Heat-resistant fluorine-free semi-alicyclic polyimide as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of high polymer materials, and particularly relates to heat-resistant fluorine-free semi-alicyclic polyimide as well as a preparation method and application thereof. The heat-resistant fluorine-free semi-alicyclic polyimide is characterized in that the semi-alicyclic polyimide composition is prepared by a polymerization reaction of diamine and dianhydride; the molar ratio of the total amount of diamine to the total amount of dianhydride is (0.9-1.1): 1; the diamine comprises a first diamine and a second diamine; and the dianhydride is fluorine-free dianhydride. According to the invention, specific dianhydride and diamine are selected to react, and a segmented heating method is adopted to optimize the preparation process, so that the prepared heat-resistant fluorine-free semi-alicyclic polyimide has better heat stability and mechanical properties.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high polymer materials, and particularly relates to a heat-resistant fluorine-free semi-alicyclic polyimide as well as a preparation method and application thereof. BACKGROUND

[0002] Polyimide (PI) is a kind of aromatic heterocyclic polymer containing imine ring in the main chain, and is also a kind of high-performance functional material. PI has excellent thermal stability, chemical corrosion resistance, moisture resistance, radiation resistance, mechanical properties and dielectric properties, and is widely used in aerospace, electrical appliances, microelectronics industry, low-temperature superconductivity, gas separation and photoetching. In recent ten years, PI has been a hot topic that people pay attention to. At present, with the progress of science and technology and the development of emerging industries, the demand for PI is increasing day by day. Due to the high stability of the chemical structure of PI and excellent physical properties, the application forms of PI products are various, and the range is wide and diverse. PI can be processed into thin films, fibers, resins, adhesives, photoresists, engineering plastics, gas separation membranes, liquid crystal alignment agents and foam plastics. Among them, the largest demand and the most widely used are PI film industry. In addition to being widely used in flexible printed circuit boards, photoresists, chip packaging and other microelectronic fields, PI films are also gradually attracting widespread attention in the fields of flexible display, organic photovoltaic solar cell panels and liquid crystal display.

[0003] Traditional polyimide materials usually exhibit yellow or brownish yellow appearance due to the existence of charge transfer complex (CTC) effect between molecular chains, which limits the further development of polyimide in application occasions requiring high transparency. In order to solve this problem, researchers have adopted innovative design of chemical structure, and through the introduction of fluorine groups, flexible ether bonds and aromatic rigid non-planar conjugated structures, the distance between molecular chains is effectively increased, and the packing density of the polymer is reduced. The purpose is to weaken the conjugation effect between polyimide molecular chains and reduce the stacking of molecular chains, so as to reduce the absorption of visible light and achieve the effect of transparency. At the same time, molecular design plays a key role in regulating the thermal stability, dimensional stability, optical properties and solubility of polyimide.

[0004] With the rapid development of electronic information industry, the requirements for material films are becoming more and more demanding. In addition to meeting the requirements of lightness, flexibility and light transmission, higher requirements for basic thermal and mechanical properties such as heat resistance and dimensional stability are put forward. Colorless and transparent polyimide (CPI) film has wide application prospects in the field of flexible electronics due to its performance advantages of conventional PI film and optical properties of optical film, and has attracted much attention. At present, CPI film mainly includes fluorine-containing type and semi-alicyclic type; among them, the research on fluorine-containing CPI film is more sufficient.

[0005] A series of fluorine-containing colorless transparent polyimide films were prepared by using 2,2'-bis(trifluoromethyl)-4,4'-diamino diphenyl ether (6FODA) and 4,4'-diamino diphenyl ether (ODA) as diamine monomers, hexafluoro dianhydride (6FDA) as anhydride monomer, introducing fluorine groups and flexible ether bonds into the monomers to construct non-planar conjugated aromatic structures, and adjusting the molar ratio of monomers in the polycondensation reaction to reduce the charge transfer complex (CTC) effect, as described in Huangtao et al., Preparation and Properties of High Heat-Resistant Colorless Transparent Polyimide Films, New Chemical Materials, 2025.12.029. The results showed that the films had excellent optical transparency and thermal stability, with a transmittance of over 80%; the thermal weight loss temperature was 500°C when the weight loss was 5%; and the carbon residue of the film was higher than 50% when the temperature reached 800°C. These films not only resist high temperatures but also achieve colorless and transparent properties. However, they face the challenges of high cost of fluorine-containing monomers, increased water absorption, large equipment investment, and extremely difficult engineering. In recent years, fluorine-containing monomers have been restricted by the international PFAS program. PFAS is known as a "persistent organic compound (POPs)" because it takes hundreds of years to degrade in soil and water. PFAS is also easily transported in the environment. When humans and animals ingest PFAS, PFAS accumulates in the body and is toxic, affecting the immune system, reproductive system, endocrine system, growth and development of infants, causing liver damage, and even increasing the risk of thyroid disease, kidney cancer, high blood pressure, testicular cancer, and other diseases.

[0006] Currently, semi-lipid ring type polyimides mostly have insufficient heat resistance and other problems. For example, Chinese Patent CN118852622A provides a fluorine-free semi-lipid ring type low CTE transparent polyimide and its preparation method and polyimide film, relating to the field of polyimides and their preparation technology. The fluorine-free semi-lipid ring type low CTE transparent polyimide is prepared by condensation reaction of a dianhydride containing alicyclic group and a diamine. The invention also provides a polyimide film prepared from the above semi-lipid ring type low CTE transparent polyimide. The product prepared by selecting specific diamines and dianhydrides and optimizing the preparation process has good optical and mechanical properties, and also has heat resistance, making up for the shortcomings of the prior art and can be used as a substrate for flexible display, solar, wearable devices, and other flexible electronics. However, its heat resistance still needs to be improved.

[0007] With the rapid development of modern science and technology, especially in the fields of optoelectronics, microelectronics, solar energy, and other high-tech fields, the performance requirements for materials are becoming higher and higher, especially for heat resistance. Therefore, it is imperative to develop a fluorine-free semi-lipid polyimide with good heat resistance while maintaining good optical and mechanical properties. SUMMARY

[0008] Based on the deficiencies of the prior art, the present application aims to provide a heat-resistant fluorine-free semi-cycloaliphatic polyimide and a preparation method and application thereof.

[0009] To achieve the above-mentioned purpose, the present application adopts the following technical solutions: On the one hand, the present application provides a heat-resistant fluorine-free semi-cycloaliphatic polyimide, wherein the semi-cycloaliphatic polyimide composition is prepared by polymerization reaction of diamines and dianhydrides; The molar ratio of the total amount of diamines to the total amount of dianhydrides is 0.9-1.1:1; The diamines comprise first diamines and second diamines; The first diamines are 4,4'-methylenebis(2,6-diethyl aniline) (M-DEA) and / or 4,4'-methylenebis(2-ethyl) aniline (O-DEA); and the second diamines are 4,4'-oxydianiline (ODA) and / or 4,4'-diaminobenzanilide (DABA).

[0010] More preferably, the first diamines are M-DEA, and the second diamines are ODA.

[0011] Preferably, the molar ratio of the first diamines to the second diamines is 3-5:5-8, more preferably 4:7.

[0012] Preferably, the dianhydrides are fluorine-free dianhydrides.

[0013] More preferably, the dianhydrides are dianhydrides containing bulky side groups selected from one of fluorene, phthalic acid, o-benzene imine, cyclododecane.

[0014] Further preferably, the dianhydrides are selected from one of 2,2'-dichloro-4,4',5,5'-biphenyl tetracarboxylic dianhydride (DCBPDA), dicyclohexyl-2,3',3,4'-tetracarboxylic dianhydride (3,4'-HBPDA), dicyclohexyl-2,2',3,3'-tetracarboxylic dianhydride (3,3'-HBPDA).

[0015] More preferably, the dianhydrides are 2,2'-dichloro-4,4',5,5'-biphenyl tetracarboxylic dianhydride.

[0016] On the other hand, the present application also provides a preparation method of the above-mentioned heat-resistant fluorine-free semi-cycloaliphatic polyimide composition, comprising the following steps: (1) mixing diamines, dianhydrides and a solvent at 0-25℃ to obtain a polyimide resin; (2) mixing the polyimide resin obtained in step (1) with an additive, and dehydrating under the protection of inert gas to obtain a polyimide.

[0017] Preferably, the solvent in step (1) is selected from at least one of N-methylpyrrolidone, N,N-dimethylformamide, γ-valerolactone, methyltetrahydrofuran, dimethylacetamide, more preferably N-methylpyrrolidone.

[0018] Preferably, the amount of the solvent added in step (1) is 4-8 times the total moles of diamine and dianhydride, more preferably 5 times the total moles of diamine and dianhydride.

[0019] Preferably, the additive in step (2) is a mixture of 3-ethynylaniline and N-ethynylaniline, and the molar ratio of the two is 0.5-1:1-1.5, more preferably 1:1.

[0020] Preferably, the amount of the additive added in step (2) is 0.3-0.6% of the total moles of diamine and dianhydride, more preferably 0.5%.

[0021] Preferably, the inert gas in step (2) is selected from one of argon, nitrogen, and helium, more preferably argon.

[0022] Preferably, the temperature in step (2) is raised in stages.

[0023] More preferably, the staged temperature raising is specifically: First stage: 25-100℃, temperature raising rate 1-3℃ / min; 100℃ for 30-50min; Second stage: 100-200℃, temperature raising rate 2-4℃ / min; 200℃ for 20-30min; Third stage: 200-300℃, temperature raising rate 1-2℃ / min; 300℃ for 30-60min.

[0024] Further preferably, the staged temperature raising is specifically: First stage: 25-100℃, temperature raising rate 2℃ / min; 100℃ for 40min; Second stage: 100-200℃, temperature raising rate 3℃ / min; 200℃ for 25min; Third stage: 200-300℃, temperature raising rate 1℃ / min; 300℃ for 50min.

[0025] Finally, the application also provides the use of the above-mentioned heat-resistant fluorine-free semi-cycloaliphatic polyimide in the preparation of polyimide films.

[0026] Compared with the prior art, the application has the following beneficial effects: (1) The present application selects specific proportion of dianhydride and diamine to react, and adds an additive to combine the method of segmented temperature rise to optimize the preparation process, so that the prepared fluorine-free semi-alicyclic polyimide has better heat resistance and mechanical properties, and significantly improves the glass transition temperature of the polyimide without reducing the light transmittance.

[0027] (2) Through the design of semi-alicyclic structure, the conjugation degree of molecular chain is reduced while avoiding the yellowing defect of high aromatic ring, and the fluorine element is completely excluded at present, so that the environmental risk and performance imbalance of fluorine-containing are solved, and the heat resistance is further improved at the same time. The effects can be achieved: 1, high transparency: the semi-alicyclic structure effectively inhibits intramolecular / electron transition, the visible light transmittance is more than 90%, and the yellowing index (YI) is less than 2; 2, excellent thermal stability: the glass transition temperature (Tg) is greater than 410 DEG C, and the heat resistance is better. 3, good mechanical properties: the tensile strength is greater than or equal to 140 MPa, and the elongation at break is greater than or equal to 20%, meeting the mechanical requirements of flexible devices; 4, environmental protection: no fluorine monomer is added, and it is green and environmentally friendly. DETAILED DESCRIPTION

[0028] The various exemplary embodiments of the present application will now be described in detail, which should not be considered as limiting the present application, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present application.

[0029] It should be understood that the terms described in the present application are only for describing the specific embodiments, and are not used to limit the present application. In addition, for the numerical range in the present application, it should be understood that each intermediate value between the upper limit and the lower limit of the range is also specifically disclosed. Each smaller range between any stated value or intermediate value in the stated range and any other stated value or intermediate value in the stated range is also included in the present application. The upper limit and the lower limit of these smaller ranges can be independently included or excluded from the range.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application pertains. Although preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials in connection with which the documents are concerned. In the event of any conflict between the content of this specification and any document incorporated by reference, the content of this specification will control.

[0031] Various modifications and changes can be made to the specific implementation of the present application described in the specification without departing from the scope or spirit of the application. Other implementations of the present application will be apparent to those skilled in the art from consideration of the specification and practice of the application. The specification and examples are illustrative only.

[0032] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having" or the like are open-ended terms that are intended to mean including, but not limited to.

[0033] In the following examples, the raw materials used are commercially available or prepared by conventional methods in the art, unless otherwise specified.

[0034] Example 1-Example 4 A heat-resistant fluorine-free semi-cycloaliphatic polyimide Prepared by polymerization of diamine and dianhydride, the composition is shown in Table 1 below.

[0035] The preparation method of Example 1 is as follows: (1) Mix diamine, dianhydride and N-methyl pyrrolidone (added amount is 5 times the total molar amount of diamine and dianhydride) at 10°C to obtain a polyimide resin; (2) Mix the polyimide resin obtained in step (1) with additives (3-ethynylaniline and N-ethynylaniline, molar ratio is 1:1), the additive is added in an amount of 0.5% of the total molar amount of diamine and dianhydride, and is heated and dehydrated under argon protection according to the following temperature rising process to obtain a polyimide; First stage: 25-100°C, heating rate 2°C / min; 100°C for 40 min; Second stage: 100-200°C, heating rate 3°C / min; 200°C for 25 min; Third stage: 200-300°C, heating rate 1°C / min; 300°C for 50 min.

[0036] The preparation method of Example 2 is as follows: (1) Mix diamine, dianhydride and N-methyl pyrrolidone (added amount is 5 times the total molar amount of diamine and dianhydride) at 10°C to obtain a polyimide resin; (2) Mix the polyimide resin obtained in step (1) with additives (3-ethynylaniline and N-ethynylaniline, molar ratio is 0.5:1), the additive is added in an amount of 0.5% of the total molar amount of diamine and dianhydride, and is heated and dehydrated under argon protection according to the following temperature rising process to obtain a polyimide; First stage: 25-100°C, heating rate 1°C / min; 100°C for 40 min; Second stage: 100-200°C, heating rate 2°C / min; 200°C for 25 min; Third stage: 200-300°C, heating rate 1°C / min; 300°C for 50 min.

[0037] The preparation method of Example 3 is as follows: (1) mixing diamine, dianhydride and N-methyl pyrrolidone (the added amount is 5 times of the total molar amount of diamine and dianhydride) at 10℃ to obtain a polyimide resin; (2) mixing the polyimide resin obtained in step (1) with additives (3-ethynylaniline and N-ethynylaniline, molar ratio is 1:1.5) and the added amount of additives is 0.5% of the total molar amount of diamine and dianhydride, and dehydrating under the following temperature rising process under argon protection to obtain a polyimide; First stage: 25-100℃, temperature rising rate 3℃ / min; 100℃ for 30min; Second stage: 100-200℃, temperature rising rate 4℃ / min; 200℃ for 30min; Third stage: 200-300℃, temperature rising rate 2℃ / min; 300℃ for 30min.

[0038] Example 4 The preparation method is the same as that of Example 1.

[0039] Table 1

[0040] Comparative Example 1 The difference from Example 1 is that the temperature rising process is different, specifically as follows: First stage: 25-100℃, temperature rising rate 4℃ / min; 100℃ for 20min; Second stage: 100-200℃, temperature rising rate 1℃ / min; 200℃ for 40min; Third stage: 200-300℃, temperature rising rate 3℃ / min; 300℃ for 20min.

[0041] Comparative Example 2 The difference from Example 1 is that the temperature rising process is different, specifically as follows: First stage: 25-150℃, temperature rising rate 2℃ / min; 150℃ for 40min; Second stage: 150-300℃, temperature rising rate 3℃ / min; 300℃ for 25min.

[0042] Comparative Example 3 The difference from Example 1 is that the first diamine is replaced by 2,2'-bis(trifluoromethyl)-4,4'-diamino diphenyl ether (6FODA).

[0043] Comparative Example 4 The difference from Example 1 is that the molar ratio of 3-ethynylaniline and N-ethynylaniline in the additive in step (2) is 1:0.

[0044] Comparative Example 5 The difference from Example 1 is that the molar ratio of 3-ethynylaniline and N-ethynylaniline in the additive of step (2) is 2:1.

[0045] Effect experiment The film performance test method is as follows: (1) The light transmittance (Tr 550nm), yellowness index, and haze of the polyimide film are tested by X-rite Ci7800 spectrophotometer. (2) The tensile strength, elongation at break, and elastic modulus of the polyimide film are tested by Shimadzu AG-X plus, 1KN, with a test speed of 5mm / min, a sample size of 10mm wide*15mm long, a test gauge of 50mm, and a gauge of 20mm. (3) The glass transition temperature (Tg) is measured by dynamic mechanical analyzer (DMA850) under the following test conditions: The measurement is carried out under a load of 0.05N and a heating rate of 3℃ / min in a nitrogen atmosphere at a temperature range of 200-400℃, and the inflection point of the curve with the maximum value is recorded as the glass transition temperature. (4) The heat shrinkage (dimensional stability) is tested according to GB / T 13542.2-2009 "Film for electrical insulation Part 2: Test methods" (150℃), and the test instrument is E04501 type 2.5 dimension (CNC image tester).

[0046] The results obtained are shown in Table 2.

[0047] Table 2

[0048] As can be seen from the data in Table 2, the heat-resistant fluorine-free semi-cycloaliphatic polyimide prepared by the example of the present application not only has good mechanical properties but also has better heat resistance, and has a higher glass transition temperature.

[0049] Finally, it should be noted that the above content is only used to illustrate the technical solutions of the present application, and is not a limitation on the protection scope of the present application. Simple modifications or equivalent replacements of the technical solutions of the present application made by those skilled in the art do not deviate from the essence and scope of the technical solutions of the present application.

Claims

1. A heat-resistant fluorine-free semi-alicyclic polyimide, characterized in that: The semi-alicyclic polyimide composition is prepared by polymerization of diamine and dianhydride; The molar ratio of the total amount of diamine to the total amount of dianhydride is 0.9-1.1:1; The diamine comprises a first diamine and a second diamine; The first diamine is 4,4'-methylenebis(2,6-diethylaniline) and / or 4,4'-methylenebis(2-ethyl)aniline; the second diamine is 4,4'-diaminodiphenyl ether and / or 4,4'-diaminobenzanilide; The dianhydride is a dianhydride that does not contain fluorine.

2. The semi-alicyclic polyimide according to claim 1, characterized in that The first diamine is 4,4'-methylenebis(2,6-diethylaniline), and the second diamine is 4,4'-diaminodiphenyl ether.

3. The semi-alicyclic polyimide according to claim 1, wherein The molar ratio of the first diamine to the second diamine is 3-5:5-8.

4. The semi-alicyclic polyimide according to claim 1, characterized in that The dianhydride is a dianhydride containing a bulky side group, and the bulky side group is selected from one of fluorene, phthalic acid, o-phenylimine, and cyclododecyl.

5. The semi-alicyclic polyimide according to claim 4, characterized in that The dianhydride is selected from one of 2,2'-dichloro-4,4',5,5'-biphenyltetracarboxylic dianhydride, dicyclohexyl-2,3',3,4'-tetracarboxylic dianhydride and dicyclohexyl-2,2',3,3'-tetracarboxylic dianhydride.

6. The method for preparing the semi-alicyclic polyimide composition according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) mixing diamine, dianhydride and solvent at 0-25°C to obtain polyimide resin; (2) The polyimide resin obtained in step (1) is mixed with additives, and the mixture is heated and dehydrated under the protection of an inert gas to obtain polyimide.

7. The preparation method according to claim 6, characterized in that The additive in step (2) is a mixture of 3-ethynylaniline and N-ethynylaniline, with a molar ratio of 0.5-1:1-1.

5.

8. The preparation method according to claim 6, characterized in that The solvent described in step (1) is selected from at least one of N-methylpyrrolidone, N,N-dimethylformamide, γ-valerolactone, methyltetrahydrofuran, and dimethylacetamide.

9. The preparation method according to claim 6, characterized in that The heating in step (2) is performed in stages. Specifically, the staged heating is as follows: The first stage: 25-100℃, heating rate 1-3℃ / min; keep warm at 100℃ for 30-50min; The second stage: 100-200℃, heating rate 2-4℃ / min; keep at 200℃ for 20-30min; The third stage: 200-300℃, heating rate 1-2℃ / min; keeping at 300℃ for 30-60min.

10. Use of the semi-alicyclic polyimide according to any one of claims 1 to 5 or the semi-alicyclic polyimide prepared by the preparation method according to any one of claims 6 to 9 in the preparation of a polyimide film.

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