JPH0830738B2 - Sign sheet - Google Patents

Description

TECHNICAL FIELD The present invention relates to a marker sheet for facilitating the detection of underground buried objects, and particularly detects information on underground buried objects by using electromagnetic waves from the ground. It relates to a sign sheet that makes it possible.

[Prior Art] At present, there are gas, water, electricity, telecommunications, sewage, and various other buried objects underground in the city. In addition to failure of these buried objects themselves, they are often dug out to lay new buried objects on the road. It is often heard that the laying situation is currently unknown because it is especially old.

Even in such a case, it is proposed that a buried sign sheet waterproofed by putting a conductive foil such as aluminum foil as a base material for the purpose of detecting the laying condition from the ground without trial digging as a buried sign. (Japanese Patent Laid-Open No. 59-26786
issue). This sign sheet uses the conductivity of aluminum foil or the like and is a method of detecting it as a kind of piping.

In addition, a buried object detection method using the radar method (Japanese Patent Laid-Open No. Sho 60
-230076) and a method of embedding a resonance element or a magnetic element (Japanese Patent Laid-Open No. 48-27762).

However, it is difficult to determine whether the detected buried object is a buried object labeling sheet or another conductive object in the marker sheet in which a conductive foil such as an aluminum foil is attached to the base material. The drawback was that there was no other way than to make a trial dig to confirm this.

In addition, the buried object detection method using the radar method can detect all buried objects, but it is necessary to set the permittivity correctly due to the difference in geology, and the buried object is located deeper than the ground. In the case of being buried, it is necessary to make the radar output high, and there are restrictions under the Radio Law, so the reality is that it is not widely used.

Further, in the method of embedding the resonance element and the magnetic element, it is necessary to embed many resonance elements in order to perform continuous detection, resulting in high cost.

[Problems to be Solved by the Invention] For the purpose of eliminating these drawbacks, the present inventors have previously proposed a marker sheet that can identify the buried position of an underground buried object and the buried object by using radio waves. are doing.

This marker sheet is a marker sheet having a resonant element formed by connecting a capacitor to a flat spiral wire.

A resonance element that resonates with a radio wave of a frequency determined for each type of buried object is attached to this sign sheet, and this sign sheet is previously buried above the buried object to perform excavation work or the like. At this time, a radio wave having a frequency determined for each type of the buried object is transmitted, and a secondary radio wave from a resonant element that resonates at the frequency is received to identify the buried object and detect the buried position.

Therefore, since the resonance element attached to the sign sheet is buried in the ground for a long period of time, some kind of protective cover is necessary to protect the resonance element.
If it is hermetically sealed with a material of 100 μm, a waterproof effect can be obtained, and a considerably great effect can be obtained in preventing corrosion of the spiral conducting wire of the resonant element.

However, in the case of covering with the above-mentioned polyethylene film, the gas barrier property is poor when buried in the ground, so that corrosion of the conductor of the resonant element occurs in a deposited soil area, hot spring area, hydrogen sulfide gas generation area, etc. No protection.
Further, if the polyethylene film having a thickness of 50 to 100 μm is hermetically sealed, when buried in the ground, the geology of the buried ground,
There is a problem that the detection ability deteriorates and fluctuates due to the influence of moisture in the soil.

The present invention is intended to obtain a marker sheet which does not have these drawbacks, that is, exhibits the following effects.

(1) Can be detected from the ground before trial digging,
It is possible to identify the information of the buried object.

(2) The detection from the ground is continuous, and the label can be used in any length.

(3) Even if a person who does not have a detector digs, it is easy to identify the presence of an embedded object on the way like a conventional continuous marking sheet (having the function of a conventional marking sheet. (4) It is inexpensive, can be continuously formed into a sheet, and can be embedded continuously.

(5) It is possible to identify a large number of items. For example, it is possible to distinguish water pipes and gas pipes.

(6) It can be used semi-permanently in all underground environments without being corroded or eroded.

[Means and Actions for Solving the Problems] In order to solve these problems, the present invention provides an underground burial marker sheet having a resonant element in which a plane spiral lead wire and a capacitor are connected, in which the resonant element is a protective coating agent. We propose a marker sheet having a dielectric constant ε and its thickness Tmm (ε / T) of 10 or less, and a resonant element sealed with a protective coating material containing a gas barrier resin. Furthermore, a marker sheet in which the protective coating material is composed of a laminate of a polyolefin and a gas barrier resin is proposed.

At least the sign sheet should reduce the influence of the ground surface.
It is often buried in the ground deeper than about 60 cm. Therefore, even in such a case, it is necessary to have sufficient detection ability.

In many areas, such as urban areas, where there are sedimentary layers or hot springs, various types of natural gas (including combustible gases such as methane, especially hydrogen sulfide gas) are found in the ground. There is a high risk of damaging the resonance element by invading the protective coating material of the above.

In addition, since it is buried in the ground, friction with the earth and sand of the buried site is also considered, so a certain level of mechanical strength is required, and a flexible material is preferable in order to withstand ground changes, vibrations, and the like.

Therefore, in order to maintain the detection ability even if the protective coating material of the resonant element is buried deep in the ground, the ratio (ε / T) of the permittivity ε and the thickness T (mm) of the protective coating material as a whole is maintained. ) Needs to be as small as 10 or less.

Further, in order to maintain the mechanical strength, it is considered that the thickness needs to be about 0.3 mm even though it depends on the resin used as the material. (Of course, it may be thinner if there is no lumps of stone and everything is soft soil such as clay.) From the viewpoint of such restrictions and costs, polyolefins, especially polyethylene (PE), polypropylene (manufacturing method, density Was considered to be the most suitable resin, but this resin does not have gas barrier properties against oxygen, hydrogen sulfide (H ₂ S), etc. Measures are needed.

H ₂ S resistant resins include polyester (PET), polyamide, ethylene-vinyl alcohol copolymer resin (EV
It was found that a gas barrier resin such as OH; saponified ethylene-vinyl acetate copolymer) or vinylidene chloride resin (PVDC) can be sufficiently used, and the present invention has been completed.

In this case, the gas barrier resin alone may be used as the protective coating material, but the laminate with the polyolefin is excellent in terms of processability and cost.

Except for H ₂ S, when a sandwich structure is adopted in which polyolefin that is not affected by acidity, alkalinity, etc. at all is the outermost layer, the middle layer, the gas barrier resin layer, and the inner layer is the polyolefin layer, heat sealing is also used. You can
It is a protective coating material that is excellent in workability and cost.

When such a structure is used, mechanical protection is carried out by polyolefin, chemical protection is carried out by gas barrier resin, and T for (ε / T) can be carried by polyolefin, so that expensive gas barrier resin is used. Has a thickness (1 to 50 microns) that can be expected to have chemical protection, and is extremely easy to handle.

 Hereinafter, the present invention will be specifically described with reference to the drawings.

 FIG. 1 is a schematic view of a part of the marker sheet.

FIG. 2 is a plan view of the resonant element, and FIG. 3 is a sectional view of the resonant element.

 FIG. 4 is a sectional view of the protective covering material.

 FIG. 5 is a laid-out layout diagram.

In FIG. 1, a marker sheet 1 is attached to a long / strip-shaped flat yarn, cloth, film, and sheet which are partially folded by attaching a resonant element 2 by thermal adhesion or spot adhesion 3 or whole surface adhesion by an adhesive or the like. It is a thing. The long strip is not limited to the folded state as shown in FIG. 1, but may be the unfolded one.

As shown in FIGS. 2 and 3, the resonance element 2 has a resonance circuit formed by connecting a thin spiral wire 4 and a capacitor 5 sandwiched from above and below by a protective covering material 8, and the periphery thereof is adhered or heat-bonded. It is adhered and hermetically sealed.

As shown in FIG. 5, the sign sheet 1 is buried above the buried object 13 at a depth of about 60 cm from the ground surface.

Then, the buried object can be detected through the resonance element 2 attached to the marker sheet 1.

For example, if the buried object is a gas pipe, a marker sheet having a resonant element 2 that responds to radio waves of a frequency determined for the gas pipe is horizontally embedded above the gas pipe, and when the gas pipe is searched. Is a detector that emits radio waves of a specific frequency for the gas pipe and receives secondary radio waves from the resonance element 2.
When the detector 14 is moved using 14 and approaches the resonance element 2, the resonance element 2 reacts and emits a secondary radio wave.

The secondary radio wave is received by a detector, converted into electricity, and displayed by a signal such as a meter, a buzzer sound or a lamp, so that the presence of the gas pipe can be determined.

This secondary radio wave resonates most strongly when the detector 14 is located directly above the resonant element 2. Therefore, the buried position of the gas pipe can be determined by searching for the position where the signal is displayed largest.

In addition, if you want to know the presence of other buried objects near the gas pipe, use a detector that emits and receives radio waves of several specific frequencies, and switch the transmission frequency to detect the presence of other buried objects. It is possible to identify and detect the buried position.

The resonant element attached to the marker sheet 1 in this way
Since it is buried in the ground at a depth of about 60 cm, it is necessary to protect the resonant element, but it is necessary to take sufficient consideration in selecting the protective covering material in order to prevent the detection ability from decreasing.

[Examples] Hereinafter, details will be described based on Examples and Comparative Examples.

(Example 1) A printed circuit board was prepared by bonding an electrolytic copper foil (thickness: 105 µm) to one surface of a polyester film (thickness: 35 µm) with an adhesive.

The spiral conducting wire 4 shown in FIG. 2 was formed on this substrate by etching. The spiral conductor 4 has an outer diameter of 15 cm, an inner diameter of 1.5 cm, a winding number of 78, and a wire width of 1.5 mm. The terminals of the capacitor were attached to the ends of the start and end of the spiral by soldering to create a resonant element with a resonant frequency of 146 KHz.

Low density polyethylene (LD
PE thickness 0.5mm) and PVDC coated biaxially oriented polypropylene (K
A resonance element 2 was prepared by sandwiching the resonance element from above and below using a laminated body in which OPP 0.03 mm) was bonded by dry lamination, and sealing the periphery by heat bonding with a heat sealer.

The detection performance is as follows. First, the resonance element is placed parallel to the ground, a detector (manufactured by Fujitecom Co., Ltd.) is used, and the probe output from the detector is placed directly above the resonance element. 148KHz) reaches the resonant element, and the distance lcm between the resonant element and the prog which can detect the radio wave radiated from the resonant element (hereinafter, “l” is referred to as “detection ability”) is obtained, and the detection ability on the ground is 130cm. It was

Then, after burying the resonant element in the ground at a depth of 60 cm, the distance between the resonant element and the prog was obtained in the same manner as above, and the detection ability at that time was 129 cm, which was almost unchanged.

In the chemical test, the detection ability of the resonant elements on the ground was measured in advance, and these resonant elements were measured for H ₂ SO ₄ , HCl, and NaOH 2 each.
A 0% concentration, a 5% concentration of salt water, a hydrogen sulfide saturated solution and hydrogen sulfide gas test were conducted to observe the corrosion of the resonance element and to detect the detection ability on the ground. The detection ability before and after the chemical test is shown in Table 1.

As a result, the difference in capacity between the ground and the ground was 0 to 2 cm, and there was almost no decrease in capacity due to underground burial.

In addition, in the chemical test, there was no abnormality in the appearance of the resonant element even after 30 days in the immersion test of H ₂ SO ₄ , HCl, and NaOH 20% each, and in the salt water 5% concentration, the capacity retention rate after the chemical test. Also kept 100%.

In the hydrogen sulfide saturated solution and hydrogen sulfide gas tests, some blackening appeared after 10 days, but the capacity retention rate was 100%, which was unchanged.

Even after 30 days, the blackening of the resonant element hardly progressed and the ability was kept 100%.

(Example 2) LDPE (thickness 0.5 mm) and PVDC (thickness 0.02 m) were used as the protective coating material.
A resonance element was prepared in the same manner as in Example 1 except that a laminate obtained by laminating m) by dry lamination was used, and the detection ability and chemical test were performed.

(Example 3) LDPE (thickness 0.5 mm) and EVOH (thickness 0.02 m) were used as the protective coating material.
The same test as in Example 1 was carried out except that the laminate of m) was used.

(Example 4) LDPE (thickness 0.5 mm) and PET (thickness 0.04 mm) were used as the protective coating material.
The same test as in Example 1 was carried out except that was used.

(Comparative Examples 1 to 10) In Comparative Example 1, polyvinyl chloride (PVC) (thickness 0.1 mm) having a high dielectric constant was used as a protective coating material, and in Comparative Example 2, polyvinyl chloride (PVC) (thickness 0.5 mm) was used. The same test as in Example 1 was performed.

In Comparative Example 3, polyethylene (LDPE) having a low dielectric constant (thickness 0.1 mm), in Comparative Example 4 LDPE (thickness 0.5 mm), in Comparative Example 5 LDPE (thickness 1.0 mm), and in Comparative Example 6, LDPE (thickness). The same test as in Example 1 was conducted using 1.0 mm × 3 sheets = 3 mm).

In Comparative Examples 7 to 10, a material having a good gas barrier property was used as a protective coating material, KOPP (thickness 0.03 mm) was used in Comparative Example 7, PVDC (thickness 0.02 mm) was used in Comparative Example 8, and EVOH was used in Comparative Example 9.
(Thickness 0.02 mm), and in Comparative Example 10 PET (thickness 0.04 m
The same test as in Example 1 was conducted using m).

 These results are summarized in Table 1.

As shown in Comparative Example 1, PVC with a large dielectric constant (thickness 0.1 m
When the protective material of m) is used, the ability to detect on the ground and in the ground is compared, and when it is buried in the ground, the capacity drops by about 30%.

When the thickness of the protective material is set to 0.5 mm (Comparative Example 2), the decrease in performance is reduced to about 18%.

Further, as can be seen in the comparison between Comparative Example 1 and Comparative Example 3 and the comparison between Comparative Example 4 and Comparative Example 4, in comparison of differences in dielectric constant with the same thickness, LDPE having a smaller dielectric constant was buried in the ground. There is little deterioration in detection ability.

Although it has not been completely clarified, one reason for this is that when the protective material having a large dielectric constant and a small thickness is coated, the protective material serves as an intermediate, and the soil or the soil component and the spiral-shaped conductor wire become the conductor. It is considered that this is because a capacitor (secondary capacitor) is formed and the capacitance of the secondary capacitor is added to the capacitor of the resonant element to shift the resonant frequency of the resonant element.

Therefore, in order to economically suppress the formation of the secondary capacitor and its capacity, it is preferable to use a material having a dielectric constant of 3.5 or less and a thickness of 0.3 to 1 mm as the protective coating material.
Represents. ) To thickness (denoted as Tmm) (ε / T) is 1
Should be 0 or less. When it is more than 10, it is not preferable because when it is buried in the ground, the detection ability deteriorates and the fluctuation becomes large.

Further, in Comparative Examples 3 to 6 for LDPE having a small water absorption rate with respect to the protective property of the resonance element, in Comparative Examples 7 to 10, chemical tests were conducted on KOPP, PVDC, EVOH and PET having good gas barrier properties.

In LDPE, since the water absorption rate is small, HCl, H ₂ SO ₄ , NaO
In the immersion test in H and salt water, there was no change in the appearance of the conducting wire of the resonance element and the capacitor, and the detection ability was also the same as before the immersion.

However, in the hydrogen sulfide saturated solution and hydrogen sulfide gas tests, the conductor blackened and the detection ability dropped to 70-80.

On the other hand, with KOPP and PVDC, which have good gas barrier properties, HCl, H ₂
There was no change in appearance or change in detection ability in SO ₄ , NaOH, salt water, saturated solution of hydrogen sulfide, and hydrogen sulfide gas test.

Materials with low gas permeability include EVOH, PET, and nylon, but EVOH and PET have poor chemical resistance.
Nylon has a large water absorption, so Comparative Example 9
EVOH and PET of Comparative Example 10 were bonded to LDPE, and the resonator element was covered with the polyethylene surface facing outside, and a chemical test was performed.

Examples 1 to 4 are LDPEs having a low dielectric constant and a low water absorption rate.
0.5mm sheet with good gas barrier properties KOPP, PVDC, EVO
A laminated material in which H and PET films were bonded together was used.

These materials showed almost no deterioration in the detection ability in the ground, and the chemical tests showed almost no reduction in the detection ability.

Therefore, the protective material is required to have low water absorption and gas barrier property.

As the material of the present invention, dielectric constant, small water absorption polyethylene, polypropylene, polystyrene, polytetrafluoroethylene, foamed polyethylene, foamed polypropylene and good gas barrier KOPP, PVDC, EVOH, PET, nylon, etc. are laminated. A material with a thickness of 0.3-1 mm is good.

[Effects of the Invention] In the marker sheet of the present invention, since the resonance element is sealed by the specific protective coating material, the spiral conductive wire of the resonance element does not corrode for a long period of time even if it is buried in the ground,
Moreover, it has the advantage that it can be used semipermanently with almost no deterioration or change in detection ability.

[Brief description of drawings]

1 is a schematic view of a part of a marker sheet, FIG. 2 is a plan view of a resonant element, FIG. 3 is a sectional view of a resonant element, FIG. 4 is a sectional view of a protective covering material, and FIG. The figure is a buried layout. 1. Marking sheet, 2. Resonance element 3. Spot adhesion part, 4. Flat spiral wire 5. Capacitor, 6. Code 7. Insulator, 8. Protective covering material 9. Seal part, 10. Polyolefin layer 11 .Gas barrier resin layer, 12.Polyolefin layer 13.Buried object, 14.Detector 15.Meter, 16.Ground surface

Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number in the agency FI technical display location G01V 3/12 B 9406-2G (72) Inventor Taiji Ota 1-3-15 Nihonbashiboridome-cho, Chuo-ku, Tokyo Heisei Polymer Co., Ltd. (72) Inventor Ryutaro Fujihira 3-2 Chidori-cho, Kawasaki-ku, Kawasaki City, Kanagawa Prefecture Showa Denko KK Kawasaki Plastics Research Laboratory (72) Inventor Masahiko Maeda, Oita City, Oita Prefecture 2 Showa Denko Shares Company Oita Research Center (56) Reference JP-A-2-253187 (JP, A) JP-A-2-210288 (JP, A) JP-A-1-250888 (JP, A) JP-A-64-38686 (JP , A)

Claims (2)

[Claims] 1. In an underground burial sign sheet having a resonant element in which a plane spiral wire and a capacitor are connected, the resonant element has a ratio of the dielectric constant ε of the protective covering material to its thickness Tmm (ε /
A marker sheet, characterized in that T) is 10 or less, and the resonator element is sealed with a protective coating material containing a gas barrier resin. 2. The sign sheet according to claim 1, wherein the protective coating material is composed of a laminate of a polyolefin and a gas barrier resin.