A phosphate ester resistant EPDM rubber material and its preparation method and application

Abstract

The present invention discloses a phosphate ester-resistant EPDM rubber material, the raw materials of which include, by weight, 140 parts of a main rubber material, 125-140 parts of a filler, 7-8 parts of a vulcanizing agent, 1.5-2.5 parts of a cross-linking agent, and 4-6 parts of calcium oxide; wherein the main rubber material comprises an oil-extended EPDM rubber 1, an oil-extended EPDM rubber 2, and a non-oil-extended EPDM rubber 3 in a weight ratio of 100:5-15:25-35. The present invention also separately discloses a preparation method for the phosphate ester-resistant EPDM rubber material and its application in a hydraulic device. The present invention can maintain stable mechanical and physical properties in high-temperature and long-term phosphate ester hydraulic oil experiments without significant volume expansion or dimensional deformation.

Description

Technical Field

[0001] The present invention relates to the field of rubber technology, and in particular to a phosphate ester resistant EPDM rubber material and a preparation method and application thereof. Background Art

[0002] With the development of aerospace, synthetic hydraulic fluids are increasingly used in aircraft hydraulic systems. LD-4 phosphate ester hydraulic fluid stands out for its high thermal and oxidative stability. It not only offers excellent corrosion resistance but also offers excellent compatibility with other materials, enhancing component stability. Consequently, LD-4 phosphate ester hydraulic fluid is widely used in hydraulic systems on aircraft such as those of Boeing, Airbus, and McDonnell Douglas.

[0003] To address the widespread use of LD-4 phosphate ester hydraulic fluid, enhancing the resistance of gaskets, washers, diaphragms, and other products in aircraft hydraulic systems to LD-4 phosphate ester hydraulic fluid has become a key research and development direction for rubber materials. Rubber materials used in aircraft hydraulic systems require not only excellent resistance to phosphate ester hydraulic fluid but also heat resistance and low compression set. Traditional rubber materials are no longer sufficient for existing aerospace hydraulic systems, necessitating improved formulations and technological innovation. Summary of the Invention

[0004] Based on the technical problems existing in the background technology, the present invention proposes a phosphate ester EPDM rubber material and its preparation method and application; the present invention can maintain its own mechanical and physical properties stable in high-temperature and long-term phosphate ester hydraulic oil experiments without obvious volume expansion and dimensional deformation.

[0005] The present invention provides a phosphate ester resistant EPDM rubber material, the raw materials of which include, by weight: 140 parts of a rubber main material, 125-140 parts of a filler, 7-8 parts of a vulcanizing agent, 1.5-2.5 parts of a co-crosslinking agent, and 4-6 parts of calcium oxide;

[0006] The main rubber material consists of oil-filled EPDM rubber 1, oil-filled EPDM rubber 2 and non-oil-filled EPDM rubber 3 in a weight ratio of 100:5-15:25-35.

[0007] Preferably, the rubber main material is composed of oil-extended EPDM rubber 1, oil-extended EPDM rubber 2 and non-oil-extended EPDM rubber 3 in a weight ratio of 100:10:30.

[0008] Preferably, the oil-filled amount of the oil-extended EPDM rubber 1 is 25-35 parts, and the content of the third monomer ethylidene norbornene is 4.4-4.6 wt%

[0009] Preferably, the oil-filled amount of the oil-extended EPDM rubber 2 is 70-80 parts, and the content of the third monomer ethylidene norbornene is 4.6-4.8 wt %.

[0010] Preferably, the content of ethylidene norbornene, the third monomer, in the non-oil-extended EPDM rubber 3 is 5.2-5.4 wt%.

[0011] The oil-filled EPDM rubber 1 may be EPDM K-8370EM, etc., the oil-filled EPDM rubber 2 may be EPDM K5467C, etc., and the non-oil-filled EPDM rubber 3 may be EPDM K8550C.

[0012] The Mooney viscosity ML(1+4) of the EPDM rubber K-8370EM at 125° C. is 55, the ethylene content is 50 wt %, the content of the third monomer ethylidene norbornene (ENB) is 4.7 wt %, and the oil filling amount is 30 parts.

[0013] The Mooney viscosity ML(1+4) of the EPDM rubber K5467C at 125° C. is 52, the ethylene content is 58 wt %, the content of the third monomer ethylidene norbornene (ENB) is 4.5 wt %, and the oil filling amount is 75 parts.

[0014] The Mooney viscosity ML(1+4) of the EPDM rubber K8550C at 125° C. is 80, the ethylene content is 55 wt %, and the content of the third monomer ethylidene norbornene (ENB) is 5.3 wt %.

[0015] The above-mentioned oil filling amount refers to the amount of oil added to 100 parts of rubber. For example, if 30 parts of oil are added to 100 parts of rubber, the total weight is 130 parts, and the oil filling amount is 30 parts.

[0016] Phosphate esters are oils with a certain degree of polarity. The present invention uses non-polar EPDM rubber as the main rubber material to improve its phosphate ester resistance. Since phosphate ester hydraulic fluids are mostly mixed with a small amount of mineral oil, which increases the swelling degree of the EPDM rubber, the present invention uses oil-extended EPDM rubbers with different oil-filling amounts to promote the precipitation of phosphate esters in the oil and reduce the swelling volume of the rubber. In addition, by adding non-oil-extended EPDM rubber with a high content of the third monomer ethylidene norbornene, the two materials are combined in appropriate proportions to improve the stability and mechanical properties of the rubber material in phosphate ester hydraulic fluid while maintaining a low swelling volume of the rubber.

[0017] Preferably, the rubber content of the phosphate ester EPDM rubber material is 35-39 wt%.

[0018] Too low a rubber content will reduce the rubber material's resistance to phosphate esters. Currently used phosphate ester-resistant rubber materials often have a high rubber content. However, the inventors have found that rubber materials with high rubber content have poor mechanical properties and a large change in swelling volume in phosphate ester hydraulic oil. Therefore, the inventors control the rubber content of the entire formula by combining oil-filled EPDM rubber and non-oil-filled EPDM rubber, so that the rubber material has a suitable rubber content, improves its stability in phosphate ester hydraulic oil, improves mechanical properties, and reduces swelling volume.

[0019] Preferably, the filler is carbon black N550.

[0020] Carbon black can improve the tensile strength, tear strength, and abrasion resistance of rubber materials. Excessive carbon black usage results in higher hardness and lower elongation in the vulcanized rubber. Inadequate carbon black usage results in lower hardness and strength in the vulcanized rubber, failing to achieve the desired reinforcement effect. This study found that selecting the appropriate type and amount of carbon black can reduce the volume expansion of rubber materials in phosphate ester hydraulic fluids and improve the hardness and elongation of the rubber material.

[0021] Preferably, the vulcanizing agent is a peroxide vulcanizing agent.

[0022] The above-mentioned vulcanizing agent can be dicumyl peroxide, vulcanizing agent DCP40, etc.; the preferred vulcanizing agent is vulcanizing agent DCP40; compared with the sulfur system, vulcanizing agent DCP40 has good heat resistance, lower compression permanent deformation, and lower cost among many peroxide vulcanizing agents.

[0023] Preferably, the auxiliary cross-linking agent is Ricon 154DA.

[0024] The present invention selects the co-crosslinking agent Ricon 154DA under the peroxide vulcanization system, which can further increase the crosslinking density of the vulcanized rubber and limit the displacement and damage between rubber molecules. Ricon 154DA is a low molecular weight polybutadiene resin with high reactivity, special hydrophobicity and excellent processing characteristics. Its polymer structure makes it have good compatibility in both saturated elastomers and unsaturated elastomers. Moreover, Ricon 154DA is a Type II auxiliary agent with good crosslinking density without affecting the curing rate, which greatly improves the stability of the rubber material in the phosphate ester. The vulcanizing agent DCP40 and the co-crosslinking agent Ricon 154DA cooperate with each other to ensure the vulcanization speed and crosslinking degree of the mixed rubber, while increasing the strength of the rubber material, increasing the elongation and improving the heat resistance of the vulcanized rubber.

[0025] The present invention uses calcium oxide to enable the rubber to have the performance characteristics of prolonged water absorption and at the same time have a large water absorption capacity. When combined with oil-filled EPDM rubber with different oil filling amounts, the swelling volume of the rubber material can be reduced without affecting the permanent compression set of the rubber material. The calcium oxide can use commercially available CaO-PP, etc.

[0026] Preferably, the raw materials of the phosphate ester EPDM rubber material further include: zinc oxide, filler oil, coupling agent, lubricant, and antioxidant.

[0027] Preferably, the weight ratio of the rubber main material to zinc oxide, filler oil, coupling agent, lubricant, and antioxidant is 140:0.8-1.2:5-15:0.8-1.2:2.5-3.5:0.8-1.2.

[0028] Preferably, the weight ratio of the main rubber material to zinc oxide, filler oil, coupling agent, lubricant, and antioxidant is 140:1:10:1:3:1.

[0029] Zinc oxide can increase the vulcanization speed and crosslinking density of EPDM rubber and improve the heat resistance of the rubber material. The present invention preferably uses indirect zinc oxide that meets the GB / T 3185-92 standard, and more preferably uses indirect zinc oxide with a zinc oxide content of 99.8% or more.

[0030] The filler oil can improve the processing performance of the rubber compound and increase the filling amount, thereby reducing the cost. The preferred filler oil of the present invention is paraffin oil.

[0031] Coupling agents can improve the compatibility of inorganic fillers and rubber, which not only improves the mechanical properties of the rubber, but also improves the heat resistance, water resistance and weather resistance, making the permanent compression deformation of the vulcanized rubber smaller.

[0032] The raw materials in the formulation of the present invention can all be obtained commercially.

[0033] The present invention also proposes a preparation method of the phosphate ester resistant EPDM rubber material, comprising the following steps: mixing the raw materials, heat refining, extruding, and then performing a first stage vulcanization and a second stage vulcanization treatment to obtain the phosphate ester resistant EPDM rubber material.

[0034] Preferably, the pressure of the first stage of vulcanization is 160-180Kgf / cm 2 , temperature is 160-180℃, time is 400-600s.

[0035] More preferably, the pressure of the first stage vulcanization is 165-175Kgf / cm 2 , temperature is 165-175℃, time is 480-600s.

[0036] Preferably, the temperature of the second stage vulcanization is 150-175° C. and the time is 1-2 hours.

[0037] More preferably, the temperature of the second-stage vulcanization is 170° C. and the time is 1 hour.

[0038] Choosing two-stage vulcanization and selecting appropriate parameters can further improve the cross-linking degree of the rubber material and improve the compression permanent set.

[0039] The present invention also proposes the application of the phosphate ester resistant EPDM rubber material in a hydraulic device.

[0040] Preferably, the hydraulic oil used in the hydraulic device is phosphate ester hydraulic oil.

[0041] The hydraulic device may be a hydraulic device used in aerospace, aviation, etc.

[0042] Beneficial effects:

[0043] The present invention adopts a combination of oil-filled EPDM rubber and non-oil-filled EPDM rubber with different oil filling amounts to control the rubber content of the entire formula, thereby improving the stability of the rubber material in phosphate ester hydraulic oil. At the same time, high-filling carbon black is used in combination to reduce the volume expansion of the formula in phosphate ester hydraulic oil. By controlling the oil filling amount of the oil-filled EPDM rubber and the third monomer content of the EPDM rubber, the rubber material has a low swelling volume and the stability and mechanical properties of the rubber material in phosphate ester hydraulic oil are improved. A suitable vulcanizing agent and a cross-linking co-agent are used in combination to increase the vulcanization speed and cross-linking degree of the mixed rubber and improve the heat resistance of the vulcanized rubber. Second-stage vulcanization is added to further increase the cross-linking degree of the rubber material and improve compression set.

[0044] Compared with existing EPDM rubber resistant to phosphate ester hydraulic oil, the present invention has high strength, low pressure deformation, and excellent heat resistance and phosphate ester resistance. The present invention can maintain its own mechanical and physical properties stable in high-temperature and long-term phosphate ester hydraulic oil experiments without obvious volume expansion and dimensional deformation. DETAILED DESCRIPTION

[0045] The technical solution of the present invention is described in detail below through specific embodiments.

[0046] The formulations of Examples 1-3 and Comparative Examples 1-7 are shown in Table 1.

[0047] Table 1 Formulas of each group (dosage unit is g)

[0048]

[0049]

[0050] The preparation methods of the above formulations are the same, including the following steps: weighing the raw materials according to the weight in Table 1, adding them into an internal mixer for mixing, filtering, and obtaining a mixture; heating the mixture in an open mixer until uniform, and then extruding it into a rubber strip, adjusting the pressure to 170Kgf / cm 2 The temperature is 175 ° C for one stage vulcanization for 600 s, and then at 170 ° C, the second stage vulcanization is carried out for 1 hour to obtain the rubber material.

[0051] Phosphate ester-resistant rubber materials usually have certain requirements for hardness, tensile strength, elongation at break, resistance to phosphate ester hardness and volume change. Among them, hardness is used to evaluate the product's ability to resist external stress without changing, tensile strength is used to evaluate the product's service life, and elongation at break is used to evaluate the product's assembly performance. The hardness and volume change in phosphate ester hydraulic oil are used to evaluate the material's stability in the phosphate ester.

[0052] The rubber materials prepared in Examples 1-3 and Comparative Examples 1-7 were subjected to performance tests and compared with commercially available hydraulic system rubber materials. The test results are shown in Table 2.

[0053] The test standard for hardness is ASTM D1415, the test standard for tensile strength is ASTM D412, the test standard for elongation at break is ASTM D412, and the test standard for phosphate ester aging resistance test is ASTM D471.

[0054] Table 2 Test results

[0055]

[0056] As can be seen from Table 2, the combined use of three EPDM rubbers to control the rubber content, the addition of appropriate amounts of carbon black, and the addition of oil-extended rubber all effectively improve the stability of the material in phosphate ester hydraulic oil. The addition of calcium oxide and the cross-linking aid Ricon 154DA also ensures the tensile strength and elongation at break of the material. Among them, the rubber material prepared in Example 3 of the present invention has excellent performance, with good hardness, tensile strength, and elongation at break. It is also more stable in phosphate ester oil, meeting the performance indicators of rubber materials for components in hydraulic systems and can well meet the performance requirements of aerospace hydraulic system components.

[0057] The phosphate-resistant EPDM rubber material prepared in Example 3 was subjected to elemental analysis. The results are shown in Table 3.

[0058] Table 3 Elemental analysis results of substances

[0059]

[0060]

[0061] It can be seen from Table 3 that the phosphate ester EPDM rubber material of the present invention can meet the EU ROHS requirements for banned substances.

[0062] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A phosphate ester resistant EPDM rubber material, characterized in that: The raw materials include, by weight: 140 parts of rubber main material, 125-140 parts of filler, 7-8 parts of vulcanizing agent, 1.5-2.5 parts of auxiliary cross-linking agent, and 4-6 parts of calcium oxide; The main rubber material is composed of oil-extended EPDM rubber 1, oil-extended EPDM rubber 2 and non-oil-extended EPDM rubber 3 in a weight ratio of 100:5-15:25-35; The oil-filled amount of the oil-extended EPDM rubber 1 is 25-35 parts, and the content of the third monomer ethylidene norbornene is 4.4-4.6wt%; The oil-filled amount of the oil-extended EPDM rubber 2 is 70-80 parts, and the content of the third monomer ethylidene norbornene is 4.6-4.8wt%; The content of the third monomer ethylidene norbornene in the non-oil-extended EPDM rubber 3 is 5.2-5.4 wt%; The rubber content of phosphate ester EPDM rubber material is 35-39wt%; The vulcanizing agent is a peroxide vulcanizing agent; the co-crosslinking agent is Ricon 154DA.

2. The phosphate ester resistant EPDM rubber material according to claim 1, characterized in that: The filler is carbon black N550.

3. The phosphate ester resistant EPDM rubber material according to claim 1, characterized in that: The raw materials of phosphate ester EPDM rubber materials also include: zinc oxide, filler oil, coupling agent, lubricant, and antioxidant.

4. The phosphate ester resistant EPDM rubber material according to claim 3, characterized in that: The weight ratio of the rubber main material to zinc oxide, filler oil, coupling agent, lubricant and antioxidant is 140:0.8-1.2:5-15:0.8-1.2:2.5-3.5:0.8-1.

2.

5. A method for preparing the phosphate ester resistant EPDM rubber material according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: uniformly mixing various raw materials, heat-refining, extruding and molding, and then performing a first-stage vulcanization and a second-stage vulcanization treatment to obtain a phosphate ester EPDM rubber material.

6. The method for preparing the phosphate ester resistant EPDM rubber material according to claim 5, characterized in that: The pressure of the first stage vulcanization is 160-180Kgf / cm 2 , temperature is 160-180℃, time is 400-600s.

7. The method for preparing the phosphate ester resistant EPDM rubber material according to claim 5, characterized in that: The temperature of the second stage vulcanization is 150-175℃ and the time is 1-2 hours.

8. Use of the phosphate ester resistant EPDM rubber material according to any one of claims 1 to 4 in a hydraulic device.

9. The application according to claim 8, characterized in that: The hydraulic oil used in the hydraulic device is phosphate ester hydraulic oil.

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