PVC pipe composition and preparation method of PVC pipe

Abstract

The invention discloses a PVC pipe composition and a preparation method of a PVC pipe, and belongs to the technical field of PVC pipes. According to the pipe, PVC resin serves as a matrix and is compounded with polyethylene resin, filler, an impact modifier, a compatilizer, a calcium-zinc composite heat stabilizer, a lubricant, an antioxidant, an ultraviolet light absorber and other components, and the comprehensive performance is remarkably improved by adding a self-made modification enhancer. Compared with the prior art, the high-speed mixing and double-screw extrusion process is adopted, and the gradient temperature control technology is combined, so that uniform dispersion and stable extrusion of each component are realized. The prepared PVC pipe has excellent high temperature resistance, impact resistance and aging resistance, and is suitable for harsh working conditions such as hot water delivery, building water supply and drainage and the like. The preparation method is simple in process, green, environment-friendly and suitable for industrial popularization.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of PVC pipe material, and particularly relates to a PVC pipe material composition and a preparation method of the PVC pipe material. BACKGROUND

[0002] Polyvinyl chloride (PVC) pipe material is widely used in building water supply and drainage, power sheath, agricultural irrigation and other fields due to its excellent corrosion resistance, mechanical strength and cost-effectiveness. However, the traditional PVC material is prone to thermal degradation, discoloration and mechanical property decline under high temperature environment, which limits its application in hot water transportation, high temperature working conditions and outdoor exposed environment. In addition, the PVC itself has poor toughness and insufficient impact resistance, and is prone to brittle fracture under low temperature or high stress conditions, which affects the safety and service life.

[0003] To improve the heat resistance and mechanical properties of PVC pipe material, the existing technology usually adopts the ways of blending with flexible resins such as polyethylene (PE), adding inorganic fillers or introducing functional additives such as flame retardant, antioxidant and ultraviolet absorption. For example, Chinese patent application CN119912768A discloses a PVC / PE blending system, and the thermal stability and flame retardant properties are improved by introducing carboxyl-containing phenylboric acid and metal oxide; CN117645764A uses phosphorus-containing siloxane polymer and silver-basalt fiber composite to endow PVC pipe material with high temperature resistance, antibacterial and impact resistance.

[0004] Although the above methods improve the comprehensive performance of PVC pipe material to some extent, there are still the following deficiencies: first, the compatibility of the reinforcing components with the PVC matrix is limited, which easily leads to uneven dispersion and weak interface; second, some functional additives have the problems of migration, precipitation or environmental unfriendliness; third, the multi-component system is complex in process, and it is difficult to balance performance improvement and processing stability. Therefore, developing a PVC pipe material with high strength, excellent temperature resistance and good processing performance, and realizing a green, controllable and industrialized preparation method, is still a key problem to be solved in the current technical field. SUMMARY

[0005] In order to solve the deficiencies in the prior art, the present application aims to provide a PVC pipe material composition with high strength, excellent temperature resistance and good processing performance, and a preparation method of the PVC pipe material.

[0006] In order to achieve the above application purpose, the present application adopts the following technical solution: A PVC pipe material composition comprises the following components by weight: PVC resin 60-70 parts, polyethylene resin 5-10 parts, filler 5-10 parts, impact modifier 3-8 parts, modified reinforcing agent 2-6 parts, compatibilizer 1-5 parts, calcium-zinc composite heat stabilizer 2-6 parts, lubricant 1-3 parts, antioxidant 0.5-2 parts, and ultraviolet absorber 0.5-1.5 parts; The modified reinforcing agent is prepared by first preparing a pretreatment product through epoxidation of linseed oil; then, ring-opening esterification of the pretreatment product with a carboxylic acid compound in the presence of cyclohexane to form a post-treatment product; and finally, ring-opening polymerization of the post-treatment product with a cyclic ester compound under the catalysis of stannous octoate, followed by precipitation and purification to obtain the modified reinforcing agent.

[0007] A method for preparing a PVC pipe is as follows, in parts by weight: PVC resin, polyethylene resin, filler, impact modifier, modified reinforcing agent, compatibilizer, calcium-zinc composite heat stabilizer, lubricant, antioxidant, and ultraviolet absorber are weighed according to the above-mentioned formula of the PVC pipe composition; the above-mentioned raw materials are put into a high-speed mixing device for premixing treatment, the stirring rate is controlled to be 800-1500 revolutions per minute, the mixing temperature is set to be 100-150°C, and the mixture is continuously mixed for 3-10 minutes; then, the obtained mixture is transferred to a twin-screw extruder for melt extrusion, the melt material is extruded through a die, rapidly cooled and shaped in a cooling water tank, and finally, a PVC pipe is obtained.

[0008] The filler is at least one of calcium carbonate, magnesium hydroxide, talc powder, montmorillonite, and sepiolite.

[0009] The compatibilizer is at least one of chlorinated polyethylene and polymethyl methacrylate.

[0010] The lubricant is at least one of paraffin wax, polyethylene wax, stearic acid, and glycerol monooleate.

[0011] The antioxidant is at least one of antioxidant 1076, antioxidant 1010, antioxidant 264, antioxidant 2246, and antioxidant 168.

[0012] The ultraviolet absorber is at least one of ultraviolet absorber UV-9, ultraviolet absorber UV-531, ultraviolet absorber UV-327, and ultraviolet absorber UV-P.

[0013] The impact modifier is at least one of methyl methacrylate-butadiene-styrene copolymer and acrylic copolymer.

[0014] The extrusion temperature is controlled by a gradient: the first heating zone is 195-205℃, the second zone is 190-200℃, the third zone is 180-190℃, the fourth zone is 175-185℃, the fifth zone is 170-180℃, and the die head outlet temperature is stabilized at 165-175℃.

[0015] A further preferred embodiment is prepared by the following method, in parts by weight: S1. Heat 30-50 parts of flaxseed oil to 60-70℃. Mix 2-6 parts of acetic acid and 15-25 parts of hydrogen peroxide at room temperature and add them to the flaxseed oil in 2-5 equal portions, with an interval of 1-3 hours between each addition. After the addition is complete, continue to react at 60-70℃ for 1-5 hours. After the reaction is complete, add the mixture to ethyl acetate and wash with water until the aqueous phase is neutral. Then concentrate the mixture and dry the final product in a vacuum oven at 40-60℃ for 5-20 hours to obtain the pretreated product. S2. Add 1-3 parts of the pretreatment product prepared in step S1, 2-6 parts of the carboxylic acid compound, and 1-3 parts of cyclohexane to a flask, heat to 75-85℃ and reflux for 2-10 hours under a nitrogen atmosphere, add the crude product to ethyl acetate, wash with water until neutral, concentrate, and vacuum dry at 50-70℃ for 5-20 hours to obtain the posttreatment product. S3. Add 0.2-0.6 parts of the post-treatment product prepared in step S2, 0.8-1.5 parts of the cyclic ester compound, and 0.002-0.006 parts of stannous octoate to a flask. Under nitrogen protection, raise the temperature to 90-105℃ and react for 5-20 hours. After the reaction is complete, add the crude product to 2-6 parts of tetrahydrofuran. While stirring, add it dropwise to 80-120 parts of petroleum ether at 0-5℃ to precipitate. Collect the precipitate and dry it in a vacuum oven at 50-60℃ for 5-10 hours to obtain the modified reinforcing agent.

[0016] The carboxylic acid compound is at least one of octanoic acid, adipic acid, and benzoic acid.

[0017] The cyclic ester compound is at least one of δ-valerolactone, lactide, and glycolide.

[0018] In this preparation method, the roles of each substance are as follows: PVC resin, as the core matrix material of pipes, provides the main mechanical strength and rigid framework.

[0019] Polyethylene resin, as an auxiliary resin, improves flexibility and impact resistance, and forms a partially compatible system with PVC.

[0020] Nano-calcium carbonate, as an inorganic filler, enhances the rigidity and dimensional stability of pipes while reducing costs.

[0021] Methyl methacrylate-butadiene-styrene copolymer as impact modifier, significantly improves the impact toughness and crack resistance of the pipe.

[0022] The modified reinforcing agent provides efficient thermal stability and compatibility through the design of epoxy groups and polymeric segments, delaying PVC degradation and enhancing overall mechanical properties.

[0023] Polymethyl methacrylate as a compatibilizer, improves melt flowability and product surface finish.

[0024] Calcium-zinc composite thermal stabilizer inhibits thermal degradation and discoloration, ensuring processing stability.

[0025] Antioxidant 1076 as the main antioxidant, prevents oxidative aging through a free radical capture mechanism, prolonging the service life of the pipe.

[0026] UV absorber UV-9 absorbs ultraviolet radiation, reducing photooxidative damage and protecting the performance of the pipe in outdoor environments.

[0027] Polyethylene wax as a lubricant, reduces melt viscosity, improves extrusion processability and demolding effect.

[0028] Linseed oil as a bio-based raw material, its unsaturated fatty acid chains provide reaction sites for epoxidation.

[0029] Acetic acid and hydrogen peroxide mixture as active reagents for epoxidation reaction, converting double bonds to epoxy groups.

[0030] Ethyl acetate as an organic solvent, used for extraction and purification of epoxidation products.

[0031] Adipic acid as a diacid, reacts with epoxy groups to form cross-linked structures, enhancing molecular weight and thermal stability.

[0032] Propylene lactone ring-opening polymerization generates polylactic acid segments, imparting rigidity, high strength and biodegradability to the product.

[0033] Stannous octoate as a catalyst, reduces the activation energy of ring ester ring-opening polymerization, controlling reaction rate and molecular weight.

[0034] Tetrahydrofuran as a good solvent, completely dissolves the crude product, ensuring the effectiveness of subsequent precipitation purification.

[0035] Petroleum ether realizes the purification and separation of the product through low-temperature precipitation.

[0036] This formula realizes the balance of high strength, temperature resistance and durability through the synergistic effect of each substance, suitable for harsh application environments.

[0037] Compared with the prior art, the present application has the beneficial technical effects: 1) The present application significantly improves the thermal stability and aging resistance of PVC pipe by introducing a self-made modified reinforcing agent, effectively delays the blackening and degradation process under high temperature conditions, and prolongs the service life of the material.

[0038] 2) The modified reinforcing agent used in the present application enhances the toughness and impact resistance of the pipe, and improves the interfacial compatibility of the filler and the base resin, making the mechanical properties of the product more balanced.

[0039] 3) The present application uses a modified reinforcing agent starting from a bio-based raw material (such as flaxseed oil), and pays attention to mild and controllable process conditions (such as gradient temperature control, nitrogen protection) during preparation. The overall process is simple and controllable, significantly improves the comprehensive performance of the pipe, and the solvents used (such as tetrahydrofuran, petroleum ether) can be reduced through recycling to reduce environmental impact, and has good industrial application prospects. DETAILED DESCRIPTION

[0040] Some material parameters and sources: PVC resin, grade: P1353K, brand: Germany VESTOLIT.

[0041] Polyethylene resin, grade: HMA-016, brand: Saudi Arabia Exxon.

[0042] Nano calcium carbonate, particle size 20nm.

[0043] Methyl methacrylate-butadiene-styrene copolymer, grade: PARALOID TM BTA-731, brand: Dow Chemical.

[0044] Polymethyl methacrylate, grade: HI-835S, brand: LG Chemical.

[0045] Calcium-zinc composite heat stabilizer, product model: BP MC 91660 KA / 2, brand: Germany Xiong.

[0046] Polyethylene wax, grade: A-C6A, brand: Honeywell.

[0047] Antioxidant 1076, product model: RIANOX® 1076, brand: Rianlon.

[0048] Ultraviolet absorber UV-9, single product model: 3453453, Wuhan Lalanbai Medicine Chemical Co., Ltd.

[0049] The remaining raw materials in the examples and comparative examples of the present application are commercially available products. Example 1

[0050] A method for preparing a PVC pipe is as follows: PVC resin 65 parts, polyethylene resin 8 parts, nano calcium carbonate 7 parts, methyl methacrylate-butadiene-styrene copolymer 5 parts, modified reinforcing agent 4 parts, polymethyl methacrylate 3 parts, calcium-zinc composite heat stabilizer 4 parts, polyethylene wax 2 parts, antioxidant 1076 1.2 parts, and ultraviolet absorber UV-9 0.8 parts; the above raw materials are put into a high-speed mixing device for premixing treatment, the stirring rate is controlled at 1200 rpm, the mixing temperature is set at 120℃, and the mixing is continued for 5 minutes, then the obtained mixture is transferred to a twin-screw extruder for melt extrusion, the extrusion temperature is controlled by gradient: the first heating zone is 200℃, the second zone is 195℃, the third zone is 185℃, the fourth zone is 180℃, and the fifth zone is 175℃, the melt material is extruded through the die, and then rapidly cooled and shaped in a cooling water tank, finally the PVC pipe is obtained.

[0051] The preparation method of the modified reinforcing agent is as follows, in terms of weight parts: S1, 40 parts of flaxseed oil is warmed to 65℃, 4 parts of acetic acid is mixed with 20 parts of hydrogen peroxide at room temperature, then added to the above flaxseed oil in 4 equal portions with an interval of 2 hours each time, after the addition is completed, continue to react at 65℃ for 3 hours, after the reaction is completed, the mixture is added to 100 parts of ethyl acetate, washed with water until the water phase is neutral, then concentrated, and the final product is dried in a vacuum oven at 50℃ for 12 hours to obtain a pretreated product; S2, 2 parts of the pretreated product prepared in step S1, 4 parts of adipic acid, and 2 parts of cyclohexane are added to a flask, warmed to 80℃ under nitrogen atmosphere and refluxed for 6 hours, the crude product is added to 50 parts of ethyl acetate and washed with water until neutral, concentrated, and dried at 60℃ under vacuum for 12 hours to obtain a post-treated product; S3, 0.4 parts of the post-treated product prepared in step S2, 1.2 parts of lactide, and 0.004 parts of stannous octoate are added to a flask, the temperature is raised to 100℃ under nitrogen protection, and the reaction is carried out for 12 hours, after the reaction is completed, the crude product is added to 4 parts of tetrahydrofuran, and under stirring, it is dropped into 100 parts of petroleum ether at 2℃ for precipitation, the precipitate is collected and dried in a vacuum oven at 50℃ for 8 hours to obtain the modified reinforcing agent. Example 2

[0052] The preparation method of the PVC pipe is basically the same as that of Example 1, the only difference is that the preparation method of the modified reinforcing agent is different.

[0053] The preparation method of the modified reinforcing agent is as follows, in terms of weight parts: S1, 40 parts of linseed oil was heated to 65℃, 4 parts of acetic acid and 20 parts of hydrogen peroxide were mixed at room temperature and then added to the above linseed oil in 4 equal portions with 2 hours interval, after the addition was completed, the reaction was continued at 65℃ for 3 hours, after the reaction was completed, the mixture was added to 100 parts of ethyl acetate, washed with water until the aqueous phase was neutral, then concentrated, and the final product was dried in a vacuum oven at 50℃ for 12 hours to obtain a pretreated product; S2, 2 parts of the pretreated product prepared in step S1, 4 parts of benzoic acid, and 2 parts of cyclohexane were added to a flask, heated to 80℃ under nitrogen atmosphere and refluxed for 6 hours, the crude product was added to 50 parts of ethyl acetate and washed with water until neutral, concentrated, and dried at 60℃ under vacuum for 12 hours to obtain a post-treated product; S3, 0.4 parts of the post-treated product prepared in step S2, 1.2 parts of lactide, and 0.004 parts of stannous octoate were added to a flask, the temperature was raised to 100℃ under nitrogen protection, and the reaction was carried out for 12 hours, after the reaction was completed, the crude product was added to 4 parts of tetrahydrofuran, and under stirring, it was dropped into 100 parts of petroleum ether at 2℃ for precipitation, the precipitate was collected and dried in a vacuum oven at 50℃ for 8 hours to obtain a modified reinforcing agent. Example 3

[0054] The preparation method of the PVC pipe was basically the same as that of Example 1, the only difference being that the preparation method of the modified reinforcing agent was different.

[0055] The preparation method of the modified reinforcing agent was as follows, in parts by weight: S1, 40 parts of linseed oil was heated to 65℃, 4 parts of acetic acid and 20 parts of hydrogen peroxide were mixed at room temperature and then added to the above linseed oil in 4 equal portions with 2 hours interval, after the addition was completed, the reaction was continued at 65℃ for 3 hours, after the reaction was completed, the mixture was added to 100 parts of ethyl acetate, washed with water until the aqueous phase was neutral, then concentrated, and the final product was dried in a vacuum oven at 50℃ for 12 hours to obtain a pretreated product; S2, 2 parts of the pretreated product prepared in step S1, 4 parts of benzoic acid, and 2 parts of cyclohexane were added to a flask, heated to 80℃ under nitrogen atmosphere and refluxed for 6 hours, the crude product was added to 50 parts of ethyl acetate and washed with water until neutral, concentrated, and dried at 60℃ under vacuum for 12 hours to obtain a post-treated product; S3, 0.4 parts of the post-treated product prepared in step S2, 1.2 parts of lactide, and 0.004 parts of stannous octoate were added to a flask, the temperature was raised to 100℃ under nitrogen protection, and the reaction was carried out for 12 hours, after the reaction was completed, the crude product was added to 4 parts of tetrahydrofuran, and under stirring, it was dropped into 100 parts of petroleum ether at 2℃ for precipitation, the precipitate was collected and dried in a vacuum oven at 50℃ for 8 hours to obtain a modified reinforcing agent. Example 4

[0056] The preparation method of the PVC pipe is basically the same as that of Example 1, the only difference being that the preparation method of the modified reinforcing agent is different.

[0057] The preparation method of the modified reinforcing agent is as follows, in parts by weight: S1, warm 40 parts of linseed oil to 65°C, mix 4 parts of acetic acid with 20 parts of hydrogen peroxide at room temperature, then add them into the above linseed oil in 4 equal portions with an interval of 2 hours each, after the addition is completed, continue to react at 65°C for 3 hours, after the reaction is completed, add the mixture into 100 parts of ethyl acetate, wash with water until the water phase is neutral, then concentrate, and finally dry the product in a vacuum oven at 50°C for 12 hours to obtain a pretreated product; S2, add 2 parts of the pretreated product prepared in step S1, 4 parts of adipic acid, and 2 parts of cyclohexane into a flask, warm to 80°C under nitrogen atmosphere and reflux for 6 hours, add the crude product into 50 parts of ethyl acetate, and wash with water until neutral, concentrate, and dry at 60°C under vacuum for 12 hours to obtain a post-treated product; S3, add 0.4 parts of the post-treated product prepared in step S2, 1.2 parts of glycolide, and 0.004 parts of stannous octoate into a flask, warm to 100°C under nitrogen protection, and react for 12 hours, after the reaction is completed, add the crude product into 4 parts of tetrahydrofuran, drop it into 100 parts of petroleum ether at 2°C under stirring for precipitation, collect the precipitate, and dry in a vacuum oven at 50°C for 8 hours to obtain a modified reinforcing agent. Example 5

[0058] The preparation method of the PVC pipe is basically the same as that of Example 1, the only difference being that the preparation method of the modified reinforcing agent is different.

[0059] The preparation method of the modified reinforcing agent is as follows, in parts by weight: S1, warm 40 parts of linseed oil to 65°C, mix 4 parts of acetic acid with 20 parts of hydrogen peroxide at room temperature, then add them into the above linseed oil in 4 equal portions with an interval of 2 hours each, after the addition is completed, continue to react at 65°C for 3 hours, after the reaction is completed, add the mixture into 100 parts of ethyl acetate, wash with water until the water phase is neutral, then concentrate, and finally dry the product in a vacuum oven at 50°C for 12 hours to obtain a pretreated product; S2, add 2 parts of the pretreated product prepared in step S1, 4 parts of adipic acid, and 2 parts of cyclohexane into a flask, warm to 80°C under nitrogen atmosphere and reflux for 6 hours, add the crude product into 50 parts of ethyl acetate, and wash with water until neutral, concentrate, and dry at 60°C under vacuum for 12 hours to obtain a post-treated product; S3, 0.4 parts of the post-treated product prepared in step S2, 1.2 parts of δ-valerolactone, 0.004 parts of stannous octoate were added into a flask, the temperature was raised to 100°C under nitrogen protection, and the reaction was carried out for 12 hours. After the reaction was completed, the crude product was added into 4 parts of tetrahydrofuran, and it was dropped into 100 parts of petroleum ether at 2°C under stirring for precipitation. The precipitate was collected and dried in a vacuum oven at 50°C for 8 hours to obtain the modified reinforcing agent.

[0060] Comparative Example 1 The preparation method of the PVC pipe was basically the same as that of Example 1, and the only difference was that the preparation method of the modified reinforcing agent was different.

[0061] The preparation method of the modified reinforcing agent was as follows, in parts by weight: S1, 40 parts of linseed oil were heated to 65°C, 4 parts of acetic acid and 20 parts of hydrogen peroxide were mixed at room temperature, and then added into the above linseed oil in 4 equal portions with an interval of 2 hours. After the addition was completed, the reaction was continued at 65°C for 3 hours. After the reaction was completed, the mixture was added into 100 parts of ethyl acetate, washed with water until the aqueous phase was neutral, and then concentrated. The final product was dried in a vacuum oven at 50°C for 12 hours to obtain a pretreated product; S2, 2 parts of the pretreated product prepared in step S1, 4 parts of butyric acid, and 2 parts of cyclohexane were added into a flask, and the temperature was raised to 80°C under nitrogen atmosphere to reflux for 6 hours. The crude product was added into 50 parts of ethyl acetate, and washed with water until neutral. After concentration, it was dried in a vacuum oven at 60°C for 12 hours to obtain a post-treated product; S3, 0.4 parts of the post-treated product prepared in step S2, 1.2 parts of δ-valerolactone, 0.004 parts of stannous octoate were added into a flask, the temperature was raised to 100°C under nitrogen protection, and the reaction was carried out for 12 hours. After the reaction was completed, the crude product was added into 4 parts of tetrahydrofuran, and it was dropped into 100 parts of petroleum ether at 2°C under stirring for precipitation. The precipitate was collected and dried in a vacuum oven at 50°C for 8 hours to obtain the modified reinforcing agent.

[0062] Comparative Example 2 The preparation method of the PVC pipe was basically the same as that of Example 1, and the only difference was that the preparation method of the modified reinforcing agent was different.

[0063] The preparation method of the modified reinforcing agent was as follows, in parts by weight: S1, 40 parts of linseed oil were heated to 65°C, 4 parts of acetic acid and 20 parts of hydrogen peroxide were mixed at room temperature, and then added into the above linseed oil in 4 equal portions with an interval of 2 hours. After the addition was completed, the reaction was continued at 65°C for 3 hours. After the reaction was completed, the mixture was added into 100 parts of ethyl acetate, washed with water until the aqueous phase was neutral, and then concentrated. The final product was dried in a vacuum oven at 50°C for 12 hours to obtain a pretreated product; S2, 2 parts of the pretreated product prepared in step S1, 4 parts of adipic acid, 2 parts of cyclohexane were added into a flask, and the temperature was raised to 80°C under nitrogen atmosphere to reflux for 6 hours. The crude product was added to 50 parts of ethyl acetate, washed with water until neutral, concentrated, and dried at 60°C under vacuum for 12 hours to obtain a post-treated product; S3, 0.4 parts of the post-treated product prepared in step S2, 1.2 parts of ε-caprolactone, 0.004 parts of stannous octoate were added into a flask, and the temperature was raised to 100°C under nitrogen protection, and reacted for 12 hours. After the reaction was completed, the crude product was added to 4 parts of tetrahydrofuran, and under stirring, it was dropped into 100 parts of petroleum ether at 2°C for precipitation. The precipitate was collected and dried in a vacuum oven at 50°C for 8 hours to obtain a modified reinforcing agent.

[0064] Comparative Example 3 The preparation method of the PVC pipe was basically the same as that of Example 1, the only difference being that the modified reinforcing agent was not added.

[0065] Test Example 1 Thermal stability test: The PVC pipes prepared in each example and comparative example were placed in a Gil aging oven, and the time required for complete blackening at a temperature of 180°C was determined.

[0066] The test results are shown in Table 1.

[0067] Table 1 Experimental protocol Blackening time / minutes Example 1 258 Example 2 245 Example 3 225 Example 4 250 Example 5 205 Comparative Example 1 185 Comparative Example 2 235 Comparative Example 3 115 Test Example 2 Mechanical property test: The PVC pipes prepared in each example and comparative example were cut into samples of specified size according to the detection standard, and then the following two mechanical evaluations were carried out: Tensile properties: According to GB / T1040.2-2022 "Determination of tensile properties of plastics - Part 2: test conditions for moulded and extruded plastics", each group of test pieces was repeatedly measured 3 times under the same temperature and humidity environment, and the average value was taken as the result; Impact resistance: According to GB / T1043.2-2018 "Determination of impact properties of plastics - Part 2: instrumented impact test", each group of samples was subjected to 3 impacts under the same conditions, and the average value was taken as the result.

[0068] The relevant test data are summarized in Table 2.

[0069] Table 2 Experimental protocol Tensile strength (MPa) Impact strength (kJ / m 2 ) Example 1 59.3 38.1 Example 2 58.0 37.5 Example 3 55.5 37.8 Example 4 58.2 32.0 Example 5 50.8 44.5 Comparative Example 1 48.2 35.3 Comparative Example 2 55.0 41.2 Comparative Example 3 40.1 25.0 The modified reinforcing agent prepared by adipic acid and propylene lactone in Example 1 has better thermal stability and mechanical properties than Example 2, Example 3 and Comparative Example 1, and the mechanism may be that adipic acid as a diacid crosslinks with the epoxy pretreatment in the S2 step to form a higher molecular weight and more stable star network structure, significantly increasing the group density, thereby delaying the thermal aging blackening process; at the same time, the crosslinking effect of adipic acid enhances the intermolecular force, and the polylactic acid segment generated by ring-opening polymerization of propylene lactone has rigidity and moderate toughness, providing good impact resistance. In contrast, the benzoic acid in Example 2, although having an aromatic structure that helps thermal stability, lacks crosslinking ability, and has slightly lower thermal stability and mechanical properties; the octanoic acid in Example 3 and the butyric acid in Comparative Example 1 are both monobasic acids, which cannot form more crosslinks, resulting in poor thermal stability and tensile strength.

[0070] The mechanism for which Example 1 has better results than Example 4, Example 5 and Comparative Example 2 may be that the polylactic acid segment generated by propylene lactone achieves the best balance in rigidity, strength and toughness, while the polyglycolic acid segment generated by glycolide has very high rigidity but is brittle, resulting in a significant decrease in impact strength and slightly poorer thermal stability in Example 4; the polyvalerolactone segment generated by δ-valerolactone is too flexible, although it improves the impact strength of Example 5, it sacrifices the tensile strength and thermal stability; the polyhexanolactone segment generated by ε-caprolactone is flexible in Comparative Example 2, but lacks rigidity, and both the tensile strength and thermal stability are lower than Example 1. Therefore, the crosslinking structure of adipic acid and the rigidity-toughness synergistic effect of propylene lactone in Example 1 together give the PVC pipe excellent comprehensive performance.

Claims

1. A PVC pipe composition, characterized in that, Comprise the following components by weight parts: PVC resin 60-70 parts, polyethylene resin 5-10 parts, filler 5-10 parts, impact modifier 3-8 parts, modified reinforcing agent 2-6 parts, compatibilizer 1-5 parts, calcium-zinc composite heat stabilizer 2-6 parts, lubricant 1-3 parts, antioxidant 0.5-2 parts and ultraviolet absorber 0.5-1.5 parts; The modified reinforcing agent is first prepared by epoxidation reaction of linseed oil to prepare a pretreatment; then the pretreatment is subjected to ring-opening esterification reaction with a carboxylic compound in the presence of cyclohexane to form a post-treatment; Finally, the post-treatment is subjected to ring-opening polymerization with a cyclic ester compound under the catalysis of stannous octoate, and after precipitation purification, the modified reinforcing agent is obtained.

2. The PVC pipe composition of claim 1, wherein, The filler is at least one of calcium carbonate, magnesium hydroxide, talc, montmorillonite and sepiolite; the compatibilizer is at least one of chlorinated polyethylene and polymethyl methacrylate.

3. The PVC pipe composition of claim 1, wherein, The lubricant is at least one of paraffin wax, polyethylene wax, stearic acid and glycerol monooleate.

4. The PVC pipe composition of claim 1, wherein, The antioxidant is at least one of antioxidant 1076, antioxidant 1010, antioxidant 264, antioxidant 2246 and antioxidant 168.

5. The PVC pipe composition of claim 1, wherein, The ultraviolet absorber is at least one of ultraviolet absorber UV-9, ultraviolet absorber UV-531, ultraviolet absorber UV-327 and ultraviolet absorber UV-P.

6. The PVC pipe composition of claim 1, wherein, The impact modifier is at least one of methyl methacrylate-butadiene-styrene copolymer and acrylic copolymer.

7. The PVC pipe composition of claim 1, wherein, The preparation method of the modified reinforcing agent is as follows, in weight parts: S1, heat 30-50 parts of linseed oil to 60-70℃, mix 2-6 parts of acetic acid with 15-25 parts of hydrogen peroxide at room temperature, then add them into the above linseed oil in 2-5 equal portions with an interval of 1-3 hours, after the addition is completed, continue to react at 60-70℃ for 1-5 hours, after the reaction is completed, add the mixture into ethyl acetate, wash with water until the aqueous phase is neutral, then concentrate, and finally dry the product in a vacuum oven at 40-60℃ for 5-20 hours to obtain the pretreatment; S2, add 1-3 parts of the pretreatment prepared in step S1, 2-6 parts of a carboxylic compound and 1-3 parts of cyclohexane into a flask, heat to 75-85℃ under nitrogen atmosphere and reflux for 2-10 hours, add the crude product into ethyl acetate, wash with water until neutral, concentrate, and dry at 50-70℃ under vacuum for 5-20 hours to obtain the post-treatment; S3, add 0.2-0.6 parts of the post-treatment prepared in step S2, 0.8-1.5 parts of a cyclic ester compound and 0.002-0.006 parts of stannous octoate into a flask, heat to 90-105℃ under nitrogen protection, and react for 5-20 hours, after the reaction is completed, add the crude product into 2-6 parts of tetrahydrofuran, drop it into 80-120 parts of petroleum ether at 0-5℃ under stirring for precipitation, collect the precipitate, and dry it in a vacuum oven at 50-60℃ for 5-10 hours to obtain the modified reinforcing agent.

8. The PVC pipe composition of claim 7, wherein, The carboxylic compound is at least one of octanoic acid, adipic acid and benzoic acid; The cyclic ester compound is at least one of delta-valerolactone, lactide, and glycolide.

9. A process for the production of PVC pipes, characterized in that, The method is as follows: The PVC pipe composition according to claim 1 is prepared by weighing the PVC resin, polyethylene resin, filler, impact modifier, modified reinforcing agent, compatibilizer, calcium-zinc composite heat stabilizer, lubricant, antioxidant and ultraviolet absorber according to the formula proportion, and then putting the raw materials into a high-speed mixing device for premixing treatment, controlling the stirring speed to be 800-1500 rpm, setting the mixing temperature to be 100-150 DEG C, and continuously mixing for 3-10 minutes, and then transferring the obtained mixture to a double-screw extruder for melt extrusion, and after the melt material is extruded through a die, it is rapidly cooled and shaped in a cooling water tank, and finally the PVC pipe is obtained.

10. The method for preparing PVC pipe as described in claim 9, characterized in that, The extrusion temperature is controlled by gradient: the first heating zone is 195-205 DEG C, the second zone is 190-200 DEG C, the third zone is 180-190 DEG C, the fourth zone is 175-185 DEG C, and the fifth zone is 170-180 DEG C, and the temperature at the outlet of the head is stabilized at 165-175 DEG C.