JPH08151634A - High-strength net body - Google Patents

Abstract

PURPOSE: To maintain the excellent tensile strength of warps and wefts made of uniaxially oriented polypropylene or ultra-polymer polyethylene core tapes and firmly high-frequency-weld intersection portions of the warps and wefts. CONSTITUTION: One or two or more core tapes made of uniaxially oriented polypropylene or ultra-polymer polyethylene are overlapped, and a thermoplastic resin having a high dielectric constant is extrusion-applied or integrally laminated on the periphery or on both the upper and lower faces to form a film tape for use as a warp 1 and a weft 2. The warps 1 and wefts 2 are intersected together at prescribed intervals, and intersection portions are high-frequency- welded. The thermoplastic resin having a high dielectric constant is dielectrically heated and firmly welded, however the core tape made of polypropylene or ultra-polymer polyethylene having a low dielectric constant is hardly dielectrically heated, the intersection portions are hardly deteriorated by heat, and the primary excellent tensile strength is maintained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground for reinforcing roads, land for construction, etc., or as a net for civil engineering to be buried in the ground to prevent subsidence of an embankment on soft ground, or for packing luggage, etc. The present invention relates to a high-strength net body which is preferably used as a net or a net for reinforcing a bed.

[0002]

2. Description of the Related Art Various types of high-strength nets made of synthetic resin have been developed and proposed for use as civil engineering nets, and the applicant of the present invention has developed a uniaxially stretched synthetic resin tape as warp yarns. As a weft thread, a high-strength net body has been already proposed, in which these are crossed with each other at a predetermined interval and the respective intersections are fused (Japanese Patent Application No. 1-32382).

This high-strength net body has various advantages such as high tensile strength, resistance to collapse, moderate flexibility and rigidity, and easy handling and manufacturing. However, when a polypropylene tape or an ultra high molecular weight polyethylene tape is used as the synthetic resin tape, there are the following problems.

[0004]

That is, a uniaxially stretched polypropylene tape or ultra-high molecular weight polyethylene tape has extremely high tensile strength. However, when this is used as a warp and a weft, for example, ultrasonic fusion at the intersection point, Since the fused portion deteriorates and the tensile strength decreases significantly,
There is a problem that it is not easy to obtain a satisfactory high-strength net. Further, these polypropylene tapes and ultra-high molecular weight polyethylene tapes have another problem that the intersections cannot be welded by high frequency.

The present invention has been made in view of the above problems, and an object of the present invention is to substantially avoid impairing the excellent tensile strength of uniaxially stretched polypropylene tapes and ultra-high molecular weight polyethylene tapes, and at the intersection points. It is to provide a high-strength net body capable of firmly welding a high frequency.

[0006]

In order to achieve the above object, the high-strength net body according to the first invention has a dielectric constant around the core tape made of uniaxially stretched polypropylene or ultra-high molecular polyethylene or both upper and lower surfaces. The present invention is characterized in that a covering tape obtained by extrusion coating or integrally laminating a high thermoplastic resin is used as warp yarns and weft yarns, these warp yarns and weft yarns are crossed with each other at predetermined intervals, and the respective intersections are high-frequency welded. .

In the high-strength net body according to the second aspect of the present invention, a plurality of core tapes made of uniaxially stretched polypropylene or ultra-high molecular weight polyethylene are stacked, and the periphery thereof is extrusion-coated with a thermoplastic resin having a high dielectric constant. It is characterized in that the covering tape is a warp yarn and a weft yarn, these warp yarns and weft yarns are crossed with each other at a predetermined interval, and the respective intersections are high-frequency welded.

Preferably, the core tape of these high-strength nets has a draw ratio of 5 to 20 and a thickness of 0.
Using a tape having a width of 05 to 1.0 mm and a width of 5 to 20 mm, a thermoplastic resin for coating is an ethylene-vinyl acetate copolymer or a vinyl chloride resin, and particularly preferably a vinyl acetate content of 5 to 35% by weight. It is coated to a thickness of 0.1 mm or more using the ethylene-vinyl acetate copolymer.

[0009]

The warp yarn and the weft yarn used in the high-strength net body of the first invention are extrusion-coated or laminated integrally with a thermoplastic resin having a high dielectric constant around or on both upper and lower sides of a core tape made of uniaxially stretched polypropylene or ultra-high molecular polyethylene. The warp yarn and weft yarn used in the high-strength net body of the second invention are also coated tapes, and a plurality of core tapes made of uniaxially stretched polypropylene or ultra-high molecular polyethylene are stacked, and a thermoplastic resin having a high dielectric constant is provided around the core tape. Since it is a coated tape that is extrusion coated with resin, when a high-frequency electric field is applied to the intersection of the warp and weft threads, the thermoplastic resin with a high dielectric constant undergoes molecular strain and friction, and is rapidly dielectrically heated and firmly welded. It At this time, since the core tape made of polypropylene or ultra-high molecular weight polyethylene having a low dielectric constant is hard to be dielectrically heated, the intersection portion thereof is hardly deteriorated by heat. Therefore, since the mesh bodies of the first invention and the second invention both maintain the excellent tensile strength of the polypropylene or ultra-high molecular weight polyethylene core tape in which the warp yarns and the weft yarns are uniaxially stretched, the strength is extremely high. Since it is large and the welding strength at the intersection of the warp yarn and the weft yarn is large, there is no fear of causing collapse or the like.

Particularly, as a core tape, the draw ratio is 5 to 2
0 times, thickness 0.05-1.0mm, width 5-20m
If m is used, a net body having extremely high tensile strength and good handleability can be obtained. Core tapes having a draw ratio of less than 5 times do not significantly improve the tensile strength due to molecular orientation, and core tapes having a draw ratio of more than 20 times show a decrease in the tensile strength due to fibrillation. Absent. Also, the draw ratio is 5
Even at ~ 20 times, the thickness is thinner than 0.05mm and the width is 5
Core tapes narrower than mm tend to lack absolute strength, but core tapes with a thickness of more than 1 mm and a width of more than 20 mm have high rigidity and poor winding and handling. It is also not preferable because it tends to occur.

On the other hand, when an ethylene-vinyl acetate copolymer or a vinyl chloride resin is used as the thermoplastic resin for coating, the high frequency weldability is good, and therefore the core tape is not damaged under mild welding conditions at the intersection point. Can be firmly welded. In particular, the ethylene-vinyl acetate copolymer containing vinyl acetate in an amount of 5 to 35% by weight has a higher high-frequency weldability as the vinyl acetate content increases, and has a melting point of 1%.
Since the temperature is as low as 40 ° C. or lower, there is no fear of damaging the core tape with heat when coating the core tape. If the content of vinyl acetate is less than 5% by weight, the high frequency weldability tends to be considerably deteriorated, and if it exceeds 35% by weight, the strength of the coating film tends to be insufficient, and thus both are not preferable. If the coating thickness of the thermoplastic resin is less than 0.1 mm, the high frequency welding strength at the intersection of the warp yarn and the weft yarn becomes insufficient, and when a large hooking force acts on the net, the intersection portion peels off and collapses. Since it may occur, it is preferable to set the coating thickness to 0.1 mm or more.

Further, when a plurality of core tapes are piled up and a surrounding tape is covered with a thermoplastic resin as warp yarns and weft yarns like the net of the second invention, the tensile strength is changed by changing the number of the core tapes piled up. Can be easily increased or decreased and the rigidity is lower in the case of stacking a plurality of core tapes than in the case of using one core tape of the total thickness, so that the tensile strength is substantially the same. Nevertheless, there is an advantage that the winding property and handleability are improved.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a partial perspective view showing an embodiment of the high-strength net body according to the first invention, and FIG. 2 is an enlarged cross-sectional view of warp threads or weft threads constituting the net body of the same embodiment.

In the high-strength net A of this embodiment, the warp yarns 1 and the weft yarns 2 are intersected at right angles with a predetermined interval so as to form a square mesh, and the warp yarns 1 and the weft yarns 2 are formed at the intersection points like a plain weave. The upper and lower relations of are alternately reversed and overlapped, and the respective intersections are high-frequency welded. The warp yarns 1 and the weft yarns 2 may intersect diagonally with respect to the length direction of the net body so as to form a rhombic mesh.
The vertical relationship of may be overlapped so that the warp yarn 1 is above or below the weft yarn 2 at all intersections.

As shown in FIG. 2, the warp yarns 1 and the weft yarns 2 constituting the high-strength net A have a thermoplastic resin having a high dielectric constant around a core tape 3 made of uniaxially stretched polypropylene or ultra-high molecular polyethylene. 4 is a coated tape extrusion-coated with 4. The core tape 3 is a band-shaped body obtained by melt-extruding polypropylene or ultra-high-molecular polyethylene at 90 to 140 ° C.
Is a tape uniaxially stretched 5 to 20 times (preferably 7 to 10 times) in the temperature range of 0.05 to 1.0.
mm (preferably 0.2 to 0.5 mm) with a width of 5
20 mm (preferably 10 to 15 mm) is used. A core tape having a draw ratio of less than 5 times does not have a very high tensile strength due to insufficient molecular orientation by drawing, while a core tape having a draw ratio of more than 20 causes a large decrease in strength due to fibrillation. Is also not desirable. Even if the core tape has a draw ratio of 5 to 20 times, a core tape having a thickness of less than 0.2 mm and a width of less than 5 mm tends to lack absolute strength. A core tape having a width of more than 1 mm and a width of more than 20 mm is also not preferable because it has high rigidity and tends to deteriorate the winding property and handleability.

As the thermoplastic resin 4 for coating the core tape 3, a resin having a high dielectric constant and good high frequency welding property, such as vinyl chloride resin or ethylene-vinyl acetate copolymer, is preferably used, and acetic acid is preferable. Vinyl content is 5 to 3
5% by weight (more preferably 15-30% by weight) of ethylene-vinyl acetate copolymer is used. In such an ethylene-vinyl acetate copolymer, the higher the content of vinyl acetate is, the higher the high frequency welding property is, and it is possible to perform the high frequency welding without damaging the core tape 3 under mild welding conditions. Since the melting point is as low as 140 ° C. or lower, there is no fear that the core tape 3 will be damaged by heat when covering the core tape 3. If the content of vinyl acetate is less than 5% by weight, the high frequency weldability tends to be considerably deteriorated, and if it exceeds 35% by weight, the strength of the coating film tends to be insufficient, which is not preferable.

The thermoplastic resin 4 has a coating thickness of 0.1 m.
m or more, preferably about 0.5 to 0.8 mm,
When the thickness is less than 0.1 mm, the welding strength at the intersection of the warp yarn 1 and the weft yarn 2 is insufficient, and when a large hooking force is applied to the net body, the intersection portion is easily peeled off to cause collapse. Further, it is desirable to form uneven wrinkles 4a on the surface of the thermoplastic resin 4 in order to prevent vertical tearing of the tape and improve the weldability.

In the high-strength net A of this embodiment, a covering tape obtained by extrusion-coating a thermoplastic resin 4 having a high dielectric constant around the uniaxially stretched core tape 3 as described above is used as the warp yarn 1 and the weft yarn 2. However, the covering tape in which the thermoplastic resin 4 having a high dielectric constant is laminated and integrated on both upper and lower surfaces of the uniaxially stretched core tape 3 may be used as the warp yarn 1 and the weft yarn 2.
In addition, a coated tape obtained by uniaxially stretching a thermoplastic resin 4 having a high dielectric constant by extrusion coating or laminating and integrating the periphery or upper and lower surfaces of a band-shaped body made of extruded unstretched polypropylene or ultrahigh molecular polyethylene. You may use as the warp 1 and the weft 2.

The intersections of the warp yarns 1 and the weft yarns 2 are high-frequency welded as described above. In that case, the same number of welding heads as the warp yarns 1 are provided in a horizontal row at the same intervals as the warp yarns. It is desirable to simultaneously weld the intersecting points arranged in a horizontal line by using high-frequency welding. The welding conditions may be appropriately set in consideration of the type of the thermoplastic resin 4, the coating thickness, etc., but normally the frequency is 10 to 40 MHz and the output is 3 to 2
0Kw, transmission time is 2-5 seconds, pressure is 2-15kgf
By adopting the condition of / cm ² , high frequency welding can be performed efficiently.

When a high frequency electric field is applied to the intersection of the warp yarn 1 and the weft yarn 2 under the above conditions, the thermoplastic resin 4 having a high dielectric constant is obtained.
Is rapidly dielectrically heated and strongly welded, but the core tape 3 made of polypropylene or ultra-high-molecular polyethylene having a low dielectric constant is hard to be dielectrically heated, and therefore is hardly thermally deteriorated at the intersection. Therefore, the obtained mesh body A has very high strength because the warp yarns 1 and the weft yarns 2 hardly impair the original excellent tensile strength of the core tape in which the warp yarns 1 and the weft yarns 2 are uniaxially stretched. Since the welding strength is high, there is no concern that it will collapse.

The intervals between the warp yarns 1 and the weft yarns 2 may be appropriately determined in consideration of the use of the mesh A, but when a particularly high strength is required, such as a mesh for civil engineering, It is desirable that the distance be about 20 to 100 mm.

FIG. 3 is a sectional view showing an example of the warp threads 10 and the weft threads 20 constituting the high-strength net body of the second invention.

The warp yarns 10 and the weft yarns 20 are formed by stacking a plurality (two in the figure) of the core tape 3 described above, and the periphery of the thermoplastic resin 4 is 0.1 mm or more (preferably, preferably).
It is composed of a covering tape extrusion-coated to a thickness of about 0.2 to 0.4 mm), and the uneven wrinkles 4a described above are similarly formed on the surface of the thermoplastic resin 4. Core tape 3
The number of layers stacked is not limited to two, but may be three or more, but if the total thickness of the stacked core tapes 3 becomes too large, the rigidity increases and the winding and handling properties of the netting decrease, so the total thickness It is desirable to appropriately determine the individual thickness of the core tape 3 and the number of the core tapes 3 so that the core tape 3 is 2.0 mm or less.

In the high-strength net body of the second invention, the warp threads 10 and the weft threads 20 as described above are crossed at right angles with an interval, and the high-strength net body A of the first invention described above is obtained. Since the intersections of the warp yarns and the weft yarns are high-frequency welded, the thermoplastic resin 4 on the surface is firmly welded by dielectric heating without substantially causing thermal deterioration of the core tape 3 which is hard to be dielectrically heated. Therefore, this net also has a very large strength, since it hardly impairs the original excellent tensile strength of the core tape 3 in which the warp threads 10 and the weft threads 20 are uniaxially stretched,
Further, since the welding strength at the intersection of the warp yarn 1 and the weft yarn 2 is also large, there is no fear of causing a collapse or the like. In addition, the tensile strength can be easily increased or decreased by changing the number of core tapes 3 to be stacked, and moreover, a plurality of core tapes 3 are stacked, one core tape having the total thickness is used. Since the rigidity is lower than that, there is an advantage that the winding property and the handleability are improved even though the tensile strength is substantially the same.

The high-strength net body as described above is used, for example, as a net for civil engineering, and is buried in the ground to reinforce the ground such as roads and land for construction, and to prevent the embankment from sinking on soft ground, or Is used as a net for packing luggage or a net for reinforcing beds.

Next, more specific examples and comparative examples of the present invention will be described.

[Example 1] A polypropylene core tape having a thickness of 0.5 mm and a width of 9 mm was uniaxially stretched at a stretch ratio of about 8 times. When the tensile strength of this core tape was measured, it was 118.3 kgf.

Next, around this core tape, an ethylene-vinyl acetate copolymer containing 25.5% by weight of vinyl acetate (trade name Ultrasen 634 manufactured by Tosoh Corporation) was used at a resin temperature of about 140.degree. It was extrusion coated to a thickness of 0.75 mm to produce a coated tape having a total thickness of 2.0 mm. The tensile strength of this coated tape was measured.
Was 119.8 kgf. When the strength retention of the coated tape was calculated based on the tensile strength (118.3 kgf) of the polypropylene core tape, it was 101.3% as shown in Table 1 below, and the strength reduction due to the resin coating was not observed, It was slightly improved.

This covering tape was used as warp and weft threads, and
A high frequency welding device (KW-3000 manufactured by Seidensha Denshi Kogyo Co., Ltd.)
(TR) was used to produce a net body by high-frequency welding the intersections of the warp yarns and the weft yarns under the conditions of a frequency of 27 MHz, an output of 3 Kw, an oscillation time of 3.0 seconds, and a pressure of ² Kgf / cm ² . Then, the tensile strength of the warp yarn (covering tape) after high frequency welding was measured, and as shown in Table 1, it was 117.5 k.
It was gf. Tensile strength of polypropylene core tape (1
When the strength retention of the coated tape after high frequency welding was calculated based on 18.3 kgf), it was 99.3% as shown in Table 1 below, and there was almost no decrease in strength due to high frequency welding. Moreover, when the welding strength at the intersection point was measured by the inter-ply pulling tension test method, it was as large as 39.3 kgf as shown in Table 1.

Example 2 Ethylene used in Example 1
In the same manner as in Example 1 except that an ethylene-vinyl acetate copolymer containing 25.0% by weight of vinyl acetate (trade name NUC3195 manufactured by Nippon Unica Co., Ltd.) was used instead of the vinyl acetate copolymer, A coated tape was made. The tensile strength of this coated tape is 11 as shown in Table 1 below.
The strength retention was 9.0 kg, based on the tensile strength (118.3 kgf) of the polypropylene core tape itself, which was 100.6%, and the strength reduction due to the resin coating was not observed and was slightly improved.

Using this covering tape as warp yarns and weft yarns, the intersections of the warp yarns and the weft yarns were subjected to high frequency welding in the same manner as in Example 1 to produce a net. Then, the tensile strength of the warp (covering tape) after the high frequency welding of the net was measured and the strength retention rate after the high frequency welding was calculated. As shown in Table 1 below, the former was 118.1 kgf and the latter was 99%. It was 0.8%, and almost no decrease in strength due to high frequency welding was observed. Also,
The welding strength at the intersection was as large as 38.2 kgf.

Example 3 Ethylene used in Example 1
In the same manner as in Example 1 except that an ethylene-vinyl acetate copolymer containing 15.5% by weight of vinyl acetate (trade name Ultrasen 634 manufactured by Tosoh Corporation) was used instead of the vinyl acetate copolymer. A coated tape was prepared. The tensile strength of this coated tape is 12 as shown in Table 1 below.
2.1 kgf, and the strength retention rate based on the tensile strength (118.3 kgf) of the polypropylene core tape itself was 103.2%, and there was no decrease in strength due to resin coating, and the strength was slightly improved. .

This coating tape was used as warp yarns and weft yarns, and the intersection of the warp yarns and the weft yarns was subjected to high frequency welding in the same manner as in Example 1 except that the high frequency transmission time was set to 5 seconds to produce a net. And the warp (covering tape) after the high frequency welding of the net body
The tensile strength was measured and the strength retention after high frequency welding was calculated. As shown in Table 1 below, the former was 118.0.
kgf and the latter were 99.7%, and almost no decrease in strength due to high frequency welding was observed. The welding strength at the intersection was 33.5 kgf, which was sufficient.

[Example 4] Polyvinyl chloride (S1003 manufactured by Kanegafuchi Chemical Industry Co., Ltd.) was applied around the polypropylene core tape prepared in Example 1 at a temperature of about 170 ° C.
Extrusion coated to a thickness of 75 mm, the total thickness is 2.0 mm
A coated tape of was prepared. The tensile strength of this coated tape is 106.3 kgf as shown in Table 1 below, and the tensile strength of the polypropylene core tape itself (118.3 kf).
The strength retention based on gf) was 89.9%, indicating a slight decrease in strength.

This coating tape was used as warp yarns and weft yarns, and the intersection of the warp yarns and the weft yarns was subjected to high frequency welding in the same manner as in Example 1 except that the high frequency transmission time was set to 2 seconds to produce a net. And the warp (covering tape) after the high frequency welding of the net body
Was measured and the strength retention after high frequency welding was calculated. As shown in Table 1 below, the former was 114.4.
kgf and the latter were 96.7%, and almost no decrease in strength due to high frequency welding was observed. In addition, the welding strength at the intersection was as large as 38.0 kgf.

[Comparative Example 1] The polypropylene core tape prepared in Example 1 was used as warp and weft as it was without resin coating, and was crossed at a right angle with an interval of 25 mm x 50 mm. Electronic Industry Co., Ltd. S
Using the ONOPET 4500P-207), the ultrasonic fusion time is 1 second, the pressurization time is 1.8 seconds, and the intersection of the weft yarn and the warp yarn is ultrasonically melted under the condition that the distance between the ultrasonic horn and the base is 0.8 mm. It was put on and a net was manufactured.

The tensile strength of the polypropylene core tape after ultrasonic fusion of this net was measured to be 42.9 kgf, and the tensile strength of the core tape before fusion (118.3 kg).
The strength retention rate based on f) is 36.
The strength decreased to about 1/3 at 3%. The fusion strength at the intersection was measured in the same manner as in Example 1, and was 5 kg.
It was as small as f or less.

[Comparative Example 2] The coated tape (tape coated with polyvinyl chloride) prepared in Example 4 was used as warp threads and weft threads, which were crossed at a right angle with an interval of 25 mm x 50 mm, and an ultrasonic horn and a base. In the same manner as in Comparative Example 1 except that the interval of was changed to 2.5 mm, the intersection of the warp yarn and the weft yarn was ultrasonically fused to produce a net.

Then, the tensile strength, the strength retention rate, and the fusion strength at the intersection point of the covering tape after ultrasonic fusion of the mesh body were determined, and as shown in Table 1 below, 49.
The strength was 4 kgf, 41.8%, and 2.5 kgf, and the strength reduction after ultrasonic fusion was large, and the fusion strength at the intersection was small.

[Comparative Example 3] The covering tape prepared in Example 2 was used as warp threads and weft threads, crossed at a right angle with an interval of 25 mm x 50 mm, an ultrasonic wave transmission time of 0.5 seconds and an ultrasonic horn. In the same manner as in Comparative Example 1 except that the stand spacing was changed to 3.0 mm, the intersections of the warp yarns and the weft yarns were ultrasonically fused to produce a net.

Then, the tensile strength, the strength retention rate, and the fusion strength at the intersection point of the covering tape after ultrasonic fusion of the net body were determined. As shown in Table 1 below,
The strength was 6.4 kgf, 98.4%, and 27.0 kgf, and the decrease in strength after ultrasonic fusion was small, but the fusion strength at the intersection was not so large.

[0043]

[Table 1]

As shown in Table 1, the nets of Examples 1 to 3 were produced by subjecting a polypropylene tape to an ethylene-vinyl acetate copolymer-coated tape to warp threads and weft threads and welding the intersecting portions by high frequency welding. In all cases, the strength of the coated tape after resin coating was not reduced, and the strength was slightly improved, and the strength retention rate of the coated tape after high frequency welding was in the 99% range, and the strength was not substantially reduced. Also, it can be seen that the strength of the intersection portion is sufficiently high in the range of 33.5 to 39.3 kgf. Further, it is found that the welding strength at the intersection portion is larger as the ethylene-vinyl acetate copolymer having a higher vinyl acetate content is used. In addition, the mesh body of Example 4 in which the intersection point portion was high-frequency welded using the vinyl chloride resin-coated tape as the warp yarn and the weft yarn, although the strength retention of the resin-coated tape was slightly low at 89.9%, It can be seen that the strength retention of the covering tape of No. 3 is as high as 96.7% and the welding strength at the intersection is as large as 38.0 kgf.

On the other hand, a polypropylene core tape is used as warp and weft as it is for ultrasonically welding the intersections, and a coating tape obtained by coating polypropylene core tape with vinyl chloride resin is used as warps and wefts. In the net body of Comparative Example 2 in which the ultrasonic welding was performed, the strength retention after ultrasonic welding was 50% or less, and the strength was remarkably decreased. Therefore, the polypropylene core tape may be significantly deteriorated by ultrasonic welding. I understand. Also, the fusion strength at the intersection point is as small as 21.5 kgf or less, which shows that it is difficult to firmly fuse by ultrasonic fusion. In addition, the mesh body of Comparative Example 3 in which the intersecting portion was ultrasonically fused by using the coated tape obtained by coating the polypropylene core tape with the ethylene-vinyl acetate copolymer as the warp and the weft, the strength retention rate of the coated tape after ultrasonic welding was used. Is as high as 98.4%, but the welding strength at the intersection is reduced to 27.0 kgf, which indicates that high-frequency welding has better welding properties than ultrasonic welding.

[Example 5] A polypropylene core tape having a thickness of 0.2 mm and a width of 10 mm, which was uniaxially stretched at a draw ratio of about 10 times, was prepared, and the tensile strength of the core tape was measured and found to be 84.5 kgf. It was

Next, around the core tape, the ethylene-vinyl acetate copolymer of Example 1 was extrusion-coated at a resin temperature of about 140 ° C. to a thickness of 0.9 mm to give a total thickness of 2. 0
mm coated tape was made. The tensile strength of this coated tape was measured and found to be 85.8 kgf. 101.5% when the strength retention of the coated tape is calculated based on the tensile strength (84.5 kgf) of the polypropylene core tape.
Therefore, the strength was not decreased by the resin coating and was slightly improved.

Using this covering tape as warp and weft,
mm at a distance of 76 mm and intersected at a right angle, and using the high frequency welding apparatus of Example 1, under the conditions of a frequency of 27 MHz, an output of 3 Kw, a transmission time of 3.0 seconds and a pressing force of ² Kgf / cm ² , High-frequency welding was applied to each intersection of the weft threads to produce a net. Then, the tensile strength of the warp (covering tape) after high frequency welding was measured to be 86.5 kgf, and the tensile strength of the polypropylene core tape (85.8 kgf).
The strength retention of the coated tape after high frequency welding calculated based on f) was as high as 102.4%, and no strength reduction due to high frequency welding was observed. Further, when the welding strength at the intersection point was measured by the inter-intersection interlocking tensile test method, 34.
It was as large as 1 kgf.

From this Example 5, the core tape has a thickness of 0.
It can be seen that a net body having a large tensile strength can be obtained even if it is as thin as 2 mm.

Example 6 A polypropylene core tape having a thickness of 0.2 mm and a width of 10 mm, which was uniaxially stretched at a draw ratio of about 10 times, and a thickness of 0.4, which was uniaxially stretched at a draw ratio of about 8 times.
mm, width 10 mm polypropylene core tape
When the tensile strength was measured by stacking both core tapes, it was 2
It was 27.2 kgf.

Next, about 14 parts of the ethylene-vinyl acetate copolymer of Example 1 was placed around both core tapes that were overlapped.
It was extrusion coated to a thickness of 0.7 mm at a resin temperature of 0 ° C. to prepare a coated tape having a total thickness of 2.0 mm. When the tensile strength of this coated tape was measured, it was 228.3 kgf. Tensile strength of superposed core tape (227.2
When the strength retention of the coated tape was calculated based on kgf), it was 100.5%, and there was no decrease in strength due to resin coating, and it was slightly improved.

This covering tape is used as warp and weft threads,
mm at a distance of 96 mm and intersected at a right angle, and using the high frequency welding apparatus of Example 1, under the conditions of a frequency of 27 MHz, an output of 3 Kw, a transmission time of 3.0 seconds and a pressing force of ² Kgf / cm ² , High-frequency welding was applied to each intersection of the weft threads to produce a net. Then, the tensile strength of the warp yarn (covering tape) after high frequency welding was measured to be 230.6 kgf, and the tensile strength of the superposed core tape (227.2 kg
The strength retention of the coated tape after high frequency welding calculated based on f) was as high as 101.5%, and no strength reduction due to high frequency welding was observed. Further, when the welding strength at the intersection points was measured by the inter-intersection hooking tensile test method, 27.
It was as large as 2 kgf.

[0053]

As is apparent from the above description, in both the high strength nets of the first and second inventions, the strength of the covering tape used as the warp yarns and the weft yarns decreases during the covering and during the high frequency fusion of the intersections. Since the core tape made of uniaxially stretched polypropylene or ultra-high molecular weight polyethylene maintains the original excellent tensile strength, the strength of the net body, especially the tensile strength, is extremely large. Since the welding strength of the intersection point is also large, there is no fear that the intersection point will peel off and collapse even if a large hooking force is applied to the net, and the production is simple and efficient mass production can be achieved. Further, the high-strength net body of the second invention can easily increase or decrease the tensile strength by changing the number of core tapes to be overlapped, and the winding property and the handleability are improved as compared with one core tape. There is also the effect of doing.

[Brief description of drawings]

FIG. 1 is a partial perspective view showing an embodiment of a high-strength net body according to the first invention.

FIG. 2 is an enlarged cross-sectional view of warp yarns or weft yarns that constitute the high-strength net body of the same embodiment.

FIG. 3 is an enlarged cross-sectional view showing an example of warp threads or weft threads constituting the high-strength net body of the second invention.

[Explanation of symbols]

A high-strength net 1 warp 2 weft 3 core tape made of uniaxially stretched polypropylene or ultra-high molecular polyethylene 4 thermoplastic resin with high dielectric constant

Claims (5)

[Claims] 1. A covering tape obtained by extrusion-coating or laminating integrally a thermoplastic resin having a high dielectric constant around or on both upper and lower sides of a core tape made of uniaxially stretched polypropylene or ultra-high molecular polyethylene as warp threads and weft threads. A high-strength net body, characterized in that the weft threads are crossed with each other at a predetermined interval and the respective intersections are high-frequency welded. 2. A plurality of core tapes made of uniaxially stretched polypropylene or ultra-high molecular weight polyethylene, and a covering tape around which a thermoplastic resin having a high dielectric constant is extrusion coated is used as warp threads and weft threads. A high-strength net body, characterized in that they are crossed with each other at a predetermined interval, and the respective intersections are welded by high frequency. 3. A core tape having a draw ratio of 5 to 20 times, a thickness of 0.05 to 1.0 mm, and a width of 5 to 20 mm. The high-strength net body described. 4. The thermoplastic resin is either an ethylene-vinyl acetate copolymer or a vinyl chloride resin, and the coating thickness thereof is 0.1 mm or more. The high-strength net body described. 5. The thermoplastic resin according to claim 1, wherein the thermoplastic resin is an ethylene-vinyl acetate copolymer containing 5 to 35% by weight of vinyl acetate, and the coating thickness is 0.1 mm or more. Strength mesh.