Composite polyvinyl chloride pipe and production method thereof

Abstract

The invention provides a composite polyvinyl chloride pipe and a production method thereof, and relates to the technical field of pipes. The composite polyvinyl chloride pipe comprises an inner layer and an outer layer, the inner layer is located inside the outer layer, the inner layer is a modified polyethylene layer, the outer layer is a modified polyvinyl chloride layer, and the modified polyethylene layer is composed of a first raw material component containing polyethylene, a first filler and maleic anhydride modified polyethylene. And the modified polyvinyl chloride layer is composed of a second raw material component containing polyvinyl chloride, a second filler, polyether amine and a heat stabilizer. According to the composite polyvinyl chloride pipe disclosed by the invention, a chemical reaction is generated on an interlayer interface between the inner layer and the outer layer, so that the interface between the inner layer and the outer layer has relatively good bonding strength.

Description

Technical Field

[0001] The invention belongs to the technical field of pipes and relates to a composite polyvinyl chloride pipe and a production method thereof. Background Art

[0002] Polyvinyl chloride is a commonly used pipe material with the characteristics of high strength, low cost and strong corrosion resistance. However, due to the addition of a small amount of additives to polyvinyl chloride during the molding process and the decomposition of polyvinyl chloride to produce hydrogen chloride, polyvinyl chloride pipes are not suitable for use in water supply systems with a conveying temperature higher than 45°C. Polyethylene has the characteristics of low surface tension and good chemical stability, but its strength is not as good as polyvinyl chloride. Therefore, combining the characteristics of polyvinyl chloride and polyethylene to prepare composite pipes can play to their strengths and avoid their weaknesses, give full play to the characteristics of the two materials, and make the performance of the pipe better. However, the surface tension of polyethylene is low, and the surface tension of polyvinyl chloride is high. The surface tension of the two polymers is quite different and the compatibility is poor. In addition, the chemical inertness of polyethylene is high, resulting in the interface of polyethylene and polyvinyl chloride not being well compatible when the co-extrusion molding process is used, the interface bonding strength is low, and the performance of the composite pipe formed does not meet expectations, or during the use of the composite pipe, the interface compatibility of the two materials becomes worse and worse, and even separation occurs, affecting the use and safety of the pipe.

[0003] Therefore, for composite pipes composed of polyethylene and polyvinyl chloride, improving the interfacial bonding strength between polyethylene and polyvinyl chloride is of great significance for practical applications. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a composite polyvinyl chloride pipe and a production method thereof.

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

[0006] A composite polyvinyl chloride pipe comprises an inner layer (1) and an outer layer (2), wherein the inner layer (1) is a modified polyethylene layer and the outer layer (2) is a modified polyvinyl chloride layer.

[0007] Preferably, the average thickness of the inner layer (1) is (0.1-5) times the average thickness of the outer layer (2).

[0008] Preferably, the modified polyethylene layer is composed of a first raw material component comprising polyethylene, a first filler and maleic anhydride modified polyethylene.

[0009] More preferably, the weight ratio of the polyethylene, the first filler and the maleic anhydride modified polyethylene is 100:(0-30):(0.5-5).

[0010] More preferably, the polyethylene is selected from one or a combination of high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene and ultra-high molecular weight polyethylene.

[0011] More preferably, the first filler is surface-modified using an epoxy silane coupling agent.

[0012] Preferably, the modified polyvinyl chloride layer is composed of a second raw material component comprising polyvinyl chloride, a second filler, polyether amine and a heat stabilizer.

[0013] More preferably, the weight percentage of the polyvinyl chloride, the second filler, the polyetheramine and the thermal stabilizer is 100:(0-20):(2-10):(0.5-3).

[0014] More preferably, the average functionality of the polyetheramine is not less than 2.3.

[0015] A method for producing a composite polyvinyl chloride pipe according to any one of the above technical solutions comprises the following steps:

[0016] S1. preparing the raw material components of the modified polyethylene layer and the raw material components of the modified polyvinyl chloride layer respectively;

[0017] S2, preparing the raw material components of the modified polyethylene layer and the raw material components of the modified polyvinyl chloride layer in step S1 into modified polyethylene masterbatch and modified polyvinyl chloride masterbatch respectively;

[0018] S3, using a double-layer co-extrusion molding process to co-extrude the modified polyethylene masterbatch and the modified polyvinyl chloride masterbatch in step S2 into a composite pipe.

[0019] The beneficial effects of the present invention are:

[0020] (1) The present invention adds maleic anhydride-modified polyethylene to the modified polyethylene layer of the inner layer, and the maleic anhydride-modified polyethylene has good compatibility with polyethylene; and adds polyetheramine to the modified polyvinyl chloride layer of the outer layer, and the polyetheramine is a plasticizer for polyvinyl chloride, which improves the processing performance of polyvinyl chloride. Moreover, at the interface between the inner layer and the outer layer, the anhydride group of the maleic anhydride-modified polyethylene and the amino group of the polyetheramine can chemically react during co-extrusion molding, so that the compatibility of the inner layer and the outer layer is greatly improved, and the interface bonding strength is significantly increased.

[0021] (2) In the present invention, the first filler in the inner layer is further surface-modified with an epoxy silane coupling agent, so that the surface of the first filler is grafted with abundant epoxy groups. When the composite pipe is co-extruded, at the interface between the inner layer and the outer layer, the polyether amine can also react with the epoxy groups, and the carboxyl groups generated by the reaction of the polyether amine and maleic anhydride grafted polyethylene can also react with the epoxy groups. Therefore, there are multiple chemical cross-linking reactions at the interface, and the formed cross-linking networks have cross-linking and entanglement effects, which further enhances the compatibility and interfacial bonding strength of the inner layer and the outer layer of the composite pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Attached Figure 1 It is a schematic structural diagram of the composite polyvinyl chloride pipe of the present invention.

[0023] 1-Inner layer, 2-Outer layer. DETAILED DESCRIPTION

[0024] The technical solution of the present invention is further illustrated and described below through specific implementation methods.

[0025] In one aspect, the present invention provides a composite polyvinyl chloride pipe, comprising an inner layer (1) and an outer layer (2), wherein the inner layer (1) is a modified polyethylene layer, and the outer layer (2) is a modified polyvinyl chloride layer. In the composite polyvinyl chloride pipe of the present invention, the inner layer is a modified polyethylene layer, which has high chemical inertness and high safety, and the outer layer is a modified polyvinyl chloride layer, which has high strength and good corrosion resistance. Therefore, the composite polyvinyl chloride pipe of the present invention can be used in a water supply system. In the composite polyvinyl chloride pipe of the present invention, there is no restriction on the outer diameter and inner diameter of the pipe, such as an outer diameter of 2 cm and an inner diameter of 1 cm, an outer diameter of 3 cm and an inner diameter of 1 cm, an outer diameter of 5 cm and an inner diameter of 2 cm, an outer diameter of 10 cm and an inner diameter of 7 cm, etc.

[0026] In a preferred embodiment of the present invention, the average thickness of the inner layer (1) is (0.1-5) times the average thickness of the outer layer (2). In the composite polyvinyl chloride pipe of the present invention, the average thickness of the inner layer (1) and the average thickness of the outer layer (2) are not particularly limited. For example, the average thickness of the inner layer (1) can be 0.1 times, 0.3 times, 0.5 times, 1 times, 1.5 times, 2 times, 2.5 times, 3 times, 3.4 times, 4 times, 4.6 times, 5 times, etc., the average thickness of the outer layer (2).

[0027] In a preferred embodiment of the present invention, the modified polyethylene layer is composed of a first raw material component including polyethylene, a first filler and maleic anhydride modified polyethylene. In the present invention, in order to solve the compatibility problem between the polyethylene layer and the polyvinyl chloride layer, maleic anhydride modified polyethylene is added to the polyethylene layer. The maleic anhydride modified polyethylene has good compatibility with polyethylene and can help the dispersion of the first filler in polyethylene, thereby improving the compatibility and dispersibility of the first filler in polyethylene. In addition, the maleic anhydride group in the maleic anhydride modified polyethylene can react chemically with the amino group of the polyetheramine in the modified polyvinyl chloride layer of the outer layer at the interface between the inner layer and the outer layer, thereby increasing the bonding strength at the interface between the inner layer and the outer layer.

[0028] In the present invention, the first raw material component may further include a lubricant, such as stearic acid amide, zinc stearate, pentaerythritol stearate, etc., and may also include a pigment, such as ultramarine, carbon black, chrome yellow, phthalocyanine blue, phthalocyanine green, etc.

[0029] In the present invention, the first filler is not particularly limited, and can be an inorganic filler such as wollastonite, solid glass microspheres, hollow glass microspheres, talc, heavy calcium carbonate, light calcium carbonate, titanium dioxide, silicon dioxide, kaolin, etc. The average particle size of the first filler is not particularly limited, and can be (0.1-10) μm, or further, the average particle size can be (0.5-5) μm. The grafting rate of maleic anhydride in the maleic anhydride modified polyethylene can be (0.2-1.5) wt%, and the melt index (190°C, 2.16 kg) can be (1-20) g / 10 min.

[0030] In a more preferred embodiment of the present invention, the weight ratio of polyethylene, the first filler and the maleic anhydride modified polyethylene is 100:(0-30):(0.5-5). For example, the weight ratio of polyethylene, the first filler and the maleic anhydride modified polyethylene can be 100:0:1 (the first filler is not added at this time), 100:10:2, 100:20:3, 100:30:4, 100:15:5, 100:20:2, etc., without special restrictions.

[0031] In a more preferred embodiment of the present invention, polyethylene is selected from one or more combinations of high density polyethylene (HDPE), medium density polyethylene (MDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE) and ultra high molecular weight polyethylene (HMWPE). Further, polyethylene can be selected from HDPE, MDPE or HMWPE.

[0032] In a more preferred embodiment of the present invention, the first filler is surface-modified with an epoxy silane coupling agent. The first filler is surface-modified with an epoxy silane coupling agent, which can increase the compatibility of the first filler with polyethylene, and can also chemically react with the amino group in the polyetheramine of the outer layer through the epoxy group, and can also chemically react with the carboxyl group produced by the reaction of the amino group of the polyetheramine and the acid anhydride of the maleic anhydride-modified polyethylene, thereby further enhancing the interfacial bonding strength between the inner layer and the outer layer. Therefore, in the present invention, there are multiple chemical reactions at the interface of the inner layer and the outer layer, including the ring-opening reaction of the amino group with the acid anhydride, the ring-opening reaction of the amino group with the epoxy group, the ring-opening reaction of the carboxyl group with the epoxy group, etc., so that the compatibility and bonding strength of the inner layer and the outer layer are further improved.

[0033] It is a common practice in the art to modify the surface of the first filler using an epoxy silane coupling agent. The epoxy silane coupling agent can be 3-glycidyloxypropyltrimethoxysilane (KH-560), 3-glycidyloxypropyltriethoxysilane (KH-561), 3-glycidyloxypropylmethyldimethoxysilane (KH-564), 3-glycidyloxypropylmethyldiethoxysilane (KH-563), β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (A-186), β-(3,4-epoxycyclohexyl)ethyltriethoxysilane (A-1861), etc., without special restrictions. A specific surface modification method is exemplified as follows: add 1 mol / L hydrochloric acid solution to 1 L of an alcohol-water solution composed of anhydrous ethanol and water in a volume ratio of 9:1, adjust the pH to 3-3.5, add 50 g of KH-560 silane coupling agent, stir for half an hour, and obtain a hydrolyzate; add 100 g of the first filler to the above hydrolyzate, ultrasonically disperse for 5 minutes, stir at room temperature for 2 hours, collect the solid, wash the solid twice with anhydrous ethanol and once with deionized water, and dry at 60°C overnight.

[0034] In a preferred embodiment of the present invention, the modified polyvinyl chloride layer is composed of a second raw material component comprising polyvinyl chloride, a second filler, a polyetheramine and a heat stabilizer. In the present invention, polyetheramine is added to the modified polyvinyl chloride layer of the outer layer. The polyetheramine can be used as a plasticizer for polyvinyl chloride to improve the processability of polyvinyl chloride, and the amino group of the polyetheramine can be used to react with the anhydride group (or epoxy group) in the modified polyethylene of the inner layer, thereby generating one or more chemical reactions at the interface between the inner layer and the outer layer, thereby improving the bonding strength at the interface. In the present invention, the second filler is not particularly limited, and can be an inorganic filler such as wollastonite, talc, heavy calcium carbonate, light calcium carbonate, titanium dioxide, solid glass microspheres, hollow glass microspheres, silicon dioxide, kaolin, etc. The average particle size of the second filler is not particularly limited, and can be (0.1-10) μm, or further, the average particle size can be (0.5-5) μm. The heat stabilizer is not particularly limited, and can be a barium zinc stabilizer, a calcium zinc stabilizer, an organic tin stabilizer, etc. In the present invention, the average molecular weight of the polyetheramine is not particularly limited, and may be (200-6000), or further, the average molecular weight may be (600-5000).

[0035] In the present invention, the second raw material component may also include lubricants, antioxidants, pigments, etc., such as polyethylene wax, oxidized polyethylene wax, oleic acid amide, stearic acid amide, zinc stearate, antioxidant 1010, antioxidant 168, etc.

[0036] In a more preferred embodiment of the present invention, the weight percentage of polyvinyl chloride, the second filler, polyetheramine and the heat stabilizer is 100:(0-20):(2-10):(0.5-3). For example, the weight percentage of polyvinyl chloride, the second filler, polyetheramine and the heat stabilizer can be 100:0:5:1 (the second filler is not added in this case), 100:10:10:1.5, 100:20:10:2, 100:15:7:1, etc.

[0037] In a more preferred embodiment of the present invention, the average functionality of the polyetheramine is not less than 2.3. Polyetheramine is also called amino-terminated polyether, and the most common ones are polyetheramines with a functionality of 2 (one polyetheramine molecule contains two primary amino groups, which is a functionality of 2) and polyetheramines with a functionality of 3 (one polyetheramine molecule contains three primary amino groups, which is a functionality of 3). In general, the more amino groups there are in the molecular structure of the polyetheramine, the higher the activity. In order to make the interfacial reaction activity of the inner layer and the outer layer higher, in the present invention, the average functionality of the polyetheramine is not less than 2.3, and further, the average functionality of the polyetheramine is not higher than 3. For example, the average functionality of the polyetheramine can be 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, etc. Of course, the average functionality of the polyetheramine of the present invention can also be lower than 2.3, but the reaction activity will be relatively poor. Under the same other conditions, the reaction at the interface will be relatively less, and the bonding strength of the interface will be relatively low, but it is still higher than the bonding strength when no chemical reaction occurs at the interface. Specifically, in the present invention, the polyetheramine can be composed of a polyetheramine with a functionality of 2 and a polyetheramine with a functionality of 3 in a certain molar ratio, such as a polyetheramine with a functionality of 2.5 can be composed of a polyetheramine with a functionality of 2 and a polyetheramine with a functionality of 3 in a molar ratio of 1:1. For example, the polyetheramine can be T403 (3 functionality), D2000 (2 functionality), D230 (2 functionality), D400 (2 functionality), FL1000 (2 functionality), etc.

[0038] Another aspect of the present invention provides a method for producing the composite polyvinyl chloride pipe according to any one of the above technical solutions, comprising the following steps:

[0039] S1. preparing the raw material components of the modified polyethylene layer and the raw material components of the modified polyvinyl chloride layer respectively;

[0040] S2, preparing the various raw material components of the modified polyethylene layer and the various raw material components of the modified polyvinyl chloride layer in step S1 into modified polyethylene masterbatch and modified polyvinyl chloride masterbatch respectively; the modified polyethylene masterbatch and the modified polyvinyl chloride masterbatch can be prepared by a single-screw extrusion method or a twin-screw extrusion method;

[0041] S3, co-extrude the modified polyethylene masterbatch and the modified polyvinyl chloride masterbatch in step S2 into a composite pipe by a double-layer co-extrusion molding process. The melting temperature of the modified polyethylene masterbatch can be controlled at (180-220)°C, the melting temperature of the modified polyvinyl chloride masterbatch can be controlled at (170-190)°C, and the co-extrusion die temperature can be controlled at (170-180)°C.

[0042] The technical scheme of the present invention is further described and illustrated below according to various embodiments. Unless otherwise specified, the parts in the following preparation examples and embodiments are parts by weight.

[0043] Preparation Example 1-3 Preparation of modified polyethylene masterbatch

[0044] Preparation Example 1

[0045] 100 parts of high-density polyethylene (melt index of 3 g / 10 min at 190°C and 2.16 kg) and 2 parts of maleic anhydride-modified polyethylene (melt index of 6 g / 10 min at 190°C and 2.16 kg, maleic anhydride grafting rate of 0.8%) were mixed and added to a twin-screw extruder. The melting temperature was (180-210)°C and the extrusion temperature was (170-180)°C for granulation to obtain modified polyethylene masterbatch.

[0046] Preparation Example 2

[0047] 100 parts of high-density polyethylene of Preparation Example 1, 20 parts of kaolin with an average particle size of 1.2 μm and 2 parts of maleic anhydride-modified polyethylene of Preparation Example 1 were mixed and added into a twin-screw extruder. The melting temperature was (180-210)°C and the extrusion temperature was (170-180)°C for granulation to obtain modified polyethylene masterbatch.

[0048] Preparation Example 3

[0049] The kaolin in Preparation Example 2 was surface treated with KH-560 in advance to obtain epoxy-modified kaolin.

[0050] The difference between Preparation Example 3 and Preparation Example 2 is that the kaolin in Preparation Example 2 is replaced by an equal weight of the above epoxy-modified kaolin. The other steps remain unchanged.

[0051] Preparation Example 4-6 Preparation of modified polyvinyl chloride masterbatch

[0052] Preparation Example 4

[0053] 100 parts of polyvinyl chloride (weight average molecular weight 90,000), 6 parts of polyetheramine (composed of polyetheramine D2000 and polyetheramine T403 in a molar ratio of 1:1) and 1.5 parts of barium zinc stabilizer are mixed and added into a twin-screw extruder. The melting temperature is (160-190)°C and the extrusion temperature is (170-180)°C for granulation to obtain modified polyvinyl chloride masterbatch.

[0054] Preparation Example 5

[0055] 100 parts of polyvinyl chloride (weight average molecular weight 80,000), 10 parts of kaolin with an average particle size of 1 μm, 6 parts of the polyetheramine of Preparation Example 4 and 1.5 parts of barium zinc stabilizer were mixed and added to a twin-screw extruder. The melting temperature was (160-190)°C and the extrusion temperature was (170-180)°C for granulation to obtain modified polyvinyl chloride masterbatch.

[0056] Preparation Example 6

[0057] 100 parts of polyvinyl chloride (weight average molecular weight 110,000), 20 parts of kaolin with an average particle size of 1 μm, 5 parts of polyetheramine (composed of polyetheramine D230, polyetheramine D2000 and polyetheramine T403 in a molar ratio of 1:1:3), 1.5 parts of barium zinc stabilizer, 1 part of polyethylene wax, 1 part of anti-aging agent 1010 and 1 part of oleic acid amide are mixed and added into a twin-screw extruder, and granulation is carried out at a melting temperature of (160-190)°C and an extrusion temperature of (170-180)°C to obtain a modified polyvinyl chloride masterbatch.

[0058] Example 1

[0059] The modified polyethylene masterbatch of Preparation Example 1 and the modified polyvinyl chloride masterbatch of Preparation Example 4 were co-extruded into a composite pipe with an inner layer of a modified polyethylene layer and an outer layer of a modified polyvinyl chloride layer using a double-layer co-extrusion molding process. The structure of the composite pipe is shown in the attached figure. Figure 1 shown.

[0060] The melting temperature of the modified polyethylene masterbatch is (180-220)°C, the melting temperature of the modified polyvinyl chloride masterbatch is (170-190)°C, and the co-extrusion die temperature is (170-180)°C.

[0061] The inner diameter of the composite pipe is 2 cm, the inner layer thickness is 2 mm, and the outer layer thickness is 8 mm.

[0062] Example 2

[0063] The difference between Example 2 and Example 1 is that the modified polyethylene masterbatch of Preparation Example 1 in Example 1 is replaced by an equal weight of the modified polyethylene masterbatch of Preparation Example 2. The other steps remain unchanged.

[0064] Example 3

[0065] The difference between Example 3 and Example 1 is that the modified polyethylene masterbatch of Preparation Example 1 in Example 1 is replaced by an equal weight of the modified polyethylene masterbatch of Preparation Example 3. The other steps remain unchanged.

[0066] Example 4

[0067] The modified polyethylene masterbatch of Preparation Example 2 and the modified polyvinyl chloride masterbatch of Preparation Example 5 were co-extruded into a composite pipe with an inner layer of a modified polyethylene layer and an outer layer of a modified polyvinyl chloride layer using a double-layer co-extrusion molding process. The co-extrusion molding process was the same as that of Example 1.

[0068] The inner diameter of the tube is 2 cm, the inner layer thickness is 1 mm, and the outer layer thickness is 8 mm.

[0069] Example 5

[0070] The difference between Example 5 and Example 4 is that the modified polyethylene masterbatch of Preparation Example 2 in Example 4 is replaced by an equal weight of the modified polyethylene masterbatch of Preparation Example 3. The other steps remain unchanged.

[0071] Example 6

[0072] The modified polyethylene masterbatch of Preparation Example 2 and the modified polyvinyl chloride masterbatch of Preparation Example 6 were co-extruded into a composite pipe with an inner layer of a modified polyethylene layer and an outer layer of a modified polyvinyl chloride layer using a double-layer co-extrusion molding process. The co-extrusion molding process is the same as the co-extrusion molding process of Example 1.

[0073] The inner diameter of the pipe is 4cm, the inner layer thickness is 4mm, and the outer layer thickness is 4mm.

[0074] Example 7

[0075] The difference between Example 7 and Example 6 is that the modified polyethylene masterbatch of Preparation Example 2 in Example 6 is replaced by an equal weight of the modified polyethylene masterbatch of Preparation Example 3. The other steps remain unchanged.

[0076] Example 8

[0077] 100 parts of polyvinyl chloride, 6 parts of polyetheramine (composed of polyetheramine D2000 and polyetheramine T403 in a molar ratio of 4:1) and 1.5 parts of barium zinc stabilizer are mixed and added into a twin-screw extruder. The melting temperature is (160-190)°C and the extrusion temperature is (170-180)°C for granulation to obtain modified polyvinyl chloride masterbatch.

[0078] The modified polyethylene masterbatch of Preparation Example 1 and the modified polyvinyl chloride masterbatch are co-extruded into a composite pipe with an inner layer of a modified polyethylene layer and an outer layer of a modified polyvinyl chloride layer by a double-layer co-extrusion molding process. The co-extrusion molding process is the same as the co-extrusion molding process of Example 1.

[0079] The inner diameter of the pipe is 2cm, the inner layer thickness is 2mm, and the outer layer thickness is 8mm.

[0080] Comparative Example 1

[0081] The difference between Comparative Example 1 and Example 1 is that the modified polyethylene masterbatch of Preparation Example 1 is replaced by an equal weight of high-density polyethylene in Preparation Example 1, and the modified polyvinyl chloride masterbatch of Preparation Example 4 is replaced by an equal weight of polyvinyl chloride in Preparation Example 4. The remaining steps remain unchanged.

[0082] Comparative Example 2

[0083] The difference between Comparative Example 2 and Example 1 is that the modified polyethylene masterbatch in Preparation Example 1 is replaced by an equal weight of high-density polyethylene in Preparation Example 1. The remaining steps remain unchanged.

[0084] Comparative Example 3

[0085] The difference between Comparative Example 3 and Example 1 is that the modified polyvinyl chloride masterbatch in Preparation Example 4 is replaced by an equal weight of polyvinyl chloride in Preparation Example 4. The remaining steps remain unchanged.

[0086] Comparative Example 4

[0087] The difference between Comparative Example 4 and Example 1 is that the modified polyvinyl chloride masterbatch of Preparation Example 4 is replaced by an equal weight of polyvinyl chloride masterbatch prepared by the following method. The other steps remain unchanged.

[0088] Preparation method of polyvinyl chloride masterbatch: 100 parts of polyvinyl chloride (weight average molecular weight 90,000), 6 parts of TOTM plasticizer, 10 parts of amino-modified kaolin with an average particle size of 1 μm and 1.5 parts of barium zinc stabilizer are mixed and added into a twin-screw extruder, the melting temperature is (160-190) ° C, the extrusion temperature is (170-180) ° C for granulation, and modified polyvinyl chloride masterbatch is obtained.

[0089] The preparation method of amino-modified kaolin is as follows: 50 g of 3-aminopropyltrimethoxysilane is added to 1 L of an alcohol-water solution composed of anhydrous ethanol and water in a volume ratio of 9:1, and the mixture is stirred for half an hour to obtain a hydrolyzate; 100 g of kaolin is added to the above hydrolyzate, ultrasonically dispersed for 5 minutes, stirred at room temperature for 2 hours, solids are collected, and the solids are washed twice with anhydrous ethanol and once with deionized water, and dried at 60°C overnight.

[0090] Performance Testing

[0091] According to the combination of the modified polyethylene masterbatch (or polyethylene) and the modified polyvinyl chloride masterbatch (or polyvinyl chloride) of the above-mentioned Examples 1-8 and Comparative Examples 1-4 respectively (for example, Example 1 is a combination of the modified polyethylene masterbatch of Preparation Example 1 and the modified polyvinyl chloride masterbatch of Preparation Example 4), a co-extrusion molding process is adopted to prepare a double-layer composite sheet with a lower layer of a modified polyethylene layer (or polyethylene layer) with a thickness of 0.8 mm and an upper layer of a modified polyvinyl chloride layer (or polyvinyl chloride layer) with a thickness of 0.8 mm.

[0092] Conventional interlayer peeling strength test: The prepared double-layer composite sheets are placed at room temperature for 24 hours, and the interlayer peeling strength of each of the double-layer composite sheets is tested using a peeling strength tester.

[0093] Thermal shock test: The prepared double-layer composite sheet was placed at room temperature for 24 hours, and then placed in a thermal shock test chamber with a humidity of 70%. The test cycle was 80°C × 4 hours and -30°C × 4 hours, and continued for 50 cycles. The interlayer peel strength was then tested according to the above method.

[0094] The results are shown in Table 1 below.

[0095] Table 1 Peel strength test results

[0096]

[0097] Therefore, according to the data results in Table 1 above, it can be seen that the composite pipe of the present invention has good interlayer peeling strength, the bonding strength between the inner modified polyethylene layer and the outer modified polyvinyl chloride layer is high, and the stability is good, and it still has a high interlayer peeling strength after the hot and cold shock test.

[0098] As described above, the basic principles, main features and advantages of the present invention are shown and described. Those skilled in the art should understand that the present invention is not limited by the above embodiments, which are only preferred embodiments of the present invention and cannot be used to limit the scope of the present invention. That is, equivalent changes and modifications made according to the scope of the present invention and the content of the specification should still be within the scope of the present invention. The scope of protection required by the present invention is defined by the attached claims and their equivalents.

Claims

1. A composite polyvinyl chloride pipe, It is characterized in that It comprises an inner layer and an outer layer, wherein the inner layer is a modified polyethylene layer, and the outer layer is a modified polyvinyl chloride layer.

2. The composite polyvinyl chloride pipe according to claim 1, It is characterized in that The average thickness of the inner layer is (0.1-5) times the average thickness of the outer layer.

3. The composite polyvinyl chloride pipe according to claim 1, It is characterized in that The modified polyethylene layer is composed of a first raw material component including polyethylene, a first filler and maleic anhydride modified polyethylene.

4. The composite polyvinyl chloride pipe according to claim 3, It is characterized in that The weight ratio of the polyethylene, the first filler and the maleic anhydride modified polyethylene is 100:(0-30):(0.5-5).

5. The composite polyvinyl chloride pipe according to claim 3, It is characterized in that The polyethylene is selected from one or a combination of high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene and ultra-high molecular weight polyethylene.

6. The composite polyvinyl chloride pipe according to claim 3, It is characterized in that The first filler is surface-modified with an epoxy silane coupling agent.

7. The composite polyvinyl chloride pipe according to claim 1, It is characterized in that The modified polyvinyl chloride layer is composed of a second raw material component including polyvinyl chloride, a second filler, polyether amine and a heat stabilizer.

8. The composite polyvinyl chloride pipe according to claim 7, It is characterized in that The weight percentage of the polyvinyl chloride, the second filler, the polyetheramine and the thermal stabilizer is 100:(0-20):(2-10):(0.5-3).

9. The composite polyvinyl chloride pipe according to claim 7, It is characterized in that The average functionality of the polyetheramine is not less than 2.

3.

10. The method for producing the composite polyvinyl chloride pipe according to any one of claims 1 to 9, It is characterized in that The following steps are involved: S1. preparing the raw material components of the modified polyethylene layer and the raw material components of the modified polyvinyl chloride layer respectively; S2, preparing the raw material components of the modified polyethylene layer and the raw material components of the modified polyvinyl chloride layer in step S1 into modified polyethylene masterbatch and modified polyvinyl chloride masterbatch respectively; S3, using a double-layer co-extrusion molding process to co-extrude the modified polyethylene masterbatch and the modified polyvinyl chloride masterbatch in step S2 into a composite pipe.

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