Random copolymerized polyimide-polyvinyl alcohol composites and their preparation methods

Abstract

This invention belongs to the field of polymer materials technology, and specifically relates to a random copolymerized polyimide-polyvinyl alcohol composite material and its preparation method. Hexafluorodianhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorenic anhydride, and 4,4'-diaminobiphenyl-2,2'-dicarboxylic acid are dissolved in N-N-dimethylacetamide and reacted under a nitrogen atmosphere to obtain a PAA acid solution. The PAA acid solution is then subjected to a gradient temperature increase reaction to obtain a random copolymerized polyimide. The random copolymerized polyimide and ILAs are dissolved in a polyvinyl alcohol solution to obtain a polyvinyl alcohol mixed solution. The mixed solution is drop-coated onto a glass plate and dried to obtain a flame-retardant, environmentally friendly, water-soluble polyvinyl alcohol composite material. This invention, by compounding the random copolymerized polyimide with the flame retardant ILAs, can reduce the amount of flame retardant ILAs used and improve the flame retardancy rating, mechanical properties, and transparency of the polyvinyl alcohol composite material.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, and specifically relates to a composite material of polyimide and polyvinyl alcohol with random copolymerization and its preparation method. Background Technology

[0002] Polyvinyl alcohol (PVA) solutions possess excellent film-forming ability, producing colorless and transparent films with high transparency, mechanical strength, flexibility, and abrasion resistance. Furthermore, PVA exhibits good biocompatibility, slowly degrading in vivo with minimal irritation to human tissues, thus finding applications in pharmaceutical and food packaging. Due to its excellent biocompatibility, it can also be used in medical membrane materials and other applications.

[0003] Existing flame-retardant polyvinyl alcohol, such as PVA / GP composite films, has poor light transmittance, and the synthesis of phosphated PVA films is complicated.

[0004] Polyimide (PI) exhibits excellent thermal stability, maintaining stable performance even at high temperatures. It possesses high strength and good toughness, and demonstrates good resistance to most organic solvents, acids, and alkalis. However, it may degrade under strong oxidizing acids (such as concentrated sulfuric acid) and high-temperature, strong alkaline environments. It is a key material in the fabrication of flexible printed circuit boards (FPCs), serving as the substrate for FPCs and enabling the boards to be flexible, thin, and lightweight. It is also used in the manufacture of alignment layers for liquid crystal displays (LCDs) and as semiconductor packaging materials.

[0005] Because traditional polyimide (PI) synthesis often involves binary copolymerization, the resulting polyimide (PI) molecules exhibit a relatively regular molecular chain arrangement. The molecular chain segments are tightly packed, with strong intermolecular forces, resulting in high density and regularity, which can affect the transparency of the material. Summary of the Invention

[0006] The object of this invention is to provide a polyimide having random copolymerization, wherein the polyimide has the following repeating structural units:

[0007]

[0008] (BPAF-DCB)-(6FDA-DCB)

[0009] Where x and y are each independent integers between 10 and 2000.

[0010] The preparation method of polyimides with random copolymerization is as follows:

[0011]

[0012] The specific preparation steps of random copolymer polyimide (PI) are as follows:

[0013] (1) First, add NN dimethylacetamide (DMAC) to a three-necked flask equipped with a mechanical stirrer. Then, add an appropriate amount of the diamine monomer 4,4'-diaminobiphenyl-2,2-dicarboxylic acid (DCB). After the diamine monomer is completely dissolved, add hexafluorodianhydride (6FDA) and 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF). Purify the apparatus with nitrogen five times to ensure that the apparatus is filled with nitrogen, thereby preventing premature hydrolysis of the anhydride monomer. Allow the reaction to proceed at room temperature for 5–12 hours to obtain PAA acid.

[0014] The total molar ratio of hexafluorodianhydride and 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride to 4,4'-diaminobiphenyl-2,2-dicarboxylic acid is 1:1; the molar ratio of hexafluorodianhydride to 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride is 1:7-7:1; and the solid content of the solution in the reaction is 12%.

[0015] (2) The obtained PAA acid was uniformly drop-coated onto the surface of a glass plate using a thermal imidization method. The plate was then placed in a muffle furnace and reacted by gradient heating. After the reaction was complete, the plate was removed from the muffle furnace, and the reaction product was scraped off the glass plate to obtain random copolymer polyimide (PI).

[0016] The gradient heating reaction process is as follows: 75℃-2h, 125℃-1h, 175℃-1h, 225℃-1h, 275℃-1h.

[0017] This invention also provides the application of random copolymer polyimide in the preparation of flame-retardant polyvinyl alcohol composite films. By adding the flame retardant L-aspartic acid phosphate ionic liquid and the char-forming agent polyimide prepared in this invention to polyvinyl alcohol, the resulting PVA composite material not only possesses excellent flame retardant properties and light transmittance, but is also water-soluble.

[0018] The specific preparation method is as follows: Weigh appropriate amounts of polyvinyl alcohol and L-aspartic acid phosphate ionic liquid according to their mass proportions, and dissolve them together in deionized water. After both are fully dissolved, add triethylamine dropwise to the solution to adjust the pH to 8. Then, add the randomly copolymerized polyimide to the above solution and allow it to completely dissolve, forming a homogeneous mixture. Next, uniformly drop-coat this mixture onto the surface of a glass plate, and after drying, obtain a water-soluble polyimide composite film with flame-retardant properties.

[0019] The flame-retardant polyvinyl alcohol composite material is composed of the following parts by weight: 100 parts polyvinyl alcohol, 5-15 parts L-aspartic acid phosphate ionic liquid, and 5-10 parts polyimide.

[0020] The preparation method of L-aspartic acid phosphate ionic liquid is as follows: L-aspartic acid, phosphoric acid and deionized water are placed in a beaker and magnetically stirred at room temperature until dissolved. Then, the temperature is raised to 80℃ and magnetically stirred for 12 hours. After the reaction is completed, the solution is extracted with ethyl acetate, the aqueous layer is retained, and the solution is dried to finally obtain a viscous transparent liquid, namely L-aspartic acid phosphate ionic liquid [Asp][H2PO4] (ILAs).

[0021] By adopting the above technical solution, the present invention has the following advantages and beneficial effects:

[0022] (1) Since the polyimide provided by the present invention is made of ternary copolymer, the regularity of the molecular chain arrangement in the material will be destroyed, thereby reducing the crystallinity and increasing the transparency.

[0023] (2) The polyimide of the present invention, when combined with the flame retardant L-aspartic acid phosphate ionic liquid, can reduce the amount of L-aspartic acid phosphate ionic liquid used, thereby reducing the production cost of the polyimide composite material and improving its flame retardant rating. Moreover, it also imparts water solubility to the polyimide composite material.

[0024] (3) The L-aspartic acid phosphate ionic liquid of the present invention is highly efficient, and can achieve flame retardant effect with low addition amount. It is halogen-free, biodegradable, stable at high temperature, has good char formation performance, good dispersibility, strong interfacial bonding, and also has antibacterial and antistatic properties. It is green synthesized and the process is simple. Attached Figure Description

[0025] Figure 1 The infrared spectrum of the polyimide resin (BPAF-DCB)-(6FDA-DCB) synthesized in Example 1 of this invention is shown. Detailed Implementation

[0026] To more clearly illustrate the present invention, the following description, in conjunction with embodiments, provides further insight. Those skilled in the art should understand that the specific descriptions below are illustrative rather than restrictive, and should not be construed as limiting the scope of protection of the present invention.

[0027] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. The experimental materials and reagents used in the following examples can be obtained commercially or through known experimental methods.

[0028] Example 1

[0029] This embodiment provides a random copolymer polyimide resin having the following repeating structural units, and the polyimide resin is named (BPAF-DCB)-(6FDA-DCB):

[0030]

[0031] The specific preparation method is as follows:

[0032] (1) Preparation of polyimide (BPAF-DCB)-(6FDA-DCB):

[0033] Hexafluorodianhydride (6FDA) and 9,9-bis(3,4-dicarboxyphenyl)fluorenedianhydride (BPAF) were pre-treated by drying in an oven at 110°C for 12 hours. Then, a three-necked flask equipped with a mechanical stirrer was prepared, and 38 ml of DMAC was added, followed by 2.7226 g of 4,4'-diaminobiphenyl-2,2-dicarboxylic acid (DCB), with a molar mass of 10 mmol. After the addition, the air in the apparatus was purged five times with nitrogen to ensure complete removal of air. Stirring was then started until DCB was completely dissolved. Subsequently, hexafluorodianhydride (6FDA) and 9,9-bis(3,4-dicarboxyphenyl)fluorenedianhydride (BPAF) were added in four separate portions, with masses of 2.2212 g and 2.2921 g respectively, each with a molar mass of 5 mmol. For the first addition, half the total amount of both substances was added. Subsequent additions were also half the amount of the previous addition, with a 40-minute interval between each batch. The final addition was to be done slowly, with close monitoring of the viscosity of the reaction system until the reaction was complete. The final solid content of the system was determined to be 12 wt%. The reaction system was then placed in an ice-water bath and stirred continuously for 18 hours. After the reaction, the PAA acid solution was collected.

[0034] The glass slide is preheated in a muffle furnace, and then the PAA acid solution obtained above is dropped onto the glass slide for thermal imidization (75℃-2h, 125℃-1h, 175℃-1h, 225℃-1h, 275℃-1h) to obtain a PI film with a thickness of 150μm. After the reaction is complete, the film is removed and scraped off the glass plate to obtain PI.

[0035] (2) The preparation method of L-aspartic acid phosphate ionic liquid is as follows: 1.331g of L-aspartic acid, 1ml of phosphoric acid and 140ml of deionized water are placed in a beaker and magnetically stirred at room temperature until dissolved. Then, the temperature is raised to 80℃ and magnetically stirred for 12h. After the reaction is completed, the solution is extracted with ethyl acetate, the aqueous layer is retained, and the solution is dried to finally obtain a viscous transparent liquid, namely L-aspartic acid phosphate ionic liquid [Asp][H2PO4] (ILAs).

[0036] (3) Preparation of PVA composite films:

[0037] Weigh 2g of polyvinyl alcohol (PVA) into a 50ml beaker, add 20ml of deionized water, and place the beaker on a stirring table. Heat the beaker to 90℃ and stir to dissolve. After complete dissolution, weigh 0.23g of L-aspartic acid phosphate ion liquid into the beaker and continue stirring for 4h to obtain a 10wt% PVA aqueous solution.

[0038] Triethylamine was added to the PVA aqueous solution to adjust the pH of the solution to 8 to facilitate the dissolution of polyimide. Then, 0.10526 g of polyimide (PI) was weighed into the PVA aqueous solution and stirred for 4 hours. After complete dissolution, the relevant PVA composite solution was obtained.

[0039] The obtained PVA composite solution was placed in an ultrasonic cleaner and agitated for 45 minutes, then allowed to stand for 6 hours to remove any air bubbles that may have been present during stirring. After complete standing, the solution was placed in a vacuum oven and a vacuum was applied to completely remove any air bubbles. The treated PVA composite solution was then uniformly drop-coated onto a glass plate and dried in an oven at 50°C for 6 hours to remove excess moisture, yielding a PVA composite film. The sample size was 150 × 50 × 0.15 mm.

[0040] Example 2

[0041] The difference between this embodiment and Example 1 is that the molar ratio of hexafluorodianhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorenic anhydride and 4,4'-diaminobiphenyl-2,2-dicarboxylic acid (DCB) in the prepared PI is 1:7:8, while the other treatment methods are the same as in Example 1.

[0042] Example 3

[0043] The difference between this embodiment and Example 1 is that the molar ratio of hexafluorodianhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorenic anhydride and 4,4'-diaminobiphenyl-2,2-dicarboxylic acid (DCB) in the prepared PI is 1:3:4, while the other treatment methods are the same as in Example 1.

[0044] Example 4

[0045] The difference between this embodiment and Example 1 is that the molar ratio of hexafluorodianhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorenic anhydride and 4,4'-diaminobiphenyl-2,2-dicarboxylic acid (DCB) in the prepared PI is 3:1:4, while the other treatment methods are the same as in Example 1.

[0046] Example 5

[0047] The difference between this embodiment and Example 1 is that the molar ratio of hexafluorodianhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorenic anhydride and 4,4'-diaminobiphenyl-2,2-dicarboxylic acid (DCB) in the prepared PI is 7:1:8, while the other treatment methods are the same as in Example 1.

[0048] Example 6

[0049] The difference between this embodiment and Embodiment 1 is that the amount of flame retardant ILAS added to the prepared composite film is 5 parts (i.e. 0.11g), while the other treatment methods are the same as in Embodiment 1.

[0050] Example 7

[0051] The difference between this embodiment and Embodiment 1 is that the amount of flame retardant ILAS added to the prepared composite film is 15 parts (i.e. 0.35g), while the other treatment methods are the same as in Embodiment 1.

[0052] Example 8

[0053] The difference between this embodiment and Example 1 is that the amount of polyimide added to the prepared composite film is 10 parts (i.e. 0.21052g), while the other treatment methods are the same as in Example 1.

[0054] Comparative Example 1

[0055] The difference between this comparative example and Example 1 is that the two dianhydride monomers used in the preparation of polyimide are replaced with one hexafluorodianhydride. The molar ratio of hexafluorodianhydride to 4,4'-diaminobiphenyl-2,2-dicarboxylic acid is 1:1. Other treatment methods are the same as in Example 1.

[0056] Comparative Example 2

[0057] The difference between this comparative example and Example 1 is that the two dianhydride monomers used in the preparation of polyimide are replaced with 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, wherein the molar ratio of 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride to 4,4'-diaminobiphenyl-2,2-dicarboxylic acid is 1:1. Other treatment methods are the same as in Example 1.

[0058] Comparative Example 3

[0059] The difference between this comparative example and Example 1 is that only PVA and flame retardant ILAs are added, and the amount of ILAs added is 15 wt% based on the weight percentage of polyvinyl alcohol (PVA). Polyimide (PI) is not added. Other treatment methods are the same as in Example 1.

[0060] Comparative Example 4

[0061] The difference between this comparative example and Example 1 is that the flame retardant L-aspartic acid phosphate ionic liquid is replaced with guanidine phosphate (GP), wherein the content of guanidine phosphate (GP) is 10 wt%, and the other treatment methods are the same as in Example 1.

[0062] The vertical combustion performance and optical properties of the prepared polyvinyl alcohol composite film were tested, and the test results are shown in Table 1.

[0063] Table 1

[0064]

[0065]

[0066] The solubility of the prepared polyvinyl alcohol composite film (Example 1) was tested, and the test results are shown in Table 2.

[0067] Table 2

[0068] solvent PVA / ILAs PVA / ILAs / PI Deionized water ++ ++

[0069] +++: Soluble at room temperature; ++: Soluble upon heating at 90°C; +: Partially soluble upon heating at 90°C; -: Insoluble.

[0070] In summary, the polyimide resin prepared in this application has a random copolymer structure and can be used as a charring agent. Compared with products containing only ILAs, the addition of random copolymer polyimide can effectively improve the flame retardant properties of the product. Furthermore, compared with polyimides synthesized using only one type of monomer, the use of random copolymer polyimide can effectively improve the transparency of the product.

[0071] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-described technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A polyimide with random copolymerization, characterized in that: The random copolymerized polyimide has the following repeating structural units: Where x and y are each independent integers between 10 and 2000.

2. The polyimide with random copolymerization according to claim 1, characterized in that, The preparation method of the polyimide is as follows: (1) Dissolve hexafluorodianhydride 6FDA, 9,9-bis(3,4-dicarboxyphenyl)fluorenic anhydride BPAF and 4,4'-diaminobiphenyl-2,2-dicarboxylic acid DCB in N,N-dimethylacetamide to obtain PAA acid solution. (2) The PAA acid solution prepared in step (1) is uniformly drop-coated onto a glass plate and subjected to a gradient heating reaction. After the reaction is complete, it is removed and scraped off the glass plate to obtain a polyimide with random copolymerization.

3. The polyimide with random copolymerization according to claim 2, characterized in that, In step (1), the total molar amount of hexafluorodianhydride and 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride is in a molar ratio of 1:1 to 4,4'-diaminobiphenyl-2,2-dicarboxylic acid; the molar ratio of hexafluorodianhydride and 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride is 1:7-7:1; and the solid content of the solution in the reaction is 12%.

4. The polyimide with random copolymerization according to claim 2, characterized in that, In step (1), the reaction conditions are: reaction at room temperature under nitrogen atmosphere for 5 to 12 hours.

5. The polyimide with random copolymerization according to claim 2, characterized in that, In step (2), the gradient temperature increase reaction is carried out in the following order: 75℃-2h, 125℃-1h, 175℃-1h, 225℃-1h, 275℃-1h.

6. An application of a polyimide with random copolymerization according to claim 1, characterized in that, The random copolymerized polyimide is used to prepare flame-retardant polyvinyl alcohol composites.

7. The application of the random copolymerized polyimide according to claim 6, characterized in that, The flame-retardant polyvinyl alcohol composite material is composed of the following components by mass: 100 parts polyvinyl alcohol, 5-15 parts L-aspartic acid phosphate ionic liquid, and 5-10 parts polyimide.

8. The application of the random copolymerized polyimide according to claim 6, characterized in that, The method for preparing the flame-retardant polyvinyl alcohol composite material is as follows: polyvinyl alcohol and L-aspartic acid phosphate ion liquid are dissolved in deionized water according to the mass fraction. After complete dissolution, triethylamine is added to adjust the pH of the solution, and then polyimide is added. After complete dissolution, the resulting mixed solution is uniformly drop-coated onto a glass plate and dried to obtain a flame-retardant polyvinyl alcohol composite material.

9. The application of the random copolymerized polyimide according to claim 8, characterized in that, Add triethylamine to adjust the pH of the solution to 8.

10. The application of the random copolymerized polyimide according to claim 7, characterized in that, The preparation method of L-aspartic acid phosphate ionic liquid is as follows: L-aspartic acid, phosphoric acid and deionized water are placed in a beaker and magnetically stirred at room temperature until dissolved. Then, the temperature is raised to 80℃ and magnetically stirred for 12 hours. After the reaction is completed, the solution is extracted with ethyl acetate, the aqueous layer is retained, and the solution is dried to finally obtain a viscous transparent liquid, namely L-aspartic acid phosphate ionic liquid [Asp][H2PO4] (ILAs).

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