A modified rubber antioxidant, a preparation method and application thereof

Abstract

This invention discloses a modified rubber antioxidant, its preparation method, and its application. The modified rubber antioxidant of this invention is obtained by reacting a phenolic compound with a p-aminodiphenylamine antioxidant in the presence of a solvent and a rhodium catalyst, through stirring and heating. The preparation conditions of the modified rubber antioxidant of this invention are mild, the preparation process is simple, and the prepared rubber antioxidant exhibits good migration resistance and higher anti-aging efficiency.

Description

Technical Field

[0001] This invention relates to the field of rubber antioxidant technology, specifically to a modified rubber antioxidant, its preparation method, and its application. Background Technology

[0002] Rubber products are widely used in daily life, but they are prone to aging during storage and use. Therefore, it is necessary to add antioxidants to slow down the aging process and extend the service life of rubber products.

[0003] Traditional p-aminodiphenylamine antioxidant 6PPD has become the most widely produced general-purpose antioxidant due to its excellent overall protective properties. However, its small molecular weight leads to problems such as poor extraction resistance, easy migration, and color contamination.

[0004] The migration of antioxidants not only reduces their anti-aging efficiency and affects the performance of rubber materials, but also harms the environment. According to relevant literature, 6PPD antioxidants that enter the environment with tire wear particles can be converted into the highly toxic substance 6PPD-quinone under the action of ozone, leading to the death of aquatic organisms and terrestrial microorganisms and impacting the ecological environment.

[0005] Patent CN 115260585 discloses a GMA-modified p-aminodiphenylamine rubber antioxidant and its preparation method. The rubber antioxidant is prepared by reacting p-aminodiphenylamine with the epoxy groups of GMA. The specific preparation method includes heating and stirring p-aminodiphenylamine and GMA to react, obtaining a fluid product, and then granulating it to obtain the final antioxidant product. The rubber antioxidant prepared by this method has better stability and lower migration rate compared to traditional antioxidants. However, this method has a long reaction time and requires high temperature. Furthermore, at room temperature, the epoxy ring-opening product of GMA and p-aminodiphenylamine is a viscous liquid, requiring subsequent granulation for easy processing, which undoubtedly increases the complexity of the process and production costs. Currently, most p-aminodiphenylamine antioxidants are modified with GMA, but their preparation methods are mostly cumbersome, and their performance cannot meet practical needs.

[0006] Patent CN115108969A discloses a highly efficient, migration-resistant antioxidant and its preparation method and application. The preparation method includes the following steps: chemically reacting a nitroxide free radical compound with a phenolic or aniline antioxidant to obtain a novel antioxidant that simultaneously possesses nitroxide free radicals and phenolic hydroxyl groups or nitroxide free radicals and amine groups in its structure. The preparation process of this method is relatively complex. Summary of the Invention

[0007] To address the aforementioned technical problems, the present invention aims to improve the migration resistance and anti-aging efficiency of p-aminodiphenylamine antioxidants. A novel modified rubber antioxidant is prepared by grafting phenolic structures onto p-aminodiphenylamine compounds, thereby improving the migration resistance and resistance to thermo-oxidative aging.

[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0009] A modified rubber antioxidant having the general structural formula shown in formula (I)

[0010]

[0011] Where R1 is a hydrogen atom or a C1-C15 long-chain alkane, long-chain olefin, or long-chain alkyne; R2 is a hydrogen atom or a C3-C12 long-chain alkane, long-chain olefin, or long-chain alkyne; and R3 is an amino or hydroxyl group.

[0012] Furthermore, the modified rubber antioxidant of the present invention is obtained by reacting a phenolic compound with a p-aminodiphenylamine antioxidant, wherein the p-aminodiphenylamine antioxidant has the general structural formula shown in formula (II).

[0013]

[0014] The phenolic compound is selected from any one of hydroquinone, resorcinol, catechol, p-aminophenol, m-aminophenol, and o-aminophenol.

[0015] Furthermore, the molar ratio of the p-aminodiphenylamine antioxidant to the phenolic compound described in this invention is 1:0.8 to 1.5, preferably 1:1 to 1.2.

[0016] Furthermore, the present invention also provides a method for preparing the above-mentioned modified rubber antioxidant, comprising: firstly, placing a p-aminodiphenylamine antioxidant and a catalyst in a solvent and heating and stirring to obtain a mixture, and then reacting the mixture with a phenolic compound to obtain the modified rubber antioxidant;

[0017] The solvent is a polar solvent, preferably methanol or ethanol, and more preferably ethanol;

[0018] The catalyst is a rhodium(III) catalyst, and the amount added is 0.1% to 0.8% of the total mass of the p-aminodiphenylamine antioxidant and phenolic compound reactants.

[0019] The specific preparation method includes the following steps:

[0020] (1) Add p-aminodiphenylamine antioxidant and catalyst to solvent and dissolve them under heating and stirring conditions to obtain a mixture;

[0021] (2) Add the phenolic compounds to the mixture obtained in step (1) in proportion and react them;

[0022] (3) The mixture obtained after the reaction in step (2) is post-treated and vacuum dried to obtain the modified rubber antioxidant of the present invention.

[0023] The heating and stirring temperature in step (1) is the same as the reaction temperature in step (2). The reaction temperature in step (2) is 120℃~180℃ and the reaction time is 2h~10h.

[0024] Further, the post-processing method in step (3) of the present invention is as follows: the mixture obtained after the reaction in step (2) is poured into cyclohexane and stirred to obtain a large amount of precipitate, then filtered and washed with cyclohexane.

[0025] Furthermore, the vacuum drying temperature in step (3) of the present invention is 50℃~95℃.

[0026] Furthermore, the modified rubber antioxidant of the present invention is applied to natural rubber and / or synthetic rubber, and the amount of antioxidant added is 1% to 3% of the raw rubber mass.

[0027] Compared with the prior art, the present invention has the following beneficial results:

[0028] (1) The preparation process of the novel modified rubber antioxidant provided by the present invention is simple and the reaction conditions are mild.

[0029] (2) The present invention uses phenolic compounds and p-aminodiphenylamine antioxidants as reactants, and obtains the novel modified rubber antioxidant with grafted phenolic structure as described in the present invention through a special catalyst reaction. The modified rubber antioxidant has better migration resistance and higher anti-aging efficiency. Detailed Implementation

[0030] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0031] The raw materials used in the examples and comparative examples are all commercially available or can be prepared in-house using methods disclosed in the prior art.

[0032] Example 1

[0033] A method for preparing a modified rubber antioxidant, comprising:

[0034] Antioxidant 6PPD was placed in a reactor, anhydrous ethanol was added, and the antioxidant 6PPD was fully dissolved under heating and stirring. 0.3% by weight of rhodium(III) catalyst was added as a catalyst, and hydroquinone was added to react. The molar ratio of antioxidant 6PPD to hydroquinone was controlled at 1:1.2, the reaction temperature was 150℃, and after reacting for 4 hours, the temperature was lowered to room temperature. The catalyst was filtered out, and the mixture after reaction was poured into cyclohexane. A large amount of precipitate was obtained by stirring, then filtered and washed with cyclohexane. Finally, the product antioxidant 1 was obtained by vacuum drying at 75℃.

[0035] Take 100 parts of styrene-butadiene rubber, 5 parts of zinc oxide, 2 parts of stearic acid, 45 parts of carbon black N330, 2 parts of accelerator, 2 parts of sulfur and 2 parts of antioxidant 1, and mix them evenly on a two-roll mill to obtain the compound.

[0036] The obtained compound rubber was vulcanized and cut into pieces to obtain dumbbell-shaped vulcanized rubber samples, which were then subjected to heat and oxygen aging resistance tests and migration resistance tests.

[0037] Example 2

[0038] A method for preparing a modified rubber antioxidant, comprising:

[0039] Antioxidant IPPD was placed in a reactor, anhydrous methanol was added, and the antioxidant IPPD was fully dissolved under heating and stirring. 0.5% by weight of rhodium(III) catalyst was added as a catalyst, and catechol was added to carry out the reaction. The molar ratio of antioxidant IPPD to catechol was controlled at 1:1.1, the reaction temperature was 140℃, and after 6 hours of reaction, the temperature was lowered to room temperature. The catalyst was filtered out, and the mixture after reaction was poured into cyclohexane. A large amount of precipitate was obtained by stirring, then filtered and washed with cyclohexane. Finally, the product antioxidant 2 was obtained by vacuum drying at 60℃.

[0040] Take 100 parts of styrene-butadiene rubber, 5 parts of zinc oxide, 2 parts of stearic acid, 45 parts of carbon black N330, 2 parts of accelerator, 2 parts of sulfur and 2 parts of antioxidant 2, and mix them evenly on a two-roll mill to obtain the compound.

[0041] The obtained compound rubber was vulcanized and cut into pieces to obtain dumbbell-shaped vulcanized rubber samples, which were then subjected to heat and oxygen aging resistance tests and migration resistance tests.

[0042] Example 3

[0043] A method for preparing a modified rubber antioxidant, comprising:

[0044] Antioxidant 7PPD was placed in a reactor, anhydrous methanol was added, and the antioxidant 7PPD was fully dissolved under heating and stirring. 0.6% by weight of rhodium(III) catalyst was added as a catalyst, and resorcinol was added to carry out the reaction. The molar ratio of antioxidant 7PPD to resorcinol was controlled at 1:1.0, the reaction temperature was 130℃, and after 8 hours of reaction, the temperature was lowered to room temperature. The catalyst was filtered out, and the mixture after the reaction was poured into cyclohexane. A large amount of precipitate was obtained by stirring, and then filtered and washed with cyclohexane. Finally, the product antioxidant 3 was obtained by vacuum drying at 50℃.

[0045] Take 100 parts of styrene-butadiene rubber, 5 parts of zinc oxide, 2 parts of stearic acid, 45 parts of carbon black N330, 2 parts of accelerator, 2 parts of sulfur and 2 parts of antioxidant 3, and mix them evenly on a two-roll mill to obtain the compound.

[0046] The obtained compound rubber was vulcanized and cut into pieces to obtain dumbbell-shaped vulcanized rubber samples, which were then subjected to heat and oxygen aging resistance tests and migration resistance tests.

[0047] Example 4

[0048] A method for preparing a modified rubber antioxidant, comprising:

[0049] Antioxidant 8PPD was placed in a reactor, anhydrous methanol was added, and the antioxidant 8PPD was fully dissolved under heating and stirring. 0.8% by weight of rhodium(III) catalyst was added as a catalyst, and p-aminophenol was added to react. The molar ratio of antioxidant 8PPD to p-aminophenol was controlled at 1:0.8, the reaction temperature was 120℃, and after reacting for 10 hours, the temperature was lowered to room temperature. The catalyst was filtered out, and the mixture after reaction was poured into cyclohexane. A large amount of precipitate was obtained by stirring, then filtered and washed with cyclohexane. Finally, the product antioxidant 4 was obtained by vacuum drying at 95℃.

[0050] Take 100 parts of styrene-butadiene rubber, 5 parts of zinc oxide, 2 parts of stearic acid, 45 parts of carbon black N330, 2 parts of accelerator, 2 parts of sulfur and 2 parts of antioxidant 4, and mix them evenly on a two-roll mill to obtain the compound.

[0051] The obtained compound rubber was vulcanized and cut into pieces to obtain dumbbell-shaped vulcanized rubber samples, which were then subjected to heat and oxygen aging resistance tests and migration resistance tests.

[0052] Example 5

[0053] A method for preparing a modified rubber antioxidant, comprising:

[0054] Antioxidant 6PPD was placed in a reactor, anhydrous methanol was added, and the antioxidant 6PPD was fully dissolved under heating and stirring. 0.1% by weight of rhodium(III) catalyst was added as a catalyst, and m-aminophenol was added to carry out the reaction. The molar ratio of antioxidant 6PPD to m-aminophenol was controlled at 1:0.9, the reaction temperature was 180℃, and after 2 hours of reaction, the temperature was lowered to room temperature. The catalyst was filtered out, and the mixture after the reaction was poured into cyclohexane. A large amount of precipitate was obtained by stirring, then filtered and washed with cyclohexane. Finally, the product antioxidant 5 was obtained by vacuum drying at 80℃.

[0055] Take 100 parts of styrene-butadiene rubber, 5 parts of zinc oxide, 2 parts of stearic acid, 45 parts of carbon black N330, 2 parts of accelerator, 2 parts of sulfur and 2 parts of antioxidant 5, and mix them evenly on a two-roll mill to obtain the compound.

[0056] The obtained compound rubber was vulcanized and cut into pieces to obtain dumbbell-shaped vulcanized rubber samples, which were then subjected to heat and oxygen aging resistance tests and migration resistance tests.

[0057] Comparative Example 1

[0058] Take 100 parts of styrene-butadiene rubber, 5 parts of zinc oxide, 2 parts of stearic acid, 45 parts of carbon black N330, 2 parts of accelerator, 2 parts of sulfur and 2 parts of antioxidant 6PPD, and mix them evenly on a two-roll mill to obtain the compound.

[0059] The obtained compound rubber was vulcanized and cut into pieces to obtain dumbbell-shaped vulcanized rubber samples, which were then subjected to heat and oxygen aging resistance tests and migration resistance tests.

[0060] Comparative Example 2

[0061] Take 100 parts of styrene-butadiene rubber, 5 parts of zinc oxide, 2 parts of stearic acid, 45 parts of carbon black N330, 2 parts of accelerator, 2 parts of sulfur and 2 parts of antioxidant 4010NA, and mix them evenly on a two-roll mill to obtain the compound.

[0062] The obtained compound rubber was vulcanized and cut into pieces to obtain dumbbell-shaped vulcanized rubber samples, which were then subjected to heat and oxygen aging resistance tests and migration resistance tests.

[0063] Performance Testing (I) Heat and Oxygen Aging Resistance Test.

[0064] The vulcanized rubber samples from each embodiment and comparative example were suspended in an aging oven at 100°C for 5 days of thermo-oxidative aging, and the mechanical properties of the vulcanized rubber before and after aging were tested. The tensile strength retention rate after aging was used to characterize its anti-aging efficiency. Tensile strength retention rate = (parameter after aging / parameter before aging) × 100%. The test results are shown in Table 1.

[0065] Table 1. Heat and oxygen aging resistance tests of the examples and comparative examples.

[0066]

[0067] As shown in Table 1, the tensile strength of the vulcanized rubber in the examples after 5 days of thermo-oxidative aging at 100°C is higher than that of the other two comparative examples, indicating that the novel rubber antioxidant prepared in this invention has better resistance to thermo-oxidative aging.

[0068] (ii) Migration resistance test.

[0069] Equal amounts of vulcanized rubber from each example and comparative example were placed in the same volume of acetonitrile solvent. After immersion at room temperature for 3 days, the UV absorbance of the acetonitrile solvent was measured, and the concentration of antioxidant was calculated to characterize the migration resistance of the antioxidant. The test results are shown in Table 2.

[0070] Table 2 shows the migration resistance tests of the examples and comparative examples.

[0071]

[0072] As shown in Table 2, after extraction with acetonitrile solvent, the concentration of antioxidant in the solution of the example samples was lower than that of the comparative sample. This indicates that the novel rubber antioxidant prepared in this invention has better migration resistance, and less antioxidant migrates into the acetonitrile solution.

[0073] In summary, the novel rubber antioxidant prepared in this invention has better resistance to heat and oxygen aging and migration resistance compared with commercial antioxidants 6PPD and 4010NA.

[0074] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is impossible to exhaustively list all embodiments here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A modified rubber antioxidant, characterized in that, It has the general structural formula shown in equation (Ⅰ). Where R1 is a hydrogen atom or a C1-C15 long-chain alkane, long-chain olefin, or long-chain alkyne; R2 is a hydrogen atom or a C3-C12 long-chain alkane, long-chain olefin, or long-chain alkyne; and R3 is an amino or hydroxyl group.

2. The modified rubber antioxidant according to claim 1, characterized in that, This modified rubber antioxidant is obtained by reacting a phenolic compound with a p-aminodiphenylamine antioxidant, wherein the p-aminodiphenylamine antioxidant has the general structural formula shown in formula (II). The phenolic compound is selected from any one of hydroquinone, resorcinol, catechol, p-aminophenol, m-aminophenol, and o-aminophenol.

3. The modified rubber antioxidant according to claim 2, characterized in that, The molar ratio of the p-aminodiphenylamine antioxidant to the phenolic compound is 1:0.8 to 1.

5.

4. The modified rubber antioxidant according to claim 2, characterized in that, The molar ratio of the p-aminodiphenylamine antioxidant to the phenolic compound is 1:1 to 1.

2.

5. A method for preparing the modified rubber antioxidant according to any one of claims 1 to 4, characterized in that, include: First, a mixture of p-aminodiphenylamine antioxidant and catalyst is heated and stirred in a solvent to obtain a solution. Then, the solution is reacted with a phenolic compound to obtain the modified rubber antioxidant. The solvent is a polar solvent; The catalyst is a rhodium catalyst, and the amount added is 0.1% to 0.8% of the total mass of the p-aminodiphenylamine antioxidant and phenolic compound reactants.

6. The preparation method according to claim 5, characterized in that, The solvent is methanol or ethanol.

7. The preparation method according to claim 5, characterized in that, The specific preparation method of the modified rubber antioxidant includes the following steps: (1) Add p-aminodiphenylamine antioxidant and catalyst to solvent and dissolve them under heating and stirring conditions to obtain a mixture; (2) Add the phenolic compounds to the mixture obtained in step (1) in proportion and react them; (3) The mixture obtained after the reaction in step (2) is post-treated and vacuum dried to obtain the modified rubber antioxidant of the present invention; The heating and stirring temperature in step (1) is the same as the reaction temperature in step (2). The reaction temperature in step (2) is 120℃~180℃ and the reaction time is 2h~10h.

8. The preparation method according to claim 7, characterized in that, The post-processing method described in step (3) is as follows: the mixture obtained after the reaction in step (2) is poured into cyclohexane and stirred to obtain a large amount of precipitate, then filtered and washed with cyclohexane.

9. The preparation method according to claim 5, characterized in that, The vacuum drying temperature in step (3) is 50℃~95℃.

10. A method for applying the modified rubber antioxidant according to any one of claims 1 to 4, characterized in that, The modified rubber antioxidant is applied to natural rubber and / or synthetic rubber, and the amount of antioxidant added is 1% to 3% of the raw rubber mass.

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