JPH10276606A - Net for culturing short-neck clam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a net for culturing short-neck clam, capable of protecting the short-neck clam from waterfowls such as sea gull, aigrette, snipe and cormorant by laying it onto sea bottom on which short-neck clam is cultured, increasing survival rate and harvest yield of short-neck clam. SOLUTION: This net for culturing short-neck clam is obtained by bundling single or plurality of a core-sheath yarn-like material having 0.8-1.2 g/ml, >=2.0 kgf tensile strength and >=0.8 kgf binding strength and comprising a core composed of a monofilament or a multifilament made of a high-melting polymer selected from a polyester, a high-density polyethylene and polypropylene and a sheath composed of a low melting point polymer selected from an ethylene- vinyl acetate copolymer, an ethylene-ethyl acrylate copolymer, a high-pressure low-density polyethylene, a straight-chain low-density ethylene-a-olefin copolymer and a polycaprolactone and lower by >=20 deg.C than the melting point of the high- melting point polymer and to afford warp and weft and thermally melting intersecting points of the warps and wefts in 1.5-2.5 intervals between warps and between wefts.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a clam culture net. More specifically, the aim is to lay clams on the seabed where the clams are cultivated, protect clams from water birds such as seagulls, white herons, shorebirds and cormorants, increase the survival rate of clams, and increase the yield of clams. .

[0002]

2. Description of the Related Art Clams are cultivated in shallow waters of organic plankton and larvae that contain a lot of organic matter such as Tokyo Bay and the Ariake Sea. Shellfish are washed away and the survival rate is very low, so there is a need for improved profitability of clam farming.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a new type of clam cultivation net which satisfies the following conditions required as a clam cultivation net without generating toxic gas during incineration. I do.・ The net has a certain gravity so that it is submerged on the seabed and not washed away by rough currents. -The mesh size must be such that the waterfowl cannot hold the clam larvae through the mesh.・ If the mesh is too small, resistance to ocean current will increase,
The mesh size must be of an appropriate size as it will be washed away or torn. -As the mesh becomes smaller, the amount of core-sheath thread used increases and the cost increases, so the mesh size should be as large as possible. -If the mesh is too small, it blocks out sunlight and hinders the growth of clams.・ To be able to make with low production cost method to reduce net cost.・ Because it may be wet with seawater and exposed to strong direct sunlight, it must have sufficient weather resistance. -If the net is heavy, the work of laying the net on the sea floor + the work of collecting it is difficult, so the specific gravity of the net should not be too heavy.・ The net is made of an inert material that does not allow algae and shells to live on the surface of the net. -The net must have enough tensile strength and binding strength to be not broken by the tensile force during work or the force of the ocean current.・ Do not generate toxic gas when incinerated after use.

[0004]

Means for Solving the Problems The present inventors examined the above-mentioned conditions required for clam cultivation nets, prototyped nets of various mesh sizes with various materials, and performed a clam cultivation test. However, they have found that a net of a specific size made of a core-sheath thread made of a specific material is useful for clam cultivation, and completed the present invention.

SUMMARY OF THE INVENTION Namely, the present invention, the core is polyester, consists of a monofilament or multifilament made of a high melting polymer selected from high density polyethylene and polypropylene, sheath ethylene - vinyl acetate copolymer, ethylene - Ethyl acrylate copolymer, high-pressure low-density polyethylene, linear low-density ethylene-α-olefin copolymer and polycaprolactone, a low-melting polymer whose melting point is 20 ° C. or more lower than the melting point of the high-melting polymer. 1. Composition: 0.8-1.2 g / ml specific gravity, tensile strength 2.
0 kgf or more, a core-sheath thread having a binding strength of 0.8 kgf or more is bundled into a warp and a weft by bundling one or more, and the interval between the warps and the weft is 1.5 to 2.5 cm, The present invention relates to a clam cultivation net whose intersection is heat-sealed.

According to certain preferred embodiments of the present invention,
In the present invention, the core is composed of a polyester multifilament, the sheath is composed of an ethylene-vinyl acetate copolymer containing carbon black, and the specific gravity is 0.8 to 1.2 g / m.
1, tensile strength 2.0kgf or more, binding strength 0.8kg
f or more, two to five core-sheath filaments are arranged in parallel contact with each other to form a warp and a weft, and the core-sheath filaments constituting the warp and the weft are woven with each other at the intersection of the warp and the weft. And the interval between the wefts is 1.5 to 2.5 cm, and at the intersection of the warp and the weft, the weft is sandwiched between a part and the rest of the plurality of core-sheath filaments constituting the warp ( Or, in the opposite state), the heat-sealed net for clam culture.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, polyester is a polymer obtained by condensation polymerization of terephthalic acid or dimethyl terephthalate with diol, and is marketed under the trade names of tetron, ester, terylene, dacron and the like. is there. In addition, biodegradable polyester bioione obtained by condensation polymerization of succinic acid and diol, biodegradable polyester biopolymer obtained by copolymerizing hydroxybutyric acid and hydroxyvaleric acid, lactide from lactic acid and ring-opening polymerization. Lacty, which is a biodegradable polyester, is included in the polyester used in the present invention. The use of a biodegradable polyester has the advantage that disposal costs do not increase because it is gradually biodegraded in seawater.

In the present invention, high-density polyethylene is defined as having a density of 0.95 g / ml or more and a crystallinity of 70 to 85.
%, A polymer obtained by polymerizing ethylene with a melting point of 130 ° C or higher, which is marketed under the trade names such as Shourex, Novatex, Ace Polyethylene HD, Suntech HD, Tonen Polyethylene, Staphrene, Hyzex, Mitsubishi Polyethylene-HD It is.

In the present invention, polypropylene is defined as having a density of 0.90 to 0.91 g / ml and a crystallinity of 70 to 90 g / ml.
% Of propylene with a melting point of 140 ° C or higher. UBE Polypro, Show Allomer, Ace Polypro, Sumitomo Noblen, UP Polypro, Chisso Polypro, Tonen Polypro, Ace Polypro, Tokuyama Polypro,
It is marketed under the trade name of Nisseki Polypro, Hypole, Mitsui Noblen, Mitsubishi Polypro, etc.

In the present invention, the ethylene-vinyl acetate copolymer is defined as having a density of 0.93 to 0.95 g / m 2 when ethylene and vinyl acetate are supplied by a high pressure polyethylene production method.
1, the crystallinity is as low as 30 to 40%, and the melting point is 65 to 95.
C is a low melting point polymer, and NUC copolymer EV
A, Suntech EVA, Shorex EVA, Evatate, Ultracene, Mitsubishi Polyethylene EVA, Evaflex, Nisseki Lexlon EVA, etc. are marketed.

In the present invention, the ethylene-ethyl acrylate copolymer has a density of 0.93 to 0.93 obtained by copolymerizing ethylene and ethyl acrylate by a high-pressure polyethylene production method.
It is a low melting point polymer having a low crystallinity of 30 to 40% at 0.95 g / ml and a melting point of 70 to 100 ° C., and NUC copolymer EEA, Evaflex EEA, Nisseki Lexlon EEA and the like are commercially available.

In the present invention, high-pressure low-density polyethylene refers to a high-pressure of 2000 to 3000 atm.
The density obtained by polymerizing ethylene using a free radical generator as a catalyst at -350 ° C is 0.915-0.925 g / ml.
Is a polymer having a crystallinity of about 40% and a melting point of 100 to 110 ° C., NUC polyethylene, Nisseki Lexlon,
It is marketed by Suntech LD, Idemitsu Polyethylene-L, UBE Polyethylene, Shoralex, Ace Polyethylene LD, Petrocene, Sumikasen, UP Polyethylene, Mirason, Mitsubishi Polyethylene-LD and the like.

In the present invention, linear low-density ethylene-
The α-olefin copolymer is a copolymer obtained by copolymerizing ethylene and butene-1, hexene-1, 4-methylpentene-1, octene-1 or the like with a Ziegler catalyst, a Phillips catalyst, a metallocene catalyst, or the like. 0.88 to 0.94 g
/ Ml, crystallinity 15-70%, melting point 80-123
C., a polymer called LLDPE or VLDPE, NUC polyethylene-L
L, Nackflex, Suntech-LL, Acepoly-LL, Moretec, Showlex-LL, Acepoly-LL, Sumikasen-L, Exelen-V
L, Ralt Zex, Neo Zex, Mitsubishi Poly-L
It is marketed under the trade name such as L.

In the present invention, polycaprolactone is defined as having a melting point of about 6 obtained by ring-opening polymerization of ε-caprolactone.
It is a biodegradable polymer at 0 ° C.
E, Daicel Placcel H and the like.

In the present invention, an inorganic filler having a density of 1.8 g / ml or more and an average particle size of 1 to 20 μm may be added.

Alumina (3.7-3.9), kaolin clay (2.58), carbon black (1.8), silica (2.3), calcium silicate (2.8-2.9),
Diatomaceous earth (1.98 to 2.02), titanium oxide (4.2
6), magnesium hydroxide (2.38), aluminum hydroxide (2.4), sericite (2.75), calcium carbonate (2.7), magnesium carbonate (2.8), talc (2.6) 2.8), feldspar powder (2.5 to 2.6), molybdenum disulfide (4.8), barium sulfate (4.4) and the like. The numbers in parentheses indicate specific gravity. If the density of the inorganic filler is less than 1.8 g / ml, the specific gravity of the polymer does not increase even if it is kneaded with the polymer at the expense of the compounding cost, and the specific gravity of the net formed is less than 0.8 g / ml, The net does not sink to the sea floor and is easily washed away by the ocean current, which is not desirable. Further, if the average particle size of the inorganic filler is less than 1 μm, the inorganic filler is aggregated, and it is difficult to mix the polymer with the polymer.
If it is 0 μm or more, it becomes difficult to produce a core-sheath thread,
Also, the mechanical strength of the formed net is weakened, which is not desirable.

In the present invention, the diameter of the core of the thread-like portion is 0.1 mm.
The range of 1 to 1.0 mm is preferable, and if it is less than 0.1 mm, the mechanical strength of the net becomes weak, and if it is larger than 1.0 mm, the material cost becomes too high and the net cost increases. And undesirable. Also, the weight of the net increases, and the work of laying the net on the seabed is laborious, which is not desirable.

In the present invention, the thickness of the sheath of the filamentous material is 0.1 mm.
It is preferably from 0.5 to 0.5 mm, and if it is less than 0.05 mm, the adhesive strength at the intersection of the warp and the weft becomes weak when the filamentous material is heat-sealed, and the net is easily broken in the sea, which is not desirable. On the other hand, if it is larger than 0.5 mm, the weight of the net increases, and the work of laying the net on the seabed is laborious, which is not desirable. The diameter of the core-sheath thread is preferably 0.2 to 2.0 mm. If it is less than 0.2 mm, the mechanical strength is not sufficient, and if it exceeds 2.0 mm, the cost increases, the workability deteriorates, and the resistance to the ocean current increases, which is not desirable.

The average specific gravity of the net of the present invention is 0.8 to 1.2 g.
/ Ml. If it is less than 0.8 g / ml, the net becomes too light, does not sink to the seabed, and is easily washed away by the ocean current, which is not desirable. When it exceeds 1.2 g / ml, the weight of the net increases, and the work of laying the net on the seabed becomes difficult, which is not desirable.

The core-sheath filament of the present invention is produced by the following two methods. First method : A polymer for a core with or without blending an inorganic filler having a density of 1.8 g / ml or more and an average particle size of 1 to 20 μm with a high melting point polymer selected from polyester, high density polyethylene and polypropylene. Make up the composition. When 100 parts by weight of the high melting point polymer is blended with the inorganic filler, the amount is less than 100 parts by weight, preferably less than 50 parts by weight. If the amount is more than 100 parts by weight, spinning becomes difficult, and the mechanical strength of the produced filamentous material becomes weak, which is not desirable. Since high-density polyethylene and polypropylene have low specific gravities, it is desirable to mix inorganic fillers with high specific gravities as much as possible as long as the mechanical strength is not weakened. 23. The polymer composition for core
The melt spinning is performed at a temperature of 0 to 300 ° C. Spinning temperature is 23
If the temperature is lower than 0 ° C., it is difficult to extrude the melt. If the temperature is higher than 300 ° C., the polymer is decomposed, and the mechanical strength of the thread is undesirably weak. The melt-spun monofilament is stretched in a heating medium such as hot air or heated water, glycerin, ethylene glycol, silicone oil or the like after water cooling, once wound up or without being wound up.
Stretching conditions such as stretching temperature and stretching ratio are 60 to 110 ° C.
It is appropriate that the film is stretched 3 to 17 times at a moderate temperature. In addition, it is preferable to perform stretching in two or more stages, and in one-stage stretching, it is difficult to stretch sufficiently, and it is difficult to obtain a high-strength monofilament. The drawn monofilament is then subjected to a relaxation heat treatment in an atmosphere at a temperature of 50 to 110 ° C. The relaxation rate at this time is suitably from 1 to 5%.

In the present invention, the core thread may be constituted by a single monofilament or a multifilament by bundling a plurality of monofilaments. The filament for the core prepared as described above was placed in a head of a polymer composition extruder for a sheath with a nipple of 20 to 200 m.
Per minute, and the ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, high-pressure low-density polyethylene, linear low-density ethylene-α-olefin copolymer A low melting polymer selected from coalesced and polycaprolactone has a density of 1.8.
g / ml or more of an inorganic filler having an average particle size of 1 to 20 μm is blended with or without the blending.
Coating at a temperature of 〜230 ° C. to a thickness of 0.05-0.5 mm to form a core-sheath thread.

The core-sheath thread must have a tensile strength and a binding strength of 2.0 kgf or more and 0.8 kgf or more, respectively. The tensile strength is the strength at which the core-sheath thread-like material is sandwiched between upper and lower locations by a chuck and is broken when pulled vertically. If the strength is less than 2.0 kgf, the net may be broken at the time of burying the net on the sea floor or by an ocean current, and the object of the present invention may not be achieved.
kgf or more is required. Further, the binding strength is such that the core-sheath thread-like material is made into a warp and a weft, and in the net of the present invention which is made by heat-welding the intersection, one of the warps forming the intersection and one of the wefts are respectively chucked. Scissors are the strengths at which the intersections that are heat welded when each is pulled break. If the bonding strength is less than 0.8 kgf, the net will be damaged during the work of laying the net on the sea floor or by the ocean current, and the object of the present invention cannot be achieved.
The above is necessary.

This core-sheath thread is singly crossed as a warp and a weft, and the intersection is thermally fused at a temperature of 60 to 130 ° C. to obtain a net for clam culture. The spacing between the warps and the wefts is preferably between 1.5 and 2.5 cm. A plurality of the core-sheath filaments may be contacted and arranged in parallel to form a warp and / or a weft. The core-sheath thread may be wound into a single warp or weft by winding a plurality of threads. The plurality of warps or wefts may be thermally welded to each other. Further, at the intersection of the warp and the weft, heat fusion is performed in a state where the weft is sandwiched between a part and the rest of the plurality of core-sheath filaments constituting the warp or vice versa. You may.

Second Method : The core polymer composition and the sheath polymer composition prepared in the first method are put into separate extruders, and the core polymer composition is heated to 230 to 300 ° C.
The polymer composition for a sheath is supplied to the core-sheath extrusion die at a temperature of 130 to 230 ° C. at a temperature of to produce a core-sheath filament.
Using this core-sheath filament, a net for clam cultivation is produced in the same manner as in the “first method”.

The net for clam cultivation of the present invention is produced by using the core-sheath filaments prepared by the above method as warps and wefts, and by plain weaving, twill weaving, satin weaving, leno weaving, Russell weaving and the like. The intersection of the mesh is heated and fused at 80 to 150 ° C. so that no meshing occurs. In the present invention, the reason for limiting the melting point of the sheath polymer to a temperature lower by at least 20 ° C. than that of the core high melting point polymer is that if the temperature of the heat fusion for net processing is too high, the tensile strength of the net is lowered, which is undesirable. It is. The clam cultivation net of the present invention can have any shape and area by heat fusion or sewing. It is desirable that the edge of the clam cultivation net of the present invention be sewn back or heat-sealed, or reinforced with a sewing tape or a fusion tape. In addition, it is desirable to attach a “hatome” to each side of the edge of the clam culture net of the present invention.
Attach a “weight” to the “Hatome” with ropes or plastic parts so that the clam cultivation net is fixed to the sea floor and is not washed away by the current.

[0026]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples.

Example 1 Molecular weight 70,000, melting point 260 ° C., density 1.38 g /
ml of polyester as a raw material, is spun by a usual melt spinning machine and stretched to obtain a single yarn denier 1
A polyester multifilament yarn of 0.4 denier, 96 filaments and a total fineness of 500 denier (0.3 mm in diameter) was prepared as a core thread. Density 0.940g / m
1, melt index 3 g / 10 min, vinyl acetate content 18%, melting point 83 ° C. 100 parts by weight of an ethylene-vinyl acetate copolymer, 5 parts by weight of carbon black having a density of 1.8 g / ml, A composition was prepared. The filament for the core is run at a speed of 100 m / min, and the polymer composition for the sheath is coated on the surface thereof with a die of a 30 mm extruder.
It was coated at 0 ° C. to a thickness of 0.1 mm to obtain a core-sheath thread having a diameter of 0.5 mm and an average density of 0.97 g / ml. The core-sheath thread was used as a warp and a weft to form a net by plain weaving, and the intersection was heat-sealed with a hot press to obtain a clam culture net (10 mx 30 m) with a mesh interval of 2 cm. The tensile strength of this net is 8.
The weight was 10 kgf and the binding strength was 1.99 kgf. The periphery of this net is made by folding a 10 cm wide polyester band in half in parallel to the longitudinal direction, wrapping it from above and below, sewing it, and attaching a 1 cm diameter metal "hatome" every 1 m. A 1kg "weight" was attached to each "Hatome" with a rope, and clams were sown in November in shallow waters of Tokyo Bay. Five months later, the clam survival rate was 97% surviving. On the other hand, the survival rate of the clam in a place where the clam culture net was not used was 27%.

Comparative Example 1 An experiment was performed in the same manner as in Example 1 except that a vinyl chloride polymer was used instead of the ethylene-vinyl acetate copolymer. Although the clam survival rate was as good as in Example 1, when the collected net was incinerated, chlorine-based harmful gas was generated.

In the present invention, the tensile test was performed as shown in FIG.
As shown in FIG. 2, the binding test was performed as shown in FIG. First, the tensile strength is determined by wrapping cellophane tapes 4 and 5 around the upper end 2 and lower end 3 of the core-sheath thread 1 and sandwiching them with the chucks 6 and 7, respectively. As shown by the circle, it is the strength when breaking. Further, the binding strength is such that the core-sheath thread-like material 11 is made into a warp 12 and a weft 13 and the intersection 14 is formed by heat welding, and the upper end of the warp 12 forming the intersection 14 and the weft The cellophane tapes 17 and 18 are wound around each of the right end portions of 13, sandwiched between the chucks 19 and 20, and the intersections 14 that are heat-welded when each is pulled, as shown by the broken line, have a strength at the time of breaking. is there.

Example 2 Density 0.90 g / ml, melt flow rate 3 g / 10
100 parts by weight of polypropylene having a melting point of 162 ° C., 5 parts by weight of carbon black having a density of 1.8 g / ml, a density of 2.7 g / ml, and calcium carbonate 50 having an average particle size of 2 μm.
By weight, the core polymer composition was prepared. On the other hand, the density is 0.93 g / ml and the melt index is 2 g / ml.
10 minutes, 100 parts by weight of ethylene-hexene-1 copolymer having a melting point of 121 ° C., 5 parts by weight of carbon black having a density of 1.8 g / ml, 50 parts by weight of talc having a density of 2.7 g / ml and an average particle diameter of 3 μm. And a sheath polymer composition was prepared. The core polymer composition was supplied at a temperature of 250 ° C. to the sheath polymer composition at a temperature of 180 ° C. from an extruder to a core-sheath extrusion die, and a core having a diameter of 1.0 mm and a thickness of 0.5 mm were supplied.
2 mm diameter, average density 1.20 g / m
1 core-sheath thread was obtained. Three core-sheath filaments are arranged side by side to form a warp and a weft, and at the intersection, each core-sheath filament is in a plain weave state. 3cm clam culture net (10
mx 30 m). The tensile strength of the net is 13.8kg
f, the binding strength was 2.3 kgf. The periphery of this net was sandwiched between the top and bottom with a film of ethylene-vinyl acetate copolymer having a width of 5 cm and a thickness of 0.3 mm, and heat-sealed.
For every 1m, attach a metal "Hatome" of 1cm,
A 1kg "weight" was attached to each "Hatome" with a rope, and in November, in a shallow water of Tokyo Bay, clams were sown with juvenile clams and fixed. Five months later, a survey of the clam production rate revealed that 94% had survived. On the other hand, the survival rate of clams in a place where no clam culture net was used was 25%.

Comparative Example 2 Example 2 was repeated except that high-density polyethylene having a melting point of 132 ° C. and a density of 0.958 g / ml and a melt flow rate of 0.8 g / 10 min was used instead of polypropylene having a melting point of 162 ° C. The same experiment as in Example 2 was performed. This net has a tensile strength of 1.6 kgf and a binding strength of 0.6 kgf.
And the mechanical strength of the net was weak, which was not desirable.

Comparative Example 3 An experiment was performed in the same manner as in Example 1 except that the diameter of the core thread made of polyester was changed to 0.09 mm. The tensile strength of this net is 1.98 kgf, the binding strength is 0.7 kgf, and the mechanical strength of the net is weak.
Not desirable.

Comparative Example 4 An experiment was conducted in the same manner as in Example 1 except that the diameter of the core thread made of polyester was changed to 1.1 mm. The mechanical strength of the net was sufficient, but when the cost was calculated, the net cost increased, which was not desirable.
In addition, the weight of the net increases, and the workability deteriorates, which is not desirable.

Comparative Example 5 The same experiment as in Example 1 was performed except that the thickness of the sheath was changed to 0.04 mm. The tensile strength of the net was 7.5 kgf and the binding strength was 0.7 kgf, which was undesired because it was broken during the work of laying the net on the sea floor or broken by the ocean current.

Comparative Example 6 The same experiment as in Example 1 was carried out except that the thickness of the sheath was changed to 1.0 mm. Although the mechanical strength of the net was sufficient, the work of laying the net on the seabed was laborious and undesirable.

Comparative Example 7 The same experiment as in Example 1 was performed except that the diameter of the core was changed to 0.1 mm and the thickness of the sheath was changed to 0.04 mm. The diameter of the core-sheath thread was 0.18 mm, and the mechanical strength was insufficient, which was not desirable.

Comparative Example 8 The same experiment as in Example 1 was performed except that the diameter of the core was changed to 1.0 mm and the thickness of the sheath was changed to 0.6 mm. The diameter of the core-sheath thread was 2.2 mm, which increased the cost and made the net difficult to handle, which was not desirable.

Comparative Example 9 The same experiment as in Example 2 was performed except that the mesh interval was changed to 1.0 mm. Increasing net costs, increasing resistance to ocean currents, dragging weights, shifting net positions, increasing shading rates and decreasing clam survival rates were undesirable.

Comparative Example 10 In Example 2, except that the mesh interval was 3 mm.
The same experiment as in Example 2 was performed. Clams were eaten significantly by waterfowl, and survival was reduced to 12%, which was undesirable.

Comparative Example 11 In Example 1, the structure of the monofilament constituting the polyester multifilament yarn was changed from a normal circular cross section to a star shape, the space was increased, and the average density was 0.7 g / ml. The same experiment as in Example 1 was performed, except that a core-sheath thread was obtained, and this was changed. Although this net could be forced to sink under the seafloor with its weight, the current caused strong buoyancy and the area around the net was damaged, which was not desirable.

Comparative Example 12 The same experiment as in Example 2 was conducted except that calcium carbonate having a density of 2.7 g / ml was replaced with barium sulfate having a density of 4.4 g / ml. With this, the average density of the obtained core-sheath thread is 1.35 g / ml,
The net made with this was heavy and poor in workability, which was not desirable.

[0042]

According to the present invention, since a core-sheath thread having a high-melting polymer as a core and a low-melting polymer as a sheath is used, a net can be formed by heat fusion, so that the production cost is low or the specific gravity is low. A heavy inorganic filler is blended and the specific gravity of the net can be adjusted. In addition, since the mesh size is in a specific range, there is an effect of eliminating clam damage from water birds, and the cost is reduced. Further, since the sizes of the warp and the weft are in a specific range, the cost is low and the strength is sufficient. In addition, there is an advantage that no harmful gas is generated even if the recovered net is incinerated. In a particularly preferred embodiment of the present invention (claim 2), the core is made of a polyester multifilament having the highest tensile strength, and the sheath is made of an ethylene-vinyl acetate copolymer having a strong adhesive strength. Two to five core-sheath filaments are arranged in parallel with each other (including the case of heat welding) and woven mutually at the intersection of the warp and the weft, and at the intersection of the warp and the weft, a plurality of warp yarns are formed. Since the weft is heat-sealed between a part of the core-sheath thread and the rest of the book (or vice versa), the net has a strong current and The effect of achieving the purpose is remarkable without being broken even by strong various stresses. Moreover, since the sheath contains Cargin Black, it has the effect of withstanding strong direct sunlight on the shore.

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating a tensile test method for measuring the tensile strength of a clam culture net according to the present invention.

FIG. 2 is a view schematically showing a binding test method for measuring the binding strength of the clam culture net of the present invention.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takehiko Nagano 3-14-13 Hoshikawa, Hodogaya-ku, Yokohama, Kanagawa

Claims (2)

[Claims] 1. A core comprising a monofilament or a multifilament made of a high-melting polymer selected from polyester, high-density polyethylene and polypropylene, and a sheath comprising ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, High-pressure low-density polyethylene, a low-melting polymer having a melting point selected from a linear low-density ethylene-α-olefin copolymer and polycaprolactone at least 20 ° C. lower than the melting point of the high-melting polymer, and a specific gravity of 0.8 ~ 1.2g / ml, tensile strength 2.0k
gf or more, a bundle of one or more core-sheath filaments having a binding strength of 0.8 kgf or more is used as a warp and a weft, and the interval between the warps and between the wefts is 1.5 to 2.5 cm. Clam cultivation net where the intersection is heat-sealed. 2. An ethylene-containing core comprising a polyester multifilament and a sheath comprising carbon black.
Consists of vinyl acetate copolymer, specific gravity 0.8-1.2 g
/ Ml, tensile strength 2.0 kgf or more, binding strength 0.8
The core-sheath filamentous material of not less than kgf
Five warp yarns and weft yarns are arranged side by side, and the core-sheath yarns constituting the warp yarns and the weft yarns are woven with each other at the intersections of the warp yarns and the weft yarns.
At the intersection of the warp and the weft, with the weft sandwiched between a part and the rest of the plurality of core-sheath filaments forming the warp (or vice versa) A clam culture net being worn.