CN210617106U - Self-balancing supercritical foaming device for multi-component multi-phase complex system - Google Patents
Self-balancing supercritical foaming device for multi-component multi-phase complex system Download PDFInfo
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Abstract
The utility model relates to a multi-component multiphase complex system self-balancing supercritical foaming device. The method comprises the following steps: the first gas steel cylinder (1) is used for storing a supercritical fluid main foaming agent; the first gas steel cylinder (1) is connected with the foaming device (11) through a constant-pressure gas output device; the liquid bottle (2) is used for storing the liquid assistant foaming agent; the liquid bottle (2) is connected with the foaming device (11); in the foaming device (11), the bottom is provided with a support member (15) for placing the foaming material. The utility model provides a contain supercritical fluid mixture of auxiliary foaming agent self-interacting foaming and fashioned technology and device under the heterogeneous system of multicomponent has realized the heterogeneous complex system self-balancing purpose of multicomponent under the supercritical foaming condition, has finally stabilized the foaming technology, has improved the cell structure, has improved the goods performance.
Description
Technical Field
The utility model relates to a device of pressure release foaming after self-balancing swelling under the supercritical state of heterogeneous multicomponent complicated system belongs to supercritical foaming technical field.
Background
In recent years, the supercritical foaming method for preparing the microporous polymer foaming material is widely concerned by new polymer materials and related industries, and the foaming material prepared by the process has the advantages of large cell density, small pore diameter, excellent performance and the like, and the method is wide in applicable polymer material range and green and environment-friendly in processing process. Although various polymer materials can obtain a porous structure by a supercritical foaming method, for the polymer materials with a high foaming temperature and a low expansion ratio, a good foaming effect can be achieved only by using a co-foaming agent in a supercritical foaming process. However, when the multi-component foaming agent mixed by the supercritical fluid and the co-foaming agent swells the non-viscous state polymer, the swelling process is extremely unstable due to the multi-component multi-phase complex system, and the fluctuation of component content or the change of phase state is extremely easy to occur due to the tiny fluctuation of the temperature or pressure of the foaming device under the actual operation condition, so that the final foamed material has extremely poor cell structure and the corresponding foamed material has poor performance. In order to fully exert the synergistic effect of the supercritical fluid and the auxiliary foaming to obviously improve the cell structure and the macroscopic performance of the foaming material, the stability problem of a multi-component multi-phase complex system needs to be solved urgently.
Patent CN202129925U proposes a set of extrusion foaming device for mixing supercritical carbon dioxide with foaming agent, which makes carbon dioxide enter into an extruder together with a measured multicomponent synergistic auxiliary agent in a liquid state at constant temperature, constant pressure and accurately measurement, and continuously and stably produces foamed plates. However, the process method matched with the device belongs to a foaming method of a viscous-state polymer matrix, the content of the polymer dissolved foaming agent is related to the injection content of the foaming agent, when the content of the foaming agent exceeds the content of the viscous-state polymer which can be dissolved, the polymer coming out of a die has obvious large foam holes and obvious defects, so that the polymer is difficult to absorb the maximum content of the foaming agent, and the optimal performance of the foaming material cannot be ensured.
Patent CN108638422A utility model discloses a microcellular injection molding foaming method using mixed foaming agent. After the chemical foaming agent and the polymer granules are uniformly mixed, the mixture is added into an injection molding machine for plasticizing, and simultaneously, the supercritical fluid state physical foaming agent is injected for injection foaming molding. The method is foaming of a viscous state polymer matrix, and the content of a polymer dissolved foaming agent is related to the content of injected foaming agent, and the saturated swelling state is not reached.
There is also a published article describing the foaming of co-blowing agents in an autoclave mixed with a supercritical fluid. The autoclaves used in the article all have very small cavities (<500 ml), the polymer sample used is also very small in size (<100cm3) Therefore, the multi-component multi-phase environment of the small-size polymer sample in the high-pressure small kettle is stable; however, those skilled in the art know that: after the equipment is amplified, due to the complexity of the processes of mixing, reacting, phase changing and the like of materials, an amplification effect often exists, so that the preparation process is different from that of small equipment, and the performance of the prepared product is obviously different. For the technical field of foaming, the assistant foaming agent and the supercritical fluid have various phase separation behaviors under different swelling conditions, so that the foaming behavior of the polymer material is unstable under the action of a mixed foaming agent, and particularly, the homogeneous state cannot be effectively maintained under the condition of high assistant foaming agent content, so that the polymer foaming material with stable cell structure cannot be produced; for laboratory foaming equipment, the mixing process is relatively easy due to the small equipment, and the difference in the permeation rates of the blowing agent and co-blowing agent has a limited effect on the production of small equipment, possibly without much difference; however, when a large-scale device is adopted, the difference is obvious, and the industrial production result on the large-scale device is difficult to achieve the same result as that of a small test. The purpose of the utility model is to ensure that the microcellular foamed polymer material is stably prepared in a system self-balancing mode under the complex state of the multi-component foaming agent containing two phases and above.
In the cavity of the high-pressure container, the supercritical fluid and the auxiliary foaming agent are mutually dissolved to form a homogeneous system and simultaneously swell the polymer material in a non-viscous state. The selected auxiliary foaming agent can be an auxiliary foaming agent suitable for a required foaming polymer material, the swelling effect on a polymer matrix is enhanced, for example, pentane, n-hexane and the like are suitable to be used as auxiliary foaming agents of PP, PE and the like due to the molecular structure, water, ethanol and the like can generate strong interaction with PPSU and the like due to the molecular polarity, and the auxiliary foaming agent is more suitable to be used as the auxiliary foaming agent.
In the prior art, the CO is generated due to the structure and molecular polarity of the CO-blowing agent2、N2When the supercritical fluid is the main foaming agent, the auxiliary foaming agent is more soluble in the polymer material in the swelling process, and the polymer component, the supercritical fluid component and the auxiliary foaming agent component reach an equilibrium state in a polymer enrichment phase along with the swelling. After the polymer-rich phase reaches the swelling equilibrium, the components of the supercritical-rich phase must be ensured to be stable inside the foaming device. However, the homogeneous phase of the polymer rich phase is very susceptible to phase separation behavior with changes in the composition of the supercritical rich phase. At this time, a region in which the content of the supercritical fluid (main blowing agent) is large and the content of the auxiliary blowing agent is small appears in the polymer matrix, resulting in a small cell diameter and a large cell density; meanwhile, a region with a large content of the co-blowing agent and a small content of the supercritical fluid (main blowing agent) will appear, resulting in a large cell diameter and a small cell density. Finally, the foam material prepared has extremely unstable foam appearance accompanied with the phenomenon of big and small holes, and the distribution of the big and small holes is extremely uneven, thus seriously affecting the service performance of polymer products. Therefore, a new method and a new device for supercritical foaming of multi-component multiphase complex systems with self-regulating function are needed to stably prepare high-performance microcellular foamed polymers.
SUMMERY OF THE UTILITY MODEL
The utility model aims at: the problems that in the process of adopting the main foaming agent and the auxiliary foaming agent, the foaming effect of the material fluctuates along with time and the foaming effect is unstable due to the difference of the permeability, the dosage and the like of the main foaming agent and the auxiliary foaming agent are solved. The utility model provides a supercritical foaming new method and new installation of self-interacting with heterogeneous multicomponent complex system, the phase equilibrium state of main foamer and auxiliary foamer can be to steady state spontaneous regulation under given temperature and pressure in this method for the component of the mixed foamer in the swelling process keeps invariable, and the pore structure homogeneity and the performance stability of the expanded material that finally obtain all obtain showing and improve.
The utility model discloses a first aspect provides:
a supercritical foaming process comprising the steps of:
and 4, swelling the polymer raw material with the supercritical fluid and the auxiliary foaming agent under the set pressure and temperature conditions, releasing pressure and foaming after reaching a homogeneous saturation state, and preparing the porous foaming material.
In one embodiment, after completion of the foaming in the 4 th step, the gas in the foaming apparatus is discharged, and after cooling, the auxiliary foaming agent is condensed into a liquid state, and gas-liquid separation is performed to recover the liquid auxiliary foaming agent and the supercritical fluid main foaming agent.
In one embodiment, the constant pressure gas output means is a booster pump, a surge tank and a pressure reducing valve connected in series, or an ISCO pump and a surge tank connected in series.
In one embodiment, step 1, the polymer feedstock is placed in the foaming device through a support member. In step 1, a space for the enrichment phase of the co-blowing agent is reserved in the foaming device, and the polymer material is placed on the space and is not contacted with the enrichment phase of the co-blowing agent.
In one embodiment, the co-blowing agent must be present in excess in step 2, but not in contact with the polymer feed. In the step 4, three phases exist in the foaming device, namely a polymer enrichment phase dissolved with supercritical fluid and a co-foaming agent, a supercritical fluid enrichment phase dissolved with the co-foaming agent and a co-foaming agent enrichment phase dissolved with the supercritical fluid.
In one embodiment, step 3 requires a temperature-raising treatment before feeding the supercritical gas main foaming agent into the foaming device.
In one embodiment, after the foaming device is at the set temperature and pressure in step 4, the supercritical fluid and the co-foaming agent inside the foaming device are in a two-phase equilibrium state with stable components, so as to ensure that the multi-component complex system (polymer, supercritical fluid and co-foaming agent) inside the non-viscous-state polymer is in a stable homogeneous equilibrium state during the swelling process of physical diffusion. Wherein the space around the polymer raw material in the foaming device is a component-stable supercritical fluid-rich phase, and the proportion of the supercritical fluid and the co-foaming agent in the phase is only related to the temperature and the pressure of the foaming device. In the swelling process of the non-viscous state polymer in the step 4, although the diffusion rate and the solubility of the supercritical fluid and the co-foaming agent in the polymer matrix are different, the temperature and the pressure of the foaming device are constant, and the ratio of the supercritical fluid to the co-foaming agent in the supercritical fluid enrichment phase is constant. Therefore, after swelling to saturation, the polymer matrix is in homogeneous equilibrium with a multi-component complex system, and the content of the swollen supercritical fluid and the co-blowing agent is only related to the temperature and the pressure of the foaming device. Benefit from the utility model discloses a from the regulation function, the homogeneous phase equilibrium of multicomponent complicated system can not destroyed at whole swelling in-process to foam nucleation and growth are all very even when guaranteeing the pressure release foaming.
In one embodiment, the foaming device is a non-viscous state polymer foam molding device.
In one embodiment, the polymeric starting materials include, but are not limited to: general-purpose plastics such as PP, PS and the like, general-purpose engineering plastics such as PET and the like, and special engineering plastics such as PPSU and the like; the polymer feedstock may be in the shape of pellets, rods, plates, or profiles.
In one embodiment, the supercritical fluid primary blowing agent is CO2、N2And the like.
In one embodiment, the liquid co-blowing agent is water, ethanol, n-hexane, pentane, acetone, HFO, HFC, or the like.
The second aspect of the present invention provides:
a supercritical foaming process comprising the steps of:
and 4, swelling the polymer raw material with the supercritical fluid and the auxiliary foaming agent under the set pressure and temperature conditions, releasing pressure and foaming after reaching a homogeneous saturation state, and preparing the porous foaming material.
In one embodiment, in step 3, a liquid co-blowing agent is also fed to the blowing means via the second mass flow output means.
In one embodiment, the liquid co-blowing agent is fed inside the foaming apparatus without being in direct contact with the polymer raw material while being in a liquid phase state.
In one embodiment, the constant pressure gas output means refers to a booster pump, a buffer tank, and a pressure reducing valve, or an ISCO pump and a buffer tank, which are connected in sequence.
In one embodiment, the first mass flow output device is a mass flow pump, and the accurately measured excess amount of the auxiliary foaming agent in the liquid bottle is injected into the foaming device through the mass flow pump.
In one embodiment, the gas blowing agent used to form the supercritical fluid is CO2、N2And the like.
In one embodiment, the liquid co-blowing agent is water, ethanol, n-hexane, pentane, acetone, HFO, HFC, or the like.
In one embodiment, the gaseous co-blowing agent may be methane or the like.
The third aspect of the present invention provides:
a supercritical foaming apparatus comprising:
the first gas steel cylinder is used for storing the main supercritical fluid foaming agent; the first gas steel cylinder is connected with the foaming device through a constant-pressure gas output device;
the liquid bottle is used for storing the liquid assistant foaming agent; the liquid bottle is connected with the foaming device;
in the foaming device, the bottom is provided with a support member for placing the foaming material.
In one embodiment, the constant pressure gas output device is a booster pump and a buffer tank which are connected in sequence, the booster pump is connected with the first gas steel cylinder, and the first buffer tank is connected with the foaming device.
In one embodiment, the buffer tank is further provided with a heating part, and the heating part is used for heating the gas in the buffer tank; in one embodiment, the heating element is a heat trace ribbon.
In one embodiment, the first buffer tank is connected to the foaming device in turn via a pressure reducing valve and a first non-return valve.
In one embodiment, the constant pressure gas output device is an ISCO pump.
In one embodiment, the bottom of the foaming device is further provided with porous ceramics for uniformly heating the liquid assistant foaming agent at the bottom.
In one embodiment, the foaming device is also connected with a back pressure valve and a gas-liquid separator in sequence; the gas-liquid separator is used for condensing and carrying out gas-liquid separation treatment on the gas emptied after foaming.
In one embodiment, the liquid bottle is connected to the foaming device in turn via a mass flow pump.
In one embodiment, the mass flow pump is connected to the foaming device via the second non-return valve, the foaming device liquid inlet in turn.
The fourth aspect of the present invention provides:
a supercritical foaming apparatus comprising:
the first gas steel cylinder is used for storing the main supercritical fluid foaming agent; the first gas steel cylinder is connected with the foaming device through a constant-pressure gas output device;
and the second gas steel cylinder is used for storing the gaseous auxiliary foaming agent and is connected to the foaming device sequentially through the cooling device and the second mass flow pump.
In one embodiment, the constant pressure gas output device is a booster pump, a buffer tank and a pressure reducing valve which are connected in sequence, or an ISCO pump and a buffer tank. The booster pump or ISCO pump is connected with the first gas cylinder, and the pressure reducing valve is connected with the foaming device.
In one embodiment, the buffer tank is further provided with a heating part, and the heating part is used for heating the gas in the buffer tank; in one embodiment, the heating element is a heat trace ribbon.
In one embodiment, the liquid bottle is used for storing the liquid assistant foaming agent; the liquid bottle is connected to the foaming device through a first mass flow pump.
In one embodiment, the first mass flow pump is connected to the foaming device through a second non-return valve.
In one embodiment, the second mass flow pump is connected to the foaming device through a third non-return valve.
The fifth aspect of the present invention provides:
the supercritical foaming device is applied to the supercritical foaming method for producing the foaming polymer material.
In one embodiment, the application refers to the application of the method for increasing the expansion ratio of the foaming polymer material and reducing the foaming temperature of the material.
Advantageous effects
1. The process solves the problems of foaming uniformity and performance stability of the large-size non-viscous flow state polymer under a multi-component multi-phase complex system, and simultaneously reduces the foaming temperature of the polymer material, improves the foaming multiplying power, improves the performance of a foamed product and the like. The method is stable and high in repeatability, solves the problem of amplification effect in industrial production of the foaming material, makes the material possible from the laboratory result to industrial application, and is suitable for amplification production.
2. Through the utility model discloses the method, polymeric material are in under the system of maximum content auxiliary foaming agent always for polymeric material can absorb the upper limit of its absorptive auxiliary foaming agent content, can improve polymeric material's foaming multiplying power by the at utmost, reduces polymeric material's foaming temperature, and the cell structure is more even, makes the polymeric material who produces possess the best performance.
3. The buffer bottle is used for conveying the main foaming agent with set pressure and the pressure stabilizing function of the pressure reducing valve, so that the buffer tank can timely supplement the main foaming agent in the high-pressure container in the process of absorbing the main foaming agent, and three phases (phase 1: main foaming agent (enriched) -auxiliary foaming agent gas (auxiliary), phase 2: liquid auxiliary foaming agent (enriched) -main foaming agent (auxiliary) and phase 3: polymer (enriched) -main foaming agent (auxiliary) -auxiliary foaming agent phase (auxiliary)) in the high-pressure container are always in dynamic balance, thereby achieving the gas self-regulation function and creating conditions for stably producing products with better performance.
4. The excessive liquid assistant foaming agent is conveyed by the liquid pump, so that the liquid assistant foaming agent deposited at the bottom can continuously supplement the assistant foaming agent consumed by absorbing the mixed foaming agent by the polymer, the three phases in the foaming device are in dynamic balance, and conditions are created for stably producing products with better performance.
The utility model discloses the technological parameter scope of technology is very wide, basically all can satisfy the industrial requirement, and pressure can be followed the lowest pressure that can carry gas and to the highest withstand voltage value that high-pressure vessel can reach (the highest withstand voltage 35MPa of high-pressure vessel in this example), and the temperature can be at the room temperature to the highest temperature range that high-pressure vessel can use (but the high-pressure vessel temperature resistance 300 ℃ that uses in this example), and the swelling time is decided according to required production material, but pressure release time manual control also can be by computer automatic control.
Drawings
Fig. 1 is a diagram of the device of the present invention.
Fig. 2 is another device diagram of the present invention.
FIG. 3 is an SEM photograph of the foamed material prepared in example 1.
FIG. 4 is an SEM photograph of the foamed material prepared in comparative experiment 1.
FIG. 5 is an SEM photograph of the foamed material prepared in comparative experiment 2.
FIG. 6 is an SEM photograph of the foamed material prepared in example 2.
FIG. 7 is an SEM photograph of the foamed material prepared in comparative experiment 3.
FIG. 8 is an SEM photograph of the foamed material prepared in comparative experiment 4.
FIG. 9 is a graph showing the change in swelling of a pressure gauge of PP + n-hexane (excess unstabilized) autoclave.
FIG. 10 is a graph showing the change in swelling of a pressure gauge of a PPSU + distilled water (excess unstabilized) high pressure vessel.
FIG. 11 is a multi-component phase diagram.
Wherein, 1, a first gas steel cylinder; 2. a liquid bottle; 3. a booster pump; 4. a first mass flow pump; 5. a buffer tank; 6. a heating member; 7. a pressure reducing valve; 8. a first check valve; 9. a foaming device liquid inlet; 10. a porous ceramic; 11. a foaming device; 12. a back pressure valve; 13. a gas-liquid separator; 14. a second check valve; 15. a support member; 16. a foaming device liquid inlet; 17. a second gas cylinder; 18. a cooling device; 19. a second mass flow pump; 20. a third non-return valve.
Detailed Description
The utility model provides a supercritical foaming method and a supercritical foaming device for stably preparing foaming products under a multi-phase and multi-component complex system due to self-adjustment. The method utilizes the synergistic foaming action of a main foaming agent and an auxiliary foaming agent, wherein the main foaming agent can be a foaming agent which is commonly used in the existing supercritical foaming, such as CO2、N2Etc.; the co-blowing agent here serves to assist the dissolution of the main blowing agent into the polymerIn the compound matrix, the polymer material is further plasticized, the glass transition temperature of the polymer material is reduced, the foaming temperature range is widened, the foaming ratio of the polymer is improved, and water, ethanol, n-hexane, pentane, acetone, HFO, HFC and the like can be adopted.
The utility model discloses well expanded material that will prepare can be for the material that can prepare through supercritical foaming method among the prior art, mainly be polymer material, include but not limited to: general-purpose plastics such as PP and PS, general-purpose engineering plastics such as PET, and special engineering plastics such as PPSU. The material shape can be granules, bars, plates or special-shaped pieces.
In the prior art, a main foaming agent and an auxiliary foaming agent are usually added into foaming equipment at the same time, and due to the influence of a plurality of factors such as the addition amount and the permeation rate of the main foaming agent and the auxiliary foaming agent in the foaming process, the proportion of the main foaming agent and the auxiliary foaming agent is often unstable in the actual foaming process, so that a multi-component complex system in a polymer in the swelling process is unstable, the foaming action is poor, and the uniformity and the performance stability of foam cells of a foaming material are poor.
In the technical scheme of the utility model, at first through pour into excessive auxiliary foaming agent into foaming equipment into, when auxiliary foaming agent is liquid in the injection process, can absorb 2~5 times accurate content auxiliary foaming agent of auxiliary foaming agent content for the polymer through the mass flow pump and carry to the high-pressure vessel chamber, make the liquid level of liquid auxiliary foaming agent be less than the polymer raw materials in this process; then, the supercritical gas (CO) is pumped by a booster pump2、N2Etc.) is conveyed to a high-pressure buffer tank (0-40 MPa) at a set pressure, then the gas in the high-pressure buffer tank is quickly conveyed to a high-pressure container cavity through a pressure reducing valve, the booster pump and the buffer tank are used for supplying supercritical fluid with stable pressure, and the buffer tank is also used for quickly conveying supercritical gas to quickly stabilize an internal system of the foaming device. The main foaming agent and the auxiliary foaming agent enter the high-pressure container cavity through the one-way valve, and then the sample in the high-pressure container cavity is under the set process conditions (temperature, pressure and the like).
Because the auxiliary foaming agent has certain vapor pressure under the set pressure and temperature conditions, a part of the auxiliary foaming agent still keeps liquid state during the swelling process, and a small amount of main foaming agent is dissolved to form a 'auxiliary foaming agent (enriched) -main foaming agent (less) phase' which is deposited at the bottom of a high-pressure container; the other part of the polymer is evaporated into a gaseous state to form a 'main foaming agent (rich) -auxiliary foaming agent (poor) phase' swelling polymer with the main foaming agent; since the polymer is not in contact with the "co-blowing agent (rich) -blowing agent (poor) phase", the "main blowing agent (rich) -co-blowing agent (poor) phase" penetrates into the polymer under the set process conditions, forming the "polymer (rich) -main blowing agent (poor) -co-blowing agent (poor) phase" inside the polymer. Along with the continuous diffusion of the main foaming agent and the auxiliary foaming agent into a sample, the main foaming agent can be continuously injected into a cavity of a high-pressure container through a pressure reducing valve which plays a role in stabilizing pressure, and the auxiliary foaming agent exists at the bottom of the cavity of the high-pressure container in an excessive manner, so that the stability of the swelling process can be realized through phase balance self-regulation (when the gaseous auxiliary foaming agent dissolved in the main foaming agent is excessive, the gaseous auxiliary foaming agent can be converted into a liquid state due to phase separation under certain conditions of temperature and pressure and is precipitated at a lower liquid layer of a foaming device, and when the consumption speed of the gaseous auxiliary foaming agent dissolved in the main foaming agent is too high, part of the liquid auxiliary foaming agent deposited at the bottom of the high-pressure container can be converted into a gaseous state under the condition of the pressure and the temperature. The excessive auxiliary foaming agent can ensure that the polymer material is always at the maximum auxiliary foaming agent content, the polymer material can absorb the maximum auxiliary foaming agent content, in the process of absorbing the auxiliary foaming agent, the auxiliary foaming agent (rich) -main foaming agent (less) phase is in dynamic balance due to the fact that the auxiliary foaming agent can be continuously provided, when the auxiliary foaming agent content deposited at the bottom is reduced, the dissolved main foaming agent returns to the main foaming agent (rich) -auxiliary foaming agent (less) phase again and then enters the polymer, and the self-balancing of the multi-component multi-phase ensures the stability of the foaming material. During the foaming process, the polymer foam is not directly contacted with the liquid co-blowing agent, but is contacted in a homogeneous system of the main blowing agent and the co-blowing agent, so that the co-blowing agent is kept at a constant dosage concentration in the whole process.
Through the self-balancing process, the pressure relief foaming is realized after a homogeneous saturation state is achieved under a multi-component complex system (a polymer component, a supercritical fluid component and a co-foaming agent component). The phase diagram of the above process is shown in fig. 11.
In the above method, the main foaming agent should be added in a constant pressure manner to the foaming device, and in order to achieve the above purpose, the pressure of the main foaming agent is maintained at a stable supply pressure, the present invention provides a method in which the function can be achieved in various manners:
1. booster pump-buffer tank scheme: the booster pump conveys supercritical foaming fluid into a high-pressure buffer tank at a set pressure, then the supercritical fluid in the high-pressure buffer tank is quickly conveyed into a high-pressure container cavity through a pressure reducing valve, the pressure of the supercritical fluid can be stabilized by the pressure reducing valve, so that the system is always in a dynamic balance state in the process of absorbing the supercritical fluid by the polymer material, when the polymer absorbs the supercritical fluid, the buffer tank provides the required supercritical fluid through the pressure reducing valve, and when the pressure in the buffer tank is lower than the set value, the booster pump provides gas for the buffer tank, so that the supercritical fluid self-regulation effect is realized.
2. ISCO pump scheme: the ISCO pump is used for replacing a booster pump and a pressure reducing valve, the ISCO pump can compress gas into the pump firstly, then the gas can be automatically pressurized in the pump, and the gas can be quickly conveyed into a buffer tank after reaching a set pressure, so that the function of the booster pump is achieved; when the conveying amount reaches the set pressure, the system is unstable due to the reduction of the foaming agent because the material absorbs the foaming agent and the like, and the second function of the ISCO pump, namely the pressure stabilizing function, plays a role, and can continuously provide supercritical fluid to keep the system in the high-pressure container stable.
In the above embodiment, the operation of foaming a polymer by using a liquid auxiliary foaming agent (for example, a liquid such as ethanol) is mainly applied, but in some other cases, the operation of foaming a polymer by using a gaseous auxiliary foaming agent or a plurality of mixed foaming agents is performed, and in the case of using a gaseous auxiliary foaming agent or a plurality of mixed foaming agent auxiliary foaming agents, the method provided by the present invention may be such that, as shown in fig. 2, the gaseous auxiliary foaming agent is connected to the foaming apparatus through the second mass flow output means, and in this manner, it is not necessary to separate the polymer foaming material in the foaming apparatus from the liquid auxiliary foaming agent, and the constant amount of the gaseous auxiliary foaming agent is controlled by the mass flow pump method.
Based on above method, the utility model provides a device as follows:
in one embodiment, the device of the present invention is shown in fig. 1.
The method comprises the following steps:
the first gas steel cylinder 1 is used for storing a supercritical fluid main foaming agent; the first gas steel cylinder 1 is connected with the foaming device 11 through a constant pressure gas output device;
the liquid bottle 2 is used for storing a liquid assistant foaming agent; the liquid bottle 2 is connected with the foaming device 11;
in the foaming device 11, the bottom is provided with a support member 15 for placing the foaming material. The foaming device 11 is a high-pressure container, and a foaming experiment place of the polymer material provides a stable temperature and pressure environment to enable the polymer material and the mixed foaming agent to be in a homogeneous system;
in one embodiment, the constant pressure gas output device is a booster pump 3 and a buffer tank 5 connected in sequence, the booster pump 3 is connected to the first gas cylinder 1, and the first buffer tank 5 is connected to the foaming device 11. The booster pump is used to provide a steady pressure to deliver the gaseous phase to the buffer tank. The gas with required specific pressure is conveyed into the buffer tank by the booster pump for several times, and then the gas in the bottle is quickly conveyed into the foaming device, so that the foaming device is in the set process condition as soon as possible, and the process is more stable
In one embodiment, the buffer tank 5 is further provided with a heating component 6, and the heating component 6 is used for heating the gas in the buffer tank 5; in one embodiment, the heating element 6 is a heat trace tape. The temperature of the high-pressure buffer tank is raised by the heat tracing belt, and the temperature in the high-pressure container cavity is prevented from being reduced after the low-temperature foaming agent is added into the foaming device because the foaming temperature in the high-pressure container is required
In one embodiment, the first buffer tank 5 is connected to the foaming device 11 in turn via a pressure reducing valve 7 and a first non-return valve 8. The pressure reducing valve stabilizes the gas pressure and ensures that the gas in the high-pressure container is always under the action of the set pressure; the check valve prevents the mixed gas from flowing back into the buffer tank when the pressure in the kettle is higher than the buffer tank.
In one embodiment, the constant pressure gas output device is an ISCO pump. The ISCO pump is adopted to replace a booster pump and a pressure reducing valve, and can form self-regulation of the adding amount of the main foaming agent and the gas auxiliary foaming agent. When the pressure in the high-pressure container cavity is increased due to excessive gas, the pressure stabilizing function of the ISCO pump enables the gas to return to the ISCO pump through the high-pressure buffer tank; the ISCO pump is able to provide gas continuously as the polymeric material absorbs the blowing agent, so that the system in the high pressure vessel is always in a steady state, which acts as a pressure relief valve and thus as a gas self regulating. The liquid co-blowing agent phase is excessive in the high-pressure container relative to the amount of the co-blowing agent capable of being absorbed by the polymer material, the excessive liquid co-blowing agent is deposited at the bottom of the high-pressure container, when the polymer material absorbs the liquid co-blowing agent, the excessive co-blowing agent enters a 'polymer material (rich) -blowing agent (little) -co-blowing agent (little)' homogeneous system from a liquid pool, and when the excessive co-blowing agent is excessive in the 'polymer material (rich) -main blowing agent (little) -co-blowing agent (little)' system, the excessive co-blowing agent is separated out from the system and deposited into the liquid co-blowing agent pool, so that the stability of the system is ensured.
In one embodiment, the bottom of the foaming device 11 is further provided with a porous ceramic 10 for uniformly heating the liquid co-foaming agent in the bottom.
In one embodiment, the foaming device 11 is also connected with a back pressure valve 12 and a gas-liquid separator 13 in sequence; the gas-liquid separator 13 is used for condensing and gas-liquid separating the gas evacuated after foaming. The back pressure valve prevents the mixed foaming agent from flowing back and maintains the outlet at a constant pressure. The gas-liquid separator 13 is used as a recovery system and is connected with an air outlet valve of a high-pressure container to recover the mixed foaming agent, the pressure and the temperature in a recovery bottle are controlled to separate phases of gas and liquid, and the recovered auxiliary foaming agent is recycled for the next foaming experiment.
In one embodiment, the liquid bottle 2 is connected to the foaming device 11 in turn via a mass flow pump 4. The mass flow pump delivers an accurately metered amount of the liquid co-blowing agent phase to the foaming device.
In one embodiment, the mass flow pump 4 is connected to the foaming device 11 via the second non return valve 14, the foaming device liquid inlet 9 in turn.
In another embodiment, the present invention is used with a device as shown in fig. 2.
The method comprises the following steps:
the first gas steel cylinder 1 is used for storing a supercritical fluid main foaming agent; the first gas steel cylinder 1 is connected with the foaming device 11 through a constant pressure gas output device;
and a second gas cylinder 17 for storing a gaseous co-blowing agent, wherein the second gas cylinder 17 is connected to the foaming device 11 through a cooling device 18 and a second mass flow pump 19 in this order.
The constant-pressure gas output device is composed of a booster pump 3, a buffer tank 5 and a pressure reducing valve 7 which are sequentially connected, the booster pump 3 is connected with the first gas steel cylinder 1, and the pressure reducing valve 7 is connected with the foaming device 11.
The buffer tank 5 is also provided with a heating part 6, and the heating part 6 is used for heating the gas in the buffer tank 5; in one embodiment, the heating element 6 is a heat trace tape.
The device also comprises a liquid bottle 2 for storing the liquid assistant foaming agent; the liquid bottle 2 is connected to a foaming device 11 by a first mass flow pump 4.
The first mass flow pump 4 is connected to the foaming device 11 through a second non-return valve 14.
The second mass flow pump 19 is connected to the foaming device 11 via a third non-return valve 20.
In this embodiment as in fig. 2, it is possible to achieve simultaneous addition of a gaseous co-blowing agent and a liquid co-blowing agent. The porous foaming material is prepared by releasing pressure and foaming after a homogeneous saturated state is achieved under a multi-component complex system (a polymer component, a supercritical fluid component, a gaseous auxiliary foaming agent component and a liquid auxiliary foaming agent component).
The specific type of the foaming device 11 is not limited in either of the modes of fig. 1 or fig. 2. The device of the utility model is suitable for the solid foaming molding of all non-viscous state polymers.
Example 1
In the apparatus shown in FIG. 1, taking the production of polypropylene foamed polymer material as an example, polypropylene (the raw material is in the form of block, about 600cm in size, 2 samples in total) is first loaded into a high-pressure vessel (about 5L in volume), excess n-hexane is pumped into the high-pressure vessel through a heated buffer tank by a liquid pump, and the high-pressure vessel is simultaneously heated to 140 ℃ and 15MPa of CO is pumped by an ISCO pump2Delivering gas to the high pressure vessel through the heated buffer tank, maintaining the ISCO pump in an open state, stabilizing the pressure in the vessel, and filling the polymer with CO2Swelling in n-hexane atmosphere for 5 hr to make polymer fully absorb CO2And n-hexane, then opening the valve for 2 seconds to release the pressure, recovering the mixed foaming agent into a recovery device, and performing phase separation on the mixed foaming agent by using the recovery device to re-extract the auxiliary foaming agent for the next experimental operation; the results of the foaming ratio and the like of the obtained foam after foaming are shown in table 1.
The differences from example 1 are: the ISCO pump only provides a delivery function, an unstable pressure.
Taking the production of polypropylene foamed polymer material as an example, firstly, polypropylene is added into a high-pressure container, excessive n-hexane is conveyed into the high-pressure container through a heated buffer tank by using a liquid pump, simultaneously, the high-pressure container is heated to 140 ℃, and 15MPa of CO is pumped by using an ISCO pump2The gas is transferred to the high pressure vessel through the heated buffer tank, the ISCO pump is turned off and the polymer is filled with CO2Swelling in n-hexane atmosphere for 5 hr to make polymer fully absorb CO2And n-hexane, then opening the valve for 2 seconds to release the pressure, recovering the mixed foaming agent into a recovery device, and performing phase separation on the mixed foaming agent by using the recovery device to re-extract the co-foaming agent for the next experimental operation.
The differences from example 1 are: the co-blowing agent is continuously fed during the swelling process using a conventional liquid pump, rather than being added in excess to the bottom of the high-pressure vessel beforehand.
Taking the production of polypropylene foamed polymer material as an example, firstly, polypropylene is added into a high-pressure container, the high-pressure container is heated to 140 ℃, and 15MPa of CO is pumped by an ISCO pump2And (3) delivering the gas into the high-pressure container through the heated buffer tank, keeping the ISCO pump in an opening state, and stabilizing the pressure in the high-pressure container. In the swelling process, normal hexane is continuously conveyed into a high-pressure container through a heated buffer tank by using a common liquid pump, and the polymer is filled with CO2Swelling in n-hexane atmosphere for 5 hr to make polymer fully absorb CO2And n-hexane, then opening the valve for 2 seconds to release the pressure, recovering the mixed foaming agent into a recovery device, and performing phase separation on the mixed foaming agent by using the recovery device to re-extract the co-foaming agent for the next experimental operation.
TABLE 1 foaming parameters of PP and blowing of n-hexane co-blowing agent under different conditions (140 ℃, 15MPa, 5 hours of swelling)
As can be seen from table 1, under the same process conditions, the aperture and the foam density of the cells obtained by unstable foam are slightly smaller than the aperture of the cells obtained by stable foam, although the foam expansion ratio measured by unstable foam is larger than the foam expansion ratio measured by stable foam, many cells can be seen to break through the SEM image (fig. 4), one cell breaks into many small holes, the overall cell morphology is not optimistic, but the SEM image of inverse stable foam (fig. 3) shows that the cells are uniform and the overall morphology is good. As can be seen from FIG. 7, the pressure gauge indication is constantly changing slowly during the swelling process, and this instability of pressure is one of the main reasons for the formation of the cell morphology as shown in the SEM image.
As can be seen from the table, the cell diameter and the expansion ratio of the foamed sample obtained by continuously feeding the co-blowing agent under the same process conditions are much smaller than those of the foamed article mixed with the excessive co-blowing agent, as can be seen from the SEM image (FIG. 5). Although the auxiliary foaming agent is continuously conveyed in the swelling process to play a synergistic role with the foaming agent so as to improve the foaming ratio of the PP and reduce the foaming temperature of the PP, the main foaming agent and the auxiliary foaming agent cannot be ensured to be always in a stable homogeneous state in the continuous conveying process, and meanwhile, the polymer material cannot be ensured to be in the maximum mixed foaming agent content, so that the effect is not good. The presence of many white small areas, which are just areas where PP is crystallized, is seen in the SEM image, which limits the increase in expansion ratio, indicating that this process condition does not reduce the foaming temperature of PP well, so that the foaming temperature of 140 ℃ is still lower than the melting point of PP.
Example 2
Taking the production of polyphenylsulfone foamed polymer material as an example, firstly, 2 samples with the shape of block and the size of about 600cm are taken into a high-pressure container (the volume is about 5L), the heat tracing bands on the high-pressure container and a buffer bottle are set to the temperature required by foaming, excess distilled water is conveyed into the high-pressure container through the buffer bottle by a liquid pump, and 20 MPa of CO is conveyed into the high-pressure container by a booster pump2Delivering gas into high-pressure container via high-pressure buffer bottle, stabilizing pressure of high-pressure container by pressure reducing valve, and filling PPSU with CO2Swelling in distilled water for 5 hr to make PPSU fully absorb CO2And distilled water, then opening a valve for 2 seconds to release pressure, recovering the mixed foaming agent into a recovery device, and utilizing the recovery device to phase-split the mixed foaming agent and re-extract the auxiliary foaming agent for the next experimental operation; the results of the foaming ratio and the like of the obtained foam after foaming are shown in table 2.
The differences from example 1 are: the ISCO pump only provides a delivery function, an unstable pressure.
Taking the production of a polyphenylsulfone foamed polymer material as an example, polyphenylsulfone is firstly added into a high-pressure container, the temperature of a heat tracing band on the high-pressure container and a buffer bottle is set to be the temperature required by foaming, excess distilled water is conveyed into the high-pressure container through the buffer bottle by a liquid pump, and 20 MPa of CO is conveyed into the high-pressure container by a booster pump2Delivering gas into the high-pressure container via the high-pressure buffer bottle, closing the pressure-reducing valve, and destabilizing the pressure in the high-pressure container to fill the PPSU with CO2Swelling in distilled water for 5 hr to make PPSU fully absorb CO2And distilled water, then opening the valve for 2 seconds to release the pressure, recovering the mixed foaming agent into a recovery device, and utilizing the recovery device to phase-separate the mixed foaming agent and re-extract the auxiliary foaming agent for the next experimental operation.
The differences from example 1 are: the co-blowing agent is continuously fed during the swelling process using a conventional liquid pump, rather than being added in excess to the bottom of the high-pressure vessel beforehand.
Taking the production of a polyphenylsulfone foamed polymer material as an example, polyphenylsulfone is firstly added into a high-pressure container, heat tracing bands on the high-pressure container and a buffer bottle are set to the temperature required by foaming, and 20 MPa of CO is added by a booster pump2The gas is conveyed into the high-pressure container through the high-pressure buffer bottle, and the pressure of the high-pressure container is stabilized by the pressure reducing valve. During the swelling process, distilled water is continuously conveyed into a high-pressure container through a buffer tank by using a common liquid pump, and the PPSU is filled with CO2Swelling in distilled water for 5 hr to make PPSU fully absorb CO2And distilled water, then opening the valve for 2 seconds to release the pressure, recovering the mixed foaming agent into a recovery device, and utilizing the recovery device to phase-separate the mixed foaming agent and re-extract the auxiliary foaming agent for the next experimental operation.
TABLE 2 foaming parameters of PPSU foaming with water-assisted foaming agent under different conditions (190 ℃, 20 MPa, 5 hours of swelling)
As can be seen from table 2, under the same process conditions, the pore diameter, the foam density and the foam expansion ratio of the cells obtained by unstable pressure foaming are slightly smaller than those obtained by stable pressure foaming, and as can be seen from fig. 7, the phenomena of large and small pores occur in the process of unstable pressure foaming, the positions of the large and small pores are not uniform, the pores are broken, the overall morphology is not good, and as can be seen from the SEM image of stable pressure foaming, the cells are uniform and the overall morphology is good (fig. 6). The change in the pressure gauge indication in FIG. 10 shows that the pressure gauge indication is always changing slowly in the case of unstable pressure, which is one of the main causes of the cell morphology shown in the SEM image.
As can be seen from Table 2, the cell diameter and the expansion ratio of the foamed sample obtained by continuously feeding the co-blowing agent under the same process conditions were smaller than those of the foamed article mixed with the excessive co-blowing agent, as can be seen from the SEM chart (FIG. 8). Although the assistant foaming agent is continuously conveyed in the swelling process to play a synergistic role with the foaming agent to improve the foaming ratio of the PPSU and reduce the foaming temperature of the PPSU, the main foaming agent and the assistant foaming agent cannot be ensured to be always in a stable homogeneous state in the continuous conveying process, and meanwhile, the polymer material cannot be ensured to be in the maximum mixed foaming agent content, so that a good effect is not achieved. Thereby ensuring that the foaming ratio and the cell diameter of the product are smaller than those under the condition of excessive assistant foaming agent.
Claims (10)
1. A supercritical foaming apparatus comprising:
the first gas steel cylinder (1) is used for storing a supercritical fluid main foaming agent; the first gas steel cylinder (1) is connected with the foaming device (11) through a constant-pressure gas output device;
the liquid bottle (2) is used for storing the liquid assistant foaming agent; the liquid bottle (2) is connected with the foaming device (11);
in the foaming device (11), the bottom is provided with a support member (15) for placing the foaming material.
2. The supercritical foaming apparatus according to claim 1, wherein the constant pressure gas output device is a booster pump (3) and a buffer tank (5) which are connected in sequence, the booster pump (3) is connected with the first gas cylinder (1), and the first buffer tank (5) is connected with the foaming apparatus (11).
3. Supercritical foaming apparatus according to claim 2, characterized in that the buffer tank (5) is further provided with a heating element (6), and the heating element (6) is used for heating the gas in the buffer tank (5).
4. Supercritical foaming device according to claim 3, wherein the heating element (6) is a heat tracing ribbon.
5. Supercritical foaming device according to claim 2, wherein the first buffer tank (5) is connected to the foaming device (11) in turn via a pressure reducing valve (7) and a first non-return valve (8).
6. The supercritical foaming apparatus according to claim 1 wherein the constant pressure gas output means is an ISCO pump.
7. Supercritical foaming apparatus according to claim 1, characterized in that the bottom of the foaming apparatus (11) is further provided with porous ceramic (10) for uniform heating of the liquid co-foaming agent in the bottom.
8. The supercritical foaming apparatus according to claim 1, characterized in that the foaming apparatus (11) is further connected with a back pressure valve (12) and a gas-liquid separator (13) in sequence; the gas-liquid separator (13) is used for condensing and carrying out gas-liquid separation treatment on the gas emptied after foaming.
9. Supercritical foaming device according to claim 1, wherein the liquid bottle (2) is connected to the foaming device (11) in turn via a first mass flow pump (4).
10. Supercritical foaming device according to claim 9, wherein the first mass flow pump (4) is connected to the foaming device (11) in turn via a second non return valve (14), the foaming device liquid inlet (9).
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| CN110480913B (en) * | 2019-09-24 | 2023-08-18 | 四川大学 | Self-balancing supercritical foaming method and device for multi-component multiphase complex system |
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