JPH0461086B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to a polyvinylidene fluoride (PVDF) monofilament with high knot strength and a method for producing the same. (Conventional technology) PVDF has a high specific gravity and a refractive index close to that of water, making it difficult to see underwater. It also has low water absorption, low surface tension, so it repels water well, has excellent weather resistance, and its bending Young's modulus is moderate. Therefore, it is suitable as a monofilament for fishing lines and fishing nets (Special Public Interest Publication in 1979).
-5359), has been corporatized. However, compared to nylon monofilament, its knot strength is low, and its applications are limited. For this reason, many studies have been made to obtain PVDF monofilaments with high knot strength. For example, Japanese Patent Publication No. 51-32667 states that it is effective to include polymethyl methacrylate, but this has not yet reached a satisfactory level. (Objective of the Invention) The object of the present invention is to provide a PVDF monofilament with high knot strength and a method for producing the same. (Structure of the Invention) As a result of various studies to achieve the above object, the present inventors found that among the factors that determine the fine structure of a monofilament, the size of the long period greatly affects the nodule strength. Approximately 200 filaments
However, by using a monofilament with a long period of 190 Å or less, the nodule strength is significantly improved. Go to the 1st
It has been found that it can be easily obtained by rapid cooling treatment after stage stretching. The present invention was made based on such knowledge, and the gist thereof is as follows. (1) PVDF monofilament with a long period of 190Å or less. (2) Melt-spun the PVDF polymer couple, cooled and solidified in an inert liquid at 50°C or lower, and subjected to first-stage stretching in a liquid or gas bath at 100-175°C. After quenching in a liquid at a temperature 80°C or more lower than the stretching temperature, it is then cooled in a gas bath at 130 to 200°C or
In a liquid bath at 130-175℃, the total stretching ratio is 6-8.
A method for producing a PVDF monofilament, which is characterized by performing stretching in the second and subsequent stages so as to double the amount. In the present invention, the long period is measured from the small-angle X-ray scattering pattern, where the distance between the film (dry plate) and the sample (monofilament) is l, the maximum width of the upper and lower scattered light with the equatorial plane as the axis of symmetry is 2a, and CuKα When the wavelength of the line is λ (=1.5418Å) and tan2d=a/l,
It is expressed as long period = λ/2sind. In the present invention, the PVDF polymer is
In addition to PVDF homopolymer, vinylidene fluoride is the main component (preferably 85% by weight or more), and this is copolymerized with tetrafluoroethylene, monochlorotrifluoroethylene, vinyl fluoride, hexafluoropropylene, perfluoroisopropoxyethylene, etc. PVDF copolymer as a component is used,
It may also be a mixture of two or more types of polymers. In order to exhibit sufficient strength characteristics, the intrinsic viscosity (in dimethylformamide at 30℃
) is 0.9 or more, preferably 1.0 or more. The monofilament of the present invention needs to have a long period of 190 Å or less, and it is particularly desirable to have a long period of 180 Å or less. It is thought that when the long period is long, the number of microstructural units for dispersing stress when subjected to complex large deformation such as a nodule is reduced, so that the nodule strength does not increase. The monofilament of the present invention can be produced by the above-mentioned method, but after the first stage drawing, quenching in a liquid at a temperature lower than the drawing temperature by 80°C or more, preferably 90°C or more lower, This is necessary to obtain a monofilament with a long period of 190 Å or less. Rapid cooling after the first stage stretching is performed using an inert liquid such as water, ethylene glycol, or glycerin. In addition, it is appropriate that the stretching ratio in the first stage is about 3 to 5 times, and after the multi-stage stretching is completed, heat treatment is performed as necessary. Note that the monofilament of the present invention contains a plasticizer,
It goes without saying that additives such as heat stabilizers, colorants, and antioxidants may also be included. The monofilament of the present invention has excellent strength characteristics and can be sufficiently applied not only to fishing lines, fishing nets, and other fishing materials, but also to filter cloths, brushes, and the like. (Example) Hereinafter, the present invention will be explained in more detail with reference to Examples. Intrinsic viscosity is the value measured at 30℃ in dimethylformamide, and wet knot strength is the value measured at 30℃.
This is a value measured using JISL1013 method. Examples and Comparative Examples PVDF with an intrinsic viscosity of 1.21 was spun at a temperature of 280°C using an extruder type melt spinning machine, the undrawn monofilament was cooled in a water bath at 30°C, and then
The first stage of stretching was performed at a stretching ratio of 3.5 times in a glycerin bath at T ₁ °C, and then quenched in a water bath at T ₂ °C.
The second stretch with a stretching ratio of 1.8 to 2.0 times in a gas atmosphere at _T3 ℃
A monofilament of about 500 denier was obtained by stage drawing (spin draw method). Table 1 shows the relationship between each temperature during the above-mentioned stretching and the long period and wet knot strength of the obtained monofilament.

【table】

[Table] (Effects of the Invention) As described above, the present invention provides a PVDF monofilament having excellent wet knot strength and a method for producing the same.

Claims (1)

[Claims] 1. A polyvinylidene fluoride monofilament having a long period of 190 Å or less. 2 Melt spinning polyvinylidene fluoride polymer,
Cooled and solidified in an inert liquid below 50℃, 100~175
The first stage of stretching is carried out in a liquid or gas bath at
After stage stretching, quenching in a liquid at a temperature 80°C or more lower than the drawing temperature, followed by cooling in a gas bath at 130 to 200°C or
A method for producing a polyvinylidene fluoride monofilament, which comprises performing stretching in the second and subsequent stages in a liquid bath at 130 to 175°C so that the total stretching ratio is 6 to 8 times.