A steel cord preparation and a process for recycling a steel cord scrap rubber composite

Abstract

This invention discloses a process for preparing steel cord and recycling waste steel wire rubber composite components, belonging to the field of steel cord production and recycling technology. The process includes: using scrap steel as raw material to process into cord steel billets, which are then rolled to obtain steel wires; immersing the wires in a pretreatment solution for surface film formation to create a protective film on the wire surface; coating the wire surface with an alloy coating; wet drawing followed by irregular twisting; immersing the waste steel wire-rubber composite component in a compound decoupling agent for targeted decoupling to obtain rubber and coated waste steel wires; immersing the coated waste steel wires in a composite recycling solution for flowing soaking to obtain separated steel wires and a coating ion solution; cleaning and drying the rubber and separated steel wires for recycling; and stepwise precipitation of the coating ion solution followed by electrolytic refining to obtain alloy metal. This invention has the advantages of low production pollution and high rubber permeability, while also enabling full-value recycling of waste steel wire rubber composite components, resulting in high resource utilization.

Description

Technical Field

[0001] This invention relates to a process for preparing steel cord and recycling waste steel wire rubber composites, belonging to the field of steel cord production technology and recycling technology. Background Technology

[0002] Steel cord, as a core reinforcing material for products such as tires and rubber hoses, directly affects the safety and lifespan of end products. Current steel cord production and recycling methods suffer from the following drawbacks: First, in the steel cord production process, traditional converter processes use molten iron as raw material, resulting in CO2 emissions of 2.0-2.5 tons per ton of steel produced, which does not comply with the "dual carbon" policy requirements. Simultaneously, existing steel cords mostly employ a tightly twisted circular structure with a rubber penetration rate of less than 85%, leading to insufficient bonding between the steel cord and rubber interface and a tendency for delamination and degumming. Furthermore, in the field of waste steel cord recycling, traditional methods often involve incineration, mechanical crushing, or strong acid immersion. Incineration produces pollutants such as dioxins, mechanical crushing damages the steel wire's performance, and strong acid immersion causes rubber degradation, resulting in a resource utilization rate of less than 60% and posing a serious risk of secondary pollution. Additionally, traditional methods cannot achieve the complete recycling of waste steel wire rubber composites. For example, waste cord recycling technologies (such as patent CN202510370020.6) only focus on metal recovery, neglecting the non-destructive regeneration of rubber, and also cannot guarantee the utilization rate of recycled resources. Therefore, developing a recycling process that minimizes production pollution, increases rubber penetration, covers a wide range of recyclable materials, and maximizes resource utilization has become a pressing technical challenge for the industry. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a process for the preparation of steel cord and the recycling of waste steel wire rubber composite parts, which has the advantages of low production pollution and high rubber permeability, and at the same time can achieve full-value recycling of waste steel wire rubber composite parts resources, resulting in high resource utilization.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0005] A process for preparing and recycling steel wire-rubber composite components includes the following steps:

[0006] Step a: Using scrap steel as raw material, the steel billet is processed into cord steel billet, which is then rolled into steel wire. The CO2 emissions for each ton of steel produced are ≤0.9 tons.

[0007] Step b: Immerse the steel wire in the pretreatment solution to form a surface film, thereby forming a protective film on the surface of the steel wire.

[0008] Step c: Coating the pretreated steel wire with a copper-zinc alloy coating to obtain coated steel wire;

[0009] Step d: The coated steel wire is wet-drawn, then twisted into an irregular shape, and finally combined with rubber to obtain a steel wire-rubber composite.

[0010] Step e involves immersing the used waste steel wire-rubber composite into a compound decoupling agent for targeted decoupling, thereby achieving non-destructive separation of the rubber and steel wire, resulting in rubber and waste steel wire with a coating.

[0011] Step f involves immersing the coated waste steel wire into a composite recycling solution for continuous soaking, allowing the coating to dissolve from the steel wire and separating the steel wire from the coating to obtain a solution of separated steel wire and coating ions.

[0012] Step g involves cleaning and drying the rubber obtained in step e and the separated steel wire obtained in step f, then recycling them, and electrolytically refining the plating ion solution obtained in step f after stepwise precipitation to obtain alloy metal.

[0013] In step b, the pretreatment solution contains the following components by mass percentage: 4-6% titanium lactate, 10-12% phytic acid, 2-4% potassium sodium tartrate, and 1-3% boric acid, with the remainder being deionized water. The surface film formation time is 0.5-2 min, and the protective film thickness is 0.05-0.2 μm. The protective film is a phytic acid-Ti chelate film with an organic-inorganic hybrid structure. It is ultra-thin and non-brittle, allowing it to deform further with the steel wire, providing both corrosion resistance and not affecting the coating of subsequent layers. Titanium lactate in the treatment solution provides the titanium source, forming a stable chelate with phytic acid to provide the inorganic framework for the film. Compared to other titanium sources, it is non-volatile and non-corrosive, has a low unit price, and can form a film in weakly acidic to near-neutral environments, reducing the risk of corrosion to the steel wire substrate. Phytic acid, as an organic ligand, forms a three-dimensional chelate network with titanium and iron on the steel wire surface, improving the flexibility and adhesion of the film. Sodium potassium tartrate, a complexing stabilizer, delays the hydrolysis of titanium lactate, ensuring preferential chelation and optimizing film uniformity. Boric acid, as a pH buffer, maintains system pH stability, preventing uneven film formation due to pH fluctuations. Deionized water is used as the solvent. Ultrasound promotes uniform deposition of chelates; bubble agitation and uniform bubble distribution prevent excessively thick local films while avoiding excessive ultrasonic erosion.

[0014] The film formation mechanism is that titanium and phytic acid chelate to form a stable titanium-phytic acid six-membered ring structure. At the same time, the hydroxyl groups of phytic acid coordinate with Fe ions on the surface of the steel wire, and finally a three-dimensional hybrid film of "Fe-phytic acid-Ti" is formed on the surface of the steel wire. The film is dense and rich in active groups such as hydroxyl and phosphate groups.

[0015] During coating, the metal ions (such as zinc and copper) in the coating can undergo coordination reactions with these active groups to form stable chemical bonds. Simultaneously, ultrasonic assistance creates uniform micron-sized pits on the film surface, providing mechanical interlocking sites for the coating and significantly improving adhesion. Furthermore, the long-chain molecules of phytic acid in the film can physically entangle with rubber molecular chains, while the active groups on the film surface can undergo cross-linking reactions with vulcanizing agents (such as sulfur and accelerators) in the rubber, strengthening interfacial adhesion.

[0016] In step c, the thickness of the copper-zinc alloy coating is 0.8~2.5 μm; the zinc content in the copper-zinc alloy coating is 60~99.5 wt%, and the copper content is 0.5~40 wt%, or the zinc content is 30~40 wt%, and the copper content is 60~70 wt%. The copper-zinc alloy coating can also be replaced with a composite coating, specifically, an alloy coating composed of copper or zinc, or copper-zinc and one or more other elements, is plated onto the surface of the pretreated steel wire. These other elements include nickel, iron, manganese, cobalt, tin, silver, lanthanum, samarium, phosphorus, and molybdenum; the proportion of other elements in the composite coating is ≤5%.

[0017] In step d, the wet drawing and subsequent irregular twisting of the coated steel wire specifically involves: wet drawing the coated steel wire to a diameter of 0.10~0.60 mm, then using a 1+n+2n irregular twisting structure. The core strand diameter is d1, the middle layer diameter is d2, and the outer layer diameter is d3, satisfying d1>d2>d3, and 0.05≤d1-d2≤0.08, 0.05≤d2-d3≤0.1. The twist pitch is 15~25 mm, and a 0.05~0.1 mm rubber-impregnated gap is formed between the outer layer strands. The resulting steel cord has a breaking strength ≥1000N, an elongation at break ≥2.0%, a rubber permeability ≥95%, and shows no red rust after 72 hours of neutral salt spray testing. This invention utilizes an irregular twisted structure, combined with differences in monofilament diameter, to create a controllable rubber penetration gap, thereby increasing the rubber penetration rate to over 95%. This solves the problem of insufficient bonding between traditional tightly packed steel cords and rubber, which leads to easy delamination.

[0018] In step e, the mass percentages of the components in the compound decoupling agent are: 3-5% silane-modified ethylenediamine, 2-4% polyethylene glycol 400, 60-70% ethanol, and the remainder is deionized water. The specific targeted decoupling process is as follows: soaking at 30-50℃ for 90-120 min, assisted by low-frequency ultrasound at 20-40 kHz. The decoupling active ingredient in the compound decoupling agent is silane-modified ethylenediamine, which specifically reacts with the interface CuxS to break chemical bonds. Polyethylene glycol 400 acts as a permeation regulator, controlling the permeation rate of the active ingredient, acting only on the interfacial adhesive layer without penetrating the rubber matrix. Ethanol and water are environmentally friendly solvents. Low-frequency ultrasound accelerates interfacial decoupling without damaging the matrix. Using intermittent mode instead of continuous ultrasound avoids the accumulation of ultrasonic energy that could cause localized heating of the soaking solution, while allowing sufficient time for the interfacial decoupling reaction, balancing separation efficiency and material non-destructiveness.

[0019] In step f, the components of the composite recovery solution are: 150-160 g / L ammonium persulfate, 100-110 g / L aminotrimethylenephosphonic acid, and the balance being water; the temperature of the flowing immersion is 40-45℃, and the pH is 2.2-2.8. The filtrate after use of the composite recovery solution can be recycled as a separation solution for coated steel by adding ammonium persulfate and aminotrimethylenephosphonic acid.

[0020] Ammonium persulfate, acting as the primary oxidant, directionally oxidizes copper, zinc, and copper-zinc alloy coatings under specific acidity, converting the coating metal into ionic form without reacting with the iron substrate of the steel wire. Phosphorus in the coating is stripped from the coating along with other metal ions and enters the solution as oxyacid anions. Aminotrimethylene phosphonic acid, as a dual-function component for chelation and corrosion inhibition, rapidly encapsulates metal ions to form stable chelates, while simultaneously forming an ultra-thin protective film on the surface of the steel wire substrate. This solution requires no complex additives, achieving efficient coating stripping while protecting the steel wire substrate through natural synergistic effects between components, and its preparation and usage are extremely simple.

[0021] In step g, the specific process of stepwise precipitation is as follows: the solution containing plating ions is filtered to remove debris and other impurities, sodium hydroxide is added to the solution and stirred, the pH is adjusted to 4.0~4.5, and copper hydroxide precipitate is obtained by static filtration. Sodium hydroxide is added to the filtrate to adjust the pH to 5.5~6.5, and zinc hydroxide precipitate is obtained by static filtration.

[0022] In step g, the specific process of electrolytic refining is as follows: dilute sulfuric acid and dilute hydrochloric acid are added to copper hydroxide and zinc hydroxide respectively, and stirred until dissolved to obtain copper sulfate electrolyte and zinc chloride electrolyte. The copper sulfate electrolyte is electrolyzed with an insoluble plate as the anode and pure copper as the cathode to obtain copper in the coating. The zinc chloride electrolyte is electrolyzed with an insoluble plate as the anode and pure zinc as the cathode to obtain zinc in the coating. The copper and zinc can be directly recovered after cleaning and drying.

[0023] This invention utilizes the differences in precipitation characteristics of various ions to promote separation. For example, silver, tin, molybdenum, iron, and rare earth ions can precipitate at low pH values. At pH less than 3.6, after filtering the precipitate, the ion concentration in the solution is measured to be 0 ppm for silver, tin, molybdenum, and rare earth ions, and 0.0011 ppm for iron ions, indicating that the solution no longer contains these metal ions. The pH is adjusted to 4.0-4.5, and after standing and filtration, copper hydroxide precipitate is obtained. Sodium hydroxide is added to the filtrate to adjust the pH to 5.5-6.5, and after standing and filtration, zinc hydroxide precipitate is obtained. Other ion precipitates, such as manganese, cobalt, and nickel, precipitate at neutral or higher pH values. By precisely adjusting the pH of the separation solution, stepwise precipitation separation of Cu²⁺ and Zn²⁺ is achieved. The precipitate products are then electrolytically refined to obtain high-purity copper and zinc. Furthermore, aminotrimethylenephosphonic acid exhibits a significantly reduced chelating ability for metal ions at pH > 3.5, allowing for the rapid release of Cu²⁺ and Zn²⁺ ions without the need for additional chelating agents. It boasts high separation efficiency, is environmentally friendly and low-cost, and features an extremely simple process. It avoids the waste of metal resources found in traditional recycling methods, achieving a resource recovery rate of ≥98%.

[0024] The rubber recovered in step e and the steel wire recovered in step g can be reused in step d, and the alloy metal recovered in step g can be reused in step c. In summary, the entire production process achieves a closed-loop environmental protection model of "production-use-recycling".

[0025] Beneficial Effects: This invention discloses a process for preparing and recycling steel wire-rubber composite parts, which obtains cord steel billets from 100% scrap steel, and reduces CO2 emissions by more than 60% compared to traditional processes; the steel cord adopts an irregular twisted structure and pre-plating pretreatment, with a rubber penetration rate of ≥95%, and no red rust after 78 hours of neutral salt spray testing, solving the problems of insufficient rubber penetration and low corrosion resistance in traditional products, and improving the service life of end products; it achieves full-value recycling of rubber, copper, zinc and iron in waste cord, with a resource recovery rate of ≥98%, which is more than 30% higher than traditional recycling methods, significantly reducing resource waste. At the same time, the separation and recycling process is simple and does not involve incineration, avoiding secondary pollution, and complying with the "dual carbon" policy and environmental protection requirements. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of the coated steel wire after irregular twisting in this invention. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to illustrate the technical solution of the present invention more clearly, and should not be used to limit the scope of protection of the present invention.

[0028] Example 1

[0029] This invention discloses a process for preparing and recycling steel wire-rubber composite parts, comprising the following steps:

[0030] (1) Steel cord preparation:

[0031] ① Scrap steel billet production: 5 mm steel billets are produced from 100% scrap steel. The CO2 emissions are 0.85 tons for every ton of steel produced.

[0032] ② Pretreatment: The 1.80 mm steel wire after billet rolling was immersed in a pretreatment solution with ultrasound. The solution contained 5% titanium lactate, 11% phytic acid, 3% sodium potassium tartrate, 2% boric acid, and the balance was deionized water. The pH was 5.5, the solution temperature was 53℃, the ultrasonic power was 225W, the frequency was 29 kHz, and the surface film was formed by compressed air bubble stirring for 1.2 min, resulting in a protective film with a thickness of 0.12 μm.

[0033] ③ Composite coating: After the pretreated steel wire is dried under nitrogen protection, the steel wire is first plated with copper, then with zinc, and then diffusion alloyed to obtain a copper-zinc alloy coating with a zinc content of 89 wt%, a copper content of 11 wt%, and a coating thickness of 1.4 μm.

[0034] ④ Irregular twisting: 1.80 mm copper-zinc alloy coated steel wire is wet-drawn to diameters of 0.38 mm, 0.32 mm, and 0.25 mm respectively, and then twisted in a 1+6+12 structure. The core strand d1 = 0.38 mm, the middle layer d2 = 0.32 mm, the outer layer d3 = 0.25 mm, the twist pitch is 20 mm, and the glue penetration gap between the outer layer monofilaments is 0.08 mm. See the detailed diagram. Figure 1 The steel cord prepared by this invention has a breaking force ≥1000N, an elongation at break ≥2.0%, a rubber permeability ≥95%, and shows no red rust after 72 hours of neutral salt spray testing.

[0035] The cords are used in the tire carcass layer, assembled in heavy-duty vehicle tires, and used until the tire is scrapped. The carcass layer is then separated and retained for recycling.

[0036] (2) Recycling of waste steel wire-rubber composite parts:

[0037] ① Targeted decoupling: The waste steel cord-rubber composite is immersed in a decoupling agent containing 4% silane-modified ethylenediamine, 3% polyethylene glycol, 65% ethanol, and the balance water. It is kept at 45℃ for 100 min and then assisted by 30 kHz low-frequency ultrasound with an ultrasonic power density of 0.4 W / cm², in an intermittent mode of 5 min every 15 min, to achieve non-destructive separation of rubber and steel wire.

[0038] ② Separation of the coating from the steel substrate: The waste steel wire with the coating is immersed in a flowing aqueous solution of 155 g / L ammonium persulfate and 105 g / L aminotrimethylenephosphonic acid at a temperature of 43℃ and a pH of 2.5. This achieves the separation of the steel wire from the coating.

[0039] ③ Resource Recycling: a) After separation, the rubber can be directly recycled after cleaning and drying; b) Waste steel wire detached from the coating can be recycled after cleaning and drying; c) The solution containing copper and zinc ions is filtered to remove debris and other impurities. Sodium hydroxide is added to the solution and stirred to adjust the pH to 4.3. After standing and filtration, copper hydroxide precipitate is obtained. Sodium hydroxide is added to the filtrate to adjust the pH to 6.0. After standing and filtration, zinc hydroxide precipitate is obtained. Dilute sulfuric acid and dilute hydrochloric acid are added to copper hydroxide and zinc hydroxide respectively, and stirred until dissolved to obtain 90.2 g / L copper sulfate and 156.4 g / L zinc chloride electrolytes. The copper sulfate electrolyte uses a titanium plate as the anode and pure copper as the cathode, with a current density of 18 A / dm² and a temperature of 32℃ to electrolyze and obtain copper from the coating. The zinc chloride electrolyte uses graphite as the anode and pure zinc as the cathode, with a current density of 23 A / dm² and a temperature of 43℃ to electrolyze and obtain zinc from the coating. After cleaning and drying, the rubber can be directly recycled. After separation, the rubber can be directly recycled after cleaning and drying.

[0040] The relevant testing items during the production process are shown in Table 1. All testing items were conducted in accordance with relevant national standards or industry specifications. The rubber penetration rate of the steel wire cord reached 96.2%, the breaking strength was 2610 N, and the elongation was 2.6%. The tensile strength of the separated rubber was 24.1 MPa, with a retention rate of 97.8%. After decoupling from the rubber, the integrity rate of the steel wire coating was 99.5%, and the metal resource recovery rate reached 98.5%.

[0041] Table 1. Results of relevant parameter testing during production.

[0042]

[0043] Example 2

[0044] This invention discloses a process for preparing and recycling steel wire-rubber composite parts, comprising the following steps:

[0045] (1) Steel cord preparation:

[0046] ① Scrap steel billet production: 5 mm steel billets are produced from 100% scrap steel. The CO2 emissions are 0.85 tons for every ton of steel produced.

[0047] ② Pretreatment: The 1.80 mm steel wire after billet rolling was immersed in a pretreatment solution with ultrasound. The solution contained 4% titanium lactate, 12% phytic acid, 2% potassium sodium tartrate, 1% boric acid, and the balance was deionized water. The pH was 5.5, the solution temperature was 53℃, the ultrasonic power was 225W, the frequency was 29 kHz, and the surface film was formed by compressed air bubble stirring for 0.5 min, resulting in a protective film with a thickness of 0.05 μm.

[0048] ③ Composite coating: After the pretreated steel wire is dried under nitrogen protection, the steel wire is first plated with copper, then with zinc, and then diffusion alloyed to obtain a copper-zinc alloy coating with a zinc content of 35 wt%, a copper content of 65 wt%, and a coating thickness of 0.8 μm.

[0049] ④ Irregular twisting: 1.80 mm copper-zinc alloy coated steel wire is wet-drawn to diameters of 0.38 mm, 0.32 mm, and 0.25 mm respectively, and then twisted in a 1+6+12 structure. The core strand d1 = 0.38 mm, the middle layer d2 = 0.32 mm, the outer layer d3 = 0.25 mm, the twist pitch is 20 mm, and the glue penetration gap between the outer layer monofilaments is 0.08 mm. See the detailed diagram. Figure 1 The steel cord prepared by this invention has a breaking force ≥1000N, an elongation at break ≥2.0%, a rubber permeability ≥95%, and shows no red rust after 72 hours of neutral salt spray testing.

[0050] The cords are used in the tire carcass layer, assembled in heavy-duty vehicle tires, and used until the tire is scrapped. The carcass layer is then separated and retained for recycling.

[0051] (2) Recycling of waste steel wire-rubber composite parts:

[0052] ① Targeted decoupling: The waste steel cord-rubber composite is immersed in a decoupling agent containing 4% silane-modified ethylenediamine, 3% polyethylene glycol 400, 70% ethanol, and the balance water. It is kept at 30℃ for 120 min and then assisted by 20 kHz low-frequency ultrasound with an ultrasonic power density of 0.4 W / cm², in an intermittent mode of 5 min every 15 min, to achieve non-destructive separation of rubber and steel wire.

[0053] ② Separation of the coating from the steel substrate: The waste steel wire with the coating is immersed in a flowing aqueous solution of 150 g / L ammonium persulfate and 110 g / L aminotrimethylenephosphonic acid at a temperature of 40°C and a pH of 2.2. This achieves the separation of the steel wire from the coating.

[0054] ③ Resource Recycling: a) After separation, the rubber can be directly recycled after cleaning and drying; b) Waste steel wire detached from the coating can be recycled after cleaning and drying; c) The solution containing copper and zinc ions is filtered to remove debris and other impurities. Sodium hydroxide is added to the solution and stirred to adjust the pH to 4.3. After standing and filtration, copper hydroxide precipitate is obtained. Sodium hydroxide is added to the filtrate to adjust the pH to 6.0. After standing and filtration, zinc hydroxide precipitate is obtained. Dilute sulfuric acid and dilute hydrochloric acid are added to copper hydroxide and zinc hydroxide respectively, and stirred until dissolved to obtain 90 g / L copper sulfate and 156 g / L zinc chloride electrolytes. The copper sulfate electrolyte uses a titanium plate as the anode and pure copper as the cathode, with a current density of 18 A / dm² and a temperature of 32℃ to electrolyze and obtain copper from the coating. The zinc chloride electrolyte uses graphite as the anode and pure zinc as the cathode, with a current density of 23 A / dm² and a temperature of 43℃ to electrolyze and obtain zinc from the coating. After cleaning and drying, the rubber can be directly recycled. After separation, the rubber can be directly recycled after cleaning and drying.

[0055] Example 3

[0056] This invention discloses a process for preparing and recycling steel wire-rubber composite parts, comprising the following steps:

[0057] (1) Steel cord preparation:

[0058] ① Scrap steel billet production: 5 mm steel billets are produced from 100% scrap steel. The CO2 emissions are 0.85 tons for every ton of steel produced.

[0059] ② Pretreatment: The 1.80 mm steel wire after billet rolling was immersed in a pretreatment solution with ultrasound. The solution contained 6% titanium lactate, 10% phytic acid, 4% potassium sodium tartrate, 3% boric acid, and the balance was deionized water. The pH was 5.5, the solution temperature was 53℃, the ultrasonic power was 225W, the frequency was 29 kHz, and the surface film was formed by compressed air bubble stirring for 2 min, resulting in a protective film with a thickness of 0.2 μm.

[0060] ③ Composite coating: After the pretreated steel wire is dried under nitrogen protection, the steel wire is first plated with copper, then with zinc, and then diffusion alloyed to obtain a copper-zinc alloy coating with a zinc content of 80 wt%, a copper content of 17 wt%, a Mn content of 3 wt%, and a coating thickness of 2.5 μm.

[0061] ④ Irregular twisting: 1.80 mm copper-zinc alloy coated steel wire is wet-drawn to diameters of 0.38 mm, 0.32 mm, and 0.25 mm respectively, and then twisted in a 1+6+12 structure. The core strand d1 = 0.38 mm, the middle layer d2 = 0.32 mm, the outer layer d3 = 0.25 mm, the twist pitch is 20 mm, and the glue penetration gap between the outer layer monofilaments is 0.08 mm. See the detailed diagram. Figure 1The steel cord prepared by this invention has a breaking force ≥1000N, an elongation at break ≥2.0%, a rubber permeability ≥95%, and shows no red rust after a 72-hour neutral salt spray test.

[0062] The cords are used in the tire carcass layer, assembled in heavy-duty vehicle tires, and used until the tire is scrapped. The carcass layer is then separated and retained for recycling.

[0063] (2) Recycling of waste steel wire-rubber composite parts:

[0064] ① Targeted decoupling: The waste steel cord-rubber composite is immersed in a decoupling agent containing 4% silane-modified ethylenediamine, 3% polyethylene glycol, 60% ethanol, and the balance water. It is kept at 50℃ for 90 min and then assisted by 40 kHz low-frequency ultrasound with an ultrasonic power density of 0.4 W / cm², in an intermittent mode of 5 min every 15 min, to achieve non-destructive separation of rubber and steel wire.

[0065] ② Separation of the coating from the steel substrate: The waste steel wire with the coating is immersed in a flowing aqueous solution of 160 g / L ammonium persulfate and 100 g / L aminotrimethylenephosphonic acid at a temperature of 45℃ and a pH of 2.8. This achieves the separation of the steel wire from the coating.

[0066] ③ Resource Recycling: a) After separation, the rubber can be directly recycled after cleaning and drying; b) Waste steel wire detached from the coating can be recycled after cleaning and drying; c) The solution containing copper and zinc ions is filtered to remove debris and other impurities. Sodium hydroxide is added to the solution and stirred to adjust the pH to 4.3. After standing and filtration, copper hydroxide precipitate is obtained. Sodium hydroxide is added to the filtrate to adjust the pH to 6.0. After standing and filtration, zinc hydroxide precipitate is obtained. Dilute sulfuric acid and dilute hydrochloric acid are added to copper hydroxide and zinc hydroxide respectively, and stirred until dissolved to obtain 90 g / L copper sulfate and 150 g / L zinc chloride electrolytes. The copper sulfate electrolyte uses a titanium plate as the anode and pure copper as the cathode, with a current density of 18 A / dm² and a temperature of 32℃ to electrolyze and obtain copper from the coating. The zinc chloride electrolyte uses graphite as the anode and pure zinc as the cathode, with a current density of 23 A / dm² and a temperature of 43℃ to electrolyze and obtain zinc from the coating. After cleaning and drying, the rubber can be directly recycled. After separation, the rubber can be directly recycled after cleaning and drying.

[0067] In summary, the present invention provides a low-emission, high-permeability rubber-coated steel cord preparation process and a waste steel wire rubber composite co-recycling process. The production process is low-emission, the recycling process is simple, the decoupling agent and separating agent can be recycled, and the rubber can be directly regenerated, truly realizing a closed-loop environmental protection model of "production-use-recycling".

[0068] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A process for preparing steel cord and recycling its waste steel wire rubber composite components, characterized in that: Includes the following steps: Step a: Using scrap steel as raw material, a cord steel billet is processed, and then rolled to obtain steel wire; Step b: Immerse the steel wire in the pretreatment solution to form a surface film, thereby forming a protective film on the surface of the steel wire. Step c: Coat the surface of the pretreated steel wire with an alloy coating to obtain coated steel wire; Step d: The coated steel wire is wet-drawn, then twisted into an irregular shape, and finally combined with rubber to obtain a steel wire-rubber composite. Step e involves immersing the used waste steel wire-rubber composite into a compound decoupling agent for targeted decoupling, thereby achieving non-destructive separation of the rubber and steel wire, resulting in rubber and waste steel wire with a coating. Step f involves immersing the coated waste steel wire into a composite recycling solution for continuous soaking, allowing the coating to dissolve from the steel wire and separating the steel wire from the coating to obtain a solution of separated steel wire and coating ions. Step g involves cleaning and drying the rubber obtained in step e and the separated steel wire obtained in step f, then recycling them, and electrolytically refining the plating ion solution obtained in step f after stepwise precipitation to obtain alloy metal.

2. The process for preparing steel cord and recycling its waste steel wire rubber composite components according to claim 1, characterized in that: In step b, the mass percentage of each component in the pretreatment solution is: 4-6% titanium lactate, 10-12% phytic acid, 2-4% potassium sodium tartrate and 1-3% boric acid, with the remainder being deionized water; the surface film formation time is 0.5-2 min; and the thickness of the protective film is 0.05-0.2 μm.

3. The process for preparing steel cord and recycling its waste steel wire rubber composite components according to claim 1, characterized in that: In step c, the thickness of the alloy coating is 0.8~2.5 μm; the zinc content in the alloy coating is 60~99.5 wt%, and the copper content is 0.5~40 wt%, or the zinc content in the alloy coating is 30~40 wt%, and the copper content is 60~70 wt%, or the alloy coating is composed of copper or zinc or copper-zinc and one or more other elements, the other elements being nickel, iron, manganese, cobalt, tin, silver, lanthanum, samarium, phosphorus, molybdenum, and the proportion of other elements in the composite coating is ≤5%.

4. The process for preparing steel cord and recycling its waste steel wire rubber composite components according to claim 1, characterized in that: In step d, the process of wet-drawing the coated steel wire and then performing irregular twisting specifically involves: wet-drawing the coated steel wire to a diameter of 0.10~0.60 mm, and then using a 1+n+2n irregular twisting structure, with the core strand monofilament diameter d1, the middle layer monofilament diameter d2, and the outer layer monofilament diameter d3, satisfying d1>d2>d3, and 0.05≤d1-d2≤0.08, 0.05≤d2-d3≤0.1, and a twist pitch of 15~25 mm, forming a glue-infiltrating gap of 0.05~0.1 mm between the outer layer monofilaments.

5. The process for preparing steel cord and recycling its waste steel wire rubber composite components according to claim 1, characterized in that: In step e, the mass percentage of each component in the compound decoupling agent is: 3-5% silane-modified ethylenediamine, 2-4% polyethylene glycol 400, 60-70% ethanol, and the remainder is deionized water; the specific process of targeted decoupling is: soaking at 30-50℃ for 90-120 min, combined with 20-40kHz low-frequency ultrasound assistance.

6. The process for preparing steel cord and recycling its waste steel wire rubber composite components according to claim 1, characterized in that: In step f, the components of the composite recovery solution are: 150~160 g / L ammonium persulfate, 100~110 g / L aminotrimethylenephosphonic acid, and the balance is water; the temperature of the flow soaking is 40~45℃, and the pH is 2.2~2.

8.

7. The process for preparing steel cord and recycling its waste steel wire rubber composite components according to claim 1, characterized in that: In step g, the specific process of stepwise precipitation is as follows: the solution containing plating ions is filtered to remove debris and other impurities, sodium hydroxide is added to the solution and stirred, the pH is adjusted to 4.0~4.5, and copper hydroxide precipitate is obtained by static filtration. Sodium hydroxide is added to the filtrate to adjust the pH to 5.5~6.5, and zinc hydroxide precipitate is obtained by static filtration.

8. The process for preparing steel cord and recycling its waste steel wire rubber composite components according to claim 1, characterized in that: In step g, the specific process of electrolytic refining is as follows: dilute sulfuric acid and dilute hydrochloric acid are added to copper hydroxide and zinc hydroxide respectively, and stirred until dissolved to obtain copper sulfate electrolyte and zinc chloride electrolyte. The copper sulfate electrolyte is electrolyzed with an insoluble plate as the anode and pure copper as the cathode to obtain copper in the coating. The zinc chloride electrolyte is electrolyzed with an insoluble plate as the anode and pure zinc as the cathode to obtain zinc in the coating.

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