CN106866964A - A kind of polyimide foam and preparation method thereof - Google Patents

Abstract

The invention relates to a preparation method of polyimide foam plastics, comprising the following steps: (1) adding aromatic diamine, a mixed solvent of low-molecular alcohol and tetrahydrofuran into a reactor, stirring evenly, adding aromatic dianhydride to react; (2) Add aromatic tetraacid to the reaction solution obtained in step (1), so that the amount of aromatic tetraacid added is (aromatic dianhydride+aromatic tetraacid): the molar ratio of aromatic diamine is 1:1, and continue Reaction to obtain a polyimide precursor solution; (3) drying the precursor solution obtained in step (2), pulverizing it into powder, spreading it into a mold, raising the temperature and foaming to obtain the final polyimide foam plastic. In the preparation method of the present invention, by substituting part of the aromatic dianhydride with an appropriate proportion of aromatic tetraacid, a precursor solution with low bulk viscosity is obtained while maintaining the final performance of the foam. At the same time, it ensures that the foaming temperature of the material matches the traditional process.

Description

A kind of polyimide foam plastics and preparation method thereof

technical field

The invention belongs to the technical field of polymer materials, and in particular relates to a polyimide foam plastic and a preparation method thereof.

Background technique

Due to its excellent comprehensive performance, polyimide foam has become one of the research hotspots in various countries in recent years. Polyimide foam has many characteristics such as good temperature resistance (-250°C ~ 450°C), excellent flame retardant and heat insulation properties, radiation resistance, low toxicity, oxidation resistance, hydrolysis resistance, and excellent sound absorption performance. It can be widely used in military and aerospace industries such as heat insulation of rockets, aircraft, aircraft carriers, submarines, etc., as well as in the field of high temperature resistance, heat insulation and noise reduction for civilian use. However, there are few types of raw materials that can be used to synthesize high-performance polyimide foam, the price is high, and the requirements for the purity of raw materials are high, and the viscosity of the synthesis system is high, which brings resistance to the wide application of this material.

The research on polyimide foam plastics began in the 1960s. At that time, the Dupont Company of the United States applied for the related patent US3249561 of polyimide foam. This patent used an acid that can generate gas and made a wet film or Injected into the mold cavity and cured at high temperature to prepare a foam with a foam density of about 40Kg/m ³ . Subsequent researches on polyimide foam have appeared in a large number, and the preparation process also tends to be diversified. CN103012793 adopts the esterification method to grind the reacted polyester amine salt precursor solution into powder, and then sends it into low-grade polyimide foam by microwave. Density of polyimide foam billets, and then pressed into polyimide foam boards of different densities. US8765830 uses two to three aromatic dianhydrides and aromatic diamines to synthesize a polyimide foam with uniform foam and excellent performance through a specific ratio. CN102850569 After the foaming precursor is obtained by mixing the dianhydride with the diamine after esterification, several additives such as amides, carboxylic acids, and ketones are added to increase the relative mobility of the polymer molecular chain, so that the final molecular weight of the polyimide Can be improved to improve performance.

Most of the above-mentioned patents use the two-step reaction of the esterification method to obtain the polyimide precursor solution, and finely adjust the ratio of raw materials or add additives to improve the performance of the polyimide foam, and the process preparation is relatively complicated. The higher viscosity precursor means that it is difficult to crush into uniform powder, and it is difficult to prepare polyimide foam with uniform pore size. Changing part of the dianhydride to tetraacid is one of the methods used to reduce the viscosity of the precursor solution when preparing polyimide materials, but there are basically no reports in the foam field. The invention prepares a series of polyimide foamed plastics with excellent performance by rationally regulating the types and ratios of tetraacids and dianhydrides, and completing foaming and imidization by one-step temperature rise.

Contents of the invention

The purpose of the present invention is to provide a new synthetic method to prepare polyimide foam plastics in order to overcome the deficiencies in the prior art, by aromatic diamine, aromatic dianhydride, aromatic four acid and mixed solvent to form low Viscosity precursor solution, after drying, can be easily crushed into powder with uniform particle size, and then form polyimide foam, which is a low-cost, easy-to-process polyimide foam preparation method.

In order to achieve the above object, the solution adopted in the present invention is: a polyimide foam preparation method, which comprises the following steps:

(1) Add the mixed solvent of aromatic diamine and low-molecular alcohol and tetrahydrofuran in the reactor, add aromatic dianhydride after stirring evenly and react;

(2) Add aromatic tetraacid to the reaction solution obtained in step (1), so that the amount of aromatic tetraacid added is (aromatic dianhydride+aromatic tetraacid): the molar ratio of aromatic diamine is 1:1, and continue Reaction obtains polyimide precursor solution;

(3) Drying the precursor solution in step (2), pulverizing it into powder, spreading it into a mold, raising the temperature and foaming to obtain the final polyimide foam plastic.

In the above preparation method, step (1) and step (2) are the preparation of precursor solution. In the traditional method, it is necessary to strictly control the equimolar ratio of aromatic dianhydride and aromatic diamine to achieve a sufficiently high bulk viscosity. Otherwise, the viscosity of the system is too low during foaming, which will cause serious foaming, or even the problem of not being able to foam. However, the high viscosity of the precursor solution is difficult for further processing such as the preparation of composite materials, and the price of the raw material of dianhydride is high, which limits the application of polyimide foam in the field of low cost requirements. The addition of the aromatic tetraacid reduces the viscosity of the precursor solution, facilitates production and processing, and maintains the performance of the polyimide foam.

In step (1), the molar ratio of the aromatic diamine to the aromatic dianhydride is 100:90 to 100:50, preferably 100:90, 100:80 or 100:70; the ratio of the low molecular weight alcohol to tetrahydrofuran 1:2 to 1:6, preferably 1:4.

The amount of the mixed solvent is configured according to the reactants accounting for 10%-30% by mass, preferably 20%.

The aromatic diamine may be at least one of diaminodiphenyl ether, diaminodiphenylmethane, p-phenylenediamine, m-phenylenediamine, diaminopyridine and bisphenol A diether diamine.

The low-molecular-weight alcohol can be an aliphatic alcohol with 1-4 carbon atoms, such as methanol, ethanol, propanol or n-butanol.

The aromatic dianhydride can be 3,3',4,4'-diphenyl ether tetraacid dianhydride, 3,3',4,4'-benzophenone tetraacid dianhydride, 3,3',4, 4'-triphenylene ether tetra-acid dianhydride, 4,4'-hexafluoroisopropylidene phthalic anhydride, 3,3',4,4'-biphenyl tetra-acid dianhydride, 3,3' , Any of 4,4'-diphenylsulfonetetracarboxylic dianhydride and 1,2,4,5-pyromellitic anhydride.

In step (2), the aromatic tetracarboxylic acid can be at least A sort of.

In the above-mentioned preparation method step (2), after the reaction, it also includes the step of adding a foam stabilizer in the mixed solution; the foam stabilizer can be polydimethylsiloxane, polyethylene oxide type nonionic surface Active agent or cationic fluorine-containing surfactant; the added amount of the foam stabilizer may be 0.5% to 4% of the mass sum of the aromatic dianhydride, aromatic diamine and aromatic diacid, specifically 2%.

In the above preparation method, the reaction temperature in step (1) may be 20°C to 50°C, preferably 30°C. The reaction time may be 2h-12h, preferably 4h-10h.

In the above-mentioned preparation method, the reaction temperature of step (2) remains the same as that of step (1). The reaction time may be 1h-10h, preferably 1h-4h.

In the above preparation method, the drying temperature in step (3) can be 20°C-60°C to remove most of the solvent. Drying conditions are electric blast box or vacuum oven.

In the above preparation method, in step (3), the dried solid is pulverized, which can be pulverized by a pulverizer or ground.

In the above preparation method, in step (3), the foaming temperature may be 200°C-300°C, preferably 220°C-280°C.

In the above preparation method, in step (3), the foaming time may be 20 minutes to 2 hours, preferably 1 hour.

Optimally, in the step (3) of the method, most of the solvents are volatilized at room temperature before being dried in a vacuum oven at a temperature of 40°C to 60°C, preferably 60°C. The drying time is 4h-24h, preferably 8h-12h.

The present invention further provides a polyimide foam obtained by the above preparation method.

Compared with the prior art, the present invention has the following advantages: in the preparation method of the polyimide foam of the present invention, by substituting part of the aromatic dianhydride with an appropriate proportion of aromatic tetraacids, the precursor solution with low bulk viscosity is obtained and simultaneously Maintain the final performance of the foam, while ensuring that the foaming temperature of the material matches the traditional process. The addition of aromatic tetra-acid also reduces the raw material cost of polyimide foam. At the same time, the preparation process of the invention is simple, and the foaming and polyimidization of the material are completed in one step without further processing. The preparation method of the polyimide foamed plastics of the present invention does not need additional foaming agent, but directly uses low-boiling point solvent for direct foaming. The prepared foam presents an open and closed cell structure, the density can be 20-120Kg/m ³ according to needs, the 5% thermal weight loss can be as high as 580°C (N ₂ ), and the oxygen index is between 38-42. With the increase of , the compressive modulus of the material increases, while the temperature resistance remains the same.

Description of drawings

Figure 1 is a graph showing the effect of different tetraacid additions on foam compressive strength.

Figure 2 is a graph of the effect of tetraacid addition on the glass transition temperature of foams.

detailed description

The present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments.

The experimental methods used in the following examples are conventional methods unless otherwise specified.

The materials and reagents used in the following examples can be obtained from commercial sources unless otherwise specified.

Example 1

(1) Mix 20.02g (0.1mol) of 4'4-diaminodiphenyl ether with 40.38g of methanol and 161.53g of tetrahydrofuran and add 27.92g (0.09mol) of 3,3',4,4' - diphenyl ether tetra-acid dianhydride, react at 50° C. for 4 hours, then add 2.54 g (0.01 mol) of pyromellitic acid and continue the reaction for 4 hours to obtain a polyimide precursor solution.

(2) The solution in step (1) was dried at room temperature, and then placed in a vacuum oven at 60° C. for 10 hours to form a brittle solid. Take it out and crush it into powder with uniform particle size.

(3) Spread the powder in step (2) in a mold with a volume of 1670 cm ³ , put it into a high-temperature furnace at 250° C. for closed mold foaming for 1 hour to obtain the final polyimide foam.

The performance of the polyimide foam in this example is measured. The density of the foam is 33.3Kg/m ³ , the glass transition temperature is 275°C, the 5% thermal weight loss is 570°C, and it is compressed to 10% compression at room temperature. The strength is 0.034MPa, the compressive modulus is 0.31MPa, and the limiting oxygen index is 50%.

Example 2

(1) Mix 20.02g (0.1mol) of 4'4-diaminodiphenyl ether with 40.38g of methanol and 161.53g of tetrahydrofuran, then add 21.71g (0.07mol) of 3,3',4,4' -Diphenyl ether tetraacid dianhydride, react at 30°C for 2 hours, then add 7.62g (0.03mol) of pyromellitic acid to continue the reaction for 1 hour, then add 1.03g of polydimethylsiloxane to obtain polyimide precursor solution.

(2) Pour out the solution in step (1) until it stops flowing, and then put it into a vacuum oven at 60° C. for 20 hours to vacuum dry to form a brittle solid. Take it out and crush it into powder with uniform particle size.

(3) Spread the powder in step (2) in a mold with a volume of 960 cm ³ , put it into a high-temperature furnace at 240° C. for closed mold foaming for 1 hour to obtain the final polyimide foam.

The properties of the polyimide foam in this example were measured. The foam had a density of 47.5Kg/m ³ , a glass transition temperature of 277°C, a 5% thermal weight loss of 564°C, and a compressive strength of 0.056MPa at room temperature. , the compressive modulus is 0.56MPa, and the limiting oxygen index is 49.8%.

Example 3

(1) Mix 19.83g (0.1mol) of 4'4-diaminodiphenylmethane with 40.23g of methanol and 160.93g of tetrahydrofuran and add 27.92g (0.09mol) of 3,3',4,4' -Diphenyl ether tetraacid dianhydride, react at 40°C for 6 hours, then add 2.54g (0.01mol) of pyromellitic acid to continue the reaction for 4 hours, then add 1.03g of polydimethylsiloxane to obtain polyimide precursor solution.

(2) Pour the solution of step (1) into a container, put it into a vacuum oven at 40° C. for 10 hours and vacuum dry it to form a brittle solid after it stops flowing. Take it out and crush it into powder with uniform particle size.

(3) Spread the powder in step (2) in a mold with a volume of 1670 cm ³ , put it into a high-temperature furnace at 250° C. for closed mold foaming for 1 hour to obtain the final polyimide foam.

The performance of the polyimide foam in this example is measured. The density of the foam is 37.8Kg/m ³ , the glass transition temperature is 273°C, the 5% thermal weight loss is 569°C, and it is compressed to 10% compression at room temperature. The strength is 0.044KPa, the compression modulus is 0.38MPa, and the limiting oxygen index is 50%.

Example 4

(1) Mix 20.02g (0.1mol) of 4'4-diaminodiphenyl ether with 40.38g of methanol and 161.53g of tetrahydrofuran and add 215.51g (0.05mol) of 3,3',4,4' -Diphenyl ether tetraacid dianhydride, react at 20°C for 4 hours, then add 12.7g (0.05mol) of pyromellitic acid to continue the reaction for 1 hour, then add 1.03g of polydimethylsiloxane to obtain polyimide precursor solution.

(2) The solution in step (1) was dried at room temperature, and then placed in a vacuum oven at 30° C. for 10 hours to form a brittle solid. Take it out and crush it into powder with uniform particle size.

(3) Spread the powder in step (2) in a mold with a volume of 1670 cm ³ , put it into a high-temperature furnace at 260° C. for closed mold foaming for 1 hour to obtain the final polyimide foam.

The performance of the polyimide foam in this example is measured. The density of the foam is 33.0Kg/m ³ , the glass transition temperature is 261°C, the 5% thermal weight loss is 565°C, and it is compressed to 10% compression at room temperature. The strength is 0.029KPa, the compression modulus is 0.28MPa, and the limiting oxygen index is 48%.

Example 5

(1) Mix 20.02g (0.1mol) of 4'4-diaminodiphenylmethane with 24.06g of methanol and 96.24g of tetrahydrofuran and add 29.00g (0.09mol) of 3,3'4,4'- Benzophenone tetracarboxylic dianhydride was reacted at 30°C for 4 hours, then 2.54g (0.01mol) of pyromellitic acid was added to continue the reaction for 2 hours, and then 1.03g of polydimethylsiloxane was added to obtain polyimellitic acid. Amine precursor solution.

(2) The solution in step (1) was dried at room temperature, and then placed in a vacuum oven at 70° C. for 10 hours to form a brittle solid. Take it out and crush it into powder with uniform particle size.

(3) Spread the powder in step (2) in a mold with a volume of 1670 cm ³ , put it into a high-temperature furnace at 280° C. for closed mold foaming for 1 hour to obtain the final polyimide foam.

The performance of the polyimide foam in this example is measured. The density of the foam is 34.5Kg/m ³ , the glass transition temperature is 263°C, the 5% thermal weight loss is 563°C, and it is compressed to 10% compression at room temperature. The strength is 0.047KPa, the compressive modulus is 0.40MPa, and the limiting oxygen index is 47%.

The above-mentioned embodiments are only to illustrate the technical method and core idea of the present invention, so that those skilled in the art can specifically understand the content of the present invention and implement it, and cannot limit the protection scope of the present invention. In addition, modifications and improvements made without departing from the principles of the present invention should also be covered within the protection scope of the present invention.

Claims (10)

1. a kind of preparation method of polyimide foam, it is characterised in that comprise the following steps：

(1) mixed solvent of aromatic diamines and low mass molecule alcohol and tetrahydrofuran is added in the reactor, is uniformly stirred Aromatic dianhydride is added to be reacted after mixing；

(2) fragrant tetracid is added in the reaction solution that step (1) is obtained, make the addition of fragrant tetracid with (aromatic dianhydride+fragrance tetracid)：The mol ratio of aromatic diamines is 1:1, and proceeding reaction, to obtain polyamides sub- Amine precursor solution；

(3) precursor solution that obtains step (2) dries, be ground into after powder to spread and heat up in mould hair Bubble obtains final polyimide foam.

2. preparation method according to claim 1, it is characterised in that：Low point described in step (1) The ratio of sub- alcohol and tetrahydrofuran is 1:2~1:6；The mixed solvent amount accounts for mass ratio according to reactant 10%~30% configuration；The aromatic diamines be diaminodiphenyl ether, MDA, p-phenylenediamine, At least one in phenylenediamine, diamino-pyridine and the ether diamine of bisphenol-A two；The low mass molecule alcohol is carbon number It is the fatty alcohol of 1-4；The aromatic dianhydride be 3,3 ', 4,4 '-oxydiphthalic, 3,3 ', 4, 4 '-benzophenone tetracarboxylic dianhydride, 3,3 ', 4,4 '-triphen diether tetracarboxylic dianhydride, 4,4 '-hexafluoro Asia isopropyl Base phthalic anhydride, 3,3 ', 4,4 '-BPDA, 3,3 ', 4,4 '-diphenyl sulphone (DPS) tetracid Any one in dianhydride and 1,2,4,5- pyromellitic dianhydrides；The aromatic dianhydride and aromatic diamines mole Than being 100:90 to 100:50；The reaction temperature is 20 DEG C~50 DEG C；The reaction time is 2h~12h.

3. preparation method according to claim 1 and 2, it is characterised in that：Described in step (1) The ratio of low mass molecule alcohol and tetrahydrofuran is specially 1:4；The mixed solvent amount is specially and accounts for matter according to reactant Amount is configured than 20%；The low mass molecule alcohol is methyl alcohol, ethanol, propyl alcohol or n-butanol；The aromatic dianhydride and virtue The mol ratio of fragrant diamines is 100:90,100:80 or 100:70；The reaction temperature is 30 DEG C；The reaction Time is 4h~10h.

4. preparation method according to claim 1 and 2, it is characterised in that：Described in step (2) Fragrant tetracid is Pyromellitic Acid, 3,3 ', 4,4 '-benzophenone tetracarboxylic, 3,3 ', 4,4 '-biphenyl At least one in tetracarboxylic acid；It is additionally included in step (2) in precursor solution and adds foam stabiliser；Institute Foam stabiliser is stated for dimethyl silicone polymer, polyoxyethylene ene-type nonionic surfactant or cationic fluorochemical Surfactant；The addition of the foam stabiliser is the quality sum of the aromatic dianhydride and aromatic diamines 0.5%~4%；Reaction temperature is identical with step (1), and the reaction time is 1h~10h.

5. preparation method according to claim 3, it is characterised in that：Fragrance described in step (2) Tetracid is Pyromellitic Acid, 3,3 ', 4,4 '-benzophenone tetracarboxylic, 3,3 ', 4,4 '-biphenyl tetracarboxylic At least one in acid；It is additionally included in step (2) in precursor solution and adds foam stabiliser；The bubble Foam stabilizers are dimethyl silicone polymer, polyoxyethylene ene-type nonionic surfactant or cationic fluorosurfactants Activating agent；The addition of the foam stabiliser is the quality sum of the aromatic dianhydride and aromatic diamines 0.5%~4%；Reaction temperature is identical with step (1), and the reaction time is 1h~10h.

6. preparation method according to claim 1 and 2, it is characterised in that：Step also includes in (2) Foam stabiliser is added in precursor solution；The foam stabiliser is dimethyl silicone polymer, polyoxyethylene Ene-type nonionic surfactant or cationic fluorosurfactants activating agent；The addition of the foam stabiliser is institute State the 2% of the quality sum of aromatic dianhydride and aromatic diamines；Reaction temperature is identical with step (1), the reaction time It is 1h-4h.

7. preparation method according to claim 4, it is characterised in that：The addition of the foam stabiliser Measure 2% of the quality sum for the aromatic dianhydride and aromatic diamines；Reaction temperature is identical with step (1), instead It is 1h-4h between seasonable.

8. preparation method according to claim 1 and 2, it is characterised in that：Drying in step (3) Temperature is 20 DEG C~60 DEG C, and drying time is 4h~24h；The temperature of foaming be 200 DEG C~300 DEG C, foaming when Between be 20min~2h；.

9. preparation method according to claim 4, it is characterised in that：Drying temperature is in step (3) 40 DEG C~60 DEG C, drying time is 8h~12h；The temperature of foaming is 220 DEG C~280 DEG C, and the time of foaming is 1h；.

10. the polyimide foam that the preparation method any one of claim 1-9 is obtained.