P-phenylenediamine antiozonant, synthetic method thereof, antiozonant composition and rubber

Abstract

The invention discloses a p-phenylenediamine antiozonant and a synthesis method thereof, an antiozonant composition and rubber, and the synthesis method of the p-phenylenediamine antiozonant comprises the following steps: adding p-dihalobenzene, p-phenylenediamine, a ligand, a catalyst and an inorganic base into a polar organic solvent for dissolving, carrying out heating reaction in an inert atmosphere, and filtering to obtain the p-phenylenediamine antiozonant. And after the reaction is finished, settling in ethanol, collecting the precipitate, washing and drying to obtain the p-phenylenediamine antiozonant. The p-phenylenediamine antiozonant disclosed by the invention is large in molecular weight, high in steric hindrance and migration-resistant, has a positive effect on long-acting protection of rubber, and is beneficial to improving the ozone resistance of the rubber and improving the durability. The ozone resistance of the rubber added with the p-phenylenediamine antiozonant is obviously improved.

Description

Technical Field

[0001] The invention belongs to the field of rubber materials, and in particular relates to an antiozonant, a synthesis method thereof, and rubber. Background Art

[0002] After prolonged use, rubber elastic components develop superficial cracks, which gradually expand under external stress. This is because diene rubbers such as NR, BR, and SBR, which contain double bonds in their backbone, are susceptible to ozone attack. Ozone attacks the rubber surface perpendicular to the tensile stress, reacting with the double bonds to form a silvery-white hard film. Under dynamic stress, this silvery-white hard film ruptures, allowing ozone to come into contact with the new rubber surface, causing damage along the depth direction and subsequently causing crack growth. The chemical mechanism is that ozone first undergoes an addition reaction with the active double bonds in the rubber to form molecular ozonides, which then rapidly decompose into carbonyls and zwitterions, which recombine to form isozonides. Zwitterions can also polymerize to form diperoxides, peroxides, and methoxyhydroperoxides.

[0003] Generally, protective wax is added to improve the static ozone resistance of rubber. Protective wax is a chemically stable saturated alkane C n H 2n+2 , added to rubber formulas to provide ozone protection. Protective wax is added during rubber compound formulation. After mixing and vulcanization at high temperatures, the protective wax dissolves in the rubber, crystallizes after cooling, and reaches a certain saturation inside the rubber. When affected by external temperature, stress, and strain, the protective wax is also affected by the external temperature and migrates to the surface of the rubber product. The migration process is from low temperature to high temperature, from low carbon to high carbon, and forms a wax film on the surface of the rubber product with a smooth surface, uniform thickness, good airtightness, tight structure, strong toughness, elasticity, strong adhesion, and not easy to fall off. This effectively curbs the erosion and aging of the rubber product surface by light, oxygen, and ozone, and prevents the surface of the rubber product from cracking.

[0004] However, the operating conditions of rubber elastic components are extremely complex. Most of them work under loads of a certain frequency. It is difficult to resist the attack of ozone by relying solely on physical protective wax. Therefore, it is necessary to add paraphenylenediamine chemical anti-ozonants, which improve the dynamic ozone resistance of rubber by directly reacting with ozone and repairing rubber molecular chains broken by ozone.

[0005] Combining protective wax with p-phenylenediamine chemical antiozonants can improve rubber's ozone resistance. However, currently, commercially available protective waxes are prone to spraying, whitening, and rainbowing on the rubber surface, resulting in a rough and matte surface. This severely impacts the appearance of rubber products, making them less resistant to aging, affecting user acceptance, and ultimately sales. Commercially available p-phenylenediamine antiozonants, primarily 6PPD and 7PPD, have low molecular steric hindrance and are not resistant to migration, making them ineffective in providing long-term protection for rubber. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the above background technology and provide a p-phenylenediamine antiozonant with little impact on the appearance of rubber products and long ozone resistance time, a synthesis method thereof, an antiozonant composition and rubber.

[0007] In order to solve the above technical problems, the technical solution proposed by the present invention is: A p-phenylenediamine antiozonant, the molecular structure of which is shown below: ; The value of n is 4-20.

[0008] As a general technical concept, the present invention also provides a method for synthesizing the above-mentioned p-phenylenediamine antiozonant, comprising the following steps: dissolving p-dihalobenzene, p-phenylenediamine, a ligand, a catalyst, and an inorganic base in a polar organic solvent, purging with nitrogen to expel oxygen (generally controlled at 30-60 minutes), heating to react under an inert atmosphere, and after the reaction is completed, settling in a large amount of ethanol, collecting the precipitate, washing, and drying to obtain the p-phenylenediamine antiozonant.

[0009] In the above synthesis method, preferably, the ligand includes one or more of 1,10-phenanthroline, triphenylphosphine, L-proline, and N-methylimidazole; the catalyst includes one or both of cuprous iodide and cuprous bromide; and the inorganic base includes one or more of potassium carbonate, potassium phosphate, and cesium carbonate. The function of the ligand is to enhance the reactivity of p-dihalobenzene and p-phenylenediamine. The preferred ligands of the present invention are more compatible with the reaction system of the present invention.

[0010] In the above synthesis method, the molar ratio of p-dihalobenzene, p-phenylenediamine, ligand, catalyst, and inorganic base is preferably 1:(1-1.2):(0.2-0.5):(0.1-0.3):(2-5). This molar ratio is advantageous for controllable and adjustable synthesis reactions, facilitates obtaining the target product, reduces raw material waste, and reduces the number of side reaction products.

[0011] In the above synthesis method, preferably, the reaction temperature is controlled to be 80-150°C and the reaction time is 12-48 hours during the temperature-elevated reaction. The above reaction temperature and reaction time are advantageous for obtaining a synthetic product with an appropriate molecular weight and utilizing the anti-ozone property.

[0012] In the above synthesis method, preferably, the polar organic solvent includes one or more of N,N-dimethylformamide, N-methylpyrrolidone and dimethyl sulfoxide.

[0013] In the above synthesis method, the synthesis is shown in the following formula: .

[0014] Wherein, X is one of fluorine, iodine, bromine and chlorine.

[0015] The synthesis method of the p-phenylenediamine antiozonant of the present invention utilizes the polymerization reaction of p-dihalobenzene and p-phenylenediamine, and the special molecular chain structure of the product is conducive to better exerting the antiozon performance.

[0016] As a general technical concept, the present invention also provides a rubber comprising a rubber matrix and the above-mentioned p-phenylenediamine antiozonant.

[0017] As a general technical concept, the present invention also provides an antiozonant composition, comprising a protective wax and the aforementioned p-phenylenediamine antiozonant, wherein the mass ratio of the protective wax to the p-phenylenediamine antiozonant is (1-3):(2-5).

[0018] The two antiozonants of the present invention have a synergistic effect. The p-phenylenediamine antiozonant and the protective wax work together to improve the antiozon performance and the appearance quality of the rubber product.

[0019] In the above-mentioned antiozonant composition, preferably, the carbon number distribution of the protective wax presents a bimodal morphology, with the highest carbon number located at C35-C38, a normal structure content of 70-80%, an isomerization content of 20-30%, and a morphology of white spherical particles with a particle size of 0.5-1.2 mm.

[0020] As a general technical concept, the present invention also provides a rubber comprising a rubber matrix and the above-mentioned antiozonant composition.

[0021] Taking natural rubber as the matrix as an example, more specifically, it includes the following components in parts by weight: 100 parts of natural rubber; 3-10 parts of zinc oxide; 1-2 parts of stearic acid; 2-5 parts of antioxidant; 10-30 parts of carbon black; 1-3 parts of p-phenylenediamine antiozonant; 2-5 parts of protective wax; 0.5-2.8 parts of sulfur; and 2-6 parts of universal accelerator.

[0022] The preparation method of the above rubber comprises the following steps: (1) Add natural rubber to a general rubber mixing equipment, add chemical peptizer and plasticize at a temperature of 90-110℃ for 3-5 minutes.

[0023] (2) Add zinc oxide, stearic acid, antioxidant, p-phenylenediamine antiozonant, protective wax, and carbon black, and mix at 90-110°C for 3-5 minutes.

[0024] (3) Cool down to below 110℃, add universal accelerator and sulfur, mix for 3-5 minutes, then pass through the open mill 3-5 times or make triangle bags 3-5 times to obtain the rubber mixture.

[0025] (4) After the rubber mix was left standing for 16 h, vulcanized rubber was prepared according to the vulcanization conditions of 150 °C, 10-30 min, and 20 MPa.

[0026] To improve the appearance quality and ozone resistance of rubber elastic components, the present invention proposes a long-lasting, high-performance antiozonant. Compared with commercially available protective waxes and paraphenylenediamine antiozonants, the paraphenylenediamine antiozonant of the present invention significantly improves ozone resistance and durability. This is because the paraphenylenediamine antiozonant of the present invention has high molecular weight, high steric hindrance, and resistance to migration, which significantly promotes the long-term protection of rubber. Combined with the specific protective wax of the present invention, which is resistant to migration and high and low temperature resistance, the synergistic effect of the two can further enhance the ozone resistance and durability of rubber, while also improving the appearance quality of rubber products.

[0027] Compared with the prior art, the advantages of the present invention are: 1. The p-phenylenediamine antiozonant of the present invention has a large molecular weight, high steric hindrance, and resistance to migration, which has a positive effect on the long-term protection of rubber, and is conducive to improving the ozone resistance and durability of rubber. By adding the p-phenylenediamine antiozonant to rubber, its ozone resistance is significantly improved.

[0028] 2. The synthesis method of the p-phenylenediamine antiozonant of the present invention is simple and easy to operate, has high universality, can share organic synthesis instruments and equipment, has high equipment versatility, and has good market application value in the rubber industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0030] Figure 1Schematic diagram of the properties of the protective wax in Example 3.

[0031] Figure 2 This is the change diagram of 1# rubber compound and 2# rubber compound under 0℃×200pphm×168h and reinforced bending conditions.

[0032] Figure 3 This is the change diagram of 1# rubber compound and 2# rubber compound under 0℃×200pphm×168h and 50% stretching.

[0033] Figure 4 The graph shows the changes of 1# rubber compound and 2# rubber compound under the conditions of 0℃×200pphm×168h, 50% stretching after freezing for 7 days.

[0034] Figure 5 This is the change diagram of 1# rubber compound and 2# rubber compound under 40℃×200pphm×336h and 50% stretching.

[0035] Figure 6 The change diagram of 1# rubber compound and 2# rubber compound under 40℃×200pphm×336h and 60% stretching.

[0036] Figure 7 This is the change chart of 1# rubber compound and 2# rubber compound after 6 months of weather aging on the roof of the rubber compound specimen.

[0037] Figure 8 This is the change diagram of 1# rubber compound and 2# rubber compound under 40℃×200pphm static ozone. DETAILED DESCRIPTION

[0038] To facilitate understanding of the present invention, the present invention will be described in more comprehensive and detailed form below in conjunction with the accompanying drawings and preferred embodiments. However, the protection scope of the present invention is not limited to the following specific embodiments.

[0039] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0040] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0041] Example 1: A p-phenylenediamine antiozonant, and a synthesis method thereof, comprising the following steps: Place p-diiodobenzene (0.1 mol) and p-phenylenediamine (0.11 mol) in a reaction vessel. Then, add cuprous iodide catalyst (0.02 mol), 1,10-phenanthroline (0.03 mol), and potassium carbonate (0.3 mol) in that order. Finally, add DMF solvent (800 mL). Nitrogen is bubbled through the reaction vessel and the temperature is raised to 100°C under a nitrogen atmosphere for 24 hours. After the reaction is complete, cool the mixture and transfer it to a large amount of ethanol for precipitation. Filter, wash, and dry the mixture to obtain the product, PHAN@1.

[0042] Example 2: A p-phenylenediamine antiozonant, and a synthesis method thereof, comprising the following steps: Place p-dichlorobenzene (0.1 mol) and p-phenylenediamine (0.11 mol) in a reaction vessel. Then, add cuprous iodide catalyst (0.03 mol), L-proline (0.04 mol), and cesium carbonate (0.5 mol) in that order. Finally, add NMP solvent (800 mL). Purge with nitrogen and heat to 150°C under a nitrogen atmosphere for 48 hours. After the reaction is complete, cool the mixture and transfer it to a large amount of ethanol for precipitation. Filter, wash, and dry to obtain the product, PHAN@2.

[0043] Example 3: An antiozonant composition comprises a protective wax and a p-phenylenediamine antiozonant of Example 1 and / or Example 2. The carbon number distribution of the protective wax is bimodal, with the highest carbon number at C37, a normal content of 77.4%, an isomer content of 22.6%, and a white spherical particle shape with a particle size of 0.8 mm. The properties are as follows: Figure 1 shown.

[0044] Application examples: Prepare the rubber compound according to the formula in Table 1. The steps are as follows: (1) Add natural rubber to a general rubber mixing equipment, add a chemical peptizer and mix for 5 minutes at a temperature of 100°C.

[0045] (2) Add zinc oxide, stearic acid, antioxidant, paraphenylenediamine antiozonant, protective wax, and carbon black, and mix at 100°C for 3 minutes.

[0046] (3) Cool down to below 110℃, add universal accelerator and sulfur, mix for 3 minutes, and then pass through the open mill 3 times to obtain the rubber compound.

[0047] (4) After the rubber mix obtained in step (3) was left to stand for 16 h, vulcanized rubber was prepared according to the vulcanization conditions of 150°C, 15 min, and 20 MPa to obtain rubber compound 2#.

[0048] The preparation method of 1# rubber compound is similar to the above method, and the formula components need to be replaced according to Table 1.

[0049] Table 1: Rubber formula (mass parts)

[0050] In order to make a more comprehensive comparison with 1# rubber compound (i.e. Figure 2-Figure 8 Ordinary protective wax in) and 2# rubber compound (ie Figure 2-Figure 8 High-performance protective wax in the ozone environment was used to optimize the ozone protection effect of physical and chemical antiozonants. High and low temperature ozone tests were designed. At the same time, in order to compare the effects of strain and parking environment, and in the low temperature ozone test, reinforced bending, post-freezing tensile, and conventional tensile tests were designed. As shown in Table 2, under an ozone environment of 0°C × 200pphm × 168h, 2 fractures occurred in the reinforced bending of 1# rubber compound, while no cracks were found in 2# rubber compound (see Table 2). Figure 2 ); 50% stretch, 2 specimens of 1# rubber material broke, 2# rubber material had no cracks (see Figure 3 ); After freezing for 7 days and stretching by 50%, one specimen of 1# rubber material broke in the middle, while 2# rubber material had no cracks (see Figure 4 In an ozone environment at 40°C × 200 pphm × 336 h, with a stretch of 50%, all three specimens of 1# rubber compound showed fine cracks, while 2# rubber compound showed no cracks (see Figure 5 ); When stretched to 60%, one specimen of 1# rubber material broke, two specimens showed large cracks, and three specimens of 2# rubber material showed small cracks, and the number of cracks was significantly less than that of 1# rubber material (see Figure 6 In summary, the high and low temperature static ozone resistance of the rubber compound using the antiozonant composition in Example 3 is significantly better than that of the ordinary rubber compound.

[0051] Table 2: Static ozone resistance of 1# and 2# rubber compounds

[0052] In order to further investigate the weather resistance of 1# and 2# rubber compounds, the conventional test piece was folded in half and placed on the roof for 6 months to observe the appearance of the folded part. Figure 7 As shown, dense and fine cracks appeared at the fold of the 1# rubber test piece, while there were no cracks at the fold of the 2# rubber test piece, which shows that the weather resistance of the rubber using the antiozonant composition in Example 3 is better than that of ordinary rubber.

[0053] As shown in Table 3, under 40℃×200pphm×336h ozone environment, Figure 8As shown, when a 1mm gasket is pressed, the surface of the 1# rubber product is obviously frosted, and small cracks appear locally after 62 hours; the surface of the 2# rubber product is glossy, without obvious frosting, and there is no crack after 168 hours. The pressure is further increased and a 2mm gasket is pressed. The surface of the 2# rubber product is still glossy, without obvious frosting, and there is no crack after 504 hours.

[0054] Table 3: Static ozone resistance of 1# and 2# rubber compounds

Claims

1. A p-phenylenediamine antiozonant, characterized in that: The molecular structure is shown below: ； The value of n is 4-20.

2. A method for synthesizing a p-phenylenediamine antiozonant according to claim 1, characterized in that: The method comprises the following steps: adding p-dihalobenzene, p-phenylenediamine, a ligand, a catalyst and an inorganic base into a polar organic solvent for dissolution, heating the mixture under an inert atmosphere for reaction, settling the mixture in ethanol after the reaction is completed, collecting the precipitate, washing the precipitate and drying the precipitate to obtain the p-phenylenediamine antiozonant.

3. The synthesis method according to claim 2, characterized in that The ligand includes one or more of 1,10-phenanthroline, triphenylphosphine, L-proline and N-methylimidazole; the catalyst includes one or both of cuprous iodide and cuprous bromide; and the inorganic base includes one or more of potassium carbonate, potassium phosphate and cesium carbonate.

4. The synthesis method according to claim 2, characterized in that The molar ratio of p-dihalobenzene, p-phenylenediamine, ligand, catalyst and inorganic base is 1: (1-1.2): (0.2-0.5): (0.1-0.3): (2-5).

5. The synthesis method according to claim 2, characterized in that During the temperature-raising reaction, the reaction temperature is controlled to be 80-150°C and the reaction time is 12-48h.

6. The synthesis method according to claim 2, characterized in that The polar organic solvent includes one or more of N,N-dimethylformamide, N-methylpyrrolidone and dimethyl sulfoxide.

7. A rubber, characterized in that: The invention comprises a rubber matrix and the p-phenylenediamine antiozonant according to claim 1 or the p-phenylenediamine antiozonant synthesized by the synthesis method according to any one of claims 2 to 6.

8. An antiozonant composition, characterized in that The invention comprises a protective wax and the p-phenylenediamine antiozonant according to claim 1 or a p-phenylenediamine antiozonant synthesized by the synthesis method according to any one of claims 2 to 6, wherein the mass ratio of the protective wax to the p-phenylenediamine antiozonant is (1-3):(2-5).

9. The antiozonant composition according to claim 8, characterized in that The carbon number distribution of the protective wax presents a bimodal form, with the highest carbon number being located at C35-C38, a normal structure content of 70-80%, an isomerization content of 20-30%, and a white spherical particle shape with a particle size of 0.5-1.2 mm.

10. A rubber, characterized in that: The invention comprises a rubber matrix and the antiozonant composition according to claim 8 or 9.

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