Environment-friendly process for synthesizing high-performance mbts with low cost and high efficiency and application thereof

Abstract

This invention belongs to the field of fine chemical rubber accelerator synthesis technology, and relates to a low-cost, high-efficiency, and environmentally friendly process for synthesizing MBTS. MBT is added to acetonitrile solvent and heated. EGCG and the metal salt CuCl2 are then added, and oxygen is introduced under sealed conditions. An oxidation reaction is carried out under stirring and oxygen circulation until the pressure no longer decreases, yielding an acetonitrile mixture containing solid MBTS. The mixture is filtered to obtain solid MBTS and filtrate C. The solid MBTS is washed with acetonitrile to obtain MBTS product and washing liquid. MBT is added to the filtrate and washing liquid for recycling. The MBTS product prepared by this invention has high purity, the preparation process is rapid, and the reaction solvent and catalyst can be recycled more than 30 times while maintaining high activity. MBTS produced using this process has a shorter vulcanization time and lower oil absorption value compared to commercially available MBTS, and can successfully produce MBTS pre-dispersion masterbatch granules DM-80.

Description

Technical Field

[0001] This invention belongs to the field of fine chemical rubber accelerator synthesis technology, specifically involving an environmentally friendly process and application for low-cost, high-efficiency synthesis of high-performance MBTS (DM). Background Technology

[0002] MBTS is a high-performance, general-purpose thiazole accelerator that can be used in natural rubber, synthetic rubber, and reclaimed rubber. It is usually used in combination with other types of accelerators. It has a high vulcanization temperature and significant after-effects. High-purity MBTS can also be used as a pharmaceutical raw material.

[0003] Currently, the main processes for synthesizing MBTS both domestically and internationally are: sodium nitrite method, chlorine method, H2O2 method, and O2-NH3•H2O method. Among these, the sodium nitrite method uses sodium nitrite, a strong carcinogen, and generates large amounts of saline wastewater and nitrogen oxides during production, violating green and environmentally friendly production requirements. The chlorine method is also highly polluting, and chlorine gas is highly toxic and prone to explosion; chlorine-containing reactions also place high demands on equipment. The NH3•H2O-O2 method is highly dangerous because the concentration of NH3 in the oxidation process is within the extreme explosive range, and it also generates large amounts of waste salt. H2O2 has become a popular oxidant in recent years due to its low toxicity and low pollution, meeting the requirements of green production. However, the hydrogen peroxide method currently generally has low yields, leading to high production costs. In 2021, Professor Yang of Zhengzhou University developed a method for synthesizing MBTS using oxygen in an aqueous phase. This method has less environmental pollution, but its product quality is poor, the reaction time is long, and it generates a large amount of wastewater.

[0004] The method of preparing MBTS using oxygen as an oxidant has been widely studied due to its low cost and environmentally friendly nature. However, the current oxygen-based MBTS synthesis process suffers from low reaction efficiency, and there is still a lack of ideal catalysts that can effectively improve product quality and catalytic efficiency.

[0005] Chinese patent CN 106831644 A reports a method for preparing MBTS by catalytic molecular oxygen oxidation in aqueous phase. It uses a combination of metal phthalocyanine compounds and metal salts as catalysts, with a reaction time of 2-18 hours. Taking cobalt phthalocyanine as an example, the product has a bluish color, resulting in low customer acceptance and low product purity.

[0006] Chinese patent CN 109180545 B reports a method for synthesizing MBTS by molecular oxygen catalysis of phenylphenolic acid in an aqueous phase. It uses phenylphenolic acid as a catalyst, has a long reaction time of about 5-18 hours, produces poor product quality, and generates a large amount of wastewater.

[0007] The methods described above all have shortcomings to varying degrees. Although water is a relatively friendly and inexpensive solvent, MBT, the raw material for synthesizing MBTS, is poorly soluble in water. Alkali or other substances need to be added to facilitate the catalytic reaction using oxidants and catalysts. Most of these reactions are time-consuming, the product quality obtained in water is poor, and the saline wastewater is difficult to recycle multiple times. Therefore, developing a low-cost, high-efficiency, high-quality, environmentally friendly process for synthesizing MBTS that reduces environmental (waste gas and wastewater) treatment costs and allows for multiple reuse of the mother liquor without affecting catalyst activity is extremely important. Summary of the Invention

[0008] This invention addresses the problems existing in traditional MBTS synthesis processes by proposing a novel, low-cost, high-efficiency, and environmentally friendly process for synthesizing high-performance MBTS, as well as its applications.

[0009] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0010] A low-cost, high-efficiency, and environmentally friendly process for synthesizing MBTS, comprising the following steps:

[0011] (1) Add MBT to the solvent acetonitrile and heat to obtain mixture A;

[0012] (2) Add EGCG and metal salt CuCl2 to mixture A to obtain mixture B;

[0013] (3) Solution B is sealed and oxygen is introduced. The oxidation reaction is carried out under stirring and oxygen circulation until the pressure no longer decreases, and an acetonitrile mixture containing MBTS solid is obtained.

[0014] (4) Filter to obtain MBTS solid and filtrate C. The MBTS solid is washed with acetonitrile to obtain MBTS product and washing solution D. The MBTS product is dried.

[0015] (5) Add MBT to filtrate C and washing solution D, and repeat steps (1)-(4).

[0016] Preferably, in step (1), the mass fraction of MBT in solution A is 2-25%, and the heating temperature is 35-60℃.

[0017] The environmentally friendly synthesis process for MBTS provided by this invention has the following reaction formula:

[0018] .

[0019] As shown in the reaction formula above, MBT, which is partially dissolved in acetonitrile, is reacted with EGCG and metal salt CuCl2 at a certain temperature while oxygen is continuously pumped in using a circulating pump (gas circulation inside the reactor). After the reaction is completed, MBTS and water are obtained, and the filtrate after the reaction is completed is recycled.

[0020] The reaction mechanism is as follows:

[0021] .

[0022] Cu 2+ It has strong oxidizing properties; it can oxidize EGCG to EGCG-O (an EGCG derivative containing an aldehyde group), while being reduced to Cu itself. + EGCG-O can activate MBT dissolved in acetonitrile, generating MBT radicals, which are then reduced to EGCG. The MBT radicals further condense to form MBTS. Cu + It continues to be oxidized to Cu 2+ The entire reaction cycle continues until all MBT is converted to MBTS.

[0023] Preferably, in step (2), the mass ratio of EGCG:CuCl2:MBT is (0.00005-0.2):(0.00002-0.05):1.

[0024] Preferably, in step (3), the oxygen pressure is 0.3-1 MPa.

[0025] Preferably, in step (4), the drying temperature is 60-150℃.

[0026] Preferably, in step (5), the amount of EGCG and CuCl2 added is reduced by 80-90% during the repetition of steps (1)-(4).

[0027] The process of this invention is carried out in the solvent acetonitrile in an anhydrous environment. Acetonitrile has a certain solubility for the raw material MBT but is almost insoluble in the product MBTS, making it a natural advantage as an ideal solvent for MBTS synthesis. Furthermore, through process development and parameter adjustment, the reaction conditions are made milder and the reaction time shorter. At approximately 60°C and an oxygen pressure of 1 MPa, the oxidation reaction is completed in less than 1 hour. The process proposed in this invention can guarantee a product yield of over 98% and a purity of over 98%. The mother liquor can be recycled more than 30 times, greatly reducing solvent consumption. It is low-cost and environmentally friendly. This invention uses O2 as the oxidant, which is of high quality and low price, and EGCG and CuCl2 as catalysts. The entire preparation process is fast and produces high-quality products.

[0028] MBTS predispersed masterbatch can improve the vulcanization speed of natural or synthetic rubber and significantly shorten scorching and vulcanization time. Currently, the highest level of MBTS available on the market for predispersion is DM-75. However, MBTS produced by this process has advantages such as good quality and performance, low oil absorption value, and fast vulcanization speed. With the adjustment of the predispersion process formula, DM-80 product has been successfully produced. Mooney data shows that DM-80 meets the technical specifications of downstream customers.

[0029] This invention proposes the application of MBTS, produced by the above process, in DM-80, and provides the preferred raw materials and their mass fractions for DM-80 production: 78-80 parts MBTS, 1-2 parts stearic acid, 2 parts paraffin wax, 7-9 parts EPDM rubber, and 10-12 parts naphthenic oil. DM-80 produced under this process formula meets customer technical specifications, with a Mooney score of approximately 50.00. The proposed solution has been included in the Shandong Provincial Key Research and Development Program, project number: 2023CXGC010605.

[0030] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0031] 1. The MBTS product prepared by the process proposed in this invention has high purity, the preparation process is rapid, and the reaction solvent and catalyst can be recycled more than 30 times while still maintaining high activity.

[0032] 2. Because the entire reaction takes place in a pure oxygen environment, the raw material is MBT, and the oxidizing power of O2 itself is not too strong, the product MBTS will not be peroxidized into sulfonic acid compounds. Compared with processes such as hydrogen peroxide, it is easier to find the endpoint and the product quality is more stable.

[0033] 3. MBTS produced using this process has a shorter vulcanization time and lower oil absorption value compared to commercially available MBTS, and can successfully produce MBTS predispersed masterbatch granules DM-80. Attached Figure Description

[0034] Figure 1 This is the liquid chromatogram of the product from Example 1.

[0035] Figure 2 The image shows the liquid chromatogram of the product after the mother liquor was recycled 30 times in Example 7.

[0036] Figure 3 The results are from the vulcanization test in Example 8. Detailed Implementation

[0037] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described below with reference to specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0038] Numerous specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways than those described herein, and therefore the invention is not limited to the specific embodiments disclosed in the following specification.

[0039] Example 1

[0040] 60g of MBT was added to 600ml of acetonitrile. The temperature inside the reactor was raised from room temperature to 60°C and kept constant to obtain a partially dissolved MBT solution. After 5 minutes, 0.1g of EGCG and 0.05g of CuCl2 were added. The reactor was kept sealed and oxygen was introduced to 1MPa. The stirring speed was set to 400r / min, and the oxygen circulation pump was turned on. When the pressure inside the reactor stopped changing, cooling water was introduced into the reactor jacket to lower the temperature. The reaction time in this embodiment was 42min. After cooling, solid MBTS and a solution containing the catalyst were obtained. The solid and filtrate were obtained by filtration. The obtained solid was washed and dried with fresh acetonitrile to obtain MBTS with a yield of 98.2% and a purity of 98.47% as determined by liquid chromatography (see Appendix). Figure 1 The filtrate and washing liquid obtained from vacuum filtration can be combined and added to the raw material MBT for recycling.

[0041] Example 2

[0042] (1) Take 40g of MBT and add it to 600ml of acetonitrile. The reaction temperature is 55℃, and a partially dissolved MBT solution A is obtained.

[0043] (2) Add 0.5g EGCG and 0.05g CuCl2 to step (1), oxygenate to 0.3MPa, set the stirring speed to 500r / min, and turn on the oxygen circulation pump. After the pressure inside the reactor no longer changes, cool down to obtain MBTS solid and solution B containing the catalyst. The reaction time in this example is 0.5h.

[0044] (3) Solution B from step (2) is obtained by filtration and can be recycled in step (1). The obtained solid is washed and dried to obtain MBTS with a yield of 98% and a purity of 98.16% as detected by liquid chromatography. Solution C obtained by washing can be mixed with solution B and recycled together in step (1).

[0045] Example 3

[0046] (1) Take 80g of MBT and add it to 1000ml of acetonitrile. The reaction temperature is 58℃, and a partially dissolved MBT solution A is obtained.

[0047] (2) Add 0.1g EGCG and 0.02g CuCl2 to step (1), oxygenate to 0.8MPa, set the stirring speed to 350r / min, and turn on the oxygen circulation pump. After the pressure inside the reactor no longer changes, cool down to obtain MBTS solid and solution B containing the catalyst. The reaction time in this example is 36min.

[0048] (3) Solution B from step (2) is obtained by filtration and can be recycled in step (1). The obtained solid is washed and dried to obtain MBTS with a yield of 98.8% and a purity of 99.28% as detected by liquid chromatography. The washed solution C can be mixed with solution B and recycled together in step (1).

[0049] Example 4

[0050] (1) Take 30g of MBT and add it to 900ml of acetonitrile. The reaction temperature is 40℃, and a partially dissolved MBT solution A is obtained.

[0051] (2) Add 0.2g EGCG and 0.04g CuCl2 to step (1), oxygenate to 0.5MPa, set the stirring speed to 750r / min, and turn on the oxygen circulation pump. After the pressure inside the reactor no longer changes, cool down to obtain MBTS solid and solution B containing the catalyst. The reaction time in this example is 54min.

[0052] (3) Solution B from step (2) is obtained by filtration and can be recycled in step (1). The obtained solid is washed and dried to obtain MBTS with a yield of 98.1% and a purity of 98.16% as determined by liquid chromatography. The washed solution C can be mixed with solution B and recycled together in step (1).

[0053] Example 5

[0054] (1) Take 100g MBT and add it to 600ml of acetonitrile. The reaction temperature is 48℃, and a partially dissolved MBT solution A is obtained.

[0055] (2) Add 0.3g EGCG and 0.06g CuCl2 to step (1), oxygenate to 0.7MPa, set the stirring speed to 550r / min, and turn on the oxygen circulation pump. After the pressure inside the vessel no longer changes, react for 1 hour, then cool down to obtain MBTS solid and solution B containing the catalyst.

[0056] (3) Solution B from step (2) is obtained by filtration and can be recycled in step (1). The obtained solid is washed and dried to obtain MBTS with a yield of 98.4% and a purity of 98.35% as detected by liquid chromatography. The washed solution C can be mixed with solution B and recycled together in step (1).

[0057] Example 6

[0058] (1) Take 60g of MBT and add it to 800ml of acetonitrile. The reaction temperature is 55℃, and a partially dissolved MBT solution A is obtained.

[0059] (2) Add 0.1g EGCG and 0.03g CuCl2 to step (1), oxygenate to 0.8MPa, set the stirring speed to 300r / min, and turn on the oxygen circulation pump. After the pressure inside the vessel no longer changes, the reaction time is 49min. Cool down to obtain MBTS solid and solution B containing the catalyst.

[0060] (3) Solution B from step (2) is obtained by filtration and can be recycled in step (1). The obtained solid is washed and dried to obtain MBTS with a yield of 98.2% and a purity of 98.90% as determined by liquid chromatography. Solution C obtained by washing can be mixed with solution B and recycled together in step (1).

[0061] Example 7

[0062] (1) Take 780ml of the mother liquor from Example 6 + 20ml of fresh acetonitrile (total 800ml), add 60g of MBT, and react at 55℃ to obtain a partially dissolved MBT solution A.

[0063] (2) Add 0.006g EGCG and 0.005g CuCl2 to step (1), oxygenate to 0.8MPa, set the stirring speed to 300r / min, and turn on the oxygen circulation pump. After the pressure inside the vessel no longer changes, react for 50min, then cool down to obtain MBTS solid and solution B containing the catalyst.

[0064] (3) Solution B from step 2 was obtained by filtration. The resulting solid was washed and dried to obtain MBTS with a yield of 98.4% and a purity of 98.75% as determined by liquid chromatography. Solution C obtained from washing was mixed with solution B (780 ml was recycled, and 20 ml of fresh acetonitrile was added; if the mother liquor was less than 780 ml, it was replenished with fresh acetonitrile; if the mother liquor was more than 780 ml, the excess mother liquor was removed and stored for later use). Steps (1)-(3) were repeated. It was verified that after the mother liquor was recycled 30 times, the yield and purity of the obtained product remained basically unchanged, and the reaction time was between 48 and 53 min. The chromatogram of the product after the mother liquor was recycled 30 times is shown in the figure. Figure 2 .

[0065] Product performance testing

[0066] 1. Vulcanization test

[0067] Following the vulcanization curve test method, 100 parts of natural rubber, 60 parts of carbon black, 2 parts of stearic acid, 10 parts of aromatic oil, 3.7 parts of ZnO-80, 1.5 parts of DM, and 0.5 parts of sulfur were used. Commercially available MBTS (manufacturer: Shanghai Maclean Biochemical Technology Co., Ltd.) was processed and tested according to the same formula. (Experiment number: the test experiment of commercially available MBTS is designated as Experiment 1, and the test experiment of MBTS prepared in Example 1 is designated as Experiment 2). The test results are shown in […]. Figure 3 The testing process was as follows: First, all materials except MBTS and sulfur were added to a 1L internal mixer in sequence and mixed evenly. The roller gap of the XK-150 open mill was adjusted to the minimum, and the mixed rubber was passed through the open mill 2-3 times. Then, the roller gap of the open mill was adjusted to 2mm for sheeting. The weights of the mixed rubber, sulfur, and accelerator MBTS were weighed according to the formula ratio. The roller gap of the open mill was adjusted to 0.25mm, and the width of the open mill baffle was adjusted. The mixed rubber was wrapped around the rollers to ensure that the rubber accumulation height between the two rollers of the open mill was greater than 1cm. The accelerator MBTS and sulfur were added in sequence. The rubber compound was cut twice and triangularly wrapped to ensure that the accelerator and vulcanizing agent were evenly dispersed. After the rubber compound was evenly dispersed, the roller gap of the open mill was adjusted to 2mm for sheeting. By comparison, it can be seen that the MBTS prepared in Example 1 of this invention has a shorter vulcanization time (t90 of 4.7min in Experiment 1 and t90 of 4.44min in Experiment 2). In addition, MBTS produced by this process and commercially available MBTS were tested according to the oil absorption value test method. By calculation, the oil absorption value of MBTS prepared in Example 1 was 12.2, and the oil absorption value of commercially available MBTS was 14.6. The test data in Examples 2-7 were not much different from those in Example 1.

[0068] 2. Mooney Test

[0069] Following the Mooney test method, 80 parts of MBTS prepared in Example 1, 1 part of stearic acid, 2 parts of paraffin wax, 7 parts of EPDM rubber, and 10 parts of naphthenic oil were added to a mixer in three batches and mixed at 50-65℃ for 8 minutes, with the temperature not exceeding 70℃. After mixing, samples were taken and processed using a roller press and tablet press. The Mooney test was then conducted at 50℃, and the measured Mooney results were 49.90, 48.80, and 50.90, respectively, meaning that all three test results were around 50. The test data in Examples 2-7 were not significantly different from those in Example 1. In a comparative experiment, the MBTS was replaced with two commercially available MBTS products (manufacturers: Shanghai Maclean Biochemical Technology Co., Ltd. and Guangdong Wengjiang Chemical Reagent Co., Ltd.). Other process formulations and testing procedures remained unchanged. After mixing, the material from the mixer did not form lumps and could not be sampled for testing, indicating that the DM-80 production failed.

[0070] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments for application in other fields. However, any simple modifications, equivalent changes, and modifications 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 protection scope of the present invention.

Claims

1. An environmentally friendly process for synthesizing high-performance MBTS at low cost and high efficiency, characterized in that... The steps are as follows: (1) Add MBT to the solvent acetonitrile and heat to obtain mixture A; (2) Add EGCG and metal salt CuCl2 to mixture A to obtain mixture B; (3) Mixture B is sealed and oxygen is introduced. Oxidation reaction is carried out under stirring and oxygen circulation until the pressure no longer decreases, and an acetonitrile mixture containing MBTS solid is obtained. (4) Filter to obtain MBTS solid and filtrate C. The MBTS solid is washed with acetonitrile to obtain MBTS product and washing solution D. The MBTS product is dried. (5) Add MBT to filtrate C and washing solution D, and repeat steps (1)-(4).

2. The environmentally friendly process for synthesizing high-performance MBTS at low cost and high efficiency according to claim 1, characterized in that... In step (1), the mass fraction of MBT in the mixture A is 2-25%, and the heating temperature is 35-60℃.

3. The environmentally friendly process for synthesizing high-performance MBTS at low cost and high efficiency according to claim 1, characterized in that... In steps (1)-(2), the mass ratio of EGCG:CuCl2:MBT is (0.00005-0.2):(0.00002-0.05):

1.

4. The environmentally friendly process for synthesizing high-performance MBTS at low cost and high efficiency according to claim 1, characterized in that... In step (3), the initial pressure of oxygen is 0.3-1 MPa.

5. The environmentally friendly process for synthesizing high-performance MBTS at low cost and high efficiency according to claim 1, characterized in that... In step (4), the drying temperature is 60-150℃.

6. The environmentally friendly process for synthesizing high-performance MBTS at low cost and high efficiency according to claim 1, characterized in that... In step (5), the amount of EGCG and CuCl2 added is reduced by 80-90% during the process of repeating steps (1)-(4).

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