JP5492010B2 - Conductive resin sheet - Google Patents

Description

      The present invention relates to a technique for a resin sheet containing carbon fibers and having conductivity.

      In general, it is known that a conductive resin sheet containing carbon black is laid, and a charged human body or object gets on or touches it to remove static electricity. In addition, it is widely used as an antistatic material and a sheet for discharging, such as those used for door plastic handles to obtain an antistatic effect and processed into a rubber ground wire to conduct and remove static electricity.

      Patent Document 1 discloses a method of removing static electricity using a cloth or nonwoven fabric having carbon fibers, specifically, a method of neutralizing static electricity of a human body. Further, Patent Document 2 discloses a rubber molded structure for charge removal and a structure for performing charge removal using carbon fiber or the like as its application.

JP2000-300396 JP 7-26069 A

The conductive resin sheet containing carbon black needs to be blended in a large amount in order to obtain conductivity. As a result, the tensile strength or the like of the material is lowered, the moldability at the time of manufacturing becomes unstable, and the designability may be lowered. Furthermore, it was not possible to obtain an excellent conductor resin sheet having a surface resistance value of 10 ³ Ω or less while maintaining these strengths and design properties.

     By the way, in the cloth and non-woven fabric described in Patent Document 1, conductivity is recognized by mixing carbon fibers. Specifically, in the case of using a cart or a car with wheels, for example, the durability of the sheet could not be maintained because of its low breaking strength.

     Furthermore, in the rubber molded structure for static elimination described in Patent Document 2, static elimination is performed using carbon fiber, but no static elimination or conductive effect was obtained depending on conditions. In the description, the carbon fiber in the exposure is controlled and the carbon fiber having a length of about 5 μm to 30 μm is preferably used. However, in such a short fiber, with respect to a normal resin or rubber, Since the particles are fine, it is impossible to obtain electrical characteristics such as a surface resistance value necessary for static elimination or conduction unless the carbon fiber is mixed in a considerably large amount. Furthermore, it is preferable that a part of the exposed carbon fiber protrudes in a hook shape, but it is difficult to make a state protruding in a hook shape after the carbon fibers are entangled. In addition, in order to make it project in the shape of a bowl, for example, the surface of the molded body is described as being polished with a grindstone. However, the design properties due to scratches are reduced by polishing. In particular, soft resins, elastomers, and rubbers are soft, so that stress is dispersed during polishing and is difficult to polish. In addition to these problems, there is a problem that costs are high for industrial use, and it is necessary to avoid such secondary processing.

     Therefore, the present invention provides a conductive resin sheet that is difficult to be destroyed even when a load of a person or a vehicle is repeatedly applied when laying, and that can obtain excellent conductivity without performing secondary processing. And

     In order to solve the above problems, the present invention is configured as follows.

In the PAN-based carbon fiber, the center distribution of the fiber length is 1.1 to 1.5 mm, and the fiber length is 50% or more and 75% or less of the sheet thickness. The PAN-based carbon fiber is contained in a weight ratio of 10 to 20%, and the PAN-based carbon fiber is exposed from the sheet surface and has a thickness of 2 to 3 mm.

According to the invention described in claim 1, in the PAN-based carbon fiber, the center distribution of the fiber length is 1.1 to 1.5 mm, and is 50% or more and 75% or less of the sheet thickness, By containing the PAN-based carbon fiber that is the fiber length in a weight ratio of 10 to 20%, the carbon fiber can be entangled, and a part of the carbon fiber can be exposed from the surface. Can demonstrate to the maximum. That is, even when the carbon fiber content is lower than that of carbon black or the like, good conductivity can be provided. Therefore, the moldability at the time of manufacture is stabilized and the designability can be prevented from being lowered. Of course, since the resin is the main component, even when it is laid or the like, it is not easily destroyed even if a load of a person or a vehicle is repeatedly applied.

      On the other hand, if the content of the PAN-based carbon fiber is less than 7%, conductivity necessary for static elimination cannot be obtained. On the other hand, when the content is more than 20%, the moldability and the design properties are significantly lowered. Furthermore, if the center distribution of the fiber lengths of the carbon fibers is smaller than 0.2 mm, the entanglement between the carbon fibers in the resin becomes very small, and the necessary conductivity cannot be obtained. On the contrary, if the center distribution of the fiber length of the carbon fiber is equal to or greater than the sheet thickness, a part of the carbon fiber cannot be exposed from the surface, and efficient conductivity cannot be obtained.

      On the other hand, if the thickness is less than 0.5 mm, the tensile strength is small, so that the durability is lowered, such as being easily broken. Conversely, if the thickness is greater than 3 mm, there is no problem in durability, but the winding diameter increases, the weight also increases, and the transportability deteriorates.

      In addition, in the electroconductive resin sheet of this invention product, the electroconductivity superior to what contained carbon black or a PICHI type | system | group carbon fiber can be obtained by using a PAN type carbon fiber. Therefore, since content can be reduced, a moldability is stabilized, the designability fall can be prevented and a durable conductive resin sheet can be obtained.

      Moreover, the length of the carbon fiber to be contained in the present invention may be sheared by applying a stress with a screw or the like when it is cut in advance and when it is produced, and contained in a product after the addition. It means the length of carbon fiber. In addition, the length measurement method used the microscope "OMRON type VC4500 3D digital fine scope", measured length by 300 time expansion, and used the average value of 10 samples.

      Further, the resin of the present invention includes vinyl chloride resin (PVC), polyethylene resin (PE), polypropylene resin (PP), acrylonitrile-butadiene-styrene copolymer resin (ABS), nylon resin (PA), polyethylene terephthalate. Resin (PET), acrylic resin (PMMA), polycarbonate resin (PC), natural rubber (NR), styrene-butadiene rubber (SBR), chloroprene rubber (CR), urethane rubber (UR), other blend rubbers, elastomers, etc. Used.

It is sectional drawing of the resin sheet concerning the form of the 1st and 2nd actual condition of this invention. It is sectional drawing of the resin sheet which provided the embossing of the unevenness | corrugation concerning the 1st and 2nd embodiment of this invention. It is a 300 times magnified photograph (on an OMRON VC4500 3D digital fine scope) on a plane in which the center distribution of the PAN-based carbon fiber length after shearing is 1.5 mm and the thickness of the vinyl chloride resin sheet is 3 mm. It is a 300 times magnified photograph (on an OMRON VC4500 3D digital fine scope) on a plane in which the center distribution of the PAN-based carbon fiber length after shearing is 1.5 mm and the thickness of the vinyl chloride resin sheet is 1 mm. It is a 300 times magnified photograph (on an OMRON VC4500 3D digital fine scope) on a plane in which the center distribution of the PAN-based carbon fiber length after shearing is 0.1 mm and the thickness of the vinyl chloride resin sheet is 3 mm.

      Embodiments of the present invention will be described.

      Vinyl chloride containing 10% and 15% PAN-based carbon fibers (toray-made PAN-based carbon short fiber thickness 7 μm, length before shearing 0.1 mm) with a center distribution of fiber length after shearing of 0.1 mm A resin sheet (hereinafter referred to as a PVC sheet) and a center distribution of fiber length after shearing are PAN-based carbon fibers having a thickness of 1.5 mm (PAN-based carbon short fiber thickness 7 μm manufactured by Toray, length before shearing 12 mm). Vinyl chloride sheets containing 10%, 15% and 20% were prepared, and the surface resistance value was measured. For comparison with carbon black, a vinyl chloride sheet containing 20% of conductive carbon black (Toka Black # 5500 made by Tokai Carbon) was prepared.

Subsequently, the surface resistance value was measured using an R8340 made by Advanced Test, which is a measuring instrument at a temperature of 23 ° C. and a humidity of 50%. Using a main electrode 50φ and a counter electrode 70φ under a load of 5 kg, a voltage of 500 V was set as a measurement condition according to JISK6911. In the case of a conductor region having a low surface resistance value (in Table 1, 10 ³ to 10 ⁴ Ω is shown), a voltage of 1 V was used as a measurement condition.

It is known that the resin sheet is less likely to be charged with static electricity and has a surface resistance value of about 10 ⁷ Ω or less that can be eliminated. The lower the surface resistance value, the higher the conductivity. Therefore, the measurement method made the surface resistance value 10 ⁷ Ω or less acceptable. Also in the table, a pass of 10 ⁷ Ω or less is indicated by ○, and a failure of 10 ⁸ Ω or more is indicated by ×. In all the following tests, the surface resistance value was set to pass 10 ⁷ Ω or less.

Consider the results in Table 1 above. When the carbon fiber content is large, the surface resistance tends to decrease in part, but does not change significantly. What is particularly important is that the longer fiber length of the carbon fiber after shearing contributes to the improvement of conductivity. However, the fact that the length is small with respect to the sheet thickness is an important condition that contributes to improvement in conductivity. What should be noted is that, in the case of a vinyl chloride sheet containing 15% and 20% of 1.5 mm carbon fiber with a center distribution of fiber length after shearing, the surface resistance value is 10 ³ Ω. Thus, it was possible to obtain excellent conductivity that could not be obtained. The PVC sheet containing 20% of conductive carbon black (Toker Black # 5500) had low conductivity and was rejected.

      In the test of Table 2, the test for confirming the influence of the length of carbon fiber with respect to the thickness of a vinyl chloride sheet was implemented. The same PAN-based carbon fiber as in Example 1 was used for the vinyl sheet 1 mm thickness and 2 mm thickness, and the content was kept constant at 10% to prepare a sample. Using PAN-based carbon fiber (Toray-made PAN-based carbon short fiber thickness 7 μm, length before shearing 12 mm), the fiber length after shearing is controlled by the mixing time with the vinyl chloride sheet, and the fiber length after shearing is adjusted. As shown in Table 2, the center distribution is 5 types of 0.25 to 1.5 mm and 0.1 mm of PAN-based carbon fiber (Toray-made PAN-based carbon short fiber thickness 7 μm, length before shearing 0.1 mm) A total of 6 types of samples were made. In the same manner as in Table 1, the surface resistance value was measured.

      Consider the results in Table 2 above. When the center distribution of the fiber length after shearing was 0.25 mm, 0.6 mm, and 0.9 mm, the PVC sheet had a thickness of 1 mm, the electrical resistance value was low, and the electrical conductivity was high and could pass. When the PVC sheet has a thickness of 2 mm, the center distribution of the fiber length after shearing was 0.25 to 1.5 mm, the electrical resistance value was low, and the electrical conductivity was high and could pass. However, at any sheet thickness, when the center distribution of the fiber length after shearing was 0.1 mm, the electrical resistance value was high, and the electrical conductivity was low and the sheet was rejected. From these facts, it can be said that the center distribution of the fiber length is 0.2 to 1.5 mm and the center distribution of the fiber length is not more than the sheet thickness is an important condition contributing to the conductivity. The fiber length should not exceed the sheet thickness, but is preferably as long as possible, and the electrical resistance can be lowered.

      In the test of Table 3, the comparative test about a PAN type | system | group carbon fiber and a PICHI type | system | group carbon fiber was done. For the PAN-based carbon fibers, the raw materials used were 3 mm and 6 mm length before shearing with a PAN-based carbon short fiber thickness of 7 μm manufactured by Toray (length after shearing: 1.1 mm). For PICHI-based carbon fibers, Osaka Gas Chemical's product numbers S-231 (carbon short fiber thickness 13 μm, pre-shear length 3.3 mm) and S-232 (carbon short fiber thickness 13 μm, pre-shear length 5) 0.5 mm) was used (length after shearing: 1.1 mm). The content was kept constant at 10%. As shown in Table 3, a 2 mm thick PVC sheet sample was prepared, and the surface resistance value was measured in the same manner as in Table 1.

Consider the results in Table 3 above. Since the surface resistance value of the sheet using the PAN-based carbon fiber was 10 ⁷ Ω or less, the conductivity was acceptable. On the other hand, since the surface resistance value of the sheet | seat using a PICHI type | system | group carbon fiber is 10 < ⁸ > (omega | ohm) or more, it was disqualified. Therefore, it was found that the PAN-based carbon fiber can contribute to the improvement of conductivity in a smaller amount than the PICHI-based carbon fiber.

      In the test of Table 4, the center distribution of fiber length after shearing is 1.1% of PAN-based carbon fiber (Toray-made PAN-based carbon short fiber thickness 7 μm, length before shearing 12 mm) 5%, 7% PVC sheet 2 mm thick samples containing 10%, 15%, 20% and 30% were prepared. The moldability after melt extrusion molding was confirmed, and the surface resistance value was measured in the same manner as in the method of Table 1.

As for the moldability of the evaluation methods in Table 4, ◯ indicates that there are no cracks or lumps, and the appearance is good. Moreover, with x, there are a crack and a lump, and an external appearance is also bad. In the table, pass is indicated by ○ and failure is indicated by ×. In addition, in the surface resistance value, 10 ⁷ Ω or less was regarded as acceptable as in the above test. Also in the table, a pass of 10 ⁷ Ω or less is indicated by ○, and a failure of 10 ⁸ Ω or more is indicated by ×.

Consider the results in Table 4 above. When the amount of PAN-based carbon fiber was 7 to 20% by weight, the moldability was good, and the surface resistance of the PVC sheet was 10 ⁷ Ω or less, and the conductivity was also acceptable.

      In the test of Table 5, the center distribution of the fiber length after shearing was PAN-based carbon fibers of 1.1 mm (PAN-based carbon short fiber thickness 7 μm manufactured by Toray, length 12 mm before shearing) of 10% and 20%. Tensile tests were performed on each of the PVC sheets contained and melt-extruded to determine the tensile strength. The measuring instrument is ORIENTEC universal tensile testing machine Tensilon RTC-1250A, the measurement conditions are room temperature 23 ° C., 50%, tensile speed 200 mm / min, gripping interval 115 mm, test sample is dumbbell No. 1-A type Was used. Moreover, in the melt extrusion molding for producing the test sample, the longitudinal direction in which the resin continuously extrudes was set to be vertical, and the orthogonal width direction was set to be horizontal.

      The evaluation method set 40 Nmm or more as a pass. In the table, pass is indicated by ○ and failure is indicated by ×.

      Consider the results in Table 5 above. It was found that the tensile strength decreases as the carbon fiber content increases. Since the content of PAN-based carbon fiber was 20% in both length and width, it can be judged that all those having a low content can be passed without problems.

      In the test of Table 6, test construction was performed in order to confirm the correlation between the tensile strength (tensile test) in Table 5 and the strength required for actual construction. A vinyl chloride sheet containing 20% by weight of the carbon fiber listed in Table 5 is fixed with adhesive on the concrete floor assumed to be a gas station, with a size of 1m x 2m. After about 2 months, the state of the test sample was visually observed.

      The evaluation method in Table 6 is based on observation. ○ means that there is no particular damage and it passes in 2 months, but it is assumed that there is a risk of damage over time. ◎ means that there is no particular damage, and it is assumed that there is no risk of damage even after one year.

      From the results of Table 6, it can be determined that the thickness can be used if the thickness is 0.5 mm or more. The thickness is preferably 2 mm or more.

      In the test of Table 7, the center distribution of the fiber length after shearing contains 0.4% of PAN-based carbon fiber (Toray made PAN-based carbon short fiber thickness 7 μm, length before shearing 12 mm) 10%, plastic About the flexible PVC sheet | seat which made the agent (DOP) constant, the thing of 0.5 mm, 1 mm, 2 mm, 3 mm, and 4 mm thickness was extrusion-molded. Each sheet was extruded with a width of 1 m and cut with a length of 2 m. Furthermore, this 1 m wide x 2 m long product was wound in a roll shape in the length direction, and it was confirmed whether or not the winding operation could be performed without any problem.

      The evaluation method of Table 7 can be wound without any problem with ◎. ○ can be wound without any problem, but has a slightly hard feeling. “△” means winding, but the winding diameter becomes large, so care must be taken. ◎ and ○ were accepted.

      From the result of Table 7, if it is a 0.5-3 mm soft vinyl chloride sheet | seat, it can wind and the conductive resin sheet which can be conveyed easily will be made. From the results of Tables 5 and 6, it can be determined that there is no problem with the breaking strength due to the thickness.

      In the test of Table 8, the center distribution of the fiber length after shearing is 7%, 10% of PAN-based carbon fibers of 1.1 mm (PAN-based carbon short fiber thickness 7 μm manufactured by Toray, length 12 mm before shearing), A PVC sheet having a thickness of 2 mm and containing 15% each was prepared. In order to confirm whether or not static electricity can be removed using these, human body voltage measurement was performed according to JIS L1023. The measurement location was measured at Osaka Prefectural Industrial Technology Research Institute. For comparison, a PVC sheet containing 5% furnace carbon black manufactured by Mitsubishi Chemical Corporation was used as a blank, and a Tohoku Rubber product name tech sheet was compared.

      A predetermined walk was performed on each test piece at a room temperature of 23 ° C. and a humidity of 20%, a human body voltage was measured, and then a voltage was obtained after 3 seconds while measuring a charge decay state. The test subject was a male adult with a height of about 170 cm and a weight of about 65 kg, and the shoes used were athletic shoes with a foam cushion layer that are generally sold.

      From the results in Table 8, it was found that the product of the present invention can obtain an excellent charge removal effect.

      FIG. 1 is a cross-sectional view of a resin sheet according to the first and second embodiments of the present invention, in which carbon fibers 11 are exposed from the surface. The carbon fiber 12 is buried in the resin sheet 10 and entangled.

      In the figure, reference numeral 10 denotes a resin, which is formed into a sheet. In general, continuous extrusion with excellent production can be applied, and long sheets can be produced.

      FIG. 2 is a cross-sectional view of the resin sheet according to the first and second embodiments of the present invention, to which uneven embossing is given at the time of molding, and the carbon fibers 11 are exposed from the surface. The carbon fiber 12 is buried in the resin sheet 10 and entangled. In the figure, the embossment 100 is provided with unevenness, and since the exposed carbon fibers are sparsely spaced, the electric field at the tip at the time of static elimination and the like rises, so that the performance can be improved.

      FIG. 3 is a 300 times magnified photograph in a plane where the center distribution of the PAN-based carbon fiber length after shearing is 1.5 mm and the thickness of the vinyl chloride resin sheet is 3 mm. This indicates that a part of the carbon fiber is exposed from the surface of the sheet, and FIG. 4 also shows that the carbon fiber is hardly exposed at a sheet thickness of 1 mm. That is, it was recognized that the center distribution of the PAN-based carbon fiber length after shearing was exposed from the surface when it was smaller than the thickness of the sheet.

      FIG. 5 is a 300 times magnified photograph in a plane in which the center distribution of the PAN-based carbon fiber length after shearing is 0.1 mm and the thickness of the vinyl chloride resin sheet is 3 mm. It was recognized that a part of the carbon fiber was exposed from the surface of the sheet. This means that if the center distribution of the carbon fiber length after shearing is smaller than the thickness, it is exposed from the surface. However, although the carbon fiber is contained in a weight ratio of 7 to 20%, the carbon fiber length contained in the fiber fiber is not in the range of 0.2 to 1.5 mm in the center distribution of the fiber length in the present invention. As can be seen, the surface resistance is high and the conductivity is low.

      From Table 1 and FIG. 3 to FIG. 5, in summary, in the PAN-based carbon fiber, the center distribution of the fiber length is 0.2 to 1.5 mm and not more than the sheet thickness. By containing a long PAN-based carbon fiber in a weight ratio of 7 to 20%, the carbon fiber can be entangled, and a part of the carbon fiber can be exposed from the surface. Conductivity can be maximized.

      As can be seen from these described examples, the content of carbon fiber for imparting conductivity can be reduced as compared with carbon black or the like. Therefore, the moldability at the time of manufacture is stabilized and the designability can be prevented from being lowered. According to the present invention, the carbon fiber can be entangled and a part of the carbon fiber can be exposed from the surface, so that the resin sheet containing the PAN-based carbon fiber is more than the one containing the carbon black or the PICHI-based carbon fiber. Excellent conductivity can be obtained. In addition, since the resin is the main component, even when laying, the load of a person or a vehicle is not easily destroyed even if it is repeatedly applied.

      In the above examples, vinyl chloride resin (PVC) has been described. As other resins, polyethylene resin (PE), polypropylene resin (PP), acrylonitrile-butadiene-styrene copolymer resin (ABS), nylon resin (PA) ), Polyethylene terephthalate resin (PET), acrylic resin (PMMA), polycarbonate resin (PC), natural rubber (NR), styrene-butadiene rubber (SBR), chloroprene rubber (CR), urethane rubber (UR), other blend rubbers It is considered that the effects similar to the same can be obtained by blending the elastomers and the like in the same manner.

      The product of the present invention can provide a sheet having a high conductivity and a high charge removal effect, both indoors and outdoors. In particular, those that have flexibility such as soft vinyl chloride resin and are controlled to have high conductivity can obtain excellent static elimination effects including static electricity. It can also be applied under construction such as the OA floor. Furthermore, those controlled from the conductivity to the semi-conductive property can be expected to prevent static electricity due to static electricity from the human body or vehicle by laying on the floor as a neutralization mat for a gas station or solvent warehouse. In addition, even in precision equipment such as ICs that fail due to electrostatic discharge during transportation, electrostatic discharge can be suppressed by laying the product of the present invention under the transportation carriage, that is, on the floor surface. Failure due to electrostatic discharge during transportation can be prevented in advance. Moreover, since it can be carried, it can be easily constructed at a necessary location.

      In addition, since carbon fibers have begun to be applied to airplane and automobile materials, they can be used as raw materials for the products of the present invention, which can be reused after defective products or after use.

DESCRIPTION OF SYMBOLS 10 Resin sheet 11 Carbon fiber exposed from one part surface 12 Carbon fiber buried and entangled 100 Embossed surface

Claims (1)

In the PAN-based carbon fiber, the center distribution of the fiber length is 1.1 to 1.5 mm, and 50% or more and 75% or less of the sheet thickness. A conductive resin sheet characterized by containing a ratio of 10 to 20%, further exposing a PAN-based carbon fiber from the sheet surface, and having a thickness of 2 to 3 mm.

Images