Macromolecular polymeric material for plastic coating of metal wire and preparation method thereof

Abstract

The invention relates to a high-molecular polymeric material for metal wire plastic coating and a preparation method, and belongs to the technical field of high-molecular materials, and a plastic coating layer is of a double-layer structure and comprises an inner layer and an outer layer. And the inner layer adopts a polyvinyl composite system which does not contain or contains little carbon black, and focuses on the adhesion, impact resistance and low temperature resistance of the metal wire. And the outer layer adopts a polyethylene / polyvinyl chloride composite system containing carbon black and titanium dioxide in a specific proportion, and focuses on wear resistance, ultraviolet resistance and weather resistance. Through one-time coating molding of a double-layer co-extrusion process, cooperation of functions of the inner layer and the outer layer is achieved through the structure, the adhesive force, environmental aging resistance, mechanical strength and long-term service life of the obtained plastic-coated wire rod are comprehensively improved, and the plastic-coated wire rod is suitable for protection application in outdoor harsh environments.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high molecular materials, in particular to a high molecular polymer material for plastic coating of metal wires and a preparation method thereof. BACKGROUND

[0002] Plastic coating on the surface of metal wires (such as steel wires) is a common protective and decorative treatment method, and its products are widely used in outdoor wire mesh, fences, aquaculture net cages and other fields, and the plastic coating layer is required to have excellent weather resistance, corrosion resistance, impact resistance and firm adhesion to the metal substrate. At present, the mainstream technical solution in this field usually adopts a single-layer structure, and a single or main resin such as polyethylene (PE) and polyvinyl chloride (PVC) is modified by adding various additives.

[0003] However, the existing technology gradually exposes its inherent limitations in actual application, mainly in the following two aspects: First, in the material system, the single or simply blended modified resin material has an insurmountable performance contradiction and ceiling.

[0004] For example, polyethylene (PE) material has excellent low temperature resistance and flexibility, but its weather resistance, ultraviolet resistance, wear resistance and rigidity are relatively insufficient; polyvinyl chloride (PVC) material has advantages in flame retardance, chemical corrosion resistance and cost control, but it has poor thermal stability, obvious low temperature brittleness, and the performance is attenuated due to the migration of plasticizer. Although the industry generally uses antioxidants, light stabilizers, fillers and other additives for modification, these efforts are often "patching" within the framework of a single material system, and it is difficult to systematically balance the rigidity and toughness, heat resistance and low temperature resistance, long-term aging resistance and processing fluidity of the material and other multiple performance requirements that are mutually contradictory. There are attempts to improve the performance of a single material by complex additive compounding in the prior art; For example, the comparative document CN112679854A discloses a composition for significantly improving the heat-oxidative aging resistance of polypropylene by a multi-dimensional additive system, but such a solution focuses on the chemical protection dimension of a single material, has a high cost, and does not involve the multi-layer composite structure design and interlayer coordination problem required for the specific application scenario of metal wire coating.

[0005] Second, in the structure design, the traditional single-layer plastic coating structure is a "performance compromise" design.

[0006] The single-layer structure attempts to meet the different functional requirements of the inside (firm adhesion to metal, high flexibility and impact resistance) and the outside (resistance to ultraviolet rays, moisture, wear and other environmental stresses) with one formula. This design results in the inability of the overmolding layer to accurately optimize the functions for the different service environments on the inside and outside of the wire, and the performance potential of the material is not fully utilized, which restricts the further improvement of the comprehensive performance and service life of the product. Although double-layer or multi-layer structure designs have appeared in other fields (such as pipeline corrosion prevention); For example, the prior art document CN111363486A discloses a radiation cross-linked polyethylene composite tape for buried steel elbow pipes, which adopts a double-layer design of a base material layer and an adhesive layer, but this scheme is designed for pipeline winding construction (non-continuous extrusion), and its core technology relies on radiation cross-linking to achieve thermal shrinkage coating, and both layers contain carbon black. This technical scheme cannot be applied to the metal wire overmolding process which requires high-speed continuous co-extrusion, and it does not provide any teaching or inspiration for solving the unique problems of wire overmolding through the differential design of the inner and outer layers, especially the avoidance of carbon black to optimize adhesion.

[0007] In summary, the prior art either modifies the formula of a single material and cannot solve the interface and functional coordination problems caused by the multi-layer structure, or the multi-layer structure scheme is targeted at a specific field (such as pipelines), and there are essential differences in application objects, product forms, core processes (such as radiation cross-linking) and material design ideas from the overmolding requirements of continuous metal wires, which cannot be directly applied or provide useful inspiration.

[0008] Therefore, there has been a long-term lack of a high-performance overmolding solution in the art that is specifically designed for continuous metal wires and can be synergistically designed from the two dimensions of material compounding and structural innovation. The market urgently needs an environmentally friendly overmolding wire that can achieve a leap-forward improvement in comprehensive performance such as adhesion, flexibility, weather resistance, wear resistance, etc. through the functional division of the inner and outer layers of a double-layer composite structure, combined with the high molecular polymer material formula and high-efficiency co-extrusion process specially designed for each layer of function. SUMMARY

[0009] The present application provides a kind of high molecular polymer material and preparation method for metal wire overmolding to solve the problems of prior art.

[0010] To solve the above technical problems, the present application is realized by the following technical scheme: In a first aspect, a high molecular polymer material for metal wire overmolding is made from raw materials comprising: Resin base material, the resin base material comprises at least two of polyethylene, polyvinyl chloride and polyolefin elastomer; Filling agent; Anti-aging agents, including hindered phenolic antioxidants and phosphite antioxidants; and toughening agents.

[0011] In one specific embodiment of the first aspect, the formulation is used to form the inner layer of the coating layer and comprises, by weight percentage: Resin substrate: First linear low-density polyethylene: 20% to 30%; Second linear low-density polyethylene: 10% to 20%; High-density polyethylene: 15% to 25%; Polyolefin elastomer: 10% to 15% Filler: Precipitated calcium carbonate: 10% to 15%; Anti-aging agents: hindered phenolic antioxidants: 0.1% to 0.3%; phosphite antioxidants: 0.1% to 0.3%; light stabilizers: 0.3% to 0.8%; Toughening agent: Plastic toughening agent: 2% to 3%; The inner layer contains no carbon black, or the carbon black content in the inner layer is less than 0.5%.

[0012] In one specific embodiment of the first aspect, the formulation used to form the outer layer of the coating layer comprises, by weight percentage: Resin base material: Polyethylene resin: 20% to 35%; Polyvinyl chloride resin: 10% to 20%; Rubber or thermoplastic elastomer: 5% to 10%; Polyolefin elastomer: 5% to 10%; Filler: 15% to 25%; Anti-aging agents: hindered phenolic antioxidants: 0.1% to 0.3%; phosphite antioxidants: 0.1% to 0.3%; light stabilizers: 0.3% to 0.8%; Carbon black: 3% to 5%; Titanium dioxide: 3% to 5%.

[0013] In one specific embodiment of the first aspect, the outer layer raw material comprises a rubber component processed by an internal mixing process, and the carbon black and rubber are fully dispersed in the internal mixer.

[0014] Secondly, a plastic-coated environmentally friendly wire includes: Metal wire; and a plastic coating covering the outside of the metal wire; The plastic coating has a double-layer structure, including an inner layer that contacts the surface of the metal wire and an outer layer that covers the outside of the inner layer; The inner layer is made of a polymer material, and the outer layer is made of a polymer material.

[0015] In one specific embodiment of the second aspect, the metal wire is hot-dip galvanized steel wire, hot-dip high-zinc steel wire, zinc-aluminum alloy steel wire, or zinc-aluminum-magnesium alloy steel wire.

[0016] In a specific embodiment of the second aspect, the total thickness of the overmolded layer is 0.4mm to 0.6mm, wherein the thickness of the inner layer is 0.15mm to 0.35mm, and the thickness of the outer layer is 0.15mm to 0.35mm.

[0017] In a third aspect, a wire mesh product is provided, which is woven or twisted from overmolded environmentally friendly wires.

[0018] In a fourth aspect, a method for preparing a polymeric material for overmolding metal wires is provided, comprising the following steps: S1: raw material pretreatment: drying the raw material components for the inner layer and the outer layer respectively; S2: mixing and granulation: S2a: after high-speed mixing of the raw material components for the inner layer, the inner layer particles are formed by a granulator; S2b: after high-speed mixing of the raw material components for the outer layer, the outer layer particles are formed by a granulator after densification in a densifier; S3: double-layer co-extrusion coating: the inner layer particles and the outer layer particles are fed into different screws of a co-extrusion system, and are coated on the outside of the metal wires by the same mold in one step to form the inner layer and the outer layer; S4: cooling and shaping: cooling the wire coated with the double-layer overmolded layer to form a solid overmolded wire.

[0019] In a specific embodiment of the fourth aspect, in step S3, the co-extrusion system adopts a double-screw structure in series, and the inner layer particles are first coated by the front screw, and then the outer layer particles are coated outside the inner layer by the rear screw.

[0020] After the cooling and shaping step, a subsequent processing step of embossing and / or code spraying is further included.

[0021] The beneficial effects of the present application are: 1. The present application combines the properties of different components by specific proportioning and compounding of polyethylene (PE), polyvinyl chloride (PVC), polyolefin elastomer (POE) and rubber components. Specifically, it has the low-temperature toughness based on PE, the rigidity based on PVC, and the high elasticity and impact resistance based on the elastomer at the designed proportion, thereby solving the limitations of single resin in meeting the multiple performance requirements of overmolded wires.

[0022] 2. Through the design of double-layer structure by functional differentiation, targeted performance optimization is realized. The double-layer co-extrusion structure enables the inner and outer layers to be independently designed to bear different functions. The inner layer adopts a low-carbon black or carbon black-free formula and is rich in toughening components, mainly to ensure the adhesion to metal wires and the overall impact resistance and low-temperature resistance. The outer layer adopts a formula containing a specific proportion of carbon black and titanium dioxide, mainly to provide ultraviolet resistance, wear resistance and weather protection. This structure design enables the different performance requirements of the inner and outer sides of the wire to be met respectively.

[0023] 3. The functionalized double-layer structure and the high molecular polymer material system support and strengthen each other. The toughness of the inner layer provides a stable support base for the outer layer, and the firm protection of the outer layer greatly delays the aging process of the inner layer and the internal metal wire. This synergistic effect makes the wire of the present application superior to traditional single-layer or simply modified plastic-coated wires in terms of mechanical properties, environmental stress cracking resistance, long-term thermal and oxidative stability, and ultraviolet aging resistance. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0025] The present application provides a high molecular polymer material for plastic coating of metal wires and a preparation method thereof.

[0026] First part: preparation and explanation of plastic coating raw materials.

[0027] The plastic coating layer of the present application is a double-layer composite structure, including an inner layer directly contacting the metal wire and an outer layer coated outside the inner layer. This design realizes the comprehensive performance that a single material cannot achieve through the functional division and synergistic effect of the inner and outer layers. Both the inner and outer layers use a high molecular polymer material system, which is prepared by selecting a variety of resin base materials, elastomers, and additives and optimizing the ratio, so as to have excellent impact resistance, environmental stress cracking resistance, low-temperature resistance, ultraviolet aging resistance, and wear resistance.

[0028] "Rubber or thermoplastic elastomer": refers to a high molecular component that can be fully mixed with fillers such as carbon black through processes such as banburying, to give the polymer material higher elasticity, wear resistance, and weather resistance. Non-limiting examples thereof include but are not limited to chlorinated polyethylene (CPE), thermoplastic polyurethane elastomer (TPU), thermoplastic vulcanized rubber (TPV), ethylene propylene diene rubber (EPDM), etc. This component is also referred to as "rubber component".

[0029] “POE”: Common abbreviation for Polyolefin Elastomer, specifically refers to copolymer based on ethylene and alpha-olefins (e.g. octene).

[0030] 1. Inner layer of high polymer material.

[0031] The design purpose of the inner layer material is to ensure firm adhesion with the metal wire and to provide the core impact resistance and low temperature resistance for the overall structure. The raw material is composed of the following components by weight percentage: 1.1 Resin and elastomer matrix.

[0032] The resin and elastomer matrix is composed of the following components by weight percentage, with a total percentage of 55% to 70%: First linear low density polyethylene (LLDPE A): 20% to 30%. This component mainly provides good processing fluidity and flexibility. To optimize performance, a grade with a melt flow rate (MFR, 190°C / 2.16kg) in the range of 1.0 to 2.0 g / 10min can be selected.

[0033] Second linear low density polyethylene (LLDPE B): 10% to 20%. This component is blended with LLDPE A to improve the melt strength and toughness of the blended system. A grade with slightly lower MFR (e.g. 0.5 to 1.0 g / 10min) and slightly wider molecular weight distribution is preferred to complement the performance of LLDPE A.

[0034] High density polyethylene (HDPE): 15% to 25%. This component provides the necessary rigidity, hardness and creep resistance, and balances the rigid and tough properties of the covering layer together with LLDPE. A grade with lower MFR (e.g. 0.1 to 0.5 g / 10min) is preferred to maintain strength.

[0035] Polyolefin elastomer (POE): 10% to 15%. This is the key toughening component. POE based on ethylene-octene copolymer has extremely low glass transition temperature (e.g. below -50°C), which can significantly improve the impact resistance and flex resistance of the material at low temperature, and is the core of ensuring the cold resistance of the inner layer.

[0036] 1.2 Filler.

[0037] The filler is precipitated calcium carbonate, and the amount is 10% to 15%. In order to maximize the negative impact on the toughness and enhance the reinforcing effect, high-purity ultra-fine calcium carbonate treated by surface activation can be used. For example, the particle size of 1250 to 2500 (about 10 μm to 5 μm) is selected, and titanium or aluminum coupling agent is used for treatment to improve the dispersion and interfacial bonding force in the polyolefin matrix, so as to reduce the cost, improve the hardness, and maintain the good toughness of the system.

[0038] 1.3 Anti-aging agent.

[0039] The inner layer anti-aging system is composed of the following three types of additives, and the total amount is 0.5% to 1.4%: Hindered phenolic antioxidant: 0.1% to 0.3%. For example, antioxidant 1010 or 1076, which is used to capture free radicals and prevent thermal oxidative degradation during processing and use.

[0040] Phosphite antioxidant: 0.1% to 0.3%. For example, antioxidant 168, which is used to decompose hydroperoxide and has a synergistic effect with hindered phenolic antioxidant, significantly improving long-term thermal stability.

[0041] Light stabilizer: 0.3% to 0.8%. The inner layer is not the main weather-resistant layer, but still needs basic protection. A composite system composed of hindered amine light stabilizer (HALS, such as light stabilizer 770) and benzotriazole ultraviolet absorber (UVA, such as UV-327) can be preferred, and the two can be compounded in a mass ratio of (2:1) to (3:1) to provide effective light protection for the inner layer and form an internal-external synergistic effect with the outer protective system.

[0042] 1.4 Toughening agent.

[0043] The toughening agent is a plastic toughening agent, and the amount is 2% to 3%. In actual formulations, the impact resistance of the inner layer can be further strengthened by adding additional non-reactive elastomer microparticles such as POE, or other high-performance toughening agents, to ensure the reliability of the inner layer as a buffer layer.

[0044] 1.5 Other processing aids and characteristics.

[0045] In order to achieve good processing and comprehensive performance of the formula, other additives can also be included, for example: Reactive compatibilizer (such as 3%-5%): for example, maleic anhydride grafted polyethylene (PE-g-MAH), which can react with the hydroxyl groups on the surface of the filler through its anhydride groups, greatly improving the interfacial bonding force, and is the key to maintaining good toughness in high-filled systems.

[0046] Lubricant (such as 0.5%-1%): such as polyethylene wax or calcium stearate, which is used to improve the processing fluidity.

[0047] Cold resistance plasticizer (e.g. 0.5-1%): such as dioctyl sebacate (DOS) or dioctyl adipate (DOA), to further reduce the polymer glass transition temperature and improve flexibility in extremely cold conditions.

[0048] Key color and functional properties, inner layer without carbon black or with less than 0.5% carbon black. This design avoids potential interference of carbon black on the bonding force of metal-plastic interface. The inner layer without carbon black usually presents the material's natural color (e.g. white), and its light-colored surface also reflects light to some extent, providing additional auxiliary light-thermal protection for the inner layer.

[0049] 2. Outer layer high polymer material.

[0050] The outer layer material is directly exposed to the external environment, and its design aims to provide excellent weather resistance, ultraviolet resistance, wear resistance, and mechanical strength, while serving as a protective layer to slow down the aging of the inner layer and metal wire.

[0051] 2.1 Resin and elastomer matrix.

[0052] The resin and elastomer matrix, by weight percentage, consists of the following components, with a total percentage of 40% to 75%: Polyethylene resin: 20% to 35%. As one of the main matrices, it provides basic weather resistance, processability, and flexibility. Linear low-density polyethylene (LLDPE) and high-density polyethylene (HDPE) can be used in combination to balance the performance.

[0053] Polyvinyl chloride resin (PVC): 10% to 20%. The introduction of this component can significantly improve the rigidity, flame retardance, and chemical corrosion resistance of the plastic-coated layer, effectively complementing the performance of polyethylene (PE).

[0054] Rubber or thermoplastic elastomer: 5% to 10%. This is a key functional component. This component can be processed through a banbury process to achieve full dispersion and combination with subsequent added fillers such as carbon black. This component can greatly improve the elasticity, flex fatigue resistance, and wear resistance of the outer layer. Examples include but are not limited to chlorinated polyethylene (CPE), thermoplastic polyurethane elastomer (TPU), thermoplastic vulcanized rubber (TPV), or ethylene propylene diene rubber (EPDM), etc.

[0055] Polyolefin elastomer (POE): 5% to 10%. Used for toughening, improving low-temperature impact performance, and improving compatibility with PE / PVC matrix to ensure uniformity and stability of the blended system.

[0056] 2.2 Filler.

[0057] The filler is used in an amount of 15% to 25%. Its main function is to adjust the cost of the material, improve the rigidity and dimensional stability. The basic filler can be calcium carbonate. To obtain a better reinforcing effect, talc powder with a flaky structure (such as 1250 mesh or more) can be used in combination with calcium carbonate to improve the rigidity, heat resistance and surface scratch resistance of the overmolding layer.

[0058] 2.3 Anti-aging agents.

[0059] The outer layer anti-aging system needs to cope with harsh outdoor environments and includes, by weight percentage: Hindered phenolic antioxidant: 0.1% to 0.3%.

[0060] Phosphite antioxidant: 0.1% to 0.3%.

[0061] The two types of antioxidants work together to provide long-term thermal and oxidative stability protection.

[0062] Light stabilizer: 0.3% to 0.8%. To cope with ultraviolet radiation, a system composed of high-efficiency hindered amine light stabilizer (HALS) and ultraviolet absorber (such as benzotriazole UVA) can be used to form a multi-level light stabilizing protection network. For the outer layer PVC component, an appropriate amount of heat stabilizer (such as calcium-zinc composite stabilizer) can also be added to ensure its stability during processing.

[0063] 2.4 Key weathering and coloring components.

[0064] This is the key to achieving the core protection function of the outer layer: Carbon black: 3% to 5%. Carbon black is the most efficient ultraviolet shielding agent and reinforcing agent. Its addition not only dyes the outer layer into a dark color with excellent weather resistance, but also absorbs and scatters ultraviolet light, improves the mechanical strength, wear resistance and thermal conductivity of the material, and is the guarantee for the long-term service of the outer layer.

[0065] Titanium dioxide (TiO2): 3% to 5%. TiO2 is a highly efficient ultraviolet reflector and white pigment. Its combination with carbon black can form a synergistic effect through reflection and absorption mechanisms, building a more robust composite weathering defense line. At the same time, the addition of TiO2 helps to adjust the color of the final product and further improves the mechanical properties and heat resistance of the material.

[0066] 2.5 Processing and modification aids.

[0067] To achieve good processing and comprehensive performance of the formula, other aids such as: Coupling agent (such as 1%-3%): used to treat the surface of inorganic fillers to improve their compatibility and dispersibility with the resin matrix.

[0068] Lubricants (e.g. 0.5-1%): to improve processing flowability.

[0069] Toughening agents (e.g. 2-3%): can be added additionally as needed to fine-tune toughness.

[0070] Tackifiers (optional): for further enhancing adhesion to the outer layer or other materials in specific scenarios.

[0071] Second part: detailed flow of the preparation process.

[0072] The plastic-coated modified environmental-friendly wire of the present application is realized through an automatic production line integrating mixing, pelletizing and double-layer co-extrusion. This process ensures the full dispersion and plasticization of the components of the high-molecular polymer material and the precise molding of the double-layer structure. Taking a production line containing a φ65mm parallel twin-screw extrusion system as an example, the specific steps are as follows: S1: raw material pretreatment and separate mixing.

[0073] Raw material pretreatment: dry each component of the inner and outer layer formulations (e.g. PVC resin, calcium carbonate, talc, etc. which are easily moisture-absorbing materials) in a 90 to 100°C forced air oven for 2 to 4 hours to reduce the moisture content to below 0.03%. If the ambient humidity is high, the polyethylene-based raw materials can be briefly dried at 60 to 70°C for 1 hour.

[0074] Masterbatch preparation: for trace components (e.g. antioxidants, light stabilizers, etc.) with an addition amount less than 1% in the inner and outer layers, adopt the principle of "a small amount for a small amount", first pre-mix a small amount (about 5% of the total weight) of resin base in a high-speed mixer for 3 to 5 minutes to make a pre-mixed masterbatch to ensure uniform dispersion in the end.

[0075] Inner layer raw material mixing: put each component of the inner layer high-molecular polymer material into a high-speed heated mixer. First mix at low speed for 1 minute, then mix at high speed, and heat through the jacket to raise the material temperature to 80 to 90°C. In this process, liquid additives (e.g. cold-resistant plasticizers) are added through an atomizing nozzle. The entire high-speed mixing time is about 7 to 10 minutes. After mixing evenly, the material can be naturally cooled or cooled to below 40°C by a cold mixer for standby.

[0076] Outer layer raw material mixing and mixing: Primary mixing: put each component of the outer layer formulation except rubber and part of the elastomer into a high-speed heated mixer and mix evenly at 100 to 110°C.

[0077] Mixing: The primary mixing material is fed into the mixer together with the key components such as rubber and carbon black. Under the action of high temperature and high shear force, the rubber molecular chain is broken down sufficiently, and the filler such as carbon black is dispersed at the nanometer level, forming a uniform blend with the resin matrix. This step is the key to ensuring that the outer layer material has excellent wear resistance and weather resistance.

[0078] S2: Granulation.

[0079] The mixed inner layer material and the outer layer material after mixing are respectively fed into the double-screw granulator and the large-screw granulator for melting, extrusion, and pelletizing to form inner layer particles and outer layer particles with uniform particle size.

[0080] The granulated particles enter the automatic storage bin and are transported to the subsequent plastic wrapping machine as needed through the PLC control system, realizing smokeless and dustless production in the workshop.

[0081] S3: Double-layer co-extrusion coating.

[0082] The inner layer particles and the outer layer particles are respectively fed into the co-extrusion system.

[0083] Extrusion system and plasticization.

[0084] The co-extrusion system adopts a double-screw structure in series. The inner layer particles first enter the front screw and form a viscous melt after plasticization. The outer layer particles then enter the subsequent screw and form a viscous melt after plasticization. The inner and outer layer melts are independently transported to the co-extrusion die.

[0085] Inner layer extruder temperature setting: Inner layer plasticization temperature: focus on low temperature plasticization to protect the performance of the inner layer material. The temperature gradient from the feeding port of the front screw to the die can be set to about 160°C, 175°C, 190°C, 200°C, and 210°C.

[0086] Outer layer plasticization temperature: due to the presence of components such as rubber, higher plasticization temperature is required. The temperature gradient from the feeding port of the subsequent screw to the die can be set to about 165°C, 185°C, 205°C, 215°C, and 225°C.

[0087] Mold forming and coating: the metal wire pre-straightened and pre-heated (about 80 to 100°C) passes through the center hole of the double-layer co-extrusion die.

[0088] In the die, the inner layer melt is first extruded through the inner channel, uniformly wrapping the metal wire surface to form the inner layer.

[0089] Subsequently, the outer layer melt is extruded through the outer channel, tightly coating the outside of the formed inner layer to form the outer layer.

[0090] This process is completed continuously in the die, and finally shaped by a precision sizing die. This process ensures that the double-layer structure has excellent interlayer bonding strength (≥ 3 N / 15 mm), the total thickness of the overmolded layer is controlled between 0.4 mm and 0.6 mm (about 0.15 mm to 0.35 mm for each of the inner and outer layers), and the concentricity error is less than 0.05 mm.

[0091] S4: Cooling and shaping.

[0092] The coated wire immediately enters the vacuum sizing cooling water tank. The water tank is divided into 2 to 3 sections, and the first section uses vacuum suction to make the overmolded layer tightly adhere to the sizing sleeve, ensuring a round shape and accurate size. The subsequent sections use spray cooling, with water temperature controlled at 10 to 20°C. Slow and staged cooling is used to avoid internal stress caused by sudden cooling, which can cause the overmolded layer to warp or reduce interlayer adhesion.

[0093] S5: Post-processing.

[0094] Air drying and printing: After leaving the cooling water tank, the surface moisture is blown dry by a high-pressure air blower. Then, through an online inkjet printer, product specifications, production dates, manufacturer logos, and other information are clearly printed on the surface of the overmolded layer.

[0095] Embossing (optional): Some products will pass through a set of embossing rollers to press regular patterns on the surface of the overmolded layer. This not only improves the appearance of the product, but more importantly, it increases the surface area, which can enhance the friction with the internal filled stones after the mesh is formed into a cage, improving the structural stability.

[0096] Winding and packaging: Finally, the finished wire is wound into neat coils by a tension-controlled winding machine, usually with a weight of 500 to 1000 kg per coil. The coils are packaged with waterproof film and woven cloth, and a certificate of conformity is attached before being stored in the warehouse.

[0097] Process control core: During the entire production process, the PLC (Programmable Logic Controller) system is used to interlock and closed-loop control key parameters such as mixing time and temperature, mixing parameters, granulation speed, extruder temperature at each section, screw speed (usually 20 to 40 rpm), and pulling speed (synchronized with the extrusion speed, about 10 to 25 m / min), etc. This ensures that the overmolded layer has uniform thickness, smooth surface, no bubbles, no impurities, and other defects, and guarantees the stability and consistency of product quality.

[0098] Part III: Examples.

[0099] Example 1: High molecular polymer double-layer overmolded wire (black outer layer and white inner layer structure).

[0100] Objective: To prepare a kind of plastic-coated wire suitable for high-standard outdoor environment (such as farmland and water conservancy projects in the severe cold regions of Northeast China), which requires excellent low-temperature toughness, impact resistance, weather resistance, and long service life.

[0101] Wire structure: This embodiment adopts a double-layer co-extrusion structure, including an inner layer and an outer layer.

[0102] Raw material formula (calculated by weight): Inner layer (white, focusing on adhesion, impact resistance, and low-temperature resistance): First linear low-density polyethylene (MFR = 1.5): 25 parts; Second linear low-density polyethylene (MFR = 0.8): 15 parts; High-density polyethylene (MFR = 0.2): 20 parts; Polyolefin elastomer (POE, ENGAGE8180): 12 parts; Active precipitated calcium carbonate (2000 mesh): 15 parts; Antioxidant 1010: 0.2 parts; Antioxidant 168: 0.2 parts; Light stabilizer 770: 0.3 parts; Ultraviolet absorber UV-327: 0.15 parts; Composite light stabilizing aid: 0.3 parts; Maleic anhydride grafted polyethylene (PE-g-MAH): 4 parts; Polyethylene wax: 0.8 parts; Decyl octyl sebacate (DOS): 0.8 parts; (The inner layer does not contain carbon black); Outer layer (black, focusing on wear resistance, weather resistance, and protection): Linear low-density polyethylene (MFR = 1.2): 20 parts; Polyvinyl chloride resin (SG-5): 15 parts; Chlorinated polyethylene (CPE, chlorine content 36%): 8 parts; Polyolefin elastomer (POE): 5 parts; Active calcium carbonate (1000 mesh): 12 parts; Talc (1250 mesh): 8 parts; Calcium-zinc stabilizer: 1.5 parts; Composite metal soap: 0.5 parts; Antioxidant 1076: 0.15 parts; Antioxidant 626: 0.15 parts; Light stabilizer 622: 0.4 parts; Ultraviolet absorber UV-326: 0.1 parts; Carbon black: 4 parts; Titanium dioxide (Ti02): 4 parts; Oxidized polyethylene: 0.8 parts; Silane coupling agent (KH-550): 1.5 parts; Preparation process: Raw material pretreatment and mixing: The inner and outer layer raw materials are weighed according to the formula. The inner layer components are mixed in a high-speed mixer at 85°C for 8 minutes, and then cooled for standby. The outer layer components (except CPE and carbon black) are preliminarily mixed in a high-speed mixer at 100°C, and then sent to a banbury mixer together with CPE and carbon black for mixing to ensure the full dispersion of carbon black.

[0103] Granulation: The mixed inner layer material and outer layer material are granulated by a double-screw granulator and a large-screw granulator respectively to form inner layer particles and outer layer particles.

[0104] Double-layer co-extrusion coating: The φ2.5mm hot-dip galvanized aluminum magnesium steel wire is straightened and preheated, and then introduced into the co-extrusion system. The inner layer particles and outer layer particles are plasticized by two extruders respectively.

[0105] Inner layer extruder temperature setting: 160°C, 175°C, 190°C, 200°C, 210°C (die head).

[0106] Outer layer extruder temperature setting: 165°C, 185°C, 205°C, 215°C, 225°C (die head).

[0107] Through the double-layer co-extrusion die, the inner layer melt is first coated on the surface of the steel wire, and the outer layer melt is immediately coated outside the inner layer to form a double-layer structure at one time.

[0108] Cooling and post-processing: The coated wire is cooled and shaped in a 15°C vacuum sizing cooling water tank, and then dried by air, coded online, and finally wound.

[0109] Final product: A high polymer double-layer plastic coated wire with a total plastic coating thickness of 0.55mm is obtained, in which the inner layer is about 0.25mm thick (white) and the outer layer is about 0.30mm thick (dark gray).

[0110] Example 2: High polymer double-layer plastic coated wire (general type).

[0111] Objective: To provide a plastic coated wire with balanced performance suitable for general scenarios (such as breeding net cages and ordinary fences).

[0112] Wire structure: same as above, using double-layer co-extrusion structure.

[0113] Raw material formula (calculated by weight parts): Inner layer (light color, focus on basic adhesion and flexibility): First linear low density polyethylene (LLDPE, MFR = 1.8 g / 10min): 22 parts; Second linear low density polyethylene (LLDPE, MFR = 0.8 g / 10min): 13 parts; High density polyethylene (HDPE, MFR = 0.3 g / 10min): 20 parts; Polyolefin elastomer (POE): 10 parts; Precipitated calcium carbonate (1500 mesh): 14 parts; Composite antioxidant (primary antioxidant 1010 and secondary antioxidant 168): 0.4 parts; Composite light stabilizer (hindered amine and ultraviolet absorber): 0.7 parts; Maleic anhydride grafted polyethylene (PE-g-MAH): 3 parts; Polyethylene wax: 0.8 parts; (Inner layer does not contain carbon black); Outer layer (black, focus on basic protection and weather resistance): Polyethylene resin (LLDPE / HDPE compound): 30 parts; Polyvinyl chloride resin (SG-5): 10 parts; Ethylene propylene diene rubber (EPDM) powder: 5 parts; Polyolefin elastomer (POE): 5 parts; Calcium carbonate: 15 parts; Talc powder (1250 mesh): 5 parts; Calcium-zinc composite stabilizer: 1.5 parts; Composite antioxidant (1076 and 626): 0.3 parts; Composite light stabilizer (622 and UV-326): 0.5 parts; Carbon black: 5 parts; Titanium dioxide (TiO2): 3 parts; Silane coupling agent (KH-550): 1.2 parts; Preparation process: Raw material pretreatment and mixing: The inner and outer layer raw materials are weighed according to the formula respectively. The inner layer components are mixed uniformly by a high-speed mixer at 80-90°C, and cooled for standby. In the outer layer components, EPDM powder, carbon black and part of polyethylene resin are fed into the internal mixer for sufficient mixing, and then the mixing masterbatch and other outer layer raw materials are mixed uniformly by a high-speed mixer.

[0114] Granulation: The mixed inner and outer layer materials are respectively melted, extruded and cut into particles by a double screw granulator to form particles with uniform particle size.

[0115] Double-layer co-extrusion coating: the preheated metal wire (such as φ2.0mm hot-dip galvanized steel wire) is introduced into the co-extrusion system. After the inner and outer layer particles are plasticized, they are coated and formed at one time through a double-layer co-extrusion die. The extrusion temperature of the inner layer is controlled at 165-210°C, and the extrusion temperature of the outer layer is controlled at 170-220°C.

[0116] Cooling and post-processing: the coated wire is cooled and shaped in a vacuum sizing tank (water temperature 15-20°C), and then air-dried, sprayed with codes, and wound.

[0117] Final product: a double-layer plastic-coated wire with a total plastic layer thickness of 0.45mm is prepared, wherein the thickness of the inner layer is about 0.20mm (light color) and the thickness of the outer layer is about 0.25mm (black). The product has good comprehensive mechanical properties, reliable weather resistance, and excellent cost performance, and is suitable for general protection fields.

[0118] Part IV: Performance testing and comparative examples.

[0119] To verify the beneficial effects of the double-layer plastic-coated wire of the high molecular polymer material, the product obtained in Example 1 is subjected to performance testing, and compared with the ordinary single-layer plastic-coated wire produced using recycled materials (as a comparative example) purchased on the market.

[0120] Test standards and methods: Tensile strength and elongation at break: according to GB / T1040-2018, samples are directly prepared from the plastic-coated wire.

[0121] Low-temperature embrittlement impact test: according to GB / T5470-2008, the plastic coating is peeled off to form a standard sample, which is tested at -25°C.

[0122] Environmental stress cracking resistance (ESCR): according to GB / T1842-2008, using Igepal CO-630 solution, conditions are 100°C, 100%.

[0123] Heat aging test: according to GB / T7141-2008, the sample is placed in a 100°C oven, and the performance retention rate after 168h of testing is tested.

[0124] Xenon lamp aging test: according to GB / T16422.2-2014, simulating outdoor ultraviolet and rain environment, testing the performance change and color difference after 1000h.

[0125] Adhesion test: using the pull-off method, according to ISO4624:2002 "Adhesion of pigmented and clear paints - Pull-off method", the bonding strength of the plastic coating and the steel wire is evaluated.

[0126] Harmful substance detection: according to GB / T26125-2011 (equivalent to IEC62321), detect the content of heavy metals such as lead, cadmium, mercury, chromium, etc.

[0127] Test result comparison: Result analysis: From the above data, it can be clearly seen that the high polymer polymeric material double-layer plastic-coated wire prepared by the application (Example 1) is superior to the comparative product using recycled materials in terms of mechanical properties, low-temperature resistance, long-term thermal stability, ultraviolet aging resistance, and adhesion to the metal substrate.

[0128] Excellent toughness: the initial elongation at break (380%) far exceeds that of the comparative example (180%), and there is no brittle fracture at low temperature, which reflects the excellent impact resistance and low-temperature resistance of the inner layer of the high polymer polymeric material.

[0129] Excellent durability: the environmental stress cracking resistance time exceeds 500 hours, the performance retention rate after thermal aging and xenon lamp aging is higher than 85%, and the color difference change (ΔE < 3.0) is small, which fully proves the long-acting protection effect brought by the synergistic effect of the outer layer carbon black / TiO2 composite protective system and the inner layer stabilizing system.

[0130] Firm structural integrity: the adhesion measured by the pull-off method is significantly improved, which proves the excellent adhesion of the inner layer formula to the metal wire in the double-layer structure.

[0131] Environmentally friendly: the environmental protection test results fully meet the ROHS standard, which is in sharp contrast to the comparative example using unknown recycled materials and exceeding the standard for heavy metals.

[0132] In summary, the application successfully provides a high-performance, long-life, and environmentally friendly plastic-coated wire through the formula design and functionalization of the double-layer structure of the high polymer polymeric material.

[0133] Although embodiments of the application have been shown and described, it is to be understood that various modifications, substitutions, replacements, and changes can be made to these embodiments without departing from the principles and spirit of the application, and the scope of the application is defined by the appended claims and their equivalents.

Claims

1. A polymeric material for coating metal wires, characterized in that: Made from raw materials containing the following components: A resin substrate, wherein the resin substrate comprises at least two of polyethylene, polyvinyl chloride, and polyolefin elastomers; filler; Anti-aging agents, including hindered phenolic antioxidants and phosphite antioxidants; and toughening agents; Its formulation is used to form the inner layer of the coating, and contains, by weight percentage: Resin substrate: First linear low-density polyethylene: 20% to 30%; Second linear low-density polyethylene: 10% to 20%; High-density polyethylene: 15% to 25%; Polyolefin elastomer: 10% to 15% Filler: Precipitated calcium carbonate: 10% to 15%; Anti-aging agents: hindered phenolic antioxidants: 0.1% to 0.3%; phosphite antioxidants: 0.1% to 0.3%; Light stabilizer: 0.3% to 0.8%; Toughening agent: Plastic toughening agent: 2% to 3%; The inner layer contains no carbon black, or the carbon black content in the inner layer is less than 0.5%. Its formulation, used to form the outer layer of the coating, contains, by weight percentage: Resin base material: Polyethylene resin: 20% to 35%; Polyvinyl chloride resin: 10% to 20%; Rubber or thermoplastic elastomer: 5% to 10%; Polyolefin elastomer: 5% to 10%; Filler: 15% to 25%; Anti-aging agents: hindered phenolic antioxidants: 0.1% to 0.3%; phosphite antioxidants: 0.1% to 0.3%; light stabilizers: 0.3% to 0.8%; Carbon black: 3% to 5%; Titanium dioxide: 3% to 5%.

2. The polymer material for coating metal wires according to claim 1, characterized in that, The outer layer contains rubber components processed by an internal mixing process, and the carbon black and rubber are fully dispersed in the internal mixer.

3. A plastic-coated environmentally friendly wire, characterized in that, include: Metal wire; And a plastic coating layer covering the outside of the metal wire; The plastic coating has a double-layer structure, including an inner layer that contacts the surface of the metal wire and an outer layer that covers the outside of the inner layer; The inner layer is made of the polymer material described in claim 1, and the outer layer is made of the polymer material described in claim 1.

4. The plastic-coated environmentally friendly wire according to claim 3, characterized in that: The metal wire is hot-dip galvanized steel wire, hot-dip high-zinc steel wire, zinc-aluminum alloy steel wire, or zinc-aluminum-magnesium alloy steel wire.

5. The plastic-coated environmentally friendly wire according to claim 3, characterized in that: The total thickness of the plastic coating is 0.4 mm to 0.6 mm, wherein the thickness of the inner layer is 0.15 mm to 0.35 mm, and the thickness of the outer layer is 0.15 mm to 0.35 mm.

6. A wire mesh product, characterized in that, The wire mesh product is woven or twisted from the plastic-coated environmentally friendly wire as described in any one of claims 3 to 5.

7. A method for preparing a polymeric material for coating metal wires, characterized in that, Includes the following steps: S1: Raw material pretreatment: The raw material components that make up the inner and outer layers are dried separately; S2: Mixing and Granulation: S2a: The raw material components of the inner layer are mixed at high speed and then granulated into inner layer particles by a granulation mechanism; S2b: The outer layer raw material components are mixed at high speed and then fed into an internal mixer for internal mixing, and then granulated into outer layer granules by a granulator. S3: Double-layer co-extrusion coating: The inner layer particles and the outer layer particles are fed into different screws of the co-extrusion system and coated onto the outside of the metal wire in one go through the same mold to form an inner layer and an outer layer; S4: Cooling and Shaping: Cooling the wire with a double-layer plastic coating to form a solid plastic-coated wire.

8. The method for preparing a polymeric material for coating metal wires according to claim 7, characterized in that, In step S3, the co-extrusion system adopts a twin-screw structure connected in series. The inner layer particles are first plasticized and coated by the preceding screw, and the outer layer particles are then plasticized and coated on the outside of the inner layer by the subsequent screw.

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