A process for the preparation of an aqueous dispersion of a methylacrylic acid-ethyl acrylate copolymer

Abstract

This invention provides a method for preparing an aqueous dispersion of methacrylic acid-ethyl acrylate copolymer, comprising the following steps: A) continuously emulsifying methacrylic acid, ethyl acrylate, surfactant, initiator, initiator activator, chain transfer catalyst, and water at high energy levels to obtain a uniform and stable monomer microemulsion; B) continuously conveying the monomer microemulsion to a pipeline reactor in an ultrasonic field for polymerization to continuously obtain an aqueous dispersion of methacrylic acid-ethyl acrylate copolymer. The preparation method of this invention significantly reduces the safety risks of the polymerization reaction, improves production efficiency and capacity, greatly reduces scale-up effects, solves the problem of batch-to-batch uniformity, and provides a new commercially viable method for preparing an aqueous dispersion of methacrylic acid-ethyl acrylate copolymer (1:1).

Description

Technical Field

[0001] This invention belongs to the field of pharmaceutical excipient preparation technology, and particularly relates to a method for preparing an aqueous dispersion of methacrylate-ethyl acrylate copolymer. Background Technology

[0002] The method for producing an aqueous dispersion of methacrylate-ethyl acrylate copolymer (1:1) was first invented and manufactured by Evonik, and is used as a pH-dependent pharmaceutical excipient in the production of enteric-coated drugs.

[0003] US4771098A reports a method for preparing a 1:1 aqueous dispersion of a methacrylic acid ethyl acrylate copolymer. The method involves first mixing methacrylic acid, ethyl acrylate, and Tween-80 into a homogeneous phase, which is then slowly added dropwise over 4 hours to an aqueous solution of sodium dodecyl sulfate, isooctyl mercaptoacetate, and ammonium sulfate at 80°C. After the addition is complete, the reaction continues for another 2 hours, yielding a 1:1 aqueous dispersion of the methacrylic acid ethyl acrylate copolymer with a viscosity of 6 mPa·s and a pH of 2.4. This patent largely solves the problem of agglomeration caused by high methacrylic acid content. However, some agglomerates still need to be filtered out. Emulsions generated at excessively high temperatures tend to have larger particle sizes. Semi-continuous reactions in industrial applications often require larger-volume reaction equipment, exhibiting significant scale-up effects and inconsistent batch-to-batch repeatability, making them unsuitable for industrial production.

[0004] The literature Polym.plast, Technol. Eng., 28(3), 289-317 (1989) reported a method for the continuous preparation of methyl methacrylate copolymer using a pipeline reactor, which greatly improved the production efficiency. However, in reality, the agglomeration phenomenon could not be well solved, and the phenomenon of polymer adhesion inside the pipeline reactor was obvious, which brought difficulties to industrialization. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing an aqueous dispersion of methacrylic acid-ethyl acrylate copolymer. The preparation method of this invention significantly reduces agglomeration and adhesion to the reactor wall during the production process, and realizes the continuous and efficient preparation of an aqueous dispersion of methacrylic acid-ethyl acrylate copolymer (1:1) using a pipeline reactor.

[0006] This invention provides a method for preparing an aqueous dispersion of methacrylate-ethyl acrylate copolymer, comprising the following steps:

[0007] A) Methacrylic acid, ethyl acrylate, surfactant, initiator, initiator activator, chain transfer catalyst and water are continuously emulsified at high energy to obtain a uniform and stable monomer microemulsion;

[0008] B) The monomer microemulsion is continuously transported to a pipeline reactor in an ultrasonic field to carry out a polymerization reaction, and a continuous aqueous dispersion of methacrylate-ethyl acrylate copolymer is obtained.

[0009] Preferably, the molar ratio of methacrylic acid to ethyl acrylate is 1:1.

[0010] Preferably, the surfactant is an alkane sulfate and Tween-80, and the mass of the surfactant is 0.8-15% of the total mass of methacrylic acid and ethyl acrylate.

[0011] Preferably, the initiator is ammonium persulfate and / or potassium persulfate; the mass of the initiator is 0.05-2% of the total mass of methacrylic acid and ethyl acrylate.

[0012] Preferably, the initiator activator is a ferrous salt and / or a bisulfite; the mass of the initiator activator is 0.01-1% of the total mass of methacrylic acid and ethyl acrylate.

[0013] Preferably, the chain transfer catalyst comprises isooctyl mercaptoacetate; the mass of the chain transfer catalyst is 0.005 to 0.5% of the total mass of methacrylic acid and ethyl acrylate.

[0014] Preferably, the mass of the water is 100-400% of the total mass of methacrylic acid and ethyl acrylate.

[0015] Preferably, the high-energy emulsification is performed using one or more of an ultrasonic generator, a high-pressure homogenizer, and a microfluidic homogenizer.

[0016] Preferably, the temperature for high-energy emulsification is 20–50°C.

[0017] Preferably, in step B), the frequency of the ultrasonic field is 25–35 kHz, the power is 100 W–3000 W, and the polymerization temperature is 40–80 °C.

[0018] This invention provides a method for preparing an aqueous dispersion of methacrylic acid-ethyl acrylate copolymer, comprising the following steps: A) continuously emulsifying methacrylic acid, ethyl acrylate, surfactant, initiator, initiator activator, chain transfer catalyst, and water at high energy to obtain a uniform and stable monomer microemulsion; B) continuously conveying the monomer microemulsion to a pipeline reactor in an ultrasonic field for polymerization to continuously obtain an aqueous dispersion of methacrylic acid-ethyl acrylate copolymer. The method utilizes continuous high-energy emulsification to obtain a fine and stable monomer microemulsion, and ultrasonic assistance to achieve more uniform mixing of materials within the pipeline reactor. Ultrasonic stimulation provides energy to prevent polymer adhesion to the inner wall of the pipeline reactor, solving the troublesome pipe blockage phenomenon in pipeline reactor polymerization. This directly and continuously obtains a polymer aqueous dispersion with a narrow molecular weight distribution and small particle size. This method significantly reduces the safety risks of the polymerization reaction, improves production efficiency and capacity, greatly reduces scale-up effects, and solves the problem of batch-to-batch uniformity. It provides a new commercially viable method for preparing an aqueous dispersion of methacrylic acid-ethyl acrylate copolymer (1:1). Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0020] Figure 1 This is a particle size distribution diagram of the methacrylate-ethyl acrylate (1:1) aqueous dispersion prepared in Example 1 of the present invention;

[0021] Figure 2 This is a particle size distribution diagram of the methacrylate-ethyl acrylate (1:1) aqueous dispersion prepared in Example 2 of the present invention;

[0022] Figure 3 This is a particle size distribution diagram of the methacrylate-ethyl acrylate (1:1) aqueous dispersion prepared in Example 3 of the present invention;

[0023] Figure 4 This is a particle size distribution diagram of the methacrylate-ethyl acrylate (1:1) aqueous dispersion prepared in Example 4 of the present invention;

[0024] Figure 5 This is a particle size distribution diagram of the methacrylate-ethyl acrylate (1:1) aqueous dispersion prepared in Comparative Example 2 of this invention;

[0025] Figure 6This is a particle size distribution diagram of the methacrylate-ethyl acrylate (1:1) aqueous dispersion prepared in Comparative Example 3 of this invention;

[0026] Figure 7 This is a particle size distribution diagram of the methacrylate-ethyl acrylate (1:1) aqueous dispersion prepared in Comparative Example 4 of the present invention. Detailed Implementation

[0027] This invention provides a method for preparing an aqueous dispersion of methacrylate-ethyl acrylate copolymer, comprising the following steps:

[0028] A) Methacrylic acid, ethyl acrylate, surfactant, initiator, initiator activator, chain transfer catalyst and water are continuously emulsified at high energy to obtain a uniform and stable monomer microemulsion;

[0029] B) The monomer microemulsion is continuously transported to a pipeline reactor in an ultrasonic field to carry out a polymerization reaction, and a continuous aqueous dispersion of methacrylate-ethyl acrylate copolymer is obtained.

[0030] In this invention, the molar ratio of methacrylic acid and ethyl acrylate is preferably 1:1.

[0031] In this invention, the surfactant is preferably an alkane sulfate and Tween-80. The alkane sulfate is preferably sodium dodecyl sulfate. The mass of the surfactant is preferably 0.8-15% of the total mass of methacrylic acid and ethyl acrylate, more preferably 1.5-8%. Specifically, the mass of the alkane sulfate is preferably 0.5-5% of the total mass of methacrylic acid and ethyl acrylate, more preferably 0.5-3%, such as 0.3%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, preferably within the range of any of the above values ​​as the upper or lower limit. The mass of Tween-80 is preferably 0.5-10% of the total mass of methacrylic acid and ethyl acrylate, more preferably 1-5%, such as 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, preferably within the range of any of the above values ​​as the upper or lower limit.

[0032] In this invention, the initiator is preferably a water-soluble initiator, more preferably ammonium persulfate and / or potassium persulfate. The mass of the initiator is preferably 0.05-2% of the total mass of methacrylic acid and ethyl acrylate, more preferably 0.1-1%, such as 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, preferably a range of values ​​with any of the above values ​​as the upper or lower limit.

[0033] In this invention, the initiator activator is preferably a reducing salt, more preferably a ferrous salt and / or a bisulfite; the mass of the initiator activator is preferably 0.01 to 1% of the total mass of methacrylic acid and ethyl acrylate, more preferably 0.02 to 0.5%, such as 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, preferably a range of values ​​with any of the above values ​​as the upper or lower limit.

[0034] In this invention, the chain transfer catalyst is preferably a thiol substance, more preferably isooctyl mercaptoacetate; the mass of the chain transfer catalyst is preferably 0.005-0.5% of the total mass of methacrylic acid and ethyl acrylate, more preferably 0.01-0.25%, such as 0.005%, 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, preferably a range of values ​​with any of the above values ​​as the upper or lower limit.

[0035] In this invention, the mass of the water is 100-400% of the total mass of methacrylic acid and ethyl acrylate, more preferably 150-300%, such as 100%, 150%, 200%, 250%, 300%, 350%, 400%, preferably a range of values ​​with any of the above values ​​as the upper or lower limit.

[0036] The present invention preferably involves first emulsifying the above-mentioned raw materials in a high-energy emulsification device to obtain a uniform and stable monomer microemulsion.

[0037] In this invention, the high-energy emulsification equipment is preferably one or a combination of several of the following: a single ultrasonic generator, a high-pressure homogenizer, and a micro-jet homogenizer.

[0038] When using an ultrasonic generator for high-energy emulsification, the frequency of the ultrasound is preferably 25–35 kHz, more preferably 30–35 kHz, such as 25 kHz, 26 kHz, 27 kHz, 28 kHz, 29 kHz, 30 kHz, 31 kHz, 32 kHz, 33 kHz, 34 kHz, 35 kHz, and preferably within the range of any of the above values ​​as the upper or lower limit. The flow rate of the material is preferably 3–10 mL / min, more preferably 5–8 mL / min, such as 3 mL / min, 4 mL / min, 5 mL / min, 6 mL / min, 7 mL / min, 8 mL / min, 9 mL / min, 10 mL / min, and preferably within the range of any of the above values ​​as the upper or lower limit. The temperature of the high-energy emulsification is preferably 20–50 °C, more preferably 30–40 °C, such as 20 °C, 25 °C, 30 °C, 35 °C, 40 °C, 45 °C, 50 °C, and preferably within the range of any of the above values ​​as the upper or lower limit.

[0039] When using a high-pressure homogenizer for high-energy emulsification, the pressure of the high-pressure homogenizer is preferably 50–150 MPa, more preferably 80–120 MPa, such as 50 MPa, 60 MPa, 70 MPa, 80 MPa, 90 MPa, 100 MPa, 110 MPa, 120 MPa, 130 MPa, 140 MPa, or 150 MPa, preferably within the range of any of the above values ​​as the upper or lower limit; the flow rate of the material is preferably 3–10 mL / min, more preferably 5–8 mL / min. For example, 3 mL / min, 4 mL / min, 5 mL / min, 6 mL / min, 7 mL / min, 8 mL / min, 9 mL / min, 10 mL / min, preferably within the range of any of the above values ​​as the upper or lower limit, the number of cycles is preferably 2 to 3 times, the temperature of the high-energy emulsification is preferably 20 to 50°C, more preferably 30 to 40°C, such as 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, preferably within the range of any of the above values ​​as the upper or lower limit.

[0040] When using a microjet homogenizer for high-energy emulsification, the jet velocity is preferably 10–25 m / s, more preferably 15–20 m / s, such as 10 m / s, 15 m / s, 20 m / s, 25 m / s, preferably within the range of any of the above values ​​as the upper or lower limit. The jet diameter is preferably 10–20 μm, more preferably 12–18 μm, such as 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, preferably within the range of any of the above values ​​as the upper or lower limit. The nozzle orifice diameter is preferably 2.5–3.5 mm, more preferably 3–3.2 mm. The pressure is preferably 50–100 MPa, more preferably 60–80 MPa, such as 5… The maximum or minimum pressure range is 0 MPa, 60 MPa, 70 MPa, 80 MPa, 90 MPa, 100 MPa, preferably any of the above values. The flow rate of the material is preferably 3 to 10 mL / min, more preferably 5 to 8 mL / min, such as 3 mL / min, 4 mL / min, 5 mL / min, 6 mL / min, 7 mL / min, 8 mL / min, 9 mL / min, 10 mL / min, preferably any of the above values. The temperature of the high-energy emulsification is preferably 20 to 50°C, more preferably 30 to 40°C, such as 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, preferably any of the above values.

[0041] After obtaining the monomer microemulsion, the present invention preferably continuously transports the monomer microemulsion to a pipeline reactor in an ultrasonic field for polymerization reaction, thereby continuously obtaining an aqueous dispersion of methacrylate-ethyl acrylate copolymer (1:1).

[0042] In this invention, the frequency of the ultrasonic field is preferably 25-35 kHz, more preferably 28-30 kHz, such as 25 kHz, 26 kHz, 27 kHz, 28 kHz, 29 kHz, 30 kHz, 31 kHz, 32 kHz, 33 kHz, 34 kHz, 35 kHz, and preferably within the range of any of the above values ​​as the upper or lower limit; the power is preferably 1000-3500 W, more preferably 1500-3000 W, such as 1000 W, 1500 W, 2000 W, 2500 W, 3000 W, 3500 W, and preferably within the range of any of the above values ​​as the upper or lower limit; the material flow rate is preferably 3-10 mL / min. The polymerization temperature is preferably 40–80°C, more preferably 50–70°C, such as 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, and preferably a range of values ​​above or below.

[0043] In this invention, the specific model of the pipeline reactor is not specifically limited, and the material of the area of ​​the pipeline reactor in contact with the material is preferably polytetrafluoroethylene.

[0044] This invention provides a method for preparing an aqueous dispersion of methacrylic acid-ethyl acrylate copolymer, comprising the following steps: A) continuously emulsifying methacrylic acid, ethyl acrylate, surfactant, initiator, initiator activator, chain transfer catalyst, and water at high energy to obtain a uniform and stable monomer microemulsion; B) continuously conveying the monomer microemulsion to a pipeline reactor in an ultrasonic field for polymerization to continuously obtain an aqueous dispersion of methacrylic acid-ethyl acrylate copolymer. The method utilizes continuous high-energy emulsification to obtain a fine and stable monomer microemulsion, and ultrasonic assistance to achieve more uniform mixing of materials within the pipeline reactor. Ultrasonic waves provide the energy to prevent polymer adhesion to the inner wall of the pipeline reactor, solving the troublesome pipe blockage phenomenon in pipeline reactor polymerization. This directly and continuously obtains a polymer aqueous dispersion with a narrow molecular weight distribution and small particle size. This method significantly reduces the safety risks of the polymerization reaction, improves production efficiency and capacity, greatly reduces the release effect, and solves the problem of batch-to-batch uniformity. It provides a new commercially viable method for preparing an aqueous dispersion of methacrylic acid-ethyl acrylate copolymer (1:1).

[0045] To further illustrate the present invention, the following detailed description of a method for preparing an aqueous dispersion of a methacrylic acid-ethyl acrylate copolymer provided by the present invention is provided in conjunction with embodiments, but it should not be construed as limiting the scope of protection of the present invention.

[0046] The performance parameters of the products prepared in the following examples and comparative examples were tested according to the following methods.

[0047] Monomer Residue Detection

[0048] Chromatographic conditions and system suitability test: Octadecylsilane-bonded silica gel was used as the stationary phase; the mobile phase consisted of 700 ml of phosphate buffer solution (8.953 g of disodium hydrogen phosphate containing twelve molecules of water of crystallization and 3.400 g of potassium dihydrogen phosphate dissolved in water and diluted to 1000 ml, with the pH adjusted to 2.0 with dilute phosphoric acid) diluted to 1000 ml with methanol; the detection wavelength was 202 nm. The resolution between the ethyl acrylate peak and the methacrylic acid peak should be no less than 2.0.

[0049] Assay Method: Preparation of Reference Solution: Accurately weigh approximately 10 mg each of methacrylic acid reference standard and ethyl acrylate reference standard, place them in the same 100 ml volumetric flask, dissolve and dilute to the mark with methanol, and shake well. Accurately measure 2 ml of the solution and place it in a 100 ml volumetric flask, dilute to the mark with methanol, and shake well. Accurately measure 50 ml of the solution, add 25 ml of water, and shake well. Preparation of Test Solution: Accurately weigh approximately 2 g of the sample and place it in a 100 ml volumetric flask, dissolve and dilute to the mark with methanol, and shake well. Accurately measure 50 ml of the solution, add 25 ml of water, and shake well. Accurately measure 20 μl each of the reference solution and the test solution, inject them into the liquid chromatograph, and record the chromatograms. Calculate the result by peak area using the external standard method.

[0050] Calculation formula:

[0051] (1) (2)

[0052] In the formula: A 样 The peak area of ​​each corresponding peak in the test solution;

[0053] A 对 The peak area of ​​each corresponding peak in the control solution;

[0054] W 样 The sample weight (mg);

[0055] W 对 This refers to the sample weight (mg) of the reference standard.

[0056] Particle size detection

[0057] Take this product, dilute it with water as the dispersion medium, and test it according to the method for determination of particle size and particle size distribution (General Rule 0982, Method III) (using a laser scattering particle size analyzer based on Mie scattering theory, such as Malvern NANO ZS90; recommended parameters are: absorptivity 0.01, viscosity 0.8827, refractive index 1.330, and temperature 25℃).

[0058] Viscosity testing

[0059] Take this product and measure its viscosity using a rotational viscometer at 20°C and a rotation speed of 30 revolutions per minute. Calculation formula:

[0060] η=K×A

[0061] Where: η - dynamic viscosity, K - coefficient, A - pointer reading (deflection angle).

[0062] Example 1

[0063] 100g methacrylic acid, 100g ethyl acrylate, 5g Tween-80, 2.5g sodium dodecyl sulfate, 0.5g ammonium persulfate, 1.0g sodium bisulfite, 0.02g ferrous sulfate, 0.02g isooctyl mercaptoacetate, 467g water.

[0064] A mixture of methacrylic acid, ethyl acrylate, and Tween-80 mercaptoacetic acid isooctyl ester was added simultaneously via a peristaltic pump at 4 ml / min to a 30 mL sealed glass bottle with magnetic stirring and only inlet and outlet, placed in an ultrasonic field with a frequency of 29 kHz and a power of 1 kW. The temperature was controlled at 37.5 ± 2.5 °C. The emulsified mixture was then passed through a 100 m long, 0.15 cm diameter polytetrafluoroethylene (PTFE) pipe reactor, placed in an ultrasonic field with a frequency of 29 kHz and a power of 2.5 kW, and the temperature was controlled at 57.5 ± 2.5 °C. At the outlet of the pipe reactor, a 1:1 aqueous dispersion of methacrylic acid-ethyl acrylate copolymer was obtained. Testing showed a monomer content of less than 50 ppm; particle size: 137 nm; viscosity: 5 mPa·s. The particle size distribution is shown in the figure. Figure 1 ,Depend on Figure 1 It can be seen that the peak position is 137.4nm.

[0065] Example 2

[0066] 100g methacrylic acid, 100g ethyl acrylate, 3g Tween-80, 2g sodium dodecyl sulfate, 0.05g ammonium persulfate, 0.05g sodium bisulfite, 0.04g ferrous sulfate, 0.03g isooctyl mercaptoacetate, 467g water.

[0067] A mixture of methacrylic acid, ethyl acrylate, and Tween-80 mercaptoacetic acid isooctyl ester was added simultaneously to a high-pressure homogenizer (100 MPa, 2 cycles) via a peristaltic pump at a rate of 4 ml / min, along with solutions of water, sodium dodecyl sulfate, ammonium persulfate, sodium bisulfite, and ferrous sulfate via the same peristaltic pump. The temperature was controlled at 27.5 ± 2.5 °C. The emulsified mixture was then passed through a 30 mL inlet / outlet pump equipped with a magnetic stirrer placed in an ultrasonic field with a frequency of 29 kHz and a power of 0.5 kW. In a sealed glass bottle, the temperature was controlled at 27.5±2.5℃. The mixture was then passed through a 100m long, 0.15cm diameter polytetrafluoroethylene (PTFE) tubular reactor. The reactor was placed in an ultrasonic field with a frequency of 29kHz and a power of 2.5kW, and the temperature was controlled at 52.5±2.5℃. At the reactor outlet, a 1:1 aqueous dispersion of ethylene acrylate copolymer was obtained. Testing showed that the monomer content was less than 50ppm; particle size: 127nm; viscosity: 4.5mPa·s. The particle size distribution is shown in the figure. Figure 2,Depend on Figure 2 It can be seen that the peak position is 126.7nm.

[0068] Example 3

[0069] 100g methacrylic acid, 100g ethyl acrylate, 3g Tween-80, 2g sodium dodecyl sulfate, 0.05g ammonium persulfate, 0.06g sodium bisulfite, 0.05g ferrous sulfate, 0.04g isooctyl mercaptoacetate, 467g water.

[0070] A mixture of methacrylic acid, ethyl acrylate, and Tween-80 mercaptoacetic acid isooctyl ester was simultaneously added at a peristaltic pump rate of 4 ml / min to a microjet apparatus (pressure 75 MPa, jet diameter 10–20 μm, nozzle orifice diameter 2.5–3.5 mm). The temperature was controlled at 27.5 ± 2.5 °C. The mixture was then passed through a 100 m long, 0.15 cm diameter polytetrafluoroethylene (PTFE) pipe reactor placed in an ultrasonic field with a frequency of 29 kHz and a power of 2.5 kW. The temperature was controlled at 52.5 ± 2.5 °C. At the outlet of the pipe reactor, a 1:1 aqueous dispersion of methacrylic acid ethyl acrylate copolymer was obtained, with a monomer content below 50 ppm; particle size: 119 nm; viscosity: 4.3 mPa·s. The particle size distribution is shown in the figure. Figure 3 ,Depend on Figure 3 It can be seen that the peak position is 119.1nm.

[0071] Example 4

[0072] 100g methacrylic acid, 100g ethyl acrylate, 3g Tween-80, 2g sodium dodecyl sulfate, 0.05g ammonium persulfate, 0.06g sodium bisulfite, 0.05g ferrous sulfate, 0.04g isooctyl mercaptoacetate, 467g water.

[0073] A mixture of methacrylic acid, ethyl acrylate, and Tween-80 mercaptoacetic acid isooctyl ester was added simultaneously via a peristaltic pump at 4 ml / min to a 30 mL sealed glass bottle with magnetic stirring and only inlet and outlet, placed in an ultrasonic field with a frequency of 29 kHz and a power of 1 kW. The temperature was controlled at 37.5 ± 2.5 °C. A microjet (pressure 50 MPa, jet diameter 10–20 μm) was also added during the mixing. In a device with a nozzle diameter of 2.5–3.5 mm, the temperature was controlled at 27.5 ± 2.5 °C. The sample was then passed through a 100 m long, 0.15 cm diameter polytetrafluoroethylene (PTFE) pipe reactor. The reactor was placed in an ultrasonic field with a frequency of 29 kHz and a power of 2.5 kW, and the temperature was controlled at 52.5 ± 2.5 °C. At the outlet of the reactor, a 1:1 aqueous dispersion of ethylene acrylate copolymer was obtained, with a monomer content of less than 50 ppm; particle size: 114 nm; viscosity: 4.3 mPa·s. The particle size distribution diagram is shown below. Figure 4 ,Depend on Figure 4 It can be seen that the peak position is 113.8nm.

[0074] Comparative Example 1

[0075] 100g methacrylic acid, 100g ethyl acrylate, 5g Tween-80, 2.5g sodium dodecyl sulfate, 0.5g ammonium persulfate, 1.0g sodium bisulfite, 0.02g ferrous sulfate, 0.02g isooctyl mercaptoacetate, 467g water.

[0076] The mixture of methacrylic acid, ethyl acrylate, and Tween-80 mercaptoacetic acid isooctyl ester was pumped at 4 ml / min via a peristaltic pump. Water, sodium dodecyl sulfate, ammonium persulfate, sodium bisulfite, and ferrous sulfate solutions were pumped at 8.5 ml / min via a peristaltic pump into a 30 mL sealed glass bottle with only inlet and outlet, equipped with a magnetic stirrer. The temperature was controlled at 37.5 ± 2.5 °C. The emulsified mixture was then passed through a 100 m long, 0.15 cm diameter polytetrafluoroethylene (PTFE) pipe reactor, with the temperature controlled at 57.5 ± 2.5 °C. At the outlet of the pipe reactor, the product contained small clumps, and the monomer input was only half complete before the reaction could not be continued due to severe blockage of the pipe, ultimately leading to the termination of the reaction.

[0077] Comparative Example 2

[0078] 100g methacrylic acid, 100g ethyl acrylate, 5g Tween-80, 2.5g sodium dodecyl sulfate, 0.5g ammonium persulfate, 1.0g sodium bisulfite, 0.02g ferrous sulfate, 0.02g isooctyl mercaptoacetate, 467g water.

[0079] A mixture of methacrylic acid, ethyl acrylate, and Tween-80 mercaptoacetic acid isooctyl ester was pumped at 4 ml / min using a peristaltic pump. A solution of water, sodium dodecyl sulfate, ammonium persulfate, sodium bisulfite, and ferrous sulfate was pumped at 8.5 ml / min using a peristaltic pump into a 30 mL sealed glass bottle with only inlet and outlet, equipped with a magnetic stirrer. The temperature was controlled at 37.5 ± 2.5 °C. The emulsified mixture was then passed through a 100 m long, 0.15 cm diameter polytetrafluoroethylene (PTFE) tubular reactor placed in an ultrasonic field with a frequency of 29 kHz and a power of 2.5 kW. The temperature was controlled at 57.5 ± 2.5 °C. At the outlet of the tubular reactor, a 1:1 aqueous dispersion of methacrylic acid ethyl acrylate copolymer was obtained, with a monomer content of 352 ppm, a particle size of 327 nm, and a viscosity of 9.2 mPa·s. The particle size distribution is shown in the figure. Figure 5 ,Depend on Figure 5 It can be seen that the peak position is 326.8nm.

[0080] Comparative Example 3

[0081] 100g methacrylic acid, 100g ethyl acrylate, 5g Tween-80, 2.5g sodium dodecyl sulfate, 0.5g ammonium persulfate, 0.01g sodium bisulfite, 0.01g ferrous sulfate, 0.02g isooctyl mercaptoacetate, 467g water.

[0082] A mixture of methacrylic acid, ethyl acrylate, and Tween-80 mercaptoacetic acid isooctyl ester was added simultaneously via a peristaltic pump at 4 ml / min to a 30 mL sealed glass bottle with magnetic stirring and only inlet and outlet, placed in an ultrasonic field with a frequency of 29 kHz and a power of 1 kW. The temperature was controlled at 37.5 ± 2.5 °C. The emulsified mixture was then passed through a 100 m long, 0.15 cm diameter polytetrafluoroethylene (PTFE) pipe reactor, placed in an ultrasonic field with a frequency of 29 kHz and a power of 2.5 kW, and the temperature was controlled at 57.5 ± 2.5 °C. At the outlet of the pipe reactor, a 1:1 aqueous dispersion of methacrylic acid-ethyl acrylate copolymer was obtained, with a monomer content of 5%, indicating a significant amount of unreacted monomer; particle size: 342 nm; viscosity: 8.4 mPa·s. The particle size distribution is shown in the figure. Figure 6 ,Depend on Figure 6 It can be seen that the peak position is 342.4nm.

[0083] Comparative Example 4

[0084] 100g methacrylic acid, 100g ethyl acrylate, 5g Tween-80, 2.5g sodium dodecyl sulfate, 0.5g ammonium persulfate, 1.0g sodium bisulfite, 0.02g ferrous sulfate, 0.02g isooctyl mercaptoacetate, 467g water.

[0085] A mixture of methacrylic acid, ethyl acrylate, and Tween-80 mercaptoacetic acid isooctyl ester was added simultaneously via a peristaltic pump at 4 ml / min to a 30 mL sealed glass bottle with magnetic stirring and only inlet and outlet, placed in an ultrasonic field with a frequency of 29 kHz and a power of 1 kW. The temperature was controlled at 37.5 ± 2.5 °C. The emulsified mixture was then passed through a 100 m long, 0.15 cm diameter polytetrafluoroethylene (PTFE) pipe reactor, placed in an ultrasonic field with a frequency of 29 kHz and a power of 2.5 kW, and the temperature was controlled at 85 °C. At the outlet of the pipe reactor, a 1:1 aqueous dispersion of methacrylic acid-ethyl acrylate copolymer was obtained, with a monomer content of less than 50 ppm, a particle size of 454 nm, and a viscosity of 9.0 mPa·s. The particle size distribution is shown in the figure. Figure 7 ,Depend on Figure 7 It can be seen that the peak position is 454.1nm.

[0086] 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 an aqueous dispersion of a methacrylate-ethyl acrylate copolymer, comprising the following steps: A) Methacrylic acid, ethyl acrylate, surfactant, initiator, initiator activator, chain transfer catalyst and water are continuously emulsified at high energy to obtain a uniform and stable monomer microemulsion; The molar ratio of methacrylic acid to ethyl acrylate is 1:1; the mass of the surfactant is 0.8-15% of the total mass of methacrylic acid and ethyl acrylate; the mass of the initiator is 0.05-2% of the total mass of methacrylic acid and ethyl acrylate; the mass of the initiator activator is 0.01-1% of the total mass of methacrylic acid and ethyl acrylate; the mass of the chain transfer catalyst is 0.005-0.5% of the total mass of methacrylic acid and ethyl acrylate; and the mass of water is 100-400% of the total mass of methacrylic acid and ethyl acrylate. B) The monomer microemulsion is continuously transported to a pipeline reactor in an ultrasonic field to carry out a polymerization reaction, and a continuous aqueous dispersion of methacrylate-ethyl acrylate copolymer is obtained.

2. The production method according to claim 1, characterized by, The surfactant is an alkane sulfate and Tween-80.

3. The production method according to claim 1, characterized by, The initiator is ammonium persulfate and / or potassium persulfate.

4. The production method according to claim 3, characterized by, The initiator activator is a ferrous salt and / or a bisulfite.

5. The preparation method according to claim 1, characterized in that, The chain transfer catalyst includes isooctyl mercaptoacetate.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The high-energy emulsification is performed using one or more of an ultrasonic generator, a high-pressure homogenizer, and a microfluidic homogenizer.

7. The preparation method according to claim 6, characterized in that, The high-energy emulsification temperature is 20~50℃.

8. The preparation method according to any one of claims 1 to 5, characterized in that, In step B), the frequency of the ultrasonic field is 25~35KHz, the power is 100W~3000W, and the polymerization temperature is 40~80℃.

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