A low-cost weather-resistant polyvinyl chloride composition for fences and a method for preparing the same

Abstract

The application discloses a low-cost fence polyvinyl chloride composition with good weather resistance and a preparation method thereof, and belongs to the technical field of polymer material recycling. The composition takes waste fence PVC recycled material as the main body, is matched with PVC resin powder and various functional additives, repairs broken molecular chains through an epoxy chain extender, cooperatively improves thermal stability through a rare earth-calcium zinc stabilizer, forms a double toughening structure through a core-shell impact modifier and chlorinated polyethylene, and cooperatively realizes long-acting anti-aging through an ultraviolet absorber, a hindered amine light stabilizer and rutile titanium dioxide. The composition has a simple beam notched impact strength of 12.8-14.2 kJ / m 2 , a color difference ΔE of less than or equal to 2.8 after aging for 1000 hours, an impact strength retention rate of greater than or equal to 85%, and a processing torque of less than or equal to 29.2 N.m, realizes high-value regeneration of the waste fence PVC, and has excellent mechanical properties, weather resistance and economy.

Description

Technical Field

[0001] This invention belongs to the field of polymer material recycling and processing technology, specifically relating to a polyvinyl chloride composition with high weather resistance and high toughness achieved by using waste polyvinyl chloride fence recycled material as a matrix and adding a small amount of ultraviolet absorber and hindered amine light stabilizer, and its preparation method. Background Technology

[0002] Fences, referring to industrial protective barriers, are primarily used in residential areas, highways, commercial areas, and public places to protect personal safety and equipment. Traditional fences, typically made of iron or wood, require secondary painting or spraying for decoration, a complex process that necessitates regular repainting and maintenance, resulting in high costs. PVC fences, due to their clean appearance, corrosion resistance, acid and alkali resistance, paint-free construction, and low maintenance costs, are increasingly replacing iron and wooden fences as outdoor isolation walls and barriers.

[0003] Due to prolonged outdoor use, PVC fencing products suffer severe degradation of their molecular chains and deterioration of their mechanical properties. Currently, the common industry practice is to shred recycled fencing and mix it with virgin materials for reuse. However, conventional technical solutions often follow the incremental approach of using virgin materials, adding large amounts of heat stabilizers, antioxidants, UV absorbers, and hindered amine light stabilizers (HALS) to compensate for the additives already consumed in the recycled materials.

[0004] However, recycled PVC fencing materials actually contain a considerable amount of residual titanium dioxide, some incompletely deactivated phenolic antioxidants, and light stabilizer skeletons. When similar additives are added in large quantities again, it is very easy to cause supersaturation of the total amount of additives, which will cause small molecules to migrate and precipitate to the surface, resulting in stickiness of the product surface, dust adsorption, and interfacial weakening effect, which will significantly reduce mechanical strength, especially impact toughness. In addition, antagonistic effects may occur between new and old stabilizers, accelerating their failure. Therefore, the utilization rate of recycled PVC materials in fencing materials is not high. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, this invention provides a polyvinyl chloride composition with high weather resistance and high toughness, which can be achieved by adding a small amount of ultraviolet absorber and hindered amine light stabilizer, and a method thereof.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A low-cost, weather-resistant polyvinyl chloride (PVC) composition for fencing, comprising, by weight, 60-70 parts recycled PVC fencing granules, 30-40 parts PVC resin powder, 9-12 parts calcium powder, 2.5-3.0 parts rare earth-calcium-zinc composite heat stabilizer, 0.8-1.2 parts epoxy chain extender, 1-3 parts acrylate core-shell impact modifier, 2.0-3.0 parts chlorinated polyethylene, 0.2-0.6 parts rutile titanium dioxide, 1.0-1.5 parts ACR processing aid, 0.1-0.2 parts phosphite hydroperoxide decomposer, 0.8-1.0 parts calcium stearate, 0.3-0.5 parts oxidized polyethylene wax, 0.1-0.2 parts UV-326 ultraviolet absorber, 0.05-0.1 parts hindered amine light stabilizer HALS-944, and 0.03-0.05 parts antioxidant 168.

[0007] Further, preferably, the epoxy chain extender is a styrene-acrylate-epoxy oligomer with an epoxy equivalent of 200-400 g / mol.

[0008] Further, preferably: the core layer of the acrylate core-shell impact modifier is polybutyl acrylate, and the shell layer is polymethyl methacrylate.

[0009] Further, preferably: the phosphite hydroperoxide decomposer is Weston 399.

[0010] The method for preparing the polyvinyl chloride composition for fencing of the present invention includes the following steps: (1) Raw material pretreatment: recycled fence PVC particles: screen particles with a particle size of 2~5mm, dry in an 80~90℃ forced air drying oven for 2 hours to remove surface adsorbed moisture and low molecular weight volatiles, and ensure that the moisture content is ≤0.3%; calcium carbonate: select 1250 mesh heavy calcium carbonate or light calcium carbonate, and dry at 110℃ for 1 hour. (2) Low temperature mixing: put the dried recycled fence PVC granules and PVC resin powder into a high-speed mixer at a speed of 800~1000 rpm, and add rare earth-calcium zinc composite heat stabilizer, epoxy chain extender, calcium stearate, phosphite hydroperoxide decomposition agent and phosphite antioxidant 168 in sequence. Stir and heat to 75~85℃ and maintain for 5~8 minutes. (3) High-temperature mixing and dispersion: Continue to add rutile titanium dioxide, acrylate core-shell impact modifier, chlorinated polyethylene, ACR processing aid, oxidized polyethylene wax and dried calcium carbonate, and heat to 110~115℃ under high-speed stirring, and mix for 8~12 minutes; (4) Low-temperature cooling discharge: The material temperature is reduced to below 40℃ at a rotation speed of 100~200 rpm; (5) The cold mixed material is fed into the preheated conical twin-screw extruder. The material is heated to melt and plasticize. The melted and plasticized material enters the confluence core through the screw and is diverted to the extrusion die. (6) Shaping and traction: The extrusion die extrudes the material to the shaping table, which cools and presses it to shape. The material is then moved out by the traction machine and cut into shape to obtain the finished product. Cooling is done by using cooling water at a temperature of 20~27℃ to obtain the fence.

[0011] Furthermore, preferably, the temperature settings for each section of the conical twin-screw extruder are as follows: Zone 1 160~165℃, Zone 2 165~170℃, Zone 3 170~175℃, Zone 4 175~178℃, Die head 180~185℃, Rotation speed: 20~28 rpm.

[0012] The beneficial effects of this invention are: (1) This invention uses recycled PVC waste fence material as the matrix and adopts a low-dose, multi-component synergistic modification strategy. Epoxy chain extenders and rare earth-calcium-zinc stabilizers synergistically repair molecular chains and enhance thermal stability efficiency; acrylate core-shell impact modifiers and chlorinated polyethylene construct a dual toughening structure to improve low-temperature impact toughness; UV-326, HALS-944, and rutile titanium dioxide achieve low-dose, long-lasting anti-aging through a physical shielding-energy transfer-quenching regeneration cycle mechanism; antioxidant 168 scavenge free radicals and reduce processing torque; calcium stearate, oxidized polyethylene wax, and ACR processing aid synergistically optimize lubrication and plasticizing properties. The components promote each other, making the composition superior to conventional virgin material formulations in key indicators such as impact strength, weather resistance color difference, processing torque, and cyclic stability, achieving a balance of low cost, high weather resistance, and high toughness.

[0013] (2) The notched impact strength of the simply supported beam of the composition of the present invention reaches 12.8~14.2 kJ / m. 2 After aging for 1000 hours, the color difference ΔE is ≤2.8, the impact strength retention rate is ≥85%, and the processing torque is ≤29.2 N·m. This achieves high-value recycling of waste fence PVC, and has excellent mechanical properties, weather resistance and economy. Detailed Implementation

[0014] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0015] The recycled PVC fence granules were obtained from commercially available waste PVC fences through crushing and screening, with a calcium stearate content of 29.6%; the PVC resin powder was purchased from Xinjiang Zhongtai Chemical's PBC-SG5; the rare earth-calcium-zinc composite heat stabilizer (brand name WWP-C) was purchased from Guangdong Weilinna New Material Technology Co., Ltd.; and the epoxy chain extender was BASF Joncryl. ADR-4400; acrylate core-shell impact modifier was purchased from Rohm and Haas, grade KM-355P; chlorinated polyethylene (CPE, type 135A) was purchased from Weifang Yaxing Chemical Co., Ltd.; rutile titanium dioxide (R-996) was purchased from Sichuan Longmang Group Co., Ltd.; ACR processing aid (grade ACR-401) was purchased from Shandong Ruifeng Polymer Materials Co., Ltd.; phosphite hydroperoxide decomposer was Weston 399; calcium stearate, oxidized polyethylene wax, ultraviolet absorber UV-326, hindered amine light stabilizer HALS-944, and antioxidant 168 were all commercially available industrial products.

[0016] Example 1

[0017] A low-cost, weather-resistant polyvinyl chloride (PVC) composition for fencing, comprising, by weight: 60 parts recycled PVC fencing granules, 40 parts PVC resin powder, 9 parts calcium powder (1250 mesh heavy calcium carbonate), 2.5 parts rare earth-calcium-zinc composite heat stabilizer, 0.8 parts epoxy chain extender, 1 part acrylate core-shell impact modifier, 2.0 parts chlorinated polyethylene, 0.2 parts rutile titanium dioxide, 1.0 part ACR processing aid, 0.1 parts phosphite hydroperoxide decomposer, 0.8 parts calcium stearate, 0.3 parts oxidized polyethylene wax, 0.1 parts UV-326 ultraviolet absorber, 0.05 parts hindered amine light stabilizer HALS-944, and 0.03 parts antioxidant 168.

[0018] Its preparation method includes the following steps: (1) Raw material pretreatment: PVC particles from the recycled fence are screened to a particle size of 2~5mm and dried in an 80℃ forced-air drying oven for 2 hours to ensure a moisture content of ≤0.3%; calcium carbonate is dried at 110℃ for 1 hour; (2) Low temperature mixing: put the dried recycled fence PVC granules and PVC resin powder into a high-speed mixer at 800 rpm, and add rare earth-calcium zinc composite heat stabilizer, epoxy chain extender, calcium stearate, phosphite hydroperoxide decomposition agent and antioxidant 168 in sequence. Stir and heat to 75°C and maintain for 5 minutes. (3) High-temperature mixing and dispersion: Continue to add rutile titanium dioxide, acrylate core-shell impact modifier, chlorinated polyethylene, ACR processing aid, oxidized polyethylene wax and dried calcium carbonate, and heat to 110°C under high-speed stirring, and mix for 8 minutes; (4) Low-temperature cooling discharge: The material temperature is reduced to below 40℃ at a rotation speed of 100 rpm; (5) Feed the cold-mixed material into the preheated conical twin-screw extruder. Set the temperature of each section as follows: Zone 1 160℃, Zone 2 165℃, Zone 3 170℃, Zone 4 175℃, Die head 180℃, and speed 20 rpm. (6) Shaping and traction: The extrusion die extrudes the material to the shaping table, cools and presses it with cooling water (temperature 20℃), and then moves it out by the traction machine to cut and shape it, thus obtaining the fence.

[0019] Example 2

[0020] A low-cost, weather-resistant polyvinyl chloride (PVC) composition for fencing, comprising, by weight: 65 parts recycled PVC fencing granules, 35 parts PVC resin powder, 10.5 parts calcium powder (1250 mesh light calcium carbonate), 2.8 parts rare earth-calcium-zinc composite heat stabilizer, 1.0 part epoxy chain extender (Joncryl ADR-4400), 2 parts acrylate core-shell impact modifier, 2.5 parts chlorinated polyethylene, 0.4 parts rutile titanium dioxide, 1.2 parts ACR processing aid, 0.15 parts phosphite hydroperoxide decomposer (Weston 399), 0.9 parts calcium stearate, 0.4 parts oxidized polyethylene wax, 0.15 parts UV absorber UV-326, 0.08 parts hindered amine light stabilizer HALS-944, and 0.04 parts antioxidant 168.

[0021] The preparation method is basically the same as that in Example 1, except that: the drying temperature in step (1) is 85℃; the rotation speed is 900 rpm, the temperature is raised to 80℃ and held for 6 minutes; the temperature is raised to 112℃ and mixed for 10 minutes; the rotation speed is 150 rpm; the temperature of each section of the extruder is set as follows: Zone 1 162℃, Zone 2 168℃, Zone 3 172℃, Zone 4 176℃, and the die head 182℃, with a rotation speed of 24 rpm; the cooling water temperature is 24℃ in step (6).

[0022] Example 3

[0023] A low-cost, weather-resistant polyvinyl chloride (PVC) composition for fencing, comprising, by weight: 70 parts recycled PVC fencing granules, 30 parts PVC resin powder, 12 parts calcium powder (1250 mesh heavy calcium carbonate), 3.0 parts rare earth-calcium-zinc composite heat stabilizer, 1.2 parts epoxy chain extender (Joncryl ADR-4400), 3 parts acrylate core-shell impact modifier, 3.0 parts chlorinated polyethylene, 0.6 parts rutile titanium dioxide, 1.5 parts ACR processing aid, 0.2 parts phosphite hydroperoxide decomposer (Weston 399), 1.0 part calcium stearate, 0.5 parts oxidized polyethylene wax, 0.2 parts UV-326 ultraviolet absorber, 0.1 parts hindered amine light stabilizer HALS-944, and 0.05 parts antioxidant 168.

[0024] The preparation method is basically the same as that in Example 1, except that: in step (1), the drying temperature is 90℃; in step (2), the rotation speed is 1000 rpm, the temperature is raised to 85℃, and held for 8 minutes; in step (3), the temperature is raised to 115℃ and mixed for 12 minutes; in step (4), the rotation speed is 200 rpm; in step (5), the temperature of each section of the extruder is set as follows: zone 1 165℃, zone 2 170℃, zone 3 175℃, zone 4 178℃, die head 185℃, and the rotation speed is 28 rpm; in step (6), the cooling water temperature is 27℃. The rest is the same as in Example 1.

[0025] Example 4

[0026] A low-cost, weather-resistant polyvinyl chloride (PVC) composition for fencing, comprising, by weight: 62 parts recycled PVC fencing granules, 38 parts PVC resin powder, 10 parts calcium powder (1250 mesh light calcium carbonate), 2.6 parts rare earth-calcium-zinc composite heat stabilizer, 0.9 parts epoxy chain extender (Joncryl ADR-4400), 1.5 parts acrylate core-shell impact modifier, 2.2 parts chlorinated polyethylene, 0.3 parts rutile titanium dioxide, 1.1 parts ACR processing aid, 0.12 parts phosphite hydroperoxide decomposer (Weston 399), 0.85 parts calcium stearate, 0.35 parts oxidized polyethylene wax, 0.12 parts UV-326 ultraviolet absorber, 0.06 parts hindered amine light stabilizer HALS-944, and 0.035 parts antioxidant 168.

[0027] The preparation method is the same as in Example 1.

[0028] Comparative Example 1 The composition is basically the same as in Example 1, except that: a low-cost, weather-resistant polyvinyl chloride composition for fencing, by weight, consists of: 100 parts PVC resin powder, 30 parts calcium powder (1250 mesh heavy calcium carbonate), 2.5 parts rare earth-calcium-zinc composite heat stabilizer, 0.8 parts epoxy chain extender, 1 part acrylate core-shell impact modifier, 2.0 parts chlorinated polyethylene, 0.2 parts rutile titanium dioxide, 1.0 part ACR processing aid, 0.1 parts phosphite hydroperoxide decomposer, 0.8 parts calcium stearate, 0.3 parts oxidized polyethylene wax, 0.5 parts UV-326 ultraviolet absorber, 0.5 parts hindered amine light stabilizer HALS-944, and 0.3 parts antioxidant 168.

[0029] Comparative Example 2 This comparative example is basically the same as Example 1, except that no epoxy chain extender is added, and PVC powder is used instead of epoxy chain extender. The other components and contents are the same as in Example 1.

[0030] Comparative Example 3 The results are basically the same as in Example 1, except that: no acrylate core-shell impact modifier is added, and PVC powder is used instead of acrylate core-shell impact modifier. The remaining components and contents are the same as in Example 1.

[0031] Comparative Example 4 It is basically the same as Example 1, except that: no hydroperoxide decomposer of phosphite is added, and PVC powder is used instead of hydroperoxide decomposer of phosphite. The other components and contents are the same as in Example 1.

[0032] Performance testing: The notched impact strength of simply supported beams was tested according to GB / T 1043.1-2008; Weather resistance was determined according to GB / T 16422.3-2022 by artificial accelerated aging test under fluorescent ultraviolet lamp (QUV-B, 340nm, irradiation intensity 0.55 W / m). 2 After aging for 1000 hours (60℃ / 8h light exposure, 50℃ / 4h condensation cycle), the color difference ΔE and impact strength retention rate were tested. Specific data are shown in Table 1.

[0033] Table 1 Performance test results of Examples 1-4 and Comparative Examples 1-4

[0034] As shown in Table 1, Comparative Example 1 used pure virgin PVC material and added high doses of UV-326 (0.5 parts) and HALS-944 (0.5 parts) according to conventional virgin material methods, while also adding a large amount of calcium powder (30 parts) for filling and reinforcement. Although the processing torque was low (22.3 N·m, and the pure virgin material had good flowability), the color difference ΔE after aging was as high as 5.3, far exceeding the 2.6 of Example 1. This is because there is no residual light stabilizer skeleton in the virgin material, and the one-time addition of a large amount of similar small molecule additives exceeds their solubility limit in PVC, resulting in migration and precipitation. The impact strength retention rate was only 68.4%, far lower than the 87.5% of Example 1. This indicates that the present invention utilizes the residual stabilizer skeleton in recycled materials to reduce costs and effectively avoid precipitation.

[0035] Comparative Example 2, made from pure virgin material without added epoxy chain extenders (replaced by PVC powder), had an impact strength of 9.8 kJ / m. 2 The retention rate after aging was 65.2%, which was lower than that of Example 1. This invention uses recycled materials as the main component; without the addition of chain extenders, the broken molecular chains cannot be repaired, and the performance will deteriorate significantly.

[0036] Comparative Example 3, without the addition of acrylate core-shell impact modifier (replaced by PVC powder), used only CPE as toughening agent, and achieved an impact strength of 10.5 kJ / m. 2 Compared to Example 1 (12.8 kJ / m³), 2 The impact toughness of the recycled material system decreased by 18.0%, and the retention rate after aging was also significantly lower, indicating that the dual toughening mechanism formed by the rigid shell-flexible core structure of the core-shell particles and the CPE elastic network is the key to obtaining high impact toughness.

[0037] Comparative Example 4, without the addition of Weston 399 (replaced by PVC powder), showed a processing torque of 27.8 N·m, but the impact retention rate after aging was only 70.1%, both worse than Example 1. This indicates that the lack of a rapid hydroperoxide decomposition agent exacerbated thermal degradation during processing. This invention combines Weston 399 with antioxidant 168, addressing both the decomposition of hydroperoxides and the capture of free radicals. This effectively protects the damaged molecular chains in the recycled material, achieving superior processing stability and aging resistance even within the recycled material matrix compared to pure virgin material (without decomposition agent).

[0038] This invention accurately identifies the value of residual additives in recycled materials and adopts a waste-based, low-dose synergistic reinforcement strategy. It outperforms conventional formulations of pure virgin materials and comparative schemes lacking key components in all key performance indicators, truly achieving the goals of low cost, high weather resistance, and high toughness.

[0039] Although embodiments of the present invention have been described above, any modifications and substitutions made by those skilled in the art without departing from the principles and spirit of the present invention are within the scope of protection claimed by the present invention.

Claims

1. A low-cost, weather-resistant polyvinyl chloride composition for fencing, characterized in that: By weight, the composition includes 60-70 parts recycled PVC fence granules, 30-40 parts PVC resin powder, 9-12 parts calcium powder, 2.5-3.0 parts rare earth-calcium-zinc composite heat stabilizer, 0.8-1.2 parts epoxy chain extender, 1-3 parts acrylate core-shell impact modifier, 2.0-3.0 parts chlorinated polyethylene, 0.2-0.6 parts rutile titanium dioxide, 1.0-1.5 parts ACR processing aid, 0.1-0.2 parts phosphite hydroperoxide decomposer, 0.8-1.0 parts calcium stearate, 0.3-0.5 parts oxidized polyethylene wax, 0.1-0.2 parts UV-326 ultraviolet absorber, 0.05-0.1 parts hindered amine light stabilizer HALS-944, and 0.03-0.05 parts antioxidant 168.

2. The low-cost, weather-resistant polyvinyl chloride composition for fencing according to claim 1, characterized in that: The epoxy chain extender is a styrene-acrylate-epoxy oligomer with an epoxy equivalent of 200–400 g / mol.

3. The low-cost, weather-resistant polyvinyl chloride composition for fencing according to claim 1, characterized in that: The core layer of the acrylate core-shell impact modifier is polybutyl acrylate, and the shell layer is polymethyl methacrylate.

4. The low-cost, weather-resistant polyvinyl chloride composition for fencing according to claim 1, characterized in that: The phosphite-based hydroperoxide decomposer is Weston 399.

5. A method for preparing a polyvinyl chloride composition for fencing as described in any one of claims 1-4, characterized in that, Includes the following steps: (1) Raw material pretreatment: recycled fence PVC granules: screen granules with a particle size of 2~5mm, dry them in a forced-air drying oven at 80~90℃ for 2 hours to remove surface adsorbed moisture and low molecular weight volatiles, and ensure that the moisture content is ≤0.3%; Calcium carbonate: Select 1250 mesh heavy calcium carbonate or light calcium carbonate, and dry at 110℃ for 1 hour; (2) Low temperature mixing: put the dried recycled fence PVC granules and PVC resin powder into a high-speed mixer at a speed of 800~1000 rpm, and add rare earth-calcium zinc composite heat stabilizer, epoxy chain extender, calcium stearate, phosphite hydroperoxide decomposition agent and antioxidant 168 in sequence. Stir and heat to 75~85℃ and maintain for 5~8 minutes. (3) High-temperature mixing and dispersion: Continue to add rutile titanium dioxide, acrylate core-shell impact modifier, chlorinated polyethylene, ACR processing aid, oxidized polyethylene wax and dried calcium carbonate, and heat to 110~115℃ under high-speed stirring, and mix for 8~12 minutes; (4) Low-temperature cooling discharge: The material temperature is reduced to below 40℃ at a rotation speed of 100~200rpm; (5) The cold mixed material is fed into the preheated conical twin-screw extruder. The material is heated to melt and plasticize. The melted and plasticized material enters the confluence core through the screw and is diverted to the extrusion die. (6) Shaping and traction: The extrusion die extrudes the material to the shaping table, which cools and presses it to shape. The material is then moved out by the traction machine and cut into shape to obtain the finished product. Cooling is done by using cooling water at a temperature of 20~27℃ to obtain the fence.

6. The preparation method according to claim 5, characterized in that: The temperature settings for each section of the conical twin-screw extruder are as follows: Zone 1 160~165℃, Zone 2 165~170℃, Zone 3 170~175℃, Zone 4 175~178℃, Die head 180~185℃, Rotation speed: 20~28 rpm.

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