A microporous, fat unit-containing polyimide film material and a method for producing the same

Abstract

This invention relates to the field of polyimide materials, specifically a microporous polyimide film material containing aliphatic units and its preparation method. Addressing the problem that the good solubility of microporous polyimides containing aliphatic units makes phase separation during imidization difficult and hinders pore formation, this invention specifically grafts compounds containing ether bonds or ester groups and monohydroxy-terminated poly(dimethylsiloxane) onto the polymer molecular chain. As chemical changes occur on the molecular chain, phase separation gradually and uniformly occurs within the film, gradually forming natural pores. This ensures uniform pore size while maximizing the preservation of the intrinsic properties of polyimide. Furthermore, this invention employs the most mature and efficient conventional polyimide film production process and equipment currently available, which is more conducive to the large-scale production of porous polyimide films and the preservation of the intrinsic properties of polyimide materials, eliminating the problems of film degradation and uneven pore size caused by additional processing steps.

Description

Technical Field

[0001] This invention relates to the field of polyimide materials, specifically a microporous polyimide thin film material containing aliphatic units and its preparation method. Background Technology

[0002] Polyimide (PI) is a special engineering plastic containing imide rings in its molecular chain. It possesses a variety of excellent properties, including dielectric properties, heat resistance, mechanical properties, chemical stability, and self-extinguishing properties. Among these properties, its heat resistance, far exceeding that of other polymer materials, is the most noteworthy. Most research both domestically and internationally has focused on PI's high heat resistance. In the new energy field, the safety of lithium-ion batteries is increasingly attracting widespread attention. The main cause of lithium battery safety accidents is that the most widely used battery separators are made of polyethylene and polypropylene. These materials have low temperature resistance, with a maximum operating temperature of only 170℃. During charging and discharging, the battery generates heat. When excessive internal heat accumulates and the temperature reaches the separator's limit, the separator shrinks and melts, causing the positive and negative electrodes to contact and short-circuit, leading to battery combustion and explosion. Furthermore, the weak polarity of polyolefin materials results in poor electrolyte wetting, inhibiting electrolyte absorption and lithium-ion passage, thus affecting battery efficiency. PI has heat resistance far exceeding that of other polymer materials. Ordinary PI can be used for a long time under conditions above 300℃. At the same time, the carbonyl group on the imide ring has strong polarity and good wetting properties for electrolyte. Preparing PI separators suitable for lithium-ion secondary batteries will be the best solution to improve the safety and service life of lithium batteries.

[0003] The presence of the imide ring is the fundamental reason why polyimide (PI) differs from other polymer materials in its heat resistance. Among PIs with different structures, those with a predominantly aromatic structure exhibit superior heat resistance. However, while fully aromatic PIs improve heat resistance, they also have a higher dielectric constant. The applications of porous polyimide films extend far beyond the new energy field. With the increasing integration of microelectronic products, materials with high dielectric constants will lose some of their competitive advantage. Specifically, as information technology advances at an increasingly rapid pace, microelectronic products are becoming increasingly miniaturized and ultra-thin. The integration of electrical components is increasing, and the spacing between wirings on chips is decreasing. Capacitive coupling and cross-interference between adjacent wirings can lead to signal lag. These more integrated electronic components require insulating layers with lower dielectric constants and dielectric losses. Currently, no commercially available dense PI film prepared with any chemical structure can meet these requirements.

[0004] To obtain PI films with higher dielectric properties, one approach is to create micropores within the film's physical structure, forming a PI-air two-phase system that significantly reduces the material's dielectric constant and dielectric loss. In the industry-renowned thermal method for producing polyimide films, during thermal imidization, as the solvent gradually evaporates at high temperatures, the molecular chains undergo cyclization at a specific temperature. At this point, the branches begin to detach, but remain in the system, promoting phase separation. In traditional polyimide film production, some polyimide structures also exhibit microphase separation during imidization. This is because the increased solvent evaporation and molecular chain cyclization in traditional polyimide film production lead to reduced polymer solubility. Furthermore, the evaporation temperature of the water and solvent removed during imidization in traditional polyimide film production is far below the polymer's glass transition temperature. This causes the pores left after water and solvent evaporation to be rapidly filled by the softened polymer, resulting in dense, non-porous traditional polyimide films.

[0005] Currently, the preparation of porous polyimide films can be broadly categorized into the following methods: doping (inorganic particles or hollow microspheres), template method, electrospinning, and phase inversion method. Based on the pore state of the formed film, they are classified as open-pore, closed-pore, and through-pore. Inorganic particle doping and template methods are mostly used to prepare open-pore films. In the inorganic particle doping method, inorganic particles are mixed into a polyamic acid solution, and after film formation, the particles are removed using a strong acid. Because the acid cannot completely penetrate the film, some particles remain, preventing the formation of a large number of through-pores. Furthermore, acid dissolution and etching can degrade the film, affecting its performance. Additionally, due to the electrostatic aggregation effect of inorganic particles, it is difficult to uniformly mix them into the high-viscosity solution, resulting in uneven pore size and distribution. The template method has a similar pore-forming mechanism to the inorganic particle doping method, also requiring strong acid treatment, and shares similar disadvantages. This method is also unsuitable for large-scale production. Electrospinning produces films with pores extending across both sides, resulting in large pore sizes, poor uniformity, and poor mechanical properties, making it difficult to meet the requirements of high-capacity, high-power lithium-ion batteries. This method also presents challenges for large-scale mass production. The phase inversion method involves preparing a semi-dry polyamic acid film and immersing it in a poor solvent, promoting phase separation from the outside in. The solvent leaching channels after phase separation form pores. Because phase separation occurs from the outside in and the degree of separation varies significantly, the pore size formed by this method differs greatly between the inner and outer sides of the film, resulting in uneven distribution. Furthermore, the method's reliance on external force to rapidly promote phase separation makes it difficult to ensure the uniformity of pore size and distribution, inevitably leading to pore collapse during subsequent imidization. Hollow microsphere doping produces films with mostly closed-pore structures. Due to the difficulty in overcoming the aggregation effect of microparticles, the uniformity of mixing directly determines the uniformity of pores. While all the above methods can form microporous structures on polyimide films, each method has significant drawbacks, with complex processes hindering large-scale film production.

[0006] On the other hand, since dielectric properties are intrinsic properties of materials, polyimides containing aliphatic units can be structurally derived to have lower dielectric constants. The aliphatic unit-containing polyimides refer to polyimides with aliphatic chains, alicyclic rings, or spirocyclic structures containing two or more carbon atoms between two aromatic rings. With an aliphatic unit structure as the main molecular chain, aliphatic polyimides are characterized by weak molecular chain rigidity, resulting in superior polymer flexibility and ductility. As lithium-ion battery separators, they are better able to prevent lithium crystal puncture in the electrolyte. Furthermore, the imide rings on the molecular chain provide significantly higher heat resistance than other types of polymers. However, aliphatic polyimides exhibit excellent solubility, which hinders phase separation and void formation during cyclization. Therefore, promoting phase separation during the imidization process of aliphatic polyimides is a challenge. Summary of the Invention

[0007] In view of this, the technical problem to be solved by the present invention is to provide a multi-microporous polyimide film material containing aliphatic units and its preparation method. The preparation method provided by the present invention can obtain a multi-microporous polyimide film material containing aliphatic units with uniform pore size and porosity, which has high mechanical properties and heat resistance, high porosity and good dielectric properties.

[0008] This invention provides a microporous polyimide film material containing aliphatic units, which is obtained by an imidization reaction of a material including aliphatic unit polyamide ester having the structure of Formula I.

[0009]

[0010] Wherein, z≥1000;

[0011] Ar1 and Ar2 are independently selected from substituted or unsubstituted aromatic groups, substituted or unsubstituted heteroaromatic groups, and substituted or unsubstituted aliphatic groups, and Ar1 and Ar2 are not simultaneously selected from substituted or unsubstituted aromatic groups or substituted or unsubstituted heteroaromatic groups.

[0012] M1 and M2 are independently selected from substituted or unsubstituted C1 to C2. 60 Aliphatic groups containing ether bonds, substituted or unsubstituted C1-C 60 aliphatic groups containing sulfide bonds, substituted or unsubstituted C1-C 60 The M1 and M2 may be the same or different, and contain an ester-based aliphatic group or a poly(dimethylsiloxane) group.

[0013] The structural unit of the polyamide ester containing aliphatic units of the present invention has M1 and M2 side chain groups. Preferably, M1 and M2 are independently selected from substituted or unsubstituted C3 to C4 groups. 30 Aliphatic groups containing ether bonds, substituted or unsubstituted C3-C 30 aliphatic groups containing sulfide bonds, substituted or unsubstituted C3-C 30 One of the following: an ester-containing aliphatic group or a poly(dimethylsiloxane) group having the structure of formula Ia;

[0014]

[0015] The x≥1 is preferably 5 to 10;

[0016] R represents an adipose chain.

[0017] The aliphatic structure of the above-mentioned aliphatic group can be a straight-chain aliphatic structure, a branched aliphatic structure, or a structure with an aliphatic ring; the above-mentioned aliphatic group can also replace functional groups, including but not limited to the following structures: -Cl, -F, or -CF3; the above-mentioned aliphatic groups containing ether bonds, aliphatic groups containing thioether bonds, and aliphatic groups containing ester groups can be aliphatic structures containing one or more ether bonds, thioether bonds, and ester groups.

[0018] In some embodiments of the present invention, the substituted or unsubstituted C1 to C 60 The aliphatic groups containing ether bonds have structures of formulas Ib to Ih:

[0019]

[0020] Wherein j1, j2 and j3 are independently at least 1, and the sum of j1, j2 and j3 is at most 59; j4 and j5 are independently at least 1, and the sum of j4 and j5 is at most 59; j6 and j7 are independently at least 1, and the sum of j6 and j7 is at most 59.

[0021] In some embodiments of the present invention, the above-described substituted or unsubstituted C3-C 30 The ester-containing aliphatic groups have structures of formulas Ii to Il:

[0022]

[0023] The polyamide ester containing aliphatic units of Formula I described in this invention has poly(dimethylsiloxane) groups, wherein the molar amount of the poly(dimethylsiloxane) groups accounts for 2% to 50% of the total molar amount of M1 and M2, preferably 17% to 22%. Less than 2% results in the film not forming pores, while more than 50% leads to excessively large pore sizes and a significant reduction in the mechanical properties of the film. This invention utilizes the M1 and M2 side chain structures in the structural units of the polyamide ester containing aliphatic units. Under thermal action, the molecular chains undergo cyclization and branch shedding. The boiling point of the shed compound is much higher than the shedding temperature, and it does not immediately volatilize but remains within the film, promoting phase separation. As the temperature increases, the self-support of the film increases. When the temperature reaches the point where a large amount of the shed compound volatilizes, the self-support within the film is sufficiently good, and the space occupied by the volatilized branch chains is retained, ultimately forming intrinsic micropores in the polyimide film. The pore-forming compound of the present invention is uniformly distributed in the polymer backbone in the form of chemical bonds, resulting in superior pore size and pore uniformity.

[0024] The structural unit of the polyamide ester containing aliphatic units of the present invention is Ar1 and Ar2 as the main chain groups. Preferably, Ar1 has one or more of the structures of formula Ar1-a to Ar1-k;

[0025]

[0026]

[0027] The Ar2 has one or more of the structures of Ar2-a to Ar2-e;

[0028]

[0029] Wherein, X is selected from hydrogen, alkyl, cycloalkyl, aryl, fluoroalkyl, hydroxyl, alkoxy, phenoxy, cyano, nitro, amino, acetamino, ester, acyl, halogen, or carboxyl; preferably, X is selected from -H, -Br, -Cl, -F, -NO2, -CN, -H, -CH3, -CH2CH3, -CH2CH2CH3, isopropyl, isobutyl, tert-butyl, cyclopentyl, cyclohexyl, phenyl, or naphthyl.

[0030] The y is an integer from 1 to 4 independently;

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

[0032]

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

[0034] The R 3 It is selected from alkyl groups with C1 or higher or fluorinated alkyl groups with C1 or higher.

[0035] Preferably, the R 3 Selected from formula R 3 -a~Form R 3 One of the -f structural groups:

[0036]

[0037] Where g≥1.

[0038] Of the above formulas Ar1-a to Ar1-k, the structure shown in formula Ar1-f is preferably... The structure shown in formula Ar1-g is preferably... The structure shown in formula Ar1-h is preferably... The structure shown in formula Ar1-i is preferably... The structure shown in formula Ar1-j is preferably... The structure shown in formula Ar1-l is preferably... The structure shown in formula Ar1-m is preferably... The structure shown in formula Ar1-o is preferably... The structure shown in formula Ar1-p is preferably... The structure shown in formula Ar1-s is preferably...

[0039] The microporous polyimide film material containing aliphatic units provided by the present invention has the structure shown in Formula II;

[0040]

[0041] Ar1, Ar2, and z are the same as in Equation I above, and will not be repeated here.

[0042] This invention also provides a method for preparing the microporous polyimide film material containing aliphatic units as described in any of the above technical solutions, comprising the following steps: subjecting a material containing aliphatic unit polyamide ester to an imidization reaction to obtain the microporous polyimide film material containing aliphatic units. The aliphatic unit polyamide ester described in this invention is the same as described above and will not be repeated.

[0043] The reaction formula for obtaining a microporous polyimide film material containing aliphatic units from the imidization reaction of the polyamide ester containing aliphatic units described in this invention is as follows:

[0044]

[0045] The imidization reaction temperature described in this invention is 50℃~350℃, preferably 80℃~300℃, and the imidization reaction time is 0.3h~30h. This invention, by designing aliphatic unit-containing polyamide ester structures—that is, changing only the intermediate structure without altering the final structure of the aliphatic unit-containing polyimide material—can achieve the stepwise imidization transformation of aliphatic unit-containing polyamide esters into aliphatic unit-containing polyimide microporous film structures through the aforementioned heat treatment within the temperature range. The design concept of using aliphatic unit-containing polyamide esters as intermediates ensures that the pore-forming compounds are uniformly distributed on the polymer molecular chains in the form of chemical bonds. Before detachment, they become integral with the polymer; after detachment, intrinsic pores are formed in situ, which is fundamentally different from other existing methods for forming pores on polyimide films. Because the branches of the aliphatic unit-containing polyamide ester form pores in situ after detachment, the resulting aliphatic unit-containing polyimide film has a uniform pore size and distribution. Furthermore, the method of this invention allows for continuous film formation using conventional thermal imidization, avoiding the adverse effects of additional processes on film performance. Simultaneously, this invention employs the most mature and efficient thermal imidization method for preparing polyimide films in the prior art, which, while maximizing the preservation of the intrinsic properties of polyimide, is more conducive to the large-scale production of microporous polyimide films, resulting in superior batch stability.

[0046] This invention employs a stepwise heating method based on the imidization progress of polyamide esters containing aliphatic units to control the formation of voids. Specifically, this invention sequentially subjects a resin containing aliphatic unit polyamide esters to a pre-curing stage and a post-high-temperature drying stage to obtain a microporous polyimide film material containing aliphatic unit polyimides. The pre-curing stage, also known as the solvent evaporation stage, has a temperature of 50°C to 150°C, preferably 80°C to 120°C, and a treatment time of 0.1 h to 10.0 h. This invention first subjects the material containing aliphatic unit polyamide esters to the pre-curing stage, which evaporates the solvent from the material to obtain a semi-dry film material that still contains residual solvent.

[0047] This invention involves pre-curing a material containing aliphatic polyamide esters, 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 escaping stage. The imidization stage is performed at a temperature of 100°C to 250°C, preferably 120°C to 180°C, for a duration of 0.1 h to 10.0 h. The pore-forming substance escaping stage is performed at a temperature of 150°C to 350°C, preferably 150°C to 300°C, more preferably 180°C to 270°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 segment names exactly; the physical and chemical changes in each stage 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. The above-mentioned thin film preparation process can also be adjusted according to the actual situation of continuous thin film production.

[0048] In some embodiments of the present invention, an adhesive comprising aliphatic polyamide ester is coated onto a carrier plate, followed by a pre-curing stage and a post-heating stage to obtain a microporous polyimide film material containing aliphatic units. The adhesive comprising aliphatic polyamide ester can be coated onto the carrier plate 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 steel plate. The present invention further involves an imidization reaction of the material comprising aliphatic polyamide ester. To facilitate pore formation, surfactants, nucleating agents, etc., can be added to the material for the imidization reaction.

[0049] In other embodiments of the present invention, an adhesive comprising aliphatic polyamide ester is coated onto a carrier plate, subjected to a pre-baking curing stage, and after the adhesive film is cured into a semi-dry film, the semi-dry film is peeled off from the carrier plate and supported by a hollow frame. For example, the edge of the film is fixed by the needle plate, chain clamp, or other equipment used in the production of existing polyimide films, and the film is supported and placed in a high-temperature environment to achieve imidization. This process enables volatiles to escape to both sides of the film, avoiding the situation where the pores on both sides are uneven due to the evaporation of solvent on one side.

[0050] The above-mentioned film preparation process is compatible with the conventional polyimide film production process. It does not require the addition of new processes and equipment on the basis of conventional polyimide film production processes and equipment. The film preparation process is efficient and low-cost, which is conducive to the rapid realization of large-scale industrial production of polyimide films with microporous aliphatic units.

[0051] Preferably, the preparation method of the microporous polyimide film material containing aliphatic units provided by the present invention includes the following steps:

[0052] S1) A monohydroxy compound is reacted with a dianhydride having the structure of formula a; wherein the monohydroxy compound is selected from substituted or unsubstituted C1-C1 compounds. 60 Aliphatic alcohols containing ether bonds, substituted or unsubstituted C1-C1 bonds 60 Thioether-containing aliphatic alcohols, substituted or unsubstituted C1-C1 alcohols 60 One or more of ester-containing aliphatic alcohols and monohydroxy-terminated poly(dimethylsiloxane) having the structure of formula b;

[0053]

[0054] S2) A diamine having the structure of formula c and the reaction product obtained in step S1) are subjected to a polymerization reaction;

[0055] H2N-Ar2-NH2 formula c;

[0056] S3) The product obtained in step S2) is subjected to an imidization reaction to obtain a microporous polyimide film material containing aliphatic units.

[0057] The reaction formula for the preparation method of the above-mentioned microporous polyimide film material containing aliphatic units is as follows:

[0058]

[0059] Specifically, in step S1) of the present invention, a monohydroxy compound and a dianhydride having the structure of formula a are reacted under the action of a catalyst, or the monohydroxy compound and a dianhydride having the structure of formula a are reacted directly without a catalyst; wherein the monohydroxy compound is selected from substituted or unsubstituted C1-C1 compounds. 60 Aliphatic alcohols containing ether bonds, substituted or unsubstituted C1-C1 bonds 60 Thioether-containing aliphatic alcohols, substituted or unsubstituted C1-C1 alcohols 60 One or more of ester-containing aliphatic alcohols and monohydroxy-terminated poly(dimethylsiloxane). Preferably, the monohydroxy compound is selected from substituted or unsubstituted C3-C4 compounds. 30 Aliphatic alcohols, substituted or unsubstituted C3-C 30 Aliphatic alcohols containing ether bonds, substituted or unsubstituted C3-C 30 Thioether-containing aliphatic alcohols, substituted or unsubstituted C3-C 30 One or more of the ester-containing aliphatic alcohols and a monohydroxy-terminated poly(dimethylsiloxane) having 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. In some embodiments of the present invention, the above-mentioned substituted or unsubstituted C1-C 60Aliphatic alcohols containing ether bonds include

[0060] Wherein j1, j2, and j3 are independently at least 1, and the sum of j1, j2, and j3 is at most 59; wherein j4 and j5 are independently at least 1, and the sum of j4 and j5 is at most 59; wherein j6 and j7 are independently at least 1, and the sum of j6 and j7 is at most 59; and wherein the above-mentioned substituted or unsubstituted C3 to C 30 Aliphatic alcohols containing ester groups include

[0061]

[0062] The reaction in step S1) of this invention is an esterification reaction, and the reaction temperature is -5℃ to 60℃, preferably 0℃ to 10℃; the reaction time in step S1) of this invention is 16h to 25h, and a portion of the product obtained is a fully esterified product, a diacid diester, whose structure is as follows: The other part is a partially esterified product, and its structural formula is as follows: The same applies to M1 and M2 as described above, and will not be repeated here.

[0063] 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.

[0064] The catalyst mentioned in step S1) of this invention may be selectively added or not added, 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: N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), γ-butyrolactone, 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-cyclohexylpyrrolidone, dimethyl sulfoxide, cresol, m-cresol, ethyl acetate, etc., or a mixture of two or more of them.

[0065] Based on extensive experimentation and analysis of chemical structure and physical properties, the inventors selected the aforementioned monohydroxy compounds as grafting compounds. These monohydroxy compounds are uniformly distributed on the polymer backbone. During baking, as the solvent continuously evaporates, the amidation reaction gradually occurs within a specific temperature range, resulting in significant phase separation. At this point, due to their high boiling points, most of the branched compounds detached during the amidation reaction remain in the film matrix. As the temperature rises, the film gradually develops a certain degree of self-support, at which point the detached side chains begin to escape, leaving behind the space they occupy, thus forming pores. Furthermore, since this invention utilizes conventional polyimide film production processes and equipment to produce polyimide films containing aliphatic units, the resulting polyimide films containing aliphatic units exhibit a very high degree of cyclization, eliminating the need for additional processes and thus maximizing the preservation of the excellent properties of polyimide.

[0066] In step S1) of this invention, after reacting a monohydroxy compound with a dianhydride having the structure of formula a, a diamine having the structure of formula c and the reaction product obtained in step S1) are subjected to a polymerization reaction.

[0067] Specifically, step S2) of the present invention includes, but is not limited to, the following implementation methods:

[0068] 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 solution containing aliphatic units. 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 undergoing an acyl chloride reaction with the acyl chloride reagent, followed by polymerization with a diamine to obtain a viscous polyamide ester solution containing aliphatic units. The reaction formula is as follows:

[0069]

[0070] 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 adhesive containing aliphatic units. In this process, the reaction product obtained in step S1) mainly consists of the fully esterified product, which is imidazoleized to convert into a diimidazole derivative, and then polymerized with a diamine to obtain a viscous polyamide ester adhesive containing aliphatic units. The reaction formula is as follows:

[0071]

[0072] 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 liquid containing aliphatic units; the condensing agent includes, but is not limited to, the following:

[0073]

[0074] 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.

[0075] 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 a microporous polyimide film material containing aliphatic units. The imidization reaction of the product obtained in step S2) is the same as described above and will not be repeated here.

[0076] This invention provides a microporous polyimide film material containing aliphatic units and its preparation method. Addressing the problem that the good solubility of aliphatic polyimides makes phase separation during imidization difficult and hinders pore formation, this invention specifically grafts compounds containing ether bonds or ester groups and monohydroxy-terminated poly(dimethylsiloxane) onto the polymer molecular chain. As chemical changes occur along the molecular chain, phase separation gradually and uniformly occurs within the film, gradually forming natural pores. This ensures uniform pore size while maximizing the preservation of the intrinsic properties of polyimide. Furthermore, this invention employs the most mature and efficient conventional polyimide film production process and equipment currently available, which is more conducive to the large-scale production of porous polyimide films and can also maximize the preservation of the intrinsic properties of the polyimide material, eliminating the problems of film degradation and uneven pore size caused by additional processing steps. The microporous polyimide film material containing aliphatic units described in this invention is an insulating material with excellent dielectric properties, which is very suitable for use in high-speed, high-frequency integrated circuits. It can also be used to prepare PI films with double-sided through-pores to replace polyolefins as lithium-ion battery separators as needed. Attached Figure Description

[0077] Figure 1 This is a SEM image of the micropores in the polyimide film containing aliphatic units prepared in Example 1.

[0078] Figure 2 This is a SEM image of the micropores in the polyimide film containing aliphatic units prepared in Example 2.

[0079] Figure 3 This is a SEM image of the micropores in the polyimide film containing aliphatic units prepared in Example 3.

[0080] Figure 4This is a SEM image of the micropores in the polyimide film containing aliphatic units prepared in Example 4.

[0081] Figure 5 This is a SEM image of the micropores in the polyimide film containing aliphatic units prepared in Example 5.

[0082] Figure 6 This is a SEM image of the micropores in the polyimide film containing aliphatic units prepared in Example 6.

[0083] Figure 7 SEM image of the micropores in the polyimide film containing aliphatic units prepared in Comparative Example 1.

[0084] Figure 8 The image shows the micropore SEM scan morphology of the polyimide film containing aliphatic units prepared in Comparative Example 2. Detailed Implementation

[0085] This invention discloses a microporous polyimide film material containing aliphatic units 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 obviously make modifications or appropriate alterations and combinations to 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.

[0086] The testing instruments, testing conditions, and methods for performing performance testing on the samples in this invention are as follows:

[0087] 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).

[0088] 2. Heat resistance: TGA-2 thermogravimetric analyzer (TGA), PerkinElmer, USA, heating rate 10℃ / min, nitrogen atmosphere.

[0089] 3. Glass transition temperature: Static thermomechanical analyzer (TMA Q400), test atmosphere is nitrogen, heating rate is 5℃ / min, temperature range is 40℃~400℃.

[0090] 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;

[0091] 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.

[0092]

[0093] In the formula, ρ1 is the sample density calculated based on mass and volume, and ρ0 is the density of polyimide.

[0094] The molecular weight range of the monohydroxy-terminated poly(dimethylsiloxane) used in the specific embodiments of the present invention is 600 to 6000.

[0095] The present invention will be further described below with reference to the embodiments:

[0096] Example 1

[0097] 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. 9.806 g of cyclobutanetetracarboxylic dianhydride (CBDA) and 120 mL of N,N-dimethylacetamide were added to the flask. 7.9 g of pyridine was added and mechanical stirring was started for about 30 min. 20.672 g of propylene glycol monolaurate and 12.087 g of poly(dimethylsiloxane) monohydroxy end-capping agent were 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 reacting at room temperature for 15 h.

[0098] After the esterification reaction was completed, a low-temperature cold bath was turned on, with the initial temperature set at -15℃. After the cold bath temperature reached the set temperature, 20.7g of DCC was added to the reaction flask and stirring was continued for about 30 minutes. Then, 10.012g of diaminodiphenyl ether (ODA) 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 temperature was set to -5℃ and the reaction was continued for 8 hours. The viscous gel was obtained by filtration.

[0099] After the synthesized viscous adhesive 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 180°C and held for 0.5 hours. The temperature was then further increased to 250°C and held for 0.5 hours to obtain a porous polyimide film containing aliphatic units.

[0100] 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 containing aliphatic units prepared in Example 1. The film's related properties are characterized as shown in Appendix Table 1.

[0101] Example 2

[0102] 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. 10.507 g of cyclopentanetetracarboxylic dianhydride (CPDA) and 120 mL of N,N-dimethylacetamide were added to the flask. 7.9 g of pyridine was added and mechanical stirring was started for about 30 min. 11.856 g of dipropylene glycol monomethyl ether and 12.087 g of poly(dimethylsiloxane) monohydroxy end-capping agent were 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 15 h.

[0103] After the esterification reaction was completed, a low-temperature cold bath was turned on, with the initial temperature set at -15℃. After the cold bath temperature reached the set temperature, 20.7g of DCC was added to the reaction flask and stirring was continued for about 30 minutes. Then, 10.012g of diaminodiphenyl ether (ODA) 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 temperature was set to -5℃ and the reaction was continued for 8 hours. The viscous gel was obtained by filtration.

[0104] After the synthesized viscous adhesive 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 containing aliphatic units.

[0105] 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 containing aliphatic units prepared in Example 2. The film's related properties are characterized as shown in Appendix Table 1.

[0106] Example 3

[0107] 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 flask. 7.9 g of pyridine was added and mechanical stirring was started for about 30 min. 13.136 g of triethylene glycol monomethyl ether and 13.570 g of poly(dimethylsiloxane) monohydroxy end-capping agent were 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 15 h.

[0108] After the esterification reaction was completed, a low-temperature cold bath was turned on, with the initial temperature set at -15℃. Once the cold bath temperature reached the set temperature, 20.7g of DCC was added to the reaction flask and stirring was continued for about 30 minutes. Then, 4.408g of 1,4-butanediamine was added in batches, followed by 80mL of N,N-dimethylacetamide. The temperature of the reaction solution was controlled at around -5℃. After all the 1,4-butanediamine was added, the cold bath temperature was set to -5℃ and the reaction was continued for 8 hours. The viscous gel was obtained by filtration.

[0109] After the synthesized viscous adhesive 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 180°C and held for 0.5 hours. The temperature was then further increased to 250°C and held for 0.5 hours to obtain a porous polyimide porous film containing aliphatic units.

[0110] 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 containing aliphatic units prepared in Example 3. The film's related properties are characterized as shown in Appendix Table 1.

[0111] Example 4

[0112] 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,N-dimethylacetamide were added to the flask. 7.9 g of pyridine was added and mechanical stirring was started for about 30 min. 13.136 g of triethylene glycol monomethyl ether and 12.087 g of poly(dimethylsiloxane) monohydroxy-terminated compound were 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 15 h.

[0113] After the esterification reaction was completed, a low-temperature cold bath was turned on, with the initial temperature set at -15℃. Once the cold bath temperature reached the set temperature, 20.7g of DCC was added to the reaction flask and stirring was continued for about 30 minutes. Then, 4.408g of 1,4-butanediamine was added in batches, followed by 80mL of N,N-dimethylacetamide. The temperature of the reaction solution was controlled at around -5℃. After all the 1,4-butanediamine was added, the cold bath temperature was set to -5℃ and the reaction was continued for 8 hours. The viscous gel was obtained by filtration.

[0114] After the synthesized viscous adhesive 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 containing aliphatic units.

[0115] 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 containing aliphatic units prepared in Example 4. The film's related properties are characterized as shown in Appendix Table 1.

[0116] Example 5

[0117] 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. 9.806 g of cyclobutanetetracarboxylic dianhydride (CBDA) and 120 mL of N,N-dimethylacetamide were added to the flask. 7.9 g of pyridine was added and mechanical stirring was started for about 30 min. 9.612 g of diethylene glycol monomethyl ether and 12.087 g of poly(dimethylsiloxane) monohydroxy end-capping agent were 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 reacting at room temperature for 15 h.

[0118] After the esterification reaction was completed, a low-temperature cold bath was turned on, with the initial temperature set at -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, 1,4-butanediamine was added in batches, followed by 80mL of N,N-dimethylacetamide. The temperature of the reaction solution was controlled at around -5℃. After all the ODA was added, the cold bath temperature was set to -5℃ and the reaction was continued for 8 hours. The mixture was then filtered to obtain a viscous gel.

[0119] After the synthesized viscous adhesive 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 containing aliphatic units.

[0120] 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 containing aliphatic units prepared in Example 5. The film's related properties are characterized as shown in Appendix Table 1.

[0121] Example 6

[0122] 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. 9.806 g of cyclobutanetetracarboxylic dianhydride (CBDA) and 120 mL of N,N-dimethylacetamide were added to the flask. 7.9 g of pyridine was added and mechanical stirring was started for about 30 min. 20.672 g of propylene glycol monolaurate and 12.087 g of poly(dimethylsiloxane) monohydroxy end-capping agent were 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 reacting at room temperature for 15 h.

[0123] After the esterification reaction was completed, a low-temperature cold bath was turned on, with the initial temperature set at -15℃. Once the cold bath temperature reached the set temperature, 20.7g of DCC was added to the reaction flask and stirring was continued for about 30 minutes. Then, 14.617g of 1,4-bis(4-aminophenoxy)benzene (1,4,4-APB) 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 temperature was set to -5℃ and the reaction was continued for 8 hours. The viscous gel was obtained by filtration.

[0124] After the synthesized viscous adhesive 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 containing aliphatic units.

[0125] 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 containing aliphatic units prepared in Example 6. The film's related properties are characterized as shown in Appendix Table 1.

[0126] Comparative Example 1

[0127] 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. 9.806 g of cyclobutanetetracarboxylic dianhydride (CBDA) and 120 mL of N,N-dimethylacetamide were added to the flask. 7.9 g of pyridine was added and the mechanical stirrer was turned on for about 30 min. 16.420 g of triethylene glycol monomethyl ether was dissolved in 50 mL of diethyl ether and added dropwise 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 15 h.

[0128] After the esterification reaction was completed, a low-temperature cold bath was turned on, with the initial temperature set at -15℃. Once the cold bath temperature reached the set temperature, 20.7g of DCC was added to the reaction flask and stirring was continued for about 30 minutes. Then, 9.913g of 4,4-diaminodiphenylmethane (MDA) 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 MDA was added, the cold bath temperature was set to -5℃ and the reaction continued for 8 hours. The viscous gel was obtained by filtration.

[0129] After the synthesized viscous adhesive 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 containing aliphatic units.

[0130] The microporous morphology of the prepared polyimide film is as follows: Figure 7 As shown, Figure 7 The image shows the SEM scan morphology of the micropores in the polyimide film containing aliphatic units prepared in Comparative Example 1. The relevant properties of the film are characterized as shown in Appendix Table 1.

[0131] Comparative Example 2

[0132] 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. 10.507 g of cyclopentanetetracarboxylic dianhydride (CPDA) and 120 mL of N,N-dimethylacetamide were added to the flask. 7.9 g of pyridine was added and the mechanical stirrer was turned on for about 30 min. 12.662 g of propylene glycol monolaurate and 30.821 g of poly(dimethylsiloxane) monohydroxy end-capping agent were 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 15 h.

[0133] After the esterification reaction was completed, a low-temperature cold bath was turned on, with the initial temperature set at -15℃. Once the cold bath temperature reached the set temperature, 20.7g of DCC was added to the reaction flask and stirring was continued for about 30 minutes. Then, 9.913g of 4,4-diaminodiphenylmethane (MDA) 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 MDA was added, the cold bath temperature was set to -5℃ and the reaction continued for 8 hours. Finally, 10g of poly(dimethylsiloxane) monohydroxy end-capping agent was added to the gel solution and stirred thoroughly for 3 hours to obtain a viscous gel solution.

[0134] After the synthesized viscous adhesive 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 containing aliphatic units.

[0135] The microporous morphology of the prepared polyimide film is as follows: Figure 8 As shown, Figure 8 The image shows the SEM scan morphology of the micropores in the polyimide film containing aliphatic units prepared in Comparative Example 2. The relevant properties of the film are characterized as shown in Appendix Table 1.

[0136] Table 1

[0137]

[0138] 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. A microporous polyimide film material containing aliphatic units, characterized in that, It is obtained by imidization reaction of materials including aliphatic unit 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, or unsubstituted aliphatic groups, and Ar1 and Ar2 are not simultaneously selected from unsubstituted aromatic groups or unsubstituted heteroaromatic groups; at least one of Ar1 and Ar2 is an unsubstituted aliphatic group. M1 and M2 are independently selected from unsubstituted C3~C 30 The aliphatic group containing ether bonds, unsubstituted C3~C 30 The polyamide ester having the structure of Formula I contains an ester-containing aliphatic group or a poly(dimethylsiloxane) group, and M1 and M2 are not the same; the aliphatic unit-containing polyamide ester has a poly(dimethylsiloxane) group, and the molar amount of the poly(dimethylsiloxane) group accounts for 17% to 22% 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 150℃~350℃, and the time is 0.1 h~10.0 h.

2. The microporous polyimide film material containing aliphatic units according to claim 1, characterized in that, M1 and M2 are independently selected from unsubstituted C3~C 30 The aliphatic group containing ether bonds, unsubstituted C3~C 30 One of the following: an ester-containing aliphatic group or a poly(dimethylsiloxane) group having the structure of formula Ia; Equation Ia; Where x≥1; R represents an adipose chain.

3. The microporous polyimide film material containing aliphatic units according to claim 1, characterized in that, The Ar1 has one or more of the structures of Ar1-a to Ar1-u; 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; Formula Ar1-l; Formula Ar1-m; Formula Ar1-n; Formula Ar1-o; Formula Ar1-p; Formula Ar1-q; Formula Ar1-r; Formula Ar1-s; Formula Ar1-t; Formula Ar1-u; The Ar2 has one or more of the structures of Ar2-e to Ar2-p; Ar2-e; Ar2-f; Ar2-g; Ar2-h; Ar2-i; Ar2-j; Ar2-k; Ar2-l; Ar2-m; Ar2-n; Ar2-o; Ar2-p; Wherein, X is selected from hydrogen, alkyl, cycloalkyl, aryl, fluoroalkyl, hydroxyl, alkoxy, phenoxy, cyano, nitro, amino, acetamino, ester, acyl, halogen or carboxyl; The y is an independent integer from 1 to 4; The R 1 and R 2 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; 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 R 3 It is selected from alkyl groups with C1 or higher or fluorinated alkyl groups with C1 or higher.

4. The microporous polyimide film material containing aliphatic units according to claim 1, characterized in that, The microporous polyimide film material containing aliphatic units has a structure of formula II; Formula II.

5. The method for preparing the multi-microporous polyimide film material containing aliphatic units according to any one of claims 1 to 4, characterized in that, Includes the following steps: Materials including aliphatic unit polyamide esters are subjected to an imidization reaction to obtain microporous aliphatic unit polyimide film materials.

6. The method for preparing the multi-microporous polyimide film material containing aliphatic units 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 selected from unsubstituted C3~C4 groups. 30 Aliphatic alcohols containing ether bonds, unsubstituted C3~C 30 One or more of ester-containing aliphatic alcohols and a 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 a microporous polyimide film material containing aliphatic units; 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 150℃~350℃, and the time is 0.1 h~10.0 h.

7. The method for preparing the multi-microporous polyimide film material containing aliphatic units according to claim 6, characterized in that, In step S1), the reaction temperature is -5℃ to 60℃, and the reaction time is 16 h to 25 h.

Images