CN108148411B

CN108148411B - Thermally processable low-Tg cyano-group-containing polyimide, polyimide film, polyimide powder and application thereof

Info

Publication number: CN108148411B
Application number: CN201810033963.XA
Authority: CN
Inventors: 刘佰军; 张莉; 井丽巍; 吴宪; 彭金武
Original assignee: Jilin University
Current assignee: Jilin University
Priority date: 2018-01-15
Filing date: 2018-01-15
Publication date: 2020-06-02
Anticipated expiration: 2038-01-15
Also published as: CN108148411A

Abstract

A thermally processable, low Tg cyano group-containing polyimide, polyimide film, polyimide powder and its preparation of flexible copper-clad foil, cyano group-containing polyimide/PEEK composite The application of membrane and cyano group-containing polyimide/Ph-PEEK composite membrane belongs to the technical field of high temperature resistant polymer materials. It is to prepare the polyimide precursor polyamic acid by reacting a cyano group-containing diamine monomer and a dianhydride monomer containing a flexible segment, and then prepare a cyano group-containing polyimide by means of heat buckle. Amine film; further attach the cyano group-containing polyimide film to the copper foil, attach the Kapton film to the other side surface of the cyano group-containing polyimide film, and form it by hot pressing at a certain temperature and pressure , the flexible clad copper foil with cyano group-containing polyimide as hot-melt adhesive was prepared. The performance parameters of the obtained flexible copper-clad foil are as follows: the peel strength reaches 1.21 N/mm, and the hardness reaches 6H.

Description

Thermally processable low-Tg cyano-group-containing polyimide, polyimide film, polyimide powder and application thereof

Technical Field

The invention belongs to the technical field of high-temperature-resistant high polymer materials, and particularly relates to cyano-containing polyimide, a polyimide film, polyimide powder and applications thereof in preparation of flexible copper-clad foils, cyano-containing polyimide/PEEK composite films and cyano-containing polyimide/Ph-PEEK composite films, wherein the cyano-containing polyimide, the polyimide film and the polyimide powder can be subjected to hot processing and have low Tg.

Background

Polyimide has excellent thermal stability, high mechanical strength and good dielectric property, and is applied to a plurality of high-tech fields such as aviation, aerospace, microelectronics and the like. Most aromatic polyimide resins, including Kapton film and the like, are not soluble in common organic solvents and are not melt-processed under heating, which also limits their wider application. Therefore, the preparation of a novel polyimide having processability, even if the imidized polymer has solubility or hot melt, is one of the important research directions in the field of polyimide preparation.

For aromatic polyimides, good hot melt processability requires polymers with low glass transition temperatures (low Tg) and high thermal stability. For example, commercial polyimide Ultem 1000 is a thermally processable resin, the main chain of which contains flexible ether linkages and isopropylidene groups, and the glass transition temperature (Tg) is around 217 ℃, and this low Tg has great advantages for melt processing of materials. Some research results show that the introduction of flexible linkages such as ether linkages into a polymer main chain having a rigid structure is one of effective strategies to improve polymer processability and solubility.

Besides the requirement of excellent thermal stability and good dissolution or melting performance, functional groups are introduced into the molecular chain of the polyimide, so that the polymer can be endowed with some new properties, and the material is provided with a wider application direction. For example, a trifluoromethyl group (-CF)₃) The introduction of the group into the molecular structure of the polyimide can reduce the dielectric constant of the polymer, improve the gas permeability and increase the light transmittance of the film. For flexible copper clad laminates, the tie layer is an important component, directly affecting the performance and service life of the product. The main components of the traditional bonding layer are generally acrylic and epoxy resins, the service temperature of the traditional bonding layer does not exceed 150 ℃, and the traditional bonding layer is easy to age at high temperature, so that the service life of the flexible copper clad foil is greatly limited. The polyimide resin has good thermal stabilityThe polyimide flexible copper clad laminate has excellent mechanical properties, and therefore is one of ideal materials for replacing epoxy glue in the polyimide flexible copper clad laminate.

Polyimide is one of ideal matrix components of composite materials as one of engineering plastics with the most excellent thermal and mechanical properties, but is affected by poor processability of the materials, and the research on compounding the materials with other high polymer materials is not very much. Polyetheretherketone represented by Victrex PEEK is taken as a kind of wholly aromatic polymer, and has excellent comprehensive properties including excellent thermal stability, chemical resistance, hydrolysis resistance, irradiation resistance and the like. However, the glass transition temperature is low, the high temperature section of the molecular chain section is easy to soften, the use of polyether-ether-ketone in the high temperature section is limited, and polyimide generally has excellent thermal stability and very high use temperature. The characteristics of the two are combined, the thermoplastic polyimide modified polyether-ether-ketone is hopefully prepared, and the composite material with excellent thermal and mechanical properties is obtained.

Disclosure of Invention

It is a first object of the present invention to provide a thermally processable, low Tg cyano group containing polyimide film material having advantages of low glass transition temperature, heat fusibility, high adhesion and excellent thermal stability, which can be used for the preparation of a polyimide flexible copper clad foil.

The second object of the present invention is to provide a method for preparing the above polyimide film containing a cyano group and a powder material.

The third purpose of the invention is to provide an application of the polyimide film material containing the cyano group in preparing a flexible copper-clad foil.

A fourth object of the present invention is to provide two composite membranes prepared based on the cyano group-containing polyimide and polyetheretherketone (PEEK, Ph-PEEK).

The thermally processable low-Tg cyano-containing polyimide film material has the structural formula as shown in the specification:

wherein R is-H or-CN; n is an integer of 5 to 500; ar is one of the following structures:

the invention relates to a preparation method of a thermally processable low-Tg cyano-containing polyimide film material, which comprises the following steps:

(1) preparing polyimide precursor polyamic acid by reacting diamine monomer containing cyano and dianhydride monomer containing flexible chain segment;

(2) preparing a polyimide film containing a cyano group from the polyimide precursor polyamic acid obtained in the step (1) in a manner of a thermal retaining ring;

(3) attaching the polyimide film containing the cyano groups obtained in the step (2) on a copper foil, attaching a Kapton film (formed by performing polycondensation and film casting on pyromellitic dianhydride PMDA and 4, 4-diaminodiphenyl ether ODA in a strong polar solvent and then performing imidization) on the other side surface of the polyimide film containing the cyano groups, and performing hot press molding at a certain temperature and pressure to obtain a flexible coated copper foil taking the polyimide containing the cyano groups as a hot melt adhesive;

(4) preparing cyano-containing polyimide powder from the polyimide precursor polyamic acid obtained in the step (1) in a chemical retaining ring mode, wherein the obtained cyano-containing polyimide powder can be dissolved in solvents such as N, N-dimethylacetamide (DMAc) or N-methylpyrrolidone (NMP);

(5) putting the cyano-containing polyimide powder obtained in the step (4) and polyether ether ketone (PEEK, Getga plastic engineering research Co., Ltd.) granules into a crusher for crushing, and performing hot press molding on the crushed powder at a certain temperature and under a certain pressure to obtain a cyano-containing polyimide/PEEK composite film;

(6) and (3) dissolving the cyano-containing polyimide powder obtained in the step (4) and phenyl side group polyether ether ketone (Ph-PEEK) in a polar aprotic organic solvent, and preparing the cyano-containing polyimide/Ph-PEEK composite membrane in a solution casting manner, wherein the polar aprotic organic solvent can be N, N-dimethylacetamide, N-dimethylformamide, dimethyl sulfoxide or N-methylpyrrolidone and the like.

The synthesis of the polyimide precursor polyamic acid in the step (1) comprises the following steps: under the conditions of no water and nitrogen, dissolving a diamine monomer containing cyano in a polar aprotic organic solvent, stirring to form a homogeneous solution, adding a dianhydride monomer containing a flexible chain segment for 3-5 times, and reacting at room temperature for 12-48 hours to obtain a polyamic acid solution; the molar ratio of the diamine monomer containing the cyano group to the dianhydride monomer containing the soft chain segment is 1: 1, the solid-to-liquid ratio of the sum of the using amounts of the diamine monomer containing the cyano group and the dianhydride monomer containing the soft chain segment to the polar aprotic organic solvent is 1 g: 5 to 30mL, the concentration of the obtained polyamic acid solution is 0.1429 to 0.25g/mL, the cyano group-containing diamine monomer is 2, 5-bis (4-amino-2-cyanophenoxy) biphenyl (DiCN-DA), 2, 5-bis (4-amino-2-cyanophenoxy) -4 '-cyano-biphenyl (TriCN-DA), etc., the soft segment-containing dianhydride monomer is 3,3',4,4 '-triphenyldiether tetracarboxylic dianhydride (HQODA), 4,4' - [ (hexafluoroisopropylidene) bis (p-phenyleneoxy) ] diphthalicylic anhydride (6FODA), etc., and the polar aprotic organic solvent is N, N-dimethylacetamide, N-dimethylformamide, dimethylsulfoxide, N-methylpyrrolidone, etc.

The preparation method of the cyano-containing polyimide film in the step (2) is as follows: diluting the polyamic acid solution obtained in the step (1) with a polar aprotic organic solvent (the concentration of the diluted polyamic acid is 0.0770-0.1111 g/mL), filtering and casting the solution on a clean glass plate by using fine gauze (300-500 meshes), drying for 4-12 h at 20-160 ℃, then performing a hot buckle reaction (gradient heating) under vacuum at 120-330 ℃, and finally naturally cooling to room temperature to obtain a cyano-containing polyimide film with the film thickness of 10-105 microns;

the preparation method of the flexible coated copper foil using the cyano-group-containing polyimide as the hot melt adhesive in the step (3) comprises the following steps: soaking a copper foil (with the thickness of 10-100 mu m) in an ethanol solution, and carrying out ultrasonic treatment for 1-4 h to remove grease on the surface of the copper foil; then placing the copper foil in 0.5-1.0 mol/L dilute sulfuric acid for soaking for 4-10 h, and removing oxides on the surface of the copper foil; then washing for 1-3 times by using distilled water, washing for 1-3 times by using absolute ethyl alcohol, and drying; attaching a polyimide film containing a cyano group to the pretreated copper foil, attaching a Kapton film (20-125 μm, manufactured by DuPont) to the other side of the polyimide film containing a cyano group, and performing hot press molding by using a hot press to obtain the flexible coated copper foil using the polyimide containing a cyano group as a hot melt adhesive.

The method for preparing the cyano-containing polyimide powder by the chemical retaining ring in the step (4) comprises the following steps: and (3) mixing the raw materials in a molar ratio of 1-1.2: 2, adding an accelerator and a dehydrating agent into the polyimide precursor polyamic acid obtained in the step (1), and stirring for 2-4 hours to perform chemical imidization reaction; after the reaction is finished, pouring the solution into absolute ethyl alcohol, separating out fibrous polyimide polymer, and extracting to obtain cyano-containing polyimide powder; wherein the dehydrating agent is acetic anhydride, and the accelerating agent is any one or a mixture of pyridine and triethylamine; the volume molar usage ratio of the dehydrating agent to the diamine monomer containing cyano is 1-2 mL: 1mol, wherein the volume molar usage ratio of the accelerator to the diamine monomer containing the cyano is 0.5-1 mL: 1 mol;

in the step (5), putting the cyano-containing polyimide powder and PEEK granules into a pulverizer to be pulverized and uniformly mixed, and performing hot press molding on the pulverized powder under the specified temperature and pressure conditions (the temperature range is 300-350 ℃ and the pressure range is 10-15 MPa) to obtain a cyano-containing polyimide/PEEK composite film with the film thickness of 10-150 microns;

weighing a certain proportion of polyimide powder containing cyano and Ph-PEEK, dissolving the polyimide powder containing cyano and Ph-PEEK in a polar aprotic organic solvent, wherein the mass ratio of the polyimide powder containing cyano to the Ph-PEEK is (1-9): 1, after the solid is completely dissolved to form a uniform and transparent solution, filtering and casting the solution on a clean glass plate by using fine gauze (300-500 meshes), and drying for 4-12 hours at the temperature of 20-160 ℃; and finally, naturally cooling to room temperature to obtain the cyano-containing polyimide/Ph-PEEK composite membrane with the membrane thickness of 10-150 microns.

Drawings

FIG. 1: a is a photograph of a polyimide film containing a cyano group, which corresponds to example 1; b is a photo of a cyano group-containing polyimide and phenyl side group polyether ether ketone composite membrane, wherein the picture b corresponds to example 7; the target membrane material is successfully prepared by adopting a solution casting method.

FIG. 2: corresponding to example 4, an infrared spectrum of a cyano-containing polyimide film material (DiCN-6FODA) when R is-CN and Ar is the structure of 4,4' - [ (hexafluoroisopropylidene) bis (p-phenyleneoxy) ] diphthalic anhydride (6 FODA).

FIG. 3: TGA profile corresponding to the cyano group-containing polyimide film prepared in example 4; from the TGA curve, it can be seen that the resulting cyano group-containing polyimide had a 5% thermogravimetric temperature of 523 ℃.

FIG. 4: DSC curve of polyimide film containing cyano group prepared corresponding to example 1; from the DSC curve, it can be seen that the Tg of the resulting cyano group-containing polyimide was 226 ℃.

FIG. 5: FIG. 5 is a photograph of a blend solution of a soluble polyetheretherketone and a polyimide having a cyano group, corresponding to example 7; it can be seen that they present a cosolvent and thus can be formed into a film by a solution casting method.

FIG. 6: TGA profile of Ph-PEEK with cyano group-containing polyimide composite membrane in example 7; as can be seen in the figure, the 5% thermal weight loss temperature of the composite membrane is 529 ℃, and the thermal stability of Ph-PEEK (5% thermal weight loss temperature is 510 ℃) is improved by adding the polyimide containing cyano groups.

Detailed Description

Example 1

In this example, a flexible copper clad foil was prepared, in which R in the general structural formula of the polyimide film material as the hot melt adhesive was — H, and Ar was 3,3',4,4' -triphenylbisethertetracarboxylic dianhydride (HQODA).

(i) Pretreatment of the surface of the copper foil: the copper foil is soaked in an ethanol solution and is subjected to ultrasonic treatment for 3 hours to remove grease on the surface of the copper foil, then the copper foil is soaked in 0.8mol/L dilute sulfuric acid for 6 hours to remove oxides on the surface of the copper foil, and the copper foil is washed once with distilled water and once with absolute ethanol and is dried.

(ii) Synthesis of polyimide precursor polyamic acid: 20.620g (50mmol) of diamine monomer (DiCN-DA) containing a cyano group is weighed into a 500mL three-necked bottle under the conditions of no water and nitrogen, 226mL of N, N-dimethylacetamide solution (with a solid content of 15%) is added, after stirring at room temperature to form a homogeneous solution, 20.115g (50mmol) of dianhydride monomer (HQODA) containing a flexible chain segment is added in three times, reaction is carried out at room temperature for 36h to obtain a light yellow polyamic acid solution (with a concentration of 0.1786g/mL), and the light yellow polyamic acid solution is kept stand for 3 h in a dry and clean environment to remove bubbles. The molar ratio of the diamine monomer containing the cyano group to the dianhydride monomer containing the soft chain segment is 1: 1, the solid-to-liquid ratio of the diamine monomer containing the cyano group and the dianhydride monomer containing the soft chain segment to the polar aprotic organic solvent is 1 g: 6 mL.

(iii) Preparation of polyimide film: n, N-Dimethylacetamide (DMAc) solvent was added to the polyamic acid solution to dilute it (the diluted polyamic acid concentration was 0.0770g/mL), the diluted solution was cast onto a clean glass plate by filtration with a fine gauze, dried in an oven at 80 ℃ for 6 hours, and then heat-buckled according to the following steps: reaction at 110 deg.c for 0.5 hr, reaction at 150 deg.c for 0.5 hr, reaction at 180 deg.c for 0.5 hr, reaction at 210 deg.c for 0.5 hr, reaction at 240 deg.c for 0.5 hr, reaction at 270 deg.c for 0.5 hr, and reaction at 310 deg.c for 0.5 hr; naturally cooling to room temperature to obtain the cyano-containing polyimide film, wherein the thickness of the obtained cyano-containing polyimide film is 10 mu m. The polyimide containing cyano groups obtained in this example was designated as DiCN-HQODA and had the following performance parameters: tg of 226 ℃ and 5% of thermal weight loss temperature of 549 ℃; the structural formula is as follows:

(iv) preparation of flexible copper-clad foil: and (3) attaching a polyimide film containing a cyano group to the copper foil (the thickness of the copper foil is 50 microns) treated in the step (i), attaching a Kapton film (manufactured by DuPont company) to the other side of the polyimide film containing the cyano group, and performing hot press molding by using a hot press under the conditions that the temperature is 350 ℃ and the pressure is 15MPa to obtain the flexible copper clad foil taking the polyimide containing the cyano group as the hot melt adhesive. The performance parameters of the flexible copper-clad foil obtained in this example are as follows: the peel strength reaches 1.21N/mm, the hardness reaches 6H, and other performance parameters of the obtained flexible copper-clad foil and the polyimide material containing the cyano-group refer to tables 1, 2 and 3.

Example 2

Referring to example 1, wherein R in the general structural formula of the polyimide film as the hot melt adhesive is-H and Ar is 4,4' - [ (hexafluoroisopropylidene) bis (p-phenyleneoxy) ] diphthalic anhydride (6FODA), the hot melt adhesive was prepared.

20.62g (50mmol) of diamine monomer containing cyano (DiCN-DA) is weighed into a 500mL three-necked bottle under the conditions of no water and nitrogen, 290mL of N, N-dimethylacetamide solution (with the solid content of 15%) is added, after stirring at room temperature to form a homogeneous solution, 30.82g (50mmol) of dianhydride monomer containing soft chain segments (6FODA) is added in three times, reaction is carried out at room temperature for 36h to obtain a light yellow polyamic acid solution (with the concentration of 0.1774g/mL), and the solution is kept stand for 4h in a dry and clean environment to remove bubbles.

The following procedure was followed in accordance with the procedure of example 1 to obtain a flexible copper-clad foil using a cyano group-containing polyimide as a hot melt adhesive. The polyimide containing cyano groups prepared in the example is named as DiCN-6FODA, and the performance parameters are as follows: tg of 217 ℃ and 5% of thermal weight loss temperature of 544 ℃; the structural formula is as follows:

the performance parameters of the flexible copper-clad foil obtained in this example are as follows: the peel strength was 0.68N/mm, the hardness was 6H, and other performance parameters of the obtained flexible copper-clad foil and cyano group-containing polyimide material are shown in tables 1, 2 and 3 (in accordance with example 1).

Example 3

Referring to example 1, wherein R in the general structural formula of the polyimide film as a hot melt adhesive is — CN, Ar is 3,3',4,4' -triphenyldiethanetetracarboxylic dianhydride (HQODA).

22.20g (50mmol) of diamine monomer containing cyano (TriCN-DA) is weighed into a 500mL three-necked bottle under the conditions of no water and nitrogen, 240mL of N, N-dimethylacetamide solution (with a solid content of 15%) is added, after stirring at room temperature to form a homogeneous solution, 20.115g (50mmol) of dianhydride monomer containing a flexible chain segment (HQODA) is added in three times, reaction is carried out for 24 hours at room temperature to obtain a light yellow polyamic acid solution (with a concentration of 0.1763g/mL), and the solution is kept stand for 3 hours in a dry and clean environment to remove bubbles. The following procedure was followed in accordance with the procedure of example 1 to obtain a flexible copper-clad foil using a cyano group-containing polyimide as a hot melt adhesive. The polyimide containing cyano group prepared in this example was named as TriCN-HQODA, and its performance parameters were as follows: tg of 238 ℃ and a 5% thermal weight loss temperature of 494 ℃ and a linear expansion coefficient (hereinafter abbreviated as CTE) of 53.69ppm/K, and the CTE of comparative example 1 is slightly reduced (the CTE of example 1 is 54.26 ppm/K); the structural formula is as follows:

the performance parameters of the flexible copper-clad foil obtained in this example are as follows: the peel strength was 1.01N/mm, the hardness was 6H, and other performance parameters of the obtained flexible copper-clad foil and cyano group-containing polyimide material are shown in tables 1, 2 and 3 (in accordance with example 1).

Example 4

Referring to example 1, wherein R in the general structural formula of the polyimide film material used as the hot melt adhesive is-CN, Ar is 4,4' - [ (hexafluoroisopropylidene) bis (p-phenyleneoxy) ] diphthalic anhydride (6 FODA).

22.20g (50mmol) of diamine monomer containing cyano (TriCN-DA) is weighed into a 500mL three-necked flask under the conditions of no water and nitrogen, 294mL of N, N-dimethylacetamide solution (with a solid content of 15%) is added, after stirring at room temperature to form a homogeneous solution, 30.82g (50mmol) of dianhydride monomer containing soft chain segments (6FODA) is added in three times, reaction is carried out at room temperature for 36h to obtain a light yellow polyamic acid solution (with a concentration of 0.1803g/mL), and the solution is kept stand for 4h in a dry and clean environment to remove bubbles. The following procedure was followed as in example 1 to obtain a flexible copper-clad foil using a cyano group-containing polyimide as a hot melt adhesive. The polyimide containing cyano groups prepared in the example is named as TriCN-6FODA, and the performance parameters are as follows: tg of 221 ℃ and a 5% thermal weight loss temperature of 523 ℃; the structural formula is as follows:

and its structure is characterized by infrared spectroscopy, as shown in figure 2.

The performance parameters of the flexible copper-clad foil obtained in this example are as follows: the peel strength was 0.79N/mm, the hardness was 6H, and other performance parameters of the obtained flexible copper-clad foil and cyano group-containing polyimide material are shown in tables 1, 2 and 3 (in accordance with example 1).

Example 5:

referring to example 1, 2.0620g (5mmol) of diamine monomer containing cyano group was weighed in a 100mL three-necked flask under anhydrous and nitrogen conditions, 20mL of N, N-dimethylacetamide solution (with a solid content of 15%) was added, after stirring at room temperature to form a homogeneous solution, 1.5511g (5mmol) of 4,4' -diphenyl ether dianhydride monomer (ODPA) was added in three portions, and after reacting at room temperature for 20 hours, 5mL of acetic anhydride and 2.5mL of pyridine were added and stirring was continued for 4 hours to perform imidization; after the reaction is finished, the solution is poured into absolute ethyl alcohol, fibrous polyimide polymer is separated out, and cyano group-containing polyimide powder is obtained through extraction, and the cyano group-containing polyimide is named as DiCN-ODA. The characterization results are similar to those in examples 1-4.

Example 6:

the cyano-containing polyimide powder and PEEK (produced by Getta engineering plastics research Co., Ltd.) were melt-blended. The method comprises the following specific steps: 20 parts of cyano group-containing polyimide powder and 80 parts of PEEK powder in example 6 were weighed, and the mixture was pulverized in a pulverizer. Weighing about 10g of (crushed) blended powder, and hot-pressing for 15min by a hot press under the conditions that the temperature is 350 ℃ and the pressure is 15MPa to obtain a composite film of the cyano-containing polyimide and the PEEK, wherein the thickness of the obtained composite film is 60 mu m. The performance parameters of the composite film obtained were as follows: the 5% thermal decomposition temperature was 503 ℃.

Example 7:

the solution blending of the cyano-containing polyimide (DiCN-ODA) powder of the chemical retaining ring and the soluble Ph-PEEK is carried out to prepare the uniform and transparent high-strength composite membrane. The method comprises the following specific steps: 0.8g and 0.2g of the cyano group-containing polyimide powder of example 6 was weighed out and dissolved in 9mL of N, N-dimethylacetamide (with a solid content of 10%), and after the solid was completely dissolved to form a uniform transparent solution, the solution was cast onto a clean glass plate by filtration with a fine gauze and dried in an oven at 120 ℃ for 10 hours. And then naturally cooling to obtain a corresponding polyimide and Ph-PEEK composite membrane with the membrane thickness of 80 microns. The 5% thermal weight loss temperature of the Ph-PEEK and cyano-containing polyimide composite membrane is 529 ℃.

Table 1: mechanical Properties of polyimide film containing cyano group

The mechanical properties of the polyimide films in Table 1 were measured at room temperature using a tensile machine having a tensile rate of 2mm/min, model number SHIMADZU AG-I1 KN, manufactured by Shimadzu corporation, Japan. The film was cut into 50mm by 5mm strips before testing, three strips per sample, and the average of three measurements was taken.

Table 2: thermal performance of polyimide films containing cyano groups

The glass transition temperature, the thermal weight loss temperature of 5% and the CTE linear expansion coefficient of the polymer are respectively determined by a Mettler-Toledo DSC 821^eType differential scanning calorimeter, TGA Pyris-1 type thermogravimetric analyzer and Mettler Toledo TMA/SDTA841e type thermomechanical analyzer; wherein, the Tg of each of the examples 1, 2, 3 and 4 is less than (or equal to) 238 ℃, and the requirement of low Tg of the thermally processable polyimide is met.

Table 3: other Properties of polyimide film containing cyano group

As shown in table 3, the test methods of the data in the table are as follows:

(1) the peel strength was measured at room temperature at a rate of 2mm/min using a SHIMADZU AG-I1 KN machine. The peel strength of the cyano polyimide film and the copper foil in the embodiments 1 and 3 is more than 1.0N/mm (1.21N/mm and 1.01N/mm respectively), and the requirement of high-performance copper-clad foil is met.

(2) The water absorption performance of the polyimide film containing the cyano-group is tested, according to the GB/T1034-2008 standard, at room temperature, the testing method is as follows, the polyimide film to be tested is dried in a clean and dry vacuum oven for 24 hours in advance, then the polyimide film is soaked in distilled water for 24 hours, the polyimide film is taken out, the surface water is wiped dry, and the water absorption rate is calculated according to the mass difference before and after soaking.

(3) The flame retardancy is based on the flammability standards of the plastic materials of UL 94.

(4) The dielectric property and the volume resistivity of the polyimide film containing the cyano are measured by an Agilent 4294A impedance analyzer, and the test frequency is 10³-10⁷Hz, the testing temperature is 25 ℃, silver paste with the diameter of 1cm on both sides is coated on a film sample, then the sample is placed in a vacuum oven to be dried for 5 hours to dry the liquid silver paste on the surface of the film, and finally the film sample is placed under an electrode to measure the dielectric constant.

(5) And (3) hardness testing: the hardness test is carried out according to GB/T6739 'Pencil hardness testing method for paint films'. Namely, a pencil (with the hardness of 2B-7H) used in the test is flattened and polished until the edge is sharp, the pencil is pushed for 1cm under the condition of forming an angle of 45 degrees with the plane and applying enough force, scratches are observed, and the hardness grade of the film material is obtained.

Claims

1. a thermally processable, low-Tg cyano-containing polyimide film material, the structural formula of which is as follows:

Wherein, R is -H or -CN; n=5～500 integer;

Ar is one of the following structures,

2. a thermally processable, low Tg cyano-containing polyimide film, characterized in that: it is prepared by the following steps,

Step (1): under anhydrous and nitrogen conditions, dissolve the cyano group-containing diamine monomer in an aprotic strong polar organic solvent, stir to form a homogeneous solution, and add the flexible segment-containing diamine in 3 to 5 times. The dianhydride monomer is reacted at room temperature for 12 to 48 hours to obtain a polyamic acid solution; the molar ratio of the cyano group-containing diamine monomer and the flexible segment-containing dianhydride monomer is 1:1, and the cyano group-containing The solid-to-liquid ratio of the sum of the amounts of diamine monomers and dianhydride monomers containing flexible segments to the aprotic strong polar organic solvent is 1 g: 5-30 mL, and the concentration of the obtained polyamic acid solution is 0.1429-0.25 g /mL, the cyano group-containing diamine monomer is 2,5-bis(4-amino-2-cyanophenoxy)biphenyl or 2,5-bis(4-amino-2-cyanophenoxy) )-4'-cyano-biphenyl, the dianhydride monomer containing the flexible segment is 3,3',4,4'-triphenylbisethertetracarboxylic dianhydride or 4,4'-[(hexafluoroiso Propylidene)bis(p-phenyleneoxy)]diphthalic anhydride, the aprotic strong polar organic solvent is N,N-dimethylacetamide, N,N-dimethylformamide, two Methyl sulfoxide or N-methylpyrrolidone;

Step (2): dilute the polyamic acid solution obtained in step (1) with a polar aprotic organic solvent to a solution with a concentration of 0.0770-0.1111 g/mL, filter the solution with fine gauze and cast it on a clean glass plate. Dry at 20～160℃ for 4～12h, then carry out thermal buckle reaction under vacuum and 120～330℃, and finally cool down to room temperature naturally to obtain a cyano group-containing polyimide film with a film thickness of 10～ 105μm.

3. A heat-processable, low-Tg cyano-containing polyimide powder, characterized in that: be that the molar ratio is that the accelerator and the dehydrating agent of 1～1.2:2 are added to the step (1) of claim 2 The obtained polyimide precursor polyamic acid is stirred for 2 to 4 hours to carry out chemical imidization reaction; after the reaction is completed, the solution is poured into absolute ethanol, and fibrous polyimide polymer is precipitated. Extraction to obtain cyano group-containing polyimide powder; wherein, the dehydrating agent is acetic anhydride, and the accelerator is any one or a mixture of both of pyridine and triethylamine; the dehydrating agent and cyanide-containing The volume molar dosage ratio of the cyano group-containing diamine monomer is 1-2 mL: 1 mol, and the volume molar dosage ratio of the accelerator and the cyano group-containing diamine monomer is 0.5-1 mL: 1 mol.

4. The application of the thermally processable, low Tg cyano group-containing polyimide film of claim 2 in the preparation of flexible copper-clad foils.

5. The application of the thermally processable, low Tg cyano group-containing polyimide powder of claim 3 in the preparation of a cyano group-containing polyimide/PEEK composite film.

6. The application of the thermally processable, low Tg cyano group-containing polyimide powder of claim 3 in the preparation of cyano group-containing polyimide/Ph-PEEK composite film.