CN215506720U - Device for preparing polyglycolic acid through low-temperature polymerization - Google Patents
Device for preparing polyglycolic acid through low-temperature polymerization Download PDFInfo
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- CN215506720U CN215506720U CN202121717270.6U CN202121717270U CN215506720U CN 215506720 U CN215506720 U CN 215506720U CN 202121717270 U CN202121717270 U CN 202121717270U CN 215506720 U CN215506720 U CN 215506720U
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Abstract
The utility model discloses a device for preparing polyglycolic acid through low-temperature polymerization. The device comprises a melt mixing kettle, an external circulating heat exchange unit coupled with the melt mixing kettle, a static mixer sequentially arranged at the downstream of the melt mixing kettle, and tackifying equipment coupled with the static mixer.
Description
Technical Field
The utility model relates to the field of polymer preparation, in particular to a device and a method for preparing polyglycolic acid by low-temperature polymerization.
Background
Polyglycolic acid (also called polyglycolic acid, abbreviated as PGA) is a biodegradable aliphatic polymer, and at present, in practical application of reactive extrusion equipment (e.g., reactive twin-screw extruder) for preparing PGA based on bulk polymerization of Glycolide (GA), glycolide usually needs to be subjected to polymerization reaction at a higher reaction temperature (e.g., 220-. However, the high reaction temperature not only means high energy consumption, but also easily causes great or serious thermal degradation of the produced PGA, which is disadvantageous for increasing the molecular weight of the final product, and also causes broadening of the molecular weight distribution of the final product, which adversely affects the mechanical properties, aging resistance, etc. of the material.
Therefore, there is an urgent need in the art to develop a device and method suitable for preparing polyglycolic acid through low-temperature polymerization.
SUMMERY OF THE UTILITY MODEL
The utility model aims to provide a device and a method for preparing polyglycolic acid through low-temperature polymerization.
In a first aspect of the utility model, a device for preparing polyglycolic acid by low-temperature polymerization is provided, which comprises a melt mixing kettle, an external circulation heat exchange unit coupled with the melt mixing kettle, a static mixer sequentially arranged at the downstream of the melt mixing kettle, and tackifying equipment coupled with the static mixer.
In another embodiment, the external circulation heat exchange unit comprises an external circulation discharge port, an external circulation feed port, an external circulation pipeline connecting the external circulation discharge port and the external circulation feed port, a heat exchanger arranged on the external circulation pipeline, and a circulation pump.
In another embodiment, the external circulation discharge port and the external circulation feed port are respectively connected to the lower part of the melting and mixing kettle, and the joint of the external circulation feed port and the lower part of the melting and mixing kettle is higher than the joint of the external circulation discharge port and the lower part of the melting and mixing kettle.
In another embodiment, the apparatus has a reaction aid storage tank connected to the melt mixing kettle feed port.
In another embodiment, the static mixer is connected with the tackifying equipment through a material conveying assembly, and the material conveying assembly comprises a material conveying pipeline connecting a discharge port of the static mixer and a feed port of the tackifying equipment, a melt pump arranged on the material conveying pipeline, and a cleaning liquid dredging pipe connected with the melt pump in parallel on the material conveying pipeline.
In another embodiment, a cleaning liquid drainage branch is arranged on a material conveying pipeline between the melt pump and the feed inlet of the tackifying device.
In another embodiment, a three-way valve is arranged at the position where the cleaning solution drain conduit is connected to the material conveying pipeline.
In another embodiment, the cleaning solution draining branch is connected with the material conveying pipeline through a three-way valve.
In another embodiment, a melt metering pump is arranged between the discharge port of the melt mixing kettle and the static mixer.
In a second aspect of the present invention, there is provided a process for the preparation of polyglycolic acid by low temperature polymerization of the apparatus provided by the present invention as described above, comprising the steps of:
(1) mixing molten glycolide with a reaction auxiliary agent to obtain a fluid premix;
(2) prepolymerizing the fluid premix obtained in step (1) in a static mixer to obtain a glycolic acid prepolymer;
(3) and (3) subjecting the glycolic acid prepolymer obtained in the step (2) to final polymerization by a tackifying device to obtain polyglycolic acid.
In another embodiment, the reaction auxiliary used in step (1) comprises a catalyst, a polyol and a dehydrating agent.
In another embodiment, glycolide is used in step (1), and the purity of the glycolide is not less than 98%; preferably not less than 98.5%; the acidity is not more than 20 mmol/kg.
In another embodiment, the catalyst is used in an amount of 0.001 to 1 wt% thereof, the polyol is used in an amount of 0.01 to 0.1 wt% thereof, and the dehydrating agent is used in an amount of 0.2 to 1 wt% thereof, based on the mass of glycolide.
In another embodiment, molten glycolide having a temperature of 90 to 120 ℃ is mixed with the reaction auxiliary in step (1).
In another embodiment, the prepolymerization is carried out in step (2) at 120-200 ℃.
In another embodiment, the static mixer used in step (2) adopts at least 2-stage gradient temperature raising method, the first stage temperature range is between 120-180 ℃, and the last stage temperature range is between 180-200 ℃.
In another embodiment, the tackifying equipment in step (3) is devolatilized under the absolute pressure of less than or equal to 500Pa and the temperature of 220-250 ℃.
Accordingly, the utility model provides a device and a method for preparing polyglycolic acid by low-temperature polymerization.
Drawings
FIG. 1 is a schematic view of an apparatus for preparing polyglycolic acid by low temperature polymerization, which is provided in example 1 of the present invention.
Detailed Description
The inventor has made extensive and intensive studies, and the utility model uses the polyol as a reactive agent to reduce the activation energy of the ring-opening polymerization reaction of glycolide, so that the glycolide can generate the ring-opening polymerization chain growth reaction at a lower reaction temperature (about 180-; in addition, the dehydrating agent is used as a reaction auxiliary agent and is added together with the catalyst and the polyalcohol at the initial stage instead of being added in the middle of the reaction, so that the complexity of the process operation is greatly reduced, and the stability of the product quality is ensured; further, utility model people still discovers through experimental contrast: the dehydrating agent and the polyhydric alcohol in the reaction auxiliary agent can play a role of synergy, and the combination of the dehydrating agent and the polyhydric alcohol is favorable for enabling the monomer (glycolide) in the reaction system to form a chain at a lower reaction temperature in the presence of a catalyst, so that the chain growth can be stably continued, and simultaneously, the thermal degradation degree of a polymer generated in the system can be inhibited, and finally the PGA with higher molecular weight and relatively narrow molecular weight distribution can be obtained. On the basis of this, the present invention has been completed.
It should be noted that in the present invention, "tackifying device" plays a role in devolatilization, and can promote further polymerization of glycolic acid prepolymer, and timely remove the generated small molecules, so as to further increase the molecular weight of the polymer, and correspondingly, the viscosity of the polymer; the "tackifying means" in the present invention may be, for example, but not limited to, a twin-screw extruder provided with only a devolatilization section.
Low-temperature polymerization preparation polyglycolic acid device
The utility model provides a device suitable for preparing polyglycolic acid by low-temperature polymerization, which comprises a melt mixing kettle, an external circulating heat exchange unit coupled with the melt mixing kettle, a static mixer sequentially arranged at the downstream of the melt mixing kettle along the material advancing direction, and tackifying equipment coupled with the static mixer.
As used herein, "coupled" means that two devices are operatively connected and in an interactive, interactive relationship with each other.
As used herein, "feed direction" refers to the direction in which the molten material travels forward.
The external circulation heat exchange unit comprises an external circulation discharge port, an external circulation feed port and an external circulation pipeline for connecting the external circulation discharge port and the external circulation feed port.
The external circulation discharge port and the external circulation feed inlet are respectively connected to the lower part of the melting mixing kettle, and the joint of the external circulation feed inlet and the lower part of the melting mixing kettle is higher than the joint of the external circulation discharge port and the lower part of the melting mixing kettle.
Preferably, in a working state, the joint of the external circulation discharge port and the lower part of the melting and mixing kettle is located below the liquid level of the molten material in the melting and mixing kettle, and further, the horizontal line of the joint of the external circulation discharge port and the lower part of the melting and mixing kettle is lower than the lower edge of the stirring blade in the melting and mixing kettle.
The junction of external circulation feed inlet and melt mixing cauldron lower part is arranged in the top of melt material liquid level in the melt mixing cauldron, furtherly, the water flat line of the junction of external circulation feed inlet and melt mixing cauldron lower part is higher than melt material liquid level in the melt mixing cauldron, but should not be too high, for example can be a little higher than melt material liquid level, does not hinder to return the feeding can.
The external circulating heat exchange unit also comprises a heat exchanger and a circulating pump which are arranged on the external circulating pipeline.
A heating jacket is arranged on the outer side of the melting and mixing kettle; aiming at the condition that no external circulating heat exchange unit exists, the temperature of the heating jacket is set to be 90-120 ℃ in a working state; aiming at the condition that an external circulation heat exchange unit is arranged, in a working state, the initial temperature of a heating jacket is set to be 85-90 ℃, after a monomer which is firstly added into a melting and mixing kettle is heated and melted, the heating jacket can stop working, at the moment, a heat preservation effect can be realized, then the melted monomer is heated and heated through the external circulation heat exchange unit, the temperature of a heat exchanger can be set to be 90-120 ℃, the flow rate of the melted monomer passing through the heat exchanger is adjusted through a circulating pump, so that the melted glycolide can be heated to be 90-120 ℃, and then the melted glycolide returns to the melting and mixing kettle through an external circulation pipeline, and the internal circulation of a reaction material in the melting and mixing kettle can be established; in order to reduce heat loss, a layer of heat-insulating jacket can be wrapped on the external circulation pipeline; in addition, the external circulation pipeline can also be provided with conventional heat tracing.
For the situation that the external circulation heat exchange unit is arranged, the heat exchange efficiency of the heat exchanger is far higher than that of the melting and mixing kettle, so that the volume of the melting and mixing kettle can be reduced in a heat supply and outward movement mode, namely, the melting and mixing kettle with smaller volume can be selected to meet the heat requirement for heating and melting glycolide aiming at a certain heat exchange (namely heating) area under the condition that the external circulation heat exchange unit exists, and the requirement for industrial space is favorably reduced; in addition, due to the establishment of the external circulation heat exchange unit, the molten glycolide enters the heat exchanger for heating through the external circulation pipeline and then circulates back to the melting and mixing kettle, so that the internal circulation flow of reaction materials can be realized, and the phenomenon that the molten glycolide in a certain area at the bottom of the kettle is not uniformly heated (for example, is excessively heated) to cause coking and deterioration due to the insufficient disturbance capacity of a stirring paddle of the melting and mixing kettle can be avoided.
And electromagnetic valves are arranged at the kettle bottom discharge port, the external circulation discharge port and the external circulation feed port of the melting mixing kettle.
The top of the melting mixing kettle is also provided with a reaction material feeding port and a reaction auxiliary agent feeding port, wherein the reaction material feeding port is connected with a weightlessness scale through a material feeding pipe, the reaction auxiliary agent feeding port is connected with a reaction auxiliary agent storage tank arranged at the upstream of the melting mixing kettle through an auxiliary agent feeding pipe, and a liquid metering pump is further arranged on the auxiliary agent feeding pipe between the reaction auxiliary agent storage tank and the reaction auxiliary agent feeding port.
In one embodiment of the utility model, the weight loss scale is connected between a discharge port at the bottom of the screen and a reaction material feed port at the top of the melt mixing kettle.
And a melt metering pump is arranged between the static mixer and the melt mixing kettle, and a kettle bottom discharge port of the melt mixing kettle is connected with a feed port of the static mixer through the melt metering pump.
And a discharge port of the static mixer is connected with a feed port of the tackifying device through a material conveying assembly.
The material conveying assembly comprises a material conveying pipeline, a melt pump and a cleaning liquid dredging pipeline, wherein the material conveying pipeline is used for connecting a discharge port of the static mixer with a feed port of the tackifying device, the melt pump is arranged on the material conveying pipeline, the cleaning liquid dredging pipeline is connected with the melt pump in parallel, and a cleaning liquid discharging branch is arranged on the material conveying pipeline between the melt pump and the feed port of the tackifying device.
Preferably, the liquid inlet end and the liquid discharge end of the cleaning liquid dredging pipeline are connected in parallel to two sides of the melt pump through a three-way valve I.
Preferably, the cleaning liquid draining branch is connected with the material conveying pipeline through a three-way valve II.
Static mixers commonly used in the art, such as, but not limited to, SK type static mixers, SX type static mixers, SV type static mixers, and the like, may be used.
The tackifying apparatus used in the present invention may be, for example, a twin-screw extruder provided with only a devolatilization section.
In the technical device, a pipeline, a material conveying pipeline, a cleaning liquid dredging pipeline, a melt metering pump, a melt pump, a three-way valve I and a three-way valve II between a kettle bottom discharge port of a melting mixing kettle and a feed inlet of a static mixer are all provided with conventional heat tracing. In addition, the model of the metering pump can be selected according to the reaction time of the materials in the melting and mixing kettle and the volume of the pipeline, and the model requirements of the melt pump and the tackifying equipment are matched with the model of the melt metering pump.
In practical application, the weightlessness scale, the liquid metering pump, the electromagnetic valve, the circulating pump, the melt metering pump, the melt pump, the tackifying device and the like in the technical device can be connected with a computer through the existing known electric connection mode, so that the online control of the PGA production is realized.
Method for preparing polyglycolic acid by low-temperature polymerization
The utility model provides a method for preparing polyglycolic acid by low-temperature polymerization, which comprises the following steps:
step one, introducing glycolide into a melting mixing kettle, after the glycolide is melted, circularly heating the glycolide between the melting mixing kettle and an external circulating heat exchange unit, when the temperature of the melted glycolide is heated to 90-120 ℃, adding a reaction auxiliary agent into the melting mixing kettle, and uniformly mixing the melted glycolide and the reaction auxiliary agent to obtain a fluid premix;
secondly, conveying the fluid premix to a static mixer for prepolymerization at the temperature of 120-200 ℃ to obtain a glycolic acid prepolymer;
and thirdly, conveying the glycolic acid prepolymer to tackifying equipment for final polymerization to obtain a polyglycolic acid product.
In the first step, the purity of the used glycolide is not less than 98 percent; preferably not less than 98.5%, and acidity not exceeding 20 mmol/kg. In one embodiment of the present invention, glycolide powder is used in the first step.
The reaction auxiliary used in the above first step comprises a catalyst, a polyhydric alcohol and a dehydrating agent; in terms of the amount of the reaction aid, the catalyst is used in an amount of about 0.001 to 1 wt% based on the mass of the glycolide powder, the polyol is used in an amount of about 0.01 to 0.1 wt% based on the mass of the glycolide powder, and the dehydrating agent is used in an amount of about 0.2 to 1 wt% based on the mass of the glycolide powder.
The catalyst may be selected from at least one of tin-based compounds, antimony-based compounds, or zinc-based compounds, such as, but not limited to, stannous octoate, stannous chloride, tin lactate, antimony trioxide, diethyl zinc, or zinc acetate dihydrate.
The polyalcohol is one or more selected from 1, 4-butanediol, glycerol, pentaerythritol, xylitol, sorbitol, 1, 6-hexanediol, triethylene glycol and dipropylene glycol.
The dehydrating agent may be selected from carbodiimide, polycarbodiimide, or carbodiimide-based compounds (such as, but not limited to, N' -diisopropylcarbodiimide, dicyclohexylcarbodiimide, etc.).
To prevent local excess concentrations of the reaction aid in molten glycolide, in one embodiment of the utility model, the reaction aid may be added dropwise to the melt-mixing kettle by injection.
In an embodiment of the present invention, in the first step, the molten glycolide and the reaction assistant circularly flow in the melting and mixing kettle, the external circulation discharge port, the external circulation feed port, and the external circulation pipeline connecting the external circulation discharge port and the external circulation feed port in the external circulation heat exchange unit coupled to the melting and mixing kettle, so as to achieve the purpose of uniform mixing.
The junction of external circulation discharge gate and melt mixing cauldron lower part is located the below of melt material liquid level in the melt mixing cauldron, furtherly, the water flat line of the junction of external circulation discharge gate and melt mixing cauldron lower part is less than the lower limb of stirring rake blade in the melt mixing cauldron.
The junction of external circulation feed inlet and melt mixing cauldron lower part is arranged in the top of melt material liquid level in the melt mixing cauldron, furtherly, the water flat line of the junction of external circulation feed inlet and melt mixing cauldron lower part is higher than melt material liquid level in the melt mixing cauldron, but should not be too high, for example can be a little higher than melt material liquid level, does not hinder to return the feeding can.
In one embodiment of the utility model, the temperature of the heat exchanger can be set to 90-120 ℃, so that the molten glycolide can be heated to 90-120 ℃, and then the molten glycolide is returned to the melt mixing kettle through an external circulation pipeline, and internal circulation of reaction materials in the melt mixing kettle can be established; in order to reduce heat loss, a layer of heat-insulating jacket can be coated on the external circulation pipeline.
The static mixer in the second step adopts at least 2-section gradient heating mode, for example, 2-10 section gradient heating mode; preferably, 3 to 7 stages are employed.
In one embodiment of the present invention, the first temperature range of the static mixer is between 120-; the last temperature range is between 180 ℃ and 200 ℃, such as but not limited to 180 ℃ and 190 ℃ and 200 ℃.
In one embodiment of the utility model, the second stage of the static mixer is increased in temperature by between 10-80 ℃ over the first stage, such as but not limited to 40-50 ℃, 20-70 ℃, 30-60 ℃, etc.; the last stage is raised from the temperature of the previous adjacent stage by 0-10 deg.C, such as but not limited to 0-5 deg.C, 5-10 deg.C, etc.
In an embodiment of the utility model, the static mixer has four sections, the first section temperature is set to be 120-.
In an embodiment of the utility model, the static mixer has five sections, the first section temperature is set to be 160-.
In one embodiment of the utility model, the total length of time the material is in the static mixer during operation is generally not more than 150 minutes, such as, but not limited to, 60-90 minutes.
The glycolic acid prepolymer obtained in the second step has a weight average molecular weight of about 5 to 15 ten thousand.
In the practical application of the static mixer, if the viscosity of the material in the fluid state between two adjacent sections is too high, a melt pump can be additionally arranged between the two adjacent sections to promote the forward flow of the material.
In the third step, the tackifying equipment is only provided with a devolatilization section, the absolute pressure of the devolatilization section is less than or equal to 500Pa, and the temperature is set to be 220-250 ℃.
Preferably, the screw length to diameter ratio of the devolatilization section is set to 30 to 100, such as, but not limited to, 40 to 50, 60 to 90, and the like.
In the production process, processing aids (such as toughening agents, compatilizers, plasticizers, chain extenders, hydrolysis regulation promoters, hydrolysis regulation inhibitors, heat stabilizers, antioxidants, antibacterial agents or lubricants and the like) can be added at the beginning of the devolatilization section of the tackifying equipment by weight loss weighing according to actual requirements.
It should be noted that, in the present technology, the tackifying device plays a role in devolatilizing, which can promote further polymerization of the glycolic acid prepolymer, and timely remove the generated small molecules to further increase the molecular weight of the polymer.
In a preferred embodiment of the utility model, the temperature of the individual lines is regulated as follows:
the temperature of a pipeline between a discharge port at the bottom of the melting and mixing kettle and a feed port of the melt metering pump is set to be 90-120 ℃, the temperature of a pipeline between a discharge port of the melt metering pump and a feed port of the static mixer is set to be 160 ℃ for the first time, and the temperature of a material conveying pipeline is set to be 250 ℃ for the second time.
The modified material produced by the process of the present invention has a molecular weight distribution index of about 1.2 to 1.6, such as, but not limited to, about 1.3 to 1.5.
As used herein, "distribution index" is a parameter D representing the breadth of the molecular weight distribution, where m (w) is the weight average molecular weight, m (n) is the number average molecular weight, D ═ 1 is a uniform molecular weight polymer, and the broader the molecular weight distribution, the greater the degree of polydispersity, the greater the numerical value of D than 1. The measurement method generally includes measuring M (w), M (n) and the ratio of M (w) to M (n) of a sample by Gel Permeation Chromatography (GPC).
The glycolide content of the reaction mass (i.e. the glycolide mass) used in the first step of the process according to the utility model can be determined by gas chromatography methods known in the art, and the acidity by potentiometric titration methods known in the art (e.g. by means of an automated potentiometric titrator).
To make the features and effects of the present invention comprehensible to those skilled in the art, general description and definitions are made below with reference to terms and expressions mentioned in the specification and claims. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
The theory or mechanism described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, i.e., the present disclosure may be practiced without limitation to any particular theory or mechanism.
All features defined herein as numerical ranges or percentage ranges, such as values, amounts, levels and concentrations, are for brevity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to cover and specifically disclose all possible subranges and individual numerical values (including integers and fractions) within the range.
As used herein, the term "about" when used to modify a numerical value means within + -5% of the error margin measured for that value.
The features mentioned above with reference to the utility model, or the features mentioned with reference to the embodiments, can be combined arbitrarily. All features disclosed in this specification may be combined in any combination, provided that there is no conflict between such features and the combination, and all possible combinations are to be considered within the scope of the present specification. Each feature disclosed in this specification may be replaced by an alternative feature serving the same, equivalent, or similar purpose. Thus, unless expressly stated otherwise, the features disclosed are merely generic examples of equivalent or similar features.
The main advantages of the utility model are:
1. the device provided by the utility model couples the melt mixing kettle, the static mixer and tackifying equipment (for example, a double-screw extruder only provided with a devolatilization section), fully and uniformly mixes glycolide and a reaction auxiliary agent through the melt mixing kettle to obtain a premix, and then introduces the premix into the static mixer for prepolymerization, wherein the premix can generate multiple shunting, confluence and redistributing when advancing in the static mixer, namely, the mixing effect is strengthened in a cross flow mode, the premix can play a role in low-shear and high-dispersion, the heat accumulation in a local area in the material can be favorably prevented and eliminated, the occurrence of side reactions such as thermal degradation and the like caused by over-high temperature in the local area due to uneven heating in the material can be effectively prevented, thereby ensuring that the glycolide can perform good prepolymerization reaction, and obtaining a glycolic acid prepolymer with a certain molecular weight, and the glycolic acid prepolymer is introduced into tackifying equipment for final polymerization, so that the time of the materials subjected to high shear action in the tackifying equipment can be effectively shortened, the side reactions such as thermal degradation and the like can be favorably inhibited, the ester exchange reaction can be favorably inhibited, the content of oligomers and/or low molecular chain substances in the system can be reduced, the molecular weight of the prepared polyglycolic acid can be remarkably improved, the molecular weight distribution index is relatively small, and the molecular weight distribution is more uniform.
2. In the design aspect of the melting and mixing kettle, the external circulation heat exchange unit coupled with the melting and mixing kettle is adopted, and the heat exchange efficiency of the heat exchanger is far higher than that of the melting and mixing kettle, so that the volume of the melting and mixing kettle can be reduced in a mode of 'heat supply and outward movement', namely, under the condition that the external circulation heat exchange unit exists, the melting and mixing kettle with a smaller volume can be selected to meet the heat requirement for heating and melting glycolide aiming at a certain required heat exchange (namely heating) area, and the requirement for the space of an industrial place is favorably reduced; in addition, due to the establishment of the external circulation heat exchange unit, the molten glycolide enters the heat exchanger for heating through the external circulation pipeline and then is circulated back to the melting and mixing kettle, so that the internal circulation flow of the reaction materials can be realized, and the phenomenon of coking and deterioration caused by nonuniform heating (for example, over-strong heating) of the molten glycolide in a certain area at the bottom of the kettle due to insufficient disturbance capacity of the stirring paddle can be avoided.
3. The utility model introduces the fluid premix of the molten glycolide into a static mixer, utilizes a cross flow mode to enhance the mixing effect between the glycolide and the reaction auxiliary agent, enables the reaction auxiliary agent to be more uniformly dispersed in a reaction system, simultaneously utilizes a gradient temperature rising mode to firstly more gently initiate the ring-opening polymerization reaction of the glycolide at a relatively low temperature within a relatively short time, then appropriately raises the temperature and appropriately prolongs the time to form a glycolic acid molecular chain which is relatively stable and has reaction activity in the reaction system, and then further increases the glycolic acid molecular chain at a relatively high temperature and within a relatively long time to obtain the glycolic acid prepolymer with a certain molecular weight A phenomenon occurs.
4. In the preparation method provided by the utility model, in the aspect of reaction auxiliary agents, the catalyst, the polyol and the dehydrating agent are compounded, wherein the introduction of the polyol is favorable for reducing the activation energy of the ring-opening polymerization reaction of glycolide, so that the ring-opening polymerization reaction of the glycolide can be carried out at a lower temperature (compared with the common condition that the glycolide needs to carry out the ring-opening polymerization at 230 ℃ in 220-), so as to generate the polyglycolic acid with high molecular weight and relatively narrow molecular weight distribution, the monomer conversion rate is favorably improved, the polymerization energy consumption can be effectively reduced, the low carbonization generation is realized, and the lower polymerization temperature is favorable for reducing or inhibiting the thermal degradation degree of the glycolic acid polymer generated in the polymerization process, so that the finally obtained polyglycolic acid has good mechanical strength and thermal aging resistance.
5. The main polymerization reaction of the utility model is carried out in a static mixer, compared with a double-screw extruder in a dynamic mixing range, the static mixer has better air tightness and can reduce the influence of oxygen and moisture on the polymerization reaction to the maximum extent.
6. The device provided by the utility model is suitable for industrial scale-up production, can be used for modifying a production line by using the existing production equipment, has good flexibility and applicability, can realize stable output of polyglycolic acid products, realizes low-carbonization production, and has good economic benefit.
The utility model will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. The experimental procedures, in which specific conditions are not noted in the following examples, are generally carried out according to conventional conditions or according to conditions recommended by the manufacturers. All percentages, ratios, proportions, or parts are by weight unless otherwise specified. The units in weight volume percent in the present invention are well known to those skilled in the art and refer to, for example, the weight (g) of solute in 100ml of solution. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In addition, any methods and materials similar or equivalent to those described herein can be used in the methods of the present invention. The preferred embodiments and materials described herein are intended to be exemplary only.
In the examples described below, the glycolide content of the purified glycolide powder concerned can be determined by gas chromatography, which is well known in the art, and the glycolide powder particlesThe diameter is determined by the mesh size of the screen, for example, by using a 70 mesh (corresponding to about 200 μm) screen or by using a 70 mesh or more screen, and the glycolide powder can be screened to have a particle size substantially satisfying "D90Less than or equal to 200 μm ", the acidity can be determined by potentiometric titration methods known in the art, for example by means of an automated potentiometric titrator.
For the test of the molecular weight and the distribution of polyglycolic acid, Gel Permeation Chromatography (GPC) method is used for the test, which is as follows:
a0.2 g sample of PGA was dissolved in 100mL of hexafluoroisopropanol solution having a sodium trifluoroacetate content of 5mmol/L, filtered through a polytetrafluoroethylene filter having a pore size of 0.4. mu.m, and 20. mu.L of the filtrate was introduced into an "LC-20 AD GPC" sample injector manufactured by Shimadzu (Japan) under test conditions: the column temperature is 40 ℃; eluent: hexafluoroisopropanol with 5mmol/L of sodium trifluoroacetate dissolved therein; the flow rate is 1 mL/min; a detector: an RI detector; and (3) correction: five different standards of polymethyl methacrylate with molecular weights varying between 7000 and 200000 were used for molecular weight correction.
In the following examples, the melt stirring tank used had a volume of 50L, the static mixer 8L, the melt metering pump had a maximum delivery flow rate of 10L/h, and the melt pump had a maximum delivery flow rate of 12L/h.
D glycolide powders used in the following examples 1 to 690Less than or equal to 200 mu m, purity more than or equal to 98.5 percent and acidity less than or equal to 20 mmol/kg.
The static mixer used in the following examples is a commercially available SK type static mixer.
Device embodiment
Provides a device for preparing polyglycolic acid by low-temperature polymerization as shown in figure 1.
The device A for preparing polyglycolic acid through low-temperature polymerization comprises a melt mixing kettle 100, an external circulation heat exchange unit 500 coupled with the melt mixing kettle, a static mixer 200 coupled with the melt mixing kettle, and tackifying equipment 300 (for example, a twin-screw extruder only provided with a devolatilization section) arranged at the downstream of the static mixer.
The external circulation heat exchange unit 500 comprises an external circulation discharge port 510, an external circulation feed port 520 and an external circulation pipeline 530 connecting the external circulation discharge port and the external circulation feed port; the external circulation discharge port 510 and the external circulation feed port 520 are respectively connected to the lower part of the melting and mixing kettle 100, and the joint of the external circulation feed port 520 and the lower part of the melting and mixing kettle 100 is higher than the joint of the external circulation discharge port 510 and the lower part of the melting and mixing kettle 100; the external circulation feed inlet 520, the circulation pump 542, the heat exchanger 541 and the external circulation discharge outlet 510 are connected in sequence on the external circulation pipeline 530.
A melt metering pump 120 is arranged between the static mixer 200 and the melting and mixing kettle 100, and a kettle bottom discharge port 110 of the melting and mixing kettle 100 is connected with a feed port of the static mixer 200 through the melt metering pump 120.
The outlet of the static mixer 200 is connected with the inlet of the viscosity increasing device 300 through the material conveying component 230.
The material conveying assembly 230 comprises a material conveying pipeline 231 for connecting the discharge port of the static mixer 200 with the feed port of the tackifying device 300, a melt pump 232 arranged on the material conveying pipeline, and a cleaning solution dredging pipeline 233 arranged in parallel with the melt pump 232, wherein a cleaning solution drainage branch 234 is arranged on the material conveying pipeline 231 between the melt pump 232 and the feed port of the tackifying device 300.
The liquid inlet end and the liquid discharge end of the cleaning liquid dredging pipeline 233 are connected in parallel to both sides of the melt pump 232 through a three-way valve 235-I.
The cleaning solution drain branch 234 is connected to the material transfer line 231 through a three-way valve 235-ii.
The top of the melt mixing kettle 100 is provided with a reaction material inlet and a reaction auxiliary agent inlet, wherein the reaction material inlet is connected with a weightlessness scale 1112 through a material inlet pipe 112, the reaction auxiliary agent inlet is connected with a reaction auxiliary agent storage tank 1110 arranged at the upstream of the melt mixing kettle through an auxiliary agent inlet pipe 111, and a liquid metering pump 1111 is further arranged on the auxiliary agent inlet pipe 111 between the reaction auxiliary agent storage tank 1110 and the reaction auxiliary agent inlet.
The pipeline between the bottom discharge port 110 of the melt mixing kettle 100 and the feed port of the static mixer 200, the material conveying pipeline 231, the cleaning liquid dredging pipeline 233, the melt metering pump 120, the melt pump 232, the three-way valve 235-I and the three-way valve 235-II are all provided with conventional heat tracing.
Preparation examples 1 to 6
Low temperature polymerization for preparing polyglycolic acid
Adjusting a weightlessness scale by a computer, controlling the feeding amount (the feeding amount can be determined according to the yield and the volume of the melting and mixing kettle) of glycolide (refining) in the melting and mixing kettle, after the glycolide in the melting and mixing kettle is completely melted, opening a circulating pump, an electromagnetic valve at an external circulating discharge port and an electromagnetic valve at an external circulating feed port by the computer, feeding the melted glycolide into a heat exchanger through an external circulating pipeline for heating and heating, returning the melted glycolide into the melting and mixing kettle through the external circulating pipeline, constructing internal circulation of reaction materials in the melting and mixing kettle, adjusting a liquid metering pump by the computer to control the adding amount of the reaction additives, adding the reaction additives while stirring, obtaining a premix in a fluid state after the materials are uniformly mixed, and then controlling the opening of the electromagnetic valve at the discharge port at the bottom of the melting and mixing kettle by the computer, and the flow rate of the premix is controlled by adjusting a melt metering pump to feed the premix into a static mixer for prepolymerization to obtain a glycolic acid prepolymer having a certain molecular weight (about 5-15 ten thousand), and then a melt pump is controlled by a computer to feed the glycolic acid prepolymer into tackifying equipment (such as a twin-screw extruder provided with only a devolatilization section) for final polymerization to obtain the PGA product. In the process, the feeding time, the feeding amount, the circulating heat exchange time and the feeding amount of the reaction auxiliary agent can be adjusted by a computer, and the reaction materials are timely supplemented into the melting and mixing kettle, so that stable and continuous production is realized.
The amounts of the reaction assistants added in examples 1 to 6 are shown in tables 1 to 1 below.
TABLE 1-1
The kinds of reaction assistants in examples 1 to 6 are shown in the following tables 1 to 2.
Tables 1 to 2
The temperatures of the molten glycolide heated by circulation in the melt-mixing tank in examples 1 to 6 are shown in tables 1 to 3 below.
Tables 1 to 3
| Item | Example 1 | Example 2 | Example 3 | Example 4 | Example 5 | Example 6 |
| Temperature (. degree.C.) | About 90 | About 114 | About 120 | About 112 | About 118 | About 120 |
Note: the time from the time that each batch of glycolide powder enters the melting and mixing kettle to the time that the premix is obtained is about 20min
The temperature parameters of the stages of the static mixer of the above examples 1-6 are shown in Table 2 below:
TABLE 2
| Item | Static mixer | First stage | Second section | Third stage | Fourth stage | Fifth stage |
| Example 1 | Four sections in total | About 120 deg.C | About 160 deg.C | About 185 deg.C | About 190 deg.C | / |
| Example 2 | Four sections in total | About 150 deg.C | About 180 deg.C | About 190 deg.C | About 198 deg.C | / |
| Example 3 | Four sections in total | About 180 deg.C | About 185 deg.C | About 195 deg.C | About 200 deg.C | / |
| Example 4 | Five sections in total | About 120 deg.C | About 170 deg.C | About 185 deg.C | About 195 deg.C | About 200 deg.C |
| Example 5 | Five sections in total | About 150 deg.C | About 160 deg.C | About 170 deg.C | About 190 deg.C | About 198 deg.C |
| Example 6 | Five sections in total | About 160 deg.C | About 170 deg.C | About 180 deg.C | About 190 deg.C | About 195 deg.C |
In examples 1-3 above, the time required for the material to pass through the static mixer was: about 5min for the first pass, about 15min for the second pass, about 20min for the third pass, and about 50min for the fourth pass.
In examples 4-6 above, the time required for the material to pass through the static mixer was: about 5min through the first stage, about 5min through the second stage, about 10min through the third stage, about 15min through the fourth stage, and about 55min through the fifth stage.
In examples 1 to 6 above, the parameter settings of the devolatilization section in the tackifying equipment are shown in the following table 3:
TABLE 3
| Item | Temperature (. degree.C.) | Absolute pressure (Pa) | Length-diameter ratio of screw | Screw rotation speed (r/min) |
| Example 1 | About 220 | 200 | 52 | 30 |
| Example 2 | About 228 | 120 | 50 | 45 |
| Example 3 | About 226 | 140 | 56 | 40 |
| Example 4 | About 235 | 100 | 54 | 35 |
| Example 5 | About 242 | 350 | 60 | 50 |
| Example 6 | About 250 |
500 | 50 | 60 |
Note: the time for the materials to pass through the devolatilization section of the tackifying equipment is controlled to be about 15min
The temperature settings of the lines from the melt mixing kettle to the viscosity increasing equipment in examples 1-6 above are shown in Table 4 below:
TABLE 4
Note: the conveying flow rates of the melt-metering pump and the melt pump used in examples 1 to 3 were set to about 6.7L/h, and the conveying flow rates of the melt-metering pump and the melt pump used in examples 4 to 6 were set to about 5.3L/h
The weight average molecular weight of glycolic acid prepolymer formed by the static mixer, the number average molecular weight, weight average molecular weight and molecular weight distribution index of polyglycolic acid produced by the tackification apparatus in examples 1 to 6 above are shown in Table 5 below.
TABLE 5
Comparative example 1
This comparative example is substantially the same as example 4, except that the reaction aid used comprises only the catalyst (i.e., stannous octoate, diethyl zinc and antimony trioxide mixed in a mass ratio of 2:1: 1), and the amount of the catalyst used is the same as in example 4.
Comparative example 2
This comparative example is substantially the same as example 4 except that the reaction assistant used comprises only a catalyst (i.e., stannous octoate, diethyl zinc and antimony trioxide mixed in a mass ratio of 2:1: 1) and a dehydrating agent (i.e., N' -diisopropylcarbodiimide), and the amounts of the catalyst and the dehydrating agent are the same as in example 4.
Comparative example 3
This comparative example used glycolide powder (D)90No more than 200 μm, purity no less than 98.5% and acidity no more than 20mmol/kg), and polyglycolic acid was prepared by a conventional reaction type twin-screw extruder (without using a static mixer), the reaction aids and the amounts thereof used were the same as in example 4, and the specific process conditions of the reaction type twin-screw extruder are shown in the following table 6-1.
TABLE 6-1
Note: in comparative example 3, glycolide powder and the reaction assistant were uniformly mixed and added from the beginning of the first stage of the mixing section, and the absolute pressure of the devolatilization section was controlled to 100Pa
Comparative example 4
This comparative example used glycolide powder (D)90No more than 200 mu m, purity no less than 98.5 percent and acidity no more than 20mmol/kg), and preparing polyglycolic acid by a conventional reaction type twin-screw extruder (without using a static mixer), wherein the reaction auxiliary used only comprises a catalyst (namely stannous octoate, diethyl zinc and antimony trioxide are mixed according to the mass ratio of 2:1: 1), the using amount of the catalyst is the same as that of example 4, and the specific process conditions of the reaction type twin-screw extruder are shown in the following table 6-2.
TABLE 6-2
Note: in comparative example 4, glycolide powder and the reaction assistant were uniformly mixed and added from the beginning of the first stage of the mixing section, and the absolute pressure of the devolatilization section was controlled to 100Pa
In the above comparative examples 3 and 4, the screw length-diameter ratios and the screw rotation speeds of the respective stages in the conventional reaction type twin-screw extruder are shown in the following tables 6 to 3.
Tables 6 to 3
| Item | Screw length to diameter ratio of mixing section | Length-diameter ratio of screw of reaction section | Devolatilization sectionLength-diameter ratio of screw | Screw rotation speed (r/min) |
| Reaction type double-screw extruder | 35 | 70 | 54 | 60 |
The polyglycolic acid prepared in the above comparative examples 1 to 4 had a number average molecular weight, a weight average molecular weight and a molecular weight distribution index, as shown in the following Table 7.
TABLE 7
| Item | Comparative example 1 | Comparative example 2 | Comparative example 3 | Comparative example 4 |
| Number average molecular weight (Mn) of molten PGA | 86486 | 102132 | 58849 | 73106 |
| Melt PGA weight average molecular weight (Mw) | 120216 | 134815 | 103574 | 141825 |
| Molecular weight distribution index of molten PGA | 1.39 | 1.32 | 1.76 | 1.94 |
Performance testing
The tensile strength and elongation at break of the polyglycolic acid prepared in examples 1 to 6 and comparative examples 1 to 4 were measured according to the test standards of GB/T1040.1 to 2006, respectively, and the specific results are shown in Table 8 below:
TABLE 8 test results
Note: the tensile rate in the above tensile test was 50mm/min
Based on the test results of table 8 above, the data for comparative example 4 and comparative examples 1-4 are emphasized. As is clear from Table 8, the tensile strength and elongation at break of the PGA material obtained in example 4 were reduced by about 5.5% and 16.7%, respectively, after the hot air aging test. Compared with example 4, the reaction promoter in comparative example 1 only contains the catalyst, the reaction promoter in comparative example 2 only contains the catalyst and the dehydrating agent, and no polyol is added to the reaction promoters in both pairs of ratios, which may be disadvantageous in reducing the activation energy of the ring-opening polymerization reaction of glycolide, so that the reaction degree is reduced compared with example 4, and is disadvantageous in improving the molecular weight of the product, which also makes the mechanical strength of the PGA products obtained in comparative examples 1 and 2 significantly lower than that of example 4; in addition to this effect, it may be disadvantageous to reduce the residual glycolide content of the final PGA product, which may result in a material with a greater deterioration in mechanical strength under relatively high temperature and humidity conditions.
Comparing the results of the tests in table 8, it can be seen that the mechanical strength and thermal aging resistance of the PGA material prepared by the conventional reaction type twin-screw extruder are significantly weaker than those of example 4 in comparison with comparative examples 3 and 4 (without using a static mixer), which may be caused by poor air tightness and heat transfer effect of the conventional reaction type twin-screw extruder, and the high shear thereof easily causes the local temperature of the reaction system to rise too fast, so that side reactions such as thermal degradation and the like occur in advance, which is unfavorable for the increase of the molecular weight of the final product, and also causes the molecular weight distribution of the final product to be broadened, which results in significant decrease of the mechanical strength and thermal aging resistance of the final PGA material.
The foregoing is merely a preferred embodiment of the utility model and is not intended to limit the scope of the utility model, which is defined by the claims appended hereto, and any other technical entity or method that is encompassed by the claims as broadly defined herein, or equivalent variations thereof, is contemplated as being encompassed by the claims.
Claims (9)
1. A device for preparing polyglycolic acid by low-temperature polymerization comprises a melt mixing kettle, an external circulating heat exchange unit coupled with the melt mixing kettle, a static mixer sequentially arranged at the downstream of the melt mixing kettle, and tackifying equipment coupled with the static mixer.
2. The device of claim 1, wherein the external circulation heat exchange unit comprises an external circulation discharge port, an external circulation feed port, an external circulation pipeline connecting the external circulation discharge port and the external circulation feed port, a heat exchanger and a circulation pump arranged on the external circulation pipeline.
3. The device of claim 2, wherein the external circulation discharge port and the external circulation feed port are respectively connected to the lower part of the melt-mixing kettle, and the joint of the external circulation feed port and the lower part of the melt-mixing kettle is higher than the joint of the external circulation discharge port and the lower part of the melt-mixing kettle.
4. The apparatus of claim 1, wherein a reaction aid storage tank is connected to the melt mixing kettle feed port.
5. The device as claimed in claim 1, wherein the static mixer is connected with the tackifying equipment through a material conveying component, and the material conveying component comprises a material conveying pipeline connecting a discharge port of the static mixer with a feed port of the tackifying equipment, a melt pump arranged on the material conveying pipeline, and a cleaning liquid drain pipe connected with the melt pump in parallel on the material conveying pipeline.
6. The apparatus as claimed in claim 5, wherein a cleaning liquid draining branch is provided on the material conveying pipeline between the melt pump and the feed inlet of the viscosity increasing device.
7. The apparatus as claimed in claim 5, wherein the cleaning liquid drain pipe is provided with a three-way valve connected to the material conveying pipeline.
8. The apparatus of claim 6 wherein said cleaning solution drain branch is connected to said material transfer line by a three-way valve.
9. The apparatus of claim 1, wherein a melt metering pump is disposed between the melt mixing kettle discharge port and the static mixer.
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| CN115672214A (en) * | 2021-07-27 | 2023-02-03 | 上海浦景化工技术股份有限公司 | Device and method for preparing polyglycolic acid through low-temperature polymerization |
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