A PEX-a pipe and preparation method thereof

Abstract

The present invention discloses a PEX-a pipe and a preparation method thereof, and relates to the technical field of plastic pipes. A PEX-a pipe comprises the following raw material components in weight percentage: 0.9-1.5% cross-linking agent; 0.4-0.6% antioxidant; 0.4-0.6% anti-UV auxiliary agent; 0.2-0.9% color powder; 0.5-3% auxiliary cross-linking agent; 0.1-0.3% dispersant; the balance is high-density polyethylene; the cross-linking agent comprises 2,5-dimethyl-2,5-di(tert-butylperoxide)hexyne-3 and di-tert-butyl peroxide, and the weight ratio of the two is (2-5): (1-5). The present invention improves the cross-linking efficiency by compounding the cross-linking agent, so that the PEX-a pipe has excellent cross-linking degree and good chlorine resistance and UV resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of plastic pipes, and in particular to a PEX-a pipe and a preparation method thereof. Background Art

[0002] As a new type of green plastic pipe, cross-linked polyethylene (PEX) pipe has excellent sanitation, high temperature resistance, corrosion resistance, creep resistance, environmental stress cracking resistance and slow crack growth resistance. Peroxide cross-linked polyethylene (PEX-a) pipe is a special high-density polyethylene (HDPE) that undergoes oxidation cross-linking during the extrusion process to form a three-dimensional network of thermosetting macromolecules and is extruded. The production of PEX-a pipes has the characteristics of simple equipment, easy control of the extrusion process and uniform pipe quality. PEX pipe special materials have the characteristics of narrow relative molecular weight distribution (MWD), uniform particle size distribution and low oligomer content.

[0003] Plastic pipes have the advantages of energy saving and environmental protection, light weight and high strength, corrosion resistance, smooth inner wall without scaling, simple construction and maintenance, and long service life. They are widely used in construction and municipal water supply and drainage, gas, heating and other fields. The design service life of plastic pipes is generally 50 years, and the aging resistance test generally only considers the thermal oxidation aging environment of the pipes. However, in the actual use environment of the pipes, the water transported may be disinfected with liquid chlorine, chlorine dioxide, chloramines, etc. The disinfectant reacts with water to produce hypochlorous acid with strong oxidizing properties. While killing bacteria, it also has a strong oxidizing effect on the pipes, which will greatly shorten the service life of the pipes. At present, in order to improve the chlorine resistance of polyethylene plastic pipes, the amount of antioxidants will be increased. However, for peroxide cross-linked polyethylene, antioxidants will capture the free radicals generated by the decomposition of peroxide cross-linking agents, thereby reducing the cross-linking efficiency of the product. Too low cross-linking will reduce the pressure resistance of the pipes.

[0004] Therefore, peroxide cross-linked polyethylene pipes must have excellent cross-linking degree and good chlorine resistance, which is an urgent problem to be solved. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a PEX-a pipe and a preparation method thereof. The present invention improves the cross-linking efficiency by compounding a cross-linking agent, so that the PEX-a pipe has excellent cross-linking degree and good chlorine resistance and UV resistance.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] In a first aspect, the present invention provides a PEX-a pipe comprising the following raw material components in weight percentage:

[0008] Cross-linking agent 0.9-1.5%; antioxidant 0.4-0.6%; anti-UV additive 0.4-0.6%; color powder 0.2-0.9%; auxiliary cross-linking agent 0.5-3%; dispersant 0.1-0.3%; the balance is high-density polyethylene; the total weight percentage is 100%;

[0009] The cross-linking agent includes 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3-ol and di-tert-butyl peroxide (DTBP), and the weight ratio of the 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3-ol and di-tert-butyl peroxide is (2-5):(1-5).

[0010] In the present invention, as the content of the crosslinking agent increases, the number of free radicals generated by the decomposition of the crosslinking agent increases rapidly, and then the number of HDPE molecules participating in the crosslinking reaction gradually increases, increasing the probability of entanglement and crosslinking between the molecular chains, so the degree of crosslinking increases rapidly; but when the crosslinking agent reaches a certain content, the increase in the degree of crosslinking gradually slows down or even decreases. If there is too much crosslinking agent, the molecular chains inside the pipe gradually form a three-dimensional network structure by crosslinking from a one-dimensional linear structure, thereby hindering the free movement of other crosslinked HDPE molecules, thereby reducing the crosslinking efficiency. If there is too little crosslinking agent, the crosslinking efficiency of the product will decrease, which will reduce the pressure resistance of the pipe.

[0011] When the weight ratio of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3 and di-tert-butyl peroxide is within the above range, there is a synergistic promotion effect, but when the compounding ratio is too large, its promotion effect on the crosslinking degree of the pipe is gradually weakened. When the compounding ratio is too small, the crosslinking efficiency of the pipe is too low, which in turn affects the performance of the pipe. Therefore, the present invention is conducive to improving the crosslinking degree of the pipe by controlling the content of the crosslinking agent in the raw material and controlling the weight ratio of the compounded crosslinking agent, so that the pipe has excellent crosslinking degree and good chlorine resistance and UV resistance.

[0012] Preferably, the weight average molecular weight of the high-density polyethylene is 150,000-200,000, preferably 170,000.

[0013] Preferably, the high-density polyethylene has a melt index of 8-12 g / 10 min at 21.6 kg and 190° C.

[0014] Preferably, the PEX-a pipe further comprises 0.05-0.1% by weight of a fluorine-containing polymer.

[0015] The invention helps to reduce production energy consumption, improve product quality and production efficiency, improve product appearance and reduce apparent viscosity by adding fluorine-containing polymer.

[0016] Preferably, the fluorine-containing polymer is polyphosphoric acid (PPA).

[0017] Preferably, the PEX-a pipe comprises the following raw material components in weight percentage:

[0018] Cross-linking agent 1-1.2%; antioxidant 0.4-0.6%; anti-UV additive 0.4-0.6%; color powder 0.5-0.8%; fluorine-containing polymer 0.05-0.1%; auxiliary cross-linking agent 1-2%; dispersant 0.1-0.3%; the balance is high-density polyethylene.

[0019] Preferably, the weight ratio of the 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3 and di-tert-butyl peroxide is any one or both of the range values ​​of 1:1, 1:2, 2:1, 2:3, 2:5, 3:1, 3:2, 3:4, 3:5, 4:1, 4:3, 4:5, 5:1, 5:2, 5:3, 5:4.

[0020] More preferably, the weight ratio of the 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3-yl and di-tert-butyl peroxide is (2-3): (2-3).

[0021] Preferably, the antioxidant includes at least two of antioxidant DLTDP, antioxidant 1010, antioxidant 1076, antioxidant B277, antioxidant 1790, antioxidant 168, and antioxidant DSTDP.

[0022] More preferably, the antioxidant includes antioxidant 1076 and antioxidant DSTDP, and the weight ratio of the antioxidant 1076 to the antioxidant DSTDP is (1-5):1, and further preferably (2-4):1.

[0023] Preferably, the anti-UV additive includes at least two of UV-234, UV-329, UV-944, UV-622, and anti-UV additive HS-300.

[0024] More preferably, the anti-UV additive includes UV-329 and UV-944, and the weight ratio of UV-329 to UV-944 is (1-3):1, and further preferably (1-2):1.

[0025] Preferably, the toner is a high temperature resistant toner, and the high temperature resistant toner is CLARIANT Polysynthren Blue RLS.

[0026] Preferably, the auxiliary cross-linking agent is the cross-linking agent TAIC.

[0027] Preferably, the dispersant is pentaerythritol stearate (PETS).

[0028] In a second aspect, the present invention further provides a method for preparing a PEX-a pipe, comprising the following steps:

[0029] The components are mixed evenly in proportion, dried and melt-blended in an extruder to obtain PEX-a pipes.

[0030] Preferably, the screw of the extruder comprises a feeding section, a compression section and a homogenizing section, and the ratio of the sum of the lengths of the plum blossom patterns of the compression section and the homogenizing section to the length of the screw is (0.5-1):3.

[0031] Preferably, the aspect ratio of the screw is 30:1.

[0032] The invention is beneficial to improving the shear strength of the screw by designing the structure of the screw, achieving better dispersion and distribution effects, so that the masterbatch pigment can be evenly mixed with the raw materials, the coloring effect is good, and the produced polyethylene pipe has good appearance quality, the outer wall is bright without lines, the inner wall is smooth without fusion lines, and the end face has no appearance quality defects such as black spots.

[0033] Preferably, the process parameters of the extruder are: barrel zone 1: 155~175°C, barrel zone 2: 155~175°C, barrel zone 3: 140~155°C, barrel zone 4: 140~155°C; mold zone 1: 150~175°C, mold zone 2: 150~175°C, mold zone 3: 160~185°C.

[0034] Preferably, the extruder screw speed is 14±1 r / min; the extrusion volume is 100 kg / h, and the infrared furnace temperature is 240-280°C.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The cross-linked polyethylene pipe of the present invention has excellent properties such as sanitation, high temperature resistance, corrosion resistance, creep resistance, environmental stress cracking resistance and slow crack growth resistance. Under the premise of ensuring the chlorine resistance of the pipe, the cross-linking efficiency of the pipe is effectively improved by compounding the cross-linking agent, ensuring that the pipe has excellent mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 1 is a schematic diagram of the structure of the screw of the present invention, 1 is a feeding section, 2 is a compression section, and 3 is a homogenization section. DETAILED DESCRIPTION

[0038] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments, but the protection scope and implementation methods of the present invention are not limited thereto.

[0039] Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0040] Example 1

[0041] This embodiment discloses a PEX-a pipe, comprising the following raw material components in weight percentage:

[0042] Cross-linking agent 0.9%; antioxidant 0.5%; anti-UV additive 0.5%; color powder 0.5%; fluorine-containing polymer 0.05%; auxiliary cross-linking agent 1%; dispersant 0.2%; the balance is high-density polyethylene, and the total weight percentage is 100%.

[0043] The crosslinker is a mixture of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3-ol (Trigonox® 145) and di-tert-butyl peroxide (TRIGONOX B) in a weight ratio of 2:3.

[0044] The antioxidants include antioxidant 1076 and antioxidant DSTDP, and the weight ratio of the antioxidant 1076 to the antioxidant DSTDP is 4:1; the anti-UV additives include UV-329 and UV-944, and the weight ratio of UV-329 to UV-944 is 1:1; the color powder is CLARIANT Polysynthren Blue RLS; the fluorine-containing polymer is polyphosphoric acid; the co-crosslinking agent is crosslinking agent TAIC; and the dispersant is pentaerythritol stearate.

[0045] This embodiment also discloses a method for preparing a PEX-a pipe, comprising the following steps:

[0046] The components are mixed evenly in proportion, dried, melt-blended in an extruder, and extruded to obtain PEX-a pipes.

[0047] like Figure 1 As shown, the total length of the screw of the extruder is 3 m, the aspect ratio of the screw is 30:1, the screw includes a feeding section 1, a compression section 2 and a homogenizing section 3, and the sum of the plum blossom lengths of the compression section 2 and the homogenizing section 3 is 0.5 m.

[0048] The process parameters of the extruder are: barrel zone 1: 155~175℃, barrel zone 2: 155~175℃, barrel zone 3: 140~155℃, barrel zone 4: 140~155℃; mold zone 1: 150~175℃, mold zone 2: 150~175℃, mold zone 3: 160~185℃.

[0049] The extruder screw speed is 14±1 r / min; the extrusion capacity is 100kg / h, and the infrared furnace temperature is 240~280℃.

[0050] Example 2

[0051] A PEX-a pipe, which is different from Example 1 in that the cross-linking agent is compounded by 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3 and di-tert-butyl peroxide in a weight ratio of 3:2.

[0052] Example 3

[0053] A PEX-a pipe, which is different from Example 1 in that the cross-linking agent is compounded by 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3 and di-tert-butyl peroxide in a weight ratio of 5:1.

[0054] Example 4

[0055] A PEX-a pipe, which is different from Example 1 in that the PEX-a pipe comprises the following raw material components in weight percentage:

[0056] Cross-linking agent 1.2%; antioxidant 0.5%; anti-UV additive 0.5%; color powder 0.5%; fluorine-containing polymer 0.05%; auxiliary cross-linking agent 1%; dispersant 0.2%; the balance is high-density polyethylene, and the total weight percentage is 100%.

[0057] The cross-linking agent is prepared by compounding 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3 and di-tert-butyl peroxide in a weight ratio of 2:3.

[0058] Example 5

[0059] A PEX-a pipe, which is different from Example 1 in that the PEX-a pipe comprises the following raw material components in weight percentage:

[0060] Cross-linking agent 1.2%; antioxidant 0.5%; anti-UV additive 0.5%; color powder 0.5%; fluorine-containing polymer 0.05%; auxiliary cross-linking agent 1%; dispersant 0.2%; the balance is high-density polyethylene, and the total weight percentage is 100%.

[0061] The cross-linking agent is prepared by compounding 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3 and di-tert-butyl peroxide in a weight ratio of 3:2.

[0062] Example 6

[0063] A PEX-a pipe, which is different from Example 1 in that the PEX-a pipe comprises the following raw material components in weight percentage:

[0064] Cross-linking agent 1.2%; antioxidant 0.5%; anti-UV additive 0.5%; color powder 0.5%; fluorine-containing polymer 0.05%; auxiliary cross-linking agent 1%; dispersant 0.2%; the balance is high-density polyethylene, and the total weight percentage is 100%.

[0065] The cross-linking agent is prepared by compounding 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3 and di-tert-butyl peroxide in a weight ratio of 5:1.

[0066] Example 7

[0067] A PEX-a pipe, which is different from Example 1 in that the PEX-a pipe comprises the following raw material components in weight percentage:

[0068] Cross-linking agent 1.5%; antioxidant 0.5%; anti-UV additive 0.5%; color powder 0.5%; fluorine-containing polymer 0.05%; auxiliary cross-linking agent 1%; dispersant 0.2%; the balance is high-density polyethylene, and the total weight percentage is 100%.

[0069] The cross-linking agent is prepared by compounding 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3 and di-tert-butyl peroxide in a weight ratio of 2:3.

[0070] Example 8

[0071] A PEX-a pipe, which is different from Example 1 in that the PEX-a pipe comprises the following raw material components in weight percentage:

[0072] Cross-linking agent 1.5%; antioxidant 0.5%; anti-UV additive 0.5%; color powder 0.5%; fluorine-containing polymer 0.05%; auxiliary cross-linking agent 1%; dispersant 0.2%; the balance is high-density polyethylene, and the total weight percentage is 100%.

[0073] The cross-linking agent is prepared by compounding 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3 and di-tert-butyl peroxide in a weight ratio of 3:2.

[0074] Example 9

[0075] A PEX-a pipe, which is different from Example 1 in that the PEX-a pipe comprises the following raw material components in weight percentage:

[0076] Cross-linking agent 1.5%; antioxidant 0.5%; anti-UV additive 0.5%; color powder 0.5%; fluorine-containing polymer 0.05%; auxiliary cross-linking agent 1%; dispersant 0.2%; the balance is high-density polyethylene, and the total weight percentage is 100%.

[0077] The cross-linking agent is prepared by compounding 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3 and di-tert-butyl peroxide in a weight ratio of 5:1.

[0078] Comparative Example 1

[0079] A PEX-a pipe, which is different from Example 1 in that the PEX-a pipe comprises the following raw material components in weight percentage:

[0080] Cross-linking agent 0.6%; antioxidant 0.5%; anti-UV additive 0.5%; color powder 0.5%; fluorine-containing polymer 0.05%; auxiliary cross-linking agent 1%; dispersant 0.2%; the balance is high-density polyethylene, and the total weight percentage is 100%.

[0081] The cross-linking agent is prepared by compounding 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3 and di-tert-butyl peroxide in a weight ratio of 2:3.

[0082] Comparative Example 2

[0083] A PEX-a pipe, which is different from Example 1 in that the PEX-a pipe comprises the following raw material components in weight percentage:

[0084] Cross-linking agent 0.6%; antioxidant 0.5%; anti-UV additive 0.5%; color powder 0.5%; fluorine-containing polymer 0.05%; auxiliary cross-linking agent 1%; dispersant 0.2%; the balance is high-density polyethylene, and the total weight percentage is 100%.

[0085] The cross-linking agent is prepared by compounding 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3 and di-tert-butyl peroxide in a weight ratio of 3:2.

[0086] Comparative Example 3

[0087] A PEX-a pipe, which is different from Example 1 in that the PEX-a pipe comprises the following raw material components in weight percentage:

[0088] Cross-linking agent 0.6%; antioxidant 0.5%; anti-UV additive 0.5%; color powder 0.5%; fluorine-containing polymer 0.05%; auxiliary cross-linking agent 1%; dispersant 0.2%; the balance is high-density polyethylene, and the total weight percentage is 100%.

[0089] The cross-linking agent is prepared by compounding 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3 and di-tert-butyl peroxide in a weight ratio of 5:1.

[0090] Comparative Example 4

[0091] A PEX-a pipe, which is different from Example 1 in that the cross-linking agent only includes 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3.

[0092] Comparative Example 5

[0093] A PEX-a pipe, which is different from Example 1 in that the cross-linking agent only includes di-tert-butyl peroxide.

[0094] Comparative Example 6

[0095] A PEX-a pipe is different from Example 1 in that the cross-linking agent is compounded by 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3 and diisopropylbenzene peroxide in a weight ratio of 2:3.

[0096] Comparative Example 7

[0097] A PEX-a pipe, which is different from Example 1 in that the cross-linking agent is compounded by dicumyl peroxide and di-tert-butyl peroxide in a weight ratio of 2:3.

[0098] Comparative Example 8

[0099] A PEX-a pipe, which is different from Example 1 in that the PEX-a pipe comprises the following raw material components in weight percentage:

[0100] Cross-linking agent 0.9%; antioxidant 0.5%; anti-UV additive 0.5%; color powder 0.5%; fluorine-containing polymer 0.05%; auxiliary cross-linking agent 1%; dispersant 0.2%; the balance is high-density polyethylene, and the total weight percentage is 100%.

[0101] The cross-linking agent is prepared by compounding 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3 and di-tert-butyl peroxide in a weight ratio of 1:5.

[0102] Comparative Example 9

[0103] A PEX-a pipe, which is different from Example 1 in that the PEX-a pipe comprises the following raw material components in weight percentage:

[0104] Cross-linking agent 1.2%; antioxidant 0.5%; anti-UV additive 0.5%; color powder 0.5%; fluorine-containing polymer 0.05%; auxiliary cross-linking agent 1%; dispersant 0.2%; the balance is high-density polyethylene, and the total weight percentage is 100%.

[0105] The cross-linking agent is prepared by compounding 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3 and di-tert-butyl peroxide in a weight ratio of 1:5.

[0106] Comparative Example 10

[0107] A PEX-a pipe, which is different from Example 1 in that the PEX-a pipe comprises the following raw material components in weight percentage:

[0108] Cross-linking agent 1.5%; antioxidant 0.5%; anti-UV additive 0.5%; color powder 0.5%; fluorine-containing polymer 0.05%; auxiliary cross-linking agent 1%; dispersant 0.2%; the balance is high-density polyethylene, and the total weight percentage is 100%.

[0109] The cross-linking agent is prepared by compounding 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3 and di-tert-butyl peroxide in a weight ratio of 1:5.

[0110] Performance Testing

[0111] 1. Cross-linking degree: The testing standard is ASTM D2765-01 (2006).

[0112] 2. Pipe performance testing

[0113]

[0114] 3. Testing of pipe hygiene performance

[0115] Connect one end of the pipe to the circulation pump, add 4 mg / L chlorine water with a pH value of 5 into the heating barrel, set the temperature of the heating barrel to 95°C, and soak for 72 hours. The chlorine water flows back into the heating barrel from the other end of the pipe.

[0116] 4. The apparent grade of the pipe is determined by the pigment dispersion test, and the test standard is GB / T 18251-2019.

[0117] 5. Anti-UV performance: The anti-UV performance is tested by the American standard ASTM F2657-21 standard test method for outdoor weathering exposure of cross-linked polyethylene (PEX) pipes.

[0118] The above test results are shown in Table 1.

[0119] Table 1

[0120]

[0121]

[0122] According to Examples 1-9 in Table 1, the present invention helps improve the crosslinking efficiency of the pipe by controlling the compounding ratio of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3 and di-tert-butyl peroxide within the range defined by the present invention, so that the pipe has excellent chlorine resistance and UV resistance. In addition, by controlling the content of the crosslinking agent in the raw material, it is helpful to improve the crosslinking degree of the pipe, so that the pipe has excellent chlorine resistance and UV resistance.

[0123] According to the comparison of Comparative Examples 1-3 with Example 1, it can be obtained that the content of the cross-linking agent in the raw material of Comparative Examples 1-3 is too low, resulting in a decrease in the cross-linking efficiency of the pipe, thereby reducing the pressure resistance and UV resistance of the pipe.

[0124] According to the comparison between Comparative Examples 4-5 and Example 1, the cross-linking agent in Comparative Examples 4-5 includes 2,5-dimethyl-2,5-di(tert-butylperoxide)hexyne-3 or di-tert-butyl peroxide, and the degree of cross-linking is lower than that in Example 1, indicating that the cross-linking efficiency of the pipe cannot be improved by using 2,5-dimethyl-2,5-di(tert-butylperoxide)hexyne-3 or di-tert-butyl peroxide alone as the cross-linking agent.

[0125] According to the comparison between Comparative Examples 6-7 and Example 1, the cross-linking agent described in Comparative Examples 6-7 is a compound of diisopropylbenzene peroxide and 2,5-dimethyl-2,5-di(tert-butylperoxide)hexyne-3 or di-tert-butyl peroxide, and the cross-linking degree of the pipe is not as good as that of Example 1, which means that only by using 2,5-dimethyl-2,5-di(tert-butylperoxide)hexyne-3 and di-tert-butyl peroxide in the present invention can the cross-linking efficiency of the pipe be greatly improved.

[0126] According to the comparison between Comparative Examples 8-10 and Example 1, the weight ratio of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3 and di-tert-butyl peroxide in Comparative Examples 8-10 is not within the range defined by the present invention, and the degree of crosslinking is lower than that in Example 1, indicating that the present invention is beneficial to improving the crosslinking efficiency by controlling the weight ratio of the compound crosslinking agent.

[0127] In summary, the present invention improves the cross-linking efficiency by controlling the content of the cross-linking agent in the raw materials and controlling the weight ratio of the compound cross-linking agent, so that the PEX-a pipe has excellent cross-linking degree and good chlorine resistance and UV resistance. In addition, the pigment coloring ability is improved by improving the screw shear strength, which is beneficial to improving the appearance quality of the pipe.

[0128] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A PEX-a pipe, characterized in that: The raw material components include the following weight percentages: Cross-linking agent 0.9-1.5%; antioxidant 0.4-0.6%; anti-UV additive 0.4-0.6%; color powder 0.2-0.9%; auxiliary cross-linking agent 0.5-3%; dispersant 0.1-0.3%; the balance is high-density polyethylene; The cross-linking agent includes 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3-ol and di-tert-butyl peroxide, and the weight ratio of the 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3-ol and di-tert-butyl peroxide is (2-5):(1-5).

2. The PEX-a pipe according to claim 1, characterized in that: The weight ratio of the 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3-ol and di-tert-butyl peroxide is (2-3): (2-3).

3. The PEX-a pipe according to claim 1, characterized in that: The PEX-a pipe also includes 0.05-0.1% by weight of a fluorine-containing polymer.

4. The PEX-a pipe according to claim 3, characterized in that: The fluorine-containing polymer is polyphosphoric acid.

5. The PEX-a pipe according to claim 1, characterized in that: The antioxidants include at least two of the antioxidant DLTDP, antioxidant 1010, antioxidant 1076, antioxidant B277, antioxidant 1790, antioxidant 168, and antioxidant DSTDP.

6. The PEX-a pipe according to claim 5, characterized in that: The antioxidant includes antioxidant 1076 and antioxidant DSTDP, and the weight ratio of the antioxidant 1076 to the antioxidant DSTDP is (1-5):

1.

7. The PEX-a pipe according to claim 1, characterized in that: The anti-UV additives include at least two of UV-234, UV-329, UV-944, UV-622, and anti-UV additive HS-300.

8. The PEX-a pipe according to claim 7, characterized in that: The anti-UV auxiliary agent includes UV-329 and UV-944, and the weight ratio of UV-329 to UV-944 is (1-3):

1.

9. The method for preparing a PEX-a pipe according to any one of claims 1 to 8, characterized in that: The following steps are involved: The components are mixed evenly according to proportion, dried and melt-blended in an extruder to obtain PEX-a pipes.

10. The method for preparing a PEX-a pipe according to claim 9, characterized in that: The screw of the extruder includes a feeding section, a compression section and a homogenizing section, and the ratio of the sum of the lengths of the plum blossom patterns of the compression section and the homogenizing section to the length of the screw is (0.5-1):3.

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