Materials, insulating materials and electrophoretic coating methods for electrophoretic formation of polyimide

Abstract

This invention provides a material for electrophoretically forming polyimide, an insulating material, and an electrophoretic coating method. The material for electrophoretically forming polyimide includes at least one of a polyamic acid oligomer structure and a polyimide oligomer structure, and also includes a thiophene-terminated structure. Because the material for electrophoretically forming polyimide provided by this invention has a thiophene-terminated structure, it can electropolymerize into a film under electrophoretic action without the need for a salt solution, forming a polyimide material. Furthermore, the film-forming effect is not affected by the molecular weight of the material, thus effectively solving the technical problem that existing methods for synthesizing polyimide by electrophoresis are not convenient enough. In addition, the voltage required for film formation by the electropolymerization method of the above material is lower than that of traditional electrophoretic deposition, thus making it more energy-efficient.

Description

Technical Field

[0001] This invention relates to the field of insulating material synthesis technology, and in particular to a material for electrophoretic formation of polyimide, an insulating material, and an electrophoretic coating method. Background Technology

[0002] Polyimide (PI) insulating materials, due to the presence of imide heterocycles in their structure, exhibit significantly superior heat resistance compared to ordinary epoxy resins or polyester insulating materials, thus meeting the thermal stability requirements of current electric vehicle motors and are widely used.

[0003] Existing polyimide insulating materials are generally formed by electrophoresis, which requires first converting the synthesized polyamic acid solution into a salt, then preparing an electrophoretic solution or electrophoretic paint for electrophoresis, and finally curing it at high temperature to form polyimide. The above method is cumbersome and has strict requirements on the molecular weight of the polymer during electrophoresis. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a material, an insulating material and an electrophoretic coating method for electrophoretically forming polyimide, so as to solve the technical problem that the existing method of synthesizing polyimide by electrophoresis is not convenient enough.

[0005] To solve the above problems, the present invention is achieved through the following technical solution:

[0006] The present invention proposes a material for electrophoretic formation of polyimide, wherein the material comprises at least one of a polyamic acid oligomer structure and a polyimide oligomer structure, and further comprises a thiophene end-capping structure.

[0007] Furthermore, the structural formula of the material is at least one of formulas (A) and (B):

[0008]

[0009] (A)(B)

[0010] in, , ,

[0011] R1 and R2 are selected from one of substituted or unsubstituted alkylene, substituted or unsubstituted aryl, and substituted or unsubstituted heteroaryl, respectively, and m is 5 to 200.

[0012] The present invention also proposes an insulating material, wherein the structural formula of the insulating material is at least one of formulas (C) and (D):

[0013]

[0014] (C)(D)

[0015] in, , ,

[0016] R1 and R2 are selected from one of substituted or unsubstituted alkylene, substituted or unsubstituted arylene, and substituted or unsubstituted heteroarylene, respectively, where m is 5~200, x is 5~200, and y is 5~200.

[0017] The present invention also proposes an electrophoretic coating method, wherein:

[0018] Provide an oligomer; wherein the oligomer has a structural formula of at least one of formulas (A) and (B):

[0019]

[0020] (A)(B)

[0021] in, , ,

[0022] R1 and R2 are selected from one of substituted or unsubstituted alkylene, substituted or unsubstituted aryl, and substituted or unsubstituted heteroaryl, respectively, and m is 5 to 200.

[0023] The oligomer is subjected to electropolymerization to generate an insulating film layer.

[0024] Furthermore, in the method, when the oligomer is a first oligomer having structural formula (A), providing the oligomer includes:

[0025] Diamine and dianhydride are added to a solvent to carry out a polymerization reaction;

[0026] After the polymerization reaction is complete, a thiophene end-capping agent is added to the reaction solution, and the reaction yields the first oligomer.

[0027] Furthermore, in the reaction system providing the oligomer, the molar ratio between the diamine, dianhydride, and thiophene end-capping agent is 0.5~1:1:0.02~1.

[0028] Furthermore, in the method, the thiophene end-capping agent is at least one selected from 3-aminothiophene, 3-hydroxythiophene, 4-bromothiophene-3-amine, methyl 3-aminothiophene-4-carboxylate, 4-chlorothiophene-3-amine, 3-amino-2-cyanothiophene, and 4-methyl-3-amine.

[0029] Further, in the method, the solvent is at least one selected from dimethyl sulfoxide, N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide; and / or

[0030] The diamine is at least one of 4,4'-diaminodiphenyl ether, m-phenylenediamine, p-phenylenediamine, 4,4'-diaminodiphenyl sulfone, 1,3-diamino-2-methylpropane, N,N-bis(4-aminophenyl)-1,4-phenylenediamine, and 9,9-bis(4-aminophenyl)fluorene; and / or

[0031] The dianhydride is at least one selected from pyromellitic anhydride, 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride, 3,3',4,4'-tetracarboxybenzophenone dianhydride, 3,3',4,4'-tetracarboxybiphenyl sulfone dianhydride, 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride, 4,4'-bis(3,4-dicarboxyphenoxy)diphenyl ether dianhydride, 4,4'-bis(3,4-dicarboxyphenoxy)benzophenone dianhydride, 4,4'-bis(3,4-dicarboxyphenoxy)diphenylmethane dianhydride, and 4,4'-bis(3,4-dicarboxyphenoxy)diphenyl sulfone dianhydride.

[0032] Furthermore, in the method, when the oligomer is a second oligomer having structural formula (B), providing the oligomer includes:

[0033] The first oligomer is imidized to obtain the second oligomer.

[0034] Further, in the method, imidizing the first oligomer to obtain the second oligomer includes:

[0035] A catalyst is added to a solution containing the first oligomer, and the mixture is stirred at 60-180 °C for 1-8 h to obtain the second oligomer. The catalyst is at least one of isoquinoline and triethylamine.

[0036] Further, in the method, when the oligomer is a first oligomer having structural formula (A), the oligomer is subjected to electropolymerization to generate an insulating film layer, comprising:

[0037] The first oligomer is polymerized by electrophoresis to generate a polyamide polymer, which is then imidized to generate the insulating film layer; or

[0038] The first oligomer was imidized to obtain a second oligomer having structural formula (B);

[0039] The second oligomer is polymerized by electrophoresis to generate a polyimide polymer, which serves as the insulating film layer.

[0040] Further, in the method, when the oligomer is a second oligomer having structural formula (B), the oligomer is subjected to electropolymerization to generate an insulating film layer, comprising:

[0041] The second oligomer is polymerized by electrophoresis to generate a polyimide polymer, which serves as the insulating film layer.

[0042] Compared with the prior art, the embodiments of the present invention have the following advantages:

[0043] In this embodiment of the invention, the material provided for electrophoretic formation of polyimide includes at least one of a polyamic acid oligomer structure and a polyimide oligomer structure, and also includes a thiophene-terminated structure. Because the above material has a thiophene-terminated structure, it can be electropolymerized into a film under electrophoretic action to form a polyimide material without the need to prepare a salt solution, and the film formation effect is not affected by the molecular weight of the above material. Therefore, it can effectively solve the technical problem that the existing method of synthesizing polyimide by electrophoresis is not convenient enough. In addition, the voltage required for film formation by electropolymerization of the above material is lower than that of traditional electrophoretic deposition, thus it is more energy-efficient.

[0044] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0045] Figure 1 This is a conversion relationship diagram between polymers corresponding to general formulas (A), (B), (C), and (D) in the embodiments of the present invention;

[0046] Figure 2 This is the infrared spectrum of the electrophoretic coating in Embodiment 4 of the present invention. Detailed Implementation

[0047] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0048] The present invention provides a material for electrophoretically forming polyimide, comprising at least one of a polyamic acid oligomer structure and a polyimide oligomer structure, and further comprising a thiophene end-capping structure.

[0049] The embodiments of the present invention provide a material for forming polyimide by electrophoretic polymerization, that is, the material provided in the embodiments of the present invention can be polymerized to form polyimide by electropolymerization.

[0050] Among them, the polyamic acid oligomer structure and the polyimide oligomer structure are the main structures for forming polyimide; the thiophene end-capped structure is the thiophene subunit located at the end of the polyamic acid oligomer structure and the polyimide oligomer structure. Since the thiophene molecule contains a sulfur atom, one of the two pairs of lone electrons of the sulfur atom is conjugated with the two double bonds to form a delocalized π bond, and lone electrons exist at its 2 and 5 positions, which can undergo oxidative polymerization under electrophoresis. This allows the above materials to be electropolymerized into films under electrophoresis without the need to prepare a salt solution, forming polyimide materials. Moreover, the film formation effect is not affected by the molecular weight of the above materials. Therefore, it can effectively solve the technical problem that the existing method of synthesizing polyimide by electrophoresis is not convenient enough. In addition, the voltage required for film formation by the above material electropolymerization method is lower than that of traditional electrophoretic deposition, thus making it more energy-efficient.

[0051] Optionally, in one embodiment, the structural formula of the above material is at least one of formulas (A) and (B):

[0052]

[0053] (A)(B)

[0054] in, , ,

[0055] R1 and R2 are selected from one of substituted or unsubstituted alkylene, substituted or unsubstituted aryl, and substituted or unsubstituted heteroaryl, respectively, and m is 5 to 200.

[0056] Among them, the material corresponding to formula (A) can be polymerized by electrophoresis and then imidized by high temperature curing to form a polyimide material, while the material corresponding to formula (B) can be directly polymerized by electrophoresis to form a polyimide material.

[0057] This invention also provides an insulating material, wherein the structural formula of the insulating material is at least one of formulas (C) and (D):

[0058]

[0059] (C)(D)

[0060] in, , ,

[0061] R1 and R2 are selected from one of substituted or unsubstituted alkylene, substituted or unsubstituted arylene, and substituted or unsubstituted heteroarylene, respectively, where m is 5~200, x is 5~200, and y is 5~200.

[0062] In this embodiment of the invention, the material corresponding to formula (D) can be directly used as a polyimide material, while the material corresponding to formula (C) can be generated by imidization to produce the material corresponding to formula (D).

[0063] The imidization method described above can be high-temperature curing, with a curing temperature of 100~400℃ and a curing time of 1~4h.

[0064] Optionally, the material corresponding to formula (C) can be imidized into formula (D) by the following temperature program: 100~150℃ / 1h, 200~250℃ / 1h, 300~400℃ / 1h.

[0065] This invention also provides an electrophoretic coating method, comprising steps 101 to 102:

[0066] Step 101: Provide an oligomer; wherein the oligomer has a structural formula of at least one of formulas (A) and (B):

[0067]

[0068] (A)(B)

[0069] in, , ,

[0070] R1 and R2 are selected from one of substituted or unsubstituted alkylene, substituted or unsubstituted aryl, and substituted or unsubstituted heteroaryl, respectively, and m is 5 to 200.

[0071] Step 102: Electropolymerize the oligomer to generate an insulating film layer.

[0072] In the electrophoretic coating method provided in this embodiment of the invention, at least one oligomer in formula (A) and (B) is used as the substrate. Taking advantage of its thiophene end-capped structure, an electrophoretic solution can be directly prepared to electropolymerize and generate an insulating film layer including polyimide. This eliminates the step of preparing a salt solution, and the film quality is not easily affected by the molecular weight of the polymer.

[0073] Optionally, in one embodiment, when the oligomer is a first oligomer having structural formula (A), step 101 above includes steps 111 to 112:

[0074] Step 111: Add diamine and dianhydride to solvent to carry out polymerization reaction;

[0075] Step 112: After the polymerization reaction is completed, a thiophene end-capping agent is added to the reaction solution to obtain the first oligomer.

[0076] In this embodiment, after dissolving diamine and dianhydride in a solvent and heating to polymerize, thiophene end-capping agent is directly added to obtain a first oligomer with structural formula (A).

[0077] Optionally, in step 111 above, the polymerization reaction temperature is 45~120℃ and the time is 4~36h.

[0078] For example, the diamine solvent is added to the reaction vessel in the solvent and stirring is started; then the dianhydride is slowly added to the vessel and the reaction vessel is heated to 45~120°C and stirred for 4~36 hours; then the thiophene end-capping agent is slowly added to the vessel and stirred for 1~8 hours to obtain the above-mentioned first oligomer.

[0079] Optionally, in the reaction system providing the oligomer, the molar ratio of diamine, dianhydride, and thiophene end-capping agent is 0.5~1:1:0.02~1. By controlling the molar ratio of diamine, dianhydride, and thiophene end-capping agent to 0.5~1:1:0.02~1, the molecular weight of the synthesized first oligomer is more appropriate, and the occurrence of side reactions can be reduced.

[0080] Optionally, in one specific embodiment of the method, the end-capping agent is at least one of 3-aminothiophene, 3-hydroxythiophene, 4-bromothiophene-3-amine, methyl 3-aminothiophene-4-carboxylate, 4-chlorothiophene-3-amine, and 3-amino-2-cyanothiophene, which can effectively end-cap the above-mentioned oligomers and form a thiophene-capped structure.

[0081] Optionally, in one specific embodiment, the solvent is at least one of dimethyl sulfoxide, N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide, which can provide a better reaction system for the polymerization of diamine with dianhydride and thiophene end-capping agent.

[0082] Optionally, in one specific embodiment, the diamine is at least one selected from 4,4'-diaminodiphenyl ether, m-phenylenediamine, p-phenylenediamine, 4,4'-diaminodiphenyl sulfone, 1,3-diamino-2-methylpropane, N,N-bis(4-aminophenyl)-1,4-phenylenediamine, and 9,9-bis(4-aminophenyl)fluorene; and / or

[0083] Optionally, in one specific embodiment, the dianhydride is at least one selected from pyromellitic tetracarboxylic anhydride, 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride, 3,3',4,4'-tetracarboxybenzophenone dianhydride, 3,3',4,4'-tetracarboxybiphenyl sulfone dianhydride, 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride, 4,4'-bis(3,4-dicarboxyphenoxy)diphenyl ether dianhydride, 4,4'-bis(3,4-dicarboxyphenoxy)benzophenone dianhydride, 4,4'-bis(3,4-dicarboxyphenoxy)diphenylmethane dianhydride, and 4,4'-bis(3,4-dicarboxyphenoxy)diphenyl sulfone dianhydride.

[0084] Optionally, in one embodiment, when the oligomer is a second oligomer having structural formula (B), step 101 includes step 113:

[0085] Step 113: Imidate the first oligomer to obtain the second oligomer.

[0086] In this embodiment, the first oligomer having structural formula (A) is directly imidized, causing its carboxyl and amine groups to condense, thereby forming the second oligomer having structural formula (B).

[0087] Optionally, in one specific embodiment, step 113 above includes:

[0088] A catalyst is added to a solution containing the first oligomer, and the mixture is stirred at 60-180°C for 1-8 h to obtain the second oligomer. The catalyst is at least one of isoquinoline and triethylamine.

[0089] In this specific embodiment, by adding catalysts such as isoquinoline and triethylamine to the first oligomer solution and then heating the reaction at 60~180°C for 1~8 hours, the first oligomer (i.e., polyamic acid oligomer) can be imidized into the second oligomer (i.e., polyimide oligomer).

[0090] In step 102 above, the oligomer is subjected to electrophoresis, that is, a film layer including polyimide is generated on the metal surface by electropolymerization, which serves as an insulating film layer.

[0091] Optionally, in one specific embodiment, when the oligomer is a first oligomer having structural formula (A), step 102 above includes:

[0092] The first oligomer is polymerized by electrophoresis to generate a polyamide polymer, which is then imidized to generate the insulating film layer; or

[0093] The first oligomer was imidized to obtain a second oligomer having structural formula (B);

[0094] The second oligomer is polymerized by electrophoresis to generate a polyimide polymer, which serves as the insulating film layer.

[0095] In this embodiment, the first oligomer having formula (A) is first polymerized by electrophoresis to form a polyamide polymer, and can then be imidized by high-temperature curing or other means to form the above-mentioned insulating film layer; the first oligomer having formula (A) can also be imidized by high-temperature curing or other means to form a second oligomer having formula (B), and then polymerized by electrophoresis to form the above-mentioned insulating film layer.

[0096] Alternatively, in another embodiment, when the oligomer is a second oligomer having structural formula (B), step 102 above includes:

[0097] The second oligomer is polymerized by electrophoresis to generate a polyimide polymer, which serves as the insulating film layer.

[0098] In this embodiment, the second oligomer having formula (B) can be directly polymerized by electrophoretic polymerization to form the above-mentioned insulating film layer without undergoing imidization processes such as high-temperature curing.

[0099] Optionally, in one embodiment, step 102 specifically includes:

[0100] The aforementioned oligomer is diluted to a mass fraction of 0.01%–20%, and an electrolyte is added to the solution to obtain an electrophoretic solution. Using this electrophoretic solution, the metal device to be coated is subjected to electrophoresis at room temperature for 5–80 seconds under an electrophoretic voltage of 1–200V and an electrode spacing of 5–100cm. The device is then air-dried at room temperature to form an insulating film layer on the device surface. The electrolyte can be any inorganic or organic salt, and the diluent can be any organic solvent or water.

[0101] Optionally, in some embodiments, the mass fraction of oligomers in the electrophoresis solution can be one or any two of the following values: 0.01%, 0.02%, 0.05%, 1%, 2%, 5%, 10%, 15%, 20%. The electrophoresis voltage in the electrophoresis process can be one or any two of the following values: 1V, 2V, 5V, 10V, 20V, 50V, 100V, 150V, 180V, 200V. The electrode spacing can be one or any two of the following values: 5cm, 8cm, 10cm, 20cm, 40cm, 50cm, 60cm, 80cm, 100cm.

[0102] In this embodiment of the invention, the conversion relationships of the polymers corresponding to each general formula (A), (B), (C), and (D) are as follows: Figure 1 As shown.

[0103] The present invention will be described in detail below through embodiments.

[0104] Performance testing methods:

[0105] (1) Withstand voltage test:

[0106] A. Connect the device under test: With the voltmeter set to "0" and the test lamp off, clamp the instrument grounding clamp to the heat sink of the device under test, and press the power switch of the device under test.

[0107] B. Set the instrument test conditions: voltage 3500V, leakage current 5mA, test time 5 seconds;

[0108] C. Place the test probe firmly against any AC input metal tab of the power cord;

[0109] D. Press the start button and observe the test results. If the over-leakage light does not illuminate within the set time, the tested model is qualified.

[0110] (2) Cross-cut test: Performed according to ASTM D3359 Method B Cross-cut tapes.

[0111] (3) Evaluation of film-forming performance: A film that forms a whole sheet on the glass, with no cracks on the film surface and remains intact after peeling is considered to have excellent film-forming performance; a film that forms a whole sheet on the glass, with no cracks on the film surface and cannot remain intact after peeling is considered to have average film-forming performance; a film that forms fragments on the glass is considered to have no film-forming performance.

[0112] (4) Molecular weight test: Performed in accordance with GB / T27843-2011 Determination of molecular weight components of chemicals.

[0113] Example 1

[0114] (1) Dissolve 200g of 4,4'-diaminodiphenyl ether in 2000g of N-methylpyrrolidone, add it into the reaction vessel, and start stirring.

[0115] (2) Slowly add 218 g of pyromellitic anhydride into the reactor, heat the reactor to 45 °C and stir continuously for 4 hours.

[0116] (3) 40 g of 3-aminothiophene was slowly added to the reactor and stirred for 2 hours to obtain the first oligomer, the structural formula of which is as follows:

[0117] .

[0118] (4) The first oligomer was diluted with N-methylpyrrolidone to a mass fraction of 5%, and lithium hexafluorophosphate was added to the solution to prepare an electrophoresis solution.

[0119] (5) A coating film was prepared by electrophoresis on a tinplate using the above electrophoresis solution. The electrophoresis voltage was 5V, the electrophoresis time at room temperature was 60s, and the electrode spacing was 10cm. The tinplate was then air-dried at room temperature for half an hour to obtain a polyamide polymer attached to the metal surface. Its structural formula is as follows:

[0120] .

[0121] (6) The polyamide polymer attached to the metal surface is heated according to the following procedure: 150℃ / 1h, 250℃ / 1h, 350℃ / 1h to imidize it, thereby obtaining the polyimide polymer on the metal surface.

[0122] Example 2

[0123] (1) Dissolve 200g of 4,4'-diaminodiphenyl ether in 2000g of N-methylpyrrolidone, add it into the reaction vessel, and start stirring.

[0124] (2) Slowly add 218 g of pyromellitic anhydride into the reactor, heat the reactor to 45 °C and stir continuously for 4 hours.

[0125] (3) 40 g of 3-aminothiophene was slowly added to the reactor and stirred for 2 hours to obtain the first oligomer, the structural formula of which is as follows:

[0126] .

[0127] (4) Add 2 g of isoquinoline to the first oligomer slurry, raise the temperature to 180 ℃ and stir for 8 hours to obtain the second oligomer, whose structural formula is as follows:

[0128] .

[0129] (5) Dilute the second oligomer with N-methylpyrrolidone to a mass fraction of 1%, and add lithium hexafluorophosphate to the solution.

[0130] (6) A coating film was prepared by electrophoresis on a tinplate using the above electrophoresis solution. The electrophoresis voltage was 20 V, the electrophoresis time at room temperature was 45 s, and the electrode spacing was 10 cm. The tinplate was then air-dried at room temperature for half an hour to obtain a polyimide polymer attached to the metal surface. Its structural formula is as follows:

[0131] .

[0132] Example 3

[0133] The difference between Example 3 and Example 1 is that 3-aminothiophene is replaced with 3-hydroxythiophene.

[0134] Example 4

[0135] The difference between Example 4 and Example 1 is that 4,4'-diaminodiphenyl ether is changed to 4,4'-diaminodiphenyl sulfone.

[0136] Example 5

[0137] The difference between Example 5 and Example 1 is that the pyromellitic anhydride is changed to 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride.

[0138] Example 6

[0139] The difference between Example 6 and Example 1 is that the amount of 4,4'-diaminodiphenyl ether added is adjusted to 109 grams.

[0140] Example 7

[0141] The difference between Example 7 and Example 1 is that the amount of 4,4'-diaminodiphenyl ether added is adjusted to 218 grams.

[0142] Example 8

[0143] The difference between Example 8 and Example 1 is that the amount of 4,4'-diaminodiphenyl ether added is adjusted to 79 grams.

[0144] Example 9

[0145] The difference between Example 9 and Example 1 is that the amount of 4,4'-diaminodiphenyl ether added is adjusted to 240 grams.

[0146] Example 10

[0147] The difference between Example 10 and Example 1 is that the amount of 3-aminothiophene added is adjusted to 4.36 grams.

[0148] Example 11

[0149] The difference between Example 11 and Example 1 is that the amount of 3-aminothiophene added is adjusted to 218 grams.

[0150] Example 12

[0151] The difference between Example 12 and Example 1 is that the amount of 3-aminothiophene added is adjusted to 3 grams.

[0152] Example 13

[0153] The difference between Example 13 and Example 1 is that the amount of 3-aminothiophene added is adjusted to 240 grams.

[0154] Example 14

[0155] The difference between Example 14 and Example 1 is that the electrophoresis voltage is adjusted to 3V.

[0156] Example 15

[0157] The difference between Example 15 and Example 1 is that the electrophoresis voltage is adjusted to 6V.

[0158] Example 16

[0159] The difference between Example 16 and Example 2 is that in step (4), isoquinoline is replaced with triethylamine.

[0160] Example 17

[0161] The difference between Example 17 and Example 2 is that in step (4), the heating temperature is adjusted to 60°C and the stirring time is 1 hour.

[0162] Example 18

[0163] The difference between Example 18 and Example 2 is that in step (4), the heating temperature is adjusted to 120°C and the stirring time is 4 hours.

[0164] Example 19

[0165] The difference between Example 19 and Example 2 is that in step (4), the heating temperature is adjusted to 50°C and the stirring time is 1 hour.

[0166] Example 20

[0167] The difference between Example 20 and Example 2 is that in step (4), the heating temperature is adjusted to 130°C and the stirring time is 4 hours.

[0168] Example 21

[0169] The difference between Example 21 and Example 2 is that the electrophoresis voltage is adjusted to 15V.

[0170] Example 22

[0171] The difference between Example 22 and Example 2 is that the electrophoresis voltage is adjusted to 22V.

[0172] Comparative Example 1

[0173] The difference between Comparative Example 1 and Example 1 is that step (3) is omitted, and in step (4), the polymerization product of step (2) is diluted with N-methylpyrrolidone to a mass fraction of 5%, and lithium hexafluorophosphate is added to the solution to prepare an electrophoresis solution.

[0174] Comparative Example 2

[0175] (1) Dilute the PI paint with R5 to 1% by mass with N-methylpyrrolidone and add lithium hexafluorophosphate to the solution to prepare an electrophoresis solution.

[0176] (2) Using the above electrophoresis solution, a paint film was prepared by electrophoresis on a tinplate, wherein the electrophoresis voltage was 150 V, the electrophoresis time at room temperature was 45 s, the electrode spacing was 10 cm, and the obtained tinplate was air-dried at room temperature for half an hour.

[0177] Comparative Example 3

[0178] (1) Dilute the PI paint with R6 to 1% by mass with N-methylpyrrolidone and add lithium hexafluorophosphate to the solution to prepare an electrophoresis solution.

[0179] (2) Using the above electrophoresis solution, a paint film was prepared by electrophoresis on a tinplate, wherein the electrophoresis voltage was 150 V, the electrophoresis time at room temperature was 45 s, the electrode spacing was 10 cm, and the obtained tinplate was air-dried at room temperature for half an hour.

[0180] Sample testing:

[0181] The first oligomer and polyamide polymer prepared in Example 1, the second oligomer prepared in Example 2, and the first oligomer in Examples 3-5 were subjected to infrared spectroscopy tests. The peak data are as follows:

[0182] Example 1: First oligomer: 1089 cm -1 1164 cm -1 1217 cm -1 1299 cm -1 1486 cm -1 1541cm -1 1654 cm -1 1717 cm -1 1775 cm -1 3132 cm -1 ;

[0183] Example 1: Polyamide polymer: 1088 cm -1 1159 cm -1 1217 cm -1 1301 cm -1 1486 cm -1 1541 cm -1 1566 cm -1 1650 cm -1 1654 cm -1 1717 cm -1 1775 cm -1 3122 cm -1 ;

[0184] Example 2: Second oligomer: 1078 cm -1 1159 cm -1 1217 cm -1 1301 cm -1 1380 cm -1 1486cm -1 1541 cm -1 1654, 1717 cm -1 1775 cm -1 3120 cm -1 .

[0185] Example 3 First oligomer: 1089 cm -1 1124 cm -1 1234 cm -1 1298 cm -1 1399 cm -1 1542cm -1 1650 cm -1 1721 cm -1 1752 cm -1 3062 cm -1 ;

[0186] Example 4 First oligomer: 1096 cm -1 1203 cm -1 1289 cm -1 1301 cm -1 1405 cm -1 1499cm -1 1659 cm -1 1692 cm -1 1800 cm -1 3201 cm -1 ;

[0187] Example 5 First oligomer: 1101 cm -1 1123 cm -1 1271 cm -1 1299 cm -1 1421 cm -1 1513cm -1 1655 cm -1 1703 cm -1 1798 cm -1 3090 cm -1 .

[0188] The infrared spectrum of the first oligomer in Example 1 is as follows: Figure 2 As shown.

[0189] Infrared spectral data of the oligomers in Examples 1-5 show that the infrared spectrum at 1420 cm⁻¹ is... -1 Nearby and 1100cm -1 The presence of characteristic peaks of the thiophene group nearby indicates that a thiophene-terminated structure has been formed;

[0190] The infrared spectral data of the polyamide polymer in Example 1 at 1660 cm⁻¹ were obtained. -1 1550 cm -1 and 1780cm -1 The presence of characteristic peaks of amide groups nearby indicates the formation of an amide structure.

[0191] The polymers obtained in Examples 1-22 above were subjected to infrared spectroscopy testing, and the peak data are as follows:

[0192] Example 1: 1117 cm -1 1159 cm -1 1217 cm -1 1345 cm -1 1325 cm -1 1375 cm -1 1496cm -1 1541 cm -1. 1654 cm -1 1717 cm -1 1775 cm -1 2925 cm -1 ;

[0193] Example 2: 1101 cm -1 1123 cm -1 1271 cm -1 1299 cm -1 1421 cm -1 1513 cm -1 1655cm -1 1703 cm -1 1798 cm -1 3090 cm -1 ;

[0194] Example 3: 1089 cm -1 1124 cm -1 1234 cm -1 1298 cm -1 1399 cm -11542 cm -1 1650cm -1 1721 cm -1 1752 cm -1 3062 cm -1

[0195] Example 4: 1096 cm -1 1203 cm -1 1289 cm -1 1301 cm -1 1405 cm -1 1499 cm -1 1659cm -1 1692 cm -1 1800 cm -1 3201 cm -1

[0196] Example 5: 1101 cm -1 1123 cm -1 1271 cm -1 1299 cm -1 1421 cm -1 1513 cm -1 1655cm -1 1703 cm -1 1798 cm -1 3090 cm -1

[0197] Example 6: 1118 cm -1 1159 cm -1 1217 cm -1 1345 cm -1 1325 cm -1 1375 cm -1 1496cm -1 1541 cm -1. 1654 cm -1 1717 cm -1 1775 cm -1 2925 cm -1

[0198] Example 7: 1116 cm -1 1159 cm -1 1217 cm -1 1345 cm -1 1325 cm -11375 cm -1 1496cm -1 1541 cm -1. 1654 cm -1 1717 cm -1 1775 cm -1 2925 cm -1

[0199] Example 8: 1117 cm -1 1159 cm -1 1217 cm -1 1345 cm -1 1325 cm -1 1375 cm -1 1496cm -1 1541 cm -1. 1654 cm -1 1717 cm -1 1775 cm -1 2925 cm -1

[0200] Example 9: 1117 cm -1 1159 cm -1 1217 cm -1 1345 cm -1 1322 cm -1 1375 cm -1 1496cm -1 1541 cm -1. 1653 cm -1 1717 cm -1 1772 cm -1 2925 cm -1

[0201] Example 10: 1117 cm -1 1158 cm -1 1217 cm -1 1345 cm -1 1325 cm -1 1375 cm -1 1496cm -1 1541 cm -1. 1654 cm -1 1717 cm -1 1775 cm -1 2925 cm -1

[0202] Example 11: 1117 cm -1 1159 cm -1 1218 cm -1 1345 cm -1 1325 cm -1 1375 cm -1 1496cm -1 1541 cm -1. 1654 cm -1 1717 cm -1 1775 cm -1 2925 cm -1

[0203] Example 12: 1117 cm -1 1159 cm -1 1217 cm -1 1345 cm -1 1325 cm -1 1375 cm -1 1496cm -1 1541 cm -1. 1654 cm -1 1713 cm -1 1773 cm -1 2925 cm -1

[0204] Example 13: 1112 cm -1 1159 cm -1 1217 cm -1 1345 cm -1 1325 cm -1 1375 cm -1 1496cm -1 1541 cm -1. 1652 cm -1 1717 cm -1 1775 cm -1 2925 cm -1

[0205] Example 14: 1117 cm -1 1159 cm -1 1217 cm -1 1345 cm -1 1325 cm -1 1375 cm -1 1496cm-1 1541 cm -1. 1654 cm -1 1717 cm -1 1775 cm -1 2925 cm -1

[0206] Example 15: 1117 cm -1 1159 cm -1 1217 cm -1 1345 cm -1 1325 cm -1 1375 cm -1 1496cm -1 1541 cm -1. 1654 cm -1 1717 cm -1 1775 cm -1 2925 cm -1

[0207] Example 16: 1101 cm -1 1125 cm -1 1271 cm -1 1299 cm -1 1421 cm -1 1513 cm -1 1655cm -1 1703 cm -1 1798 cm -1 3090 cm -1

[0208] Example 17: 1101 cm -1 1123 cm -1 1271 cm -1 1299 cm -1 1426 cm -1 1513 cm -1 1656cm -1 1703 cm -1 1795 cm -1 3090 cm -1

[0209] Example 18: 1101 cm -1 1123 cm -1 1271 cm -1 1299 cm -1 1426 cm-1 1513 cm -1 1655cm -1 1706 cm -1 1798 cm -1 3090 cm -1

[0210] Example 19: 1101 cm -1 1121 cm -1 1271 cm -1 1299 cm -1 1421 cm -1 1513 cm -1 1655cm -1 1703 cm -1 1798 cm -1 3091 cm -1

[0211] Example 20: 1101 cm -1 1123 cm -1 1271 cm -1 1299 cm -1 1421 cm -1 1513 cm -1 1655cm -1 1703 cm -1 1798 cm -1 3090 cm -1

[0212] Example 21: 1117 cm -1 1159 cm -1 1215 cm -1 1345 cm -1 1325 cm -1 1375 cm -1 1496cm -1 1541 cm -1. 1655 cm -1 1717 cm -1 1775 cm -1 2925 cm -1

[0213] Example 22: 1117 cm -1 1159 cm -1 1217 cm -1 1345 cm -1 1325 cm-1 1375 cm -1 1496cm -1 1541 cm -1. 1654 cm -1 1715 cm -1 1775 cm -1 2925 cm -1

[0214] The infrared spectral data of the polyimide polymers in Examples 1-22 show the presence of imide groups and thiophene subunits, indicating that polyimide materials have been formed through thiophene oxidative polymerization.

[0215] The molecular weights of the polymers in Examples 1 to 22 were tested, and the m, x, and y values ​​of each example were calculated as shown in Table 1.

[0216] Table 1

[0217]

[0218] The electrophoretic coatings of Examples 1-22 and Comparative Examples 1 and 2 were subjected to cross-cut adhesion test, voltage withstand test, and film formation performance test, respectively. The results are shown in Table 2 below:

[0219] Table 2

[0220]

[0221] As can be seen from the comparison of Examples 1, 3, 10-13 and Comparative Example 1 in Table 2, the addition of the end-capping agent enables the oligomer material to polymerize into a film by electrophoresis without the need to prepare a salt solution, and the amount of end-capping agent added is directly related to the film formation effect.

[0222] As can be seen from the comparison of Examples 1, 6-9 in Table 2, the polymer film with better performance is obtained when the ratio of diamine to dianhydride is in the range of 0.5 to 1:1.

[0223] As can be seen from the comparison of Examples 1, 14-15 in Table 2, an electrophoresis voltage of 5V is more conducive to the polymerization of the first oligomer material provided in the embodiments of the present invention into a film.

[0224] As can be seen from Comparative Examples 2 and 17-20 in Table 2, the first oligomer can be completely imidized into the second oligomer by stirring at a temperature of 60-180°C for 1-8 hours.

[0225] As can be seen from Table 2, Comparative Examples 2 and 21-22, an electrophoresis voltage of 20V is more conducive to the polymerization of the second oligomer material provided in the embodiments of the present invention into a film.

[0226] As shown in Table 2, the electrophoretic coating prepared by the material provided in the embodiments of the present invention can form a good film at a lower voltage and meet the requirements of voltage resistance and adhesion test.

[0227] In summary, the material provided in this embodiment for electrophoretically forming polyimide includes at least one of a polyamic acid oligomer structure and a polyimide oligomer structure, and also includes a thiophene-terminated structure. Because the above material has a thiophene-terminated structure, it can be electropolymerized into a film under electrophoretic action to form a polyimide material without the need to prepare a salt solution, and the film formation effect is not affected by the molecular weight of the above material. Therefore, it can effectively solve the technical problem that the existing method of synthesizing polyimide by electrophoresis is not convenient enough. In addition, the voltage required for film formation by electropolymerization of the above material is lower than that of traditional electrophoretic deposition, thus it is more energy-efficient.

[0228] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the present invention.

[0229] The present invention has provided a detailed description of a material, insulating material, and electrophoretic coating method for electrophoretically forming polyimide. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. An insulating material, characterized in that, The insulating material has a structural formula of at least one of formulas (C) and (D): in, R1 and R2 are selected from one of substituted or unsubstituted alkylene, substituted or unsubstituted arylene, and substituted or unsubstituted heteroarylene, respectively, where m is 5 to 200, x is 5 to 200, and y is 5 to 200.

2. An electrophoretic coating method, characterized in that, include: Provide an oligomer; wherein the oligomer has a structural formula of at least one of formulas (A) and (B): in, R1 and R2 are selected from one of substituted or unsubstituted alkylene, substituted or unsubstituted arylene, and substituted or unsubstituted heteroarylene, respectively, and m is 5 to 200. The oligomer is subjected to electropolymerization to generate an insulating film layer.

3. The method according to claim 2, characterized in that, In the case that the oligomer is a first oligomer having the structural formula (A), the oligomer is provided comprising: Diamine and dianhydride are added to a solvent to carry out a polymerization reaction; After the polymerization reaction is complete, a thiophene end-capping agent is added to the reaction solution, and the reaction yields the first oligomer.

4. The method according to claim 3, characterized in that, In the reaction system providing the oligomer, the molar ratio between the diamine, dianhydride and thiophene end-capping agent is 0.5–1:1:0.02–1.

5. The method according to claim 3, characterized in that, The thiophene end-capping agent is at least one of 3-aminothiophene, 3-hydroxythiophene, 4-bromothiophene-3-amine, methyl 3-aminothiophene-4-carboxylate, 4-chlorothiophene-3-amine, and 3-amino-2-cyanothiophene.

6. The method according to claim 3, characterized in that, The solvent is at least one selected from dimethyl sulfoxide, N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide; and / or The diamine is at least one of 4,4'-diaminodiphenyl ether, m-phenylenediamine, p-phenylenediamine, 4,4'-diaminodiphenyl sulfone, 1,3-diamino-2-methylpropane, N,N-bis(4-aminophenyl)-1,4-phenylenediamine, and 9,9-bis(4-aminophenyl)fluorene; and / or The dianhydride is at least one selected from pyromellitic anhydride, 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride, 3,3',4,4'-tetracarboxybenzophenone dianhydride, 3,3',4,4'-tetracarboxybiphenyl sulfone dianhydride, 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride, 4,4'-bis(3,4-dicarboxyphenoxy)diphenyl ether dianhydride, 4,4'-bis(3,4-dicarboxyphenoxy)benzophenone dianhydride, 4,4'-bis(3,4-dicarboxyphenoxy)diphenylmethane dianhydride, and 4,4'-bis(3,4-dicarboxyphenoxy)diphenyl sulfone dianhydride.

7. The method according to claim 3, characterized in that, In the case that the oligomer is a second oligomer having structural formula (B), the oligomer is provided comprising: The first oligomer is imidized to obtain the second oligomer.

8. The method according to claim 7, characterized in that, The first oligomer is imidized to obtain the second oligomer, comprising: A catalyst is added to a solution containing the first oligomer, and the mixture is stirred at 60–180°C for 1–8 h to obtain the second oligomer. The catalyst is at least one of isoquinoline and triethylamine.

9. The method according to claim 2, characterized in that, In the case where the oligomer is a first oligomer having structural formula (A), electropolymerization of the oligomer is performed to generate an insulating film layer, comprising: The first oligomer is polymerized by electrophoresis to generate a polyamic acid polymer, which is then imidized to generate the insulating film layer; or The first oligomer was imidized to obtain a second oligomer having structural formula (B); The second oligomer is polymerized by electrophoresis to generate a polyimide polymer, which serves as the insulating film layer.

10. The method according to claim 2, characterized in that, In the case where the oligomer is a second oligomer having structural formula (B), electropolymerization of the oligomer is performed to generate an insulating film layer, comprising: The second oligomer is polymerized by electrophoresis to generate a polyimide polymer, which serves as the insulating film layer.

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