Polyimide and polyvinyl alcohol composite material with random copolymerization and preparation method thereof

Abstract

The invention belongs to the technical field of high polymer materials, and particularly relates to a polyimide and polyvinyl alcohol composite material with random copolymerization and a preparation method thereof. The preparation method comprises the following steps: dissolving hexafluorodianhydride, 9, 9-bis (3, 4-dicarboxylphenyl) fluorene dianhydride and 4, 4 '-diaminobiphenyl-2, 2'-dicarboxylic acid in N-N dimethylacetamide, and reacting in a nitrogen atmosphere to obtain a PAA acid solution; and carrying out gradient heating reaction on the PAA acid solution to obtain the random copolymerized polyimide. The preparation method comprises the following steps: dissolving random copolymerized polyimide and ILAs in a polyvinyl alcohol solution to obtain a polyvinyl alcohol mixed solution; and dispensing the mixed solution on a glass plate, and drying to obtain the environment-friendly water-soluble polyvinyl alcohol composite material with flame retardance. The random copolymerized polyimide and the flame retardant ILAs are compounded, so that the dosage of the flame retardant ILAs can be reduced, and the flame retardant grade, the mechanical property and the transparency of the polyvinyl alcohol composite material are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and particularly relates to a polyimide and polyvinyl alcohol composite material with random copolymerization and a preparation method thereof. Background Art

[0002] The polyvinyl alcohol (PVA) solution has good film-forming ability. The formed film is colorless and transparent, with high transparency, mechanical strength, flexibility and wear resistance. At the same time, PVA has good biocompatibility, can be slowly degraded in vivo, and has less irritation to human tissues. Therefore, it is applied in the fields of medicine and food packaging. Due to its good biocompatibility, it can also be used in medical membrane materials and other aspects.

[0003] Existing flame-retardant polyvinyl alcohol, such as the PVA / GP composite film, has poor light transmittance, and the phosphoric acid esterified PVA film has complex synthesis steps.

[0004] Polyimide (PI) has excellent thermal stability and can maintain stable performance in high-temperature environments. The material has high strength and good toughness. It has good tolerance to most organic solvents, acids and alkalis. However, it may degrade in strong oxidizing acids (such as concentrated sulfuric acid) and high-temperature strong alkali environments. It is a key material for preparing flexible printed circuit boards (FPCs). As the base material of FPCs, it enables the circuit boards to have characteristics such as bendability and thinness; it is also used in the alignment layer of liquid crystal displays (LCDs) and semiconductor packaging materials.

[0005] Since the synthesis of traditional polyimide (PI) often adopts the form of binary copolymerization, the formed polyimide (PI) molecular arrangement shows a relatively regular molecular chain arrangement. The molecular chain segments are arranged closely, the intermolecular force is strong, and it has high density and regularity, which will affect the transparency of the material. Summary of the Invention

[0006] The purpose of the present invention is to provide a polyimide with random copolymerization, and the polyimide has the following repeating structural units:

[0007]

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

[0009] Wherein, x and y are each independently an integer from 10 to 2000.

[0010] The preparation method of the polyimide with random copolymerization has the following synthesis route:

[0011]

[0012] The specific preparation method steps of the random copolymerization type polyimide PI are as follows:

[0013] (1) First, add N-N dimethylacetamide (DMAC) into a three-necked flask equipped with mechanical stirring. Then, add an appropriate amount of diamine monomer 4,4'-diaminobiphenyl-2,2-dicarboxylic acid (DCB). After the diamine monomer is completely dissolved, add hexafluorodiacid anhydride (6FDA) and 9,9-bis(3,4-dicarboxyphenyl) fluorene dianhydride (BPAF), and displace with nitrogen 5 times to ensure that the device is filled with nitrogen, thereby preventing premature hydrolysis of the acid anhydride monomer. Wait for the reaction to occur at room temperature for 5 - 12 h to obtain PAA acid;

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

[0015] (2) Adopt the thermal imidization method. Drop the obtained PAA acid evenly onto the surface of a glass plate, and then place it in a muffle furnace and react in a gradient heating manner. After the reaction is completely finished, take it out from the muffle furnace, scrape the reaction product off the glass plate, and finally obtain an amorphous copolymer polyimide (PI).

[0016] Among them, the process of gradient heating reaction is: 75°C - 2 h, 125°C - 1 h, 175°C - 1 h, 225°C - 1 h, 275°C - 1 h.

[0017] The present invention also provides the application of the amorphous copolymer polyimide, which is used to prepare a flame-retardant polyvinyl alcohol composite film. Add the flame retardant L-aspartic acid phosphate ionic liquid and the char-forming agent polyimide prepared by the present invention into polyvinyl alcohol. The obtained PVA composite material not only has excellent flame retardant performance and light transmittance, but also is soluble in water.

[0018] The specific preparation method is as follows: According to the mass parts, weigh an appropriate amount of polyvinyl alcohol and L-aspartic acid phosphate ionic liquid, and dissolve them together in deionized water. After the two are fully dissolved, dropwise add triethylamine to the solution to adjust the pH value of the solution to 8. Then, add the amorphous copolymer polyimide into the above solution. After it is completely dissolved, a uniform mixed solution is formed. Then, uniformly drop the mixed solution onto the surface of a glass plate, and through drying treatment, finally obtain a water-soluble polyimide composite film with flame retardant performance.

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

[0020] The preparation method of L - aspartic acid phosphate ionic liquid is as follows: Take L - aspartic acid, phosphoric acid and deionized water in a beaker. After magnetic stirring at room temperature until dissolved, raise the temperature to 80 °C and stir magnetically for 12 h. After the reaction, extract the solution with ethyl acetate, retain the aqueous layer, dry the solution, and finally obtain a viscous transparent liquid, namely L - aspartic acid phosphate ionic liquid [Asp][H 2 PO 4 (ILAs).

[0021] Due to the above - mentioned technical solution, the present invention has the following advantages and beneficial effects:

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

[0023] (2) After the polyimide of the present invention is compounded with the flame retardant L - aspartic acid phosphate ionic liquid, the amount of L - aspartic acid phosphate ionic liquid can be reduced, which not only reduces the production cost of the polyimide composite material but also improves its flame retardant grade. Moreover, it endows the polyimide composite material with water solubility.

[0024] (3) The L - aspartic acid phosphate ionic liquid of the present invention is highly efficient, and the flame retardant effect can be achieved with a low addition amount. It is halogen - free, biodegradable, thermally stable at high temperature, has good char - forming performance, good dispersibility, strong interfacial bonding, and also has properties such as antibacterial and antistatic. It is green - synthesized and has a simple process. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is the infrared spectrum of the polyimide resin (BPAF - DCB)-(6FDA - DCB) synthesized in Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] To illustrate the present invention more clearly, the following examples are used to further describe the present invention. Those skilled in the art should understand that the content specifically described below is illustrative rather than restrictive, and should not be used to limit the protection scope of the present invention.

[0027] The experimental methods used in the following examples are all conventional methods unless otherwise specified. The experimental materials, reagents, etc. used in the following experimental examples can all be obtained through commercial channels or known experimental methods.

[0028] Example 1

[0029] This example provides a random copolymerized polyimide resin with the following repeating structural unit. This 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] Preheat hexafluorodiacid anhydride (6FDA) and 9,9-bis(3,4-dicarboxyphenyl) fluorene dianhydride (BPAF) in an oven at 110 °C for 12 hours of drying pretreatment. Then, prepare a three-necked flask equipped with a mechanical stirring device, inject 38 ml of DMAC into it, and add 4,4'-diaminobiphenyl-2,2-dicarboxylic acid (DCB) with a mass of 2.7226 g and a molar amount of 10 mmol. After the addition is completed, displace the air in the device with nitrogen five times to ensure that the air is completely removed. Start stirring until DCB is completely dissolved. Subsequently, add hexafluorodiacid anhydride (6FDA) and 9,9-bis(3,4-dicarboxyphenyl) fluorene dianhydride (BPAF) in four portions, with masses of 2.2212 g and 2.2921 g respectively, and molar amounts of 5 mmol each. For the first addition, add half of the total amount of the two, and then the addition amount for each subsequent addition is half of the previous one, with an interval of 40 minutes between each addition batch. For the last addition, it needs to be carried out slowly, and closely observe the viscosity change of the reaction system until the reaction is completely finished. After measurement, the solid content of the final system is determined to be 12 wt%. Then, place the reaction system in an ice-water bath environment and stir continuously for 18 hours. After completion, collect the resulting PAA acid solution.

[0034] Preheat the glass slide in a muffle furnace in advance, and then drop-coat the above-obtained PAA acid solution on the glass slide for thermal imidization (75 °C - 2 h, 125 °C - 1 h, 175 °C - 1 h, 225 °C - 1 h, 275 °C - 1 h) to obtain a PI film with a thickness of 150 μm. After the reaction is complete, take it out and scrape it off from the glass plate to obtain PI.

[0035] (2) The preparation method of L-aspartic acid phosphate ionic liquid is as follows: Take 1.331 g of L-aspartic acid, 1 ml of phosphoric acid and 140 ml of deionized water in a beaker. After magnetically stirring at room temperature until dissolved, raise the temperature to 80 °C and magnetically stir for 12 h. After the reaction is completed, extract the solution with ethyl acetate, retain the aqueous layer, dry the solution, and finally obtain a viscous transparent liquid, namely L-aspartic acid phosphate ionic liquid [Asp][H 2 PO 4 (ILAs).

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

[0037] Weigh 2 g of polyvinyl alcohol (PVA) into a 50-ml beaker, add 20 ml of deionized water, and place it on a magnetic stirrer. Heat the mixture to 90 °C and stir until it dissolves completely. After complete dissolution, weigh 0.23 g of L-aspartic acid phosphate ionic liquid into the beaker and continue stirring for 4 h to obtain a 10 wt% PVA aqueous solution.

[0038] Add triethylamine to the PVA aqueous solution to adjust the pH value of the solution to 8 for facilitating the dissolution of polyimide. Then weigh 0.10526 g of polyimide (PI) into the PVA aqueous solution and stir for 4 h. After complete dissolution, a relevant PVA composite solution is obtained.

[0039] Put the obtained PVA composite solution into an ultrasonic cleaner and shake it for 45 min, then let it stand for 6 h to remove the bubbles that may be contained in the solution during stirring. After complete standing, put it into a vacuum oven to evacuate the air to completely remove the bubbles contained in the solution. Then evenly drop-coat the treated PVA composite solution on a glass plate and place it in an oven to dry at 50 °C for 6 h to remove the excess moisture, obtaining a PVA composite film. The sample size is 150×50×0.15 mm.

[0040] Example 2

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

[0042] Example 3

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

[0044] Example 4

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

[0046] Example 5

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

[0048] Example 6

[0049] The difference between this example and Example 1 lies in that the addition amount of the flame retardant ILAs in the prepared composite film is 5 parts (i.e., 0.11 g), and other treatment methods are the same as those in Example 1.

[0050] Example 7

[0051] The difference between this example and Example 1 lies in that the addition amount of the flame retardant ILAs in the prepared composite film is 15 parts (i.e., 0.35 g), and other treatment methods are the same as those in Example 1.

[0052] Example 8

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

[0054] Comparative Example 1

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

[0056] Comparative Example 2

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

[0058] Comparative Example 3

[0059] The difference between this comparative example and Example 1 lies in that only PVA and the flame retardant ILAs are added, and the addition amount of ILAs is expressed as 15 wt% according to the weight percentage of polyvinyl alcohol (PVA), and polyimide (PI) is not added, and other treatment methods are the same as those 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), where the content of guanidine phosphate (GP) is 10 wt%, and other treatment means are the same as those in Example 1.

[0062] The vertical burning 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 dissolution performance 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 when heated at 90 °C; +: Partially soluble when heated 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 the products only added with ILAs, adding random copolymer polyimide can effectively improve the flame retardant performance of the products. In addition, compared with the polyimide synthesized by only using one type of dianhydride monomer, using random copolymer polyimide can effectively improve the transparency of the products.

[0071] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with the preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art of this patent, without departing from the scope of the technical solution of the present invention, can make some changes or modifications using the above-mentioned technical content as equivalent change equivalent embodiments. However, as long as it does not depart from the content of the technical solution of the present invention, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention still fall within the scope of the present invention.

Claims

1. A polyimide having random copolymerization, characterized in that: The polyimide with random copolymerization has the following repeating structural units: Wherein, x and y are each independently an integer ranging from 10 to 2000.

2. The polyimide with random copolymerization according to claim 1, characterized in that The steps of preparing the polyimide are as follows: (1) dissolving hexafluorodianhydride 6FDA, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride BPAF, and 4,4'-diaminobiphenyl-2,2-dicarboxylic acid DCB in NN-dimethylacetamide to react and obtain a PAA acid solution; (2) The PAA acid solution prepared in step (1) is evenly dropped onto a glass plate for a gradient temperature reaction. After the reaction is complete, the PAA acid solution is taken out and scraped off the glass plate to obtain a polyimide having random copolymerization.

3. The polyimide with random copolymerization according to claim 2, characterized in that: In step (1), the molar ratio of the total molar amount 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%.

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: a gradient temperature increase reaction is carried out in the following program: 75°C-2h, 125°C-1h, 175°C-1h, 225°C-1h, 275°C-1h.

6. An application of the polyimide with random copolymerization according to claim 1, characterized in that: The polyimide with random copolymerization is used for preparing a flame-retardant polyvinyl alcohol composite material.

7. The use of polyimide with random copolymerization according to claim 6, characterized in that: The flame-retardant polyvinyl alcohol composite material comprises, by weight, 100 parts of polyvinyl alcohol, 5-15 parts of L-aspartic acid phosphate ion liquid, and 5-10 parts of polyimide.

8. The use of polyimide with random copolymerization according to claim 6, characterized in that: The preparation method of 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 mass fractions, triethylamine is added to adjust the pH value of the solution after the solution is completely dissolved, and then polyimide is added, and after the solution is completely dissolved, the obtained mixed solution is evenly dripped on a glass plate and dried to obtain a flame-retardant polyvinyl alcohol composite material.

9. The use of polyimide with random copolymerization according to claim 8, characterized in that: Triethylamine was added to adjust the solution to pH=8.

10. The use of polyimide with random copolymerization according to claim 7, characterized in that: The preparation method of L-aspartic acid phosphate ionic liquid is as follows: take L-aspartic acid, phosphoric acid and deionized water in a beaker, stir magnetically at room temperature until dissolved, raise the temperature to 80°C and stir magnetically for 12 hours, and after the reaction is completed, extract the solution with ethyl acetate, retain the water layer, and dry the solution to finally obtain a viscous transparent liquid, namely L-aspartic acid phosphate ionic liquid [Asp][H2PO4] (ILAs).

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