JP3036181B2 - Method for producing high-strength polyvinylidene fluoride monofilament - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polyvinylidene fluoride monofilament, and more particularly, to a method for producing a high strength polyvinylidene fluoride monofilament suitable mainly for fishing line.

[0002]

2. Description of the Related Art Polyvinylidene fluoride monofilaments are excellent in toughness, impact resistance, transparency, light resistance, etc., are easily immersed in water at a high specific gravity, and have a refractive index close to that of water, and surface reflection of light in water. It has the characteristic that it is extremely low, so it has excellent properties especially for fishing lines and fishing nets.

[0003] Polyvinylidene fluoride monofilaments are always required to improve the above-mentioned properties, but are required to be thinner and stronger.

[0004] Conventionally, as a polyvinylidene fluoride monofilament, for example, as described in JP-A-63-112717, the surface birefringence and the average birefringence of a cross section perpendicular to the fiber axis are defined within a specific range. What has been known is known, and this polyvinylidene fluoride monofilament is highly evaluated in the market for its excellent properties.

[0005] However, particularly in fishing line applications, monofilaments having a higher strength are required even at a rate of about 0.1 g / d.
Much research has been done on improving the 0.1 g / d strength. Here, it is necessary to pay special attention not only to simply improving the strength but also to maintaining other characteristics at a certain level or more.

[0006]

SUMMARY OF THE INVENTION The present invention has been made based on the above background, and has as its object the purpose of the present invention to be superior to polyvinylidene fluoride monofilaments obtained in the prior art. An object of the present invention is to provide a method for producing a high-strength polyvinylidene fluoride monofilament having characteristics.

[0007]

In order to achieve the above object, a method for producing a high-strength polyvinylidene fluoride monofilament according to the present invention comprises a medium oriented polyvinylidene fluoride having a birefringence of 30 × 10 ^-3 or less. The birefringence of 35 × 10 ⁻³ or more is obtained by stretching the monofilament at a discharge portion under a normal pressure atmosphere containing a rare gas element of 60 mol% or more in a range of 1.2 to 6.0 times. It is characterized by being a highly oriented polyvinylidene fluoride monofilament.

[0008] In the present invention, the discharge portion may be:
At least one electrode surface is formed by a high voltage applied to a pair of electrodes covered with a dielectric.

The intermediate oriented polyvinylidene fluoride monofilament used in the method of the present invention can be obtained, for example, by the following method.

That is, a polyvinylidene fluoride-based resin chip is melt-spun into a spun monofilament, introduced into a cooling zone, and cooled and solidified using a liquid cooling medium to form a low orientation polyvinylidene fluoride-based monofilament. None, the low orientation polyvinylidene fluoride monofilament is wound around a take-up roller and taken up.

The polyvinylidene fluoride resin chips used for melt spinning preferably have an intrinsic viscosity index (ηinh) of 0.8 or more, measured with a 0.4 g / cc solution of dimethylformamide, particularly preferably 1.0 or more. Are preferred.
If the intrinsic viscosity index (ηinh) is less than 0.8, it is difficult to obtain the intended high-strength polyvinylidene fluoride monofilament.

Further, the polyvinylidene fluoride resin chip is not limited to a polyvinylidene fluoride homopolymer, but at least 80 mol% of the repeating structural units of the molecular chain is composed of vinylidene fluoride, and the copolymer component is less than 20 mol%. May be contained in the range. Examples of the copolymer component include tetrafluoroethylene, trifluoromonochloroethylene, and hexafluoropropylene. In addition, when the copolymer component is contained in an amount of 20 mol% or more, the crystallinity decreases, which is not preferable.

The liquid cooling medium used for cooling and solidifying the spun monofilament is 10 ° C. or less,
Preferably, water adjusted to a temperature of 5 ° C. or lower, or a hydrogen-substituted or unsubstituted aliphatic hydrocarbon, trichlene, methylene chloride and the like are mentioned.

The above cooling conditions are selected and set according to quality setting conditions such as the viscosity, thickness and draft rate of the spun monofilament.

When the spun monofilament is passed through a high-temperature atmosphere zone before being introduced into the cooling zone, the high-temperature atmosphere is 16
At 0 ° C. to 350 ° C., the length is 500 mm or less, and the conditions of this high temperature atmosphere region are selected and set according to the viscosity, thickness, draft rate, and cooling conditions of the spun monofilament in the cooling region.

The drawn low-orientation polyvinylidene fluoride monofilament has a birefringence of 30 × 10 ⁻³ or less, preferably 10 × 10 ⁻³ to 2 by continuous first-stage drawing.
It is a 6 × 10 ⁻³ intermediately oriented polyvinylidene fluoride monofilament. This first-stage stretching has a stretching ratio of 2.
The stretching bath may be a hot water bath, a dry heat furnace, an ethylene glycol bath or a heating medium bath such as rapeseed oil.

The temperature of the first stage stretching bath is 50 in the case of a warm water bath.
To 90 ° C., 100 to 400 ° C. for a dry heat furnace, and 60 to 150 ° C. for a heating medium bath. The residence time of the monofilament in the bath is determined by the polymer composition of the monofilament,
It is selected and set depending on viscosity, thickness, stretching speed, stretching ratio, and the like.

In the method of the present invention, the intermediate oriented polyvinylidene fluoride monofilament obtained as described above is drawn in a discharge portion under a normal pressure atmosphere containing a rare gas element of 60 mol% or more.

In the present invention, the gas composition of the above-mentioned stretching atmosphere is extremely important, and discharge is performed in a normal pressure atmosphere containing 60 mol% or more of a rare gas. Instead of a discharge (called a corona discharge), the discharge is similar to a glow discharge that occurs under reduced pressure. The higher the content of the rare gas, the more uniform and stable the discharge becomes. Therefore, it is preferable that the rare gas contains 80 mol% or more, particularly 90 mol% or more.

The above discharge can supply more electric power to the discharge as compared with the spark discharge. Further, when the stretching is performed in the discharge, it is possible to achieve high orientation while suppressing thermal crystallization during stretching of the monofilament.

The normal pressure in the present invention means that pressure is not positively reduced or pressurized. In order to keep the concentration of rare gases within the above range, rare gases are supplied and atmospheric pressure is slightly increased. There is no problem to do.

As the rare gas used in the present invention, one or more of helium, neon, argon, krypton, xenon, radon and the like are used, and argon and helium are particularly preferred.

As the stretching apparatus used when carrying out the method of the present invention, for example, the apparatus shown in FIG. 1 is exemplified.

FIG. 1 is a schematic longitudinal sectional view showing an example of a stretching apparatus used in the method of the present invention. In FIG. 1, Y represents a polyvinylidene fluoride monofilament to be subjected to a stretching treatment, and 5 represents a voltage to be applied. For power supply.

The discharge in the above device is generated by applying a high voltage to conductive electrodes 1 and 2 made of metal or the like provided facing each other. 4 is used. Conductor electrode 1,
As the dielectric covering the surface of No. 2, a material having a sufficient withstand voltage with respect to the applied voltage, such as rubber, glass and ceramic, is selected. A range of 1 to 5 mm is preferred.

In order to maintain a stable discharge, the distance between the conductor electrodes 1 and 2 is preferably 5 mm or less.
4, both electrodes 1 and 2 may be in contact with each other.

The frequency of the voltage applied to the conductor electrodes 1 and 2 is preferably selected in the range of 5 to 2000 KHz. If the frequency is less than 5 KHz, the discharge is difficult to start,
It is difficult to match at frequencies higher than Hz. More preferably, it is 20 to 500 KHz. The voltage applied to the conductor electrodes 1 and 2 is set to 1 to stabilize the discharge.
It is preferably 10 KV, particularly preferably 1 to 8 KV.

In the method of the present invention, the stretching ratio of the stretching during the discharge varies depending on the physical properties of the intermediate oriented polyvinylidene fluoride monofilament to be stretched.
Within the range of 6.0, the birefringence of the obtained polyvinylidene fluoride monofilament is set to a high orientation of 35 × 10 ⁻³ or more. In addition, since the breakage of the monofilament during stretching increases when the stretching ratio is high, the stretching ratio is preferably set to 1.2 to 3.0 times.

Further, if the birefringence of the finally obtained polyvinylidene fluoride monofilament is less than 35 × 10 ^-3 , it becomes difficult to obtain the intended high strength polyvinylidene fluoride monofilament. Not preferred.

The above-mentioned highly oriented polyvinylidene fluoride monofilament is wound as it is or after being subjected to heat treatment for stretching and / or relaxation under high tension as needed.

As described above, the intermediate oriented polyvinylidene fluoride monofilament is stretched in a discharge portion under a normal pressure atmosphere containing a rare gas element of 60 mol% or more, so that the crystal can be formed in comparison with the conventional hot stretching method. It is possible to stretch the film while suppressing the formation of the filament, thereby enabling high-magnification stretching, and achieving a higher orientation of the polyvinylidene fluoride monofilament.

The stretching in the discharge portion under the normal pressure atmosphere may be performed in one step, or may be performed in two or more steps.

[0033]

The high-strength polyvinylidene fluoride monofilament obtained by the method of the present invention, which is characterized by drawing in a discharge portion under a normal pressure atmosphere containing a rare gas, is obtained by drawing by a conventional hot drawing method. Compared to polyvinylidene fluoride monofilament, the molecular weight decrease during stretching is low,
Crystallization is suppressed and high orientation is achieved.

The high-strength polyvinylidene fluoride monofilament obtained by the method of the present invention has a difference (δ △ nS-C) between the birefringence (△ nS) of the surface layer and the birefringence (△ nc) of the center. ) Is preferably -6 × 10 ^-3 to -20 ×
It is in the range of 10 ^-3 . That is, since the monofilament surface layer has a lower orientation than the central part, the surface layer is flexible,
Because the stress concentrated on the surface layer is reduced by bending,
Nodule strength increases.

Thus, a high-strength polyvinylidene fluoride monofilament can be obtained by the method of the present invention. This high-strength polyvinylidene fluoride monofilament is particularly useful for fishery materials such as fishing line and fishing net, agricultural and forestry materials for tree protection, etc. It is preferably used for multidirectional applications such as reinforcing materials such as rubber and resin and materials for transporting heavy objects.

[0036]

Next, the present invention will be described based on examples.
The method for measuring the physical properties of the polyvinylidene fluoride monofilament obtained by the method of the present invention is as follows.

(A) Intrinsic viscosity index ηinh: A sample was dissolved in dimethylformamide at a concentration of 0.4 g / cc and measured at 30 ° C. using an Ostwald viscometer.

(B) Birefringence Δn: Determined by a normal Berek compensator method using a POH-type polarizing microscope manufactured by Nippon Kogaku Kogyo Co., Ltd. using white light as a light source.

(C) Tensile strength, tensile elongation, knot strength, knot elongation and initial elastic modulus: according to JIS-L1017. That is, take a sample in a skein shape,
After standing for 24 hours in a RH temperature and humidity control room, the measurement was performed using a Tensilon UTM-4-100 type tensile tester manufactured by Orientec Co., Ltd. at a test length of 25 cm and a tensile speed of 30 cm / min.

Example 1 A polyvinylidene fluoride polymer chip having an intrinsic viscosity index of 1.2 was melted at 260 ° C. in a spinning machine, spun through a die having a pore diameter of 1.0 mm, and further subjected to a polyethylene glycol bath at 20 ° C. The resultant was cooled in air to obtain an undrawn monofilament. The birefringence of the undrawn monofilament obtained here is 1.
It was 5 × 10 ⁻³ .

Next, this undrawn monofilament was
The film is stretched 3.0 times in a polyethylene glycol stretching bath at 60 ° C., and subsequently the polyethylene glycol is removed in a warm water bath at 80 ° C., so that the birefringence is 12 × 10 ^−3.
Of the intermediate oriented monofilament was obtained.

The spinning discharge amount of the intermediate oriented monofilament was adjusted to 630D after drawing in the next step.

Next, the intermediate oriented monofilament was drawn 2.1 times through a discharge portion under an atmospheric pressure atmosphere containing argon gas using the apparatus shown in FIG. The electrode used was a copper rod-shaped electrode coated with glass (thickness: 1 mm). The effective length of the electrode was 100 cm, the applied voltage for discharge was 4.5 KV, the frequency was 110 KHz, and the argon concentration was 92 mol%.

The obtained polyvinylidene fluoride monofilament has a tensile strength of 6.0 g / d, a tensile elongation of 24%, a knot strength of 4.2 g / d, a knot elongation of 21%, and a birefringence of 38.1 ×.
10 ^-3, the difference in birefringence between the surface layer portion and the center portion of the monofilament was -6.8 × 10 ^-3.

Comparative Example 1 The undrawn monofilament obtained in the same manner as in Example 1 was used in a polyethylene glycol drawing bath at 165 ° C.
The film was stretched 5 times, and subsequently, the polyethylene glycol was removed in a hot water bath at 80 ° C to obtain a polyvinylidene fluoride monofilament. The obtained polyvinylidene fluoride monofilament had a high tensile strength of 6.5 g / d, but had a very low knot strength of 2.7 g / d. .

Comparative Example 2 The intermediate oriented monofilament obtained in the same manner as in Example 1 was drawn in a polyethylene glycol drawing bath at 165 ° C., but could be drawn only up to twice. The tensile strength of the polyvinylidene fluoride monofilament having an overall draw ratio of 6 was 4.6 g / d, and the knot strength was 3.4 g / d.

Example 2 The undrawn monofilament obtained in the same manner as in Example 1 was used in a polyethylene glycol drawing bath at 165 ° C.
After stretching 5 times, the polyethylene glycol was removed in a warm water bath at 80 ° C. to obtain an intermediate oriented monofilament having a birefringence of 23 × 10 ⁻³ .

Using the same apparatus as in Example 1, the intermediate oriented monofilament was stretched 1.5 times through a discharge portion under an atmospheric pressure atmosphere containing an argon gas. The applied voltage for discharging is 5 KV, and the frequency is 11 KV.
0 KHz and the concentration of argon was 80 mol%.

The obtained polyvinylidene fluoride monofilament has a tensile strength of 6.3 g / d, a tensile elongation of 21%, a knot strength of 4.6 g / d, a knot elongation of 19%, and a birefringence of 43.2.
× 10 ^-3 , and the difference in birefringence between the surface portion and the central portion of the monofilament was -9 × 10 ^-3 .

[0050]

According to the method of the present invention, the stretching in the discharge portion under the normal pressure atmosphere suppresses the crystallization at the time of stretching and achieves high orientation, that is, enables smooth stretching, This enables low tension drawing, and makes it possible to easily obtain a high-strength polyvinylidene fluoride monofilament having high quality characteristics.

Further, the high-strength polyvinylidene fluoride monofilament obtained by the method of the present invention makes use of the characteristics of high strength and high elongation to reinforce fishery materials such as fishing lines, fishing nets and glue nets, and rubber belts. -It can be effectively used for transportation materials such as slings and ropes, and for civil engineering materials such as fences and rock fall prevention.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of a stretching apparatus used in carrying out the present invention.

[Explanation of symbols]

 Y: Fiber 1, 2: Conductor electrode 3, 4: Dielectric 5: Power supply

Claims (2)

(57) [Claims] 1. A method for producing a polyvinylidene fluoride monofilament, comprising the steps of: preparing an intermediate oriented polyvinylidene fluoride monofilament having a birefringence of 30 × 10 ⁻³ or less by 60 mol%;
By stretching in the range of 1.2 to 6.0 times in the discharge portion under the normal pressure atmosphere containing the above rare gas elements, highly oriented polyvinylidene fluoride monofilament having a birefringence of 35 × 10 ⁻³ or more. And producing a high-strength polyvinylidene fluoride monofilament. 2. The discharge part under normal pressure atmosphere is formed by a high voltage applied to a pair of electrodes whose at least one electrode surface is covered with a dielectric. For producing high-strength polyvinylidene fluoride monofilaments.