JPH0274841A - Detecting sensor - Google Patents

Abstract

PURPOSE:To make it possible to perform stable detection for a long period by coating the outside of a detecting part comprising a macromolecular material incorporating conducting filler which holds a pair of conductors in a mutually isolated pattern with a permeable ultraviolet-ray shielding layer. CONSTITUTION:A fluid detecting sensor 1 has the following constitution. A detecting part 2 comprises a conductive macromolecular composition formed in a sheet state. Two conductors 3 and 3 are arranged on one surface of the detecting part 2 in an isolated pattern. The detecting part and the conductors are held with two sheets 4 and 4 which have an ultraviolet-ray shielding effect and can selectively pass fluid to be detected as a unitary body. In the permeable ultraviolet-ray shielding layer 4, a filler having an ultraviolet-ray shielding effect is dispersed in a macromolecular material. When the fluid detecting sensor 1 is installed outdoors and exposed to sunshine, harmful ultraviolet rays are shielded by the ultraviolet-ray shielding layer 4 and do not reach the detecting part 2. Therefore, decomposition and deterioration of the conductive macromolecular composition constituting the detecting part 2 are blocked, and the stable detection for a long period can be carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a detection sensor that is capable of detecting heavy oil, gas, etc. and has excellent weather resistance.

[Conventional technology]

Conventional sensors of this type include one in which a tetrafluoroethylene resin sheet containing a conductive filler such as carbon black is used, and two conductors are supported at a distance by this sheet. When oil enters between the carbon particles dispersed inside the sheet, the conductivity of the sheet decreases due to the tunnel effect, and oil leakage can be detected by capturing this as a change in the electrical resistance between the conductors. (See Japanese Patent Publication No. 59-47256).

[Problem to be solved by the invention]

In many cases, such sensors have a structure in which a conductive sheet that detects oil leakage is further covered with a polymeric material such as tetrafluoroethylene resin to protect it from water resistance and weather resistance. However, when installed outdoors, the electrical resistance of the conductive sheet that serves as the sensor increases over time, resulting in a problem in that oil leakage cannot be detected.

The present invention has been made in view of the problems of the prior art, and an object thereof is to provide a detection sensor that enables stable detection over a long period of time.

[Means to solve the problem]

In order to solve the problems of the conventional technology, the present inventors conducted intensive studies and found that the deterioration of the sensing part over time is mainly caused by ultraviolet rays in sunlight. I came up with this idea. For this reason, the present invention includes a sensing section made of a polymer material including at least one pair of conductors, a conductive filler that holds the conductors apart from each other, and a sensing section that covers at least the outside side of the sensing section. The detection sensor includes a transparent ultraviolet blocking layer provided on the outside of the sensor.

[Effect]

In this invention, the sensing part is made of a composition in which conductive particles such as carbon black are dispersed in a polymeric material, and the conductive filler particles form a chain structure or
Alternatively, conductivity is imparted by approaching within a distance of several amperes.

When this sensing part is installed outdoors and exposed to sunlight, the polymeric material supporting the conductive filler is degraded by the ultraviolet rays therein, and its physical properties change. As a result, it is thought that the chain structure of the filler particles present inside the filler particles is destroyed or the distance between the particles increases, resulting in a decrease in conductivity.

Furthermore, when the conductive filler is carbon black,
As polymer materials deteriorate, radicals containing oxygen and hydrogen atoms, such as quinone groups, hydroquinol groups, and carboxyl groups, increase on the surface of the polymer material, and these radicals capture π electrons that play a role in electrical conduction. It is presumed that this decreases the conductivity of the metal.

Therefore, in the present invention, a transparent ultraviolet blocking layer is provided to cover the sensing portion to prevent deterioration of the sensing portion due to ultraviolet rays, thereby enabling stable detection for a long period of time even under outdoor exposure conditions.

〔Example〕

FIG. 1 is a partially cutaway perspective view showing an eleventh embodiment of a fluid detection sensor according to the present invention. The illustrated fluid detection sensor 1 has two conductors 3.3 spaced apart from each other on one surface of a sensing part 2 made of a conductive polymer composition formed in a sorted manner, and these conductors have an ultraviolet blocking effect. It has a structure in which it is sandwiched between two sheets 4.4 that can selectively transmit the fluid to be detected.

Here, the sensing part 2 is configured to, for example, add 10 to 50% by weight of carbon black to a polytetrafluoroethylene resin powder, add a liquid lubricant to the mixture, and extrude and roll a sheet. Or 1.2 to 1 in both directions.
A material stretched by about 4 times is preferably used.

Next, the transparent ultraviolet blocking layer 4 is made by dispersing a filler having an ultraviolet blocking effect in a polymer material, for example, by adding 1 to 50% by weight of titanium oxide to tetrafluoroethylene resin powder. A sheet formed in the same manner as the sensing part 2 is used. With this molding method,
The sheet 4 is made slightly porous and allows oil etc. to selectively permeate through it due to the water repellency of the tetrafluoroethylene resin.

Note that instead of titanium oxide, it is also possible to use alumina, zinc oxide, calcium carbonate, talc, etc. In addition to these white fillers, dark coloring agents such as lead chromate and iron oxide can also be used. It also has a UV blocking effect. When adding these fillers to polymer materials, it is convenient to perform surface treatment using a silane coupling agent, titanate coupling agent, etc. In this case, a water-repellent coupling agent may be used. The treatment also has the effect of strengthening the water resistance of the ultraviolet blocking layer 4.

In addition, the polymeric materials constituting the ultraviolet blocking layer 4 include:
In addition to tetrafluoroethylene resin, it is also possible to use other fluorine-based resins or olefin-based resins that have been made porous to the extent that the fluid to be detected can pass through them. It is selected accordingly. In addition, instead of the above-mentioned colored UV blocking agent, for example, a benzophenone-based, benzodoazole-based, or phenylsalicylate-based UV absorbing agent may be used, and by converting the ultraviolet rays into heat within this ultraviolet blocking layer 4. , the ultraviolet rays reaching the sensing section 2 may be prevented or reduced. Furthermore, it is of course possible to use these ultraviolet absorbers and the ultraviolet screening agent in combination.

The fluid detection sensor I configured in this manner is suitable for use, for example, in detecting an oil film on a water surface.

That is, water is blocked by the ultraviolet blocking layer 4 made of a water-repellent polytetrafluoroethylene resin as a base material, and does not penetrate into the interior. On the other hand, since oil has a smaller critical surface tension than the tetrafluoroethylene resin, it easily passes through the micropores and reaches the sensing section 2. Furthermore, the oil that has reached the sensing part 2 penetrates inside and fills the spaces between the carbon particles.
Break their electrical continuity. As a result, the sensing part 2
The electrical resistance value increases, and this change in electrical resistance is detected by the sensing section 2.
Oil leakage can be detected by detecting it with a detector connected to the other end side of the pair of conductors 3.3 in contact with. When this fluid detection sensor 1 is installed outdoors and exposed to sunlight, harmful ultraviolet rays are removed by the ultraviolet blocking layer 4.
Since the light does not reach the sensing part 2 because it is blocked by the light, deterioration and deterioration of the conductive polymer composition constituting the sensing part 2 are prevented, and stable detection can be performed over a long period of time.

FIG. 2 shows another embodiment of the fluid detection sensor according to the present invention. The illustrated fluid detection sensor lO has one conductor 11
is covered with a sensing part 12 made of the same conductive polymer composition as in the embodiment in FIG. 1, and the other conductor 13 is attached to this,
These are held in a braided body 14 made of coarsely braided metal wires, and the outer side of the braided body 14 is covered with a transparent ultraviolet blocking layer 15 similar to the embodiment shown in FIG.

In this case, the transparent ultraviolet blocking layer I5 is similar to that of the embodiment shown in FIG. There is. The oil that has passed through the transparent ultraviolet blocking layer 15 passes through the gaps between the metal wires of the braided body 14 and passes through the sensing section 12.
and increases the electrical resistance value of the sensing part 12. This change in electrical resistance value is detected by a detector connected to the conductor 11 and the conductor 13 to detect oil leakage.

In both of the above embodiments, the conductive polymer composition constituting the sensing portion 2.12 is not limited to the combination of tetrafluoroethylene resin and carbon black, but may also be, for example, metal fine powder or carbon instead of carbon black. Conductive fillers such as fibers may be used, and other fluororesins, olefin resins, rubber, etc. may be used in place of the tetrafluoroethylene resin, and in this case, it must be made porous. It is not necessary to do so; it may be swollen by the fluid to be detected. The combination of these polymeric materials and conductive fillers and their charge are selected depending on the type of fluid to be detected.

Furthermore, a sensing part 2.12 and a transparent ultraviolet blocking layer 4.15
If the material of the sensor is also considered, it is possible to detect other fluids other than music, such as conductive liquids or organic solvent vapor (gas), and the range of applications is extremely wide.

〔Effect of the invention〕

As explained above, according to the sensor of the present invention, a transmitting ultraviolet blocking layer is provided at least on the outside side of the sensing portion made of a polymeric material containing a conductive filler, and the conductive filler is protected against ultraviolet rays when installed outdoors. Since the structure prevents deterioration of the material and deterioration of the polymer material, there is no change in the conductivity of the sensing part over time, making stable detection possible over a long period of time.

Note that this invention is not limited to the above-mentioned embodiments; for example, this invention may be applied to increasing the number of conductors, providing a water-resistant protective layer outside the transparent ultraviolet blocking layer, or applying to a gas detection sensor. Of course, various modifications within the technical idea are possible.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view showing one embodiment of a fluid detection sensor according to the present invention, and FIG. 2 is a perspective view of a fluid detection sensor showing another embodiment. 2.12 + sensing part, 3, 11.13: conductor, 4.15:
Transparent UV blocking layer. Patent applicant Jun Kosha Co., Ltd.

Claims (1)

[Claims] (1) A sensing section made of a polymer material including at least one pair of conductors and a conductive filler that holds the conductors apart from each other, and a sensing section provided outside the sensing section so as to cover at least the outside side of the sensing section. A detection sensor equipped with a transparent UV blocking layer.