CN116178599A - Micro-reaction synthesis method of low molecular weight polyacrylic acid - Google Patents

Abstract

The invention discloses a micro-reaction synthesis method of low-molecular-weight polyacrylic acid, which belongs to the technical field of water treatment. The method comprises: reacting an acrylic acid solution, an initiator solution and a polymerization inhibitor solution in a microchannel reactor synthesis device to obtain a series of low molecular weight polyacrylic acid products with a number average molecular weight between 800-5000 and a polymer dispersion index less than 1.5 . The invention adopts a microchannel reactor synthesis device to realize the synthesis of the acrylic acid oligomer with controllable molecular weight, strengthens the mixing, mass transfer and heat transfer processes in the polymerization reaction process, greatly shortens the reaction time, and improves the polymerization efficiency.

Description

A kind of micro-reaction synthesis method of low molecular weight polyacrylic acid

technical field

The invention belongs to the technical field of water treatment, and in particular relates to a micro-reaction synthesis method of low-molecular-weight polyacrylic acid.

Background technique

Polyacrylic acid products are a kind of scale inhibitor and dispersant commonly used in water treatment, and the annual consumption in my country is more than 3 billion yuan. As a water treatment agent, studies at home and abroad have confirmed that the smaller the molecular weight and narrower distribution of polyacrylic acid, the stronger its anti-scaling performance. At present, the molecular weight of polyacrylic acid obtained by the free radical polymerization preparation process commonly used in China is basically above 2000, and there are problems such as wide molecular weight distribution, insufficient purity, and unstable quality. At the same time, the traditional synthesis process is produced by batch reactors. Because the traditional stirred tanks have low performance in terms of mixing and heat transfer of polymer solutions, it is easy to cause uneven distribution of acrylic acid concentration during the reaction process, resulting in local hot spots, and further This leads to the loss of control of the reaction system, auto-acceleration effect or even detonation, which eventually leads to low equipment processing capacity, wide product molecular weight distribution, and poor batch stability, which greatly limits the performance of polyacrylic acid products.

The same polymer, due to factors such as product molecular weight, molecular weight distribution, residual monomer content, and by-product content, directly determines the performance of the product and the safety of use, and also directly determines the value of the product. Therefore, the development The controllable preparation process of low molecular weight polyacrylic acid can effectively improve the performance of existing products.

Contents of the invention

The polymerization reaction has high requirements on the heat transfer and mixing of the reactor, and the defects of the traditional tank reactor in this regard become one of the bottlenecks in obtaining high-performance polymerization products. The invention provides a micro-reaction synthesis method of low-molecular-weight polyacrylic acid, which can prepare a series of low-molecular-weight polyacrylic acid products with a number-average molecular weight of 800-5000 g/mol and a polymer dispersion index of less than 1.5.

The object of the present invention is achieved through the following technical solutions:

The invention provides a micro-reaction synthesis method of low-molecular-weight polyacrylic acid, comprising: reacting an acrylic acid solution, an initiator solution and a polymerization inhibitor solution in a microchannel reactor synthesis device to obtain a number-average molecular weight between 800-5000 g/mol Among them, a series of low-molecular-weight polyacrylic acid products with a polymer dispersibility index less than 1.5; wherein, the concentration of the initiator used is 5%-50% of the mass of the acrylic acid; the amount of the inhibitor used is 1-10% of the mass of the initiator; Described microchannel reactor synthesis device comprises microchannel reactor group (1) and back pressure valve (2) to form in series; Equipped with metering pump feeding system (3) and heat transfer oil temperature control system (4); The channel reactors are all equipped with two feed ports and one discharge port; the reaction residence time in the synthesis device of the microchannel reactor is 0.1-60s, and the reaction temperature is 90°C-140°C.

In the micro-reaction synthesis method described in the present invention, the channel aperture of the channel reactor group is preferably square or circular, the effective inner diameter is 200 μm-2000 μm, and there are a number of elliptical internal mixing channels in the channel; a single micro The microchannel length of the channel reactor is 0.5-2.0m.

In the micro-reaction synthesis method described in the present invention, preferably, the micro-channel reactor group is used in combination with 2-6 micro-channel reactors in series.

In the micro-reaction synthesis method of the present invention, the acrylic acid solution is calculated by weight percentage, each component and its content are 20% to 100% of acrylic acid, 0% to 80% of water, and 0% to 40% of isopropanol; The solution is calculated by weight percentage, each component and its content are initiator 4-40%, water 60-96%; the polymerization inhibitor solution is calculated by weight percentage, each component and its content are polymerization inhibitor 5-10%, The balance is water. Further preferably, the injection mass ratio of the acrylic acid solution and the initiator solution is 1:1.

In the micro-reaction synthesis method of the present invention, the initiator is ammonium persulfate or potassium persulfate; the polymerization inhibitor is hydroquinone, tetramethylpiperidinol nitroxide free radical or p-hydroxyanisole or phenothiazines.

A micro-reaction synthesis method of low-molecular-weight polyacrylic acid of the present invention has advantages and positive effects:

1. The process flow is simple and continuous production can be realized;

2. The reaction time is short, the mass and heat transfer rate is fast, and the energy consumption is low;

3. Low safety risk, strong controllability and small amplification effect.

Description of drawings

Fig. 1 is the structural representation of the synthesis device of microchannel reactor of the present invention.

Among them, 1 is a microchannel reactor group, 2 is a back pressure valve, 3 is a metering pump feeding system, and 4 is a temperature control system.

Detailed ways

The technical solutions of the present invention will be further described below in conjunction with specific embodiments. The content described in the embodiments of the present invention is only used to illustrate the technical solutions of the present invention, and shall not and will not limit the scope of the technical solutions claimed in the present invention.

Example 1:

The microchannel reactor synthesis device shown in Figure 1 is adopted, including six microchannel reactors connected in series. The specifications of a single microchannel reactor are: channel inner diameter 2000μm, microchannel length 0.8m, liquid holdup 30mL; Propanol 20%, initiator solution (B) by weight percentage, each component and its content are 16% of ammonium persulfate and 84% of water. The flow rates of A and B are both 90mL/min. Both A and B are injected simultaneously from the two inlets of the first microchannel reactor, and the materials at the outlet of the sixth microchannel reactor are discharged, and cooled in an ice-water bath immediately after discharge. The reaction temperature was set as follows: the first microchannel reactor was not heated, the second, third and fourth reactors were heated to 115°C, and the fifth and sixth reactors were not heated. The residence time of the material from the 1st to the 6th is 60s. The back pressure was set at 0.2MPa.

The reaction result is: polyacrylic acid molecular weight Mn=4360g/mol, PDI=1.29, acrylic acid conversion rate is 99.3%.

Example 2

The microchannel reactor synthesis device shown in Figure 1 is used, including a microchannel reactor group composed of three microchannel reactors connected in series. The specifications of a single microchannel reactor are: channel inner diameter 1000 μm, microchannel length 0.7m, liquid holdup 6mL; acrylic acid solution (A) is calculated by weight percentage, and each component and its content are 60% of acrylic acid and 40% of isopropanol , Initiator solution (B) by weight percentage, each component and its content are ammonium persulfate 3%, water 97%. The flow rates of A and B are both 36mL/min, and the residence time of the material from the first to the third is 15s; both A and B are simultaneously injected from the two inlets of the first microchannel reactor, and the third microchannel reactor The material at the outlet of the reactor is discharged, and immediately cooled in an ice-water bath after discharge. The reaction temperature is set as follows: the first microchannel reactor is not heated, and the second and third are heated to 120°C. The back pressure was set at 0.3MPa.

The reaction result is: polyacrylic acid molecular weight Mn=4185g/mol, PDI=1.41, acrylic acid conversion rate is 99.1%.

Example 3

The microchannel reactor synthesis device shown in Figure 1 is adopted, which includes a microchannel reactor group composed of two microchannel reactors connected in series. The specifications of a single microchannel reactor are: channel inner diameter 200 μm, microchannel length 2.0 m, liquid holdup 1 mL; acrylic acid solution (A) is calculated by weight percentage, and each component and its content are 20% acrylic acid and 80% isopropanol , The initiator solution (B) is calculated by weight percentage, and each component and its content are 10% of ammonium persulfate and 90% of water. The flow rates of A and B are both 60mL/min, and the residence time of the material from the first to the second is 1s; both A and B are simultaneously injected from the two inlets of the first microchannel reactor, and the second microchannel reactor The material at the outlet of the reactor is discharged, and immediately cooled in an ice-water bath after discharge. The reaction temperature is set as follows: two sets are heated to 140°C at the same time. The back pressure was set at 0.6MPa.

The reaction result is: polyacrylic acid molecular weight Mn=855g/mol, PDI=1.12, acrylic acid conversion rate 98.5%.

Example 4

The microchannel reactor synthesis device shown in Figure 1 is used, including a microchannel reactor group composed of three microchannel reactors connected in series. The specifications of a single unit are: channel inner diameter 1600μm, microchannel length 0.5m, liquid holdup 12mL; acrylic acid solution (A) by weight percentage, each component and its content are 100% acrylic acid, initiator solution (B) by weight percentage Each component and its content are ammonium persulfate 40%, water 60%, and the polymerization inhibitor solution (C) is calculated by weight percentage. Each component and its content are 10% for polymerization inhibitor 701, and the balance is water . The flow rate of A and B is 180mL/min, the flow rate of C is 90mL/min, and the residence time of material in the 1st, 2 two microchannel reactors is 4s; The two inlets are injected simultaneously, and the material is discharged from the outlet of the third microchannel reactor, and the polymerization inhibitor solution is injected into one inlet of the third microchannel reactor. Cool in a water bath immediately after discharge. The reaction temperature is set as follows: the first and second sets are heated to 120°C at the same time. The back pressure was set at 0.3MPa.

The reaction result is: polyacrylic acid molecular weight Mn=1296g/mol, PDI=1.20, acrylic acid conversion rate is 99.2%.

Example 5

The microchannel reactor synthesis device shown in Figure 1 is used, including a microchannel reactor group composed of three microchannel reactors connected in series. The specifications of a single unit are: channel inner diameter 1600μm, microchannel length 0.5m, liquid holdup 12mL; acrylic acid solution (A) is calculated by weight percentage, each component and its content are 80% acrylic acid, 20% water, initiator solution (B ) by weight percentage, each component and its content are ammonium persulfate 16%, water 84%, and the polymerization inhibitor solution (C) is by weight percentage, each component and its content are hydroquinone 5%, and the remaining The amount is water. The flow rates of A and B are both 60mL/min, and the flow rate of C is 30mL/min; the residence time of the material in the first and second microchannel reactors is 12s, and A and B all flow from the first two microchannel reactors. The two inlets are injected at the same time, and the material is discharged from the outlet of the third microchannel reactor, and one inlet of the third microchannel reactor is injected into C. Cool in a water bath immediately after discharge. The reaction temperature is set as follows: the first and second sets are heated to 90°C at the same time. The back pressure was set at 0.1MPa.

The reaction result is: polyacrylic acid molecular weight Mn=2267g/mol, PDI=1.20, acrylic acid conversion rate 99.0%.

Claims (6)

1. A micro-reaction synthesis method of low molecular weight polyacrylic acid is characterized in that: reacting an acrylic acid solution, an initiator solution and a polymerization inhibitor solution in a micro-channel reactor synthesis device to obtain a series of low-molecular-weight polyacrylic acid products with the number average molecular weight of 800-5000g/mol and the polymer dispersity index of less than 1.5; wherein the initiator is used at a concentration of 5-50% of the mass of the acrylic acid; the polymerization inhibitor is used in an amount of 1-10% of the mass of the initiator; the microchannel reactor synthesis device comprises a microchannel reactor group (1) and a back pressure valve (2) which are connected in series; a metering pump feeding system (3) and a heat conducting oil temperature control system (4) are arranged; each microchannel reactor is provided with two feed inlets and one discharge outlet; the reaction residence time of the reaction in the synthesis device of the microchannel reactor is 0.1-60s, and the reaction temperature is 90-140 ℃.

2. The micro-reaction synthesis method according to claim 1, wherein: the aperture of the micro-channel reactor group is square or round, the effective inner diameter is 200-2000 mu m, and the channels are provided with oval internal mixing channels with different numbers; the microchannel length of a single microchannel reactor is 0.5-2.0m.

3. The micro-reaction synthesis method according to claim 1, wherein: the micro-channel reactor group is formed by combining 2-6 micro-channel reactors in series.

4. The micro-reaction synthesis method according to claim 1, wherein: the acrylic acid solution comprises, by weight, 20-100% of acrylic acid, 0-80% of water and 0-40% of isopropanol; the initiator solution comprises 4-40% of initiator and 60-96% of water according to weight percentage; the polymerization inhibitor solution comprises 5-10% of polymerization inhibitor and the balance of water according to weight percentage.

5. The micro-reaction synthesis method according to claim 1, wherein: the initiator is ammonium persulfate or potassium persulfate; the polymerization inhibitor is hydroquinone, tetramethyl piperidinol nitroxide radical or p-hydroxyanisole or phenothiazine.

6. The method for synthesizing a micro-reaction according to claim 4, wherein: the mass ratio of the acrylic acid solution to the initiator solution is 1:1.

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