JPH07258910A - Production of hot water-resistant polyvinyl alcohol fiber - Google Patents

Abstract

PURPOSE:To provide a method for industrially producing polyvinyl alcohol(PVA) having high strength and excellent hot water resistance in good productivity. CONSTITUTION:In producing a hot water-resistant PVA fiber by thermally drawing PVA undrawn fiber in a multistage of two or more stages, and then, subjecting the drawn fiber to heat treatment, (1) heat treatment is applied to a PVA fiber to which a catalyst promoting dehydration reaction has added thereto, (2) two or more heating rollers are used as heat treating devices and each roller surface temperature is set to 100-300 deg.C and <=10.0% relax is applied to the yarn between heating rollers and (3) final winding rate is set to 100-600m/min.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to polyvinyl alcohol having high strength and excellent hot water resistance (hereinafter referred to as PV
Called A. ) It relates to a method for industrially producing fibers with high productivity.

[0002]

2. Description of the Related Art PVA fibers have higher strength and elastic modulus than fibers of polyamide, polyester, polyacrylonitrile, etc. and are not only used as fibers for industrial materials, which are their main applications, but recently, asbestos substitute fibers. It is also used as a cement reinforcement material.

In recent years, as a method for further increasing the strength and elastic modulus of PVA fibers, gel spinning of high molecular weight polyethylene-
PV with a molecular weight of 500,000 or more based on the same concept as super stretching
A method using A is proposed. As a result, a fiber having a high strength and a high elastic modulus comparable to that of polyparaphenylene terephthalamide fiber, which is a representative of high strength and a high elastic modulus fiber, is obtained although it does not reach the polyethylene fiber by the so-called gel spinning method. .

In order to improve the hot water resistance of PVA fibers, a method of acetalization with formalin or the like has been proposed in the past, and recently, as described in JP-A-2-133605, acrylic acid-based resins have been proposed. A method of blending a polymer and spinning it, a method of causing a dehydration reaction by heat treatment after applying a catalyst for promoting the dehydration reaction as described in JP-A-4-126829 have been proposed.

[0005] Such high strength, high modulus fiber,
In addition, a factor that prevents the expansion of applications of PVA fibers having excellent hot water resistance is that the final winding speed of an industrial PVA fiber production line is slow at around 100 m / min.

In order to solve the above-mentioned drawbacks, the present inventors used a heating roller and a hot air heater in Japanese Patent Application No. 5-193976, etc. to obtain a final winding speed of 100 to 600 m / min, and a PVA fiber. We have proposed a method that can be manufactured at high speed. However, according to the above method, PVA fibers can be produced at high speed, but PVA fibers having improved hot water resistance cannot be produced at high speed.

[0007]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned drawbacks, and is capable of producing PVA fibers having high strength and hot water resistance at an epoch-making high speed and with high productivity. It is a technical subject to provide a method for producing an aqueous PVA fiber.

[0008]

The present inventors have arrived at the present invention as a result of extensive studies to solve the above problems.

That is, according to the present invention, (1) a catalyst for accelerating the dehydration reaction is added when the PVA unstretched fiber is hot-stretched in two or more stages and then heat-treated to produce a heat-resistant water-soluble PVA fiber. Heat treatment of the existing PVA fiber, (2)
Two or more heating rollers are used as a heat treatment device, the surface temperature of each roller is 100 to 300 ° C, and the yarn is relaxed by 10.0% or less between each heating roller. (3) The final winding speed is 100 to The gist is a method for producing a hot water-resistant PVA fiber, which is set to 600 m / min.

The present invention will be described in detail below.

P constituting the undrawn fiber used in the present invention
VA preferably has a degree of polymerization of 1500 or more. If the degree of polymerization is lower than 1500, the number of molecular chain ends that tend to become defective increases, and it becomes difficult to obtain high-strength, high-modulus fibers.
The saponification degree is preferably 99% or more.

Prior to spinning PVA, PVA is dissolved in a solvent to prepare a spinning dope. As the solvent, dimethyl sulfoxide (hereinafter referred to as DMSO), ethylene glycol, water or the like can be used. In this, the spread state of the molecular chain when PVA is dissolved in the solvent,
Considering the degree of entanglement of molecular chains, the stability as a solvent, the amorphous state at the time of gelation, the degree of entanglement of molecules at that time, and working problems, DMSO and water are particularly preferable. It should be noted that additives such as PVA antioxidant and heat-resistant agent may be mixed and used in this solution.

The concentration of PVA in the spinning dope is 2 to 35% by weight.
It is preferable to adjust to the range. If the concentration is less than 2% by weight, the spinnability is reduced, and if it exceeds 35% by weight, the viscosity is increased, the uniformity of the spinning dope is reduced, and the spinnability is reduced.

The spinning method may be either a dry-wet spinning method or a wet-spinning method. In the case of the dry-wet spinning method, the spinning dope is discharged from the spinneret, passed through a gas layer, and then extruded into a coagulation bath. Make PVA fibers. In the case of the wet spinning method, the spinneret is immersed in the solution in the coagulation bath and the spinning solution is extruded into the solution to produce PVA fiber. The number of holes of the die used at this time may be singular or plural.

As the liquid used in the coagulation bath, lower alcohols such as methanol, ethanol and propanol which have a coagulation-extracting action, alkaline aqueous solution of Glauber's salt, acetones, ethers, and a mixed solution of these with a solvent of PVA, etc. However, methanol or an alkaline aqueous solution of Glauber's salt is particularly preferable in terms of coagulation rate and solvent extraction rate.

As described above, the coagulation and the solvent extraction may not be performed simultaneously, but the coagulation and the extraction may be performed separately. In this case, the solvent may be extracted using the above solution in a cooling bath using decalin, paraffin oil or the like, or after solidifying once using boric acid or the like.

The fibers obtained as described above are dried,
The monofilament or multifilament unstretched fiber is used. When the drawing is carried out in the spinning step, the drawing is carried out during the solvent extraction or after the solvent extraction, and the drawing bath is followed by drying.

In the present invention, it is necessary to improve the hot water resistance by heat-treating the fiber provided with a catalyst for promoting the dehydration reaction (hereinafter referred to as the catalyst) to form a crosslinked layer on the fiber surface. . The method of applying the catalyst to the fiber is to add the catalyst to the undrawn fiber stage and draw it,
There are a method of performing heat treatment and a method of applying a catalyst and then performing heat treatment after stretching, but the former is preferable. In addition, unless a catalyst is applied and a crosslinked layer is not formed, it is dissolved in hot water, which is not preferable.

When the catalyst is added before the undrawn fiber stage, the catalyst is added to the spinning stock solution, or the catalyst is added to the inside of the fiber by adding the catalyst to the coagulation bath or the extraction bath. , There is a method of applying to the fiber after solvent extraction, but a method of adding the catalyst to the coagulation bath or the extraction bath so that the catalyst is contained even inside the fiber,
The method of applying to the fiber after solvent extraction is preferable. When applied to the fibers after solvent extraction, it is preferable to use the catalyst together with the oil agent, that is, to mix the catalyst with the oil agent. If the catalyst and the oil agent are applied separately, not only the process becomes complicated, but also the permeation amount of the catalyst is reduced, high-speed drawing and heat treatment cannot be performed in the subsequent process, and the development of hot water resistance becomes insufficient.
The catalyst can be applied to the drawn fiber in the same manner as the undrawn fiber.

The catalyst applied to the PVA fiber may be one that can dehydrate PVA by applying heat, for example, inorganic acids such as sulfuric acid, hydrochloric acid, phosphoric acid, polyphosphoric acid, acetic acid, itaconic acid, alkylsulfonic acid. , Monoalkyl phosphate, monodialkyl phosphate, polyacrylic acid and the like can be adopted. Among these, inorganic acids, particularly phosphoric acid, are preferable from the viewpoint of thermal decomposition reaction and dehydration reaction with respect to PVA. In addition, the oil agent to be mixed with the catalyst is not particularly limited, but polyoxyethylene sorbitan trioleate, polyoxyethylene oleyl ether, polyoxyethylene lauryl amino ether, etc. as a main component, and mineral oil as a diluent, So-called straight oil agents are preferred.

Although the amount of the catalyst applied varies depending on the type, it is preferably 0.01 to 5.0% by weight based on the PVA fiber. If the amount of catalyst added is less than 0.01% by weight, it becomes difficult for the dehydration reaction to occur uniformly on the surface of the fiber.
If it is more than 0% by weight, the dehydration effect is too strong and the strength is apt to be lowered, which is not preferable.

In the present invention, the unstretched fibers are subjected to hot drawing subsequent to spinning or after being once wound and then in multiple stages of two or more stages. The heating means at the time of stretching is not particularly limited, and a heating roller, a hot air oven, or a combination thereof can be used. Further, it is preferable that the stretching ratio in the hot stretching is set so that the total stretching ratio is 15 times or more.

Next, the heat-stretched fiber is subjected to heat treatment, and it is necessary to use a heating roller as a heat treatment method. In addition to heating rollers, there are hot blast stoves, hot plates, etc. as heat treatment equipment. In the hot blast stoves, since the fibers move at high speed in the furnace, heat can only be indirectly applied to the fibers, so a large amount of heat is required. In order to apply heat, it is necessary to lengthen the furnace length, which is not preferable in terms of operation and economy. Also,
The hot plate can directly apply heat to the fiber, but since the fiber surface rubs against the plate surface at high speed,
This will damage the fiber surface.

After using two or more heating rollers, relax between each heating roller by a speed ratio of 10.0% or less, preferably 8.0% or less, and more preferably 5.0% or less with respect to the front roller. It must be given and heat treated. If this relaxation rate exceeds 10.0%, thermal relaxation of the molecular chain will occur more than necessary, and crystallization will occur in the state of thermal relaxation, resulting in an extreme decrease in strength.

The surface temperature of the heating roller used in the present invention must be set to 100 to 300 ° C. If the surface temperature is less than 100 ° C, the dehydration reaction due to crystallization or the action of the catalyst does not proceed, and if it exceeds 300 ° C, coloring is caused by thermal deterioration, which is not preferable.

In the present invention, two or more heating rollers are used for the PVA fiber after catalyst addition which has been subjected to hot drawing in two or more steps, and the surface temperature of each roller is 100 to 300 ° C. The heat treatment with a relaxation rate of 10.0% or less relaxes the molecular chains in a tense state due to hot drawing, and forms a crosslinked layer on the surface of the fiber by the dehydration reaction due to the action of the catalyst. It is possible to produce monofilament or multifilament PVA fibers having hot water resistance at a high final winding speed of 100 to 600 m / min. The present invention can of course be applied even when the final winding speed is less than 100 m / min. Further, if the heating roller used in the above heat treatment is wrapped in a roller box or the like, it becomes possible to suppress the release of heat from the surface of the heating roller, the heat treatment effect of the heating roller is improved, and the PVA fiber obtained is The hot water resistance can be improved and the production speed can be increased.

[0027]

EXAMPLES Next, the present invention will be specifically described by way of examples. In the present invention, the hot water resistance is represented by the peak temperature of the melting (dissolution) curve obtained under the following conditions. Equipment used: DSC-2C type differential scanning calorimeter manufactured by Perkin Elmer Inc. Temperature rising rate: 10 ° C / min Sample cell: High pressure (50 atm) cell Sample preparation method: 5 mg of fiber sample cut to a length of about 50 mm and 10 mg of water Together with it, it is enclosed in a sample cell.

Examples 1 and Comparative Examples 1 to 3 Dry PVA having an average degree of polymerization of 4000 was dissolved in DMSO at 120 ° C. so that the concentration was 15% by weight. When melting, a closed vessel was used and the inside was replaced with nitrogen. This solution
It was discharged from a die with a hole diameter of 0.3 mm and 300 holes at a temperature of 105 ° C and dropped into a coagulation bath consisting of methanol containing 0.05% by weight phosphoric acid. After DMSO in the coagulated fiber was further extracted with methanol, the fiber was dried at 80 ° C to prepare an unstretched fiber containing 0.045% by weight of phosphoric acid.

The undrawn fiber obtained above was subjected to hot drawing and heat treatment. The hot drawing is the first heating roller at 80 ℃ and the second at 170 ℃.
The heating roller, the first hot air stove having an inlet temperature of 169 ° C. and the outlet temperature of 235 ° C. arranged between the first and second heating rollers and having a length of 4 m, the third heating roller of 170 ° C., the second and third heating rollers Using a second hot air stove with an inlet temperature of 174 ° C, an outlet temperature of 225 ° C, and a length of 6 m, the total draw ratio was 16.5 times.

In the heat treatment, two heating rollers at 200 ° C. were used with a relaxation rate set to 1.0% in Example 1, and in Comparative Example 1, a hot plate of 4 m at 250 ° C. was used.
Then, a 6-meter hot air stove was used with an inlet temperature of 200 ℃ and an outlet temperature of 250 ℃.
In Comparative Example 3, heating rollers at 200 ° C and 250 ° C were used.
Used with a relaxation rate of 11%. The final winding speed at that time was 400 m / min. Heat treatment conditions and PV obtained
Table 1 shows the physical properties of the A fiber.

[0031]

[Table 1]

As is clear from Table 1, in Example 1,
A PVA fiber having a strength of 16.3 g / d and a hot water resistance of 136 ° C. and high strength and high heat resistance was obtained. On the other hand, in Comparative Example 1 in which the hot plate was used as the heat treatment device, only fibers having a low hot water resistance of 118 ° C were obtained, and single yarn breakage and yarn breakage occurred frequently. Also,
In Comparative Example 2 using the hot air oven, only fibers having a hot water resistance of 103 ° C could be obtained. Furthermore, in Comparative Example 3 in which the relaxation rate was 11%, although the hot water resistance was 142 ° C. and high hot water resistance, only fibers having a low strength of 9.3 g / d could be obtained.

Example 2, Comparative Examples 4 to 6 Dry PVA having an average degree of polymerization of 4000 was dissolved in DMSO at 120 ° C. to a concentration of 15% by weight. The dissolution was performed by using a closed container and replacing the inside with nitrogen. When the obtained solution was subjected to dry-wet spinning at a dope temperature of 105 ° C, the pore size was 0.3 mm and the number of holes was 300.
It was discharged from the die at 105 ° C and dropped into a coagulation bath consisting of methanol. After coagulation and extraction, 0.2 equivalents of phosphoric acid was added to polyoxyethylene oleyl ether, a catalyst was attached to the fiber with an oiling roller, and dried at 80 ° C.
An undrawn fiber was produced.

The hot stretching was carried out by arranging a first heating roller at 80 ° C., a second heating roller at 170 ° C., a first heating roller and a second heating roller at an inlet temperature of 169 ° C. and an outlet temperature of 235 ° C. and a length of 4 m. First
The hot blast stove was placed between the 3rd heating roller of 170 ℃ and the 2nd and 3rd heating rollers. The inlet temperature was 174 ℃ and the outlet temperature was 225 ℃.
Using a second hot air stove with a length of 6 m at ℃, the total draw ratio was 15.7
I went to double.

The heat treatment after the hot drawing was performed by changing the temperature of the heating roller. The final winding speed at that time is 500 m / min
And Table 2 shows the heat treatment conditions and the physical properties of the obtained PVA fiber.
Shown in.

[0036]

[Table 2]

As is clear from Table 2, in Example 2,
High-strength, high-heat-resistant water PVA fiber with strength of 17.0 g / d and hot-water resistance of 138 ° C was obtained. On the other hand, in Comparative Example 4 using the heating roller at 280 ° C, the hot water resistance was 108 ° C, and in Comparative Example 5 using the heating roller at 80 ° C, only fibers having the hot water resistance of 98 ° C were obtained. Further, in Comparative Example 6 using a heating roller at 350 ° C, the hot water resistance was 138 ° C, which was good, but only colored fibers could be obtained.

Reference Example 1 The undrawn fiber prepared in Example 2 was used for hot drawing and heat treatment. The hot drawing was performed by using a first heating roller of 80 ° C, a second heating roller of 170 ° C, an inlet temperature of 160 ° C, an outlet temperature of 230 ° C, and a first hot-air stove with a length of 2 m, which were arranged between the first and second heating rollers. In addition, the inlet temperature 174 ° C and the outlet temperature 225 were placed between the third heating roller of 170 ℃ and the second and third heating rollers.
Using a second hot air stove with a length of 4 m and a total draw ratio of 16.0
I went to double.

The heat treatment was performed by setting the heating roller at 200 ° C. and the heating roller at 210 ° C. to a relaxation rate of 1.0%.
The final winding speed at this time was 20 m / min. The obtained fiber was PVA fiber having high strength and high hot water resistance, with a strength of 18.2 g / d and a hot water resistance of 140 ° C.

[0040]

EFFECTS OF THE INVENTION According to the present invention, heretofore impossible.
It is possible to obtain PVA fibers with a high speed of 0 m / min or more, high strength, and excellent hot water resistance, which dramatically improves the productivity of PVA fibers with excellent hot water resistance.
It is expected that the use as a fiber for industrial materials will be expanded.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuya Nagatomi 23 Uji Kozakura, Uji City, Kyoto Prefecture Unitika Co., Ltd. Central Research Institute (72) Inventor Naoji Ichise 23 Uji Kozakura, Uji City, Kyoto Unitika Co., Ltd. Central Research Institute (72) Inventor Shinya Takagi 23, Uji Kozakura, Uji City, Kyoto Unitika Ltd. Central Research Laboratories

Claims (1)

[Claims] 1. When a heat-resistant polyvinyl alcohol fiber is produced by heat-treating unstretched polyvinyl alcohol fiber in multiple stages of two or more stages, (1) a catalyst for accelerating the dehydration reaction is added. Heat treatment of polyvinyl alcohol fiber, (2) Use two or more heating rollers as a heat treatment device, and set the surface temperature of each roller to 100-300 ℃.
The yarn is relaxed by 10.0% or less between each heating roller. (3) The final winding speed is 100 to 600m / min.
A method for producing a hot water-resistant polyvinyl alcohol fiber, comprising: