Modified cashew nut oil, rubber plasticizer and preparation method and application thereof

Abstract

The present invention discloses modified cashew nut oil, rubber plasticizer and preparation method and application thereof. The modified cashew nut oil provided by the present invention can be used as a rubber plasticizer, and the rubber plasticizer provided by the present invention can significantly prolong the scorch time of rubber, effectively solving the problem of processing safety; and the process for preparing the rubber plasticizer is simple, low-cost, environmentally friendly, and conducive to industrial promotion, overcoming the polycyclic aromatic hydrocarbon content problem of petroleum-based rubber plasticizers. According to different selections of end-capping agents and cross-linking agents, the present invention has obvious adjustability for scorch time and vulcanization time; in addition, while improving processing performance, the present invention does not significantly affect the mechanical properties of the rubber compound.

Description

Technical Field

[0001] The invention relates to the technical field of rubber industry, and in particular to modified cashew nut oil, a rubber plasticizer and a preparation method thereof. Background Art

[0002] Rubber processing oil is a processing aid used in rubber production and a type of rubber plasticizer. It can significantly improve the processing properties of rubber and directly affect the quality of rubber products. An ideal processing oil should have the following conditions: (1) good compatibility; (2) low volatility; (3) good processability, damage resistance, and lubricity; (4) good stability; and (5) sufficient source.

[0003] The petroleum-based operating oils commonly used today contain a certain amount of polycyclic aromatic hydrocarbons, which pollute the environment during use and waste disposal. They are not only non-renewable, but also carcinogenic to humans, and are subject to increasingly stringent restrictions on their use. In contrast, bio-based oils, as a renewable resource with low cost, wide sources, and low toxicity, are gaining more and more attention.

[0004] Cashew nut oil is a byproduct of cashew nut processing. It is an industrial raw material with a wide range of sources and has good compatibility with most rubbers. The main component of cashew nut oil is formula (a), and its characteristic functional groups include a phenolic hydroxyl group, a long-chain alkane containing fifteen carbon atoms, and several carbon-carbon double bonds on the chain. Among them, the long-chain alkane can play a plasticizing role, reduce the viscosity of the mixed rubber within a certain dosage range, and is conducive to the mixing of fillers, thereby improving the tensile properties and tear resistance of the vulcanized rubber; the carbon-carbon double bond can participate in and promote the cross-linking reaction of the rubber, thereby enhancing certain mechanical properties of the rubber; the phenolic hydroxyl group can form hydrogen bonds with inorganic fillers, which helps to evenly disperse the fillers, and can act as a free radical scavenger, making it act as a reactive antioxidant, thereby improving the thermal oxidation aging resistance and oil resistance of the vulcanized rubber.

[0005]

[0006] However, there is a defect when cashew nut oil is used as a rubber plasticizer: it affects the vulcanization characteristics of the rubber, especially causing a serious shortening of the scorch time. Some researchers have investigated the processing performance of cashew nut oil in nitrile rubber. With the increase of cashew nut oil dosage, the minimum torque (ML) and maximum torque (MH) of the rubber are significantly reduced, and the scorch time (t10) and vulcanization time (t90) of the rubber are significantly shortened; others have found that when phosphorylated cashew nut oil is used as a plasticizer for polyvinyl chloride, the scorch time (t5, t10, t50) are shortened to a certain extent; and when modified cashew nut oil is used as a plasticizer for EPDM rubber, the scorch time and torque are reduced with the increase of dosage.

[0007] Too short a scorch time will undoubtedly reduce the processing safety of rubber. Although it has advantages such as strong plasticity, good compatibility, environmental protection and low toxicity, this defect greatly limits its development prospects. Summary of the invention

[0008] In order to overcome the defects of the above-mentioned prior art, the present invention proposes a modified cashew nut oil, a rubber plasticizer and a preparation method and application thereof, the reaction process is simple, and all raw materials are suitable for industrial production. When the modified cashew nut oil provided by the present invention is used as a rubber plasticizer, the scorch time is significantly extended, which effectively solves the problem of processing safety; and overcomes the problem of polycyclic aromatic hydrocarbon content of petroleum-based plasticizers.

[0009] This is achieved specifically through the following technical solutions:

[0010] A rubber plasticizer, characterized in that it comprises the following structural formula:

[0011]

[0012] Where R = C 15 H 31-n , n = 0, 2, 4 or 6,

[0013] R1 is any one of a methyl group, an ethyl group, an isopropyl group, an acetyl group, a propionyl group, a butyryl group, an acryloyl group, a glycidyl group or an isocyanate group.

[0014] The preparation method of the rubber plasticizer comprises the following steps:

[0015] S1: Cashew nut oil, catalyst C1 and a capping agent are mixed and reacted at room temperature to obtain hydroxyl-capped cardanol.

[0016] Further, in step S1, the blocking agent is one or more of methyl iodide, methyl bromide, ethyl iodide, ethyl bromide, isopropyl iodide, isopropyl bromide, acetic anhydride, propionic anhydride, butyric anhydride, acetyl chloride, propionyl chloride, butyryl chloride, acryloyl chloride, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, ethyl butyrate, epichlorohydrin and isocyanate.

[0017] Furthermore, in step S1, the catalyst C1 is one or more of an inorganic acid, an acidic inorganic salt, an organic acid, a solid acid, a Lewis acid, an organic base, an inorganic base, or a basic inorganic salt.

[0018] The inorganic acid includes but is not limited to sulfuric acid, hydrochloric acid, hydrofluoric acid, phosphoric acid and perchloric acid; the acidic inorganic salt includes but is not limited to zinc perchlorate and sodium bisulfite; the organic acid includes but is not limited to oxalic acid, citric acid and p-toluenesulfonic acid; the solid acid includes but is not limited to perfluorosulfonic acid resin, acidic bentonite and active tin dioxide; the Lewis acid includes but is not limited to AlCl3, FeCl3, BF3; the organic base includes but is not limited to pyridine, dipyridine, diethylamine, triethylamine and tributylamine; the inorganic base includes but is not limited to sodium hydroxide or potassium hydroxide; the alkaline inorganic salt includes but is not limited to sodium carbonate, potassium carbonate, sodium sulfate, potassium sulfate or sodium bicarbonate.

[0019] Preferably, in step S1, the reaction time is 12-24 hours.

[0020] The present invention also provides a modified cashew nut oil comprising the following structural formula:

[0021]

[0022] Where R = C 15 H 31-n , R2 is located at the ortho or para position of the benzene ring, n=0, 2, 4 or 6, 2≤ m≤6, m is a positive integer;

[0023] R3 is H, and R2 is a group obtained by removing one or two hydrogen atoms from any one of ethylene glycol, propylene glycol, pentaerythritol, bornene, ethylidene norbornene, dicyclopentadiene, coumarone resin, divinylbenzene, terephthalene or trimesic alcohol. When R2 is at the terminal position of the polymer, R2 is a group obtained by removing one hydrogen atom from any one of ethylene glycol, propylene glycol, pentaerythritol, bornene, ethylidene norbornene, dicyclopentadiene, coumarone resin, divinylbenzene, terephthalene or trimesic alcohol; when R2 is at the non-terminal position of the polymer, R2 is a group obtained by removing two hydrogen atoms from any one of ethylene glycol, propylene glycol, pentaerythritol, bornene, ethylidene norbornene, dicyclopentadiene, coumarone resin, divinylbenzene, terephthalene or trimesic alcohol.

[0024] The present invention also provides another modified cashew nut oil, comprising the following structural formula:

[0025]

[0026] Where R = C 15 H 31-n , R2 is located at the ortho or para position of the benzene ring, n=0, 2, 4 or 6, 2≤ m≤6, m is a positive integer;

[0027] R3 is one of methyl, ethyl, isopropyl, acetyl, propionyl, butyryl or acryloyl; R2 is a group obtained by removing one or two hydrogen atoms from any one of formaldehyde, paraformaldehyde, ethylene glycol, propylene glycol, pentaerythritol, urotropine, bornene, ethylidene norbornene, dicyclopentadiene, coumarone resin, hexamethoxymethylmelamine, furfural, divinylbenzene, terephthalic acid or trimesic acid. When R2 is at the terminal position of the polymer, R2 is a group obtained by removing one hydrogen atom from any one of the following compounds: formaldehyde, paraformaldehyde, ethylene glycol, propylene glycol, pentaerythritol, urotropine, bornene, ethylidene norbornene, dicyclopentadiene, coumarone resin, hexamethoxymethyl melamine, furfural, divinylbenzene, terephthalic acid alcohol or pyromellitic acid trimethanol; when R2 is at the non-terminal position of the polymer, R2 is a group obtained by removing two hydrogen atoms from any one of the following compounds: formaldehyde, paraformaldehyde, ethylene glycol, propylene glycol, pentaerythritol, urotropine, bornene, ethylidene norbornene, dicyclopentadiene, coumarone resin, hexamethoxymethyl melamine, furfural, divinylbenzene, terephthalic acid alcohol or pyromellitic acid trimethanol.

[0028] The present invention also provides a rubber plasticizer comprising the following structural formula:

[0029]

[0030] Where R = C 15 H 31-n , n=0, 2, 4 or 6.

[0031] When R3 is H, R2 is a group obtained by removing one or two hydrogen atoms from any one of ethylene glycol, propylene glycol, pentaerythritol, bornene, ethylidene norbornene, dicyclopentadiene, coumarone resin, divinylbenzene, terephthalene or trimesic alcohol. When R2 is at the terminal position of the polymer, R2 is a group obtained by removing one hydrogen atom from any one of ethylene glycol, propylene glycol, pentaerythritol, bornene, ethylidene norbornene, dicyclopentadiene, coumarone resin, divinylbenzene, terephthalene or trimesic alcohol; when R2 is at the non-terminal position of the polymer, R2 is a group obtained by removing two hydrogen atoms from any one of ethylene glycol, propylene glycol, pentaerythritol, bornene, ethylidene norbornene, dicyclopentadiene, coumarone resin, divinylbenzene, terephthalene or trimesic alcohol.

[0032] When R3 is one of methyl, ethyl, isopropyl, acetyl, propionyl, butyryl or acryloyl; R2 is the group obtained by removing one or two hydrogen atoms from any one of formaldehyde, paraformaldehyde, ethylene glycol, propylene glycol, pentaerythritol, urotropine, bornene, ethylidene norbornene, dicyclopentadiene, coumarone resin, hexamethoxymethyl melamine, furfural, divinylbenzene, terephthalic acid or trimesic acid. When R2 is at the terminal position of the polymer, R2 is a group obtained by removing one hydrogen atom from any one of the following compounds: formaldehyde, paraformaldehyde, ethylene glycol, propylene glycol, pentaerythritol, urotropine, bornene, ethylidene norbornene, dicyclopentadiene, coumarone resin, hexamethoxymethyl melamine, furfural, divinylbenzene, terephthalic acid alcohol or pyromellitic acid trimethanol; when R2 is at the non-terminal position of the polymer, R2 is a group obtained by removing two hydrogen atoms from any one of the following compounds: formaldehyde, paraformaldehyde, ethylene glycol, propylene glycol, pentaerythritol, urotropine, bornene, ethylidene norbornene, dicyclopentadiene, coumarone resin, hexamethoxymethyl melamine, furfural, divinylbenzene, terephthalic acid alcohol or pyromellitic acid trimethanol.

[0033] The preparation method of the modified cashew nut oil or rubber plasticizer comprises the following steps:

[0034] S2: mixing the hydroxyl-terminated cardanol with a crosslinking agent and a catalyst C2, and heating the mixture to react to obtain the modified cashew nut oil or rubber plasticizer.

[0035] Further, in step S2, the cross-linking agent is one or more of formaldehyde, paraformaldehyde, ethylene glycol, propylene glycol, pentaerythritol, urotropine, bornene, ethylidene norbornene, dicyclopentadiene, coumarone resin, hexamethoxymethyl melamine, furfural, divinylbenzene, terephthalic acid or trimesic acid.

[0036] Furthermore, in step S2, the catalyst C2 is one or more of sulfuric acid, hydrochloric acid, phosphoric acid, oxalic acid, citric acid, p-toluenesulfonic acid, AlCl3, FeCl3, and BF3.

[0037] Preferably, in step S2, the reaction time is 1-3 hours;

[0038] Preferably, in step S2, the heating temperature is 90-140°C.

[0039] The present invention also provides the use of the rubber plasticizer or modified cashew nut oil in tire rubber processing, especially in adjusting the scorch time and vulcanization time.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] The rubber plasticizer provided by the present invention has a wide range of raw material sources, a simple preparation process, low cost, and is environmentally friendly, which is conducive to industrial promotion and overcomes the polycyclic aromatic hydrocarbon content problem of petroleum-based plasticizers; it can significantly prolong the scorch time and effectively solve the problem of processing safety; the key components in the present invention are the end-capping agent and the cross-linking agent, which can be selected according to different types of the end-capping agent and the cross-linking agent, and the scorch time and the vulcanization time have obvious adjustability; in addition, the present invention will not significantly affect the mechanical properties of the rubber material while improving the processing performance. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] Comparative Example

[0044] Unmodified cashew nut oil (raw material) was used as cashew nut oil a.

[0045] Example 1 (Preparation of modified cashew nut oil b)

[0046] The synthetic route is as follows:

[0047]

[0048] Specific steps:

[0049] S2: Add 300g cashew nut oil and 5g oxalic acid into a flask, stir evenly and heat to 100°C; slowly add 21g of 37-40% formaldehyde aqueous solution into the flask using a constant pressure dropping funnel, and keep warm at 90°C for 3 hours after the addition is complete; remove water and unreacted formaldehyde by reduced pressure distillation to obtain modified cashew nut oil b.

[0050] Example 2 (Preparation of modified cashew nut oil c)

[0051] The synthetic route is as follows:

[0052]

[0053] Specific steps:

[0054] S1: Add 340g cashew nut oil and 120g acetic anhydride into a flask, mix and stir evenly; then add 3g citric acid into the flask, stir at room temperature for 15 hours; remove the unreacted acetic anhydride and generated acetic acid by reduced pressure distillation to obtain modified cashew nut oil c.

[0055] Example 3 (Preparation of modified cashew nut oil d)

[0056] The synthetic route is as follows:

[0057]

[0058] Specific steps:

[0059] S1: 375g of cashew nut oil and 125g of acetic anhydride were added to a flask, and the mixture was stirred at room temperature; 5g of sodium bisulfite was added thereto, and the mixture was stirred at room temperature for 12 hours; the residual acetic acid and acetic anhydride were removed by distillation under reduced pressure to obtain hydroxy-terminated cardanol (intermediate).

[0060] S2: 300 g of the above-mentioned hydroxyl-terminated cardanol (intermediate) and 22 g of a 37-40% formaldehyde aqueous solution are added to a flask, mixed evenly, heated to 90° C., 5 g of hydrochloric acid is added, and the reaction is continued for 2 hours; the generated water and unreacted formaldehyde are removed by reduced pressure distillation to obtain modified cashew oil d.

[0061] Example 4 (Preparation of modified cashew nut oil e)

[0062] The synthetic route is as follows:

[0063]

[0064] Specific steps:

[0065] S1: Add 480g cashew nut oil and 120g epichlorohydrin into a flask, mix and stir evenly; then add 6g sodium hydroxide into the flask, stir at room temperature for 16 hours; distill under reduced pressure and wash with water 2 to 3 times to obtain modified cashew nut oil e.

[0066] Example 5 (Preparation of modified cashew nut oil f)

[0067] The synthetic route is as follows:

[0068]

[0069] Specific steps:

[0070] S2: 300g cashew nut oil and 25g ethylene glycol were added to a flask, mixed evenly, heated to 130°C, and 5g zinc perchlorate was added, and the reaction was continued for 2.5 hours; the generated water and unreacted ethylene glycol were removed by reduced pressure distillation to obtain modified cashew nut oil f.

[0071] Example 6 (Preparation of modified cashew nut oil g)

[0072] The synthetic route is as follows:

[0073]

[0074] Specific steps:

[0075] S2: Add 500g cashew nut oil and 110g terephthalate into a flask, mix well, heat to 125°C, add 6.5g AlCl3, and continue the reaction for 3 hours; obtain modified cashew nut oil g after reduced pressure distillation.

[0076] Example 7 (Preparation of modified cashew nut oil h)

[0077] The synthetic route is as follows:

[0078]

[0079] Specific steps:

[0080] S1: Add 380g cashew nut oil and 205g butyric anhydride into a flask, and stir evenly at room temperature; then add 5.8g potassium hydroxide, and continue stirring at room temperature for 18 hours; remove butyric acid by vacuum distillation to obtain hydroxyl-terminated cardanol (intermediate);

[0081] S2: 220 g of the above-mentioned hydroxyl-terminated cardanol (intermediate) and 80 g of terephthalic acid methanol were added into a flask, mixed evenly, heated to 135° C., 5 g of AlCl 3 was added, and the reaction was continued for 3 hours; and modified cashew nut oil h was obtained by distillation under reduced pressure.

[0082] Example 8 (Preparation of modified cashew nut oil i)

[0083] The synthetic route is as follows:

[0084]

[0085] Specific steps:

[0086] S1: 440g cashew nut oil and 160g triethylamine were added to a flask and stirred at room temperature; 160g propionyl chloride was slowly added dropwise thereto using a constant pressure dropping funnel, and stirring was continued at room temperature for 18 hours after completion of the addition; residual propionyl chloride and hydrochloric acid were removed by distillation under reduced pressure, and washed with water 2-3 times to obtain hydroxy-terminated cardanol (intermediate);

[0087] S2: 300 g of the above-mentioned hydroxyl-terminated cardanol (intermediate) and 30 g of ethylene glycol were added to a flask, mixed evenly, heated to 140° C., and 5 g of p-toluenesulfonic acid was added. The reaction was continued for 2 hours; the generated water and unreacted ethylene glycol were removed by reduced pressure distillation to obtain modified cashew oil i.

[0088] Example 9 (Preparation of modified cashew nut oil j)

[0089] The modified cashew nut oils c and f obtained in Examples 2 and 5 were mixed in a ratio of 1:1 to obtain modified cashew nut oil j.

[0090] Example 10 (Preparation of rubber plasticizer)

[0091] The preparation methods of the rubber plasticizer bj are respectively the same as the preparation methods of the modified cashew nut oil bj.

[0092] Experimental Example 1 (Testing and Characterization of Modified Cashew Oil)

[0093] Table 1 shows the end-capping agent and cross-linking agent used in preparing cashew nut oil a and modified cashew nut oil bf, j. The viscosity, flash point and H NMR spectrum ( 1 H NMR) test, and the test results are shown in Table 2 below.

[0094] Table 1.

[0095]

[0096] Table 2. Test results

[0097]

[0098] Note: af, j in Tables 1 and 2 represent cashew oil a and modified cashew oil bf, j respectively.

[0099] From the results in the above table, it can be seen that compared with the unmodified cashew nut oil raw material, the viscosity and flash point of the product obtained by the present invention are significantly changed. The cross-linked modified products of modified cashew nut oil b, d, f, j, etc. 1 H NMR can prove that the modification of each group of products is successful.

[0100] Experimental Example 2 (Polycyclic Aromatic Hydrocarbons Test of Modified Cashew Oil)

[0101] The cashew nut oil a in comparative example and the modified cashew nut oils bf and j in Examples 1-5 and 9 were tested for polycyclic aromatic hydrocarbons. The results are shown in Table 3. It can be seen from the test results that the raw materials and preparation processes of Examples 1-5 and 9 do not contain polycyclic aromatic hydrocarbons.

[0102] Table 3.

[0103]

[0104] Note: af, j in Table 3 correspond to cashew oil a and modified cashew oil bf, j respectively; according to the AfPS (German Product Safety Committee) and EU regulations on polycyclic aromatic hydrocarbons, BaP means that the content of benzo(a)pyrene must be less than 1ppm, and the sum of 8 items must be less than 10ppm. The sum of 8 items refers to the sum of the contents of benzo(a)anthracene + chrysene + benzo(b)fluoranthene + benzo(k)fluoranthene + benzo(j)fluoranthene + benzo(e)pyrene + benzo(a)pyrene + dibenzo(a,h)anthracene.

[0105] Experimental Example 3 (Preparation of Tread Rubber Compositions A, B, C, D, E, F, and J)

[0106] The tread rubber composition was prepared according to the formulation in Table 4.

[0107] Table 4. Tread rubber composition formula

[0108]

[0109]

[0110] Note: af, j in Table 4 represent cashew oil a and modified cashew oil bf, j respectively.

[0111] Experimental Example 4 (Processing and Mechanical Properties of Tread Rubber Composition)

[0112] The processing performance and mechanical property test results of the tread rubber composition prepared in Experimental Example 3 are shown in Table 5 below.

[0113] Table 5. Processing performance test results of rubber compositions

[0114]

[0115] From the results in Table 5, it can be seen that the scorch time and vulcanization time of the unmodified cashew nut oil raw material are very short, the Mooney scorch (T5) is 11 minutes, and the scorch time (T 10 ) is 0.82 minutes, and the curing time (T 90 ) is 12 minutes; the rubber plasticizer prepared by the present invention can significantly improve the processing properties of the rubber, T5 can be extended to 18 minutes or even more than 1 hour, T 10 The maximum time can be extended to 1.28 minutes, T 90 The maximum can be extended to 19.69 minutes; more importantly, according to the different selection of the end-capping agent and the cross-linking agent, the present invention has obvious adjustability on the scorch time and the vulcanization time. In addition, while improving the processing performance, the present invention has no significant effect on the mechanical properties of the rubber compound.

[0116] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A rubber plasticizer, characterized in that: Contains any of the following structural formulas: 、 、 、 ； Where R = C 15 H 31-n , n = 0, 2, 4 or 6; The method for preparing the rubber plasticizer comprises one of the following steps: (1) S1: cashew nut oil, catalyst C1 and a capping agent are mixed and reacted at room temperature to obtain hydroxyl-capped cardanol; S2: mixing the hydroxyl-terminated cardanol with the crosslinking agent and the catalyst C2, and heating the mixture to react to obtain the rubber plasticizer; or (2) mixing cashew nut oil, a cross-linking agent and a catalyst C2, and heating the mixture to react to obtain the rubber plasticizer; The catalyst C1 is one of sulfuric acid, hydrochloric acid, hydrofluoric acid, phosphoric acid, perchloric acid, zinc perchlorate, sodium bisulfite, oxalic acid, citric acid, p-toluenesulfonic acid, perfluorosulfonic acid resin, acidic bentonite, activated tin dioxide, AlCl3, FeCl3, BF3, pyridine, dipyridine, diethylamine, triethylamine, tributylamine, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium sulfate, potassium sulfate or sodium bicarbonate; The catalyst C2 is one of sulfuric acid, hydrochloric acid, phosphoric acid, oxalic acid, citric acid, p-toluenesulfonic acid, AlCl3, FeCl3 or BF3; The end-capping agent is one of acetic anhydride and propionyl chloride; The cross-linking agent is one of formaldehyde and ethylene glycol.

2. Use of the rubber plasticizer according to claim 1 in tire rubber processing.

Images