JP2927304B2 - Method for producing polyvinyl alcohol-based synthetic fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a high-strength, high-elasticity polyvinyl alcohol (hereinafter referred to as "high-strength, high-modulus polyvinyl alcohol") which is useful as a reinforcing material for cement or rubber or as an industrial material such as a rope. (Abbreviated as PVA) based synthetic fiber.

<Conventional technology> Conventionally, PVA-based synthetic fibers have the highest strength and high elastic modulus among general-purpose fibers as molding materials such as plastics and rubbers, and hydraulic inorganic materials such as cement and masonry. As a reinforcing material, and also as a general industrial material such as a rope and a cable.

In recent years, attempts have been made to further increase the strength and modulus of elasticity and to approach a so-called super fiber such as aramid or polyarylate.For example, as shown in JP-A-60-122632, PVA is converted into an organic solvent. A method of dissolving and dry-wet spinning has been proposed. Further, JP-A-1-298208 discloses that an aqueous PVA solution containing boric acid or borate is used as a spinning solution, and the coagulation bath temperature is 55 to 95 ° C.
And high, spinning into an alkaline aqueous coagulation bath containing salts,
It has been shown that by stretching the obtained spun yarn at a high magnification of 17 times or more, a PVA-based synthetic fiber having high strength and high elastic modulus can be obtained.

Both employ special spinning methods and conditions,
Along with the effect of enabling high orientation and high crystallization of A molecules and increasing the degree of polymerization of PVA, not only mechanical properties such as strength and elastic modulus, but also hot water resistance have been improved.

However, such fibers are basically made of PVA, which is a water-soluble polymer, and their hot water resistance is not sufficient as long as an amorphous region exists.

Recently, studies have been made to further improve the hot water resistance while maintaining the strength and elastic modulus as much as possible.
JP-A-84587 and JP-A-1-156517 disclose such means.

In the former, a PVA-based synthetic fiber with a strength of 15 g / d or more or a cord obtained by twisting the PVA-based synthetic fiber is subjected to a cross-linking treatment.However, in order to treat a fiber in which molecular orientation and crystallization are progressing. In addition, a cross-linking agent must be applied at a high temperature and high concentration for a long time, and the resulting fiber has a large decrease in strength and elastic modulus, and the formed cross-linking structure is mainly unevenly distributed on the fiber surface. When it comes in contact with water, the central part of the fiber swells or dissolves. In order to uniformly penetrate the cross-linking agent in the cross-sectional direction of the fiber, the application conditions must be made severer, resulting in a different decrease in strength and elastic modulus. In addition, such a process involves complicated and long steps, resulting in extremely high manufacturing costs.

On the other hand, in the latter, although the process is simplified by a method of applying a cross-linking agent before hot drawing, in order to intentionally distribute the cross-linked structure to the fiber surface,
It is described that a crosslinkable agent must be applied after drawing at least three times after spinning.

Fibers obtained by such a method also swell or dissolve from the central portion of the fibers upon contact with hot water, as in the case of the above, and it is not considered that they have sufficient hot water resistance. I can't say.

That is, with the conventional technology, a high-strength, high-modulus PVA-based synthetic fiber having sufficient hot water resistance could not be produced in a simple process at low cost.

<Problems to be Solved by the Invention> The present invention provides a PVA-based synthetic fiber having sufficient hot water resistance and high strength and high elasticity by using an aqueous solvent and an aqueous coagulation bath as described in JP-A-1-298208 described above. It is intended to be manufactured in a simple process and at low cost by using the manufacturing method used.

<Means for Solving the Problems> The present inventors have found that it is sufficient to infiltrate the cross-linking agent uniformly in the cross-sectional direction of the fiber and to form a cross-linked structure not only on the fiber surface but also on the central part. Is considered to be extremely effective in obtaining PVA-based synthetic fibers having strength and elastic modulus,
As a result of intensive studies, the present inventors have found that the intended fiber can be produced in a simple process at a low cost by employing a specific means described later.

That is, the method of the present invention comprises: (1) spinning an aqueous solution of a polyvinyl alcohol-based polymer containing boric acid or borate into a high-temperature alkaline coagulation bath at 55 to 95 ° C. containing salts having a dehydrating ability; , 1.5 times or more of stretching, neutralization, wet heat stretching of 1.0 to 2.0 times, the stretching ratio up to here is 2.0 to 5.0 times, after washing with water,
An aqueous solution of a salt is brought into contact with an aqueous solution of salt adjusted to a water content of 50 to 300% by weight with respect to the polymer, and an acidic salt of a polyvalent strong acid with an alkali metal or an alkaline earth metal, and an ammonium salt of a strong acid with ammonia. And at least one salt selected from salts of strong acids and transition metals with the polymer in an amount of 50 to 5000
A process for producing a polyvinyl alcohol-based synthetic fiber, comprising applying 0 ppm, drying, and subsequently stretching at 220 ° C. or higher so that the total draw ratio is 17 times or higher.

(2) An aqueous solution of a polyvinyl alcohol-based polymer containing boric acid or a borate and one or more surfactants in an amount of 1 to 20% by weight based on the polymer is used as a spinning dope, and this is a salt having a dehydrating ability. Spun into a high-temperature alkaline coagulation bath at 55 to 95 ° C containing 1.5 times or more of stretching and neutralization, 1.0 to 2.0
And then stretched to 2.0 to 5.0 times the wet heat and then washed with water and adjusted to a water content of 50 to 300% by weight with respect to the polymer. Contact an aqueous solution of at least one salt selected from an acidic salt with a class of metals, an ammonium salt of a strong acid with ammonia and a salt of a strong acid with a transition metal, and applying the salt to the polymer in an amount of 50 to 50,000 ppm and drying. Followed by 220 ° C
A method for producing a polyvinyl alcohol-based synthetic fiber, wherein the stretching is performed so that the total draw ratio is 20 times or more.

As a drug for improving hot water resistance, a specific salt with high affinity for PVA is also dissolved in water with high affinity for PVA, and this is brought into contact with the water-containing state of Itoshino to convert the salt into fiber. It is to penetrate the inside evenly.

As a method for producing PVA fiber utilizing this method, the present method comprises spinning an aqueous solution of the above-mentioned PVA-based polymer containing boric acid or borate into a high-temperature coagulation bath at 55 to 95 ° C containing salts having a dehydrating ability. This technique is to collect the technology, but in addition to the effect of this technology to enhance the stretchability, it also reduces the crystallinity of the water-containing itoshino after washing, and allows the acid to uniformly penetrate inside the fiber. This is because it also has a very advantageous effect for the purpose of the present invention of facilitating the facilitation.
In addition, since the stretching and the wet heat stretching of the yarn from the coagulation bath both inhibit the permeability of the salt, the stretching ratio from spinning to the wet heat stretching is suppressed to 2 to 5 times. Thus, salt penetration can be facilitated, but that alone is not enough,
In order to further promote penetration, the water content of itoshino when applying an aqueous solution of a specific salt is controlled to 50 to 3000% by weight with respect to the polymer. It is a necessary means to do.

Further, the present invention employs a production system in which one or more surfactants are further added to the spinning dope in an amount of 1 to 20% by weight based on the polymer, thereby further promoting salt penetration. However, in combination with the fact that the stretchability can be further improved, a PVA fiber having a higher strength and a higher elastic modulus and further improved hot water resistance can be obtained.

 Hereinafter, the present invention will be described in detail.

The degree of polymerization of PVA is 1500 or more, preferably 3000 or more, more preferably 5000 or more. The higher the degree of polymerization, the easier it is to obtain hot water resistance, strength and elastic modulus. The saponification degree is not particularly limited since it is saponified in a coagulation bath, but is preferably 95 mol% or more. Further, a copolymer of another monomer having a vinyl group at a ratio of 10 mol% or less may be used. In addition, the PVA concentration and the concentration of boric acid or borate in the spinning dope may be appropriately adjusted depending on the degree of polymerization. Of course, even if the pH of the spinning solution is adjusted using acetic acid, oxalic acid, or the like, there is no problem at all.

On the other hand, when one or more surfactants are added to the spinning dope, as described above, salt penetration can be promoted and stretchability can also be increased, but the addition rate is preferably 1 to 20. It must be in the range of weight% / polymer. If the amount is less than 1% by weight / polymer, the effect cannot be obtained, and if the amount is more than 20% by weight / polymer, poor coagulation occurs. As the type of surfactant, nonionic, anionic,
Any cation or amphoteric can be used, but a combination that produces a precipitate (eg, an anion and a cation) is not preferred when two or more are used in combination.
Also preferred are nonions, especially HLB13
~ 19 are preferred in terms of the strength and elastic modulus of the resulting fiber.

The spinning method may be ordinary wet spinning or dry-wet spinning having an air or an inert gas layer between the nozzle surface and the coagulation bath liquid surface.

The temperature of the coagulation bath is 55-95 ° C, preferably 60-85 ° C. If the temperature is lower than 55 ° C., the crystallinity of the water-containing thread at the time of contact with the aqueous salt solution is too high, so that it does not easily penetrate into the interior of the fiber and has no stretchability. If the temperature exceeds 95 ° C., the coagulation bath will boil or the single fibers will stick, making it impossible to spin. The alkali component and the dehydrating salt component of the coagulation bath may each be a known component such as caustic soda and sodium sulfate.

Stretching, neutralization, wet heat stretching, and water washing may be performed according to a conventional method after spinning, but roller stretching and wet heat stretching are each 1.5 times or more, 1.0 to 2.0 times, and stretching from spinning to wet heat stretching. The magnification must be 2.0 to 5.0 times. The first drawing after spinning is carried out in the subsequent neutralization step, and the wet heat drawing after the neutralization is carried out in the subsequent washing step to prevent swelling of the fiber or extreme structural damage of the fiber. Although it is necessary and indispensable, if these stretching ratios are too large, the orientation or crystallization of the shinoshino occurs, which impedes the penetration of salt. In other words, it is necessary to balance the suppression of swelling in the subsequent step and the securing of salt permeability, and as a result of various studies, the first stretching after solidification is 1.5 times or more, and the wet heat stretching is 1.0 to 2.0 times. And the product of both, that is, the draw ratio from spinning to wet heat drawing can be well balanced only within a limited range of 2.0 to 5.0 times.

After washing with water, itoshino has a water content of 50-
After adjusting to 300% by weight, it is brought into contact with an aqueous solution of a salt.
In the present specification, the water content is Here, A: the weight after centrifugal dehydration of itoshino at 3,000 rpm x 5 minutes B: the weight of itoshino after drying at 100 ° C for 4 hours.

If the water content is less than 50% by weight / polymer, the salt cannot penetrate into the interior, and if it exceeds 300% by weight / polymer, even if the salt penetrates into the interior of the fiber, water will diffuse to the fiber surface during drying. As a result, not only salts move to the surface and are unevenly distributed, but also dry sticking tends to occur. The method of adjusting the water content is not particularly limited, but the water temperature in the washing step and the residence time,
Alternatively, it may be squeezed after washing with water or lightly dried.

As the chemical used to improve the hot water resistance, the salt was selected from among a number of isocyanates and epoxies, because the PVA was used to make it penetrate evenly into the fiber.
This is due to the consideration of the affinity with. Therefore, as the salt in the present invention, an acid salt of a polyvalent strong acid such as sulfuric acid or phosphoric acid with an alkali metal or an alkaline earth metal, an ammonium salt of a strong acid with ammonia, and a salt of a strong acid with a transition metal are used. You. Specifically, primary potassium phosphate, secondary potassium phosphate, primary sodium phosphate, secondary sodium phosphate, acidic potassium sulfate, calcium calcium phosphate, ammonium sulfate, ammonium phosphate, primary ammonium phosphate , Ammonium phosphate dibasic, potassium ammonium phosphate, copper sulfate, cobalt nitrate, manganese chloride and the like.

The method for applying these salts may be any of dipping, spraying, and roller touching.
It must be between 50 and 50000 ppm, preferably between 100 and 5000 ppm. If the amount is less than 50 ppm / polymer, the effect is not exhibited. If the amount exceeds 50,000 ppm / polymer, the acetylation of the fiber is remarkably deteriorated, and the strength and elastic modulus are significantly reduced. Subsequently, drying and stretching are performed according to a conventional method, but the stretching temperature is 220 ° C.
Otherwise, the crosslinking reaction by the salt does not proceed. Further, in order to obtain sufficient strength, it is necessary to make the total stretching ratio 17 times or more. When a surfactant is added to the spinning dope, the film is further stretched so that high stretching is possible and 20 times or more.

Furthermore, if necessary, the drawn yarn may be heat-treated to further improve the hot water resistance.

The present invention will be described in detail with reference to the examples, but the present invention is not limited to these examples.

In the examples, the elongation / elasticity and hot water resistance are measured by the following methods.

(1) High elongation / elasticity: Sample: Multifilament yarn 80T / m twisted yarn Method: Measured with an Instron tensile tester in accordance with JIS L-1017.

(2) Hot water resistance: The fiber was cut to 5 mm, dispersed in water at a bath ratio of 1: 500, transferred to an autoclave container, treated with hot water at 140 ° C. for 1 hour, and the undissolved portion was separated. dry.

As hot water resistance.

Example 1 PVA having a polymerization degree of 3500 and a saponification degree of 98.5 mol% was dissolved in water at a concentration of 13%, and boric acid was added at 2% / polymer to prepare a spinning solution. The spinning solution was wet-spun from a 1000-hole nozzle into a coagulation bath at 60 ° C. containing 30 g / l of sodium hydroxide and 330 g / l of sodium sulfate. After the bath was separated, the film was stretched by 2 times with a roller, neutralized, stretched by 1.5 times in wet heat, and washed with water at a stretch ratio up to 3 times. After washing with water, 75% of the water content of the polymer is immersed in a 5000 ppm aqueous solution of ammonium sulfate.
000ppm / Polymer is applied and dried.
The film was stretched to 24 times and heat-treated at 235 ° C. for 30 seconds.

The obtained fiber had a strength of 18.2 g / d and a modulus of elasticity of 350 g / d and a hot water resistance of 90%.

Comparative Examples 1 and 2 A sample obtained in exactly the same manner as in Example 1 except that no ammonium sulfate was applied (Comparative Example 1) and a sample of Comparative Example 1 were placed in an aqueous solution of 10% by weight of ammonium sulfate at 60 ° C. for 30 minutes. It was immersed, washed for 5 minutes, dried, and heat-treated at 200 ° C. for 5 minutes to obtain a post-treated fiber (Comparative Example 2). Table 1 shows the respective physical properties.

As shown in Table 1, the effect of improving the hot water resistance by the cross-linking treatment of the present invention is remarkable, and the strength and elastic modulus are greatly reduced and the hot water resistance is insufficient with the conventional post-treatment.
Observation of the sample after the hot water treatment of Comparative Example 2 showed that the central portion of the single fiber was partially swollen and dissolved.

Comparative Example 3 (Control) The same PVA as in Example 1 was dissolved in dimethylsulfoxide at 12%, and a 3 mm air gap was taken from a 750-hole nozzle, followed by dry / wet spinning to a methanol bath. After extracting and performing 4 times wet stretching while drying, immersing in a 10 wt% methanol solution of cumene hydroperoxide,
The film was stretched twice in dry heat. This fiber has a fineness of 18 g / d and an elastic modulus of 300 g / d
The hot water resistance was 55%. The sample after the hot water treatment was partially swollen or dissolved in the central portion of the single fiber as in Comparative Example 2.

Comparative Examples 4 to 6 Based on the conditions of Example 1, a coagulation bath temperature, roller stretching,
Only the wet heat draw ratio was changed. Table 2 shows the conditions and the fiber properties obtained.

In Comparative Example 4 where the coagulation bath temperature is low, the stretchability is low and the strength is not obtained. In addition, hot water resistance is low due to poor salt penetration. In Comparative Example 5 in which the roller stretching ratio was low, the fibers swelled due to neutralization, and the strength was extremely low. In Comparative Example 6, in which the magnification from spinning to wet heat stretching is high, the hot water resistance is low due to poor penetration of the salt.

Examples 2 and 3 and Comparative Examples 7 and 8 PVA having a degree of polymerization of 7000 and a degree of saponification of 99.2 mol% was dissolved in water at a concentration of 8%, and boric acid was 3% / polymer and nonylphenol was used as a surfactant. An ethylene oxide 30 mol adduct (HLB17) was added to a 10 wt% polymer to prepare a spinning stock solution. The spinning solution is sodium hydroxide 20 g / l, sodium sulfate 360 g / l
After wet spinning to a coagulation bath at 70 ° C., a 3.0-fold roller stretching, neutralization, and 1.4-fold wet-heat stretching were performed, and the stretching ratio up to this point was 4.2 times. Subsequently, it was washed with water, squeezed, and immersed in various concentrations of ammonium phosphate aqueous solution at a water content of 140%, and the salt adhesion rate was 30 ppm relative to the polymer (Comparative Example 7) and 100 ppm (Example). 2), 7000 ppm (Example 3), 700
After giving 00 ppm (Comparative Example 8), it was dried and stretched by dry heat at 240 ° C. The results are shown in Table 3.

Obviously, in order to satisfy both the strength and the hot water resistance, the amount of the salt attached must be within the range of the present invention.

Comparative Examples 9 and 10 In Example 2, the water content of Ishino immersed in ammonium phosphate was changed to 30 wt% / polymer by light drying (Comparative Example 9). Also, 350wt% /
The same treatment as in Example 2 was performed except that the polymer was used (Comparative Example 10).

In Comparative Example 9, the hot water resistance was 40%, and the salt did not uniformly penetrate into the fiber, so the center of the fiber was eluted. In Comparative Example 10, in the drying step, sticking between the single fibers was so severe that the dry heat drawing was stopped.

<Effects of the Invention> Whereas the conventional method for producing high-strength PVA fibers mainly involves surface crosslinking, the present invention involves contacting a salt with high-moisture content Shinoshino, followed by drying and drawing by dry heat. Cross-linking is uniformly applied to the inside of the fiber at the same time as oriented crystallization of molecules, thereby improving hot water resistance and obtaining cross-linked PVA fiber with high strength and high heat water resistance without adding new equipment and manufacturing process. Therefore, it is possible to manufacture at low cost. Therefore, the obtained high-strength and high-temperature water-resistant PVA fiber is superior in cost performance compared to other super fibers such as conventional PVA fiber and para-aramid, and is used in the field of rubber materials such as hoses, tires and belts, and FRC. And can be widely used in fields such as FRP.

Continuation of the front page (56) References JP-A-1-298208 (JP, A) JP-A-2-169709 (JP, A) JP-A-2-249705 (JP, A) JP-B-49-12126 (JP) , B1) Japanese Patent Publication No. 46-28220 (JP, B1)

Claims (2)

(57) [Claims] An aqueous solution of a polyvinyl alcohol-based polymer containing boric acid or borate is used as a spinning solution, which is spun into a high-temperature alkaline coagulation bath at 55 to 95 ° C. containing salts having a dehydrating ability, and 1.5 times or more. Stretching, neutralization, wet heat stretching of 1.0-2.0 times and the stretching ratio up to 2.0-5.0 times, after washing with water, the water content is adjusted to 50-300% by weight with respect to the polymer. 1 selected from acid salts of polyvalent strong acids with alkali metals or alkaline earth metals, ammonium salts of strong acids with ammonia, and salts of strong acids with transition metals
Contacting an aqueous solution of at least one kind of salt, applying the salt to the polymer in an amount of 50 to 50,000 ppm, drying, and subsequently stretching at 220 ° C. or more, so that the total draw ratio is 17 times or more. For producing polyvinyl alcohol-based synthetic fibers. 2. An aqueous spinning solution containing a boric acid or a borate and a polyvinyl alcohol polymer containing 1 to 20% by weight of one or more surfactants with respect to the polymer is used as a spinning dope, and this is used as a spinning solution. Spun into a high-temperature alkaline coagulation bath at 55 to 95 ° C containing salts, stretched 1.5 times or more, neutralized, 1.0 times
~ 2.0 times, the stretching ratio up to here is 2.0 ~ 5.0 times wet heat stretching, after washing with water, the water content is 50 ~ 300 to the polymer
At least one salt selected from the group consisting of an acidic salt of a polyvalent strong acid and an alkali metal or an alkaline earth metal, an ammonium salt of a strong acid and ammonia, and a salt of a strong acid and a transition metal, in itoshino adjusted to a weight%. Aqueous solution of the above, the salt is applied to the polymer in an amount of 50 to 50,000 ppm, dried, and subsequently stretched at 220 ° C. or more so that the total stretching ratio becomes 20 times or more. Fiber manufacturing method.