CN105694091A - Low-density polyimide aerogel and preparation method thereof - Google Patents

Abstract

The invention provides low-density polyimide aerogel and a preparation method thereof. The preparation method includes preparing midbody, polyimide acid salt, dissolving the salt in the water to sufficiently expand according to a certain proportion, generating transparent and stable aerogel. The aerogel can be stored for a long time without significant degradation and is high in molecular weight, and product performance is excellent and stable. The aerogel is high in contraction performance through the vacuum drying process after freezing, and is low in density. In addition, the process of the method is low in device cost, safer and easy to control as compared with a super-critical drying method. The polyimide aerogel produced has low density and excellent comprehensive performance.

Description

A kind of low-density polyimide aeroge and preparation method thereof

Technical field

The present invention relates to a kind of low-density polyimide aeroge and preparation method thereof, belong to high-performance porous material preparing technical field。

Background technology

Aeroge is a class disperse medium is the dry state gel rubber material of air, can be divided into several classes such as inorganic and organic polymer aeroge by its chemical composition。Inorganic aerogels material has the heat insulation and resistance to environmental stability of excellence, but matter is crisp, frangible, mechanical property is relatively poor。Organic polymer aeroge then has more excellent combination property, and including light weight, flexibility, synthetic route is various, be prone to the characteristics such as processing and use。And polyimides is as a kind of high-performance polymer, it is the good basis material preparing aeroge, there is thermal stability and the mechanical flexibility of excellence。

At present, the preparation of polyimide aerogels mainly through preparing polyamic acid presoma in high boiling solvent such as DMF, DMAc, NMP etc., polyimides wet gel is obtained through high temperature or chemical imidization, then low boiling point solvent displacement high boiling solvent is adopted, then through supercritical drying to remove solvent, it is thus achieved that polyimide aerogels。

There is following defect in above-mentioned preparation method: adopts high boiling solvent, be difficult to eliminate in replacement process, and performance and processing to material all create adverse influence, and environment also can be had a negative impact by the removal process of the low boiling point solvent of displacement；The polyamic acid prepared can be degraded rapidly in depositing process, causes its molecular weight reduction, finally affects the performance of polyimide aerogels；And the complex process of supercritical drying is loaded down with trivial details, production efficiency is low, and product cost is higher, it is difficult to realize the scale of aeroge, preparation rapidly and efficiently。Additionally, the density of cross-linking type PI aeroge prepared by prior art is general higher, this improves the aeroge cost as heat-barrier material undoubtedly, causes the defect that heat-proof quality is not enough, it is difficult to reach the requirement of aerogel heat-proof basic material simultaneously。

At present, AspenAerogels company of the U.S. adopt PMDA and ODA be monomer, through supercritical carbon dioxide dry technology prepare line style PI aeroge density up to 30Kg/m³。But, shrinkage factor during this material supercritical drying is very big, is not suitable for commercial production。US National Aeronautics and Space Administration (NASA) Glenn research center adopts eight (aminophenyl) silsesquioxane (OAPS) and 1,3, the heat-proof quality of the polyimide aerogels that 5-tri-(4-amino-benzene oxygen) benzene (TAB) is prepared for cross-linking agent is better, but its density is up to 100Kg/m³Above。Meanwhile, the preparation of this kind of cross-linking type and line style PI aeroge all needs to use Supercritical Drying Technology, this preparation method of PI aeroge is still had shortcoming such as above-mentioned such as complex process, production efficiency be low and product cost is high。

And Wu Wei of BJ University of Aeronautics & Astronautics's Materials Academy et al., in " preparation of polyimides enhancing montmorillonite Aerogel Nanocomposites material and performance study " literary composition, have employed cryodesiccated method and prepare aerogel composite。This makes the preparation of aeroge not only without replacing high boiling solvent, and without adopting supercritical drying mode, is greatly optimized the preparation technology of aeroge, and equipment cost is relatively low。But, the polyamic acid molecular weight prepared in the method is low, and the homogeneous polyamic acid gel brine with suitable concn cannot be prepared, the concentration of PAA is down to 0.5wt% by the present inventor also cannot obtain homogeneous polyamic acid gel brine, and the concentration of the polyamic acid gel brine that can prepare is extremely low。Therefore, have impact on the combination property of product, make the mechanical property of gained PI aeroge, density and heat-proof quality all not ideal enough。Additionally, the aeroge prepared in the method is mainly with montmorillonite for matrix, polyimides is only used as reinforcing agent and uses, and this is difficult to fundamentally to solve, and its density is higher, matter is crisp easily falls slag, the dissatisfactory defect of heat-proof quality。

Therefore, need that a kind of heat-proof quality of research and development is excellent, density is low at present badly, and the easy manageable polyimide aerogels of preparation technology。

Summary of the invention

For solving above-mentioned problems of the prior art, the present invention provide a kind of prepare intermediate can long-term storage, preparation process is easily controllable, equipment requirements is low, the preparation method of polyimide aerogels with low cost and eco-friendly, and density is low, heat-proof quality is excellent to provide one, and the polyimide aerogels that combination property is good。

The low-density polyimide aeroge of the present invention is by preparing the hydrogel of polyimide precursor and this hydrogel lyophilization being prepared, and specifically includes following steps:

1) diamine monomer is dissolved in organic solvent, after diamidogen is completely dissolved, adds dianhydride monomer, after stirring 1-5 hour, stand, obtain wet gel；

2) to step 1) gained wet gel adds tertiary amine, stand 0.5-2 hour after stirring, obtain wet gel；

3) by step 2) gained wet gel is poured slowly in acetone, has solid to precipitate out in acetone gradually, and will precipitate out product filtration drying etc., obtain polyamic acid salt powder；

4) step 3 is taken) gained polyamic acid salt is soluble in water, and stand aging (i.e. ageing) after a period of time, obtain polyamic acid gel brine；After chilled for the polyamic acid gel brine of gained, lyophilization in freezer dryer, obtain polyamic acid salt aeroge；

5) by step 4) gained polyamic acid salt aeroge high temperature imidization, obtain polyimide aerogels；

Wherein, diamine monomer is 4,4 '-diaminodiphenyl ether, and dianhydride monomer is bibenzene tetracarboxylic dianhydride。

Preferably, step 1) in the mol ratio of dianhydride monomer and diamine monomer be (1-1.05): 1。

Preferably, step 2) in tertiary amine be triethanolamine or triethylamine。

Preferably, step 2) middle tertiary amine consumption is dianhydride monomer molal quantity 2 times added。

Preferably, step 4) polyamic acid salt is soluble in water, and making concentration is 0.5wt%-1.5wt%。

Preferably, step 4) in standing aging (i.e. ageing) time be 2-4 days。

Preferably, step 1) in organic solvent be DMF, N,N-dimethylacetamide or N-Methyl pyrrolidone。

Preferably, step 4) in freezing temperature be-25 DEG C to-5 DEG C, cooling time is 8-12 hour, and cryodesiccated temperature is-40 DEG C to-5 DEG C, and sublimation drying is 36-48 hour。

Preferably, step 5) in the heating process of polyamic acid salt aeroge high temperature imidization be: 80 DEG C 0.5 hour, 100 DEG C 0.5 hour, 120 DEG C 0.5 hour, 150 DEG C 0.5 hour, 250 DEG C 1 hour, 300 DEG C 2 hours。

Additionally, the present invention also provides for the low-density polyimide aeroge that a kind of said method prepares。

Adopting freeze-drying to substitute supercritical drying in the PI aeroge preparation method of the present invention, equipment cost is low, technical process handy and safe and easily controllable。Described method prepares intermediate polyamic acid salt, can long-term storage will not obvious degradation；Gained polyamic acid molecular weight is high, described polyamic acid salt is soluble in water by a certain percentage can be fully swelling, generates transparent hydrogel homogeneous, constitutionally stable, at concentrations up to 1.5wt%, resisted shrinkage ability in chilled final vacuum dry run is strong, PI excellent product performance and stable；Additionally, the solvent that prepolymerization reaction adopts can reclaim in fractional distillation, decrease discharging of waste liquid pressure and cost of manufacture。And adopt the PI aeroge that preparation method of the present invention prepares to have less density, and more excellent heat stability and heat-proof quality。

Detailed description of the invention

In order to make those skilled in the art be more fully understood that the present invention program, the technical scheme in the embodiment of the present invention will be clearly and completely described below, it is clear that described embodiment is only the embodiment of a present invention part, rather than whole embodiments。Based on the embodiment in the present invention, the every other embodiment that those of ordinary skill in the art obtain under not making creative work premise, all should belong to the scope of protection of the invention。

Wherein, the data test condition of polyimide aerogels is as follows:

Density: being obtained divided by volume by the quality of airsetting blob of viscose, aeroge is processed into regular shape, measures its quality with analytical balance, measures its size with slide gauge and ruler, calculates the density obtaining aeroge。

Shrinkage factor: measure after aerogel block body freezing respectively with slide gauge and ruler and the size of length after lyophilization, width and thickness direction, using the meansigma methods of length, width and thickness direction shrinkage factor as shrinkage factor。

Room temperature thermal conductivity: adopt the test of HotDiskTPS2500 type thermal constant analyser。Method of testing: transition plane heat source method；Sample size: 50mm × 40mm × 10mm。Test philosophy and process: use thermal resistive materials nickel, make continuous double-stranded slice-shaped temperature-independent probe after etched process。Probe had both been used as thermal source, popped one's head in used also as dynamic temperature。When carrying out thermal conductance test, the HotDisk probe placement of plane is between two panels sample, and contact probe head is the plane of sample。Make the probe temperature rise several years by applying pulse voltage, simultaneously and record resistance (temperature) increase the relation with the time。Test condition is: ambient temperature 25 DEG C, instrument power 0.01W, 80 seconds testing times。By recording the change of voltage within a period of time, mathematical model can directly obtain the thermal conductivity of sample。

Heat decomposition temperature: adopt U.S.'s TA company Q50 type thermogravimetric analyzer to carry out thermogravimetic analysis (TGA), N₂Atmosphere, 10 DEG C/min of heating rate, temperature elevating range is from 25 DEG C～900 DEG C。Taking weight-loss ratio 5% place is heat decomposition temperature。

Intrinsic viscosity: taking a certain amount of PAA resin to be tested, the solution being configured to the DMAc that mass fraction is 0.5% is about 25ml。Adopt Ubbelohde viscometer, under 30 DEG C and normal pressure, in same viscometer, record the solvent of same volume and time t that solution flows through₀And t₁(all test is averaged for three times), adopts one point method, calculates through equation below and obtains intrinsic viscosity:

$\[\mathrm{\η}\]=\underset{\mathrm{\ρ}\→0}{\lim }\frac{ln\left(\frac{\mathrm{\η}1}{\mathrm{\η}0}\right)}{\mathrm{\ρ}}=\underset{\mathrm{\ρ}\→0}{\lim }\frac{ln\left(\frac{t1}{t0}\right)}{\mathrm{\ρ}}$

Embodiment 1:

Equipped with in the 250mL three-necked bottle of mechanical stirring device, weigh 6.07g (30.35mmol) 4,4 '-diaminodiphenyl ether (4,4 '-ODA) it is dissolved in 91gN, in N-dimethyl acetylamide (DMAc), being dividedly in some parts 9.10g (30.96mmol) bibenzene tetracarboxylic dianhydride (BPDA) after diamidogen is completely dissolved, now the solid content of solution is about 15%, stands to obtain polyamic acid (PAA) after stirring four hours。It is added dropwise over 6.14g (60.68mmol) triethylamine (TEA) more wherein, after continuing to stir, stands 30min and obtain wet gel。The wet gel of gained is poured slowly in acetone, through filtering, wash, dry, pulverizing, obtains polyamic acid salt (PAS) powder。Wherein, the intrinsic viscosity η testing gained polyamic acid is 2.36。

The PAS powder taking 0.3g is dissolved in 29.7g water, obtains the gel that homogeneous solid content is 1% after aging 72 hours, is poured in mould in the environment of-25 DEG C to-5 DEG C freezing, carries out lyophilization 36h subsequently in the freeze drying equipment of-40 DEG C to-5 DEG C。The demoulding temperature programming, heating process is: 80 DEG C 0.5 hour, 100 DEG C 0.5 hour, 120 DEG C 0.5 hour, 150 DEG C 0.5 hour, 250 DEG C 1 hour, 300 DEG C 2 hours, obtain polyimide aerogels。Gained polyimide aerogels shrinkage factor is 12%, and density is 12.5kg/m³, room temperature thermal conductivity 0.018W/m K, heat decomposition temperature is 554 DEG C。

Embodiment 2:

In Example 1, the polyamic acid salt powder 0.225g of gained is dissolved in 29.775g water, aging 72 hours, obtain 0.75% polyamic acid gel brine, be poured in mould in the environment of-25 DEG C to-5 DEG C freezing, in the freeze drying equipment of-40 DEG C to-5 DEG C, carry out lyophilization 36h subsequently。The demoulding temperature programming, heating process is: 80 DEG C 0.5 hour, 100 DEG C 0.5 hour, 120 DEG C 0.5 hour, 150 DEG C 0.5 hour, 250 DEG C 1 hour, 300 DEG C 2 hours, obtain polyimide aerogels。Gained polyimide aerogels shrinkage factor is 16%, density 8.8kg/m³, room temperature thermal conductivity 0.016W/m K, heat decomposition temperature is 551 DEG C。

Embodiment 3:

In Example 1, the polyamic acid salt powder 0.15g of gained is dissolved in 29.85g water, the polyamic acid gel brine that homogeneous solid content is 0.5% is obtained after aging 72 hours, it is freezing to be poured in mould in the environment of-25 DEG C to-5 DEG C, carries out lyophilization 36h subsequently in the freeze drying equipment of-40 DEG C to-5 DEG C。The demoulding temperature programming, heating process is: 80 DEG C 0.5 hour, 100 DEG C 0.5 hour, 120 DEG C 0.5 hour, 150 DEG C 0.5 hour, 250 DEG C 1 hour, 300 DEG C 2 hours, obtain polyimide aerogels。Gained polyimide aerogels shrinkage factor is 18%, density 6.6kg/m³, room temperature thermal conductivity 0.014W/m K, heat decomposition temperature is 550 DEG C。

Embodiment 4:

Equipped with in the 500mL three-necked bottle of mechanical stirring device, weigh 12.14g (60.7mmol) 4,4 '-diaminodiphenyl ether (4,4 '-ODA) it is dissolved in 182.8gN, in N-dimethyl acetylamide (DMAc), being dividedly in some parts 18.2g (61.91mmol) bibenzene tetracarboxylic dianhydride (BPDA) after diamidogen is completely dissolved, now the solid content of solution is about 15%, stand after stirring four hours, obtain polyamic acid (PAA)。It is added dropwise over 12.26g (121.4mmol) triethylamine (TEA) more wherein, after continuing to stir, stands 30min and obtain wet gel。The wet gel of gained is poured slowly in acetone, through filtering, wash, dry, pulverizing, obtains polyamic acid salt (PAS) powder。Wherein, the intrinsic viscosity η testing gained polyamic acid is 2.68。

The PAS powder taking 3g is dissolved in 297g water, the polyamic acid gel brine that homogeneous solid content is 1% is obtained after aging 72 hours, it is freezing to be poured in mould in the environment of-25 DEG C to-5 DEG C, carries out lyophilization 48h subsequently in the freeze drying equipment of-40 DEG C to-5 DEG C。The demoulding temperature programming, heating process is: 80 DEG C 0.5 hour, 100 DEG C 0.5 hour, 120 DEG C 0.5 hour, 150 DEG C 0.5 hour, 250 DEG C 1 hour, 300 DEG C 2 hours, obtain polyimide aerogels。Gained polyimide aerogels shrinkage factor is 12%, and density is 14kg/m³, room temperature thermal conductivity 0.019W/m K, heat decomposition temperature is 554 DEG C。

Embodiment 5:

In Example 4, the polyamic acid salt powder 2.25g of gained is dissolved in 297.75g water, the polyamic acid gel brine that homogeneous solid content is 0.75% is obtained after aging 72 hours, it is freezing to be poured in mould in the environment of-25 DEG C to-5 DEG C, carries out lyophilization 48h subsequently in the freeze drying equipment of-40 DEG C to-5 DEG C。The demoulding temperature programming, heating process is: 80 DEG C 0.5 hour, 100 DEG C 0.5 hour, 120 DEG C 0.5 hour, 150 DEG C 0.5 hour, 250 DEG C 1 hour, 300 DEG C 2 hours, obtain polyimide aerogels。Gained polyimide aerogels shrinkage factor is 16%, density 10kg/m³, room temperature thermal conductivity 0.017W/m K, heat decomposition temperature is 552 DEG C。

Embodiment 6:

In Example 4, the polyamic acid salt powder 1.5g of gained is dissolved in 298.5g water, the polyamic acid gel brine that homogeneous solid content is 0.5% is obtained after aging 72 hours, it is freezing to be poured in mould in the environment of-25 DEG C to-5 DEG C, carries out lyophilization 48h subsequently in the freeze drying equipment of-40 DEG C to-5 DEG C。The demoulding temperature programming, heating process is: 80 DEG C 0.5 hour, 100 DEG C 0.5 hour, 120 DEG C 0.5 hour, 150 DEG C 0.5 hour, 250 DEG C 1 hour, 300 DEG C 2 hours, obtain polyimide aerogels。Gained polyimide aerogels shrinkage factor is 18%, density 7.0kg/m³, room temperature thermal conductivity 0.014W/m K, heat decomposition temperature is 550 DEG C。

Embodiment 7

In Example 4, the polyamic acid salt powder 4.5g of gained is dissolved in 295.5g water, the polyamic acid gel brine that homogeneous solid content is 1.5% is obtained after aging 72 hours, it is freezing to be poured in mould in the environment of-25 DEG C to-5 DEG C, carries out lyophilization 48h subsequently in the freeze drying equipment of-40 DEG C to-5 DEG C。The demoulding temperature programming, heating process is: 80 DEG C 0.5 hour, 100 DEG C 0.5 hour, 120 DEG C 0.5 hour, 150 DEG C 0.5 hour, 250 DEG C 1 hour, 300 DEG C 2 hours, obtain polyimide aerogels。Gained polyimide aerogels shrinkage factor is 12%, density 22.0kg/m³, room temperature thermal conductivity 0.027W/m K, heat decomposition temperature is 551 DEG C。

Embodiment 8:

In Example 4, polyamic acid salt (PAS) the powder 0.6g of gained is dissolved in 29.4g water, and namely concentration is 2%, finds to still have part pas resin complete swelling can not generate gel in water under this concentration after aging 96 hours。Therefore, exceeding this concentration can not adopt the method for the present invention to prepare polyimide aerogels。

Embodiment 9:

In Example 4, the polyamic acid salt powder 1.5g of gained is dissolved in 298.5g water, the polyamic acid gel brine that homogeneous solid content is 0.5% is obtained after aging 72 hours, it is freezing to be poured in mould in the environment of-25 DEG C to-5 DEG C, carries out lyophilization 48h subsequently in the freeze drying equipment of-40 DEG C to-5 DEG C。The demoulding temperature programming, to 300 DEG C, obtain polyimide aerogels。Gained polyimide aerogels shrinkage factor is 52%, density 21.0kg/m³, room temperature thermal conductivity 0.036W/m K, heat decomposition temperature is 550 DEG C。

The above, above example only in order to technical scheme to be described, is not intended to limit；Although the present invention being described in detail with reference to previous embodiment, it will be understood by those within the art that: the technical scheme described in foregoing embodiments still can be modified by it, or wherein portion of techniques feature is carried out equivalent replacement；And these amendments or replacement, do not make the essence of appropriate technical solution depart from the scope of various embodiments of the present invention technical scheme。

Claims (10)

1. the preparation method of a low-density polyimide aeroge, it is characterised in that this preparation method, by preparing the hydrogel of polyimide precursor and by this hydrogel lyophilization, prepares polyimide aerogels, specifically includes following steps:

1) diamine monomer is dissolved in organic solvent, after diamidogen is completely dissolved, adds dianhydride monomer, after stirring 1-5 hour, stand, obtain wet gel；

2) to step 1) gained wet gel adds tertiary amine, stand 0.5-2 hour after stirring, obtain wet gel；

3) by step 2) gained wet gel is poured slowly in acetone, has solid to precipitate out in acetone gradually, will precipitate out product filter, dry, obtain polyamic acid salt；

4) step 3 is taken) gained polyamic acid salt is soluble in water, and stand aging, obtain polyamic acid gel brine；After chilled for the polyamic acid gel brine of gained, lyophilization in freezer dryer, obtain polyamic acid salt aeroge；

5) by step 4) gained polyamic acid salt aeroge high temperature imidization, obtain polyimide aerogels；

Wherein, diamine monomer is 4,4 '-diaminodiphenyl ether, and dianhydride monomer is bibenzene tetracarboxylic dianhydride。

2. preparation method as claimed in claim 1, it is characterised in that step 1) in the mol ratio of dianhydride monomer and diamine monomer be (1-1.05): 1。

3. preparation method as claimed in claim 1, it is characterised in that step 1) in organic solvent be DMF, N,N-dimethylacetamide or N-Methyl pyrrolidone。

4. preparation method as claimed in claim 1, it is characterised in that step 2) in tertiary amine be triethanolamine or triethylamine。

5. preparation method as claimed in claim 1, it is characterised in that step 2) middle tertiary amine consumption is dianhydride monomer molal quantity 2 times added。

6. preparation method as claimed in claim 1, it is characterised in that step 4) polyamic acid salt is soluble in water, and making concentration is 0.5wt%-1.5wt%。

7. preparation method as claimed in claim 1, it is characterised in that step 4) in the aging time be 2-4 days。

8. preparation method as claimed in claim 1, it is characterised in that step 4) in freezing temperature be-25 DEG C to-5 DEG C, cooling time is 8-12 hour, and cryodesiccated temperature is-40 DEG C to-5 DEG C, and sublimation drying is 36-48 hour。

9. preparation method as claimed in claim 1, it is characterised in that step 5) in the heating process of polyamic acid salt aeroge high temperature imidization be: 80 DEG C 0.5 hour, 100 DEG C 0.5 hour, 120 DEG C 0.5 hour, 150 DEG C 0.5 hour, 250 DEG C 1 hour, 300 DEG C 2 hours。

10. a low-density polyimide aeroge, it is characterised in that described low-density polyimide aeroge adopts the preparation method as described in claim 1-9 any claim to prepare。