Migration-resistant antioxidant, preparation method therefor and use thereof

Abstract

A migration-resistant antioxidant, a preparation method therefor and the use thereof. The method comprises reacting a substance of formula I and nitric acid such that H in -CH- at the para-position of amino is condensed with nitro to obtain a nitrated substance, then performing hydrogenation reduction on nitro of the nitrated substance under the action of a catalyst to obtain an intermediate product, and hydrogenating the intermediate product and a ketone under the action of a catalyst to obtain the migration-resistant antioxidant II. Starting materials are convenient to purchase and transport, and the present invention involves high product yield, low cost, simple operation and low environmental pollution. Therefore, the present invention has industrial development prospects.

Description

A class of migration-resistant antioxidants, their preparation methods and applications Technical Field

[0001] This invention relates to a class of migration-resistant antioxidants, their preparation methods and applications, belonging to the field of rubber technology. Background Technology

[0002] During processing, storage, and use, rubber is subject to a combination of internal and external factors, leading to aging phenomena such as softening, stickiness, hardening, cracking, brittleness, spotting, mold growth, loss of gloss, and color changes. Rubber antioxidants are substances that can prevent or delay rubber aging. Currently, p-phenylenediamine antioxidants dominate the rubber antioxidant market, with antioxidant 4020 (N(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) being the most widely used. It possesses excellent protective properties, but its drawbacks are also significant, including toxicity, color contamination, and poor migration resistance. The most serious problem is its tendency to migrate from the rubber system, a phenomenon commonly known as blooming, thus failing to provide full protection. Specifically, during long-term use or storage, rubber antioxidants migrate from the interior of rubber products to the rubber surface, significantly reducing the effective protective layer. Current research indicates that the loss due to poor migration resistance is severe, resulting in less than 50% of traditional antioxidants actually functioning within the rubber structure.

[0003] Therefore, there is an urgent need to develop a new type of antioxidant that is low in toxicity, free of color pollution, and highly resistant to migration. Summary of the Invention

[0004] In order to improve the migration resistance of traditional antioxidants, enhance their protective efficiency, and reduce economic losses caused by antioxidant migration, this invention provides a class of migration-resistant antioxidants, their preparation methods, and applications.

[0005] This invention improves traditional amine antioxidants by increasing their molecular weight, thus producing a class of antioxidants with high migration resistance. This overcomes the shortcomings of traditional antioxidants, such as poor migration resistance and easy discoloration, and enhances their protective effect in rubber.

[0006] The migration-resistant antioxidant of the present invention has the structure shown in Formula II below:

[0007] In Formula II, R2 and R3 are independently selected from aminoalkyl, aminoaryl, aminoalkylaryl, or aminoarylalkyl, but are not limited thereto.

[0008] Furthermore, the aminoalkyl group has the structural formula -NHR4, where R4 is an alkyl group with 3-6 carbon atoms, such as isopropyl, 1,3-dimethylbutyl, etc.

[0009] The preparation method of the above-mentioned migration-resistant antioxidant includes the following steps:

[0010] 1) Nitration: Dissolve the substance described in Formula I in a solvent, add an acid mixture dropwise to the base liquid at a certain temperature, control the reaction temperature, and obtain the nitrated substance;

[0011] 2) Reduction: In a high-pressure reactor, the nitrated substance is dissolved in an organic solvent, a catalyst is added, hydrogen gas is introduced to reduce the nitrated substance, the catalyst is filtered out, the solvent and water are removed, and the amination substance is obtained.

[0012] R1* represents amino, alkyl, or aminoalkyl, with the definition of aminoalkyl consistent with that in Formula II;

[0013] 3) Condensation: In a high-pressure reactor, the amination substance and the ketone undergo ketamine dehydration condensation under the action of a catalyst and hydrogen. After the reaction is completed, the ketone and the by-product alcohol are removed to obtain the migration-resistant antioxidant.

[0014] Furthermore, in step 1), R1 in formula I is selected from, but not limited to, nitro, amino, alkyl, aminoalkyl, or hydrogen.

[0015] Furthermore, in step 1), the solvent is methanol, ethanol, isopropanol, methyl isobutyl methanol, or methyl isopropyl methanol; the preferred solvent is ethanol.

[0016] Further, in step 1), the mass ratio of the solvent to the substance described in Formula I is 8 to 16:1; preferably, the mass ratio of the solvent to the substance described in Formula I is 10 to 13:1.

[0017] Further, in step 1), the acid mixture is a mixture of concentrated nitric acid and concentrated sulfuric acid, with a molar ratio of 1 to 2:1. Preferably, the molar ratio of concentrated nitric acid to concentrated sulfuric acid in the acid mixture is 1.5:1. The concentrated nitric acid refers to an aqueous solution of nitric acid with a concentration of ≥68%, and the concentrated sulfuric acid refers to an aqueous solution of sulfuric acid with a concentration of ≥98%.

[0018] Further, in step 1), the molar ratio of nitric acid in the acid mixture to the molar ratio of the substance described in Formula I is 1.3 to 1.8:1, preferably, the molar ratio of nitric acid in the acid mixture to the molar ratio of the substance described in Formula I is 1.5 to 1.6:1.

[0019] Furthermore, in step 1), the dropping rate of the acid mixture is controlled at 10-30 min, and preferably at 25 min.

[0020] Furthermore, in step 1), the reaction temperature is -5℃ to 10℃, and controlling the temperature can effectively reduce the formation of by-products; preferably, the reaction temperature is -2℃ to 2℃.

[0021] Furthermore, in step 1), after the reaction is complete, the mother liquor is concentrated and crystallized, the solvent is recycled, the product is washed with water until neutral, and dried to obtain the nitrated substance.

[0022] Furthermore, in step 2), the organic solvent is one or a mixture of two or more of methanol, ethanol, isopropanol, and methyl isobutyl methanol, preferably ethanol.

[0023] Furthermore, in step 2), the mass ratio of the nitrated substance to the organic solvent is 1:(5-20).

[0024] Furthermore, in step 2), the catalyst is one or a mixture of two or more of the following: copper-based catalyst, palladium on carbon catalyst, platinum on carbon catalyst, Raney nickel, Raney ketone, and Raney palladium. Preferably, the catalyst is a Raney nickel catalyst.

[0025] Furthermore, in step 2), the amount of catalyst added is 1%-8% of the mass of the nitrated substance, preferably 2%-4% of the mass of the nitrated substance.

[0026] Furthermore, in step 2), the reaction temperature is 60-100℃ and the hydrogen pressure is 1-4MPa; preferably, the reaction temperature is 70-80℃ and the hydrogen pressure is 2-3MPa.

[0027] Furthermore, in step 2), after the reaction no longer consumes hydrogen, the catalyst is filtered out and recycled. The mother liquor is subjected to vacuum distillation to remove water, the solvent is reused, and after drying, the product amination substance is obtained.

[0028] Furthermore, in step 3), the mass ratio of the amination substance to the ketone is 1:8-15, preferably 1:10-12.

[0029] Furthermore, in step 3), the catalyst and its amount are the same as in step 2), and the mass of the amination substance is the same as the mass of the nitration substance, that is, the amount of catalyst added is 1%-8% of the mass of the amination substance, preferably, the amount of catalyst added is 2%-4% of the mass of the amination substance.

[0030] Furthermore, in step 3), the reaction temperature is 60-100℃ and the hydrogen pressure is 1-4MPa; preferably, the reaction temperature is 80-90℃ and the hydrogen pressure is 3-4MPa.

[0031] Furthermore, in step 3), after the reaction consumes no more hydrogen, the catalyst is filtered out and recycled. The mother liquor is then subjected to vacuum distillation to remove ketones, byproduct alcohols and water, and dried to obtain a migration-resistant antioxidant.

[0032] The present invention has the following beneficial effects:

[0033] 1. In this invention, the substance described in Formula I is reacted with nitric acid. The H in the -CH- group of the amino group condenses with the nitro group to obtain the nitrated substance. The nitro group of the nitrated substance is then hydrogenated and reduced under the action of a catalyst to obtain an intermediate product. The intermediate product is then hydrogenated with a ketone under the action of a catalyst to obtain the migration-resistant antioxidant of Formula II. This migration-resistant antioxidant has a tortuous and long molecular chain, which not only has a good anti-aging effect, but more importantly, it has a slow migration rate in plastics and rubber, exhibiting high migration resistance and making it less prone to blooming in plastics and rubber.

[0034] 2. Compared with traditional antioxidants, this invention can improve the heat and oxygen aging resistance and tensile fatigue performance of rubber with less antioxidant dosage, while maintaining good original tensile strength, original elongation at break, static ozone aging performance and dynamic ozone aging performance. Attached Figure Description

[0035] Figure 1 shows the NMR of the final product obtained in Example 1. 12 C spectrum;

[0036] Figure 2 shows the NMR of the final product obtained in Example 2. 12 C spectrum;

[0037] Figure 3 shows the rubber compound after dynamic ozone aging for 24 hours.

[0038] Figure 4 shows the rubber compound after static ozone aging for 24 hours. Detailed Implementation

[0039] To further illustrate the technical means and effects adopted by the present invention in order to achieve the intended purpose, the following detailed description of specific embodiments and effects is provided.

[0040] Example 1

[0041] The preparation method of the migration-resistant antioxidant is as follows:

[0042] Using the compound of formula I as a raw material, When R1 is aminopropane, Formula I is N-isopropyl-N'-phenyl-p-phenylenediamine (molecular weight 226.3);

[0043] 1) Nitrification

[0044] 22.6 g of N-isopropyl-N'-phenyl-p-phenylenediamine was dissolved in 226 g of ethanol. 23.90 g of an acid mixture was added dropwise to the system over 30 min, with the reaction temperature controlled at 1 °C. 26.3 g of the nitrated substance (molecular weight: 271) was obtained, with a yield of 97.0% based on N-isopropyl-N'-phenyl-p-phenylenediamine. The reaction equation is as follows:

[0045] 2) Restoration

[0046] In a 1L high-pressure reactor, 27.1g of the nitrated substance was dissolved in 271g of ethanol. 1.36g of Raney nickel catalyst was added, and the nitrated substance was reduced by 2MPa of hydrogen gas at 70°C. The reaction continued until the pressure inside the reactor no longer changed. The catalyst was filtered off, and the ethanol and water were removed under reduced pressure. The ethanol was recycled, yielding 23.3g of the amination substance (molecular weight 241). The yield based on the nitrated substance was 96.7%. The reaction equation is as follows:

[0047] 3) Condensation

[0048] In a 1L high-pressure reactor, 24.1g of the amination material, 241g of methyl isobutyl ketone, and the catalyst from step 2) were reused. Hydrogen gas was introduced at 4MPa, and the reaction temperature was 80℃ to carry out ketone-amine dehydration condensation. After the reaction was completed, the ketone and byproducts methyl isobutyl methanol and water were removed by vacuum distillation. The ketone was reused, yielding 31.5g of the final product, a migration-resistant antioxidant (molecular weight 325). The yield based on the amination material was 96.9%. The reaction equation is as follows:

[0049] The NMR spectrum of the final product, the migration-resistant antioxidant, is shown in Figure 1.

[0050] Example 2

[0051] The preparation method of the migration-resistant antioxidant is as follows:

[0052] Using the compound of formula I as a raw material, When R1 is a nitro group, Formula I is 4-nitrodiphenylamine (molecular weight 214.2).

[0053] 1) Nitrification

[0054] 21.4 g of 4-nitrodiphenylamine was dissolved in 214 g of ethanol. 23.90 g of an acid mixture was added dropwise over 30 min, with the reaction temperature controlled between -2°C and 2°C. This yielded 26.4 g of the nitrated substance (molecular weight: 277), with a yield of 95.3% based on 4-nitrodiphenylamine. The reaction equation is as follows:

[0055] 2) Restoration

[0056] In a 1L high-pressure reactor, 27.7g of the nitrated substance was dissolved in 277g of ethanol. 1.39g of Raney nickel catalyst was added, and the nitrated substance was reduced by 3MPa hydrogen gas at 70°C. The reaction continued until the pressure inside the reactor no longer changed. The catalyst was filtered off, and the ethanol and water were removed under reduced pressure. The ethanol was reused, yielding 19.2g of the amination substance (molecular weight 199). The yield based on the nitrated substance was 96.5%. The reaction equation is as follows:

[0057] 3) Condensation

[0058] In a 1L high-pressure reactor, 19.9g of the amination material, 199g of methyl isobutyl ketone, and the catalyst from step 2) were reused. Hydrogen gas was introduced at 3MPa, and the reaction temperature was 80℃ to carry out ketone-amine dehydration condensation. After the reaction was completed, the ketone was removed by vacuum distillation and reused with the byproduct methyl isobutyl methanol and water to obtain 34.1g of the final product, an anti-migration antioxidant (molecular weight 352). The yield based on the amination material was 96.9%. The reaction equation is as follows:

[0059] The NMR spectrum of the final product, the migration-resistant antioxidant, is shown in Figure 2.

[0060] Example 3

[0061] The preparation method of the migration-resistant antioxidant is as follows:

[0062] Using the compound of formula I as a raw material, When R1 is aminopropane, Formula I is N-isopropyl-N'-phenyl-p-phenylenediamine (molecular weight 226.3);

[0063] 1) Nitrification

[0064] 22.6 g of N-isopropyl-N'-phenyl-p-phenylenediamine was dissolved in 226 g of ethanol. 23.90 g of an acid mixture, consisting of a 1.5:1 mass ratio of 68% nitric acid and 98% sulfuric acid, was added dropwise to the system over 30 min. The dropping temperature was controlled at 1 °C. After the addition was complete, the reaction was continued at this temperature for 1 h, yielding 26.3 g of the nitrated substance (molecular weight: 271). The yield, based on N-isopropyl-N'-phenyl-p-phenylenediamine, was 97.0%. The reaction equation is as follows:

[0065] 2) Restoration

[0066] The reaction was carried out in a 1L high-pressure reactor. 27.1g of the nitrated substance was dissolved in 271g of ethanol, and 1.36g of Raney nickel catalyst was added. The nitrated substance was reduced at 70°C by introducing hydrogen gas at 2MPa. When the hydrogen pressure dropped to 1.5MPa, hydrogen gas was introduced again to bring the pressure back to 2MPa. The reaction continued until the pressure inside the reactor no longer changed. After the reaction, the catalyst was filtered out and reused. Ethanol and water were removed under reduced pressure, and the ethanol was reused, yielding 23.3g of the amination substance (molecular weight 241). The yield based on the nitrated substance was 96.7%. The reaction equation is as follows:

[0067] 3) Condensation

[0068] 24.1 g of the amination material, 241 g of methyl isobutyl ketone, and 1.36 g of the recycled Raney nickel catalyst from step 2) were added to a 1 L high-pressure reactor. Hydrogen gas was introduced at 4 MPa, and the reaction temperature was controlled at 80 °C for ketone-amine dehydration condensation. When the hydrogen pressure dropped to 2 MPa, hydrogen gas was introduced again to bring the pressure back to 4 MPa. The reaction continued until the pressure inside the reactor no longer changed. After the reaction was complete, the catalyst was filtered out for reuse. Ketones, byproduct methyl isobutyl methanol, and byproduct water were removed by vacuum distillation. The ketones were reused, yielding 31.5 g of the final product, a migration-resistant antioxidant (molecular weight 325). The yield based on the amination material was 96.9%. The reaction equation is as follows:

[0069] The NMR spectrum of the final product, the migration-resistant antioxidant, is shown in Figure 1.

[0070] Example 4

[0071] The preparation method of the migration-resistant antioxidant is as follows:

[0072] Using the compound of formula I as a raw material, When R1 is a nitro group, Formula I is 4-nitrodiphenylamine (molecular weight 214.2).

[0073] 1) Nitrification

[0074] 21.4 g of 4-nitrodiphenylamine was dissolved in 214 g of ethanol. Then, 23.90 g of an acid mixture (a mixture of 68 wt% nitric acid and 98 wt% sulfuric acid in a mass ratio of 1.5:1) was added dropwise over 30 min. The dropping temperature was controlled at -2 °C to 2 °C. After the addition was complete, the reaction was continued at this temperature for 1 h, yielding 26.4 g of the nitrated substance (molecular weight: 277), with a yield of 95.3% based on 4-nitrodiphenylamine. The reaction equation is as follows:

[0075] 2) Restoration

[0076] The reaction was carried out in a 1L high-pressure reactor. 27.7g of the nitrated substance was dissolved in 277g of ethanol, and 1.39g of Raney nickel catalyst was added. The nitrated substance was reduced at 70°C by introducing hydrogen gas at 3MPa. When the hydrogen pressure dropped to 2MPa, hydrogen gas was introduced again to bring the pressure back to 3MPa. The reaction continued until the pressure inside the reactor no longer changed. After the reaction, the catalyst was filtered out and reused. Ethanol and water were removed under reduced pressure, and the ethanol was reused, yielding 19.2g of the amination substance (molecular weight 199). The yield based on the nitrated substance was 96.5%. The reaction equation is as follows:

[0077] 3) Condensation

[0078] 19.9 g of the amination material, 199 g of methyl isobutyl ketone, and 1.39 g of the recycled Raney nickel catalyst from step 2) were added to a 1 L high-pressure reactor. Hydrogen gas was introduced at 3 MPa, and the reaction temperature was controlled at 80 °C for ketone-amine dehydration condensation. When the hydrogen pressure dropped to 2 MPa, hydrogen gas was introduced again to bring the pressure back to 3 MPa. The reaction continued until the pressure inside the reactor no longer changed. After the reaction was complete, the catalyst was filtered out for reuse. Ketones, byproducts methyl isobutyl methanol and water were removed by vacuum distillation. The ketones were reused, yielding 34.1 g of the final product, a migration-resistant antioxidant (molecular weight 352). The yield based on the amination material was 96.9%. The reaction equation is as follows:

[0079] The NMR spectrum of the final product, the migration-resistant antioxidant, is shown in Figure 2.

[0080] Experimental Example 1

[0081] Performance verification

[0082] 1. Rubber compound formulation and preparation

[0083] Rubber compound formulation (parts by weight): SSBR 96.25 parts, BR 30 parts, silica 80 parts, N220 5 parts, ZnO-80 3 parts, SA 1 part, S175 8 parts, SA 1 part, protective wax 1.5 parts, RD 1 part, DPG-80 2.5 parts, tread resin 30 parts, S-80 2 parts, CBS-80 2 parts, and antioxidant from Example 1 or Example 2 2 parts. Meanwhile, the antioxidant prepared in the embodiments of the present invention was replaced with antioxidant 4020 as a comparison, and a blank control was used without the antioxidant of the present invention, respectively labeled as 1# blank, 2# 4020, 3# Example 1, and 4# Example 2.

[0084] 2. Test methods for various performance parameters of the rubber compound

[0085] Processing performance test: A scorch test was conducted using a Mooney viscometer in accordance with the national standard GB / T 1233-92.

[0086] Vulcanization characteristics: The P3555 B2 disc vulcanizer manufactured by Beijing Huanfeng Rubber & Plastic Machinery Manufacturing Plant was used for testing according to GB / T9869-1997. The test temperature was 160℃ and the test time was 60min.

[0087] Mechanical properties: The tensile properties of the vulcanizate were determined according to GB / T 528-2009 using a CMT 4104 electronic tensile testing machine manufactured by Shenzhen Xin Sansi Materials Testing Co., Ltd.; the compression set was determined according to GB / T 7759-1996 using cylindrical specimens of 29.0 mm × 12.5 mm at 100℃ for 72 h, with a pre-compression rate of 25%.

[0088] Ozone resistance: Ozone resistance was tested according to GB / T 11206-2009 "Rubber Aging Test - Surface Cracking Method". The test results are shown in Table 1, Figure 3, and Figure 4.

[0089] Table 1

[0090] As can be seen from Table 1, the scorch time of rubber compounds #2-#4 with added antioxidants is shorter than that of rubber compound #1 without antioxidants. The vulcanization rate of rubber compounds with antioxidants from Example 1 or Example 2 is significantly faster than that of rubber compounds with antioxidant 4020. The addition of antioxidants reduces the modulus and TB of the rubber compounds, while the elongation at break is basically the same.

[0091] Figures 3 and 4 show the state diagrams of different rubber compounds (1#, 2#, 3#, and 4#) after dynamic ozone aging for 24 hours and static ozone aging for 24 hours, respectively. Figure 3 shows that the protective effects of Examples 1, 2#, and antioxidant 4020 are basically equivalent. Figure 4 shows that Example 2 has the best protective effect, followed by antioxidant 4020. Examples 1 and 2 exhibit significant resistance to discoloration and migration.

[0092] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been shown above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A migration-resistant antioxidant, the structure of which is shown in Formula II below: In formula II, R2 and R3 are selected from, but not limited to, aminoalkyl, aminoaryl, aminoalkylaryl or aminoarylalkyl.

2. The preparation method of the migration-resistant antioxidant according to claim 1, comprising the following steps: 1) nitration: the material described in formula I is dissolved in a solvent, an acid mixture is added dropwise to the bottom liquid at a certain temperature, the reaction temperature is controlled, and the nitrated material is obtained; 2) Reduction: in a high-pressure reactor, the nitrated material is dissolved in an organic solvent, a catalyst is added, and hydrogen is introduced to reduce the nitrated material. The catalyst is filtered out, and the solvent and water are removed to obtain the aminated material; R1* represents amino, alkyl or aminoalkyl; 3) condensation: in a high-pressure reactor, the aminated substance and ketone are subjected to ketone amine dehydration condensation in the presence of a catalyst and hydrogen, after the reaction is completed, the ketone and by-product alcohol are removed, to obtain a migration-resistant antioxidant; 3. The preparation method according to claim 2, in step 1), R1 in formula I is selected from nitro, amino, alkyl, aminoalkyl or hydrogen.

4. The preparation method according to claim 2, in step 1), the solvent is methanol, ethanol, isopropanol, methyl isobutyl carbinol, methyl isopropyl carbinol, and the mass ratio of the solvent to the substance of formula I is 8-16:1; preferably, the mass ratio of the solvent to the substance of formula I is 10-13:

1.

5. The preparation method according to claim 2, in step 1), the acid mixture is a mixture of concentrated nitric acid and concentrated sulfuric acid, and the molar ratio of the concentrated nitric acid to the concentrated sulfuric acid is 1-2:1, and the molar ratio of the nitric acid in the acid mixture to the substance of formula I is 1.3-1.8:

1.

6. The preparation method according to claim 2, in step 1), the dropping speed of the acid mixture is controlled at 10-30 min, preferably 25 min, and the reaction temperature is -5-10°C; after the reaction is completed, the mother liquor is concentrated and crystallized, the solvent is reused, the product is washed with water until neutral, and then dried to obtain the nitrated substance.

7. The preparation method according to claim 2, in step 2), the organic solvent is one or a mixture of two or more of methanol, ethanol, isopropanol and methyl isobutyl carbinol, and the catalyst is one or a mixture of two or more of copper-based catalyst, palladium-carbon catalyst, platinum-carbon catalyst, Raney nickel, Raney ketone and Raney palladium.

8. The preparation method according to claim 2, in step 2), the addition amount of the catalyst is 1%-8% of the mass of the nitrated substance, the reaction temperature is 60-100°C, and the hydrogen pressure is 1-4 MPa; preferably, the reaction temperature is 70-80°C, the hydrogen pressure is 2-3 MPa, after the reaction no longer consumes hydrogen, the catalyst is filtered out, recovered and reused, the mother liquor is distilled under reduced pressure to remove water, the solvent is reused, and then dried to obtain the aminated substance.

9. The preparation method according to claim 2, in step 3), the mass ratio of the aminated substance to the ketone is 1:8-15, the catalyst and its amount are the same as in step 2), and the mass of the aminated substance is the same as that of the nitrated substance.

10. The preparation method according to claim 2, in step 3), the reaction temperature is 60-100°C, and the hydrogen pressure is 1-4MPa; after the reaction no longer consumes hydrogen, the catalyst is filtered out, recovered and reused, the ketone, by-product alcohol and water are removed from the mother liquor by distillation under reduced pressure, and then dried to obtain the migration-resistant antioxidant.

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