Corrosion-resistant plastic-coated composite pipe and method for manufacturing the same

Abstract

The application relates to the technical field of plastic-coated composite pipes, and discloses a corrosion-resistant plastic-coated composite pipe and a preparation method thereof. The corrosion-resistant plastic-coated composite pipe comprises a steel pipe base pipe and a plastic coating arranged on the outer surface of the steel pipe base pipe, and the plastic coating comprises a fusion-bonded epoxy layer, a glue layer and a polyethylene layer arranged in sequence from inside to outside. The polyethylene layer comprises the following component raw materials in parts by weight: 80 parts of high-density polyethylene, 10-15 parts of metallocene polyethylene, 6-12 parts of vinyl copolymer, 15-20 parts of filler, 2-4 parts of antioxidant and 6-8 parts of plasticizer. The vinyl copolymer comprises ethylene-butene copolymer and ethylene-hexene copolymer in a weight ratio of 1-9:1. Through the technical scheme, the problem that the corrosion resistance of the plastic-coated composite pipe needs to be improved is solved.

Description

Technical Field

[0001] This invention relates to the field of plastic-coated composite pipe technology, specifically to a corrosion-resistant plastic-coated composite pipe and its preparation method. Background Technology

[0002] Plastic-coated composite pipes are pipes that organically combine steel pipes with plastic coatings. They combine the high strength and good impact resistance of steel pipes with the corrosion resistance and wear resistance of plastic coatings, and are widely used in fluid transportation in petrochemical, municipal water supply and drainage, fire protection, marine engineering and other fields.

[0003] During the use of plastic-coated composite pipes, the outer plastic coating layer is a crucial barrier against external corrosive media (such as acids, alkalis, salts, and humid environments). Currently, most common plastic-coated composite pipes use materials such as polyethylene and epoxy resin as the main coating material. Although this improves the corrosion resistance of the pipe to a certain extent, problems such as media penetration may still occur during long-term use or in complex corrosive environments, leading to a weakening of the protective effect and consequently affecting the service life and operational safety of the pipeline.

[0004] Therefore, a plastic-coated composite pipe with good corrosion resistance is proposed, which is of great significance for extending the service life of plastic-coated composite pipes. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a corrosion-resistant plastic-coated composite pipe and its preparation method. The corrosion-resistant plastic-coated composite pipe provided by this invention incorporates a vinyl copolymer of ethylene-butene copolymer and ethylene-hexene copolymer into its polyethylene layer. By rationally combining the two, the problem of the need to improve the corrosion resistance of existing coated composite pipes is solved.

[0006] The specific technical solution of the present invention is as follows: According to one aspect of the present invention, a corrosion-resistant plastic-coated composite pipe is provided, comprising a steel pipe base and a plastic coating layer disposed on the outer surface of the steel pipe base, wherein the plastic coating layer comprises a fusion-bonded epoxy layer, an adhesive layer, and a polyethylene layer disposed sequentially from the inside to the outside; The polyethylene layer comprises the following components in parts by weight: 80 parts high-density polyethylene, 10-15 parts metallocene polyethylene, 6-12 parts vinyl copolymer, 15-20 parts filler, 2-4 parts antioxidant, and 6-8 parts plasticizer; The vinyl copolymers include ethylene-butene copolymers and ethylene-hexene copolymers in a weight ratio of 1 to 9:1.

[0007] In the above technical solution, the melt mass flow rate of the ethylene-butene copolymer at 190℃ and 2.16kg is 1.2g / 10min; The melt flow rate of the ethylene-hexene copolymer at 190°C and 2.16 kg is 2.0~3.5 g / 10 min.

[0008] In the above technical solution, the weight ratio of ethylene-butene copolymer to ethylene-hexene copolymer is 2~5:1.

[0009] In the above technical solution, the raw material of the filler includes the following components in parts by weight: 40-45 parts titanium dioxide, 5-10 parts silicon dioxide, 1-4 parts titanate coupling agent, 2 Acrylamide group 2 3-7 parts of methylpropanesulfonic acid.

[0010] In the above technical solution, the 2 Acrylamide group 2 The weight ratio of methylpropanesulfonic acid to the titanate coupling agent is 1.5 to 3:1.

[0011] In the above technical solution, the method for preparing the filler includes the following steps: A1. The titanium dioxide and silicon dioxide are blended and ground to obtain a blend; A2. Dissolve the titanate coupling agent in isopropanol, add the blend, mix, and dry to obtain the pretreated blend. A3, the above 2 Acrylamide group 2 Methylpropanesulfonic acid is dissolved in ethanol, added to the pretreated blend, mixed, and dried to obtain the filler.

[0012] In the above technical solution, the raw material of the polyethylene layer also includes 4 to 6 parts of lubricant.

[0013] In the above technical solution, the lubricant includes one or two of polyethylene wax and zinc stearate; The antioxidant includes one or more of antioxidant 1010, antioxidant 1024, and antioxidant 1076; The plasticizer includes one or more of dioctyl phthalate, diisononyl phthalate, and diisodecyl phthalate.

[0014] In the above technical solution, the raw material of the fusion-bonded epoxy layer includes epoxy resin; The adhesive layer is made from an ethylene-acrylic acid copolymer.

[0015] According to another aspect of the present invention, the present invention also provides a method for preparing the above-mentioned corrosion-resistant plastic-coated composite pipe, comprising the following steps: A fusion-bonded epoxy layer and an adhesive layer are sequentially disposed on the outside of the steel pipe base. The raw materials of the polyethylene layer are blended, extruded, and coated on the outside of the adhesive layer. The composite is then pressurized to obtain the corrosion-resistant plastic-coated composite pipe.

[0016] Compared with existing technologies, this invention provides a corrosion-resistant plastic-coated composite pipe. A plastic coating layer, consisting of a fusion-bonded epoxy layer, an adhesive layer, and a polyethylene layer, is formed on the outer layer of a steel pipe base. The fusion-bonded epoxy layer is tightly bonded to the steel pipe base, effectively isolating corrosive media from direct contact with the steel pipe and providing an initial protective barrier. The outermost layer of the fusion-bonded epoxy layer is the adhesive layer, which enhances the adhesion between the fusion-bonded epoxy layer and the polyethylene layer, ensuring the structural stability of the plastic coating layer and guaranteeing overall protective performance. The outermost polyethylene layer, using high-density polyethylene as the main material, imparts basic mechanical properties and corrosion resistance to the plastic coating layer. Combined with metallocene polyethylene, ethylene copolymer, fillers, and additives, a dense and stable polyethylene layer is obtained, effectively providing protection. Finally, through the rational use of each layer, a plastic-coated composite pipe with stable structure and excellent corrosion resistance is obtained.

[0017] In the polyethylene layer, the ethylene copolymers include ethylene-butene copolymers and ethylene-hexene copolymers. Ethylene-butene copolymers have relatively flexible molecular chains and good toughness, which can effectively buffer external forces and prevent the polyethylene layer from cracking due to external forces. At the same time, they have good processing fluidity and can form a denser structure. Ethylene-hexene copolymers have a more compact molecular arrangement and higher stability. The presence of ethylene-hexene copolymers can further hinder the penetration of corrosive substances. By using these two ethylene copolymers together and reasonably adjusting the composition ratio, the overall structural density and stability of the polyethylene layer can be effectively improved, thereby improving the corrosion resistance of the coated composite pipe. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention more apparent, the invention is described in detail below. It should be understood that the invention is not limited to the description herein.

[0019] High-density polyethylene In the polyethylene layer of this invention, high-density polyethylene is the main matrix component. Its crystallinity is relatively high and its molecular arrangement is relatively compact, which gives the polyethylene layer good structural stability and corrosion resistance. It can withstand a certain pressure, ensuring that the pipeline is not easily deformed during use. At the same time, it also gives the composite pipe good corrosion resistance.

[0020] Metallocene polyethylene In this invention, metallocene polyethylene and high-density polyethylene are used together in the polyethylene layer, which can play a toughening role in the polyethylene layer and reduce the risk of breakage when the composite pipe is subjected to external impact.

[0021] ethylene-butene copolymer and ethylene-hexene copolymer In the polyethylene layer of this invention, high-density polyethylene is used as the matrix material, and vinyl copolymers of ethylene-butene copolymer and ethylene-hexene copolymer are introduced at the same time. By using ethylene-butene copolymer and ethylene-hexene copolymer together, a more dense and stable polyethylene layer can be obtained, which is beneficial to improving the corrosion resistance of the coated composite pipe.

[0022] In addition, the weight ratio of ethylene-butene copolymer and ethylene-hexene copolymer in this invention is 1 to 9:1, for example, it can be 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, or 9:1.

[0023] In this invention, the melt flow rates of the ethylene-butene copolymer and the ethylene-hexene copolymer are limited, such that the melt flow rate of the ethylene-butene copolymer at 190℃ and 2.16kg is 1.2g / 10min, and the melt flow rate of the ethylene-hexene copolymer at 190℃ and 2.16kg is 2.0~3.5g / 10min. By optimizing the content ratio of the ethylene-butene copolymer with a melt flow rate of 1.2g / 10min at 190℃ and 2.16kg to the ethylene-hexene copolymer with a melt flow rate of 2.0~3.5g / 10min, the combined effect of the two is better and can be more conducive to improving the corrosion resistance of the coated composite pipe.

[0024] filler In this invention, the raw materials for the filler include titanium dioxide, silicon dioxide, titanate coupling agent, and 2... Acrylamide group 2 Methylpropanesulfonic acid. The filler uses titanium dioxide and silicon dioxide as inorganic powder materials. Titanium dioxide has high hardness and rigidity, which can enhance the overall strength of the coated composite pipe. The presence of silicon dioxide can fill the pores formed by titanium dioxide and the pores inside the polyethylene layer, making the polyethylene layer structure more compact. However, directly adding inorganic powders of titanium dioxide and silicon dioxide to the organic matrix of high-density polyethylene easily leads to agglomeration of inorganic powders, limiting the reinforcing effect of the filler. In this invention, a titanate coupling agent is used to pretreat the surface of the inorganic powders of titanium dioxide and silicon dioxide, which can reduce the agglomeration of titanium dioxide and silicon dioxide, resulting in a uniform polyethylene layer, giving the coated composite pipe good impact resistance. Furthermore, the inventors discovered that using 2... Acrylamide group 2 Methylpropanesulfonic acid and titanate coupling agents are used together to surface treat titanium dioxide and silicon dioxide, which can improve the impact resistance of plastic-coated composite pipes. The speculated reason is that the titanate coupling agent acts as a bridge between the inorganic filler and the organic polymer, enhancing the interfacial bonding between the inorganic powder and other components in the polyethylene layer. Acrylamide group 2 The addition of methylpropanesulfonic acid, used in conjunction with titanate coupling agent, to jointly treat inorganic powders allows titanium dioxide and silicon dioxide to be dispersed more uniformly and stably in the polyethylene layer than using titanate coupling agent alone, thereby further improving the impact resistance of the coated composite pipe.

[0025] In this invention, the titanate coupling agent can be any titanate coupling agent known in the art that can be used in coated composite pipes, and this invention is not limited to the titanate coupling agents listed below. As an example, the titanate coupling agent can be isopropyl tris(dioctyl pyrophosphate) titanate, tetraisopropyl di(dioctyl phosphite) titanate, isopropyl triisostearoyl titanate, preferably isopropyl tris(dioctyl pyrophosphate) titanate.

[0026] In this invention, the average particle size of titanium dioxide is 30~80μm, for example, it can be any point value among 30μm, 40μm, 50μm, 60μm, 70μm, and 80μm and the range between two points, preferably 45~60μm; the average particle size of silicon dioxide is 50~100nm, for example, it can be any point value among 50nm, 60nm, 70nm, 80nm, 90nm, and 100nm and the range between two points, preferably 60~80nm.

[0027] antioxidants In this invention, the antioxidant can be any antioxidant known in the art that can be used in coated composite pipes, and the invention is not limited to the antioxidants listed below. As an example, the antioxidant can be antioxidant 1010, antioxidant 1024, antioxidant 168, antioxidant 626, or antioxidant 1076, preferably antioxidant 1010, antioxidant 1024, or antioxidant 1076, and more preferably antioxidant 1010. In this invention, the addition of the antioxidant can reduce the degradation of the polymer in the polyethylene layer and improve the stability of the polyethylene layer.

[0028] plasticizer In this invention, the plasticizer can be any plasticizer known in the art that can be used in coated composite pipes, and the invention is not limited to the plasticizers listed below. As an example, the plasticizer can be dioctyl phthalate, diisononyl phthalate, or diisodecyl phthalate, preferably diisononyl phthalate. In this invention, the addition of the plasticizer during the processing of the polyethylene layer improves the processing fluidity of the polyethylene system, making the polyethylene easier to mold during extrusion coating, enabling more uniform coating on the outer side of the adhesive layer, and ensuring the consistency of the coating thickness and surface quality.

[0029] lubricant In this invention, the lubricant can be any lubricant known in the art that can be used for coated composite pipes, and the invention is not limited to the lubricants listed below. As an example, the lubricant can be polyethylene wax, zinc stearate, and preferably polyethylene wax. In this invention, the addition of the lubricant can reduce the internal friction between the substances in the polyethylene system, as well as the external friction between the material and the processing equipment. This makes the polyethylene layer run more smoothly during extrusion and molding, reducing energy consumption and improving processing efficiency.

[0030] steel pipe base pipe In this invention, the steel pipe base serves as the supporting structure for the entire composite pipe, providing the necessary strength and rigidity to withstand internal fluid pressure and various external loads. The presence of the steel pipe base ensures the stability and safety of the pipeline under various complex environments, and is fundamental to guaranteeing the normal operation of the pipeline.

[0031] Fusion bonded epoxy layer In this invention, the fusion-bonded epoxy layer directly contacts the steel pipe base, exhibiting excellent adhesion and firmly bonding to the steel pipe surface. Together with the adhesive layer and the polyethylene layer, it forms a coating layer with a strong protective barrier, providing excellent corrosion protection for the steel pipe. The raw materials for the fusion-bonded epoxy layer include epoxy resin, ethylene-vinyl acetate copolymer, petroleum resin, degassing agent, and curing agent. The degassing agent is a known degassing agent for coated composite pipes, and this invention is not limited to the degassing agents listed below. As an example, the degassing agent can be stearic acid or benzoin, preferably benzoin. The curing agent is a known curing agent for coated composite pipes, and this invention is not limited to the curing agents listed below. As an example, the curing agent can be phthalic anhydride, maleic anhydride, or 2-methylimidazole, preferably 2-methylimidazole.

[0032] In this invention, the raw materials for the fusion-bonded epoxy layer include epoxy resin, ethylene-vinyl acetate copolymer, petroleum resin, degassing agent, and curing agent. In the fusion-bonded epoxy layer, the epoxy resin accounts for 50-60 parts by weight, preferably 55-58 parts; the ethylene-vinyl acetate copolymer accounts for 12-16 parts by weight, preferably 15-16 parts; the petroleum resin accounts for 8-15 parts by weight, preferably 12-15 parts; the degassing agent accounts for 2-5 parts by weight, preferably 3.5-4 parts; and the curing agent accounts for 1.5-3.5 parts by weight, preferably 2-3 parts.

[0033] Adhesive layer In this invention, the adhesive layer has good adhesion and is used to bond the fusion-bonded epoxy layer and polyethylene layer. This ensures that the three-layer structure of the plastic coating layer remains tightly bonded under various environmental conditions, without delamination or peeling. This maintains the integrity of the overall structure of the plastic coating layer, thereby ensuring the corrosion resistance and impact resistance of the plastic-coated composite pipe.

[0034] In this invention, the adhesive layer comprises ethylene-acrylic acid copolymer, polyvinyl butyral, polyisobutylene, and a plasticizer. In the adhesive layer, the ethylene-acrylic acid copolymer comprises 45-55 parts by weight, preferably 50-53 parts; polyvinyl butyral comprises 15-20 parts by weight, preferably 16-18 parts; polyisobutylene comprises 15-18 parts by weight; and the plasticizer comprises 3-5 parts by weight.

[0035] polyethylene layer The raw materials for the polyethylene layer of the present invention include high-density polyethylene, metallocene polyethylene, vinyl copolymer, filler, antioxidant, and plasticizer. In the polyethylene layer, the high-density polyethylene comprises 70-90 parts by weight, preferably 80-85 parts, more preferably 80 parts; the metallocene polyethylene comprises 10-15 parts by weight, preferably 12-14 parts; the vinyl copolymer comprises 6-12 parts by weight, preferably 10-12 parts, more preferably 12 parts; the filler comprises 15-20 parts by weight, preferably 18-20 parts; the antioxidant comprises 2-4 parts by weight, preferably 3-4 parts; and the plasticizer comprises 6-8 parts by weight, preferably 7-8 parts.

[0036] filler In this invention, the raw materials for the filler include titanium dioxide, silicon dioxide, titanate coupling agent, and 2... Acrylamide group 2 Methylpropanesulfonic acid. In the filler, the weight percentages are: titanium dioxide 40-45 parts; silicon dioxide 5-10 parts; titanate coupling agent 1-4 parts; 2 Acrylamide group 2 The weight of methylpropanesulfonic acid is 3 to 7 parts.

[0037] In this invention, by optimizing and adjusting 2 Acrylamide group 2 The ratio of methylpropanesulfonic acid and titanate coupling agent, when 2 Acrylamide group 2 When the weight ratio of methylpropanesulfonic acid to titanate coupling agent is 1.5 to 3:1, the impact resistance of the plastic-coated composite pipe can be further improved.

[0038] Methods for preparing fillers The present invention also provides a method for preparing the filler as described above, comprising the following steps: A1. Titanium dioxide and silicon dioxide are blended and ground to obtain a blend; A2. Dissolve the titanate coupling agent in isopropanol, add it to the blend, mix, and dry to obtain the pretreated blend; A3, 2 Acrylamide group 2 Methylpropanesulfonic acid is dissolved in ethanol, added to the pretreated blend, mixed, and dried to obtain the filler.

[0039] In this invention, the filler is prepared using a stepwise method. First, titanium dioxide and silicon dioxide are powdered together to obtain a blend. Then, the blend is surface-pretreated with a titanate coupling agent, followed by the application of 2... Acrylamide group 2 Methylpropanesulfonic acid is used for surface composite preparation, and the filler is prepared in steps, including titanate coupling agent and 2 Acrylamide group 2 Methylpropanesulfonic acid can fully react with the inorganic powders in the system without competition between them, thus improving the success rate of filler composite. Furthermore, in this invention, during grinding in step A1, the grinding speed is 200-300 rpm and the grinding time is 20-30 min; during mixing in steps A2 and A3, stirring is used, with each stirring speed independently at 400-600 rpm and each stirring time independently at 40-60 min.

[0040] Preparation method of corrosion-resistant plastic-coated composite pipe This invention provides a method for preparing the plastic-coated composite pipe as described above, comprising the following steps: A fusion-bonded epoxy layer and an adhesive layer are sequentially applied to the outside of the steel pipe base. The raw materials for the polyethylene layer are blended, extruded, and coated onto the outside of the adhesive layer. The composite is then pressurized to obtain a corrosion-resistant plastic-coated composite pipe.

[0041] In this invention, when a fusion-bonded epoxy layer is set on the outside of a steel pipe base, the raw materials for the fusion-bonded epoxy layer are blended, extruded, and pulverized to obtain fusion-bonded epoxy layer powder. The fusion-bonded epoxy layer powder is then fused onto the outside of the steel pipe base to obtain the fusion-bonded epoxy layer. When an adhesive layer is set on the outside of the fusion-bonded epoxy layer, the raw materials for the adhesive layer are blended, extruded, and pulverized to obtain adhesive layer powder. The adhesive layer powder is then applied to the outside of the fusion-bonded epoxy layer to obtain the adhesive layer.

[0042] To further illustrate the present invention, detailed descriptions will be provided below through the following embodiments. The raw materials used in the following embodiments and comparative examples of the present invention are all commercially available products, including: high-density polyethylene (DMDA-8008H); metallocene polyethylene (E1018MA); ethylene-butene copolymer with a melt flow rate of 1.2 g / 10 min at 190°C and 2.16 kg (ENGAGE™ 7467); and ethylene-butene copolymer with a melt flow rate of 1.4 g / 10 min at 190°C and 2.16 kg (SABIC). ® LLDPE 120NT; Ethylene-hexene copolymer, melt flow rate of 3.5 g / 10 min at 190°C and 2.16 kg, model Exceed™ 3518PA; Ethylene-hexene copolymer, melt flow rate of 2.0 g / 10 min at 190°C and 2.16 kg, model Exceed™ 2018MA; Ethylene-hexene copolymer, melt flow rate of 1.0 g / 10 min at 190°C and 2.16 kg, model Enable™ 2010ME; Titanium dioxide, average particle size of 50 μm; Silica, average particle size of 80 nm; Epoxy resin, model SM601; Ethylene-vinyl acetate copolymer, model EVA 3176; Petroleum resin, using C9 petroleum resin; Ethylene-acrylic acid copolymer, model EAA 5980; Polyvinyl butyral, model B17HX; Polyisobutylene, model HRD850.

[0043] Example 1 A method for preparing a corrosion-resistant plastic-coated composite pipe includes the following steps: S1. Mix 50 parts epoxy resin, 12 parts ethylene-vinyl acetate copolymer, 8 parts petroleum resin, 2 parts benzoin and 1.5 parts 2-methylimidazole evenly, extrude and pulverize to obtain fusion-bonded epoxy layer powder; mix 45 parts ethylene-acrylic acid copolymer, 15 parts polyvinyl butyral, 15 parts polyisobutylene and 3 parts diisononyl phthalate evenly, extrude and pulverize to obtain adhesive layer powder. S2. The fusion-bonded epoxy layer powder is fused to the outside of the steel pipe base to obtain the fusion-bonded epoxy layer. Adhesive layer powder is then applied to the outside of the fusion-bonded epoxy layer to obtain the adhesive layer. S3. 80 parts high-density polyethylene, 10 parts metallocene polyethylene, 3 parts ethylene-butene copolymer (melt flow rate of 1.2 g / 10 min at 190℃ and 2.16 kg), 3 parts ethylene-hexene copolymer (melt flow rate of 2.0 g / 10 min at 190℃ and 2.16 kg), 15 parts filler, 2 parts antioxidant 1010 and 6 parts diisononyl phthalate are blended, extruded, coated on the outside of the adhesive layer, and pressure-composite to obtain a corrosion-resistant plastic-coated composite pipe. The method for preparing the filler includes the following steps: 40 parts of titanium dioxide and 10 parts of silicon dioxide were blended and milled at 250 rpm for 20 min to obtain a blend. 4 parts of isopropyl tris(dioctyl pyrophosphate) titanate were dissolved in 80 parts of isopropanol, added to the blend, stirred at 500 rpm for 50 min, and dried to obtain the filler.

[0044] Example 2 A method for preparing a corrosion-resistant plastic-coated composite pipe includes the following steps: S1. Mix 55 parts epoxy resin, 15 parts ethylene-vinyl acetate copolymer, 12 parts petroleum resin, 3.5 parts benzoin and 2 parts 2-methylimidazole evenly, extrude and pulverize to obtain fusion-bonded epoxy layer powder; mix 50 parts ethylene-acrylic acid copolymer, 18 parts polyvinyl butyral, 16 parts polyisobutylene and 4 parts diisononyl phthalate evenly, extrude and pulverize to obtain adhesive layer powder. S2. The fusion-bonded epoxy layer powder is fused to the outside of the steel pipe base to obtain the fusion-bonded epoxy layer. Adhesive layer powder is then applied to the outside of the fusion-bonded epoxy layer to obtain the adhesive layer. S3. 80 parts of high-density polyethylene, 12 parts of metallocene polyethylene, 10.8 parts of ethylene-butene copolymer (melt flow rate of 1.2 g / 10 min at 190℃ and 2.16 kg), 1.2 parts of ethylene-hexene copolymer (melt flow rate of 2.0 g / 10 min at 190℃ and 2.16 kg), 18 parts of filler, 3 parts of antioxidant 1010 and 7 parts of diisononyl phthalate are blended, extruded, coated on the outside of the adhesive layer, and pressure-bonded to obtain a corrosion-resistant plastic-coated composite pipe. The method for preparing the filler includes the following steps: 40 parts of titanium dioxide and 10 parts of silicon dioxide were blended and milled at 250 rpm for 20 min to obtain a blend. 4 parts of isopropyl tris(dioctyl pyrophosphate) titanate were dissolved in 80 parts of isopropanol, added to the blend, stirred at 500 rpm for 50 min, and dried to obtain the filler.

[0045] Example 3 A method for preparing a corrosion-resistant plastic-coated composite pipe includes the following steps: S1. Mix 60 parts epoxy resin, 16 parts ethylene-vinyl acetate copolymer, 15 parts petroleum resin, 5 parts benzoin and 3 parts 2-methylimidazole evenly, extrude and pulverize to obtain fusion-bonded epoxy layer powder; mix 55 parts ethylene-acrylic acid copolymer, 20 parts polyvinyl butyral, 18 parts polyisobutylene and 5 parts diisononyl phthalate evenly, extrude and pulverize to obtain adhesive layer powder. S2. The fusion-bonded epoxy layer powder is fused to the outside of the steel pipe base to obtain the fusion-bonded epoxy layer. Adhesive layer powder is then applied to the outside of the fusion-bonded epoxy layer to obtain the adhesive layer. S3. 80 parts of high-density polyethylene, 15 parts of metallocene polyethylene, 10.8 parts of ethylene-butene copolymer (melt flow rate of 1.2 g / 10 min at 190℃ and 2.16 kg), 1.2 parts of ethylene-hexene copolymer (melt flow rate of 3.5 g / 10 min at 190℃ and 2.16 kg), 20 parts of filler, 4 parts of antioxidant 1010 and 8 parts of diisononyl phthalate are blended, extruded, coated on the outside of the adhesive layer, and pressure-composite to obtain a corrosion-resistant plastic-coated composite pipe. The method for preparing the filler includes the following steps: 40 parts of titanium dioxide and 10 parts of silicon dioxide were blended and milled at 250 rpm for 20 min to obtain a blend. 4 parts of isopropyl tris(dioctyl pyrophosphate) titanate were dissolved in 80 parts of isopropanol, added to the blend, stirred at 500 rpm for 50 min, and dried to obtain the filler.

[0046] Example 4 A method for preparing a corrosion-resistant plastic-coated composite pipe includes the following steps: S1. Mix 55 parts epoxy resin, 15 parts ethylene-vinyl acetate copolymer, 12 parts petroleum resin, 3.5 parts benzoin and 2 parts 2-methylimidazole evenly, extrude and pulverize to obtain fusion-bonded epoxy layer powder; mix 50 parts ethylene-acrylic acid copolymer, 18 parts polyvinyl butyral, 16 parts polyisobutylene and 4 parts diisononyl phthalate evenly, extrude and pulverize to obtain adhesive layer powder. S2. The fusion-bonded epoxy layer powder is fused to the outside of the steel pipe base to obtain the fusion-bonded epoxy layer. Adhesive layer powder is then applied to the outside of the fusion-bonded epoxy layer to obtain the adhesive layer. S3. 80 parts of high-density polyethylene, 12 parts of metallocene polyethylene, 6 parts of ethylene-butene copolymer (melt flow rate of 1.2 g / 10 min at 190℃ and 2.16 kg), 6 parts of ethylene-hexene copolymer (melt flow rate of 2.0 g / 10 min at 190℃ and 2.16 kg), 18 parts of filler, 3 parts of antioxidant 1010 and 7 parts of diisononyl phthalate are blended, extruded, coated on the outside of the adhesive layer, and pressure-composite to obtain a corrosion-resistant plastic-coated composite pipe. The method for preparing the filler includes the following steps: 40 parts of titanium dioxide and 10 parts of silicon dioxide were blended and milled at 250 rpm for 20 min to obtain a blend. 4 parts of isopropyl tris(dioctyl pyrophosphate) titanate were dissolved in 80 parts of isopropanol, added to the blend, stirred at 500 rpm for 50 min, and dried to obtain the filler.

[0047] Example 5 A method for preparing a corrosion-resistant plastic-coated composite pipe includes the following steps: S1. Mix 55 parts epoxy resin, 15 parts ethylene-vinyl acetate copolymer, 12 parts petroleum resin, 3.5 parts benzoin and 2 parts 2-methylimidazole evenly, extrude and pulverize to obtain fusion-bonded epoxy layer powder; mix 50 parts ethylene-acrylic acid copolymer, 18 parts polyvinyl butyral, 16 parts polyisobutylene and 4 parts diisononyl phthalate evenly, extrude and pulverize to obtain adhesive layer powder. S2. The fusion-bonded epoxy layer powder is fused to the outside of the steel pipe base to obtain the fusion-bonded epoxy layer. Adhesive layer powder is then applied to the outside of the fusion-bonded epoxy layer to obtain the adhesive layer. S3. 80 parts of high-density polyethylene, 12 parts of metallocene polyethylene, 8 parts of ethylene-butene copolymer (melt flow rate of 1.2 g / 10 min at 190℃ and 2.16 kg), 4 parts of ethylene-hexene copolymer (melt flow rate of 2.0 g / 10 min at 190℃ and 2.16 kg), 18 parts of filler, 3 parts of antioxidant 1010 and 7 parts of diisononyl phthalate are blended, extruded, coated on the outside of the adhesive layer, and pressure-composite to obtain a corrosion-resistant plastic-coated composite pipe. The method for preparing the filler includes the following steps: 40 parts of titanium dioxide and 10 parts of silicon dioxide were blended and milled at 250 rpm for 20 min to obtain a blend. 4 parts of isopropyl tris(dioctyl pyrophosphate) titanate were dissolved in 80 parts of isopropanol, added to the blend, stirred at 500 rpm for 50 min, and dried to obtain the filler.

[0048] Example 6 A method for preparing a corrosion-resistant plastic-coated composite pipe includes the following steps: S1. Mix 55 parts epoxy resin, 15 parts ethylene-vinyl acetate copolymer, 12 parts petroleum resin, 3.5 parts benzoin and 2 parts 2-methylimidazole evenly, extrude and pulverize to obtain fusion-bonded epoxy layer powder; mix 50 parts ethylene-acrylic acid copolymer, 18 parts polyvinyl butyral, 16 parts polyisobutylene and 4 parts diisononyl phthalate evenly, extrude and pulverize to obtain adhesive layer powder. S2. The fusion-bonded epoxy layer powder is fused to the outside of the steel pipe base to obtain the fusion-bonded epoxy layer. Adhesive layer powder is then applied to the outside of the fusion-bonded epoxy layer to obtain the adhesive layer. S3. 80 parts of high-density polyethylene, 12 parts of metallocene polyethylene, 10 parts of ethylene-butene copolymer (melt flow rate of 1.2 g / 10 min at 190℃ and 2.16 kg), 2 parts of ethylene-hexene copolymer (melt flow rate of 2.0 g / 10 min at 190℃ and 2.16 kg), 18 parts of filler, 3 parts of antioxidant 1010 and 7 parts of diisononyl phthalate are blended, extruded, coated on the outside of the adhesive layer, and pressure-composite to obtain a corrosion-resistant plastic-coated composite pipe. The method for preparing the filler includes the following steps: 40 parts of titanium dioxide and 10 parts of silicon dioxide were blended and milled at 250 rpm for 20 min to obtain a blend. 4 parts of isopropyl tris(dioctyl pyrophosphate) titanate were dissolved in 80 parts of isopropanol, added to the blend, stirred at 500 rpm for 50 min, and dried to obtain the filler.

[0049] Example 7 A method for preparing a corrosion-resistant plastic-coated composite pipe includes the following steps: S1. Mix 55 parts epoxy resin, 15 parts ethylene-vinyl acetate copolymer, 12 parts petroleum resin, 3.5 parts benzoin and 2 parts 2-methylimidazole evenly, extrude and pulverize to obtain fusion-bonded epoxy layer powder; mix 50 parts ethylene-acrylic acid copolymer, 18 parts polyvinyl butyral, 16 parts polyisobutylene and 4 parts diisononyl phthalate evenly, extrude and pulverize to obtain adhesive layer powder. S2. The fusion-bonded epoxy layer powder is fused to the outside of the steel pipe base to obtain the fusion-bonded epoxy layer. Adhesive layer powder is then applied to the outside of the fusion-bonded epoxy layer to obtain the adhesive layer. S3. 80 parts of high-density polyethylene, 12 parts of metallocene polyethylene, 10.8 parts of ethylene-butene copolymer (melt flow rate of 1.2 g / 10 min at 190℃ and 2.16 kg), 1.2 parts of ethylene-hexene copolymer (melt flow rate of 1.0 g / 10 min at 190℃ and 2.16 kg), 18 parts of filler, 3 parts of antioxidant 1010 and 7 parts of diisononyl phthalate are blended, extruded, coated on the outside of the adhesive layer, and pressure-composite to obtain a corrosion-resistant plastic-coated composite pipe. The method for preparing the filler includes the following steps: 40 parts of titanium dioxide and 10 parts of silicon dioxide were blended and milled at 250 rpm for 20 min to obtain a blend. 4 parts of isopropyl tris(dioctyl pyrophosphate) titanate were dissolved in 80 parts of isopropanol, added to the blend, stirred at 500 rpm for 50 min, and dried to obtain the filler.

[0050] Example 8 A method for preparing a corrosion-resistant plastic-coated composite pipe includes the following steps: S1. Mix 55 parts epoxy resin, 15 parts ethylene-vinyl acetate copolymer, 12 parts petroleum resin, 3.5 parts benzoin and 2 parts 2-methylimidazole evenly, extrude and pulverize to obtain fusion-bonded epoxy layer powder; mix 50 parts ethylene-acrylic acid copolymer, 18 parts polyvinyl butyral, 16 parts polyisobutylene and 4 parts diisononyl phthalate evenly, extrude and pulverize to obtain adhesive layer powder. S2. The fusion-bonded epoxy layer powder is fused to the outside of the steel pipe base to obtain the fusion-bonded epoxy layer. Adhesive layer powder is then applied to the outside of the fusion-bonded epoxy layer to obtain the adhesive layer. S3. 80 parts of high-density polyethylene, 12 parts of metallocene polyethylene, 10.8 parts of ethylene-butene copolymer (melt flow rate of 1.4 g / 10 min at 190℃ and 2.16 kg), 1.2 parts of ethylene-hexene copolymer (melt flow rate of 2.0 g / 10 min at 190℃ and 2.16 kg), 18 parts of filler, 3 parts of antioxidant 1010 and 7 parts of diisononyl phthalate are blended, extruded, coated on the outside of the adhesive layer, and pressure-bonded to obtain a corrosion-resistant plastic-coated composite pipe. The method for preparing the filler includes the following steps: 40 parts of titanium dioxide and 10 parts of silicon dioxide were blended and milled at 250 rpm for 20 min to obtain a blend. 4 parts of isopropyl tris(dioctyl pyrophosphate) titanate were dissolved in 80 parts of isopropanol, added to the blend, stirred at 500 rpm for 50 min, and dried to obtain the filler.

[0051] Example 9 A method for preparing a corrosion-resistant plastic-coated composite pipe includes the following steps: S1. Mix 55 parts epoxy resin, 15 parts ethylene-vinyl acetate copolymer, 12 parts petroleum resin, 3.5 parts benzoin and 2 parts 2-methylimidazole evenly, extrude and pulverize to obtain fusion-bonded epoxy layer powder; mix 50 parts ethylene-acrylic acid copolymer, 18 parts polyvinyl butyral, 16 parts polyisobutylene and 4 parts diisononyl phthalate evenly, extrude and pulverize to obtain adhesive layer powder. S2. The fusion-bonded epoxy layer powder is fused to the outside of the steel pipe base to obtain the fusion-bonded epoxy layer. Adhesive layer powder is then applied to the outside of the fusion-bonded epoxy layer to obtain the adhesive layer. S3. 80 parts of high-density polyethylene, 12 parts of metallocene polyethylene, 10.8 parts of ethylene-butene copolymer (melt flow rate of 1.4 g / 10 min at 190℃ and 2.16 kg), 1.2 parts of ethylene-hexene copolymer (melt flow rate of 1.0 g / 10 min at 190℃ and 2.16 kg), 18 parts of filler, 3 parts of antioxidant 1010 and 7 parts of diisononyl phthalate are blended, extruded, coated on the outside of the adhesive layer, and pressure-bonded to obtain a corrosion-resistant plastic-coated composite pipe. The method for preparing the filler includes the following steps: 40 parts of titanium dioxide and 10 parts of silicon dioxide were blended and milled at 250 rpm for 20 min to obtain a blend. 4 parts of isopropyl tris(dioctyl pyrophosphate) titanate were dissolved in 80 parts of isopropanol, added to the blend, stirred at 500 rpm for 50 min, and dried to obtain the filler.

[0052] Example 10 A method for preparing a corrosion-resistant plastic-coated composite pipe includes the following steps: S1. Mix 55 parts epoxy resin, 15 parts ethylene-vinyl acetate copolymer, 12 parts petroleum resin, 3.5 parts benzoin and 2 parts 2-methylimidazole evenly, extrude and pulverize to obtain fusion-bonded epoxy layer powder; mix 50 parts ethylene-acrylic acid copolymer, 18 parts polyvinyl butyral, 16 parts polyisobutylene and 4 parts diisononyl phthalate evenly, extrude and pulverize to obtain adhesive layer powder. S2. The fusion-bonded epoxy layer powder is fused to the outside of the steel pipe base to obtain the fusion-bonded epoxy layer. Adhesive layer powder is then applied to the outside of the fusion-bonded epoxy layer to obtain the adhesive layer. S3. 80 parts of high-density polyethylene, 12 parts of metallocene polyethylene, 10 parts of ethylene-butene copolymer (melt flow rate of 1.2 g / 10 min at 190℃ and 2.16 kg), 2 parts of ethylene-hexene copolymer (melt flow rate of 2.0 g / 10 min at 190℃ and 2.16 kg), 18 parts of filler, 3 parts of antioxidant 1010 and 7 parts of diisononyl phthalate are blended, extruded, coated on the outside of the adhesive layer, and pressure-composite to obtain a corrosion-resistant plastic-coated composite pipe. The method for preparing the filler includes the following steps: 40 parts of titanium dioxide and 10 parts of silicon dioxide were blended and milled at 250 rpm for 20 min to obtain a blend; 4 parts of 2 Acrylamide group 2 Methylpropanesulfonic acid was dissolved in 80 parts of ethanol, added to the blend, stirred at 500 rpm for 50 min, and dried to obtain the filler.

[0053] Example 11 A method for preparing a corrosion-resistant plastic-coated composite pipe includes the following steps: S1. Mix 55 parts epoxy resin, 15 parts ethylene-vinyl acetate copolymer, 12 parts petroleum resin, 3.5 parts benzoin and 2 parts 2-methylimidazole evenly, extrude and pulverize to obtain fusion-bonded epoxy layer powder; mix 50 parts ethylene-acrylic acid copolymer, 18 parts polyvinyl butyral, 16 parts polyisobutylene and 4 parts diisononyl phthalate evenly, extrude and pulverize to obtain adhesive layer powder. S2. The fusion-bonded epoxy layer powder is fused to the outside of the steel pipe base to obtain the fusion-bonded epoxy layer. Adhesive layer powder is then applied to the outside of the fusion-bonded epoxy layer to obtain the adhesive layer. S3. 80 parts of high-density polyethylene, 12 parts of metallocene polyethylene, 10 parts of ethylene-butene copolymer (melt flow rate of 1.2 g / 10 min at 190℃ and 2.16 kg), 2 parts of ethylene-hexene copolymer (melt flow rate of 2.0 g / 10 min at 190℃ and 2.16 kg), 18 parts of filler, 3 parts of antioxidant 1010 and 7 parts of diisononyl phthalate are blended, extruded, coated on the outside of the adhesive layer, and pressure-composite to obtain a corrosion-resistant plastic-coated composite pipe. The method for preparing the filler includes the following steps: A1. 40 parts of titanium dioxide and 10 parts of silicon dioxide were blended and milled at 250 rpm for 20 min to obtain the blend. A2. Dissolve 1 part of isopropyl tris(dioctyl pyrophosphoryloxy) titanate in 80 parts of isopropanol, add the blend, stir at 500 rpm for 50 min, dry, and obtain the pretreated blend. A3, divide 3 portions into 2 Acrylamide group 2 Methylpropanesulfonic acid was dissolved in 80 parts of ethanol, added to the pretreated blend, stirred at 500 rpm for 50 min, and dried to obtain the filler.

[0054] Example 12 A method for preparing a corrosion-resistant plastic-coated composite pipe includes the following steps: S1. Mix 55 parts epoxy resin, 15 parts ethylene-vinyl acetate copolymer, 12 parts petroleum resin, 3.5 parts benzoin and 2 parts 2-methylimidazole evenly, extrude and pulverize to obtain fusion-bonded epoxy layer powder; mix 50 parts ethylene-acrylic acid copolymer, 18 parts polyvinyl butyral, 16 parts polyisobutylene and 4 parts diisononyl phthalate evenly, extrude and pulverize to obtain adhesive layer powder. S2. The fusion-bonded epoxy layer powder is fused to the outside of the steel pipe base to obtain the fusion-bonded epoxy layer. Adhesive layer powder is then applied to the outside of the fusion-bonded epoxy layer to obtain the adhesive layer. S3. 80 parts of high-density polyethylene, 12 parts of metallocene polyethylene, 10 parts of ethylene-butene copolymer (melt flow rate of 1.2 g / 10 min at 190℃ and 2.16 kg), 2 parts of ethylene-hexene copolymer (melt flow rate of 2.0 g / 10 min at 190℃ and 2.16 kg), 18 parts of filler, 3 parts of antioxidant 1010 and 7 parts of diisononyl phthalate are blended, extruded, coated on the outside of the adhesive layer, and pressure-composite to obtain a corrosion-resistant plastic-coated composite pipe. The method for preparing the filler includes the following steps: A1. 45 parts of titanium dioxide and 5 parts of silicon dioxide were blended and milled at 250 rpm for 20 min to obtain the blend. A2. Dissolve 4 parts of isopropyl tris(dioctyl pyrophosphoryloxy) titanate in 80 parts of isopropanol, add the blend, stir at 500 rpm for 50 min, dry, and obtain the pretreated blend. A3, divide 4 portions into 2 Acrylamide group 2 Methylpropanesulfonic acid was dissolved in 80 parts of ethanol, added to the pretreated blend, stirred at 500 rpm for 50 min, and dried to obtain the filler.

[0055] Example 13 A method for preparing a corrosion-resistant plastic-coated composite pipe includes the following steps: S1. Mix 55 parts epoxy resin, 15 parts ethylene-vinyl acetate copolymer, 12 parts petroleum resin, 3.5 parts benzoin and 2 parts 2-methylimidazole evenly, extrude and pulverize to obtain fusion-bonded epoxy layer powder; mix 50 parts ethylene-acrylic acid copolymer, 18 parts polyvinyl butyral, 16 parts polyisobutylene and 4 parts diisononyl phthalate evenly, extrude and pulverize to obtain adhesive layer powder. S2. The fusion-bonded epoxy layer powder is fused to the outside of the steel pipe base to obtain the fusion-bonded epoxy layer. Adhesive layer powder is then applied to the outside of the fusion-bonded epoxy layer to obtain the adhesive layer. S3. 80 parts of high-density polyethylene, 12 parts of metallocene polyethylene, 10 parts of ethylene-butene copolymer (melt flow rate of 1.2 g / 10 min at 190℃ and 2.16 kg), 2 parts of ethylene-hexene copolymer (melt flow rate of 2.0 g / 10 min at 190℃ and 2.16 kg), 18 parts of filler, 3 parts of antioxidant 1010 and 7 parts of diisononyl phthalate are blended, extruded, coated on the outside of the adhesive layer, and pressure-composite to obtain a corrosion-resistant plastic-coated composite pipe. The method for preparing the filler includes the following steps: A1. 45 parts of titanium dioxide and 5 parts of silicon dioxide were blended and milled at 250 rpm for 20 min to obtain the blend. A2. Dissolve 1 part of isopropyl tris(dioctyl pyrophosphoryloxy) titanate in 80 parts of isopropanol, add the blend, stir at 500 rpm for 50 min, dry, and obtain the pretreated blend. A3, divide 7 portions into 2 Acrylamide group 2 Methylpropanesulfonic acid was dissolved in 80 parts of ethanol, added to the pretreated blend, stirred at 500 rpm for 50 min, and dried to obtain the filler.

[0056] Example 14 A method for preparing a corrosion-resistant plastic-coated composite pipe includes the following steps: S1. Mix 55 parts epoxy resin, 15 parts ethylene-vinyl acetate copolymer, 12 parts petroleum resin, 3.5 parts benzoin and 2 parts 2-methylimidazole evenly, extrude and pulverize to obtain fusion-bonded epoxy layer powder; mix 50 parts ethylene-acrylic acid copolymer, 18 parts polyvinyl butyral, 16 parts polyisobutylene and 4 parts diisononyl phthalate evenly, extrude and pulverize to obtain adhesive layer powder. S2. The fusion-bonded epoxy layer powder is fused to the outside of the steel pipe base to obtain the fusion-bonded epoxy layer. Adhesive layer powder is then applied to the outside of the fusion-bonded epoxy layer to obtain the adhesive layer. S3. 80 parts of high-density polyethylene, 12 parts of metallocene polyethylene, 10 parts of ethylene-butene copolymer (melt flow rate of 1.2 g / 10 min at 190℃ and 2.16 kg), 2 parts of ethylene-hexene copolymer (melt flow rate of 2.0 g / 10 min at 190℃ and 2.16 kg), 18 parts of filler, 3 parts of antioxidant 1010 and 7 parts of diisononyl phthalate are blended, extruded, coated on the outside of the adhesive layer, and pressure-composite to obtain a corrosion-resistant plastic-coated composite pipe. The method for preparing the filler includes the following steps: A1. 45 parts of titanium dioxide and 5 parts of silicon dioxide were blended and milled at 250 rpm for 20 min to obtain the blend. A2. Dissolve 2 parts of isopropyl tris(dioctyl pyrophosphoryloxy) titanate in 80 parts of isopropanol, add the blend, stir at 500 rpm for 50 min, dry, and obtain the pretreated blend. A3, divide 6 portions into 2 Acrylamide group 2 Methylpropanesulfonic acid was dissolved in 80 parts of ethanol, added to the pretreated blend, stirred at 500 rpm for 50 min, and dried to obtain the filler.

[0057] Example 15 A method for preparing a corrosion-resistant plastic-coated composite pipe includes the following steps: S1. Mix 55 parts epoxy resin, 15 parts ethylene-vinyl acetate copolymer, 12 parts petroleum resin, 3.5 parts benzoin and 2 parts 2-methylimidazole evenly, extrude and pulverize to obtain fusion-bonded epoxy layer powder; mix 50 parts ethylene-acrylic acid copolymer, 18 parts polyvinyl butyral, 16 parts polyisobutylene and 4 parts diisononyl phthalate evenly, extrude and pulverize to obtain adhesive layer powder. S2. The fusion-bonded epoxy layer powder is fused to the outside of the steel pipe base to obtain the fusion-bonded epoxy layer. Adhesive layer powder is then applied to the outside of the fusion-bonded epoxy layer to obtain the adhesive layer. S3. 80 parts of high-density polyethylene, 12 parts of metallocene polyethylene, 10 parts of ethylene-butene copolymer (melt flow rate of 1.2 g / 10 min at 190℃ and 2.16 kg), 2 parts of ethylene-hexene copolymer (melt flow rate of 2.0 g / 10 min at 190℃ and 2.16 kg), 18 parts of filler, 3 parts of antioxidant 1010 and 7 parts of diisononyl phthalate are blended, extruded, coated on the outside of the adhesive layer, and pressure-composite to obtain a corrosion-resistant plastic-coated composite pipe. The method for preparing the filler includes the following steps: A1. 45 parts of titanium dioxide and 5 parts of silicon dioxide were blended and milled at 250 rpm for 20 min to obtain the blend. A2. Dissolve 4.8 parts of isopropyl tris(dioctyl pyrophosphoryloxy) titanate in 80 parts of isopropanol, add the blend, stir at 500 rpm for 50 min, dry, and obtain the pretreated blend. A3, divide 3.2 portions into 2 Acrylamide group 2 Methylpropanesulfonic acid was dissolved in 80 parts of ethanol, added to the pretreated blend, stirred at 500 rpm for 50 min, and dried to obtain the filler.

[0058] Example 16 A method for preparing a corrosion-resistant plastic-coated composite pipe includes the following steps: S1. Mix 55 parts epoxy resin, 15 parts ethylene-vinyl acetate copolymer, 12 parts petroleum resin, 3.5 parts benzoin and 2 parts 2-methylimidazole evenly, extrude and pulverize to obtain fusion-bonded epoxy layer powder; mix 50 parts ethylene-acrylic acid copolymer, 18 parts polyvinyl butyral, 16 parts polyisobutylene and 4 parts diisononyl phthalate evenly, extrude and pulverize to obtain adhesive layer powder. S2. The fusion-bonded epoxy layer powder is fused to the outside of the steel pipe base to obtain the fusion-bonded epoxy layer. Adhesive layer powder is then applied to the outside of the fusion-bonded epoxy layer to obtain the adhesive layer. S3. 80 parts of high-density polyethylene, 12 parts of metallocene polyethylene, 10 parts of ethylene-butene copolymer (melt flow rate of 1.2 g / 10 min at 190℃ and 2.16 kg), 2 parts of ethylene-hexene copolymer (melt flow rate of 2.0 g / 10 min at 190℃ and 2.16 kg), 18 parts of filler, 3 parts of antioxidant 1010 and 7 parts of diisononyl phthalate are blended, extruded, coated on the outside of the adhesive layer, and pressure-composite to obtain a corrosion-resistant plastic-coated composite pipe. The method for preparing the filler includes the following steps: 40 parts of titanium dioxide and 10 parts of silicon dioxide were blended and milled at 250 rpm for 20 min to obtain the filler.

[0059] Comparative Example 1 A method for preparing a corrosion-resistant plastic-coated composite pipe includes the following steps: S1. Mix 55 parts epoxy resin, 15 parts ethylene-vinyl acetate copolymer, 12 parts petroleum resin, 3.5 parts benzoin and 2 parts 2-methylimidazole evenly, extrude and pulverize to obtain fusion-bonded epoxy layer powder; mix 50 parts ethylene-acrylic acid copolymer, 18 parts polyvinyl butyral, 16 parts polyisobutylene and 4 parts diisononyl phthalate evenly, extrude and pulverize to obtain adhesive layer powder. S2. The fusion-bonded epoxy layer powder is fused to the outside of the steel pipe base to obtain the fusion-bonded epoxy layer. Adhesive layer powder is then applied to the outside of the fusion-bonded epoxy layer to obtain the adhesive layer. S3. 80 parts of high-density polyethylene, 12 parts of metallocene polyethylene, 12 parts of ethylene-butene copolymer (melt flow rate of 1.2 g / 10 min at 190℃ and 2.16 kg), 18 parts of filler, 3 parts of antioxidant 1010 and 7 parts of diisononyl phthalate are blended, extruded, coated on the outside of the adhesive layer, and pressure-composite to obtain a corrosion-resistant plastic-coated composite pipe. The method for preparing the filler includes the following steps: 40 parts of titanium dioxide and 10 parts of silicon dioxide were blended and milled at 250 rpm for 20 min to obtain a blend. 4 parts of isopropyl tris(dioctyl pyrophosphate) titanate were dissolved in 80 parts of isopropanol, added to the blend, stirred at 500 rpm for 50 min, and dried to obtain the filler.

[0060] Comparative Example 2 A method for preparing a corrosion-resistant plastic-coated composite pipe includes the following steps: S1. Mix 55 parts epoxy resin, 15 parts ethylene-vinyl acetate copolymer, 12 parts petroleum resin, 3.5 parts benzoin and 2 parts 2-methylimidazole evenly, extrude and pulverize to obtain fusion-bonded epoxy layer powder; mix 50 parts ethylene-acrylic acid copolymer, 18 parts polyvinyl butyral, 16 parts polyisobutylene and 4 parts diisononyl phthalate evenly, extrude and pulverize to obtain adhesive layer powder. S2. The fusion-bonded epoxy layer powder is fused to the outside of the steel pipe base to obtain the fusion-bonded epoxy layer. Adhesive layer powder is then applied to the outside of the fusion-bonded epoxy layer to obtain the adhesive layer. S3. 80 parts of high-density polyethylene, 12 parts of metallocene polyethylene, 12 parts of ethylene-hexene copolymer (melt mass flow rate of 2.0 g / 10 min at 190℃ and 2.16 kg), 18 parts of filler, 3 parts of antioxidant 1010 and 7 parts of diisononyl phthalate are blended, extruded, coated on the outside of the adhesive layer, and pressure-composite to obtain a corrosion-resistant plastic-coated composite pipe. The method for preparing the filler includes the following steps: 40 parts of titanium dioxide and 10 parts of silicon dioxide were blended and milled at 250 rpm for 20 min to obtain a blend. 4 parts of isopropyl tris(dioctyl pyrophosphate) titanate were dissolved in 80 parts of isopropanol, added to the blend, stirred at 500 rpm for 50 min, and dried to obtain the filler.

[0061] Comparative Example 3 A method for preparing a corrosion-resistant plastic-coated composite pipe includes the following steps: S1. Mix 55 parts epoxy resin, 15 parts ethylene-vinyl acetate copolymer, 12 parts petroleum resin, 3.5 parts benzoin and 2 parts 2-methylimidazole evenly, extrude and pulverize to obtain fusion-bonded epoxy layer powder; mix 50 parts ethylene-acrylic acid copolymer, 18 parts polyvinyl butyral, 16 parts polyisobutylene and 4 parts diisononyl phthalate evenly, extrude and pulverize to obtain adhesive layer powder. S2. The fusion-bonded epoxy layer powder is fused to the outside of the steel pipe base to obtain the fusion-bonded epoxy layer. Adhesive layer powder is then applied to the outside of the fusion-bonded epoxy layer to obtain the adhesive layer. S3. 80 parts of high-density polyethylene, 12 parts of metallocene polyethylene, 18 parts of filler, 3 parts of antioxidant 1010 and 7 parts of diisononyl phthalate are blended, extruded, coated on the outside of the adhesive layer, and pressure-composite to obtain a corrosion-resistant plastic-coated composite pipe. The method for preparing the filler includes the following steps: 40 parts of titanium dioxide and 10 parts of silicon dioxide were blended and milled at 250 rpm for 20 min to obtain a blend. 4 parts of isopropyl tris(dioctyl pyrophosphate) titanate were dissolved in 80 parts of isopropanol, added to the blend, stirred at 500 rpm for 50 min, and dried to obtain the filler.

[0062] Experimental Example The polyethylene layer samples of the plastic-coated composite pipes prepared in Examples 1-16 and Comparative Examples 1-3 were subjected to the following performance tests: (1) Impact strength test: The impact strength was tested according to the method specified in GB / T 1843-2008 "Determination of impact strength of plastic cantilever beam", with a notch of type A, a sample size of 80mm×10mm, and a thickness of 4mm; (2) Corrosion resistance test: The sample was soaked in 30wt% sulfuric acid for 48h and then the impact strength of the acid-treated sample was tested according to the above impact strength test method. The sample size was 80mm×10mm and the thickness was 4mm. The test results are shown in Table 1.

[0063] Table 1 Performance test results of Examples 1-16 and Comparative Examples 1-3

[0064] Compared with Comparative Examples 1-3, Examples 1-16, calculated according to the impact strength retention rate = impact strength after acid treatment / impact strength × 100%, showed an improved impact strength retention rate, reaching over 90.0%. This indicates that the addition of vinyl copolymers formed by ethylene-butene copolymer and ethylene-hexene copolymer to the polyethylene layer of the plastic-coated composite pipe, through the combined use of the two, can improve the corrosion resistance of the polyethylene layer of the plastic-coated composite pipe, thereby enhancing the corrosion resistance of the plastic-coated composite pipe.

[0065] Compared with Examples 2, 4, and 7-9, the impact strength retention rate of the polyethylene layer prepared in Examples 5-6 was improved, reaching over 97.0%. This indicates that by selecting the melt flow rates of the ethylene-butene copolymer and the ethylene-hexene copolymer, such that the melt flow rate of the ethylene-butene copolymer at 190℃ and 2.16kg is 1.2g / 10min and the melt flow rate of the ethylene-hexene copolymer at 190℃ and 2.16kg is 2.0-3.5g / 10min, and by reasonably controlling the content ratio of the ethylene-butene copolymer and the ethylene-hexene copolymer, when the weight ratio of the ethylene-butene copolymer with a melt flow rate of 1.2g / 10min to the ethylene-hexene copolymer with a melt flow rate of 2.0-3.5g / 10min is 2-5:1, the corrosion resistance of the coated composite pipe can be further improved.

[0066] Compared with Examples 6, 10, and 16, the polyethylene layers prepared in Examples 11-15 still maintained an impact strength retention rate of over 97.0%, while the impact strength before corrosion was improved, indicating that the use of 2 Acrylamide group 2 Methylpropanesulfonic acid and titanate coupling agent are used together to treat the surface of titanium dioxide and silicon dioxide, which can improve the impact resistance of the plastic-coated composite pipe while ensuring corrosion resistance.

[0067] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A corrosion-resistant plastic-coated composite pipe, characterized in that, It includes a steel pipe base and a plastic coating layer disposed on the outer surface of the steel pipe base. The plastic coating layer includes a fusion-bonded epoxy layer, an adhesive layer, and a polyethylene layer disposed sequentially from the inside to the outside. The polyethylene layer comprises the following components in parts by weight: 80 parts high-density polyethylene, 10-15 parts metallocene polyethylene, 6-12 parts vinyl copolymer, 15-20 parts filler, 2-4 parts antioxidant, and 6-8 parts plasticizer; The vinyl copolymers include ethylene-butene copolymers and ethylene-hexene copolymers in a weight ratio of 1 to 9:

1.

2. The corrosion-resistant plastic-coated composite pipe according to claim 1, characterized in that, The melt flow rate of the ethylene-butene copolymer at 190°C and 2.16 kg is 1.2 g / 10 min. The melt flow rate of the ethylene-hexene copolymer at 190°C and 2.16 kg is 2.0~3.5 g / 10 min.

3. The corrosion-resistant plastic-coated composite pipe according to claim 2, characterized in that, The weight ratio of ethylene-butene copolymer to ethylene-hexene copolymer is 2~5:

1.

4. The corrosion-resistant plastic-coated composite pipe according to claim 1, characterized in that, The raw material for the filler comprises the following components in parts by weight: 40-45 parts titanium dioxide, 5-10 parts silicon dioxide, 1-4 parts titanate coupling agent, 2 Acrylamide group 2 3-7 parts of methylpropanesulfonic acid.

5. The corrosion-resistant plastic-coated composite pipe according to claim 4, characterized in that, The 2 Acrylamide group 2 The weight ratio of methylpropanesulfonic acid to the titanate coupling agent is 1.5 to 3:

1.

6. The corrosion-resistant plastic-coated composite pipe according to claim 4, characterized in that, The method for preparing the filler includes the following steps: A1. The titanium dioxide and silicon dioxide are blended and ground to obtain a blend; A2. Dissolve the titanate coupling agent in isopropanol, add the blend, mix, and dry to obtain the pretreated blend. A3, the above 2 Acrylamide group 2 Methylpropanesulfonic acid is dissolved in ethanol, added to the pretreated blend, mixed, and dried to obtain the filler.

7. The corrosion-resistant plastic-coated composite pipe according to claim 1, characterized in that, The raw materials for the polyethylene layer also include 4 to 6 parts of lubricant.

8. The corrosion-resistant plastic-coated composite pipe according to claim 7, characterized in that, The lubricant includes one or both of polyethylene wax and zinc stearate; The antioxidant includes one or more of antioxidant 1010, antioxidant 1024, and antioxidant 1076; The plasticizer includes one or more of dioctyl phthalate, diisononyl phthalate, and diisodecyl phthalate.

9. The corrosion-resistant plastic-coated composite pipe according to claim 1, characterized in that, The raw material for the fusion-bonded epoxy layer includes epoxy resin; The adhesive layer is made from an ethylene-acrylic acid copolymer.

10. A method for preparing a corrosion-resistant plastic-coated composite pipe, used to prepare a corrosion-resistant plastic-coated composite pipe as described in any one of claims 1 to 9, characterized in that, Includes the following steps: A fusion-bonded epoxy layer and an adhesive layer are sequentially disposed on the outside of the steel pipe base. The raw materials of the polyethylene layer are blended, extruded, and coated on the outside of the adhesive layer. The composite is then pressurized to obtain the corrosion-resistant plastic-coated composite pipe.

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