JP2503092B2 - Method for producing polyvinyl alcohol-based synthetic fiber - Google Patents

Description

TECHNICAL FIELD The present invention relates to a technique of wet- or dry-wet spinning an aqueous solution of a polyvinyl alcohol-based polymer (hereinafter, PVA) containing a surfactant into an alkaline coagulation bath. .

[Prior art]

PVA fiber has the highest strength and elasticity among general-purpose fibers, and is widely used as a reinforcing material for hydraulic materials such as cement and gypsum, as well as for organic moldings such as plastic and rubber, and widely used in industrial materials such as ropes. There is. In recent years, in such a field, a fiber which is a general-purpose fiber and has strength and elastic modulus equivalent to so-called super fiber such as aramid fiber has been demanded. At PVA, various attempts are being made to achieve this.

For example, the present inventors have previously applied for a patent and proposed a method of wet spinning a PVA aqueous solution containing boric acid or a borate into an alkaline coagulating bath having a dehydrating ability at a high temperature of 55 to 95 ° C.

[Problems to be Solved by the Invention]

However, although high-performance fibers can be obtained by such a method, there are cases where the stretchability is unstable in terms of fiber production, and further improvement in industrial production has been desired. Furthermore, the whitening phenomenon was easily observed in the fibers obtained by the conventional techniques. Whitening of fibers means the presence of macroscopic voids on the order of the wavelength of light, which is disadvantageous not only in the low density of fibers but also in water resistance and fatigue resistance as well as strength and elastic modulus. Although the mechanism of whitening is not clear at present, because of the strong interaction between PVA molecules,
It is presumed that the internal structure is destroyed due to the stress during stretching.

By adding a relatively large amount of a surfactant to the spinning dope, the present inventors stabilize the stretching even if whitening occurs in the fiber, resulting in higher strength, higher elasticity, water resistance and fatigue resistance. As a result of earnest studies to provide a PVA-based fiber having excellent properties, the present invention has been achieved.

On the other hand, it is known to add a trace amount of a surfactant to a PVA aqueous solution. For example, Japanese Examined Patent Publication (Kokoku) No. 43-7429 discloses one type of nonionic or anionic surfactants, or a similar type,
A technique is described that enables the use of a large nozzle by using a spinning dope containing a trace amount of two or more different types of additives, but the addition rate of the surfactant is 0.
The amount is 015 to 0.15% by weight, which is at most 0.5% by weight in terms of the addition ratio to PVA from the examples, and the addition ratio is lower than the present invention by a digit. Furthermore, the purpose of adding a surfactant is to stabilize the spinning tone when a large nozzle is used, which is completely different from the purpose of the present invention, and the above-mentioned effect which is the object of the present invention can be obtained as a practical effect. Absent.

[Means for solving the problem]

In the method of the present invention, 1 to 20% by weight of PVA is added to an aqueous solution of PVA having a degree of polymerization of 1500 or more in an amount of 1 to 20% by weight based on PVA as a spinning stock solution, and the solution is wet or dry in an alkaline aqueous coagulation bath. The spinning is carried out by a spinning method so that the total draw ratio is 20 times or more.

The PVA used has a degree of polymerization of 1500 or more, preferably 3000 or more,
More preferably, it is 5000 or more. The PVA concentration may be adjusted appropriately according to the degree of polymerization. Generally, when the degree of polymerization of PVA is high, the stretchability is often impaired, but the method of the present invention causes no problem. Further, since the unsaponifiable portion of PVA is saponified by using an alkaline aqueous coagulation bath, the saponification degree is not particularly limited, but if it is too low, gelation is difficult, so 95 mol% or more is preferable.

It is known to add boric acid or borate to the spinning dope when spinning the PVA aqueous solution into such an alkaline aqueous coagulation bath, but it is also possible to use these in the present invention, and for pH adjustment. Of course, addition of organic acids such as acetic acid, tartaric acid and oxalic acid may be used. The amount of boric acid or borate added is preferably 0.5 to 5% by weight with respect to PVA in order to obtain a high-strength / high-modulus fiber.

As the surfactant to be added, anion, cation,
Any of the amphoteric and nonionic compounds may be used alone or in combination. However, a combination that causes precipitation by complexing (for example, a combination of an anion and a cation) is not preferable.

The appropriate addition rate of the surfactant is 1 to 20% by weight based on PVA. If the amount is less than 1% by weight, the effect is small, it cannot be highly stretched, and the whitening associated with the stretching becomes remarkable, which is not preferable. On the contrary, 20% by weight
If the addition rate exceeds 10, the solidification will be insufficient.
Adhesion occurs between the single fibers, and the molecular orientation due to stretching does not proceed, so the expected physical properties cannot be obtained.

A PVA aqueous solution added with a surfactant, especially in a system in which layer separation occurs due to the addition of a surfactant to form particles, the stretchability is improved and the whitening inhibitory force is remarkable, preferable. Nonionic surfactants are particularly effective as the surfactant having such particle forming ability, and it is more preferable to add 3% by weight or more to PVA.

The nonionic type includes polyethylene glycol type such as higher alcohol ethylene oxide adduct, alkylphenol ethylene oxide adduct, fatty acid ethylene oxide adduct, polyhydric alcohol fatty acid ester ethylene oxide adduct, higher alkylamine ethylene oxide adduct, and glycerol. Of fatty acid ester of pentaerythritol, fatty acid ester of pentaerythritol, or polyhydric alcohol type such as alkyl ether of polyhydric alcohol, and the HLB value is preferably 6 or more, particularly preferably in the range of 12 to 19.

Further, if the particle size in the stock solution is large, defects will occur in the fiber and the physical properties will be degraded, so it is necessary to reduce this. The particle size is 100 μm or less, preferably 50 μm or less, more preferably 20 μm or less. As a means to miniaturize,
There are a mechanical method in which stirring or vibration is applied by a mixer or the like, and a chemical method in which an anion, cation, or amphoteric surfactant is used in combination at a ratio of 1 to 50% by weight with respect to the nonionic surfactant.

The temperature of the spinning dope is preferably 80 to 140 ° C, particularly 90 to 130
C is preferred.

Further, what is important in spinning the spinning dope is to spin the spinning dope within the shortest possible time after adding the surfactant to the spinning dope, and within 5 hours, preferably within 1 hour, and more preferably 30 Spinning within minutes is essential.

In an aqueous solution in which a surfactant and PVA coexist, layer separation occurs as described above, but this progresses over time, and eventually the undiluted solution gels, and spinning and stretching become impossible. Of.

The method of spinning within the shortest possible time after the addition of the surfactant is
It is effective to add a surfactant in batch or in-line to the PVA aqueous solution in which PVA is dissolved and defoaming is completed, mix, and immediately spin.

If the surfactant is added from the stage of dissolving the PVA, the PVA of the surfactant will coexist in the undiluted solution for a long time through the dissolution and defoaming, but this can be avoided by the addition method. it can.

The water-based coagulation bath is the same as the normal Glauber's salt bath or ammonium sulfate bath.
In order to form a core and reduce the stretchability, it is necessary to make it alkaline so that it has a gelling ability. As the alkaline component, sodium hydroxide, potassium hydroxide, and other caustic alkalis are mainly used. It is of course possible to use a salt having a dehydrating ability such as Glauber's salt together. 250 g / min or more in the case of alkali alone bath, preferably 3
At a concentration of 00g /, when using salts together, 5g / alkali
As described above, the amount of salt is 200 g / or more, and it is preferable that the concentration of salt is close to saturation. The temperature of the coagulation bath is not particularly limited, but when boric acid or borate is used as the spinning dope, it is preferably 55 to 95 ° C. As the spinning method, any of a normal wet method and a dry method (a method in which the spinning solution is once discharged into a gas such as air and the discharged yarn is immediately introduced into a coagulating bath to be solidified) can be adopted.

As the treatment after coagulation, neutralization, wet heat stretching, washing with water, drying, dry heat stretching may be carried out according to a conventional method, but the total stretching ratio is 20 times or more, preferably 25 times or more. It is preferable in order to obtain the high strength and high elasticity PVA function which is the object of the invention.

〔The invention's effect〕

The fiber obtained by such a method has excellent mechanical properties, and particularly when a spinning dope containing particles is used, the fiber obtained is transparent and has few voids, and therefore is excellent in water resistance and fatigue resistance. . Therefore, it is preferably used as a reinforcing fiber for cement, plastics, rubber and the like. In particular, it is suitable as a tire cord because it has improved fatigue resistance, which was conventionally insufficient with PVA fibers. In addition, it is also effective for general industrial materials such as ropes and cables.

 The present invention will be described below with reference to examples.

The presence or absence of particles in the spinning dope and the mechanical properties of the fibers were measured by the following methods.

Presence / absence of particles in the spinning dope and particle size Observe with a differential interference microscope or phase contrast microscope, select dozens of arbitrary particles, find their diameter, and divide the total by the number. "Particle size".

Fiber strength, elongation and elastic modulus JIS-L-1013 in an atmosphere of temperature 20 ° C and relative humidity 65%
In accordance with the above, a multi-filament yarn with a sample length of 20 cm was measured with an Instron tester at a pulling speed of 10 cm / min. The initial elastic modulus was obtained from the elongation-load curve.

The presence or absence of whitening of the fibers was judged by the naked eye.

Examples 1 to 3 and Comparative Examples 1 to 3 PVA having a polymerization degree of 3500 and a saponification degree of 98% was dissolved in water at a concentration of 12%, and boric acid was added thereto in an amount of 2% by weight based on PVA.
After defoaming the solution, nonylphenol ethylene oxide 20
No molar adduct (nonion HLB value = 16) was added (Comparative Example 1), 0.5 wt% relative to PVA (Comparative Example 2), 2 wt%
(Example 1) 5 wt% (Example 2), 15 wt% (Example 3), 25 wt% (Comparative Example 3) were added and stirred to prepare a spinning dope. The spinning stock solution heated to 130 ° C. was immediately wet spun through a nozzle into a 70 ° C. aqueous coagulation bath consisting of sodium hydroxide 20 g / and Glauber's salt 320 g /, and allowed to separate at a speed of 6 m / min. Then, roller stretching, neutralization, wet heat stretching, washing with water and drying were carried out according to a conventional method. Subsequently, dry heat drawing was carried out at 240 ° C. and wound on a bobbin. However, the stretching rate at which the sample was collected was 0.8 times the stretching rate at which the sample was broken.

 A series of data is shown in Table 1.

As is clear from this table, the stretching is stable only within the range of the present invention, the mechanical properties of the obtained fiber are excellent, and whitening does not occur. The fibers of these examples also had good water resistance and fatigue resistance.

Comparative Example 4 The spinning dope used in Example 3 was allowed to stand at 90 ° C. for 20 hours and then spun under the same conditions as in the above Example.

A gel-like substance was partially observed in the spinning dope, and winding with a roller occurred frequently. Further, the stretchability was also extremely unstable.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shoji Akiyama 1 stock company Kuraray 2045 Sakata, Kurashiki City, Okayama Prefecture (72) Inventor Fumio Nakahara 1-2-1, Kaigan Dori, Okayama City, Okayama Stock Company Kuraray Examiner Takuko Funakoshi (56) References JP-A-61-160414 (JP, A) JP-A-62-289606 (JP, A) JP-A-62-162010 (JP, A) JP-B-53- 1368 (JP, B1) Actual public Sho 43-7429 (JP, Y1)

Claims (5)

(57) [Claims] 1. A wet aqueous alkaline coagulation bath, which is prepared by adding 1 to 20% by weight of one or more surfactants to an aqueous solution of a polyvinyl alcohol-based polymer having a degree of polymerization of 1500 or more as a spinning stock solution. A method for producing a polyvinyl alcohol-based synthetic fiber, which comprises spinning or dry-wet spinning, and stretching so that the total stretching ratio is 20 times or more. 2. The degree of polymerization containing boric acid or borate is
1,500 or more polyvinyl alcohol-based polymer aqueous solution with one or more surfactants per polymer 1
What is added is -20% by weight as a spinning stock solution, which is wet- or dry-wet spun into an alkaline aqueous coagulation bath at a temperature of 55 to 95 ° C and stretched so that the total stretching ratio is 20 times or more. A method for producing a polyvinyl alcohol-based synthetic fiber. 3. A method for producing a polyvinyl alcohol-based synthetic fiber according to claim 1 or 2, wherein a solution in which particles separated into layers by adding a surfactant to an aqueous solution of a polyvinyl alcohol-based polymer is used as a spinning stock solution. Method. 4. The method for producing a polyvinyl alcohol-based synthetic fiber according to claim 1, wherein the spinning is performed within 5 hours after adding the surfactant to the spinning dope. 5. The polyvinyl alcohol-based synthesis according to any one of claims 1 to 4, wherein the polyvinyl alcohol is dissolved and defoamed, and then a surfactant is added, mixed and spun. Fiber manufacturing method.