CN114920932B - High-temperature-resistant thermosetting polyimide precursor solution with good stability and preparation method - Google Patents
High-temperature-resistant thermosetting polyimide precursor solution with good stability and preparation method Download PDFInfo
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- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G73/00—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups C08G12/00 - C08G71/00
- C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
- C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
- C08G73/1067—Wholly aromatic polyimides, i.e. having both tetracarboxylic and diamino moieties aromatically bound
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
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- C08G73/00—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups C08G12/00 - C08G71/00
- C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
- C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
- C08G73/1003—Preparatory processes
- C08G73/1007—Preparatory processes from tetracarboxylic acids or derivatives and diamines
- C08G73/101—Preparatory processes from tetracarboxylic acids or derivatives and diamines containing chain terminating or branching agents
- C08G73/1014—Preparatory processes from tetracarboxylic acids or derivatives and diamines containing chain terminating or branching agents in the form of (mono)anhydrid
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- C08G73/00—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups C08G12/00 - C08G71/00
- C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
- C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
- C08G73/1039—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors comprising halogen-containing substituents
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- C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
- C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
- C08G73/1042—Copolyimides derived from at least two different tetracarboxylic compounds or two different diamino compounds
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- C08J2379/00—Characterised by the use of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing nitrogen with or without oxygen, or carbon only, not provided for in groups C08J2361/00 - C08J2377/00
- C08J2379/04—Polycondensates having nitrogen-containing heterocyclic rings in the main chain; Polyhydrazides; Polyamide acids or similar polyimide precursors
- C08J2379/08—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
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Abstract
The invention discloses a high-temperature-resistant thermosetting polyimide precursor solution with good stability and a preparation method thereof, and relates to a polyimide precursor solution and a preparation method thereof. Solves the problems of poor stability and unsatisfactory heat resistance of the existing thermosetting polyimide precursor solution. The imide precursor solution is prepared from aromatic diamine, aromatic dianhydride, a blocking agent, a polar solvent, water and tertiary amine; the preparation method comprises the following steps: 1. weighing; 2. dividing into parts; 3. reacting a polar solvent, aromatic diamine, aromatic dianhydride and a blocking agent; 4. drying; 5. mixing water, tertiary amine and polyamide acid powder; the preparation method is used for preparing the high-temperature-resistant thermosetting polyimide precursor solution with good stability.
Description
Technical Field
The invention relates to polyimide precursor solution and a preparation method thereof.
Background
In the field of water-based paint, research and development of water-based epoxy paint, water-based acrylic paint and water-based polyurethane paint have been advanced in correlation. Although these three aqueous paints have excellent effects in terms of corrosion resistance and environmental protection, when applied as a coating on the surface of a metal substrate, they are prone to various problems such as warping and slag falling, especially under high temperature conditions.
Thermosetting polyimides can be classified into PMR type polyimides, acetylene-terminated polyimides, phenylacetylene-terminated polyimides, depending on the type of capping agent. The phenylacetylene-terminated polyimide has the advantages of difficult generation of polar small molecules, low viscosity of oligomers, wide processing window and the like. Because the alkynyl structure of the end capping agent forms a bodily form net structure after being heated, polyimide resin formed by end capping of the phenylacetylene end capping agent has excellent thermal property, and the polyimide resin can be prepared into aqueous solution with good stability and can be applied to the field of coatings to be used as a heat-resistant coating. However, after the thermosetting polyimide precursor is subjected to end capping, the polymer has a smaller molecular weight and a higher end group occupation ratio, so that a high-rigidity main chain structure cannot be stretched due to the fact that a chain segment with a sufficient length is not provided, and a small part of solute which can be dissolved in a solvent is less and dissolved is easy to separate out. Meanwhile, the lower modulus is brought about by the smaller molecular weight of the short-chain polyimide precursor aqueous solution, and the stability of the prepared aqueous solution is poor due to the extremely short molecular chain. Therefore, it is difficult to synthesize a homogeneous thermosetting polyimide precursor solution which imparts excellent heat resistance to the polyimide precursor solution, and to use the polyimide precursor solution as an aqueous coating material or an aqueous adhesive.
Disclosure of Invention
The invention aims to solve the problems of poor stability and unsatisfactory heat resistance of the existing thermosetting polyimide precursor solution, and further provides a high-temperature-resistant thermosetting polyimide precursor solution with good stability and a preparation method.
A high-temperature resistant thermosetting polyimide precursor solution with good stability is prepared from aromatic diamine, aromatic dianhydride, a blocking agent, a polar solvent, water and tertiary amine; the molar ratio of the aromatic diamine to the aromatic dianhydride is (1.1-2) 1; the mol ratio of the aromatic diamine to the end capping agent is (1-5.5): 1; the mass ratio of the tertiary amine to the aromatic diamine is (0.2-2): 1;
the aromatic diamine is 3, 5-diaminobenzoic acid, 4 '-diaminobiphenyl-2, 2' dicarboxylic acid or 6,6 '-diamino-3, 3' -methylene dibenzoic acid;
the aromatic dianhydride is 4,4' - (hexafluoroisopropyl) diphthalic anhydride;
the end-capping agent is 4-phenylethynyl phthalic anhydride;
the tertiary amine is one or the combination of more of 2- (tert-butylamino) ethanol, N-ethylpiperazine and isoquinoline;
the structural formula of the polyamic acid salt repeating unit in the polyimide precursor solution is as follows:
n=1 to 10;
said R is 1 Is that
Said R is 2 Is that
The preparation method of the high-temperature-resistant thermosetting polyimide precursor solution with good stability is carried out according to the following steps:
1. weighing aromatic diamine, aromatic dianhydride, end-capping agent, polar solvent, water and tertiary amine;
the molar ratio of the aromatic diamine to the aromatic dianhydride is (1.1-2) 1; the mol ratio of the aromatic diamine to the end capping agent is (1-5.5): 1; the mass ratio of the tertiary amine to the aromatic diamine is (0.2-2): 1;
the aromatic diamine is 3, 5-diaminobenzoic acid, 4 '-diaminobiphenyl-2, 2' dicarboxylic acid or 6,6 '-diamino-3, 3' -methylene dibenzoic acid;
the aromatic dianhydride is 4,4' - (hexafluoroisopropyl) diphthalic anhydride;
the end-capping agent is 4-phenylethynyl phthalic anhydride;
the tertiary amine is one or the combination of more of 2- (tert-butylamino) ethanol, N-ethylpiperazine and isoquinoline;
2. dividing the weighed aromatic dianhydride into a first part of aromatic dianhydride, a second part of aromatic dianhydride and a third part of aromatic dianhydride according to the mass ratio of 2:1:1, and dividing the weighed end capping agent into a first part of end capping agent and a second part of end capping agent according to the mass ratio of 1:1;
3. mixing polar solvent and aromatic diamine and reacting for 0.5-1 h under the condition of room temperature and stirring to obtain a reaction system, raising the reaction temperature of the reaction system to 50-70 ℃, adding a first part of aromatic dianhydride into the reaction system and reacting for 0.5-1 h under the condition of 50-70 ℃ and stirring, adding a second part of aromatic dianhydride after the reaction, reacting for 0.5-1 h under the condition of 50-70 ℃ and stirring, adding a third part of aromatic dianhydride, reacting for 1-2 h under the condition of 50-70 ℃ and stirring, adding a first part of end-capping agent, reacting for 1-2 h under the condition of 50-70 ℃ and stirring, finally adding a second part of end-capping agent, and reacting for 1-2 h under the condition of 50-70 ℃ and stirring to obtain a reacted solution;
4. drying the reacted solution to obtain polyamic acid powder;
5. and (3) mixing the weighed water, tertiary amine and polyamide acid powder prepared in the step (IV), and stirring and dissolving the powder to obtain the high-temperature-resistant thermosetting polyimide precursor solution with good stability.
The beneficial effects of the invention are as follows:
1. the invention adopts a novel main chain structure polyimide precursor aqueous solution preparation-thermosetting polyimide structure. Because the blocking agent containing alkynyl is introduced into the system, the ethynyl is crosslinked after being heated to obtain a space network structure, so that the glass transition temperature, the modulus and the mechanical property of the aqueous solution are improved. The aromatic dianhydride is 4,4' - (hexafluoroisopropyl) diphthalic anhydride with fluorine atom structure, and the larger bond energy of-C-F-is of great significance for increasing the glass transition temperature.
2. The polar group-carboxylic acid group is introduced into the structure, and the electron-withdrawing property of the carboxylic acid group is strong, so that the polar solvent which is water-soluble is easy to dissolve, the solubility of the obtained solution is improved well, and the stability of the aqueous solution is ensured. The aromatic diamine structure of the present invention does not contain an electron-withdrawing bridging structure, which means that the diamine itself has high basicity. This has a promoting effect on maintaining the stability of the aqueous solution which is originally shown to be alkaline. Compared with the prior monomer selection of phenylacetylene end capped polyimide, for example: full-aromatic dianhydride pyromellitic anhydride, diphenyl tetracarboxylic dianhydride with asymmetric structure and flexible structure. Although such dianhydrides are more electron-affinity, they tend to be more reactive with diamines. But far less soluble than the aromatic dianhydride 4,4' - (hexafluoroisopropyl) isophthalic anhydride containing a larger volume of fluorine atoms involved in the design. In addition, the polyamic acid salt solution obtained by introducing a tertiary amine having a complexing effect into the solution has better stability than the polyamic acid solution. Therefore, when tertiary amine and 4,4' - (hexafluoroisopropyl) diphthalic anhydride having polar solvent solubility are combined, excellent aqueous solution stability is brought about even under conditions such as high rigidity, a small molecular weight main chain structure, a rigid group, and the like, which adversely affect the solubility.
3. Since thermoplastic polyimide has insolubility and infusibility, the processing stage of amorphous polyimide can only be stopped at the precursor stage. There are many advantages over thermoset polyimides: first, thermosetting polyimide is more excellent in processability. On the other hand, thermosetting polyimide after crosslinking can give the polymer high strength, good heat resistance, high modulus, etc. characteristics, which are also not comparable to thermoplastic polyimide. When the phenylethynyl-terminated thermosetting polyimide precursor aqueous solution is used as a water-based coating or a water-based adhesive to be coated on the surface of a metal substrate, phenylethynyl groups are heated and crosslinked to generate a larger crosslinking density, so that the polymer containing the phenylethynyl groups has extremely stable structure and thermal stability. The metal substrate is provided with excellent high temperature resistance and use protection, and the occurrence of cracking of the surface of the coating is avoided. Meanwhile, no byproducts are generated in the crosslinking process, so that the generation of bubbles is well eliminated, and the gap between the coating or adhesive and the metal substrate is minimized. Even though the phenylethynyl group brings such a high crosslinking density to the polymerization, it does not become too hard at high temperature operation, protecting the processability of the solution. Finally, the polymer terminated by the phenylethynyl end-capping agent can control the solution performance within a desired range due to the limited molecular weight.
4. In addition, after the phenylacetylene capped fluorine-containing dianhydride and the carboxyl diamine are combined, under the condition of the phenylacetylene capped controlled crosslinking density, the heat resistance and the use temperature of the thermosetting polyimide are further improved by virtue of the bulky fluorine-containing side group. And when the aqueous solution is used as a coating, the beneficial adhesive force of the aqueous solution on the surface of the substrate and the adhesive force after heat aging test are unexpectedly realized by virtue of the adhesive force of the surface of the metal substrate caused by carboxyl and the high Wen Lianduan movement capability caused by a fluorine-containing structure.
Drawings
Fig. 1 is an infrared spectrum of a polyimide precursor solution, 1 is example one, 2 is comparative example one, 3 is comparative example two, 4 is comparative example three, and 5 is comparative example four.
Detailed Description
The first embodiment is as follows: the high-stability high-temperature-resistant thermosetting polyimide precursor solution is prepared from aromatic diamine, aromatic dianhydride, a blocking agent, a polar solvent, water and tertiary amine; the molar ratio of the aromatic diamine to the aromatic dianhydride is (1.1-2) 1; the mol ratio of the aromatic diamine to the end capping agent is (1-5.5): 1; the mass ratio of the tertiary amine to the aromatic diamine is (0.2-2): 1;
the aromatic diamine is 3, 5-diaminobenzoic acid, 4 '-diaminobiphenyl-2, 2' dicarboxylic acid or 6,6 '-diamino-3, 3' -methylene dibenzoic acid;
the aromatic dianhydride is 4,4' - (hexafluoroisopropyl) diphthalic anhydride;
the end-capping agent is 4-phenylethynyl phthalic anhydride;
the tertiary amine is one or the combination of more of 2- (tert-butylamino) ethanol, N-ethylpiperazine and isoquinoline;
the structural formula of the polyamic acid salt repeating unit in the polyimide precursor solution is as follows:
n=1 to 10;
said R is 1 Is that
Said R is 2 Is that
In the specific embodiment, firstly, aromatic diamine with a polar group side group and aromatic dianhydride containing a trifluoro structure are dissolved in a polar solvent, and finally, an end capping agent containing alkynyl is introduced for end capping to generate polyimide precursor solution. In order to ensure a very small change in molecular weight, the resulting polyamic acid precursor solution is precipitated into a powder and dissolved in a mixed solvent of water and a tertiary amine. The obtained aqueous solution has the advantages of ensuring good stability under certain use temperature conditions and improving the defect of poor heat resistance. In addition, most of the solvent in the process is water, so that the requirements of water-based paint and the like on environmental protection and cost saving are met.
The beneficial effects of this concrete implementation are:
1. the specific embodiment adopts a novel polyimide precursor aqueous solution preparation of a main chain structure, namely a thermosetting polyimide structure. Because the blocking agent containing alkynyl is introduced into the system, the ethynyl is crosslinked after being heated to obtain a space network structure, so that the glass transition temperature, the modulus and the mechanical property of the aqueous solution are improved. In addition, the aromatic dianhydride according to the embodiment is 4,4' - (hexafluoroisopropyl) diphthalic anhydride with fluorine atom structure, and the larger bond energy of-C-F-is of great importance for increasing the glass transition temperature.
2. The polar group-carboxylic acid group is introduced into the structure, and the electron-withdrawing property of the carboxylic acid group is strong, so that the polar solvent which is water-soluble is easy to dissolve, the solubility of the obtained solution is improved well, and the stability of the aqueous solution is ensured. Since the aromatic diamine structures of this embodiment do not contain electron withdrawing bridging structures, it is shown that the diamine itself has high basicity. This has a promoting effect on maintaining the stability of the aqueous solution which is originally shown to be alkaline. Compared with the prior monomer selection of phenylacetylene end capped polyimide, for example: full-aromatic dianhydride pyromellitic anhydride, diphenyl tetracarboxylic dianhydride with asymmetric structure and flexible structure. Although such dianhydrides are more electron-affinity, they tend to be more reactive with diamines. But far less soluble than the aromatic dianhydride 4,4' - (hexafluoroisopropyl) isophthalic anhydride containing a larger volume of fluorine atoms involved in the design. In addition, the polyamic acid salt solution obtained by introducing a tertiary amine having a complexing effect into the solution has better stability than the polyamic acid solution. Therefore, when tertiary amine and 4,4' - (hexafluoroisopropyl) diphthalic anhydride having polar solvent solubility are combined, excellent aqueous solution stability is brought about even under conditions such as high rigidity, a small molecular weight main chain structure, a rigid group, and the like, which adversely affect the solubility.
3. Since thermoplastic polyimide has insolubility and infusibility, the processing stage of amorphous polyimide can only be stopped at the precursor stage. There are many advantages over thermoset polyimides: first, thermosetting polyimide is more excellent in processability. On the other hand, thermosetting polyimide after crosslinking can give the polymer high strength, good heat resistance, high modulus, etc. characteristics, which are also not comparable to thermoplastic polyimide. When the phenylethynyl-terminated thermosetting polyimide precursor aqueous solution is used as a water-based coating or a water-based adhesive to be coated on the surface of a metal substrate, phenylethynyl groups are heated and crosslinked to generate a larger crosslinking density, so that the polymer containing the phenylethynyl groups has extremely stable structure and thermal stability. The metal substrate is provided with excellent high temperature resistance and use protection, and the occurrence of cracking of the surface of the coating is avoided. Meanwhile, no byproducts are generated in the crosslinking process, so that the generation of bubbles is well eliminated, and the gap between the coating or adhesive and the metal substrate is minimized. Even though the phenylethynyl group brings such a high crosslinking density to the polymerization, it does not become too hard at high temperature operation, protecting the processability of the solution. Finally, the polymer terminated by the phenylethynyl end-capping agent can control the solution performance within a desired range due to the limited molecular weight.
4. In addition, after the phenylacetylene capped fluorine-containing dianhydride and the carboxyl diamine are combined, under the condition of the phenylacetylene capped controlled crosslinking density, the heat resistance and the use temperature of the thermosetting polyimide are further improved by virtue of the bulky fluorine-containing side group. And when the aqueous solution is used as a coating, the beneficial adhesive force of the aqueous solution on the surface of the substrate and the adhesive force after heat aging test are unexpectedly realized by virtue of the adhesive force of the surface of the metal substrate caused by carboxyl and the high Wen Lianduan movement capability caused by a fluorine-containing structure.
The second embodiment is as follows: the first difference between this embodiment and the specific embodiment is that: the aromatic diamine, the aromatic dianhydride and the end capping agent are used as mixture, and the mass ratio of the total mass of the mixture to the polar solvent is 1 (2-10); the mass ratio of the total mass of the mixture to the water is 1 (1.5-19). The other is the same as in the first embodiment.
And a third specific embodiment: this embodiment differs from one or both of the embodiments in that: the polar solvent is one or a combination of several of N, N '-dimethylacetamide, N' -dimethylformamide and N-methylpyrrolidone. The other is the same as the first or second embodiment.
The specific embodiment IV is as follows: the preparation method of the high-temperature-resistant thermosetting polyimide precursor solution with good stability in the embodiment comprises the following steps:
1. weighing aromatic diamine, aromatic dianhydride, end-capping agent, polar solvent, water and tertiary amine;
the molar ratio of the aromatic diamine to the aromatic dianhydride is (1.1-2) 1; the mol ratio of the aromatic diamine to the end capping agent is (1-5.5): 1; the mass ratio of the tertiary amine to the aromatic diamine is (0.2-2): 1;
the aromatic diamine is 3, 5-diaminobenzoic acid, 4 '-diaminobiphenyl-2, 2' dicarboxylic acid or 6,6 '-diamino-3, 3' -methylene dibenzoic acid;
the aromatic dianhydride is 4,4' - (hexafluoroisopropyl) diphthalic anhydride;
the end-capping agent is 4-phenylethynyl phthalic anhydride;
the tertiary amine is one or the combination of more of 2- (tert-butylamino) ethanol, N-ethylpiperazine and isoquinoline;
2. dividing the weighed aromatic dianhydride into a first part of aromatic dianhydride, a second part of aromatic dianhydride and a third part of aromatic dianhydride according to the mass ratio of 2:1:1, and dividing the weighed end capping agent into a first part of end capping agent and a second part of end capping agent according to the mass ratio of 1:1;
3. mixing polar solvent and aromatic diamine and reacting for 0.5-1 h under the condition of room temperature and stirring to obtain a reaction system, raising the reaction temperature of the reaction system to 50-70 ℃, adding a first part of aromatic dianhydride into the reaction system and reacting for 0.5-1 h under the condition of 50-70 ℃ and stirring, adding a second part of aromatic dianhydride after the reaction, reacting for 0.5-1 h under the condition of 50-70 ℃ and stirring, adding a third part of aromatic dianhydride, reacting for 1-2 h under the condition of 50-70 ℃ and stirring, adding a first part of end-capping agent, reacting for 1-2 h under the condition of 50-70 ℃ and stirring, finally adding a second part of end-capping agent, and reacting for 1-2 h under the condition of 50-70 ℃ and stirring to obtain a reacted solution;
4. drying the reacted solution to obtain polyamic acid powder;
5. and (3) mixing the weighed water, tertiary amine and polyamide acid powder prepared in the step (IV), and stirring and dissolving the powder to obtain the high-temperature-resistant thermosetting polyimide precursor solution with good stability.
Fifth embodiment: the fourth difference between this embodiment and the third embodiment is that: in the first step, aromatic diamine, aromatic dianhydride and end capping agent are used as mixture, and the mass ratio of the total mass of the mixture to the polar solvent is 1 (2-10); the mass ratio of the total mass of the mixture to the water in the first step is 1 (1.5-19). The other is the same as in the fourth embodiment.
Specific embodiment six: this embodiment differs from the fourth or fifth embodiment in that: the polar solvent in the first step is one or a combination of several of N, N '-dimethylacetamide, N' -dimethylformamide and N-methylpyrrolidone. The others are the same as those of the fourth or fifth embodiment.
Seventh embodiment: the present embodiment differs from one of the fourth to sixth embodiments in that: in the third step, the adding speed of the first part of aromatic dianhydride, the second part of aromatic dianhydride and the third part of aromatic dianhydride is 5.0 g/min-7.5 g/min. The others are the same as those of the fourth to sixth embodiments.
Eighth embodiment: the present embodiment differs from one of the fourth to seventh embodiments in that: the stirring in the third step is performed under the condition that the stirring speed is 200 rpm-500 rpm. The others are the same as in the fourth to seventh embodiments.
Detailed description nine: the present embodiment differs from one of the fourth to eighth embodiments in that: and step four, drying for 15-20 hours under the condition that the temperature is 50-80 ℃. The others are the same as in embodiments four to eight.
Detailed description ten: this embodiment differs from one of the fourth to ninth embodiments in that: and step five, stirring and dissolving the powder, namely stirring the powder at a temperature of between 5 and 60 ℃ until the powder is dissolved. The others are the same as in the fourth to ninth embodiments.
The following examples are used to verify the benefits of the present invention:
embodiment one:
the preparation method of the high-temperature-resistant thermosetting polyimide precursor solution with good stability is carried out according to the following steps:
1. weighing aromatic diamine, aromatic dianhydride, end-capping agent, polar solvent, water and tertiary amine; wherein, aromatic diamine, aromatic dianhydride and end capping agent are used as mixture;
the molar ratio of the aromatic diamine to the aromatic dianhydride is 1.1:1; the molar ratio of the aromatic diamine to the end capping agent is 5.5:1; the mass ratio of the total mass of the mixture to the polar solvent is 1:2.3; the mass ratio of the total mass of the mixture to the water is 1:4; the mass ratio of the tertiary amine to the aromatic diamine is 0.3:1;
the aromatic diamine is 6,6 '-diamino-3, 3' -methylene dibenzoic acid (MBAA);
the aromatic dianhydride is 4,4' - (hexafluoroisopropyl) diphthalic anhydride (6 FDA);
the end-capping agent is 4-phenylethynyl phthalic anhydride (4-PEPA);
the tertiary amine is 2- (tertiary butylamino) ethanol;
2. dividing the weighed aromatic dianhydride into a first part of aromatic dianhydride, a second part of aromatic dianhydride and a third part of aromatic dianhydride according to the mass ratio of 2:1:1, and dividing the weighed end capping agent into a first part of end capping agent and a second part of end capping agent according to the mass ratio of 1:1;
3. mixing polar solvent and aromatic diamine under the condition of room temperature and stirring, reacting for 0.5h to obtain a reaction system, increasing the reaction temperature of the reaction system to 50 ℃, adding a first part of aromatic dianhydride into the reaction system under the condition of 50 ℃ and stirring, reacting for 1h, adding a second part of aromatic dianhydride after the reaction, reacting for 1h under the condition of 50 ℃ and stirring, adding a third part of aromatic dianhydride, reacting for 2h under the condition of 50 ℃ and stirring, adding a first part of end-capping agent, reacting for 1h under the condition of 60 ℃ and stirring, finally adding a second part of end-capping agent, and reacting for 1h under the condition of 60 ℃ and stirring to obtain a reacted solution;
4. drying the reacted solution to obtain polyamic acid powder;
5. mixing the weighed water, tertiary amine and polyamide acid powder prepared in the step four, and stirring and dissolving the powder to obtain polyimide precursor solution.
The polar solvent in the first step is N, N' -dimethylacetamide.
In the third step, the first part of aromatic dianhydride, the second part of aromatic dianhydride and the third part of aromatic dianhydride are added at a rate of 7.5g/min.
The stirring in the third step was performed at a stirring speed of 300 rpm.
The drying in the fourth step is specifically drying for 20 hours under the condition that the temperature is 80 ℃.
And fifthly, stirring and dissolving the powder, namely stirring the powder at the temperature of 50 ℃.
The structural formula of the polyamic acid salt repeating unit in the polyimide precursor solution is as follows:
said n=10;
said R is 1 Is that
Said R is 2 Is that
Embodiment two: the first difference between this embodiment and the first embodiment is that: the molar ratio of the aromatic diamine to the end capping agent in the first step is 4.5:1; said n=8. The other is the same as in the first embodiment.
Embodiment III: the first difference between this embodiment and the first embodiment is that: the molar ratio of the aromatic diamine to the end capping agent in the first step is 3.5:1; said n=6. The other is the same as in the first embodiment.
Embodiment four: the first difference between this embodiment and the first embodiment is that: the molar ratio of the aromatic diamine to the end capping agent in the first step is 2.5:1; said n=4. The other is the same as in the first embodiment.
Fifth embodiment: the first difference between this embodiment and the first embodiment is that: the molar ratio of the aromatic diamine to the end capping agent in the first step is 1.5:1; said n=2. The other is the same as in the first embodiment.
Comparative experiment one: the first difference between this comparative experiment and the example is: the aromatic dianhydride in the first step is 3,3', 4' -Benzophenone Tetracarboxylic Dianhydride (BTDA). The other is the same as in the first embodiment.
The structural formula of the polyamic acid salt repeating unit in the polyimide precursor solution is as follows:
n＝10；
said R is 1 Is that
Said R is 2 Is that
Comparison experiment II: the first difference between this comparative experiment and the example is: the aromatic diamine in the first step is 3,3 '-diaminodiphenyl sulfone (3, 3' -DDS). The other is the same as in the first embodiment.
The structural formula of the polyamic acid salt repeating unit in the polyimide precursor solution is as follows:
n＝10；
said R is 1 Is that
Said R is 2 Is that
Comparison experiment three: the first difference between this comparative experiment and the example is: the end capping agent in the first step is 4- (1-propynyl) phthalic anhydride. The other is the same as in the first embodiment.
The structural formula of the polyamic acid salt repeating unit in the polyimide precursor solution is as follows:
n＝10；
said R is 1 Is that
The saidR of (2) 2 Is that
Comparison experiment four: the first difference between this comparative experiment and the example is: the use of blocking agents is eliminated. The other is the same as in the first embodiment.
The structural formula of the polyamic acid salt repeating unit in the polyimide precursor solution is as follows:
n＝10；
said R is 1 Is that
Said R is 2 Is that
Comparison experiment five: the first difference between this comparative experiment and the example is: the use of tertiary amines is eliminated. The other is the same as in the first embodiment.
Examples one to five, comparative experiments one to five, monomers, endcapping agents, tertiary amines, and repeat units are detailed in the following table:
TABLE 1
Solution stability test:
the polyimide precursor solutions prepared in examples one to five and comparative experiments one to five were taken out 10g, and then were placed under 50 ℃ for 15 minutes, and then were moved to 40 ℃ for 15 minutes, and then were moved to 30 ℃ for 15 minutes, and then were moved to 20 ℃ for 15 minutes, and then were moved to 10 ℃ for 15 minutes, and finally were moved to 0 ℃ for 15 minutes, and after the completion, were rapidly sent to a freezer at-50 ℃ for 15 minutes, and then were moved to-40 ℃ for 15 minutes, and then were moved to-30 ℃ for 15 minutes, and then were moved to-20 ℃ for 15 minutes, and were moved to-10 ℃ for 15 minutes, and were circulated, wherein the oscillation frequency was 100 times/minute.
Record whether the aqueous solution is precipitated during the test: if so, recording the time of precipitation; if neither precipitate, the second cycle test was started, and the test procedure was the same as the first, except that the oscillation time at each temperature was changed to 30 minutes, and the oscillation time at each temperature was 60 minutes for the third test, and the results are shown in tables 2-1, 2-2, and 2-3, wherein Δ represents the dissolution state and O represents the precipitation state.
Table 2-1 cycle one (solution at each temperature kept oscillating for 15 minutes):
| system of | -50℃ | -40℃ | -30℃ | -20℃ | -10℃ | 0℃ | 10℃ | 20℃ | 30℃ | 40℃ | 50℃ |
| Example 1 | △ | △ | △ | △ | △ | △ | △ | △ | △ | △ | △ |
| Example two | △ | △ | △ | △ | △ | △ | △ | △ | △ | △ | △ |
| Example III | △ | △ | △ | △ | △ | △ | △ | △ | △ | △ | △ |
| Example IV | △ | △ | △ | △ | △ | △ | △ | △ | △ | △ | △ |
| Example five | △ | △ | △ | △ | △ | △ | △ | △ | △ | △ | △ |
| Comparative experiment one | ○ | ○ | ○ | ○ | ○ | ○ | ○ | △ | △ | △ | △ |
| Comparative experiment two | △ | △ | △ | △ | △ | △ | △ | △ | △ | △ | △ |
| Comparative experiment three | △ | △ | △ | △ | △ | △ | △ | △ | △ | △ | △ |
| Comparative experiment four | ○ | ○ | ○ | ○ | ○ | △ | △ | △ | △ | △ | △ |
| Comparative experiment five | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ |
Table 2-2 cycle two (solution kept oscillating for 30 minutes at each temperature):
table 2-3 cycle three (solution kept oscillating for 60 minutes at each temperature):
| system of | -50℃ | -40℃ | -30℃ | -20℃ | -10℃ | 0℃ | 10℃ | 20℃ | 30℃ | 40℃ | 50℃ |
| Example 1 | △ | △ | △ | △ | △ | △ | △ | △ | △ | △ | △ |
| Example two | △ | △ | △ | △ | △ | △ | △ | △ | △ | △ | △ |
| Example III | ○ | ○ | ○ | ○ | △ | △ | △ | △ | △ | △ | △ |
| Example IV | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ |
| Example five | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ |
| Comparative experiment one | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ |
| Comparative experiment two | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ |
| Comparative experiment three | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ |
| Comparative experiment four | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ |
| Comparative experiment five | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ |
From the results of the first to fifth tests, it can be seen that the short-chain polymers having a small number of repeating units are weak in maintaining the stability of the aqueous solution while ensuring the system is unchanged. This demonstrates that, although the introduction of an aromatic dianhydride having a fluorine atom structure with an aromatic diamine having a carboxylic acid group and capping with a capping agent having a phenylacetylene group can greatly improve the stability of the solution, the examples of longer molecular chains and larger molecular weights are more remarkable in the ability to maintain stability.
From the results of the stability test of examples one to five and comparative experiment one, it can be seen that the aromatic dianhydride having fluorine atom has the greatest ability to maintain the stability of aqueous solution while ensuring that the aromatic diamine and the capping agent are unchanged. This shows that aromatic dianhydrides having a stronger bond energy and a larger volume of fluorine atom structure can bring better stability to the main chain than aromatic dianhydrides having a higher carbonyl structure or nucleophilicity.
From the results of the stability test of examples one to five and the comparative experiment two, it can be seen that the aromatic diamine having a carboxylic acid group has the greatest ability to maintain the stability of the aqueous solution while ensuring that the aromatic dianhydride and the capping agent are unchanged. This illustrates that carboxylic acid groups with hydrophilicity may provide better stability to the backbone than the introduction of flexible structures or bulky side groups may provide less intermolecular forces to the backbone.
From the results of the three stability tests of the first to fifth examples and the comparative experiment, it can be seen that the replacement of the other kinds of end-capping agents does not bring about as good stability as the 4-phenylethynyl phthalic anhydride under the condition of ensuring that the aromatic dianhydride and the aromatic diamine are unchanged. 4-phenylethynyl phthalic anhydride containing more benzene rings has stronger pi-pi conjugated effect and stronger electron withdrawing capability, so that better polarity is brought to the aqueous solution.
From the results of the stability test of examples one to five and the comparative experiment four, it can be seen that the introduction of the blocking agent does not bring about as good stability as the 4-phenylethynyl phthalic anhydride under the condition of ensuring that the aromatic dianhydride and the aromatic diamine are unchanged. This means that thermoplastic polyimide has too large a molecular weight and too close intermolecular packing, and water molecules are hardly inserted therein to be dispersed.
From the results of the five stability tests of examples one to five and the comparative experiments, it can be seen that the solution is not kept stable, even insoluble, without introducing tertiary amine solution into the solution under the condition of ensuring that the aromatic diamine and the aromatic dianhydride end-capping agent are unchanged. This means that the stability of the polyamic acid salt solution is stronger than that of the polyamic acid solution due to the effect of ions.
Related test of thermal properties:
the polyimide precursor solutions prepared in examples one to five and comparative experiments one to five were taken out by 10g and coated on a glass plate to a thickness of 50. Mu.m. The polyimide film is obtained after curing after heat preservation for 1 hour at 100 ℃,1 hour at 200 ℃,1 hour at 300 ℃ and 2 hours at 400 ℃. The resulting films may be subjected to thermogravimetric analyzer Testing (TGA), differential scanning calorimeter testing (DSC). Because the film was brittle, a glass cloth was selected that was impregnated with 60 grams of solution per square meter to prepare a sample, and the resulting sample was tested using a dynamic thermal mechanical analyzer (DMA), as detailed in table 3. The polyamide acid powder prepared in the step four can be directly used for DSC testing of the curing peak top temperature Tp. The test results are shown in Table 3.
5% thermal weight loss temperature: the test uses a thermogravimetric analyzer (TGA). Heating rate: 10 ℃/min; test atmosphere: air.
Glass transition temperature and storage modulus: the test uses a dynamic thermo-mechanical analyzer (DMA). Heating up at a speed of 5 ℃/min; test atmosphere: nitrogen gas.
Degree of cure: differential Scanning Calorimeter (DSC). And (3) heating to 400 ℃ at a speed of 20 ℃/min, and cooling to room temperature at a speed of 30 ℃/min.
TABLE 3 thermal Properties
| System of | Tg(℃) | T5％(℃) | Tp(℃) | E’(MPa)(40℃) | E’(MPa)(400℃) |
| Example 1 | 422 | 558 | 196 | 3089 | 2234 |
| Example two | 418 | 540 | 191 | 2897 | 1998 |
| Example III | 411 | 534 | 188 | 2682 | 1889 |
| Example IV | 409 | 528 | 186 | 2401 | 1568 |
| Example five | 404 | 519 | 181 | 2259 | 1337 |
| Comparative experiment one | 387 | 506 | 184 | 2889 | 1403 |
| Comparative experiment two | 354 | 505 | 178 | 1987 | 1004 |
| Comparative experiment three | 394 | 523 | 181 | 2973 | 1419 |
| Comparative experiment four | 351 | 447 | 178 | 3322 | 1681 |
| Comparative experiment five | 416 | 543 | 182 | 2978 | 2074 |
As can be seen from the results of the thermal performance tests of the first to fifth examples and the first and second comparative experiments, the glass transition temperatures of the first to fifth examples measured by DMA can reach more than 400 ℃ and the glass transition temperature of the first comparative example is below 390 ℃, wherein the glass transition temperature of the second comparative experiment is only 354 ℃. The storage modulus of examples one to five corresponding to comparative experiment one was above 2000MPa at 40℃and comparative experiment two was below 2000 MPa. The loss modulus at 400℃is less than 1000MPa for examples one to five and for comparative example two, while for comparative experiment one is greater than 1000MPa. This means that, while the aromatic diamine having carboxylic acid groups introduced therein and the phenylethynyl group-containing capping agent are ensured to have unchanged conditions, the aromatic dianhydride having carbonyl groups, 3', 4' -benzophenone tetracarboxylic dianhydride, may have a high glass transition temperature as 4,4' - (hexafluoroisopropyl) diphthalic anhydride, but has a high modulus loss and a low hardness at high temperatures. Meanwhile, under the condition of ensuring that the conditions of the aromatic dianhydride into which fluorine atoms are introduced and the phenylethynyl-containing end-capping agent are unchanged, the aromatic diamine with a flexible structure is introduced, and the aromatic diamine with a lower modulus loss can be brought like the aromatic diamine with a carboxylic acid group, but the glass transition temperature and the 5% thermal weight loss temperature are lower due to the excessively obvious weakening effect on the rigidity of a main chain. This demonstrates that monomers that introduce fluorine or carboxylic acid groups into the system alone, while giving good thermal performance, are far less excellent than the two that are added to each other.
From the results of the thermal performance test of examples one to five and the comparative experiment three, it can be seen that the glass transition temperatures of examples one to five and the comparative example three, which were tested by DMA, can reach over 390 ℃. The storage modulus of the third comparative example reaches more than 2900MPa at 40 ℃, and the loss modulus at 400 ℃ is more than 1000MPa. This demonstrates that while capping with 4- (1-propynyl) phthalic anhydride can lead to the same higher glass transition temperature and storage modulus, the loss modulus is greater, the melt viscosity is greater, and processability is inferior to that of 4-phenylethynyl phthalic anhydride.
From the results of the thermal performance tests of examples one through five and comparative experiment four, it can be seen that the 5% thermal weight loss temperature of comparative example four is lower, below 500 ℃. This shows that thermoplastic polyimide has too large a molecular weight and too long a molecular backbone, while providing a strong rigidity to the backbone, lacks more benzene rings containing pi-pi conjugation than systems containing phenylethynyl capping agents, resulting in increased heat loss.
From the results of the five thermal performance tests of examples one to five and the comparative experiments, it can be seen that whether tertiary amine is introduced has little effect on the thermal performance of the solution.
Thermal aging test:
polyimide precursor solutions prepared in examples one to five and comparative experiments one to five were coated on the surfaces of the steel sheet and the aluminum sheet, respectively. The polyimide film is obtained after curing after heat preservation for 1 hour at 100 ℃,1 hour at 200 ℃,1 hour at 300 ℃ and 2 hours at 400 ℃, and the polyimide film is subjected to heat aging test at 300 ℃ and 350 ℃ for 500 hours respectively, the surface state of the polyimide film is recorded, and the cracking morphology and size are recorded if the polyimide film is cracked. The test results are shown in Table 4-1 (delta: showing the integrity of the film surface;. O: showing the presence of small bubbles or microcracks on the film surface;. X: the complete chipping of the film), and 4-2.
TABLE 4-1
| System of | 300 ℃ steel sheet | Aluminum sheet at 300 DEG C | 350 ℃ steel sheet | 350 ℃ aluminum sheet |
| Example 1 | △ | △ | △ | △ |
| Example two | △ | △ | △ | △ |
| Example III | △ | △ | ○ | △ |
| Example IV | ○ | △ | ○ | △ |
| Example five | ○ | △ | × | ○ |
| Comparative experiment one | △ | △ | × | × |
| Comparative experiment two | × | × | × | × |
| Comparative experiment three | ○ | △ | ○ | ○ |
| Comparative experiment four | × | ○ | × | × |
| Comparative experimentsFive kinds of | △ | △ | ○ | ○ |
TABLE 4-2
From the heat aging test results of examples one to five, it can be seen that the degree of aging resistance is directly proportional to the number of repeating units. The greater the number of repeating units, the greater the degree of aging resistance. Meanwhile, the degree of aging resistance of the coating applied to the steel sheet and the aluminum sheet respectively is different. It can be clearly seen that the surface of the aluminum sheet is coated with the least damaged after the high-temperature, long-time heat aging process. It is described that the heat resistance is extremely excellent by acting on the surface of the aluminum sheet, and this result is unexpected.
From the results of the heat aging tests of examples one to five and comparative experiments one and two, it can be seen. When both are introduced into the system alone, the expectation of performance improvement is not realized. Only the simultaneous introduction of the aromatic dianhydride containing fluorine atoms and the aromatic diamine containing carboxylic acid groups into the system is of great significance for improving the thermal aging resistance. Compared with aromatic dianhydride containing carbonyl, dianhydride with fluorine atom can maintain high temperature condition to raise the stability of system. The diamine containing carboxylic acid groups gives more excellent adhesion to the metal substrate than the aromatic diamine containing a flexible structure. Under the action of both fluorine atoms and carboxylic acid groups, the system is not easy to crack when acting on the surface of the metal substrate at high temperature, and a complete state is maintained.
From the results of the thermal aging tests of examples one to five and comparative experiment three, it can be seen that the introduction of 4-phenylethynyl phthalic anhydride into the oligomer was more resistant to aging than the introduction of 4- (1-propynyl) o-phenyltetracarboxylic acid into the oligomer as a capping agent under the conditions of the curing step, keeping the number of aromatic dianhydride, aromatic diamine and repeating unit introduced unchanged, which suggests that the introduction of more capping agent containing benzene rings was more significant for improving the strong heat resistance rating. And the aging resistance of the aluminum sheet coated on the surface of the aluminum sheet is better.
From the results of the thermal aging tests of examples one to five and comparative experiment four, it can be seen that the thermoplastic polyimide produced was less resistant to aging than the thermosetting polyimide produced after being end-capped, under the conditions of the curing step, keeping the number of aromatic dianhydride, aromatic diamine, and repeating unit introduced unchanged. This suggests that thermoplastic polyimides, while possessing a relatively high glass transition temperature, have not undergone endcapping, an irregular backbone structure, resulting in a reduced degree of aging resistance. And the aging resistance of the aluminum sheet coated on the surface of the aluminum sheet is better.
From the results of the heat aging tests of examples one to five and comparative experiment five, it can be seen that the addition of tertiary amine can improve the aging resistance to some extent under the conditions of the curing step, keeping the number of the aromatic dianhydride, aromatic diamine, and repeating unit introduced unchanged. And the aging resistance of the aluminum sheet coated on the surface of the aluminum sheet is better.
In summary, the design of introducing 4-phenylethynyl phthalic anhydride into an oligomer to terminate and form a thermosetting polyimide is truly expected to have a high 5% weight loss temperature, a high glass transition temperature, a high storage modulus, a low loss modulus and a high aging resistance compared with thermoplastic polyimide or other capping agents. The introduced aromatic diamine containing more hydrophilic carboxylic acid groups and aromatic dianhydride containing a large-volume fluorine atom structure not only can improve the stability of the aqueous solution, but also does not influence the thermal performance of the aqueous solution. In the test process, it was found that the effect of amplifying performance can be achieved only when both the aromatic diamine containing carboxylic acid groups and the aromatic dianhydride containing fluorine atoms are introduced to exist in a unified system at the same time. The tertiary amine is introduced into the solution to generate the polyamic acid salt solution, so that the solution is provided with better stability while the thermal performance is not affected. Unexpectedly, the solution exhibited extreme heat resistance when applied as a coating to aluminum sheets during the test-was tested under heat aging conditions of 300℃and 350℃for a long period of 500 hours, respectively.
Fig. 1 is an infrared spectrum of a polyimide precursor solution, 1 is example one, 2 is comparative example one, 3 is comparative example two, 4 is comparative example three, and 5 is comparative example four. Curves 1-4 at 2210cm -1 There was a distinct phenylethynyl absorption peak, indicating successful capping. 1610cm -1 、1371cm -1 、1360cm -1 Corresponding to the C-N absorption vibration peak in the precursor imide. 736cm -1 Corresponds to the absorption peak of the carbonyl c=o stretching vibration in the precursor imide. The synthesis of the corresponding precursors of each case was determined by infrared spectroscopy.
Claims (10)
1. A high-temperature-resistant thermosetting polyimide precursor solution with good stability is characterized in that the solution is prepared from aromatic diamine, aromatic dianhydride, a blocking agent, a polar solvent, water and tertiary amine; the molar ratio of the aromatic diamine to the aromatic dianhydride is (1.1-2) 1; the mol ratio of the aromatic diamine to the end capping agent is (1-5.5): 1; the mass ratio of the tertiary amine to the aromatic diamine is (0.2-2): 1;
the aromatic diamine is 3, 5-diaminobenzoic acid, 4 '-diaminobiphenyl-2, 2' dicarboxylic acid or 6,6 '-diamino-3, 3' -methylene dibenzoic acid;
the aromatic dianhydride is 4,4' - (hexafluoroisopropyl) diphthalic anhydride;
the end-capping agent is 4-phenylethynyl phthalic anhydride;
the tertiary amine is one or the combination of more of 2- (tert-butylamino) ethanol, N-ethylpiperazine and isoquinoline;
the structural formula of the polyamic acid salt repeating unit in the polyimide precursor solution is as follows:
n=1 to 10;
said R is 1 Is that
Said R is 2 Is that
2. The high-stability high-temperature-resistant thermosetting polyimide precursor solution is characterized in that aromatic diamine, aromatic dianhydride and a blocking agent are used as mixture, and the mass ratio of the total mass of the mixture to the polar solvent is 1 (2-10); the mass ratio of the total mass of the mixture to the water is 1 (1.5-19).
3. The high-stability high-temperature-resistant thermosetting polyimide precursor solution according to claim 1, wherein the polar solvent is one or a combination of several of N, N '-dimethylacetamide, N' -dimethylformamide and N-methylpyrrolidone.
4. The method for preparing the high-temperature-resistant thermosetting polyimide precursor solution with good stability as claimed in claim 1, which is characterized by comprising the following steps:
1. weighing aromatic diamine, aromatic dianhydride, end-capping agent, polar solvent, water and tertiary amine;
the molar ratio of the aromatic diamine to the aromatic dianhydride is (1.1-2) 1; the mol ratio of the aromatic diamine to the end capping agent is (1-5.5): 1; the mass ratio of the tertiary amine to the aromatic diamine is (0.2-2): 1;
the aromatic diamine is 3, 5-diaminobenzoic acid, 4 '-diaminobiphenyl-2, 2' dicarboxylic acid or 6,6 '-diamino-3, 3' -methylene dibenzoic acid;
the aromatic dianhydride is 4,4' - (hexafluoroisopropenyl) diphthalic anhydride;
the end-capping agent is 4-phenylethynyl phthalic anhydride;
the tertiary amine is one or the combination of more of 2- (tert-butylamino) ethanol, N-ethylpiperazine and isoquinoline;
2. dividing the weighed aromatic dianhydride into a first part of aromatic dianhydride, a second part of aromatic dianhydride and a third part of aromatic dianhydride according to the mass ratio of 2:1:1, and dividing the weighed end capping agent into a first part of end capping agent and a second part of end capping agent according to the mass ratio of 1:1;
3. mixing polar solvent and aromatic diamine and reacting for 0.5-1 h under the condition of room temperature and stirring to obtain a reaction system, raising the reaction temperature of the reaction system to 50-70 ℃, adding a first part of aromatic dianhydride into the reaction system and reacting for 0.5-1 h under the condition of 50-70 ℃ and stirring, adding a second part of aromatic dianhydride after the reaction, reacting for 0.5-1 h under the condition of 50-70 ℃ and stirring, adding a third part of aromatic dianhydride, reacting for 1-2 h under the condition of 50-70 ℃ and stirring, adding a first part of end-capping agent, reacting for 1-2 h under the condition of 50-70 ℃ and stirring, finally adding a second part of end-capping agent, and reacting for 1-2 h under the condition of 50-70 ℃ and stirring to obtain a reacted solution;
4. drying the reacted solution to obtain polyamic acid powder;
5. and (3) mixing the weighed water, tertiary amine and polyamide acid powder prepared in the step (IV), and stirring and dissolving the powder to obtain the high-temperature-resistant thermosetting polyimide precursor solution with good stability.
5. The preparation method of the high-temperature-resistant thermosetting polyimide precursor solution with good stability according to claim 4, which is characterized in that in the first step, aromatic diamine, aromatic dianhydride and a blocking agent are used as mixture, and the mass ratio of the total mass of the mixture to the polar solvent is 1 (2-10); the mass ratio of the total mass of the mixture to the water in the first step is 1 (1.5-19).
6. The method for preparing a high-temperature-resistant thermosetting polyimide precursor solution with good stability according to claim 4, wherein the polar solvent in the first step is one or a combination of several of N, N '-dimethylacetamide, N' -dimethylformamide and N-methylpyrrolidone.
7. The method for preparing a high temperature resistant thermosetting polyimide precursor solution with good stability according to claim 4, wherein the first part of aromatic dianhydride, the second part of aromatic dianhydride and the third part of aromatic dianhydride in the third step are added at a rate of 5.0g/min to 7.5g/min.
8. The method for preparing a high temperature resistant thermosetting polyimide precursor solution with good stability according to claim 4, wherein the stirring in the third step is performed at a stirring speed of 200rpm to 500 rpm.
9. The method for preparing a high-temperature-resistant thermosetting polyimide precursor solution with good stability according to claim 4, wherein the drying in the fourth step is specifically performed at 50-80 ℃ for 15-20 h.
10. The method for preparing a high-temperature-resistant thermosetting polyimide precursor solution with good stability according to claim 4, wherein the powder is dissolved by stirring in the fifth step, specifically, the powder is dissolved by stirring at a temperature of 5-60 ℃.
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| CN107108887A (en) * | 2014-12-30 | 2017-08-29 | 韩国爱思开希可隆Pi股份有限公司 | Cross-linking type water insoluble thermoplastic polyamic acid and preparation method thereof |
| CN107207747A (en) * | 2014-12-30 | 2017-09-26 | 韩国爱思开希可隆Pi股份有限公司 | Thermal welding multilayer polyimide film using cross-linking type water insoluble thermoplastic polyamic acid and preparation method thereof |
| CN107250215A (en) * | 2015-02-20 | 2017-10-13 | 沙特基础工业全球技术有限公司 | Poly- (amic acid) synthesis and the conversion of paramount molecular weight polyimides |
| CN111386299A (en) * | 2017-09-19 | 2020-07-07 | E.I.内穆尔杜邦公司 | Low color polymers for use in electronic devices |
| CN110818897A (en) * | 2019-11-11 | 2020-02-21 | 同济大学 | Benzoxazine-terminated polyimide precursor and preparation method thereof |
| CN113493566A (en) * | 2021-08-03 | 2021-10-12 | 中化学科学技术研究有限公司 | End-capping reagent for preparing polyimide material, polyimide material and preparation method thereof |
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