KR20240098705A - Fluororubber-based Composition for Sealing - Google Patents

Abstract

According to the present disclosure, a fluororubber-based composition capable of suppressing product deformation and rupture in low-temperature and high-pressure environments, which are problems in low-temperature fluororubber-based compositions, and a sealing member manufactured therefrom are described.

Description

Fluororubber-based composition for sealing {Fluororubber-based Composition for Sealing}

The present disclosure relates to sealing compositions. More specifically, the present disclosure relates to a fluororubber-based composition and a sealing member manufactured therefrom that can suppress product deformation and rupture in low-temperature and high-pressure environments, which are problems in low-temperature fluororubber-based compositions.

Sealing members made of rubber or elastomer materials are used in a variety of applications and environments, such as the oil and gas industry. Representative examples of such sealing members include gaskets, hoses, and O-rings. In particular, the O-ring is assembled in a groove and comes into contact with the sliding surface by pressing, thereby providing a sealing force due to rebound elasticity. It can be provided, has good elasticity and processability, and is generally made of a rubber-based or elastomer material that is harder than metal. In particular, fluororubber-based materials have excellent heat resistance, oil resistance, etc., and are widely used as vulcanization molding materials for various sealing members in a wide range of fields such as automobiles and various industrial machines.

However, depending on the physical and chemical factors of the environment, the sealing material (specifically, the O-ring material) needs to meet certain physical properties. As an example, in the case of a gasoline direct injection engine, fuel is directly injected into the combustion chamber through a high-pressure injector, mixed with air and compressed, and then an electric spark is generated at the spark plug to induce the combustion stroke. It is operated, and airtightness is maintained by using an O-ring to prevent fuel leakage in the process of continuously supplying high-pressure fuel. If the O-ring's airtightness is exposed to a low temperature (-40°C) environment, the O-ring may shrink and its sealing performance may rapidly deteriorate.

In this regard, the industry uses fluororubber-based resins (or low-temperature fluorinated elastomers (FKM)) that can provide the desired mechanical and sealing performance at temperatures below -10 ℃, but are insufficient at the cryogenic temperature of -40 ℃. It tends to exhibit sealing performance. As an example, AFLAS polymer, commercially available from Asahi Glass, is reported to have a TR10 of about 2°C.

In consideration of the above-mentioned operating environment, a technology has been developed to improve physical properties such as sealing properties and impact resistance by introducing various additives (e.g., cross-linking agents) into fluororubber-based components (Japanese Patent Publication No. 2008-814406) ho, etc.).

However, in the case of fluororubber-based materials, especially fluororubber-based elastomers containing tetrafluoroethylene as a copolymerization component, flexibility is fundamentally reduced in low-temperature environments, making it difficult to maintain sealing (sealing or airtight) properties. In addition, when using inorganic fillers or fillers for the purpose of improving the performance of fluororubber, a phenomenon in which the inorganic fillers are split at high pressure due to reduced compatibility with the fluororubber matrix may occur, making it difficult to achieve sufficient improvement in physical properties.

In particular, it is difficult to meet the recently changing driving environment of vehicles and the fuel efficiency and output requirements with only the existing specifications (low temperature: -30 ℃, high pressure: 350 bar), and more severe environments (low temperature: -40 ℃, high pressure: 650 bar or higher) are difficult to meet. ), seal members that can maintain stable sealing performance, especially O-ring members for high-pressure injectors, are required.

One embodiment of the present disclosure seeks to provide a fluorine rubber-based composition that overcomes the limitations of the prior art and can exhibit good sealing performance even under low temperature and high pressure conditions.

Another embodiment of the present disclosure seeks to provide an O-ring for a high-pressure injector that can exhibit good sealing performance in a low-temperature and high-pressure environment.

According to the first aspect of the present disclosure,

(a) 100 parts by weight of fluoroelastomer;

(b) 15 to 25 parts by weight of surface modified wollastonite particles having an aspect ratio of less than 10;

(c) 25 to 40 parts by weight of carbon black having an average particle diameter in the range of 25 to 100 μm; and

(d) 3 to 20 parts by weight of a silica-based filler having a specific surface area (BET) in the range of 50 to 200 m2/g;

Includes,

At this time, a fluororubber-based composition for sealing having a Mooney viscosity (measured by M ISO289-1; ML ₁₊₁₀ (121°C)) of 50 or less is provided.

According to an exemplary embodiment, the surface-modified wollastonite particles may have an average particle diameter of 1 to 10 ㎛.

According to an exemplary embodiment, the surface-modified wollastonite particles may be surface-treated with a silane-based compound.

According to an exemplary embodiment, the silica-based filler may be surface-treated with a silane-based compound or a silazane-based compound.

According to an exemplary embodiment, the carbon black may have a specific surface area (BET) in the range of 10 to 100 m2/g.

According to an exemplary embodiment, the fluorine content in the fluororubber is at least 50%, and the molecular weight (Mw) of the fluororubber may range from 50,000 to 120,000, as measured by gel permeation chromatography.

According to an exemplary embodiment, the temperature (TR ₁₀ (M 6724)) corresponding to 10% retraction of the fluoroelastomer may be -30° C. or lower.

According to the second aspect of the present disclosure,

A sealing member comprising a molded product of the above-described fluororubber-based composition is provided.

According to an exemplary embodiment, the sealing member may be an O-ring for a high pressure injector.

According to an exemplary embodiment, the molded article may satisfy at least one of the following physical properties (i) to (iii):

(i) tensile strength of 15 to 25 MPa (M 6518),

(ii) 100% modulus (M 6518) of 10 to 15 MPa, and

(iii) Elongation at break between 130 and 180% (M 6518).

According to an exemplary embodiment, the molding may exhibit a hardness of 80 to 95 (Shore A; M6511) and/or a hardness of 85 to 95 (International Rubber Hardness Degrees (IRHD), M6511).

According to an exemplary embodiment, the temperature (TR ₁₀ (M 6724)) corresponding to 10% retraction of the molded product may be -30° C. or lower.

The fluororubber-based composition for sealing according to an embodiment of the present disclosure is based on the existing fluororubber-based composition by reducing the hysteresis and increasing the rebound of the fluororubber (elastomer) while maintaining the advantages of each material of a plurality of additives that meet specific property requirements. It provides the advantage of effectively suppressing the deterioration of sealing performance due to rupture and deformation at low temperature and high pressure, which is a problem in sealing members. In particular, it is expected to be widely commercialized in the future, as it can maintain good sealing performance even in extremely low temperature and high pressure environments when applied to O-ring members of high-pressure injectors for vehicles.

FIG. 1A is a cross-sectional view showing the schematic structure of a high-pressure injector with an O-ring installed as a sealing member, and FIG. 1B is a photograph showing the appearance of the O-ring manufactured in the example;
Figure 2 shows an anti-leakage test (experimental conditions: 90°C, On/Off, 32 seconds (1 cycle/300 hours (1 cycle/300 hours 200790 times)) This is a graph showing the results;
Figure 3 is a graph showing changes in temperature and pressure conditions when performing a leakage prevention test over time for a high-pressure injector installed with an O-ring manufactured according to an embodiment (temperature: range from -40 to -20 ° C, pressure from 600 to 750 bar); and
Figure 4 is a graph showing changes in temperature and pressure conditions when performing a leakage prevention test over time for a high-pressure injector equipped with an O-ring manufactured according to an embodiment (temperature: range from -40 to -20 ° C, pressure from 700 to 800 bar)

The present invention can all be achieved by the following description. The following description should be understood as describing preferred embodiments of the present invention, but the present invention is not necessarily limited thereto. In addition, the attached drawings are intended to aid understanding, and the present invention is not limited thereto, and details regarding individual configurations can be appropriately understood based on the specific purpose of the related description described later.

“Carbon black” refers to an aggregate of carbon black crystallites with a hexagonal network structure of carbon atoms formed by forming a six-membered carbon ring through incomplete combustion or thermal decomposition of hydrocarbons, and then passing through a polycyclic aromatic compound through a process such as dehydrogenation condensation. It has a two-dimensional order compared to normal graphite, which has a three-dimensional structure. The atomic structure model of carbon black can be expressed as structural formula 2 below.

[Structural Formula 2]

The relative density of carbon black is known to be approximately in the range of 1.76 to 1.9 depending on the grade. The primary dispersable units of carbon black are expressed as aggregates (separate rigid colloidal entities), which in the case of most carbon blacks are spheres fused together. forms. These spheres are called primary particles or nodules. In addition, carbon black may exhibit differences in chemical composition depending on the source, which is illustratively shown in Table 1 below.

type carbon
(%) hydrogen
(%) Oxygen
\(%) sulfur
(%) nitrogen
(%) ash
(%) volatility
(%) Furnace (rubber-grade) 97.3-99.3 0.2-0.8 0.2-1.5 0.2-1.2 0.05-0.3 0.1-1.0 0.6-1.5 Medium 99.4 0.3-0.5 0.12 or less 0.25 or less - 0.2-0.38 Thermal acetylene black 99.8 0.05-0.1 0.1-0.15 0.02-0.05 - - <0.4

“Silica” may refer to a material with a tetrahedral structure formed by one silicon atom bonded to four oxygen atoms.

“Mooney Viscosity” can refer to the viscosity used in rubber raw polymer or rubber compound, and is usually the most basic index for evaluating the physical properties of unvulcanized rubber. It is being used as.

In this specification, when “including” a certain component, this means that it may further include other components, unless otherwise stated.

Terms such as “on” or “above” and “below” or “below” can be understood to describe a relative positional relationship between components or members, and can be understood as “located above” or “below”. The term “located” can be understood as expressing a relative positional relationship not only in a state of being in contact with a specific object, but also in a state of not being in contact with a specific object.

The fluororubber-based resin composition according to an embodiment of the present disclosure largely includes fluororubber (elastomer), surface-modified wollastonite particles, carbon black, and silica-based filler, and provides sealing or airtightness, especially under low temperature and high pressure operating conditions. It can be applied to various members, especially O-ring members for high pressure injectors.

Fluorine rubber (elastomer)

According to one embodiment, fluoroelastomer or fluoroelastomer is a synthetic polymer that contains fluorine and has properties similar to rubber, and may mean that it has a degree of fluorination above a certain level. Specifically, fluororubbers may typically be copolymers, terpolymers, etc., and may be selected from types that have good thermal stability, processability, mechanical properties, and/or chemical resistance, and are capable of crosslinking (especially crosslinking by peroxide). . In particular, it is desirable to use a type of fluororubber with excellent low-temperature flexibility, and TR ₁₀ (M 6724), which is the temperature corresponding to 10% shrinkage, is, for example, about -30 ℃ or less, specifically about -35 ℃. It may have properties of ℃ or lower, more specifically, about -40 ℃ or lower.

According to an exemplary embodiment, the fluorine content of the fluoroelastomer is, for example, at least about 50% by weight, specifically about 55 to 90% by weight, more specifically about 57 to 80% by weight, especially specifically about 60 to 75% by weight. It may be in the % range. In certain embodiments, the fluorine content in the fluoroelastomer may range, for example, from about 62 to 71% by weight, specifically about 66 to 70% by weight. In this regard, since the fluorine content affects low-temperature flexibility, fluid resistance, chemical resistance, solvent resistance, etc., it may be advantageous to appropriately adjust it within the above-mentioned range.

According to an exemplary embodiment, the molecular weight (M _w ) of the fluororubber, as measured by gel permeation chromatography, is for example about 50,000 to 120,000, specifically about 55,000 to 110,000, more specifically about 60,000. It may range from 100,000 to 100,000. According to a specific example, the molecular weight (M _w ) of the fluororubber may be adjusted, for example, in the range of about 65,000 to 95,000, specifically about 70,000 to 80,000.

Additionally, in an exemplary embodiment, the tensile strength of the fluoroelastomer (measured after curing for 16 hours at 230°C; M 6518) is, for example, about 10 to 20 MPa, specifically about 14 to 19 MPa, more specifically about 15 It may range from to 17 MPa.

According to an exemplary embodiment, the 100% modulus (measured after curing for 16 hours at 230° C.; M 6518) of the fluoroelastomer is, for example, about 6 to 7.5 MPa, specifically about 6.5 to 7.3 MPa, specifically about 6.9 to about 6.9. It can represent a range of 7.1 MPa.

According to an exemplary embodiment, elongation at break (16 hours at 230° C. Measured after curing; M 6518) may be adjusted, for example, in the range of about 150 to 190%, specifically about 160 to 180%, and more specifically about 165 to 175%.

According to an exemplary embodiment, the hardness (Shore A; M 6511) of the fluororubber may be adjusted to range, for example, from about 60 to 95, specifically from about 70 to 90, and more specifically from about 80 to 85. .

In exemplary embodiments, the fluororubber is, for example, vinylidene fluoride/hexafluoropropylene copolymer, vinylidene fluoride/tetrafluoroethylene/hexafluoropropylene copolymer, vinylidene fluoride/chlorotrifluoroethylene Copolymer, tetrafluoroethylene/propylene copolymer, hexafluoroethylene/ethylene-based copolymer, tetrafluoroethylene/perfluoroalkyl vinyl ether copolymer, vinylidene fluoride/tetrafluoroethylene/perfluoroalkyl vinyl It may be an ether copolymer, propylene/tetrafluoroethylene alternating polymer, vinylidene fluoride/hexafluoropropylene/tetrafluoroethylene terpolymer, vinylidene fluoride/propylene/tetrafluoroethylene terpolymer, etc., and may be used alone. It can be used as or in combination. The above-mentioned fluororubber can typically be produced by emulsion polymerization or the like.

According to an exemplary embodiment, the fluorine rubber may have a repeating unit represented by General Formula 1 below.

[General Formula 1]

According to this specific example, in the case of fluorine polymer, the Mooney Viscosity (ML ₁₊₁₀ (121°C)) of fluorine rubber measured by M ISO289-1 is, for example, about 50 or less, specifically about 20. It is advantageous to use one adjusted to a range of from about 25 to 48, more specifically about 25 to 45. In this regard, when the degree of pattern of the fluororubber exceeds a certain level, the low-temperature physical properties of the molded product decrease rapidly, which tends to cause a decrease in sealing performance due to rupture and deformation at low temperature and high pressure. Therefore, it is desirable to select a fluororubber having a Mooney viscosity equivalent to the above-mentioned range.

According to an exemplary embodiment, commercially available fluororubber products can be used, for example, brand names VPL 85540 (Solvay), LTFE 6400ZC (3M), etc.

Surface modified wollastonite particles

According to one embodiment of the present disclosure, the fluororubber-based composition for sealing may contain wollastonite, specifically surface-modified wollastonite particles, as a non-reinforced filler. These wollastonite particles can be used to improve the dimensional stability, scratch and heat resistance of fluoroelastomer. Wollastonite is represented by the chemical formula Ca ₃ (Si ₃ O ₉ ) and may be a natural calcium silicate formed by reacting quartz and calcium carbonate at a temperature of, for example, about 400 to 500° C., specifically, about 420 to 480° C.

According to an exemplary embodiment, the wollastonite may contain, for example, about 40 to 60% by weight (specifically about 45 to 55% by weight) of SiO ₂ , about 35 to 55% by weight (specifically about 40 to 50% by weight) CaO, about 0.2 to 2% by weight (specifically about 0.5 to 1.5% by weight) Al ₂ O ₃ , about 0.2 to 2% by weight (specifically about 0.5 to 1.5% by weight) MgO, and 0.01 to 1.5% by weight ( Specifically, it may contain about 0.1 to 1% by weight of Fe ₂ O ₃ and has a melting point of about 1,540°C, showing high heat resistance. In particular, it may be in the form of an aggregate of coarse-grained, leafy crystal structures.

In one embodiment, the wollastonite particles may have an aspect ratio adjusted to range from, for example, less than about 10, specifically about 3 to 5, more specifically about 3.5 to 4.5, and particularly specifically about 3.7 to 4.3. there is. At this time, as the aspect ratio exceeds a certain level, the particle size increases and the surface area decreases, which reduces compatibility with the matrix component, fluoroelastomer, and thus tends to be easily split at high pressure, within the above-mentioned range. It is advantageous to use wollastonite particles with an aspect ratio to be controlled. This use of wollastonite particles with a relatively low aspect ratio as a non-reinforcing filler can be said to be distinct from that recognized in existing fluoroelastomer compositions.

According to one embodiment, wollastonite particles are used after surface modification. By surface treatment, the wollastonite particles sufficiently interact with the fluoroelastomer to have increased bonding strength, thereby improving the physical properties and, in particular, suppressing the shrinkage of the fluoroelastomer composition. Provides a function to effectively suppress the phenomenon. As an example, surface-modified wollastonite particles may be surface-treated with a silane-based compound. In this regard, silane-based compounds for surface treatment of wollastonite particles include, for example, 3-aminopropylmethyldiethoxysilane, bis(dimethylamino)dimethylsilane, aminopropyltriethoxysilane, aminopropyltrimethoxysilane, It may be at least one selected from the group consisting of aminoethylaminopropyltrimethoxysilane, aminoethylaminopropylmethyldimethoxysilane, aminoethylaminopropyltrimethoxysilane, and dimethyldiethoxysilane.

In an exemplary embodiment, the average particle diameter of the surface-treated wollastonite particles may range, for example, from about 1 to 10 μm, specifically from about 2 to 7 μm, and more specifically from about 3 to 5 μm. If the particle size of the surface-treated wollastonite is too large, it may cause a decrease in physical properties due to reduced compatibility with fluoroelastomer, while if it is too small, it may be difficult to secure price competitiveness due to an increase in manufacturing price. Accordingly, it may be advantageous to use surface treated wollastonite particles of controlled size within the above-described range.

In this embodiment, the surface-modified wollastonite particles are, for example, about 15 to 25 parts by weight, specifically about 17 to 23 parts by weight, more specifically about 18 to 21 parts by weight, based on 100 parts by weight of the fluorine-based portion that is the matrix component. It can be used in the range of parts by weight. If the amount of surface-modified wollastonite particles used is too low, the effect of improving dimensional stability, scratch resistance, heat resistance, etc. may be insufficient, while if it is too high, the Mooney viscosity may be excessively increased, so within the above-mentioned range. It is desirable to adjust it at .

carbon black

According to one embodiment of the present disclosure, the fluororubber-based composition for sealing may contain carbon black, and the carbon black is a reinforcement that improves sealing performance by reducing the hysteresis of the fluororubber and increasing the repulsion force even under high pressure conditions. Functions as a filler. In particular, when carbon black is added to fluoroelastomer, it can change not only mechanical strengths such as tensile strength, tear strength, and abrasion resistance, but also physical strengths such as hardness, strength, rebound elasticity, and rate of change of elasticity.

In order to exercise the function of the filler as described above, stress needs to be smoothly transmitted at the interface between the surface of the added carbon black and the fluorine rubber. If this is not the case, a boundary layer is formed and pores corresponding to the size of the carbon black particles are generated, which may reduce the mechanical properties. In addition, it may be advantageous to use a type of carbon black with a high structure and a relatively low surface area, which increases surface activity and improves the physical bonding force and van der Waals between the surface of the carbon black particle and the fluoroelastomer. This is because mechanical properties can be further improved by increasing the Waals bond. In this regard, “structure of carbon black” refers to the degree of aggregation of primary particles forming aggregates, and “highly structured carbon black” may mean having a high degree of coagulation. there is.

In this embodiment, the carbon black may have an average particle diameter ranging from about 25 to 100 ㎛, specifically about 35 to 80 ㎛, and more specifically about 40 to 65 ㎛. The average particle size of carbon black is a factor that affects the structure of carbon black. If it is too large, it has a low structure, so it may be advantageous to use carbon black with an average particle size in the above-mentioned range.

In this regard, carbon black is commercially available as N330, N539, N550, N650, N660, N765, N774, etc. depending on the average particle size, and has small shrinkage deformation during extrusion, can provide a smooth surface, and has good heat conduction properties. It may be advantageous to use a type having .

Meanwhile, according to an exemplary embodiment, the carbon black has a specific surface area (BET) ranging from, for example, about 10 to 100 m2/g, specifically about 15 to 80 m2/g, and more specifically about 35 to 60 m2/g. ) can have. Since the specific surface area of carbon black affects the bonding between carbon black particles and fluorine content, it may be advantageous to use a type appropriately adjusted within the above-mentioned range.

The fluororubber-based composition for sealing according to one embodiment includes, for example, about 25 to 40 parts by weight, specifically about 27 to 35 parts by weight, and more specifically about 30 to 32 parts by weight of carbon black, based on 100 parts by weight of fluororubber. It may contain. If the carbon black content is too low, the mechanical properties deteriorate, while if it is too high, the hardness of the rubber increases excessively, making it difficult to secure the function of the sealing member in a high-pressure environment. Therefore, it is recommended to adjust it within the above-mentioned range. It can be advantageous.

Silica-based filler

The fluororubber-based composition for sealing according to an embodiment of the present disclosure contains a silica-based filler along with carbon black as a reinforcing filler.

In this embodiment, the silica-based filler is used for the purpose of improving the mechanical strength of the fluororubber-based sealing member. In an exemplary embodiment, the silica-based filler may be amorphous or crystalline and may include fumed silica, precipitated silica, or a combination thereof. As an example, the silica-based filler may include amorphous silica, and such amorphous silica may be produced by reacting sodium silicate with sulfuric acid. According to certain embodiments, the silica-based filler may mean pure silica in the narrow sense, but in the broad sense it may mean any component having a tetrahedron structure of SiO ₄ as a base unit, for example, sodium aluminum silicate, calcium It can be understood that silicates, etc. are also included. In addition, it may be advantageous for the purity of the silica-based filler to be as high as possible, for example, about 95% or more, specifically about 97% or more, and more specifically about 98% or more, but is not limited thereto.

According to one embodiment, the specific surface area (BET) of the silica-based filler is, for example, about 50 to 200 m2/g, specifically about 70 to 150 m2/g, more specifically about 80 to 100 m2/g. It can be. In this regard, to the extent that the specific surface area of the silica-based filler can be determined considering the compatibility of the matrix component with other additive components, including fluororubber, a type adjusted within the above-mentioned range can be used.

Additionally, in exemplary embodiments, the bulk density of the silica-based filler may range, for example, from about 0.35 g/cm3 or less, specifically from about 0.2 to 0.3 g/cm3, and more specifically from about 0.22 to 0.28 g/cm3. However, this may be understood as an example.

Meanwhile, according to an exemplary embodiment, the silica-based filler may be used in a surface-treated (modified) form. In this regard, it is an ingredient used in surface treatment and sufficiently interacts with fluororubber, which is a matrix component, to improve the bonding strength between fluororubber and silica-based filler, thereby suppressing the increase in Mooney viscosity and reducing the compression set. Compounds that can improve physical properties such as can be used.

According to an exemplary embodiment, as a surface treatment agent for the silica-based filler, for example, at least one selected from the group consisting of silane-based compounds and silazane-based compounds can be used.

According to exemplary embodiments, silane-based compounds for surface treatment include, for example, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, dimethylethoxysilane, and phenyltriethoxysilane. Silane, hexyltrimethoxysilane, hexyltriethoxysilane, decyltrimethoxysilane, trifluoropropyltrimethoxysilane, hexamethyldisiloxane, trimethylmethoxysilane, ethyltrimethoxysilane, trimethylethoxysilane, Bis(dimethylamino)dimethylsilane, aminopropyltriethoxysilane, aminopropyltrimethoxysilane, aminoethylaminopropyltrimethoxysilane, aminoethylaminopropylmethyldimethoxysilane, aminoethylaminopropyltrimethoxysilane and dimethyl It may be at least one selected from the group consisting of diethoxysilane. In addition, the silazane-based compound for surface treatment may be, for example, at least one selected from the group consisting of divinyltetramethyldisilazane, octamethylcyclotetrasilazane, and hexamethyldisilazane.

According to one embodiment, the silica-based filler may be used, for example, about 3 to 20 parts by weight, specifically about 5 to 15 parts by weight, and more specifically about 7 to 13 parts by weight, based on 100 parts by weight of fluororubber. . In this regard, if the content of the silica-based filler is too small, it is difficult to increase the mechanical properties of the fluororubber-based composition for sealing to the desired level, whereas if it is too large, the miscibility between the fluororubber, silica-based filler and other additives not only deteriorates. Rather, it can reduce productivity. Therefore, it may be desirable to use it in an amount adjusted within the above-mentioned range.

optional ingredients

According to the present disclosure, at least one optional additive may be further included for the purpose of improving the properties of the fluororubber-based composition for sealing, which will be described in more detail below.

- Cross-linking agent

According to an exemplary embodiment, the fluororubber-based composition may contain peroxide, specifically organic peroxide, as a crosslinking agent.

Such peroxides may be any type known in the art without particular limitation, as long as they are capable of forming radicals under heating. As an example, 1,1-di(t-hexylperoxy)-3,5,5-trimethylcyclohexane, 2,5-dimethylhexane-2,5-dihydroperoxide, di-t-butyl peroxide , t-butylcumyl peroxide, dicumyl peroxide, α,α'-bis(t-butylperoxy)-p-diisopropylbenzene, 2,5-dimethyl-2,5-di(t-butylperoxy) )-3-hexyne, 2,5-dimethyl-2,5-di(t-butylperoxy)-hexane, dibenzoyl peroxide, t-butylperoxybenzene, 2,5-dimethyl-2,5-di Examples include (benzoylperoxy)hexane, t-butylperoxymaleic acid, and t-hexylperoxyisopropylmonocarbonate, which can be used alone or in combination of two or more types. More specifically, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane can be used as a crosslinking agent.

According to an exemplary embodiment, the crosslinking agent, specifically the peroxide, is, for example, about 1.5 to 3 parts by weight, specifically about 1.7 to 2.8 parts by weight, more specifically about 2 to 2.5 parts by weight, based on 100 parts by weight of fluororubber. Can be used as a range. In this regard, considering the cross-linking efficiency of peroxide, etc., it may be advantageous to control the amount of cross-linking agent used within the above-mentioned range.

- Cross-linking preparation

According to an exemplary embodiment, when peroxide crosslinking by a crosslinking agent, particularly peroxide, is involved, a polyfunctional unsaturated compound can be used together as a crosslinking aid. In this regard, polyfunctional unsaturated compounds can improve mechanical strength, compression set, etc., such as tri(meth)allyl isocyanurate, tri(meth)allyl cyanurate, and triallyl trimelli. Tate, N,N´-m-phenylenebismaleimide, diallyl phthalate, tris(diallylamine)-s-triazine, triallyl phosphite, ethylene glycol di(meth)acrylate, diethylene glycol di(meth) ) Acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, 1,3-polybutadiene, etc. can be used alone or in combination of two or more.

According to an exemplary embodiment, the polyfunctional unsaturated compound ranges, for example, from about 1 to 4 parts by weight, specifically from about 2 to 3.5 parts by weight, and more specifically from about 2.5 to 3 parts by weight, based on 100 parts by weight of fluororubber. can be used as At this time, since the amount of the polyfunctional unsaturated compound used affects the curing reaction, it may be advantageous to appropriately adjust it within the above-mentioned range.

- Zinc oxide (ZnO)

According to an exemplary embodiment, the fluororubber-based composition for sealing may further include zinc oxide for the purpose of increasing cross-linking density by preventing side chain reaction during the cross-linking process, and the physical properties of the sealing member can be improved depending on the amount used. . Zinc oxide is a white inorganic compound, and the size of zinc oxide particles suitable for this embodiment may range, for example, from about 200 to 700 nm, specifically from about 250 to 600 nm, and more specifically from about 300 to 550 nm. However, it is not necessarily limited to this.

Illustratively, the amount of zinc oxide used may be selected in the range of, for example, about 3 to 7 parts by weight, specifically about 3.5 to 6.5 parts by weight, and more specifically about 4 to 6 parts by weight, based on 100 parts by weight of fluororubber. However, this may be understood as an example.

- Processing aids

The fluororubber-based composition for sealing according to an exemplary embodiment may further contain a fatty acid derivative, wax, or a combination (blend) thereof as a processing aid for the purpose of providing a good lubricating function. At this time, the fatty acid may include a saturated or unsaturated bond, and the number of carbon atoms may be in the range of, for example, about 10 to 20, specifically about 12 to 18. Additionally, the wax may be a paraffin wax (consisting of highly crystalline hydrocarbons due to their linear structure) and/or a microcrystalline wax.

According to an exemplary embodiment, the amount of the processing aid component used is, for example, about 0.5 to 2 parts by weight, specifically about 0.7 to 1.6 parts by weight, and more specifically about 1 to 1.5 parts by weight, based on 100 parts by weight of fluororubber. Can be selected from a range.

Preparation of fluororubber-based composition

According to an exemplary embodiment, a fluororubber-based composition, specifically a crosslinkable fluororubber-based composition, may be prepared using methods known in the art. As an example, fluororubber, surface-modified wollastonite particles, carbon black, silica-based fillers, optional additives, etc. are added to a mixing device such as a Banbury mixer, kneader, roll-mill, continuous mixer, single-screw extruder, or twin-screw extruder. It can be manufactured by kneading, and in this case, individual components may be mixed in a dissolved or dispersed form in a solvent.

In this regard, the order of addition of individual components is not particularly limited, but if possible, components that are resistant to modification or decomposition due to elevated temperature or heat are combined with the fluoroelastomer first, and components that have a tendency to modify or decompose are added later. It may be advantageous to knead by combining. The combination or kneading temperature of the individual components is not particularly limited, but when a cross-linking agent is contained, it may be advantageous to adjust the temperature to a temperature where a uniform mixing is achieved and a cross-linking reaction does not occur as much as possible. As an example, the kneading temperature may be adjusted in the range of, for example, about 70 to 130 °C, specifically about 80 to 110 °C, and more specifically about 85 to 105 °C, but this can be understood as an example. .

Manufacturing of sealing members

According to an exemplary embodiment, the above-described fluororubber-based composition may be molded into a sealing member by a molding process known in the art, such as extrusion, injection molding, blow molding, press molding, etc. According to an exemplary embodiment, the crosslinking reaction by a crosslinking agent (specifically, peroxide) may occur simultaneously or sequentially during molding. As an example, a sealing member including a molded product or a cured (cross-linked) molded product can be manufactured by filling a mold with a cavity corresponding to at least one sealing member with a rubber-based composition and heating the mold.

According to an exemplary embodiment, the curing reaction is performed under temperature conditions of, for example, about 140 to 250 °C, specifically about 150 to 220 °C, more specifically about 170 to 200 °C, for about 0.1 to 24 hours (specifically, about It can be carried out over 0.5 to 12 hours). Alternatively, the curing reaction may be carried out in a two-step manner, as an example, the first curing (crosslinking) step is, for example, at about 140 to 200 ° C. (specifically about 150 to 180 ° C.) at a temperature of about 0.1 to 180 ° C. It is carried out over 1 hour (specifically about 0.3 to 0.5 hours), and the second curing (crosslinking) step is, for example, at about 150 to 270 ° C. (specifically about 200 to 250 ° C.) for about 1 to 24 hours (specifically. It can also be performed over a period of about 3 to 12 hours. However, this is understood to be illustrative, and the present disclosure is not limited thereto. In the second curing step of the above-described two-step curing (crosslinking) reaction, various impurities contained in the molded product, such as peroxide residues, may be decomposed and removed. Additionally, the pressure during molding/curing may be adjusted in the range of, for example, about 10 to 25 MPa, specifically about 15 to 20 MPa, and more specifically about 17 to 19 MPa.

According to an exemplary embodiment, a molding (specifically, a cured (cross-linked) molding) manufactured from the above-described fluororubber-based composition may satisfy at least one of the following physical properties (i) to (iii):

(i) a tensile strength (M 6518) of about 15 to 25 MPa (specifically about 16 to 20 MPa, more specifically about 17 to 18 MPa),

(ii) a 100% modulus (M 6518) of about 10 to 15 MPa (specifically about 11 to 14.5 MPa, more specifically about 12 to 14 MPa), and

(iii) Elongation at break (M 6518) of about 130 to 180% (specifically about 140 to 170%, more specifically about 145 to 165%).

According to certain embodiments, it may be advantageous to satisfy all of the above-described properties (i) to (iii).

Additionally, according to an exemplary embodiment, the molding (specifically a cured (cross-linked) molding) has a hardness (Shore) of, for example, about 80 to 95 (specifically, about 85 to 92, more specifically about 87 to 90). A; M 6511), and/or may represent a hardness (International Rubber Hardness Degrees (IRHD), M 6511) of about 85 to 95 (specifically about 87 to 93, more specifically about 89 to 92). You can.

In addition, according to an exemplary embodiment, the temperature (TR ₁₀ ; M 6724) corresponding to 10% retraction of the molding is, for example, about -30 ° C or less, specifically about -45 to -35 ° C, more Specifically, it may range from about -43 to -40°C.

According to an exemplary embodiment, a molded product manufactured from a fluorine rubber composition can be applied to areas requiring airtightness in various fields, such as vehicles, general appliances, and electrical appliances. In exemplary embodiments, sealing members may include O-rings, gaskets, oil seals, bearing seals, etc. However, it is not limited to this, and can be applied to cushioning materials, dustproof materials, wire covering materials, industrial belts, tubes, hoses, and sheets in addition to sealing members. In a specific embodiment, the sealing member may be an O-ring, and in particular, the fluororubber-based composition according to this embodiment has excellent flexibility even at low temperatures and has good mechanical properties in a high pressure environment, so it is an O-ring member, specifically, high pressure. It is suitable as a material for O-ring members for injectors.

As an example, the schematic structure of a high-pressure injector with an O-ring installed as a sealing member is shown in FIG. 1.

Referring to the drawing, an O-ring 3 is interposed to provide airtightness between the high pressure injector 1, specifically, the upper outer peripheral surface of the high pressure injector and the inner peripheral surface of the valve 2. At this time, the valve (2) is responsible for transferring the supplied fuel to the high pressure injector (3). In particular, the O-ring 3 seals the fuel in the fuel rail coupled with the injector and must prevent fuel from leaking into the injector, so there is a need to maintain sealing performance even during low-temperature and high-pressure injection. The O-ring member manufactured by molding the fluorine-based high-build composition according to this embodiment is particularly advantageous in that it exhibits flexibility at low temperatures and mechanical properties that can withstand high pressure.

Hereinafter, preferred examples are presented to aid understanding of the present invention, but the following examples are provided to facilitate understanding of the present invention and do not limit the present invention thereto.

Example

Details regarding the materials used and evaluation in this Example and Comparative Example are shown in Tables 2 and 3 below.

matter Detail VPL85540 FKM, Solvay (Mooney viscosity: 45) PL958 FKM, Solvay (Mooney viscosity: 53) 600AST CaSiO ₃ , TREMIN 283 600 AST, HPF The Mineral Engineers Tixolex 17 14.5(SiO ₂ )·Al ₂ O ₃ ·1.4(Na ₂ O), EBROSIL SA60, IQE ZnO ZnO, KS-1, Hanil Chemical Industry Co., Ltd. TAIC-50 Triallyl Isocyanurate, RUMAX TAIC-50PD, Humantech Co., Ltd. FEF C, CORAX N550, ORION Engineered Carbons HT-290 Blend of fatty acid derivatives and waxes, STRUKTOL HT 290, STRUKTOL 25B-40 2,5-Dimethyl-2,5-di(t-butylperoxy )hexane, PERHEXA 25B-40, NOF Corporation

item KS standard note Hardness (Shore A) M 6511 Hardness (IRHD) M 6511 tensile strength M 6518 100% modulus M 6518 Elongation at break M 6518 importance ISO 2781 Low temperature/high pressure leak evaluation - self-assessment TR10 (Temperature Retraction Test) M 6724 - Measures the extent to which stretched rubber shrinks as the temperature rises after being frozen at low temperature.

- TR10 indicates the temperature at which the initial stretched length decreases by 10%.

A crosslinkable fluoroelastomer composition was prepared by using the materials listed in Table 2 above and adding individual components to a kneader according to the composition listed in Table 4 below. Thereafter, the fluorine rubber composition was put into a press molding device and subjected to primary curing by applying heat and pressure for 10 minutes. At this time, the temperature was set to 180°C and the pressure was set to 17.65 MPa. Afterwards, secondary curing was performed over 16 hours, where the temperature was set at 230°C and the pressure was set at 17.65 MPa. Accordingly, a sample as shown in Figure 1b was prepared.

Hardness (Shore A), hardness (IRHD), tensile strength, 100% modulus, elongation at break, specific gravity, and TR10 were measured for the samples prepared according to each of the examples and comparative examples and are shown in Table 4 below.

In addition, O-rings were manufactured by crosslinking and molding the crosslinkable fluoroelastomer compositions according to each of the Examples and Comparative Examples. The results of a leakage test (temperature: -40°C, pressure: 750 bar and 600 bar) on the manufactured O-ring are shown in Table 4 below.

ingredient Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 VPL85540 100 100 100 100 - PL958 - - - - 100 600AST 20 0 30 20 20 Tixolex 17 10 30 0 10 10 ZnO 5 5 5 5 5 TAIC-50 3 3 3 3 3 FEF 30 30 30 20 30 HT-290 1.2 1.2 1.2 1.2 1.2 25B-40 2 2 2 2 2 Hardness (Shore A) 88 86 83 79 92 Hardness (IRHD) 90 88 85 82 94 Tensile Strength (MPa) 17.4 16.2 14.2 14.0 22.1 100% modulus (MPa) 12.3 9.9 7.8 7.5 16.1 Elongation at break (%) 155 165 175 180 182 importance 1.964 1.952 1.958 1.912 1.974 750 bar leak assessment O X X X X 600 bar leak rating O X X X O TR ₁₀ -40.6 -40.5 -40.4 -40.5- -24.3

As described in the table above, the fluororubber composition according to the example showed TR ₁₀ of -40.6°C and effectively prevented leakage even in a high pressure environment of 600 bar or more. In particular, it is noteworthy that it not only exhibits excellent sealing performance in low temperature and high pressure environments, but also has good overall mechanical properties.

On the other hand, in the case of Comparative Example 1, which did not contain wollastonite (in particular, surface-modified wollastonite) particles, the overall mechanical properties were lowered, and it was especially undesirable in terms of the high-pressure leakage prevention effect. Comparative Example 2, which did not contain silica-based fillers, also had reduced mechanical properties compared to Example 1, and the high-pressure leakage prevention ability was not satisfactory. Meanwhile, according to Comparative Example 3, because the carbon black content was lower than that of Example 1, the mechanical properties were significantly reduced, and as a result, an effective leak prevention function was not achieved in a high pressure environment. In addition, in the case of Comparative Example 4, fluororubber with relatively low low-temperature properties (flexibility), especially fluororubber with Mooney viscosity exceeding a certain level, was used, and the mechanical strength was at a higher level compared to Example 1. However, it had insufficient low-temperature properties, and in particular, as the pressure increased, the leakage prevention effect deteriorated.

In this way, in the example, fluororubber with excellent low-temperature properties is used as a matrix component, and by providing a balanced function between the plurality of additives added, it is noteworthy that good mechanical properties and sealing performance can be achieved in extremely low temperature and high pressure environments. .

Example 2

Assessing the impact of high pressure repetitive cycles

The O-ring prepared in Example 1 was installed in a high-pressure injector and tested for leakage prevention while repeating the cycle at a pressure of 750 bar (experimental conditions: 90°C, On/Off, 32 seconds (1 cycle/300 hours (200,790 times)) was performed, and the cycle conditions and evaluation results are shown in Figure 2.

Referring to the drawing, no leakage of the O-ring was observed even when a high pressure environment was repeatedly created. Therefore, it was confirmed that the O-ring member according to the example had excellent durability.

Example 3

Evaluation of leakage prevention performance at low temperatures according to pressure changes

When performing a leakage prevention test over time on a high-pressure injector equipped with an O-ring manufactured according to an example, leakage prevention was evaluated while changing temperature and pressure conditions. At this time, the test conditions are shown in Figures 3 and 4.

Referring to the drawing, in the case of the O-ring manufactured according to the example, no leakage occurred even under conditions where the O-ring was cooled to -40°C and the maximum pressure was set to 750 bar and 800 bar.

All simple modifications or changes of the present invention fall within the scope of the present invention, and the specific scope of protection of the present invention will be made clear by the appended claims.

Claims (16)

(a) 100 parts by weight of fluoroelastomer;
(b) 15 to 25 parts by weight of surface modified wollastonite particles having an aspect ratio of less than 10;
(c) 25 to 40 parts by weight of carbon black having an average particle diameter in the range of 25 to 100 μm; and
(d) 3 to 20 parts by weight of a silica-based filler having a specific surface area (BET) in the range of 50 to 200 m2/g;
Includes,
At this time, the fluororubber-based composition for sealing has a Mooney viscosity (measured by M ISO289-1; ML ₁₊₁₀ (121°C)) of 50 or less. The fluoroelastomer-based composition for sealing according to claim 1, wherein the surface-modified wollastonite particles have an average particle diameter in the range of 1 to 10 ㎛. The fluororubber-based composition for sealing according to claim 1, wherein the surface-modified wollastonite particles are surface-treated with a silane-based compound. The method of claim 3, wherein the silane-based compound used for surface treatment of the wollastonite particles is 3-aminopropylmethyldiethoxysilane, bis(dimethylamino)dimethylsilane, aminopropyltriethoxysilane, aminopropyltrimethoxysilane, A fluororubber-based composition for sealing, characterized in that it is at least one selected from the group consisting of aminoethylaminopropyltrimethoxysilane, aminoethylaminopropylmethyldimethoxysilane, aminoethylaminopropyltrimethoxysilane, and dimethyldiethoxysilane. The fluororubber-based composition for sealing according to claim 1, wherein the silica-based filler is surface-treated with a silane-based compound or a silazane-based compound. The method of claim 5, wherein the silane-based compound used for surface treatment of the silica-based filler is methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, dimethylethoxysilane, and phenyltrimethoxysilane. Ethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, decyltrimethoxysilane, trifluoropropyltrimethoxysilane, hexamethyldisiloxane, trimethylmethoxysilane, ethyltrimethoxysilane, trimethylethoxy Silane, bis(dimethylamino)dimethylsilane, aminopropyltriethoxysilane, aminopropyltrimethoxysilane, aminoethylaminopropyltrimethoxysilane, aminoethylaminopropylmethyldimethoxysilane, aminoethylaminopropyltrimethoxysilane and dimethyldiethoxysilane. The method of claim 5, wherein the silazane-based compound used for surface treatment of the silica-based filler is selected from the group consisting of divinyltetramethyldisilazane, octamethylcyclotetrasilazane, and hexamethyldisilazane. A fluororubber-based composition for sealing, characterized in that it contains at least one fluororubber-based composition. The fluororubber-based composition for sealing according to claim 1, wherein the carbon black has a specific surface area (BET) in the range of 10 to 100 m2/g. The sealing material of claim 1, wherein the fluorine content in the fluororubber is at least 50%, and the molecular weight (M _w ) of the fluororubber is in the range of 50,000 to 120,000, as measured by gel permeation chromatography. For fluororubber-based compositions. The method of claim 1, wherein the fluororubber composition for sealing contains 1,1-di(t-hexylperoxy)-3,5,5-trimethylcyclohexane, 2,5-dimethylhexane-2,5-di as a crosslinking agent. Hydroperoxide, di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, α,α'-bis(t-butylperoxy)-p-diisopropylbenzene, 2,5-dimethyl- 2,5-di(t-butylperoxy)-3-hexene, 2,5-dimethyl-2,5-di(t-butylperoxy)-hexane, dibenzoyl peroxide, t-butylperoxybenzene, Characterized by further comprising at least one selected from the group consisting of 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butylperoxymaleic acid, and t-hexylperoxyisopropylmonocarbonate. A fluorine rubber-based composition for sealing. The method of claim 10, wherein the fluororubber composition for sealing includes tri(meth)allyl isocyanurate, tri(meth)allyl cyanurate, triallyl trimellitate, and N,N'-m-phenylene as a crosslinking aid. Bismaleimide, diallyl phthalate, tris(diallylamine)-s-triazine, triallyl phosphite, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, neopentyl glycol di(meth) A fluororubber-based composition for sealing, characterized in that it further comprises at least one selected from the group consisting of acrylate, trimethylolpropane tri(meth)acrylate, and 1,3-polybutadiene. A sealing member comprising a molded product of the fluororubber-based composition according to any one of claims 1 to 11. The sealing member according to claim 12, wherein the sealing member is an O-ring for a high pressure injector. The sealing member according to claim 12, wherein the molded product satisfies at least one of the following physical properties (i) to (iii):
(i) tensile strength of 15 to 25 MPa (M 6518),
(ii) 100% modulus (M 6518) of 10 to 15 MPa, and
(iii) Elongation at break of 130 to 180% (M 6518). The sealing member according to claim 14, wherein the molded product exhibits a hardness of 80 to 95 (Shore A; M6511) and/or a hardness of 85 to 95 (International Rubber Hardness Degrees (IRHD), M6511). The sealing member according to claim 12, wherein the temperature (TR ₁₀ (M 6724)) corresponding to 10% retraction of the molded product is -30° C. or lower.