CN113337923B - Core-shell type low-dielectric-resistance flame-retardant polyimide-based fiber material and preparation method thereof - Google Patents

Core-shell type low-dielectric-resistance flame-retardant polyimide-based fiber material and preparation method thereof Download PDF

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CN113337923B
CN113337923B CN202110591606.7A CN202110591606A CN113337923B CN 113337923 B CN113337923 B CN 113337923B CN 202110591606 A CN202110591606 A CN 202110591606A CN 113337923 B CN113337923 B CN 113337923B
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polyamic acid
polysilsesquioxane
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周钰明
徐健行
鲍杰华
卜小海
张一卫
孙伯旺
王明亮
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Southeast University
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Abstract

The invention discloses a core-shell type low-dielectric flame-retardant polyimide-based fiber material and a preparation method thereof, wherein a phosphate-based compound, a symmetrical aromatic aldehyde compound and amino polysilsesquioxane are subjected to Kabachnik-Fields reaction to prepare phosphate-based amino polysilsesquioxane, aromatic diamine and aromatic dianhydride amide are subjected to reaction to prepare polyamic acid, the phosphate-based amino polysilsesquioxane and the polyamic acid amide are subjected to reaction to prepare modified polyamic acid, modified polyamic acid solutions and polyamic acid solutions in different paths in a micro injection pump are spun by a coaxial electrostatic spinning method to prepare the core-shell type modified polyamide acid fiber material, and finally the core-shell type low-dielectric flame-retardant polyimide-based fiber material is prepared by heat treatment, wherein the core of the material is polyimide fiber, the shell is modified polyimide, the dielectric constant is lower than 2.2, and the oxygen index LOI is higher than 35%, the flame-retardant epoxy resin composition has excellent dielectric and flame-retardant properties, and has good application prospects in the preparation fields of related materials such as 5G, printed circuit boards, photoelectricity, aerospace and the like.

Description

Core-shell type low-dielectric-resistance flame-retardant polyimide-based fiber material and preparation method thereof
Technical Field
The invention relates to the field of fiber materials and preparation thereof, in particular to a core-shell type low-dielectric flame-retardant polyimide-based fiber material and a preparation method thereof.
Background
Aromatic polyimide fibers are widely used as a high-performance polymer fiber as a matrix material for electronic products and a structural material for aerospace vehicles because of their excellent dielectric properties, thermal stability, mechanical properties, and optical properties. With the coming of the internet era, the research and development and the use of 5G or even higher frequency communication technology have greatly increased the demand of society on electronic products, and the high frequency communication technology has put forward higher requirements on various performances of packaging materials of electronic products.
Due to high frequency electromagnetic waves, the dielectric constant of the dielectric material of the interconnect layer of the microelectronic device is required to be less than 2.3 to reduce interconnect delay and dielectric loss. The material generates a certain dielectric loss in the signal transmission process due to the dielectric constant, thereby causing the temperature of the electronic device to rise and influencing the transmission of electromagnetic signals. Meanwhile, conventionally used polyimides undergo severe thermal degradation due to the generation of internal heat when exposed to ultraviolet rays. Prolonged use and continued exposure to high energy radiation can even lead to ignition of the host material. Most commercially available PIs have dielectric constants between 3.0 and 3.5 depending on their chemical structure, which is not sufficient to meet the requirements in the near future.
Based on the Clausius-Mosotti equation, extensive and intensive research is carried out on the preparation of low dielectric constant PI at home and abroad, and the preparation is mainly divided into two directions of low-polarity PI and porous PI. The cavity structure and the siloxane bond of the cage type oligomeric silsesquioxane molecule have the functions of reducing the dielectric constant and improving the flame retardant property. The introduction of cage-type oligomeric silsesquioxanes into polymers has proven to be an effective method for reducing the dielectric constant of polymers. The formation of the polymer/polysilsesquioxane composite may simultaneously reduce the dielectric constant and enhance the flame retardant properties of the polymer. It is also noteworthy that flame retardant materials such as phosphorus, halogen incorporation can provide sustainable heat resistance and protection of host matrix materials. However, there are limited reports available on polymer matrix precursors based on phosphorus and halogen derivatives. Patent CN 111286076A relates to an aminopropyl-polysilsesquioxane modified polyimide aerogel, a preparation method and application thereof, and specifically relates to a polyimide aerogel prepared by taking aminopropyl-polysilsesquioxane as a cross-linking agent and carrying out ternary polymerization on aromatic diamine and aromatic dianhydride to prepare a polyamic acid solution, swelling and curing in a high-pressure reaction kettle, and finally carrying out normal-pressure fractional drying. The invention requires high pressure, is not easy to obtain the aminopropyl-polysilsesquioxane raw material as the cross-linking node, cannot ensure the mechanical property, does not consider to improve the flame retardant property of the material, and is difficult to develop and apply on a large scale.
Disclosure of Invention
The invention aims to solve the problems in the prior art, and the first aim of the invention is to provide a core-shell type low-dielectric flame-retardant polyimide-based fiber material.
The second purpose of the invention is to provide a preparation method of the core-shell type low-dielectric flame-retardant polyimide-based fiber material.
The technical scheme is that in order to achieve the purpose, the invention can adopt the following technical scheme: a core-shell low-dielectric-resistance flame-retardant polyimide-based fiber material comprises a core and a shell, wherein the core is made of polyimide fibers, and the diameter of the core is 10-100 nm; the shell is made of modified polyimide fibers, and the thickness of the shell layer is 10-100 nm.
The invention also discloses a preparation method of the core-shell type low-dielectric flame-retardant polyimide-based fiber material, which is specifically prepared by carrying out segmented temperature zone heat treatment on core-shell type modified polyimide fibers, wherein the core is polyimide fibers, and the shell is modified polyimide fibers;
the core-shell type modified polyamic acid fiber is prepared by spinning modified polyamic acid solution and polyamic acid solution in different paths in a micro-injection pump by adopting a coaxial electrostatic spinning method;
the modified polyimide fiber is generated by performing heat treatment on a modified polyamic acid solution at a segmented temperature zone on the surface of the polyimide fiber core;
the modified polyamic acid solution is prepared by carrying out amidation reaction on phosphate-based amino polysilsesquioxane and polyamic acid, and the polyamic acid solution is prepared by carrying out amidation reaction on aromatic diamine and aromatic dianhydride.
Further, the preparation method comprises the following steps:
step a) preparation of phosphate-based amino polysilsesquioxane, N at room temperature2In the atmosphere, amino polysilsesquioxane, symmetrical aromatic aldehyde compound andadding a low-boiling-point solvent into a reaction kettle, reacting for 2-10 hours at 55-120 ℃, then reducing the temperature to 10-25 ℃, adding a phosphate compound and absolute ethyl alcohol, uniformly mixing, dropwise adding 10-40 wt.% of inorganic auxiliary agent aqueous solution within 0.5-4 hours, increasing the temperature to 55-85 ℃, continuing to react for 4-12 hours, carrying out reduced pressure distillation at 50-60 ℃ for 0.5-1 hour, extracting with absolute methyl alcohol, washing with petroleum ether, carrying out suction filtration for 3-5 times, finally standing at 50-60 ℃ for 12-24 hours, and cooling to room temperature to obtain the phosphate-based amino polysilsesquioxane;
step b) preparation of the polyamic acid solution N at room temperature2In the atmosphere, adding aromatic diamine, aromatic dianhydride and a high-boiling-point solvent into a reaction kettle, stirring for 8-20 h at 0-10 ℃, then heating to 25 ℃, and standing for 8-15 h to obtain a polyamic acid solution;
step c) preparation of modified polyamic acid solution N at room temperature2In the atmosphere, adding aromatic diamine, aromatic dianhydride and a high-boiling-point solvent into a reaction kettle, stirring for 8-20 h at 0-10 ℃, adding the phosphate-based amino polysilsesquioxane synthesized in the step a), performing ultrasonic treatment for 0.5-1 h, continuing stirring for 8-20 h, heating to 25 ℃, and standing for 8-15 h to obtain a modified polyamic acid solution;
step d) preparing core-shell type modified polyamide acid based fiber, namely adding the polyamide acid solution prepared in the step b) and the modified polyamide acid solution prepared in the step c) into an external path and/or an internal path of a micro-injection pump respectively by adopting a coaxial electrostatic spinning method, and spinning to obtain the core-shell type modified polyamide acid based fiber;
and e) preparing the core-shell type low-dielectric flame-retardant polyimide-based fiber material, namely performing segmented temperature zone heat treatment on the core-shell type modified polyamide-based fiber at the temperature of 60-310 ℃, and cooling to room temperature to obtain the core-shell type low-dielectric flame-retardant polyimide-based fiber material.
Further, the structural formula of the modified polyamic acid prepared in step c) is as follows:
Figure BDA0003089482040000031
wherein the polymerization degree m is 10-80; the number of repeating units n is 1, 2, 4.
Furthermore, in the step a), the mass ratio of the amino polysilsesquioxane, the symmetric aromatic aldehyde compound, the low boiling point solvent, the phosphate compound, the absolute ethyl alcohol, the absolute methyl alcohol, the petroleum ether and the inorganic auxiliary agent aqueous solution is (1-5): 0.05-2): 10-50: (1-5): 10-40): 20-80): 20-100): 5-20;
in the step b), the mass ratio of the aromatic diamine to the aromatic dianhydride to the high-boiling-point solvent is (1-2) to (1-3) to (10-20);
in the step c), the mass ratio of the phosphate-based amino polysilsesquioxane to the aromatic diamine to the aromatic dianhydride to the high boiling point solvent is (0.5-0.8) to (1-2) to (1-3) to (10-20).
Further, the low-boiling point solvent in the step a) is one of pentane, trichloromethane and acetone; the symmetrical aromatic aldehyde compound is 2, 4, 6-trimethyl benzaldehyde or 3, 4, 5-trihydroxy benzaldehyde; the phosphate compound is 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide or 3-fluoro-9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide; the inorganic auxiliary agent aqueous solution is a sodium carbonate aqueous solution or a potassium carbonate aqueous solution.
Still further, the amino polysilsesquioxane of step a) is one of aminoethylheptyl-polysilsesquioxane, aminopropylheptyl-polysilsesquioxane, aminopentylgeptyl-polysilsesquioxane, aminoethylfluoromethyl-polysilsesquioxane, aminopropylfluoromethyl-polysilsesquioxane, aminopentylfluoromethyl-polysilsesquioxane.
Further, the aromatic diamine in step b) and step c) is 4, 4' -diaminodiphenyl ether; the aromatic dianhydride is 1, 2, 4, 5-benzenetetracarboxylic anhydride; the high boiling point solvent is one of N, N-dimethylformamide, N-methylpyrrolidone and N, N-dimethylacetamide;
the solid content of the modified polyamic acid solution in the step b) is 15-30 wt.%;
the solid content of the polyamic acid solution in step c) is 10-35 wt.%; the ultrasonic power of ultrasonic treatment is 600-900W.
Furthermore, the injection speed of the path inside the micro-injection pump used in the coaxial electrostatic spinning method in the step d) is 0.5-1.0 mL/h, the injection speed of the path outside the micro-injection pump is 0.5-1.5 mL/h, the aperture of the coaxial capillary tube of the micro-injection pump is 0.04-0.1 mm, and the output voltage is 15-30 kV.
Further, the heat treatment procedure of the segmented temperature zone in the step e) is 60-120 ℃ for 6-10 h; 120-200 ℃ for 4-8 h; 200 to 300 ℃ for 4 to 8 hours.
Has the advantages that: the invention has the following advantages:
1) the prepared fiber material has a nano-scale cavity structure and also has a functional compound of phosphorus-silicon flame retardant factors, and can reduce the dielectric constant of polyimide and improve the flame retardant property of the polyimide at the same time.
2) The used amino polysilsesquioxane molecules have rich silicon-oxygen bonds, so that the fiber material has higher mechanical property, hydrophobic property and thermal stability, and the cage-shaped three-dimensional structure of the amino polysilsesquioxane molecules is introduced, thereby being beneficial to further improving the dielectric property of the polyimide fiber material while keeping good mechanical property.
3) Synthesizing phosphate-based amino polysilsesquioxane through Kabachnik-Fields reaction, wherein the phosphate modified polysilsesquioxane is an organic compound with nano pores, and the dielectric constant of the polyimide fiber is reduced by introducing air with the dielectric constant of 1 according to a Debye formula; the aromatic aldehyde compound used in the synthesis of the phosphate-based polysilsesquioxane has a symmetrical molecular structure, and phosphate-based polysilsesquioxane molecules have larger steric hindrance and are beneficial to reducing the dielectric constant of the polyimide fiber. The amino polysilsesquioxane molecule is introduced into the polyimide continuous phase as a dispersed phase, so that the comprehensive performance of the polyimide fiber is improved.
4) The phosphate compound is used as a phosphorus source, the amino polysilsesquioxane is used as a silicon source, and the flame retardant property of the polyimide fiber material is obviously improved by utilizing the synergistic flame retardant effect of carbon, nitrogen and phosphorus atoms. The phosphate amino polysilsesquioxane burns in the presence of oxygen to release phosphorus-containing free radicals and carbon dioxide, and the phosphorus-containing free radicals have a quenching effect and accelerate the formation of coke residues; the siloxane compound is heated to form stable silicon dioxide in the combustion process, and the silicon dioxide improves the stability of the coke residual carbon; the polysilsesquioxane modified by the phosphate group has good structural compatibility with a polyimide continuous phase, the modified polysilsesquioxane effectively improves the compactness of carbon residue, and the dense coke residue containing phosphorus and silicon serves as a physical barrier for preventing organic gas from being released, so that the flow and the transfer of heat between polyimide fibers and the outside are reduced, and the flame retardance of the fiber material is further improved.
5) The method utilizes the difference of the concentration of polyamic acid solution in the external path and/or the internal path of a micro injection pump to prepare the core-shell type modified polyimide fiber, and in the process of removing the solvent by the heat treatment of the modified polyamic acid, the volatilization rates of the solvent in the core and the shell of the polyamic acid fiber are different, and air is introduced by separating the core and the shell, so that the dielectric constant of the fiber can be effectively reduced, meanwhile, the core-shell structure also improves the flame retardant efficiency of the synergistic flame retardant of various flame retardant elements such as nitrogen, phosphorus, silicon and the like, and simultaneously improves the mechanical processing performance of the polyimide fiber material.
Drawings
FIG. 1 is a schematic infrared spectrum of a core-shell type low-dielectric flame-retardant polyimide-based fiber material prepared in example 1.
Detailed Description
The dielectric constant and oxygen index measurement methods in examples 1 to 5 were as follows:
(1) the dielectric constant and the loss angle are measured by a Hioki3532-50 impedance analyzer by adopting a parallel plate capacitor method. And plating conductive silver layers on two sides of the polyimide material to prepare a circular sample with the diameter of 6mm and a certain thickness. And (3) measuring the parallel equivalent capacitance of the round sample within 1 kHz-1 MHz at 25 ℃, measuring three different positions of each sample to obtain a group of parallel data, and taking the average value of the group of data.
The specific dielectric constant calculation formula is as follows:
Figure BDA0003089482040000061
wherein d is the thickness of the film; a is the effective electrode face; epsilon0Representative is a vacuum dielectric constant of 8.854 × 10-12F/m。
(2) The flame retardant performance test was performed on an oxygen index meter using the limiting oxygen index method. The clamped sample is vertically placed in a transparent combustion cylinder, the proportion of oxygen and nitrogen is adjusted, the upper end of the sample is ignited, then the combustion phenomenon is observed, and the continuous combustion time or the combustion distance is compared with the specified limit, so that the lowest oxygen concentration can be measured. The test standard adopts 'oxygen index method for textile combustion performance test' GB/T5454-1997.
Example 1:
a preparation method of a core-shell low-dielectric flame-retardant polyimide-based fiber material comprises the following steps:
a) at room temperature, N2In the atmosphere, 1.7g of aminoethylheptyl-polysilsesquioxane, 0.4g of 2, 4, 6-trimethylbenzaldehyde and 20g of acetone are added into a reaction kettle to react for 10 hours at 55 ℃, then the temperature is reduced to 10 ℃, 1.1g of 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 10g of absolute ethyl alcohol are added, after uniform mixing, 15g of sodium carbonate solution (dissolved in 10mL of water) is dripped, after 0.5 hour of dripping is finished, the temperature is adjusted to 55 ℃, the reaction is carried out for 4 hours, the reduced pressure distillation at 50 ℃ is carried out for 0.5 hour, 30mL of absolute methyl alcohol is used for extraction, 60mL of petroleum ether is used for washing and suction filtration for 3 times, finally, the mixture is placed at 50 ℃ for 20 hours and cooled to room temperature, and the phosphate-based amino polysilsesquioxane is prepared;
b) at room temperature, N2In the atmosphere, adding 1.0g of 4, 4' -diaminodiphenyl ether, 8g N, N-dimethylacetamide aromatic dianhydride and 1.5g of 1, 2, 4, 5-benzenetetracarboxylic anhydride into a reaction kettle, adjusting the temperature to 0 ℃, reacting for 20 hours, then heating to 25 ℃, and standing for 15 hours to obtain a polyamic acid solution;
c) at room temperature, N2Under an atmosphere, 1.0g of 4, 4' -diaminodiphenyl ether, 1.5g of 1, 2, 4, 5-benzenetetracarboxylic anhydride and 10g of benzene were addedg N, adding N-dimethylacetamide into a reaction kettle, adjusting the temperature to 0 ℃, stirring for 20h, adding 0.5g of phosphate amino polysilsesquioxane, carrying out ultrasonic treatment for 0.5h under 600W, continuing stirring for 8h, heating to 25 ℃, and standing for 8h to obtain a modified polyamide acid solution;
d) respectively adding a polyamic acid solution and a modified polyamic acid solution into an external path and/or an internal path of a micro-injection pump by adopting a coaxial electrostatic spinning method, wherein the injection speed of the external path of the micro-injection pump is 0.6mL/h, the injection speed of the internal path of the micro-injection pump is 0.5mL/h, the aperture of a coaxial capillary tube of the micro-injection pump is 0.04mm, and the output voltage is 20 kV;
e) carrying out heat treatment on the core-shell structure modified polyamide fiber in a segmented temperature zone to obtain a core-shell low-dielectric flame-retardant polyimide-based fiber material; the heat treatment program of the segmented temperature zone is 80 ℃ and 10 hours; 150 ℃ for 8 h; 300 ℃ for 4 h.
Tests show that the dielectric constant of the core-shell type low-dielectric-resistance flame-retardant polyimide-based fiber material is 1.9, and the oxygen index LOI is 39%; fig. 1 shows an infrared spectrum of a finished core-shell low-dielectric flame-retardant polyimide-based fiber material.
Example 2:
a preparation method of a core-shell low-dielectric flame-retardant polyimide-based fiber material comprises the following steps:
a) at room temperature, N2Adding 2.8g of aminoethyl fluoromethyl-polysilsesquioxane, 0.8g of 3, 4, 5-trihydroxybenzaldehyde and 40g of pentane into a reaction kettle, reacting for 4 hours at 110 ℃, adjusting the temperature to 25 ℃, adding 1.7g of 3-fluoro-9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 18g of absolute ethyl alcohol, uniformly mixing, dropwise adding 16g of potassium carbonate solution (dissolved in 11mL of water), adjusting the temperature to 55 ℃ after 0.6 hour of dropwise addition, reacting for 10 hours, distilling at 55 ℃ under reduced pressure for 0.5 hour, extracting with 45mL of absolute methyl alcohol, washing with 65mL of petroleum ether, carrying out suction filtration for 3 times, standing for 14 hours at 50 ℃, and cooling to room temperature to obtain phosphate-based amino polysilsesquioxane;
b) at room temperature, N2Under an atmosphere, 1.2g of 4, 4' -diaminodiphenyl ether, 9.6g N, N-dimethylacetamide aromatic dianhydride and 1.8g of 1, 2, 4, 5-benzene were addedAdding tetracarboxylic anhydride into a reaction kettle, adjusting the temperature to 2 ℃, reacting for 18h, heating to 25 ℃, and standing for 12h to obtain a polyamic acid solution;
c) at room temperature, N2In the atmosphere, adding 1.2g of 4, 4' -diaminodiphenyl ether, 1.8g of 1, 2, 4, 5-benzenetetracarboxylic anhydride and 12g N, N-dimethylacetamide into a reaction kettle, adjusting the temperature to 2 ℃, stirring for 18h, adding 1g of phosphate-based amino polysilsesquioxane, carrying out ultrasonic treatment for 0.5h at 800W, continuing stirring for 8h, heating to 25 ℃, and standing for 9h to obtain a modified polyamic acid solution;
d) by adopting a coaxial electrostatic spinning method, adding a polyamic acid solution and a modified polyamic acid solution into an external path and/or an internal path of a micro-injection pump respectively, wherein the injection speed of the external path of the micro-injection pump is 0.7mL/h, the injection speed of the internal path of the micro-injection pump is 0.5mL/h, the aperture of a coaxial capillary of the micro-injection pump is 0.06mm, and the output voltage is 15 kV.
e) And performing heat treatment on the core-shell structure modified polyamide fiber in a segmented temperature zone to obtain the core-shell low-dielectric flame-retardant polyimide-based fiber material. The heat treatment program of the segmented temperature zone is 80 ℃ and 8 hours; 150 ℃ for 10 h; 290 ℃ and 4 h.
Tests show that the dielectric constant of the core-shell type low-dielectric-resistance flame-retardant polyimide-based fiber material is 1.8, and the oxygen index LOI is 43%.
Example 3:
a preparation method of a core-shell low-dielectric flame-retardant polyimide-based fiber material comprises the following steps:
a) at room temperature, N2In the atmosphere, 3.4g of aminopentylgeptyl-polysilsesquioxane, 1g of 2, 4, 6-trimethylbenzaldehyde and 44g of trichloromethane are added into a reaction kettle to react for 8 hours at 75 ℃, then the temperature is adjusted to 15 ℃, 2.3g of 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 20g of absolute ethyl alcohol are added, 14g of sodium carbonate (dissolved in 11mL of water) is dropwise added after uniform mixing, the temperature is adjusted to 60 ℃ after 1h of dropwise addition, the reaction is carried out for 6 hours, reduced pressure distillation is carried out at 55 ℃ for 0.8 hour, 70mL of absolute methyl alcohol is used for extraction, 90mL of petroleum ether is used for washing and suction filtration for 3 times, finally, the mixture is placed at 55 ℃ for 18 hours and cooled to room temperature, and the phosphate-based amino polysilsesquioxane is prepared;
b) at room temperature, N2In the atmosphere, adding 1.2g of 4, 4' -diaminodiphenyl ether, 10g N, N-dimethylacetamide aromatic dianhydride and 2.0g of 1, 2, 4, 5-benzenetetracarboxylic anhydride into a reaction kettle, adjusting the temperature to 0 ℃, reacting for 16h, then heating to 25 ℃, and standing for 10h to obtain a polyamic acid solution;
c) at room temperature, N2In the atmosphere, adding 1.2g of 4, 4' -diaminodiphenyl ether, 2.0g of 1, 2, 4, 5-benzenetetracarboxylic anhydride and 12g N, N-dimethylacetamide into a reaction kettle, adjusting the temperature to 0 ℃, stirring for 16h, adding 1.3g of phosphate-based amino polysilsesquioxane, carrying out ultrasonic treatment for 0.5h by 700W, continuing stirring for 8h, heating to 25 ℃, and standing for 11h to obtain a modified polyamic acid solution;
d) by adopting a coaxial electrostatic spinning method, adding a polyamic acid solution and a modified polyamic acid solution into an external path and/or an internal path of a micro-injection pump respectively, wherein the injection speed of the external path of the micro-injection pump is 0.7mL/h, the injection speed of the internal path of the micro-injection pump is 0.6mL/h, the aperture of a coaxial capillary of the micro-injection pump is 0.07mm, and the output voltage is 30 kV.
e) And performing heat treatment on the core-shell structure modified polyamide fiber in a segmented temperature zone to obtain the core-shell low-dielectric flame-retardant polyimide-based fiber material. The heat treatment program of the segmented temperature zone is 70 ℃ and 6 hours; 160 ℃ for 8 h; 300 ℃ for 3 h.
Tests show that the dielectric constant of the core-shell type low-dielectric-resistance flame-retardant polyimide-based fiber material is 2.1, and the oxygen index LOI is 38%.
Example 4:
a preparation method of a core-shell low-dielectric flame-retardant polyimide-based fiber material comprises the following steps:
a) at room temperature, N2Adding 3.9g of aminoethyl fluoromethyl polysilsesquioxane, 0.9g of 3, 4, 5-trihydroxybenzaldehyde and 45g of trichloromethane into a reaction kettle, reacting for 2 hours at 120 ℃, then adjusting the temperature to 25 ℃, adding 2.5g of 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 33g of absolute ethyl alcohol, uniformly mixing, dropwise adding 15g of potassium carbonate solution (dissolved in 11mL of water), after 0.5 hour of dropwise addition, adjusting the temperature to 55 ℃, reacting for 10 hours, distilling for 0.5 hour at 55 ℃, and using 75mL of absolute methylExtracting with alcohol, washing with 110mL petroleum ether, vacuum filtering for 4 times, standing at 55 deg.C for 12 hr, and cooling to room temperature to obtain phosphate-based amino polysilsesquioxane;
b) at room temperature, N2In the atmosphere, adding 1.6g of 4, 4' -diaminodiphenyl ether, 13g N, N-dimethylacetamide aromatic dianhydride and 2.4g of 1, 2, 4, 5-benzenetetracarboxylic anhydride into a reaction kettle, adjusting the temperature to 2 ℃, reacting for 14h, then heating to 25 ℃, and standing for 9h to obtain a polyamic acid solution;
c) at room temperature, N2In the atmosphere, adding 1.6g of 4, 4' -diaminodiphenyl ether, 2.4g of 1, 2, 4, 5-benzenetetracarboxylic anhydride and 15g N, N-dimethylacetamide into a reaction kettle, adjusting the temperature to 2 ℃, stirring for 11h, adding 1.5g of phosphate-based amino polysilsesquioxane, carrying out ultrasonic treatment at 900W for 0.5h, continuing stirring for 8h, heating to 25 ℃, and standing for 13h to obtain a modified polyamic acid solution;
d) by adopting a coaxial electrostatic spinning method, adding a polyamic acid solution and a modified polyamic acid solution into an external path and/or an internal path of a micro-injection pump respectively, wherein the injection speed of the external path of the micro-injection pump is 0.8mL/h, the injection speed of the internal path of the micro-injection pump is 0.7mL/h, the aperture of a coaxial capillary of the micro-injection pump is 0.08mm, and the output voltage is 25 kV.
e) And performing heat treatment on the core-shell structure modified polyamide fiber in a segmented temperature zone to obtain the core-shell low-dielectric flame-retardant polyimide-based fiber material. The heat treatment program of the segmented temperature zone is 70 ℃ and 9 hours; 160 ℃ for 10 h; 310 ℃ for 7 h.
Tests show that the dielectric constant of the core-shell type low-dielectric-resistance flame-retardant polyimide-based fiber material is 1.9, and the oxygen index LOI is 41%.
Example 5:
a preparation method of a core-shell low-dielectric flame-retardant polyimide-based fiber material comprises the following steps:
a) at room temperature, N2In an atmosphere, 4.6g of aminopropylfluoromethyl-polysilsesquioxane, 1.5g of 2, 4, 6-trimethylbenzaldehyde and 48g of trichloromethane were charged into a reaction vessel, reacted at 95 ℃ for 6 hours, followed by adjusting the temperature to 20 ℃ and then 2.9g of 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide was added thereto to prepare a solutionAnd 28g of absolute ethyl alcohol, uniformly mixing, dropwise adding 9g of sodium carbonate solution (dissolved in 12mL of water), after 0.5h of dripping, adjusting the temperature to 55 ℃, reacting for 10h, distilling at 55 ℃ under reduced pressure for 0.5h, extracting with 130mL of absolute methyl alcohol, washing with 200mL of absolute ethyl alcohol, carrying out suction filtration for 3 times, finally standing at 60 ℃ for 16h, and cooling to room temperature to obtain the phosphate-based amino polysilsesquioxane;
b) at room temperature, N2In the atmosphere, adding 2.0g of 4, 4' -diaminodiphenyl ether, 14g N, N-dimethylacetamide aromatic dianhydride and 3.0g of 1, 2, 4, 5-benzenetetracarboxylic anhydride into a reaction kettle, adjusting the temperature to 0 ℃, reacting for 12 hours, then heating to 25 ℃, and standing for 8 hours to obtain a polyamic acid solution;
c) at room temperature, N2In the atmosphere, adding 2.0g of 4, 4' -diaminodiphenyl ether, 3.0g of 1, 2, 4, 5-benzenetetracarboxylic anhydride and 16g N, N-dimethylacetamide into a reaction kettle, adjusting the temperature to 0 ℃, stirring for 8 hours, adding 1.7g of phosphate-based amino polysilsesquioxane, carrying out ultrasonic treatment for 0.5 hour at 800W, continuing stirring for 8 hours, heating to 25 ℃, and standing for 15 hours to obtain a modified polyamic acid solution;
d) by adopting a coaxial electrostatic spinning method, adding a polyamic acid solution and a modified polyamic acid solution into an external path and/or an internal path of a micro-injection pump respectively, wherein the injection speed of the external path of the micro-injection pump is 0.9mL/h, the injection speed of the internal path of the micro-injection pump is 0.8mL/h, the aperture of a coaxial capillary of the micro-injection pump is 0.1mm, and the output voltage is 15 kV.
e) And performing heat treatment on the core-shell structure modified polyamide fiber in a segmented temperature zone to obtain the core-shell low-dielectric flame-retardant polyimide-based fiber material. The heat treatment program of the segmented temperature zone is 85 ℃ and 9 hours; 150 ℃ for 7 h; 305 ℃ for 7 h.
Tests show that the dielectric constant of the core-shell type low-dielectric-resistance flame-retardant polyimide-based fiber material is 2.1, and the oxygen index LOI is 37%.

Claims (9)

1. A preparation method of a core-shell type low-dielectric flame-retardant polyimide-based fiber material is characterized in that the core-shell type modified polyamide acid fiber is prepared by heat treatment of a segmented temperature zone, a core is made of polyimide fiber, and the diameter of the core is 10-100 nm; the shell is made of modified polyimide fiber; the thickness of the shell layer is 10-100 nm;
the core-shell type modified polyamic acid fiber is prepared by spinning modified polyamic acid solution and polyamic acid solution in different paths in a micro-injection pump by adopting a coaxial electrostatic spinning method;
the modified polyimide fiber is generated by performing heat treatment on a modified polyamic acid solution at a segmented temperature zone on the surface of the polyimide fiber core;
the modified polyamic acid solution is prepared by carrying out amidation reaction on phosphate-based amino polysilsesquioxane and polyamic acid, and the polyamic acid solution is prepared by carrying out amidation reaction on aromatic diamine and aromatic dianhydride;
the phosphate-based amino polysilsesquioxane is prepared by carrying out Kabachnik-Fields reaction on a phosphate-based compound, a symmetrical aromatic aldehyde compound and amino polysilsesquioxane.
2. The method for preparing a core-shell low-dielectric flame-retardant polyimide-based fiber material according to claim 1, which comprises the following steps:
step a) preparation of phosphate-based amino polysilsesquioxane, N at room temperature2In the atmosphere, adding amino polysilsesquioxane, a symmetric aromatic aldehyde compound and a low-boiling point solvent into a reaction kettle, reacting for 2-10 h at 55-120 ℃, then reducing the temperature to 10-25 ℃, adding a phosphate compound and absolute ethyl alcohol, uniformly mixing, dropwise adding 10-40 wt.% of an inorganic auxiliary agent aqueous solution within 0.5-4 h, raising the temperature to 55-85 ℃, continuing to react for 4-12 h, distilling at 50-60 ℃ under reduced pressure for 0.5-1 h, extracting with absolute methyl alcohol, washing with petroleum ether, performing suction filtration for 3-5 times, finally standing at 50-60 ℃ for 12-24 h, and cooling to room temperature to obtain phosphate-based amino polysilsesquioxane;
step b) preparation of the polyamic acid solution N at room temperature2In an atmosphere, adding aromatic diamine, aromatic dianhydride and a high-boiling-point solvent into a reaction kettle, stirring for 8-20 h at 0-10 ℃, then heating to 25 ℃, and standing for 8-15 h to obtain a polyamic acid solution;
step c) preparation of modified polyamic acid solution N at room temperature2In the atmosphere, adding aromatic diamine, aromatic dianhydride and a high-boiling-point solvent into a reaction kettle, stirring for 8-20 h at 0-10 ℃, adding the phosphate-based amino polysilsesquioxane synthesized in the step a), performing ultrasonic treatment for 0.5-1 h, continuing stirring for 8-20 h, heating to 25 ℃, and standing for 8-15 h to obtain a modified polyamic acid solution;
step d) preparing core-shell type modified polyamide acid based fiber, namely adding the polyamide acid solution prepared in the step b) and the modified polyamide acid solution prepared in the step c) into an external path and/or an internal path of a micro-injection pump respectively by adopting a coaxial electrostatic spinning method, and spinning to obtain the core-shell type modified polyamide acid based fiber;
and e) preparing the core-shell type low-dielectric flame-retardant polyimide-based fiber material, namely performing segmented temperature zone heat treatment on the core-shell type modified polyamide-based fiber at the temperature of 60-310 ℃, and cooling to room temperature to obtain the core-shell type low-dielectric flame-retardant polyimide-based fiber material.
3. The method for preparing the core-shell low-dielectric flame-retardant polyimide-based fiber material as claimed in claim 2, wherein the structural general formula of the modified polyamic acid prepared in the step c) is as follows:
Figure DEST_PATH_IMAGE001
wherein the polymerization degree m is 10-80; the number of repeating units n is 1, 2, 4.
4. The method for preparing a core-shell low-dielectric flame-retardant polyimide-based fiber material according to claim 2, wherein the method comprises the following steps:
in the step a), the mass ratio of the amino polysilsesquioxane, the symmetric aromatic aldehyde compound, the low boiling point solvent, the phosphate compound, the absolute ethyl alcohol, the absolute methyl alcohol, the petroleum ether and the inorganic auxiliary agent aqueous solution is (1-5): 0.05-2): 10-50): 1-5): 10-40): 20-80 ]: 20-100): 5-20;
in the step b), the mass ratio of the aromatic diamine to the aromatic dianhydride to the high-boiling-point solvent is (1-2) to (1-3) to (10-20);
in the step c), the mass ratio of the phosphate-based amino polysilsesquioxane to the aromatic diamine to the aromatic dianhydride to the high boiling point solvent is (0.5-0.8) to (1-2) to (1-3) to (10-20).
5. The method for preparing a core-shell low-dielectric flame-retardant polyimide-based fiber material according to claim 2, wherein the method comprises the following steps:
the low-boiling-point solvent in the step a) is one of pentane, trichloromethane and acetone; the symmetrical aromatic aldehyde compound is 2, 4, 6-trimethyl benzaldehyde or 3, 4, 5-trihydroxy benzaldehyde; the phosphate compound is 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide or 3-fluoro-9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide; the inorganic auxiliary agent aqueous solution is a sodium carbonate aqueous solution or a potassium carbonate aqueous solution.
6. The method for preparing a core-shell low-dielectric flame-retardant polyimide-based fiber material according to claim 2, wherein the method comprises the following steps: the amino polysilsesquioxane in the step a) is one of amino ethyl heptyl-polysilsesquioxane, amino propyl heptyl-polysilsesquioxane, amino pentyl heptyl-polysilsesquioxane, amino ethyl fluoromethyl-polysilsesquioxane, amino propyl fluoromethyl-polysilsesquioxane and amino pentyl fluoromethyl-polysilsesquioxane.
7. The method for preparing a core-shell low-dielectric flame-retardant polyimide-based fiber material according to claim 2, wherein the method comprises the following steps:
the aromatic diamine in the steps b) and c) is 4, 4' -diaminodiphenyl ether; the aromatic dianhydride is 1, 2, 4, 5-benzenetetracarboxylic anhydride; the high boiling point solvent is one of N, N-dimethylformamide, N-methylpyrrolidone and N, N-dimethylacetamide;
the solid content of the modified polyamic acid solution in the step b) is 15-30 wt.%;
the solid content of the polyamic acid solution in step c) is 10-35 wt.%; the ultrasonic power of ultrasonic treatment is 600-900W.
8. The method for preparing a core-shell low-dielectric flame-retardant polyimide-based fiber material according to claim 2, wherein the method comprises the following steps: the injection speed of the path inside the micro-injection pump used in the coaxial electrostatic spinning method in the step d) is 0.5-1.0 mL/h, the injection speed of the path outside the micro-injection pump is 0.5-1.5 mL/h, the aperture of the coaxial capillary tube of the micro-injection pump is 0.04-0.1 mm, and the output voltage is 15-30 kV.
9. The method for preparing a core-shell low-dielectric flame-retardant polyimide-based fiber material according to claim 2, wherein the method comprises the following steps: the heat treatment procedure of the segmented temperature zone in the step e) is 60-120 ℃ and 6-10 h; 120-200 ℃ for 4-8 h; 200 to 300 ℃ for 4 to 8 hours.
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CN104499085A (en) * 2014-11-19 2015-04-08 南通大学 Method for improving strength, modulus, thermal stability and water resistance of polyimide fiber
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