A polyimide-silicone composite foam material with uniform and controllable cells and a preparation method thereof

Abstract

This invention relates to the field of polymer foaming materials technology, specifically to a method for preparing a polyimide-silicone composite foam material with uniform and controllable cell size. The method includes mixing a third polymethylene polyphenyl isocyanate, a black prepolymer, a polyimide precursor solution, a siloxane prepolymer, deionized water, triethylamine, and a foam stabilizer to obtain a foaming system; foaming and curing to obtain cured foam; and heat-treating and cooling the cured foam to obtain the polyimide-silicone composite foam material. The polyimide-silicone composite foam material prepared by this method exhibits excellent performance.

Description

Technical Field

[0001] This invention relates to the field of polymer foaming materials technology, specifically to a method for preparing a polyimide-silicone composite foam material with uniform and controllable cell size. Background Technology

[0002] Polyimide (PI) foam has excellent thermal insulation, flame retardancy, and radiation resistance, but pure PI foam is brittle, prone to cell merging, and has a wide size distribution. Organosilicon (polysiloxane) has flexible molecular chains and heat resistance, and can form a rigid-flexible composite system with PI.

[0003] Chinese patent CN102702726B discloses a method for preparing polyimide foam and a product that uses isocyanate and PI precursor for chemical foaming, but does not involve the introduction of organosilicon components or the regulation of the effect of siloxane content on cell evolution. Chinese patent CN104356364A discloses organosilicon-modified polyimide foam and its preparation method, which discloses physical blending of organosilicon and PI solution for re-foaming. However, relying solely on blending can easily cause phase separation and does not provide a specific optimal content range for siloxane prepolymer. The uniformity of cells and compression resilience are still not ideal.

[0004] In summary, there is an urgent need for a polyimide-silicone composite foam material with uniform and controllable cell structure, as well as a method for preparing PI / silicone composite foam by in-situ composite and precise control of siloxane prepolymer content. Summary of the Invention

[0005] The present invention aims to solve the technical problem of how to provide a polyimide-organosilicon composite foam material with uniform and controllable cell structure, as well as a method for preparing PI / organosilicon composite foam by in-situ composite and precise control of siloxane prepolymer content.

[0006] To achieve the above objectives, the first aspect of the present invention provides a method for preparing a polyimide-silicone composite foam material with uniform and controllable cell size, comprising the following steps:

[0007] S1. Mix the first polymethylene polyphenyl polyisocyanate with the first 3,3',4,4'-benzophenone tetracarboxylic dianhydride and carry out the first reaction to obtain the black material prepolymer.

[0008] The second 3,3',4,4'-benzophenone tetracarboxylic dianhydride, methanol and N,N-dimethylformamide were mixed and subjected to an esterification reaction to obtain a polyimide precursor solution.

[0009] α,ω-bis(hydroxypropyl)polydimethylsiloxane was mixed with dibutyltin dilaurate, dehydrated and chain-extended, and then a second polymethylene polyphenyl polyisocyanate was added to carry out a second reaction to obtain a siloxane prepolymer.

[0010] S2. Mix the third polymethylene polyphenyl polyisocyanate, black prepolymer, polyimide precursor solution, siloxane prepolymer, deionized water, triethylamine and foam stabilizer to obtain a foaming system, foam and cure to obtain cured foam.

[0011] S3. The cured foam is heat-treated and cooled to obtain the polyimide-silicone composite foam material.

[0012] The second aspect of the present invention provides a method for preparing the above-mentioned polyimide-silicone composite foam material with uniform and controllable pore size. The polyimide-silicone composite foam material has an average pore size of 100-300 μm, a pore size distribution that exhibits a unimodal normal distribution, a 5wt% thermal weight loss temperature ≥600℃, a nitrogen carbon residue rate ≥69wt% at 800℃, and a compression modulus ≥3.2MPa.

[0013] The beneficial effects of this invention are as follows:

[0014] (1) The specific siloxane prepolymer content in the polyimide-silicone composite foam material provided by the present invention makes the foam cells significantly finer and more uniform, with an average pore size of 100-300 μm and a pore size distribution that is unimodal.

[0015] (2) The polyimide-silicone composite foam material provided by this invention has excellent performance, specifically: 5wt% thermal decomposition temperature ≥600℃, nitrogen char residue rate ≥70wt% at 800℃, compression modulus ≥3.3MPa, compressive strength 0.29MPa, and energy absorption per unit volume 0.061MJ / m³. 3 ;

[0016] (3) The preparation method provided by the present invention adopts in-situ reaction foaming to avoid macroscopic phase separation, and the PI phase and the siloxane phase are chemically bonded. Detailed Implementation

[0017] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0018] In this invention, the inventors discovered that by preparing hydroxyl-terminated siloxane prepolymers and adding them at a specific mass fraction of the total mass of the foaming system, a polyimide-silicone composite foam material with uniform and controllable pore size and its preparation method are provided. This reduces the average pore size of the polyimide-silicone composite foam material to 100–300 μm, with an optimal value of 190 μm, while also maintaining high char residue (>70%) and excellent compressive modulus / energy absorption.

[0019] The first aspect of this invention provides a method for preparing a polyimide-silicone composite foam material with uniform and controllable cell size, comprising the following steps:

[0020] S1. Mix the first polymethylene polyphenyl polyisocyanate with the first 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA) and carry out the first reaction to obtain the black prepolymer;

[0021] The second 3,3',4,4'-benzophenone tetracarboxylic dianhydride, methanol and N,N-dimethylformamide were mixed and subjected to an esterification reaction to obtain a polyimide precursor solution.

[0022] α,ω-bis(hydroxypropyl)polydimethylsiloxane was mixed with dibutyltin dilaurate, dehydrated and chain-extended, and then a second polymethylene polyphenyl polyisocyanate was added to carry out a second reaction to obtain a siloxane prepolymer.

[0023] S2. Mix the third polymethylene polyphenyl polyisocyanate, black prepolymer, polyimide precursor solution, siloxane prepolymer, deionized water, triethylamine and foam stabilizer to obtain a foaming system, foam and cure to obtain cured foam.

[0024] S3. The cured foam is heat-treated and cooled to obtain the polyimide-silicone composite foam material.

[0025] In this invention, the siloxane prepolymer is hydroxyl-terminated. Combined with the preparation method described above, it is possible to obtain a polyimide-silicone composite foam material with an average pore size reduced to 100-300 μm, with an optimal size of 190 μm, while also achieving a high char residue rate (>70%) and excellent compressive modulus / energy absorption properties.

[0026] According to the present invention, in step S1, the molar ratio of the first polymethylene polyphenyl polyisocyanate to the first 3,3',4,4'-benzophenone tetracarboxylic dianhydride is 1:0.45 to 0.55.

[0027] According to the present invention, the conditions for the first reaction include: the temperature of the first reaction is 20~30°C, and the time of the first reaction is 10~14h.

[0028] According to the present invention, in step S1, the molar ratio of the second 3,3',4,4'-benzophenone tetracarboxylic dianhydride, methanol and N,N-dimethylformamide is 1:1.8 to 2.2:6 to 32.

[0029] According to the present invention, the conditions for the esterification reaction include: the temperature of the esterification reaction is 50~80°C, and the time of the esterification reaction is 3~5h.

[0030] According to the present invention, in step S1, the molar ratio of α,ω-bis(hydroxypropyl)polydimethylsiloxane to dibutyltin dilaurate is 100:0.6~0.9.

[0031] According to the present invention, a second polymethylene polyphenyl polyisocyanate is added such that n(-NCO):n(-OH) is 1.8 to 2.2: 2.8 to 3.2.

[0032] According to the present invention, the conditions for dehydration and chain extension include: a dehydration and chain extension temperature of 145-155°C and a dehydration and chain extension time of 10-14 hours.

[0033] According to the present invention, the conditions for the second reaction include: the temperature of the second reaction is 20~50°C, and the time of the second reaction is 1~3h.

[0034] In this invention, the siloxane prepolymer is a hydroxyl-terminated siloxane prepolymer.

[0035] According to the present invention, in step S2, based on the total mass of the third polymethylene polyphenyl polyisocyanate, black prepolymer, polyimide precursor solution, siloxane prepolymer, deionized water, triethylamine and foam stabilizer, the mass fraction of the third polymethylene polyphenyl polyisocyanate is 3-8%, the mass fraction of the black prepolymer is 25-35%, the mass fraction of the polyimide precursor solution is 12-18%, the mass fraction of the siloxane prepolymer is 40-55%, the mass fraction of triethylamine is 0.5-1.5%, the mass fraction of the foam stabilizer is 1.5-2.5%, and the balance is deionized water.

[0036] In this invention, when the mass fraction of the siloxane prepolymer is too high, the siloxane prepolymer will cause bubble collapse or structural deterioration; <30wt% of the prepolymer has coarse pores and poor compactness.

[0037] According to the present invention, the foam stabilizer is AK8805.

[0038] In this invention, the specific mass fraction of the siloxane prepolymer results in excellent performance of the prepared polyimide-silicone composite foam material.

[0039] According to a preferred embodiment of the present invention, in step S2, based on the total mass of the third polymethylene polyphenyl polyisocyanate, black prepolymer, polyimide precursor solution, siloxane prepolymer, deionized water, triethylamine, and foam stabilizer, the mass fraction of the third polymethylene polyphenyl polyisocyanate is 5-7%, the mass fraction of the black prepolymer is 25-30%, the mass fraction of the polyimide precursor solution is 12-15%, the mass fraction of the siloxane prepolymer is 48-52%, the mass fraction of triethylamine is 0.5-1.0%, the mass fraction of the foam stabilizer is 1.5-2.5%, and the balance is deionized water.

[0040] According to the present invention, in step S2, the foaming conditions include: a foaming temperature of 20~35℃ and a foaming time of 0.5~1.0h.

[0041] According to the present invention, the curing conditions include: a curing temperature of 20~35℃ and a curing time of 12~24h.

[0042] According to the present invention, in step S3, the heat treatment conditions include: holding at 195-205°C for 1.5-2.5 hours, and then raising the temperature to 215-225°C and holding for 1.5-2.5 hours.

[0043] According to the present invention, in step S3, the cooling conditions include cooling to 20~35°C.

[0044] The second aspect of the present invention provides a method for preparing the above-mentioned polyimide-silicone composite foam material with uniform and controllable pore size. The polyimide-silicone composite foam material has an average pore size of 100-300 μm, a pore size distribution that exhibits a unimodal normal distribution, a 5wt% thermal weight loss temperature ≥600℃, a nitrogen carbon residue rate ≥69wt% at 800℃, and a compression modulus ≥3.2MPa.

[0045] Test methods

[0046] In this invention, the average pore size, pore size distribution, and 5wt% thermogravimetric temperature (T) of the polyimide-silicone composite foam material are specified. d5％ The nitrogen carbon residue at 800℃ and the compression modulus were measured using conventional methods in the field.

[0047] The technical solution of the present invention will be further described in detail below with reference to the embodiments. Obviously, the embodiments described herein are only some embodiments of the present invention and are not intended to limit the present invention. All other embodiments implemented by those skilled in the art based on the embodiments of the present invention without creative improvements are within the protection scope of the present invention.

[0048] The reagents used in the examples and comparative examples are conventional reagents in the art and are all commercially available.

[0049] PM200 is Wanhua Chemical's polymethylene polyphenyl polyisocyanate (polyMDI).

[0050] T12 is dibutyltin dilaurate.

[0051] Example 1

[0052] S1. The first polymethylene polyphenyl polyisocyanate and the first 3,3',4,4'-benzophenone tetracarboxylic dianhydride were mixed at a molar ratio of 1:0.5 and subjected to a first reaction at 25°C for 12 hours to obtain the black prepolymer.

[0053] The second 3,3',4,4'-benzophenone tetracarboxylic dianhydride, methanol, and N,N-dimethylformamide were mixed and subjected to esterification at 60°C for 4 hours to obtain a polyimide precursor solution; the molar ratio of the second 3,3',4,4'-benzophenone tetracarboxylic dianhydride, methanol, and N,N-dimethylformamide was 1:2:6.5.

[0054] α,ω-bis(hydroxypropyl)polydimethylsiloxane was mixed with dibutyltin dilaurate, dehydrated and chain-extended at 150°C for 12 h, and then a second polymethylene polyphenyl polyisocyanate was added to carry out a second reaction to obtain a siloxane prepolymer; the molar ratio of α,ω-bis(hydroxypropyl)polydimethylsiloxane to dibutyltin dilaurate was 100:0.75, and the addition of the second polymethylene polyphenyl polyisocyanate made the n(-NCO):n(-OH) ratio 2:3;

[0055] S2. Mix 1.10g of PM200, 5.10g of black prepolymer, 2.50g of PI precursor solution, 9.38g of siloxane prepolymer, 0.23g of deionized water, 0.12g of triethylamine, and 0.34g of AK8805.

[0056] Based on the total mass of the aforementioned third polymethylene polyphenyl polyisocyanate, black prepolymer, polyimide precursor solution, siloxane prepolymer, deionized water, triethylamine, and foam stabilizer, a foaming system is obtained by mixing 5.86% by mass of the third polymethylene polyphenyl polyisocyanate, 27.17% by mass of the black prepolymer, 13.32% by mass of the polyimide precursor solution, 50% by mass of the siloxane prepolymer, 0.64% by mass of the triethylamine, and 1.81% by mass of the foam stabilizer, with the balance being deionized water.

[0057] The foam was foamed at 25°C for 0.5 hours and then cured at 25°C for 24 hours to obtain cured foam.

[0058] S3. Heat-treat the cured foam at 200℃ for 2 hours, then raise it to 220℃ for 2 hours, and cool it to 25℃ to obtain polyimide-silicone composite foam material A1.

[0059] The cells exhibit a uniform mixture of closed and open cells, with an average pore size of 190 μm and a unimodal distribution. The compressive modulus is 3.39 MPa, the compressive strength is 0.29 MPa, and the energy absorbed per unit volume is 0.061 MJ / m³. 3 Td5% = 604.12℃, Td10% = 611.91℃, residual carbon 73.59%. FT-IR characterization shows 1780 cm⁻¹ -1 1720cm -1 The peak is characteristic of imide, 1020–1080 cm⁻¹ -1 These are characteristic peaks of Si-O-Si.

[0060] Example 2

[0061] Polyimide-silicone composite foam material was prepared according to the preparation method of Example 1, except that the siloxane prepolymer was 6.25 g with a mass fraction of 40 wt%.

[0062] A polyimide-silicone composite foam material A2 was prepared.

[0063] The pore size is significantly reduced, with an average pore diameter of 100–300 μm, and is relatively uniform. The compressive modulus is 3.20 MPa, the compressive strength is 0.30 MPa, Td5% = 600.43℃, and the residual carbon content is 69.92%.

[0064] Comparative Example 1

[0065] Polyimide-silicone composite foam material was prepared according to the preparation method of Example 1, except that 6.25 g of siloxane prepolymer was not added, with a mass fraction of 0 wt%.

[0066] A polyimide-silicone composite foam material DA1 was prepared.

[0067] The foam is pale yellow with large pores (400–700 μm) and localized co-occurrence. Compressive strength is 0.25 MPa. d5％ =558℃.

[0068] Comparative Example 2

[0069] Polyimide-silicone composite foam material was prepared according to the preparation method of Example 1, except that the siloxane prepolymer was 1.04 g with a mass fraction of 10 wt%.

[0070] Polyimide-silicone composite foam material DA2 was prepared.

[0071] The cell size is slightly smaller but not uniform. The compressive modulus is 2.1 MPa.

[0072] Comparative Example 3

[0073] Polyimide-silicone composite foam material was prepared according to the preparation method of Example 1, except that the amount of siloxane prepolymer was 2.34 g with a mass fraction of 20 wt%.

[0074] A polyimide-silicone composite foam material DA3 was prepared.

[0075] The cell size distribution has improved, but is still relatively wide. The compressive modulus is 2.5 MPa.

[0076] Comparative Example 4

[0077] Polyimide-silicone composite foam material was prepared according to the preparation method of Example 1, except that the amount of siloxane prepolymer was 4.02 g with a mass fraction of 30 wt%.

[0078] A polyimide-silicone composite foam material DA4 was prepared.

[0079] The pores are becoming finer, and some areas are becoming more uniform. T d5％ =582℃.

[0080] Comparative Example 5

[0081] Polyimide-silicone composite foam material was prepared according to the preparation method of Example 1, except that the siloxane prepolymer was 14.06 g with a mass fraction of 60 wt%.

[0082] A polyimide-silicone composite foam material DA5 was prepared.

[0083] The cell structure remained relatively uniform, but some cell walls were slightly thicker, resulting in a slight decrease in compressive modulus (3.05 MPa). d5％ =598℃.

[0084] Comparative Example 6

[0085] Polyimide-silicone composite foam material was prepared according to the preparation method of Example 1, except that the amount of siloxane prepolymer was 21.86 g with a mass fraction of 70 wt%.

[0086] A polyimide-silicone composite foam material DA6 was prepared.

[0087] It can foam, but there are localized large pores and a few bubble walls that have fractured; the bubbles have not collapsed. The compressive stress level is slightly elevated but unstable. T d5％ =591℃.

[0088] Comparative Example 7

[0089] Polyimide-silicone composite foam material was prepared according to the preparation method of Example 1, except that the mass fraction of the siloxane prepolymer was 75 wt%. Foaming collapse.

[0090] Comparative Example 8

[0091] Polyimide-silicone composite foam material was prepared according to the preparation method of Example 1, except that the mass fraction of the siloxane prepolymer was 80 wt%. Foaming collapse.

[0092] By comparing the examples and comparative examples, it can be seen that the polyimide-silicone composite foam material provided by the present invention has excellent performance. Specifically, the 5wt% thermal decomposition temperature is ≥600℃, the nitrogen char residue rate at 800℃ is ≥70wt%, the compressive modulus is ≥3.3MPa, the compressive strength is 0.29MPa, and the energy absorption per unit volume of the preferred embodiment is 0.061MJ / m³. 3

[0093] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a polyimide-silicone composite foam material with uniform and controllable cell size, characterized in that, Includes the following steps: S1. Mix the first polymethylene polyphenyl polyisocyanate with the first 3,3',4,4'-benzophenone tetracarboxylic dianhydride and carry out the first reaction to obtain the black prepolymer. The second 3,3',4,4'-benzophenone tetracarboxylic dianhydride, methanol and N,N-dimethylformamide were mixed and subjected to an esterification reaction to obtain a polyimide precursor solution. α,ω-bis(hydroxypropyl)polydimethylsiloxane was mixed with dibutyltin dilaurate, dehydrated and chain-extended, and then a second polymethylene polyphenyl polyisocyanate was added to carry out a second reaction to obtain a siloxane prepolymer. S2. Mix the third polymethylene polyphenyl polyisocyanate, black prepolymer, polyimide precursor solution, siloxane prepolymer, deionized water, triethylamine and foam stabilizer to obtain a foaming system, foam and cure to obtain cured foam. S3. The cured foam is heat-treated and cooled to obtain the polyimide-silicone composite foam material.

2. The method for preparing the polyimide-silicone composite foam material with uniform and controllable cell structure according to claim 1, characterized in that, In step S1, the molar ratio of the first polymethylene polyphenyl polyisocyanate to the first 3,3',4,4'-benzophenone tetracarboxylic dianhydride is 1:0.45 to 0.55; The conditions for the first reaction include: the temperature of the first reaction is 20~30℃, and the reaction time is 10~14h.

3. The method for preparing the polyimide-silicone composite foam material with uniform and controllable cell structure according to claim 1, characterized in that, In step S1, the molar ratio of the second 3,3',4,4'-benzophenone tetracarboxylic dianhydride, methanol, and N,N-dimethylformamide is 1:1.8 to 2.2:6 to 32; The conditions for the esterification reaction include: a temperature of 50-80°C and a reaction time of 3-5 hours.

4. The method for preparing the polyimide-silicone composite foam material with uniform and controllable cell structure according to claim 1, characterized in that, In step S1, the molar ratio of α,ω-bis(hydroxypropyl)polydimethylsiloxane to dibutyltin dilaurate is 100:0.6~0.9; The addition of a second polymethylene polyphenyl polyisocyanate resulted in an n(-NCO):n(-OH) ratio of 1.8–2.2:2.8–3.

2. The conditions for dehydration and chain extension include: a dehydration and chain extension temperature of 145–155°C and a dehydration and chain extension time of 10–14 h; The conditions for the second reaction include: the temperature of the second reaction is 20~50℃, and the reaction time is 1~3h.

5. The method for preparing the polyimide-silicone composite foam material with uniform and controllable cell structure according to claim 1, characterized in that, In step S2, based on the total mass of the third polymethylene polyphenyl polyisocyanate, black prepolymer, polyimide precursor solution, siloxane prepolymer, deionized water, triethylamine, and foam stabilizer, the mass fraction of the third polymethylene polyphenyl polyisocyanate is 3-8%, the mass fraction of the black prepolymer is 25-35%, the mass fraction of the polyimide precursor solution is 12-18%, the mass fraction of the siloxane prepolymer is 40-55%, the mass fraction of triethylamine is 0.5-1.5%, the mass fraction of the foam stabilizer is 1.5-2.5%, and the balance is deionized water.

6. The method for preparing the polyimide-silicone composite foam material with uniform and controllable cell structure according to claim 5, characterized in that, In step S2, based on the total mass of the third polymethylene polyphenyl polyisocyanate, black material prepolymer, polyimide precursor solution, siloxane prepolymer, deionized water, triethylamine, and foam stabilizer, the mass fraction of the third polymethylene polyphenyl polyisocyanate is 3-7%, the mass fraction of the black material prepolymer is 25-30%, the mass fraction of the polyimide precursor solution is 12-15%, the mass fraction of the siloxane prepolymer is 48-52%, the mass fraction of triethylamine is 0.5-1.0%, the mass fraction of the foam stabilizer is 1.5-2.5%, and the balance is deionized water.

7. The method for preparing the polyimide-silicone composite foam material with uniform and controllable cell structure according to claim 1, characterized in that, In step S2, the foaming conditions include: a foaming temperature of 20~35℃ and a foaming time of 0.5~1h; The curing conditions include: a curing temperature of 20~35℃ and a curing time of 12~24h.

8. The method for preparing the polyimide-silicone composite foam material with uniform and controllable cell structure according to claim 1, characterized in that, In step S3, the heat treatment conditions include: holding at 195-205℃ for 1.5-2.5 hours, and then raising the temperature to 215-225℃ and holding for 1.5-2.5 hours.

9. The method for preparing the polyimide-silicone composite foam material with uniform and controllable cell structure according to claim 5, characterized in that, In step S3, the cooling conditions include cooling to 20~35°C.

10. The polyimide-silicone composite foam material with uniform and controllable cell structure prepared by the method of any one of claims 1-9 is characterized in that, The polyimide-silicone composite foam material has an average pore size of 100–300 μm, a pore size distribution that exhibits a unimodal normal distribution, a 5wt% thermal weight loss temperature ≥600℃, a nitrogen carbon residue rate ≥69wt% at 800℃, and a compression modulus ≥3.2MPa.