An intrinsic porous polyimide film material and a preparation method thereof

Abstract

This invention relates to the field of polyimide materials, specifically an intrinsically porous polyimide film material and its preparation method. The preparation method provided by this invention, without altering the traditional thermal method for producing polyimide films, involves designing a unique polyamide ester intermediate structure with specially long side chains. This intermediate is then thermally imidized using commercial film production processes to obtain an intrinsically porous microporous polyimide film. Only the polymer intermediate is changed, without altering the final polymer structure. No post-processing or surface etching is required. The pore-forming groups are uniformly distributed on the polymer molecular backbone in the form of chemical bonds, ensuring the uniformity of pore size and porosity. The intrinsically porous polyimide film material obtained by the method provided by this invention exhibits excellent mechanical properties, heat resistance, dielectric properties, and high pore density. Furthermore, the use of conventional film production processes facilitates the continuous large-scale production of microporous films.

Description

Technical Field

[0001] This invention relates to the field of polyimide materials, specifically an intrinsic porous polyimide film material and its preparation method. Background Technology

[0002] Polyimide (PI), as a polymer material, has been widely used in aerospace, electrical and electronic fields due to its excellent comprehensive properties, including heat resistance, mechanical properties, and chemical stability. PI film is the most widely used and mature product among PI materials, driving the leapfrog development of microelectronic devices, new energy utilization, and aerospace technologies. However, with technological advancements and the iteration of related products, increasingly stringent requirements are being placed on the performance of polyimide materials.

[0003] The traditional manufacturing process of dense polyimide films and the performance differences associated with different chemical structures have been extensively studied, resulting in relatively mature technical routes and structural systems. However, with the miniaturization, lightweighting, and integration of microelectronic products, the spacing between wirings in integrated circuits is becoming increasingly smaller. This leads to a significant increase in signal hysteresis caused by capacitive coupling and cross-interference between adjacent wires, making the demand for insulating materials with lower dielectric constants increasingly urgent. Currently, commercially available polyimide films can no longer meet the requirements for low dielectric properties. How to reduce the dielectric constant and dielectric loss of PI films is a major challenge for future upgrades and iterations of microelectronic products. In other fields, the demand for novel polyimide materials is also increasing. For example, in the new energy sector, the separator in lithium-ion secondary batteries is a key component. Currently, polyolefin porous films are widely used as lithium-ion battery separators. However, these films have inherent drawbacks such as low heat resistance and poor wetting properties with the electrolyte. The maximum operating temperature of polyolefin separators is 170℃. During charging and discharging, the battery generates heat. Overcharging or improper use can lead to a rapid accumulation of heat inside the battery. When the temperature exceeds the separator's upper limit, the separator shrinks and melts, causing a short circuit, which can lead to combustion and explosion. Currently, the safety of lithium-ion batteries has attracted widespread attention. Under the national policy of vigorously developing new energy sources, developing new separator materials with higher overall performance to replace polyolefin separators has become an urgent problem to be solved for lithium-ion secondary batteries.

[0004] Previous research on improving the dielectric properties of PI films has largely focused on polymer structure design. However, dielectric properties are an inherent property of materials, and it's impossible to significantly reduce the dielectric constant and dielectric loss simply by altering the structure. It is well known that air has the lowest dielectric constant in nature, at 1.0. Therefore, by creating microporous structures on PI films to form a polyimide-air two-phase system, the dielectric properties of the material can be significantly improved. By adjusting the structure and ratio of the pore-forming agent, the microporous structure can be made to connect the pores on both sides of the film.

[0005] Currently, the existing publicly available patents disclose several methods for forming pores in polyimide films, including electrospinning, physical doping, template method, and phase inversion method.

[0006] I. Electrospinning: This method involves jetting a polymer solution into fine filaments under an electrostatic field. These filaments are then stacked to form a nonwoven film. The thin porous structures prepared by this method tend to have large pore sizes, resulting in poor mechanical properties. Furthermore, this method is difficult to scale up for the production of porous polyimide films.

[0007] II. Physical doping method: Dopants include easily decomposable polymers (polystyrene, polyethylene glycol, etc.), inorganic particles, and inorganic porous fillers. Using easily decomposable polymers as porogens can easily lead to pore collapse when the doping amount is too high, making it difficult to obtain polyimide films with high porosity. Using inorganic materials as porogens requires strong acid treatment after film formation to remove inorganic particles, leaving pores on the film. Due to agglomeration, achieving uniform mixing of inorganic particles is a challenge; furthermore, acid has difficulty penetrating the film interior, resulting in porogen residue and pores mostly on the outer surface of the film; simultaneously, acid treatment easily degrades the film structure, adversely affecting the film's mechanical properties.

[0008] Third, the template method produces porous structures with uniform pore size and porosity distribution. However, this method also involves post-film deposition acid etching, inevitably leading to film degradation. Furthermore, this method is difficult to scale up for mass production.

[0009] IV. Phase Inversion Method: This method involves coating and baking polyamic acid to form a semi-dry film. The semi-dry film is then immersed in a poor solvent to induce phase separation. After phase separation, the solvent precipitates through channels, forming pores in the solid phase. The pore structure formed by this method is affected by the amount of residual solvent in the semi-dry film and the precipitation process, resulting in poor uniformity of pore size and pore distribution.

[0010] The aforementioned pore-forming methods have all achieved the preparation of porous polyimide films. However, due to the inherent drawbacks of each method, the resulting porous films still exhibit shortcomings in pore size, pore distribution uniformity, mechanical properties, and scalability for mass production. This prevents the widespread application of porous polyimide films in various fields. Therefore, how to efficiently and cost-effectively produce porous polyimide films with uniform pore size and distribution and excellent overall performance remains a pressing problem to be solved. Summary of the Invention

[0011] In view of this, the technical problem to be solved by the present invention is to provide an intrinsically porous polyimide film material and a method for preparing the same. The preparation method provided by the present invention can obtain a high-performance intrinsically porous polyimide film material with uniform pore size and porosity.

[0012] The present invention provides an intrinsic porous polyimide film material, which is obtained by an imidization reaction of a material comprising a polyamide ester having a structure of Formula I;

[0013]

[0014] Wherein, z≥1000;

[0015] Ar1 and Ar2 are independently selected from substituted or unsubstituted aromatic groups, substituted or unsubstituted heteroaromatic groups, substituted or unsubstituted aliphatic groups, and substituted or unsubstituted aliphatic heterocyclic groups.

[0016] M1 and M2 are independently selected from C1 to C2. 60 The alkyl or poly(dimethylsiloxane) group, and M1 and M2 may be the same or different.

[0017] The polyamide ester of the present invention has structural units having M1 and M2 side chain groups, wherein M1 and M2 are independently selected from C1 to C2. 60 The alkyl or poly(dimethylsiloxane) group, and M1 and M2 may be the same or different; wherein, C1 to C 60 The alkyl groups include C1 to C2. 60 aliphatic straight-chain alkyl, C1-C 60 aliphatic branched alkyl groups and C1-C 60 Aliphatic cycloalkyl groups, preferably C8 to C96. 30 The alkyl group; the poly(dimethylsiloxane) group is preferably a poly(dimethylsiloxane) group having the structure of formula Ia;

[0018]

[0019] The x≥1 is preferably an integer from 3 to 8;

[0020] R represents an adipose chain.

[0021] In some embodiments of the present invention, M1 and M2 are independently selected from C8 to C9. 30 The alkyl group or poly(dimethylsiloxane) group having the structure of formula Ia, and M1 and M2 may be the same or different.

[0022] The polyamide ester having Formula I structure according to the present invention has a poly(dimethylsiloxane) group, that is, the structural unit of the polyamide ester includes M1 and M2, both of which are selected from C1 to C2. 60 The polyamide ester having the structure of Formula I contains alkyl structural units and at least one structural unit selected from poly(dimethylsiloxane) groups in M1 and M2. The poly(dimethylsiloxane) group comprises 2% to 50% of the total molar amount of M1 and M2, preferably 12% to 18%. When the proportion is less than 2%, the resulting material is non-porous or has excessively low porosity (≤8%). When the proportion is greater than 50%, the resulting material has excessively large pore size (≥20 μm average) and the mechanical properties of the film decrease sharply. This invention utilizes the side chain structures of M1 and M2 in the structural units of the polyamide ester to achieve microphase separation and side group breakage during high-temperature cyclization, thereby forming a microporous structure within the material. Since the microporous groups are chemically bonded to the molecular backbone before imidization, the pore size and porosity distribution remaining after their breakage are uniform. Intrinsic micropores are formed during a continuous material preparation process without the need for other auxiliary steps. The macroscopic and microscopic structures of the material are not affected by other processes, thus the intrinsic porous polyimide material exhibits excellent mechanical properties.

[0023] The intrinsic porous polyimide film material of this invention includes aromatic polyimide materials and their copolymers, as well as block and graft copolymers. Ar1 and Ar2 in this invention are independently selected from substituted or unsubstituted aromatic groups, substituted or unsubstituted heteroaromatic groups, substituted or unsubstituted aliphatic groups, and substituted or unsubstituted aliphatic heterocyclic groups. The main chain of the intrinsic porous polyimide film material of this invention may also contain other heteroatoms, such as polyamide-imide, polyhydrazide-imide, and polyesterimide. Considering the temperature resistance characteristics of porous polyimide films, the main chain preferably has an aromatic structure with superior high-temperature resistance.

[0024] Preferably, the structure of Ar1 has one or more of the structures of Ar1-a to Ar1-k;

[0025]

[0026] The Ar2 structure has one or more of the Ar2-a to Ar2-e structures;

[0027]

[0028] Wherein, X1 and X2 are independently selected from hydrogen, alkyl, cycloalkyl, aryl, fluoroalkyl, hydroxyl, alkoxy, phenoxy, cyano, nitro, amino, acetamino, ester, acyl, halogen or carboxyl;

[0029] The n and m are independent integers from 1 to 4;

[0030] The R 1 and R 3 The group is independently selected from the groups shown in Formulas 1 to 17;

[0031] The R 2 and R 4 The group is independently selected from the groups shown in Formulas 1 to 13;

[0032]

[0033] Wherein, X 1 and X 2 The group is independently selected from hydrogen, alkyl, cycloalkyl, aryl, fluoroalkyl, hydroxyl, alkoxy, phenoxy, cyano, nitro, amino, acetamino, ester, acyl, halogen or carboxyl, and preferably selected from -H, -Br, -Cl, -F, -NO2, -CN, -H, -CH3, -CH2CH3, -CH2CH2CH3, isopropyl, isobutyl, tert-butyl, cyclopentyl, cyclohexyl, phenyl or naphthyl;

[0034] The y is an integer from 1 to 4.

[0035] Of the above formulas Ar1-a to Ar1-k, the structure shown in formula Ar1-a is preferably... The structure shown in formula Ar1-b is preferably... The structure shown in formula Ar1-e is preferably... or The structure shown in formula Ar1-h is preferably... The structure shown in formula Ar1-i is preferably... The R 1 As described above, further details will not be repeated; the structure shown in formula Ar1-k is preferably... The R 2 X1 and n1 are the same as above, and will not be repeated.

[0036] The intrinsic porous polyimide film material provided by this invention is an intrinsically porous polyimide film material with intrinsic micropores, high temperature resistance, low dielectric, high strength, and high wettability, and has a structure of formula II;

[0037]

[0038] Ar1, Ar2, and z are the same as described above and will not be repeated here.

[0039] The present invention also provides a method for preparing the intrinsic porous polyimide film material described in any of the above technical solutions, comprising the following steps:

[0040] Materials including polyamide esters are subjected to an imidization reaction to obtain intrinsic porous polyimide film materials.

[0041] The polyamide ester described in this invention is the same as described above, and will not be repeated here.

[0042] The reaction formula for obtaining intrinsic porous polyimide film material by imidization of polyamide ester according to the present invention is as follows:

[0043]

[0044] This invention employs a known conventional thermal imidization process to imidize materials including polyamide esters, thereby obtaining intrinsically porous polyimide film materials. The imidization reaction temperature is 50℃~350℃, preferably 80℃~300℃, and the reaction time is 0.3h~30h. The method for preparing intrinsically porous polyimide film materials provided by this invention only requires thermal imidization of materials including polyamide esters, eliminating the need for other cumbersome processes such as precipitate phase separation and acid / alkali etching that could affect film performance. By controlling pore formation through heat treatment within the aforementioned temperature range, the gradual imidization of polyamide esters into intrinsically porous polyimide film structures can be achieved.

[0045] Specifically, this invention involves subjecting a polyamide ester-containing adhesive to a pre-curing stage followed by a high-temperature post-curing stage to obtain an intrinsic porous polyimide film material. The pre-curing stage, also known as a solvent evaporation stage, is performed at a temperature of 50°C to 150°C, preferably 80°C to 100°C, for a duration of 0.1 h to 10.0 h. This invention first treats the polyamide ester-containing material with the pre-curing stage to evaporate the solvent, resulting in a semi-dry film material that still contains residual solvent. Preferably, the residual solvent accounts for 20% to 50% of the total mass of the semi-dry film.

[0046] This invention involves pre-curing a material comprising polyamide ester, followed by a post-heating high-temperature treatment of the resulting film material. This post-heating high-temperature treatment includes a sequential imidization stage and a pore-forming substance evaporation stage. The imidization stage is performed at a temperature of 100°C to 250°C, preferably 120°C to 200°C, for a duration of 0.1 h to 10.0 h. The pore-forming substance evaporation stage is performed at a temperature of 180°C to 350°C, preferably 200°C to 300°C, for a duration of 0.1 h to 10.0 h. The chemical and physical changes in these three stages do not necessarily follow the exact naming conventions of each stage; the physical and chemical changes may overlap. For clarity, the stage's main physical and chemical changes are used for naming. In addition to the segmented heating method described above, a gradient heating method can also be used for imidization, with a preferred heating rate of 0.1°C / min to 5°C / min.

[0047] More specifically, this invention involves coating a polyamide ester-containing material solution onto a carrier plate, followed by a pre-curing stage and a post-heating stage to obtain an intrinsically porous polyimide film material. The coating of the polyamide ester-containing material solution onto the carrier plate can be done using adhesive coating equipment well-known in the art, and the coating method can be slit coating, baffle coating, spin coating, spray coating, or cast coating. The carrier plate can be a continuous steel strip, polyester film, copper foil, aluminum foil, glass, or mirror-finish steel plate. This invention also involves an imidization reaction of the polyamide ester-containing material. To further facilitate pore formation, surfactants, nucleating agents, etc., can be added to the material for the imidization reaction.

[0048] The intrinsic porous polyimide film material prepared by the method of this invention typically achieves an imidization degree of over 90%, with 100% imidization being the most preferred. The entire imidization reaction can be carried out on a carrier plate, or after the pre-curing stage, the cured film can be peeled off the carrier plate and its edges fixed using existing equipment in polyimide film production, such as pin plates and chain clamps. The supported film is then placed in a high-temperature environment to achieve imidization. This process allows residual solvents and pore-forming agents to evaporate to both sides of the film, avoiding uneven pore size caused by solvent evaporation to one side. Furthermore, this method is compatible with existing polyimide film production processes and equipment, enabling the production of microporous polyimide films using existing equipment, thus facilitating the industrialization of microporous polyimide films.

[0049] Preferably, the method for preparing the intrinsically porous polyimide film material provided by the present invention includes the following steps:

[0050] S1) A monohydroxy compound is reacted with a dianhydride having the structure of formula a; the monohydroxy compound is selected from C1 to C2.60 Alkyl alcohols and monohydroxy-terminated poly(dimethylsiloxane) having the structure of formula b;

[0051]

[0052] S2) A diamine having the structure of formula c and the reaction product obtained in step S1) are subjected to a polymerization reaction;

[0053] H2N-Ar2-NH2 formula c;

[0054] S3) The product obtained in step S2) is subjected to an imidization reaction to obtain an intrinsic porous polyimide film material.

[0055] The reaction formula for the preparation method of the above-mentioned intrinsic porous polyimide film material is as follows:

[0056]

[0057] Specifically, the present invention first reacts a monohydroxy compound with a dianhydride having the structure of formula a under the action of a catalyst, or directly reacts a monohydroxy compound with a dianhydride having the structure of formula a without a catalyst; wherein the monohydroxy compound is selected from two types, one of which is C1 to C2. 60 Alkyl alcohols, including C1 to C2 60 aliphatic straight-chain alkyl alcohols, C1-C 60 aliphatic branched alkyl alcohols and C1-C 60 Aliphatic cycloalkyl alcohols, preferably C8-C96. 30 One is an alkyl alcohol; the other is a monohydroxy-terminated poly(dimethylsiloxane) with the structure of formula b, wherein R and x in formula b are the same as R and x in the aforementioned formula Ia, and will not be repeated here; the reaction is an esterification reaction, and part of the product obtained is a fully esterified product, a diacid diester, whose structure is The other part is a partially esterified product, with the following structural formula: or The same applies to M1 and M2 as described above, and will not be repeated here.

[0058] In step S1) of this invention, the monohydroxy-terminated poly(dimethylsiloxane) accounts for 2% to 50% of the total amount of the monohydroxy compound, preferably 12% to 18%. By adjusting the proportion of the monohydroxy-terminated poly(dimethylsiloxane) in the monohydroxy compound, this invention can effectively control the intrinsic micropore size and pore density of the film.

[0059] The catalyst in step S1) of this invention may be selectively added or omitted, and the catalyst may be a tertiary amine well known in the art. The reaction in step S1) of this invention is carried out in a solvent, which includes, but is not limited to, the following compounds: toluene, xylene, dichlorobenzene, ethanol, isopropanol, n-butanol, cyclohexanol, ethylene glycol, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, 2,2′-dimethoxyethyl ether, acetone, acetonitrile, methyl ethyl ketone, cyclohexanone, tetrahydrofuran, dioxane, N-methylpyrrolidone, N-cyclohexylpyrrolidone, N,N-dimethylacetamide, dimethyl sulfoxide, cresol, m-cresol, ethyl acetate, γ-butyrolactone, etc., or mixtures thereof. The reaction temperature in step S1) of this invention is -5℃ to 60℃, preferably 0℃ to 10℃; the reaction time in step S1) of this invention is 6h to 16h, and the more specific reaction time varies depending on the activity of different reactants.

[0060] In step S1) of this invention, after reacting a monohydroxy compound with a dianhydride having the structure of formula a, step S2) involves polymerizing a diamine having the structure of formula c with the reaction product obtained in step S1). The reactants involved in the polymerization reaction in step S2) include a diamine having the structure of formula c. The Ar2 is the same as the Ar2 described in Formula I above, and will not be repeated here.

[0061] Specifically, step S2) of the present invention includes, but is not limited to, the following implementation methods:

[0062] Method 1: The reaction product obtained in step S1) undergoes an acyl chloride reaction, and then the resulting material is polymerized with a diamine having the structure of formula c to obtain a viscous polyamide ester-containing adhesive. The acyl chloride reagent used in the acyl chloride reaction of this invention is SOCl2. In this process, the reaction product obtained in step S1) mainly consists of a fully esterified product, a diacid diester, which undergoes an acyl chloride reaction to obtain a diester diacyl chloride, and then polymerizes with a diamine to obtain a viscous polyamide ester-containing adhesive. The reaction formula is as follows:

[0063]

[0064] Method 2: The reaction product obtained in step S1) is imidazoleized, and then the resulting material is polymerized with a diamine having the structure of formula C to obtain a viscous polyamide ester solution. In this process, the reaction product obtained in step S1) mainly consists of a fully esterified product, a diacid diester, which is imidazoleized to a diimidazole derivative, and then polymerized with a diamine to obtain a viscous polyamide ester solution. The reaction formula is as follows:

[0065]

[0066] Method 3: Under the action of a condensing agent, the reaction product obtained in step S1) and a diamine having the structure of formula c are subjected to a polymerization reaction to obtain a viscous polyamide ester adhesive; the condensing agent includes, but is not limited to, the following:

[0067]

[0068] The polymerization reaction described in this invention is carried out in a polar solvent, which includes, but is not limited to, N,N′-dimethylformamide (DMF), N,N′-dimethylacetamide (DMAc), N-methylpyrrolidone, dimethyl sulfoxide (DMSO), tetrahydrofuran / methanol mixture (THF / MeOH), etc.

[0069] In step S2) of this invention, after polymerizing the diamine having the structure of formula c and the reaction product obtained in step S1), the product obtained in step S2) is subjected to an imidization reaction to obtain an intrinsic porous polyimide film material. The imidization reaction of the product obtained in step S2) is the same as described above and will not be repeated here.

[0070] The method for preparing intrinsically porous polyimide film materials provided by this invention results in intrinsically microporous polyimide films whose pore size is formed during the thermal imidization of polyamide esters with special branched structures to form polyimide. Therefore, the key is to synthesize polyamide esters with special branched chains and use them as raw materials for imidization. In most structures, unbranched polyamic acid also undergoes brief phase separation during traditional polyimide film production processes. However, this phase separation is caused by solvent evaporation and increased molecular chain cyclization, which reduces solubility. In traditional film preparation, the temperature at which the water and solvent removed during imidization evaporate is much lower than the glass transition temperature (Tg) of the polymer. This causes the pores left after the water and solvent evaporate to be quickly filled by the softened polymer. Therefore, these polyimide films are dense and non-porous, and do not form microporous structures. This invention selects a compound with a specific structure to graft onto the main molecular chain to generate a polyamide ester with a special structural branch. As the temperature increases, the solvent gradually evaporates. When the temperature is raised to a certain level, the large aliphatic side chains and poly(dimethylsiloxane) side chains in the polyamide ester begin to undergo cyclization and branch shedding. The polymer gradually transitions from easily soluble polyamide ester to difficult-to-dissolve polyimide. The large aliphatic side chains and poly(dimethylsiloxane) side chains remain in the film after shedding, promoting phase separation of the system. As the temperature increases, the film's support becomes greater. After the detached side chain compounds evaporate and escape from the film, they leave pores inside the film.

[0071] The method for preparing intrinsically porous polyimide film materials provided by this invention is based on microphase separation, making full use of the phase change that occurs in the polymer system during thermal imidization to obtain intrinsically microporous polyimide films. This differs from the conventional process of preparing porous polyimide films based on precipitation phase inversion. The conventional process of producing porous polyimide films based on precipitation phase inversion involves coating polyamic acid, followed by shallow baking to obtain a semi-dry polyamic acid film. The semi-dry polyamic acid film is then immersed in a poor solvent to promote rapid phase separation and precipitation of polyamic acid. During the solid-liquid phase separation process, the liquid (solvent) overflows from the solid phase to form pores. The pores formed in this way have poor uniformity. During the subsequent high-temperature thermal imidization process, the pores will collapse to a certain extent during the dehydration and cyclization of the polymer molecular chains. Without the support of external forces (such as supercritical carbon dioxide extraction), it is difficult to ensure the formation of pores with uniform pore size and distribution. Because no other processes that could degrade the film are involved in the film production process, the film prepared by this invention retains the intrinsic properties of polyimide film to the maximum extent. Furthermore, because the film preparation process fully utilizes the traditional production process of polyimide film, the prepared porous film has a very high degree of cyclization and possesses high strength, high toughness, and high heat resistance.

[0072] This invention provides an intrinsically porous polyimide film material and its preparation method. The method synthesizes a polyamide ester with special long side chains and then thermally imidizes it to obtain a high-temperature resistant, high-strength intrinsically porous polyimide film. This method only modifies the polymer intermediate without altering the final polymer structure, eliminating the need for post-processing or surface etching. The method, without changing the traditional thermal method for producing polyimide films, designs a unique polyamide ester intermediate structure and employs the most conventional and efficient process in commercial film production to obtain the intrinsically porous polyimide film. The pore-forming groups are uniformly distributed on the polymer molecular backbone in the form of chemical bonds, ensuring the uniformity of pore size and porosity. The intrinsically porous polyimide film obtained by this method exhibits excellent mechanical properties, heat resistance, dielectric properties, and high pore density. Furthermore, the use of conventional film production processes facilitates the continuous large-scale production of microporous films. Attached Figure Description

[0073] Figure 1 This is a SEM image of the micropores in the polyimide film prepared in Example 1.

[0074] Figure 2 This is a SEM image of the micropores in the polyimide film prepared in Example 2.

[0075] Figure 3This is a SEM image of the micropores in the polyimide film prepared in Example 3;

[0076] Figure 4 This is a SEM image of the micropores in the polyimide film prepared in Example 4.

[0077] Figure 5 This is a SEM image of the micropores in the polyimide film prepared in Example 5.

[0078] Figure 6 This is a SEM image of the micropores in the polyimide film prepared in Example 6.

[0079] Figure 7 SEM image of the micropores in the polyimide film prepared in Comparative Example 1;

[0080] Figure 8 The image shows the SEM scan morphology of the micropores in the polyimide film prepared in Comparative Example 2. Detailed Implementation

[0081] This invention discloses an intrinsic porous polyimide film material and its preparation method. Those skilled in the art can refer to the content of this document and appropriately modify the process parameters to achieve the same result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments, and those skilled in the art can clearly modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0082] The testing instruments and conditions used for performance testing of the samples in the comparative examples and embodiments of this invention are as follows:

[0083] 1. Microstructure characterization: The microstructure of the gold-sputtered microporous polyimide film was observed using an XL30 field emission environmental scanning electron microscope (SEM) (FEI, USA).

[0084] 2. Heat resistance: TGA-2 thermogravimetric analyzer (TGA), PerkinElmer, USA, heating rate 10℃ / min, nitrogen atmosphere.

[0085] 3. Glass transition temperature: Static thermomechanical analyzer (TMA Q400), test atmosphere is nitrogen, heating rate is 5℃ / min, temperature range is 40℃~400℃.

[0086] 4. Mechanical properties: Mechanical property testing machine (Instron-1121 type), tensile rate 5mm / min, sample strip size 50mm×10mm, the test result is the average value of 10 test sample strips;

[0087] 5. Porosity Testing: This invention employs a density calculation method. The porous film is cut into 20mm × 20mm square samples using a die cutter. The film mass is weighed and its thickness is measured. The density of the sample is calculated; the density of polyimide is 1.4 g / cm³. 3 Porosity can be calculated using the following formula.

[0088]

[0089] In the formula, ρ1 is the sample density calculated based on mass and volume, and ρ0 is the density of polyimide.

[0090] The molecular weight range of the monohydroxy-terminated poly(dimethylsiloxane) used in the specific embodiments of the present invention is 600 to 6000.

[0091] The present invention will be further described below with reference to the embodiments:

[0092] Example 1

[0093] A 500 mL three-necked round-bottom flask equipped with a nitrogen inlet and a mechanical stirrer was placed in a low-temperature cold bath at 0 °C. 10.906 g of pyromellitic dianhydride (PMDA) and 120 mL of N-methylpyrrolidone were added to the flask. 10.2 g of triethylamine was added and the mechanical stirrer was turned on for 30 min. 16.398 g of lauryl alcohol and 7.252 g of poly(dimethylsiloxane) monohydroxy end-capping were slowly added to the reaction solution. After the addition was completed, the reaction was continued for 8 h. The low-temperature cold bath was then turned off, and the reaction was continued at room temperature for 10 h.

[0094] After the esterification reaction was completed, the low-temperature cold bath was turned on and the temperature was set to -15℃. After the cold bath temperature reached the set temperature, 20.7g of DCC was added to the reaction flask and the mixture was stirred for about 30 minutes. Then, 10.012g of diaminodiphenyl ether (ODA) was added in batches, followed by 100mL of N-methylpyrrolidone. The temperature of the reaction solution was controlled at -5℃. After all the ODA was added, the cold bath was turned off and the reaction was continued at room temperature for 8 hours. The solids were filtered off to obtain a viscous gel.

[0095] After the synthesized viscous adhesive solution was allowed to stand and degas, it was coated onto a glass plate and baked in an 80°C oven for 1.0 h until the adhesive film was completely cured. The adhesive film was then peeled off from the glass plate and fixed around the edges of the peeled adhesive film onto a hollow stainless steel frame. The film was then placed in a high-temperature oven and the oven temperature was increased from 120°C to 200°C and held for 0.5 h. The temperature was then further increased to 300°C and held for 0.5 h to obtain a porous polyimide film.

[0096] The microporous morphology of the prepared polyimide film is as follows: Figure 1 As shown, Figure 1The image shows the SEM scan morphology of the micropores in the polyimide film prepared in Example 1. The film's related properties are characterized as shown in Table 1.

[0097] Example 2

[0098] A 500 mL three-necked round-bottom flask equipped with a nitrogen inlet and a mechanical stirrer was placed in a low-temperature cold bath at 0 °C. 10.906 g of pyromellitic dianhydride (PMDA) and 120 mL of N-methylpyrrolidone were added to the three-necked flask. 10.2 g of triethylamine was added and the mechanical stirrer was turned on for 30 min. 11.330 g of n-octanol and 7.856 g of poly(dimethylsiloxane) monohydroxy end-capping were slowly added to the reaction solution. After the addition was completed, the reaction was continued for 8 h. The low-temperature cold bath was then turned off, and the reaction was continued at room temperature for 10 h.

[0099] After the esterification reaction was completed, the low-temperature cold bath was turned on and the temperature was set to -15℃. After the cold bath temperature reached the set temperature, 20.7g of DCC was added to the reaction flask and stirred for about 30 minutes. Then, 10.012g of diaminodiphenyl ether (ODA) was added in batches and the reaction solution temperature was set to -5℃. After all the ODA was added, the cold bath was turned off and the reaction continued at room temperature for 8 hours. The solids were filtered off to obtain a viscous gel.

[0100] After the synthesized viscous adhesive solution was allowed to stand and degas, it was coated onto a glass plate and baked in an 80°C oven for 1.0 h until the adhesive film was completely cured. The adhesive film was then peeled off from the glass plate and fixed around the edges of the peeled adhesive film onto a hollow stainless steel frame. The film was then placed in a high-temperature oven and the oven temperature was increased from 120°C to 200°C and held for 0.5 h. The temperature was then further increased to 300°C and held for 0.5 h to obtain a porous polyimide film.

[0101] The microporous morphology of the prepared polyimide film is as follows: Figure 2 As shown, Figure 2 The image shows the SEM scan morphology of the micropores in the polyimide film prepared in Example 2. The film-related properties are characterized as shown in Table 1.

[0102] Example 3

[0103] A 500 mL three-necked round-bottom flask equipped with a nitrogen inlet and a mechanical stirrer was placed in a low-temperature cold bath at 0 °C. 14.711 g of biphenyl dianhydride (BPDA) and 120 mL of N-methylpyrrolidone were added to the flask. 7.9 g of pyridine was added and the mechanical stirrer was turned on for 30 min. 16.398 g of lauryl alcohol and 8.142 g of poly(dimethylsiloxane) monohydroxy end-capping were slowly added to the reaction solution. After the addition was completed, the reaction was continued for 8 h. The low-temperature cold bath was then turned off and the reaction was continued at room temperature for 10 h.

[0104] After the esterification reaction was completed, a low-temperature cold bath was turned on and the temperature was set to -15℃. After the cold bath temperature reached the set temperature, 12.13g of thionyl chloride was added to the reaction flask and the reaction was carried out at low temperature for 6 hours. After the reaction was completed, 10.012g of diaminodiphenyl ether (ODA) was added to the reaction flask in batches, and 100mL of N-methylpyrrolidone was added. The reaction solution temperature was set to -5℃. After all the ODA was added, the cold bath was turned off and the reaction was continued at room temperature for 8 hours. The viscous gel was obtained by filtration.

[0105] After the synthesized viscous adhesive solution was allowed to stand and degas, it was coated onto a glass plate and baked in an 80°C oven for 1 hour until the adhesive film was fully cured. The adhesive film was then peeled off from the glass plate and fixed around the edges of the peeled adhesive film onto a hollow stainless steel frame. The film was then placed in a high-temperature oven and the oven temperature was increased from 120°C to 200°C and held for 0.5 hours. The temperature was then further increased to 300°C and held for 0.5 hours to obtain a porous polyimide film.

[0106] The microporous morphology of the prepared polyimide film is as follows: Figure 3 As shown, Figure 3 The image shows the SEM scan morphology of the micropores in the polyimide film prepared in Example 1. The film's related properties are characterized as shown in Table 1.

[0107] Example 4

[0108] A 500 mL three-necked round-bottom flask equipped with a nitrogen inlet and a mechanical stirrer was placed in a low-temperature cold bath at 0 °C. 14.711 g of biphenyl dianhydride (BPDA) and 120 mL of N-methylpyrrolidone were added to the flask. 7.9 g of pyridine was added and the mechanical stirrer was turned on for 30 min. 11.460 g of n-octanol and 8.142 g of poly(dimethylsiloxane) monohydroxy end-capping were slowly added to the reaction solution. After the addition was completed, the reaction was continued for 8 h. The low-temperature cold bath was then turned off, and the reaction was continued at room temperature for 10 h.

[0109] After the esterification reaction was completed, a low-temperature cold bath was turned on and the temperature was set to -15℃. After the cold bath temperature reached the set temperature, 12.13g of thionyl chloride was added to the reaction flask and reacted at low temperature for 6 hours. 10.012g of diaminodiphenyl ether (ODA) was added in batches, and the temperature of the reaction solution was controlled at around -5℃. After all the ODA was added, the cold bath was turned off and the reaction was continued at room temperature for 8 hours. The solution was filtered to obtain a viscous gel.

[0110] After the synthesized viscous adhesive solution was allowed to stand and degas, it was coated onto a glass plate and baked in an 80°C oven for 1 hour until the adhesive film was fully cured. The adhesive film was then peeled off from the glass plate and fixed around the edges of the peeled adhesive film onto a hollow stainless steel frame. The film was then placed in a high-temperature oven and the oven temperature was increased from 120°C to 200°C and held for 0.5 hours. The temperature was then further increased to 300°C and held for 0.5 hours to obtain a porous polyimide film.

[0111] The microporous morphology of the prepared polyimide film is as follows: Figure 4 As shown, Figure 4 The image shows the SEM scan morphology of the micropores in the polyimide film prepared in Example 1. The film's related properties are characterized as shown in Table 1.

[0112] Example 5

[0113] A 500 mL three-necked round-bottom flask equipped with a nitrogen inlet and a mechanical stirrer was placed in a low-temperature cold bath at 0 °C. 14.711 g of biphenyltetracarboxylic dianhydride (BPDA) and 120 mL of N,N-dimethylacetamide were added to the three-necked flask. 10.2 g of triethylamine was added and the mechanical stirrer was turned on for 30 min. 11.460 g of isooctyl alcohol and 7.252 g of poly(dimethylsiloxane) monohydroxy end-capping solvent were slowly added to the reaction solution. After the addition was completed, the reaction was continued for 8 h. The low-temperature cold bath was then turned off, and the reaction was continued at room temperature for 10 h.

[0114] After the esterification reaction was completed, the low-temperature cold bath was turned on and the temperature was set to -15℃. After the cold bath temperature reached the set temperature, 20.7g of DCC was added to the reaction flask and the mixture was stirred for about 30 minutes. Then, 10.012g of diaminodiphenyl ether (ODA) was added in batches, and 100mL of N,N-dimethylacetamide was added to control the temperature of the reaction solution to around -5℃. After all the ODA was added, the cold bath was turned off and the reaction was carried out at room temperature for 8 hours. The solids were then filtered off to obtain a viscous gel.

[0115] After the synthesized viscous adhesive solution was allowed to stand and degas, it was coated onto a glass plate and baked in an 80°C oven for 1 hour until the adhesive film was fully cured. The adhesive film was then peeled off from the glass plate and fixed around the edges of the peeled adhesive film onto a hollow stainless steel frame. The film was then placed in a high-temperature oven and the oven temperature was increased from 120°C to 200°C and held for 0.5 hours. The temperature was then further increased to 300°C and held for 0.5 hours to obtain a porous polyimide film.

[0116] The microporous morphology of the prepared polyimide film is as follows: Figure 5 As shown, Figure 5 The image shows the SEM scan morphology of the micropores in the polyimide film prepared in Example 1. The film's related properties are characterized as shown in Table 1.

[0117] Example 6

[0118] A 500 mL three-necked round-bottom flask equipped with a nitrogen inlet and a mechanical stirrer was placed in a low-temperature cold bath at 0 °C. 10.906 g of pyromellitic dianhydride (PMDA), 120 mL of N-methylpyrrolidone, and 10.2 g of triethylamine were added to the flask. The mechanical stirrer was turned on for 30 min. 11.460 g of isooctyl alcohol and 8.142 g of poly(dimethylsiloxane) monohydroxy end-capping were slowly added to the reaction solution. After the addition was completed, the reaction was continued for 8 h. The low-temperature cold bath was then turned off, and the reaction solution was allowed to continue to react at room temperature for 10 h.

[0119] After the esterification reaction was completed, the low-temperature cold bath was turned on and the temperature was set to -15℃. After the cold bath temperature reached the set temperature, 20.7g of DCC was added to the reaction flask and the mixture was stirred for about 30 minutes. Then, 10.012g of diaminodiphenyl ether (ODA) was added in batches, followed by 100mL of N-methylpyrrolidone. The temperature of the reaction solution was controlled at around -5℃. After all the ODA was added, the cold bath was turned off and the reaction was continued at room temperature for 8 hours. The solids were filtered off to obtain a viscous gel.

[0120] After the synthesized viscous adhesive solution is allowed to stand and degas, it is coated onto a glass plate and placed in an 80°C baking oven for 0.5–2 hours to fully cure the adhesive film. The adhesive film is then peeled off from the glass plate and fixed around its edges onto a hollow stainless steel frame. The film is then placed in a high-temperature oven, and the oven temperature is increased from 120°C to 200°C and held for 0.5–1 hour. The temperature is then further increased to 300°C and held for 0.5 hours to obtain a porous polyimide film.

[0121] The microporous morphology of the prepared polyimide film is as follows: Figure 6 As shown, Figure 6 The image shows the SEM scan morphology of the micropores in the polyimide film prepared in Example 1. The film's related properties are characterized as shown in Table 1.

[0122] Comparative Example 1

[0123] A 500 mL three-necked round-bottom flask equipped with a nitrogen inlet and a mechanical stirrer was placed in a low-temperature cold bath at 0 °C. 14.711 g of biphenyl tetracarboxylic dianhydride (BPDA), 120 mL of N,N-dimethylacetamide, and 7.9 g of pyridine were added to the flask. The mechanical stirrer was turned on for 30 min. 18.634 g of lauryl alcohol was slowly added to the reaction solution. After the addition was completed, the reaction was continued for 8 h. The low-temperature cold bath was then turned off, and the reaction solution was allowed to continue to react at room temperature for 10 h.

[0124] After the esterification reaction was completed, a low-temperature cold bath was turned on and the temperature was set to -15℃. After the cold bath temperature reached the set temperature, 20.7g of DCC was added to the reaction flask and the mixture was stirred for about 30 minutes. Then, 12.415g of diaminodiphenyl sulfone (4,4-DDS) was added in batches, followed by 100mL of N,N-dimethylacetamide. The temperature of the reaction solution was controlled at around -5℃. After all the ODA was added, the cold bath was turned off and the reaction was continued at room temperature for 8 hours. The mixture was then filtered to obtain a viscous gel.

[0125] After the above viscous adhesive solution is allowed to stand and degas, it is coated onto a glass plate and placed in an 80°C baking oven for 1 hour to fully cure the adhesive film. The adhesive film is then peeled off from the glass plate, and the peeled adhesive film is fixed around the edges on a hollow stainless steel frame and placed in a high-temperature oven. The oven temperature is increased from 120°C to 200°C and held for 0.5 hours. The temperature is then further increased to 300°C and held for 0.5 hours to obtain a porous polyimide film.

[0126] The microporous morphology of the prepared polyimide film is as follows: Figure 7 As shown, Figure 7 The SEM scan morphology of the micropores in the polyimide film prepared in Comparative Example 1 is shown in Table 1. The relevant properties of the film are characterized as shown in Table 1.

[0127] Comparative Example 2

[0128] A 500 mL three-necked round-bottom flask equipped with a nitrogen inlet and a mechanical stirrer was placed in a low-temperature cold bath at 0 °C. 14.711 g of biphenyl dianhydride (BPDA), 120 mL of N,N-dimethylacetamide, and 7.9 g of pyridine were added to the flask. The mechanical stirrer was turned on for 30 min. 9.317 g of lauryl alcohol and 30.217 g of poly(dimethylsiloxane) monohydroxy end-capping agent were slowly added to the reaction solution. After the addition was completed, the reaction was continued for 8 h. The low-temperature cold bath was then turned off, and the reaction solution was allowed to continue to react at room temperature for 10 h.

[0129] After the esterification reaction was completed, a low-temperature cold bath was turned on and the temperature was set to -15℃. After the cold bath temperature reached the set temperature, 20.7g of DCC was added to the reaction flask and the mixture was stirred for about 30 minutes. Then, 12.415g of diaminodiphenyl sulfone (4,4-DDS) was added in batches, followed by 100mL of N,N-dimethylacetamide. The temperature of the reaction solution was controlled at around -5℃. After all the ODA was added, the cold bath was turned off and the reaction was continued at room temperature for 8 hours. The mixture was then filtered to obtain a viscous gel.

[0130] After the above viscous adhesive solution is allowed to stand and degas, it is coated onto a glass plate and placed in an 80°C baking oven for 1 hour to fully cure the adhesive film. The adhesive film is then peeled off from the glass plate, and the peeled adhesive film is fixed around the edges on a hollow stainless steel frame and placed in a high-temperature oven. The oven temperature is increased from 120°C to 200°C and held for 0.5 hours. The temperature is then further increased to 300°C and held for 0.5 hours to obtain a porous polyimide film.

[0131] The microporous morphology of the prepared polyimide film is as follows: Figure 8 As shown, Figure 8 The SEM scan morphology of the micropores in the polyimide film prepared in Comparative Example 2 is shown in Table 1. The relevant properties of the film are characterized as shown in Table 1.

[0132] Table 1

[0133]

[0134]

[0135] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An intrinsically porous polyimide film material, characterized in that, It is obtained by imidization reaction of materials including polyamide esters having the structure of Formula I; Equation I; Wherein, z≥1000; Ar1 and Ar2 are independently selected from unsubstituted aromatic groups, unsubstituted heteroaromatic groups, unsubstituted aliphatic groups, or unsubstituted aliphatic heterocyclic groups. M1 and M2 are independently selected from C8~C 30 The polyamide ester having the structure of Formula I has an alkyl or poly(dimethylsiloxane) group, and M1 and M2 are not the same; the polyamide ester having the structure of Formula I has a poly(dimethylsiloxane) group, and the molar amount of the poly(dimethylsiloxane) group accounts for 12% to 18% of the total molar amount of M1 and M2; the poly(dimethylsiloxane) group is derived from a monohydroxy-terminated poly(dimethylsiloxane) with a molecular weight of 600. The imidization reaction includes, in sequence, a pre-baking curing stage, an imidization stage, and a pore-forming material escaping stage. The pre-baking and curing section is processed at a temperature of 50℃ to 150℃ for a time of 0.1 h to 10.0 h. The imidization process is performed at a temperature of 100℃ to 250℃ for a time of 0.1 h to 10.0 h. The temperature of the pore-forming material escaping section is 180℃~350℃, and the time is 0.1 h~10.0 h.

2. The intrinsic porous polyimide film material according to claim 1, characterized in that, M1 and M2 are independently selected from C8~C 30 Alkyl groups or poly(dimethylsiloxane) groups having the structure of formula Ia; Equation Ia; Where x≥1; R represents an adipose chain.

3. The intrinsic porous polyimide film material according to claim 1, characterized in that, The structure of Ar1 has one or more of the structures of Ar1-a to Ar1-k; Formula Ar1-a; Formula Ar1-b; Formula Ar1-c; Formula Ar1-d; Formula Ar1-e; Formula Ar1-f; Formula Ar1-g; Formula Ar1-h; Formula Ar1-i; Formula Ar1-j; Formula Ar1-k; The Ar2 structure has one or more of the Ar2-a to Ar2-e structures; Ar2-a; Ar2-b; Ar2-c; Ar2-d; Ar2-e; Wherein, X1 and X2 are independently selected from hydrogen, alkyl, cycloalkyl, aryl, fluoroalkyl, hydroxyl, alkoxy, phenoxy, cyano, nitro, amino, acetamino, ester, acyl, halogen or carboxyl; The n1 and m are independent integers from 1 to 4; The R 1 and R 3 The group is independently selected from the group of the structure shown in Formulas 1 to 7 or Formulas 10 to 11 and Formulas 14 to 17; The R 2 and R 4 The group is independently selected from the group represented by Formulas 1 to 7 or Formulas 10 to 11; Formula 1; Formula 2; Formula 3; Equation 4; Formula 5; Formula 6; Formula 7; Formula 10; Formula 11; Equation 14; Formula 15; Formula 16; Equation 17; Wherein, X 1 and X 2 It is independently selected from hydrogen, alkyl, cycloalkyl, aryl, fluoroalkyl, hydroxyl, alkoxy, phenoxy, cyano, nitro, amino, acetamino, ester, acyl, halogen or carboxyl; The y is an integer from 1 to 4.

4. The intrinsic porous polyimide film material according to claim 1, characterized in that, The intrinsic porous polyimide film material has a structure of Formula II; Formula II.

5. The method for preparing the intrinsically porous polyimide film material according to any one of claims 1 to 4, characterized in that, Includes the following steps: Materials including polyamide esters are subjected to an imidization reaction to obtain intrinsic porous polyimide films.

6. The method for preparing the intrinsic porous polyimide film material according to claim 5, characterized in that, Specifically, the following steps are included: S1) A monohydroxy compound is reacted with a dianhydride having the structure of formula a; wherein the monohydroxy compound is C8~C9. 30 The alkyl alcohol and the monohydroxy-terminated poly(dimethylsiloxane) having the structure of formula b; the monohydroxy-terminated poly(dimethylsiloxane) has a molecular weight of 600; Formula a; Formula b; R is a fatty chain; S2) A diamine having the structure of formula c and the reaction product obtained in step S1) are subjected to a polymerization reaction; Formula c; S3) The product obtained in step S2) is subjected to an imidization reaction to obtain an intrinsic porous polyimide film material; The imidization reaction includes, in sequence, a pre-baking curing stage, an imidization stage, and a pore-forming material escaping stage. The pre-baking and curing section is processed at a temperature of 50℃ to 150℃ for a time of 0.1 h to 10.0 h. The imidization process is performed at a temperature of 100℃ to 250℃ for a time of 0.1 h to 10.0 h. The temperature of the pore-forming material escaping section is 180℃~350℃, and the time is 0.1 h~10.0 h.

7. The method for preparing the intrinsic porous polyimide film material according to claim 6, characterized in that, In step S1), the reaction temperature is -5℃ to 60℃, and the reaction time is 6 h to 16 h.

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