A low-dielectric, easily soluble polyisoimide adhesive, its preparation method and application

Abstract

The application provides a low-dielectric and easily-dissolved polyisoimide adhesive as well as a preparation method and application thereof. The preparation raw materials of the polyisoimide adhesive include a combination of anhydride, diamine, end-capping agent, dehydrating agent and solvent. Through the collocation of the above-mentioned raw materials, the polyisoimide adhesive has excellent solubility and temperature resistance, and also has a lower curing temperature. Furthermore, the anhydride includes 9,9-bis(trifluoromethyl) xanthene tetra carboxylic dianhydride and / or 2,2'-difluoromethyl-4,4',5,5'-biphenyl tetra carboxylic dianhydride and hexafluoro dianhydride. The fluorine groups are successfully introduced into the structure of the polyisoimide adhesive, thereby effectively reducing the dielectric constant and dielectric loss tangent value of the polyisoimide adhesive, so that the polyisoimide adhesive also has excellent dielectric performance.

Description

Technical Field

[0001] This invention belongs to the field of adhesive technology, specifically relating to a low-dielectric, easily soluble polyisoimide adhesive, its preparation method, and its application. Background Technology

[0002] Polyimide (PI), as a high-performance polymer, has excellent heat resistance, radiation resistance, and electrical properties, and is currently widely used in aerospace, microelectronics, and other technical fields. Furthermore, polyimide adhesives are increasingly favored due to their excellent heat resistance and high-temperature bonding properties. However, due to the large number of rigid groups in the molecular structure, polyimide generally has poor solubility in most solvents, which poses a significant obstacle to the coating process.

[0003] Polyimide adhesives are generally classified into condensation-type, thermoplastic, and addition-type adhesives based on their processing and synthesis methods. Condensation-type polyimide adhesives undergo a curing process that involves the dehydration and cyclization of polyamic acid, resulting in water generation and potential porosity defects, making them unsuitable for large-area bonding. CN108641665A discloses a polyimide adhesive and its preparation method, obtained by curing a polyimide adhesive prepolymer. The raw materials for preparing the polyimide adhesive prepolymer are an aromatic diamine containing a biphenyl structure, an aromatic diamine containing a siloxane structure, an aromatic dianhydride, and a capping agent. The preparation method involves dissolving the polyimide adhesive prepolymer in an organic solvent to obtain a homogeneous solution; coating the homogeneous solution onto the surface of the materials to be bonded; removing the organic solvent; and curing to obtain the polyimide adhesive, thus completing the bonding of the materials. This polyimide adhesive can be applied to the bonding of high-temperature resistant components in fields such as aerospace, precision machinery, and petrochemicals.

[0004] CN103483586A discloses a modified polyimide resin whose molecular structure contains repeating units of the following segments: polysiloxane polyimide segments, alicyclic polyimide segments, and aromatic polyimide segments; and the molar content of the polysiloxane polyimide segments, alicyclic polyimide segments, and aromatic polyimide segments in the chemical formula of the modified polyimide resin is 20-40%, 20-50%, and 30-60%, respectively. This modified polyimide resin can be used as a toughening agent for epoxy resin adhesives, and compared with epoxy adhesives toughened with nitrile rubber, it has superior properties, such as higher heat aging resistance and a higher glass transition temperature.

[0005] However, the polyimide resins provided in the prior art are difficult to combine excellent solubility, temperature resistance, and low curing temperature, while having a high dielectric constant, which limits their application in some electronic devices.

[0006] Therefore, developing a polyisoimide adhesive with excellent solubility, temperature resistance, and low curing temperature and dielectric constant is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the purpose of this invention is to provide a low dielectric and easily soluble polyisoimide adhesive, its preparation method and application. By selecting and matching the raw materials, the polyisoimide adhesive obtained has excellent solubility and temperature resistance, as well as a low curing temperature and dielectric constant.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a low dielectric and easily soluble polyisoimide adhesive, wherein the raw materials for preparing the polyisoimide adhesive include acid anhydride, diamine, end-capping agent, dehydrating agent and solvent;

[0010] The anhydride includes any one or a combination of at least two of 9,9-bis(trifluoromethyl)oxanthracene tetracarboxylic dianhydride, 2,2'-difluoromethyl-4,4',5,5'-biphenyltetracarboxylic dianhydride, or hexafluorodianhydride.

[0011] The polyisoimide adhesive provided by this invention comprises a combination of acid anhydride, diamine, end-capping agent, dehydrating agent, and solvent. The acid anhydride includes any one or at least two of 9,9-bis(trifluoromethyl)oxanthracene tetracarboxylic dianhydride, 2,2'-difluoromethyl-4,4',5,5'-biphenyltetracarboxylic dianhydride, or hexafluorodianhydride. By limiting the acid anhydride to include 9,9-bis(trifluoromethyl)oxanthracene tetracarboxylic dianhydride, 2,2'-difluoromethyl-4,4',5,5'-biphenyltetracarboxylic dianhydride, or hexafluorodianhydride, fluorine groups are successfully introduced into the structure of the polyisoimide adhesive, effectively reducing the dielectric constant and dielectric loss tangent of the polyisoimide adhesive. Simultaneously, through the selection and combination of other components, asymmetric isoimide groups and end-capping agents are successfully introduced, resulting in the polyisoimide adhesive also exhibiting excellent solubility and temperature resistance, as well as a low curing temperature.

[0012] It should be noted that the "low dielectric" in the "low dielectric, easily soluble polyisoimide adhesive" described in this invention refers to the dielectric constant of the polyisoimide adhesive provided by this invention being no higher than 3.2.

[0013] Preferably, the content of acid anhydride in the raw materials for preparing the polyisoimide adhesive is 30 to 35 parts by weight, such as 30.5 parts by weight, 31 parts by weight, 31.5 parts by weight, 32 parts by weight, 32.5 parts by weight, 33 parts by weight, 33.5 parts by weight, 34 parts by weight, or 34.5 parts by weight.

[0014] Preferably, the diamine content in the raw materials for preparing the polyisoimide adhesive is 45-50 parts by weight, for example, 45.5 parts by weight, 46 parts by weight, 46.5 parts by weight, 47 parts by weight, 47.5 parts by weight, 48 parts by weight, 48.5 parts by weight, 49 parts by weight, or 49.5 parts by weight, etc.

[0015] Preferably, the diamine comprises N,N′-(2,2′-bis(trifluoromethyl)-[1,1′-biphenyl]-4,4′-diyl)bis(4-aminobenzamide).

[0016] Preferably, the content of the end-capping agent in the raw materials for preparing the polyisoimide adhesive is 15 to 25 parts by weight, such as 15 parts by weight, 16 parts by weight, 17 parts by weight, 18 parts by weight, 19 parts by weight, 20 parts by weight, 21 parts by weight, 22 parts by weight, or 23 parts by weight.

[0017] Preferably, the capping agent comprises acetylene phthalic anhydride.

[0018] As a preferred technical solution of the present invention, selecting acetylene phthalic anhydride as the end-capping agent can end the obtained polyisoimide adhesive with acetylene groups, thereby having better solubility, temperature resistance and lower curing temperature.

[0019] Preferably, the dehydrating agent comprises trifluoroacetic anhydride.

[0020] Preferably, the solvent in the raw materials for preparing the polyisoimide adhesive includes any one or a combination of at least two of N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, or tetrahydrofuran.

[0021] In a second aspect, the present invention provides a method for preparing the polyisoimide adhesive as described in the first aspect, the method comprising the following steps:

[0022] (1) Mix acid anhydride, diamine and solvent, add end-capping agent to react, and obtain imide monomer solution;

[0023] (2) The imide monomer solution obtained in step (1) is mixed with a dehydrating agent to obtain the polyisoimide adhesive.

[0024] Preferably, the mixing and reaction in step (1) are carried out under nitrogen protection.

[0025] Preferably, the mixing time in step (1) is 3 to 5 hours, such as 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours, 4 hours, 4.2 hours, 4.4 hours, 4.6 hours or 4.8 hours.

[0026] Preferably, the reaction time in step (1) is 1 to 3 hours, for example, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours, 2 hours, 2.2 hours, 2.4 hours, 2.6 hours or 2.8 hours.

[0027] Preferably, the solid content of the imide monomer solution in step (1) is 10-20%, such as 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18% or 19%.

[0028] Preferably, the mixing in step (2) is carried out under ice bath conditions.

[0029] Preferably, the mixing method in step (2) specifically includes: adding the dehydrating agent dropwise to the imide monomer solution in step (1).

[0030] Preferably, the mixing time in step (2) is 3 to 5 hours, such as 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours, 4 hours, 4.2 hours, 4.4 hours, 4.6 hours or 4.8 hours.

[0031] Preferably, after the mixing in step (2) is completed, the steps of washing, filtering and vacuuming are also included.

[0032] Preferably, the washing includes washing with deionized water.

[0033] Preferably, the filtration method is vacuum filtration.

[0034] Preferably, the vacuuming temperature is 50-70°C, such as 52°C, 54°C, 56°C, 58°C, 60°C, 62°C, 64°C, 66°C, or 68°C.

[0035] Preferably, the vacuuming time is 2 to 4 hours, such as 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours, 3 hours, 3.2 hours, 3.4 hours, 3.6 hours, or 3.8 hours.

[0036] As a preferred embodiment of the present invention, the preparation method of the polyisoimide adhesive includes the following steps:

[0037] (1) Under nitrogen protection, acid anhydride, diamine and solvent are mixed for 3-5 hours, and end-capping agent is added and reacted for 1-3 hours to obtain an imide monomer solution with a solid content of 10-20%.

[0038] (2) Under ice bath conditions, the dehydrating agent is added dropwise to the imide monomer solution with a solid content of 10-20% obtained in step (1), and mixed for 3-5 hours to obtain a dark yellow polyisoimide solution. The solution is washed with deionized water until it is neutral, filtered, and vacuumed at 50-70°C for 2-4 hours to obtain the polyisoimide adhesive.

[0039] Thirdly, the present invention provides an application of the polyisoimide adhesive as described in the first aspect in electronic devices or aerospace.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] The polyisoimide adhesive provided by this invention comprises a combination of acid anhydride, diamine, end-capping agent, dehydrating agent, and solvent. This combination of raw materials results in an isoimide adhesive with excellent solubility and temperature resistance, as well as a low curing temperature. Furthermore, the acid anhydride is specifically defined as 9,9-bis(trifluoromethyl)oxanthracene tetracarboxylic dianhydride and / or 2,2'-difluoromethyl-4,4',5,5'-biphenyltetracarboxylic dianhydride and hexafluorodianhydride, successfully introducing fluorine groups into the structure of the polyisoimide adhesive and effectively reducing its dielectric constant and dielectric loss tangent. Specifically, the polyisoimide adhesive provided by this invention has a dielectric constant of 2.8–3.1 at 1 MHz, a maximum exothermic temperature of 236–256 °C, and a Tg of 335–372 °C. Detailed Implementation

[0042] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0043] Example 1

[0044] A low-dielectric, easily soluble polyisoimide adhesive, the preparation method of which includes the following steps:

[0045] (1) Under nitrogen protection, 32 parts by weight of 9,9-bis(trifluoromethyl)oxanthracene tetracarboxylic dianhydride and 47 parts by weight of N,N′-(2,2′-bis(trifluoromethyl)-[1,1′-biphenyl]-4,4′-diyl)bis(4-aminobenzamide) were dissolved in N,N-dimethylformamide and mixed at room temperature for 4 h. Then, 21 parts by weight of acetylenyl phthalic anhydride were added and reacted for 2 h to obtain an imide monomer solution with a solid content of 15%.

[0046] (2) Under ice bath conditions, trifluoroacetic anhydride was slowly added dropwise to the imide monomer solution with a solid content of 15% obtained in step (1), and mixed for 4 hours under vigorous stirring to obtain a dark yellow polyisoimide solution. The solution was washed repeatedly with deionized water until it was neutral, filtered, and then vacuumed at 60°C for 3 hours to obtain the polyisoimide adhesive.

[0047] Example 2

[0048] A low-dielectric, easily soluble polyisoimide adhesive, the preparation method of which includes the following steps:

[0049] (1) Under nitrogen protection, 35 parts by weight of 2,2'-difluoromethyl-4,4',5,5'-biphenyltetracarboxylic dianhydride and 45 parts by weight of N,N′-(2,2′-bis(trifluoromethyl)-[1,1′-biphenyl]-4,4′-diyl)bis(4-aminobenzamide) were dissolved in N,N-dimethylformamide and mixed at room temperature for 5 h. Then, 20 parts by weight of acetylenyl phthalic anhydride were added and reacted for 3 h to obtain an imide monomer solution with a solid content of 20%.

[0050] (2) Under ice bath conditions, trifluoroacetic anhydride was slowly added dropwise to the imide monomer solution with a solid content of 20% obtained in step (1), and mixed for 5 hours under vigorous stirring to obtain a dark yellow polyisoimide solution. The solution was washed repeatedly with deionized water until it was neutral, filtered, and then vacuumed at 50°C for 4 hours to obtain the polyisoimide adhesive.

[0051] Example 3

[0052] A low-dielectric, easily soluble polyisoimide adhesive, the preparation method of which includes the following steps:

[0053] (1) Under nitrogen protection, 33 parts by weight of 9,9-bis(trifluoromethyl)oxanthracene tetracarboxylic dianhydride and 48 parts by weight of N,N′-(2,2′-bis(trifluoromethyl)-[1,1′-biphenyl]-4,4′-diyl)bis(4-aminobenzamide) were dissolved in N,N-dimethylformamide and mixed at room temperature for 3 h. Then, 19 parts by weight of acetylenyl phthalic anhydride were added and reacted for 1 h to obtain an imide monomer solution with a solid content of 10%.

[0054] (2) Under ice bath conditions, trifluoroacetic anhydride is slowly added dropwise to the imide monomer solution with a solid content of 10% obtained in step (1), and mixed for 3 hours under vigorous stirring to obtain a dark yellow polyisoimide solution. The solution is washed repeatedly with deionized water until it is neutral, filtered, and then vacuumed at 70°C for 2 hours to obtain the polyisoimide adhesive.

[0055] Example 4

[0056] A low-dielectric, easily soluble polyisoimide adhesive differs from Example 1 only in that hexafluorodianhydride is used instead of 9,9-bis(trifluoromethyl)oxanthracene tetracarboxylic dianhydride; all other components, dosages, and preparation methods are the same as in Example 1.

[0057] Example 5

[0058] A low-dielectric, easily soluble polyisoimide adhesive differs from Example 1 only in that 2,2'-difluoromethyl-4,4',5,5'-biphenyltetracarboxylic dianhydride and hexafluorodianhydride in a mass ratio of 1:1 are used to replace 9,9-bis(trifluoromethyl)oxanthracenetetracarboxylic dianhydride. All other components, dosages, and preparation methods are the same as in Example 1.

[0059] Example 6

[0060] A low dielectric and easily soluble polyisoimide adhesive differs from Example 1 only in that, in step (2) of the preparation method, the ice bath condition is replaced with the -15°C condition, while the other components, amounts and steps are the same as in Example 1.

[0061] Example 7

[0062] A low dielectric and easily soluble polyisoimide adhesive differs from Example 1 only in that, in step (2) of the preparation method, the ice bath condition is replaced with the -20°C condition, while the other components, amounts and steps are the same as in Example 1.

[0063] Comparative Example 1

[0064] A polyisoimide adhesive differs from Example 1 only in that 3,3',4,4'-biphenyltetracarboxylic dianhydride is used instead of 9,9-bis(trifluoromethyl)oxanthracenetetracarboxylic dianhydride; all other components, dosages, and preparation methods are the same as in Example 1.

[0065] Comparative Example 2

[0066] A polyisoimide adhesive differs from Example 1 only in that 9,9-bis(trifluoromethyl)oxanthracene tetracarboxylic dianhydride is replaced with 4,4'-(4,4'-isopropyldiphenoxy)bis(phthalic anhydride), while the other components, dosages, and preparation methods are the same as in Example 1.

[0067] Comparative Example 3

[0068] A polyisoimide adhesive, which differs from Example 1 only in that step (1) does not involve adding 17 parts by weight of acetylene phthalic anhydride and reacting for 2 hours. All other components, amounts and steps are the same as in Example 1.

[0069] Performance testing:

[0070] Sample preparation: Dissolve the polyisoimide adhesive provided in the examples and comparative examples in 30% NMP, apply it evenly to the surfaces to be bonded, remove most of the solvent at 100-150°C, and bond when the bonding surface is viscous and has no obvious bubbles.

[0071] (1) Dielectric properties: Tested according to the test methods provided in ASTM A893 / A893M-2003(2015);

[0072] (2) Solubility: At 25℃, the sample was put into different solvents and stirred thoroughly and allowed to stand for 48h. The solubility was observed and the insoluble matter was filtered out. The solubility was calculated.

[0073] (3) Maximum heat release temperature: The temperature range was 25-400℃, and the heating rate was 5℃ / min, 10℃ / min, 15℃ / min and 20℃ / min, respectively, using a differential scanning calorimeter under a nitrogen atmosphere.

[0074] (4) Temperature resistance: The glass transition temperature (Tg) of the sample was tested using a dynamic thermomechanical analyzer. The temperature range was 25 to 400℃ in air atmosphere, and the heating rate was 5℃ / min.

[0075] The polyisoimide adhesives provided in Examples 1-7 and Comparative Examples 1-3 were tested according to the above test methods, and the test data are shown in Table 1.

[0076] Table 1

[0077]

[0078] As can be seen from the data in Table 1, the polyisoimide adhesive provided by the present invention has a low dielectric constant and excellent temperature resistance. Specifically, the polyisoimide adhesives provided in Examples 1 to 7 have a dielectric constant of 2.8 to 3.1, a maximum exothermic temperature of 236 to 256°C, and a Tg of 335 to 372°C under 1MHz conditions.

[0079] Comparing the data of Example 1 and Comparative Examples 1-2, it can be seen that the polyisoimide adhesive obtained by replacing the dianhydride specified in this application with a fluorine-free dianhydride has a higher dielectric constant and poorer heat resistance.

[0080] Comparing the data from Example 1 and Comparative Example 3, it can also be seen that omitting the step of adding acetylene phthalic anhydride for reaction also results in a higher dielectric constant and poorer heat resistance in the final polyisoimide adhesive.

[0081] The applicant declares that this invention illustrates a low-dielectric, easily soluble polyisoimide adhesive, its preparation method, and its application through the above embodiments. However, this invention is not limited to the above embodiments, meaning that this invention does not necessarily rely on the above embodiments for implementation. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of the raw materials in the product of this invention, additions of auxiliary components, and selection of specific methods, all fall within the protection and disclosure scope of this invention.

Claims

1. A low-dielectric, easily soluble polyisoimide adhesive, characterized in that, The raw materials for preparing the polyisoimide adhesive include 30-35 parts by weight of acid anhydride, 45-50 parts by weight of diamine, 15-25 parts by weight of end-capping agent, dehydrating agent and solvent; The acid anhydride is 2,2'-difluoromethyl-4,4',5,5'-biphenyltetracarboxylic dianhydride; The diamine is N,N′-(2,2′-bis(trifluoromethyl)-[1,1′-biphenyl]-4,4′-diyl)bis(4-aminobenzamide); The dielectric constant of the polyisoimide adhesive is not higher than 3.2, and it is completely soluble in NMP, DMF, DMAc and THF.

2. The polyisoimide adhesive according to claim 1, characterized in that, The capping agent includes acetylene phthalic anhydride.

3. The polyisoimide adhesive according to claim 1, characterized in that, The dehydrating agent includes trifluoroacetic anhydride.

4. The polyisoimide adhesive according to claim 1, characterized in that, The solvent in the raw materials for preparing the polyisoimide adhesive includes any one or a combination of at least two of N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, or tetrahydrofuran.

5. A method for preparing the polyisoimide adhesive as described in any one of claims 1 to 4, characterized in that, The preparation method includes the following steps: (1) Mix acid anhydride, diamine and solvent, add end-capping agent to react and obtain imide monomer solution; (2) The imide monomer solution obtained in step (1) is mixed with a dehydrating agent to obtain the polyisoimide adhesive.

6. The preparation method according to claim 5, characterized in that, The mixing and reaction in step (1) are carried out under nitrogen protection.

7. The preparation method according to claim 5, characterized in that, The mixing time in step (1) is 3 to 5 hours.

8. The preparation method according to claim 5, characterized in that, The reaction time in step (1) is 1 to 3 hours.

9. The preparation method according to claim 5, characterized in that, The solid content of the imide monomer solution in step (1) is 10-20%.

10. The preparation method according to claim 5, characterized in that, The mixing in step (2) is carried out under ice bath conditions.

11. The preparation method according to claim 5, characterized in that, The mixing method in step (2) specifically includes adding the dehydrating agent dropwise into the imide monomer solution in step (1).

12. The preparation method according to claim 5, characterized in that, The mixing time in step (2) is 3 to 5 hours.

13. The preparation method according to claim 5, characterized in that, After the mixing process is completed in step (2), the steps of washing, filtering and vacuuming are also included.

14. The preparation method according to claim 13, characterized in that, The washing process includes washing with deionized water.

15. The preparation method according to claim 13, characterized in that, The filtration method is vacuum filtration.

16. The preparation method according to claim 13, characterized in that, The vacuuming temperature is 50~70℃.

17. The preparation method according to claim 13, characterized in that, The vacuuming time is 2-4 hours.

18. The application of a polyisoimide adhesive as described in any one of claims 1 to 4 in electronic devices or aerospace applications.

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