NO344891B1

NO344891B1 - Method for manufacturing fishing net

Info

Publication number: NO344891B1
Application number: NO20181438A
Authority: NO
Inventors: Hidehito Andoh; Kohei Ikeda
Original assignee: Unitika Ltd
Priority date: 2017-11-10
Filing date: 2018-11-08
Publication date: 2020-06-15
Also published as: NO20181438A1

Description

SPECIFICATION

METHOD FOR MANUFACTURING FISHING NET

BACKGROUND OF THE INVENTION

TECHNICAL FIELD

[0001]

The present invention relates to a method for manufacturing a fishing net having high strength, particularly to a method for manufacturing a fishing net composed of a plastic net.

BACKGROUND ART

[0002]

Conventionally, it has been well known that a core-sheath type composite filament comprising a core component formed from polyethylene terephthalate and a sheath component formed from polyester copolymer or polyolefin having a melting point lower than that of polyethylene terephthalate is used as a material for a mesh sheet. It has also been well known that a coarse fabric is woven using a multifilament yarn made of core-sheath type composite filaments as warp and weft, and that an intersection of the warp and the weft is fused by melting the sheath component by heat treatment to form the mesh sheet (see JP 2001-271270 A and JP 2009-299209 A). In this context, the intersection of the warp and the weft is fused for preventing mesh slippage. The fusion of the intersections can be generated at a pressure from both upper side and lower sides, even if it is conducted by non-pressure heat treatment, the warp and the weft outside the intersections are hardly fused in the heat treatment, such that some of the intersections are selectively fused. The mesh sheet is generally covered on an outside surface of a temporary structure such as a scaffold at a construction site and is used for preventing foreign falling objects and the like from jumping out of the temporary structure, so that there is no drawback even if some of portions except for the intersections are not fused.

[0003]

However, a high-rigid plastic sheet in which portions outside the intersections are fused is sometimes necessary for industrial applications other than the mesh sheets. For example, a culturing fishing net, which is a kind of the fishing nets, is easily worn down by continuous contacts with fishes, and fishes may cut off the net by its mouth, so that a plastic type sheet is very suitable for the culturing fishing net. In order to obtain the plastic sheet, it is considered that heat treatment is performed while the sheet is pressed as described in JP 2001-271270 A and JP 2009-299209 A. However, when heat treatment is conducted under pressure for producing the plastic sheet, the sheet becomes very rigid and can only be treated in the form of a flat plate, because it is very difficult to wind it up as a scroll.

Document JP 2016056487 describes a sheath-core composite polyamide monofilament by compositing polyamide and a polyamide resin other than the polyamide, a cross section of the monofilament shows a sheath-core cross section, the sheath part has the polyamide and the core part has the polyamide resin other than the polyamide.

SUMMARY OF THE INVENTION

[0005]

An object of the present invention is to provide a method for manufacturing a fishing net comprising a plastic net, which can be easily handled by winding or folding and has highly rigid intersections, although the plastic net is strong.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]

FIG. 1 is a schematic plan view illustrating a strand according to an embodiment of the plastic net of the present invention.

FIG. 2 is a schematic plan view illustrating a part of strands and intersections according to an embodiment of the plastic net of the present invention.

FIG. 3 is a photograph showing a plan view of an embodiment of the plastic net of the present invention.

FIG. 4 is a schematic diagram illustrating a state of a test piece in measuring intersection strength of the plastic nets obtained in Examples and Comparative Examples; and

FIG. 5 is a schematic diagram illustrating a state of a test piece in measuring tensile strength of the plastic nets obtained in Examples and Comparative Examples.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006]

The present invention provides a method for manufacturing a fishing net comprising a plastic net, wherein strands and intersections are formed by a specific method using a specific core-sheath type composite filament and then heat treating to obtain the plastic net, thus solving the above problem. Thus, the present invention is to provide a method for manufacturing a fishing net, the method comprising:

a step of preparing a multifilament yarn formed by bundling a plurality of core-sheath type composite filaments, wherein a core component is made of polyamide B and a sheath component is made of polyamide A having a melting point lower than the polyamide B, a mass ratio of the core component and the sheath component being core component : sheath component = 1 to 3 : 1, a step of obtaining a net constructed with strands and intersections, using a yarn thread obtained by paralleling a plurality of the multifilament yarns, a step of heat-treating the net to melt the sheath component of the yarn threads constituting the strands and the intersections, followed by solidifying, thus obtaining a plastic net constructed with solidified strands and solidified intersections, in which the core component is existent as an initial fiber form in a matrix formed of the sheath component; and

a step of forming the fishing net using the plastic net.

[0007]

In the present invention, the core-sheath type composite filament having the core component of polyamide A and the sheath component of polyamide A having a melting point lower than the polyamide A is prepared. In the coresheath type composite filament, a mass ratio of the core component to the sheath component is core component : sheath component = 1 to 3 : 1. The polyamide A which is formed into the sheath component would form a matrix of a fiber-reinforced plastic material. Consequently, when the mass ratio of the sheath component is lower than the lower limit of the above range, it hardly forms the matrix. When the mass ratio of the sheath component is higher than the upper limit of the above range, a diameter or a number of the core component decreases and the strength of the fiber-reinforced plastic material deteriorates. A fineness of the core-sheath type composite filament ranges from 4 dtex to 20 dtex. A plurality of core-sheath type composite filaments are bundled to form a multifilament yarn. The number of bundled filaments can be within the range of 30 to 400.

[0008]

Subsequently, a plurality of multifilament yarns are paralleled to obtain a yarn thread. The number of paralleled yarns can be about 5 to about 20. The net constructed with strands and intersections may be obtained by applying the plurality (for example, 2 threads to 10 threads) of yarn threads to a net making machine or a Russell knitting machine. The plurality (for example, 2 lines to 10 lines) of yarn threads may also be applied to a braid net making machine to braid the plurality of yarn threads to form a net constructed with the strands 1 and the intersections 2. In the present specification, the term "intersection" is meant by a portion at which adjacent strands are crossed with each other. FIG.

1 is a schematic diagram illustrating the strand 1 in which four yarn threads 11, 12, 13, and 14 are braided. The strand 1 is formed by repeating a process of crossing the yarn thread 11 with the yarn thread 12, crossing the yarn thread 12 with the yarn threads 11 and 13, crossing the yarn thread 13 with the yarn threads 12 and 14, and crossing the yarn thread 14 with the yarn thread 13. When the yarn threads are braided, each yarn thread may not be twisted or may be twisted. By twisting the yarn thread, the core-sheath type composite filaments constituting the strands 1 and the intersections 2 are intimately contacted so as to improve the rigidity of the fishing net. Accordingly, whether the yarn thread is twisted and how much extent the yarn thread is twisted may be determined in consideration of a balance between rigidity and flexibility of the fishing net. The intersections 2 may be formed in the form of knot by binding the strands 1, 1 formed as a braid, but it can preferably be in the form of knotless by penetrating the yarn threads 11, 12, 13, and 14 constituting the two strands 1, 1 into one another (see FIG.2). The net is mainly used as a fishing net such as a culturing fishing net, so that the knotless net without having roughness formed by knots is preferable due to little damage to fishes.

[0009]

The obtained net is subjected to heat treatment. A temperature of the heat treatment is higher than or equal to a melting point of the polyamide A of the sheath component, for example ranging from 140 ºC to 200 ºC. Only the sheath component of the core-sheath type composite filament constituting the yarn thread is fused by the heat treatment. The heat treatment may be conducted either without pressure or under pressure, but it may preferably be conducted without pressure, for imparting flexibility for easy winding. When the sheath component is cooled after the heat treatment, the fused sheath component is solidified, and the solidified strands 1 and the solidified intersections 2 constitute fiber-reinforced plastic material in a matrix of the polyamide A of the sheath component. In the case where the yarn threads are braided in the present invention, the strands 1 and the intersections 2 are constructed in a braided form and the core-sheath type composite filaments constituting the yarn thread are in close and strong contact with each other, thus the fused sheath component easily forms the matrix even if the heat treatment is conducted without pressure. As a result, the solidified strands 1 and the solidified intersections 2 are formed into the fiber-reinforced plastic material in which the core component maintaining the original fiber form is present in the matrix formed by melting and solidifying the sheath, to obtain the plastic net constructed with the fiber-reinforced plastic material. The resulting plastic net is employed and fabricated into fishing nets, such as a fixed fishing net, a cage fishing net, a culturing fishing net and the like.

[0010]

The plastic net obtained by the process of the present invention is constructed with the strands 1 and the intersections 2. A region surrounded by the strands 1 and the intersections 2 is an opening and can be referred to as a mesh 3. As illustrated in FIG.3, a shape of the mesh 3 may be a square mesh, or can be another form such as a rhomboid mesh. The intersections 2 can preferably be knotless as illustrated in FIG.3, but the intersections 2 may be in the form of a knot. A diameter of the strand 1 ranges from about 2 mm to about 7 mm and an area of the intersection 2 ranges from about 25 mm<2 >to about 80 mm<2>. An area of the mesh 3 ranges from about 2 cm<2 >to about 20 cm<2>.

[0011]

The solidified strands 1 and the solidified intersections 2 are formed by the fiber-reinforced plastic material in which the sheath component constitutes the matrix and the core component exists in the matrix as an initial fibrous form. That is, a fiber-reinforced plastic material in which the polyamide A constitutes a matrix and a plurality of polyamide B filaments are present in the matrix is formed.

[0012]

The fishing net obtained by the method of the present invention is formed from a high strength fiber-reinforced plastic material in which the polyamide A constitutes a matrix and the polyamide B filaments are present in the matrix. Since the polyamide is more flexible than polyethylene telephthalate and the like, the resulting fishing net is easily wound and easily folded, although it is plastic. Accordingly, the fishing net formed from the plastic net of the present invention is highly strong and rigid in use and can be conveyed as a wound scroll before and after use, thus it has technical effects of being easy to handle. In addition, since the polyamide A is compatible with the polyimide B, the intersections show high strength and the resulting fishing net is very difficult to cut off in use.

EXAMPLES

[0013]

Example 1

A core-sheath type composite filaments having a fineness of about 7.3 dtex with core component : sheath component = 3 : 1 (mass ratio) was prepared from a core component made of polyamide 6 having a melting point of 225 ºC and a sheath component made of polyamide copolymer having a melting point of 155 ºC. Then, 192 core-sheath type composite filaments were bundled to obtain the multifilament yarns of 1,400 dtex/192 filaments. Eight multifilament yarns were paralleled to obtain a yarn thread. Three yarn threads were applied to a twisted knotless net making machine while twisted to obtain a knotless net. The knotless net was introduced into a pin tenter type heat treatment apparatus and subjected to a heat treatment in an atmosphere at 175 ºC for 3 minutes while tension was applied in the width direction of the knotless net. Subsequently, the knotless net was left at a room temperature and cooled to obtain a plastic net. In the plastic net, a diameter of the strand was about 4 mm, a knotless area was about 50 mm<2>, a mesh was square, and an area of the mesh was about 10 cm<2>. A culturing fishing net having a tubular parallelepiped shape was obtained using the plastic net.

[0014]

Example 2

A polyamide core-sheath type composite filaments having the fineness of about 7.3 dtex with core component : sheath component = 3 : 1 (mass ratio) was prepared from a core component made of polyamide 6 having a melting point of 225 ºC and a sheath component made of polyamide copolymer having a melting point of 155 ºC. Then, 192 core-sheath type composite filaments were bundled to obtain the multifilament yarns of 1,400 dtex/192 filaments. Eight multifilament yarns were paralleled to obtain a yarn thread. Three yarn threads were applied to a braid net making machine for braiding to obtain a knotless net having strands and intersections as shown in Fig.2. The knotless net was introduced into a pin tenter type heat treatment apparatus and subjected to a heat treatment in an atmosphere at 175 ºC for 3 minutes while tension was applied in the width direction of the knotless net. Subsequently, the knotless net was left at a room temperature and cooled to obtain a plastic net. In the plastic net, a diameter of the strand was about 4 mm, a knotless area was about 50 mm<2>, a mesh was square, and an area of the mesh was about 10 cm<2>. A culturing fishing net having a tubular parallelepiped shape was obtained using the plastic net, as described in Example 1.

[0015]

Comparative Example 1

A core-sheath type composite filament having the fineness of about 8.7 dtex with core component : sheath component = 3 : 1 (mass ratio) were prepared using a core component made of polyethylene terephthalate having a melting point of 260 ºC and a sheath component made of polyester copolymer having a melting point of 160 ºC. Then, 192 core-sheath type composite filaments were bundled to obtain the multifilament yarns of 1,670 dtex/192 filaments. A plastic net was obtained as generally described in Example 1, with the exception that the resulting multifilament yarns were employed and that the atmospheric temperature during the heat treatment was changed to 180 ºC.

[0016]

Comparative Example 2

A core-sheath type composite filament having the fineness of about 8.7 dtex with core component : sheath component = 3 : 1 (mass ratio) were prepared using a core component made of polyethylene terephthalate having a melting point of 260 ºC and a sheath component made of polyester copolymer having a melting point of 160 ºC. Then, 192 core-sheath type composite filaments were bundled to obtain the multifilament yarns of 1,670 dtex/192 filaments. A plastic net was obtained as generally described in Example 2, with the exception that the resulting multifilament yarns were employed and that the atmospheric temperature during the heat treatment was changed to 180 ºC.

[0017]

Although all the plastic nets obtained by the methods according to Examples 1 and 2 and Comparative Examples 1 and 2 were strong, the plastic nets of Comparative Examples 1 and 2 were hardly wound in comparison with the plastic nets obtained in Examples 1 and 2. This is because the strands and the intersections of the latter plastic nets were made of the fiber-reinforced plastic material in which the matrix was polyester copolymer. That is, the polyester copolymer has poor flexibility compared with polyamide, and is highly compatible with polyethylene terephthalate filament so that the fiber-reinforced plastic material constituting the strands and the intersections is rigid.

[0018]

[Measurement of Intersection Strength]

A test piece consisting a total of 9 meshes, of which 3 meshes are in a longitudinal direction and 3 meshes are in a longitudinal direction, as shown in FIG. 4, was taken from the plastic nets obtained in Example 2 and Comparative Example 2. An intersection surrounded by a mark O in FIG.4 was hooked and pulled in an arrow direction and its strength (intersection strength) was measured when the intersection was broken. An autograph manufactured by Shimadzu Corporation was used as a measuring instrument and the measurement was conducted under a condition of a tensile speed of 10 cm/min. As a result, the plastic net of Example 2 had an intersection strength of 2,572 N, and that of Comparative Example 2 had an intersection strength of 2,096 N.

[0019]

[Measurement of Tensile Strength]

From the plastic nets obtained in Example 2 and Comparative Example 2, a central portion of the strands in a weft direction was cut in parallel to a warp direction to obtain a test piece as shown in FIG.5. The upper and lower ends in FIG.5 were grasped by a chuck and pulled in an arrow direction to measure a strength (tensile strength) when the strand in the warp direction was cut. An autograph manufactured by Shimadzu Corporation was used as a measuring instrument, and a measurement was conducted under conditions of a distance between the chucks of 25 cm and the tensile speed of 30 cm/min. As a result, the plastic net of Example 2 had a tensile strength of 1,904 N, and that of Comparative Example 2 had a tensile strength of 1,713 N.

Claims

WHAT IS CLAIMED IS:

1. A method for manufacturing a fishing net, the method comprising: a step of preparing a multifilament yarn formed by bundling a plurality of core-sheath type composite filaments, wherein a core component is made of polyamide B and a sheath component is made of polyamide A having a melting point lower than the polyamide B, a mass ratio of the core component and the sheath component being core component : sheath component = 1 to 3 : 1, a step of obtaining a net constructed with strands and intersections, using a yarn thread obtained by paralleling a plurality of the multifilament yarns, a step of heat-treating the net to melt the sheath component of the yarn threads constituting the strands and the intersections, followed by solidifying, thus obtaining a plastic net constructed with solidified strands and solidified intersections, in which the core component is existent as an initial fiber form in a matrix formed of the sheath component; and

a step of forming the fishing net using the plastic net.

2. The method according to claim 1, wherein a net is obtained by either twisting a plurality of the yarn threads to obtain a net constructed with strands and intersections, or braiding the plurality of the yarn threads to obtain a net constructed with strands and intersections.

3. The method according to claim 1, wherein the plurality of the yarn threads are twisted when braided.

4. The method according to claim 1 or 2, wherein the heat-treating is conducted without pressure.

5. The method according to claim 1, wherein the intersections are knotless.