Preparation method of polyacrylonitrile-based pre-oxidized fiber paper

Abstract

The invention provides a preparation method of polyacrylonitrile-based pre-oxidized fiber paper. The preparation method comprises the following steps: (1) fully cleaning a polyacrylonitrile-based protofilament felt with a specific specification and thickness in an organic solvent, removing an oil agent on the surface of the fiber, and fully drying the polyacrylonitrile-based protofilament felt; (2) fixing the protofilament felt obtained in the step (1) in a flat and smooth clamping plate, and applying specific pressure intensity; (3) putting the flat and smooth clamping plate with the precursor felt in the step (2) into a vacuum furnace for primary pre-oxidation, and enabling the precursor fibers to generate controllable fusion and crosslinking; (4) taking out the sample obtained in the step (3), fixing the sample in the porous clamping plate again, and applying specific pressure intensity; (5) placing the porous clamping plate with the sample in the step (4) in a high-temperature oven for secondary pre-oxidation; and (6) taking out the sample obtained in the step (5), fully cleaning in an organic solvent, and drying to obtain the clean polyacrylonitrile-based pre-oxidized fiber paper. According to the preparation method, the polyacrylonitrile-based pre-oxidized fiber paper with high tear strength and high flame-retardant and heat-insulating properties can be quickly and efficiently prepared.

Description

Technical Field

[0001] The invention relates to a method for preparing polyacrylonitrile-based pre-oxidized silk paper. Background Art

[0002] As a flame retardant and heat insulating material with excellent performance, polyacrylonitrile preoxidized yarn is widely used in various industries. At present, it is mainly used in the form of preoxidized felt and preoxidized cloth, which limits its application scope. At the same time, due to the low density and high air permeability of preoxidized felt and preoxidized cloth, there is still a lot of heat convection during use, resulting in a decrease in flame retardant and heat insulating effect. Therefore, increasing the bulk density of preoxidized fibers and preparing high-density, low-permeability preoxidized yarn paper has become one of the most promising development directions.

[0003] The traditional preparation process of pre-oxidized silk paper is to crush the pre-oxidized fibers and mix them evenly with pulp, and then use traditional papermaking technology to prepare the pre-oxidized silk paper. The pre-oxidized silk paper prepared by this process has problems such as low pre-oxidized silk content, poor flame retardant properties, and poor mechanical properties, which is not conducive to its market application.

[0004] This study melts and cross-links the raw silk fibers under vacuum, high temperature and high pressure to produce a high-density, high-strength mesh structure, forming the basic framework structure of pre-oxidized silk paper, and then further oxidizes it in high-temperature air under fixed size conditions, greatly increasing the proportion of heat-resistant trapezoidal structures in its molecules, improving flame retardant and thermal insulation properties, while avoiding the shrinkage of the fiber structure that destroys the mesh structure, and finally preparing polyacrylonitrile-based pre-oxidized silk cloth. The preparation process described in this study can greatly improve the mechanical properties and flame retardant and thermal insulation properties of pre-oxidized silk paper. Summary of the invention

[0005] The invention provides a novel preparation method for the problems that the current method for preparing polyacrylonitrile-based preoxidized silk paper has complex process and poor product performance.

[0006] The present invention solves the above technical problems through the following technical means:

[0007] (1) The polyacrylonitrile-based raw fiber felt of a specific thickness is fully washed in an organic solvent, the oil agent on the fiber surface is removed, and then the fiber is fully dried;

[0008] (2) fixing the raw silk felt obtained in step (1) on a flat and smooth clamping plate and applying a specific pressure;

[0009] (3) placing the flat and smooth plywood with the raw fiber felt obtained in step (2) in a vacuum furnace for primary pre-oxidation;

[0010] (4) taking out the sample obtained in step (3) and re-fixing it in a porous clamping plate, and applying a specific pressure;

[0011] (5) placing the porous clamping plate with the sample obtained in step (4) in a high-temperature oven for secondary pre-oxidation;

[0012] (6) After taking out the sample obtained in step (5), it is thoroughly cleaned and dried in an organic solvent to obtain clean polyacrylonitrile-based pre-oxidized silk paper.

[0013] Preferably, the thickness of the polyacrylonitrile-based precursor felt in step (1) is ≤5 mm.

[0014] Preferably, the specific pressure applied by the flat and smooth clamping plate in step (2) is 0.001 MPa to 0.1 MPa.

[0015] Preferably, the initial pre-oxidation temperature in step (3) is 200-260°C.

[0016] Preferably, the initial pre-oxidation time in step (3) is 5 to 30 minutes.

[0017] Preferably, the hole diameter of the porous splint in step (4) is ≥1 mm.

[0018] Preferably, the specific pressure in step (4) is 0.001 MPa to 0.1 MPa.

[0019] Preferably, the secondary pre-oxidation temperature in step (5) is 230-300°C.

[0020] Preferably, the secondary pre-oxidation time in step (5) is 5 to 60 minutes.

[0021] The advantages of the present invention are:

[0022] This study melts and cross-links the raw silk fibers under vacuum, high temperature and high pressure to produce a high-density, high-strength mesh structure, forming the basic framework structure of pre-oxidized silk paper, and then further oxidizes it in high-temperature air under fixed size conditions, greatly increasing the proportion of heat-resistant trapezoidal structures in its molecules, improving flame retardant and thermal insulation properties, while avoiding the shrinkage of the fiber structure that destroys the mesh structure, and finally preparing polyacrylonitrile-based pre-oxidized silk cloth. The preparation process described in this study can greatly improve the mechanical properties and flame retardant and thermal insulation properties of pre-oxidized silk paper. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The present invention is a process flow chart of a method for preparing polyacrylonitrile-based pre-oxidized silk paper. DETAILED DESCRIPTION

[0024] The specific technical solutions of the present invention are further described below to help those skilled in the art to further understand the present invention.

[0025] Example 1

[0026] The method for preparing the polyacrylonitrile pre-oxidized silk paper described in this embodiment is specifically carried out according to the following steps:

[0027] (1) Set the weight to 200g / m 2 , a 2mm thick polyacrylonitrile-based precursor felt (made from Shanghai Petrochemical 48K large-tow precursor) was immersed and cleaned in an ethanol solution for 2 hours and then fully dried;

[0028] (2) fixing the raw silk felt obtained in step (1) on a flat and smooth clamping plate and applying a pressure of 0.005 MPa;

[0029] (3) placing the flat and smooth plywood with the raw silk felt obtained in step (2) in a vacuum furnace and pre-oxidizing it at 260° C. for 15 minutes;

[0030] (4) Take out the sample obtained in step (3) and re-fix it in a porous clamp with a pore diameter of 2 mm and a pore density of 5 / cm 2 , and apply a pressure of 0.005MPa;

[0031] (5) placing the porous clamping plate with the sample obtained in step (4) in a high-temperature oven and performing secondary pre-oxidation at 250° C. for 40 min;

[0032] (6) taking out the sample obtained in step (5), washing it thoroughly in an ethanol solution, and then drying it;

[0033] According to the above steps, a clean polyacrylonitrile-based pre-oxidized silk paper was prepared with a thickness of only 0.5 mm and a single fiber density of 1.36 g / m 3 The limiting oxygen index of pre-oxidized silk paper is 34%, and the tear strength of pre-oxidized silk paper is 56N.

[0034] Example 2

[0035] The method for preparing the polyacrylonitrile pre-oxidized silk paper described in this embodiment is specifically carried out according to the following steps:

[0036] (1) Set the weight to 400g / m 2 , a 4mm thick polyacrylonitrile-based precursor felt (made from Shanghai Petrochemical 48K large-tow precursor) was immersed and cleaned in an ethanol solution for 2 hours and then fully dried;

[0037] (2) fixing the raw silk felt obtained in step (1) on a flat and smooth clamping plate and applying a pressure of 0.02 MPa;

[0038] (3) placing the flat and smooth plywood with the raw silk felt obtained in step (2) in a vacuum furnace and pre-oxidizing it at 260° C. for 25 min;

[0039] (4) Take out the sample obtained in step (3) and re-fix it in a porous clamp with a pore diameter of 2 mm and a pore density of 5 / cm 2 , and apply a pressure of 0.02MPa;

[0040] (5) placing the porous clamping plate with the sample obtained in step (4) in a high-temperature oven and performing secondary pre-oxidation at 250° C. for 60 min;

[0041] (6) taking out the sample obtained in step (5), washing it thoroughly in an ethanol solution, and then drying it;

[0042] According to the above steps, a clean polyacrylonitrile-based pre-oxidized silk paper was prepared with a thickness of only 0.8 mm and a single fiber density of 1.40 g / m 3 The limiting oxygen index of pre-oxidized silk paper is 39%, and the tear strength of pre-oxidized silk paper is 115N.

[0043] Example 3

[0044] The method for preparing the polyacrylonitrile pre-oxidized silk paper described in this embodiment is specifically carried out according to the following steps:

[0045] (1) Set the weight to 200g / m 2 , a 2mm thick polyacrylonitrile-based precursor felt (made from Shanghai Petrochemical 48K large-tow precursor) was immersed and cleaned in an ethanol solution for 2 hours and then fully dried;

[0046] (2) fixing the raw silk felt obtained in step (1) on a flat and smooth clamping plate and applying a pressure of 0.02 MPa;

[0047] (3) placing the flat and smooth plywood with the raw silk felt obtained in step (2) in a vacuum furnace and pre-oxidizing it at 270° C. for 15 minutes;

[0048] (4) Take out the sample obtained in step (3) and re-fix it in a porous clamp with a pore diameter of 2 mm and a pore density of 5 / cm 2 , and apply a pressure of 0.02MPa;

[0049] (5) placing the porous clamping plate with the sample obtained in step (4) in a high-temperature oven and performing secondary pre-oxidation at 270° C. for 15 min;

[0050] (6) taking out the sample obtained in step (5), washing it thoroughly in an ethanol solution, and then drying it;

[0051] According to the above steps, a clean polyacrylonitrile-based pre-oxidized silk paper was prepared with a thickness of only 0.8 mm and a single fiber density of 1.37 g / m 3 The limiting oxygen index of pre-oxidized silk paper is 36%, and the tear strength of pre-oxidized silk paper is 73N.

[0052] Example 4

[0053] The method for preparing the polyacrylonitrile pre-oxidized silk paper described in this embodiment is specifically carried out according to the following steps:

[0054] (1) Set the weight to 400g / m 2 , a 4mm thick polyacrylonitrile-based precursor felt (made from Shanghai Petrochemical 48K large-tow precursor) was immersed and cleaned in an ethanol solution for 2 hours and then fully dried;

[0055] (2) fixing the raw silk felt obtained in step (1) on a flat and smooth clamping plate and applying a pressure of 0.02 MPa;

[0056] (3) placing the flat and smooth plywood with the raw silk felt obtained in step (2) in a vacuum furnace and pre-oxidizing it at 270° C. for 15 minutes;

[0057] (4) Take out the sample obtained in step (3) and re-fix it in a porous clamp with a pore diameter of 2 mm and a pore density of 5 / cm 2 , and apply a pressure of 0.02MPa;

[0058] (5) placing the porous clamping plate with the sample obtained in step (4) in a high-temperature oven and performing secondary pre-oxidation at 270° C. for 15 min;

[0059] (6) taking out the sample obtained in step (5), washing it thoroughly in an ethanol solution, and then drying it;

[0060] According to the above steps, a clean polyacrylonitrile-based pre-oxidized silk paper was prepared with a thickness of only 0.5 mm and a single fiber density of 1.38 g / m 3 The limiting oxygen index of pre-oxidized silk paper is 35%, and the tear strength of pre-oxidized silk paper is 98N.

Claims

1. A method for preparing polyacrylonitrile-based pre-oxidized silk paper, characterized in that: The following steps are involved: (1) The polyacrylonitrile-based raw fiber felt of a specific thickness is fully washed in an organic solvent, the oil agent on the fiber surface is removed, and then the fiber is fully dried; (2) fixing the raw silk felt obtained in step (1) on a flat and smooth clamping plate and applying a specific pressure; (3) placing the flat and smooth plywood with the raw fiber felt obtained in step (2) in a vacuum furnace for primary pre-oxidation; (4) taking out the sample obtained in step (3) and re-fixing it in a porous clamping plate, and applying a specific pressure; (5) placing the porous clamping plate with the sample obtained in step (4) in a high-temperature oven for secondary pre-oxidation; (6) After taking out the sample obtained in step (5), it is thoroughly cleaned and dried in an organic solvent to obtain clean polyacrylonitrile-based pre-oxidized silk paper.

2. The method for preparing polyacrylonitrile-based pre-oxidized silk paper according to claim 1, characterized in that: The thickness of the polyacrylonitrile-based raw fiber felt in the step (1) is ≤5 mm.

3. The method for preparing polyacrylonitrile-based pre-oxidized silk paper according to claim 1, characterized in that: The specific pressure applied by the flat and smooth clamping plate in step (2) is 0.001MPa to 0.1MPa.

4. The method for preparing polyacrylonitrile-based pre-oxidized silk paper according to claim 1, characterized in that: The initial pre-oxidation temperature in step (3) is 200-260°C.

5. The method for preparing polyacrylonitrile-based pre-oxidized silk paper according to claim 1, characterized in that: The initial pre-oxidation time in step (3) is 5 to 30 minutes.

6. The method for preparing polyacrylonitrile-based pre-oxidized silk paper according to claim 1, characterized in that: The hole diameter of the porous splint in step (4) is ≥1 mm.

7. The method for preparing polyacrylonitrile-based pre-oxidized silk paper according to claim 1, characterized in that: The specific pressure in step (4) is 0.001 MPa to 0.1 MPa.

8. The method for preparing polyacrylonitrile-based pre-oxidized silk paper according to claim 1, characterized in that: The secondary pre-oxidation temperature in step (5) is 230-300°C.

9. The method for preparing polyacrylonitrile-based pre-oxidized silk paper according to claim 1, characterized in that: The secondary pre-oxidation time in step (5) is 5 to 60 minutes.

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