Non-black conductive polytetrafluoroethylene composition and molded article

Abstract

The purpose of the present invention is to provide a non-black polytetrafluoroethylene composition having excellent conductivity, and a molded article. The present disclosure relates to a non-black conductive polytetrafluoroethylene composition comprising polytetrafluoroethylene and a non-black conductive filler comprising at least one selected from the group consisting of antimony-doped tin oxide and phosphorus-doped tin oxide.

Description

Technical Field

[0001] The present disclosure relates to a non-black conductive polytetrafluoroethylene composition and a molded article. Background Art

[0002] As is well known, in order to impart conductivity to a fluororesin, a conductive filler is added thereto.

[0003] Patent Document 1 describes a white conductive fluororesin composition containing a heat-meltable fluororesin and zinc oxide powder.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2013-136675 Summary of the Invention

[0007] Technical Problem to be Solved by the Invention

[0008] An object of the present disclosure is to provide a non-black polytetrafluoroethylene composition and a molded article having excellent conductivity.

[0009] Means for Solving the Technical Problem

[0010] The present disclosure (1) is a non-black conductive polytetrafluoroethylene composition, which comprises polytetrafluoroethylene and a non-black conductive filler, and the non-black conductive filler contains at least one selected from the group consisting of antimony-doped tin oxide and phosphorus-doped tin oxide.

[0011] The present disclosure (2) is the non-black conductive polytetrafluoroethylene composition according to the present disclosure (1), wherein the volume resistivity is 1.0×10 3 ~1.0×10 7 Ω·cm.

[0012] The present disclosure (3) is the non-black conductive polytetrafluoroethylene composition according to the present disclosure (1) or (2), wherein the content of the non-black conductive filler is 10 to 40% by mass based on the composition.

[0013] The present disclosure (4) is a molded article obtained by molding the non-black conductive polytetrafluoroethylene composition arbitrarily combined with any one of the present disclosures (1) to (3).

[0014] The present disclosure (5) is the molded article according to the present disclosure (4), wherein the molded article is a sealing material.

[0015] Effects of the Invention

[0016] According to the present disclosure, a non-black polytetrafluoroethylene composition and a molded article having excellent conductivity can be provided. Detailed implementation mode

[0017] The following specifically describes the present disclosure.

[0018] The present disclosure relates to a non-black conductive PTFE composition (hereinafter also referred to as the composition of the present disclosure), which contains polytetrafluoroethylene (PTFE) and a non-black conductive filler, and the non-black conductive filler contains at least one selected from the group consisting of antimony-doped tin oxide and phosphorus-doped tin oxide.

[0019] In the past, as the conductive filler added to PTFE, generally black carbon black was used, and it was difficult to obtain a non-black molded body. The composition of the present disclosure is non-black by containing a specific non-black conductive filler, and has excellent designability. In addition, the conductivity is also excellent.

[0020] The above PTFE may be high molecular weight PTFE.

[0021] The above PTFE preferably has a standard specific gravity (SSG) of 2.130 to 2.280. The above standard specific gravity is more preferably 2.135 or more, and further preferably 2.230 or less, and still further preferably 2.200 or less. The above standard specific gravity is measured using a sample molded according to ASTM D4894 and the water displacement method according to ASTM D792.

[0022] Regarding the "high molecular weight" of PTFE, it means that the above standard specific gravity is within the above range.

[0023] The above PTFE preferably has non-melt secondary processability. Non-melt secondary processability means the property that the melt flow rate cannot be measured at a temperature higher than the melting point according to ASTM D-1238 and D-2116, in other words, the property that it is not easy to flow even in the melting temperature region.

[0024] The above PTFE preferably has a melting point of 324 to 360 °C. The above melting point is the value obtained as the temperature corresponding to the maximum value in the heat of fusion curve when heating at a rate of 10 °C / minute using a differential scanning calorimetry (DSC) device.

[0025] The above PTFE may be a homopolymer of TFE or a modified PTFE containing polymerization units based on TFE (TFE units) and polymerization units based on modified monomers (modified monomer units). The above modified PTFE may contain 99.0 mass% or more of TFE units and 1.0 mass% or less of modified monomer units. In addition, the above modified PTFE may be composed only of TFE units and modified monomer units.

[0026] In the above-mentioned modified PTFE, the content of the modified monomer unit is preferably in the range of 0.00001 to 1.0% by mass relative to all the polymer units. As the lower limit of the content of the modified monomer unit, 0.0001% by mass is more preferable, 0.001% by mass is further preferable, 0.005% by mass is still further preferable, and 0.010% by mass is particularly more preferable. As the upper limit of the content of the modified monomer unit, 0.90% by mass is more preferable, 0.50% by mass is further preferable, 0.40% by mass is still further preferable, 0.30% by mass is particularly more preferable, 0.20% by mass is particularly still further preferable, 0.15% by mass is particularly preferably, and 0.10% by mass is particularly more preferably.

[0027] In this specification, the above-mentioned modified monomer unit refers to a part of the molecular structure of PTFE and is derived from the modified monomer.

[0028] The content of each of the above-mentioned polymer units can be calculated by appropriately combining NMR, FT-IR, elemental analysis, and X-ray fluorescence analysis according to the type of monomer.

[0029] As the above-mentioned modified monomer, there is no particular limitation as long as it can copolymerize with TFE. For example, perfluoroolefins such as hexafluoropropylene [HFP]; hydrogen-containing fluorinated olefins such as trifluoroethylene and vinylidene fluoride [VDF]; perhaloolefins such as chlorotrifluoroethylene; perfluoro vinyl ether and perfluoro allyl ether; (perfluoroalkyl) ethylene, ethylene, etc. In addition, the modified monomer used may be one kind or two or more kinds.

[0030] As the above-mentioned perfluoro vinyl ether, there is no particular limitation. For example, the following general formula (A):

[0031] CF 2 =CF-ORf(A)

[0032] (In the formula, Rf represents a perfluoro organic group) and other perfluoro unsaturated compounds. In this specification, the above-mentioned "perfluoro organic group" refers to an organic group in which all hydrogen atoms bonded to carbon atoms are replaced by fluorine atoms. The above-mentioned perfluoro organic group may have an ether oxygen.

[0033] As the above-mentioned perfluoro vinyl ether, for example, perfluoro(alkyl vinyl ether) [PAVE] in which Rf in the above general formula (A) is a perfluoroalkyl group having 1 to 10 carbon atoms can be mentioned. The number of carbon atoms of the above-mentioned perfluoroalkyl group is preferably 1 to 5.

[0034] As the perfluoroalkyl group in the above-mentioned PAVE, for example, perfluoromethyl, perfluoroethyl, perfluoropropyl, perfluorobutyl, perfluoropentyl, perfluorohexyl, etc. can be mentioned.

[0035] As the above-mentioned perfluoro vinyl ether, examples further include substances in which Rf in the above general formula (A) is a perfluoro(alkoxyalkyl) group having 4 to 9 carbon atoms, substances in which Rf is a group represented by the following formula:

[0036] [Chemical Formula 1]

[0037]

[0038] (wherein m represents an integer of 0 or 1 to 4), substances in which Rf is a group represented by the following formula:

[0039] [Chemical Formula 2]

[0040]

[0041] (wherein n represents an integer of 1 to 4), etc.

[0042] As (perfluoroalkyl)ethylene (PFAE), there is no particular limitation. For example, (perfluorobutyl)ethylene (PFBE), (perfluorohexyl)ethylene, etc. can be cited.

[0043] As perfluoroallyl ether, for example, the general formula (B):

[0044] CF 2 =CF-CF 2 -ORf 1 (B)

[0045] (wherein Rf 1 represents a perfluoro organic group) represents a fluorine monomer.

[0046] The above-mentioned Rf 1 is preferably a perfluoroalkyl group having 1 to 10 carbon atoms or a perfluoroalkoxyalkyl group having 1 to 10 carbon atoms. As the above-mentioned perfluoroallyl ether, it is preferably selected from at least one of the group consisting of CF 2 =CF-CF 2 -O-CF 3 、CF 2 =CF-CF 2 -O-C 2 F 5 、CF 2 =CF-CF 2 -O-C 3 F 7 、and CF 2 =CF-CF 2 -O-C 4 F 9 ; more preferably selected from at least one of the group consisting of CF 2 =CF-CF 2 -O-C 2 F 5, CF 2 = CF - CF 2 -O - C 3 F 7 , and CF 2 = CF - CF 2 -O - C 4 F 9 at least one selected from the group consisting of, more preferably CF 2 = CF - CF 2 -O - CF 2 CF 2 CF 3 .

[0047] The above - mentioned PTFE is preferably granular, and the average particle size is preferably 1 - 2000 μm. More preferably, the above - mentioned average particle size is 1000 μm or less, and further preferably 700 μm or less. Additionally, more preferably, it is 10 μm or more, and further preferably 15 μm or more. When the average particle size is too large, it may be difficult to mold and mix with fillers. When the average particle size is too small, the fluidity of the PTFE composition may deteriorate.

[0048] The above - mentioned average particle size is measured using a laser diffraction particle size distribution measuring device, without using a cascade, at a dispersion pressure of 3.0 bar, and is the particle size corresponding to 50% of the particle size distribution integral (volume - based). As the laser diffraction particle size distribution measuring device, for example, HELOS&RODOS manufactured by JEOL Ltd. can be used.

[0049] The above - mentioned PTFE is preferably PTFE molding powder. The above - mentioned PTFE molding powder is a powder obtained by suspension polymerization of TFE. The above - mentioned suspension polymerization can be carried out by a known method. For example, without using an anionic fluorinated surfactant or using a limited amount, a polymerization initiator is dispersed in an aqueous medium, and monomers required to form the above - mentioned PTFE are polymerized, and the suspension polymerization particles of PTFE can be directly separated.

[0050] The above - mentioned PTFE molding powder can be obtained by granulating the particles obtained by polymerization using a known method.

[0051] In the composition of the present disclosure, the content of the above - mentioned PTFE in the above - mentioned composition is preferably 60 - 90% by mass, more preferably 70 - 90% by mass, and further preferably 70 - 85% by mass.

[0052] The non - black conductive filler in the composition of the present disclosure contains at least one selected from the group consisting of antimony - doped tin oxide and phosphorus - doped tin oxide.

[0053] By using the above-mentioned specific non-black conductive filler, a non-black PTFE composition with excellent conductivity can be obtained even without using zinc oxide.

[0054] In addition, the above-mentioned non-black conductive filler can impart excellent conductivity even in a small amount, so the tensile fracture strength and the tensile fracture elongation are not likely to deteriorate.

[0055] The above-mentioned non-black conductive filler may be composed of at least one selected from the group consisting of antimony-doped tin oxide and phosphorus-doped tin oxide, or the base material particles may be coated with at least one selected from the group consisting of antimony-doped tin oxide and phosphorus-doped tin oxide.

[0056] The above-mentioned non-black conductive filler preferably does not contain zinc oxide.

[0057] In the case of setting a coating method using at least one selected from the group consisting of antimony-doped tin oxide and phosphorus-doped tin oxide, examples of the above-mentioned base material particles include talc, mica, glass flakes, SiO 2 flakes, TiO 2 flakes, Al 2 O 3 flakes, etc. Among them, talc and mica are preferred.

[0058] In the case of setting a coating method using at least one selected from the group consisting of antimony-doped tin oxide and phosphorus-doped tin oxide, the amount of the above-mentioned coating is preferably 20 to 40% by mass with respect to the total amount of the coating and the above-mentioned base material particles.

[0059] As the above-mentioned non-black conductive filler, at least one selected from the group consisting of (a) antimony-doped tin oxide particles, (b) particles obtained by coating at least one base material particle selected from the group consisting of talc and mica with antimony-doped tin oxide, and (c) phosphorus-doped tin oxide particles is preferred. From the aspect of more excellent conductivity, at least one selected from the group consisting of (a) antimony-doped tin oxide particles and (b) particles obtained by coating at least one base material particle selected from the group consisting of talc and mica with antimony-doped tin oxide is more preferred.

[0060] The above-mentioned non-black conductive filler preferably has an average particle size of 1 to 100 μm, more preferably 1 to 30 μm, and further preferably 1 to 10 μm.

[0061] The above-mentioned average particle size is measured using a laser diffraction particle size distribution measuring device, without using a cascade, at a dispersion pressure of 3.0 bar, and is the particle size corresponding to 50% of the particle size distribution integral (volume basis). As the laser diffraction particle size distribution measuring device, for example, HELOS&RODOS manufactured by JEOL Ltd. can be used.

[0062] In the composition of the present disclosure, the content of the above non-black conductive filler is preferably 10 to 40% by mass, more preferably 10 to 30% by mass, and still more preferably 15 to 30% by mass with respect to the composition.

[0063] The composition of the present disclosure may contain only the above PTFE and the above non-black conductive filler, or may contain other components as needed.

[0064] As the above other components, various additives such as metals, inorganic or organic reinforcing fillers, compatibilizers, lubricants (fluorocarbon, carbon graphite, molybdenum disulfide), and stabilizers can be combined and incorporated.

[0065] The composition of the present disclosure can be obtained, for example, by mixing the above PTFE, the above non-black conductive filler, and other components added as needed using a mixer such as a V-type blender, a drum mixer, a Henschel mixer, a ball mixer, or a Lodige mixer.

[0066] The composition of the present disclosure has conductivity. From the aspect of more excellent conductivity, the volume resistivity is preferably 1.0×10 3 to 1.0×10 7 Ω·cm, more preferably 1.0×10 3 to 6.0×10 6 Ω·cm, still more preferably 1.0×10 3 to 2.0×10 6 Ω·cm, and particularly preferably 1.0×10 4 to 2.0×10 6 Ω·cm.

[0067] The above volume resistivity is determined by the following method.

[0068] After the composition is compression molded at a molding pressure of 50 MPa and then fired at 370°C, a cylindrical molded body (outer diameter 12 mm, height 40 mm) is obtained. The DC resistance of this molded body is measured using a digital multimeter (HT26: manufactured by HT ITALIA), and the volume resistivity (Ω·cm) is calculated by the following formula.

[0069] Volume resistivity (Ω·cm) = measured value (Ω) × cross-sectional area of the cylinder (cm 2 ) / height of the cylinder (cm)

[0070] Here, the cross-sectional area of the cylinder is the cross-sectional area based on the plane perpendicular to the height direction.

[0071] The composition of the present disclosure can be suitably used as a molding material. The present disclosure also relates to a molded body obtained by molding the composition of the present disclosure.

[0072] The molded article of the present disclosure is non - black and has excellent designability. In addition, it also has excellent conductivity.

[0073] Furthermore, the molded article of the present disclosure has good tensile fracture strength and tensile fracture elongation.

[0074] As a method for molding the composition of the present disclosure, there is no particular limitation, and examples thereof include compression molding, plunger extrusion molding, isostatic pressing molding, etc. Among them, compression molding is preferred.

[0075] The shape of the molded article of the present disclosure is not particularly limited, and examples thereof include sheet - like, film - like, ring - like, rod - like, tubular, fibrous, etc.

[0076] The molded article of the present disclosure is expected to be used in sealing materials such as gaskets and seals, OA equipment rollers and pipe applications, as well as in the hygienic piping of foods, pharmaceuticals, etc., and the inner lining of tanks.

[0077] Among them, sealing materials such as gaskets and seals are preferred.

[0078] Examples

[0079] Examples are given below to illustrate the present disclosure in more detail, but the present disclosure is not limited to these examples.

[0080] The following raw materials are used in the examples and comparative examples.

[0081] <Polytetrafluoroethylene (PTFE)>

[0082] PTFE1: POLYFLON M - 18F, manufactured by Daikin Industries, Ltd., TFE homopolymer, standard specific gravity (SSG): 2.164, melting point: 345 °C, average particle size: 20 μm.

[0083] <Conductive filler>

[0084] Carbon black

[0085] Non - black conductive filler (1): Zinc oxide

[0086] Non - black conductive filler (2): Antimony - doped tin oxide (average particle size: 5 μm)

[0087] Non - black conductive filler (3): Phosphorus - doped tin oxide (average particle size: 4 μm)

[0088] Various physical properties are measured by the following methods.

[0089] <Average particle size>

[0090] Using a laser diffraction particle size distribution analyzer (HELOS&RODOS manufactured by JEOL Ltd.), measurements were taken without using a cascade at a dispersion pressure of 3.0 bar, corresponding to the particle size at which the integral of the particle size distribution (volume basis) is 50%.

[0091] <Melting point>

[0092] It was determined as the temperature corresponding to the maximum value in the heat of fusion curve when heating at a rate of 10 °C / min using a differential scanning calorimetry (DSC) apparatus.

[0093] <Volume resistivity>

[0094] After press-molding the PTFE composition at a molding pressure of 50 MPa, it was fired at 370 °C to obtain a cylindrical molded body (outer diameter 12 mm, height 40 mm). The DC resistance of this molded body was measured using a digital multimeter (HT26: manufactured by HT ITALIA), and the volume resistivity (Ω·cm) was calculated by the following formula.

[0095] Volume resistivity (Ω·cm) = Measured value (Ω) × Cross-sectional area of the cylinder (cm 2 ) / Height of the cylinder (cm)

[0096] Here, the cross-sectional area of the cylinder is the cross-sectional area based on the plane perpendicular to the height direction.

[0097] <Tensile fracture strength, Tensile fracture elongation>

[0098] Measured according to ASTM D4745.

[0099] Comparative Example 1

[0100] 97 parts by mass of the polytetrafluoroethylene resin powder (the above PTFE1) obtained by suspension polymerization and 3 parts by mass of the above carbon black were mixed using a Henschel mixer to obtain a PTFE composition.

[0101] Comparative Examples 2 - 4 and Examples 1 - 5

[0102] As described in Table 1, the type and filling amount of the conductive filler were changed, and except for this, PTFE compositions were obtained in the same manner as in Comparative Example 1.

[0103] The results are shown in Table 1.

[0104]

Claims

1. A non-black conductive polytetrafluoroethylene composition comprising polytetrafluoroethylene and a non-black conductive filler, the non-black conductive filler comprising at least one selected from the group consisting of antimony-doped tin oxide and phosphorus-doped tin oxide.

2. The non-black conductive polytetrafluoroethylene composition according to claim 1, wherein, The volume resistivity is 1.0×10 3 Ω·cm to 1.0×10 7 Ω·cm.

3. The non-black conductive polytetrafluoroethylene composition according to claim 1 or 2, wherein, the content of the non-black conductive filler is 10% to 40% by mass relative to the composition.

4. A molded article obtained by molding the non-black conductive polytetrafluoroethylene composition according to any one of claims 1 to 3.

5. The molded article according to claim 4, wherein, the molded article is a sealing material.

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