CN113461991A

CN113461991A - Polychlorotrifluoroethylene film and preparation method and application thereof

Info

Publication number: CN113461991A
Application number: CN202110928504.XA
Authority: CN
Inventors: 沈佳斌; 何露; 郭少云
Original assignee: Sichuan University
Current assignee: Sichuan University
Priority date: 2021-08-13
Filing date: 2021-08-13
Publication date: 2021-10-01
Anticipated expiration: 2041-08-13
Also published as: CN113461991B

Abstract

The invention discloses a polychlorotrifluoroethylene film, a preparation method and application thereof, and belongs to the technical field of polychlorotrifluoroethylene film preparation. The preparation method comprises the following steps: the PCTFE suspension obtained by dispersing PCTFE in the mixed dispersion medium is supported on the surface of the substrate material, dried, sintered, and then the substrate material is removed. This method is different from the method of producing a polymer film using a molding machine such as an extrusion apparatus or a casting apparatus. The method has no high requirement on the fluidity of the polymer melt, can be molded without the action of extra high-pressure high shear, and can effectively avoid the degradation of the PCTFE in the hot processing process, thereby better maintaining the advantageous properties of the PCTFE and developing a new method for processing and molding the PCTFE film. The PCTFE film obtained by the method has high transparency and water vapor barrier property, low dielectric loss and good mechanical strength and toughness. Has wide application prospect.

Description

Polychlorotrifluoroethylene film and preparation method and application thereof

Technical Field

The invention relates to the technical field of preparation of polychlorotrifluoroethylene films, and particularly relates to a polychlorotrifluoroethylene film and a preparation method and application thereof.

Background

Polychlorotrifluoroethylene (PCTFE) was one of the first fluoroplastics developed and commercialized. The unique molecular structure of PCTFE gives it many excellent properties such as good chemical stability, weatherability, transparency, non-flammability, biocompatibility, low temperature toughness, barrier properties, and dielectric properties. Nowadays, the PCTFE has played an indispensable role in some application links of high-end technology industries such as aerospace, national defense and military industry, electronic and electrical industry, pharmaceutical and chemical industry and the like. For example, in the aspects of aerospace, the coating can be used as an electronic instrument packaging film and a light-emitting device protective layer, a wear-resistant and corrosion-resistant mechanical part, a carrier rocket liquid fuel pipeline, a sealing part and the like; a corrosive gas isolating membrane for separating uranium 235 in the aspects of national defense and military industry, a soft valve plate of a nuclear energy boiler, a liquid oxygen and liquid fuel sealing element, a switch and the like; the electronic and electrical aspects are used for corrosion-resistant electronic and electrical appliance insulation components and precise electronic instrument packaging films; the chemical engineering is mainly used for inflating valves, spherical container components, various chemical corrosion resistant pumps, valves, pipelines, plates, coatings, gaskets, and the like; can be used as packaging film of medical equipment, packaging film of medicine, and ultraviolet sterilization medical equipment.

The melting temperature of PCTFE is 211-216 ℃, but the heat transfer efficiency of PCTFE is very slow, so that the melt viscosity at 230 ℃ is still as high as (5-50) xL 0⁶Poise, and therefore sufficient process flowability can be imparted to the PCTFE only by maintaining higher temperatures and pressures. However, under high heat and high shear, PCTFE is degraded (PCTFE processing temperature window is narrow) and toxic and harmful fluorine-containing gas is released, which can cause great harm to human body and equipment. Therefore, the forming process of the PCTFE film has extremely high requirements on equipment and formula, and related technologies are monopolized by foreign enterprises such as hounwell, japan major and the like, so that no commercial PCTFE film product exists in China at present.

The domestic existing preparation method of the PCTFE film is usually matched with a specially designed forming machine, and a film product with excellent performance cannot be obtained by simply using conventional polymer forming processing equipment.

In view of this, the invention is particularly proposed.

Disclosure of Invention

One of the purposes of the invention is to provide a preparation method of a polychlorotrifluoroethylene film, which has no high requirement on the fluidity of a polymer melt, can be formed without the action of extra high-pressure high shear, can effectively avoid the degradation of PCTFE in the hot processing process, thereby better maintaining the advantageous properties of PCTFE and opening up a new method for processing and forming the PCTFE film.

The second purpose of the invention is to provide a polychlorotrifluoroethylene film obtained by the above preparation method, which has high transparency and water vapor barrier property, low dielectric loss and good mechanical strength and toughness.

The invention also aims to provide application of the polychlorotrifluoroethylene film.

The invention can be realized as follows:

in a first aspect, the present invention provides a method for preparing a polychlorotrifluoroethylene film, comprising the steps of: the polychlorotrifluoroethylene suspension obtained by dispersing polychlorotrifluoroethylene in a mixed dispersion medium is supported on the surface of a substrate material, dried, sintered, and then the substrate material is removed.

In an alternative embodiment, the mixed dispersion medium comprises primarily water.

In an alternative embodiment, the water is deionized water.

In an alternative embodiment, the mixed dispersion medium further includes a surfactant or a water-soluble alcohol substance.

In an alternative embodiment, the surfactant comprises at least one of a non-fluorinated surfactant and a fluorinated surfactant.

In an alternative embodiment, the non-fluorosurfactant comprises at least one of sodium dodecylbenzenesulfonate, cetyltrimethylammonium chloride, cetyltrimethylammonium bromide and sodium hexadecylsulfate, and the fluorosurfactant comprises at least one of sodium perfluorobutylsulfonate, ammonium perfluorononanoate, sodium perfluorodecyloxybenzenesulfonate and ammonium pentadecafluorodecanoate.

In an alternative embodiment, the surfactant is used in an amount of 1 to 10 wt% of the polychlorotrifluoroethylene.

In an alternative embodiment, the water-soluble alcohol comprises at least one of methanol, ethanol, propanol, butanol, ethylene glycol, propylene glycol, butylene glycol, and glycerol.

In an alternative embodiment, the water-soluble alcohol is used in an amount of 40 to 170 wt% based on the amount of deionized water.

In an alternative embodiment, the mixed dispersion medium further contains a pH adjusting agent so that the pH of the mixed dispersion medium is 5 to 13.

In an alternative embodiment, the polychlorotrifluoroethylene has an average particle size of from 50 to 600 nm.

In an alternative embodiment, the content of polychlorotrifluoroethylene in the polychlorotrifluoroethylene suspension is from 5 to 70% by weight.

In an alternative embodiment, the dispersion is carried out under stirring conditions.

In an alternative embodiment, the dispersion is carried out under mechanical stirring for 6 to 48 hours.

In alternative embodiments, the means of supporting comprises coating or impregnation.

In alternative embodiments, the coating comprises spraying or spin coating.

In an alternative embodiment, when the support means is coating, the polychlorotrifluoroethylene suspension is coated to a thickness of from 10 to 200 μm.

In an alternative embodiment, the substrate material is washed before carrying the polychlorotrifluoroethylene suspension.

In alternative embodiments, the substrate material comprises glass, stainless steel plate, PI film, or titanium plate.

In an alternative embodiment, the surface of the substrate material is a smooth surface.

In an alternative embodiment, the drying temperature is 40-120 ℃.

In an alternative embodiment, the sintering temperature is 200-280 ℃ and the sintering time is 10-60 min.

In an optional embodiment, the sintering is performed by heating to 200-250 ℃ at a heating rate of 10-20 ℃/min for 5-20min, and then heating to 250-280 ℃ for 5-40 min.

In an alternative embodiment, removing substrate material comprises: the sintered substrate material carrying the polychlorotrifluoroethylene suspension was quenched in cold water, followed by peeling off the substrate material.

In a second aspect, the present invention also provides a polychlorotrifluoroethylene film produced by the method of any one of the preceding embodiments.

In an alternative embodiment, the polychlorotrifluoroethylene film has a thickness of from 2 to 80 μm.

In an alternative embodiment, the polychlorotrifluoroethylene film has a light transmittance of > 85% and a water vapor transmission rate of < 0.006g/m at 38 ℃ and 90% RH²24h, dielectric loss < 0.003 at 10GHz, tensile elongation at break > 50% and tensile strength > 24 MPa.

In a third aspect, the present invention also provides the use of a polychlorotrifluoroethylene film according to the preceding embodiments, for example in the preparation of materials for aerospace, defense and military industry, electronics and electrical or pharmaceutical and chemical industry.

The following beneficial effects of the invention include:

the PCTFE films provided herein are prepared by supporting the suspension on a substrate material, followed by drying, sintering, and removing the substrate material. The whole process is carried out in the environment without high temperature (the highest molding temperature is not higher than 280 ℃) and high force field (including extrusion or shearing force), thereby avoiding the degradation of PCTFE in the traditional processing process, keeping the performance advantage of PCTFE to the maximum extent and opening up a new method for processing and molding the PCTFE film.

The PCTFE film prepared by the method has high transparency, high water vapor barrier property, low dielectric loss and good mechanical strength and toughness, and can be widely applied to the fields of aerospace, national defense and military industry, electronics and electrical industry or pharmaceutical and chemical industry.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

The polychlorotrifluoroethylene film provided by the present application, and the preparation method and application thereof are specifically described below.

The inventor indicates through research that: although the PCTFE film product can be prepared by the prior art, the PCTFE is inevitably degraded due to the high processing temperature and continuous mechanical transmission, high electric power cost is generated, and complicated matched equipment is required to be built. In addition, PCTFE is hardly soluble in any solvent at normal temperature, which makes the solution film-forming method unsuitable for producing a PCTFE film.

In view of the above, the present application provides a method for preparing a polychlorotrifluoroethylene film, which mainly comprises the following steps: the polychlorotrifluoroethylene suspension obtained by dispersing polychlorotrifluoroethylene in a mixed dispersion medium is supported on the surface of a substrate material, dried, sintered, and then the substrate material is removed.

The method produces a PCTFE film by supporting a suspension on a substrate material, followed by drying, sintering, and removing the substrate material. The method has no high requirement on the fluidity of polymer melt, can also form the PCTFE without the action of extra high-pressure high-shear, namely, the whole process is carried out in the environment without high temperature (the highest forming temperature is not higher than 280 ℃) and high force field (including extrusion or shear force), thereby effectively avoiding the degradation of the PCTFE in the traditional processing process, furthest maintaining the performance advantage of the PCTFE and opening up a new method for processing and forming the PCTFE film.

In an alternative embodiment, the polychlorotrifluoroethylene used is in the form of a powder having an average particle diameter of from 50 to 600 nm. If the average particle diameter of the polychlorotrifluoroethylene used is outside the range of 50 to 600nm, it is liable to cause the suspension to lose fluidity or to settle rapidly.

The content of polychlorotrifluoroethylene in the polychlorotrifluoroethylene suspension may be 5 to 70% by weight, such as 5%, 10%, 20%, 30%, 40%, 50%, 60% or 70% by weight, etc., and may be any other value within the range of 5 to 70% by weight.

It is worth mentioning that if the content of polychlorotrifluoroethylene in the polychlorotrifluoroethylene suspension is less than 5% by weight, a uniform and complete coating surface cannot be obtained, and that more than 70% by weight results in complete loss of fluidity of the suspension and failure of effective coating.

In an alternative embodiment, the mixed dispersion medium comprises primarily water (e.g., deionized water). In addition, the mixed dispersion medium may further include a surfactant or a water-soluble alcohol substance. That is, the mixed dispersion medium may be obtained by mixing water with a surfactant, or may be obtained by mixing water with a water-soluble alcohol.

The mixed dispersion medium used in the method can reduce the surface tension of the mixed dispersion medium on one hand, and can effectively regulate and control the particle accumulation morphology of the suspension after drying on the other hand.

It is worth emphasizing that: the properties of the final sintered film material are closely related to the packing of the PCTFE particles during drying. During the suspension drying process, as the liquid volatilizes, the particles in the drying body will migrate through the maragini flow or capillary flow, thereby presenting different particle packing conditions. Furthermore, as the gas-liquid interface recedes into the interparticle space, capillary stresses are developed (proportional to the surface tension of the liquid, inversely proportional to the diameter of the liquid column), which, when the magnitude of the internal stresses exceeds the strength of the dry film, will produce periodic cracks in the dry film.

When the deionized water and the surfactant are combined, the surfactant can play two roles, on one hand, because the liquid volatilization rate of the edge part is higher, the concentration gradient of the surfactant can be generated, and further Maragini flow from the edge to the center is generated, and the capillary flow from the center to the edge is counteracted, so that the phenomenon of 'coffee ring' is effectively inhibited, and the dry film shape with uniformly accumulated particles is obtained; on the other hand, the addition of the surfactant makes the surface tension of the liquid lower, and thus the capillary stress generated during drying is smaller, and the generation of cracks can be effectively suppressed.

When the combination of the deionized water and the water-soluble alcohol is used, taking ethanol as an example, the introduction of the ethanol reduces the surface tension of the deionized water on one hand, so that the PCTFE can be stably dispersed; on the other hand, in the drying process, ethanol can volatilize before deionized water, the surface tension of the liquid is reduced along with the volatilization of the ethanol, and the coated suspension is quickly gelatinized and loses fluidity, so that the uneven accumulation of particles caused by internal flow is avoided. The uniform and compact particle packing enables the PCTFE particles to be mutually welded in the sintering process, and PCTFE molecular chains are mutually entangled, so that a complete film with excellent performance is obtained.

Optionally, the surfactant comprises at least one of a non-fluorinated surfactant and a fluorinated surfactant.

Among them, the non-fluorine surfactant may include, for example, at least one of sodium dodecylbenzenesulfonate, cetyltrimethylammonium chloride, cetyltrimethylammonium bromide and sodium cetylsulfate. The fluorosurfactant can include, for example, at least one of sodium perfluorobutyl sulfonate, ammonium perfluorononanoate, sodium perfluorodecyloxybenzenesulfonate, and ammonium pentadecafluorodecanoate.

In alternative embodiments, the surfactant may be used in an amount of 1 to 10 wt%, such as 1 wt%, 2 wt%, 5 wt%, 8 wt%, or 10 wt%, etc., of the polychlorotrifluoroethylene, and may also be any other value within the range of 1 to 10 wt%.

It is to be noted that if the amount of the surfactant is less than 1% by weight, PCTFE cannot be stably dispersed in water; above 10 wt%, the PCTFE film tends to have deteriorated properties (e.g., decreased mechanical properties, decreased light transmittance, increased dielectric loss, and increased water vapor transmission rate).

The water-soluble alcohol substance may include, for example, at least one of methanol, ethanol, propanol (preferably isopropanol), butanol, ethylene glycol, propylene glycol, butylene glycol and glycerol.

In alternative embodiments, the amount of water-soluble alcohol may be 40-170 wt%, such as 40 wt%, 50 wt%, 80 wt%, 100 wt%, 120 wt%, 150 wt%, or 170 wt%, or any other value within the range of 40-170 wt% of the deionized water.

It is to be noted that if the amount of the water-soluble alcohol is less than 40% by weight, PCTFE cannot be stably dispersed in the water-alcohol mixture; above 170 wt%, the coated surface may develop a large number of cracks during drying, and a complete PCTFE film cannot be obtained by sintering.

Further, the mixed dispersion medium may further contain a pH adjusting agent (e.g., hydrochloric acid, an aqueous solution of sodium hydroxide, or ammonia water) so that the pH of the mixed dispersion medium is 5 to 13. The stability of the polychlorotrifluoroethylene suspension can be further improved by adding a pH adjusting agent to the mixed dispersion medium.

In an alternative embodiment, the dispersion is carried out under stirring conditions, and specifically, the dispersion can be carried out under stirring conditions of 300-500rpm (such as 400rpm) for 6-48 h.

In the present application, the support of the chlorotrifluoroethylene suspension on the substrate material may, for example, comprise coating or impregnation. Wherein the coating may comprise spraying or spin coating.

When the support means is coating, the thickness of the applied polychlorotrifluoroethylene suspension may be 10 to 200. mu.m, such as 10 μm, 20 μm, 50 μm, 80 μm, 100 μm, 150 μm or 200 μm, and the like, and may also be other thickness values in the range of 10 to 200. mu.m.

In some preferred embodiments, the substrate material may also be cleaned prior to carrying the polychlorotrifluoroethylene suspension. Specifically, the washing may be performed with deionized water and ethanol.

In alternative embodiments, the substrate material may comprise, for example, glass, stainless steel plate, PI film, or titanium plate, among others. Preferably, the surface of the substrate material used is a smooth surface, and the substrate material used is resistant to high temperatures.

In the present application, the drying temperature may be 40 to 120 ℃, such as 40 ℃, 50 ℃, 80 ℃, 100 ℃ or 120 ℃, or any other value within the range of 40 to 120 ℃.

The whole drying process can be carried out on an automatic coating machine with temperature control or in an oven, and the substrate material is kept horizontal in the drying process.

In the present application, the sintering temperature can be 200-280 ℃, such as 200 ℃, 210 ℃, 220 ℃, 230 ℃, 240 ℃, 250 ℃, 260 ℃, 270 ℃ or 280 ℃, and can also be any other value within the range of 200-280 ℃. The sintering time may be 10-60min, such as 10min, 20min, 30min, 40min or 60min, and may be any other value within the range of 10-60 min.

In a preferred embodiment, the sintering is performed by heating to 200-250 ℃ at a heating rate of 10-20 ℃/min for 5-20min (e.g., 10min), and then heating to 250-280 ℃ for 5-40min (e.g., 20 min).

The whole sintering process can be carried out in a sintering furnace with programmable temperature rise, and the substrate material is kept horizontal in the sintering process.

In this application, removing substrate material may include: the sintered substrate material carrying the polychlorotrifluoroethylene suspension was quenched in cold water, followed by peeling off the substrate material.

Specifically, after sintering, the substrate material and the polychlorotrifluoroethylene carried by the substrate material are immediately put into cold water for quenching, so that the polychlorotrifluoroethylene is rapidly peeled from the substrate material, and a film with better transparency is obtained.

Correspondingly, the application also provides a polychlorotrifluoroethylene film prepared by the preparation method.

In an alternative embodiment, the thickness of the polychlorotrifluoroethylene film may be, but is not limited to, 2 to 80 μm. The thickness of the final film can be adjusted by changing the coating thickness or the solid content of the chlorotrifluoroethylene in the suspension according to the application requirements of different occasions.

In an alternative embodiment, the resulting polychlorotrifluoroethylene film has a light transmittance of > 85% and a water vapor transmission rate of < 0.006g/m at 38 ℃ and 90% RH²24h, dielectric loss < 0.003 at 10GHz, tensile elongation at break > 50% and tensile strength > 24 MPa.

In addition, the application also provides the application of the polychlorotrifluoroethylene film, for example, the polychlorotrifluoroethylene film can be used in the fields of aerospace, national defense and military industry, electronics and electrical industry, pharmaceutical and chemical industry and the like, and can be specifically used for preparing corresponding materials in the fields.

The features and properties of the present invention are described in further detail below with reference to examples.

Example 1

This example provides a preparation method of a polychlorotrifluoroethylene film, which comprises the following steps:

firstly, weighing 2g of sodium dodecyl benzene sulfonate, dissolving the sodium dodecyl benzene sulfonate in 80g of deionized water, adding the sodium dodecyl benzene sulfonate and 80g of PCTFE powder into a stirring tank, setting the rotating speed of a stirrer to be 400rpm, mixing for 24 hours, and adjusting the pH value of a system to be 10.0 by using ammonia water to obtain a PCTFE suspension with good stability. Next, a wet film of PCTFE suspension was coated on the borosilicate glass as a substrate material in a thickness of 40 μm by using an automatic coater. Then, the wet film was thoroughly dried by setting the coater temperature to 60 ℃. And then, moving the glass and the dry film carried by the glass into a sintering furnace together, placing the glass and the dry film carried by the glass horizontally, setting the heating rate to be 20 ℃/min, sintering the glass at 210 ℃ for 15min, and sintering the glass at 260 ℃ for 35 min. Finally, the glass and the film carried by the glass are put into water to be quenched, and a PCTFE transparent film (with yellow color) with the thickness of about 10 microns is obtained.

Example 2

1.5g of sodium perfluorobutylsulfonate and 0.5g of sodium hexadecyl sulfate were weighed out and dissolved in 80g of deionized water, and the procedure and equipment were the same as in example 1. Finally, a PCTFE colorless transparent film with the thickness of about 10 μm is obtained.

Example 3

40mL of ethanol and 40mL of deionized water were weighed and mixed well before being added to the stirred tank along with 80g of PCTFE powder. The remaining procedure and equipment were the same as in example 1. Finally, a colorless and transparent PCTFE film with the thickness of about 10 μm is obtained.

Example 4

30mL of isopropanol, 20mL of ethylene glycol and 30mL of deionized water were weighed and mixed uniformly, and the rest of the procedure was the same as in example 1, to finally obtain a colorless and transparent PCTFE film having a thickness of about 10 μm.

Example 5

Firstly, weighing 40mL of isopropanol and 40mL of deionized water, uniformly mixing, adding the isopropanol and 80g of irregular PCTFE powder into a stirring tank, setting the rotation speed of a stirrer to be 400rpm, stirring for 24 hours, and adjusting the pH value of a system to be 11.0 by using ammonia water to obtain a PCTFE suspension with good stability. Next, a wet film of PCTFE suspension was coated on the stainless steel sheet as a substrate material to a thickness of 100 μm using an automatic coater. Then, the wet film was thoroughly dried by setting the coater temperature to 80 ℃. And then, the stainless steel and the dry film carried by the stainless steel are moved into a sintering furnace together and placed horizontally, the heating rate is set to be 20 ℃/min, the stainless steel is sintered for 6min at 240 ℃ and then sintered for 15min at 280 ℃. Finally, the stainless steel and the film carried by the stainless steel are put into water to be quenched, and a colorless and transparent PCTFE film with the thickness of about 40 mu m is obtained.

Example 6

Firstly, weighing 40mL of isopropanol and 40mL of deionized water, uniformly mixing, adding the isopropanol and 57g of irregular PCTFE powder into a stirring tank, setting the rotation speed of a stirrer to be 400rpm, stirring for 24 hours, and adjusting the pH value of a system to be 9.0 by using ammonia water to obtain a PCTFE suspension with good stability. Next, a wet film of PCTFE suspension was coated on the stainless steel sheet to a thickness of 200 μm using an automatic coater set at a coater temperature of 80 ℃ using a stainless steel sheet as a substrate material. The rest of the procedure was the same as in example 5. Finally, a colorless and transparent PCTFE film with the thickness of about 80 μm is obtained.

Example 7

The procedure and apparatus were the same as in example 5 except that a titanium plate was used as the substrate material. Finally, a colorless transparent PCTFE film of about 30 μm was obtained.

Example 8

Setting the heating rate at 10 ℃/min, sintering at 250 ℃ for 10min, and sintering at 280 ℃ for 10 min. The rest of the procedure and equipment were the same as in example 5. Finally, a colorless transparent film of about 40 μm is obtained.

Example 9

The coating was replaced by dipping and dried in a forced air oven at 80 ℃. The rest of the procedure was the same as in example 5. Finally, a colorless transparent PCTFE film of about 35 μm was obtained.

Test examples

The PCTFE films obtained in examples 1-9 were subjected to performance tests, and the results are shown in Table 1, wherein the test standards for light transmittance (%) are described in GB/T2410-2008, and the water vapor transmission rate (g/m)²24h, 38 ℃, 90% RH)The test standards refer to GB/T21529-.

TABLE 1 test results

As can be seen from Table 1, the polychlorotrifluoroethylene film prepared by the preparation method provided by the application has high transparency and water vapor barrier property, low dielectric loss and good mechanical strength and toughness.

Comparative example:

comparative example 1

The sintering time at 260 ℃ in example 1 is prolonged from 35min to 50min, other conditions are not changed, the prepared film is deepened in yellowing degree, even the film is blackened due to local excessive decomposition, the tensile elongation at break is reduced to 23%, and the dielectric loss at 10GHz is increased to 0.02.

Comparative example 2

The addition of "1.5 g of sodium perfluorobutylsulfonate and 0.5g of sodium hexadecyl sulfate" in example 2 was changed to "2 g of sodium hexadecyl sulfate", and the film prepared was transparent but yellowish in color without changing the other conditions.

Comparative example 3

The 'weighing of 40mL of deionized water and 40mL of absolute ethyl alcohol' in the example 3 is changed into 'weighing of 10mL of deionized water and 70mL of absolute ethyl alcohol', other conditions are not changed, a large number of cracks are generated in the wet film in the drying process, and then the complete film cannot be obtained.

Comparative example 4

The method changes the 'weighing 30mL of isopropanol, 20mL of ethylene glycol and 30mL of deionized water' in the example 4 into 'weighing 10mL of isopropanol, 10mL of ethylene glycol and 60mL of deionized water', and other conditions are not changed, so that a stably dispersed suspension cannot be obtained, and a complete film cannot be obtained.

Comparative example 5

In example 5, the pH value was adjusted to 11.0 by ammonia water instead of 4.0 by dilute hydrochloric acid, and the light transmittance of the product was reduced to 85% and the water vapor transmission rate was increased to 0.006g/m²24h, tensile strength and 10GHz dielectric loss of 24.3MPa and 0.003, respectively.

Comparative example 6

In example 6, the "coater temperature setting of 80 ℃ was changed to" coater temperature setting of 140 ℃, and other conditions were not changed, so that a large number of cracks were generated in the wet film during the drying process, and a complete film could not be obtained after sintering.

Comparative example 7

The temperature rise rate in the example 8 was changed to 30 ℃/min, and the film prepared was subjected to local cracking under otherwise unchanged conditions.

Comparative example 8

The maximum sintering temperature in example 8 is adjusted from 280 ℃ to 300 ℃, other conditions are not changed, the prepared film is yellow, even has a blackening phenomenon caused by excessive decomposition locally, the tensile elongation at break is reduced to 20 percent, and the dielectric loss at 10GHz is increased to 0.01.

Comparative example 9

The polychlorotrifluoroethylene raw material is filmed by a melt tape casting method, the molding temperature is 280 ℃, and the film product with the thickness of about 40 mu m is prepared. Compared with the film prepared in example 8, the cast film had a transmittance of 88%, exhibited remarkable anisotropy in mechanical properties, and had a tensile strength of 22MPa in the direction perpendicular to the casting direction.

In summary, the present application provides methods for forming PCTFE films that utilize a suspension supported on a substrate material that is subsequently dried, sintered, and removed. The whole process is carried out in the environment without high temperature (the highest molding temperature is not higher than 280 ℃) and high force field (including extrusion or shearing force), thereby avoiding the degradation of PCTFE in the traditional processing process, keeping the performance advantage of PCTFE to the maximum extent and opening up a new method for processing and molding the PCTFE film.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A preparation method of a polychlorotrifluoroethylene film is characterized by comprising the following steps: the polychlorotrifluoroethylene suspension obtained by dispersing polychlorotrifluoroethylene in a mixed dispersion medium is supported on the surface of a substrate material, dried, sintered, and then the substrate material is removed.

2. The production method according to claim 1, wherein the mixed dispersion medium mainly comprises water;

preferably, the water is deionized water;

preferably, the mixed dispersion medium further comprises a surfactant or a water-soluble alcohol substance;

preferably, the surfactant comprises at least one of a non-fluorine surfactant and a fluorine-containing surfactant;

preferably, the non-fluorine-containing surfactant comprises at least one of sodium dodecylbenzene sulfonate, cetyltrimethylammonium chloride, cetyltrimethylammonium bromide and sodium hexadecyl sulfate, and the fluorine-containing surfactant comprises at least one of sodium perfluorobutyl sulfonate, ammonium perfluorononanoate, sodium perfluorodecyloxybenzenesulfonate and ammonium pentadecyldecanoate;

preferably, the surfactant is used in an amount of 1 to 10 wt% of the polychlorotrifluoroethylene;

preferably, the water-soluble alcohol substance includes at least one of methanol, ethanol, propanol, butanol, ethylene glycol, propylene glycol, butylene glycol and glycerol;

preferably, the amount of the water-soluble alcohol substance is 40-170 wt% of the amount of the deionized water;

preferably, the mixed dispersion medium further contains a pH regulator so that the pH value of the mixed dispersion medium is 5-13;

preferably, the average particle size of the polychlorotrifluoroethylene is from 50 to 600 nm;

preferably, the content of the polychlorotrifluoroethylene in the polychlorotrifluoroethylene suspension is from 5 to 70% by weight.

3. The method according to claim 2, wherein the dispersion is carried out under stirring;

preferably, the dispersion is carried out under mechanical stirring conditions at a stirring speed of 300-500rpm for 6-48 h.

4. The method according to claim 1, wherein the supporting means includes coating or impregnation;

preferably, the coating comprises spraying or spin coating;

preferably, when the supporting mode is coating, the thickness of the coating of the polychlorotrifluoroethylene suspension is 10 to 200 μm;

preferably, before carrying the polychlorotrifluoroethylene suspension, the method further comprises washing the substrate material.

5. The method according to claim 4, wherein the substrate material comprises glass, a stainless steel plate, a PI film, or a titanium plate;

preferably, the surface of the substrate material is a smooth surface.

6. The method according to claim 1, wherein the drying temperature is 40 to 120 ℃.

7. The method as claimed in claim 1, wherein the sintering temperature is 200-280 ℃ and the sintering time is 10-60 min;

preferably, the sintering is performed by heating to 200-250 ℃ at a heating rate of 10-20 ℃/min for 5-20min, and then heating to 250-280 ℃ for 5-40 min.

8. The method of claim 1, wherein removing the substrate material comprises: quenching the sintered substrate material carrying the polychlorotrifluoroethylene suspension in cold water, and subsequently peeling off the substrate material.

9. A polychlorotrifluoroethylene film produced by the production process according to any one of claims 1 to 8;

preferably, the thickness of the polychlorotrifluoroethylene film is 2 to 80 μm;

preferably, the polychlorotrifluoroethylene film has a light transmittance of > 85% and a water vapor transmission rate of < 0.006g/m at 38 ℃ and 90% RH²24h, dielectric loss < 0.003 at 10GHz, tensile elongation at break > 50% and tensile strength > 24 MPa.

10. Use of a polychlorotrifluoroethylene film according to claim 9 in the preparation of materials for aerospace, defense and military, electronics and electrical or pharmaceutical chemicals.