Wear-resistant non-toxic polypropylene modified plastic and production process

Abstract

This invention relates to the field of polymer materials technology, specifically to a wear-resistant and non-toxic modified polypropylene plastic and its production process. The plastic comprises a polypropylene matrix, an organic-inorganic hybrid composite wear-resistant system, a food-grade toughening compatibilizer, and a composite stabilizing agent. The polypropylene matrix is ​​a blend of homopolymer polypropylene and random copolymer polypropylene. The organic-inorganic hybrid composite wear-resistant system includes surface-modified nanocomposite wear-resistant fillers, a food-grade polymeric wear-resistant lubricant, and an α / β composite nucleating agent. All components of this product are food contact grade, possessing excellent wear resistance, hardness, and impact toughness, with no toxic or harmful substances leaching out, meeting the safety standards for food contact materials. This invention solves the pain point of existing polypropylene materials that cannot simultaneously achieve wear resistance, food safety, and mechanical properties. The product exhibits excellent comprehensive performance, good food contact safety, and a stable and controllable production process, making it suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a wear-resistant and non-toxic modified polypropylene plastic and its production process. Background Technology

[0002] This invention relates to the field of polymer material modification technology, specifically to a modified polypropylene plastic and its production process. Polypropylene, as a general-purpose thermoplastic with excellent comprehensive properties, possesses outstanding advantages such as low density, balanced mechanical properties, good processability and moldability, strong chemical stability, and low cost. It is one of the most widely used plastic materials in food contact applications such as food packaging, catering utensils, and food processing equipment parts, and its market demand and application scale continue to expand.

[0003] However, general-purpose polypropylene has inherent defects such as low surface hardness and poor wear resistance. In long-term reciprocating friction and high-frequency scraping scenarios, it is very easy to develop surface scratches, wear and chipping, and mechanical property degradation. This not only significantly shortens the service life of the products, but the plastic debris generated by wear can also directly pose food safety hazards, seriously limiting its in-depth application and large-scale promotion in food contact scenarios with high wear resistance requirements.

[0004] Current technologies for abrasion-resistant modification of polypropylene (PP) primarily improve wear resistance by adding inorganic abrasion-resistant fillers, solid lubricants, and glass fiber reinforcement. However, these methods generally suffer from difficult-to-reconcile technical drawbacks. Firstly, conventional inorganic fillers such as talc, calcium carbonate, and glass fiber have poor compatibility with the PP matrix, easily leading to agglomeration and uneven dispersion. While improving wear resistance, these fillers significantly reduce the material's impact toughness, making the product brittle and unable to simultaneously achieve both abrasion resistance and comprehensive mechanical properties. Secondly, existing abrasion-resistant modification systems often add non-food-grade abrasion-resistant additives, plasticizers, and compatibilizers, which can easily lead to the release of harmful substances such as bisphenol A, phthalates, and heavy metals. This fails to meet national safety standards for food contact materials, posing serious toxicity and safety risks. Thirdly, existing modification processes struggle to achieve uniform dispersion of abrasion-resistant fillers and stable control of the PP crystal structure, easily resulting in additive migration and large batch-to-batch performance fluctuations. This makes it impossible to simultaneously meet the stringent requirements of food contact applications for both material safety and abrasion resistance. Summary of the Invention

[0005] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a wear-resistant, non-toxic modified polypropylene plastic and its production process.

[0006] (II) Technical Solution A wear-resistant and non-toxic modified polypropylene plastic, comprising the following components by weight: 35-55 parts homopolymer polypropylene, 20-35 parts random copolymer polypropylene, 3-10.8 parts organic-inorganic hybrid composite wear-resistant system, 3-8 parts food-grade toughening compatibilizer, and 0.3-1.1 parts composite stabilizing agent. The organic-inorganic hybrid composite wear-resistant system comprises 2-6 parts of modified nanocomposite wear-resistant filler, 1-4 parts of food-grade polymeric wear-resistant lubricant, and 0.2-0.8 parts of α / β composite nucleating agent; wherein the modified nanocomposite wear-resistant filler is a nano-diatomite-fumed silica composite powder modified with silane coupling agent KH550, with a particle size of 50-200 nm and a mass ratio of nano-diatomite to fumed silica of 3:1-1:1; the food-grade polymeric wear-resistant lubricant is an ultra-high molecular weight silicone masterbatch with food-grade polypropylene as a carrier, with an effective silicone content of 48%-52%; the α / β composite nucleating agent has a mass ratio of α nucleating agent to β nucleating agent of 1:2-2:1, the α nucleating agent is a food-grade sorbitol nucleating agent, and the β nucleating agent is a food-grade amide nucleating agent; The food-grade toughening compatibilizer is a maleic anhydride-grafted polyolefin elastomer with a grafting rate of 1.0%-1.8%. The composite stabilizing agent includes 0.1-0.5 parts of food-grade compound antioxidant and 0.2-0.6 parts of food-grade lubricant. The food-grade compound antioxidant is composed of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1. The food-grade lubricant is calcium stearate.

[0007] Preferably, in the organic-inorganic hybrid composite wear-resistant system, the mass ratio of modified nanocomposite wear-resistant filler, food-grade polymeric wear-resistant lubricant, and α / β composite nucleating agent is 4:2:1.

[0008] Preferably, the melt flow rate of the homopolymer polypropylene is 10-25 g / 10 min (230℃, 2.16 kg), the melt flow rate of the random copolymer polypropylene is 5-15 g / 10 min (230℃, 2.16 kg), and the mass ratio of homopolymer polypropylene to random copolymer polypropylene is 3:2-2:1.

[0009] Preferably, the food-grade toughening compatibilizer has a melt flow rate of 1-5 g / 10 min (190°C, 2.16 kg) and an addition amount of 4-6 parts by weight.

[0010] Preferably, the mass ratio of α nucleating agent to β nucleating agent in the α / β composite nucleating agent is 1:1, and the amount added is 0.4-0.6 parts by weight.

[0011] Preferably, in the composite stabilizing agent, the amount of food-grade compound antioxidant added is 0.2-0.4 parts by weight, and the amount of food-grade lubricant added is 0.3-0.5 parts by weight.

[0012] Preferably, the production process of the wear-resistant and non-toxic modified polypropylene plastic includes the following steps: S1 Raw Material Pretreatment: Weigh the modified nanocomposite wear-resistant filler according to the ratio, place it in a high-speed mixer, and dry and activate it for 15-25 minutes at 100-110℃ and 800-1200rpm to remove moisture from the powder and complete the secondary surface activation to obtain activated wear-resistant filler. S2 Stepwise Premixing: First, add the homopolymer polypropylene and random copolymer polypropylene weighed according to the formula to a high-speed mixer and mix for 3-5 minutes at 60-70℃ and 500-800 rpm; then add food-grade toughening compatibilizer, activated wear-resistant filler, and α / β composite nucleating agent, and continue mixing for 5-8 minutes while maintaining the temperature and speed; finally, add food-grade polymeric wear-resistant lubricant and composite stabilizing agent, and mix for 2-4 minutes at 1000-1500 rpm to obtain the premixed material; S3 Two-Stage Melt Extrusion Granulation: The premixed material is fed into a twin-screw extruder and a two-stage temperature-controlled extrusion process is adopted. The temperature of the first-stage extrusion section is 180-195℃, the temperature of the second-stage homogenization extrusion section is 195-210℃, the main machine speed is 300-450rpm, the feeding frequency is 15-25Hz, and the entire extrusion process adopts negative pressure devolatilization treatment with a vacuum degree ≥0.08MPa. After water cooling, air drying and pelletizing, the extruded strips are used to obtain primary modified particles. S4 Low-Temperature Annealing and Shaping: The primary modified particles are placed in a forced-air drying oven and annealed at 80-90℃ for 2-4 hours to eliminate internal stress in the particles and promote crystal form perfection. After cooling to room temperature, wear-resistant and non-toxic modified polypropylene plastic products are obtained.

[0013] Preferably, in step S3, the temperature zones of the twin-screw extruder are specifically set as follows: Zone 1 180℃, Zone 2 185℃, Zone 3 190℃, Zone 4 195℃, Zone 5 200℃, Zone 6 205℃, Zone 7 210℃, Zone 8 205℃, and Die Head 200℃.

[0014] Preferably, in step S1, the activation treatment temperature of the modified nanocomposite wear-resistant filler is 105℃, the rotation speed is 1000rpm, and the treatment time is 20min.

[0015] Preferably, in step S4, the annealing temperature is 85°C and the processing time is 3 hours.

[0016] (iii) Beneficial technical effects Compared with existing technologies, the beneficial effects of this invention are: By innovatively designing an organic-inorganic hybrid composite wear-resistant system, the wear resistance of the material has been significantly improved. At the same time, through the synergistic effect of multiple components, the industry problem of the imbalance between wear resistance and impact toughness in traditional wear-resistant modification has been effectively solved. This gives the material excellent wear resistance, surface hardness and impact resistance, greatly improving the scratch resistance and long service life of the product, and making it stable and adaptable to high-frequency use scenarios with long-term reciprocating friction.

[0017] All components are made from food-grade raw materials that meet national safety standards for food contact materials, eliminating the introduction of toxic and harmful substances from the source. At the same time, through optimized system design, the leaching of harmful substances such as bisphenol A, phthalate plasticizers, and heavy metals is avoided. The migration of harmful substances is far below the national standard limit, providing excellent food contact safety and making it widely applicable to various food-contact usage scenarios.

[0018] By performing surface modification and secondary activation treatment on inorganic wear-resistant fillers, the compatibility between the fillers and the polypropylene matrix was significantly improved, effectively avoiding the problem of filler agglomeration and achieving uniform dispersion of wear-resistant functional components in the matrix. At the same time, through the compound design of α / β composite nucleating agents, the precise control of the polypropylene crystal structure was achieved, further promoting the synergistic improvement of the material's rigidity, toughness and wear resistance, and ensuring the uniformity and long-term stability of the material's performance.

[0019] Through a process design involving stepwise premixing, two-stage melt extrusion, negative pressure devolatilization, and low-temperature annealing, the dispersion effect of each component is further enhanced, effectively reducing the residue and precipitation of small molecules, eliminating internal stress in the material, improving the crystal structure, and enhancing the batch stability of the product. Moreover, the production process is environmentally friendly and controllable, with no toxic or harmful substances generated, making it suitable for large-scale industrial production. Attached Figure Description

[0020] Figure 1 This is a production process flow diagram of a wear-resistant and non-toxic modified polypropylene plastic disclosed in this invention; Figure 2 These are bar graphs showing the wear amount and notched impact performance of the examples and comparative examples; Figure 3 This is a comparison chart of the overall performance of radar systems in the embodiment and the comparative example. Detailed Implementation

[0021] according to Figures 1 to 3 The specific embodiments of the present invention are as follows: The present invention will be further described in detail and completely below with reference to specific embodiments, comparative examples, and performance verification. The following embodiments are only used to clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Non-substantial adjustments and improvements made by those skilled in the art based on the core concept of the present invention should fall within the scope of protection of the present invention. The raw materials used in the embodiments and comparative examples of the present invention are all commercially available compliant products, and all raw materials involving food contact comply with the relevant requirements of GB 4806.6-2016 "Plastic Materials and Articles for Food Contact". Specific raw material specifications are uniformly and clearly defined as follows: 1. Homopolymer polypropylene (PP-H): melt flow rate of 18 g / 10 min (test conditions: 230℃, 2.16 kg), food grade; 2. Random copolymer polypropylene (PP-R): melt flow rate of 10 g / 10 min (test conditions: 230℃, 2.16 kg), food grade; 3. Modified nanocomposite wear-resistant filler: Nano-diatomite-fumed silica composite powder modified with silane coupling agent KH550, with a particle size of 50-200nm, a mass ratio of nano-diatomite to fumed silica of 2:1, and a silane coupling agent grafting amount of 1.2%-1.8% of the total powder mass, food grade; 4. Food-grade high molecular weight wear-resistant lubricant: Ultra-high molecular weight silicone masterbatch with food-grade polypropylene as carrier, with an effective silicone content of 50%, food grade; 5. α / β composite nucleating agent: The α nucleating agent is a food-grade sorbitol nucleating agent (Millad 3988), and the β nucleating agent is a food-grade amide nucleating agent (TMB-5), both of which comply with the relevant standards for food contact materials; 6. Food-grade toughening compatibilizer: maleic anhydride-grafted polyolefin elastomer (POE-g-MAH), grafting rate 1.5%, melt flow rate 3g / 10min (test conditions: 190℃, 2.16kg), food grade; 7. Food-grade compound antioxidant: Food-grade antioxidant 1010 and food-grade antioxidant 168 are compounded in a mass ratio of 1:1; 8. Food-grade lubricant: calcium stearate, food grade.

[0022] Example 1 This embodiment provides a wear-resistant and non-toxic modified polypropylene plastic, which, by weight, consists of: 45 parts homopolymer polypropylene, 28 parts random copolymer polypropylene, 7 parts organic-inorganic hybrid composite wear-resistant system, 5 parts food-grade toughening compatibilizer, and 0.7 parts composite stabilizing agent. The organic-inorganic hybrid composite wear-resistant system includes: 4 parts of modified nanocomposite wear-resistant filler, 2 parts of food-grade polymer wear-resistant lubricant, and 1 part of α / β composite nucleating agent; the mass ratio of α nucleating agent to β nucleating agent in the α / β composite nucleating agent is 1:1. The compound stabilizing agent includes: 0.3 parts of food-grade compound antioxidant and 0.4 parts of food-grade lubricant.

[0023] The production process of the wear-resistant and non-toxic modified polypropylene plastic in this embodiment includes the following steps: S1 Raw Material Pretreatment: Weigh the modified nanocomposite wear-resistant filler according to the above ratio, place it in a high-speed mixer, and dry and activate it for 20 minutes at 105℃ and 1000rpm. Remove the adsorbed moisture in the powder by high-speed shearing and constant temperature drying, and at the same time complete the secondary activation of the silane coupling agent to enhance the surface reactivity of the powder and obtain activated wear-resistant filler, which is then sealed for later use. S2 Stepwise Premixing: First, add the homopolymer polypropylene and random copolymer polypropylene weighed according to the formula to a high-speed mixer and mix for 4 minutes at 65℃ and 600 rpm to ensure that the two polypropylene matrix resins are fully mixed and form a continuous phase system. Then, add food-grade toughening compatibilizer, activated wear-resistant filler, and α / β composite nucleating agent, and continue mixing for 6 minutes at 65℃ and 600 rpm to ensure that the compatibilizer fully coats the wear-resistant filler and nucleating agent powders, and builds an interfacial bonding bridge between the filler and the matrix in advance to avoid powder agglomeration during subsequent melt extrusion. Finally, add food-grade polymeric wear-resistant lubricant and composite stabilizing agent, increase the speed to 1200 rpm, and mix at 65℃ for 3 minutes. High-speed shearing ensures that the low-added functional additives are evenly dispersed in the premixed system to obtain a uniform and stable premixed material. S3 Two-Stage Melt Extrusion Granulation: The premixed material is fed into a co-rotating parallel twin-screw extruder, employing a two-stage temperature-controlled extrusion process. The first-stage extrusion section, from the feeding section to the melting section, is set at a temperature of 180-195℃ to achieve stable resin melting and initial dispersion of fillers, preventing premature decomposition of additives due to high temperatures. The second-stage homogenization extrusion section, from the mixing section to the die head section, is set at a temperature of 195-210℃ to achieve deep mixing and dispersion of components and system homogenization. The specific temperature settings for each zone of the twin-screw extruder are: Zone 1 180℃, Zone 2 185℃, Zone 3 190℃, Zone 4 195℃, Zone 5 200℃, Zone 6 205℃, Zone 7... The temperature is set at 210℃, 205℃ in zone 8, and 200℃ at the die head; the main machine speed is set at 380rpm, and the feeding frequency is set at 20Hz to ensure that the material residence time in the barrel is 90-120s, balancing dispersion effect and production efficiency; during the extrusion process, the dual-stage vacuum devolatilization system is activated throughout, and the vacuum degree is stably controlled at ≥0.09MPa to fully remove small molecule volatiles, residual moisture, and oligomers from the system, reducing the risk of additive precipitation; the extruded molten strip is cooled and shaped in a 30-40℃ circulating water cooling tank, and then the surface moisture is thoroughly dried by a high-pressure air knife before being sent to a pelletizer to obtain primary modified particles with uniform particle size; S4 Low-Temperature Annealing and Shaping: The primary modified particles are spread evenly in a tray with a layer thickness of ≤5cm. The tray is placed in a forced-air drying oven and annealed at 85℃ for 3 hours to eliminate the internal stress generated by the particles during the rapid cooling process of extrusion. At the same time, it promotes the growth of polypropylene crystal nuclei and the perfection and stability of the crystal form, avoiding warping and deformation after the product is formed. After annealing, the particles are naturally cooled to room temperature in a dry environment to obtain wear-resistant and non-toxic modified polypropylene plastic products.

[0024] Example 2 This embodiment provides a wear-resistant and non-toxic modified polypropylene plastic, which, by weight, consists of: 35 parts homopolymer polypropylene, 20 parts random copolymer polypropylene, 3 parts organic-inorganic hybrid composite wear-resistant system, 3 parts food-grade toughening compatibilizer, and 0.3 parts composite stabilizing agent. The organic-inorganic hybrid composite wear-resistant system includes: 2 parts of modified nanocomposite wear-resistant filler, 0.8 parts of food-grade polymer wear-resistant lubricant, and 0.2 parts of α / β composite nucleating agent; the mass ratio of α nucleating agent to β nucleating agent in the α / β composite nucleating agent is 1:2. The compound stabilizing agent includes: 0.1 parts of food-grade compound antioxidant and 0.2 parts of food-grade lubricant.

[0025] The production process of the wear-resistant and non-toxic modified polypropylene plastic in this embodiment includes the following steps: S1 Raw Material Pretreatment: Weigh the modified nanocomposite wear-resistant filler according to the above ratio, place it in a high-speed mixer, and dry and activate it for 25 minutes at 100℃ and 800 rpm to obtain activated wear-resistant filler, which is then sealed for later use. S2 Stepwise Premixing: First, add the homopolymer polypropylene and random copolymer polypropylene weighed according to the formula to a high-speed mixer and mix for 5 minutes at 60℃ and 500 rpm; then add food-grade toughening compatibilizer, activated wear-resistant filler, and α / β composite nucleating agent, and continue mixing for 8 minutes while maintaining the temperature and speed; finally, add food-grade polymeric wear-resistant lubricant and composite stabilizing agent, increase the speed to 1000 rpm, and mix for 4 minutes while maintaining the temperature to obtain the premixed material; S3 Two-Stage Melt Extrusion Granulation: The premixed material is fed into a twin-screw extruder. The temperature of the first-stage extrusion section of the two-stage temperature-controlled extrusion process is 180-190℃, and the temperature of the second-stage homogenization extrusion section is 190-205℃. The specific temperature settings for each zone of the twin-screw extruder are: Zone 1 180℃, Zone 2 182℃, Zone 3 186℃, Zone 4 190℃, Zone 5 195℃, Zone 6 200℃, Zone 7 205℃, Zone 8 202℃, and the die head 198℃. The main extruder speed is set to 300 rpm, and the feeding frequency is set to 15 Hz. The vacuum degree throughout the extrusion process is ≥0.08 MPa. The extruded material is water-cooled, air-dried, and pelletized to obtain primary modified particles. S4 Low-Temperature Annealing and Shaping: The primary modified particles are placed in a forced-air drying oven and annealed at 80℃ for 4 hours. After naturally cooling to room temperature, wear-resistant and non-toxic modified polypropylene plastic products are obtained.

[0026] Example 3 This embodiment provides a wear-resistant and non-toxic modified polypropylene plastic, which, by weight, consists of: 55 parts homopolymer polypropylene, 35 parts random copolymer polypropylene, 10.8 parts organic-inorganic hybrid composite wear-resistant system, 8 parts food-grade toughening compatibilizer, and 1.1 parts composite stabilizing agent. The organic-inorganic hybrid composite wear-resistant system includes: 6 parts of modified nanocomposite wear-resistant filler, 4 parts of food-grade polymer wear-resistant lubricant, and 0.8 parts of α / β composite nucleating agent; the mass ratio of α nucleating agent to β nucleating agent in the α / β composite nucleating agent is 2:1. The compound stabilizing agent includes: 0.5 parts of food-grade compound antioxidant and 0.6 parts of food-grade lubricant.

[0027] The production process of the wear-resistant and non-toxic modified polypropylene plastic in this embodiment includes the following steps: S1 Raw Material Pretreatment: Weigh the modified nanocomposite wear-resistant filler according to the above ratio, place it in a high-speed mixer, and dry and activate it for 15 minutes at 110℃ and 1200rpm to obtain activated wear-resistant filler, which is then sealed for later use. S2 Stepwise Premixing: First, add the homopolymer polypropylene and random copolymer polypropylene weighed according to the formula to a high-speed mixer and mix for 3 minutes at 70℃ and 800 rpm; then add food-grade toughening compatibilizer, activated wear-resistant filler, and α / β composite nucleating agent, and continue mixing for 5 minutes while maintaining the temperature and speed; finally, add food-grade polymeric wear-resistant lubricant and composite stabilizing agent, increase the speed to 1500 rpm, and mix for 2 minutes while maintaining the temperature to obtain the premixed material; S3 Two-Stage Melt Extrusion Granulation: The premixed material is fed into a twin-screw extruder. The temperature of the first-stage extrusion section of the two-stage temperature-controlled extrusion process is 185-195℃, and the temperature of the second-stage homogenization extrusion section is 195-210℃. The specific temperature settings for each zone of the twin-screw extruder are: Zone 1 185℃, Zone 2 188℃, Zone 3 192℃, Zone 4 195℃, Zone 5 200℃, Zone 6 205℃, Zone 7 210℃, Zone 8 208℃, and the die head 205℃. The main extruder speed is set to 450 rpm, and the feeding frequency is set to 25 Hz. The vacuum degree throughout the extrusion process is ≥0.092 MPa. The extruded strip is water-cooled, air-dried, and pelletized to obtain primary modified particles. S4 Low-Temperature Annealing and Shaping: The primary modified particles are placed in a forced-air drying oven and annealed at 90℃ for 2 hours. After naturally cooling to room temperature, wear-resistant and non-toxic modified polypropylene plastic products are obtained.

[0028] Example 4 This embodiment provides a wear-resistant and non-toxic modified polypropylene plastic, which, by weight, consists of: 40 parts homopolymer polypropylene, 30 parts random copolymer polypropylene, 7 parts organic-inorganic hybrid composite wear-resistant system, 5 parts food-grade toughening compatibilizer, and 0.8 parts composite stabilizing agent. The organic-inorganic hybrid composite wear-resistant system includes: 4 parts of modified nanocomposite wear-resistant filler, 2 parts of food-grade polymer wear-resistant lubricant, and 1 part of α / β composite nucleating agent, with a mass ratio of 4:2:1; the mass ratio of α nucleating agent to β nucleating agent in the α / β composite nucleating agent is 1:1. The compound stabilizing agent includes: 0.35 parts of food-grade compound antioxidant and 0.45 parts of food-grade lubricant.

[0029] The production process steps and parameters in this embodiment are completely consistent with those in Embodiment 1.

[0030] Comparative Example 1 This comparative example is a blank polypropylene control group. The formulation consists of: 73 parts homopolymer polypropylene, 28 parts random copolymer polypropylene, 5 parts food-grade toughening compatibilizer, and 0.7 parts composite stabilizing agent. No organic-inorganic hybrid composite wear-resistant system is added, and the specifications and proportions of the other raw materials are completely consistent with those in Example 1.

[0031] The production process and parameters of this comparative example are completely consistent with those of Example 1.

[0032] Comparative Example 2 This comparative example serves as the control group for the unmodified wear-resistant filler. The formulation consists of: 45 parts homopolymer polypropylene, 28 parts random copolymer polypropylene, 7 parts organic-inorganic hybrid composite wear-resistant system, 5 parts food-grade toughening compatibilizer, and 0.7 parts composite stabilizing agent. Among them, the modified nanocomposite wear-resistant filler in the organic-inorganic hybrid composite wear-resistant system is replaced with an equal mass, particle size, and ratio of unmodified nanodiatomite-fumed silica composite powder without silane coupling agent KH550. The specifications and ratios of the remaining raw materials are completely consistent with those in Example 1.

[0033] The production process and parameters of this comparative example are completely consistent with those of Example 1.

[0034] Comparative Example 3 This comparative example is a control group without composite nucleating agent. The formulation consists of: 45 parts homopolymer polypropylene, 28 parts random copolymer polypropylene, 6 parts organic-inorganic hybrid composite wear-resistant system, 5 parts food-grade toughening compatibilizer, and 0.7 parts composite stabilizing agent. Among them, no α / β composite nucleating agent is added to the organic-inorganic hybrid composite wear-resistant system. Only 4 parts modified nanocomposite wear-resistant filler and 2 parts food-grade polymeric wear-resistant lubricant are retained. The specifications and proportions of the remaining raw materials are completely consistent with those in Example 1.

[0035] The production process and parameters of this comparative example are completely consistent with those of Example 1.

[0036] Comparative Example 4 This comparative example is a control group using conventional production processes. The formulation and raw material specifications are completely identical to those of Example 1. The production process does not employ the stepwise premixing, two-stage temperature-controlled extrusion, vacuum devolatilization, and low-temperature annealing processes of this invention. The specific steps are as follows: 1. Raw material mixing: Add all the raw materials of the formula into a high-speed mixer at one time, and mix for 10 minutes at 65℃ and 1200rpm to obtain the mixture. 2. Single-stage melt extrusion granulation: The mixture is fed into a twin-screw extruder and a single-stage isothermal extrusion process is adopted. The temperature of all temperature zones is set to 200℃, the main engine speed is 380rpm, the feeding frequency is 20Hz, and the vacuum devolatilization system is not turned on during the extrusion process. The extruded strip is water-cooled, air-dried, and pelletized to obtain modified particles. 3. No low-temperature annealing or shaping treatment is performed; the modified particles are directly used as the finished product.

[0037] Comparative Example 5 This comparative example is a conventional wear-resistant polypropylene formulation in the prior art. By weight, the formulation consists of: 73 parts homopolymer polypropylene, 20 parts industrial-grade talc, 5 parts polyolefin elastomer (POE), 1 part calcium stearate, 0.5 parts antioxidant 1010, and 0.5 parts antioxidant 168. All raw materials are industrial-grade, not food-grade.

[0038] This comparative example uses a conventional polypropylene modification production process, which is completely consistent with the production process of Comparative Example 4.

[0039] Performance testing and verification: The polypropylene modified plastic products prepared in Examples 1-4 and Comparative Examples 1-5 were used to prepare standard test strips according to the corresponding national standards. After conditioning in an environment of 23°C and 50% relative humidity for 24 hours, performance tests were conducted. The test standards are as follows: 1. Wear test: The test shall be conducted in accordance with GB / T 3960-2016 "Test Method for Sliding Friction and Wear of Plastics"; 2. Rockwell hardness test: The test shall be conducted in accordance with GB / T 3398.2-2008 "Determination of hardness of plastics - Part 2: Rockwell hardness", using the HRR scale; 3. Notched impact strength test of simply supported beam: The test was conducted in accordance with GB / T 1043.1-2008 "Determination of impact properties of simply supported plastic beams - Part 1: Non-instrumental impact test", with a test temperature of 23℃. 4. Food contact safety testing: Heavy metal and specific element migration tests were conducted in accordance with GB 4806.7-2016 "Plastic Materials and Products for Food Contact", Bisphenol A migration was tested in accordance with GB 31604.10-2016, and phthalate migration was tested in accordance with GB31604.30-2016.

[0040] Test results show that: The modified plastics prepared in Examples 1-4 all exhibit abrasion loss ≤ 0.008 g / 1000 cycles, Rockwell hardness ≥ 85 HRR, and notched impact strength of a simply supported beam at 23°C ≥ 15 kJ / m. 2 The results are far superior to the modified polypropylene in Examples 1-4. Furthermore, the migration levels of heavy metals and specific elements in Examples 1-4 are all below 10% of the limits set in GB 4806.7, and no bisphenol A or phthalate plasticizers were detected, fully meeting the safety requirements for food contact materials. Among these, Example 4, using the optimal formulation, exhibits the best overall performance, achieving an optimal balance between abrasion loss, hardness, and impact strength, with minimal batch-to-batch performance fluctuations.

[0041] Comparative Example 1, without the organic-inorganic hybrid composite wear-resistant system of the present invention, showed a significant increase in wear loss, a significant decrease in hardness, and extremely poor wear resistance, failing to meet the requirements of high wear resistance applications. Comparative Example 2 used unmodified wear-resistant fillers, which had poor compatibility with the matrix, resulting in significant agglomeration. This not only limited the improvement in wear resistance but also led to a significant decrease in impact strength and material embrittlement. Comparative Example 3, without the addition of α / β composite nucleating agents, could not achieve synergistic regulation of the polypropylene crystal form, resulting in a mismatch between material hardness and impact strength, and a significant decrease in wear resistance. Comparative Example 4 used conventional production processes, resulting in uneven dispersion of components, a large amount of residual small-molecule volatiles, unresolved internal stress, large fluctuations in material properties, and a significant decrease in both wear resistance and impact resistance, with a significant risk of additive precipitation. Comparative Example 5 used existing conventional industrial-grade wear-resistant formulations. Although wear resistance was improved to some extent, impact strength decreased significantly, and the migration of heavy metals and harmful substances far exceeded the limits for food contact materials, posing a serious safety risk and making it unsuitable for food contact applications.

[0042] The wear resistance and core mechanical properties data of the examples and comparative examples are compared in the table below: Table 1 ; The following table compares the food contact safety performance data of the examples and the comparative examples: Table 2 ; In summary, the data in the table clearly demonstrates that the wear-resistant and non-toxic modified polypropylene plastics prepared in Examples 1-4 of this invention exhibit excellent comprehensive performance. Compared to the comparative examples, they not only possess superior wear resistance, higher Rockwell hardness, and better impact toughness, but also meet national standards for the migration of harmful substances related to food contact safety, with no harmful components detected. Among these, Example 4 demonstrates the best comprehensive performance. The comparative examples, either due to the absence of a core wear-resistant system, the lack of modification processes, or the use of conventional production processes and non-food-grade raw materials, all suffer from insufficient wear resistance and mechanical properties, and substandard safety performance. This fully demonstrates the innovation and practicality of the formulation design and production process of this invention, effectively solving the pain point of existing modified polypropylene materials that struggle to simultaneously achieve wear resistance, non-toxicity, and comprehensive mechanical properties.

[0043] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A wear-resistant and non-toxic modified polypropylene plastic, characterized in that, By weight, it includes the following components: 35-55 parts homopolymer polypropylene, 20-35 parts random copolymer polypropylene, 3-10.8 parts organic-inorganic hybrid composite wear-resistant system, 3-8 parts food-grade toughening compatibilizer, and 0.3-1.1 parts composite stabilizing agent. The organic-inorganic hybrid composite wear-resistant system comprises 2-6 parts of modified nanocomposite wear-resistant filler, 1-4 parts of food-grade polymeric wear-resistant lubricant, and 0.2-0.8 parts of α / β composite nucleating agent; wherein the modified nanocomposite wear-resistant filler is a nano-diatomite-fumed silica composite powder modified with silane coupling agent KH550, with a particle size of 50-200 nm and a mass ratio of nano-diatomite to fumed silica of 3:1-1:1; the food-grade polymeric wear-resistant lubricant is an ultra-high molecular weight silicone masterbatch with food-grade polypropylene as a carrier, with an effective silicone content of 48%-52%; the α / β composite nucleating agent has a mass ratio of α nucleating agent to β nucleating agent of 1:2-2:1, the α nucleating agent is a food-grade sorbitol nucleating agent, and the β nucleating agent is a food-grade amide nucleating agent; The food-grade toughening compatibilizer is a maleic anhydride-grafted polyolefin elastomer with a grafting rate of 1.0%-1.8%. The composite stabilizing agent includes 0.1-0.5 parts of food-grade compound antioxidant and 0.2-0.6 parts of food-grade lubricant. The food-grade compound antioxidant is composed of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:

1. The food-grade lubricant is calcium stearate.

2. The wear-resistant, non-toxic modified polypropylene plastic according to claim 1, characterized in that, In the organic-inorganic hybrid composite wear-resistant system, the mass ratio of modified nanocomposite wear-resistant filler, food-grade polymeric wear-resistant lubricant, and α / β composite nucleating agent is 4:2:

1.

3. The wear-resistant, non-toxic modified polypropylene plastic according to claim 1, characterized in that, The homopolymer polypropylene has a melt flow rate of 10-25 g / 10 min (230℃, 2.16 kg), the random copolymer polypropylene has a melt flow rate of 5-15 g / 10 min (230℃, 2.16 kg), and the mass ratio of homopolymer polypropylene to random copolymer polypropylene is 3:2-2:

1.

4. The wear-resistant, non-toxic modified polypropylene plastic according to claim 1, characterized in that, The food-grade toughening compatibilizer has a melt flow rate of 1-5 g / 10 min (190℃, 2.16 kg) and is added in an amount of 4-6 parts by weight.

5. The wear-resistant, non-toxic modified polypropylene plastic according to claim 1, characterized in that, The mass ratio of α nucleating agent to β nucleating agent in the α / β composite nucleating agent is 1:1, and the amount added is 0.4-0.6 parts by weight.

6. The wear-resistant, non-toxic modified polypropylene plastic according to claim 1, characterized in that, In the composite stabilizing agent, the amount of food-grade compound antioxidant added is 0.2-0.4 parts by weight, and the amount of food-grade lubricant added is 0.3-0.5 parts by weight.

7. A production process for the wear-resistant, non-toxic modified polypropylene plastic as described in claim 1, characterized in that, Includes the following steps: S1 Raw Material Pretreatment: Weigh the modified nanocomposite wear-resistant filler according to the ratio, place it in a high-speed mixer, and dry and activate it for 15-25 minutes at 100-110℃ and 800-1200rpm to remove moisture from the powder and complete the secondary surface activation to obtain activated wear-resistant filler. S2 Stepwise Premixing: First, add the homopolymer polypropylene and random copolymer polypropylene weighed according to the formula to a high-speed mixer and mix for 3-5 minutes at 60-70℃ and 500-800 rpm; then add food-grade toughening compatibilizer, activated wear-resistant filler, and α / β composite nucleating agent, and continue mixing for 5-8 minutes while maintaining the temperature and speed; finally, add food-grade polymeric wear-resistant lubricant and composite stabilizing agent, and mix for 2-4 minutes at 1000-1500 rpm to obtain the premixed material; S3 Two-Stage Melt Extrusion Granulation: The premixed material is fed into a twin-screw extruder and a two-stage temperature-controlled extrusion process is adopted. The temperature of the first-stage extrusion section is 180-195℃, the temperature of the second-stage homogenization extrusion section is 195-210℃, the main machine speed is 300-450rpm, the feeding frequency is 15-25Hz, and the entire extrusion process adopts negative pressure devolatilization treatment with a vacuum degree ≥0.08MPa. After water cooling, air drying and pelletizing, the extruded strips are used to obtain primary modified particles. S4 Low-Temperature Annealing and Shaping: The primary modified particles are placed in a forced-air drying oven and annealed at 80-90℃ for 2-4 hours to eliminate internal stress in the particles and promote crystal form perfection. After cooling to room temperature, wear-resistant and non-toxic modified polypropylene plastic products are obtained.

8. The production process of the wear-resistant and non-toxic modified polypropylene plastic according to claim 7, characterized in that, In step S3, the temperature zones of the twin-screw extruder are specifically set as follows: Zone 1 180℃, Zone 2 185℃, Zone 3 190℃, Zone 4 195℃, Zone 5 200℃, Zone 6 205℃, Zone 7 210℃, Zone 8 205℃, and Die Head 200℃.

9. The production process of the wear-resistant and non-toxic modified polypropylene plastic according to claim 7, characterized in that, In step S1, the activation treatment temperature of the modified nanocomposite wear-resistant filler is 105℃, the rotation speed is 1000rpm, and the treatment time is 20min.

10. The production process of the wear-resistant and non-toxic modified polypropylene plastic according to claim 7, characterized in that, In step S4, the annealing temperature is 85°C and the processing time is 3 hours.

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