A continuous production apparatus for low molecular weight polyglycolic acid

Abstract

The utility model belongs to polyglycolic acid production equipment technical field relates to a kind of low molecular weight polyglycolic acid continuous production device, including first reaction kettle, second reaction kettle, third reaction kettle, fourth reaction kettle, fifth reaction kettle, first branch, second branch and third branch;The first reaction kettle, second reaction kettle, third reaction kettle, fourth reaction kettle and fifth reaction kettle are sequentially communicated along material flow direction;The first reaction kettle is also communicated with third reaction kettle by first branch;The first reaction kettle is also communicated with fourth reaction kettle by second branch;The third reaction kettle is also communicated with fifth reaction kettle by third branch.The utility model can avoid that conveying pipeline occurs frequent blockage, to make low molecular weight polyglycolic acid continuous production.

Description

Technical Field

[0001] This utility model belongs to the technical field of polyglycolic acid production equipment, and relates to a continuous production device for low molecular weight polyglycolic acid. Background Technology

[0002] The process of producing polyglycolic acid from dimethyl oxalate includes: hydrogenation of dimethyl oxalate to produce methyl glycolate; then, under the action of a catalyst, methyl glycolate undergoes condensation polymerization to form polyglycolic acid; the condensation polymerization includes prepolymerization (referred to as prepolymerization) and final condensation polymerization. In prepolymerization, methyl glycolate undergoes multiple prepolymerization reactions to gradually form low molecular weight polyglycolic acid (intermediate product); then, the low molecular weight polyglycolic acid (intermediate product) further undergoes final condensation polymerization to obtain high molecular weight polyglycolic acid, i.e., polyglycolic acid. In actual production, prepolymerization is a crucial step in the production of polyglycolic acid from dimethyl oxalate, and the success of the prepolymerization process directly affects the subsequent final condensation polymerization process.

[0003] The existing prepolymer production equipment consists of multiple prepolymer reactors connected in series, through which methyl glycolate with a purity >97% is introduced for a step-by-step reaction. Methyl glycolate is prepolymerized to produce polyglycolic acid with a purity of 95%. After further multi-stage prepolymerization, it finally forms polyglycolic acid with a purity of 95%, which is low molecular weight polyglycolic acid (intermediate product). Although existing prepolymerization equipment can produce low molecular weight polyglycolic acid (PGA), methyl glycolate with a purity >97% requires a sufficient residence time in the prepolymerization reactor to obtain PGA that meets purity requirements. However, as the prepolymerization reaction progresses, the purity of the PGA increases, meaning the PGA content in the material transported to the next stage becomes increasingly higher. Furthermore, as the PGA content generated in each stage of prepolymerization increases, its viscosity also rises. The high-viscosity PGA generated in the previous reactor requires a longer time to be transported to the next stage reactor, making it difficult to deliver the high-viscosity PGA to subsequent reactors in a timely and stable manner, resulting in poor production continuity and low production efficiency. In addition, the increased viscosity of PGA can cause frequent blockages in the reactor's transport pipelines, requiring shutdown and maintenance in case of blockage, making it difficult to achieve continuous and stable prepolymerization. Utility Model Content

[0004] To address the technical problems of poor continuity, low production efficiency, and frequent blockages in pipelines in the existing production of low molecular weight polyglycolic acid, which makes it difficult to achieve continuous and stable prepolymerization of low molecular weight polyglycolic acid, this utility model provides a continuous production device for low molecular weight polyglycolic acid.

[0005] This invention adds a first branch, a second branch, and a third branch to the existing five reaction vessels connected in series. This ensures continuous and stable delivery of the reaction materials while avoiding frequent blockages in the delivery pipelines, thereby enabling continuous and stable production of low molecular weight polyglycolic acid and improving production efficiency.

[0006] To achieve the above objectives, the technical solution adopted by this utility model is as follows:

[0007] A continuous production apparatus for low molecular weight polyglycolic acid, characterized in that it comprises a first reaction vessel, a second reaction vessel, a third reaction vessel, a fourth reaction vessel, a fifth reaction vessel, a first branch, a second branch, and a third branch;

[0008] The first, second, third, fourth, and fifth reactors are connected sequentially along the material flow direction; the first reactor is also connected to the third reactor via a first branch; the first reactor is also connected to the fourth reactor via a second branch; and the third reactor is also connected to the fifth reactor via a third branch.

[0009] Furthermore, a second reaction vessel level gauge is also provided on the second reaction vessel.

[0010] Furthermore, a third reaction vessel level gauge is also provided on the third reaction vessel.

[0011] Furthermore, the fourth reactor is also equipped with a fourth reactor level gauge.

[0012] Furthermore, a fifth reaction vessel level gauge is also provided on the fifth reaction vessel.

[0013] Further specified, a first flow regulating valve is provided between the first reactor and the second reactor; a second flow regulating valve is provided on the first branch; and a third flow regulating valve is provided on the second branch.

[0014] Further specified, a fifth flow regulating valve is provided between the third and fourth reactors; and a sixth flow regulating valve is provided on the third branch.

[0015] Further specified, a fourth flow regulating valve is provided between the second and third reactors; and a seventh flow regulating valve is provided between the fourth and fifth reactors.

[0016] Furthermore, a transfer pump is provided between the third and fourth reactors; and the transfer pump is located between the third reactor and the third branch.

[0017] Compared with the prior art, the beneficial effects of this utility model are:

[0018] 1. In this utility model, by adding a first branch, a second branch, and a third branch to five reactors connected in series, the low-purity prepolymer product at the front end is transported across stages and mixed with the high-purity prepolymer product at the back end. On the one hand, the low-purity prepolymer product has low viscosity, which facilitates the timely and stable transport of prepolymer reaction products at each stage and improves production efficiency. On the other hand, it can avoid the problem of frequent pipeline blockage caused by the transport of large amounts of high-viscosity polyglycolic acid and ensure the continuous production of low molecular weight polyglycolic acid.

[0019] 2. This utility model installs level gauges on the second, third, fourth, and fifth reaction vessels to monitor the liquid level in each vessel in real time. By controlling the liquid level within a certain range, the prepolymerization reaction in each reaction vessel can be carried out normally, thereby improving the continuity and stability of the production system.

[0020] 3. In this utility model, by setting multiple flow regulating valves and multiple reactor level gauges, the flow rate of the material conveyed in each branch is adjusted by the multiple flow regulating valves; and in conjunction with the multiple reactor level gauges, the continuity, stability and controllability of low molecular weight polyglycolic acid production are ensured.

[0021] In summary, the low molecular weight polyglycolic acid continuous production device provided by this utility model has a simple structure and is easy to operate; it enables methyl glycolate with a purity >97% to generate low molecular weight polyglycolic acid through continuous prepolymerization reaction, avoiding production shutdowns and maintenance caused by pipeline blockage, and saving economic losses and maintenance costs caused by shutdowns. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the continuous production apparatus for low molecular weight polyglycolic acid according to this utility model.

[0023] In the picture:

[0024] 10-First reactor; 101-Infeed line; 102-Discharge line; 20-Second reactor; 201-Second reactor level gauge; 30-Third reactor; 301-Third reactor level gauge; 40-Fourth reactor; 401-Fourth reactor level gauge; 50-Fifth reactor; 501-Fifth reactor level gauge; 60-Transfer pump; 70-First branch; 80-Second branch; 90-Third branch; 100-First flow control valve; 110-Second flow control valve; 120-Third flow control valve; 130-Fourth flow control valve; 140-Fifth flow control valve; 150-Sixth flow control valve; 160-Seventh flow control valve. Detailed Implementation

[0025] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present utility model without creative effort are within the scope of protection of the present utility model.

[0026] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0027] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in sequences other than those illustrated or described herein.

[0028] See Figure 1 This utility model provides a continuous production device for low molecular weight polyglycolic acid, including a first reaction vessel 10, a second reaction vessel 20, a third reaction vessel 30, a fourth reaction vessel 40, a fifth reaction vessel 50, a first branch line 70, a second branch line 80 and a third branch line 90.

[0029] The first reactor 10, the second reactor 20, the third reactor 30, the fourth reactor 40, and the fifth reactor 50 are connected sequentially along the material flow direction; the first reactor 10 is also connected to the third reactor 30 through the first branch 70; the first reactor 10 is also connected to the fourth reactor 40 through the second branch 80; and the third reactor 30 is also connected to the fifth reactor 50 through the third branch 90.

[0030] In this invention, the first reaction vessel 10, the second reaction vessel 20, the third reaction vessel 30, the fourth reaction vessel 40, and the fifth reaction vessel 50 are all prepolymerization reaction vessels, so that methyl glycolate with a purity >97% undergoes a multi-stage prepolymerization reaction through the five reaction vessels to generate low molecular weight polyglycolic acid.

[0031] Preferably, in this embodiment, a feed line 101 and a discharge line 102 are respectively provided on the first reactor 10. The feed line 101 is used to feed methyl glycolate with a purity >97% into the first reactor 10. The methyl glycolate with a purity >97% enters the first reactor 10 and, under a slight positive pressure of 130°C and 2KPa-3KPa, yields polyglycolic acid with a purity of 40%. Then, it enters the second reactor 20 through the discharge line 102 and is subjected to a slight positive pressure of 150°C and 2KPa-3KPa. Under the following conditions, 60% pure polyglycolic acid is obtained; then it enters the third reactor 30, and under the conditions of 170℃ and 70KPaA absolute pressure, 70% pure polyglycolic acid is obtained; then it continues to enter the fourth reactor 40, and under the conditions of 180℃ and 30KPaA absolute pressure, 80% pure polyglycolic acid is obtained; finally, it enters the fifth reactor 50, and under the conditions of 220℃ and 1.5KPaA absolute pressure, 95% pure polyglycolic acid product is obtained, which is the low molecular weight polyglycolic acid produced by the prepolymerization unit.

[0032] Meanwhile, the 40% purity polyglycolic acid exiting the first reactor 10 is further divided into two branch lines: the first branch line connects to the third reactor 30 via the first branch line 70, and the second branch line connects to the fourth reactor 40 via the second branch line 80; and the 70% purity polyglycolic acid exiting the third reactor 30 is also divided into a branch line, namely, connected to the fifth reactor 50 via the third branch line 90. In other words, in addition to the first reactor 10 supplying a portion of the 40% purity polyglycolic acid to the second reactor 20, a portion of the 40% purity polyglycolic acid is also diverted to the third reactor 30 via the first branch line 70 and to the fourth reactor 40 via the second branch line 80; in addition to the third reactor 30 supplying a portion of the 70% purity polyglycolic acid to the fourth reactor 40, the remaining portion of the 70% purity polyglycolic acid is diverted to the fifth reactor 50 via the third branch line 90. This method involves diverting and paralleling low-purity polyglycolic acid (PGA) to the third reactor 30, the fourth reactor 40, and the fifth reactor 50. This diverts the low-purity PGA generated in the first reactor 10 to the third reactor 30 and the fourth reactor 40, where it is mixed with the high-purity PGA in the corresponding reactors. Simultaneously, the low-purity PGA generated in the third reactor 30 is transported to the fifth reactor 50 and mixed with the high-purity PGA. In other words, this invention achieves the mixing of low-purity and high-purity PGA through parallel diversion and transportation. On one hand, the low-purity PGA has low viscosity, facilitating the timely and stable transport of PGA of different purities generated at each stage, thus improving production efficiency. On the other hand, it avoids frequent pipe blockages caused by transporting large amounts of high-viscosity PGA, ensuring continuous production of low-molecular-weight PGA.

[0033] In this embodiment, a second reaction vessel level gauge 201 is also provided on the second reaction vessel 20 to monitor the level of 40% pure polyglycolic acid in the second reaction vessel 20.

[0034] In this embodiment, a third reaction vessel level gauge 301 is also installed on the third reaction vessel 30. The third reaction vessel level gauge 301 monitors the liquid levels of 40% pure polyglycolic acid and 60% pure polyglycolic acid in the third reaction vessel 30.

[0035] In this embodiment, a fourth reaction vessel level gauge 401 is also installed on the fourth reaction vessel 40. The fourth reaction vessel level gauge 401 monitors the liquid levels of 40% pure polyglycolic acid and 70% pure polyglycolic acid in the fourth reaction vessel 40.

[0036] In this embodiment, a fifth reaction vessel level gauge 501 is also installed on the fifth reaction vessel 50. The fifth reaction vessel level gauge 501 monitors the liquid levels of 80% pure polyglycolic acid and 70% pure polyglycolic acid in the fifth reaction vessel 50.

[0037] In this embodiment, a first flow regulating valve 100 is provided between the first reaction vessel 10 and the second reaction vessel 20; that is, a first flow regulating valve 100 is provided on the discharge pipeline 102; the flow rate of 40% pure polyglycolic acid delivered from the first reaction vessel 10 to the second reaction vessel 20 is adjusted by the first flow regulating valve 100.

[0038] In this embodiment, a second flow regulating valve 110 is provided on the first branch 70; the flow rate of 40% pure polyglycolic acid delivered from the first reactor 10 to the third reactor 30 is adjusted by the second flow regulating valve 110.

[0039] In this embodiment, a third flow regulating valve 120 is provided on the second branch 80; the flow rate of 40% pure polyglycolic acid delivered from the first reactor 10 to the fourth reactor 40 is adjusted by the third flow regulating valve 120.

[0040] In this embodiment, a fifth flow regulating valve 140 is provided between the third reactor 30 and the fourth reactor 40; the flow rate of 70% pure polyglycolic acid delivered from the third reactor 30 to the fifth reactor 50 is adjusted by the fifth flow regulating valve 140.

[0041] In this embodiment, a sixth flow regulating valve 150 is provided on the third branch 90. The flow rate of 70% pure polyglycolic acid delivered from the third reactor 30 to the fifth reactor 50 is adjusted by the sixth flow regulating valve 150.

[0042] In this embodiment, a fourth flow regulating valve 130 is also provided between the second reactor 20 and the third reactor 30; and a seventh flow regulating valve 160 is provided between the fourth reactor 40 and the fifth reactor 50. During operation, the fourth flow regulating valve 130 regulates the flow rate of 60% purity polyglycolic acid supplied from the second reactor 20 to the third reactor 30; and the seventh flow regulating valve 160 regulates the flow rate of 80% purity polyglycolic acid supplied from the fourth reactor 40 to the fifth reactor 50.

[0043] In this embodiment, a transfer pump 60 is also provided between the third reactor 30 and the fourth reactor 40; and the transfer pump 60 is located between the third reactor 30 and the third branch 90; the transfer pump 60 enables the material coming out of the bottom of the third reactor 30 to be divided into two streams and flow quickly into the fourth reactor 40 and the fifth reactor 50, thereby accelerating the material conveying speed and improving production efficiency.

[0044] In practice, to ensure the continuity and stability of low molecular weight polyglycolic acid production, the liquid levels in the second reactor 20, third reactor 30, fourth reactor 40, and fifth reactor 50 are monitored by level gauges 201, 301, 401, and 50 respectively. Simultaneously, the liquid levels in the second reactor 20, third reactor 30, fourth reactor 40, and fifth reactor 50 are monitored by flow control valves 100, 110, 120, 130, 140, 150, and 160 to maintain the liquid levels within a certain range, ensuring the normal operation of the prepolymerization reaction in each reactor and improving the continuity and stability of the production system.

[0045] Specifically, during operation, the liquid level in the second reactor 20 is controlled at 60% of the height of its reactor equipment (i.e., 2 / 3); the liquid levels in the third reactor 30, the fourth reactor 40, and the fifth reactor 50 are all controlled at 80% of the height of their respective reactor equipment (i.e., 4 / 5). This effectively ensures that the purity of the final low molecular weight polyglycolic acid reaches 95%. At this time, the production unit operates stably and continuously, and there are no pipeline blockage problems.

[0046] The above describes the continuous production device for low molecular weight polyglycolic acid provided by this utility model. It solves the problems of poor material conveying continuity, low production efficiency, and frequent blockage of conveying pipelines in the production of polyglycolic acid from dimethyl oxalate. It realizes the continuous and stable production of low molecular weight polyglycolic acid, which not only improves production efficiency but also greatly reduces the frequency of shutdowns to clear pipelines, thus saving maintenance costs and reducing various losses caused by shutdowns.

[0047] The above are merely preferred embodiments of this utility model and are not intended to limit the scope of this utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A continuous production apparatus for low molecular weight polyglycolic acid, characterized in that, It includes a first reactor (10), a second reactor (20), a third reactor (30), a fourth reactor (40), a fifth reactor (50), a first branch (70), a second branch (80), and a third branch (90); The first reactor (10), the second reactor (20), the third reactor (30), the fourth reactor (40), and the fifth reactor (50) are connected sequentially along the material flow direction; the first reactor (10) is also connected to the third reactor (30) through the first branch (70); the first reactor (10) is also connected to the fourth reactor (40) through the second branch (80); the third reactor (30) is also connected to the fifth reactor (50) through the third branch (90).

2. The continuous production apparatus for low molecular weight polyglycolic acid according to claim 1, characterized in that, The second reactor (20) is also equipped with a second reactor level gauge (201).

3. The continuous production apparatus for low molecular weight polyglycolic acid according to claim 2, characterized in that, The third reactor (30) is also equipped with a third reactor level gauge (301).

4. The continuous production apparatus for low molecular weight polyglycolic acid according to claim 3, characterized in that, The fourth reactor (40) is also equipped with a fourth reactor level gauge (401).

5. The continuous production apparatus for low molecular weight polyglycolic acid according to claim 4, characterized in that, The fifth reactor (50) is also equipped with a fifth reactor level gauge (501).

6. The continuous production apparatus for low molecular weight polyglycolic acid according to claim 1, characterized in that, A first flow regulating valve (100) is provided between the first reactor (10) and the second reactor (20); a second flow regulating valve (110) is provided on the first branch (70); and a third flow regulating valve (120) is provided on the second branch (80).

7. The continuous production apparatus for low molecular weight polyglycolic acid according to claim 6, characterized in that, A fifth flow regulating valve (140) is provided between the third reactor (30) and the fourth reactor (40); a sixth flow regulating valve (150) is provided on the third branch (90).

8. The continuous production apparatus for low molecular weight polyglycolic acid according to claim 7, characterized in that, A fourth flow regulating valve (130) is provided between the second reactor (20) and the third reactor (30); a seventh flow regulating valve (160) is provided between the fourth reactor (40) and the fifth reactor (50).

9. The continuous production apparatus for low molecular weight polyglycolic acid according to any one of claims 1-8, characterized in that, A transfer pump (60) is also provided between the third reactor (30) and the fourth reactor (40); and the transfer pump (60) is located between the third reactor (30) and the third branch (90).

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