A method for improving the spinnability of polyacrylonitrile spinning solution

Abstract

The application discloses a method for improving the spinnability of polyacrylonitrile spinning solution, comprising the following steps: determining the molecular weight of initial polyacrylonitrile; selecting at least two different molecular weight of blending polyacrylonitrile, which are respectively recorded as the first blending polyacrylonitrile and the second blending polyacrylonitrile; obtaining the first blending polyacrylonitrile with the first blending mass fraction x1 and the second blending polyacrylonitrile with the second blending mass fraction x2 based on preset configuration information; wherein, the preset configuration information is the corresponding relationship between the molecular weight of target polyacrylonitrile and the molecular weight of the first blending polyacrylonitrile, the first blending mass fraction x1 and the molecular weight of the second blending polyacrylonitrile, the second blending mass fraction x2; mixing the spinning solution of the first blending polyacrylonitrile and the spinning solution of the second blending polyacrylonitrile to obtain the spinning solution of target polyacrylonitrile. The method can improve the spinnability of polyacrylonitrile, while taking into account the strength of the original wire, the stability of the jet extrusion and the stretchability.

Description

Technical Field

[0001] This application relates to the field of carbon fiber production and preparation technology, and in particular to a method for improving the spinnability of polyacrylonitrile spinning solution. Background Technology

[0002] Polyacrylonitrile-based carbon fiber (PAN-CF) is prepared from PAN precursor fibers through a high-temperature heat treatment process involving pre-oxidation and carbonization. High-quality PAN precursor fibers are the prerequisite and key to preparing high-performance PAN-CF; therefore, the development of new carbon fiber products often starts with improving the quality of PAN precursor fibers.

[0003] However, changes in the production process of PAN precursor fibers are often accompanied by problems such as sizing and sizing, which lead to unstable spinning and extrusion or unstable drawing of filaments and broken fibers, resulting in poor spinnability. This seriously restricts the innovation of production technology and the development of new carbon fiber products.

[0004] PAN precursor yarn is formed from PAN spinning solution through spinning, shearing, coagulation, heating, and stretching. Therefore, improving the spinnability of PAN spinning solution is an urgent problem to be solved. Summary of the Invention

[0005] To address the aforementioned technical problems, this application aims to provide a method for improving the spinnability of polyacrylonitrile spinning solutions. This method can regulate the molecular weight distribution of polyacrylonitrile spinning solutions by blending polyacrylonitrile with different molecular weights, thereby improving the spinnability of polyacrylonitrile while taking into account the strength of the precursor fiber, the stability of the spinning and extrusion, and the drawability. This provides a strategy for improving the quality of PAN precursor fibers in the development of new carbon fiber products.

[0006] This application provides a method for improving the spinnability of polyacrylonitrile spinning solutions, including: Determine the molecular weight of the initial polyacrylonitrile; Based on the initial molecular weight of polyacrylonitrile, at least two polyacrylonitriles with different molecular weights are selected to be mixed, and are respectively denoted as the first polyacrylonitrile to be mixed and the second polyacrylonitrile to be mixed. Based on the preset configuration information, the first blend mass fraction is obtained. x 1. Mass parts of the first polyacrylonitrile to be blended and the second blend x 2. The second polyacrylonitrile to be blended; wherein, the preset configuration information is the molecular weight of the target polyacrylonitrile and the molecular weight of the first polyacrylonitrile to be blended, and the first blending mass fraction. x 1 and the molecular weight of the second polyacrylonitrile to be blended, and the second blend mass fraction. x The correspondence of 2; The spinning solution of the first polyacrylonitrile to be mixed is mixed with the spinning solution of the second polyacrylonitrile to be mixed to obtain the spinning solution of the target polyacrylonitrile.

[0007] In some embodiments of this application, the molecular weight of the first polyacrylonitrile to be mixed is smaller than the molecular weight of the initial polyacrylonitrile; The molecular weight of the second polyacrylonitrile to be mixed is greater than that of the first polyacrylonitrile to be mixed.

[0008] In some embodiments of this application, the ratio of the molecular weight of the first polyacrylonitrile to be mixed to the molecular weight of the initial polyacrylonitrile is less than the ratio of the molecular weight of the second polyacrylonitrile to be mixed to the molecular weight of the initial polyacrylonitrile.

[0009] In some embodiments of this application, the polyacrylonitrile to be mixed further includes a third polyacrylonitrile to be mixed; The molecular weight of the third polyacrylonitrile to be mixed is greater than the molecular weight of the initial polyacrylonitrile; The molecular weight of the second polyacrylonitrile to be mixed is between the molecular weight of the first polyacrylonitrile to be mixed and the molecular weight of the third polyacrylonitrile to be mixed.

[0010] In some embodiments of this application, the ratio of the molecular weight of the first polyacrylonitrile to be mixed to the molecular weight of the initial polyacrylonitrile is 0.5-0.8:1; The ratio of the molecular weight of the second polyacrylonitrile to the molecular weight of the initial polyacrylonitrile is 0.8-1.2:1; The ratio of the molecular weight of the third polyacrylonitrile to the molecular weight of the initial polyacrylonitrile is 1.2-1.5:1.

[0011] In some embodiments of this application, the selection of at least two polyacrylonitriles with different molecular weights to be mixed includes: Based on the initial weight-average molecular weight of polyacrylonitrile, at least two polyacrylonitriles with different weight-average molecular weights are selected to be mixed.

[0012] In some embodiments of this application, the determination of the initial molecular weight of polyacrylonitrile includes: The weight-average molecular weight and number-average molecular weight of the initial polyacrylonitrile were determined. Z Average molecular weight.

[0013] In some embodiments of this application, the preset configuration information includes the following formula: (Equation 1) (Equation 2) (Equation 3) (Equation 4) in, x 3 represents the third blending fraction of the third polyacrylonitrile to be blended; Mw1 The weight-average molecular weight of the first polyacrylonitrile to be mixed; M w2 The weight-average molecular weight of the second polyacrylonitrile to be mixed is 1. M w3 The weight-average molecular weight of the third polyacrylonitrile to be mixed; M w This represents the initial weight-average molecular weight of polyacrylonitrile; M n1 The number-average molecular weight of the first polyacrylonitrile to be mixed; M n2 The number-average molecular weight of the second polyacrylonitrile to be mixed; M n3 The number-average molecular weight of the third polyacrylonitrile to be mixed; M n The initial number-average molecular weight of polyacrylonitrile; M z1 The first polyacrylonitrile to be mixed Z Average molecular weight; M z2 For the second polyacrylonitrile to be mixed Z Average molecular weight; M z3 For the second polyacrylonitrile to be mixed Z Average molecular weight; M z For the initial polyacrylonitrile Z Average molecular weight; k 1. k 2 is a preset proportional constant.

[0014] In some embodiments of this application, the... k The range of values ​​for 1 is M n1 / M n < k 1< M n3 / M n The k The range of values ​​for 2 is M w1 M z1 / ( Mw M z )< k 2< M w3 M z3 / ( M w M z )and M n1 M z1 / ( M n M z )< k 1 k 2< M n3 M z3 / ( M n M z ).

[0015] In some embodiments of this application, the molecular weight of the initial polyacrylonitrile is determined by a combination of gel permeation chromatography-multi-angle laser light scattering-differential refractive index detection.

[0016] The technical solution provided in this application may include the following beneficial effects: The method of this application can control the molecular weight distribution of polyacrylonitrile spinning solution by blending polyacrylonitrile with different molecular weights, thereby improving the spinnability of polyacrylonitrile while taking into account the strength of the precursor fiber, the stability of the spinneret extrusion and the stretchability, providing a strategy for improving the quality of PAN precursor fiber in the development of new carbon fiber products.

[0017] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0018] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0019] Figure 1 This is a flowchart illustrating a method for improving the spinnability of a polyacrylonitrile spinning solution according to an exemplary embodiment. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with the embodiments and accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be arbitrarily combined with each other.

[0021] PAN precursor yarn is formed from PAN spinning solution through spinning, shearing, coagulation, heating, and stretching. The spinnability of the PAN spinning solution can generally be adjusted by controlling its physical properties (such as apparent viscosity, molecular weight, and solid content) or spinning process parameters (such as coagulation bath temperature / concentration, drying temperature, and draw ratio). However, these process adjustments are constrained by practical needs, namely, the difficulty in balancing spinnability with economy (e.g., solid content cannot be too low) and product performance (e.g., draw ratio cannot be too low). Therefore, the improvement in spinnability is not ideal.

[0022] The molecular weight and molecular weight distribution of fiber-forming polymers are intrinsic factors affecting their spinnability. Number-average molecular weight (NMR) M n = ∑ m i / ∑( N A m i / M i ) = 1 / ∑( N A oh i / M i ); M n , m i , N A , M i , oh i (representing number-average molecular weight, mass of the i-th unit, Avogadro's constant, molar mass of the i-th unit, and mass fraction, respectively) is the average molecular weight with quantity as the statistical weight. The flow properties of the polymer are related to... M n Closely related; weight-average molecular weight ( M w = ∑ oh i M i ;M w (Weight-average molecular weight) is the average molecular weight with weight as the statistical weight, which determines the strength properties; Z Average molecular weight ( M z =∑ oh i M i 2 / ∑ oh i M i PAN is the average molecular weight with weight squared as the statistical weight, and it is related to the elongation and flexibility of the polymer. The spinnability of PAN spinning solution can be adjusted by changing the molecular weight of PAN; however, it is difficult to simultaneously control shear flow stability, tensile flexibility, and precursor fiber strength, i.e., it is difficult to directionally regulate all properties at the same time. M n , M z and M w .

[0023] To address the aforementioned technical problems, this application provides a method for improving the spinnability of polyacrylonitrile spinning solutions, comprising: determining the molecular weight of the initial polyacrylonitrile; selecting at least two polyacrylonitrile molecules with different molecular weights to be blended, respectively designated as the first polyacrylonitrile to be blended and the second polyacrylonitrile to be blended; and obtaining the first blending mass fraction based on preset configuration information. x 1. Mass parts of the first polyacrylonitrile to be blended and the second blend x 2. The second polyacrylonitrile to be blended; wherein, the preset configuration information is the molecular weight of the target polyacrylonitrile, the molecular weight of the first polyacrylonitrile to be blended, and the first blending mass fraction. x 1. The molecular weight of the second polyacrylonitrile to be blended and the second blend mass fraction. x The correspondence in step 2 is as follows: The spinning solution of the first polyacrylonitrile to be mixed with the spinning solution of the second polyacrylonitrile to be mixed are mixed to obtain the spinning solution of the target polyacrylonitrile. By blending polyacrylonitrile with different molecular weights, the molecular weight distribution of the polyacrylonitrile spinning solution is controlled to improve the spinnability of polyacrylonitrile, while also taking into account the strength of the precursor fiber, the stability of the spinneret extrusion, and the drawability, providing a strategy for improving the quality of PAN precursor fiber in the development of new carbon fiber products.

[0024] The specific embodiments described below are intended to help those skilled in the art understand this embodiment, but this embodiment is not limited to the specific embodiments described below.

[0025] In one exemplary embodiment, reference is made to Figure 1 This application provides a method for improving the spinnability of polyacrylonitrile spinning solution, comprising: S100, Determine the molecular weight of the initial polyacrylonitrile.

[0026] In step S100, the initial polyacrylonitrile refers to the original polyacrylonitrile that has not been blended and adjusted. The initial polyacrylonitrile can be used as a reference to adjust the spinnability of the polyacrylonitrile spinning solution.

[0027] S200. Based on the initial molecular weight of polyacrylonitrile, select at least two polyacrylonitriles with different molecular weights to be mixed, and denoted as the first polyacrylonitrile to be mixed and the second polyacrylonitrile to be mixed, respectively.

[0028] In step S200, the number of polyacrylonitrile to be mixed can be two, three, or other similar quantities. For example, when two polyacrylonitriles with different molecular weights are selected, the two polyacrylonitriles can be respectively designated as the first polyacrylonitrile to be mixed and the second polyacrylonitrile to be mixed.

[0029] S300. Based on the preset configuration information, the first blend mass fraction is obtained. x 1. Mass parts of the first polyacrylonitrile to be blended and the second blend x 2. The second polyacrylonitrile to be blended; wherein, the preset configuration information is the molecular weight of the target polyacrylonitrile, the molecular weight of the first polyacrylonitrile to be blended, and the first blending mass fraction. x 1. The molecular weight of the second polyacrylonitrile to be blended and the second blend mass fraction. x The correspondence between 2.

[0030] In step S300, the preset configuration information can be set according to the selected quantity of polyacrylonitrile to be blended. For example, when two polyacrylonitriles with different molecular weights are selected, it is necessary to ensure the first blend mass fraction. x 1 and second blending mass parts x The sum of 2 is 1; when three different molecular weights of polyacrylonitrile are selected for blending, the mass fraction of the first blend must be guaranteed. x 1. Second blending mass parts x 2. Mass fraction of the third blend x The sum of 3 is 1.

[0031] S400. The spinning solution of the first polyacrylonitrile to be mixed is mixed with the spinning solution of the second polyacrylonitrile to be mixed to obtain the spinning solution of the target polyacrylonitrile.

[0032] In step S400, the spinning solution of the first polyacrylonitrile to be blended and the spinning solution of the second polyacrylonitrile to be blended are respectively mixed according to the first blending mass fraction. x 1 and the second blend mass fraction x 2. Mix to obtain the spinning solution of the target polyacrylonitrile.

[0033] In this embodiment, the molecular weight distribution of the polyacrylonitrile spinning solution is controlled by blending polyacrylonitrile with different molecular weights, thereby improving the spinnability of polyacrylonitrile while taking into account the strength of the precursor fiber, the stability of the spinneret extrusion and the stretchability, providing a strategy for improving the quality of PAN precursor fiber in the development of new carbon fiber products.

[0034] In one exemplary embodiment, the molecular weight of the first polyacrylonitrile to be mixed is smaller than the molecular weight of the initial polyacrylonitrile. The molecular weight of the second polyacrylonitrile to be mixed is greater than that of the first polyacrylonitrile to be mixed.

[0035] In this embodiment, by making the molecular weight of the first polyacrylonitrile to be mixed smaller than the molecular weight of the initial polyacrylonitrile, and the molecular weight of the second polyacrylonitrile to be mixed larger than the molecular weight of the initial polyacrylonitrile, the spinnability of the target polyacrylonitrile spinning solution can be better controlled. When comparing the molecular weights of the various polyacrylonitriles, molecular weights using the same characterization method must be selected, and the different characterization methods selected for the molecular weights can be set according to requirements.

[0036] For example, when controlling the spinnability of polyacrylonitrile spinning solutions, it is necessary to ensure that the strength of the target polyacrylonitrile is basically consistent with the strength of the initial polyacrylonitrile. Therefore, when selecting polyacrylonitriles of different molecular weights to be mixed, it is necessary to base the selection on the weight-average molecular weight of the initial polyacrylonitrile. M w This makes the weight-average molecular weight of the first polyacrylonitrile to be mixed... M w1 Smaller than the initial polyacrylonitrile M w The weight-average molecular weight of the second polyacrylonitrile to be mixed M w2 Greater than the initial polyacrylonitrile M w .

[0037] If the toughness of the target polyacrylonitrile needs to be substantially consistent with that of the initial polyacrylonitrile, then when selecting polyacrylonitriles of different molecular weights to be mixed, it is necessary to base the selection on the initial polyacrylonitrile. Z The weight-average molecular weight of the first polyacrylonitrile to be mixed is determined by the average molecular weight. M z1 Smaller than the initial polyacrylonitrile M z The weight-average molecular weight of the second polyacrylonitrile to be mixed M z2 Greater than the initial polyacrylonitrile M z .

[0038] In an exemplary embodiment, the ratio of the molecular weight of the first polyacrylonitrile to be mixed to the molecular weight of the initial polyacrylonitrile is less than the ratio of the molecular weight of the second polyacrylonitrile to be mixed to the molecular weight of the initial polyacrylonitrile.

[0039] In this embodiment, by making the ratio of the molecular weight of the first polyacrylonitrile to be mixed to the molecular weight of the initial polyacrylonitrile smaller than the ratio of the molecular weight of the second polyacrylonitrile to be mixed to the molecular weight of the initial polyacrylonitrile, the spinnability of the target polyacrylonitrile spinning solution can be better controlled.

[0040] In one exemplary embodiment, the polyacrylonitrile to be mixed further includes a third polyacrylonitrile to be mixed; The molecular weight of the third polyacrylonitrile to be mixed is greater than the molecular weight of the initial polyacrylonitrile. The molecular weight of the second polyacrylonitrile to be mixed is between that of the first and third polyacrylonitrile to be mixed.

[0041] In this embodiment, by selecting three different molecular weights of polyacrylonitrile to be blended, the spinnability of the target polyacrylonitrile spinning solution can be adjusted while taking into account its shear flow stability, tensile flexibility and filament strength properties.

[0042] In an exemplary embodiment, the ratio of the molecular weight of the first polyacrylonitrile to be mixed to the molecular weight of the initial polyacrylonitrile is 0.5-0.8:1; The ratio of the molecular weight of the second polyacrylonitrile to that of the initial polyacrylonitrile is 0.8-1.2:1; The ratio of the molecular weight of the third polyacrylonitrile to that of the initial polyacrylonitrile is 1.2-1.5:1.

[0043] For example, in one embodiment, the ratio of the molecular weight of the first polyacrylonitrile to be mixed to the molecular weight of the initial polyacrylonitrile is 0.5:1. The ratio of the molecular weight of the second polyacrylonitrile to that of the initial polyacrylonitrile is 0.8:1. The ratio of the molecular weight of the third polyacrylonitrile to that of the initial polyacrylonitrile is 1.2:1.

[0044] In another embodiment, the ratio of the molecular weight of the first polyacrylonitrile to be mixed to the molecular weight of the initial polyacrylonitrile is 0.6:1; The ratio of the molecular weight of the second polyacrylonitrile to that of the initial polyacrylonitrile is 1.0:1. The ratio of the molecular weight of the third polyacrylonitrile to that of the initial polyacrylonitrile is 1.4:1.

[0045] In another embodiment, the ratio of the molecular weight of the first polyacrylonitrile to be mixed to the molecular weight of the initial polyacrylonitrile is 0.8:1; The ratio of the molecular weight of the second polyacrylonitrile to that of the initial polyacrylonitrile is 1.2:1. The ratio of the molecular weight of the third polyacrylonitrile to that of the initial polyacrylonitrile is 1.5:1.

[0046] In one exemplary embodiment, at least two polyacrylonitriles of different molecular weights are selected, including: Based on the initial weight-average molecular weight of polyacrylonitrile, at least two polyacrylonitriles with different weight-average molecular weights are selected to be mixed.

[0047] To ensure that the mechanical strength of the target polyacrylonitrile after blending remains essentially unchanged from that of the initial polyacrylonitrile, the weight-average molecular weight of the target polyacrylonitrile needs to be essentially the same as that of the initial polyacrylonitrile. Therefore, in this embodiment, the weight-average molecular weight of the initial polyacrylonitrile is used as a benchmark, and two polyacrylonitriles with different weight-average molecular weights are selected for blending.

[0048] In one exemplary embodiment, determining the molecular weight of the initial polyacrylonitrile includes: Determine the weight-average molecular weight and number-average molecular weight of the initial polyacrylonitrile. Z Average molecular weight.

[0049] In this embodiment, the weight-average molecular weight and number-average molecular weight of the initial polyacrylonitrile were measured. Z Number-average molecular weight (NAM) can be directionally controlled to adjust the number-average molecular weight and weight-average molecular weight of the target polyacrylonitrile while maintaining the weight-average molecular weight unchanged. Z Average molecular weight.

[0050] In one exemplary embodiment, the preset configuration information includes the following formula: (Equation 1) (Equation 2) (Equation 3) (Equation 4) in, x 3 represents the third blending fraction of the third polyacrylonitrile to be blended; M w1 The weight-average molecular weight of the first polyacrylonitrile to be mixed; M w2 The weight-average molecular weight of the second polyacrylonitrile to be mixed is 1. M w3 The weight-average molecular weight of the third polyacrylonitrile to be mixed; M w This represents the initial weight-average molecular weight of polyacrylonitrile; M n1 The number-average molecular weight of the first polyacrylonitrile to be mixed; M n2 The number-average molecular weight of the second polyacrylonitrile to be mixed; M n3 The number-average molecular weight of the third polyacrylonitrile to be mixed; M n The initial number-average molecular weight of polyacrylonitrile; M z1 The first polyacrylonitrile to be mixed Z Average molecular weight; M z2 For the second polyacrylonitrile to be mixed Z Average molecular weight; M z3 For the second polyacrylonitrile to be mixed Z Average molecular weight; M z For the initial polyacrylonitrile Z Average molecular weight; k 1. k 2 is a preset proportional constant.

[0051] In this embodiment, according to the preset configuration information, it can be ensured that the weight-average molecular weight of the target polyacrylonitrile after blending is basically the same as that of the initial polyacrylonitrile, and the number-average molecular weight of the target polyacrylonitrile is... Z The average molecular weight can be determined by a preset proportional constant. k 1. k 2. Adjustments were made, taking into account the strength of the precursor fiber, the stability of the spinneret extrusion, and the stretchability, providing a strategy for improving the quality of PAN precursor fiber in the development of new carbon fiber products.

[0052] Based on equations (1), (2), (3), and (4), the solution to the equation can be obtained as follows: (Equation 5) (Equation 6) (Equation 7) in, (Equation 8) (Equation 9) (Equation 10) (Equation 11) (Equation 12) (Equation 13) (Equation 14) (Equation 15) (Equation 16).

[0053] In this embodiment, k 1. k 2 is an adjustable proportional constant, and the specific value can be set according to the molecular weight of the first polyacrylonitrile to be mixed, the third polyacrylonitrile to be mixed, and the initial polyacrylonitrile.

[0054] In an exemplary embodiment, the k The range of values ​​for 1 is M n1 / M n < k 1< M n3 / M n The k The range of values ​​for 2 is M w1 M z1 / ( M w M z )< k 2< M w3 M z3 / ( M w M z )and M n1 / M z1 / ( M n M z )< k 1 k 2< M n3 / M z3 / ( M n M z ).

[0055] For example, the number-average molecular weight of the first polyacrylonitrile to be mixedM n1 The weight-average molecular weight is 9.4. M w1 It is 21.43. Z Average molecular weight M z1 The number average molecular weight was 32.78; the third polyacrylonitrile to be mixed had a number average molecular weight of 32.78. M n3 It is 29.58, and the weight-average molecular weight is... M w3 It is 38.39. Z Average molecular weight M z3 The initial number-average molecular weight of polyacrylonitrile was 70.18. M n The weight-average molecular weight is 17.24. M w It is 26.53. Z Average molecular weight M z The value is 51.8. k The value of 1 is in the range of 0.55 < k 1 < 1.72, k The value of 2 is in the range of 0.51 < k 2 < 1.96 and 0.35 < k 1 k 2 < 2.32. For example, k 1 is 0.90. k 2 is 1.05.

[0056] In one exemplary embodiment, the molecular weight of the initial polyacrylonitrile was determined using a combination of gel permeation chromatography-multi-angle laser light scattering-differential refractive index detection.

[0057] In this embodiment, the molecular weight of the initial polyacrylonitrile was determined by a combination of gel permeation chromatography (GPC), multi-angle laser light scattering (SLS), and differential refractive index (RI).

[0058] The method for preparing PAN polymer is as follows: using the common coating-drying method, PAN polymer is prepared from PAN spinning solution; that is, the PAN spinning solution is coated into a thin film to facilitate the full displacement of the solvent in it, and the solvent in the spinning solution is replaced by a double diffusion method using methanol, ethanol or water, which are poor solvents for PAN. Finally, the washed PAN film is dried to obtain PAN polymer.

[0059] The molecular weight determination method is as follows: 0.05 mol / L LiBr / DMF is used as the mobile phase; porous monodisperse cross-linked polystyrene is used as the stationary phase; a 3-5 mg / mL dilute solution (heating is required to dissolve) is prepared using the dried PAN film as the solvent and the mobile phase; the sample solution filtered through a pinhole filter is then injected into the system. Before use, the system is tested with a standard (e.g., PS). M w =13.6 kDa, PDI = M w / M n = 1.055) correction; with the refractive index increment dn / dc = 0.0837 mL / g as the known parameter, the calculation was performed using the BIC ParSEC Chromatography software.

[0060] To more clearly explain the technical solution of this application, this application provides specific embodiments for improving the spinnability of polyacrylonitrile spinning solutions. The beneficial effects of selecting the above-mentioned ranges of various parameters will be explained through specific experimental data provided in the specific embodiments.

[0061] Example Example 1: A method for improving the spinnability of polyacrylonitrile spinning solution, comprising the following steps: (1) Dip a glass rod into the initial PAN spinning solution and weigh it by difference to obtain 1.0473 g of initial PAN spinning solution. Spread it evenly on a 20 cm × 20 cm glass plate. Place the glass plate in a deionized water solution to displace the organic solvent and obtain a solidified polymer film. Peel off the solidified polymer film and use absorbent paper towels to absorb the water on the surface of the polymer film. Then place the polymer film in a 105 ℃ drying oven for 60 min to obtain a PAN film. Using 0.05 mol / L LiBr / DMF as the mobile phase and porous monodisperse cross-linked polystyrene as the stationary phase, 15.0 mg of dried PAN film was added to a 5 mL colorimetric tube, and the mobile phase solvent was added to make initial volume. The colorimetric tube was capped and sealed, and heated in a 60 ℃ water bath with occasional shaking during heating. After about 2 h, the sample was completely dissolved. The colorimetric tube was then cooled to room temperature in conventional water and further diluted to volume, and the solution to be tested was prepared by shaking. The sample solution was filtered through a 0.45 μm pinhole filter membrane and then injected into the system. Before use, the system was tested with a standard (PS). M w = 13.6 kDa, PDI = M w / M n= 1.055) correction; with the refractive index increment dn / dc = 0.0837 mL / g as a known parameter, input into the BIC ParSEC Chromatography software for calculation to obtain the initial number-average molecular weight, weight-average molecular weight, and Z The average molecular weight is listed in Table 1.

[0062] (2) Three types of polyacrylonitrile to be mixed, with low, medium, and high molecular weights respectively, were selected and designated as PAN-1 (first type), PAN-2 (second type), and PAN-3 (third type). PAN-2 used the initial polyacrylonitrile. PAN-1 and PAN-3 were commercially available. PAN films were prepared using the coating-drying method described in step (1). Their number-average molecular weight, weight-average molecular weight, and molecular weight were measured using GPC-SLS-RI. Z The average molecular weight is listed in Table 1.

[0063] (3) Set the proportional constant k 1. k 2 are 0.90 and 1.00 respectively. Based on the system of equations (1) to (4), the solution to the system of equations is obtained by solving equations (5) to (16). x 1 = 33.0% x 2 = 50.2% x 3 = 16.8%.

[0064] (4) Prepare a PAN / DMSO solution with solute mass compositions of PAN-1, PAN-2, and PAN-3 of 33.0%, 50.2%, and 16.8%, respectively, and a solid content of 20.0%. Specifically, mix 65.97 kg of PAN-1, 100.45 kg of PAN-2, 33.58 kg of PAN-3, and 800 kg of DMSO (dimethyl sulfoxide) in a dissolving vessel and stir at 80 °C and 160 rpm for 24 h before pumping into a degassing vessel. Set the parameters in the degassing vessel as follows: temperature 50 °C, gauge pressure 5 kPa, residence time 5 h to obtain the spinning solution of the target polyacrylonitrile.

[0065] Example 2: This example is basically the same as Example 1, except for the proportionality constant. k 1. k 2 is adjusted to 0.85 and 1.00, and the solution to the system of equations is obtained as follows: x 1 = 50.2% x 2 = 24.3% x3 = 25.5%. Prepare a PAN / DMSO solution with solute mass compositions of 50.2%, 24.3%, and 25.5% for PAN-1, PAN-2, and PAN-3, respectively, and a solid content of 20.0%. This is achieved by mixing 100.29 kg of PAN-1, 48.66 kg of PAN-2, 51.05 kg of PAN-3, and 800 kg of DMSO in a dissolving vessel.

[0066] Example 3: This example is basically the same as Example 1, except for the proportionality constant. k 1. k 2 is adjusted to 0.90 and 0.95, and the solution to the system of equations is: x 1 = 25.0% x 2 = 67.5% x 3 = 7.5%. Prepare a PAN / DMSO solution with solute mass compositions of 50.2%, 24.3%, and 25.5% for PAN-1, PAN-2, and PAN-3, respectively, and a solid content of 20.0%. This is achieved by mixing 50.04 kg of PAN-1, 134.90 kg of PAN-2, 15.06 kg of PAN-3, and 800 kg of DMSO in a dissolving vessel.

[0067] Example 4: This example is basically the same as Example 1, except for the proportionality constant. k 1. k 2 is adjusted to 0.90 and 1.10, and the solution to the system of equations is obtained as follows: x 1 = 48.9% x 2 = 15.8% x 3 = 35.3%. A PAN / DMSO solution with a solid content of 20.0% and a solute mass composition of PAN-1, PAN-2, and PAN-3 of 48.9%, 15.8%, and 35.3% respectively was prepared by mixing 97.83 kg of PAN-1, 31.56 kg of PAN-2, 70.61 kg of PAN-3, and 800 kg of DMSO in a dissolving vessel.

[0068] Example 5: This example is basically the same as Example 1, except for the proportionality constant. k 1. k 2 is adjusted to 0.90 and 1.05, and the solution to the system of equations is obtained as follows: x 1 = 40.9% x 2 = 33.0% x3 = 26.1%. A PAN / DMSO solution with a solute mass composition of 40.9%, 33.0%, and 7.5% for PAN-1, PAN-2, and PAN-3, and a solid content of 20.0%, was prepared by mixing 81.90 kg of PAN-1, 66.01 kg of PAN-2, 52.09 kg of PAN-3, and 800 kg of DMSO in a dissolving vessel.

[0069] Comparative Example 1: Comparative Example 1 is the initial polyacrylonitrile.

[0070] Performance testing The properties of the target polyacrylonitrile obtained by blending in the examples and the initial polyacrylonitrile of the control examples were tested according to the following method, and the test results are listed in Table 2.

[0071] 1. Molecular weight: Samples were taken from the spinning solution of the target polyacrylonitrile, and PAN films were prepared according to the coating-drying method in step (1). The number-average molecular weight, weight-average molecular weight, and molecular weight of the films were measured using GPC-SLS-RI. Z Average molecular weight.

[0072] 2. Operational stability: The spinning solution of the target polyacrylonitrile after degassing and the spinning solution of the initial polyacrylonitrile in Control Example 1 were pumped into the spinning line respectively, and the precursor yarn was prepared by dry-jet wet spinning; the number of spinning and filament breakage times in 12 h were counted to evaluate its operational stability.

[0073] 3. Mechanical properties: The breaking strength and elastic modulus of the prepared precursor fibers were measured to evaluate the changes in the properties of the precursor fibers.

[0074] Table 1. Molecular weight parameters of polyacrylonitrile

[0075] Table 2 Performance test results of polyacrylonitrile in the examples and control examples

[0076] As can be seen from Tables 1 and 2, the weight-average molecular weight of the target polyacrylonitrile in the examples is similar to that of the initial polyacrylonitrile, indicating that the molecular weight blending and calculation method of this application has strong guiding significance and facilitates rapid quantitative adjustment of PAN molecular weight.

[0077] As can be seen from Table 2, compared to Control Example 1, after 5 adjustments in the embodiments... k 1. k After 2, the number of filament breakages in 12 hours in Example 5 decreased from 12 to 2, and the number of filament breakages due to steaming decreased from 9 to 3, significantly improving spinnability. This demonstrates that the method of blending to control the molecular weight distribution of polyacrylonitrile proposed in this application effectively improves the spinnability of the spinning solution.

[0078] As shown in Table 2, compared with Control Example 1, the mechanical properties of the PAN precursor fibers prepared in Examples 1-5 did not change significantly. This is because the weight-average molecular weight was controlled in the design of the PAN blends in this application. M w As can be seen from this, the method proposed in this application takes into account the strength of the precursor fiber, the stability of the spinneret extrusion, and the stretchability, and can provide an efficient strategy for improving the quality of PAN precursor fiber in the development of new carbon fiber products.

[0079] It should be noted that, in this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0080] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit it. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A method for improving the spinnability of polyacrylonitrile spinning solution, characterized in that, include: Determine the molecular weight of the initial polyacrylonitrile; Based on the initial molecular weight of polyacrylonitrile, three different molecular weights of polyacrylonitrile to be mixed were selected and denoted as the first polyacrylonitrile to be mixed, the second polyacrylonitrile to be mixed, and the third polyacrylonitrile to be mixed, respectively. Based on the preset configuration information, the first blend mass fraction is obtained. x 1. Mass parts of the first polyacrylonitrile to be blended and the second blend x 2. The number of the second and third blending parts of polyacrylonitrile to be mixed x 3. The third polyacrylonitrile to be blended; wherein, the preset configuration information is the molecular weight of the target polyacrylonitrile and the molecular weight of the first polyacrylonitrile to be blended, and the first blending mass fraction. x 1. The molecular weight of the second polyacrylonitrile to be blended and the second blending mass fraction. x 2. The molecular weight and mass fraction of the third polyacrylonitrile to be blended. x The correspondence of 3; The spinning solution of the first polyacrylonitrile to be mixed, the spinning solution of the second polyacrylonitrile to be mixed, and the spinning solution of the third polyacrylonitrile to be mixed are mixed to obtain the spinning solution of the target polyacrylonitrile. The preset configuration information includes the following formula: (Equation 1) (Equation 3) (Equation 4) in, M w1 The weight-average molecular weight of the first polyacrylonitrile to be mixed; M w2 The weight-average molecular weight of the second polyacrylonitrile to be mixed is 1. M w3 The weight-average molecular weight of the third polyacrylonitrile to be mixed; M w This represents the initial weight-average molecular weight of polyacrylonitrile; M n1 The number-average molecular weight of the first polyacrylonitrile to be mixed; M n2 The number-average molecular weight of the second polyacrylonitrile to be mixed; M n3 The number-average molecular weight of the third polyacrylonitrile to be mixed; M n The initial number-average molecular weight of polyacrylonitrile; M z1 The first polyacrylonitrile to be mixed Z Average molecular weight; M z2 For the second polyacrylonitrile to be mixed Z Average molecular weight; M z3 For the second polyacrylonitrile to be mixed Z Average molecular weight; M z For the initial polyacrylonitrile Z Average molecular weight; k 1. k 2 is the preset proportional constant; The k The range of values ​​for 1 is M n1 / M n < k 1< M n3 / M n The k The range of values ​​for 2 is M w1 M z1 / ( M w M z )< k 2< M w3 M z3 / ( M w M z )and M n1 M z1 / ( M n M z )< k 1 k 2< M n3 M z3 / ( M n M z ).

2. The method for improving the spinnability of polyacrylonitrile spinning solution according to claim 1, characterized in that, The molecular weight of the first polyacrylonitrile to be mixed is smaller than the molecular weight of the initial polyacrylonitrile; The molecular weight of the second polyacrylonitrile to be mixed is greater than that of the first polyacrylonitrile to be mixed.

3. The method for improving the spinnability of polyacrylonitrile spinning solution according to claim 1, characterized in that, The ratio of the molecular weight of the first polyacrylonitrile to be mixed to the molecular weight of the initial polyacrylonitrile is less than the ratio of the molecular weight of the second polyacrylonitrile to be mixed to the molecular weight of the initial polyacrylonitrile.

4. The method for improving the spinnability of polyacrylonitrile spinning solution according to claim 2, characterized in that, The molecular weight of the third polyacrylonitrile to be mixed is greater than the molecular weight of the initial polyacrylonitrile; The molecular weight of the second polyacrylonitrile to be mixed is between the molecular weight of the first polyacrylonitrile to be mixed and the molecular weight of the third polyacrylonitrile to be mixed.

5. The method for improving the spinnability of polyacrylonitrile spinning solution according to claim 4, characterized in that, The ratio of the molecular weight of the first polyacrylonitrile to be mixed to the molecular weight of the initial polyacrylonitrile is 0.5-0.8:1; The ratio of the molecular weight of the second polyacrylonitrile to the molecular weight of the initial polyacrylonitrile is 0.8-1.2:1; The ratio of the molecular weight of the third polyacrylonitrile to the molecular weight of the initial polyacrylonitrile is 1.2-1.5:

1.

6. The method for improving the spinnability of polyacrylonitrile spinning solution according to any one of claims 1-5, characterized in that, The selection of three different molecular weight polyacrylonitriles to be mixed includes: Based on the initial weight-average molecular weight of polyacrylonitrile, three polyacrylonitriles with different weight-average molecular weights were selected for mixing.

7. The method for improving the spinnability of polyacrylonitrile spinning solution according to claim 4, characterized in that, The determination of the initial molecular weight of polyacrylonitrile includes: The weight-average molecular weight and number-average molecular weight of the initial polyacrylonitrile were determined. Z Average molecular weight.

8. The method for improving the spinnability of polyacrylonitrile spinning solution according to claim 1, characterized in that, The molecular weight of the initial polyacrylonitrile was determined by a combination of gel permeation chromatography, multi-angle laser light scattering, and differential refractive index detection.

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