Black thermoplastic polyimide and preparation method and application thereof

Abstract

The application discloses black thermoplastic polyimide and a preparation method and application thereof, and relates to the technical field of polyimide. The application discloses thermoplastic polyimide with a new structure, and the structure of the thermoplastic polyimide is as follows, wherein diamine is ABABP and PNDA; and dianhydride is BPTME and BPDA. The application selects PNDA containing a chromophore group imido (-N-H-), and thus the thermoplastic polyimide with a black appearance is prepared without using black fillers.

Description

Technical Field

[0001] This invention relates to the field of polyimide technology, and in particular to a black thermoplastic polyimide, its preparation method, and its applications. Background Technology

[0002] Flexible copper clad laminate (FCCL) is an important application form in the field of flexible circuits in flexible electronics technology. It is mainly composed of conductors (such as copper foil layers) and organic insulating substrates. Because FCCL has very stringent requirements in practical applications, the organic insulating base film needs to have excellent heat resistance, insulation properties, mechanical properties, dielectric properties, adhesion properties, and low cost.

[0003] Polyimide (PI) is a super engineering polymer material containing an imide ring structure. Its highly conjugated molecular chain structure, strong intra- and inter-molecular chain interactions, and high bond energy and high polarity of CN and C=O bonds endow it with a variety of excellent properties that can meet the stringent requirements of organic insulating base films.

[0004] Traditional FCCL manufacturing processes use a three-layer method, where adhesives are used to bond the film and copper foil together. However, the use of traditional adhesives such as polyacrylates and epoxy resins leads to decreased heat resistance and increased thickness and dielectric constant of the FCCL. Therefore, a two-layer method has emerged. This two-layer process uses thermoplastic polyimide (TPI) instead of traditional adhesives. Given the high commercialization rate of PI core films, the core of this process lies in the research and development of TPI adhesive films. Due to its excellent heat resistance, hydrophobicity, orientation, strong adhesion to the substrate, and low dielectric loss, TPI shows great promise for application in two-layer FCCLs.

[0005] Furthermore, due to considerations such as reducing light corrosion of copper foil, protecting intellectual property, and aesthetics, specialty FCCLs have received increasing attention. Among them, black PI (BPI) films have garnered significant interest due to their excellent light-shielding properties, radiation resistance, corrosion resistance, thermal stability, and flame retardancy. Traditional BPI preparation methods involve adding black fillers such as carbon black to a polyamic acid (PAA) solution. However, black fillers are conductive and may agglomerate, leading to increased conductivity and decreased insulation of the PI. Moreover, traditional methods typically use non-thermoplastic polyimides with very low toughness, which also significantly impacts the material properties and service life of the PI.

[0006] Chinese patent CN107250277A discloses a composition for forming a release layer, comprising polyamic acid obtained by reacting an aromatic diamine with an aromatic tetracarboxylic dianhydride, and an organic solvent. The aromatic diamine comprises an aromatic diamine containing at least one of ester bonds and ether bonds, and / or the aromatic tetracarboxylic dianhydride contains at least one of ester bonds and ether bonds. The polyamic acid disclosed in this patent is not a black polyamic acid and lacks properties such as light-blocking, radiation resistance, corrosion resistance, thermal stability, and flame retardancy.

[0007] In view of this, in order to overcome the shortcomings of existing cultivation methods, the present invention provides a black thermoplastic polyimide, its preparation method and application. Summary of the Invention

[0008] The purpose of this invention is to provide a black thermoplastic polyimide, its preparation method and application. The prepared thermoplastic polyimide has a black appearance, good thermoplasticity, excellent high-temperature dimensional stability and excellent dielectric properties, which can meet the application requirements of two-layer special FCCL.

[0009] To achieve the above-mentioned objectives, the technical solution of this invention is as follows:

[0010] On one hand, the present invention provides a black thermoplastic polyimide, the structure of which is shown in the following formula:

[0011]

[0012] Where n is a positive integer;

[0013] Dihydride is

[0014]

[0015] diamine is

[0016]

[0017] Furthermore, the present invention provides a method for preparing the above-mentioned black thermoplastic polyimide, comprising the following steps:

[0018] (1) Two diamine monomers and aprotic strong polar solvents are mixed to form a homogeneous solution, which is then mixed with two dianhydride monomers to undergo a polymerization reaction to obtain a polyamic acid solution;

[0019] (2) After the polyamic acid solution is formed into a film or spun, it is heated to dehydrate and form a ring, which is then transformed into black thermoplastic polyimide.

[0020] Preferably, in step (1), the two diamine monomers are 2-(4-aminobenzoic acid ester)-5-aminobiphenyl (ABABP) and 4-aminophenyl-2,5-pyridinediamine (PNDA);

[0021] The structure of ABABP is as follows:

[0022]

[0023] The structure of PNDA is as follows:

[0024]

[0025] Preferably, in step (1), the two dianhydride monomers are biphenyl benzoate-3,3',4,4'-tetracarboxylic acid dianhydride (BPTME) and 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (BPDA);

[0026] The structure of BPTME is as follows:

[0027]

[0028] The structure of BPDA is as follows:

[0029]

[0030] Preferably, in step (1), the aprotic strongly polar solvent is N-methylpyrrolidone (NMP).

[0031] More preferably, in step (1), the molar ratio of BPTME, BPDA, ABABP and PNDA is 2:8:3-4:6-7.

[0032] More preferably, in step (1), the molar ratio of BPTME, BPDA, ABABP and PNDA is 2:8:4:6.

[0033] Preferably, in step (2), the heating procedure is as follows: 80℃ / 1h; 120℃ / 1h; 150℃ / 1h; 180℃ / 1h; 250℃ / 1h; 300℃ / 1h.

[0034] In another aspect, the present invention provides a flexible copper-clad laminate, comprising copper foil and the aforementioned black thermoplastic polyimide.

[0035] Finally, this invention provides the application of the aforementioned black thermoplastic polyimide in flexible circuits.

[0036] The beneficial effects of this invention are as follows:

[0037] (1) In this invention, PNDA containing chromophore imino (-NH-) was selected to prepare a black thermoplastic polyimide without using black filler.

[0038] (2) Compared with thermoplastic polyimide materials prepared using TMBPA, BPDA, APAB, and TFMB, the thermoplastic polyimide materials prepared using BPTME, BPDA, PNDA, and ABABP in this invention are not only fluorine-free, but also have a moderate T g It features low dielectric constant, low dielectric loss, lower CTE, and excellent high-temperature dimensional stability. Attached Figure Description

[0039] Figure 1 The images shown are FTIR spectra of embodiments and comparative examples of the present invention.

[0040] Figure 2 The DMA spectra are for embodiments and comparative examples of the present invention.

[0041] Figure 3 The TMA spectra are for embodiments and comparative examples of the present invention.

[0042] Figure 4 The TGA-DTG spectra are for embodiments and comparative examples of the present invention. Detailed Implementation

[0043] The following non-limiting embodiments are intended to enable those skilled in the art to gain a more comprehensive understanding of the present invention, but do not limit the invention in any way. The following description is merely an exemplary illustration of the scope of protection of the present invention, and those skilled in the art can make various changes and modifications to the invention based on the disclosed content, which should also fall within the scope of protection of the present invention.

[0044] The present invention will be further described below by way of specific embodiments. Unless otherwise specified, all chemical reagents used in the embodiments of the present invention were obtained through conventional commercial means. Unless otherwise specified, all contents mentioned below are mass contents. Unless otherwise specified, it is understood that the process was carried out at room temperature.

[0045] The structure of BPTME is as follows:

[0046]

[0047] The structure of BPDA is as follows:

[0048]

[0049] The structure of ABABP is as follows:

[0050]

[0051] The structure of PNDA is as follows:

[0052]

[0053] The structure of bisphenol A type diether dianhydride (TMBPA) is as follows:

[0054]

[0055] The structure of 4-aminobenzoic acid-4-aminophenyl ester (APAB) is as follows:

[0056]

[0057] The structure of 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl (TFMB) is as follows:

[0058]

[0059] Example 1

[0060] Black thermoplastic polyimide films were prepared using a two-step thermal imidization method with BPTME, BPDA, ABABP, and PNDA. Specifically:

[0061] Soluble polyamic acid (PEsAA) precursors were first prepared via polycondensation of starting monomers, as follows: PNDA (11.9550 g, 0.06 mol), ABABP (12.1736 g, 0.04 mol), and an appropriate amount of ultra-dry NMP solvent were added to a 250 mL three-necked round-bottom glass flask equipped with a mechanical stirrer, thermometer, nitrogen inlet, and cold water bath. The flask was then immersed in a cold water bath with an internal temperature below 10°C. Simultaneously, dry nitrogen gas was introduced into the flask, and after stirring for 30 minutes, a clear diamine solution was obtained. Then, BPTME (10.6886 g, 0.02 mol) and BPDA (23.5376 g, 0.08 mol) were added sequentially to the diamine solution, along with additional NMP solvent to provide a reaction mixture with an initial solids content of 25 wt%. After stirring for 1 hour, the cold bath was removed, and the reaction temperature gradually reached room temperature. Polymerization continued for 24 hours to obtain a viscous PEsAA solution. The system was diluted to a solids content of 15 wt% by adding additional NMP solvent. The diluted PEsAA solution was filtered through a 0.45 μm PTFE syringe to remove insoluble impurities.

[0062] Purified PEsAA solution was cast onto clean borosilicate glass (150mm × 100mm × 3mm) using a coating applicator (AFA-II, Shanghai Meiyu Equipment Co., Ltd., China), and the thickness of the initial liquid film was controlled by adjusting the gap distance of the casting blade. The glass substrate was then heat-dried in a programmable oven under nitrogen atmosphere using heating programs of 80℃ / 1h, 120℃ / 1h, 150℃ / 1h, 180℃ / 1h, 250℃ / 1h, and 300℃ / 1h. After heat treatment, the naturally cooled glass substrate was immersed in deionized water. The polyesterimide film was peeled off from the substrate, resulting in a black, stand-alone film. After drying at 120℃ for 3h, various properties of the film were evaluated.

[0063] Example 2

[0064] Black thermoplastic polyimide films were prepared using a two-step thermal imidization method with BPTME, BPDA, ABABP, and PNDA. Specifically:

[0065] The thin film preparation process was the same as in Example 1, except that the amount of monomers added was different; specific data are shown in Table 1. The obtained thin films were then evaluated for various properties.

[0066] Table 1

[0067]

[0068] Comparative Example 1

[0069] Thermoplastic polyimide films prepared by a two-step thermal imidization method using TMBPA, BPDA, APAB, and TFMB are as follows:

[0070] The thin film preparation process was the same as in Example 1, except for the addition of monomers and their content; specific data are shown in Table 2. The obtained thin films were then evaluated for various properties.

[0071] Comparative Example 2

[0072] Thermoplastic polyimide films prepared by a two-step thermal imidization method using TMBPA, BPDA, APAB, and TFMB are as follows:

[0073] The thin film preparation process was the same as in Example 1, except for the addition of monomers and their content; specific data are shown in Table 2. The obtained thin films were then evaluated for various properties.

[0074] Table 2

[0075]

[0076] Result detection:

[0077] 1. Methods for evaluating the structure of thin films

[0078] Fourier transform infrared spectroscopy (FTIR): The prepared thin film was measured using a Shimadzu Iraffinity-1S Fourier transform infrared spectrometer with a measurement range of 4000-500 cm⁻¹. -1 This test can obtain the infrared spectrum of the thin film.

[0079] 2. Methods for evaluating the thermal properties of thin films

[0080] Dynamic mechanical analysis (DMA): The prepared thin film was tested in nitrogen atmosphere at a heating rate of 5 °C / min and a frequency of 1 Hz on a TA Q800 thermal analysis system. This test can obtain the glass transition temperature (Tg) of the thin film. g )data.

[0081] Thermomechanical analysis (TMA): The prepared thin film was tested in a nitrogen atmosphere using a Netzsch TMA402F3 thermal analysis system at a heating rate of 5 °C / min. This test yielded the linear coefficient of thermal expansion (CTE) data for the thin film.

[0082] Thermogravimetric analysis (TGA) and its derivative TGA (DTG): The prepared thin films were tested in a nitrogen atmosphere using a Netzsch TG 209F3 thermogravimetric analyzer at a heating rate of 20 °C / min. This test yields the 5% weight loss temperature (Tg) of the thin films. 5％ The temperatures at which the first and second most rapid thermal decompositions occur (T) max1 T max2 ) and the residual weight ratio at 750°C (R w750 )data.

[0083] 3. Methods for evaluating the dielectric properties of thin films

[0084] Dielectric properties: Silver electrodes were fabricated on both sides of the PI sample, pre-dried at 100°C for 1 hour using conductive silver paint, and then precisely cut into small pieces (1cm × 1cm × 3mm). The dielectric constant was measured at 10GHz using an Agilent 4294A precision impedance analyzer at room temperature. k ) and dielectric loss (D f The data is recorded as the average of 5 parallel samples.

[0085] 4. Methods for evaluating the optical properties of thin films

[0086] Color parameters: The prepared thin film was measured using an i7 spectrophotometer from X-rite (USA). Color parameters were calculated according to the CIE Lab equation: L * This represents the brightness of the thin film, where 100 represents white and 0 represents black; a* Positive values ​​represent red, and negative values ​​represent green; b * Positive values ​​represent yellow, and negative values ​​represent blue; haze represents fog.

[0087] Table 3

[0088]

[0089] T g Glass transition temperature; T 5％ The temperature at which the weight decreases by 5%; T max1 The temperature at which the first decomposition occurs fastest; T max2 : The temperature at which the second decomposition occurs fastest; R w750 : Percentage of components by weight at 750℃; CTE: Coefficient of linear thermal expansion in the range of 100-200℃; D k Dielectric constant; D f Dielectric loss.

[0090] Table 4

[0091] sample <![CDATA[L * ]]> <![CDATA[a * ]]> <![CDATA[b * ]]> haze (%) Example 1 23.74 38.06 40.91 0.00 Example 2 11.21 34.20 19.32 0.08 Comparative Example 1 94.29 -0.95 7.46 0.01 Comparative Example 2 93.95 -1.09 8.77 0.03

[0092] L * This represents the brightness of the thin film, where 100 represents white and 0 represents black; a * Positive values ​​represent red, and negative values ​​represent green; b * Positive values ​​represent yellow, and negative values ​​represent blue; haze represents fog.

[0093] according to Figure 1 As shown in the FTIR spectrum and Table 4, the black polyimide film material was successfully obtained using the preparation method of this invention. Figure 2 The DMA spectrum shows that the black polyimide film material prepared by this invention has good thermoplasticity.

[0094] As can be seen from the data in Table 3, compared with the thermoplastic polyimide film materials prepared by TMBPA, BPDA, APAB and TFMB in Comparative Examples 1 and 2, the thermoplastic polyimide film materials prepared by BPTME, BPDA, PNDA and PAPAB in Examples 1 and 2 have the advantages of being fluorine-free, black, and having a moderate T... g In addition to low dielectric constant and low dielectric loss, it also has low CTE and excellent high-temperature dimensional stability.

[0095] Therefore, the black thermoplastic polyimide film material prepared by the two-step thermal imidization method proposed in this invention has excellent comprehensive properties, and the preparation process is simple to operate, the reaction is controllable, and the reaction products are adjustable. This implementation scheme has good industrialization prospects in two-layer special FCCL at high frequency.

[0096] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A black thermoplastic polyimide, characterized in that, The structure of the thermoplastic polyimide is shown in the following formula: Where n is a positive integer; Dihydride is diamine is 2. The method for preparing the thermoplastic polyimide according to claim 1, characterized in that, Includes the following steps: (1) Two diamine monomers and aprotic strong polar solvents are mixed to form a homogeneous solution, which is then mixed with two dianhydride monomers to undergo a polymerization reaction to obtain a polyamic acid solution; (2) After the polyamic acid solution is formed into a film or spun, it is heated to dehydrate and form a ring, which is then transformed into black thermoplastic polyimide.

3. The preparation method according to claim 2, characterized in that, In step (1), the two diamine monomers are ABABP and PNDA; The structure of ABABP is as follows: The structure of PNDA is as follows:

4. The preparation method according to claim 2, characterized in that, In step (1), the two dianhydride monomers are BPTME and BPDA; The structure of BPTME is as follows: The structure of BPDA is as follows:

5. The preparation method according to claim 2, characterized in that, In step (1), the aprotic strong polar solvent is N-methylpyrrolidone.

6. The preparation method according to any one of claims 3-4, characterized in that, In step (1), the molar ratio of BPTME, BPDA, ABABP and PNDA is 2:8:3-4:6-7.

7. The preparation method according to claim 6, characterized in that, In step (1), the molar ratio of BPTME, BPDA, ABABP, and PNDA is 2:8:4:

6.

8. The preparation method according to claim 2, characterized in that, In step (2), the heating procedure is as follows: 80℃ / 1h; 120℃ / 1h; 150℃ / 1h; 180℃ / 1h; 250℃ / 1h; 300℃ / 1h.

9. A flexible copper-clad laminate, characterized in that, Includes copper foil and the black thermoplastic polyimide as described in claim 1.

10. The application of the black thermoplastic polyimide of claim 1 in flexible circuits.

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