An EPDM rubber / fluororubber compatibilizer and its preparation method and application

Abstract

The present invention discloses an EPDM / fluororubber compatibilizer, its preparation method, and application, belonging to the technical field of rubber additives. The present invention utilizes a reversible free radical grafting reaction to graft small fluorine-containing molecular chains onto the main chain of a polypropylene molecule. The resulting EPDM / fluororubber compatibilizer is prepared by regulating the grafting rate. The compatibilizer is applied to the blending and modification of fluororubber and EPDM, overcoming the poor compatibility of the two rubbers during the blending process. This allows the EPDM modified with fluororubber to possess ideal high-temperature resistance and aging resistance, as well as excellent mechanical properties.

Description

Technical Field

[0001] The invention belongs to the technical field of rubber additives, and particularly relates to an EPDM rubber / fluororubber compatibilizer for improving the blending compatibility of the two rubbers, thereby improving the heat resistance and aging resistance of the EPDM rubber. Background Art

[0002] Ethylene propylene diene monomer (EPDM) is a terpolymer of ethylene, propylene, and a small amount of non-conjugated dienes. Its primary polymer chain is fully saturated, resulting in extremely flexible molecules. It also exhibits excellent resistance to ozone, corrosion, and low temperatures, making it an ideal choice for automotive hoses, sealing strips, and electrical insulation. However, EPDM is typically only suitable for long-term use below 150°C. Long-term exposure to high temperatures can significantly damage the product, especially under thermal and oxidative conditions. EPDM requires the ability to withstand higher operating temperatures, meaning it must exhibit superior high-temperature and aging resistance, to meet market demand. Consequently, extensive research is being conducted on EPDM and its modification to enhance its heat and aging resistance.

[0003] One approach to improving performance is compounding EPDM with heat-resistant rubbers, including silicone rubber, acrylic rubber, and fluororubber. Fluororubber (FKM) molecules contain highly electronegative fluorine atoms, which shield the carbon atoms in the main chain, resulting in excellent high-temperature resistance and mechanical properties. However, using it alone is too expensive. Therefore, an appropriate amount of fluororubber can be added to EPDM for blending and modification to improve its heat and aging resistance. However, FKM is a polar rubber, while EPDM is a non-polar rubber. Their different polarities result in poor compatibility when blended, and therefore, the desired performance cannot be achieved. Summary of the Invention

[0004] The present invention provides an EPDM / fluororubber compatibilizer, which can improve the compatibility of EPDM and FKM when the EPDM is blended and modified with fluororubber, thereby achieving an ideal modification effect, and can improve the heat resistance and aging resistance of the EPDM while also improving the mechanical properties.

[0005] The present invention provides a method for preparing an EPDM rubber / fluororubber compatibilizer, which specifically comprises the following preparation steps: adding 100-200 parts of polypropylene powder, 1-2 parts of an antioxidant and 5-10 parts of 1-fluoropropene to a mixing torque rheometer, mixing at 180°C and 80-100 rpm for 5 minutes, then adding 0.2-0.4 parts of sulfur and 0.2-0.4 parts of tetramethylthiuram monosulfide (TMTM) and continuing to mix for 5-10 minutes, placing the mixed raw materials in a flat-plate vulcanizer and reacting at 180°C for 5-10 minutes to obtain the EPDM rubber / fluororubber compatibilizer.

[0006] Furthermore, the mass ratio of the polypropylene powder to 1-fluoropropylene is 20-25:1; the mass ratio of the polypropylene powder to sulfur and TMTM is 500:1:1; and the polypropylene powder is homopolymer polypropylene with a number average molecular weight of 30,000.

[0007] Specifically, the EPDM rubber / fluororubber compatibilizer of the present invention is based on polypropylene molecular chains, and uses sulfur and thiuram compound TMTM as free radical initiators for grafting reactions. By reacting with fluorinated monomer 1-fluoropropylene through a reversible free radical reaction, small fluorinated molecular chains are grafted onto the main chain of polypropylene molecules (the specific reaction principle is shown in the attached figure). Figure 1 As shown). Under 180°C, sulfur and TMTM first crack to generate free radicals, which then initiate a reaction with polypropylene to generate carbon-centered free radicals. A reversible equilibrium reaction exists between the disulfide bond free radicals and the carbon-centered free radicals, which can inhibit the degradation of polypropylene and the homopolymerization of 1-fluoropropylene, and can also induce the double bonds in 1-fluoropropylene to be grafted onto the main chain carbon-centered free radicals to form a small molecule branched structure. The EPDM rubber / fluororubber compatibilizer has the following chemical structure:

[0008] (Formula I);

[0009] The present invention adopts 1-fluoropropylene grafting to modify polypropylene, thereby synthesizing a new type of EPDM / fluororubber compatibilizer. The polypropylene main chain has a main chain structure similar to that of EPDM and is also a non-polar molecular chain, so it has good compatibility with EPDM. The grafted fluorine-containing side chains, due to the presence of fluorine atoms, make the molecule have a certain polarity and improve the compatibility with FKM.

[0010] The present invention also provides an EPDM rubber / fluororubber compatibilizer prepared by the above preparation method.

[0011] The present invention also provides a modified EPDM rubber, which comprises the following raw material components in parts by weight: 60-80 parts of EPDM rubber, 10-30 parts of fluororubber, 5-10 parts of EPDM rubber / fluororubber compatibilizer, 50-100 parts of reinforcing agent, 1-3 parts of antioxidant, 3-5 parts of cross-linking agent, 1-3 parts of auxiliary cross-linking agent, 5-10 parts of zinc oxide, and 2-10 parts of plasticizer, wherein the EPDM rubber / fluororubber compatibilizer is the EPDM rubber / fluororubber compatibilizer prepared above in the present invention.

[0012] Furthermore, the EPDM rubber includes at least one of ENB type and DCPD type.

[0013] Furthermore, the reinforcing agent is carbon black N550.

[0014] Furthermore, the antioxidant is selected from at least one of N,N-dibutyldithiocarbamate nickel NBC and styrenated diphenylamine DDA.

[0015] Furthermore, the cross-linking agent is 1,4-bis(tert-butylperoxyisopropyl)benzene.

[0016] Furthermore, the auxiliary cross-linking agent is triallyl cyanurate.

[0017] Furthermore, the plasticizer includes one or more of dioctyl phthalate, dibutyl phthalate, and dimethyl phthalate.

[0018] The present invention also provides a preparation method of modified EPDM rubber, which specifically comprises the following steps: placing a formulated amount of EPDM rubber, fluororubber, EPDM rubber / fluororubber compatibilizer and reinforcing agent in an 80°C oven for drying for 12 hours to remove moisture therefrom, then adding the dried EPDM rubber, fluororubber and EPDM rubber / fluororubber compatibilizer into an internal mixer, mixing at 100°C and 30-50 r / min for 2-5 minutes, adding zinc oxide, a plasticizer and an antioxidant, and continuing to mix for 2-5 minutes, then adding the reinforcing agent in three equal portions, mixing for 5-10 minutes, and then draining the rubber to obtain a rubber mix; adding the rubber mix into an open mill, adding a crosslinking agent and a co-crosslinking agent, and mixing evenly, and then standing for 12 hours for vulcanization, with the vulcanization temperature being 155-180°C and the vulcanization time being 5-10 minutes, to finally prepare the modified EPDM rubber.

[0019] The present invention also provides an application of the modified EPDM rubber in the fields of automobile hoses and automobile sealing strips.

[0020] Compared with the prior art, the present invention has the following beneficial effects: the EPDM rubber / fluororubber compatibilizer provided by the present invention uses elemental sulfur and a thiuram compound TMTM as free radical initiators for a grafting reaction, adopts a reversible free radical reaction, grafts 1-fluoropropylene onto a polypropylene main chain, and introduces polar small molecule fluorine-containing side chains onto a non-polar main chain to prepare a fluororubber and EPDM rubber compatibilizer capable of overcoming the problem of poor compatibility between the two rubbers during the blending process. Furthermore, by regulating the grafting rate, the modified EPDM rubber has ideal high temperature resistance and aging resistance, while also having excellent mechanical properties.

[0021] The present invention also provides a modified EPDM rubber composition containing the EPDM rubber / fluororubber compatibilizer. The EPDM rubber is used as the main material, and fluororubber is added to the composition for blending and modification. Test results demonstrate that the addition of the EPDM rubber / fluororubber compatibilizer improves the blending of the two rubbers, resulting in a product with excellent heat and aging resistance, as well as mechanical properties. By modifying the EPDM rubber, the present invention helps further enhance the application scenarios of EPDM, enabling its widespread use in higher temperature environments, and is of great significance for extending the service life of products made from EPDM. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the chemical reaction principle of the preparation process of the EPDM rubber / fluororubber compatibilizer described in the present invention. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments; the technical features designed in the different implementation modes of the present invention described below can be combined with each other as long as they do not conflict with each other; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0024] In the description of the present invention, it should be noted that all terms used in the present invention (including technical terms and scientific terms) have the same meanings as those generally understood by ordinary technicians in the field to which the present invention belongs, and should not be understood as limiting the present invention; it should be further understood that the terms used in the present invention should be understood to have meanings consistent with the meanings of these terms in the context of this specification and in the relevant fields, and should not be understood in an idealized or overly formal sense, unless explicitly defined as such in the present invention.

[0025] The main experimental materials used in the following embodiments and comparative examples of the present invention include:

[0026] EPDM rubber: EPDM4045, Jilin Petrochemical Company of China National Petroleum Corporation;

[0027] Fluororubber: brand 2462, Zhonghao Chenguang Chemical Research Institute Co., Ltd.

[0028] Polypropylene powder: homopolymer polypropylene ELTEX HL001P, Solvay, number average molecular weight 30,000;

[0029] Sulfur: S-80, Jiaxing Beihua Polymer Additives Co., Ltd.

[0030] Reinforcing agent: carbon black N550, Ningbo Detai Chemical Co., Ltd.

[0031] Antioxidant: styrenated diphenylamine DDA, Rhein Chemie (Qingdao) Co., Ltd.

[0032] Cross-linking agent: 1,4-bis(tert-butylperoxyisopropyl)benzene, Akzo Nobel;

[0033] Cross-linking agent: triallyl cyanurate, Shanghai Pande 1025-15-6;

[0034] Plasticizer: Dioctyl phthalate, BASF.

[0035] Example 1

[0036] A modified EPDM rubber comprises the following raw material components in parts by weight: 70 parts of EPDM rubber, 20 parts of fluororubber, 7.5 parts of EPDM rubber / fluororubber compatibilizer, 75 parts of reinforcing agent, 2 parts of antioxidant, 4 parts of crosslinking agent, 2 parts of auxiliary crosslinking agent, 7.50 parts of zinc oxide, and 6 parts of plasticizer.

[0037] The preparation method of the EPDM rubber / fluororubber compatibilizer is as follows: 100 parts of polypropylene powder, 1 part of antioxidant and 5 parts of 1-fluoropropylene are added to a mixing torque rheometer, and mixed at 180°C and 100 rpm for 5 minutes, followed by adding 0.2 parts of sulfur and 0.2 parts of tetramethylthiuram monosulfide (TMTM) and continuing to mix for 5-10 minutes. The mixed raw materials are placed in a flat-plate vulcanizer and reacted at 180°C for 10 minutes to obtain the EPDM rubber / fluororubber compatibilizer, that is, the mass ratio of polypropylene powder to 1-fluoropropylene in this embodiment is 20:1

[0038] The preparation method of the modified EPDM rubber comprises the following steps: placing a formulated amount of EPDM rubber, fluororubber, EPDM rubber / fluororubber compatibilizer and reinforcing agent in an 80°C oven for drying for 12 hours to remove moisture therefrom; then adding the dried EPDM rubber, fluororubber and EPDM rubber / fluororubber compatibilizer into an internal mixer; mixing for 5 minutes at 100°C and 50 r / min; adding zinc oxide, a plasticizer and an antioxidant; continuing to mix for 5 minutes; then adding the reinforcing agent in three equal portions; mixing for 5 minutes and then draining the rubber to obtain a rubber mix; adding the rubber mix into an open mill; adding a crosslinking agent and a co-crosslinking agent and mixing evenly; standing for 12 hours and then vulcanizing at a vulcanization temperature of 160°C and a vulcanization time of 7 minutes to finally prepare the modified EPDM rubber.

[0039] Example 2

[0040] A modified EPDM rubber comprises the following raw material components in parts by weight: 70 parts of EPDM rubber, 20 parts of fluororubber, 7.5 parts of EPDM rubber / fluororubber compatibilizer, 75 parts of reinforcing agent, 2 parts of antioxidant, 4 parts of crosslinking agent, 2 parts of auxiliary crosslinking agent, 7.50 parts of zinc oxide, and 6 parts of plasticizer.

[0041] The preparation method of the EPDM rubber / fluororubber compatibilizer is as follows: 100 parts of polypropylene powder, 1 part of antioxidant and 4 parts of 1-fluoropropene are added to a mixing torque rheometer, and mixed at 180°C and 100 rpm for 5 minutes. Subsequently, 0.2 parts of sulfur and 0.2 parts of tetramethylthiuram monosulfide (TMTM) are added and mixing is continued for 5-10 minutes. The mixed raw materials are placed in a flat-plate vulcanizer and reacted at 180°C for 10 minutes to obtain the EPDM rubber / fluororubber compatibilizer, that is, the mass ratio of polypropylene powder to 1-fluoropropene described in this embodiment is 25:1.

[0042] The preparation method of the modified EPDM rubber comprises the following steps: placing a formulated amount of EPDM rubber, fluororubber, EPDM rubber / fluororubber compatibilizer and reinforcing agent in an 80°C oven for drying for 12 hours to remove moisture therefrom; then adding the dried EPDM rubber, fluororubber and EPDM rubber / fluororubber compatibilizer into an internal mixer; mixing for 5 minutes at 100°C and 50 r / min; adding zinc oxide, a plasticizer and an antioxidant; continuing to mix for 5 minutes; then adding the reinforcing agent in three equal portions; mixing for 5 minutes and then draining the rubber to obtain a rubber mix; adding the rubber mix into an open mill; adding a crosslinking agent and a co-crosslinking agent and mixing evenly; standing for 12 hours and then vulcanizing at a vulcanization temperature of 160°C and a vulcanization time of 7 minutes to finally prepare the modified EPDM rubber.

[0043] Example 3

[0044] A modified EPDM rubber comprises the following raw material components in parts by weight: 80 parts of EPDM rubber, 30 parts of fluororubber, 10 parts of EPDM rubber / fluororubber compatibilizer, 100 parts of reinforcing agent, 3 parts of antioxidant, 5 parts of crosslinking agent, 3 parts of auxiliary crosslinking agent, 10 parts of zinc oxide, and 10 parts of plasticizer.

[0045] The preparation method of the EPDM rubber / fluororubber compatibilizer is as follows: 100 parts of polypropylene powder, 1 part of antioxidant and 4 parts of 1-fluoropropene are added to a mixing torque rheometer, and mixed at 180°C and 100 rpm for 5 minutes. Subsequently, 0.2 parts of sulfur and 0.2 parts of tetramethylthiuram monosulfide (TMTM) are added and mixing is continued for 5-10 minutes. The mixed raw materials are placed in a flat-plate vulcanizer and reacted at 180°C for 10 minutes to obtain the EPDM rubber / fluororubber compatibilizer, that is, the mass ratio of polypropylene powder to 1-fluoropropene described in this embodiment is 25:1.

[0046] The preparation method of the modified EPDM rubber comprises the following steps: placing a formulated amount of EPDM rubber, fluororubber, EPDM rubber / fluororubber compatibilizer and reinforcing agent in an 80°C oven for drying for 12 hours to remove moisture therefrom; then adding the dried EPDM rubber, fluororubber and EPDM rubber / fluororubber compatibilizer into an internal mixer; mixing for 5 minutes at 100°C and 50 r / min; adding zinc oxide, a plasticizer and an antioxidant; continuing to mix for 5 minutes; then adding the reinforcing agent in three equal portions; mixing for 5 minutes and then draining the rubber to obtain a rubber mix; adding the rubber mix into an open mill; adding a crosslinking agent and a co-crosslinking agent and mixing evenly; standing for 12 hours and then vulcanizing at a vulcanization temperature of 160°C and a vulcanization time of 7 minutes to finally prepare the modified EPDM rubber.

[0047] Comparative Example 1

[0048] A modified EPDM rubber, wherein the amount of polypropylene powder used in the preparation process of the EPDM rubber / fluororubber compatibilizer is 100 parts, and the amount of 1-fluoropropylene is 5.5 parts, that is, the mass ratio of polypropylene powder to 1-fluoropropylene is 18:1, and the rest of the formula and process are the same as those in Example 1.

[0049] Comparative Example 2

[0050] A modified EPDM rubber, wherein the amount of polypropylene powder used in the preparation process of the EPDM rubber / fluororubber compatibilizer is 100 parts, and the amount of 1-fluoropropylene is 3.7 parts, that is, the mass ratio of polypropylene powder to 1-fluoropropylene is 27:1, and the rest of the formula and process are the same as those in Example 1.

[0051] Comparative Example 3

[0052] A modified EPDM rubber is prepared without adding an EPDM rubber / fluororubber compatibilizer. The remaining formula and process are the same as those in Example 1.

[0053] Performance Testing

[0054] The performance testing standards of the present invention are as follows: Shore A hardness is tested in accordance with GB / T 531.1-2008, "Rubber, vulcanized or thermoplastic rubber - Test method for indentation hardness - Part 1: Shore durometer method (Shore hardness)." Tensile properties are tested in accordance with GB / T 528-2009, "Rubber, vulcanized or thermoplastic rubber - Determination of tensile stress-strain properties." Hot air aging resistance is tested in accordance with GB / T 3512-2001, "Rubber, vulcanized or thermoplastic rubber - Hot air accelerated aging and heat resistance test." Aging crack resistance is tested as follows: a vulcanized rubber specimen (5 cm × 1 cm × 2 mm) is aged in a high-temperature aging chamber. After aging, the specimen is left at room temperature for at least 2 hours, then attached to a cylinder of the same diameter and bent into the same arc. The number and size of surface cracks on the specimen are observed and compared.

[0055] The heat aging resistance and mechanical and physical properties of each formula product are as follows:

[0056]

[0057] The data in the table above demonstrate that by adjusting the mass ratio of polypropylene powder to 1-fluoropropylene during the preparation of the EPDM / Fluororubber compatibilizer, the grafting rate of fluorinated groups can be controlled. Within a specific range of grafting rates, products with ideal high-temperature resistance, aging resistance, and mechanical properties can be obtained when applied to modified EPDM systems. However, when the grafting rate of fluorinated groups is too high, the polarity of the EPDM / Fluororubber compatibilizer increases, leading to aggregation of fluorinated groups. When the grafting rate is too low, the number of hydrogen bonds that can form with the fluorinated groups is too low, both of which affect the compatibility between EPDM and Fluororubber. Therefore, the experimental results demonstrate that, other conditions remaining unchanged, a mass ratio of polypropylene powder to 1-fluoropropylene of 20-25:1 achieves ideal modification and compatibility. Furthermore, when no EPDM / Fluororubber compatibilizer is added, the significant difference in polarity between the two rubbers results in suboptimal high-temperature resistance, aging resistance, and mechanical properties.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an EPDM rubber / fluororubber compatibilizer, characterized in that: The preparation method specifically comprises the following steps: adding 100-200 parts of polypropylene powder, 1-2 parts of antioxidant and 5-10 parts of 1-fluoropropene into a mixing torque rheometer, mixing at 180°C and 80-100 rpm for 5 minutes, then adding 0.2-0.4 parts of sulfur and 0.2-0.4 parts of tetramethylthiuram monosulfide (TMTM) and continuing to mix for 5-10 minutes, placing the mixed raw materials into a flat-plate vulcanizer and reacting at 180°C for 5-10 minutes to obtain the EPDM rubber / fluororubber compatibilizer; the mass ratio of the polypropylene powder to 1-fluoropropene is 20-25:

1.

2. The method for preparing the EPDM rubber / fluororubber compatibilizer according to claim 1, characterized in that: The mass ratio of the polypropylene powder to sulfur and TMTM is 500:1:1; the polypropylene powder is homopolymer polypropylene with a number average molecular weight of 30,000.

3. An EPDM rubber / fluororubber compatibilizer prepared according to the method for preparing an EPDM rubber / fluororubber compatibilizer according to any one of claims 1 to 2.

4. Use of the EPDM rubber / fluororubber compatibilizer according to claim 3 in the preparation of modified EPDM rubber.

5. The use of the EPDM rubber / fluororubber compatibilizer according to claim 4 in the preparation of modified EPDM rubber, characterized in that: The modified EPDM rubber comprises the following raw material components in parts by weight: 60-80 parts of EPDM rubber, 10-30 parts of fluororubber, 5-10 parts of EPDM rubber / fluororubber compatibilizer, 50-100 parts of reinforcing agent, 1-3 parts of antioxidant, 3-5 parts of crosslinking agent, 1-3 parts of auxiliary crosslinking agent, 5-10 parts of zinc oxide, and 2-10 parts of plasticizer.

6. Use of the EPDM rubber / fluororubber compatibilizer according to claim 5 in the preparation of modified EPDM rubber, characterized in that: The reinforcing agent is carbon black N550.

7. Use of the EPDM rubber / fluororubber compatibilizer according to claim 5 in the preparation of modified EPDM rubber, characterized in that: The antioxidant is selected from at least one of N,N-dibutyldithiocarbamate nickel NBC and styrenated diphenylamine DDA.

8. Use of the EPDM rubber / fluororubber compatibilizer according to claim 5 in the preparation of modified EPDM rubber, characterized in that: The cross-linking agent is 1,4-bis(tert-butylperoxyisopropyl)benzene, or the auxiliary cross-linking agent is triallyl cyanurate.

9. Use of the EPDM rubber / fluororubber compatibilizer according to claim 5 in the preparation of modified EPDM rubber, characterized in that: The plasticizer includes one or more of dioctyl phthalate, dibutyl phthalate and dimethyl phthalate.

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