CN109762188B - Method for continuously preparing PVDF (polyvinylidene fluoride) film with high beta crystal content by adopting melt extrusion-rolling - Google Patents
Method for continuously preparing PVDF (polyvinylidene fluoride) film with high beta crystal content by adopting melt extrusion-rolling Download PDFInfo
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Abstract
The invention belongs to the field of organic film preparation, and discloses a method for continuously preparing a PVDF film with high beta-crystal content by adopting melt extrusion-rolling, which comprises the following steps: putting the PVDF granules into a vacuum oven to remove moisture to obtain dried PVDF granules, putting the dried PVDF granules into a miniature double-screw extruder, extruding the PVDF granules through a rectangular die to obtain a flat PVDF sheet, drawing the PVDF sheet into an open mill for rolling, obtaining a PVDF film with high beta crystal content after rolling, introducing the PVDF film with high beta crystal content into a three-roller calender for cooling, and collecting the PVDF film into a coil. The method continuously produces the PVDF film with high beta-crystal content by adopting a melt extrusion-rolling mode, has the advantages of easily obtained raw materials, simple process, safety, environmental protection and higher economic benefit.
Description
Technical Field
The invention belongs to the field of preparation of high polymer materials and organic films, and particularly relates to a method for continuously preparing a PVDF film with high beta-crystal content by adopting melt extrusion-rolling.
Background
Polyvinylidene fluoride (PVDF) has excellent physical and chemical properties such as high mechanical strength, thermal stability, chemical stability, radiation resistance, oxidation resistance, good processability and the like, is popular with researchers, and is one of the best materials in the fields of anticorrosion process and harsh acid-base conditions in industry. PVDF has excellent pyroelectricity, piezoelectricity, and ferroelectricity in a polymer system, and is one of the most widely used materials at present. The PVDF piezoelectric film is a high molecular film, and has the characteristics of small volume, light weight, chemical corrosion resistance, good flexibility and processability, low acoustic impedance, wide frequency response, high dielectric strength, good stability and the like. The common crystal forms of PVDF are alpha phase, beta phase and gamma phase, the spontaneous polarization intensity of the beta phase is the maximum, high piezoelectricity and pyroelectric property are shown, and the relative content of the beta phase plays a decisive role in the piezoelectric property of the PVDF film. Therefore, increasing the relative content of beta phase becomes one of the key technical problems for preparing high-performance piezoelectric and pyroelectric films.
At present, a PVDF film mainly comprising alpha crystal is obtained through melt processing, and factors influencing the transformation from the alpha crystal form to the beta crystal form are many, including temperature, added solvent, nucleating agent, copolymer, external mechanical force or electric field and the like. The type of the crystal is regulated and controlled by controlling the crystallization temperature and the crystallization speed, and the beta crystal can be generated by controlling the cooling temperature and accelerating the cooling speed or adding ionic liquid in the thermally induced phase separation method.
Chinese patent CN101463140B discloses a high purity beta-phase PVDF film, a preparation method and its application in piezoelectric film preparation, the patent uses a thermally induced phase separation method using ionic liquid as diluent, although the addition of solvent can induce it to generate beta crystal, the introduction of foreign substance can affect its compatibility and be harmful to human body and environment, the polarization of PVDF film increases the processing difficulty, which is far from the actual industrial production, and is not beneficial to guiding industrial production.
Therefore, it is urgent to find a method which is simple in process, safe, environment-friendly and suitable for industry to prepare the PVDF film with high beta crystal content.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a method for continuously preparing a PVDF film with high beta-crystal content by adopting melt extrusion-rolling, which has the characteristics of good continuity, simple process, safety and environmental protection.
A method for continuously preparing a PVDF film with high beta-crystal content by adopting melt extrusion-rolling comprises the following steps:
A. putting the PVDF granules into a vacuum oven to remove water, and obtaining dry PVDF granules after 12-24 hours;
B. b, putting the dried PVDF granules obtained in the step A into a miniature double-screw extruder, and performing melt extrusion through a rectangular die to obtain a flat PVDF sheet;
C. b, drawing the flat PVDF sheet obtained in the step B into an open mill for rolling to obtain a PVDF film with high beta crystal content;
D. and D, cooling the PVDF film with high beta crystal content obtained in the step C by a three-roll calender and collecting the PVDF film into a roll.
Further, the temperature of the vacuum oven in the step A is set to be 60-80 ℃.
Further, in the step B, the temperature of a screw of the miniature double-screw extruder is 175-190 ℃, the temperature of a neck ring mold is 175-190 ℃, the size of the neck ring mold is 5mm in length, 2mm in width, and the speed of the screw is 10-30 r/min.
Further, in the step C, the receiving distance of the open mill is 10-30 cm, the temperature of two rollers of the open mill is 80-120 ℃, the rotating speed of the two rollers is 2.0-5.0 r/min, and the gap between the two rollers is 0.1-1 mm.
Has the advantages that:
1. the invention adopts a method of combining melt extrusion and rolling to prepare the PVDF film with high beta crystal content, uses common PVDF granules as raw materials, and applies mechanical force in the rolling process to convert the configuration of PVDF molecules from an alpha crystal form to a beta crystal form; no other reagent is added, the preparation process is ensured to be nontoxic and pollution-free, and meanwhile, the method has the characteristics of easily obtained materials, simple process, easy control, convenient operation, low cost, high production efficiency and the like, and has higher safety benefit and economic benefit.
2. The method can be used for continuously preparing the PVDF membrane with high beta crystal content in a large scale, can be used in industrial production, and solves the problem that the existing preparation method is difficult to realize the large scale preparation.
Drawings
FIG. 1 is a schematic diagram of a process for preparing a PVDF membrane with high beta crystal content according to the present invention;
FIG. 2 is an FTIR infrared absorption spectrum of a PVDF film prepared in example 10 of the present invention; note: 120-0.1-2; expressed as "open mill temperature-roller spacing-roller speed", and so on.
Detailed Description
The apparatus and materials used in the following embodiments are as follows:
PVDF pellets (Acoma, France PVDF 201; Hamman plastics, Suzhou);
A micro double screw extruder (model SJSZ-A; Wuhan Ruizi plastics machinery, Inc.);
open mill (model XH-401 CEW-120; Xihua detection instruments Co., Ltd.);
three-roll calender (zhangjiagang jiang machinery limited);
fourier Infrared Spectroscopy (FTIR) (model Nicolet iS 50; Thermo Fisher).
The receiving distance of the open mill in the following examples is the distance from the die of the miniature twin-screw extruder to the open mill.
Example 1
Putting the PVDF granules into a vacuum oven for drying, removing water, taking out after 24 hours, putting into a miniature double-screw extruder, setting the screw temperature at 175 ℃, the neck mold temperature at 190 ℃ and the screw rotating speed at 20r/min, and extruding through a rectangular neck mold with the length of 5mm multiplied by the width of 2mm to obtain a PVDF sheet; and (2) dragging the PVDF sheet into an open mill for rolling, wherein the horizontal distance between the open mill and a neck mold is 10cm, the temperature of two rollers of the open mill is 100 ℃, the gap between the two rollers is 0.1mm, and the rotating speed of the two rollers is 2.0r/min, finally obtaining the PVDF film, cooling and collecting the PVDF film into a coil through a three-roller calender, analyzing by FTIR (infrared spectroscopy) and calculating that the content of beta crystals in the PVDF film is 82%.
Example 2
Putting the PVDF granules into a vacuum oven for drying, removing water, taking out after 18 hours, putting into a miniature double-screw extruder, setting the screw temperature at 180 ℃, the neck ring mold temperature at 180 ℃, the screw rotating speed at 20r/min, and extruding through a rectangular neck ring mold with the length of 5mm multiplied by the width of 2mm to obtain a PVDF sheet; and (2) dragging the PVDF sheet into an open mill for rolling, wherein the horizontal distance between the open mill and a neck mold is 10cm, the temperature of two rollers of the open mill is 100 ℃, the gap between the two rollers is 0.1mm, and the rotating speed of the two rollers is 3.0r/min, finally obtaining the PVDF film, cooling and collecting the PVDF film into a coil through a three-roller calender, analyzing by FTIR (infrared spectroscopy) and calculating the content of beta crystals in the PVDF film to be 85%.
Example 3
Putting the PVDF granules into a vacuum oven for drying, removing water, taking out after 12 hours, putting into a micro double-screw extruder, setting the screw temperature to be 185 ℃, the neck ring mold temperature to be 185 ℃, the screw rotating speed to be 20r/min, and extruding through a rectangular neck ring mold with the length of 5mm multiplied by the width of 2mm to obtain a PVDF sheet; and (2) dragging the PVDF sheet into an open mill for rolling, wherein the horizontal distance between the open mill and a neck mold is 15cm, the temperature of two rollers of the open mill is 80 ℃, the gap between the two rollers is 0.3mm, and the rotating speed of the two rollers is 4.0r/min, finally obtaining the PVDF film, cooling and collecting the PVDF film into a coil through a three-roller calender, analyzing by FTIR (infrared spectroscopy) and calculating the content of beta crystals in the PVDF film to be 50%.
Example 4
Putting the PVDF granules into a vacuum oven for drying, removing water, taking out after 12 hours, putting into a micro double-screw extruder, setting the screw temperature to be 185 ℃, the neck ring mold temperature to be 185 ℃, the screw rotating speed to be 15r/min, and extruding through a rectangular neck ring mold with the length of 5mm multiplied by the width of 2mm to obtain a PVDF sheet; and (2) dragging the PVDF sheet into an open mill for rolling, wherein the horizontal distance between the open mill and a neck mold is 10cm, the temperature of two rollers of the open mill is 100 ℃, the gap between the two rollers is 0.5mm, and the rotating speed of the two rollers is 5.0r/min, finally obtaining the PVDF film, cooling and collecting the PVDF film into a coil through a three-roller calender, analyzing by FTIR (infrared spectroscopy) and calculating that the content of beta crystals in the PVDF film is 46%.
Example 5
Putting the PVDF granules into a vacuum oven for drying, removing water, taking out after 18 hours, putting into a miniature double-screw extruder, setting the screw temperature at 180 ℃, the neck ring mold temperature at 180 ℃, the screw rotating speed at 20r/min, and extruding through a rectangular neck ring mold with the length of 5mm multiplied by the width of 2mm to obtain a PVDF sheet; and (2) dragging the PVDF sheet into an open mill for rolling, wherein the horizontal distance between the open mill and a neck mold is 15cm, the temperature of two rollers of the open mill is 80 ℃, the gap between the two rollers is 0.3mm, and the rotating speed of the two rollers is 3.0r/min, finally obtaining the PVDF film, cooling and collecting the PVDF film into a coil through a three-roller calender, analyzing by FTIR (infrared spectroscopy) and calculating that the content of beta crystals in the PVDF film is 53%.
Example 6
Putting the PVDF granules into a vacuum oven for drying, removing water, taking out after 12 hours, putting into a micro double-screw extruder, setting the screw temperature to be 185 ℃, the neck ring mold temperature to be 185 ℃, the screw rotating speed to be 20r/min, and extruding through a rectangular neck ring mold with the length of 5mm multiplied by the width of 2mm to obtain a PVDF sheet; and (2) dragging the PVDF sheet into an open mill for rolling, wherein the horizontal distance between the open mill and a neck mold is 15cm, the temperature of two rollers of the open mill is 100 ℃, the interval between the two rollers is 0.1mm, and the rotating speed of the two rollers is 4.0r/min, finally obtaining the PVDF film, cooling and collecting the PVDF film into a coil through a three-roller calender, analyzing by FTIR (infrared spectroscopy) and calculating the content of beta crystals in the PVDF film to be 80%.
Example 7
Putting the PVDF granules into a vacuum oven for drying, removing water, taking out after 12 hours, putting into a miniature double-screw extruder, setting the screw temperature to be 185 ℃, the neck ring mold temperature to be 175 ℃, the screw rotating speed to be 20r/min, and extruding through a rectangular neck ring mold with the length of 5mm multiplied by the width of 2mm to obtain a PVDF sheet; and (2) dragging the PVDF sheet into an open mill for rolling, wherein the horizontal distance between the open mill and a neck mold is 20cm, the temperature of two rollers of the open mill is 120 ℃, the interval between the two rollers is 1.0mm, and the rotating speed of the two rollers is 2.0r/min, finally obtaining the PVDF film, cooling and collecting the PVDF film into a coil through a three-roller calender, analyzing by FTIR (infrared spectroscopy) and calculating the content of beta crystals in the PVDF film to be 30%.
Example 8
Putting the PVDF granules into a vacuum oven for drying, removing water, taking out after 12 hours, putting into a miniature double-screw extruder, setting the screw temperature to be 190 ℃, the neck ring mold temperature to be 180 ℃, the screw rotating speed to be 10r/min, and extruding through a rectangular neck ring mold with the length of 5mm multiplied by the width of 2mm to obtain a PVDF sheet; and (2) dragging the PVDF sheet into an open mill for rolling, wherein the horizontal distance between the open mill and a neck mold is 15cm, the temperature of two rollers of the open mill is 100 ℃, the interval between the two rollers is 0.5mm, and the rotating speed of the two rollers is 3.0r/min, finally obtaining the PVDF film, cooling the PVDF film through a three-roller calender and collecting the PVDF film into a coil, analyzing by FTIR (infrared spectroscopy) and calculating the content of beta crystals in the PVDF film to be 50%.
Example 9
Putting the PVDF granules into a vacuum oven for drying, removing water, taking out after 12 hours, putting into a micro double-screw extruder, setting the screw temperature to be 185 ℃, the neck ring mold temperature to be 185 ℃, the screw rotating speed to be 30r/min, and extruding through a rectangular neck ring mold with the length of 5mm multiplied by the width of 2mm to obtain a PVDF sheet; and (2) dragging the PVDF sheet into an open mill for rolling, wherein the horizontal distance between the open mill and a neck mold is 30cm, the temperature of two rollers of the open mill is 100 ℃, the interval between the two rollers is 0.5mm, and the rotating speed of the two rollers is 2.0r/min, finally obtaining the PVDF film, cooling the PVDF film through a three-roller calender and collecting the PVDF film into a coil, and analyzing by FTIR (infrared spectroscopy) and calculating the content of beta crystals in the PVDF film to be 43%.
Example 10
This embodiment is substantially the same as embodiment 6, and the same points are not described again, except that: the temperatures of the two rollers of the open mill are both 120 ℃, the rotating speeds of the two rollers are respectively set to be 2.0, 3.0, 4.0 and 5.0r/min, and PVDF films are respectively obtained. The absorbance was analyzed by FTIR, as shown in FIG. 2, and then the content of β -crystal in the PVDF film was calculated, as shown in Table 1.
TABLE 1 influence of the rotational speed of the two rolls of the open mill on the beta-Crystal content
| Grouping | Rotation speed of two rollers of open mill (r/min) | Content of F (. beta.) (%) |
| Experiment 1 | 2.0 | 88 |
| Experiment 2 | 3.0 | 60 |
| Experiment 3 | 4.0 | 50 |
| Experiment 4 | 5.0 | 53 |
As can be seen from the above table, when the temperature of the two rolls of the open mill is 120 ℃, the gap between the two rolls is 0.1mm, and the rotating speed of the two rolls is 2.0r/min, the content of beta-crystal in the prepared PVDF film is the highest and is 88%.
It should be understood that the detailed description and specific examples, while indicating embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
Claims (1)
1. A method for continuously preparing a PVDF film with high beta crystal content by adopting melt extrusion-rolling is characterized by comprising the following steps:
A. putting the PVDF granules into a vacuum oven to remove water, wherein the temperature of the oven is 80 ℃, and obtaining dried PVDF granules after 12 hours;
B. b, putting the dried PVDF granules obtained in the step A into a miniature double-screw extruder, and performing melt extrusion through a rectangular die to obtain a flat PVDF sheet; the screw temperature of the micro double-screw extruder is 185 ℃, the temperature of the neck ring mold is 185 ℃, the size of the neck ring mold is 5mm in length multiplied by 2mm in width, and the screw speed is 20 r/min;
C. b, drawing the flat PVDF sheet obtained in the step B into an open mill for rolling to obtain a PVDF film with high beta crystal content; the receiving distance of the open mill is 15cm, the temperature of two rollers of the open mill is 120 ℃, the rotating speed of the two rollers is 2.0r/min, and the gap between the two rollers is 0.1 mm;
D. and D, cooling the PVDF film with high beta crystal content obtained in the step C by a three-roll calender and collecting the PVDF film into a roll.
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