Solid waste metal short fiber reinforced recycled plastic-polyurethane composite sleeper material composition, composite sleeper and preparation method and application thereof

Abstract

The application discloses a solid waste metal short fiber reinforced recycled plastic-polyurethane composite sleeper material composition, a composite sleeper and a preparation method and application thereof, and relates to the technical fields of railway track engineering materials, composite material forming and solid waste resource utilization. The composite sleeper comprises a composite base and a solid waste metal short fiber reinforced material dispersed in the composite base; the composite base comprises a recycled plastic base phase and a polyurethane colloid base phase; the application forms a bearing structure among the recycled plastic base phase, the polyurethane colloid base phase and the solid waste metal short fiber through waste recycling plastic hot melting regeneration, solid waste metal short fiber dispersion reinforcement and polyurethane colloid base forming, and continuous pultrusion forming, so that the problems of low strength, insufficient creep resistance, low pull-out resistance of spikes, poor fatigue reliability and the like of the traditional recycled plastic sleeper can be solved, and the solid waste metal fiber does not need to be subjected to high-cost deep decomposition and complete separation.

Description

Technical Field

[0001] This invention relates to the fields of railway track engineering materials, composite material molding and solid waste resource utilization technology, and more specifically to solid waste metal short fiber reinforced recycled plastic-polyurethane composite sleeper material composition, composite sleeper and its preparation method and application. Background Technology

[0002] Railway sleepers are crucial load-bearing components in railway track structures. Their functions include supporting the rails, maintaining track gauge, transmitting train loads, providing track elasticity, and maintaining track geometric stability. Existing railway sleepers mainly include wooden sleepers, concrete sleepers, steel sleepers, and composite material sleepers.

[0003] Wooden sleepers suffer from drawbacks such as high consumption of timber resources, insufficient corrosion resistance, and service life significantly affected by the environment. Concrete sleepers are widely used, but their heavy weight, insufficient elasticity, and high difficulty in maintenance and replacement limit their application in bridges, tunnels, vibration-damping tracks, and special tracks. Ordinary plastic sleepers and recycled plastic sleepers have the advantages of being lightweight, corrosion-resistant, recyclable, and easy to process, but their mechanical strength, long-term creep performance, and fastener connection reliability remain important factors restricting their engineering applications.

[0004] In recent years, recycled plastic railway sleepers have been considered an important direction for realizing the resource utilization of plastic solid waste. After being crushed, washed, hot-melted, recycled, and molded, waste plastics can be used to produce railway sleeper components with a certain load-bearing capacity. However, traditional recycled plastic railway sleepers usually rely mainly on the plastic matrix itself for load-bearing capacity, which has low strength, a large coefficient of linear expansion, and insufficient load-bearing capacity.

[0005] Due to the complex sources of waste plastics, the degree of aging, molecular weight, impurity content, and proportion of different plastic components of the materials fluctuate, making recycled plastic sleepers prone to the following problems: First, the material strength and stiffness are insufficient, and the rail-bearing area is prone to local deformation under the cyclic load of the train; second, long-term creep deformation is large, reducing the gauge holding capacity and the stability of fastener connections; third, the material around the spike holes has insufficient pull-out resistance, making it prone to hole wall crushing, loosening, and fatigue damage; fourth, the material properties have large dispersion, making it difficult to meet the reliability requirements for long-term service.

[0006] On the other hand, waste tires, waste steel wire ropes, metal processing waste, and other industrial solid waste contain a large amount of metal fibrous materials. These solid waste metal fibers have high tensile strength and good reinforcement potential. If they can be used as short fiber reinforcement materials for railway sleepers, it will help improve the bending resistance, crack resistance, fatigue resistance, and creep resistance of recycled plastic railway sleepers.

[0007] However, existing methods for utilizing solid waste metal fibers often require pyrolysis, chemical treatment, mechanical stripping, deep separation, or high-purification to remove rubber, plastic, oil, oxide layers, or other deposits from their surfaces. These processes not only increase energy consumption and costs but also reduce the economic viability of using solid waste metal fibers in large-scale engineering materials.

[0008] Therefore, it is necessary to propose a new composite sleeper material system and preparation method, in which waste recycled plastic is regenerated by hot melting to form the main molding matrix, while polyurethane colloid is used as a synergistic matrix phase to fill internal pores and interface defects, and short fibers of solid waste metal are dispersed in the composite matrix as reinforcing materials. In this way, the mechanical properties and service reliability of recycled plastic sleepers can be improved without using long fibers or performing high-cost deep separation. Summary of the Invention

[0009] The technical problem to be solved by this invention is that traditional recycled plastic sleepers are mainly supported by a single recycled plastic matrix, resulting in insufficient strength, stiffness, creep resistance, pull-out resistance of spikes, and fatigue reliability.

[0010] The technical problem that this invention aims to solve further is that the direct resource utilization of solid waste metal fibers is difficult, and the traditional decomposition, separation and high purification processes are costly and difficult to use on a large scale as materials for rail engineering.

[0011] The technical problem to be further solved by the present invention is the lack of interfacial bonding between the short metal fibers and the recycled plastic matrix, the large number of pores, the low stress transfer efficiency, and the easy pull-out of fibers during fatigue.

[0012] To address the aforementioned technical problems, this invention provides a solid waste metal short fiber reinforced recycled plastic-polyurethane composite railway sleeper material composition. The composition comprises a composite matrix and solid waste metal short fiber reinforcing material dispersed within the composite matrix.

[0013] The composite matrix comprises a recycled plastic matrix phase and a polyurethane colloidal matrix phase.

[0014] Among them, the recycled plastic matrix phase is formed by crushing, washing, drying and hot melting of waste recycled plastic, and mainly undertakes the functions of overall sleeper molding, dimensional maintenance and basic load bearing;

[0015] The polyurethane colloidal matrix phase is formed by the curing of polyurethane colloid. It is mainly distributed and fills the pores inside the recycled plastic matrix phase and the interface region between the short fibers of solid waste metal and the recycled plastic matrix phase. Together with the recycled plastic matrix phase, it constitutes the composite matrix of the sleeper, which helps to improve the porosity and interface defects inside the sleeper, and improve the interfacial bonding performance, toughness and fatigue energy dissipation capacity.

[0016] The solid waste metal short fiber reinforced material is dispersed in the composite matrix in a discontinuous form, and mainly undertakes the functions of tensile, bending and crack resistance reinforcement.

[0017] The solid waste metal short fiber reinforcement material is a discontinuous short fiber reinforcement material, not a long fiber, nor a continuous reinforcement fiber that runs through the entire length of the sleeper. After being chopped, screened, cleaned of impurities, and optionally treated with degreasing, derusting, and coupling, it can be directly thermally melt-bonded with recycled waste plastic granules.

[0018] The pultrusion molding described in this invention refers to the continuous passage of a recycled plastic melt composite containing short fibers from solid waste metals through a sleeper section forming die under the action of a traction device, thereby forming a continuous sleeper profile or sleeper blank. This molding method does not require the reinforcing material to be long or continuous fibers. The short fibers from solid waste metals are only randomly distributed, locally oriented, or semi-directionally distributed under the action of melt flow and traction, and do not form continuous reinforcing bundles along the entire length of the sleeper.

[0019] According to a preferred embodiment of the present invention, based on 100 parts by weight of the recycled plastic matrix phase, the solid waste metal short fiber reinforcing material comprises 5-30 parts by weight, the polyurethane colloidal matrix phase comprises 5-40 parts by weight, and further comprises 1-15 parts by weight of compatibilizer, 0.1-5 parts by weight of coupling agent, 0.1-5 parts by weight of antioxidant, 0.1-8 parts by weight of lubricant, and 0-30 parts by weight of inorganic filler.

[0020] According to a preferred embodiment of the present invention, the waste recycled plastic is selected from one or more of waste polyethylene, waste high-density polyethylene, waste polypropylene, waste polyvinyl chloride, waste polyamide, waste polyester, waste polystyrene, and waste rubber-plastic composite materials.

[0021] According to a preferred embodiment of the present invention, the polyurethane colloidal matrix phase is formed by curing one or more of the following: a two-component polyurethane colloid, a one-component moisture-curing polyurethane colloid, a modified polyurethane colloid, and a polyurethane elastomer colloid. The polyurethane colloidal matrix phase and the recycled plastic matrix phase together constitute the composite matrix of the sleeper, rather than serving merely as a surface coating, external adhesive, or temporary sealant.

[0022] According to a preferred embodiment of the present invention, the solid waste metal short fiber reinforcing material is selected from one or more of the following: chopped steel cord fibers from waste tires, chopped steel wire rope fibers from waste steel wire ropes, waste metal processing wires, waste steel fibers, waste stainless steel fibers, waste copper-clad steel fibers, and waste aluminum alloy short fibers.

[0023] According to a preferred embodiment of the present invention, the length of the solid waste metal short fiber reinforced material is 3-80 mm, preferably 5-50 mm; the diameter is 0.03-2.00 mm, preferably 0.05-1.20 mm; and the aspect ratio is 10-400, preferably 20-250.

[0024] According to a preferred embodiment of the present invention, the surface of the solid waste metal short fiber reinforced material is allowed to retain rubber residues, plastic residues, oxide layers, coatings, or a small amount of organic deposits. The solid waste metal short fiber reinforced material does not require thermal cracking, chemical dissolution, complete stripping, or high-purity separation treatment; it only needs to be chopped, sieved, impurity removed, dried, and optionally degreased, derusted, surface roughened, or coupled before it can be used in the composite sleeper material composition.

[0025] According to a preferred embodiment of the present invention, the solid waste metal short fiber reinforcement material is randomly distributed, semi-directionally distributed, or discontinuously distributed with a certain orientation along the longitudinal direction of the sleeper in the composite matrix; the solid waste metal short fiber reinforcement materials do not form a continuous metal reinforcement bundle or a continuous metal conductive path along the length direction of the sleeper.

[0026] The present invention also provides a composite railway sleeper prepared using the above composition, the composite railway sleeper comprising a sleeper body, the sleeper body comprising a recycled plastic-polyurethane composite matrix and a solid waste metal short fiber reinforcing material dispersed in the composite matrix.

[0027] According to a preferred embodiment of the present invention, the sleeper body includes a rail-bearing area, a spike hole area, a sleeper center area, and a sleeper bottom area. The content of solid waste metal short fibers in the rail-bearing area and the spike hole area is higher than that in the sleeper center area and the sleeper bottom area; or, the content of polyurethane colloidal matrix phase in the rail-bearing area and the spike hole area is higher than that in the sleeper center area and the sleeper bottom area.

[0028] According to a preferred embodiment of the present invention, an insulating protective layer is provided on the outer side of the sleeper body. The insulating protective layer is mainly formed of recycled plastic matrix phase and / or polyurethane colloidal matrix phase, which is used to isolate the solid waste metal short fiber reinforcement material from the external environment and reduce the risk of metal short fiber exposure, corrosion and formation of conductive paths.

[0029] The present invention also provides a method for preparing the above-mentioned composite sleeper, comprising the following steps: S1: The waste plastic is sorted, crushed, washed and dried to obtain recycled plastic pellets; S2: The solid waste metal fibrous waste is chopped, screened, impurities removed and dried to obtain solid waste metal short fiber reinforced material; S3: The waste plastic recycled granules, solid waste metal short fiber reinforcing material, compatibilizer, coupling agent, antioxidant, lubricant and optional inorganic filler are premixed and then hot-melted in a melt mixing equipment to obtain recycled plastic melt composite material containing solid waste metal short fiber; S4: The recycled plastic melt composite material is fed into a pultrusion molding die and continuously passes through the molding die under the action of a traction device to form a continuous sleeper profile or a sleeper blank. S5: After cooling the sleeper blank, polyurethane colloid is injected through the reserved injection hole, allowing it to enter the internal pores and short fiber interface, and after curing, the composite sleeper is obtained.

[0030] According to a preferred embodiment of the present invention, in step S1, the waste recycled plastic is crushed to a particle size of 5-30 mm, the drying temperature is 60-120℃, the drying time is 2-12 h, and the moisture content after drying is not higher than 0.5%.

[0031] According to a preferred embodiment of the present invention, the temperature for hot-melt bonding in step S3 is 150-220°C. In step S4, the traction speed for pultrusion is 0.05-2.00 m / min, and the molding pressure is 1-10 MPa. In step S5, the injection pressure of the polyurethane colloid is 0.1-0.5 MPa, the curing temperature is room temperature to 60°C, and the curing time is 12-72 h.

[0032] As can be seen from the above technical solution, compared with the prior art, the present invention has the following technical effects: (1) A composite matrix is ​​formed by combining recycled plastic matrix phase and polyurethane colloid matrix phase. The polyurethane colloid fills the internal pores and short fiber interfaces of the recycled plastic matrix, which can improve the problems of insufficient strength, insufficient toughness and insufficient long-term reliability of traditional recycled plastic sleepers with a single matrix.

[0033] (2) Using short fibers of solid waste metal as reinforcement material can improve the bending resistance, crack resistance, pull-out resistance and fatigue resistance of sleepers.

[0034] (3) The reinforcing material used is short fiber rather than continuous long fiber, which can be melt-blended and continuously pultruded with waste plastic recycled granules. It has strong process adaptability and is convenient for large-scale continuous production.

[0035] (4) Allowing a small amount of rubber, plastic, oxide layer or organic deposits to remain on the surface of solid waste metal short fibers does not require high-cost deep decomposition and complete separation, which can reduce the cost of resource utilization of solid waste metal fibers.

[0036] (5) It can simultaneously dispose of waste plastics and solid waste metal fibers, realizing the resource utilization of the two types of solid waste, and has good environmental benefits and engineering application value. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of the overall structure of the solid waste metal short fiber reinforced recycled plastic-polyurethane composite railway sleeper of the present invention.

[0039] Figure 2 This is a schematic diagram of the continuous pultrusion molding process for the composite sleeper of the present invention.

[0040] In the figure: 1-Sleeper body; 2-Short fiber reinforced material of solid waste metal; 3-Polyurethane matrix phase; 4-Recycled plastic matrix phase. Detailed Implementation

[0041] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] The composite sleeper of this invention comprises a composite matrix and short fiber reinforcement material from solid waste metal. The composite matrix includes a recycled plastic matrix phase and a polyurethane colloidal matrix phase. The recycled plastic matrix phase is a thermoplastic matrix formed by the hot-melt regeneration of waste recycled plastic; the polyurethane colloidal matrix phase is a tough matrix formed by the curing of polyurethane colloid. Together, they constitute the load-bearing matrix of the sleeper.

[0043] The recycled plastic matrix phase primarily provides the sleeper with continuous molding capability, overall dimensional stability, and basic load-bearing capacity. The polyurethane colloidal matrix phase mainly fills the pores and interface defects within the recycled plastic matrix phase, while simultaneously improving the sleeper's internal toughness, interfacial adhesion, and fatigue energy dissipation capacity. Solid waste metal short fiber reinforcement is dispersed within the composite matrix, primarily providing tensile, flexural, and crack resistance reinforcement.

[0044] The composite sleeper material comprises the following components: based on 100 parts by weight of the recycled plastic matrix phase, 5-30 parts by weight of solid waste metal short fiber reinforcing material, 5-40 parts by weight of polyurethane colloidal matrix phase, and also includes 1-15 parts by weight of compatibilizer, 0.1-5 parts by weight of coupling agent, 0.1-5 parts by weight of antioxidant, 0.1-8 parts by weight of lubricant, and 0-30 parts by weight of inorganic filler.

[0045] When the content of short fibers from solid waste metals is too low, the improvement in the bending, cracking, and pull-out resistance of recycled plastic sleepers is not significant; when the content of short fibers from solid waste metals is too high, it can easily lead to fiber agglomeration, decreased melt fluidity, increased pultrusion molding resistance, and may increase the risk of localized conductivity. Therefore, the preferred content of short fibers from solid waste metals is 10-25 parts by weight.

[0046] The recycled plastics described in this invention can originate from household waste plastics, industrial waste plastics, waste plastic components from rail transit, packaging plastics, waste pipes, waste sheets, waste turnover boxes, waste pallets, waste nylon components, or other heat-melt recyclable plastics. The recycled plastics can be a single type of plastic or a mixture of plastics. To improve the performance stability of composite sleepers, it is preferable to perform preliminary sorting and compatibility modification on the recycled plastics.

[0047] After being crushed, the waste recycled plastic particles are preferably 5-30 mm in size. After washing, they should be dried, preferably with a moisture content not exceeding 0.5%, more preferably not exceeding 0.2%. Excessive moisture content can easily lead to bubbles, pores, and interface defects during the hot-melt recycling process, reducing the mechanical properties of the sleepers.

[0048] The solid waste metal short fiber reinforced material described in this invention is a discontinuous short fiber reinforced material. It can be derived from waste tire steel cord, waste steel wire rope, metal cutting waste wire, steel fiber scraps, waste stainless steel fiber, waste copper-clad steel wire, waste aluminum alloy fiber, or other fibrous solid waste. The solid waste metal short fiber reinforced material is not required to have a regular circular cross-section, nor is a completely clean surface required. It can have curved, rough, flattened, twisted, coated, or have a small amount of surface deposits. These morphologies can, to some extent, improve the mechanical interlocking effect between it and the recycled plastic matrix phase and the polyurethane colloidal matrix phase.

[0049] The solid waste metal short fiber reinforced material described in this invention is not a long fiber reinforced material. Its length is significantly shorter than the length of the sleeper and it does not run longitudinally through the entire sleeper. Preferably, the length of the solid waste metal short fiber is 3-80 mm, more preferably 5-50 mm; the diameter is 0.03-2.00 mm, more preferably 0.05-1.20 mm; and the aspect ratio is 10-400, more preferably 20-250.

[0050] When the length of short fibers from solid waste metals is less than 3 mm, their effect on bridging cracks and improving flexural toughness is limited; when the length is greater than 80 mm, the fibers are prone to entanglement during mixing and pultrusion, affecting dispersion uniformity and molding stability. Therefore, by controlling the range of short fiber lengths, both reinforcing effect and processing performance can be balanced.

[0051] The method for preparing the composite railway sleeper of the present invention includes the following steps: The first step is the pretreatment of waste recycled plastics. The waste recycled plastics are sorted to remove metal blocks, wood chips, mud, glass, and large impurities that are clearly unsuitable for hot-melt recycling. The waste recycled plastics are then crushed into 5-30 mm particles, washed, and dried. The preferred drying temperature is 60-120℃, and the preferred drying time is 2-12 hours. The moisture content of the dried waste plastic recycled particles is preferably no higher than 0.5%, more preferably no higher than 0.2%.

[0052] The second step is the pretreatment of short solid waste metal fibers. The fibrous waste metal fibers are chopped to a length of 3-80 mm. They are then screened to remove excessively long fiber clumps, powdery impurities, and large blocky impurities. For short solid waste metal fibers with heavy oil stains, degreasing treatment can be performed; for those with significant surface rust, light rust removal or surface roughening treatment can be performed; for those requiring improved interfacial adhesion, silane coupling, titanate coupling, phosphating, plasma treatment, or other surface modification treatments can be applied. This invention does not require complete removal of residual rubber, plastic, or oxide layers from the surface of the short solid waste metal fibers. This feature avoids costly deep decomposition and complete separation processes, reducing raw material processing costs.

[0053] The third step is hot melt compounding. Waste plastic recycled granules, solid waste metal short fiber reinforcement, compatibilizer, coupling agent, antioxidant, lubricant, and optional inorganic filler are added to a mixing device for premixing. The premixed material is then fed into a twin-screw extruder, internal mixer, continuous mixer, or other hot melt compounding equipment for melt bonding. The hot melt temperature is determined according to the type of waste plastic, preferably 150-220℃. During the hot melt compounding process, the recycled plastic melts and coats the solid waste metal short fibers. Under shearing and mixing action, the solid waste metal short fibers are dispersed in the recycled plastic melt, forming a recycled plastic melt composite material containing solid waste metal short fibers.

[0054] The fourth step is continuous pultrusion molding. The recycled plastic molten composite containing short fibers from solid waste metal is fed into a pultrusion molding die for the sleeper section. Under the action of a traction device, the molten composite continuously passes through the die, and after shaping, compaction, and cooling, forms a continuous sleeper profile or sleeper blank. It should be noted that pultrusion molding in this invention does not mean that the reinforcing material must be long fibers or continuous fibers. The reinforcing material in this invention is short fibers from solid waste metal. While the short fibers can undergo a certain flow-induced orientation as the molten composite passes through the die, they are still discontinuously distributed and do not run the entire length of the sleeper.

[0055] Step 5: Polyurethane colloid injection and curing. After the sleeper blank cools to a suitable temperature, polyurethane colloid is injected through pre-drilled injection holes, allowing it to penetrate the internal pores and short fiber interfaces. After curing, the polyurethane colloid forms a polyurethane colloid matrix phase, which together with the recycled plastic matrix phase constitutes the composite matrix.

[0056] The pultrusion molding process involves a traction speed of 0.05-2.00 m / min and a molding pressure of 1-10 MPa. The polyurethane colloid is injected at a pressure of 0.1-0.5 MPa, cured at room temperature to 60°C, and cured for 12-72 hours.

[0057] Example 1 A solid waste metal short fiber reinforced recycled plastic-polyurethane composite railway sleeper, the material composition of which is: 100 parts by weight of recycled waste high-density polyethylene; 15 parts by weight of chopped steel cord fibers from waste tires; 10 parts by weight of two-component polyurethane colloid; 5 parts by weight of maleic anhydride grafted polyethylene compatibilizer; 1 part by weight of silane coupling agent KH-550; 0.5 parts by weight of antioxidant B225; 1 part by weight of lubricant EBS; and 15 parts by weight of calcium carbonate filler.

[0058] The chopped fibers of steel cord from waste tires are 5-30 mm in length.

[0059] Waste high-density polyethylene (HDPE) recycled material, chopped steel cord fibers from waste tires, compatibilizers, coupling agents, antioxidants, lubricants, and calcium carbonate fillers are hot-melt mixed to obtain a recycled plastic melt composite material containing solid waste metal short fibers. This composite material is then continuously pultruded using a sleeper section mold to form a sleeper blank. After the sleeper blank cools to a suitable temperature, a two-component polyurethane colloid is injected through pre-drilled injection holes, allowing it to penetrate the internal pores and the short fiber interface. After the polyurethane colloid cures, a solid waste metal short fiber reinforced recycled plastic-polyurethane composite sleeper is obtained.

[0060] The specific preparation process parameters in this embodiment are as follows: Waste high-density polyethylene recycled material is crushed to a particle size of 5-25 mm, dried at 80℃ for 6 hours, and the moisture content after drying is no higher than 0.2%; chopped steel cord fibers from waste tires are screened, impurities removed, and dried at 60℃ for 4 hours; hot melt compounding is performed using a twin-screw extruder with a hot melt temperature of 200-210℃ and a screw speed of 80 r / min; during pultrusion molding, the molten composite material passes through the sleeper section die under the action of the traction device, with a pultrusion traction speed of 0.5 m / min, a molding pressure of 5 MPa, and a die setting section temperature of 180℃; after the sleeper blank cools to below 40℃, a two-component polyurethane colloid is injected with an injection pressure of 0.3 MPa, a curing temperature of room temperature, and a curing time of 48 hours.

[0061] Example 2 A solid waste metal short fiber reinforced recycled plastic-polyurethane composite sleeper suitable for high-load lines has the following material composition: 100 parts by weight of mixed recycled waste polyethylene and waste polypropylene; 28 parts by weight of chopped waste steel wire rope fibers; 18 parts by weight of two-component polyurethane colloid; 6 parts by weight of maleic anhydride grafted polypropylene compatibilizer; 1.5 parts by weight of coupling agent KH-550; 0.8 parts by weight of antioxidant B225; 1.5 parts by weight of lubricant EBS; and 25 parts by weight of fly ash.

[0062] The chopped fibers from waste steel wire rope are 10-50 mm in length. The sleeper bearing area and spike hole area adopt a local enrichment design for short fibers, that is, to increase the content of solid waste metal short fibers in this area, and at the same time to increase the content of polyurethane colloidal matrix phase through local injection.

[0063] The preparation method is the same as in Example 1. The specific preparation process parameters in this example are as follows: the waste polyethylene and waste polypropylene mixed recycled material is sorted and crushed into 5-25 mm particles, dried at 80℃ for 6 h, and the moisture content after drying is not higher than 0.2%; the waste steel wire rope short fiber is chopped, screened and impurity removed, and then surface treated with silane coupling agent, and dried at 60℃ for 4 h; the hot melt mixing adopts a twin-screw extruder, the hot melt temperature is 200-210℃, and the screw speed is 80 r / min; during the pultrusion molding process, the pultrusion traction speed is 0.5 m / min, the molding pressure is 10 MPa, and the die shaping section temperature is 180℃; after the sleeper blank is cooled to below 40℃, the two-component polyurethane colloid is injected, the injection pressure is 0.3 MPa, the curing temperature is room temperature, and the curing time is 48 h.

[0064] Example 3 A recycled plastic-polyurethane composite railway sleeper prepared using short fibers from solid waste metals with residual rubber on the surface has the following material composition: 100 parts by weight of recycled mixed plastic material; 25 parts by weight of chopped steel cord fibers from waste tires with residual rubber on the surface; 20 parts by weight of modified polyurethane colloid; 8 parts by weight of maleic anhydride-grafted polyethylene compatibilizer; 2 parts by weight of coupling agent KH-550; 1 part by weight of antioxidant B225; 5 parts by weight of lubricant EBS; and 20 parts by weight of mineral powder.

[0065] The chopped steel cord fibers from waste tires undergo no pyrolysis or complete stripping; they are only chopped, screened, cleaned, dried, and coupled. A small amount of rubber residue remaining on the surface of the short fibers serves as part of the interfacial transition structure in the composite system, working with the polyurethane colloidal matrix phase to improve the interfacial compatibility between the short fibers and the recycled plastic matrix phase. This embodiment can reduce the pretreatment cost of solid waste metal short fibers and improve the direct utilization efficiency of solid waste metal fibrous waste in railway sleepers.

[0066] The preparation method is the same as in Example 1. The specific preparation process parameters in this example are as follows: the waste mixed plastic recycled material is sorted and crushed, and the particle size is controlled to be 5-25 mm. It is dried at 80℃ for 6 h, and the moisture content after drying is not higher than 0.2%. The short-cut fibers of waste tire steel cord with residual rubber on the surface are 5-40 mm in length. After short cutting, screening and impurity removal, only light surface coupling treatment is performed. No further thermal cracking or complete peeling is performed. After treatment, it is dried at 60℃ for 4 h. The hot melt mixing is carried out using a twin-screw extruder with a hot melt temperature of 200-210℃ and a screw speed of 80 r / min. During the pultrusion molding process, the pultrusion traction speed is 0.5 m / min, the molding pressure is 10 MPa, and the mold setting section temperature is 180℃. After the sleeper blank is cooled to below 40℃, a two-component polyurethane colloid is injected with an injection pressure of 0.3 MPa, a curing temperature of room temperature, and a curing time of 48 h.

[0067] The solid waste metal short fiber reinforced recycled plastic-polyurethane composite sleeper of this invention can be used to prepare composite sleepers for railway engineering using recycled waste plastics and solid waste metal short fibers. Its raw materials are widely available, and the preparation process has the potential for continuous production, which can reduce the disposal pressure of waste plastics and fibrous metal solid waste.

[0068] This invention improves the structural performance and long-term service reliability of recycled plastic railway sleepers by using hot-melt recycled plastic pultrusion molding, polyurethane colloid as a matrix, and solid waste metal short fiber reinforcement. It is suitable for ordinary railways, heavy-haul railways, urban rail transit, industrial and mining railways, bridge lines, tunnel lines, and special vibration reduction lines, and has good engineering application prospects.

[0069] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0070] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A composite railway sleeper material composition made of solid waste metal short fiber reinforced recycled plastic-polyurethane, characterized in that, The composition comprises a composite matrix and a solid waste metal short fiber reinforcement material dispersed in the composite matrix; The composite matrix comprises a recycled plastic matrix phase and a polyurethane colloidal matrix phase; The recycled plastic matrix phase is formed by the recycling of waste plastics through crushing, washing, drying, and hot melting. The polyurethane colloidal matrix phase is formed by curing polyurethane colloidal phase, and together with the recycled plastic matrix phase, it constitutes the composite matrix of the sleeper. The solid waste metal short fiber reinforcement material is a discontinuous short fiber reinforcement material, whose length is less than that of the sleeper and does not run through the entire sleeper longitudinally.

2. The composition according to claim 1, characterized in that, Based on 100 parts by weight of the recycled plastic matrix phase, the solid waste metal short fiber reinforcing material comprises 5-30 parts by weight, the polyurethane colloidal matrix phase comprises 5-40 parts by weight, and also includes 1-15 parts by weight of compatibilizer, 0.1-5 parts by weight of coupling agent, 0.1-5 parts by weight of antioxidant, 0.1-8 parts by weight of lubricant, and 0-30 parts by weight of inorganic filler.

3. The composition according to claim 1, characterized in that, The recycled plastics are selected from one or more of the following: waste polyethylene, waste high-density polyethylene, waste polypropylene, waste polyvinyl chloride, waste polyamide, waste polyester, waste polystyrene, and waste rubber-plastic composite materials. The polyurethane colloid matrix phase is formed by curing one or more of the following: two-component polyurethane colloid, one-component moisture-curing polyurethane colloid, modified polyurethane colloid, and polyurethane elastomer colloid. The polyurethane colloidal matrix phase is used as a component of the composite matrix to fill the internal pores and short fiber interface regions of the recycled plastic matrix phase, rather than serving as a surface coating or external adhesive.

4. The composition according to claim 1, characterized in that, The solid waste metal short fiber reinforcement material is selected from one or more of the following: chopped fibers from waste tire steel cord, chopped fibers from waste steel wire rope, waste metal processing wire, waste steel fiber, waste stainless steel fiber, waste copper-clad steel fiber, and waste aluminum alloy short fiber. The solid waste metal short fiber reinforced material has a length of 3-80 mm, a diameter of 0.03-2.00 mm, and an aspect ratio of 10-400. The surface of the solid waste metal short fiber reinforced material is allowed to retain rubber residues, plastic residues, oxide layers, coatings or organic deposits. It does not need to undergo thermal cracking, chemical dissolution, complete stripping or high purification separation treatment. It can be used after only short cutting, screening, impurity removal, drying and optional degreasing, derusting, surface roughening or coupling treatment.

5. The composition according to claim 4, characterized in that, The solid waste metal short fiber reinforcement material is randomly distributed, semi-directionally distributed, or discontinuously distributed with a certain orientation along the longitudinal direction of the sleeper in the composite matrix; the solid waste metal short fiber reinforcement materials do not form a continuous metal reinforcement bundle or a continuous metal conductive path along the length direction of the sleeper.

6. A solid waste metal short fiber reinforced recycled plastic-polyurethane composite railway sleeper, characterized in that, The composite sleeper includes a sleeper body, which is prepared using the composition described in any one of claims 1-5; The sleeper body includes a rail bearing area, a spike hole area, a middle area of ​​the sleeper, and a bottom area of ​​the sleeper.

7. The composite sleeper according to claim 6, characterized in that, The content of solid waste metal short fiber reinforcement material in the rail bearing area and the spike hole area is higher than that in the middle area and bottom area of ​​the sleeper; or, the content of polyurethane colloidal matrix phase in the rail bearing area and the spike hole area is higher than that in the middle area and bottom area of ​​the sleeper. An insulating protective layer is provided on the outer side of the sleeper body, and the insulating protective layer is formed of recycled plastic matrix phase and / or polyurethane colloidal matrix phase.

8. A method for preparing a composite railway sleeper as described in claim 7, characterized in that, Includes the following steps: S1: The waste plastic is sorted, crushed, washed and dried to obtain recycled plastic pellets; S2: The solid waste metal fibrous waste is chopped, screened, impurities removed and dried to obtain solid waste metal short fiber reinforced material; S3: The waste plastic recycled granules, solid waste metal short fiber reinforcing material, compatibilizer, coupling agent, antioxidant, lubricant and optional inorganic filler are premixed and then hot-melted in a melt mixing equipment to obtain recycled plastic melt composite material containing solid waste metal short fiber; S4: The recycled plastic melt composite material is fed into a pultrusion molding die and continuously passes through the molding die under the action of a traction device to form a continuous sleeper profile or a sleeper blank. S5: After cooling the sleeper blank, polyurethane colloid is injected through the reserved injection hole, allowing it to enter the internal pores and short fiber interface, and after curing, the composite sleeper is obtained.

9. The preparation method according to claim 8, characterized in that, The temperature for hot-melt bonding in step S3 is 150-220℃; The traction speed of the pultrusion molding in step S4 is 0.05-2.00 m / min, and the molding pressure is 1-10 MPa; The pultrusion molding described in step S4 does not require the reinforcing material to be long fibers or continuous fibers. The solid waste metal short fiber reinforcing material only has flow-induced orientation or local orientation in the pultrusion direction. The injection pressure of the polyurethane colloid in step S5 is 0.1-0.5 MPa, the curing temperature is room temperature to 60℃, and the curing time is 12-72 h.

10. The application of the composite sleeper as described in claim 7 in ordinary railways, heavy-haul railways, urban rail transit, industrial and mining railways, bridge lines, tunnel lines, vibration-damping lines, or track structures made of recycled materials.

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