Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2002-06-27
2004-01-13
Lipman, Bernard (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S250000
Reexamination Certificate
active
06677416
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a vinylidene fluoride resin monofilament and a production method thereof.
BACKGROUND ART
A monofilament made of vinylidene fluoride resin is of use as a material, for example, for fishing lines, fishing nets, rope materials, and so on because of its excellent physical and chemical properties, particularly, the properties including excellent mechanical strength and durability, little swelling with water leading to little degradation of strength in water, and so on. Among these uses, the filament, particularly, for the fishing lines is required to have the property of leaving less “twisting” or “curling” due to a winding propensity and the property of easily relieving the winding propensity, the property of demonstrating high mechanical strength, e.g., knot strength with a knot in the filament, and so on.
The conventional vinylidene fluoride resin monofilaments applied to the fishing lines required to satisfy such various properties include, for example those described in 1) Japanese Patent Application Laid-Open No. 10-298825 filed by Applicant, 2) Japanese Patent Applications Laid-Open No. 04-91215 and No. 07-138810, 3) Japanese Patent Application Laid-Open No. 11-131320 filed by Applicant, and so on.
DISCLOSURE OF THE INVENTION
Incidentally, in order to enhance the knot strength of the vinylidene fluoride resin monofilament, an effective way is to increase the drawing ratio in production to orient the filament in high degree of orientation, but the highly oriented monofilament tends to have the winding propensity easier. The vinylidene fluoride resin monofilament described in above 1) was improved in the winding propensity by setting of the low drawing ratio in production, but this resulted in insufficient improvement in the knot strength.
On the other hand, the vinylidene fluoride resin monofilaments described in above 2) were intended for improvement in the knot strength or improvement in wear resistance, but were not intended for improvement in the winding propensity. Further, the vinylidene fluoride resin monofilament described in above 3) was one obtained by subjecting a highly oriented monofilament in a fixed length state to a thermal treatment at a fixed temperature for a fixed period of time. This achieved the improvement in the winding propensity while preventing the degradation of mechanical strength. However, this thermal treatment in the fixed length state had to be carried out with the use of a large-diameter bobbin over a long period of time, and the batch treatment raised the problem of degradation of productivity.
Therefore, the present invention has been accomplished under such circumstances and an object of the present invention is to provide a vinylidene fluoride resin monofilament and a production method thereof capable of increasing the production efficiency while achieving both satisfactory knot strength and improving capability of the winding propensity.
In order to achieve the above object, the inventors have conducted elaborate research and found out the relaxation thermal treatment conditions for satisfactorily restraining the degradation of the knot strength. From the viewpoint associated with the properties of the vinylidene fluoride resin monofilament, the inventors found that a vinylidene fluoride resin monofilament satisfying a predetermined knot strength according to the filament size and having a predetermined knot elongation and linear elongation is excellent in the improving capability of the winding propensity, thus accomplishing the present invention.
Namely, a vinylidene fluoride resin monofilament according to the present invention is a vinylidene fluoride resin monofilament comprising a vinylidene fluoride resin and satisfies the relation represented by Eq (1) below;
Y≧d
3
×2×10
−7
−d
2
×2×10
−4
+d
×1.17×10
−2
+73.11 (1),
wherein a knot elongation is not less than 24% and a straight elongation is not less than 30%. In the equation, d indicates the diameter (&mgr;m) of the monofilament, and Y a knot strength (kgf/mm
2
) thereof.
It was proved that such a vinylidene fluoride resin monofilament had the sufficient knot strength comparable to those of the conventional monofilaments and enhanced its improving capability of the winding propensity. Here the diameter d of the monofilament is preferably 0.05-1.85 mm and more preferably 290-550 &mgr;m.
A production method of the vinylidene fluoride resin monofilament according to the present invention is a production method suitable for production of the vinylidene fluoride resin monofilament of the present invention, which comprises a drawing step of drawing a melt-spun vinylidene fluoride resin monofilament; and a dry thermal relaxation treatment step of subjecting the vinylidene fluoride resin monofilament thus drawn, to a relaxation thermal treatment in a gas phase at a temperature between 220° C. inclusive and 300° C., preferably between 250 and 290° C., and under such conditions that a relaxation rate falls between 4% inclusive and 10%, preferably between 7 and 9%, and that a passing time is not more than 5 seconds, preferably between 1 and 5 seconds. In the normal relaxation thermal treatment, the degradation of the mechanical strength, e.g., the knot strength, tends to become more prominent with increase in the relaxation rate. In contrast to it, according to the present invention, the knot strength of the vinylidene fluoride resin monofilament before the relaxation thermal treatment is maintained or is little degraded even if the relaxation rate is so high as in the above range, and the improving capability of the winding propensity is enhanced.
Further, it is extremely preferable for the production of the vinylidene fluoride resin monofilament of the present invention that in the drawing step, the melt-spun vinylidene fluoride resin monofilament is drawn at a drawing ratio of not less than 5.9, more preferably 5.9-6.2.
The terms “straight elongation,” “knot strength,” “knot elongation,” and “passing time” in the present invention are values defined as below. If the drawing process involves two or more stages of drawing, the “drawing ratio” refers to a total value of drawing ratios in respective stages, i.e., an overall drawing ratio at an end of the drawing process.
<Straight elongation>: ultimate elongation under ordinary temperature of a sample filament drawn with TENSILON/UTM-III-100 available from TOYO BALDWIN Co., LTD and under the conditions of the chuck-chuck distance (sample length) of 30 cm and the drawing speed (head speed) of 30 cm/min.
<Knot strength and knot elongation>: breaking tenacity and elongation of a sample filament with a knot in central part of the sample length, drawn as in the measurement of the foregoing straight elongation.
<Passing time>: time in which a predetermined portion of the vinylidene fluoride resin monofilament passes through the gas phase or for which it stays in the gas phase.
Best Mode for Carrying Out the Invention
The following will describe the preferred embodiments of the vinylidene fluoride resin monofilament and production method thereof according to the present invention.
Vinylidene Fluoride Resin
A homopolymer of vinylidene fluoride can be preferably used as the vinylidene fluoride resin used in the present invention. Without having to be limited to this, other applicable vinylidene fluoride resins include copolymers of a vinylidene fluoride monomer and one or more monomers copolymerizable therewith; mixtures of these copolymers with the homopolymer of vinylidene fluoride; and so on.
Examples of the monomers copolymerizable with vinylidene fluoride include tetrafluoroethylene, hexafluoropropylene, trifluoroethylene, chlorotrifluoroethylene, vinyl fluoride, and so on, which can be used singly or in a mixed state of two or more monomers. The content of vinylidene fluoride units in these vinylidene fluoride resins is preferably not less than 50 mol %, more preferably not less than 60 mol %, and
Imamura Shingo
Munakata Kazuyuki
Sato Takashi
Kureha Chemical Industry Company Limited
Lipman Bernard
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