CN117069999A - A method for catalytically degrading carbon fiber reinforced resin matrix composite materials - Google Patents

Abstract

The invention relates to a method for catalytically degrading carbon fiber-reinforced resin-based composite materials, which solves the technical problems of traditional chemical recycling methods such as long processing time, complex processes, and serious fiber damage. It includes the following steps: S1. Carbon fiber to be degraded After the resin-based composite material is cut, it is put into the first group of catalysts and heat-maintained under normal pressure; the first group of catalysts is one or more of ferrous sulfate, magnesium sulfate, and zinc sulfate; S2. After the carbon fiber resin-based composite material treated in step S1 is taken out, cleaned and dried, it is placed in a second set of catalysts and kept at room temperature; the second set of catalysts are acetyl chloride, o-chlorobenzoyl chloride, and terephthalate. One or more forms of formyl chloride; S3. Take out the product and clean it with ethanol to obtain regenerated carbon fiber with a clean surface. The invention can be used for recycling of carbon fiber reinforced resin matrix composite materials.

Description

A method for catalytically degrading carbon fiber reinforced resin matrix composite materials

Technical field

The present invention relates to a method for recycling carbon fiber reinforced resin matrix composite materials, and specifically to a method for catalytically degrading carbon fiber reinforced resin matrix composite materials.

Background technique

Carbon fiber is a lightweight and high-strength fiber. Carbon fiber composite materials prepared from carbon fiber have the advantages of high specific strength, high specific modulus, corrosion resistance, etc., and are widely used in sporting goods, rail transportation, aerospace and other fields.

As the amount of carbon fiber composite materials increases year by year, more and more composite materials will reach the end of their life cycle. The carbon fiber in carbon fiber composite materials has a high value. If it is burned or landfilled through traditional methods, it will undoubtedly cause huge damage to carbon fiber resources. Wasteful and polluting the environment. Therefore, these waste materials are in urgent need of recycling. However, since the fibers obtained by recycling are usually in a chopped state and have poor dispersion, and after the recycling process, many surface defects will appear on the surface of the fiber, so the interface bonding performance with the resin matrix is poor, resulting in recycling The application range of fibers is limited, so existing recycled fibers are generally used as fillers.

There are currently a variety of methods for recycling carbon fiber composite materials. During the recycling process, the resin matrix is degraded and the fibers are stripped away, thereby achieving the purpose of recycling carbon fibers. Degradation methods mainly include mechanical recycling, pyrolysis recycling, chemical recycling, etc.

Mechanical recycling is currently a relatively mature recycling method. The process generally includes crushing and screening of composite materials by physical means such as rolling, chopping, and grinding. The recovered fibers can be used directly without any post-processing. However, the mechanical properties of fibers will be greatly damaged due to physical effects such as extrusion and cutting during the mechanical recycling process, and the fiber shape after treatment is poor. Therefore, the application fields of regenerated fibers obtained after mechanical recycling are severely limited. . Thermal degradation method is the most complete recycling method currently developed and the only method that has been successfully industrialized. Thermal degradation methods include fluidized bed recovery, pyrolysis recovery, and superheated steam recovery. The pyrolysis recycling method mainly decomposes resin under the action of oxidation and heat. Although the recycling efficiency is high and the types of recycled fibers are diverse, the recycling process requires huge energy consumption, and some liquid by-products are toxic to the environment and human body. .

Chemical recycling does not require excessive processing temperatures. The waste is soaked in an organic solution. Under certain temperature conditions, the resin molecules are cracked into soluble small molecules under the action of the solvent, thereby peeling off the carbon fibers. The range of solvents that can be selected is very wide. According to the different states of the recovery solution, it can be divided into dissolution catalytic recovery and supercritical solvent recovery methods. However, most current chemical recovery methods require the use of strong oxidizing reagents such as strong acids and alkalis, which require high recovery equipment and cause environmental pollution. At the same time, they are accompanied by problems such as long recovery time and complex recovery processes. Some recovery methods require high temperature and high pressure, and After treatment, the fiber needs to undergo complex post-processing procedures to obtain regenerated fiber with a cleaner surface.

The Chinese invention patent with authorization announcement number 114044936B discloses a method for catalytic steam pyrolysis to recover carbon fiber resin matrix composite materials, which solves the problems of high temperature, long processing time and serious damage to carbon fibers in the existing steam pyrolysis method. , which includes the following steps: S1. Put the two sets of catalysts into the reaction vessel according to the preset ratio; S2. Cut the carbon fiber composite material to be degraded and put it into the catalyst of step S1, add water vapor, and heat it under normal pressure. , heat preservation; S3. Take out the product and clean it with ultrasonic to obtain recycled carbon fiber with clean surface.

The above methods mainly have the following problems:

(1) The reaction temperature is too high, which easily produces more energy consumption;

(2) The mechanical properties of the regenerated fiber obtained by this method are reduced due to the high temperature environment, resulting in serious limitations in its application fields;

(3) This method is aimed at catalytic degradation in special gas environments and does not have universal applicability in ordinary gas environments.

Contents of the invention

The purpose of the present invention is to solve the technical problems of the existing technology such as high reaction temperature, long processing time, complex procedures, and serious fiber damage, and provide a method for catalytically degrading carbon fiber reinforced resin matrix composites at a lower temperature faster and more completely. Materials methods.

To this end, the present invention provides a method for catalytically degrading carbon fiber-reinforced resin-based composite materials, which includes the following steps: S1. After cutting the carbon fiber-reinforced resin-based composite materials to be degraded, put them into the first group of catalysts and keep them warm under normal pressure. Processing; the first group of catalysts is one or more of ferrous sulfate, magnesium sulfate, and zinc sulfate, with a concentration of 1 to 5 mol/L; S2. Take out the carbon fiber resin-based composite material processed in step S1 Then, wash with ethanol, dry, put into the second group of catalysts, and keep it at room temperature; the second group of catalysts is one or more of acetyl chloride, o-chlorobenzoyl chloride, and terephthaloyl chloride. The solvent is one or more of ethanol, tetrahydrofuran, and N,N-dimethylformamide; the mass ratio of solute and solvent in the second group of catalysts is 1: (1-5); S3, take out the product, Clean with ethanol to obtain regenerated carbon fiber with clean surface.

Preferably, in step S1, the thickness of the cut carbon fiber resin matrix composite material is 1 to 20 mm.

Preferably, in step S1, the carbon fiber resin matrix composite material is kept in the first group of catalysts under normal pressure for 30 to 200 minutes at a temperature of 50 to 150°C. The higher the temperature or the longer the holding time, the higher the resin removal rate. However, excessively high processing temperature or processing time may cause irreversible performance damage to the fiber.

Preferably, in the step S1, the resin matrix of the carbon fiber resin matrix composite material is a thermosetting resin or a thermoplastic resin. The thermosetting resin includes epoxy resin, phenolic resin and unsaturated polyester; the thermoplastic resin includes polyethersulfone, nylon 6 , Nylon 66.

Preferably, in step S1, the carbon fiber form of the carbon fiber resin matrix composite material includes chopped fibers, continuous fibers, carbon fiber cloth or powder fibers.

Preferably, in step S1, the fibers of the carbon fiber resin matrix composite material are polyacrylonitrile-based carbon fibers or pitch-based carbon fibers.

Preferably, in step S2, the carbon fiber resin matrix composite material is kept in the second group of catalysts under normal pressure for 60 to 300 minutes; the temperature is 50 to 200°C. The higher the temperature or the longer the holding time, the higher the resin removal rate. However, excessively high processing temperature or processing time may cause irreversible performance damage to the fiber.

The invention has the following beneficial effects:

(1) The catalyst in the present invention can catalyze the degradation of the resin matrix in the waste carbon fiber resin matrix composite material, and can fully degrade the resin matrix and remove impurities involved;

(2) The method provided by the invention degrades composite materials step by step. The selected catalyst can efficiently break specific chemical bonds in the resin system. The first group of catalysts plays a role; the second group of catalysts are several specially selected catalysts. , can effectively degrade resin;

(3) The method provided by the present invention does not require excessively high temperatures during the reaction process, and the recovery efficiency is high. The mechanical property retention rate of recycled carbon fiber that can be obtained by this method can reach more than 95%, and the interface properties between the fiber and the resin matrix will not be significantly reduced;

(4) The fiber treated in the present invention can be washed with ethanol without the need for other solvents, which reduces the number of processes and environmental pollution.

Description of the drawings

Figure 1 is an SEM image of the fiber surface recovered under the conditions of adding zinc sulfate and acetyl chloride/ethanol in the present invention;

Figure 2 is an SEM image of the fiber surface recovered under the conditions of adding magnesium sulfate and terephthaloyl chloride/ethanol in the present invention.

Detailed ways

The present invention will be further described below in conjunction with examples.

Example 1

The carbon fiber in the selected waste carbon fiber resin matrix composite material is Toray T700, the fiber single filament tensile strength is 4.90GPa, and the resin matrix is 4,5-epoxyhexane-1,2-dicarboxylic acid diglycidyl ester ( TDE-85), the curing agent is 4,4`-diaminodiphenylmethane (DDM), the carbon fiber is PAN-based fiber, the form of the carbon fiber is continuous fiber, and the carbon fiber weight content is 60%.

This embodiment provides a method for recycling carbon fibers in discarded carbon fiber resin matrix composite materials. The specific steps are as follows:

1. Cut the 10mm thick carbon fiber resin composite material into appropriate size and put it into the reaction device;

2. Put the material into 1 mol/L magnesium sulfate and treat it at 100°C for 60 minutes. Wash it with ethanol and put it into an acetyl chloride/N, N-dimethylformamide mixed solution. The mixing mass ratio is 1:2. Insulated at 200℃ for 150min;

3. Take out the product and wash it ultrasonically with ethanol.

By weighing the material before and after treatment, it was found that the degradation rate of the resin was approximately 98%. According to the ASTM-D3379 standard, the carbon fiber was subjected to a single-filament tensile test. The obtained single-filament tensile strength was 4.81GPa, and the mechanical strength retention rate was 98.2%.

Example 2

The carbon fiber in the selected waste carbon fiber resin-based composite material is chopped Toray T700, the fiber tensile strength is 4.90GPa, the resin matrix is nylon 6, the carbon fiber is PAN-based fiber, the form of the carbon fiber is chopped fiber, among which the carbon fiber The weight content is 60%.

This embodiment provides a method for recycling carbon fibers in discarded carbon fiber resin matrix composite materials. The specific steps are as follows:

1. Cut the 4mm thick carbon fiber resin composite material into appropriate size and put it into the reaction device;

2. Put the material into 2 mol/L ferrous sulfate and treat it at 50°C for 30 minutes. Wash it with ethanol and put it into a mixed solution of terephthaloyl chloride/tetrahydrofuran. The mixing mass ratio is 1:5 and keep it warm at 50°C. 300min;

3. Take out the product and wash it ultrasonically with ethanol.

By weighing the material before and after treatment, it was found that the degradation rate of the resin was approximately 96%. According to the ASTM-D790 standard, the recycled fibers were combined with resin to prepare composite materials. The measured bending strength was 2.96Gpa, and the mechanical strength retention rate was 95.7%.

Example 3

The carbon fiber in the selected waste carbon fiber resin matrix composite material is Toray T800, the fiber tensile strength is 5.49GPa, and the resin matrix is 4,5-epoxyhexane-1,2-dicarboxylic acid diglycidyl ester (TDE- 85), the curing agent is diaminodiphenyl sulfone (DDS), the carbon fiber is PAN-based fiber, the form of the carbon fiber is continuous fiber, and the carbon fiber weight content is 60%.

This embodiment provides a method for recycling carbon fibers in discarded carbon fiber resin matrix composite materials. The specific steps are as follows:

1. Cut the 20mm thick carbon fiber resin composite material into appropriate size and put it into the reaction device;

2. Put the material into 5 mol/L ferrous sulfate and treat it at 50°C for 200 minutes. Wash it with ethanol and put it into a terephthaloyl chloride/ethanol mixed solution. The mixing mass ratio is 1:3 and keep it warm at 120°C. 100min;

3. Take out the product and wash it ultrasonically with ethanol.

By weighing the material before and after treatment, it was found that the degradation rate of the resin was approximately 96%. According to the ASTM-D3379 standard, the carbon fiber was subjected to a single-filament tensile test. The obtained single-filament tensile strength was 5.32GPa, and the mechanical strength retention rate was 96.9%.

Example 4

The carbon fiber in the selected waste carbon fiber resin-based composite material is chopped Toray T800, the fiber tensile strength is 5.49GPa, the resin matrix is nylon 66, the carbon fiber is PAN-based fiber, the form of the carbon fiber is chopped fiber, and the carbon fiber weight content is 60%.

This embodiment provides a method for recycling carbon fibers in discarded carbon fiber resin matrix composite materials. The specific steps are as follows:

1. Cut the 20mm thick carbon fiber resin composite material into appropriate size and put it into the reaction device;

2. Put the material into 2 mol/L zinc sulfate and treat it at 200°C for 50 minutes. Wash it with ethanol and put it into the o-chlorobenzoyl chloride/N, N-dimethylformamide mixed solution. The mixing mass ratio is 1 :1, keep at 150℃ for 60min;

3. Take out the product and wash it ultrasonically with ethanol.

By weighing the material before and after treatment, it was found that the degradation rate of the resin was approximately 99%. According to the ASTM-D790 standard, the recycled fibers were combined with resin to prepare composite materials. The measured bending strength was 3.23Gpa, and the mechanical strength retention rate was 97.6%.

Example 5

The carbon fiber in the selected waste carbon fiber resin-based composite material is Toray T700, the fiber tensile strength is 4.90GPa, the resin matrix is nylon 66, the carbon fiber is PAN-based fiber, the form of the carbon fiber is chopped fiber, and the carbon fiber weight content is 60 %.

This embodiment provides a method for recycling carbon fibers in discarded carbon fiber resin matrix composite materials. The specific steps are as follows:

1. Cut the 1mm thick carbon fiber resin composite material into appropriate size and put it into the reaction device;

2. Put the material into 2 mol/L ferrous sulfate and treat it at 100°C for 150 minutes. Wash it with ethanol and put it into the o-chlorobenzoyl chloride/N,N-dimethylformamide mixed solution. The mixing mass ratio is 1:4, keep at 120℃ for 200min;

3. Take out the product and wash it ultrasonically with ethanol.

By weighing the material before and after treatment, it was found that the degradation rate of the resin was approximately 97%. According to the ASTM-D3379 standard, the carbon fiber was subjected to a single-filament tensile test. The obtained single-filament tensile strength was 4.83GPa, and the mechanical strength retention rate was 98.6%.

Compared with the existing carbon fiber recycling technology, the present invention has high recycling efficiency, low energy consumption and low processing temperature. It solves the problems of long operation time and high energy consumption of the chemical recycling process. Compared with other traditional recovery methods using only catalysts, , this method can degrade the resin more effectively, and at the same time, the two-step treatment has different effects and can be recycled more efficiently.

After recycling, the fiber remains in good condition, with no obvious defect structure on the surface, and the mechanical properties of the fiber itself are retained to a great extent. Carbon fiber retains the same form after recycling, making it still valuable.

However, the above are only specific embodiments of the present invention, and should not be used to limit the scope of the present invention. Therefore, the replacement of equivalent components, or equivalent changes and modifications made in accordance with the patent protection scope of the present invention, should be It still falls within the scope of the claims of the present invention.

Claims (7)

1. The method for catalytically degrading the carbon fiber reinforced resin matrix composite material is characterized by comprising the following steps of:

s1, cutting a carbon fiber resin matrix composite material to be degraded, then placing the cut carbon fiber resin matrix composite material into a first group of catalysts, and carrying out heat preservation treatment under normal pressure; the first group of catalysts are one or more of ferrous sulfate, magnesium sulfate and zinc sulfate, and the concentration is 1-5 mol/L;

s2, taking out the carbon fiber resin matrix composite material treated in the step S1, cleaning, drying, putting into a second group of catalysts, and carrying out heat preservation treatment at normal temperature; the second group of catalysts are one or more of acetyl chloride, o-chlorobenzoyl chloride and terephthaloyl chloride, and the solvent is one or more of ethanol, tetrahydrofuran and N, N-dimethylformamide; the mass ratio of the solute to the solvent in the second group of catalysts is 1 (1-5);

and S3, taking out the product, and cleaning to obtain the regenerated carbon fiber with a clean surface.

2. The method for catalytic degradation of carbon fiber resin matrix composite according to claim 1, wherein in the step S1, the thickness of the cut carbon fiber resin matrix composite is 1-20 mm.

3. The method for catalytic degradation of carbon fiber resin matrix composite according to claim 1, wherein in step S1, the carbon fiber resin matrix composite is subjected to heat preservation in a first group of catalysts at normal pressure for 30-200 min and at a temperature of 50-150 ℃.

4. The method for catalytic degradation of carbon fiber resin-based composite material according to claim 1, wherein in step S1, the resin matrix of the carbon fiber resin-based composite material is a thermosetting resin, a thermoplastic resin, the thermosetting resin including epoxy resin, phenolic resin and unsaturated polyester; thermoplastic resins include polyethersulfone, nylon 6, nylon 66.

5. The method for catalytic degradation of carbon fiber resin-based composite material according to claim 1, wherein in step S1, the carbon fiber morphology of the carbon fiber resin-based composite material comprises chopped fibers, continuous fibers, carbon fiber cloth, or powder fibers.

6. The method for catalytic degradation of carbon fiber resin-based composite material according to claim 1, wherein in step S1, the fibers of the carbon fiber resin-based composite material are polyacrylonitrile-based carbon fibers or pitch-based carbon fibers.

7. The method for catalytic degradation of carbon fiber resin matrix composite according to claim 1, wherein in the step S2, the carbon fiber resin matrix composite is subjected to heat preservation in a second group of catalysts under normal pressure for 60-300 min; the temperature is 50-200 ℃.