Preparation method of high-temperature-resistant low-precipitation polyester film

Abstract

The invention belongs to the technical field of polyester films, and relates to a preparation method of a high-temperature-resistant low-precipitation polyester film, which comprises the following steps: sequentially crystallizing, dedusting and drying a polyester raw material, carrying out melt extrusion by a melt extruder, feeding into a coarse filter, feeding a polyester melt subjected to coarse filtration into a devolatilization device, and carrying out devolatilization to obtain the high-temperature-resistant low-precipitation polyester film. The polyester melt subjected to devolatilization enters a metering extruder and a fine filter in sequence, the polyester melt subjected to fine filtration enters a die head through a melt pipe, is extruded from the die head and is cooled by a sheet casting roller to form a thick sheet, and then the thick sheet is subjected to the procedures of longitudinal stretching, transverse stretching, heat setting and traction rolling in sequence to prepare the high-temperature-resistant low-precipitation polyester film. The devolatilization device comprises a shell, a screw rod, an electric field generating device and a plurality of star-shaped rotors mounted in the shell. The content of low molecules in the polyester film is greatly reduced through the specially designed devolatilization device, the quality of the prepared polyester film is better, and high temperature resistance and low precipitation performance are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of polyester films and relates to a method for preparing a high-temperature resistant and low-precipitation polyester film. Background Art

[0002] High temperature resistant low precipitation polyester film is used in many fields due to its high temperature resistance and low precipitation characteristics. However, with the development of society, the performance requirements for high temperature resistant low precipitation polyester film are increasing. Therefore, it is necessary to develop a high temperature resistant low precipitation polyester film with better performance.

[0003] At present, the preparation of high temperature resistant and low precipitation polyester film is mainly divided into two types:

[0004] The first is to add a coating barrier layer, coating the polyester film surface with a low precipitation coating by precision coating technology or a dense metal coating by vacuum sputtering technology to reduce the precipitation of low molecular weight substances inside the polyester base film.

[0005] For example, patent application 202010832023.4 discloses a high temperature resistant and low precipitation protective film and its preparation method, which uses aluminized polyester film as the substrate, applies acrylic pressure-sensitive adhesive on one side of the aluminized polyester film, and then adheres the release film, and then adheres the positioning film on the other side. However, this method requires post-processing, has low production efficiency, and the coating thickness is relatively large, generally exceeding 1μm; in addition, the metal coating also changes the original surface physical properties of the polyester film, and the use field has limitations. At present, it can generally only be used in the packaging field, and because the metal coating is generally colored, some fields that require colorless and transparent cannot be used, such as the optical field.

[0006] Due to the limitations of metal plating, patent application 202111526407.4 discloses a low precipitation polyester film and a preparation method thereof. The prepared polyester film includes a polyester base film and a low precipitation coating coated on the surface of the polyester base film. The low precipitation coating is obtained by coating and curing a water-soluble coating liquid. One hundred parts by mass of the water-soluble coating liquid includes 4 to 12 parts by mass of a water-soluble resin, 85 to 95 parts by mass of deionized water, 0.5 to 3 parts by mass of a cross-linking agent, and 0.1 to 0.3 parts by mass of a surfactant. The preparation method is to evenly apply the water-soluble coating liquid on the surface of the polyester base film, heat-dry at 120°C for 1 minute, and obtain a low precipitation polyester film. However, if secondary coating is required, the low-precipitation coating on the surface of the polyester base film will contaminate the secondary coating liquid, causing difficulties in subsequent processing. In addition, after long-term use, low molecular weight substances will precipitate to the interface between the polyester film and the coating barrier layer to form snowflake-like marks, affecting the appearance of the film. The negative impact of low molecular weight precipitates cannot be completely eliminated.

[0007] The second method is to increase the molecular weight of the polyester raw material by secondary polymerization of the polyester chips, reduce the content of small molecules in the raw material to a certain extent, and slow down the precipitation rate of small molecular weight substances inside the film.

[0008] For example, patent application 201611231717.2 discloses a high-temperature, low-precipitation optical polyester base film and its preparation method. The high-temperature, low-precipitation optical polyester base film prepared by the present invention is composed of a three-layer co-extruded film composite of ABA, and the raw material of the A layer is composed of 65% to 85% of polyethylene terephthalate and 15% to 35% of polyester silicon masterbatch; the raw material of the B layer is composed of 50% to 85% of polyethylene terephthalate and 15% to 50% of nano-silica polyester masterbatch. The preparation method of the polyester base film is: the nano-silica polyester masterbatch, PET, special adhesive polyester and ordinary silicon masterbatch prepared by the in-situ growth method are mixed into the raw materials of the A layer and the B layer, and after melting, they are co-extruded through the ABA three layers, and then biaxially stretched and heat-set to form the raw materials. However, the preparation of the high-temperature, low-precipitation optical polyester base film requires the use of large-scale polymerization equipment, and the precipitation resistance is poor.

[0009] In order to improve the precipitation resistance, the prior art also combines the above two methods. Although the precipitation resistance time is increased, the problem of low-molecular precipitates cannot be completely eliminated, and precipitation will eventually occur. For example, patent application 202110196595.2 discloses a low-precipitation polyester film and its preparation method, the preparation method of which is to first select the raw materials of each component according to the ratio, and then adopt a plane biaxial stretching process, and obtain a low-precipitation polyester film through crystallization drying, melt extrusion, film casting, longitudinal stretching, coating, transverse stretching, transverse shaping, traction and winding, and slitting process. Although the patent improves the precipitation resistance of the low-precipitation polyester film prepared by the above two methods, the problems existing in these two methods will also exist in this patent, such as the need to use large-scale polymerization equipment in its preparation process, the low-precipitation coating on the surface of the polyester base film during the secondary coating will contaminate the secondary coating liquid, which will bring difficulties to subsequent processing, and low molecules will precipitate to the interface between the polyester film and the coating barrier layer after long-term use to form snowflake-shaped marks.

[0010] Therefore, it is of great significance to need a method for preparing a high temperature resistant and low precipitation polyester film to solve the above problems. Summary of the invention

[0011] The purpose of the present invention is to solve the problems existing in the prior art and provide a method for preparing a high temperature resistant and low precipitation polyester film.

[0012] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0013] A method for preparing a high-temperature resistant low-precipitation polyester film, wherein the polyester raw material is first crystallized, dusted, and dried in sequence, and then melt-extruded by a melt extruder and then enters a coarse filter, the polyester melt after coarse filtration first enters a devolatilization device for devolatilization to remove low molecular weight molecules in the melt as much as possible, and then the polyester melt after devolatilization enters a metering extruder and a fine filter in sequence, the polyester melt after fine filtration enters a die head through a melt pipe, is extruded from the die head, and is cooled by a casting roller to form a thick sheet, and then the thick sheet is sequentially subjected to the steps of longitudinal stretching, transverse stretching, heat setting, and traction and winding to prepare a high-temperature resistant low-precipitation polyester film;

[0014] The devolatilization device comprises a shell, a screw, an electric field generating device and a plurality of star-shaped rotors;

[0015] The shell is a double-layer structure, with an air extraction port at the upper end of the shell, a feed port at one side of the upper part, and a feeding port at the side opposite to the feed port at the bottom. The feeding port is connected to the screw cavity of the metering extruder as a whole, that is, forming an integrated pipeline for placing the screw;

[0016] The left section of the screw passes through the feed port and is installed on the bottom side wall of the housing, and the right section is installed in the screw cavity of the metering extruder;

[0017] The electric field generating device comprises an upper plate-shaped electrode, a lower plate-shaped electrode and a high-voltage generator (which can generate a DC voltage of 200 to 300 kV, and the high-voltage generator is equivalent to a power source, and there is no special requirement for its installation position, which is determined according to the on-site conditions). The upper plate-shaped electrode and the lower plate-shaped electrode are respectively installed directly above and directly below the shell, and the upper plate-shaped electrode is connected to the positive electrode of the high-voltage generator through the upper plate-shaped electrode wire, and the lower plate-shaped electrode is connected to the negative electrode of the high-voltage generator through the lower plate-shaped electrode wire;

[0018] A plurality of star-shaped rotors are installed in the shell from top to bottom and are fixed to the inner walls of the shell on both sides opposite to each other through support rods. The length direction of the support rods is perpendicular to the length direction of the screw rods. Any two adjacent star-shaped rotors are staggered in the vertical direction.

[0019] As the preferred technical solution:

[0020] In the method for preparing a high temperature resistant and low precipitation polyester film as described above, the surface of the upper plate-shaped electrode is coated with an upper plate-shaped electrode protective layer, and the surface of the lower plate-shaped electrode is coated with a lower plate-shaped electrode protective layer.

[0021] A method for preparing a high temperature resistant and low precipitation polyester film as described above, wherein the shell is made of zirconium oxide or boron nitride, or other high strength and heat resistant (resistant to high temperature of 300°C) inorganic non-metallic materials, and the roughness Rz of the inner surface of the shell is less than 1 μm;

[0022] The star-shaped rotor is made of zirconium oxide or boron nitride, or other high-strength and heat-resistant (300°C high temperature resistant) inorganic non-metallic materials. The surface roughness Rz of the star-shaped rotor is less than 0.3 μm.

[0023] The upper plate-shaped electrode and the lower plate-shaped electrode are made of the same material, which is stainless steel or aluminum alloy, or other conductive metal materials;

[0024] The upper plate-shaped electrode protection layer and the lower plate-shaped electrode protection layer are made of the same material, which is a high-temperature resistant (300° C. resistant) and highly insulating material such as plastic, rubber or ceramic.

[0025] A method for preparing a high temperature resistant and low precipitation polyester film as described above, wherein the polyester raw materials are film-grade polyester chips and silica masterbatch chips, and the mass ratio of the film-grade polyester chips to the silica masterbatch chips is 9:1;

[0026] The intrinsic viscosity of film-grade polyester chips is 0.64 to 0.68 dL / g;

[0027] The silica particle content in the silica masterbatch slices is 3000ppm.

[0028] In the method for preparing a high temperature resistant and low precipitation polyester film as described above, crystallization refers to boiling treatment at 170-175° C. for 5 minutes in a fluidized bed to fully crystallize the polyester raw material so that the surface of the polyester raw material is crystallized into a relatively loose hard shell, which facilitates the escape of moisture inside the slices in the subsequent drying stage;

[0029] The raw materials need to be dusted before entering the drying tower to remove the dust and wires generated during the transportation of the raw materials. These dust and wires are easily degraded to produce small molecules during the extrusion and melting process, which is not conducive to the anti-precipitation performance. And the dust removal of the raw materials helps to improve the apparent quality of the final film product;

[0030] Drying refers to drying in a drying tower in a pure nitrogen atmosphere at 165-175°C (nitrogen can be recycled after drying to ensure that its dew point temperature is below -70°C) for 5-6 hours to reduce the moisture content of the polyester raw material to below 50ppm;

[0031] The dried raw materials need to pass through a buffer tank and a pipeline when entering the melt extruder from the drying tower. During this process, a pure nitrogen atmosphere at 165-175°C needs to be continuously introduced into the buffer tank and the pipeline to isolate oxygen and water vapor and protect the polyester chips from being affected by oxygen and water vapor and causing degradation.

[0032] In the method for preparing the high temperature resistant and low precipitation polyester film as described above, the melt extrusion temperature is 275-285°C.

[0033] In the method for preparing a high temperature resistant and low precipitation polyester film as described above, the filtration accuracy of the coarse filter is 20 μm, and the filtration accuracy of the fine filter is 10 μm.

[0034] In the method for preparing a high-temperature resistant and low-precipitation polyester film as described above, the vacuum degree in the devolatilization device is below -70 kPa, and the residence time of the polyester melt after coarse filtration in the devolatilization device is more than 5 minutes.

[0035] In the method for preparing a high-temperature resistant and low-precipitation polyester film as described in any of the above items, the content of low-molecule substances with a molecular weight below 12,000 in the polyester raw material is 0.3wt%, and the content of low-molecule substances with a molecular weight below 12,000 in the high-temperature resistant and low-precipitation polyester film is below 0.2wt‰. If the devolatilization step is omitted, on the one hand, the polyester raw material contains a higher content of low-molecule substances, and on the other hand, new low-molecule substances will be generated through the links of transportation, crystallization, extrusion, etc., so the low-molecule substances in the final film will be much higher than the content in the original polyester raw material (the content is in the range of 1 to 3wt%).

[0036] The method for preparing a high temperature resistant low precipitation polyester film as described above, wherein the high temperature resistant low precipitation polyester film has a thickness of 10000m 2 The number of coke point defects is less than 10.

[0037] Principle of the invention:

[0038] After testing, the precipitated substances on the surface of the film are mainly additives, catalysts, low molecules that are not fully polycondensed in place, and low molecules produced by thermal degradation and oxygen degradation in the production process. Therefore, the present invention starts from the source of low molecules, adds a specially designed devolatilization device between the melt extruder and the metering extruder connected in series in the prior art, greatly reduces the low molecular content inside the polyester film through the devolatilization technology, and reduces the generation of low molecules by thermal degradation and oxygen degradation in the high-temperature production process by isolating oxygen and water vapor, thereby achieving the purpose of low precipitation. Due to the large viscosity of the PET melt, low molecules are not easy to overflow from the melt. The devolatilization device of the present invention uses multiple star-shaped rotors to rotate to dilute the melt due to the action of centrifugal force, so that low molecules can be converted into gas and overflow under high temperature and low pressure environment. The role of the high-voltage electric field is to give a downward force to the polar PET molecules, so that the bubble film generated by the rotation of the star-shaped rotors can be broken to accelerate the overflow of low molecules and make the bottom melt more compact, and the internal low-molecular bubbles are squeezed to the surface by extrusion to accelerate the overflow.

[0039] Beneficial effects:

[0040] (1) The present invention provides a method for preparing a high temperature resistant low precipitation polyester film. By subjecting the polyester raw material to crystallization, dust removal, drying and devolatilization treatment, in particular, using a specially designed devolatilization device for devolatilization, the low molecular weight content inside the polyester film can be greatly reduced, so that the low molecular weight content with a molecular weight below 12,000 in the high temperature resistant low precipitation polyester film is below 0.2 wt‰, and the raw material after dust removal treatment is helpful to improve the apparent quality of the final film product; in addition, during the high temperature production process, the generation of low molecular weights due to thermal degradation and oxygen degradation is reduced by isolating oxygen and water vapor, thereby achieving the purpose of low precipitation.

[0041] (2) A method for preparing a high-temperature resistant and low-precipitation polyester film according to the present invention, wherein a devolatilization device uses a plurality of star-shaped rotors, which rotate to dilute the melt due to the centrifugal force, thereby facilitating the low-molecular-weight PET molecules to be converted into gas and overflow under a high-temperature and low-pressure environment; in addition, the high-voltage electric field generated by the electric field generating device also gives a downward force to the polar PET molecules, thereby facilitating the rupture of the bubble membrane generated by the rotation of the star-shaped rotors, accelerating the overflow of the low-molecular-weight PET molecules and making the bottom melt more compact, and squeezing the internal low-molecular-weight bubbles to the surface to accelerate the overflow.

[0042] (3) The present invention provides a method for preparing a high temperature resistant low precipitation polyester film. The method accelerates the overflow by squeezing most of the low molecular bubbles to the surface through a devolatilization device. This allows more low molecular bubbles to overflow and less residue to remain during the preparation of the high temperature resistant low precipitation polyester film. There is no need to frequently shut down the machine to replace the fine filter, resulting in higher production efficiency. In addition, since there are fewer low molecular bubbles, the quality of the produced high temperature resistant low precipitation polyester film is also improved.

[0043] (4) The high temperature resistant and low precipitation polyester film prepared by the present invention can achieve high temperature resistance and low precipitation performance without subsequent processing, and is simple to prepare, while also meeting the use requirements of high-end fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a schematic structural diagram of the devolatilization device of the present invention;

[0045] Among them, 1.1-upper plate-shaped electrode wire, 1.2-lower plate-shaped electrode wire, 1.3-upper plate-shaped electrode, 1.4-lower plate-shaped electrode, 1.5-upper plate-shaped electrode protective layer, 1.6-lower plate-shaped electrode protective layer, 2-shell, 2.1-exhaust port, 2.2-feed port, 2.3-heat transfer oil interlayer, 3-star rotor, 4-screw. DETAILED DESCRIPTION

[0046] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0047] The testing methods of the relevant performance indicators in the following embodiments and comparative examples are as follows:

[0048] Low molecular weight content below 12000: The high temperature resistant low precipitation polyester film prepared in each embodiment and comparative example is first frozen with liquid nitrogen for 5 minutes, then crushed into powder with a crusher, and then the crushed powder is put into a Soxhlet extractor, extracted with chloroform at 90°C for 24 hours, and finally the extracted solution is dried at 105°C. The precipitated low molecular weight powder is weighed and analyzed by gel permeation chromatography GPC to obtain the low molecular weight content below 12000.

[0049] Every 10000m 2 Coke point defect: Before winding up each embodiment and comparative example, the high temperature resistant low precipitation polyester film was continuously inspected by a micro-visual defect detector (with an accuracy of 0.066 mm).

[0050] Haze: The high temperature resistant and low precipitation polyester films prepared in the examples and comparative examples were tested according to the haze test method in the American standard ASTM-D1003-07.

[0051] Example 1

[0052] A method for preparing a high temperature resistant and low precipitation polyester film, comprising the following steps:

[0053] (1) Preparation of raw materials;

[0054] Film-grade polyester chips: The manufacturer is Sinopec Yizheng Chemical Fiber Co., Ltd., the brand is FG604, and the intrinsic viscosity is 0.64dL / g;

[0055] Silica masterbatch slices: The silica particle content in the silica masterbatch slices is 3000ppm;

[0056] (2) preparing polyester raw materials;

[0057] The film-grade polyester chips and the silica masterbatch chips are mixed evenly in a mass ratio of 9:1 to obtain a polyester raw material;

[0058] The content of low molecular weight polyester with a molecular weight below 12,000 in the obtained polyester raw material is 0.3 wt%;

[0059] (3) boiling the polyester raw material obtained in step (2) at 170° C. for 5 min in a fluidized bed to fully crystallize it, then performing dust removal, and then drying it in a drying tower at 175° C. in a pure nitrogen atmosphere for 5 h, and then conveying it to a melt extruder through a buffer tank and a pipeline in a pure nitrogen atmosphere at 175° C., and then filtering it through a coarse filter after extrusion by the melt extruder; wherein the melt extrusion temperature is 285° C., and the filtration accuracy of the coarse filter is 20 μm;

[0060] (4) The polyester melt after coarse filtration first enters a devolatilization device for devolatilization for 5 minutes, and then enters a metering extruder and a fine filter in sequence. The polyester melt after fine filtration enters a die head through a melt pipe, and after being extruded from the die head, it passes through a casting roller and is cooled to 20° C. to form a non-oriented thick sheet; wherein the vacuum degree in the devolatilization device is -70 kPa, the temperature in the devolatilization device is 285° C., and the filtration accuracy of the fine filter is 10 μm;

[0061] like Figure 1 As shown, the devolatilization device used above comprises a housing, a screw 4, an electric field generating device and three star-shaped rotors 3;

[0062] The shell is made of zirconium oxide, and the roughness Rz of the inner surface of the shell is 1 μm;

[0063] The shell is a double-layer structure, and a heat-conducting oil interlayer 2.3 is provided between the double layers for heating and heat preservation of the device. An air extraction port 2.1 is provided at the upper end of the shell, a feed port 2.2 is provided at one side of the upper part, and a feed port is provided at the bottom on the side opposite to the feed port 2.2. The feed port is connected to the screw cavity of the metering extruder as a whole and is used to place the screw 4;

[0064] The left section of the screw 4 passes through the feed port and is installed on the bottom side wall of the housing 2, and the right section is installed in the screw cavity of the metering extruder;

[0065] The electric field generating device comprises an upper plate-shaped electrode 1.3, a lower plate-shaped electrode 1.4 and a high voltage generator. The upper plate-shaped electrode 1.3 and the lower plate-shaped electrode 1.4 are respectively installed directly above and directly below the housing 2. The upper plate-shaped electrode 1.3 is connected to the positive electrode of the high voltage generator through the upper plate-shaped electrode wire 1.1, and the lower plate-shaped electrode 1.4 is connected to the negative electrode of the high voltage generator through the lower plate-shaped electrode wire 1.2.

[0066] The surface of the upper plate-shaped electrode 1.3 is coated with an upper plate-shaped electrode protection layer 1.5, and the surface of the lower plate-shaped electrode 1.4 is coated with a lower plate-shaped electrode protection layer 1.6;

[0067] The upper plate-shaped electrode 1.3 and the lower plate-shaped electrode 1.4 are made of the same material, stainless steel or aluminum alloy;

[0068] The three star-shaped rotors 3 are installed in the housing 2 from top to bottom, and are fixed to the inner walls of the housing 2 on both sides opposite to each other through support rods. The length direction of the support rods is perpendicular to the length direction of the screw 4. Any two adjacent star-shaped rotors 3 are staggered in the vertical direction.

[0069] The material of the star rotor 3 is zirconia, and the surface roughness Rz of the star rotor 3 is 0.3 μm;

[0070] (5) The thick sheet obtained in step (4) is heated to 80° C. by a longitudinal preheating roller and then enters a far-infrared longitudinal stretching system to form a unidirectional sheet. The unidirectional sheet then enters a transverse stretching system, is heated to 120° C. in a preheating section, and then enters a stretching section for transverse stretching. The transversely stretched film is cooled to 70° C. after heat setting, and then is pulled. During the pulling process, the temperature drops to 25° C. and then is rolled into a large shaft product. Finally, it is cut into specified specifications by a slitting machine to obtain a high-temperature resistant and low-precipitation polyester film; wherein the longitudinal stretching ratio is 2.8 times, the longitudinal stretching temperature is 150° C., the transverse stretching ratio is 4 times, the transverse stretching temperature is 135° C., and the heat setting temperature is 225° C.;

[0071] The thickness of the finally obtained high temperature resistant low precipitation polyester film is 50μm; the content of low molecular weight below 12000 in the high temperature resistant low precipitation polyester film is 0.18wt‰; 2 There are 7 char point defects; the haze of the high temperature resistant low precipitation polyester film is 3.2%, and the haze of the high temperature resistant low precipitation polyester film increases by 0.4% after being treated at 150°C for 60 minutes.

[0072] Comparative Example 1

[0073] A method for preparing a high temperature resistant polyester film is basically the same as that in Example 1, except that in step (4), the polyester melt after coarse filtration does not enter a devolatilization device but directly enters a metering extruder.

[0074] The thickness of the finally obtained high temperature resistant polyester film is 50μm; the content of low molecular weight with a molecular weight below 12000 in the high temperature resistant polyester film is 12wt‰; the content of low molecular weight with a molecular weight below 12000 in the high temperature resistant polyester film is 12wt‰; 2 The number of char defects is 1000; the haze of the high temperature resistant polyester film is 3.4%, and then after being treated at 150°C for 60 minutes, the haze increases by 2.2%.

[0075] Comparing Comparative Example 1 with Example 1, it can be seen that the content of low molecular weight below 12000 in the high temperature resistant polyester film prepared in Comparative Example 1 is too high. 2There are too many coke material defects, and the haze after heat treatment increases significantly. This is because the melt will degrade under the action of high temperature and strong shear force after passing through the melt extruder, resulting in a large amount of low molecular weight doped in the melt. Some of these low molecular weights continue to degrade and carbonize into black or brown coke materials in the subsequent metering extruder and die head, resulting in too many coke material defects on the high temperature resistant polyester film; in addition, due to the thermal degradation and oxygen degradation that occur during the preparation process, the high temperature resistant polyester film will also contain a large number of low molecular weights. These low molecular weights will slowly migrate to the surface of the film due to thermal motion in the high temperature resistant polyester film, and the higher the temperature, the faster the migration speed. The low molecular weights that migrate to the surface of the film will also condense into frost-like white powder, thereby increasing the haze value of the film.

[0076] Example 2

[0077] A method for preparing a high temperature resistant and low precipitation polyester film, comprising the following steps:

[0078] (1) Preparation of raw materials;

[0079] Film-grade polyester chips: The manufacturer is Sinopec Yizheng Chemical Fiber Co., Ltd., the brand is FG604, and the intrinsic viscosity is 0.68dL / g;

[0080] Silica masterbatch slices: The silica particle content in the silica masterbatch slices is 3000ppm;

[0081] (2) preparing polyester raw materials;

[0082] The film-grade polyester chips and the silica masterbatch chips are mixed evenly in a mass ratio of 9:1 to obtain a polyester raw material;

[0083] The content of low molecular weight polyester with a molecular weight below 12,000 in the obtained polyester raw material is 0.3 wt%;

[0084] (3) boiling the polyester raw material obtained in step (2) at 173° C. for 5 min in a fluidized bed to fully crystallize it, then performing dust removal, and then drying it in a drying tower at 169° C. in a pure nitrogen atmosphere for 5.5 h, and then conveying it to a melt extruder through a buffer tank and a pipeline in a pure nitrogen atmosphere at 169° C., and then passing through the melt extruder and filtering it in a coarse filter; wherein the melt extrusion temperature is 280° C., and the filtration accuracy of the coarse filter is 20 μm;

[0085] (4) The polyester melt after coarse filtration first enters a devolatilization device for devolatilization for 7 minutes, and then enters a metering extruder and a fine filter in sequence. The polyester melt after fine filtration enters a die head through a melt pipe, and after being extruded from the die head, it passes through a casting roller and is cooled to 25° C. to form a non-oriented thick sheet; wherein the vacuum degree in the devolatilization device is -75 kPa, the temperature in the devolatilization device is 280° C., and the filtration accuracy of the fine filter is 10 μm;

[0086] like Figure 1 As shown, the devolatilization device used above includes a shell, a screw, an electric field generating device and three star-shaped rotors;

[0087] The shell is made of boron nitride, and the roughness Rz of the inner surface of the shell is 0.8μm;

[0088] The shell is a double-layer structure, with a heat-conducting oil interlayer between the double layers for heating and heat preservation of the device. An air extraction port is provided at the upper end of the shell, a feed port is provided at one side of the upper part, and a feeding port is provided at the side opposite to the feed port at the bottom. The feeding port is connected to the screw cavity of the metering extruder as a whole and is used to place the screw.

[0089] The left section of the screw passes through the feed port and is installed on the bottom side wall of the housing, and the right section is installed in the screw cavity of the metering extruder;

[0090] The electric field generating device comprises an upper plate-shaped electrode, a lower plate-shaped electrode and a high voltage generator, wherein the upper plate-shaped electrode and the lower plate-shaped electrode are respectively installed directly above and directly below the shell, the upper plate-shaped electrode is connected to the positive electrode of the high voltage generator through the upper plate-shaped electrode wire, and the lower plate-shaped electrode is connected to the negative electrode of the high voltage generator through the lower plate-shaped electrode wire;

[0091] The surface of the upper plate-shaped electrode is coated with an upper plate-shaped electrode protective layer, and the surface of the lower plate-shaped electrode is coated with a lower plate-shaped electrode protective layer;

[0092] The upper plate electrode and the lower plate electrode are made of the same material, stainless steel or aluminum alloy;

[0093] The three star-shaped rotors are installed in the housing from top to bottom and are fixed to the inner walls of the housing on both sides opposite to each other through support rods. The length direction of the support rods is perpendicular to the length direction of the screw. Any two adjacent star-shaped rotors are arranged in a staggered manner in the vertical direction.

[0094] The material of the star rotor is boron nitride, and the surface roughness Rz of the star rotor is 0.2μm;

[0095] (5) The thick sheet obtained in step (4) is heated to 90° C. by a longitudinal preheating roller and then enters a far-infrared longitudinal stretching system to form a unidirectional sheet. The unidirectional sheet then enters a transverse stretching system, is heated to 100° C. in a preheating section, and then enters a stretching section for transverse stretching. The transversely stretched film is cooled to 50° C. after heat setting, and then is pulled. During the pulling process, the temperature drops to 25° C. and then rolled into a large shaft product. Finally, it is cut into specified specifications by a slitting machine to obtain a high-temperature resistant and low-precipitation polyester film; wherein the longitudinal stretching ratio is 3.8 times, the longitudinal stretching temperature is 180° C., the transverse stretching ratio is 3 times, the transverse stretching temperature is 120° C., and the heat setting temperature is 235° C.;

[0096] The thickness of the finally obtained high temperature resistant low precipitation polyester film is 50μm; the content of low molecular weight below 12000 in the high temperature resistant low precipitation polyester film is 0.18wt‰; 2 There are 8 char point defects; the haze of the high temperature resistant low precipitation polyester film is 3.8%, and the haze of the high temperature resistant low precipitation polyester film increases by 0.4% after being treated at 150°C for 60 minutes.

[0097] Example 3

[0098] A method for preparing a high temperature resistant and low precipitation polyester film, comprising the following steps:

[0099] (1) Preparation of raw materials;

[0100] Film-grade polyester chips: The manufacturer is Sinopec Yizheng Chemical Fiber Co., Ltd., the brand is FG604, and the intrinsic viscosity is 0.66dL / g;

[0101] Silica masterbatch slices: The silica particle content in the silica masterbatch slices is 3000ppm;

[0102] (2) preparing polyester raw materials;

[0103] The film-grade polyester chips and the silica masterbatch chips are mixed evenly in a mass ratio of 9:1 to obtain a polyester raw material;

[0104] The content of low molecular weight polyester with a molecular weight below 12,000 in the obtained polyester raw material is 0.3 wt%;

[0105] (3) boiling the polyester raw material obtained in step (2) at 175° C. for 5 min in a fluidized bed to fully crystallize it, then performing dust removal, and then drying it in a drying tower at 165° C. in a pure nitrogen atmosphere for 6 h, and then conveying it to a melt extruder through a buffer tank and a pipeline in a pure nitrogen atmosphere at 165° C., and then passing through the melt extruder and filtering it in a coarse filter; wherein the melt extrusion temperature is 275° C., and the filtration accuracy of the coarse filter is 20 μm;

[0106] (4) The polyester melt after coarse filtration first enters a devolatilization device for devolatilization for 6 minutes, and then enters a metering extruder and a fine filter in sequence. The polyester melt after fine filtration enters a die head through a melt pipe, and after being extruded from the die head, it passes through a casting roller and is cooled to 40° C. to form a non-oriented thick sheet; wherein the vacuum degree in the devolatilization device is -78 kPa, the temperature in the devolatilization device is 280° C., and the filtration accuracy of the fine filter is 10 μm;

[0107] like Figure 1 As shown, the devolatilization device used above includes a shell, a screw, an electric field generating device and three star-shaped rotors;

[0108] The shell is made of zirconium oxide, and the roughness Rz of the inner surface of the shell is 0.8 μm;

[0109] The shell is a double-layer structure, with a heat-conducting oil interlayer between the double layers for heating and heat preservation of the device. An air extraction port is provided at the upper end of the shell, a feed port is provided at one side of the upper part, and a feeding port is provided at the side opposite to the feed port at the bottom. The feeding port is connected to the screw cavity of the metering extruder as a whole and is used to place the screw.

[0110] The left section of the screw passes through the feed port and is installed on the bottom side wall of the housing, and the right section is installed in the screw cavity of the metering extruder;

[0111] The electric field generating device comprises an upper plate-shaped electrode, a lower plate-shaped electrode and a high voltage generator, wherein the upper plate-shaped electrode and the lower plate-shaped electrode are respectively installed directly above and directly below the shell, the upper plate-shaped electrode is connected to the positive electrode of the high voltage generator through the upper plate-shaped electrode wire, and the lower plate-shaped electrode is connected to the negative electrode of the high voltage generator through the lower plate-shaped electrode wire;

[0112] The surface of the upper plate-shaped electrode is coated with an upper plate-shaped electrode protective layer, and the surface of the lower plate-shaped electrode is coated with a lower plate-shaped electrode protective layer;

[0113] The upper plate electrode and the lower plate electrode are made of the same material, stainless steel or aluminum alloy;

[0114] The three star-shaped rotors are installed in the housing from top to bottom and are fixed to the inner walls of the housing on both sides opposite to each other through support rods. The length direction of the support rods is perpendicular to the length direction of the screw. Any two adjacent star-shaped rotors are arranged in a staggered manner in the vertical direction.

[0115] The material of the star rotor is boron nitride, and the surface roughness Rz of the star rotor is 0.2μm;

[0116] (5) The thick sheet obtained in step (4) is heated to 86° C. by a longitudinal preheating roller and then enters a far-infrared longitudinal stretching system to form a unidirectional sheet. The unidirectional sheet then enters a transverse stretching system, is heated to 112° C. in a preheating section, and then enters a stretching section for transverse stretching. The transversely stretched film is cooled to 63° C. after heat setting, and then is pulled. During the pulling process, the temperature drops to 25° C. and then is rolled into a large shaft product. Finally, it is cut into specified specifications by a slitting machine to obtain a high-temperature resistant and low-precipitation polyester film; wherein the longitudinal stretching ratio is 3.2 times, the longitudinal stretching temperature is 165° C., the transverse stretching ratio is 3.6 times, the transverse stretching temperature is 131° C., and the heat setting temperature is 250° C.;

[0117] The thickness of the finally obtained high temperature resistant low precipitation polyester film is 50μm; the content of low molecular weight below 12000 in the high temperature resistant low precipitation polyester film is 0.19wt‰; 2 There are 4 char point defects; the haze of the high temperature resistant low precipitation polyester film is 3.5%, and the haze of the high temperature resistant low precipitation polyester film increases by 0.5% after being treated at 150°C for 60 minutes.

[0118] Example 4

[0119] A method for preparing a high temperature resistant and low precipitation polyester film, comprising the following steps:

[0120] (1) Preparation of raw materials;

[0121] Film-grade polyester chips: The manufacturer is Sinopec Yizheng Chemical Fiber Co., Ltd., the brand is FG604, and the intrinsic viscosity is 0.64dL / g;

[0122] Silica masterbatch slices: The silica particle content in the silica masterbatch slices is 3000ppm;

[0123] (2) preparing polyester raw materials;

[0124] The film-grade polyester chips and the silica masterbatch chips are mixed evenly in a mass ratio of 9:1 to obtain a polyester raw material;

[0125] The content of low molecular weight polyester with a molecular weight below 12,000 in the obtained polyester raw material is 0.3 wt%;

[0126] (3) boiling the polyester raw material obtained in step (2) at 175° C. for 5 min in a fluidized bed to fully crystallize it, then performing dust removal, and then drying it in a drying tower at 170° C. in a pure nitrogen atmosphere for 5 h, then conveying it to a melt extruder through a buffer tank and a pipeline in a pure nitrogen atmosphere at 170° C., and then filtering it through a coarse filter after extrusion by the melt extruder; wherein the melt extrusion temperature is 278° C., and the filtration accuracy of the coarse filter is 20 μm;

[0127] (4) The polyester melt after coarse filtration first enters a devolatilization device for devolatilization for 5 minutes, and then enters a metering extruder and a fine filter in sequence. The polyester melt after fine filtration enters a die head through a melt pipe, and after being extruded from the die head, it passes through a casting roller and is cooled to 30° C. to form a non-oriented thick sheet; wherein the vacuum degree in the devolatilization device is -72 kPa, the temperature in the devolatilization device is 280° C., and the filtration accuracy of the fine filter is 10 μm;

[0128] like Figure 1 As shown, the devolatilization device used above includes a shell, a screw, an electric field generating device and three star-shaped rotors;

[0129] The shell is made of boron nitride, and the roughness Rz of the inner surface of the shell is 1 μm;

[0130] The shell is a double-layer structure, with a heat-conducting oil interlayer between the double layers for heating and heat preservation of the device. An air extraction port is provided at the upper end of the shell, a feed port is provided at one side of the upper part, and a feeding port is provided at the side opposite to the feed port at the bottom. The feeding port is connected to the screw cavity of the metering extruder as a whole and is used to place the screw.

[0131] The left section of the screw passes through the feed port and is installed on the bottom side wall of the housing, and the right section is installed in the screw cavity of the metering extruder;

[0132] The electric field generating device comprises an upper plate-shaped electrode, a lower plate-shaped electrode and a high voltage generator, wherein the upper plate-shaped electrode and the lower plate-shaped electrode are respectively installed directly above and directly below the shell, the upper plate-shaped electrode is connected to the positive electrode of the high voltage generator through the upper plate-shaped electrode wire, and the lower plate-shaped electrode is connected to the negative electrode of the high voltage generator through the lower plate-shaped electrode wire;

[0133] The surface of the upper plate-shaped electrode is coated with an upper plate-shaped electrode protective layer, and the surface of the lower plate-shaped electrode is coated with a lower plate-shaped electrode protective layer;

[0134] The upper plate electrode and the lower plate electrode are made of the same material, stainless steel or aluminum alloy;

[0135] The three star-shaped rotors are installed in the housing from top to bottom and are fixed to the inner walls of the housing on both sides opposite to each other through support rods. The length direction of the support rods is perpendicular to the length direction of the screw. Any two adjacent star-shaped rotors are arranged in a staggered manner in the vertical direction.

[0136] The material of the star rotor is zirconia, and the surface roughness Rz of the star rotor is 0.3μm;

[0137] (5) The thick sheet obtained in step (4) is heated to 85° C. by a longitudinal preheating roller and then enters a far-infrared longitudinal stretching system to form a unidirectional sheet. The unidirectional sheet then enters a transverse stretching system, is heated to 115° C. in a preheating section, and then enters a stretching section for transverse stretching. The transversely stretched film is cooled to 55° C. after heat setting, and then is pulled. During the pulling process, the temperature drops to 25° C. and then is rolled into a large shaft product. Finally, it is cut into specified specifications by a slitting machine to obtain a high-temperature resistant and low-precipitation polyester film; wherein the longitudinal stretching multiple is 3 times, the longitudinal stretching temperature is 170° C., the transverse stretching multiple is 3.3 times, the transverse stretching temperature is 125° C., and the heat setting temperature is 238° C.;

[0138] The thickness of the finally obtained high temperature resistant low precipitation polyester film is 50μm; the content of low molecular weight below 12000 in the high temperature resistant low precipitation polyester film is 0.18wt‰; 2 There are 9 char point defects; the haze of the high temperature resistant low precipitation polyester film is 3.6%, and the haze of the high temperature resistant low precipitation polyester film increases by 0.4% after being treated at 150°C for 60 minutes.

[0139] Example 5

[0140] A method for preparing a high temperature resistant and low precipitation polyester film, comprising the following steps:

[0141] (1) Preparation of raw materials;

[0142] Film-grade polyester chips: The manufacturer is Sinopec Yizheng Chemical Fiber Co., Ltd., the brand is FG604, and the intrinsic viscosity is 0.66dL / g;

[0143] Silica masterbatch slices: The silica particle content in the silica masterbatch slices is 3000ppm;

[0144] (2) preparing polyester raw materials;

[0145] The film-grade polyester chips and the silica masterbatch chips are mixed evenly in a mass ratio of 9:1 to obtain a polyester raw material;

[0146] The content of low molecular weight polyester with a molecular weight below 12,000 in the obtained polyester raw material is 0.3 wt%;

[0147] (3) boiling the polyester raw material obtained in step (2) at 170° C. for 5 min in a fluidized bed to fully crystallize it, then performing dust removal, and then drying it in a drying tower at 175° C. in a pure nitrogen atmosphere for 5.5 h, and then conveying it to a melt extruder through a buffer tank and a pipeline in a pure nitrogen atmosphere at 175° C., and then passing through the melt extruder and filtering it in a coarse filter; wherein the melt extrusion temperature is 280° C., and the filtration accuracy of the coarse filter is 20 μm;

[0148] (4) The polyester melt after coarse filtration first enters a devolatilization device for devolatilization for 6 minutes, and then enters a metering extruder and a fine filter in sequence. The polyester melt after fine filtration enters a die head through a melt pipe, and after being extruded from the die head, it passes through a casting roller and is cooled to 28° C. to form a non-oriented thick sheet; wherein the vacuum degree in the devolatilization device is -70 kPa, the temperature in the devolatilization device is 283° C., and the filtration accuracy of the fine filter is 10 μm;

[0149] like Figure 1 As shown, the devolatilization device used above includes a shell, a screw, an electric field generating device and three star-shaped rotors;

[0150] The shell is made of zirconium oxide, and the roughness Rz of the inner surface of the shell is 1 μm;

[0151] The shell is a double-layer structure, with a heat-conducting oil interlayer between the double layers for heating and heat preservation of the device. An air extraction port is provided at the upper end of the shell, a feed port is provided at one side of the upper part, and a feeding port is provided at the side opposite to the feed port at the bottom. The feeding port is connected to the screw cavity of the metering extruder as a whole and is used to place the screw.

[0152] The left section of the screw passes through the feed port and is installed on the bottom side wall of the housing, and the right section is installed in the screw cavity of the metering extruder;

[0153] The electric field generating device comprises an upper plate-shaped electrode, a lower plate-shaped electrode and a high voltage generator, wherein the upper plate-shaped electrode and the lower plate-shaped electrode are respectively installed directly above and directly below the shell, the upper plate-shaped electrode is connected to the positive electrode of the high voltage generator through the upper plate-shaped electrode wire, and the lower plate-shaped electrode is connected to the negative electrode of the high voltage generator through the lower plate-shaped electrode wire;

[0154] The surface of the upper plate-shaped electrode is coated with an upper plate-shaped electrode protective layer, and the surface of the lower plate-shaped electrode is coated with a lower plate-shaped electrode protective layer;

[0155] The upper plate electrode and the lower plate electrode are made of the same material, stainless steel or aluminum alloy;

[0156] The three star-shaped rotors are installed in the housing from top to bottom and are fixed to the inner walls of the housing on both sides opposite to each other through support rods. The length direction of the support rods is perpendicular to the length direction of the screw. Any two adjacent star-shaped rotors are arranged in a staggered manner in the vertical direction.

[0157] The material of the star rotor is boron nitride, and the surface roughness Rz of the star rotor is 0.3μm;

[0158] (5) The thick sheet obtained in step (4) is heated to 82° C. by a longitudinal preheating roller and then enters a far-infrared longitudinal stretching system to form a unidirectional sheet. The unidirectional sheet then enters a transverse stretching system, is heated to 110° C. in a preheating section, and then enters a stretching section for transverse stretching. The transversely stretched film is cooled to 60° C. after heat setting, and then is pulled. During the pulling process, the temperature drops to 25° C. and then is rolled into a large shaft product. Finally, it is cut into specified specifications by a slitting machine to obtain a high-temperature resistant and low-precipitation polyester film; wherein the longitudinal stretching ratio is 3.5 times, the longitudinal stretching temperature is 158° C., the transverse stretching ratio is 3.5 times, the transverse stretching temperature is 127° C., and the heat setting temperature is 243° C.;

[0159] The thickness of the finally obtained high temperature resistant low precipitation polyester film is 50μm; the content of low molecular weight below 12000 in the high temperature resistant low precipitation polyester film is 0.19wt‰; 2 There are 8 char point defects; the haze of the high temperature resistant low precipitation polyester film is 3.2%, and the haze of the high temperature resistant low precipitation polyester film increases by 0.4% after being treated at 150°C for 60 minutes.

[0160] Example 6

[0161] A method for preparing a high temperature resistant and low precipitation polyester film, comprising the following steps:

[0162] (1) Preparation of raw materials;

[0163] Film-grade polyester chips: The manufacturer is Sinopec Yizheng Chemical Fiber Co., Ltd., the brand is FG604, and the intrinsic viscosity is 0.65dL / g;

[0164] Silica masterbatch slices: The silica particle content in the silica masterbatch slices is 3000ppm;

[0165] (2) preparing polyester raw materials;

[0166] The film-grade polyester chips and the silica masterbatch chips are mixed evenly in a mass ratio of 9:1 to obtain a polyester raw material;

[0167] The content of low molecular weight polyester with a molecular weight below 12,000 in the obtained polyester raw material is 0.3 wt%;

[0168] (3) boiling the polyester raw material obtained in step (2) at 172° C. for 5 min in a fluidized bed to fully crystallize it, then performing dust removal, and then drying it in a drying tower at 165° C. in a pure nitrogen atmosphere for 6 h, and then conveying it to a melt extruder through a buffer tank and a pipeline in a pure nitrogen atmosphere at 175° C., and then passing through the melt extruder and filtering it in a coarse filter; wherein the melt extrusion temperature is 283° C., and the filtration accuracy of the coarse filter is 20 μm;

[0169] (4) The polyester melt after coarse filtration first enters a devolatilization device for devolatilization for 6 minutes, and then enters a metering extruder and a fine filter in sequence. The polyester melt after fine filtration enters a die head through a melt pipe, and after being extruded from the die head, it passes through a casting roller and is cooled to 30° C. to form a non-oriented thick sheet; wherein the vacuum degree in the devolatilization device is -72 kPa, the temperature in the devolatilization device is 285° C., and the filtration accuracy of the fine filter is 10 μm;

[0170] like Figure 1 As shown, the devolatilization device used above includes a shell, a screw, an electric field generating device and three star-shaped rotors;

[0171] The shell is made of boron nitride, and the roughness Rz of the inner surface of the shell is 0.8μm;

[0172] The shell is a double-layer structure, with a heat-conducting oil interlayer between the double layers for heating and heat preservation of the device. An air extraction port is provided at the upper end of the shell, a feed port is provided at one side of the upper part, and a feeding port is provided at the side opposite to the feed port at the bottom. The feeding port is connected to the screw cavity of the metering extruder as a whole and is used to place the screw.

[0173] The left section of the screw passes through the feed port and is installed on the bottom side wall of the housing, and the right section is installed in the screw cavity of the metering extruder;

[0174] The electric field generating device comprises an upper plate-shaped electrode, a lower plate-shaped electrode and a high voltage generator, wherein the upper plate-shaped electrode and the lower plate-shaped electrode are respectively installed directly above and directly below the shell, the upper plate-shaped electrode is connected to the positive electrode of the high voltage generator through the upper plate-shaped electrode wire, and the lower plate-shaped electrode is connected to the negative electrode of the high voltage generator through the lower plate-shaped electrode wire;

[0175] The surface of the upper plate-shaped electrode is coated with an upper plate-shaped electrode protective layer, and the surface of the lower plate-shaped electrode is coated with a lower plate-shaped electrode protective layer;

[0176] The upper plate electrode and the lower plate electrode are made of the same material, stainless steel or aluminum alloy;

[0177] The three star-shaped rotors are installed in the housing from top to bottom and are fixed to the inner walls of the housing on both sides opposite to each other through support rods. The length direction of the support rods is perpendicular to the length direction of the screw. Any two adjacent star-shaped rotors are arranged in a staggered manner in the vertical direction.

[0178] The material of the star rotor is boron nitride, and the surface roughness Rz of the star rotor is 0.2μm;

[0179] (5) The thick sheet obtained in step (4) is heated to 87° C. by a longitudinal preheating roller and then enters a far-infrared longitudinal stretching system to form a unidirectional sheet. The unidirectional sheet then enters a transverse stretching system, is heated to 108° C. in a preheating section, and then enters a stretching section for transverse stretching. The transversely stretched film is cooled to 65° C. after heat setting, and then is pulled. During the pulling process, the temperature drops to 25° C. and then is rolled into a large shaft product. Finally, it is cut into specified specifications by a slitting machine to obtain a high-temperature resistant and low-precipitation polyester film; wherein the longitudinal stretching ratio is 3.3 times, the longitudinal stretching temperature is 162° C., the transverse stretching ratio is 3.2 times, the transverse stretching temperature is 130° C., and the heat setting temperature is 230° C.;

[0180] The thickness of the finally obtained high temperature resistant low precipitation polyester film is 50μm; the content of low molecular weight below 12000 in the high temperature resistant low precipitation polyester film is 0.2wt‰; 2 There are 6 char point defects; the haze of the high temperature resistant low precipitation polyester film is 3.4%, and the haze of the high temperature resistant low precipitation polyester film increases by 0.3% after being treated at 150°C for 60 minutes.

[0181] Example 7

[0182] A method for preparing a high temperature resistant and low precipitation polyester film, comprising the following steps:

[0183] (1) Preparation of raw materials;

[0184] Film-grade polyester chips: The manufacturer is Sinopec Yizheng Chemical Fiber Co., Ltd., the brand is FG604, and the intrinsic viscosity is 0.67dL / g;

[0185] Silica masterbatch slices: The silica particle content in the silica masterbatch slices is 3000ppm;

[0186] (2) preparing polyester raw materials;

[0187] The film-grade polyester chips and the silica masterbatch chips are mixed evenly in a mass ratio of 9:1 to obtain a polyester raw material;

[0188] The content of low molecular weight polyester with a molecular weight below 12,000 in the obtained polyester raw material is 0.3 wt%;

[0189] (3) boiling the polyester raw material obtained in step (2) at 173° C. for 5 min in a fluidized bed to fully crystallize it, then performing dust removal, and then drying it in a drying tower at 173° C. in a pure nitrogen atmosphere for 6 h, and then conveying it to a melt extruder through a buffer tank and a pipeline in a pure nitrogen atmosphere at 165° C., and then filtering it in a coarse filter after extrusion by the melt extruder; wherein the melt extrusion temperature is 285° C., and the filtration accuracy of the coarse filter is 20 μm;

[0190] (4) The polyester melt after coarse filtration first enters a devolatilization device for devolatilization for 5 minutes, and then enters a metering extruder and a fine filter in sequence. The polyester melt after fine filtration enters a die head through a melt pipe, and after being extruded from the die head, it passes through a casting roller and is cooled to 32° C. to form a non-oriented thick sheet; wherein the vacuum degree in the devolatilization device is -73 kPa, the temperature in the devolatilization device is 285° C., and the filtration accuracy of the fine filter is 10 μm;

[0191] like Figure 1 As shown, the devolatilization device used above includes a shell, a screw, an electric field generating device and three star-shaped rotors;

[0192] The shell is made of zirconium oxide, and the roughness Rz of the inner surface of the shell is 0.8 μm;

[0193] The shell is a double-layer structure, with a heat-conducting oil interlayer between the double layers for heating and heat preservation of the device. An air extraction port is provided at the upper end of the shell, a feed port is provided at one side of the upper part, and a feeding port is provided at the side opposite to the feed port at the bottom. The feeding port is connected to the screw cavity of the metering extruder as a whole and is used to place the screw.

[0194] The left section of the screw passes through the feed port and is installed on the bottom side wall of the housing, and the right section is installed in the screw cavity of the metering extruder;

[0195] The electric field generating device comprises an upper plate-shaped electrode, a lower plate-shaped electrode and a high voltage generator, wherein the upper plate-shaped electrode and the lower plate-shaped electrode are respectively installed directly above and directly below the shell, the upper plate-shaped electrode is connected to the positive electrode of the high voltage generator through the upper plate-shaped electrode wire, and the lower plate-shaped electrode is connected to the negative electrode of the high voltage generator through the lower plate-shaped electrode wire;

[0196] The surface of the upper plate-shaped electrode is coated with an upper plate-shaped electrode protective layer, and the surface of the lower plate-shaped electrode is coated with a lower plate-shaped electrode protective layer;

[0197] The upper plate electrode and the lower plate electrode are made of the same material, stainless steel or aluminum alloy;

[0198] The three star-shaped rotors are installed in the housing from top to bottom and are fixed to the inner walls of the housing on both sides opposite to each other through support rods. The length direction of the support rods is perpendicular to the length direction of the screw. Any two adjacent star-shaped rotors are arranged in a staggered manner in the vertical direction.

[0199] The material of the star rotor is zirconia, and the surface roughness Rz of the star rotor is 0.3μm;

[0200] (5) The thick sheet obtained in step (4) is heated to 85° C. by a longitudinal preheating roller and then enters a far-infrared longitudinal stretching system to form a unidirectional sheet. The unidirectional sheet then enters a transverse stretching system, is heated to 118° C. in a preheating section, and then enters a stretching section for transverse stretching. The transversely stretched film is cooled to 52° C. after heat setting, and then is pulled. During the pulling process, the temperature drops to 25° C. and then is rolled into a large shaft product. Finally, it is cut into specified specifications by a slitting machine to obtain a high-temperature resistant and low-precipitation polyester film; wherein the longitudinal stretching ratio is 3.4 times, the longitudinal stretching temperature is 175° C., the transverse stretching ratio is 3.8 times, the transverse stretching temperature is 135° C., and the heat setting temperature is 230° C.;

[0201] The thickness of the finally obtained high temperature resistant low precipitation polyester film is 50μm; the content of low molecular weight below 12000 in the high temperature resistant low precipitation polyester film is 0.18wt‰; 2 There are 8 char point defects; the haze of the high temperature resistant low precipitation polyester film is 3.5%, and the haze of the high temperature resistant low precipitation polyester film increases by 0.4% after being treated at 150°C for 60 minutes.

[0202] Example 8

[0203] A method for preparing a high temperature resistant and low precipitation polyester film, comprising the following steps:

[0204] (1) Preparation of raw materials;

[0205] Film-grade polyester chips: The manufacturer is Sinopec Yizheng Chemical Fiber Co., Ltd., the brand is FG604, and the intrinsic viscosity is 0.68dL / g;

[0206] Silica masterbatch slices: The silica particle content in the silica masterbatch slices is 3000ppm;

[0207] (2) preparing polyester raw materials;

[0208] The film-grade polyester chips and the silica masterbatch chips are mixed evenly in a mass ratio of 9:1 to obtain a polyester raw material;

[0209] The content of low molecular weight polyester with a molecular weight below 12,000 in the obtained polyester raw material is 0.3 wt%;

[0210] (3) boiling the polyester raw material obtained in step (2) at 175° C. for 5 min in a fluidized bed to fully crystallize it, then performing dust removal, and then drying it in a drying tower at 168° C. in a pure nitrogen atmosphere for 5.5 h, and then conveying it to a melt extruder through a buffer tank and a pipeline in a pure nitrogen atmosphere at 170° C., and then passing through the melt extruder and filtering it in a coarse filter; wherein the melt extrusion temperature is 280° C., and the filtration accuracy of the coarse filter is 20 μm;

[0211] (4) The polyester melt after coarse filtration first enters a devolatilization device for devolatilization for 5 minutes, and then enters a metering extruder and a fine filter in sequence. The polyester melt after fine filtration enters a die head through a melt pipe, and after being extruded from the die head, it passes through a casting roller and is cooled to 30° C. to form a non-oriented thick sheet; wherein the vacuum degree in the devolatilization device is -70 kPa, the temperature in the devolatilization device is 280° C., and the filtration accuracy of the fine filter is 10 μm;

[0212] like Figure 1 As shown, the devolatilization device used above includes a shell, a screw, an electric field generating device and three star-shaped rotors;

[0213] The shell is made of boron nitride, and the roughness Rz of the inner surface of the shell is 0.8μm;

[0214] The shell is a double-layer structure, with a heat-conducting oil interlayer between the double layers for heating and heat preservation of the device. An air extraction port is provided at the upper end of the shell, a feed port is provided at one side of the upper part, and a feeding port is provided at the side opposite to the feed port at the bottom. The feeding port is connected to the screw cavity of the metering extruder as a whole and is used to place the screw.

[0215] The left section of the screw passes through the feed port and is installed on the bottom side wall of the housing, and the right section is installed in the screw cavity of the metering extruder;

[0216] The electric field generating device comprises an upper plate-shaped electrode, a lower plate-shaped electrode and a high voltage generator, wherein the upper plate-shaped electrode and the lower plate-shaped electrode are respectively installed directly above and directly below the shell, the upper plate-shaped electrode is connected to the positive electrode of the high voltage generator through the upper plate-shaped electrode wire, and the lower plate-shaped electrode is connected to the negative electrode of the high voltage generator through the lower plate-shaped electrode wire;

[0217] The surface of the upper plate-shaped electrode is coated with an upper plate-shaped electrode protective layer, and the surface of the lower plate-shaped electrode is coated with a lower plate-shaped electrode protective layer;

[0218] The upper plate electrode and the lower plate electrode are made of the same material, stainless steel or aluminum alloy;

[0219] The three star-shaped rotors are installed in the housing from top to bottom and are fixed to the inner walls of the housing on both sides opposite to each other through support rods. The length direction of the support rods is perpendicular to the length direction of the screw. Any two adjacent star-shaped rotors are arranged in a staggered manner in the vertical direction.

[0220] The material of the star rotor is zirconia, and the surface roughness Rz of the star rotor is 0.3μm;

[0221] (5) The thick sheet obtained in step (4) is heated to 87° C. by a longitudinal preheating roller and then enters a far-infrared longitudinal stretching system to form a unidirectional sheet. The unidirectional sheet then enters a transverse stretching system, is heated to 120° C. in a preheating section, and then enters a stretching section for transverse stretching. The transversely stretched film is cooled to 60° C. after heat setting, and then is pulled. During the pulling process, the temperature drops to 25° C. and then is rolled into a large shaft product. Finally, it is cut into specified specifications by a slitting machine to obtain a high-temperature resistant and low-precipitation polyester film; wherein the longitudinal stretching ratio is 3.2 times, the longitudinal stretching temperature is 180° C., the transverse stretching ratio is 3.6 times, the transverse stretching temperature is 125° C., and the heat setting temperature is 242° C.;

[0222] The thickness of the finally obtained high temperature resistant low precipitation polyester film is 50μm; the content of low molecular weight below 12000 in the high temperature resistant low precipitation polyester film is 0.19wt‰; 2 There are 7 char point defects; the haze of the high temperature resistant low precipitation polyester film is 3.6%, and the haze of the high temperature resistant low precipitation polyester film increases by 0.5% after being treated at 150°C for 60 minutes.

Claims

1. A method for preparing a high temperature resistant and low precipitation polyester film, characterized in that: The polyester raw material is first crystallized, dusted, and dried in sequence, and then melted and extruded by a melt extruder and then enters a coarse filter. The polyester melt after coarse filtration first enters a devolatilization device for devolatilization, and then the devolatilized polyester melt enters a metering extruder and a fine filter in sequence. The polyester melt after fine filtration enters a die head through a melt pipe, and after being extruded from the die head, it is cooled by a casting roller to form a thick sheet, and then the thick sheet is sequentially subjected to the processes of longitudinal stretching, transverse stretching, heat setting, and traction and winding to obtain a high temperature resistant and low precipitation polyester film. The devolatilization device comprises a shell, a screw, an electric field generating device and a plurality of star-shaped rotors; The shell is a double-layer structure, with an air extraction port at the upper end of the shell, a feed port at one side of the upper part, and a feeding port at the side opposite to the feed port at the bottom. The feeding port is connected to the screw cavity of the metering extruder as a whole and is used to place the screw; The left section of the screw passes through the feed port and is installed on the bottom side wall of the housing, and the right section is installed in the screw cavity of the metering extruder; The electric field generating device comprises an upper plate-shaped electrode, a lower plate-shaped electrode and a high voltage generator, wherein the upper plate-shaped electrode and the lower plate-shaped electrode are respectively installed directly above and directly below the shell, the upper plate-shaped electrode is connected to the positive electrode of the high voltage generator through the upper plate-shaped electrode wire, and the lower plate-shaped electrode is connected to the negative electrode of the high voltage generator through the lower plate-shaped electrode wire; A plurality of star-shaped rotors are installed in the shell from top to bottom and are fixed to the inner walls of the shell on both sides opposite to each other through support rods. The length direction of the support rods is perpendicular to the length direction of the screw rods. Any two adjacent star-shaped rotors are staggered in the vertical direction.

2. The method for preparing a high temperature resistant and low precipitation polyester film according to claim 1, characterized in that: The surface of the upper plate-shaped electrode is covered with an upper plate-shaped electrode protection layer, and the surface of the lower plate-shaped electrode is covered with a lower plate-shaped electrode protection layer.

3. The method for preparing a high temperature resistant and low precipitation polyester film according to claim 2, characterized in that: The shell is made of zirconium oxide or boron nitride, and the roughness Rz of the inner surface of the shell is less than 1 μm; The material of the star rotor is zirconium oxide or boron nitride, and the surface roughness Rz of the star rotor is less than 0.3μm; The upper plate electrode and the lower plate electrode are made of the same material, stainless steel or aluminum alloy; The upper plate-shaped electrode protection layer and the lower plate-shaped electrode protection layer are made of the same material, which is plastic, rubber or ceramic.

4. The method for preparing a high temperature resistant and low precipitation polyester film according to claim 1, characterized in that: The polyester raw materials are film-grade polyester chips and silica masterbatch chips, and the mass ratio of film-grade polyester chips to silica masterbatch chips is 9:1; The intrinsic viscosity of film-grade polyester chips is 0.64 to 0.68 dL / g; The silica particle content in the silica masterbatch slices is 3000ppm.

5. The method for preparing a high temperature resistant and low precipitation polyester film according to claim 1, characterized in that: Crystallization refers to boiling treatment at 170-175°C in a fluidized bed for 5 min; Drying refers to drying in a drying tower at 165-175°C in a pure nitrogen atmosphere for 5-6 hours.

6. The method for preparing a high temperature resistant and low precipitation polyester film according to claim 1, characterized in that: The melt extrusion temperature is 275-285°C.

7. The method for preparing a high temperature resistant and low precipitation polyester film according to claim 1, characterized in that: The filtration accuracy of the coarse filter is 20μm, and the filtration accuracy of the fine filter is 10μm.

8. The method for preparing a high temperature resistant and low precipitation polyester film according to claim 1, characterized in that: The vacuum degree in the devolatilization device is below -70 kPa, and the residence time of the polyester melt after coarse filtration in the devolatilization device is more than 5 minutes.

9. The method for preparing a high temperature resistant and low precipitation polyester film according to any one of claims 1 to 8, characterized in that: The content of low molecular weight molecules with a molecular weight below 12000 in the high temperature resistant and low precipitation polyester film is below 0.2wt‰.

10. The method for preparing a high temperature resistant and low precipitation polyester film according to claim 9, characterized in that: High temperature resistant low precipitation polyester film inside every 10000m 2 The number of coke point defects is less than 10.

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