Method for manufacturing a steel bar body

Abstract

Provided is a method for manufacturing a steel reinforcing bar in which a thermoplastic resin material is sufficiently impregnated in a reinforcing fiber material and integrated with the reinforcing fiber material to exhibit sufficient strength. The method is a method for manufacturing a steel reinforcing bar (Sc) in which a polypropylene (PP) resin is impregnated in basalt fibers (Fb) and integrated with the basalt fibers (Fb), in which non-flat bundle-shaped basalt fibers (Fb) are passed through an accumulation tank (2) in which a liquid thermoplastic resin material is accumulated, and the non-flat bundle-shaped basalt fibers (Fb) that have passed through the accumulation tank (2) are flattened in the accumulation tank (2), and the PP resin is impregnated between the basalt fibers (Fb), and the flattened basalt fibers (Fb) impregnated with the PP resin are again formed into non-flat bundle shapes.

Description

Technical Field

[0001] This invention relates to a method for manufacturing steel bars that can be used to reinforce concrete and the like. Background Technology

[0002] As a type of reinforcing bar, basalt fiber reinforcing bars, which replace existing iron reinforcing bars, have attracted attention for their ability to maintain the strength of concrete over a long period without rusting. For example, as shown in Patent Document 1, a reinforcing bar with a structure using basalt fiber bundles as the core material and surrounding it with a thermoplastic resin layer of a specified thickness has been proposed. Furthermore, conventional methods for forming the resin layer around the core material, as shown in Patent Document 1, have mostly employed impregnation methods, such as passing the core material through a molten resin solution or emulsion.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2012-251378 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] However, when using the impregnation method, if the thermoplastic resin material does not sufficiently impregnate the basalt fibers used as reinforcing fibers, there is a problem that the steel bar may not have sufficient strength.

[0008] Therefore, the present invention addresses this problem and aims to provide a method for manufacturing a steel bar in which a thermoplastic resin material is fully impregnated and integrated with a reinforcing fiber material to achieve sufficient strength.

[0009] means for solving problems

[0010] To achieve the above objective, the present invention provides a method for manufacturing a steel bar (Sc) integrally formed by impregnating a thermoplastic resin material within a reinforcing fiber material (Fb). In this method, the non-flat bundle of the reinforcing fiber material (Fb) is passed through a storage tank (2) containing liquid thermoplastic resin material. The non-flat bundle of reinforcing fiber material (Fb) is flattened within the storage tank (2), and thermoplastic resin material is impregnated between the reinforcing fiber materials (Fb). The flat reinforcing fiber material (Fb) impregnated with thermoplastic resin material is then bundled and shaped into a non-flat bundle.

[0011] In this first invention, by flattening the bundled reinforcing fiber material in a storage tank and fully impregnating the reinforcing fiber material with thermoplastic resin material, the steel bar obtained by bundling it again into a non-flat bundle exhibits sufficient strength.

[0012] In this second invention, a plurality of rods (21-23) are horizontally arranged in the above-mentioned accumulation tank (2), so that the above-mentioned non-flat bundled reinforcing fiber material (Fb) is suspended and passes through between these rods (21-23) in a pressed state, thereby pressing the reinforcing fiber material (Fb) into a flat state.

[0013] In this second invention, a simple, bundled reinforcing fiber material can be flattened.

[0014] In this third invention, the outer periphery of the aforementioned reinforcing fiber material (St) after being bundled and molded is covered with other thermoplastic resin materials with a specified fastening force.

[0015] In this third invention, the outer periphery of the reinforcing fiber material is coated with other thermoplastic resin materials, thus providing a good feel and excellent chemical resistance. Furthermore, since the outer periphery of the reinforcing fiber material is coated with a specified fastening force, the strength of the reinforcing fiber material is significantly increased.

[0016] In this fourth invention, a film material (Lh) of a specified width of the other thermoplastic resin material is wrapped around and covered on the outer periphery of the above-mentioned bundled reinforcing fiber material (Fb) with a specified fastening force.

[0017] In this fourth invention, since the reinforcing fiber material is wound and shaped by a membrane material with a specified fastening force, its shape can be made into a shape that is close to an aesthetically pleasing circle in cross-section, and the strength of the reinforcing fiber material is greatly increased by winding the membrane material with a specified fastening force.

[0018] In this fifth invention, before coating with the other thermoplastic resin materials described above, a long strip (4) extending in the length direction of the reinforcing fiber material (St) and having excellent tensile strength is integrally fused to at least one location on the outer periphery of the bundled reinforcing fiber material (St). The long strip (4) can be a filament.

[0019] In this fifth invention, the tensile strength of the reinforced fiber material after bundling and molding is significantly improved.

[0020] In this sixth invention, a connecting device is welded to the end of the reinforcing fiber material (St) that is coated with the other thermoplastic resin material.

[0021] In this sixth invention, reinforcing fiber materials of a certain length can be interconnected to form a steel bar of a specified length.

[0022] The symbols in parentheses above are shown for reference to correspond with the specific mechanisms described in the embodiments described later.

[0023] Invention Effects

[0024] As described above, according to the manufacturing method of the present invention, it is possible to manufacture a steel bar in which thermoplastic resin material is fully impregnated and integrated with reinforcing fiber material to exert sufficient strength. Attached Figure Description

[0025] Figure 1 This is a partial perspective view of a manufacturing apparatus for implementing the manufacturing method of the present invention.

[0026] Figure 2 This is a magnified view of a portion of the manufacturing equipment.

[0027] Figure 3 This is an enlarged view of the main parts of the manufacturing equipment.

[0028] Figure 4 This is a three-dimensional view of the inside of the accumulation tank in the state where molten resin has not yet accumulated.

[0029] Figure 5 This is a cross-sectional schematic diagram of the accumulation tank.

[0030] Figure 6 This is a cross-sectional view of the original rod.

[0031] Figure 7 It is a 3D diagram of a winding machine.

[0032] Figure 8 It is a 3D view of the winding machine in operation.

[0033] Figure 9 This is a cross-sectional view of the reinforcing bar.

[0034] Figure 10 This is a diagram showing the alkali resistance of the steel bar.

[0035] Figure 11 This is a diagram showing the water resistance of the reinforcing bar.

[0036] Figure 12 This is a graph showing the change in tensile strength of a steel bar under heating conditions.

[0037] Figure 13 This is a cross-sectional schematic diagram of the accumulation tank in other embodiments.

[0038] Figure 14 This is a cross-sectional view of the reinforcing bar in another embodiment.

[0039] Symbol Explanation

[0040] 1…extruder, 2…accumulation tank, 21, 22, 23…rod, 3…line assembly equipment, 4…filament (strip), 7…winder, Fb…reinforcing fiber material, Lh…membrane material, Sc…steel bar, St…original bar, Sy…coating layer. Detailed Implementation

[0041] Furthermore, the embodiments described below are merely examples, and various design modifications made by those skilled in the art without departing from the spirit of the invention are also included within the scope of the invention.

[0042] An example of a manufacturing apparatus for implementing the method of the present invention will be described below. Figure 1 This is a view of the upstream side of the manufacturing apparatus, in which an extruder 1 is provided with a known structure having a feed hopper 11 for supplying polypropylene (PP) resin, which is a thermoplastic resin material, and an accumulation tank 2 is connected to its outlet side to accumulate the heated and molten PP resin output from the extruder 1.

[0043] In this embodiment, basalt fibers, serving as reinforcing fiber material, are drawn from four spools (not shown) in the form of approximately circular, non-flat rovings, each consisting of 4000 strands of 17μm diameter wire bundled together. The four drawn basalt fibers are then fed to a yarn-forming device 3 located on the upper surface of the frame of the extruder 1. For the yarn-forming device 3, as... Figure 2 As shown, the large-diameter ring 31 and the small-diameter ring 32 are arranged alternately, and the four basalt fibers pass through the outer peripheral hole of the large-diameter ring 31 and the central hole of the small-diameter ring 32 of the thread-making device 3 alternately and are pulled into a straight line.

[0044] After being aligned, each basalt fiber passes through four horizontally positioned cylindrical heaters 5 and is heated to the same temperature as the molten PP resin stored in the downstream storage tank 2. Figure 3 As shown, the heated basalt fiber Fb is changed from a horizontal orientation to a downward orientation via pulley 61, and is supplied to the lower accumulation tank 2 through the heat-insulating cylindrical guide 62. In this way, because heated basalt fiber is supplied to the accumulation tank 2, the undesirable situation of PP resin solidifying around the cooled basalt fiber will not occur.

[0045] In the accumulation tank 2, such as Figure 4 As shown, three cylindrical rods 21, 22, and 23, serving as pressing components, are horizontally arranged at approximately equal intervals within molten liquid PP resin. In this embodiment, among the three cylindrical rods 21 to 23, as follows: Figure 5As shown, the supplied basalt fibers Fb are suspended by a central cylindrical rod 22 and a cylindrical rod 23 located downstream of it, and pulled downstream. During the process of being suspended by the cylindrical rods 22 and 23 and pulled out, the generally circular, non-flat bundles of basalt fibers Fb are pressed against the circumferential surfaces of these cylindrical rods 22 and 23 and unfolded into a flattened state (see reference). Figure 4 Then, molten PP resin is efficiently and thoroughly impregnated between the individual filaments of the basalt fiber Fb, which have been unfolded into flat filaments.

[0046] Basalt fibers Fb, fully impregnated with PP resin, pass through the central hole of the guide plate 24 located on the downstream side of the cylindrical rod 23 and are bundled again there. They then pass through the through hole of the cylindrical molding die 25 at the outlet of the accumulation tank 2 and are formed into an irregularly shaped, non-flat original rod St.

[0047] An example of the cross-sectional shape of the original rod St is shown below. Figure 6 For the original rod St, PP resin is fully and well impregnated within the basalt fiber filament. On the other hand, basalt fiber whisker-like protrusions are generated on the outer periphery of the original rod St, which raises concerns about poor hand feel and potential deterioration due to chemical reactions when used as a reinforcement in concrete.

[0048] Therefore, through such Figure 7 The winding machine 7 shown winds a thermoplastic resin (PP resin in this embodiment) film Lh of a predetermined width, which is another thermoplastic resin material, around the outer periphery of the original rod St, which is pulled out from the molding die and moves downstream. The winding machine 7 includes a holding arm 72 that protrudes horizontally from the outer periphery of the rotating body 71, on which the rolled PP resin film Lh is held, as shown. Figure 8 As shown, the rotating body is rotated by fixing the front end of the PP resin film Lh to the original rod St. The PP resin film Lh is thus wound into a spiral shape around the moving original rod St with a predetermined clamping force, while maintaining a certain overlap with each other. An example of the film thickness of the PP resin film Lh is 40 μm, and a PP resin film Lh with a thickness of 20 μm to 100 μm is preferred.

[0049] The wound PP resin film Lh is heated by the original rod St, causing its inner circumference to melt and adhere tightly to the outer circumference of the original rod St, forming a coating layer with a smooth outer surface. This coating covers the whisker-like protrusions and secures the entire circumference of the original rod St with the PP resin film Lh, resulting in an approximately circular cross-section. This yields the steel bar Sc as the final product. An example of this cross-section is shown below. Figure 9 In the figure, Sy represents the coating layer.

[0050] After being cooled by a cooling device, the steel bar Sc is clamped by a pair of retrieval belts and pulled out. The steel bar Sc manufactured using this method has sufficient PP resin impregnated between the basalt fiber Fb wires, and the entire circumference of the steel bar Sc is firmly secured by a PP resin film Lh coating, thus exhibiting sufficient strength. Furthermore, by forming the coating layer Sy, it has a good feel, excellent chemical resistance, and an aesthetically pleasing, nearly circular cross-section.

[0051] When 30 steel bars manufactured through the above processes are bundled together to form a large-diameter steel bar with a diameter of 13 mm, an example of tensile strength measured by JIS A1192 can reach over 125 kN. Considering that the tensile strength obtained by the existing impregnation method in a large-diameter steel bar with the same diameter and structure is about 90 kN, the tensile strength increases by about 1.4 times. In addition, regarding the alkali resistance, which is a problem when used as a reinforcing bar in concrete, 30 of the above-mentioned steel bars (Sc) were bundled together (tensile strength about 130 kN, tensile stress about 2240 MPa) and impregnated in an alkaline solution (pH 12-13 of ordinary concrete), and the results after 7 days and 28 days are shown. Figure 10 Although its tensile strength decreased slightly from the initial 119.1kN to 107.1kN and 106.0kN, it remained above 100kN.

[0052] In addition, such as Figure 11 As shown, the strength reduction exhibited almost the same tendency after immersion in alkaline solution at 60°C and warm water for 7 days, respectively. Therefore, it can be concluded that the strength reduction is due to the warm water rather than the alkaline solution. Thus, as... Figure 12 As shown, if the change in tensile strength is measured in air at 60°C instead of warm water, the tensile strength increases over time. It can be assumed that if the weight of the steel bar Sc decreases and the moisture is removed during this period, resulting in an absolutely dry state, the tensile strength increases. Therefore, even if moisture is present, although the tensile strength of the aforementioned steel bar Sc temporarily decreases slightly, it shows that it recovers as drying continues.

[0053] (Other implementation methods)

[0054] In the accumulation tank, such as Figure 13 As shown, pressing basalt fibers onto two cylindrical rods located on the upstream side allows for more efficient flattening of the basalt fibers. Furthermore, the pressing component does not necessarily have to be cylindrical, nor does it have to be a rod in itself.

[0055] In addition to the method of winding the PP resin film described above, other methods for forming a coating layer around the original rod body include extruding the PP resin that will become the coating layer into a cylindrical shape around the original rod body, and covering it with a heat-shrinkable resin tube.

[0056] In addition to PP resin, polyethylene resin, nylon resin, and polyester resin can also be used as thermoplastic resin materials. Furthermore, in addition to basalt fiber, inorganic fibers such as glass fiber and carbon fiber, as well as organic fibers such as aramid fiber and acrylic fiber, can also be used as reinforcing fiber materials.

[0057] Before the outer periphery of the original rod St is covered by the coating layer Sy, such as Figure 14 As shown in its cross-section, filaments such as cotton yarn with excellent tensile strength can be integrally fused at radially symmetrical positions on the outer periphery of the original rod St. That is, if from the molding die 25 ( Figure 5 A filament 4 is drawn out along the length of the original rod St, which is still in a hot and molten state. The filament 4 is then well fused to the original rod St and integrated with it. Then, the filament 4 is covered with a coating layer Sy to form an integral original rod St, which is then cooled to produce a steel bar Sc. This steel bar Sc has a more significant improvement in tensile strength.

[0058] As the filament 4, in addition to cotton yarn, vinylon filament, nylon filament, PP filament, nylon silk, nylon rope, etc. can also be used. Furthermore, it is not limited to filaments; any long strip with excellent tensile strength extending along the length of the original rod is acceptable. Additionally, the long strips do not necessarily need to be arranged in pairs at radially symmetrical positions on the outer periphery of the original rod; they can be arranged in one, three, or more locations on the outer periphery, and the spacing between them does not need to be equal in the circumferential direction.

[0059] As the aforementioned elongated body, a metal rod or strip with excellent electrical conductivity, such as copper, can be used.

[0060] Alternatively, a connecting device for connecting other original rods of a certain length that have formed a coating layer can be fused to the outer periphery of the end of the original rod. This connecting device preferably has a cylindrical portion that covers the outer periphery of the coating layer and is fused to the molten coating layer, and more preferably has a screw portion formed on the inner periphery of the cylindrical portion.

[0061] In the above embodiments, it is not necessary to form a cladding layer, and the original bar can also be used as the steel bar of the final product.

Claims

1. A method for manufacturing a reinforcing bar, characterized in that, It is a method for manufacturing steel bars that are integrally formed by impregnating a thermoplastic resin material within a reinforcing fiber material, wherein, The non-flat bundles of reinforcing fiber material are passed through a storage tank containing molten thermoplastic resin material. The non-flat bundles of reinforcing fiber material are flattened in the storage tank, and thermoplastic resin material is impregnated between the reinforcing fiber materials. The flat reinforcing fiber material impregnated with thermoplastic resin material is then bundled and shaped into a non-flat bundle to form a rod. The outer periphery of the rod before cooling is covered by a coating layer formed of other thermoplastic resin material with a specified fastening force. The inner periphery of the coating layer is tightly fitted to the outer periphery of the rod and the entire cross-section of the rod maintains an approximately circular shape through the specified fastening force.

2. The method for manufacturing a reinforcing bar according to claim 1, wherein, Multiple rods are horizontally arranged in the accumulation tank, so that the bundled reinforcing fiber material is suspended and passes through between these rods in a pressed state, thereby pressing the reinforcing fiber material into a flat state.

3. The method for manufacturing a reinforcing bar according to claim 1, wherein, The coating layer is formed by wrapping and covering the outer periphery of the original rod body before cooling with a specified fastening force with a film material of a specified width of the other thermoplastic resin material.

4. The method for manufacturing a reinforcing bar according to claim 1, wherein, Before being coated with the coating layer, a long strip extending in the length direction of the reinforcing fiber material and increasing its tensile strength is integrally fused at at least one location on the outer periphery of the original rod.

5. The method for manufacturing a reinforcing bar according to claim 4, wherein, The elongated body was constructed using filamentous material.

6. The method for manufacturing a reinforcing bar according to any one of claims 1 to 5, wherein, A connecting device is welded to the end of the original rod that is covered by the coating layer.

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