CN117700785A - Preparation method of polyimide film with low water absorption rate - Google Patents
Preparation method of polyimide film with low water absorption rate Download PDFInfo
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- CN117700785A CN117700785A CN202311632138.9A CN202311632138A CN117700785A CN 117700785 A CN117700785 A CN 117700785A CN 202311632138 A CN202311632138 A CN 202311632138A CN 117700785 A CN117700785 A CN 117700785A
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- polyimide film
- water absorption
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- diaminopyridine
- absorption rate
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- 229920001721 polyimide Polymers 0.000 title claims abstract description 70
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 56
- 238000010521 absorption reaction Methods 0.000 title claims abstract description 50
- 238000002360 preparation method Methods 0.000 title claims abstract description 17
- 229920005575 poly(amic acid) Polymers 0.000 claims abstract description 33
- 238000000034 method Methods 0.000 claims abstract description 25
- VHNQIURBCCNWDN-UHFFFAOYSA-N pyridine-2,6-diamine Chemical compound NC1=CC=CC(N)=N1 VHNQIURBCCNWDN-UHFFFAOYSA-N 0.000 claims abstract description 14
- 238000004519 manufacturing process Methods 0.000 claims abstract description 12
- VLDPXPPHXDGHEW-UHFFFAOYSA-N 1-chloro-2-dichlorophosphoryloxybenzene Chemical compound ClC1=CC=CC=C1OP(Cl)(Cl)=O VLDPXPPHXDGHEW-UHFFFAOYSA-N 0.000 claims abstract description 9
- ZHDTXTDHBRADLM-UHFFFAOYSA-N hydron;2,3,4,5-tetrahydropyridin-6-amine;chloride Chemical compound Cl.NC1=NCCCC1 ZHDTXTDHBRADLM-UHFFFAOYSA-N 0.000 claims abstract description 9
- 239000002798 polar solvent Substances 0.000 claims abstract description 9
- 238000006116 polymerization reaction Methods 0.000 claims abstract 3
- 238000003756 stirring Methods 0.000 claims description 24
- 229910000831 Steel Inorganic materials 0.000 claims description 14
- 239000010959 steel Substances 0.000 claims description 14
- 239000007787 solid Substances 0.000 claims description 12
- FXHOOIRPVKKKFG-UHFFFAOYSA-N N,N-Dimethylacetamide Chemical compound CN(C)C(C)=O FXHOOIRPVKKKFG-UHFFFAOYSA-N 0.000 claims description 11
- 238000001035 drying Methods 0.000 claims description 8
- 239000004952 Polyamide Substances 0.000 claims description 7
- 239000002253 acid Substances 0.000 claims description 7
- 238000005266 casting Methods 0.000 claims description 7
- 238000001914 filtration Methods 0.000 claims description 7
- 229920002647 polyamide Polymers 0.000 claims description 7
- ZMXDDKWLCZADIW-UHFFFAOYSA-N Vilsmeier-Haack reagent Natural products CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims description 6
- 239000002904 solvent Substances 0.000 claims description 3
- HNJBEVLQSNELDL-UHFFFAOYSA-N pyrrolidin-2-one Chemical compound O=C1CCCN1 HNJBEVLQSNELDL-UHFFFAOYSA-N 0.000 claims description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 abstract description 8
- 239000011889 copper foil Substances 0.000 abstract description 8
- 238000013329 compounding Methods 0.000 abstract description 2
- 230000007797 corrosion Effects 0.000 abstract description 2
- 238000005260 corrosion Methods 0.000 abstract description 2
- 238000004090 dissolution Methods 0.000 abstract description 2
- 239000002861 polymer material Substances 0.000 abstract description 2
- ANSXAPJVJOKRDJ-UHFFFAOYSA-N furo[3,4-f][2]benzofuran-1,3,5,7-tetrone Chemical compound C1=C2C(=O)OC(=O)C2=CC2=C1C(=O)OC2=O ANSXAPJVJOKRDJ-UHFFFAOYSA-N 0.000 description 18
- 238000006243 chemical reaction Methods 0.000 description 15
- 230000000052 comparative effect Effects 0.000 description 10
- 229910001220 stainless steel Inorganic materials 0.000 description 8
- 239000010935 stainless steel Substances 0.000 description 8
- 239000004642 Polyimide Substances 0.000 description 7
- 238000012360 testing method Methods 0.000 description 6
- GTDPSWPPOUPBNX-UHFFFAOYSA-N ac1mqpva Chemical compound CC12C(=O)OC(=O)C1(C)C1(C)C2(C)C(=O)OC1=O GTDPSWPPOUPBNX-UHFFFAOYSA-N 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 239000000178 monomer Substances 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- JUJWROOIHBZHMG-UHFFFAOYSA-N Pyridine Chemical group C1=CC=NC=C1 JUJWROOIHBZHMG-UHFFFAOYSA-N 0.000 description 2
- 238000007334 copolymerization reaction Methods 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- -1 heterocyclic diamine Chemical class 0.000 description 2
- 125000000623 heterocyclic group Chemical group 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 238000003786 synthesis reaction Methods 0.000 description 2
- CBCKQZAAMUWICA-UHFFFAOYSA-N 1,4-phenylenediamine Chemical compound NC1=CC=C(N)C=C1 CBCKQZAAMUWICA-UHFFFAOYSA-N 0.000 description 1
- RNFJDJUURJAICM-UHFFFAOYSA-N 2,2,4,4,6,6-hexaphenoxy-1,3,5-triaza-2$l^{5},4$l^{5},6$l^{5}-triphosphacyclohexa-1,3,5-triene Chemical compound N=1P(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP=1(OC=1C=CC=CC=1)OC1=CC=CC=C1 RNFJDJUURJAICM-UHFFFAOYSA-N 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 150000004984 aromatic diamines Chemical class 0.000 description 1
- 125000003118 aryl group Chemical group 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 150000004985 diamines Chemical class 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 239000012153 distilled water Substances 0.000 description 1
- 238000010292 electrical insulation Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 239000003063 flame retardant Substances 0.000 description 1
- 238000009472 formulation Methods 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- 125000005462 imide group Chemical group 0.000 description 1
- 230000008676 import Effects 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 238000004377 microelectronic Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 229920003223 poly(pyromellitimide-1,4-diphenyl ether) Polymers 0.000 description 1
- 238000006068 polycondensation reaction Methods 0.000 description 1
- 229920006254 polymer film Polymers 0.000 description 1
- 230000000379 polymerizing effect Effects 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 238000007363 ring formation reaction Methods 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
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- Manufacture Of Macromolecular Shaped Articles (AREA)
- Macromolecular Compounds Obtained By Forming Nitrogen-Containing Linkages In General (AREA)
Abstract
The invention belongs to the technical field of high polymer material manufacturing, and relates to a preparation method of a polyimide film with low water absorption rate, wherein 4, 4-diaminodiphenyl ether is dissolved in an aprotic strongly polar solvent, and then pyromellitic dianhydride is added and stirred for dissolution; then adding 2, 6-diaminopyridine, and carrying out polymerization reaction to obtain polyamic acid solution; then preparing a polyimide film with low water absorption rate by a thermal imidization method; the film has low water absorption and low shrinkage, can effectively reduce the shrinkage in the process of preparing the flexible circuit board by compounding the polyimide film and the copper foil, avoid the flexible circuit board from warping and curling, improve the yield of the flexible circuit board, avoid the corrosion of water molecules to the copper foil, and improve the service life of the flexible circuit board; the preparation method is simple, low in cost, suitable for large-scale popularization and wide in market prospect.
Description
Technical field:
the invention belongs to the technical field of high polymer material manufacturing, and relates to a polyimide film with low water absorption rate and a preparation method thereof.
The background technology is as follows:
polyimide film (Polyimide film) is also called as gold film, is a heterocyclic polymer film containing imide groups in the main chain, has excellent radiation resistance, creep resistance and insulativity, and also has excellent mechanical property and flame retardant property, low CTE (coefficient of linear expansion) and high support property, and is widely applied to key fields such as military industry, aerospace, microelectronics, LEDs, power batteries, high-iron electromagnetic wires, wind power generation and the like.
The preparation process of the polyimide film adopts a two-step process, wherein the first step is to generate polyamide acid through polycondensation reaction of aromatic diamine and aromatic dianhydride or heterocyclic dianhydride and heterocyclic diamine, and the second step is to generate polyimide through thermal or chemical dehydration cyclization and obtain the polyimide film through biaxial stretching. Wherein the synthesis reaction of the polyamic acid in the first step is the key to determine the molecular weight and molecular chain structure of the polyimide, and the molecular weight of the polyamic acid is usually controlled by monitoring the viscosity of the system at the end of the reaction; polyimide film products with different molecular chain structures are prepared through the selection of different diamine and dianhydride monomer materials.
Polyimide film is used as a key material in the flexible circuit board (FPC) field, and is combined with copper foil in the circuit board to play a role in isolation and insulation, and polyimide film materials currently used for the flexible circuit board are mainly provided by foreign enterprises, such as Kapton series polyimide films prepared by using PMDA/ODA as a main raw material through chemical imidization by Dupont, and Apical series polyimide films prepared by using PMDA/ODA/PDA as a main raw material through a chemical method in Japanese.
The polyimide film produced by the formula and the process has the problem of higher water absorption rate, the water absorption rate of the polyimide film can lead to expansion of the film in the production process of the flexible circuit board, and the moisture evaporation of the expanded film and the copper foil can lead to shrinkage of the film in the thermal processing process after the film is attached to the copper foil, and finally, the produced flexible circuit board is led to warp and curl, so that the domestic polyimide film cannot be applied to the manufacture of the flexible circuit board and can only be used in the field of simple electrical insulation.
The invention comprises the following steps:
the invention mainly aims to overcome the defects in the prior art, and provides a low-water-absorption polyimide film and a preparation method thereof, wherein the polyimide molecular chain structure is changed by introducing heterocyclic diamine monomer containing pyridine structure, and the polyimide film with low water-absorption is produced by a thermal imidization process, so that the problems of large expansion and shrinkage caused by high water absorption of the polyimide film and warping and curling caused by application of the polyimide film to a flexible circuit board are solved.
In order to achieve the above object, the present invention provides a method for preparing a polyimide film with low water absorption, comprising the following steps:
(1) Dissolving 4, 4-diaminodiphenyl ether (ODA) in an aprotic strongly polar solvent, then adding pyromellitic dianhydride, and stirring to dissolve; then adding 2, 6-Diaminopyridine (DAP), and polymerizing at 25-60 ℃ for 4-7 hours under normal pressure to obtain polyamic acid solution;
(2) And (3) preparing the polyamide acid solution obtained in the step (1) into a polyimide film with low water absorption rate through a thermal imidization method.
The aprotic highly polar solvent selected in step (1) comprises any one or a combination of N, N dimethylacetamide, dimethylformamide and pyrrolidone, wherein the water content of the solvent is less than 300ppm; acidity <200ppm, wherein the solvent is preferably N, N dimethylacetamide.
Controlling the addition amount of the aprotic polar solvent in the step (1) to control the solid content of the aprotic polar solvent to be between 15 and 30 percent, preferably 20 percent; solid content= (pmda+oda+dap)/(pmda+oda+dap+aprotic strongly polar solvent) mass×100%.
The molar amount of the pyromellitic dianhydride in the step (1) is equal to the sum of the molar amounts of the 4, 4-diaminodiphenyl ether and the 2, 6-diaminopyridine, and the pyromellitic dianhydride is added at one time.
The 2, 6-diaminopyridine in the step (1) is added rapidly after the pyromellitic dianhydride is dissolved, so that the influence of the hydrolysis of the pyromellitic dianhydride on the molecular weight of the polyamide acid is avoided, the molecular weight of the polyamide acid is characterized by viscosity, and the final viscosity is controlled to be 75+/-5 Pa.s under the condition of 45 ℃.
The molar amount of 2,6 diaminopyridine in step (1) is 10% to 30%, preferably 20% to 25%, of the total molar amount of 4,4 diaminodiphenyl ether and 2,6 diaminopyridine.
The polyimide film is prepared by the thermal imidization method in the step (2), specifically, the polyimide film is prepared by firstly defoaming and filtering a polyamic acid solution, then metering the solution by a gear pump, extruding the solution on an annular steel belt of a casting machine for drying at the drying temperature of 140-200 ℃, stripping the dried solution from the steel belt, and then performing high-temperature imidization by a biaxial stretcher at the imidization temperature of 380-450 ℃.
According to the invention, 2,6 diaminopyridine is added into a PMDA and ODA system, so that the number of-o-structures in a polyimide molecular chain is reduced, the hydrogen bond reaction with water molecules is reduced, meanwhile, the introduction of pyridine ring structures increases the crystal structure of the polyimide molecular chain rod chain segments which are partially piled up, and the diffusion speed of the water molecules in the polyimide molecular chain is reduced, so that the water absorption rate of polyimide is reduced.
Compared with the prior art, the invention has the following advantages:
(1) The invention uses thermal imidization to produce the polyimide film with low water absorption, which avoids the defects of complex chemical imidization process, import dependence on equipment, high manufacturing cost, poor environmental protection and the like.
(2) The polyimide film with low water absorption rate prepared by the method has low water absorption rate, so that the shrinkage rate of the polyimide film and the copper foil in the process of compounding and preparing the flexible circuit board can be effectively reduced, the flexible circuit board is prevented from being warped and curled, and the yield of the flexible circuit board is improved.
(3) The polyimide film with low water absorption rate prepared by the method has low water absorption rate, avoids the corrosion of water molecules on the copper foil, simultaneously avoids the problem that the service life of the flexible circuit board is influenced by ageing of the film caused by entering of the water molecules among the film molecules, and prolongs the service life of the flexible circuit board.
In conclusion, the polyimide film prepared by the method has low water absorption and shrinkage, improves the dimensional stability of the polyimide film, can be compounded with copper foil to manufacture a flexible circuit board, improves the yield of the flexible circuit board, and prolongs the service life of the flexible circuit board; the preparation method is simple, low in cost, suitable for large-scale popularization and wide in market prospect.
Detailed Description
The invention is further illustrated by the following examples.
Example 1:
the embodiment relates to a preparation method of a polyimide film with low water absorption rate, which comprises the following steps:
(1) Adding metered N, N-dimethylacetamide into a stainless steel reaction kettle, starting stirring, adding 0.9mol of ODA (4, 4-diaminodiphenyl ether), stirring for about 20 minutes until the ODA is fully dissolved, adding 1mol of PMDA (pyromellitic dianhydride), continuously stirring for about 15 minutes until the PMDA is dissolved, rapidly adding 0.1mol of DAP (2, 6-diaminopyridine), reacting for 6 hours at the temperature of 50 ℃ under normal pressure to obtain a polyamide acid solution with the solid content of 20%, and detecting the viscosity of the polyamide acid solution to be 75+/-5 Pa.s at the temperature of 45 ℃;
(2) And (3) defoaming and filtering the polyamic acid solution, metering the solution by a gear pump, extruding the solution on an annular steel belt of a casting machine for drying at 160 ℃, stripping the dried solution from the steel belt, and performing high-temperature imidization on the dried solution in a biaxial stretching machine at 400 ℃ to prepare the polyimide film with low water absorption.
Example 2:
the embodiment relates to a preparation method of a polyimide film with low water absorption rate, which comprises the following steps:
(1) Adding metered N, N-dimethylacetamide into a stainless steel reaction kettle, stirring, adding 0.85mol of ODA, stirring for about 20 minutes until the ODA is fully dissolved, and adding 1mol of PMDA; after stirring for about 15 minutes until PMDA is dissolved, 0.15mol of DAP is rapidly added; reacting for 6 hours at the normal pressure and the temperature of 50 ℃ to obtain a polyamic acid solution with the solid content of 20 percent, and detecting the viscosity of the polyamic acid solution to be 75+/-5 Pa.s at the temperature of 45 ℃;
(2) And (3) defoaming and filtering the polyamic acid solution, metering the solution by a gear pump, extruding the solution on an annular steel belt of a casting machine for drying at 160 ℃, stripping the dried solution from the steel belt, and performing high-temperature imidization on the dried solution in a biaxial stretching machine at 400 ℃ to prepare the polyimide film with low water absorption.
Example 3:
the embodiment relates to a preparation method of a polyimide film with low water absorption rate, which comprises the following steps:
(1) Adding metered N, N-dimethylacetamide into a stainless steel reaction kettle, starting stirring, adding 0.80mol of ODA, stirring for about 20 minutes until the ODA is fully dissolved, and adding 1mol of PMDA; stirring was continued for about 15 minutes until PMDA dissolved, followed by rapid addition of 0.20mol of DAP; reacting for 6 hours at the normal pressure and the temperature of 50 ℃ to obtain a polyamic acid solution with the solid content of 20 percent, and detecting the viscosity of the polyamic acid solution to be 75+/-5 Pa.s at the temperature of 45 ℃;
(2) And (3) defoaming and filtering the polyamic acid solution, metering the solution by a gear pump, extruding the solution on an annular steel belt of a casting machine for drying at 160 ℃, stripping the dried solution from the steel belt, and performing high-temperature imidization on the dried solution in a biaxial stretching machine at 400 ℃ to prepare the polyimide film with low water absorption.
Example 4:
the embodiment relates to a preparation method of a polyimide film with low water absorption rate, which comprises the following steps:
(1) Adding metered N, N-dimethylacetamide into a stainless steel reaction kettle, starting stirring, adding 0.75mol of ODA, stirring for about 20 minutes until the ODA is fully dissolved, and adding 1mol of PMDA; stirring was continued for about 15 minutes until PMDA dissolved, followed by rapid addition of 0.25mol of DAP; reacting for 6 hours at the normal pressure and the temperature of 50 ℃ to obtain a polyamic acid solution with the solid content of 20 percent, and detecting the viscosity of the polyamic acid solution to be 75+/-5 Pa.s at the temperature of 45 ℃;
(2) And (3) defoaming and filtering the polyamic acid solution, metering the solution by a gear pump, extruding the solution on an annular steel belt of a casting machine for drying at 160 ℃, stripping the dried solution from the steel belt, and performing high-temperature imidization on the dried solution in a biaxial stretching machine at 400 ℃ to prepare the polyimide film with low water absorption.
Example 5:
the embodiment relates to a preparation method of a polyimide film with low water absorption rate, which comprises the following steps:
(1) Adding metered N, N-dimethylacetamide into a stainless steel reaction kettle, starting stirring, adding 0.70mol of ODA, stirring for about 20 minutes until the ODA is fully dissolved, and adding 1mol of PMDA; stirring is continued for about 15 minutes until PMDA is dissolved, and then 0.30mol of DAP is quickly added; reacting for 6 hours at the normal pressure and the temperature of 50 ℃ to obtain a polyamic acid solution with the solid content of 20 percent, and detecting the viscosity of the polyamic acid solution to be 75+/-5 Pa.s at the temperature of 45 ℃;
(2) And (3) defoaming and filtering the polyamic acid solution, metering the solution by a gear pump, extruding the solution on an annular steel belt of a casting machine for drying at 160 ℃, stripping the dried solution from the steel belt, and performing high-temperature imidization on the dried solution in a biaxial stretching machine at 400 ℃ to prepare the polyimide film with low water absorption.
Example 6
In this example, performance tests were performed on the polyimide films prepared in examples 1 to 5, and 4 comparative examples were set, respectively:
comparative example 1: the preparation method of the polyamic acid solution comprises the following steps: adding metered N, N-dimethylacetamide into a stainless steel reaction kettle, stirring, adding 1mol of ODA, stirring for about 20 minutes until the ODA is fully dissolved, and adding 1mol of PMDA; the reaction is carried out for 6 hours under the condition of keeping the reaction temperature of 50 ℃ under normal pressure to obtain a polyamic acid solution with the solid content of 20 percent, and the viscosity of the polyamic acid solution is 75+/-5 Pa.s under the condition of 45 ℃; the method for preparing polyimide film from polyamic acid solution was the same as in example 1.
Comparative example 2: the preparation method of the polyamic acid solution comprises the following steps: adding metered N, N dimethylacetamide into a stainless steel reaction kettle, adding 0.80mol of ODA after stirring is started, adding 1mol of PMDA after stirring for about 20 minutes until the ODA is fully dissolved, adding 0.20mol of PDA (p-phenylenediamine) after stirring for about 15 minutes until the PMDA is dissolved, and reacting for 6 hours under the condition that the reaction temperature is kept at 50 ℃ under normal pressure to obtain a polyamic acid solution with 20% of solid content, wherein the viscosity of the polyamic acid solution is 75+/-5 Pa.s under the condition that the temperature is 45 ℃; the method for preparing polyimide film from polyamic acid solution was the same as in example 1.
Comparative example 3: the preparation method of the polyamic acid solution comprises the following steps: adding metered N, N-dimethylacetamide into a stainless steel reaction kettle, stirring, adding 0.80mol of ODA and 0.2mol of DAP, stirring for about 20 minutes until the ODA and the DAP are fully dissolved, and adding 1mol of PMDA; the reaction is carried out for 6 hours under the condition of keeping the reaction temperature of 50 ℃ under normal pressure to obtain a polyamic acid solution with the solid content of 20 percent, and the viscosity of the polyamic acid solution is 75+/-5 Pa.s under the condition of 45 ℃; the method for preparing polyimide film from polyamic acid solution was the same as in example 1.
TABLE 1 monomer formulation for polyamic acid synthesis
The polyimide films prepared in examples 1 to 5 and comparative examples 1 to 3 were subjected to water absorption and shrinkage tests as follows:
(1) Water absorption rate: using an electronic analytical balance, test conditions: soaking in distilled water for 24 hours; the test was performed according to the method specified in GB/T13542.6-2006.
(2) Shrinkage ratio: adopting a two-dimensional image tester, and testing conditions: 200 ℃/1h, tested according to the method specified in GB/T13542.6-2006. The test results are shown in Table 2.
TABLE 2 film property test results
As can be seen from table 2: example 1-example 5 the addition of DAP significantly reduced the water absorption of the polyimide film compared to comparative example 1, and the water absorption showed a significant decrease trend with increasing DAP addition, and the shrinkage of the polyimide film also showed a decrease trend with decreasing water absorption, when the molar content of DAP and the molar content of ODA reached 4: after 1, the decrease in water absorption and shrinkage began to slow down. By comparison of example 3 with comparative example 2, the polyimide film incorporating DAP had lower water absorption and lower shrinkage than the polyimide film incorporating PDA. Example 3 was compared with comparative example 3, in which DAP was added in the same amount but in a different order, and in which random copolymerization was used in comparative example 3 and isotactic copolymerization was used in example 3; comparative example 3 is significantly higher in water absorption and shrinkage than example 3. Therefore, the PMDA is added for dissolution, and then the DAP is added, so that the water absorption rate and the shrinkage rate of the film are reduced.
Claims (10)
1. The preparation method of the polyimide film with low water absorption rate is characterized by comprising the following specific steps:
(1) Dissolving 4, 4-diaminodiphenyl ether in an aprotic strongly polar solvent, then adding pyromellitic dianhydride, and stirring to dissolve; then adding 2, 6-diaminopyridine, and carrying out polymerization reaction to obtain polyamic acid solution;
(2) And (3) preparing the polyamide acid solution obtained in the step (1) into a polyimide film with low water absorption rate through a thermal imidization method.
2. The method for producing a low water absorption polyimide film according to claim 1, wherein the aprotic highly polar solvent selected in step (1) comprises any one or a combination of N, N dimethylacetamide, dimethylformamide and pyrrolidone; the water content of the solvent is <300ppm; acidity <200ppm.
3. The method for producing a low water absorption polyimide film according to claim 1, wherein the polymerization conditions in the step (1) are: normal pressure, temperature 25-60 deg.c and time 4-7 hr.
4. The method for producing a low water absorption polyimide film according to claim 1, wherein the amount of aprotic highly polar solvent added in step (1) is controlled so that the solid content of the solution is controlled to 15 to 30%.
5. The method for producing a low water absorption polyimide film according to claim 4, wherein the solid content is controlled to 20%.
6. The method for producing a low water absorption polyimide film according to claim 1, wherein the molar amount of pyromellitic dianhydride in step (1) is equal to the sum of the molar amounts of 4,4 diaminodiphenyl ether and 2,6 diaminopyridine.
7. The method for producing a low water absorption polyimide film according to claim 1, wherein the molar amount of 2,6 diaminopyridine in the step (1) is 10% to 30% of the total molar amount of 4,4 diaminodiphenyl ether and 2,6 diaminopyridine.
8. The method for preparing a polyimide film with low water absorption according to claim 7, wherein the molar amount of 2,6 diaminopyridine is 20% -25% of the total molar amount of 4,4 diaminodiphenyl ether and 2,6 diaminopyridine.
9. The method for preparing the polyimide film with low water absorption rate according to claim 1, wherein the thermal imidization method in the step (2) is characterized in that the polyimide film is prepared by firstly defoaming and filtering a polyamic acid solution, then metering the solution through a gear pump, extruding the solution on an annular steel belt of a casting machine for drying, stripping the dried solution from the steel belt, and then performing imidization at high temperature in a biaxial stretcher.
10. The low water absorption polyimide film prepared by the method of any one of claims 1 to 9.
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