Polyimide-polytetrafluoroethylene composite material based on hot rolling method and preparation method thereof

Abstract

The invention discloses a polyimide-polytetrafluoroethylene composite material based on a hot rolling method and a preparation method thereof, and belongs to the technical field of composite materials, and the preparation method comprises the following steps: S1, preparation of a polyamide acid film: respectively and quantitatively weighing diamine and dianhydride of PI, dissolving in an organic solvent, and polymerizing to obtain a polyamide acid solution, spreading the polyamic acid solution into a film, and gradually heating in a drying oven to remove the organic solvent to obtain a polyamic acid film; and S2, preparation of a PTFE material: selecting a PTFE dispersed material or a PTFE suspended material, and preparing a low-density PTFE film through blank making, calendering, stretching and heat setting, or preparing a high-density PTFE plate through sintering, rotary cutting and other processes. The problems that in the prior art, when a PTFE / PI composite material is prepared, the bonding strength is insufficient, the machining difficulty is large, and a thick PTFE layer is difficult to prepare are solved. The method has the advantages of being wide in application range and high in controllability.

Description

Technical Field

[0001] The invention relates to the technical field of composite materials, and in particular to a polyimide-polytetrafluoroethylene composite material based on a hot roller method and a preparation method thereof. Background Art

[0002] Polytetrafluoroethylene (PTFE) material has good acid and alkali resistance and good chemical environment resistance due to its fully fluorinated carbon chain structure and highly symmetrical molecular chain structure. On this basis, PTFE has good high temperature resistance, long-term use temperature at 260°C, and decomposition temperature above 400°C; at the same time, it also has the characteristics of self-lubrication, and its friction coefficient is 0.12-0.07. High molecular weight PTFE also has good mechanical properties, high toughness, low dielectric constant, and excellent electrochemical properties, but the molecular structure of PTFE also makes PTFE difficult to process. Conventional chemical solvents cannot dissolve PTFE or make it swell, and its melt viscosity is very high, which makes the secondary processing of PTFE material very difficult.

[0003] The molecular structure of polyimide material (PI) is composed of benzene ring structure and amide ring structure. Its decomposition temperature is above 450℃ and its long-term use temperature is 300℃. Its rigid benzene ring and amide ring structure give PI high mechanical properties. Its tensile strength is 500MPa and it can still maintain high strength under high temperature conditions. Generally, PI material is yellow or brown. This is because the large number of rigid benzene rings and amide ring structures in the PI molecular chain are conducive to the formation of charge transfer complexes (CTC) on them by electrons, which makes PI material more absorbent and reduces the light transmittance of the material itself. However, replacing some hydrogen atoms on the PI molecular chain with fluorine atoms can effectively prevent the generation of CTC, improve the light transmittance of PI and reduce the yellowness of the material.

[0004] How to combine the excellent properties of the two materials to obtain a material with good high temperature resistance, high mechanical strength, excellent chemical resistance, low friction coefficient and self-lubricating properties has become a research focus in recent years. The commonly used technology currently uses polyperfluoroethylene propylene (FEP) as a binder for PTFE to compound it with other materials, but this method has poor high temperature resistance. The performance of the FEP adhesive layer above 260°C decreases, resulting in a decrease in the overall performance of the composite layer. The composite method of PTFE and PI by high temperature hot pressing has low bonding strength and poor long-term stability.

[0005] PI is a thermosetting material and is difficult to reprocess after molding, but its precursor polyamic acid (PAA) material can be dissolved in a variety of organic solvents and has low processing difficulty. By combining PTFE with PAA, the bonding strength of the composite material can be effectively improved. On this basis, the PAA material can be imidized to obtain a PTFE / PI composite layer with high bonding strength.

[0006] Therefore, there is an urgent need for a polyimide-polytetrafluoroethylene composite material based on a hot roller method and a preparation method thereof, so as to develop a PTFE / PI composite material with better performance and easier processing to meet the needs of high-performance applications. Summary of the invention

[0007] To this end, the present invention provides a polyimide-polytetrafluoroethylene composite material based on a hot roller method and a preparation method thereof, so as to solve the problems of insufficient bonding strength, great processing difficulty, and difficulty in preparing a thicker PTFE layer when preparing PTFE / PI composite materials in the prior art.

[0008] In order to achieve the above object, the present invention provides the following technical solutions:

[0009] According to a first aspect of the present invention, a method for preparing a polyimide-polytetrafluoroethylene composite material based on a hot roller method is provided, comprising the following steps:

[0010] S1. Preparation of polyamic acid film: quantitatively weighing the diamine and dianhydride of PI, respectively, and dissolving them in an organic solvent for polymerization to obtain a polyamic acid solution, then spreading the polyamic acid solution into a film, and gradually heating it in an oven to remove the organic solvent to obtain a polyamic acid film;

[0011] S2. Preparation of PTFE materials: Select PTFE dispersion or PTFE suspension, and prepare low-density PTFE film by blanking, calendering, stretching, and heat setting, or prepare high-density PTFE sheet by sintering, rotary cutting and other processes;

[0012] S3. Composite treatment: The polyamic acid film and PTFE material obtained in S1 and S2 are placed in a composite processing device for composite treatment to obtain a polyimide-polytetrafluoroethylene composite material.

[0013] Furthermore, the steps of preparing the low-density PTFE film from the PTFE dispersion in S2 are as follows:

[0014] A low-density PTFE film is obtained by selecting PTFE dispersed material and subjecting it to blank making, calendering, stretching and heat setting operations, wherein the stretching ratio is 1-5 times and the heat setting temperature is within the range of 360-390°C.

[0015] Furthermore, the steps of preparing the high-density PTFE sheet from the PTFE suspension in S2 are as follows:

[0016] The high-density PTFE sheet is obtained after the PTFE suspension is subjected to operations such as blanking, sintering, and rotary cutting, wherein the blanking pressure is within the range of 15-35MPa and the sintering temperature is within the range of 360-390°C.

[0017] Furthermore, the suspended PTFE raw material in S2 includes one or more of soluble polytetrafluoroethylene, modified PTFE, films or plates obtained by blending modified PTFE with pure PTFE suspended particles, and PTFE ethylene films or plates with PTFE suspended materials mixed with glass fiber, carbon fiber and carbon nanotube reinforced fillers.

[0018] Furthermore, S3 includes the following specific steps:

[0019] The polyamic acid film and PTFE material obtained by S1 and S2 are placed at the unwinding end of the composite processing equipment, and the PTFE material and the polyamic acid film are pulled through the downward pressing pre-lamination roller to pre-lamination the two materials. After pre-lamination, they are pulled into the first heating box, the second heating box, and the third heating box in sequence for heating curing and composite treatment, and then pass through the first cooling roller, the second cooling roller, the third cooling roller, and the fourth cooling roller in sequence for cooling, and finally are rolled up at the winding end to obtain the PTFE / PI composite material.

[0020] Furthermore, the composite treatment of the polyamic acid film and the PTFE material in S3 includes dehydration, solvent removal, pre-imidization, final imidization and PTFE / PI composite, wherein:

[0021] The temperature of the first heating box for dehydration operation is 100-180°C;

[0022] The temperature of the second heating box for removing the solvent is 180-220°C;

[0023] The temperature of the third pre-imidization hot box is 240-290°C;

[0024] The temperature of the heating roller for final imidization and PTFE / PI composite was 320-370°C.

[0025] Furthermore, the cooling process of the composite material includes two modes, wherein:

[0026] Cooling mode 1 sets the temperature of the first cooling roller at 300-320°C; the temperature of the second cooling roller at 260-300°C; the temperature of the third cooling roller at 150-200°C; the temperature of the fourth cooling roller is controlled at room temperature by passing cooling water;

[0027] Cooling mode 2 controls the temperature of the first cooling roller at 150-200°C; the temperature of the second cooling roller at 80-150°C; the temperature of the third cooling roller at 25-50°C; the temperature of the fourth cooling roller is controlled below 25°C by passing cooling water.

[0028] Furthermore, the thickness of the polyamic acid film in S3 is in the range of 0.01-2 mm, the thickness of the PTFE material is in the range of 0.01-4 mm, and the composite rate is 0.02-2 m / min.

[0029] Furthermore, the organic solvent includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide, n-methylpyrrolidone, ethanol, and isopropanol.

[0030] Furthermore, the low-density PTFE film in S2 is uniaxially stretched or biaxially stretched.

[0031] The present invention has the following advantages:

[0032] 1. In this application, the PAA curing molding process is combined with the PTFE composite process, which significantly improves the performance of the composite material and realizes direct bonding between PI and PTFE without the need for an additional bonding layer, thereby avoiding the problem of degradation of the bonding layer performance at high temperatures. By using molded PTFE materials, the PTFE layer is ensured to have a high density and a wide range of thickness options, which is suitable for a variety of application scenarios.

[0033] 2. This application fully considers the different temperature conditions required in the PAA curing process and the temperature conditions for PTFE melting, ensuring the strength and density of the PI material and the degree of imidization of the PI material itself; by combining the final imidization process of the pre-imidized PAA with the melting process of the PTFE material, the overall consistency of the material is improved. In addition, the application of the hot roller method not only completes the final imidization of PAA, ensuring the high temperature resistance of the PI material, but also makes the PTFE / PI interface fully bonded, and the PTFE side exceeds its melting point, but the PI can withstand the tension during the composite process, ensuring the stability of the preparation process.

[0034] 3. This application uses a hot roller method to complete the final imidation of pre-imidated PAA and the combination of PTFE / PI. The pre-imidated PAA first contacts the hot roller for final imidation. At this time, PAA is converted into PI, and its high temperature resistance is further increased. At the same time, PI transfers heat to the PTFE side to fully combine the PTFE / PI interface. At this time, the physical properties of the PTFE side exceed its melting point, but the imidated PI can bear the tension during the composite process to ensure stability during the preparation process. At the same time, on this basis, the cooling rate of the composite layer is further considered. By adjusting the temperature of the 1st cooling roller-4, the crystallinity and physical properties of PTFE and PI can be controlled, further improving the application field of the composite material. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the implementation methods or the description of the prior art. Obviously, the drawings in the following description are only exemplary, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.

[0036] The structures, proportions, sizes, etc. illustrated in this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with the technology. They are not used to limit the conditions under which the present invention can be implemented, and therefore have no substantial technical significance. Any structural modification, change in proportion or adjustment of size shall still fall within the scope of the technical contents disclosed in the present invention without affecting the effects and purposes that can be achieved by the present invention.

[0037] Figure 1 A process flow chart of a method for preparing a polyimide-polytetrafluoroethylene composite material based on a hot roller method provided by the present invention;

[0038] In the figure: 1. Polyimide unwinding end; 2. Polytetrafluoroethylene unwinding end; 3. Pre-pressing roller; 4. 1st heating box; 5. 2nd heating box; 6. 3rd heating box; 7. Waste gas treatment equipment; 8. Heating roller; 9. 1st cooling roller; 10. 2nd cooling roller; 11. 3rd cooling roller; 12. 4th cooling roller; 13. Finished product winding end. DETAILED DESCRIPTION

[0039] The following is a description of the implementation of the present invention by specific embodiments. People familiar with the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] The present invention provides a method for preparing a polyimide-polytetrafluoroethylene composite material based on a hot roller method, comprising the following steps:

[0041] S1. Preparation of polyamic acid film: quantitatively weighing the diamine and dianhydride of PI, respectively, and dissolving them in an organic solvent for polymerization to obtain a polyamic acid (PAA) solution, spreading the polyamic acid solution (PAA) into a film, and gradually heating it in an oven to remove the organic solvent to obtain a polyamic acid film;

[0042] Among them, the molecular structures of PAA and PI are as follows:

[0043]

[0044] S2. Preparation of PTFE materials: Select PTFE dispersion or PTFE suspension, and prepare low-density PTFE film by blanking, calendering, stretching, and heat setting, or prepare high-density PTFE sheet by sintering, rotary cutting and other processes;

[0045] S3. Composite treatment: The PAA material (polyamic acid film) and PTFE material obtained in S1 and S2 are placed in a composite processing device for composite treatment to obtain a polyimide-polytetrafluoroethylene composite material.

[0046] Specifically, the steps for preparing the low-density PTFE film from the PTFE dispersion in S2 are as follows:

[0047] The PTFE dispersion material is selected and subjected to blanking, calendering, stretching and heat setting operations to obtain a uniaxially stretched or biaxially stretched low-density PTFE film, the stretching ratio is 1-5 times, and the heat setting temperature is within the range of 360-390°C.

[0048] Specifically, the steps of preparing the high-density PTFE sheet from the PTFE suspension in S2 are as follows:

[0049] The high-density PTFE sheet is obtained after the PTFE suspension is subjected to operations such as blanking, sintering, and rotary cutting. The blanking pressure is within the range of 15-35MPa, and the sintering temperature is within the range of 360-390°C.

[0050] Specifically, the suspended PTFE raw materials in S2 include: one or more of soluble polytetrafluoroethylene (PFA), modified PTFE, films or plates obtained by blending modified PTFE with pure PTFE suspended particles, and PTFE ethylene films or plates with PTFE suspended materials mixed with glass fiber, carbon fiber and carbon nanotube reinforced fillers.

[0051] Among them, S3 includes the following specific steps:

[0052] like Figure 1 As shown, the PAA material (polyamic acid film) and PTFE material obtained by S1 and S2 are placed at the unwinding end of the composite processing equipment, and the PTFE material and the PAA material (polyamic acid film) are pulled through the downward pressing pre-pressing roller to pre-press the two materials to obtain a composite material. After pre-pressing, they are pulled into the first heating box, the second heating box, and the third heating box in sequence to perform composite treatments such as dehydration, solvent removal, pre-imidization of the PAA layer in the composite material, final imidization of the PAA layer of the composite material, and PTFE / PI composite. Then, they pass through the first cooling roller, the second cooling roller, the third cooling roller, and the fourth cooling roller in sequence for cooling, and finally are wound up at the winding end to obtain the PTFE / PI composite material.

[0053] The composite treatment of PAA material (polyamic acid film) and PTFE material in S3 includes dehydration, solvent removal, pre-imidization, final imidization and PTFE / PI composite, wherein:

[0054] The temperature of the first heating box for dehydration operation is 100-180°C;

[0055] The temperature of the second heating box for removing the solvent is 180-220°C;

[0056] The temperature of the third pre-imidization hot box is 240-290°C;

[0057] The temperature of the heating roller for final imidization and PTFE / PI composite was 320-370°C.

[0058] Among them, there are two optional modes for the cooling process of composite materials:

[0059] Cooling mode 1 sets the temperature of the first cooling roller at 300-320°C; the temperature of the second cooling roller at 260-300°C; the temperature of the third cooling roller at 150-200°C; the temperature of the fourth cooling roller is controlled at room temperature - 80°C by passing cooling water;

[0060] Cooling mode 2 controls the temperature of the first cooling roller at 150-200°C; the temperature of the second cooling roller at 80-150°C; the temperature of the third cooling roller at 25-50°C; the temperature of the fourth cooling roller is controlled below 25°C by passing cooling water;

[0061] Specifically, the thickness of the PAA material in S3 is in the range of 0.01-2 mm, and the thickness of the PTFE material is in the range of 0.01-4 mm.

[0062] Specifically, the composite rate in S3 is 0.02-2 m / min. When the composite mode is plate composite and the PAA material thickness is in the range of 2-0.5 mm, the composite speed is more preferably 0.02-0.5 m / min; when the composite mode is film composite and the PAA material thickness is in the range of 0.5-0.01 mm, the composite speed is more preferably 0.5-2 m / min.

[0063] Among them, the monomers selected for PAA are 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (BAPAF) or 4,4'-diaminodiphenyl ether (ODA) and 4,4'-(hexafluoroisopropylene)phthalic anhydride (6FDA), pyromellitic anhydride (PMDA) or 4,4'-biphenyl ether dianhydride (ODPA) to obtain polyamic acid solutions PAA (6FDA / BAPAF), PAA (6FDA / ODA), PAA (PMDA / ODA) and PAA (ODPA / ODA); the above PAA solutions can also be mixed in any proportion to obtain a blended PAA solution.

[0064] Among them, the organic solvent includes: one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), n-methylpyrrolidone (NMP), ethanol, and isopropanol. Preferably, this application uses N,N-dimethylformamide (DMF).

[0065] Example 1

[0066] This embodiment provides a method for preparing a polyimide-polytetrafluoroethylene composite material based on a hot roller method, which specifically includes the following steps:

[0067] S1. Preparation of polyamic acid film:

[0068] 4,4'-diaminodiphenyl ether (ODA) and 4,4'-biphenyl ether dianhydride (ODPA) are quantitatively weighed respectively, dissolved in N,N-dimethylformamide (DMF) for polymerization to obtain a polyamic acid solution, then the polyamic acid solution is spread into a film, and the N,N-dimethylformamide (DMF) is removed by gradually increasing the temperature in an oven to obtain a polyamic acid film;

[0069] S2. Preparation of PTFE sheet:

[0070] Select PTFE suspension, subject the PTFE suspension to 30MPa pressure forming, sintering at 370°C, and rotary cutting to obtain a high-density suspended PTFE sheet with a thickness of 2mm;

[0071] S3. Composite processing:

[0072] The polyamic acid film and the high-density suspended PTFE sheet obtained by S1 and S2 are placed at the unwinding end of the composite processing equipment, and the polyamic acid film and the high-density suspended PTFE sheet are pulled in sequence, and the two materials are pre-laminated using a pre-lamination roller to obtain a polyimide-polytetrafluoroethylene composite material.

[0073] The composite processing specifically includes the following processes:

[0074] Compounding rate: Set the overall compounding rate to 0.1m / min, and then pull the PTFE material and PAA material into the heating process:

[0075] The first heating box: the temperature is 120℃, and the residence time is 90min;

[0076] The second heating box: the temperature is 220℃, and the residence time is 65min;

[0077] The third heating box: the temperature is 280℃, the residence time is 70min;

[0078] Heating roller: The temperature is 350°C and the residence time is 13 min to complete the transformation of PAA to PI and the compounding of PI and PTFE.

[0079] Waste gas treatment: The organic gas and moisture generated by the heating process and the volatilization of imide are removed through the waste gas treatment equipment and treated harmlessly.

[0080] Then the polyamic acid film and high-density suspended PTFE sheet are pulled into the cooling process:

[0081] 1st cooling roller: temperature is 320℃;

[0082] Second cooling roller: temperature is 280°C;

[0083] The third cooling roller: the temperature is 150°C;

[0084] The 4th cooling roller: The temperature is controlled at room temperature by passing cooling water, and the PTFE / PI composite material sheet is obtained after the cooling operation is completed.

[0085] Example 2

[0086] This embodiment provides a method for preparing a polyimide-polytetrafluoroethylene composite material based on a hot roller method, which specifically includes the following steps:

[0087] S1. Preparation of polyamic acid film:

[0088] 4,4'-diaminodiphenyl ether (ODA) and 4,4'-(hexafluoroisopropylene) diphthalic anhydride (6FDA) are quantitatively weighed respectively, dissolved in N,N-dimethylformamide (DMF) for polymerization to obtain a polyamic acid solution, then the polyamic acid solution is spread into a film, and the N,N-dimethylformamide (DMF) is gradually heated in an oven to remove the polyamic acid film;

[0089] S2. Preparation of PTFE sheet:

[0090] Select PTFE suspension, subject the PTFE suspension to 30MPa pressure forming, sintering at 370°C, and rotary cutting to obtain a high-density suspended PTFE sheet with a thickness of 1.5mm;

[0091] S3. Composite treatment: The polyamic acid film and high-density suspended PTFE sheet obtained in S1 and S2 are placed at the unwinding end of the composite processing equipment, and the polyamic acid film and high-density suspended PTFE sheet are pulled in sequence, and the two materials are pre-laminated using a pre-lamination roller to obtain a polyimide-polytetrafluoroethylene composite material.

[0092] The composite processing specifically includes the following processes:

[0093] Composite rate: Set the overall composite rate to 0.1m / min, and then pull the polyamic acid film and high-density suspended PTFE sheet into the heating process:

[0094] The first heating box: the temperature is 120℃, and the residence time is 90min;

[0095] The second heating box: the temperature is 220℃, and the residence time is 65min;

[0096] The third heating box: the temperature is 280℃, the residence time is 70min;

[0097] Heating roller: The temperature is 350°C and the residence time is 13 min to complete the transformation of PAA to PI and the compounding of PI and PTFE.

[0098] Waste gas treatment: The organic gas and moisture generated by the heating process and the volatilization of imide are removed through the waste gas treatment equipment and treated harmlessly.

[0099] Then the polyamic acid film and high-density suspended PTFE sheet are pulled into the cooling process:

[0100] 1st cooling roller: temperature is 160℃;

[0101] The second cooling roller: the temperature is 100°C;

[0102] The third cooling roller: the temperature is 25°C;

[0103] The 4th cooling roller: The temperature is controlled at 20°C by passing cooling water; after the cooling operation is completed, a transparent PTFE / PI composite material sheet is obtained.

[0104] Example 3

[0105] This embodiment provides a method for preparing a polyimide-polytetrafluoroethylene composite material based on a hot roller method, which specifically includes the following steps:

[0106] S1. Preparation of polyamic acid film:

[0107] 4,4'-diaminodiphenyl ether (ODA) and 4,4'-(hexafluoroisopropylene) diphthalic anhydride (6FDA) are quantitatively weighed respectively, dissolved in N,N-dimethylformamide (DMF) for polymerization to obtain a polyamic acid solution, then the polyamic acid solution is spread into a film, and the N,N-dimethylformamide (DMF) is gradually heated in an oven to remove the polyamic acid film;

[0108] S2. Preparation of PTFE sheet:

[0109] A soluble polytetrafluoroethylene (PFA) with a thickness of 2 mm is selected, the soluble polytetrafluoroethylene (PFA) is subjected to a pressure of 30 MPa to form a blank, sintered at 370° C., and a PTFE sheet with a thickness of 1.5 mm is obtained by operations such as rotary cutting;

[0110] S3. Composite treatment: The polyamic acid film and PTFE material obtained in S1 and S2 are placed at the unwinding end of the composite processing equipment, and the PTFE material and the polyamic acid film are pulled in sequence, and the two materials are pre-laminated using a pre-lamination roller to obtain a polyimide-polytetrafluoroethylene composite material.

[0111] The composite processing specifically includes the following processes:

[0112] Composite rate: Set the overall composite rate to 0.15m / min, and then pull the PTFE material and polyamic acid film into the heating process:

[0113] The first heating box: the temperature is 120℃, and the residence time is 90min;

[0114] The second heating box: the temperature is 220℃, and the residence time is 65min;

[0115] The third heating box: the temperature is 280℃, the residence time is 70min;

[0116] Heating roller: The temperature is 330°C and the residence time is 13 min to complete the transformation of PAA to PI and the compounding of PI and PTFE.

[0117] Waste gas treatment: The organic gas and moisture generated by the heating process and the volatilization of imide are removed through the waste gas treatment equipment and treated harmlessly.

[0118] Then the PTFE material and polyamic acid film (PAA material) are pulled into the cooling process:

[0119] 1st cooling roller: temperature is 160℃;

[0120] The second cooling roller: the temperature is 100°C;

[0121] The third cooling roller: the temperature is 25°C;

[0122] The 4th cooling roller: The temperature is controlled at 20°C by passing cooling water; after the cooling operation is completed, a transparent PFA / PI composite material sheet is obtained.

[0123] Example 4

[0124] This embodiment provides a method for preparing a polyimide-polytetrafluoroethylene composite material based on a hot roller method, which specifically includes the following steps:

[0125] S1. Preparation of polyamic acid film:

[0126] 4,4'-diaminodiphenyl ether (ODA) and 4,4'-biphenyl ether dianhydride (ODPA) were quantitatively weighed respectively, dissolved in N,N-dimethylformamide (DMF) for polymerization to obtain a polyamic acid solution, then the polyamic acid solution was spread into a film, and the N,N-dimethylformamide (DMF) was gradually heated in an oven to remove the N,N-dimethylformamide (DMF), to obtain a 0.15 mm polyamic acid film;

[0127] S2. Preparation of PTFE film:

[0128] Select PTFE suspension, subject the PTFE suspension to a pressure of 30 MPa, subject it to a sintering process at 370°C, and obtain a PTFE film with a thickness of 0.1 mm by peeling and other operations;

[0129] S3. Composite treatment: The polyamic acid film and PTFE film obtained in S1 and S2 are placed at the unwinding end of the composite processing equipment, and the polyamic acid film and PTFE film are pulled in sequence, and the two materials are pre-laminated using a pre-lamination roller to obtain a polyimide-polytetrafluoroethylene composite material.

[0130] The composite processing specifically includes the following processes:

[0131] Composite rate: Set the overall composite rate to 1.5m / min, and then pull the polyamic acid film and PTFE film into the heating process:

[0132] The first heating box: the temperature is 120℃, and the residence time is 6min;

[0133] The second heating box: the temperature is 220℃, and the residence time is 4.3min;

[0134] The third heating box: the temperature is 280°C, and the residence time is 4.6 minutes;

[0135] Heating roller: The temperature is 350°C, and the surface heating time is about 0.85 min, completing the transformation of PAA to PI and the compounding of PI and PTFE.

[0136] Waste gas treatment: The organic gas and moisture generated by the heating process and the volatilization of imide are removed through the waste gas treatment equipment and treated harmlessly.

[0137] Then the polyamic acid film and PTFE film are pulled into the cooling process:

[0138] 1st cooling roller: temperature is 320℃;

[0139] Second cooling roller: temperature is 280°C;

[0140] The third cooling roller: the temperature is 150°C;

[0141] The 4th cooling roller: The temperature is controlled at room temperature by passing cooling water, and a transparent PTFE / PI composite film material is obtained after the cooling operation is completed.

[0142] Example 5

[0143] This embodiment provides a method for preparing a polyimide-polytetrafluoroethylene composite material based on a hot roller method, which specifically includes the following steps:

[0144] S1. Preparation of polyamic acid film:

[0145] 4,4'-diaminodiphenyl ether (ODA) and 4,4'-biphenyl ether dianhydride (ODPA) were quantitatively weighed respectively, dissolved in N,N-dimethylformamide (DMF) for polymerization to obtain a polyamic acid solution, then the polyamic acid solution was spread into a film, and the N,N-dimethylformamide (DMF) was gradually heated in an oven to remove the N,N-dimethylformamide (DMF), to obtain a 0.1 mm polyamic acid film;

[0146] S2. Preparation of PTFE film or sheet:

[0147] A PTFE dispersion is selected, and the PTFE dispersion is subjected to blanking, calendering, stretching, and heat setting operations to obtain a uniaxially stretched low-density PTFE film, with a stretching ratio of 3 times, a heat setting temperature of 380° C., and a PTFE film thickness of 0.05 mm.

[0148] S3. Composite treatment: The polyamic acid film and the low-density PTFE film obtained in S1 and S2 are placed at the unwinding end of the composite processing equipment, and the polyamic acid film and the low-density PTFE film are pulled in sequence, and the two materials are pre-laminated using a pre-lamination roller to obtain a polyimide-polytetrafluoroethylene composite material.

[0149] The composite processing specifically includes the following processes:

[0150] Composite rate: Set the overall composite rate to 2m / min, and then pull the polyamic acid film and low-density PTFE film into the heating process:

[0151] The first heating box: the temperature is 120℃, and the residence time is 3min;

[0152] The second heating box: the temperature is 220℃, and the residence time is 3.3min;

[0153] The third heating box: the temperature is 280°C, and the residence time is 3.5 minutes;

[0154] Heating roller: The temperature is 350°C, and the surface heating time is about 0.65 min, completing the transformation of PAA to PI and the compounding of PI and PTFE.

[0155] Waste gas treatment: The organic gas and moisture generated by the heating process and the volatilization of imide are removed through the waste gas treatment equipment and treated harmlessly.

[0156] Then the polyamic acid film and low-density PTFE film are pulled into the cooling process:

[0157] 1st cooling roller: temperature is 320℃;

[0158] Second cooling roller: temperature is 280°C;

[0159] The third cooling roller: the temperature is 150°C;

[0160] The 4th cooling roller: The temperature is controlled at room temperature by passing cooling water, and the PTFE / PI composite membrane material is obtained after the cooling operation is completed.

[0161] Comparative Example 1: This example is used as a comparative example of Example 1:

[0162] 1. A polyamic acid (PAA (ODPA / ODA)) obtained by polymerization of 4,4'-biphenyl ether dianhydride (ODPA) and 4,4'-diaminodiphenyl ether (ODA) was selected, and N,N-dimethylformamide (DMF) solution was used as the raw material solution. A PAA film with a thickness of 0.03 mm was obtained by solution casting and removal of the DMF solvent, and a sintering and curing operation was performed on the PAA film. The sintering temperature was maintained at 350°C for 30 minutes, and the heating and cooling rates were 5°C / min, and a PI film with a thickness of 0.03 mm was obtained.

[0163] 2. Select pure PTFE suspension material, make blanks under 30MPa pressure, sinter at 370℃, and peel to obtain high-density suspended PTFE sheet with a thickness of 0.05mm.

[0164] 3. After the PTFE film and the PI film are pre-pressed, they are passed through an electric heating oven at 480°C at a speed of 5 m / min and then heated and sintered to obtain a composite film.

[0165] The bonding performance test was performed on Examples 1-5 and Comparative Example 1. The test results are shown in Table 1:

[0166] Table 1: Performance analysis of PI / PTFE composites prepared from different raw materials

[0167]

[0168] in conclusion:

[0169] 1. Bond strength analysis: It can be seen from the test results of Examples 1 to 5 that the composite materials prepared by the present invention all showed non-bonding surface damage after the peel test, which indicates that the bonding strength of the composite materials is very high and the bonding surface can withstand the peeling force without being damaged. In contrast, the composite material prepared in Comparative Example 1 showed bonding surface damage after the peel test, indicating that its bonding strength is low and the bonding surface cannot withstand the peeling force. This further proves the significant advantage of the preparation process of the present invention in improving the bonding strength of composite materials.

[0170] 2. Influence of material type on bonding strength:

[0171] Suspended PTFE: Whether compounded with PAA (ODPA / ODA) or PAA (6FDA / ODA), it exhibits high bonding strength;

[0172] PFA: After compounding with PAA (6FDA / ODA), it also shows high bonding strength;

[0173] Dispersed PTFE: After compounding with PAA (ODPA / ODA), it also exhibits high bonding strength.

[0174] Different types of PTFE and PAA composite materials all show higher bonding strength, especially in the case of suspended PTFE, PFA and dispersed PTFE and PAA composite.And in Comparative Example 1, after the high-density suspended PTFE sheet material of sintering molding is composited with PI film, the bonding strength is relatively low, indicating that the direct combination of PAA and PTFE by pre-subidation, and the final subidation and PTFE / PI composite are completed at high temperature, forming a stronger interface bond.This is because the pre-subidation PAA is combined with PTFE at high temperature, and the heat released during the conversion of PAA into PI helps the softening of PTFE and the combination with PI, thereby forming a more solid interface.And in the present application, by multi-stage temperature control (such as dehydration, desolvation, pre-subidation, final subidation), it is ensured that PAA is fully combined with PTFE in the process of being converted into PI.

[0175] 3. Thickness and shape analysis

[0176] Sheet and film: Whether it is sheet (2.9mm, 3.0mm) or film (0.20mm, 0.11mm, 0.05mm), the composite material shows high bonding strength;

[0177] Influence of thickness: Composite materials of different thicknesses (from 0.05 to 3.0 mm) all exhibited relatively high bonding strength, indicating that the composite materials prepared by the present technical solution have a wide range of thicknesses.

[0178] This part proves that the preparation method of the present application is suitable for composite materials of different thicknesses and shapes, and has stable bonding performance. The composite materials can maintain high bonding strength at different thicknesses, ensuring the quality and performance of the composite materials over a larger thickness range, which is very important for industrial production and practical applications.

[0179] In summary, the present invention significantly improves the bonding strength and performance consistency of the composite material by optimizing the combination of the PAA curing molding process and the PTFE composite process. Whether it is a plate or a film, composite materials of different thicknesses all show high bonding strength, indicating that the composite material prepared by the present invention has high bonding strength, stable performance and wide applicability. These advantages make the technical solution have significant advantages in preparing high-performance PTFE / PI composite materials, and are suitable for a variety of high-performance application requirements.

[0180] Although the present invention has been described in detail above by general description and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A method for preparing a polyimide-polytetrafluoroethylene composite material based on a hot roller method, characterized in that: The following steps are involved: S1. Preparation of polyamic acid film: quantitatively weighing the diamine and dianhydride of PI, respectively, and dissolving them in an organic solvent for polymerization to obtain a polyamic acid solution, then spreading the polyamic acid solution into a film, and gradually heating it in an oven to remove the organic solvent to obtain a polyamic acid film; S2. Preparation of PTFE materials: Select PTFE dispersion or PTFE suspension, and prepare low-density PTFE film by blanking, calendering, stretching, and heat setting, or prepare high-density PTFE sheet by sintering, rotary cutting and other processes; S3. Composite treatment: The polyamic acid film and PTFE material obtained in S1 and S2 are placed in a composite processing device for composite treatment to obtain a polyimide-polytetrafluoroethylene composite material.

2. The method for preparing a polyimide-polytetrafluoroethylene composite material based on a hot roller method according to claim 1, characterized in that: The steps of preparing low-density PTFE film from the PTFE dispersion in S2 are as follows: A low-density PTFE film is obtained by selecting PTFE dispersed material and subjecting it to blank making, calendering, stretching and heat setting operations, wherein the stretching ratio is 1-5 times and the heat setting temperature is within the range of 360-390°C.

3. The method for preparing a polyimide-polytetrafluoroethylene composite material based on a hot roller method according to claim 2, characterized in that: The steps of preparing high-density PTFE sheet from PTFE suspension in S2 are as follows: The high-density PTFE sheet is obtained after the PTFE suspension is subjected to operations such as blanking, sintering, and rotary cutting, wherein the blanking pressure is within the range of 15-35MPa and the sintering temperature is within the range of 360-390°C.

4. The method for preparing a polyimide-polytetrafluoroethylene composite material based on a hot roller method according to claim 3, characterized in that: The suspended PTFE raw materials in S2 include: one or more of soluble polytetrafluoroethylene, modified PTFE, films or plates obtained by blending modified PTFE with pure PTFE suspended particles, and PTFE ethylene films or plates with PTFE suspended materials mixed with glass fiber, carbon fiber and carbon nanotube reinforced fillers.

5. The method for preparing a polyimide-polytetrafluoroethylene composite material based on a hot roller method according to claim 1, characterized in that: The S3 includes the following specific steps: The polyamic acid film and PTFE material obtained by S1 and S2 are placed at the unwinding end of the composite processing equipment, and the PTFE material and the polyamic acid film are pulled through the downward pressing pre-lamination roller to pre-lamination the two materials. After pre-lamination, they are pulled into the first heating box, the second heating box, and the third heating box in sequence for heating curing and composite treatment, and then pass through the first cooling roller, the second cooling roller, the third cooling roller, and the fourth cooling roller in sequence for cooling, and finally are rolled up at the winding end to obtain the PTFE / PI composite material.

6. The method for preparing a polyimide-polytetrafluoroethylene composite material based on a hot roller method according to claim 5, wherein the composite treatment of the polyamic acid film and the PTFE material in S3 comprises dehydration, solvent removal, pre-imidization, final imidization and PTFE / PI composite, wherein: The temperature of the first heating box for dehydration operation is 100-180°C; The temperature of the second heating box for removing the solvent is 180-220°C; The temperature of the third pre-imidization hot box is 240-290°C; The temperature of the heating roller for final imidization and PTFE / PI composite was 320-370°C.

7. The method for preparing a polyimide-polytetrafluoroethylene composite material based on a hot roller method according to claim 5, characterized in that: The cooling process of the composite material includes two modes, wherein: Cooling mode 1 sets the temperature of the first cooling roller at 300-320°C; the temperature of the second cooling roller at 260-300°C; the temperature of the third cooling roller at 150-200°C; the temperature of the fourth cooling roller is controlled at room temperature by passing cooling water; Cooling mode 2 controls the temperature of the first cooling roller at 150-200°C; the temperature of the second cooling roller at 80-150°C; the temperature of the third cooling roller at 25-50°C; the temperature of the fourth cooling roller is controlled below 25°C by passing cooling water.

8. The method for preparing a polyimide-polytetrafluoroethylene composite material based on a hot roller method according to claim 6, characterized in that: The thickness of the polyamic acid film in S3 is in the range of 0.01-2 mm, the thickness of the PTFE material is in the range of 0.01-4 mm, and the composite rate is 0.02-2 m / min.

9. The method for preparing a polyimide-polytetrafluoroethylene composite material based on a hot roller method according to claim 8, characterized in that: The organic solvent includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide, n-methylpyrrolidine, ethanol and isopropanol.

10. The method for preparing a polyimide-polytetrafluoroethylene composite material based on a hot roller method according to claim 5, characterized in that: The low-density PTFE film S2 is uniaxially stretched or biaxially stretched.

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