Industrialized preparation method of benzoate plasticizer
By using ethylene glycol dibutyl ether as a water-carrying agent, the esterification reaction of benzoate plasticizers is optimized, and the problem of high color and hydroxyl values is solved, and the risk of pipeline blockage is reduced, which improves reaction efficiency and product quality.
Patent Information
- Application Number
- CN202510301508.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-14
- Publication Date
- 2025-07-04
AI Technical Summary
In the prior art, the industrial production of benzoate plasticizers has problems with high color and high hydroxyl value, and there is a risk of pipeline blockage during the reflow process.
Ethylene glycol dibutyl ether was used as the aqueous agent, with a boiling point of 202°C, and an esterification reaction was carried out with a benzoate plasticizer under condensation and reflux conditions, the reaction temperature and time were controlled, and the reaction system was optimized. The ratio of polyol to benzoic acid was 1.150-1.025:2, and the catalyst was monobutyl tin oxide, etc., and the esterification reaction was carried out.
It reduces the colority and hydroxyl value of benzoate plasticizers, reduces the accumulation of benzoic acid in the water distributor and condenser tube, improves the reaction rate and yield, and reduces the risk of pipeline blockage.
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Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of benzoate synthesis, and particularly relates to a method for industrial preparation of benzoate plasticizers. Background Art
[0002] At present, there are mainly three process routes for the synthesis of benzoate plasticizers: transesterification method, acyl halide method and direct esterification method. Among them, the transesterification method will produce small molecule alcohols, increasing the treatment process. At the same time, the price of methyl benzoate or ethyl benzoate is higher than that of benzoic acid, so this process is not economical; the acyl halide method will generate by-products such as HCl, which will cause relatively serious corrosion to equipment, etc., and by-products such as HCl will also increase the manufacturing cost. Therefore, the direct esterification method is often used in the current industrial production method of benzoate plasticizers.
[0003] However, large-scale production is different from microscale reaction. At present, the products industrially produced by the direct esterification method on the market have problems of high colority (Platinum-Cobalt color number greater than 30) and high hydroxyl value, and further post-treatment is required.
[0004] On the other hand, during the process of industrial large-scale production in kilograms and tons, during the reflux process, a small amount of benzoic acid will evaporate into the reflux pipe and the water separator for condensation due to azeotropy. The melting point of benzoic acid is 122.13 °C, which is a solid at room temperature, and benzoic acid is slightly soluble in water (0.85 / 100 ml at 50 °C, 4.55 / 100 ml at 90 °C). The solid density of benzoic acid is greater than that of water, and there is a risk of blocking the water separator.
[0005] Therefore, a method for industrial preparation of benzoate plasticizers is proposed, so that the colority and hydroxyl value of the benzoate plasticizers produced by industrial large-scale production are lower, and at the same time, the reaction system can be optimized and the risk of pipeline blockage during the reflux process of production can be reduced. Summary of the Invention
[0006] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. For this reason, the present invention provides a method for industrial preparation of benzoate plasticizers; the invention can make the colority and hydroxyl value of the benzoate plasticizers produced by industrial large-scale production lower, and at the same time can optimize the reaction system and reduce the risk of pipeline blockage during the reflux process of production.
[0007] The inventive concept of the present invention is as follows: The boiling points of conventional water-carrying agents such as toluene, benzene, carbon tetrachloride, etc. are relatively low, while the reaction temperature is 200°C - 250°C. This results in the premature reflux of water-carrying agents such as toluene during the heating process before the reaction starts. Even in a stirred reaction system, the water-carrying agent in the reflux state can only stay briefly in the upper layer of the reaction system and randomly boil and vaporize, unable to penetrate into the middle and lower layers of the reaction system, resulting in limited function of toluene. At the same time, using low-boiling solvents such as toluene may, on the one hand, prevent the reaction system from reaching the reaction temperature; on the other hand, violent reflux may cause a large amount of reaction materials to be carried out, affecting the yield. Therefore, a water-carrying agent with a boiling point close to the reaction temperature is required.
[0008] The first aspect of the present invention provides a method for industrial preparation of benzoate plasticizers.
[0009] Specifically, a method for industrial preparation of benzoate plasticizers, the preparation method includes esterification reaction of polyol, benzoic acid, catalyst, and water-carrying agent under the condition of condensation reflux to obtain the benzoate plasticizer; the boiling point of the polyol is greater than 180°C; the molar ratio of the polyol to the benzoic acid is 1.150 - 1.025:2; the amount of the polyol used is greater than or equal to 1.5 mol, and the amount of the benzoic acid used is greater than or equal to 3 mol; the water-carrying agent includes ethylene glycol dibutyl ether.
[0010] Compared with the prior art, the beneficial effects of the method for industrial preparation of benzoate plasticizers provided by this first aspect are as follows: Innovatively use ethylene glycol dibutyl ether as the water-carrying agent in the industrial preparation method of benzoate plasticizers. The boiling point of ethylene glycol dibutyl ether is 202°C, the boiling point of benzoic acid is 249°C, and the boiling point of the polyol is greater than 180°C, which can reduce the chromaticity and hydroxyl value of the large-scale production of benzoate plasticizers; at the same time, the benzoic acid in the water separator and condenser is significantly reduced; ethylene glycol dibutyl ether can also promote the forward reaction, improve the reaction rate, and make the reaction more complete; ensure that benzoic acid can be dissolved in the solvent, reduce the risk of benzoic acid precipitation, and improve the yield.
[0011] Preferably, the amount of the polyol used is greater than or equal to 15 mol, and the amount of the benzoic acid used is greater than or equal to 30 mol; more preferably, the amount of the polyol used is greater than or equal to 150 mol, and the amount of the benzoic acid used is greater than or equal to 300 mol; further preferably, the amount of the polyol used is greater than or equal to 150 mol and less than or equal to 1500 mol, and the amount of the benzoic acid used is greater than or equal to 300 mol and less than or equal to 3000 mol.
[0012] Preferably, the polyol includes at least one of propylene glycol, dipropylene glycol, and diethylene glycol.
[0013] Preferably, the molar ratio of the polyol to the benzoic acid is 1.150 - 1.025:2.
[0014] Preferably, the water-carrying agent is ethylene glycol dibutyl ether.
[0015] Preferably, the addition amount of the water-carrying agent is 5 - 20 wt% of the mass of the benzoic acid.
[0016] Preferably, the catalyst includes at least one of monobutyltin oxide, stannous oxide, stannous oxalate, stannous octoate, and dibutyltin dilaurate.
[0017] Preferably, the addition amount of the catalyst is 0.05 - 0.5 wt% of the total mass of the polyol, the benzoic acid, and the water-carrying agent.
[0018] Preferably, the reaction temperature of the esterification reaction is 200 - 240 °C; more preferably, the reaction temperature of the esterification reaction is 200 - 235 °C.
[0019] Preferably, the temperature control step of the esterification reaction includes first slowly heating from room temperature to 200 - 210 °C and holding for 2.5 - 3.5 h, and then heating to 230 - 235 °C and holding for 4.5 - 5.5 h; more preferably, the temperature control step of the esterification reaction includes first slowly heating from room temperature to 200 - 210 °C and holding for 2.9 - 3.1 h, and then heating to 230 - 235 °C and holding for 4.9 - 5.1 h.
[0020] Preferably, the feeding gas atmosphere of the esterification reaction is a nitrogen atmosphere.
[0021] Preferably, the outlet temperature of the condenser is 40 - 80 °C.
[0022] Preferably, the esterification reaction further includes a reaction device, and the reaction device includes a reaction kettle, a stirring device, a condenser, and a water separator.
[0023] Preferably, the hydroxyl value of the benzoate plasticizer is less than or equal to 5.0 mgKOH / g; more preferably, the hydroxyl value of the benzoate plasticizer is less than or equal to 4.5 mgKOH / g.
[0024] Preferably, the platinum-cobalt color number of the benzoate plasticizer is less than or equal to 30; more preferably, the platinum-cobalt color number of the benzoate plasticizer is less than or equal to 25.
[0025] Preferably, the preparation method further includes a post-treatment step, and the post-treatment step includes vacuum distillation, alkali washing, water washing, and dehydration.
[0026] Preferably, the temperature of the vacuum distillation is 200 - 230 °C and the time is 1.5 - 2.5 h.
[0027] Preferably, the solvent used in the caustic washing includes an aqueous sodium hydroxide solution containing 4.5 - 5.5 wt%, the amount of the aqueous sodium hydroxide solution is 15 - 25 wt% of the benzoate plasticizer, the temperature of the caustic washing is 80 - 90 °C, and the time of the caustic washing is 0.25 - 0.75 h.
[0028] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Innovatively use ethylene glycol dibutyl ether as the water-carrying agent in the industrial preparation method of benzoate plasticizer. The boiling point of ethylene glycol dibutyl ether is 202 °C, the boiling point of benzoic acid is 249 °C, and the boiling point of polyol is greater than 180 °C, which can reduce the chromaticity and hydroxyl value of the benzoate plasticizer in large-scale production; at the same time, the benzoic acid in the water separator and the condenser tube is significantly reduced; ethylene glycol dibutyl ether can also promote the forward reaction, improve the reaction rate, and make the reaction more complete; ensure that benzoic acid can be dissolved in the solvent, reduce the risk of benzoic acid precipitation, and improve the yield. Description of the Drawings
[0029] Figure 1 It is a picture of the accumulation of solids in the water separator after the reaction in Example 1; Figure 2 It is a picture of the accumulation of solids in the water separator after the reaction in Comparative Example 4. Detailed Embodiments
[0030] In order to make the technical solutions described in the present invention clearer and more understandable to those skilled in the art, the following examples are listed for illustration. It should be noted that the following examples do not limit the scope of protection required by the present invention.
[0031] Unless otherwise specified, the raw materials, reagents or devices used in the following examples can be obtained from conventional commercial channels or can be obtained by existing known methods.
[0032] In the present invention, the test method for platinum-cobalt chromaticity: GB / T 3143 (combined with the standard curve method).
[0033] In the present invention, the test method for hydroxyl value: GB / T 12008.3.
[0034] Examples 1 - 3 The preparation device for the benzoate plasticizer is: a 10 L reaction kettle with a stirring device, and the reaction kettle can be equipped with a condenser tube with a water separator.
[0035] The preparation method for the benzoate plasticizer is: (1) After evacuating and replacing nitrogen in a 10L reactor equipped with a stirring device, while stirring, add polyols (dipropylene glycol, diethylene glycol, or propylene glycol), benzoic acid, ethylene glycol dibutyl ether (15wt% of the mass of benzoic acid), and stannous oxide (0.2wt% of the total mass of dipropylene glycol, benzoic acid, and ethylene glycol dibutyl ether). After feeding, install a condenser with a water separator to form a reaction system; (2) Heat the reaction system from room temperature to 200°C at a rate of 5°C / min and stir for 3h, then heat to 235°C at a rate of 5°C / min and stir for 5h to obtain the crude product; during heating and reaction, control the flow rate of the coolant in the condenser and maintain the steam temperature at the outlet of the condenser in the range of 50 - 60°C; (3) Naturally cool the crude product to 220°C, remove the condenser and carry out vacuum distillation for 2h, collect the heavy phase (unevaporated product); use a 5wt% sodium hydroxide aqueous solution equivalent to 20wt% of the mass of the heavy phase to carry out alkali washing at 80 - 90°C for 0.5h, let it stand for liquid separation, collect the organic phase, and carry out alkali washing 2 times in total; wash with water 2 times to obtain the finished benzoate plasticizer.
[0036] After the reaction is completed, check the status of the water separator and condenser, transfer out all the solids therein and measure the weight and record it in Table 1.
[0037] The dosages of dipropylene glycol, benzoic acid, ethylene glycol dibutyl ether, and stannous oxide are recorded in Table 1.
[0038] Detect the hydroxyl value and platinum-cobalt color number of the prepared benzoate plasticizer and record them in Table 1.
[0039] Comparative Examples 1 - 3 The differences between Comparative Examples 1 - 3 and Example 1 are that the raw materials and dosages are different. The raw materials and dosages of Comparative Examples 1 - 3 are recorded in Table 1, and the remaining preparation methods are the same.
[0040] After the reaction is completed, check the status of the water separator and condenser, transfer out all the solids therein and measure the weight and record it in Table 1.
[0041] Detect the hydroxyl value and platinum-cobalt color number of the prepared benzoate plasticizer and record them in Table 1.
[0042] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that ethylene glycol dibutyl ether is replaced with toluene in equal mass (i.e., 15wt% of the mass of benzoic acid). The raw materials and dosages of Comparative Example 4 are recorded in Table 1, and the remaining preparation methods are the same.
[0043] The preparation method of the benzoate plasticizer is as follows: After evacuating and replacing nitrogen in a 10L reactor equipped with a stirring device, while stirring, dipropylene glycol, benzoic acid, toluene (15wt% of the mass of benzoic acid), and stannous oxide (0.2wt% of the total mass of dipropylene glycol, benzoic acid, and ethylene glycol dibutyl ether) were added. After feeding, a condenser with a water separator was installed to form a reaction system. (2) The reaction system was heated from room temperature to 200°C at a rate of 5°C / min and stirred for 3 hours, and then heated to 235°C at a rate of 5°C / min and stirred for 5 hours to obtain a crude product. During heating and reaction, the flow rate of the coolant in the condenser was controlled, the drainage of the water separator was controlled regularly to prevent condensed water from flowing back into the reaction system, and the steam temperature at the outlet of the condenser was maintained in the range of 50 - 60°C. (3) The crude product was naturally cooled to 220°C, the condenser was removed, and vacuum distillation was carried out for 2 hours to collect the heavy phase (unevaporated product). The heavy phase was washed with a 5wt% aqueous sodium hydroxide solution equivalent to 20wt% of its mass at 80 - 90°C for 0.5 hours, allowed to stand for liquid separation, and the organic phase was collected. This alkali washing was carried out 2 times in total; it was washed with water 2 times to obtain the finished benzoate plasticizer.
[0044] After the reaction was completed, the states of the water separator and the condenser were checked, and all the solids in them were transferred out and weighed, and the results were recorded in Table 1.
[0045] The hydroxyl value and platinum-cobalt color number of the prepared benzoate plasticizer were detected and recorded in Table 1.
[0046] Figure 1 It is a picture of the accumulation of solids in the water separator after the reaction of Example 1. Figure 2 It is a picture of the accumulation of solids in the water separator after the reaction of Comparative Example 4. It can be clearly seen that after the reaction of Comparative Example 4, a large amount of white benzoic acid solids accumulated in the water separator, and the height of the solids occupied the entire water storage space in the water separator. While after the reaction of Example 1, the accumulation of white solids in the water separator was significantly less.
[0047] Table 1 Raw material dosages of Examples 1 - 3 and Comparative Examples 1 - 4, and the hydroxyl value and platinum-cobalt color number of the corresponding plasticizers Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Dipropylene glycol (mol) 20.7 20.7 20.7 25.0 20.7 Diethylene glycol (mol) 22.0 Propylene glycol (mol) 23.0 Benzoic acid (mol) 36.0 40.0 40.0 36.0 36.0 36.0 36.0 Catalyst dosage (wt%) 0.20 0.15 0.15 0.20 0.60 0.20 0.20 Ethylene glycol dibutyl ether (wt%) 15 10 5 0 15 15 Toluene (wt%) 15 Hydroxyl value (mgKOH / g) 2.5 3.0 2.3 21.3 1.8 12.3 16.4 Platinum-cobalt color number 18 20 22 32 53 22 35 Solid mass in water separator and condenser tube (g) 51.6 64.3 41.2 273.4 82.4 73.1 242.6 Note: The catalyst dosage is the percentage (wt%) of the total mass of dipropylene glycol, benzoic acid, and ethylene glycol dibutyl ether, the ethylene glycol dibutyl ether dosage is the percentage (wt%) of the mass of benzoic acid, and the toluene dosage is the percentage (wt%) of the mass of benzoic acid.
[0048] Compared with Example 1, in Comparative Example 1, no water-carrying agent was added during the reaction, and a large amount of benzoic acid was found to precipitate during both the reaction and vacuum distillation processes, indicating that benzoic acid did not react completely.
[0049] In Comparative Example 3, compared with Example 1, the alcohol-acid ratio was increased to 1.25:2, and more mono-esters were produced in the reaction product, resulting in a relatively high hydroxyl value of the product.
[0050] In Comparative Example 4, ethylene glycol dibutyl ether in Example 1 was replaced with toluene. The hydroxyl value of the finally obtained product was 16.4 mgKOH / g, indicating that there were more mono-esters in the obtained product. At the same time, the platinum-cobalt color number was 35, indicating that there were more side reactions in the reaction process than in Example 1.
[0051] Comparative Example 5 The difference between Comparative Example 5 and Example 1 was that the reaction system was scaled down by 100 times in equal proportion: the amounts of raw materials (dipropylene glycol, benzoic acid, catalyst, ethylene glycol dibutyl ether) were scaled down by 100 times, and a 100 mL round-bottom flask with magnetic stirring and a condenser that could be installed was selected as the preparation device, and the rest of the preparation methods were the same.
[0052] After the reaction was completed, the states of the condenser and the water separator were checked, and all the solids in them were transferred out and weighed, which was 0.53 g.
[0053] The hydroxyl value of the prepared benzoate plasticizer was detected to be 2.7, and the platinum-cobalt chromaticity was 20.
[0054] Comparative Example 6 The difference between Comparative Example 6 and Comparative Example 4 was that the reaction system was scaled down by 100 times in equal proportion: the amounts of raw materials (dipropylene glycol, benzoic acid, catalyst, ethylene glycol dibutyl ether) were scaled down by 100 times, and a 100 mL round-bottom flask with magnetic stirring and a condenser that could be installed was selected as the preparation device, and the rest of the preparation methods were the same.
[0055] After the reaction was completed, the states of the condenser and the water separator were checked, and all the solids in them were transferred out and weighed, which was 0.71 g, similar to that of Comparative Example 5. In Comparative Example 6, the reaction scale of benzoic acid was reduced to 0.36 moL, and the scaled-down reaction system did not show the problems of relatively high hydroxyl value and relatively high chromaticity that occurred in Comparative Example 4.
[0056] The hydroxyl value of the prepared benzoate plasticizer was detected to be 2.3, and the platinum-cobalt chromaticity was 25.
Claims
1. An industrial preparation method of a benzoate plasticizer, characterized in that, The preparation method includes an esterification reaction of a polyol, benzoic acid, a catalyst, and a water-carrying agent under the condition of condensation reflux to obtain the benzoate plasticizer; The boiling point of the polyol is greater than 180 °C; The molar ratio of the polyol to the benzoic acid is 1.150 - 1.025:2; the amount of the polyol used is greater than or equal to 1.5 mol, and the amount of the benzoic acid used is greater than or equal to 3 mol; The water-carrying agent includes ethylene glycol dibutyl ether.
2. The preparation method according to claim 1, characterized in that, The polyol includes at least one of propylene glycol, dipropylene glycol, and diethylene glycol.
3. The preparation method according to claim 1, wherein, The amount of the polyol used is greater than or equal to 15 mol, and the amount of the benzoic acid used is greater than or equal to 30 mol.
4. The preparation method according to claim 1, characterized in that, The addition amount of the water-carrying agent is 5 - 20 wt% of the mass of the benzoic acid.
5. The preparation method according to claim 1, characterized in that, The catalyst includes at least one of monobutyltin oxide, stannous oxide, stannous oxalate, stannous octoate, and dibutyltin dilaurate.
6. The preparation method according to claim 1, wherein, The reaction temperature of the esterification reaction is 200 - 240 °C.
7. The preparation method according to claim 6, characterized in that, The temperature control step of the esterification reaction includes slowly heating from room temperature to 200 - 210 °C and holding for 2.5 - 3.5 h, and then heating to 230 - 235 °C and holding for 4.5 - 5.5 h.
8. The preparation method according to claim 1, characterized in that, The esterification reaction further includes a reaction device, and the reaction device includes a reaction kettle, a stirring device, a condenser, and a water separator.
9. The preparation method according to claim 1, wherein The hydroxyl value of the benzoate plasticizer is less than or equal to 5.0 mgKOH / g; the platinum-cobalt color number of the benzoate plasticizer is less than or equal to 30.
10. The preparation method according to claim 1, wherein, The preparation method further includes a post-treatment step, and the post-treatment step includes vacuum distillation, alkali washing, water washing, and dehydration.