A polypropylene pipe with a significantly connected porous open-cell structure and a preparation method thereof

Abstract

The present invention provides a polypropylene pipe with a significantly connected porous open-cell structure and a preparation method thereof. The method is to melt and extrude a blend of syndiotactic polypropylene and isotactic polypropylene in a specific ratio into a pipe blank, and then prepare an open-cell porous polypropylene pipe through selective chemical etching of cyclohexane under specific conditions. The prepared pipe has a microporous structure feature of interconnected pores inside its pipe wall, and is extremely suitable for applications as biomedical materials.

Description

[0001] This application is a divisional application, the original application number is: 202210893082.1, the application date is July 27, 2022, and the name of the invention is: A chemically etched open-hole porous polypropylene pipe and its preparation method. Technical Field

[0002] The invention relates to the technical field of polypropylene pipes, and in particular to a chemically etched open-hole porous polypropylene pipe and a preparation method thereof. Background Art

[0003] Since the discovery of stereoselective olefin polymerization in 1954, people have entered a new era of polyolefin synthesis. Thanks to this, polypropylene (PP) has been industrially produced and applied on a large scale since 1957, and related research has been continuously carried out and deepened, which has made polypropylene products enduring. Generally speaking, polypropylene products are processed in a variety of ways, including injection molding, extrusion, etc., so that they can be processed into products of various forms and uses. Among them, various spare parts, pipes, plastic woven products, film products, etc. prepared from polypropylene have been extremely widely used. At present, polypropylene has become the second largest polymer material in the world. In addition, as a multi-purpose polymer material, polypropylene has attracted the attention of many researchers with its special crystallization, controlled polymerization of polyolefins, and the influence of processing conditions on polymorphic structures.

[0004] Although both syndiotactic polypropylene (sPP) and isotactic polypropylene (iPP) are polypropylene materials, their performance is different due to their different structures. Compared with iPP, the molecular chain flexibility of sPP is poor and it is relatively less likely to crystallize, which also leads to many differences in performance. This difference directly leads to the melting point, glass transition temperature, crystallization temperature and crystallinity of sPP being lower than iPP. Compared with iPP products, sPP products have higher transparency, impact resistance, toughness and elasticity. However, the density, hardness, tensile strength and rigidity of sPP are lower than those of iPP. Moreover, with the increase of the degree of polymerization and syndiotacticity of sPP, the melting point and crystallization temperature of sPP are improved.

[0005] In the literature, the study of sPP and iPP blends found that iPP / sPP blends are phase separated. The evaluation found that the Flory-Huggins interaction parameter of the sPP / iPP mixture is almost zero, indicating that the interaction in the mixture is very weak. From this, the researchers proposed a mixture state close to phase separation, or in other words, the iPP / sPP mixture is immiscible. For the iPP-based blend, sPP is dispersed in the iPP matrix in an island structure.

[0006] Polypropylene pipes have excellent comprehensive properties, such as low thermal conductivity, high temperature resistance, corrosion resistance, and can be hot melt welded, etc., and are widely used in fields such as cold and hot water transportation in buildings. However, currently in the biomedical field, there is a need for a porous pipe for biomedical use, and this porous pipe needs to have a bionic structure similar to blood vessels, that is, the pipe wall has an open pore structure for cell adsorption, and there are also connected micropores inside the pipe wall for cell metabolism. Obviously, the currently uniformly dense polypropylene pipes cannot meet such requirements. Summary of the Invention

[0007] According to the problems raised in the above-mentioned prior art, the present invention provides a chemically etched open pore porous polypropylene pipe and its preparation method. This method is to select a blend of syndiotactic polypropylene and isotactic polypropylene in a specific ratio and melt-spin extrude it into a pipe blank, and then prepare an open pore porous polypropylene pipe through selective chemical etching of cyclohexane under specific conditions. The prepared pipe has a microporous structure feature of interconnected pores inside its pipe wall, and is extremely suitable for application as a biomedical material.

[0008] To achieve the above object, the present invention is realized by a technical solution composed of the following technical measures.

[0009] On the one hand, the present invention provides a preparation method for a chemically etched open pore porous polypropylene pipe, which mainly includes the following steps:

[0010] (1) Select syndiotactic polypropylene (sPP) and isotactic polypropylene (iPP), mix and reserve them according to a mass ratio of (18 - 22):(78 - 82) or (38 - 42):(58 - 62) as a mixture.

[0011] (2) Extrude the mixture in step (1) through a rotary extruder, melt-spin extrude it into a pipe blank, and then cool and size it to obtain a polypropylene pipe; wherein, the rotary extruder includes a rotatable extrusion end component.

[0012] (3) Immerse the polypropylene pipe obtained in step (2) in cyclohexane, and prepare an open pore porous polypropylene pipe through selective chemical etching of cyclohexane.

[0013] The main principle of the present invention is based on the accidental discovery of the inventor. Based on the blend composed of sPP and iPP, cyclohexane can selectively dissolve sPP under certain conditions. However, in the iPP / sPP mixture material mainly composed of iPP, sPP is dispersed in the iPP matrix in an island structure. By chemically etching the sPP in it, only the sPP on the surface of the material can be dissolved, and the inside of the material still shows the characterization of iPP / sPP blend.

[0014] Through further research and exploration by the inventors, it was found that at a specific iPP / sPP blend ratio, through the extrusion end rotation function of a rotary extruder and then via selective chemical etching with cyclohexane, it is possible to etch to the inner wall of the pipe so that it exhibits porous characteristics consistent with the outer surface, and the holes formed by the etching also have a structurally interconnected feature due to the action of the extrusion end rotation. This property can meet various requirements of such pipes in practical applications. For example, in the field of biomedical materials, cells can adsorb on the open pore structure of the pipe wall, and there are interconnected micropores inside the pipe wall for cell metabolism.

[0015] In this article, the "syndiotactic polypropylene (sPP)" described in step (1) is a conventional syndiotactic polypropylene in the art, which can be obtained from commercial sources or prepared by oneself.

[0016] In this article, the "isotactic polypropylene (iPP)" described in step (1) is a conventional isotactic polypropylene in the art, which can be obtained from commercial sources or prepared by oneself.

[0017] In one embodiment, the raw material forms of the syndiotactic polypropylene (sPP) and isotactic polypropylene (iPP) described in step (1) can include, but are not limited to, powder and pellet forms, and can also be determined according to the applicable raw material forms of the rotary extruder used in step (2). When mixing and preparing for use, it can also include pretreatment processes or other technical means described in the prior art applicable to polypropylene pipe processes, such as washing and drying. However, it should be noted that the selection of the above embodiments should not affect the mass ratio of sPP and iPP.

[0018] In this article, the "rotary extruder" described in step (2) is an extruder with a rotatable extrusion end and suitable for pipe preparation. In one embodiment, the rotation of the extrusion end can be a rotatable die, a rotatable mandrel, or both a rotatable die and a rotatable mandrel. It should be noted that the die can also be referred to as the head of the extruder, that is, the rotation of the extrusion end is achieved through the rotation of the head.

[0019] In a preferred embodiment, the "rotary extruder" described in step (2) is the patented device "A Device for Preparing High-Performance Polymer Pipes" (CN101337425B) independently developed by the applicant of the present invention. Further, when melting and rotating to extrude the pipe blank, the rotation modes include any one of the die rotating alone, the mandrel rotating alone, the die and the mandrel rotating in the same direction, and the die and the mandrel rotating in the opposite direction.

[0020] In one embodiment, for the "melt spinning and extrusion of the tube blank" in step (2), the rotation rate at the extrusion end is 10 - 40 rpm. If the rotation rate is lower than this value, the holes inside the etched tube wall cannot be connected. If the rotation rate is higher than this value, the molten tube blank is likely to break during the melt spinning and extrusion process, and the product cannot be obtained.

[0021] In one embodiment, for the "melt spinning and extrusion of the tube blank" in step (2), except for the rotation rate at the extrusion end, the other specific process parameters can refer to the existing technologies in the art or the specific processing parameters of the selected syndiotactic polypropylene (sPP) and isotactic polypropylene (iPP), such as the melt temperature window data of commercially available isotactic polypropylene.

[0022] In one embodiment, the "cooling and sizing" in step (2) is a conventional process method in the field of pipe preparation. For example, the tube blank is cooled and sized through a vacuum sizing and cooling device.

[0023] In a preferred embodiment, the selective chemical etching with cyclohexane in step (3) is carried out at a temperature of 40 - 60 °C for 30 - 90 minutes.

[0024] On the other hand, the present invention provides an open-cell porous polypropylene pipe obtained by the above preparation method.

[0025] On the other hand, the present invention provides the application of the above open-cell porous polypropylene pipe in the biomedical field.

[0026] The present invention has the following beneficial effects:

[0027] 1. The preparation method of the present invention utilizes the selective chemical etching of cyclohexane on syndiotactic polypropylene, which is discovered accidentally, and cooperates with melt spinning and extrusion to successfully prepare a polypropylene pipe with open cells and a microporous structure feature of interconnected pores inside the tube wall.

[0028] 2. The present invention verifies through actual experiments the conditions necessary for the microporous structure feature of interconnected pores inside the product tube wall, and finds that this feature is present only at a specific iPP / sPP blend ratio.

[0029] 3. Through the comparative analysis of a large number of SEM images obtained by the present invention, it is found that the higher the rotation rate during the preparation process, the more obvious the interconnected holes inside the tube wall; and based on the evaluation of the obviousness of the interconnected holes inside the tube wall, the reverse rotation of the die and the mandrel > the co-rotation of the die and the mandrel > the single rotation of the mandrel ≈ the single rotation of the die.

[0030] 4. The preparation process of the present invention is relatively simple and easy to implement. The prepared product is extremely suitable for the requirements of porous tubes for biomedical use and has a bionic structure similar to blood vessels, that is, the tube wall has an open-hole structure for cell adsorption, and there are also connected micropores inside the tube wall for cell metabolism.

[0031] Explanatory drawings of the specification

[0032] Figure 1 This is the SEM image after cutting of the open-hole porous polypropylene tube prepared in Example 6 of the present invention with a rotation rate set at 40 rpm. It can be clearly observed from the figure that there are connected holes inside the tube wall.

[0033] Figure 2 This is the SEM image after cutting of the open-hole porous polypropylene tube prepared in Example 6 of the present invention with a rotation rate set at 30 rpm. It can be clearly observed from the figure that there are connected holes inside the tube wall.

[0034] Figure 3 This is the SEM image after cutting of the open-hole porous polypropylene tube prepared in Example 6 of the present invention with a rotation rate set at 20 rpm. It can be relatively clearly observed from the figure that there are connected holes inside the tube wall.

[0035] Figure 4 This is the SEM image after cutting of the open-hole porous polypropylene tube prepared in Example 6 of the present invention with a rotation rate set at 10 rpm. It can be relatively clearly observed from the figure that there are connected holes inside the tube wall.

[0036] Figure 5 This is the SEM image after cutting of the open-hole porous polypropylene tube prepared in Example 5 of the present invention with a rotation rate set at 40 rpm. It can be clearly observed from the figure that there are connected holes inside the tube wall.

[0037] Figure 6 This is the SEM image after cutting of the open-hole porous polypropylene tube prepared in Example 5 of the present invention with a rotation rate set at 30 rpm. It can be clearly observed from the figure that there are connected holes inside the tube wall.

[0038] Figure 7 This is the SEM image after cutting of the open-hole porous polypropylene tube prepared in Example 5 of the present invention with a rotation rate set at 20 rpm. It can be relatively clearly observed from the figure that there are connected holes inside the tube wall.

[0039] Figure 8 This is the SEM image after cutting of the open-hole porous polypropylene tube prepared in Example 5 of the present invention with a rotation rate set at 10 rpm. It can be relatively clearly observed from the figure that there are connected holes inside the tube wall.

[0040] Figure 9SEM image of the cut open-cell porous polypropylene pipe prepared in Example 4 of the present invention with a rotation rate of 40 rpm. It can be clearly observed from the figure that there are connected holes inside the pipe wall.

[0041] Figure 10 SEM image of the cut open-cell porous polypropylene pipe prepared in Example 4 of the present invention with a rotation rate of 30 rpm. It can be clearly observed from the figure that there are connected holes inside the pipe wall.

[0042] Figure 11 SEM image of the cut open-cell porous polypropylene pipe prepared in Example 4 of the present invention with a rotation rate of 20 rpm. It can be relatively clearly observed from the figure that there are connected holes inside the pipe wall.

[0043] Figure 12 SEM image of the cut open-cell porous polypropylene pipe prepared in Example 4 of the present invention with a rotation rate of 10 rpm. It can be relatively clearly observed from the figure that there are connected holes inside the pipe wall.

[0044] Figure 13 Another-angle SEM image of the cut open-cell porous polypropylene pipe prepared in Example 2 of the present invention. It can be extremely clearly observed from the figure that there are holes inside the pipe wall.

[0045] Figure 14 SEM image of the cut polypropylene pipe prepared in Comparative Example 1 of the present invention. It can be found from the figure that there are no holes inside the pipe wall. The SEM characterization of Comparative Example 2 and the polypropylene pipe prepared by the direct extrusion method without rotational extrusion is consistent with this. Detailed Description of the Invention

[0046] To further understand the present invention, the preferred embodiments of the present invention will be described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the invention. Those skilled in the art can draw on the content of this article and appropriately modify the process parameters to achieve. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art, and they are all regarded as included in the present invention. The method and application of the present invention have been described through preferred embodiments, and those skilled in the art can obviously make changes or appropriate alterations and combinations to the methods and applications described herein without departing from the content, spirit, and scope of the present invention to implement and apply the technology of the present invention. Although it is believed that those of ordinary skill in the art are fully aware of the following terms, the following definitions are still stated to help illustrate the subject matter disclosed by the present invention.

[0047] As used herein, the term "comprising" is synonymous with "primarily comprising", and is inclusive or open-ended, and does not exclude additional unrecited elements or method steps. "Containing" is a technical term used in claim language, meaning that the element exists, but other elements can also be added and still form an element or method within the scope of the claim.

[0048] The present invention provides a method for preparing a chemically etched open-cell porous polypropylene pipe, which mainly comprises the following steps:

[0049] (1) Select syndiotactic polypropylene (sPP) and isotactic polypropylene (iPP), mix them according to a mass ratio of (18 - 22):(78 - 82) or (38 - 42):(58 - 62) for standby, and use them as the mixed material;

[0050] (2) Extrude the mixed material in step (1) through a rotary extruder to melt and rotate and extrude a pipe blank, and then obtain a polypropylene pipe through cooling and sizing; wherein, the rotary extruder includes a rotatable extrusion end component;

[0051] (3) Immerse the polypropylene pipe obtained in step (2) in cyclohexane, and prepare an open-cell porous polypropylene pipe through selective chemical etching of cyclohexane.

[0052] In this article, the "syndiotactic polypropylene (sPP)" described in step (1) is a conventional syndiotactic polypropylene in the art, which can be of commercial origin or self-made.

[0053] In a preferred embodiment, the "syndiotactic polypropylene (sPP)" described in step (1) is preferably a syndiotactic polypropylene with a crystallinity of 6% - 16%, such as LW0120 (Hunan Liwei), LW0109 (Hunan Liwei).

[0054] In this article, the "isotactic polypropylene (iPP)" described in step (1) is a conventional isotactic polypropylene in the art, which can be of commercial origin or self-made.

[0055] In a preferred embodiment, the "isotactic polypropylene (iPP)" described in step (1) is preferably an isotactic polypropylene with a crystallinity of 36% - 46%, such as T30S (Dushanzi Petrochemical).

[0056] In one embodiment, the syndiotactic polypropylene (sPP) and isotactic polypropylene (iPP) in step (1), their raw material forms can include but are not limited to powder and pellet, and can also be determined according to the applicable raw material form of the rotary extruder used in step (2). When mixing and preparing for use, it can also include the pretreatment process or other technical means recorded in the prior art applicable to the polypropylene pipe process, such as washing, drying, etc. However, it should be noted that the selection of the above embodiments should be based on not affecting the mass ratio of sPP and iPP.

[0057] In one embodiment, the mass ratio of syndiotactic polypropylene (sPP) to isotactic polypropylene (iPP) is (18 - 22):(78 - 82) or (38 - 42):(58 - 62), such as 18.5:81.5, 19:81, 20:80, 21:79, 21.5:81.5, 38.5:61.5, 39:61, 40:60, 41:59, 41.5:58.5 or any range or point value therebetween.

[0058] In this article, the "rotary extruder" mentioned in step (2) is an extruder with a rotatable extrusion end and applicable to pipe preparation. In one embodiment, the rotation of the extrusion end can be a rotatable die, a rotatable mandrel, or both a rotatable die and a rotatable mandrel. It should be noted that the die can also be referred to as the head of the extruder, that is, the rotation of the extrusion end is achieved through the rotation of the head.

[0059] In a preferred embodiment, the "rotary extruder" mentioned in step (2) is the patented device "A Device for Preparing High-Performance Polymer Pipes" (CN101337425B) independently developed by the applicant of the present invention. Further, for the molten rotary extrusion of the tube blank, the rotation modes include any one of the die rotating alone, the mandrel rotating alone, the die and the mandrel rotating in the same direction, and the die and the mandrel rotating in the opposite direction.

[0060] In one embodiment, for the "melt spinning and extruding tube blank" in step (2), the rotation rate at the extrusion end is 10 - 40 rpm, such as 12 rpm, 15 rpm, 20 rpm, 25 rpm, 30 rpm, 35 rpm, 38 rpm, or any range or point value therebetween. In a preferred embodiment, substituting the rotation rate at the extrusion end into "a device for preparing high-performance polymer pipes", that is, the above rotation method is also applicable to this rotation rate. Further, the die and the mandrel rotate in the same direction, and the rotation rates of the die and the mandrel can be the same or different; the die and the mandrel rotate in the opposite direction, and the rotation rates of the die and the mandrel can be the same or different. Furthermore, the rotation rate of the extrusion end (die and / or mandrel) can be linearly variable or non-linearly variable, and preferably the range of the variable rotation rate is limited within 10 - 40 rpm.

[0061] It should be noted that when substituting the rotation rate at the extrusion end into "a device for preparing high-performance polymer pipes", the rotation rate range must be limited within 10 - 40 rpm. Below this rotation rate, the holes in the etched pipe wall cannot be connected, and above this rotation rate, it is easy for the molten tube blank to break during the rotation extrusion process, and the product cannot be prepared. In addition, it should be noted that through actual experimental tests, when the method of the die and the mandrel rotating in the opposite direction is selected, this rotation rate limitation still applies.

[0062] In one embodiment, for the "melt spinning and extruding tube blank" in step (2), in addition to the rotation rate at the extrusion end, the specific process parameters can refer to the existing technologies in the art or the specific processing parameters of the selected syndiotactic polypropylene (sPP) and isotactic polypropylene (iPP), such as the melt temperature window data of commercially available isotactic polypropylene.

[0063] In one embodiment, the "cooling and sizing" in step (2) is a conventional process method in the field of pipe preparation, such as cooling and sizing the tube blank through a vacuum sizing and cooling device.

[0064] In one embodiment, the selective chemical etching with cyclohexane in step (3) is carried out at a temperature of 40°C - 60°C for 30 min - 90 min; this condition is to meet the selective chemical etching with cyclohexane. If the temperature is lower than 40°C (such as room temperature 20 - 30°C), sPP will show a swelling phenomenon rather than dissolution in cyclohexane, and at the same time, too high a temperature is likely to cause safety risks during the use of cyclohexane; the etching time is to ensure that only sPP is etched. If the etching time is too long (exceeding 90 min), the iPP in the sample will also be swollen, resulting in changes in the dimensions of the pipe.

[0065] In one embodiment, the outer diameter of the polypropylene tube in step (2) is set to 1-8 mm, and the inner diameter is preferably set at 0.5-1.5 mm. It should be noted that after the selective chemical etching in step (3), for the prepared porous polypropylene tube with openings, its size may change negligibly, but it basically does not affect its use.

[0066] The present application will be further explained in detail below with reference to the embodiments. However, those skilled in the art should understand that these embodiments are provided for illustrative purposes only and are not intended to limit the present application.

[0067] Embodiments

[0068] The embodiments of the present application will be described in detail below in conjunction with the embodiments. However, those skilled in the art will understand that the following embodiments are only used to illustrate the present application and should not be regarded as limiting the scope of the present application. For those conditions not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. For those reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase. The present application should not be construed as being limited by the specific embodiments described.

[0069] 1. Preparation method

[0070] (1) Select syndiotactic polypropylene and isotactic polypropylene, mix them according to the specified mass ratio for standby as the mixture.

[0071] (2) The mixture in step (1) is melt-rotary extruded into a tube blank via a rotary extruder, and then cooled and sized to obtain a polypropylene tube with an outer diameter of 3 mm, an inner diameter of 1 mm or 0.5 mm (i.e., a wall thickness of 1 mm or 1.25 mm); wherein, the rotary extruder is the patented device "A device for preparing high-performance polymer tubes" (CN101337425B) independently developed by the applicant of the present invention.

[0072] (3) The polypropylene tube obtained in step (2) is immersed in cyclohexane, and through the selective chemical etching of cyclohexane, it is etched at a temperature of 40°C to 60°C for 30 min to 90 min to prepare a porous polypropylene tube with openings.

[0073] 2. Testing method

[0074] The samples are observed by a FEI Inspect F-SEM instrument at an acceleration voltage of 20 kV.

[0075] Examples 1-2, Comparative Examples 1-2

[0076] In Examples 1-2 and Comparative Examples 1-2, the mass ratio of syndiotactic polypropylene (sPP) and isotactic polypropylene (iPP) was studied as a variable, and the resulting open-cell porous polypropylene pipes were prepared as shown in Table 1 below:

[0077] Table 1: Mass ratio as a variable

[0078]

[0079] Surprisingly, it was found through actual experiments that the presence of connected holes inside the pipe wall only occurred in special proportion cases. For this reason, the inventors of this invention application conducted multiple repeated experiments on the sPP:iPP = 3:7 ratio (Comparative Example 1), and the results were consistent. The reason for this phenomenon is not yet clear. Therefore, based on experimental facts, the protection scope of the present invention has been further limited in a realistic manner.

[0080] Examples 3-6

[0081] In Examples 3-6, the die and mandrel rotation modes and rotation rates of a rotary extruder were studied as variables, and the resulting open-cell porous polypropylene pipes were prepared as shown in Table 2 below:

[0082] Table 1: Die and mandrel rotation as variables

[0083]

[0084] Note: The positive and negative values of the rotation rate are used to distinguish the co-rotation and counter-rotation of the die and the mandrel.

[0085] In Examples 3-6, tests were carried out through different rotation modes respectively, and open-cell porous polypropylene pipes were prepared at rotation rates of 10 rpm, 20 rpm, 30 rpm, and 40 rpm.

[0086] Based on SEM photo analysis, in the overall trend, the higher the rotation rate, the more obvious the connected holes inside the pipe wall; and based on evaluating the obviousness of the connected holes inside the pipe wall, die and mandrel counter-rotation > die and mandrel co-rotation > mandrel alone rotation ≈ die alone rotation.

[0087] Examples 7-10 and Comparative Examples 3-4

[0088] In Examples 7-10 and Comparative Examples 3-4, the variables of the selective chemical etching process conditions of cyclohexane were studied, and the resulting open-cell porous polypropylene pipes were prepared as shown in Table 3 below:

[0089] Table 1: Chemical etching conditions as variables

[0090]

[0091] In Examples 7 to 10, open-cell porous polypropylene pipes were prepared under different chemical etching conditions. After SEM observation of the samples, no significant differences were found.

[0092] In Comparative Example 3, the etching temperature was lower than 40 °C, simulating normal temperature. After SEM observation of the sample, no etching occurred on the inner and outer surfaces of the pipe wall, and sPP was not dissolved.

[0093] In Comparative Example 4, the etching time exceeded 90 min. After SEM observation of the sample, although connected holes also appeared inside the pipe wall, due to the swelling of iPP, the problem of serious deformation of the pipe size was serious and it could not be used as a product.

[0094] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A method for preparing a polypropylene pipe with a significantly connected porous open-cell structure, characterized in that It mainly includes the following steps: (1) Select syndiotactic polypropylene and isotactic polypropylene, mix them according to a mass ratio of 2:8 for standby, and use them as the mixed material; (2) Pass the mixed material in step (1) through a rotary extruder to melt and rotarily extrude a tube blank, and then obtain a polypropylene tube through cooling and sizing; wherein, the rotary extruder includes a rotatable extrusion end component; When melt-rotary extruding the tube blank, the rotation speed of the extrusion end is 30 - 40 rpm; When melt-rotary extruding the tube blank, the rotation mode is that the die and the mandrel rotate in opposite directions; (3) Immerse the polypropylene tube obtained in step (2) in cyclohexane, and prepare an open-cell porous polypropylene tube through selective chemical etching with cyclohexane; The selective chemical etching with cyclohexane is carried out at a temperature of 40 °C for 60 minutes.

2. The open-cell porous polypropylene tube obtained by the preparation method described in claim 1.

3. The application of the open-cell porous polypropylene tube described in claim 2 in the preparation of materials in the biomedical field.

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