WO2025066980A1 - Phosphorus-containing trianhydride monomer and preparation method therefor, and polyimide material, preparation method therefor and use thereof - Google Patents

Abstract

A phosphorus-containing trianhydride monomer and a preparation method therefor, and a polyimide material, a preparation method therefor and a use thereof. The phosphorus-containing trianhydride monomer has a structure as shown in formula (I): Formula (I), wherein R2 is a residue of a substituted or unsubstituted C6-C30 aromatic hydrocarbon that has lost two H atoms, or a residue of a substituted or unsubstituted C2-C30 heterocyclic aromatic hydrocarbon that has lost two H atoms. By using the provided phosphorus-containing trianhydride monomer for preparing a polyimide material, an internally-uniform porous structure can be formed, and the polyimide material has good mechanical properties and achieves both the flame retardant property and the sound absorption property.

Description

Phosphorus-containing trianhydride monomer and preparation method thereof, polyimide material and preparation method and application thereof

Priority information

This application claims priority and benefits of patent application No. 202311267750.0 filed with the State Intellectual Property Office of China on September 27, 2023, and the entire text of which is incorporated herein by reference.

Technical Field

The present invention relates to the field of polyimide preparation, and in particular to a phosphorus-containing trianhydride monomer and a preparation method thereof, a polyimide material and a preparation method and application thereof.

Background Art

The noise and vibration problem not only seriously affects the quietness of the car, the comfort of the passengers and the living environment of the residents along the highway, but also causes the main mechanical equipment of new energy vehicles to wear and fatigue or even fail during operation, which not only reduces the service life of the equipment but also threatens the safe operation of the car. The flame retardancy of the car directly affects the driving safety. Therefore, it is necessary to improve the flame retardancy and sound absorption properties of automotive materials.

CN202976826U provides a multi-layer composite sound absorbing material with flame retardant and heat insulating functions. The multi-layer composite sound absorbing material is a multi-layer composite structure, including a first porous thermal insulation material layer, a hard damping sound insulation material layer and a second porous moisture-retaining material layer. It requires multiple layers or multiple materials to be composited, and the process is complicated.

CN103694703A discloses a polyimide foam composite material. The raw materials of the polyimide foam composite material include glass microspheres and graphene sheets, and also include nano-carbon fibers. A highly efficient heat-insulating and sound-absorbing lightweight material is prepared through a molding process. The disadvantage is that it cannot have both sound-absorbing and flame-retardant properties.

CN111087618B discloses a sound-absorbing and noise-reducing polyimide foam, which forms cavity resonance by adding hollow glass microbeads, and is combined with a subsequent material softening process and the introduction of a sound-absorbing wedge structure to improve the matching degree between the material acoustic impedance and the air acoustic impedance, thereby improving the sound-absorbing and noise-reducing performance of the polyimide. In order to maintain the performance, this patent specifically adds a flame retardant.

The performance of polyimide formed by the existing technology is mainly flame retardant, and the intrinsic material performance is limited. It is difficult to achieve dual functions or multi-functions. It requires multiple layers or multiple materials to be composited, and the formula and process are complicated and the cost is high. Therefore, there is a need for a polyimide material that can simultaneously meet the requirements of flame retardant and sound absorption properties for automotive materials.

Summary of the invention

The purpose of the present invention is to overcome the difficulty of polyimide materials in the prior art to have both flame retardant properties and sound absorption In order to solve the problem of performance, a phosphorus-containing trianhydride monomer and a preparation method thereof, a polyimide material and a preparation method and application thereof are provided. The phosphorus-containing trianhydride monomer has phosphorus as the main skeleton, and its structure is easy to be combined with diamine to prepare a porous polyimide material with uniform pore size distribution.

In order to achieve the above-mentioned object, the present disclosure provides a phosphorus-containing trianhydride monomer in a first aspect, wherein the phosphorus-containing trianhydride monomer has a structure as shown in formula (I):

Wherein, _R2 is a residue of a substituted or unsubstituted _C6 - _C30 aromatic hydrocarbon which has lost two hydrogen atoms, or a residue of a substituted or unsubstituted _C2 - _C30 heterocyclic aromatic hydrocarbon which has lost two hydrogen atoms.

The second aspect of the present disclosure provides a method for preparing the aforementioned phosphorus-containing trianhydride monomer, the method comprising the following steps:

(1) in the presence of a catalyst, reacting a compound represented by the general formula Br-R ₂ -OMe with magnesium powder to prepare a Grignard reagent, and then reacting the compound with phosphorus trihalide to obtain a Grignard reagent 1, wherein R ₂ is a residue of a substituted or unsubstituted C ₆ -C ₃₀ aromatic hydrocarbon that has lost 2 H atoms, or a residue of a substituted or unsubstituted C ₂ -C ₃₀ heterocyclic aromatic hydrocarbon that has lost 2 H atoms;

(2) subjecting the compound 1 to a first hydrolysis reaction in an acid solution to obtain a compound 2;

(3) heating the compound 2 and the cyano-containing intermediate to obtain compound 3;

(4) subjecting the compound 3 to a second hydrolysis reaction in an alkaline solution to obtain compound 4;

(5) subjecting the compound 4 to a dehydration reaction to obtain the phosphorus-containing trianhydride monomer.

The third aspect of the present disclosure provides a polyimide material, wherein the polyimide material comprises a repeating unit structure represented by formula (IV) and a connecting group R ₁ between the repeating units represented by formula (IV):

Wherein, _R2 is a substituted or unsubstituted _C6 - _C30 aromatic hydrocarbon residue which has lost 2 Hs, or a substituted or unsubstituted _C2 - _C30 heterocyclic aromatic hydrocarbon residue which has lost 2 Hs, preferably a phenylene residue, a biphenyl residue which has lost 2 Hs, or a naphthalene residue which has lost 2 Hs; _R1 is a substituted or unsubstituted alkylene residue, a substituted or unsubstituted arylene residue, or a substituted or unsubstituted heteroarylene residue.

A fourth aspect of the present disclosure provides a method for preparing a polyimide material, wherein the method comprises:

(A) dissolving a phosphorus-containing trianhydride monomer, a diisocyanate, and a diamine in a solvent, and performing a polymerization reaction to obtain a polymerization product;

(B) heating the polymerization product in the presence of a surfactant to obtain a polyimide material;

The phosphorus-containing trianhydride monomer is the phosphorus-containing trianhydride monomer described in the first aspect.

A fifth aspect of the present disclosure provides a polyimide material prepared by the preparation method described in the fourth aspect.

A sixth aspect of the present disclosure provides an application of the polyimide material described in the third aspect or the fifth aspect in a flame retardant and sound absorbing material for automobiles.

Through the above technical solution, the following beneficial technical effects can be obtained:

(1) The phosphorus-containing trianhydride monomer provided by the present disclosure has phosphorus as the main body and has a trianhydride structure. The preparation process is simple and it is easy to prepare a foamed polyimide material with a diamine.

(2) In the present disclosure, preferably, the provided phosphorus-containing trianhydride monomer is used to prepare a polyimide material, which can form an internally uniform porous structure with good mechanical properties and both flame retardant and sound absorbing properties.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a scanning electron microscope image of the porous polyimide material of Example 1;

FIG. 2 is a scanning electron microscope image of the porous polyimide material of Comparative Example 1.

DETAILED DESCRIPTION

The endpoints and any values of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, the endpoint values of each range and the individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

In a first aspect, the present disclosure provides a phosphorus-containing trianhydride monomer, wherein the phosphorus-containing trianhydride monomer has a structure as shown in formula (I):

Wherein, _R2 is a residue of a substituted or unsubstituted _C6 - _C30 aromatic hydrocarbon which has lost two hydrogen atoms, or a residue of a substituted or unsubstituted _C2 - _C30 heterocyclic aromatic hydrocarbon which has lost two hydrogen atoms.

According to the present disclosure, preferably, _R2 is a phenylene group, a residue of biphenyl losing two H groups, or a residue of naphthalene losing two H groups. The polyimide material prepared by the phosphorus-containing trianhydride monomer having the above _R2 structure has better heat resistance and flame retardancy and is more suitable for commercialization.

In the present disclosure, the phosphorus-containing trianhydride monomer has phosphorus as the main skeleton, and phosphorus is introduced into the anhydride monomer to obtain a novel phosphorus-containing trianhydride monomer structure, which is used to prepare polyimide materials, and helps to improve flame retardant properties while ensuring mechanical properties.

More preferably, the phosphorus-containing trianhydride monomer is at least one of the compounds represented by the following structural formulas:

The second aspect of the present disclosure provides a method for preparing the aforementioned phosphorus-containing trianhydride monomer, the method comprising the following steps:

(1) in the presence of a catalyst, reacting a compound represented by the general formula Br-R ₂ -OMe with magnesium powder to prepare a Grignard reagent, and then reacting the compound with phosphorus trihalide to obtain a Grignard reagent 1, wherein R ₂ is a residue of a substituted or unsubstituted C ₆ -C ₃₀ aromatic hydrocarbon that has lost 2 H atoms, or a residue of a substituted or unsubstituted C ₂ -C ₃₀ heterocyclic aromatic hydrocarbon that has lost 2 H atoms;

(2) subjecting the compound 1 to a first hydrolysis reaction in an acid solution to obtain a compound 2;

(3) heating the compound 2 and the cyano-containing intermediate to obtain compound 3;

(4) subjecting the compound 3 to a second hydrolysis reaction in an alkaline solution to obtain compound 4;

(5) subjecting the compound 4 to a dehydration reaction to obtain the phosphorus-containing trianhydride monomer.

In the present disclosure, the compound structure generated in each step of the preparation process of the phosphorus-containing trianhydride monomer is as follows:

According to the present disclosure, preferably, the reaction conditions of the Grignard reaction in step (1) include: a reaction temperature of 0-120°C, preferably 0-45°C; and a reaction time of 2-24h, preferably 4-18h.

In the present disclosure, preferably, _R2 is a phenylene group, a residue obtained by losing two H atoms of biphenyl, or a residue obtained by losing two H atoms of naphthalene.

In the present disclosure, the type of the catalyst is not particularly limited, and can be a conventional Grignard reagent catalyst in the art, preferably iodine and/or 1,2-dibromoethane. The amount of the catalyst is not particularly limited, as long as the Grignard reagent can be prepared.

In the present disclosure, preferably, after the Grignard reaction in step (1) is completed, the product is further quenched, extracted, dried and concentrated. The quenching can be performed using at least one of water, glacial acetic acid and saturated ammonium chloride solution, preferably saturated ammonium chloride solution.

In the present disclosure, the extraction and drying conditions are not particularly limited, and those skilled in the art can make adaptive adjustments as needed. Preferably, the quenched product is extracted with ethyl acetate, and the organic phase obtained by the extraction is dried and concentrated with anhydrous sodium sulfate to obtain the compound 1.

According to the present disclosure, preferably, the molar ratio of the compound represented by the general formula Br-R ₂ -OMe, magnesium powder and phosphorus trihalide is (2-4):(2-4):1, preferably (2.5-3.5):(2.5-3.5):1. Adding the reaction raw materials according to the above molar ratio for Grignard reaction can make the phosphorus trihalide react fully.

According to the present disclosure, preferably, the compound represented by the general formula Br-R ₂ -OMe is selected from at least one of 4-methoxybromobenzene, 3-methoxybromobenzene and 4-bromo-4'-methoxybiphenyl. In the present disclosure, a Grignard reagent prepared by using a compound represented by the general formula Br-R ₂ -OMe is subjected to a Grignard reaction with phosphorus trihalide to prepare a compound 1 with phosphorus as the main body, and subsequently a phosphorus-containing trianhydride monomer is further prepared based on compound 1, and the preparation process is simple.

According to the present disclosure, preferably, the phosphorus trihalide is phosphorus trichloride and/or phosphorus tribromide.

According to the present disclosure, preferably, the cyano group-containing intermediate is 4-nitrophthalonitrile.

According to the present disclosure, preferably, the acid solution in step (2) is a mixed solution of acetic acid and hydrobromic acid, preferably a mixed solution of excess acetic acid and saturated hydrobromic acid. In the present disclosure, the saturated hydrobromic acid is hydrobromic acid with a concentration of 48%.

According to the present disclosure, preferably, the conditions of the first hydrolysis reaction include: a reaction temperature of 0-120°C, preferably 60-100°C; and a reaction time of 6-18h, preferably 8-16h.

In the present disclosure, preferably, step (2) further comprises extracting and separating the reaction product after the first hydrolysis reaction is cooled to room temperature. The extraction is not particularly limited and may be the same as or different from the extraction described in step (1). After the extraction, the organic phase is taken out and an alkali solution is added dropwise thereto to separate the aqueous phase. The alkali solution is a strong alkali solution, preferably a sodium hydroxide solution and/or a potassium hydroxide solution.

According to a preferred embodiment of the present disclosure, the alkali solution is a 5-10 wt % sodium hydroxide solution. The amount of the alkali solution is not particularly limited, as long as the aqueous phase can be separated.

In the present disclosure, after washing the aqueous phase with dichloromethane, an acid solution is added to adjust the pH of the aqueous phase solution to acidic, and the compound 2 is obtained after filtration. Preferably, the pH value of the aqueous phase solution after pH adjustment is less than 3, and the preferred pH value is 1-2. The acid in the acid solution is a conventional acid in the art, preferably selected from at least one of hydrochloric acid, nitric acid and sulfuric acid.

In the present disclosure, the amount and concentration of the acid solution are not particularly limited. Those skilled in the art can make adaptive adjustments based on the pH value of the aqueous solution so that the pH value of the aqueous solution after the pH adjustment is less than 3.

According to the present disclosure, preferably, the conditions for the heating reaction in step (3) include: a heating temperature of 80-120° C., preferably 90-110° C.; and a heating time of 2-10 h, preferably 3-8 h.

According to the present disclosure, preferably, the molar ratio of the compound 2 to the cyano-containing intermediate in step (3) is 1:2-4, preferably 1:2-3. The heating reaction of the compound 2 and the cyano-containing intermediate under the above conditions can make the heating reaction more complete.

In the present disclosure, step (3) further comprises a solvent, and the compound 2 and the cyano-containing intermediate are subjected to a heating reaction in the presence of a solvent. The solvent is selected from at least one of dimethyl sulfoxide, N-methylpyrrolidone, N,N-dimethylformamide and N,N-dimethylacetamide. The amount of the solvent added is not particularly limited, and those skilled in the art can make adaptive adjustments according to the conditions of the heating reaction. Preferably, the amount of the solvent added is such that the total molar concentration of the compound 2 and the cyano-containing intermediate in the solvent is 0.5-5 mol/L.

In the present disclosure, preferably, after the heating reaction in step (3) is completed, the step further includes cooling to room temperature and purifying the heating reaction product. According to a preferred embodiment of the present disclosure, purification is performed by column chromatography.

According to the present disclosure, preferably, the reaction conditions of the second hydrolysis in step (4) include: reaction time of 5-15h, Preferably, the time is 7-12 hours. In the present disclosure, the second hydrolysis reaction is carried out at room temperature.

In the present disclosure, preferably, the alkaline solution in step (4) is a strong alkaline solution, and the alkali is preferably potassium hydroxide and/or sodium hydroxide. According to a preferred embodiment of the present disclosure, the alkaline solution is a potassium hydroxide solution with an alkali concentration of 5-10wt%.

In the present disclosure, preferably, after the second hydrolysis reaction is completed, the second hydrolysis product is further recrystallized. The conditions for the recrystallization are not particularly limited, and glacial acetic acid is preferably used for recrystallization.

According to the present disclosure, preferably, the conditions for the dehydration reaction in step (5) include: reaction time of 6-36 h, preferably 12-30 h; reaction temperature of 45-180° C., preferably 60-120° C.

In the present disclosure, preferably, the dehydration reaction is carried out in the presence of a dehydrating agent, and the dehydrating agent is a mixed solution of an acid anhydride and a corresponding acid, preferably acetic acid and acetic anhydride. The dehydration reaction is carried out using the above dehydrating agent to dehydrate the carboxyl group adjacent to the terminal of the benzene ring of compound 4 to obtain a phosphorus-containing trianhydride monomer structure of formula (I).

In the present disclosure, step (5) further comprises recrystallizing the dehydration reaction product. The conditions for the recrystallization are not particularly limited, and glacial acetic acid is preferably used for recrystallization.

According to a particularly preferred embodiment of the present disclosure, a method for preparing a phosphorus-containing trianhydride monomer comprises the following steps:

(1) in the presence of a catalyst, reacting a compound represented by the general formula Br-R ₂ -OMe with magnesium powder to prepare a Grignard reagent, and then reacting the compound with phosphorus trihalide to obtain a Grignard reagent 1, wherein R ₂ is a residue of a substituted or unsubstituted C ₆ -C ₃₀ aromatic hydrocarbon that has lost 2 H atoms, or a residue of a substituted or unsubstituted C ₂ -C ₃₀ heterocyclic aromatic hydrocarbon that has lost 2 H atoms;

(2) subjecting the compound 1 to a first hydrolysis reaction in an acid solution to obtain a compound 2;

(3) heating the compound 2 and 4-nitrophthalonitrile to obtain compound 3;

(4) subjecting the compound 3 to a second hydrolysis reaction in an alkaline solution to obtain compound 4;

(5) subjecting the compound 4 to a dehydration reaction to obtain the phosphorus-containing trianhydride monomer;

The compound represented by the general formula Br-R ₂ -OMe is at least one selected from 4-methoxybromobenzene, 3-methoxybromobenzene and 4-bromo-4'-methoxybiphenyl;

The molar ratio of compound 2 to 4-nitrophthalonitrile in step (3) is 1:2-3.

The third aspect of the present disclosure provides a polyimide material, wherein the polyimide material comprises a repeating unit structure represented by formula (IV) and a connecting group R ₁ between the repeating units represented by formula (IV):

Wherein, _R2 is a substituted or unsubstituted _C6 - _C30 aromatic hydrocarbon residue which has lost 2 Hs, or a substituted or unsubstituted _C2 - _C30 heterocyclic aromatic hydrocarbon residue which has lost 2 Hs, preferably a phenylene residue, a biphenyl residue which has lost 2 Hs, or a naphthalene residue which has lost 2 Hs; _R1 is a substituted or unsubstituted alkylene residue, a substituted or unsubstituted arylene residue, or a substituted or unsubstituted heteroarylene residue.

In the present disclosure, the _R1 can be introduced by the added diisocyanate and/or diamine, that is, the _R1 is a structural fragment other than the two isocyanate groups in the diisocyanate, or a structural fragment other than the two amine groups in the diamine.

According to the present disclosure, preferably, the viscosity of the polyimide material is 5000-100000 mPa·s, preferably 20000-80000 mPa·s. In the present disclosure, the viscosity is the viscosity of the polyimide material measured at 25° C. Measured by a rotational viscometer, which can characterize the molecular weight of the polyimide material.

According to the present disclosure, preferably, the polyimide material further comprises an end-capping group, which can be end-capped by reacting the molecular chain end of the formed polyimide with a compound having a dicarboxylic anhydride group (phosphorus-containing trianhydride monomer of formula (I)) or an amine group (diamine). For example, dicarboxylic anhydride can be introduced for end-capping, or an excess of trianhydride monomer or diamine can be added for end-capping.

In the present disclosure, the polyimide material is observed under a scanning electron microscope, and it can be seen that it has a uniform porous structure, good mechanical properties, and both flame retardant properties and sound absorption properties.

In the present disclosure, the composition and structure of the polyimide material (including information on repeating units, connecting groups and end-capping groups) can be determined and analyzed by infrared spectroscopy.

In the present disclosure, the repeating structural unit included in the polyimide material is preferably derived from a phosphorus-containing trianhydride monomer of formula (II) or (III); the linking group _R1 is preferably derived from diphenylmethane diisocyanate, toluene diisocyanate, 4,4'-diaminodiphenyl ether or p-phenylenediamine; the end-capping group is preferably derived from a phosphorus-containing trianhydride monomer of formula (II), a phosphorus-containing trianhydride monomer of formula (III), 4,4'-diaminodiphenyl ether, or p-phenylenediamine.

A fourth aspect of the present disclosure provides a method for preparing a polyimide material, the method comprising:

(A) dissolving a phosphorus-containing trianhydride monomer, a diisocyanate, and a diamine in a solvent, and performing a polymerization reaction to obtain a polymerization product. things;

(B) heating the polymerization product in the presence of a surfactant to obtain a polyimide material;

The phosphorus-containing trianhydride monomer is the phosphorus-containing trianhydride monomer described in the first aspect.

According to the present disclosure, preferably, the conditions of the polymerization reaction in step (A) include: a reaction temperature of 20-180°C, preferably 25-120°C; a reaction time of 4-24h, preferably 6-18h. The aforementioned phosphorus-containing trianhydride monomer is used to carry out a polymerization reaction with diisocyanate and diamine under the above-mentioned polymerization reaction conditions to obtain a porous polyimide material with uniform pore size distribution, which has both flame retardant properties and sound absorption properties. If the polymerization reaction temperature is too high, the porous polyimide material obtained by polymerization will have uneven pores; if the polymerization reaction temperature is too low, the degree of polymerization will be low, and the mechanical properties of the product will be poor.

In the present disclosure, the average pore size of the polyimide material is obtained by randomly selecting 20 holes in an electron microscope image, measuring the farthest distance between the two ends of the hole, and calculating the average value. The average pore size is 0.1-10 μm, preferably 0.5-5 μm. The foaming condition of the polyimide material is obtained by scanning electron microscopy.

In the present disclosure, the phosphorus-containing trianhydride monomer reacts with diisocyanate, that is, the anhydride group reacts with the isocyanate group, and different phosphorus-containing trianhydride monomers can be connected to generate a polyimide product and carbon dioxide, and the generated carbon dioxide gas is used for foaming; the phosphorus-containing trianhydride monomer can also react with diamine, that is, the anhydride group reacts with the amino group, and the foaming amount and the pore size formed by foaming are adjusted to obtain a polyimide foam material with uniform pore size distribution. And the diamine and phosphorus-containing trianhydride monomers can also be used to form the end-capping group of the polyimide.

In the present disclosure, the polymerization reaction equipment of step (A) only needs to be able to carry out the polymerization reaction. Preferably, the polymerization reaction is carried out in a reactor.

In the present disclosure, preferably, the step (A) is carried out under stirring, and the stirring rate is not particularly limited, and those skilled in the art can make adaptive adjustments according to the polymerization reaction conditions.

According to the present disclosure, preferably, the molar ratio of the phosphorus-containing trianhydride monomer, the solvent, the diisocyanate and the diamine is (0.1-0.95): (0.5-50): (0.05-0.9): 1, preferably (0.6-0.95): (3-10): (0.05-0.4): 1. The phosphorus-containing trianhydride monomer, the diisocyanate, the diamine and the solvent are adjusted to a specific molar ratio for polymerization reaction, phosphorus is introduced into the polyimide material through the phosphorus-containing trianhydride monomer, and the diisocyanate is used as a foaming agent to make the pore size distribution of the polyimide material uniform. While ensuring the mechanical properties of the polyimide material, the flame retardant and sound absorption properties of the polyimide material are improved. The amount of the phosphorus-containing trianhydride monomer and the diamine used is excessive compared to the diisocyanate, and an end-capping group for forming the molecular chain in the polyimide is also provided.

The present disclosure has no particular limitation on the manner of adding the phosphorus-containing trianhydride monomer, diisocyanate and diamine, and they may be added separately or together.

According to a preferred embodiment of the present disclosure, the phosphorus-containing trianhydride monomer reacts with the diisocyanate for 0.5-2h, and then the diamine is added. The polyimide material prepared by reacting in the above-mentioned addition order has good mechanical properties and can be made into a multi- The porous material is more tough.

In the present disclosure, the diamine can provide a residue portion other than the amino group of the diamine in the chemical composition and structure of the polyimide material, realize the connection of the phosphorus-containing trianhydride monomer, and can provide an end-capping group in the polyimide material. Preferably, the diamine is selected from at least one of 4,4'-diaminodiphenyl ether, m-phenylenediamine, p-phenylenediamine, 4,4'-diaminodiphenyl sulfone, 1,3-diamino-2-methylpropane, N,N-bis(4-aminophenyl)-1,4-phenylenediamine and 9,9-bis(4-aminophenyl)fluorene.

In the present disclosure, preferably, the diisocyanate is selected from at least one of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate and lysine diisocyanate. In the diisocyanate, except for the isocyanate group, the remaining residue part remains in the structure of the polyimide material to provide a connecting group for connecting the phosphorus-containing trianhydride monomer.

In the present disclosure, preferably, the solvent is selected from at least one of dimethyl sulfoxide, N-methylpyrrolidone, N,N-dimethylformamide and N,N-dimethylacetamide.

In the present disclosure, the heating method of the heating in step (B) is gradient heating. According to a preferred embodiment of the present disclosure, the gradient heating is divided into three stages, and the temperature of the latter stage is 80-120°C higher than that of the previous stage.

The heating temperature of the first stage is 100-200°C, preferably 130-170°C, and the heating time is 0.1-2h; the heating temperature of the second stage is 200-300°C, preferably 230-270°C, and the heating time is 0.1-2h; the heating temperature of the third stage is 300-400°C, preferably 330-370°C, and the heating time is 0.1-2h. Under the above-mentioned gradient heating conditions, the carbon dioxide in the polyimide material can be slowly released to form a polyimide foam material with a uniform pore structure.

In the present disclosure, the types of the surfactant are well known to those skilled in the art. Preferably, the surfactant is selected from at least one of polyurethane rigid foam silicone oil, polyether and polysilane.

In the present disclosure, the amount of the surfactant is not particularly limited, and those skilled in the art can make adaptive adjustments as needed to ensure that the polyimide material is subsequently obtained. Preferably, the amount of the surfactant is 0.1-10wt%, preferably 1-5wt% of the polymerization product in step (A).

According to a preferred embodiment of the present disclosure, a method for preparing a polyimide material comprises:

(A) dissolving a phosphorus-containing trianhydride monomer, a diisocyanate, and a diamine in a solvent, and performing a polymerization reaction to obtain a polymerization product;

(B) heating the polymerization product in the presence of a surfactant to obtain a polyimide material;

The phosphorus-containing trianhydride monomer is a phosphorus-containing trianhydride monomer of formula (II) or formula (III);

The conditions of the polymerization reaction in step (A) include: reaction temperature of 25-120° C.; reaction time of 6-18 h;

The molar ratio of the phosphorus-containing trianhydride monomer, solvent, diisocyanate and diamine is (0.6-0.95): (3-10): (0.05-0.4): 1.

A fifth aspect of the present disclosure provides a polyimide material prepared by the preparation method described in the fourth aspect.

A sixth aspect of the present disclosure provides an application of the polyimide material described in the third aspect or the fifth aspect in a flame retardant and sound absorbing material for automobiles.

In the present disclosure, the polyimide material has both flame retardant and sound absorbing properties. When used in flame retardant and sound absorbing materials, the impact of noise and vibration can be significantly reduced. The average sound absorption coefficient can reach 0.4, the limiting oxygen index can reach 37%, and the flame retardant property is good.

The present disclosure will be described in detail below through examples and comparative examples. In the following examples and comparative examples, unless otherwise specified, the reagents and materials used can be obtained commercially, and the room temperature is 25°C;

Polyether Silok-2008N was purchased from Guangzhou Silok Company;

Limiting oxygen index: Use limiting oxygen index tester to test according to GB/T2406.2-2009;

Average sound absorption coefficient: Use a standing wave tube to test the sound absorption coefficient of the center frequency of the six octaves of 125, 250, 500, 1000, 2000 and 4000 Hz of the test material, and take the arithmetic mean as the average sound absorption coefficient;

Nuclear magnetic resonance hydrogen spectrum data: measured using nuclear magnetic resonance hydrogen spectrometer;

The foaming condition was obtained by observing the polyimide material under scanning electron microscope;

The viscosity is the viscosity of the polyimide material measured at 25° C. It is measured by a rotational viscometer.

Preparation Example 1 Phosphorus-containing trianhydride monomer

(1) 3 mol of 4-methoxybromobenzene and 3 mol of magnesium powder react under the initiation of a catalytic amount of iodine to prepare a Grignard reagent, 1 mol of phosphorus trichloride is added dropwise in an ice water bath, the reaction is carried out at 25° C. for 10 h, and then quenched with a saturated ammonium chloride solution. After extraction with ethyl acetate, the organic phase obtained by the extraction is dried over anhydrous sodium sulfate and concentrated to obtain compound 1;

(2) Compound 1 was added to excess acetic acid and 48 wt% hydrobromic acid for the first hydrolysis reaction at 60°C for 12 hours. After the reaction was completed and the temperature was cooled to room temperature, the mixture was extracted with ethyl acetate. After the organic phase was taken out, a 10 wt% sodium hydroxide solution was slowly added dropwise to separate the aqueous phase. The aqueous phase was washed three times with dichloromethane, adjusted to pH 2 with hydrochloric acid, and filtered to obtain compound 2;

(3) 1 mol of compound 2 and 2 mol of 4-nitrophthalonitrile were dissolved in 20 mol of N,N-dimethylformamide, heated to 100° C. for reaction for 5 hours, and the reaction product was cooled to room temperature and purified by column chromatography to obtain compound 3;

(4) dissolving compound 3 in a 10 wt % potassium hydroxide solution to perform a second hydrolysis reaction for 10 hours, and then recrystallizing with glacial acetic acid to obtain compound 4;

(5) Compound 4 was dissolved in a mixed solution of acetic acid and acetic anhydride for dehydration reaction at 80° C. for 24 hours, and then recrystallized with glacial acetic acid to obtain phosphorus-containing trianhydride monomer 1.

The nuclear magnetic resonance hydrogen spectrum data of phosphorus-containing trianhydride monomer 1: ¹ H NMR (500 MHz, Chloroform-d) δ8.03 (d, J=8.1 Hz, 1H), 7.51 (d, J=2.1 Hz, 1H), 7.44-7.39 (m, 2H), 7.36 (dd, J=8.0, 2.0 Hz, 1H), 6.98 (ddd, J=9.8, 8.4, 1.5 Hz, 2H). It can be determined that the phosphorus-containing trianhydride monomer having the structure shown in the above formula (II) is formed.

Preparation Example 2 Phosphorus-containing trianhydride monomer

(1) 3 mol of 4-bromo-4'-methoxybiphenyl and 3 mol of magnesium powder reacted under the initiation of a catalytic amount of iodine to prepare a Grignard reagent, 1 mol of phosphorus trichloride was added dropwise in an ice-water bath, reacted at 0°C for 10 h, and then quenched with a saturated ammonium chloride solution. After extraction with ethyl acetate, the organic phase obtained by the extraction was dried over anhydrous sodium sulfate and concentrated to obtain compound 1;

(2) Compound 1 was added to excess acetic acid and 48 wt% hydrobromic acid for a first hydrolysis reaction at 80°C for 12 hours. After the reaction was completed and the temperature was lowered to room temperature, the mixture was extracted with ethyl acetate. After the organic phase was taken out, a 10 wt% sodium hydroxide solution was slowly added dropwise to separate the aqueous phase. The aqueous phase was washed three times with dichloromethane, and then hydrochloric acid was added to adjust the pH to less than 2, and the mixture was filtered to obtain Compound 2;

(3) 1 mol of compound 2 and 2 mol of 4-nitrophthalonitrile were dissolved in 10 mol of N,N-dimethylformamide, heated to 100° C. for reaction for 5 hours, and the reaction product was cooled to room temperature and purified by column chromatography to obtain compound 3;

(4) Compound 3 was dissolved in a 10 wt % potassium hydroxide solution to perform a second hydrolysis reaction for 10 hours, and then recrystallized with glacial acetic acid to obtain Compound 4;

(5) Compound 4 was dissolved in a mixed solution of acetic acid and acetic anhydride for dehydration reaction at a temperature of 60° C. for 24 hours, and then recrystallized from glacial acetic acid to obtain phosphorus-containing trianhydride monomer 2.

The nuclear magnetic resonance hydrogen spectrum data of the phosphorus-containing trianhydride monomer 2: ¹ H NMR (500 MHz, Chloroform-d) δ8.03 (d, J=8.0 Hz, 1H), 7.73-7.68 (m, 2H), 7.62 (td, J=8.3, 1.5 Hz, 2H), 7.51 (d, J=2.1 Hz, 1H), 7.39-7.33 (m, 3H), 7.20-7.14 (m, 2H). It can be determined that the phosphorus-containing trianhydride monomer having the structure shown in the above formula (III) is formed.

Example 1

(A) phosphorus-containing trianhydride monomer 1, N,N-dimethylformamide, diphenylmethane diisocyanate, and 4,4'-diaminodiphenyl ether in a molar ratio of 0.7:10:0.3:1 are sequentially added into a reaction kettle in the order of phosphorus-containing trianhydride monomer 1, N,N-dimethylformamide, and diphenylmethane diisocyanate, and stirring is started. After reacting for 0.5 h, 4,4'-diaminodiphenyl ether is added. The reaction temperature is 25° C. and stirred for 8 hours;

(B) After the reaction is completed and the temperature drops to room temperature, Silok-2008N (the amount added is 5% of the total mass of the polymerization product in step (A)) is added, and after stirring for 1 hour, the solution is poured into a mold and heated in a gradient manner at 120° C. for 1 hour, 200° C. for 2 hours, and 300° C. for 2 hours to obtain a porous polyimide material.

Example 2

(A) phosphorus-containing trianhydride monomer 1, N,N-dimethylformamide, diphenylmethane diisocyanate, and p-phenylenediamine in a molar ratio of 0.7:10:0.3:1 are sequentially added into a reaction kettle in the order of phosphorus-containing trianhydride monomer 1, N,N-dimethylformamide, and diphenylmethane diisocyanate, and stirring is started. After reacting for 0.5 h, p-phenylenediamine is added, the reaction temperature is 45° C., and stirring is performed for 12 hours;

(B) After the reaction is completed and the temperature drops to room temperature, Silok-2008N (the amount added is 5% of the total mass of the polymerization product in step (A)) is added, and after stirring for 1 hour, the solution is poured into a mold and heated in a gradient manner at 120° C. for 1 hour, 200° C. for 2 hours, and 300° C. for 2 hours to obtain a porous polyimide material.

Example 3

(A) phosphorus-containing trianhydride monomer 1, N,N-dimethylformamide, toluene diisocyanate, and p-phenylenediamine in a molar ratio of 0.6:8:0.25:1 are sequentially added into a reaction kettle in the order of phosphorus-containing trianhydride monomer 1, N,N-dimethylformamide, and toluene diisocyanate, and stirring is started. After reacting for 0.5 h, p-phenylenediamine is added, the reaction temperature is 100° C., and stirring is performed for 24 hours;

(B) After the reaction is completed and the temperature drops to room temperature, Silok-2008N (5% of the total mass of the polymerization product in step (A)) is added, and after stirring for 1 hour, the solution is poured into a mold and heated in a gradient manner of 120° C. for 1 hour, 200° C. for 2 hours, and 300° C. for 2 hours to obtain a porous polyimide material.

Example 4

The polyimide material was prepared according to the method of Example 3, except that the phosphorus-containing trianhydride monomer 1 was replaced by an equimolar amount of the phosphorus-containing trianhydride monomer 2 to obtain a porous polyimide material.

Example 5

The polyimide material was prepared according to the method of Example 1, except that the molar ratio of phosphorus-containing trianhydride monomer 1, toluene diisocyanate, p-phenylenediamine, and N,N-dimethylformamide in step (A) was 0.5:0.5:1:6 to obtain a porous polyimide material.

Comparative Example 1

(A) p-phenylenediamine, pyromellitic anhydride, diphenylmethane diisocyanate, and N,N-dimethylformamide in a molar ratio of 1:0.7:0.3:10 are sequentially added into a reaction kettle, stirring is started, the reaction kettle is controlled at 45° C., and stirring is performed for 12 hours;

(B) After cooling to room temperature, Silok-2008N (5% of the total mass of the mixed solution in step (A)) was added, and after stirring for 1 hour, the solution was poured into a mold and heated (120°C for 1 hour, 200°C for 2 hours, and 300°C for 2 hours) to obtain a porous polyimide material.

Comparative Example 2

The polyimide material was prepared according to the method of Example 1, except that the phosphorus-containing trianhydride monomer in step (A) was replaced by an equimolar amount of (di-3,3',4,4'tetracarboxylic dianhydride benzene) phenoxyphosphine.

Comparative Example 3

The polyimide material was prepared according to the method of Example 1, except that no diisocyanate was added in step (A).

Test Case

The limiting oxygen index, foaming condition and average sound absorption index of the polyimide materials prepared in the examples and comparative examples were tested, and the results are shown in Table 1.

Average pore size: less than 3μm is small, and greater than or equal to 3μm is large.

Table 1

From the results in Table 1, it can be seen that the polyimide materials prepared in Examples 1-4 of the present disclosure have uniform internal foaming, small pore size, and significantly better flame retardancy and sound absorption properties. The dianhydride used in Example 1 and Example 2 is different from the diamine, and although the main chain structure is different, the performance difference is not large, which shows that the trianhydride monomer is suitable for different polyimide structures.

The isocyanates used in Example 2 and Example 3 are different, but the performance is significantly better than that of the comparative example, proving that different isocyanates can also be applied to the phosphorus-containing trianhydride monomer disclosed in the present invention. Compared with Example 1, Example 4 changes the trianhydride monomer, and the performance difference is not much, which shows that the trianhydride monomer disclosed in the present invention has a stable effect. Compared with Example 1, Example 5 adjusts the molar ratio of the raw materials for preparing the polyimide material, and the limiting oxygen index is slightly lower than that of Example 1, and the foaming is poor, but the overall flame retardant and sound absorption properties are better than those of the comparative example.

FIG. 1 is a scanning electron microscope image of the porous polyimide material of Example 1. It can be observed in FIG. 1 that the pore size of the polyimide material of Example 1 is small and evenly distributed.

The one-dimensional rigid structure in Comparative Example 1 is not conducive to foaming, the pore size is larger than that of Examples 1-4, and the sound absorption coefficient is low. Comparative Example 1 does not contain phosphorus, and the limiting oxygen index is low. FIG2 is a scanning electron microscope image of the porous polyimide material of Comparative Example 1. FIG2 shows that the pore size of the polyimide material of Comparative Example 1 is large, and the internal pore size distribution is uneven.

Comparative Example 2 does not use the phosphorus-containing trianhydride monomer disclosed in the present invention, and the prepared polyimide material has a larger pore size and non-uniform foaming. The limiting oxygen index and the average sound absorption coefficient are both low, and the flame retardancy and sound absorption performance are poor. In the comparative example 3, no diisocyanate is added during the preparation of the polyimide, no bubbles are generated, and the sound absorption performance is not good.

The preferred embodiments of the present disclosure are described in detail above, but the present disclosure is not limited thereto. Within the technical concept of the present disclosure, the technical solution of the present disclosure can be subjected to a variety of simple modifications, including combining various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present disclosure and belong to the protection scope of the present disclosure.

Claims (19)

A phosphorus-containing trianhydride monomer, wherein the phosphorus-containing trianhydride monomer has a structure as shown in formula (I):
Wherein, _R2 is a residue of a substituted or unsubstituted _C6 - _C30 aromatic hydrocarbon which has lost two hydrogen atoms, or a residue of a substituted or unsubstituted _C2 - _C30 heterocyclic aromatic hydrocarbon which has lost two hydrogen atoms. The phosphorus-containing trianhydride monomer according to claim 1, wherein _R2 is a residue of phenylene, biphenyl losing 2 H, or a residue of naphthalene losing 2 H. The phosphorus-containing trianhydride monomer according to claim 1 or 2, wherein the phosphorus-containing trianhydride monomer is at least one of the compounds represented by the following structural formula:
in, A method for preparing the phosphorus-containing trianhydride monomer according to any one of claims 1 to 3, wherein the method comprises the following steps: (1) in the presence of a catalyst, reacting a compound represented by the general formula Br-R ₂ -OMe with magnesium powder to prepare a Grignard reagent, and then reacting the compound with phosphorus trihalide to obtain a Grignard reagent 1, wherein R ₂ is a residue of a substituted or unsubstituted C ₆ -C ₃₀ aromatic hydrocarbon that has lost 2 H atoms, or a residue of a substituted or unsubstituted C ₂ -C ₃₀ heterocyclic aromatic hydrocarbon that has lost 2 H atoms; (2) subjecting the compound 1 to a first hydrolysis reaction in an acid solution to obtain a compound 2; (3) heating the compound 2 and the cyano-containing intermediate to obtain compound 3; (4) subjecting the compound 3 to a second hydrolysis reaction in an alkaline solution to obtain compound 4; (5) subjecting the compound 4 to a dehydration reaction to obtain the phosphorus-containing trianhydride monomer. The preparation method according to claim 4, wherein the reaction conditions of the Grignard reaction in step (1) include: a reaction temperature of 0-120° C.; a reaction time of 2-24 h; Alternatively, the reaction conditions of the Grignard reaction in step (1) include: reaction temperature of 0-45° C.; reaction time of 4-18 h. The preparation method according to claim 4 or 5, wherein the molar ratio of the compound represented by the general formula Br-R ₂ -OMe, magnesium powder and phosphorus trihalide is (2-4):(2-4):1; Alternatively, the molar ratio of the compound represented by the general formula Br-R ₂ -OMe, magnesium powder and phosphorus trihalide is (2.5-3.5):(2.5-3.5):1. The preparation method according to any one of claims 4 to 6, wherein the compound represented by the general formula Br-R ₂ -OMe is at least one selected from 4-methoxybromobenzene, 3-methoxybromobenzene and 4-bromo-4'-methoxybiphenyl; And/or, the phosphorus trihalide is phosphorus trichloride and/or phosphorus tribromide; And/or, the cyano group-containing intermediate is 4-nitrophthalonitrile. The preparation method according to any one of claims 4 to 7, wherein the acid solution in step (2) is a mixed solution of acetic acid and hydrobromic acid; Alternatively, the acid solution in step (2) is a mixed solution of excess acetic acid and saturated hydrobromic acid. The preparation method according to any one of claims 4 to 8, wherein the conditions of the first hydrolysis reaction include: a reaction temperature of 0 to 120° C.; a reaction time of 6 to 18 h; And/or, the conditions of the heating reaction in step (3) include: heating temperature of 80-120° C.; heating time of 2-10 h; And/or, in step (3), the molar ratio of compound 2 to the cyano-containing intermediate is 1:2-4. The preparation method according to any one of claims 4 to 9, wherein the reaction conditions of the second hydrolysis in step (4) include: a reaction time of 5 to 15 hours; And/or, the conditions of the dehydration reaction in step (5) include: reaction time of 6-36h; reaction temperature of 45-180°C. A polyimide material, wherein the polyimide material comprises a repeating unit structure represented by formula (IV) and a connecting group R ₁ between the repeating units represented by formula (IV):
wherein R ₂ is a residue of a substituted or unsubstituted C ₆ -C ₃₀ aromatic hydrocarbon that has lost 2 H atoms, or a residue of a substituted or unsubstituted C ₂ -C ₃₀ heterocyclic aromatic hydrocarbon that has lost 2 H atoms; The R ₁ is a substituted or unsubstituted alkylene group, a substituted or unsubstituted arylene group, or a substituted or unsubstituted heteroarylene group. The polyimide material according to claim 11, wherein _R2 is a residue of phenylene, biphenyl losing 2 H, or a residue of naphthalene losing 2 H; And/or, the polyimide material further comprises a capping group. The polyimide material according to claim 11 or 12, wherein the viscosity of the polyimide material is 5000-100000mPa·s; Alternatively, the viscosity of the polyimide material is 20000-80000 mPa·s. A method for preparing a polyimide material, wherein the method comprises: (A) dissolving a phosphorus-containing trianhydride monomer, a diisocyanate, and a diamine in a solvent, and performing a polymerization reaction to obtain a polymerization product; (B) heating the polymerization product in the presence of a surfactant to obtain a polyimide material; The phosphorus-containing trianhydride monomer is the phosphorus-containing trianhydride monomer according to any one of claims 1 to 3. The preparation method according to claim 14, wherein the conditions of the polymerization reaction in step (A) include: a reaction temperature of 20-180° C.; a reaction time of 4-24 h; Alternatively, the conditions of the polymerization reaction in step (A) include: reaction temperature of 25-120° C.; reaction time of 6-18 h. The preparation method according to claim 14 or 15, wherein the molar ratio of the phosphorus-containing trianhydride monomer, the solvent, the diisocyanate and the diamine is (0.1-0.95): (0.5-50): (0.05-0.9): 1; Alternatively, the molar ratio of the phosphorus-containing trianhydride monomer, the solvent, the diisocyanate and the diamine is (0.6-0.95):(3-10):(0.05-0.4):1. The preparation method according to any one of claims 14 to 16, wherein the diamine is selected from at least one of 4,4'-diaminodiphenyl ether, m-phenylenediamine, p-phenylenediamine, 4,4'-diaminodiphenyl sulfone, 1,3-diamino-2-methylpropane, N,N-bis(4-aminophenyl)-1,4-phenylenediamine and 9,9-bis(4-aminophenyl)fluorene; And/or, the diisocyanate is selected from at least one of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate and lysine diisocyanate; and/or, the solvent is selected from at least one of dimethyl sulfoxide, N-methylpyrrolidone, N,N-dimethylformamide and N,N-dimethylacetamide; And/or, the surfactant is selected from at least one of polyurethane rigid foam silicone oil, polyether and polysilane; And/or, the amount of the surfactant used is 0.1-10 wt % of the polymerization product in step (A), or the amount of the surfactant used is 1-5 wt % of the polymerization product in step (A). A polyimide material prepared by the preparation method described in any one of claims 14 to 17. Use of the polyimide material described in claim 11, 12, 13 or 18 in flame retardant sound absorbing materials for automobiles.