CN115418019B - Preparation method of polyimide film for heat-conducting graphite - Google Patents

Preparation method of polyimide film for heat-conducting graphite Download PDF

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CN115418019B
CN115418019B CN202211229437.3A CN202211229437A CN115418019B CN 115418019 B CN115418019 B CN 115418019B CN 202211229437 A CN202211229437 A CN 202211229437A CN 115418019 B CN115418019 B CN 115418019B
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polyimide
film
conveying
acid resin
support
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CN115418019A (en
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王文静
唐伟
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Zhonghui Ruineng Fengyang New Material Technology Co ltd
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Zhonghui Ruineng Fengyang New Material Technology Co ltd
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C41/00—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor
    • B29C41/24—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor for making articles of indefinite length
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G73/00—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups C08G12/00 - C08G71/00
    • C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
    • C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
    • C08G73/1003—Preparatory processes
    • C08G73/1007—Preparatory processes from tetracarboxylic acids or derivatives and diamines
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G73/00—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups C08G12/00 - C08G71/00
    • C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
    • C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
    • C08G73/1067—Wholly aromatic polyimides, i.e. having both tetracarboxylic and diamino moieties aromatically bound
    • C08G73/1071—Wholly aromatic polyimides containing oxygen in the form of ether bonds in the main chain
    • C—CHEMISTRY; METALLURGY
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    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/18—Manufacture of films or sheets
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    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
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    • C08J2379/00—Characterised by the use of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing nitrogen with or without oxygen, or carbon only, not provided for in groups C08J2361/00 - C08J2377/00
    • C08J2379/04—Polycondensates having nitrogen-containing heterocyclic rings in the main chain; Polyhydrazides; Polyamide acids or similar polyimide precursors
    • C08J2379/08—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract

The invention relates to a preparation method of a polyimide film for heat-conducting graphite, which comprises the following steps of preparing montmorillonite modified dispersion liquid, preparing polyamide acid resin, preparing polyimide gel film and preparing the polyimide film, wherein a tape casting machine is adopted for processing when the polyimide gel film is prepared. The PMDA/ODA-based polyimide film provided by the invention has the advantages that the molecular orientation degree is insufficient due to unreasonable selection of resin and filler, small molecular gas is difficult to overflow to form a foaming effect in the graphitization process, a high-quality heat-conducting graphite film is difficult to prepare, and in addition, in the tape casting process for preparing the graphite film, a scraper is required to be manually adjusted for producing polyimide films with different thicknesses or different widths, the precision is poor, the production precision of the polyimide film is influenced, and the like.

Description

Preparation method of polyimide film for heat-conducting graphite
Technical Field
The invention relates to the field of polyimide films for heat-conducting graphite, in particular to a preparation method of a polyimide film for heat-conducting graphite.
Background
The traditional heat dissipation materials are metals with high heat conductivity such as copper, silver and aluminum, but with the increase of the heat productivity of electronic components, the requirements of microelectronic products cannot be met. The graphite flake has the characteristics of high heat dissipation efficiency, small occupied space, light weight, uniform heat conduction along two directions and the like, and can uniformly distribute heat on a two-dimensional plane so as to effectively transfer the heat. Therefore, in recent years, the heat sink has been attracting attention as a heat sink for electronic devices, and has a wide application prospect in the fields of microelectronic packaging and integration.
In the last 70 th century, japanese scientists discovered that Polyimide (PI) films were carbonized and graphitized to obtain highly oriented graphite thermal conductive films that were close to single crystal graphite structures. However, the conventional Polyimide (PI) film is difficult to prepare a stable graphite film, and the prepared graphite film has low thermal conductivity, poor mechanical property and bending resistance, and is easy to fall off powder and break in the preparation and use processes. With the spread of 5G communications, there is an increasing need for thermal management materials with excellent properties.
Polyimide itself has excellent properties, and the preparation of graphite films from polyimide is becoming more and more important. A large number of artificial graphite films fired from polyimide are currently used in electronic devices. However, the heat conduction and mechanical properties of the graphite film prepared from the existing PMDA/ODA type polyimide are not ideal, each property of the polyimide graphite film depends on polyimide serving as a raw material, the polyimide film of the traditional PMDA/ODA system has the characteristics of low foaming rate, low film forming rate and poor heat conduction property in the process of firing the graphite film, and the reasons of the fact that the PMDA/ODA-based polyimide film is unreasonable in resin and filler selection is mainly proved by a large number of references and experiments, the molecular orientation degree is insufficient, small molecular gas is difficult to overflow to form a foaming effect in the graphitization process, and the high-quality heat conduction graphite film is difficult to prepare. On this basis, how to regulate the resin structure and film forming process of polyimide to obtain an artificial graphite film excellent in thermal conductivity and mechanical properties is a subject of current urgent study.
Disclosure of Invention
First, the technical problem to be solved
The preparation method of the polyimide film for the heat-conducting graphite can solve the technical problems.
(II) technical scheme
Aiming at the problems of the background technology, the invention aims to provide a preparation method of a polyimide film for heat conduction graphite, and the technical scheme adopted by the invention is as follows:
the preparation method of the polyimide film for the heat-conducting graphite comprises the following steps:
(1) Preparing montmorillonite modified dispersion liquid: adding montmorillonite with different particle diameters subjected to acidification or amination surface treatment into an NMP polar solvent, mixing, and performing ultrasonic dispersion to form uniform montmorillonite modified dispersion;
(2) Preparation of a polyamic acid resin: adding the montmorillonite modified dispersion liquid obtained in the step (1) into a mixed solvent, continuously stirring, then sequentially adding diamine monomer and dianhydride monomer, and performing polycondensation reaction to obtain polyamide acid resin;
(3) Preparation of polyimide gel films: carrying out tape casting on the polyamide acid resin obtained in the step (2) by a tape casting machine, then carrying out high-temperature heating treatment, and obtaining a polyimide gel film after partial imidization;
(4) Preparing a polyimide film: and (3) heating the polyimide gel film obtained in the step (3) at a high temperature, and transversely and longitudinally biaxially stretching to obtain the polyimide film.
Preferably, the montmorillonite in the step (1) is M813515 montmorillonite K-10, the montmorillonite particle size is 50-100nm, and the montmorillonite addition amount is 0.5% -1.5% of the polyimide film mass.
Preferably, the montmorillonite modified dispersion in the step (1) has a solid content of 25%.
Preferably, the mixed solvent in the step (2) is a mixed solvent of Dimethylacetamide (DMAC) and N-methylpyrrolidone (NMP), and the mass ratio is 70:30.
preferably, the diamine monomer in the step (2) is a combination of 4,4 'diaminodiphenyl ether (ODA) and p-Phenylenediamine (PDA), and the molar ratio of the diamine monomer 4,4' diaminodiphenyl ether (ODA) to p-Phenylenediamine (PDA) is 85:15.
preferably, the dianhydride monomer in the step (2) is a combination of pyromellitic dianhydride (PMDA) and 3,3', 4' -biphenyl tetracarboxylic dianhydride (s-BPDA), and the molar ratio of pyromellitic dianhydride (PMDA) to 3,3', 4' -biphenyl tetracarboxylic dianhydride (s-BPDA) is 10:90.
preferably, the molar ratio of diamine monomer to dianhydride monomer in step (2) is 1:1.
Preferably, the high temperature heating treatment in the step (3) is heating at 60 ℃ for 1h,120 ℃ for 0.5h, and 180 ℃ for 0.5h.
Preferably, the partial imines in step (3) have an imidization degree of > 40% and the imidization gives polyimide gel films having a solvent content of < 25%.
The preparation of the polyamic acid film by adopting the casting machine comprises the following steps:
s1, preparing operation: filtering the polyamic acid resin, defoaming the filtered polyamic acid resin, and pouring the defoamed polyamic acid resin into a liquid storage frame through a pouring pipe;
s2, adjusting operation: starting a bidirectional cylinder control and adjustment mechanism to adjust according to the width of the polyimide gel film to be prepared, and synchronously adjusting the width of a discharging pipe to ensure that the discharging width of the discharging pipe corresponds to the prepared polyimide gel film;
s3, placing and conveying: the glass plate used for bearing the polyamide acid resin is placed on a conveying mechanism, the conveying mechanism drives the glass plate to move at a constant speed from front to back, and an adjusting mechanism limits the moving glass plate;
s4, coating and scraping: according to the width of the glass plate and the thickness of the glass plate to be coated with the polyamic acid resin, a scraper mechanism is matched with the opening and closing branched chains, the polyamic acid resin is uniformly coated on the glass plate, and the excessive polyamic acid resin is scraped in the movement of the glass plate;
s5, heat treatment: the glass plate coated with the polyamic acid resin is taken out from the conveying mechanism and then subjected to heating treatment, and the polyamic acid resin on the glass plate is partially imidized to obtain the polyimide gel film.
The casting machine comprises a substrate, wherein an adjusting and conveying device is arranged on the substrate, and a coating device is arranged on the adjusting and conveying device;
the adjusting and conveying device comprises a conveying support arranged on the substrate, conveying mechanisms are arranged on the conveying support, adjusting holes are symmetrically formed in the conveying support, a supporting flat plate is arranged on the conveying support, a bidirectional cylinder is arranged at the lower end of the supporting flat plate, and adjusting mechanisms are symmetrically arranged on the bidirectional cylinder;
the conveying mechanism comprises conveying rollers arranged on the front side and the rear side of the conveying support through bearings, a conveying belt is arranged between the two conveying rollers, the left side of the conveying roller positioned at the front end of the conveying support is connected with a conveying motor through a coupler, the conveying motor is arranged on the conveying support through a motor seat, and the upper end face of the supporting flat plate is attached to the conveying belt;
the adjusting mechanism comprises an adjusting rod arranged on the bidirectional cylinder, the adjusting rod is arranged in an adjusting hole in a sliding mode, a moving hole is formed in the conveying support, a moving rod is arranged in the moving hole in a sliding mode, the moving rod is connected with the adjusting rod through a connecting plate, an adjusting execution plate is arranged on the moving rod, and the lower end face of the adjusting execution plate is attached to the conveying belt;
the coating device comprises a liquid storage frame arranged on the conveying support, a filling pipe is arranged at the upper end of the liquid storage frame, a discharging pipe is arranged at the lower end of the liquid storage frame, a scraper mechanism is arranged on the conveying support, and an opening and closing branched chain is arranged in the discharging pipe;
the scraper mechanism comprises a rotating pipe arranged on the conveying support through a bearing, an installation groove is uniformly formed in the rotating pipe along the circumferential direction of the rotating pipe, a scraper support is arranged in the installation groove in a sliding mode, a reset spring is arranged between the scraper support and the rotating pipe, a supporting rod is arranged on the scraper support, the supporting rod is positioned in the rotating pipe, a scraper plate is arranged on the scraper support, clamping grooves are symmetrically formed in the left side and the right side of the scraper plate, a control motor is arranged at the left end of the conveying support through a motor base, an output shaft of the control motor is connected with the left end of the rotating pipe through a coupler, and an opening structure is arranged at the right end of the rotating pipe.
The control branched chain comprises a control cylinder arranged at the right end of the conveying support, a control support used for extruding the abutting rod is arranged on the control cylinder, the control support is located in the rotary pipe, and the control support is of a Z-shaped structure.
The widths of the scraper plates positioned in the mounting grooves are sequentially increased along the clockwise direction of the rotary pipe.
The shielding grooves are symmetrically formed in the left end and the right end of the conveying support, shielding frames used for shielding the discharging pipe are arranged in the shielding grooves in a sliding mode, the shielding frames are connected with the discharging pipe in a sliding mode, and the shielding frames are fixed on the adjusting execution plate.
The opening and closing branched chain comprises an opening and closing plate arranged in the discharging pipe through a pin shaft, an opening and closing hole is formed in the discharging pipe, an opening and closing frame is slidably arranged in the opening and closing hole, a supporting spring is arranged between the opening and closing frame and the outer wall of the discharging pipe, the opening and closing frame abuts against a cam block, and the cam blocks are symmetrically arranged on the left side and the right side of the rotating pipe.
(III) beneficial effects
1. The introduction of the rigid monomers BPDA and PDA can improve the orientation degree of polyimide molecules, and is beneficial to foaming; meanwhile, the proportion of the BPDA and the PDA is regulated, so that the rapid low-temperature imidization can be realized, the influence of high-temperature imidization thermal disturbance on the molecular orientation is reduced, and the structural orientation of polyimide molecules is improved.
2. The BPDA is introduced to improve the carbon residue after graphitization, improve the free radical density of amorphous carbon, be more beneficial to the conversion of amorphous carbon into crystalline carbon in the high-temperature graphitization process and improve the quality of graphitized materials.
3. The mixed solvent NMP/DMAC with different boiling points is selected, so that desolvation and imidization in the film forming process are facilitated under a specific proportion, the molecular orientation degree is improved, and the foaming capacity is improved.
4. The foaming agent is modified montmorillonite, the montmorillonite is of a layered multi-hollow structure, the function of fixing nitrogen is achieved, the nitrogen content in amorphous carbon in the graphitization process is improved, the amorphous carbon recrystallization process in the graphitization process is facilitated, and the graphite quality is improved.
5. The product is used for firing the graphite film by downstream customers, and the graphite film has higher heat conductivity, mechanical ductility, flexibility and the like, and is an ideal heat dissipation material for terminal electronic products.
6. The curtain coating machine of preparation polyamic acid glued membrane design can carry out automatic regulation to the polyimide film of different width and different thickness, can be according to the quick change mode of actual production demand, can improve the efficiency of producing the polyimide film of different specifications, and accommodation is wide, need not the manual work according to polyimide film adjustment scraper blade, and the width that can adjust the coating of the open and shut branched chain and adjustment mechanism of design in the curtain coating machine in the operation mutually support in addition, has practiced thrift the time of retrieving polyamic acid resin, has improved the availability ratio of polyamic acid resin.
Drawings
FIG. 1 is a process flow diagram of a method for preparing a polyimide film for heat-conducting graphite according to the invention;
FIG. 2 is a schematic view of the structure of the casting machine of the present invention;
FIG. 3 is a cross-sectional view of FIG. 2 of the present invention;
FIG. 4 is an enlarged view of a portion of FIG. 3A in accordance with the present invention;
FIG. 5 is an enlarged view of a portion of the invention at B of FIG. 3;
FIG. 6 is a schematic view of the structure of the invention between the substrate, the conditioning conveyor and the coating device;
FIG. 7 is a cross-sectional view of the regulated delivery device of the present invention;
FIG. 8 is a cross-sectional view of the invention between the feed carrier, discharge tube, scraper mechanism and the opening and closing arm;
fig. 9 is a flowchart of the present invention for preparing a polyamic acid film using a casting machine.
Detailed Description
Example 1:
as shown in fig. 1 to 9, the preparation method of the polyimide film for the heat-conducting graphite comprises the following steps:
(1) Preparing montmorillonite modified dispersion liquid: 50g of acidified montmorillonite, M81351, is mixed with 200g of NMP polar solvent5. Montmorillonite K-10 with particle diameter of 50-100nm and specific surface area of 240 m 2 And (3) carrying out ultrasonic dispersion for 2 hours, wherein the addition amount of the solution is 0.5-1.5% of the mass of the polyimide film in the step (4), so as to form uniform montmorillonite modified dispersion liquid, and the solid content of the montmorillonite modified dispersion liquid is 25%;
(2) Preparation of a polyamic acid resin: under nitrogen atmosphere, dimethylacetamide (DMAC) and N-methylpyrrolidone (NMP) were added as a mixed solvent in a 500mL reactor at a mass ratio of 70:30, 2.2g of the montmorillonite modified dispersion obtained in the step (1) was added to the mixed solvent, the temperature was set to 25 ℃, stirring was continued, 39.0g of 4,4' -diaminodiphenyl ether (ODA) and 0.4g of p-Phenylenediamine (PDA) were added as diamine monomers, and stirring was continued for 30 minutes, after confirming dissolution of the monomers, 5.0g of pyromellitic dianhydride (PMDA) and 60.9g of 3,3', 4' -biphenyl tetracarboxylic dianhydride (s-BPDA) were added as dianhydride monomers, and the final addition was adjusted to give a final viscosity of 150000 to 200000 cps. After the addition is completed, stirring for 1h while maintaining the temperature to polymerize the polyamic acid solution so that the final viscosity is 180000 centipoise, and performing polycondensation reaction to generate polyamic acid resin;
(3) Preparation of polyimide gel films: filtering and defoaming the polyimide resin obtained in the step (2), carrying out tape casting by a tape casting machine, adjusting the thickness of a doctor blade to 500um, coating the polyimide resin on a glass plate by the doctor blade, heating the glass plate at 60 ℃ for 1h, heating the glass plate at 120 ℃ for 0.5h, heating the glass plate at 180 ℃ for 0.5h, partially imidizing the glass plate to obtain a polyimide gel film, wherein the imidization degree is more than 40%, and the solvent content of the polyimide gel film is less than 25% after imidization;
(4) Preparing a polyimide film: fixing the polyimide gel film obtained in the step (3) on a cutting board, fixing four edges, heating at high temperature, heating at 200 ℃ for 5min, heating at 350 ℃ for 3min and heating at 400 ℃ for 3min, and transversely and longitudinally stretching to obtain the polyimide film with the thickness of 50 um.
The preparation of the polyamic acid film by adopting the casting machine comprises the following steps:
s1, preparing operation: filtering the polyamic acid resin, defoaming the filtered polyamic acid resin, and pouring the defoamed polyamic acid resin into the liquid storage frame 41 through a pouring pipe;
s2, adjusting operation: starting a bidirectional cylinder 24 to control an adjusting mechanism 25 to adjust according to the width of the polyamide acid adhesive film to be prepared, and synchronously adjusting the width of a discharging pipe 44 so that the discharging width of the discharging pipe 44 corresponds to the prepared polyimide gel film;
s3, placing and conveying: the glass plate used for bearing the polyamide acid resin is placed on a conveying mechanism 22, the conveying mechanism 22 drives the glass plate to move at a constant speed from front to back, and an adjusting mechanism 25 limits the moving glass plate;
s4, coating and scraping: according to the width of the glass plate and the thickness of the glass plate to be coated with the polyamic acid resin, the scraper mechanism 45 is matched with the opening and closing branched chains 46, the polyamic acid resin is uniformly coated on the glass plate, and the excessive polyamic acid resin is scraped in the movement of the glass plate;
s5, heat treatment: the glass plate coated with the polyamic acid resin is taken out from the conveyor 22 and then subjected to heat treatment, and the polyamic acid resin on the glass plate is partially imidized to obtain a polyimide gel film.
The casting machine comprises a substrate 1, wherein an adjusting and conveying device 2 is arranged on the substrate 1, and a coating device 4 is arranged on the adjusting and conveying device 2;
the polyimide acid resin is injected into the coating device 4, the glass plate is placed on the adjusting and conveying device 2 in operation, the glass plate is driven to move at a constant speed by the adjusting and conveying device 2, the polyimide acid resin is uniformly smeared on the glass plate by the coating device 4, the redundant polyimide acid resin falls onto the adjusting and conveying device 2, and the redundant polyimide acid resin on the adjusting and conveying device 2 is recovered along with the circulating motion of the adjusting and conveying device 2.
The adjusting and conveying device 2 comprises a conveying support 21 arranged on the substrate 1, a conveying mechanism 22 is arranged on the conveying support 21, adjusting holes are symmetrically formed in the conveying support 21, a supporting flat plate 23 is arranged on the conveying support 21, a bidirectional cylinder 24 is arranged at the lower end of the supporting flat plate 23, and an adjusting mechanism 25 is symmetrically arranged on the bidirectional cylinder 24;
the conveying mechanism 22 comprises conveying rollers 221 arranged on the front side and the rear side of the conveying support 21 through bearings, a conveying belt 222 is arranged between the two conveying rollers 221, a conveying motor 223 is connected to the left side of the conveying roller 221 positioned at the front end of the conveying support 21 through a coupler, the conveying motor 223 is installed on the conveying support 21 through a motor seat, and the upper end face of the supporting flat plate 23 is attached to the conveying belt 222;
after the glass plate is placed on the conveying belt 222, the conveying motor 223 is started to drive the conveying roller 221 to rotate, the conveying roller 221 drives the conveying belt 222 to circularly move in the rotating process, and the conveying belt 222 drives the glass plate to uniformly move from front to back in the circulating process.
The adjusting mechanism 25 comprises an adjusting rod 251 mounted on the bidirectional air cylinder 24, the adjusting rod 251 is slidably arranged in an adjusting hole, the conveying bracket 21 is provided with a moving hole, a moving rod 252 is slidably arranged in the moving hole, the moving rod 252 is connected with the adjusting rod 251 through a connecting plate 253, an adjusting executing plate 254 is arranged on the moving rod 252, and the lower end face of the adjusting executing plate 254 is attached to the conveying belt 222;
according to the width of the glass plate to be placed on the conveying belt 222, the bidirectional air cylinder 24 is started, the bidirectional air cylinder 24 drives the adjusting rods 251 on two sides to carry out opposite adjusting operation in the moving process, the adjusting rods 251 drive the adjusting execution plates 254 to carry out synchronous movement in the moving process through the mutual matching between the connecting plates 253 and the moving rods 252, the two adjusting execution plates 254 control the distance between the two adjusting execution plates 254 in the adjusting operation, the adjusting execution plates 254 can be attached to the end face of the glass plate, the adjusting execution plates 254 are provided with balls, the balls are attached to the end face of the glass plate in the operation, the fact that the adjusting execution plates 254 can limit the end face of the glass plate is guaranteed, meanwhile, the conveying belt 222 is not influenced to drive the glass plate to move is guaranteed, and accordingly polyimide acid resin can be evenly smeared on the upper end face of the glass plate in the operation.
The coating device 4 comprises a liquid storage frame 41 arranged on the conveying support 21, a filling pipe is arranged at the upper end of the liquid storage frame 41, a discharging pipe 44 is arranged at the lower end of the liquid storage frame 41, a scraper mechanism 45 is arranged on the conveying support 21, and an opening and closing branched chain 46 is arranged in the discharging pipe 44;
the designed scraper mechanism 45 can be selectively adjusted according to the glass plate driving specification in operation, so that polyimide films with different widths can be produced adaptively, and the designed opening and closing branched chain 46 can reduce the amount of polyimide acid resin falling into the conveying belt 222 in operation, so that the waste of materials is reduced, and the time for recycling the polyimide acid resin is saved.
The scraper mechanism 45 comprises a rotary pipe 451 arranged on the conveying support 21 through a bearing, a mounting groove is uniformly formed in the rotary pipe 451 along the circumferential direction of the rotary pipe 451, a scraper support 452 is arranged in the mounting groove in a sliding mode, a reset spring is arranged between the scraper support 452 and the rotary pipe 451, an abutting rod 453 is arranged on the scraper support 452, the abutting rod 453 is positioned in the rotary pipe 451, a scraper plate 454 is arranged on the scraper support 452, clamping grooves are symmetrically formed in the left side and the right side of the scraper plate 454, a control motor 455 is arranged at the left end of the conveying support 21 through a motor base, an output shaft of the control motor 455 is connected with the left end of the rotary pipe 451 through a coupler, the right end of the rotary pipe 451 is of an opening structure, and a control branched chain 456 is arranged at the right end of the conveying support 21.
After the position of the adjustment performing plate 254 is adjusted, the control motor 455 is started to rotate the rotating pipe 451, and the rotating pipe 451 controls the proper doctor plate 454 to move between the two adjustment performing plates 254 during rotation, the width of the doctor plate 454 is equal to the width of the glass plate to be placed, and then the doctor plate 454 is moved downward by adjusting the gap between the doctor brackets 452 by controlling the branched chain 456, and the distance between the doctor plate 454 and the glass plate is equal to the thickness of the polyimide acid resin to be coated on the glass plate.
The control branched chain 456 comprises a control cylinder 4561 installed at the right end of the conveying support 21, a control support 4562 for extruding the abutting rod 453 is arranged on the control cylinder 4561, the control support 4562 is located in the rotary pipe 451, and the control support 4562 is in a Z-shaped structure.
The control cylinder 4561 is started to drive the control bracket 4562 to carry out telescopic motion in specific operation, the control bracket 4562 extrudes the abutting rod 453 in the process of motion, the abutting rod 453 after extrusion drives the scraper bracket 452 to move downwards, thereby the scraper plate 454 is driven to carry out height adjustment through the scraper bracket 452, the auxiliary limit can be carried out on glass plates with different specifications in specific operation through adopting the technical scheme, thereby polyimide films with different specifications can be produced in operation, in addition, the thickness of polyimide acid resin coated on the glass plates can be controlled, the polyimide films with different sizes and thicknesses can be produced in actual production operation, the application range is wide, manual adjustment is not required, labor force is saved, and meanwhile, the precision of producing polyimide films with different specifications is improved.
The width of the scraper plate 454 in the installation groove increases gradually along the clockwise direction of the rotary tube 451, so that the scraper plate 454 with corresponding specification for glass plates with different widths can cooperate, manual selection of the scraper plate 454 is not needed, the automation degree is high, and the precision of producing polyimide films with different specifications can be improved compared with manual selection or adjustment of the scraper plate 454.
Shielding grooves are symmetrically formed in the left end and the right end of the conveying support 21, shielding frames 211 for shielding the discharging pipe 44 are slidably arranged in the shielding grooves, the shielding frames 211 are slidably connected with the discharging pipe 44, and the shielding frames 211 are fixed on the adjusting execution plate 254;
the adjusting execution plate 254 synchronously drives the shielding frame 211 to move in position in the process of position adjustment, the shielding frame 211 can control and adjust the opening width of the discharging pipe 44 in the process of movement, so that the width of the discharging opening of the discharging pipe 44 corresponds to that of the glass plate, the condition that polyimide acid resin directly falls onto the conveying belt 22 from the discharging pipe 44 is avoided, and the glass plates with various different widths can be adaptively adjusted in operation by adopting the technical scheme.
The opening and closing branched chain 46 comprises an opening and closing plate 461 arranged in the discharging pipe 44 through a pin shaft, an opening and closing hole is formed in the discharging pipe 44, an opening and closing frame 462 is slidably arranged in the opening and closing hole, a supporting spring is arranged between the opening and closing frame 462 and the outer wall of the discharging pipe 44, the opening and closing frame 462 abuts against a cam block 463, and the cam blocks 463 are symmetrically arranged on the left side and the right side of the rotating pipe 451;
when polyimide acid resin is required to be coated on a glass plate in operation, the control motor 455 drives the rotating tube 451 to synchronously control the cam block 463 to adjust, so that the opening and closing frame 462 is abutted against the concave position of the cam block 463, the opening and closing plate 461 at the moment is abutted against the inner wall of the discharging tube 44 under the action of the supporting spring, the discharging tube 44 is in an opening state in the state, the polyimide acid resin can be smoothly discharged from the discharging tube 44 and coated on the glass plate, when the polyimide acid resin is not required to be coated on the glass plate, the motor 455 drives the rotating tube 451 to synchronously control the cam block 463 to adjust, the opening and closing frame 462 is abutted against the convex position of the cam block 463, and the opening and closing plate 461 at the moment is abutted against the inner wall of the other end of the discharging tube 44 under the action of the opening and closing frame 462, the discharging tube 44 at the moment is in a closed state, and the polyimide acid resin cannot be discharged.
Example 2:
as shown in fig. 1 to 9, the preparation method of the polyimide film for the heat-conducting graphite comprises the following steps:
the procedure and method were the same as in example 1 except that the montmorillonite-modified dispersion added in step (2) was 4.4 g.
Comparative example 1:
the preparation method of the polyimide film for the heat-conducting graphite comprises the following steps:
step (1) was removed, and the other methods were the same as in example 1.
Comparative example 2:
the preparation method of the polyimide film for the heat-conducting graphite comprises the following steps:
the procedure of example 1 was repeated except that 39.8g of 4,4' -diaminodiphenyl ether (ODA) was added as the diamine monomer in step (2), and after stirring for 30 minutes, it was confirmed that the monomer was dissolved, 43.4g of pyromellitic dianhydride (PMDA) was added as the dianhydride monomer.
The degree of molecular orientation is evaluated based on the birefringence value of the anisotropic material, the birefringence: the birefringence of the polyimide film was measured using a refractive index and film thickness measuring system (model: 2010 prism) manufactured by Metricon, inc. (the refractive index was measured in TE mode and TM mode using a light source having a wavelength of 594nm at 23 ℃ in the environment of measurement, and the measured "(value of refractive index in TE mode) - (value of refractive index in TM mode)" was used as the birefringence.
Coefficient of thermal diffusion: the measuring instrument is a diffusion heat conduction instrument LFA467 produced by German relaxation-resistant company; the test temperature is room temperature; the test mode is In-Plane; the light spot is 14mm; the shielding gas is nitrogen.
Preparation of artificial graphite film: the method for preparing the artificial graphite film is not limited, and a conventional method is adopted. The polyimide films obtained in examples and comparative example 1 were used as raw materials to obtain corresponding artificial graphite films.
Figure 964718DEST_PATH_IMAGE002

Claims (9)

1. The preparation method of the polyimide film for the heat-conducting graphite comprises the following steps:
(1) Preparing montmorillonite modified dispersion liquid: adding montmorillonite with different particle diameters subjected to acidification or amination surface treatment into an NMP polar solvent, mixing, and performing ultrasonic dispersion to form uniform montmorillonite modified dispersion;
(2) Preparation of a polyamic acid resin: adding the montmorillonite modified dispersion liquid obtained in the step (1) into a mixed solvent, continuously stirring, then sequentially adding diamine monomer and dianhydride monomer, and performing polycondensation reaction to obtain polyamide acid resin;
(3) Preparing a polyamide acid adhesive film: carrying out tape casting treatment on the polyamide acid resin obtained in the step (2) by a tape casting machine, and obtaining a polyimide gel film after partial imidization;
(4) Preparing a polyimide composite film: heating the polyimide gel film obtained in the step (3) at high temperature, and transversely and longitudinally stretching in two directions to obtain a polyimide composite film;
the casting machine comprises a substrate (1), wherein an adjusting and conveying device (2) is arranged on the substrate (1), and a coating device (4) is sequentially arranged on the adjusting and conveying device (2) from front to back;
the adjusting and conveying device (2) comprises a conveying support (21) arranged on the substrate (1), a conveying mechanism (22) is arranged on the conveying support (21), adjusting holes are symmetrically formed in the conveying support (21), a supporting flat plate (23) is arranged on the conveying support (21), a bidirectional cylinder (24) is arranged at the lower end of the supporting flat plate (23), and an adjusting mechanism (25) is symmetrically arranged on the bidirectional cylinder (24);
the coating device (4) comprises a liquid storage frame (41) arranged on the conveying support (21), a filling pipe is arranged at the upper end of the liquid storage frame (41), a discharging pipe (44) is arranged at the lower end of the liquid storage frame (41), a scraper mechanism (45) is arranged on the conveying support (21), and an opening and closing branched chain (46) is arranged in the discharging pipe (44);
the scraper mechanism (45) comprises a rotary pipe (451) arranged on the conveying support (21) through a bearing, mounting grooves are uniformly formed in the rotary pipe (451) along the circumferential direction of the rotary pipe, a scraper support (452) is slidably arranged in the mounting grooves, a reset spring is arranged between the scraper support (452) and the rotary pipe (451), an abutting rod (453) is arranged on the scraper support (452), the abutting rod (453) is positioned in the rotary pipe (451), a scraper plate (454) is arranged on the scraper support (452), clamping grooves are symmetrically formed in the left side and the right side of the scraper plate (454), a control motor (455) is arranged at the left end of the conveying support (21) through a motor cabinet, an output shaft of the control motor (455) is connected with the left end of the rotary pipe (451) through a coupler, the right end of the rotary pipe (451) is of an opening structure, and a control branched chain (456) is arranged at the right end of the conveying support (21);
the control branched chain (456) comprises a control cylinder (4561) arranged at the right end of the conveying support (21), a control support (4562) used for extruding the abutting rod (453) is arranged on the control cylinder (4561), the control support (4562) is positioned in the rotary pipe (451), and the control support (4562) is in a Z-shaped structure;
the opening and closing branched chain (46) comprises an opening and closing plate (461) arranged in the discharging pipe (44) through a pin shaft, an opening and closing hole is formed in the discharging pipe (44), an opening and closing frame (462) is slidably arranged in the opening and closing hole, a supporting spring is arranged between the opening and closing frame (462) and the outer wall of the discharging pipe (44), the opening and closing frame (462) abuts against a cam block (463), and the cam blocks (463) are symmetrically arranged on the left side and the right side of the rotating pipe (451);
the polyimide gel film is prepared by adopting a tape casting machine, and comprises the following steps:
s1, preparing operation: filtering the polyamic acid resin, defoaming the filtered polyamic acid resin, and then pouring the defoamed polyamic acid resin into a liquid storage frame (41) through a pouring pipe;
s2, adjusting operation: starting a bidirectional cylinder (24) to control an adjusting mechanism (25) to adjust according to the width of the polyamide acid adhesive film to be prepared, and synchronously adjusting the width of a discharging pipe (44) to ensure that the discharging width of the discharging pipe (44) corresponds to the prepared polyamide acid adhesive film;
s3, placing and conveying: the glass plate used for bearing the polyamide acid resin is placed on a conveying mechanism (22), the conveying mechanism (22) drives the glass plate to move at a constant speed from front to back, and an adjusting mechanism (25) limits the moving glass plate;
s4, coating and scraping: according to the width of the glass plate and the thickness of the glass plate to be coated with the polyamic acid resin, a scraper mechanism (45) is matched with an opening and closing branched chain (46), the polyamic acid resin is uniformly coated on the glass plate, and the excessive polyamic acid resin is scraped in the movement of the glass plate;
s5, heat treatment: the glass plate coated with the polyamic acid resin is taken out from the conveying mechanism (22) and then subjected to heating treatment, and the polyamic acid resin on the glass plate is partially imidized to obtain a polyimide gel film.
2. The method for preparing polyimide film for heat conductive graphite according to claim 1, wherein the montmorillonite in the step (1) is M813515 montmorillonite K-10, and the montmorillonite has a particle size of 50-100nm.
3. The method for producing a polyimide film for thermally conductive graphite according to claim 1, wherein the solid content of the montmorillonite-modified dispersion in the step (1) is 25%.
4. The method for preparing the polyimide film for the heat-conducting graphite according to claim 1, wherein the mixed solvent in the step (2) is a mixed solvent of Dimethylacetamide (DMAC) and N-methylpyrrolidone (NMP) in a mass ratio of 70:30.
5. The method for preparing a polyimide film for thermally conductive graphite according to claim 1, wherein the diamine monomer in the step (2) is a combination of 4,4 'diaminodiphenyl ether (ODA) and p-Phenylenediamine (PDA), and the molar ratio of the diamine monomer 4,4' diaminodiphenyl ether (ODA) to p-Phenylenediamine (PDA) is 85:15.
6. The method according to claim 1, wherein the dianhydride monomer in the step (2) is a combination of pyromellitic dianhydride (PMDA) and 3,3', 4' -biphenyl tetracarboxylic dianhydride (s-BPDA), and the molar ratio of pyromellitic dianhydride (PMDA) to 3,3', 4' -biphenyl tetracarboxylic dianhydride (s-BPDA) is 10:90.
7. The method of claim 1, wherein the molar ratio of diamine monomer to dianhydride monomer in the step (2) is 1:1.
8. The method for producing a polyimide film for thermally conductive graphite according to claim 1, wherein the high-temperature heat treatment in the step (3) is heating at 60 ℃ for 1h,120 ℃ for 0.5h, and 180 ℃ for 0.5h.
9. The method for preparing polyimide film for heat conductive graphite according to claim 1, wherein the imidization degree of the part of the imines in the step (3) is more than 40%, and the solvent content of the obtained polyamic acid film after imidization is less than < 25%.
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