CN108102096A - The method that Kapton is prepared using pyromellitic acid dianhydride - Google Patents

Abstract

The invention discloses a method for preparing polyimide film by using pyromellitic dianhydride. Using 3,4‑difluorobenzaldehyde, p-nitroacetophenone, ammonium acetate and acetic acid to prepare dinitro monomer 4‑(3,4‑difluorophenyl)‑2,6 bis(4‑nitro Phenyl)pyridine, then add hydrazine hydrate to react to obtain diamine monomer 4-(3,4-difluorophenyl)-2,6 bis(4-aminophenyl)pyridine, then react with pyromellitic dianhydride The precursor polyamic acid (PAA) solution was prepared by reaction, and the film was cast on the mold, and then the mold was placed in an oven at 80°C overnight, and then placed in a muffle furnace for thermal imidization reaction, and finally the polyamide was obtained. imide film. The method of the invention is simple to operate, easy to be popularized and applied on a large scale, and the prepared polyimide polyimide film has excellent heat resistance, solvent resistance, hydrophobicity, good tensile performance and certain shape memory performance , has a certain application prospect in military industry and aerospace.

Description

Method for preparing polyimide film by using pyromellitic dianhydride

technical field

The invention belongs to the technical field of intelligent composite materials, in particular to a method for preparing a polyimide film by using pyromellitic dianhydride.

Background technique

With the development of social science, human beings put forward higher requirements for large-scale construction in the exploration of space. Some large-scale structural components of spacecraft, due to size constraints, need to be folded before launch. Recovering its original shape under certain conditions, shape memory polymers have become one of the most promising materials due to their unique shape memory mechanism and properties. At present, the main applications of SMP in aerospace vehicles include complex structural components such as solar cell arrays, antennas, and brackets. However, most spacecraft operate in low earth orbit, and its ambient temperature is between -160~+120 ℃, but the T _g of commonly used SMPs are mainly concentrated at low and medium temperatures (-10~+120 ℃). Studies have shown that in order to enable a polymer to be used for a long time, its T _g usually needs to be higher than the ambient temperature by more than 50 ℃. Therefore, there is a need to develop novel SMPs with high _Tg .

Polyimide refers to an aromatic heterocyclic polymer containing imide characteristic groups in its main chain structural unit. Because of its rigid structure of imide ring and benzene ring plane conjugation in its molecular main chain, polyimide Imine has some excellent properties superior to most polymers, such as super high temperature resistance, low thermal expansion coefficient, low dielectric constant and good mechanical properties, and has been widely used in aerospace, electrical, automotive, microelectronics, etc. field. The thermosetting polyimide obtained by chemical crosslinking also has the characteristics of strong structural stability, not easy to creep, etc., and can be used for a long time in harsh environments. Due to its outstanding thermal stability and good mechanical properties, shape memory polyimide makes up for the shortcomings of traditional shape memory polymers, and is expected to be used as a matrix material for large structural components in aerospace and other fields.

Although polyimide is a representative polymer with excellent comprehensive properties, the molecular chains of most aromatic polyimides are very rigid, which makes it difficult to process them, which limits their use in some special field applications. Conventional polyimide can no longer meet people's requirements, and the development of new high-performance polyimide has become the goal of today's researchers. In order to solve the above shortcomings, researchers have done a lot of research. Structural modification is an effective method to improve the performance of polyimide. Special groups are introduced into the molecular backbone of polyimide, such as flexible groups, large substituents, non-coplanar structures, asymmetric structures, Such as: -O-, -S-, -CH ₂ -, -SO ₂ -, fluorine-containing groups, aliphatic groups, etc.

In this application, we introduced fluorine-containing groups and pyridine rings into the main chain of polyimide through molecular design to improve the dissolution resistance of the polymer and maintain its mechanical properties and thermal stability. A new type of thermosetting fluorine-containing In addition to the good performance of ordinary resins, polyimide polymers also have a certain shape memory effect. This idea has not been reported in the literature.

Contents of the invention

The purpose of the present invention is to provide a kind of method utilizing pyromellitic dianhydride to prepare polyimide film.

The specific steps are:

(1) In a 500 mL three-necked flask equipped with magnetic stirring, reflux condenser and nitrogen inlet, add 3,4-difluorobenzaldehyde (15.00 g, n=0.11 mol), p-nitroacetophenone ( 34.86 g, n=0.21 mol), ammonium acetate (97.63 g, n=1.27 mol) and acetic acid (200 mL), start magnetic stirring, and after passing N ₂ for half an hour, heat to 125 °C for 12 h until the reaction is complete Finally, the obtained mixture was suction-filtered to obtain a light yellow solid, which was dried in a vacuum oven at 120 °C for 12 h, and the obtained product was recrystallized with DMF to obtain needle-like crystals, which were dinitromonomer 4-(3 ,4-difluorophenyl)-2,6 bis(4-nitrophenyl)pyridine, referred to as FPNP.

(2) In a 500 mL three-necked flask equipped with magnetic stirring, reflux condenser, constant pressure dropping funnel and nitrogen inlet and outlet, add the dinitromonomer 4-(3,4 -Difluorophenyl)-2,6bis(4-nitrophenyl)pyridine (8.00 g, n=18.46 mmol), Pd/C (2.00 g) and ethanol (152 mL), turn on the magnetic stirring, pass into After half an hour of nitrogen gas, heat to 85 °C and reflux. When the temperature stabilizes at 85 °C, start to add 45 mL of hydrazine hydrate dropwise. After 1 h of hydrazine hydrate, stop the reaction after continuing to stir and reflux for 8 h. Filtrate to remove Pd/C to obtain a clear and light yellow solution, use a rotary evaporator to distill under reduced pressure to remove ethanol and unreacted hydrazine hydrate, obtain a light yellow solid and dry it overnight at 120 °C in a vacuum oven. The crude product was recrystallized from ethanol to obtain a light yellow solid which is the diamine monomer 4-(3,4-difluorophenyl)-2,6-bis(4-aminophenyl)pyridine, FPAP for short.

(3) Add the diamine monomer 4-(3,4-difluorophenyl)-2,6 bis(4 -Aminophenyl)pyridine (0.6500 g, 1.741 mmol) and NMP (4.68 g), stirred for 1 h under nitrogen protection, then added pyromellitic dianhydride (0.3797 g, 1.741 mmol) in ice bath for 4 h, in Stir at room temperature for 24 h to obtain a viscous precursor polyamic acid (PAA) solution. Prepare a PAA solution with a solid content of 5 wt.% in NMP solvent, cast a film on the mold, and then place the mold in an oven at 80 °C Overnight, then placed in a muffle furnace for thermal imidization, the temperature was programmed to rise at 120°C, 150°C, 180°C, 200°C, 250°C and 300°C for 1 hour each, and after cooling down to room temperature, put the mold into distilled water Demoulding and drying to obtain a polyimide film at last.

The method of the present invention is simple to operate, easy to popularize and apply on a large scale, and the prepared polyimide polyimide film has excellent heat resistance, solvent resistance, hydrophobicity, good tensile performance and certain shape memory performance , has a certain application prospect in military industry and aerospace.

Description of drawings

Figure 1 is the FT-IR spectrum of the dinitromonomer 4-(3,4-difluorophenyl)-2,6bis(4-nitrophenyl)pyridine prepared in the example of the present invention.

Fig. 2 is the FT-IR spectrum of the diamine monomer 4-(3,4-difluorophenyl)-2,6 bis(4-aminophenyl)pyridine prepared in the example of the present invention.

Fig. 3 is ^{the 1} H-NMR (a) and ¹³ C-NMR (b) spectrum (DMSO-d ₆ ).

Fig. 4 is a contrast photo of the outline of the droplets on the polyimide film prepared in the embodiment of the present invention.

Detailed ways

Example:

(1) In a 500 mL three-necked flask equipped with magnetic stirring, reflux condenser and nitrogen inlet, add 3,4-difluorobenzaldehyde (15.00 g, n=0.11 mol), p-nitroacetophenone ( 34.86 g, n=0.21 mol), ammonium acetate (97.63 g, n=1.27 mol) and acetic acid (200 mL), start magnetic stirring, and after passing N ₂ for half an hour, heat to 125 °C for 12 h until the reaction is complete Finally, the obtained mixture was suction-filtered to obtain a light yellow solid, which was dried in a vacuum oven at 120 °C for 12 h, and the obtained product was recrystallized with DMF to obtain needle-like crystals, which were dinitromonomer 4-(3 ,4-difluorophenyl)-2,6 bis(4-nitrophenyl)pyridine, referred to as FPNP.

(2) In a 500 mL three-necked flask equipped with magnetic stirring, reflux condenser, constant pressure dropping funnel and nitrogen inlet and outlet, add the dinitromonomer 4-(3,4 -Difluorophenyl)-2,6bis(4-nitrophenyl)pyridine (8.00 g, n=18.46 mmol), Pd/C (2.00 g) and ethanol (152 mL), turn on the magnetic stirring, pass into After half an hour of nitrogen gas, heat to 85 °C and reflux. When the temperature stabilizes at 85 °C, start to add 45 mL of hydrazine hydrate dropwise. After 1 h of hydrazine hydrate, stop the reaction after continuing to stir and reflux for 8 h. Filtrate to remove Pd/C to obtain a clear and light yellow solution, use a rotary evaporator to distill under reduced pressure to remove ethanol and unreacted hydrazine hydrate, obtain a light yellow solid and dry it overnight at 120 °C in a vacuum oven. The crude product was recrystallized from ethanol to obtain a light yellow solid which is the diamine monomer 4-(3,4-difluorophenyl)-2,6-bis(4-aminophenyl)pyridine, FPAP for short.

(3) Add the diamine monomer 4-(3,4-difluorophenyl)-2,6 bis(4 -Aminophenyl)pyridine (0.6500 g, 1.741 mmol) and NMP (4.68 g), stirred for 1 h under nitrogen protection, then added pyromellitic dianhydride (0.3797 g, 1.741 mmol) in ice bath for 4 h, in Stir at room temperature for 24 h to obtain a viscous precursor polyamic acid (PAA) solution. Prepare a PAA solution with a solid content of 5 wt.% in NMP solvent, cast a film on the mold, and then place the mold in an oven at 80 °C Overnight, then placed in a muffle furnace for thermal imidization, the temperature was programmed to rise at 120°C, 150°C, 180°C, 200°C, 250°C and 300°C for 1 hour each, and after cooling down to room temperature, put the mold into distilled water Demoulding and drying to obtain a polyimide film at last.

The properties of the polyimide film prepared in this example were characterized, and it was found that its glass transition temperature was 372°C, its T _5% thermogravimetric loss temperature was 600°C, its T _10% thermogravimetric loss temperature was 622°C, and its T _d was 580°C. ℃, the carbon residue rate at 800 ℃ is 73%, showing excellent heat resistance; at the same time, it is insoluble in conventional organic solvents and has good solvent resistance; in addition, the contact angle is 94.3°, showing excellent Finally, it has good tensile properties and certain shape memory properties. Its tensile strength and elongation at break are 75 MPa and 7.8%, respectively, and its shape fixation rate and shape recovery rate reach 68.33% and 69.11%.

Claims (1)

1. a method utilizing pyromellitic dianhydride to prepare polyimide film is characterized in that concrete steps are: (1) In a 500 mL three-neck flask equipped with magnetic stirring, reflux condenser and nitrogen inlet, add 0.11 mol 3,4-difluorobenzaldehyde, 0.21 mol p-nitroacetophenone, 1.27 mol ammonium acetate and 200 mL of acetic acid, started magnetic stirring, and after passing _N2 for half an hour, heated to 125 °C for 12 h. After the reaction was completed, the obtained mixture was suction-filtered to obtain a light yellow solid, which was dried in a vacuum oven at 120 °C for 12 h. h, recrystallizing the obtained product with DMF to obtain needle crystals, which is the dinitro monomer 4-(3,4-difluorophenyl)-2,6 bis(4-nitrophenyl)pyridine; (2) In a 500 mL three-necked flask equipped with magnetic stirring, reflux condenser, constant pressure dropping funnel and nitrogen inlet and outlet, add 18.46 mmol of the dinitromonomer 4-(3 ,4-difluorophenyl)-2,6bis(4-nitrophenyl)pyridine, 2.00 g Pd/C and 152 mL ethanol, turn on the magnetic stirring, pass nitrogen gas for half an hour, heat to 85 °C, reflux, When the temperature was stabilized at 85 °C, 45 mL of hydrazine hydrate was added dropwise, and the hydrazine hydrate was dropped for 1 h. After continuing to stir and reflux for 8 h, the reaction was stopped. Then, excess tetrahydrofuran was added and filtered while hot to remove Pd/C, and a clear and light The yellow solution was distilled under reduced pressure using a rotary evaporator to remove ethanol and unreacted hydrazine hydrate to obtain a light yellow solid and dry it in a vacuum oven at 120 °C overnight, then recrystallize the obtained crude product with ethanol to obtain a light yellow solid That is, the diamine monomer 4-(3,4-difluorophenyl)-2,6 bis(4-aminophenyl)pyridine; (3) Add 1.741 mmol of the diamine monomer 4-(3,4-difluorophenyl)-2,6bis (4-Aminophenyl)pyridine and 4.68 g NMP were stirred for 1 h under the protection of nitrogen, then 1.741 mmol of pyromellitic dianhydride was added in ice bath for 4 h, and stirred at room temperature for 24 h to obtain a viscous precursor polymer. The amic acid solution was prepared with NMP solvent as a precursor polyamic acid solution with a solid content of 5 wt.%. The film was cast on the mold, and then the mold was placed in an oven at 80 °C overnight, and then placed in a muffle furnace for heating. For imidization, the temperature was programmed to rise at 120°C, 150°C, 180°C, 200°C, 250°C and 300°C for 1 hour each. amine film.