Polyurethane foam synthetic sleeper extrusion die, device, method and synthetic sleeper

Abstract

This invention belongs to the field of composite material preparation technology, specifically relating to a pultrusion mold, apparatus, method, and synthetic railway sleeper for polyurethane foam. The mold body comprises four baffles that enclose a cavity. Each baffle includes a baffle body for forming the cavity and an extension protruding outward from the cavity at its end. One end of the baffle body abuts against the side of an adjacent baffle, and the other end of the baffle abuts against the end of another adjacent baffle. A driving component for applying force into the cavity is provided on the baffle body, and a driving device for applying abutting force is provided on the extension. The driving device is connected to a baffle slot, and the extension is located within the baffle slot. This invention effectively improves product quality uniformity, increases product lateral strength, enhances product performance, and has a high degree of automation.

Description

Technical Field

[0001] This invention belongs to the field of composite material preparation technology, specifically relating to a pultrusion die, apparatus, method, and synthetic railway sleeper for polyurethane foam. Background Technology

[0002] Traditional polyurethane foam synthetic railway sleepers are composite materials produced through a foaming and pultrusion process, using continuous fibers as reinforcement, polyurethane as the matrix material, and additives. While they have longitudinal continuous fiber reinforcement, resulting in relatively strong performance, they lack transverse fiber reinforcement and rely primarily on the strength of the polyurethane foam resin itself. This leads to extremely low transverse performance and weak transverse strength, making them prone to application risks such as low pull-out strength of threaded spikes, product delamination, and transverse cracking.

[0003] To address the issue of low lateral strength in products, many domestic institutions have conducted relevant research in this area.

[0004] Patent application CN106349446A developed a fiber with a reinforcing fiber content greater than 60% and a density higher than 840 g / cm³. 3 High-fiber-content, high-density polyurethane foam synthetic sleepers improve the overall lateral strength of the product by increasing product density and glass fiber content. While this method is effective, it also significantly increases product cost as density increases. Furthermore, excessively high glass fiber content and product density result in excessive product rigidity, which does not meet the product's requirements for shock absorption and lightweighting.

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

[0006] Authorized patent CN108504085B and patent application CN119800780A propose a method where, during the body molding process, continuous glass fibers impregnated with polyurethane resin are sequentially wrapped with glass fiber fabric. The polyurethane-impregnated continuous fibers and glass fiber fabric are then simultaneously fed into a lamination device, followed by foaming and curing. This method aims to improve the lateral strength of the product through the fiber fabric (glass fiber cloth / reinforcing felt, etc.) surrounding the product. While this technology is theoretically effective and economical, a significant practical problem remains: after curing the sleeper blank, each surface needs to be sanded 2-4mm to remove burrs and then painted for weather protection. However, the cured fiber fabric layer typically does not exceed 2mm in thickness. During body molding, the surrounding fiber fabric is almost completely sanded away, resulting in no actual lateral reinforcement in the product. CN108504085B deliberately avoids this issue; CN119800780A proposes adding release paper to avoid surface sanding and spraying, but the feasibility of this technology is questionable. Firstly, the use of release agents / release paper in production is a routine operation, and its effect is to facilitate product demolding, but it cannot eliminate flash and subsequent sanding. In the industry, there has never been a real product with reinforcing fabric / felt wrapped around the product surface. Therefore, how to improve the lateral strength of the product has become a difficult point in the industry. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a pultrusion mold, device, method and synthetic railway sleeper for polyurethane foam, which effectively improves the uniformity of product quality, improves the transverse strength of the product, improves the performance of the product, and has a high degree of automation.

[0008] This invention provides a pultrusion die for a polyurethane foam synthetic railway sleeper, including a die body. The die body is composed of four baffles that form a cavity. Each baffle includes a baffle body for forming the cavity and an extension portion protruding out of the cavity at the end of the baffle body. One end of the baffle body abuts against the side of an adjacent baffle, and the side of the other end of the baffle abuts against the end of another adjacent baffle.

[0009] The baffle body is provided with a driving member for applying force into the cavity, and the extension is provided with a driving device for applying abutment force.

[0010] The drive device is connected to a baffle slot, and the extension is located in the baffle slot.

[0011] This invention provides a preparation apparatus for polyurethane foam synthetic railway sleepers, including a transmission platform for transmitting core material, a positioning device arranged sequentially along the transmission direction of the core material, an extrusion die for the core material to pass through and a cutting device as described above.

[0012] It also includes a roller, on which a fiber fabric is disposed, the fiber fabric wrapping around the surface of the core material and entering the extrusion die together;

[0013] It also includes a resin feeding device for injecting resin into the pultrusion die;

[0014] A flaw detector is also installed at the location of the cutting device.

[0015] Preferably, the rollers are disposed at the upper and lower ends of the transmission platform, and the platform also includes a preforming fixture located between the positioning device and the extrusion die. The preforming fixture preforms the surface of the fiber fabric into a shape that matches the four surfaces of the core material.

[0016] Preferably, the feeding device includes a storage tank I, a storage tank II, and a mixing nozzle. The materials in the storage tank I and the storage tank II enter the mixing nozzle through pipes for mixing. The mixed materials then enter the extrusion die through pipes to impregnate the core material whose surface is covered with fiber fabric.

[0017] Preferably, it further includes a traction clamping mechanism disposed between the extrusion die and the cutting device, the traction clamping mechanism being used to pull the core material whose surface is covered with fiber fabric after curing.

[0018] This invention provides a method for preparing polyurethane foam synthetic railway sleepers, using the aforementioned preparation apparatus, and includes the following steps:

[0019] The cut core material is placed on the transmission platform, the fiber fabric is placed into the roller, so that the fiber fabric covers the surface of the core material, and the material is placed into the feeding device.

[0020] 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 surface covered with fiber fabric enters the extrusion die. The mixed material is controlled to enter the extrusion die. After the material is fully impregnated, it is cured and molded in the extrusion die.

[0021] After curing and molding, the core material with a surface covered with fiber fabric is inspected by a flaw detector to determine the connection positions of different core materials.

[0022] The cutting device cuts the core material, whose surface is covered with fibrous fabric after curing, at the above-mentioned connection position to obtain a polyurethane foam synthetic sleeper.

[0023] Preferably, the rollers are arranged at the upper and lower ends of the transmission platform, and the preparation device further includes a preforming fixture located between the positioning device and the extrusion die. The preforming fixture preforms the surface of the fiber fabric into a shape that matches the four surfaces of the core material and covers the surface of the core material.

[0024] Preferably, the core material, whose surface is covered with fibrous fabric after curing, moves under the action of the traction clamping mechanism; the material is a non-foaming resin.

[0025] This invention provides a polyurethane foam synthetic railway sleeper, which is prepared using the aforementioned preparation method.

[0026] The beneficial effects of this invention are that by wrapping the entire product with one or more layers of felt or cloth, the transverse strength of traditional polyurethane foam synthetic sleepers can be greatly improved, reducing the risk of product delamination and transverse cracking; at the same time, this molding method also has the advantages of being fast, efficient, and low-cost.

[0027] The traditional process of wrapping a reinforcing felt / fabric around the surface of a blank involves several composite felts with lateral reinforcement on the surface of the blank during production. Glass fiber, composite felt, and polyurethane foam are fused together and fill the laminator cavity, then cured to form the sleeper blank. This process is overly idealistic and difficult to implement in practice. This is mainly because the surface of the blank needs to be sanded 2mm-4mm to remove burrs, while the thickness of the composite felt / fabric is generally less than 0.5mm. Therefore, the reinforcing fabric / felt is completely sanded, and the actual product does not have the reinforcement of felt / fabric. Another more common process involves manually laying up fabric on the sanded blank surface, but this process is extremely slow and costly, and the quality is inconsistent due to manual laying up. Therefore, how to quickly and efficiently reinforce traditional polyurethane foam synthetic sleepers with lateral fabric reinforcement remains a major challenge for the industry.

[0028] This invention employs a split molding process. After the blank is prepared, it undergoes sanding to obtain a sanded blank, i.e., the core material. Then, a transversely reinforcing fiber fabric is wrapped around the surface of the core material and cured. Using the pultrusion die of this invention can avoid the influence of core material dimensional deviations on the traction force, making the entire traction process more stable. At the same time, it can maintain a relatively uniform amount of resin impregnation in various parts of the fiber fabric, avoiding product performance instability.

[0029] This invention can quickly reinforce the product surface by wrapping it with felt / cloth. It is highly automated, and the production is continuous, stable and controllable. At the same time, the overall bending resistance of the produced product is greatly improved.

[0030] The polyurethane foam synthetic sleeper of the present invention has strong design flexibility. The skin can be pultruded using different fiber cloth layers, such as 0° fiber, 0° / 90° biaxial cloth, ±45° biaxial cloth, etc., and can be selected and designed in a targeted manner according to the product application scenario, performance requirements, etc.

[0031] This invention uses biaxial fabric polyurethane pultrusion, resulting in a smooth and flat surface, better appearance quality, and stronger adhesion to paint. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the extrusion die for the polyurethane foam synthetic railway sleeper of the present invention.

[0033] Figure 2 This is a schematic diagram of the apparatus for preparing the polyurethane foam synthetic railway sleeper of the present invention.

[0034] Figure 3 This is a schematic diagram of the structure of the polyurethane foam synthetic railway sleeper of the present invention.

[0035] Figure 4 This is a schematic diagram of the preforming tooling of the present invention. Figure 4 (a) is a structural schematic diagram of the first preformed plate. Figure 4 (b) is a structural schematic diagram of the second preform. Figure 4 (c) is a structural schematic diagram of the third preform.

[0036] In the figure, 1 is the cavity, 2 is the baffle, 21 is the baffle body, 22 is the extension, 3 is the pressure-bearing cylinder, 4 is the sealing cylinder, 41 is the connecting rod, and 42 is the baffle slot.

[0037] 5. Pultrusion die, 6. Core material, 7. Transmission platform, 8. Positioning device, 9. Fiber fabric, 10. Roller, 11. Preforming tooling, 12. Storage tank I, 13. Storage tank II, 14. Mixing gun head, 15. Traction clamping mechanism, 16. Flaw detector, 17. Cutting device, 18. Skin. Detailed Implementation Example 1

[0038] like Figure 1 As shown, this embodiment 1 is a pultrusion mold 5 for polyurethane foam synthetic railway sleeper, including a mold body. The mold body is composed of four baffles 2 that surround a cavity 1. The baffle 2 includes a baffle body 21 for forming the cavity 1 and an extension 22 protruding out of the cavity 1 and disposed at the end of the baffle body 21. 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.

[0039] The baffle body 21 is provided with a driving member for applying force to the cavity 1, and the extension 22 is provided with a driving device for applying abutment force.

[0040] The shape of the cavity 1 matches the shape of the final product, the polyurethane foam synthetic sleeper, and is rectangular, usually square. Therefore, the rectangular cavity 1 is obtained by enclosing the four baffles 2 at 90° to each other. 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 together form a baffle 2. When installed, one end of the baffle body 21 abuts against the side of the adjacent baffle 2, and the other side of the baffle 2 abuts against the end of another adjacent baffle 2.

[0041] like Figure 1 The right end of the lowermost baffle 2 abuts against the side of the adjacent baffle 2 (i.e., the right side baffle of the lowermost baffle 2) (specifically, the connection position between the baffle body 21 and the extension 22), and the side of the left end of the lowermost baffle 2 (i.e., the connection position between the baffle body 21 and the extension 22 of the lowermost baffle 2) abuts against the end (i.e., the lower part) of another adjacent baffle 2 (i.e., the left side baffle of the lowermost baffle 2). Each baffle 2 is arranged in the above manner. Therefore, the size of the cavity 1 can be adjusted by controlling the length of the baffle body 21 on the baffle 2 (the length of the baffle 2 is fixed; the longer the baffle body 21, the shorter the extension 22).

[0042] The baffle body 21 is equipped with a driving component (i.e., a pressure cylinder 3) for applying force into the cavity 1. Since the pultrusion die 5 can be placed on a fixed platform, such as a fixed frame or the ground, the lower part of the bottom baffle body 21 is a fixed platform. The pultrusion die 5 will apply downward pressure due to gravity, and the fixed platform itself has an upward reaction force, which acts as the driving component. In other words, the fixed platform is equivalent to the driving component. At this time, it is only necessary to set driving components on the other three sides of the baffle body 21. Figure 1 As shown. Of course, if the pultrusion die 5 is suspended, four driving components (i.e., pressure cylinders 3) are required. The pressure cylinders 3 can apply pressure to the cavity 1 to control the size of the cavity 1. The pressure cylinders 3 are equipped with limit devices. In continuous operation, the movement distance of the pressure cylinders 3 is 1-2mm. Within this range of movement, the pressure of the pressure cylinders 3 controls the baffle 2.

[0043] The extension 22 is provided with a driving device (i.e., a sealing cylinder 4, of which there are 4) for applying abutment force. The abutment force mentioned in this invention is the force of one end of the baffle body 21 abutting against the side of the adjacent baffle 2. The sealing cylinder 4 applies pressure and transmits it to the extension 22. The extension 22 and the baffle body 21 are integrated. The force is transmitted to the side of the adjacent baffle 2 through the baffle body 21. The force applied by the driving member to the baffle body 21 on the baffle 2 and the force applied by the adjacent driving device to the extension 22 of the adjacent baffle 2 are opposite in direction and cancel each other out, so that the adjacent baffles 2 are in tight contact without gaps, i.e., sealed.

[0044] The structural design of this application can control the size of cavity 1 (by changing the dimensions of cavity 1) and maintain a seal during the process before, during and after the change, which facilitates subsequent curing and molding.

[0045] The driving device (i.e., the sealing cylinder 4) is connected to a baffle slot 42 (i.e., the piston rod end of the sealing cylinder 4 is connected to the baffle slot 42). The extension 22 is located in the baffle slot 42, which facilitates the connection and force application between the sealing cylinder 4 and the extension 22. There is a 2-4mm clearance between the baffle slot 42 and the extension 22, which allows the baffle to move left and right.

[0046] Due to space constraints, a connecting rod 41 is provided between the baffle slot 42 and the sealing cylinder 4 in this embodiment, so that the position of the sealing cylinder 4 does not have to be on the extension line of the baffle 2, which facilitates the arrangement.

[0047] Generally, during pultrusion, if the final product cross-sectional dimensions are designed to be 240mm × 240mm and the fiber fabric 9 has a designed thickness of 5mm, then the core material 6 (i.e., the sanded blank) is designed to be 230mm × 230mm. However, due to the sanding precision of the blank being ±1mm, the actual sanded blank size may be as small as 229mm × 229mm and as large as 231mm × 231mm. In practice, the blank size is first adjusted to the minimum blank size of 229mm × 229mm, and the cavity size of the baffle 2 is adjusted to the minimum limit of 239mm × 239mm. If the sanded blank size is too large during pultrusion, the entire cavity 1 will be in an oversaturated state, and the expansion force within the cavity 1 will cause the baffle 2 to move backward, thus making the cavity 1 larger. When the sanded blank size decreases, the expansion force within the cavity 1 will decrease, and the pressure cylinder 3 will push the baffle 2 forward, thus making the cavity 1 smaller. This allows the cavity 1 of the entire pultrusion die 5 to be finely adjusted in size according to changes in the blank size.

[0048] In traditional pultrusion processes, the position and size of the mandrel are fixed. In this embodiment 1, the sanded blank serves as the pultrusion mandrel and is in motion. Each sanded blank will have a certain dimensional deviation. For example, if the required blank cross-sectional size is 230mm × 230mm, the actual cross-sectional size of each blank may fluctuate by ±1mm. A sudden increase in the size of the sanded blank can easily cause mold blockage during pultrusion; conversely, if the sanded blank size is too small, the density of the fiber fabric wrapped around the mold may be insufficient, thus affecting the strength of the surface fiber reinforcement layer. This fluctuation in the blank cross-sectional size can easily cause instability in the entire pultrusion process, making it impossible to implement. This embodiment 1, through adjustment of the cavity 1 size and extrusion compaction, adaptively adjusts and avoids the impact of fluctuations in the blank cross-sectional size and blank movement on pultrusion, greatly improving product quality. Example 2

[0049] This embodiment 2 describes a preparation device for polyurethane foam synthetic railway sleepers, such as... Figure 2 As shown, it includes a transmission platform 7 for driving the core material 6, a positioning device 8, a pultrusion die 5 for the core material 6 to pass through and as described in Example 1, and a cutting device 17 arranged sequentially along the transmission direction of the core material 6.

[0050] It also includes a roller 10, on which a fiber fabric 9 is disposed, which wraps around the surface of the core material 6 and enters the extrusion die 5 together;

[0051] It also includes a resin feeding device for injecting resin into the pultrusion die 5;

[0052] A flaw detector 16 is also installed at the location of the cutting device 17.

[0053] The core material 6 is the sanded blank, and the transmission platform 7 can be a conveyor belt, such as a roller conveyor belt, as long as it can transmit the core material 6.

[0054] The positioning device 8 is used to position the core material 6 on the transmission platform 7 to align it with the extrusion die 5, ensuring that the core material 6 is located as centrally as possible within the extrusion die 5. The positioning device 8 can consist of multiple positioning rods positioned at both ends of the core material 6 to ensure that the core material 6 is positioned correctly.

[0055] The cutting device 17 is a conventional cutting device used to cut the core material 6 whose surface is covered with fiber fabric 9 after curing. In fact, the core material 6 is already cut before entering the pultrusion die 5. However, since the fiber fabric 9 is continuous, the core material 6 covered with fiber fabric 9 appears continuous from the outside after curing and requires cutting with the cutting device 17. A flaw detector 16 can be used to determine the connection point of the two core materials 6, and then the cutting device 17 is used to cut at that connection point. The flaw detector 16 can scan for cracks inside the product; this is existing technology and can be the ULTRA DC2 composite material flaw detector. In conventional pultrusion processes, cutting is typically done at a fixed length. If the required length is 3000mm, it is done using photoelectric sensing or mechanical methods, with a typical length deviation of ±2mm. However, with fixed-length cutting, errors accumulate during continuous cutting, making it difficult to align the cut position with the end 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 final product dimensions match the core material 6 dimensions. The cutting device 17 uses a grinding wheel with a thickness of 5-10mm. Since the gap between any two sanded blanks is typically 0-2mm, detecting internal gaps using the flaw detector 16 and then cutting with the grinding wheel ensures that each cut is made at the end of the core material 6.

[0056] The roller 10 holds a bundle of rolled fiber fabric 9. The fiber fabric is one or more of the following: continuous fiber, chopped strand mat, continuous mat, stitch-woven mat, composite mat, biaxial fabric, triaxial fabric, and uniaxial fabric, preferably biaxial fabric. The roller 10 is used both for unwinding and for positioning the fiber fabric 9, ensuring it is parallel and square on the surface of the core material 6. The roller 10 and the corresponding fiber fabric 9 can be positioned on all four surfaces of the core material 6, or only on the upper and lower surfaces. The fiber fabric 9 is then wrapped around two surfaces of the core material 6 by a pre-forming fixture 11. Preferably, the roller 10 is positioned at both ends of the transmission platform 7, i.e., there are two rollers 10 and two corresponding fiber fabrics 9. The roller 10 also includes a pre-forming fixture 11 located between the positioning device 8 and the extrusion die 5. The pre-forming fixture 11 pre-shapes the surface of the fiber fabric 9 to match the two surfaces of the core material 6. Figure 2 As shown, the preforming fixture 11 preforms the cross-section of the fiber fabric 9 at the lower end of the transmission platform 7 into an L-shape, i.e., two perpendicular surfaces. The two sides of the L-shape are respectively matched with the two adjacent sides of the core material 6, as shown. Figure 2 As shown, the lower fiber fabric 9 has an L-shaped cross-section with two sides corresponding to the bottom and right sides of the core material 6, respectively. The upper fiber fabric 9 has an L-shaped cross-section with two sides corresponding to the left and top sides of the core material 6, respectively.

[0057] The preforming fixture 11 comprises two L-shaped forming plates, such that the two fiber fabrics 9 each form an L-shape and cover the four surfaces of the core material 6. Figure 4 As shown, the preforming fixture 11 includes three preforming plates arranged sequentially along the forward direction of the fiber fabric 9, namely the first preforming plate (e.g., Figure 4 (a) shown), the second preformed plate (as shown) Figure 4 (b) shown) and the third preform (as shown) Figure 4 (c) As shown, the preformed plate includes two straight plates at a certain angle. The angle between the two straight plates of the first preformed plate is 140-160° (preferably 150°), the angle between the two straight plates of the second preformed plate is 130-140° (preferably 135°), and the angle between 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 overlap and enter the next process.

[0058] The feeding device includes a storage tank I 12, a storage tank II 13, and a mixing nozzle 14. The materials in the storage tanks I 12 and II 13 are mixed by entering the mixing nozzle 14 through pipes. The mixed materials are then entered through pipes into the extrusion die 5 to impregnate the core material 6 whose surface is covered with fiber fabric 9. That is, the upper end of the extrusion die 5 has a hole, and the mixed materials enter the extrusion die 5 through the hole through pipes.

[0059] 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, with the high-temperature curing section generally divided into three segments. The length of the pultrusion die 5 is generally 0.8m-3.5m depending on the pultruded product, and the length of the impregnation section is generally 0.2m-0.6m. A longer die results in better impregnation and curing effects, but also greater traction resistance. In this invention, the die length is 1.5m, and the impregnation section length is 0.4m. After the core material 6 is wrapped with fiber fabric 9, continuous pultrusion is performed, with adhesive injection occurring simultaneously. The flow rate of the adhesive injection is controlled to ensure sufficient impregnation of the fiber fabric. The pultrusion speed in this invention is 0.4m / min.

[0060] The high-temperature curing section uses three sets of L-shaped heating plates, one above the other, to wrap the mold, thus achieving three-stage temperature control. The heating plates are heated by resistance wires.

[0061] It also includes a traction clamping mechanism 15 disposed between the extrusion die 5 and the cutting device 17. The traction clamping mechanism 15 is used to pull the core material 6, whose surface is covered with fiber fabric 9, after curing. Since there is a large friction between the core material 6, whose surface is covered with fiber fabric 9, and the extrusion die 5, the traction clamping mechanism 15 can effectively pull the core material 6, whose surface is covered with fiber fabric 9, out of the extrusion die 5 and into subsequent processes. The traction 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

[0062] Example 3 is a method for preparing a polyurethane foam synthetic railway sleeper, using the preparation apparatus described in Example 2, and includes the following steps:

[0063] Place the cut core material 6 onto the transmission platform 7, place the fiber fabric 9 into the roller 10 so that the fiber fabric 9 covers the surface of the core material 6, and put the material into the feeding device.

[0064] The transmission platform 7 is started, and the positioning device 8 controls the position of the core material 6 so that it is located in the center of the extrusion die 5. The core material 6, whose surface is covered with fiber fabric 9, enters the extrusion die 5. The mixed material is controlled to enter the extrusion die 5. After the material is fully impregnated, it is cured and formed in the extrusion die 5.

[0065] After curing and molding, the core material 6 with the surface wrapped with fiber fabric 9 is inspected by flaw detector 16 to determine the connection position of different core materials 6;

[0066] The cutting device 17 cuts the core material 6, whose surface is covered with fiber fabric 9 after curing, at the above-mentioned connection position to obtain a polyurethane foam synthetic sleeper.

[0067] The roller 10 is disposed at the upper and lower ends of the transmission platform 7. The preparation device also includes a preforming fixture 11 located between the positioning device 8 and the extrusion die 5. The preforming fixture 11 preforms the surface of the fiber fabric 9 into a shape that matches the two surfaces of the core material 6 and covers the surface of the core material 6.

[0068] After curing and molding, the core material 6, whose surface is covered with fiber fabric 9, moves under the action of the traction clamping mechanism 15.

[0069] Specifically, the detailed preparation process is as follows:

[0070] (1) Blank Positioning: The surface of the produced polyurethane foam synthetic sleeper is sanded to obtain a sanded blank, i.e., core material 6. The sanded blank is placed on the transmission platform 7, and the sanded blank is transferred into the extrusion die 5 by the rotation of the transmission platform 7. If the cross-sectional dimension of the cavity 1 of the die is 240mm If the outer layer of fabric is designed to be 5mm thick and the rough blank is 240mm in diameter, then the sanded blank size needs to be 230mm. 230mm. Before the sanded blank enters the pultrusion die 5, there are two sets of positioning devices 8, one at the front and one at the back, and one at the left and right, which mainly keep the sanded blank at the left and right center position of the cavity 1 of the pultrusion die 5. The sanded blank is kept at the upper and lower center position of the cavity 1 of the pultrusion die 5 by adjusting the height of the pultrusion die 5.

[0071] (2) Fiber Fabric Design: The fiber fabric 9 is rolled up and placed on the roller 10. The roller 10 and the fiber fabric 9 consist of two sets, upper and lower. The upper set is responsible for the upper and left wall thickness of the formed skin, and the lower set is responsible for the lower and right wall thickness of the formed skin. The width of the fiber fabric 9 is determined according to the width of the cavity of the formed product cross section. For example, if the cross section of the formed product is 240... 240mm, the width of the upper cavity plus the width of the left cavity equals 480mm. Similarly, the width of the lower cavity plus the width of the right cavity also equals 480mm. Therefore, the width of the fiber fabric is generally the required cavity width plus a 5% allowance, resulting in a total fabric width of 480mm for both the upper and lower layers. 1.05 = 504mm. The extra allowance is mainly due to the need for overlap and transition at the corners of the upper and lower fabrics. The areal density of fiber fabric 9 is 100-1500 g / m². 2 One or more layers of fiber fabric can be stacked. Fiber fabric type 9 can also be stacked in different ways, such as using fiber fabric with symmetrical [90° / 0°]s layup, or fiber fabric with counter-layup [±45° / 0°]s layup, etc. In addition to the top and bottom two-piece wrapping design (each piece needs to be folded into an L-shape), fiber fabric 9 can also use a cavity wrapping design with two pieces on the left and right (each piece needs to be folded into an L-shape) or four pieces on each side.

[0072] (3) Pre-forming tooling positioning: Since the fiber fabric 9 is initially unfolded into a planar state, and the upper fiber fabric is responsible for forming the upper wall thickness and the left wall thickness, a pre-forming tooling 11 is needed for transition before the fiber fabric enters the cavity. This mainly allows the planar fiber fabric to gradually transition into a 90-degree bent fiber fabric (L-shaped cross-section) and smoothly enter the cavity 1. The pre-forming tooling 11 includes three devices for gradual transition: front, middle and rear.

[0073] (4) Resin injection: The resin (i.e. the material) used for impregnation 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 either closed or open. In this case, the fiber fabric is passed through a pool filled with resin for impregnation, and then the resin-impregnated fiber fabric is directly placed into the mold for curing and molding, without the need for an impregnation box.

[0074] This invention preferably uses polyurethane resin, and preferably uses a dipping box (part of the pultrusion die 5 acts as the dipping box). The main reason is that polyurethane resin is particularly sensitive to environmental temperature and humidity. Open dipping would allow the polyurethane resin to easily absorb moisture from the air, thus affecting the molding process. The polyurethane resin contains isocyanate (i.e., the material in storage tank I 12), mainly diphenylmethane diisocyanate; and a polyol blend (i.e., the material in storage tank II 13), wherein the polyol blend does not contain a foaming agent. Both components are metered separately and then mixed in the mixing nozzle 14. The mixed resin is then injected into the pultrusion die 5 through a dispensing hose.

[0075] (5) High-temperature curing of the mold: After the fiber fabric 9 enters the pultrusion mold 5, the resin injected by the injection hose begins to impregnate the fiber fabric 9 and begins to cure and form in the pultrusion mold 5 as the pultrusion runs. The length of the pultrusion mold 5 is generally 1-2m. The pultrusion mold 5 is generally subject to three-stage temperature control: the front stage is the preheating stage, with a temperature of 40-80℃, the middle stage is 120-180℃, and the rear stage is 160-200℃.

[0076] (6) Traction pultrusion: The resin-impregnated fiber fabric is cured at high temperature after being passed through the pultrusion die 5. After being demolded, it is cured and then pulled back and forth by two alternating traction clamping mechanisms 15 to form a continuous and stable traction.

[0077] (7) Cutting: Finally, according to the actual length required by the product, the cutting device 17 is used to cut to a fixed length, so that the core material 6 is wrapped with a layer of reinforcing fiber fabric.

[0078] 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 the material of the resin-impregnated fiber fabric 9 after curing. The thickness of the skin 18 can be 0.5-10mm. Example 4

[0079] The performance of different polyurethane foam synthetic railway sleepers was measured. The new polyurethane foam synthetic railway sleeper was prepared using the method described in Example 3 above. The product's cross-sectional dimensions were designed as follows: the skin 18 was a rectangular sheet with a uniform cross-section of 200mm × 140mm and a wall thickness of 5mm; the core material 6 had a cross-sectional dimension of 190mm × 130mm and a core material density of 0.74g / cm³. 3 .

[0080] Comparative Example 1 is a traditional polyurethane foam composite sleeper, with the same material as core material 6 and a cross-sectional size of 200mm×140mm.

[0081] The sleeper is reinforced laterally using a [90° / 0°]s fabric layer, with non-foamed polyurethane resin at a content of 25%; the core material 6 is a traditional polyurethane foam synthetic sleeper with a density of 0.74 g / cm³. 3 The performance comparisons between the novel polyurethane foam synthetic railway sleeper and the product of Comparative Example 1 are shown in Tables 1 and 2.

[0082] Table 1. Comparison of test results between polyurethane foam synthetic railway sleepers and Comparative Example 1.

[0083]

[0084] Table 2 Comparison of Performance Test Results of Product Skin and Core Materials

[0085]

[0086] The performance of different polyurethane foam synthetic railway sleepers was measured. The new polyurethane foam synthetic railway sleeper was prepared using the method described in Example 3 above. The product's cross-sectional dimensions were designed as follows: the skin 18 was a rectangular sheet with a uniform cross-section of 240mm × 240mm and a wall thickness of 5mm; the core material 6 had a cross-sectional dimension of 230mm × 230mm and a density of 0.8g / cm³. 3 .

[0087] Comparative Example 2 is a traditional polyurethane foam composite sleeper, with the same material as core material 6. The cross-sectional dimensions of Comparative Example 2 are 240mm × 240mm.

[0088] Laterally reinforced pultrusion is performed using a [±45° / 0° / 90°]s fabric layer, with non-foamed polyurethane resin as the resin content (20%); the core material 6 is a traditional polyurethane foam synthetic sleeper with a density of 0.8 g / cm³. 3 The performance comparisons of the prepared polyurethane foam synthetic sleepers and core material 6 are shown in Tables 3 and 4.

[0089] Table 3 Comparison of test results of polyurethane foam synthetic sleepers and core materials 6 finished products

[0090]

[0091] Table 4 Comparison of performance test results of polyurethane foam synthetic sleepers and core materials 6

[0092] Example 5

[0093] This invention employs a split molding process, which mainly involves two steps. The first step is the fabrication of the core material 6, using the traditional polyurethane foam synthetic sleeper preparation method and a polyurethane pultrusion foaming process. The second step is the secondary pultrusion of the sleeper surface skin, using a non-foamed polyurethane resin pultrusion process. This process differs fundamentally from the traditional non-foamed polyurethane pultrusion process. In traditional non-foamed polyurethane pultrusion, the mandrel is fixed, while this invention creatively uses the core material 6 as the mandrel of the pultrusion die, and the mandrel is mobile with fluctuating dimensions. Its die design principle, cutting principle, etc., are all significantly different from traditional polyurethane pultrusion.

[0094] The resin materials used in the preparation of the skin in this invention differ from those used in the preparation of the core material 6. The core material 6 is a traditional polyurethane foam-based sleeper, using expanded polyurethane, where the polyol mixture contains a foaming agent and water. 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 groups in the polyol to produce urethane. The cured resin product is rigid polyurethane foam, which, when combined with continuous fibers, becomes a polyurethane foam-based sleeper. Polyurethane foam has advantages such as low density due to its porous structure, but it has poor strength. In contrast, the polyurethane used in the skin is non-foamed polyurethane, whose polyol mixture does not contain water and does not undergo a foaming reaction. The isocyanate and polyol condensate to form polyurethane. The cured product is continuous and dense, without pores, and possesses high strength and high molecular chain density. Therefore, by using non-foamed polyurethane resin to impregnate the fiber fabric, the skin's strength is far higher than that of the core material, and ultimately, only a few millimeters of skin are needed to significantly improve the overall strength of the product.

[0095] Traditional core materials are integrally molded with fiber fabric, but this often results in poor skin strength due to the subsequent sanding process removing the surface fiber fabric, leading to minimal overall lateral reinforcement. The main reason is that during integral molding, the resin used to impregnate the continuous fibers and the surface reinforcing fiber fabric is the same (if two different resin systems are used, their chemical reactions and curing temperatures differ, causing severe interference). Both are foamed polyurethane resin. The reinforcing layer formed by this foamed resin and the fiberglass fabric has poor lateral properties, offering minimal improvement to the finished product's performance. This invention uses a split molding process, where the resin used to impregnate the fiber fabric is pultrusion polyurethane resin, a non-foamed polyurethane resin. The cured product is continuous and dense, without bubbles, and possesses high strength and high molecular chain density.

[0096] Table 5 compares the properties of the polyurethane foaming resin used in the polyurethane foam sleeper and the polyurethane resin used in the skin. Because the skin of this invention is manufactured using a split molding process, in addition to polyurethane resin, vinyl resin, unsaturated resin, epoxy resin, etc., can also be used for pultrusion, offering a wider range of options and greater applicability.

[0097]

[0098] In addition to significantly improving the strength of the product, this invention also has the following advantages:

[0099] (1) The limitations of traditional polyurethane foam composite sleeper laminators result in rectangular cross-sections of the molded products, and the straight corners are easily damaged during transportation and installation. If the corners are rounded in a secondary process, the cost is too high. In this invention, since the skin is made of ordinary polyurethane pultrusion, the mold can be designed to round the straight corners, so that the straight corners of the molded skin products can be turned into rounded corners, thereby solving the problem of easy damage to the products.

[0100] (2) Traditional polyurethane foam synthetic sleepers have a cellular structure on the surface. After sanding, the surface usually needs to be puttyed and then painted. This can make the paint more beautiful and reduce the amount of paint used (the sleeper surface has a cellular structure, and the paint is easily absorbed by the cellular structure if putty is not applied). However, the skin of the present invention is made of non-foamed polyurethane pultrusion, and the product is continuous and dense. It has no cellular structure, and the skin surface does not need to be sanded or puttyed. It can be directly painted.

[0101] (3) In addition to direct painting, the skin surface can also be painted without paint. The polyurethane pultrusion of the skin generally uses aromatic polyurethane, which contains benzene rings, has strong molecular chain rigidity, and high resin mechanical strength, but poor resistance to yellowing, and generally requires surface painting for protection. In this application, in addition to aromatic polyurethane, aliphatic polyurethane can also be used for the polyurethane resin used for the skin. This polyurethane contains straight-chain 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 further painting.

[0102] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of protection of this application is limited to these examples; within the framework of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of one or more embodiments of this application as described above, which are not provided in detail for the sake of brevity.

[0103] One or more embodiments in this application are intended to cover 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 in this application should be included within the protection scope of this application.

Claims

1. A pultrusion die for a polyurethane foam synthetic railway sleeper, characterized in that, The mold body is composed of four baffles (2) that form a cavity (1). The baffles (2) include a baffle body (21) for forming the cavity (1) and an extension (22) protruding from the cavity (1) at the end of the baffle body (21). 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 cavity (1), and the extension (22) is provided with a driving device for applying abutment force. The drive device is connected to a baffle slot (42), and the extension (22) is located in the baffle slot (42).

2. A preparation apparatus for polyurethane foam synthetic railway sleepers, characterized in that, It includes a transmission platform (7) for driving the core material (6), a positioning device (8) arranged sequentially along the transmission direction of the core material (6), a pultrusion die and a cutting device (17) for the core material (6) to pass through as described in claim 1. It also includes a roller (10) on which a fiber fabric (9) is disposed, the fiber fabric (9) wrapping around the surface of the core material (6) and entering the extrusion die together; It also includes a resin feeding device for injecting resin into the pultrusion die; A flaw detector (16) is also installed at the location of the cutting device (17).

3. The preparation apparatus as described in claim 2, characterized in that, The roller (10) is set 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. 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 apparatus as described in claim 2, characterized in that, The feeding device includes a storage tank I (12), a storage tank II (13) and a mixing gun head (14). The materials in the storage tank I (12) and the storage tank II (13) are mixed by entering the mixing gun head (14) through the pipe. The mixed materials are then entered through the pipe into the extrusion die to impregnate the core material (6) whose surface is covered with fiber fabric (9).

5. The preparation apparatus as described in claim 2, characterized in that, It also includes a traction clamping mechanism (15) disposed between the extrusion die and the cutting device (17), the traction clamping mechanism (15) being used to pull the core material (6) whose surface is covered with fiber fabric (9) after curing.

6. A method for preparing a polyurethane foam synthetic railway sleeper, characterized in that, The preparation is carried out using the apparatus described in any one of claims 2-5, and includes the following steps: Place the cut core material (6) onto the transmission platform (7), put the fiber fabric (9) into the roller (10) so that the fiber fabric (9) covers the surface of the core material (6), and put the material into the feeding device. Start the transmission platform (7), and the positioning device (8) controls the position of the core material (6) so that it is located in the center of the extrusion die. The core material (6) with the surface covered with fiber fabric (9) enters the extrusion die. Control the mixed material to enter the extrusion die. After the material is fully impregnated, it is solidified and molded in the extrusion die. After curing and molding, the core material (6) with the surface wrapped with fiber fabric (9) is inspected by a flaw detector (16) to determine the connection position of different core materials (6); The cutting device (17) cuts the core material (6) whose surface is covered with fiber fabric (9) after curing 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 set at the upper and lower ends of the transmission platform (7). The preparation device also includes a preforming fixture (11) located between the positioning device (8) and the extrusion die. The preforming fixture (11) preforms the surface of the fiber fabric (9) into a shape that matches 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, characterized in that, The core material (6) with the surface covered by fiber fabric (9) after curing and molding moves under the action of the traction clamping mechanism (15); the material is a non-foaming resin.

9. A polyurethane foam synthetic railway sleeper, characterized in that, It is prepared by the preparation method described in any one of claims 6-8.

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