Fluororubber / fluorosilicone rubber valve for automobile fuel tank and preparation method of fluororubber / fluorosilicone rubber valve

Abstract

The invention discloses a rubber valve for an automobile fuel tank and a preparation method of the rubber valve, and belongs to the technical field of rubber products. The rubber valve for the automobile fuel tank is prepared from the following raw materials: rubber, auxiliaries and mica sheets, the rubber is fluororubber or fluorosilicone rubber. The mica sheet is added into the rubber compound, so that a scale crystalline lens structure is formed on the surface of a rubber product, the viscosity of a rubber sealing surface is effectively reduced, and the opening performance and durability of a valve are improved. Meanwhile, the production process is simplified, the production cost is reduced, and the method has a wide application prospect.

Description

Technical Field

[0001] The present invention belongs to the field of rubber products, and particularly relates to a fluoroelastomer / fluorosilicone rubber valve for an automotive fuel tank, especially a fluoroelastomer / fluorosilicone rubber valve whose rubber sealing surface adhesiveness is reduced by adding mica flakes and a preparation method thereof. Background Art

[0002] In an automotive fuel tank system, its normal operation is usually achieved by valve body components such as a fuel filling shut-off valve (FLVV), a breather valve (GVV / ROV / GRV), a check valve (ICV), a fuel tank isolation valve (FTIV), etc. Among them, the rubber valve is one of the most critical sealing components. The rubber valve is a key sealing component, and its performance directly affects the sealing and safety of the fuel tank. Currently, the commonly used rubber materials are fluoroelastomer (FKM) or fluorosilicone rubber (FVMQ). These materials have good oil resistance, high temperature resistance, and chemical stability. However, during the use of the rubber valve, its sealing surface is prone to adhesion, resulting in an increase in the opening pressure of the valve and affecting the normal operation of the fuel tank.

[0003] To solve this problem, in the prior art, methods such as coating talcum powder, molybdenum disulfide, or polytetrafluoroethylene (PTFE) coating on the rubber surface are usually adopted. Although these methods can reduce adhesion to a certain extent, there are problems such as easy coating peeling and poor durability, and they increase the complexity and cost of the production process. Summary of the Invention

[0004] In view of the above problems, the present invention provides a fluoroelastomer / fluorosilicone rubber valve with reduced adhesiveness and a preparation method thereof. By adding mica flakes to the fluoroelastomer / fluorosilicone rubber compound, a scaly crystal structure is formed on the surface of the rubber product, thereby effectively reducing the adhesiveness of the rubber sealing surface and improving the opening performance and durability of the valve.

[0005] The first aspect of the present invention is to disclose a rubber valve for an automotive fuel tank. The raw materials for preparation include rubber, additives, and mica flakes;

[0006] The rubber is fluoroelastomer or fluorosilicone rubber.

[0007] In some embodiments of the present invention, the additives include a filler, calcium hydroxide, magnesium oxide, and a vulcanizing agent; preferably, the filler is carbon black N990; preferably, the vulcanizing agent is bisphenol AF.

[0008] Carbon black N990, as a filler, improves the processing performance of rubber (it can enhance the flexibility, anti-aging performance and heat generation rate of rubber) and physical properties (it can significantly reduce the compression set of the rubber compound, improve the dynamic properties of the rubber compound, and maintain the original oil resistance, medium resistance and high and low temperature aging resistance of the rubber). An appropriate amount of calcium hydroxide can increase the hardness, tensile strength and abrasion resistance of fluororubber. At the same time, it can also reduce the viscosity of the rubber and improve its fluidity, thus facilitating processing and molding. During the high-temperature vulcanization process of fluororubber, trace amounts of acidic substances (such as hydrogen fluoride) will be generated, and these acidic substances will erode the rubber molecular chain, affecting the performance and service life of the rubber. Magnesium oxide can absorb these acidic substances, prevent them from damaging the rubber molecular chain, protect the molecular structure of the rubber, and extend the service life of the product. Magnesium oxide can also be used as a reinforcing agent for fluororubber. By generating a strong physical adsorption effect with fluororubber molecules, it can improve the mechanical properties such as the tensile strength and modulus at a specified elongation of the vulcanizate. At the same time, magnesium oxide can effectively improve the thermal stability of fluororubber, reduce the performance degradation during use in high-temperature environments, and ensure that rubber products can maintain reliability within a wide temperature range. Bisphenol AF, used as a vulcanizing agent, the final product of fluororubber containing bisphenol AF is easy to process and has excellent properties, including compression set, chemical resistance and thermal stability.

[0009] In some embodiments of the present invention, the auxiliary agent includes a vulcanizing agent, and preferably the vulcanizing agent is bis-25 vulcanizing agent.

[0010] During the vulcanization process of fluorosilicone rubber, the bis-25 vulcanizing agent decomposes to generate free radicals, and these free radicals react with the unsaturated bonds in the fluorosilicone rubber molecules to form cross-linking bonds, thereby transforming the fluorosilicone rubber from a liquid or semi-solid state to a solid state, with better physical and chemical properties.

[0011] In some embodiments of the present invention, the weight percentage of the mica flakes in all raw materials is 0.5%-10%, preferably 2%-3%.

[0012] In some embodiments of the present invention, it includes the following components in parts by weight: 50-70 parts of fluororubber, 20-30 parts of filler, 1-5 parts of calcium hydroxide, 1-5 parts of magnesium oxide, 1-3 parts of vulcanizing agent, 0.5-10 parts of mica flakes; preferably 60-65 parts of fluororubber, 22-28 parts of filler, 3-5 parts of calcium hydroxide, 2-5 parts of magnesium oxide, 1-3 parts of vulcanizing agent, 1-8 parts of mica flakes.

[0013] In some embodiments of the present invention, it includes the following components in parts by weight: 80-100 parts of fluorosilicone rubber, 1-5 parts of vulcanizing agent, 0.5-10 parts of mica flakes; preferably 90-98 parts of fluorosilicone rubber, 1-3 parts of vulcanizing agent, 1-8 parts of mica flakes.

[0014] In some embodiments of the present invention, the particle size of the mica flakes is 50 mesh to 400 mesh, preferably 100 mesh to 300 mesh.

[0015] The second aspect of the present invention is to disclose a preparation method of the rubber valve for an automobile fuel tank described in the first aspect, which is characterized by including the following steps:

[0016] S01, rubber mixing;

[0017] S02, valve forming.

[0018] In some embodiments of the present invention, in S01, the rubber mixing is two-stage mixing, including the following steps:

[0019] First-stage mixing: adding raw rubber, additives calcium hydroxide, magnesium oxide, mica flakes and filler carbon black, mixing, discharging the rubber, obtaining the first-stage rubber, and storing it;

[0020] Second-stage mixing: after the first-stage rubber is stored, re-introducing it, adding a vulcanizing agent, mixing, discharging the rubber, and then passing through the processes of open mill sheeting and air cooling.

[0021] Preferably, in the first-stage mixing, mixing for 5 - 8 minutes, discharging temperature 115°C - 125°C, obtaining the first-stage rubber, and storing it for at least 8 h;

[0022] Preferably, in the second-stage mixing, mixing for 3 - 5 minutes, discharging temperature 95°C - 105°C.

[0023] In some embodiments of the present invention, in S01, in the first-stage mixing, after obtaining the first-stage rubber, it is stored for at least 8 h. If the storage time is insufficient, it will affect the processing stability of the rubber compound and ultimately affect the product performance.

[0024] In some embodiments of the present invention, in S01, the fluorosilicone rubber raw rubber is cut into small pieces, gradually fed into the nip of the open mill to form a continuous wrap-around state; adjusting the roll gap to form a continuous wrap-around rubber, spreading the vulcanizing agent and mica flakes on the rubber tape, folding the rubber tape to wrap the vulcanizing agent, and at the same time coiling and remixing to complete the fluorosilicone rubber mixing.

[0025] In some embodiments of the present invention, in S02, it includes the following steps:

[0026] S21, putting the mixed rubber compound and the plastic or metal skeleton after spraying the adhesive into a compression or injection mold for vulcanization molding;

[0027] S22: deburring, secondary vulcanization, cleaning, and inspection of the vulcanized rubber product to obtain the final rubber valve.

[0028] In some embodiments of the present invention, in S02, during vulcanization molding, the vulcanization temperature is 160 - 180 °C, the vulcanization pressure is 100 - 180 kg / cm 2 , and the vulcanization time is 100 - 360 s.

[0029] Advantages of the present invention:

[0030] By adding mica flakes to the fluororubber / fluorosilicone rubber blend, a scaly crystal structure is formed on the surface of the rubber product, effectively reducing the adhesiveness of the rubber sealing surface and improving the opening performance and durability of the valve. At the same time, the present invention simplifies the production process, reduces the production cost, and has broad application prospects. For the fluororubber / fluorosilicone rubber valve with mica flakes added in the present invention, the scaly crystal structure of the mica flakes forms micro-protrusions on the rubber surface, reducing the actual contact area between the valve disc and the valve seat, and playing a physical barrier effect. Specifically, it can:

[0031] 1) Reduce adhesiveness: By adding mica flakes to the fluorosilicone rubber, a crystal structure is formed on the surface of the rubber product, effectively reducing the adhesiveness of the rubber sealing surface and reducing the valve opening pressure.

[0032] 2) Improve durability: The mica flakes are embedded in the rubber matrix without the risk of falling off, improving the wear resistance and aging resistance of the rubber product and extending the service life of the valve.

[0033] 3) Simplify the production process: Compared with the traditional methods of coating talcum powder, molybdenum disulfide or PTFE coatings, the present invention directly adds mica flakes to the blend, simplifying the production process and reducing the production cost. Description of the drawings

[0034] Figure 1 It is a 30 - fold enlarged view of the mica - modified rubber in Example 2. Detailed implementation manners

[0035] The following specific examples illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0036] Unless otherwise specified, the examples and comparative examples are parallel tests with the same components, component contents, preparation steps, and preparation parameters. The particle size of the mica flakes in the examples and comparative examples is 100 mesh.

[0037] Fluororubber implementation manners

[0038] A preparation method for a fluororubber valve for an automotive fuel tank

[0039] Table 1 Fluororubber Formula Table (by weight percentage)

[0040]

[0041]

[0042] *, the fluororubber is a copolymer of 1,1,2,3,3,3 - hexafluoro - 1 - propene, 1,1 - difluoroethylene, and tetrafluoroethylene.

[0043] (1) Rubber mixing:

[0044] I. Raw material preparation: According to the requirements of the fluororubber formula, weigh the fluororubber, carbon black, calcium hydroxide, magnesium oxide, bisphenol AF, and mica flakes in a certain proportion.

[0045] II. Mixing process

[0046] 1. Selection of mixing equipment: In the present invention, a 35L internal mixer is selected for mixing. The initial temperature of the mixing chamber is set ≤ 50°C, and the rotor speed is 20 - 40 rpm. In the implementation of this fluororubber, the initial temperature of the mixing chamber is set at 40°C, and the rotor speed is 30 rpm.

[0047] 2. Selection of mixing method: Two - stage mixing method is adopted:

[0048] 2.1 First - stage mixing: Fluororubber raw rubber → processing aids (calcium hydroxide, magnesium oxide, mica flakes) → filler (carbon black) → mix for 5 - 8 minutes, discharge temperature 120°C, and obtain the first - stage rubber, which is parked for at least 8h. In the implementation of this fluororubber, it is 8h.

[0049] 2.2 Second - stage mixing: After the first - stage rubber has been parked for 8 hours, it is re - introduced into the mixing chamber, and the vulcanizing agent (bisphenol AF) is added, mixed for 3 - 5 minutes, discharge temperature 100°C, and then through the open - mill rolling and air - cooling processes.

[0050] (2) Valve forming

[0051] I. Raw material preparation: The FKM fluororubber compound after mixing, the plastic or metal skeleton sprayed with adhesive.

[0052] II. Vulcanization: In the present invention, the compound is put into a compression or injection mold for vulcanization molding. The vulcanization temperature is 160 - 180°C, the vulcanization pressure is 100 - 180 kg / cm 2 , and the vulcanization time is 100 - 360s. In the example of this fluororubber, the vulcanization temperature is 170°C, the vulcanization pressure is 150 kg / cm 2 , and the vulcanization time is 200s.

[0053] III. Post-treatment: The vulcanized rubber products are trimmed, secondarily vulcanized, cleaned, and inspected to obtain the final rubber valves.

[0054] Take the valves obtained in the examples and comparative examples and conduct the opening force test. This test is a basic test for fuel tank valves, and the main test equipment is a pressure gauge and a flow meter. The results are shown in Table 2.

[0055] Table 2 Test Results of the Opening Force of Fluoroelastomer Valves *

[0056] Normal temperature (23°C) / KPa High temperature (83°C × 3 h) / KPa Example 1 25.5 28.8 Example 2 25.3 28.7 Example 3 26.1 29.0 Comparative Example 1 26.5 29.1

[0057] * Test conditions: Opening force ≤ 34 Kpa.

[0058] Take the valves obtained in the examples and comparative examples and conduct the medium resistance test. Test standards: ASTM D 2240, ASTM D412, ASTM D 471. The results are shown in Table 3.

[0059] Table 3 Test Results of the Medium Resistance of Fluoroelastomer Valves *

[0060] Hardness change % Tensile strength change % Elongation at break change % Volume change % Example 1 -2 -23.1 -15.1 6.9 Example 2 -2 -22.3 -14.8 6.6 Example 3 -2 -22.6 -15.5 7.1 Comparative Example 1 -2 -23.7 -16.8 7.5

[0061] * Test conditions: Resistance to fuel C at 23°C × 70 h.

[0062] Fluorosilicone Implementation

[0063] A preparation method of a fluorosilicone rubber valve for an automotive fuel tank

[0064] Table 4 Fluorosilicone Rubber Formula Table (weight percentage)

[0065]

[0066]

[0067] *, the fluorosilicone rubber is a polytrifluoropropylsiloxane premixed rubber.

[0068] (1) Rubber mixing:

[0069] I. Raw material preparation: According to the requirements of the fluorosilicone rubber formula, weigh the fluorosilicone rubber, bis(2,5-dimethyl-2,5-di(tert-butylperoxy)hexane) curing agent, and mica flakes in a certain proportion.

[0070] II. Mixing process:

[0071] 1. Selection of mixing equipment: In the present invention, a 14-inch open mill is selected for mixing (the front roll is slow, the rear roll is fast, and the roll speed ratio is 1:1.2). The temperature of the front roll of the open mill is controlled at 25 - 35°C (maintained at a low temperature by cold water circulation), and the temperature of the rear roll is controlled at 30 - 40°C. In this example, the temperature of the front roll of the open mill is controlled at 30°C (maintained at a low temperature by cold water circulation), and the temperature of the rear roll is controlled at 35°C.

[0072] 2. Operating steps:

[0073] 2.1 Plasticizing the raw rubber (5 - 10 minutes)

[0074] 2.1.1 Feeding the raw rubber onto the roll: Cut the fluorosilicone rubber raw rubber into small pieces and gradually feed them into the nip of the open mill (the initial roll gap is set at 3 - 5 mm) to form a continuous wrapped roll state.

[0075] 2.1.2 Adding the vulcanizing agent: Adjust the roll gap to 2 - 3 mm to form a continuous wrapped roll rubber. Evenly sprinkle the bis(2,5 - dimethyl - 2,5 - di(t - butylperoxy)hexane) vulcanizing agent and mica flakes on the rubber tape, and immediately fold the tape to wrap the vulcanizing agent. At the same time, roll and knead 6 - 8 times to complete the fluorosilicone rubber mixing.

[0076] (2) Valve forming

[0077] I. Raw material preparation: The FVMQ fluorosilicone rubber compound after mixing, and the plastic or metal skeleton sprayed with the adhesive.

[0078] II. Vulcanization: In the present invention, put the compound into a compression or injection mold for vulcanization molding. The vulcanization temperature is 160 - 180 °C, the vulcanization pressure is 100 - 180 kg / cm 2 , and the vulcanization time is 100 - 360 s. In this fluorosilicone rubber embodiment, the vulcanization temperature is 180 °C, the vulcanization pressure is 120 kg / cm 2 , and the vulcanization time is 200 s.

[0079] III. Post - treatment: Deburr, second - stage vulcanize, clean, and inspect the vulcanized rubber product to obtain the final rubber valve.

[0080] The test indicators and methods are the same as those of the fluororubber, and the results are shown in Tables 5 and 6.

[0081] Table 5 Test results of the opening force of the fluorosilicone rubber valve *

[0082] Normal temperature (23°C) / KPa High temperature (83°C × 3 h) / KPa Example 1 27.4 30.5 Example 2 26.8 29.9 Example 3 28.6 31.3 Comparative Example 1 29.2 32.6

[0083] * Test conditions: The opening force ≤ 34 Kpa.

[0084] Table 6 Test results of the medium resistance of the fluorosilicone rubber valve *

[0085] Hardness change % Tensile strength change % Elongation at break change % Volume change % Example 1 -7 -33.6 -28.2 20.1 Example 2 -6.6 -31.2 -27.1 19.9 Example 3 -7.1 -32.5 -28.8 20.3 Comparative Example 1 -7.9 -35.2 -29 22.6

[0086] * Test conditions: Resistance to fuel C at 23 °C × 70 h.

[0087] The above has described in detail the preferred specific embodiments and examples of the present invention. However, the present invention is not limited to the above - mentioned embodiments and examples. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the concept of the present invention.

Claims

1. A rubber valve for an automobile fuel tank, characterized in that: The raw materials for the preparation include rubber, additives and mica flakes; The rubber is fluorine rubber or fluorine silicone rubber.

2. The rubber valve for automobile fuel tank according to claim 1, characterized in that: The auxiliary agent includes a filler, calcium hydroxide, magnesium oxide and a vulcanizing agent; preferably, the filler is carbon black N990; preferably, the vulcanizing agent is bisphenol AF; Alternatively, the auxiliary agent comprises a vulcanizing agent, and preferably the vulcanizing agent is a di-25 vulcanizing agent.

3. The rubber valve for automobile fuel tank according to claim 1 or 2, characterized in that: The weight percentage of the mica flakes in all raw materials is 0.5%-10%, preferably 2%-3%.

4. The rubber valve for automobile fuel tank according to any one of claims 1 to 3, characterized in that: The composition comprises the following components in parts by weight: 50-70 parts of fluororubber, 20-30 parts of filler, 1-5 parts of calcium hydroxide, 1-5 parts of magnesium oxide, 1-3 parts of vulcanizing agent, 0.5-10 parts of mica flakes; preferably 60-65 parts of fluororubber, 22-28 parts of filler, 3-5 parts of calcium hydroxide, 2-5 parts of magnesium oxide, 1-3 parts of vulcanizing agent, 1-8 parts of mica flakes; Or, 80-100 parts of fluorosilicone, 1-5 parts of vulcanizing agent, and 0.5-10 parts of mica flakes; preferably, 90-98 parts of fluorosilicone, 1-3 parts of vulcanizing agent, and 1-8 parts of mica flakes.

5. The rubber valve for automobile fuel tank according to any one of claims 1 to 4, characterized in that: The particle size of the mica flakes is 50 mesh to 400 mesh, preferably 100 mesh to 300 mesh.

6. A method for preparing a rubber valve for an automobile fuel tank according to any one of claims 1 to 5, characterized in that: The following steps are involved: S01, rubber mixing; S02, valve molding.

7. The method for preparing a rubber valve for an automobile fuel tank according to claim 6, characterized in that: In S01, the rubber mixing is a two-stage mixing, comprising the following steps: First stage mixing: adding additives such as calcium hydroxide, magnesium oxide, mica flakes and filler carbon black to the raw rubber, mixing, draining, obtaining a first stage of rubber, and setting aside; Second stage mixing: after the first stage of rubber is stopped, it is re-added, vulcanizing agent is added, mixed, rubber is discharged, and then the sheet is produced and air-cooled. Preferably, in the first stage of mixing, mixing is performed for 5-8 minutes, the discharge temperature is 115°C-125°C, and a first stage of rubber is obtained, which is then left for at least 8 hours; Preferably, in the second stage mixing, the mixing time is 3-5 minutes and the debinding temperature is 95°C-105°C.

8. The method for preparing a rubber valve for an automobile fuel tank according to claim 6 or 7, characterized in that: In S01, the fluorosilicone raw rubber is cut into small pieces and gradually fed into the roll gap of the mixing mill to form a continuous roll wrapping state; the roll spacing is adjusted to form a continuous roll wrapping state, the vulcanizer and mica flakes are sprinkled on the tape, the folded tape is wrapped around the vulcanizer, and the tape is rolled and refined at the same time to complete the fluorosilicone mixing.

9. The method for preparing a rubber valve for an automobile fuel tank according to any one of claims 6 to 8, characterized in that: In S02, the following steps are included: S21, placing the mixed rubber material and the plastic or metal frame sprayed with adhesive into a compression or injection mold for vulcanization molding; S22: The vulcanized rubber product is subjected to edge removal, two-stage vulcanization, cleaning, and inspection to obtain a final rubber valve.

10. The method for preparing a rubber valve for an automobile fuel tank according to any one of claims 6 to 9, characterized in that: In S02, during vulcanization molding, the vulcanization temperature is 160-180℃, and the vulcanization pressure is 100-180kg / cm 2 , vulcanization time 100-360s.

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