A kind of polyimide with low expansion coefficient and preparation method thereof

Abstract

The present invention provides a polyimide with a low expansion coefficient and a preparation method thereof, wherein the polyimide is selected from at least one of the compounds shown in structural formulas 1 to 9. The preparation method comprises the following steps: mixing a diamine monomer, a dianhydride monomer, a catalyst, an entrainer, a solvent and an auxiliary agent, fully dissolving, reacting at 150°C to 250°C for 10h to 25h, adding methanol to form a precipitate, filtering, washing the solid with methanol, and then vacuum drying to obtain the polyimide. The present invention introduces a suitable diamine monomer (such as 2,4-dihydrazine-5-nitropyrimidine) on the main chain of the polyimide polymer, introduces multiple hydrogen bond donors and acceptors such as multiple amine groups, imino groups and nitro groups into the diamine monomer, and simultaneously forms an intramolecular and intermolecular hydrogen bond network, so that the thermal expansion coefficient of the polyimide film prepared by the polyimide is greatly reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of polyimide materials, and in particular relates to a polyimide with a low expansion coefficient and a preparation method thereof. Background Art

[0002] Transparent polyimide (CPI) is a kind of organic polymer containing an imide ring (-CO-NR-CO-) in the main chain. Due to its high optical transparency and heat resistance, it is widely used in flexible substrates, electronic integrated circuits, aerospace and other fields. However, the polyimide film prepared from polyimide currently has the disadvantage of a high thermal expansion coefficient, which needs to be further improved. Summary of the invention

[0003] Based on this, the object of the present invention is to provide a polyimide, wherein the polyimide film prepared by the polyimide has the advantage of a low thermal expansion coefficient.

[0004] To achieve the above object, the present invention adopts the following technical solution.

[0005] A polyimide, wherein the polyimide is selected from at least one of the compounds shown in the following structural formula:

[0006]

[0007] In some embodiments, the polyimide is selected from at least one of the compounds shown in the following structural formula:

[0008]

[0009] The present invention also provides a method for preparing the polyimide as described above, wherein the method comprises the following steps: mixing a diamine monomer, a dianhydride monomer, a catalyst, an azeotropic agent, a solvent and an auxiliary agent, fully dissolving them, reacting them at 150° C. to 250° C. for 10 h to 25 h, adding methanol to form a precipitate, filtering, washing the solid with methanol, and then vacuum drying to obtain the polyimide; the diamine monomer is selected from at least one of the following compounds:

[0010]

[0011] The dianhydride monomer is selected from at least one of the following compounds:

[0012]

[0013] In some embodiments, the molar ratio of the diamine monomer to the dianhydride monomer is 1:1.

[0014] In some embodiments, the reaction is carried out at 180° C. to 210° C. for 15 h to 20 h.

[0015] In some embodiments, the vacuum drying condition is: drying at 120°C to 160°C for 20h to 30h.

[0016] In some embodiments, the catalyst is selected from isoquinoline; and / or, the azeotropic agent is selected from toluene; and / or, the solvent is selected from N-methylpyrrolidone; and / or, the auxiliary agent is selected from m-cresol.

[0017] The present invention also provides a polyimide film, which is prepared from the polyimide described above.

[0018] In some embodiments, the solid content of polyimide in the polyimide film is 5 wt % to 10 wt %.

[0019] In some embodiments, the thermal expansion coefficient of the polyimide film is 8.7 ppm / K-12.9 ppm / K.

[0020] In some embodiments, the glass transition temperature of the polyimide film is 391°C to 423°C.

[0021] The invention provides a polyimide, which is prepared from a suitable diamine monomer and a dianhydride monomer. A suitable diamine monomer (for example, 2,4-dihydrazine-5-nitropyrimidine) is introduced into the main chain of a polyimide polymer, and multiple hydrogen bond donors and acceptors such as multiple amine groups, imine groups and nitro groups are introduced into the diamine monomer, and intramolecular and intermolecular hydrogen bond networks are formed at the same time, so that the thermal expansion coefficient of a polyimide film prepared from the polyimide is greatly reduced. DETAILED DESCRIPTION

[0022] The experimental methods in the following examples of the present invention, where no specific conditions are specified, are usually carried out under conventional conditions or under conditions recommended by the manufacturers. The various commonly used chemical reagents used in the examples are all commercially available products.

[0023] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0024] The terms "including" and "having" and any variations thereof of the present invention are intended to cover non-exclusive inclusions. For example, a process, method, device, product or equipment comprising a series of steps is not limited to the listed steps or modules, but may optionally include steps not listed, or may optionally include other steps inherent to these processes, methods, products or equipment.

[0025] In the present invention, the term "multiple" refers to two or more than two. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0026] The following describes the invention in conjunction with specific embodiments.

[0027] Example 1

[0028] This embodiment provides a polyimide film, which is prepared by the following method:

[0029] In a sealed 500mL three-necked flask with a water separator, add compound a: 2,4-dihydrazine-5-nitropyrimidineaniline (2.406g, 13mmol), compound d: 1,4,5,8-naphthalenetetracarboxylic anhydride (3.484g, 13mmol), 0.2ml isoquinoline, 5mL toluene, 45mL m-cresol and 200ml N-methylpyrrolidone, purge with nitrogen for 15min, stir the system at room temperature for 1h to fully dissolve, then heat to 200℃ and react for 18h. As the reaction proceeds, the water and toluene generated by the reaction form an azeotrope and are carried into the water separator by nitrogen. Among them, compound a and compound d are:

[0030]

[0031] After the reaction is completed, the mixture is cooled to room temperature and 500 ml of methanol is added. A large amount of filamentous precipitates appear. The solid is filtered and washed three times with methanol. The solid is vacuum dried at 150° C. for 24 h to obtain a filamentous polyimide precipitate. The structural formula is shown in Structural Formula 1:

[0032]

[0033] The dried filamentous polyimide precipitate was redissolved in anhydrous DMF, the solid content was controlled to 7.5wt%, and deaeration was performed. Then the polyimide glue was poured onto the substrate, the height of the stainless steel scraper was adjusted, and the polyimide glue was baked at four temperatures of 50°C, 120°C, 160°C, and 200°C, respectively, with a total baking time of 240 minutes, to obtain a polyimide film with the following structure, intramolecular and intermolecular hydrogen bond network:

[0034]

[0035] Example 2

[0036] This embodiment provides a polyimide film, which is prepared by the following method:

[0037] In a sealed 500mL three-necked flask with a water separator, add 13mmol of compound a, 13mmol of compound e, 0.2ml of isoquinoline, 5mL of toluene, 45mL of m-cresol and 200ml of N-methylpyrrolidone, purge with nitrogen for 15min, stir the system at room temperature for 1h to fully dissolve, and then heat to 180℃ to react for 20h. As the reaction proceeds, the water and toluene generated by the reaction form an azeotrope and are carried into the water separator by nitrogen. Among them, compound a and compound e are:

[0038]

[0039] After the reaction was completed, the mixture was cooled to room temperature and 500 ml of methanol was added. A large amount of filamentous precipitates appeared. The solid was filtered and washed three times with methanol. The solid was vacuum dried at 150° C. for 24 h to obtain a filamentous polyimide precipitate. The structural formula is shown in Structural Formula 4:

[0040]

[0041] The dried filamentous polyimide precipitate was redissolved in anhydrous DMF, the solid content was controlled to be 10wt%, and the polyimide glue was poured onto the substrate. The height of the stainless steel scraper was adjusted and the polyimide film was baked at four temperatures of 50°C, 120°C, 160°C, and 200°C for a total baking time of 240 minutes to obtain the polyimide film.

[0042] Example 3

[0043] This embodiment provides a polyimide film, which is prepared by the following method:

[0044] In a sealed 500mL three-necked flask with a water separator, add 13mmol of compound b, 13mmol of compound f, 0.2ml of isoquinoline, 5mL of toluene, 45mL of m-cresol and 200ml of N-methylpyrrolidone, purge with nitrogen for 15min, stir the system at room temperature for 1h to fully dissolve, and then heat to 210℃ to react for 16h. As the reaction proceeds, the water and toluene generated by the reaction form an azeotrope and are carried into the water separator by nitrogen. Among them, compound b and compound f are:

[0045]

[0046] After the reaction was completed, the mixture was cooled to room temperature and 500 ml of methanol was added. A large amount of filamentous precipitates appeared. The solid was filtered and washed three times with methanol. The solid was vacuum dried at 150° C. for 24 h to obtain a filamentous polyimide precipitate. The structural formula is shown in Structural Formula 8:

[0047]

[0048] The dried filamentous polyimide precipitate was redissolved in anhydrous DMF, the solid content was controlled to be 5wt%, and the polyimide glue was poured onto the substrate. The height of the stainless steel scraper was adjusted and the polyimide film was baked at four temperatures of 50°C, 120°C, 160°C, and 200°C for a total baking time of 240 minutes to obtain the polyimide film.

[0049] Comparative Example 1

[0050] This comparative example provides a polyimide film, which is prepared by the following method:

[0051] In a sealed 500mL three-necked flask with a water separator, add 13mmol of 4,4'-diaminobiphenyl, 13mmol of 1,4,5,8-naphthalenetetracarboxylic anhydride, 0.2ml of isoquinoline, 5mL of toluene, 45mL of m-cresol and 200ml of N-methylpyrrolidone, purge with nitrogen for 15min, stir the system at room temperature for 1h to fully dissolve, then heat to 200℃ and react for 18h. As the reaction proceeds, the water and toluene generated by the reaction form an azeotrope and are carried into the water separator by nitrogen.

[0052] After the reaction was completed, the mixture was cooled to room temperature and 500 ml of methanol was added. A large amount of filamentous precipitates appeared. The solid was filtered and washed three times with methanol. The solid was dried in vacuum at 150° C. for 24 h to obtain filamentous polyimide precipitates.

[0053] The dried filamentous polyimide precipitate was redissolved in anhydrous DMF, the solid content was controlled to 7.5wt%, and degassing was performed. Then the polyimide glue was poured onto the substrate, the height of the stainless steel scraper was adjusted, and the polyimide film was baked at four temperatures of 50°C, 120°C, 160°C, and 200°C for a total baking time of 240 minutes to obtain the polyimide film.

[0054] The thermal expansion coefficient and glass transition temperature of the polyimide films prepared in the above examples and comparative examples were tested: the thermal expansion coefficient was tested by thermal analysis, and the glass transition temperature was tested by differential scanning calorimetry (DSC).

[0055] The results are shown in Table 1:

[0056] Table 1

[0057] Group Thermal expansion coefficient (ppm / K) Glass transition temperature Example 1 9.1 391℃ Example 2 8.7 405℃ Example 3 12.9 423℃ Comparative Example 1 45.6 341℃

[0058] It can be seen from the above results that the polyimide film prepared by the present invention has a low thermal expansion coefficient of 9.1 ppm / K to 12.9 ppm / K, and a glass transition temperature of 391°C to 423°C.

[0059] Compared with Example 1, the polyimide synthesis monomer in Comparative Example 1 is replaced with 4,4'-diaminobiphenyl, resulting in a significant increase in the thermal expansion coefficient of the prepared polyimide film and a significant decrease in the glass transition temperature.

[0060] In summary, the present invention introduces a suitable diamine monomer (such as 2,4-dihydrazino-5-nitropyrimidine) into the main chain of the polyimide polymer, introduces multiple hydrogen bond donors and acceptors such as multiple amine groups, imine groups and nitro groups into the diamine monomer, and simultaneously forms an intramolecular and intermolecular hydrogen bond network, so that the thermal expansion coefficient of the polyimide film prepared by the polyimide is greatly reduced.

[0061] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0062] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A polyimide, characterized in that: The polyimide is selected from at least one of the following structural formulas: Where n is the degree of polymerization; The preparation method of the polyimide comprises the following steps: mixing a diamine monomer, a dianhydride monomer, a catalyst, an azeotropic agent, a solvent and an auxiliary agent, fully dissolving them, reacting them at 150° C. to 250° C. for 10 h to 25 h, adding methanol to form a precipitate, filtering, washing the solid with methanol, and then vacuum drying to obtain the polyimide; the diamine monomer is selected from at least one of the following compounds: The dianhydride monomer is selected from at least one of the following compounds:

2. The polyimide according to claim 1, characterized in that The polyimide is selected from at least one of the following structural formulas:

3. The method for preparing a polyimide according to claim 1 or 2, characterized in that: The preparation method comprises the following steps: mixing a diamine monomer, a dianhydride monomer, a catalyst, an azeotropic agent, a solvent and an auxiliary agent, fully dissolving them, reacting them at 150° C. to 250° C. for 10 h to 25 h, adding methanol to form a precipitate, filtering, washing the solid with methanol, and then vacuum drying to obtain the polyimide; the diamine monomer is selected from at least one of the following compounds: The dianhydride monomer is selected from at least one of the following compounds:

4. The preparation method according to claim 3, characterized in that: The molar ratio of the diamine monomer to the dianhydride monomer is 1:

1.

5. The preparation method according to claim 3, characterized in that: React at 180℃~210℃ for 15h~20h.

6. The preparation method according to claim 3, characterized in that: The vacuum drying conditions are: drying at 120° C. to 160° C. for 20 h to 30 h.

7. The preparation method according to claim 3, characterized in that: The catalyst is selected from isoquinoline; and / or the entrainer is selected from toluene; and / or the solvent is selected from N-methylpyrrolidone; and / or the auxiliary agent is selected from m-cresol.

8. A polyimide film, characterized in that: The polyimide film is prepared from the polyimide according to claim 1 or 2.

9. The polyimide film according to claim 8, characterized in that During the preparation of the polyimide film, polyimide is dissolved in anhydrous DMF, and the solid content is controlled to be 5wt% to 10wt%.

10. The polyimide film according to claim 8, wherein The thermal expansion coefficient of the polyimide film is 8.7 ppm / K-12.9 ppm / K; and / or the glass transition temperature of the polyimide film is 391° C.-423° C.

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