JPS63120107A - High-strength and high-elastic modulus polyvinyl alcohol based fiber having excellent hot water resistance and production thereof - Google Patents

Abstract

PURPOSE:To obtain PVA based fibers having excellent tensile strength, elastic modulus and hot water resistance, by spinning a high-molecular weight PVA based polymer solution, drawing the resultant coagulated yarn at a high draw ratio and acetalizing the drawn yarn at a specific stretching ratio. CONSTITUTION:A solution of a PVA based polymer having at least 2500 polymerization degree is spun by a dry jet-wet spinning or gel spinning method. The resultant coagulated yarn is drawn at a draw ratio of at least 15 and then subjected to acetalization treatment at -10-7% stretching ratio so that the acetalization degree may be 5-15mol%. Thereby the aimed fibers having >=18g/d tensile strength, >=250g/d elastic modulus and >=120 deg.C hot water resistance are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a high-strength, high-modulus polyvinyl alcohol (hereinafter abbreviated as PVA) fiber d'3 having excellent hot water resistance and a method for producing the same.

[Prior Art] Conventionally, PVA-based fibers have been widely used in industrial fields such as ropes, fishing nets, sewing threads, canvases, and rubber reinforcements due to their excellent mechanical properties.

However, since the polymer itself of PVA-based fibers is essentially water-soluble, its application to fields requiring hot water resistance has been severely restricted.

By the way, the present inventors previously wet-dry spun PVA with a high polymerization degree of 1500 or more as a PVA-based fiber with excellent hot water resistance and mechanical performance, and then subjected the yarn to drawing of 201'E or more. By that.

It was proposed (Japanese Unexamined Patent Publication No. 126312/1982) that PVA fibers that are difficult to dissolve even in fresh water could be obtained, but subsequent (σ) research revealed that even with the PVA fibers that were designed for high distribution, It was found that hot water resistance was insufficient due to the remaining amorphous portion, and that if the fiber was left in hot water of 105 to 110° C. for a long time, it would still dissolve.

As a means of improving hot water resistance, which is an essential drawback of such PVA-based fibers, a method is generally known in which the fibers are insolubilized (acetalized) by reacting with aldehydes such as formalin. When subjected to acetalization treatment with an acetalization degree of 20 to 30 mol% or more,
Although the hot water resistance is improved, it is related to the high degree of acetalization.

The crystallinity and degree of orientation of the PVA fiber itself decreases, resulting in a significant decrease in mechanical performance. Therefore, this kind of hot water resistance improvement method that involves a decrease in mechanical performance is completely unsuitable for industrial fibers that require a high level of mechanical performance, and has been limited to textile fibers for clothing. .

[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-based fiber having excellent mechanical performance 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 2500, a tensile strength of 18 g/d or more, and an elastic modulus of 2501 J/d or more; and hot water resistance of 120°
High strength and high modulus polyvinyl alcohol fiber with excellent hot water resistance of C or higher.

(2) Dry-wet spinning or gel spinning a polyvinyl alcohol polymer solution having a degree of polymerization of at least 2500, stretching the resulting coagulated yarn at least 15 times, and then
High strength and high elasticity with excellent hot water resistance, characterized in that the drawn yarn is acetalized so that the degree of acetalization is 5 mol% or more and 15 mol% or less under a stretch rate of -10 to 7%. Production method of polyvinyl alcohol fiber.

This can be achieved by

That is, the PVA fiber according to the present invention has at least 25
00. Preferably 3000 or more, more preferably 35
It is composed of a polymer with a high polymerization degree of 0.00 or more. The use of such a polymer with an extremely high degree of polymerization, together with the specification of the spinning means described below, allows the resulting fibers to have a tensile strength of 18 g/d or higher, preferably 20 q/d or higher, and more preferably 21 g/d or higher. g/d or more, elastic modulus is 250 g/d
As described above, it becomes possible for the first time to achieve high strength and high elastic modulus, preferably 280 g/d or more, more preferably 300 g/d or more.

The PVA-based polymer contains completely saponified PVA, and a small amount of olefin additives such as ethylene, propylene, styrene, acrylic acid and its alkyl esters, methacrylic acid and its alkyl esters, and itaconic acid in the main chain. Polymerized PVA polymers can be mentioned, and a particularly preferred PVA-based polymer is completely saponified PVA with a degree of saponification of 99 mol% or more.

Further, the fiber of the present invention obtained from the above-mentioned highly polymerized polymer has a hot water resistance of at least 120°C, preferably 125-120°C.
The essential requirement is that the temperature be 60°C.

Hot water resistance here means that 100 mg of PVA fibers cut to about 5 mm in length and 5 ml of water are sealed in a Pyrex glass ampoule with an outer diameter of iQ mm and an inner diameter of 8 mm, and then placed in a silicon bath at a heating rate of 1°C. The temperature rises in / minute, and the corresponding! It is indicated by the temperature (°C) at which the 1i fiber completely melts.

As already mentioned, since the polymer itself of PVA fibers is inherently soluble in water, its application to fields where hot water resistance is required is severely limited. In contrast, the above-mentioned fibers of the present invention not only have high strength and high elastic modulus, but also have hot water resistance of 12
Since the temperature has been significantly improved to 0°C or higher, it will be particularly effective as an industrial fiber that requires hot water resistance.

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

The above-mentioned highly polymerized PVA-based polymer is produced using a normal wet spinning method, in which 1 q of the PVA-based polymer is dissolved in hot water and a spinning stock solution of 1 q is passed through a spinneret into a coagulation bath consisting of sulfur salt or an aqueous alkaline salt solution. In the method of discharging the spinning solution, the stability of the spinning solution and the stretchability and denseness of the pseudo-rigid yarn are extremely reduced. This becomes difficult.

In order to make such a highly polymerized PVA-based polymer into a dense and highly extensible coagulated thread, it is effective to adopt a dry-wet spinning method or a gel spinning method. This makes it possible to obtain high-strength, high-modulus polyvinyl alcohol fibers, which are the object of the invention.

Therefore, the dry-wet spinning method and the 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.

At this time, as a solvent for the spinning stock solution, dimethyl sulfoxide (DMSO), glycerin, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyhydric alcohols such as trimethylolpropane, ethylene diamine, diethylene amine organic solvents such as saturated aqueous solutions of amines such as resorcinol, formamide, and urea, or salt-free aqueous solutions such as lithium halides such as lithium bromide and lithium chloride, zinc chloride, aluminum chloride, aluminum chloride, and magnesium chloride. , or a mixed solvent thereof, preferably a solvent having a high dissolving power for PVA-based polymers, particularly DMSO, ethylene glycol, glycerin, and ethylene diamine.

Diethylene 1 to liamine are preferable.

The coagulant is compatible with the solvent of the spinning dope and is a non-solvent for the PVA polymer, such as methanol, ethanol, and acetone.

Benzene, toluene, a mixed solvent of these and the solvent of the spinning dope, and an aqueous solution of inorganic salts are used.

Next, in the gel spinning method, the spinning dope is discharged from a spinneret 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 dope. This spinning method involves cooling and gelling the yarn (without substantially changing the polymer concentration of the yarn).

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, glycerin and ethylene glycol.

Propylene glycol, diethylene glycol.

triethylene glycol, tetraethylene glycol,
Examples include polyhydric alcohols such as trimethylolpropane, benzenesulfonamide, caprolactam, and other solvents that are nonvolatile at room temperature, but glycerin and ethylene glycol are preferred.

In addition, as a cooling bath, one that is not miscible with the solvent of the above-mentioned spinning dope and is non-solvent for the PVA-based polymer;
For example, decalin, trichlorethylene, carbon tetrachloride, paraffin oil, etc. are used.

In the above-mentioned dry-wet spinning or gel spinning, 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 approximately 20%.
It is preferable to control the polymer concentration and temperature of the spinning dope so that the range is 0 to 5000 poise, preferably 500 to 2000 poise. If the viscosity of the spinning dope in the discharge section is lower than 200 poise or exceeds 5000 poise, the spinnability of the spinning dope will drop significantly and stable spinning will become difficult, which is not preferred.

Such a spinning stock solution is used in both dry and wet spinning or gel spinning, when it is heated above the liquid level of a coagulation bath or a cooling bath.
It is discharged through a spinneret installed at a position of ~200 mm, and the discharged yarn is air or nitrogen.

After running through an inert atmosphere such as helium or argon, it is introduced into the coagulation bath or cooling bath.

If the distance that the discharged yarn travels in the air or inert atmosphere is less than about 2 mm, the discharged yarn is likely to break due to fluctuations in the liquid level, and spinning stability deteriorates.
If it exceeds mm, it is not preferable because adhesion between the single yarns constituting the discharged yarn tends to occur.

Further, the temperature of the coagulation bath is usually in the range of 0 to 30°C.

On the other hand, the temperature of the cooling bath is determined by the gelation temperature of the spinning dope, and is preferably in the range of 0 to 60°C. In other words, when the temperature is higher than 60°C, the cooling efficiency of the discharged yarn is insufficient and the gelled yarn becomes soft, making it difficult to run the yarn stably in subsequent steps such as desolvation and stretching. However, when the temperature drops below 0℃, a special cold fJl
It requires equipment and is not desirable.

For example, 15 width Q% of PVA with a degree of polymerization of 3000
In the case of glycerin solution, its gelation temperature is approximately 103°C
In order to discharge this solution from a spinneret nozzle and cool the resulting discharged yarn, the temperature of the cooling bath is preferably 30° C. or lower.

The depth and length of the cooling bath are not particularly limited, but when discharging as a multifilament, the single fibers that make up the multifilament are sufficiently cooled in the cooling bath before being bundled. The temperature, depth, and length of the cooling bath should be appropriately set so that gelation is completed.

The obtained coagulated thread or gelled thread is stretched after removing the solvent by employing various means such as a heating tube, a heating medium bath, and a hot plate. In this case, the total stretching ratio must be at least 15 times, preferably 18 times or more, relative to the undrawn yarn. Stretching at such a high magnification becomes possible only by using the above-mentioned specific spinning methods such as wet spinning or gel spinning, and by using a highly polymerized polymer, PVA fibers with high physical properties, which is the object of the present invention, can be obtained. I'm here because I can.

Thus obtained PVA type 1! Since the fibers are highly drawn and oriented, they have excellent quality and have improved hot water resistance to the extent that they do not dissolve even in boiling water.
When treated in pressurized water at temperatures above .degree. C., it resulted in dissolution or a significant decrease in strength, and was still insufficient in terms of hot water resistance.

Therefore, in the present invention, as a specific means for maintaining the hot water resistance of PVA fiber at at least 120°C,
For example, highly drawn and oriented PVA fibers are subjected to acetal treatment such that the degree of acetalization is 5 mol% or more and 15 mol% or less, thereby producing PVA fibers with excellent mechanical properties and hot water resistance. urge At this time, if the degree of acetalization is less than 5 mol%, the hot water resistance will be insufficient, while if it exceeds 15 mol%, the strength will be poor.

The decrease in elastic modulus also becomes apparent, and mechanical performance is likely to be impaired.

In addition, in order to suppress the decrease in mechanical performance as much as possible during the acecool treatment, it is effective to process the drawn yarn at a stretch rate of -10 to 7%, preferably -5 to 5%. is. Stretch rate during acetal treatment is 7%
If it exceeds , thread breakage during acetal treatment will increase,
Stable operation becomes difficult, and when the stretch rate is less than 110%, the mechanical performance of the fibers, especially the elastic modulus, decreases significantly.

The aldehyde compound used for this aretal treatment is not particularly limited, but has a desired tensile strength.

In order to achieve the elastic modulus, formalin and benzaldehyde are preferably used.

In this way, in PVA fiber, the degree of acetalization is 5.
Conventional P
This is completely unexpected from VA fibers, and can be said to have been achieved for the first time because of the integral combination of a high degree of polymerization of the PVA polymer and a specialized spinning means, as in the present invention.

Furthermore, it has become possible to reduce the degree of acetalization required to improve hot water resistance.

Deterioration in mechanical performance during acetal treatment is greatly suppressed, and PVA-based fibers with excellent tensile strength and elastic modulus can be obtained.

Of course, the means for improving the hot water resistance of the fibers of the present invention is not limited to the above-mentioned acetalization treatment using an aldehyde compound.

[Effects of the Invention] The PVA-based fiber of the present invention has hot water resistance of 120° C. or higher and a tensile strength of 18 CI/d or higher.

Tire cord, which had previously been difficult to develop in terms of hot water resistance, has extremely superior hot water resistance and mechanical performance compared to conventional PVA fibers, with a bullet [1 modulus of 250 g/d or more]. It is extremely useful as it enables the development of new application fields for PVA-based fibers, such as rubber reinforcement for belts, hoses, etc., ropes, conveyor belts, and FRP.

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

In this example, the degree of polymerization of PVA, the tensile strength, and the initial elastic modulus of the PVA-based fibers 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.

too(Pn)=1 , 613XIO(1([77]
x 10'1/8.29) However, [η]: ml/g (2) Tensile strength and initial modulus of PVA fiber The fibers were conditioned in advance at 20°C and 65% relative humidity for 24 hours. ,
Take out the single yarn and make a trial length of 2Qmm.

Single yarn strength and initial elastic modulus were measured using a tensile test chamber at a tensile speed of 100 mm/min.

Example 1 Vinyl acetate was polymerized using azobisisobutyronitrile at a temperature of 50°C to obtain completely saponified PVA with a degree of polymerization of 3800 (polymerization rate 20%).

PVA was dissolved in DMSO at 80°C, and the polymer concentration was 12
% by weight of the spinning stock solution was prepared, and it was discharged into the air using a nozzle with a hole diameter of 00OBmmφ and 50 holes, and after running through the air at a distance of about 5 mm (distance between the nozzle surface and the coagulation bath liquid level), 20
It was introduced into a methanol 1 pseudo-solid bath containing 5,000 m% of DMSO at a temperature of 0.degree.

The obtained undrawn yarn was washed with methanol, cold-stretched by a factor of 4 using double rollers, and dried using heated rollers at 80°C. The dried yarn was passed through a heating tube with a nitrogen stream at 235° C., stretched five times, and wound up using a winder.

The total stretching ratio of the obtained drawn yarn was 20 times, the single yarn fineness was 2.0 d, and the single yarn strength was 21.89/d.

The elongation was 6.0%2 and the modulus of elasticity was 350g〆d.

This drawn thread was fixed on a stainless steel frame and treated with formalin 50g/l and sodium sulfate 100g/l.

in a formalization bath consisting of 200 g/l sulfuric acid at 60°C.
Tension formalization treatment (stretch rate: 0%) was performed. At this time, by changing the processing time, yarns with different degrees of formalization are created, and the tensile strength of each yarn is 1
Elastic modulus, degree of formalization, and hot water resistance were measured.

The results are shown in Table 1.

(Hereinafter, blank space) Example 2 Using pivalic acid dimyl phosphinate as an initiator, -
Low-temperature photopolymerization of vinyl acetate was carried out at a temperature of 30°C, and 1q of completely saponified PVA with a degree of polymerization of 11,500 was obtained (polymerization rate of 1
8%).

The obtained P-VA was dissolved in ethylene glycol at 180°C to prepare a spinning stock solution having a polymer concentration of 6% by weight.

This spinning stock solution was kept at 180°C and the pore diameter was 0.15mmφ.
It was discharged into the air using a nozzle with 20 holes, introduced into a cooling bath made of decalin at 10° C. approximately 20 mm below the nozzle surface, cooled and gelled, and taken off at a take-up speed of 10 m/min. .

The resulting undrawn gelled yarn was washed with methanol to remove ethylene glycol, dried with a drying roller at 60°C, and then stretched 19 times in a heating cylinder at 255°C in a nitrogen atmosphere. Then, it was wound up with a winder.

The single yarn strength of the drawn yarn was 24.0!11/d.
.

The elastic modulus was 480 g/d.

This drawn yarn was fixed to a stainless steel frame and subjected to the same formalization treatment as in Example 1, resulting in a yarn with a degree of formalization of 13.5 mol %.

The obtained yarn had a tensile strength of 23.89/d, an elastic modulus of 420 g/d, and a hot water resistance of 140°C.

Actual rJ Counterexample 3 Using α,α゛-azobisdimedylvaleronitrile as an initiator, bulk polymerization of vinyl acetate was carried out at a temperature of 30°C, yielding 1q of completely saponified PVA with a degree of polymerization of 6500 (polymerization rate 20%). ).

The obtained PV8 has a polymer temperature of 10% and a mouth hole diameter of o.
, iommφ, and was made into fibers in the same manner as in Example 1, and stretched to a total stretching ratio of 18.5 times in a heating cylinder at 250°C.

The single yarn strength of the obtained drawn yarn was 23.2 (1/d).

The elastic modulus was 390 g/d.

This drawn yarn was introduced into a formalizing bath similar to that used in Example 1 using a roller, and was taken up by the roller in a rough and continuous manner, wound up in a winder, washed with water, and dried.

At this time, the stretching rate was changed depending on the speed of the roller on the exit side of the formalizing bath, and the formalizing process was performed.

The tensile strength 2 elastic modulus, degree of formalization, and hot water resistance of the obtained yarn were measured, and the results are shown in Table 2.

(Hereafter, margin)

Claims (2)

[Claims] (1) High strength and excellent hot water resistance, consisting of a polyvinyl alcohol polymer with a degree of polymerization of at least 2500, a tensile strength of 18 g/d or more, an elastic modulus of 250 g/d or more, and a hot water resistance of 120°C or more. High modulus polyvinyl alcohol fiber. (2) Dry-wet spinning or gel spinning a polyvinyl alcohol polymer solution having a degree of polymerization of at least 2500, stretching the resulting coagulated yarn at least 15 times, and then
High strength and high elasticity with excellent hot water resistance, characterized in that the drawn yarn is acetalized so that the degree of acetalization is 5 mol% or more and 15 mol% or less under a stretch rate of -10 to 7%. Production method of polyvinyl alcohol fiber.