Method for improving spinnability of polyacrylonitrile spinning solution

Abstract

The invention discloses a method for improving spinnability of a polyacrylonitrile spinning solution. The method comprises the following steps: measuring the molecular weight of initial polyacrylonitrile; based on the molecular weight of the initial polyacrylonitrile, selecting at least two kinds of polyacrylonitrile to be mixed with different molecular weights, and respectively recording the polyacrylonitrile to be mixed as first polyacrylonitrile to be mixed and second polyacrylonitrile to be mixed; based on preset configuration information, obtaining first to-be-mixed polyacrylonitrile with a first blending mass fraction x1 and second to-be-mixed polyacrylonitrile with a second blending mass fraction x2; wherein the preset configuration information is a corresponding relationship between the molecular weight of the target polyacrylonitrile and the molecular weight of the first to-be-mixed polyacrylonitrile, the first blending mass fraction x1, the molecular weight of the second to-be-mixed polyacrylonitrile and the second blending mass fraction x2; and mixing the spinning solution of the first to-be-mixed polyacrylonitrile with the spinning solution of the second to-be-mixed polyacrylonitrile to obtain the spinning solution of the target polyacrylonitrile. According to the method, the spinning property of polyacrylonitrile can be improved, and meanwhile, the precursor strength, the spinning extrusion stability and the draftability are considered.

Description

Technical Field

[0001] The present application relates to the technical field of carbon fiber production and preparation, and in particular to a method for improving the spinnability of polyacrylonitrile spinning solution. Background Art

[0002] Polyacrylonitrile-based carbon fiber (PAN-CF) is prepared from PAN precursor by high-temperature heat treatment of pre-oxidation-carbonization. High-quality PAN precursor is the premise and key to the preparation of high-performance PAN-CF. Therefore, the development of new carbon fiber products also starts with the quality improvement of PAN precursor.

[0003] However, changes in the production process of PAN raw fiber are often accompanied by problems such as pulp loss and board sticking, resulting in unstable spinneret extrusion or unstable drafting of hairy and broken fibers, i.e., poor spinnability, which seriously restricts the innovation of production process technology and the development of new carbon fiber products.

[0004] PAN raw fibers are formed by spinning solution through shearing, coagulation, heating and drawing. Therefore, how to improve the spinnability of PAN spinning solution is an urgent problem to be solved. Summary of the invention

[0005] In order to solve the above technical problems, the present application aims to provide a method for improving the spinnability of polyacrylonitrile spinning solution. This method can improve the spinnability of polyacrylonitrile by blending polyacrylonitrile of different molecular weights and regulating the molecular weight distribution of the polyacrylonitrile spinning solution, while taking into account the strength of the precursor, the stability of the spinneret extrusion and the stretchability, thereby providing a strategy for improving the quality of PAN precursor in the development of new carbon fiber products.

[0006] The present application provides a method for improving the spinnability of polyacrylonitrile spinning solution, comprising:

[0007] Determine the molecular weight of initial polyacrylonitrile;

[0008] Based on the molecular weight of the initial polyacrylonitrile, at least two polyacrylonitrile to be mixed with different molecular weights are selected and recorded as the first polyacrylonitrile to be mixed and the second polyacrylonitrile to be mixed respectively;

[0009] Based on the preset configuration information, a first polyacrylonitrile to be mixed with a first blending mass fraction x1 and a second polyacrylonitrile to be mixed with a second blending mass fraction x2 are obtained; wherein the preset configuration information is a correspondence between the molecular weight of the target polyacrylonitrile and the molecular weight of the first polyacrylonitrile to be mixed, the first blending mass fraction x1, and the molecular weight of the second polyacrylonitrile to be mixed, and the second blending mass fraction x2;

[0010] 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.

[0011] In some embodiments of the present application, the molecular weight of the first polyacrylonitrile to be mixed is less than the molecular weight of the initial polyacrylonitrile;

[0012] The molecular weight of the second polyacrylonitrile to be mixed is greater than the molecular weight of the first polyacrylonitrile to be mixed.

[0013] In some embodiments of the present application, the ratio of the molecular weight of the first polyacrylonitrile to be mixed to the molecular weight of the initial polyacrylonitrile is smaller than the ratio of the molecular weight of the second polyacrylonitrile to be mixed to the molecular weight of the initial polyacrylonitrile.

[0014] In some embodiments of the present application, the polyacrylonitrile to be mixed further includes a third polyacrylonitrile to be mixed;

[0015] The molecular weight of the third polyacrylonitrile to be mixed is greater than the molecular weight of the initial polyacrylonitrile;

[0016] 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.

[0017] In some embodiments of the present 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;

[0018] The ratio of the molecular weight of the second polyacrylonitrile to be mixed to the molecular weight of the initial polyacrylonitrile is 0.8-1.2:1;

[0019] The ratio of the molecular weight of the third polyacrylonitrile to be mixed to the molecular weight of the initial polyacrylonitrile is 1.2-1.5:1.

[0020] In some embodiments of the present application, the selecting of at least two polyacrylonitrile with different molecular weights to be mixed includes:

[0021] Based on the weight average molecular weight of the initial polyacrylonitrile, at least two polyacrylonitrile with different weight average molecular weights to be mixed are selected.

[0022] In some embodiments of the present application, the determination of the molecular weight of the initial polyacrylonitrile comprises:

[0023] The weight average molecular weight, number average molecular weight and Z average molecular weight of the initial polyacrylonitrile were measured.

[0024] In some embodiments of the present application, the preset configuration information includes the following formula:

[0025] x1+x2+x3=1 (Formula 1)

[0026] x1M w1 +x2M w2 +x3M w3 =Mw (Formula 2)

[0027]

[0028] Wherein, x3 is the third blending portion of the third polyacrylonitrile to be mixed;

[0029] M w1 is the weight average molecular weight of the first polyacrylonitrile to be mixed;

[0030] M w2 is the weight average molecular weight of the second polyacrylonitrile to be mixed;

[0031] M w3 is the weight average molecular weight of the third polyacrylonitrile to be mixed;

[0032] M w is the weight average molecular weight of the initial polyacrylonitrile;

[0033] M n1 is the number average molecular weight of the first polyacrylonitrile to be mixed;

[0034] M n2 is the number average molecular weight of the second polyacrylonitrile to be mixed;

[0035] M n3 is the number average molecular weight of the third polyacrylonitrile to be mixed;

[0036] M n is the number average molecular weight of initial polyacrylonitrile;

[0037] M z1 is the Z average molecular weight of the first polyacrylonitrile to be mixed;

[0038] M z2 is the Z average molecular weight of the second polyacrylonitrile to be mixed;

[0039] M z3 is the Z average molecular weight of the second polyacrylonitrile to be mixed;

[0040] M z is the Z-average molecular weight of the initial polyacrylonitrile;

[0041] k1 and k2 are preset proportional constants.

[0042] In some embodiments of the present application, the value range of k1 is M n1 / M n <k1<M n3 / M n , the value range of k2 is M w1 M z1 / (M w M z ) <k2<Mw3 M z3 / (M w M z ) and M n1 M z1 / (M n M z ) <k1k2<M n3 M z3 / (M n M z ).

[0043] In some embodiments of the present application, the molecular weight of the initial polyacrylonitrile is measured by gel permeation chromatography-multi-angle laser light scattering-differential refractive index detection.

[0044] The technical solution provided by this application may have the following beneficial effects:

[0045] The method of the present application can regulate the molecular weight distribution of polyacrylonitrile spinning solution by blending polyacrylonitrile of different molecular weights to improve the spinnability of polyacrylonitrile, while taking into account the strength of the precursor, the stability of the spinneret extrusion and the drawability, providing a strategy for improving the quality of PAN precursor in the development of new carbon fiber products.

[0046] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0048] Figure 1 The present invention is a flow chart of a method for improving the spinnability of polyacrylonitrile spinning solution according to an exemplary embodiment. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme of the present application will be clearly and completely described below in combination with the embodiments of the present application and the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present application. It should be noted that, in the absence of conflict, the embodiments in the present application and the features in the embodiments can be arbitrarily combined with each other.

[0050] PAN raw fibers are formed from PAN spinning solution by spinneret shearing, coagulation, heating, and stretching. Generally, the spinnability of PAN spinning solution can be adjusted by adjusting the physical parameters of PAN spinning solution (such as apparent viscosity, molecular weight, solid content, etc.) or spinning process parameters (such as coagulation bath temperature / concentration, drying temperature, stretching multiple, etc.). However, the above process adjustment is constrained by actual needs, that is, it is difficult to balance spinnability with economy (such as solid content cannot be too low) and product performance (such as stretching multiple cannot be too low), so the improvement effect of spinnability is not ideal.

[0051] The molecular weight and molecular weight distribution of fiber-forming polymers are intrinsic factors affecting their spinnability. i / ∑(N A m i / M i )=1 / ∑(N A ω i / M i );M n 、m i 、N A 、M i ,ω i represents the number average molecular weight, the mass of the i-th unit, Avogadro constant, the molar mass of the i-th unit, and mass fraction, respectively. It is the average molecular mass with the number as the statistical weight. The flow properties of the polymer are related to M n Closely related; weight average molecular weight (M w =∑ω i M i ;M w The weight average molecular weight is the average molecular weight with weight as the statistical weight, which determines the strength properties; the Z average molecular weight (M z =∑ω i M i 2 / ∑ω i M i ) is the average molecular weight with the square of the weight as the statistical weight, which is related to the elongation and flexibility of the polymer. The spinnability of PAN spinning solution can be adjusted by adjusting the molecular weight of PAN, but it is difficult to take into account the shear flow stability, tensile flexibility and strength properties of the original fiber, that is, it is difficult to simultaneously and directionally regulate the M n 、M z and M w .

[0052] In order to solve the above technical problems, the present application provides a method for improving the spinnability of polyacrylonitrile spinning solution, including: determining the molecular weight of the initial polyacrylonitrile; based on the molecular weight of the initial polyacrylonitrile, selecting at least two polyacrylonitrile with different molecular weights to be mixed, respectively recorded as the first polyacrylonitrile to be mixed and the second polyacrylonitrile to be mixed; based on the preset configuration information, obtaining the first polyacrylonitrile to be mixed with the first blending mass fraction x1 and the second polyacrylonitrile to be mixed with the second blending mass fraction x2; wherein the preset configuration information is the corresponding relationship between the molecular weight of the target polyacrylonitrile and the molecular weight of the first polyacrylonitrile to be mixed, the first blending mass fraction x1, and the molecular weight of the second polyacrylonitrile to be mixed, and the second blending mass fraction x2; 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. By blending polyacrylonitrile with different molecular weights, the molecular weight distribution of the polyacrylonitrile spinning solution is regulated to improve the spinnability of the polyacrylonitrile, while taking into account the strength of the precursor, the stability of the spinneret extrusion and the drawability, providing a strategy for improving the quality of PAN precursor in the development of new carbon fiber products.

[0053] Some specific implementation modes described below are intended to facilitate those skilled in the art to understand the present embodiment, and the present embodiment is not limited to some specific implementation modes described below.

[0054] In an exemplary embodiment, referring to Figure 1 The present application provides a method for improving the spinnability of polyacrylonitrile spinning solution, comprising:

[0055] S100, determine the initial molecular weight of polyacrylonitrile.

[0056] 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.

[0057] S200, based on the molecular weight of the initial polyacrylonitrile, selecting at least two polyacrylonitrile to be mixed with different molecular weights, which are respectively recorded as the first polyacrylonitrile to be mixed and the second polyacrylonitrile to be mixed.

[0058] In step S200, the number of polyacrylonitrile to be mixed can be two, three, etc. For example, when two polyacrylonitrile to be mixed with different molecular weights are selected, the two polyacrylonitrile to be mixed can be respectively recorded as the first polyacrylonitrile to be mixed and the second polyacrylonitrile to be mixed.

[0059] S300, based on preset configuration information, obtaining a first to-be-blended polyacrylonitrile of a first blending mass fraction x1 and a second to-be-blended polyacrylonitrile of a second blending mass fraction x2; wherein the preset configuration information is a correspondence between the molecular weight of the target polyacrylonitrile and the molecular weight of the first to-be-blended polyacrylonitrile, the first blending mass fraction x1, and the molecular weight of the second to-be-blended polyacrylonitrile, the second blending mass fraction x2.

[0060] In step S300, the preset configuration information can be set according to the number of selected polyacrylonitrile to be mixed. For example, when two polyacrylonitrile with different molecular weights are selected, it is necessary to ensure that the sum of the first blending mass fraction x1 and the second blending mass fraction x2 is 1; when three polyacrylonitrile with different molecular weights are selected, it is necessary to ensure that the sum of the first blending mass fraction x1, the second blending mass fraction x2, and the third blending mass fraction x3 is 1.

[0061] S400, mixing the first spinning solution of the polyacrylonitrile to be mixed with the second spinning solution of the polyacrylonitrile to be mixed to obtain the spinning solution of the target polyacrylonitrile.

[0062] In step S400, the spinning solution of the first polyacrylonitrile to be mixed and the spinning solution of the second polyacrylonitrile to be mixed are mixed according to the first blending mass fraction x1 and the second blending mass fraction x2, respectively, to obtain the spinning solution of the target polyacrylonitrile.

[0063] In this embodiment, the molecular weight distribution of the polyacrylonitrile spinning solution is regulated by blending polyacrylonitrile of different molecular weights to improve the spinnability of polyacrylonitrile, while taking into account the strength of the precursor, the stability of the spinneret extrusion and the stretchability, providing a strategy for improving the quality of PAN precursor in the development of new carbon fiber products.

[0064] In an exemplary embodiment, the molecular weight of the first polyacrylonitrile to be mixed is less than the molecular weight of the initial polyacrylonitrile;

[0065] The molecular weight of the second polyacrylonitrile to be mixed is greater than the molecular weight of the first polyacrylonitrile to be mixed.

[0066] In this embodiment, the molecular weight of the first polyacrylonitrile to be mixed is smaller than the molecular weight of the initial polyacrylonitrile, and the molecular weight of the second polyacrylonitrile to be mixed is larger than the molecular weight of the initial polyacrylonitrile, so as to better regulate the spinnability of the target polyacrylonitrile spinning solution. When comparing the molecular weights of the polyacrylonitrile, the molecular weights of the same characterization method need to be selected, and the different characterization methods of the selected molecular weights can be set according to the needs.

[0067] For example, when the spinnability of polyacrylonitrile spinning solution is regulated, it is necessary to keep the strength of the target polyacrylonitrile basically consistent with the strength of the initial polyacrylonitrile. Therefore, when selecting polyacrylonitrile with different molecular weights to be mixed, it is necessary to adjust the weight average molecular weight M of the initial polyacrylonitrile based on the weight average molecular weight M of the initial polyacrylonitrile. w , so that the weight average molecular weight M of the first mixed polyacrylonitrile w1 Less than the initial polyacrylonitrile M w , the weight average molecular weight M of the second polyacrylonitrile to be mixed w2 Greater than the initial polyacrylonitrile M w .

[0068] If the toughness of the target polyacrylonitrile needs to be kept basically consistent with the toughness of the initial polyacrylonitrile, when selecting polyacrylonitrile with different molecular weights to be mixed, it is necessary to make the weight average molecular weight M of the first polyacrylonitrile to be mixed equal to 1:1 based on the Z average molecular weight of the initial polyacrylonitrile. z1 Less than the initial polyacrylonitrile M z , the weight average molecular weight M of the second polyacrylonitrile to be mixed z2 Greater than the initial polyacrylonitrile M z .

[0069] 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 smaller than the ratio of the molecular weight of the second polyacrylonitrile to be mixed to the molecular weight of the initial polyacrylonitrile.

[0070] In this embodiment, the ratio of the molecular weight of the first polyacrylonitrile to be mixed to the initial polyacrylonitrile molecular weight is made smaller than the ratio of the molecular weight of the second polyacrylonitrile to be mixed to the initial polyacrylonitrile molecular weight, so as to better control the spinnability of the target polyacrylonitrile spinning solution.

[0071] In an exemplary embodiment, the polyacrylonitrile to be mixed further includes a third polyacrylonitrile to be mixed;

[0072] The molecular weight of the third polyacrylonitrile to be mixed is greater than the molecular weight of the initial polyacrylonitrile;

[0073] 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.

[0074] In this embodiment, by selecting three polyacrylonitrile with different molecular weights for blending, the spinnability of the target polyacrylonitrile spinning solution can be adjusted while taking into account its shear flow stability, tensile flexibility and raw fiber strength properties.

[0075] 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;

[0076] The ratio of the molecular weight of the second polyacrylonitrile to be mixed to the molecular weight of the initial polyacrylonitrile is 0.8-1.2:1;

[0077] The ratio of the molecular weight of the third polyacrylonitrile to be mixed to the molecular weight of the initial polyacrylonitrile is 1.2-1.5:1.

[0078] Exemplarily, 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;

[0079] The ratio of the molecular weight of the second polyacrylonitrile to be mixed to the molecular weight of the initial polyacrylonitrile is 0.8:1;

[0080] The ratio of the molecular weight of the third polyacrylonitrile to be mixed to the molecular weight of the initial polyacrylonitrile is 1.2:1.

[0081] 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;

[0082] The ratio of the molecular weight of the second polyacrylonitrile to be mixed to the molecular weight of the initial polyacrylonitrile is 1.0:1;

[0083] The ratio of the molecular weight of the third polyacrylonitrile to be mixed to the molecular weight of the initial polyacrylonitrile is 1.4:1.

[0084] 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;

[0085] The ratio of the molecular weight of the second polyacrylonitrile to be mixed to the molecular weight of the initial polyacrylonitrile is 1.2:1;

[0086] The ratio of the molecular weight of the third polyacrylonitrile to be mixed to the molecular weight of the initial polyacrylonitrile is 1.5:1.

[0087] In an exemplary embodiment, at least two polyacrylonitrile with different molecular weights are selected to be mixed, including:

[0088] Based on the weight average molecular weight of the initial polyacrylonitrile, at least two polyacrylonitrile materials to be mixed have different weight average molecular weights.

[0089] In order to ensure that the mechanical strength of the target polyacrylonitrile and the initial polyacrylonitrile after blending remains basically unchanged, it is necessary to make the weight average molecular weight of the target polyacrylonitrile and the weight average molecular weight of the initial polyacrylonitrile remain basically the same. Therefore, this embodiment takes the weight average molecular weight of the initial polyacrylonitrile as a benchmark and selects two polyacrylonitriles with different weight average molecular weights to be mixed.

[0090] In an exemplary embodiment, determining the molecular weight of initial polyacrylonitrile includes:

[0091] The weight average molecular weight, number average molecular weight and Z average molecular weight of the initial polyacrylonitrile were determined.

[0092] In this embodiment, by measuring the weight average molecular weight, number average molecular weight and Z average molecular weight of the initial polyacrylonitrile, the number average molecular weight and Z average molecular weight of the target polyacrylonitrile can be directionally regulated while keeping the weight average molecular weight unchanged.

[0093] In an exemplary embodiment, the preset configuration information includes the following formula:

[0094] x1+x2+x3=1 (Formula 1)

[0095] x1M w1 +x2M w2 +x3M w3 =M w (Formula 2)

[0096]

[0097] Wherein, x3 is the third blending portion of the third polyacrylonitrile to be mixed;

[0098] M w1 is the weight average molecular weight of the first polyacrylonitrile to be mixed;

[0099] M w2 is the weight average molecular weight of the second polyacrylonitrile to be mixed;

[0100] M w3 is the weight average molecular weight of the third polyacrylonitrile to be mixed;

[0101] M w is the weight average molecular weight of the initial polyacrylonitrile;

[0102] M n1 is the number average molecular weight of the first polyacrylonitrile to be mixed;

[0103] M n2 is the number average molecular weight of the second polyacrylonitrile to be mixed;

[0104] M n3 is the number average molecular weight of the third polyacrylonitrile to be mixed;

[0105] M n is the number average molecular weight of initial polyacrylonitrile;

[0106] M z1 is the Z average molecular weight of the first polyacrylonitrile to be mixed;

[0107] M z2 is the Z average molecular weight of the second polyacrylonitrile to be mixed;

[0108] M z3 is the Z average molecular weight of the second polyacrylonitrile to be mixed;

[0109] M z is the Z-average molecular weight of the initial polyacrylonitrile;

[0110] k1 and k2 are preset proportional constants.

[0111] 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 the weight average molecular weight of the initial polyacrylonitrile, and the number average molecular weight and Z average molecular weight of the target polyacrylonitrile can be adjusted by preset proportional constants k1 and k2. The adjustment range takes into account the raw yarn strength, spindle extrusion stability and stretchability, providing a strategy for improving the quality of PAN raw yarn in the development of new carbon fiber products.

[0112] According to (Formula 1), (Formula 2), (Formula 3), and (Formula 4), the solution of the equation can be obtained as follows:

[0113]

[0114] in,

[0115] m=d2-d3 (Formula 8)

[0116] h=d1-d3 (Formula 9)

[0117] d i =a i -cb i (Formula 10)

[0118]

[0119] c=k1M n (Formula 13)

[0120]

[0121] e i =M wi M zi (Formula 16).

[0122] In this embodiment, k1 and k2 are set adjustable proportional constants, and specific values ​​can be set according to the molecular weights of the first to-be-mixed polyacrylonitrile, the third to-be-mixed polyacrylonitrile and the initial polyacrylonitrile.

[0123] In an exemplary embodiment, the value range of k1 is M n1 / M n <k1<M n3 / M n , the value range of k2 is M w1 M z1 / (M w M z ) <k2<Mw3 M z3 / (M w M z ) and M n1 / M z1 / (M n M z ) < k1k2 < M n3 / M z3 / (M n M z ).

[0124] Exemplarily, the number-average molecular weight M n1 of the first polyacrylonitrile to be mixed is 9.4, the weight-average molecular weight M w1 is 21.43, and the z-average molecular weight M z1 is 32.78; the number-average molecular weight M n3 of the third polyacrylonitrile to be mixed is 29.58, the weight-average molecular weight M w3 is 38.39, and the z-average molecular weight M z3 is 70.18; the number-average molecular weight M n of the initial polyacrylonitrile is 17.24, the weight-average molecular weight M w is 26.53, and the z-average molecular weight M z is 51.8. Then the value range of k1 is 0.55 < k1 < 1.72, the value range of k2 is 0.51 < k2 < 1.96 and 0.35 < k1k2 < 2.32. For example, k1 is 0.90 and k2 is 1.05.

[0125] In one exemplary embodiment, the molecular weight of the initial polyacrylonitrile is measured by a combination of gel permeation chromatography - multi-angle laser light scattering - differential refractive index detection method.

[0126] In this embodiment, the molecular weight of the initial polyacrylonitrile is measured by a combination of gel permeation chromatography (GPC) - multi-angle laser light scattering (SLS) - differential refractive index detection method (RI).

[0127] The method for preparing the PAN polymer is as follows: using the general coating - drying method, preparing the PAN polymer from the PAN spinning solution; that is, spreading the PAN spinning solution into a film to facilitate the full replacement of the solvent therein, using PAN poor solvents such as methanol, ethanol or water to replace the solvent in the spinning solution in a double-diffusion manner, and finally drying the washed PAN film to obtain the PAN polymer.

[0128] The molecular weight test method is: use 0.05mol / L LiBr / DMF as the mobile phase; use porous monodisperse cross-linked polystyrene as the stationary phase; take the dried PAN film, use the mobile phase as the solvent to prepare a 3-5mg / mL dilute solution (heating is required to dissolve), and inject the sample solution after filtering through a pinhole filter membrane. Before use, the system is tested with standard samples (egPS; M w =13.6KDa,PDI=M w / M n =1.055) correction; the refractive index increment dn / dc=0.0837mL / g was used as the known parameter and input into the software BICParSEC Chromatography for calculation.

[0129] In order to more clearly explain the technical solution of the present application, the present application lists specific examples of improving the spinnability of polyacrylonitrile spinning solution, and the beneficial effects of selecting the above ranges of each parameter will be explained by giving specific experimental data through specific examples.

[0130] Example

[0131] Embodiment 1: A method for improving the spinnability of polyacrylonitrile spinning solution, comprising the following steps:

[0132] (1) Dipping a glass rod into the initial PAN spinning solution, weighing by differential subtraction to obtain 1.0473 g of the initial PAN spinning solution, and evenly spreading it on a 20 cm × 20 cm glass plate; placing the glass plate in a deionized water solution to displace the organic solvent therein to obtain a solidified polymer film; peeling off the solidified polymer film, and absorbing the moisture on the surface of the polymer film with an absorbent paper towel, and then placing the polymer film in a 105°C forced air drying oven for 60 min to obtain a PAN film. 0.05 mol / L LiBr / DMF was used as the mobile phase, and porous monodisperse cross-linked polystyrene was used as the stationary phase; 15.0 mg of the dried PAN film was added to a 5 mL colorimetric tube, and the mobile phase solvent was added to make up the volume initially; the colorimetric tube was sealed and heated in a 60°C water bath, and was shaken from time to time during the heating process. After about 2 hours, the sample was completely dissolved; the colorimetric tube was placed in regular water and cooled to room temperature, and then further made up the volume, and the solution to be tested was prepared by shaking; the sample solution after the solution to be tested was filtered through a 0.45 mm pinhole filter membrane was injected and run; before use, the system was tested with standard samples (PS; M w =13.6KDa, PDI=M w / M n =1.055) correction; the refractive index increment dn / dc=0.0837mL / g was input into the BIC ParSEC Chromatography software for calculation to obtain the number average molecular weight, weight average molecular weight and Z average molecular weight of the initial polyacrylonitrile, and the data of each molecular weight are listed in Table 1.

[0133] (2) Select three kinds of polyacrylonitrile to be mixed with low, medium and high molecular weights, respectively, and record them as the first polyacrylonitrile to be mixed PAN-1, the second polyacrylonitrile to be mixed PAN-2, and the third polyacrylonitrile to be mixed PAN-3. Among them, PAN-2 uses the initial polyacrylonitrile, PAN-1 and PAN-3 can be obtained from the market, and the PAN film is prepared according to the coating-drying method of step (1). The number average molecular weight, weight average molecular weight and Z average molecular weight of each are measured by GPC-SLS-RI, and the data of each molecular weight are listed in Table 1.

[0134] (3) The proportional constants k1 and k2 are set to 0.90 and 1.00 respectively. Based on the equation group of (Formula 1) to (Formula 4), the solutions of the equation group are obtained as x1=33.0%, x2=50.2%, and x3=16.8% according to (Formula 5) to (Formula 16).

[0135] (4) A PAN / DMSO solution with a solute mass composition of 33.0%, 50.2% and 16.8% for PAN-1, PAN-2 and PAN-3 and a solid content of 20.0% was prepared, i.e., 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) were stirred and mixed in a dissolving kettle, and the mixture was stirred at 80° C. and 60 rpm for 24 h, and then pumped into a degassing kettle; the parameters in the degassing kettle were set as follows: temperature 50° C., gauge pressure 5 kPa, residence time 5 h, and a spinning solution of the target polyacrylonitrile was obtained.

[0136] Example 2: This example is basically the same as Example 1, except that the proportional constants k1 and k2 are adjusted to 0.85 and 1.00, respectively, and the solution of the equation system is x1=50.2%, x2=24.3%, and x3=25.5%. A PAN / DMSO solution with a solute mass composition of 50.2%, 24.3%, and 25.5% for PAN-1, PAN-2, and PAN-3 and a solid content of 20.0% is prepared, that is, 100.29 kg of PAN-1, 48.66 kg of PAN-2, 51.05 kg of PAN-3, and 800 kg of DMSO are stirred and mixed in a dissolving kettle.

[0137] Example 3: This example is basically the same as Example 1, except that the proportional constants k1 and k2 are adjusted to 0.90 and 0.95, respectively, and the solution of the equation system is x1=25.0%, x2=67.5%, and x3=7.5%. A PAN / DMSO solution with a solute mass composition of 50.2%, 24.3%, and 25.5% for PAN-1, PAN-2, and PAN-3 and a solid content of 20.0% is prepared, that is, 50.04 kg of PAN-1, 134.90 kg of PAN-2, 15.06 kg of PAN-3, and 800 kg of DMSO are stirred and mixed in a dissolving kettle.

[0138] Example 4: This example is basically the same as Example 1, except that the proportional constants k1 and k2 are adjusted to 0.90 and 1.10, respectively, and the solution of the equation system is x1 = 48.9%, x2 = 15.8%, and x3 = 35.3%. A PAN / DMSO solution with a solute mass composition of 48.9%, 15.8%, and 35.3% for PAN-1, PAN-2, and PAN-3 and a solid content of 20.0% is prepared, that is, 97.83 kg of PAN-1, 31.56 kg of PAN-2, 70.61 kg of PAN-3, and 800 kg of DMSO are stirred and mixed in a dissolving kettle.

[0139] Example 5: This example is basically the same as Example 1, except that the proportional constants k1 and k2 are adjusted to 0.90 and 1.05, respectively, and the solution of the equation system is x1 = 40.9%, x2 = 33.0%, and 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% is prepared, that is, 81.90 kg of PAN-1, 66.01 kg of PAN-2, 52.09 kg of PAN-3, and 800 kg of DMSO are stirred and mixed in a dissolving kettle.

[0140] Comparative Example 1: Comparative Example 1 is the initial polyacrylonitrile.

[0141] Performance Testing

[0142] The properties of the target polyacrylonitrile obtained by blending in the example and the initial polyacrylonitrile of the control example were tested according to the following method, and the test results are listed in Table 2.

[0143] 1. Molecular weight: Samples were taken from the spinning solution of the target polyacrylonitrile and a PAN film was prepared according to the coating-drying method of step (1). The number average molecular weight, weight average molecular weight and Z average molecular weight were measured by GPC-SLS-RI.

[0144] 2. Operation stability: The spinning solution of the target polyacrylonitrile after degassing and the spinning solution of the initial polyacrylonitrile of control example 1 were pumped into the spinning line respectively, and the raw silk was prepared by dry-wet spinning; the number of spinning and steam-drawn broken silks in 12 hours was counted to evaluate its operation stability.

[0145] 3. Mechanical properties: The breaking strength and elastic modulus of the prepared raw silk were measured to evaluate the changes in the raw silk properties.

[0146] Table 1 Molecular weight parameters of polyacrylonitrile

[0147]

[0148] Table 2 Performance test table of polyacrylonitrile of embodiment and control example

[0149]

[0150] It can be seen from Tables 1 and 2 that the weight average molecular weight of the target polyacrylonitrile in the embodiment is close to the weight average molecular weight of the initial polyacrylonitrile, indicating that the molecular weight blending and calculation method of the present application has strong guidance and is convenient for rapid quantitative debugging of PAN molecular weight.

[0151] According to Table 2, compared with Control Example 1, after adjusting k1 and k2 in the embodiment 5 times, the number of broken filaments during 12h spinning in Example 5 was reduced from 12 times to 2 times, and the number of broken filaments during steaming and drawing was reduced from 9 times to 3 times, and the spinnability was significantly improved, indicating that the method for blending and regulating the molecular weight distribution of polyacrylonitrile proposed in the present application effectively improves the spinnability of the spinning solution.

[0152] According to Table 2, compared with the control example 1, the mechanical properties of the PAN raw fibers prepared in Examples 1-5 did not change significantly. This is because the weight average molecular weight M is controlled in the design of the blended PAN in the present application. w It can be seen that the method proposed in this application takes into account the strength of the precursor, the stability of the spinneret extrusion and the drawability, and can provide an efficient strategy for improving the quality of PAN precursor in the development of new carbon fiber products.

[0153] It should be noted that, in this article, the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0154] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application is described in detail with reference to the above embodiments, a person skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for improving the spinnability of polyacrylonitrile spinning solution, characterized in that: include: Determine the molecular weight of initial polyacrylonitrile; Based on the molecular weight of the initial polyacrylonitrile, at least two polyacrylonitrile to be mixed with different molecular weights are selected and recorded as the first polyacrylonitrile to be mixed and the second polyacrylonitrile to be mixed respectively; Based on the preset configuration information, a first polyacrylonitrile to be mixed with a first blending mass fraction x1 and a second polyacrylonitrile to be mixed with a second blending mass fraction x2 are obtained; wherein the preset configuration information is a correspondence between the molecular weight of the target polyacrylonitrile and the molecular weight of the first polyacrylonitrile to be mixed, the first blending mass fraction x1, and the molecular weight of the second polyacrylonitrile to be mixed, and the second blending mass fraction x2; 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.

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 less than the molecular weight of the initial polyacrylonitrile; The molecular weight of the second polyacrylonitrile to be mixed is greater than the molecular weight 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 smaller 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 polyacrylonitrile to be mixed also 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.

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 be mixed 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 be mixed 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 to 5, characterized in that: The step of selecting at least two polyacrylonitrile with different molecular weights to be mixed comprises: Based on the weight average molecular weight of the initial polyacrylonitrile, at least two polyacrylonitrile with different weight average molecular weights to be mixed are selected.

7. The method for improving the spinnability of polyacrylonitrile spinning solution according to claim 4, characterized in that: The method of determining the molecular weight of initial polyacrylonitrile comprises: The weight average molecular weight, number average molecular weight and Z average molecular weight of the initial polyacrylonitrile were measured.

8. The method for improving the spinnability of polyacrylonitrile spinning solution according to claim 7, characterized in that: The preset configuration information includes the following formula: x1+x2+x3=1 (Formula 1) x1M w1 +x2M 22 +x3M w3 =M w (Formula 2) Wherein, x3 is the third blending portion of the third polyacrylonitrile to be mixed; M w1 is the weight average molecular weight of the first polyacrylonitrile to be mixed; M w2 is the weight average molecular weight of the second polyacrylonitrile to be mixed; M w3 is the weight average molecular weight of the third polyacrylonitrile to be mixed; M w is the weight average molecular weight of the initial polyacrylonitrile; M n1 is the number average molecular weight of the first polyacrylonitrile to be mixed; M n2 is the number average molecular weight of the second polyacrylonitrile to be mixed; M n3 is the number average molecular weight of the third polyacrylonitrile to be mixed; M n is the number average molecular weight of initial polyacrylonitrile; M z1 is the Z average molecular weight of the first polyacrylonitrile to be mixed; M z2 is the Z average molecular weight of the second polyacrylonitrile to be mixed; M z3 is the Z average molecular weight of the second polyacrylonitrile to be mixed; M z is the Z-average molecular weight of the initial polyacrylonitrile; k1 and k2 are preset proportional constants.

9. The method for improving the spinnability of polyacrylonitrile spinning solution according to claim 8, characterized in that: The value range of k1 is M n1 / M n <k1<M n3 / M n , the value range of k2 is M w1 M z1 / (M w M z ) <k2<M w3 M z3 / (M w M z ) and M n1 M z1 / (M n M z ) <k1k2<M n3 M z3 / (M n M z ).

10. The method for improving the spinnability of polyacrylonitrile spinning solution according to claim 1, characterized in that: The molecular weight of the initial polyacrylonitrile is measured by gel permeation chromatography-multi-angle laser light scattering-differential refractive index detection.

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