Crosslinked PVC pipe material with good thermal stability and high strength and preparation method thereof

Abstract

The application belongs to the technical field of plastic processing, and particularly relates to a cross-linked PVC pipe material with good heat stability and high strength and a preparation method thereof. The PVC pipe material is composed of the following raw materials: PVC resin, organic tin stabilizer, initiator, triallyl isocyanurate, polyethylene imine, impact modifier, thermal reversible cross-linking agent, auxiliary cross-linking agent, benzoyl chloride, acid absorbent, processing aid and composite lubricant. By grafting primary amine and secondary amine groups on the polyvinyl chloride molecular chain, reactive cross-linking is carried out in the pipe extrusion process, so that the strength of the pipe is greatly improved. Due to the presence of primary amine and secondary amine, chemical reaction with hydrogen chloride produced by PVC decomposition can be carried out, and at the same time, the hydrogen chloride is quickly neutralized with the acid absorbent, so that the decomposition of PVC material is effectively prevented, and the heat resistance of the pipe is improved. The prepared PVC pipe material has good heat stability, high strength and good low-temperature impact resistance.

Description

Technical Field

[0001] This invention belongs to the field of plastic processing technology, specifically relating to cross-linked PVC pipes with good thermal stability and high strength, and their preparation method. Background Technology

[0002] In the field of plastic materials, polyvinyl chloride (PVC) pipes have long been widely recognized and used due to their excellent chemical stability and superior electrical insulation. PVC pipes not only possess excellent corrosion resistance and remain stable in various chemical environments, but also exhibit outstanding electrical insulation properties, making them irreplaceable in fields such as power and communications. However, despite their excellent performance in many aspects, the poor thermal stability and low heat resistance of PVC pipes have remained a bottleneck restricting their further expansion into more diverse applications.

[0003] Specifically, PVC resin is prone to decomposition at high temperatures, leading to a significant decline in its physical properties. When the temperature exceeds a certain threshold, PVC pipes not only soften and deform but may also undergo thermal decomposition, releasing harmful gases such as hydrogen chloride. This not only reduces the service life of the pipes but may also pose potential hazards to the environment and human health. Furthermore, PVC pipes have weak pressure resistance at high temperatures, making them unsuitable for some special applications requiring high pressure and high temperature environments.

[0004] Therefore, technological improvements and innovations are particularly important to address the shortcomings in the thermal stability and heat resistance of PVC pipes. Chinese patent CN109897306A discloses a heat-resistant PVC water pipe formula, comprising the following raw materials by weight: 80-120 parts PVC, 10-16 parts calcium carbonate, 15-30 parts calcium stearate, 20-50 parts butylated hydroxyanisole, 20-40 parts di-zinc phthalate, 2-6 parts trimethylolpropane trimethacrylate, 15-30 parts titanium dioxide, 5-10 parts potassium citrate, 6-8 parts ferrous sulfate, 10-20 parts zinc oxide, 4-6 parts aluminum hydroxide, 5-10 parts hexamethylphosphoric triamine, 2-4 parts ultramarine, 1-3 parts chlorinated paraffin, 1-3 parts PE wax, 2-6 parts seaweed powder, 4-6 parts MBS, and 0.2-0.6 parts polymer additives. The PVC pipes made with this formula have good heat resistance and oxidation resistance, thus improving their overall performance. However, the addition of plasticizers in this formula results in lower pipe strength and insufficient pressure resistance. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a cross-linked PVC pipe with good thermal stability and high strength. This is achieved by grafting primary and secondary amine groups onto the polyvinyl chloride molecular chain, followed by reactive cross-linking during pipe extrusion, thereby significantly improving the pipe's strength. The presence of primary and secondary amines allows for chemical reaction with hydrogen chloride produced during PVC decomposition, and simultaneously, in conjunction with an acid scavenger, rapidly neutralizes the hydrogen chloride, effectively preventing the decomposition of PVC and thus improving the pipe's heat resistance. Furthermore, the cross-linking method used is thermally reversible, allowing for the recycling and reuse of pipe waste. The resulting pipe exhibits good thermal stability, high strength, and excellent low-temperature impact resistance.

[0006] Another objective of this invention is to provide a method for preparing cross-linked PVC pipes with good thermal stability and high strength, which is scientific, reasonable, simple and easy to implement.

[0007] The technical solution adopted in this invention is as follows:

[0008] The aforementioned cross-linked PVC pipe with good thermal stability and high strength comprises the following raw materials in parts by weight:

[0009] PVC resin: 100 parts;

[0010] Organotin stabilizer: 1-3 parts;

[0011] Initiator: 0.5-1.0 parts;

[0012] Triallyl isocyanurate: 1-3 parts;

[0013] Polyethyleneimine: 3-5 parts;

[0014] Impact modifier: 3-5 parts;

[0015] Thermally reversible crosslinking agent: 2-5 parts;

[0016] Crosslinking agent: 1-3 parts;

[0017] Benzoyl chloride: 1-2 parts;

[0018] Acid absorbent: 3-8 parts;

[0019] Processing aids: 1.0-1.5 parts;

[0020] Compound lubricant: 1-3 parts.

[0021] The PVC resin is produced by suspension polymerization, with an average degree of polymerization of 950-1050 and an apparent density of 0.50-0.58 g / mL.

[0022] The organotin stabilizer is thiol methyltin or thiol octyltin, preferably thiol methyltin.

[0023] The initiator is an organic peroxide, preferably dicumyl peroxide. The initiator initiates a crosslinking reaction between polyethyleneimine and triallyl isocyanurate and PVC resin, thereby introducing polyethyleneimine into the polyvinyl chloride molecular chain.

[0024] The impact modifier is acrylate or chlorinated polyethylene, preferably chlorinated polyethylene rubber CM3510, purchased from Shandong Rike Chemical Co., Ltd.; CM3510 is a saturated thermoplastic elastomer with low Mooney viscosity and easy processing.

[0025] The thermally reversible crosslinking agent is sodium dicyclopentadiene dicarboxylate.

[0026] The crosslinking agent is tert-amylamine, which can react with benzoyl chloride to further increase the degree of crosslinking of the pipe, thereby increasing the tensile strength of the pipe.

[0027] The acid absorbent is a synthetic hydrotalcite, preferably AC-207 from Cheng-Ho Technology Co., Ltd. Because AC-207 contains hydroxide ions, it can chemically react with the hydrogen chloride produced by the decomposition of polyvinyl chloride, rapidly neutralizing the hydrogen chloride and nipping the decomposition of polyvinyl chloride in the bud, thus improving the thermal stability of polyvinyl chloride. Simultaneously, its addition also acts as a rigid particle toughening agent, further improving the toughness of the pipe without reducing its strength.

[0028] The processing aid is ACR, preferably PA-20 from Kaneka Corporation of Japan;

[0029] The composite lubricant is a mixture of three lubricants: calcium stearate, paraffin wax, and polyethylene wax, in a mass ratio of (1-3):(3-5):(3-5).

[0030] The preparation method of the cross-linked PVC pipe with good thermal stability and high strength includes the following steps:

[0031] (1) Add PVC resin, organotin stabilizer, initiator, triallyl isocyanate, polyethyleneimine, processing aid and composite lubricant to a high-speed mixer and mix. The mixing speed is 1000-1500 r / min, the mixing time is 5-10 min, and the mixing temperature is 110-120℃. After mixing, discharge the material to a low-speed mixer and cool it to 40-45℃ to obtain the mixture.

[0032] (2) The mixture obtained in step (1) is added to a twin-screw extruder for reactive grafting. The twin-screw extrusion temperature is 130-160℃ to obtain a polyvinyl chloride mixture.

[0033] (3) Add the polyvinyl chloride mixture obtained in step (2) into a high-speed mixer, then add acid absorber, impact modifier, thermally reversible crosslinking agent, co-crosslinking agent and benzoyl chloride, mix for 2-3 minutes, the mixing speed is 1000-1500 r / min, the mixing temperature is 110-120℃, and the mixed material is obtained.

[0034] (4) The mixed material obtained in step (3) is added to a 65 / 132 type conical twin-screw extruder and extruded to obtain a cross-linked PVC pipe with a diameter of 32mm, good thermal stability and high strength. The extruder temperature is 170-190℃ and the die temperature is 185℃.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] This invention introduces polyethyleneimine into the polyvinyl chloride (PVC) molecular chain through an initiator. The primary and secondary amines in polyethyleneimine have a good synergistic effect with the acid scavenger, reacting chemically with hydrogen chloride to rapidly neutralize the hydrogen chloride produced by PVC decomposition, thus nipping PVC decomposition in the bud and significantly improving the thermal stability of PVC. Simultaneously, the addition of a small amount of acid scavenger acts as a rigid particle toughening agent, further improving the toughness of the pipe without reducing its strength. The addition of the impact modifier chlorinated polyethylene rubber significantly improves the pipe's low-temperature impact resistance, and because the amount added is small, it does not affect the pipe's mechanical properties. The addition of a thermally reversible crosslinking agent further improves the pipe's strength, and the crosslinking used is thermally reversible, allowing for the recycling and reuse of waste pipe materials. The addition of a co-crosslinking agent further increases the degree of crosslinking, thereby further improving the pipe's strength. After the above modifications, the PVC pipes prepared by the method of the present invention for making cross-linked PVC pipes with good thermal stability and high strength have both good thermal stability and high strength and toughness, which can meet the performance requirements of heat and pressure resistance of pipes, and can also meet the requirements of low temperature impact resistance of pipes. Detailed Implementation

[0037] The present invention will be further described below with reference to the embodiments, but these embodiments do not limit the implementation of the present invention.

[0038] Unless otherwise specified, the raw materials used in the examples and comparative examples are all commercially available materials, and the process methods used in the examples and comparative examples are all conventional methods in the art.

[0039] The following is a description of some of the raw materials used in Examples 1-7 and the comparative examples:

[0040] PVC resin S-1000 was purchased from Sinopec Qilu Petrochemical Company.

[0041] Thiol methyltin SW-977 was purchased from Hubei Benxing New Materials Co., Ltd.

[0042] Thiol octyltin T890F, purchased from Shanghai Yexing Industrial Co., Ltd.;

[0043] Polyethylene rubber CM3510 was purchased from Shandong Rike Chemical Co., Ltd.

[0044] Acrylate ACM-M, purchased from Shandong Rike Chemical Co., Ltd.;

[0045] Sodium dicyclopentadiene dicarboxylate, purchased from Jiaxing Baimateng New Materials Co., Ltd.;

[0046] The initiator, benzoyl peroxide, was purchased from Jinan Yucai Chemical Co., Ltd.

[0047] Synthetic hydrotalcite AC-207 was purchased from Cheng Ho Technology Co., Ltd.

[0048] Processing aid PA-20 was purchased from Kaneka Chemical Co., Ltd., Japan.

[0049] Example 1

[0050] The aforementioned cross-linked PVC pipe with good thermal stability and high strength comprises the following raw materials in parts by weight:

[0051] PVC resin S-1000: 100 parts;

[0052] Thiol Methyltin SW-977: 1 part;

[0053] Dicumyl peroxide: 0.5 parts;

[0054] Triallyl isocyanurate: 1 part;

[0055] Polyethyleneimine: 3 parts;

[0056] Polyethylene rubber CM3510: 3 parts;

[0057] Sodium dicyclopentadiene dicarboxylate: 2 parts;

[0058] tert-amylamine: 1 part;

[0059] Benzoyl chloride: 1 part;

[0060] Synthetic hydrotalcite AC-207: 3 parts;

[0061] Processing aid PA-20: 1 part;

[0062] Compound lubricant: 1 part;

[0063] The PVC resin S-1000 is produced by suspension polymerization, with an average degree of polymerization of 1000 and an apparent density of 0.54±0.02 g / mL.

[0064] The composite lubricant is a mixture of three lubricants: calcium stearate, paraffin wax, and polyethylene wax, in a mass ratio of 2:4:4.

[0065] The preparation method of the cross-linked PVC pipe with good thermal stability and high strength includes the following steps:

[0066] (1) Add PVC resin, methyltin mercaptan, dicumyl peroxide, triallyl isocyanate, polyethyleneimine, processing aids and composite lubricant to a high-speed mixer and mix. The mixing speed is 1000 r / min, the mixing time is 10 min, and the mixing temperature is 110℃. After mixing, discharge the material into a low-speed mixer and cool it to 40℃ to obtain the mixture.

[0067] (2) The mixture obtained in step (1) is added to a twin-screw extruder for reactive grafting. The twin-screw extrusion temperature is 130°C to obtain a polyvinyl chloride mixture.

[0068] (3) Add the polyvinyl chloride mixture obtained in step (2) into a high-speed mixer, then add synthetic hydrotalcite, polyethylene rubber, sodium dicyclopentadiene dicarboxylate, tert-amylamine and benzoyl chloride, mix for 2 min, the mixing speed is 1500 r / min, the mixing temperature is 110℃, and the mixed material is obtained.

[0069] (4) The mixed material obtained in step (3) is added to a 65 / 132 type conical twin-screw extruder and extruded to obtain a cross-linked PVC pipe with a diameter of 32mm, good thermal stability and high strength. The extruder temperature is 170℃ and the die temperature is 185℃.

[0070] Example 2

[0071] The aforementioned cross-linked PVC pipe with good thermal stability and high strength comprises the following raw materials in parts by weight:

[0072] PVC resin S-1000: 100 parts;

[0073] Thiol methyltin SW-977: 1.5 parts;

[0074] Dicumyl peroxide: 0.6 parts;

[0075] Triallyl isocyanurate: 1.5 parts;

[0076] Polyethyleneimine: 3.5 parts;

[0077] Polyethylene rubber CM3510: 3.5 parts;

[0078] Sodium dicyclopentadiene dicarboxylate: 3 parts;

[0079] tert-amylamine: 1.2 parts;

[0080] Benzoyl chloride: 1.2 parts;

[0081] Synthetic hydrotalcite AC-207: 4 parts;

[0082] Processing aid PA-20: 1 part;

[0083] Compound lubricant: 1.5 parts;

[0084] The composite lubricant is a mixture of three lubricants: calcium stearate, paraffin wax, and polyethylene wax, in a mass ratio of 2:3:5.

[0085] The preparation method of the cross-linked PVC pipe with good thermal stability and high strength includes the following steps:

[0086] (1) Add PVC resin, methyltin mercaptan, dicumyl peroxide, triallyl isocyanate, polyethyleneimine, processing aids and composite lubricant to a high-speed mixer and mix. The mixing speed is 1500 r / min, the mixing time is 5 min, and the mixing temperature is 120℃. After mixing, discharge the material into a low-speed mixer and cool it to 45℃ to obtain the mixture.

[0087] (2) The mixture obtained in step (1) is added to a twin-screw extruder for reactive grafting. The twin-screw extrusion temperature is 160°C to obtain a polyvinyl chloride mixture.

[0088] (3) Add the polyvinyl chloride mixture obtained in step (2) into a high-speed mixer, then add synthetic hydrotalcite, polyethylene rubber, sodium dicyclopentadiene dicarboxylate, tert-amylamine and benzoyl chloride, mix for 3 min, the mixing speed is 1000 r / min, the mixing temperature is 120℃, and after the solvent evaporates, the mixed material is obtained.

[0089] (4) The mixed material obtained in step (3) is added to a 65 / 132 type conical twin-screw extruder and extruded to obtain a cross-linked PVC pipe with a diameter of 32mm, good thermal stability and high strength. The extruder temperature is 190℃ and the die temperature is 185℃.

[0090] Example 3

[0091] The aforementioned cross-linked PVC pipe with good thermal stability and high strength comprises the following raw materials in parts by weight:

[0092] PVC resin S-1000: 100 parts;

[0093] Thiol Methyltin SW-977: 2 parts;

[0094] Dicumyl peroxide: 0.7 parts;

[0095] Triallyl isocyanurate: 2 parts;

[0096] Polyethyleneimine: 4 parts;

[0097] Polyethylene rubber CM3510: 4 parts;

[0098] Sodium dicyclopentadiene dicarboxylate: 4 parts;

[0099] tert-amylamine: 2 parts;

[0100] Benzoyl chloride: 1.5 parts;

[0101] Synthetic hydrotalcite AC-207: 6 parts;

[0102] Processing aid PA-20: 1.5 parts;

[0103] Compound lubricant: 2 parts;

[0104] The composite lubricant is a mixture of three lubricants: calcium stearate, paraffin wax, and polyethylene wax, in a mass ratio of 3:3:4.

[0105] The preparation method of the cross-linked PVC pipe with good thermal stability and high strength includes the following steps:

[0106] (1) PVC resin, methyltin mercaptan, dicumyl peroxide, triallyl isocyanate, polyethyleneimine, processing aids and composite lubricant are added to a high-speed mixer and mixed at a speed of 1300 r / min for 8 min and a temperature of 115°C. After mixing, the material is discharged into a low-speed mixer and cooled to 43°C to obtain a mixture.

[0107] (2) The mixture obtained in step (1) is added to a twin-screw extruder for reactive grafting. The twin-screw extrusion temperature is 150°C to obtain a polyvinyl chloride mixture.

[0108] (3) Add the polyvinyl chloride mixture obtained in step (2) into a high-speed mixer, then add synthetic hydrotalcite, polyethylene rubber, sodium dicyclopentadiene dicarboxylate, tert-amylamine and benzoyl chloride, mix for 3 min, the mixing speed is 1300 r / min, the mixing temperature is 115℃, and after the solvent evaporates, the mixed material is obtained.

[0109] (4) The mixed material obtained in step (3) is added to a 65 / 132 type conical twin-screw extruder and extruded to obtain a cross-linked PVC pipe with a diameter of 32mm, good thermal stability and high strength. The extruder temperature is 180℃ and the die temperature is 185℃.

[0110] Example 4

[0111] The aforementioned cross-linked PVC pipe with good thermal stability and high strength comprises the following raw materials in parts by weight: PVC resin S-1000: 100 parts;

[0112] Thiol Methyltin SW-977: 2 parts;

[0113] Dicumyl peroxide: 0.8 parts;

[0114] Triallyl isocyanurate: 2.5 parts;

[0115] Polyethyleneimine: 4.5 parts;

[0116] Polyethylene rubber CM3510: 4.2 parts;

[0117] Sodium dicyclopentadiene dicarboxylate: 3.5 parts;

[0118] tert-amylamine: 2.5 parts;

[0119] Benzoyl chloride: 1.6 parts;

[0120] Synthetic hydrotalcite AC-207: 5 parts;

[0121] Processing aid PA-20: 1.3 parts;

[0122] Compound lubricant: 2.5 parts;

[0123] The composite lubricant is a mixture of calcium stearate, paraffin wax, and polyethylene wax in a mass ratio of 3:3:4. The preparation method for the cross-linked PVC pipe with good thermal stability and high strength is the same as in Example 3.

[0124] Example 5

[0125] The aforementioned cross-linked PVC pipe with good thermal stability and high strength comprises the following raw materials in parts by weight: PVC resin S-1000: 100 parts;

[0126] Thiol methyltin SW-977: 2.2 parts;

[0127] Dicumyl peroxide: 0.9 parts;

[0128] Triallyl isocyanurate: 3 parts;

[0129] Polyethyleneimine: 5 parts;

[0130] Polyethylene rubber CM3510: 4.5 parts;

[0131] Sodium dicyclopentadiene dicarboxylate: 4.5 parts;

[0132] tert-amylamine: 2.2 parts;

[0133] Benzoyl chloride: 1.8 parts;

[0134] Synthetic hydrotalcite AC-207: 7 parts;

[0135] Processing aid PA-20: 1.4 parts;

[0136] Composite lubricant: 1.8 parts;

[0137] The composite lubricant is a mixture of calcium stearate, paraffin wax, and polyethylene wax in a mass ratio of 3:3:4. The preparation method for the cross-linked PVC pipe with good thermal stability and high strength is the same as in Example 3.

[0138] Example 6

[0139] The aforementioned cross-linked PVC pipe with good thermal stability and high strength comprises the following raw materials in parts by weight: PVC resin S-1000: 100 parts;

[0140] Thiol methyltin SW-977: 2.8 parts;

[0141] Dicumyl peroxide: 1 part;

[0142] Triallyl isocyanurate: 3 parts;

[0143] Polyethyleneimine: 4 parts;

[0144] Polyethylene rubber CM3510: 5 parts;

[0145] Sodium dicyclopentadiene dicarboxylate: 5 parts;

[0146] tert-amylamine: 3 parts;

[0147] Benzoyl chloride: 2 parts;

[0148] Synthetic hydrotalcite AC-207: 8 parts;

[0149] Processing aid PA-20: 1.5 parts;

[0150] Compound lubricant: 3 parts;

[0151] The composite lubricant is a mixture of calcium stearate, paraffin wax, and polyethylene wax in a mass ratio of 1:5:4. The preparation method for the cross-linked PVC pipe with good thermal stability and high strength is the same as in Example 3.

[0152] Example 7

[0153] The aforementioned cross-linked PVC pipe with good thermal stability and high strength comprises the following raw materials in parts by weight: PVC resin S-1000: 100 parts;

[0154] Thiol Octyltin T890F: 2 parts;

[0155] Benzoyl peroxide: 0.7 parts;

[0156] Triallyl isocyanurate: 2 parts;

[0157] Polyethyleneimine: 4 parts;

[0158] Acrylate ACM-M: 4 parts;

[0159] Sodium dicyclopentadiene dicarboxylate: 4 parts;

[0160] tert-amylamine: 2 parts;

[0161] Benzoyl chloride: 1.5 parts;

[0162] Synthetic hydrotalcite AC-207: 6 parts;

[0163] Processing aid PA-20: 1.5 parts;

[0164] Compound lubricant: 2 parts;

[0165] The composite lubricant is a mixture of three lubricants: calcium stearate, paraffin wax, and polyethylene wax, in a mass ratio of 3:3:4.

[0166] The preparation method of the cross-linked PVC pipe with good thermal stability and high strength is the same as that in Example 3.

[0167] Comparative Example 1

[0168] The difference from Example 3 is that dicumyl peroxide, triallyl isocyanate and polyethyleneimine were not added to the formulation components, and the amount of synthetic hydrotalcite added was 10 parts by weight, while the rest were the same as in Example 3.

[0169] Comparative Example 2

[0170] The difference from Example 3 is that the amount of polyethyleneimine added in the formulation is 10 parts by weight, and no synthetic hydrotalcite is added; otherwise, it is the same as Example 3.

[0171] Comparative Example 3

[0172] The difference from Example 3 is that sodium dicyclopentadiene dicarboxylate, tert-amylamine, and benzoyl chloride were not added to the formulation components; otherwise, they are the same as in Example 3.

[0173] Comparative Example 4

[0174] The difference from Example 3 is that tert-amylamine was not added to the formulation components, but otherwise it is the same as Example 3.

[0175] Comparative Example 5

[0176] The difference from Example 3 is that chlorinated polyethylene rubber was not added to the formulation components, and chlorinated polyethylene was added in a quantity of 4 parts by weight instead of chlorinated polyethylene rubber. Otherwise, it is the same as Example 3.

[0177] Comparative Example 6

[0178] The PVC pipe is composed of the following raw materials in parts by weight:

[0179] PVC resin S-1000: 100 parts;

[0180] Thiol Methyltin SW-977: 2 parts;

[0181] Polyethyleneimine: 4 parts;

[0182] Polyethylene rubber CM3510: 4 parts;

[0183] Sodium dicyclopentadiene dicarboxylate: 1.5 parts;

[0184] tert-amylamine: 4 parts;

[0185] Benzoyl chloride: 2 parts;

[0186] Synthetic hydrotalcite AC-207: 6 parts;

[0187] Processing aid PA-20: 1.5 parts;

[0188] Compound lubricant: 2 parts;

[0189] Everything else is the same as in Example 3.

[0190] The PVC pipes prepared in Examples 1-7 and Comparative Examples 1-6 were subjected to performance tests, and the test methods are as follows:

[0191] Tensile strength (MPa): Refer to GB / T1040.2-2006;

[0192] Elongation at break (%): Refer to GB / T 1040.2-2006;

[0193] Change rate of elongation at break after 60℃ damp heat aging (%): Refer to GB / T 1040.2-2006; Damp heat aging conditions: (60±2)℃, relative humidity, (95±5)%, time 30d;

[0194] 0℃ Notched Impact Test (kJ / m) 2(Refer to GB / T14152-2001);

[0195] The test results are shown in Table 1-2:

[0196] Table 1 Performance test results of the embodiments

[0197]

[0198] As shown in Table 1, the PVC pipes prepared in Examples 1-7 have a tensile strength of over 55 MPa, and in particular, the low-temperature drop hammer impact strength at 0°C reaches 20 kJ / m. 2 The above demonstrates that the PVC pipe prepared according to the embodiments of the present invention has high toughness, and the elongation at break after aging is almost unchanged, indicating that the PVC pipe prepared according to the embodiments of the present invention has good thermal stability.

[0199] Table 2 Comparative Performance Test Results

[0200]

[0201] As can be seen from the data in Table 2, Comparative Example 1, which only used an acid scavenger (increased to 10 parts by weight) and did not introduce polyethyleneimine into the PVC molecular chain, showed a significantly higher rate of change in elongation at break after 60°C hygrothermal aging compared to Example 3. Furthermore, the increased amount of acid scavenger was equivalent to an increase in filler content, resulting in a substantial decrease in the elongation at break of the pipe material. Comparative Example 2, which introduced polyethyleneimine into the PVC molecular chain (increased to 10 parts by weight) but did not add an acid scavenger, also showed a significantly higher rate of change in elongation at break after 60°C hygrothermal aging compared to Example 3, indicating a good synergistic effect between the acid scavenger and polyethyleneimine. Compared to Example 3, Comparative Example 3 did not use a crosslinking method but only underwent ordinary modification. Due to the use of a small amount of impact modifier, the 0°C low-temperature drop hammer impact strength of the pipe material was significantly improved. Compared to Example 3, the tensile strength and elongation at break were significantly reduced; Comparative Example 4, due to the absence of a crosslinking agent, had a low degree of crosslinking, resulting in reduced tensile strength and elongation at break, as well as reduced 0°C low-temperature drop hammer impact strength, and a certain increase in the rate of change of elongation at break after 60°C humid heat aging; Comparative Example 5 did not use chlorinated polyethylene rubber, but instead used chlorinated polyethylene, and its 0°C low-temperature drop hammer impact strength was significantly reduced compared to Example 3; Comparative Example 6, compared to Example 3, did not add dicumyl peroxide and triallyl isocyanate, and the compatibility between polyethyleneimine and PVC was poor, thus causing a decrease in the tensile strength and elongation at break of the pipe material. At the same time, its synergy with the acid scavenger was worse, and the rate of change of elongation at break after 60°C humid heat aging was also somewhat increased compared to Example 3.

Claims

1. A cross-linked PVC pipe with good thermal stability and high strength, characterized in that, The ingredients include the following parts by weight: PVC resin: 100 parts; Organotin stabilizer: 1-3 parts; Initiator: 0.5-1.0 parts; Triallyl isocyanurate: 1-3 parts; Polyethyleneimine: 3-5 parts; Impact modifier: 3-5 parts; Thermally reversible crosslinking agent: 2-5 parts; Crosslinking agent: 1-3 parts; Benzoyl chloride: 1-2 parts; Acid absorbent: 3-8 parts; Processing aids: 1.0-1.5 parts; Compound lubricant: 1-3 parts.

2. The cross-linked PVC pipe with good thermal stability and high strength according to claim 1, characterized in that, The PVC resin has an average degree of polymerization of 950-1050 and an apparent density of 0.50-0.58 g / mL.

3. The cross-linked PVC pipe with good thermal stability and high strength according to claim 1, characterized in that, The organotin stabilizer is thiol methyltin or thiol octyltin.

4. The cross-linked PVC pipe with good thermal stability and high strength according to claim 1, characterized in that, The initiator is an organic peroxide.

5. The cross-linked PVC pipe with good thermal stability and high strength according to claim 1, characterized in that, The impact modifier is acrylate or chlorinated polyethylene.

6. The cross-linked PVC pipe with good thermal stability and high strength according to claim 1, characterized in that, The thermally reversible crosslinking agent is sodium dicyclopentadiene dicarboxylate.

7. The cross-linked PVC pipe with good thermal stability and high strength according to claim 1, characterized in that, The crosslinking agent is tert-amylamine.

8. The cross-linked PVC pipe with good thermal stability and high strength according to claim 1, characterized in that, The acid absorbent mentioned is synthetic hydrotalcite.

9. The cross-linked PVC pipe with good thermal stability and high strength according to claim 1, characterized in that, The processing aid is ACR; the composite lubricant is a mixture of calcium stearate, paraffin wax, and polyethylene wax.

10. A method for preparing a cross-linked PVC pipe with good thermal stability and high strength as described in any one of claims 1-9, characterized in that, The steps are as follows: (1) Add PVC resin, organotin stabilizer, initiator, triallyl isocyanate, polyethyleneimine, processing aid and composite lubricant into a high-speed mixer and mix. The mixing speed is 1000-1500 r / min, the mixing time is 5-10 min, and the mixing temperature is 110-120℃. After mixing, cool to 40-45℃ to obtain the mixture. (2) The mixture obtained in step (1) is added to a twin-screw extruder for reactive grafting. The twin-screw extrusion temperature is 130-160℃ to obtain a polyvinyl chloride mixture. (3) Add the polyvinyl chloride mixture obtained in step (2) into a high-speed mixer, then add acid absorber, impact modifier, thermally reversible crosslinking agent, co-crosslinking agent and benzoyl chloride, mix for 2-3 minutes, the mixing speed is 1000-1500 r / min, the mixing temperature is 110-120℃, and the mixed material is obtained. (4) Add the mixed material obtained in step (3) into a twin-screw extruder for extrusion to obtain cross-linked PVC pipe with good thermal stability and high strength. The extruder temperature is 170-190℃.

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