Preparation method of methacrylic acid 2-butoxyethyl ester

Abstract

The invention provides a preparation method of methacrylic acid 2-butoxyethyl ester, and belongs to the technical field of organic synthesis. According to the invention, p-hydroxyanisole (MEHQ) and 2, 2, 6, 6-tetramethylpiperidine oxide (TEMPO) are used as polymerization inhibitors at the same time, and the dual polymerization inhibitors are synergistically used, so that the auto-polymerization of methyl methacrylate (MMA) and 2-butoxyethyl methacrylate is reduced, and the conversion rate is increased.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology, specifically relating to a method for preparing 2-butoxyethyl methacrylate. Background Technology

[0002] 2-Butoxyethyl methacrylate, as a high-performance acrylate functional monomer, exhibits broad application value and technological advantages in the field of polymer materials. The unique butoxyethoxy side chain in the 2-butoxyethyl methacrylate molecular structure endows the polymer with excellent flexibility and substrate wettability, while retaining the high reactivity of the acrylate groups, making it an ideal choice for preparing high-performance polymers and copolymers.

[0003] Currently, 2-butoxyethyl methacrylate is mainly prepared via a protonic acid catalytic method (such as concentrated sulfuric acid or p-toluenesulfonic acid). This method causes severe corrosion to equipment and generates significant amounts of hazardous waste. Furthermore, because acrylate compounds tend to self-polymerize, and protonic acid catalysts promote this self-polymerization, the reaction yield is low. Existing technologies often use polymerization inhibitors to prevent the self-polymerization of acrylate monomers. While this improves the yield (crude product output) to some extent, the 2-butoxyethyl methacrylate content in the product remains low, and the conversion rate (pure product output) is not significantly improved. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing 2-butoxyethyl methacrylate. The preparation method provided by this invention has a high conversion rate.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing 2-butoxyethyl methacrylate, comprising the following steps: Methyl methacrylate, ethylene glycol monobutyl ether, tetrabutyl titanate, a first organic solvent, 2,2,6,6-tetramethylpiperidine oxide and p-hydroxyanisole were mixed and subjected to transesterification to obtain a mother liquor. The mother liquor was first distilled under reduced pressure to obtain the crude product; A second organic solvent, an acid solution, and an alkali metal salt solution are added to the crude product, followed by solid-liquid separation to obtain a liquid phase. The liquid phase was subjected to oil-water separation, and the resulting oil phase was subjected to a second vacuum distillation to obtain 2-butoxyethyl methacrylate.

[0006] Preferably, the mass ratio of 2,2,6,6-tetramethylpiperidine oxide, p-hydroxyanisole, and methyl methacrylate is (0.01~0.02):(0.015~0.025):(100~350).

[0007] Preferably, the molar ratio of methyl methacrylate to ethylene glycol monobutyl ether is (3~7):1.

[0008] Preferably, the molar ratio of methyl methacrylate to tetrabutyl titanate is (100~300):(1~2).

[0009] Preferably, the molar ratio of methyl methacrylate to the first organic solvent is (6~15):1.

[0010] Preferably, the mixing involves mixing other raw materials, adding a portion of methyl methacrylate, heating to the temperature for transesterification, and then continuing to add the remaining methyl methacrylate dropwise; the portion of methyl methacrylate is 30-70% of the total mass of methyl methacrylate.

[0011] Preferably, the temperature of the transesterification reaction is 80~100℃.

[0012] Preferably, the transesterification reaction takes 4 to 8 hours.

[0013] Preferably, the pressure of the first vacuum distillation is -0.09 to -0.1 MPa and the temperature is 80 to 100°C; the pressure of the second vacuum distillation is -0.09 to -0.1 MPa and the temperature is 100 to 120°C.

[0014] Preferably, the acid solution is hydrochloric acid or sulfuric acid.

[0015] This invention provides a method for preparing 2-butoxyethyl methacrylate, comprising the following steps: mixing methyl methacrylate, ethylene glycol monobutyl ether, tetrabutyl titanate, a first organic solvent, 2,2,6,6-tetramethylpiperidine oxide, and p-hydroxyanisole, and then subjecting the mixture to a transesterification reaction to obtain a mother liquor; subjecting the mother liquor to a first vacuum distillation to obtain a crude product; adding a second organic solvent, an acid, and an alkali metal salt solution to the crude product, followed by solid-liquid separation to obtain a liquid phase; subjecting the liquid phase to oil-water separation, and subjecting the resulting oil phase to a second vacuum distillation to obtain 2-butoxyethyl methacrylate. This invention simultaneously uses p-hydroxyanisole (MEHQ) and 2,2,6,6-tetramethylpiperidine oxide (TEMPO) as polymerization inhibitors. The synergistic use of these two inhibitors reduces the self-polymerization of methyl methacrylate (MMA) and 2-butoxyethyl methacrylate, thereby improving the conversion rate. Results from the examples show that the preparation method provided by this invention yields crude 2-butoxyethyl methacrylate with a purity higher than 85% and a conversion rate higher than 37%. Attached Figure Description

[0016] Figure 1 This is the gas chromatogram of the product obtained in Example 1 of the present invention; Figure 2 This is the gas chromatogram of the product obtained in Example 2 of the present invention; Figure 3 The gas chromatogram of the product obtained in Comparative Example 1 of this invention; Figure 4 The gas chromatogram of the product obtained in Comparative Example 2 of this invention; Figure 5 This is the gas chromatogram of the product obtained in Comparative Example 3 of the present invention. Detailed Implementation

[0017] All raw materials used in this invention are not particularly restricted in their source; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0018] There are no particular restrictions on the purity of any of the raw materials used in this invention, but industrially pure raw materials are preferred.

[0019] This invention provides a method for preparing 2-butoxyethyl methacrylate, comprising the following steps: Methyl methacrylate, ethylene glycol monobutyl ether, tetrabutyl titanate, a first organic solvent, 2,2,6,6-tetramethylpiperidine oxide and p-hydroxyanisole were mixed and subjected to transesterification to obtain a mother liquor. The mother liquor was first distilled under reduced pressure to obtain the crude product; A second organic solvent, an acid solution, and an alkali metal salt solution are added to the crude product, followed by solid-liquid separation to obtain a liquid phase. The liquid phase was subjected to oil-water separation, and the resulting oil phase was subjected to a second vacuum distillation to obtain 2-butoxyethyl methacrylate.

[0020] In this invention, methyl methacrylate, ethylene glycol monobutyl ether, tetrabutyl titanate, a first organic solvent, 2,2,6,6-tetramethylpiperidine oxide and p-hydroxyanisole are mixed and subjected to transesterification to obtain a mother liquor.

[0021] In this invention, the preferred molar ratio of methyl methacrylate to ethylene glycol monobutyl ether is (3-7):1, more preferably (4-6):1; as one embodiment of this invention, the molar ratio of methyl methacrylate to ethylene glycol monobutyl ether can be 3:1, 4:1, 5:1, 6:1, or 7:1. The transesterification reaction of methyl methacrylate and ethylene glycol monobutyl ether is shown in the following formula: .

[0022] Excess MMA is beneficial for the transesterification reaction and can further improve the product yield.

[0023] In this invention, the molar ratio of methyl methacrylate to tetrabutyl titanate is preferably (100~300):(1~2), more preferably (100~300):2. Tetrabutyl titanate is a catalyst for transesterification, and a molar ratio to MMA within the above range is beneficial for improving the yield.

[0024] In this invention, the preferred mass ratio of 2,2,6,6-tetramethylpiperidine oxide, p-hydroxyanisole, and methyl methacrylate is (0.01~0.02):(0.015~0.025):(100~350), more preferably 0.015:0.02:(100~350). As one embodiment of this invention, the mass ratio of 2,2,6,6-tetramethylpiperidine oxide, p-hydroxyanisole, and methyl methacrylate can be 0.015:0.02:129, 0.015:0.02:150, 0.015:0.02:180, 0.015:0.02:200, 0.015:0.02:250, or 0.015:0.02:300. TEMPO and MEHQ, as dual polymerization inhibitors, can suppress the self-polymerization of acrylate monomers. When the mass ratio of TEMPO, MEHQ to MMA is within the above range, it is beneficial to suppress the self-polymerization of MMA and 2-butoxyethyl methacrylate, thereby further improving the conversion rate.

[0025] In this invention, the molar ratio of methyl methacrylate to the first organic solvent is preferably (6-15):1, more preferably (8-12):1; as one embodiment of this invention, the molar ratio of methyl methacrylate to the first organic solvent can be 6:1, 6.5:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, or 14:1. The first organic solvent can dissolve the raw materials, allowing them to fully contact each other, lowering the reaction temperature, and reducing MMA self-polymerization; the amount of the first organic solvent within the above range is beneficial for further improving the yield and conversion rate.

[0026] In one embodiment of the present invention, the first organic solvent may be toluene.

[0027] In this invention, the mixing is preferably performed by mixing other raw materials, adding a portion of methyl methacrylate, heating to the temperature for transesterification, and then continuing to add the remaining methyl methacrylate dropwise. The portion of methyl methacrylate is preferably 30-70% of the total mass of methyl methacrylate, more preferably 40-60%. Stepwise addition of MMA helps to suppress its self-polymerization and further improves the yield. In an embodiment of this invention, the remaining MMA is added dropwise using a constant pressure funnel over a period of 4 hours, with continuous stirring.

[0028] In this invention, the temperature of the transesterification reaction is preferably 80-100°C, more preferably 90°C. A temperature within this range is beneficial for the transesterification reaction and reduces the self-polymerization of MMA, thereby further improving the yield.

[0029] In this invention, the transesterification reaction time is preferably 4-8 hours, more preferably 6-7 hours. The transesterification reaction time is calculated from the completion of MMA addition. A transesterification reaction time within the above range is beneficial for the complete progress of the transesterification reaction, further improving the yield.

[0030] In one embodiment of the present invention, the transesterification reaction can be carried out in a four-necked flask with continuous stirring.

[0031] After obtaining the mother liquor, the present invention performs a first vacuum distillation on the mother liquor to obtain the crude product.

[0032] In this invention, the pressure of the first vacuum distillation is preferably -0.09 to -0.1 MPa, more preferably -0.095 MPa; the temperature of the first vacuum distillation is preferably 80 to 100°C, more preferably 90°C. This invention removes excess MMA and byproduct methanol through the first vacuum distillation; parameters of the first vacuum distillation within the above ranges are beneficial for the removal of MMA and methanol.

[0033] As one embodiment of the present invention, the system obtained by the first vacuum distillation can be cooled to 30°C using a water bath to obtain the crude product.

[0034] After obtaining the crude product, the present invention adds a second organic solvent, an acid solution and an alkali metal salt solution to the crude product, and then performs solid-liquid separation to obtain a liquid phase.

[0035] In one embodiment of the present invention, the second organic solvent can be the same as the first organic solvent, specifically toluene; the amount of the second organic solvent can be 1 to 1.5 times the mass of ethylene glycol monobutyl ether. The present invention uses the second organic solvent to dissolve oil-soluble substances in the reaction system.

[0036] In this invention, the acid solution is preferably hydrochloric acid or sulfuric acid, more preferably hydrochloric acid. Both hydrochloric acid and sulfuric acid are common acids that can react with tetrabutyl titanate to form titanium dioxide precipitate, and they do not react with other substances in the reaction system, which is beneficial for product purification. As one embodiment of this invention, the mass concentration of the hydrochloric acid can be 37%, and the amount used can be 20-60% of the mass of tetrabutyl titanate.

[0037] In one embodiment of the present invention, the alkali metal salt solution can be a saturated sodium chloride solution, and the amount of the saturated sodium chloride solution can be 1 to 2 times the total mass of the organic solvents (the sum of the masses of the first organic solvent and the second organic solvent). The present invention uses an alkali metal salt solution to dissolve water-soluble byproducts in the reaction system. The alkali metal salt solution has a good demulsification effect and is less prone to reaction, which is beneficial for further improving the purity of the product.

[0038] In one embodiment of the present invention, a second organic solvent, an acid solution, and an alkali metal salt solution can be added sequentially to the crude product, and then the resulting mixture can be stirred for 1 hour.

[0039] In one embodiment of the present invention, the solid-liquid separation can be achieved through filtration; the filtration material can be diatomaceous earth. Diatomaceous earth is a macroporous inorganic filter material with excellent particle adsorption properties, which can improve the retention effect on solids. In an embodiment of the present invention, the thickness of the diatomaceous earth is 2 cm. After filtration, the resulting filter cake can be rinsed with a second organic solvent, and the washing liquid is incorporated into the filtrate.

[0040] The present invention does not particularly limit the filtration operation; solid-liquid separation can be achieved using conventional filtration methods in the art. The present invention removes titanium dioxide precipitate and other solid impurities generated from the reaction of tetrabutyl titanate with acid through filtration.

[0041] After obtaining the liquid phase, the present invention performs oil-water separation on the liquid phase, and performs a second vacuum distillation on the obtained oil phase to obtain 2-butoxyethyl methacrylate.

[0042] As one embodiment of the present invention, the oil-water separation method can be to separate the liquids by stirring and allowing them to stand. The present invention does not have a particular limitation on the method of liquid separation, and any conventional liquid separation method in the art can be used to achieve oil-water separation.

[0043] In this invention, the pressure of the second vacuum distillation is preferably -0.09 to -0.1 MPa, more preferably -0.095 MPa; the temperature of the second vacuum distillation is preferably 100 to 120°C, more preferably 100 to 110°C. In an embodiment of this invention, the temperature of the second vacuum distillation is 120°C. The boiling point of toluene is 110°C, and the boiling point of 2-butoxyethyl methacrylate is 228°C. The second vacuum distillation can recover toluene and remove low-boiling-point byproducts and impurities, thereby improving the purity of 2-butoxyethyl methacrylate. The parameters of the second vacuum distillation within the above ranges are beneficial for the removal of organic solvents, low-boiling-point byproducts, and impurities, further improving the product purity.

[0044] This invention uses both MEHQ and TEMPO as polymerization inhibitors. The synergistic use of the two inhibitors reduces the self-polymerization of MMA and 2-butoxyethyl methacrylate, thereby improving the conversion rate. By reducing the self-polymerization of raw materials and products, product quality can be improved. At the same time, it also avoids problems such as equipment blockage and improves the stability of equipment operation.

[0045] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0046] Example 1 A method for preparing 2-butoxyethyl methacrylate, comprising the following steps: MMA (75.06 g), ethylene glycol monobutyl ether (29.84 g), tetrabutyl titanate (4.54 g), toluene (18.43 g), TEMPO (0.015 g), and MEHQ (0.02 g) were added to a four-necked flask and stirred until homogeneous. The mixture was then heated to 90 °C. Separately, 54.33 g of MMA was added to a constant pressure funnel and then added dropwise to the four-necked flask. After the addition was complete (4 h), stirring was continued for 6 h. The mixture was then subjected to a first vacuum distillation at 90 °C and -0.095 MPa. Distillation was stopped when no more distillate was produced. The reaction system was cooled to 30°C in a water bath. Toluene (36.55 g), hydrochloric acid (37%, 2.05 g), and saturated brine (71.79 g) were added sequentially to a four-necked flask. The mixture was stirred for 1 h and filtered through diatomaceous earth (2 cm thick). The filter cake was washed with toluene (3.65 g) and added to the filtrate. The filtrate was allowed to stand and separated. The resulting oil phase was subjected to a second vacuum distillation at 120°C and -0.095 MPa to obtain 20.7 g of product, with a yield of 44%.

[0047] Example 2 A method for preparing 2-butoxyethyl methacrylate, comprising the following steps: MMA (75.06 g), ethylene glycol monobutyl ether (29.84 g), tetrabutyl titanate (9.08 g), toluene (18.43 g), TEMPO (0.015 g), and MEHQ (0.02 g) were added to a four-necked flask and stirred until homogeneous. The mixture was then heated to 90 °C. Separately, 54.33 g of MMA was added to a constant pressure funnel and then added dropwise to the four-necked flask. After the addition was complete (4 h), stirring was continued for 6 h. The mixture was then subjected to a first vacuum distillation at 90 °C and -0.095 MPa. Distillation was stopped when no more distillate was produced. The reaction system was cooled to 30°C in a water bath. Toluene (36.55 g), hydrochloric acid (37%, 2.05 g), and saturated brine (71.79 g) were added sequentially to a four-necked flask. The mixture was stirred for 1 h and filtered through diatomaceous earth (2 cm thick). The filter cake was washed with toluene (3.65 g) and the filtrate was added. The filtrate was allowed to stand and separated. The resulting oil phase was subjected to a second vacuum distillation at 120°C and -0.095 MPa to obtain 28.2 g of product, with a yield of 60%.

[0048] Comparative Example 1 A method for preparing 2-butoxyethyl methacrylate, comprising the following steps: MMA (75.06 g), ethylene glycol monobutyl ether (29.84 g), tetrabutyl titanate (4.54 g), toluene (18.43 g), and TEMPO (0.035 g) were added to a four-necked flask and stirred until homogeneous. The mixture was then heated to 90°C. Separately, 54.33 g of MMA was added to a constant pressure funnel and then added dropwise to the four-necked flask. After the addition was complete (4 h), stirring was continued for 6 h. The mixture was then subjected to a first vacuum distillation at 90°C and -0.095 MPa until no more distillate was obtained. Stop distillation, cool the reaction system to 30°C in a water bath, and add toluene (36.55 g), hydrochloric acid (37%, 2.05 g), and saturated brine (71.79 g) sequentially to a four-necked flask. Stir for 1 h, filter with diatomaceous earth (2 cm thick), wash the filter cake with toluene (3.65 g), and add the filtrate. Allow the filtrate to stand and separate the layers. Perform a second vacuum distillation on the obtained oil phase at 90°C and -0.095 MPa to obtain 19.7 g of product, with a yield of 42%.

[0049] Comparative Example 2 A method for preparing 2-butoxyethyl methacrylate, comprising the following steps: MMA (75.06 g), ethylene glycol monobutyl ether (29.84 g), tetrabutyl titanate (9.08 g), toluene (18.43 g), and MEHQ (0.035 g) were added to a four-necked flask and stirred until homogeneous. The mixture was then heated to 90°C. Separately, 54.33 g of MMA was added to a constant pressure funnel and then added dropwise to the four-necked flask. After the addition was complete (4 h), stirring was continued for 6 h. The mixture was then subjected to a first vacuum distillation at 90°C and -0.095 MPa until no more distillate was obtained. Stop distillation, cool the reaction system to 30°C in a water bath, and add toluene (36.55 g), hydrochloric acid (37%, 2.05 g), and saturated brine (71.79 g) sequentially to a four-necked flask. Stir for 1 h, filter with diatomaceous earth (2 cm thick), wash the filter cake with toluene (3.65 g), and add the filtrate. Allow the filtrate to stand and separate the layers. Perform a second vacuum distillation on the obtained oil phase at 90°C and -0.095 MPa to obtain 22.8 g of product, with a yield of 48%.

[0050] Comparative Example 3 A method for preparing 2-butoxyethyl methacrylate, comprising the following steps: MMA (75.06 g), ethylene glycol monobutyl ether (29.84 g), tetrabutyl titanate (9.08 g), toluene (18.43 g), and TEMPO (0.035 g) were added to a four-necked flask and stirred until homogeneous. The mixture was then heated to 90°C. Separately, 54.33 g of MMA was added to a constant pressure funnel and then added dropwise to the four-necked flask. After the addition was complete (4 h), stirring was continued for 6 h. The mixture was then subjected to a first vacuum distillation at 90°C and -0.095 MPa until no more distillate was obtained. Stop distillation, cool the reaction system to 30°C in a water bath, and add toluene (36.55 g), hydrochloric acid (37%, 2.05 g), and saturated brine (71.79 g) sequentially to a four-necked flask. Stir for 1 h, filter with diatomaceous earth (2 cm thick), wash the filter cake with toluene (3.65 g), and add the filtrate. Allow the filtrate to stand and separate the layers. Perform a second vacuum distillation on the obtained oil phase at 90°C and -0.095 MPa to obtain 24.4 g of product, with a yield of 52%.

[0051] Test Example 1 The products obtained in Examples 1-2 and Comparative Examples 1-3 were analyzed by gas chromatography. The chromatographic data are recorded in Tables 1-5, and the chromatograms are shown below. Figures 1-5 As shown.

[0052] Table 1. Gas Chromatography Data Record of the Product Obtained in Example 1

[0053] From Table 1 and Figure 1 As can be seen, the product obtained in Example 1 contains 85.98% 2-butoxyethyl methacrylate and has a conversion rate (relative to ethylene glycol monobutyl ether) of 37.86%.

[0054] Table 2. Gas chromatographic data record of the product obtained in Example 2

[0055] From Table 2 and Figure 2 It can be seen that the product obtained in Example 2 contains 91.83% 2-butoxyethyl methacrylate and has a conversion rate of 55.08%.

[0056] Table 3. Gas chromatographic data record of the product obtained in Comparative Example 1

[0057] From Table 3 and Figure 3 It can be seen that the product obtained in Comparative Example 1 contains 20.06% 2-butoxyethyl methacrylate, and the conversion rate is 8.40%.

[0058] Table 4. Gas chromatographic data record of the product obtained in Comparative Example 2

[0059] From Table 4 and Figure 4 It can be seen that the product obtained in Comparative Example 2 contains 48.64% 2-butoxyethyl methacrylate and has a conversion rate of 23.59%.

[0060] Table 5. Gas chromatographic data record of the product obtained in Comparative Example 3

[0061] From Table 5 and Figure 5 It can be seen that the product obtained in Comparative Example 3 contains 70.06% 2-butoxyethyl methacrylate and has a conversion rate of 36.36%.

[0062] As can be seen from the above examples and comparative examples, the preparation method provided by the present invention has a high conversion rate.

[0063] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing 2-butoxyethyl methacrylate, comprising the following steps: Methyl methacrylate, ethylene glycol monobutyl ether, tetrabutyl titanate, a first organic solvent, 2,2,6,6-tetramethylpiperidine oxide and p-hydroxyanisole were mixed and subjected to transesterification to obtain a mother liquor. The mother liquor was first distilled under reduced pressure to obtain the crude product; A second organic solvent, an acid solution, and an alkali metal salt solution are added to the crude product, followed by solid-liquid separation to obtain a liquid phase. The liquid phase was subjected to oil-water separation, and the resulting oil phase was subjected to a second vacuum distillation to obtain 2-butoxyethyl methacrylate.

2. The preparation method according to claim 1, characterized in that, The mass ratio of 2,2,6,6-tetramethylpiperidine oxide, p-hydroxyanisole, and methyl methacrylate is (0.01~0.02):(0.015~0.025):(100~350).

3. The preparation method according to claim 1, characterized in that, The molar ratio of methyl methacrylate to ethylene glycol monobutyl ether is (3~7):

1.

4. The preparation method according to claim 1, characterized in that, The molar ratio of methyl methacrylate to tetrabutyl titanate is (100~300):(1~2).

5. The preparation method according to claim 1, characterized in that, The molar ratio of methyl methacrylate to the first organic solvent is (6~15):

1.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The mixing process involves mixing other raw materials, adding a portion of methyl methacrylate, heating to the temperature for transesterification, and then continuing to add the remaining methyl methacrylate dropwise. The portion of methyl methacrylate constitutes 30-70% of the total mass of methyl methacrylate.

7. The preparation method according to claim 1, characterized in that, The transesterification reaction is carried out at a temperature of 80~100℃.

8. The preparation method according to claim 1 or 7, characterized in that, The transesterification reaction takes 4 to 8 hours.

9. The preparation method according to claim 1, characterized in that, The pressure of the first vacuum distillation is -0.09 to -0.1 MPa, and the temperature is 80 to 100°C; the pressure of the second vacuum distillation is -0.09 to -0.1 MPa, and the temperature is 100 to 120°C.

10. The preparation method according to claim 1, characterized in that, The acid solution is hydrochloric acid or sulfuric acid.

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