A method for deoiling and antioxidizing oil-containing copper scrap
By using a two-stage gradient heating mixing process with organic solvents and copper scrap containing synthetic oil, followed by vacuum distillation, the problem of difficult degreasing and oxidation of copper scrap containing synthetic oil was solved, achieving efficient grease removal and copper scrap protection.
Patent Information
- Application Number
- CN202610487027.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-04-14
- Publication Date
- 2026-05-29
AI Technical Summary
Existing technologies are insufficient for efficiently removing grease from copper scrap containing synthetic oil, and the heat treatment process can easily lead to oxidation of the copper scrap, resulting in a decrease in the quality of the copper scrap.
Organic solvents were mixed with copper scrap containing synthetic oil in an inert atmosphere in a two-stage gradient heating process. The first stage was used to remove free oil, and the second stage was a passivation reaction at 180~200℃ to generate reducing hydrogen to passivate fatty acids. Then, distillation was carried out under vacuum conditions.
It achieves efficient removal of grease from copper scrap containing synthetic oil, reduces the oil content of copper scrap, effectively inhibits copper scrap oxidation, and improves the quality of copper scrap.
Smart Images
Figure CN122105143A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of resource utilization technology for oily metal solid waste, and more specifically, to a method for degreasing and preventing oxidation of oily copper scrap. Background Technology
[0002] Cutting oil is inevitably used in the cutting and finishing of copper products, resulting in oil-containing copper shavings. Currently, cutting oils used in industry are mainly divided into two categories: mineral oil-based and synthetic oil-based. In recent years, to improve lubrication performance and meet environmental regulations, synthetic cutting oils have been widely used due to their excellent thermal stability and biodegradability, leading to an increase in the production of synthetic oil-containing copper shavings.
[0003] Existing processes for degreasing oily copper scrap mainly include mechanical centrifugal degreasing, low-temperature drying, inert atmosphere heat treatment, and vacuum thermal degreasing. These methods have good degreasing effects on copper scrap containing mineral oil.
[0004] However, synthetic oils and mineral oils differ significantly in their physicochemical properties: synthetic oils typically have a higher viscosity index, better thermal stability, and lower volatility. When processing copper scrap containing synthetic oil, these characteristics result in suboptimal degreasing techniques—these copper scraps require higher-temperature heat treatment to break down their oil film structure, leading to a significant increase in energy consumption and the risk of copper scrap oxidation.
[0005] Currently, research on degreasing treatment of copper scrap containing synthetic oil is lacking. With the increasing use of synthetic oils in machining, developing efficient degreasing technologies suitable for synthetic oil systems has become a pressing technical challenge for the copper processing industry. Summary of the Invention
[0006] This invention proposes a method for degreasing and preventing oxidation of oily copper scrap. This method utilizes organic solvents to fully act at the copper-oil interface under heating and an inert atmosphere, passivating fatty acids and their pyrolysis intermediates. This not only achieves efficient degreasing of copper scrap containing synthetic oil, but also inhibits the oxidation of copper scrap.
[0007] To achieve the above objectives, the technical solution provided by the present invention is as follows:
[0008] This invention provides a method for degreasing and preventing oxidation of oily copper scrap. The method includes: mixing oily copper scrap with an organic solvent under an inert atmosphere and a two-stage gradient heating process, wherein the first stage of mixing is used to remove free oil from the oily copper scrap, and the second stage of mixing is at a temperature of 180~200℃ to obtain a solvent-copper scrap mixture; wherein the organic solvent used includes a main solvent and a co-solvent, and can generate reducing hydrogen during the mixing process; and distilling the solvent-copper scrap mixture under an inert atmosphere and a vacuum degree ≤10kPa to obtain solid copper scrap.
[0009] It should be noted that the inventor has long been committed to the research on degreasing and resource utilization of oily metal solid waste. In the process of applying traditional degreasing treatment methods to the degreasing treatment of oily copper scrap, it was accidentally discovered that the oil content of the solid copper scrap obtained after treatment of a batch of oily copper scrap was still not ideal.
[0010] To address the aforementioned issues, the inventors investigated the source and composition of this batch of oily copper scrap, discovering that the oil in this batch of oily copper scrap contained a significant amount of synthetic oil. Copper scrap containing synthetic oil differs from copper scrap containing mineral oil. The main components of the oil in mineral oil-based copper scrap are alkanes and alkenes, while the main components of the oil in synthetic oil-based copper scrap are fatty acids, fatty acid esters, and various polar additives, exhibiting significant polarity and chemical activity. Synthetic oil forms chemical adsorption / complexes with the copper surface; it easily forms fatty acid copper soaps, which adhere firmly to the surface. Mechanical degreasing generally only removes free oil and is less effective at removing more firmly bound chemically bonded oil. Furthermore, to obtain copper scrap with a lower oil content, heat treatment is generally required. Although a vacuum or inert atmosphere can reduce the oxygen partial pressure during heat treatment, synthetic oil still generates oxidizing intermediates such as oxygen-containing free radicals during pyrolysis, which easily induces oxidation on the copper scrap surface. In addition, existing treatments for oily copper scraps often focus solely on "de-oiling," neglecting the interfacial chemical reactions and oxidation risks associated with synthetic oily copper scraps during heat treatment, leading to a decline in the quality of the resulting copper scraps.
[0011] This invention employs an organic solvent mixed with copper scrap containing synthetic oil. This organic solvent disrupts the oil-solid interface adsorption balance, promoting the desorption of grease from the copper scrap. More importantly, at 180-200°C, the organic solvent remains sufficiently on the surface of the copper scrap and at the oil-metal interface, preferentially reacting with chemically adsorbed oil and fatty acids. This passivates the chemical activity of the grease, consumes oxidative intermediates generated during pyrolysis, and inhibits the oxidation of the copper scrap.
[0012] In this treatment method, the organic solvent used includes a main solvent and a co-solvent. The combination of the main solvent and the co-solvent provides better penetration and dissolution performance, that is, it is used to better penetrate and dissolve copper scrap containing synthetic oil. The first stage of mixing is mainly used to remove free oil from copper scrap containing synthetic oil, efficiently dissolve free oil, thereby breaking the oil film wrapped in synthetic oil, and providing a basis for the subsequent second stage passivation.
[0013] The reaction temperature for the organic solvent and copper scrap containing synthetic oil was selected to be 180-200℃. At room temperature, the organic solvent hardly produces reducing hydrogen or undergoes a passivation reaction with the chemically adsorbed oil and fatty acids in the synthetic oil. Therefore, it cannot weaken the binding force between the fatty acids and the copper scrap, nor the oxidizing property of the fatty acids. During the subsequent high-temperature vacuum separation process, the fatty acids remain adhered to the surface of the copper scrap and oxidize it. Therefore, increasing the mixing temperature of the organic solvent and the copper scrap containing synthetic oil allows for a passivation reaction and the generation of reducing hydrogen.
[0014] The present invention also provides another method for degreasing and preventing oxidation of oily copper scrap, the method comprising: treating the synthetic oil-containing copper scrap to remove free oil, thereby reducing the content of free oil therein, to obtain synthetic oil-containing copper scrap with free oil removed; mixing the synthetic oil-containing copper scrap with free oil removed with an organic solvent at 180~200°C and under an inert atmosphere to obtain a solvent-copper scrap mixture, wherein the organic solvent used can generate reducing hydrogen during the mixing process; and distilling the solvent-copper scrap mixture under an inert atmosphere and a vacuum degree ≤10kPa to obtain solid copper scrap.
[0015] Furthermore, the synthetic oil-containing copper scraps and organic solvent are mixed at 180-200°C for 30-60 minutes under a pressure of 0.5-1.0 MPa. Mixing the organic solvent and synthetic oil-containing copper scraps under pressure helps reduce the volatilization of the organic solvent, thereby facilitating sufficient contact between the organic solvent and the oil-containing copper scraps.
[0016] Furthermore, the process of mixing the synthetic oil-containing copper scraps with the organic solvent under an inert pressure atmosphere and a two-stage gradient temperature increase is described, specifically, the mass ratio of the synthetic oil-containing copper scraps to the organic solvent is 100:5~15.
[0017] Furthermore, the total mass of the main solvent and the co-solvent is 100%, wherein the main solvent accounts for 65% to 80%, and the main solvent is N-methylpyrrolidone, and the co-solvent is diethylene glycol ethyl ether.
[0018] Furthermore, the copper scrap containing synthetic oil is mixed with an organic solvent under an inert pressurized atmosphere and a two-stage gradient temperature increase. Specifically, the mixing temperature in the first stage is 120~160℃ and the mixing time is 20~30min, while the mixing time in the second stage is 30~60min.
[0019] Furthermore, the solvent-copper shavings mixture is distilled under an inert atmosphere and a vacuum degree ≤10kPa. Specifically, the distillation process includes a two-stage gradient temperature distillation, wherein the first stage distillation temperature is 140~150℃ and the distillation time is 40~60min, and the second stage distillation temperature is 240~260℃ and the distillation time is 25~35min.
[0020] Furthermore, the organic solvent used is selected from any one or a combination of isopropanol, methanol, and ethanol, and the mass ratio of the synthetic oil-containing copper scrap to the organic solvent is 100:2~5.
[0021] Furthermore, the solvent-copper shavings mixture is distilled under an inert atmosphere and a vacuum degree ≤10kPa. Specifically, the distillation temperature is 240~260℃ and the distillation time is 65~95min.
[0022] Furthermore, the process of removing free oil from the copper scrap containing synthetic oil specifically involves centrifugal degreasing. Centrifugal degreasing removes free oil from the copper scrap to prevent it from interfering with subsequent mixing of organic solvents with the copper scrap and the vacuum distillation process.
[0023] Compared with the prior art, the technical solution provided by this invention has the following advantages: (1) This invention optimizes the treatment method for oily copper scrap. Specifically, the synthetic oil-containing copper scrap is mixed with an organic solvent at 180-200°C under an inert atmosphere. At this time, the organic solvent can disrupt the oil-solid interface adsorption balance and promote the desorption of synthetic oil from the copper scrap. More importantly, the organic solvent reacts with the chemically adsorbed oil and fatty acids in the copper scrap, thereby passivating the reactivity of free fatty acids, consuming the oxidative intermediates generated during pyrolysis, and inhibiting the oxidation of copper scrap. In the subsequent high-temperature vacuum separation process, this effectively reduces the problem of copper scrap oxidation caused by fatty acids still adhering to the surface of the copper scrap.
[0024] (2) This invention further optimizes the treatment method for oily copper scrap. Specifically, the oily copper scrap and organic solvent are mixed in a two-stage gradient heating process at 180-200°C under an inert atmosphere. The first stage of mixing is used to remove free oil from the oily copper scrap, and the second stage of mixing at 180-200°C yields a solvent-copper scrap mixture. This treatment method allows the organic solvent and subsequent passivation process to be carried out in the same container, eliminating the need for material transfer between different containers. Furthermore, the mixing process of the organic solvent and copper scrap, as well as the subsequent distillation process, can all be completed in the same container, such as a reaction vessel, further eliminating the need for material transfer between different containers. In addition, the distillation process includes a two-stage gradient heating distillation, simplifying the subsequent solvent recovery process. Attached Figure Description
[0025] Figure 1 This is a process flow diagram of the treatment of copper scraps containing synthetic oil in Embodiment 1 of the present invention.
[0026] Figure 2 This is a GC-MS spectrum of synthetic oil copper scrap dissolved in ethyl acetate in an embodiment of the present invention. Detailed Implementation
[0027] To further understand the content of this invention, the invention will be described in detail with reference to the embodiments.
[0028] Experimental materials and equipment Experimental materials: copper shavings containing synthetic oil (taken from the turning process of a precision instrument factory, with an initial oil content of 8.92%), isopropanol, methanol, and ethanol.
[0029] Experimental equipment: centrifugal oil separator, horizontal vacuum reactor, condensation recovery system, rotary evaporator, Soxhlet extraction apparatus, electronic balance, etc.
[0030] The oil content determination method referred to in this invention refers to the oil phase determination method in USEPA 3540C-1196 standard, which involves extraction with organic solvents and calculation of the oil content based on mass loss. The specific calculation formula is as follows:
[0031] In Formula 1 above The solid oil content is expressed as a percentage. m0 is the mass of the solid phase before extraction, i.e., the mass of the dried sludge, and m1 is the mass of the solid phase after treatment, i.e., the mass of the obtained solid residue.
[0032] GC-MS compositional analysis was performed on copper scrap containing synthetic oil, referencing... Figure 2As shown, fatty acids are the main components, accounting for over 97%, and all exist in the form of fatty acid methyl esters. Methyl 13,14-octadecadienoic acid has the highest proportion, reaching 44.17%; followed by methyl cis-12-octadecadienoic acid, accounting for 23.79%; methyl stearate accounts for 12.14%; methyl hexadecanoate accounts for 10.08%; methyl 12,13-tetradecadienoic acid accounts for 8.62%; and unsaturated fatty acid methyl esters (mono-) The content of methyl esters (including alkenes and dienes) exceeds 70%, saturated fatty acid methyl esters account for about 27%, and there are also small amounts of branched fatty acid methyl esters such as methyl 2-methylundecanoate. The carbon chain length is mainly C17-C19 long chain, covering the C12-C21 range. The total proportion of non-fatty acid components is about 3%, mainly including hexathiocycloalkanes, octathiocycloalkanes and other sulfur-cyclic compounds, as well as nitrogen / phosphorus / boron-containing organic compounds such as N-(1H-tetrazole-5-yl)decanoamide, dipentylethylphosphonate and other cyclic hydrocarbon impurities such as cyclododecyne.
[0033] Example 1 This embodiment provides a method for degreasing and preventing oxidation of oily copper scraps, the method being as follows: Figure 1 As shown, the specific steps include the following: S1. Dissolution and Reduction: N-methylpyrrolidone (NMP) and diethylene glycol ethyl ether (DE) are uniformly mixed at a mass ratio of 80:20 to prepare a composite organic solvent. 1 kg of oil-containing copper scrap and 100 g of the composite organic solvent are loaded into a reaction vessel and the reaction vessel is sealed. Nitrogen gas is introduced into the reaction vessel to purge the air inside and maintain the system pressure at 1.0 MPa. The heating program is started, and the temperature is increased from room temperature to 150°C at a rate of 10°C / min and held for 25 min for the first stage of low-temperature impregnation and oil dissolution. Then, the temperature is increased from 150°C to 200°C at a rate of 10°C / min and held for 30 min for the second stage of high-temperature reduction and passivation, resulting in a solvent-copper scrap mixture.
[0034] S2. Vacuum distillation: After the heat preservation period, gradually release the pressure in the reactor. Start the vacuum system to maintain the absolute pressure inside the reactor at 1.3 kPa. In the first stage, maintain the temperature of the reactor at 150°C and hold for 60 min. Condense and recover the organic composite solvent. In the second stage, raise the temperature from 150°C to 250°C at a rate of 10°C / min and hold for 30 min. Condense and recover the grease. The residue in the reactor is the recovered solid copper shavings.
[0035] The composite organic solvent recovered from S2 can be reused in S1 after being replenished with fresh composite organic solvent to the set ratio.
[0036] In the above processing method, both S1 dissolution and reduction and S2 vacuum distillation can be completed in the same reactor, eliminating the need for material transfer between different containers.
[0037] The oil content, deoiling rate, and oxidation rate of the solid copper scraps obtained in Example S2 are detailed in Table 1.
[0038] Example 2 This embodiment provides a method for degreasing and preventing oxidation of oily copper scraps, specifically including the following steps: S1. Dissolution and Reduction: NMP and DE are uniformly mixed at a mass ratio of 70:30 to prepare a composite organic solvent. 1 kg of oil-containing copper scrap and 100 g of the composite organic solvent are loaded into a reaction vessel and the vessel is sealed. Nitrogen gas is introduced into the reaction vessel to purge the air inside and maintain the system pressure at 0.8 MPa. The heating program is started, and the temperature is increased from room temperature to 160°C at a rate of 10°C / min and held for 20 min for the first stage of low-temperature impregnation and oil dissolution. Then, the temperature is increased from 160°C to 180°C at a rate of 10°C / min and held for 60 min for the second stage of high-temperature reduction and passivation, resulting in a solvent-copper scrap mixture.
[0039] S2. Vacuum distillation: After the heat preservation period, gradually release the pressure in the reactor. Start the vacuum system to maintain the absolute pressure inside the reactor at 1.3 kPa. In the first stage, maintain the temperature of the reactor at 145°C and hold for 40 min. Condense and recover the organic composite solvent. In the second stage, raise the temperature from 145°C to 260°C at a rate of 10°C / min and hold for 25 min. Condense and recover the grease. The residue in the reactor is the recovered solid copper shavings.
[0040] The composite organic solvent recovered from S2 can be reused in S1 after being replenished with fresh composite organic solvent to the set ratio.
[0041] The oil content, deoiling rate, and oxidation rate of the solid copper scraps obtained in Example S2 are detailed in Table 1.
[0042] Example 3 This embodiment provides a method for degreasing and preventing oxidation of oily copper scraps, specifically including the following steps: S1. Dissolution and Reduction: NMP and DE are uniformly mixed at a mass ratio of 65:35 to prepare a composite organic solvent. 1 kg of oil-containing copper scrap and 100 g of the composite organic solvent are loaded into a reaction vessel and the vessel is sealed. Nitrogen gas is introduced into the reaction vessel to purge the air inside and maintain the system pressure at 0.5 MPa. The heating program is started, and the temperature is increased from room temperature to 120°C at a rate of 10°C / min and held for 30 min for the first stage of low-temperature impregnation and oil dissolution. Then, the temperature is increased from 120°C to 190°C at a rate of 10°C / min and held for 40 min for the second stage of high-temperature reduction and passivation, resulting in a solvent-copper scrap mixture.
[0043] S2. Vacuum distillation: After the heat preservation period, gradually release the pressure in the reactor. Start the vacuum system to maintain the absolute pressure inside the reactor at 1.3 kPa. In the first stage, maintain the temperature of the reactor at 140°C and hold for 50 min. Condense and recover the organic composite solvent. In the second stage, raise the temperature from 140°C to 250°C at a rate of 10°C / min and hold for 30 min. Condense and recover the grease. The residue in the reactor is the recovered solid copper shavings.
[0044] The composite organic solvent recovered from S2 can be reused in S1 after being replenished with fresh composite organic solvent to the set ratio.
[0045] The oil content, deoiling rate, and oxidation rate of the solid copper scraps obtained in Example S2 are detailed in Table 1.
[0046] Example 4 This embodiment provides a method for degreasing and preventing oxidation of oily copper scraps. The difference between the other embodiments 1 is that the amount of composite organic solvent used in S1 is different. Specifically, the amount of composite organic solvent used is 50g, and the other operations are basically the same.
[0047] The oil content, deoiling rate, and oxidation rate of the solid copper scraps obtained in Example S2 are detailed in Table 1.
[0048] Example 5 This embodiment provides a method for degreasing and preventing oxidation of oily copper scraps. The difference between the other embodiments 1 is that the amount of composite organic solvent used in S1 is different. Specifically, the amount of composite organic solvent used is 150g. The other operations are basically the same.
[0049] The oil content, deoiling rate, and oxidation rate of the solid copper scraps obtained in Example S2 are detailed in Table 1.
[0050] Example 6 This embodiment provides a method for degreasing and preventing oxidation of oily copper scraps, specifically including the following steps: S1. Pretreatment of copper scrap containing synthetic oil: 1 kg of oily copper scrap is evenly loaded into a centrifugal degreasing machine and centrifuged at 3000 rpm for 10 min to obtain copper scrap containing synthetic oil after the removal of free oil.
[0051] S2, Dissolution and Reduction: Transfer the copper scrap containing synthetic oil obtained in S1 (after removing free oil) to a reactor, add 30g of isopropanol, mix thoroughly, and then seal the reactor. Purge the reactor with nitrogen to purge the air inside and maintain the system pressure at 1.0 MPa. Start the heating program, raising the temperature from room temperature to 200℃ at a rate of 10℃ / min, and hold at this temperature for 40 min to obtain a solvent-copper scrap mixture.
[0052] S3. Vacuum distillation: After the heat preservation is completed, the pressure in the reactor is gradually released. The vacuum system is started to maintain the absolute pressure inside the reactor at 1.3 kPa, and then the temperature is further increased to 260°C and held for 65 min. During this process, the volatiles in the reactor are condensed and recovered to obtain a solvent-oil mixture. The residue in the reactor is the recovered solid copper shavings.
[0053] S4. Under normal pressure, the solvent-oil mixture obtained from the condensation and recovery in S3 is subjected to rotary evaporation at a speed of 50 rpm and a water bath temperature of 80 ℃ to obtain unreacted isopropanol; the residue in the rotary evaporation flask is the recovered oil after the organic solvent has been removed.
[0054] The isopropanol obtained in S4 is further purified and reused in S2 as a solvent and reducing agent. The recovered oil obtained in S4 can be used directly or after further purification.
[0055] The oil content, deoiling rate, and oxidation rate of the solid copper scraps obtained in Example S3 are detailed in Table 1. The deoiling rate was calculated using the following formula:
[0056] In Formula 2 above This indicates the initial oil content of the copper scrap containing synthetic oil, that is, the oil content of the copper scrap before centrifugation. 1 represents the oil content of the copper filings containing synthetic oil obtained after pretreatment and removal of free oil. The oil content is the percentage of solid copper scrap obtained by vacuum distillation.
[0057] Example 7 This embodiment provides a method for degreasing and preventing oxidation of oily copper scrap. The method specifically includes the following steps: S1, Pre-treatment of copper scrap containing synthetic oil: 1 kg of oily copper scrap is evenly loaded into a centrifugal degreasing machine and centrifuged at 3000 rpm for 10 min to obtain copper scrap containing synthetic oil after removing free oil.
[0058] S2, Dissolution and Reduction: Transfer the copper scraps obtained in S1 to a reaction vessel, add 30g of isopropanol, mix thoroughly, and then seal the reaction vessel. Purge nitrogen gas into the reaction vessel to purge the air inside and maintain the system pressure at 0.5 MPa. Start the heating program, raising the temperature from room temperature to 180°C at a rate of 10°C / min, and hold at this temperature for 60 min to obtain a solvent-copper scrap mixture.
[0059] S3. Vacuum distillation: After the heat preservation is completed, the pressure in the reactor is gradually released. The vacuum system is started to maintain the absolute pressure inside the reactor at 1.3 kPa, and then the temperature is further increased to 240°C and held for 80 min. During this process, the volatiles in the reactor are condensed and recovered to obtain a solvent-oil mixture. The residue in the reactor is the recovered solid copper shavings.
[0060] S4. Under normal pressure, the solvent-grease mixture obtained from the condensation and recovery in S3 is subjected to rotary evaporation at a speed of 50 rpm and a water bath temperature of 80 ℃ to obtain unreacted organic solvent; the residue in the rotary evaporation flask is the recovered grease from which the organic solvent has been removed.
[0061] The oil content, deoiling rate, and oxidation rate of the solid copper scraps obtained in Example S3 are detailed in Table 1.
[0062] Example 8 This embodiment provides a method for degreasing and preventing oxidation of oily copper scraps, which specifically includes the following steps: S1. Pretreatment of copper scrap containing synthetic oil: 1 kg of oily copper scrap is evenly loaded into a centrifugal degreasing machine and centrifuged at 3000 rpm for 10 min to obtain copper scrap containing synthetic oil after the removal of free oil.
[0063] S2, Dissolution and Reduction: Transfer the copper scraps obtained in S1 to a reaction vessel, add 30g of isopropanol, mix thoroughly, and then seal the reaction vessel. Purge nitrogen gas into the reaction vessel to purge the air inside and maintain the system pressure at 0.8 MPa. Start the heating program, raising the temperature from room temperature to 190℃ at a rate of 10℃ / min, and hold at this temperature for 50 min to obtain a solvent-copper scrap mixture.
[0064] S3. Vacuum distillation: After the heat preservation is completed, the pressure in the reactor is gradually released. The vacuum system is started to maintain the absolute pressure inside the reactor at 1.3 kPa, and then the temperature is further increased to 300°C and held for 80 min. During this process, the volatiles in the reactor are condensed and recovered to obtain a solvent-oil mixture. The residue in the reactor is the recovered solid copper shavings.
[0065] S4. Under normal pressure, the solvent-grease mixture obtained from the condensation and recovery in S3 is subjected to rotary evaporation at a speed of 50 rpm and a water bath temperature of 80 ℃ to obtain unreacted organic solvent; the residue in the rotary evaporation flask is the recovered grease from which the organic solvent has been removed.
[0066] The oil content, deoiling rate, and oxidation rate of the solid copper scraps obtained in Example S3 are detailed in Table 1.
[0067] Example 9 This embodiment provides a method for degreasing and preventing oxidation of oily copper scraps. The difference between this method and Example 6 is that the specific type of organic solvent used in S2 is different. The organic solvent is ethanol. The rest of the operations are basically the same.
[0068] The oil content, deoiling rate, and oxidation rate of the solid copper scraps obtained in Example S3 are detailed in Table 1.
[0069] Example 10 This embodiment provides a method for degreasing and preventing oxidation of oily copper scraps. The difference between this method and Example 6 is that the specific type of organic solvent used in S2 is different. Methanol is specifically selected as the organic solvent. The rest of the operations are basically the same.
[0070] The oil content, deoiling rate, and oxidation rate of the solid copper scraps obtained in Example S3 are detailed in Table 1.
[0071] Example 11 This embodiment provides a method for degreasing and preventing oxidation of oily copper scraps. The difference between this method and Example 6 is that the amount of organic solvent used in S2 is different. Specifically, the amount of organic solvent used is 20g of isopropanol, while the rest of the operation is basically the same.
[0072] The oil content, deoiling rate, and oxidation rate of the solid copper scraps obtained in Example S3 are detailed in Table 1.
[0073] Example 12 This embodiment provides a method for degreasing and preventing oxidation of oily copper scraps. The difference between this method and Example 6 is that the amount of organic solvent used in S2 is different. Specifically, the amount of organic solvent used is 50g of isopropanol, while the rest of the operation is basically the same.
[0074] The oil content, deoiling rate, and oxidation rate of the solid copper scraps obtained in Example S3 are detailed in Table 1.
[0075] Comparative Example 1 This comparative example provides a method for degreasing and preventing oxidation of oily copper scraps. The difference between this method and Example 1 is that in the dissolution and reduction step S1, the second stage of high-temperature reduction passivation is not performed. Instead, only the first stage of low-temperature impregnation and oil dissolution is performed, and the mixing time of this stage is extended. Specifically, the first stage of low-temperature impregnation and oil dissolution is carried out at 150°C for 55 minutes. The remaining operations are basically the same.
[0076] The oil content, deoiling rate, and oxidation rate of the solid copper scraps obtained in this comparative example are detailed in Table 2.
[0077] Comparative Example 2 This comparative example provides a method for degreasing and preventing oxidation of oily copper scraps. The difference between this method and Example 1 is that the low-temperature wetting and oil-dissolving temperature in the first stage of the S1 dissolution and reduction step is different. Specifically, the low-temperature wetting and oil-dissolving temperature in the first stage is carried out at 110°C, while the other operations are basically the same.
[0078] The oil content, deoiling rate, and oxidation rate of the solid copper scraps obtained in this comparative example are detailed in Table 2.
[0079] Table 1. Operating parameters and performance data of the obtained solid copper chips for each embodiment.
[0080] Comparative Example 3 This comparative example provides a method for degreasing and preventing oxidation of oily copper scraps. The difference between this method and Example 1 is that in the S1 dissolution and reduction step, the first stage of low-temperature wetting and oil dissolution is not carried out. Instead, the second stage of high-temperature reduction and passivation is carried out directly, and the mixing time of this stage is extended. Specifically, the second stage of high-temperature reduction and passivation is carried out at 200°C for 55 minutes. The remaining operations are basically the same.
[0081] The oil content, deoiling rate, and oxidation rate of the solid copper scraps obtained in this comparative example are detailed in Table 2.
[0082] Comparative Example 4 This comparative example provides a method for degreasing and preventing oxidation of oily copper scraps. The difference between this method and Example 1 is that the temperature of the second stage of low-temperature impregnation and oil dissolution is different in the S1 dissolution and reduction step. Specifically, the second stage of low-temperature impregnation and oil dissolution is carried out at 210°C, while the other operations are basically the same.
[0083] The oil content, deoiling rate, and oxidation rate of the solid copper scraps obtained in this comparative example are detailed in Table 2.
[0084] Comparative Example 5 This comparative example provides a method for degreasing and preventing oxidation of oily copper scraps. The difference between this method and Example 1 is that the pressure of the inert atmosphere is different in the dissolution and reduction step S1. Specifically, the two-stage gradient heating and mixing in this step are carried out at 0.1 MPa, and the other operations are basically the same.
[0085] The oil content, deoiling rate, and oxidation rate of the solid copper scraps obtained in this comparative example are detailed in Table 2.
[0086] Comparative Example 6 This comparative example provides a method for degreasing and preventing oxidation of oily copper scraps. The difference between this method and Example 1 is that the solvent used in the dissolution and reduction step S1 is different. Only a single solvent is used, specifically 100g of NMP as the solvent. The rest of the operations are basically the same.
[0087] The oil content, deoiling rate, and oxidation rate of the solid copper scraps obtained in this comparative example are detailed in Table 1.
[0088] Comparative Example 7 This comparative example provides a method for degreasing and preventing oxidation of oily copper scraps. The difference between this method and Example 1 is that the solvent used in the dissolution and reduction step S1 is different. Only a single solvent is used, specifically 100g of DE as the solvent. The rest of the operations are basically the same.
[0089] The oil content, deoiling rate, and oxidation rate of the solid copper scraps obtained in this comparative example are detailed in Table 2.
[0090] Comparative Example 8 This comparative example provides a method for degreasing and preventing oxidation of oily copper scraps. The difference between this method and Example 6 is that centrifugal degreasing is not performed, and the dissolution and reduction with organic solvents under heating, pressure, and an inert atmosphere are not carried out. That is, the S1 and S2 operations are omitted. The copper scraps containing synthetic oil are placed in a reaction vessel, the vacuum system is started, and the absolute pressure inside the reaction vessel is maintained at 1.3 kPa. Then, the temperature is further raised to 260°C and held for 3 hours. During this process, the volatiles in the reaction vessel are condensed and recovered to obtain a solvent-oil mixture. The residue in the reaction vessel is the recovered solid copper scraps.
[0091] The oil content, deoiling rate, and oxidation rate of the solid copper scraps obtained in this comparative example are detailed in Table 2.
[0092] Comparative Example 9 This comparative example provides a method for degreasing and preventing oxidation of oily copper scraps. The difference between this method and Example 6 is that the copper scraps are not dissolved and reduced with organic solvents under heating, pressure and an inert atmosphere, i.e., the S2 operation is omitted. The remaining operations are basically the same.
[0093] The oil content, deoiling rate, and oxidation rate of the solid copper scraps obtained in this comparative example are detailed in Table 2.
[0094] Comparative Example 10 This comparative example provides a method for degreasing and preventing oxidation of oily copper scraps. The difference between this method and Example 6 is that centrifugal degreasing is not performed, i.e., operation S1 is omitted. The remaining operations are basically the same.
[0095] The oil content, deoiling rate, and oxidation rate of the solid copper scraps obtained in this comparative example are detailed in Table 2.
[0096] Comparative Example 11 This comparative example provides a method for degreasing and preventing oxidation of oily copper scrap. The difference from Example 6 is that isopropanol is not added as an organic solvent in step S2. Specifically, in S2, the centrifugally degreased copper scrap is transferred to a reaction vessel, mixed thoroughly, and then the reaction vessel is sealed. Nitrogen gas is introduced into the reaction vessel to purge the air inside and maintain the system pressure at 1.0 MPa. The heating program is started, raising the temperature from room temperature to 200°C at a rate of 10°C / min and holding at that temperature for 40 minutes. The remaining operations are essentially the same.
[0097] The oil content, deoiling rate, and oxidation rate of the solid copper scraps obtained in this comparative example are detailed in Table 2.
[0098] Comparative Example 12 This comparative example provides a method for degreasing and preventing oxidation of oily copper scraps. The difference between this method and Example 6 is that the dissolution and reduction temperature in S2 is different. Specifically, the oily copper scraps after centrifugation and degreasing are mixed with isopropanol at 170°C. The remaining operations are basically the same.
[0099] The oil content, deoiling rate, and oxidation rate of the solid copper scraps obtained in this comparative example are detailed in Table 2.
[0100] Comparative Example 13 This comparative example provides a method for degreasing and preventing oxidation of oily copper scraps. The difference between this method and Example 6 is that the dissolution and reduction temperature in S2 is different. Specifically, the oily copper scraps after centrifugation and degreasing are mixed with isopropanol at 210°C. The remaining operations are basically the same.
[0101] The oil content, deoiling rate, and oxidation rate of the solid copper scraps obtained in this comparative example are detailed in Table 2.
[0102] Comparative Example 14 This comparative example provides a method for degreasing and preventing oxidation of oily copper scrap. The difference between this method and Example 6 is that the dissolution and reduction step in S2 is omitted, and isopropanol is added during the vacuum distillation process in S3. Specifically, 30g of isopropanol and 1kg of pretreated oily copper scrap are added to the reaction vessel and mixed evenly. The temperature is increased from room temperature to 260°C at a rate of 10°C / min and held for 65min to obtain a solvent-copper scrap mixture. The remaining operations are basically the same.
[0103] The oil content, deoiling rate, and oxidation rate of the solid copper scraps obtained in this comparative example are detailed in Table 2.
[0104] Comparative Example 15 This comparative example provides a method for degreasing and preventing oxidation of oily copper scraps. The difference between this method and Example 6 is that the dissolution and reduction operation in S2 is omitted, and the vacuum distillation in S3 is replaced with drying. The specific drying conditions are as follows: drying is carried out under an inert atmosphere at a temperature of 120°C for 60 minutes. The remaining operations are basically the same.
[0105] The oil content, deoiling rate, and oxidation rate of the solid copper scraps obtained in this comparative example are detailed in Table 2.
[0106] Table 2 shows the operating parameters and performance data of the obtained solid copper chips for each comparative example.
[0107] The following conclusions can be drawn from Tables 1 and 2: (1) Comparing Example 1 with Comparative Example 1, it can be seen that if only the first stage of penetration and dissolution is carried out, the added organic solvent fails to generate reducing hydrogen at the temperature of this stage, so it cannot passivate the chemically adsorbed oil and fatty acids in the synthetic grease. As a result, the solid copper scrap obtained after vacuum distillation has a high oil content, i.e. a low deoiling rate, and a high oxidation rate. Comparing Example 1 with Comparative Example 3, it can be seen that if only the second stage of passivation reduction is carried out during the dissolution and reduction process, the free oil contained in the oily copper scrap will seriously interfere with the subsequent dissolution and reduction and vacuum distillation process. As a result, the solid copper scrap obtained after vacuum distillation has a high oil content, a low deoiling rate, and a high oxidation rate.
[0108] (2) A comparison of the parameters in Examples 6-9 and Comparative Examples 12-13 shows that temperature control is crucial during the dissolution-reduction process in step 2. At 170°C and below, the resulting solid copper scrap has a higher oil content, i.e., a lower deoiling rate and a higher oxidation rate. The reasoning is as follows: at lower dissolution-reduction temperatures, the fatty acids contained in the synthetic oil in the copper scrap hardly react with the organic solvent and do not produce active hydrogen. Therefore, the oxidizing property of the fatty acids and their binding with the copper scrap cannot be weakened. In the subsequent vacuum distillation process, the fatty acids adhere to the surface of the copper scrap, thus exacerbating the oxidation problem. Conversely, if the temperature during the dissolution-reduction process is increased to 210°C and above, the temperature is too high and the process is under pressure. The organic solvent will easily polymerize and coke with the oil and adhere to the copper scrap, which is not conducive to deoiling in the subsequent vacuum distillation process. Therefore, the dissolution-reduction temperature is controlled at 180°C to 200°C.
[0109] (3) As can be seen from the parameter comparison of Examples 1-3 and Comparative Example 5, pressure is crucial during the dissolution and reduction process. At 180℃~200℃, the evaporation of organic solvent will be aggravated, which is not conducive to the full contact between organic solvent and oily copper scrap, making it difficult for organic solvent to play its role in degreasing oil. By increasing the pressure, the evaporation of organic solvent is reduced, and the organic solvent is kept in a liquid state as much as possible, so that the organic solvent can have full contact with oily copper scrap. Furthermore, in the pretreatment method for removing free oil, as can be seen from the parameter comparison of Examples 1 and Examples 4-5, further increasing the amount of organic solvent has a weaker promoting effect on further reducing the oil content, further improving the degreasing rate, and further reducing the oxidation rate. Excessive use of organic solvent will also increase the degreasing cost. Therefore, the mass ratio of synthetic oily copper scrap to composite organic solvent is 100:5~15.
[0110] (4) As can be seen from the comparison of parameters between Example 6 and Comparative Example 10, if the copper scrap containing synthetic oil is not centrifuged to remove free oil before vacuum distillation, the free oil in this part will seriously interfere with the subsequent dissolution, reduction and vacuum distillation process, resulting in a high oil content, low deoiling rate and high oxidation rate of the obtained solid copper scrap.
[0111] (5) From Examples 1-3 and Comparative Examples 6-7, compared with using a single organic solvent, the use of a composite organic solvent resulted in the following: If only NMP was used, the surface of the copper scrap was coated with non-polar free oil. NMP is highly polar but has a high surface tension, making it difficult to quickly penetrate the oil film. The solvent could not fully contact the inner layer of bound oil, resulting in incomplete removal of the bound oil. If only DE was used, it could only dissolve the free oil and was completely ineffective against fatty acid copper soaps and chemically adsorbed bound oil, resulting in insufficient oil removal depth. The combined use of both can achieve a synergistic effect of efficient penetration, deep dissolution, and reduction oil removal, ensuring that the oil removal rate and copper scrap quality meet the standards.
[0112] The present invention and its embodiments have been described above illustratively. This description is not restrictive, and the figures shown are only one embodiment of the present invention; the actual structure is not limited thereto. Therefore, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, such designs should fall within the protection scope of the present invention.
Claims
1. A method for degreasing and preventing oxidation of oily copper scraps, characterized in that, include: Synthetic oil-containing copper scraps are mixed with an organic solvent under an inert atmosphere and with a two-stage gradient temperature increase. The first stage of mixing is used to remove free oil from the synthetic oil-containing copper scraps. The second stage of mixing is at a temperature of 180~200℃ to obtain a solvent-copper scrap mixture. The organic solvent used includes a main solvent and a co-solvent, and can generate reducing hydrogen during the mixing process. The solvent-copper shavings mixture was distilled under an inert atmosphere and a vacuum of ≤10 kPa to obtain solid copper shavings.
2. A method for degreasing and preventing oxidation of oily copper scraps, characterized in that, include: The copper scrap containing synthetic oil is subjected to a free oil removal treatment to reduce the content of free oil, resulting in copper scrap containing synthetic oil with the free oil removed. The copper scrap containing synthetic oil with the free oil removed is mixed with an organic solvent at 180~200℃ and under an inert atmosphere to obtain a solvent-copper scrap mixture, wherein the organic solvent used can generate reducing hydrogen during the mixing process. The solvent-copper shavings mixture was distilled under an inert atmosphere and a vacuum of ≤10 kPa to obtain solid copper shavings.
3. The method for degreasing and preventing oxidation of oily copper scraps according to claim 1 or 2, characterized in that, The synthetic oil-containing copper scraps and organic solvents are mixed at 180~200℃ for 30~60 min and under a pressure of 0.5~1.0 MPa.
4. The method for degreasing and preventing oxidation of oily copper scraps according to claim 1, characterized in that, The process involves mixing copper scrap containing synthetic oil with an organic solvent under an inert pressurized atmosphere and a two-stage gradient heating. Specifically, the mass ratio of the copper scrap containing synthetic oil to the organic solvent is 100:5~15.
5. The method for degreasing and preventing oxidation of oily copper scraps according to claim 4, characterized in that, The total mass of the main solvent and the co-solvent is 100%, wherein the main solvent accounts for 65% to 80%, and the main solvent is N-methylpyrrolidone, and the co-solvent is diethylene glycol ethyl ether.
6. The method for degreasing and preventing oxidation of oily copper scraps according to claim 5, characterized in that, The synthetic oil-containing copper scraps were mixed with an organic solvent under an inert pressure atmosphere and a two-stage gradient temperature increase. Specifically, the mixing temperature in the first stage was 120~160℃ and the mixing time was 20~30min, while the mixing time in the second stage was 30~60min.
7. The method for degreasing and preventing oxidation of oily copper scraps according to any one of claims 4-6, characterized in that, The solvent-copper shavings mixture is distilled under an inert atmosphere and a vacuum of ≤10kPa. Specifically, the distillation process includes a two-stage gradient temperature distillation, wherein the first stage distillation temperature is 140~150℃ and the distillation time is 40~60min, and the second stage distillation temperature is 240~260℃ and the distillation time is 25~35min.
8. The method for degreasing and preventing oxidation of oily copper scraps according to claim 2, characterized in that, The organic solvent used is selected from any one or a combination of isopropanol, methanol, and ethanol, and the mass ratio of the synthetic oil-containing copper scrap to the organic solvent is 100:2~5.
9. The method for degreasing and preventing oxidation of oily copper scraps according to claim 8, characterized in that, The solvent-copper scrap mixture is distilled under an inert atmosphere and a vacuum of ≤10 kPa. Specifically, the distillation temperature is 240~260℃ and the distillation time is 65~95 min.
10. The method for degreasing and preventing oxidation of oily copper scraps according to any one of claims 2, 8-9, characterized in that, The process of removing free oil from copper scrap containing synthetic oil specifically involves centrifugal deoiling.