CN115782268A - Production device and production method of polymer microporous foamed pipe - Google Patents
Production device and production method of polymer microporous foamed pipe Download PDFInfo
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Abstract
The invention discloses a production device and a production method of a polymer microcellular foamed pipe, wherein the production method is realized on the basis of a mould and a high-pressure closed container capable of driving the mould to rotate, and a thermoplastic polymer or a compound thereof is molded to obtain a pre-foamed pipe; cutting the pre-foamed pipe into pipes with the length not longer than that of the mold, and placing the pipes in the mold; placing a mould containing a pipe in a closed reaction kettle, introducing a supercritical fluid into the closed reaction kettle, and soaking the pipe in the supercritical fluid at a corresponding temperature and pressure, wherein the mould is always in a rotating state in the reaction kettle; and cooling the temperature in the reaction kettle for a period of time, quickly relieving the pressure, and taking out the pipe in the die to obtain the polymer microporous foamed pipe.
Description
Technical Field
The invention relates to a production device of a polymer microcellular foamed pipe, and also relates to a production method of the polymer microcellular foamed pipe.
Background
In recent years, tubular products using polymers or composites thereof as main raw materials have been widely used in the fields of building water supply and drainage, urban pipe networks, chemical industry transportation, and the like. Meanwhile, due to the advantages of sound insulation, shock absorption, heat insulation, raw material saving and the like, the polymer microporous foamed product has wide application prospect in the industries of packaging, construction, electronics, automobile industry, aerospace, aviation and the like. Furthermore, the open-cell foam material is a foam material with continuous phase and gas phase, the substrate material exists in continuous cell walls, and the unique three-dimensional open-cell structure has excellent absorption and penetration performance, and has wide application in the fields of sound absorption, electric conduction, optics, filtration, adsorption and the like, and particularly has great potential application prospect in the fields of biological medicine materials (drug controlled release, bone tissue culture, biological dialysis) and the like. However, the polymer microcellular foamed pipe obtained by combining the two materials is relatively rare, on one hand, the existing foamed pipe is mainly closed, the foaming ratio is often low, and the foaming advantage is difficult to embody; on the other hand, the cellular structure of the foamed pipe obtained by the existing method is difficult to control accurately, the mechanical property and other service performance of the product are obviously reduced, and the popularization and the application of the product are hindered. In several types of mainstream processing methods such as extrusion, injection, high-pressure container (kettle pressure or mould pressure) and the like of a supercritical fluid microcellular foaming product, the high-pressure container method is easier to obtain uniform cells in the whole product, and the cells have high density, small size, high uniformity degree and more obvious and convenient control. When the plate is processed, the upper surface and the lower surface of the plate can be conveniently cut off; the mould and the equipment for processing the plate can be easily opened and closed up and down, so that the pressure control is convenient and free; the plate can conveniently realize the control homogenization of pressure and temperature on the whole plane in the links of infiltration, temperature rise, pressure rise, temperature reduction, pressure release and the like.
Compared with a plate, the tubular product has a complex shape, which provides challenges for product shaping, demolding, uniform control of foam holes and the like, and particularly when the wall of the tubular product is thick, the consistency of process conditions such as temperature, pressure, temperature and pressure change rate and the like of each part of the pipe wall is almost impossible under the existing conditions, and the foam holes are difficult to realize precise regulation and control; the inner and outer walls of the formed pipe are difficult to be cut off after being similar to a plate, so that a product with better inner and outer surface quality needs to be directly obtained.
For the microcellular foamed polymer products having cells obtained by using the change of state parameters such as pressure or temperature, a skin layer containing no cells is often present on the outer surface of the product, mainly because the skin layer of the product is in direct contact with the outside, and thus the poor state with the outside is difficult to be formed, and the poor state is often also a main factor for inducing the formation and fixation of the cells. For the polymer microcellular foamed pipe, the solid outer wall of the inner and outer surfaces of the polymer microcellular foamed pipe can also affect the opening effect of the polymer microcellular foamed pipe, if the inner and outer walls are closed, the inner and outer walls are always required to be removed in advance when the pipe needing the opening function is applied, and corresponding troubles are brought to the application of the pipe.
In the application of the open-cell material, the orientation direction of the cells also has a certain effect, for example, the sound absorption coefficient can be obviously different from other directions in the orientation direction of the cells. In the supercritical fluid foaming, it is possible to control the direction of pressure release or control the orientation of cells, but for large-sized pipes, the direction of pressure release at each part is difficult to homogenize, and thus, it is generally difficult to obtain thick-walled pipes with uniformly oriented cells.
Disclosure of Invention
The invention aims to: the invention aims to provide a production device and a production method of a polymer microporous foamed pipe, the method realizes the accurate control of internal micropores (aperture, pore orientation and pore uniformity) and foaming multiplying power of the foamed pipe by combining a specific mould and a closed high-pressure device which can drive the mould to rotate with a specific process route, the obtained microporous foamed pipe has uniform, small and dense pores and good orientation consistency, and both the inner wall and the outer wall of the pipe have open pore structures, so that the pipe has good mechanical property and can better exert the advantages of the internal micropores of a product.
The technical scheme is as follows: the invention relates to a production device of a polymer microcellular foaming pipe, which comprises a die; the die comprises a first fixing frame, a second fixing frame and an inner die core, wherein the first fixing frame and the second fixing frame are arranged oppositely, and the inner die core is fixed on the first fixing frame; the first fixing frame and the second fixing frame are respectively provided with cylindrical grooves which are annularly arranged and correspond to each other, the device also comprises an outer module, the outer module consists of a plurality of ribs which are annularly arranged, and the ribs of the outer module are arranged in one-to-one correspondence with the cylindrical grooves on the fixing frame; two ends of each rib are respectively connected with the first fixing frame and the second fixing frame through limiting screws; the fixing frame is characterized by also comprising a compression spring arranged in the cylindrical groove, wherein one end of the compression spring is connected with an end point of the cylindrical groove, which is far away from the center of the fixing frame, and the other end of the compression spring is connected with a limit screw which transversely slides in the cylindrical groove through the compression spring; the cylindrical groove is of a through hole structure, and the transverse length of the cylindrical groove is 10-100 mm.
The height of the inner mold core is not larger than the distance between the first fixing frame and the second fixing frame; the height of the inner mold core is not less than the length of the pre-foaming pipe blank; the outer diameter of the inner mold core is consistent with the inner diameter of the pre-foaming pipe blank.
The number of the ribs is determined according to the size of an inner ring formed after the ribs are combined and the size of the ribs, and the size of the inner ring formed after the ribs are combined is adaptive to the shape of the pre-foaming pipe blank.
Preferably, when the outer shape of the prefoamed pipe blank and the outer shape of the ribs are both circular, the number of ribs is determined to be not more than (R1 + R2) × 3.14/R2 when the diameters of the prefoamed pipe blank and the ribs are R1 and R2, respectively, and this value is generally determined to be an integral multiple of 4 for the sake of processing convenience, and if the outer dimensions of both ends of the prefoamed pipe blank are different, the smaller of the values determined by the dimensions of both ends is taken, and further, the diameter of the ribs is 6mm or more because of strength requirements.
The mould comprises a motor, a mould body, a mould tube blank, a high-pressure closed container and a motor, wherein the mould body is arranged in the container, the high-pressure closed container drives the mould to rotate, a cavity body in transmission connection with the motor through a coupler is arranged in the container, the size of the cavity body is consistent with that of the mould, the mould body for loading the pre-foaming tube blank is arranged in the cavity body, and the cavity body is driven by the motor to rotate.
The method for producing the polymer microcellular foamed pipe based on the production device comprises the following steps:
(1) Selecting at least two thermoplastic polymers and forming a blend by melt blending or solution blending;
(2) Performing molding processing on the blend to obtain a pre-foamed pipe, wherein the wall thickness of the pre-foamed pipe is 1-20 mm;
(3) Intercepting a pre-foaming pipe, wherein the length of the pre-foaming pipe is equal to the length of the required pipe/(1 + linear shrinkage factor delta of the blend), so as to obtain a pre-foaming pipe blank;
(4) Uniformly coating PVA aqueous solution on the inner surface and the outer surface of the pre-foamed pipe blank, and forming a PVA coating on the inner surface and the outer surface of the pre-foamed pipe blank, wherein the initial thickness of the PVA coating is 30-50 mu m;
(5) Drying the pre-foamed pipe blank until the PVA coating is completely shaped, coating PVA aqueous solution on the outer surface of the pre-foamed pipe blank again, wherein the formed coating thickness is equivalent to the initial thickness in the step (4), and when the coated PVA aqueous solution is not dried, wrapping and winding n layers on the outer surface of the pre-foamed pipe blank by using a film; the film coated on the outer surface of the pre-foaming pipe blank provides pressure to play a limiting role, and simultaneously plays a buffering role in the foaming process of the pipe blank by utilizing the toughness of the film; the heat-resistant super-tough film means that the heat softening temperature is higher than T Dipping in water At least 20 degrees, and at T Put When the high-tensile-speed tensile strength is used, the elongation at break is more than 100 percent at the high-tensile-speed of 500 mm/min; the number n of film winding layers is determined according to the tensile modulus M of the film at high temperature, and can be estimated by the following formula: n is equal to P Medicine for treating chronic gastritis /P Time release *P Dipping in water The integer is rounded, i.e. n is considered to be related to the following factors: film at high temperature T Placing the Tensile strength M at high drawing speed of 500mm/min and pressure P of supercritical fluid Dipping in water Initial pressure release rate P of a high-pressure vessel at the moment of opening Medicine for treating chronic gastritis Desired depressurization Rate P of Pre-foamed tubing at initial pressure relief after Pre-impregnation Time release (ii) a P of the Pre-foamed pipes in the invention Time release 7.5 to 10MPa;
(6) After the films are adhered, sleeving the pre-foamed pipe blank on an inner mold core of a mold, surrounding the pre-foamed pipe blank by an outer mold set, and adjusting ribs of the outer mold set to a position larger than the outer diameter of the pre-foamed pipe blank;
(7) Placing the mould containing the prefoaming pipe blank in a closed high-pressure container, introducing supercritical fluid into the closed high-pressure container, and heating at high temperature T Dipping in water And a high voltage P Dipping in water Soaking the lower prefoaming pipe blank in a supercritical fluid; wherein, the mould is always in a rotating state in the high-pressure container;
(8) After a soaking time t Dipping in water Then, the temperature T in the high-pressure container is measured Put Reducing the temperature to 5-20 ℃ below the melting point of the polymer, stopping the rotation of the mold after the temperature is balanced, quickly opening the high-pressure container, and relieving the pressure to obtain a microporous foamed pipe tightly connected with the mold;
(9) And (3) immersing the mould with the microporous foamed pipe in water, removing the PVA coating on the surface of the inner wall of the mould, taking the pipe out of the mould, removing the film layer, and removing the PVA coating on the surface of the outer wall of the pipe to obtain the polymer microporous foamed pipe.
Wherein, in the step (1), the melting point difference of the polymer which is compounded is more than 20 ℃, when the melt strength of the polymer with low melting point is tested by a weight measuring method or a force measuring method, the difference of the melt strength of the polymer with low melting point and the melt strength of the polymer with low melting point is more than 50 percent, the mass ratio of the polymer with low melting point is 10 to 30 percent, and the mass ratio of the polymer with high melting point is 70 to 90 percent.
The main reasons for the above-mentioned material requirements are: the larger difference between the melting point of the low-melting-point polymer and the melting point of the high-melting-point polymer indicates that the melt strength of the low-melting-point polymer is greatly changed under the influence of temperature, and because the foaming is carried out near the melting point of the high-melting-point polymer, the low-melting-point polymer can be cracked in the foaming process, so that open-cell foaming is realized.
Wherein, in the step (3), the linear shrinkage rate delta of the blend is determined by the length ratio of the blend in a certain direction at high temperature and room temperature: δ = length at high temperature L High (a) Length at room temperature L Chamber -1, said high temperature being equal to T Placing the 。
Wherein, in the step (5), the layer thickness ratio alpha of the PVA coating before and after drying is 0.4-0.6. Within this ratio, the bonding between the PVA coating and the foam is tighter, and when too low or too high, the bonding between the PVA coating and the foam is poor.
Wherein, in the step (7), the pressure P of the supercritical fluid in the high-pressure vessel Dipping in water Is 10-50MPA, T Soaking in water The temperature is 0 to 5 ℃ below the melting point of the polymer, and the soaking time t Dipping in water Is 5 to 30 minutes; the rotating speed of the die in the high-pressure container is 300-900 r/min.
Wherein, in the step (7), the supercritical fluid is supercritical nitrogen or supercritical carbon dioxide or a composite of the two.
Wherein, in the step (8), the initial pressure releasing speed P of the high-pressure container at the opening moment Medicine for treating chronic gastritis Is 30 to 70 MPa/s.
The average sound absorption coefficient of the polymer microporous foamed pipe exceeds 0.8 when the polymer microporous foamed pipe is applied to sound absorption materials.
The working process of the invention is as follows:
after the pre-foamed pipe blank is prepared, taking down the limiting screw in the cylindrical groove on the second fixing frame, taking the second fixing frame away, sleeving the pre-foamed pipe blank on the inner mold core, enabling the pre-foamed pipe blank to be positioned between the inner mold core and the outer mold group, fixedly connecting the second fixing frame with the rib through the limiting screw again, and respectively contacting two ends of the pre-foamed pipe blank with the first fixing frame and the second fixing frame, so that the pre-foamed pipe blank is placed in a cavity between the inner mold core and the outer mold group of the mold; adjusting a limit screw, determining the position of each rib in the outer module after the compression spring is completely compressed by adjusting the moving distance of the rib in the cylindrical groove, and changing the overall dimension of the final foamed pipe; the mould loaded with the prefoaming pipe blank is placed in a high-pressure container, a cavity which is in transmission connection with a motor through a coupling is arranged in the container, the size of the cavity is consistent with that of the mould, the mould is placed in the cavity, the mould is heated in a closed container and is simultaneously soaked in the supercritical fluid, the prefoaming pipe blank can be quickly soaked in the supercritical fluid under the action of rotation, and meanwhile, the temperature distribution of each part of the prefoaming pipe blank is uniform, so that each part of the prefoaming pipe blank is uniformly soaked.
When the pressure in the container is removed, the supercritical fluid in the pre-foamed pipe blank is converted into gas, the material begins to expand and foam, the pre-foamed pipe blank in the mold expands outwards on one hand, but the surface of the pre-foamed pipe blank is wrapped by n layers of films, in addition, ribs also have pressure on the pipe under the action of the spring, however, as the strength of the films and the spring is still smaller than the opening force formed by the gas foaming in the pipe, the bubble holes can still grow, but the foaming speed is greatly controlled and cannot be too fast, the purpose of controllable foaming is achieved, when the pipe expands to a certain size, the elongation of the films exceeds the limit, the films break and fail, but the compression degree of the spring is high along with the expansion of the pipe, the compression force provided by the spring limits the faster growth of the bubble holes, therefore, the bubble holes in the pipe still grow in a limited state, the foaming of each part of the pipe is more uniform, until each rib on the mold reaches the limit position of the limit screw, at the moment, the pressure in the high-pressure container also basically removes, and at the moment, the temperature of the pipe at the melting temperature of the material is higher and the pipe can be fixed and the shape of the pipe can be shaped quickly; and taking the mold out of the high-pressure container, opening the second fixing frame, and taking the obtained foamed pipe out of the mold.
In addition, the inner diameter of the pipe corresponds to the size of an inner mold core of the mold, and the inner diameter of the pipe is only 0.04-0.1 mm larger than that of the inner mold core of the mold, namely, the difference is two times of the thickness of the PVA layer; the outer diameter of the pipe corresponds to the position of each rib of the outer module of the mould, and the outer diameter of the pipe is smaller than the inner diameter of a cavity formed by each rib of the mould and is equal to twice (according to the diameter) the thickness of the two layers of PVA coatings and the n layers of film layers.
The foamed pipe obtained by the method is a tubular product, the pipe wall of the foamed pipe is provided with a large number of mutually communicated micropores, the surfaces of the inner wall and the outer wall of the pipe also have open pore structures, the sizes of the micropores are uniform, the diameters of the micropores are within 50 micrometers, the size deviation of the pores can be controlled within 5 micrometers, the orientation of the micropores along the wall thickness direction is excellent, the foaming rate of the pipe is between 3 and 10, the inner diameter of the pipe is 10mm or more, the wall thickness of the pipe is between 3mm and 200mm, the section of the pipe is in a circular, oval or other rotary shape, and the section size of the pipe is unchanged or regularly changed.
The product of the invention also has excellent sound absorption effect, the sound absorption coefficient of the product is measured by using a transfer function method, the average sound absorption coefficient of the product measured in the frequency range of 200-2000 Hz exceeds 0.8, and the product is a class I sound absorption material.
Has the advantages that: compared with the prior art, the invention has the following remarkable effects:
(1) The method can realize the accurate control of the foaming cellular structure of the pipe, and can regulate and control the size of the cells and improve the limited degree of the long and large process of the cells through the combined action (regulating the pressure) of the film coating and the spring, thereby improving the uniformity of the cells, ensuring that the size difference of the cells at the same wall thickness of the pipe is very small, ensuring that the size difference of the cells at different wall thicknesses of the pipe is also very small, and ensuring that the uniformity of the cells is favorable for improving various mechanical properties and sound absorption functions of the material;
(2) The orientation direction of the foam holes can be accurately controlled, because the gaps among the ribs of the die are equivalent to a main air passage when pressure relief is carried out, the micropores on the film are equivalent to secondary air passages, the uniform distribution of the main air passages and the secondary air passages can keep uniform and smooth at the moment of opening the high-pressure container, and the directions of the main air passages and the secondary air passages are all radial along the pipe wall, so that the orientation directions of the micropores of the obtained pipe are very consistent; the foam holes with consistent orientation are also beneficial to improving the uniformity of the mechanical property of the material and the sound absorption effect;
(3) The foamed pipe can be conveniently separated from the die without damaging the pipe, and the PVA coating can enable the molded product to be rapidly separated from the inner die core without damage; meanwhile, the PVA coating can enable the inner wall surface and the outer wall surface of the pipe to have open pore structures, so that the foamed pipe with open pores on the surface can be directly obtained, the inner surface and the outer surface of the foamed pipe are not required to be subjected to open pore processing, and the quality of the inner surface and the outer surface of the pipe is good;
(4) The moving position of the rib in the cylindrical groove is determined by adjusting the position of the limiting screw of the mould, so that the appearance of the final foamed pipe is controlled, the foaming multiplying power of the pipe is accurately regulated and controlled, and products with different foaming multiplying powers are produced on one set of mould;
(5) The moving position of the rib in the cylindrical groove is determined by adjusting the position of the die limiting screw, so that the appearance of the final foamed pipe is controlled, the foamed forming of a special-shaped pipe product can be realized, and a product with a changed shape can be produced on one die;
(6) The infiltration efficiency and uniformity of the supercritical fluid in the material are improved through high-speed rotation, and the consistency of process conditions such as temperature, pressure, temperature and pressure change rate and the like of a certain thick-wall pipe at each part is realized, so that the production efficiency of the foamed pipe is improved, and the infiltration time of the 10mm thick pre-foamed pipe can be as short as 5 minutes.
Drawings
FIG. 1 is a process flow diagram of the method of the present invention for preparing a polymer microcellular foamed pipe;
FIG. 2 is a schematic structural view of a mold;
FIG. 3 is a schematic view of the mold after expansion to release the rib open;
FIG. 4 is a schematic view of a mold placed in a high pressure vessel;
FIG. 5 is a schematic external view of a pre-expanded tubular blank with a fixed turning section;
FIG. 6 is a schematic external view of a pre-expanded tubular blank having a regularly varying inclined turning section;
FIG. 7 is a scanning electron microscope image of the cell morphology of the foamed pipe article prepared in example 1 at a low magnification;
FIG. 8 is a high magnification scanning electron microscope image of the cell morphology of the foamed tubing article made in example 1;
FIG. 9 is a scanning electron microscope image of the cell morphology of the foamed pipe article prepared in comparative example 1;
FIG. 10 is a scanning electron microscope image of the cell morphology of the foamed pipe article prepared in example 2 at a low magnification;
FIG. 11 is a high magnification scanning electron micrograph of the cell morphology of the foamed tubing article made in example 2;
FIG. 12 is a scanning electron microscope image of the cell morphology of the foamed pipe article prepared in comparative example 2;
FIG. 13 is a scanning electron microscope image of the cell morphology of the foamed pipe article prepared in comparative example 3;
FIG. 14 is a scanning electron microscope image of the cell morphology of the foamed pipe article prepared in example 3 at a low magnification;
FIG. 15 is a high magnification scanning electron micrograph of the cell morphology of the foamed tubing article made in example 3;
FIG. 16 is a scanning electron microscope image of the cell morphology of the foamed pipe article prepared in comparative example 4.
Detailed Description
As shown in FIG. 4, the high pressure vessel of the present invention comprises an upper cover plate 12 and a lower box body 15, wherein the cover plate 12 and the box body 15 are sealed and no gas leakage occurs in the range of 0-70 MPA and 0-260 ℃, the cover plate 12 is provided with an injection port 17, supercritical fluid is injected into the vessel through the injection port 17 and controls the pressure in the vessel, a cylindrical reaction chamber 18 is arranged in the box body 15, the cylindrical reaction chamber 18 is arranged in a groove of the box body 15, the side wall of the box body 15 is further provided with a temperature control device 16, a pre-foamed pipe 14 is arranged in a mold 8, the mold 8 is arranged in the reaction chamber 18, the reaction chamber 18 is connected with an external motor through a coupling 11, the motor rotates to drive the reaction chamber 18 to rotate, thereby driving the mold 8 to rotate, when the upper cover plate 12 is separated from the lower box body 15, the high pressure vessel is rapidly opened, and the response time is within 0.05 second.
Example 1
A method for producing polypropylene/linear low density polyethylene microporous foamed pipes by using supercritical fluid comprises the following steps:
in the aspect of raw materials, the used polypropylene (PP) is common commercial domestic T30S, the melting point of the polypropylene is 165 ℃, the used Linear Low Density Polyethylene (LLDPE) is common commercial domestic 7050, the melting point of the Linear Low Density Polyethylene (LLDPE) is 120 ℃, the melt strength of the material measured at 120 ℃ and 165 ℃ is 1.16 g and 0.52g respectively according to a weight measuring method, a high pressure (70 MPA) and high temperature (250 ℃) resistant sealable container shown in figure 4 is adopted, gas leakage does not occur in the ranges of 0-70 MPA and 0-260 ℃ after the container is sealed, a cavity which is in transmission connection with a motor through a coupler is arranged in the container, a mold for loading a pre-foamed pipe blank is arranged in the cavity, and the cavity rotates under the driving of the motor.
The PVA used was a commercially available 1788, and was dissolved in distilled water twice the mass thereof at room temperature to prepare an aqueous PVA solution. The used temperature-resistant super-tough film (R260 porous isolation Teflon FEP film) with micropores can resist high temperature of 260 degrees and is commercially available, the thickness of the film is 20 micrometers, the pore diameter of the film is 10 micrometers, the pore spacing is 8 millimeters, the elongation at break of the film is 182 percent, and the tensile strength of the film is 21.3MPa, wherein the elongation at break is actually measured at a tensile speed of 500mm/min at 150 degrees.
The method is implemented based on a die, as shown in fig. 2, the die 8 comprises a first fixing frame 31 and a second fixing frame 32 which are oppositely arranged, and an inner die core 4 fixed on the first fixing frame 31; the first fixing frame 31 and the second fixing frame 32 are respectively provided with cylindrical grooves 5 which are annularly arranged and correspond to each other, the mold 8 further comprises an outer module 1, the outer module 1 is composed of a plurality of ribs 6 which are annularly arranged, and the ribs 6 of the outer module 1 are arranged in one-to-one correspondence with the cylindrical grooves 5 on the fixing frame 3; two ends of the rib 6 are respectively connected with the first fixing frame 31 and the second fixing frame 32 through limiting screws 7; the mould 8 is still including setting up compression spring 2 in cylindrical groove 5, and the extreme point that 3 center one side of mount was kept away from to compression spring 2 one end and cylindrical groove 5 is connected, and the compression spring 2 other end is connected with stop screw 7, and stop screw 7 passes through compression spring 2 and transversely slides in cylindrical groove 5.
Wherein the shape of the rib is a straight round bar with the diameter of 6mm, the number of the ribs is determined according to the value not more than (20 + 6) × 3.14/6, and 12 ribs are selected for convenient processing.
The method specifically comprises the following steps:
(1) Mixing a pure PP material and an LLDPE material according to the weight percentage of 7:3, after mixing, extruding and melt blending to obtain a PP/LLDPE blend, and determining the linear shrinkage delta of the blend between 150 degrees and 25 degrees to be 1.5% through experiments;
(2) The PP/LLDPE blend is processed into a pre-foamed pipe with the inner diameter of 9.96mm and the outer diameter of 20mm through extrusion molding, the shape of the pre-foamed pipe is shown in figure 5, and the drawing ratio of the material in the extrusion process is 3;
(3) Cutting a pre-foamed pipe with the length equal to 295.6mm to obtain a pre-foamed pipe blank;
(4) Uniformly coating a layer of PVA aqueous solution on the inner surface and the outer surface of the pre-foamed pipe blank, wherein the thickness of the coating is 50 microns;
(5) Putting the pre-foamed pipe blank into an air-blast drying oven for drying until PVA is completely shaped, measuring the thickness of the pre-foamed pipe blank to be about 20 microns, coating PVA aqueous solution on the outer surface of the pre-foamed pipe blank again, wherein the use amount of the PVA aqueous solution is close to that of the first time, and when the pre-foamed pipe blank is not dried, coating and winding 3 layers of the outer surface by using a temperature-resistant super-tough film with micropores;
wherein the number of layers is determined by the film at a high temperature T Put Estimated at a high drawing speed of 500mm/min at a tensile strength M of 21.3MPa, i.e. n is equal to P Medicine for treating chronic gastritis /P Time release *P Dipping in water Per M and integer, pressure P of supercritical fluid Dipping in water 15MPa, initial pressure release rate P of the high-pressure vessel at the moment of opening Medicine for treating chronic gastritis 30MPa, the expected pressure reduction rate P of the pre-foamed pipe blank during initial pressure release after pre-soaking Time release Is 7.5MPa;
(6) Sleeving the processed pre-foamed pipe blank on an inner mold core of a mold, surrounding an outer mold group outside the pipe, and adjusting ribs of the outer mold group to the position with the inner diameter (the inner diameter of a cavity enclosed by the outer mold group) of 40.1 mm;
(7) Placing the mould containing the prefoaming pipe blank in a closed high-pressure container, introducing supercritical fluid into the closed high-pressure container, and soaking the prefoaming pipe blank in supercritical CO at 165-15 MPA 2 For 5 minutes, wherein the mold is rotated at a speed of 900r/min in a high-pressure vessel;
(8) Reducing the temperature in the high-pressure container to 145 ℃, balancing the internal temperature after 20-60 minutes, stopping the rotation of the mold, quickly opening the high-pressure container, and relieving the pressure to obtain a microporous foamed pipe tightly connected with the mold;
(9) Immersing the microporous foamed pipe in water, removing the PVA layer on the surfaces of the inner wall and the outer wall of the microporous foamed pipe, removing the film layer, and taking the pipe out of the mold to obtain the pipe with open pores on the surface and excellent surface quality; the outer diameter of the pipe is 40mm, and the foaming ratio of the pipe is 5 times.
The tubular article obtained in example 1 was subjected to a ring crush strength test, and the ring crush strength was 1623KN/100mm. Meanwhile, the morphology of the cells in the product is observed, and the results are shown in fig. 7-8, it is found that the uniformity of the cells is good, and the average size deviation of the cells at different wall thicknesses in the wall thickness direction (the up-down direction of fig. 7) is within 5 microns, the cells have orientation in the wall thickness direction and are all open-cell structures, and the open-cell rate of the cells reaches 95.5% through tests.
The sound absorption coefficient is measured by using a transfer function method, the average sound absorption coefficient of the pipe wall measured in the frequency range of 200-2000 Hz reaches 0.901, and the obtained product has excellent sound absorption effect.
Comparative example 1
To illustrate the effect of the present invention, comparative example 1 is described, wherein the preparation process of the raw materials is similar to that of example 1, the raw materials used are polypropylene (PP) with a melting point of 165 ° in T30S, which is a commercially available product, and Linear Low Density Polyethylene (LLDPE) with a melting point of 120 ° in 7050, which is a commercially available product, and the two raw materials are completely the same as example 1, a high pressure (70 MPA) and high temperature (250 ℃) resistant sealable container with an inner diameter of 50mm is used, gas leakage does not occur in the ranges of 0 to 70MPA and 0 to 260 ° after the container is sealed, a cavity which is in transmission connection with a motor through a coupling is provided in the container, and the structure is substantially the same as that of example 1. The only difference is: however, comparative example 1 did not use the mold used in example 1, nor did it use the film and mold to regulate the cells as in example 1; the production method of the polymer microcellular foamed pipe refers to the conventional method and specifically comprises the following steps:
(1) Mixing a pure PP material and an LLDPE material according to the weight percentage of 7:3, after mixing, extruding, melting and blending to obtain a PP/LLDPE blend, extruding and molding the PP/LLDPE blend into a pre-foamed pipe with the inner diameter of 10mm and the outer diameter of 20mm, wherein the drawing ratio of the material in the extrusion process is 3, and cutting the pipe into pipes with the length of 300 mm;
(2) Directly placing the tube in a sealed high-pressure container, and adding supercritical CO 2 Introducing into a sealed high-pressure container, and soaking at 175 ℃ and 15MPA for 30 minutes; (unsuccessful test after 5 minutes of 165 degree immersion corresponding to example 1)
(3) The temperature in the high-pressure container is cooled to 145 ℃, the pressure is quickly relieved after 10 minutes, the pipe in the high-pressure container is taken out, the foaming sizes of all parts of the pipe are not uniform, the inner and outer sizes are not uniform, and the foaming multiplying power of the pipe is about 8 times.
The tubular article obtained in comparative example 1 was tested for ring crush strength, and the optimum ring crush strength was only 1137KN/100mm. Meanwhile, the cell morphology in the article was observed, and the result is shown in FIG. 9.
The sound absorption coefficient is measured by using a transfer function method, and the average sound absorption coefficient of the pipe wall is 0.553 measured in the frequency range of 200-2000 Hz.
It can be seen from the comparison between example 1 and comparative example 1 that, in comparative example 1, the tubular member was not foamed under controlled conditions, so that the cells were very uneven, the cell density and cell size at each site were very different, the cells had a certain open cell structure, but the open cell ratio was only 53%, the cell orientation uniformity was very poor, the tubular member had a very poor appearance, the inner and outer wall surfaces were solid structures, and the size difference at each site was very large. In addition, as can be seen from the comparison of the sound absorption coefficients, the sound absorption effect of the comparative example is much worse than that of example 1, and the sound absorption effect of example 1 is better.
Example 2
A method for producing polypropylene/linear low density polyethylene microporous foamed pipes by using supercritical fluid comprises the following steps:
in the aspect of raw materials, the used polypropylene (PP) is common commercially available domestic T30S, the melting point of the PP is 165 ℃, the used Linear Low Density Polyethylene (LLDPE) is common commercially available domestic 7050, the melting point of the LLDPE is 120 ℃, a sealable container which is high pressure resistant (70 MPA) and high temperature resistant (250 ℃) is adopted, gas leakage does not occur in the range of 0-70 MPA and 0-260 ℃ after the container is sealed, a cavity which is in transmission connection with a motor through a coupling is arranged in the container, a mold for loading a pre-foamed pipe blank is arranged in the cavity, and the cavity rotates under the driving of the motor.
The PVA used was a commercially available 1788, and was dissolved in distilled water twice the mass thereof at room temperature to prepare an aqueous PVA solution. The used temperature-resistant super-tough film (R260 porous isolation Teflon FEP film) with micropores can resist high temperature of 260 degrees and is commercially available, the thickness of the film is 20 micrometers, the pore diameter of the film is 10 micrometers, the pore spacing is 8 millimeters, the elongation at break of the film is 182 percent, and the tensile strength of the film is 21.3MPa, wherein the elongation at break is actually measured at a tensile speed of 500mm/min at 150 degrees.
The method is implemented based on a die, as shown in fig. 2, the die 8 comprises a first fixing frame 31 and a second fixing frame 32 which are oppositely arranged, and an inner die core 4 fixed on the first fixing frame 31; the first fixing frame 31 and the second fixing frame 32 are respectively provided with cylindrical grooves 5 which are annularly arranged and correspond to each other, the die 8 further comprises an outer die set 1, the outer die set 1 is composed of a plurality of ribs 6 which are annularly arranged, and the ribs 6 of the outer die set 1 are arranged in one-to-one correspondence with the cylindrical grooves 5 on the fixing frame 3; two ends of the rib 6 are respectively connected with the first fixing frame 31 and the second fixing frame 32 through limiting screws 7; the mould 8 is still including setting up compression spring 2 in cylindrical groove 5, and the extreme point that 3 center one side of mount was kept away from to compression spring 2 one end and cylindrical groove 5 is connected, and the compression spring 2 other end is connected with stop screw 7, and stop screw 7 passes through compression spring 2 and transversely slides in cylindrical groove 5.
Wherein the shape of the rib is a straight round bar with the diameter of 10mm, the number of the ribs respectively determined at the two ends of the pre-foaming pipe blank is not more than (90 + 10) × 3.14/10 and (100 + 10) × 3.14/10, and finally 28 ribs are selected.
The method comprises the following steps:
(1) Mixing a pure PP material and an LLDPE material according to the weight percentage of 7:3, after mixing, extruding and melt blending to obtain a PP/LLDPE blend, and determining the linear shrinkage delta of the blend between 150 degrees and 25 degrees to be 1.5% through experiments;
(2) The PP/LLDPE blend was processed into a pre-expanded tubular blank having a length of 98.5mm, an inner radius of 69.94mm at one end, an outer radius of 90mm, an inner radius of 79.94mm at the other end and an outer radius of 100mm by compacting at 10MPA pressure and a temperature of 200 ℃, the outer shape of which is shown in FIG. 6;
(3) Uniformly coating a layer of PVA aqueous solution on the inner surface and the outer surface of the pre-foamed pipe blank, wherein the thickness of the coating is 50 micrometers;
(4) Putting the pre-foamed pipe blank into an air-blast drying oven for drying until PVA is completely shaped, measuring the thickness of the pre-foamed pipe blank to be about 30 microns, coating PVA aqueous solution on the outer surface of the pre-foamed pipe blank again, wherein the use amount of the PVA aqueous solution is close to that of the first time, and when the pre-foamed pipe blank is not dried, coating 5 layers of the winding outer surface by using a temperature-resistant super-tough film with micropores;
wherein the number of layers is determined by the film at a high temperature T Placing the Estimated at a high drawing speed of 500mm/min at a tensile strength M of 21.3MPa, i.e. n is equal to P Medicine for treating chronic gastritis /P Time release *P Dipping in water Per M and get integerPressure P of a supercritical fluid Dipping in water 20MPa, initial pressure release rate P of the high-pressure vessel at the moment of opening Medicine for curing cancer 40MPa, the expected pressure reduction rate P of the pre-foamed pipe blank during initial pressure release after pre-soaking Time release Is 8MPa;
(5) Sleeving the treated pre-foamed pipe blank on an inner mold core of a mold, surrounding an outer mold group outside the pipe, and adjusting ribs at two ends of the outer mold group to positions with the inner diameters of 160.16mm and 170.16mm respectively;
(6) Placing the mould containing the prefoaming pipe blank in a closed high-pressure container, introducing supercritical fluid into the closed high-pressure container, and soaking the prefoaming pipe blank in supercritical N at 160-20 MPA 2 The middle 10 minutes, wherein the mould rotates at the speed of 300r/min in a high-pressure container;
(7) Reducing the temperature in the high-pressure container to 155 ℃, balancing the internal temperature after 20-60 minutes, stopping the rotation of the mold, quickly opening the high-pressure container, and relieving the pressure to obtain a microporous foamed pipe tightly connected with the mold;
(8) Immersing the microporous foamed pipe in water, removing the PVA layer on the surfaces of the inner wall and the outer wall of the microporous foamed pipe, removing the film layer, and taking the pipe out of the mold to obtain the pipe with open pores on the surface and excellent surface quality; the outer radii of both ends of the pipe are 160mm and 170mm, respectively, and the expansion ratio of the pipe is about 6.36 times.
The disk-shaped article obtained in example 2 was subjected to a longitudinal compression strength test, and the pressure applied was as high as 2942KN/100mm. Meanwhile, the morphology of the cells in the product is observed, and the results are shown in fig. 10-11, it is found that the uniformity of the cells is good, and the average size deviation of the cells at different wall thicknesses in the wall thickness direction (the up-down direction of fig. 10) is within 5 microns, the cells have orientation in the wall thickness direction and are all open-cell structures, and the open-cell rate of the cells reaches 93.7% through tests.
The sound absorption coefficient is measured by a transfer function method, and the average sound absorption coefficient of the pipe wall obtained in the embodiment is 0.884 measured in the frequency range of 200-2000 Hz.
Comparative example 2
To illustrate the effect of the present invention, comparative example 2 is illustrated, the preparation process of the raw material is similar to that of example 2, in the raw material aspect, the polypropylene (PP) used is a common commercially available domestic T30S, the melting point thereof is 165 degrees, the Linear Low Density Polyethylene (LLDPE) used is a common commercially available domestic 7050, the melting point thereof is 120 degrees, a sealable container with high pressure resistance (70 MPA) and high temperature resistance (250 degrees) is used, the inner diameter thereof is 170mm, no gas leakage occurs in the range of 0 to 70MPA and 0 to 260 degrees after the container is sealed, a cavity which is in transmission connection with a motor through a coupling is arranged in the container, and the structure thereof is basically consistent with that of example 2. The only differences are: however, comparative example 2 did not use the die used in example 2, nor did it use the film and die to regulate the cells as per example 2; the production method of the polymer microcellular foamed pipe refers to the conventional method and specifically comprises the following steps:
(1) Mixing a pure PP material and an LLDPE material according to the weight percentage of 7:3, similarly to example 2, the mixture was compacted under a pressure of 10MPA and a temperature of 200 ℃ and processed into a prefoamed tube blank having a length of 98.5mm, an inner radius of 69.97mm at one end and an outer radius of 90mm at the other end, an inner radius of 79.97mm and an outer radius of 100mm at the other end;
(2) Directly placing the prefoamed pipe blank in a closed high-pressure container, and adding supercritical N 2 Introducing into a sealed high-pressure container, and soaking at 180 deg.C and 20MPA for 40 min; (10 minutes after 160 degree immersion corresponding to example 2, the experiment was unsuccessful)
(3) And (3) cooling the temperature in the high-pressure container to 155 ℃, opening the high-pressure container after 10 minutes, quickly relieving the pressure, taking out the pipe in the high-pressure container, wherein the foaming sizes of all parts of the pipe are not uniform, the inner and outer sizes are not uniform, and the foaming multiplying power of the pipe is about 7.7 times.
The tubular article prepared in comparative example 2 was tested for longitudinal compression strength, and the best result for longitudinal compression strength was 2267KN/100mm. Meanwhile, the cell morphology in the article was observed, and the result is shown in FIG. 12. In FIG. 12, the left-right direction is the wall thickness direction, and it can be seen that the cells are oriented substantially along this direction, but the cell sizes at different wall thicknesses vary greatly.
It can be seen from the comparison between example 2 and comparative example 2 that, since the pipe in comparative example 2 is not foamed under controlled conditions, the cells are very uneven, the cell density and cell size at each site are very different, the cells have a certain open cell structure, but the open cell ratio is only 62.8%, the appearance of the pipe is very poor, the size difference at each site is also very large, and the inner and outer wall surfaces are solid structures.
The sound absorption coefficient is measured by a transfer function method, and the average sound absorption coefficient of the pipe wall obtained in the embodiment is 0.475 measured in the frequency range of 200-2000 Hz.
Comparative example 3
To illustrate the effect of the present invention, comparative example 3 is shown, the preparation process of the raw material is similar to that of example 2, in the raw material aspect, the polypropylene (PP) used is ordinary commercially available domestic T30S, the melting point thereof is 165 degrees, the Linear Low Density Polyethylene (LLDPE) used is ordinary commercially available domestic 7050, the melting point thereof is 120 degrees, a sealable container with high pressure resistance (70 MPA) and high temperature resistance (250 degrees) is used, the inner diameter thereof is 170mm, no gas leakage occurs in the range of 0 to 70MPA and 0 to 260 degrees after the container is sealed, a cavity which is in transmission connection with a motor through a coupling is arranged in the container, and the structure thereof is basically consistent with that of example 2. The only difference is: comparative example 3 the mold used in example 2 was used, but the film and mold were not used to regulate the cells as in example 2; the method specifically comprises the following steps:
(1) Mixing a pure PP material and an LLDPE material according to the weight percentage of 7:3, after mixing, extruding and melt blending to obtain a PP/LLDPE blend, and determining the linear shrinkage delta of the blend between 150 degrees and 25 degrees to be 1.5% through experiments;
(2) The PP/LLDPE blend was processed into a pre-expanded tubular blank having a length of 98.5mm, an inner radius of 70mm at one end and an outer radius of 90mm at the other end, and an inner radius of 80mm and an outer radius of 100mm at 200 ℃ by compacting at 10MPA pressure, the outer shape of which is shown in FIG. 6;
(3) Sleeving a pre-foamed pipe blank on an inner mold core of a mold, surrounding an outer mold group outside a pipe, and adjusting ribs at two ends of the outer mold group to positions with inner diameters of 160mm and 170mm respectively;
(4) Placing a mould containing a pipeIntroducing supercritical fluid into a sealed high-pressure container, and soaking the pipe in supercritical N at 160-20 MPA 2 For 10 minutes, wherein the mold is rotated at a speed of 300r/min in a high pressure vessel;
(5) Reducing the temperature in the high-pressure container to 155 ℃, stopping the rotation of the mold after the temperature is balanced, quickly opening the high-pressure container, and instantly releasing the pressure to obtain the microporous foamed pipe tightly connected with the mold;
(6) Because the sizes of the two ends are different, although the microcellular foamed pipe is tightly sleeved on the inner mold core of the mold, the microcellular foamed pipe can be separated from the inner mold core of the mold once the pipe shows the movement, so that the pipe is obtained, the outer radiuses of the two ends are 160mm and 170mm respectively, and the foaming ratio of the pipe is about 6.37 times.
The tubular part prepared in comparative example 3 was tested for longitudinal compressive strength, and the best result of the longitudinal compressive strength was 2451KN/100mm. Meanwhile, the cell morphology in the article was observed, and the result is shown in FIG. 13. In fig. 13, the left-right direction is the wall thickness direction, and it can be seen that the uniformity of the orientation of the cells is poor, but the difference of the cell sizes at different wall thicknesses is significant, and even the cell sizes at the same wall thickness are greatly different.
The sound absorption coefficient is measured by a transfer function method, and the average sound absorption coefficient of the pipe wall obtained by the comparative example is 0.522 measured in the frequency range of 200-2000 Hz.
It can be seen from the comparison between example 2 and comparative example 3 that, although the pipe in comparative example 3 is foamed under a certain controllable condition, the degree of control is not precise, so that the cells are not uniform, the cell density and cell size of each part are greatly different, the cells have a certain open cell structure, and the open cell ratio is as high as 83.1%, but the appearance of the obtained pipe is not perfect, the inner and outer wall surfaces have relatively thick solid layers, and the size difference of each part is also large, so that the pipe cannot be directly put into use.
Meanwhile, as can be seen from the sound absorption effect, compared with example 2, the sound absorption effects of comparative example 2 and comparative example 3 are much different from that of example 2, and the sound absorption effect of example 2 is very good.
Example 3
A method for producing thermoplastic polyurethane microcellular foamed pipes by using supercritical fluid comprises the following steps:
in the aspect of raw materials, two Thermoplastic Polyurethanes (TPU) with different hardness degrees are used, the TPU is respectively 60D and 75A which are sold in the common market, the melting points of the TPU are respectively 170 ℃ and 150 ℃, the melt strength of the 75A material measured at 170 ℃ and 150 ℃ is respectively 17.1mN and 9.3mN according to a force measuring method, a sealable container with high pressure resistance (70 MPA) and high temperature resistance (250 ℃) is adopted, gas leakage does not occur in the ranges of 0-70 MPA and 0-260 ℃ after the container is sealed, a cavity which is in transmission connection with a motor through a coupling is arranged in the container, a mold for loading a prefoaming tube blank is arranged in the cavity, and the cavity rotates under the driving of the motor.
The PVA used was a conventional commercially available 1788 product, and was dissolved in distilled water twice the mass thereof at room temperature to prepare an aqueous PVA solution. The used temperature-resistant super-tough film (R260 porous isolation Teflon FEP film) with micropores can resist high temperature of 260 degrees and is commercially available, the thickness of the film is 20 micrometers, the pore diameter of the film is 10 micrometers, the pore spacing is 8 millimeters, the elongation at break of the film is 182 percent, and the tensile strength of the film is 21.3MPa, wherein the elongation at break is actually measured at a tensile speed of 500mm/min at 150 degrees.
The method is implemented based on a die, as shown in fig. 2, the die 8 comprises a first fixing frame 31 and a second fixing frame 32 which are oppositely arranged, and an inner die core 4 fixed on the first fixing frame 31; the first fixing frame 31 and the second fixing frame 32 are respectively provided with cylindrical grooves 5 which are annularly arranged and correspond to each other, the mold 8 further comprises an outer module 1, the outer module 1 is composed of a plurality of ribs 6 which are annularly arranged, and the ribs 6 of the outer module 1 are arranged in one-to-one correspondence with the cylindrical grooves 5 on the fixing frame 3; two ends of the rib 6 are respectively connected with the first fixing frame 31 and the second fixing frame 32 through limiting screws 7; the mould 8 is still including setting up the compression spring 2 in cylindrical groove 5, and the extreme point that 3 center one side of mount was kept away from with cylindrical groove 5 to compression spring 2 one end is connected, and the compression spring 2 other end is connected with stop screw 7, and stop screw 7 passes through compression spring 2 and in cylindrical groove 5 lateral sliding.
Wherein the shape of the rib is a straight round bar with the diameter of 10mm, the number of the ribs is determined according to the value not more than (60 + 10) × 3.14/10, and 20 ribs are selected for convenient processing.
The method comprises the following steps:
(1) Two TPU materials are mixed according to the weight percentage of 7:3 obtaining a TPU blend through solvent blending after mixing, and determining that the linear shrinkage delta of the blend between 150 degrees and 25 degrees is 1.0 percent through experiments;
(2) The TPU blend is processed into a pre-foamed pipe with the inner diameter of 49.96mm and the outer diameter of 60mm through extrusion molding, and the shape of the pre-foamed pipe is shown in figure 5;
(3) Cutting a pre-foamed pipe with the length equal to 495.0mm to obtain a pre-foamed pipe blank;
(4) Uniformly coating a layer of PVA aqueous solution on the inner surface and the outer surface of the pre-foamed pipe blank, wherein the thickness of the coating is 50 microns;
(5) Putting the pre-foamed pipe blank into an air-blast drying oven for drying until PVA is completely shaped, measuring the thickness of the pre-foamed pipe blank to be about 20 microns, coating PVA aqueous solution on the outer surface of the pre-foamed pipe blank again, wherein the use amount of the PVA aqueous solution is close to that of the first time, and when the pre-foamed pipe blank is not dried, coating 5 layers of the winding outer surface by using a temperature-resistant super-tough film with micropores;
wherein the number of layers is determined by the film at a high temperature T Put Estimated at a high drawing speed of 500mm/min at a tensile strength M of 21.3MPa, i.e. n is equal to P Medicine for treating chronic gastritis /P Time release *P Dipping in water Per M and integer, pressure P of co-intermediate supercritical fluid Dipping in water 25MPa, initial pressure release rate P of the high-pressure vessel at the moment of opening Medicine for treating chronic gastritis 50MPa, the expected pressure reduction rate P of the pre-foamed pipe blank during initial pressure release after pre-soaking Time release Is 10MPa;
(6) Sleeving the treated pre-foamed pipe blank on an inner mold core of a mold, surrounding an outer mold group outside the pipe, and adjusting ribs of the outer mold group to the position of 120.14mm in inner diameter;
(7) Placing the mould containing the prefoaming pipe blank in a closed high-pressure container, introducing supercritical fluid into the closed high-pressure container, and soaking the prefoaming pipe blank in supercritical CO at 165-25 MPA 2 Middle 10 minutes, wherein the mold is at heightRotating the inside of the pressure container at the speed of 600 r/min;
(8) Reducing the temperature in the high-pressure container to 150 ℃, keeping the internal temperature balanced after 20-60 minutes, stopping the rotation of the mold, quickly opening the high-pressure container, and relieving the pressure to obtain a microporous foamed pipe tightly connected with the mold;
(9) Immersing the microporous foamed pipe in water, removing the PVA layer on the surfaces of the inner wall and the outer wall of the microporous foamed pipe, removing the film layer, and taking the pipe out of the mold to obtain the pipe with open pores on the surface and excellent surface quality; the outer diameter of the pipe is 120mm, and the expansion ratio of the pipe is 10.82 times.
The tubular article obtained in example 3 was subjected to a ring crush strength test, and was not crushed. Meanwhile, the morphology of the cells in the product is observed, and the results are shown in fig. 14-15, it is found that the uniformity of the cells is good, and the cells are all open-cell structures, and tests show that the open-cell rate of the cells reaches 97.9%, and in the wall thickness direction (the up-down direction of fig. 14), the average size deviation of the cells at different wall thicknesses is within 5 micrometers, and the cells all have orientation along the wall thickness direction.
The sound absorption coefficient is measured by a transfer function method, and the average sound absorption coefficient of the pipe wall obtained in the embodiment is 0.921 in a frequency range of 200-2000 Hz.
Comparative example 4
To illustrate the effect of the present invention, comparative example 4 is given, the preparation process of the raw materials is similar to that of example 3, two Thermoplastic Polyurethanes (TPU) with different hardness degrees are used in the raw materials, which are respectively common commercial 60D and 75A, the melting points of the two polyurethanes are respectively 170 degrees and 150 degrees, a sealable container with high pressure resistance (70 MPA) and high temperature resistance (250 degrees) is adopted, the inner diameter is 50mm, no gas leakage occurs in the ranges of 0-70 MPA and 0-260 degrees after the container is sealed, a cavity connected with a motor through a coupling in a transmission manner is arranged in the container, and the structure of the cavity is basically consistent with that of example 3. The only difference is: comparative example 4, however, did not use the mold used in example 3, nor did it use the film and mold to manipulate the cells as in example 3; the production method of the polymer microcellular foamed pipe refers to the conventional method and specifically comprises the following steps:
(1) Two TPU materials are mixed according to the weight percentage of 7:3, mixing, blending by using a solvent to obtain a TPU blend, extruding and molding the TPU blend into a pre-foamed pipe with the inner diameter of 50mm and the outer diameter of 60mm, wherein the drawing ratio of the material in the extrusion process is 3, and cutting the pipe into pipes with the length of 500 mm;
(2) Directly placing the tube in a sealed high-pressure container, and adding supercritical CO 2 Introducing into a sealed high-pressure container, and soaking at 180 deg.C and 25MPA for 30 min; (unsuccessful test after 10 minutes of 165 degree immersion corresponding to example 3)
(3) And cooling the temperature in the high-pressure container to 150 ℃, quickly relieving pressure after 10 minutes, taking out the pipe in the high-pressure container, wherein the foaming sizes of all parts of the pipe are not uniform, the inner and outer sizes are not uniform, and the foaming ratio of the pipe is about 13.2 times.
The morphology of the cells in the tubular article made in comparative example 4 was observed and the results are shown in FIG. 16. It can be seen from the comparison between example 3 and comparative example 4 that, in comparative example 4, the pipe is not foamed under a controllable condition, so that the cells are very uneven, the cell density and cell size of each part are very different, the cells have a certain open-cell structure, but the open-cell ratio is only 72.9%, the uniformity of cell orientation is very poor, the appearance of the pipe is very poor, the inner and outer wall surfaces are solid structures, and the size difference of each part is very large.
The sound absorption coefficient is measured by using a transfer function method, the average sound absorption coefficient of the pipe wall obtained in the comparative example 4 is measured to be 0.499 in the frequency range of 200-2000 Hz, and the comparison with the example 3 shows that the sound absorption effect of the comparative example 4 is much poorer than that of the example 3, and the sound absorption effect of the example 3 is excellent.
Claims (10)
1. A production device of polymer microcellular foamed pipes is characterized in that: comprising a mould (8); the mould (8) comprises a first fixing frame (31), a second fixing frame (32) and an inner mould core (4) fixed on the first fixing frame (31), wherein the first fixing frame and the second fixing frame are oppositely arranged; the first fixing frame (31) and the second fixing frame (32) are respectively provided with cylindrical grooves (5) which are annularly arranged and correspond to each other, the external module (1) is composed of a plurality of ribs (6) which are annularly arranged, and the ribs (6) of the external module (1) and the cylindrical grooves (5) on the fixing frame (3) are arranged in a one-to-one correspondence manner; two ends of the rib (6) are respectively connected with the first fixing frame (31) and the second fixing frame (32) through limiting screws (7); still including setting up compression spring (2) in cylindrical groove (5), compression spring (2) one end is kept away from the extreme point of mount (3) center one side with cylindrical groove (5) and is connected, and compression spring (2) other end is connected with stop screw (7), stop screw (7) are through compression spring (2) lateral sliding in cylindrical groove (5).
2. The apparatus for producing polymer microcellular foamed tubing according to claim 1, wherein: the height of the inner mold core (4) is not more than the distance between the first fixing frame (31) and the second fixing frame (32); the height of the inner mold core (4) is not less than the length of the pre-foaming tube blank; the outer diameter of the inner mold core (4) is consistent with the inner diameter of the pre-foaming tube blank.
3. The apparatus for producing polymer microcellular foamed tubing according to claim 1, wherein: the mould is characterized by further comprising a high-pressure closed container driving the mould to rotate, a cavity connected with a motor through a coupling in a transmission mode is arranged in the container, the size of the cavity is consistent with that of the mould, the mould for loading the pre-foaming pipe blank is arranged in the cavity, and the cavity is driven by the motor to rotate.
4. The method for producing the polymer microcellular foamed pipe material based on the production apparatus of claim 3, characterized by comprising the steps of:
(1) Selecting at least two thermoplastic polymers and forming a blend by melt blending or solution blending;
(2) Molding the blend to obtain a pre-foamed pipe, wherein the wall thickness of the pre-foamed pipe is 1-20 mm;
(3) Intercepting a pre-foamed pipe, wherein the length of the pre-foamed pipe is equal to the length of the required pipe/(1 + linear shrinkage factor delta of the blend), so as to obtain a pre-foamed pipe blank;
(4) Uniformly coating PVA aqueous solution on the inner surface and the outer surface of the pre-foamed pipe blank, and forming a PVA coating on the inner surface and the outer surface of the pre-foamed pipe blank, wherein the initial thickness of the PVA coating is 30-50 mu m;
(5) Drying the pre-foamed pipe blank until the PVA coating is completely formed, coating the outer surface of the pre-foamed pipe blank with PVA aqueous solution again to form a coating with the thickness equal to the initial thickness of the step (4), and wrapping and winding n layers on the outer surface of the pre-foamed pipe blank by using a film when the coated PVA aqueous solution is not dried;
(6) After the films are adhered, sleeving the pre-foamed pipe blank on an inner mold core of a mold, surrounding the pre-foamed pipe blank by an outer mold set, and adjusting ribs of the outer mold set to a position larger than the outer diameter of the pre-foamed pipe blank;
(7) Placing a mould containing a prefoaming pipe blank in a closed high-pressure container, introducing supercritical fluid into the closed high-pressure container, and heating at high temperature T Dipping in water And a high voltage P Dipping in water Soaking the lower prefoaming pipe blank in a supercritical fluid; wherein, the mould is always in a rotating state in the high-pressure container;
(8) After the soaking time t Dipping in water Then, the temperature T in the high-pressure container is measured Put Reducing the temperature to be 5-20 ℃ below the melting point of the polymer, stopping the rotation of the mold after the temperature is balanced, quickly opening a high-pressure container, and relieving pressure to obtain a microporous foamed pipe tightly connected with the mold;
(9) And (3) immersing the mould with the microporous foamed pipe in water, removing the PVA coating on the surface of the inner wall of the mould, taking the pipe out of the mould, removing the film layer, and removing the PVA coating on the surface of the outer wall of the pipe to obtain the polymer microporous foamed pipe.
5. The method of producing polymer microcellular foamed tubing according to claim 4, wherein: in the step (1), the melting point difference of the polymer which is compounded is more than 20 ℃, when the melt strength of the low-melting polymer is tested by a weight measuring method or a force measuring method, the melt strength difference between the two melting points is more than 50 percent, the mass ratio of the low-melting polymer is 10 to 30 percent, and the mass ratio of the high-melting polymer is 70 to 90 percent.
6. Process for producing polymer microcellular foamed pipes according to claim 4The method is characterized in that: in step (3), the linear shrinkage factor δ of the blend is determined by the length ratio of the blend in the high temperature and real temperature Shi Mou direction: δ = length at high temperature L Height of Length at room temperature L Chamber -1, said high temperature being equal to T Put 。
7. The method of producing polymer microcellular foamed tubing according to claim 4, wherein: in the step (5), the layer thickness ratio alpha of the PVA coating before and after drying is 0.4-0.6.
8. The method of producing polymer microcellular foamed tubing according to claim 4, wherein: in the step (7), in the high-pressure container, the supercritical fluid is supercritical nitrogen or supercritical carbon dioxide or a composite of the supercritical nitrogen and the supercritical carbon dioxide, and the pressure P of the supercritical fluid Dipping in water Is 10-50MPA, T Dipping in water 0-5 ℃ below the melting point of the polymer, and soaking time t Dipping in water Is 5 to 30 minutes; the rotating speed of the die in the high-pressure container is 300-900 r/min.
9. The method of producing polymer microcellular foamed tubing according to claim 4, wherein: in step (8), the initial pressure release speed P of the high-pressure container at the opening moment Medicine for treating chronic gastritis Is 30 to 70 MPa/s.
10. The use of the polymer microcellular foamed pipe produced by the method according to claim 4 in sound absorption materials, wherein: the average sound absorption coefficient of the polymer microporous foamed pipe exceeds 0.8.
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| CN202211645429.7A CN115782268A (en) | 2022-12-16 | 2022-12-16 | Production device and production method of polymer microporous foamed pipe |
| PCT/CN2023/081546 WO2024124718A1 (en) | 2022-12-16 | 2023-03-15 | Production device and production method for polymeric microcellular foamed pipe |
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| CN202211645429.7A CN115782268A (en) | 2022-12-16 | 2022-12-16 | Production device and production method of polymer microporous foamed pipe |
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| CN202211645429.7A Pending CN115782268A (en) | 2022-12-16 | 2022-12-16 | Production device and production method of polymer microporous foamed pipe |
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| CN (1) | CN115782268A (en) |
| WO (1) | WO2024124718A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2024124718A1 (en) * | 2022-12-16 | 2024-06-20 | 江苏科技大学 | Production device and production method for polymeric microcellular foamed pipe |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103042647B (en) * | 2012-11-08 | 2015-05-20 | 江苏微赛新材料科技有限公司 | Method for producing polypropylene micro-porous foamed thick board |
| CN105522675A (en) * | 2015-12-17 | 2016-04-27 | 华南理工大学 | Method for preparing non-cortical-layer foaming materials based on microcellular foaming injection molding |
| CN113085220B (en) * | 2021-03-03 | 2023-04-21 | 江苏科技大学 | Continuous fiber reinforced thermoplastic composite micro-foaming product and forming method and device thereof |
| CN115782268A (en) * | 2022-12-16 | 2023-03-14 | 江苏科技大学 | Production device and production method of polymer microporous foamed pipe |
-
2022
- 2022-12-16 CN CN202211645429.7A patent/CN115782268A/en active Pending
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2024124718A1 (en) * | 2022-12-16 | 2024-06-20 | 江苏科技大学 | Production device and production method for polymeric microcellular foamed pipe |
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| WO2024124718A1 (en) | 2024-06-20 |
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