JPH0355565B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing polyvinylidene monofilament fluoride, which has high roundness and transparency and is particularly suitable for use in fishing lines, fishing nets, and the like. Polyfluorinated vinylidene monofilament has excellent toughness, impact resistance, transparency, and weather resistance, and has a high specific gravity (1.8) and a low refractive index of water (1.33).
It has a refractive index (1.42) close to 1.42, and has extremely low surface reflection in water, making it particularly useful as a fishing line material. However, in addition to the above-mentioned characteristics, the roundness of the monofilament is strongly required for fishing line, but conventional polyfluorinated vinylidene monofilament particularly satisfies both the roundness and transparency. It couldn't be called anything. In other words, the cooling conditions after melt extrusion are generally a major factor in the roundness and transparency of monofilaments made of crystalline polymers.
Under conventional cooling conditions for producing monofilaments from polyvinylidene fluoride, it was not possible to produce monofilaments that satisfied both roundness and transparency. Conventional cooling methods for vinylidene polyfluoride monofilament include, for example, the method of using water at room temperature as a cooling medium (for example,
22574) and a method of cooling at 60 to 140°C using a cooling medium with low thermal conductivity such as glycerin (Japanese Patent Publication No. 55-36389), but the former method does not improve roundness. However, the latter method can only provide a monofilament with satisfactory circularity and significantly impaired transparency. In this way, the roundness of monofilaments made of crystalline polymers depends on slow cooling conditions with high cooling temperatures, and conversely, the transparency depends on rapid cooling conditions with low cooling temperatures. Under the cooling conditions of , the transparency is impaired, and under the cooling conditions using water at room temperature, the shape stability during the cooling process is reduced, resulting in impaired roundness. The inventors of the present invention conducted extensive studies with the aim of obtaining polyvinylidene monofilament with excellent balance between roundness and transparency, and as a result, they selected a specific cooling medium and set the cooling temperature to specific conditions. It has been found that the above objective can be effectively achieved through control. That is, the present invention provides a method for manufacturing polyvinylidene fluoride monofilament by linearly melt-extruding polyvinylidene fluoride and subsequently cooling it in a liquid bath, in which at least one selected from ethylene glycol and its polymer is used as a cooling medium. The present invention provides a method for producing a polyvinylidene fluoride monofilament, which is characterized by using one type of polyvinylidene monofilament and cooling at a temperature of 0 to 50°C. The present invention uses a compound extremely inert to polyvinylidene fluoride, that is, at least one selected from ethylene glycol and its polymer, particularly polyethylene glycol, as a cooling medium, and a relatively low temperature zero ~50
It is characterized by cooling at a temperature of 10°C to 30°C, particularly preferably 10 to 30°C. The vinylidene fluoride used in the present invention is a polyvinylidene fluoride homopolymer or copolymer containing 95% by weight or more of a vinylidene fluoride component.
Other copolymer components that account for less than 5% by weight include tetrafluoroethylene, trifluoromonochloroethylene, and trifluoroethylene. Further, polyvinylidene fluoride having a vinylidene fluoride component of 95% by weight or more may be blended with other vinylidene fluoride homopolymers and/or copolymer polymers. When melt-extruding polyvinylidene fluoride, a normal melt-spinning machine can be used, and the specific conditions are: polymer temperature of 230 to 320°C, extrusion pressure of 10 to 500 Kg/cm ² , spinneret hole diameter of 0.1 to 3 mm, and spinning. speed
Examples include a range of 0.3 to 100 m/min, and these can be selected as appropriate. In the present invention, polyvinylidene fluoride after melt extrusion is immediately introduced into a cooling bath and rapidly cooled to below its melting point. The length of the cooling bath used here can be arbitrarily selected, but is usually 0.5 to 2 m, and the residence time of the linear object in the cooling bath is suitably in the range of 5 to 30 seconds. As the cooling medium used here, as mentioned above, at least one kind selected from ethylene glycol and its polymer, preferably polyethylene glycol. Circularity cannot be satisfied, and refrigerants that are even slightly active against polyvinylidene fluoride, such as trichlorethylene, are undesirable because they have an adverse effect on the transparency of the monofilament. The cooling temperature of the cooling bath is 0 to 50℃, especially 10℃.
It is preferable to maintain the temperature in the range of ~30°C; if it is less than 0°C, the roundness will be impaired, and if it exceeds 50°C, the transparency will be impaired, which is not preferred. Although the mechanism by which a polyvinylidene monofilament with excellent balance of circularity and transparency can be obtained by the method of the present invention is not necessarily clear, it is important to note that the cooling rate of each part in the cross-sectional direction of the thread during the cooling process is appropriate. This is considered to be due to the improvement in roundness without impairing transparency. In addition, in the present invention, by adopting the above-mentioned cooling conditions, the viscosity of the cooling bath becomes appropriate, so the running of the yarn in the cooling bath is stabilized, and the incidental effect of reducing unevenness in wire diameter is achieved. You can also get In particular, when polyethylene glycol is used as a cooling medium, the viscosity can be controlled within an appropriate range, for example, 50 to 150 cps, depending on the degree of polymerization, and the degree of polymerization is selected according to the predetermined cooling temperature. This has the advantageous advantage that the cooling bath can be maintained at an appropriate viscosity. In addition, the cooling medium used in the present invention is a high-boiling point compound, and therefore has an extremely advantageous industrial advantage in that it can be commonly used as a heating medium in subsequent processes such as stretching. . Thus, the polyvinylidene fluoride monofilament cooled by the method of the present invention is then stretched and heat-set as necessary to obtain a product, and the resulting product has excellent circularity and transparency, and
Since it is also highly strong, it is particularly useful for fishing applications such as fishing lines and fishing nets. The present invention will be explained in more detail below using Examples. Note that the oblateness and wire diameter unevenness, which are evaluation criteria for roundness in Examples, were measured by the following method. First, the wire diameter of the monofilament was measured using a laser wire diameter machine (M501A manufactured by Anritsu Electric Co., Ltd.).
Short axis)/(long axis+breadth axis)×100 is expressed as oblateness (%), and standard deviation (σn−1)/average value×100 (CV) is expressed as wire diameter unevenness (%). Further, the transparency is the result of visually judging the monofilament in the form of a strand, and each symbol is based on the following evaluation. ◎: Extremely good 〇: Good △: Poor ×: Extremely inferior Example 1 Polyvinylidene fluoride polymer chip with an intrinsic viscosity index (ηinh) of 1.2 at 30°C in a 0.4 g/cc dimethylformamide solution (melting point Tm = 177℃) using an extruder type spinning machine at 260℃ to 2.0mm
After melt extrusion through a nozzle, the material was cooled in a polyethylene glycol bath at 20° C. via a short air-cooling section in between, and wound up at a take-up speed of 6 m/min. The diameter of the undrawn monofilament obtained is 0.5
mm, and the evaluation results of flatness, wire diameter unevenness, and transparency were good as shown in Table 1. Example 2 and Comparative Examples 1 to 5 The cooling medium or cooling bath temperature was variously changed as shown in Table 1, and the special properties of polyvinylidene fluoride monofilaments obtained in the same manner as in Example 1 were evaluated. The results were as shown in Table-1.

[Table] As is clear from the results in Table 1, according to the method of the present invention (Examples 1 and 2), a monofilament with excellent roundness and transparency and small unevenness in wire diameter can be obtained. On the other hand, when the cooling temperature is high (Comparative Example 1) and when other solvents are used and the cooling temperature is high (Comparative Examples 2 and 3), the transparency is particularly reduced, and when hot water is used (Comparative Example In 3), the roundness also decreases. Furthermore, when water is used as a cooling medium (Comparative Example 4), the roundness and wire diameter unevenness are significantly reduced, and when trichlene is used (Comparative Example 5), transparency is also extremely reduced.

Claims (1)

[Claims] 1. Linear melt extrusion of polyvinylidene fluoride,
A method for producing a polyvinylidene fluoride monofilament by subsequent cooling in a liquid bath, using at least one member selected from ethylene glycol and its polymer as a cooling medium, and cooling at a temperature of 0 to 50°C. A method for producing a polyfluorinated vinylidene monofilament, characterized by the following.