Steel belt corrugated pipe and preparation method thereof

Abstract

The invention discloses a steel belt corrugated pipe which comprises a polyethylene coating layer, a steel belt, a polyethylene pipe body and a bonding resin layer. The whole cross section of the steel belt is in an arch bridge shape, the two sides of the steel belt horizontally extend to form fixing parts, the top ends of wave crests of the steel belt are vertically sunken downwards to form flat pits, and the bottom ends of the flat pits are horizontal and flush with the bottom faces of the fixing parts. The steel belt is spirally wound on the periphery of the polyethylene pipe body, the surface of the steel belt is coated with the bonding resin layer, the polyethylene wrapping layer covers the surfaces of the polyethylene pipe body and the steel belt, the flat pits are filled with the polyethylene wrapping layer to form a supporting interlayer, and the top ends of the flat pits are filled with the polyethylene wrapping layer to form a complete arch-bridge-shaped structure. A complete arch-bridge-shaped steel belt of an existing steel belt corrugated pipe is improved, the top ends of the wave crests of the steel belt corrugated pipe are downwards and vertically sunken to form the flat pits, and the supporting columns which vertically and downwards directly act on the peripheral wall of the polyethylene pipe body are arranged in the centers of the wave crests after forming, so that the overall ring stiffness of the pipe can be greatly improved, and the anti-pressure capacity of the pipe can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of pipes, and in particular to a steel strip corrugated pipe and a preparation method thereof. Background Art

[0002] The full name of steel belt corrugated pipe is steel belt reinforced polyethylene (PE) spiral corrugated pipe, which can also be called steel belt reinforced polyethylene drainage pipe, steel belt reinforced drainage pipe, etc. It uses polyethylene as the inner and outer layer matrix material, and the steel belt waveform body coated with high-performance adhesive resin and bent into shape as the main supporting structure. It is a spiral corrugated pipe that is compounded into an integral whole on the production line through winding and extrusion. It combines the high stiffness and high strength of steel and the corrosion resistance, wear resistance and flexibility of plastic to make up for the low ring stiffness of larger diameter all-plastic buried drainage pipes.

[0003] The current steel belt corrugated pipe uses an arch-shaped curved cross-section of the steel belt. If the soil where the pipeline is buried contains a lot of gravel or the soil is prone to agglomeration or shrinkage, this structure will cause the stress points to be concentrated on the top of the wave crest. The top of the steel belt wave crest is the maximum stress point, and the wave crest position has no support, which can easily cause the wave crest to collapse. Once the wave crest collapses, the arch-shaped stress structure will collapse, further causing deformation of the pipe body. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a steel strip corrugated pipe to solve the technical problem in the background technology.

[0005] The technical solution of the present invention is:

[0006] A steel belt corrugated pipe comprises a polyethylene coating, a steel belt, a polyethylene pipe body and an adhesive resin layer; the cross section of the steel belt is in the shape of an arch bridge as a whole, with fixed parts extending horizontally on both sides, the top of the wave crest is vertically depressed downward to form a flat pit, the bottom of the flat pit is horizontal and flush with the bottom surface of the fixed part; the steel belt is spirally wound around the polyethylene pipe body, the surface of the steel belt is coated with an adhesive resin layer, the polyethylene coating layer covers the polyethylene pipe body and the surface of the steel belt, and fills the inside of the flat pit to form a supporting interlayer, and fills the top of the flat pit to form a complete arch bridge structure.

[0007] Furthermore, the bottom and the top of the two side walls of the flat pit are both connected in an arc transition.

[0008] Furthermore, the thickness of the supporting interlayer is 2-3 times the thickness of the polyethylene coating layer.

[0009] The present invention also provides a method for preparing the above-mentioned steel strip corrugated pipe, comprising the following steps:

[0010] (1) Steel strip pretreatment: Degreasing and rust removal of the steel strip to improve the bonding strength between the steel strip and polyethylene;

[0011] (2) One-step forming of steel strip: straighten the pre-treated steel strip and extrude it into the corresponding cross-sectional structure through a bending die;

[0012] (3) Secondary forming of steel strip: The steel strip after primary forming is pressed into a spiral shape by a forming machine;

[0013] (4) Resin coating: coating the surface of the steel strip after secondary molding with a high-performance adhesive resin;

[0014] (5) Extruding the inner layer of polyethylene: extruding polyethylene granules through an extruder to form a polyethylene tube body;

[0015] (6) Winding: Wrapping a steel strip coated with a high-performance adhesive resin around the outer circumference of the polyethylene pipe;

[0016] (7) Extruding the outer layer of polyethylene: The polyethylene particles are extruded through an extruder to form a polyethylene coating layer, which wraps the steel belt and the polyethylene tube body, fills the inside of the flat pit, and shapes the top;

[0017] (8) Shape and finalize the extruded tube to ensure that the size and shape of the tube meet the requirements.

[0018] Furthermore, when the extruder performs extrusion molding, the temperature of the feed section is controlled at 160-180°C; the temperature of the compression section is set at 180-200°C; the temperature of the metering section is controlled at 200-220°C; and the temperature of the die head is controlled at 210-230°C.

[0019] Furthermore, the polyethylene used in the polyethylene pipe body is modified by grafting with acrylic acid, and the grafting rate is controlled at 10%-15%.

[0020] The present invention is beneficial in that:

[0021] The present invention improves the complete arch bridge-shaped steel belt of the previous steel belt corrugated pipe, and the top of the wave crest is vertically depressed downward to form a flat pit, so that when the polyethylene coating layer is extruded, the molten polyethylene will fill into the flat pit to form a supporting interlayer. Moreover, the bottom end of the flat pit is horizontal and flush with the bottom surface of the fixed part, so that there is a supporting column at the center of the wave crest that directly acts on the outer peripheral wall of the polyethylene pipe body vertically downward, and this supporting column is composed of a steel belt with double wall thickness and a supporting interlayer. The supporting interlayer also prevents the two side walls of the flat pit from deforming inward during extrusion, which can greatly improve the overall ring stiffness of the pipe and improve its compressive resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic cross-sectional view of the tube wall of the present invention.

[0023] In the figure: 1-polyethylene tube body, 2-steel belt, 21-peak, 22-fixing part, 23-flat pit, 3-polyethylene coating layer, 31-support interlayer. DETAILED DESCRIPTION

[0024] The specific embodiments of the present invention are further described below in conjunction with the accompanying drawings. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0025] like Figure 1 As shown:

[0026] A steel belt corrugated pipe comprises a polyethylene coating 3, a steel belt 2, a polyethylene pipe body 1 and an adhesive resin layer (a very thin coating, so it is not shown in the figure, but this does not affect the understanding and implementation of the technical solution of the present invention); the cross-section of the steel belt 2 is an arch bridge shape as a whole, with fixed parts 22 extending horizontally on both sides, and the top of its wave crest 21 is vertically depressed downward to form a flat pit 23, and the bottom end of the flat pit 23 is horizontal and flush with the bottom surface of the fixed part; the steel belt 2 is spirally wound around the outer periphery of the polyethylene pipe body 1, and the surface of the steel belt 2 is coated with an adhesive resin layer, the polyethylene coating 3 covers the polyethylene pipe body 1 and the surface of the steel belt, and fills the inside of the flat pit 23 to form a supporting interlayer 31, and fills the top of the flat pit 23 to form a complete arch bridge structure.

[0027] The present invention improves the complete arch bridge-shaped steel belt of the previous steel belt corrugated pipe, and the top of its wave crest is vertically depressed downward to form a flat pit 23. In this way, when the polyethylene coating layer 3 is extruded, the molten polyethylene will fill into the flat pit 23 to form a supporting interlayer 31. It is recommended that the inner width of the flat pit 23 is 2-3 times the thickness of the polyethylene coating layer 3.

[0028] Moreover, the bottom end of the flat pit 23 is horizontal and flush with the bottom surface of the fixed part, so that there is a support column in the center of the wave crest that directly acts vertically downward on the outer wall of the polyethylene tube body 1, and this support column is composed of a double-thickness steel belt and a support interlayer 31. The support interlayer 31 also prevents the two side walls of the flat pit 23 from deforming inward during extrusion, which can greatly improve the overall ring stiffness of the pipe and improve its compressive resistance.

[0029] The present invention also provides a method for preparing the above-mentioned steel strip corrugated pipe, comprising the following steps:

[0030] (1) Steel strip pretreatment: Degreasing and rust removal of the steel strip to improve the bonding strength between the steel strip and polyethylene;

[0031] (2) One-step forming of the steel strip: The pre-treated steel strip is straightened and extruded into a corresponding cross-sectional structure through a bending die. To facilitate the design and drawing of the die, the bottom and top of the two side walls of the flat pit 23 are both arc-shaped transitions at the joints.

[0032] (3) Secondary forming of steel strip: The steel strip after primary forming is pressed into a spiral shape by a forming machine;

[0033] (4) Resin coating: Coating the surface of the steel strip after secondary molding with a high-performance adhesive resin to enhance the bonding performance between the steel strip and polyethylene;

[0034] (5) Extruding the inner layer of polyethylene: extruding polyethylene particles through an extruder to form a polyethylene tube body 1;

[0035] (6) Winding: Winding a steel belt coated with a high-performance adhesive resin around the outer periphery of the polyethylene pipe body 1 to form a steel belt reinforcement layer;

[0036] (7) Extruding the outer layer of polyethylene: The polyethylene particles are extruded through an extruder to form a polyethylene coating layer 3, which wraps the steel belt 2 and the polyethylene tube body 1, fills the inside of the flat pit 23, and shapes the top end;

[0037] (8) Shape and finalize the extruded tube to ensure that the size and shape of the tube meet the requirements.

[0038] During extrusion, the temperature is controlled as follows:

[0039] 1. Feed section temperature: generally around 160-180°C, this area is mainly used for preliminary heating and conveying of polyethylene (PE) raw materials. Lower temperatures can prevent the raw materials from "bridging" at the feed inlet (the raw materials accumulate at the feed inlet and cannot enter the screw smoothly), and help compact the material.

[0040] 2. Compression section temperature: The temperature is usually set at 180-200℃. At this stage, the screw compresses the material to gradually melt it. Properly increasing the temperature is conducive to the plasticization of the material, allowing the polyethylene molecular chains to flow and mix better, preparing for subsequent extrusion.

[0041] 3. Metering section temperature: The temperature of this section is about 200-220℃. The main function of this area is to accurately control the flow and pressure of the melt. The higher temperature can ensure the uniformity and fluidity of the polyethylene melt, so that the melt can be smoothly extruded through the die to form the inner or outer layer of the pipe.

[0042] 4. Die temperature: The die is where the melt is finally extruded, and the temperature should be controlled at 210-230°C. This temperature range ensures that the melt has good fluidity during extrusion, can be evenly wrapped around the steel strip or form the inner layer of the pipe, and is beneficial to the molding quality of the pipe, avoiding surface defects and other problems.

[0043] Since the steel belt corrugated pipe is mainly used for underground drainage and sewage pipes, the polyethylene used in the polyethylene pipe body 1 is modified by acrylic acid grafting. The polyethylene pipe grafted with acrylic acid has better hydrophilicity. When used to transport some fluids containing water, it can reduce the friction between the fluid and the pipe wall and improve the fluid transportation efficiency. The grafting rate is controlled at about 10%-15% according to demand.

[0044] The pressure is controlled as follows:

[0045] 1. Screw back pressure: generally between 10-30MPa. Back pressure refers to the pressure exerted by the melt in the screw's backward direction during the screw's rotation. Appropriate back pressure can fully mix and plasticize the material in the screw, improving the quality of the polyethylene melt. If the back pressure is too low, the material may be mixed unevenly, affecting the performance of the pipe; if the back pressure is too high, it will increase the load on the motor and may even damage the equipment.

[0046] 2. Extrusion pressure: When extruding the inner or outer layer of polyethylene, the extrusion pressure is usually around 20-50MPa. This pressure range can ensure that the melt can be extruded smoothly through the die, and can keep the pipe in a certain shape and dimensional accuracy during the extrusion process. The pressure is also related to factors such as the wall thickness of the pipe and the extrusion speed, and needs to be adjusted according to actual production conditions.

[0047] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments are made without departing from the principles and spirit of the present invention, and still fall within the scope of protection of the present invention.

Claims

1. A steel belt corrugated pipe, characterized in that: It includes a polyethylene coating, a steel belt, a polyethylene tube body and an adhesive resin layer; the cross-section of the steel belt is an overall arch bridge shape, with fixed parts extending horizontally on both sides, and the top of its wave crest is vertically depressed downward to form a flat pit, and the bottom of the flat pit is horizontal and flush with the bottom surface of the fixed part; the steel belt is spirally wound around the outer periphery of the polyethylene tube body, and the surface of the steel belt is coated with an adhesive resin layer, the polyethylene coating layer covers the polyethylene tube body and the surface of the steel belt, and fills the inside of the flat pit to form a supporting interlayer, and fills the top of the flat pit to form a complete arch bridge structure.

2. The steel strip corrugated pipe according to claim 1, characterized in that: The bottom and the top of the two side walls of the flat pit are both connected in an arc transition.

3. The steel strip corrugated pipe according to claim 1, characterized in that: The thickness of the supporting interlayer is 2-3 times the thickness of the polyethylene coating layer.

4. A method for preparing a steel strip corrugated pipe according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) Steel strip pretreatment: Degreasing and rust removal of the steel strip to improve the bonding strength between the steel strip and polyethylene; (2) One-step forming of steel strip: straighten the pre-treated steel strip and extrude it into a corresponding cross-sectional structure through a bending die; (3) Secondary forming of steel strip: The steel strip after primary forming is pressed into a spiral shape by a forming machine; (4) Resin coating: coating the surface of the steel strip after secondary molding with a high-performance adhesive resin; (5) Extruding the inner layer of polyethylene: extruding polyethylene granules through an extruder to form a polyethylene tube body; (6) Winding: Wrapping a steel strip coated with a high-performance adhesive resin around the outer circumference of the polyethylene pipe; (7) Extruding the outer layer of polyethylene: The polyethylene particles are extruded through an extruder to form a polyethylene coating layer, which wraps the steel belt and the polyethylene tube body, fills the inside of the flat pit, and shapes the top; (8) Shape and finalize the extruded tube to ensure that the size and shape of the tube meet the requirements.

5. The method for preparing a steel strip corrugated pipe according to claim 4, characterized in that: When the extruder performs extrusion molding, the temperature of the feeding section is controlled at 160-180°C; the temperature of the compression section is set at 180-200°C; the temperature of the metering section is controlled at 200-220°C; and the temperature of the die head is controlled at 210-230°C.

6. The method for preparing a steel strip corrugated pipe according to claim 4, characterized in that: The polyethylene used in the polyethylene pipe body is modified by grafting with acrylic acid, and the grafting rate is controlled at 10%-15%.

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