A modified liquid polydiene rubber and its application

Abstract

This invention discloses a modified liquid polydiene rubber and its applications, belonging to the field of rubber technology. The modified liquid polydiene rubber is prepared by an amidation reaction of maleic anhydride-grafted liquid polydiene and p-phenylenediamine monomers; the grafting mass fraction of the maleic anhydride-grafted liquid polydiene does not exceed 20%. It uses liquid polybutadiene rubber (or liquid polyisoprene rubber) as the main component, exhibiting good processing performance and compatibility with the rubber matrix, improving rubber processing performance and promoting the dispersion of antioxidants in the rubber. The modified liquid polybutadiene has a higher molecular weight and higher double bond content than traditional antioxidants, allowing it to form a three-dimensional network structure with the rubber matrix during vulcanization, significantly reducing the migration rate of antioxidants and making it difficult to be extracted by water or oil during use. This effectively suppresses blooming and extends the protective life, facilitating its application.

Description

Technical Field

[0001] This invention relates to the field of rubber technology, and more particularly to a modified liquid polydiene rubber and its applications, including rubber products. Background Technology

[0002] Rubber products are widely used in transportation, construction, aerospace, and defense industries. However, during use, they are susceptible to heat, oxygen, ozone, and mechanical fatigue, leading to the breakage or cross-linking of rubber molecular chains. This manifests as hardening, cracking, discoloration, and a decline in mechanical properties, severely affecting the service life and safety of the products. To delay the aging of rubber products, antioxidants are usually added to the formulation.

[0003] Currently, commonly used antioxidants are mainly small-molecule aromatic amine compounds of the p-phenylenediamine class, such as antioxidant 6PPD (i.e., N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine), suitable for both natural and synthetic rubber. However, traditional antioxidants suffer from problems such as easy migration, extraction, and blooming, which not only cause discoloration of the rubber surface and reduce its protective effect, but also pollute the environment. With increasing attention to environmental and health issues, the development of a new, green antioxidant resistant to migration has become an urgent need for the industry. Summary of the Invention

[0004] To address the problems of easy migration and environmental pollution associated with existing antioxidants, this invention provides a modified liquid polydiene rubber and its application. The modified liquid polydiene rubber, when used as a rubber antioxidant, can effectively inhibit the migration problem of traditional antioxidants, achieving high performance requirements such as long-lasting protection, environmental friendliness, and low toxicity. It has significant application value in the development of green and high-performance rubber products.

[0005] This invention provides a modified liquid polydiene rubber, which is prepared by an amidation reaction of maleic anhydride-grafted liquid polydiene and p-phenylenediamine monomers; the grafting mass fraction of the maleic anhydride-grafted liquid polydiene does not exceed 20%.

[0006] In some embodiments, the maleic anhydride-grafted liquid polydiene is maleic anhydride-grafted liquid polybutadiene and / or maleic anhydride-grafted liquid polyisoprene, with a maleic anhydride grafting mass fraction of 1-20%.

[0007] In some embodiments, the grafting mass fraction of the maleic anhydride-grafted liquid polydiene is 2-10%.

[0008] In some embodiments, the p-phenylenediamine monomer is one or more of N-phenyl-1,4-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, and N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine.

[0009] In some embodiments, the amidation reaction is performed at a temperature of 120-150°C.

[0010] In some embodiments, the amidation reaction is carried out in the presence of a catalyst, which is a pyridine-based substance.

[0011] In some embodiments, the amidation reaction is carried out under a protective atmosphere for 1-5 hours.

[0012] This invention provides the application of the modified liquid polydiene rubber in the preparation of rubber products.

[0013] The present invention provides a rubber product comprising raw rubber and additives, wherein the additives include the modified liquid polydiene rubber.

[0014] In some embodiments, the raw rubber is one or more of natural rubber, styrene-butadiene rubber, and cis-butadiene rubber; the additives include one or more of fillers, vulcanizing agents, activators, silane coupling agents, processing aids, and protective agents.

[0015] Liquid polybutadiene, as a low molecular weight, room-temperature flowable rubber, exhibits good compatibility with solid rubber, can plasticize rubber and improve the abrasion resistance of rubber compounds, and possesses excellent migration resistance. Developing polymeric antioxidants based on liquid polybutadiene and similar materials can leverage their superior properties to effectively inhibit the migration problems of traditional antioxidants, achieving long-lasting protection, environmental friendliness, low toxicity, and high performance.

[0016] This invention provides a multifunctional modified liquid polydiene rubber (hereinafter referred to as modified liquid rubber), prepared by grafting liquid polydiene with maleic anhydride and then reacting it with p-phenylenediamines such as N-phenyl-1,4-phenylenediamine via an amidation reaction. This modified liquid rubber can be modified liquid polybutadiene rubber or modified liquid polyisoprene rubber, and has the following significant advantages: It uses liquid polybutadiene rubber (or liquid polyisoprene rubber) as the main component, exhibiting good processability and compatibility with the rubber matrix, thus improving rubber processing performance and promoting the dispersion of antioxidants in the rubber. The modified liquid polybutadiene and other components have higher molecular weights and higher double bond content than traditional antioxidants, allowing them to form a three-dimensional network structure with the rubber matrix during vulcanization, significantly reducing the migration rate of antioxidants and making them difficult to extract by water or oil during use, effectively suppressing blooming and extending the protective life.

[0017] Furthermore, the modified liquid polybutadiene rubber exhibits excellent abrasion resistance, effectively improving the abrasion resistance of tires and other rubber products and reducing pollution caused by fine particles entering the environment during product use. This invention, by controlling the maleic anhydride grafting rate (1%~20%) and its reaction degree with N-phenyl-1,4-phenylenediamine, can meet the needs of different rubber products, overcoming the shortcomings of traditional antioxidants with their single-structure products. Compared with traditional antioxidants, this product not only provides long-lasting and stable protection in rubber but also reduces blooming and environmental pollution problems, making it particularly suitable for applications such as tires. Attached Figure Description

[0018] Figure 1 The 1H NMR spectrum of the modified liquid rubber S1 in this embodiment of the invention;

[0019] Figure 2 The infrared spectrum of the modified liquid rubber S1 in this embodiment of the invention;

[0020] Figure 3 The 1H NMR spectrum of the modified liquid rubber S2 in this embodiment of the invention;

[0021] Figure 4 The infrared spectrum of the modified liquid rubber S2 in this embodiment of the invention;

[0022] Figure 5 This is a schematic diagram illustrating the retention rate of the tensile strength of the vulcanized rubber over time in an embodiment of the present invention.

[0023] Figure 6 This is a DIN wear diagram of the vulcanized rubber according to an embodiment of the present invention. Detailed Implementation

[0024] The technical solutions in the embodiments of this application are described clearly and completely below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0025] Traditional antioxidants are mostly small-molecule aromatic amine compounds, which exist only in physically dispersed form in rubber and have no chemical bond with the matrix. They easily migrate to the surface along the concentration gradient and are extracted. Although there have been attempts to directly mix antioxidants with liquid polybutadiene in the past, these are only physically mixed systems with the following limitations: there are no chemical bonds between molecules, resulting in limited resistance to migration; the mixing and dispersion are uneven, and the system is prone to phase separation; the system has poor stability and long-term effectiveness.

[0026] This invention provides a modified liquid polydiene rubber, which is prepared by an amidation reaction of maleic anhydride-grafted liquid polydiene and p-phenylenediamine monomers; the grafting mass fraction of the maleic anhydride-grafted liquid polydiene does not exceed 20%.

[0027] The modified liquid polydiene rubber provided by this invention can be used as a rubber antioxidant, which can effectively inhibit the migration problem of traditional antioxidants, achieve high performance requirements such as long-lasting protection, environmental protection and low toxicity, and is conducive to its application in rubber products such as tires.

[0028] In this embodiment of the invention, maleic anhydride-grafted liquid polydiene, p-phenylenediamine monomers, and catalyst are placed in a reaction vessel, preferably mixed uniformly and heated under a protective atmosphere (such as a nitrogen atmosphere) to carry out an amidation reaction, thereby preparing the modified liquid polydiene rubber product, which is preferably a modified liquid polybutadiene rubber.

[0029] The main raw materials for preparing the modified liquid polydiene rubber described in this invention are maleic anhydride-grafted liquid polybutadiene and maleic anhydride-grafted polyisoprene, which have good processing properties and are commercially available. Taking maleic anhydride-grafted liquid polybutadiene (number average molecular weight 3000-30000 g / mol) as an example, maleic anhydride is used as a polar grafting monomer, chemically bonded to the main chain of liquid polybutadiene (LPB), introducing carboxylic anhydride groups; the mass fraction of maleic anhydride grafting is controlled at 1-20%, further at 2-10%, for example, 3%, 5%, 6%, 7%. Too low a grafting mass fraction can easily affect the reactivity, while too high a fraction reduces the rubber compatibility. Furthermore, the liquid polybutadiene (LPB) can be replaced with liquid polyisoprene (LIR).

[0030] Furthermore, another raw material is a p-phenylenediamine monomer, preferably one or more of N-phenyl-1,4-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, and N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, more preferably N-phenyl-1,4-phenylenediamine (PPD) or N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD). N-phenyl-1,4-phenylenediamine is also known as p-aminodiphenylamine or 4-aminodiphenylamine. For example, the mass ratio of maleic anhydride-grafted liquid polybutadiene to p-aminodiphenylamine can be 50:3.2-6.6.

[0031] This invention primarily achieves covalent bonding between antioxidants and liquid rubber at the molecular level through a chemical grafting-amidation reaction, representing a key technological breakthrough. Preferably, the amidation reaction is carried out at a temperature of 120-150°C, and more preferably 130-140°C, to ensure amidation proceeds while avoiding side reactions (such as crosslinking or thermal decomposition). The amidation reaction described in this invention is preferably conducted in the presence of a catalyst; the catalyst can be a pyridine-based substance such as 4-dimethylaminopyridine (DMAP) to promote the efficient ring-opening reaction between carboxylic anhydrides and amine groups.

[0032] In this embodiment of the invention, the above-described reaction system can be heated for 1-5 hours, more preferably 2-4 hours. Subsequently, it is cooled to room temperature (15-25°C); the resulting product is washed with anhydrous ethanol, allowed to stand and separate into layers, and the lower layer of liquid is taken off and dried to obtain the modified liquid rubber product.

[0033] In some embodiments of the present invention, the modified liquid polybutadiene rubber contains benzene ring groups and amide structures, etc., and has multiple functionalities such as anti-aging and wear resistance; after the amide reaction, the mass fraction of the groups can be 1-10%. The embodiments of the present invention achieve a three-in-one effect of processing oil, antioxidant, and structural additive through molecular design, forming a multifunctional modified liquid rubber with a chemically anchored structure, which can significantly improve the migration resistance, aging resistance, and rubber compatibility of the antioxidant, far exceeding the effect of traditional compounding systems.

[0034] Furthermore, the present invention provides the application of the modified liquid polydiene rubber in the preparation of rubber products. Specifically, the present invention provides a rubber article comprising raw rubber and additives, wherein the additives include the modified liquid polydiene rubber.

[0035] In some embodiments, the raw rubber is one or more of natural rubber, styrene-butadiene rubber, and cis-butadiene rubber, and any conventional grade is acceptable; the additives include one or more of fillers, vulcanizing aids, activators, silane coupling agents, processing aids, and protective aids.

[0036] The aforementioned multifunctional modified liquid rubber can be widely used in various rubber matrix systems, and its composition includes: raw rubber system (natural rubber, styrene-butadiene rubber and cis-butadiene rubber, etc.), filler (silica and / or carbon black), vulcanization aid (sulfur and accelerator), activator (zinc oxide and / or stearic acid), silane coupling agent, processing aid aromatic oil, and protective aid RD.

[0037] The modified liquid polydiene rubber can be added in an amount of 30-40 parts by weight relative to 100 parts by weight of raw rubber (such as a mixture of styrene-butadiene rubber and cis-butadiene rubber). This invention does not impose any special restrictions on the type or proportion of additives in the rubber products. For example, the silica filler can be 60-80 parts by weight; the silane coupling agent can be Si69, used in 5-6 parts by weight.

[0038] In a specific embodiment of the present invention, the initial temperature of the internal mixer can be set to 80°C and the rotation speed to 50 rpm. By weight, 50-70 parts of solution-polymerized styrene-butadiene rubber and 30-50 parts of cis-butadiene rubber can be added to the internal mixer and mixed for 1-3 minutes. Then, 60-80 parts of silica, 5-6 parts of silane coupling agent Si69, 1-2 parts of stearic acid, 3-4 parts of zinc oxide, 0.5-1 part of antioxidant RD, and 30-40 parts of modified liquid polybutadiene rubber are added and mixed for 5-10 minutes before discharge at a discharge temperature of 150°C. Finally, the internal mixer can be cooled to 60°C, and the discharged compound is put back into the internal mixer with the addition of 1-2 parts of sulfur, 2 parts of accelerator TBBS, and 2 parts of accelerator DPG. The compound is discharged after 3-5 minutes at a discharge temperature of 80°C. Adjust the rolling temperature of the open mill to 50℃, and pass the mixed rubber through the open mill multiple times to produce sheets. Let the sheets stand at room temperature for 8 hours, and then vulcanize them at 150-170℃ for 10-20 minutes to obtain vulcanized rubber samples.

[0039] Tests have shown that the embodiments of the present invention improve the wear resistance and aging resistance of the rubber compound, while also exhibiting good processing performance.

[0040] To better understand the technical content of this invention, specific embodiments are provided below to further illustrate the invention. The substances used in these embodiments are commercially available.

[0041] Example 1

[0042] 50 g of maleic anhydride-grafted liquid polybutadiene (3000 g / mol, the same in the following examples), 3.2 g of p-aminodiphenylamine, and 0.052 g of 4-dimethylaminopyridine were added to a 500 mL three-necked flask and mixed thoroughly under a nitrogen atmosphere. The mixture was then heated to 140 °C and reacted for 3 hours, followed by cooling to room temperature. The product was washed with 500 mL of anhydrous ethanol, allowed to stand to separate into layers, and the lower layer was collected and dried to obtain the modified liquid rubber product S1. Its 1H NMR and IR spectra are shown below. Figure 1 , Figure 2 .

[0043] Example 2

[0044] 50 g of maleic anhydride-grafted liquid polybutadiene (6% by mass), 6.6 g of p-aminodiphenylamine, and 0.063 g of 4-dimethylaminopyridine were added to a 500 mL three-necked flask and mixed thoroughly under a nitrogen atmosphere. The mixture was then heated to 140 °C and reacted for 3 hours, followed by cooling to room temperature. The product was washed with 500 mL of anhydrous ethanol, allowed to stand for separation, and the lower layer was collected and dried to obtain the modified liquid rubber product S2. Its 1H NMR and IR spectra are shown below. Figure 3 , Figure 4 .

[0045] According to the proton nuclear magnetic resonance spectrum (NMR spectrum) 1 (H NMR) The signal at 4.9-5.5 ppm corresponds to the -CH=CH- of the polybutadiene backbone and 1,2-structured side chains; the -CH- peak of the secondary amine adjacent aromatic ring appears at 6.95-7.15 ppm, indicating the successful introduction of the N-phenyl group; the signal at 2.8-3.3 ppm corresponds to the proton at the -CH- ortho position of the amide and maleic anhydride five-membered ring, and the area ratio of this to the -CH- peak of the secondary amine adjacent aromatic ring at 6.95-7.15 ppm is 3:4, proving that the reaction efficiency reaches 100%.

[0046] According to Fourier transform infrared spectroscopy (FTIR), maleic anhydride-grafted liquid polybutadiene at 1785 cm⁻¹... -1 Located at 1863cm -1 A typical absorption peak for the carbonyl group (C=O) on the anhydride ring appears at 3380 cm⁻¹; after the reaction of maleic anhydride-grafted liquid polybutadiene with p-aminodiphenylamine, an absorption peak appears at 3380 cm⁻¹. -1 The appearance of the -NH- stretching vibration peak confirms the amidation reaction with aromatic amines, while the peak originally at 1780 cm⁻¹... -1 Located at 1860cm -1 The absorption peak at the carbonyl group (C=O) of the ester disappears and changes to 1704 cm⁻¹. -1 The absorption peak of the ester carbonyl group (C=O) in the imine structure.

[0047] Application Comparison Example 1

[0048] The internal mixer was initially set to 80°C and 50 rpm. 70 parts solution-polymerized styrene-butadiene rubber (SBR) and 30 parts butadiene rubber (BR) were added to the mixer and mixed for 1 minute. Then, 70 parts silica, 5.6 parts silane coupling agent Si69, 2 parts stearic acid, 3.5 parts zinc oxide, 1 part antioxidant RD, and 35 parts environmentally friendly aromatic oil V700 were added and mixed for 7 minutes before discharge at 150°C. Finally, the mixer was cooled to 60°C, and the discharged rubber compound was returned to the mixer with the addition of 1.7 parts sulfur, 2 parts accelerator TBBS, and 2 parts accelerator DPG. The compound was discharged after 4 minutes at 80°C. The open mill roll temperature was adjusted to 50°C, and the compound was passed through the open mill 8 times to produce sheets. The sheets were left at room temperature for 8 hours, then vulcanized at 160°C for 20 minutes. The resulting vulcanized rubber was designated C1.

[0049] Application Example 1

[0050] The internal mixer was initially set to 80°C and 50 rpm. 70 parts solution-polymerized styrene-butadiene rubber and 30 parts butadiene rubber were added to the mixer and mixed for 1 minute. Then, 70 parts silica, 5.6 parts silane coupling agent Si69, 2 parts stearic acid, 3.5 parts zinc oxide, 1 part antioxidant RD, and 35 parts modified liquid polybutadiene rubber S1 were added and mixed for 7 minutes before discharge at 150°C. Finally, the mixer was cooled to 60°C, and the discharged rubber compound was returned to the mixer with the addition of 1.7 parts sulfur, 2 parts accelerator TBBS, and 2 parts accelerator DPG. The compound was discharged after 4 minutes at 80°C. The open mill roll temperature was adjusted to 50°C, and the compound was passed through the open mill 8 times to produce sheets. The sheets were left at room temperature for 8 hours, then vulcanized at 160°C for 20 minutes. The resulting vulcanized rubber was designated C2.

[0051] Application Example 2

[0052] The internal mixer was initially set to 80°C and 50 rpm. 70 parts solution-polymerized styrene-butadiene rubber and 30 parts butadiene rubber were added to the mixer and mixed for 1 minute. Then, 70 parts silica, 5.6 parts silane coupling agent Si69, 2 parts stearic acid, 3.5 parts zinc oxide, 1 part antioxidant RD, and 35 parts modified liquid polybutadiene rubber S2 were added and mixed for 7 minutes before discharge at 150°C. Finally, the mixer was cooled to 60°C, and the discharged mixture was returned to the mixer with 1.7 parts sulfur, 2 parts accelerator TBBS, and 2 parts accelerator DPG added. The mixture was discharged after 4 minutes at 80°C. The open mill roll temperature was adjusted to 50°C, and the mixture was passed through the open mill 8 times to produce sheets. The sheets were left at room temperature for 8 hours, then vulcanized at 160°C for 20 minutes. The resulting vulcanized rubber was designated C3.

[0053] Using C1 as a control, the effect of replacing traditional environmentally friendly aromatic oil V700 with modified liquid polybutadiene on the properties of rubber compounds was investigated. First, the Mooney viscosity results in Table 1 show that there was no significant difference in the Mooney viscosity of the compound after replacing the traditional aromatic oil with modified liquid rubber, indicating that liquid polybutadiene has the same effect as a processing oil and can ensure good processing performance of the rubber compound. Second, the lower the DIN abrasion value in Table 1, the better the abrasion resistance of the vulcanized rubber compound. Compared to C1, replacing the traditional aromatic oil with modified liquid rubber improved the abrasion resistance of vulcanized rubber C2 by approximately 44% and C3 by approximately 22%, indicating a significant improvement in the abrasion resistance of the rubber compound.

[0054] Third, such as Figure 5 As shown, the vulcanizates C2 and C3, using modified liquid rubber, retained more than 90% of their tensile strength after aging at 100°C for 5 days, while the reference sample C1 only retained about 85%. This indicates that modified liquid polybutadiene can not only replace traditional aromatic oils to improve processing performance, but also further enhance the wear resistance and aging resistance of the rubber compound.

[0055] Figure 6 This is a DIN wear chart; the lower the value, the better the wear resistance.

[0056] The Mooney viscosity test was conducted using the standard ASTM D1646 (ML 100 ℃ (1 + 4) min); the DIN wear was measured according to the standard GB / T 9867–2008.

[0057] Table 1. Summary of Properties of Vulcanized Rubber

[0058]

[0059] As can be seen from the above embodiments, the embodiments of the present invention can improve the processing performance of rubber and promote the dispersion of antioxidants in rubber. The modified liquid polybutadiene, etc., has a high content of double bonds in its main chain, which can form a three-dimensional network structure with the rubber matrix during vulcanization, significantly reducing the migration rate of antioxidants and making it difficult to be extracted by water or oil during use, effectively suppressing blooming and extending the protective life. Furthermore, the modified liquid polybutadiene rubber has excellent abrasion resistance, which can effectively improve the abrasion resistance of tires and other rubber products, reducing pollution problems caused by fine particles entering the environment during product use. The present invention can meet the needs of different rubber products. This product not only has a long-lasting and stable protective effect in rubber, but also reduces blooming and environmental pollution problems, making it particularly suitable for applications such as tires.

[0060] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only for the purpose of helping to understand the method and core ideas of the present invention. The above descriptions are only preferred embodiments of the present invention. It should be noted that due to the limitations of textual expression, while there are objectively infinite specific structures, those skilled in the art can make several improvements, modifications, or changes without departing from the principles of the present invention, and can also combine the above technical features in an appropriate manner. These improvements, modifications, changes, or combinations, or the direct application of the inventive concept and technical solution to other situations without modification, should all be considered within the scope of protection of the present invention.

Claims

1. A modified liquid polydiene rubber, characterized in that, It is prepared by amidation reaction of maleic anhydride-grafted liquid polydiene and p-phenylenediamine monomers; the grafting mass fraction of the maleic anhydride-grafted liquid polydiene does not exceed 20%.

2. The modified liquid polydiene rubber according to claim 1, characterized in that, The maleic anhydride-grafted liquid polydiene is maleic anhydride-grafted liquid polybutadiene and / or maleic anhydride-grafted liquid polyisoprene, with a maleic anhydride grafting mass fraction of 1-20%.

3. The modified liquid polydiene rubber according to claim 2, characterized in that, The grafting mass fraction of the maleic anhydride-grafted liquid polydiene is 2-10%.

4. The modified liquid polydiene rubber according to claim 1, characterized in that, The p-phenylenediamine monomers are one or more of N-phenyl-1,4-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, and N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine.

5. The modified liquid polydiene rubber according to any one of claims 1-4, characterized in that, The amidation reaction is performed at a temperature of 120-150°C.

6. The modified liquid polydiene rubber according to claim 5, characterized in that, The amidation reaction is carried out in the presence of a catalyst, which is a pyridine-based substance.

7. The modified liquid polydiene rubber according to claim 6, characterized in that, The amidation reaction is carried out under a protective atmosphere for 1-5 hours.

8. The use of the modified liquid polydiene rubber according to any one of claims 1-7 in the preparation of rubber products.

9. A rubber product comprising raw rubber and additives, characterized in that, The additive includes the modified liquid polydiene rubber according to any one of claims 1-7.

10. The rubber product according to claim 9, characterized in that, The raw rubber is one or more of natural rubber, styrene-butadiene rubber, and butadiene rubber; The additives include one or more of the following: fillers, vulcanization aids, activators, silane coupling agents, processing aids, and protective aids.

Images