JPS648978B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a fishing net with low specific gravity, high buoyancy, and excellent knot strength, impact resistance, elastic recovery, flexibility, etc., and particularly to a fishing net suitable for bottom gillnets. Among fishing nets, gillnets are used to select the target fish's swimming layer and set it in such a way as to block it, and catch the fish by making them stick or reel in the net. There are nets etc. Conventionally, fishing nets for this type of gillnet were operated by using a large number of floats or adjusting the number of sinkers in order to improve the tension of the net according to the topography of the seabed. The floats and sinkers had to be adjusted depending on the waves, making it difficult to secure an appropriate operating position, and depending on the conditions, the coverage rate was low. Therefore, in order to improve the operability when setting fishing nets in general, for example, resins with high specific gravity such as polyvinylidene chloride filament are used, lead containing high specific gravity is added to the filament, and resins containing inorganic substances are used. Improvements such as coating have been made. However, when using such high-density fishing nets for bottom gillnets, especially in areas where there are many obstacles such as rocks, algae, and ship debris, and where the shape of the sea bed varies, the net There were operational problems, such as the net becoming sagging, getting entangled in obstacles and damaging the net, and eventually having to be abandoned. In order to solve the above-mentioned operational problems of bottom gillnets, the present inventors conducted various experiments regarding the specific gravity of nets, and as a result, the net specific gravity for bottom gillnets was 0.84 or less, especially
It has been found that a material with a low specific gravity of about 0.6 to 0.8 is preferable. Conventionally, filaments of polypropylene, polyethylene, etc. have been used in such low specific gravity fishing nets, and depending on the application, it has been put into practical use to make them into hollow monofilaments with even lower specific gravity. However, fishing nets made of these materials have the drawbacks of low strength, poor impact resistance, and poor elastic recovery. On the other hand, fishing nets made of nylon filament
It is widely used in the field of gillnets due to its strength, impact resistance, elastic recovery, and excellent netting properties.
In terms of specific gravity, it was not suitable for the aforementioned bottom gill net, and it was necessary to further reduce the specific gravity. It is possible to reduce the specific gravity of this nylon filament by using a hollow monofilament, and as the degree of hollowness increases, the apparent specific gravity gradually decreases, but in this case, as the degree of hollowness increases, the strength also decreases at the same time. It is known that when the diameter of the hollow part becomes 1/2 or more of the outer diameter of the filament, that is, the degree of hollowness becomes 0.25 or more, the strength decreases particularly significantly (Special Publication No. 51-24426). was low, at most 0.25 or less. However, in order to obtain a mesh specific gravity of, for example, 0.8 suitable for the aforementioned bottom gillnet, it is necessary that the hollowness of the hollow monofilament be approximately 0.3.
However, in the case of hollow nylon monofilament with a fineness of 1000 deniers or more, which is normally used for fishing nets, if the hollowness exceeds 0.2, the knot strength decreases by 15 to 30% compared to solid nylon monofilament; Hollowness is 0.20 for over 2000 denier
If the net weight exceeds this value, it is difficult from the viewpoint of production technology and physical properties, and a fishing net that can be used as a fishing net has not yet been obtained. In view of these circumstances, the present invention aims to solve the above problems and provides a fishing net with low specific gravity while retaining the excellent properties of nylon such as strength, impact resistance, elastic recovery, and flexibility. . That is, in the present invention, the fiber has continuous hollows in the longitudinal direction, the hollowness (H) is 0.26≦H≦0.45, and the fineness is 100 to 100.
500 denier and knot strength of 3.5g/d
It is characterized by using a net yarn made by aligning a plurality of the polyamide hollow monofilaments mentioned above or by subjecting them to gentle twisting. The polyamide in the present invention is a polyamide that has the ability to form fibers that can be melt-spun, such as nylon 6, nylon
66, nylon 6 and 10, and their copolymers, braided polymers, and the like. The polyamide hollow monofilament used in the present invention has a hollowness degree (H) of 0.26≦H≦0.45.
is within the range of Here, the degree of hollowness is defined by the composition ratio a/a+b of the cross-sectional area (a) of the hollow portion and the cross-sectional area (b) of the resin portion. If the hollowness (H) is less than 0.26, the apparent specific gravity is
If it exceeds 0.85, the required low specific gravity cannot be obtained, and if it exceeds 0.45, the knot strength of the hollow monofilament will drop significantly, which is not preferable.
Such hollow monofilaments can be produced, for example, by spinning using a coextrusion die while injecting air depending on the required degree of hollowness, or by flattening a molten polymer through a circular slit as shown in Figure 1. It is produced by extruding several fibers, fusing them while incorporating air, spinning them, and then stretching them at the required stretching ratio. FIG. 2 is a cross-sectional view of a hollow monofilament made using the slit shown in FIG. In this case, by adjusting the dimensions of the slits and the number of slits, the degree of hollowness and the cross-sectional shape can be changed as appropriate. Further, the hollow monofilament has a fineness of
It must be between 100 and 500 denier. If the fineness is less than 100 denier, the strength per single thread is low, and when used as a fishing net, there will be many breaks due to fish grinding, while if the fineness exceeds 500 denier, the knot strength will decrease, and it is usually used for bottom gill nets. It is not suitable because the knot strength (3.5 g/d) required for the thread cannot be obtained. That is, in the present invention, it is necessary to increase the degree of hollowness in order to lower the apparent specific gravity, but as a result, the outer diameter of the obtained monofilament becomes significantly large. Fineness of diameter 0.4mm and inner diameter 0.26mm is 744
Equivalent to denier. Considering that this outer diameter of 0.4 mm corresponds to 1288 denier in the case of a solid monofilament, it can be seen how large the apparent diameter of the hollow monofilament is. Therefore, when obtaining a monofilament that satisfies the apparent specific gravity of about 0.6 to 0.8 of the bottom gillnet fabric, which is the objective of the present invention, by a normal spinning method, the larger the fineness, the more
The strain that occurs during cooling in the cross-sectional direction of the fiber remains, and it is extremely difficult to eliminate it.
As is clear from Japanese Patent Publication No. 51-2442626, a skin-core structure occurs due to non-uniformity during cooling, and this is because the degree of orientation and crystallinity differ between the outer layer and the inner layer of the filament. , this structural difference causes a decrease in nodule strength. the result,
In order to suppress structural differences during cooling as much as possible, it is necessary to limit the fineness of the monofilament, and with this in mind, the range of 100 to 500 deniers was set. Next, when the hollow monofilament is used, a plurality of the hollow monofilaments are arranged together, or if necessary, the hollow monofilament is further intertwined or twisted to form a net yarn. In this case, the number of hollow monofilaments can be appropriately selected depending on the type of fishing net to be obtained, but usually 4 to 12 are used. In addition, when twisting, a gentle twist of 100 T/M or less is generally sufficient, and if the number of twists is too large, it is not preferable because the flexibility will be lost and the fish will not be able to enjoy it. The net yarn thus obtained is knitted into the fishing net of the present invention in the same manner as in the case of natural or synthetic fibers according to known techniques. The thus knitted fishing net of the present invention is not only suitable for fishing nets, especially bottom gill nets, but can also be used for bird prevention nets and the like which are floated on the water surface. The effect of the hollow monofilament fishing net of the present invention having the above structure is that the hollowness of the monofilament is increased to 0.26 to 0.45, so the apparent specific gravity is 0.63 to 0.84, which is lower than that of conventional fishing nets. Therefore, it not only has high buoyancy and requires less adjustment of floats and sinkers, but also has no sagging bottom and has good tension and net structure, making it possible to operate gillnets in areas with many obstacles that are considered to be a treasure trove of fish. can be significantly improved. Furthermore, since the fishing net of the present invention is composed of hollow monofilaments with a relatively low denier of 100 to 500 deniers, it is easier to manufacture than hollow monofilaments with a high denier. By using a plurality of these yarns to make a fishing net, a fishing net with higher knot strength than a net yarn using a single solid monofilament of equivalent fineness and a high hooking strength can be obtained. Since it is made by pulling the books together or twisting them gently, it has the advantage of being able to utilize the attraction of a single hollow monofilament to the fish. Furthermore, the fishing net of the present invention retains the properties of polyamide such as excellent transparency, flexibility, knot fixation, and net shape.
It goes without saying that it is practical in the field of paper nets, and is particularly suitable for use in bottom gill nets. The present invention will be explained in more detail below with reference to Examples. Example Using a 6-chip nylon with a sulfuric acid viscosity of 3.4, a 30-hole nozzle with a normal circular spinning hole and a slit as shown in Figure 1 was used, and the degree of hollowness was varied and the temperature
After melt spinning at 250 to 270℃, cooling with 10℃ water, stretching 5.3 times with 90℃ hot water and a 200℃ heater to obtain two fibers with target finenesses of 350 denier and 450 denier.
Solid monofilaments and hollow monofilaments with different degrees of hollowness were made for each species. The degree of hollowness of the hollow monofilament was changed by using different nozzles of the slit dimension.
An example of the dimension of the slits is that the slit width is 0.21 mm, the width between the slits is 0.1 mm, and the outside diameter of the slits is 1.68 mm (for sample number 8 in Table 1). Furthermore, for comparison, the target fineness was 1100.
Solid and hollow monofilaments of denier, 2000 denier and 2640 denier were made. The results of measuring the physical properties of these monofilaments are shown in Tables 1 and 2.

【table】

[Table] In both of the above tables, "hollowness" refers to a cross-sectional photograph of a hollow monofilament (approximately 60x magnification), the hollow part and the resin part are cut out, and the weight of the hollow part (a) and the weight of the resin part are calculated. (b) was measured and shown as the value of a/a+b. The "apparent specific gravity" is calculated using the following formula 1.140 (1-a/a+b) in the case of a hollow monofilament, assuming that the specific gravity of a solid nylon monofilament is 1.140. "Nodule strength" was measured according to JISL1070. The "knot strength retention rate" is expressed as the knot strength of hollow monofilament/knot strength of solid monofilament x 100. As is clear from Table 1, the hollowness is 0.26 when the target fineness is 350 denier or 450 denier.
If the hollowness is less than 0.84, the desired low specific gravity cannot be obtained, and if the hollowness exceeds 0.45, the nodule strength will be extremely reduced. On the other hand, when the target fineness is 1,000 denier or more, as shown in Table 2, a hollow monofilament with a target fineness of 1,000 denier cannot satisfy the knot strength unless the hollowness is 0.25 or less. In the case of 2000 deniers or more, it is difficult to increase the degree of hollowness in terms of manufacturing, and therefore the degree of hollowness becomes small, making it impossible to obtain a hollow monofilament with a low specific gravity. On the other hand, the hollow monofilament in the fineness range of the present invention can have a required low specific gravity within the hollowness range of the present invention, and has a knot strength retention rate of 85 to 95%. It had satisfactory knot strength. Next, the fineness of 330 denier and hollowness as shown in Table 1 above.
7 of hollow monofilament of 0.31 (sample number 4)
6 hollow monofilaments with a fineness of 435 denier and a hollowness of 0.45 (sample number 9).
Three types of net threads were made with a twist of 60T/M, and these threads were used to make fishing nets with a mesh size of 160 mm using double frog knots. On the other hand, for comparison, a fishing net with a similar fabric was made using a single solid monofilament net yarn of the same target fineness. The results of measuring the physical properties of these net yarns and fabrics are shown in Table 3.

【table】

[Table] In Table 3, "knot strength" (for twisted yarn) was measured according to JIS L1034. "Hook strength" (first stitch diagonal direction) was measured according to JIS L1043. The "reversal rate" is a measure of the misalignment of the mesh knots and is calculated from the following formula. Reversal rate (%) = Strength when turning knots with strong net hooking / Strength when cutting knots with strong net hooking x 10
0 As is clear from Table 3, the knot strength of the hollow monofilament yarn of the present invention is 6 to 8% higher than that of the conventional net yarn made of a single solid monofilament in the required low specific gravity range. Moreover, the hooking strength of the net fabric obtained from it is 15 to 20% higher than that of the net fabric obtained from a single solid monofilament yarn, and the reversal rate is also about 20% higher. It was hot.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an example of a spinning hole used for spinning a hollow monofilament in a fishing net of the present invention, and FIG. 2 is a cross-sectional view of a hollow monofilament produced by the same nozzle. 1...Slit, 2...Hollow part, 3...Resin part.

Claims (1)

[Claims] 1 The fibers have continuous hollow holes in the longitudinal direction, with a hollowness (H) of 0.26≦H≦0.45 and a fineness of 100 to 500.
A hollow monofilament fishing net characterized by using net yarn made by aligning or gently twisting a plurality of polyamide hollow monofilaments that are denier and have a knot strength of 3.5 g/d or more. .