A bimetallic steel skeleton polyethylene composite pipe and a preparation method thereof

Abstract

The application relates to the technical field of composite pipes, and discloses a bimetal steel framework polyethylene composite pipe and a preparation method thereof. The bimetal steel framework polyethylene composite pipe comprises, from inside to outside, a polyethylene inner layer, a bimetal steel framework reinforcing layer and a polyethylene outer layer. The raw materials of the polyethylene inner layer and the polyethylene outer layer each independently comprise the following components in parts by weight: 50 parts of polyethylene, 5-8 parts of styrene maleic anhydride copolymer, 3-5 parts of maleic anhydride grafted polyethylene, 40-50 parts of antistatic flame-retardant masterbatch and 1-3 parts of antioxidant. The mass content of maleic anhydride in the styrene maleic anhydride copolymer is 10-20%, and the grafting rate of maleic anhydride in the maleic anhydride grafted polyethylene is 0.8-2.0%. Through the technical scheme, the problem of poor pressure resistance of the bimetal steel framework polyethylene composite pipe in the related art is solved.

Description

Technical Field

[0001] This invention relates to the field of composite pipe technology, specifically to a bimetallic steel-reinforced polyethylene composite pipe and its preparation method. Background Technology

[0002] Bimetallic steel-reinforced polyethylene composite pipe, a new type of steel-plastic composite pipe, typically consists of an inner polyethylene layer, a middle bimetallic reinforcing skeleton layer, and an outer polyethylene layer. The middle bimetallic skeleton layer includes a steel skeleton reinforcement layer providing structural support, a steel wire winding reinforcement layer, and an adhesive resin layer providing bonding, thus providing axial and circumferential stiffness to the composite pipe. The inner and outer polyethylene pipes provide chemical protection, giving the bimetallic steel-reinforced polyethylene composite pipe high strength, high rigidity, and corrosion resistance. It is widely used in oil and gas transportation, municipal water supply and drainage, and mining slurry transportation.

[0003] When used for conveying slurry in mines, bimetallic steel-reinforced polyethylene composite pipes are prone to delamination and separation of the inner polyethylene layer, bimetallic reinforcing skeleton layer, and outer polyethylene layer under transient impact from hard objects within the slurry, reducing the overall pressure resistance of the pipe. Therefore, it is urgent to improve the pressure resistance of bimetallic steel-reinforced polyethylene composite pipes. Summary of the Invention

[0004] This invention proposes a bimetallic steel-reinforced polyethylene composite pipe and its preparation method, which solves the problem of poor pressure resistance of bimetallic steel-reinforced polyethylene composite pipes in related technologies.

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

[0006] This invention proposes a bimetallic steel-reinforced polyethylene composite pipe, comprising a polyethylene inner layer, a bimetallic steel-reinforced layer, and a polyethylene outer layer arranged sequentially from the inside to the outside. The bimetallic steel-reinforced layer comprises a steel-reinforced layer, a first adhesive resin layer, a steel wire winding reinforcement layer, and a second adhesive resin layer arranged sequentially from the inside to the outside.

[0007] The raw materials for the polyethylene inner layer and the polyethylene outer layer each independently comprise the following components in parts by weight:

[0008] 50 parts polyethylene, 5-8 parts styrene-maleic anhydride copolymer, 3-5 parts maleic anhydride-grafted polyethylene, 40-50 parts antistatic flame-retardant masterbatch, and 1-3 parts antioxidant.

[0009] The maleic anhydride content in the styrene-maleic anhydride copolymer is 10% to 20%, and the grafting rate of maleic anhydride in the maleic anhydride-grafted polyethylene is 0.8% to 2.0%.

[0010] As a further technical solution, the mass content of maleic anhydride in the styrene-maleic anhydride copolymer is 16%, and the grafting rate of maleic anhydride in the maleic anhydride-grafted polyethylene is 0.8%~1.0%.

[0011] In this invention, the inventors discovered that when the mass content of maleic anhydride in the styrene-maleic anhydride copolymer is 16% and the grafting rate of maleic anhydride in the maleic anhydride-grafted polyethylene is 0.8%~1.0%, the pressure resistance of the bimetallic steel-reinforced polyethylene composite pipe is further improved.

[0012] As a further technical solution, the polyethylene is high-density polyethylene, and the density of high-density polyethylene is 930~965 kg / m³. 3 .

[0013] In this invention, compared with ordinary polyethylene, high-density polyethylene has a denser structure, higher tensile strength and hardness, and better corrosion resistance, thereby improving the mechanical strength, corrosion resistance and durability of bimetallic steel-reinforced polyethylene composite pipes.

[0014] As a further technical solution, the antioxidant includes one or more of antioxidant 168, antioxidant 1010, and antioxidant 626.

[0015] As a further technical solution, the raw material of the inner polyethylene layer also includes 1 to 3 parts of ethylene-acrylic acid copolymer, and the raw material of the outer polyethylene layer also includes 1 to 3 parts of polycaprolactone.

[0016] In this invention, ethylene-acrylic acid copolymer is added to the inner layer of polyethylene, and polycaprolactone is added to the outer layer of polyethylene. On the one hand, the ethylene-acrylic acid copolymer in the inner layer synergistically with the styrene-maleic anhydride copolymer, and the polycaprolactone in the outer layer synergistically with the styrene-maleic anhydride copolymer, further improving the pressure resistance of the bimetallic steel skeleton polyethylene composite pipe. On the other hand, the addition of ethylene-acrylic acid copolymer improves the interfacial bonding strength between the inner polyethylene layer and the steel skeleton reinforcement layer in the bimetallic steel skeleton reinforcement layer, and the addition of polycaprolactone improves the interfacial bonding strength between the adhesive resin layer and the outer polyethylene layer in the bimetallic steel skeleton reinforcement layer. This makes the bonding between the layers of the bimetallic steel skeleton polyethylene composite pipe tighter, avoiding debonding and delamination defects under instantaneous impact, and further improving the pressure resistance of the bimetallic steel skeleton polyethylene composite pipe.

[0017] As a further technical solution, the mass content of acrylic acid in the ethylene-acrylic acid copolymer is 10%~15%, and the weight average molecular weight of polycaprolactone is 20000~30000.

[0018] In this invention, when the mass content of acrylic acid in the ethylene-acrylic acid copolymer is 10%~15%, sufficient carboxyl polar groups are ensured to form effective interfacial bonds with the active sites on the surface of the steel skeleton reinforcement layer, thereby improving the interfacial bonding strength between the polyethylene inner layer and the steel skeleton reinforcement layer, and thus further improving the pressure resistance of the bimetallic steel skeleton polyethylene composite pipe. When the weight average molecular weight of polycaprolactone is 20,000~30,000, the flexible molecular chains of polycaprolactone are long enough and the molecular chain diffusion rate is moderate, which can not only synergize with the styrene-maleic anhydride copolymer, but also improve the interfacial bonding strength with the second adhesive resin layer, further improving the pressure resistance of the bimetallic steel skeleton polyethylene composite pipe.

[0019] As a further technical solution, the raw material of the steel skeleton reinforcement layer includes reinforcing strips, which include fiber reinforcing strips, steel wire reinforcing strips, or steel cord reinforcing strips. The raw materials of the first bonding resin layer and the second bonding resin layer each independently include bonding resin, and the bonding resin meets the following condition: density ≥ 0.940 g / cm³. 3 Melt flow rate (190℃, 5kg) ≥1.5g / 10min, Vicat softening point ≥120℃, elongation at break ≥500%.

[0020] In this invention, the bonding resin can be any commercially available polyethylene pipe bonding resin, provided that its density is ≥0.940 g / cm³. 3 The melt flow rate (190℃, 5kg) is ≥1.5g / 10min, the Vicat softening point is ≥120℃, and the elongation at break is ≥500%. For example, the bonding resin comprises the following components in parts by weight: 12-36 parts of polyethylene grafted with maleic anhydride, 45-65 parts of polyethylene, 14-20 parts of silicon carbide whiskers, and 3-5 parts of ethylene-vinyl acetate copolymer; preferably: 20 parts of polyethylene grafted with maleic anhydride (maleic anhydride grafting rate of 1.2%-2.0%), 60 parts of polyethylene, 16 parts of silicon carbide whiskers, and 4 parts of ethylene-vinyl acetate copolymer.

[0021] In this invention, the conditions that the bonding resin must meet are specified to ensure that the first bonding layer and the second bonding layer provide sufficient interfacial bonding performance, so that the bimetallic steel skeleton polyethylene composite pipe also has a certain pressure resistance under high temperature and high pressure conditions.

[0022] As a further technical solution, the antistatic and flame-retardant masterbatch has an antistatic performance of ≤1×10⁻⁶. 6 For Ω-type alcohol torches, the maximum single burning time for flame-emitting combustion is ≤10s, and the maximum single burning time for flameless combustion is ≤60s.

[0023] In this invention, the antistatic and flame-retardant masterbatch can be any commercially available antistatic and flame-retardant masterbatch specifically for polyethylene pipes, requiring an antistatic performance ≤1×10⁻⁶.6 For Ω, the maximum single burning time of flaming combustion with an alcohol torch is ≤10s, and the maximum single burning time of flameless combustion is ≤60s. For example, the antistatic flame-retardant masterbatch includes the following components in parts by weight: 50 parts of high-density polyethylene, 4-8 parts of carbon black, 1-3 parts of maleic anhydride-grafted polyethylene, and 5-8 parts of flame retardant; preferably: 50 parts of high-density polyethylene, 8 parts of carbon black, 3 parts of maleic anhydride-grafted polyethylene (maleic anhydride grafting rate of 1.2%-2.0%), and 8 parts of red phosphorus flame retardant.

[0024] As a further technical solution, the number of layers of the steel wire winding reinforcement layer and the second adhesive resin layer are the same and both have a number of ≥2.

[0025] In this invention, depending on the pressure of the pipe, the steel wire winding reinforcement layer and the second adhesive resin layer can be multiple layers. For example, the number of layers of the steel wire winding reinforcement layer and the second adhesive resin layer can be 2, 3 or 4.

[0026] This invention also proposes a method for preparing the bimetallic steel-reinforced polyethylene composite pipe, comprising the following steps:

[0027] S1. After blending the raw materials for the polyethylene inner layer, the mixture is extruded, shaped, and cooled to obtain the first polyethylene inner layer.

[0028] S2. A reinforcing strip is wound around the outer wall of the first polyethylene inner layer to obtain a steel skeleton reinforcing layer. Adhesive resin is coated on the surface of the steel skeleton reinforcing layer and cured to obtain a first adhesive resin layer. Steel wire is wound around the first adhesive resin layer to obtain a steel wire wound reinforcing layer. Adhesive resin is then coated on the surface of the steel wire wound reinforcing layer and cured to obtain a second adhesive resin layer, forming a bimetallic steel skeleton reinforcing layer.

[0029] S3. The raw materials for the outer layer of polyethylene are blended, extruded, and coated on the outside of the bimetallic steel skeleton reinforcement layer. After cooling, a bimetallic steel skeleton polyethylene composite pipe is obtained.

[0030] The working principle and beneficial effects of this invention are as follows:

[0031] In this invention, the raw materials for the inner and outer polyethylene layers are optimized. Using polyethylene as the matrix, a styrene-maleic anhydride copolymer is introduced. This not only improves the interfacial bonding strength between the inner polyethylene layer and the bimetallic steel skeleton reinforcement layer, but also enhances the interfacial bonding strength between the outer polyethylene layer and the bimetallic skeleton reinforcement layer. This effectively reduces delamination and separation defects in the bimetallic steel skeleton polyethylene composite pipe under instantaneous impact, thereby improving the pressure resistance and structural stability of the bimetallic steel skeleton polyethylene composite pipe. The mass content of maleic anhydride in the styrene-maleic anhydride copolymer is limited to 10%~20%, and the grafting rate of maleic anhydride in the maleic anhydride-grafted polyethylene is 0.8%~2.0%. This allows the styrene-maleic anhydride copolymer and the maleic anhydride-grafted polyethylene to synergistically improve the compatibility between the styrene-maleic anhydride copolymer and the polyethylene matrix, ensuring stable interfacial bonding and enabling the bimetallic steel skeleton polyethylene composite pipe to maintain high pressure resistance. Detailed Implementation

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0033] In the following embodiments and comparative examples:

[0034] Polyethylene, model number: high-density polyethylene 23050;

[0035] Antistatic and flame-retardant masterbatch raw materials (by weight): 50 parts high-density polyethylene, 8 parts carbon black, 3 parts maleic anhydride-grafted polyethylene (maleic anhydride grafting rate of 1.2%~2.0%), and 8 parts red phosphorus flame retardant.

[0036] The antioxidant is antioxidant 168;

[0037] The reinforcing strip is a steel wire reinforcing strip;

[0038] The adhesive resin has the part number EP258 and is manufactured by Guangzhou Lushan New Materials Co., Ltd.

[0039] The preparation method of the bimetallic steel-reinforced polyethylene composite pipes in Examples 1-13 below includes the following steps:

[0040] S1. After blending the raw materials for the polyethylene inner layer, the mixture is extruded, shaped, and cooled to obtain the first polyethylene inner layer.

[0041] S2. A reinforcing strip is wound around the outer wall of the first polyethylene inner layer to obtain a steel skeleton reinforcing layer. Adhesive resin is coated on the surface of the steel skeleton reinforcing layer and cured to obtain a first adhesive resin layer. Steel wire is wound around the first adhesive resin layer to obtain a steel wire wound reinforcing layer. Adhesive resin is then coated on the surface of the steel wire wound reinforcing layer and cured to obtain a second adhesive resin layer, forming a bimetallic steel skeleton reinforcing layer.

[0042] S3. The raw materials for the outer layer of polyethylene are blended, extruded, and coated onto the outside of the bimetallic steel skeleton reinforcement layer. After cooling, a bimetallic steel skeleton polyethylene composite pipe is obtained.

[0043] The nominal outer diameter of the bimetallic steel-reinforced polyethylene composite pipes in Examples 1-13 is 225 mm, and the nominal pressure is 2.5 MPa.

[0044] Example 1

[0045] A bimetallic steel-reinforced polyethylene composite pipe includes an inner polyethylene layer, a bimetallic steel-reinforced layer, and an outer polyethylene layer arranged sequentially from the inside to the outside. The bimetallic steel-reinforced layer includes a steel-reinforced layer, a first adhesive resin layer, a steel wire winding reinforcement layer, and a second adhesive resin layer arranged sequentially from the inside to the outside.

[0046] The raw materials for both the inner and outer polyethylene layers comprise the following components in parts by weight:

[0047] 50 parts polyethylene, 8 parts styrene-maleic anhydride copolymer, 5 parts maleic anhydride-grafted polyethylene, 40 parts antistatic and flame-retardant masterbatch, and 1 part antioxidant.

[0048] The maleic anhydride content in the styrene-maleic anhydride copolymer is 10%, and the grafting rate of maleic anhydride in the maleic anhydride-grafted polyethylene is 1.2%~2.0%.

[0049] Example 2

[0050] A bimetallic steel-reinforced polyethylene composite pipe includes an inner polyethylene layer, a bimetallic steel-reinforced layer, and an outer polyethylene layer arranged sequentially from the inside to the outside. The bimetallic steel-reinforced layer includes a steel-reinforced layer, a first adhesive resin layer, a steel wire winding reinforcement layer, and a second adhesive resin layer arranged sequentially from the inside to the outside.

[0051] The raw materials for both the inner and outer polyethylene layers comprise the following components in parts by weight:

[0052] 50 parts polyethylene, 5 parts styrene-maleic anhydride copolymer, 3 parts maleic anhydride-grafted polyethylene, 50 parts antistatic and flame-retardant masterbatch, 3 parts antioxidant.

[0053] The maleic anhydride content in the styrene-maleic anhydride copolymer is 10%, and the grafting rate of maleic anhydride in the maleic anhydride-grafted polyethylene is 1.2%~2.0%.

[0054] Example 3

[0055] A bimetallic steel-reinforced polyethylene composite pipe includes an inner polyethylene layer, a bimetallic steel-reinforced layer, and an outer polyethylene layer arranged sequentially from the inside to the outside. The bimetallic steel-reinforced layer includes a steel-reinforced layer, a first adhesive resin layer, a steel wire winding reinforcement layer, and a second adhesive resin layer arranged sequentially from the inside to the outside.

[0056] The raw materials for both the inner and outer polyethylene layers comprise the following components in parts by weight:

[0057] 50 parts polyethylene, 8 parts styrene-maleic anhydride copolymer, 5 parts maleic anhydride-grafted polyethylene, 40 parts antistatic and flame-retardant masterbatch, and 1 part antioxidant.

[0058] The maleic anhydride content in the styrene-maleic anhydride copolymer is 16%, and the grafting rate of maleic anhydride in the maleic anhydride-grafted polyethylene is 1.2%~2.0%.

[0059] Example 4

[0060] A bimetallic steel-reinforced polyethylene composite pipe includes an inner polyethylene layer, a bimetallic steel-reinforced layer, and an outer polyethylene layer arranged sequentially from the inside to the outside. The bimetallic steel-reinforced layer includes a steel-reinforced layer, a first adhesive resin layer, a steel wire winding reinforcement layer, and a second adhesive resin layer arranged sequentially from the inside to the outside.

[0061] The raw materials for both the inner and outer polyethylene layers comprise the following components in parts by weight:

[0062] 50 parts polyethylene, 8 parts styrene-maleic anhydride copolymer, 5 parts maleic anhydride-grafted polyethylene, 40 parts antistatic and flame-retardant masterbatch, and 1 part antioxidant.

[0063] The maleic anhydride content in the styrene-maleic anhydride copolymer is 16%, and the grafting rate of maleic anhydride in the maleic anhydride-grafted polyethylene is 0.8%~1.0%.

[0064] Example 5

[0065] A bimetallic steel-reinforced polyethylene composite pipe includes an inner polyethylene layer, a bimetallic steel-reinforced layer, and an outer polyethylene layer arranged sequentially from the inside to the outside. The bimetallic steel-reinforced layer includes a steel-reinforced layer, a first adhesive resin layer, a steel wire winding reinforcement layer, and a second adhesive resin layer arranged sequentially from the inside to the outside.

[0066] The raw material for the polyethylene inner layer comprises the following components in parts by weight:

[0067] 50 parts polyethylene, 8 parts styrene-maleic anhydride copolymer, 5 parts maleic anhydride-grafted polyethylene, 40 parts antistatic and flame-retardant masterbatch, 1 part antioxidant, 1 part ethylene-acrylic acid copolymer.

[0068] The maleic anhydride content in the styrene-maleic anhydride copolymer is 16% by mass; the grafting rate of maleic anhydride in the maleic anhydride-grafted polyethylene is 0.8%~1.0%; and the acrylic acid content in the ethylene-acrylic acid copolymer is 7.5% by mass.

[0069] The raw material for the polyethylene outer layer comprises the following components in parts by weight:

[0070] 50 parts polyethylene, 8 parts styrene-maleic anhydride copolymer, 5 parts maleic anhydride-grafted polyethylene, 40 parts antistatic and flame-retardant masterbatch, 1 part antioxidant, and 1 part polycaprolactone.

[0071] The maleic anhydride content in the styrene-maleic anhydride copolymer is 16%, and the grafting rate of maleic anhydride in maleic anhydride-grafted polyethylene is 0.8%~1.0%.

[0072] The weight-average molecular weight of polycaprolactone is 15,000.

[0073] Example 6

[0074] A bimetallic steel-reinforced polyethylene composite pipe includes an inner polyethylene layer, a bimetallic steel-reinforced layer, and an outer polyethylene layer arranged sequentially from the inside to the outside. The bimetallic steel-reinforced layer includes a steel-reinforced layer, a first adhesive resin layer, a steel wire winding reinforcement layer, and a second adhesive resin layer arranged sequentially from the inside to the outside.

[0075] The raw material for the polyethylene inner layer comprises the following components in parts by weight:

[0076] 50 parts polyethylene, 5 parts styrene-maleic anhydride copolymer, 3 parts maleic anhydride-grafted polyethylene, 50 parts antistatic and flame-retardant masterbatch, 3 parts antioxidant; 3 parts ethylene-acrylic acid copolymer.

[0077] The maleic anhydride content in the styrene-maleic anhydride copolymer is 16% by mass, the grafting rate of maleic anhydride in the maleic anhydride-grafted polyethylene is 0.8%~1.0%, and the maleic anhydride content in the ethylene-acrylic acid copolymer is 7.5% by mass.

[0078] The raw material for the polyethylene outer layer comprises the following components in parts by weight:

[0079] 50 parts polyethylene, 5 parts styrene-maleic anhydride copolymer, 3 parts maleic anhydride-grafted polyethylene, 50 parts antistatic and flame-retardant masterbatch, 3 parts antioxidant; 3 parts polycaprolactone.

[0080] The maleic anhydride content in the styrene-maleic anhydride copolymer is 16%, the grafting rate of maleic anhydride in the maleic anhydride-grafted polyethylene is 0.8%~1.0%, and the weight average molecular weight of polycaprolactone is 15000.

[0081] Example 7

[0082] A bimetallic steel-reinforced polyethylene composite pipe includes an inner polyethylene layer, a bimetallic steel-reinforced layer, and an outer polyethylene layer arranged sequentially from the inside to the outside. The bimetallic steel-reinforced layer includes a steel-reinforced layer, a first adhesive resin layer, a steel wire winding reinforcement layer, and a second adhesive resin layer arranged sequentially from the inside to the outside.

[0083] The raw material for the polyethylene inner layer comprises the following components in parts by weight:

[0084] 50 parts polyethylene, 8 parts styrene-maleic anhydride copolymer, 5 parts maleic anhydride-grafted polyethylene, 40 parts antistatic and flame-retardant masterbatch, 1 part antioxidant, 1 part ethylene-acrylic acid copolymer.

[0085] The maleic anhydride content in the styrene-maleic anhydride copolymer is 16% by mass, the grafting rate of maleic anhydride in the maleic anhydride-grafted polyethylene is 0.8%~1.0%, and the maleic anhydride content in the ethylene-acrylic acid copolymer is 20% by mass.

[0086] The raw material for the polyethylene outer layer comprises the following components in parts by weight:

[0087] 50 parts polyethylene, 8 parts styrene-maleic anhydride copolymer, 5 parts maleic anhydride-grafted polyethylene, 40 parts antistatic and flame-retardant masterbatch, 1 part antioxidant, and 1 part polycaprolactone.

[0088] The maleic anhydride content in the styrene-maleic anhydride copolymer is 16%, the grafting rate of maleic anhydride in the maleic anhydride-grafted polyethylene is 0.8%~1.0%, and the weight average molecular weight of polycaprolactone is 40,000.

[0089] Example 8

[0090] A bimetallic steel-reinforced polyethylene composite pipe includes an inner polyethylene layer, a bimetallic steel-reinforced layer, and an outer polyethylene layer arranged sequentially from the inside to the outside. The bimetallic steel-reinforced layer includes a steel-reinforced layer, a first adhesive resin layer, a steel wire winding reinforcement layer, and a second adhesive resin layer arranged sequentially from the inside to the outside.

[0091] The raw material for the polyethylene inner layer comprises the following components in parts by weight:

[0092] 50 parts polyethylene, 8 parts styrene-maleic anhydride copolymer, 5 parts maleic anhydride-grafted polyethylene, 40 parts antistatic and flame-retardant masterbatch, 1 part antioxidant, 1 part ethylene-acrylic acid copolymer.

[0093] The maleic anhydride content in the styrene-maleic anhydride copolymer is 16% by mass, the grafting rate of maleic anhydride in the maleic anhydride-grafted polyethylene is 0.8%~1.0%, and the maleic anhydride content in the ethylene-acrylic acid copolymer is 10% by mass.

[0094] The raw material for the polyethylene outer layer comprises the following components in parts by weight:

[0095] 50 parts polyethylene, 8 parts styrene-maleic anhydride copolymer, 5 parts maleic anhydride-grafted polyethylene, 40 parts antistatic and flame-retardant masterbatch, 1 part antioxidant, and 1 part polycaprolactone.

[0096] The maleic anhydride content in the styrene-maleic anhydride copolymer is 16%, the grafting rate of maleic anhydride in the maleic anhydride-grafted polyethylene is 0.8%~1.0%, and the weight average molecular weight of polycaprolactone is 40,000.

[0097] Example 9

[0098] A bimetallic steel-reinforced polyethylene composite pipe includes an inner polyethylene layer, a bimetallic steel-reinforced layer, and an outer polyethylene layer arranged sequentially from the inside to the outside. The bimetallic steel-reinforced layer includes a steel-reinforced layer, a first adhesive resin layer, a steel wire winding reinforcement layer, and a second adhesive resin layer arranged sequentially from the inside to the outside.

[0099] The raw material for the polyethylene inner layer comprises the following components in parts by weight:

[0100] 50 parts polyethylene, 8 parts styrene-maleic anhydride copolymer, 5 parts maleic anhydride-grafted polyethylene, 40 parts antistatic and flame-retardant masterbatch, 1 part antioxidant, 1 part ethylene-acrylic acid copolymer.

[0101] The maleic anhydride content in the styrene-maleic anhydride copolymer is 16% by mass, the grafting rate of maleic anhydride in the maleic anhydride-grafted polyethylene is 0.8%~1.0%, and the maleic anhydride content in the ethylene-acrylic acid copolymer is 15% by mass.

[0102] The raw material for the polyethylene outer layer comprises the following components in parts by weight:

[0103] 50 parts polyethylene, 8 parts styrene-maleic anhydride copolymer, 5 parts maleic anhydride-grafted polyethylene, 40 parts antistatic and flame-retardant masterbatch, 1 part antioxidant, and 1 part polycaprolactone.

[0104] The maleic anhydride content in the styrene-maleic anhydride copolymer is 16%, the grafting rate of maleic anhydride in the maleic anhydride-grafted polyethylene is 0.8%~1.0%, and the weight average molecular weight of polycaprolactone is 40,000.

[0105] Example 10

[0106] A bimetallic steel-reinforced polyethylene composite pipe includes an inner polyethylene layer, a bimetallic steel-reinforced layer, and an outer polyethylene layer arranged sequentially from the inside to the outside. The bimetallic steel-reinforced layer includes a steel-reinforced layer, a first adhesive resin layer, a steel wire winding reinforcement layer, and a second adhesive resin layer arranged sequentially from the inside to the outside.

[0107] The raw material for the polyethylene inner layer comprises the following components in parts by weight:

[0108] 50 parts polyethylene, 8 parts styrene-maleic anhydride copolymer, 5 parts maleic anhydride-grafted polyethylene, 40 parts antistatic and flame-retardant masterbatch, 1 part antioxidant, 1 part ethylene-acrylic acid copolymer.

[0109] The maleic anhydride content in the styrene-maleic anhydride copolymer is 16% by mass, the grafting rate of maleic anhydride in the maleic anhydride-grafted polyethylene is 0.8%~1.0%, and the maleic anhydride content in the ethylene-acrylic acid copolymer is 15% by mass.

[0110] The raw material for the polyethylene outer layer comprises the following components in parts by weight:

[0111] 50 parts polyethylene, 8 parts styrene-maleic anhydride copolymer, 5 parts maleic anhydride-grafted polyethylene, 40 parts antistatic and flame-retardant masterbatch, 1 part antioxidant, and 1 part polycaprolactone.

[0112] The maleic anhydride content in the styrene-maleic anhydride copolymer is 16%, the grafting rate of maleic anhydride in the maleic anhydride-grafted polyethylene is 0.8%~1.0%, and the weight average molecular weight of polycaprolactone is 20,000.

[0113] Example 11

[0114] A bimetallic steel-reinforced polyethylene composite pipe includes an inner polyethylene layer, a bimetallic steel-reinforced layer, and an outer polyethylene layer arranged sequentially from the inside to the outside. The bimetallic steel-reinforced layer includes a steel-reinforced layer, a first adhesive resin layer, a steel wire winding reinforcement layer, and a second adhesive resin layer arranged sequentially from the inside to the outside.

[0115] The raw material for the polyethylene inner layer comprises the following components in parts by weight:

[0116] 50 parts polyethylene, 8 parts styrene-maleic anhydride copolymer, 5 parts maleic anhydride-grafted polyethylene, 40 parts antistatic and flame-retardant masterbatch, 1 part antioxidant, 1 part ethylene-acrylic acid copolymer.

[0117] The maleic anhydride content in the styrene-maleic anhydride copolymer is 16% by mass, the grafting rate of maleic anhydride in the maleic anhydride-grafted polyethylene is 0.8%~1.0%, and the maleic anhydride content in the ethylene-acrylic acid copolymer is 15% by mass.

[0118] The raw material for the polyethylene outer layer comprises the following components in parts by weight:

[0119] 50 parts polyethylene, 8 parts styrene-maleic anhydride copolymer, 5 parts maleic anhydride-grafted polyethylene, 40 parts antistatic and flame-retardant masterbatch, 1 part antioxidant, and 1 part polycaprolactone.

[0120] The maleic anhydride content in the styrene-maleic anhydride copolymer is 16%, the grafting rate of maleic anhydride in the maleic anhydride-grafted polyethylene is 0.8%~1.0%, and the weight average molecular weight of polycaprolactone is 30,000.

[0121] Example 12

[0122] A bimetallic steel-reinforced polyethylene composite pipe includes an inner polyethylene layer, a bimetallic steel-reinforced layer, and an outer polyethylene layer arranged sequentially from the inside to the outside. The bimetallic steel-reinforced layer includes a steel-reinforced layer, a first adhesive resin layer, a steel wire winding reinforcement layer, and a second adhesive resin layer arranged sequentially from the inside to the outside.

[0123] The raw materials for both the inner and outer polyethylene layers comprise the following components in parts by weight:

[0124] 50 parts polyethylene, 8 parts styrene-maleic anhydride copolymer, 5 parts maleic anhydride-grafted polyethylene, 40 parts antistatic and flame-retardant masterbatch, 1 part antioxidant, 1 part ethylene-acrylic acid copolymer.

[0125] The maleic anhydride content in the styrene-maleic anhydride copolymer is 16%, the grafting rate of maleic anhydride in the maleic anhydride-grafted polyethylene is 0.8%~1.0%, and the maleic anhydride content in the ethylene-acrylic acid copolymer is 20%.

[0126] Example 13

[0127] A bimetallic steel-reinforced polyethylene composite pipe includes an inner polyethylene layer, a bimetallic steel-reinforced layer, and an outer polyethylene layer arranged sequentially from the inside to the outside. The bimetallic steel-reinforced layer includes a steel-reinforced layer, a first adhesive resin layer, a steel wire winding reinforcement layer, and a second adhesive resin layer arranged sequentially from the inside to the outside.

[0128] The raw materials for both the inner and outer polyethylene layers comprise the following components in parts by weight:

[0129] 50 parts polyethylene, 8 parts styrene-maleic anhydride copolymer, 5 parts maleic anhydride-grafted polyethylene, 40 parts antistatic and flame-retardant masterbatch, 1 part antioxidant, and 1 part polycaprolactone.

[0130] The maleic anhydride content in the styrene-maleic anhydride copolymer is 16%, the grafting rate of maleic anhydride in the maleic anhydride-grafted polyethylene is 0.8%~1.0%, and the weight average molecular weight of polycaprolactone is 40,000.

[0131] Comparative Example 1

[0132] A bimetallic steel-reinforced polyethylene composite pipe includes an inner polyethylene layer, a bimetallic steel-reinforced layer, and an outer polyethylene layer arranged sequentially from the inside to the outside. The bimetallic steel-reinforced layer includes a steel-reinforced layer, a first adhesive resin layer, a steel wire winding reinforcement layer, and a second adhesive resin layer arranged sequentially from the inside to the outside.

[0133] The raw materials for both the inner and outer polyethylene layers comprise the following components in parts by weight:

[0134] 50 parts polyethylene, 5 parts maleic anhydride grafted polyethylene, 40 parts antistatic and flame-retardant masterbatch, 1 part antioxidant.

[0135] The grafting rate of maleic anhydride in maleic anhydride-grafted polyethylene is 1.2% to 2.0%.

[0136] Comparative Example 2

[0137] A bimetallic steel-reinforced polyethylene composite pipe includes an inner polyethylene layer, a bimetallic steel-reinforced layer, and an outer polyethylene layer arranged sequentially from the inside to the outside. The bimetallic steel-reinforced layer includes a steel-reinforced layer, a first adhesive resin layer, a steel wire winding reinforcement layer, and a second adhesive resin layer arranged sequentially from the inside to the outside.

[0138] The raw materials for both the inner and outer polyethylene layers comprise the following components in parts by weight:

[0139] 50 parts polyethylene, 8 parts styrene-maleic anhydride copolymer, 5 parts maleic anhydride-grafted polyethylene, 40 parts antistatic and flame-retardant masterbatch, and 1 part antioxidant; the maleic anhydride content in the styrene-maleic anhydride copolymer is 5% by mass, and the grafting rate of maleic anhydride in the maleic anhydride-grafted polyethylene is 1.2%~2.0%.

[0140] Comparative Example 3

[0141] A bimetallic steel-reinforced polyethylene composite pipe includes an inner polyethylene layer, a bimetallic steel-reinforced layer, and an outer polyethylene layer arranged sequentially from the inside to the outside. The bimetallic steel-reinforced layer includes a steel-reinforced layer, a first adhesive resin layer, a steel wire winding reinforcement layer, and a second adhesive resin layer arranged sequentially from the inside to the outside.

[0142] The raw materials for both the inner and outer polyethylene layers comprise the following components in parts by weight:

[0143] 50 parts polyethylene, 8 parts styrene-maleic anhydride copolymer, 5 parts maleic anhydride-grafted polyethylene, 40 parts antistatic and flame-retardant masterbatch, and 1 part antioxidant; the maleic anhydride content in the styrene-maleic anhydride copolymer is 25%, and the grafting rate of maleic anhydride in the maleic anhydride-grafted polyethylene is 1.2%~2.0%.

[0144] Example 14

[0145] A bimetallic steel-reinforced polyethylene composite pipe includes, from the inside out, an inner polyethylene layer, a steel skeleton reinforcement layer, a first adhesive resin layer, a steel wire winding reinforcement layer, a second adhesive resin layer, a steel wire winding reinforcement layer, a second adhesive resin layer, and an outer polyethylene layer, with the raw materials of each layer being the same as in Example 1;

[0146] The method for preparing the bimetallic steel-reinforced polyethylene composite pipe in this embodiment includes the following steps:

[0147] S1. After blending the raw materials for the polyethylene inner layer, the mixture is extruded, shaped, and cooled to obtain the first polyethylene inner layer.

[0148] S2. A reinforcing strip is wound around the outer wall of the first polyethylene inner layer to obtain a steel skeleton reinforcing layer. Adhesive resin is coated on the surface of the steel skeleton reinforcing layer and cured to obtain a first adhesive resin layer. Steel wire is wound around the first adhesive resin layer to obtain a steel wire wound reinforcing layer. Adhesive resin is then coated on the surface of the steel wire wound reinforcing layer and cured to obtain a second adhesive resin layer. The steps of the steel wire wound reinforcing layer and the second adhesive resin layer are repeated once outside the second adhesive resin layer to form a bimetallic steel skeleton reinforcing layer.

[0149] S3. The raw materials for the outer layer of polyethylene are blended, extruded, and coated onto the outside of the bimetallic steel skeleton reinforcement layer. After cooling, a bimetallic steel skeleton polyethylene composite pipe is obtained.

[0150] Example 15

[0151] A bimetallic steel-reinforced polyethylene composite pipe comprises, from the inside out, an inner polyethylene layer, a steel-reinforced layer, a first adhesive resin layer, a steel wire winding reinforcement layer, a second adhesive resin layer, a steel wire winding reinforcement layer, a second adhesive resin layer, a steel wire winding reinforcement layer, a second adhesive resin layer, and an outer polyethylene layer, the raw materials of each layer being the same as in Example 1;

[0152] The method for preparing the bimetallic steel-reinforced polyethylene composite pipe in this embodiment includes the following steps:

[0153] S1. After blending the raw materials for the polyethylene inner layer, the mixture is extruded, shaped, and cooled to obtain the first polyethylene inner layer.

[0154] S2. A reinforcing strip is wound around the outer wall of the first polyethylene inner layer to obtain a steel skeleton reinforcing layer. Adhesive resin is coated on the surface of the steel skeleton reinforcing layer and cured to obtain a first adhesive resin layer. Steel wire is wound around the first adhesive resin layer to obtain a steel wire wound reinforcing layer. Adhesive resin is then coated on the surface of the steel wire wound reinforcing layer and cured to obtain a second adhesive resin layer. The steps of the steel wire wound reinforcing layer and the second adhesive resin layer are repeated twice outside the second adhesive resin layer to form a bimetallic steel skeleton reinforcing layer.

[0155] S3. The raw materials for the outer layer of polyethylene are blended, extruded, and coated onto the outside of the bimetallic steel skeleton reinforcement layer. After cooling, a bimetallic steel skeleton polyethylene composite pipe is obtained.

[0156] Example 16

[0157] A bimetallic steel-reinforced polyethylene composite pipe comprises, from the inside out, an inner polyethylene layer, a steel skeleton reinforcement layer, a first adhesive resin layer, a steel wire winding reinforcement layer, a second adhesive resin layer, a steel wire winding reinforcement layer, a second adhesive resin layer, a steel wire winding reinforcement layer, a second adhesive resin layer, a steel wire winding reinforcement layer, a second adhesive resin layer, a steel wire winding reinforcement layer, a second adhesive resin layer, and an outer polyethylene layer. The raw materials of each layer are the same as in Example 1.

[0158] The method for preparing the bimetallic steel-reinforced polyethylene composite pipe in this embodiment includes the following steps:

[0159] S1. After blending the raw materials for the polyethylene inner layer, the mixture is extruded, shaped, and cooled to obtain the first polyethylene inner layer.

[0160] S2. A reinforcing strip is wound around the outer wall of the first polyethylene inner layer to obtain a steel skeleton reinforcing layer. Adhesive resin is coated on the surface of the steel skeleton reinforcing layer and cured to obtain a first adhesive resin layer. Steel wire is wound around the first adhesive resin layer to obtain a steel wire wound reinforcing layer. Adhesive resin is then coated on the surface of the steel wire wound reinforcing layer and cured to obtain a second adhesive resin layer. The steps of the steel wire wound reinforcing layer and the second adhesive resin layer are repeated 3 times on the outside of the second adhesive resin layer to form a bimetallic steel skeleton reinforcing layer.

[0161] S3. The raw materials for the outer layer of polyethylene are blended, extruded, and coated onto the outside of the bimetallic steel skeleton reinforcement layer. After cooling, a bimetallic steel skeleton polyethylene composite pipe is obtained.

[0162] For bimetallic steel-reinforced polyethylene composite pipes, the key indicators for evaluating their pressure resistance are short-term hydrostatic strength and burst strength. The short-term hydrostatic strength test examines whether the pipe will permeate or rupture under a relatively high pressure (1.5 times the nominal pressure) for 1 hour. The burst strength test uses an instantaneous burst test to determine the maximum pressure limit the pipe can withstand. Experiments 1 and 2 will be used below to evaluate the pressure resistance of the bimetallic steel-reinforced polyethylene composite pipes in each embodiment.

[0163] Experimental Example 1: Short-term hydrostatic strength test

[0164] The bimetallic steel-reinforced polyethylene composite pipes of Examples 1-16 were subjected to pressure tests according to the methods specified in GB / T 15560-1995 "Plastic Pipes for Fluid Transportation - Hydraulic Instantaneous Burst and Pressure Resistance Test Methods". The short-term hydrostatic strength was tested, specifically whether the pipe would leak or rupture at a test temperature of 20°C, a test time of 1 hour, and a test pressure of 1.5 times the nominal pressure. The results are shown in Table 1 below.

[0165] Table 1. Short-term hydrostatic strength test results of samples from Examples 1-16

[0166]

[0167] As can be seen from Table 1, the bimetallic steel-reinforced polyethylene composite pipes of Examples 1 to 16 did not crack or leak during the short-term hydrostatic strength test, meeting the requirements of CJ / T 189-2007 "Steel wire mesh reinforced plastic (polyethylene) composite pipes and fittings".

[0168] Experiment Example 2: Explosive Strength Test

[0169] The bimetallic skeleton polyethylene composite pipes of Examples 1-13 and Comparative Examples 1-3 were subjected to instantaneous burst tests according to the method in GB / T 15560-1995 "Hydraulic Instantaneous Burst and Pressure Resistance Test Method for Plastic Pipes for Fluid Transportation". The burst strength was tested by increasing the pressure to the point of bursting within 60-70 seconds at a test temperature of 20°C. The burst pressure was used to characterize the burst strength. The results are shown in Table 2 below:

[0170] Table 2. Instantaneous burst test results of samples from Examples 1-13 and Comparative Examples 1-3

[0171]

[0172] Compared with Comparative Examples 1-3, the burst strength of the bimetallic skeleton polyethylene composite pipes in Examples 1-13 was significantly improved, indicating that the introduction of a styrene-maleic anhydride copolymer with a maleic anhydride mass content of 10%-20% into the inner and outer polyethylene layers of the present invention improved the pressure resistance of the bimetallic skeleton polyethylene composite pipe. A comparison of Example 1 with Examples 3-4 shows that when the maleic anhydride mass content of the styrene-maleic anhydride copolymer is 16%, the pressure resistance of the bimetallic skeleton polyethylene composite pipe is further improved. A comparison of Example 4 with Examples 5-13 shows that the addition of ethylene-vinyl acetate copolymer to the inner polyethylene layer and polycaprolactone to the outer polyethylene layer further improves the pressure resistance of the bimetallic skeleton polyethylene composite pipe. Furthermore, when the mass content of acrylic acid in the ethylene-vinyl acetate copolymer is 10-15% and the weight-average molecular weight of polycaprolactone is 20,000-30,000, the pressure resistance of the bimetallic skeleton polyethylene composite pipe is further improved.

[0173] 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 bimetallic steel-reinforced polyethylene composite pipe, characterized in that, It includes a polyethylene inner layer, a bimetallic steel skeleton reinforcement layer and a polyethylene outer layer arranged sequentially from the inside to the outside. The bimetallic steel skeleton reinforcement layer includes a steel skeleton reinforcement layer, a first adhesive resin layer, a steel wire winding reinforcement layer and a second adhesive resin layer arranged sequentially from the inside to the outside. The raw materials for the polyethylene inner layer and the polyethylene outer layer each independently comprise the following components in parts by weight: 50 parts polyethylene, 5-8 parts styrene-maleic anhydride copolymer, 3-5 parts maleic anhydride-grafted polyethylene, 40-50 parts antistatic flame-retardant masterbatch, and 1-3 parts antioxidant. The maleic anhydride content in the styrene-maleic anhydride copolymer is 10%~20%, and the grafting rate of maleic anhydride in the maleic anhydride-grafted polyethylene is 0.8%~2.0%. The raw material for the inner layer of polyethylene also includes 1 to 3 parts of ethylene-acrylic acid copolymer, and the raw material for the outer layer of polyethylene also includes 1 to 3 parts of polycaprolactone. The ethylene-acrylic acid copolymer contains 10% to 15% acrylic acid by mass, and the polycaprolactone has a weight-average molecular weight of 20,000 to 30,000.

2. The bimetallic steel-reinforced polyethylene composite pipe according to claim 1, characterized in that, The maleic anhydride content in the styrene-maleic anhydride copolymer is 16%, and the grafting rate of maleic anhydride in the maleic anhydride-grafted polyethylene is 0.8%~1.0%.

3. The bimetallic steel-reinforced polyethylene composite pipe according to claim 1, characterized in that, The polyethylene is high-density polyethylene, and the density of the high-density polyethylene is 930~965 kg / m³. 3 .

4. The bimetallic steel-reinforced polyethylene composite pipe according to claim 1, characterized in that, The antistatic and flame-retardant masterbatch has an antistatic property of ≤1×10⁻⁶. 6 For Ω-type alcohol torches, the maximum single burning time for flame-emitting combustion is ≤10s, and the maximum single burning time for flameless combustion is ≤60s.

5. The bimetallic steel-reinforced polyethylene composite pipe according to claim 1, characterized in that, The antioxidant includes one or more of antioxidant 168, antioxidant 1010, and antioxidant 626.

6. The bimetallic steel-reinforced polyethylene composite pipe according to claim 1, characterized in that, The raw material for the steel skeleton reinforcement layer includes reinforcing strips, which may include fiber reinforcement strips, steel wire reinforcement strips, or steel cord reinforcement strips. The raw materials for the first and second bonding resin layers each independently include bonding resins, and the bonding resins satisfy the following condition: density ≥ 0.940 g / cm³. 3 The melt flow rate at 190℃ and 5kg is ≥1.5g / 10min, the Vicat softening point is ≥120℃, and the elongation at break is ≥500%.

7. A bimetallic steel-reinforced polyethylene composite pipe according to claim 6, characterized in that, The number of layers in the wire winding reinforcement layer and the second adhesive resin layer is the same, and the number of layers in both is ≥2.

8. A method for preparing a bimetallic steel-reinforced polyethylene composite pipe according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1. After blending the raw materials for the polyethylene inner layer, the mixture is extruded, shaped, and cooled to obtain the first polyethylene inner layer. S2. A reinforcing strip is wound around the outer wall of the first polyethylene inner layer to obtain a steel skeleton reinforcing layer. Adhesive resin is coated on the surface of the steel skeleton reinforcing layer and cured to obtain a first adhesive resin layer. Steel wire is wound around the first adhesive resin layer to obtain a steel wire wound reinforcing layer. Adhesive resin is then coated on the surface of the steel wire wound reinforcing layer and cured to obtain a second adhesive resin layer, forming a bimetallic steel skeleton reinforcing layer. S3. The raw materials for the outer layer of polyethylene are blended, extruded, and coated on the outside of the bimetallic steel skeleton reinforcement layer. After cooling, a bimetallic steel skeleton polyethylene composite pipe is obtained.

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