Extrusion and drawing die, device and method for polyurethane foam synthetic sleeper and synthetic sleeper

Abstract

The invention belongs to the technical field of composite material preparation, and particularly relates to an extrusion-drawing die, device and method for a polyurethane foam synthetic sleeper and the synthetic sleeper. The extrusion-drawing die comprises a die body, and the die body is composed of four baffles defining a cavity; each baffle comprises a baffle body for forming a cavity and an extension part which is arranged at the end part of the baffle body and protrudes out of the cavity, one end of the baffle body is propped against the side part of the adjacent baffle, and the side part of the other end of the baffle is propped against the end part of the other adjacent baffle; the baffle body is provided with a driving piece used for applying force to the interior of the cavity, and the extending part is provided with a driving device used for applying abutting force. The driving device is connected with a baffle clamping groove, and the extending part is located in the baffle clamping groove. The device effectively improves the product quality uniformity, improves the transverse strength of the product, improves the product performance, and is high in automation degree.

Description

Technical Field

[0001] The invention belongs to the technical field of composite material preparation, and in particular relates to an extrusion die, a device, a method and a synthetic sleeper for a polyurethane foam synthetic sleeper. Background Art

[0002] Traditional polyurethane foam synthetic sleepers are composite materials made from continuous fibers as reinforcement, polyurethane as a matrix material, and additives, produced through a foaming and pultrusion process. While the continuous fibers reinforce the longitudinal direction, resulting in superior performance, the cross-sectional area lacks fiber reinforcement, relying primarily on the strength of the polyurethane foam resin itself for support. This results in extremely poor transverse performance, and weak transverse strength can easily lead to application risks such as low pullout resistance of screw spikes, delamination, and transverse cracking.

[0003] In order to solve the problem of low lateral strength of products, many domestic units have conducted relevant research in this regard.

[0004] Patent application CN106349446A has developed a reinforced fiber with a content of more than 60% and a density of more than 840g / cm 3 High-fiber content, high-density polyurethane foam synthetic sleepers are made by increasing product density and glass fiber content to improve the overall lateral strength of the product. Although this method is effective, as the density increases, the product cost will also increase significantly. At the same time, the glass fiber content and product density are too high, and the product rigidity is too large, which is inconsistent with the product's shock absorption and lightweight requirements.

[0005] Patent application CN118418322A proposes adding chopped fibers to the product body to improve the transverse strength of the product. However, if the chopped fibers are too short, the transverse reinforcement effect on the product is limited. If the chopped fibers are too long, the fluidity of the resin is affected, making the process very difficult to implement.

[0006] Authorized patent CN108504085B and patent application CN119800780A propose wrapping a polyurethane-impregnated continuous glass fiber with a glass fiber fabric during the main body molding process. The polyurethane-impregnated continuous fiber and glass fiber fabric are then simultaneously fed into a laminating machine for foaming and curing. This wrapping of fiber fabric (glass cloth / reinforcement mat, etc.) improves the product's lateral strength. While this technical approach is theoretically effective and economical, it faces a significant practical challenge. After the sleeper blank is matured and removed from the mold, each surface must be sanded to a depth of 2-4 mm to remove burrs and then painted for weather resistance. However, the thickness of this wrapping fiber fabric, typically no more than 2 mm after curing, is almost completely removed during the main body molding process, resulting in no lateral reinforcement in the actual product. CN108504085B deliberately avoids this problem; CN119800780A proposes adding release paper to avoid surface grinding and spraying, but the feasibility of this technical statement is questionable. First of all, the use of release agent / release paper in production is a routine operation, and its effect is to facilitate product demoulding, but it cannot eliminate flash and subsequent grinding and sanding. In the industry, there has been no real product with reinforced cloth / felt wrapped on the product surface. Therefore, how to improve the lateral strength of the product has become an industry difficulty. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a polyurethane foam synthetic sleeper extrusion die, device, method and synthetic sleeper, which effectively improve the uniformity of product quality, improve the lateral strength of the product, improve the product performance, and have a high degree of automation.

[0008] An embodiment of the present invention provides a pultrusion die for a polyurethane foam synthetic rail sleeper, comprising a die body, the die body being composed of four baffles that enclose a cavity, the baffles comprising a baffle body for forming the cavity and an extension provided at the end of the baffle body and protruding outside the cavity, one end of the baffle body abutting against a side of an adjacent baffle, and the other end of the baffle abutting against the end of another adjacent baffle; The baffle body is provided with a driving member for applying force to the interior of the cavity, and the extension portion is provided with a driving device for applying abutting force; The driving device is connected to a baffle slot, and the extending portion is located in the baffle slot.

[0009] An embodiment of the present invention provides a device for preparing a polyurethane foam synthetic sleeper, comprising a transmission platform for transmitting a core material, a positioning device sequentially arranged along the transmission direction of the core material, an extrusion die as described above for the core material to pass through, and a cutting device; It also includes a roller, on which a fiber fabric is provided, and the fiber fabric is wrapped around the surface of the core material and enters the extrusion die together; Also included is a feeding device for pouring resin into the pultrusion die; A flaw detector is also provided at the position of the cutting device.

[0010] Preferably, the rollers are arranged at the upper and lower ends of the transmission platform, and further include a preforming tooling located between the positioning device and the extrusion die, wherein the preforming tooling preforms the surface of the fiber fabric into a shape matching the four surfaces of the core material.

[0011] Preferably, the feeding device includes a storage barrel I, a storage barrel II and a mixing gun head. The materials in the storage barrel I and the storage barrel II enter the mixing gun head through a pipeline for mixing. The mixed materials enter the extrusion die through a pipeline to impregnate the core material with the surface wrapped with fiber fabric.

[0012] Preferably, it further comprises a traction and clamping mechanism provided between the pultrusion die and the cutting device, wherein the traction and clamping mechanism is used to pull the core material whose surface is wrapped with fiber fabric after solidification.

[0013] The embodiment of the present invention provides a method for preparing a polyurethane foam synthetic sleeper, which is carried out using the above-mentioned preparation device and includes the following steps: Place the cut core material on the transmission platform, place the fiber fabric on the roller so that the fiber fabric covers the surface of the core material, and place the material into the feeding device; The transmission platform is started, and the positioning device controls the position of the core material so that it is located in the center of the extrusion die. The core material with the fiber fabric wrapped on the surface enters the extrusion die. The mixed material is controlled to enter the extrusion die. After the material is fully infiltrated, it is solidified and formed in the extrusion die. The core material with the surface wrapped with fiber fabric after solidification is inspected by a flaw detector to determine the connection position of different core materials; The cutting device cuts the core material with the surface wrapped with fiber fabric after solidification at the above-mentioned connection position to obtain the polyurethane foam synthetic sleeper.

[0014] Preferably, the roller is arranged at the upper and lower ends of the transmission platform, and the preparation device also includes a preforming tooling located between the positioning device and the extrusion die, and the preforming tooling preforms the surface of the fiber fabric into a shape matching the four surfaces of the core material and covers the surface of the core material.

[0015] Preferably, the core material whose surface is wrapped with fiber fabric after solidification is moved under the action of the traction and clamping mechanism; the material is non-foaming resin.

[0016] The embodiment of the present invention provides a polyurethane foam synthetic sleeper, which is prepared by adopting the preparation method.

[0017] The beneficial effects of the present invention are that, by wrapping a layer / multiple layers of felt / cloth all around the product, the lateral strength of the traditional polyurethane foam synthetic sleeper can be greatly improved, and the risk of product delamination and lateral cracking can be reduced; at the same time, the molding method also has the advantages of being fast, efficient, and low-cost.

[0018] The traditional process of wrapping a layer of reinforcing felt / cloth on the surface of the blank is to set several composite felts with lateral reinforcement on the surface of the blank during production. The glass fiber, composite felt, and polyurethane foam are integrated into one and fill the laminating machine cavity. After aging, they are formed into rail sleeper blanks. This process implementation path is too ideal and difficult to implement in practice. This is mainly because the surface of the blank after production needs to be sanded 2mm-4mm to remove burrs, and the thickness of the composite felt / cloth is generally less than 0.5mm. Therefore, the reinforced cloth / felt will be completely sanded, and the actual product will not be wrapped with cloth / felt reinforcement. Another more conventional process implementation path is to manually wrap the sanded blank surface with cloth, but this process path has extremely slow production efficiency and extremely high cost. At the same time, the quality of manual cloth wrapping is unstable. Therefore, how to quickly and efficiently reinforce traditional polyurethane foam synthetic sleepers with lateral cloth is a major problem in the industry.

[0019] The present invention utilizes split-part molding. After the blank is prepared, it is sanded to produce a sanded blank, i.e., the core material. The core material is then coated with a transversely reinforced fiber fabric and cured to form the finished product. The pultrusion die of the present invention prevents the impact of core material dimensional deviations on traction force, ensuring a smoother traction process. Furthermore, it ensures a relatively uniform amount of resin impregnation across all parts of the fiber fabric, preventing unstable product performance.

[0020] The present invention can quickly wrap felt / cloth on the surface of the product for reinforcement, has a high degree of automation, and the production is continuous, stable and controllable. At the same time, the overall bending resistance of the produced product is greatly improved.

[0021] The polyurethane foam synthetic sleeper of the present invention has strong product designability, and the skin can be pultruded with different fiber cloth layers, such as 0° fiber, 0° / 90° biaxial cloth, ±45° biaxial cloth, etc., and can be targetedly selected and designed according to product usage scenarios, performance requirements, etc.

[0022] The invention adopts biaxial cloth polyurethane pultrusion, has a smooth surface, better appearance quality, and stronger adhesion to paint. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic structural diagram of the extrusion die for the polyurethane foam synthetic sleeper of the present invention.

[0024] Figure 2 It is a structural schematic diagram of the preparation device of the polyurethane foam synthetic sleeper of the present invention.

[0025] Figure 3 It is a schematic structural diagram of the polyurethane foam synthetic sleeper of the present invention.

[0026] Figure 4 It is a structural schematic diagram of the preforming tooling of the present invention. Figure 4 (a) is a schematic structural diagram of the first preformed plate, Figure 4 (b) is a schematic structural diagram of the second preformed plate. Figure 4 (c) is a schematic structural diagram of the third preformed plate.

[0027] In the figure, 1 is the cavity, 2 is the baffle, 21 is the baffle body, 22 is the extension part, 3 is the pressure-bearing cylinder, 4 is the dense cylinder, 41 is the connecting rod, and 42 is the baffle slot; 5. Extrusion die, 6. Core material, 7. Transmission platform, 8. Positioning device, 9. Fiber fabric, 10. Roller, 11. Preforming tooling, 12. Storage barrel I, 13. Storage barrel II, 14. Mixing gun head, 15. Traction and clamping mechanism, 16. Flaw detector, 17. Cutting device, 18. Skin. DETAILED DESCRIPTION Example 1

[0028] like Figure 1 As shown, this embodiment 1 is a pultrusion die 5 for a polyurethane foam synthetic sleeper, comprising a die body, the die body being composed of four baffles 2 that enclose a cavity 1. The baffles 2 include a baffle body 21 for forming the cavity 1 and an extension 22 provided at the end of the baffle body 21 and protruding outside the cavity 1. One end of the baffle body 21 abuts against the side of an adjacent baffle 2, and the other end of the baffle 2 abuts against the end of another adjacent baffle 2. The baffle body 21 is provided with a driving member for applying force to the interior of the cavity 1 , and the extension portion 22 is provided with a driving device for applying abutting force.

[0029] The shape of the cavity 1 matches the shape of the final product, i.e., the polyurethane foam synthetic sleeper, which is a rectangle, generally a square. Therefore, four baffles 2 are enclosed at 90° to each other to obtain a rectangular cavity 1. The four sides of the rectangle are the baffles 2. More precisely, the four sides of the rectangle are the baffle bodies 21 of the baffles 2. Each baffle 2 includes a baffle body 21 and an extension 22. The baffle body 21 and the extension 22 form a baffle 2 as a whole. When set, one end of the baffle body 21 abuts against the side of the adjacent baffle 2, and the side of the other end of the baffle 2 abuts against the end of another adjacent baffle 2.

[0030] like Figure 1As described above, the right end of the lowest baffle 2 abuts the side of the adjacent baffle 2 (i.e., the right baffle of the lowest baffle 2) (specifically, the connection between the baffle body 21 and the extension 22), and the left end of the lowest baffle 2 (i.e., the connection between the baffle body 21 and the extension 22) abuts the end (i.e., the lower portion) of another adjacent baffle 2 (i.e., the left baffle of the lowest baffle 2). Each baffle 2 is arranged in this manner, so the size of the mold cavity 1 can be adjusted by controlling the length of the baffle body 21 on each baffle 2 (the length of the baffle 2 is fixed; the longer the baffle body 21, the shorter the extension 22).

[0031] The baffle body 21 is provided with a driving member (i.e., a pressure-bearing cylinder 3) for applying force to the interior of the cavity 1. Since the present pultrusion die 5 can be placed on a fixed platform, such as a fixed frame or the ground, the lower part of the baffle body 21 at the bottom is a fixed platform. The pultrusion die 5 will be pressed downward by the influence of gravity. The fixed platform itself has an upward reaction force, which plays the role of a driving member. That is, the fixed platform is equivalent to the driving member. At this time, it is only necessary to set the driving members on the baffle body 21 on the other three sides, that is, Figure 1 As shown. Of course, if the pultrusion die 5 is suspended, four drive components (i.e., pressure cylinders 3) are required. Pressure cylinders 3 apply pressure to the interior of cavity 1, controlling its dimensions. Pressure cylinders 3 are equipped with limiters. In continuous operation, the travel of pressure cylinders 3 is 1-2 mm. Within this range, the pressure from pressure cylinders 3 controls baffle 2.

[0032] The extension portion 22 is provided with a driving device (i.e., a dense cylinder 4, 4 in number) for applying abutting force. The abutting force described in the present invention is the force when one end of the baffle body 21 abuts against the side of the adjacent baffle 2. The dense cylinder 4 applies pressure and transmits it to the extension portion 22. The extension portion 22 and the baffle body 21 are integrated and transmitted to the side of the adjacent baffle 2 through the baffle body 21. The force applied by the driving member on the baffle body 21 on the baffle 2 and the force applied by the adjacent driving device on the extension portion 22 of the adjacent baffle 2 are in opposite directions and offset each other, so that the adjacent baffles 2 are in close contact with each other without leaving any gaps, i.e., sealed.

[0033] By adopting the structural design of the present application, the size of the cavity 1 can be controlled (the size of the cavity 1 can be changed), and the sealing can be maintained before, during and after the change process, which facilitates subsequent curing and molding.

[0034] The drive device (i.e., the compacting cylinder 4) is connected to a baffle slot 42 (i.e., the piston rod end of the compacting cylinder 4 is connected to the baffle slot 42). The extension 22 is located in the baffle slot 42, facilitating the connection and force application between the compacting cylinder 4 and the extension 22. A 2-4 mm clearance is provided between the baffle slot 42 and the extension 22, facilitating the left-right movement of the baffle.

[0035] Due to space limitations, in this embodiment, a connecting rod 41 is provided between the baffle slot 42 and the compact cylinder 4 so that the compact cylinder 4 may not be located on the extension line of the baffle 2 , facilitating arrangement.

[0036] Generally speaking, during pultrusion, if the cross-sectional dimensions of the final product are designed to be 240mm×240mm and the thickness of the fiber fabric 9 is designed to be 5mm, then the core material 6 (i.e., the sanding blank) is designed to be 230mm×230mm. However, due to the ±1mm sanding accuracy of the blank, the actual sanding blank size may be as small as 229mm×229mm and as large as 231mm×231mm. In specific implementation, the minimum blank size of 229mm×229mm is first adjusted, and the size of the cavity where the baffle 2 is spliced ​​is adjusted to the minimum limit of 239mm×239mm. During the pultrusion process, if the sanding blank size is too large, the entire cavity 1 will be oversaturated, and the expansion force within the cavity 1 will cause the baffle 2 to move backward, thereby increasing the size of the cavity 1. When the sanding blank size decreases, the expansion force within the cavity 1 will decrease, and the pressure cylinder 3 will push the baffle 2 forward, thereby reducing the size of the cavity 1. Therefore, the size of the cavity 1 of the entire pultrusion die 5 can be fine-tuned according to the change of the blank size.

[0037] In the traditional pultrusion process, the position and size of the core rod are fixed. This embodiment 1 is equivalent to a sanded blank as a pultrusion core rod, and is in a moving state. There will be certain deviations in the size of each sanded blank. For example, if the required blank cross-sectional size is 230mm×230mm, the actual cross-sectional size of each blank will fluctuate by ±1mm. If the sanded blank is suddenly too large, it is easy to cause pultrusion mold blockage; and if the sanded blank is too small, it is easy to cause the fiber fabric wrapped in the outer layer of the mold to be not dense enough, thereby affecting the strength of the surface fiber reinforcement layer. The fluctuation of the cross-sectional size of the blank can easily cause the entire pultrusion process to be unstable and unable to be implemented. This embodiment 1 adjusts the size of the cavity 1 and extrudes densely, and adaptively adjusts to avoid the influence of the fluctuation of the cross-sectional size of the blank and the fluctuation of the blank movement on pultrusion, thereby greatly improving the quality of the product. Example 2

[0038] This embodiment 2 is a preparation device for a polyurethane foam synthetic sleeper, such as Figure 2As shown, it includes a transmission platform 7 for transmitting the core material 6, a positioning device 8 arranged in sequence along the transmission direction of the core material 6, a pultrusion die 5 for the core material 6 to pass through and as described in Example 1, and a cutting device 17; It also includes a roller 10, on which a fiber fabric 9 is provided. The fiber fabric 9 is wrapped around the surface of the core material 6 and enters the pultrusion die 5 together. Also includes a feeding device for pouring resin into the pultrusion die 5; A flaw detector 16 is also provided at the position of the cutting device 17 .

[0039] The core material 6 is a sanded blank, and the transmission platform 7 can be a conveyor belt, such as a roller conveyor belt, as long as it can realize the transmission of the core material 6.

[0040] The positioning device 8 is used to position the left and right positions of the core material 6 on the conveying platform 7 so that it is aligned with the pultrusion die 5, and to ensure that the core material 6 is located in the center of the pultrusion die 5. The positioning device 8 can be a plurality of positioning rods, which are provided at the left and right ends of the core material 6 to ensure that the position of the core material 6 meets the requirements.

[0041] The cutting device 17 is a conventional cutting device 17, used to cut the core material 6 after solidification and forming, with the surface wrapped with fiber fabric 9. In practice, the core material 6 is already cut before entering the pultrusion die 5, but the fiber fabric 9 is continuous. Therefore, the core material 6 after solidification and forming, with the surface wrapped with fiber fabric 9, appears continuous from the outside and needs to be cut using the cutting device 17. The flaw detector 16 can be used to detect the connection between the two core materials 6, and then the cutting device 17 is used to cut at this connection. The flaw detector 16 can scan for cracks within the product and is a prior art flaw detector, such as the ULTRA DC2 composite material flaw detector. In conventional pultrusion processes, cutting is generally done to a fixed length. If the required length is 3000mm, fixed-length cutting is performed using photoelectric sensing or mechanical methods. The cutting length deviation can generally reach ±2mm. If fixed-length cutting is used, errors will inevitably accumulate during continuous cutting, ultimately making it difficult to align the cutting position with the end position of the original sanded blank. In this embodiment, a flaw detector 16 is used to determine the connection position of the two core materials 6, ensuring that the size of the final product is the same as the size of the core materials 6. The cutting device 17 uses a grinding wheel with a thickness of 5-10mm. The gap between two sanded blanks is generally 0-2mm. Therefore, the internal gap detection of the product by the flaw detector 16 and then cutting with the grinding wheel can ensure that each cut is at the end position of the core material 6.

[0042] The fiber fabric 9 rolled up in a ball is placed on the roller 10. The fiber fabric is a mixture of one or more of continuous fiber, chopped strand mat, continuous mat, stitched mat, composite mat, biaxial cloth, triaxial cloth, and uniaxial cloth, preferably biaxial cloth. The roller 10 is used for both unwinding and positioning the fiber fabric 9 so that it is parallel and square to the surface of the core material 6. The roller 10 and the corresponding fiber fabric 9 can be arranged on the four surfaces of the core material 6, or only on the upper and lower surfaces of the core material 6, and the fiber fabric 9 is wrapped on the two surfaces of the core material 6 by a preforming tooling 11. Preferably, the roller 10 is arranged at the upper and lower ends of the transmission platform 7, that is, there are two rollers 10 and corresponding fiber fabrics 9, and also includes a preforming tooling 11 located between the positioning device 8 and the extrusion die 5, and the preforming tooling 11 preforms the surface of the fiber fabric 9 into a shape that matches the two surfaces of the core material 6. As Figure 2 As shown, the preforming tool 11 preforms the cross section of the fiber fabric 9 at the lower end of the transmission platform 7 into an L-shape, that is, two vertical surfaces, and the two sides of the L-shape are matched with the two adjacent sides of the core material 6 respectively, as shown in FIG. Figure 2 As shown, the two L-shaped cross-sections of the preformed fiber fabric 9 at the lower end correspond to the bottom and right sides of the core material 6, including the bottom and right sides of the core material 6; the two L-shaped cross-sections of the preformed fiber fabric 9 at the upper end correspond to the left and top sides of the core material 6, including the left and top sides of the core material 6.

[0043] The preforming tooling 11 comprises two L-shaped forming plates, so that the two fiber fabrics 9 are formed into L shapes and covered on the four surfaces of the core material 6. Figure 4 As shown, the preforming tooling 11 includes three preforming plates arranged in sequence along the advancing direction of the fiber fabric 9, namely the first preforming plate (such as Figure 4 (a)), the second preformed plate (as shown Figure 4 (b)) and the third preformed plate (as shown Figure 4 (c) shows), the preformed plate includes two straight plates at a certain angle, the angle of the two straight plates of the first preformed plate is 140-160° (preferably 150°), the angle of the two straight plates of the second preformed plate is 130-140° (preferably 135°), and the angle of the two straight plates of the third preformed plate is 90°. Finally, under the action of the third preformed plate, one fiber fabric 9 is L-shaped, the two fiber fabrics 9 are rectangular as a whole, and the two L-shaped fiber fabrics are overlapped and enter the next process.

[0044] The feeding device includes a storage barrel I 12, a storage barrel II 13 and a mixing gun head 14. The materials in the storage barrel I 12 and the storage barrel II 13 enter the mixing gun head 14 through a pipeline for mixing. The mixed materials enter the extrusion die 5 through a pipeline to infiltrate the core material 6 with the fiber fabric 9 wrapped on the surface. That is, a hole is opened at the upper end of the extrusion die 5, and the mixed material enters the extrusion die 5 from the hole through the pipeline.

[0045] Along the moving direction of the core material 6, the pultrusion die 5 is divided into an impregnation section and a high-temperature curing section, and the high-temperature curing section is generally divided into three sections. Depending on the pultruded product, the length of the pultrusion die 5 is generally 0.8m-3.5m, and the length of the impregnation section is generally 0.2m-0.6m. The longer the die, the better the impregnation and curing effects, but the greater the traction resistance. The length of the die of the present invention is 1.5m, and the length of the impregnation section is 0.4m. After the surface of the core material 6 is wrapped with the fiber fabric 9, it is continuously pultruded and injected while pultruding. The flow rate of the injected glue is controlled to ensure that the fiber fabric is fully impregnated. The pultrusion speed of the present invention is 0.4m / min.

[0046] The high-temperature curing section uses upper and lower L-shaped heating plates to wrap the mold, with a total of three groups at the front, middle and rear, to achieve three-stage temperature control heating. The heating plates are heated by resistance wires.

[0047] The traction and clamping mechanism 15 is provided between the pultrusion die 5 and the cutting device 17. The traction and clamping mechanism 15 is used to pull the core material 6 with the fiber fabric 9 wrapped on the surface after solidification. Since there is a large friction between the core material 6 with the fiber fabric 9 wrapped on the surface after solidification and the pultrusion die 5, the traction and clamping mechanism 15 can effectively pull the core material 6 with the fiber fabric 9 wrapped on the surface after solidification and to enter the subsequent process. The traction and clamping mechanism 15 is a conventional structure and can be a parallelogram mechanism, a cross-fixing mechanism, a screw mechanism, a gear mechanism, a swing mechanism, etc. Example 3

[0048] Example 3 is a method for preparing a polyurethane foam synthetic sleeper, which is carried out using the preparation device described in Example 2 and includes the following steps: Place the cut core material 6 on the transmission platform 7, place the fiber fabric 9 on the roller 10, so that the fiber fabric 9 covers the surface of the core material 6, and place the material into the feeding device; The transmission platform 7 is started, and the positioning device 8 controls the position of the core material 6 so that it is located at the center of the pultrusion die 5. The core material 6 with the fiber fabric 9 wrapped on the surface enters the pultrusion die 5. The mixed material is controlled to enter the pultrusion die 5. After the material is fully infiltrated, it is solidified and formed in the pultrusion die 5. The core material 6 with the fiber fabric 9 wrapped on the surface after solidification is inspected by a flaw detector 16 to determine the connection positions of different core materials 6; The cutting device 17 cuts the core material 6 with the surface wrapped with the fiber fabric 9 after solidification at the above-mentioned connection position to obtain a polyurethane foam synthetic sleeper.

[0049] The roller 10 is arranged at the upper and lower ends of the transmission platform 7. The preparation device also includes a preforming tooling 11 located between the positioning device 8 and the extrusion die 5. The preforming tooling 11 preforms the surface of the fiber fabric 9 into a shape matching the two surfaces of the core material 6 and covers the surface of the core material 6.

[0050] The core material 6 , whose surface is covered with the fiber fabric 9 after solidification, moves under the action of the traction and clamping mechanism 15 .

[0051] Specifically, the detailed process of the preparation method is: (1) Blank positioning: The surface of the polyurethane foam synthetic sleeper is sanded to obtain a sanded blank, i.e., the core material 6. The sanded blank is placed on the transmission platform 7, and the transmission platform 7 is rotated to transmit the sanded blank to the extrusion die 5. If the cross-sectional size of the mold cavity 1 is 240mm 240mm, the thickness of the fiber fabric wrapped around the outside is designed to be 5mm, so the sanding blank size needs to be 230mm Before the sanded blank enters the pultrusion die 5, two sets of left and right positioning devices 8 are installed. Their main function is to keep the sanded blank in the left and right center of the cavity 1 of the pultrusion die 5. The pultrusion die 5 is adjusted up and down to ensure that the sanded blank is in the upper and lower center of the cavity 1 of the pultrusion die 5.

[0052] (2) Fiber fabric design: The fiber fabric 9 is rolled into a ball and placed on the roller 10. The roller 10 and the fiber fabric 9 consist of two groups, the upper group is responsible for the upper wall thickness and the left wall thickness of the formed skin, and the lower group is responsible for the lower wall thickness and the right wall thickness of the formed skin. The width of the fiber fabric 9 is determined according to the width of the molded product section cavity. For example, if the molded product section is 240 240mm, the width of the upper cavity + the width of the left cavity is 480mm. Similarly, the width of the lower cavity + the width of the right cavity is also 480mm. The width of the fiber fabric is generally the required cavity width plus 5% margin, so the width of the upper and lower fabrics is 480. 1.05 = 504 mm. The excess margin is mainly due to the need for overlap transition of the upper and lower fabrics at the corners. The surface density of the fiber fabric 9 is 100-1500 g / m 2One or more layers of fiber fabric can be stacked, and different types of fiber fabric 9 can be stacked, such as using a [90° / 0°]s symmetrical layer or a [±45° / 0°]s counter-layer. In addition to the upper and lower two-piece wrapping design (each piece needs to be folded into an L shape), the fiber fabric 9 can also be wrapped in a cavity design with two left and right pieces (each piece needs to be folded into an L shape), or four pieces each.

[0053] (3) Pre-forming tooling positioning: Since the fiber fabric 9 is initially unfolded into a flat state, the upper fiber fabric is responsible for forming the upper wall thickness and the left wall thickness. Therefore, before the fiber fabric enters the cavity, a pre-forming tooling 11 is required for transition. The main purpose is to allow the flat fiber fabric to gradually transition to a 90-degree bent fiber fabric (with an L-shaped cross section) and smoothly enter the cavity 1. The pre-forming tooling 11 includes three devices, front, middle, and back, for gradual transition.

[0054] (4) Resin injection: The impregnated resin (i.e. material) can be polyurethane resin, vinyl resin, unsaturated resin, or epoxy resin, with polyurethane resin being preferred. If vinyl resin, unsaturated resin, or epoxy resin is used, the impregnation method can be closed or open, i.e., the fiber fabric is impregnated after passing through a pool filled with resin, and then the fiber fabric impregnated with resin is directly placed in a mold for curing and molding, without the need for an impregnation box.

[0055] The present invention prefers polyurethane resin, preferably using a dipping box (a portion of the pultrusion die 5 functions as the dipping box). This is primarily because polyurethane resin is particularly sensitive to ambient temperature and humidity. Using an open dipping process, the resin readily absorbs moisture from the air, which can affect molding. The polyurethane resin comprises an isocyanate (i.e., the material in storage tank I 12), primarily diphenylmethane diisocyanate; and a polyol blend (i.e., the material in storage tank II 13), which does not contain a foaming agent. The two components are metered separately by a metering device and then mixed in a mixing gun 14. The mixed resin is then injected into the pultrusion die 5 via a glue injection hose.

[0056] (5) Mold high temperature curing: After the fiber fabric 9 enters the pultrusion die 5, the resin injected by the injection hose begins to infiltrate the fiber fabric 9 and begins to solidify and form in the pultrusion die 5 as the pultrusion is running. The length of the pultrusion die 5 is generally 1-2m. The pultrusion die 5 generally has three-stage temperature control. The front section is the preheating section, the temperature is generally 40-80℃, the middle section is 120-180℃, and the rear end is 160-200℃.

[0057] (6) Traction and pultrusion: The fiber fabric impregnated with resin passes through the pultrusion die 5 and is cured at high temperature. After exiting the die, it is already solidified and is pulled back and forth by two alternately running traction clamping mechanisms 15, thereby forming continuous and stable traction.

[0058] (7) Cutting: Finally, the cutting device 17 is used to cut the product to a fixed length according to the actual length required by the product, so that the surface of the core material 6 is wrapped with a layer of reinforcing fiber fabric.

[0059] The final product structure is as follows Figure 3 As shown, a skin 18 is formed on the surface of the core material 6. The skin 18 is a material formed by curing the fiber fabric 9 impregnated with resin. The thickness of the skin 18 can be 0.5-10 mm. Example 4

[0060] The performance of different polyurethane foam synthetic sleepers was measured. The new polyurethane foam synthetic sleeper was prepared using the preparation method of Example 3. The cross-sectional dimensions of the product were designed as follows: the skin 18 was a rectangular cross-section with a cross-sectional dimension of 200 mm × 140 mm and a wall thickness of 5 mm; the core material 6 had a cross-sectional dimension of 190 mm × 130 mm and a core material density of 0.74 g / cm 3 .

[0061] Comparative Example 1 is a traditional polyurethane foam synthetic sleeper, which is made of the same material as the core material 6 and has a cross-sectional size of 200 mm×140 mm.

[0062] The [90° / 0°]s cloth layer is used for transverse reinforcement pultrusion. The resin is non-foamed polyurethane resin with a resin content of 25%. The core material 6 is a traditional polyurethane foamed synthetic sleeper with a density of 0.74g / cm 3 The performance comparison of the prepared novel polyurethane foam synthetic sleeper and the product of Comparative Example 1 is shown in Table 1 and Table 2.

[0063] Table 1 Comparison of test results of polyurethane foam synthetic sleepers and finished products of comparative example 1

[0064] Table 2 Comparison of product skin and core material performance test results

[0065] The performance of different polyurethane foam synthetic sleepers was measured. The new polyurethane foam synthetic sleeper was prepared by the preparation method of Example 3. The cross-sectional dimensions of the product were designed as follows: the skin 18 was a rectangular cross-section with a cross-sectional dimension of 240 mm × 240 mm and a wall thickness of 5 mm; the core material 6 had a cross-sectional dimension of 230 mm × 230 mm and a density of 0.8 g / cm 3 .

[0066] Comparative Example 2 is a traditional polyurethane foam synthetic sleeper, the material of which is the same as that of core material 6, and the cross-sectional size of Comparative Example 2 is 240 mm×240 mm.

[0067] The [±45° / 0° / 90°]s cloth layer is used for transverse reinforcement pultrusion. The resin is non-foamed polyurethane resin with a resin content of 20%. The core material 6 is a traditional polyurethane foamed synthetic sleeper with a density of 0.8g / cm 3 The product performance comparison of the prepared polyurethane foam synthetic sleeper and core material 6 is shown in Table 3 and Table 4.

[0068] Table 3 Comparison of test results of polyurethane foam synthetic sleepers and core material 6 finished products

[0069] Table 4 Comparison of performance test results of polyurethane foam synthetic sleepers and core material 6 Example 5

[0070] The present invention adopts split molding, and the process molding method included mainly has two steps. The first is the production of core material 6, which is a traditional polyurethane foam synthetic sleeper preparation method, using a polyurethane pultrusion foaming molding process; the second is the secondary pultrusion of the sleeper surface with a skin, which is a non-foaming polyurethane resin pultrusion process. This process is essentially different from the traditional non-foaming polyurethane pultrusion process. The traditional non-foaming polyurethane pultrusion core rod is fixed, while the present invention creatively uses the core material 6 as the core rod of the extrusion die, and the core rod is movable, and the size of the core rod fluctuates. Its mold design principle, cutting principle, etc. are very different from traditional polyurethane pultrusion.

[0071] The resin material used in the skin of the present invention is different from the resin material used in the core material 6. The core material 6 is a conventional polyurethane foam synthetic sleeper, and the polyurethane used is a foamed polyurethane, in which the polyol mixture contains water as a foaming agent. During molding, after the isocyanate and polyol mixture are mixed, the -NCO in the isocyanate reacts with water to produce CO2 gas. Simultaneously, the -NCO reacts with the hydroxyl group in the polyol to produce urethane. The cured resin product is a rigid polyurethane foam, which, when combined with continuous fiber, becomes a polyurethane foam synthetic sleeper. Due to its cellular structure, polyurethane foam offers advantages such as low density, but also suffers from poor strength. The polyurethane used in the skin is a non-foamed polyurethane. The polyol mixture contains no water, so there is no foaming reaction. The isocyanate and polyol undergo a polycondensation reaction to form polyurethane. The cured product is continuous and dense, free of cells, and exhibits high strength and high molecular chain density. Therefore, by impregnating the fiber fabric with the non-foamed polyurethane resin, the skin is much stronger than the core material. Ultimately, simply wrapping the skin with a few millimeters can significantly improve the overall strength of the product.

[0072] The traditional core material surface is integrally molded with a fiber fabric wrapped around it. In addition to the surface fiber fabric being polished off during the later sanding process, the skin strength is also extremely low, resulting in an insignificant lateral reinforcement effect on the product as a whole. The main reason is that during integral molding, the resin impregnating the continuous fiber and the resin impregnating the surface reinforcing fiber fabric are the same (if two different resin systems are used, the chemical reactions of the two resin systems are different, the curing temperatures are different, etc., and there will be serious interference between them), both of which are foamed polyurethane resins. The reinforcing layer formed by this foamed resin and glass fiber fabric has poor lateral performance and has little improvement on the performance of the finished product. The present invention adopts split molding, and the resin impregnating the fiber fabric is a polyurethane resin for pultrusion, which is a non-foamed polyurethane resin. The cured product is continuous and dense, has no bubbles, and has high strength and high molecular chain density.

[0073] Table 5 compares the properties of the polyurethane foam resin used in the polyurethane foam synthetic sleeper and the polyurethane resin used in the skin. Since the skin of the present invention is formed in separate pieces, in addition to polyurethane resin, vinyl resin, unsaturated resin, epoxy resin, etc. can also be used for pultrusion, thus expanding the range of options and enhancing applicability.

[0074]

[0075] In addition to greatly improving the strength of the product, the present invention also has the following advantages: (1) Due to the limitations of traditional polyurethane foam synthetic sleeper laminating machines, the cross-section of the formed product is rectangular, and the straight corners are easily damaged during transportation and installation. If the corners are rounded through a secondary process, the cost is too high. Since the skin of the present invention is made of ordinary polyurethane pultrusion, its mold can be designed to round the straight corners, so that the straight corners of the formed skin product can be turned into rounded corners, thus solving the problem of the product being easily damaged.

[0076] (2) Since the surface of traditional polyurethane foam synthetic sleepers has a cellular structure, it is generally necessary to scrape putty before spraying paint after sanding the surface. On the one hand, this can make the paint more beautiful, and on the other hand, it can also reduce the amount of paint used (the surface of the sleeper has a cellular structure, and the paint sprayed without putty is easily absorbed by the pores); the skin of the present invention adopts non-foaming polyurethane pultrusion, the product is continuous and dense, and it has no pores. The skin surface does not need to be sanded or puttyed, and can be directly sprayed with paint.

[0077] (3) In addition to being able to be directly sprayed with paint, the surface of the skin can also be made paint-free. The polyurethane pultrusion of the skin generally uses aromatic polyurethane, which contains benzene rings, has strong molecular chain rigidity, and has high mechanical strength, but poor yellowing resistance, and generally requires surface spraying with paint for protection. In this application, the polyurethane resin for the skin can use not only aromatic polyurethane but also aliphatic polyurethane, which contains linear or cyclic aliphatic hydrocarbons, has high molecular chain flexibility, and excellent UV resistance. Therefore, if aliphatic polyurethane is used for pultrusion, the skin does not need to be further sprayed with paint.

[0078] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of protection of the present application is limited to these examples. In line with the present application, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of different aspects of one or more embodiments of the present application as described above, which are not provided in detail for the sake of simplicity.

[0079] The one or more embodiments of this application are intended to encompass all such substitutions, modifications, and variations that fall within the broad scope of this application. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of one or more embodiments of this application should be included in the scope of protection of this application.

Claims

1. A polyurethane foam synthetic sleeper extrusion die, characterized in that: The mold body comprises a mold body, wherein the mold body is composed of four baffles (2) that enclose a mold cavity (1), the baffle (2) comprising a baffle body (21) for forming the mold cavity (1) and an extension (22) provided at the end of the baffle body (21) and protruding outside the mold cavity (1), one end of the baffle body (21) abuts against the side of an adjacent baffle (2), and the side of the other end of the baffle (2) abuts against the end of another adjacent baffle (2); The baffle body (21) is provided with a driving member for applying force to the interior of the cavity (1), and the extension portion (22) is provided with a driving device for applying abutting force; The driving device is connected to a baffle slot (42), and the extension portion (22) is located in the baffle slot (42).

2. A device for preparing a polyurethane foam synthetic sleeper, characterized in that: It comprises a transmission platform (7) for transmitting the core material (6), positioning devices (8) arranged in sequence along the transmission direction of the core material (6), a pultrusion die and a cutting device (17) as claimed in claim 1 through which the core material (6) passes; It also includes a roller (10), on which a fiber fabric (9) is provided, and the fiber fabric (9) is wrapped around the surface of the core material (6) and enters the pultrusion die together; Also included is a feeding device for pouring resin into the pultrusion die; A flaw detector (16) is also provided at the position of the cutting device (17).

3. The preparation device according to claim 2, characterized in that: The roller (10) is arranged at the upper and lower ends of the transmission platform (7), and also includes a preforming tool (11) located between the positioning device (8) and the extrusion die, and the preforming tool (11) preforms the surface of the fiber fabric (9) into a shape that matches the four surfaces of the core material (6).

4. The preparation device according to claim 2, characterized in that: The feeding device comprises a storage barrel I (12), a storage barrel II (13) and a mixing gun head (14); the materials in the storage barrel I (12) and the storage barrel II (13) enter the mixing gun head (14) through a pipeline for mixing; the mixed materials enter the extrusion die through the pipeline to impregnate the core material (6) whose surface is wrapped with fiber fabric (9).

5. The preparation device according to claim 2, characterized in that: It also includes a traction clamping mechanism (15) arranged between the pultrusion die and the cutting device (17), wherein the traction clamping mechanism (15) is used to pull the core material (6) whose surface is wrapped with fiber fabric (9) after solidification.

6. A method for preparing a polyurethane foam synthetic sleeper, characterized in that: The method is carried out using the preparation device according to any one of claims 2 to 5, comprising the following steps: Place the cut core material (6) on the transmission platform (7), place the fiber fabric (9) on the roller (10), wrap the fiber fabric (9) around the surface of the core material (6), and place the material into the feeding device; The transmission platform (7) is started, and the positioning device (8) controls the position of the core material (6) so that it is located at the center of the extrusion die. The core material (6) with the fiber fabric (9) wrapped on the surface enters the extrusion die, and the mixed material is controlled to enter the extrusion die. After the material is fully infiltrated, it is solidified and formed in the extrusion die; The core material (6) having the surface wrapped with the fiber fabric (9) after solidification is inspected by a flaw detector (16) to determine the connection positions of different core materials (6); The cutting device (17) cuts the core material (6) whose surface is wrapped with the fiber fabric (9) after solidification at the above-mentioned connection position to obtain a polyurethane foam synthetic sleeper.

7. The preparation method according to claim 6, characterized in that: The roller (10) is arranged at the upper and lower ends of the transmission platform (7). The preparation device also includes a preforming tool (11) located between the positioning device (8) and the extrusion die. The preforming tool (11) preforms the surface of the fiber fabric (9) into a shape matching the four surfaces of the core material (6) and covers the surface of the core material (6).

8. The preparation method according to claim 6, wherein: The core material (6) whose surface is wrapped with fiber fabric (9) after solidification and molding is moved under the action of the traction clamping mechanism (15); the material is non-foaming resin.

9. A polyurethane foam synthetic sleeper, characterized in that: The method is described in any one of claims 6 to 8.

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