CN114181392A - High-solid-content low-viscosity polyamic acid solution and preparation method and application thereof - Google Patents
High-solid-content low-viscosity polyamic acid solution and preparation method and application thereof Download PDFInfo
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Abstract
The invention relates to a high-solid-content low-viscosity polyamic acid solution, a preparation method and application thereof, and solves the problems that gel is easy to lose fluidity and the next step of coating or spinning cannot be carried out when the solid content is high in the synthesis process of the polyamic acid solution in the prior art. The method comprises the following steps: carrying out condensation polymerization reaction on dianhydride monomer and diamine monomer in a reaction solvent to obtain high-concentration polyamic acid gel with solid content of more than 30% and difficult processing, wherein the viscosity range is 1000000-2000000 cP; adding a dehydrating agent and a catalyst into the high-concentration polyamic acid gel, and fully mixing, wherein the polyamic acid gel is gradually disentangled to obtain a polyamic acid solution with good fluidity and low viscosity, and the viscosity range is 1000-10000 cP. The high-solid-content low-viscosity polyamic acid solution obtained by the method is used for coating and spinning, the prepared polyimide film has more excellent mechanical property and lower thermal expansion coefficient, and the polyimide fiber has higher draw ratio and better mechanical property.
Description
Technical Field
The invention belongs to the technical field of materials, and particularly relates to a high-solid-content low-viscosity polyamic acid solution as well as a preparation method and application thereof.
Technical Field
Polyimide is a high-performance polymer containing an imide ring in a molecular main chain, and is widely applied to the fields of aviation, aerospace, microelectronics, rail transit, nuclear industry and the like due to excellent thermo-mechanical properties, irradiation resistance, low thermal expansion coefficient and electrical insulation. The common products of polyimide are in the forms of films, fibers and the like, and the preparation method of the products mainly adopts a two-step method, namely, a polyamic acid solution is synthesized firstly, and then the final polyimide product is obtained through chemical imidization or thermal imidization. Therefore, high quality polyamic acid solutions are critical to the preparation of high performance polyimide products.
It was found that the solid content of the polyamic acid solution is increased by a proper amount, for example, from 10% to 19%, and the tensile strength and modulus of the polyimide fiber are improved to different degrees, respectively from 0.72GPa and 42.2GPa to 1.21GPa and 99.9GPa (RSC adv.,2015,5,69555), and it is seen that the polyimide prepared from the high-solid polyamic acid solution has better mechanical properties. However, when the solution solids content is too high, the solution viscosity rises rapidly and even gels due to strong hydrogen bonding interactions, losing further processing properties.
Patent CN 103788651B discloses a polyamic acid solution with low apparent viscosity and a preparation method thereof, wherein the addition of trimethylchlorosilane can make the apparent viscosity of the polyamic acid solution decrease by more than 90%, but the addition of trimethylchlorosilane can affect the mechanical properties and thermal decomposition temperature of the final polyimide product.
Patent CN 104292459B discloses a preparation method of polyimide material with high solid content and low viscosity, which obtains polyamic acid solution with viscosity ranging from 500-.
Patent CN 112409612 a discloses a method for preparing a polyamic acid solution with high solid content and low viscosity, wherein the polyamic acid solution prepared by adding ammonium carboxylate gemini surfactant has excellent tape casting processability.
Although some researches and developments on polyimide materials with high solid content and low viscosity exist in the prior art, the method disclosed by the invention has some problems, in the preparation process of the polyimide materials with high solid content and low viscosity in the prior art, after other reagents (chlorosilane, surfactant and the like) are added, the solid content can be improved, the viscosity can be reduced, and the subsequent processing and forming performances can be improved, but the mechanical properties and the thermal properties of the final polyimide product can be influenced while the viscosity of the high solid content polyamic acid solution is reduced in the prior art. Therefore, there is a need to develop a preparation process for obtaining a polyamic acid solution with high solid content and low viscosity, which can improve the processing performance and ensure that the mechanical and thermal properties of the polyimide product prepared from the polyamic acid solution are not affected.
Disclosure of Invention
The invention aims to overcome the problems of high viscosity, easy gel loss and fluidity loss and difficult processing of high-solid-content polyamic acid solution in the prior art, and provides a preparation method of the high-solid-content low-viscosity polyamic acid solution.
In order to achieve the purpose, the invention discloses a high-solid-content low-viscosity polyamic acid solution and a preparation method thereof, wherein the preparation method comprises the following steps:
(1) adding diamine monomer and dianhydride monomer into a reaction solvent, and fully stirring to perform condensation polymerization reaction to obtain polyamic acid gel with the solid content of more than 30%, loss of fluidity and difficulty in processing, wherein the viscosity range is 1000000-2000000cP, and the solid content of the polyamic acid gel is 30-35 wt%;
(2) adding a certain amount of dehydrating agent and catalyst into the polyamic acid gel according to a certain proportion, fully stirring, and gradually disentangling the polyamic acid gel to obtain a polyamic acid solution with good fluidity and low viscosity, wherein the viscosity range is 1000 plus 10000 cP.
Preferably, the solid content of the polyamic acid gel in the step (1) is 10% to 50%, the viscosity is 1000000-2000000cP, the fluidity is lost, and the coating or spinning is difficult. The molar ratio of dianhydride monomer to diamine monomer is 0.98:1-1.02: 1. The solution of the low-viscosity polyamic acid in the step (2) has good fluidity for coating and spinning, and the viscosity range is 1000-10000 cP.
Preferably, the dianhydride monomer in step (1) is one or more of 3,3 ', 4,4 ' -Benzophenone Tetracarboxylic Dianhydride (BTDA), 3 ', 4,4 ' -biphenyl tetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), 2,3 ', 3,4 ' -biphenyl tetracarboxylic dianhydride (α -BPDA), bisphenol a type dianhydride (BPADA), 4,4 ' -oxydiphthalic anhydride (ODPA), hexafluoroisopropylene phthalic acid (6FDA), diphenyl sulfide Tetracarboxylic Dianhydride (TDPA), and 3,3 ', 4,4 ' -diphenyl sulfone tetracarboxylic dianhydride mixed in any proportion;
preferably, the diamine monomer in step (1) is one or more of p-Phenylenediamine (PDA), m-phenylenediamine, 4 '-diaminodiphenyl ether (ODA), 2- (4-aminophenyl) -5-aminobenzimidazole (BIA), 4' -diaminodiphenyl sulfone, 4 '-diamino-2, 2' -bistrifluoromethylbiphenyl (TFMB) mixed in any proportion; the reaction solvent is one of N, N-Dimethylformamide (DMF), N-dimethylacetamide (DMAc), N-vinyl pyrrolidone (NMP) and dimethyl sulfoxide (DMSO).
Preferably, the volume ratio of the dehydrating agent to the catalyst in the step (2) is 5:1-1:5, and the molar ratio of the dehydrating agent to the dianhydride monomer is 0.2:1-0.8:1.
Preferably, the dehydrating agent in the step (2) is one or more of acetic anhydride, propionic anhydride and butyric anhydride; the catalyst is one or a mixture of pyridine, triethylamine, imidazole, isoquinoline, 2-methylpyridine and 3-methylpyridine.
Another object of the present invention is to provide a polyamic acid solution having a high solid content and a low viscosity prepared by the above method and a method for processing a polyimide film or fiber obtained from the solution.
Preferably, the prepared polyamic acid solution is coated on a glass plate, the thickness of the polyamic acid solution is about 30 mu m, and the polyamic acid solution is sequentially heated for 1h at the temperature of 60 ℃, 135 ℃ and 300 ℃ respectively to obtain a corresponding polyimide film; or further filtering and defoaming the prepared polyamic acid solution, spinning by adopting a wet spinning process, and cyclizing the obtained nascent fiber by sequentially passing through hot furnaces at 270 ℃, 350 ℃ and 430 ℃ to obtain the corresponding polyimide fiber.
Preferably, the tensile strength of the obtained film is 150-350MPa, and the tensile modulus is 2-10 GPa; the tensile strength of the fiber is 1.2-4.4GP, and the tensile modulus is 18-150 GPa.
Compared with the prior art, the invention has the beneficial effects that:
(1) the dehydrating agent and the catalyst are added into the high-solid-content polyamic acid gel, so that the strong hydrogen bond interaction in the polyamic acid gel is destroyed, the viscosity of the polyamic acid gel can be greatly reduced, and the processing performance of the polyamic acid gel is improved, so that the polyamic acid gel can be directly used as a raw material for preparing a polyimide film or a fiber;
(2) the polyimide film obtained by further processing the imidized polyimide solution with the high-solid-content low-viscosity polyamide acid solution prepared by the method has higher in-plane orientation, more stable and optimized performance, more excellent mechanical property and lower thermal expansion coefficient, and the polyimide fiber has higher draw ratio and better mechanical property.
(3) The method has simple process operation, does not need to change the prior synthesis and processing equipment, and is easy for industrialized production.
Drawings
FIGS. 1 to 5 show the gel state of polyamic acid before (a) adding an imidizing agent and the solution state of polyamic acid after (b) adding an imidizing agent in examples 1 to 5 of the present invention, respectively.
FIGS. 6-10 are graphs showing the change in loss tangent (Tan) of the polyamic acid solution with solid content at different angular frequencies during the dynamic rheology test in comparative examples 1-5, respectively, according to the invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar modules or modules having the same or similar functionality throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.
In the description herein, references to the description of "one embodiment," "another embodiment," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
The present invention will be further described with reference to specific examples, but the present invention is not limited to the following examples. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
Compared with the preparation process of the polyimide material with high solid content and low viscosity in the prior art, the preparation process has the advantages that other reagents (such as chlorosilane and a surfactant) are added to reduce the viscosity of the polyimide material so as to improve the processing performance of the polyimide material, but the mechanical property and the thermal property of a final polyimide product can be influenced while the viscosity of the polyamic acid solution with high solid content is reduced in the prior art. According to the high-solid-content low-viscosity polyamic acid solution disclosed by the invention, the selection and component proportion of a proper imidization reagent are regulated and controlled to obtain the low-viscosity polyamic acid solution with proper imidization degree, solid content and accurate viscosity range, so that the mechanical properties such as mechanical properties and chemical properties such as thermal properties of a finally obtained polyimide product are prevented from being adversely affected while the later-stage processing performance is ensured.
The following specific examples and comparative examples are provided to illustrate the embodiments of the present invention in one step.
Example 1
(1) 10.594g (0.05297mol) of ODA is dissolved in 50mL of DMAc solvent, after diamine is completely dissolved, 11.547g (0.05297mol) of PMDA is added into the system in batches, and the reaction is continued for 24 hours under the condition of ice water bath (0 ℃), thus obtaining polyamic acid gel with the solid content of 32 wt%, the viscosity of 1918000cP, and the coating or spinning is difficult to be carried out after the fluidity is lost;
(2) adding 2.0mL (0.0212mol) of acetic anhydride and 1.0mL of pyridine into the gel, and stirring for 12h at room temperature (30 ℃) to uniformly mix the mixture to obtain the high-solid-content low-viscosity polyamide acid solution with imidization degree of 20 percent and good fluidity, wherein the viscosity is 8130 cP.
FIGS. 1(a) and (b) are views showing the gel state of polyamic acid before the imidizing agent is added (a) and the solution state of polyamic acid after the imidizing agent is added (b) in example 1, respectively. Comparison clearly shows that, after the addition of the imidizing agent specified in the present application, although the solids content is increased, the viscosity is reduced, and the gel-like state is converted into a clear, homogeneous, more fluid, low-viscosity polyamic acid solution.
Comparative example 1
4.942g (0.02471mol) of ODA is dissolved in 50mL of DMAc solvent, after diamine is completely dissolved, 5.386g (0.02471mol) of PMDA is added into the system in batches, and the reaction is continued for 24 hours under the condition of ice-water bath (0 ℃) to obtain polyamic acid solution with the solid content of 18 weight percent and the viscosity of 8500 cP.
FIG. 6 shows the change of loss tangent (Tan) of the polyamic acid solution with solid content at different angular frequencies during the dynamic rheology test in comparative example 1, and according to Winter and Chambon theories, the loss tangent (Tan) at the time of solution-gel transition is independent of angular frequency, and it is known that the solution-gel transition occurs when the solid content exceeds 18% during the conventional synthesis of the polyamic acid solution in comparative example 1, and the subsequent coating or spinning is difficult. Therefore, in order to ensure the processing fluidity, the solid content of the polyamic acid solution described in comparative example 1 in the conventional synthesis process was up to 18%.
To examine the properties of the polyimide film or fiber obtained by processing the polyamic acid solution prepared by the method of the present invention. (1) Coating the prepared polyamic acid solution on a glass plate to obtain a film with the thickness of about 30 mu m, and sequentially heating the polyamic acid solution for 1h at the temperature of 60 ℃, 135 ℃ and 300 ℃ respectively to obtain a corresponding polyimide film; (2) filtering and defoaming the prepared polyamic acid solution, spinning by adopting a wet spinning process, and cyclizing the obtained nascent fiber by sequentially passing through a hot furnace at 270 ℃, 350 ℃ and 430 ℃ to obtain the corresponding polyimide fiber. The properties of the polyimide film and fiber are as follows:
TABLE 1 comparison of polyimide film and fiber Properties
| Tensile strength | Tensile modulus | Elongation at break | Coefficient of thermal expansion | Maximum draw ratio | |
| Example 1 (film) | 165.6MPa | 2.81GPa | 49％ | 28.3ppm/℃ | / |
| COMPARATIVE EXAMPLE 1 (film) | 130.1MPa | 1.89GPa | 46％ | 32.8ppm/℃ | / |
| Example 1 (fiber) | 1.21GPa | 18.9GPa | 13％ | / | 5.5 |
| COMPARATIVE EXAMPLE 1 (fiber) | 0.82GPa | 11.9 |
15％ | / | 4.0 |
Example 2
(1) Dissolving 5.417g (0.05016mol) of PDA in 50mL of DMAc solvent, after diamine is completely dissolved, adding 14.747g (0.05016mol) of BPDA into the system in batches, and continuously reacting for 24 hours under the condition of ice-water bath (0 ℃) to obtain polyamic acid gel with the solid content of 30 wt%, wherein the viscosity is 1826000cP, and the polyamic acid gel loses flowability and is difficult to coat or spin;
(2) adding 1.0mL (0.01mol) of acetic anhydride and 0.5mL of pyridine into the gel, and stirring for 12h at room temperature (30 ℃) to uniformly mix the acetic anhydride and the pyridine to obtain the high-solid-content low-viscosity polyamide acid solution with imidization degree of 10% and good fluidity, wherein the viscosity is 7850 cP.
FIGS. 2(a) and (b) are views showing the gel state of polyamic acid before the imidizing agent is added (a) and the solution state of polyamic acid after the imidizing agent is added (b) in example 2, respectively. Comparison clearly shows that, after the addition of the imidizing agent specified in the present application, although the solids content is increased, the viscosity is reduced, and the gel-like state is converted into a clear, homogeneous, more fluid, low-viscosity polyamic acid solution.
Comparative example 2
2.775g (0.02569mol) of PDA is dissolved in 50mL of DMAc solvent, after diamine is completely dissolved, 7.553g (0.02569mol) of BPDA is added into the system in batches, and reaction is continued for 24h under the condition of ice-water bath (0 ℃) to obtain a polyamic acid solution with the solid content of 18 weight percent and the viscosity of 8380 cP.
FIG. 7 shows the change of loss tangent (Tan) of the polyamic acid solution with solid content at different angular frequencies during the dynamic rheology test in comparative example 2, and according to Winter and Chambon theories, the loss tangent (Tan) at the time of solution-gel transition is independent of angular frequency, and it is known that the solution-gel transition occurs when the solid content exceeds 20% during the conventional synthesis of the polyamic acid solution in comparative example 2, and the subsequent coating or spinning is difficult. Therefore, in order to ensure the processing fluidity, the solid content of the polyamic acid solution of comparative example 2 in the conventional synthesis process is up to 20%.
To examine the properties of the polyimide film or fiber obtained by processing the polyamic acid solution prepared by the method of the present invention. (1) Coating the prepared polyamic acid solution on a glass plate to obtain a film with the thickness of about 30 mu m, and sequentially heating the polyamic acid solution for 1h at the temperature of 60 ℃, 135 ℃ and 300 ℃ respectively to obtain a corresponding polyimide film; (2) filtering and defoaming the prepared polyamic acid solution, spinning by adopting a wet spinning process, and cyclizing the obtained nascent fiber by sequentially passing through a hot furnace at 270 ℃, 350 ℃ and 430 ℃ to obtain the corresponding polyimide fiber. The properties of the polyimide film and fiber are as follows:
TABLE 2 comparison of polyimide film and fiber Properties
Example 3
(1) 8.964g (0.04482mol) of ODA is dissolved in 50mL of DMAc solvent, after diamine is completely dissolved, 7.898(0.04482mol) of BPDA is added into the system in batches, and the reaction is continued for 24 hours under the condition of ice water bath (0 ℃) to obtain polyamic acid gel with the solid content of 32 wt%, wherein the viscosity is 1768000cP, and the polyamic acid gel loses the fluidity and is difficult to coat or spin;
(2) 2.5mL (0.02689mol) of acetic anhydride and 1.25mL of pyridine are added into the gel, and the mixture is stirred for 5 hours at room temperature (30 ℃) to be uniformly mixed, so that the high-solid-content low-viscosity polyamide acid solution with imidization degree of 30% and good fluidity is obtained, and the viscosity is 5650 cP.
FIGS. 3(a) and (b) are graphs showing the gel state of polyamic acid before the imidizing agent is added (a) and the solution state of polyamic acid after the imidizing agent is added (b) in example 3, respectively. Comparison clearly shows that, after the addition of the imidizing agent specified in the present application, although the solids content is increased, the viscosity is reduced, and the gel-like state is converted into a clear, homogeneous, more fluid, low-viscosity polyamic acid solution.
Comparative example 3
4.181g (0.02091mol) of ODA is dissolved in 50mL of DMAc solvent, after diamine is completely dissolved, 6.147g (0.02091mol) of BPDA is added into the system in batches, and the reaction is continued for 24 hours under the condition of ice-water bath (0 ℃) to obtain polyamic acid solution with the solid content of 18 weight percent and the viscosity of 8570 cP.
FIG. 8 shows the change of loss tangent (Tan) of the polyamic acid solution with solid content at different angular frequencies during the dynamic rheology test in comparative example 3, and according to Winter and Chambon theories, the loss tangent (Tan) at the time of solution-gel transition is independent of angular frequency, and it is known that the solution-gel transition occurs when the solid content exceeds 18% during the conventional synthesis of the polyamic acid solution in comparative example 3, and the subsequent coating or spinning is difficult. Therefore, in order to ensure the processing fluidity, the solid content of the polyamic acid solution of comparative example 3 in the conventional synthesis process is up to 18%.
To examine the properties of the polyimide film or fiber obtained by processing the polyamic acid solution prepared by the method of the present invention. (1) Coating the prepared polyamic acid solution on a glass plate to obtain a film with the thickness of about 30 mu m, and heating the film for 1h at the temperature of 60 ℃, 135 ℃ and 300 ℃ respectively to obtain a corresponding polyimide film; (2) filtering and defoaming the prepared polyamic acid solution, spinning by adopting a wet spinning process, and cyclizing the obtained nascent fiber by sequentially passing through a hot furnace at 270 ℃, 350 ℃ and 430 ℃ to obtain the corresponding polyimide fiber. The properties of the polyimide film and fiber are as follows:
TABLE 3 comparison of polyimide film and fiber Properties
| Tensile strength | Tensile modulus | Elongation at break | Coefficient of thermal expansion | Maximum draw ratio | |
| Example 3 (film) | 181.9MPa | 3.05GPa | 71％ | 41.2ppm/℃ | / |
| COMPARATIVE EXAMPLE 3 (film) | 143.6MPa | 2.46GPa | 66％ | 46.9ppm/℃ | / |
| Example 3 (fiber) | 1.81GPa | 46.3GPa | 6.5％ | / | 6.9 |
| COMPARATIVE EXAMPLE 3 (fiber) | 1.2GPa | 30.6GPa | 9.8％ | / | 5.0 |
Example 4
(1) 3.792g (0.03511mol) of PDA and 3.010g (0.01505mol) of ODA are dissolved in 50mL of DMAc solvent, after diamine is completely dissolved, 14.747(0.05016mol) of BPDA is added into the system in batches, and the reaction is continued for 24 hours in an ice-water bath (0 ℃) condition to obtain a polyamic acid gel with the solid content of 30 wt%, the viscosity is 1958000cP, and the polyamic acid gel loses fluidity and is difficult to coat or spin;
(2) 2.4mL (0.02508mol) of acetic anhydride and 1.7mL of pyridine are added into the gel, and the mixture is stirred for 12 hours at room temperature (30 ℃) to be uniformly mixed, so that the high-solid-content low-viscosity polyamide acid solution with imidization degree of 25% and good fluidity is obtained, and the viscosity is 6250 cP.
FIGS. 4(a) and (b) are graphs showing the gel state of polyamic acid before the imidizing agent is added (a) and the solution state of polyamic acid after the imidizing agent is added (b) in example 4, respectively. Comparison clearly shows that, after the addition of the imidizing agent specified in the present application, although the solids content is increased, the viscosity is reduced, and the gel-like state is converted into a clear, homogeneous, more fluid, low-viscosity polyamic acid solution.
Comparative example 4
1.942g (0.01798mol) of PDA and 1.541g (0.00771mol) of ODA are dissolved in 50mL of DMAc solvent, after diamine is completely dissolved, 7.553g (0.02569mol) of BPDA is added into the system in batches, and reaction is continued for 24 hours under the condition of ice-water bath (0 ℃) to obtain a polyamic acid solution with the solid content of 18 weight percent and the viscosity of 8730 cP.
FIG. 9 shows the change of loss tangent (Tan) of the polyamic acid solution with solid content at different angular frequencies during the dynamic rheology test in comparative example 4, and according to Winter and Chambon theories, the loss tangent (Tan) at the time of solution-gel transition is independent of angular frequency, and it is known that the solution-gel transition occurs when the solid content exceeds 20% during the conventional synthesis of the polyamic acid solution in comparative example 4, and the subsequent coating or spinning is difficult. Therefore, in order to ensure the processing fluidity, the solid content of the polyamic acid solution of comparative example 4 in the conventional synthesis process was up to 20%.
To examine the properties of the polyimide film or fiber obtained by processing the polyamic acid solution prepared by the method of the present invention. (1) Coating the prepared polyamic acid solution on a glass plate to obtain a film with the thickness of about 30 mu m, and heating the film for 1h at the temperature of 60 ℃, 135 ℃ and 300 ℃ respectively to obtain a corresponding polyimide film; (2) filtering and defoaming the prepared polyamic acid solution, spinning by adopting a wet spinning process, and cyclizing the obtained nascent fiber by sequentially passing through a hot furnace at 270 ℃, 350 ℃ and 430 ℃ to obtain the corresponding polyimide fiber. The properties of the polyimide film and fiber are as follows:
TABLE 4 comparison of polyimide film and fiber Properties
Example 5
(1) 4.334g (0.04012mol) of PDA and 2.247g (0.01003mol) of BIA are dissolved in 50mL of DMAc solvent, after diamine is completely dissolved, 14.747(0.05016mol) of BPDA is added into the system in batches, and the reaction is continued for 24 hours under the condition of ice water bath (0 ℃) to obtain polyamic acid gel with the solid content of 30 wt%, the viscosity is 1806000cP, and the polyamic acid gel loses fluidity and is difficult to coat or spin;
(2) 0.9(0.01003mol) of acetic anhydride and 0.45mL of pyridine are added into the gel, and the mixture is stirred for 24 hours at room temperature (30 ℃) to be uniformly mixed, so that the high-solid-content low-viscosity polyamide acid solution with imidization degree of 10 percent and good fluidity is obtained, and the viscosity is 5080 cP.
FIGS. 5(a) and (b) are graphs showing the gel state of polyamic acid before the imidizing agent is added (a) and the solution state of polyamic acid after the imidizing agent is added (b) in example 5, respectively. Comparison clearly shows that, after the addition of the imidizing agent specified in the present application, although the solids content is increased, the viscosity is reduced, and the gel-like state is converted into a clear, homogeneous, more fluid, low-viscosity polyamic acid solution.
Comparative example 5
2.220g (0.02055mol) of PDA and 1.151g (0.00514mol) of BIA are dissolved in 50mL of DMAc solvent, 7.553g (0.02569mol) of BPDA is added into the system in batches after diamine is completely dissolved, and reaction is continued for 24 hours under the condition of ice-water bath (0 ℃) to obtain a polyamic acid solution with the solid content of 18 wt% and the viscosity of 9210 cP.
FIG. 10 shows the change of loss tangent (Tan) with solid content of the polyamic acid solution at different angular frequencies during the dynamic rheology test in comparative example 5, and according to Winter and Chambon theories, the loss tangent (Tan) at the time of solution-gel transition is independent of angular frequency, and it is known that the solution-gel transition occurs when the solid content exceeds 18% during the conventional synthesis of the polyamic acid solution in comparative example 5, and the subsequent coating or spinning is difficult. Therefore, in order to ensure the processing fluidity, the solid content of the polyamic acid solution described in comparative example 5 in the conventional synthesis process was up to 18%.
To examine the properties of the polyimide film or fiber obtained by processing the polyamic acid solution prepared by the method of the present invention. (1) Coating the prepared polyamic acid solution on a glass plate to obtain a film with the thickness of about 30 mu m, and heating the film for 1h at the temperature of 60 ℃, 135 ℃ and 300 ℃ respectively to obtain a corresponding polyimide film; (2) filtering and defoaming the prepared polyamic acid solution, spinning by adopting a wet spinning process, and cyclizing the obtained nascent fiber by sequentially passing through a hot furnace at 270 ℃, 350 ℃ and 430 ℃ to obtain the corresponding polyimide fiber. The properties of the polyimide film and fiber are as follows:
TABLE 5 comparison of polyimide film and fiber Properties
| Tensile strength | Tensile modulus | Elongation at break | Coefficient of thermal expansion | Maximum draw ratio | |
| Example 5 (film) | 350.3MPa | 7.73 |
25％ | 8.8ppm/℃ | / |
| COMPARATIVE EXAMPLE 5 (film) | 246.9MPa | 5.87 |
22％ | 9.6ppm/℃ | / |
| Example 5 (fiber) | 3.98GPa | 141.2GPa | 2.9％ | / | 4.3 |
| COMPARATIVE EXAMPLE 5 (fiber) | 3.21GPa | 124.4GPa | 3.4％ | / | 3.0 |
As can be seen from tables 1-5, the preparation method of the invention can solve the problems of large viscosity and difficult processing of the high-solid content polyamic acid solution, and the polyimide film processed by the solution prepared by the method has more excellent mechanical property and lower thermal expansion coefficient, and the polyimide fiber has higher draw ratio and better mechanical property.
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of the technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.
Claims (7)
1. A preparation method of a high-solid-content low-viscosity polyamic acid solution comprises the following steps:
(1) adding diamine monomer and dianhydride monomer into a reaction solvent, and fully stirring to perform condensation polymerization reaction to obtain polyamic acid gel with the solid content of more than 30%, loss of fluidity and difficulty in processing, wherein the viscosity range is 1000000-2000000cP, and the solid content of the polyamic acid gel is 30-35 wt%;
(2) adding a certain amount of dehydrating agent and catalyst into the polyamic acid gel according to a certain proportion, fully stirring, and gradually disentangling the polyamic acid gel to obtain a polyamic acid solution with good fluidity and low viscosity, wherein the viscosity range is 1000 plus 10000 cP.
2. The method as claimed in claim 1, wherein the solid content of the polyamic acid gel in step (1) is 10% -50%, the viscosity is 1000000-2000000cP, the fluidity is lost, and the coating or spinning is difficult; the molar ratio of the dianhydride monomer to the diamine monomer is 0.98:1-1.02: 1; the low-viscosity polyamic acid solution in the step (2) has good fluidity for coating and spinning, and the viscosity range is 1000-10000 cP.
3. The method according to claim 1 or 2, wherein the dianhydride monomer in step (1) is one or more of 3,3 ', 4,4 ' -benzophenone tetracarboxylic dianhydride, 3 ', 4,4 ' -biphenyl tetracarboxylic dianhydride, pyromellitic dianhydride, 2,3 ', 3,4 ' -biphenyl tetracarboxylic dianhydride, bisphenol a type dianhydride, 4,4 ' -oxydiphthalic anhydride, hexafluoroisopropylene phthalic acid, diphenyl sulfide tetracarboxylic dianhydride, and 3,3 ', 4,4 ' -diphenyl sulfone tetracarboxylic dianhydride mixed in an arbitrary ratio; the diamine monomer is one or more of p-phenylenediamine, m-phenylenediamine, 4 '-diaminodiphenyl ether, 2- (4-aminophenyl) -5-aminobenzimidazole, 4' -diaminodiphenyl sulfone and 4,4 '-diamino-2, 2' -bistrifluoromethyl biphenyl which are mixed in any proportion; the reaction solvent is one of N, N-dimethylformamide, N-dimethylacetamide, N-vinyl pyrrolidone and dimethyl sulfoxide.
4. The method according to claim 1, wherein the volume ratio of the dehydrating agent to the catalyst in the step (2) is 5:1 to 1:5, and the molar ratio of the dehydrating agent to the dianhydride monomer is 0.2:1 to 0.8:1.
5. The method according to claim 1, wherein the dehydrating agent in step (2) is a mixture of one or more of acetic anhydride, propionic anhydride, butyric anhydride; the catalyst is one or a mixture of pyridine, triethylamine, imidazole, isoquinoline, 2-methylpyridine and 3-methylpyridine.
6. A method for preparing a high-solid-content low-viscosity polyamic acid solution and a polyimide film or fiber processed therefrom according to any one of claims 1 to 5, comprising:
further, coating the prepared polyamic acid solution on a glass plate to obtain a film with the thickness of about 30 microns, and sequentially heating the polyamic acid solution for 1 hour at 60 ℃, 135 ℃ and 300 ℃ respectively to obtain a corresponding polyimide film; or further filtering and defoaming the prepared polyamic acid solution, spinning by adopting a wet spinning process, and cyclizing the obtained nascent fiber by sequentially passing through hot furnaces at 270 ℃, 350 ℃ and 430 ℃ to obtain the corresponding polyimide fiber.
7. The method for processing the polyimide film or fiber as claimed in claim 6, wherein the resulting film has a tensile strength of 150-350MPa, a tensile modulus of 2-10 GPa; or the tensile strength of the obtained fiber is 1.2-4.4GP, and the tensile modulus is 18-150 GPa.
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| CN116103780A (en) * | 2023-02-14 | 2023-05-12 | 江苏奥神新材料股份有限公司 | High-toughness high-strength polyimide fiber and preparation method thereof |
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| US4487911A (en) * | 1979-07-23 | 1984-12-11 | The P. D. George Company | Stable polyamic acids |
| JP2012102215A (en) * | 2010-11-09 | 2012-05-31 | Kaneka Corp | Method for manufacturing polyamic acid solution and polyimide |
| CN104292459A (en) * | 2014-10-21 | 2015-01-21 | 倚顿新材料（苏州）有限公司 | Preparation method of high-solid-content and low-viscosity polyimide material |
| CN112062956A (en) * | 2019-06-11 | 2020-12-11 | 北京化工大学 | Elastic polyimide gel and its prepn and application |
| CN112409612A (en) * | 2020-09-30 | 2021-02-26 | 孙利滨 | Preparation method of high-solid-content low-viscosity polyamic acid solution |
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| US4487911A (en) * | 1979-07-23 | 1984-12-11 | The P. D. George Company | Stable polyamic acids |
| JP2012102215A (en) * | 2010-11-09 | 2012-05-31 | Kaneka Corp | Method for manufacturing polyamic acid solution and polyimide |
| CN104292459A (en) * | 2014-10-21 | 2015-01-21 | 倚顿新材料（苏州）有限公司 | Preparation method of high-solid-content and low-viscosity polyimide material |
| CN112062956A (en) * | 2019-06-11 | 2020-12-11 | 北京化工大学 | Elastic polyimide gel and its prepn and application |
| CN112409612A (en) * | 2020-09-30 | 2021-02-26 | 孙利滨 | Preparation method of high-solid-content low-viscosity polyamic acid solution |
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| CN116103780A (en) * | 2023-02-14 | 2023-05-12 | 江苏奥神新材料股份有限公司 | High-toughness high-strength polyimide fiber and preparation method thereof |
| CN116103780B (en) * | 2023-02-14 | 2024-04-16 | 江苏奥神新材料股份有限公司 | High-toughness high-strength polyimide fiber and preparation method thereof |
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