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

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

[0001] Priority information

[0002] 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

[0003] The present disclosure 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

[0004] Noise and vibration issues not only seriously impact interior quietness, passenger comfort, and the living environment of residents along highways, but also cause wear, fatigue, and even failure of key mechanical components in new energy vehicles. This reduces their service life and threatens the vehicle's safe operation. Flame retardancy in vehicles directly impacts driving safety. Therefore, it is crucial to improve the flame retardancy and sound absorption properties of automotive materials.

[0005] 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.

[0006] 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 high-efficiency heat-insulating and sound-absorbing lightweight material is prepared through a molding process. The disadvantage is that it cannot have both sound absorption and flame retardant properties.

[0007] CN111087618B discloses a sound-absorbing and noise-reducing polyimide foam. By adding hollow glass microspheres to form cavity resonance, combined with a subsequent material softening process and the introduction of a sound-absorbing wedge structure, the matching degree between the material's acoustic impedance and the air's acoustic impedance is improved, thereby enhancing the sound absorption and noise reduction performance of the polyimide. In order to maintain performance, this patent specifically adds a flame retardant.

[0008] The polyimide properties of existing technologies are primarily flame retardant, with limited intrinsic material properties. Dual or multifunctional properties are difficult to achieve, requiring multiple layers or composite materials, complex formulations and processes, and high costs. Therefore, a polyimide material is needed that can simultaneously meet the requirements for flame retardancy and sound absorption for automotive applications.

[0009] Summary of the Invention

[0010] The purpose of the present disclosure is to overcome the problem in the prior art that polyimide materials are difficult to have both flame retardant properties and sound absorption properties. 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 cooperate with diamine to prepare a porous polyimide material with uniform pore size distribution.

[0011] In order to achieve the above-mentioned object, the present disclosure provides a phosphorus-containing trianhydride monomer in a first aspect. The phosphorus-containing trianhydride monomer has a structure as shown in formula (I):

[0012] Wherein, R2 is substituted or unsubstituted C6-C 30 Aromatic residues that have lost 2 H groups, or substituted or unsubstituted C2-C 30 Heterocyclic aromatic hydrocarbons have lost 2 H residues.

[0013] A second aspect of the present disclosure provides a method for preparing the aforementioned phosphorus-containing trianhydride monomer, the method comprising the following steps:

[0014] (1) In the presence of a catalyst, a compound represented by the general formula Br-R2-OMe is reacted with magnesium powder to prepare a Grignard reagent, which is then subjected to a Grignard reaction with phosphorus trihalide to obtain compound 1, wherein R2 is a substituted or unsubstituted C6-C 30 Aromatic residues that have lost 2 H groups, or substituted or unsubstituted C2-C 30 Heterocyclic aromatic hydrocarbons are residues that have lost 2 H atoms;

[0015] (2) subjecting the compound 1 to a first hydrolysis reaction in an acid solution to obtain compound 2;

[0016] (3) heating the compound 2 and the cyano-containing intermediate to obtain compound 3;

[0017] (4) subjecting the compound 3 to a second hydrolysis reaction in an alkaline solution to obtain compound 4;

[0018] (5) subjecting the compound 4 to a dehydration reaction to obtain the phosphorus-containing trianhydride monomer.

[0019] 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 R1 between the repeating units represented by formula (IV):

[0020] Wherein, R2 is substituted or unsubstituted C6-C 30 Aromatic residues that have lost 2 H groups, or substituted or unsubstituted C2-C 30The heterocyclic aromatic hydrocarbon residue having lost two H atoms is preferably a phenylene residue, a biphenyl residue or a naphthalene residue having lost two H atoms; R1 is a substituted or unsubstituted alkylene group, a substituted or unsubstituted arylene group or a substituted or unsubstituted heteroarylene group.

[0021] A fourth aspect of the present disclosure provides a method for preparing a polyimide material, wherein the method comprises:

[0022] (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;

[0023] (B) heating the polymerization product in the presence of a surfactant to obtain a polyimide material;

[0024] The phosphorus-containing trianhydride monomer is the phosphorus-containing trianhydride monomer described in the first aspect.

[0025] The fifth aspect of the present disclosure provides a polyimide material prepared by the preparation method described in the fourth aspect.

[0026] 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.

[0027] Through the above technical solution, the following beneficial technical effects can be obtained:

[0028] (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.

[0029] (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

[0030] FIG1 is a scanning electron microscope image of the porous polyimide material of Example 1;

[0031] FIG2 is a scanning electron microscope image of the porous polyimide material of Comparative Example 1. DETAILED DESCRIPTION

[0032] The endpoints of the ranges and any values ​​disclosed herein 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 endpoints of each range, the endpoints of each range and 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 to be specifically disclosed herein.

[0033] 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):

[0034] Wherein, R2 is substituted or unsubstituted C6-C 30 Aromatic residues that have lost 2 H groups, or substituted or unsubstituted C2-C 30 Heterocyclic aromatic hydrocarbons have lost 2 H residues.

[0035] According to the present disclosure, preferably, R2 is a phenylene group, a biphenyl group with two H residues missing, or a naphthalene group with two H residues missing. The polyimide material subsequently prepared from the phosphorus-containing trianhydride monomer containing the above R2 structure has better heat resistance and flame retardancy and is more suitable for commercialization.

[0036] In the present disclosure, the phosphorus-containing trianhydride monomer is based on phosphorus. 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 retardancy while ensuring mechanical properties.

[0037] More preferably, the phosphorus-containing trianhydride monomer is at least one of the compounds represented by the following structural formula:

[0038] A second aspect of the present disclosure provides a method for preparing the aforementioned phosphorus-containing trianhydride monomer, the method comprising the following steps:

[0039] (1) In the presence of a catalyst, a compound represented by the general formula Br-R2-OMe is reacted with magnesium powder to prepare a Grignard reagent, which is then subjected to a Grignard reaction with phosphorus trihalide to obtain compound 1, wherein R2 is a substituted or unsubstituted C6-C 30 Aromatic residues that have lost 2 H groups, or substituted or unsubstituted C2-C 30 Heterocyclic aromatic hydrocarbons are residues that have lost 2 H atoms;

[0040] (2) subjecting the compound 1 to a first hydrolysis reaction in an acid solution to obtain compound 2;

[0041] (3) heating the compound 2 and the cyano-containing intermediate to obtain compound 3;

[0042] (4) subjecting the compound 3 to a second hydrolysis reaction in an alkaline solution to obtain compound 4;

[0043] (5) subjecting the compound 4 to a dehydration reaction to obtain the phosphorus-containing trianhydride monomer.

[0044] In the present disclosure, the compound structure generated in each step of the preparation process of the phosphorus-containing trianhydride monomer is as follows:

[0045] 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 2-24 h, preferably 4-18 h.

[0046] In the present disclosure, preferably, R2 is a phenylene group, a residue obtained by losing two H atoms in a biphenyl group, or a residue obtained by losing two H atoms in a naphthalene group.

[0047] 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 elemental iodine and / or 1,2-dibromoethane. The amount of the catalyst used is not particularly limited, as long as the Grignard reagent can be prepared.

[0048] 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.

[0049] 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 extraction is dried and concentrated with anhydrous sodium sulfate to obtain the compound 1.

[0050] According to the present disclosure, preferably, the molar ratio of the compound represented by the general formula Br-R2-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 to carry out the Grignard reaction can fully react the phosphorus trihalide.

[0051] According to the present disclosure, preferably, the compound represented by the general formula Br-R2-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 from a compound represented by the general formula Br-R2-OMe is reacted with a phosphorus trihalide to produce a phosphorus-based compound 1. Subsequently, a phosphorus-containing trianhydride monomer is further prepared based on compound 1, and the preparation process is simple.

[0052] According to the present disclosure, preferably, the phosphorus trihalide is phosphorus trichloride and / or phosphorus tribromide.

[0053] According to the present disclosure, preferably, the cyano group-containing intermediate is 4-nitrophthalonitrile.

[0054] 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%.

[0055] 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.

[0056] 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 alkaline solution is added dropwise thereto to separate the aqueous phase. The alkaline solution is a strong alkaline solution, preferably a sodium hydroxide solution and / or a potassium hydroxide solution.

[0057] 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.

[0058] 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 then filtered to obtain Compound 2. Preferably, the pH value of the aqueous phase solution after pH adjustment is less than 3, preferably a pH value of 1-2. The acid in the acid solution is a conventional acid in the art, preferably at least one selected from hydrochloric acid, nitric acid, and sulfuric acid.

[0059] 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 pH adjustment is less than 3.

[0060] 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.

[0061] 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.

[0062] 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 situation of the heating reaction. Preferably, the amount of the solvent added is such that the total molar concentration of compound 2 and the cyano-containing intermediate in the solvent is 0.5-5 mol / L.

[0063] 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.

[0064] According to the present disclosure, preferably, the reaction conditions of the second hydrolysis in step (4) include: a reaction time of 5-15 hours, preferably 7-12 hours. In the present disclosure, the second hydrolysis reaction is carried out at room temperature.

[0065] 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 5-10 wt%.

[0066] 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.

[0067] 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.

[0068] In the present disclosure, the dehydration reaction is preferably carried out in the presence of a dehydrating agent, which is a mixed solution of an acid anhydride and a corresponding acid, preferably acetic acid and acetic anhydride. The dehydration reaction using the above-mentioned dehydrating agent can dehydrate the carboxyl group adjacent to the terminal benzene ring of compound 4 to obtain a phosphorus-containing trianhydride monomer structure of formula (I).

[0069] 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.

[0070] According to a particularly preferred embodiment of the present disclosure, a method for preparing a phosphorus-containing trianhydride monomer comprises the following steps:

[0071] (1) In the presence of a catalyst, a compound represented by the general formula Br-R2-OMe is reacted with magnesium powder to prepare a Grignard reagent, which is then subjected to a Grignard reaction with phosphorus trihalide to obtain compound 1, wherein R2 is a substituted or unsubstituted C6-C 30 Aromatic residues that have lost 2 H groups, or substituted or unsubstituted C2-C 30 Heterocyclic aromatic hydrocarbons are residues that have lost 2 H atoms;

[0072] (2) subjecting the compound 1 to a first hydrolysis reaction in an acid solution to obtain compound 2;

[0073] (3) heating the compound 2 and 4-nitrophthalonitrile to obtain compound 3;

[0074] (4) subjecting the compound 3 to a second hydrolysis reaction in an alkaline solution to obtain compound 4;

[0075] (5) subjecting the compound 4 to a dehydration reaction to obtain the phosphorus-containing trianhydride monomer;

[0076] The compound represented by the general formula Br-R2-OMe is selected from at least one of 4-methoxybromobenzene, 3-methoxybromobenzene and 4-bromo-4'-methoxybiphenyl;

[0077] The molar ratio of compound 2 to 4-nitrophthalonitrile in step (3) is 1:2-3.

[0078] 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 R1 between the repeating units represented by formula (IV):

[0079] Wherein, R2 is substituted or unsubstituted C6-C 30 Aromatic residues that have lost 2 H groups, or substituted or unsubstituted C2-C 30 The heterocyclic aromatic hydrocarbon residue having lost two H atoms is preferably a phenylene residue, a biphenyl residue or a naphthalene residue having lost two H atoms; R1 is a substituted or unsubstituted alkylene group, a substituted or unsubstituted arylene group or a substituted or unsubstituted heteroarylene group.

[0080] In the present disclosure, the R1 can be introduced by the added diisocyanate and / or diamine, that is, the R1 is a structural segment other than the two isocyanate groups in the diisocyanate, or a structural segment other than the two amine groups in the diamine.

[0081] According to the present disclosure, the viscosity of the polyimide material is preferably 5,000-100,000 mPa·s, preferably 20,000-80,000 mPa·s. In the present disclosure, the viscosity is the viscosity of the polyimide material measured at 25°C using a rotational viscometer. This can characterize the molecular weight of the polyimide material.

[0082] According to the present disclosure, the polyimide material preferably further comprises an end-capping group, which can be formed by reacting the molecular chain ends 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, end-capping can be achieved by introducing a dicarboxylic anhydride, or by adding an excess of a trianhydride monomer or a diamine.

[0083] 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.

[0084] In the present disclosure, the composition and structure of the polyimide material (including information on repeating units, linking groups and end-capping groups) can be determined and analyzed by infrared spectroscopy.

[0085] In the present disclosure, the repeating structural units included in the polyimide material are preferably derived from a phosphorus-containing trianhydride monomer of formula (II) or formula (III); the linking group R1 is preferably derived from diphenylmethane diisocyanate, toluene diisocyanate, 4,4'-diaminodiphenyl ether or p-phenylenediamine; and 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.

[0086] A fourth aspect of the present disclosure provides a method for preparing a polyimide material, the method comprising:

[0087] (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;

[0088] (B) heating the polymerization product in the presence of a surfactant to obtain a polyimide material;

[0089] The phosphorus-containing trianhydride monomer is the phosphorus-containing trianhydride monomer described in the first aspect.

[0090] According to the present disclosure, preferably, the conditions for the polymerization reaction in step (A) include: a reaction temperature of 20-180°C, preferably 25-120°C; and a reaction time of 4-24h, preferably 6-18h. By using the aforementioned phosphorus-containing trianhydride monomer, diisocyanate, and diamine to carry out a polymerization reaction under the aforementioned polymerization reaction conditions, a porous polyimide material with uniform pore size distribution can be prepared, which has both flame retardant 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.

[0091] In the present disclosure, the average pore size of the polyimide material is determined by randomly selecting 20 pores from an electron microscope image, measuring the distance between the farthest ends of the pores, and calculating the average value. The average pore size is 0.1-10 μm, preferably 0.5-5 μm. The foaming behavior of the polyimide material is determined by scanning electron microscopy.

[0092] In the present disclosure, a phosphorus-containing trianhydride monomer reacts with a diisocyanate, i.e., the anhydride group reacts with the isocyanate group. Different phosphorus-containing trianhydride monomers can be linked to form a polyimide product and carbon dioxide, which is then used for foaming. The phosphorus-containing trianhydride monomer can also react with a diamine, i.e., the anhydride group reacts with the amine group, to adjust the foaming amount and the size of the pores formed by foaming, thereby producing a polyimide foam material with a uniform pore size distribution. Furthermore, the diamine and phosphorus-containing trianhydride monomers can also be used to form end-capping groups in the polyimide.

[0093] 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.

[0094] In the present disclosure, preferably, the step (A) is carried out under stirring. The stirring rate is not particularly limited and can be adaptively adjusted by those skilled in the art according to the polymerization reaction conditions.

[0095] According to the present disclosure, preferably, the molar ratio of the phosphorus-containing trianhydride monomer, solvent, diisocyanate, and 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. By adjusting the phosphorus-containing trianhydride monomer, diisocyanate, diamine, and solvent to a specific molar ratio for polymerization, phosphorus is introduced into the polyimide material through the phosphorus-containing trianhydride monomer, and the diisocyanate serves 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 retardancy and sound absorption properties of the polyimide material are improved. The amount of the phosphorus-containing trianhydride monomer and diamine used is excess compared to the diisocyanate, and also provides end-capping groups for forming the molecular chains in the polyimide.

[0096] The present disclosure has no particular limitation on the manner of adding the phosphorus-containing trianhydride monomer, diisocyanate, and diamine, which may be added separately or together.

[0097] According to a preferred embodiment of the present disclosure, the phosphorus-containing trianhydride monomer reacts with the diisocyanate for 0.5-2 hours before adding the diamine. The polyimide material prepared by reacting in this order has good mechanical properties and the porous material has stronger toughness.

[0098] 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, thereby connecting the phosphorus-containing trianhydride monomer and providing 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.

[0099] 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, the remaining residue, excluding the isocyanate group, remains in the structure of the polyimide material, providing a linking group for connecting to the phosphorus-containing trianhydride monomer.

[0100] 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.

[0101] In the present disclosure, the heating method of 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.

[0102] The heating temperature in the first stage is 100-200°C, preferably 130-170°C, and the heating time is 0.1-2 hours. The heating temperature in the second stage is 200-300°C, preferably 230-270°C, and the heating time is 0.1-2 hours. The heating temperature in the third stage is 300-400°C, preferably 330-370°C, and the heating time is 0.1-2 hours. Under the above-mentioned gradient heating conditions, the carbon dioxide in the polyimide material is slowly released, forming a polyimide foam material with a uniform pore structure.

[0103] 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.

[0104] In the present disclosure, the amount of the surfactant is not particularly limited, and those skilled in the art can adjust the amount 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).

[0105] According to a preferred embodiment of the present disclosure, a method for preparing a polyimide material comprises:

[0106] (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;

[0107] (B) heating the polymerization product in the presence of a surfactant to obtain a polyimide material;

[0108] The phosphorus-containing trianhydride monomer is a phosphorus-containing trianhydride monomer of formula (II) or formula (III);

[0109] The conditions of the polymerization reaction in step (A) include: reaction temperature of 25-120° C.; reaction time of 6-18 h;

[0110] 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.

[0111] The fifth aspect of the present disclosure provides a polyimide material prepared by the preparation method described in the fourth aspect.

[0112] 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.

[0113] In the present disclosure, the polyimide material has both flame retardant and sound absorbing properties. When used in flame retardant and sound absorbing materials, it can significantly reduce the impact of noise and vibration. The average sound absorption coefficient can reach 0.4, the limiting oxygen index can reach 37%, and the flame retardant property is good.

[0114] 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;

[0115] Polyether Silok-2008N was purchased from Guangzhou Silok Company;

[0116] Limiting oxygen index: Use limiting oxygen index tester to test in accordance with GB / T2406.2-2009;

[0117] 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 average as the average sound absorption coefficient;

[0118] H NMR spectrum data: measured using H NMR spectrometer;

[0119] The foaming condition was obtained by observing the polyimide material under scanning electron microscopy;

[0120] The viscosity is the viscosity of the polyimide material measured at 25° C. It is measured using a rotational viscometer.

[0121] Preparation Example 1 Phosphorus-containing trianhydride monomer

[0122] (1) 3 mol of 4-methoxybromobenzene 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. The reaction was carried out at 25°C for 10 h and then quenched with a saturated ammonium chloride solution. The organic phase was extracted with ethyl acetate, dried over anhydrous sodium sulfate, and concentrated to obtain compound 1.

[0123] (2) Compound 1 was added to excess acetic acid and 48 wt% hydrobromic acid for a first hydrolysis reaction at 60°C for 12 hours. After the reaction was complete and the mixture was cooled to room temperature, it was extracted with ethyl acetate. After the organic phase was removed, 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.

[0124] (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 5 hours, and the reaction product was cooled to room temperature and purified by column chromatography to obtain compound 3;

[0125] (4) Compound 3 was dissolved in a 10 wt% potassium hydroxide solution to undergo a second hydrolysis reaction for 10 hours, and then recrystallized from glacial acetic acid to obtain Compound 4;

[0126] (5) Compound 4 was dissolved in a mixed solution of acetic acid and acetic anhydride to undergo a dehydration reaction at a temperature of 80° C. for 24 hours, and then recrystallized with glacial acetic acid to obtain phosphorus-containing trianhydride monomer 1.

[0127] H NMR spectrum data of phosphorus-containing trianhydride monomer 1: 1H NMR (500 MHz, Chloroform-d) δ 8.03 (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 was confirmed that the phosphorus-containing trianhydride monomer formed the structure represented by the aforementioned formula (II).

[0128] Preparation Example 2 Phosphorus-containing trianhydride monomer

[0129] (1) 3 mol of 4-bromo-4'-methoxybiphenyl reacted with 3 mol of magnesium powder 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. The reaction was carried out at 0°C for 10 h and then quenched with a saturated ammonium chloride solution. The organic phase was extracted with ethyl acetate, dried over anhydrous sodium sulfate, and concentrated to obtain compound 1.

[0130] (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 complete and the temperature was cooled to room temperature, the mixture was extracted with ethyl acetate. After the organic phase was removed, 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.

[0131] (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 5 hours, and the reaction product was cooled to room temperature and purified by column chromatography to obtain compound 3;

[0132] (4) Compound 3 was dissolved in a 10 wt% potassium hydroxide solution to undergo a second hydrolysis reaction for 10 hours, and then recrystallized from glacial acetic acid to obtain Compound 4;

[0133] (5) Compound 4 was dissolved in a mixed solution of acetic acid and acetic anhydride to undergo a 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.

[0134] The nuclear magnetic resonance hydrogen spectrum data of the phosphorus-containing trianhydride monomer 2: 1H NMR (500 MHz, Chloroform-d) δ 8.03 (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 was confirmed that the phosphorus-containing trianhydride monomer formed the structure represented by the aforementioned formula (III).

[0135] Example 1

[0136] (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 added to 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;

[0137] (B) After the reaction was completed and the temperature was cooled to room temperature, Silok-2008N was added (the addition amount was 5% of the total mass of the polymerization product in step (A)). After stirring for 1 hour, the solution was 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.

[0138] Example 2

[0139] (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 stirred. After the reaction is carried out for 0.5 h, p-phenylenediamine is added. The reaction temperature is 45° C. and stirred for 12 hours.

[0140] (B) After the reaction was completed and the temperature was cooled to room temperature, Silok-2008N (5% of the total mass of the polymerization product in step (A)) was added and stirred for 1 hour. The solution was then poured into a mold and heated in a gradient of 120°C for 1 hour, 200°C for 2 hours, and 300°C for 2 hours to obtain a porous polyimide material.

[0141] Example 3

[0142] (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 added to a reactor 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 stirred for 24 hours.

[0143] (B) After the reaction was completed and the temperature was cooled to room temperature, Silok-2008N (5% of the total mass of the polymerization product in step (A)) was added and stirred for 1 hour. The solution was then poured into a mold and heated in a gradient of 120° C. for 1 hour, 200° C. for 2 hours, and 300° C. for 2 hours to obtain a porous polyimide material.

[0144] Example 4

[0145] A polyimide material was prepared according to the method of Example 3, except that the phosphorus-containing trianhydride monomer 1 was replaced with an equal molar amount of phosphorus-containing trianhydride monomer 2, to obtain a porous polyimide material.

[0146] Example 5

[0147] A 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.

[0148] Comparative Example 1

[0149] (A) p-phenylenediamine, pyromellitic anhydride, diphenylmethane diisocyanate, and N,N-dimethylformamide in a molar ratio of 1:0.7:0.3:10 were sequentially added into a reaction kettle, and stirring was started. The reaction kettle was controlled at 45° C. and stirred for 12 hours;

[0150] (B) After cooling to room temperature, Silok-2008N (5% of the total mass of the mixed solution in step (A)) was added and stirred for 1 hour. The solution was then 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.

[0151] Comparative Example 2

[0152] A 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.

[0153] Comparative Example 3

[0154] A polyimide material was prepared according to the method of Example 1, except that no diisocyanate was added in step (A).

[0155] Test Case

[0156] 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.

[0157] Average pore size: less than 3μm is small, and greater than or equal to 3μm is large.

[0158] Table 1

[0159] The results in Table 1 indicate that the polyimide materials produced in Examples 1-4 of the present disclosure exhibit uniform internal foaming, smaller pore sizes, and significantly improved flame retardancy and sound absorption. The dianhydrides used in Examples 1 and 2 differ from the diamines, and while their backbone structures differ, the performance differences are minimal, demonstrating that the tertianhydride monomer is suitable for use in different polyimide structures.

[0160] Although different isocyanates were used in Examples 2 and 3, both exhibited significantly better performance than the comparative example, demonstrating that different isocyanates can be used with the phosphorus-containing trianhydride monomer disclosed herein. Compared to Example 1, Example 4 employed a different trianhydride monomer, but with minimal performance differences, demonstrating the stability of the trianhydride monomer disclosed herein. Compared to Example 1, Example 5 employed an adjusted molar ratio for the polyimide material. While the limiting oxygen index was slightly lower than that of Example 1, foaming was poor, but overall flame retardancy and sound absorption properties were superior to those of the comparative example.

[0161] FIG1 is a scanning electron microscope image of the porous polyimide material of Example 1. As shown in FIG1 , the pore size of the polyimide material of Example 1 is small and evenly distributed.

[0162] The one-dimensional rigid structure in Comparative Example 1 is not conducive to foaming, resulting in larger pore sizes than in Examples 1-4 and a low sound absorption coefficient. Comparative Example 1 lacks phosphorus and has a low limiting oxygen index. Figure 2 shows a scanning electron micrograph of the porous polyimide material in Comparative Example 1, showing that the polyimide material in Comparative Example 1 exhibits larger pore sizes and an uneven internal pore size distribution.

[0163] Comparative Example 2, which did not utilize the disclosed phosphorus-containing trianhydride monomer, produced a polyimide material with large pores, uneven foaming, a low limiting oxygen index and average sound absorption coefficient, and poor flame retardancy and sound absorption properties. Comparative Example 3, in which no diisocyanate was added during the polyimide preparation process, produced no bubbles and exhibited poor sound absorption properties.

[0164] 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, various simple variations of the technical solution of the present disclosure may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed by the present disclosure and fall within the scope of protection of the present disclosure.

Claims

1. A phosphorus-containing trianhydride monomer, wherein: The phosphorus-containing trianhydride monomer has a structure as shown in formula (I): Wherein R2 is a substituted or unsubstituted C6-C 30 Aromatic residues that have lost 2 H, or substituted or unsubstituted C2-C 30 Heterocyclic aromatic hydrocarbons lose 2 H residues.

2. The phosphorus-containing trianhydride monomer according to claim 1, wherein R2 is a phenylene group, a residue obtained by losing two H atoms in biphenyl, or a residue obtained by losing two H atoms in naphthalene.

3. The phosphorus-containing trianhydride monomer according to claim 1 or 2, wherein The phosphorus-containing trianhydride monomer is at least one of the compounds shown in the following structural formula: in, 4. 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, a compound represented by the general formula Br-R2-OMe is reacted with magnesium powder to prepare a Grignard reagent, and then the Grignard reagent is reacted with phosphorus trihalide to obtain compound 1, wherein R2 is a substituted or unsubstituted C6-C 30 Aromatic residues that have lost 2 H, or substituted or unsubstituted C2-C 30 Heterocyclic aromatic hydrocarbons lose 2 H residues; (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.

5. The preparation method according to claim 4, wherein: The reaction conditions of the Grignard reaction in step (1) include: reaction temperature of 0-120° C.; 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.

6. The preparation method according to claim 4 or 5, wherein: The molar ratio of the compound represented by the general formula Br-R2-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-R2-OMe, magnesium powder and phosphorus trihalide is (2.5-3.5):(2.5-3.5):

1.

7. The preparation method according to any one of claims 4 to 6, wherein The compound represented by the general formula Br-R2-OMe is selected from at least one of 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.

8. 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.

9. The preparation method according to any one of claims 4 to 8, wherein The conditions of the first hydrolysis reaction include: reaction temperature of 0-120°C; reaction time of 6-18h; 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.

10. 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 5-15 h; And / or, the conditions of the dehydration reaction in step (5) include: reaction time of 6-36h; reaction temperature of 45-180°C.

11. A polyimide material, wherein: The polyimide material contains a repeating unit structure shown in formula (IV) and a connecting group R1 between the repeating units shown in formula (IV): Wherein R2 is a substituted or unsubstituted C6-C 30 Aromatic residues that have lost 2 H, or substituted or unsubstituted C2-C 30 Heterocyclic aromatic hydrocarbons lose 2 H residues; The R1 is a substituted or unsubstituted alkylene group, a substituted or unsubstituted arylene group, or a substituted or unsubstituted heteroarylene group.

12. The polyimide material according to claim 11, wherein R2 is a phenylene group, a biphenyl group with two H atoms missing, or a naphthalene group with two H atoms missing; And / or, the polyimide material further comprises a capping group.

13. The polyimide material according to claim 11 or 12, wherein: The viscosity of the polyimide material is 5000-100000 mPa·s; Alternatively, the viscosity of the polyimide material is 20000-80000 mPa·s.

14. 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.

15. The preparation method according to claim 14, wherein: The conditions of the polymerization reaction in step (A) include: reaction temperature of 20-180° C.; 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.

16. 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.

17. The preparation method according to any one of claims 14 to 16, wherein The diamine is at least one selected from 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).

18. The polyimide material prepared by the preparation method according to any one of claims 14 to 17.

19. Use of the polyimide material according to claim 11, 12, 13 or 18 in flame retardant sound absorbing materials for automobiles.

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