Production process of PVC-C ardealite industrial fluid steel-plastic composite pipe

Abstract

The invention relates to the technical field of production processes of plastic composite pipes, and particularly discloses a production process of a PVC-C ardealite industrial fluid steel-plastic composite pipe, which comprises the following steps: step 1, adopting resin as a raw material, and producing an inner plastic pipe by using a twin-screw extruder; 2, the outer surface of the inner plastic pipe is evenly coated with a hot melt adhesive layer through a hot melt adhesive extruder; 3, the steel takes a steel belt as a raw material, the inner plastic pipe is wrapped to produce the spiral steel pipe, and 4, heat is induced outside the spiral steel pipe to enable the hot melt adhesive layer to be secondarily melted to bond the spiral steel pipe and the inner plastic pipe; and 5, after high-frequency heating of the spiral steel pipe, the outer surface of the steel pipe is rapidly coated with an outer rubber layer and an outer plastic layer made of PVC-C materials, and a finished pipe is obtained after cooling. The technical problems that in the prior art, when a PVC-C steel-plastic composite pipe is produced, an inner pipe and a steel pipe are coated with hot melt adhesive to be combined into a whole in a sleeved mode after being produced respectively, the steel pipe and the inner pipe are connected only through the hot melt adhesive, the bonding strength is limited, and steel-plastic separation exists are solved.

Description

Technical Field

[0001] This invention relates to the field of plastic composite pipe manufacturing technology, specifically to a manufacturing process for PVC-C phosphogypsum industrial fluid steel-plastic composite pipes. Background Art

[0002] Chlorinated polyvinyl chloride (PVC-C) is a high-performance engineering plastic made by chlorination modification of ordinary polyvinyl chloride (PVC). Through chlorination treatment, the chlorine content of PVC resin is increased from 56% to 63%-69%, significantly enhancing the polarity of the molecular chains. This chemical modification breaks through the temperature resistance limit of traditional PVC, endowing the material with a three-in-one property of high temperature resistance, strong corrosion resistance, and high flame retardancy, making it a revolutionary material for industrial fluid pipelines in harsh environments such as fire protection and chemical processing.

[0003] However, currently, domestic steel-plastic composite pipe manufacturers primarily use PE, PP, PVC, or ABS materials for the inner lining of their products. Products using PVC-C as both the inner and outer lining materials are relatively rare in the industry. This is likely because PVC-C steel-plastic composite pipes are formed by bonding a metal layer (usually steel) to a plastic layer (PVC-C) using adhesives or a hot-melt process. The coefficients of thermal expansion of metal and plastic differ significantly (steel approximately 12 × 10⁻⁶). -6 / ℃, PVC-C is approximately 6-8×10 -6 When used in industrial fluids (at temperatures ranging from 100°C to 100°C), the asynchronous expansion and contraction of the two materials during thermal cycling or high-temperature environments can cause shear stress and lead to interface debonding. This can result in the inner plastic lining of the PVC-C steel-plastic composite pipe shrinking during transportation, construction, and use due to thermal cycling, potentially causing it to slip out of the steel pipe.

[0004] To address the aforementioned issue of PVC-C steel-plastic composite pipes easily shrinking due to inner tube diameter reduction, existing technologies utilize hot melt adhesive between the PVC-C material and the steel pipe. This adhesive's bonding strength enhances the connection between the PVC-C material and the steel. For example, patent application CN201010501725.0 discloses a CPVC-lined steel-plastic composite pipe and its production method. This method adjusts the hot melt adhesive and the bonding process involving ventilation, pressure holding, and medium-frequency heating and pressurization, ensuring a tight fit between the inner tube and the steel pipe in the produced PVC-C steel-plastic composite pipe. This avoids adverse consequences caused by the different expansion or contraction of the PVC-C inner tube and the steel pipe when transporting liquids with alternating hot and cold temperatures.

[0005] While the methods described above, which adjust the hot melt adhesive and lamination process, can mitigate the adverse effects of differing expansion and contraction between the inner and steel pipes in PVC-C steel-plastic composite pipes to some extent, the process involves manufacturing the inner and steel pipes separately, then coating the inner pipe with hot melt adhesive and fitting it inside the steel pipe. Since the connection between the steel pipe and the inner pipe relies solely on the hot melt adhesive, the bonding strength is limited, and the phenomenon of steel-plastic separation still exists. Summary of the Invention

[0006] The purpose of this invention is to provide a production process for PVC-C phosphogypsum industrial fluid steel-plastic composite pipes, in order to solve the technical problem mentioned above in the prior art where the inner pipe and steel pipe are produced separately and then coated with hot melt adhesive to be joined together. The connection between the steel pipe and the inner pipe relies solely on the hot melt adhesive, resulting in limited bonding strength and separation of steel and plastic.

[0007] To solve the above problems, the technical solution adopted by the present invention is as follows: a production process for PVC-C phosphogypsum industrial fluid steel-plastic composite pipe, comprising the following steps: Step 1, Inner Plastic Tube Extrusion and Sizing: Using PVC-C industrial grade resin as raw material, the inner plastic tube is obtained by extrusion and cooling using a twin-screw extruder; Step 2, Inner Adhesive Coating: Apply a hot melt adhesive layer evenly to the outer surface of the inner plastic tube using a hot melt adhesive extruder; Step 3, Steel pipe forming and welding: Using steel strip as the raw material for spiral steel pipe, the inner plastic tube is wrapped to produce spiral steel pipe. When the steel strip is rolled, it compresses the hot melt adhesive layer. Step 4: High-frequency heating of the steel pipe: The induced heat on the outside of the spiral steel pipe causes the hot melt adhesive layer on the outside of the inner plastic pipe to melt a second time, bonding the steel pipe and the inner plastic pipe together. Step 5, Outer Adhesive and Outer Plastic Composite: After the steel pipe is heated by high frequency in step 4, an outer adhesive layer is quickly applied to the outer surface of the steel pipe through a hot melt adhesive extruder. Then, an outer plastic layer of PVC-C material is applied through a plastic extruder. After cooling, it becomes the finished PVC-C phosphogypsum industrial fluid steel-plastic composite pipe.

[0008] The beneficial effects of this implementation plan are as follows: 1. While existing technologies can mitigate the adverse effects of different expansion and contraction between the inner and steel pipes of PVC-C steel-plastic composite pipes by adjusting the hot melt adhesive and lamination method, the process involves manufacturing the inner and steel pipes separately, then coating the inner pipe with hot melt adhesive and fitting it into the steel pipe. If the hot melt adhesive is too thick, the outer diameter of the inner pipe becomes too large, making it difficult to insert into the pre-made steel pipe. If the adhesive is too thin, insufficient hot melt adhesive between the steel pipe and the inner pipe after insertion can easily lead to bonding cavities, poor contact at the bonding surfaces, and unsatisfactory bonding results. Furthermore, the connection between the steel pipe and the inner pipe relies solely on the hot melt adhesive, resulting in limited bonding strength and a tendency for steel-plastic separation. This makes process control difficult and product quality unstable. In contrast, this application involves directly applying hot melt adhesive after manufacturing the inner plastic pipe, and then directly winding steel strips around the hot melt adhesive layer to produce the spiral steel pipe. Therefore, when producing spiral steel pipes by winding steel strips around inner plastic tubes, the hot melt adhesive layer is compressed, causing the deformation to cover the contact surface between the inner plastic tube and the steel pipe. When the hot melt adhesive layer melts a second time to bond the steel pipe and the inner plastic tube, the hot melt adhesive easily covers the bonding surface between the steel pipe and the inner plastic tube, forming a good bond. Furthermore, because the hot melt adhesive layer is compressed when the spiral steel pipe is wound, it is easier to penetrate into the microporous structure of the steel pipe surface during the second melting, forming a mechanical interlocking anchor. Therefore, compared with the prior art, the hot melt adhesive of this application has better bonding contact, and the PVC-C phosphogypsum industrial fluid steel-plastic composite pipe produced has less steel-plastic separation.

[0009] Furthermore, the formulation of the PVC-C industrial-grade resin consists of the following components in parts by weight: 100-150 parts chlorinated polyvinyl chloride resin, 2.0-5.0 parts organotin stabilizer TM181, 0.5-15 parts phosphogypsum, 0.3-1.5 parts calcium stearate, 0.2-1.0 parts EBS, 0.4-2.5 parts PE wax, and OPE... The formula comprises 0.5-2.2 parts of impact modifier, 7.0-12.5 parts of impact modifier, and 0.4-2.5 parts of solid plasticizer. In existing technologies, to meet the strength requirements of industrial fluids, all PVC-C pipes have relatively thick walls, resulting in high overall costs. However, the formulation of the PVC-C industrial-grade resin in this application differs from existing technologies, containing phosphogypsum. By adjusting other components in combination with phosphogypsum, the pipes made from the PVC-C industrial-grade resin used in this application exhibit greater strength and better corrosion resistance. Therefore, while meeting the strength and corrosion resistance requirements of industrial fluids, the wall thickness is reduced, lowering production costs. Furthermore, phosphogypsum is a solid waste generated from the wet-process phosphoric acid production. The continuous growth in global annual phosphate fertilizer production has led to a surge in phosphogypsum stockpiles. China's annual emissions exceed 80 million tons, with accumulated stockpiles exceeding 300 million tons, and the comprehensive utilization rate has long been below 10%. The multi-level pollution caused by its open-air storage has become one of the core contradictions restricting the sustainable development of the chemical industry. After adding phosphogypsum in this application, not only is the strength of the pipe increased and the thickness reduced, but the phosphogypsum is also consumed, achieving the purpose of treating waste with waste.

[0010] Furthermore, the hot melt adhesive is a PVC-C specific adhesive resin, and its formulation consists of the following components in percentage: 15% graft masterbatch, 45% tackifying resin, 15% LDPE, and 25% POE. POE is a polyolefin elastomer, and the hot melt adhesive layer has a certain deformation capacity. Under slight extrusion of the spiral steel pipe, it deforms, allowing the hot melt adhesive to repeatedly contact the inner surface of the steel pipe and the outer surface of the inner plastic pipe, preventing any areas of poor contact.

[0011] Furthermore, in step 3, after the steel strip is uncoiled and the ends of the two coils are welded together, a spiral steel pipe is formed by pressing the edges with a roller, and the welding between the steel strips is carried out by tungsten inert gas argon arc welding.

[0012] Furthermore, during the welding of the steel strip, it is necessary to ensure that there is at least a 0.1mm gap between the inner plastic tube and the spiral steel tube. The inner plastic tube should not be damaged during the welding process of the spiral steel tube.

[0013] Furthermore, in step 3, the steel strip is compressed during coiling, and the compression of the spiral steel pipe is 3%-5% of the thickness of the hot melt adhesive layer.

[0014] Furthermore, in step 3, before the steel strip is made into a spiral steel pipe, it needs to undergo uncoiling, welding of the two coils of steel strip at the ends, and edge trimming. After that, the steel strip is subjected to edge finishing and grinding, and steel strip cleaning pretreatment.

[0015] Furthermore, the inner plastic tube wrapped by the steel strip is formed into a spiral steel pipe using a roller pressing edge method. Attached Figure Description

[0016] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0017] The following detailed description illustrates the specific implementation method: Implementation, for example, attached Figure 1 As shown: A manufacturing process for PVC-C phosphogypsum industrial fluid steel-plastic composite pipes includes the following steps: General Methodology Step 1, Inner Plastic Tube Extrusion and Sizing: Using PVC-C industrial grade resin as raw material, the inner plastic tube is obtained by extrusion and cooling using a twin-screw extruder; Step 2, Inner Adhesive Coating: Apply a hot melt adhesive layer evenly to the outer surface of the inner plastic tube using a hot melt adhesive extruder; Step 3, Steel pipe forming and welding: Using steel strip as the raw material for spiral steel pipe, the inner plastic tube is wrapped to produce spiral steel pipe. When the steel strip is rolled, it compresses the hot melt adhesive layer. Step 4, High-frequency heating of steel pipe: After the spiral steel pipe is formed in step 3, heat is induced on the outside of the spiral steel pipe to melt the hot melt adhesive layer on the outside of the inner plastic pipe a second time and bond the spiral steel pipe and the inner plastic pipe. Step 5, Outer Adhesive and Outer Plastic Composite: After the spiral steel pipe is heated by high frequency in step 4, an outer adhesive layer is quickly applied to the outer surface of the steel pipe through a hot melt adhesive extruder. Then, an outer plastic layer of PVC-C material is applied through a plastic extruder. After cooling, it becomes the finished PVC-C phosphogypsum industrial fluid steel-plastic composite pipe.

[0018] The hot melt adhesive mentioned above is a PVC-C specific adhesive resin, and its specific components are as follows:

[0019] The composition of the PVC-C industrial grade resin is shown in the table below:

[0020] Example 1 The main process flow of PVC-C phosphogypsum industrial fluid steel-plastic composite pipe is briefly described below: 1) Inner plastic tube extrusion sizing: The inner plastic tube is produced using a dedicated twin-screw extruder for PVC. Before molding, the raw material, PVC-C industrial-grade resin, must be well plasticized. The formulation of the PVC-C industrial-grade resin consists of the following components by weight: 100 parts chlorinated polyvinyl chloride resin, 2.0 parts organotin stabilizer TM181, 0.5 parts phosphogypsum, 0.3 parts calcium stearate, 0.2 parts EBS, 0.4 parts PE wax, 0.5 parts OPE, 7.0 parts impact modifier, and 0.4 parts solid plasticizer. Vacuum sizing and immersion cooling are used to cool and form the inner plastic tube in a shorter distance. The production of the inner plastic tube requires smooth inner and outer walls, precise control of the outer diameter of the inner tube, and high roundness.

[0021] 2) Inner adhesive coating: After the inner plastic tube is cooled and formed, a hot melt adhesive layer is evenly coated on the outer surface of the inner plastic tube using a hot melt adhesive extruder. The quality requirement for the hot melt adhesive layer is that the thickness of the adhesive layer is uniform in both the circumferential and axial directions. The hot melt adhesive is composed of the following components in percentage: grafted masterbatch 15%, tackifying resin 45%, LDPE 15%, and POE 25%.

[0022] 3) Steel strip pretreatment: After the steel strip undergoes uncoiling, welding of the two coils at their ends, and edge trimming, the steel strip is pre-treated by edge finishing and grinding, and cleaning. This process is crucial to the forming and welding quality of the steel strip. After treatment, the steel strip has excellent forming and welding performance, ensuring the mechanical properties and strength requirements of the steel pipe weld.

[0023] 4) Steel pipe forming and welding: After the steel strip pretreatment is completed, the steel strip wraps around the inner plastic tube and forms a spiral steel pipe using a roller pressing edge method. It is worth noting that when forming the spiral steel pipe here, its diameter is slightly smaller than the outer diameter of the inner plastic tube after the hot melt adhesive layer is applied, creating a compression amount. In this embodiment, the compression amount of the spiral steel pipe is controlled to be 5% of the hot melt adhesive layer thickness; for example, if the outer diameter of the inner plastic tube is 50mm, the hot melt adhesive layer thickness is 1mm, and the total outer diameter is 52mm, then 5% of 1mm equals 0.05mm, therefore the inner diameter of the spiral steel pipe is controlled to be 51.95mm. This allows the spiral steel pipe to slightly compress the hot melt adhesive layer. Since the hot melt adhesive in this application contains 25% POE, which is a polyolefin elastomer, the hot melt adhesive layer has a certain deformation capacity. Under the slight compression of the spiral steel pipe, deformation occurs, allowing the hot melt adhesive to repeatedly contact the inner surface of the steel pipe and the outer surface of the inner plastic tube, preventing poor contact. The welding between the steel strips uses tungsten inert gas (TIG) argon arc welding. During welding, to prevent high-temperature damage to the inner tube at the weld pool, regardless of the inner plastic tube's diameter, a hot melt adhesive layer of at least 0.1mm to 0.2mm must be maintained between the inner plastic tube and the spiral steel pipe. This station is equipped with an eddy current flaw detector to inspect the weld quality. If any weld defects are found, a defect mark will be sprayed onto the defective area at the spraying station and then cut off.

[0024] 5) High-frequency heating of steel pipes: High-frequency heating of spiral steel pipes (also known as induction heating) is a non-contact rapid heating method that uses a high-frequency electromagnetic field to heat conductive materials (mainly metals). The heat generated in the electromagnetic field is transferred through the spiral steel pipe, causing the temperature of the spiral steel pipe, hot melt adhesive layer, and inner plastic pipe to rise rapidly. When the hot melt adhesive layer outside the inner plastic pipe melts a second time, heating continues for 10 minutes to completely melt and bond the hot melt adhesive layer to the spiral steel pipe and the inner plastic pipe, ensuring that the spiral steel pipe and the inner plastic pipe are composited into a whole.

[0025] 6) Composite of outer adhesive and outer plastic: After the spiral steel pipe is heated by high frequency, when the hot melt adhesive layer is completely melted a second time, hot melt adhesive is quickly applied to the outer surface of the spiral steel pipe through a hot melt adhesive extruder to form an outer adhesive layer. The hot melt adhesive composition of the outer adhesive layer is the same as that of the inner hot melt adhesive layer. Immediately afterwards, an outer plastic layer is applied through a plastic extruder. The outer plastic layer also uses the same PVC-C industrial-grade resin as the inner plastic pipe. The outer adhesive layer and outer plastic layer are applied rapidly after high-frequency heating, and the process is completed while the hot melt adhesive layer is still in a molten state to ensure bonding quality.

[0026] 7) Post-processing of finished pipes: The cooled finished pipe has good strength and rigidity, can withstand downward traction force, and is cut to length (6m, 9m or 12m, etc.) after marking at a fixed distance.

[0027] 8) After sawing, the steel-plastic pipes are trimmed or sealed and packaged.

[0028] As can be seen from the above basic process, the multi-layer composite process is continuous yet relatively independent, making full use of diameter measurement, flaw detection and other means to facilitate quality control of each process and form continuous and stable production.

[0029] Example 2 The difference between Example 2 and Example 1 is that the formulation of PVC-C industrial grade resin consists of the following components by mass parts: 125 parts chlorinated polyvinyl chloride resin, 3.5 parts organotin stabilizer TM181, 7.5 parts phosphogypsum, 0.9 parts calcium stearate, 0.6 parts EBS, 1.45 parts PE wax, 1.35 parts OPE, 9.5 parts impact modifier, and 1.45 parts solid plasticizer. The extrusion compression of the spiral steel pipe is controlled at 3% of the hot melt adhesive layer thickness.

[0030] Example 3 The difference between Example 3 and Example 1 is that the PVC-C industrial-grade resin formulation consists of the following components by weight: 150 parts chlorinated polyvinyl chloride resin, 5.0 parts organotin stabilizer TM181, 15 parts phosphogypsum, 1.5 parts calcium stearate, 1.0 part EBS, 2.5 parts PE wax, 2.2 parts OPE, 12.5 parts impact modifier, and 2.5 parts solid plasticizer. The controlled extrusion compression of the spiral steel pipe is 4% of the hot melt adhesive layer thickness.

[0031] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific structures and characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A production process for PVC-C phosphogypsum industrial fluid steel-plastic composite pipes, characterized in that: Includes the following steps: Step 1, Inner Plastic Tube Extrusion and Sizing: Using PVC-C industrial grade resin as raw material, the inner plastic tube is obtained by extrusion and cooling using a twin-screw extruder; Step 2, Inner Adhesive Coating: Apply a hot melt adhesive layer evenly to the outer surface of the inner plastic tube using a hot melt adhesive extruder; Step 3, Steel pipe forming and welding: Using steel strip as the raw material for spiral steel pipe, the inner plastic tube is wrapped to produce spiral steel pipe. When the steel strip is rolled, it compresses the hot melt adhesive layer. Step 4, High-frequency heating of steel pipe: After the spiral steel pipe is formed in step 3, heat is induced on the outside of the spiral steel pipe to melt the hot melt adhesive layer on the outside of the inner plastic pipe a second time and bond the spiral steel pipe and the inner plastic pipe. Step 5, Outer Adhesive and Outer Plastic Composite: After the spiral steel pipe is heated by high frequency in step 4, an outer adhesive layer is quickly applied to the outer surface of the steel pipe through a hot melt adhesive extruder. Then, an outer plastic layer of PVC-C material is applied through a plastic extruder. After cooling, it becomes the finished PVC-C phosphogypsum industrial fluid steel-plastic composite pipe.

2. The production process of the PVC-C phosphogypsum industrial fluid steel-plastic composite pipe according to claim 1, characterized in that: The formulation of the PVC-C industrial grade resin includes the following components in parts by weight: 100-150 parts of chlorinated polyvinyl chloride resin, 2.0-5.0 parts of organotin stabilizer TM181, 0.3-1.5 parts of calcium stearate, 0.2-1.0 parts of EBS, 0.4-2.5 parts of PE wax, 0.5-2.2 parts of OPE, 7.0-12.5 parts of impact modifier, and 0.4-2.5 parts of solid plasticizer.

3. The production process of the PVC-C phosphogypsum industrial fluid steel-plastic composite pipe according to claim 1, characterized in that: The PVC-C industrial grade resin also includes 0.5-15 parts of phosphogypsum.

4. The production process of the PVC-C phosphogypsum industrial fluid steel-plastic composite pipe according to claim 2, characterized in that: The hot melt adhesive is a special adhesive resin for PVC-C, and its formula consists of the following components in percentage: 15% grafting masterbatch, 45% tackifying resin, 15% LDPE, and 25% POE.

5. The production process of the PVC-C phosphogypsum industrial fluid steel-plastic composite pipe according to claim 1, characterized in that: In step 3, after the steel strip is uncoiled and the ends of the two coils are welded together, a spiral steel pipe is formed by pressing the edges with a roller. The welding between the steel strips is done by tungsten inert gas argon arc welding.

6. The production process of the PVC-C phosphogypsum industrial fluid steel-plastic composite pipe according to claim 5, characterized in that: When welding the steel strip, it is necessary to ensure that there is at least a 0.1mm gap between the inner plastic tube and the spiral steel tube.

7. The production process of the PVC-C phosphogypsum industrial fluid steel-plastic composite pipe according to claim 1, characterized in that: In step 3, the steel strip is compressed during coiling, and the compression of the spiral steel pipe is 3%-5% of the thickness of the hot melt adhesive layer.

8. The production process of the PVC-C phosphogypsum industrial fluid steel-plastic composite pipe according to claim 1, characterized in that: In step 3, before the steel strip is made into a spiral steel pipe, it needs to undergo uncoiling, welding of the two coils of steel strip at the ends, and edge trimming. After that, the steel strip is subjected to edge finishing and grinding, and steel strip cleaning pretreatment.

9. The production process of the PVC-C phosphogypsum industrial fluid steel-plastic composite pipe according to claim 8, characterized in that: The inner plastic tube wrapped with steel strip is formed into a spiral steel pipe by roller pressing edge method.

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