A method for recycling carbon / carbon composite material machining scraps

Abstract

The invention discloses a recycling method for carbon / carbon composite material machining scraps. The recycling method first uses heat treatment to completely carbonize organic phases such as sizing agents, resins, tars, etc. that may exist in the scraps, and removes other metal impurity elements; then carbon deposition is performed on the crushed and pulverized scraps to obtain initial materials with different aspect ratios; then the initial materials are screened into four categories according to size; then the four categories of materials, solid thermosetting phenolic resin and asphalt in a set proportion are taken to make a mixed material; then the mixed material is granulated into granular materials for easy storage and ready use; then the granular materials are filled into a mold for hot pressing and curing, which can effectively ensure the uniformity of the materials; finally, the carbon / carbon composite material is made through conventional post-processing. The recycling method provided by the invention has simple process, high waste utilization rate, low price and excellent performance.

Description

Technical Field

[0001] The invention relates to the technical field of carbon / carbon composite plate preparation, in particular to a method for recycling machining scraps of carbon / carbon composite materials. Background Art

[0002] With the widespread application of carbon / carbon composite materials, their processing brings more and more scraps, carbon powder, etc. Since carbon fiber itself has a high value, this part of waste has a large potential value. How to effectively utilize and develop its value is an urgent problem that needs to be solved in the industry.

[0003] However, there are some problems with the existing methods of utilizing carbon / carbon composite waste: first, a considerable proportion of short fibers is still required, resulting in high costs. In addition, it is difficult to achieve absolute uniform dispersion of short fibers during the mixing process, making the stability of the resulting products questionable; second, only a portion of the processing waste is selected for recycling, and the value of the waste is not fully utilized. Summary of the invention

[0004] The invention provides a method for recycling carbon / carbon composite material machining scraps, which is used to overcome the defects of the prior art such as high cost, poor uniformity of prepared products, and low scrap utilization rate.

[0005] To achieve the above object, the present invention provides a method for recycling carbon / carbon composite material machining scraps, comprising the following steps:

[0006] S1: Heat treatment of the collected scraps and then crushing;

[0007] S2: crush the scraps after crushing according to the set size;

[0008] S3: using chemical vapor deposition to perform carbon deposition on the crushed scraps to obtain an initial material;

[0009] S4: screening the initial material into Class A material, Class B material, Class C material and Class D material according to the size, and performing the crushing and chemical vapor deposition again on the material that does not meet the size requirements until the size belongs to one of the four types of materials;

[0010] Class A materials are powdery materials; Class B materials are 1-3 mm fibrous materials; Class C materials are 3-5 mm fibrous materials; Class D materials are 5-10 mm fibrous materials;

[0011] S5: Mixing the A material, the B material, the C material, the D material, the solid thermosetting phenolic resin and the asphalt in proportion, stirring evenly to obtain a mixed material;

[0012] S6: Granulating the mixed material to obtain granular material;

[0013] S7: spreading the granular material into a mold and curing it by hot pressing;

[0014] S8: Carrying a carbonization treatment on the workpiece with the mold after solidification and demoulding;

[0015] S9: The carbonized workpiece is impregnated, cured, carbonized and sintered in sequence to obtain a carbon / carbon composite material.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. The recycling method of the machining scraps of carbon / carbon composite materials provided by the present invention first utilizes heat treatment to completely carbonize the organic phases such as sizing agents, resins, tars, etc. that may exist in the scraps, and removes other metallic impurity elements; then carbon deposition is performed on the crushed and pulverized scraps to obtain initial materials with different aspect ratios; then the initial materials are screened into four categories according to their sizes; then the four categories of materials, solid thermosetting phenolic resins and asphalt in set proportions are taken to make a mixed material; then the mixed material is granulated into granular materials for easy storage and ready use; then the granular materials are filled into the mold for hot pressing and curing, which can effectively ensure the uniformity of the materials; finally, the carbon / carbon composite materials are made through conventional post-processing. The recycling method provided by the present invention has a simple process, high waste utilization rate, and low price. The prepared carbon / carbon composite materials have excellent performance and a density of 1.00 to 1.35 g / cm 3 .

[0018] 2. The method for recycling carbon / carbon composite material machining scraps provided by the present invention utilizes carbon deposition to differentiate the crushed materials, and grows whiskers of different lengths from fibrous materials with a certain aspect ratio through deposition, thereby increasing their aspect ratio to achieve fiber-like properties. The fibrous materials can be used as reinforcements for subsequent products to replace the currently commonly used short fiber reinforcements, thereby effectively reducing production costs.

[0019] 3. In the recycling method of carbon / carbon composite material machining scraps provided by the present invention, the initial material is screened into Class A material, Class B material, Class C material and Class D material according to the size, and the Class A material, Class B material, Class C material and Class D material are mixed according to the set ratio. Mixing materials with different aspect ratios can improve the structural strength of the product and hinder crack propagation.

[0020] 4. The method for recycling carbon / carbon composite material machining scraps provided by the present invention ensures the uniformity of the mixed material itself by stirring, and then obtains granular material by granulation, which is filled into the mold in the form of granular material. This can avoid the separation and aggregation of materials of different phases during material filling and hot pressing, thereby avoiding the problem of uneven product material and effectively improving the quality stability of the product. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0023] Unless otherwise specified, all drugs / reagents used were commercially available.

[0024] The present invention provides a method for recycling carbon / carbon composite material machining scraps, comprising the following steps:

[0025] S1: The collected scraps are heat treated and then crushed.

[0026] The main sources of scraps are: scraps generated by carbon fiber preform manufacturers in the process of preform preparation, and scraps generated by carbon-carbon manufacturers in the process of machining semi-finished products / finished products.

[0027] S2: crush the scraps after crushing according to the set size;

[0028] S3: using chemical vapor deposition to perform carbon deposition on the crushed scraps to obtain an initial material;

[0029] S4: screening the initial material into Class A material, Class B material, Class C material and Class D material according to the size, and performing the crushing and chemical vapor deposition again on the material that does not meet the size requirements until the size belongs to one of the four types of materials;

[0030] Class A materials are powdery materials; Class B materials are 1-3 mm fibrous materials; Class C materials are 3-5 mm fibrous materials; Class D materials are 5-10 mm fibrous materials;

[0031] S5: Mix the A-type material, the B-type material, the C-type material, the D-type material, the solid thermosetting phenolic resin and the asphalt in proportion, stir evenly, and obtain a mixed material.

[0032] The use of solid resin and asphalt can avoid the problem of uneven mixing and dispersion of liquid resin with fiber and powder.

[0033] S6: Granulating the mixed material to obtain granular material;

[0034] S7: spreading the granular material into a mold and curing it by hot pressing;

[0035] S8: Carrying a carbonization treatment on the workpiece with the mold after solidification and demoulding;

[0036] S9: The carbonized workpiece is impregnated, cured, carbonized and sintered in sequence to obtain a carbon / carbon composite material.

[0037] Preferably, in step S1, the heat treatment is specifically:

[0038] Stage 1: room temperature to 1200°C for 10 hours;

[0039] The second stage: heating from 1200℃ to 1800℃, time 12h;

[0040] The third stage is to keep the temperature at 1800℃ for 3-5 hours. The heat treatment removes the organic phases such as sizing agent, resin, tar, etc. that may exist in the scraps, completely carbonizes them, and removes other metal impurity elements.

[0041] Preferably, in step S3, the carrier gas for carbon deposition is one of a mixture of propane and nitrogen, a mixture of propylene and nitrogen, and a mixture of natural gas and nitrogen.

[0042] The flow rates are proportional, propane: nitrogen = 16:1 to 1:8. Propylene: nitrogen = 16:1 to 1:8.

[0043] Natural gas:nitrogen = 16:1 ~ 1:8.

[0044] Preferably, the deposition temperature of the carbon deposition is 980-1050° C., and the deposition time is 80-100 h, so as to control the size of the deposited material within an available range.

[0045] Preferably, in step S5, the mass percentage of the A material in the mixture is 20-60%, the mass percentage of the B material is 1-10%, the mass percentage of the C material is 1-10%, the mass percentage of the D material is 1-10%, the mass percentage of the solid thermosetting phenolic resin is 10-60%, and the mass percentage of the asphalt is 1-10%. Through multiple experiments, it is found that the product prepared under this ratio has better performance (performance including mechanical properties, material uniformity and stability).

[0046] Preferably, in the mixture, the mass percentage of Class A material is 20%, the mass percentage of Class B material is 10%, the mass percentage of Class C material is 10%, the mass percentage of Class D material is 10%, the mass percentage of solid thermosetting phenolic resin is 40%, and the mass percentage of asphalt is 10%.

[0047] Preferably, the mass percentage of Class A material in the mixture is 40%, the mass percentage of Class B material is 8%, the mass percentage of Class C material is 5%, the mass percentage of Class D material is 1%, the mass percentage of solid thermosetting phenolic resin is 38%, and the mass percentage of asphalt is 8%.

[0048] Preferably, in the mixture, the mass percentage of Class A material is 60%, the mass percentage of Class B material is 1%, the mass percentage of Class C material is 1%, the mass percentage of Class D material is 5%, the mass percentage of solid thermosetting phenolic resin is 32%, and the mass percentage of asphalt is 1%.

[0049] Preferably, in step S7, the temperature of the hot pressing curing is 180-250°C and the pressure is 1-3.5 MPa.

[0050] Preferably, in step S8, the temperature of the carbonization treatment is 700-1000° C., and the time is 3-5 hours.

[0051] Example 1

[0052] This embodiment provides a method for recycling carbon / carbon composite material machining scraps, comprising the following steps:

[0053] S1: The collected scraps are heat treated and then crushed.

[0054] The specific heat treatment is:

[0055] Stage 1: room temperature to 1200°C for 10 hours;

[0056] The second stage: heating from 1200℃ to 1800℃, time 12h;

[0057] The third stage is to keep warm at 1800℃ for 3h.

[0058] S2: crush the scraps after crushing according to the set size.

[0059] S3: Carbon deposition is performed on the crushed scraps by using chemical vapor deposition to obtain initial materials.

[0060] Carbon deposition is specifically:

[0061] The temperature was raised from room temperature to 980°C for 8 hours;

[0062] Keep warm at 980℃ for 80h.

[0063] S4: Screening the initial material into Class A material, Class B material, Class C material and Class D material according to the size, and performing the above-mentioned crushing and chemical vapor deposition again on the material whose size does not meet the requirements until the size belongs to one of the four types of materials;

[0064] Class A materials are powdery materials; Class B materials are 1-3 mm fibrous materials; Class C materials are 3-5 mm fibrous materials; Class D materials are 5-10 mm fibrous materials.

[0065] S5: Mix Class A material, Class B material, Class C material, Class D material, solid thermosetting phenolic resin and asphalt in proportions of 20%, 10%, 10%, 10%, 40% and 10%, stir evenly to obtain a mixed material.

[0066] S6: Granulate the mixture using a twin-screw extruder granulator to obtain granular material.

[0067] S7: According to the volume density after molding 1.35g / cm 3 Calculate the required amount of granular material, spread the granular material evenly into the mold, and heat-press and cure it on a hot press.

[0068] S8: The workpiece with the mold after solidification and demoulding is subjected to carbonization treatment at 900°C.

[0069] S9: The carbonized workpiece is impregnated, cured, carbonized and sintered in sequence to obtain a carbon / carbon composite material.

[0070] Example 2

[0071] This embodiment provides a method for recycling carbon / carbon composite material machining scraps, comprising the following steps:

[0072] S1: The collected scraps are heat treated and then crushed.

[0073] The specific heat treatment is:

[0074] Stage 1: room temperature to 1200°C for 10 hours;

[0075] The second stage: heating from 1200℃ to 1800℃, time 12h;

[0076] The third stage is to keep warm at 1800℃ for 4h.

[0077] S2: crush the scraps after crushing according to the set size.

[0078] S3: Carbon deposition is performed on the crushed scraps by using chemical vapor deposition to obtain initial materials.

[0079] Carbon deposition is specifically:

[0080] The temperature was raised from room temperature to 1000°C for 8 hours;

[0081] Keep warm at 1000℃ for 90h.

[0082] S4: Screening the initial material into Class A material, Class B material, Class C material and Class D material according to the size, and performing the above-mentioned crushing and chemical vapor deposition again on the material whose size does not meet the requirements until the size belongs to one of the four types of materials;

[0083] Class A materials are powdery materials; Class B materials are 1-3 mm fibrous materials; Class C materials are 3-5 mm fibrous materials; Class D materials are 5-10 mm fibrous materials.

[0084] S5: Mix Class A material, Class B material, Class C material, Class D material, solid thermosetting phenolic resin and asphalt in proportions of 40%, 8%, 5%, 1%, 38% and 8%, stir evenly to obtain a mixed material.

[0085] S6: Granulate the mixture using a twin-screw extruder granulator to obtain granular material.

[0086] S7: According to the volume density after molding 1.00g / cm 3 Calculate the required amount of granular material, spread the granular material evenly into the mold, and heat-press and cure it on a hot press.

[0087] S8: The workpiece with the mold after solidification and demoulding is subjected to carbonization treatment at 1000°C.

[0088] S9: The carbonized workpiece is impregnated, cured, carbonized and sintered in sequence to obtain a carbon / carbon composite material.

[0089] Example 3

[0090] This embodiment provides a method for recycling carbon / carbon composite material machining scraps, comprising the following steps:

[0091] S1: The collected scraps are heat treated and then crushed.

[0092] The specific heat treatment is:

[0093] Stage 1: room temperature to 1200°C for 10 hours;

[0094] The second stage: heating from 1200℃ to 1800℃, time 12h;

[0095] The third stage is to keep warm at 1800℃ for 5h.

[0096] S2: crush the scraps after crushing according to the set size.

[0097] S3: Carbon deposition is performed on the crushed scraps by using chemical vapor deposition to obtain initial materials.

[0098] Carbon deposition is specifically:

[0099] The temperature was raised from room temperature to 1050°C for 8 hours;

[0100] Keep warm at 1050℃ for 100h.

[0101] S4: Screening the initial material into Class A material, Class B material, Class C material and Class D material according to the size, and performing the above-mentioned crushing and chemical vapor deposition again on the material whose size does not meet the requirements until the size belongs to one of the four types of materials;

[0102] Class A materials are powdery materials; Class B materials are 1-3 mm fibrous materials; Class C materials are 3-5 mm fibrous materials; Class D materials are 5-10 mm fibrous materials.

[0103] S5: Mix Class A material, Class B material, Class C material, Class D material, solid thermosetting phenolic resin and asphalt in proportions of 60%, 1%, 1%, 5%, 32% and 1%, stir evenly to obtain a mixed material.

[0104] S6: Granulate the mixture using a twin-screw extruder granulator to obtain granular material.

[0105] S7: According to the volume density after molding 1.20g / cm 3 Calculate the required amount of granular material, spread the granular material evenly into the mold, and heat-press and cure it on a hot press.

[0106] S8: The workpiece with the mold after solidification and demoulding is subjected to a carbonization treatment at 600°C.

[0107] S9: The carbonized workpiece is impregnated, cured, carbonized and sintered in sequence to obtain a carbon / carbon composite material.

[0108] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for recycling carbon / carbon composite material machining scraps, characterized in that: The following steps are involved: S1: Heat treatment of the collected scraps and then crushing; S2: crush the scraps after crushing according to the set size; S3: using chemical vapor deposition to perform carbon deposition on the crushed scraps to obtain an initial material; S4: screening the initial material into Class A material, Class B material, Class C material and Class D material according to the size, and performing the crushing and chemical vapor deposition again on the material that does not meet the size requirements until the size belongs to one of the four types of materials; Class A materials are powdery materials; Class B materials are 1~3mm fibrous materials; Class C materials are 3~5mm fibrous materials; Class D materials are 5~10mm fibrous materials; S5: Mixing the A-type material, the B-type material, the C-type material, the D-type material, the solid thermosetting phenolic resin and the asphalt in proportion, stirring evenly to obtain a mixed material; The mass percentage of the mixed material is 20-60% for the Class A material, 1-10% for the Class B material, 1-10% for the Class C material, 1-10% for the Class D material, 10-60% for the solid thermosetting phenolic resin, and 1-10% for the asphalt; S6: Granulating the mixed material to obtain granular material; S7: spreading the granular material into a mold and curing it by hot pressing; S8: Carrying a carbonization treatment on the workpiece with the mold after solidification and demoulding; S9: The carbonized workpiece is impregnated, cured, carbonized and sintered in sequence to obtain a carbon / carbon composite material.

2. The method for recycling carbon / carbon composite material machining scraps according to claim 1, characterized in that: In step S1, the heat treatment is specifically: Stage 1: room temperature to 1200°C for 10 hours; The second stage: heating from 1200℃ to 1800℃, time 12h; The third stage is to keep warm at 1800℃ for 3~5h.

3. The method for recycling carbon / carbon composite material machining scraps according to claim 1, characterized in that: In step S3, the carrier gas for carbon deposition is one of a mixture of propane and nitrogen, a mixture of propylene and nitrogen, and a mixture of natural gas and nitrogen.

4. A method for recycling carbon / carbon composite material machining scraps according to claim 1 or 3, characterized in that: The carbon deposition temperature is 980-1050° C., and the deposition time is 80-100 h.

5. The method for recycling carbon / carbon composite material machining scraps according to claim 1, characterized in that: The mass percentage of Class A material in the mixture is 20%, the mass percentage of Class B material is 10%, the mass percentage of Class C material is 10%, the mass percentage of Class D material is 10%, the mass percentage of solid thermosetting phenolic resin is 40%, and the mass percentage of asphalt is 10%.

6. The method for recycling carbon / carbon composite material machining scraps according to claim 1, characterized in that: The mass percentage of Class A material in the mixture is 40%, the mass percentage of Class B material is 8%, the mass percentage of Class C material is 5%, the mass percentage of Class D material is 1%, the mass percentage of solid thermosetting phenolic resin is 38%, and the mass percentage of asphalt is 8%.

7. The method for recycling carbon / carbon composite material machining scraps according to claim 1, characterized in that: The mass percentage of Class A material in the mixture is 60%, the mass percentage of Class B material is 1%, the mass percentage of Class C material is 1%, the mass percentage of Class D material is 5%, the mass percentage of solid thermosetting phenolic resin is 32%, and the mass percentage of asphalt is 1%.

8. The method for recycling carbon / carbon composite material machining scraps according to claim 1, characterized in that: In step S7, the temperature of the hot pressing curing is 180-250°C and the pressure is 1-3.5 MPa.

9. The method for recycling carbon / carbon composite material machining scraps according to claim 1, characterized in that: In step S8, the temperature of the carbonization treatment is 700-1000°C and the time is 3-5 hours.