CN117700740A

CN117700740A - Polyimide containing benzoxazine suspension side group and preparation method and application thereof

Info

Publication number: CN117700740A
Application number: CN202311772435.3A
Authority: CN
Inventors: 陈文求; 陈伟; 余洋; 牛翔; 贺娟; 李桢林; 范和平
Original assignee: Huashuo Electronic Materials Wuhan Co ltd; HAISO TECHNOLOGY CO LTD; Jianghan University
Current assignee: Huashuo Electronic Materials Wuhan Co ltd; HAISO TECHNOLOGY CO LTD; Jianghan University
Priority date: 2023-12-21
Filing date: 2023-12-21
Publication date: 2024-03-15

Abstract

The invention belongs to the technical field of polyimide resin materials, and particularly relates to polyimide containing benzoxazine suspension side groups, and a preparation method and application thereof. The polyimide is prepared by taking soluble polyimide resin containing phenol hanging side groups, monofunctional aromatic amine compounds and aldehyde compounds as raw materials through polymerization reaction, wherein the molar ratio of phenolic hydroxyl groups to the monofunctional aromatic amine compounds to the aldehyde compounds in the soluble polyimide resin containing the phenol hanging side groups is 1:0.8 to 1.2:1.6 to 2.5. The polyimide resin containing the benzoxazine suspension side group has extremely low dielectric constant, dielectric loss and water absorption rate, higher peel strength on copper foil or PI film, excellent soldering resistance, dimensional stability and flexibility, and low cost, and is suitable for flexible printed circuit boards with medium and low dielectric loss.

Description

Polyimide containing benzoxazine suspension side group and preparation method and application thereof

Technical Field

The invention belongs to the technical field of polyimide resin materials, and particularly relates to polyimide containing benzoxazine suspension side groups, and a preparation method and application thereof.

Background

Taking a flexible copper clad laminate as an example, a common flexible copper clad laminate is prepared by compounding a Polyimide (PI), polyester (PET) or Polynaphthalene (PEN) film serving as an insulating medium film with a copper foil. The preparation of the adhesive is carried out by a three-layer method in the early years in the industry, namely, the adhesive is bonded with acrylic ester or epoxy adhesive. The obtained three-layer flexible copper clad laminate has higher peeling strength, but the heat resistance of the adhesive layer determines that the high temperature resistance is poor. The flexible copper clad laminate of the two-layer method without glue developed in recent years is actually obtained by adding an extremely thin thermoplastic polyimide material on the surface of a thermosetting polyimide film as an adhesive to bond the thermoplastic polyimide material and the copper foil together. The excellent high temperature resistance makes the flexible copper clad laminate become a flexible printed circuit board, especially a multilayer board, since the advent of the flexible copper clad laminate. However, the common flexible copper clad laminate (two-layer method and three-layer method), adhesive film/sheet, cover film, insulating medium film thereof, and adhesive used cannot meet the use requirements of the high-frequency and high-speed flexible printed circuits such as the above 5G communication and mobile Internet.

At present, the commercialized special insulating medium film materials for the low-dielectric flexible copper-clad plate mainly comprise two kinds of Liquid Crystal Polymer (LCP) and Modified Polyimide (MPI). LCP, although having excellent dielectric properties at high frequencies, has limited sources and little space for modification due to molecular structure, especially multilayer board processing is relatively poor; MPI mainly contains fluorine, has the advantages of high raw material cost, halogen containing harm, relatively low binding force with copper foil, relatively complex preparation process, relatively low mechanical strength of film, relatively high water absorption and the like. In addition, because the production, manufacture and use of the MPI flexible copper clad laminate are completely the same as those of the conventional polyimide flexible copper clad laminate, MPI becomes the main choice of flexible printed circuit base materials.

Meanwhile, due to the core technology of manufacturing the two layers of flexible copper clad laminate, key performance indexes such as heat resistance, adhesiveness, dimensional stability and the like of the polyimide film and the copper foil are balanced. Currently, the industry is mainly solved by using a combination of thermoplastic polyimide and thermosetting polyimide, such as two-coating thermal imidization plus one hot press compounding process (see specifically US P20070178323A1, US P20040063900A1, WO 2007083526 A1) represented by japan brillouin corporation and two-coating thermal imidization plus one hot press compounding process (US P20030012882, US P20070149758, CN 1527763 a) represented by japan new japanese iron corporation. Both techniques have respective advantages and disadvantages, wherein the thermoplastic polyimide is compounded with a copper foil or a thermosetting polyimide film, particularly with a thermosetting polyimide film, and the most important performance index, namely the bonding strength, is completely dependent on the physical winding action between two polyimide molecular chains and has no chemical bonding action, so that the performance index is often slightly higher than the related industry standard value. In addition, the preparation technology and related products of the two TPI composite films are monopoly operated by the two Japanese companies alone, and the sources of the two TPI composite films are greatly limited.

In recent years, many universities, research institutes or enterprises are developing researches on low dielectric modified polyimide for three major substrates (adhesive films/sheets, cover films and flexible copper clad laminates) of flexible printed circuits at home and abroad. For example, chinese patent CN 105644064A, CN 113307971A, CN 111019345a and the like synthesized thermosetting PI containing benzimidazole or benzoxazole structure with high heat resistance and high dimensional stability, by means of chemical bonding between benzimidazole or benzoxazole and copper ions therein to improve adhesion with copper foil. Chinese patent CN 102304228A, CN 102408564A, CN 105644055A, CN 110204717a and the like have improved adhesion to thermosetting polyimide films and copper foil by synthesizing thermoplastic polyimide containing reactive side groups such as hydroxyl, carboxyl, nitrile, sulfonic acid groups and the like. Chinese patent CN 104513395a synthesizes polyimide having an epoxy group in the main chain to improve adhesion with copper foil. Chinese patent CN 115286756a discloses a benzoxazine-terminated flexible polyimide resin prepared from primary amine-terminated flexible polyimide oligomer, aldehyde compound and monofunctional phenol compound as reactants. By utilizing the characteristics that benzoxazine can undergo ring-opening polymerization under a heating condition and small molecules are not released in a curing process, the adhesive which has low dielectric constant and dielectric loss and can meet the requirements of high-frequency flexible copper-clad plate adhesion, tin soldering resistance and the like can be prepared after curing, so that the adhesive material formed by the benzoxazine can meet the requirements of the high-frequency flexible copper-clad plate through the characteristics of benzoxazine resin. However, since the benzoxazine structure is located at both ends of the flexible polyimide, the density of subsequent thermal crosslinking thereof is relatively low, and finally the contribution to the adhesiveness and heat resistance thereof is limited. Most importantly, the main chain or side chain of the flexible polyimide contains long-chain alkyl or/and alkoxy aliphatic structures, so that the heat resistance of the flexible polyimide is inferior to that of common thermoplastic polyimide.

Chinese patent CN 101353424B discloses a thermoplastic polyimide resin containing active phenolic hydroxyl side groups and a flexible copper-clad plate made therefrom. The bonding force of the interface between the cyanate ester component in the thermosetting polyimide resin and the active phenolic hydroxyl group on the thermoplastic polyimide main chain is enhanced by the chemical action of the cyanate ester component and the active phenolic hydroxyl group, so that the peeling strength of the whole flexible copper-clad plate is improved. From its specification [0082], it is known that the cyanate ester resin is dispersed in a precursor polyamic acid solution of a thermosetting polyimide by high-speed shearing. However, it is known from the relevant technical literature that Lewis acids (including carboxylic acids) are catalysts for the autopolymerization of cyanate monomers. Thus, the stability of the cyanate ester-containing thermosetting polyamic acid solution remains to be further verified. In addition, the dielectric constants and dielectric losses of thermoplastic polyimides and thermosetting polyimides synthesized from the amine monomers and anhydride monomers disclosed in this patent are not described.

Disclosure of Invention

The invention aims to provide polyimide containing a benzoxazine suspension side group and a preparation method and application thereof, the polyimide containing the benzoxazine suspension side group can be subjected to ring-opening polymerization under the heating condition by virtue of the characteristics that small molecules are not released in the curing process, and the polyimide containing the benzoxazine suspension side group can be prepared into an adhesive with low dielectric constant and dielectric loss after curing, and can meet the requirements of adhesiveness, soldering resistance, dimensional stability, bending resistance and the like of a high-frequency flexible printed circuit board base material, and the prepared polyimide cured product containing the benzoxazine suspension side group has extremely low dielectric constant (2.99-3.34), dielectric loss (0.005-0.0082) and water absorption rate (1-1.3 wt.%), and the adhesive film/sheet, the cover film or the flexible copper-clad plate for a flexible printed circuit, which are prepared from the polyimide containing the benzoxazine suspension side group, has higher peeling strength, excellent bending resistance and dip soldering resistance.

The invention solves the technical problems through the following technical proposal.

The first object of the invention is to provide a polyimide containing a benzoxazine hanging side group, wherein the polyimide is prepared by taking soluble polyimide resin containing a phenol hanging side group, a monofunctional aromatic amine compound and an aldehyde compound as raw materials through polymerization reaction, and the mole ratio of phenolic hydroxyl groups, the monofunctional aromatic amine compound and the aldehyde compound in the soluble polyimide resin containing the phenol hanging side group is 1:0.9 to 1.3:1.8 to 2.5.

Further, the number average molecular weight Mn of the soluble polyimide resin containing the phenol hanging side group is 1000-100000, and the hydroxyl value is 2-100 mgKOH/g.

Further, the preparation method of the soluble polyimide resin containing phenol hanging side groups comprises the following steps:

the aromatic diamine is prepared by taking a first aromatic diamine monomer, a second aromatic diamine monomer and aromatic tetracarboxylic dianhydride as raw materials and sequentially carrying out low-temperature solution copolycondensation, high Wen Gongfei dehydration two-step reaction or one-step solution polymerization reaction in a first solvent.

Further, the first aromatic diamine monomer is at least one of aromatic diamine compounds containing phenol side groups;

The second aromatic diamine monomer is 4,4' -diaminodiphenyl ether, 3,4' -diaminodiphenyl ether, 4' -diaminobenzophenone, 3,4' -diaminobenzophenone, 4' -diaminodiphenylmethane 3,4' -diaminodiphenyl methane, 4' -diaminodiphenyl sulfone, 3,4' -diaminodiphenyl sulfone at least one of 2,2' -bis (4 ' -aminophenyl) propane, 2' -bis [ 4' - (4 ' -aminophenoxy) phenyl ] propane;

the aromatic tetracarboxylic dianhydride monomer is at least one of 3,3', 4' -tetracarboxylic dianhydride benzophenone, 4' -oxydiphthalic anhydride and bisphenol A dianhydride;

the first solvent is at least one of N, N '-dimethylformamide, N' -dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, m-cresol, cyclopentanone, cyclohexanone and methylcyclohexane.

Further, the ratio of the sum of the molar amounts of the first aromatic diamine monomer and the second aromatic diamine monomer to the molar amount of the aromatic tetracarboxylic dianhydride is 0.9 to 1.1:1, wherein the mole ratio of the first aromatic diamine monomer to the second aromatic diamine monomer is 1-99: 80-20.

Further, the monofunctional aromatic amine compound has a structure as shown below:

Wherein R is ₁ 、R ₂ 、R ₃ 、R ₄ Or R is ₅ Each substituent is independently H, alkyl, alkoxy, cycloalkyl, or aryl, and wherein one or more substituents are H; the number of carbon atoms in the alkyl group and the cycloalkyl group is 1 to 10.

Further, the aldehyde compound is formaldehyde and/or paraformaldehyde.

The second object of the invention is a method for preparing the polyimide containing the benzoxazine suspension side group, which comprises the following steps:

mixing soluble polyimide resin containing pendant phenol groups, a monofunctional aromatic amine compound and an aldehyde compound, and then adding a second solvent to perform polymerization reaction for 0.5-10 h at 60-180 ℃ to obtain a solution of polyimide containing pendant benzoxazine groups;

the second solvent is used for controlling the polyimide solid content of the benzoxazine suspension side group to be 10-40 wt%, and the second solvent is at least one of N, N '-dimethylformamide, N' -dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, m-cresol, cyclopentanone, cyclohexanone, methylcyclohexane, toluene, xylene and dioxane.

The third object of the invention is the application of the polyimide containing the benzoxazine suspension side group in preparing a low-dielectric flexible printed circuit board, and the adhesive film/sheet for the flexible printed circuit, which is made of the polyimide containing the benzoxazine suspension side group; or: coating the polyimide coating containing the benzoxazine suspension side group on one side or two sides of the insulating medium film to obtain a rubberized covering film for the flexible printed circuit; or: the flexible copper-clad plate for the flexible printed circuit consists of an insulating medium film, a coating layer of polyimide containing benzoxazine suspension side groups and copper foil pressed on the coating layer, wherein the coating layer is coated on one side or two sides of the insulating medium film.

Further, the insulating medium film is at least one of a polyimide film, a polyester film, a polynaphthalate film, a liquid crystal polymer film, a polyether-ether-ketone film or a polyphenylene sulfide film, and the thickness of the base material film is 5-100 mu m; the thickness of the adhesive film/sheet or coating prepared by the polyimide containing the benzoxazine suspension side group is 2-50 mu m; the copper foil is electrolytic copper foil or rolled copper foil, the thickness is 1/4-3 oz, and the roughness Rz of the pressed surface is less than or equal to 1.5 mu m.

Compared with the prior art, the invention has the following beneficial effects:

according to the invention, by means of the characteristic that the benzoxazine pendant side group can undergo ring-opening polymerization under a heating condition and small molecules are not released in the curing process, the adhesive with low dielectric constant and dielectric loss and meeting the requirements of adhesiveness, soldering resistance, dimensional stability, bending property and the like of the high-frequency flexible printed circuit board substrate can be prepared after curing. The position and the content of the benzoxazine suspension side group are strictly controlled by means of molecular design, formula adjustment and the like, so that the crosslinked network structure and the density of a cured product of the benzoxazine suspension side group are regulated and controlled, and the performance index is optimized.

The polyimide containing the large-volume benzoxazine suspension side group has very low reactivity (generally considered as basically no reaction) in the room temperature range (-20 ℃ to 50 ℃), and the benzoxazine suspension side group can continue to undergo ring-opening reaction at the temperature of more than or equal to 150 ℃ to play a role in curing and crosslinking, so that the whole polyimide adhesive containing the benzoxazine suspension side group has good B-stage (namely, is not completely cured) stability, and the polyimide containing the large-volume benzoxazine suspension side group structure is synthesized to ensure the organic solubility and further has good solution processability, and is used as a semi-cured adhesive film/sheet or a cover film or a flexible copper-clad plate to ensure good processability, room temperature storage stability and the like in the preparation process of a flexible printed circuit.

Compared with the existing LCP or fluorine-containing MPI, the invention has wide sources of raw materials and low cost, and the obtained polyimide containing the benzoxazine suspension side group has extremely low dielectric constant (2.99-3.34), dielectric loss (0.005-0.0082) and water absorption (1-1.3 wt.%) and excellent dimensional stability; the adhesive film/sheet, the cover film or the flexible copper-clad plate for the flexible printed circuit, which are prepared by polyimide containing the benzoxazine suspension side group, have higher peeling strength, excellent flexibility and dip soldering resistance, and low cost, and are suitable for flexible printed circuit boards with medium and low dielectric loss.

Detailed Description

In order to enable those skilled in the art to better understand the technical solutions of the present invention, the following description clearly and completely describes the technical solutions in the embodiments of the present invention. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

It should be noted that the technical terms used in the present invention are only for describing specific embodiments, and are not intended to limit the scope of the present invention, and various raw materials, reagents, instruments and equipment used in the following embodiments of the present invention may be purchased commercially or prepared by existing methods unless otherwise specifically described.

The polyimide containing the benzoxazine pendent group is prepared by taking soluble polyimide resin containing the phenol pendent group, a monofunctional aromatic amine compound and an aldehyde compound as raw materials through polymerization reaction, wherein the mole ratio of phenolic hydroxyl groups, the monofunctional aromatic amine compound and the aldehyde compound of the soluble polyimide resin containing the phenol pendent group is 1:0.9 to 1.3:1.8 to 2.5.

The polyimide containing a large-volume benzoxazine suspension side group structure is synthesized to ensure the organic solubility of the polyimide so as to ensure good solution processability, and meanwhile, the proper amount of benzoxazine suspension side group can undergo ring-opening polymerization under the heating condition without releasing small molecules in the curing process, so that the adhesive with low dielectric constant and dielectric loss can be prepared after curing, and the adhesive can meet the requirements of the adhesiveness, soldering resistance, dimensional stability, bending property and the like of a high-frequency flexible printed circuit board substrate. The position and the content of the benzoxazine suspension side group are strictly controlled by means of molecular design, formula adjustment and the like, so that the crosslinked network structure and the density of a cured product of the benzoxazine suspension side group are regulated and controlled, and the performance index is optimized.

In some preferred embodiments, the soluble phenol pendant group-containing polyimide resin has a number average molecular weight Mn of 1000 to 100000 and a hydroxyl number of 2 to 100mgKOH/g. The preparation method comprises the following steps:

In some preferred embodiments, the first aromatic diamine monomer is at least one of an aromatic diamine compound comprising a pendant phenol group; the aromatic diamine compound containing the phenol side group has the following structural formula:

in some embodiments, the aromatic diamine compound containing a pendant phenol group is:

In some preferred embodiments, the ratio of the sum of the molar amounts of the first aromatic diamine monomer and the second aromatic diamine monomer to the molar amount of the aromatic tetracarboxylic dianhydride is 0.9 to 1.1:1, wherein the mole ratio of the first aromatic diamine monomer to the second aromatic diamine monomer is 1-99: 80-20.

In some preferred embodiments, the monofunctional aromatic amine compound has the structure shown below:

wherein R is ₁ 、R ₂ 、R ₃ 、R ₄ Or R is ₅ Substituents are each independently H, alkyl, alkoxy, cycloalkyl or aryl. In some embodiments, R ₁ 、R ₂ 、R ₃ 、R ₄ Or R is ₅ One or more substituents in the substituents are H; the number of carbon atoms in the alkyl group and the cycloalkyl group is 1 to 10. In some specific embodiments, the monofunctional aromatic amine compound is aniline, para-methylaniline, para-methoxyaniline, para-cyclohexylaniline, and the like.

In some preferred embodiments, the aldehyde compound is formaldehyde and/or paraformaldehyde.

The preparation method of the polyimide containing the benzoxazine suspension side group comprises the following steps:

mixing soluble polyimide resin containing phenol hanging side groups, a monofunctional aromatic amine compound and an aldehyde compound, and then adding a second solvent to perform polymerization reaction for 0.5-10 h at 60-180 ℃;

the dosage of the second solvent is 10-40 wt.% of the polyimide solid content containing benzoxazine suspension side groups, and the second solvent is at least one of N, N '-dimethylformamide, N' -dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, m-cresol, cyclopentanone, cyclohexanone, methylcyclohexane, toluene, xylene and dioxane.

The polyimide containing the large-volume benzoxazine suspension side group has very low reactivity (generally considered as basically no reaction) in the room temperature range (-20 ℃ to 50 ℃), the benzoxazine suspension side group can continue to undergo ring-opening reaction at the temperature of more than or equal to 150 ℃ to play a role in curing and crosslinking, and the characteristic of the polyimide adhesive is that the whole polyimide adhesive containing the benzoxazine suspension side group has good B-stage (namely, is not completely cured) stability, so that the polyimide containing the large-volume benzoxazine suspension side group structure is synthesized to ensure the organic solubility of the polyimide and further has good solution processability, and the polyimide adhesive can be used as a semi-cured adhesive film/sheet, a cover film or a flexible copper-clad plate in the preparation process of a flexible printed circuit to ensure the polyimide adhesive has good processability, room temperature storage stability and the like.

The application of the polyimide containing the benzoxazine suspension side group in preparing the low-dielectric flexible copper-clad plate, and the adhesive film/sheet for the flexible printed circuit, which is prepared from the polyimide containing the benzoxazine suspension side group; or: coating the polyimide coating containing the benzoxazine suspension side group on one side or two sides of the insulating medium film to obtain a rubberized covering film for the flexible printed circuit; or: the flexible copper-clad plate for the flexible printed circuit consists of an insulating medium film, a coating layer of polyimide containing benzoxazine suspension side groups and copper foil pressed on the coating layer, wherein the coating layer is coated on one side or two sides of the insulating medium film.

In some preferred embodiments, the insulating medium film is at least one of a polyimide film, a polyester film, a polynaphthalate film, a liquid crystal polymer film, a polyetheretherketone film or a polyphenylene sulfide film, and the thickness of the substrate film is 5-100 μm; the thickness of the adhesive film/sheet or coating prepared by the polyimide containing the benzoxazine suspension side group is 2-50 mu m; the copper foil is electrolytic copper foil or rolled copper foil, the thickness is 1/4-3 oz, and the roughness Rz of the pressed surface is less than or equal to 1.5 mu m.

The invention is further illustrated by the following specific examples:

example 1

The preparation of the polyimide resin containing phenol hanging side groups is as follows:

4.325g of 3- (p-hydroxyphenoxy) -1, 5-diaminobenzene, 36.041g of 4,4' -diaminodiphenyl ether, 105.139g of bisphenol A dianhydride and 824g of N-methylpyrrolidone were reacted by stirring at 4℃for 24 hours by introducing nitrogen. Then 40.84g of acetic anhydride and 20.24g of triethylamine were added thereto and the reaction was continued with stirring at 4℃for 24 hours. After the reaction is finished, pouring the reaction solution into 5L of deionized water to separate out, and filtering, washing and drying to obtain the corresponding soluble polyimide resin solid containing the phenol hanging side group. The hydroxyl value is about 8mgKOH/g and the Mn is about 65000g/mol.

The preparation of the polyimide containing pendant benzoxazine groups is as follows:

100g of the soluble polyimide resin solid containing phenol hanging side groups, 1.32g of aniline, 0.98mL of 30% formaldehyde solution, 400g of N, N' -dimethylformamide and 66g of toluene are added into a reaction vessel with a reflux condensation dispenser, stirred and dissolved, and then heated to 120 ℃ for reflux reaction for 8 hours. And cooling to room temperature after the reaction is finished, and obtaining the polyimide resin solution containing the benzoxazine pendant group, wherein the solid content of the polyimide resin solution is about 18%.

Example 2

2.904g of 4,4' -diamino-4 ' -hydroxytriphenylmethane, 38.044g of 3,4' -diaminodiphenyl ether, 105.659g of bisphenol A dianhydride and 1075g of N-methylpyrrolidone were introduced into the reactor, and the mixture was stirred and reacted at 10℃for 12 hours. Then 40.84g of acetic anhydride and 15.82g of pyridine were added thereto and the reaction was continued with stirring at 10℃for 24 hours. After the reaction is finished, pouring the reaction solution into 5L of deionized water for precipitation, and filtering, washing and drying to obtain the corresponding soluble polyimide resin solid containing the phenol side group. The hydroxyl value is about 4mgKOH/g and the Mn is about 25000g/mol.

100g of soluble polyimide resin solid containing phenol hanging side groups, 1.26g of p-cyclohexylaniline, 0.47mL of 30% formaldehyde solution, 350g of N, N' -dimethylformamide and 56g of toluene are added into a reaction vessel with a reflux condensation dispenser, stirred and dissolved, and then heated to 140 ℃ for reflux reaction for 6 hours. And cooling to room temperature after the reaction is finished, and obtaining the polyimide resin solution containing the benzoxazine pendant group, wherein the solid content of the polyimide resin solution is about 20%.

Example 3

14.568g of 4,4' -diamino-4 ' -hydroxytriphenylamine, 31.838g of 4,4' -diaminobenzophenone, 105.139g of bisphenol A dianhydride and 1111g of N-methylpyrrolidine were reacted by introducing nitrogen gas at 10℃under stirring for 12 hours. 400g of toluene were then added and the temperature was raised to 150℃and the reaction was refluxed for 8 hours, and the water produced by the reaction was separated out by means of a Dean-Stark apparatus. And after the reaction is finished, toluene in the reaction solution is distilled off, and the solution of the corresponding soluble polyimide resin containing the phenol side group is obtained after cooling to room temperature, wherein the solid content is about 25%. The hydroxyl value is about 25mgKOH/g and the Mn is about 50000g/mol.

400g of the soluble polyimide resin solution containing phenol hanging side groups and having the solid content of about 25%, 2.94g of aniline, 2.01mL of 30% formaldehyde solution and 71g of toluene are added into a reaction vessel with a reflux condensation dispenser, stirred and dissolved, and then heated to 130 ℃ for reflux reaction for 6 hours. And cooling to room temperature after the reaction is finished, and obtaining the polyimide resin solution containing the benzoxazine pendant group, wherein the solid content of the polyimide resin solution is 22%.

Example 4

2- (4 ' -hydroxyphenyl) -4, 4' -diaminodiphenyl ether 29.233g, 4' -diaminodiphenyl sulfone 24.830g, 4' -oxydiphthalic anhydride 62.352g and N, N ' -dimethylacetamide 1047g were reacted by stirring at 10℃for 12 hours by introducing nitrogen. Then 40.84g of acetic anhydride and 20.24g of triethylamine were added thereto and the reaction was continued with stirring at 10℃for 24 hours. After the reaction is finished, pouring the reaction solution into 5L of deionized water to separate out, and filtering, washing and drying to obtain the soluble polyimide resin solid containing the phenol side group. The hydroxyl value was about 51mgKOH/g and the Mn was about 85000g/mol.

100g of the soluble polyimide resin solid containing phenol hanging side groups, 8.29g of aniline, 5.29g of 30% paraformaldehyde, 400g of N, N' -dimethylformamide and 53g of toluene are added into a reaction vessel with a reflux condensation dispenser, stirred and dissolved, and then heated to 120 ℃ for reflux reaction for 8 hours. And cooling to room temperature after the reaction is finished, and obtaining the polyimide resin solution containing the benzoxazine pendant group, wherein the solid content of the polyimide resin solution is about 20%.

Example 5

17.622g of 4,4' -diamino-4 ' -hydroxy-triphenylbenzene, 33.948g of 2,2' -di (4 ' -aminophenyl) propane, 61.422g of 4,4' -oxydiphthalic anhydride and 1016g of N-methylpyrrolidone are introduced into the mixture, and the mixture is stirred and reacted for 12 hours at 10 ℃. 400g of toluene were then added and the temperature was raised to 150℃and the reaction was refluxed for 8 hours, and the water produced by the reaction was separated out by means of a Dean-Stark apparatus. And after the reaction is finished, toluene in the reaction solution is distilled off, and the solution of the soluble polyimide resin containing the phenol side group is obtained after cooling to room temperature, wherein the solid content is about 20%. The hydroxyl value was about 25mgKOH/g and the Mn was about 30000g/mol.

500g of the soluble polyimide resin solution containing phenol hanging side groups and about 20% of solid content, 4.78g of p-methylaniline, 2.65g of paraformaldehyde and 30g of toluene are added into a reaction vessel with a reflux condensation dispenser, stirred and dissolved, and then heated to 150 ℃ for reflux reaction for 6 hours. And cooling to room temperature after the reaction is finished, and obtaining the polyimide resin solution containing the benzoxazine pendant group, wherein the solid content of the polyimide resin solution is about 20%.

Example 6

21.504g of 4- (4 '-hydroxy) phenyl-2, 6-bis [ 4' - (4 '-aminophenoxy) phenyl ] pyridine 65.682g of 2,2' -bis [ 4'- (4' -aminophenoxy) phenyl ] propane, 3',4,4' -tetracarboxylic acid dianhydride benzophenone 65.090g and N-methyl pyrrolidone 1116g are introduced into the reactor, and the mixture is stirred and reacted for 12 hours at 10 ℃; 400g of toluene were then added and the temperature was raised to 150℃and the reaction was refluxed for 8 hours, and the water produced by the reaction was separated out by means of a Dean-Stark apparatus. And after the reaction is finished, toluene in the reaction solution is distilled off, and the solution of the soluble polyimide resin containing the phenol side group is obtained after cooling to room temperature, wherein the solid content is about 22%. The hydroxyl value is about 15mgKOH/g and the Mn is about 45000g/mol.

454g of the soluble polyimide resin solution containing the phenol hanging side group and having the solid content of about 22%, 3.33g of p-methoxyaniline, 1.68g of paraformaldehyde and 65g of toluene are added into a reaction vessel with a reflux condensation dispenser, stirred and dissolved, and then heated to 100 ℃ for reflux reaction for 10 hours. And cooling to room temperature after the reaction is finished, and obtaining the polyimide resin solution containing the benzoxazine pendant group, wherein the solid content of the polyimide resin solution is about 18%.

Comparative example 1

The difference from example 1 is that: in the preparation step of polyimide resin containing phenol hanging side group, 4.325g of 3- (p-hydroxyphenoxy) -1, 5-diaminobenzene is changed into 2.163g of m-phenylenediamine, and the obtained solid resin is directly heated and dissolved by N, N' -dimethylformamide to prepare polyimide solution with the solid content of about 18 percent; meanwhile, the preparation steps of polyimide containing benzoxazine hanging side groups are not treated, and the other polyimide is unchanged. The hydroxyl value of the obtained polyimide resin was about 8mgKOH/g, and the Mn was about 65000g/mol.

2.163g of m-phenylenediamine, 36.041g of 4,4' -diaminodiphenyl ether, 105.139g of bisphenol A type dianhydride and 824g of N-methylpyrrolidone are introduced into nitrogen, and stirring is carried out for reaction for 24 hours at the temperature of 4 ℃; then adding 40.84g of acetic anhydride and 20.24g of triethylamine, and continuously stirring at 4 ℃ for reaction for 24 hours; after the reaction is finished, pouring the reaction solution into 5L of deionized water to separate out, and filtering, washing and drying to obtain the corresponding soluble polyimide resin solid containing the phenol hanging side group.

Comparative example 2

The difference from example 1 is that: in the preparation step of polyimide resin containing phenol hanging side groups, 4.325g of 3- (p-hydroxyphenoxy) -1, 5-diaminobenzene is changed into 3.685g of 5-phenoxy-1, 3-diaminobenzene, and the obtained solid resin is directly heated and dissolved into polyimide solution with the solid content of about 18% by using N, N' -dimethylformamide; meanwhile, the polyimide containing the benzoxazine suspension side group is not treated in the preparation steps, and the other polyimide is unchanged; the hydroxyl value of the obtained polyimide resin containing the benzene hanging side group is about 8mgKOH/g, and the Mn is about 63000g/mol.

3.685g of 5-phenoxy-1, 3-diaminobenzene, 36.041g of 4,4' -diaminodiphenyl ether, 105.139g of bisphenol A type dianhydride and 824g of N-methylpyrrolidone are introduced into nitrogen, and stirring and reacting for 24 hours at the temperature of 4 ℃; then 40.84g of acetic anhydride and 20.24g of triethylamine were added thereto and the reaction was continued with stirring at 4℃for 24 hours. After the reaction is finished, pouring the reaction solution into 5L of deionized water to separate out, and filtering, washing and drying to obtain the corresponding soluble polyimide resin solid containing the phenol hanging side group.

Comparative example 3

The difference from example 1 is that: the preparation steps of polyimide without benzoxazine hanging side groups are treated, and the other steps are unchanged.

4.325g of 3- (p-hydroxyphenoxy) -1, 5-diaminobenzene, 36.041g of 4,4' -diaminodiphenyl ether, 105.139g of bisphenol A dianhydride and 824g of N-methylpyrrolidone were reacted by stirring at 4℃for 24 hours by introducing nitrogen. Then 40.84g of acetic anhydride and 20.24g of triethylamine were added thereto and the reaction was continued with stirring at 4℃for 24 hours. Pouring the reaction solution into 5L of deionized water to precipitate after the reaction is finished, and filtering, washing and drying to obtain a corresponding soluble polyimide resin solid containing phenol hanging side groups; the hydroxyl value is about 8mgKOH/g and the Mn is about 65000g/mol.

Comparative example 4

The difference from example 4 is that: in the preparation step of the polyimide resin containing phenol hanging side groups, 29.233g of 2- (4 '-hydroxyphenyl) -4, 4' -diaminodiphenyl ether and 24.830g of 4,4 '-diaminodiphenyl sulfone are changed into 55.543g of 2- (4' -hydroxyphenyl) -4,4 '-diaminodiphenyl ether and 2.483g of 4,4' -diaminodiphenyl sulfone, and the other materials are unchanged. The hydroxyl value of the obtained polyimide resin containing the phenol hanging side group is about 51mgKOH/g, and the Mn is about 85000g/mol.

55.543g of 2- (4 ' -hydroxyphenyl) -4, 4' -diaminodiphenyl ether, 2.483g of 4,4' -diaminodiphenyl sulfone, 62.352g of 4,4' -oxydiphthalic anhydride and 1047g of N, N ' -dimethylacetamide are introduced into a reactor, and stirred and reacted for 12 hours at 10 ℃; then 40.84g of acetic anhydride and 20.24g of triethylamine were added thereto and the reaction was continued with stirring at 10℃for 24 hours. After the reaction is finished, pouring the reaction solution into 5L of deionized water to separate out, and filtering, washing and drying to obtain the soluble polyimide resin solid containing the phenol side group.

Comparative example 5

The difference from example 4 is that: the preparation of polyimide resin containing pendant phenol groups was carried out by changing 62.352g of "4,4 '-oxydiphthalic anhydride" to 62.042g of "4,4' -oxydiphthalic anhydride", and the others. The hydroxyl value of the obtained polyimide resin containing the phenol hanging side group is about 49mgKOH/g, and the Mn is about 150000g/mol.

2- (4 ' -hydroxyphenyl) -4, 4' -diaminodiphenyl ether 29.233g, 4' -diaminodiphenyl sulfone 24.830g, 4' -oxydiphthalic anhydride 62.042g and N, N ' -dimethylacetamide 1047g are introduced into a reactor, and stirred and reacted for 12 hours at 10 ℃; then 40.84g of acetic anhydride and 20.24g of triethylamine were added thereto and the reaction was continued with stirring at 10℃for 24 hours. After the reaction is finished, pouring the reaction solution into 5L of deionized water to separate out, and filtering, washing and drying to obtain the soluble polyimide resin solid containing the phenol side group.

Comparative example 6

The difference from example 5 is that: in the preparation step of the phenol hanging side group polyimide resin, "4,4 '-diamino-4" -hydroxy mesitylene 17.622g "was changed to" 1, 3-bis (4' -aminophenyl) -5-phenylbenzene 16.822g ". The solid content of the obtained solution of the soluble polyimide resin containing the benzene side groups is about 20 percent, and the Mn of the resin is about 32000g/mol.

17.622g of 4,4' -diamino-4 ' -hydroxy-triphenyl benzene, 33.948g of 2,2' -di (4 ' -aminophenyl) propane, 61.422g of 4,4' -oxydiphthalic anhydride and 1016g of N-methylpyrrolidone are introduced into a reactor, and the mixture is stirred and reacted for 12 hours at 10 ℃; 400g of toluene were then added and the temperature was raised to 150℃and the reaction was refluxed for 8 hours, and the water produced by the reaction was separated out by means of a Dean-Stark apparatus. And (3) evaporating toluene in the reaction liquid after the reaction is finished, and cooling to room temperature to obtain a solution of the soluble polyimide resin containing the phenol side groups.

Meanwhile, the benzoxazine-terminated polyimide was prepared as follows:

500g of the soluble polyimide resin solution containing the benzene hanging side group and having the solid content of about 20%, 0.4g of phenol, 0.26g of paraformaldehyde and 65g of toluene are added into a reaction vessel with a reflux condensation dispenser, stirred and dissolved, and then heated to 150 ℃ for reflux reaction for 6 hours. After the reaction, cooling to room temperature to obtain the benzoxazine-terminated polyimide resin solution with the solid content of about 18%.

Coating the resin glue solution obtained in the examples 1-6 and the comparative examples 1-6 on two sides of a commercial thermosetting PI film with the thickness of 5-100 mu m (the unified is taken as an example of 25 mu m in this time), controlling the thickness of the coating to be 2-10 mu m (the unified is taken as an example of 3 mu m-5 mu m in this time), drying and removing the solvent to obtain a double-sided glued PI film, overlapping the glue surface of the double-sided glued PI film with the corresponding copper foil (the electrolytic copper foil unified is taken as 1oz in this time), performing rapid lamination at the temperature of 180 ℃, and then sequentially placing the laminated film in a baking oven at 180 ℃ and 220 ℃ for 1h for curing to obtain a double-sided flexible copper-clad plate test sample; or the adhesive surface of the PI film with single or double surfaces is overlapped with the corresponding copper foil (the electrolytic copper foil with 1oz in this time) smooth surface, and then is rapidly pressed at 180 ℃, and then is sequentially placed in a baking oven at 180 ℃ and 220 ℃ to be baked for 1h for curing, so that a covering film test sample can be obtained.

Or coating the resin glue solution obtained in the examples 1-6 on a PET release film surface through a coating machine, controlling the thickness of the coating to be 5-50 mu m (this time, taking 25 mu m as an example), drying and removing the solvent to obtain an adhesive film/sheet, transferring the adhesive film/sheet to a PI surface of a commercial flexible copper-clad plate (25 mu m PI/0.5oz EDCu), coating the PI surface of another commercial flexible copper-clad plate on the PI surface, finally performing rapid lamination at the temperature of 180 ℃, and then sequentially placing the adhesive film/sheet in a baking oven at the temperature of 180 ℃ and 220 ℃ for curing for 1 hour to obtain the adhesive film/sheet test sample.

The double-sided flexible copper-clad laminate test samples, the coverlay test samples, and the adhesive film/sheet test samples obtained in examples 1 to 6 and comparative examples 1 to 6 described above were examined. The test method of the correlation performance is as follows:

(1) Peel strength: the test was performed as described in GB/T13557-2017 at 7.2.

(2) Thermal stress (float welding): the test was carried out according to GB/T13557-2017 at 8.2.

(3) Resin fluidity: the test was performed as per appendix B in GB/T14709-2017.

(4) Dimensional stability: according to GB/T13557-2017, tested in TD and MD directions, respectively.

(5) Folding endurance: the test was carried out according to GB/T13557-2017 at 7.4.

(6) Dielectric constant and dielectric loss (10 GHz): the test was performed using a vector network analyzer with a 10GHz resonant cavity (i.e., SPDR method).

(7) Water absorption rate: the test was carried out according to GB/T13557-2017 at 10.2.

The properties of the double-sided flexible copper clad laminates, the cover films and the adhesive films/sheets obtained in examples 1 to 6 and comparative examples 1 to 6 are shown in tables 1 and 2, respectively.

Table 1 test results of double-sided flexible copper clad laminates, coverlay films and adhesive films/sheets prepared in examples 1 to 6

Table 2 test results of double-sided flexible copper clad laminates, coverlay films and adhesive films/sheets prepared in comparative examples 1 to 6

As can be seen from tables 1 and 2:

(1) In comparison with example 1, comparative examples 1, 2 and 3, the peel strength of the double-sided flexible copper clad laminate or the cover film or the adhesive film/sheet obtained by using the soluble polyimide resin having the same main chain structure and no side group, or having the same main chain structure and the side group being phenyl, or having the same main chain structure and the side group being phenol group (i.e., no benzoxazine pendant side group), respectively, was relatively low, and most importantly, the thermal expansion coefficient was significantly increased, and the water absorption rates of comparative examples 2 and 3 were also high.

(2) In comparative example 4, the molar ratio of the first aromatic diamine monomer (here, 2- (4 '-hydroxyphenyl) -4,4 "-diaminodiphenyl ether) to the second aromatic diamine monomer (here, 4' -diaminodiphenyl sulfone) was 95:5, the molar ratio of the first aromatic diamine monomer to the second aromatic diamine monomer is 1-99: 80-20'. Comparing the test results with example 4, it was found that the sample of comparative example 4 was significantly worse than example 4 in terms of peel strength, thermal stress (float weld), thermal expansion coefficient, dielectric constant, dielectric loss, water absorption, and the like.

(3) In comparative example 5, since the Mn of the obtained phenol pendant group-containing polyimide resin was about 150000g/mol, which exceeded the "number average molecular weight Mn of the soluble phenol pendant group-containing polyimide resin in the range of 1000 to 100000" required by the present invention, the obtained resin was insoluble in the relevant organic solvent, and thus, the subsequent sample preparation and test were impossible.

(4) In comparative example 6, a soluble benzene-side group-containing polyimide resin having an amino-terminated and backbone structure exactly the same as in example 5 but having a phenyl group as a side group was prepared, and thus a corresponding benzoxazine-terminated soluble benzene-side group-containing polyimide resin was prepared. Comparative example 6 exhibited poor peel strength and thermal expansion coefficient as compared with example 5.

It should be noted that, when numerical ranges are referred to in the present invention, it should be understood that two endpoints of each numerical range and any numerical value between the two endpoints are optional, and because the adopted step method is the same as the embodiment, in order to prevent redundancy, the present invention describes a preferred embodiment. While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. It is therefore intended that the following claims be interpreted as including the preferred embodiments and all such alterations and modifications as fall within the scope of the invention.

It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.

Claims

1. The polyimide containing the benzoxazine pendent group is characterized in that the polyimide is prepared by taking soluble polyimide resin containing the phenol pendent group, a monofunctional aromatic amine compound and an aldehyde compound as raw materials through polymerization reaction, and the molar ratio of phenolic hydroxyl groups to the monofunctional aromatic amine compound to the aldehyde compound in the soluble polyimide resin containing the phenol pendent group is 1:0.9 to 1.3:1.8 to 2.5.

2. The benzoxazine pendant group-containing polyimide according to claim 1, wherein the soluble phenol pendant group-containing polyimide resin has a number average molecular weight Mn of 1000 to 100000 and a hydroxyl number of 2 to 100mgKOH/g.

3. The benzoxazine pendant group-containing polyimide according to claim 1, wherein the preparation method of the soluble phenol pendant group-containing polyimide resin comprises the following steps:

4. The benzoxazine pendant side group-containing polyimide of claim 3, wherein said first aromatic diamine monomer is at least one of aromatic diamine compounds containing a phenol side group;

5. The benzoxazine pendant-containing polyimide of claim 3, wherein the ratio of the sum of the molar amounts of the first aromatic diamine monomer and the second aromatic diamine monomer to the molar amount of aromatic tetracarboxylic dianhydride is from 0.9 to 1.1:1, wherein the mole ratio of the first aromatic diamine monomer to the second aromatic diamine monomer is 1-99: 80-20.

6. The benzoxazine pendant side group-containing polyimide according to claim 1, wherein said monofunctional aromatic amine compound has the structure shown below:

wherein R is ₁ 、R ₂ 、R ₃ 、R ₄ Or R is ₅ Substituents are each independently H, alkyl, alkoxy, cycloalkyl or aryl; r is R ₁ 、R ₂ 、R ₃ 、R ₄ Or R is ₅ One or more substituents in the substituents are H; the number of carbon atoms in the alkyl group and the cycloalkyl group is 1 to 10.

7. The benzoxazine pendant-containing polyimide according to claim 1, wherein the aldehyde compound is formaldehyde and/or paraformaldehyde.

8. A method of preparing a benzoxazine pendant group-containing polyimide according to any one of claims 1 to 7, comprising the steps of:

9. Use of a benzoxazine pendant group-containing polyimide according to any one of claims 1 to 7 for the preparation of low dielectric flexible printed circuit boards, characterized in that said benzoxazine pendant group-containing polyimide is used as an adhesive film/sheet for flexible printed circuits; or: coating the polyimide coating containing the benzoxazine suspension side group on one side or two sides of the insulating medium film to obtain a rubberized covering film for the flexible printed circuit; or: the flexible copper-clad plate for the flexible printed circuit consists of an insulating medium film, a coating layer of polyimide containing benzoxazine suspension side groups and copper foil pressed on the coating layer, wherein the coating layer is coated on one side or two sides of the insulating medium film.

10. The use according to claim 9, wherein the insulating medium film is at least one of a polyimide film, a polyester film, a polynaphthalate film, a liquid crystal polymer film, a polyetheretherketone film or a polyphenylene sulfide film, and the thickness of the insulating medium film is 5 to 100 μm; the thickness of the adhesive film/sheet or coating prepared by the polyimide containing the benzoxazine suspension side group is 2-50 mu m; the copper foil is electrolytic copper foil or rolled copper foil, the thickness is 1/4-3 oz, and the roughness Rz of the pressed surface is less than or equal to 1.5 mu m.