Method and device for reducing polyacrylonitrile precursor defects by controlling coagulating bath ammonification

Abstract

The invention provides a method and a device for reducing polyacrylonitrile precursor defects by controlling coagulating bath ammoniation. The coagulating bath ammoniation control method comprises the following steps: S1, uniformly mixing an organic reagent and water to obtain a coagulating bath solution; s2, mixing an ammoniation reagent with the coagulating bath solution to obtain a mixed mother solution; and S3, controlling the addition of the ammoniation coagulating bath mother liquor through a pH online monitoring test and feedback. The invention also provides a device for implementing the method. According to the method and the device provided by the invention, when the coagulating bath is subjected to ammoniation treatment, full ammoniation treatment can be ensured, and meanwhile, the concentration of ammonium ions is controllable; and the obtained polyacrylonitrile fiber has the advantages of smooth surface, fewer grooves and good homogeneity, and is suitable for popularization and application.

Description

Technical Field

[0001] The invention relates to the field of polyacrylonitrile-based carbon fiber spinning, and in particular to a method and a device for controlling ammoniaization in a coagulation bath to reduce defects of polyacrylonitrile precursor. Background Art

[0002] The groove structure on the surface of carbon fiber is formed in the coagulation process of polyacrylonitrile precursor preparation stage, and then gradually evolves through pre-oxidation and carbonization stages and finally forms the physical groove structure on the surface of carbon fiber. The formation of wrinkles or grooves on the surface of the precursor is related to the coagulation double diffusion behavior of the spinning solution. During the coagulation process of the polymer solution, the solvent inside the polymer solution undergoes double diffusion with the coagulation bath, and the solution inside the spinning stream leaves, causing the fiber surface to collapse and wrinkle. Since the outside of the fibril begins to crystallize before the inside, the macromolecular chains in the crystalline area are arranged regularly and the deformation ability is weaker than that of the amorphous area. When the subsequent stretching is applied, this inhomogeneity of crystallization eventually leads to wrinkles or grooves on the surface of the precursor. Improving the hydrophilicity of the polymer solution during coagulation can slow down the coagulation rate of the polymer solution, thereby reducing the defects of the fiber formation structure. Summary of the invention

[0003] In order to overcome the defects of the prior art, the technical problem to be solved by the present invention is a method and device for controlling the ammoniaization of a coagulation bath to reduce defects of polyacrylonitrile precursor. Therefore, the present invention proposes a method for adding an ammoniaizing agent to prepare a coagulation bath, controlling the surface morphology of the spinning solution during the coagulation and forming process, and thus reducing defects of polyacrylonitrile precursor, and provides a device for implementing the method.

[0004] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0005] A method for controlling ammonia in a coagulation bath to reduce defects in polyacrylonitrile precursor fibers comprises the following steps:

[0006] S1: uniformly mixing the organic reagent and water to obtain a coagulation bath solution;

[0007] S2 ammoniating agent is mixed with the coagulation bath solution to obtain a mixed mother solution;

[0008] S3 controls the addition of ammoniacal coagulation bath mother liquor through the pH online monitoring and feedback system.

[0009] According to the above method, in step S1, the organic reagent is one of dimethyl sulfoxide (DMSO) or N,N-dimethylformamide (DMF).

[0010] According to the above method, the mass ratio of the organic reagent to water is 4:6 to 7:3.

[0011] According to the above method, in step S1, the temperature of the coagulation bath solution is -10 to 30°C.

[0012] According to the above method, in step S2, the pH value of the coagulation bath ammonia is in the range of 8 to 10, preferably 9.0 to 9.5.

[0013] According to the above method, in step S2 or S3, the pH value is detected online by an industrial pH meter.

[0014] According to the above method, in step S3, the feedback control condition for adding the coagulation bath mother solution is that the pH of the primary coagulation bath obtained by mixing is X±0.1, and X is 7.0 to 9.0, preferably 8.0 to 8.5.

[0015] The present invention also proposes a device for controlling the ammoniation of a coagulation bath to reduce defects of PAN-based raw fibers. The device includes a storage tank, a metering pump, a delivery pipeline, and a coagulation bath tank. The storage tank is connected to the metering pump and the coagulation bath tank in sequence through the delivery pipeline.

[0016] According to the above method, a stirring device and a refrigeration device are provided in the storage tank, and the mixing storage tank is connected to the primary coagulation bath through a metering pump.

[0017] According to the above method, the storage temperature of the mixed liquid in the storage tank is -10 to 30°C.

[0018] After adopting the above technical solution, the present invention has the following beneficial effects:

[0019] The present invention proposes that when the coagulation bath is subjected to ammoniation treatment, the ammoniation treatment can be ensured to be sufficient and the concentration of ammonium ions can be controlled; the hydrophilicity of the polymer solution during coagulation molding can be improved and the double diffusion effect can be reduced; the obtained polyacrylonitrile fiber has a smooth surface, fewer grooves, good homogeneity, and is suitable for popularization and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic diagram of a device for controlling ammoniaization of a coagulation bath to reduce defects of polyacrylonitrile precursor provided by the present invention;

[0021] Figure 2 This is a scanning electron microscope (SEM) image of the PAN precursor obtained in Example 1 of the present invention;

[0022] Figure 3 This is a SEM image of the PAN raw silk obtained in Example 2 of the present invention;

[0023] Figure 4 This is a SEM image of the PAN raw fiber prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0024] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0025] The present invention uses the following device to control the ammoniaization of the coagulation bath to reduce the defects of the polyacrylonitrile precursor

[0026] like Figure 1 The device shown includes a storage tank, a metering pump, a delivery pipeline, and a coagulation bath, wherein the storage tank is connected to the metering pump and the coagulation bath in sequence through the delivery pipeline. A stirring device and a refrigeration device are provided in the storage tank, and the storage temperature of the mixed liquid in the storage tank is -10 to 30°C.

[0027] Example 1

[0028] DMSO and water are mixed evenly in a mass ratio of 4:6 to obtain a coagulation bath solution; ammonium carbonate with a mass concentration of 20% is mixed with the coagulation bath solution in a mass ratio of 8:2 to obtain a coagulation bath ammoniated mother liquor, the pH value of the coagulation bath ammoniated mother liquor is 9.0, and the storage temperature of the mixed solution is 10°C. In the spinning coagulation forming stage, the coagulation bath ammoniated mother liquor is added to the primary coagulation bath through a metering pump, and the amount of the ammoniated coagulation bath mother liquor added is controlled by pH online monitoring and feedback. The pH value of the primary coagulation bath is controlled to be about 7.8±0.1, and the temperature of the coagulation bath solution is 10°C. The surface morphology of the raw silk is observed by scanning electron microscopy. Figure 2 As shown, the fiber surface has many wrinkles.

[0029] Example 2

[0030] The same as Example 1, except that the pH of the primary coagulation bath was adjusted to 8.2±0.1. The surface morphology of the precursor was observed by scanning electron microscopy. Figure 3 As shown, the obtained polyacrylonitrile fiber has a smooth surface, fewer grooves and good homogeneity.

[0031] Example 3

[0032] The same as Example 1, except that the pH of the primary coagulation bath was adjusted to 8.8±0.1. The surface morphology of the precursor was observed by scanning electron microscopy. Figure 4 As shown, the fiber surface has fewer wrinkles, but the fiber side surface has deeper grooves.

[0033] In the present invention, dimethyl sulfoxide (DMSO) can be replaced by N,N-dimethylformamide (DMF).

[0034] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for reducing defects of polyacrylonitrile precursor by controlling ammonia in a coagulation bath, characterized in that: The method comprises the following steps: S1: uniformly mixing the organic reagent and water to obtain a coagulation bath solution; S2 ammoniating agent is mixed with the coagulation bath solution to obtain a mixed mother solution; S3 controls the addition of ammoniacal coagulation bath mother liquor through online pH monitoring and feedback control.

2. The method of reducing defects of polyacrylonitrile precursor by controlling ammonia in a coagulation bath according to claim 1, characterized in that: In step S1, the organic reagent in the coagulation bath solution is dimethyl sulfoxide (DMSO) or N,N-dimethylformamide (DMF).

3. A method for reducing defects of polyacrylonitrile precursor by controlling ammonia in a coagulation bath according to claim 1 or 2, characterized in that: In step S1, the mass ratio of the organic reagent to water is 4:6 to 7:

3.

4. The method of controlling the ammoniaization of a coagulation bath to reduce defects of polyacrylonitrile precursor according to claim 1, characterized in that: In step S1, the temperature of the coagulation bath solution is -10°C to 30°C.

5. The method of reducing defects of polyacrylonitrile precursor by controlling ammonia in a coagulation bath according to claim 1, characterized in that: In step S2, the aminating agent is an aqueous solution of ammonium carbonate with a mass concentration of 10% to 40%.

6. The method of controlling the ammoniaization of a coagulation bath to reduce defects of polyacrylonitrile precursor according to claim 1, characterized in that: In step S2, the mixing ratio of the ammoniating agent and the coagulation bath solution is controlled to be 9.0 to 9.5 according to the pH value of the mother solution; in step S2 or S3, the pH value is detected online by an industrial pH meter.

7. The method of reducing defects of polyacrylonitrile precursor by controlling ammonia in a coagulation bath according to claim 1, characterized in that: In step S3, the feedback control condition for adding the coagulation bath mother solution is that the pH of the primary coagulation bath obtained by mixing is X±0.1, and X is 8.0-8.

5.

8. A device for reducing defects of polyacrylonitrile precursor by controlled coagulation bath ammoniation according to any one of claims 1 to 7, characterized in that: The device includes A material storage tank, a metering pump, a delivery pipeline, and a coagulation bath, wherein the material storage tank is sequentially connected to the metering pump and the coagulation bath through a delivery pipeline.

9. The device for controlling the ammoniaization of a coagulation bath to reduce defects of polyacrylonitrile precursor according to claim 8, characterized in that: The storage tank is provided with a stirring device and a refrigeration device.

10. The device for controlling ammoniaization of a coagulation bath to reduce defects of polyacrylonitrile precursor according to claim 8, characterized in that: The storage temperature of the mixed liquid in the storage tank is -10 to 30°C.

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