerization degree of 0.00 or more. Using such a polymer with an extremely high degree of polymerization allows the fiber to have a tensile strength of 15 g/d or more, preferably 18 g/d.
/d or more, more preferably 20 g/d or more, an elastic modulus of 250 g/d or more, preferably 28 Qg/d or more,
Furthermore, it becomes possible for the first time to achieve high strength and high elastic modulus, preferably 300 g/[1 or more.

Further, the fiber of the present invention obtained from the high polymerization degree polymer has a hot water resistance of at least 120'C1, preferably 125'C1.
0 or more, and even better, 130'C or more,
In addition, it is an essential requirement that the steam resistance index be at least 50 or higher, preferably 60 or higher. The hot water resistance and steam resistance index of the fibers of the present invention were determined according to the following measurement method.

In other words, hot water resistance is determined by fixing one end of the coat prepared using the method described below, and applying 0.5 g per coat to the other end.
Applying a load of・The coat uses raw yarn of 1000 to 2000 deniers, and the twist coefficient in the following formula is adjusted to 1800 to create a twin-stripe cord.

Twist coefficient = number of twists [times/10cm] X v'T7! 8 x Cal'+ of thread.

In addition, the steam resistance index is determined using the code created above.
One end of the cord is fixed and the other end is coated.
A load of 5 kg was applied to the central part of the coat at a temperature of 120°C.
Spray saturated water vapor of "C" for 10 minutes to create a treated code. Find the strength (TS) of this cord, and calculate the strength retention using the following formula from this and the strength (TSo) of the untreated coat, which was determined separately. This is a numerical value that is obtained by calculating the strength retention rate (RT) and expressing the dimensionless directivity of the obtained strength retention rate as a steam resistance index.

however·, T.S. RT (%) = -X 100″ (%) TS.

As already mentioned, the polymer itself of PVA-based 8&' fibers is inherently soluble in water, which greatly limits its application to fields where hot water resistance and steam resistance are required.

On the other hand, the fibers of the present invention described above have not only high strength and high modulus of elasticity, but also hot water resistance and steam heat resistance, so that they exhibit remarkable effects as industrial fibers.

Next, an example of the means for producing the fiber of the present invention will be described.

The PVA-based polymer includes completely saponified PVA, and a small amount of olefinic monomers such as ethylene, propylene, styrene, acrylic acid and its alkyl esters, methacrylic acid and its alkyl esters, and itaconic acid are copolymerized in the main chain. Among them, particularly preferred PVA-based polymers include those with a saponification degree of 99.
Completely saponified PVA with a mole % or more is preferable.

The above-mentioned high-strength, high-modulus PXiA-based fibers with excellent hot water resistance are manufactured using the normal wet spinning method, in which a spinning stock solution obtained by dissolving a PVA-based polymer in hot water is passed through a spinning nozzle using glauber's salt or alkaline salts. It can also be obtained by discharging it into a coagulation bath consisting of an aqueous solution, but the stability of the spinning solution
Since the resulting coagulated yarn has low drawability, it is effective to adopt the dry/wet spinning method or the Kel spinning method. Namely.

By spinning such a highly polymerized PVA-based polymer using such a spinning method, a dense coagulated filament is obtained, and the drawing ratio can be increased in the subsequent drawing step, resulting in a high molecular blending ratio and crystallization. This results in fibers with high strength and high modulus of elasticity. Therefore, the dry/wet spinning method and gel spinning method in the present invention will be explained.

First, the dry/wet spinning method means that the spinning stock solution is not directly discharged into a coagulation bath, but is first discharged into a microscopic space in an inert atmosphere such as air, and then the discharged yarn is introduced into a coagulation bath and coagulated. This is a spinning method that allows At this time, the spinning stock solution includes dimethyl sulfoxide (hereinafter abbreviated as DMSO), glycerin,
Polyhydric alcohols such as ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and trimethylolpropane, amines such as ethylene diamine and diethylene triamine, and organic systems such as saturated aqueous VA liquids of resorcinol, formamide, and urea. Examples include solvents, aqueous solutions of water, lithium halide saponides such as lithium bromide and lithium chloride, inorganic salts such as sodium cyanate, zinc chloride, aluminum chloride, and magnesium chloride, and mixed solvents thereof. , preferably a solvent with high dissolving power for PVA-based polymers, especially D
MSO, ethylene glycol, glycerin, ethylenediamine, and diethylenetriamine are preferable.

In addition, as a coagulant, one that is compatible with the solvent of the spinning dope and is a non-solvent for the PVA polymer, such as methanol, ethanol, acetone, zene, toluene, or a combination of these and the spinning dope. A mixed solvent with a solvent, an aqueous solution of an inorganic salt, etc. are used.

Next, in the gel spinning method, a spinning solution is discharged from a spinning nozzle into a microscopic space in an inert atmosphere, and then the discharged yarn is introduced into a cooling bath that is immiscible with the solvent of the spinning solution (
(without substantially changing the polymer concentration of the discharged yarn)
This is a spinning method that involves cooling and kelizing.

As a solvent for the spinning dope in this gel spinning method, PV
It is preferable to use a polymer that gels when the solution obtained by heating and dissolving the A-based polymer at a high temperature is cooled.

Specifically, examples include polyhydric alcohols such as glycerin, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and trimethylolpropane, and solvents that are non-volatile at room temperature such as benzenesulfonamide and caprolactam. However, glycerin and ethylene glycol are preferred.

In addition, in the cooling bath, for the solvent of the spinning dope,
Those that are immiscible and are non-solvents for PVA-based polymers, such as deca phosphorus, trichlorethylene, carbon tetrachloride, paraffin oil, etc., are used.

In the above-mentioned dry/wet spinning method or Kel spinning method, the viscosity of the spinning dope depends on the degree of polymerization of the polymer, the polymer concentration of the spinning dope, and the spinning temperature, but the viscosity of the spinning dope at the discharge part is about 200 to 5000 mm, Preferably 500-3000
It is preferable to control the polymer concentration and temperature of the spinning mill so as to fall within the range of voice. If the viscosity of the spinning stock in the discharge section is lower than 200 voices or exceeds 5,000 voices, the spinnability of the spinning dope decreases and stable spinning becomes difficult, which is not preferable.

In either the dry/wet spinning method or the gel spinning method, such a spinning stock solution is discharged through a spinning nozzle installed at a position of 3 to 200 mm above the liquid level of the coagulation bath or cooling bath, and the discharged yarn is is introduced into the coagulation bath or cooling bath after traveling in an inert gas atmosphere such as air, nitrogen, pallium, or argon. The distance that the discharged yarn travels in the air or inert gas atmosphere is approximately 3 m.
If it is less than 200 mm, the discharged yarn will break due to fluctuations in the liquid level, and the spinning stability will tend to deteriorate, and if it exceeds 200 mm, there will be significant adhesion between the single yarns that make up the discharged yarn. This is not preferable because it tends to cause unevenness in fineness.

In addition, in dry and wet spinning methods, the temperature of the coagulation bath is usually 0 to 0.
It is in the range of 50'C. On the other hand, in the gel spinning method, the temperature of the cooling bath is determined by the gelation temperature of the spinning stock solution.
It is usually preferable to keep the temperature in the range of -10 to 30°C. In other words, when it is higher than 30G, the gelling yarn becomes soft due to insufficient cooling efficiency of the discharged yarn, and it becomes difficult to run the yarn stably during the subsequent steps such as desolvation and stretching. However, when the temperature is lower than -10°C, special cooling equipment is required, which is not desirable.

For example, in the case of a 15% by weight glycerin solution of PVA with a degree of polymerization of 3000, its gelation temperature is about 103°C. The temperature of the bath is preferably 30'C or less.

In addition, the depth and length of the coagulation bath in the dry/wet spinning method and the cooling bath in the gel spinning method are not particularly limited, but when discharging the multifilament as a multifilament, the multifilament Before the constituent single fibers are bundled, they are sufficiently coagulated in a coagulation bath or sufficiently cooled in a cooling bath,
The temperature, depth, and length of the cooling bath should be appropriately set so that solidification or gelation is completed.

After removing the solvent, the coagulated or gelled yarn is stretched in a washing bath or a wet heat bath, and then subjected to dry heat using various means such as a heating tube, a heating medium bath, and a hot plate. Stretched.

In order to obtain excellent mechanical properties, which is the object of the present invention, it is necessary to use a polymer with a high degree of polymerization as a raw material and to make the stretching ratio as high as possible. In this case, the total stretching ratio is at least 9 times that of the undrawn yarn;
It is preferably 12 times or more, more preferably 16 times or more.

The upper limit of the total stretching ratio is 9, which is the maximum stretching ratio described below.
The content is preferably about 5%, and if it exceeds this, not only will the stability in the drawing process be impaired, but the resulting yarn will tend to become fluffy, which is not preferred. The maximum draw ratio is the draw ratio applied to the yarn in the drawing process by gradually increasing it to 1.
This refers to the stretching ratio at which all yarns break when stretched.

Such high-magnification stretching is possible by employing a specific spinning method such as the dry/wet spinning method or gel spinning method, and the PVA fiber with high physical properties, which is the object of the present invention, can be obtained.

The PVA fibers thus stretched have excellent crystallinity because they are highly stretched and oriented, and have improved hot water resistance to the extent that they do not dissolve even in boiling water.
When treated in pressurized steam at a temperature of 0.degree. C. or higher, the material was still unsatisfactory in terms of hot water resistance, such as dissolution or a significant decrease in strength.

Therefore, in the present invention, as a specific means for increasing the hot water resistance of the PVA fiber to at least 120'C and the steam resistance index to at least 50, we add a crosslinking agent to the yarn in the drawing process. After adhering, the yarn is further subjected to prescribed stretching and heat treatment in a subsequent step,
As a result, both mechanical properties and hot water resistance are improved.
Made of VA-based high-strength fiber. At this time, it is necessary to stretch the yarn at least 3 times or more, preferably 3.5 times to 7 times, before attaching the crosslinking agent.

If the stretching ratio of the yarn is less than 3 times, the cross-linking agent will penetrate into the inside of the fiber, resulting in a decrease in the drawability in the "subsequent" process, or excessive cross-linking, resulting in damage to the resulting fiber. Mechanical properties will be impaired.

Examples of the crosslinking agent used in the present invention include organic peroxides such as hydroperoxide, dialkyl peroxide, peroxyketal, and peroxyester;
Isocyanate compound, blocked isocyanate-1.
These compounds include, but are not limited to, urethane-based compounds, epoxy-based compounds, and the like, and one or more of these compounds may be used in combination.

The application method includes a method in which the crosslinking agent is used in the form of an organic solvent solution, an aqueous solution, or an aqueous emulsion, and the fiber yarn is immersed in the solution, a method in which the crosslinking agent is applied by contact with the fiber through a roll, or a method in which the solution is applied to the fiber. There are methods such as spraying onto the yarn, but any method may be used.

In this way, it is possible to obtain a PVA-based fiber that does not dissolve even in hot water of 120'C or more and has a tenacity retention rate of 50% or more after being exposed to saturated steam at 120'C. This is completely unexpected from conventional PVA-based fibers, and can be achieved for the first time by adopting a polymer with a high degree of polymerization, specifying the spinning means, and integrally combining the treatment with a crosslinking agent as in the present invention. It can be achieved.

[Effects of the Invention] The PVA-based fiber of the present invention has hot water resistance of 120° C. or higher, steam resistance with a steam resistance index of 50 or higher, a tensile strength of 153/d or higher, and an elastic modulus of 250 g/d or higher. d or more, which is significantly superior to PVA-based fibers in terms of hot water resistance, steam heat resistance, and mechanical performance.
Tire cords, ■belts, comb reinforcements such as bows, ropes, and conveyor belts, which have been difficult to develop due to their hot water resistance.

This makes it possible to develop PXIA-based fibers into new fields of use, such as for FRP, and its usefulness is extremely large.

The present invention will be specifically described below with reference to Examples.

In this example, the polymerization degree of P■)\, the tensile strength and initial elastic modulus of the PVA fiber, and the cord strength and elongation physical properties were determined as follows.

(1) Degree of polymerization of PVA Based on JIS K6726, the degree of polymerization (Pn) was calculated from the intrinsic viscosity [η] of the aqueous solution at 30° C. using the following formula.

log (Pn)=1.613
([η] Take out the single yarn, test length 20mn1, tensile speed 10m
Single yarn strength and initial elastic modulus were measured using a tensile tester under the conditions of m/min.
Based on L1017, take a sample in a container and heat at 20℃, 65℃.
The strength and elongation of the cord was measured after being left at a temperature and humidity of %RH for 24 hours using a "Tensilon"u'rM-tn type tensile tester (manufactured by Toyo Baldwin Co., Ltd.) at a test length of 25 cm and a tensile speed of 30 mm/min. Physical properties were measured. The chuck used was an air zipper for cords.

Example 1 Completely saponified PVA with a polymerization degree of 3800 (saponification degree 99)
．． 9 molX) to dimethyl sulfoxide (hereinafter D
rvt SO) to make a spinning stock solution with a concentration of 17% by weight, which was discharged from a spinneret with a hole diameter of 0.08 mm and a number of holes of 600, and after running through approximately 5 mm of air for 1 time,
The sample was introduced into a methanol coagulation bath containing 8% by weight of DMSO at 20°C for coagulation, and taken off at a takeoff speed of 10 m/min.

The obtained coagulated yarn was washed with methanol, cold-rolled in four layers using double rollers, and dried with heated rollers at 80°C to obtain a primary drawn yarn.

Then, the fibers were introduced into a room temperature treatment solution containing a crosslinking agent to adhere the crosslinking agent to the yarn. Note that a 16% by weight methanol solution of cumene hydroperoxide was used as the crosslinking agent treatment liquid.

The yarn subjected to the above treatment was introduced into an air bath heated to 245'C, stretched five times, applied with an oil agent, and wound up.

The total stretching ratio of the obtained secondary drawn yarn was 20 times, and 1.
- Tal fineness is 1538 denier and number of filaments is 60
The fiber was composed of 0.0 denier, had a single fiber fineness of 2°6 denier, a strength of 22.0 g/d, and a modulus of elasticity of 308 g/d.

Using this yarn, a cord was created using the method described in the text. The hot water resistance and steam heat resistance index of this cord were determined by the method described in the text, and the results are shown in Table 1.

Comparative Example 1 A second drawn yarn was obtained by the method of Example 1 except that the crosslinking agent treatment step was omitted in the step of obtaining the second drawn yarn.

1. The total thickness of the second drawn yarn was 20 times, and I
- Tal fineness is 1536 denier, number of filaments is 6
00, single yarn fineness 2°5 denier, strength 22.4g/d, elastic modulus 3e) Ig/d! It had fi fiber properties.

Using this yarn, a coat was prepared in the same manner as in Example 1, and the hot water resistance and steam resistance index of this cord were determined.
The results are shown in Table 1.

Comparative Example 2 and Example 2 Primary drawn yarns of Comparative Example 2 and Example 2 were obtained in the same manner as in Example 1, except that the spinneret and the primary drawing rate were changed. Here the hole diameter is 0.08mm
φ,? A spinneret with a number of L of 400 was used. The primary spreading magnifications in Comparative Example 2 and Example 2 are 2x and 5°, respectively.

The obtained primary drawn yarn was treated in the same manner as in Example 1. In Comparative Example 20 secondary stretching, the stretching property was not sufficient and a yarn with a total stretching ratio of only 8.6 times could be obtained.

In Example 2, the same treatment as in Example 1 was possible. The total stretching ratio of the obtained secondary drawn yarn was 19.8 times, the total fineness was 1530 denier, and the number of filaments was 400. The fiber properties were as follows: single fiber fineness: 3.7 denier, strength: 19.73/d, and elastic modulus: 280 g/d.

A cord of this yarn was prepared in the same manner as in Example 1, and the hot water resistance and steam resistance index of this cord were determined, and the results are shown in Table 1.

Comparative Example 3 For comparison, the hot water resistance and steam heat resistance index of a commercially available vinylon yarn (manufactured by Kuraray Co., Ltd., Type I 800-1000-75501) was investigated.

The total fineness of this fiber was 1770 deniers, the single fiber strength was 13.6 g/d, and the fiber physical properties were that the elastic modulus was 208 g/d.

A coat was made using this fiber by the method described in the text. The number of first twists and the number of first twists were both 30 times per 10 C111.

The hot water resistance and steam resistance index of the obtained coat were determined by the method of Example 1. Note that here, the load applied to the cord was 0.6 ICg per cord.

The results obtained are shown in Table 1.

Claims (2)

[Claims] (1) Consisting of a polyvinyl alcohol polymer with a degree of polymerization of at least 1500, a tensile strength of 15 g/d or more, an elastic modulus of 250 g/d or more, a hot water resistance of 120°C or more, and a steam resistance index of High strength and high elastic modulus polyvinyl alcohol fiber with excellent hot water resistance of 50 or higher. (2) Spinning a polyvinyl alcohol polymer solution with a degree of polymerization of at least 1500, drawing the obtained yarn at least three times, then treating the drawn yarn with a crosslinking agent, and then drawing it. A method for producing high-strength, high-modulus polyvinyl alcohol fibers with excellent hot water resistance, which comprises performing dry heat stretching at a magnification of 3 times or more.