High elongation oil resistant composite rubber, preparation thereof and use of the composite rubber

Abstract

The application discloses a high-elongation oil-resistant composite rubber which comprises the following raw materials in parts by weight: rubber compound 100 parts, filling reinforcing agent 30-40 parts, softening plasticizer 10-15 parts, zinc oxide 2-5 parts, stearic acid 1-3 parts, anti-aging agent 4-5.5 parts, tackifier LS506 1-2 parts, vulcanizing agent 2-3 parts, vulcanization accelerator 1.2-2.5 parts, and other additives 0-6 parts. The composite rubber is obtained through pre-plasticizing, one-stage mixing, two-stage mixing, vulcanization forming, chlorination and water washing of the rubber compound. The obtained composite rubber has the breaking strength of 40-50 kN / m, the elongation at break of 400%-700%, the tear of less than 12 mm, and the slightly bitter or non-bitter taste, and can meet the application in the pasture animal nipple product.

Description

Technical Field

[0001] This invention relates to the field of rubber functional improvement technology, and in particular to a high elongation oil-resistant composite rubber, its preparation and application. Background Technology

[0002] In the market, dairy farm nipples are commonly made primarily of natural rubber and nitrile rubber. Due to the introduction of highly polar acrylonitrile structural units in the molecular chain, nitrile rubber has excellent oil resistance, ensuring that dairy farm nipples can effectively resist the swelling and erosion of milk powder when used by calves and lambs to suckle milk. This prevents the nipples from softening, deforming, or even developing an odor due to prolonged contact with milk. Natural rubber has excellent elasticity and low-temperature performance, mimicking the softness and elasticity of cow teats, improving the calves' acceptance and sucking comfort. Therefore, dairy farm nipples made primarily of natural rubber and nitrile rubber are widely used.

[0003] However, existing dairy nipple products made from the aforementioned materials on the market may experience slight deformation within a short period of use, causing the cut (the sealed cut made for drinking milk) to leak and become unsealed, necessitating replacement. Furthermore, after a period of use, the products may become brittle, with the nipple tip easily bitten or the cut extending, leading to leakage. The nipple products may also develop noticeable cracks, resulting in their abandonment. Moreover, existing nipple products have a bitter taste, which makes cattle and sheep dislike sucking milk from these products, reducing their appetite.

[0004] Therefore, rubber compounds made primarily from natural rubber and nitrile rubber cannot adequately meet the requirements for product use in terms of elongation, oil resistance, and taste. Summary of the Invention

[0005] The present invention provides a high elongation oil-resistant composite rubber, which aims to solve the above-mentioned defects of composite rubber in terms of elongation, oil resistance and product taste, and thus solve the problems of slight deformation, cuts and bitter taste on the surface of rubber materials in a short period of time during actual use.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] A high elongation oil-resistant composite rubber, by weight, comprises the following raw materials: 100 parts rubber compound, 30-40 parts filler and reinforcing agent, 10-15 parts softening plasticizer, 2-5 parts zinc oxide, 1-3 parts stearic acid, 4-5.5 parts antioxidant, 1-2 parts tackifier LS506, 2-3 parts vulcanizing agent, 1.2-2.5 parts vulcanization accelerator, and 0-6 parts other additives.

[0008] The rubber compound includes natural rubber (NR), nitrile rubber (NBR) and styrene-butadiene rubber (SBR), and the ratio of natural rubber: styrene-butadiene rubber: nitrile rubber by mass is 1:(1~1.5):(0.4~0.8).

[0009] In the rubber compound, the mass ratio of the total mass of non-polar natural rubber and non-polar styrene-butadiene rubber to the mass of polar nitrile rubber is 1:(0.16~0.4).

[0010] The acrylonitrile structural unit content in the nitrile rubber is 30wt%~35wt%.

[0011] Preferably, the natural rubber is one or both of standard rubber or smoked sheet rubber.

[0012] Preferably, the reinforcing filler is composed of one or more of carbon black N550, calcined kaolin, and silica.

[0013] Preferably, the softening plasticizer comprises naphthenic oil and polar oil. The naphthenic oil is one or both of KN4006 or KN4010, and the polar oil is composed of one or more of dioctyl adipate (DOA), diisooctyl sebacate (DOS), trioctyl trimellitate (TOTM), and dibutyl diglyceride adipate, with the naphthenic oil and polar oil in a mass ratio of 1:0.5~1. The polar oil allows the surface of the product obtained after vulcanization of the composite rubber to remain smooth, and during application, it allows the milk and rubber to form an interface, preventing milk residue from remaining for a long time and avoiding premature milk buildup or mold growth on the nipple.

[0014] Preferably, the antioxidant is composed of one or more of antioxidant CPL, antioxidant 4010NA, antioxidant CTU, and microcrystalline wax. The antioxidant can enhance the ozone resistance, light resistance, and service life of the composite rubber product after vulcanization.

[0015] Preferably, the vulcanization accelerator is one or more of vulcanization accelerator CZ-80, vulcanization accelerator DM-80, or vulcanization accelerator TT-75.

[0016] Preferably, the vulcanizing agent is ordinary sulfur, and the effective sulfur content in the ordinary sulfur is 80wt~99wt%.

[0017] In this invention, other additives include one or both of the coupling agent SI69 and the activator PEG4000.

[0018] The present invention also provides a method for preparing a high elongation oil-resistant composite rubber, comprising the following steps:

[0019] S1: Pre-mixing of rubber compound: Take natural rubber, nitrile rubber and styrene-butadiene rubber according to the ratio and mix them in an internal mixer for 5~20 minutes to obtain rubber compound. The rubber compound is then sheeted out through a two-roll mill. The sheeted rubber compound is left at room temperature for 4~10 hours.

[0020] S2: First stage mixing: Take 100 parts of the above rubber compound, and according to the formula, take the filler, reinforcing agent, softening plasticizer, zinc oxide, stearic acid, antioxidant, and tackifier LS506 and mix them in an internal mixer for 8~15 minutes. When the discharge temperature is set to 125~135℃, discharge the material to the open mill for sheeting. After sheeting, let the rubber compound stand for 8~12 hours under a constant temperature of 17~25℃ to obtain the first stage mixture.

[0021] S3: Two-stage mixing: According to the formula, take the above-mentioned first-stage mixture, vulcanizing agent, and vulcanization accelerator and mix them in a rubber mixing mill under the conditions of 80-100℃ and 0.3-0.4MPa for 10-30 minutes. After the mixture is uniformly mixed, discharge it to the open mill at a discharge temperature of 60-90℃ to turn it into sheets and obtain sheet-like pre-vulcanized rubber. Let the pre-vulcanized rubber cool and stand for 8-12 hours under a constant temperature of 17-25℃.

[0022] S4: Vulcanization molding: The pre-vulcanized rubber compound is placed into the injection molding machine and injected into the mold cavity. The product is vulcanized at a pressure of 12~18MPa and a temperature of 150~175℃ for 100~300s to obtain the vulcanized product.

[0023] S5: Chlorination: First, immerse the vulcanized product in a 5%~10% dilute hydrochloric acid solution for 10~15 seconds to remove the release agent, oil, or oxide layer from the surface of the vulcanized product. After the hydrochloric acid washing is completed, wash it with a 5%~10% sodium carbonate solution for 10~15 seconds, and then rinse it with deionized water 2~4 times. After cleaning, immerse the vulcanized product in a 3%~5% sodium hypochlorite solution, adjust the pH value to 2.5~3.5 with hydrochloric acid, vibrate under ultrasonic conditions, keep the solution temperature at 30~40℃, and chlorinate for 10~30 seconds.

[0024] S6: Washing: Rinse 2-4 times with deionized water, dry, and then let stand for 12-24 hours under constant temperature and humidity conditions of 23-25℃ and 45-55% to obtain the product.

[0025] The present invention has the following beneficial effects:

[0026] Composite rubber uses natural rubber, styrene-butadiene rubber (SBR), and nitrile rubber (NBR) as its backbone. SBR possesses excellent abrasion resistance, flexural strength (resistance to repeated sucking and tearing), and high mechanical strength. As an intermediate, SBR can increase the compatibility between natural rubber and NBR. Natural rubber has excellent elasticity and low-temperature performance, a soft feel, and increases the product's tear resistance. NBR is known for its excellent oil and solvent resistance, delaying the expansion of cracks. As a result, composite rubber has good abrasion resistance, oil resistance, high mechanical strength, good elasticity, and delays the expansion of cracks.

[0027] The composite rubber utilizes a combination of non-polar natural rubber, non-polar styrene-butadiene rubber (SBR), and polar nitrile rubber (NBR). Furthermore, the NBR enhances the oil resistance of the composite rubber. Through the use of tackifiers, the non-polar and polar rubbers achieve excellent compatibility and mixing. A key innovation of this invention is the mass ratio of the total mass of non-polar natural rubber and non-polar SBR to the mass of polar NBR in the rubber compound is 1:(0.16~0.4).

[0028] The composite rubber prepared by this invention has a tensile strength of 40~50kN / m, an elongation at break of 400%~700%, a tear thickness of less than 12mm, and a slightly bitter or non-bitter taste.

[0029] The composite rubber prepared by this invention is used in veterinary nipple products for ranches. Detailed Implementation

[0030] To make the technical problems, technical solutions, and beneficial effects of the present invention clearer and more understandable, the embodiments of the present invention will be further described in detail.

[0031] In this embodiment, the antioxidant CPL (chemical name: p-cresol dicyclopentadiene butylated product) mentioned is a phenolic antioxidant, antioxidant 4010NA is also known as N-isopropyl-N'-phenyl p-phenylenediamine, and antioxidant CTU is composed of a thiourea derivative, mainly composed of monomers such as diphenylthiourea, styrene, and 2-methylstyrene emulsion.

[0032] The vulcanization accelerator CZ-80 is 80% N-cyclohexyl-2-benzothiazole sulfenamide, the vulcanization accelerator DM-80 is 80% dibenzothiazole disulfide, and the vulcanization accelerator TT-75 is 75% tetramethylthiuram disulfide.

[0033] A high elongation oil-resistant composite rubber, by weight, comprises the following raw materials: 100 parts rubber compound, 30-40 parts filler and reinforcing agent, 10-15 parts softening plasticizer, 2-5 parts zinc oxide, 1-3 parts stearic acid, 4-5.5 parts antioxidant, 1-2 parts tackifier LS506, 2-3 parts vulcanizing agent, 1.2-2.5 parts vulcanization accelerator, and 2-6 parts other additives.

[0034] The rubber compound includes natural rubber (NR), nitrile rubber (NBR) and styrene-butadiene rubber (SBR), and the ratio of natural rubber: styrene-butadiene rubber: nitrile rubber by mass is 1:(1~1.5):(0.4~0.8).

[0035] In the rubber compound, the mass ratio of the total mass of non-polar natural rubber and non-polar styrene-butadiene rubber to the mass of polar nitrile rubber is 1:(0.16~0.4).

[0036] The natural rubber is one or both of standard rubber or smoked sheet rubber.

[0037] The reinforcing filler is composed of one or more of carbon black N550, calcined kaolin, and silica.

[0038] The softening plasticizer includes naphthenic oil and polar oil. The naphthenic oil is one or both of KN4006 or KN4010. The polar oil is composed of one or more of dioctyl adipate (DOA), diisooctyl sebacate (DOS), trioctyl trimellitate (TOTM), and dibutyl diglyceride adipate. The naphthenic oil and polar oil are composed in a mass ratio of 1:0.5 to 1.

[0039] The antioxidant is composed of one or more of antioxidants CPL, antioxidant 4010NA, antioxidant CTU, and microcrystalline wax.

[0040] The vulcanization accelerator is one or more of vulcanization accelerators CZ-80, DM-80, or TT-75.

[0041] The vulcanizing agent is vulcanizing agent S-80.

[0042] Other additives include one or both of the coupling agent SI69 and the surfactant PEG4000.

[0043] Microcrystalline wax, using microcrystalline wax with a melting point of 80℃.

[0044] The preparation of a high elongation oil-resistant composite rubber includes the following steps:

[0045] S1: Pre-mixing of rubber compound: Take natural rubber, nitrile rubber and styrene-butadiene rubber according to the ratio and mix them in an internal mixer for 5~20 minutes to obtain rubber compound. The rubber compound is then sheeted out through a two-roll mill. The sheeted rubber compound is left at room temperature for 4~10 hours.

[0046] S2: First stage mixing: Take 100 parts of the above rubber compound, and according to the formula, take the filler, reinforcing agent, softening plasticizer, zinc oxide, stearic acid, antioxidant, and tackifier LS506 and mix them in an internal mixer for 8~15 minutes. When the discharge temperature is set to 125~135℃, discharge the material to the open mill for sheeting. After sheeting, let the rubber compound stand for 8~12 hours under a constant temperature of 17~25℃ to obtain the first stage mixture.

[0047] S3: Two-stage mixing: According to the formula, take the above-mentioned first-stage mixture, vulcanizing agent, and vulcanization accelerator and mix them in a rubber mixing mill under the conditions of 80-100℃ and 0.3-0.4MPa for 10-30 minutes. After the mixture is uniformly mixed, discharge it to the open mill at a discharge temperature of 60-90℃ to turn it into sheets and obtain sheet-like pre-vulcanized rubber. Let the pre-vulcanized rubber cool and stand for 8-12 hours under a constant temperature of 17-25℃.

[0048] S4: Vulcanization molding: The pre-vulcanized rubber compound is placed into the injection molding machine and injected into the mold cavity. The product is vulcanized at a pressure of 12~18MPa and a temperature of 150~175℃ for 100~300s to obtain the vulcanized product.

[0049] S5: Chlorination: First, immerse the vulcanized product in a 5%~10% dilute hydrochloric acid solution for 10~15 seconds to remove the release agent, oil, or oxide layer from the surface of the vulcanized product. After the hydrochloric acid wash, wash it in a 5%~10% sodium carbonate solution for 10~15 seconds, and then rinse it with deionized water 2~4 times. After cleaning, immerse the vulcanized product in a 3%~5% sodium hypochlorite solution, adjust the pH value to 2.5~3.5 with hydrochloric acid, vibrate under ultrasonic conditions, keep the solution temperature at 30~40℃, and chlorinate for 10~30 seconds.

[0050] S6: Washing: Rinse 2-4 times with deionized water, dry, and then let stand for 12-24 hours under constant temperature and humidity conditions of 23-25℃ and 45-55% to obtain the product. Example 1

[0051] A high elongation oil-resistant composite rubber, by weight, comprises the following raw materials: 35 parts natural rubber (using standard rubber, grade SVR-3L, origin Vietnam), 15 parts nitrile rubber (grade NBR1052, origin Zhenjiang, acrylonitrile structural unit content 33%), 50 parts styrene-butadiene rubber (grade SBR1502, PetroChina Jilin Chemical), 30 parts reinforcing agent carbon black N550, 5 parts calcined kaolin (particle size 4000 mesh), 5 parts naphthenic oil (grade KN4010, origin Karamay), 5 parts polar oil dioctyl adipate (DOA), 5 parts zinc oxide, 1 part stearic acid, 1.5 parts antioxidant CPL, 1.5 parts antioxidant 4010NA, 1 part microcrystalline wax, and 1 part tackifier LS506. 2 parts, vulcanizing agent S-80 (sulfur content is 80%) 2.3 parts, vulcanization accelerator CZ-80 1.5 parts, vulcanization accelerator DM-80 1 part.

[0052] The compound rubber is prepared by the following method: Pre-mixing of rubber compound: Natural rubber, nitrile rubber and styrene-butadiene rubber in the above proportions are mixed in a mixer for 15 minutes to obtain rubber compound. The rubber compound is then sheeted through an open mill and left at room temperature for 8 hours; Primary mixing: 100 parts of the above rubber compound are taken and, according to the proportions, filler, reinforcing agent, softening plasticizer, zinc oxide, stearic acid, antioxidant, and tackifier LS506 are mixed in a mixer. The mixing time is 60 minutes. When the discharge temperature is set at 130℃ (equipment surface temperature), the material is discharged to the open mill for sheeting. After sheeting, the rubber compound is allowed to stand at a constant temperature of 25℃ for 12 hours to obtain the first-stage mixture. The second-stage mixing involves taking the above first-stage mixture, vulcanizing agent, and vulcanization accelerator according to the formula and mixing them in a rubber mixing mill at 90℃ and 0.35MPa for 30 minutes. After uniform mixing, the material is discharged to the open mill at a discharge temperature of 70℃. The rubber compound is processed into sheets to obtain pre-vulcanized rubber material. The pre-vulcanized rubber material is cooled and allowed to stand at a constant temperature of 25℃ for 12 hours. Vulcanization molding: The pre-vulcanized rubber material is placed into an injection molding machine and injected into the mold cavity. The product is vulcanized at a pressure of 15±1MPa and a temperature of 165℃ for 250 seconds to obtain the vulcanized product. Chlorination: The vulcanized product is first immersed in a 5% dilute hydrochloric acid solution for 10 seconds to remove mold release agent, oil, or oxidation from the surface of the vulcanized product. After the first layer is washed with hydrochloric acid, it is washed with a 5% sodium carbonate solution for 15 seconds, then rinsed with deionized water 2-4 times. The washed sulfurized product is then immersed in a 4% sodium hypochlorite solution, and the pH value is adjusted to 2.5-3.5 with hydrochloric acid. The solution is then vibrated under ultrasonic conditions, with the solution temperature maintained at 30-40℃ and the chlorination time at 20 seconds. After washing with deionized water 2-4 times, the product is dried and then allowed to stand for 24 hours under constant temperature and humidity conditions of 25℃ and 50% to obtain the final product.

[0053] The performance test results of the product obtained by the above formula and preparation method are as follows:

[0054] Tear strength was determined according to method B of standard GB / T529-2008, and elongation at break was tested according to type I specimen of standard GB / T528-2009.

[0055] Product tear test: Use pliers to vertically open the cut (7mm long) of the vulcanized nipple product by 20mm and observe the tear condition. If the tear does not extend to more than 12mm, it is considered acceptable.

[0056] Deformation and leakage: Place the product in a milk cart and leave it outdoors for 6 hours a day to feed calves. Observe for 6 months to see if there is any leakage. If no leakage is observed after 6 months, it can be judged as qualified. If deformation and leakage are observed within 6 months, it is judged as unqualified.

[0057] Bitterness: Ask 5 people to taste the bitterness of the product with their tongues, classifying it into four levels from light to dark: no bitterness, slight bitterness, obvious bitterness, and irritating bitterness. No bitterness and slight bitterness are acceptable. If more than 3 people identify obvious bitterness or above, it is unacceptable. If more than 3 people identify slight bitterness or below, it is acceptable and the report should describe the most intense bitterness.

[0058] Other: This refers to options that are not specifically specified but are clearly unacceptable and cannot be selected. Example 2

[0059] Same as Example 1, except that the ratio of nitrile rubber and styrene-butadiene rubber, and the ratio of naphthenic oil reinforcing agent carbon black N550 are different. The rest are the same. The specific formula is prepared as shown in Table 1. Example 3

[0060] Similar to Example 1, except that other additives are added, including coupling agent SI69 and activator PEG4000. The specific formulation is shown in Table 1. Example 4

[0061] Similar to Example 2, except that other additives are added, including coupling agent SI69 and activator PEG4000. The specific formulation is shown in Table 1.

[0062] Comparative Example 1:

[0063] Same as Example 1. The biggest difference is that EPDM rubber is used instead of nitrile rubber, and the specific formula is shown in Table 1.

[0064] Comparative Example 2:

[0065] Similar to Example 1, the biggest difference is that only naphthenic oil is added, and no polar oil is added. The specific formula is shown in Table 1.

[0066] Comparative Example 3:

[0067] Similar to Example 1, the biggest difference is that the amount of polar oil is increased. After increasing the amount of polar oil, the amount of calcined kaolin filler is increased accordingly to balance the hardness, while reducing the production cost. The specific formula is shown in Table 1.

[0068] Comparative Example 4:

[0069] Similar to Example 1, the biggest difference is that the vulcanized product is not chlorinated. The specific formula is shown in Table 1.

[0070] Comparative Example 5:

[0071] Similar to Example 1, the biggest difference is that the rubber compound uses only natural rubber and styrene-butadiene rubber, and does not use nitrile rubber. The specific formula is shown in Table 1.

[0072] Comparative Example 6:

[0073] Similar to Example 1, the biggest difference is that the amount of polar nitrile rubber used is increased, so that the amount of polar nitrile rubber and the total amount of non-polar natural rubber and styrene-butadiene rubber reach 1:1. The specific formula is shown in Table 1.

[0074] Table 1

[0075]

[0076] Note 1: (15) in the table represents the amount of EPDM rubber used.

[0077] The performance test results of Examples 1-4 and Comparative Examples 1-6 are shown in Table 2.

[0078] Table 2

[0079]

[0080] Examples 1 to 4 of this invention show that the tear strength of the product can reach 40-48 kN / m and the elongation at break can reach 470%-680%. This indicates that the present invention uses a composite rubber with natural rubber, styrene-butadiene rubber and nitrile rubber as the skeleton, and is reinforced by filling with reinforcing agents. After being processed and molded, the product's performance shows no leakage within 6 months. After chlorination treatment, its surface has a slight or no bitter taste, which well meets the requirements of the product's application field.

[0081] In this invention, in Comparative Example 1, compared to Example 1, deformation and leakage occurred after 2 months because EPDM rubber was used instead of nitrile rubber. In Comparative Example 5, compared to Example 1, only natural rubber and styrene-butadiene rubber were used in the rubber compound, and nitrile rubber was not used. In the deformation and leakage test, deformation and leakage occurred after 4 months. This shows that nitrile rubber, as one of the base rubbers of the rubber compound of this invention, has an irreplaceable role in the application fields of the product of this invention.

[0082] In this invention, Comparative Example 2, compared to Example 1, only added naphthenic oil and did not add polar oil. In the deformation and leakage test, it was found that deformation and leakage occurred after 5 months, indicating that polar oil has a good synergistic effect on polar nitrile rubber, which is beneficial to improving the performance of composite rubber.

[0083] In this invention, compared with Example 1, Comparative Example 3 showed that after increasing the amount of polar oil, the product surface developed a white bloom after 3 months of use. This indicates that when the amount of polar oil added to the formula reaches a certain level, the product will exude oil and carry away easily migratable substances, causing the product surface to bloom and affecting the product's performance. Therefore, the combined results of Comparative Example 2 and Comparative Example 3 demonstrate that the improvement of the performance of composite rubber by using naphthenic oil and polar oil in a mass ratio of 1:0.5~1 is also a significant discovery of this invention.

[0084] In this invention, Comparative Example 4 uses the same product formula and product preparation process as Example 1. The difference is that Example 1 undergoes product chlorination treatment, while Comparative Example 4 does not. The bitterness of Example 1 is slight, while the bitterness of Comparative Example 4 is obvious. This shows that the present invention, through chlorination of the vulcanized product, makes the surface of the product smooth and masks the bitterness, thereby improving the taste of the pasture veterinary nipple product during use.

[0085] In Comparative Example 6 of this invention, the amount of polar nitrile rubber used was increased so that the ratio of polar nitrile rubber to the total amount of non-polar natural rubber and styrene-butadiene rubber reached 1:1. Performance testing showed that the product had a tear thickness greater than 13mm, and deformation and leakage occurred after 4 months. Ozone cracking occurred during use, indicating that using excessive amounts of polar nitrile rubber could not improve the various properties of the product. Only when the mass ratio of the total mass of non-polar natural rubber and non-polar styrene-butadiene rubber to the mass of polar nitrile rubber was within the range of 1:(0.16~0.4) did the product have better performance, meeting the application requirements of composite rubber in veterinary nipple products for ranches.

[0086] The above embodiments merely illustrate implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A method for preparing a high elongation oil-resistant composite rubber, characterized in that, By weight, the composition includes the following raw materials: 100 parts rubber compound, 30-40 parts filler and reinforcing agent, 10-15 parts softening and plasticizing agent, 2-5 parts zinc oxide, 1-3 parts stearic acid, 4-5.5 parts antioxidant, and LS506 tackifier. The rubber compound comprises 1-2 parts of natural rubber, 2-3 parts of vulcanizing agent, 1.2-2.5 parts of vulcanization accelerator, and 0-6 parts of other additives. The rubber compound includes natural rubber, nitrile rubber, and styrene-butadiene rubber (SBR). The ratio of natural rubber to SBR to nitrile rubber is 1:(1-1.5):(0.4-0.8) by mass. The mass ratio of the total mass of non-polar natural rubber and non-polar SBR to the mass of polar nitrile rubber in the rubber compound is 1:(0.16-0.4). The acrylonitrile structural unit content of the nitrile rubber is 30wt%-35wt%. The softening plasticizer includes naphthenic oil and polar oil, and the naphthenic oil and polar oil are composed in a mass ratio of 1:0.5-1. Its preparation method includes the following steps: S1: Pre-mixing of rubber compound: Take natural rubber, nitrile rubber and styrene-butadiene rubber according to the ratio and mix them in an internal mixer for 5~20 minutes to obtain rubber compound. The rubber compound is then sheeted out through a two-roll mill. The sheeted rubber compound is left at room temperature for 4~10 hours. S2: First stage mixing: Take 100 parts of the above rubber compound, and according to the formula, take the filler, reinforcing agent, softening plasticizer, zinc oxide, stearic acid, antioxidant, and tackifier LS506 and mix them in an internal mixer for 8~15 minutes. When the discharge temperature is set to 125~135℃, discharge the material to the open mill for sheeting. After sheeting, let the rubber compound stand for 8~12 hours under a constant temperature of 17~25℃ to obtain the first stage mixture. S3: Two-stage mixing: According to the formula, take the above-mentioned first-stage mixture, vulcanizing agent, and vulcanization accelerator and mix them in a rubber mixing mill under the conditions of 80-100℃ and 0.3-0.4MPa for 10-30 minutes. After the mixture is uniformly mixed, discharge it to the open mill at a discharge temperature of 60-90℃ to turn it into sheets and obtain sheet-like pre-vulcanized rubber. Let the pre-vulcanized rubber cool and stand for 8-12 hours under a constant temperature of 17-25℃. S4: Vulcanization molding: The pre-vulcanized rubber compound is placed into the injection molding machine and injected into the mold cavity. The product is vulcanized at a pressure of 12~18MPa and a temperature of 150~175℃ for 100~300s to obtain the vulcanized product. S5: Chlorination: First, immerse the vulcanized product in a 5%~10% dilute hydrochloric acid solution for 10~15 seconds to remove the release agent, oil, or oxide layer from the surface of the vulcanized product. After the hydrochloric acid washing, wash it in a 5%~10% sodium carbonate solution for 10~15 seconds, and then rinse it with deionized water 2~4 times. After cleaning, immerse the vulcanized product in a 3%~5% sodium hypochlorite solution, adjust the pH value to 2.5~3.5 with hydrochloric acid, vibrate under ultrasonic conditions, keep the solution temperature at 30~40℃, and chlorinate for 10~30 seconds. S6: Washing: Rinse 2-4 times with deionized water, dry, and then let stand for 12-24 hours under constant temperature and humidity conditions of 23-25℃ and 45-55% to obtain the product.

2. The high elongation oil-resistant composite rubber prepared by the preparation method of the high elongation oil-resistant composite rubber according to claim 1, characterized in that: By weight, the composition includes the following raw materials: 100 parts rubber compound, 30-40 parts filler and reinforcing agent, 10-15 parts softening and plasticizing agent, 2-5 parts zinc oxide, 1-3 parts stearic acid, 4-5.5 parts antioxidant, and LS506 tackifier. The rubber compound comprises 1-2 parts of natural rubber, 2-3 parts of vulcanizing agent, 1.2-2.5 parts of vulcanization accelerator, and 0-6 parts of other additives. The rubber compound includes natural rubber, nitrile rubber, and styrene-butadiene rubber (SBR). The ratio of natural rubber to SBR to nitrile rubber by mass is 1:(1-1.5):(0.4-0.8). The mass ratio of the total mass of non-polar natural rubber and non-polar SBR to the mass of polar nitrile rubber in the rubber compound is 1:(0.16-0.4). The acrylonitrile structural unit content of the nitrile rubber is 30wt%-35wt%. The softening plasticizer includes naphthenic oil and polar oil, and the naphthenic oil and polar oil are composed in a mass ratio of 1:0.5-1.

3. The high elongation oil-resistant composite rubber according to claim 2, characterized in that: The natural rubber is one or both of standard rubber or smoked sheet rubber.

4. The high elongation oil-resistant composite rubber according to claim 2, characterized in that: The reinforcing filler is composed of one or more of carbon black N550, calcined kaolin, and silica.

5. The high elongation oil-resistant composite rubber according to claim 2, characterized in that: The naphthenic oil is one or both of KN4006 and KN4010.

6. The high elongation oil-resistant composite rubber according to claim 2, characterized in that: The polar oil is composed of one or more of dioctyl adipate, diisooctyl sebacate, and dibutyl diglyceride adipate.

7. The high elongation oil-resistant composite rubber according to claim 2, characterized in that: The antioxidant is composed of one or more of antioxidants CPL, antioxidant 4010NA, antioxidant CTU, and microcrystalline wax.

8. The high elongation oil-resistant composite rubber according to claim 2, characterized in that: The vulcanization accelerator is one or more of vulcanization accelerators CZ-80, DM-80, or TT-75.

9. The high elongation oil-resistant composite rubber according to claim 2, characterized in that: The vulcanizing agent is vulcanizing agent S-80.

10. The application of the high elongation oil-resistant composite rubber prepared by the method of preparation of high elongation oil-resistant composite rubber according to claim 1 in veterinary nipple products for ranches.

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