JP7706145B2 - Monofilament for fishing nets - Google Patents

Description

The present invention relates to monofilaments that make up fishing nets.

The performance required for fishing nets includes high strength, flexibility, and ease of dyeing, and monofilaments made of polyamide resin are mainly used for them, and among polyamide resins, polyamide 6 resin and polyamide 6/66 copolymer resin are particularly used. Fishing nets made of polyamide resin are flexible, so they do not take up much space on the ship and can be loaded in large quantities.

On the other hand, fixed fishing nets such as fixed shore nets are often made of polyester resin, which has good dimensional stability and a high specific gravity so that it does not waver even slightly in the wind and waves. Furthermore, polyester resins are improved to increase the specific gravity, or fluorine-based monofilaments and polyester monofilaments are combined to increase the specific gravity.

The filaments that make up the net, which is made of the polyamide resin mentioned above, can easily stretch due to external forces such as its own weight, water resistance, the weight of the catch, and external forces such as friction with the seabed and tension when being hauled up, causing the mesh to open and allowing caught fish to slip out. In particular, in the case of bottom trawling nets, friction with the seabed, as well as the resulting tension when being pulled, can cause the net to stretch more than necessary, leading to the net breaking. When being hauled up, the fishing net comes into contact with the side of the ship, and this contact friction can also cause the net to break.

A fishing net made of polyamide resin that contains aromatic group-containing polyamide units has been disclosed, with the aim of improving both flexibility and strength.

JP 2004-250556 A

The objective of the present invention is to provide a monofilament for a fishing net made of polyamide resin that maintains the strength required for the fishing net while maintaining the advantages of polyamide resin such as flexibility, and is dimensionally stable and does not easily stretch when an external force is applied or when water is absorbed.

The inventors focused on the phenomenon in which polyamide monofilaments change dimensions when an external force is applied.

Polyamide fibers are generally considered to have good abrasion resistance, and are ideally used for bag fabrics and the like. Bag fabrics are made of woven fabrics, and the abrasion resistance in this case is evaluated when the surface of the woven fabric rubs against something, not when an external force is applied to the fibers in the direction of the fiber axis.

When an external force is applied in the axial direction of the filament, polyamide filaments tend to stretch easily under low load, and to stretch even more when they absorb moisture. When stretching occurs, the filament diameter becomes smaller at the stretched area, making it more susceptible to damage. When used as a fishing net, the net is pulled stronger than the friction of the net surface, and therefore it is often rubbed against other objects while an external force is applied in the axial direction of the filaments that make up the net. Therefore, the inventors wondered whether it would be possible to provide a monofilament for fishing nets that can maintain its durability when an external force is applied in the axial direction of the filaments and friction occurs.

The inventors then carried out research to achieve the above object. As a result, they discovered that by compounding a polyester-based resin in a specific ratio with the core of a filament made of polyamide-based resin, the polyester-based resin region in the core plays a role in suppressing elongation and deformation when a load is applied to the filament, and arrived at the present invention.

That is, the present invention provides a core-sheath type composite monofilament for fishing nets, characterized in that the core of the filament is made of polyester resin and the sheath of the filament is made of polyamide resin, the proportion of the polyamide resin in the filament is 80 to 90 volume %, and the cross-sectional area of the composite filament is 7.8 x ^{10-3 mm2} to 5.0 x ^{10-1 mm2} .

The present invention will be described in detail below.

The fishing net monofilament of the present invention is a composite of polyamide resin and polyester resin in a core-sheath structure, with the core being made of polyester resin and the sheath being made of polyamide resin. In the core-sheath structure, the number of cores may be one or may be multiple (2 to 5 cores), but it is preferable that the number is one.

The cross-sectional shape of the monofilament is not particularly limited and may be circular, elliptical, polygonal, etc., but a circular cross section is preferable in terms of mechanical properties and versatility. The cross-sectional shape of the core is also not limited to circular and may be irregular.

The polyamide resin constituting the sheath is not particularly limited as long as it has an amide group in the molecule, and examples include nylon 6, nylon 66, nylon 69, nylon 46, nylon 610, nylon 1010, nylon 11, nylon 12, nylon 6T, nylon 9T, polymetaxylene adipamide, and copolymers or blends of these components.

The polyester resin constituting the core is not particularly limited as long as it has an ester bond in the molecule. For example, aromatic polyesters include polyethylene terephthalate, polybutylene terephthalate, polypropylene terephthalate, etc., and aliphatic polyesters include polylactic acid, polybutylene succinate, polycaprolactone, etc. In addition, as long as the object of the present invention is not hindered, the above-mentioned polyesters may be blended together, or the above-mentioned polyesters may be blended with polyesters copolymerized with other components. Examples of other components that can be copolymerized include dicarboxylic acids such as isophthalic acid, naphthalene dicarboxylic acid, 5-sodium sulfoisophthalic acid, phthalic anhydride, sebacic acid, adipic acid, and succinic acid, and diol components such as ethanediol, propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and cyclohexanedimethanol. A polyester thermoplastic elastomer or a polyester thermoplastic elastomer composition may be added to the polyester. The amount added is at most 10% by mass in the core, and preferably 2 to 8% by mass. By including a polyester thermoplastic elastomer or a polyester thermoplastic elastomer composition in the polyester of the core, the bonding at the interface between the sheath made of polyamide resin and the core made of polyester resin is improved, and it is preferable that the fiber is less likely to stretch when an external force is applied in the fiber axis direction.

The relative viscosity of polyester resins is preferably 1.4 or more, more preferably 1.5 or more, in order to have the desired mechanical properties. Note that a higher relative viscosity tends to result in higher mechanical properties, but taking into consideration ease of handling, the upper limit of the relative viscosity is preferably about 1.65. The relative viscosity of polyesters was measured at 20°C using an Ubbelohde viscometer with a 0.5% concentration of an equal mass mixture of phenol and tetrachloroethane as the solvent.

In addition, as long as the object of the present invention can be achieved, the polyamide resin or polyester resin constituting the monofilament may contain various additives as necessary, such as crystal nucleating agents, matting agents, pigments, light resistance agents, weather resistance agents, antioxidants, antibacterial agents, fragrances, heat stabilizers, plasticizers, dyes, surfactants, surface modifiers, various inorganic and organic electrolytes, fine powders, flame retardants, and compatibilizers.

The fishing net monofilament of the present invention is mainly composed of polyamide resin, and has a major feature in that a polyester resin is arranged in the core of the monofilament composed of the polyamide resin. Since the monofilament is mainly composed of polyamide resin, it has excellent flexibility and good dyeability, compared to, for example, a monofilament composed only of polyester resin. And, by continuously arranging the polyester resin in the core part of the monofilament mainly composed of such polyamide resin in the filament axial direction, when an external force is applied to the monofilament, or when the polyamide resin is subjected to its own weight due to moisture absorption or water absorption due to its resin characteristics, the polyester resin has excellent dimensional stability, so that the shape is maintained in the axial direction of the monofilament and deformation due to elongation of the monofilament itself is suppressed. And, since deformation due to elongation is unlikely to occur, thinning (deformation) in the axial direction of the filament is suppressed, and damage due to wear is unlikely to occur. In contrast, if a monofilament is made only of polyamide resin, it will easily deform in the axial direction when an external force is applied, and the deformed area will become thinner. Stress due to wear and tear will concentrate in the thinner area, causing damage to progress at an accelerated rate, leading to easy breakage.

In the present invention, in order to achieve the above-mentioned effects, the proportion of polyamide-based resin in the monofilament is 80 to 90% by volume. By making the proportion of polyamide-based resin in the monofilament 80 % by volume or more, the monofilament is excellent in flexibility, has good dyeability, and exhibits sufficient practical strength for use in fishing nets. On the other hand, by making the proportion of polyamide-based resin 90% by volume or less, the dimensional stability and abrasion resistance due to the polyester-based resin are dramatically improved .

The cross-sectional area of the cross section of the fishing net monofilament of the present invention when cut perpendicularly to the filament axis direction is 7.8×10 ^-3 mm ² to 5.0×10 ^-1 mm ^2. By making the cross-sectional area 7.8×10 ^-3 mm ² or more, fuzzing is unlikely to occur due to friction caused by contact with the seabed, the side of a ship, etc. On the other hand, by making the cross-sectional area 5.0×10 ^-1 mm ² or less, the strength per single yarn can be effectively exerted and the flexibility of the yarn can be maintained, resulting in good processability during knitting of the net. Here, the cross-sectional area is calculated from a photograph taken with a micro scoop.

The fishing net monofilament of the present invention can be obtained by the following method. First, a core-sheath composite nozzle is used to melt-spin a polyamide resin in the sheath and a polyester resin in the core, with the ratio of the polyamide resin being 80 to 90% by volume. Next, the yarn obtained by melt spinning is cooled in a water bath and drawn after being wound up as an undrawn yarn or without being wound up. Hot drawing is performed at a draw ratio of 4 to 8 times. As a heating means for hot drawing, hot drawing is performed in a hot water bath or by using a heated roller. After hot drawing, a winding operation is continuously performed to obtain the desired monofilament.

The obtained monofilament can be used to obtain a fishing net with the desired structure using a net weaving machine. When applied to a net weaving machine, it can be used in the form of a monofilament thread consisting of a single strand, or in the form of a bundle of multiple monofilaments.

The fishing net monofilament of the present invention has excellent dimensional stability and abrasion resistance, and is therefore particularly effective for use in non-fixed fishing nets such as bottom trawls and gill nets.

The fishing net monofilament of the present invention has excellent flexibility, good dyeability, and sufficient practical strength for a fishing net, while also having dramatically improved dimensional stability and abrasion resistance, making it possible to provide a fishing net with excellent dimensional stability and abrasion resistance.

FIG. 2 shows a schematic perspective view of a bending wear test for evaluating wear resistance.

The present invention will now be described with reference to examples. Note that the present invention is not limited to the following examples. The measurement methods for the characteristics and the like in the examples are as follows.
(1) Tensile strength (N) and elongation (%)
Since monofilaments are usually wound, the required amount was unwound and left at room temperature for 24 hours or more, and the maximum strength and breaking elongation were measured using a constant-speed extension type tensile tester. The conditions of the tensile test were a pulling speed of 300 mm/min, a gripping distance of 250 mm, and the average values measured with n=5 were taken as the tensile strength (N) and elongation (%).

(2) Knot Strength The strength at break was measured using a constant-speed extension type tensile tester in accordance with JIS L 1013. Knots were measured for both knotting methods a) and b) described in JIS L 1013, with a tensile speed of 300 mm/min and a gripping distance of 250 mm, with n=5 for each knotting method a) and b), and the average value was taken as the knot strength (N).

(3) Abrasion resistance (flexion type abrasion test)
The wear body was a metal round bar with a diameter of 20 mm, with sandpaper #1500 attached to the side. A sample (monofilament) was brought into contact with the wear body at an angle of 90 degrees, and a predetermined load was applied to one end of the sample, which was rubbed back and forth with a stroke width of 120 mm and a stroke speed of 35 times/min, and the number of reciprocations until the sample broke was measured. Measurements were performed on n=3 samples, and the average of the obtained numbers was taken as the wear number for wear resistance. The predetermined load was 3.0 kg per cross-sectional area ( ^mm2 ) of the sample. For example, in the case of a circular cross section and a wire diameter of 0.2 mm, a load of 94 g was applied.
For the evaluation of wet abrasion, abrasion tests were performed using samples that had been immersed in water at room temperature for 24 hours or more. After the start of the abrasion test, water was not applied to the samples.

Figure 1 shows a schematic perspective view of the bending wear test used to measure wear resistance.

Example 1
As the polyamide-based resin to be placed in the sheath, a blend of 90 mass% polyamide 6 resin (manufactured by Unitika Ltd., product name A1030BRF) and 10 mass% nylon 6-66 copolymer resin (manufactured by DSM, product name "Novamid 2030J") was prepared.
As the polyester resin to be disposed in the core, a polyethylene terephthalate resin (manufactured by Unitika, product name "NEH2070") having a relative viscosity ηrel of 1.55 was prepared.

The resins were weighed so that the volume ratio was polyamide resin (sheath)/polyester resin (core)=80/20, and melt spun from a 2.0 mmφ×9H spinneret at a polymer temperature of 280° C. and a spinning speed of 16 m/min (the number of cores was one). The melt spun yarn was cooled in a water bath at 30° C. at a speed of 16 m/min, and then stretched 3.5 times in a warm bath at 95° C. without winding (first-stage stretching), then stretched 1.4 times in a dry heat atmosphere at 175° C. without winding (second-stage stretching), and then relaxed and wound up (total stretching ratio 4.9 times). The obtained core-sheath type composite monofilament had a yarn diameter of 0.462 mm, a cross-sectional area of 1.68×10 ⁻¹ mm ² (fineness 1997 dtex), a tensile strength of 5.3 cN/dtex, an elongation of 22.0% and a knot strength of 3.1 cN/dtex.

Comparative Example 1
As the polyamide-based resin, a blend of 90 mass % of polyamide 6 resin (manufactured by Unitika Ltd., product name A1030BRF) and 10 mass % of nylon 6-66 copolymer resin (manufactured by DSM, product name "Novamid 2030J") was prepared.

The blended polyamide resin was melt-spun at a polymer temperature of 245° C. from a 2.5 mmφ×24H spinneret at a spinning speed of 26 m/min. The melt-spun yarn was cooled in a 10° C. water bath at a speed of 26 m/min, and then stretched 3.4 times in a 90° C. warm bath without winding (first-stage stretching), then stretched 1.4 times in a dry heat atmosphere at 165° C. without winding (second-stage stretching), and then relaxed and wound (total stretching ratio 4.6 times). The monofilament made of only polyamide obtained had a yarn diameter of 0.459 mm, a cross-sectional area of 1.65×10 ⁻¹ mm ² (fineness 1717 dtex), a tensile strength of 6.1 cN/dtex, an elongation of 19.2%, and a knot strength of 3.9 cN/dtex. The evaluation results of abrasion resistance are shown in Table 1.

Reference example 2
As the polyamide-based resin to be placed in the sheath, a blend of 75 mass% nylon 6-66 copolymer resin (manufactured by DSM, product name "Novamid 2330J") and 25 mass% nylon 6-66 copolymer resin (manufactured by DSM, product name "Novamid 2030J") was prepared.
As the polyester resin to be disposed in the core, a polyethylene terephthalate resin (manufactured by Unitika, product name "NEH2070") having a relative viscosity ηrel of 1.55 was prepared.

The resins were weighed so that the volume ratio was polyamide resin (sheath)/polyester resin (core)=70/30, and melt spun from a 1.8 mmφ×6H spinneret at a polymer temperature of 270° C. and a spinning speed of 17.4 m/min (the number of cores was one). The melt spun yarn was cooled in a water bath at 10° C. at a speed of 17.4 m/min, and then stretched 3.8 times in a warm bath at 85° C. without winding (first-stage stretching), then stretched 1.53 times in a dry heat atmosphere at 180° C. without winding (second-stage stretching), and then relaxed and wound up (total stretching ratio 5.8 times). The obtained core-sheath type composite monofilament had a yarn diameter of 0.203 mm, a cross-sectional area of 3.23×10 ^-2 mm ² , a tensile strength of 6.8 cN/dtex, an elongation of 13.8%, and a knot strength of 4.2 cN/dtex. In Reference Example 2, the tensile strength, elongation, and knot strength were measured for six monofilaments (fineness 2600 dtex/6f). The evaluation results of abrasion resistance are shown in Table 1.

Reference example 3
A core-sheath composite monofilament was obtained in the same manner as in Reference Example 2, except that a blend of 95% by mass of polyethylene terephthalate resin (manufactured by Unitika, product name "NEH2070") with a relative viscosity ηrel = 1.55 and 5% by mass of a polyester-based thermoplastic elastomer composition (manufactured by Mitsubishi Chemical Corporation, product name "Modic GQ331") was used as the resin disposed in the core. The obtained core-sheath composite monofilament had a thread diameter of 0.198 mm, a cross-sectional area of 3.07 x ^{10-2 mm2} , a tensile strength of 7.4 cN/dtex, an elongation of 14.0%, and a knot strength of 4.4 cN/dtex. In Reference Example 3, the tensile strength, elongation, and knot strength were measured when six monofilaments were aligned (fineness 2339 dtex/6f). The evaluation results of abrasion resistance are shown in Table 1.

Comparative Example 2
As the polyamide resin, a blend of 75 mass % nylon 6-66 copolymer resin (manufactured by DSM, product name "Novamid 2330J") and 25 mass % nylon 6-66 copolymer resin (manufactured by DSM, product name "Novamid 2030J") was prepared.

The polymer was melt-spun at a polymer temperature of 255° C. from a 0.8 mmφ×54H spinneret at a spinning speed of 25 m/min. The melt-spun yarn was cooled in a 12° C. water bath at a speed of 25 m/min, and then drawn 3.5 times in a 95° C. warm bath without winding (first-stage drawing), and then drawn 1.7 times in a dry heat atmosphere at 215° C. without winding (second-stage drawing), and then relaxed and wound (total draw ratio 6.0 times). The obtained fiber had a yarn diameter of 0.200 mm, a cross-sectional area of 3.14×10 ⁻² mm ² , a tensile strength of 8.6 cN/dtex, an elongation of 20.9%, and a knot strength of 4.7 cN/dtex. In Comparative Example 2, the tensile strength, elongation and knot strength were measured for six monofilaments (fineness: 2355 dtex/6f).

The monofilament of Example 1 had sufficient mechanical properties for practical use as a fishing net monofilament. Furthermore, as is clear from Table 1, the monofilament had improved dimensional stability, and thus exhibited significantly superior abrasion resistance compared to Comparative Examples 1 and 2.

Claims (2)

A monofilament for a fishing net, which is a core-sheath type composite monofilament, the filament being composed of a core made of a polyester resin and a sheath made of a polyamide resin, the proportion of the polyamide resin in the filament being 80 to 90 volume %, and the cross-sectional area of the composite filament being 7.8 x ^{10-3 mm2} to 5.0 x ^{10-1 mm2} . 2. The monofilament for a fishing net according to claim 1, wherein the fishing net is a bottom trawl or a gill net .

Images