Environment-friendly auxiliary agent for recycling PVC plastic processing, preparation method and application

Abstract

The application discloses an environment-friendly auxiliary agent for recycling PVC plastic processing, a preparation method and application, and comprises the following components by weight: environment-friendly calcium-zinc stabilizer 20-40 parts, lubricant 10-20 parts, modified polyoxyethylene 10-20 parts, and nano-montmorillonite 10-20 parts; the modified polyoxyethylene is prepared by solution reaction modification of polyoxyethylene, silane coupling agent and zinc stearate; the environment-friendly auxiliary agent is added in the PVC plastic recycling process, and the extrusion stability time and elongation at break of the PVC plastic recycling sample are obviously improved; the environment-friendly auxiliary agent is helpful to improve the thermal stability and product mechanical properties of the PVC recycling plastic sample after secondary processing of the recycled PVC plastic; the preparation method is simple in operation steps, low in requirement for operators, free of toxic and harmful substances in the preparation process, and meets the requirements of green processing process and energy saving and emission reduction.

Description

Technical Field

[0001] This invention relates to the field of polymer plastic additives technology, specifically to an environmentally friendly additive for the processing of recycled PVC plastics, its preparation method, and its application. Background Technology

[0002] PVC (polyvinyl chloride) is the general-purpose plastic with the highest domestic production capacity. As of 2022, my country's annual PVC resin output exceeded 18 million tons. PVC resin is widely used in various industries such as water supply and drainage pipes, home decoration materials, door and window profiles, film materials, and wire and cable materials. PVC plastic products are also a recyclable polymer material. With the expanding application range of PVC plastic products, a large amount of waste PVC material is generated annually. Therefore, improving the processing efficiency of PVC material recycling and producing recycled PVC products has become a hot topic for PVC material manufacturers in recent years.

[0003] Since PVC plastic products have already undergone a complete production and processing cycle, the secondary heating during recycling can further degrade the thermal stability and mechanical properties of PVC plastics. For example, this can lead to processing instability during production and reduced mechanical properties of recycled products. Furthermore, the wide variety of sources and inconsistent quality of recycled PVC plastics further increases the difficulty of secondary recycling and processing, making it easier to waste resources. This invention proposes an environmentally friendly additive for recycling PVC plastics, its preparation method, and its application, aiming to solve the problems of reduced thermal stability and mechanical properties during secondary recycling. Summary of the Invention

[0004] The purpose of this invention is to overcome the deficiencies in the existing technology and provide an environmentally friendly additive for the processing of recycled PVC plastics, its preparation method, and its application. When added to the PVC plastic recycling process, the environmentally friendly additive of this invention significantly improves the extrusion stability time and elongation at break of recycled PVC plastic samples. In other words, the environmentally friendly additive of this invention helps improve the thermal stability and mechanical properties of recycled PVC plastic samples after secondary processing. The preparation method of this invention has simple operation steps, requires minimal operator skill, and generates no toxic or harmful substances during the preparation process, thus meeting the requirements of green processing and energy conservation and emission reduction.

[0005] One objective of this invention is to design an environmentally friendly additive for the recycling of PVC plastics, comprising the following weight components: 20-40 parts of environmentally friendly calcium-zinc stabilizer, 10-20 parts of lubricant, 10-20 parts of modified polyethylene oxide, and 10-20 parts of nano-montmorillonite; wherein the modified polyethylene oxide is prepared by solution reaction modification of polyethylene oxide, silane coupling agent, and zinc stearate.

[0006] The preferred technical solution is that the environmentally friendly calcium-zinc stabilizer is a powder solid with a particle size range of 40-100μm and a pH value range of 8-9.

[0007] Another preferred technical solution is that the lubricant is one or more of polyethylene wax, stearic acid, oxidized polyethylene wax, and ethylene bis-stearamide.

[0008] A preferred technical solution is that, in the preparation process of the modified polyethylene oxide: the mass ratio of polyethylene oxide, silane coupling agent, and zinc stearate is 100:30-50:20-50, the silane coupling agent used is one of KH 550 and KH 570, the solvent used is chloroform, and the mass ratio of the total mass of polyethylene oxide, silane coupling agent, and zinc stearate to the mass of the solvent is 1:4-8.

[0009] The second objective of this invention is to provide a method for preparing an environmentally friendly additive for the processing of recycled PVC plastics. The preparation of the aforementioned environmentally friendly additive includes the following steps:

[0010] S1: Polyoxyethylene, silane coupling agent, and zinc stearate are placed in a certain amount of chloroform solvent at a mass ratio of 100:30-50:20-50. The mixture is stirred and reacted at a temperature of 40-60℃ for 3-5 hours. After the reaction is completed, the solvent is heated to evaporate completely to obtain the modified polyoxyethylene primary product.

[0011] S2: Place the modified polyethylene oxide primary product obtained in step S1 in an oven and dry it at a temperature of 70-80℃ for 7-8 hours to obtain modified polyethylene oxide;

[0012] S3: Place 20-40 parts of environmentally friendly calcium-zinc stabilizer, 10-20 parts of lubricant, 10-20 parts of modified polyethylene oxide, and 10-20 parts of nano-montmorillonite into a high-speed mixer, heat to 55-65℃ and stir for 15-30 minutes to obtain a mixture.

[0013] S4: Transfer the mixture prepared in step S3 to an extruder and granulate it at 90-110°C and 30-50 rpm to obtain the environmentally friendly additive product.

[0014] A preferred technical solution is that, in step S2, the moisture content of the modified polyethylene oxide is <0.1%.

[0015] Another preferred technical solution is that, in step S4, the environmentally friendly additive is a solid granule.

[0016] The third objective of this invention is to propose an application of an environmentally friendly additive for the processing of recycled PVC plastics, wherein the environmentally friendly additive is used as an additive in the secondary recycling process of PVC plastics.

[0017] A preferred technical solution is that the environmentally friendly additive is added in an amount of 1 to 3 parts per 100 parts of PVC plastic.

[0018] The advantages and beneficial effects of this invention are as follows:

[0019] 1. Polyethylene oxide (PEO) is a thermoplastic organic compound. It is a soft, high-strength, malleable resin with high viscosity and polar CO groups. It has good compatibility with polar PVC plastics containing C-Cl groups and disperses well in the PVC matrix, which helps improve the toughness and strength of recycled PVC plastics. However, it is prone to hydrolysis. When affected by the moisture content of recycled PVC plastics, its molecular chains are easily hydrolyzed and broken, forming active free radicals, which can cause degradation of recycled PVC plastics and lead to color differences in the processed products. Zinc stearate, as a good heat stabilizer for PVC materials, can effectively capture the active free radicals generated during PVC degradation. It also easily combines with the organic free radicals generated by PEO hydrolysis, preventing color differences in the processed products. However, its affinity with PEO is poor, and it cannot fully improve the hydrolytic stability of PEO. Silane coupling agents are effective additives for improving the compatibility of high-molecular-weight compounds with low-molecular-weight compounds. They are also easily hydrolyzed. Due to their short molecular chains, their reactivity with water is higher than that of polyethylene oxide (PEO), and the hydrolysis products cannot generate active free groups, thus preventing the active decomposition of recycled PVC plastics. When PEO, zinc stearate, and silane coupling agents are pre-composite to form a ternary composite system, compared with simultaneous mixing of PEO, silane coupling agents, zinc stearate, environmentally friendly stabilizers, lubricants, and nano-montmorillonite, the silane coupling agent has a higher affinity between PEO and zinc stearate. Water tends to react more readily with the more reactive silane coupling agent, thus the silane coupling agent can more effectively protect PEO from hydrolysis and improve the overall hydrolytic stability of the system. Therefore, the modified PEO in the ternary composite system improves the discoloration time during the reprocessing of recycled PVC plastics and extends the stabilization time of the recycled PVC plastic processing system, thereby ensuring that the environmentally friendly additive of this invention for recycled PVC plastic processing can significantly improve the thermal stability and reduce the mechanical properties of the product during the secondary recycling process of PVC plastics.

[0020] 2. The proper ratio of modified polyethylene oxide, nano-montmorillonite, environmentally friendly calcium-zinc stabilizer, and lubricant can affect the degree of plasticization during the secondary recycling process of PVC plastics. The degree of plasticization during the secondary recycling process of PVC plastics can affect the mechanical properties of the material. A moderate degree of plasticization will allow the PVC material to maintain optimal mechanical properties. Nano-montmorillonite is an inorganic nanomaterial that has the effect of toughening high-molecular organic materials. At the same time, the silane coupling agent in the modified polyethylene oxide ternary composite system can further improve the compatibility between inorganic and organic components. Inorganic nano-montmorillonite and modified polyethylene oxide play a synergistic toughening role in the secondary recycling process of PVC materials. Therefore, an environmentally friendly additive for recycling PVC plastics according to the present invention can significantly improve the elongation at break of PVC plastics after secondary recycling, and further improve the mechanical properties of PVC plastics after secondary recycling.

[0021] 3. The present invention provides a method for preparing an environmentally friendly additive for recycling PVC plastics. The method has simple operation steps, low requirements for operators, and no toxic or harmful substances are generated during the preparation process, which meets the requirements of green processing and energy conservation and emission reduction.

[0022] 4. The environmentally friendly additive for processing recycled PVC plastics of the present invention can be used as an additive in the secondary recycling process of PVC plastics. It requires a small amount and can significantly improve the thermal stability and mechanical properties of secondary recycled PVC plastic products. Detailed Implementation

[0023] The specific embodiments of the present invention will be further described below with reference to examples. These examples are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0024] Example 1

[0025] An environmentally friendly additive for recycling PVC plastics comprises the following components by weight: 20 parts of environmentally friendly calcium-zinc stabilizer, 10 parts of lubricant, 10 parts of modified polyethylene oxide, and 10 parts of nano-montmorillonite; wherein the modified polyethylene oxide is prepared by solution reaction modification of polyethylene oxide, silane coupling agent, and zinc stearate.

[0026] Preferably, the environmentally friendly calcium-zinc stabilizer is a powder solid with a particle size range of 40-100μm and a pH value range of 8-9; the lubricant is polyethylene wax; in the preparation process of the modified polyethylene oxide: the mass ratio of polyethylene oxide, silane coupling agent, and zinc stearate is 100:30:20, the silane coupling agent used is KH 550, the solvent used is chloroform, and the mass ratio of the total mass of polyethylene oxide, silane coupling agent, and zinc stearate to the mass of the solvent is 1:4.

[0027] The preparation method of this environmentally friendly additive includes the following steps:

[0028] S1: Polyethylene oxide (PEO), silane coupling agent, and zinc stearate are placed in a certain amount of chloroform solvent at a mass ratio of 100:30:20. The mixture is stirred and reacted at 40°C for 5 hours. After the reaction is completed, the solvent is heated to evaporate completely to obtain the modified polyethylene oxide primary product.

[0029] S2: Place the modified polyethylene oxide primary product obtained in step S1 in an oven and dry it at 70°C for 8 hours to obtain modified polyethylene oxide.

[0030] S3: Place 20 parts of environmentally friendly calcium-zinc stabilizer, 10 parts of lubricant, 10 parts of modified polyethylene oxide, and 10 parts of nano-montmorillonite into a high-speed mixer, heat to 55℃ and stir for 30 minutes to obtain a mixture;

[0031] S4: Transfer the mixture prepared in step S3 to an extruder and granulate it at 90°C and 50 rpm to obtain the environmentally friendly additive product.

[0032] Preferably, in step S2, the moisture content of the modified polyethylene oxide is <0.1%; in step S4, the environmentally friendly additive is a solid granule.

[0033] Example 2

[0034] An environmentally friendly additive for recycling PVC plastics comprises the following components by weight: 30 parts of environmentally friendly calcium-zinc stabilizer, 15 parts of lubricant, 15 parts of modified polyethylene oxide, and 15 parts of nano-montmorillonite; wherein the modified polyethylene oxide is prepared by solution reaction modification of polyethylene oxide, silane coupling agent, and zinc stearate.

[0035] Preferably, the environmentally friendly calcium-zinc stabilizer is a powder solid with a particle size range of 40-100μm and a pH value range of 8-9; the lubricant is stearic acid and oxidized polyethylene wax, with a mass ratio of 1:1; in the preparation process of modified polyethylene oxide: the mass ratio of polyethylene oxide, silane coupling agent, and zinc stearate is 100:40:35, the silane coupling agent used is KH 550, the solvent used is chloroform, and the mass ratio of the total mass of polyethylene oxide, silane coupling agent, and zinc stearate to the mass of the solvent is 1:5.

[0036] The preparation method of this environmentally friendly additive includes the following steps:

[0037] S1: Polyethylene oxide (PEO), silane coupling agent, and zinc stearate are placed in a certain amount of chloroform solvent at a mass ratio of 100:40:35. The mixture is stirred and reacted at 50°C for 4 hours. After the reaction is completed, the solvent is heated to evaporate completely to obtain the modified polyethylene oxide primary product.

[0038] S2: Place the modified polyethylene oxide precursor obtained in step S1 in an oven and dry it at 75°C for 7.5 hours to obtain modified polyethylene oxide;

[0039] S3: Place 30 parts of environmentally friendly calcium-zinc stabilizer, 15 parts of lubricant, 15 parts of modified polyethylene oxide, and 15 parts of nano-montmorillonite into a high-speed mixer, heat to 60℃ and stir for 27 minutes to obtain a mixture.

[0040] S4: Transfer the mixture prepared in step S3 to an extruder and granulate it at 100°C and 40 rpm to obtain the environmentally friendly additive product.

[0041] Preferably, in step S2, the moisture content of the modified polyethylene oxide is <0.1%; in step S4, the environmentally friendly additive is a solid granule.

[0042] Example 3

[0043] An environmentally friendly additive for recycling PVC plastics comprises the following components by weight: 40 parts of environmentally friendly calcium-zinc stabilizer, 20 parts of lubricant, 20 parts of modified polyethylene oxide, and 20 parts of nano-montmorillonite; wherein the modified polyethylene oxide is prepared by solution reaction modification of polyethylene oxide, silane coupling agent, and zinc stearate.

[0044] Preferably, the environmentally friendly calcium-zinc stabilizer is a powder solid with a particle size range of 40-100μm and a pH value range of 8-9; the lubricant is stearic acid, oxidized polyethylene wax, and ethylene bis-stearamide, with a mass ratio of 1:1:1; in the preparation process of modified polyethylene oxide: the mass ratio of polyethylene oxide, silane coupling agent, and zinc stearate is 100:50:50, the silane coupling agent used is KH 570, the solvent used is chloroform, and the mass ratio of the total mass of polyethylene oxide, silane coupling agent, and zinc stearate to the mass of the solvent is 1:8.

[0045] The preparation method of this environmentally friendly additive includes the following steps:

[0046] S1: Polyethylene oxide (PEO), silane coupling agent, and zinc stearate are placed in a certain amount of chloroform solvent at a mass ratio of 100:50:50. The mixture is stirred and reacted at 60°C for 3 hours. After the reaction is completed, the solvent is evaporated completely by heating to obtain the modified polyethylene oxide primary product.

[0047] S2: Place the modified polyethylene oxide primary product obtained in step S1 in an oven and dry it at 80°C for 7 hours to obtain modified polyethylene oxide.

[0048] S3: Place 40 parts of environmentally friendly calcium-zinc stabilizer, 20 parts of lubricant, 20 parts of modified polyethylene oxide, and 20 parts of nano-montmorillonite into a high-speed mixer, heat to 60℃ and stir for 27 minutes to obtain a mixture;

[0049] S4: Transfer the mixture prepared in step S3 to an extruder and granulate it at 110°C and 30 rpm to obtain the environmentally friendly additive product.

[0050] Preferably, in step S2, the moisture content of the modified polyethylene oxide is <0.1%; in step S4, the environmentally friendly additive is a solid granule.

[0051] Application Example 1-3 and Comparative Example 1-4

[0052] The environmentally friendly additives prepared in Examples 1-3 were added one-to-one to the PVC plastic recycling process in Application Examples 1-3. A blank comparative example 1 of recycled PVC plastic without additives was also provided, along with comparative examples 2-4 of recycled PVC plastic containing physically added polyethylene oxide, silane coupling agent, zinc stearate, environmentally friendly calcium-zinc stabilizer, lubricant, and nano-montmorillonite. The amounts of each additive added in comparative examples 2-4 were equal to those added in Examples 1-3 after conversion. The component ratios are detailed in Table 1 below.

[0053] Table 1. Composition ratios of recycled PVC plastics in Examples 1-3 and Comparative Examples 1-4

[0054] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Application Example 1 Application Example 2 Application Example 3 Recycling PVC plastic 100 100 100 100 100 100 100 Polyethylene - 0.13 0.27 0.4 - - - Silane coupling agents - 0.04 0.08 0.12 - - - Zinc stearate - 0.03 0.05 0.08 - - - lubricant - 0.2 0.4 0.6 - - - Environmentally friendly calcium and zinc stabilizers - 0.4 0.8 1.2 - - - Nano-montmorillonite - 0.2 0.4 0.6 - - - Environmentally friendly additives - - - - 1 2 3

[0055] The material components from Comparative Examples 1-4 and Application Examples 1-3 were placed in a single-screw extruder (Dr. Collin E 30P) and the continuous extrusion stabilizer time of the recycled PVC plastic samples was tested at 185°C and 35 rpm. This time, i.e., the time from the start of the extrusion process to the appearance of decomposition and discoloration in the recycled PVC plastic samples, is detailed in Table 2 below.

[0056] The material components from Comparative Examples 1-4 and Application Examples 1-3 were placed in a single-screw extruder (Dr. Collin E 30P) and PVC samples were extruded at 185°C and 35 rpm. Standard strips (150 mm × 10 mm × 2 mm) of uniform size were prepared from the PVC samples extruded for 20–30 minutes. According to the test methods specified in GB / T 1040.1-2018 "Determination of Tensile Properties of Plastics Part 1: General Rules", the corresponding standard strips from Comparative Examples 1-4 and Application Examples 1-3 were tested for elongation at break in a tensile testing machine. The test results are detailed in Table 2 below.

[0057] Table 2. Test results of recycled PVC plastic samples from Examples 1-3 and Comparative Examples 1-4.

[0058]

[0059] The experimental data in Table 2 show that:

[0060] (i) The extrusion stabilization time of the recycled PVC plastics prepared in Comparative Examples 2-4 and Application Examples 1-3 was higher than that of the blank Comparative Example 1. The extrusion stabilization time of the recycled PVC plastics prepared in Comparative Examples 2-4 was less than 80 min, while the extrusion stabilization time of the recycled PVC plastics prepared in Application Examples 1-3 was more than 80 min. This indicates that adding the environmentally friendly additive of the present invention during the PVC plastic recycling process can significantly improve the extrusion stabilization time of the PVC recycled samples. Furthermore, the improvement effect of modified polyethylene oxide on the extrusion stabilization time of the PVC recycled samples is significantly better than that of directly adding polyethylene oxide, silane coupling agent, and zinc stearate in the PVC plastic recycling process through physical mixing.

[0061] (ii) The elongation at break of the recycled PVC samples prepared in Comparative Examples 2-4 and Application Examples 1-3 was higher than that of the blank Comparative Example 1. Furthermore, the elongation at break of the recycled PVC samples prepared in Comparative Examples 2-4 was all below 50%, while the elongation at break of the recycled PVC samples prepared in Application Examples 1-3 was all above 50%. This indicates that adding the environmentally friendly additives of the present invention during the PVC plastic recycling process can significantly improve the elongation at break of the recycled PVC samples. Moreover, the modified polyethylene oxide and inorganic nano-montmorillonite play a synergistic toughening role in the secondary recycling and processing of PVC materials. Therefore, the elongation at break of the recycled PVC samples prepared in Application Examples 1-3 was significantly better than that of the recycled PVC samples prepared in Comparative Examples 2-4.

[0062] In summary, the environmentally friendly additives of this invention, when used in the PVC plastic recycling process, significantly improve the extrusion stability time and elongation at break of PVC plastic recycled samples. In other words, the environmentally friendly additives of this invention help improve the thermal stability and mechanical properties of PVC recycled plastic samples after secondary processing, thus achieving the purpose of the invention.

[0063] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An environmentally friendly additive for processing recycled PVC plastics, characterized in that, It comprises the following components by weight: 20-40 parts of environmentally friendly calcium-zinc stabilizer, 10-20 parts of lubricant, 10-20 parts of modified polyethylene oxide, and 10-20 parts of nano-montmorillonite; wherein the modified polyethylene oxide is prepared by solution reaction modification of polyethylene oxide, silane coupling agent, and zinc stearate. The preparation method of the modified polyethylene oxide specifically includes the following steps: S1: Polyoxyethylene, silane coupling agent, and zinc stearate are placed in a certain amount of chloroform solvent at a mass ratio of 100:30-50:20-50. The mixture is stirred and reacted at a temperature of 40-60℃ for 3-5 hours. After the reaction is completed, the solvent is heated to evaporate completely to obtain the modified polyoxyethylene primary product. S2: Place the modified polyethylene oxide primary product obtained in step S1 in an oven and dry it at a temperature of 70~80℃ for 7~8h to obtain modified polyethylene oxide.

2. The environmentally friendly additive for recycling PVC plastics as described in claim 1, characterized in that, The environmentally friendly calcium-zinc stabilizer is a powder solid with a particle size range of 40-100μm and a pH value range of 8-9.

3. The environmentally friendly additive for recycling PVC plastics as described in claim 1, characterized in that, The lubricant is one or more of polyethylene wax, stearic acid, oxidized polyethylene wax, and ethylene bis-stearamide.

4. The environmentally friendly additive for recycling PVC plastics as described in any one of claims 1 to 3, characterized in that, In the preparation process of the modified polyethylene oxide: the mass ratio of polyethylene oxide, silane coupling agent, and zinc stearate is 100:30-50:20-50, the silane coupling agent used is one of KH 550 or KH 570, the solvent used is chloroform, and the mass ratio of the total mass of polyethylene oxide, silane coupling agent, and zinc stearate to the mass of solvent is 1:4~8.

5. A method for preparing an environmentally friendly additive for processing recycled PVC plastics as described in claim 4, characterized in that, Includes the following steps: S1: Polyoxyethylene, silane coupling agent, and zinc stearate are placed in a certain amount of chloroform solvent at a mass ratio of 100:30-50:20-50. The mixture is stirred and reacted at a temperature of 40-60℃ for 3-5 hours. After the reaction is completed, the solvent is heated to evaporate completely to obtain the modified polyoxyethylene primary product. S2: Place the modified polyethylene oxide primary product obtained in step S1 in an oven and dry it at a temperature of 70~80℃ for 7~8h to obtain modified polyethylene oxide; S3: Place 20-40 parts of environmentally friendly calcium-zinc stabilizer, 10-20 parts of lubricant, 10-20 parts of modified polyethylene oxide, and 10-20 parts of nano-montmorillonite into a high-speed mixer, heat to 55-65℃ and stir for 15-30 minutes to obtain a mixture. S4: Transfer the mixture prepared in step S3 to an extruder and granulate it at 90~110℃ and 30~50rpm to obtain the environmentally friendly additive product.

6. The method for preparing the environmentally friendly additive for recycling PVC plastics as described in claim 5, characterized in that, In step S2, the moisture content of the modified polyethylene oxide is <0.1%.

7. The method for preparing the environmentally friendly additive for recycling PVC plastics as described in claim 5, characterized in that, In step S4, the finished environmentally friendly additive is a solid granule.

8. The application of the environmentally friendly additive for recycling PVC plastics as described in any one of claims 1 to 4, characterized in that, The aforementioned environmentally friendly additives are used as auxiliaries in the secondary recycling process of PVC plastics.

9. The application of the environmentally friendly additive for recycling PVC plastics as described in claim 8, characterized in that, The environmentally friendly additive is added in an amount of 1 to 3 parts per 100 parts of PVC plastic.

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