Method for treating waste liquid generated during carbon fiber recovery from CFRP based on low temperature and dialysis

Abstract

The invention belongs to the technical field of CFRP composite material recovery, and particularly relates to a method for treating waste liquid generated during carbon fiber recovery from CFRP based on low temperature and dialysis. According to the method, zinc chloride in the waste liquid can be separated out, and a solid epoxy resin degradation product can be separated out, so that the problems of environmental pollution and resource waste caused by recycling the carbon fibers from the waste CFRP are effectively solved. The method does not need large instruments and equipment, and is low in cost and simple and effective to operate.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite material recycling, and in particular relates to a method for recycling waste liquid obtained when carbon fiber is recovered from carbon fiber reinforced polymer (CFRP) based on low temperature and dialysis treatment. Background Art

[0002] Carbon fiber composites (CFRP) are widely used in aerospace, automobile manufacturing, military equipment and civilian products due to their light weight, high strength and weather resistance. CFRP is made by curing carbon fiber (CF) with a thermosetting resin (usually epoxy resin) as a matrix. In order to reduce environmental pollution and economic losses caused by random discarding, carbon fiber is often recycled by degrading epoxy resin for reuse.

[0003] Supercritical method and solvothermal method are two effective methods for recovering carbon fiber from CFRP. These two methods are easy to mass produce and have low material cost, so they become a promising recycling method (HYDE JR, LESTER E, KINGMANS, et al. Supercritical propanol, a possible route to composite carbon fibre recovery: A viability study [J]. Composites Part A: Applied Science and Manufacturing, 2006, 37(11): 2171-5. ZHAO C, SHITIAN M, MA W, et al. Methods for recovering carbon fiber from carbon-fiber-reinforced polymer (CFRP) composites. US9790346 (B2).). However, the disadvantage of these two methods is that they produce a large amount of n-propanol homogeneous waste liquid containing epoxy resin degradation products, thus causing secondary pollution. Even homogeneous waste liquid containing inorganic zinc chloride and epoxy resin degradation products is produced (Qiang Yongyong, Zhao Yan, Wang Like. Research on the method of recycling CFRP under polyethylene glycol / zinc chloride conditions [J]. Engineering Plastics Application, 2020, 48(01): 63-67+85.). Prior art used the vacuum distillation method to study the treatment of propanol waste liquid containing epoxy resin degradation products (Mu Quanyi, Kang Shaofu, Hu Zhiqiang. Epoxy resin degradation method, solvent system for epoxy resin degradation and recovery method. CN202210173707.7.). However, this method has high requirements for recovery equipment and process conditions, and does not consider the separation and removal of inorganic salts in the waste liquid. Summary of the invention

[0004] Based on the shortcomings of the prior art, this technology proposes a method for treating waste liquid generated when recovering carbon fiber from CFRP, using n-propanol homogeneous waste liquid containing zinc chloride and epoxy resin degradation products, and allowing the solution to separate into layers by standing at low temperature: separating and drying the lower layer of solution to obtain zinc chloride, and dialyzing the upper layer of solution to obtain the degraded resin generated during the recovery process. This technology separates and treats the recovered liquid to minimize the pollution of the recovered product to the environment and the waste of resources.

[0005] To achieve the above object, the present invention adopts the following scheme to achieve: Step 1: selecting a homogeneous waste liquid of n-propanol containing zinc chloride and epoxy resin degradation products; Step 2: allowing the waste liquid obtained in step 1 to stand at low temperature to obtain a stratified solution; Step 3: After the step 2 is allowed to stand at low temperature, the lower layer is separated and dried to obtain zinc chloride; Step 4: The upper layer solution obtained after the low temperature treatment in step 2 is dialyzed and the solid epoxy resin degradation product is scraped off from the semipermeable membrane.

[0006] Preferably, the low temperature in step 2 ranges from -10°C to -20°C, and the treatment time ranges from 24 hours to 48 hours.

[0007] Preferably, in step 4, a polyethylene glycol dialysate with a molecular weight of 6000 and a mass fraction of 30%-50% is selected; the molecular weight cutoff of the dialysis membrane is 100-500, and the dialysis time is 12 hours to 24 hours.

[0008] Compared with the prior art, the present invention has the following beneficial effects: (1) It can simultaneously separate and remove zinc chloride and epoxy resin degradation products from waste liquid; (2) No need for large instruments and equipment; (3) The operation method is simple and effective. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is the n-propanol homogeneous waste liquid containing zinc chloride and epoxy resin degradation products in step 1 of the present invention.

[0010] Figure 2 The waste liquid is obtained by standing at low temperature to obtain the stratified waste liquid in step 2 of the present invention.

[0011] Figure 3 The solid product of epoxy resin degradation is recovered after dialysis treatment in step 4 of the present invention. Specific implementation methods The present invention will be described in more detail and comprehensively by way of examples below, but the protection scope of the present invention is not limited to these specific examples. Any other technical solutions obtained by ordinary technicians in the field without making innovative work based on the examples in the present invention should be within the protection scope of the present invention.

[0013] Example 1 10 g zinc chloride, 1 g CFRP and 16 g n-propanol were reacted in a reactor at 200 °C for 24 hours to obtain a waste liquid such as Figure 1 The waste liquid was left to stand at -20°C for 24 hours and then stratified. Figure 2 The lower layer solution was separated and dried to obtain zinc chloride; the upper layer solution was dialyzed with 30% polyethylene glycol dialysate with a molecular weight of 6000 using a dialysis membrane with a molecular weight cutoff of 500 for 24 hours, and then the solid product of epoxy resin was obtained by scraping it from the semipermeable membrane, such as Figure 3 .

[0014] Example 2 12 g zinc chloride, 1 g CFRP and 20 g n-propanol were reacted in a reactor at 210°C for 24 hours to obtain a waste liquid such as Figure 1 The waste liquid was left to stand at -10°C for 48 hours and then stratified. Figure 2 The lower solution was separated and dried to obtain zinc chloride; the upper solution was dialyzed for 24 hours using a 40% polyethylene glycol dialysate with a molecular weight of 6000 and a dialysis membrane with a molecular weight cutoff of 100, and then the solid product of epoxy resin was scraped off from the semipermeable membrane, such as Figure 3 .

[0015] Example 3 14 g zinc chloride, 1 g CFRP and 24 g n-propanol were reacted in a reactor at 220°C for 24 hours to obtain a waste liquid such as Figure 1 The waste liquid was left to stand at -20°C for 48 hours and then stratified. Figure 2 The lower solution was separated and dried to obtain zinc chloride; the upper solution was dialyzed for 12 hours using a 50% polyethylene glycol dialysate with a molecular weight of 6000 and a dialysis membrane with a molecular weight cutoff of 500, and then the solid product of epoxy resin was obtained by scraping it off from the semipermeable membrane, such as Figure 3 .

Claims

1. A method for recovering waste liquid generated when carbon fiber is recovered from CFRP based on low temperature and dialysis treatment, characterized in that Follow these steps: Step 1: selecting a homogeneous waste liquid of n-propanol containing zinc chloride and epoxy resin degradation products; Step 2: allowing the waste liquid obtained in step 1 to stand at low temperature to obtain a stratified solution; Step 3: After the step 2 is allowed to stand at low temperature, the lower layer is separated and dried to obtain zinc chloride; Step 4: The upper layer solution obtained after the low temperature treatment in step 2 is dialyzed and the solid epoxy resin degradation product is scraped off from the semipermeable membrane.

2. A method for recovering waste liquid generated when carbon fiber is recovered from CFRP based on low temperature and dialysis treatment according to claim 1, characterized in that: The low temperature in step 2 ranges from -10°C to -20°C, and the treatment time ranges from 24 hours to 48 hours.

3. The method for recovering waste liquid generated when carbon fiber is recovered from CFRP based on low temperature and dialysis treatment according to claim 1, characterized in that: In step 4, a polyethylene glycol dialysate with a molecular weight of 6000 and a mass fraction of 30%-50% is selected; the molecular weight cutoff of the dialysis membrane is 100-500, and the dialysis time is 12 hours to 24 hours.

Images