Dyeable polyimide fibers and methods for making the same

Abstract

The present application provides a dyeable polyimide fiber and a preparation method thereof, the preparation method comprising blending and spinning two different polyamide acid solutions A and B, the polyamide acid solution A being obtained by mixed reaction of diamine monomer A and dianhydride monomer B, and the polyamide acid solution B being obtained by mixed reaction of diamine monomer C and dianhydride monomer D, the molecular chain of the polyamide acid solution A in the blended fiber having a planar symmetric ring structure, high mechanical property and high thermal stability; the molecular chain of the polyamide acid solution B containing a high density of C=O and -O- groups, which can form intermolecular forces with active dyes to improve the dyeability of the fiber. Moreover, the polymerization stock solution produced by the blending process is composed of two phases, and different phases provide different functions. Compared with the multi-component copolymerization process, the blending process greatly reduces the production control difficulty under the premise of meeting the same physical and chemical properties.

Description

Technical Field

[0001] This invention belongs to the field of materials science and technology, specifically relating to a dyeable polyimide fiber and its preparation method. Background Technology

[0002] Polyimide (PI) fiber, as an important type of high-performance fiber, possesses superior mechanical properties, chemical resistance, thermal oxidation stability, and radiation resistance, giving it a greater advantage over other polymer fibers in high-temperature and radioactive environments. With the gradual development of downstream applications, polyimide fiber is expanding from conventional high-temperature filtration to high-temperature protective apparel. The apparel industry requires fibers with certain dyeing properties to meet the diverse color requirements of fabrics. However, due to its dense structure and the lack of groups in its molecular chain that interact with dye molecules, polyimide fiber is difficult to dye. Furthermore, the color-producing method mentioned in Chinese invention patent CN105780177A, which uses solution dyeing, suffers from drawbacks such as complex processes, limited color selectivity, and high production costs. Summary of the Invention

[0003] The purpose of this invention is to address the above-mentioned shortcomings of the prior art by providing a method for preparing dyeable polyimide fibers and the method thereof.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] The first objective of this invention is to provide a method for preparing dyeable polyimide fibers, comprising the following steps:

[0006] S1. Preparation of polyamic acid solution A: Diamine monomer A and dianhydride monomer B are reacted in N,N-dimethylacetamide solvent to obtain polyamic acid solution A;

[0007] S2, Preparation of polyamic acid solution B: Diamine monomer C and dianhydride monomer D are reacted in N,N-dimethylacetamide solvent to obtain polyamic acid solution B;

[0008] S3. Preparation of blended solution: Polyamic acid solution A and polyamic acid solution B are added to the mixing tank and mixed evenly to obtain polyamic acid mixed spinning solution;

[0009] S4. Spinning: The polyamic acid mixed spinning solution obtained in step S3 is filtered and degassed, and then transported to the dry spinning channel through a spinning metering pump and spinneret. Hot air is introduced to evaporate the solvent and solidify the solution to obtain nascent fibers.

[0010] S5, cyclization and stretching: The nascent fibers obtained in step S4 are treated in a thermal environment of 150-350℃ for 0.5-3 hours and stretched 1-3 times at 350-450℃;

[0011] S6. Oiling and cutting: Oil the fibers obtained in step S5 and cut them to obtain the finished polyimide fiber product.

[0012] Furthermore, in step S1, the diamine monomer A is selected from one or more of 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, and 2-(4-aminophenyl)-5-aminobenzimidazole; the dianhydride monomer B is selected from one or more of pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, and 2,3,3',4'-biphenyltetracarboxylic dianhydride.

[0013] Furthermore, in step S2, the diamine monomer C is selected from one or more of 4,4'-diaminobenzoyl aniline, 3,4'-diaminobenzoyl aniline, p-phenylenediamine, and m-phenylenediamine; the dianhydride monomer D is selected from one or more of 4,4'-oxophthalic anhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, and bisphenol A type diether dianhydride.

[0014] Furthermore, in step S3, the molar ratio of polyamic acid solution A to polyamic acid solution B is 5:1 to 1:4.

[0015] Further, the specific process of step S1 is as follows: add diamine monomer A and dianhydride monomer B at -5 to 20°C, stir and react for 6 to 12 hours under nitrogen protection to obtain polyamic acid stock solution; control the solid content between 20 and 35 wt%; wherein the molar ratio of diamine monomer A and dianhydride monomer B is 0.98 to 1:1.02 to 1.

[0016] Furthermore, the molar ratio of the sum of the diamine monomer A and the diamine monomer C to the sum of the dianhydride monomer B and the dianhydride monomer D is 1:(0.99~1.05).

[0017] Furthermore, the temperature of the hot air in step S4 is 180–260°C.

[0018] A second objective of the present invention is to provide polyimide fibers prepared by the above method.

[0019] Furthermore, the polyimide fiber has a tensile strength of 3.5–4.5 cN / dtex and an elongation of 11.7%–22.3%.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] (1) This invention provides a dyeable polyimide fiber and its preparation method. The preparation method includes blending and spinning two different polyamic acid solutions A and B. Polyamic acid solution A is obtained by mixing and reacting diamine monomer A and dianhydride monomer B. Polyamic acid solution B is obtained by mixing and reacting diamine monomer C and dianhydride monomer D. In the blended fiber, the molecular chain of polyamic acid solution A has a planar symmetrical ring structure, which has high mechanical properties and high thermal stability. The molecular chain of polyamic acid solution B contains a high density of C=O and -O- bonds, which can form intermolecular forces with reactive dyes and improve the dyeability of the fiber.

[0022] (2) The polymer raw liquid produced by the blending process of the present invention consists of two phases, and different phases provide different functions. Compared with the multi-component copolymerization process, the blending process greatly reduces the difficulty of production control while meeting the same physical and chemical properties.

[0023] (3) The present invention uses mechanical blending to prepare spinning solution, which is simple and has no special requirements for environment or equipment.

[0024] (4) The blended fiber materials prepared by this invention have a wide range of sources, mature processes, high production efficiency, and low cost. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the specific embodiments of this invention are described in further detail below. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0026] The N,N-dimethylacetamide used in this invention is abbreviated as DMAC.

[0027] Example 1

[0028] (1) Under nitrogen protection, 4,4'-diaminodiphenyl ether, 2-(4-aminophenyl)-5-aminobenzimidazole and pyromellitic dianhydride were added to solvent DMAC and mixed in a molar ratio of 6:4:10. The mixture was reacted at 0°C for 24 hours to obtain polyamic acid solution A with a solid content of 25%.

[0029] (2) Under nitrogen protection, 4,4'-diaminobenzoyl aniline, p-phenylenediamine, 4,4'-oxophthalic anhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride were added to solvent DMAC and mixed in a molar ratio of 7:3:8:2. The mixture was reacted at 0°C for 18 hours to obtain polyamic acid solution B with a solid content of 25%.

[0030] (3) Add the above polyamic acid solution A and polyamic acid solution B to the mixing vessel at a molar ratio of 1:1 and mix evenly to obtain polyamic acid mixed spinning solution.

[0031] (4) The above polyamic acid mixture is filtered and degassed, and then transported to the dry spinning channel through a spinning metering pump and spinneret. Hot air at 240°C is introduced to evaporate the solvent and solidify the original solution to obtain nascent fibers.

[0032] (5) The nascent fibers obtained above are treated in a thermal environment of 320°C for 1 hour and stretched twice at 400°C.

[0033] (6) The fibers obtained above are oiled and cut to obtain the finished product.

[0034] The following methods were used to test the physical and mechanical properties of the finished product:

[0035] Strength and elongation: GB / T 14337-2022 Test method for tensile properties of chemical fiber short fiber;

[0036] Linear density: GB / T 14335-2008 Test method for linear density of short chemical fibers;

[0037] Dyeing performance: GB / T2401-2006 Determination of fiber saturation value, dye saturation value and saturation factor when dyeing acrylic fibers with cationic dyes.

[0038] The physical and mechanical properties of the finished product are as follows: strength 4.5 cN / dtex, elongation 22.3%, linear density 1.67 dtex; soap fastness grade 4, water fastness grade 5, and artificial light fastness grade 5.

[0039] Example 2

[0040] (1) Under nitrogen protection, 4,4'-diaminodiphenyl ether, 2-(4-aminophenyl)-5-aminobenzimidazole and pyromellitic dianhydride were added to solvent DMAC and mixed in a molar ratio of 7:3:10. The mixture was reacted at 0°C for 24 hours to obtain polyamic acid solution A with a solid content of 25%.

[0041] (2) Under nitrogen protection, 4,4'-diaminobenzoyl aniline, p-phenylenediamine, bisphenol A type diether dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride were added to solvent DMAC and mixed. The molar ratio was 6:4:7:3. The mixture was reacted at 0°C for 18 hours to obtain polyamic acid solution B with a solid content of 25%.

[0042] (3) Add the above polyamic acid solution A and polyamic acid solution B to the mixing vessel at a molar ratio of 1:1 and mix evenly to obtain polyamic acid mixed spinning solution.

[0043] (4) The above polyamic acid mixture is filtered and degassed, and then transported to the dry spinning channel through a spinning metering pump and spinneret. Hot air at 240°C is introduced to evaporate the solvent and solidify the original solution to obtain nascent fibers.

[0044] (5) The nascent fibers obtained above are treated in a thermal environment of 320°C for 1 hour and stretched twice at 400°C.

[0045] (6) The fibers obtained above are oiled and cut to obtain the finished product.

[0046] The physical and mechanical properties of the finished product are as follows: strength is 4.3 cN / dtex, elongation is 19.8%, linear density is 1.67 dtex; soap fastness is grade 4, water fastness is grade 4, and artificial light fastness is grade 5.

[0047] Example 3

[0048] (1) Under nitrogen protection, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 2-(4-aminophenyl)-5-aminobenzimidazole and pyromellitic dianhydride were added to solvent DMAC and mixed in a molar ratio of 4:4:2:10. The mixture was reacted at 0°C for 24 hours to obtain polyamic acid solution A with a solid content of 25%.

[0049] (2) Under nitrogen protection, 4,4'-diaminobenzoyl aniline, 4,4'-oxophthalic anhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride were added to solvent DMAC and mixed in a molar ratio of 7:3:10. The mixture was reacted at 0°C for 18 hours to obtain polyamic acid solution B with a solid content of 25%.

[0050] (3) Add the above polyamic acid solution A and polyamic acid solution B to the mixing vessel at a molar ratio of 1:1 and mix evenly to obtain polyamic acid mixed spinning solution.

[0051] (4) The above polyamic acid mixture is filtered and degassed, and then transported to the dry spinning channel through a spinning metering pump and spinneret. Hot air at 240°C is introduced to evaporate the solvent and solidify the original solution to obtain nascent fibers.

[0052] (5) The nascent fibers obtained above are treated in a thermal environment of 320°C for 1 hour and stretched twice at 400°C.

[0053] (6) The fibers obtained above are oiled and cut to obtain the finished product.

[0054] The physical and mechanical properties of the finished product are as follows: strength is 3.5 cN / dtex, elongation is 13.2%, linear density is 1.67 dtex; soap fastness is grade 5, water fastness is grade 5, and artificial light fastness is grade 5.

[0055] Example 4

[0056] (1) Under nitrogen protection, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 2-(4-aminophenyl)-5-aminobenzimidazole and pyromellitic dianhydride were added to solvent DMAC and mixed in a molar ratio of 4:3:3:10. The mixture was reacted at 0°C for 24 hours to obtain polyamic acid solution A with a solid content of 15%.

[0057] (2) Under nitrogen protection, 4,4'-diaminobenzoyl aniline, 4,4'-oxophthalic anhydride, bisphenol A type diether dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride were added to solvent DMAC and mixed in a molar ratio of 5:5:5:5. The mixture was reacted at 0°C for 18 hours to obtain polyamic acid solution B with a solid content of 25%.

[0058] (3) Add the above polyamic acid solution A and polyamic acid solution B to the mixing vessel at a molar ratio of 1:1 and mix evenly to obtain polyamic acid mixed spinning solution.

[0059] (4) The above polyamic acid mixture is filtered and degassed, and then transported to the dry spinning channel through a spinning metering pump and spinneret. Hot air at 240°C is introduced to evaporate the solvent and solidify the original solution to obtain nascent fibers.

[0060] (5) The nascent fibers obtained above are treated in a thermal environment of 320°C for 1 hour and stretched twice at 400°C.

[0061] (6) The fibers obtained above are oiled and cut to obtain the finished product.

[0062] The physical and mechanical properties of the finished product are as follows: strength is 3.7 cN / dtex, elongation is 17.27%, linear density is 1.67 dtex; soap fastness is grade 4, water fastness is grade 5, and artificial light fastness is grade 5.

[0063] Comparative Example 1:

[0064] 1) Under nitrogen protection, 4,4'-diaminodiphenyl ether, 2-(4-aminophenyl)-5-aminobenzimidazole and pyromellitic dianhydride were added to solvent DMAC and mixed in a molar ratio of 6:4:10. The mixture was reacted at 0°C for 24 hours to obtain a polyamic acid solution with a solid content of 15%.

[0065] (2) The above polyamic acid mixture is filtered and degassed, and then transported to the dry spinning channel through a spinning metering pump and a spinneret. Hot air at 240°C is introduced to evaporate the solvent and solidify the original solution to obtain nascent fibers.

[0066] (3) The nascent fibers obtained above are treated in a thermal environment at 320°C for 1 hour and stretched twice at 400°C.

[0067] (4) The fibers obtained above are oiled and cut to obtain the finished product.

[0068] The physical and mechanical properties of the finished product were tested as follows: strength was 7.5 cN / dtex, elongation was 6.2%, and linear density was 1.67 dtex; it could not be dyed.

[0069] Comparative Example 2:

[0070] (1) Under nitrogen protection, 4,4'-diaminobenzoyl aniline, 4,4'-oxophthalic anhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride were added to solvent DMAC and mixed. The molar ratio was 7:3:10. The mixture was reacted at 0°C for 18 hours to obtain polyamic acid solution A with a solid content of 25%.

[0071] (2) Under nitrogen protection, 4,4'-diaminobenzoyl aniline, p-phenylenediamine, 4,4'-oxophthalic anhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride were mixed in a molar ratio of 7:3:8:2 and reacted at 0°C for 18 hours to obtain polyamic acid solution B with a solid content of 25%.

[0072] (3) Add the above polyamic acid solution A and polyamic acid solution B to the mixing vessel at a molar ratio of 1:1 and mix evenly to obtain polyamic acid mixed spinning solution.

[0073] (4) The above polyamic acid mixture is filtered and degassed, and then transported to the dry spinning channel through a spinning metering pump and spinneret. Hot air at 240°C is introduced to evaporate the solvent and solidify the original solution to obtain nascent fibers.

[0074] (5) The nascent fibers obtained above are treated in a thermal environment of 320°C for 1 hour and stretched twice at 400°C.

[0075] (6) The fibers obtained above are oiled and cut to obtain the finished product.

[0076] The physical and mechanical properties of the finished product are as follows: strength is 3.1 cN / dtex, elongation is 19.4%, linear density is 1.67 dtex; soap fastness is grade 4, water fastness is grade 5, and artificial light fastness is grade 5.

[0077] Comparative Example 3:

[0078] (1) Under nitrogen protection, 4,4'-diaminobenzoyl aniline, 4,4'-oxophthalic anhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride were added to solvent DMAC and mixed. The molar ratio was 7:3:10. The mixture was reacted at 0°C for 18 hours to obtain polyamic acid solution A with a solid content of 25%.

[0079] (2) Under nitrogen protection, 4,4'-diaminobenzoyl aniline, p-phenylenediamine, bisphenol A type diether dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride were added to solvent DMAC and mixed. The molar ratio was 6:4:7:3. The mixture was reacted at 0°C for 18 hours to obtain polyamic acid solution B with a solid content of 25%.

[0080] (3) Add the above polyamic acid solution A and polyamic acid solution B to the mixing vessel at a molar ratio of 1:1 and mix evenly to obtain polyamic acid mixed spinning solution.

[0081] (4) The above polyamic acid mixture is filtered and degassed, and then transported to the dry spinning channel through a spinning metering pump and spinneret. Hot air at 240°C is introduced to evaporate the solvent and solidify the original solution to obtain nascent fibers.

[0082] (5) The nascent fibers obtained above are treated in a thermal environment of 320°C for 1 hour and stretched twice at 400°C.

[0083] (6) The fibers obtained above are oiled and cut to obtain the finished product.

[0084] The physical and mechanical properties of the finished product are as follows: strength is 2.6 cN / dtex, elongation is 27.9%, linear density is 1.67 dtex; soap fastness is grade 4, water fastness is grade 5, and artificial light fastness is grade 5.

[0085] To better illustrate the dyeing effect of the polyimide fibers of the present invention, the applicant conducted the following research:

[0086] The cationic dyes selected are any one of S-BG blue, FBL red, and X-GL yellow, all of which are commercially available.

[0087] The fibers prepared in Example 1 were pretreated to remove oiling agents. After washing, the fibers were air-dried at room temperature for later use. The fibers were then immersed in a dye bath containing 5% cationic dye at a ratio of 1:20. The dye bath was heated from room temperature to 130°C at a rate of 2°C / min, and then held at that temperature for 60 min. After dyeing, the fibers underwent post-treatment such as washing to obtain dark green polyimide colored fibers with a tensile strength of 3.5–4.1 cN / dtex, an elongation of approximately 20.8%, a soap fastness grade of 4, a water fastness grade of 5, and an artificial light fastness grade of 5.

[0088] For any points not covered above, existing technologies shall apply.

[0089] Although specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the direction of the invention or exceeding the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for producing dyeable polyimide fibers, characterized by, The method comprises the following steps: S1, preparation of polyamide acid solution A: diamine monomer A and dianhydride monomer B are reacted in a solvent N,N-dimethylacetamide to obtain polyamide acid solution A; S2, preparation of polyamide acid solution B: diamine monomer C and dianhydride monomer D are reacted in a solvent N,N-dimethylacetamide to obtain polyamide acid solution B; S3, preparation of mixed stock solution: polyamide acid solution A and polyamide acid solution B are added into a mixing kettle in a molar ratio of 1:1, and are uniformly mixed to obtain polyamide acid mixed spinning solution; S4, spinning: the polyamide acid mixed spinning solution obtained in step S3 is filtered and defoamed, and is then conveyed to a dry spinning duct through a spinning metering pump and a spinneret, hot air at 240 DEG C is introduced to evaporate the solvent and solidify the stock solution, and nascent fibers are obtained; S5, cyclization and drafting: the nascent fibers obtained in step S4 are treated in a hot environment at 150-350 DEG C for 0.5-3h, and are stretched by 1-3 times at 350-450 DEG C; S6, oiling and cutting: the fibers obtained in step S5 are oiled and cut to obtain polyimide fiber products; The diamine monomer A is 4,4'-diamino diphenyl ether and 2-(4-aminophenyl)-5-aminobenzimidazole, the dianhydride monomer B is pyromellitic dianhydride, and the molar ratio of the 4,4'-diamino diphenyl ether, 2-(4-aminophenyl)-5-aminobenzimidazole and pyromellitic dianhydride is 6:4:10; the diamine monomer C is 4,4'-diaminobenzanilide and p-phenylenediamine; the dianhydride monomer D is 3,3',4,4'-biphenyl tetracarboxylic dianhydride and 4,4'-oxydiphthalic anhydride, and the molar ratio of the 4,4'-diaminobenzanilide, p-phenylenediamine, 4,4'-oxydiphthalic anhydride and 3,3',4,4'-biphenyl tetracarboxylic dianhydride is 7:3:8:2; Alternatively, the diamine monomer A is 4,4'-diamino diphenyl ether and 2-(4-aminophenyl)-5-aminobenzimidazole, the dianhydride monomer B is pyromellitic dianhydride, and the molar ratio of the 4,4'-diamino diphenyl ether, 2-(4-aminophenyl)-5-aminobenzimidazole and pyromellitic dianhydride is 7:3:10; the diamine monomer C is 4,4'-diaminobenzanilide and p-phenylenediamine; the dianhydride monomer D is bisphenol A type diether dianhydride and 3,3',4,4'-biphenyl tetracarboxylic dianhydride, and the molar ratio of the 4,4'-diaminobenzanilide, p-phenylenediamine, bisphenol A type diether dianhydride and 3,3',4,4'-biphenyl tetracarboxylic dianhydride is 6:4:7:

3. The specific process of step S1 is: the diamine monomer A and the dianhydride monomer B are added at -5-20 DEG C, and are stirred and reacted under nitrogen protection for 6-12h to obtain a polyamide acid stock solution; the solid content is controlled to be between 15-25wt%; 2. The production method according to claim 1, characterized by The molar ratio of the diamine monomer A and the dianhydride monomer B is 0.98-1:1.02-1. ​ 3. The production method according to claim 1, characterized by, The specific process of step S2 is: adding diamine monomer C and dianhydride monomer D at -5-20℃, stirring and reacting under nitrogen protection for 6-12h to obtain a polyamic acid stock solution; the solid content is controlled to be between 15-25wt%; wherein the molar ratio of diamine monomer C to dianhydride monomer D is 0.98-1:1.02-1.

4. The production method according to claim 1, characterized by, The molar ratio of the sum of the diamine monomer A and the diamine monomer C to the sum of the dianhydride monomer B and the dianhydride monomer D is 1:(0.99-1.05).

5. A polyimide fiber prepared by the preparation method of any one of claims 1-4.

6. The polyimide fiber according to claim 5, wherein The tensile strength of the polyimide fiber is 3.5-4.5 cN / dtex, and the elongation is 11.7%-22.3%.