JP2023178194A - Sealing resin composition and seal - Google Patents

Abstract

To provide a sealing resin composition and a seal which are able to be used in a high-temperature and high-pressure gas.SOLUTION: The sealing resin composition is used in a piston ring 1 for sealing for a gas. When a molded article of the sealing resin composition is subjected to dynamic viscoelasticity measurement, E1' and E2' are each 4.0×108 Pa or more, where E1' and E2' refer to storage moduli at temperatures of 30°C and 200°C, respectively, and the peak temperature of the loss tangent tanδ of the molded article of the sealing resin composition is 150°C or higher.SELECTED DRAWING: Figure 1

Description

The present invention relates to a sealing resin composition and a seal used in a seal for sealing gas, and particularly to a resin composition and a piston ring used in a piston ring of a reciprocating compressor for hydrogen gas.

At hydrogen stations, many seals are used to seal hydrogen in reciprocating compressors for hydrogen gas, pressure accumulators for storing hydrogen gas, dispensers for supplying hydrogen gas to fuel cell vehicles (FCVs), etc. has been done. Furthermore, in an FCV, a seal is used in a pressure reducing valve and the like for reducing the pressure of hydrogen in a high-pressure hydrogen tank and supplying the reduced pressure gas to a fuel cell. Therefore, there is a need for a seal that has high hydrogen gas sealing properties and can be used for a long period of time in high-pressure hydrogen gas.

In particular, piston rings used as seals in reciprocating compressors for hydrogen gas at hydrogen stations must withstand harsh environments of high temperature and pressure, and are resistant to dimensional changes even when exposed to such environments for long periods of time. Changes are also required to be small. A typical reciprocating compressor for hydrogen gas has a structure that includes a piston and a cylinder, and compresses hydrogen gas by reciprocating the piston with respect to the cylinder. In such reciprocating compressors, an annular piston ring has conventionally been used for the purpose of sealing hydrogen gas in a gap between a piston and a cylinder. The piston ring is mounted in an annular groove provided in the piston. In this case, the outer circumferential surface of the piston ring contacts the inner circumferential surface of the cylinder, and the side surface of the piston ring contacts the side surface of the annular groove, thereby sealing the hydrogen gas. The piston rings used are required to further improve their wear resistance in harsh environments of high temperature and pressure. In a hydrogen station, the operating temperature of the compressor is, for example, approximately 150° C. to 200° C. in Non-Patent Document 1.

For example, Patent Document 1 discloses a reciprocating compressor for hydrogen gas and its piston ring. Patent Document 1 states that the total amount of polytetrafluoroethylene (PTFE) resin and one of polyetheretherketone (PEEK) resin and polyimide (PI) resin is 50% by mass or more of the total, and , a resin piston ring that does not contain polyphenylene sulfide (PPS) resin is described. Patent Document 1 states that by setting the tensile strength of the piston ring within a range of greater than 15 MPa and less than 100 MPa, sealing performance can be maintained over a longer operating period than piston rings outside this range.

Further, in Patent Document 2, a sliding member used in a reciprocating compressor for hydrogen gas is provided on one member of a piston member and a cylinder liner, and is provided relative to the other member (sliding member). A ring-shaped sliding member made of resin that slides is described. Patent Document 2 states that by forming an amorphous carbon film on the sliding surfaces of both the sliding member and the slidable member, the replacement life of the sliding member due to wear can be extended. Note that the surface portion of the amorphous carbon film has a higher carbon content than the inner portion. It is said that this amorphous carbon film preferably does not contain sulfur. Furthermore, it is preferable that the sliding member is, for example, a desulfurized member that has been exposed to a hydrogen atmosphere before being incorporated into a compressor.

Japanese Patent Application Publication No. 2020-180600 Patent No. 6533631

70MPa Hydrogen Station Technical Standards Review Committee Report, High Pressure Gas Safety Association, February 2012

Patent Document 1 mentioned above focuses on tensile strength among the various properties of piston rings, and by adjusting this within an appropriate range, the high sealing performance of piston rings can be maintained for a long time even when PPS resin is not added. It is expected that this will be sustainable over a period of time. Note that the "tensile strength" may be a value measured based on JIS K7161 (Plastics - Test method for tensile properties Part 1: General rules).

However, in reciprocating compressors for hydrogen gas, resin piston rings are used in harsh environments with high temperatures and pressures, so in terms of pressure resistance and wear resistance, the physical properties of resin (strength, elasticity, properties (e.g., physical properties at room temperature) become more important than physical properties in the room temperature region. Furthermore, since the resin is a viscoelastic body, it is considered necessary to consider viscoelastic properties as well.

The present invention was made in view of the above circumstances, and an object of the present invention is to provide a sealing resin composition and a seal that can be used in high temperature and high pressure gas, particularly hydrogen gas.

The sealing resin composition of the present invention is a sealing resin composition used for a seal for sealing gas, and when a molded article of the sealing resin composition is subjected to dynamic viscoelasticity measurement, the temperature is 30°C. _The storage elastic modulus at a temperature of 200° C. is E ₁ ′, and the storage elastic modulus at a temperature of ^200° C. is E _{2 ′} . The term "molded object" as used herein refers to a molded object formed by a well-known method such as injection molding, compression molding, or extrusion molding, or a machined product of these molded objects, and includes seal products ( (Piston rings, valve bodies, valve seats, gland packings, lip seals, etc.) are also included. Furthermore, the term "gas" in this specification is a general concept meaning gas, and includes gaseous fuel and the like. For example, it may be a gas such as hydrogen, natural gas, or ammonia.

The molded article of the sealing resin composition is characterized in that the peak temperature of the loss tangent tan δ is 150° C. or higher.

It is characterized in that the relationship between E _{1 ′} and E ₂ ′ satisfies the following formula: E ₂ ′/E ₁ ′=0.70 or more and 1.0 or less.

The base resin of the sealing resin composition is characterized in that it is an aromatic polyetherketone resin, a thermoplastic PI resin, or a polyamideimide (PAI) resin. Furthermore, the aromatic polyetherketone resin is characterized in that it has a glass transition point of 150°C or higher.

The sealing resin composition contains a carbon material having a sulfur atom content of 200 ppm or less, and the carbon material is at least one selected from the group consisting of carbon fiber, graphite, and coke powder, The sealing resin composition is characterized in that the carbon material is contained in a total amount of 5% to 50% by volume based on the entirety of the sealing resin composition.

The molded article of the sealing resin composition is characterized in that the content of sulfur atoms is 250 ppm or less.

The seal of the present invention is characterized in that it is made of a molded article of the resin composition for a seal. Further, the seal is a piston ring of a reciprocating compressor that compresses hydrogen gas.

The sealing resin composition of the present invention has a storage modulus of E ₁ ' at a temperature of 30° C. and an E ₂ storage modulus of storage elasticity at a temperature of 200° C. when a molded article of the sealing resin composition is measured for dynamic viscoelasticity. ', E ₁ ' and E ₂ ' are each 4.0×10 ⁸ Pa or more, and more preferably, the peak temperature of the loss tangent tan δ is 150° C. or more. Since the molded body has a high peak temperature of E ₂ ' and tan δ, it is difficult to deform and wear easily even at high temperatures, so it is suitable as a seal used, for example, in high temperature and high pressure hydrogen gas. It is particularly suitable as a piston ring for a reciprocating compressor that compresses hydrogen gas.

In addition, since the relationship between E ₁ ' and E ₂ ' satisfies the formula E ₂ '/E ₁ ' = 0.70 or more and 1.0 or less, the change in elastic modulus due to temperature is small and it can be applied to seals. , can maintain stable sealing performance over a wide temperature range from near room temperature to high temperatures.

When filling an FCV with hydrogen gas compressed by a reciprocating compressor, if sulfur components are mixed into the hydrogen gas, there is a risk that the performance of the fuel cell will deteriorate. , a carbon material with a sulfur atom content of 200 ppm or less is blended, and the sulfur atom content is 250 ppm or less with respect to the entire sealing resin composition, so as exemplified in Patent Document 2 above. It is possible to reduce the mixing of sulfur components into the hydrogen gas without performing desulfurization treatment in a special atmosphere, and it is possible to suppress the performance deterioration of the fuel cell in the FCV.

FIG. 1 is a perspective view of an example of a piston ring made of the sealing resin composition of the present invention. FIG. 1 is a cross-sectional view of an example of a reciprocating compressor for hydrogen gas using a piston ring made of the sealing resin composition of the present invention. 3 shows the dynamic viscoelasticity measurement results (relationship between temperature and storage modulus E') in Example 4. 3 shows the dynamic viscoelasticity measurement results (relationship between temperature and loss tangent tanδ) in Example 4. FIG. 1 is a schematic diagram of a pin-on-disk testing machine.

The present inventor has developed a resin composition in which the storage elastic modulus E ₁ ′ at a temperature of 30° C. and the storage elastic modulus E _{2 ′} at a temperature of 200° C. are within a predetermined range when dynamic viscoelasticity measurements are performed on a molded article of the resin composition. Furthermore, the resin composition whose loss tangent tan δ is within a predetermined range and whose ratio of E _{1 ′} and E ₂ ′ satisfies a predetermined formula can be used at high temperatures (for example, about 100°C to 200°C) and high pressures. It has been found that the sealing resin composition is suitable for use in hydrogen gas. The present invention is based on such knowledge.

The sealing resin composition of the present invention has a storage modulus of E ₁ ' at a temperature of 30°C and an E ₂ ' of storage elasticity at a temperature of 200°C when a molded article of the resin composition is measured for dynamic viscoelasticity. Then, it is preferable that E ₁ ′ and E ₂ ′ are each 4.0×10 ⁸ Pa or more. When the above E _{1 ′} and E ₂ ′ are less than 4.0×10 ⁸ Pa, when the molded article of the resin composition is used as a seal for sealing high-pressure hydrogen gas, for example, deformation occurs during use. becomes large, and there is a possibility that the predetermined sealing performance cannot be satisfied.

In this specification, the storage elastic modulus E', loss elastic modulus E'', and loss tangent tan δ are obtained by dynamic viscoelasticity measurement in tensile mode at a measurement frequency of 10 Hz using a molded article of the above-mentioned sealing resin composition. This is the measured value.

The storage elastic modulus E ₁ ' at a temperature of 30° C. is more preferably 1.0×10 ⁹ Pa or more, and even more preferably 2.0×10 ⁹ Pa or more. On the other hand, E ₁ ' is, for example, 1.0×10 ¹⁰ Pa or less, and may be 6.0×10 ⁹ Pa or less.

The storage modulus E ₂ ' at a temperature of 200° C. is more preferably 1.0×10 ⁹ Pa or more, and even more preferably 2.0×10 ⁹ Pa or more. On the other hand, E ₂ ′ is, for example, 1.0×10 ¹⁰ Pa or less, and may be 6.0×10 ⁹ Pa or less.

The loss tangent tan δ is a value obtained by dividing the loss elastic modulus E'' by the storage elastic modulus E', and there is a relationship of tan δ = (E''/E'). The loss tangent tan δ is calculated using the storage modulus E' and the loss modulus E" at each temperature. The peak temperature of the loss tangent tan δ is calculated from the storage modulus E' and the loss modulus E" at each temperature. In the tan δ curve obtained by calculating and plotting the tan δ of the temperature, this is the temperature at which tan δ becomes maximum (see, for example, FIG. 4).

The peak temperature of the loss tangent tan δ is not particularly limited, but is preferably 150°C or higher, more preferably 170°C or higher, even more preferably 200°C or higher, and may be 250°C or higher. The upper limit of the peak temperature of the loss tangent tan δ is not particularly limited, but is, for example, 400° C. or lower, and may be 300° C. or lower. Further, the peak value of the loss tangent tan δ is, for example, 0.03 to 0.30.

Moreover, it is preferable that the sealing resin composition of the present invention satisfies the following formula: E ₂ ′/E ₁ ′=0.30 or more and 1.0 or less. Within this range, changes in the elastic modulus of the molded body at 30° C. to 200° C. are suppressed, making it easier to maintain stable sealing performance in this temperature range. More preferably, the formula E ₂ '/E ₁ '=0.50 or more and 1.0 or less is satisfied, and still more preferably the formula _E2 '/ _E1 '=0.70 or more and 1.0 or less is satisfied. Further, the following formula may be satisfied: E ₂ ′/E ₁ ′=0.80 or more and 1.0 or less. E ₂ ′/E ₁ ′ may be less than 1.0.

A reciprocating compressor for hydrogen gas may repeatedly compress hydrogen gas in a range of, for example, about 30°C to about 200°C. Therefore, by defining the ratio of the storage modulus in the high temperature region to the storage modulus in the room temperature region as described above, the rate of decrease from the storage modulus E ₁ ' at 30°C to the storage modulus E ₂ ' at 200°C can be determined as follows. can be suppressed. As a result, it becomes easier to maintain stable sealing performance over a wide temperature range from room temperature to high temperature.

The above-mentioned dynamic viscoelastic properties such as storage modulus E', loss modulus E'', and loss tangent tan δ can be measured using, for example, a dynamic viscoelasticity measuring device "DMS6100" (Hitachi High-Tech Science Co., Ltd.). Measurement can be performed using a strip-shaped test piece made of a resin composition under the following conditions: distance between chucks 20 mm, tension mode, measurement frequency 10 Hz, strain amplitude 10 μm (sine wave), and temperature increase rate 2° C./min. E', E", and tan δ for each temperature are obtained as measurement results, and _E1 ' and _E2 ' are obtained as storage moduli E' corresponding to predetermined temperatures (30° C., 200° C.), respectively. Although the size of the strip-shaped test piece is not particularly limited, it may be, for example, 2 mm x 5 mm x 45 mm.

The specific composition of the sealing resin composition of the present invention will be explained below.

The sealing resin composition of the present invention has a base resin as a main component. The type of this base resin is not limited, and the peak temperatures of E ₁ ′, E ₂ ′, tan δ and (E ₂ ′/E ₁ ′) of the molded article of the resin composition described above can be easily adjusted to desired ranges. Resins are preferred. Specifically, in order to increase the peak temperature of tan δ, it is preferable to select a resin with a high glass transition point as the base resin. A well-known method can be used to measure the glass transition point. For example, the peak temperature of tan δ in dynamic viscoelasticity measurement may be regarded as the glass transition point, and it can also be measured by differential scanning calorimetry (DSC). In the present invention, the base resin preferably has a glass transition point of 140° C. or higher as measured by DSC.

When the glass transition point is high, the peak temperature of tan δ becomes high, and the storage modulus E' is likely to be maintained without significantly decreasing to around the peak temperature of tan δ. From the viewpoint of setting the peak temperature of tan δ to 150° C. or higher, for example, an aromatic polyetherketone resin, a thermoplastic PI resin, a thermosetting PI resin, or a PAI resin can be used as the base resin. Further, from the viewpoint of satisfying the mathematical formula of E _{2 ′} /E ₁ ′=0.70 or more and 1.0 or less, it is particularly preferable that the glass transition point of the base resin as measured by DSC is 200° C. or more.

It is preferable that the peak temperatures of E ₁ ′, E ₂ ′, and tan δ described above change little before and after the molded article of the sealing resin composition is exposed to a high temperature and high pressure gas. For example, when a molded article of the sealing resin composition is exposed to gas at a pressure of 82 MPa and a temperature of 200° C. for 192 hours, the rate of change in E ₁ ′ and E ₂ ′ is within ±20% based on before exposure. It is preferably within ±10%, and more preferably within ±10%. Further, the rate of change in the peak temperature of tan δ is preferably within ±10%, more preferably within ±5%. The above gas is, for example, hydrogen gas.

Moreover, it is preferable that the base resin is an injection moldable resin. If injection molding is possible, the degree of design freedom is increased and seals of various shapes can be accommodated.

Examples of resins that can easily satisfy the desired ranges of the peak temperatures of E ₁ ′, E ₂ ′, tan δ, and (E ₂ ′/E ₁ ′) and can be injection molded include, for example, aromatic polyesters. Examples include ether ketone resin, thermoplastic PI resin, and PAI resin.

Aromatic polyetherketone resin is a general term for resins in which benzene rings are bonded with ether groups and ketone groups, and is also called polyaryletherketone resin. Examples of the aromatic polyetherketone resin include PEEK resin, polyetherketone (PEK) resin, polyetherketoneketone (PEKK) resin, and polyetherketoneetherketoneketone (PEKEKK) resin.

When using aromatic polyetherketone resin, PEEK resin is preferred from the viewpoint of cost. PEEK resin has a chemical structure shown in the following formula (1), and the glass transition point of PEEK resin measured by DSC is 143°C. In the present invention, the PEEK resin can be used without any limitations on the average molecular weight, molecular weight distribution, etc. The melt viscosity of PEEK resin at a shear rate of 1000/s and a temperature of 400° C. is not particularly limited, but for example, in the case of a piston ring, the melt viscosity should be 200 Pa s to 550 Pa s according to a measurement method based on ISO 11443. is preferred. By keeping it within this range, it becomes easy to ensure sufficient wear resistance while making molding processing by injection molding possible. The above melt viscosity is more preferably 300 Pa·s to 500 Pa·s.

From the viewpoint of wear resistance under high temperatures, aromatic polyetherketone resins with a glass transition point higher than that of PEEK resin are more preferable, and aromatic polyetherketone resins with a glass transition point of 150° C. or higher as measured by DSC are particularly preferred. preferable. Specifically, PEK resin (glass transition point: 160° C.), PEKK resin (glass transition point: 160 to 165° C.), PEKEKK resin (glass transition point: 170° C.), etc. can be used. For example, PEK resin has a chemical structure shown in formula (2) below.

When the glass transition point of an aromatic polyetherketone resin measured by DSC is 150 to 160°C, the melt viscosity at a shear rate of 1000/s and a temperature of 400°C is 100 Pa·s to 550 Pa· by a measurement method based on ISO 11443. It may be s. By setting it within this range, it becomes easy to ensure sufficient wear resistance as a piston ring used in a reciprocating compressor, for example, while making molding processing by injection molding possible. Furthermore, if the glass transition point measured by DSC of the aromatic polyetherketone resin is 160 to 170°C, even if the melt viscosity at a shear rate of 1000/s and a temperature of 420°C is 100 Pa·s to 550 Pa·s. good. By setting it within this range, it becomes easy to ensure sufficient wear resistance as a piston ring used in a reciprocating compressor, for example, while making molding processing by injection molding possible.

A plurality of aromatic polyetherketone resins having different types and melt viscosities may be mixed and used in the resin composition of the present invention. Aromatic polyetherketone resin does not contain a sulfur atom in its molecular structure as shown in formulas (1) and (2) above, but it is (Solvents containing sulfur atoms) may be contained as impurities.

Specific commercial products of PEEK resin include: Victrex Japan Co., Ltd.: PEEK 90P, PEEK 150P, PEEK 380P, PEEK 450P, PEEK 650P; Polypla Evonik Co., Ltd.: VESTAKEEP 1000P, VESTAKEEP 2000P, VESTAKEEP 3 000P, VESTAKEEP 4000P , VESTAKEEP 5000P, etc. can be used. Furthermore, even when using PEEK resin, a special PEEK resin having higher heat resistance than general PEEK resin having a glass transition point of 143° C. can be used. Examples of such commercial products include KetaSpire (registered trademark) PEEK XT-920 FP manufactured by Solvay Specialty Polymers Japan Co., Ltd., which has a glass transition point of 170°C.

As a specific commercial product of PEK resin, HT P22 manufactured by Victrex Japan Co., Ltd. can be used, as a PEKEKK resin, ST P45 manufactured by Victrex Japan Co., Ltd. can be used, and as a PEKK resin, manufactured by Arkema Co., Ltd. : Kepstan (registered trademark) PEKK 6000 series, 7000 series, 8000 series can be used.

The thermoplastic PI resin is preferably a resin that has a high glass transition point and high melting point and can be melt-molded by injection molding or the like. Specifically, as shown in formula (3) below, imide groups with excellent thermal properties and mechanical strength surround aromatic groups in the repeating unit of the molecular structure, but they do not absorb energy such as heat. Imide-based resins with a structure that has multiple ether bond parts that exhibit appropriate melting characteristics when added are often used. A thermoplastic PI resin having two is preferred.

（式中、Ｘは直接結合、炭素数１～１０の炭化水素基、六フッ素化されたイソプロピリデン基、カルボニル基、チオ基およびスルホン基からなる群より選ばれた基を表し、Ｒ_１～Ｒ_４は水素、炭素数１～５の低級アルキル基、炭素数１～５の低級アルコキシ基、塩素または臭素を表し、互いに同じであっても異なっていてもよい。Ｙは炭素数２以上の脂肪族基、環式脂肪族基、単環式芳香族基、縮合多環式芳香族基、芳香族基が直接または架橋基により相互に連結された非縮合多環式芳香族基からなる群から選ばれた４価の基を表す。）

(wherein _, R ₄ represents hydrogen, a lower alkyl group having 1 to 5 carbon atoms, a lower alkoxy group having 1 to 5 carbon atoms, chlorine or bromine, and may be the same or different from each other. Y is a lower alkyl group having 1 to 5 carbon atoms, and may be the same or different from each other. A group consisting of an aliphatic group, a cycloaliphatic group, a monocyclic aromatic group, a fused polycyclic aromatic group, and a non-fused polycyclic aromatic group in which aromatic groups are interconnected directly or through a bridging group. represents a tetravalent group selected from )

Commercially available thermoplastic PI resins include Aurum (registered trademark) manufactured by Mitsui Chemicals, Inc., Surprim (registered trademark) manufactured by Mitsubishi Gas Chemical Co., Ltd., and the like. Of these two types, Aurum, which satisfies the above formula (3), has a glass transition point of 250° C. and a melting point of 388° C., and is particularly preferred because it has extremely excellent heat resistance. In Aurum, X in the above formula (3) is a direct bond, and R ₁ to R ₄ are all hydrogen. Examples of Aurum grades that can be used in the resin composition of the present invention include PD250, PD400, PD450, and PD500.

PAI resin is a resin having imide bonds and amide bonds in the polymer main chain. For example, as the PAI resin, an aromatic PAI resin in which an imide bond and an amide bond are bonded via an aromatic group as shown in the following formula (4) can be used.

（式中、Ｒ_１は少なくとも１つのベンゼン環を含む３価の芳香族基を表し、Ｒ_２は２価の有機基を表し、Ｒ_３は水素、メチル基またはフェニル基を表す。）

(In the formula, R ₁ represents a trivalent aromatic group containing at least one benzene ring, R ₂ represents a divalent organic group, and R ₃ represents hydrogen, a methyl group, or a phenyl group.)

Such aromatic PAI resins include PAI resins prepared from mono- or diacyl halide derivatives of aromatic primary diamines, such as diphenylmethane diamine, and aromatic tribasic acid anhydrides, such as trimellitic anhydride; There are PAI resins made from tribasic acid anhydrides and aromatic diisocyanate compounds, such as diphenylmethane diisocyanate.

Commercially available PAI resins include Torlon (registered trademark) manufactured by Solvay Specialty Polymers Japan Co., Ltd. and the like. Examples of the Torlon grade that can be used in the resin composition of the present invention include 4000T.

Furthermore, the base resin has a gas permeability of 7.0×10 ⁻¹² mol/(m ² ·s·Pa) or less, for example, of 4.0 It is preferably not more than ×10 ⁻¹² mol/(m ² ·s·Pa). For example, if a base resin with a gas permeability exceeding 4.0×10 ^-12 mol/(m ² s Pa) is used, dimensional changes and physical properties of the molded article of the resin composition may occur in high temperature and high pressure gas. There is a risk that the changes will be significant. The gas permeability is more preferably 1.0×10 ⁻¹² mol/(m ² ·s·Pa) to 3.5×10 ⁻¹² mol/(m ² ·s·Pa). The above gas is, for example, hydrogen gas.

In the sealing resin composition, the base resin preferably contains 50% to 95% by volume, more preferably 60% to 90% by volume, and 70% to 80% by volume based on the entire resin composition. It is more preferable that the content is % by volume.

The sealing resin composition of the present invention blends a carbon material into a base resin such as an aromatic polyetherketone resin, a thermoplastic PI resin, or a PAI resin for the purpose of improving strength, elastic modulus, friction and wear characteristics, etc. It is preferable. The "carbon material" in this specification is not limited in the presence or absence of crystallinity and its degree, and may contain sulfur atoms if unintentional. Examples of the carbon material include carbon fiber, graphite, coke powder, etc., and one type of carbon material among these may be blended alone, or a plurality of types may be blended in combination. The content of sulfur atoms contained in the carbon material is preferably 200 ppm or less, more preferably 100 ppm or less, and particularly preferably 50 ppm or less. Furthermore, polytetrafluoroethylene (PTFE) resin, which is a solid lubricant, may be blended with the base resin. In the sealing resin composition of the present invention, it is preferable to blend at least one of a carbon material and a PTFE resin, and more preferably to blend both a carbon material and a PTFE resin. Note that frictional wear characteristics are important when the seal is a moving seal such as a piston ring.

The content of sulfur atoms contained in the carbon material (% by mass relative to the total amount (100% by mass) of each carbon material used) can be measured by a well-known analytical method. For example, an inductively coupled plasma mass spectrometer (ICP-MS) may be used. For the purpose of more accurate measurement, a triple quadrupole inductively coupled plasma mass spectrometer (ICP-MS/MS) may be used. As a pretreatment method for analysis, for example, a method of filtering the decomposition liquid obtained by acid decomposition using a microwave sample pretreatment device and obtaining a supernatant as an analysis sample can be mentioned. It can be confirmed that the decomposition residue does not contain sulfur atoms using a known analytical method such as a fluorescent X-ray analyzer.

The carbon fiber may be pitch-based or PAN-based, which are classified based on raw materials. The firing temperature is not limited, and either a graphitized product fired at a high temperature of 2000°C or higher or a carbonized product fired at about 1000 to 1500°C may be used. Furthermore, although either chopped fiber or milled fiber may be used, it is preferable to use milled fiber with a short fiber length from the viewpoint of friction and wear characteristics.

Commercially available milled fibers that can be used in the present invention include pitch-based carbon fibers manufactured by Kureha Corporation: Kureka M-101S, M-101F, M-101T, M-104T, M-107T, M-201S, M- Examples include 201F. Examples of PAN-based carbon fibers include HT M800 160MU and HT M100 40MU manufactured by Teijin Corporation, and Torayca MLD-30 and MLD-300 manufactured by Toray Industries, Inc.

In the case of pitch-based carbon fiber, the raw material pitch contains sulfur as an impurity. Also, in the case of PAN-based carbon fibers, when sulfuric acid is used for surface treatment, sulfur may remain. As the carbon fiber, it is preferable to use PAN-based carbon fiber, which has a relatively lower content of sulfur atoms than pitch-based carbon fiber.

The average fiber length of the carbon fibers used in the present invention is not particularly limited, but short fibers of 20 μm to 200 μm are preferable. When the average fiber length is less than 20 μm, it is difficult to obtain the effect of improving wear resistance, and when it exceeds 200 μm, carbon fibers that are broken during sliding tend to enter the sliding surface, causing damage and wear to cylinders and the like. Note that the average fiber length in this specification is the number average fiber length.

Graphite is a solid lubricant and can improve the friction and wear characteristics of the resin composition. Further, as the graphite, either natural graphite or artificial graphite may be used. The shape of the particles may be scaly, granular, spherical, etc., and any of them may be used. Examples of commercially available graphite that can be used in the present invention include natural graphite ACP made by Nippon Graphite Industries Co., Ltd., and artificial graphite TIMREX KS6, KS25, and KS44 made by Imerys GC Japan Co., Ltd. In addition, spherical graphite (or spherical carbon) obtained by firing resin particles may also be used; for example, Air Water Bell Pearl Co., Ltd.'s Bell Pearl C800, C2000, etc., which are obtained by firing phenolic resin particles, may be used. Can be used. The 50% particle diameter (D ₅₀ ) of graphite is not limited, but is preferably 3 μm to 50 μm, more preferably 10 μm to 30 μm. If it exceeds 50 μm, the tensile elongation properties of the resin composition may deteriorate.

Coke powder can improve the wear resistance of the resin composition. The _D50 of coke powder is not limited, but is preferably 3 μm to 50 μm, more preferably 10 μm to 30 μm. If it exceeds 50 μm, the tensile elongation properties of the resin composition may deteriorate.

The sealing resin composition preferably contains at least one type of carbon material such as carbon fiber, graphite, coke powder, etc., and preferably contains a total of 5% to 50% by volume of the carbon material based on the entire resin composition. The content is more preferably 5% to 35% by volume, and even more preferably 5% to 25% by volume. If the total blending amount of carbon materials is less than 5% by volume, it is difficult to obtain the effect of improving wear resistance, and if it exceeds 35% by volume, the melt viscosity of the resin composition increases, and in the case of molded products with thin walled parts. This makes injection molding difficult. If it exceeds 50% by volume, the melt viscosity becomes extremely high, making injection molding itself difficult. As the carbon material, for example, carbon fiber and graphite can be used in combination.

PTFE resin is a solid lubricant and can improve the friction and wear characteristics of the resin composition. As the PTFE resin, any of molding powder produced by suspension polymerization, fine powder produced by emulsion polymerization, and recycled PTFE may be employed. In order to stabilize the fluidity of the resin composition, it is preferable to use recycled PTFE, which is less likely to become fibrous due to shearing during molding and less likely to increase melt viscosity. Recycled PTFE refers to heat-treated (heat history-added) powder, powder that has been irradiated with γ-rays, electron beams, or the like. For example, molding powder or fine powder that has been heat treated, powder that has been further irradiated with gamma rays or electron beams, powder that has been ground into molded molding powder or fine powder, and powder that has been subsequently irradiated with gamma rays or electron beams. There are types such as irradiated powder, molding powder, or fine powder irradiated with gamma rays or electron beams. There is also a type that is further heat treated after irradiation with gamma rays or electron beams. The D ₅₀ of the PTFE resin is not particularly limited, but it is more preferably 10 μm to 50 μm.

Commercially available PTFE resins that can be used in the present invention include: Kitamura Co., Ltd.: KTL-610, KTL-610A, KTL-450, KTL-350, KTL-8N, KTL-8F, KTL-400H, Mitsui Chemours Fluoro Products Co., Ltd.: Teflon (registered trademark) 7-J, TLP-10, AGC Co., Ltd.: Fluon G163, L150J, L169J, L170J, L172J, L173J, L182J, Daikin Industries, Ltd.: Polyflon M-15, 3M Examples include Dyneon TF9205 and TF9207 manufactured by Japan Co., Ltd. It may also be a PTFE resin modified with a perfluoroalkyl ether group, a fluoroalkyl group, or another side chain group having fluoroalkyl. Among the above, PTFE resins irradiated with gamma rays or electron beams are manufactured by Kitamura Co., Ltd.: KTL-610, KTL-610A, KTL-450, KTL-350, KTL-8N, KTL-8F, AGC Co., Ltd. Manufacturers: Fluon L169J, L170J, L172J, L173J, L182J, etc.

The sealing resin composition preferably contains 5% to 25% by volume of PTFE resin based on the entire resin composition. If the amount of the PTFE resin blended is less than 5% by volume, it is difficult to obtain an effect of improving friction and wear properties, and if it exceeds 25% by volume, the tensile elongation properties of the resin composition may deteriorate. The blending amount of the PTFE resin is more preferably 10% by volume to 20% by volume.

The 50% particle diameter (D ₅₀ ) of the PTFE resin, graphite, and coke powder blended into the sealing resin composition of the present invention is the particle diameter at the point where the cumulative value is 50% when the particle diameter distribution is a cumulative distribution. It can be measured using a particle size distribution measuring device that utilizes a laser light scattering method.

In addition to the carbon material and the PTFE resin, the seal resin composition may contain well-known additives for resins to the extent that the effects of the present invention are not impaired. Examples of additives include glass fibers, aramid fibers, inorganic substances (mica, talc, calcium carbonate, boron nitride, etc.), whiskers (calcium carbonate, potassium titanate, etc.), colorants (iron oxide, titanium oxide, carbon black, etc.) ), other resin components, etc. When the content of sulfur atoms in the resin additive exceeds 200 ppm, it is preferable that the amount of this additive is 3% by volume or less based on the entire resin composition. Further, the resin composition may contain a carbon material containing more than 200 ppm of sulfur atoms, but the content of the carbon material must be 3% by volume or less based on the entire resin composition. is preferred. The sealing resin composition preferably does not contain sulfides such as molybdenum disulfide and tungsten disulfide.

From the above, a particularly preferable form of the sealing resin composition of the present invention has E _{1 ′} and E ₂ ′ of 4.0×10 ⁸ Pa or more (preferably 2.0×10 ⁹ Pa or more)) and tan δ of An injection moldable resin composition having a peak temperature of 150° C. or higher and satisfying E ₂ /E ₁ = 0.50 or more and 1.0 or less, wherein the carbon material is added to the entire resin composition. It is a resin composition containing 5% to 35% by volume in total and 5% to 25% by volume of PTFE resin.

A seal made of the sealing resin composition described above is suitably used in high pressure gas. It is used at a high pressure of 30 MPa to 120 MPa, preferably 65 MPa to 110 MPa, and more preferably 80 MPa to 100 MPa. If the seal is a piston ring of a reciprocating compressor for hydrogen gas, it is used in this pressure range and under no lubrication conditions, and the typical specification is the discharge pressure of a reciprocating compressor for hydrogen gas at a hydrogen station. It is particularly suitable as a seal for use in hydrogen gas at a certain 82 MPa. It is also particularly suitable as a seal for use in hydrogen gas at a typical FCV tank internal pressure of 70 MPa.

An embodiment in which the above resin composition is used for a piston ring will be described below.

The materials constituting the resin composition are mixed as necessary using a Henschel mixer, an axial mixer, a ball mixer, a ribbon blender, etc., and then melt-kneaded using a melt extruder such as a twin-screw kneading extruder, Molding pellets can be obtained. Note that the carbon material, PTFE resin, and the above-mentioned resin additives may be introduced by side feeding when melt-kneading with a twin-screw extruder or the like. Piston rings can be molded by injection molding using these molding pellets. Additional machining or complete machining may be performed using an injection molding material to obtain a predetermined piston ring shape.

An example of a piston ring using the resin composition of the present invention and a reciprocating compressor to which the piston ring is applied will be described based on FIGS. 1 and 2. FIG. 1 is a perspective view showing an example of a piston ring. As shown in FIG. 1, the piston ring 1 is an annular body having a substantially rectangular cross section. The corners of the inner circumferential surface 1b of the ring and both side surfaces 1c of the ring may be chamfered in a straight or curved manner, and when the seal ring is manufactured by injection molding, there is a portion protruding from the mold at this portion. A stepped portion may be provided.

Further, the piston ring 1 is a cut type ring having one abutment 1a, and is expanded in diameter by elastic deformation and is installed in an annular groove of the piston. Since the piston ring 1 has the abutment 1a, the diameter is expanded by gas pressure during use, and the outer circumferential surface 1d comes into close contact with the inner circumferential surface of the cylinder. The shape of the abutment 1a is not limited, and may be a straight cut type, an angle cut type, etc., but the compound step cut type shown in Fig. 1 is adopted because it has excellent sealing properties. It is preferable.
Note that the piston ring of the present invention is not limited to a piston ring made of a single member as shown in FIG. 1, but may be a piston ring formed into an annular shape by combining a plurality of members.

FIG. 2 is a sectional view of an example of a reciprocating compressor for hydrogen gas using the piston ring of FIG. 1. Reciprocating compressors for hydrogen gas are installed at hydrogen stations and the like, and the compressed hydrogen gas is used to fill FCVs and hydrogen engine vehicles. A compression mechanism section 2 of a reciprocating compressor for hydrogen gas includes a cylinder 3 and a piston 4, and the piston 4 is connected to a piston rod 5. A plurality of annular grooves for mounting the piston rings 1 are arranged on the outer circumferential surface of the piston 4, and the piston ring 1 expands in diameter by elastic deformation and is incorporated into each annular groove one by one. The number of piston rings attached to the piston is not particularly limited, and in FIG. 2, six seal rings are attached. Hydrogen gas is introduced into the compression chamber 6, compressed by the piston 4 reciprocating with respect to the cylinder 3, and then discharged to the outside.

Below, a method for manufacturing a piston ring as a seal using the sealing resin composition of the present invention will be described. Note that not only piston rings but other seals can also be manufactured in the same manner.

When the above-mentioned sealing resin composition has an aromatic polyetherketone resin as its main component, it is heat-treated in one of the following states: an injection molded material, a piston ring cut from an injection molded material, or a piston ring manufactured by injection molding. It is preferable to carry out. This heat treatment is preferably carried out at a maximum temperature of 150°C to 330°C (more preferably 200°C to 250°C). The maximum temperature for heat treatment is 150°C because the melting point of diphenyl sulfone is 127°C, and the molecular chains of aromatic polyetherketone resins are easy to move if it is above the glass transition point, making it easy to remove diphenylsulfone by evaporation. It is preferable that it is above. When the maximum temperature is less than 150°C, it is difficult to obtain the effect of reducing the sulfur content, and when the maximum temperature exceeds 250°C, deformation tends to occur when heat treatment is performed after injection molding. Further, it is more preferable that the temperature is higher than the operating temperature of the piston ring, and even more preferably that the temperature is 30° C. or more higher than the operating temperature. Further, the time for holding at the maximum temperature is not particularly limited, but is, for example, 4 to 8 hours. This heat treatment is effective in reducing sulfur in the piston ring, and can previously reduce sulfur-containing gas generated during use of the piston ring. In addition, it is also effective in that diphenylsulfone remaining in the aromatic polyetherketone resin can be removed by evaporation.

Moreover, it is preferable that the heat treatment is performed in the atmosphere. For example, in Patent Document 2, a method of desulfurizing a sliding member is exemplified by exposing it to a hydrogen atmosphere, but since the exposure is not in the air but in a special atmosphere, a special exposure device is required. Since it handles hydrogen, safety measures against fire and explosion are required, resulting in high costs. On the other hand, by performing the above heat treatment in the air, there is no need for heat treatment in a special atmosphere such as exposure to a hydrogen atmosphere (desulfurization treatment), so there is no need for special exposure equipment, and strict safety is achieved. No countermeasures are required and costs are low.

When DSC measurements are performed on injection molded materials, piston rings cut from injection molded materials, or piston rings manufactured by injection molding after the above heat treatment, it is found that during the temperature raising process, in the case of no heat treatment, An invisible endothermic peak (hereinafter referred to as an endothermic peak due to thermal history) appears. Since the endothermic peak due to thermal history appears at a temperature equal to or slightly higher than the maximum temperature of heat treatment (within +20 degrees), it is possible to estimate the maximum temperature of heat treatment. Due to the heat treatment, the piston ring has an endothermic peak due to thermal history in the range of 150°C to 330°C (preferably in the range of 200°C to 250°C) during the temperature increase process of differential scanning calorimetry. It is preferable. In this case, the piston ring has an endothermic peak in the range of 150° C. to 330° C. in addition to the endothermic peak derived from the melting point of the aromatic polyetherketone resin. Note that the measurement by DSC can be performed, for example, at a temperature increase rate of 15 degrees/minute and in nitrogen gas.

When the resin composition has a thermoplastic PI resin as its main component, it is subjected to crystallization treatment (heat treatment) in any of injection molded materials, piston rings cut from injection molded materials, and piston rings manufactured by injection molding. ) is preferable. For example, when the above-mentioned Aurum manufactured by Mitsui Chemicals, Inc. is used as the thermoplastic PI resin, since it hardly crystallizes during injection molding, the degree of crystallinity may be increased by crystallization treatment. The conditions for the crystallization treatment are, for example, a maximum temperature of 280 to 320° C. in the air or nitrogen, and may be maintained at the maximum temperature for 2 hours or more. The degree of crystallinity after crystallization treatment is preferably 20% to 40%. The degree of crystallinity can be measured by a well-known method such as measuring the heat of fusion of crystals using DSC.

When the above resin composition has PAI resin as its main component, post-curing (heat treatment) is performed on the injection molded material, the piston ring cut from the injection molded material, or the piston ring manufactured by injection molding. It is preferable to do so from the viewpoint of mechanical strength. The post-cure conditions may be, for example, in the atmosphere at a maximum temperature of 250° C. to 260° C., and may be maintained at the maximum temperature for 15 hours or more.

The heat treatment, the crystallization treatment, and the post-cure are preferably carried out also in terms of removing a small amount of active sulfur contained in the resin composition.

Thermoplastic PI resin does not contain diphenyl sulfone, which remains in the case of PEEK resin, so it has a low sulfur atom content, and compared to PAI resin, the heat treatment time can be set shorter, so it is suitable for the sealing resin of the present invention. Particularly preferred as a base resin for the composition.

The content of sulfur atoms contained in a molded article (such as a piston ring) made of the sealing resin composition of the present invention can be measured using, for example, an inductively coupled plasma mass spectrometer (ICP-MS). For the purpose of more accurate measurement, a triple quadrupole inductively coupled plasma mass spectrometer (ICP-MS/MS) may be used. As a pretreatment method for analysis, for example, a method of filtering the decomposition liquid obtained by acid decomposition using a microwave sample pretreatment device and obtaining a supernatant as an analysis sample can be mentioned. It can be confirmed that the decomposition residue does not contain sulfur atoms using a known analytical method such as a fluorescent X-ray analyzer.

The content of sulfur atoms contained in the molded object (piston ring, etc.) made of the sealing resin composition of the present invention is preferably 0.1% by mass or less based on the total amount (100% by mass) of the resin composition. , more preferably 0.050% by mass or less, further preferably 0.025% by mass (250ppm) or less, particularly preferably 0.020% by mass (200ppm) or less.

Hereinafter, the present invention will be explained in more detail with reference to Examples. However, the present invention is not limited to the following examples.

Examples 1 to 4, Comparative Example 1, Comparative Example 2
Using PEEK resin, PEK resin, thermoplastic PI resin, PTFE resin, and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) resin as the base resin, a resin composition was prepared at the blending ratio (volume %) shown in Table 1. Created. The resin composition of Example 1 contains a PTFE resin as a filler, but does not contain a carbon material. The resin compositions of Examples 2 and 4 contain PTFE resin and carbon material (a combination of carbon fiber and graphite) as fillers, and the resin composition of Example 3 contains PTFE resin and carbon fiber. It includes.

The raw materials used for each resin composition are shown below. The content of sulfur atoms was measured by ICP-MS/MS and was 200 ppm or less for carbon fiber (CF-1) and carbon fiber (CF-2). Graphite was selected to have a sulfur atom content of 50 ppm or less as measured by ICP-MS/MS.

(1) PEEK resin [PEEK]
Victrex Japan Co., Ltd.: PEEK 450P (glass transition point 143℃, melt viscosity 350Pa・s (shear rate 1000/s, temperature 400℃))
(2) PEK resin [PEK]
Victrex Japan Co., Ltd.: HT P22 (glass transition point 152°C, melt viscosity 190 Pa・s (shear rate 1000/s, temperature 400°C))
(3) Thermoplastic PI resin [TPI]
Mitsui Chemicals Co., Ltd.: PD400
(4) PTFE resin [PTFE-1]
Mitsui Chemours Fluoro Products Co., Ltd.: Teflon (registered trademark) 7-J
(5) PFA resin [PFA]
Mitsui Chemours Fluoro Products Co., Ltd.: Teflon (registered trademark) 420HP-J
(6) PTFE resin [PTFE-2]
Kitamura Co., Ltd.: KTL-450 (D ₅₀ : 22μm)
(7) Carbon fiber [CF-1]
Kureha Co., Ltd.: Kureha M-107T (average fiber length 400μm)
(8) Carbon fiber [CF-2]
Teijin Corporation: HT M100 40MU (average fiber length 40μm)
(9) Graphite [GRP]
Imerys GC Japan Co., Ltd.: TIMREX KS25 (D ₅₀ : 10μm)

The resin compositions of Examples 1 to 4 and Comparative Example 2 were prepared by making pellets using a twin-screw kneading extruder using powders obtained by dry mixing raw materials, and molding them into pellets by injection molding into No. 4 dumbbell test pieces (compliant with ASTM D638). A thickness of 3.2 mm) was molded.

No. 4 dumbbell test pieces made of the PEEK resin compositions (Examples 1 and 2) and the PEK resin composition (Example 3) were heat-treated at a maximum temperature of 200°C and a holding time at the maximum temperature of 4 hours. Further, a No. 4 dumbbell test piece made of the thermoplastic PI resin composition (Example 4) was subjected to crystallization treatment at a maximum temperature of 320° C. and a holding time at the maximum temperature of 2 hours. A rectangular test piece measuring 2 mm x 5 mm x 45 mm was cut out by machining from the center of the heat-treated or crystallized No. 4 dumbbell test piece. A No. 4 dumbbell test piece made of the PFA resin composition (Comparative Example 2) was machined from a similar strip-shaped test piece without performing the above heat treatment or the above crystallization treatment.

Regarding the No. 4 dumbbell test pieces of Examples 1 to 4, the sulfur atom content was measured according to the following procedure. A No. 4 dumbbell test piece was frozen and crushed, and the resulting decomposition liquid was filtered by acid decomposition using a microwave sample pretreatment device to obtain a supernatant as an analysis sample. This analytical sample was analyzed by ICP-MS/MS. In addition, it was confirmed by a fluorescent X-ray analyzer that the decomposition residue did not contain sulfur atoms.

Note that the PTFE resin composition of Comparative Example 1, which cannot be injection molded, was obtained by machining a rectangular test piece of 2 mm x 5 mm x 45 mm from a fired body obtained by compression molding and firing using powder obtained by dry mixing raw materials. It was carved out by

<Dynamic viscoelasticity measurement>
Using the strip-shaped test pieces of Examples 1 to 4, Comparative Example 1, and Comparative Example 2, the test pieces were measured using a dynamic viscoelasticity measuring device "DMS6100" (Hitachi High-Tech Science Co., Ltd.) in tension mode with a distance between chucks of 20 mm. The dynamic viscoelastic properties with respect to temperature were measured under the conditions of a measurement frequency of 10 Hz, a strain amplitude of 10 μm (sine wave), and a temperature increase rate of 2° C./min. The peak temperature of tan δ, the storage elastic modulus E ₁ ′ at 30° C., the storage elastic modulus E ₂ ′ at 200° C., and E ₂ ′/E ₁ ′ are shown in Table 1 together with the measurement results of sulfur atoms.

Further, regarding Example 4, the relationship between temperature and storage modulus E' is shown in FIG. 3, and the relationship between temperature and tan δ is shown in FIG. 4. As shown in FIG. 3, it can be seen that the storage modulus E' is maintained without decreasing much in the temperature range from 30°C to 200°C. Further, from the tan δ curve shown in FIG. 4, the tan δ peak temperature of Example 4 was calculated to be 273°C.

<Friction and wear test>
Regarding the resin compositions of Examples 1 to 4 and Comparative Example 2, injection molding materials of φ8×20 mm were molded by injection molding using the above-mentioned pellets. The PEEK resin compositions (Example 1, Example 2) and the PEK resin composition (Example 3) were heat-treated at a maximum temperature of 200°C and a holding time at the maximum temperature of 4 hours. Further, the thermoplastic PI resin composition (Example 4) was crystallized at a maximum temperature of 320° C. for a holding time of 2 hours at the maximum temperature.
After performing the above heat treatment or the above crystallization treatment, a pin test piece of φ3×13 mm was obtained by machining. Note that for the PTFE resin composition of Comparative Example 1, which cannot be injection molded, a similar pin test piece was cut out by machining from a fired body obtained by compression molding and firing using powder obtained by dry mixing raw materials.
Using the pin test piece, a friction and wear test was conducted using a pin-on-disk tester shown in FIG. As shown in Fig. 5, the rotating disk 8 was rotated in an atmospheric atmosphere at a temperature of 150°C with the test surfaces of the three pin test pieces 7 pressed against the surface of the rotating disk 8 of the testing machine with the following surface pressure. . The specific test conditions are as follows, and the material of the rotating disk 8 is SUS304. Note that this test condition assumes the usage conditions of the piston ring in a reciprocating compressor for hydrogen gas.
(Test condition)
Circumferential speed: 4.8m/min
Surface pressure: 4MPa
Lubrication: None (dry)
Temperature: 150℃
Time: 50 hours After the test, the amount of change in the height of the pin test piece 7 before and after the test was measured, and the specific wear amount was calculated from the average value of the three pieces. Table 1 shows the results.

As shown in Table 1, the PEEK resin composition (Example 1 and Example 2), the PEK resin composition (Example 3), and the thermoplastic PI resin composition (Example 4) have E ₁ ', E ₂ ' was 4.0×10 ⁸ or more, and the peak temperature of tan δ was 150° C. or more. As described above, since the molded bodies made of the resin compositions of Examples 1 to 4 have high peak temperatures of E ₂ ' and tan δ, they are difficult to deform at high temperatures and can be suitably used as seals, especially when hydrogen gas is It is suitable as a piston ring for a reciprocating compressor. Further, in Example 4, E ₂ ′/E ₁ ′ satisfies the range of 0.70 or more and 1.0 or less. This makes it particularly suitable for seals because the change in elastic modulus due to temperature is small, and when applied to seals, stable sealing performance can be maintained over a wide temperature range from near room temperature to high temperatures.

Since the E ₂ ′ of the molded body made of the resin composition of Comparative Example 1 and Comparative Example 2 is 1/2 or less of the E ₂ ′ of Example 1, it can be used, for example, in a reciprocating compressor for hydrogen gas. When applied to seals used at high temperatures, such as piston rings, there is a risk of increased deformation and wear during use. Examples 1 to 4, in which E ₂ ′ is 4.0×10 ⁸ Pa or more, have better wear resistance than Comparative Examples 1 and 2, and in particular, E ₂ ′ is 2.0×10 ⁹ Examples 3 and 4, which were Pa or higher, had even better abrasion resistance.

Further, the molded bodies made of the resin compositions of Examples 1 to 4 had a sulfur atom content of 200 ppm or less, and in particular, Example 3 and Example 4 had a sulfur atom content of 100 ppm or less.

The sealing resin composition of the present invention can be used for sealing gas. It is difficult to deform under high temperatures, and the change in elastic modulus due to temperature is small, so by applying it to seals for hydrogen gas, it is possible to maintain stable sealing performance over a wide temperature range from near room temperature to high temperatures, especially at high temperatures and high pressures. Suitable for piston rings of reciprocating compressors for hydrogen gas used in hydrogen gas.

1 Piston ring 2 Compression mechanism part 3 Cylinder 4 Piston 5 Piston rod 6 Compression chamber 7 Pin test piece 8 Rotating disk

Claims (9)

A sealing resin composition used for a seal for sealing gas, the composition comprising:
When the dynamic viscoelasticity of the molded article of the sealing resin composition is measured, E ₁ ' and E ₂ ' are the storage modulus at a temperature of 30°C and E ₂ ' is the storage modulus at a _temperature of 200°C. A sealing resin composition characterized in that each of ' is 4.0×10 ⁸ Pa or more. 2. The sealing resin composition according to claim 1, wherein the molded article of the sealing resin composition has a peak temperature of loss tangent tan δ of 150° C. or higher. 3. The seal according to claim 1, wherein the relationship between E ₁ ' and E ₂ ' satisfies the following formula: E ₂ '/E ₁ '=0.70 or more and 1.0 or less. Resin composition. 3. The sealing resin composition according to claim 1, wherein the base resin of the sealing resin composition is an aromatic polyetherketone resin, a thermoplastic polyimide resin, or a polyamideimide resin. 5. The sealing resin composition according to claim 4, wherein the aromatic polyetherketone resin has a glass transition point of 150° C. or higher. A carbon material having a sulfur atom content of 200 ppm or less is blended in the sealing resin composition, and the carbon material is at least one selected from the group consisting of carbon fiber, graphite, and coke powder, The sealing resin composition according to claim 1 or 2, wherein the carbon material is contained in a total amount of 5% to 50% by volume based on the entire sealing resin composition. 3. The sealing resin composition according to claim 1, wherein the molded article of the sealing resin composition has a sulfur atom content of 250 ppm or less. A seal comprising a molded article of the sealing resin composition according to claim 1 or 2. 9. The seal according to claim 8, wherein the seal is a piston ring of a reciprocating compressor that compresses hydrogen gas.

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