Polyimides, process for their preparation and use thereof

Abstract

The application relates to the field of high polymer materials, and discloses a polyimide as well as a preparation method and application thereof. The preparation method comprises the following steps: reacting diamine and dianhydride in the presence of an ether solvent to obtain a polyimide solution, and obtaining the polyimide through precipitation; wherein the ether solvent is an aromatic ether containing 1-3 ether bonds; and the reaction conditions comprise the following: the reaction temperature is 120-220 DEG C; and the reaction time is 3-12 h. The ether solvent used in the method has good solubility to dianhydride, diamine and a prepolymer generated in the reaction, so that the reaction is more efficient; and the polyimide prepared by the method has high molecular weight, processability and good mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of polymer materials, specifically to a polyimide, its preparation method, and its applications. Background Technology

[0002] Polyimide is a high-performance polymer with a glass transition temperature greater than 180°C. It possesses high strength, heat resistance, and chemical resistance, making it widely applicable in fields such as automotive, telecommunications, aerospace, power / electronics, transportation, and healthcare. US4680373 discloses a method for preparing polyimide by polymerizing aromatic diamines and aromatic dianhydrides in aprotic polar solvents such as o-dichlorobenzene using a phosphorus-based organic salt as a catalyst. However, phosphorus-based catalysts are costly, and solvent-resistant polyimides cannot be formed to high molecular weight using this method. Therefore, there is an urgent need to develop a method for preparing high molecular weight polyimides. Summary of the Invention

[0003] The purpose of this invention is to overcome the problem that existing methods for preparing polyimides are difficult to obtain high molecular weight polyimides. This invention provides a polyimide, its preparation method, and its application. The ether solvent used in this method has good solubility for dianhydrides, diamines, and the prepolymers generated in the reaction, making the reaction more efficient. The polyimide prepared by this method has high molecular weight, processability, and good mechanical properties.

[0004] To achieve the above objectives, a first aspect of the present invention provides a method for preparing polyimide, characterized in that the method comprises:

[0005] In the presence of an ether solvent, a diamine and a dianhydride are reacted to obtain a polyimide solution, which is then precipitated to obtain the polyimide.

[0006] The ether solvent is an aromatic ether containing 1-3 ether bonds;

[0007] The reaction conditions include: a reaction temperature of 120-220℃ and a reaction time of 3-12h.

[0008] A second aspect of the present invention provides a polyimide prepared by the preparation method described in the first aspect.

[0009] The third aspect of the present invention provides the application of a polyimide prepared by the preparation method described in the first aspect or the polyimide polymer material described in the second aspect.

[0010] Through the above technical solutions, the polyimide, its preparation method, and its application provided by the present invention achieve the following beneficial effects:

[0011] The ether solvent used in this invention has good solubility for dianhydrides, diamines, and the prepolymers produced in the reaction, making the reaction more efficient. The polyimide prepared by this method has high molecular weight, processability, and good mechanical properties.

[0012] This invention obtains high molecular weight polyimide through a one-step reaction without the use of a catalyst, thereby reducing the preparation cost of polyimide. Detailed Implementation

[0013] 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.

[0014] The first aspect of this invention provides a method for preparing polyimide, characterized in that the method comprises:

[0015] In the presence of an ether solvent, a diamine and a dianhydride are reacted to obtain a polyimide solution, which is then precipitated to obtain the polyimide.

[0016] The ether solvent is an aromatic ether containing 1-3 ether bonds;

[0017] The reaction conditions include: a reaction temperature of 120-220℃ and a reaction time of 3-12h.

[0018] The ether solvent used in the preparation method of the present invention has good solubility for dianhydrides, diamines and the prepolymers generated in the reaction, making the reaction more efficient. The polyimide prepared by this method has high molecular weight, processability and good mechanical properties.

[0019] This invention obtains high molecular weight polyimide through a one-step reaction without the use of a catalyst, thereby reducing the preparation cost of polyimide.

[0020] According to the present invention, the ether solvent contains one and / or two ether bonds, and when the above-mentioned type is satisfied, it has better solubility for dianhydrides, diamines and prepolymers generated in the reaction, thereby making the reaction more efficient.

[0021] According to the present invention, the ether solvent comprises compounds with structures shown in formula (1) and / or formula (2):

[0022]

[0023] Wherein, R1 is a C1-C3 alkyl group; R2-R5 are each independently H or OR', and R2-R5 are not simultaneously H or OR', and R' is a C1-C3 alkyl group.

[0024] In this invention, when the aromatic ether meets the above-mentioned type, it has better solubility for dianhydrides, diamines, and prepolymers generated in the reaction, which is more conducive to the formation of high molecular weight polyimide.

[0025] In some specific embodiments of the present invention, the aromatic ether is selected from anisole (R7 is -OCH3, R8-R...). 10 (R7 and R8 are -OCH3, R9 and R8 are -OCH3) 10 (H) and p-phenylenedimethyl ether (R7 and R) 10 It is -OCH3, and R8 and R9 are at least one of H).

[0026] According to the present invention, the diamine is an aromatic diamine.

[0027] According to the present invention, the aromatic diamine is selected from at least one of 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl ether, m-phenylenediamine and p-phenylenediamine.

[0028] In one embodiment of the present invention, the aromatic diamine is a combination of 4,4'-diaminodiphenyl ether and 4,4'-diaminodiphenyl sulfone. The present invention does not particularly limit the molar ratio of the two, for example, the molar ratio of 4,4'-diaminodiphenyl ether and 4,4'-diaminodiphenyl sulfone is 1:0.1-10.

[0029] According to the present invention, the dianhydride is an aromatic dianhydride.

[0030] According to the present invention, the aromatic dianhydride comprises at least one compound with the structure shown in formula (3)-(8):

[0031]

[0032] Among them, formula (5) is 4,4'-oxobisphthalic anhydride, formula (6) is 3,4'-oxobisphthalic anhydride, formula (7) is 3,3'-oxobisphthalic anhydride, formula (8) is 3,3',4,4'-benzophenone tetracarboxylic dianhydride, formula (9) is biphenyl dianhydride, and formula (10) is 2,2-bis(4-(3,4-dicarboxyphenoxy)benzyl)propane dianhydride.

[0033] In one embodiment of the present invention, the aromatic dianhydride is a combination of 3,3',4,4'-benzophenone tetracarboxylic dianhydride and 4,4'-oxophthalic anhydride; the present invention does not particularly limit the molar ratio of the two, for example, the molar ratio of 3,3',4,4'-benzophenone tetracarboxylic dianhydride and 4,4'-oxophthalic anhydride is 1:0.1-10.

[0034] According to the present invention, the reaction conditions include: a reaction temperature of 160-200℃ and a reaction time of 3-6 hours. When the reaction conditions meet the above range, it is beneficial to control the molecular weight of the polyimide, so that the prepared polyimide has good mechanical properties and further optimized processing performance.

[0035] According to the present invention, the molar ratio of the diamine and the dianhydride is 1:0.95-1; when the above range is met, it is beneficial for the two to carry out the polymerization reaction and to control the molecular weight of the polyimide; when preferably 1:0.94-0.96, it is beneficial to control the molecular weight of the polyimide within a reasonable range, so that the prepared polyimide has both good mechanical properties and processing properties.

[0036] According to the present invention, based on the total weight of the dianhydride, the diamine, and the ether solvent, the total content of the dianhydride and the diamine is 10-50 wt%. When the above range is met, it is beneficial to generate high molecular weight polyimide. When it is preferably 15-40 wt%, it is beneficial to control the molecular weight of polyimide by controlling the solubility of the dianhydride, the diamine, and the prepolymer generated in the reaction, so that the prepared polyimide has good mechanical properties and further optimized processing performance.

[0037] According to the present invention, the method further includes adding a capping agent to the reaction system.

[0038] According to the present invention, the molar ratio of the diamine to the capping agent is 1:0.01-0.25; when the above range is met, it is beneficial for the capping agent to react with the end groups of the polymer, thereby improving the thermal stability of the polyimide.

[0039] According to the present invention, the capping agent is selected from at least one of phthalic anhydride (C8H4O3), aniline and methylamine.

[0040] According to the present invention, based on the total weight of the dianhydride, the diamine, the capping agent, and the ether solvent, the total content of the dianhydride, the diamine, and the capping agent is 10-50 wt%. When the above range is met, it is beneficial to generate high molecular weight polyimide. When it is preferably 15-40 wt%, it is beneficial to control the molecular weight of polyimide by controlling the solubility of the dianhydride, the diamine, and the prepolymer generated in the reaction, so that the prepared polyimide has good mechanical properties and further optimized processing performance.

[0041] According to the present invention, the reaction is carried out under the protection of nitrogen or an inert atmosphere, thereby protecting the raw materials from oxidation.

[0042] According to the present invention, the precipitation includes the following steps: cooling the polyimide solution to room temperature; and / or adding a precipitant to the polyimide solution.

[0043] In this invention, the ether solvent provides a simpler post-processing method. For solvent-resistant polyimide, when a certain molecular weight is reached, the polyimide precipitates in the solvent in powder form, eliminating the need to add a precipitant during post-processing and improving production cycle efficiency.

[0044] According to the present invention, when using a precipitant, the present invention does not particularly limit the type of precipitant, for example, the precipitant is water or ethanol.

[0045] According to the present invention, the method further includes washing and drying the precipitated polyimide.

[0046] According to the present invention, there is no particular limitation on the washing method. For example, ethanol is used as the eluent, and the washing is performed once or multiple times.

[0047] According to the present invention, the drying method is not particularly limited, for example, drying at 120-150°C for 6-12 hours in a vacuum oven.

[0048] A second aspect of the present invention provides a polyimide prepared by the preparation method described in the first aspect.

[0049] According to the present invention, the polyimide prepared by the present invention has a viscosity of 0.3-0.8 dL / g at 30°C, preferably 0.33-0.5 dL / g;

[0050] And / or, the polyimide has a melt index of 0.5-20 g / 10 min at 350 °C and a load of 12.5 kg, preferably 3-13 g / 10 min;

[0051] And / or, the polyimide, after molding, has a tensile strength ≥90MPa, a flexural strength ≥120MPa, and a flexural modulus ≥2.5GPa.

[0052] In this invention, the molecular weight of polyimide is evaluated by measuring its viscosity. The viscosity of polyimide is measured at 30°C using N-methylpyrrolidone (NMP) as a solvent. Under certain conditions, the viscosity of polyimide is directly proportional to its molecular weight.

[0053] In this invention, the processing performance of polyimide is represented by its melt index at 350°C and a load of 12.5 kg. Under the above conditions, a melt index in the range of 0.5-20 g / 10 min indicates that the polyimide is processable, and a melt index preferably of 3-13 g / 10 min indicates that the polyimide has good processing performance.

[0054] This invention provides an exemplary molding method, comprising: drying the prepared polyimide powder at 150-170℃ for 7-8 hours, placing it in a mold for molding, maintaining the pressure at 200-300℃ and 5-10MPa for 15-20 minutes, and then maintaining the pressure at 300-350℃ and 10-15MPa for 10-15 minutes; then turning off the pressure, cooling, demolding, and testing the mechanical properties of the sample. This invention employs a two-stage molding process to avoid the formation of pores in the product.

[0055] The third aspect of this invention provides the application of the polyimide prepared by the preparation method described in the first aspect or the polyimide described in the second aspect in polymer materials.

[0056] This invention does not particularly limit the type of polymer material, such as high-strength and dimensionally stable connectors, housings of ordinary and miniature relays, circuit boards, coils, flexible circuits, mirrors, and high-precision dense fiber optic components.

[0057] The present invention will be described in detail below through embodiments. In the following embodiments and comparative examples:

[0058] Viscosity: The polyimides prepared in the examples and comparative examples were measured at 30°C using N-methylpyrrolidone (NMP) as solvent.

[0059] Tensile strength: Measured according to GB / T 1040.2-2006.

[0060] Bending strength: Measured according to GB / T 9341-2008.

[0061] Flexural modulus: Measured according to GB / T 9341-2008.

[0062] Melt flow index: Measured according to GB / T 3682-2000.

[0063] Dihydrides: 2,2-bis(4-(3,4-dicarboxyphenoxy)benzyl)propane dianhydride has the structure shown in formula (10); 4,4'-oxobisphthalic anhydride has the structure shown in formula (5); 3,4'-oxobisphthalic anhydride has the structure shown in formula (6); 3,3',4,4'-benzophenone tetracarboxylic dianhydride has the structure shown in formula (8).

[0064] Ether solvents: Anisole (R7 is -OCH3, R8 is -R) 10 (H), containing one ether bond; p-phenylenedimethyl ether (R7 and R) 10 It is -OCH3, R8 and R9 are H), and contains two ether bonds.

[0065] The raw materials used in the following examples and comparative examples are commercially available conventional products.

[0066] Example 1

[0067] (1) Under nitrogen protection, 4,4'-diaminodiphenyl sulfone (2.483 g, 10 mmol), 2,2-bis(4-(3,4-dicarboxyphenoxy)benzyl)propane dianhydride (4.9447 g, 9.5 mmol), phthalic anhydride (C8H4O3) (0.2962 g, 2 mmol) and 18 g of anisole were mixed, heated to 170 °C, and reacted under reflux for 6 h to obtain a polyimide solution;

[0068] (2) Cool the obtained polyimide solution to room temperature, pour it into ethanol to precipitate solid powder, and filter to obtain solid powder;

[0069] (3) The obtained solid powder was washed twice with ethanol and dried in a vacuum oven at 120°C for 8 hours to obtain polyimide S1.

[0070] Example 2

[0071] (1) Under nitrogen protection, 4,4'-diaminodiphenyl sulfone (24.83 g, 100 mmol), 4,4'-oxobisphthalic anhydride (29.4709 g, 95 mmol), phthalic anhydride (C8H4O3) (2.9622 g, 20 mmol) and 229 g of p-phenylenedimethyl ether were mixed, heated to 200 °C, and reacted for 8 h to obtain an imide solution;

[0072] (2) Cool the obtained polyimide solution to room temperature, precipitate solid powder, and filter to obtain solid powder;

[0073] (3) The obtained solid powder was washed twice with ethanol and dried in a vacuum oven at 120°C for 8 hours to obtain polyimide S2.

[0074] Example 3

[0075] (1) Under nitrogen protection, 4,4'-diaminodiphenyl sulfone (24.83 g, 100 mmol), 3,4'-oxobisphthalic anhydride (29.4709 g, 95 mmol), phthalic anhydride (C8H4O3) (2.9622 g, 20 mmol) and 229 g of p-phenylenediamine were mixed, heated to 190 °C, and reacted for 8 h to obtain a polyimide solution;

[0076] (2) Cool the obtained polyimide solution to room temperature, pour it into ethanol to precipitate solid powder, and filter to obtain solid powder;

[0077] (3) The obtained solid powder was washed twice with ethanol and dried in a vacuum oven at 120°C for 8 hours to obtain polyimide S3.

[0078] Example 4

[0079] (1) Under nitrogen protection, 4,4'-diaminodiphenyl sulfone (22.347 g, 90 mmol), 4,4'-diaminodiphenyl ether (2.002 g, 10 mmol), 4,4'-oxophthalic anhydride (29.4709 g, 95 mmol), phthalic anhydride (C8H4O3) (2.9622 g, 20 mmol) and 227 g of p-phenylenedimethyl ether were mixed, heated to 200 °C, and reacted for 12 h to obtain a polyimide solution;

[0080] (2) Cool the obtained polyimide solution to room temperature, pour it into ethanol to precipitate solid powder, and filter to obtain solid powder;

[0081] (3) The obtained solid powder was washed twice with ethanol and dried in a vacuum oven at 120°C for 8 hours to obtain polyimide S4.

[0082] Example 5

[0083] (1) Under nitrogen protection, 4,4'-diaminodiphenyl sulfone (24.83 g, 100 mmol), 4,4'-oxophthalic anhydride (26.5238 g, 85.5 mmol), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (3.0612 g, 9.5 mmol), phthalic anhydride (C8H4O3) (2.9622 g, 20 mmol) and 230 g of p-phenylenedimethyl ether were mixed, heated to 200 °C, and reacted for 8 h to obtain a polyimide solution;

[0084] (2) Cool the obtained polyimide solution to room temperature, pour it into ethanol to precipitate solid powder, and filter to obtain solid powder;

[0085] (3) The obtained solid powder was washed twice with ethanol and dried in a vacuum oven at 120°C for 8 hours to obtain polyimide S5.

[0086] Example 6

[0087] Polyimide S6 was prepared according to the method of Example 1, except that the amount of solvent used was different from that in Example 1, as detailed in Table 1.

[0088] Example 7

[0089] Polyimide S7 was prepared according to the method of Example 1, except that the reaction time was different from that in Example 1, as detailed in Table 1.

[0090] Examples 8-9

[0091] Polyimide S8-S9 was prepared according to the method of Example 1, except that the reaction temperature, reaction time and solvent amount were different from those in Example 1, as detailed in Table 1.

[0092] Examples 10-11

[0093] Polyimide S10-S11 was prepared according to the method of Example 1, except that the molar ratio of dianhydride and diamine was different from that in Example 1, as detailed in Table 1.

[0094] Comparative Example 1

[0095] Polyimide D1 was prepared according to the method of Example 1, except that the anisole in Example 1 was replaced with o-dichlorobenzene, as detailed in Table 1.

[0096] Comparative Example 2

[0097] Polyimide D2 was prepared according to the method of Example 2, except that the p-phenylenedimethyl ether in Example 2 was replaced with o-dichlorobenzene, as detailed in Table 1.

[0098] Comparative Example 3

[0099] Polyimide D3 was prepared according to the method of Example 1, except that the anisole in Example 1 was replaced with n-pentyl ether, as detailed in Table 1.

[0100] Table 1

[0101]

[0102]

[0103] Note: Raw material content refers to the total mass content of dianhydride, diamine, capping agent, and ether solvent, based on the total weight of dianhydride, diamine, and capping agent; diamine: dianhydride is a molar ratio; diamine: capping agent is a molar ratio.

[0104] Test Example 1

[0105] The viscosity of the polyimides prepared in each example and comparative example was measured, and the specific test results are shown in Table 2.

[0106] Test Example 2

[0107] The melt index of the polyimides prepared in each example and comparative example was determined, and the specific test results are shown in Table 2.

[0108] Test Example 3

[0109] The polyimides prepared in each example and comparative example were molded and then subjected to mechanical property tests. The specific steps were as follows: the prepared polyimide powder was dried at 160℃ for 8 hours, then placed in a mold for molding, and held at 250℃ and 10MPa for 20 minutes, and then held at 350℃ and 15MPa for 15 minutes. Then the pressure was turned off, the temperature was lowered, the mold was removed, and the mechanical properties of the specimens were tested. The specific test results are shown in Table 2.

[0110] Table 2

[0111]

[0112] As can be seen from the results in Table 2, high molecular weight polyimides can be obtained by using the ether solvent of the present invention in Examples 1-11, and the obtained polyimides have processability and good mechanical properties.

[0113] Among them, the polyimides prepared in Examples 2-5 and Comparative Example 2 have solvent resistance and cannot be dissolved at room temperature when viscosity testing is performed; if they are to be dissolved, the temperature needs to be increased to the reaction temperature or above, which will cause the solvent to evaporate (testing needs to be done in an open system under normal pressure). Therefore, the viscosity of the polyimides prepared in Examples 2-5 and Comparative Example 2 cannot be measured, and the molecular weight of the polyimides is indirectly represented by mechanical properties.

[0114] Comparative Examples 1 and 2 failed to produce polyimides with mechanical strength because the solvents used could not dissolve the raw materials and intermediates during the reaction, resulting in the inability of the dianhydride and diamine to react continuously to produce long molecular chains. Consequently, the resulting polyimide powder had a low molecular weight, which prevented it from being molded into test specimens and thus lacked mechanical strength.

[0115] The polyimides prepared in Comparative Examples 1 and 2 had too low molecular weights, resulting in excessive fluidity during melt flow index testing, making it impossible to measure the melt flow index and thus lacking processability. The polyimide prepared in Comparative Example 3 had too high melt flow index and lacked processability.

[0116] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing polyimide, characterized in that, The method includes: reacting a diamine, a dianhydride, and a capping agent in the presence of an ether solvent to obtain a polyimide solution, and then precipitating the polyimide. The ether solvent is an aromatic ether containing 1-3 ether bonds; Wherein, the diamine is selected from at least one of 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl ether, m-phenylenediamine and p-phenylenediamine; the dianhydride is an aromatic dianhydride; the molar ratio of the diamine to the dianhydride is 1:0.94-0.96; Wherein, based on the total weight of the dianhydride, the diamine, and the ether solvent, the total content of the dianhydride and the diamine is 15-40 wt%; The reaction conditions include: a reaction temperature of 160-200℃ and a reaction time of 3-12 h.

2. The preparation method according to claim 1, characterized in that, The ether solvent contains one or two ether bonds.

3. The preparation method according to claim 2, characterized in that, The ether solvents include compounds with structures shown in formula (1) and / or formula (2): Equation (1); Equation (2); Wherein, R1 is a C1-C3 alkyl group; R2-R5 are each independently H or OR', and R2-R5 are not simultaneously H or OR', and R' is a C1-C3 alkyl group.

4. The preparation method according to claim 1, characterized in that, The aromatic dianhydride includes at least one compound with the structure shown in formulas (3) to (8): Equation (3); Equation (4); Equation (5); Equation (6); Equation (7); Equation (8).

5. The preparation method according to any one of claims 1-4, characterized in that, The reaction conditions include a reaction time of 3-6 hours.

6. The preparation method according to any one of claims 1-4, characterized in that, The molar ratio of the diamine to the capping agent is 1:0.01-0.

25.

7. The preparation method according to any one of claims 1-4, characterized in that, The capping agent is selected from at least one of phthalic anhydride, aniline, and methylamine.

8. The preparation method according to any one of claims 1-4, characterized in that, Based on the total weight of the dianhydride, the diamine, the capping agent, and the ether solvent, the total content of the dianhydride, the diamine, and the capping agent is 10-50 wt%. And / or, the reaction is carried out under an inert atmosphere.

9. The preparation method according to claim 8, characterized in that, Based on the total weight of the dianhydride, the diamine, the capping agent, and the ether solvent, the total content of the dianhydride, the diamine, and the capping agent is 15-40 wt%.

10. The preparation method according to any one of claims 1-4, characterized in that, The precipitation process includes the following steps: The polyimide solution is cooled to room temperature; and / or a precipitant is added to the polyimide solution.

11. The preparation method according to claim 10, wherein, The method further includes washing and drying the precipitated polyimide.

12. A polyimide prepared by any one of claims 1-11.

13. The polyimide according to claim 12, characterized in that, The polyimide has a viscosity of 0.3-0.8 dL / g at 30°C; And / or, the polyimide has a melt index of 0.5-20 g / 10min at 350°C and a load of 12.5 kg; And / or, the polyimide, after molding, has a tensile strength ≥90 MPa, a flexural strength ≥120 MPa, and a flexural modulus ≥2.5 GPa.

14. The polyimide according to claim 13, wherein, The viscosity of the polyimide at 30°C is 0.33-0.5 dL / g; And / or, the polyimide has a melt index of 3-13 g / 10 min at 350°C and a load of 12.5 kg.

15. The application of a polyimide prepared by any one of claims 1-11 or a polyimide according to any one of claims 12-14 in high-strength and dimensionally stable connectors, housings of general and miniature relays, circuit boards, coils, flexible circuits, mirrors, and high-precision dense fiber optic components.

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