CN115105633A

CN115105633A - Chemical etching open-pore porous polypropylene pipe and preparation method thereof

Info

Publication number: CN115105633A
Application number: CN202210893082.1A
Authority: CN
Inventors: 李怡俊; 韩莹; 宋力; 付锋; 袁苑; 蒋佳; 李柯; 朱江维
Original assignee: Hunan Liwei New Material Co ltd; Sichuan University
Current assignee: Hunan Liwei New Material Co ltd; Sichuan University
Priority date: 2022-07-27
Filing date: 2022-07-27
Publication date: 2022-09-27
Anticipated expiration: 2042-07-27
Also published as: CN116899023A; CN116899022A; CN115105633B

Abstract

The invention provides a chemical etching open-cell porous polypropylene pipe and a preparation method thereof, the method comprises the steps of selecting the blending, melting, rotating and extruding syndiotactic polypropylene and isotactic polypropylene in a specific proportion into a pipe blank, and then preparing the open-cell porous polypropylene pipe by selective chemical etching of cyclohexane under specific conditions, wherein the prepared pipe has the characteristic of interconnected micropore structures in the pipe wall, and is extremely suitable for application as biomedical materials.

Description

Chemical etching open-pore porous polypropylene pipe and preparation method thereof

Technical Field

The invention relates to the technical field of polypropylene pipes, in particular to a chemical etching open-cell porous polypropylene pipe and a preparation method thereof.

Background

Since the discovery of stereoselective olefin polymerizations in 1954, new polyolefin synthesis era has been entered. To benefit from this, polypropylene (PP) has been produced and used industrially on a large scale since 1957, and research thereon has been continuously and intensively carried out, which makes polypropylene articles durable. In general, polypropylene articles are processed in a variety of ways, including injection molding, extrusion, and the like, to enable them to be processed into articles of various shapes and applications. Among them, various parts, pipes, plastic woven products, film products, etc. made of polypropylene are widely used, and polypropylene has become the second largest polymer material in global production. Also, polypropylene is a versatile polymer material, its particular crystallization, controlled polymerization of polyolefins, and the effect of processing conditions on polymorphic structures, among others, have attracted the attention of numerous researchers.

Although syndiotactic polypropylene (sPP) and isotactic polypropylene (iPP) are both polypropylene materials, the difference in performance between them is caused by the difference in structure between them. Compared with iPP, sPP has a less flexible molecular chain and is relatively less prone to crystallization, thus bringing about many differences in properties. This difference directly results in sPP having a lower melting point, glass transition temperature, crystallization temperature, and crystallinity than iPP. sPP articles have higher clarity, impact strength, toughness and elasticity than iPP articles. However, sPP has lower density, hardness, tensile strength and stiffness than iPP. Further, as the degree of polymerization and the degree of syndiotacticity of sPP increase, the melting point, crystallization temperature, etc. of sPP increase.

In literature reports, iPP/sPP blends were found to phase separate by studies on sPP blends with iPP. The evaluation found that the Flory-Huggins interaction parameter of the sPP/iPP mixture was almost zero, indicating that the interaction in the mixture was weak. Thus, researchers have proposed a near phase separated mixture state, or in other words, that an iPP/sPP mixture is immiscible, with sPP dispersed in the iPP matrix in an islands-in-the-sea configuration for the iPP-based blend.

The polypropylene pipe has excellent comprehensive performance, such as low thermal conductivity, high temperature resistance, corrosion resistance, hot-melt welding and the like, and is widely applied to the fields of cold and hot water conveying in buildings and the like. However, in the biomedical field, a requirement for a porous pipe for biomedicine is provided, and the porous pipe needs to have a bionic structure similar to a blood vessel, namely, the pipe wall of the pipe is provided with an open pore structure for cell adsorption, and communicated micropores exist inside the pipe wall for cell metabolism. Polypropylene pipes with a uniform and dense texture do not clearly meet such requirements.

Disclosure of Invention

According to the problems of the prior art, the invention provides a chemical etching open-pore porous polypropylene pipe and a preparation method thereof, the method comprises the steps of selecting blending, melting, rotating and extruding syndiotactic polypropylene and isotactic polypropylene in a specific proportion into a pipe blank, and preparing the open-pore porous polypropylene pipe through selective chemical etching of cyclohexane under specific conditions, wherein the prepared pipe has the characteristic of interconnected microporous structures in the pipe wall, and is extremely suitable for being used as a biomedical material.

In order to achieve the purpose, the invention adopts the technical scheme formed by the following technical measures.

In one aspect, the invention provides a preparation method of a chemical etching open-cell porous polypropylene pipe, which mainly comprises the following steps:

(1) selecting syndiotactic polypropylene (sPP) and isotactic polypropylene (iPP) according to a mass ratio of (18-22): (78-82) or (38-42): (58-62) mixing for later use to obtain a mixture;

(2) melting the mixture obtained in the step (1) by a rotary extruder, carrying out rotary extrusion on the tube blank, and cooling and sizing to obtain a polypropylene tube; wherein the rotary extruder comprises rotatable extrusion end pieces;

(3) and (3) immersing the polypropylene pipe obtained in the step (2) in cyclohexane, and preparing the open-pore porous polypropylene pipe through selective chemical etching of the cyclohexane.

The main principle of the present invention is based on the discovery by the inventors that, by chance, cyclohexane can selectively dissolve sPP under certain conditions, based on a blend of sPP and iPP. However, in the iPP/sPP mixture material mainly based on iPP, sPP is dispersed in an iPP matrix in a sea-island structure, and the sPP in the iPP mixture material is etched by a chemical etching method, so that only sPP on the surface of the material can be dissolved, and the iPP/sPP blending characteristics are still presented in the material.

Through further research and exploration of the inventor, the inventor finds that under a specific iPP/sPP blending ratio, the pipe wall can be etched to present a porous characteristic consistent with the outer surface through the extrusion end rotating function of the rotating extruder and the selective chemical etching of cyclohexane, and the holes formed by etching also have the mutually communicated structural characteristic under the rotating action of the extrusion end. The characteristic can meet various requirements of the pipe in practical application, for example, in the field of biomedical materials, cells can be adsorbed on the open pore structure of the pipe wall, and communicated micropores are formed in the pipe wall for cell metabolism.

In this context, the "syndiotactic polypropylene (sPP)" in step (1) is conventional in the art and may be obtained from commercial sources or from the home-made sources.

Herein, the isotactic polypropylene (iPP) described in step (1) is a conventional isotactic polypropylene in the art, and may be commercially available or may be obtained by self-production.

In one embodiment, the raw material forms of the syndiotactic polypropylene (sPP) and the isotactic polypropylene (iPP) in step (1) may include, but are not limited to, powder, pellets, and may be determined according to the suitable raw material forms of the rotary extruder used in step (2). When mixed for use, the polypropylene pipe may also comprise a pretreatment process described in the prior art, which is suitable for polypropylene pipe processing, or other technical means, such as washing, drying, etc. However, it should be noted that the above embodiment should be selected so as not to affect the mass ratio of sPP to iPP.

In this context, the "rotary extruder" in step (2) is an extruder whose extrusion end is rotatable and is suitable for the production of pipes, and in one embodiment, the extrusion end rotation may be a rotatable die, a rotatable core rod, a rotatable die and a rotatable core rod. It should be noted that the die can also be referred to as a head of the extruder, i.e. the rotation of the extrusion end is achieved by the rotation of the head.

In a preferred embodiment, said "rotary extruder" in step (2) is a proprietary plant "a device for making high performance polymer pipes" (CN101337425B) developed by the applicant of the present invention. Furthermore, the molten rotary extrusion pipe blank rotates in any one of a mode that the neck ring mold rotates independently, a mode that the core rod rotates independently, a mode that the neck ring mold rotates in the same direction with the core rod, and a mode that the neck ring mold rotates in the opposite direction with the core rod.

In one embodiment, in the step (2), "molten-state rotationally extruded tube blank", the rotation speed of the extrusion end is 10 to 40rpm, which is lower than the rotation speed, the inner holes in the etched tube wall cannot be communicated, and higher than the rotation speed, the molten-state tube blank is easily broken in the process of rotationally extruding, and the product cannot be prepared.

In one embodiment, the "melt spin extruded pipe embryo" in step (2), except for the extrusion end rotation rate, may be referred to the state of the art, and may also be referred to the specific processing parameters of the selected syndiotactic polypropylene (sPP) and isotactic polypropylene (iPP), such as the melting temperature window data of commercially available isotactic polypropylene.

In one embodiment, the "cooling sizing" in step (2) is a process conventional in the art of pipe making, such as cooling sizing the pipe stock by a vacuum sizing cooler.

In a preferred embodiment, the selective chemical etching by cyclohexane in the step (3) is etching at a temperature of 40 to 60 ℃ for 30 to 90 min.

In another aspect, the invention provides an open-cell porous polypropylene pipe obtained by the preparation method.

In another aspect, the invention provides the use of the above open-cell porous polypropylene pipe in the biomedical field.

The invention has the following beneficial effects:

1. the preparation method of the invention successfully prepares the polypropylene pipe with porous openings and interconnected microporous structure characteristics in the pipe wall by utilizing the selective chemical etching of the syndiotactic polypropylene based on the cyclohexane discovered by accident and the mutual coordination of the cyclohexane and the melt rotary extrusion.

2. The invention verifies the necessary conditions for the interconnected microporous structure characteristics in the pipe wall of the product through practical experiments, and finds that the characteristics are only achieved under the specific iPP/sPP blending ratio.

3. According to the invention, through comparison and analysis of SEM images obtained by a large number of experiments, the higher the rotation rate in the preparation process is, the more obvious the holes communicated with the interior of the tube wall are; and based on the evaluation of the obvious degree of the holes communicated with the interior of the tube wall, the reverse rotation of the neck ring and the core rod is greater than the same-direction rotation of the neck ring and the core rod is greater than the independent rotation of the core rod which is approximately equal to the independent rotation of the neck ring.

4. The preparation process is simple and easy to realize, and the prepared product is extremely suitable for the requirements of porous pipes for biomedicine and has a bionic structure similar to a blood vessel, namely, the pipe wall of the pipe not only has an open pore structure for cell adsorption, but also has communicated micropores for cell metabolism.

Drawings

FIG. 1 is a SEM image after cutting of an open-cell porous polypropylene tube prepared when the rotation speed of example 6 of the present invention was set at 40 rpm. It can be clearly seen from the figure that the inner part of the pipe wall is provided with communicated holes.

FIG. 2 is a SEM image after cutting of an open-cell porous polypropylene tube prepared in example 6 of the present invention with a rotation speed of 30rpm set. It can be clearly seen from the figure that the inner part of the pipe wall is provided with communicated holes.

FIG. 3 is a SEM image after cutting of an open-cell porous polypropylene tube prepared when the rotation speed of example 6 of the present invention is set at 20 rpm. The communicated holes in the tube wall can be clearly observed from the figure.

FIG. 4 is a SEM image after cutting of an open-cell porous polypropylene tube prepared in example 6 of the present invention with a rotation speed of 10rpm set. It can be seen clearly from the figure that the inside of the tube wall has communicating holes.

FIG. 5 is a SEM image after cutting of an open-cell porous polypropylene tube prepared when the rotation speed of example 5 of the present invention is set at 40 rpm. It can be clearly seen from the figure that the inner part of the pipe wall is provided with communicated holes.

FIG. 6 is a SEM image after cutting of an open-cell porous polypropylene tube prepared in example 5 of the present invention with a rotation speed of 30rpm set. It can be clearly seen from the figure that the inner part of the pipe wall is provided with communicated holes.

FIG. 7 is a SEM image after cutting of an open-cell porous polypropylene tube prepared when the rotation speed of example 5 of the present invention is set at 20 rpm. It can be seen clearly from the figure that the inside of the tube wall has communicating holes.

FIG. 8 is a SEM image after cutting of an open-cell porous polypropylene tube prepared when the rotation speed is set to 10rpm in example 5 of the present invention. It can be seen clearly from the figure that the inside of the tube wall has communicating holes.

FIG. 9 is a SEM image after cutting of an open-cell porous polypropylene tube prepared when the rotation speed is set to 40rpm in example 4 of the invention. It can be clearly seen from the figure that the inner part of the pipe wall is provided with communicated holes.

FIG. 10 is a SEM image after cutting of an open-cell porous polypropylene tube prepared in example 4 of the present invention with a rotation speed of 30rpm set. It can be clearly seen from the figure that the inner part of the pipe wall is provided with communicated holes.

FIG. 11 is a SEM image after cutting of an open-cell porous polypropylene tube prepared when the rotation speed is set to 20rpm in example 4 of the invention. It can be seen clearly from the figure that the inside of the tube wall has communicating holes.

FIG. 12 is a SEM image after cutting of an open-cell porous polypropylene tube prepared when the rotation speed is set to 10rpm in example 4 of the present invention. It can be seen clearly from the figure that the inside of the tube wall has communicating holes.

FIG. 13 is an SEM image of an open-cell porous polypropylene tube prepared in example 2 of the present invention after another angle cutting. The holes in the tube wall are clearly visible in the figure.

FIG. 14 is a SEM image of polypropylene tubing made according to comparative example 1 of the present invention after cutting. It can be seen from the figure that the tube wall has no holes inside. Comparative example 2, and SEM images of polypropylene tubing made without rotary extrusion using a direct extrusion protocol are consistent.

Detailed Description

For a further understanding of the present invention, the following description of the preferred embodiments of the present invention is given in conjunction with the examples, but it is to be understood that these descriptions are only intended to further illustrate the features and advantages of the present invention, and not to limit the claims of the present invention. Those skilled in the art can modify the process parameters appropriately to achieve the desired results with reference to the disclosure herein. It is expressly intended that all such similar substitutes and modifications which would be obvious to those skilled in the art are deemed to be included within the invention. While the methods and applications of this invention have been described in terms of preferred embodiments, it will be apparent to those of ordinary skill in the art that variations and modifications in the methods and applications described herein, as well as other suitable variations and combinations, may be made to implement and use the techniques of this invention without departing from the spirit and scope of the invention. While the following terms are believed to be well understood by those of ordinary skill in the art, the following definitions are set forth to aid in the description of the presently disclosed subject matter.

As used herein, the term "comprising" is synonymous with "consisting essentially of and is inclusive or open-ended and does not exclude additional unrecited elements or method steps. "comprising" is a term of art used in the claim language and means that the recited element is present but other elements may be added and still form an element or method within the scope of the claim.

The invention provides a preparation method of a chemical etching open-cell porous polypropylene pipe, which mainly comprises the following steps:

(2) melting the mixture obtained in the step (1) by a rotary extruder, carrying out rotary extrusion on the tube blank, and cooling and sizing to obtain a polypropylene tube; wherein the rotary extruder comprises a rotatable extrusion end piece;

In a preferred embodiment, the "syndiotactic polypropylene (sPP)" in step (1) is preferably a syndiotactic polypropylene having a crystallinity of from 6% to 16%, such as LW0120 (Hunan Li), LW0109 (Hunan Li).

In a preferred embodiment, the "isotactic polypropylene (iPP)" in step (1), preferably an isotactic polypropylene having a crystallinity of 36% to 46%, such as T30S (crested).

In one embodiment, the raw material forms of the syndiotactic polypropylene (sPP) and isotactic polypropylene (iPP) in step (1) may include, but are not limited to, powder, pellets, and may be determined according to the suitable raw material forms of the rotary extruder used in step (2). When mixed for use, the mixture may also include the pretreatment processes described in the prior art which are suitable for the polypropylene pipe process, or other technical means, such as washing, drying, etc. However, it is noted that the above embodiment should be selected so as not to affect the mass ratio of sPP to iPP.

In one embodiment, the mass ratio of syndiotactic polypropylene (sPP) to isotactic polypropylene (iPP) is (18-22): (78-82) or (38-42): (58-62), for example 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 therebetween.

In one embodiment, the "melt-spun extruded pipe blank" in step (2) has an extrusion end rotation rate of 10 to 40rpm, such as 12rpm, 15rpm, 20rpm, 25rpm, 30rpm, 35rpm, 38rpm, or any range or point value therebetween. In a preferred embodiment, the extrusion tip rotation rate is substituted into "an apparatus for producing high performance polymer tubing", i.e., the above rotation modes are also applicable to this rotation rate. Further, the neck ring mold and the core rod rotate in the same direction, and the rotation rates of the neck ring mold and the core rod can be the same or different; the neck ring and the core rod rotate in opposite directions, and the rotation rates of the neck ring and the core rod can be the same or different. Furthermore, the rotation speed of the extrusion end (the die and/or the core rod) can be changed linearly or nonlinearly, and the change of the rotation speed is preferably limited within a range of 10-40 rpm.

It should be noted that when the rotation speed of the extrusion end is substituted into the "apparatus for preparing a high-performance polymer tube", the rotation speed range must be limited within 10-40 rpm, which is lower than the rotation speed, the inner holes of the tube wall after etching cannot be connected, and which is higher than the rotation speed, the tube blank in a molten state is easily broken in the process of rotary extrusion, and the product cannot be prepared. It should be noted that, through practical experimental tests, the limitation of the rotation rate still applies when the mode of contra-rotating the die and the core rod is selected.

In one embodiment, the selective chemical etching by cyclohexane in the step (3) is etching for 30min to 90min at the temperature of 40 ℃ to 60 ℃; the condition is to meet the selective chemical etching of cyclohexane, if the temperature is lower than 40 ℃ (for example, the normal temperature is 20-30 ℃), sPP is shown as a swelling phenomenon in cyclohexane and is not dissolved, and meanwhile, the cyclohexane is easy to cause safety risk in the use process due to too high temperature; the etching time is to ensure that the etched part is only sPP, and if the etching time is too long (more than 90min), iPP in the sample is also swelled, so that the size of the pipe changes.

In one embodiment, the polypropylene tube in the step (2) has an outer diameter of 1 to 8mm, and preferably an inner diameter of 0.5 to 1.5 mm. It should be noted that after the selective chemical etching in step (3), the size of the prepared open-cell porous polypropylene pipe may change negligibly, but does not substantially affect the use thereof.

The present application will be explained in further detail below with reference to examples. However, it will be understood by those skilled in the art that these examples are provided for illustrative purposes only and are not intended to limit the present application.

Examples

Embodiments of the present application will be described in detail below with reference to examples, but those skilled in the art will appreciate that the following examples are only illustrative of the present application and should not be construed as limiting the scope of the present application. The examples, in which specific conditions are not specified, were carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are conventional products which are commercially available, and are not indicated by manufacturers. This application is not to be construed as limited to the particular embodiments set forth herein.

1. Preparation method

(1) Selecting syndiotactic polypropylene and isotactic polypropylene, and mixing for later use according to a specified mass ratio to serve as a mixture;

(2) melting and rotationally extruding the mixture obtained in the step (1) into a pipe blank through a rotary extruder, and cooling and sizing to obtain a polypropylene pipe with the outer diameter of 3mm and the inner diameter of 1mm or 0.5mm (namely the pipe wall thickness is 1mm or 1.25 mm); wherein, the rotary extruder is a patent device developed by the applicant of the invention, namely 'a device for preparing high-performance polymer pipes' (CN 101337425B);

(3) and (3) immersing the polypropylene pipe obtained in the step (2) in cyclohexane, and etching for 30-90 min at the temperature of 40-60 ℃ through selective chemical etching of cyclohexane to prepare the open-pore porous polypropylene pipe.

2. Test method

The samples were observed by an FEI aspect F-SEM instrument at an accelerating voltage of 20 kV.

Examples 1 to 2 and comparative examples 1 to 2

In examples 1 to 2 and comparative examples 1 to 2, the mass ratio of syndiotactic polypropylene (sPP) to isotactic polypropylene (iPP) was investigated as a variable, and the resulting open-cell porous polypropylene pipe was prepared as shown in Table 1 below:

table 1: mass ratio being a variable

It has been surprisingly found through practical experiments that whether the pipe wall has connected pores inside only occurs in a specific proportion, and the inventor of the present application aims at the sPP: iPP ═ 3: the 7-ratio (comparative example 1) is subjected to repeated experimental verification, the results are consistent in characterization, and the reason of the phenomenon is not clarified for a while. The invention is thus based on experimental facts, the fact being that the scope of protection is further defined.

Examples 3 to 6

In examples 3 to 6, the rotation mode and rotation rate of the neck ring and the core rod of the rotary extruder were studied as variables to prepare the obtained open-cell porous polypropylene pipe, as shown in table 2 below:

table 1: with die and mandrel rotating by variable amounts

Note: the positive and negative values of the rotation rate are the same rotation and opposite rotation of the mold and the core rod.

In examples 3 to 6, the open-cell porous polypropylene pipes were prepared by different rotation methods and rotation rates of 10rpm, 20rpm, 30rpm and 40 rpm.

Based on SEM photo analysis, in the general trend, the higher the rotation rate is, the more obvious the communicated holes in the tube wall are; and based on the evaluation of the obvious degree of the holes communicated with the interior of the tube wall, the reverse rotation of the neck ring and the core rod is greater than the same-direction rotation of the neck ring and the core rod is greater than the independent rotation of the core rod which is approximately equal to the independent rotation of the neck ring.

Examples 7 to 10 and comparative examples 3 to 4

In examples 7 to 10 and comparative examples 3 to 4, the variables of the selective chemical etching process conditions of cyclohexane were studied to prepare the obtained open-cell porous polypropylene pipes, as shown in table 3 below:

table 1: the chemical etching conditions being variable

In examples 7 to 10, the open-cell porous polypropylene tube was prepared under different chemical etching conditions, and the samples were observed by SEM imaging without significant difference.

In comparative example 3, the etching temperature was lower than 40 ℃, and in order to simulate normal temperature, the sample was observed by SEM, and no etching occurred on the surface and inside of the tube wall, and sPP was not dissolved.

In comparative example 4, the etching time exceeded 90min, and the sample was observed through SEM photography, and although there were also connected holes in the tube wall, the problem of dimensional deformation of the tube was severe due to swelling of iPP, and it could not be used as a product.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, simplifications, and equivalents which do not depart from the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims

1. A preparation method of a chemical etching open-pore porous polypropylene pipe is characterized by mainly comprising the following steps:

(1) selecting syndiotactic polypropylene and isotactic polypropylene according to the mass ratio of (18-22): (78-82) or (38-42): (58-62) mixing for later use to obtain a mixture;

2. The method of claim 1, wherein: and (3) performing melt rotation to extrude the pipe blank in the step (2), wherein the rotation mode comprises any one of independent rotation of the neck ring mold, independent rotation of the core rod, equidirectional rotation of the neck ring mold and the core rod and opposite rotation of the neck ring mold and the core rod.

3. The production method according to claim 1 or 2, characterized in that: and (3) performing melt-spinning extrusion on the pipe blank in the step (2), wherein the rotation rate of an extrusion end is 10-40 rpm.

4. The method of claim 1, wherein: in the step (3), the selective chemical etching by cyclohexane is carried out for 30-90 min at the temperature of 40-60 ℃.

5. The open-cell porous polypropylene pipe prepared by the preparation method of claim 1.

6. Use of the open-celled, porous polypropylene tubing of claim 5 in biomedical applications.