JPH0373838A - Detecting sensor - Google Patents

Abstract

PURPOSE:To allow stable detection over a long period of time by coating the surfaces of conductive carbon material particles dispersed in a sensing part with a ladder type silicone polymer having excellent weatherability and water repellency. CONSTITUTION:The detecting sensor 1 is constituted by connecting two conductors 4, 4 via solderless terminals 3 to both ends of the sensing part 2 consisting of a conductive high-polymer compsn. formed to a sheet shape so as to face each other, then crimping and integrating the assembly thereof by two sheets 6, 6 which can selectively allow the permeation of the fluid to be detected. The sensing part 2 is constituted by forming the film of the ladder type silicone polymer on the surface of carbon black particles. A permeable sheath 6 consists of a high-polymer material, such as tetrafluoroethylene resin, and the material formed to a sheet shape is used. The sensor 1 constituted in such a manner is shut off of water by the sheath 6 and oil permeates the fine holes thereof and arrives at the sensing part 2. The oil arriving at the sensing part 2 increases the electric resistance value of the sensing part.

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]

As a conventional sensor of this type, there is one in which a tetrafluoroethylene resin sheet containing a conductive carbon material such as carbon black or graphite is used, and two conductors are separated and supported by this sorting. When oil enters between the conductive carbon particles dispersed inside the sheet, the conductivity of the sheet decreases due to the tunnel effect, and this can be interpreted as a change in the electrical resistance between the conductors.
It is configured to detect leakage (Special Publication Act, 1987-).
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 value of the conductive sheet that is the sensing part increases over time, and as a result, the conductivity decreases when originally detecting oil and changes in ambient temperature and humidity. There has been an unresolved problem in that it is easy to misidentify a decrease in conductivity due to disturbances such as changes and issue false alarms.

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

[Means to solve the problem]

Therefore, as a result of repeated studies on decolorization in order to solve the problems of the conventional technology, the present inventor found that the decrease in conductivity of the sensing part over time is caused by changes in the surface state of the conductive carbon material particles contained inside. The present invention was devised based on this finding. Therefore, the present invention includes at least one pair of conductors, a sensing section made of a polymeric material in which conductive carbon material is dispersed and holds the conductors apart from each other, and a transparent outer layer provided outside the sensing section. The sensing sensor is characterized in that the conductive carbon material of the sensing portion is coated with a ladder-type silicone polymer.

The ladder-type silicone-based polymer used in the present invention is one obtained by condensing flaky organonorsesquioxane oligomers (ladder-type silicone-based oligomers) having a ladder structure as shown in the following formula by heating. The cured product has excellent weather resistance and water exchangeability, and is also highly hard.

Conductive carbon material particles are dispersed in a solution in which an organosilsesquioxane oligomer having a ladder structure is dissolved in a polar solvent such as alcohol, ester, or ketone, or an aromatic solvent such as toluene, and after the solvent is removed. Heat. Due to this heating, the organosilsesquioxane oligomer condenses on the surface of the conductive carbon material particles, causing bridge formation at one end of the ladder and between the ladders.
The 5t-0-St bond forms a ladder-type polyorganosilsesquioxane. At that time, the ladder-type silicone oligomer also reacts and bonds with functional groups such as hydroxyl groups and carboxyl groups present on the surface of the conductive carbon material particles. The polymer membrane is chemically immobilized. The amount of ladder-type silicone oligomer used varies depending on the material and properties (particle size, surface area, etc.) of the conductive carbon material, but the weight ratio of the ladder-type silicone oligomer to the conductive carbon material is 1 to 1.
IO weight %, preferably selected in the range of 3 to 511i weight %. Furthermore, although the condensation reaction of ladder-type silicone oligomers proceeds by heating alone, it can be carried out at low temperatures and in a short time by adding a catalyst.

[Effect]

In this type of sensor, the sensing part is made of a composition in which conductive carbon particles such as carbon black are blended into a polymeric material, and the conductive particles form a chain structure or are arranged within a few angstroms. By approaching the distance, conductivity is imparted. In conventional sensors, when installed outdoors and exposed to sunlight, conductive carbon particles within the sensing part receive energy from ultraviolet rays and react with oxygen and water in the air, forming quinone and carbonyl groups on the surface. , radicals containing oxygen and hydrogen atoms such as hydroxyl groups increase. It is thought that these capture the π electrons that play a role in conduction, thereby reducing the conductivity of the sensing section.

Therefore, in this invention, the surface of the conductive carbon material particles mixed in the sensing part is covered with a ladder-type soricone polymer that has excellent weather resistance and water exchangeability in order to shield it from oxygen and water. It has a structure that prevents deterioration. As a result, the stability of the sensing portion over time is greatly increased, and it can be used outdoors.[Embodiment] FIG. 1 is a partially cutaway perspective view showing an embodiment of the detection sensor according to the present invention. The illustrated detection sensor l has two conductors 4.4 connected to both ends of a sensing part 2 made of a conductive polymer composition formed in a sheet shape through crimp terminals 3 so as to face each other. After that, two reinforcing metal wires 5.5 are placed apart from each other along this sensing part 2, and two sorting wires 6.6 are placed through which the fluid to be detected can selectively pass. It has an integrated structure that is sandwiched between the two.

Next, the sensing section 2 will be explained in detail using a specific example. First, carbon black is dispersed in toluene, and a ladder-type silicone oligomer (for example, 0v
Glass Reain manufactured by ens-111inots
The structure of GR950 is shown by the following formula. ) After removing toluene, the ladder-type noricone-based oligomer is condensed by heating at 130° C. for 1 hour to form a layer of ladder-type noricone-based polymer on the surface of the carbon black particles. Note that a catalyst may be added to promote the condensation reaction. Add 20 parts by weight of carbon black surface-treated in this way to 80 parts by weight of fine tetrafluoroethylene resin powder, add a limb lubricant to the mixture, and extrude and roll a sheet. Alternatively, the sensing part 2 was obtained by stretching the film in both directions by about 1.2 to 14 times.

In addition, the permeable jacket 6 is made of a polymer 47 such as tetrafluoroethylene resin, and is made in the same manner as the sensing part 2, although the N type of the limb lubricant and the drying conditions are slightly different. It is used in the form of a sheet. By such a molding method, the sheet 6 is made slightly porous, and the water repellency of the tetrafluoroethylene resin allows oil films and the like to selectively permeate therethrough. In order to protect the sensing part 2, white fillers such as titanium oxide, alumina, zinc oxide, calcium carbonate, and talc, and dark colorants such as lead chromate and iron oxide may be used as necessary. It may also be added to the transparent jacket 6 as a UV blocker. 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 has the advantage that the water resistance of the permeable jacket 6 can be strengthened.

The 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 permeable outer covering 6 made of water-repellent tetrafluoroethylene resin, and does not penetrate into the interior. On the other hand, since oil has a smaller critical surface tension than tetrafluoroethylene resin, it easily passes through the micropores and does not reach the sensing part 2. Therefore, the life of the detection sensor l is significantly extended compared to the conventional one.

In the above embodiment, reinforcing metal wires 5.5 are placed on both sides of the sensing portion 2 to prevent deformation of the sensing portion 2.
It is not necessary to provide this, for example, a pair of conductors 4
．． 4 may be arranged in parallel on both side edge portions of the sensing portion 2, thereby obtaining a reinforcing effect.

In the present invention, the surface electrical continuity of carbon black particles is interrupted. As a result, the electrical resistance value of the sensing part 2 increases, and oil leakage is detected by detecting this change in electrical resistance with a detector connected to the other end of the pair of conductors 4.4 in contact with the sensing part 2. be able to. In this detection sensor 1, the carbon black particles dispersed in the sensing part 2 are covered and protected by a ladder-type silicone polymer, so even if exposed to sunlight outdoors, the sensing part 2
The conductive polymer composition may be condensed with a ladder-type oligomer that changes the characteristics of the conductive polymer composition.

There are various types of n-based oligomers, such as those in which the side chains bonded to silicon atoms are all methyl groups, or as mentioned above, both methyl groups and phenyl groups, but after condensation, the ladder type polymer is It has the property of being easily swollen or soluble in hard rubber, which has a high proportion of phenyl groups.

Therefore, when targeting limbs with high hydrophobicity, surface treatment of carbon black using a carbon black with a high proportion of phenyl groups will make it easier for the surface of the carbon black particles to be exposed when the limbs arrive. , the detection sensitivity can be increased. Therefore, the type of oligomer should be selected appropriately depending on the properties of the liquid to be determined.

FIG. 2 shows another embodiment of the detection sensor according to the present invention. In the illustrated detection sensor 10, one conductor 11 is made of a sensing portion 1 made of a conductive polymer composition similar to that of the embodiment in FIG.
2, the other conductor 13 is attached to this, these are held in a braided body 14 made of coarsely braided metal wires, and the outside thereof is further covered with a transparent jacket 15 similar to the embodiment in FIG. The structure is as follows.

In the above embodiments, the conductive polymer composition constituting the sensing parts 2 and 12 is not limited to the combination of tetrafluoroethylene resin and carbon black, and for example, conductive carbon such as graphite may be used instead of carbon black. Other fluororesins, olefin resins, etc. may also be used instead of tetrafluoroethylene resin.

The combination of these polymeric materials and conductive carbon materials and their filling amount are selected depending on the type of fluid to be detected, but preferably 10 to 50% by weight of the polymeric material.

Furthermore, if the materials of the sensing parts 2 and 12 and the permeable jacket 6.15 are considered, it is also possible to detect fluids in the pond other than songs, such as conductive limbs or organic solvent vapor (gas). , and its scope of application is extremely wide.

〔Effect of the invention〕

As explained above, according to the detection sensor of the present invention,
The surface of the conductive carbon material particles dispersed in the sensing part is coated with a ladder-type silicone polymer that has excellent weather resistance and water resistance to prevent deterioration due to oxidation. There is no change over time, making stable detection possible over a long period of time.

Although not shown as an example, a ladder-type silicone oligomer may be impregnated and condensed on the surface of the transparent jacket or the sensing portion, separately from the surface treatment of the conductive carbon material particles. In this case, the hardness of the resulting ladder-type silicone polymer is so high that the conductivity changes even with external forces such as tension.
This has a great effect on protecting the sensing part from damage, and further improves the stability of the detection sensor.

Note that the present invention is not limited to the above-mentioned embodiments. For example, the present invention can be modified by increasing the number of conductors, providing a water-resistant protective layer on the outside of the permeable jacket, or applying the present invention to a gas detection sensor. Various modifications within the technical concept are of course possible.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view showing one embodiment of a detection sensor according to the present invention, and FIG. 2 is a perspective view of a detection sensor showing another embodiment. 2.12 + sensing part, 4.1 +, + 3: conductor, 6.1
5: Transparent envelope.

Claims (1)

[Claims] (1) Detection comprising at least one pair of conductors, a sensing section made of a polymeric material in which a conductive carbon material is dispersed and holding the conductors spaced apart from each other, and a transparent jacket provided outside the sensing section. A detection sensor characterized in that the conductive carbon material of the sensing portion is coated with a ladder-type silicone polymer.