JP2022072842A - Polyvinylidene fluoride fiber and method for producing the same - Google Patents

Abstract

To provide a polyvinylidene fluoride fiber comprising an ultrahigh molecular weight polyvinylidene fluoride and having excellent tensile strength, and to provide a method for producing the same.SOLUTION: A method for producing a polyvinylidene fluoride fiber comprises a step of dissolving a polyvinylidene fluoride fiber, which is composed of a polyvinylidene fluoride having an intrinsic viscosity of 1.8 dl/g or more and has a tensile strength of 0.9 GPa or more, and a polyvinylidene fluoride having an intrinsic viscosity of 1.8 dl/g or more, in an ionic liquid, to obtain a spinning solution, a dry/wet spinning step of dry/wet spinning by using the spinning solution to obtain an undrawn fiber, and a drawing step of drawing the undrawn fiber.SELECTED DRAWING: None

Description

The present invention relates to polyvinylidene fluoride fiber and a method for producing the same.

Fibers made of polyvinylidene fluoride (PVDF) have higher heat resistance, weather resistance and corrosion resistance than general-purpose resin fibers, and various types of fishing lines, fishing nets, hollow fiber membrane reinforcing threads, ropes and clothing, etc. It is used as an industrial material.
However, PVDF fibers generally do not have sufficient tensile strength. Therefore, various methods for improving the tensile strength of PVDF fibers have been proposed.

According to Patent Document 1, the tensile strength of PVDF fiber is improved by changing the crystal structure by devising a molding method so that the crystal melting point is set only at 178 ° C. or higher, which is not possible with ordinary melt spinning. It is disclosed to do.

Special Fair 4-009203 Gazette

However, there is also a need for a method different from the method disclosed in Patent Document 1 to improve the tensile strength of PVDF fibers without specially devising a molding method. For that purpose, it is considered effective to use an ultra-high molecular weight PVDF, but according to the study by the present inventors, for example, an ultra-high molecular weight PVDF having an intrinsic viscosity of 1.8 dl / g or more has a melt viscosity. It was confirmed that melt spinning was not possible because the molecular weight was too high.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a polyvinylidene fluoride fiber having an excellent tensile strength, which is made of an ultrahigh molecular weight polyvinylidene fluoride, and a method for producing the same.

As a result of diligent research to solve the above problems, the present inventors have used an ionic liquid as a solvent for the spinning solution in dry-wet spinning using ultra-high molecular weight vinylidene fluoride. We have found that a vinylidene compound fiber can be obtained and that the obtained fiber has excellent tensile strength, and completed the present invention.

That is, the present invention relates to a polyvinylidene fluoride fiber having an intrinsic viscosity of 1.8 dl / g or more and having a tensile strength of 0.9 GPa or more.

In the fiber, the weight average molecular weight of the polyvinylidene fluoride is preferably 1 million or more.

Further, the present invention comprises a step of dissolving polyvinylidene fluoride having an intrinsic viscosity of 1.8 dl / g or more in an ionic liquid to obtain a spinning solution.
A dry-wet spinning step of obtaining undrawn fibers by dry-wet spinning using the spinning solution, and a dry-wet spinning step.
The present invention relates to a method for producing polyvinylidene fluoride fiber, which comprises a drawing step of stretching the unstretched fiber.

In the production method, the weight average molecular weight of the polyvinylidene fluoride is preferably 1 million or more.

In the dry-wet spinning step, the single-hole discharge amount of the spinning solution discharged from the spinning nozzle is preferably 0.1 g / min or more.

The present invention also relates to a fishing line made of the polyvinylidene fluoride fiber.

According to the present invention, it is possible to provide a polyvinylidene fluoride fiber having an excellent tensile strength and made of vinylidene fluoride having an ultrahigh molecular weight and a method for producing the same.

<Polyvinylidene fluoride fiber>
The polyvinylidene fluoride fiber of the present invention is made of polyvinylidene fluoride having an intrinsic viscosity of 1.8 dl / g or more, and has a tensile strength of 0.9 GPa or more.

In the present invention, polyvinylidene fluoride (hereinafter, also referred to as “PVDF”) includes a homopolymer of vinylidene fluoride (VDF) and a copolymer of VDF and other monomers. As the other monomer in the copolymer, for example, a monomer derived from an alkene having 2 to 10 carbon atoms and having at least one hydrogen atom substituted with a fluorine atom is used. Examples of such a monomer include ethylene tetrafluoride, propylene hexafluoride, ethylene trifluoride, ethylene trifluoride chloride, vinyl fluoride and the like.

As the PVDF, an ultrahigh molecular weight PVDF is used. In the present invention, the molecular weight of PVDF is defined by the intrinsic viscosity, but if necessary, it is also defined by the weight average molecular weight.

As the intrinsic viscosity of PVDF, for example, 2.1 dl / g or more is preferable, and 3.1 dl / g or more is more preferable.

As the weight average molecular weight of PVDF, for example, 700,000 or more is preferable, 900,000 or more is more preferable, and 1 million or more is further preferable.

The method for producing such an ultra-high molecular weight PVDF is not particularly limited, and for example, it can be produced by emulsion polymerization or suspension polymerization. Examples of commercially available PVDF products include KF polymer 7200, KF polymer 7300, and the like (all manufactured by Kureha Corporation).

The PVDF fiber of the present invention includes both monofilament and multifilament aspects. In addition to tensile strength, PVDF fiber is also excellent in other physical properties such as tensile elongation.

As the tensile strength of the PVDF fiber, for example, 1.2 GPa or more is preferable, and 1.4 GPa or more is more preferable.

The tensile elongation of the PVDF fiber is, for example, preferably 10% or more, more preferably 12% or more, still more preferably 15% or more.

<Manufacturing method of PVDF fiber>
The method for producing PVDF fiber of the present invention comprises a step of dissolving vinylidene fluoride having an intrinsic viscosity of 1.8 dl / g or more in an ionic liquid to obtain a spinning solution, and a dry-wet spinning method using the spinning solution. A dry-wet spinning step of obtaining unstretched fibers and a drawing step of stretching the unstretched fibers are included.

(Step to obtain a solution for spinning)
The step of obtaining a solution for spinning is a step of preparing a solution in which PVDF having an intrinsic viscosity of 1.8 dl / g or more and a super high molecular weight is dissolved in an ionic liquid.

As the ultra-high molecular weight PVDF, the same PVDF as described as the raw material of the PVDF fiber described above is used.

As the ionic liquid, ammonium-based, imidazolium-based, pyridinium-based, pyrrolidinium-based, etc. can be used as the cation species, and halogen-based, phosphoric acid-based, tetrafluoroborate, dicyanamide, bistrifluoromethylsulfonylimide, etc. can be used as the anion species. However, the present invention is not particularly limited to these, and may be other than these. Among these, as the cation species, an imidazolium type, particularly a 1,3-dialkylimidazolium type is preferable from the viewpoint of solubility in PVDF and handling temperature. Further, as the anion species, halogen-based and phosphoric acid-based are preferable, and chlorine ion is more preferable.

Examples of the cation species having an imidazolium type and the anion species having a halogen type include 1,3-dialkylimidazolium chloride and the like. Among these, 1-butyl-3-methylimidazolium chloride, 1-pentyl-3-methylimidazolium chloride, 1-hexyl-3-methylimidazolium chloride, 1-octyl-3-methylimidazolium chloride and theirs. Mixtures are preferred.

Examples of the cation species having an imidazolium type and the anion species having a phosphoric acid type include 1,3-dialkylimidazolium diethyl phosphate and 1,3-dialkylimidazolium dimethyl phosphate. Among them, 1-ethyl-3-methylimidazolium diethyl phosphate is preferable.

The concentration of PVDF in the spinning solution is not particularly limited, but from the viewpoint of excellent tensile strength of the obtained PVDF fiber, it is preferably 3% by mass or more and 20% by mass or less, more preferably 5% by mass or more and 15% by mass or less, 6 More preferably, it is by mass or more and 12% by mass or less.

(Dry-wet spinning process)
The dry-wet spinning step is a step of obtaining undrawn fibers by dry-wet spinning using the spinning solution obtained in the step of obtaining a spinning solution. The operation of dry-wet spinning is not particularly limited, and dry-wet spinning can be performed by a conventionally used dry-wet spinning device. For example, according to a conventional method, the spinning solution in the undiluted solution tank can be once discharged into the air from the spinning nozzle and introduced into the coagulating liquid to obtain unstretched fibers.

The temperature of the spinning solution is not particularly limited as long as it can be kept stable in the stock solution tank without changing over time. For example, it is usually 80 to 150 ° C, preferably 100 to 140 ° C. ..

The composition of the coagulating liquid is not particularly limited, and examples thereof include water, lower alcohols such as methanol and ethanol, acetone, and a mixture thereof, or a mixed liquid containing the above-mentioned ionic liquid in the coagulating liquid. Further, the temperature of the coagulating liquid is not particularly limited, and is usually, for example, −20 to 60 ° C., preferably 0 to 20 ° C.

The discharge amount of the spinning solution from the spinning nozzle is not particularly limited, and for example, the single-hole discharge amount is preferably 0.1 g / min or more, and more preferably 0.5 g / min or more.

In the dry-wet spinning method, the air layer between the discharge hole of the spinning nozzle and the liquid level of the coagulating liquid is generally called an air gap. In the present invention, the distance between the discharge hole of the spinning nozzle and the liquid level of the coagulating liquid is not particularly limited in the air gap, and is usually 5 mm or more and 300 mm or less, preferably 10 mm or more and 100 mm or less. The gas temperature in the air gap is not particularly limited, and is usually 0 ° C. or higher and 200 ° C. or lower, preferably 10 ° C. or higher and 100 ° C. or lower. When the solution viscosity is extremely high and the fluidity is poor, it is also preferable to install a heater in the air gap to heat the atmosphere to improve the fluidity, if necessary.

The fibers that have passed through the coagulation liquid are wound by a winding roller, for example, via a feed roller according to a conventional method, whereby unstretched fibers of PVDF are obtained.

(Drying process)
In the method for producing PVDF fibers of the present invention, the unstretched fibers obtained in the dry-wet spinning step may be dried as a drying step after the dry-wet spinning step is completed and before the drawing step described later. The drying method is not particularly limited, and examples thereof include a method of leaving the fibers in a chamber adjusted to a predetermined temperature and humidity.

(Stretching process)
The drawing step is a step of drawing the unstretched fibers obtained in the dry-wet spinning step to obtain PVDF fibers. Through this drawing step, PVDF fibers having high tensile strength can be finally obtained.

The stretching operation is not particularly limited, and the unstretched fiber can be stretched by a conventionally used stretching device. The stretching may be performed by heat stretching using, for example, an oven, a heating chamber, a heating plate, a heating furnace, or the like, or by immersing in a heated solvent, for example, a liquid bath such as heated water or glycerin for wet stretching. You may go. Further, it is preferable to provide a feed roller and a take-up roller, respectively, before and after the stretching device, apart from the stretching device, corresponding to the fiber traveling direction.

The stretching temperature is not particularly limited, and in the case of thermal stretching, for example, it is usually 120 ° C. or higher and 190 ° C. or lower, preferably 150 ° C. or higher and 180 ° C. or lower. When wet stretching is performed in water, for example, it is usually 10 ° C. or higher and 90 ° C. or lower, preferably 20 ° C. or higher and 40 ° C. or lower.

Further, in the stretching step, the stretching ratio is not particularly limited, but is preferably 6 times or more, and more preferably 8 times or more. If the draw ratio is less than 6 times, the tensile strength of the obtained PVDF fiber may not be increased.

The stretching may be one-step stretching or multi-step stretching of two or more steps. When performing multi-stage stretching, the stretching temperature and stretching ratio may be different from each other. When performing multi-stage stretching, the above-mentioned stretching ratio means the total stretching ratio obtained by accumulating the stretching ratios in each stage.

As described above, it is preferable to provide a feed roller and a take-up roller before and after the drawing device, respectively. It is preferable to preheat the feed roller. The temperature of the preheating is not particularly limited, but is preferably 30 ° C. or higher and 60 ° C. or lower, and more preferably 40 ° C. or higher and 55 ° C. or lower. By performing the preheating, it is possible to prevent the unstretched fibers from being cold-stretched on the bobbin of the feed roller and whitening due to the formation of voids, and it is also possible to improve the draw ratio. In the case of multi-stage stretching, preheating can be performed on the feed roller provided in front of any stretching device used for multi-stage stretching. As a more specific embodiment, for example, when a stretching device for heat stretching such as a heating chamber is used as the stretching device, a preheating unit is provided in front of the heat stretching device to cover the entire feed roller. Examples of the heating temperature include a method of heating the feed roller at a temperature of 30 ° C. or higher and 60 ° C. or lower, more preferably 40 ° C. or higher and 55 ° C. or lower.

(Mitigation process)
In the method for producing PVDF fiber of the present invention, the drawn fiber may be relaxed after the drawing step is completed. The relaxation temperature is not particularly limited, and for example, from the viewpoint of obtaining PVDF fibers having high tensile strength, it is usually 130 ° C. or higher and 180 ° C. or lower, preferably 150 ° C. or higher and 170 ° C. or lower. The relaxation operation is not particularly limited, and the same equipment as in the stretching step can be used.

The PVDF fiber of the present invention can be suitably used as various industrial materials such as fishing line, fishing net, reinforcing thread of hollow fiber membrane, rope and clothing.

Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples, but the present invention is not limited to the following Examples. The methods for measuring the characteristics or physical properties of polyvinylidene fluoride and polyvinylidene fluoride fibers in Examples and Comparative Examples are as follows.

(Intrinsic viscosity)
It was measured according to ISO 1628-1. Specifically, the intrinsic viscosity of polyvinylidene fluoride is such that a sample prepared from pellets of vinylidene fluoride is dissolved in N, N-dimethylformamide at a concentration of 0.4 g / dl, and the temperature of the obtained solution is 30 ° C. Intrinsic viscosity was measured with a Ubbelohde viscometer.

(Weight average molecular weight)
The weight average molecular weight of polyvinylidene fluoride is a polymethylmethacrylate-equivalent value measured by gel permeation chromatography (GPC).

(Fineness)
The polyvinylidene fluoride fiber was left overnight in a constant temperature and humidity chamber having a temperature of 20 ° C. and a relative humidity of 65%, and then the fineness (dtex) was measured using a fineness measuring device (“DENION DC-21” manufactured by Search). ..

(Tensile strength and tensile elongation)
The tensile strength and tensile elongation of the polyvinylidene fluoride fiber were measured according to JIS L1013-8.5.1. That is, using a Strograph RII type tensile tester manufactured by Toyo Seiki Co., Ltd., the stress when the sample breaks in a room with a temperature of 20 ° C. and a relative humidity of 65% at a test length of 20 mm and a tensile speed of 20 mm / min. The tensile strength (cN / dtex and GPa) and the elongation (%) at break were calculated by measuring the elongation (measurement number 5). At this time, in order to prevent breakage at the chuck, the sample was wound around a cylinder having a diameter of 13 mm mounted in front of each of the upper and lower chucks three times, and then fixed with the chuck. Since the elongation recorded by the tensile tester includes slip due to the elongation due to the thread in the cylinder portion, the boundary between the winding portion and the measuring portion of the upper cylinder is obtained in order to obtain the actual elongation value. Is marked, the value of the slip is read, the value obtained by doubling the value of the slip is taken as the size of the slip of the upper and lower winding parts, and the value subtracted from the measured elongation is the actual size of the elongation. As a result, the elongation was calculated.

<Manufacturing of polyvinylidene fluoride fiber>
[Example 1]
As the polyvinylidene fluoride, a homopolymer of polyvinylidene fluoride (“KF Polymer 7300” manufactured by Kureha Co., Ltd., weight average molecular weight 1.1 million, intrinsic viscosity 3.1 dl / g), which is hereinafter abbreviated as “P1”, is used, and this P1 is used. , 1-Butyl-3-methylimidazolium chloride (BmimCl, manufactured by Sigma-Aldrich), which is an ionic liquid, was dissolved to prepare a spinning solution having a P1 concentration of 6% by mass. Next, this spinning solution was introduced into the undiluted solution tank of the spinning device, kept at 120 ° C., and the single-hole discharge amount was 0.3 g / min from the spinning nozzle (1 hole, hole diameter 0.51 mm, hole length 18 mm). The spinning solution was solidified and made into fibers by once discharging it into the air, introducing it into the coagulating liquid, and passing the coagulating liquid through the coagulating liquid. In the environment in which the spinning solution was discharged, dry-wet spinning was performed in air at a temperature of 25 ° C. (room temperature) with an air gap of 10 mm from the spinning nozzle to the coagulation bath. The composition of the coagulating liquid was water, and the temperature was 2 ° C.
The unstretched fibers drawn from the coagulating liquid were introduced into a water bath at 30 ° C. via a feed roller, and wet-stretched in water at a draw ratio of 1.5 times.
Next, as two-stage stretching, heat stretching was performed at a stretching ratio of 6.3 times in a heating chamber at 180 ° C. to obtain polyvinylidene fluoride fiber having a total stretching ratio of 9.5 times.
The fineness, tensile strength, and tensile elongation of the obtained polyvinylidene fluoride fiber were measured. The results are shown in Table 1.

[Example 2]
The total draw ratio was the same as in Example 1 except that the P1 concentration in the spinning solution was changed to 8% by mass, the two-stage stretching was performed at 170 ° C., and the draw ratio was changed to 5.3 times. An 8.0-fold polyvinylidene fluoride fiber was obtained. Table 1 shows the physical characteristics of the obtained polyvinylidene fluoride fiber.

[Example 3]
The P1 concentration in the spinning solution was changed to 8% by mass, the two-step stretching was performed at 140 ° C., the stretching ratio was changed to 1.3 times, and the three-step stretching was newly performed by a heating plate at 170 ° C. Polyvinylidene fluoride fibers having a total draw ratio of 8.5 times were obtained in the same manner as in Example 1 except that the heat stretching was performed at a draw ratio of 4.3 times. Table 1 shows the physical characteristics of the obtained polyvinylidene fluoride fiber.

[Example 4]
The total draw ratio was the same as in Example 1 except that the P1 concentration in the spinning solution was changed to 10% by mass, the two-stage stretching was performed at 168 ° C, and the draw ratio was changed to 5.3 times. An 8.0-fold polyvinylidene fluoride fiber was obtained. Table 1 shows the physical characteristics of the obtained polyvinylidene fluoride fiber.

[Example 5]
The P1 concentration in the spinning solution is changed to 12% by mass, and in the drawing step, when the drawn fiber after the completion of the one-stage drawing is drawn in two stages, it is provided in front of the heating chamber which is a drawing device for the two-stage drawing. Examples except that a preheating section covering the entire feed roller was provided, the feed roller was preheated at 50 ° C., two-stage stretching was performed at 165 ° C., and the stretching ratio was changed to 5.0 times. In the same manner as in No. 1, a polyvinylidene fluoride fiber having a total draw ratio of 7.5 times was obtained. Table 1 shows the physical characteristics of the obtained polyvinylidene fluoride fiber.

[Comparative Example 1]
As the polyvinylidene fluoride, a homopolymer of polyvinylidene fluoride (“KF Polymer 1300” manufactured by Kureha Co., Ltd., weight average molecular weight of 350,000 to 390,000, intrinsic viscosity of 1.3 dl / g), which is abbreviated as “P2”, is used. P2 is put into the hopper of a 35 mmφ extruder, melt-mixed in the extruder at a temperature of 200 to 290 ° C., melt-extruded from a 0.8 mmφ nozzle attached to the tip of the extruder, rapidly cooled in water, and is a conventional method. Therefore, the undrawn fibers of polyvinylidene fluoride were obtained by winding with a take-up roller.
Next, the obtained unstretched fiber was stretched at a draw ratio of 5.5 times in heated glycerin at 169 ° C. as a one-step drawing, and a draw ratio of 1 in a heated glycerin at 174 ° C. as a two-step drawing. 1. Stretching was performed 1 times, and as a 3-step stretching, the fiber was stretched at a draw ratio of 0.9 times in heated glycerin at 165 ° C. to obtain a polyvinylidene fluoride fiber having a total draw ratio of 5.8 times. Table 1 shows the physical characteristics of the obtained polyvinylidene fluoride fiber.

[Comparative Example 2]
Using P1 instead of P2 as polyvinylidene fluoride, melt spinning of P1 was attempted in the same manner as in Comparative Example 1. However, since the melt had a very high viscosity and was colored by thermal decomposition, melt spinning could not be applied by the same method as in Comparative Example 1.

From Table 1, it can be seen that PVDF fibers having excellent tensile strength can be obtained by using an ionic liquid as a solvent for the spinning solution in dry / wet spinning using a super high molecular weight PVDF.

Claims (6)

It consists of polyvinylidene fluoride having an intrinsic viscosity of 1.8 dl / g or more.
A polyvinylidene fluoride fiber characterized by a tensile strength of 0.9 GPa or more. The polyvinylidene fluoride fiber according to claim 1, wherein the polyvinylidene fluoride has a weight average molecular weight of 1 million or more. A step of dissolving polyvinylidene fluoride having an intrinsic viscosity of 1.8 dl / g or more in an ionic liquid to obtain a spinning solution, and
A dry-wet spinning step of obtaining undrawn fibers by dry-wet spinning using the spinning solution, and a dry-wet spinning step.
A method for producing polyvinylidene fluoride fiber, which comprises a drawing step of stretching the unstretched fiber. The method for producing polyvinylidene fluoride fiber according to claim 3, wherein the polyvinylidene fluoride has a weight average molecular weight of 1 million or more. The method for producing polyvinylidene fluoride fiber according to claim 3 or 4, wherein in the dry-wet spinning step, the single-hole discharge amount of the spinning solution discharged from the spinning nozzle is 0.1 g / min or more. A fishing line made of polyvinylidene fluoride fiber according to claim 1 or 2.