High-strength environment-friendly nitrile rubber and preparation method thereof

Abstract

The invention relates to high-strength environment-friendly nitrile rubber which comprises a rubber matrix, an active agent, a filler, an accelerant, an antioxidant and a modifier, the preparation method of the nitrile rubber comprises the following steps: S1, plasticating and softening the rubber matrix in an open mill; s2, adding an active agent and an antioxidant into the internal mixer, and mixing; s3, adding a filler into the internal mixer to obtain an NBR rubber compound; s4, carrying out thin-passing on the NBR rubber compound through an open mill; s5, adding an accelerant into the open mill, and rolling to obtain sheets; s6, vulcanizing the NBR rubber compound to obtain the high-strength environment-friendly nitrile rubber. Through an innovative nitrosamine-free accelerant combination and composite filler system, the mechanical property and the aging resistance of the nitrile rubber are remarkably improved while environmental protection and safety are guaranteed.

Description

Technical Field

[0001] This invention belongs to the field of nitrile rubber material preparation technology, specifically relating to a high-strength environmentally friendly nitrile rubber and its preparation method. Background Technology

[0002] Nitrile butadiene rubber (NBR) is widely used in key components such as seals and oil pipes in the automotive, aerospace, and petroleum industries due to its excellent oil resistance. However, because NBR is not self-reinforcing, its basic mechanical properties are relatively poor, requiring proper formulation design and vulcanization cross-linking to meet practical application requirements.

[0003] In rubber formulation systems, silica is an important reinforcing filler that can improve the overall performance of NBR. However, its surface contains a large number of hydroxyl groups, which makes it prone to agglomeration in non-polar rubber matrices, resulting in poor dispersibility and becoming a weak point in performance. Surface modification to improve dispersibility and interfacial bonding is an important way to promote the full bonding between silica and rubber matrix.

[0004] The vulcanization system, a key component of rubber formulations, is a crucial factor determining the performance of rubber products. Currently, commonly used vulcanization systems typically employ accelerators containing secondary amine groups in their molecular structure, such as TMTD, ZDC, and NOBS. These accelerators readily generate nitrosamine compounds during vulcanization, posing a potential health threat to operators. To mitigate this risk, existing formulations need to be optimized by employing environmentally friendly accelerators that do not produce harmful substances during vulcanization. This will enable the development of rubber materials that combine high strength with environmental friendliness.

[0005] Therefore, there is an urgent need in this field for a new and systematic solution that can not only fundamentally eliminate the formation of nitrosamines and meet the most stringent environmental standards, but also achieve excellent physical and mechanical properties and long-lasting heat aging resistance of the product through innovative design and synergistic effects among the formulation components. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings and deficiencies of existing technologies by providing a high-strength, environmentally friendly nitrile rubber and its preparation method. Through an innovative combination of nitrosamine-free accelerators and composite filler systems, the mechanical properties and aging resistance of nitrile rubber are significantly improved while ensuring environmental safety.

[0007] The technical problem solved by this invention is achieved through the following technical solution: A high-strength, environmentally friendly nitrile rubber, wherein the composition and weight parts of the nitrile rubber are as follows: 100 parts of rubber matrix; the rubber matrix is ​​NBR, and the acrylonitrile content of the NBR is 41%; The surfactant comprises 4-5 parts zinc oxide and 0.5-1 part stearic acid; The filler comprises 20-30 parts of carbon black N330 and 10-20 parts of silica; The accelerator comprises 1.5-2.0 parts of TBzTD and 0.5-1.0 parts of ZDiBC; Antioxidant, wherein the antioxidant comprises 1.0 to 1.5 parts of antioxidant 445 and 1.0 to 1.5 parts of paraffin; The modifier comprises 1.5 to 2.5 parts of silane coupling agent Si-69 and 0.5 to 1 part of lanthanum oxide.

[0008] A method for preparing high-strength, environmentally friendly nitrile rubber, comprising the following steps: S1. Plasticize the rubber matrix NBR in a two-roll mill for 3-5 minutes at a temperature of 40-60℃ to enhance its fluidity and plasticity, and then add the softened NBR to a mixer. S2. Add zinc oxide, stearic acid, antioxidant 445 and paraffin to the internal mixer and mix for 3-5 minutes to achieve uniform mixing. S3. After the internal mixer temperature reaches 80~110℃, add 1 / 3 of the carbon black and mix for 2~3 minutes. Then add the silica modified with silane coupling agent and 1 / 3 of the carbon black and mix for 3~5 minutes. Finally, add the remaining carbon black and mix for 3 minutes to obtain NBR compound. S4. Take out the NBR compound from the internal mixer, pass it through a two-roll mill, repeatedly cut the rubber and make triangular wraps for 2-3 minutes, adjust the roller spacing, and sheet the BR compound. Let it stand for 6-12 hours. S5. Preheat the open mill, add accelerators TBzTD and ZDiBC in small amounts multiple times, repeatedly cut the rubber and make triangular wraps for 3-4 minutes, adjust the roller spacing, and roll out sheets for vulcanization. S6. Select a vulcanization temperature of 150~170℃, a vulcanization pressure of 3-5MPa, and a vulcanization time of 10~15min to vulcanize the NBR compound of S5 to obtain high-strength environmentally friendly nitrile rubber.

[0009] The advantages and beneficial effects of this invention are as follows: 1. This invention combines rare earth oxide lanthanum oxide (La2O3) with silane coupling agent Si-69 to construct a novel silica surface modification system. This system is not a simple compound, but rather a unique “silica-Si-69-lanthanum oxide” ternary composite filler formed by pre-compositing the two with silica in acetone solvent.

[0010] 2. This invention does not use traditional promoters that produce carcinogenic nitrosamines (such as TMTD, NOBS, etc.), but creatively selects an environmentally friendly composite system of tetrabenzylthiuram disulfide (TBzTD) and zinc diisobutyl dithiocarbamate (ZDiBC).

[0011] 3. The mixing process of the present invention first softens the rubber compound through an open mill; then, in the internal mixing stage, carbon black and pre-modified silica composite filler are added in batches to ensure uniform dispersion of the filler; finally, in the open mill stage, environmentally friendly accelerators are added at low temperature to ensure scorch safety during processing and avoid premature vulcanization of the rubber compound.

[0012] 4. The addition of zinc oxide to the nitrile rubber component of the present invention can form a highly efficient zinc soap activation center, and the addition of stearic acid can disperse zinc oxide particles. The synergistic use of the two can soften the rubber compound for easy processing and also promote the vulcanization system.

[0013] 5. The antioxidant 445 of this invention can effectively capture and eliminate free radicals generated in rubber under thermal and oxygen stress, inhibiting the degradation of the polymer backbone at the molecular level. The physical antioxidant paraffin can form a dense, flexible protective film on the surface of the product, constituting a solid external physical barrier. Through dual physical and chemical protection, the aging problem of the material is significantly inhibited.

[0014] 6. This invention modifies silica by adding a silane coupling agent and lanthanum oxide to an acetone solution. First, the silane coupling agent is added to the acetone solvent, then lanthanum oxide particles are added and ultrasonically dispersed for 15-20 minutes. Then silica is added, and the stirring speed is controlled at 500-700 r / min. Lanthanum oxide binds to the surface of silica through physical adsorption or chemical bonding with the hydrolysis products of the silane coupling agent, forming a silica-silane coupling agent-lanthanum oxide composite filler. This enhances the reinforcing effect of silica and improves the vulcanization and anti-aging properties of rubber. At the same time, a certain amount of carbon black N330 is added to significantly improve the mechanical properties of rubber.

[0015] 7. This invention employs an environmentally friendly vulcanization accelerator system free of nitrosamine risks, composed of accelerators TBzTD and ZDiBC. TBzTD, as a delayed-acting main accelerator, enhances the extremely high scorch safety of the rubber compound. Upon reaching the vulcanization temperature, it decomposes to release active sulfur, smoothly initiating the crosslinking reaction. ZDiBC, as an ultra-fast accelerator, possesses excellent resistance to reduction and heat resistance, producing a significant synergistic effect with TBzTD. This combination not only provides smooth and rapid vulcanization characteristics, resulting in a denser and more uniform vulcanized rubber network, but also facilitates the formation of more thermally stable monosulfide and disulfide bonds. This significantly improves the tensile strength and tear resistance of the vulcanized rubber, and the stable bond structure it forms endows the product with excellent resistance to heat and oxygen aging. Detailed Implementation

[0016] The present invention will be further described in detail below through specific embodiments. The following embodiments are merely descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.

[0017] An innovative high-strength, environmentally friendly nitrile rubber is described in the following proportions by weight: 100 parts of rubber matrix; the rubber matrix is ​​NBR, and the acrylonitrile content of the NBR is 41%; The surfactant comprises 4-5 parts zinc oxide and 0.5-1 part stearic acid; The filler comprises 20-30 parts of carbon black N330 and 10-20 parts of silica; The accelerator comprises 1.5-2.0 parts of TBzTD and 0.5-1.0 parts of ZDiBC; Antioxidant, wherein the antioxidant comprises 1.0 to 1.5 parts of antioxidant 445 and 1.0 to 1.5 parts of paraffin; The modifier comprises 1.5 to 2.5 parts of silane coupling agent Si-69 and 0.5 to 1 part of lanthanum oxide.

[0018] A method for preparing high-strength, environmentally friendly nitrile rubber, the innovation of which lies in the following steps in preparing the nitrile rubber: S1. Plasticize the rubber matrix NBR in a two-roll mill for 3-5 minutes at a temperature of 40-60℃ to enhance its fluidity and plasticity, and then add the softened NBR to a mixer. S2. Add zinc oxide, stearic acid, antioxidant 445 and paraffin to the internal mixer and mix for 3-5 minutes to achieve uniform mixing. S3. After the internal mixer temperature reaches 80~110℃, add 1 / 3 of the carbon black and mix for 2~3 minutes. Then add the silica modified with silane coupling agent and 1 / 3 of the carbon black and mix for 3~5 minutes. Finally, add the remaining carbon black and mix for 3 minutes to obtain NBR compound. The modification process is as follows: Silane coupling agent and lanthanum oxide are added to acetone solution to modify silica. First, the silane coupling agent is added to the acetone solvent, then lanthanum oxide particles are added and ultrasonically dispersed for 15-20 minutes. Then silica is added, and the stirring speed is controlled at 500-700 r / min. Lanthanum oxide is attached to the silica surface by physical adsorption or chemical bonding with the hydrolysis products of silane coupling agent, forming silica-silane coupling agent-lanthanum oxide composite filler, which enhances the reinforcing effect of silica and improves the vulcanization performance and anti-aging performance of rubber. At the same time, in order to significantly improve the mechanical properties of rubber, a certain amount of carbon black N330 is added. S4. Take out the NBR compound from the internal mixer, pass it through a two-roll mill, repeatedly cut the rubber and make triangular wraps for 2-3 minutes, adjust the roller spacing, and sheet the BR compound. Let it stand for 6-12 hours. S5. Preheat the open mill, add accelerators TBzTD and ZDiBC in small amounts multiple times, repeatedly cut the rubber and make triangular wraps for 3-4 minutes, adjust the roller spacing, and roll out sheets for vulcanization. S6. Select a vulcanization temperature of 150~170℃, a vulcanization pressure of 3-5MPa, and a vulcanization time of 10~15min to vulcanize the NBR compound of S5 to obtain high-strength environmentally friendly nitrile rubber.

[0019] Examples 1-6 are identical in composition except for the modified system, carbon black, and accelerator. Examples 1-3 determine the ratio of carbon black to silica and the accelerator to select the formulation with optimal tensile strength and anti-aging properties for the rubber. Examples 4-6 determine the effect of lanthanum oxide content on rubber properties. The components of Examples 1-6 are shown in Table 1.

[0020] Table 1 Components of Examples 1-6

[0021] Vulcanization performance: The vulcanization performance of NBR samples was tested using a rotorless vulcanizer according to the GB / T16584-1996 test standard. The tensile strength was tested using Type I dumbbell specimens for products implementing 1 to 6 according to the GB / T528-2009 test standard.

[0022] Thermal aging performance: Tested according to GB / T3512-2014, the products of Examples 1-6 were placed in a forced-air drying oven at 70℃ for 24 hours, then removed and left to stand for 16 hours. Tensile data were then tested using Type I dumbbell specimens according to GB / T 528-2009. The performance of Examples 1-6 is shown in Table 2.

[0023] Table 2 Performance Tables of Examples 1-6

[0024] Compared with Examples 1-3, as the amount of carbon black and accelerator increases, the tensile strength of NBR increases, the elongation decreases, and the vulcanization time and scorch time are shortened. In summary, Example 2 has higher overall performance, significantly improved mechanical properties, and a relatively longer scorch time.

[0025] Compared with Examples 4-6, the addition of an appropriate amount of lanthanum oxide-modified silica significantly enhanced the heat aging resistance of NBR, especially Example 5, which exhibited the best overall performance.

[0026] This invention combines rare earth oxide lanthanum oxide (La2O3) with silane coupling agent Si-69 to construct a novel silica surface modification system. This system is not a simple compound, but rather a unique “silica-Si-69-lanthanum oxide” ternary composite filler formed by pre-combining the two with silica in acetone solvent.

[0027] This invention does not use traditional promoters that produce carcinogenic nitrosamines (such as TMTD, NOBS, etc.), but creatively selects an environmentally friendly composite system of tetrabenzylthiuram disulfide (TBzTD) and zinc diisobutyl dithiocarbamate (ZDiBC).

[0028] The mixing process of this invention first softens the rubber compound using an open mill; then, during the internal mixing stage, carbon black and pre-modified silica composite filler are added in batches to ensure uniform dispersion of the filler; finally, during the open milling stage, an environmentally friendly accelerator is added at low temperature to ensure scorch safety during processing and to prevent premature vulcanization of the rubber compound.

[0029] The addition of zinc oxide to the nitrile rubber component of this invention can form highly efficient zinc soap activation centers, and the addition of stearic acid can disperse zinc oxide particles. The synergistic use of the two can soften the rubber compound for easier processing and also promote the vulcanization system.

[0030] The antioxidant 445 of this invention can effectively capture and eliminate free radicals generated in rubber under thermal and oxygen stress, inhibiting the degradation of the polymer backbone at the molecular level. The physical antioxidant paraffin can form a dense, flexible protective film on the surface of the product, constituting a solid external physical barrier. Through dual physical and chemical protection, the aging problem of the material is significantly inhibited.

[0031] This invention modifies silica by adding a silane coupling agent and lanthanum oxide to an acetone solution. First, the silane coupling agent is added to the acetone solvent, then lanthanum oxide particles are added and ultrasonically dispersed for 15-20 minutes. Then, silica is added, and the stirring speed is controlled at 500-700 r / min. Lanthanum oxide binds to the surface of silica through physical adsorption or chemical bonding with the hydrolysis products of the silane coupling agent, forming a silica-silane coupling agent-lanthanum oxide composite filler. This enhances the reinforcing effect of silica and improves the vulcanization and anti-aging properties of rubber. At the same time, a certain amount of carbon black N330 is added to significantly improve the mechanical properties of rubber.

[0032] 7. This invention employs an environmentally friendly vulcanization accelerator system free of nitrosamine risks, composed of accelerators TBzTD and ZDiBC. TBzTD, as a delayed-acting main accelerator, enhances the extremely high scorch safety of the rubber compound. Upon reaching the vulcanization temperature, it decomposes to release active sulfur, smoothly initiating the crosslinking reaction. ZDiBC, as an ultra-fast accelerator, possesses excellent resistance to reduction and heat resistance, producing a significant synergistic effect with TBzTD. This combination not only provides smooth and rapid vulcanization characteristics, resulting in a denser and more uniform vulcanized rubber network, but also facilitates the formation of more thermally stable monosulfide and disulfide bonds. This significantly improves the tensile strength and tear resistance of the vulcanized rubber, and the stable bond structure it forms endows the product with excellent resistance to heat and oxygen aging.

[0033] Although embodiments of the invention have been disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, variations, and modifications are possible without departing from the spirit and scope of the invention and the appended claims. Therefore, the scope of the invention is not limited to the contents disclosed in the embodiments.

Claims

1. A high-strength, environmentally friendly nitrile rubber, characterized in that: The composition and weight parts of the nitrile rubber are as follows: 100 parts of rubber matrix; the rubber matrix is ​​NBR, and the acrylonitrile content of the NBR is 41%; The surfactant comprises 4-5 parts zinc oxide and 0.5-1 part stearic acid; The filler comprises 20-30 parts of carbon black N330 and 10-20 parts of silica; The accelerator comprises 1.5-2.0 parts of TBzTD and 0.5-1.0 parts of ZDiBC; Antioxidant, wherein the antioxidant comprises 1.0 to 1.5 parts of antioxidant 445 and 1.0 to 1.5 parts of paraffin; The modifier comprises 1.5 to 2.5 parts of silane coupling agent Si-69 and 0.5 to 1 part of lanthanum oxide.

2. A method for preparing high-strength, environmentally friendly nitrile rubber, characterized in that: The method for preparing the nitrile rubber as described in claim 1 comprises the following steps: S1. Plasticize the rubber matrix NBR in a two-roll mill for 3-5 minutes at a temperature of 40-60℃ to enhance its fluidity and plasticity, and then add the softened NBR to a mixer. S2. Add zinc oxide, stearic acid, antioxidant 445 and paraffin wax to the internal mixer and mix for 3-5 minutes to achieve uniform mixing. S3. After the internal mixer temperature reaches 80~110℃, add 1 / 3 of the carbon black and mix for 2~3 minutes. Then add the silica modified with silane coupling agent and 1 / 3 of the carbon black and mix for 3~5 minutes. Finally, add the remaining carbon black and mix for 3 minutes to obtain NBR compound. S4. Take out the NBR compound from the internal mixer, pass it through a two-roll mill, repeatedly cut the rubber and make triangular wraps for 2-3 minutes, adjust the roller spacing, and sheet the BR compound. Let it stand for 6-12 hours. S5. Preheat the open mill, add accelerators TBzTD and ZDiBC in small amounts multiple times, repeatedly cut the rubber and make triangular wraps for 3-4 minutes, adjust the roller spacing, and roll out sheets for vulcanization. S6. Select a vulcanization temperature of 150~170℃, a vulcanization pressure of 3-5MPa, and a vulcanization time of 10~15min to vulcanize the NBR compound of S5 to obtain high-strength environmentally friendly nitrile rubber.

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