Flame retardant polyimide resin and polyimide film and preparation method and use thereof

Abstract

The invention discloses a flame-retardant polyimide resin and a polyimide film, and a preparation method and application thereof, and relates to the technical field of flame-retardant materials. The invention designs a phosphorus-based dianhydride with a novel structure for synthesizing polyimide, introduces a phosphorus-based group into a polymer main chain, improves the flame-retardant performance of the material from the perspective of molecular design, and avoids the use of inorganic flame retardants, which causes a loss of material strength. At the same time, a long-chain alkyl diamine is used in combination with the flexibility of the phosphorus-based dianhydride itself, and a flexible part is introduced into a polymer chain segment, so as to facilitate a tighter rearrangement of the molecular chain and the formation of a crystal region, thereby improving its mechanical properties.

Description

Technical Field

[0001] The invention relates to the technical field of flame retardant materials, and in particular to a flame retardant polyimide resin and a polyimide film, and a preparation method and application thereof. Background Art

[0002] With the continuous development of the electronics industry, electronic devices are gradually developing towards high miniaturization, integration, multi-function and high frequency, which will inevitably generate heat concentration, seriously affecting the service life of electronic devices. Therefore, it is often necessary to rely on insulating coating materials to improve. In recent years, with the rise of the new energy electric vehicle industry, the insulation coating of power batteries has put forward new application requirements for the film material industry, because the heat dissipation of power batteries and their motors is a crucial link in the safety and stability of electric vehicles. The current method used in the industry is to wrap the power battery and motor with an insulating film and immerse it in a coolant. The coolant was mainly water-based in the early days, and was later changed to oily considering many factors. The main components are glycerin, ethylene glycol, additives and a small amount of water adsorbed during use.

[0003] At present, polyimide film is still one of the main materials used for power battery and motor coating. However, the intrinsic thermal conductivity of polyimide is very low, and there is no microscopic heat conduction path in the internal structure, which leads to high interface thermal resistance and poor thermal conductivity of the material itself, which is not conducive to the rapid conduction of heat and easily leads to local overheating or even spontaneous combustion, greatly limiting its wide application.

[0004] Therefore, in the prior art, the thermal conductivity of polyimide is generally improved by adding inorganic fillers, but this often leads to a serious loss of the mechanical properties of the film and a significant decrease in the service life, which is often not worth the cost.

[0005] Therefore, it is necessary to develop a new polyimide film with excellent thermal conductivity, and it is hoped that it will have both good mechanical strength and certain flame retardancy to meet the application under harsh conditions (such as when the power battery is working). Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a new type of polyimide resin and a preparation method thereof, and to prepare a polyimide film from the polyimide resin, so that the polyimide has the advantages of high thermal conductivity, high flame retardancy and high mechanical strength, and is more suitable for application in the field of new energy power battery coating.

[0007] The technical problem to be solved by the present invention is achieved by adopting the following technical solutions:

[0008] One of the objects of the present invention is to provide a polyimide resin, the structural formula of which is as follows:

[0009]

[0010] Where Ar1 is

[0011] Ar2 is selected from Any of the following:

[0012] R1 is m = 6 to 12;

[0013] R2 is selected from Any of the following:

[0014] P = 5-10;

[0015] X = 0.01-0.2;

[0016] n=6~100.

[0017] The second object of the present invention is to provide a method for preparing a polyimide resin, comprising the following steps:

[0018] (1) Phosphorus dianhydride, Condensation reaction with H2N-R1-NH2 and H2N-R2-NH2 produces polyamic acid;

[0019] (2) The polyamic acid undergoes imidization reaction to obtain a polyimide resin.

[0020] The structural formula of the phosphorus dianhydride is as follows:

[0021]

[0022] The third object of the present invention is to provide a polyimide film made of the polyimide resin.

[0023] A fourth object of the present invention is to provide the use of the polyimide film as an outer film of a lithium battery.

[0024] The beneficial effects of the present invention are as follows: the present invention designs a phosphorus-based dianhydride of a novel structure for synthesizing polyimide, introduces a phosphorus-based group into a polymer main chain, improves the flame retardant properties of the material from a molecular design perspective, and avoids the use of inorganic flame retardants that result in a loss of material strength; at the same time, a long-chain alkyl diamine is used in combination with the flexibility of the phosphorus-based dianhydride itself, and a flexible portion is introduced into the polymer chain segment, so as to facilitate a tighter rearrangement of the molecular chain and the formation of a crystal region, thereby improving its mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is the infrared spectrum of the polyimide resin prepared in Example 2. DETAILED DESCRIPTION

[0026] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below in conjunction with specific embodiments.

[0027] The present invention provides a polyimide resin, the structural formula of which is as follows:

[0028]

[0029] Where Ar1 is

[0030] Ar2 is selected from Any of the following:

[0031] R1 is m = 6 to 12;

[0032] R2 is selected from Any of the following:

[0033] P = 5-10;

[0034] X = 0.01-0.2;

[0035] n=6~100.

[0036] Further, X = 0.01 to 0.1. In some preferred embodiments, X = 0.01 to 0.05.

[0037] Furthermore, n=15-75. In some preferred embodiments, n=20-50.

[0038] The present invention provides a method for preparing the polyimide resin, comprising the following steps:

[0039] (1) Phosphorus dianhydride, Condensation reaction with H2N-R1-NH2 and H2N-R2-NH2 produces polyamic acid;

[0040] (2) The polyamic acid undergoes imidization reaction to obtain a polyimide resin.

[0041] The structural formula of the phosphorus dianhydride is as follows:

[0042]

[0043] The preparation method of the phosphorus dianhydride comprises the following steps:

[0044] (1) 1-chloro-4,5-dimethylnaphthalene undergoes a substitution reaction with 4-chlorophenol to obtain 1-(4-chlorophenyl ether)-4,5-dimethylnaphthalene;

[0045] (2) 1-(4-chlorophenylether)-4,5-dimethylnaphthalene is oxidized to obtain 1-(4-chlorophenylether)-4,5-dicarboxynaphthalene;

[0046] (3) 1-(4-chlorophenyl ether)-4,5-dicarboxy naphthalene undergoes a substitution reaction with bis(phenyl phosphate)resorcinol phosphate to obtain tetracarboxylic acid phenol phosphate;

[0047] (4) The phosphorus dianhydride is obtained by condensing the tetracarboxylic acid phenol phosphate.

[0048] The synthetic route is as follows:

[0049]

[0050] In step (1), the molar ratio of 1-chloro-4,5-dimethylnaphthalene to 4-chlorophenol is 1:(1-1.1). A slightly excess amount of 4-chlorophenol can make the 1-chloro-4,5-dimethylnaphthalene react as completely as possible.

[0051] In step (2), the oxidation reaction uses at least one of potassium permanganate, potassium dichromate, and cobalt acetate as an oxidant, but is not limited thereto. Under the action of the oxidant, the methyl group on the benzene ring is oxidized to a carboxylic acid.

[0052] In step (3), the molar ratio of 1-(4-chlorophenyl ether)-4,5-dicarboxy naphthalene to bis(phenyl phosphate)resorcinol phosphate is (2 to 2.2): 1. A slightly excess amount of 1-(4-chlorophenyl ether)-4,5-dicarboxy naphthalene can make the bis(phenyl phosphate)resorcinol phosphate react as completely as possible.

[0053] In steps (1) and (3), the substitution reaction uses at least one of potassium carbonate, sodium carbonate, sodium acetate, triethylamine, pyridine, and N,N-diisopropylethylamine as an acid binding agent, but is not limited thereto. The acid binding agent neutralizes the hydrogen chloride generated by the substitution reaction and promotes the forward progress of the substitution reaction.

[0054] In step (4), the condensation reaction uses acetic anhydride as a dehydrating agent. Under the action of the dehydrating agent, the carboxylic acid molecules are dehydrated to form anhydrides.

[0055] The invention provides a polyimide film, which is made of the polyimide resin. The polyimide film can be prepared by a casting method, a spin coating method, a scraping method, etc. commonly used in the art.

[0056] The invention provides the use of the polyimide film as an outer film of a lithium battery.

[0057] Example 1

[0058] Preparation of phosphorus dianhydride:

[0059] (1) 1-chloro-4,5-dimethylnaphthalene (38 g, 200 mmol), 4-chlorophenol (12.8 g, 100 mmol), sodium carbonate (21.2 g, 200 mmol) and 250 mL of toluene were added to a reactor, and the mixture was heated to reflux and stirred for 8 h. After the reaction was completed, the reaction solution was washed with water until it was neutral, and the toluene was removed by rotary evaporation until a small amount of solid was precipitated. The reaction solution was cooled and allowed to stand to precipitate a large amount of yellow solid. The solid was filtered, the residue was washed with water, dried, and passed through a C18 column to obtain 1-(4-chlorophenylether)-4,5-dimethylnaphthalene with a yield of 87.6%. 1 HNMR(DMSO)2.65(m,6H,2CH3);6.95(d,1H,1CH);6.5(d,1H,1CH);7.08(d,1H, 1CH); 7.24 (t, 1H, 1CH); 7.94 (d, 1H, 1CH); 6.84 (d, 2H, 2CH); 7.25 (d, 2H, 2CH).

[0060] (2) Add 24 g of 1-(4-chlorophenylether)-4,5-dimethylnaphthalene and 300 mL of 2% potassium permanganate aqueous solution to the reactor, heat to reflux and stir to react for 12 h. After the reaction is completed, filter the reaction solution, wash the filter residue with water, and dry it to obtain 1-(4-chlorophenylether)-4,5-dicarboxynaphthalene with a yield of 85.8%. 1 H NMR (DMSO) 11-12 (s, 2H, 2COOH); 8.65 (d, 1H, 1CH); 8.89 (d, 1H, 1CH); 7.16 (d, 1H , 1CH); 7.88 (t, 1H, 1CH); 8.78 (d, 1H, 1CH); 6.88 (d, 2H, 2CH); 7.25 (d, 2H, 2CH).

[0061] (3) Add 1-(4-chlorophenylether)-4,5-dicarboxynaphthalene (20.56 g, 60 mmol), bis(phenyl phosphate)resorcinol phosphate (12.66 g, 30 mmol), 150 mL of m-cresol and potassium carbonate (8.28 g, 60 mmol) to the reactor, heat to 150° C. and stir to react for 3 h. After the reaction is completed, add the reaction solution to water to precipitate a large amount of dark yellow solid, filter, wash with water until neutral, and pass through a C18 chromatographic column to obtain tetracarboxylic acid phenol phosphate with a yield of 64%. 1H NMR (DMSO) 11-12 (s, 4H, 4COOH); 8.65 (d, 2H, 2CH); 8.89 (d, 2H, 2CH); 7.16 (d, 2H, 2CH); 7.92 (t, 2H, 2CH); 8.79 (d, 2H, 2CH); 6.78 (d, 4H , 4CH); 6.65 (d, 4H, 4CH); 6.67 (d, 4H, 4CH); 7.17 (t, 4H, 4CH); 6.82 (t, 2H, 2CH); 6.20 (s, 1H, 1CH); 6.29 (d, 2H, 2CH); 6.95 (t, 1H, 1CH).

[0062] 19.8 g of tetracarboxylic acid phenol phosphate and 120 mL of acetic anhydride were added to the reactor, heated to reflux and stirred for 8 h. After the reaction, the reaction solution was added to methanol, stirred, and the solid was precipitated, filtered, washed with methanol, and dried to obtain 16.6 g of phosphorus dianhydride with a yield of 84%. 1 H NMR (DMSO) 8.65 (d, 2H, 2CH); 8.89 (d, 2H, 2CH); 7.16 (d, 2H, 2CH); 7.92 (t, 2H, 2CH); 8.79 (d, 2H, 2CH); 6.78 (d, 4H, 4CH); 6.6 5 (d, 4H, 4CH); 6.67 (d, 4H, 4CH); 7.17 (t, 4H, 4CH); 6.82 (t, 2H, 2CH); 6.20 (s, 1H, 1CH); 6.29 (d, 2H, 2CH); 6.95 (t, 1H, 1CH).

[0063] Example 2

[0064] Under nitrogen protection, add the phosphorus dianhydride (147.3g, 0.15mol), hexamethylenediamine (20.9g, 0.18mol) and 800mL of meta-cresol prepared in Example 1 to the reactor, add benzoic acid (42.7g, 0.35mol) and isoquinoline (45.2g, 0.35mol) after complete dissolution, and heat to 160°C for stirring and reaction for 6h. After the reaction is completed, add the reaction solution to ethanol, stir, and a light yellow solid is precipitated, filter, wash the filter residue with ethanol, and dry to obtain a solid reactant. Dissolve the solid reactant in 2000mL of N-methylpyrrolidone, add 4,4′-diaminodiphenyl ether (164g, 0.82mol), add pyromellitic anhydride (185.3g, 0.85mol) after complete dissolution, and stir the reaction at room temperature for 15h to obtain a polyamic acid solution. The polyamic acid solution was coated into a film, dried, and finally subjected to imidization reaction (120°C / 60min, 175°C / 15min, 250°C / 15min, 320°C / 10min) to obtain a polyimide film.

[0065] Example 3

[0066] Under nitrogen protection, add the phosphorus dianhydride (147.3g, 0.15mol), hexamethylenediamine (19.2g, 0.165mol) and 800mL of meta-cresol prepared in Example 1 to the reactor, add benzoic acid (42.7g, 0.35mol) and isoquinoline (45.2g, 0.35mol) after complete dissolution, and heat to 160°C for stirring and reaction for 6h. After the reaction is completed, add the reaction solution to ethanol, stir, and a light yellow solid is precipitated, filter, wash the filter residue with ethanol, and dry to obtain a solid reactant. Dissolve the solid reactant in 2000mL of N-methylpyrrolidone, add 4,4′-diaminodiphenyl ether (167g, 0.835mol), add pyromellitic anhydride (185.3g, 0.85mol) after complete dissolution, and stir the reaction at room temperature for 15h to obtain a polyamic acid solution. The polyamic acid solution was coated into a film, dried, and finally subjected to imidization reaction (120°C / 60min, 175°C / 15min, 250°C / 15min, 320°C / 10min) to obtain a polyimide film.

[0067] Example 4

[0068] Under nitrogen protection, add the phosphorus dianhydride (147.3g, 0.15mol), hexamethylenediamine (34.8g, 0.3mol) and 800mL of meta-cresol prepared in Example 1 to the reactor, add benzoic acid (42.7g, 0.35mol) and isoquinoline (45.2g, 0.35mol) after complete dissolution, and heat to 160°C for stirring and reaction for 6h. After the reaction is completed, add the reaction solution to ethanol, stir, and a light yellow solid is precipitated, filter, wash the filter residue with ethanol, and dry to obtain a solid reactant. Dissolve the solid reactant in 2000mL of N-methylpyrrolidone, add 4,4′-diaminodiphenyl ether (140g, 0.7mol), add pyromellitic anhydride (185.3g, 0.85mol) after complete dissolution, and stir the reaction at room temperature for 15h to obtain a polyamic acid solution. The polyamic acid solution was coated into a film, dried, and finally subjected to imidization reaction (120°C / 60min, 175°C / 15min, 250°C / 15min, 320°C / 10min) to obtain a polyimide film.

[0069] Example 5

[0070] Under nitrogen protection, add the phosphorus dianhydride (147.3g, 0.15mol) prepared in Example 1, 1,1-dodecanediamine (33.1g, 0.165mol) and 800mL of meta-cresol to the reactor, add benzoic acid (42.7g, 0.35mol) and isoquinoline (45.2g, 0.35mol) after complete dissolution, and heat to 160°C for stirring and reaction for 6h. After the reaction is completed, add the reaction solution to ethanol, stir, and a light yellow solid is precipitated, filter, wash the filter residue with ethanol, and dry to obtain a solid reactant. Dissolve the solid reactant in 2000mL of N-methylpyrrolidone, add 4,4′-diaminodiphenyl ether (167g, 0.835mol), add pyromellitic anhydride (185.3g, 0.85mol) after complete dissolution, and stir the reaction at room temperature for 15h to obtain a polyamic acid solution. The polyamic acid solution was coated into a film, dried, and finally subjected to imidization reaction (120°C / 60min, 175°C / 15min, 250°C / 15min, 320°C / 10min) to obtain a polyimide film.

[0071] Comparative Example 1

[0072] Under nitrogen protection, add pyromellitic anhydride (32.7g, 0.15mol), hexamethylenediamine (20.9g, 0.18mol) and 800mL of m-cresol to the reactor, add benzoic acid (42.7g, 0.35mol) and isoquinoline (45.2g, 0.35mol) after complete dissolution, heat to 160℃ and stir for 6h. After the reaction is completed, add the reaction solution to ethanol and stir, a light yellow solid precipitates, filter, wash the filter residue with ethanol, and dry to obtain a solid reactant. Dissolve the solid reactant in 2000mL of N-methylpyrrolidone, add 4,4′-diaminodiphenyl ether (164g, 0.82mol), add pyromellitic anhydride (185.3g, 0.85mol) after complete dissolution, stir at room temperature for 15h to obtain a polyamic acid solution. The polyamic acid solution was coated into a film, dried, and finally subjected to imidization reaction (120°C / 60min, 175°C / 15min, 250°C / 15min, 320°C / 10min) to obtain a polyimide film.

[0073] Comparative Example 2

[0074] The method of Example 5 was followed, except that the molar ratio of phosphorus dianhydride to 1,1-dodecanediamine was adjusted from 1:1.1 to 1:1.08. As a result, the solubility of the polymer decreased due to its high crystallinity, and the polymer precipitated, and the reaction was terminated.

[0075] The polyimide films obtained in the above examples and comparative examples were tested for mechanical properties and flame retardancy. The test results are shown in Table 1.

[0076] Mechanical properties test: in accordance with standard GB / T 1040-1998.

[0077] Flame retardancy test: According to the standard GB / T 5169.5-2020, record the maximum time that the polyimide film can withstand blackening and carbonization but no perforation during needle flame burning.

[0078] Molecular weight test: Agilent 1100 Series high performance liquid chromatograph, polystyrene as standard, injection volume 50.000 μL, DMF as mobile phase, flow rate 1.000 mL / min, column temperature 25°C; weigh 0.0500 g of polyimide resin and dissolve it in 2.00 mL of chromatographically pure DMF, filter it with a 0.45 μm filter membrane after it is completely dissolved, and then measure its molecular weight with high performance liquid chromatography.

[0079] Table 1

[0080]

[0081] As can be seen from Table 1, the present invention improves the flame retardancy of the polyimide resin by using a novel phosphorus dianhydride monomer and introducing aliphatic diamine to form a local block, and also improves the mechanical strength of the polyimide resin by forming a crystalline region.

[0082] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A polyimide resin, characterized in that: The structural formula of the polyimide resin is as follows: Where Ar1 is Ar2 is selected from Any of the following: R1 is m = 6 to 12; R2 is selected from Any of the following: P＝5～10； X＝0.01～0.2； n＝6～100。 2. The polyimide resin according to claim 1, characterized in that: X＝0.01～0.1。 3. The polyimide resin according to claim 2, characterized in that: X＝0.01～0.05。 4. The polyimide resin according to claim 1, characterized in that: n＝15～75。 5. The polyimide resin according to claim 4, characterized in that: n＝20～50。 6. The method for preparing a polyimide resin according to any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: (1) Phosphorus dianhydride, Condensation reaction with H2N-R1-NH2 and H2N-R2-NH2 produces polyamic acid; (2) The polyamic acid undergoes imidization reaction to obtain a polyimide resin.

7. The preparation method according to claim 6, characterized in that: The structural formula of the phosphorus dianhydride is as follows:

8. The preparation method according to claim 7, characterized in that: The preparation method of the phosphorus dianhydride comprises the following steps: (1) 1-chloro-4,5-dimethylnaphthalene undergoes a substitution reaction with 4-chlorophenol to obtain 1-(4-chlorophenyl ether)-4,5-dimethylnaphthalene; (2) 1-(4-chlorophenylether)-4,5-dimethylnaphthalene is oxidized to obtain 1-(4-chlorophenylether)-4,5-dicarboxynaphthalene; (3) 1-(4-chlorophenyl ether)-4,5-dicarboxy naphthalene undergoes a substitution reaction with bis(phenyl phosphate)resorcinol phosphate to obtain tetracarboxylic acid phenol phosphate; (4) The phosphorus dianhydride is obtained by condensing the tetracarboxylic acid phenol phosphate.

9. A polyimide film, made from the polyimide resin according to any one of claims 1 to 5 or the polyimide resin prepared by the preparation method according to any one of claims 6 to 8.

10. Use of the polyimide film according to claim 9 as an outer film of a lithium battery.

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