JPH04126829A - Production of high-tenacity polyvinyl alcohol-based fiber excellent in hot water resistance - Google Patents

Abstract

PURPOSE:To obtain the subject fiber, excellent in productivity, high strength and hot water resistance and useful as industrial materials, etc., by applying an acid to yarn of PVA having a prescribed liquid content or above before dry hot drawing so as to provide a pickup within a specific range, drying the resultant yarn and dry hot drawing the dried yarn at a high temperature and a high draw ratio. CONSTITUTION:A spinning solution containing PVA dissolved therein is wet or dry-jet wet spun into an organic solvent-based coagulation bath such as dimethyl sulfoxide at <=20 deg.C and then dry hot drawn to produce PVA-based fiber. In the process, an acid such as phosphoric acid is brought into contact with the yarn with >=30%/PVA liquid content in a step before dry hot drawing so as to provide 5-10000ppm pickup thereof based on the PVA. The resultant yarn is then dried and dry hot drawn at >=220 deg.C so as to afford >=15 times total draw ratio.

Description

[Detailed Description of the Invention] <Industrial Application Fields> The present invention is directed to a high-strength polyhinyl alcohol (hereinafter abbreviated as P V , A) that has good hot water resistance and is useful in fields such as reinforcing materials for cement and rubber. )-based fiber manufacturing method.

Conventional technology> Conventionally, among general-purpose polymer fibers, PVA fiber 941 has higher strength and elastic modulus than polyester, polyamide, polyacrylonitrile fibers, etc., and has been used not only for industrial materials but also for cement, rubber, etc. It is used as a reinforcing material. In recent years, polyethylene, a general-purpose polymer, has been developed by gel spinning and super-stretching ultra-high molecular weight raw materials.
It was found that high strength and high elastic modulus fibers were obtained. However, polyethylene itself has a low melting point and insufficient heat resistance, and as a reinforcing fiber, it has poor adhesion to the matrix.

Therefore, attempts have been made to increase the strength and modulus of other general-purpose polymers by using the gel-spinning ultra-stretching technique.

Among them, PVA has the same planar zigzag structure as polyethylene and has active hydroxyl groups, so it is easy to form intermolecular hydrogen bonds, making it possible to obtain fibers with high strength, high elastic modulus, high heat resistance, and high affinity. For example, JP-A-59-100
No. 710, Japanese Unexamined Patent Publication No. 1303111/1984, etc. are proposed in No. 1. These PVA fibers have higher strength and higher modulus than commercially available PVA fibers, and are superior in heat resistance to the aforementioned polyethylene fibers. On the other hand, PVA fibers have a problem of poor hot water resistance because the polymer itself is soluble in water. Although the hot water resistance of the above-mentioned high-strength, high-modulus PVA fiber is improved compared to conventional PVA fibers, it is not sufficient.Therefore, a proposal has been made to improve the hot water resistance of high-strength PVA fibers. There is. For example, in JP-A-83-120H] No. 7::! ,,5 to 15% to the drawn yarn after stretching 15 or more points
It has been proposed that the acetalization of

However, only light acetalization does not have a sufficient effect of improving hot water resistance, and the process is complicated. In Mafco JP-A No. 1-156517, the yarn is spun and drawn by three times or more, and a crosslinking agent such as a single-headed peroxide, an isonoanate compound, or an evoquino compound is applied to the surface of the partially drawn yarn, It has been proposed that the fiber surface be crosslinked by subsequent dry heat stretching. However, since the crosslinking agent is present on the surface and mainly performs surface crosslinking, the stretchability is insufficient and the elastic modulus is as low as 310 g/d at most. There is also the problem of having to handle special organic compounds that require careful attention in terms of safety and health. Furthermore, in JP-A-2-84587, in order to improve the fatigue resistance of PVA fiber cords, PV fiber cords with a strength of 15 g/d or more are
It has been proposed to treat A fibers with crosslinking agents such as organic compounds such as aldehydes, isocyanates, organic peroxides, and carboxylic acids, and inorganic compounds such as phosphoric acid, hydrochloric acid, and titanium. However, in order to perform post-treatment on drawn high-strength fibers in which molecular orientation and crystallization have progressed, treatment must be performed at high concentrations and/or at high temperatures and/or for long periods of time, resulting in decreased strength. This is also a problem in the manufacturing process, and as a result, the manufacturing cost increases. Also, JP-A-2-1.
No. 33605 (Hey, it has been proposed that PVA and acrylic acid polymer be blend-spun to avoid forming crosslinks between the two polymers, and further crosslinked by adding a crosslinking agent such as an organic peroxide. However, the addition of about 2% or more of PVA, which does not affect strength, is not sufficient in terms of strength.Additionally, there are various problems as polymers other than PVA are added to the stock solution.

As described above, various crosslinking methods have been proposed to improve the hot water resistance and fatigue resistance of high-strength PVA fibers, but there is no method that satisfies both performance and manufacturing cost.

<Problems to be Solved by the Invention> Accordingly, the present invention aims to obtain f-coll VA fibers with excellent hot water resistance and strength, which are useful as reinforcing materials for cement and rubber, through a simple manufacturing process.

<Means for Solving the Problems> In pursuit of the above-mentioned problems, the present inventors brought acid into the yarn by bringing the acid into contact with the yarn in a high liquid content state before dry heat stretching as described below. By uniformly infiltrating the fiber and drying and then dry-heat stretching, it is possible to obtain a fiber having a crosslinked structure uniformly not only on the surface of the fiber but also inside the fiber in a manufacturing process that is simpler than that of known methods. Recognizing that the strength, resistance to hot water, etc. are intrusive, we have arrived at the present invention.

In the present invention, when introducing crosslinking to improve the hot water resistance of high-strength PVA fibers, a crosslinking agent is applied to drawn yarns that have been subjected to dry heat drawing to undergo molecular orientation and crystallization, in a known method. In contrast, when crosslinking is mainly introduced on the fiber surface,
The purpose is to infiltrate the crosslinking agent into the fibers to achieve uniform crosslinking.The type and amount of the crosslinking agent when infiltrating the crosslinking agent into the fibers, as well as the liquid content of the thread By adjusting the fibers appropriately, the crosslinking agent is uniformly permeated into the fibers, and then dry heat stretching is performed to effect oriented crystallization and dehydration crosslinking at the same time, thereby introducing uniform crosslinking.

This method is also characterized in that it can be obtained through a simpler manufacturing process than known methods. That is, P'V A as a crosslinking agent
Essentially, the key point is to use an acid that has an affinity for it, and to contact it in a state where the liquid content of the thread is high and the acid can easily soak in the acid.

The present invention will be explained in more detail below. P used in the present invention
The degree of polymerization of VA is not particularly limited, and it is preferable to use PVA with a higher degree of polymerization because it has excellent strength and hot water resistance. As in the present invention, when hot water resistance is improved by uniformly crosslinking with acid (=1) after dry heat stretching, two effects are required: a high degree of polymerization, "exhibition of hot water resistance properties", and two effects. It is preferable that the average degree of polymerization determined from the viscosity of an aqueous solution at 30° C. is 3000 or more.Furthermore, it is preferable that the average degree of polymerization is 7000 or more because the synergistic effect of improving hot water resistance due to uniform crosslinking is particularly large.PV used, The saponification degree is preferably 98 mol% or more, more preferably 99 mol% or more.Furthermore, 999 mol% or more is particularly preferable from the viewpoint of hot water resistance.
A may be a PVA-based polymer obtained by copolymerizing other vinyl group-containing monomers such as ethylene, iconic acid, and hinylpyrrolidone in a ratio of 10 mol % or less.・Solvents for PVA used in the present invention include dimethylsulfoginoto (hereinafter abbreviated as DMSO), chrycerin, edylenocricol, dimethylformamide, dimethylimidazolinonone, water, and an aqueous solution of Rodan's salt. Examples include solvents and mixed solvents of these solvents. PVA is dissolved at a temperature suitable for each solvent and defoamed to obtain a spinning stock solution.

The obtained spinning stock solution is passed through a nozzle and subjected to wet or dry-wet spinning into a coagulation bath at 20° C. or lower that is mainly composed of an organic solvent such as methanol, ethanol, or acetone that exhibits a coagulation effect on PVA. Of course, a mixed solvent of a coagulating organic solvent and a stock solvent can also be used as the coagulating bath. If the temperature of the coagulation bath exceeds 20°C, the solidified yarn will become non-uniform and high strength fibers cannot be obtained. Coagulation bath temperature 10℃
The following is preferable because the solidified thread becomes more homogeneous. In addition, so-called "gel spinning" is a system that solidifies only by cooling, and is usually extruded into the air, and in the present invention, "gel spinning" is included in the dry-wet spinning described herein It is something that will be done.

Itoshino solidified in a coagulation bath is wet stretched, solvent extracted, dried,
Although dry heat stretching is performed, in the present invention, PVA is
In order to dehydrate and crosslink the PV
One of the most important points is to apply 5 to 1.0.000 ppm of acid to Itoshino based on A. Examples of crosslinking agents for PVA include aldehydes, isonanoates, epoxies, methylols, organic peroxides, organic acids, and inorganic acids. and inorganic acids. Examples of the acids of the present invention include carboxylic acids and sulfonic acids having 1 to 5 carbon atoms, nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, and the like.

Furthermore, those that decompose at 220 to 260°C to produce acids are also included. Preferred are sulfuric acids and phosphoric acids which are volatile during dry heat stretching and have a strong dehydration catalyst effect.

It may be advantageous to use a catalyst to promote the crosslinking reaction, such as urea when using phosphoric acid. Acid is applied to itoshino with a liquid content of 30%/PVA or more in the process before dry heat stretching.
~10.000ppm/pvΔ Is it necessary to attach to the bone? If the liquid content is less than 30%, the acid will not penetrate uniformly into the inside of the thread basket, which is not preferable. Liquid content: 80%/P
II A or higher is preferable for salo in terms of uniformity.

In addition, the liquid content of the thread in the present invention refers to the liquid content of the thread in the process by hand shaking it forcefully three times to remove the liquid, and then quickly measuring its weight (w
+)L, and then drying under reduced pressure until the coagulation bath and stock solvent completely evaporate and a permanent jujube is obtained, and the percentage of molded clay is measured (W, )L, which is the value (W) given by the following formula.

The amount of acid attached varies depending on the acid strength, the temperature during dry heat stretching, and the residence time, but if it is less than 5 ppm/pVA, the dehydration crosslinking during dry heat stretching will be insufficient, so it will not be possible to achieve the desired hot water resistance improvement effect. I can't get it. It is more preferably 15 ppm/PVA or more, and most preferably 40 ppm or more. Particularly when using a strong acid such as phosphoric acid or sulfuric acid, if the amount of acid attached exceeds 10,000 ppm, the decomposition reaction takes precedence over dehydration crosslinking during dry heat drawing, which is disadvantageous as it reduces the warp strength. It is difficult to select the appropriate amount of acid to be applied depending on the acid strength, temperature and residence time during dry heat stretching.

The step of applying an acid is not particularly limited as long as it must be done before the dry heat stretching or the liquid content of the thread is 30%/P to 18 or more before the dry heat stretching. For example, an acid may be present in the oil solution bath immediately before drying, or an acid may be added to the solvent extraction bath of the oil solution solution. Furthermore, an acid may be added to the bath in which the stock solution is discharged from the nozzle and solidified. In this case, the uniformity inside the fiber is excellent, but the following baths (wet drawing bath,
If the same concentration of acid is not added to the extraction bath, oil bath, etc., there is a possibility that the acid will be washed away, so it is preferable to add acid to all the baths.

The thread solidified in the coagulation bath is washed with an extract of a coagulable organic solvent such as methanol to remove the stock solvent in the system, and then dried. It is preferable to perform O wet stretching in one stage or more preferably in multiple stages for a total of twice or more before drying, since this can prevent hardening during drying. A more preferable wet stretching ratio is 25 to 55 times. A wet stretching ratio of more than 6 times should be avoided since single filament breakage and cross-sectional deformation are likely to occur. The drying temperature is preferably 30°C to 150°C in terms of drying efficiency and performance. More preferably, the temperature is between 50°C and 120°C.

Next, the temperature was set at 220°C so that the total stretching ratio was 15 times or more.
One of the important points of the present invention is to conduct dry heat stretching at a temperature of .degree. When dry-heat-stretching the raw yarn after drying with an acid, we were concerned that the dry-heat stretchability would be significantly reduced due to crosslinking of PVA, and that the oriented crystallization of the molecules would not be able to be performed sufficiently. The key point of the present invention is the discovery that, surprisingly, if the type, amount, and state of crosslinking agent, as well as the dry heat stretching temperature, are selected, the dry heat stretchability hardly decreases. Ta.

The reason for this is unknown, but it is presumed that during dry heat stretching, physical structural changes due to molecular orientation crystallization take precedence, followed by chemical structural changes due to dehydration crosslinking. The acid selected in the present invention as a crosslinking agent applied before dry heat stretching is considered to be excellent because it has such a function. The strength and degree of dehydration crosslinking of the fibers depends on the type of acid applied (acid strength)
It should be selected appropriately as it varies depending on the balance between the amount, dry heat stretching temperature and residence time. - As an example, find the stretching temperature and residence time that give the highest strength without adding an acid, and draw the acid-added raw yarn at almost the same stretching temperature and stretching time to reach a degree of crosslinking of 30-100. %,
What is necessary is to determine the amount of a predetermined acid to be applied. The degree of crosslinking here refers to a bath ratio of 1:10 in hot water at a temperature 5°C higher than the temperature at which the drawn yarn of PVAwk fibers to which no acid is added is completely dissolved.
After processing for 1 hour at 0.000, undissolved fibers were removed at 300.
When filtering with mesh wire mesh, remove 80% of the gel remaining on the wire mesh.
The undissolved residual amount when dried under reduced pressure at ℃ until constant weight is measured, and calculated from the residual ratio with respect to the amount of f used at the beginning.

The stretching temperature varies depending on the degree of polymerization of PVA, but is 220°C.
Must be above.

High polymerization variants require high temperatures, but temperatures above 270°C are not preferred because decomposition occurs first. If the total stretching ratio including wet stretching and dry heat stretching is less than 15 times, the fiber strength will be low, so it must be 15 times or more.

It is preferable that the total draw ratio be higher, but in consideration of the occurrence of fluff and yarn breakage, it should be set at 075 to 0.95 times the maximum draw ratio. After dry heat stretching, crystallization may be promoted by further performing fixed length heat treatment or dry heat shrinkage to promote dehydration crosslinking.

As described above, cross-linking is achieved by bringing a predetermined amount of acid into contact with itoshino having a high liquid content, allowing the acid to uniformly permeate into the interior, and then drying, and performing oriented crystallization of molecules and dehydration cross-linking during dry heat stretching. can be uniformly applied to the inside of the fiber, making it possible to inexpensively produce PVA fibers with excellent hot water resistance and fatigue resistance.

<Effect of the invention> While the conventional crosslinking treatment method for high-strength PVA fibers mainly involved surface crosslinking, in the present invention, acid is added to threads with a high liquid content, and dry heat stretching is performed after drying. At the same time as molecular orientation crystallization, cross-linking is applied uniformly to the inside of the fiber, thereby improving hot water resistance and producing high-strength, highly hot-water resistant cross-linked PVA without adding new equipment or manufacturing processes.
Since fibers can be obtained, it can be manufactured at low cost. Therefore, the obtained high-strength, hot water-resistant PVA fiber has excellent cost performance compared to other super fibers such as conventional PVA fiber and rose aramid, and is used in the rubber material field such as hoses and tires, as well as in FR fibers.
It can be widely used in the field of reinforcing materials such as C and FRP.

The present invention will be explained in detail below using Examples, but the present invention is not limited to these Examples.

Example 1 P with viscosity average polymerization degree of 4100 and saponification degree of 99.8 mol%
VA was mixed with DMS O1 so that the concentration was 9.5% by weight.
: was added and dissolved in a nitrogen atmosphere at 70°C. Get it
The spinning dope was wet-spun into a coagulation bath (first bath) consisting of methanol/DMSO=7/3 (weight ratio) at 3°C through a nozzle with a hole diameter of 0.12 mm and a number of holes of 300, and the obtained coagulated yarn was The sample was further immersed in the same methanol/DMSO bath (second bath) as the second bath. Next, 50 ppm of phosphoric acid was immersed in a C-containing methanol bath (third bath) to extract DMSO, and at the same time, the phosphoric acid was allowed to permeate into the thread bag. The liquid content of the itoshino after the second bath was 290%. Then phosphoric acid 50
D is immersed in a methanol bath (fourth bath) containing ppm at 40°C to perform wet stretching, with a total stretching ratio of 5 times, and then passed through a methanol bath (fifth bath) containing soppm phosphoric acid.
M SO was further extracted and dried with hot air at 100°C. In this way, phosphoric acid was reduced to 120 ppm/PV
After drying, a yarn with A attached was obtained. Next, when the film was stretched in a hot air oven having a temperature gradient of 200° C. in the first furnace and 236° C. in the second furnace, the total stretching ratio could be up to 21 times. The total residence time in the furnace during 21 times stretching was 79 seconds.

This 21 times drawn yarn was colored black-purple, and it was assumed that a dehydration crosslinking reaction had occurred. Yarn strength is 18.7g/d
Met. In addition, this thread was immersed in hot water at 150°C for 1 hour in oak crepe, taken out and dried, and the strength remaining rate was measured and was 92%, which showed almost no decrease, indicating excellent hot water resistance.

Comparative Example 1 Spinning and drawing were performed in the same manner as in Example 1 except that phosphoric acid was not added to the 1st to 5th baths. The total stretching ratio could be up to 21.5 times.

The obtained drawn yarn was only slightly yellow colored. Yarn strength was 19.6 g/d.

The threads were immersed in hot water at various temperatures for one hour in an autoclave and then taken out to observe the state of dissolution. As a result, it was almost completely dissolved in hot water of 135° C. or higher, and the thread shape was not maintained.

Comparative Example 2 The drawn yarn obtained in Comparative Example 1 was immersed in an aqueous solution containing 10% phosphoric acid and 25% urea at 60°C for 30 minutes, immersed in water for 5 minutes at room temperature, dried at 80°C, and then dried at 190°C. Heat treatment was carried out for 6 minutes. The obtained fibers were colored deep purple, and the same tendency as in Example I was observed. Although the hot water resistance was excellent at 145° C., the yarn strength was 15.3 g/d, which was lower than that of Example 1 and Comparative Example 1, which was unsatisfactory for a high-strength PVA fiber with a degree of polymerization of 4100.

Example 2 P with viscosity average polymerization degree of 8000 and saponification degree of 99.8 mol%
DMSO was added to VA and dissolved by heating at 70° C. under a nitrogen atmosphere to obtain a PVA solution with a concentration of 7%. This spinning dope is mixed with a pore size of 0
．． Wet spinning was performed from a 15 mm nozzle with 500 holes into a coagulation bath (first bath) consisting of methanol/DMSO = 7/3 at 6°C, and the coagulated thread obtained was mixed with methanol/DMSO = 9
Wet stretching was carried out in a wet stretching bath (second bath) of /1 to make the total bending stretching ratio 4 times, then the DMS O was extracted through a methanol bath (third bath), and dried with hot air at 70°C. .

Add 60p each of phosphoric acid and urea to all baths from 1st to 3rd baths.
It was added so that it became pm and loop pm. In this example, since phosphoric acid was added to the first bath, the liquid content of the thread at the time of contact with the acid was 500% or more. After drying, the amount of phosphoric acid attached to the yarn was 150 ppm.

Next, this raw yarn was dry-heat-stretched using a dry-heat stretching machine having furnace temperatures of 150°C, 180°C, and 246°C so that the total stretching ratio was 20.5 times. The residence time at this time was 38 seconds at 150℃, 1
The heating time was 29 seconds at 80°C and 20 seconds at 246°C.

The obtained 7'7 drawn yarn was colored deep purple, and the strength of the yarn was 2O, tg/d. Further, this thread was immersed in hot water at 165° C. for 1 hour in an autoclave, taken out, and the strength remaining after drying was measured and found to be 90%.

A control uncrosslinked yarn produced in the same manner without adding phosphoric acid had a hot water resistance of 140°C. Furthermore, from Example 1 and Comparative Example 1, the effect of improving hot water resistance due to crosslinking at a polymerization degree of 4100 was 15°C.
On the other hand, the effect of this example at a polymerization degree of 8000 is 25° C., and the higher the polymerization degree PVA, the greater the improvement effect.

Example 3 PV with viscosity average polymerization degree of 6000 and saponification degree of 992 mol%
DMSO was added to A and dissolved by heating at 70° C. under a nitrogen atmosphere to obtain a PVA solution with a concentration of 8%. This spinning dope is mixed with a pore size of 0
．． Air gap I from 18 mm, 100 hole nozzle
Methanol/DMSO at -5°C as cm = 80/
Wet-dry spinning was carried out in a first bath consisting of 20 ml.

The obtained coagulated yarn was wet-stretched in the same manner as in Example 2, and DMSO
After extraction, sulfuric acid is added to the final methanol bath just before drying, and the sulfuric acid is applied to the threads using a roller touch method, followed by drying. The liquid content of Itoshino when it comes into contact with sulfuric acid is 190%. After drying, the amount of sulfuric acid attached to the thread was 80 ppm. Next, this yarn was placed in the second furnace 2 at 1f+go°C.
The yarn strength of the drawn yarn obtained by dry heat stretching with a drawing machine at 39°C to a total stretching ratio of 20 times is 19.1 g, /
d, and the hot water resistance is excellent at 155℃.

Example 4 P with viscosity average polymerization degree of 3500 and saponification degree of 99.9 mol%
Glycerin was added to VA and dissolved by heating at 180° C. in a nitrogen atmosphere to obtain a PVA solution with a concentration of 14%. This spinning dope was wet-dry spun into a first bath of methanol/chrycerin-85/15 at -10° C. through a nozzle with a hole diameter of 0.16 mm and a number of holes of 150, with an air cap of 5 mm.

The obtained coagulated yarn was mixed with methanol/glycerin at 40°C.
9515 wet stretching bath, and then D in a methanol extraction bath containing 200 ppm of phosphoric acid.
After washing with MS O, it was dried. The liquid content of the thread after wet stretching was 150%. Also, the amount of phosphoric acid attached is 300 ppm.
Met. Next, this yarn was passed through the first furnace at 180°C and the second furnace.
Dry heat stretching was performed using a stretching machine at 32° C. so that the total stretching ratio was 22 times.

The yarn strength of the drawn yarn thus obtained was 1.6.3 g/d, and the hot water resistance was 1.11° C., which were very excellent considering the use of PVA with a degree of polymerization of 3500.

Patent applicant RiRashi Co., Ltd.

Claims (1)

[Claims] When producing polyvinyl alcohol fibers by dry-heat stretching after wet or dry-wet spinning a spinning stock solution in which polyvinyl alcohol is dissolved in an organic solvent-based coagulation bath at 20°C or lower, the liquid content in the step before dry-heat stretching is 30%. %/polyvinyl alcohol or higher, bring the acid into contact with polyvinyl alcohol in an amount of 5 to 10,000 ppm, dry, and then dry heat to a temperature of 220°C or higher and a total stretching ratio of 15 times or higher. A method for producing high-strength polyvinyl alcohol fibers with excellent hot water resistance, which involves stretching.