Polyimide film for optical fiber and preparation method thereof

Abstract

The invention provides a polyimide film for optical fibers and a preparation method of the polyimide film, preparation raw materials of polyamide acid slurry for optical fibers comprise aromatic diamine, aromatic dianhydride, ester functional monomers, an organic solvent and a coupling agent, and the ester functional monomers comprise diamino-containing ester and / or ester containing dianhydride groups; the specific ester functional monomer is added into the preparation raw materials, and the coupling agent is added in a matched manner, so that a polyimide coating formed by coating the polyamide acid slurry for the optical fiber outside a bare optical fiber has good adhesion, flexibility, heat resistance and tensile property, can effectively protect the optical fiber, also has excellent chemical peelability, and is suitable for popularization and application. The optical fiber can be quickly dissolved or fused after being infiltrated into a chemical reagent, so that the optical fiber can be thoroughly stripped from a base material without damaging the base material, and connection and use of the optical fiber are facilitated.

Description

[0001] This application is a divisional application. The application number of the parent application is 202410396542.9, the application date is April 2, 2024, and the name of the invention is "A polyamide acid slurry for optical fiber, its preparation method and application". Technical Field

[0002] The present invention relates to the technical field of coatings, and in particular to a polyimide film for optical fiber and a preparation method thereof. Background Art

[0003] Since the transmission loss of light in optical fiber is much lower than the loss of electricity in wire transmission, optical fiber is used for long-distance information transmission. It is a fiber made of glass or plastic, suitable for large-scale data transmission and interference-free data transmission in the telecommunications field, and will not be affected by electric or magnetic fields. In order to improve the strength and flexibility of optical fiber, a protective layer is usually coated on the outer layer of the optical fiber, where the material of the protective layer is mainly polymethyl methacrylate (PMMA). The glass transition temperature of traditional PMMA is generally around 100°C, and even the glass transition temperature of modified PMMA will not exceed 150°C. Due to working conditions, signal transmission needs to be achieved in a high temperature (over 250°C) environment, such as sensor signal transmission of aerospace vehicles, oil mine exploration signal transmission, etc.

[0004] Coating a protective layer on the outer layer of the optical fiber is mainly to protect the internal optical fiber. In actual use, the interface part needs to be stripped of the protective layer before use. Conventional stripping schemes include physical stripping and chemical stripping. Among them, although physical stripping can effectively remove the protective layer, it is easy to damage the optical fiber layer; chemical stripping mainly involves immersing the optical fiber in chemical reagents to soften, dissolve or decompose it, which is not only highly efficient but also will not damage the optical fiber layer.

[0005] CN1222897A discloses a method for manufacturing a coated optical fiber with a strippable polyimide coating, the method comprising the following steps, namely, pulling the optical fiber through a curable polyamic acid solution to form a coating on the fiber and curing the coated fiber, and then exposing the cured coating to a polar organic solvent such as acetone to strip the cured coating from the optical fiber; the invention also provides a fiber with a strippable polyimide coating, the method is particularly suitable for heavy metal fluoride fibers and chalcogenide fibers that transmit optical signals in the infrared region. The method can effectively strip the protective layer; however, in actual use, it is found that the adhesion between the fluorine-containing coating and the optical fiber is low, and the joint after corrosion is easy to further separate, which reduces the degree of protection for the optical fiber.

[0006] Therefore, in view of the above technical problems, it is urgent to develop a polyamide acid slurry for optical fiber that has excellent heat resistance, high adhesion and chemical strippability. Summary of the invention

[0007] In view of the deficiencies in the prior art, the object of the present invention is to provide a polyimide film for optical fiber and a preparation method thereof. The polyimide coating formed by coating the polyamic acid slurry on the outside of the bare optical fiber has good adhesion, flexibility, heat resistance and tensile properties, which can effectively protect the optical fiber. At the same time, it also has excellent chemical strippability, which facilitates the connection and use of the optical fiber.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a polyamic acid slurry for optical fiber, wherein the raw materials for preparing the polyamic acid slurry for optical fiber include aromatic diamine, aromatic dianhydride, ester functional monomer, organic solvent and coupling agent;

[0010] The ester functional monomers include esters containing diamino groups and / or esters containing dianhydride groups.

[0011] The raw materials for preparing the polyamic acid slurry for optical fiber provided by the present invention include aromatic diamines, aromatic dianhydrides, ester functional monomers, organic solvents and coupling agents, and the ester functional monomers are limited to include esters containing diamino groups and / or esters containing dianhydride groups; by adding the above-mentioned specific ester functional monomers to the preparation raw materials, and adding coupling agents in combination, the obtained polyamic acid slurry is coated on the outside of the bare optical fiber and the polyimide coating formed after high-temperature imidization has good adhesion, flexibility, heat resistance and tensile properties, can effectively protect the optical fiber, and enable the optical fiber to stably work for at least 3000 hours at 250°C. At the same time, it also has excellent chemical strippability, can be quickly dissolved or melted after being infiltrated into chemical reagents (such as sulfuric acid), and can be effectively stripped from the substrate without damaging the substrate, which is convenient for the connection and use of the optical fiber.

[0012] Preferably, the mass percentage of aromatic diamine and aromatic dianhydride in the raw material for preparing the polyamic acid slurry for optical fiber is 18-32%, for example, 20%, 22%, 24%, 26%, 28% or 30%, and more preferably 19-30%.

[0013] As a preferred technical solution of the present invention, the mass percentage of aromatic diamine and aromatic dianhydride in the raw materials for preparing the polyamic acid slurry for optical fiber is limited to 18-32%, so that the obtained polyamic acid slurry for optical fiber has both excellent processing performance and mechanical properties; on the one hand, if the mass percentage of aromatic diamine and aromatic dianhydride is too low, the viscosity of the polyamic acid slurry for optical fiber will be too low, and more coating passes will be required, and the strength of the polyimide coating formed after high-temperature imidization will be reduced; on the other hand, if the mass percentage of aromatic diamine and aromatic dianhydride is too high, the viscosity of the polyamic acid slurry for optical fiber will be too high, which is not conducive to coating.

[0014] Preferably, the molar ratio of anhydride groups to amino groups in the raw materials for preparing the polyamic acid slurry for optical fiber is 1:(0.95-1.05), for example, 1:0.96, 1:0.97, 1:0.98, 1:0.99, 1:1, 1:1.01, 1:1.02, 1:1.03 or 1:1.04, etc.

[0015] Preferably, the aromatic diamine includes any one of p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenyl ether, 2,2'-bis(trifluoromethyl)diaminobiphenyl, 4,4'-diaminobenzanilide, 2,2'-bis[4-(4-aminophenoxyphenyl)]propane, 4,4'-diaminodiphenyl sulfone, 2-(4-aminophenyl)-5-aminobenzimidazole, 2,2-bis(4-hydroxy-3-aminophenyl)propane, 4,4'-bis(3-aminophenoxy)diphenyl sulfone, 4,4'-diamino-2,2'-dimethyl-1,1'-biphenyl, 4,4'-diamino-biphenyl or 9,9-bis(4-aminophenyl)fluorene, or a combination of at least two thereof.

[0016] Preferably, the aromatic dianhydride comprises aromatic tetracarboxylic dianhydride.

[0017] Preferably, the aromatic tetracarboxylic dianhydride includes 2,2',3,3'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, (4-phthalic anhydride)formyloxy-4-phthalate, bis[(3,4-dianhydride)phenyl]terephthalate, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, p-phenylene-diphenyltrimethic acid Any one of ester dianhydride, 4,4'-terephthalic anhydride, pyromellitic dianhydride, 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride, 2,2-bis(4-(3,4-dicarboxyphenoxy)phenyl)hexafluoropropane dianhydride, 2,2-bis(4-(3,4-dicarboxybenzoyloxy)phenyl)hexafluoropropane dianhydride or 2,2'-bis(trifluoromethyl)-4,4'-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride or a combination of at least two thereof.

[0018] Preferably, the ester functional monomer includes an ester containing a diamino group, and the molar ratio of the diamino group-containing ester to the aromatic diamine is 1:(1-10), for example, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7 or 1:8, etc.; if the addition ratio of the diamino group-containing ester is too high, the high temperature resistance of the polyamic acid slurry for optical fiber will decrease to a certain extent, and the requirement for long-term use under high temperature will not be met; if the addition ratio of the diamino group-containing ester is too low, the chemical stripping property of the polyimide coating formed by imidization of the polyamic acid slurry for optical fiber will decrease to a certain extent, and the chemical stripping will not be thorough or the stripping time will be too long.

[0019] Preferably, the diamino-containing ester has at least one of the following structures:

[0020]

[0021] In the above structure, R is independently selected from any one of H, methyl, ethyl or -CF3, and X is independently selected from any one of -O-, -S- or -SO2-.

[0022] Preferably, the bisamino-containing ester includes any one of [4-(4-aminobenzoyl)oxyphenyl]4-aminobenzoate (ABHQ), di-p-aminophenyl terephthalate (BAPT) or p-aminophenyl p-aminobenzoate (APAB) or a combination of at least two thereof.

[0023] Preferably, the ester monomer includes an ester containing a dianhydride group, and the molar ratio of the ester containing a dianhydride group to the aromatic dianhydride is 1:(1-10), for example, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7 or 1:8, etc.; if the addition ratio of the ester containing a dianhydride group is too high, the high temperature resistance of the polyamic acid slurry for optical fiber will decrease to a certain extent, and the requirement for long-term use under high temperature will not be met; if the addition ratio of the ester containing a dianhydride group is too low, the chemical stripping of the polyimide coating formed by the polyamic acid slurry will be incomplete or the stripping time will be too long, and the chemical strippability will decrease.

[0024] Preferably, the ester containing a bisanhydride group has at least one of the following structures:

[0025]

[0026] In the above structure, R is independently selected from any one of H, methyl, ethyl or -CF3, and X is independently selected from any one of -O-, -S-, -SO2- or methylene.

[0027] Preferably, the ester containing a bis-anhydride group includes any one of phenyl bis(trimellitate) dianhydride (TAHQ), bis[(3,4-dianhydride)phenyl]terephthalate (PHAP) or (4-phthalic anhydride)formyloxy-4-phthalate (8CI) or a combination of at least two thereof.

[0028] Preferably, the organic solvent comprises a non-protonated organic solvent, further preferably any one of N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, γ-butyrolactone, propylene glycol monomethyl ether, cyclopentanone, cyclohexanone, ethyl acetate, toluene or methyl ethyl ketone or a combination of at least two thereof, and further preferably N,N-dimethylformamide and N,N-dimethylacetamide.

[0029] Preferably, the coupling agent comprises a silane coupling agent.

[0030] In the present invention, there is no special requirement for the specific type of the silane coupling agent, and a conventional commercial silane coupling agent can be selected. For example, γ-aminopropyltriethoxysilane (KH550) can be selected.

[0031] Preferably, the raw materials for preparing the polyamic acid coating also include a capping agent.

[0032] Preferably, the end-capping agent includes a monoamine compound or a monocarboxylic acid compound.

[0033] Preferably, the viscosity of the polyamic acid slurry is 3000-30000 cp (eg, 5000, 7000, 9000, 13000, 15000, 19000, 21000, 25000, 27000 or 29000, etc.), more preferably 5000-15000 cp.

[0034] In a second aspect, the present invention provides a method for preparing the polyamic acid slurry for optical fiber as described in the first aspect, the preparation method comprising: copolymerizing aromatic diamine, aromatic dianhydride and ester functional monomers in an organic solvent, adding a coupling agent for mixing, and obtaining the polyamic acid slurry for optical fiber.

[0035] Preferably, the copolymerization reaction temperature is 25 to 60°C, such as 30°C, 35°C, 40°C, 45°C, 50°C or 55°C, and more preferably 35 to 55°C.

[0036] Preferably, the copolymerization reaction time is 3 to 24 h, for example, 4 h, 5 h, 6 h, 7 h, 8 h, 10 h, 12 h, 14 h, 16 h, 18 h, 20 h or 22 h.

[0037] Preferably, after the reaction is completed, a step of adding a capping agent to perform a capping reaction is further included.

[0038] In a third aspect, the present invention provides a polyimide film, wherein the polyimide film is obtained by subjecting the polyamic acid slurry described in the first aspect to an imidization reaction.

[0039] Preferably, the temperature of the imidization reaction is 60-400°C, for example, 100°C, 150°C, 200°C, 250°C, 300°C or 350°C.

[0040] In a fourth aspect, the present invention provides a polyimide optical fiber, comprising a bare optical fiber and the polyimide film as described in the third aspect coated outside the bare optical fiber.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] (1) The raw materials for preparing the polyamic acid slurry for optical fiber provided by the present invention include aromatic diamine, aromatic dianhydride, ester functional monomer, organic solvent and coupling agent, and the ester monomer includes ester containing diamino group and / or ester containing dianhydride group; by adding ester functional monomer and coupling agent to the raw materials for preparation, the polyimide formed by the polyamic acid slurry for optical fiber after high-temperature imidization has excellent high temperature resistance, adhesion and mechanical properties, and also has excellent chemical strippability, can be quickly dissolved or melted after being soaked in chemical reagents, and then completely stripped from the substrate without damaging the substrate, and is suitable for protective coating of optical fiber;

[0043] (2) Specifically, the polyimide film formed by the polyamic acid slurry for optical fiber provided by the present invention has a tensile strength of up to 146-179 MPa, an elongation at break of 59-76%, an adhesion of up to 5B, a Tg of 371-396°C, and a dissolution time of only 2-4 min. DETAILED DESCRIPTION

[0044] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0045] Unless otherwise specified, the raw materials involved in the specific implementation methods of the present invention are all conventional commercially available materials, and the instruments and equipment involved are all conventional instruments and equipment in the art.

[0046] In particular, the test methods for solid content and viscosity involved in the specific embodiments of the present invention are as follows:

[0047] (1) Viscosity: The viscosity of the paint was tested at 25°C using an American Boller cone and plate viscometer.

[0048] (2) Solid content: Take an aluminum foil pan with a diameter of 60 mm and weigh it as m0; take 1±0.1 g of the paint sample and place it in the aluminum pan, and weigh the weight of the aluminum pan plus the paint (m1); put the aluminum pan containing the paint in a forced air oven at 180±5°C, take it out after 1 hour, and weigh the mass of the aluminum pan containing the paint (m2); Solid content = (m2-m0) / (m1-m0)×100%.

[0049] Example 1

[0050] A polyamic acid slurry for optical fiber, having a viscosity of 9672cp and a solid content of 23.8%;

[0051] The preparation method of the polyamic acid slurry for optical fiber comprises: adding N,N-dimethylacetamide (DMAc, 608g) into a 1L reactor, then adding 4,4'-diaminodiphenyl ether (ODA, 86.9g, 0.43mol) into the reactor, then heating the reactor temperature to 40°C, adding pyromellitic anhydride (PMDA, 85.19g, 0.39mol) and phenyl di(trimellitic acid) anhydride (TAHQ, 19.89g, 0.04mol), maintaining the reaction at 40°C for 10h, finally lowering the system temperature to room temperature, adding γ-aminopropyltriethoxysilane (0.8g) and stirring for 2h, and obtaining the polyamic acid slurry for optical fiber.

[0052] Example 2

[0053] A polyamic acid slurry for optical fiber, having a viscosity of 10465cp and a solid content of 23.3%;

[0054] The preparation method of the polyamic acid slurry for optical fiber comprises: adding N,N-dimethylacetamide (DMAc, 608g) into a 1L reactor, then adding 4,4'-diaminodiphenyl ether (ODA, 86.9g, 0.43mol) into the reactor, then heating the reactor temperature to 40°C, adding pyromellitic dianhydride (PMDA, 85.19g, 0.39mol) and bis[(3,4-dianhydride)phenyl]terephthalate (PHAP, 0.04mol), maintaining the reaction at 40°C for 10h, finally lowering the system temperature to room temperature, adding γ-aminopropyltriethoxysilane (0.8g) and stirring for 2h, and obtaining the polyamic acid slurry for optical fiber.

[0055] Example 3

[0056] A polyamic acid slurry for optical fiber, having a viscosity of 11083cp and a solid content of 23.1%;

[0057] The preparation method of the polyamic acid slurry for optical fiber comprises: adding N,N-dimethylacetamide (DMAc, 608g) into a 1L reactor, then adding 4,4'-diaminodiphenyl ether (ODA, 89.3g, 0.45mol) into the reactor, then heating the reactor temperature to 40°C, adding pyromellitic dianhydride (PMDA, 87.57g, 0.4mol) and (4-phthalic anhydride) formyloxy-4-phthalate (8CI, 15.08g, 0.05mol), maintaining the reaction at 40°C for 10h, finally lowering the system temperature to room temperature, adding γ-aminopropyltriethoxysilane (0.8g) and stirring for 2h, and obtaining the polyamic acid slurry for optical fiber.

[0058] Example 4

[0059] A polyamic acid slurry for optical fiber, having a viscosity of 8956cp and a solid content of 19.7%;

[0060] The preparation method of the polyamic acid slurry for optical fiber comprises: adding N,N-dimethylacetamide (DMAc, 640g) into a 1L reactor, then adding 4,4'-diaminodiphenyl ether (ODA, 66.5g, 0.33mol) and [4-(4-aminobenzoyl)oxyphenyl] 4-aminobenzoate (ABHQ, 12.86g, 0.04mol) into the reactor, then heating the reactor temperature to 40°C, adding pyromellitic dianhydride (PMDA, 80.48g, 0.37mol), maintaining the reaction temperature at 40°C for 10h, finally lowering the system temperature to room temperature, adding γ-aminopropyltriethoxysilane (0.8g) and stirring for 2h, to obtain the polyamic acid slurry for optical fiber.

[0061] Example 5

[0062] A polyamic acid slurry for optical fiber, having a viscosity of 9874cp and a solid content of 19.5%;

[0063] The preparation method of the polyamic acid slurry for optical fiber comprises: adding N,N-dimethylacetamide (DMAc, 640g) into a 1L reactor, then adding 4,4'-diaminodiphenyl ether (ODA, 66.5g, 0.33mol) and di-p-aminophenyl terephthalate (BAPT, 12.86g, 0.04mol) into the reactor, then heating the reactor temperature to 40°C, adding pyromellitic dianhydride (PMDA, 80.48g, 0.37mol), maintaining the reaction temperature at 40°C for 10h, finally lowering the system temperature to room temperature, adding γ-aminopropyltriethoxysilane (0.8g) and stirring for 2h, and obtaining the polyamic acid slurry for optical fiber.

[0064] Example 6

[0065] A polyamic acid slurry for optical fiber, having a viscosity of 12401cp and a solid content of 19.7%;

[0066] The preparation method of the polyamic acid slurry for optical fiber comprises: adding N,N-dimethylacetamide (DMAc, 640g) into a 1L reactor, then adding 4,4'-diaminodiphenyl ether (ODA, 68.46g, 0.34mol) and p-aminophenyl para-aminobenzoate (APAB, 8.671g, 0.04mol) into the reactor, then heating the reactor temperature to 40°C, adding pyromellitic dianhydride (PMDA, 82.86g, 0.38mol), maintaining the reaction temperature at 40°C for 10h, finally lowering the system temperature to room temperature, adding γ-aminopropyltriethoxysilane (0.8g) and stirring for 2h, and obtaining the polyamic acid slurry for optical fiber.

[0067] Example 7

[0068] A polyamic acid slurry for optical fiber, which differs from Example 1 in that the added amount of PMDA is 0.3 mol, the added amount of TAHQ is 0.13 mol, and other substances, amounts and preparation methods are the same as those in Example 1.

[0069] Example 8

[0070] A polyamic acid slurry for optical fiber, which differs from Example 1 in that the added amount of PMDA is 0.2 mol, the added amount of TAHQ is 0.23 mol, and other substances, amounts and preparation methods are the same as those in Example 1.

[0071] Comparative Example 1

[0072] A polyamic acid slurry for optical fiber, having a viscosity of 13655cp and a solid content of 19.1%;

[0073] The preparation method of the polyamic acid slurry comprises: adding N,N-dimethylacetamide (DMAc, 640g) into a 1L reactor, then adding 4,4'-diaminodiphenyl ether (ODA, 76.58g, 0.38mol) into the reactor, then heating the reactor temperature to 40°C, adding pyromellitic anhydride (PMDA, 83.42g, 0.38mol), maintaining the reaction temperature at 40°C for 10h, finally lowering the system temperature to room temperature, adding γ-aminopropyltriethoxysilane (0.8g) and stirring for 2h to obtain the polyamic acid slurry for optical fiber.

[0074] Comparative Example 2

[0075] A polyamic acid slurry for optical fiber, having a viscosity of 10145cp and a solid content of 19%;

[0076] The preparation method of the polyamic acid slurry for optical fiber comprises: adding N,N-dimethylacetamide (DMAc, 640g) into a 1L reactor, then adding 4,4'-diaminodiphenyl ether (ODA, 61.32g, 0.3mol) into the reactor, then heating the reactor temperature to 40°C, adding 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA, 98.67g, 0.3mol), maintaining the reaction at 40°C for 10h, finally lowering the system temperature to room temperature, adding γ-aminopropyltriethoxysilane (0.8g) and stirring for 2h to obtain the polyamic acid slurry for optical fiber.

[0077] Comparative Example 3

[0078] A polyamic acid slurry for optical fiber, which differs from Example 1 in that γ-aminopropyltriethoxysilane is not added for stirring, and other substances, amounts and steps are the same as those in Example 1.

[0079] Performance Testing:

[0080] (1) Tensile strength and elongation at break: The optical fiber was first subjected to high-temperature imidization with a polyamic acid slurry to obtain a polyimide film sample; wherein the high-temperature imidization conditions were: heating at a heating rate of 5°C / min in the range of 60 to 400°C for 8 h;

[0081] The polyimide film samples were then tested according to JIS K7127. The test conditions were: using an electric mechanical universal testing machine (manufactured by INSTRON) with a test speed of 5 m / min and a load cell of 5 kN and 0.05 N for tensile testing.

[0082] (2) Adhesion: Referring to ASTM D3359-09, the adhesion of the polyimide film formed by coating the polyamic acid slurry on the glass surface was measured by tape.

[0083] (3) Tg: The polyamic acid slurry is first subjected to high temperature imidization to obtain a polyimide resin film; wherein the conditions for the high temperature imidization are: heating at a temperature rise rate of 5°C / min in a range of 60 to 400°C for 8 hours;

[0084] Then, it was tested using a scanning differential thermal analyzer (TAInstrument, model Q200).

[0085] (4) Chemical strippability: The optical fiber was first subjected to high-temperature imidization with a polyamic acid slurry to obtain a polyimide film with a thickness of 25 μm. The high-temperature imidization conditions were as follows: heating at a heating rate of 5°C / min in the range of 60 to 400°C for 8 h. The polyimide film was then cut into 5×5 mm films and immersed in concentrated sulfuric acid (concentration of 98%). The film dissolution or breaking time was recorded.

[0086] The polyamic acid slurry for optical fiber provided in Examples 1 to 8 and Comparative Examples 1 to 3 was tested according to the above test method. The test results are shown in Table 1:

[0087] Table 1

[0088] Tensile strength / MPa Elongation at break / % Adhesion Tg / ℃ Dissolution time / min Example 1 168 67 5B 389 3 Example 2 158 60 5B 391 3 Example 3 164 61 5B 396 5 Example 4 146 59 5B 387 3 Example 5 151 67 5B 381 3 Example 6 156 66 5B 394 4 Example 7 179 76 5B 371 2 Example 8 188 89 5B 266 0.5 Comparative Example 1 128 85 5B 399 Insoluble Comparative Example 2 131 64 5B 280 Insoluble Comparative Example 3 168 68 2B 389 3

[0089] According to the data in Table 1, it can be seen that the polyimide film formed by the polyamic acid slurry for optical fiber provided by the present invention has excellent mechanical properties, adhesion properties, high temperature resistance and chemical strippability;

[0090] Specifically, the polyimide films formed by the polyamic acid slurry for optical fiber provided in Examples 1 to 7 have a tensile strength of up to 146 to 179 MPa, an elongation at break of 59 to 76%, an adhesion of up to 5B, a Tg of 371 to 396°C, and a dissolution time of only 2 to 4 min;

[0091] Compared with Examples 1 to 7, the polyimide film formed by the polyamic acid slurry for optical fiber provided in Comparative Examples 1 to 2 is still difficult to dissolve after being immersed in sulfuric acid for 8 hours, and has almost no chemical strippability;

[0092] Compared with Example 1, the adhesion between the polyimide film formed by the polyamic acid slurry for optical fiber provided in Comparative Example 3 and the substrate is only 2B, and the adhesion performance is poor, which is caused by the lack of addition of a coupling agent;

[0093] Compared with Example 1, the high temperature resistance of the polyimide film formed by the polyamic acid slurry for optical fiber provided in Example 8 is also reduced, because the molar ratio of pyromellitic anhydride and phenyl di(trimellitic acid ester) anhydride (ester functional monomer) is too low.

[0094] The applicant declares that the present invention illustrates a polyamic acid slurry for optical fiber and its preparation method and application through the above embodiments, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of various raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a polyimide film for optical fiber, characterized in that: The preparation method comprises the following steps: The optical fiber is obtained by subjecting the polyamic acid slurry to imidization reaction; The temperature of the imidization reaction is 60-400°C; The raw materials for preparing the polyamic acid slurry for optical fiber include aromatic diamine, aromatic dianhydride, ester functional monomer, organic solvent and coupling agent; The ester functional monomers include esters containing diamino groups and / or esters containing dianhydride groups; The molar ratio of the ester functional monomer to the aromatic diamine is 1:2 to 10; The molar ratio of anhydride groups to amino groups in the raw materials for preparing the polyamic acid slurry for optical fiber is 1:0.95-1.

05.

2. The method for preparing a polyimide film for optical fiber according to claim 1, characterized in that: The aromatic diamine includes any one of p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenyl ether, 2,2'-bis(trifluoromethyl)diaminobiphenyl, 4,4'-diaminobenzanilide, 2,2'-bis[4-(4-aminophenoxyphenyl)]propane, 4,4'-diaminodiphenyl sulfone, 2-(4-aminophenyl)-5-aminobenzimidazole, 2,2-bis(4-hydroxy-3-aminophenyl)propane, 4,4'-bis(3-aminophenoxy)diphenyl sulfone, 4,4'-diamino-2,2'-dimethyl-1,1'-biphenyl, 4,4'-diamino-biphenyl or 9,9-bis(4-aminophenyl)fluorene, or a combination of at least two thereof; The aromatic dianhydride includes aromatic tetracarboxylic dianhydride.

3. The method for preparing a polyimide film for optical fiber according to claim 1 or 2, characterized in that: The ester containing diamino group includes any one of [4-(4-aminobenzoyl)oxyphenyl]4-aminobenzoate, di-p-aminophenyl terephthalate or p-aminophenyl p-aminobenzoate or a combination of at least two thereof; The ester containing a bis-anhydride group includes any one of phenyl bis(trimellitate) dianhydride, bis[(3,4-dianhydride)phenyl]terephthalate or (4-phthalic anhydride)formyloxy-4-phthalate or a combination of at least two thereof.

4. The method for preparing a polyimide film for optical fiber according to claim 3, characterized in that: The organic solvent includes a non-protonated organic solvent, and the non-protonated organic solvent is any one of N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, γ-butyrolactone, propylene glycol monomethyl ether, cyclopentanone, cyclohexanone, ethyl acetate, toluene or methyl ethyl ketone, or a combination of at least two thereof; The coupling agent includes a silane coupling agent.

5. The method for preparing a polyimide film for optical fiber according to claim 4, characterized in that: The raw materials for preparing the polyamic acid slurry for optical fiber also include a capping agent; The end-capping agent includes a monoamine compound or a monocarboxylic acid compound.

6. The method for preparing a polyimide film for optical fiber according to claim 5, characterized in that: The preparation method of the polyamic acid slurry for optical fiber comprises: polymerizing aromatic diamine, aromatic dianhydride and ester functional monomer in an organic solvent, adding a coupling agent for mixing, and obtaining the polyamic acid slurry for optical fiber.

7. The method for preparing a polyimide film for optical fiber according to claim 6, characterized in that: The polymerization reaction temperature is 25 to 60° C., and the polymerization reaction time is 3 to 24 hours; After the polymerization reaction is completed, the step of adding a capping agent to carry out a capping reaction is also included.

8. A polyimide film for optical fiber prepared by the preparation method according to any one of claims 1 to 7.

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